Conductance through contact barriers of a finite length quantum wire

We use the technique of bosonization to understand a variety of recent experimental results on the conductivity of a quantum wire. The quantum wire is taken to be a finite-length Luttinger liquid connected on two sides to semi-infinite Fermi liquids through contacts. The contacts are modeled as (short) Luttinger liquids bounded by localized one-body potentials. We use effective actions and the renormalization group to study the effects of electronic interactions within the wire, the length of the wire, finite temperature and a magnetic field on the conductivity. We explain the deviations of the conductivity away from 2Ne^2/h in wires which are not too short as arising from renormalization effects caused by the repulsive interactions. We also explain the universal conductance corrections observed in different channels at higher temperatures. We study the effects of an external magnetic field on electronic transport through this system and explain why odd and even spin split bands show different renormalizations from the universal conductance values. We discuss the case of resonant transmission and of the possibility of producing a spin-valve which only allows electrons of one value of the spin to go through. We compare our results for the conductance corrections with experimental observations. We also propose an experimental test of our model of the contact regions.Comment: LaTeX, 65 pages, 3 eps figure

The American Recovery and Reinvestment Act

The COVID-19 Pandemic has caused the worst economic decline since the Great Depression. Both President Trump and Biden have passed stimulus packages to get the economy to recovery as quickly as possible. Since these packages have just been implemented there is no way to know the possible long term impacts they will have on the economy. The ARRA stimulus package that was implemented in 2009 was the last stimulus package to be passed by the US Government before the COVID-19 pandemic. This makes it the best comparison point for the most recent stimulus packages. This paper aims to find out the effectiveness of the ARRA stimulus using two approaches. One uses simulations of increasing government spending to see the impact of increasing all of the stimulus while the other looks at the estimated economic impact of each program funded by the ARRA. The first approach found that if the stimulus was five times greater then the economy would have recovered by 2012. The second approach found putting more funding into programs with a higher chance of increasing economic activity could have closed the worst part of the recession only if all of the funding was used at once. These approaches help to give insight to what can make a stimulus more effective at setting the economy on a course for recovery

Packing-induced conformational and functional changes in the subunits of α-crystallin

The heteroaggregate α-crystallin and homoaggregates of its subunits, αA- and αB-crystallins, function like molecular chaperones and prevent the aggregation of several proteins. Although modulation of the chaperone-like activity of α-crystallin by both temperature and chaotropic agents has been demonstrated in vitro, the mechanism(s) of its regulationin vivo have not been elucidated. The subunits of α-crystallin exchange freely, resulting in its dynamic and variable quaternary structure. Mixed aggregates of the α-crystallins and other mammalian small heat shock proteins (sHSPs) have also been observedin vivo. We have investigated the time-dependent structural and functional changes during the course of heteroaggregate formation by the exchange of subunits between homoaggregates of αA- and αB-crystallins. Native isoelectric focusing was used to follow the time course of subunit exchange. Circular dichroism revealed large tertiary structural alterations in the subunits upon subunit exchange and packing into heteroaggregates, indicating specific homologous and heterologous interactions between the subunits. Subunit exchange also resulted in quaternary structural changes as demonstrated by gel filtration chromatography. Interestingly, we found time-dependent changes in chaperone-like activity against the dithiothreitol-induced aggregation of insulin, which correlated with subunit exchange and the resulting tertiary and quaternary structural changes. Heteroaggregates of varying subunit composition, as observed during eye lens epithelial cell differentiation, generated by subunit exchange displayed differential chaperone-like activity. It was possible to alter chaperone-like activity of preexisting oligomeric sHSPs by alteration of subunit composition by subunit exchange. Our results demonstrate that subunit exchange and the resulting structural and functional changes observed could constitute a mechanism of regulation of chaperone-like activity of α-crystallin (and possibly other mammalian sHSPs) in vivo

Transport in quantum wires

With a brief introduction to one-dimensional channels and conductance quantisation in mesoscopic systems, we discuss some recent experimental puzzles in these systems, which include reduction of quantised conductances and an interesting {\it odd-even} effect in the presence of an in-plane magnetic field. We then discuss a recent non-homogeneous Luttinger liquid model proposed by us, which addresses and gives an explanation for the reduced conductances and the {\it odd-even} effect. We end with a brief summary and discussion of future projects.Comment: Talk presented at the International Discussion Meeting on Mesoscopic and Disordered systems, December, 2000, 16 pages, 2 figure

ESTIMATION OF PRIMIDONE IN COMMERCIAL DOSAGE FORMS USING A SIMPLE AND CONVENIENT HPLC METHOD

ABSTRACT A simple fast and precise reverse phase high performance liquid chromatographic method has been developed for the determination of Primidone Tablets. A symmetry (5µ, 150 x 4 .6mm column) in isocratic mode with methanol: Water (50:50) as mobile phase. The Flow rate is1.0ml/min and effluent is monitored at 210nm

Minimizing radiographic contrast administration during coronary angiography using a novel contrast reduction system: A multicenter observational study of the DyeVert™ plus contrast reduction system

ObjectiveTo evaluate contrast media (CM) volume (CMV) saved using the DyeVert™ Plus Contrast Reduction System (DyeVert Plus System, Osprey Medical) in patients undergoing diagnostic coronary angiogram (CAG) and/or percutaneous coronary interventional (PCI) procedures performed with manual injections.BackgroundCurrent guidelines advocate for monitoring and minimization of the total volume of CM in chronic kidney disease (CKD) patients undergoing invasive cardiac procedures. The DyeVert Plus System is an FDA cleared device designed to reduce CMV delivered during angiography and permit real‐time CMV monitoring.MethodsWe performed a multicenter, single‐arm, observational study. Eligible subjects were ≥ 18 years old with baseline estimated glomerular filtration rate (eGFR) 20–60 mL/min/1.73 m2. The primary endpoint was % CMV saved over the total procedure. A secondary objective was to evaluate adverse events (AEs) related to DyeVert Plus System or to CM use.ResultsA total of 114 subjects were enrolled at eight centers. Mean age was 72 ± 9 years, 72% were male, and mean body mass index was 29 ± 5. Baseline eGFR was 43 ± 11 mL/min/1.73 m2. CAG‐only was performed in 65% of cases. One hundred and five subjects were evaluable for the primary endpoint. Mean CMV attempted was 112 ± 85 mL (range 22–681) and mean CMV delivered was 67 ± 51 mL (range 12–403), resulting in an overall CMV savings of 40.1 ± 8.8% (95% CI 38.4, 41.8; P 0.3 mg/dL from baseline) was reported in 11 cases with seven occurring in subjects with baseline eGFR < 30 and three AKI events were attributed to CM. AKI rates increased as CMV/eGFR ratios increased.ConclusionsThese data suggest DyeVert Plus System use in CKD patients undergoing CAG and/or PCI results in clinically meaningful CMV savings while maintaining image quality.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149537/1/ccd27935_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149537/2/ccd27935.pd

Can fingernail quality predict bone damage in Type 2 diabetes mellitus? a pilot study

Type 2 diabetes mellitus (T2DM) adversely affects the normal functioning, intrinsic material properties, and structural integrity of many tissues, including bone. It is well known that the clinical utility of areal bone mineral density (aBMD) is limited to assess bone strength in individuals with T2DM. Therefore, there is a need to explore new diagnostic techniques that can better assist and improve the accuracy of assessment of bone tissue quality. The present study investigated the link between bone and fingernail material/compositional properties in type 2 diabetes mellitus (T2DM). For that, femoral head and fingernail samples were obtained from twenty-five adult female patients (with/without T2DM) with fragility femoral neck fractures undergoing hemi/total hip arthroplasty. Cylindrical cores of trabecular bone were subjected to micro-CT, and lower bone volume fraction was observed in the diabetic group than the non-diabetic group due to fewer and thinner trabeculae in individuals with T2DM. The material and compositional properties of bone/fingernail were estimated using nanoindentation and Fourier Transform Infrared Spectroscopy, respectively. Both bone/fingernails in T2DM had lower reduced modulus (Er), hardness (H), lower Amide I and Amide II area ratio (protein content), higher sugar-to-matrix ratio, and relatively high carboxymethyl-lysine (CML) content compared with non-diabetic patients. Sugar-to-matrix ratio and relative CML content were strongly and positively correlated with HbA1c for both bone/fingernail. There was a positive correlation between bone and fingernail glycation content. Our findings provide evidence that the degradation pattern of bone and fingernail properties go hand-in-hand in individuals with T2DM. Hence, the fingernail compositional/material properties might serve as a non-invasive surrogate marker of bone quality in T2DM; however, further large-scale studies need to be undertaken

Transport through quasi-ballistic quantum wires: the role of contacts

We model one-dimensional transport through each open channel of a quantum wire by a Luttinger liquid with three different interaction parameters for the leads, the contact regions and the wire, and with two barriers at the contacts. We show that this model explains several features of recent experiments, such as the flat conductance plateaux observed even at finite temperatures and for different lengths, and universal conductance corrections in different channels. We discuss the possibility of seeing resonance-like structures of a fully open channel at very low temperatures.Comment: revtex, 5 pages, 1 eps figure; clarifications added in light of new experiment

Junction of several weakly interacting quantum wires: a renormalization group study

We study the conductance of three or more semi-infinite wires which meet at a junction. The electrons in the wires are taken to interact weakly with each other through a short-range density-density interaction, and they encounter a general scattering matrix at the junction. We derive the renormalization group equations satisfied by the S-matrix, and we identify its fixed points and their stabilities. The conductance between any pair of wires is then studied as a function of physical parameters such as temperature. We discuss the possibility of observing the effects of junctions in present day experiments, such as the four-terminal conductance of a quantum wire and crossed quantum wires.Comment: RevTeX, 13 pages, including 4 eps figure