712 research outputs found
The clinical anatomy of the cephalic vein in the deltopectoral triangle
Identification and recognition of the cephalic vein in the deltopectoral triangle
is of critical importance when considering emergency catheterization procedures.
The aim of our study was to conduct a cadaveric study to access data
regarding the topography and the distribution patterns of the cephalic vein as
it relates to the deltopectoral triangle. One hundred formalin fixed cadavers
were examined. The cephalic vein was found in 95% (190 right and left) specimens,
while in the remaining 5% (10) the cephalic vein was absent. In 80%
(152) of cases the cephalic vein was found emerging superficially in the lateral
portion of the deltopectoral triangle. In 30% (52) of these 152 cases the cephalic
vein received one tributary within the deltopectoral triangle, while in 70%
(100) of the specimens it received two. In the remaining 20% (38) of cases the
cephalic vein was located deep to the deltopectoral fascia and fat and did not
emerge through the deltopectoral triangle but was identified medially to the
coracobrachialis and inferior to the medial border of the deltoid. In addition,
in 4 (0.2%) of the specimens the cephalic vein, after crossing the deltopectoral
triangle, ascended anterior and superior to the clavicle to drain into the subclavian
vein. In these specimens a collateral branch was observed to communicate
between the cephalic and external jugular veins. In 65.2% (124) of the cases
the cephalic vein traveled with the deltoid branch of the thoracoacromial trunk.
The length of the cephalic vein within the deltopectoral triangle ranged from
3.5 cm to 8.2 cm with a mean of 4.8 ± 0.7 cm. The morphometric analysis
revealed a mean cephalic vein diameter of 0.8 ± 0.1 cm with a range of 0.1 cm
to 1.2 cm. The cephalic vein is relatively large and constant, usually allowing
for easy cannulation. (Folia Morphol 2008; 67: 72-77
A multi-machine scaling of halo current rotation
Halo currents generated during unmitigated tokamak disruptions are known to develop
rotating asymmetric features that are of great concern to ITER because they can dynamically
amplify the mechanical stresses on the machine. This paper presents a multi-machine analysis
of these phenomena. More specifically, data from C-Mod, NSTX, ASDEX Upgrade, DIII-D,
and JET are used to develop empirical scalings of three key quantities: (1) the machinespecific minimum current quench time, τCQ; (2) the halo current rotation duration, trot; and (3)
the average halo current rotation frequency, fh . These data reveal that the normalized rotation
duration, trot/τCQ, and the average rotation velocity, vh , are surprisingly consistent from
machine to machine. Furthermore, comparisons between carbon and metal wall machines
show that metal walls have minimal impact on the behavior of rotating halo currents. Finally,
upon projecting to ITER, the empirical scalings indicate that substantial halo current rotation
above fh = 20 Hz is to be expected. More importantly, depending on the projected value of
τCQ in ITER, substantial rotation could also occur in the resonant frequency range of 6–20 Hz.
As such, the possibility of damaging halo current rotation during unmitigated disruptions in
ITER cannot be ruled out.EURATOM 633053RCUK Energy Programme EP/ I501045Princeton University DE-AC02-09CH1146
Black holes in which the electrostatic or scalar equation is solvable in closed form
We show that the method used in the Schwarzschild black hole for finding the
elementary solution of the electrostatic equation in closed form cannot extend
in higher dimensions. By contrast, we prove the existence of static,
spherically symmetric geometries with a non-degenerated horizon in which the
static scalar equation can be solved in closed form. We give the explicit
results in 6 dimensions. We determine moreover the expressions of the
electrostatic potential and of the static scalar field for a point source in
the extremal Reissner-Nordstrom black holes in higher dimensions.Comment: 20 pages, no figur
Fast Searching in Packed Strings
Given strings and the (exact) string matching problem is to find all
positions of substrings in matching . The classical Knuth-Morris-Pratt
algorithm [SIAM J. Comput., 1977] solves the string matching problem in linear
time which is optimal if we can only read one character at the time. However,
most strings are stored in a computer in a packed representation with several
characters in a single word, giving us the opportunity to read multiple
characters simultaneously. In this paper we study the worst-case complexity of
string matching on strings given in packed representation. Let be
the lengths and , respectively, and let denote the size of the
alphabet. On a standard unit-cost word-RAM with logarithmic word size we
present an algorithm using time O\left(\frac{n}{\log_\sigma n} + m +
\occ\right). Here \occ is the number of occurrences of in . For this improves the bound of the Knuth-Morris-Pratt algorithm.
Furthermore, if our algorithm is optimal since any
algorithm must spend at least \Omega(\frac{(n+m)\log
\sigma}{\log n} + \occ) = \Omega(\frac{n}{\log_\sigma n} + \occ) time to
read the input and report all occurrences. The result is obtained by a novel
automaton construction based on the Knuth-Morris-Pratt algorithm combined with
a new compact representation of subautomata allowing an optimal
tabulation-based simulation.Comment: To appear in Journal of Discrete Algorithms. Special Issue on CPM
200
Thermally assisted magnetization reversal in the presence of a spin-transfer torque
We propose a generalized stochastic Landau-Lifshitz equation and its
corresponding Fokker-Planck equation for the magnetization dynamics in the
presence of spin transfer torques. Since the spin transfer torque can pump a
magnetic energy into the magnetic system, the equilibrium temperature of the
magnetic system is ill-defined. We introduce an effective temperature based on
a stationary solution of the Fokker-Planck equation. In the limit of high
energy barriers, the law of thermal agitation is derived. We find that the
N\'{e}el-Brown relaxation formula remains valid as long as we replace the
temperature by an effective one that is linearly dependent of the spin torque.
We carry out the numerical integration of the stochastic Landau-Lifshitz
equation to support our theory. Our results agree with existing experimental
data.Comment: 5 figure
Dimensional Dependence of Black Hole Formation in Self-Similar Collapse of Scalar Field
We study classical and quantum self-similar collapses of a massless scalar
field in higher dimensions, and examine how the increase in the number of
dimensions affects gravitational collapse and black hole formation. Higher
dimensions seem to favor formation of black hole rather than other final
states, in that the initial data space for black hole formation enlarges as
dimension increases. On the other hand, the quantum gravity effect on the
collapse lessens as dimension increases. We also discuss the gravitational
collapse in a brane world with large but compact extra dimensions.Comment: Improved a few arguments and added a figur
Constraining Primordial Non-Gaussianity with High-Redshift Probes
We present an analysis of the constraints on the amplitude of primordial
non-Gaussianity of local type described by the dimensionless parameter . These constraints are set by the auto-correlation functions (ACFs) of two
large scale structure probes, the radio sources from NRAO VLA Sky Survey (NVSS)
and the quasar catalogue of Sloan Digital Sky Survey Release Six (SDSS DR6
QSOs), as well as by their cross-correlation functions (CCFs) with the cosmic
microwave background (CMB) temperature map (Integrated Sachs-Wolfe effect).
Several systematic effects that may affect the observational estimates of the
ACFs and of the CCFs are investigated and conservatively accounted for. Our
approach exploits the large-scale scale-dependence of the non-Gaussian halo
bias. The derived constraints on {} coming from the NVSS CCF and
from the QSO ACF and CCF are weaker than those previously obtained from the
NVSS ACF, but still consistent with them. Finally, we obtain the constraints on
() and () from
NVSS data and SDSS DR6 QSO data, respectively.Comment: 16 pages, 8 figures, 1 table, Accepted for publication on JCA
Interstellar MHD Turbulence and Star Formation
This chapter reviews the nature of turbulence in the Galactic interstellar
medium (ISM) and its connections to the star formation (SF) process. The ISM is
turbulent, magnetized, self-gravitating, and is subject to heating and cooling
processes that control its thermodynamic behavior. The turbulence in the warm
and hot ionized components of the ISM appears to be trans- or subsonic, and
thus to behave nearly incompressibly. However, the neutral warm and cold
components are highly compressible, as a consequence of both thermal
instability in the atomic gas and of moderately-to-strongly supersonic motions
in the roughly isothermal cold atomic and molecular components. Within this
context, we discuss: i) the production and statistical distribution of
turbulent density fluctuations in both isothermal and polytropic media; ii) the
nature of the clumps produced by thermal instability, noting that, contrary to
classical ideas, they in general accrete mass from their environment; iii) the
density-magnetic field correlation (or lack thereof) in turbulent density
fluctuations, as a consequence of the superposition of the different wave modes
in the turbulent flow; iv) the evolution of the mass-to-magnetic flux ratio
(MFR) in density fluctuations as they are built up by dynamic compressions; v)
the formation of cold, dense clouds aided by thermal instability; vi) the
expectation that star-forming molecular clouds are likely to be undergoing
global gravitational contraction, rather than being near equilibrium, and vii)
the regulation of the star formation rate (SFR) in such gravitationally
contracting clouds by stellar feedback which, rather than keeping the clouds
from collapsing, evaporates and diperses them while they collapse.Comment: 43 pages. Invited chapter for the book "Magnetic Fields in Diffuse
Media", edited by Elisabete de Gouveia dal Pino and Alex Lazarian. Revised as
per referee's recommendation
'Education, education, education' : legal, moral and clinical
This article brings together Professor Donald Nicolson's intellectual interest in professional legal ethics and his long-standing involvement with law clinics both as an advisor at the University of Cape Town and Director of the University of Bristol Law Clinic and the University of Strathclyde Law Clinic. In this article he looks at how legal education may help start this process of character development, arguing that the best means is through student involvement in voluntary law clinics. And here he builds upon his recent article which argues for voluntary, community service oriented law clinics over those which emphasise the education of students
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
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