A generalized right truncated bivariate Poisson regression model is proposed in this paper. Estimation and tests for goodness of fit and over or under dispersion are illustrated for both untruncated and right truncated bivariate Poisson regression models using marginal-conditional approach. Estimation and test procedures are illustrated for bivariate Poisson regression models with applications to Health and Retirement Study data on number of health conditions and the number of health care services utilized. The proposed test statistics are easy to compute and it is evident from the results that the models fit the data very well. A comparison between the right truncated and untruncated bivariate Poisson regression models using the test for nonnested models clearly shows that the truncated model performs significantly better than the untruncated model. The bivariate Poisson models have emerged to address an increasingly important area of research with a wide range of applications in various fields where paired count data are correlated. Data on paired counts arise commonly in various areas of research such as traffic accidents , medical research , epidemiology (number of episodes of depression and number of visits to doctors), marketing , sports , econometrics (job switching voluntarily or involuntarily), etc. As mentioned, a typical example of such dependence arises in the traffic accidents where the extent of physical injuries may lead to fatalities. Leiter and Hamdan  suggesteThe bivariate Poisson distributions have been developed following various assumptions. Among those, the most comprehensive one has been proposed by Kocherlakota and Kocherlakota . The bivLeiter and Hamdan  suggesteY1 be the number of occurrences of the first event in a given interval follow a Poisson distribution with parameter λ1 and the probability of the second event, Y2, for given Y1, where Y2 = Y21 + … + Yy12, be Poisson with parameter, λ1y1, y21, …, yy12 = 0, 1, …. Then the marginal, conditional and joint distributions of Y1 and Y2 can be shown as followsLet Multiplying the marginal and conditional distributions shown above, we obtain the following joint distributionY2 isThe probability mass function for Y1 and Y2 do not allow same joint probability mass function from g(y2)g(y1 ∣ y2) and g(y1)g(y2 ∣ y1) which is expected as we observe from corresponding marginal probabilities.It is noteworthy that in the proposed model, the marginal models for The bivariate Poisson-Poisson expression in λ1 = x′β1, ln λ2 = x′β2, where, The link functions are ln E(Y1) = μ1 = λ1 and E(Y2) = μ2 = λ1λ2. Hence, Hence, we can show that The log likelihood function isY1 be the number of occurrences of the first event in a given interval which has a truncated Poisson distribution with mass functionLet Y2, for given y1, where Y2 = Y21 + … + Yy12, the total number of second event cases among the truncated y1 events in the specified time interval, is:Then the probability of the second event, Y1 and Y2 can be shown as followsMultiplying the conditional and marginal probability functions, the joint distribution of The truncated Poisson-Poisson expression can be expressed as bivariate exponential form as followsY1 can be shown asThe expected value of 7 and 26 .Y2 can be expressed asSimilarly the conditional expected value for λ1 = x′β1, ln λ2 = x′β2, where x′ = , The link functions in model T1y1 can be shown asymptotically as a χ2 with 2 degrees of freedom. Hence T1 is distributed asymptotically as χ2 with 2(k1 + 1) degrees of freedom as each T1y1 is independent chi-square, k1 + 1 is the number of groups of distinct y1 values such as Y1 = 0 with frequency n0, Y1 = 1 with frequency n1, …, Y1 = k1 with frequency nk1, In Sections 2 and 3, the proposed generalized models for untruncated or right truncated data are based on marginal and conditional probabilities as functions of covariates, we need to use a test for goodness of fit suitable for such models. A test for goodness of fit is proposed for the bivariate Poisson-Poisson model  using maH0: the data follow the proposed truncated bivariate Poisson model and, H1: the data do not follow the proposed truncated bivariate Poisson model. The modified test statistic for testing the goodness of fit is:T1y1 can be shown asymptotically as a χ2 with 2 degrees of freedom. Hence T1 is distributed asymptotically as χ2 with 2(k1 + 1) degrees of freedom as each T1y1 is independent chi-square, k1 + 1 is the number of groups of distinct y1 values such as Y1 = 0 with frequency n0, Y1 = 1 with frequency n1, …, Y1 = k1 with frequency nk1, V1 and V2|1 are the variances of Y1 and Y2 given Y1 respectively 11) to deh = P(Yri = kr), H = P(Yri ≤ kr) and then using these values we can estimate φr for the truncated model.Using the mean, variance and correction factor  for righA test for over(under)dispersion, T2, is proposed assuming adjusted variances for the marginal mean of Y1 and conditional means of Y2 given Y1 = y1. If there is over(under)dispersion, then the test results in acceptance of the null hypothesis that the expected values are equal to the adjusted variances.T2 for untruncated bivariate Poisson regression model is:T2y1 can be shown asymptotically as a χ2 with 2 degrees of freedom. Hence T2 is distributed asymptotically as χ2 with 2(k1 + 1) degrees of freedom as each T2y1 is independent chi-square, u denotes untruncated model, k1 + 1 is the number of distinct counts observed for Y1. Similarly, for right truncated model T2 can be defined as follows:T2y1 can be shown asymptotically as a χ2 with 2 degrees of freedom. Hence T2 is distributed asymptotically as χ2 with 2(k1 + 1) degrees of freedom as each T2y1 is independent chi-square, t denotes truncated model.Then In the above tests for the goodness of fit, specific models (proposed models) are tested. Hence, the test for goodness of fit may be termed equivalently as the test for specification of the proposed models.θ is the natural link function which is a function of expected value of Y, b(θ) is a function of θ, a(ϕ) is dispersion parameter and c is a function of y and ϕ. We can obtain expected value and variance of Y from E(Y) = b′(θ) and Var(Y) = a(ϕ)b′′(θ) where b′′(θ) is the variance function, Var[E(Y)]. From the probability function we can show that θ = ln μ1, E(Y1) = μ1, and Var(Y1) = μ1/ϕ1. Similarly, using the conditional probability function for Y2 given Y1 = y1, we find θ = ln μ2y1, E(Y2|y1) = μ2y1 and Var(Y2|y1) = μ2y1/ϕ2.Voung  developet or standard normal test for large sample wheref is the probability function for model with parameter vector θ and g the probability function for model with parameter vector θ′ andThe Voung test is a p = number of parameters in numerator in model f and q = number of parameters in denominator in model g. If V > 1.96 then model in the numerator is favored and if V < −1.96 then model in the denominator is favored.Adjusted Vuong test isY1) as mentioned by doctors and utilization of healthcare services (Y2) where utilization of healthcare services include services from hospital, nursing home, doctor, and home care. The explanatory variables are: gender , age (in years), race  and veteran status . The sample size is 5568.The models proposed in this paper are applied to the tenth wave of the Health and Retirement Study . The outY1) and utilization of health care services (Y2) and sample variances. The average number of conditions is 2.63 and the variance (2.05) appears to be lower than the mean. The average number of utilization of health care services is 0.77 and the corresponding variance is slightly higher (0.79). The measure of correlation between number of conditions and utilization of health care services can be estimated by Y1) and utilization of health care services (Y2) are 0.80 and 1.05, respectively. A test for over(under)dispersion using T2 indicates that there might be statistically significant over(under) dispersion in the bivariate count data. This indicates slight overdispersion for utilization of health care services and underdispersion for number of conditions. Using the mean, variance and correction factor [The dispersion parameters for number of conditions ′, β2∗ = ′, H0: β∗ = 0, the following likelihood ratio test is used The estimates for the right truncated bivariate Poisson model are displayed in The estimated dispersion parameters for untruncated models, vely see . AdjustiT1, that both untruncated and truncated bivariate Poisson regression models fit the data very well. In other words, the null hypotheses may be accepted in favor of the proposed models. To make a more precise decision about the choice of the better model, the Voung test is employed. We have used the Voung test for comparing non-nested models because non-nested models can not be compared using the classical likelihood ratio based tests. The use of bivariate count regression models can provide very useful insights for analyzing repeated measures data emerging from various fields including health. In this paper, a comprehensive methodology has been displayed to deal with different types of problems associated with bivariate count data. In this paper, a new model is proposed using the Poisson-Poisson marginal-conditional approach for both untruncated and truncated data. In reality, there may be influence of right truncation for analyzing such data and the application displayed in this paper clearly demonstrates substantial change in the estimates of regression parameters. A generalized linear model for the bivariate Poisson-Poisson regression model is developed for the right truncated data. The proposed model is applied to the Health and Retirement Study data on number of conditions and utilization of healthcare services. The problem of under or overdispersion in the count data is also examined and appropriate procedures for adjusting the standard errors are also shown. Tests for both goodness of fit and overdispersion have been used and it is observed that the models fit well to the bivariate count data and the extent of under or overdispersion are not found to be significant in the application to the data on number of conditions and utilization of healthcare services from the Health and Retirement Study. In order to select a better model, an extended test for non-nested models for bivariate count data is shown in this paper and it is found that the right truncated bivariate Poisson model is a better choice for the health data used in this study.Similarly,


There is an error in the seventh sentence of the Abstract. The correct sentence is: On the other hand, a recent study reported that the Stx2 production level in O157 strains was determined mainly by the subtypes of Stx2a phage .There are errors in the penultimate and final sentences of the Abstract. The correct sentences are: In the presence of MMC, subclade 8b strains produced significantly greater amounts of Stx2 than clade 6 strains carrying ϕStx2a_δ. In this study, we propose that Stx2 production in subclade 8b strains in the presence of MMC might be enhanced due to genetic factors other than ϕStx2a_δ.There is an error in the third sentence of the final paragraph of the Discussion section. The correct sentence is: The level of Stx2 production in subclade 8b strains isolated in Chiba Prefecture in the presence of MMC may be enhanced by genetic factors other than ϕStx2a_δ.


This study also demonstrates that the catalytic activity and selectivity of CO2 reduction to CO and CH4 products can be systematically tailored by varying the size of the Pd nanocrystals supported on the Nb2O5 nanorods. Using large Pd nanocrystals, this study achieves CO and CH4 production rates as high as 0.75 and 0.11 mol h−1 gPd−1, respectively. By contrast, using small Pd nanocrystals, a CO production rate surpassing 18.8 mol h−1 gPd−1 is observed with 99.5% CO selectivity. These performance metrics establish a new milestone in the champion league of catalytic nanomaterials that can enable solar‐powered gas‐phase heterogeneous CO2 reduction. The remarkable control over the catalytic performance of Pd@Nb2O5 is demonstrated to stem from a combination of photothermal, electronic and size effects, which is rationally tunable through nanochemistry.This study has designed and implemented a library of hetero‐nanostructured catalysts, denoted as Pd@Nb The photothermal effect in these hetero‐nanostructure materials arises from broadband optical absorption and nonradiative relaxation of photoexcited surface plasmons or intra‐/interband electrons in the metal nanocomponents.Powered by both the heat and light from the sun, the photothermal strategy is extremely appealing for developing superior gas‐phase CO2 reduction rates and selectivity in metal–metal oxide hetero‐nanostructures. For example, charge transfer between the metal and metal oxide constituents can influence the surface charge on the metal nanocrystal and hence its activity and selectivity toward CO2 reduction.2 reduction is to engineer size, shape, or a dynamic restructuring of the nanocrystals.Several groups have demonstrated that surface electronic properties can greatly influence photocatalytic CO2 hydrogenation activity and selectivity of nanostructured Pd@Nb2O5 toward either CO or CH4 reduction products. A library of Pd@Nb2O5 nanomaterials with gradually increasing Pd nanocrystal sizes and loadings is synthesized and investigated as photothermal catalysts for the reduction of CO2. In a batch reactor under simulated light with illumination intensities of 4.2 W cm−2, using 0.1% Pd@Nb2O5, a CO production rate as high as 18.8 mol h−1 gPd−1 is observed with 99.5% CO selectivity. In stark contrast, using 10% Pd@Nb2O5, we achieve a CO production rate surpassing 0.75 mol h−1 gPd−1 and a CH4 production rate of 0.11 mol h−1 gPd−1. The selectivity to methane on 10% Pd@Nb2O5 is higher by a factor of 24 than that on 0.1% Pd@Nb2O5. To simulate more industrially relevant conditions, photocatalytic measurements were also carried out in a gas‐phase flow‐photoreactor using an illumination intensity of 2.1 W cm−2. A remarkable light‐driven CO2‐to‐CO conversion rate of 0.91 mol h−1 gPd−1 was obtained with an unprecedented turnover frequency (TOF) as high as 0.61 s−1 and an energy conversion efficiency exceeding 0.23%. This represents a new milestone in the champion league of gas‐phase light powered CO2 reduction catalysts in the absence of external heating. The results of this study show that “photothermal engineering” of the catalytic properties of Pd@Nb2O5 hetero‐nanostructures can be used to tailor the activity and selectivity of the gas‐phase CO2 reduction reaction, an advance that with further materials and process engineering could enable the development of CO2 refineries powered by the heat and light of the sun.Herein, we combine these strategies to tune and optimize the photothermal CO22.12O5 samples with gradually increasing Pd loadings, labeled as 0.1% to 15% Pd (which is associated with the wt% of Pd in the samples), were synthesized via a two‐step process . Pd@Nb2O5 samples were prepared via a straightforward microwave‐assisted hydrothermal reduction strategy using Na2PdCl4. The elemental Pd content in each Pd@Nb2O5 sample was determined by inductively coupled plasma‐atomic emission spectroscopy (ICP‐AES), with the results being listed in Table S1 (Supporting Information).A library of Pd@Nbss Figure1. The Figure2O5 samples with loadings of 0.1%, 3%, and 10%. High‐resolution TEM (HRTEM) images  and Pd (020) planes are measured to be 2.32 and 1.95 Å, respectively, and the HRTEM image revealed the preferential growth of (111) facets in the Pd nanocrystal. The observed interfacial orientation relationship between the Pd and Nb2O5 defines that Pd (111) is aligned parallel to the (401) plane of Nb2O5.2O5 samples with Pd loading higher than 5%. For low loading samples with Pd nanocrystals in the size range of 5 nm or lower, this is more difficult to observe because of X‐ray line broadening. To provide more insight into the smallest Pd nanocrystals, synchrotron radiation EXAFS spectroscopy was utilized to unravel the phase and atomic structure of the Pd@Nb2O5 samples with low loadings. The obtained spectra for these Pd@Nb2O5 samples  reflect a decrease in the coordination number (CN) of Pd atoms for these samples relative to the bulk Pd reference material . These results suggest that the size of the supported Pd nanoparticles (NPs) is reduced in samples at low Pd loadings. Qualitative analysis of the Pd K‐edge EXAFS spectra from the supported Pd nanoparticles, as shown in Figure 13 clusters (CN ≈ 6).The composition and phase of the Pd nanocrystals were further characterized by powder X‐ray diffraction (PXRD) and synchrotron extended X‐ray absorption fine structure (EXAFS) spectroscopy. As shown in Figure S4 (Supporting Information), the characteristic PXRD patterns of metallic Pd were observed for Pd@Nb2O5 exhibits semiconducting behavior with a strong electronic bandgap absorption only in the ultraviolet (UV) spectral range with a wavelength less than 400 nm , with a monotonic decrease in diffuse reflectance with the increase of Pd loading. According to Mie theory,2O5 hetero‐nanostructures, which grows with Pd loading, primarily originates from interband and intraband transitions of Pd nanocrystals.Pristine Nbd Figure a. Accord2O5 and Pd@Nb2O5 hetero‐nanostructures to directly measure the local temperatures of the samples. The local temperature was extracted from an analysis of the observed linear shift in the position of the niobium—oxygen phonon modes with increasing temperature.2O5, 0.5% Pd@Nb2O5, and 5% Pd@Nb2O5 at around 990 cm−1 under a set of different incident laser power levels. At the power level of 12 mW, the local temperatures of Pd@Nb2O5 samples are estimated to be 414 K for 0.1% Pd@Nb2O5 and 670 K for 0.5% Pd@Nb2O5 while the temperature of 5% Pd@Nb2O5 at the same power level is estimated to be as high as 743 K . These observations verify that the observed reactions between CO2 and H2 over the Pd@Nb2O5 hetero‐nanostructures are light driven. When the batch photoreaction was carried out using pristine Nb2O5 nanorod samples, only trace amounts of 13CO and 13CH4 were detected under the same illumination and reaction conditions. As shown in Figure 2O5 samples is much less than that of pristine Nb2O5 samples throughout the UV, visible, and NIR spectral regions. Additionally, it shows a decreasing trend in diffuse reflectance along with the increase of Pd loading. This phenomenon indicates that a significant amount of light is absorbed by Pd nanocrystals in the Pd@Nb2O5 samples. Clearly, the presence of Pd nanocrystals enables efficient absorption of light and subsequently causes photoinduced catalytic activity.In order to demonstrate the catalytic hydrogenation of CO2 reduction over different samples was determined using gas chromatography, and the results are plotted in Figure2O5 with 0.1% Pd, we observed a remarkable CO2‐to‐CO hydrogenation rate as high as 18.8 mol h−1 gPd−1 , representing a new benchmark in the champion league of light‐driven gas‐phase CO2 reduction. We also achieved a CO production rate of 0.75 mol h−1 gPd−1 and a CH4 production rate of 0.11 mol h−1 gPd−1 with 10% Pd@Nb2O5. The selectivity for CH4 production exhibits an increasing trend with the increase in Pd loading. The selectivity of the methanation conversion on 10% Pd@Nb2O5 rises dramatically with an observed 24‐fold increase relative to 0.1% Pd@Nb2O5 . According to the Raman measurements in Figure 2O5 can be increased dramatically from ambient to as high as 743 K, merely by the photothermal effect of the Pd “nanoheaters.” Hence, it is reasonable to propose that the underlying catalytic mechanism over the Pd@Nb2O5 hetero‐nanostructures involves the absorption of light and efficient thermalization of absorbed energy, resulting in elevated local temperatures in the Pd@Nb2O5 catalysts, which lead to the acceleration of the CO2 hydrogenation reaction. As shown in Figure S7 (Supporting Information), the reverse water gas shift (RWGS) rates, the methanation rates, and the CH4/CO selectivity all increase along with the enhancement of light intensity. This indicates that the selectivity is related to photothermal capability of the samples. Then we investigated the size effect under dark condition with external heating. We conducted dark tests at 160 °C, which is the highest operating temperature we can reach by external heating in our reactor system. We compared the selectivity of two samples (0.5% and 10% Pd), as shown in Figure S8 (Supporting Information). It is concluded that the selectivity toward CH4 does increase along with the size of Pd nanocrystals. The selectivity is therefore related to both the local temperature and the size of Pd nanocrystals.To obtain further insights into the activity and selectivity of the photoinduced catalytic process, 10% Pd@Nb4 selectivity was also investigated  were prepared, and their hydrogenation rates evaluated under identical conditions. If the hydrogenation rates are driven by a photochemical process, in which electron–hole pairs are generated upon light absorption by Nb2O5, and then transferred to Pd for activating CO2, then the CH4 selectivity should be independent of the catalyst weight. Nevertheless, the results in Figure 4 selectivity for a film weighing 2 mg  in contrast to a higher CH4 selectivity for a film weighing 6 mg. This weight effect likely originates from an elevated local temperature generated by a larger population of Pd “nanoheaters.” Therefore, the selectivity in hydrogenation is attributable to photothermal‐driven kinetics, and this light‐driven photothermal effect influences the methanation more effectively than the RWGS process.The sample weight dependence of the CH2 is its stability, which describes its capacity for long‐term utilization. A repeat of the initial measurement using the 3% Pd@Nb2O5 catalyst was conducted , reproducing the rate of around 1.7 mol h−1 gPd−1. The results demonstrate not only that the 3% Pd@Nb2O5 catalyst is capable of converting gaseous CO2 to CO at an appreciable rate, but also that it is stable under these reaction conditions and can produce rates consistent with the initially measured values even after being irradiated continuously for seven sequential tests.Another important parameter to consider when designing a catalyst for light‐driven hydrogenation of COIn general, the activities of photocatalysts reported in the literature degrade with sequential testing for various factors including sintering, photodegradation, catalyst poisoning, and adventitious contamination. By contrast, our photothermal catalysts instead display a slight rate enhancement with the increased testing time. With its superior catalytic performance and long‐term stability, this “nanoheater” photothermal strategy,] which can be expanded to include other nanometals with much lower materials cost, is a promising route to scaling up processes for the heterogeneous catalytic hydrogenation of carbon dioxide using renewable solar energy.32O5 samples, Brunauer–Emmett–Teller (BET) measurements were performed, as shown in Table S3 (Supporting Information), indicating that the specific surface areas of these samples are similar in the range 80–90 m2 g−1. The affinity of a photocatalyst's surface for CO2 has also been identified as a critical factor influencing photocatalytic activity.] To verify Pd@Nb2O5 samples' affinity for CO2, the CO2 capture capacity was determined for each sample using thermogravimetric analysis (TGA). Moreover, the CO2 capture capacities of the Pd@Nb2O5 nanomaterials are also normalized to the surface area of each sample for more accurate comparison. Figure S10 (Supporting Information) reveals that the surface‐area‐normalized CO2 capture capacities of pristine Nb2O5, 0.1%, 0.5%, and 1% Pd, are similar at 0.50, 0.48, 0.47, and 0.48 µmol CO2 m−2, respectively. There is a notable decrease in the normalized CO2 capture capacity for samples with Pd loading beyond 3%, which could be ascribed to the reduced amount of exposed Nb2O5 surface, suggesting that Pd does not assist with the affinity of CO2 for reaction with hydrogen.In comparison with bulk forms of metal or metal oxide catalysts, nanostructured analogs are expected to provide more active sites to promote catalytic reaction, due to their large surface areas.2. To compare the catalytic activity more accurately, we calculated the TOF for CO and CH4 production as a function of active surface Pd sites, which was determined via selective CO chemisorption; these results are shown in Figure −2, the TOFPd CO values for the 3% and 10% Pd samples were similar at 0.51 and 0.50 s−1, respectively, while the TOFPd methane value for the 10% Pd sample (0.073 s−1) is 2.4 times higher than that of the 3% Pd sample (0.03 s−1).In this work, we have been able to demonstrate a highly efficient and stable photothermal‐catalytic system with tunable selectivity for the reduction of CO2 hydrogenation properties of the Pd@Nb2O5 samples were also evaluated in a light‐powered flow photoreactor, which is relevant to more practical operating conditions in industry. In the light‐flow system, we achieved a high gas‐phase light CO production rate of 0.91 mol h−1 gPd−1 and TOFPd CO as high as 0.61 s−1 over a 10% Pd@Nb2O5 sample with illumination intensities of 2.1 W cm−2.The photocatalytic CO2 reduction. As shown in Table S5 (Supporting Information), 0.23% energy conversion efficiency is achieved in the flow system over 10% Pd@Nb2O5, while 0.05% energy conversion efficiency is obtained in the batch system over 0.1% Pd@Nb2O5. Notably, even at these low loadings of Pd, photothermal hydrogenation of CO2 still shows a leading‐edge efficiency when compared with literature examples. With materials and process engineering optimization, the performance metrics of these hetero‐nanostructured catalysts can likely be further enhanced and, with the use of more earth‐abundant elements, the cost of the process can be reduced.We also evaluated the energy conversion efficiency of these photoreactions in both batch‐ and flow‐type reactors for gas‐phase CO2O5 samples, from which we clearly observed the 3d5/2 and 3d3/2 peaks shifted from 334.5 and 340 eV, respectively, for 15% Pd to 336.4 and 342 eV, respectively, for 0.1% Pd. Such a shifting is plotted as a function of Pd loading and shown in FigureTo investigate the elemental composition, bonding information, and electronic properties of the samples, X‐ray photoelectron spectroscopy (XPS) and ultra‐violet photoemission spectroscopy (UPS) measurements were performed. Figure S12 (Supporting Information) illustrates the Pd 3d core level XPS spectra of the set of Pd@Nb2O5, electrons are transferred from the initially d electron‐rich metal (Pd) to the metal oxide (Nb2O5), which has empty states in its conduction band. Charge transfer of this type can lead to a positively charged Pd surface.2O5 sample, 0.1% Pd sample, and 10% Pd sample to measure their respective work functions, which dictate the position of the Fermi level with reference to the vacuum level. As shown in Figure Ef of composite Pd@Nb2O5 are located less negatively compared with that of pristine Nb2O5. This implies that at the heterojunction between Pd and Nb2O5, electrons will flow from Pd to Nb2O5 to equilibriate the chemical potential, resulting in the formation of positively charged Pd atoms.An electron donor–electron acceptor interaction model can be used to explain the shift in Pd binding energy; at the interface between the Pd and the Nb2 hydrogenation reaction. Notably, Ef of the 0.1% Pd sample locates closer to the vacuum level compared with that of the 10% Pd sample; thus, more charge transfer from Pd to Nb2O5 would take place with the former compared to the latter.With this model, the positively charged Pd surface can affect the strength of binding of adsorbed reactants, intermediates, and products.2 reduction on this Pd@Nb2O5 catalyst, a series of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements was performed in a flow cell under reaction operando conditions.2O5 , Pd(211) surfaces, and a model Pd55 nanocrystal were selected to model terrace, edge, and corner sites, respectively . Figure 4 production pathways was recently executed in details, which agrees with mechanistic assertions in this study.2 on Pd nanocrystals.Density functional theory (DFT) calculations were conducted to rationalize the size effect of Pd nanocrystals on the COly Figure6a. The2 to CO versus CH4 on Pd@Nb2O5 is presented in Figure 2O5 support, which drives the CO2 hydrogenation reaction via the formate pathway. As a result of electron donation from Pd to the Nb2O5 support, the Pd nanocrystals develop a positive surface charge that is more pronounced for the smaller Pd nanocrystals . The conversion of CO2 on Pd can form coordinated formate (HCO2) on the surface of Nb2O5, located at the interface between Pd and Nb2O5. A surface acetal (H2CO2) could then be formed via transfer of a second H from Pd to the coordinated formate. Subsequent reaction of the acetal could involve a concerted transfer of H from the Pd to the acetal to form a surface methoxide (CH3O) and surface hydroxyl (OH) groups. The methoxide could react further with H spilled over from the Pd to form CH4 and H2O that then desorb from the surface of the Nb2O5 nanorods. It is also possible to consider the Nb2O5 surface sites that capture CO2 molecules to be active sites in the CO2 conversion. We calculated the TOF for CO and CH4 production as a function of active surface Nb2O5 active sites, which was determined by multiplying the CO2 capture capacity by the surface area of each sample; these results are shown in Table S4 (Supporting Information).Alternative reaction mechanisms may also be responsible for the observations described above.2O5 catalyst in the photothermal hydrogenation of CO2, mentioned earlier and displayed graphically . Recall that thermal reactions on nanostructured catalysts often suffer from deactivation caused by loss of surface area induced by sintering. This is not found to be the case for the photothermal hydrogenation of CO2 where the size of the Pd nanocrystals remains essentially unchanged before and after the catalyst testing. It seems that in the case of the photothermally driven heterogeneous catalytic hydrogenation of CO2 described in this study, where the active palladium “nanoheaters” can achieve local temperatures that are high enough to drive the conventional thermal reactions, the heating and surface chemistry is spatially confined to the interface between the Pd nanocrystals and the Nb2O5 nanorods, thereby unable to cause the macroscopic heating of the entire nanostructured catalyst required to cause sintering, loss of surface area, and lack of stability. To delve deeper into this proposal would require first principles quantum and classical mechanical analyses of the effect of size on heat diffusion and transfer from the nanoscale to the macroscale,2O5 nanorod.In closing, it is worth commenting on a likely cause of the extraordinary long‐term stability observed for the Pd@Nb42 on Pd@Nb2O5 has been shown to be an effective strategy for optimizing the activities and selectivities, stabilities, and efficiencies of the reverse water gas shift and methanation reactions, taking their performance metrics into the champion league of catalysts. It is envisioned that this approach will work equally well for earth‐abundant and low‐cost M@MOx hetero‐nanostructures, an advance that speaks well for their implementation in future solar‐powered CO2 refineries.Photothermal engineering of the catalytic hydrogenation of CO52O5Preparation of Nb: A mass of 340 mg niobium powder  was dissolved in a hydrochloric acid solution  in a Pyrex beaker, which was then stirred and ultrasonicated for half an hour. The solution was subsequently transferred into a 50 mL Teflon‐lined stainless steel autoclave, and the hydrothermal reaction was performed at T = 200 °C for 24 h. After the hydrothermal synthesis, the obtained product was washed three times with deionized water, and the powder was dried in a vacuum oven at T = 70 °C for 12 h.2O5 Hetero‐NanostructurePreparation of Pd@Nb: Nanostructured Pd@Nb2O5 samples with different loadings of Pd were synthesized via a microwave‐assisted reaction. In a typical microwave synthesis, 50 mg of nanorods was suspended in anhydrous ethanol (20 mL), in a Pyrex vessel with 40 mL capacity. A stock solution of Na2PdCl4  in anhydrous ethanol (20 mL) was then prepared with a concentration of 1 mg mL−1. A certain amount of Pd precursor solution was added to the dispersion, which was then sonicated for 30 min. Subsequently, the vessel was capped and transferred to the microwave reactor . After being washed with deionized water for three times, the sample was dried into a vacuum oven at T = 70 °C for 12 h, followed by a post‐treatment at 120 °C in air for 24 h to obtain the Pd@Nb2O5 nanostructured samples.Characterization: The morphologies of the Pd@Nb2O5 catalysts were assessed using a Hitachi H‐7000 transmission electron microscope at 100 kV. PXRD patterns were obtained using a Bruker D2‐Phaser X‐ray diffractometer with Cu Kα radiation at 30 kV. The amount of Pd in the hetero‐nanostructures was detected using ICP−AES (Thermo Electron Corp. Adv. ER/S). Prior to the ICP measurements, the hetero‐nanostructures were immersed in concentrated nitric acid with agitation for 12 h to dissolve the Pd@Nb2O5.To determine the surface area, Pd@Nb2O5 catalysts were outgassed overnight at 80 °C and then analyzed by volumetric nitrogen adsorption at 77 K using a Quantachrome Autosorb‐1‐C. The surface area was calculated based on the BET theory. XPS was performed using a Perkin Elmer Phi 5500 ESCA spectrometer in an ultrahigh vacuum chamber with a base pressure of 1 × 10−9 Torr. The spectrometer used an Al Kα X‐ray source operating at 15 kV and 27 A. Calculations were made by fitting C 1s peak to 284.5 eV, and samples were prepared by compacting a uniform layer of the materials on a carbon tape. During the measurement, survey and high‐resolution C 1s, O 1s, Nb 3d, and Pd 3d spectra were recorded. All data analyses were carried out using the Multipak fitting program.HRTEM images were acquired using the aberration‐corrected JEOL JEM‐ARM200CF transmission electron microscope operated at 200 keV. With a spherical aberration corrector, the TEM images can achieve 0.11 nm spatial resolution.2 adsorption capacity was determined using thermogravimetric analysis . Each sample (≈5 mg) was first heated at a rate of 10 °C min−1 to 120 °C under a nitrogen flow of 100 mL min−1. This condition was maintained for 1 h to remove any adsorbed moisture. Subsequently, the gas flow was switched to carbon dioxide at 100 mL min−1 under the same temperature for 2 h. The weight gain between the N2 and CO2 gas streams was directly used for CO2 capacity calculation, which was normalized to the surface area of each sample.CO−8 Torr. UV radiation was produced from He Iα (21.22 eV), and a bias of −15 V was applied to measure the spectrum.Ultraviolet photoemission spectroscopy was performed using a PHI 5500 multitechnique system. The samples were prepared by drop‐casting the suspension of the materials onto silicon wafers. The measurement was conducted under a pressure of ≈102O5‐supported Pd nanoparticles were acquired using transmission detection for the Nb K‐edge and fluorescence detection for the Pd K‐edge. Samples were cooled to 90 K using a cryostatic sample holder in order to suppress thermal lattice vibrations, thereby enhancing the intensity of the observed EXAFS signal intensity. X‐ray absorption near edge structure (XANES) spectra were background‐subtracted and normalized for more accurate comparison, with Nb and Pd metal foils being used to energy‐calibrate each spectrum. Data processing and EXAFS fitting were performed using WinXAS software≈2.75 Å in length. For PdO, direct Pd–O and Pd–Pd single scattering paths of ≈2.02 and 3.05 Å in length were included in the region of interest. The slight difference between the Pd 0.1% sample and other supported Pd nanoparticles was attributed to noise in the XAS data, due to the low relative concentration of Pd in this sample. It should also be considered that the presence of surface defects can decrease the observed CNs obtained from EXAFS fitting, and so this might also contribute to these low numbers. Likewise, the gradually increasing Debye–Waller factor (σ2) values could be equally attributable to the small size or increased structural disorder of the Pd nanoparticles. The slightly shorter Pd—Pd bond length of the 0.1% Pd sample was, however, indicative of very small nanoparticles, especially in conjunction with the observed CN values.X‐ray absorption spectroscopy (XAS) analysis of the Pd nanoparticles and reference materials was performed using the Sector 20‐BM beamline of the advanced Photon Source at Argonne National Laboratory in Argonne, IL, USA. XAS spectra were obtained from reference foils and powders in transmission detection mode, while the spectra for Nb2O5 and Nb2O5 samples onto borosilicate glass microfiber filters, and the weight of powder on each film was ≈2 mg.Diffuse reflectance spectra of the samples were determined using a Lambda 1050 UV/Vis/NIR spectrometer from Perkin Elmer, which was equipped with an integrating sphere with a diameter of 150 mm. The samples for analysis were films prepared by drop‐casting aqueous dispersions of Pd@Nb−1 to 120 °C under vacuum, and this condition was maintained at 120 °C for 5 h. Subsequently, the gas flow was switched to H2 and the sample was heated at 10 °C min−1 until the temperature reached 250 °C. This condition was maintained for 2 h under H2 flow prior to be evacuated for 2 h. Then the sample was cooled down to 40 °C. The vacuum–volumetric isotherm measurement was then performed at 40 °C. The combined amount of physisorbed and chemisorbed CO was first measured, then, a vacuum was pulled on the sample to remove the physisorbed CO while the chemically adsorbed CO remained bound to the metal. A second isotherm was measured which represented only the physisorbed amount of CO. The physisorbed isotherm was then subtracted from the combined isotherm to determine the chemisorbed isotherm.CO chemisorption was measured using an Autosorb iQ analyzer (Quantachrome Instruments). As for pretreatment, each sample (200 mg to 1 g) was first heated at a rate of 5 °C min−1 resolution, using an average of 64 scans. Powder samples were placed into the holder without packing or dilution. A background IR spectrum was taken following 1.5 h of purging under He at 150 °C. Different mixtures of gases were then introduced into the cell, with flow rates controlled by electronic mass flow controllers. In all transient experiments, 5% of H2 diluted in He was first introduced for 20 min, followed by 15 min of pure He. Pure CO2 was then introduced into the cell, again followed by 15 min of He. Finally, a mixture of H2 and CO2  was flowed for 30 min. A total flow rate of 20 mL min−1 was used for all gas mixtures, and a temperature of 240 °C was maintained for all experiments. DRIFT spectra were recorded every ≈90 s when a new gas mixture was introduced, then every ≈5–10 min after 10 min time durations.In situ DRIFT spectra were collected on a Thermo Scientific iS50 series Fourier transform infrared (FT‐IR) instrument equipped with a Harrick Praying Mantis DRIFT accessory. Each spectrum was recorded at 4 cmGas‐Phase Catalytic Measurements—Batch System: The batch‐system‐based gas‐phase catalytic measurements were carried out in a custom‐built 12 mL stainless steel batch reactor with a fused silica view port sealed with a Viton O‐ring.2 (the illumination area was 1 cm2), which was then loaded into a custom‐built stainless steel batch reactor with a volume of 12 mL, followed by filling the reactor with CO2 and H2 gas at 1:1 ratio to a total pressure of 27 psi. In order to confirm with complete certainty that the products stem from reactant CO2 gaseous molecule rather than adventitious carbon sources, isotope‐tracing experiments were carried out using 13CO2 . The filter with the catalyst was then loaded into the reactor, which was evacuated using an Alcatel dry pump prior to being purged with H2 (99.9995%) at a flow rate of 20 mL min−1. The reactor was first evacuated and then injected with 13CO2 followed by H2 at a 1:1 ratio to a total pressure of 27 psi prior to being sealed. An Omega PX309 pressure transducer was used to monitor the presser inside the reactor. Samples were irradiated using a 300 W Xe lamp for durations of 30 min. No external heating source was connected to the reactor during the photothermal gas‐phase test. The analysis of product gases was conducted with a flame ionization detector (FID) installed in an SRI‐8610 gas chromatograph (GC) with a 6′ Haysep D column. Isotopically labeled product gases were measured using an Agilent 7890A gas chromatographic mass spectrometer with a 60 m GS‐CarbonPLOT column fed to the mass spectrometer.In a typical gas‐phase test, 2 mg of samples was deposited onto a borosilicate filter support having an area of 1.2 cmGas‐Phase Catalytic Measurements—Flow System: The photothermal reduction of CO2 by H2 was carried out in a cylindrical flow reactor modeled as a continuously stirred tank reactor of volume ≈12 mL. A 300 W Xe lamp (Newport) was used as the light source for the reaction. The measured intensity was ≈2.1 W cm−2. CO2 and H2 flow rates were controlled between 0.1 and 2 sccm by two mass flow controllers (Alicat MC‐2SCCM‐D/5M). After leak testing and evacuation of the reaction system, CO2 (Grade 5.0) and H2 (Grade 5.5) of ratio 1:1–1:4 were introduced. The concentrations of CO and CH4 products in the effluent gas were periodically sampled and analyzed by a gas chromatograph (SRI 8610) with an FID using He as the carrier gas.Gas‐Phase Catalytic Measurements—Theoretical Methods: DFT calculations were conducted using the plane‐wave basis in the Quantum Espresso software.−6 Ry was used, and Davidson iterative diagonalization algorithm was employed. All calculations were spin‐polarized with the local‐spin‐density approximation.The bulk structure of palladium was first relaxed using a supercell containing 32 Pd atoms, giving a lattice constant of 3.9425 Å, which was in good agreement with other literature values.Transition state information was obtained using NEB calculations with the climbing image method.Eads) was defined by Eadsorbate/surface is the total energy of the surface containing the adsorbed species, Eadsorbate is the total energy of the free adsorbate (in the gas phase at noninteracting distance), and Esurface is the total energy of either the bare surfaces or cluster. By this definition, negative adsorption enthalpies indicate exothermic adsorption. The adsorption energies of *H (−2.853 eV), *CO (−1.995 eV), and *OH (−2.461 eV) on Pd(111) closely matched those from other study .To verify the DFT results, the adsorption energies and transition state energies were compared with other literature values. The enthalpy of adsorption , a MATLAB script was written to construct octahedral NPs of different diameters. The script was written in such a way that the final NP had the same face‐centered cubic internal structure as bulk Pd and was externally enclosed by (111) and (100) planes to give an external octahedral structure. The atoms that belong to bulk, terrace, edge, and corner sites were then counted. These sites were defined by their coordination numbers, with bulk atoms having the largest coordination number (12) and corner atoms having the smallest (5).The authors declare no conflict of interest.SupplementaryClick here for additional data file.


Microdevices consisting of two adjacent suspended silicon nitride membranes were fabricated to measure the thermal transport properties of the nanowires in vacuum. Single Sb2Se3 nanowires with different diameters and nanowire bundles were carefully placed on the device to bridge the two membranes. The relationship of temperature difference on each heating/sensing suspension membranes with joule heating was accurately determined. A single Sb2Se3 nanowire with a diameter of ~ 680 nm was found to have a thermal conductivity (kNW) of 0.037 ± 0.002 W/m·K. The thermal conductivity of the nanowires is more than an order of magnitude lower than that of bulk materials (k ~ 0.36–1.9 W/m·K) and highly conductive (σ ~ 3 × 104 S/m) Sb2Se3 single nanowires (k ~ 1 W/m·K). The measured Seebeck coefficient with a positive value of ~ 661 μV/K is comparable to that of highly conductive Sb2Se3 single nanowires (~ 750 μV/K). The thermal transport between wires with different diameters and nanowire bundles was compared and discussed.In this study, we measured the thermal conductivity and Seebeck coefficient of single Sb Recovering waste heat and converting it into electrical energy with thermoelectric generators is an effective measure against global warming and environmental impact of climate change. Thermoelectric devices that are noiseless (no moving parts), inherently reliable without any maintenance, and environmentally friendly have attracted increasing attentionet al.34578910111214151617181920Thermoelectric power generation is based on the Seebeck effect, in which a temperature gradient is converted into an electric current. The applications of bulk thermoelectrics in cost-effective devices are limited by their low efficiency. Thus, new materials with improved thermoelectric power efficiency need to be developed. Dresselhaus 2VI3-type semiconductors possess band gap energies ranging from 2.2 eV  to 0.21 eV . Sb2Se3 is a layered semiconductor with an orthorhombic crystal structure; this material has been studied because of its switching effects232Se3 semiconductors have been commonly used as absorbers to fabricate cost-effective solar cells and Hall effect devices2Se3 films are widely applied in optical materials, thermoelectric cooling, and power conversion devices because of their high thermoelectric power2Se3 nanostructures . Several studies have analyzed the electrical properties and photoresponse of Sb2Se3 nanomaterials2728293031322Se3 nanostructures remain lacking.V2Se3 NWs and NW bundles were used to measure the thermal transport properties of NWs. The thermal conductivity of the NWs was more than an order of magnitude lower than that of bulk materials in previous measurements. The measured Seebeck coefficient is about two-fold lower than that of the bulk. We also investigated the effects of NW diameters and van der Waals interface between NWs on thermal conductivity.In the present study, microfabricated devices hybridized with individual Sb2Se3 NW samples with a high-quality single-crystalline property were produced from a single source precursor, namely, Sb[Se2P(OiPr)2]3. These materials have already been studied and were demonstrated elsewhere34352Se3 NWs, and morphology characterization can be found in the 2Se3 with a ratio of 1:1.5 as determined by powder X-ray diffractometry  was positioned between two membranes using of a nanomanipulator. The device was placed in a vacuum chamber (10−7 Torr) at room temperature to avoid thermal radiation loss, making Sb2Se3 NW the only pathway to transport heat between the heating and sensing membranes. A detailed description of the measurement techniques and uncertainty analysis can be found in refs Suspended microdevices fabricated on SiNh) caused joule heat generation and a consequent temperature rise ΔTh (ΔTh = Th − T0) from the thermal bath temperature T0. A certain amount of heat generated by the Cr/Au coil on the heating membrane was transported to the sensing membrane (with a resistance Rs), either through an individual Sb2Se3 NW or NW bundle with negligible heat loss. Heat conduction via the Sb2Se3 NWs or NW bundles increases the temperature of the sensing membrane (ΔTs = Ts − T0). The temperature difference between the heating and sensing membranes was controlled within 12 degree to prevent heat radiation. Using a simple heat transfer modelNW, and the suspending beams, Gb, by using the following equations: h, and Qh and Qb are the joule heat generated in the heating membrane and metallic wire of the suspending beams, respectively. Under thermal steady state condition, the thermal conductivities through a single Sb2Se3 NW or a NW bundle can be retrieved using the above equations by measuring the temperature coefficients of resistance from both membranes, ΔTh, ΔTs, and joule heat power P.The application of a direct current voltage to the Cr/Au coil on the heating membrane (with a resistance Ro: resistance at temperature To) with a value of 5.7 × 10−8 K−1 for the sensing membrane was determined by fitting the slope of the curve (s) on the sensing membrane were recorded when the heating membrane was joule-heated by applying an electrical current within the range of 4–12 μA (h) as a function of input joule heat was determined  = 0.037 W/m·K, respectively. The measured thermal conductivity, kNW, is composed of contributions from both the electronic part (ke) and the phonon part (kph). It is written as: kNW = ke + kph. The electronic contribution to the thermal conductivity of NWs can be calculated using the Wiedemann-Franz law: ke = σLwT, where Lw is the Lorenz number. We estimated the ke ~ 1.9 × 10−9 W/m·K for σ = 4.37 × 10−4 S/m using a Lorenz number Lw = 1.45 × 10−8 V2/K2 ph. Therefore, the measured NW thermal conductivity is governed by the lattice thermal conductivity.he curve . With th 4–12 μA . We meas 4–12 μA , respecttermined . By read2Se3 NWs that we measured is 0.037 ± 0.002 W/m·K. The measured thermal conductivity is more than an order of magnitude lower than those of bulk materials in previous measurements (~0.36–1.9 W/m·K)et al.2Se3 nanocrystals , which was about 2.5-fold lower than that of bulk. Our results suggested that the thermal conductivity of the NWs was only raised by nearly two orders of magnitude even when the electrical conductivity of the NWs was increased by 8 orders of magnitude.Since the electrical resistance of the heating and sensing membranes was determined by a four-point probe technique, the maximum uncertainty of the electrical resistance values is less than 0.225%. The uncertainty in the thermal conductivity arises from measurement errors in voltage, current, temperature, and dimensions of the membranes. The width and length of the membranes are measured with a scanning electron microscope. The metal film thickness of membranes is measured with a Dektak surface profiler (with a resolution of 0.1 nm). The errors produced by the dimension measurements are estimated to be less than 3%. The total error in the thermal conductivity value is estimated to be within 5.5%. Therefore, the thermal conductivity of the Sb2Se3 NWs prepared at different temperatures are similar in surface roughness and crystallinity as measured from HRTEM images  and less heat transferred compared to NW A and NW B. However, amount of heat transferred to the sensing membrane through the bundle (NW C) was still lower than that of a single 120 nm-diameter NW. In the NW bundle, the weak van der Waals adhesion energy between NWs results in a low possibility for phonon transmission through the van der Waal interfaces46484950et al.Interestingly, the NW bundle (NW C) gives the lowest temperature rise on the sensing membrane among the three samples, even though it has the largest total cross section. Although thermal conductivity measurements made on an individual 120 nm-diameter NW . When values of the measured σ (4.37 × 10−4 S/m) and S (661 μV/K) of the NWs are incorporated into above expression, we get a ZT value of approximately 1.55 × 10−6 at 300 K. Since ke is rather small in compared to kph, therefore, the electrical conductivity can be increased without significantly affecting the total thermal conductivity (ke + kph). Also the reduced dimensionality did not significantly affect the Seebeck coefficient.The Seebeck coefficient S of the NW B was obtained using the 2ω technique with above microdevices. For this method, an AC current at frequency ω was applied, which produces joule heating in the membrane with a frequency of 2ω. The heat generated causes a temperature oscillation that passes through to the NW. Using the four-probe technique, the temperature difference ΔT(2ω) across the NW can be measured, along with the voltage drop ΔV(2ω). Thus, a positive Seebeck coefficient of the NW B was obtained from S = ΔV(2ω)/ΔT(2ω) ≈ 661 μV/K . This va382Se3 NWs and NW bundles were investigated using a microfabricatde suspended device at room temperature. We demonstrated microdevices and techniques that can measure the thermal properties of highly resistive single Sb2Se3 NWs and NW bundles. The relationship of temperature difference on each heating/sensing suspension membranes with joule heating was accurately determined. A single Sb2Se3 NW with a diameter of 680 nm was found to have a thermal conductivity of 0.037 ± 0.002 W/m·K. The thermal conductivity of the NWs is more than an order of magnitude lower than that of bulk materials. The thermal conductivity of a NW decreases as its diameter is reduced. The NWs in the NW bundles interact through van der Waals interactions, which reduce thermal transport. A positive Seebeck coefficient of ≈ 661 μV/K was obtained, which is comparable to that of highly conductive NWs, but is about a factor of two lower than bulk due to the increased scattering of higher surface defects and charge trap states in NWs. These excellent thermal properties indicate that Sb2Se3 NWs are promising candidates for thermoelectrical energy conversion nanomaterials.In Summary, thermoelectric properties of individual solvothermally prepared single-crystalline SbHow to cite this article: Ko, T.-Y. et al. Thermal and Thermoelectric Transport in Highly Resistive Single Sb2Se3 Nanowires and Nanowire Bundles. Sci. Rep. 6, 35086; doi: 10.1038/srep35086 (2016).


At a low pulse voltage (1.6–2.3 V), a conductance switching delay of a few seconds was observed in some SL areas, where the switch to the high conductance state (HCS) is accompanied with an SL expansion under the strong electric field of the SPM probe. At a high pulse voltage (2.5–3.0 V), the HCS current was unstable and decayed in a few seconds; this is ascribed to the degradation of the HCS crystal phase under excessive heating. The reversible conductance change under a pulse voltage of opposite polarity emphasised the role of the electric field in the phase-transition mechanism.Chalcogenide superlattice (SL) phase-change memory materials are leading candidates for non-volatile, energy-efficient electric memory where the electric conductance switching is caused by the atom repositioning in the constituent layers. Here, we study the time evolution of the electric conductance in [(GeTe) It was found that superlattice films consisting of periodic nanometre-thick layers of GeTe and Sb2Te4 in ref. 2Te3 in ref. 2Te3)(3 nm)]15 SLs using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) has shown SL grains with mixed Ge/Sb atomic layers prepared by molecular beam epitaxial growth on the Sb-terminated surfaces of Si(111)18There have been significant efforts in the fabrication of novel non-volatile memory cells91013142/(Sb2Te3)1]4 SLs by employing scanning probe microscopy (SPM) and scanning probe lithography (SPL). SPM is a powerful technique for investigating the conductance states of solid films because of its high spatial resolution. SPL has emerged as a type of lithography for academic research, and it combines the ability to create nanoscale features and to handle soft matter such as proteins and polymers2/(Sb2Te3)1]4 SL, as it has the simplest SL unit cell structure consisting of (GeTe)2/Sb2Te3 units. By holding a sharp metal probe at a predefined distance from the SL surface  SLs in ref. IN = 2.1 V, and 200 pJ at VIN = 2.8 V, as shown in 2/(Sb2Te3)5]8 SLs grown on a tungsten film2Te3 layers, different degrees of Ge/Sb mixing and changes to the layer thicknessUnder pulse excitation, the SL conductance switching occurred above a threshold voltage of VThe reversible switching was confirmed in separate measurements where an ERASE voltage pulse of negative polarity and a second READ period were added at each stop point, resulting in a WRITE-ERASE pattern. A WRITE voltage of +2.3 V and a time duration of 500 ms were selected as optimal parameters for the SL conductance switching with an injection energy of 15–100 pJ. An ERASE voltage of −2.6 V and a duration of 500 ms were used to create sufficiently strong electric field reversal. The typical behaviour of the current response is shown in Different switching behaviour was observed at WRITE (ERASE) pulse amplitudes of +2.6 V (−2.8 V). The HCS current appeared and decayed within ~2 s after both WRITE and ERASE voltage pulses in The fact that the HCS current appeared at both positive and negative voltage polarity indicates that two similar HCSs were created under the strong electric field from the SPM tip normal to the SL film surface.2/(Sb2Te3)1]4 SLs. Geometrical reordering of atoms in the SL layers results in a change in the SL volume. The fact that the SL suddenly expands by ~3.4% upon conductance state switching, as shown in 1310The results obtained suggest that different factors contribute to the variability observed in the conductance state switching of the [(GeTe)2/Sb2Te1]4 SLs. VIN ~2.8 V. A large fraction of the SL responses (group C2) showed a delay in the conductance switching, a behaviour that is observed in ferroelectric materials where a persistent polarisation produced by an external electric field controls the charge transport properties. The delay time varied between ~3 s at VIN = 2.1 V and 5 × 10−3 s at 2.8 V. The presence of the delay in the current switching provides evidence that the WRITE current is unlikely to be the primary trigger for the conductance change in group C2. Alternatively, a strong electric field from the probe tip may induce electric polarisation of the SL. The electric field applied was estimated using a capacitor model including the vacuum gap and the SL film. A minimum vacuum gap of 0.44 nm was estimated from a sum of the inter-atomic distance in the top Sb2Te3 layer , referred to as group C1, showed a LCS-to-HCS transition with a delay shorter than 6 ms (the time resolution in our setup). A long (0.1–3 s) delay in the conductance state transition was observed in 40% of the responses, referred to as group C2. The remaining part (~8%), referred to as group C3, showed no conductance switching below steady HCS current after excitation at 2.1 and 2.3 V is shown in IN > 3.0 V, a regrowth of SL grains has been reported in ref. unsteady HCS current was caused by excessive heating because of the hot electrons injected from the SPM tip at VIN ~2.8 V and the injected electric energy above 200 pJ. Alternatively, at VIN ~2.3 V, the steady HCS current in 4The excitation voltage and the excitation current are two competing factors in conductance state switching. A IN >3.0 V in ref. The obtained data suggest the following mechanism for conductance switching. When the pulse voltage is above the switching threshold, high-energy electrons were injected into the SL from the SPM probe through the vacuum gap. The injected energetic electrons cause (i) excitation of atomic bonds and (ii) generation of phonons, which in turn activate atom re-bonding and displacement under the strong electric field beneath the SPM probe. An optimal crystal structure was achieved either in the short period of time (for group C1) when a strong electric field of ~0.1 MV/cm and a high electron current were applied or after the time delay required to complete the structural transition at a low electric field (for group C2). An increase in the transverse electric conduction by ~300-fold and an expansion of the SL film are the manifestations of significant structural changes during the LCS-to-HCS transition. We assume that the transition occurs on a short time scale (<1 ms) for group C1, although we are unable to resolve it with our time resolution. At a high voltage and high current injection, the phonon generation process prevails, leading to excessive heating of the SL grain and causing the unsteady HCS current shown in 2/(Sb2Te3)1]4 SLs grains by employing SPM and SPL techniques. Three groups of SL responses were recognised by their behaviour under voltage pulse excitation. The HCS current delay observed in some areas of the SL film provides evidence that the strong electric field applied causes long-lasting changes in the SL structure. The data emphasise the role of the electric field in local conductance switching of the SL films.In conclusion, HCS current values and a different switching dynamic were observed for individual [(GeTe)2/(Sb2Te3)1]4 films were grown on Si(100) substrates by a two-step process that involved using an Ar-ion sputtering system with a base pressure of 1.8 × 10−4 Pa. Reverse sputtering of a 3′ Si substrate was performed at a power of 100 W with an Ar flow rate of 10 sccm. The growth process included the following: (1) the deposition of a 3-nm-thick Sb2Te3 seed layer at room temperature and subsequent annealing at 230 °C, and (2) the deposition of 4 periods of GeTe(0.8 nm)/Sb2Te3(1 nm) by repeated sputtering of GeTe and Sb2Te3 alloy targets at a pressure of 0.5 Pa, with an Ar flow rate of 10 sccm, a power of 20 W and a substrate temperature of 230 °CSL [(GeTe)−7 Pa) at room temperature was used222522252930IN) of 1.0–2.9 V and a duration (Δt) of 0.05–3.2 s were used; the voltage was applied to the sample. Time-dependent changes in the SPM probe height, sample voltage and SPM current were recorded with a time interval of 6 ms.For SPM measurements, an Omicron SPM operating in an ultra-high vacuum chamber 2/Sb2Te3 Superlattices. Sci. Rep.6, 33223; doi: 10.1038/srep33223 (2016).


A consistent diurnal cycle of sCI concentration is estimated for the UK sites with increasing levels during daylight hours, peaking just after midday. The seasonal pattern of sCI shows higher levels in spring with peaks around May due to the higher levels of O3. The ozone weekend effect resulted in higher sCI in UK urban areas during weekend. The sCI data were modeled using the information provided by the Air Quality Improvement Research Program (AQIRP) and found that the modeled production was five‐ to six‐fold higher than our estimated data, and therefore the estimated sCI concentrations in this study are thought to be lower estimates only. Compared with nighttime, 1.3‐ to 1.8‐fold higher sCI exists under daytime conditions. Using the levels of sCI estimated at Marylebone Road, globally the oxidation rates of NO2 + sCI (22.4 Gg/yr) and SO2 + sCI (37.6 Gg/yr) in urban areas can increase their effect in the troposphere and potentially further alter the oxidizing capacity of the troposphere. Further investigations of modeled sCI show that CH3CHOO (64%) and CH2OO (13%) are dominant among all contributing sCI at the UK sites.Levels of the stabilized Criegee Intermediate (sCI), produced via the ozonolysis of unsaturated volatile organic compounds (VOCs), were estimated at two London urban sites (Marylebone Road and Eltham) and one rural site (Harwell) in the UK over the period of 1998–2012. The steady‐state approximation was applied to data obtained from the NETCEN  database, and the levels of annual average sCI were estimated to be in the range of 30–3000 molecules cm Criegee Intermediates (CI) can be formed from the ozonolysis of alkenes with a range of energies and those termed “stabilized” Criegee intermediates (sCI) have less energy than is required to decompose rapidly and may have lifetimes of sufficient length that they can react with coreactants in the atmosphere 2, and hydrocarbons. The sCI can react with various atmospheric compounds, “Criegee scavengers,” including H2O, water dimer ((H2O)2), NO2, SO2, alcohols, aldehydes, and carboxylic acids, thus these sCI can play a significant role in controlling the budget of many tropospheric species , NO3, O3, SO2, H2SO4, organic acids, carbonyl compounds, secondary organic aerosol) where CI can undergo rapid unimolecular decomposition in the main with a branching fraction of α, and the remaining is the stabilized CI with a branching fraction of (1–α). The decomposition of the CI gives a number of products including OH, CO−1 2, SO2, NO2, and carboxylic acids are of appreciable concentrations to act as the sinks of sCI and indeed H2O for most sCI and (H2O)2 for CH2OO are believed to be the dominant sinks. The rate constants from the reactions of sCI + H2O and sCI + (H2O)2 range from 1.0 × 10−14 to 2.0 × 10−19 cm3 molecule−1 s−1 and 1.6 × 10−11 to 2.6 × 10−14 cm3 molecule−1 s−1, respectively  data archive The recent experimental evidence confirms the existence of sCI Assuming the steady‐state approximation of sCI, the rate of total production of sCI and the rate of loss of sCI are equal, i.e.,Considering all the productions and losses of sCI, it is possible to construct a steady‐state equation to calculate the concentration of sCI2O and (H2O)2, the loss processes via NO2, SO2, and RCOOH are negligible, so the loss process of sCI can be represented by 2k + 3k[H2O] + 4k[(H2O)2]. Therefore, [sCI] now becomesComparing the unimolecular thermal loss and the losses by Hcis‐2‐butene, trans‐2‐butene, trans‐2‐pentene) and O3 hourly data were obtained via the NETCEN data base. The instrument used to monitor hydrocarbons was a Chrompack CP9000 VOCAIR system, a GC fitted with an automated thermos‐desorption/cryogenic trapping system. The standards supplied by the National Physical Laboratory (NPL) contained 26 component mixtures in nitrogen. The detailed description of the network, the VOCAIR system and the data handling, and analysis can be found in Dollard and co‐workers The available nine unsaturated hydrocarbons . Using the fraction of sCI (1‐α) of 0.5 2OO), CI‐2 (RCHOO), and CI‐3 (R2COO). Taking account of the unimolecular loss rate (2k) of 11.6 s−1 for CI‐1 −1 for CI‐2 −1 for CI‐3 2O (k3) of 2.4 × 10−16 cm3 molecules−1 s−1 for CI‐1 −19 cm3 molecules−1 s−1 for syn‐CI‐2 −15 cm3 molecules−1 s−1 for anti‐CI‐2 −15 cm3 molecules−1 s−1 for CI‐3 2OO with (H2O)2 (4k) of 5.4 × 10−12 cm3 molecules−1 s−1 for CI‐1 −14 cm3 molecules−1 s−1 for syn‐CI‐2 −11 cm3 molecules−1 s−1 for anti‐CI‐2 −13 cm3 molecules−1 s−1 for CI‐3 2O], [(H2O)2], and temperature data  were obtained from UK Meteorological office chemistry transport model, STOCHEM . From the total sCI production and sCI loss, the steady‐state sCI concentrations were calculated for all three UK sites. Using the lower and upper limits of the rate coefficient from different literature for the unimolecular loss , the loss due to the reaction with H2O , and the loss due to the reaction with (H2O)2 , a range of sCI concentrations were calculated.The rate coefficients used in the production of sCI from the reactions of alkenes with OData for the generation of the sCI levels were obtained from three different sites, dictated by the availability of data. The selected areas have a range of environments . Sites are different, being impacted heavily by vehicles  through to being heavily impacted by VOCs from vegetation . All sites are at ground level and have continuous hourly data of all the species required for the calculation. The site description is summarized in Table –3) is found at the polluted urban site, Marylebone Road, whereas lower concentration is found at the rural site, Harwell (90 ± 100 molecules cm–3). The maximum sCI levels returned are 58,710 molecules cm–3 for Marylebone Road, 6350 molecules cm–3 for London Eltham, and 5080 molecules cm–3 for Harwell and correspond with the highest alkene levels  and ozone levels . Considering the range of unimolecular loss and the loss due to the reactions with H2O and (H2O)2, the concentrations of sCI are found in the range of 30–730 molecules cm–3 for Harwell, 100–2980 molecules cm–3 for Marylebone Road, and 40–940 molecules cm–3 for London Eltham. Thorough analysis of the measurement sites over the years with the most complete data sets were studied to gain a good representation of sCI production as possible. Only nine alkene measurement data were used in the estimation of sCI in this study, but, many other alkenes  can exist in the urban and rural atmosphere that would lead to a greater sCI output. The availability of the alkenes data was sporadic, with occasions when data existed for only 1 or none are excluded from the calculation. So, the estimation values of sCI are considered to be lower estimates, and it is therefore vital to the understanding of the sCI‐oxidizing ability that in‐depth analysis of the more complex alkenes is pursued. A wider number of alkenes measured would lead to a better overall picture of the impact of sCI in the atmosphere, but the current analysis provides some important parameters that can inform future studies.Table 3. The alkene levels show a diurnal cycle peaking during rush hours (9:00 am and 7:00 pm) for London Eltham and Marylebone Road sites when the emission of anthropogenic VOCs is at its greatest  shows a consistent diurnal cycle with increasing levels during daylight hours, peaking just after midday before decreasing into the night  , thus the role of NOx for altering O3 concentrations between weekend and weekdays is minimal.The sCI concentrations for all sites vary slightly throughout the week, as shown in Fig. The monthly average variation of sCI concentrations over the time series of 1998–2012 for the UK sites is shown in Fig. 3 can be found in MCM website (http://mcm.leeds.ac.uk/MCM/search.htt). The sCI concentrations calculated using modeled alkene data have a similar diurnal cycle with peaks during the afternoon  than the estimated data. This is to be expected given the number of alkenes used in the model versus the available alkenes used in the estimation of sCI. Nonetheless, the magnitude of the difference could be of great significance, with increased levels of sCI in the atmosphere will increase their overall effect on the oxidizing cycle and have consequences for other atmospheric species. It is clear that this analysis is purely an example; it is impossible to say with certainty whether the ratios calculated using the AQIRP data are appropriate for the urban areas of UK or that the ratio method will be representative throughout the year, but the analysis can give a sensible way to estimate the unmeasured portion of the alkenes. However, adding in these approximate levels of known alkenes that are present in urban environments but not measured raises the estimated sCI significantly. Furthermore, emissions of naturally occurring alkenes, e.g., monoterpenes, sesquiterpenes, which are not accounted for, could have a significant additional impact on sCI levels, particularly in spring and summer months. It is clear, that if we want to fully understand the role of sCI in the troposphere, that more comprehensive measurements of alkenes are required.A model calculation was performed with the study of the tailpipe exhausts from catalytic convertor equipped motor vehicles which was carried out in 1995 as part of the AQIRP detailing percentage composition of nonmethane hydrocarbons (NMHCs) from these emissions see Fig. a, similasee Fig. b and simsee Fig. c when co3CHOO  and CH2OO  contribute approximately 64% and 13%, respectively, to the total sCI concentration. In addition to these two species, C2H5CHOO  and (CH3)2COO  account for approximately 8% and 4% of the total sCI concentrations. These results are different to previous percentage contribution results of sCI in eastern United States 2OO (a significant contribution from isoprene) and ∼20% APINBOO (sCI from only α‐pinene) to the total sCI concentration. The reaction of (H2O)2 with CH2OO has the fastest rate of the reaction and has become the most important to the sCI loss rate 2OO in the estimation of the total sCI and found that CH3CHOO, C2H5CHOO, and (CH3)2COO can contribute 73, 9, and 5%, respectively to the total sCI concentration.The contribution of individual modeled sCI species to the total modeled sCI concentrations has been investigated see Fig.  and foun2 and SO2. NETCEN database gives the annual average NO2, SO2, O3 levels of 50.0, 3.1, and 7.6 ppbv, respectively, for Marylebone Road in 2012. If the global urban areas is of 3.5 million km26 molecules cm−3, the average day–night boundary layer height is of 550 m  considering the surface level sCI, NO2, SO2, O3 concentrations of Marylebone Road, which are constant throughout the urban boundary layer, and the rate coefficients of the reactions of sCI + NO2 and sCI + SO2 are of ksCI+NO2 ∼2.0 × 10−12 cm3 molecules−1 s−1 and ksCI+SO2 ∼4.0 × 10−11 cm3 molecules−1 s−1, respectively, a back‐of‐the‐envelope calculation gives the upper limit oxidation rates of NO2 + sCI (22.4 Gg/yr) and SO2 + sCI (37.6 Gg/yr) to produce NO3 and SO3 in urban areas, which are notable comparing with the most conventional oxidation rates of NO2+O3 (50.8 Tg/yr) and SO2 + OH (0.64 Tg/yr) in urban areas. The further reactions of NO3 and SO3 can produce alkyl nitrates and H2SO4, respectively, which can form organic aerosol in the urban areas. The high levels of aerosols in the urban areas can negatively affect human health and local air quality. They can have a net cooling effect on climate by changing the earth's energy budget by scattering and absorbing the radiation or acting as cloud condensation nuclei. The consequences of sCI concentrations in urban areas are important, but it is an area of much needed study and more research is required to gain a more comprehensive understanding of the potential impacts of sCI.The impact of sCI in the atmosphere has been investigated with considering two significant reactions of sCI with NO3 in May result in an overall increase in the sCI production. A clear diurnal cycle of sCI peaking just after midday was found for all sites. Comparatively lower weekday sCI concentrations are seen than weekend in UK urban sites. The concentration of anthropogenic VOCs saw a dramatic decrease over the years due to EU legislation and was accompanied by an overall decrease in sCI production over the years for urban sites. Increased alkenes data set in model calculation resulted in a significant increase in sCI, so our estimated sCI concentrations are low estimates; and overall sCI concentrations in these areas have the potential to be higher than initially thought. The two sCI, CH3CHOO (64%) and CH2OO (13%), are the dominant in the UK urban atmosphere among all contributing sCI.The steady‐state method has been applied to estimate the concentrations of sCI at two urban sites  and one rural site (Harwell) in the UK over the period 1998–2012 from trace gas data provided by the NETCEN database. All sites have higher sCI levels in spring months and lower in winter months, with peaks around May. Higher levels of ODisclaimer: Supplementary materials have been peer‐reviewed but not copyedited.Supplementary MaterialClick here for additional data file.


Coturnix japonica) embryos to selective agonists of estrogen receptor alpha (ERα). In contrast, the male copulatory behavior is only weakly affected by developmental exposure to an ERα agonist. To further elucidate the respective roles of ERα and ERβ in estrogen-induced disruption of sexual differentiation, we exposed Japanese quail embryos in ovo to the selective ERα agonist 16α-lactone-estradiol (16αLE2), the selective ERβ agonist WAY-200070, or both substances in combination. The ERα agonist feminized the testes in male embryos and reduced cloacal gland size in adult males. Furthermore, anomalous retention and malformations of the Müllerian ducts/oviducts were seen in embryos and juveniles of both sexes. The ERβ agonist did not induce any of these effects and did not influence the action of the ERα agonist. Male copulatory behavior was not affected by embryonic exposure to either the ERα- or the ERβ-selective agonist but was slightly suppressed by treatment with the two compounds combined. Our results suggest that the reproductive organs become sexually differentiated consequent to activation of ERα by endogenous estrogens; excessive activation of ERα, but not ERβ, during embryonic development may disrupt this process. Our results also suggest that the demasculinizing effect of estrogens on male copulatory behavior is only partly mediated by ERα and ERβ, and may rather involve other estrogen-responsive pathways.Excess estrogen exposure of avian embryos perturbs reproductive organ development in both sexes and demasculinizes the reproductive behaviors of adult males. We have previously shown that these characteristic effects on the reproductive organs also can be induced by exposure of Japanese quail ( Coturnix japonica), the female embryo produces substantially higher levels of estradiol and estrone than the male embryo from at least embryonic day 5 (E5), which is at the onset of morphological sex differentiation of the gonads [in ovo exposure to xenoestrogens such as 1-(2-chlorophenyl)-1-(4-chlorophenyl)-2,2,2-trichloroethane  [The sexual differentiation in birds is largely dependent on the plasma levels of gonadal estrogens; estrogens produced by the female embryo induce a female phenotype whereas the male phenotype develops at low estrogen concentrations. In Japanese quail  , 15, eth,p’-DDT) , 17, bis,p’-DDT)  and diet,p’-DDT) , 18.in ovo [In female quail, the brain is permanently organized by endogenous gonadal estrogens acting during a critical window of embryonic development in such a way that females are unable to display male-typical copulatory behavior in adulthood even when supplied with testosterone to adequate plasma levels , 19, 20.in ovo , 22. Thein ovo , 11.Endogenous estrogens and many of the known xenoestrogens act by activating either or both subtypes of nuclear estrogen receptors (ERs), α and β. The nuclear ERs function as transcription factors that upon ligand-binding form dimers that can bind to estrogen response elements of specific target genes and regulate their expression. The subtypes ERα and ERβ show differential expression patterns and may induce similar, specific or even opposing effects on gene expression and have partly different physiological roles , 24. SomThe temporal and spatial expression patterns of ERα and ERβ may provide insight into their respective physiological functions. In quail, ERα mRNA is expressed in left and right gonad of both sexes from at least E5, i.e. at the onset of morphological sex differentiation, and in Müllerian ducts from at least E7 . In the 2; 0.3 μg/egg) from E3 does not affect the male copulatory behavior at doses that markedly affect the reproductive organ differentiation [2, we concluded that activation of ERα alone affects the reproductive organs but is not sufficient to affect the copulatory behavior [We have previously shown that embryonic exposure of quail to the selective ERα agonists propyl-pyrazole-triol  and 16α-lactone-estradiol  does not affect reproductive organ development, suggesting that ERβ is not involved in this process and does not mediate the effects of xenoestrogens on the reproductive organs in birds .2 (ERα-selective), WAY-200070 , or both ER ligands in combination. Our results suggest that excessive activation of ERα, but not ERβ, during embryonic development disrupts sex differentiation of the reproductive organs whereas the organization of male copulatory behavior during embryo development is only weakly affected by combined activation of these receptors.The aim of the present work was to elucidate the roles of ERα and ERβ in estrogen-induced disruption of sexual differentiation of reproductive organs and male copulatory behavior in Japanese quail. Embryos were exposed to 16αLE2 were generously provided by Wyeth Research  and Bayer Schering Pharma AG , respectively.The ERβ selective agonist WAY  , also re2 is a steroidal compound and is a close derivative of estradiol. The transactivational activity of 16αLE2 on human ERα (hERα) in vitro is 30% that of estradiol [2 shows a 250-fold selectivity for hERα over hERβ in reporter cells [16αLEstradiol  and 16αLer cells , 38. WAYer cells . Its biner cells .384 in hERα is replaced by Met336 in hERβ, and Met421 in hERα is replaced by Ile373 in hERβ [2 and WAY for ERα and ERβ, respectively, is achieved through the hERα Met421/hERβ Ile373 residue substitution [2 and WAY are ER-subtype specific also in quail.There are two amino acid differences between hERα and hERβ in the ligand binding pocket; Leu in hERβ . The sel2. Embryos were dissected on E16, i.e. 1–2 days before anticipated hatching. The 300 μg-dose was not completely dissolved in the vehicle and was given as a suspension. In the second experiment, eggs were injected on E3 with vehicle, 100 μg WAY, 0.3 μg 16αLE2 or a combination of 100 μg WAY and 0.3 μg 16αLE2. Juvenile birds were examined by necropsy and adult male birds were tested regarding copulatory behavior performance before being necropsied. 16αLE2 was given at a dose (0.3 μg/egg) which in previous studies caused severe reproductive organ abnormalities but no effect on male copulatory behavior [The experiments and animal care were carried out according to the recommendations by the Swedish Board of Agriculture and were approved by the Uppsala Ethical Committee for Research on Animals . The animals were euthanized quickly by decapitation, and efforts were made to minimize suffering. Animals showing signs of illness were immediately euthanized. Japanese quail eggs were purchased from Olstorp  and were placed in an egg incubator at 37°C and 60% humidity and were automatically turned every third hour. The day that the eggs were placed in the incubator was defined as embryonic day 0 (E0). Following three days of incubation, i.e. on E3, the eggs were candled and unfertilized eggs or eggs containing dead embryos were removed. Test substances were injected into the yolk of fertile eggs through a small hole made at the blunt end of the egg. The holes were then sealed with melted paraffin wax and the eggs were returned to the incubator. The injected substance is continuously taken up when the yolk is utilized. The vehicle was a peanut oil:lecithin mixture  which was emulsified in propylene glycol  by ultra-sonication. The injection volume was 20 μl. Egg weights were approximately 15 g. In the first experiment, eggs were injected on E3 with vehicle, 100 or 300 μg of the ERβ agonist WAY, or 0.3 μg of the ERα agonist 16αLEbehavior .in ovo to WAY or 16αLE2, as described in the previous section, and were dissected on E16. At this developmental stage the gonads are sexually dimorphic and the sexes are easily distinguishable in control animals. In treated embryos, sexing may be more difficult and the treated embryos were therefore also genetically sexed using a PCR-based method [in situ using a digital slide caliper and the testis size (length × width) was calculated. To confirm ovotestis formation, the left testis was collected and prepared for histology. In females, abnormalities of the left Müllerian duct were noted and the length of the retained part of the right Müllerian duct was measured.In the first experiment, embryos were exposed d method . In eachThe left testis from the embryos was processed for histological examination as described previously . Brieflyin ovo to WAY, 16αLE2 or to a combination of these compounds. The birds were examined when they were juvenile (3 weeks old) or when they had reached sexual maturity (8–9 weeks old). On E14 the eggs were placed in hatching boxes, the automatic turning of the eggs was turned off and the relative humidity in the incubator was increased to 70%. The chicks hatched on days 17 to 20 of incubation, but only those hatching on days 17 to 18 were included in the experiment. Males and females were first raised together but were separated at the age of three weeks. The males were housed in individual cages from the age of four weeks. Feed (turkey starter) and water were provided ad libitum and the daily photoperiods were cycles of 16 h light and 8 h dark, simulating long days. All birds were weighed when they were 1 week, 2 weeks, and 3 weeks old. Males were also weighed after the behavioral tests were completed (~9 weeks old).In the second experiment, quail embryos were exposed Juvenile female and male quail were dissected at the age of 3 weeks and their reproductive organs were examined. Eleven control females and 8–9 randomly chosen males from each group were spared for behavioral tests at sexual maturity. Frequencies of males with partially developed oviduct on either side were recorded. Gonado-somatic index (GSI = 100 × testis weight / body weight) and testis weight ratio (left testis weight / right testis weight) were calculated for males. In females, oviductal abnormalities such as partial development of the right oviduct (longer than 10 mm) and malformation of the left oviduct were recorded.th week after hatching. The male was paired with a sexually mature control female in a small test cage  and the behavior was observed and recorded on video for 2 minutes. Each male was paired with a new female every test occasion. The individual behaviors in the copulatory sequence that were scored were neck grab, mount attempt, mount, and cloacal contact movements, as described previously [Male sexual behaviors were recorded as described previously . Brieflyeviously . The anaFive days after the last behavioral test (when birds were ~9 weeks old), the males were dissected and their reproductive organs were examined as described above for the juvenile males. In addition, the cloacal gland area (length × width) was recorded. Blood was collected immediately following decapitation and was centrifuged at 1000 × g. The plasma was collected and frozen at -20°C for subsequent testosterone analysis. The plasma testosterone concentration was determined using a solid phase radioimmunoassay kit  which has previously been validated for analysis of testosterone in quail plasma .Frequencies of embryo mortality, hatching, and reproductive organ abnormalities were analyzed using one-sided Fisher's exact test. Differences in body weight, gonad size, testis weight ratio and cloacal gland area were tested using one-way analysis of variance (ANOVA). Following the ANOVA, all treated groups were compared with the control using Dunnett’s multiple comparison test. Due to non-Gaussian distributions or differences in variance between groups, testis cortex area, length of right Müllerian duct and behaviors were analyzed using Kruskal-Wallis ANOVA, followed by Dunn's multiple comparison test. The treatment groups were compared with the control. Correlation between plasma testosterone concentration and copulatory behavior was analyzed with linear regression. Differences were considered significant when p-values were below 0.05. The statistical analyses were computed using GraphPad Prism .2, suggesting lack of general toxicity at the doses tested.Mortality and beak-to-rump length by E16 and number of dissected embryos of each sex are shown in 2  was significantly increased in the groups treated with 16αLEd 16αLE2 . The vasd 16αLE2 . Typical2 or to the combination of 16αLE2 and WAY displayed grossly malformed oviductal structures on one or both sides  and in three out of nine males in the combination group (not significant). The observed deformities included irregular shape, granulated surface and discoloration. In the 16αLE2 group, one adult had two small epididymides and another lacked epididymis on both sides. In the combination group one adult male displayed a misshapen left epididymis. The organs showing abnormal appearance were not further examined. The gonado-somatic index (testis weight / body weight) was not affected by treatment in neither juvenile nor adult males  and one completely black testis found in a male treated with the combination of 16αLElt males . The tes control . The clo and WAY .2 that only mounted at two of the five test occasions. The fraction of the five trials in which cloacal contact movements were displayed at least once was significantly reduced by the combination of WAY and 16αLE2 . The concentration  of the control females was 1.3 ± 0.6, of the control males 8 ± 4, of the WAY-treated males 10 ± 5, of the 16αLE2 and the ERβ-selective agonist WAY. Reproductive organ development was affected by the ERα agonist, but not by the ERβ agonist. The male copulatory behavior was not affected by either of the ER agonists when administered alone, but was slightly suppressed by a combination of the two compounds.In the present study we explored the roles of ERα and ERβ in estrogen-induced disruption of avian sex differentiation by exposing Japanese quail embryos to the ERα-selective agonist 16αLEIn birds, gonadal estrogens act during critical periods of development to promote female sexual differentiation of reproductive organs and behavior and therefore embryonic exposure to estrogenic compounds may disrupt sex differentiation of the reproductive organs and demasculinize reproductive behaviors as manifested later in life . The qua2 caused abnormal development of the embryonic Müllerian ducts and in juveniles malformations of the oviducts were found on both right and left side . In males, the ERα agonist caused anomalous development of oviductal structures, decreased size of the cloacal gland and feminized testes. In male embryos, the left testis was ovary-like in shape (flattened), size (large) and histological appearance (thick cortex with oocyte-like germ cells). The right testis was reduced in size which partly resembles the strong regression of the right ovary seen in control females. Testicular deformities were found in adult males exposed to the ERα agonist and the left / right testis weight ratio was high compared with the control. Such effects on the reproductive organs have previously been described in for instance chicken, quail and gulls following embryonic exposure to excess estrogen or estrogenic compounds [2 and another selective ERα-agonist, PPT [2 and WAY caused a response comparable to that of 16αLE2 alone. In accordance, the ERβ agonist DPN did not affect reproductive organ development in chicken embryos [In females, the ERα agonist 16αLEompounds –18, 42. ist, PPT , 33–35.  embryos .Our previous studies have shown that male copulatory behavior in quail is efficiently suppressed by exposure to non-selective ER agonists when administered from E3, whereas ERα-selective agonists do not affect this behavior at doses that markedly affect the reproductive organ differentiation , 33, 34.2 (0.3 μg/egg) nor the ERβ agonist WAY (100 μg/egg) significantly suppressed the behavior when tested alone. When administered together these substances significantly reduced the number of tests where cloacal contact movements were shown  in nuclei that are implicated in male reproductive behaviors in adulthood . In the re shown . It has 2 and WAY are known to cross the blood-brain barrier in rodents and exert effects in the brain [The modest effect on the copulatory behavior is likely not a consequence of limited uptake of the substances to the brain as both16αLEhe brain –47. PossThe results from our present and previous studies suggest that ERα, but not ERβ, is involved in female differentiation of the ovary and Müllerian duct/oviduct in birds and that exogenous compounds that activate ERα may disturb this process and cause abnormal development of the reproductive organs in both sexes. The modest effect on male copulatory behavior by the ERα and ERβ agonists, separately and in combination, suggests that the organizational effects of estrogens on this behavior during development is mainly mediated by other estrogen-responsive pathways than those activated by ERα and ERβ.S1 Fig384 (*) and Met421 (#) which correspond to hERβ Met336 and Ile373, respectively. The sequence alignment shows that the amino acid residues in both these positions are conserved between hERα and quail ERα (qERα) whereas hERβ Met336 (*) is replaced by a leucine residue in qERβ. The selectivity of 16αLE2 for ERα and of WAY for ERβ is however conferred by the hERα Met421 /hERβ Ile373 (#) residue substitution which is conserved between the two species. The protein sequences were retrieved from NCBI and aligned using BioEdit Sequence Alignment Editor. The accession numbers are: P03372.2 for hERα, AAN63674.1 for qERα, NP_001428.1 for hERβ and O93511.2 for qERβ.The ruler shows the amino acid residue positions in the human ERα (hERα). The highlights indicate the position of the two amino acids residues that differ between hERα and hERα in the ligand binding pocket; these are hERα Leu(DOCX)Click here for additional data file.S1 Data(XLSX)Click here for additional data file.S1 File(DOCX)Click here for additional data file.