A Schottky/2-DEG varactor diode for millimeter and submillimeter wave multiplier applications

A new Schottky diode is investigated for use as a multiplier element in the millimeter and submillimeter wavelength regions. The new diode is based on the Schottky contact at the edge of a 2-dimensional electron gas (2-DEG). As a negative voltage is applied to the Schottky contact, the depletion layer between the Schottky contact and the 2-DEG expands and the junction capacitance decreases, resulting in a nonlinear capacitance-voltage characteristic. In this paper, we outline the theory, design, fabrication, and evaluation of the new device. Recent results include devices having cutoff frequencies of 1 THz and above. Preliminary multiplier results are also presented

Novel Fine-Structure in the Low-Energy Excitation Spectrum of a High-Tc Superconductor by Polarization Dependent Photoemission

Angle-resolved photoemission spectroscopy is performed on single crystals of the single-layer high-Tc superconductor Bi(2)Sr(2-x)La(x)CuO(6+d) at optimal doping (x=0.4) in order to study in great detail the Zhang-Rice (ZR) singlet band at the Fermi level. Besides the high crystal quality the advantages of a single-layer material are the absence of bilayer effects and the distinct reduction of thermal broadening. Due to the high energy and angle resolution and, most important, due to the controlled variation of the polarization vector of the synchrotron radiation the emission from the ZR singlet band reveals a distinct fine-structure. It consists of two maxima, the first showing only weak and the second at EF extremely strong polarization dependence. However, our observation has enormous consequences for line shape analyses and the determination of pseudo gaps by photoemission.Comment: 10 pages, 2 figures. to appear in PRB (Rapid Comm.

Fibroblasts Express Immune Relevant Genes and Are Important Sentinel Cells during Tissue Damage in Rainbow Trout (Oncorhynchus mykiss)

Fibroblasts have shown to be an immune competent cell type in mammals. However, little is known about the immunological functions of this cell-type in lower vertebrates. A rainbow trout hypodermal fibroblast cell-line (RTHDF) was shown to be responsive to PAMPs and DAMPs after stimulation with LPS from E. coli, supernatant and debris from sonicated RTHDF cells. LPS was overall the strongest inducer of IL-1β, IL-8, IL-10, TLR-3 and TLR-9. IL-1β and IL-8 were already highly up regulated after 1 hour of LPS stimulation. Supernatant stimuli significantly increased the expression of IL-1β, TLR-3 and TLR-9, whereas the debris stimuli only increased expression of IL-1β. Consequently, an in vivo experiment was further set up. By mechanically damaging the muscle tissue of rainbow trout, it was shown that fibroblasts in the muscle tissue of rainbow trout contribute to electing a highly local inflammatory response following tissue injury. The damaged muscle tissue showed a strong increase in the expression of the immune genes IL-1β, IL-8 and TGF-β already 4 hours post injury at the site of injury while the expression in non-damaged muscle tissue was not influenced. A weaker, but significant response was also seen for TLR-9 and TLR-22. Rainbow trout fibroblasts were found to be highly immune competent with a significant ability to express cytokines and immune receptors. Thus fish fibroblasts are believed to contribute significantly to local inflammatory reactions in concert with the traditional immune cells

Comparing the transcriptomes of embryos from domesticated and wild Atlantic salmon (Salmo salar L.) stocks and examining factors that influence heritability of gene expression

Background  Due to selective breeding, domesticated and wild Atlantic salmon are genetically diverged, which raises concerns about farmed escapees having the potential to alter the genetic composition of wild populations and thereby disrupting local adaptation. Documenting transcriptional differences between wild and domesticated stocks under controlled conditions is one way to explore the consequences of domestication and selection. We compared the transcriptomes of wild and domesticated Atlantic salmon embryos, by using a custom 44k oligonucleotide microarray to identify perturbed gene pathways between the two stocks, and to document the inheritance patterns of differentially-expressed genes by examining gene expression in their reciprocal hybrids.  Results  Data from 24 array interrogations were analysed: four reciprocal cross types (W♀×W♂, D♀×W♂; W♀×D♂, D♀×D♂)×six biological replicates. A common set of 31,491 features on the microarrays passed quality control, of which about 62% were assigned a KEGG Orthology number. A total of 6037 distinct genes were identified for gene-set enrichment/pathway analysis. The most highly enriched functional groups that were perturbed between the two stocks were cellular signalling and immune system, ribosome and RNA transport, and focal adhesion and gap junction pathways, relating to cell communication and cell adhesion molecules. Most transcripts that were differentially expressed between the stocks were governed by additive gene interaction (33 to 42%). Maternal dominance and over-dominance were also prevalent modes of inheritance, with no convincing evidence for a stock effect.  Conclusions  Our data indicate that even at this relatively early developmental stage, transcriptional differences exist between the two stocks and affect pathways that are relevant to wild versus domesticated environments. Many of the identified differentially perturbed pathways are involved in organogenesis, which is expected to be an active process at the eyed egg stage. The dominant effects are more largely due to the maternal line than to the origin of the stock. This finding is particularly relevant in the context of potential introgression between farmed and wild fish, since female escapees tend to have a higher spawning success rate compared to males

Current and emerging developments in subseasonal to decadal prediction

Weather and climate variations of subseasonal to decadal timescales can have enormous social, economic and environmental impacts, making skillful predictions on these timescales a valuable tool for decision makers. As such, there is a growing interest in the scientific, operational and applications communities in developing forecasts to improve our foreknowledge of extreme events. On subseasonal to seasonal (S2S) timescales, these include high-impact meteorological events such as tropical cyclones, extratropical storms, floods, droughts, and heat and cold waves. On seasonal to decadal (S2D) timescales, while the focus remains broadly similar (e.g., on precipitation, surface and upper ocean temperatures and their effects on the probabilities of high-impact meteorological events), understanding the roles of internal and externally-forced variability such as anthropogenic warming in forecasts also becomes important. The S2S and S2D communities share common scientific and technical challenges. These include forecast initialization and ensemble generation; initialization shock and drift; understanding the onset of model systematic errors; bias correct, calibration and forecast quality assessment; model resolution; atmosphere-ocean coupling; sources and expectations for predictability; and linking research, operational forecasting, and end user needs. In September 2018 a coordinated pair of international conferences, framed by the above challenges, was organized jointly by the World Climate Research Programme (WCRP) and the World Weather Research Prograame (WWRP). These conferences surveyed the state of S2S and S2D prediction, ongoing research, and future needs, providing an ideal basis for synthesizing current and emerging developments in these areas that promise to enhance future operational services. This article provides such a synthesis

Breakdown behavior of low-power pseudomorphic AlGaAs/InGaAs 2-D MESFET's

We report the breakdown behavior of the two-dimensional (2-D) MESFET, which is a low-power heterodimensional transistor having dual side gates that contact the edge of the two-dimensional electron gas (2-DEG) channel in a double-side planar-doped pseudomorphic Al0:24Ga0:76As/In0:17Ga0:83As material structure. Low output conductance (less than 6 mS/mm for VGS = 0 V) and low gate leakage current (less than 100 nA) are measured out to a drain-source bias of 20 V, indicating that the effects of impact ionization are reduced in the 2-D MESFET. Excellent off-state drain-source and drain-gate breakdown voltages are experimentally measured to be 20 and 21 V, respectively. We attribute these high breakdown values to the electric and geometric properties of the heterodimensional Schottky metal/2-DEG junction

Study of breakdown mechanism in 2D MESFET\u2019s

In this work we have characterized and studied the impact-ionization-induced instabilities in the output characteristics of these devices. The instabilities appear as an increase of the output conductance, gD. Based on the value of gD, the output characteristics can be separated into three different regions, each corresponding to a different impact ionization regime: Region I, no impact-ionization and very low values of gD; Region II, starting of impact-ionization regime (pre-avalanche) and corresponding slight increase of gD; Region III, onset of carrier avalanche and consequent large increase in gD. In support of this picture we observed the same correlation between impact ionization and gD also changing device biasing and temperature

Parasitic bipolar effects leading to on-state breakdown in 2D-MESFET\u2019s

In this work we have studied and characterized the impact-ionization-induced instabilities in the output characteristics of two-dimensional MESFET\u2019s. The instabilities appear as an increase of the output conductance, gD. By performing a complete set of DC measurements at different temperature and electroluminescence measurements, in different bias conditions, we were able to correlate the kinks in the output characteristics with different impact ionization regimes, including the possible onset of a parasitic bipolar effect

Untersuchungen an Viton-gedichteten Balgzugschieberventilen

A large number of Viton-sealed UHV valves for vacuum separation of pipe and component sections are needed for the outlet systems, beam tubes and experimental systems of the BESSY II storage ring. By way of loan, the CETEC, Edwards, MDC, VAT, Varian and VSE companies provided valves which were tested at BESSY to obtain criteria for comparison prior to decision-making. All valves were subjected to the same tests. (orig.)Available from TIB Hannover: RO 8093(180) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman