Dangling Bonds in Hexagonal Boron Nitride as Single-Photon Emitters.

Hexagonal boron nitride has been found to host color centers that exhibit single-photon emission, but the microscopic origin of these emitters is unknown. We propose boron dangling bonds as the likely source of the observed single-photon emission around 2 eV. An optical transition where an electron is excited from a doubly occupied boron dangling bond to a localized B p_{z} state gives rise to a zero-phonon line of 2.06 eV and emission with a Huang-Rhys factor of 2.3. This transition is linearly polarized with the absorptive and emissive dipole aligned. Because of the energetic position of the states within the band gap, indirect excitation through the conduction band will occur for sufficiently large excitation energies, leading to the misalignment of the absorptive and emissive dipoles seen in experiment. Our calculations predict a singlet ground state and the existence of a metastable triplet state, in agreement with experiment

Testing the Task-Media Fit: The Effects of Task Equivocality on Social Presence of Mobile Video-Mediated Communication

Since social presence theory was introduced, many researchers have tried to apply it to various technology-mediated communication media, including E-Mail, videoconferencing, and instant messengers. Yet few researches have investigated the influence of mobile video-mediated communication (VMC) on the social presence despite prevalence in business practices. In this paper, a research model is developed to test the relationship between the mobile VMC (video telephony and video chatting) and the level of social presence. And the task equivocality, whether it’s an intellective task or a negotiation task, is also considered as moderating variables, based on the task-media fit proposition. Hence, mobile video chatting could be suggested as an alternative media of mobile video telephony for less equivocal informative tasks according to this study

Trends and Associated Factors of Use of Opioid, Heroin, and Cannabis Among Patients for Emergency Department Visits in Nevada: 2009–2017

To examine trends and contributing factors of opioid, heroin, and cannabis-associated emergency department (ED) visits in Nevada. The 2009 to 2017 Nevada State ED database (n = 7,950,554 ED visits) were used. Use of opioid, heroin, and cannabis, respectively, was identified by the International Classification of Diseases, 9th & 10th Revisions. Three multivariable models, one for each of the 3 dependent variables, were conducted. Independent variables included year, insurance status, race/ethnicity, use of other substance, and mental health conditions. The number of individuals with opioid, heroin, cannabis-associated ED visits increased 3%, 10%, and 23% annually from 2009 to 2015, particularly among 21 to 29 age group, females, and African Americans. Use of other substance (odds ratio [OR] = 3.91; 95% confidence interval [CI] = 3.84, 3.99; reference - no use of other substance), mental health conditions (OR = 2.48; 95% CI = 2.43, 2.53; reference – without mental health conditions), Medicaid (OR = 1.41; 95% CI = 1.38, 1.44; reference – non-Medicaid), Medicare (OR = 1.44; 95% CI = 1.39, 1.49; reference – non-Medicare) and uninsured patients (OR = 1.52; 95% CI = 1.49, 1.56; reference - insured) were predictors of all three substance-associated ED visits. With a steady increase in trends of opioid, heroin, and cannabis-associated ED visits in recent years, the main contributing factors include patient sociodemographic factors, mental health conditions, and use of other substances

The visibility of environmental rights in the EU legal order: eurolegalism in action?

The current article responds to a key puzzle and a question. First, why, given the potential for ‘rights talk’ that has been seen in other countries and other policy areas, have environmental rights in the EU legal order been relatively invisible until recently? And second, with Daniel Kelemen’s influential work on Eurolegalism arguing that the EU has become much more reliant on US-style adversarial legalism, including a shift towards rights-based litigation, do EU environmental rights fit the picture Kelemen has painted, or are they an exception? The article explores the visibility of EU environmental rights at EU level and then seeks to explain the possible reasons for visibility/invisibility

HI Properties of Low Luminosity Star-Forming Galaxies in the KPNO International Spectroscopic Survey

New HI observations are presented for a complete sample of 109 low luminosity star-forming galaxies taken from the KPNO International Spectroscopic Survey (KISS), the first CCD-based wide-field objective-prism survey for emission-line galaxies. This sample consists of all star-forming galaxies with M_B > -18.0 and cz < 11,000 km/s from the first Halpha-selected survey list. Overall, 97 out of 109 galaxies have been detected in HI. We confirm the weak trend of increasing gas richness with decreasing luminosity found by previous authors. Gas richness is also shown to be weakly anti-correlated with metallicity. The dependence of star formation rates (SFRs) and HI gas depletion timescales on metallicity is examined. The median solar metallicity based SFR and gas depletion timescale are 0.1639 M_sun/yr and 5 Gyrs, respectively. Corrections for variations in metallicity decreases SFRs by about 0.5 dex and increases gas depletion timescales by an average of about 8 Gyrs. The majority of galaxies in this sample still have large reservoirs of HI gas, and despite their large current star formation rates, could have formed stars in a quasi-continuous manner for a Hubble time. Finally, we present the first HI mass function for low luminosity star-forming galaxies and show that this subpopulation contributes 10-15% of the overall HI density in the local universe. We conclude that if the HI mass function of the Universe does indeed have a steeply rising low-mass slope as suggested by previous authors, it is not due to the population of low luminosity star-forming galaxies.Comment: 27 pages, 13 figures, 4 tables. Accepted for publication in the Astronomical Journa

Clostridium difficile in the ICU

Clostridium difficile has become an increasingly common infectious agent in the healthcare setting. It is generally associated with antibiotic use and causes diarrhea as well as other complications such as pseudomembranous colitis (PMC) and toxic megacolon. This organism poses a serious threat to patients in the intensive care unit (ICU) as it increases hospital length of stay, morbidity, and mortality. Recurrence rates are typically higher in the ICU population as those patients usually have immunocompromised systems, more exposure to antibiotics and proton pump inhibitors, loss of normal nutritional balance, and alterations in their colonic flora. Emergence of more virulent and pathogenic strains has made combating the infection even more difficult. Newer therapies, chemotherapeutic agents, and vaccinations are on the horizon. However, the most effective treatments to date are ceasing the inciting agent, reduction in the use of proton pump inhibitors, and prevention of the disease. In this chapter, we will explore the risk factors, diagnosis, treatment, and prevention of C. difficile infections (CDI) in the ICU