A 3,500-year tree-ring record of annual precipitation on the northeastern Tibetan Plateau

An annually resolved and absolutely dated ring-width chronology spanning 4,500 y has been constructed using subfossil, archaeological, and living-tree juniper samples from the northeastern Tibetan Plateau. The chronology represents changing mean annual precipitation and is most reliable after 1500 B.C. Reconstructed precipitation for this period displays a trend toward more moist conditions: the last 10-, 25-, and 50-y periods all appear to be the wettest in at least three and a half millennia. Notable historical dry periods occurred in the 4th century BCE and in the second half of the 15th century CE. The driest individual year reconstructed (since 1500 B.C.) is 1048 B.C., whereas the wettest is 2010. Precipitation variability in this region appears not to be associated with inferred changes in Asian monsoon intensity during recent millennia. The chronology displays a statistical association with the multidecadal and longer-term variability of reconstructed mean Northern Hemisphere temperatures over the last two millennia. This suggests that any further large-scale warming might be associated with even greater moisture supply in this region

Design of an electrostatic precipitator for a novel bituminous coal-fired circulating fluidised bed combustion power plant in Namibia

Coal-fired power plants utilising fluidised bed technologies emit copious amounts of fly-ash, which is harmful to people owing to its particulate nature. A planned 300 MW power plant will have an electrostatic precipitator (ESP) for fly-ash emissions control, in line with power generation industry best practices. This ESP should meet a fly-ash emission limit value ≤ 50 mg/Nm3. This paper details the design process and resultant technical specifications of a cold-side, single-stage, and plate-wire dry ESP designed for the power plant. The ESP will consist of twin-chambers with quadruple-fields (2 4 315 m3) and octonary bus-sections independently energised by individual high-frequency three-phase switched integrated rectifiers (70 kV, 800 mA) to maximise ionisation. Dynamically balanced, single-impact, tumbling hammer rappers (857.5 rpm) will dislodge fly-ash from the collector plates into mass-flow wedge-shaped hoppers. A specific collection area (≥ 56.9 m2/m3/s) and an ESP index (≥ 709.2 (kV/cm)2m2/m3/s) should guarantee a collection efficiency (  ≥ 99.5 %) and the specified emission limit value at 100 % boiler capacity and normal operating conditions (gas velocity ≤ 2.4 m/s; gas temperature ≤ 137 ℃; fly-ash loading ≤ 10 000 kg/Nm3; resistivity ≤ 1010 Ω‧cm). The design was successfully verified in principle using the validation square method, in conjunction with the leading comparable historical case studies approach. It is recommended to simulate ESP designs using suitable programs like Comsol Multiphysics and construct a pilot plant before attempting scaled-up construction and commissioning. Highlights           A cold-side, single-stage plate-wire dry ESP system designed. Theoretical collection efficiency in excess of 99.5%. High-frequency, three-phase switched integrated rectifiers to be used for ionisation

Preliminary spectral analysis of near-real-time radon data

Fast Fourier analysis of the near-real-time radon data collected since 1977 by the Caltech automated radon-thoron monitoring system has been carried out in order to determine if any characteristic frequency components are present that can be associated either with precursors to seismicity or with environmental factors. Preliminary results indicate that during "quiet" periods with low seismicity and no rainfall the spectral power is distributed as 1/f. Before four local earthquakes a departure from this 1/f behavior was observed at low frequency. During periods of heavy rainfall an increase in both low and high frequency power was observed. The spectral power of the large radon anomaly observed prior to the October 15, 1979 Imperial Valley earthquake was found to have a 1/f distribution but with power at all frequencies about four times greater than that of data from "quiet" periods

Stable Magnetic Universes Revisited

A regular class of static, cylindrically symmetric pure magnetic field metrics is rederived in a different metric ansatz in all dimensions. Radial, time dependent perturbations show that for dimensions d>3 such spacetimes are stable at both near r\approx0 and large radius r\rightarrow\infty. In a different gauge these stability analysis and similar results were known beforehand. For d=3, however, simultaneous stability requirement at both, near and far radial distances can not be reconciled for time - dependent perturbations. Restricted, numerical geodesics for neutral particles reveal a confinement around the center in the polar plane. Charged, time-like geodesics for d=4 on the other hand are shown numerically to run toward infinity.Comment: 11 pages, 3figure

Remarks on the classification of quasitoric manifolds up to equivariant homeomorphism

We give three sufficient criteria for two quasitoric manifolds (M,M') to be (weakly) equivariantly homeomorphic. We apply these criteria to count the weakly equivariant homeomorphism types of quasitoric manifolds with a given cohomology ring.Comment: 11 page

Networked VAX/LSI/CAMAC Data Acquisition System Development

Recent development of the Caltech data acquisition system installed in 1981, which runs on a VAX-11/750, a Peritek Q-bus network, LSI-11s, and CAMAC, is described. In this system, the DEC VMS and RT-11 operating systems are supported on the VAX "host" and LSI-11 "front-end" computers by a VMS device driver and network host program, and a bootable RT-11 device driver. Network "utility" and "control" programs provide general purpose support for communication between front-end and host software. Data acquisition software tools are provided for writing programs to run nuclear physics experiments. A system similar to Caltech's was installed at the University of Rochester in 1982. The network has been tested for speed and real-time response. After including all software overhead required by data acquisition, it was found that the system could transfer buffers and acknowledge their receipt at a net speed of 127 KB per second with a 35% load on the host computer. The network software is currently being rehosted on Ethernet hardware at Caltech in a multiple host - many front-end computer configuration. Compatibility with the current Peritek network software will be maintained

Saving the Greater Adjutant Stork by Changing Perceptions and Linking to Assamese Traditions in India

https://ojs.ethnobiology.org/index.php/ebl/article/view/1648https://ojs.ethnobiology.org/index.php/ebl/article/view/164