We study the temperature dependence of the underlying mechanisms related to the signal strength and imaging depth in photoacoustic imaging. The presented theoretical and experimental results indicate that imaging depth can be improved by lowering the temperature of the intermediate medium that the laser passes through to reach the imaging target. We discuss the temperature dependency of optical and acoustic properties of the intermediate medium and their changes due to cooling. We demonstrate that the SNR improvement of the photoacoustic signal is mainly due to the reduction of Grüneisen parameter of the intermediate medium which leads to a lower level of background noise. These findings may open new possibilities toward the application of biomedical laser refrigeration. PAI combines the technological advances of both optical and acoustic imaging, i.e., the high intrinsic contrast of optical imaging and the spatial resolution of ultrasound imaging4. Every material, including bodily substances, has a specific optical absorption coefficient unique to endogenous chromospheres in cells3. The substance to be imaged is illuminated by a nanosecond pulsed laser of a specific wavelength which correlates to the highest absorption coefficient of the subject8. The amplitude of a photoacoustic signal, Photoacoustic Imaging (PAI) is a promising functional and molecular imaging technique for a wide range of biomedical applications19. There are also studies showing the temperature dependency of the scattering coefficient of the tissue24. There is not sufficient evidence about how the absorption coefficient of tissue alters with temperature, particularly in the range of temperature investigated in our study24.The temperature dependency of the Grüneisen parameter has previously been explored in several studies28. Following thermal nonlinearity theorem, Simandoux et al., investigated the thermal-based nonlinear PA generation to discriminate between different types of absorbers29. Zharov developed an ultrasharp nonlinear photothermal (PT) and PA spectroscopy system, which enables an enhancement in specificity and sensitivity of PT/PA spectral analysis30. Based on the same principle, Tian et al. developed a dual-pulse nonlinear photoacoustic technique31. Wang et al., developed a Grüneisen relaxation photoacoustic microscopy (GR-PAM) system in which two laser pulses with a specified time delay were employed, one for thermal tagging, the other one for signal generation9. They showed that when the second laser pulse excites the tagged absorbers within the thermal relaxation time, a stronger photoacoustic signal than the initial one is obtained. In another configuration, they used a continuous wave (CW) laser for thermal tagging and observed that the performance of their method is diminished. Although this scheme enhances the photoacoustic signal generated from the imaging target, the same mechanism can compromise the penetration depth due to the undesired thermal excitation of intermediate medium.Recently several research groups have developed temperature-dependent PA systems based on the dependence of Grüneisen parameter to temperature, in biological tissues9. Here, we propose to decrease the temperature of the intermediate medium while keeping the temperature of the imaging target constant. In biological tissues due to multiple scattering, the fluence is significantly affected and the photons are greatly scattered especially after they reach the diffusion limit . Such scattered photons generate background PA signals which reduce the signal-to-noise ratio (SNR) of the PA signal generated from the imaging target. Cooling the intermediate medium reduces such background signals, and increases the SNR of the PA signal of the imaging target.There have been studies that have utilized the temperature dependence of Grüneisen parameter to improve the PA image by increasing the temperature of the imaging target without increasing the temperature of the intermediate mediumIn this study, we report the theoretical considerations and experimental observations for the SNR enhancement in photoacoustic imaging by cooling the intermediate medium. The proposed cooling mechanism opens up the possibility of using the laser refrigeration technology in the future. This approach creates an efficient channel through the biological tissue layers, which in turn, can significantly improve the penetration depth in photoacoustic imaging.p0, is generated according to Eq. The process of signal acquisition in photoacoustic imaging is comprised of three steps: laser light illumination, conversion of deposited optical energy to initial pressure via thermoelastic expansion, and a broad-band PA wave propagation through the medium. In PA imaging, the initial pressure, 32 and its approximation, i.e., the diffusion equation34. Different tissues are characterized by their optical properties, namely, absorption coefficient, scattering coefficient, anisotropy, and refractive index. As light passes through the tissue, it is attenuated due to the absorption and scattering. Hence, any change in these parameters can alter the fluence; leading to a change in the PA signal amplitude.Biological tissues are highly scattering in visible and near infrared (NIR) range. Light propagation has a sophisticated behavior in tissues, and can be described by the radiative transfer equationβ is the thermal expansion coefficient, vs is the speed of sound in the medium and Cp is the heat capacity at a constant pressure. There is also an acoustic attenuation coefficient, Grüneisen parameter is defined as:35. The background noise level is determined by calculating the velocity potential at different temperatures. We consider a tissue with a uniform speed of sound, vs, inside which there is an imaging target. There is an ultrasound transducer placed on the surface of the tissue. PA waves generated from the target at the distance r from the transducer reach the transducer at time t = r/vs. The PA waves from a hemispherical shell with a radius r and a thickness dr = vsdt reach the transducer at times between t − dt/2 to t + dt/2. The noise, PAnoise, is calculated from the PA contribution of the shell that is not in the imaging region, as described by equation . Laufer et al. reported a 0.5% °C−1 reduced scattering coefficient increase in dermis and 0.14% °C−1 decrease in sub-dermis with changing the temperature from 25 to 40 °C24. They related different temperature dependency schemes to compositions of skin layers; dermis is largely composed of protein, and sub-dermis fat. Cletus et al. found a negative scattering coefficient change with temperature rise for intralipid21, and Jaywant et al. reported a positive scattering coefficient change for bovine muscle23. They both are consistent with Laufer’s findings. Jaywant also found that there is only a slight change in the scattering coefficient of bovine brain tissue with the temperature rise23 which can be due to the opposite effects of fat and protein scattering coefficient change with the temperature rise. Troy et al. reported a positive scattering coefficient change for prostate tissue22. Yeo et al. studied the porcine and found an increase in the scattering coefficient with the temperature rise19. Ouyang et al. studied the rat skin tissue and found a decrease in the scattering coefficient with temperature rise9. Jaywant23et al. observed a positive scattering coefficient change with temperature rise in the liver tissue, while Larina et al17. reported no change in the optical attenuation of liver tissue. Although, most of the studies reported changes in the scattering coefficient with the temperature change, are in agreement with each other, there are some discrepancies in the literature. The reason for the discrepancies could be due to different condition of the tissue samples or the wavelength of light they have used.There is only a few studies on temperature-dependence of the optical properties. Changes in the reduced scattering coefficient in temperatures above 55 °C are mostly related to substantial structural changes in the tissue, e.g., proteins coagulation24, for such tissue, we expect a decrease in the scattering coefficient as the temperature drops. With respect to absorption coefficient, there was no study showing a significant change in absorption coefficient of the tissue with temperature change24. There is evidence that the absorption coefficient of water is changed with temperature42. However, water is not the main absorber in the tissue and the absorption coefficient of tissue cannot be deduced solely based on the temperature dependency of absorption coefficient of water.We use chicken breast tissue in our experiments as an intermediate medium, which contains protein. According to the literature19. The change of the Grüneisen parameter with the temperature is due to the temperature dependency of the thermal expansion coefficient. Larina et al., showed 1.5% °C−1 increase in the Grüneisen parameter in a biological tissue17.There is a large body of literature, claimed that Grüneisen parameter is the major contributor in the PA signal change with the temperatureFigure µa = 0.3 cm−1 and µs′ = 10 cm−1)43. A rod with 1 mm thickness was placed inside the tissue as the imaging target. Absorption coefficient of the target is set to 30 cm−1 to be much greater than intermediate medium. We used a homogenous light with a beam diameter of 1 cm for illumination. A transducer with 4 mm2 area is located on top of the sample and at the center.We performed the simulations at different distances from the illumination source (tissue depths): 5 to 30 mm, at 5 mm increments, and at seven temperatures: 5 °C to 35 °C, at 5 °C increments. Background medium was a slab homogenous tissue, with the optical properties similar to that of chicken breast tissue , we measured the PA signal amplitude generated from the imaging target (PAtrue) embedded in an intermediate medium as well as the PA signal amplitude from the same location when the imaging target is removed, i.e., background signal (PAnoise). The PAsignal is then computed as PAtrue − PAnoise. The SNR of the PA signal is calculated by  does not change with the temperature change of the intermediate medium. This was expected because the temperature (and the Grüneisen parameter) of the imaging target is constant. Moreover, the scattering coefficient of the intermediate medium in this experiment is assumed to be constant at different temperatures, which results in the same fluence at the target. Therefore, the PAsignal becomes constant according to Eq. PAnoise) when the temperature droped, and that resulted in a SNR increase.In the first set of simulations, the Grüneisen parameter of the intermediate medium is decreased with the temperature at a rate of 1.5% °Cant Fig. . The Grü−1 24 while Grüneisen parameter remains constant. However these results demonstrate SNR improvement of PA signal with lowering the temperature, the improvement is less than that obtained in the first set of simulations. We observed that PAsignal increases at lower temperatures due to the greater fluence (as a results of lower light scattering) reaching the target. On the other hand, the background noise increases with lowering the temperature. Both effects become more significant at greater depths.Figure In the third set of simulations, the effect of temperature on Grüneisen parameter and scattering coefficient are taken into account Fig. . These sWe first explored the temperature dependence of photoacoustic imaging in a water phantom. The experimental setup in this case is the same as shown in Fig. 47 for image reconstruction.Figure To be able to provide a quantitative comparison between the obtained images, we report, in Fig. The paramount feature in Fig. 17. This means that the background noise is also decreased more rapidly with lowering the temperature in water compared to that in the tissue, hence a more rapid change of SNR in the water experiment is seen.According to the simulation results Fig. , the cha42. When the intermediate medium is only water  and photoacoustic tomography (PAT)55.The proposed approach provides a benchmark demonstration on improving the signal strength due to the two-step excitation of the absorber medium on one hand, and a better imaging depth due to the cooling of the intermediate medium, on the other hand. Laser cooling has not yet been extended to biological molecules because of their complex structures. However, this complexity makes biomolecules potentially good candidates for this purpose, due to possessing permanent electric dipole moments that lead to long-range, tunable, anisotropic dipole–dipole interactionsSome of the future studies include, developing PA spectroscopy to find the optimum wavelength at which the proposed method is most efficient; implementing laser refrigeration setup and creating a low-temperature channel rather than bringing down the temperature of the whole intermediate media; exploring the most optimum ultrasound frequency in the detection unit; and exploring laser refrigeration in different configurations of PAI, i.e., PAM and PAT.We demonstrated, through several sets of simulation and experiment, that the SNR of the photoacoustic signal generated from a black wire as an imaging target at different depths, is improved by lowering the temperature of the intermediate medium (from 35 °C to 5 °C) between the PA sensor and the target. Initially water was used as the intermediate medium, then chicken breast tissue. Simulations showed that the improvement is mainly due to the reduction of Grüneisen parameter of the medium which leads to a lower level of background noise. They also showed a decrease in the scattering coefficient of the intermediate medium which further improved the SNR of the PA signal. Since there was no evidence about how the absorption coefficient of tissue changes with temperature, particularly in the range of temperatures investigated in this study, the temperature dependence of the PA signal strength due to changes in absorption coefficient was not investigated.Compared to other depth improvement methods in PA imaging, the method presented here does not require a complicated setup and it is still noninvasive. These findings may open new possibilities toward the application of biomedical laser refrigeration.


Selective Serotonin re-uptake inhibitors (SSRIs) are a class of psychotropic drugs used to treat depression in both adolescents and pregnant or breast-feeding mothers as well as in the general population. Recent research on rodents points to long-lasting behavioural effects of pre- and perinatal exposure to SSRIs which last into adulthood. In fish however, studies on effects of developmental exposure to SSRIs appears to be non-existent. In order to study effects of developmental SSRI exposure in fish, three-spine sticklebacks were exposed to 1.5 µg/l of the SSRI citalopram in the ambient water for 30 days, starting two days post-fertilisation. After approximately 100 days of remediation in clean water the fish were put through an extensive battery of behavioural tests. Feeding behaviour was tested as the number of bites against a piece of food and found to be increased in the exposed fish. Aggression levels were measured as the number of bites against a mirror image during 10 min and was also found to be significantly increased in the exposed fish. Novel tank behaviour and locomotor activity was tested in an aquarium that had a horizontal line drawn half-way between the bottom and the surface. Neither the latency to the first transition to the upper half, nor the number of transitions or the total time spent in the upper half was affected by treatment. Locomotor activity was significantly reduced in the exposed fish. The light/dark preference was tested in an aquarium where the bottom and walls were black on one side and white on the other. The number of transitions to the white side was significantly reduced in the exposed fish but there was no effect on the latency to the first transition or the total time spent in the white half. The results in the current study indicate that developmental SSRI exposure causes long-lasting behavioural effects in fish and contribute to the existing knowledge about SSRIs as environmental pollutants. Selective serotonin re-uptake inhibitors (SSRIs) are a group of anti-depressants which act on the evolutionarily ancient and highly conserved serotonergic system. They exert their effect by inhibiting the re-uptake of serotonin (5-HT) into the pre-synaptic nerve terminal, thus causing an elevated level of serotonin in the synaptic cleft. SSRIs are typically lipophilic  to a dose of 1.5 µg/l citalopram in the surrounding water. Pilot studies in zebrafish have indicated that the lower limit for concentrations that will produce behavioural alterations in on-going exposure of adult fish is between 0.1 and 1 µg/l. The concentration used in the current study was chosen as a compromise that was likely to obtain useful results without being too far from environmental concentrations. Thus, the chosen concentration of 1.5 µg/l is a concentration which is approximately one order of magnitude higher than is commonly found in polluted waters but which has been found in extreme cases. At the same time it was deemed high enough, compared to the effective range in adult exposures, to be likely to produce an effect. We hypothesised that exposure to the SSRI citalopram during development would cause long-lasting anxiogenic effects similar to what has been observed in rodents. We employ a battery of behavioural tests designed to measure anxiety, aggression, feeding behaviour and locomotor behaviour, further described below. Those tests were choosen because they are well known and characterised tests that measure behaviours known to be affected by serotonin and by exposure to SSRIs.In the light of the increasing use of fish as model organisms for research on pharmaceuticals in both environmental and clinical contexts, it is important to fill the knowledge gap regarding the effects of developmental exposure to SSRI in fish. In this study, we take the first steps towards acquiring this missing knowledge by quantifying a range of behavioural measures after developmental exposure of three-spine sticklebacks  was purchased from Sigma-Aldrich and a stock solution was prepared by dissolving 10 mg of citalopram in 1 l of milliQ water. No vehicle was used. The stock solution was stored under dark conditions in a refrigerator. Since the water volume of the exposure aquaria was 6 l, an initial dose of 0.9 ml stock solution was administered to each aquarium, yielding a concentration of 1.5 µg/l. When half the water was subsequently changed, 0.45 ml of stock solution was added to compensate for the amount lost.Artemia nauplii. Since Artemia can survive for an extended time in brackish water, it was possible to give the fry a constant access to nauplii. From approximately 50 dpf they were fed daily to satiation with frozen bloodworms or Cyklops. At 77–84 dpf the sticklebacks were labelled using VIE  tags. Labelling was performed under MS222 anaesthesia. Two strands of elastomer were used, one on each side of the dorsal spines. The elastomer tags denoted sibling group and treatment. One fish died for unknown reasons shortly after tagging. After tagging, both control and exposed fish were pooled in one big aquarium (117 × 107 × 63 cm) where they were allowed to develop in clean water for 7–8 weeks before they were transported to the stickleback facility at Södertörn university for further development and behavioural testing. After the move to Södertörn university the fish were kept in holding tanks with a flow-through system. The water was fresh, aerated tap water and was kept at a temperature of 12–15 °C and the day:night cycle was changed to 8:16. All handling of experimental animals was permitted by the Ethical Committee on Animal experiments in northern Stockholm (dnr N 22/15) and complies with current Swedish law. All behavioural testing took place between 8 a.m. and 1 p.m. and feeding took place between 3 p.m. and 5 p.m. During testing, all staff left the room and the behaviour was recorded on video. The videos were analysed manually and blindly, as the colour tags could only be seen using a specialised lamp. The order of the behavioural tests was scototaxis—novel tank—feeding—aggression. For the novel tank scototaxis and feeding tests, fish were selected randomly from the main holding tank. The fish that had been used for one test was kept separated from the main bulk of fish in order not to test the same fish twice. Once a behavioural test was over, the fish that had been used were transferred back to the main holding tank. Two weeks were allowed to pass between the scototaxis and novel tank test and between the novel tank and feeding tests. For the aggression test, the fish that had been used for the feeding test were simply re-used as they were already in the test aquaria.Sticklebacks were caught at the Askö laboratory in the Trosa archipelago on the Swedish east coast  and were transported to the stickleback facility at Stockholm university within 24 h where the fish were kept in 0.5% artificial brackish water and a water temperature of approximately 20 °C. Details of the timing of different events during the study are summarised in Table Fish were kept solitarily in smaller aquaria (28.5 × 19.8 × 19.6 cm) for one week prior to the feeding test. During this time they continued to be fed daily as before and the aquaria were cleaned every second day. The fish were fed a piece of frozen bloodworms in their home tank. Behaviour was recorded on video for 10 min and was quantified manually at a later point. The number of attacks on food was used as a measure of food intake. In the cases where a fish would spit the food out only to immediately eat it again, only one attack was counted since the secondary ingestion was deemed as food handling. This method has been employed for three-spine sticklebacks previously and is described in more detail in Kellner et al. .Danio rerio) (Ariyomo and Watt Betta splendens)  (Archard and Braithwaite Onchorynchus mykiss)  were omitted from analysis. Using a mirror image to measure aggression is a common method for quantification of aggressive behaviour and has been used previously for zebrafish  test setup was achieved if the fish were carefully netted directly from their holding tank and then transferred to the NT test aquarium, rather than going through a pre-treatment beaker as described by Egan et al. . Two tesLepomis gibbosus) , filled to a depth of approximately 16 cm. The aquaria were divided into a black and a white half and had a transparent, removable compartment in the middle. Fish were taken from their home tank and allowed to acclimatise for 5 min in the central, transparent compartment. The transparent section was then removed, allowing the fish to swim freely. Behaviour was recorded for 10 min. During analysis, notes were taken of the number of crossings from the dark to the white side of the aquarium and frequency and duration of such detours. Scototaxis has previously been used for several fish species including zebrafish  in R (version 3.2.2). For the NT test (including locomotor activity), feeding and scototaxis data, sibling group and date of recording were used as random factors. For the aggression data only sibling group was used as random factor. All analyses dealing with count data  were analysed assuming a Poisson distribution. All models were checked with q–q plots and residual plots and were found not to be over-dispersed. For time data and weight, a Gaussian distribution was assumed. Testing for effects of sibling groups was done similarly but with sibling group used as fixed factor and treatment as random factor. To extract the means and confidence intervals used in the plots in this study from the model , the effects package (version 2.3-0) in R was used. This package extracts the main effects as well as lower and upper 95% confidence limits. Thus, for all analyses using transformations, the plotted means and confidence intervals are back-transformed model estimates. The Anova function from the car package (version 2.1-1) in R was used to extract N = 15) for the treated fish and 35.7 (N = 15) for the control fish. There was a statistically significant effect of treatment on the number of attacks on food  while the corresponding number for control fish was 29.4 (N = 13), resulting in a statistically significant effect . Two fish died as a result of accidental injury during the NT testing phase.χ2 = 1.40, p = 0.23, data not shown) on the latency to the first cross to the upper half. The mean number of crosses to the upper half of the aquarium was 10.8 for the control fish and 10.3 for the exposed fish. There was no statistically significant effect of treatment on this variable . The mean time spent in the upper half of the aquarium was 133.2 s for the control fish and 133.6 s for the exposed contingent. There was no significant effect of treatment  on the total time spent in the upper part of the aquarium. Latency to the first cross  and the number of crosses of the horizontal midline  were significantly affected by sibling group but there was no effect of sibling group on the total time spent in the upper half . The mean locomotor activity count for the exposed fish was 123.7 while the mean activity count for the control fish was 132.5. Locomotor activity was significantly affected by treatment .The number of fish included in the analysis was 44 for the exposed contingent and 48 for the control (see Table N = 62) for the exposed fish and 11.8 (N = 80) for the control fish  for the treated fish and 252 s (N = 80) seconds for the control fish. The difference was not statistically significant  for the exposed fish and 189 (N = 80) for the control fish. There was no statistically significant effect of treatment on the total time spent on the white side of the aquarium  but not on the latency to enter the white side .Light/dark preference was tested by placing the fish in an aquarium with a white and a black half and the results are shown in Fig. N = 60) and in the control group 1.39 g (N = 63). There was no statistically significant treatment*sex interaction  or any significant effect of treatment  or sex  on weight. Weight was significantly affected by sibling group .Mean final weight in the exposed group was 1.37 g   (Kohlert et al. Locomotor activity was reduced in the exposed fish compared to controls in the current study. Reduced locomotor activity as a result of developmental SSRI treatment has previously been reported for rodents by Ansorge  while MaThere was no significant difference between the exposed fish and the control fish in the novel tank test and only in one variable out of three in the scototaxis test. The effects of developmental citalopram exposure on anxiety-related behaviours were unexpectedly small in light of the pronounced anxiolytic effects seen during exposure in adult three-spine sticklebacks (Kellner et al. 3 receptor (Smit-Rigter et al. The mechanism behind the observed effects of developmental SSRI exposure is not clear but a commonly reported effect in developmentally exposed adult rats (Maciag et al. Effects of SSRI on both boldness, locomotor activity, aggression and feeding behaviour are believed to have ecological effects in aquatic ecosystems. Monoamines like serotonin regulate behaviour in response to stressors in different ways depending on the type of stressor faced by the fish. Individuals with high extracellular serotonin levels tend to be more risk taking in the interaction with predators but less aggressive towards conspecifics (Bell et al. The current study demonstrates a large variation between sibling groups with regard to feeding, aggression, scototaxis, and the number of detours that the fish did to the upper part of the aquarium as well as the latency to the first detour to the upper half in the NT test. As an example, Fig. In conclusion, the current study indicates behavioural effects of developmental exposure to SSRIs in fish which are largely consistent with the results previously reported from developmental exposure in rodents. Those results include increased aggression, reduced locomotor behaviour and possibly an aversive response to novelty. Feeding behaviour was enhanced in this study which is not in accord with previous studies on rodents. So far, research on behavioural and ecological effects of developmental SSRI exposure in fish has been absent. If compared to studies of on-going SSRI exposure however, the current study indicates that in fish, the behavioural consequences of developmental exposure are largely opposite to what has been observed during on-going exposure which complicates the predictions of ecological impact of SSRI pollution.


Urine production in the kidney is generally thought to be an energy-intensive process requiring large amounts of metabolic activity to power active transport mechanisms. This study uses a thermodynamic analysis to evaluate the minimum work requirements for urine production in the human kidney and provide a new perspective on the energy costs of urine production. In this study, black-box models are used to compare the Gibbs energy inflow and outflow of the overall kidney and physiologically-based subsections in the kidney, to calculate the work of separation for urine production.The results describe the work done during urine production broadly and for specific scenarios. Firstly, it shows glomerular filtration in both kidneys requires work to be done at a rate of 5 mW under typical conditions in the kidney. Thereafter, less than 54 mW is sufficient to concentrate the filtrate into urine, even in the extreme cases considered. We have also related separation work in the kidney with the excretion rates of individual substances, including sodium, potassium, urea and water. Lastly, the thermodynamic calculations indicate that plasma dilution significantly reduces the energy cost of separating urine from blood.A comparison of these thermodynamic results with physiological reference points, elucidates how various factors affect the energy cost of the process. Surprisingly little energy is required to produce human urine, seeing that double the amount of work can theoretically be done with all the energy provided through pressure drop of blood flow through the kidneys, while the metabolic energy consumption of the kidneys could possibly drive almost one hundred times more separation work. Nonetheless, the model’s outputs, which are summarised graphically, show the separation work’s nuances, which can be further analysed in the context of more empirical evidence. Human kidneys consume a large amount of oxygen representing substantial metabolic energy: approximately 21.3 W/kg, which is equal to that of the heart and more than the brain . In addiThis paper is aimed at providing an alternative perspective to urine production, as opposed to studying specific mechanisms and metabolic energy consumption. It focuses on the work done in the broader urine production processes and outlines the relationship between excretion rates and minimum work requirements, which may be characteristic of the system.A number of studies have investigated the work required of the human kidneys. Newburgh  built onThe model used in this study is based only on the specifications of the inlet and outlet streams and we consider only the work required to achieve the separation of the urine from the blood. At such a high-level, the particular mechanism of separation is not important, but it is possible to determine the lowest possible work cost of separating urine from blood. We will thus use an abstract representation of the renal system. Nonetheless, we will mention some of the current uncertainties in the field, such that they may be taken into account when evaluating the results.The kidney is a separation system designed to maintain homeostasis: blood circulating through the body is kept at near constant solute concentrations, through the removal of waste and excess substances by the kidney . On averIn their review of the nephrology literature, Sands and Layton  show thaThe methodology described below is similar to practises commonly used in the study of industrial chemical processes. Our approach uses limited renal mass flow and concentration data from the literature to determine the mass flow rates and concentrations of all the streams of the model, through mass balance calculations. Once the mass flow has been calculated, one can then determine the minimum work required for separating urine from blood, using thermodynamic principles to quantify the Gibbs energy (G) associated with the streams.We have modelled the kidneys on two levels of abstraction: one where the two kidneys are represented by a single black box; the other where the urine production process is split into two parts, each represented by a different black box see Fig.  below. TThe model represents kidneys operating at steady state, which entails assuming there is no depletion or accumulation of mass or energy. By making this assumption we can use daily volumetric flow data for the calculations.The first level of the model, depicted as the solid borderline in Fig. The second level of the model, outlined with the dashed borderlines in Fig. In summary, the first level of the model contains no information regarding the internal processes in the kidney, while only the most basic process steps are included in the second level of the model. In addition, the valve symbols in Fig. There are sufficient published data describing flow rates and concentrations in the human renal system to perform the theoretical calculations. This data, together with the assumptions made, will be discussed next. The reader may consult the The main components of blood plasma and their concentrations are listed in Table The solute excretion rates used in the model are shown in Table The issue of electro-neutrality deserves some attention. The authors decided to use mean solute concentrations for urine, rather than an arbitrary combination of other concentrations that would be closer to electrolytic neutrality. Adjusting the rates of sodium and chloride excretion in the model (using the link in at the end of the paper) to achieve electro-neutrality could affect the results by as little as 1 mW. There are, however, other factors to consider. On the one hand, the concentrations that give electro-neutrality cannot be determined precisely without a significant increase in the complexity of the model, to take into account the charge of proteins. On the other hand, when adjusting the excretion rates relative to the established baseline, it is easy to ensure that for every mole of monovalent positive ions transferred, one mole of monovalent negative ions must also be transferred, such that the electric charge of the solution does not increase. Any changes made to the amount of sodium or potassium ions excreted when doing the sensitivity analysis is therefore accompanied by equal changes in the amount of negative ions excreted.The concentration of water was also considered in the model. The molar concentration of pure water at a temperature of 37 °C is 55.14 mol/l  and thisThe pressure in the kidney varies throughout the day: the kidney controls the pressure drop through vasoconstriction at various points and thereby manipulates flow rates . For theAs blood flows through the kidney, its hydrostatic pressure drops, which can either be used to overcome friction as the fluid flows along a tube or for separation work, such as filtration. It is unclear what fraction of the energy associated with pressure drop is used to drive flow and what is used to concentrate urine. Pressure measurements have been reported at various points in the kidney in the literature and when looking at the structure of the kidney, some of these measured pressure drops must be mainly due to friction losses as there is thought to be no separation occurring over these sections of the kidney. For this reason we assumed in the model that the energy associated with these pressure losses cannot perform work for filtration or for the recovery of filtrate. These losses are marked by the valve symbol in Fig. The last input component required by the model is the filtration fraction of the glomerulus. The available data show that approximately 900 l/day of plasma is processed to produce 180 l/day of filtrate , 34. ThiThe model used in this study, with calculation steps described below, can be downloaded using the link given in at the end of the paper. Also, for the reader’s convenience, all of the assumptions made while using the equations below are listed in the amount of water excreted to be the variable parameter, resulting in the concentration of solutes in the urine being variable. Once these variables have been allocated values, the flow rates of the various substances in the blood leaving the kidney can be determined as the difference between the arterial blood flow rate and the flow rate of urine.The above data are sufficient to compute the mass flows of the black-box models, as shown here. For the overall black-box model, we set a number of parameters: the excretion rates of solutes as per the median values in Table A complete model of the flow rates in the two sub-processes, represented by two black-box models inside of the kidney, requires two more quantities. Firstly, we assumed the concentrations of the filtrate and efferent blood plasma are equal to that of the arterial blood, with the exception of the efferent plasma containing all the proteins and the filtrate containing none. Secondly, the mass flow rates are set by the filtration fraction of 20%, as discussed above. This completes the mass flow data for all the streams considered in this study, from which we derived the concentrations, volumes and mole fractions, as required for the thermodynamic calculations.Once the mass flow in the system can be described in terms of molecular flow rates and mole fractions, we can calculate the Gibbs energy (G). By definition, G includes all energy available for useful work and can include work done by pressure gradients, concentration gradients and chemical reactions . At thisG can be calculated as :1\documeG = Gibbs energy flow (W);μj = chemical potential  of component j (J/mol); andN = molar flow rate of component j (mol/s).Where:In addition, the extent by which pressure affects chemical potential can be quantified as follows :\documenBy assuming the liquids are incompressible, the equation becomes:P1 = reference pressure, chosen as ambient pressure (Pa);P2 = system pressure (Pa);T1 = reference temperature, chosen as the body’s temperature, 310 K; andj (m3/mol).Where:Furthermore, the effect of mixing in a mixture can be expressed as :\documenxj = molar fraction of component j in the total mixture (dimensionless);μj0 = chemical potential of a pure component (J/mol);γj = activity coefficient of component j (dimensionless); andR = the ideal gas constant (8.3144621 J/mol.K).Where:Vj).These calculations were simplified by taking activity coefficients as unity, based on a review of available data , 24, 37.Putting the above equations together, we obtain:P2-P1 = Pg, we obtain Eq. Next we set a reference point at which pure chemical compounds have a standard chemical potential of zero, at a temperature of 310 K and a pressure of 1 bar. Assuming that there is no reaction inside the fluids, the system temperature is 310 K and all pressure measurements are in gauge pressure, such that The first term on the right hand side of Eq. Gtotal) is equal to the combined work associated with changes in pressure and changes in the extent of separation:Here, the total change in Gibbs energy , the work associated with pressure change (Wpres) and the work associated with separation (Wsep). A sample calculation is available through the link in at the end of the paper.By using the calculated mass flow parameters and the available pressure data in these equations, we calculated the G associated with each stream. This served as a basis for analysing the total change in G  is sufficient to produce a range of urine volumes up to 18 l/day, there may be additional energy costs for the real system. For example, it is known that there are pressure drops due to friction in the afferent and efferent blood streams, before and after the glomeruli, as discussed in the Even though the results indicate that the potential work that can be done from the total change in G  in the overall system and its dependency on the rate at which different substances are excreted. The results are depicted as contours of Wsep in a two-dimensional plain. These contours in the graphs are the boundaries of the attainable region for different amounts of energy applied. For example, Wsep for the overall system is less than 45 mW within the “+45 mW” contour. We have not included Wpres in the contours such that we can have clarity that the quantity of work required to separate the substances is independent of which mechanism carries out the work.The overall black-box model is dependent on more factors than those considered in Figs. Figure In the above graphs, the water excretion rate associated with minimum work shifts dramatically: from 8.4 l/day in Fig. The optimum point is lowest on Fig. Beyond the results depicted graphically, there are additional numerical results that are of interest. The calculations depicted in Fig. At one point on the +45 mW contour, the concentration of sodium is 2.8 times higher in the urine than in the blood. What is more, elsewhere on the same +45 mW contour the sodium concentration in the urine goes down to one twentieth of the concentration in the blood. For urea this ratio of concentrations ranges from 432 to 0.03 times that in blood. This means that the boundary lines for the thermodynamically attainable region in the graphs are not always determined by the concentration gradient between the blood and the urine. At some point other substances’ concentration differences between the blood and filtrate would limit urine production.The model offers an opportunity to build on the work of Newburgh , who firFigures The results depicted in Fig. The model correlates well with other studies. According to Fig. These theoretical calculation results from simplified models of the kidney do correspond to empirically measured results. Indeed, the urine volume that minimises work requirements is approximately equal to the water intake requirement for a person. A review of empirical studies shows that a water intake of 2.5 l/day is needed by the average inactive man to maintain constant levels of hydration over several days . This stActual energy consumption in the kidneys is two orders of magnitude larger than the theoretical amount of energy needed to do the work associated with separating a urine stream from blood. The kidneys use about 7% of the oxygen consumed by the body , and thepres) to drive separation (Wsep).The results obtained from the first overall model of the kidneys, Fig. By splitting the model into two compartments, as in Fig. Filtration takes place in the first compartment, which represent the glomeruli. Figure Now that the concentration gradient created by glomerular filtration has been quantified as a 5 mW work investment, we know the maximum quantity of work that can be done with the concentration gradient is 5 mW. The concentration gradient between the efferent blood and the filtrate could thus possibly be used to drive the recovery of filtrate later in the system, as discussed by Letts et al. .The work requirements for the second compartment, the tubular system, reaches a minimum point at 2.39 l/day similar to the results of the overall system, as shown in Fig. The sensitivity analysis of the solutes excreted further showed the incongruity between the 6 W of metabolic energy consumption of the kidneys and the amount of separation work done. Separation work done in the overall process only amounts to 45 mW when extreme amounts of a particular solute are excreted. In addition, the results show that when sodium, potassium and urea excretion are at the maximum of their reference ranges, while urine volume is low at 1 l/day, the separation work requirement is only 54 mW. Other researchers have similarly concluded that the overall kidneys’ separation work is between 19 and 44 mW . With thBy correlating extreme excretion rates, which have been measured empirically in medical cases, with specific model results, it is possible to further assess the maximum work capacity of the kidneys. There have been reports of urine production volumes of up to 20 l/day in humans  and the Other extreme cases are the known minimum water excretion rate and the maximum urine concentration. The lower daily urine volume limit is known as the “obligatory urine” production rate. It is roughly 0.5 l/day for the average adult . Such a This amount of work is also sufficient to reach the maximum urine concentration achievable by humans, which is 1.2 mol/l  as mentiNote that it is possible to produce a smaller daily volume of urine, with the same rate of doing work, by reducing the amount of potassium chloride or urea excreted. Decreasing urea excretion to the bottom of the reference range will drop the minimum urine flow rate to 0.2 l/day, while implementing the same change on potassium chloride excretion brings the lower limit down to 0.4 l/day. This is clear from the 45 mW contours in Figs. Lastly, we will mention one more medical condition that can be used to quantify the exact limitation of the kidneys to do separation work. It can be seen in Figs. Newburgh  first suAs a thought experiment that illustrates this point, one can imagine a perfectly hydrated person, with 3 litres of blood plasma, who rapidly drinks 1 litre of water. If one assumes that the total volume of water is absorbed into the blood, without entering other compartments of the body, the model shows that diluting the blood to this extent will increase the water excretion rate possible with 45 mW of separation work by 1.9 l/day. Hence, the system response to increased water ingestion is to excrete the extra volume ingested automatically, unless a smaller amount of energy is applied to do separation work. Figure There are many more factors to consider in a system as complex as human physiology. From a physiological perspective, for example, not all the additional water may be taken up in the blood. From a thermodynamic perspective, the extent of this feedback would be dependent on a person’s initial plasma volume. More measurements from empirical experiments are required for a conclusive analysis on the relation between water ingestion and renal workload. Nonetheless, as our first approximation has demonstrated, such thermodynamic feedback might be utilised by the body.There are factors that will make the energy required in the kidney more than the effective amount of separation work done, but the possibility also exists that the work requirement in the tubular system may be less than estimated. Factors that could increase the energy requirement include inefficiencies such as the diffusion of ions back into the filtrate , as wellγ) in the G, as shown in Equation The model’s results show that in the glomeruli 13 mW of power is spent via pressure drop, while creation of a protein-free filtrate makes 5 mW available in the form of a concentration gradient. Thus, 38% of the pressure drop in the glomeruli is invested in the creation of a protein-free filtrate. However, the non-ideal behaviour of proteins, particularly serum albumin, has not been taken into account and it may significantly affect the efficiency of energy storage. Consider, for example, Cameron et al.  has studThis study has produced results in agreement with previous theoretical and empirical studies, and then proceeded further to analyse a vast array of scenarios for urine concentrations. In particular, large amounts of data have been generated describing the variation of separation work requirements caused by changes in sodium, potassium and urea excretion. Although these numerical results may provide more insights when combined with additional empirical evidence, this paper builds arguments for two main conclusions: the first relates to the amount of energy required, while the second relates to the sensitivities of the system.We conclude that the separation work requirement (around 20 to 54 mW) is two orders of magnitude smaller than the metabolic energy consumed by the kidneys (6 W), and less than half of the total work available from pressure (128 mW). The black-box models used in this study do not indicate how this energy might be utilised or whether the human kidneys could utilise this energy. However, it is theoretically possible for a system to exist that applies only the pressure from afferent blood to produce the same urine and purified blood that the kidneys produce.An investigation into the model’s sensitivity to other parameters showed unexpected thermodynamic characteristics of the system. The results indicated that more dilute plasma fed into the kidney results in lower energy costs for larger urine volumes. This effect is such that for each additional 100 ml of water by which the plasma is diluted, the feasible urine volume increases by 190 ml, if the quantity of work associated with separation is kept constant at 45 mW. More data from empirical experiments are required to determine whether this renal control mechanism is actually used by human kidneys.Further progress may be made with the line of investigation used in this study, through more detailed modelling, specifically by relating plasma concentration to urine production or incorporating the dynamic behaviour of plasma proteins. Indeed, we cannot claim to have a complete understanding of the glomerular energy storage mechanism, which entails the creation of a protein concentration gradient, without considering data on the non-ideal behaviour of human serum albumin.


However, very little is known about circular granular ratchets, startling devices able to convert vertical vibrations into rotations of the device. Here, we report results of systematic numerical investigations of the operational characteristics of circular granular ratchets. Several distinct behaviors are identified and explained in terms of the inner flow fields of the ratchet. All dynamical regimes found are robust and should not be difficult to observe in laboratory experiments.Ratchets are simple mechanical devices which combine spatial asymmetry and nonequilibrium to produce counterintuitive transport of particles. The operation and properties of  Such transport is easily seen when particles are subjected to a spatially asymmetric potential  combined with a driving force whose temporal average vanishes . This transport phenomenon is called 12. Linear ratchets were studied at a classical and quantum level, and both from theoretical and experimental points of view13. In contrast, circular ratchets14 have not yet been studied in detail.Ratchets operate in two basic geometrical configurations, linear or circular. Transport phenomena in linear ratchets have been extensively investigated and have a well-documented history stretching over more than a centuryFigure The purpose of the present paper is to report results of systematic numerical simulations of the dynamical behavior of a circular ratchet and to study its behavior on the parameters of driving and the internal states assumed by the granular material due to these parameters. A difficulty faced in laboratory experiments is the need of adjusting materials and physical dimensions when sweeping extended parameter intervals. Such variations are more easily implemented and explored in simulations, which can efficiently reveal general trends and appropriate parameter intervals to perform experiments. This is our major motivation for the present study.r containing viscoelastic, frictionless spherical particles. We consider a two dimensional simulation where the motion of the particles is restricted to the plane defined by the dented circle. Only to compute the moment of inertia of the ratchet device, we consider the geometry indicated by the cutaway view in Fig. α. The symmetry of every individual tooth is controlled by the angle α1. We consider α1 ∈  where α1 = α/2 corresponds to symmetric teeth. The axis of the ratchet is vibrated periodically in the vertical direction with the time dependent displacement asin(ωt), as indicated. Gravity points downwards along the vertical direction. To initialize the system, the particles are placed at the center of the ratchet from where they are released to fall down, under the action of gravity, to form a packing at the bottom of the ratchet. Before the sinusoidal driving is activated, we enforce a suitable equilibration phase during which the particles dissipate their kinetic energy completely. Further details of the setup and the simulation method can be found in Sec. Methods. A movie illustrating the dynamics of the system can be found at www.mss.cbi.fau.de/sup/ratchet_dynamics.mp4.Figure γ ≡ α1/α. In the simulation shown in Fig. α1/α = 0. As seen from the figure, the rotation angle ϕ essentially follows a straight line, whose inclination gives the speed of rotation. By varying the ratio α1/α one may tune the magnitude and the sign of the speed. This is illustrated in Fig. When vibrated, the circular ratchet displays several dynamical regimes. One of the simplest possible ones is a steady rotation, positive or negative as illustrated in Fig. The fact that the circular ratchet starts to rotate when vibrated shows that the particles inside the ratchet exert a net torque on it. To measure this torque we vibrate the ratchet but lock its rotational degree of freedom. This means that only a one-way coupling between the particles and the ratchet device is considered: While the dynamics of the ratchet influences the dynamics of the particles, the particles are not allowed to influence the motion of the ratchet, preventing it from rotating. In other words, the ratchet is mounted in a way that does not allow rotation.In Fig. The constant driving torque measured for the rotationally locked ratchet suggests, that the freely rotating ratchet would accelerate continuously. However, what one observes is that, after a transient, the ratchet rotates with a constant angular speed. This implies the presence of a second torque, counteracting the driving torque.To determine the torque limiting the angular velocity we vibrate it as before, but additionally enforce rotation at a given angular velocity. Using the forces from the DEM simulations we then measure the torque exerted by the particles on the ratchet. Figure I = 0.0012 kgm2 is the moment of inertia of the rotatable dented cylinder. M ≈ 1.09 ⋅ 10−4 Nm is the driving torque resulting from the interaction between the particles and the vibrated dented cylinder  = ϕ0 and Figure Equation entclass1pt{minimaSo far we studied the ratchet for driving parameters which allow for a certain excitation of the particles but operating in a situation where gravity limits their motion to the bottom of the ratchet  may no longer be well-fitted by a straight line, implying that the ratchet rotation speed is not constant. In fact, the rotation speed gets larger and larger, indicating that in the fluidized regime, for high driving frequencies, the decelerating mechanisms break down gradually. The remaining (now dominating) driving torques accelerate the rotation of the ratchet. Measuring the average rotation speed is, of course, meaningless in this regime. For this reason, in Fig. ω ≈ 400 s−1 clearly separates two markedly different dynamical regimes. For g which is vibrated sinusoidally in vertical direction with the amplitude a and frequency ω enters the gas-like fluidized state once the dimensionless shaking acceleration Γ = aω2/ g exceeds a certain system specific value which is typically sharply larger than one15. Under conditions of weightlessness there is no such transition between a fluidized and a sediment-like regime and, thus, no stationary state in which the ratchet rotates at constant angular velocity. Instead, the acceleration of the rotation is always finite and decreases continuously as the vibration frequency is reduced  the sloshing motion becomes unstable. Eventually, the whole material collapses and sticks to the (rough) wall resulting in a constant rotation velocity corresponding to the driving frequency . The simulation method corresponding to the solution of this system of ODEs is often referred to as DEM. This method dates back to works by Rahman and Verlet17, where it has been used to study the physics of simple fluids. Subsequently, motivated by other applications21, the method was later adapted to deal with granular systems. A comprehensive survey of the method can be found in e.g.22. Due to its historic origin, DEM is also often referred to as (force-based) molecular dynamics (MD).The dynamics of the circular ratchet shown in Fig. i and j with radii Ri and Rj located at positions i and j is described by the interaction forceY, ν and Reff denote the Young’s modulus, the Poisson’s ratio and the effective radius Reff = RiRj/(Ri + Rj), respectively. ξ is defined as the mutual compression of two particles in contact. The elastic part Fel of this widely used collision model25 is given by the familiar Hertz contact force26. The dissipative part, Fdis, was first motivated in ref.27 and then rigorously derived in refs29 Note that only the approach in ref.28 leads to an analytic expression for the parameter Adis as a function of the elastic and viscous material parameters. Equation The particles inside the circular ratchet are modeled as frictionless viscoelastic spheres. Further we consider a two dimensional simulation where the motion of the particles is restricted to the plane defined by the dented circle see Fig. . The cond) along the sharp edged saw teeth, resulting in the ratchet profile shown in Fig. dw which enclose the dented cylinder as shown in Fig. 14. For the 2D simulations presented in this work, they are not explicitly relevant. They are only considered to compute the mass and the moment of inertia of the ratchet device, where the material parameters indicated in Table The particle-wall interaction is modeled similar to the particle-particle interaction. When a particle impacts the wall (the dented cylinder), we consider a virtual particle which is located such that the contact point between the virtual and the physical particle is located exactly at the position where the physical particle impacts the wall. The material parameters and the radius of the virtual particle is chosen identical to the physical particles and the interaction force between the physical and the virtual particles is then computed according to the interaction force, Eq. The video mentioned in the text is available at www.mss.cbi.fau.de/sup/ratchet_dynamics.mp4.Supplementary Video File


Studies have demonstrated that social skill interventions and classroom supports are effective for pupils with intellectual disability. Such interventions have been demonstrated to reduce the risk of developing mental disorders, majority of which have their onset during the period of youth. Most young people with intellectual disability in low-resource settings do not have access to interventions that would enable or enhance their participation in society. The aim of this study was to investigate the effect of a social skills training for pupils with intellectual disability attending a special school in Southwest Nigeria.Explore social skills curriculum, teachers were trained to give lessons to the participants 3–4 times a week for 8 weeks in their classrooms. Social skills level of participants was assessed with the Matson evaluation of social skills for individuals with severe retardation (MESSIER) at baseline and immediately after the intervention. Paired t tests, Wilcoxon signed-rank test, Mann–Whitney U test and the Kruskal–Wallis Test were used to assess for pre and post intervention changes in social skills scores and analysis of changes in social skills across socio-demographic variables at p < 0.05.Thirty pupils with mild to moderate intellectual disability participated in the study. Utilising the The mean age of the participants was 15.70 ± 1.89 years. At baseline, 18 of the participants (63.3 %) had moderate social skills impairment, 2 (6.7 %) had none or minimal impairments and 10 (30 %) had severe impairments. At the end of the intervention, there was a 20 % reduction in the number of participants in the severe social skills impairment category and 13.3 % increase in the number of participants in the ‘none or minimal’ social skills category. The mean pre and post- intervention total social skills scores were 126.63 ± 17.91 and 135.97 ± 20.81 respectively with a mean difference of 9.34 .Explore social skills curriculum was administered. Advocacy should be made for the development and incorporation of social skills curricula into routine teaching of pupils with developmental disabilities.The social skills of pupils with intellectual disability who participated in this study improved significantly during the 8 weeks the  Deficits in social skills are critical components of intellectual disability (ID) , 2 and rThe impact of poor social skills could be severe during the period of adolescence , becauseInterventions that focused on improving the social skills of young people with intellectual disability tended to improve their participation and ability to cope in the community , 25, 26.Pupils need social skills to learn effectively in school settings  and manyDespite the fact that a higher proportion of persons with intellectual disability live in low and middle-income countries , 37, verWith the aim of devising culturally appropriate, low intensity, easily to administer interventions to improve outcomes for young persons with intellectual disability, this study investigates the effect of a teacher administered classroom-based curriculum on the social skills of pupils with moderate to severe intellectual disability.The study was carried out at the Home School for Handicapped Children, Ibadan, Southwest, Nigeria. It was established in 1964 by the State government to cater for the learning needs of children and adolescents with intellectual disability. The school is an outreach institution of the Centre for Child and Adolescent Mental Health, with which both authors are affiliated. Mental health professionals from this centre pay regular visits to the school to offer on-site consultation, in-service training and support for staff. The school admits children ages 10–19 years from all the six states in the Southwest geopolitical zone of Nigeria, thereby providing services to an estimated population of 27,581,992 . The StaThere is a 40-bed capacity hostel located within the same compound as the school. The hostel was running in full capacity as at the time of study. There were six carers looking after the pupils in the hostel on a shift arrangement. Two carers run a day or night shift at every point in time and assist the pupils with activities of daily living such as self-care, getting ready for school and feeding. The carers had a maximum of 12 years of education but with no special training for the care of children with disabilities. Each of them had spent an average of 5 years as carers in the boarding section of the facility.Teachers in the school reported that they utilise the same teaching packages as is used by mainstream schools in the district. They adapt this for their use in the school. They also indicated that they did not have teaching aids such as charts, pictures, and graphs. Majority of these teachers had no training in special education. Aside from the three classrooms used for academic sessions and a hostel facility, there is a very large open field the size of half a football pitch where the young people run around and play. There are no other facilities.There were a total of 40 pupils in the hostel during the period of the study. Only 29 out of the 40 pupils were attending classes and they were included in the study. The remaining 11 of the residents remained within the residential facility and could not attend classes because they had “profoundly mentally retarded” with other associated medical disorders such as severe physical disability and poorly controlled epilepsy, hence were excluded from the study. The only pupil in the day service participated in the study bringing the total number of participants to 30. The 30 participants were between the ages of 12–19 years  and 53 % were males. Ninety-seven percent of participants (29) lived in the residential facility located within the school premises. Other characteristics of the participants are shown in Table The MESSIER  is an 85Informants are instructed to rate each item’s occurrence on a Likert-type scale, with ‘never’, ‘rarely’, ‘sometimes’, and ‘often’ The negative subscale score was calculated by reverse coding all items on the negative verbal, negative nonverbal, and negative general subscales. Also the items of the positive verbal, positive nonverbal, and positive general subscales were added together to generate the positive subscale. Total score of the MESSIER was calculated by adding the scores on the positive and negative scales together. The MESSIER has been shown to have good psychometric properties, with an internal consistency of r = 0.94, inter-rater of r = 0.73 and test–retest reliability of r = 0.86 after 2–3 weeks , 41.Explore social skills curriculum .Permission to adapt the Explore curriculum into the social and cultural context. Firstly, an introduction and a preliminary review of the Explore curriculum to identify areas requiring specific attention was conducted. Sections from the curriculum were discussed as a group consisting of two researchers and six teachers; this served as a template for the teachers who suggested changes. Secondly, a meeting to reconcile the different suggestions was held and the teachers and the researchers agreed upon the different changes. These changes were made based on relevance of items to study setting and cultural considerations. Finally, a day training on the use of the adapted curriculum was held with the teachers; the training included practical demonstrations of lessons from the curriculum followed by demonstrations by the teachers. All teachers participating in the intervention were provided with free copies of the adapted Explore curriculum. Teachers were also provided with an overview of the curriculum and the aim of the study. They participated in practical sessions of some selected lessons from the curriculum.A series of step-wise activities were conducted to achieve the goal of adaptation of the Explore curriculum was estimated by the recording of the duration of lessons and the extent to which each of the 15 lessons was taught. Based on these criteria, coverage of lessons among teachers was estimated to range from 60 to 85 %.A total of 15 lessons from the ten domains of the adapted curriculum were then selected, to be covered within the 8 weeks of the study, at an average of two lessons per week. The teachers and investigators taking into consideration priority social issues within the context, selected the 15 lessons. As a fidelity measure, the teachers’ coverage of the 15 lessons of the The study took place between October 2013 and March 2014. The intelligent quotient (IQ) of the participants was assessed using the Wechsler Intelligence Scale for Children, Fourth Edition (WISC-IV)  by the fAt baseline, socio-demographic information were obtained about each pupil directly from their hostel caregivers. The caregivers were also interviewed about the pupils by authors using the Matson Evaluation of Social Skills for Individuals with Severe Retardation, except for the only pupil in the day service whose demographic and MESSIER information was obtained from the class teacher. Information about participants’ parents was retrieved from the records obtained at the point of admission to the school.Explore curriculum three times a week; with each lesson lasting for 45 min. Each lesson consisted of an introduction of the topic of discussion, self-talk story, where the teacher gave a narrative overview of the topic, and role-plays. Activities within each lesson allowed for the pupils to play active roles through effective systems of communication and social interaction. The teachers and investigators facilitated the role-plays. For example, a lesson on meeting a new person would place a pupil in either a new or old student role as they worked through meeting a new person. Participants received lessons from the curriculum for 8 weeks (February–March), at the end of March; post-intervention data was gathered using the same procedures that were used at baseline.Participants received lessons in their classrooms from the adapted The data obtained was entered into the Statistical package for Social Sciences (SPSS) version 20. The paired t test was used to determine the difference between the pre-intervention and post-intervention scores on the social skills of the participants. The significance of the changes within categories of social skills impairment between pre and post intervention was tested using the Wilcoxon signed-rank test. Pre and post intervention analysis of MESSIER scores across socio-demographic variables was investigated using the Mann–Whitney U Test and the Kruskal–Wallis Test. Pearson correlation coefficients were used to evaluate the associations between IQ scores and social skills pre as well as post intervention. A fidelity analysis was done using multivariate analysis of variance (MANOVA) to analyse the gain scores of these groups on MESSIER using class as the independent variable. Reliable change index (RCI) was calculated using the methodology outlined by Jacobson and Truax ; the difEthical approval to conduct this study was obtained from the Oyo state Ethical Review Committee and permission to carry out the study was also obtained from the Oyo state Ministry of Education. Written consent containing information about the study was obtained from the participants’ parents or caregivers before the study. The study was also explained to the participants.Table Table Figure Using standard deviation difference of 2.90 and a standard error of 4.39 (based on the pre and post intervention scores on the MESSIER) and the reported internal consistency reliability of 0.94, we calculated the reliable change index (RCI) of 12.16. Based on this RCI, 12 participants (40 %) showed reliable improvement, 2 (6.7) showed reliable deteriorated and the remaining 16 (53.3 %) showed no reliable change.Table Table 2 = 0.405) and Group B  were within the medium range.Fidelity analysis was carried out to evaluate the extent to which teachers’ coverage was associated with pupils’ gains by creating groups based on overall teacher reported coverage of lessons from the curriculum. There were three groups: Group 1 included students from class A where teacher reported 85 % coverage, Group 2 included students from class B where teachers reported 70 % coverage and 60 % coverage was reported by teachers in class C constituting Group 3. A multivariate analysis of variance (MANOVA) was used to analyse the gain scores of these groups on MESSIER using class as the independent variable. Descriptive analysis on the MANOVA showed that Group A had the highest mean gain (27.88). Although the overall MANOVA was not significant; Wilks Lambda = 0.313, F =  = 0.787, p = 0.611, the effect size for Group A  over three times higher than the rate of 11 % obtained in a study of adolescents in mainstream schools in the same community as the current study . It has All participants in our study except one were living in the boarding house; this finding is a reflection of what happens to children with intellectual disability in the developing world. Cultural beliefs and attitudes about children with disability and their family are still largely negative. In many parts of Africa, children with disability are seen as “objects of shame”, who should be hidden away , 50. ThiAll the participants scored below 69 on the test of intelligence and this score is defined as extremely low IQ on the WISC category. This is not surprising, according to the International Classification of Disease (ICD-10), an IQ below 70, in addition to assessment of adaptive skills, is an important criterion that is required for making the diagnosis of intellectual disability . MoreoveIn the current study, virtually all participants had severe and profound levels of social skills impairment at baseline. The association between intellectual disability and social skills impairment is well established across the life cycle , 62. A sAlthough our study did not investigate the reasons for impaired social skills in the participants but some of the reasons alluded to the close relationship between impairments in social skills and intellectual disability are that individuals with intellectual disability often have problems detecting and understanding contextual clues and situations, identifying emotional and social relationships, and understanding others’ feelings and perceptions.A key finding from our study was the significant difference in the mean change between the pre- and post-intervention scores on the social skills scales after 8 weeks of classroom-based intervention. In a randomised control trial of 222 adolescents with developmental disabilities in the United States the application of a social skills training programme called, “Working at Gaining Employment Skills (WAGES)” obtained significant improvements in the mean score difference between pre and post assessments of the adolescents on the Social Skills Rating System (SSRS) in the intervention group (Mean difference = 1.52) when compared to a control group (Mean difference = 0.51) . A systeAlthough our study find statistically significant difference in the social skills scores of the participants, however, it was difficult to measure the clinical evidence of this change; the absolute pre- and post-intervention scores were both within the moderate impairment in social skills. This is not surprising because the duration of the intervention was short and longer period of intervention is needed to record significant clinical evidence of this change in social skills. The traditional reliable change index provides one criterion by which the clinician may establish whether or not an observed change following an intervention is not due to chance . The autThe cut-off criterion defined as leaving treatment in a normal state has been described as a more powerful determinant of Reliable and Clinical Significance Index (RCSI) than the reliable change index which is changing to a degree not attributable to chance . ReachinInterestingly, the correlational analysis between IQ sores and pre-intervention social skills scores showed that participants with higher IQ scores had more social skills deficits. Greater severity of ID has been associated with more impairment in the range of communication skills, hence, there is a significant reduction in both positive and negative behaviours . IndividExplore curriculum is important because studies have shown higher incidences of challenging behaviours and psychopathology in young people with intellectual disability [The finding of improvements in social skills with the sability , 68. Stusability –71 and rsability . One wayExpectedly, the results of the fidelity analysis indicated that students with higher levels of teacher-rated coverage had greater gains in social skills. Another explanation for the greater gain aside the higher coverage might be because the participants in class A, where the highest gain was recorded, had the least disability. However, these two factors might be interrelated; higher teacher coverage could be due to the fact that participants in this class had lesser degree of disability in the first place. A more significant finding in this study is the fact that the participants in the other classes with more severe forms of disability also had appreciable changes in their social skills at the end of the 8-week intervention. This suggests that greater changes might have been recorded with a longer duration of the intervention; this finding is important for policy and planning in settings where there is a dearth of information on effective interventions for individuals with intellectual disability.Fidelity of implementation is traditionally defined as the determination of how well an intervention is implemented in comparison with the original programme design during an efficacy and/or effectiveness study , 73. MowThe findings in this study are important because they reveal that social skills of young people with intellectual disability can be improved over a relatively short period of time through teacher mediated classroom-based interventions. This is especially useful for a low-resource setting like the study site where the concept of task shifting is important to enable persons with developmental disabilities access services . The parThe findings from this study would be useful for advocating for and implementing inclusive education in a region where a large proportion of young persons with developmental disabilities are locked away in institutions, abandoned by their parents, or simply kept behind doors at home without any form of access to education or health services .Sub-Saharan Africa is home to a large number of young people with intellectual disability . A majorThe findings are also relevant for policy making and designing educational packages for individuals with intellectual disability. Article 24 of the United Nations Convention of the Rights of Person with Disabilities, states that children with disabilities should be able to participate in the general education system and be educated in mainstream schools .Currently, there are no structured educational plans and packages for this population in most parts of sub-Saharan Africa. For instance in Nigeria, teachers in schools for persons with intellectual disability are provided with the same curriculum as for mainstream schools. The mainstream school curriculum caters for core academic content areas like writing, reading and mathematics and fails to address issues such as adaptive functioning . TherefoAlthough, the findings from this study contribute to existing knowledge, it is important to recognise that the study has several limitations. First, the sample for the study was relatively small this limits the generalisation of the findings. Second, because of the small size of the school, randomization, which could have provided for more robust findings, was not possible, hence future efforts with larger sample size and a randomised design might allow for broad generalisation of the findings. A third limitation of this study is the fact that the MESSIER was originally designed to measure social skills among adults with ID. But considering that resources are scarce especially for individuals with disabilities in the study setting, sometimes instruments are used outside the range of the original design. A way forward is to consider a thorough adaptation of this and other related instruments for use in this age group. Another important limitation is that we relied on caregivers who were aware of the participants’ conditions for the outcome rating. The caregivers’ ratings, especially the post-intervention data may have been affected by their awareness of and familiarity with participants’ conditions. This problem can be resolved in the future using a multi informant approach including data from teachers, caregivers, parents and through the use of direct assessment.This study supports findings from previous studies showing the association between impaired social skills and intellectual disability among adolescents. A very important outcome from the study is the improvement in social skills after 8 weeks of a teacher facilitated classroom-based intervention. The results from this study have the potential to influence educational policy thereby allowing for inclusive education of young people with intellectual disability in low-income settings.