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Progress of All-inorganic Cesium Lead-free Perovskite Solar Cells
Get PDFMetal halide-based perovskite solar cells (PSCs) have developed rapidly due to exceptional optoelectronic properties of perovskite materials (such as high optical absorption coefficient, long charge carrier lifetime, long diffusion length, high carrier mobility and tunable bandgaps) and low-cost fabrication processes. The record power conversion efficiency has exceeded 24%, demonstrating the great potential for photovoltaic application. However, the lead toxicity and instability still present as major obstacles for commercialization. In principle, Pb can be replaced with other less-toxic as well as environmentally benign metals, such as Ag, Na, Sn, Ge, Bi, Sb and Ti, to solve the toxicity issue. Replacing methylammonium (MA(+)) or formamidinium (FA(+)) with cesium (Cs+) represents a promising direction to address the instability issue. Herein, we review the recent progress of all-inorganic cesium lead-free halide PSCs. At the end, we outline challenges and future directions.journal articl
The Role of Ventral Tegmental Area and Nucleus Accumbens in the Kamin Blocking Effect
Get PDFOkinawa Institute of Science and Technology Graduate UniversityDoctor of PhilosophyThe overall aim of the research described in this thesis is to identify neural substrates underlying the Kamin blocking effect. This phenomenon is crucial for understanding of the neural mechanisms of associative learning. Kamin blocking refers to the finding that conditioned responding to a cue is attenuated when it is paired with a reinforcer in the presence of another cue which has previously been conditioned using that reinforcer. The blocking effect suggests that associative learning is driven by prediction errors, and is not based purely on temporal contiguity between events. In the context of appetitive classical conditioning, recent evidence suggests that the ventral tegmental area and the nucleus accumbens play a role in computing reward prediction error. The current study shows that blocking inhibition in the ventral tegmental area or inactivating the nucleus accumbens neurons during compound cue conditioning attenuates Kamin blocking. Inactivating the nucleus accumbens during single cue conditioning also attenuates Kamin blocking. Taken together, these findings suggest that inhibition in the ventral tegmental area, inhibitory output from the nucleus accumbens, and learning in the nucleus accumbens play crucial roles in the Kamin blocking effect. Previous studies show that dopamine transients track the theoretical reward prediction error during appetitive classical conditioning, and the reduction in the dopamine response evoked by the reward when it is expected has been suggested to play a role in the Kamin blocking effect. In support of this hypothesis, the current study also found that goal tracking rats, in which expected rewards have previously been shown to evoke a robust dopamine response, did not express the Kamin blocking effect. Conversely, sign trackers, in which expected rewards evoke a diminished dopamine response, expressed the blocking effect. These findings are discussed in relation to psychological theory of learning and the possible underlying neural mechanisms.doctoral thesi
Cholinergic interneurons in striatal microcircuit dynamics studied with anatomical and behavioral methods
Get PDFOkinawa Institute of Science and Technology Graduate UniversityDoctor of PhilosophyBasal ganglia (BG) refer to a group of nuclei in the brain’s subcortical regions. They are associated with cerebral cortex, thalamus and brainstem structures that perform many functions including motor control, procedural learning and memory. The largest nucleus of the BG is striatum that has two major neuronal cell types: medium spiny neurons and interneurons. This thesis focuses on one class of interneurons containing choline acetyltransferase (ChAT), the cholinergic interneurons (ChIs). This thesis investigated the role of ChIs in striatal microcircuit dynamics by anatomical and behavior approaches. ChIs participate in voluntary motor control, associated in learning, procedural memory, action selection, planning and execution of movement, through strong cholinergic inputs to other striatal neurons. However, the basic anatomical properties of ChIs after targeted lesion is poorly understood, though others have studied the behavioral consequences of toxin injection. The immunotoxin ribosome inactivating protein (saporin, sap) physically linked to choline acetyltransferase (ChAT-sap) selectively damaged striatal ChIs in toxin-treated mice monitored at 2, 4 and 6 weeks after application of the toxin. Systematic random cell counting, reach-to-grasp behavior task and open field test (OFT) was used to explore anatomical and behavioral differences in animals where the ChIs were destroyed in dorsolateral striatum (DLS). The thesis analyses yielded an unexpected outcome of specific ChIs lesion in DLS where vesicular acetylcholine transporter (vAChT) positive terminal numbers increased while the numbers of neurons themselves were reduced. The increase in vAChT positive terminals might derive from compensatory axonal sprouting from surviving ChIs, or from afferent axonal terminal fields of cholinergic mesopontine neurons. But the source was not further investigated in this study. In addition, thestudy showed the decreased number of ChIs in injection site with no recovery after 2, 4, and 6 weeks’ time in this study. The thesis also reports the effect of a selective depletion of ChIs from the DLS in a reach-to-grasp task. The mean percentage of successful grasps for the last 6 training sessions was almost half of the value for intact control, and sham operated mice. These results indicate that striatal depletion of ChIs impairs success rate, learning, motor skills in the reach-to-grasp task was observed. These results suggest that the participation of ChIs in striatal mediated motor learning impacts the function of the whole striatal microcircuitry. The lack of ChIs also altered rearing behavior (total number and duration), travelled distance and speed of movement in an open field. In addition, the results are consistent with an important participation of acetylcholine in striatal mediated behaviors possibly by their significant innervation from motor cortex.doctoral thesi
Flow of wormlike micellar solutions around microfluidic cylinders with high aspect ratio and low blockage ratio
Get PDFWe employ time-resolved flow velocimetry and birefringence imaging methods to study the flow of a well-characterized shear-banding wormlike micellar solution around a novel glass-fabricated microfluidic circular cylinder. In contrast with typical microfluidic cylinders, our geometry is characterized by a high aspect ratio alpha = H/W = 5 and a low blockage ratio beta = 2r/W = 0.1, where H and W are the channel height and width, and the cylinder radius r = 20 mum. The small cylinder radius allows access up to very high Weissenberg numbers 1.9 </= Wi = lambdaMU/r </= 3750 (where lambdaM is the Maxwell relaxation time) while inertial effects remain entirely negligible (Reynolds number, Re < 10-4). At low Wi values, the flow remains steady and symmetric and a birefringent region (indicating micellar alignment and tensile stress) develops downstream of the cylinder. Above a critical value Wic approximately 60 the flow transitions to a steady asymmetric state, characterized as a supercritical pitchfork bifurcation, in which the fluid takes a preferential path around one side of the cylinder. At a second critical value Wic2 approximately 130, the flow becomes time-dependent, with a characteristic frequency f0 approximately 1/lambdaM. This initial transition to time dependence has characteristics of a subcritical Hopf bifurcation. Power spectra of the measured fluctuations become complex as Wi is increased further, showing a gradual slowing down of the dynamics and emergence of harmonics. A final transition at very high Wic3 corresponds to the re-emergence of a single peak in the power spectrum but at much higher frequency. We discuss this in terms of possible flow-induced breakage of micelles into shorter species with a faster relaxation time.journal articl
Rapid task-dependent tuning of the mouse olfactory bulb
Get PDFAdapting neural representation to rapidly changing behavioural demands is a key challenge for the nervous system. Here, we demonstrate that the output of the primary olfactory area of the mouse, the olfactory bulb, is already a target of dynamic and reproducible modulation. The modulation depends on the stimulus tuning of a given neuron, making olfactory responses more discriminable through selective amplification in a demand-specific way.journal articl
De novo transcription of multiple Hox cluster genes takes place simultaneously in early Xenopus tropicalis embryos
Get PDFhox genes are found as clusters in the genome in most bilaterians. The order of genes in the cluster is supposed to be correlated with the site of expression along the anterior-posterior body axis and the timing of expression during development, and these correlations are called spatial and temporal collinearity, respectively. Here we studied the expression dynamics of all hox genes of the diploid species Xenopus tropicalis in four Hox clusters (A-D) by analyzing high-temporal-resolution RNA-seq databases and the results showed that temporal collinearity is not supported, which is consistent with our previous data from allotetraploid X enopus laevis Because the temporal collinearity hypothesis implicitly assumes the collinear order of gene activation, not mRNA accumulation, we determined for the first time the timing of when new transcripts of hox genes are produced, by detecting pre-spliced RNA in whole embryos with reverse transcription and quantitative PCR (RT-qPCR) for all hoxa genes as well as several selected hoxb, hox c and hoxd genes. Our analyses showed that, coinciding with the RNA-seq results, hoxa genes started to be transcribed in a non-sequential order, and found that multiple genes start expression almost simultaneously or more posterior genes could be expressed earlier than anterior ones. This tendency was also found in hoxb and hoxc genes. These results suggest that temporal collinearity of hox genes is not held during early development of Xenopus.journal articl
GenoDup Pipeline: a tool to detect genome duplication using the dS-based method
Get PDFUnderstanding whole genome duplication (WGD), or polyploidy, is fundamental to investigating the origin and diversification of organisms in evolutionary biology. The wealth of genomic data generated by next generation sequencing (NGS) has resulted in an urgent need for handy and accurate tools to detect WGD. Here, I present a useful and user-friendly pipeline called GenoDup for inferring WGD using the dS-based method. I have successfully applied GenoDup to identify WGD in empirical data from both plants and animals. The GenoDup Pipeline provides a reliable and useful tool to infer WGD from NGS data.journal articl
Possible observation of quantum spin-nematic phase in a frustrated magnet
Get PDFWater freezes into ice in winter and evaporates into vapor in summer. Scientifically, the transformations between solid, liquid, and gas are called phase transitions and can be classified through the changes in symmetry which occur in each case. A fourth phase of matter was discovered late in the 19th century: the liquid crystal nematic, in which rod- or disk-shaped molecules align like the atoms in a solid, while continuing to flow like a liquid. Here we report thermodynamic evidence of a quantum analog of the classical nematic phase, the quantum spin nematic (SN). In an SN, the spins of a quantum magnet select a common axis, like a nematic liquid crystal, while escaping conventional magnetic order. Our state-ofthe-art thermal measurements in high pulsed magnetic fields up to 33 T on the copper mineral volborthite with spin 1/2 on a frustrated lattice provide thermodynamic evidence for SN order, half a century after the theoretical proposal [Blume M, Hsieh YY (1969) J Appl Phys 40:1249; Andreev AF, Grishchuk IA (1984) J Exp Theor Phys 97:467-475].journal articl
High‐resolution archaellum structure reveals a conserved metal‐binding site
Get PDFMany archaea swim by means of archaella. While the archaellum is similar in function to its bacterial counterpart, its structure, composition, and evolution are fundamentally different. Archaella are related to archaeal and bacterial type IV pili. Despite recent advances, our understanding of molecular processes governing archaellum assembly and stability is still incomplete. Here, we determine the structures of Methanococcus archaella by X-ray crystallography and cryo-EM. The crystal structure of Methanocaldococcus jannaschii FlaB1 is the first and only crystal structure of any archaellin to date at a resolution of 1.5 angstrom, which is put into biological context by a cryo-EM reconstruction from Methanococcus maripaludis archaella at 4 angstrom resolution created with helical single-particle analysis. Our results indicate that the archaellum is predominantly composed of FlaB1. We identify N-linked glycosylation by cryo-EM and mass spectrometry. The crystal structure reveals a highly conserved metal-binding site, which is validated by mass spectrometry and electron energy-loss spectroscopy. We show invitro that the metal-binding site, which appears to be a widespread property of archaellin, is required for filament integrity.journal articl
Negligible‐Pb‐Waste and Upscalable Perovskite Deposition Technology for High‐Operational‐Stability Perovskite Solar Modules
Get PDFAn upscalable perovskite film deposition method combining raster ultrasonic spray coating and chemical vapor deposition is reported. This method overcomes the coating size limitation of the existing stationary spray, single‐pass spray, and spin‐coating methods. In contrast with the spin‐coating method (>90% Pb waste), negligible Pb waste during PbI2 deposition makes this method more environmentally friendly. Outstanding film uniformity across the entire area of 5 cm × 5 cm is confirmed by both large‐area compatible characterization methods (electroluminescence and scattered light imaging) and local characterization methods (atomic force microscopy, scanning electron microscopy, photoluminescence mapping, UV–vis, and X‐ray diffraction measurements on multiple sample locations), resulting in low solar cell performance decrease upon increasing device area. With the FAPb(I0.85Br0.15)3 (FA = formamidinium) perovskite layer deposited by this method, champion solar modules show a power conversion efficiency of 14.7% on an active area of 12.0 cm2 and an outstanding shelf stability (only 3.6% relative power conversion efficiency decay after 3600 h aging). Under continuous operation (1 sun light illumination, maximum power point condition, dry N2 atmosphere with <5% relative humidity, no encapsulation), the devices show high light‐soaking stability corresponding to an average T80 lifetime of 535 h on the small‐area solar cells and 388 h on the solar module.journal articl