Atomic Evolution Mechanism and Suppression of Edge Threading Dislocations in Nitride Remote Heteroepitaxy.

The majority of dislocations in nitride epilayers are edge threading dislocations (TDs), which diminish the performance of nitride devices. However, it is extremely difficult to reduce the edge TDs due to the lack of available slip systems. Here, we systematically investigate the formation mechanism of edge TDs and find that besides originating at the coalescence boundaries, these dislocations are also closely related to geometrical misfit dislocations at the interface. Based on this understanding, we propose a novel strategy to reduce the edge TD density of the GaN epilayer by nearly 1 order of magnitude via graphene-assisted remote heteroepitaxy. The first-principles calculations confirm that the insertion of graphene dramatically reduces the energy barrier required for interfacial sliding, which promotes a new strain release channel. This work provides a unique approach to directly suppress the formation of edge TDs at the source, thereby facilitating the enhanced performance of photoelectronic and electronic devices.

ß-Ga2O3 Air-Channel Field-Emission Nanodiode with Ultrahigh Current Density and Low Turn-On Voltage.

Field-emission nanodiodes with air-gap channels based on single ß-Ga2O3 nanowires have been investigated in this work. With a gap of ∼50 nm and an asymmetric device structure, the proposed nanodiode achieves good diode characteristics through field emission in air at room temperature. Measurement results show that the nanodiode exhibits an ultrahigh emission current density, a high enhancement factor of >2300, and a low turn-on voltage of 0.46 V. More impressively, the emission current almost keeps constant over a wide range (8 orders of magnitude) of air pressures below 1 atm. Meanwhile, the fluctuation in field-emission current is below 8.7% during long-time monitoring, which is better than the best reported field-emission device based on ß-Ga2O3 nanostructures. All of these results indicate that ß-Ga2O3 air-gapped nanodiodes are promising candidates for vacuum electronics that can also operate in air.

Interferons are key cytokines acting on pancreatic islets in type 1 diabetes.

AIMS/HYPOTHESIS: The proinflammatory cytokines IFN-α, IFN-γ, IL-1ß and TNF-α may contribute to innate and adaptive immune responses during insulitis in type 1 diabetes and therefore represent attractive therapeutic targets to protect beta cells. However, the specific role of each of these cytokines individually on pancreatic beta cells remains unknown. METHODS: We used deep RNA-seq analysis, followed by extensive confirmation experiments based on reverse transcription-quantitative PCR (RT-qPCR), western blot, histology and use of siRNAs, to characterise the response of human pancreatic beta cells to each cytokine individually and compared the signatures obtained with those present in islets of individuals affected by type 1 diabetes. RESULTS: IFN-α and IFN-γ had a greater impact on the beta cell transcriptome when compared with IL-1ß and TNF-α. The IFN-induced gene signatures have a strong correlation with those observed in beta cells from individuals with type 1 diabetes, and the level of expression of specific IFN-stimulated genes is positively correlated with proteins present in islets of these individuals, regulating beta cell responses to 'danger signals' such as viral infections. Zinc finger NFX1-type containing 1 (ZNFX1), a double-stranded RNA sensor, was identified as highly induced by IFNs and shown to play a key role in the antiviral response in beta cells. CONCLUSIONS/INTERPRETATION: These data suggest that IFN-α and IFN-γ are key cytokines at the islet level in human type 1 diabetes, contributing to the triggering and amplification of autoimmunity.

RNAi-Mediated Suppression of OsBBTI5 Promotes Salt Stress Tolerance in Rice.

This study explores the impact of RNAi in terms of selectively inhibiting the expression of the OsBBTI5 gene, with the primary objective of uncovering its involvement in the molecular mechanisms associated with salt tolerance in rice. OsBBTI5, belonging to the Bowman-Birk inhibitor (BBI) family gene, is known for its involvement in plant stress responses. The gene was successfully cloned from rice, exhibiting transcriptional self-activation in yeast. A yeast two-hybrid assay confirmed its specific binding to OsAPX2 (an ascorbate peroxidase gene). Transgenic OsBBTI5-RNAi plants displayed insensitivity to varying concentrations of 24-epibrassinolide in the brassinosteroid sensitivity assay. However, they showed reduced root and plant height at high concentrations (10 and 100 µM) of GA3 immersion. Enzyme activity assays revealed increased peroxidase (POD) and superoxide dismutase (SOD) activities and decreased malondialdehyde (MDA) content under 40-60 mM NaCl. Transcriptomic analysis indicated a significant upregulation of photosynthesis-related genes in transgenic plants under salt stress compared to the wild type. Notably, this study provides novel insights, suggesting that the BBI gene is part of the BR signaling pathway, and that OsBBTI5 potentially enhances stress tolerance in transgenic plants through interaction with the salt stress-related gene OsAPX2.

The power of TOPMed imputation for the discovery of Latino-enriched rare variants associated with type 2 diabetes.

AIMS/HYPOTHESIS: The Latino population has been systematically underrepresented in large-scale genetic analyses, and previous studies have relied on the imputation of ungenotyped variants based on the 1000 Genomes (1000G) imputation panel, which results in suboptimal capture of low-frequency or Latino-enriched variants. The National Heart, Lung, and Blood Institute (NHLBI) Trans-Omics for Precision Medicine (TOPMed) released the largest multi-ancestry genotype reference panel representing a unique opportunity to analyse rare genetic variations in the Latino population. We hypothesise that a more comprehensive analysis of low/rare variation using the TOPMed panel would improve our knowledge of the genetics of type 2 diabetes in the Latino population. METHODS: We evaluated the TOPMed imputation performance using genotyping array and whole-exome sequence data in six Latino cohorts. To evaluate the ability of TOPMed imputation to increase the number of identified loci, we performed a Latino type 2 diabetes genome-wide association study (GWAS) meta-analysis in 8150 individuals with type 2 diabetes and 10,735 control individuals and replicated the results in six additional cohorts including whole-genome sequence data from the All of Us cohort. RESULTS: Compared with imputation with 1000G, the TOPMed panel improved the identification of rare and low-frequency variants. We identified 26 genome-wide significant signals including a novel variant (minor allele frequency 1.7%; OR 1.37, p=3.4 × 10-9). A Latino-tailored polygenic score constructed from our data and GWAS data from East Asian and European populations improved the prediction accuracy in a Latino target dataset, explaining up to 7.6% of the type 2 diabetes risk variance. CONCLUSIONS/INTERPRETATION: Our results demonstrate the utility of TOPMed imputation for identifying low-frequency variants in understudied populations, leading to the discovery of novel disease associations and the improvement of polygenic scores. DATA AVAILABILITY: Full summary statistics are available through the Common Metabolic Diseases Knowledge Portal ( https://t2d.hugeamp.org/downloads.html ) and through the GWAS catalog ( https://www.ebi.ac.uk/gwas/ , accession ID: GCST90255648). Polygenic score (PS) weights for each ancestry are available via the PGS catalog ( https://www.pgscatalog.org , publication ID: PGP000445, scores IDs: PGS003443, PGS003444 and PGS003445).

Unlocking the Potential of Carbon Quantum Dots for Cell Imaging, Intracellular Localization, and Gene Expression Control in Arabidopsis thaliana (L.) Heynh.

Utilizing carbon quantum dots (CQDs) as biomaterials for delivering small substances has gained significant attention in recent research. However, the interactions and mechanisms of action of CQDs on plants have received relatively little focus. Herein, we investigated the transportation of CQDs into various organs of Arabidopsis thaliana (L.) Heynh. via the vessel system, leading to the epigenetic inheritance of Argonaute family genes. Our findings reveal that CQDs may interact with microRNAs (miRNAs), leading to the repression of post-transcriptional regulation of target genes in the cytoplasm. Transcriptome and quantitative PCR analyses demonstrated consistent gene expression levels in offspring. Moreover, microscopic observations illustrated rapid CQD localization on cell membranes and nuclei, with increased nuclear entry at higher concentrations. Notably, our study identified an alternative regulatory microRNA, microRNA172D, for the Argonaute family genes through methylation analysis, shedding light on the connection between CQDs and microRNAs.

Fast and High-Efficiency Synthesis of Capsanthin in Pepper by Transient Expression of Geminivirus.

The color of the chili fruit is an important factor that determines the quality of the chili, as red chilies are more popular among consumers. The accumulation of capsanthin is the main cause of reddening of the chili fruit. Capsanthin is an important metabolite in carotenoid metabolism, and its production level is closely linked to the expression of the genes for capsanthin/capsorubin synthase (CCS) and carotenoid hydroxylase (CrtZ). We reported for the first time that the synthesis of capsanthin in chili was enhanced by using a geminivirus (Bean Yellow Dwarf Virus). By expressing heterologous ß-carotenoid hydroxylase (CrtZ) and ß-carotenoid ketolase (CrtW) using codon optimization, the transcription level of the CCS gene and endogenous CrtZ was directly increased. This leads to the accumulation of a huge amount of capsanthin in a very short period of time. Our results provide a platform for the rapid enhancement of endogenous CCS activity and capsanthin production using geminivirus in plants.

Atomic-Scale Mechanism of Spontaneous Polarity Inversion in AlN on Nonpolar Sapphire Substrate Grown by MOCVD.

The performance of nitride devices is strongly affected by their polarity. Understanding the polarity determination and evolution mechanism of polar wurtzite nitrides on nonpolar substrates is therefore critically important. This work confirms that the polarity of AlN on sapphire prepared by metal-organic chemical vapor deposition is not inherited from the nitrides/sapphire interface as widely accepted, instead, experiences a spontaneous polarity inversion during the growth. It is found that at the initial growth stage, the interface favors the nitrogen-polarity, rather than the widely accepted metal-polarity or randomly coexisting. However, the polarity subsequently converts into the metal-polar situation, at first locally then expanding into the whole area, driven by the anisotropy of surface energies, which results in universally existing inherent inverse grain boundaries. Furthermore, vertical two-dimensional electron accumulation originating from the lattice symmetry breaking at the inverse grain boundary is first revealed. This work identifies another cause of high-density defects in nitride epilayers, besides lattice mismatch induced dislocations. These findings also offer new insights into atomic structure and determination mechanism of polarity in nitrides, providing clues for its manipulation toward the novel hetero-polarity devices.

Continuous Single-Crystalline GaN Film Grown on WS2 -Glass Wafer.

Use of 2D materials as buffer layers has prospects in nitride epitaxy on symmetry mismatched substrates. However, the control of lattice arrangement via 2D materials at the heterointerface presents certain challenges. In this study, the epitaxy of single-crystalline GaN film on WS2 -glass wafer is successfully performed by using the strong polarity of WS2 buffer layer and its perfectly matching lattice geometry with GaN. Furthermore, this study reveals that the first interfacial nitrogen layer plays a crucial role in the well-constructed interface by sharing electrons with both Ga and S atoms, enabling the single-crystalline stress-free GaN, as well as a violet light-emitting diode. This study paves a way for the heterogeneous integration of semiconductors and creates opportunities to break through the design and performance limitations, which are induced by substrate restriction, of the devices.

Heterogeneously integrated InGaN-based green microdisk light-emitters on Si (100).

Heterogeneous integration of nitrides on Si (100) is expected to open the door to the new possibilities for this material system in the fields of high-speed integrated photonics and information processing. In this work, GaN epitaxial layer grown on the patterned sapphire substrate is transferred onto Si (100) by a combination of wafer bonding, laser lift-off and chemical mechanical polishing (CMP) processes. The GaN epilayer transferred is uniformly thinned down to 800 nm with a root mean square surface roughness as low as 2.33 Å. The residual stress within the InGaN quantum wells transferred is mitigated by 79.4% after the CMP process. Accordingly, its emission wavelength exhibits a blue shift of 8.8 nm, revealing an alleviated quantum-confined Stark effect. Based on this platform, an array of microcavities with diverse geometrics and sizes are fabricated, by which optically-pumped green lasing at ∼505.8 nm is achieved with a linewidth of ∼0.48 nm from ∼12 µm microdisks. A spontaneous emission coupling factor of around 10-4 is roughly estimated based on the light output characteristics with increasing the pumping densities. Lasing behaviors beyond the threshold suggest that the microdisk suffers less thermal effects as compared to its undercut counterparts. The electrically-injected microdisks are also fabricated, with a turn-on voltage of ∼2.0 V and a leakage current as low as ∼2.4 pA at -5 V. Being compatible with traditional semiconductor processing techniques, this work provides a feasible solution to fabricate large-area heterogeneously integrated optoelectronic devices based on nitrides.

Transparent dual-band ultraviolet photodetector based on graphene/p-GaN/AlGaN heterojunction.

Versatile applications have driven a desire for dual-band detection that enables seeing objects in multiple wavebands through a single photodetector. In this paper, a concept of using graphene/p-GaN Schottky heterojunction on top of a regular AlGaN-based p-i-n mesa photodiode is reported for achieving solar-/visible-blind dual-band (275 nm and 365 nm) ultraviolet photodetector with high performance. The highly transparent graphene in the front side and the polished sapphire substrate at the back side allows both top illumination and back illumination for the dual band detection. A system limit dark current of 1×10-9 A/cm2 at a negative bias voltage up to -10 V has been achieved, while the maximum detectivity obtained from the detection wavebands of interests at 275 nm and 365 nm are ∼ 9.0 ×1012 cm·Hz1/2/W at -7.5 V and ∼8.0 × 1011 cm·Hz1/2/W at +10 V, respectively. Interestingly, this new type of photodetector is dual-functional, capable of working as either photodiode or photoconductor, when switched by simply adjusting the regimes of bias voltage applied on the devices. By selecting proper bias, the device operation mode would switch between a high-speed photodiode and a high-gain photoconductor. The device exhibits a minimum rise time of ∼210 µs when working as a photodiode and a maximum responsivity of 300 A/W at 6 µW/cm2 when working as a photoconductor. This dual band and multi-functional design would greatly extend the utility of detectors based on nitrides.

Graphene-Nanorod Enhanced Quasi-Van Der Waals Epitaxy for High Indium Composition Nitride Films.

The nitride films with high indium (In) composition play a crucial role in the fabrication of In-rich InGaN-based optoelectronic devices. However, a major limitation is In incorporation requiring a low temperature during growth at the expense of nitride dissociation. Here, to overcome this limitation, a strain-modulated growth method, namely the graphene (Gr)-nanorod (NR) enhanced quasi-van der Waals epitaxy, is proposed to increase the In composition in InGaN alloy. The lattice transparency of Gr enables constraint of in-plane orientation of nitride film and epitaxial relationships at the heterointerface. The Gr interlayer together with NRs buffer layer substantially reduces the stress of the GaN film by 74.4%, from 0.9 to 0.23 GPa, and thus increases the In incorporation by 30.7%. The first principles calculations confirm that the release of strain accounts for the dramatic improvement. The photoluminescence peak of multiple quantum wells shifts from 461 to 497 nm and the functionally small-sized cyan light-emitting diodes of 7 × 9 mil2 are demonstrated. These findings provide an efficient approach for the growth of In-rich InGaN film and extend the applications of nitrides in advanced optoelectronic, photovoltaic, and thermoelectric devices.

Alteration of the gut microbiota in rhesus monkey with spontaneous osteoarthritis.

BACKGROUND: The spontaneous osteoarthritis (OA) in rhesus macaque is similar to OA in human, which maintains an upright body posture and shows very similar biomechanical properties of bones to humans. At present, there is no good treatment for OA. This study aims to explore relationship between OA and intestinal microbiota, and provide a reference for the treatment of clinical OA. RESULTS: We collected colonic contents of the 20 rhesus macaque (6-15 years old, female) for intestinal microbiota analysis by metagenomics sequencing, of which 10 were spontaneous OA monkeys and 10 were normal monkeys. Our results showed the diversity of gut microbiota in monkeys with OA was decreased compared to the normal monkeys (p = 0.16). Mollicutes, Tenericutes, Coprobacillus and Faecalitalea may be biomarkers for the monkeys of OA. Lactobacillus found significantly increased in OA monkeys. Prevotella and Ruminococcus were higher in the normal group than OA group. Zinc/manganese transport system permease protein (p = 0.0011) and Cyclopropane-fatty-acyl-phospholipid synthase (p = 0.0012) are a microbiota metabolic pathway related to cartilage production. CONCLUSIONS: Our results indicate that the diversity and composition of intestinal microbiota in monkeys with OA are different compared to the normal monkeys. we have found microbes that may be a biomarker for the diagnosis of osteoarthritis. Functional analysis of the microbiota also predicts cartilage damage in the monkeys with osteoarthritis. Non-human primates are closely related to humans, so this study can provide a reference for the development of drugs for the treatment of OA.

Effects of remote sediment phosphor plates on high power laser-based white light sources.

Phosphor-converted blue laser diodes are regarded as the next-generation high-brightness solid-state lighting sources. However, it is difficult to obtain white light with high angular color uniformity due to the Gaussian distribution of the laser light sources. Meanwhile, laser excitation power density of the light source is high, which would bring serious heating effects to the phosphor layers. In this study, a strategy has been proposed to solve the problem by using remote sediment phosphor plates. In detail, we have compared the effects of remote sediment/non-sediment phosphor plates to the phosphor-converted blue laser diodes on the overall light output characteristics, angular optical distribution properties, as well as their thermal performance. The emission from sediment phosphor samples has been found more divergent, and angular deviation in the correlated color temperature of the emitted light could be greatly reduced from 1486 to 294 K, yet with only 5% luminous flux loss, as compared to non-sediment phosphor samples. Most importantly, the sediment phosphor sample pushes the power damage threshold up to 588.1 W/cm2 (non-sediment sample: 512.3 W/cm2). Our work has demonstrated the sediment phosphor plates would ameliorate the angular color uniformity for the laser-based lighting source, while extending its lifespan with improved thermal stability.

Circularly polarized light emission from a GaN micro-LED integrated with functional metasurfaces for 3D display.

This Letter proposes a circularly polarized (CP) light GaN micro-LED which is integrated with functional metasurfaces. The one-dimensional metallic nanograting can achieve a high transverse electric (TE) reflectivity (${{\rm{R}}_{\rm{TE}}}$) and extinction ratio (ER) of TE and transverse magnetic (TM) waves, which is highly polarized output for micro-LEDs. Besides, the nanograting, which is integrated on the bottom of the GaN layer, can also support a resonant cavity, together with the top distributed Bragg reflector, which can shape the radiation pattern. By optimizing the structure parameters of nanograting, the ${{\rm{R}}_{\rm{TE}}}$ achieves over 80%, and the ER reaches higher than 38 dB at 450 nm for the GaN micro-LED. Additionally, the metasurface, which acts as a quarter-wave plate, was investigated to control the phase delay between the polarization state of the electric wave in two orthogonal components. Finally, the circular shape of the transmitted pattern denotes the high performance of the metasurface which is integrated in the micro-LED for CP light emission. The work reported in this Letter might provide potential application in a 3D polarized light display.

Understanding homoepitaxial growth of horizontal kinked GaN nanowires.

Epitaxial horizontal nanowires (NWs) have attracted much attention due to their easily large-scale integration. From the reported literature, epitaxial growth is usually driven by minimization of strain between NW and substrate, which governs the growth along with specific crystallographic orientation. Here, we report the first homoepitaxial growth of horizontal GaN NWs from a surface-directed vapor-liquid-solid growth method. The NWs grow along with six symmetry-equivalent 〈1-100〉 (m-axis) directions, exhibiting a random 60°/120° kinked configuration. Owing to homoepitaxial growth, strain could be eliminated. From the obtained results, we suggest that the formation the horizontal NWs, and their growth direction /orientation is not directly related to the strain minimization. A general rule based on the epitaxial relationship and potential low-index growth orientation is proposed for understanding the arrangement of epitaxial horizontal NWs. It is deduced that kinking of the horizontal NWs was attributed to unintentional guided growth determined by the roughness of the substrates' surface. This study provides an insight for a better understanding of the evolution of epitaxial horizontal NWs, especially for the growth direction/orientation.

Multiplexing multifoci optical metasurfaces for information encoding in the ultraviolet spectrum.

Recently, optical metasurfaces have attracted much attention due to their versatile features in manipulating phase, polarization, and amplitude of both reflected and transmitted light. Because it controls over four degrees of freedom: phase, polarization, amplitude, and wavelength of light wavefronts, optical cryptography is a promising technology in information security. So far, information encoding can be implemented by the metasurface in one-dimensional (1D) mode (either wavelength or polarization) and in a two-dimensional (2D) mode of both wavelength and polarization. Here, we demonstrate multiplexing multifoci optical metasurfaces for information encoding in the ultraviolet spectrum both in the 1D and 2D modes in the spatial zone, composed of high-aspect-ratio aluminum nitride nanorods, which introduce discontinuous phases through the Pancharatnam-Berry phase to realize multifoci in the spatial zone. Since the multiplexed multifocal optical metasurfaces are sensitive to the helicity of the incident light and the wavelength is within the ultraviolet spectrum, the security of the information encrypted by it would be guaranteed.

Combined transcriptome and proteome profiling of the pancreatic ß-cell response to palmitate unveils key pathways of ß-cell lipotoxicity.

BACKGROUND: Prolonged exposure to elevated free fatty acids induces ß-cell failure (lipotoxicity) and contributes to the pathogenesis of type 2 diabetes. In vitro exposure of ß-cells to the saturated free fatty acid palmitate is a valuable model of lipotoxicity, reproducing features of ß-cell failure observed in type 2 diabetes. In order to map the ß-cell response to lipotoxicity, we combined RNA-sequencing of palmitate-treated human islets with iTRAQ proteomics of insulin-secreting INS-1E cells following a time course exposure to palmitate. RESULTS: Crossing transcriptome and proteome of palmitate-treated ß-cells revealed 85 upregulated and 122 downregulated genes at both transcript and protein level. Pathway analysis identified lipid metabolism, oxidative stress, amino-acid metabolism and cell cycle pathways among the most enriched palmitate-modified pathways. Palmitate induced gene expression changes compatible with increased free fatty acid mitochondrial import and ß-oxidation, decreased lipogenesis and modified cholesterol transport. Palmitate modified genes regulating endoplasmic reticulum (ER) function, ER-to-Golgi transport and ER stress pathways. Furthermore, palmitate modulated cAMP/protein kinase A (PKA) signaling, inhibiting expression of PKA anchoring proteins and downregulating the GLP-1 receptor. SLC7 family amino-acid transporters were upregulated in response to palmitate but this induction did not contribute to ß-cell demise. To unravel critical mediators of lipotoxicity upstream of the palmitate-modified genes, we identified overrepresented transcription factor binding sites and performed network inference analysis. These identified LXR, PPARα, FOXO1 and BACH1 as key transcription factors orchestrating the metabolic and oxidative stress responses to palmitate. CONCLUSIONS: This is the first study to combine transcriptomic and sensitive time course proteomic profiling of palmitate-exposed ß-cells. Our results provide comprehensive insight into gene and protein expression changes, corroborating and expanding beyond previous findings. The identification of critical drivers and pathways of the ß-cell lipotoxic response points to novel therapeutic targets for type 2 diabetes.

Crystal phase evolution in kinked GaN nanowires.

Seed-catalysed growth has been proved to be an ideal method to selectively tune the crystal structure of III-V nanowires along its growth axis. However, few results on relevant nitride NWs have been reported. In this study, we demonstrate the growth of epitaxial kinked wurtzite (WZ)/zinc-blende (ZB) heterostructure GaN NW arrays under the oxygen rich condition using hydride vapour-liquid-solid vapour phase epitaxy (VLS-HVPE). The typical GaN crystal includes WZ and ZB phases throughout the whole NW structure. A detailed structural analysis indicates that a stacking faults free zone was occasionally observed near the NW tips and in the relatively long kinked 〈11-23〉 directions segments (>200 nm). Furthermore, some NWs (<5%) develop phase boundaries, resulting in kinking and crystal phase evolution. A layer-by-layer growth mode was proposed to explain the crystal phase evolution along the phase boundaries. This study provides new insights into the controlled growth of wurtzite (WZ)/zinc-blende (ZB) heterostructure GaN NW.

Design of AlN ultraviolet metasurface for single-/multi-plane holography.

The metasurface promises an unprecedented way for manipulating wavefronts and has strengths in large information capacity for the hologram. However, strong absorption loss for most dielectric materials hinders the realization of such a metasurface operating in the ultraviolet (UV) spectrum. Herein, aluminum nitride (AlN) with an ultrawide bandgap has been utilized as the material of the UV metasurface for multi-plane holography, increasing the information capacity and security level of information storage simultaneously. The metasurface for multi-plane holography achieving a correlation coefficient of over 0.8 with three reconstructed images has been investigated, and also the single-plane holography at an efficiency of 34.05%. Our work might provide potential application in UV nanophotonics.