Simulated [111] Si-SiGe terahertz quantum cascade laser

The prospect of developing a silicon laser has long been an elusive goal, mainly due to the indirect band gap and large effective carrier masses. We present a design for a terahertz intersubband laser grown on the [111] crystal plane and simulate performance using a rate equation method including scattering due to alloy disorder, interface roughness, carrier-phonon and Coulombic interactions. We predict gain greater than 40 cm-1 and a threshold current density of 70 A/cm2

The limiting distribution of the likelihood ratio statistic minus 21 n lambda sub n under a class of local alternatives, part 1. Minimum average risk decision procedures for the noncentral chi-square distribution, part 2

Limiting distribution of likelihood ratio statistic under class of local alternatives and minimum average risk decision procedures for noncentral chi-square distributio

Tacrolimus analysis: A comparison of different methods and matrices

We determined the trough blood and plasma concentrations of tacrolimus from the day of transplantation through 30 days posttransplantation in four liver and four kidney transplant patients by three different methods. The first method involved a solid phase extraction of the blood or plasma using Sep-Pak columns (SPs) followed by quantitation of tacrolimus using an enzyme-linked immunosorbent assay (ELISA); the second method involved a liquid-liquid extraction using methylene chloride (MC) followed by quantitation of tacrolimus using the ELISA, and the third method involved a high-performance liquid chromatography (HPLC) fractionation of the extract obtained from the solid-phase extraction and quantitation of tacrolimus in the fractions by ELISA. The trough plasma tacrolimus concentrations ranged from 0.1 to 5.2 ng/ml. While the trough plasma concentrations of tacrolimus were similar and independent of the method of analysis in kidney transplant patients and in liver transplant patients with normal biochemical profile, in patients with liver dysfunction, tacrolimus plasma concentrations were higher when measured by SP-ELISA and MC-ELISA methods as compared to the HPLC-ELISA method. In plasma samples obtained from liver transplant patients with liver dysfunction, the presence of some metabolites that cross-reacted with the antibody used in the ELISA could be documented in the HPLC fraction corresponding to the metabolites. This indicates that while tacrolimus metabolites that cross-react significantly with the antibody used in the ELISA do not accumulate in kidney transplant patients, they can appear in the plasma of patients with liver dysfunction. The trough blood tacrolimus concentrations in patients were significantly higher than the corresponding plasma concentrations and ranged from 1.4 to 107 ng/ml. The trough blood tacrolimus concentrations were similar and independent of the method of analysis in kidney and liver transplant patients, suggesting unchanged tacrolimus to be the major component in the blood. The HPLC fractions corresponding to the metabolites of tacrolimus did not contain any components that cross-reacted with the antibody used. This study documents that the methods used in this study for the analysis of blood concentrations of tacrolimus appear to be specific for the parent tacrolimus and can be used in future pharmacokinetic and clinical studies. © 1995 Raven Press, Ltd., New York

From Hashtags to Shopping Bags: Measuring the Rise of eWOM through Social Media and its Impact on Travelers’ Shopping Patterns

The rise of the Internet and the proliferation of social media has amplified the importance of understanding the consumer decision-making process. Not surprisingly, travel industry marketers are devoting greater portions of their marketing budgets towards harnessing the power of social media and electronic word-of-mouth (eWOM) as a tool to influence consumer preferences. Yet, to accomplish this goal, marketers need to understand that people differ in their motivation to spread eWOM through social media, and there exists a crucial distinction between organic (consumer-initiated) versus incentivized (company-promoted) eWOM. Therefore, the objective of this study is to draw insights from the nascent eWOM literature and interviews with cross-border travelers to investigate heterogeneity in social media use and the differential impact on travel-related intentions and behaviours. Using a conceptual mapping methodology, our preliminary findings demonstrate patterns of social, opinion forming, and trip planning aspects. Implications for marketers are discussed

Rethinking Resident Perceptions of Tourism in British Columbia, Canada

This joint academic/practitioner report segments British Columbia, Canada residents to provide destination managers with new ways to better understand resident perceptions of tourism. The data collection was conducted in April and May of 2022 and had a total of 2,265 valid responses. It was also a practical objective to conduct this research in a manner that is repeatable in jurisdictions beyond British Columbia. This report has confirmed five distinct categories of residents’ perceptions toward tourism, including socio-cultural, economic, environmental, job/career, and Indigenous impacts. In addition to the categories of impacts, a cluster analysis has revealed six clusters of residents based on the five categories: Tourism Ambassadors, Tourism Supporters, Socio-cultural and Tourism Economic Supporters, Neutrals, Concerns about Careers and Environment, and Tourism Adversaries. Managerial implications and opportunities for future destination management and governance are discussed

Theory and design of quantum cascade lasers in (111) n-type Si/SiGe

Although most work towards the realization of group IV quantum cascade lasers (QCLs) has focused on valence band transitions, there are many desirable properties associated with the conduction band. We show that the commonly cited shortcomings of n-type Si/SiGe heterostructures can be overcome by moving to the (111) growth direction. Specifically, a large band offset and low effective mass are achievable and subband degeneracy is preserved. We predict net gain up to lattice temperatures of 90 K in a bound-to-continuum QCL with a double-metal waveguide, and show that a Ge interdiffusion length of at least 8 Å across interfaces is tolerable

Evaluating RNA Structural Flexibility: Viruses Lead the Way.

Our understanding of RNA structure has lagged behind that of proteins and most other biological polymers, largely because of its ability to adopt multiple, and often very different, functional conformations within a single molecule. Flexibility and multifunctionality appear to be its hallmarks. Conventional biochemical and biophysical techniques all have limitations in solving RNA structure and to address this in recent years we have seen the emergence of a wide diversity of techniques applied to RNA structural analysis and an accompanying appreciation of its ubiquity and versatility. Viral RNA is a particularly productive area to study in that this economy of function within a single molecule admirably suits the minimalist lifestyle of viruses. Here, we review the major techniques that are being used to elucidate RNA conformational flexibility and exemplify how the structure and function are, as in all biology, tightly linked

Identification of unique reciprocal and non reciprocal cross packaging relationships between HIV-1, HIV-2 and SIV reveals an efficient SIV/HIV-2 lentiviral vector system with highly favourable features for in vivo testing and clinical usage.

BACKGROUND: Lentiviral vectors have shown immense promise as vehicles for gene delivery to non-dividing cells particularly to cells of the central nervous system (CNS). Improvements in the biosafety of viral vectors are paramount as lentiviral vectors move into human clinical trials. This study investigates the packaging relationship between gene transfer (vector) and Gag-Pol expression constructs of HIV-1, HIV-2 and SIV. Cross-packaged vectors expressing GFP were assessed for RNA packaging, viral vector titre and their ability to transduce rat primary glial cell cultures and human neural stem cells. RESULTS: HIV-1 Gag-Pol demonstrated the ability to cross package both HIV-2 and SIV gene transfer vectors. However both HIV-2 and SIV Gag-Pol showed a reduced ability to package HIV-1 vector RNA with no significant gene transfer to target cells. An unexpected packaging relationship was found to exist between HIV-2 and SIV with SIV Gag-Pol able to package HIV-2 vector RNA and transduce dividing SV2T cells and CNS cell cultures with an efficiency equivalent to the homologous HIV-1 vector however HIV-2 was unable to deliver SIV based vectors. CONCLUSION: This new non-reciprocal cross packaging relationship between SIV and HIV-2 provides a novel way of significantly increasing bio-safety with a reduced sequence homology between the HIV-2 gene transfer vector and the SIV Gag-Pol construct thus ensuring that vector RNA packaging is unidirectional.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are