Although resting-state functional magnetic resonance imaging (fMRI) studies have observed dynamically changing brain-wide networks of correlated activity, fMRI’s dependence on hemodynamic signals makes results challenging to interpret. Meanwhile, emerging techniques for real-time recording of large populations of neurons have revealed compelling fluctuations in neuronal activity across the brain that are obscured by traditional trial averaging. To reconcile these observations, we use wide-field optical mapping to simultaneously record pan-cortical neuronal and hemodynamic activity in awake, spontaneously behaving mice. Some components of observed neuronal activity clearly represent sensory and motor function. However, particularly during quiet rest, strongly fluctuating patterns of activity across diverse brain regions contribute greatly to interregional correlations. Dynamic changes in these correlations coincide with changes in arousal state. Simultaneously acquired hemodynamics depict similar brain-state-dependent correlation shifts. These results support a neural basis for dynamic resting-state fMRI, while highlighting the importance of brain-wide neuronal fluctuations in the study of brain state. Shahsavarani et al. investigate the dynamic correlation structure of cortex-wide neuronal activity and hemodynamics in awake mice using wide-field optical mapping. They demonstrate a relationship between neuronal correlation dynamics, arousal level, and behavior that is reproduced by hemodynamic correlations. Results support a neural basis for fMRI-based dynamic functional connectivity mapping.  However, analysis of ongoing “resting-state” activity, recorded using functional magnetic resonance imaging (fMRI) has revealed interregional correlation patterns among spatially distinct brain regions, depicting the brain as a collection of functionally interconnected networks.13 However, results have not yet been sufficiently robust and reliable to achieve clinical significance. One factor hindering the interpretation of results, and refinement of analysis methods, is the dependence of fMRI signals on brain hemodynamics rather than neuronal activity. Meanwhile, methods capable of capturing and decoding properties of real-time brain-wide resting-state neuronal activity have been limited. Insights into the nature and properties of the brain-wide neural activity underlying signals detected and analyzed in fMRI rs-dFC are needed, both to reconcile our understanding of this activity across scales and species and to be able to leverage observations of this activity to understand the human brain in health and disease.Analyses of dynamic changes in functional connectivity during an fMRI session have revealed potential biomarkers of neurological and psychiatric disease.14 Leveraging fluorescent calcium indicators expressed in excitatory neurons, WFOM has previously been used to demonstrate that resting-state hemodynamics in the brain of awake mice can be largely predicted by baseline fluctuations in the excitatory neuronal activity.15 Here, we leverage improved, red-shifted calcium indicators in cortical neurons to visualize these neuronal patterns with a higher spatiotemporal resolution. We combine this imaging of neuronal activity with simultaneous mapping of cortical hemodynamics and detailed recordings of spontaneous behavior and pupil dynamics in awake mice to analyze the relationship between real-time brain activity, brain state, and behavior.Wide-field optical mapping (WFOM) is a technique that can image both neuronal activity and hemodynamics across the entire dorsal cortex of the awake, behaving mouse.We observed robust, real-time patterns of ongoing neuronal activity across the brain that exhibited rich spatiotemporal correlation structures, while also including clear functional representations of sensory and motor behaviors. Correlations between neural activity in different cortical areas exhibited relatively stable patterns across animals when averaged across 10 minute epochs and reveal a compelling functional cortical topography. However, a moving-window correlation approach confirmed that neural correlation patterns shift and change over time, consistent with fMRI rs-dFC. Analysis of the relationship between different correlation states and behavior revealed consistent changes in correlation, not only before, during, and after spontaneous locomotion but also with varying arousal levels during quiescence or rest. Reduced arousal level was accompanied by an increase in the amplitude of neural fluctuations, predominantly in the anterior lateral frontal cortex, reducing the correlation between anterior and posterior brain regions. These resting-state neuronal fluctuations cannot be detected in trial-averaged data owing to their random phase and do not correspond to any discernable sensory input or motor output.Repeating the same analysis on simultaneously recorded cortical hemodynamics data revealed that similar behavioral state transitions could be detected. Comparison of neural and hemodynamic signals confirmed that hemodynamics provide a temporally low-pass filtered representation of neuronal activity. Analysis of the frequency-dependence of correlations found relatively good agreement between neuronal and hemodynamic correlation patterns at lower frequencies. Importantly, neuronal correlation patterns remained consistent even when neuronal signals were high-pass filtered to retain frequencies exceeding those represented by hemodynamics. This finding supports the broadband nature of the neuronal activity underlying dynamic correlations and explains why lower-frequency hemodynamics are able to capture similar correlation features and transitions.Our results support converging evidence that dynamic, brain-wide patterns of neural activity are fundamental to understanding brain states and help to resolve our understanding of the structure and temporal variability of functional connectivity across species and scales.17  . A similg [HbR]) ii, whilg [HbR]) i. Groomg [HbR]) vi.In addition to neuronal events related to sensory and motor function, distinct fluctuations in neuronal activity and hemodynamics are also clearly visible during periods of rest when only minimal movements and sensory stimuli occur, particularly in more anterior regions . These aTo explore spatiotemporal correlation patterns across the cortex, it is essential to have a robust frame of reference that enables comparisons over time and between mice. By applying spatiotemporal clustering methods to neural data, regions that are temporally correlated can be delineated. This analysis reveals striking, symmetric and reproducible cortical “functional topographies,” with finest detail observed when clustering is applied to data collected during periods of quiet rest. By applying a data-driven process to refine cluster centroids see , it was 19 the faster dynamics and higher spatial fidelity in red-shifted Thy1-jRGECO1a mice provided a significantly more detailed structure.17 Compared with a standard mouse brain atlas in 21This topographic parcellation is important for two main reasons. First, it provides a robust basis for downstream analysis of dimensionally reduced and registered WFOM data, and thus comparisons between mice. Second, these spatiotemporally derived functional parcellations reveal a consistent and anatomically recognizable topography of the cortex depicting well-defined, bilaterally symmetric regions based only on the functional dynamics of each region during rest. Although prior studies using mice expressing the green fluorescent calcium-sensitive indicator GCaMP have revealed consistent yet relatively coarse parcellations of the mouse cortex,With this ROI framework in place, we could explore and compare correlation relationships between different cortical regions. Time courses were extracted from each ROI, and then correlation matrices were computed by calculating Pearson correlation coefficients (zero-lag correlation) between the time series of each ROI pair, resulting in a symmetric 92 × 92 correlation map. Although this average, long-epoch neural correlation pattern is relatively consistent across five mice i-iv, ifIt is not surprising that locomotion has a measurable effect on cortical correlations. Therefore, in orderto further probe correlation variability overtime, we next calculated inter-regional correlations within 10-s moving windows, focusing on five distinct types of epochs: (1) during the onset of locomotion, (2) during periods of sustained locomotion, (3) during locomotion offset, (4) during rest immediately after locomotion , and (5) during rest from 40 to 50 s after locomotion (sustained rest) see . Figure For each of the five mice, the average neural correlation map within each of these behavioral epochs was calculated using locomotion bouts selected from multiple days of recordings  fit. Fit coefficients for each real-time 10-s-windowed correlation map represent the contribution of each behavioral correlation state map to the cortical correlation pattern at that moment in time see .22 the average pupil diameter of our mice after locomotion offset followed a decreasing trend , (2) the visual cortex becomes less bilaterally symmetric , and (3) the anterior lateral frontal cortex becomes less synchronized with the posterior brain regions . Although interregional correlations will be altered by functional representations of locomotion, and may even be affected by locomotion-related motion artifacts, here we explore how neural signals in different brain regions contribute to observed changes in correlation patterns between locomotion and rest states. We find that during rest compared with locomotion, (1) the anterior lateral frontal cortex becomes more bilaterally symmetric  signal.26 Unless otherwise noted, a 1.5-s lag was used15 to account for the anticipated delay of the hemodynamic response compared with neuronal activity, and hemodynamic data were temporally low-pass filtered at a cutoff frequency of 0.25 Hz to remove contamination from heart rate and breathing frequencies, as detailed in The above analysis sequence was thus repeated using simultaneously acquired measurements of changes in As with neural activity, anterior-posterior decorrelation during rest is a prominent feature of the hemodynamic correlations. The raw differences in correlation maps between initial and sustained rest in  = 0.22) .We also confirmed that the hemodynamic sustained-rest state was accompanied by a smaller pupil diameter, consistent with a lower arousal level. These findings provide evidence that the correlation dynamics of hemodynamic data capture sufficient information to encode the same behavioral-state-related changes observable in the correlation structure of neural activity.27 However, although the hemodynamic signal shows equivalent spectral power in lower frequency ranges, there is a clear cutoff at around <0.5 Hz, consistent with the temporal low-pass filtering effect of the cerebral vasculature.1515  in the primary visual cortex (V1), as well as frontal regions, are predictive of engagement in a visual task. In agreement with our results, this study recognized that task-engagement-related signals were not restricted to the cortical region engaged in the task. The suppression of rapid fluctuations in cortical neural activity by locomotion or movement has also been reported in the auditory cortex in mice31 and motor cortex in primates.33 Measuring intracellular membrane potentials, local field potentials (LFPs), and electroencephalography (EEG), a similar property was found in the mouse barrel cortex, where the resting-state fluctuations (1–5 Hz) were damped by active whisking.35 Vinck et al.22 recorded LFPs in mouse V1, finding that locomotion suppresses low-frequency LFP fluctuations (1–4 Hz), whereas stopping locomotion gradually increases low-frequency LFP power with a time course strongly correlated with pupil size. Interestingly, these higher-bandwidth electrophysiology measurements found a concomitant decrease in LFP gamma oscillations (55–66 Hz) during rest and an increase in these bands during locomotion. While using calcium indicators limited our ability to detect higher frequency shifts, our results suggest that a similar effect may be observed at higher frequencies across wider cortical regions.Our observations of dynamic resting neural activity, most strongly in the anterior lateral frontal, lateral somatosensory and visual cortices, are consistent with a range of other studies across modalities, species, and cortical areas. For example, wide-field neuronal GCaMP imaging has been used in mice36 then our findings may indicate reduced multisensory integration during periods of quiescence. This result could be consistent with EEG studies in humans that have shown that anesthesia decreases anterior-posterior synchronization and increases the bilateral coupling of the prefrontal cortex,37 a result recapitulated in rats using intracortical event-related potentials.38We also observed that the anterior frontal cortex was less correlated with the posterior sensory regions during rest. If stronger synchronization, or functional connectivity between cortical brain regions can be considered as a measure of the information integration,43 However, these anterior lateral frontal areas are not well represented in classical mouse brain atlases . In this context, such fluctuations would be regarded as task-independent noise. Experimental paradigms that average multiple repeated trials of stimuli or tasks will also average out these important signatures of brain state , thereby46 Meanwhile, the lack of correlation patterns in high-pass-filtered hemodynamic data underscores that the origin of dynamic correlation patterns and shifts in neural data cannot be due to residual hemodynamic cross-talk.We demonstrated that hemodynamic signals could differentiate between distinct behavior-driven states and identify switching between high and low arousal levels during rest. This result shows that, despite the relative complexity of the coupling between neural activity and brain hemodynamics, and the low temporal frequency content of the hemodynamic data, sufficient information about neural dynamics is retained in hemodynamic signals to depict similar correlation patterns and behavioral-state-dependent correlation dynamics. Our observation that high-frequency components of neural signals showed similar correlation patterns to low-frequency bands for both neural and hemodynamic signals is consistent with cross-frequency coupling across our 10-Hz measurement bandwidth. This finding suggests that hemodynamics  are providing information relevant to the properties of broadband spontaneous neural dynamics and do not just encode an independent source of low-frequency neural fluctuations.47 Using rs-dFC, previous work has shown that spontaneous fluctuations in the BOLD signal  are dynamically coherent.48 Although a growing body of research has been focusing on linking functional connectivity dynamics to mental processes, cognition, behavior, and disease,53 the origins and interpretation of ongoing time-varying synchrony patterns, and their relationships to disease states, have been the subject of significant debate.55 Our results demonstrate that dynamic changes in neuronal and hemodynamic correlation patterns can capture transitions in moment-to-moment brain states and arousal levels. A possible source of disease-related changes could thus be the sensitivity of resting-state fMRI to a patient’s physical and emotional response to the experience of undergoing an fMRI scan,56 which could include variations in alertness, anxiety, sleep transitions, mind wandering, restrained motion, or motor intents . It is therefore possible that disease-specific responses to the fMRI experience could underlie some of the predictive properties of dynamic functional connectivity transitions, particularly in psychiatric disease states. Conversely, several disease states, including glioma and acute stroke, have been shown to cause disturbances to both neurovascular coupling and the dynamic and correlation properties of resting-state neuronal activity in awake mice.58 In these cases, pathophysiological changes could more directly explain changes in the representations of these disease states in both task and resting-state fMRI assessments.Widespread interest in resting-state fMRI stems from its potential to explore the human brain’s functional organization in both health and disease.Overall, our results demonstrate that fluctuations in brain-wide neural and hemodynamic correlation patterns depict significant shifts and changes in the dynamic properties of brain activity see . A signiAlthough cortical hemodynamics were found to depict many features of neuronal correlations, hemodynamic correlation patterns were overall more variable across epochs than neural correlations, and residuals of our NNLS fits were higher for hemodynamic data. Higher noise levels and contamination of hemodynamic data with heart and breathing rate signals could have contributed to these effects. However, we also only explored coupling between Thy1-jRGECO1a-dependent neural activity and hemodynamics. Additional influences on hemodynamics could include coupling to other neural subtypes, including interneurons, and other origins of slow drifts or modulations of hemodynamics such as global brain modulations and systemic blood pressure and flow modulations.22 This 10-s window also enabled us to evaluate inherently slower hemodynamic correlation patterns, enabling comparisons with the dynamics captured during resting-state fMRI. However, we acknowledge that the higher bandwidth of the neural and behavioral data acquired here could be used to evaluate transitions between more rapid and transient behavioral states that could be represented over correlation windows as short as 1–2 s. Such higher dimensional states likely encode detail about more rapid pupil fluctuations,60 more complex and non-overt behavior, whisking dynamics, and rapid transients in spontaneous neural activity (preparatory activity) that preceded locomotion onset. Our data suggest that continued exploration of neural dynamics and their relationship to brain state over a broad spectral range will likely provide further insights into brain-wide neural communication.Another important parameter in our analysis was our choice of a 10-s moving window over which to calculate our neural and hemodynamic Pearson correlations. This window size was chosen to capture transitions in behavioral states on a similar time frame to our relatively simple assessment of the mouse’s overt spontaneous behaviors and transitions in arousal, which occurred on the timescale of slow fluctuations in pupil diameter.Future studies could leverage WFOM experiments (as well as datasets shared from this work) for development and testing of fMRI analysis methods, with neural data providing a ground-truth comparison. Studies could be extended to measurements of voltage, rather than calcium-sensitive indicators, and could record the activity of a range of neuronal  cell types. These measurements could also permit finer dissection of the contributions of different cell types to correlation patterns and their relationships to complex behaviors across broad frequency ranges. Additional studies could incorporate specific stimuli and tasks to test the effects of external influences on brain dynamics, as well as optogenetic, pharmaceutical and disease-related perturbations to better characterize their effects on neuronal and hemodynamic signals, their correlation dynamics, and their relationships to behavior.elizabeth.hillman@columbia.edu).Further information and requests for reagents and resources should be directed to the This study did not generate new unique reagents.http://dx.doi.org/10.17632/xd93nswg6h.1.Data generated and analyzed in this study  has been deposited and made accessible for analysis through Mendeley Data: https://doi.org/10.5281/zenodo.7860561.Code used for the main preprocessing and analysis steps has been shared via GitHub: Any additional information required to reanalyze the data reported in this paper is available from the Transgenic male adult Thy1-jRGECO1a mice expressing red-shifted calcium indicators were used in this study. The mice were bred from the line Tg(Thy1-jRGECO1a)GP8.20Dkim/J, purchased from the Jackson Laboratory. The mice were three months old when the experiments began. Mice were initially bred and housed in the animal facility at Columbia University. They were maintained up to five per cage with ad libitum access to food and water at a constant temperature (19–22°C) and humidity (40–50%) on a 12:12-hour light/dark cycle. After preparatory surgery, and between imaging sessions, animals were housed in individual cages within a satellite housing room close to the imaging system, maintaining consistent environmental conditions as detailed above. All animal procedures were reviewed and approved by the Institutional Animal Care and Use Committee at Columbia University in the City of New York (Protocol Number: AC-AAAS3453).in vivo wide-field optical mapping (WFOM), a thinned-skull cranial window was created between the coronal and lambdoid sutures by anesthetizing mice using isoflurane, stabilizing the head in a stereotactic frame, retracting the scalp and gently thinning the skull to translucency with a dental burr. A thin layer of cyanoacrylate glue was then applied to the thinned skull to provide protection, reduce skull regrowth and improve transparency. A custom-made laser-cut acrylic head-plate was then glued to the edges of the skull to enable head fixation during imaging. Throughout this preparatory surgery body temperature was monitored and maintained using a heating pad and temperature probe. Mice were administered the analgesic buprenorphine for two days after surgery.To prepare each mouse for Longitudinal imaging measurements were acquired in a cohort of five age-matched mice. Acquisition started at least two days after surgery with at most 10 repeated 10-min recording sessions within one experimental session, up to eight experimental sessions spanning eight weeks. Before each recording, the cranial window was cleaned with deionized water, fully dried and covered with a glycerol mixture and glass coverslip to reduce specular reflections. After each experimental session, the headplate was cleaned, mice were removed from the imaging rig and returned to their home cage.61 was used to extract parameters from behavioral videos. Pupil size was tracked using eight circumferential points, fitting a circle to these eight points to estimate pupil diameter. To track whisking, nine points were used to annotate three visible whiskers (three points for each whisker) on the left side of the mouse’s face. Whisker speed was computed as the average frame-by-frame differences between the x-y coordinates of each whisker, calculated by Euclidean distance. The wheel’s rotary motion was recorded using a rotary encoder, and wheel movement velocity was computed as a locomotion measure. The time courses of pupil diameter, whisking speed and wheel velocity were used to quantify mouse behavior.Two BFS-U3–16S2M-CS USB 3.1 Blackfly S Monochrome Cameras were used to monitor mouse behavior at a rate of 60 fps under infrared light illumination (850-nm wavelength with a HOYA R72 INFRARED filter). Both behavioral cameras were triggered to capture images at the same time as each WFOM image frame to ensure synchronization. One camera was widely angled to record the whole left side of the mouse’s body, and a mirror was placed below the wheel at a 45° angle to monitor the mouse’s paw movements. The other camera was set to closely capture the left side of the mouse’s face to record pupil and whisker movements. The open-source tracking software DeepLabCutData were acquired using a custom-made WFOM system, as depicted in All data were analyzed using MATLAB (Mathworks). Statistical analyses were performed using non-parametric Wilcoxon rank-sum and Kruskal-Wallis tests, except in The boxplots of the violin plots shown in , and 7D 14 JRGECO fluorescence recordings were further corrected for hemodynamic cross-talk and converted into Reflectance recordings were used to estimate changes in concentrations of oxyhemoglobin 14The time-varying changes in cortical hemodynamics accompanying neural activity impose a varying absorption pattern on raw detected jRGECO1a fluorescence. Both the lime (565 nm) excitation light and the red (~630 nm) fluorescence light will experience attenuation from hemoglobin, and the wavelength-dependence of the absorption properties of oxy- and deoxy-hemoglobin requires a correction that considers both wavelengths. As derived below, we approximate this correction factor as a combination of the signals detected in our green and red reflectance data. The accuracy of this correction can be judged by observing how well it removes vessel-like artifacts in converted fluorescence data, as seen in Lime excitation light with intensity Combining these 3 equations, we see:If we divide this detected signal by a baseline signal , we cancel out the temporally constant initial intensity term Dividing by the baseline reflectance image, we similarly get:14 If we assume that our red reflectance experiences a similar absorption coefficient as our red fluorescence emission, and our green reflectance experiences a similar absorption coefficient as our lime fluorescence excitation, then the reflectance measurements can be used to approximate the time-varying absorption component of Here, it is important to consider that Producing a measurement proportional to the percentage change in jRGECOIa fluorescence. The unknowns in this equation are For raw data time courses and images shown in For all correlation analysis, time courses were extracted from regions of interest determined through parcellation for each mouse (detailed below), spatially registered for each recording session, and taken as the average red, green and lime signal within each ROI. Unless otherwise stated, the only pre-processing of these raw WFOM reflectance and fluorescence signals for correlation analysis was temporal low-pass filtering with a cutoff frequency of 6.5 Hz to reduce global heart-rate-dependent signals followed by hemodynamic correction and conversion to [Hb]. The frequency analysis of neural and hemodynamic signals revealed breathing vascular artifacts around the frequency range of 1–4 Hz that were prominent in the hemodynamic reflectance measurements, but not fluorescence. To avoid spurious correlations, hemodynamic data were further low-pass filtered at 0.25 Hz. Filtering procedures were performed using zero-phase filters (filtfilt) in MATLAB (Mathworks) with a filter order of 20 and a pass-band ripple of 0.2. These data were used in In To generate our cortical topography, k-means clustering was run with a wide range of parameters and cluster numbers across many mice, sessions and epochs. The general spatial structure of parcellation results was found to be widely consistent, although the most detailed and clear delineation was found when clustering data during periods of quiet rest  where temporal centroids for each clustering result were used as a basis set NNLS generates spatial representations To generate a generalized parcellation that would permit consistent comparisons across all mice, we then performed the following procedure. K-means clustering with 100 replicates, correlation distance metric and 46 clusters was applied to one hemisphere of data during a 60-s rest period from one mouse. The resulting spatial clusters . The most commonly occurring mode map for these clustering steps was chosen as the final map for each mouse.Each mouse-specific ROI map was registered onto the brain image of each mouse in each session and used to extract time-series data as detailed above. To reduce the effects of small motion artifacts, averaged signals were extracted from each of these 92 ROIs from raw data . These signals were then converted to Unless otherwise noted, the pairwise Pearson correlation coefficients between time courses for the 92 ROIs were calculated over 10-s temporal windows, resulting in 92 × 92 correlation maps. Before computing correlation matrices, the first-degree polynomial trends in windowed hemodynamic data were removed.k-means algorithm applied to the correlation map data  within each hemisphere were found using the data see . These gAlthough data in a full 92×92 correlation map can be visualized as 92 sequential cortical maps  for locomotion bouts lasting at least 5 s, with at least 60 s post-locomotion rest. The sustained rest state was calculated as the average correlation map over 10 s, starting 40 s after locomotion cessation for the same bouts as for the initial rest state.22 that found that pupil size, on average, returns to baseline around 40 s after mice stop running. Our results are consistent with this observation as illustrated in The 40 s delay chosen for the sustained rest state was based on prior workTo determine whether the average behavioral correlation states derived as detailed above are predictive of real-time mouse behavior, a non-negative least squares (NNLS) fit was performed using these five correlation states The goodness of fit between each real-time correlation map and the model prediction was evaluated as 12345


The reproductive success of flowering plants, which directly affects crop yield, is sensitive to environmental changes. A thorough understanding of how crop reproductive development adapts to climate changes is vital for ensuring global food security. In addition to being a high-value vegetable crop, tomato is also a model plant used for research on plant reproductive development. Tomato crops are cultivated under highly diverse climatic conditions worldwide. Targeted crosses of hybrid varieties have resulted in increased yields and abiotic stress resistance; however, tomato reproduction, especially male reproductive development, is sensitive to temperature fluctuations, which can lead to aborted male gametophytes, with detrimental effects on fruit set. We herein review the cytological features as well as genetic and molecular pathways influencing tomato male reproductive organ development and responses to abiotic stress. We also compare the shared features among the associated regulatory mechanisms of tomato and other plants. Collectively, this review highlights the opportunities and challenges related to characterizing and exploiting genic male sterility in tomato hybrid breeding programs. Flowering plants are among the most successful living organisms at least partly because of their morphological diversity and ability to grow in various ecological niches, which is primarily because of reproductive innovations , whereas the secretory tapetum, which is more common among plants , provides nutrients through the liquid in the locule that bathes the developing microspore  and microgametogenesis   was the first verified structural male-sterile tomato mutant, with vestigial stamens adhering to the carpels  mutants were initially identified as sterile mutants, which displayed failure of male and female gametophyte formation , a well-characterized repression domain   Kaul . In tomas Bishop . The tomms1035 resulting from a spontaneous mutation shows degenerating microspores with enlarged vacuoles during meiosis. A gene mapping analysis revealed that Ms1035 encodes a bHLH transcription factor and is homologous to the Arabidopsis gene DYSFUNCTIONAL TAPETUM 1 (DYT1)  and ABORTED MICROSPORES (AMS), the latter of which encodes a master regulator of tapetal development involved in the synthesis of lipidic and phenolic components essential for pollen wall patterning and flavonoid production , respectively, are downregulated. In addition to ms1035, the tomato male sterility 32 (ms32) mutant fails to undergo meiosis; its mutated locus was mapped to a putative gene (Solyc01g081100) homologous to the Arabidopsis bHLH89/91 gene  and OsMYB80, which are homologs of AtAMS and AtMYB80, respectively , Recombinant Escherichia coli ATP-dependent DNA helicase (RECQ) and AAAATPase FIDGETIN-LIKE-1 , which encodes a protein that recognizes and repairs errors in DNA sequences, disrupts tomato male meiosis where half of the meiocytes stalled at the zygotene stage or combined to form diploid tetrads, which substantially inhibits normal pollen formation , which leads to the generation of haploid microspores. Meiosis comprises the following five key stages: meiotic entry, recombination initiation, chromosome synapsis, resolution of recombination intermediates, and the second meiotic division Ma . DefectiPhalaenopsis, in which a specialized generative pole microtubule system appears at the future generative cell pole prior to nuclear migration , two-in-one (tio) and kinesin- 12A/ 12B , while also partially rescuing the pollen viability of the Slpif3 mutant, suggesting that auxin regulates tomato PMI by modulating the expression of genes related to microtubules and the cell cycle. Furthermore, sugar metabolism-associated signaling pathways are involved in pollen mitosis in tomato. Recent research demonstrated that SlSWEET5b facilitates tomato pollen mitosis and maturation by mediating the transport of apoplasmic hexose into developing pollen cells , which is essential for establishing male germ cells , leading to decreased pollen dispersal and fruit set in tomato  and BRASSINAZOLE-RESISTANT1 (BZR1) alter the timing of ROS production and delay tapetal PCD in tomato , which substantially activates the expression of heat responsive genes. In Arabidopsis and tomato hsfa1 mutants, the expression levels of many HS-responsive genes are lower than normal, resulting in vegetative tissues with HS-insensitive phenotypes , the key gene for callose biosynthesis. The miR160 regulated expression of ARF17 is also required for its function during anthers development in Arabidopsis  levels decrease in tomato anthers, which results in the altered transcription of many pollen development-related genes (Yang et al. 6A may influence tomato pollen development under cold conditions. Similar to cold stress, drought conditions can interfere with tapetal development by preventing or delaying the induction of PCD in developing tomato pollen grains (Lamin-Samu et al. Cold stress is another prevalent abiotic factor affecting the growth and development of plants, especially subtropical vegetable crops. In res Fig. B (Pan etres Fig. . The inhArabidopsis, a prion-like domain in ELF3 functions as a putative thermo-sensor to undergo protein phase transition that results in the formation of liquid droplets in response to increasing temperatures (Jung et al. ANANTHA to repress its expression (Huang et al. Increases in the global population as well as climate changes are major issues that must be addressed to maintain agricultural production and food security. In addition to increasing crop yields, minimizing abiotic stress-induced production losses is a major objective among plant researchers. Thoroughly characterizing the mechanism regulating male fertility and identifying novel stress resistance genes associated with male reproductive development may enable the generation of stress-resistant germplasm resources suitable for biotechnology-based crop breeding. Research regarding reproductive stress tolerance has continued to progress because multiple strategies have been applied. For example, protein phase separations have been revealed to contribute to plant adaptive responses to cellular pH changes, temperature fluctuations, and oxidative stress. In


The recent concurrence of electrical grid failure eventsin timewith extreme temperatures is compounding the population health risksof extreme weather episodes. Here, we combine simulated heat exposuredata during historical heat wave events in three large U.S. citiesto assess the degree to which heat-related mortality and morbiditychange in response to a concurrent electrical grid failure event.We develop a novel approach to estimating individually experiencedtemperature to approximate how personal-level heat exposure changeson an hourly basis, accounting for both outdoor and building-interiorexposures. We find the concurrence of a multiday blackout event withheat wave conditions to more than double the estimated rate of heat-relatedmortality across all three cities, and to require medical attentionfor between 3% (Atlanta) and more than 50% (Phoenix) of the totalurban population in present and future time periods. Our results highlightthe need for enhanced electrical grid resilience and support a morespatially expansive use of tree canopy and high albedo roofing materialsto lessen heat exposures during compound climate and infrastructurefailure events. Thisstudy estimates the potential heat-related health impactsof concurrent heat wave and blackout events across three large U.S.cities. Most recently,in June of 2021, electrical grid failures associated with a heat waveof historical intensity in the Pacific Northwest of the United Statesresulted in a loss of power to tens of thousands of customers, atleast 600 excess deaths, and more than 3500 emergency department visitsfor heat illness.4 Persistent drought conditions in the Western UnitedStates are further reducing the capacity of regional electrical generationand distribution systems to manage surges in electrical demand inthis and other regions confronting climate-driven pressures on criticalinfrastructure.5The incidence of electrical grid failureor “blackout”events is increasing across the United States. Since 2015, when theU.S. Energy Information Administration commenced monthly reportingon major blackout events , the number of suchevents nationwide has more than doubled, increasing by 151% between2015–16 and 2020–21 1. The ma8 in this paper, we estimatethe likelihood of health impacts through the development of an individual-levelheat risk model accounting for hourly indoor and outdoor heat exposuresand person-level risk characteristics. We then simulate the influenceof urban heat management strategies on heat-related mortality andmorbidity, as well as the impact of more intense heat wave eventsprojected with continued global scale warming in future time periods.Despite a rising incidence of electrical grid failures,few studieshave sought to directly assess the public health risks of compoundclimate and infrastructure failure events. Here, we estimate heat-relatedmortality and morbidity resulting from heat wave events of historicalduration and intensity occurring simultaneously with simulated blackoutconditions for the full urban populations of Atlanta, Georgia; Detroit,Michigan; and Phoenix, Arizona. Building on prior work modeling building-interiorheat exposures resulting from concurrent heat wave and blackout eventsacross these three cities,This paper reports results from the Three-City Heat and ElectricalGrid Failure Adaptation Study (3HEAT), which is focused on compoundclimate and infrastructure failure events in three large U.S. citiescharacterized by distinct regional climates and population characteristics.The cities of Atlanta, Georgia; Detroit, Michigan; and Phoenix, Arizonawere selected to include three distinct climate zones in which approx.75% of the U.S. population resides, as well as variable demographicand climatic risk factors for heat illness. A collaboration between Arizona State University,the Georgia Instituteof Technology, and the University of Michigan, the 3HEAT study examinesthree questions largely unaddressed by the literature on climate andhealth: (1) How does individual heat exposure change during concurrentheat wave and blackout events, relative to heat wave conditions witha fully operational electrical grid? (2) How do estimated public healthimpacts, including heat-related mortality and morbidity, change duringconcurrent heat wave and blackout events, relative to heat wave conditionswith a fully operational electrical grid? (3) How do these estimatedhealth impacts change in response to citywide urban heat managementplanning and to a growing intensity of heat wave conditions over time?12 Given that a grid failure has only limited impacts on outdoortemperatures but may substantially elevate building-interior temperatures,a reliance on outdoor temperature alone also fails to capture thechanging nature of heat exposure during concurrent heat wave and blackoutevents.The first of these three study questions requires that we modelheat exposure for both outdoor and building-interior environments.Established approaches to estimating health impacts associated withheat exposure are typically reflective of outdoor temperatures only,often measured at a single location, such as a metropolitan airportweather station, and therefore do not account for variable exposuresfor individuals in different locations of the city.14 IET provides a metric of human heat exposurethat accounts for exposure changes as individuals move between indoorand outdoor environments during a 24 h period. Under blackout conditions,indoor heat exposures will rise, particularly for individuals whowould otherwise have access to mechanical air conditioning in thehome when the electrical grid is operational. The result is a risein their IET and subsequent heat risk. We report the magnitude ofthis exposure change for different building types in a series of priorpapers.15To address this limitation of conventional approachesto assessingheat risk, we derive for this study a heat exposure metric referredto in prior work as “individually experienced temperature”or IET.19 Using urban-scale climate models,in combination with building energy simulation tools, we spatiallydisaggregate heat exposure to the level of the residential parcel,accounting for both how ambient temperatures vary across the urbanenvironment and how these environmental temperatures influence building-interiortemperatures for different classes of residential structures.To assesshow elevated heat exposures during concurrent heat waveand blackout conditions may impact health outcomes, we devise a novelapproach to estimating individual heat risk. Established exposure-responsefunctions widely used in heat risk assessment are responsive to outdoortemperature measurements only, often derived from the same singlelocation for a full urban population.T′) for each residentthrough the statistical association between estimated building-interiortemperatures and a single airport weather station temperature (T) for every hour of the day during heat wave conditionswith an operational electrical grid . Based on thisstatistical association, we then adjust outdoor temperatures to scalewith rising IET (due to building-interior temperatures) during blackoutconditions, yielding an analog outdoor temperature that can be usedwith established exposure-response functions for heat-related mortalityand morbidity. The result is an outdoor temperature metric (T′) adjusted to reflect an elevated indoor heat burdenduring blackout conditions . The modified builtenvironment has the general effect of lowering the analog air temperaturesused to estimate individual heat risk. However, more intense heatwaves in future time periods result in elevated analog temperatures,serving to enhance heat risk.Our research accomplished twoprincipal tasks: (1) estimation ofindividually experienced temperature (IET) and (2) estimation of populationhealth impacts from a concurrent heat wave and blackout event. Eachof these tasks is described in turn.20) and subsequently simulated with WRF.Estimationof IET required three sets of data inputs: (1) modeled outdoor ambienttemperatures, (2) modeled building-interior temperatures, and (3)daily activity patterns for each resident, allowing for the individualassignment of location-specific outdoor and building-interior temperaturesby time of day. We simulated outdoor and building-interior temperaturesduring historical heat wave events in each city with the Weather Researchand Forecasting (WRF) model and the U.S. Department of Energy EnergyPlusbuilding energy model (version 8.6), respectively. Historical heatwave events were classified as any 5 day period between 1980 and 2009in which daily average air temperatures met or exceeded the 97.5thpercentile of daily average temperature. Subsequently, the 90th percentileheat wave from each 30 year period in each city was selected and consideredrepresentative of the base period climate. The resulting heat waveperiods identified were August 14–18, 1995 (Atlanta); June15–19, 1994 (Detroit); and July 20–24, 2006 (Phoenix).Projected future heat waves representative of ∼2055 (mid-century)and ∼2085 (late century) were identified in the same way  two-way coupled WRF + BEP simulations were carried out usinga nested grid configuration, enabling the downscaling of the large-scalesynoptic flow from the coarsest outer grids to the finest inner gridsacross each of the three study regions. We made use of RCP 8.5 forboth mid- and late-century time periods to assess the highest emissionscenarios and to incorporate continuing uncertainty over achievableglobal emission reductions this century. Trees are represented inWRF-BEP as a simplification of the BEP-Tree model.21 Tree shading of impervious surfaces  is calculated according to Beer’s law, accounting forforward transmission of shortwave radiation through leaves. For simplicityand to conserve energy, all shortwave radiation intercepted by treefoliage is assumed to be converted to transpiration and thereforedoes not impact air temperature via sensible heat flux. This representsa maximum impact scenario of well-watered trees on air temperature.In the current formulation, trees do not impact wind or longwave radiation,both factors that can slightly counter the shading and transpirationcooling effect. A more complete description of the tree implementationis given in Stone et al.7To capture the dynamics of an urban setting, the building effectparameterization (BEP) multilayer urban canopy model was selectedin WRF. High-resolution  scalederived from the WRF model runs in each city. The location-specificeffects of tree shading and shading from adjacent buildings were notcaptured in our modeling. For a complete description of our approachto building-interior temperature simulation, please see Stone et al.Individual hourly exposures to outdoorand building-interior temperatureswere constructed from a synthetic population dataset for each cityand national time–activity pattern survey data. The unavailabilityof location-specific identifiers for individuals in U.S. Census datarequires that “synthetic” population datasets be developedfor a range of demographic and economic analyses linking individualresidents to geographic boundaries more disaggregated than Censusblocks. For this study, we acquired synthetic population data fromRTI International (RTI Synthpop), which depicts each resident of aCensus block group as a randomly positioned point within the blockgroup boundaries and assigns to these points demographic characteristicsincluding age, sex, race, and income. As the total number of residentsper block group is reported by the U.S. Census Bureau, but not thespecific address of each resident, each person included in the RTISynthpop digital map must be assigned to a specific address, enablinga set of building characteristics to be associated with each resident.To carry out this task, we made use of a geographic informationsystem (ESRI ArcGIS) to assign each resident to a unique address andresidential structure through the creation of a circular buffer aroundeach multifamily building or single-family house. First, any syntheticpersons located within a 500-foot radius of a high-rise multifamilybuilding (defined as more than five stories in height) were assignedto that building. Second, any synthetic persons located within a 250-footradius of a low-rise multifamily building (defined as five storiesin height or less) were assigned to that building. Lastly, all remainingsynthetic persons were assigned to the nearest single-family home.This procedure resulted in the assignment of specific residentialstructure characteristics, including building-interior temperatures,to each resident of the three cities.22 We extracted time use datafrom respondents in each of the three study cities during the period2004–2015. There were 2958 respondents that met the inclusioncriteria and completed a total of 59,774 logged activities on thesurvey. Each activity was assigned to one of five location categoriesbased on the nature of the recorded activity code, using guidancefrom Hoehne et al.23 The location categoriesinclude indoor home, indoor away , outdoor home,outdoor away, and vehicle. The time–activity profiles of ATUSrespondents from each respective city were then assigned to each syntheticresident based on common attributes between the two datasets, includingage, sex, occupation, and income. In assigning time–activityprofiles to synthetic residents of each city, we drew randomly fromthe ATUS respondents who were assigned to the same combination ofage, sex, occupation, and income categories. IETs for each hour werecalculated for each synthetic person as the proportion of time spentin each of the five environmental conditions  multiplied by the temperaturein each of the respective environment and then summed for each hourof the day.Individual time–activitypatterns were derived from theAmerican Time Use Survey (ATUS), conducted annually by the U.S. Bureauof Labor.24 Building-interior temperaturesduring the Power On scenario are responsive to the type (or absence)of air conditioning system assigned to each structure. For structureswith central AC systems, we assumed a constant set-point temperatureof 24 °C during Power On conditions.7Building-interior temperatures were simulated inresponse to ambientheat wave conditions for two sets of electrical grid scenarios forthe same 5 day heat wave period: (1) the grid is assumed to be fullyoperational (Power On) and (2) the grid is assumed to be fully nonoperational(Power Off) across the municipal extent of each city. For the PowerOn scenario, we made use of a mechanical air conditioning prevalencemodel to estimate the probability that central air conditioning, partialair conditioning (window AC units), or no mechanical air conditioningis available within each residential structure. Requiring as inputparcel tax records reporting the home value, owner-occupied status,housing age, and housing structure type, combined with data on cooling-degreedays within each city, AC prevalence was estimated with a regressionmodel found in prior work to predict the presence of central or partialAC systems at the parcel level with a model accuracy of 84 and 82%,respectively.25 In prior work, we found the median duration of recent U.S.blackout events impacting 1 million customers or more to be approx.120 h, consistent with the large-scale events simulated herein.8 During blackout conditions, building-interiortemperatures are responsive to localized outdoor temperatures andthe specific characteristics of the building prototype . For all residential structure types, windows are assumedto be opened at any time during concurrent heat wave and blackoutconditions that ambient ventilation would have the effect of loweringindoor temperatures. Under the Power Off scenario, all residents ofeach city were assumed to remain in their residential structures (theindoor home location) due to the assumed inoperability of transportationsystems and blackout conditions at the workplace.For all scenarios in which the electrical grid is nonoperational,we assume 48 h of complete blackout conditions for every residentialstructure across the three cities and then restore power over theremaining 72 h of the heat wave based on the proximity of each structureto electrical grid substations. Electrical power is assumed to berestored to residential structures most proximate to these substationnodes first, with structures more distant from these nodes assigneda lower temporal priority in power restoration.Figure S1.IET is estimatedfor each synthetic resident based on daily time–activitypatterns, simulated outdoor and building-interior temperatures associatedwith each activity, and outdoor and building-interior temperaturesassociated with variable heat exposure scenarios. Each exposure scenariois detailed in We estimated the probabilityof heat-related mortality or morbidity for each resident during the5 day heat wave and in response to each of the scenario conditionspresented in 26 for a 10 day period, including five consecutivedays of historic heat wave conditions and five subsequent days notcharacterized by heat wave conditions. We make use of airport weatherstation data to match the meteorological data used in the derivationof RR for emergency department visits in Atlanta and Phoenix and mostcommonly used to derive RR for heat-associated mortality.Step 1: Hourly outdoor temperatures from the nearest airport weatherstation in each city were downloaded from the Integrated Surface DatabaseStep2: For both the extreme heat and nonextreme heat days, averagedaily IETs were joined with average daily airport temperatures foreach resident by day .T′) or the inflated temperature corresponding to blackout IETvalues, for these building type and demographic combinations. To doso, a mixed effect linear regression was fit to model IET as a functionof outdoor airport temperature and building characteristics, age,sex, income, and occupation as followsX is a vector of individual characteristics.Step 3. We then used the derived IET-outdoortemperature associationsfor unique combinations of building type, age, sex, income, and occupationto estimate “analog” outdoor temperature  visits are only available for two of ourthree study cities: Atlanta27 and Phoenix.17 Details on each of these exposure-response functionsare provided in Step 4. We next substituted 28 and cause-specific ED visits.29 The attributable fractions, derived from thenonextreme heat relative risks (RRs) for each person-day, were thenmultiplied by the total daily burdens. This estimated the fractionalburdens for each person-day on a nonextreme heat day.Step 5. The total daily burdens were calculated asthe productof the age/sex/race category population and the category-specificincidence rate obtained for each health outcome: mean daily all-natural-causemortalityStep 6.For the extreme heat days in each city, the heat-attributableburdens were subtracted from the total daily burden to derive the“baseline health burden” or non-heat-associated burdenfor each age/sex/race category.Figure S2). As a final step, we sum the heat-attributableburdens over the 5 day heat wave to estimate the total risk of heat-relatedmortality or morbidity. Estimated aggregate risks are limited to amaximum of 1 per person.Step 7. The extreme heat daysin our study were unusually high-temperatureevents and may therefore have resulted in mortality and morbiditybeyond the annual rates observed in the total health burden data.Therefore, rather than using the attributable fractions from step5, which assume that the attributable burdens were fractions of observedtotal burdens, we multiplied the extreme-heat-event RRs by the baselineburdens from step 6 to estimate the extreme-heat-event-attributableburdens for each person-day. Thus, the baseline burdens from step6 allow estimated attributable burden to exceed the observed historicaltotal burden for each city during simulated heat wave conditions with an operationalelectrical grid (Power On scenario) is 0.5 in Atlanta ,15 in Detroit , and 1.3 in Phoenix   to more than doublethe estimated rate of heat mortality in Atlanta and Detroit, wheremaximum outdoor and building-interior temperatures reach about 35°C in the late afternoon and remain above a daily minimum temperatureof 25 °C (Atlanta) or 22 °C (Detroit). In Phoenix, wherethe lowest daily high temperature over the 5 day heat wave is 43 °Cand daily minimum temperatures average 32 °C, the rate of heat-relatedmortality increases by about 700% relative to the Power On scenario,reflecting the extremity of heat exposures in a desert city in theabsence of mechanical AC. As reported in 30Heat management strategies in the form of street trees and coolroofing measurably reduce heat-related mortality across the threecities, particularly in Phoenix. An increase from present-day treecanopy shading of roadways to an average of 50% across all streetsis found to reduce the estimated rate of heat mortality by 14 and19% in Atlanta and Detroit, respectively, and by 27% in Phoenix. Inresponse to the installation of highly reflective cool roofs for allbuilding types citywide, the rate of heat-related mortality fallsby 21% in Atlanta, 23% in Detroit, and 66% in Phoenix. We attributethe disproportionate benefits of cool roofing in Phoenix to the extremityof temperatures during heat wave conditions, during which rates ofevapotranspiration from trees may be reduced, lessening the coolingeffects of tree canopy.Projectedwarming by middle (∼2055) and late (∼2085)century under the RCP 8.5 global emissions trajectory further amplifiesestimated heat-related mortality, particularly by late century. Inresponse to a mid-century heat wave of comparable intensity to thehistorical event modeled in the base period, the rate of heat-relatedmortality increases by 50% in Atlanta, 58% in Detroit, and 19% inPhoenix relative to the base period. By late century, the rate ofheat-related mortality increases by 93%, 281%, and 104% in Atlanta,Detroit, and Phoenix, respectively. Relative to population size, whichremains fixed at present-year levels for the future warming scenarios,the rate of heat mortality in Phoenix from a concurrent heat waveand blackout event is projected to exceed 1% of the total modeledpopulation in mid-century and approach 2% of the population by latecentury.27 Employing the same analog temperature approach used to estimateheat-related mortality, we estimate the number of ED visits in responseto our six scenarios in The estimated number of ED visits resulting from a5 day heat wavesubstantially increases in response to simulated blackout conditions.Based on health surveillance data recording daily emergency departmentvisits for heat-related conditions, exposure-response functions havebeen derived to associate daily ED visits with temperature changein two of our three study cities: Atlanta and Phoenix.Citywide urban heat management strategies reduceheat-related morbidityassociated with a concurrent heat wave and blackout event in bothcities. An expansion of street trees to 50% shading over roadwaysreduces the rate of ED visits by almost 70% in Atlanta and 8% in Phoenix.The conversion of all building roofs to cool materials reduces therate of ED visits by 80% in Atlanta and 15% in Phoenix.Accountingfor more intense heat waves in future years, a concurrentheat wave and blackout event by mid-century increases the ED visitrate in Atlanta approx. 7-fold to more than 20,000 per 100,000 population.The ED visit rate in Phoenix increases by 7% over the base year PowerOff scenario. By late century, the fraction of the urban populationrequiring emergency medical services from the simulated compound climateand infrastructure failure event is estimated as more than 40% inAtlanta and 68% in Phoenix.32 Our measure of IET,accounting for individual-level heat exposures responsive to localizedoutdoor and indoor climates, provides a more accurate metric of individualheat exposure than the use of single, stationary outdoor temperaturesensors at regional weather stations. While the substitution of IETin exposure-response functions does not result in elevated estimatesof heat wave mortality or morbidity relative to prior studies whenelectrical grids are assumed to be operational,34 the simulated loss of mechanical AC for residents with access toAC systems greatly elevates indoor heat exposures, serving in turnto elevate the analog temperatures used herein to estimate healthimpacts. Simulated blackout conditions for a historical 5 day heatwave more than doubled the rate of heat mortality in Atlanta and Detroitand increased the rate of heat mortality in Phoenix—where averageheat wave temperatures exceed 37 °C—to almost 1% of thetotal urban population.We estimate a magnitude of health risksassociated with a compoundclimate and infrastructure failure event across the three large U.S.cities that is well in excess of prior work focused on extreme heatevents in urbanized areas.The more pronounced risk of heat mortalityand morbidity in Phoenixrelative to Atlanta and Detroit can be attributed both to the highertemperatures experienced during an extreme heat wave event and a disproportionateimpact of blackout conditions for cities with a high AC prevalence.Ambient heat wave temperatures in Phoenix reach a maximum intensity9–10 °C greater than daily high temperatures in Atlantaor Detroit, while minimum temperatures only fall to 32 °C, sustaininghigh heat exposures over a full 24 h period for successive days. Inaddition to more intense heat wave conditions for residents of Phoenix,the loss of electrical power produces a disproportionately greatershift in individual heat exposures than estimated for residents ofAtlanta or Detroit. Reported in 36 Representing approx. 1.6% of the estimated total unhoused population,this estimate of the heat-mortality rate among a population lackingregular access to shelter or mechanical air conditioning falls withinthe same order of magnitude of what we estimate to result from a concurrentheat wave and blackout event for the full Phoenix population (∼1%).An important limitation of this reference dataset for the Phoenixpopulation, however, is the surveillance period, which is reflectiveof a full warm season as opposed to a single, intense heat wave event.In addition, differences in the baseline health and acclimatizationto extreme heat between these two populations may yield differentoutcomes.While none of the cities included in the study has experienceda concurrent heat wave and blackout event of the intensity and durationmodeled herein, recent surveillance data focused on the unhoused populationin Phoenix find a heat-mortality rate comparable to that estimatedto result from a citywide compound climate and infrastructure failureevent. The Maricopa County Public Health Agency, which serves morethan 90% of the Phoenix metropolitan population, reported 130 heat-relateddeaths among an unhoused population of approx. 8200 during 2021 ora heat-mortality rate of 1580 per 100,000.Our estimates do not account for individuals’behavioraladaptations or the actions of first responders during such a severeheat crisis. In reality, if a blackout event was regionally localized,many individuals would be able to leave their homes and travel tocooler locations. We also do not account for potential governmentalresponses to a concurrent heat wave and blackout, such as evacuationof the most vulnerable to heat illness or the deployment of mobilepower generators for cooling centers. Other important sources of uncertaintyin our analysis include (1) the degree to which measures of relativerisk based on outdoor temperatures are reflective of indoor heat exposures,(2) uncertainties in the precision of the ambient and indoor temperaturemodels used for the study, (3) uncertainties in behaviors and locationsof individuals throughout the day and hence their daily IETs, and(4) uncertainties in the exposure-response functions in the appliedepidemiology studies (including the changing nature of populationsusceptibility with a period of prolonged heat exposure).37 Phoenix has less than3000 emergency department beds38). Importantly,the exposure-response functions used in this study reflect heat morbidityrates during historical surveillance periods in which regional electricalgrids are fully or largely operational. The inability of regionalemergency medical systems to treat widespread heat illness duringperiods of electrical system inoperability due to the large numberof residents requiring medical care may indicate that a higher rateof heat mortality than estimated by our approach would result.Theselimiting assumptions notwithstanding our results suggestthat the extent of heat morbidity in Atlanta and Phoenix resultingfrom a concurrent heat wave and blackout event carries the potentialto overwhelm regional emergency medical systems. With almost threepercent of the urban population in Atlanta estimated to require emergencymedical care and more than half of the Phoenix population, the capacityof regional emergency departments to effectively treat heat illnesswould be exceeded in both cities  pedestrians and thus may underestimate the full benefits of thisstrategy.Conventional urban heat managementstrategies, including an enhancementof citywide street tree canopy and the use of high albedo roofingmaterials, potentially carry significant benefits for lessening heatrisk during concurrent heat wave and blackout events. Across the threestudy cities, street trees lessened heat-related mortality by an averageof 20%, while cool roofing could lessen heat-related mortality byan average of 37%. Both strategies also were highly effective at reducingestimated heat morbidity in Atlanta and Phoenix, with the modeledincrease in street trees and cool roofing associated with an averagereduction in ED visits of 39 and 48%, respectively. While we did notsimulate the effects of both enhanced street tree area and cool roofingsimultaneously, other studies have found the combination of thesestrategies to yield a marginally lower cooling effect than the sumof these two strategies modeled independently.44 illustrating the potential to achieve this level of canopy coverover streets in a highly urbanized environment. Likewise, we set roofalbedo values at levels presently achievable with commercially availableproducts for both commercial and residential roofs. We believe theheat management targets set in this study are ambitious but physicallyattainable over time in each of the study cities, albeit with differinglevels of investment needed in supporting infrastructure and morepronounced constraints on water resources for irrigation in Phoenix.We assume an extent of tree canopy shading over roadwaysthat exceedspresent canopy extents in each of the study cities but likely wouldbe achievable over time for all but the largest roadways. While citywidedata on street tree coverage over roadways are not available for Atlanta,Detroit, or Phoenix, data for Chicago, as an example, find streetsto be shaded by an average of 35% when measured at the Census blockgroup level, with 14% of all block groups found presently to havetree shading of roadways at 50% or greater,45 In this study, we findthe health impact of a multiday electrical grid failure event duringheat wave conditions, and in the absence of cooling interventions,to be substantially greater than the estimated levels of heat mortalityand morbidity associated with a heat wave alone. We further find thisamplifying effect of infrastructure failure on health outcomes torise rapidly by middle to late century, as heat wave intensities exceedhistorical levels. Widespread physical changes to the built environmentof cities, enhancing evapotranspiration, shading, and solar reflection,carry the potential to measurably reduce estimated levels of heatillness and death.A rising potential for compound climate and infrastructure failureevents in large cities of the U.S. highlights a pronounced vulnerabilityof urban populations confronting more extreme heat in all regionsof the country.


Total anomalous pulmonary venous connection (TAPVC) is a rare congenital cardiovascular malformation in which all four pulmonary veins anomalously drain into the right atrium (RA) either directly or indirectly. There are four main types based on the site of connection. Any type of TAPVC may be associated with obstruction and presents early in the neonatal period with cyanosis, tachycardia, or respiratory distress. We present four cases of all types of TAPVC and its imaging findings in multidetector computed tomography (MDCT) angiography. Cardiac CT and magnetic resonance imaging (MRI) are very useful in delineating the anatomy and drainage pathway of anomalous pulmonary veins. MDCT angiography is noninvasive and easily available, and rapid image acquisition is possible with high spatial resolution. Since early diagnosis and surgical correction are necessary for the survival of these neonates, rapid image acquisition using MDCT angiography can be preferred over MRI. Total anomalous pulmonary venous connection (TAPVC) is an uncommon congenital cardiovascular malformation in which all four pulmonary veins fail to drain into the left atrium and anomalously drain into the right atrium (RA) or to any of the systemic veins either directly or indirectly . The incIn the evaluation of TAPVC, chest radiography, echocardiography, catheter angiography, multidetector computed tomography (MDCT) angiography, and magnetic resonance imaging (MRI) are useful. Due to recent advances in technology, MDCT angiography has become a reliable and noninvasive tool for diagnosing and planning treatment for pulmonary vein anomalies .We report MDCT angiography findings of four cases of TAPVC: supracardiac type, cardiac type, mixed type (supracardiac and intracardiac), and a rare form of infracardiac type of TAPVC draining into the portal vein.Cardiac CT procedureAll patients were imaged using a 128-slice MDCT  in our institution. Patients were adequately sedated, if needed, and positioned in a caudocranial position with arms above the head, and electrocardiogram (ECG) leads were appropriately connected. The retrospectively gated non-contrast phase was done with as small field of view (FOV) as possible. Intravenous nonionic iodinated contrast medium was then administered (iohexol (Contrapaque) 300 mg) using a dual-head power injector at a flow rate of 1-1.5 mL/second for children and 5 mL/second for adults and a volume calculated as (delay + scan time) × flow rate (not more than 600 mg I/kg body weight). CARE Dose 4D  allowed for further minimization of radiation dose while maintaining adequate resolution for anatomical delineation. Images were analyzed in a cardiac CT post-processing workstation using Syngo.via version VB60A_HF01 , which generates multiplanar reconstruction (MPR) and volume rendering technique (VRT) images for additional aid.Case 1A two-year-and-six-month-old child with an unremarkable birth history had recurrent episodes of upper respiratory tract infection. On examination, she was found to have a systolic murmur. Chest radiograph findings were mild cardiomegaly with widened superior mediastinum Figure . EchocarCase 2A 30-year-old male patient, who was diagnosed with congenital heart disease 15 years ago, has been under medical management and has presented with complaints of shortness of breath for three days. On examination, the patient had central cyanosis, a generalized constant murmur, and coarse inspiratory crepitations in bilateral lung fields. A chest radiograph showed cardiomegaly with pulmonary plethora. Echocardiography findings were suspicious for intracardiac TAPVC and ASD. CT pulmonary angiography revealed all four dilated pulmonary veins forming a confluence Figure  and draiCase 3A two-month-old child presented to the emergency department with tachypnea, hypotension, and mild cyanosis. The child had a generalized constant heart murmur, slight pulmonary rales, and mild hepatomegaly on examination. A chest and abdominal radiograph showed non-homogeneous opacities in the right upper lung zone, with prominent pulmonary vasculature, an apparently normal cardiac silhouette, and an enlarged liver shadow, as seen in Figure Case 4A one-month-old child presented with respiratory distress, poor feeding, and lethargy. The child had bradycardia and hypokalemia and was mechanically ventilated in view of desaturation. Echocardiography showed two pulmonary veins draining into a dilated coronary sinus with OS-ASD and grossly dilated right-sided cavities. Cardiac CT revealed the right upper and bilateral lower pulmonary veins forming a confluence and draining into the coronary sinus Figure . The lefTotal anomalous pulmonary venous return (TAPVR), also known as total anomalous pulmonary venous connection, represents 1%-5% of cardiovascular congenital anomalies . This tyEmbryology of pulmonary veinsThe pulmonary buds develop from the foregut and are initially surrounded by the splanchnic plexus. This plexus drains into the systemic venous system, specifically the cardinal and umbilical vitelline veins. During gestation at 27-29 days, the primitive left atrium gives rise to the primitive common pulmonary vein. This vein connects to the lungs and establishes connections with the pulmonary portion of the splanchnic plexus, forming the pulmonary plexus. The pulmonary venous plexus becomes disconnected from the systemic circulation by detaching from the splanchnic plexus. Four individual pulmonary veins, two on each side, develop and drain to the common pulmonary vein. The four pulmonary vessels eventually drain into the left atrium through an orifice located on the posterior wall . The perTAPVC is classified into four categories based on the sites where the abnormal connection occurs , namely,The supracardiac type is the most common type, accounting for 45%-55% of TAPVC cases. In this type, the confluent vessel usually empties into the innominate vein or the right or left superior vena cava ,11 as inThe cardiac type is the second common type presenting in 20%-30% of cases. It is diagnosed when the pulmonary veins converge to form a common vessel and then horizontally connect to the right atrium (RA) via the coronary sinus (CS) Figure , 4B or aThe infracardiac type is the third most common type. The pulmonary veins join to form a vertical vessel that travels caudally through the esophageal hiatus and drains into the IVC, portal vein, hepatic veins, or ductus venosus. This type accounts for 13%-25% of cases. In case 3, the vertical vein is seen draining into the portal vein as seen in Figure The mixed type is the least common type with less than 10% of the cases, in which the right and left pulmonary tributaries drain at two or more different levels ,12. In oClinical manifestationPatients' presenting complaints vary depending on the severity of the obstruction and the resistance of the pulmonary vessels. In case of severe obstruction, neonates present within the first 12 hours of life with manifestations such as dyspnea, tachypnea, tachycardia, hypoxemia, and metabolic acidosis. It is necessary to perform surgical correction within the first few days of life for neonates to survive . PatientInvestigationsThe details of the anatomy and drainage of the pulmonary veins are essential for proper preoperative planning . Chest rCatheter angiography has been considered the gold standard for diagnosis, but it is an invasive and expensive method that requires hospitalization . It doesManagementAccurate diagnosis is crucial for effective treatment, which typically involves surgical intervention. Improvements in diagnostic imaging have resulted in the accurate depiction of this complex entity, and advanced surgical techniques have decreased postoperative mortality rates . The maiTable We have briefly described the embryology and imaging presentation of all four types of TAPVC with case illustration. Both MRI and cardiac CT angiography can provide precise anatomy and drainage details of pulmonary veins, which is essential for preoperative planning, especially in mixed and infracardiac types of TAPVC. Cardiac CT is noninvasive and easily available and allows rapid image acquisition for evaluating critically ill neonates and infants.


This paper presents a study on the temperature dependent photo-elastic coefficient in single-crystal silicon with (100) and (110) orientations at a wavelength of 1550 nm. The measurement of the photo-elastic coefficient was performed using a polarimetric scheme across a wide temperature range from 5 to 300 K. The experimental setup employed high-sensitivity techniques and incorporated automatic beam path correction, ensuring precise and accurate determination of the coefficient’s values. The results show excellent agreement with previous measurements at room temperature, specifically yielding a value of  While its indirect band gap of approximately 1.12 eV renders it unsuitable for visible spectrum applications due to high interband absorption, it exhibits low optical absorption in the near-infrared band beyond 1200 nm, making it highly advantageous for high-power applications. The prevalence of powerful and stable lasers operating at 1550 nm in fiber-optic communication further positions silicon as a favorable choice for optical components. Moreover, its low mechanical loss at cryogenic temperatures8 suggests its applicability in low thermal noise experiments such as gravitational wave detectors10 and laser frequency stabilization cavities12 and micro-scale optomechanical systems in the quantum regime. For these applications, the photoelasticity of silicon is a curse and blessing at the same time. High photoelastic coefficients typically go along with large optomechanical couplings. That can be exploited in measurement systems employing, for example, micro-scale oscillators13.Silicon is widely recognized for its extensive use as an optical material in both macroscopic and microscopic optomechanical applications17. To address these limitations, cooling the optical components to cryogenic temperatures presents a potential solution to mitigate both birefringence and photo-elastic noise.Additionally, however, statistical temperature fluctuations in optical components result in refractive index changes and subsequent phase fluctuations due to the influence of the photo-elastic coefficient. This phenomenon, known as photo-elastic noise, plays a critical role in limiting the sensitivity of high-precision opto-mechanical measurements such as future gravitational wave detectors as the Einstein Telescope or Cosmic Explorer15. The substantial mass of these components induce significant mechanical stresses, which, in turn, generate a refractive index profile through the photoelastic coefficient In addition, applications involving massive optical components and high laser powers often encounter challenges associated with photo-elastic effects18, despite the majority of potential applications operating or being proposed for operation at temperatures below that threshold 16, concerns arise regarding the photoelastic behavior of key optical interferometer components. The acquired data has now unlocked the potential for novel optimizations in the blueprint of the detector. Furthermore, the influence of photoelasticity on ongoing laser stabilization cavities could constitute a notable noise source14. For this application, the available material will also lay the foundation for future enhancements and improvements of measurement sensitivity.Recent investigations into the role of photoelasticity within the proposed gravitational wave detector, the Einstein Telescope, suggest challenges in meeting the specified requirements, even at room temperatureThe acquired data holds the potential to intricately inform the development of pioneering optomechanical experiments and components established on cryogenic silicon platforms. Significantly, the material parameters unveiled in this study provide a granular understanding, enabling the meticulous incorporation of photoelastic coupling—one of the foremost optomechanical coupling mechanisms—into the blueprinting of upcoming innovations.Supplementary Information.