49,960 research outputs found
Heat and Mass Transfer in Cold Regions Soils
The work upon which this report is based was made possible by a cooperative
aid agreement between the U.S. Forest Service, Institute of Northern
Forestry, Fairbanks, Alaska, and the Institute of Water Resources, University
of Alaska. Contributions to this study were also made by the University of
California at Davis and Ohio State University. The collection of winter
data on pore pressures was made possible by a separate grant by the Office
of Water Research and Technology (project A-053 ALAS)
Hydrologic Properties of Subarctic Organic Soils
Completion Report
for
U. S. Forest Service
Institute of Northern Forestry
Cooperative Agreement No. 16 USC 581; 581a-581iThe need for understanding the natural system and how it responds
to various stresses is important; this is especially so in an environment
where the climate not only sustains permafrost, but develops
massive seasonal frost as well. Consequently, the role of the shallow
surface organic layer is also quite important. Since a slight change in
the soil thermal regime may bring about a phase change in the water or
ice, therefore, the system response to surface alterations such as
burning can be quite severe. The need for a better understanding of the
behavior and properties of the organic layer is, therefore, accentuated.
The central theme of this study was the examination of the hydrologic
and hydraulic properties of subarctic organic soils. Summarized
in this paper are the results of three aspects of subarctic organic soil
examinations conducted during the duration of the project. First, a
field site was set up in Washington Creek with the major emphasis on
measuring numerous variables of that soil system during the summer. The
greatest variations in moisture content occur in the thick organic soils
that exist at this site. Our major emphasis was to study the soil
moisture levels in these soils. This topic is covered in the first
major section, including associated laboratory studies. Those laboratory
studies include investigations of several hydraulic and hydrologic
properties of taiga organic and mineral soils. Second, some field data
on organic moisture levels was collected at the site of prescribed burns
in Washington Creek to ascertain the sustainability of fires as a function
of moisture levels. This portion of the study is described under the
second major heading. The last element of this study was a continued
application of the two-dimensional flow model that was developed in an
earlier study funded by the U. S. Forest Service, Institute of Northern
Forestry, and reported by Kane, Luthin, and Taylor (1975a).
Many of the results and concepts gathered in the field work were
integrated into the modeling effort, which is aimed at producing better
estimates of the hydrologic effects of surface disturbances in the black
spruce taiga subarctic ecosystem. This knowledge should also contribute
to better fire management decisions of the same system.The work upon which this report is based was made possible by a
cooperative aid agreement funded by the U. S. Forest Service, Institute
of Northern Forestry, Fairbanks, Alaska. Contribution to this study was
also made by Ohio State University
Analysis of the second order exchange self energy of a dense electron gas
We investigate the evaluation of the six-fold integral representation for the
second order exchange contribution to the self energy of a three dimensional
electron gas at the Fermi surface.Comment: 6 page
Transcriptional profiling of SNAI2 regulated genes in primary human keratinocytes.
Epithelial to mesenchymal transition transcription factors (EMT-TFs) such as SNAI2 have been found to be expressed endogenously in epidermal stem and progenitor cells and downregulated upon differentiation. The presence of SNAI2 in progenitor cells is necessary to repress the expression of differentiation genes by binding directly to their promoters. SNAI2 is downregulated upon differentiation which allows expression of differentiation genes. Furthermore overexpression of SNAI2 can block the differentiation process suggesting that the levels of SNAI2 are crucial to epidermal cell fate decisions. To address on a genome wide level the genes that are impacted by changing the levels of SNAI2, we performed microarray analysis on SNAI2 knockdown and overexpressing epidermal progenitor cells. Here we provide a detailed methods and analysis on these microarray data which has been deposited in Gene Expression Omnibus (GEO): GSE55269
Absence of Domain Wall Roughening in a Transverse Field Ising Model with Long-Range Interactions
We investigate roughening transitions in the context of transverse-field
Ising models. As a modification of the transverse Ising model with short range
interactions, which has been shown to exhibit domain wall roughening, we have
looked into the possibility of a roughening transition for the case of
long-range interactions, since such a system is physically realized in the
insulator LiHoF4. The combination of strong Ising anisotropy and long-range
forces lead naturally to the formation of domain walls but we find that the
long-range forces destroy the roughening transition.Comment: 7 pages, 5 figures, revtex
Simulations of satellite Doppler wind observations
This study will involve two objectives: (1) to develop, through computer simulations, optimal satellite-based sensor scanning techniques for direct measurement of tropospheric winds on the meso- and synoptic scales; and (2) to construct simulations of remotely measured wind fields for assessing impact of such fields on the diagnosis and prognosis of atmospheric phenomena through the use of Observing System Simulation Experiments (OSSE). Using the LAWS Simulation Model (LSM), various global coverage scenarios have been investigated as part of an effort to define the optimal orbit, configuration and sampling strategies for observations of winds for use in global circulation models. Simulated data sets have been provided to GSFC, FSU and several LAWS team members. Particular emphasis has been on providing realistic cloud cover, cirrus backscatter, aerosol distribution and wind variance on scales less than 600 km. Progress is currently being made to incorporate other remote sensors (AIRS/AMSU, STIKSCAT) into the global OSSEs
Practical quantum key distribution over a 48-km optical fiber network
The secure distribution of the secret random bit sequences known as "key"
material, is an essential precursor to their use for the encryption and
decryption of confidential communications. Quantum cryptography is a new
technique for secure key distribution with single-photon transmissions:
Heisenberg's uncertainty principle ensures that an adversary can neither
successfully tap the key transmissions, nor evade detection (eavesdropping
raises the key error rate above a threshold value). We have developed
experimental quantum cryptography systems based on the transmission of
non-orthogonal photon states to generate shared key material over
multi-kilometer optical fiber paths and over line-of-sight links. In both
cases, key material is built up using the transmission of a single-photon per
bit of an initial secret random sequence. A quantum-mechanically random subset
of this sequence is identified, becoming the key material after a data
reconciliation stage with the sender. Here we report the most recent results of
our optical fiber experiment in which we have performed quantum key
distribution over a 48-km optical fiber network at Los Alamos using photon
interference states with the B92 and BB84 quantum key distribution protocols.Comment: 13 pages, 7 figures, .pdf format submitted to Journal of Modern
Optic
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