Uniform electron gases

We show that the traditional concept of the uniform electron gas (UEG) --- a homogeneous system of finite density, consisting of an infinite number of electrons in an infinite volume --- is inadequate to model the UEGs that arise in finite systems. We argue that, in general, a UEG is characterized by at least two parameters, \textit{viz.} the usual one-electron density parameter $\rho$ and a new two-electron parameter $\eta$. We outline a systematic strategy to determine a new density functional $E(\rho,\eta)$ across the spectrum of possible $\rho$ and $\eta$ values.Comment: 8 pages, 2 figures, 5 table

Perceived stress during the prenatal period: assessing measurement invariance of the Perceived Stress Scale (PSS‑10) across cultures and birth parity

Maternal prenatal stress places a substantial burden on mother’s mental health. Expectant mothers in low- and middle-income countries (LMICs) have thus far received less attention than mothers in high-income settings. This is particularly problematic, as a range of triggers, such as exposure to traumatic events (e.g. natural disasters, previous pregnancy losses) and adverse life circumstances (e.g. poverty, community violence), put mothers at increased risk of experiencing prenatal stress. The ten-item Perceived Stress Scale (PSS-10) is a widely recognised index of subjective experience of stress that is increasingly used in LMICs. However, evidence for its measurement equivalence across settings is lacking. This study aims to assess measurement invariance of the PSS-10 across eight LMICs and across birth parity. This research was carried out as part of the Evidence for Better Lives Study (EBLS, vrc.crim.cam.ac.uk/vrcresearch/EBLS). The PSS-10 was administered to N = 1,208 expectant mothers from Ghana, Jamaica, Pakistan, the Philippines, Romania, South Africa, Sri Lanka and Vietnam during the third trimester of pregnancy. Confirmatory factor analysis suggested a good model fit of a two-factor model across all sites, with items on experiences of stress loading onto a negative factor and items on perceived coping onto a positive factor. Configural and metric, but not full or partial scalar invariance, were established across all sites. Configural, metric and full scalar invariance could be established across birth parity. On average, first-time mothers reported less stress than mothers who already had children. Our findings indicate that the PSS-10 holds utility in assessing stress across a broad range of culturally diverse settings; however, caution should be taken when comparing mean stress levels across sites

Dental and periodontal phenotype in sclerostin knockout mice.

Sclerostin is a Wnt signalling antagonist that controls bone metabolism. Sclerostin is expressed by osteocytes and cementocytes; however, its role in the formation of dental structures remains unclear. Here, we analysed the mandibles of sclerostin knockout mice to determine the influence of sclerostin on dental structures and dimensions using histomorphometry and micro-computed tomography (μCT) imaging. μCT and histomorphometric analyses were performed on the first lower molar and its surrounding structures in mice lacking a functional sclerostin gene and in wild-type controls. μCT on six animals in each group revealed that the dimension of the basal bone as well as the coronal and apical part of alveolar part increased in the sclerostin knockout mice. No significant differences were observed for the tooth and pulp chamber volume. Descriptive histomorphometric analyses of four wild-type and three sclerostin knockout mice demonstrated an increased width of the cementum and a concomitant moderate decrease in the periodontal space width. Taken together, these results suggest that the lack of sclerostin mainly alters the bone and cementum phenotypes rather than producing abnormalities in tooth structures such as dentin

Exposure to Electronic Cigarettes Impairs Pulmonary Anti-Bacterial and Anti-Viral Defenses in a Mouse Model

Electronic cigarettes (E-cigs) have experienced sharp increases in popularity over the past five years due to many factors, including aggressive marketing, increased restrictions on conventional cigarettes, and a perception that E-cigs are healthy alternatives to cigarettes. Despite this perception, studies on health effects in humans are extremely limited and in vivo animal models have not been generated. Presently, we determined that E-cig vapor contains 7 x 10(11) free radicals per puff. To determine whether E-cig exposure impacts pulmonary responses in mice, we developed an inhalation chamber for E-cig exposure. Mice that were exposed to E-cig vapor contained serum cotinine concentrations that are comparable to human E-cig users. E-cig exposure for 2 weeks produced a significant increase in oxidative stress and moderate macrophage-mediated inflammation. Since, COPD patients are susceptible to bacterial and viral infections, we tested effects of E-cigs on immune response. Mice that were exposed to E-cig vapor showed significantly impaired pulmonary bacterial clearance, compared to air-exposed mice, following an intranasal infection with Streptococcus pneumonia. This defective bacterial clearance was partially due to reduced phagocytosis by alveolar macrophages from E-cig exposed mice. In response to Influenza A virus infection, E-cig exposed mice displayed increased lung viral titers and enhanced virus-induced illness and mortality. In summary, this study reports a murine model of E-cig exposure and demonstrates that E-cig exposure elicits impaired pulmonary anti-microbial defenses. Hence, E-cig exposure as an alternative to cigarette smoking must be rigorously tested in users for their effects on immune response and susceptibility to bacterial and viral infections