Predicting rare events in chemical reactions: application to skin cell proliferation

In a well-stirred system undergoing chemical reactions, fluctuations in the reaction propensities are approximately captured by the corresponding chemical Langevin equation. Within this context, we discuss in this work how the Kramers escape theory can be used to predict rare events in chemical reactions. As an example, we apply our approach to a recently proposed model on cell proliferation with relevance to skin cancer [P.B. Warren, Phys. Rev. E {\bf 80}, 030903 (2009)]. In particular, we provide an analytical explanation for the form of the exponential exponent observed in the onset rate of uncontrolled cell proliferation.Comment: New materials and references added. To appear in Physical Review

Limits on MeV Dark Matter from the Effective Number of Neutrinos

Thermal dark matter that couples more strongly to electrons and photons than to neutrinos will heat the electron-photon plasma relative to the neutrino background if it becomes nonrelativistic after the neutrinos decouple from the thermal background. This results in a reduction in N_eff below the standard-model value, a result strongly disfavored by current CMB observations. Taking conservative lower bounds on N_eff and on the decoupling temperature of the neutrinos, we derive a bound on the dark matter particle mass of m_\chi > 3-9 MeV, depending on the spin and statistics of the particle. For p-wave annihilation, our limit on the dark matter particle mass is stronger than the limit derived from distortions to the CMB fluctuation spectrum produced by annihilations near the epoch of recombination.Comment: 5 pages, 1 figure, discussion added, references added and updated, labels added to figure, to appear in Phys. Rev.

Quenched chiral logarithms in lattice QCD with exact chiral symmetry

We examine quenched chiral logarithms in lattice QCD with overlap Dirac quark. For 100 gauge configurations generated with the Wilson gauge action at $\beta = 5.8$ on the $8^3 \times 24$ lattice, we compute quenched quark propagators for 12 bare quark masses. The pion decay constant is extracted from the pion propagator, and from which the lattice spacing is determined to be 0.147 fm. The presence of quenched chiral logarithm in the pion mass is confirmed, and its coefficient is determined to be $\delta = 0.203 \pm 0.014$, in agreement with the theoretical estimate in quenched chiral perturbation theory. Further, we obtain the topological susceptibility of these 100 gauge configurations by measuring the index of the overlap Dirac operator. Using a formula due to exact chiral symmetry, we obtain the $\eta'$ mass in quenched chiral perturbation theory, $m_{\eta'} = (901 \pm 64)$ Mev, and an estimate of $\delta = 0.197 \pm 0.027$, which is in good agreement with that determined from the pion mass.Comment: 24 pages, 6 EPS figures; v2: some clarifications added, to appear in Physical Review

The Expected Mass Function for Low Mass Galaxies in a CDM Cosmology: Is There a Problem?

It is well known that the mass function for_halos_ in CDM cosmology is a relatively steep power law for low masses, possibly too steep to be consistent with observations. But how steep is the_galaxy_ mass function? We have analyzed the stellar and gas mass functions of the first massive luminous objects formed in a \Lambda CDM universe, as calculated in the numerical simulation described in Gnedin (2000ab). We found that while the dark matter mass function is steep, the stellar and gas mass functions are flatter for low mass objects. The stellar mass function is consistently flat at the low mass end. Moreover, while the gas mass function follows the dark matter mass function until reionization at z~7, between z=7 and z=4, the gas mass function also flattens considerably at the low mass end. At z=4, the gas and stellar mass functions are fit by a Schechter function with \alpha ~ -1.2 +/- 0.1, significantly shallower than the dark matter halo mass function and consistent with some recent observations. The baryonic mass functions are shallower because (a) the dark matter halo mass function is consistent with the Press-Schechter formulation at low masses n(M) M^-2 and (b) heating/cooling and ionization processes appear to cause baryons to collect in halos with the relationship M_b M_d^4 at low masses. Combining (a) and (b) gives n(M_b) M_b^-5/4, comparable to the simulation results. Thus, the well known observational fact that low mass galaxies are underabundant as compared to expectations from numerical dark matter simulations or Press-Schechter modeling of CDM universes emerges naturally from these results, implying that perhaps no ``new physics'' beyond the standard model is needed.Comment: Submitted to ApJ, 17 pages including 6 figure

Contact Binary Variables as X-ray Sources

We present cross-identification of archived X-ray point sources with W UMa variable stars found in the All-Sky Automated Survey (ASAS). In a surveyed sky area of 300 square degrees of ASAS, 36 W UMa stars have been found associated with X-ray emission. We compute the distances of these W UMa systems and hence their X-ray luminosities. Our data support the "supersaturation" phenomenon seen in these fast rotators, namely that the faster a W UMa star rotates, the weaker its X-ray luminosity.Comment: 10 pages, 2 figures, 1 table; submitted to A

Oligodendroglioma cells lack glutamine synthetase and are auxotrophic for glutamine, but do not depend on glutamine anaplerosis for growth

In cells derived from several types of cancer, a transcriptional program drives high consumption of glutamine (Gln), which is used for anaplerosis, leading to a metabolic addiction for the amino acid. Low or absent expression of Glutamine Synthetase (GS), the only enzyme that catalyzes de novo Gln synthesis, has been considered a marker of Gln-addicted cancers. In this study, two human cell lines derived from brain tumors with oligodendroglioma features, HOG and Hs683, have been shown to be GS-negative. Viability of both lines depends from extracellular Gln with EC of 0.175 ± 0.056 mM (Hs683) and 0.086 ± 0.043 mM (HOG), thus suggesting that small amounts of extracellular Gln are sufficient for OD cell growth. Gln starvation does not significantly affect the cell content of anaplerotic substrates, which, consistently, are not able to rescue cell growth, but causes hindrance of the Wnt/β-catenin pathway and protein synthesis attenuation, which is mitigated by transient GS expression. Gln transport inhibitors cause partial depletion of intracellular Gln and cell growth inhibition, but do not lower cell viability. Therefore, GS-negative human oligodendroglioma cells are Gln-auxotrophic but do not use the amino acid for anaplerosis and, hence, are not Gln addicted, exhibiting only limited Gln requirements for survival and growth

The NASA/GSFC hydrogen maser program: A review of recent data

Data is presented on the phase and frequency stability, over time periods extending to one week, of the new NR field operable hydrogen masers developed by the Applied Physics Laboratory (APL) and the older NX and NP field operable hydrogen masers developed by Goddard Space Flight Center and maintained and upgraded by Bendix Field Engineering Corporation (BFEC). Data is presented on the NR masers in the laboratory showing frequency stabilities well into the 10 to the -15th power range and phase stabilities well into the 100 ps range for periods of up to one day. Data is presented on upgraded NP masers in the laboratory showing that the frequency stability has been improved substantially to virtually the NR level. VLBI data is presented on the phase difference between NX-2 at Owens Valley, California and NR-2 at Fort Davis, Texas for a one week period showing, after removal of a constant frequency drift, a 350 ps RMS phase stability

Sustainability of Community Engagement at Institutions of Higher Education: A Look at Compassion Fatigue and the College Student Mental Health Crisis

This study investigated one of the many factors contributing to the sustainability of community engagement efforts at institutions of higher education. Extensive literature shows that burnout and compassion fatigue disproportionately affect those in caring roles and helping professions. Moreover, studies have found significant correlations between levels of burnout and compassion fatigue and the likelihood of human error, which directly affects the safety and long-term outcomes of people within their care. However, there is still limited exploration of how these phenomena may manifest, and similarly, cause unintentional harm to vulnerable populations, in the context of student community engagement efforts. This paper considers the pervasiveness of the college student mental health crisis, particularly amid a year rife with grief and instability co-created by the COVID-19 pandemic and immense socio-political conflict. Participants included 46 college students, and data were collected between March and April 2020 using an anonymous online survey. Results revealed that participants had high compassion satisfaction scores (M=42.19 out of 50) and relatively low burnout (M=21.14 out of 50) and secondary traumatic stress scores (M=22.83 out of 50). Although these results differed from the authors’ original hypotheses, the information presented in this paper calls for further investigation into how students can be supported in ways that minimize compassion fatigue and boost compassion satisfaction. Katherine Chiu (she/her) earned her Bachelor of Science in Health Sciences with a concentration in Public Health Education and minors in Pre-Medicine and Medical Humanities from James Madison University in 2020. She recently finished working as the Engagement Fellow for Economic and Community Development at Professional & Continuing Education in Harrisonburg, Virginia. Briana Craig (she/her) is a proud alumnus of James Madison University, where she received a M.A. in Psychological Science (quantitative concentration) and a B.S. in Psychology with a statistics minor. She now works as a Research Associate for Westat, a research contracting company based in Rockville, Maryland. Naomi Rabago (she/her/hers) is a senior Social Work major and Service-Learning Coordinator with Community Service-Learning. She has been involved in and held leadership positions in groups all over campus, including Ethical Reasoning in Action, the Alternative Break Program, and the Marching Royal Dukes. Authors\u27 note We would like to thank all of the professional staff working in the Community Service-Learning office at James Madison University. Without their guidance, support, and encouragement over the course of several years, this project would not have been possible. We are deeply grateful for their mentorship, and they have inspired us beyond words. We would also like to thank the Virginia Engage Journal editors, Steve Grande and Emily Kohl, for providing thoughtful feedback, engaging in meaningful conversations, and supporting us through our first experience publishing research

A Case of Back to The Future: Paediatric Abdominal Pain. Thorough History, Examination And Senior Clinician Involvement Remain Imperative For Successful Management

INTRODUCTION: The inherent variability of the history and exam in paediatrics make acute abdominal pain a diagnostic challenge. Investigations such as white-cell-count (WCC), C-reactive-protein and radiological studies have been advocated to help objectify management. Whilst Computed Tomography is accurate, the amount of radiation involved renders it unacceptable and thus many view ultrasonographyas an acceptable alternative. But do these tests add value? METHODS: Retrospective review between 2002–2012. Data was collected for children under sixteen with acute abdominal pain undergoing investigation with ultrasound and haematological testing. For 2005,a retrospective review was conducted for children presenting with abdominal pain to obtain data on demographics, history and examination findings. Analysis for diagnostic accuracy was undertaken. RESULTS: 5000 records were reviewed, and 1744 records included. 6% of children developed appendicitis. Findings of worsening pain, associated with nausea or vomiting yielded moderate sensitivities and specificities (combined values over 70%). Fever was non-specific. Localised tenderness is the most sensitive exam finding and rebound tenderness is the most specific, both having values over 90%. WCC and CRP offer similar sensitivities and specificities, both producing results under 80%. Only 30% of ultrasounds visualised the appendix, significantly dampening the sensitivity below 75%. The incidence of appendicitis in the non-visualised group was 8%. Conclusion No test is useful for ruling out appendicitis. Given that the incidence of appendicitis is higher in the non-visualised group, this is especially so with ultrasonography. Clinical examination with senior input is the most sensible strategy for managing children with acute abdominal pain