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Intramolecular Mannich and Michael Annulation Reactions of Lactam Derivatives Bearing Enals To Afford Bicyclic N-Heterocycles
Get PDFAcid-catalyzed intramolecular vinylogous Mannich reactions and intramolecular Michael reactions affording pyrrolizinone-fused N-heterocycles from hydroxylactam derivatives bearing enals have been developed. Depending on the substituent on the hydroxylactam, the enal moiety acted either as a nucleophile (i.e., as an enol/enolate) or as an electrophile to react with the N-acyliminium ion or enamide generated from the hydroxylactam moiety, respectively. The reactions were demonstrated in the construction of fused N-heterocycles with 5- to 8-membered rings.journal articl
Determination of Carrier Diffusion Length Using Transient Electron Photoemission Microscopy in the GaAs/InSe Heterojunction
Get PDFCarrier diffusion length and lifetime parameters for electron transport at nanoscale semiconductor slabs have been fitted using a 1D model and the decay data extracted from transient photoemission electron microscopy. Meanwhile, a conventional photoluminescence quenching measurement needs two separate samples with an active material between blocking and quenching layers to characterize the carrier transport properties. In this work, only one few-layer monocrystalline sample of gamma-InSe containing different thicknesses of active material is used to obtain a common diffusion coefficient consistent with previously reported values for vertical carrier diffusion in layered InSe.journal articl
Direct Metal‐Free Chemical Vapor Deposition of Graphene Films on Insulating Substrates for Micro‐Supercapacitors with High Volumetric Capacitance
Get PDFDirect, metal‐free synthesis of graphene films on insulating substrates in a controlled manner is of great importance for applications in (opto)electronic and energy storage devices. Graphene films are fabricated on fused silica substrates without metal catalyst via chemical vapor deposition (CVD), using propionic acid as a carbon source. Film‐thickness is readily adjustable between 5 and 45 nm by changing the deposition time and flow rate of the precursor, displaying sheet resistance in the range of 0.27–1.86 kΩ□−1. The resulting graphene films are directly integrated into micro‐supercapacitors without film transfer or liquid‐phase processing, and demonstrate ultrahigh operation rates up to 1000 V s−1. Moreover, these films exhibit excellent rate capabilities, achieving a high volumetric capacitance of 131 F cm−3 at 10 mV s−1.journal articl
Characteristic cerebral structural changes identified using voxel-based morphometry in patients with post-surgical chronic myelopathic pain
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Cryo-EM Structures of Centromeric Tri-nucleosomes Containing a Central CENP-A Nucleosome
Get PDFThe histone H3 variant CENP-A is a crucial epigenetic marker for centromere specification. CENP-A forms a characteristic nucleosome and dictates the higher-order configuration of centromeric chromatin. However, little is known about how the CENP-A nucleosome affects the architecture of centromeric chromatin. In this study, we reconstituted tri-nucleosomes mimicking a centromeric nucleosome arrangement containing the CENP-A nucleosome, and determined their 3D structures by cryoelectron microscopy. The H3-CENP-A-H3 tri-nucleosomes adopt an untwisted architecture, with an outward-facing linker DNA path between nucleosomes. This is distinct from the H3-H3-H3 tri-nucleosome architecture, with an inward-facing DNA path. Intriguingly, the untwisted architecture may allow the CENP-A nucleosome to be exposed to the solvent in the condensed chromatin model. These results provide a structural basis for understanding the 3D configuration of CENP-A-containing chromatin, and may explain how centromeric proteins can specifically target the CENP-A nucleosomes buried in robust amounts of H3 nucleosomes in centromeres.journal articl
Postnatal liver functional maturation requires Cnot complex-mediated decay of mRNAs encoding cell cycle and immature liver genes
Get PDFLiver development involves dramatic gene expression changes mediated by transcriptional and post-transcriptional control. Here, we show that the Cnot deadenylase complex plays a crucial role in liver functional maturation. The Cnot3 gene encodes an essential subunit of the Cnot complex. Mice lacking Cnot3 in liver have reduced body and liver masses, and they display anemia and severe liver damage. Histological analyses indicate that Cnot3-deficient (Cnot3(-/-) ) hepatocytes are irregular in size and morphology, resulting in formation of abnormal sinusoids. We observe hepatocyte death, increased abundance of mitotic and mononucleate hepatocytes, and inflammation. Cnot3(-/-) livers show increased expression of immune response-related, cell cycle-regulating and immature liver genes, while many genes relevant to liver functions, such as oxidation-reduction, lipid metabolism and mitochondrial function, decrease, indicating impaired liver functional maturation. Highly expressed mRNAs possess elongated poly(A) tails and are stabilized in Cnot3(-/-) livers, concomitant with an increase of the proteins they encode. In contrast, transcription of liver function-related mRNAs was lower in Cnot3(-/-) livers. We detect efficient suppression of Cnot3 protein postnatally, demonstrating the crucial contribution of mRNA decay to postnatal liver functional maturation.journal articl
The Effect of Decomposed PbI2 on Microscopic Mechanisms of Scattering in CH3NH3PbI3 Films
Get PDFHybrid organic-inorganic perovskites (HOIPs) exhibit long electronic carrier diffusion length, high optical absorption coefficient, and impressive photovoltaic device performance. At the core of any optoelectronic device lie the charge transport properties, especially the microscopic mechanism of scattering, which must efficiently affect the device function. In this work, CH3NH3PbI3 (MAPbI(3)) films were fabricated by a vapor solution reaction method. Temperature-dependent Hall measurements were introduced to investigate the scattering mechanism in MAPbI(3) films. Two kinds of temperature-mobility behaviors were identified in different thermal treatment MAPbI(3) films, indicating different scattering mechanisms during the charge transport process in films. We found that the scattering mechanisms in MAPbI(3) films were mainly influenced by the decomposed PbI2 components, which could be easily generated at the perovskite grain boundaries (GBs) by releasing the organic species after annealing at a proper temperature. The passivation effects of PbI2 in MAPbI(3) films were investigated and further discussed with emphasis on the scattering mechanism in the charge transport process.journal articl
A hybrid de novo genome assembly of the honeybee, Apis mellifera, with chromosome-length scaffolds
Get PDFBackground: The ability to generate long sequencing reads and access long-range linkage information is revolutionizing the quality and completeness of genome assemblies. Here we use a hybrid approach that combines data from four genome sequencing and mapping technologies to generate a new genome assembly of the honeybee Apis mellifera. We first generated contigs based on PacBio sequencing libraries, which were then merged with linked-read 10x Chromium data followed by scaffolding using a BioNano optical genome map and a Hi-C chromatin interaction map, complemented by a genetic linkage map.
Results: Each of the assembly steps reduced the number of gaps and incorporated a substantial amount of additional sequence into scaffolds. The new assembly (Amel_HAv3) is significantly more contiguous and complete than the previous one (Amel_4.5), based mainly on Sanger sequencing reads. N50 of contigs is 120-fold higher (5.381 Mbp compared to 0.053 Mbp) and we anchor >98% of the sequence to chromosomes. All of the 16 chromosomes are represented as single scaffolds with an average of three sequence gaps per chromosome. The improvements are largely due to the inclusion of repetitive sequence that was unplaced in previous assemblies. In particular, our assembly is highly contiguous across centromeres and telomeres and includes hundreds of AvaI and AluI repeats associated with these features.
Conclusions: The improved assembly will be of utility for refining gene models, studying genome function, mapping functional genetic variation, identification of structural variants, and comparative genomics.journal articl
Simple, narrow, and robust atomic frequency reference at 993 nm exploiting the rubidium (Rb) 5S1/2 to 6S1/2 transition using one-color two-photon excitation
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Secondary flows of viscoelastic fluids in serpentine microchannels
Get PDFSecondary flows are ubiquitous in channel flows, where small velocity components perpendicular to the main velocity appear due to the complexity of the channel geometry and/or that of the flow itself such as from inertial or non-Newtonian effects. We investigate here the inertialess secondary flow of viscoelastic fluids in curved microchannels of rectangular cross-section and constant but alternating curvature: the so-called “serpentine channel” geometry. Numerical calculations (Poole et al. J Non-Newton Fluid Mech 201:10–16, 2013) have shown that in this geometry, in the absence of elastic instabilities, a steady secondary flow develops that takes the shape of two counter-rotating vortices in the plane of the channel cross-section. We present the first experimental visualization evidence and characterisation of these steady secondary flows, using the complementary techniques of quantitative microparticle image velocimetry in the centreplane of the channel, and confocal visualisation of dye-stream transport in the cross-sectional plane. We show that the measured streamlines and the relative velocity magnitude of the secondary flows are in qualitative agreement with the numerical results. In addition to our techniques being broadly applicable to the characterisation of three-dimensional flow structures in microchannels, our results are important for understanding the onset of instability in serpentine viscoelastic flows.journal articl