Mechanisms for Lasing with Cold Atoms as the Gain Medium

We realize a laser with a cloud of cold rubidium atoms as gain medium, placed in a low-finesse cavity. Three different regimes of laser emission are observed corresponding respectively to Mollow, Raman and Four Wave Mixing mechanisms. We measure an output power of up to 300 $\mu$W and present the main properties of these different lasers in each regime

Treatment of Young Children with HIV Infection: Using Evidence to Inform Policymakers

PMCID: PMC3404108This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Effects of 1,25-Dihydroxycholecalciferol on Recovery and Resolution of Late Transient Neonatal Hypocalcemia

Background. Late transient neonatal hypocalcemia with hyperphosphatemia is potentially life-threatening. The use of 1.25 dihydroxycholecalciferol in the management of neonatal hypocalcemia is unexplored. Objective. We hypothesized adding 1.25 dihydroxycholecalciferol to intravenous continuous calcium infusion (CaI) will achieve accelerated correction of hypocalcemia. Design/Methods. A controlled double-blind randomized placebo group was organized to compare the addition of 1.25 dihydroxycholecalciferol to CaI in 3–14 day old neonates presenting with hypocalcemia, hyperphosphatemia and seizures. Ionized calcium and phosphorus were measured to adjust CaI and maintain eucalcemia. Time to resolution of hypocalcemia was defined as time from starting CaI to the first ionized calcium of ≥1.1 mmol/L. CaI was discontinued when ionized calcium levels were ≥1.1 mmol/L on two measurements and the infant tolerated feeds. Results. Fourteen neonates were studied without statistical difference between groups. Time to correction of hypocalcemia for 1,25 dihydroxycholecalciferol versus placebo was 7.2  ±  1.9 versus 11.5  ±  3.4 hours respectively (p = .26). The duration of CaI was 15.0  ±  1.5 versus 24.8  ±  4.4 hours respectively (p = .012). Conclusions. The addition of 1.25 dihydroxycholecalciferol to standard CaI therapy reduced the duration of CaI, but did not reduce the time to correct hypocalcemia in neonates with late transient hypocalcemia

Collapse Dynamics of a Homopolymer: Theory and Simulation

We present a scaling theory describing the collapse of a homopolymer chain in poor solvent. At time t after the beginning of the collapse, the original Gaussian chain of length N is streamlined to form N/g segments of length R(t), each containing g ~ t monomers. These segments are statistical quantities representing cylinders of length R ~ t^{1/2} and diameter d ~ t^{1/4}, but structured out of stretched arrays of spherical globules. This prescription incorporates the capillary instability. We compare the time-dependent structure factor derived for our theory with that obtained from ultra-large-scale molecular dynamics simulation with explicit solvent. This is the first time such a detailed comparison of theoretical and simulation predictions of collapsing chain structure has been attempted. The favorable agreement between the theoretical and computed structure factors supports the picture of the coarse-graining process during polymer collapse.Comment: 4 pages, 3 figure

The impact of COVID-19 on patient engagement with primary healthcare: lessons from the saudi primary care setting

BACKGROUND: There have been significant achievements in controlling COVID-19 in Saudi Arabia (SA), but as in most healthcare settings worldwide, health services have been seriously disrupted. Also, with pandemic control measures such as lockdowns and curfews, and innovations such as digital health services, the delivery of primary healthcare (PHC) services has dramatically changed. However, little is known about patients' experiences of PHCs during the pandemic, their views on the pandemic-related interventions in SA, and patient views on impact on their medical care. METHODS: Qualitative semi-structured online interviews were conducted for twenty-four Saudi patients across SA aged 18 and above who were diverse in terms of age, gender, education and health status. Data were analysed using thematic analysis yielding four major themes as an impact of COVID-19 on patient engagement with PHCs. RESULTS: The COVID-19 pandemic has had profound mixed impacts on patient engagement with PHC in SA. Fear of infection or of breaking lockdown rules has negatively impacted the utilisation of PHCs but positively changed patients' attitudes towards seeking medical help for self-limiting conditions. The pandemic has also negatively impacted routine preventive care at PHCs, especially for patients with long-term health conditions. The mandatory use of some digital health services in SA that existed pre-pandemic has provided patients with a perception of better care during the pandemic. Yet, a lack of awareness of optional digital health services, such as virtual clinics, hindered optimal use. Despite pandemic-related disruption of patient engagement with PHCs, the reduced waiting time in PHC centres and healthcare providers' communication and empathy during the pandemic contributed to patients' perceptions of better care compared to pre-pandemic. However, patients living outside the main cities in SA perceived care quality as less good during the pandemic compared to PHCs in the main cities in SA. CONCLUSION: The lessons learned from patients' experiences and views of PHCs during the pandemic were beneficial in promoting patient engagement with PHCs. The digital health services mandated in response to the pandemic have accelerated digital health innovation in SA and allowed patients to recognise the benefits of digital health. This has huge potential for increasing continuous patient engagement with PHCs. Yet, patients' experiences of digital health services during the pandemic are essential for informing appropriate implementation and utilisation of e-health services. Patients' positive experiences of PHCs during the pandemic, such as the reduction in waiting times and the perception of improved healthcare providers' professionalism, communication and empathy, can be built on to sustain engagement with PHC services. These findings might have significance for clinicians and policymakers to support patient engagement with PHCs, particularly in healthcare systems like SA that struggle with the overuse of emergency departments (EDs) for PHC-treatable conditions

Chimera States for Coupled Oscillators

Arrays of identical oscillators can display a remarkable spatiotemporal pattern in which phase-locked oscillators coexist with drifting ones. Discovered two years ago, such "chimera states" are believed to be impossible for locally or globally coupled systems; they are peculiar to the intermediate case of nonlocal coupling. Here we present an exact solution for this state, for a ring of phase oscillators coupled by a cosine kernel. We show that the stable chimera state bifurcates from a spatially modulated drift state, and dies in a saddle-node bifurcation with an unstable chimera.Comment: 4 pages, 4 figure