127 research outputs found
Direct demonstration of circulating currents in a controllable -SQUID generated by a 0 to transition of the weak links
A controllable -SQUID is a DC SQUID with two controllable
-junctions as weak links. A controllable -junction consists of a
superconducting - normal metal - superconducting Josephson junction with two
additional contacts to the normal region of the junction. By applying a voltage
over these contacts it is possible to control the sate of the junction,
i.e. a conventional (0) state or a -state, depending on the magnitude of
. We demonstrate experimentally that, by putting one junction into a
-state, a screening current is generated around the SQUID loop at integer
external flux. To be able to do this, we have fabricated controllable
-junctions, based on Cu-Nb or Ag-Nb, in a new geometry. We show that at
1.4 K only the Nb-Ag device shows the transition to a -state as a function
of consistent with theoretical predictions. In a controllable SQUID
based on Nb-Ag we observe, a part from a screening current at integer external
flux, a phase shift of of the oscillations under suitable
current bias, depending on the magnitude of .Comment: 11 pages, 12 figures, subm. to Phys. Rev.
Evidence of two-electron tunneling interference in Nb/InAs junctions
The impact of junction transparency in driving phase-coherent charge transfer
across diffusive semiconductor-superconductor junctions is demonstrated. We
present conductivity data for a set of Nb-InAs junctions differing only in
interface transparency. Our experimental findings are analyzed within the
quasi-classical Green-function approach and unambiguously show the physical
processes giving rise to the observed excess zero-bias conductivity.Comment: 10 pages (RevTex), 4 figures (PostScript), accepted for pubblication
in Physical Review
Nonequilibrium Josephson effect in mesoscopic ballistic multiterminal SNS junctions
We present a detailed study of nonequilibrium Josephson currents and
conductance in ballistic multiterminal SNS-devices. Nonequilibrium is created
by means of quasiparticle injection from a normal reservoir connected to the
normal part of the junction. By applying a voltage at the normal reservoir the
Josephson current can be suppressed or the direction of the current can be
reversed. For a junction longer than the thermal length, , the
nonequilibrium current increases linearly with applied voltage, saturating at a
value equal to the equilibrium current of a short junction. The conductance
exhibits a finite bias anomaly around . For symmetric
injection, the conductance oscillates -periodically with the phase
difference between the superconductors, with position of the minimum
( or ) dependent on applied voltage and temperature. For
asymmetric injection, both the nonequilibrium Josephson current and the
conductance becomes -periodic in phase difference. Inclusion of barriers
at the NS-interfaces gives rise to a resonant behavior of the total Josephson
current with respect to junction length with a period . Both
three and four terminal junctions are studied.Comment: 21 pages, 19 figures, submitted to Phys. Rev.
Presentation, diagnosis and clinical course of the spectrum of progressive-fibrosing interstitial lung diseases
Although these conditions are rare, a proportion of patients with interstitial lung diseases (ILDs) may develop a progressive-fibrosing phenotype. Progressive fibrosis is associated with worsening respiratory symptoms, lung function decline, limited response to immunomodulatory therapies, decreased quality of life and, potentially, early death. Idiopathic pulmonary fibrosis may be regarded as a model for other progressive-fibrosing ILDs. Here we focus on other ILDs that may present a progressive-fibrosing phenotype, namely idiopathic nonspecific interstitial pneumonia, unclassifiable idiopathic interstitial pneumonia, connective tissue disease-associated ILDs (e.g. rheumatoid arthritis-related ILD), fibrotic chronic hypersensitivity pneumonitis, fibrotic chronic sarcoidosis and ILDs related to other occupational exposures. Differential diagnosis of these ILDs can be challenging, and requires detailed consideration of clinical, radiological and histopathological features. Accurate and early diagnosis is crucial to ensure that patients are treated optimally
International collaborative follow - up investigation of graduating high school students’ understandings of the nature of scientific inquiry: is progress Being made?
Understandings of the nature of scientific inquiry (NOSI), as opposed to engaging students in inquiry learning experiences, are included in science education reform documents around the world. However, little is known about what students have learned about NOSI during their pre-college school years. The purpose of this large-scale follow-up international project (i.e. 32 countries and regions, spanning six continents and including 3917 students for the high school sample) was to collect data on what exiting high school students have learned about NOSI. Additionally, the study investigated changes in 12th grade students’ NOSI understandings compared to seventh grade (i.e. 20 countries and regions) students’ understandings from a prior investigation [Lederman et al. (2019). An international collaborative investigation of beginning seventh grade students’ understandings of scientific inquiry: Establishing a baseline. Journal of Research in Science Teaching, 56(4), 486–515. https://doi.org/10.1002/tea.21512]. This study documents and discusses graduating high school students’ understandings and compares their understandings to seventh grade students’ understandings of the same aspects of scientific inquiry for each country. It is important to note that collecting data from each of the 130+ countries globally was not feasible. Similarly, it was not possible to collect data from every region of each country. A concerted effort was made, however, to provide a relatively representative picture of each country and the world
A review of bronchiolitis obliterans syndrome and therapeutic strategies
Lung transplantation is an important treatment option for patients with advanced lung disease. Survival rates for lung transplant recipients have improved; however, the major obstacle limiting better survival is bronchiolitis obliterans syndrome (BOS). In the last decade, survival after lung retransplantation has improved for transplant recipients with BOS. This manuscript reviews BOS along with the current therapeutic strategies, including recent outcomes for lung retransplantation
Development of a Three Dimensional Multiscale Computational Model of the Human Epidermis
Transforming Growth Factor (TGF-β1) is a member of the TGF-beta superfamily ligand-receptor network. and plays a crucial role in tissue regeneration. The extensive in vitro and in vivo experimental literature describing its actions nevertheless describe an apparent paradox in that during re-epithelialisation it acts as proliferation inhibitor for keratinocytes. The majority of biological models focus on certain aspects of TGF-β1 behaviour and no one model provides a comprehensive story of this regulatory factor's action. Accordingly our aim was to develop a computational model to act as a complementary approach to improve our understanding of TGF-β1. In our previous study, an agent-based model of keratinocyte colony formation in 2D culture was developed. In this study this model was extensively developed into a three dimensional multiscale model of the human epidermis which is comprised of three interacting and integrated layers: (1) an agent-based model which captures the biological rules governing the cells in the human epidermis at the cellular level and includes the rules for injury induced emergent behaviours, (2) a COmplex PAthway SImulator (COPASI) model which simulates the expression and signalling of TGF-β1 at the sub-cellular level and (3) a mechanical layer embodied by a numerical physical solver responsible for resolving the forces exerted between cells at the multi-cellular level. The integrated model was initially validated by using it to grow a piece of virtual epidermis in 3D and comparing the in virtuo simulations of keratinocyte behaviour and of TGF-β1 signalling with the extensive research literature describing this key regulatory protein. This research reinforces the idea that computational modelling can be an effective additional tool to aid our understanding of complex systems. In the accompanying paper the model is used to explore hypotheses of the functions of TGF-β1 at the cellular and subcellular level on different keratinocyte populations during epidermal wound healing
SMC complexes differentially compact mitotic chromosomes according to genomic context
Structural maintenance of chromosomes (SMC) protein complexes are key determinants of chromosome conformation. Using Hi-C and polymer modelling, we study how cohesin and condensin, two deeply conserved SMC complexes, organize chromosomes in the budding yeast Saccharomyces cerevisiae. The canonical role of cohesin is to co-align sister chromatids, while condensin generally compacts mitotic chromosomes. We find strikingly different roles for the two complexes in budding yeast mitosis. First, cohesin is responsible for compacting mitotic chromosome arms, independently of sister chromatid cohesion. Polymer simulations demonstrate that this role can be fully accounted for through cis-looping of chromatin. Second, condensin is generally dispensable for compaction along chromosome arms. Instead, it plays a targeted role compacting the rDNA proximal regions and promoting resolution of peri-centromeric regions. Our results argue that the conserved mechanism of SMC complexes is to form chromatin loops and that distinct SMC-dependent looping activities are selectively deployed to appropriately compact chromosomes
- …