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Extreme heat poses significant threats to human life and ecosystems. Quantifying the effects of anthropogenic climate change on extreme heat has remained challenging, in part due to the short observational record. Here, we isolate the most slowly varying component of the frequency at which the historical 90th and 99th percentiles were exceeded in observational records from 1955 to 2021 by using a statistical method called low‐frequency component analysis. The emerging spatiotemporal signal in the changing frequency of temperature extremes can be attributed to a shift of the temperature distribution by local warming of the annual‐mean daily maximum temperature. The shift explains over 80% of the interannual variability in the frequency at which the historical 90th percentile is exceeded in the tropics and up to 50% in higher latitudes. This work connects variability in the frequency of extreme surface temperatures to variability in mean local warming. Plain Language Summary Over the past few decades, regions across the globe have experienced substantial increases in surface temperature extremes, posing significant threats to human life, as well as critical agriculture and energy sectors. Due to the relatively short observational record, it has been difficult to disentangle the relative roles of natural variability and anthropogenic forcing in driving changes to temperature extremes. Here, we introduce a simple framework for understanding the increasing frequency of surface temperature extremes by employing a statistical method to isolate the most slowly changing, and hence most likely anthropogenic, component of surface temperature extremes. We find that the emerging signal in the changing frequency of temperature extremes is largely driven by a shift in the temperature distribution by mean local warming. The shift explains over 80% of the observed variability in exceeding the 90th percentile in the tropics and up to 50% in higher latitudes. It also explains why changes in the frequency of extremes appear to be more rapid than changes closer to the center of the temperature distribution. This work offers guidance for climate risk assessment and adaptation strategies by connecting variability in the frequency of extreme temperatures to variability in mean warming at a given location. Key Points Shifting the surface temperature distribution by mean local warming explains much of the frequency increase in observed temperature extremes Mean local warming explains 80% of the observed variability in 90th percentile exceedance in the tropics and up to 50% in higher latitudes Narrower temperature distributions in the tropics are associated with a larger increase in extreme heat frequency compared to midlatitudes

Calcium imaging with protein-based indicators 1 , 2 is widely used to follow neural activity in intact nervous systems, but current protein sensors report neural activity at timescales much slower than electrical signalling and are limited by trade-offs between sensitivity and kinetics. Here we used large-scale screening and structure-guided mutagenesis to develop and optimize several fast and sensitive GCaMP-type indicators 3 – 8 . The resulting ‘jGCaMP8’ sensors, based on the calcium-binding protein calmodulin and a fragment of endothelial nitric oxide synthase, have ultra-fast kinetics (half-rise times of 2 ms) and the highest sensitivity for neural activity reported for a protein-based calcium sensor. jGCaMP8 sensors will allow tracking of large populations of neurons on timescales relevant to neural computation. Using large-scale screening and structure-guided mutagenesis, fast and sensitive GCaMP sensors are developed and optimized with improved kinetics without compromising sensitivity or brightness.

Calcium imaging with genetically encoded calcium indicators (GECIs) is routinely used to measure neural activity in intact nervous systems. GECIs are frequently used in one of two different modes: to track activity in large populations of neuronal cell bodies, or to follow dynamics in subcellular compartments such as axons, dendrites and individual synaptic compartments. Despite major advances, calcium imaging is still limited by the biophysical properties of existing GECIs, including affinity, signal-to-noise ratio, rise and decay kinetics and dynamic range. Using structure-guided mutagenesis and neuron-based screening, we optimized the green fluorescent protein-based GECI GCaMP6 for different modes of in vivo imaging. The resulting jGCaMP7 sensors provide improved detection of individual spikes (jGCaMP7s,f), imaging in neurites and neuropil (jGCaMP7b), and may allow tracking larger populations of neurons using two-photon (jGCaMP7s,f) or wide-field (jGCaMP7c) imaging.

Guidelines for fine-tuning spectral and chemical properties of fluorophore are introduced, resulting in four new Janelia Fluor dyes, JF 503 , JF 525 , JF 585 and JF 635 , that span the visible region and align well with standard laser lines. Pushing the frontier of fluorescence microscopy requires the design of enhanced fluorophores with finely tuned properties. We recently discovered that incorporation of four-membered azetidine rings into classic fluorophore structures elicits substantial increases in brightness and photostability, resulting in the Janelia Fluor (JF) series of dyes. We refined and extended this strategy, finding that incorporation of 3-substituted azetidine groups allows rational tuning of the spectral and chemical properties of rhodamine dyes with unprecedented precision. This strategy allowed us to establish principles for fine-tuning the properties of fluorophores and to develop a palette of new fluorescent and fluorogenic labels with excitation ranging from blue to the far-red. Our results demonstrate the versatility of these new dyes in cells, tissues and animals.

Expanding the palette of fluorescent dyes is vital to push the frontier of biological imaging. Although rhodamine dyes remain the premier type of small-molecule fluorophore owing to their bioavailability and brightness, variants excited with far-red or near-infrared light suffer from poor performance due to their propensity to adopt a lipophilic, nonfluorescent form. We report a framework for rationalizing rhodamine behavior in biological environments and a general chemical modification for rhodamines that optimizes long-wavelength variants and enables facile functionalization with different chemical groups. This strategy yields red-shifted ‘Janelia Fluor’ (JF) dyes useful for biological imaging experiments in cells and in vivo. A general tuning strategy is introduced for improving the utility of rhodamines for biological imaging applications. The strategy yielded bright, versatile and bioavailable far-red and near-infrared ‘Janelia Fluor’ dyes.

A simple and general chemical structure change to a panel of cell-permeable small-molecule fluorophores increases their brightness and photostability, which will enable improved single-molecule studies and super-resolution imaging. Specific labeling of biomolecules with bright fluorophores is the keystone of fluorescence microscopy. Genetically encoded self-labeling tag proteins can be coupled to synthetic dyes inside living cells, resulting in brighter reporters than fluorescent proteins. Intracellular labeling using these techniques requires cell-permeable fluorescent ligands, however, limiting utility to a small number of classic fluorophores. Here we describe a simple structural modification that improves the brightness and photostability of dyes while preserving spectral properties and cell permeability. Inspired by molecular modeling, we replaced the N , N -dimethylamino substituents in tetramethylrhodamine with four-membered azetidine rings. This addition of two carbon atoms doubles the quantum efficiency and improves the photon yield of the dye in applications ranging from in vitro single-molecule measurements to super-resolution imaging. The novel substitution is generalizable, yielding a palette of chemical dyes with improved quantum efficiencies that spans the UV and visible range.

Genetically encoded voltage indicators (GEVIs) enable monitoring of neuronal activity at high spatial and temporal resolution. However, the utility of existing GEVIs has been limited by the brightness and photostability of fluorescent proteins and rhodopsins. We engineered a GEVI, called Voltron, that uses bright and photostable synthetic dyes instead of protein-based fluorophores, thereby extending the number of neurons imaged simultaneously in vivo by a factor of 10 and enabling imaging for significantly longer durations relative to existing GEVIs. We used Voltron for in vivo voltage imaging in mice, zebrafish, and fruit flies. In the mouse cortex, Voltron allowed single-trial recording of spikes and subthreshold voltage signals from dozens of neurons simultaneously over a 15-minute period of continuous imaging. In larval zebrafish, Voltron enabled the precise correlation of spike timing with behavior.

The fluorescent glutamate indicator iGluSnFR enables imaging of neurotransmission with genetic and molecular specificity. However, existing iGluSnFR variants exhibit low in vivo signal-to-noise ratios, saturating activation kinetics and exclusion from postsynaptic densities. Using a multiassay screen in bacteria, soluble protein and cultured neurons, we generated variants with improved signal-to-noise ratios and kinetics. We developed surface display constructs that improve iGluSnFR’s nanoscopic localization to postsynapses. The resulting indicator iGluSnFR3 exhibits rapid nonsaturating activation kinetics and reports synaptic glutamate release with decreased saturation and increased specificity versus extrasynaptic signals in cultured neurons. Simultaneous imaging and electrophysiology at individual boutons in mouse visual cortex showed that iGluSnFR3 transients report single action potentials with high specificity. In vibrissal sensory cortex layer 4, we used iGluSnFR3 to characterize distinct patterns of touch-evoked feedforward input from thalamocortical boutons and both feedforward and recurrent input onto L4 cortical neuron dendritic spines. iGluSnFR variants with improved signal-to-noise ratios and targeting to postsynaptic sites have been developed, enabling the analysis of glutamatergic neurotransmission in vivo as illustrated in the mouse visual and somatosensory cortex.

Genome-wide epigenetic marks regulate gene expression, but the amount and function of variability in these marks are poorly understood. Working with human-derived samples, Onuchic et al. examined disease-associated genetic variation and sequence-dependent allele-specific methylation at gene regulatory loci. Regulatory sequences within individual chromosomal DNA molecules showed full or no methylation at specific sites corresponding to “on” and “off” switches. Interestingly, methylation did not occur on each DNA molecule, resulting in a variable fraction of methylated chromosomes. This stochastic type of gene regulation was more common for rare genetic variants, which may suggest a role in human disease. Science , this issue p. eaar3146 Genome-wide analyses of epigenetic markers in human cells identify allele-specific functions that affect gene expression in health and disease. To assess the impact of genetic variation in regulatory loci on human health, we constructed a high-resolution map of allelic imbalances in DNA methylation, histone marks, and gene transcription in 71 epigenomes from 36 distinct cell and tissue types from 13 donors. Deep whole-genome bisulfite sequencing of 49 methylomes revealed sequence-dependent CpG methylation imbalances at thousands of heterozygous regulatory loci. Such loci are enriched for stochastic switching, which is defined as random transitions between fully methylated and unmethylated states of DNA. The methylation imbalances at thousands of loci are explainable by different relative frequencies of the methylated and unmethylated states for the two alleles. Further analyses provided a unifying model that links sequence-dependent allelic imbalances of the epigenome, stochastic switching at gene regulatory loci, and disease-associated genetic variation.

Sugarcane bagasse is generated in huge quantities worldwide which can be converted into high-end valuable products. A major portion of bagasse is converted into Sugarcane Bagasse Ash (SCBA) by burning it at a high temperature in industries. Proper utilization of SCBA instead of landfilling can reduce the harmful environmental effects. In this paper, application of bagasse ash as a green adsorbent for the removal of Fuchsin Basic (FB) dye was investigated. SCBA was characterized using XRD, FTIR, SEM-EDS, BET for insights into its properties. Parameters like contact time, pH, temperature, initial concentration and adsorbent dosage were varied and their impact on dye removal was studied. A maximum removal around 78% (for 10 mg/L dye concentration, 3 g/L adsorbent dosage, 7 pH, 60 min and 25 °C) was achieved using SCBA. Adsorption equilibrium was investigated and Langmuir model fitted best (q max = 9.1706 mg/g and k l = 0.1690 L/mg, R 2  = 0.9939) as compared to Freundlich and Temkin models. Additionally, kinetics studies revealed that Pseudo second order (R 2  = 0.9998) was superior over other kinetic models. Thermodynamic study confirmed the endothermic adsorption of FB on SCBA and FB removal of 50% was observed even after four cycles indicating reusability of adsorbent after regeneration. Use of SCBA directly as adsorbent without excessive pretreatment promises to be an attractive option.