14,526 research outputs found
Using an Ice Core to Characterize the Climatic History of Antarctica
Between 20 November and 14 December 1984, a remote tent camp was operated in the Dominion Range (center point, 85° 15\u27 S 166° 10 \u27E) on an ice-covered massif located at the confluence of the heads of the Beardmore and Mill Glaciers in the Transantarctic Mountains. The camp was occupied by four members of the Glacier Research Group (University of New Hampshire) and three members of the Polar lee Coring Office (PICO) (University of Nebraska). The main task at the site was to retrieve an ice core from which chemical and physical time series will be made available to help in assessing: (1) current stability of the east antarctic ice sheet, (2) current models concerning the recent glacial history of the Transantarctic Mountains, (3) the presence of relatively high frequency (100 per 100 years) climatic signals, and (4) the possible relationships between volcanic and/or solar activities and climatic change
Renormalized energy concentration in random matrices
We define a "renormalized energy" as an explicit functional on arbitrary
point configurations of constant average density in the plane and on the real
line. The definition is inspired by ideas of [SS1,SS3]. Roughly speaking, it is
obtained by subtracting two leading terms from the Coulomb potential on a
growing number of charges. The functional is expected to be a good measure of
disorder of a configuration of points. We give certain formulas for its
expectation for general stationary random point processes. For the random
matrix -sine processes on the real line (beta=1,2,4), and Ginibre point
process and zeros of Gaussian analytic functions process in the plane, we
compute the expectation explicitly. Moreover, we prove that for these processes
the variance of the renormalized energy vanishes, which shows concentration
near the expected value. We also prove that the beta=2 sine process minimizes
the renormalized energy in the class of determinantal point processes with
translation invariant correlation kernels.Comment: last version, to appear in Communications in Mathematical Physic
Fluid/solid transition in a hard-core system
We prove that a system of particles in the plane, interacting only with a
certain hard-core constraint, undergoes a fluid/solid phase transition
Influence of oxygen ordering kinetics on Raman and optical response in YBa_2Cu_3O_{6.4}
Kinetics of the optical and Raman response in YBa_2Cu_3O_{6.4} were studied
during room temperature annealing following heat treatment. The superconducting
T_c, dc resistivity, and low-energy optical conductivity recover slowly,
implying a long relaxation time for the carrier density. Short relaxation times
are observed for the B_{1g} Raman scattering -- magnetic, continuum, and phonon
-- and the charge transfer band. Monte Carlo simulations suggest that these two
relaxation rates are related to two length scales corresponding to local oxygen
ordering (fast) and long chain and twin formation (slow).Comment: REVTeX, 3 pages + 4 PostScript (compressed) figure
Emergence of long memory in stock volatility from a modified Mike-Farmer model
The Mike-Farmer (MF) model was constructed empirically based on the
continuous double auction mechanism in an order-driven market, which can
successfully reproduce the cubic law of returns and the diffusive behavior of
stock prices at the transaction level. However, the volatility (defined by
absolute return) in the MF model does not show sound long memory. We propose a
modified version of the MF model by including a new ingredient, that is, long
memory in the aggressiveness (quantified by the relative prices) of incoming
orders, which is an important stylized fact identified by analyzing the order
flows of 23 liquid Chinese stocks. Long memory emerges in the volatility
synthesized from the modified MF model with the DFA scaling exponent close to
0.76, and the cubic law of returns and the diffusive behavior of prices are
also produced at the same time. We also find that the long memory of order
signs has no impact on the long memory property of volatility, and the memory
effect of order aggressiveness has little impact on the diffusiveness of stock
prices.Comment: 6 pages, 6 figures and 1 tabl
The effect of flight line spacing on radioactivity inventory and spatial feature characteristics of airborne gamma-ray spectrometry data
Airborne Gamma Spectrometry (AGS) is well suited to the mapping of radioactivity in the environment. Flight parameters (e.g. speed and line spacing) directly affect the rate of area coverage, cost, and data quality of any survey. The influences of line spacing have been investigated for data from inter‐tidal, coastal and upland environments with a range of <sup>137</sup>Cs activity concentrations and depositional histories. Estimates of the integrated <sup>137</sup>Cs activity (‘inventory’) within specified areas and the shapes of depositional features were calculated for subsets of the data at different line spacings. Features with dimensions greater than the line spacing show variations in inventory and area of less than 3%, and features with dimensions less than the line spacing show larger variations and a decreased probability of detection. The choice of line spacing for a task is dependent on the dimensions of the features of interest and required edge definition. Options for line spacing for different tasks are suggested. It is noted that for regional mapping, even 5–10 km line spacing can produce useful data
Guidebook for field trips in central New Hampshire and contiguous areas: 63rd annual meeting October 2 and 3, 1971 Concord, New Hampshire: table of contents, maps, forward
front matte
Guidebook for field trips in central New Hampshire and contiguous areas: 63rd annual meeting October 2 and 3, 1971 Concord, New Hampshire
Geologic fieldtrips in New Hampshir
Direct detection and characterization of foot-and-mouth disease virus in East Africa using a field-ready real-time PCR platform
Effective control and monitoring of foot-and-mouth disease (FMD) relies upon rapid and accurate disease confirmation. Currently, clinical samples are usually tested in reference laboratories using standardized assays recommended by The World Organisation for Animal Health (OIE). However, the requirements for prompt and serotype-specific diagnosis during FMD outbreaks, and the need to establish robust laboratory testing capacity in FMD-endemic countries have motivated the development of simple diagnostic platforms to support local decision-making. Using a portable thermocycler, the T-COR™ 8, this study describes the laboratory and field evaluation of a commercially available, lyophilized pan-serotype-specific real-time RT-PCR (rRT-PCR) assay and a newly available FMD virus (FMDV) typing assay (East Africa-specific for serotypes: O, A, Southern African Territories [SAT] 1 and 2). Analytical sensitivity, diagnostic sensitivity and specificity of the pan-serotype-specific lyophilized assay were comparable to that of an OIE-recommended laboratory-based rRT-PCR (determined using a panel of 57 FMDV-positive samples and six non-FMDV vesicular disease samples for differential diagnosis). The FMDV-typing assay was able to correctly identify the serotype of 33/36 FMDV-positive samples (no cross-reactivity between serotypes was evident). Furthermore, the assays were able to accurately detect and type FMDV RNA in multiple sample types, including epithelial tissue suspensions, serum, oesophageal–pharyngeal (OP) fluid and oral swabs, both with and without the use of nucleic acid extraction. When deployed in laboratory and field settings in Tanzania, Kenya and Ethiopia, both assays reliably detected and serotyped FMDV RNA in samples (n = 144) collected from pre-clinical, clinical and clinically recovered cattle. These data support the use of field-ready rRT-PCR platforms in endemic settings for simple, highly sensitive and rapid detection and/or characterization of FMDV
The Origin of Time Asymmetry
It is argued that the observed Thermodynamic Arrow of Time must arise from
the boundary conditions of the universe. We analyse the consequences of the no
boundary proposal, the only reasonably complete set of boundary conditions that
has been put forward. We study perturbations of a Friedmann model containing a
massive scalar field but our results should be independent of the details of
the matter content. We find that gravitational wave perturbations have an
amplitude that remains in the linear regime at all times and is roughly time
symmetric about the time of maximum expansion. Thus gravitational wave
perturbations do not give rise to an Arrow of Time. However density
perturbations behave very differently. They are small at one end of the
universe's history, but grow larger and become non linear as the universe gets
larger. Contrary to an earlier claim, the density perturbations do not get
small again at the other end of the universe's history. They therefore give
rise to a Thermodynamic Arrow of Time that points in a constant direction while
the universe expands and contracts again. The Arrow of Time does not reverse at
the point of maximum expansion. One has to appeal to the Weak Anthropic
Principle to explain why we observe the Thermodynamic Arrow to agree with the
Cosmological Arrow, the direction of time in which the universe is expanding.Comment: 41 pages, DAMTP R92/2
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