Photometric Monitoring of the Gravitationally Lensed Ultraluminous BAL Quasar APM08279+5255

We report on one year of photometric monitoring of the ultraluminous BAL quasar APM 08279+5255. The temporal sampling reveals that this gravitationally lensed system has brightened by ~0.2 mag in 100 days. Two potential causes present themselves; either the variability is intrinsic to the quasar, or it is the result of microlensing by stars in a foreground system. The data is consistent with both hypotheses and further monitoring is required before either case can be conclusively confirmed. We demonstrate, however, that gravitational microlensing can not play a dominant role in explaining the phenomenal properties exhibited by APM 08279+5255. The identification of intrinsic variability, coupled with the simple gravitational lensing configuration, would suggest that APM 08279+5255 is a potential golden lens from which the cosmological parameters can be derived and is worthy of a monitoring program at high spatial resolution.Comment: 17 pages, with 2 figures. Accepted for publication in P.A.S.

Effect of a Single Bout of Prior Moderate Exercise on Cutaneous Perfusion in Type 2 Diabetes

In diabetic individuals, increased shunting of circulation away from the skin may exist, contributing to their greater risk for ulcerations and poor cutaneous healing. In a prospective study (1), we previously found a lower skin perfusion during local heating in the foot dorsum of sedentary type 2 diabetic individuals compared with active people without diabetes. This defect was present despite normal increases in skin interstitial nitric oxide (NO), suggesting that NO is either ineffective or not involved (2). A prior bout of maximal exercise also lessened the impaired responsiveness to local heating of the dorsal foot in active type 2 diabetic individuals but not in their sedentary counterparts (3). Thus, this study examined the effect of a single bout of prior moderate cycle exercise on dorsal foot cutaneous perfusion and interstitial NO

Cutaneous Blood Flow in Type 2 Diabetic Individuals After an Acute Bout of Maximal Exercise

OBJECTIVE - We previously demonstrated a positive association between chronic aerobic exercise and dorsal foot skin blood flow during local heating in type 2 diabetic individuals. Thus, we hypothesized that a prior acute bout of maximal exercise would also have positive effects on postexercise blood now. RESEARCH DESIGN AND METHODS - Subjects consisted of 32 individuals with type 2 diabetes and 26 nondiabetic control subjects further subdivided based on their physical activity status diabetic exerciser (DE), diabetic sedentary (DS), control exerciser (CE), or control sedentary. Dorsal foot cutaneous blood flow was measured noninvasively by continuous laser-Doppler assessment at baseline and during local heating to 44°C before and after a maximal bout of cycle exercise. Interstitial nitric oxide (NO) levels were measured concurrently in the foot dorsum. RESULTS - increases in blood flow and its responsiveness to local heating to 44°C were significantly lower in both diabetic groups compared with CE before maximal exercise, but perfusion responsiveness remained lower in DS subjects only after exercise (P \u3c 0.05). Baseline skin blood flow was not different among groups preexercise, but it was significantly increased postexercise in DE subjects only. Interstitial NO levels were not significantly different at either time. At baseline, groups differed only in HbA1c, fasting serum glucose, HDL cholesterol, and insulin resistance (homeostasis model assessment method). CONCLUSIONS - All diabetic individuals exhibit a blunted responsiveness of cutaneous blood flow with local heating to 44°C before maximal exercise compared with active nondiabetic individuals, but after an exercise bout, it remains significantly blunted only in diabetic individuals who are sedentary. These findings occur independently of changes in interstitial NO levels

Algebraic description of spacetime foam

A mathematical formalism for treating spacetime topology as a quantum observable is provided. We describe spacetime foam entirely in algebraic terms. To implement the correspondence principle we express the classical spacetime manifold of general relativity and the commutative coordinates of its events by means of appropriate limit constructions.Comment: 34 pages, LaTeX2e, the section concerning classical spacetimes in the limit essentially correcte

Survival of a submarine canyon during long-term outbuilding of a continental margin

Net-depositional submarine canyons are common in continental slope strata, but how they survive and prograde on constructional margins is poorly understood. In this study we present field evidence for the coevolution of a submarine canyon and the adjacent continental slope. Using a three-dimensional seismic data cube that images the Ebro margin (northwest Mediterranean), we identify a preserved canyon on a middle Pleistocene paleosurface and relate it directly to its expression on the present-day seafloor. A subparallel stacking pattern of seismic reflectors, similar to that seen between prograding clinoforms in intercanyon areas, is observed between the modern and paleocanyon thalwegs. The concavity of the modern long profile differs from the convex-concave long profile on the middle Pleistocene surface, suggesting a long-term change in canyon sedimentation. We interpret this change as a shift to a canyon dominated by turbidity currents from one strongly influenced by the pattern of sedimentation that built the open-slope canyon interfluves. We find support for our interpretation in previous studies of the Ebro margin

Classical and quantum chaos in a circular billiard with a straight cut

We study classical and quantum dynamics of a particle in a circular billiard with a straight cut. This system can be integrable, nonintegrable with soft chaos, or nonintegrable with hard chaos, as we vary the size of the cut. We use a quantum web to show differences in the quantum manifestations of classical chaos for these three different regimes.Comment: LaTeX2e, 8 pages including 3 Postscript figures and 4 GIF figures, submitted to Phys. Rev.