2,672 research outputs found
Giant suppression of the Drude conductivity due to quantum interference in disordered two-dimensional systems
Temperature and magnetic field dependences of the conductivity in heavily
doped, strongly disordered two-dimensional quantum well structures
GaAs/InGaAs/GaAs are investigated within wide conductivity and
temperature ranges. Role of the interference in the electron transport is
studied in the regimes when the phase breaking length crosses over the
localization length with lowering temperature,
where and are the Fermi quasimomentum and mean free path,
respectively. It has been shown that all the experimental data can be
understood within framework of simple model of the conductivity over
delocalized states. This model differs from the conventional model of the weak
localization developed for and by one point: the
value of the quantum interference contribution to the conductivity is
restricted not only by the phase breaking length but by the
localization length as well. We show that just the quantity
rather than
, where is the dephasing time and
, is responsible for the temperature and
magnetic field dependences of the conductivity over the wide range of
temperature and disorder strength down to the conductivity of order .Comment: 11 pages, 15 figure
Strong Modification of the Nonlinear Optical Response of Metallic Subwavelength Hole Arrays
The influence of hole shape on the nonlinear optical properties of metallic subwavelength hole arrays is investigated. It is found that the amount of second harmonics generated can be enhanced by changing the hole shape. In part this increase is a direct result of the effect of hole shape on the linear transmission properties. Remarkably, in addition to enhancements that follow directly from the linear properties of the array, we find a hot hole shape. For rectangular holes the effective nonlinear response is enhanced by more than 1 order of magnitude for one particular aspect ratio. This enhancement can be attributed to slow propagation of the fundamental wavelength through the holes which occurs close to the hole cutoff
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Case Study Shows Disconnect on Civic Journalism's Role
This in-depth case study examines attempts to transform a traditional newsroom to one oriented around civic journalism principles, offering a unique look at the resistance toward those principles even in a digital environment that facilitates new audience relationships. Civic journalism emphasizes understanding and addressing community concerns from a citizen perspective. This study finds that journalists still struggle to integrate citizensβ contributions into newsroom practice in meaningful ways
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Newswork within a Culture of Job Insecurity: Producing News amidst Organizational and Industry Uncertainty
Rapid change in the news industry and the prevalence of layoffs, buyouts, and closings have led many newsworkers to experience job insecurity and worry about their long-term futures in journalism. Our research uses a case study of employees at an independently owned media company in the United States to explore the various ways newsworkers respond to this culture of job insecurity and how their responses affect efforts to change news practices. Findings demonstrate that those who believe their jobs are at risk are unlikely to change their practices and even some who perceive job security are reticent to initiate change. As a result, the culture of job insecurity in the news industry has a limiting effect on changes to journalism practice
Enhancement of toxin- and virus-neutralizing capacity of single-domain antibody fragments by N-glycosylation
Single-domain antibody fragments (VHHs) have several beneficial properties as compared to conventional antibody fragments. However, their small size complicates their toxin- and virus-neutralizing capacity. We isolated 27 VHHs binding Escherichia coli heat-labile toxin and expressed these in Saccharomyces cerevisiae. The most potent neutralizing VHH (LT109) was N-glycosylated, resulting in a large increase in molecular mass. This suggests that N-glycosylation of LT109 improves its neutralizing capacity. Indeed, deglycosylation of LT109 decreased its neutralizing capacity three- to fivefold. We also studied the effect of glycosylation of two previously isolated VHHs on their ability to neutralize foot-and-mouth disease virus. For this purpose, these VHHs that lacked potential N-glycosylation sites were genetically fused to another VHH that was known to be glycosylated. The resulting fusion proteins were also N-glycosylated. They neutralized the virus at at least fourfold-lower VHH concentrations as compared to the single, non-glycosylated VHHs and at at least 50-fold-lower VHH concentrations as compared to their deglycosylated counterparts. Thus, we have shown that N-glycosylation of VHHs contributes to toxin- and virus-neutralizing capacity
Faecalibacterium prausnitzii Strain HTF-F and Its Extracellular Polymeric Matrix Attenuate Clinical Parameters in DSS-Induced Colitis
Date of Acceptance: 26/02/2015 Funding: The authors received no specific funding for this work.Peer reviewedPublisher PD
Studies on the Induction of Antigen-Specific Antibody in Anti-CD40 Cultured Human B Lymphocytes
Costimulatory signals provided by T cells are required for B cells to produce specific antibody to T-dependent antigen. We have investigated the suitability of using the CD40 culture system for the proliferation and differentiation of Ag-specific human B cells using cytomegalovirus (CMV) or tetanus toxoid (TT) as antigen. We modified the CD40 culture system (CD32- transfected L cells, anti-CD40, and IL-4) by applying a sequential cytokine stimulation and compared total B-cell cultures with antigen-specific B cells preselected by panning. The detection of specific antibody became possible when antigen-selected B cells were cultured for 7 days in the CD40 system to induce clonal expansion, followed by the addition of IL-2 and IL10 for an additional 7 days to induce plasma-cell differentiation. We conclude that our intial inability to detect specific antibody in the CD40 system is due to overgrowth of nonspecific B cell clones and that selection of antigen-specific B cells by panning overcomes this problem. Induction of antigen-specific antibody production was found to be optimal when the initial
contact with antigen during panning was limited to between 1 to 24 hours
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