Development of a Verification Technique for On-wafer Noise Figure Measurement Systems

We present the development of a verification technique for on-wafer noise figure (NF) measurement systems. As the key element of the technique, a verification device consisting of a mismatched attenuator and a low noise amplifier (LNA) has been developed. The attenuator and the LNA are fabricated on two separate chips but joined with a bondwire. The verification procedure based on the device has also been developed and tested on an on-wafer vector network analyzer system with a noise measurement option across the frequency range from 2 GHz to 20 GHz. It has also been found that the bondwire contributes to negligible effect on the system when NF is high e.g. 3 dB but slightly higher when NF is smaller e.g. 1 dB

Calibration on the fly—a novel two-port S-parameter measurement method for on-wafer leaky systems

In this article, we present a two-port on-wafer scattering parameter measurement method to tackle the issue of crosstalk between probes. The proposed method treats the crosstalk separately during the system calibration and the device measurement stages because the crosstalk during these stages is often different due to changes in the measurement conditions after the probes have been calibrated. For example, device under test (DUT) and calibration standards are often situated on different substrates, or the distance between probes during calibration is different from that during DUT measurement. Based on this concept, we develop a new error model in which the crosstalk is treated as a standalone two-port error network in parallel with the two-port calibration standards or DUTs. The two-port crosstalk error generated during probing, ECT, is removed in the system calibration and corrected during the measurement of the DUT by using a dummy pair of open-circuit standards that are fabricated on the same substrate as the DUT. Since the crosstalk is corrected while measuring the DUT, rather than during system calibration, we call this method ``calibration on the fly'' (COF). The method is demonstrated using measurements of a 10-dB attenuator between 140 and 220 GHz

Моделирование формирования структуры металломатричных композитов в процессе синтеза с оценкой эффективных свойств

Работа посвящена моделированию процесса кристаллизации композита с металлической матрицей и твердыми включениями с учетом условий синтеза (давление, скорость охлаждения), моделированию процесса формирования переходной зоны между частицами и матрицей и расчету эффективных свойств получаемых композитов.The work is devoted to modeling the crystallization process of metal matrix composite with solid inclusions, taking into account the synthesis conditions (pressure, cooling rate), to modeling the formation of the transition zone between particles and matrix, and calculating the effective properties of the resulting composites

MIF Signal Transduction Initiated by Binding to CD74

Macrophage migration inhibitory factor (MIF) accounts for one of the first cytokine activities to have been described, and it has emerged recently to be an important regulator of innate and adaptive immunity. MIF is an upstream activator of monocytes/macrophages, and it is centrally involved in the pathogenesis of septic shock, arthritis, and other inflammatory conditions. The protein is encoded by a unique but highly conserved gene, and X-ray crystallography studies have shown MIF to define a new protein fold and structural superfamily. Although recent work has begun to illuminate the signal transduction pathways activated by MIF, the nature of its membrane receptor has not been known. Using expression cloning and functional analysis, we report herein that CD74, a Type II transmembrane protein, is a high-affinity binding protein for MIF. MIF binds to the extracellular domain of CD74, and CD74 is required for MIF-induced activation of the extracellular signal–regulated kinase–1/2 MAP kinase cascade, cell proliferation, and PGE2 production. A recombinant, soluble form of CD74 binds MIF with a dissociation constant of ∼9 × 10−9 Kd, as defined by surface plasmon resonance (BIAcore analysis), and soluble CD74 inhibits MIF-mediated extracellular signal–regulated kinase activation in defined cell systems. These data provide a molecular basis for MIF's interaction with target cells and identify it as a natural ligand for CD74, which has been implicated previously in signaling and accessory functions for immune cell activation

Fragility of foot process morphology in kidney podocytes arises from chaotic spatial propagation of cytoskeletal instability

Kidney podocytes’ function depends on fingerlike projections (foot processes) that interdigitate with those from neighboring cells to form the glomerular filtration barrier. The integrity of the barrier depends on spatial control of dynamics of actin cytoskeleton in the foot processes. We determined how imbalances in regulation of actin cytoskeletal dynamics could result in pathological morphology. We obtained 3-D electron microscopy images of podocytes and used quantitative features to build dynamical models to investigate how regulation of actin dynamics within foot processes controls local morphology. We find that imbalances in regulation of actin bundling lead to chaotic spatial patterns that could impair the foot process morphology. Simulation results are consistent with experimental observations for cytoskeletal reconfiguration through dysregulated RhoA or Rac1, and they predict compensatory mechanisms for biochemical stability. We conclude that podocyte morphology, optimized for filtration, is intrinsically fragile, whereby local transient biochemical imbalances may lead to permanent morphological changes associated with pathophysiology

Novel Retinoic Acid Receptor Alpha Agonists for Treatment of Kidney Disease

Development of pharmacologic agents that protect podocytes from injury is a critical strategy for the treatment of kidney glomerular diseases. Retinoic acid reduces proteinuria and glomerulosclerosis in multiple animal models of kidney diseases. However, clinical studies are limited because of significant side effects of retinoic acid. Animal studies suggest that all trans retinoic acid (ATRA) attenuates proteinuria by protecting podocytes from injury. The physiological actions of ATRA are mediated by binding to all three isoforms of the nuclear retinoic acid receptors (RARs): RARα, RARβ, and RARγ. We have previously shown that ATRA exerts its renal protective effects mainly through the agonism of RARα. Here, we designed and synthesized a novel boron-containing derivative of the RARα-specific agonist Am580. This new derivative, BD4, binds to RARα receptor specifically and is predicted to have less toxicity based on its structure. We confirmed experimentally that BD4 binds to RARα with a higher affinity and exhibits less cellular toxicity than Am580 and ATRA. BD4 induces the expression of podocyte differentiation markers (synaptopodin, nephrin, and WT-1) in cultured podocytes. Finally, we confirmed that BD4 reduces proteinuria and improves kidney injury in HIV-1 transgenic mice, a model for HIV-associated nephropathy (HIVAN). Mice treated with BD4 did not develop any obvious toxicity or side effect. Our data suggest that BD4 is a novel RARα agonist, which could be used as a potential therapy for patients with kidney disease such as HIVAN

Improved Huff Model for Estimating Urban Rail Transit Station Catchment Areas considering Station Choices

Estimating urban rail transit station catchment areas is of great significance to deepening our understanding of Transit-Oriented Development in Chinese megacities. This study investigated station choices of residents and considered that residents may not only pay attention to the proximity to stations when the URT system develops into a relatively mature network. An improved Huff model was proposed to calculate the probability of residents’ station choice, which considered the station attractiveness. The station attractiveness is measured by three variables: walk score, public transport accessibility level, and service and facility index. The additive form based on multicriteria decision is adopted to incorporate experts’ opinions on the importance of three variables. In this study, extended catchment areas that can be accessed by cycling and feeder bus services are adopted to replace the conventional pedestrian-oriented catchment areas. A case study of Xi’an, China, was used to validate the applicability of the proposed methodology. The results revealed that the methodology effectively solved the problem. The findings could be used as a reference and provide technical support to policymakers and city planners with regard to the transport facilities configuration for URT station catchment areas, which contributes to facilitating transit-oriented development

Improved Huff Model for Estimating Urban Rail Transit Station Catchment Areas considering Station Choices

Estimating urban rail transit station catchment areas is of great significance to deepening our understanding of Transit-Oriented Development in Chinese megacities. This study investigated station choices of residents and considered that residents may not only pay attention to the proximity to stations when the URT system develops into a relatively mature network. An improved Huff model was proposed to calculate the probability of residents’ station choice, which considered the station attractiveness. The station attractiveness is measured by three variables: walk score, public transport accessibility level, and service and facility index. The additive form based on multicriteria decision is adopted to incorporate experts’ opinions on the importance of three variables. In this study, extended catchment areas that can be accessed by cycling and feeder bus services are adopted to replace the conventional pedestrian-oriented catchment areas. A case study of Xi’an, China, was used to validate the applicability of the proposed methodology. The results revealed that the methodology effectively solved the problem. The findings could be used as a reference and provide technical support to policymakers and city planners with regard to the transport facilities configuration for URT station catchment areas, which contributes to facilitating transit-oriented development.</jats:p