The Effects of Scaling and Bias Configuration on Operating-Voltage Constraints in SiGe HBTs for Mixed-Signal Circuits

This paper presents a comprehensive picture of operating-voltage constraints in SiGe heterojunction bipolar transistors, addressing breakdown-related issues as they relate to technology generation, bias configuration, and operating-current density. New definitions for breakdown voltage, adopted from standard measurements, are presented. Practical design implications and physical origins of breakdown are explored using calibrated 2-D simulations and quasi-3-D compact models. Device-level analysis of ac instabilities and power performance, which is relevant to mixed-signal circuit design, is presented, and implications of the relaxed voltage constraints for common-base operation are explored.     

Antimisting action of polymeric additives in jet fuels

Polymeric solutes in jet fuel can serve to increase greatly the droplet size and reduce flammability in fuel sprays created by high-velocity wind shear. Photographic and spark-ignition studies show that high molecular weight polyisobutylenes can be effective at levels below 100 ppm, where they cause only slight increases in fuel viscosity. The effectiveness of the polymers increases with molecular weight and is very well correlated by the elongational viscosity of the solution, as measured by the ductless siphon height.     

On Common–Base Avalanche Instabilities in SiGe HBTs

This paper presents a detailed investigation of the key device-level factors that contribute to the bias-dependent features observed in common-base (CB) dc instability characteristics of advanced SiGe HBTs. Parameters that are relevant to CB avalanche instabilities are identified, extracted from measured data, and carefully analyzed to yield improved physical insight, a straightforward estimation methodology, and a practical approach to quantify and compare CB avalanche instabilities. The results presented support our simple theory and show that CB-instability characteristics are strongly correlated with the parasitic base and emitter resistances. The influence of weak quasi-pinch-in effects are shown to contribute additional complexity to the bias dependence of the CB-instability threshold. Measured data from several technology nodes, including next-generation (300-GHz) SiGe HBTs, are presented and compared. Experimental analysis comparing different device geometries and layouts shows that while device size plays an important role in CB avalanche instabilities across bias, these parameters are not sensitive to standard transistor layout variations. However, novel measurements on emitter-ring tetrode transistor structures demonstrate the influence of perimeter-to-area ratio on CB stability and highlight opportunities for novel transistor layouts to increase .     

The novel signal peptides, pedibin and Hym-346, lower positional value thereby enhancing foot formation in hydra

Signaling molecules affecting patterning processes are usually proteins and rarely peptides. Two novel peptides, pedibin and Hym-346, that are closely related to one another have been isolated from Hydra vulgaris and Hydra magnipapillata. Several experiments indicate that both cause a reduction in the positional value gradient, the principle patterning process governing the maintenance of form in the adult hydra. The peptides cause an increase in the rate of foot regeneration following bisection of the body column. Treatment of animals with either peptide for an extended period of time resulted in an apical extension of the range of expression of CnNk-2 along the body column. Such an extension is correlated with a decrease in positional value. Transplantation of tissue treated with Hym-346 results in an increase in the fraction forming feet, and aggregates derived from Hym-346 tissue form more feet and fewer heads. The latter two experiments provide a direct measure of the lowering of positional value in the treated tissue. These results suggest that peptides play signaling roles in patterning processes in cnidaria and, plausibly, in more complex metazoans as well.     

Analysis of RNA phage fr coat protein assembly by insertion, deletion and substitution mutagenesis

A structure-function analysis of the icosahedral RNA bacteriophagefr coat protein (CP) assembly was undertaken using linker-insertion,deletion and substitution mutagenesis. Mutations were specificallyintroduced into either pre-existing or artificially createdrestriction enzyme sites within fr CP gene expressed in Escherichiacoli from a recombinant plasmid. This directs synthesis of wildtype protein that undergoes self-assembly and forms capsid-likeparticles indistinguishable morphologically and immunologicallyfrom native phage particles. A series of fr CP variants containingsequence alterations in the regions which are (i) exposed onthe external surface of capsid or (ii) located on the contactingareas between CP subunits were obtained and their assembly propertiesinvestigated. The majority of mutants demonstrated reductionof assembly ability and formed either CP dimers (mutations atresidues 2, 10, 63 or 129) or both dimer and capsid structures(residue 2 or 69). The exceptions were variants demonstratingnormal assembly and containing insertions at residues 2, 50or 129 of thefr CP. A third type of assembled structure wasformed by a variant with a single amino acid substitution I104T.The aA-helix region (residues 97-111) is particularly sensitiveto mutation and any alteration in this region decreases accumulationof mutant protein in E.coli. The relative contributions of particularfr CP domains in maintenance of capsid structural integrityas well as the possible capsid assembly mechanism are discussed.     

Compact Modeling of Mutual Thermal Coupling for the Optimal Design of SiGe HBT Power Amplifiers

Most bipolar-transistor compact models incorporate some level of self-heating capability in order to determine the impact of thermal effects on circuit performance. Techniques for predicting mutual-thermal-coupling effects, however, are not readily available within most commercial CAD platforms. Presented in this brief is a technique which allows for the easy modification of design-kit-supplied models to predict and optimize mutual thermal coupling using commonly available CAD tools such as Cadence and Spectre.     

Degradation of polymers during aerosol formation from antimisting polymer solutions

Degradation of polyisobutylenes as a consequence of spraying jet-fuel solutions of these polymers was studied as a function of polymer molecular weight and concentration and the spray conditions. Assessment of the degradation was made by measuring the maximum ductless siphon height h^* for sprayed samples and comparing this with prespray values. Two polymers, L-160 from Exxon and B-288 from BASF ( M _v = 4.1× 10⁶ and 11.9 × 10⁶), were studied to concentrations of 3000 and 2000 ppm, respectively. Degradation was found to be extremely sensitive to the air speed used in wind-shear spraying, above a critical value of approximately 30–40 m/s. At the highest air speed employed, 135 m/s, degradation was so severe that h^* values were reduced nearly to Newtonian (solvent) values, for all concentrations of both polymer additives. The implications of these results are important for designing effective antimisting fluids.     

THE EFFECT OF ANTIMISTING ADDITIVES ON FLAMMABIL1TY OF JET FUELS

High molecular weight (MW) polyisobutylenes were effective in suppressing flammability of Jet-A fuel sprays when present at concentrations of 100 ppm or less in the fuel. Six polyisobutylene solutes, with viscosity-average MW ranging from 0.7 to 12 million, were tested in wind-shear created fuel sprays against both spark and flame ignition sources. Air velocities up to 140 m/s and fuel/air mass ratios up to 10 were used to examine effects of spray conditions on solute concentrations necessary to prevent ignition. The effectiveness of the additives increased directly with their MW for both spark and flame ignition, with the higher-MW polymers providing flammability suppression at concentrations that caused less than 20 percent increases in fuel viscosity.     

Molecular Processes in Stress Urinary Incontinence: A Systematic Review of Human and Animal Studies

Stress urinary incontinence (SUI) is a common and burdensome condition. Because of the large knowledge gap around the molecular processes involved in its pathophysiology, the aim of this review was to provide a systematic overview of genetic variants, gene and protein expression changes related to SUI in human and animal studies. On 5 January 2021, a systematic search was performed in Pubmed, Embase, Web of Science, and the Cochrane library. The screening process and quality assessment were performed in duplicate, using predefined inclusion criteria and different quality assessment tools for human and animal studies respectively. The extracted data were grouped in themes per outcome measure, according to their functions in cellular processes, and synthesized in a narrative review. Finally, 107 studies were included, of which 35 used animal models (rats and mice). Resulting from the most examined processes, the evidence suggests that SUI is associated with altered extracellular matrix metabolism, estrogen receptors, oxidative stress, apoptosis, inflammation, neurodegenerative processes, and muscle cell differentiation and contractility. Due to heterogeneity in the studies (e.g., in examined tissues), the precise contribution of the associated genes and proteins in relation to SUI pathophysiology remained unclear. Future research should focus on possible contributors to these alterations.