2,403 research outputs found
Comparison of clinical signs and outcomes between dogs with presumptive ischemic myelopathy and dogs with acute non compressive nucleus pulposus extrusion
Neoplastic transformation of mouse C3H 10T1/2 and syrian hymster embryo cells by different types of ionizing radiation
Acute Herniation of Nondegenerate Nucleus Pulposus: Acute Noncompressive Nucleus Pulposus Extrusion and Compressive Hydrated Nucleus Pulposus Extrusion
The structure of one-relator relative presentations and their centres
Suppose that G is a nontrivial torsion-free group and w is a word in the
alphabet G\cup\{x_1^{\pm1},...,x_n^{\pm1}\} such that the word w' obtained from
w by erasing all letters belonging to G is not a proper power in the free group
F(x_1,...,x_n). We show how to reduce the study of the relative presentation
\^G= to the case n=1. It turns out that an
"n-variable" group \^G can be constructed from similar "one-variable" groups
using an explicit construction similar to wreath product. As an illustration,
we prove that, for n>1, the centre of \^G is always trivial. For n=1, the
centre of \^G is also almost always trivial; there are several exceptions, and
all of them are known.Comment: 15 pages. A Russian version of this paper is at
http://mech.math.msu.su/department/algebra/staff/klyachko/papers.htm . V4:
the intoduction is rewritten; Section 1 is extended; a short introduction to
Secton 5 is added; some misprints are corrected and some cosmetic
improvements are mad
Temporal Evolution of Financial Market Correlations
We investigate financial market correlations using random matrix theory and
principal component analysis. We use random matrix theory to demonstrate that
correlation matrices of asset price changes contain structure that is
incompatible with uncorrelated random price changes. We then identify the
principal components of these correlation matrices and demonstrate that a small
number of components accounts for a large proportion of the variability of the
markets that we consider. We then characterize the time-evolving relationships
between the different assets by investigating the correlations between the
asset price time series and principal components. Using this approach, we
uncover notable changes that occurred in financial markets and identify the
assets that were significantly affected by these changes. We show in particular
that there was an increase in the strength of the relationships between several
different markets following the 2007--2008 credit and liquidity crisis.Comment: 15 pages, 10 figures, 1 table. Accepted for publication in Phys. Rev.
E. v2 includes additional section
Doodles on surfaces
Doodles were introduced in but were restricted to embedded circles in the 2-sphere. Khovanov, extended the idea to immersed circles in the 2-sphere. In this paper we further extend the range of doodles to any closed oriented surfaces. Uniqueness of minimal representatives is proved, and various example of doodles are given with their minimal representatives. We also introduce the notion of virtual doodles, and show that there is a natural one-to-one correspondence between doodles on surfaces and virtual doodles on the plane
Evaluation of be-38 percent al alloy final report, 27 jun. 1964 - 28 feb. 1965
Mechanical properties, microstructural features, and general metallurgical quality of beryllium- aluminum allo
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Comparison of free tropospheric western Pacific air mass classification schemes for the PEM-West A experiment
During September/October 1991, NASA's Global Tropospheric Experiment (GTE) conducted an airborne field measurement program (PEM-West A) in the troposphere over the western Pacific Ocean. In this paper we describe and use the relative abundance of the combustion products C2H2 and CO to classify air masses encountered during PEM-West A based on the degree that these tracers were processed by the combined effects of photochemical reactions and dynamical mixing (termed the degree of atmospheric processing). A large number of trace compounds (e.g., C2H6, C3H8, C6H6, NOy, and O3) are found to be well correlated with the degree of atmospheric processing that is reflected by changes in the ratio of C2H2/CO over the range of values from ∼0.3 to 2.0 (parts per trillion volume) C2H2/ (parts per billion volume) CO. This C2H2/CO-based classification scheme is compared to model simulations and to two independent classification schemes based on air mass back-trajectory analyses and lidar profiles of O3 and aerosols. In general, these schemes agree well, and in combination they suggest that the functional dependence that other observed species exhibit with respect to the C2H2/CO atmospheric processing scale can be used to study the origin, sources, and sinks of trace species and to derive several important findings. First, the degree of atmospheric processing is found to be dominated by dilution associated with atmospheric mixing, which is found to primarily occur through the vertical mixing of relatively recent emissions of surface layer trace species. Photochemical reactions play their major role by influencing the background concentrations of trace species that are entrained during the mixing (i.e., dilution) process. Second, a significant noncontinental source(s) of NO (and NOx) in the free troposphere is evident. In particular, the enhanced NO mixing ratios that were observed in convected air masses are attributed to either emissions from lightning or the rapid recycling of NOy compounds. Third, nonsoluble trace species emitted in the continental boundary layer, such as CO and hydrocarbons, are vertically transported to the upper troposphere as efficiently as they are to the midtroposphere. In addition, the mixing ratios of CO and hydrocarbons in the upper troposphere over the western Pacific may reflect a significant contribution from northern hemisphere land areas other than Asia. Finally, we believe that these results can be valuable for the quantitative evaluation of the vertical transport processes that are usually parameterized in models. Copyright 1996 by the American Geophysical Union
Improving signal-to-noise resolution in single molecule experiments using molecular constructs with short handles
We investigate unfolding/folding force kinetics in DNA hairpins exhibiting
two and three states with newly designed short dsDNA handles (29 bp) using
optical tweezers. We show how the higher stiffness of the molecular setup
moderately enhances the signal-to-noise ratio (SNR) in hopping experiments as
compared to conventional long handles constructs (approximately 700 bp). The
shorter construct results in a signal of higher SNR and slower
folding/unfolding kinetics, thereby facilitating the detection of otherwise
fast structural transitions. A novel analysis of the elastic properties of the
molecular setup, based on high-bandwidth measurements of force fluctuations
along the folded branch, reveals that the highest SNR that can be achieved with
short handles is potentially limited by the marked reduction of the effective
persistence length and stretch modulus of the short linker complex.Comment: Main paper: 20 pages and 6 figures. Supplementary Material: 25 page
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