Dynamics of Fermat potentials in non-perturbative gravitational lensing

We present a framework, based on the null-surface formulation of general relativity, for discussing the dynamics of Fermat potentials for gravitational lensing in a generic situation without approximations of any kind. Additionally, we derive two lens equations: one for the case of thick compact lenses and the other one for lensing by gravitational waves. These equations in principle generalize the astrophysical scheme for lensing by removing the thin-lens approximation while retaining the weak fields.Comment: Accepted for publication in Phys. Rev.

Therapeutic potential of targeting sphingosine kinases and sphingosine 1-phosphate in hematological malignancies

Sphingolipids, such as ceramide, sphingosine and sphingosine 1-phosphate (S1P) are bioactive molecules that have important functions in a variety of cellular processes, which include proliferation, survival, differentiation and cellular responses to stress. Sphingolipids have a major impact on the determination of cell fate by contributing to either cell survival or death. Although ceramide and sphingosine are usually considered to induce cell death, S1P promotes survival of cells. Sphingosine kinases (SPHKs) are the enzymes that catalyze the conversion of sphingosine to S1P. There are two isoforms, SPHK1 and SPHK2, which are encoded by different genes. SPHK1 has recently been implicated in contributing to cell transformation, tumor angiogenesis and metastatic spread, as well as cancer cell multidrug-resistance. More recent findings suggest that SPHK2 also has a role in cancer progression. This review is an overview of our understanding of the role of SPHKs and S1P in hematopoietic malignancies and provides information on the current status of SPHK inhibitors with respect to their therapeutic potential in the treatment of haematological cancers

Quasar Proper Motions and Low-Frequency Gravitational Waves

We report observational upper limits on the mass-energy of the cosmological gravitational-wave background, from limits on proper motions of quasars. Gravitational waves with periods longer than the time span of observations produce a simple pattern of apparent proper motions over the sky, composed primarily of second-order transverse vector spherical harmonics. A fit of such harmonics to measured motions yields a 95%-confidence limit on the mass-energy of gravitational waves with frequencies <2e-9 Hz, of <0.11/h*h times the closure density of the universe.Comment: 15 pages, 1 figure. Also available at http://charm.physics.ucsb.edu:80/people/cgwinn/cgwinn_group/index.htm

Gravitational Radiation and Very Long Baseline Interferometry

Gravitational waves affect the observed direction of light from distant sources. At telescopes, this change in direction appears as periodic variations in the apparent positions of these sources on the sky; that is, as proper motion. A wave of a given phase, traveling in a given direction, produces a characteristic pattern of proper motions over the sky. Comparison of observed proper motions with this pattern serves to test for the presence of gravitational waves. A stochastic background of waves induces apparent proper motions with specific statistical properties, and so, may also be sought. In this paper we consider the effects of a cosmological background of gravitational radiation on astrometric observations. We derive an equation for the time delay measured by two antennae observing the same source in an Einstein-de Sitter spacetime containing gravitational radiation. We also show how to obtain similar expressions for curved Friedmann-Robertson-Walker spacetimes.Comment: 31 pages plus 3 separate figures, plain TeX, submitted to Ap

Beyond the 1984 Perspective: Narrow Focus on Modern Wildfire Trends Underestimates Future Risks to Water Security

The western United States remains well below historical wildfire activity, yet misconceptions abound in the public and news media that the area burning by wildfire each year in the American West is unprecedented. We submit that short‐term records of wildfire and a disproportionate focus on recent fire trends within high‐profile science stoke these misconceptions. Furthermore, we highlight serious risks to long‐term water security (encompassing water supply, storage, and quality) that have only recently been recognized and are underestimated as the result of skewed perspectives of wildfire. Compiling several data sets, we illustrate a comprehensive history of western wildfire, demonstrate that the majority of western settlement occurred during an artificially and anomalously low period of wildfire in the twentieth century, and discuss the troubling implications the misalignment of wildfire activity and human development may have for the long‐term projections of water security. A crucial first step toward realigning public perspectives will require scientists and journalists to present recent increases in wildfire area within the context and scale of longer‐term trends. Second, proper housing development and resource management will require an appreciation for the differing western ecosystems and the flexibility to adopt varied approaches. These actions are critical for realigning public understanding of both the direct and indirect risks associated with wildfire and ensuring adequate and appropriate measures are taken as we navigate a future of increasing fire in the West

Immune and acute phase markers in exercising adults

Many reports have documented the anti-inflammatory effects of regular exercise in adults. However clinicians and researchers remain uncertain on selecting specific biomarkers that are useful for predicting or monitoring chronic inflammatory states and/or disease. Clearer identification of markers (or clusters of markers) in physically active individuals that vary from established references ranges will indicate the extent of the purported anti-inflammatory effect of regular exercise. Physically active adults were recruited from the community to participate in a prospective study comparing self-reported health outcomes and exercise activity across 150 days of dietary intervention. Of the 450 participants recruited, 64 males (mean age 37.4 y, mean BMI = 25.3) and 59 females (mean age 40.4y, mean BMI= 23.4) agreed to supply a baseline blood sample taken at rest. A total of 187 analytes were measured by standard techniques on these pre-intervention samples including 11 immune markers (cell-types and immunoglobulins) and 11 acute phase reactants (WCC, albumin, haptoglobin, CRP, C3, C4, IGF-1, transferrin, iron, ferritin & ceruloplasmin). We compared baseline values with relevent hospital reference range (RR) values where these are assumed to be more reflective of a much less physically-active community population. A total of 5 out of 11 of the acute phase reactants (Hapt, C3, Fer, Trf (for females), and ceruloplasmin (for males)) had \u3e10% of values below the low ‘cut-off end’ of the relevant RR. Three immune cell-types (CD19, CD8 & CD16/56) had \u3e10% of values below the ‘low-cut-off end’ of the relevant RR. In contrast 25% of subjects had an IgE value that exceeded the RR. Collectively our results support the notion that regular exercise or physical activity exerts an anti-inflammatory affect. The results suggest putative roles for a host of exercise associated adaptive mechanisms beyond the generally accepted role for IL-6 derived from skeletal muscle and\or visceral fat. We conclude that across a host of measures, exercising adults have values for immune and acute phase reactants largely within, but at the non-inflammatory ‘end’ of clinical reference ranges

The effect of exercise on innate mucosal immunity

METHODS The authors conducted a prospective observational study comparing salivary lactoferrin and lysozyme concentration over 5 months (chronic changes) in elite rowers (n=17, mean age 24.3+/-4.0 years) with sedentary individuals (controls) (n=18, mean age=27.2+/-7.1 years) and a graded exercise test to exhaustion (acute changes) with a cohort of elite rowers (n=11, mean age 24.7+/-4.1). RESULTS Magnitudes of differences and changes were interpreted as a standardised (Cohen's) effect size (ES). Lactoferrin concentration in the observational study was approximately 60% lower in rowers than control subjects at baseline (7.9+/-1.2 microg/ml mean+/-SEM, 19.4+/-5.6 microg/ml, p=0.05, ES=0.68, 'moderate') and at the midpoint of the season (6.4+/-1.4 microg/ml mean +/- SEM, 21.5+/-4.2 microg/ml, p=0.001, ES=0.89, 'moderate'). The concentration of lactoferrin at the end of the study was not statistically significant (p=0.1) between the groups. There was no significant difference between rowers and control subjects in lysozyme concentration during the study. There was a 50% increase in the concentration of lactoferrin (p=0.05, ES=1.04, 'moderate') and a 55% increase in lysozyme (p=0.01, ES=3.0, 'very large') from pre-exercise to exhaustion in the graded exercise session. CONCLUSION Lower concentrations of these proteins may be indicative of an impairment of innate protection of the upper respiratory tract. Increased salivary lactoferrin and lysozyme concentration following exhaustive exercise may be due to a transient activation response that increases protection in the immediate postexercise period