Type-II Superlattice Heterojunction Photodetector with Optoelectronic Characterization and Analytical/ Numerical Simulation

This chapter focuses on characterization, modeling, and simulation about the type-II superlattices photodetector application. Despite dramatic improvements in type-II superlattices in the past 15 years, challenges still exist in InAs/GaSb and InAs/GaInSb superlattices: The diffusion current, Shockley-Read-Hall (SRH) recombination current, tunneling current, and surface leakage current at elevated temperature. To establish a set of modeling and simulation input parameters, in-depth materials and device characterization at different conditions are carried out for initial materials and device models. Based on input parameters, we will describe the development of analytical and numerical models of InAs/GaSb and InAs/GaInSb type-II superlattice-structured materials and device systems. At the end of this chapter, the fitting of modeled and simulated data will be performed to compare empirical data and modeling results at a set of temperature, which will provide guidance to achieve the higher performance

Spectral Responses in Quantum Efficiency of Emerging Kesterite Thin-Film Solar Cells

The spectral responses in quantum efficiency provide essential information about current generation, recombination, and diffusion mechanisms in a photodetector, photodiode, and photovoltaic devices as the quantum efficiency is a function of the voltage and light biases and the spectral content of the bias light and/or location of the devices. Recently, P-type Kesterite thin-film solar cells are emerging as they have a high absorption coefficient (>104 cm−1) and ideal direct bandgap (1.4–1.5 eV), which make them a perfect candidate for photovoltaic application. However, a champion device from Zincblende (CdTe) or Chalcopyrite (CIGS) solar cells shows ~21% efficiency (<21.5%, First Solar and <21.7%, ZSW, respectively) while Kesterite devices suffer from severe losses with <12.6% efficiency. Furthermore, the maximum theoretical efficiency based on Shockley-Queisser limit is about 32.2%, which indicates there is much room for the improvement. Consequently, the implication from the current situation highlights the need for a systematic analysis of the loss mechanism in Kesterite devices. In this work, we carried out a systematic study of the efficiency limiting factors based on quantum efficiency to model the quantum efficiency response of current CZTSSe thin-film solar cells. This will provide the guidance for proper interpretation of device behaviors when it is measured by quantum efficiency

Transgenic wheat expressing a barley class II chitinase gene has enhanced resistance against Fusarium graminearum

Fusarium head blight (FHB; scab), primarily caused by Fusarium graminearum, is a devastating disease of wheat worldwide. FHB causes yield reductions and contamination of grains with trichothecene mycotoxins such as deoxynivalenol (DON). The genetic variation in existing wheat germplasm pools for FHB resistance is low and may not provide sufficient resistance to develop cultivars through traditional breeding approaches. Thus, genetic engineering provides an additional approach to enhance FHB resistance. The objectives of this study were to develop transgenic wheat expressing a barley class II chitinase and to test the transgenic lines against F. graminearum infection under greenhouse and field conditions. A barley class II chitinase gene was introduced into the spring wheat cultivar, Bobwhite, by biolistic bombardment. Seven transgenic lines were identified that expressed the chitinase transgene and exhibited enhanced Type II resistance in the greenhouse evaluations. These seven transgenic lines were tested under field conditions for percentage FHB severity, percentage visually scabby kernels (VSK), and DON accumulation. Two lines (C8 and C17) that exhibited high chitinase protein levels also showed reduced FHB severity and VSK compared to Bobwhite. One of the lines (C8) also exhibited reduced DON concentration compared with Bobwhite. These results showed that transgenic wheat expressing a barley class II chitinase exhibited enhanced resistance against F. graminearum in greenhouse and field conditions

Plug-in nanoliter pneumatic liquid dispenser with nozzle design flexibility

This paper presents a novel plug-in nanoliter liquid dispensing system with a plugand-play interface for simple and reversible, yet robust integration of the dispenser. A plug-in type dispenser was developed to facilitate assembly and disassembly with an actuating part through efficient modularization. The entire process for assembly and operation of the plug-in dispenser is performed via the plug-and-play interface in less than a minute without loss of dispensing quality. The minimum volume of droplets pneumatically dispensed using the plug-in dispenser was 124 nl with a coefficient of variation of 1.6%. The dispensed volume increased linearly with the nozzle size. Utilizing this linear relationship, two types of multinozzle dispensers consisting of six parallel channels (emerging from an inlet) and six nozzles were developed to demonstrate a novel strategy for volume gradient dispensing at a single operating condition. The droplet volume dispensed from each nozzle also increased linearly with nozzle size, demonstrating that nozzle size is a dominant factor on dispensed volume, even for multinozzle dispensing. Therefore, the proposed plug-in dispenser enables flexible design of nozzles and reversible integration to dispense droplets with different volumes, depending on the application. Furthermore, to demonstrate the practicality of the proposed dispensing system, we developed a pencil-type dispensing system as an alternative to a conventional pipette for rapid and reliable dispensing of minute volume droplets. (C) 2015 AIP Publishing LLC.open114sciescopu

Examining the transcriptional response in wheat Fhb1 near-isogenic lines to Fusarium graminearum infection and deoxynivalenol treatment

Citation: Hofstad, A. N., Nussbaumer, T., Akhunov, E., Shin, S., Kugler, K. G., Kistler, H. C., . . . Muehlbauer, G. J. (2016). Examining the transcriptional response in wheat Fhb1 near-isogenic lines to Fusarium graminearum infection and deoxynivalenol treatment. Plant Genome, 9(1). https://doi.org/10.3835/plantgenome2015.05.0032Fusarium head blight (FHB) is a disease caused predominantly by the fungal pathogen Fusarium graminearum that affects wheat and other small-grain cereals and can lead to severe yield loss and reduction in grain quality. Trichothecene mycotoxins, such as deoxynivalenol (DON), accumulate during infection and increase pathogen virulence and decrease grain quality. The Fhb1 locus on wheat chromosome 3BS confers Type II resistance to FHB and resistance to the spread of infection on the spike and has been associated with resistance to DON accumulation. To gain a better genetic understanding of the functional role of Fhb1 and resistance or susceptibility to FHB, we examined DON and ergosterol accumulation, FHB resistance, and the whole-genome transcriptomic response using RNA-seq in a near-isogenic line (NIL) pair carrying the resistant and susceptible alleles for Fhb1 during F. graminearum infection and DON treatment. Our results provide a gene expression atlas for the resistant and susceptible wheat–F. graminearum interaction. The DON concentration and transcriptomic results show that the rachis is a key location for conferring Type II resistance. In addition, the wheat transcriptome analysis revealed a set of Fhb1-responsive genes that may play a role in resistance and a set of DON-responsive genes that may play a role in trichothecene resistance. Transcriptomic results from the pathogen show that the F. graminearum genome responds differently to the host level of resistance. The results of this study extend our understanding of host and pathogen responses in the wheat–F. graminearum interaction. © Crop Science Society of America

Properties of spin 1/2 triangular lattice antiferromagnets: CuRE2Ge2O8 (RE=Y, La)

We found new two-dimensional (2D) quantum (S=1/2) antiferromagnetic systems: CuRE2Ge2O8 (RE=Y and La). According to our analysis of high-resolution X-ray and neutron diffraction experiments, the Cu-network of CuRE2Ge2O8 (RE=Y and La) exhibits a 2D triangular lattice linked via weak bonds along the perpendicular b-axis. Our bulk characterizations from 0.08 to 400 K show that they undergo a long-range order at 0.51(1) and 1.09(4) K for the Y and La systems, respectively. Interestingly, they also exhibit field induced phase transitions. For theoretical understanding, we carried out the density functional theory (DFT) band calculations to find that they are typical charge-transfer-type insulators with a gap of Eg = 2 eV. Taken together, our observations make CuRE2Ge2O8 (RE=Y and La) additional examples of low-dimensional quantum spin triangular antiferromagnets with the low-temperature magnetic ordering.Comment: 15 pages, 6 figures, and 1 tabl

Homeostatic interferon-lambda response to bacterial microbiota stimulates preemptive antiviral defense within discrete pockets of intestinal epithelium

Interferon-lambda (IFN-λ) protects intestinal epithelial cells (IECs) from enteric viruses by inducing expression of antiviral IFN-stimulated genes (ISGs). Here, we find that bacterial microbiota stimulate a homeostatic ISG signature in the intestine of specific pathogen-free mice. This homeostatic ISG expression is restricted to IECs, depends on IEC-intrinsic expression of IFN-λ receptor

Mutant U2AF1-induced alternative splicing of H2afy (macroH2A1) regulates B-lymphopoiesis in mice

Somatic mutations in spliceosome genes are found in ∼50% of patients with myelodysplastic syndromes (MDS), a myeloid malignancy associated with low blood counts. Expression of the mutant splicing factor U2AF1(S34F) alters hematopoiesis and mRNA splicing in mice. Our understanding of the functionally relevant alternatively spliced target genes that cause hematopoietic phenotypes in vivo remains incomplete. Here, we demonstrate that reduced expression of H2afy1.1, an alternatively spliced isoform of the histone H2A variant gene H2afy, is responsible for reduced B cells in U2AF1(S34F) mice. Deletion of H2afy or expression of U2AF1(S34F) reduces expression of Ebf1 (early B cell factor 1), a key transcription factor for B cell development, and mechanistically, H2AFY is enriched at the EBF1 promoter. Induced expression of H2AFY1.1 in U2AF1(S34F) cells rescues reduced EBF1 expression and B cells numbers in vivo. Collectively, our data implicate alternative splicing of H2AFY as a contributor to lymphopenia induced by U2AF1(S34F) in mice and MDS

Establishing the carrier scattering phase diagram for ZrNiSn-based half-Heusler thermoelectric materials

Chemical doping is one of the most important strategies for tuning electrical properties of semiconductors, particularly thermoelectric materials. Generally, the main role of chemical doping lies in optimizing the carrier concentration, but there can potentially be other important effects. Here, we show that chemical doping plays multiple roles for both electron and phonon transport properties in half-Heusler thermoelectric materials. With ZrNiSn-based half-Heusler materials as an example, we use high-quality single and polycrystalline crystals, various probes, including electrical transport measurements, inelastic neutron scattering measurement, and first-principles calculations, to investigate the underlying electron-phonon interaction. We find that chemical doping brings strong screening effects to ionized impurities, grain boundary, and polar optical phonon scattering, but has negligible influence on lattice thermal conductivity. Furthermore, it is possible to establish a carrier scattering phase diagram, which can be used to select reasonable strategies for optimization of the thermoelectric performance.Comment: 21 pages, 5 figure