Long-Time Tails and Anomalous Slowing Down in the Relaxation of Spatially Inhomogeneous Excitations in Quantum Spin Chains

Exact analytic calculations in spin-1/2 XY chains, show the presence of long-time tails in the asymptotic dynamics of spatially inhomogeneous excitations. The decay of inhomogeneities, for $t\to \infty$, is given in the form of a power law $$(t/\tau_{Q}) ^{-\nu_{Q}}$$ where the relaxation time $\tau_{Q}$ and the exponent $\nu_{Q}$ depend on the wave vector $Q$, characterizing the spatial modulation of the initial excitation. We consider several variants of the XY model (dimerized, with staggered magnetic field, with bond alternation, and with isotropic and uniform interactions), that are grouped into two families, whether the energy spectrum has a gap or not. Once the initial condition is given, the non-equilibrium problem for the magnetization is solved in closed form, without any other assumption. The long-time behavior for $t\to \infty$ can be obtained systematically in a form of an asymptotic series through the stationary phase method. We found that gapped models show critical behavior with respect to $Q$, in the sense that there exist critical values $Q_{c}$, where the relaxation time $\tau_{Q}$ diverges and the exponent $\nu_{Q}$ changes discontinuously. At those points, a slowing down of the relaxation process is induced, similarly to phenomena occurring near phase transitions. Long-lived excitations are identified as incommensurate spin density waves that emerge in systems undergoing the Peierls transition. In contrast, gapless models do not present the above anomalies as a function of the wave vector $Q$.Comment: 25 pages, 2 postscript figures. Manuscript submitted to Physical Review

State of the climate in 2013

In 2013, the vast majority of the monitored climate variables reported here maintained trends established in recent decades. ENSO was in a neutral state during the entire year, remaining mostly on the cool side of neutral with modest impacts on regional weather patterns around the world. This follows several years dominated by the effects of either La Niña or El Niño events. According to several independent analyses, 2013 was again among the 10 warmest years on record at the global scale, both at the Earths surface and through the troposphere. Some regions in the Southern Hemisphere had record or near-record high temperatures for the year. Australia observed its hottest year on record, while Argentina and New Zealand reported their second and third hottest years, respectively. In Antarctica, Amundsen-Scott South Pole Station reported its highest annual temperature since records began in 1957. At the opposite pole, the Arctic observed its seventh warmest year since records began in the early 20th century. At 20-m depth, record high temperatures were measured at some permafrost stations on the North Slope of Alaska and in the Brooks Range. In the Northern Hemisphere extratropics, anomalous meridional atmospheric circulation occurred throughout much of the year, leading to marked regional extremes of both temperature and precipitation. Cold temperature anomalies during winter across Eurasia were followed by warm spring temperature anomalies, which were linked to a new record low Eurasian snow cover extent in May. Minimum sea ice extent in the Arctic was the sixth lowest since satellite observations began in 1979. Including 2013, all seven lowest extents on record have occurred in the past seven years. Antarctica, on the other hand, had above-average sea ice extent throughout 2013, with 116 days of new daily high extent records, including a new daily maximum sea ice area of 19.57 million km2 reached on 1 October. ENSO-neutral conditions in the eastern central Pacific Ocean and a negative Pacific decadal oscillation pattern in the North Pacific had the largest impacts on the global sea surface temperature in 2013. The North Pacific reached a historic high temperature in 2013 and on balance the globally-averaged sea surface temperature was among the 10 highest on record. Overall, the salt content in nearsurface ocean waters increased while in intermediate waters it decreased. Global mean sea level continued to rise during 2013, on pace with a trend of 3.2 mm yr-1 over the past two decades. A portion of this trend (0.5 mm yr-1) has been attributed to natural variability associated with the Pacific decadal oscillation as well as to ongoing contributions from the melting of glaciers and ice sheets and ocean warming. Global tropical cyclone frequency during 2013 was slightly above average with a total of 94 storms, although the North Atlantic Basin had its quietest hurricane season since 1994. In the Western North Pacific Basin, Super Typhoon Haiyan, the deadliest tropical cyclone of 2013, had 1-minute sustained winds estimated to be 170 kt (87.5 m s-1) on 7 November, the highest wind speed ever assigned to a tropical cyclone. High storm surge was also associated with Haiyan as it made landfall over the central Philippines, an area where sea level is currently at historic highs, increasing by 200 mm since 1970. In the atmosphere, carbon dioxide, methane, and nitrous oxide all continued to increase in 2013. As in previous years, each of these major greenhouse gases once again reached historic high concentrations. In the Arctic, carbon dioxide and methane increased at the same rate as the global increase. These increases are likely due to export from lower latitudes rather than a consequence of increases in Arctic sources, such as thawing permafrost. At Mauna Loa, Hawaii, for the first time since measurements began in 1958, the daily average mixing ratio of carbon dioxide exceeded 400 ppm on 9 May. The state of these variables, along with dozens of others, and the 2013 climate conditions of regions around the world are discussed in further detail in this 24th edition of the State of the Climate series. © 2014, American Meteorological Society. All rights reserved

Automated cycle sequencing of PCR templates: Relationships between fragment size, concentration and Strand renaturation rates on sequencing efficiency

With the Applied Biosystems 373A automated DNA sequencer, we have systematically investigated the amounts of double-stranded PCR fragments of varying size (200, 564, and 1126 bp) required to give sequence of defined lengths, up to the maximum possible. Sequencing was performed on purified double-stranded PCR products using the dye-terminator chemistry and a thermal cycling procedure. The minimal template concentrations allowing determination of short sequences (160 bases) were essentially identical for the fragments studied. Maximal possible sequence determination from the 200 bp fragment was achieved over a wide concentration range, despite the fact that within this range a significant fraction of the template renatured by the mid-point of the sequencing reaction time-course. We conclude that the cyclic sequencing process overcomes competitive strand reannealing of double-stranded PCR products. The sequencing concentration-response curves for the 564 bp and 1126 bp fragments were similar to each other, although the minimal template concentrations required to read >300 bases were slightly increased for the 564 bp fragment. Excess template is undesirable for optimal sequence length determination, but this is unlikely to be solely due to strand reannealing as single-stranded M13 templates in super-optimal concentrations also showed marked reduction in sequencing efficiency

Effect of Basiline lipid levels II: changes in plasma lipoprotein fracrions during hydrochlorothiazide and amiloride [Moduretic] treatment of hypertension

No Abstrac

Effects of Storage Temperature, pH and Time on Urinary Albumin Level

The storage of urine samples at 2-8°C and at -20°C for several weeks is a common laboratory practice in research and epidemiological studies to facilitate batch analysis. Despite numerous studies, there is no agreement on how stable albumin is in urine and the best way to store such urine specimen. Random urine samples were obtained from 15 patients with nephropathy and end stage renal failure. Urinary pH and specific gravity of freshly voided urine were determined before storage. A portion of each urine samples were stored at voided pH and another portion stored at neutral pH (7.0) after adjustment with acid or base at 4°C and -20°C for 10 weeks. Pre -analytical treatment of samples involved vortex mixing or centrifuging urine samples before measurement of urinary albumin. Albumin levels were determined at 0, 2, 4 and 10 weeks in both vortex mixed and centrifuged samples using standard spectrophotometric methods. Mean pH and specific gravity of fresh urine samples were 5.82 ± 0.71 and 1.009±0.004 respectively. Significant decreases (p< 0.05) were observed in urinary albumin levels at 4°C at the 4th week. Significant changes were seen at the 10th week in samples stored at -20°C in pH unadjusted samples. Vortex mixing or centrifuging of sample of did not restore decreases in albumin level. No significant difference was observed in the pH adjusted group after 10 weeks of storage at -20°C.These results suggest that where long term storage (6-10 weeks) of urine samples is required, samples should be stored at -20°C. However, in medium term storage (2-4 weeks) storage at 4°C may require the adjustment of the pH to neutral (7.0) before storage to obtain reliable results

Effect of baseline lipid levels I: influence on plasma total cholesterol and triglyceride changes during treatment of hypertension with a combination of hydrochlorothiazide and amiloride [Moduretic]

No Abstrac