48,252 research outputs found
Spheromak formation and sustainment studies at the sustained spheromak physics experiment using high-speed imaging and magnetic diagnostics
A high-speed imaging system with shutter speeds as fast as 2 ns and double frame capability has been used to directly image the formation and evolution of the sustained spheromak physics experiment (SSPX) [E. B. Hooper et al., Nucl. Fusion 39, 863 (1999)]. Reproducible plasma features have been identified with this diagnostic and divided into three groups, according to the stage in the discharge at which they occur: (i) breakdown and ejection, (ii) sustainment, and (iii) decay. During the first stage, plasma descends into the flux conserver shortly after breakdown and a transient plasma column is formed. The column then rapidly bends and simultaneously becomes too dim to photograph a few microseconds after formation. It is conjectured here that this rapid bending precedes the transfer of toroidal to poloidal flux. During sustainment, a stable plasma column different from the transient one is observed. It has been possible to measure the column diameter and compare it to CORSICA [A. Tarditi et al., Contrib. Plasma Phys. 36, 132 (1996)], a magnetohydrodynamic equilibrium reconstruction code which showed good agreement with the measurements. Elongation and velocity measurements were made of cathode patterns also seen during this stage, possibly caused by pressure gradients or E×B drifts. The patterns elongate in a toroidal-only direction which depends on the magnetic-field polarity. During the decay stage the column diameter expands as the current ramps down, until it eventually dissolves into filaments. With the use of magnetic probes inserted in the gun region, an X point which moved axially depending on current level and toroidal mode number was observed in all the stages of the SSPX plasma discharge
Origin of the fast magnetization tunneling in the single-molecule magnet [Ni(hmp)(tBuEtOH)Cl]4
We present high-frequency angle-dependent EPR data for crystals of
[NixZn1-x(hmp)(t-BuEtOH)Cl]4 (x = 1 and 0.02). The x = 1 complex behaves as a
single-molecule magnet at low temperatures, displaying hysteresis and
exceptionally fast magnetization tunneling. We show that this behavior is
related to a 4th-order transverse crystal-field interaction, which produces a
significant tunnel-splitting (~10 MHz) of the ground state of this S = 4
system. The magnitude of the 4th-order anisotropy, and the dominant axial term
(D), can be related to the single-ion interactions (Di and Ei) at the
individual NiII sites, as determined for the x = 0.02 crystals.Comment: 11 pages including 2 figure
Evaluation of high temperature structural adhesives for extended service, phase 4
The evaluation of three phenylquinoxaline polymers as high temperature structural adhesives is presented. These included an experimental crisskubjabke oiktner (X-PQ) and two experimental materials (PPQ-2501) and (PPQ-HC). Lap shear, crack extension, and climing drum peel specimens were fabricated from all three polymers, and tested after thermal, combined thermal/humidity, and stressed Skydrol exposure. All three polymers generally performed well as adhesives at initial test temperatures from 219K (-67 F) to 505K (450 F) and after humidity exposure. The 644K (700 F) cured test specimens exhibited superior Skydrol resistance and thermal stability at 505K (450 F) when compared to the 602K (625 F) cured test specimens
Gravity in Dynamically Generated Dimensions
A theory of gravity in dimensions is dynamically generated from a
theory in dimensions. As an application we show how dynamically coupled
gravity theories can reduce the effective Planck mass.Comment: 7 pages, LaTeX (Revtex
Serving children: the impact of poverty on children's experiences of services
This study arose from the identification of a gap in knowledge and corresponding need for the development of a better contemporary understanding of children's experiences of poverty. Focusing on children aged 10 - 14 years, the study aimed to provide a perspective on the lives of children and young people affected by poverty in Scotland through comparing the experiences of children living in poverty with those more economically advantaged
Topological Interactions in Warped Extra Dimensions
Topological interactions will be generated in theories with compact extra
dimensions where fermionic chiral zero modes have different localizations. This
is the case in many warped extra dimension models where the right-handed top
quark is typically localized away from the left-handed one. Using
deconstruction techniques, we study the topological interactions in these
models. These interactions appear as trilinear and quadrilinear gauge boson
couplings in low energy effective theories with three or more sites, as well as
in the continuum limit. We derive the form of these interactions for various
cases, including examples of Abelian, non-Abelian and product gauge groups of
phenomenological interest. The topological interactions provide a window into
the more fundamental aspects of these theories and could result in unique
signatures at the Large Hadron Collider, some of which we explore.Comment: 40 pages, 10 figures, 2 tables; modifications in the KK parity
discussion, final version at JHE
Mirages and enhanced magnetic interactions in quantum corrals
We develop a theory for the interactions between magnetic impurities in
nanoscopic systems. The case of impurities in quantum corrals built on the
(111) Cu surface is analyzed in detail. For elliptical corrals with one
impurity, clear magnetic mirages are obtained. This leads to an enhancement of
the inter-impurity interactions when two impurities are placed at special
points in the corral. We discuss the enhancement of the conduction electron
response to the local perturbation in other nanoscopic systems.Comment: 7 pages, 5 figure
Clinical applications of the progesterone receptor antagonist mifepristone during early pregnancy and its application in therapeutic abortion
Mifepristone (RU 38,486) is a new synthetic steroid which is antagonistic to progesterone at the receptor level. Mifepristone has been demonstrated to cause spontaneous abortion of early pregnancies when taken orally. When used in combination with a prostaglandin analogue the termination success rate is increased. The studies performed in this thesis were designed to further investigate the clinical effects of mifepristone in the first and second trimesters of pregnancy, and to study the mechanism of action of the drug.
These studies examined:
1) . The efficacy and side-effects of mifepristone (600mg)
in combination with a prostaglandin E1 lmg (Gemeprost)
pessary for early termination of pregnancy.
2) . The effect of mifepristone on prostaglandin metabolite
levels in the first and second trimesters of pregnancy.
3). The effect of mifepristone on progesterone and
oestrogen receptor concentrations in the decidua and
placenta in early pregnancy.
4). The physiological and clinical effects of progesterone
inhibition with mifepristone in the second trimester.
5). The placental transfer of mifepristone during the
second trimester and its influence upon maternal and fetal
steroid concentrations
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