3,891 research outputs found
Large Magnetoresistance in Co/Ni/Co Ferromagnetic Single Electron Transistors
We report on magnetotransport investigations of nano-scaled ferromagnetic
Co/Ni/Co single electron transistors. As a result of reduced size, the devices
exhibit single electron transistor characteristics at 4.2K. Magnetotransport
measurements carried out at 1.8K reveal tunneling magnetoresistance (TMR)
traces with negative coercive fields, which we interpret in terms of a
switching mechanism driven by the shape anisotropy of the central wire-like Ni
island. A large TMR of about 18% is observed within a finite source-drain bias
regime. The TMR decreases rapidly with increasing bias, which we tentatively
attribute to excitation of magnons in the central island.Comment: 12 pages (including 4 figures). Accepted for publishing on AP
Power Utility Maximization in Discrete-Time and Continuous-Time Exponential Levy Models
Consider power utility maximization of terminal wealth in a 1-dimensional
continuous-time exponential Levy model with finite time horizon. We discretize
the model by restricting portfolio adjustments to an equidistant discrete time
grid. Under minimal assumptions we prove convergence of the optimal
discrete-time strategies to the continuous-time counterpart. In addition, we
provide and compare qualitative properties of the discrete-time and
continuous-time optimizers.Comment: 18 pages, to appear in Mathematical Methods of Operations Research.
The final publication is available at springerlink.co
Analyzing capacitance-voltage measurements of vertical wrapped-gated nanowires
The capacitance of arrays of vertical wrapped-gate InAs nanowires are
analyzed. With the help of a Poisson-Schr"odinger solver, information about the
doping density can be obtained directly. Further features in the measured
capacitance-voltage characteristics can be attributed to the presence of
surface states as well as the coexistence of electrons and holes in the wire.
For both scenarios, quantitative estimates are provided. It is furthermore
shown that the difference between the actual capacitance and the geometrical
limit is quite large, and depends strongly on the nanowire material.Comment: 15 pages, 6 Figures included, to appear in Nanotechnolog
High prevalence of cardiovascular and respiratory abnormalities in advanced, intensively treated (transplanted) myeloma: The case for âlate effectsâ screening and preventive strategies
Objectives: Modern management of myeloma has significantly improved survival, with increasing numbers of patients living beyond a decade. However, little is known about the long-term cardiovascular and respiratory status of intensively treated and multiply relapsed survivors.
Methods: We performed detailed cardiovascular and respiratory evaluations in patients with intensively treated, advanced but stable myeloma. All patients had received at least two lines of treatment, including at least one haematopoietic stem cell transplantation procedure, but had stable, controlled disease and were off active treatment at the time of evaluation.
Results: Thirty-two patients with a median duration of 6 years (range 2â12) from original diagnosis of myeloma and three lines (range 2â6) of treatment were evaluated. Despite normal physical examination in the majority, there was a high prevalence of sub-clinical cardiac and respiratory dysfunction, reflected by abnormalities of electrocardiography (45%), echocardiography (50%), serum N-terminal pro-B-type natriuretic peptide level (NT-pro-BNP, 50%), and pulmonary function testing (45%). NT-pro-BNP level correlated negatively with quality of life (Pâ=â0.012) and positively with serum ferritin (Pâ=â0.027). Dyspnoea score correlated with BMI (Pâ=â0.001). Risk factors for cardiovascular disease (obesity, hypertension, hyperlipidaemia, and hyperinsulinaemia) were common.
Discussion: Even in the absence of overt clinical features, the majority of intensively treated long-term survivors of myeloma have established cardiovascular and/or respiratory dysfunction, above levels expected in the general population of a similar age.
Conclusion: This study supports routine screening and lifestyle modification combined with primary and secondary preventive strategies to reduce cardiovascular and respiratory disease and to preserve quality of life in transplanted myeloma patients
The obscured gamma-ray and UHECR universe
Auger results on clustering of > 60 EeV ultra-high energy cosmic ray (UHECR)
ions and the interpretation of the gamma-ray spectra of TeV blazars are
connected by effects from the extragalactic background light (EBL). The EBL
acts as an obscuring medium for gamma rays and a reprocessing medium for UHECR
ions and protons, causing the GZK cutoff. The study of the physics underlying
the coincidence between the GZK energy and the clustering energy of UHECR ions
favors a composition of > 60 EeV UHECRs in CNO group nucleons. This has
interesting implications for the sources of UHECRs. We also comment on the
Auger analysis.Comment: 11 pages, 10 figures, in the International Conference on Topics in
Astroparticle and Underground Physics (TAUP) 2007, Sendai, Japan, September
11-15, 200
The effect of dilatancy and compaction on the stability of fluid infiltrated fault gouge
see Abstract Volum
Testing Consumer Rationality using Perfect Graphs and Oriented Discs
Given a consumer data-set, the axioms of revealed preference proffer a binary
test for rational behaviour. A natural (non-binary) measure of the degree of
rationality exhibited by the consumer is the minimum number of data points
whose removal induces a rationalisable data-set.We study the computational
complexity of the resultant consumer rationality problem in this paper. This
problem is, in the worst case, equivalent (in terms of approximation) to the
directed feedback vertex set problem. Our main result is to obtain an exact
threshold on the number of commodities that separates easy cases and hard
cases. Specifically, for two-commodity markets the consumer rationality problem
is polynomial time solvable; we prove this via a reduction to the vertex cover
problem on perfect graphs. For three-commodity markets, however, the problem is
NP-complete; we prove thisusing a reduction from planar 3-SAT that is based
upon oriented-disc drawings
CO_2 on Titan
A sharp stratospheric emission feature at 667 cm^(â1) in the Voyager infrared spectra of Titan is associated with the Îœ_2 Q branch of CO_2. A coupling of photochemical and radiative transfer theory yields an average mole fraction above the 110 mbar level of ÆCO_2 = 1.5 ± ^(1.5)_(0.8) x 10^(-9), with most of the uncertainty being due to imprecise knowledge of the vertical distribution. CO_2 is found to be in a steady state, with its abundance being regulated principally by the âŒ72 K cold trap near the tropopause and secondarily by the rate at which water-bearing meteoritic material enters the top of the atmosphere. An influx of water about 0.4 times that at the top of the terrestrial atmosphere is consistent with a combination of the observed CO_2 abundance and a steady state CO mole fraction of 1.1Ă10^(â4); the theoretical value for CO is close to the value observed by Lutz et al. (1983), although there are large margins for error in both numbers. If steady state conditions for CO prevail, little information is available regarding the evolution of Titan's atmosphere
A review of hippocampal activation in postâtraumatic stress disorder
Postâtraumatic stress disorder (PTSD) is often characterized by deficits in memory encoding and retrieval and aberrant fear and extinction learning. The hippocampus plays a critical role in memory and contextual processing and has been implicated in intrinsic functional connectivity networks involved in selfâreferential thought and memoryârelated processes. This review focuses on hippocampal activation findings during memory and fear and extinction learning tasks, as well as resting state hippocampal connectivity in individuals with PTSD. A preponderance of functional neuroimaging studies to date, using memory, fear learning, and extinction tasks, report decreased or âcontrols comparableâ hippocampal activation in individuals with PTSD, which is usually associated with poorer performance on the task imaged. Existing evidence thus raises the possibility that greater hippocampal recruitment in PTSD participants may be required for similar performance levels. Studies of resting state functional connectivity in PTSD predominantly report reduced withinânetwork connectivity in the default mode network (DMN), as well as greater coupling between the DMN and salience network (SN) via the hippocampus. Together, these findings suggest that deficient hippocampal activation in PTSD may be associated with poorer performance during memory, extinction recall, and fear renewal tasks. Furthermore, studies of resting state connectivity implicate the hippocampus in decreased withinânetwork DMN connectivity and greater coupling with SN regions characteristic of PTSD.The hippocampus plays a key role in memory, fear learning and extinction, and default mode network resting state connectivity, all processes which have known deficits in postâtraumatic stress disorder (PTSD). In this review, we examine recent fMRI studies on hippocampal function in PTSD and controls and identify critical areas for future research to explore.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153031/1/psyp13357.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153031/2/psyp13357_am.pd
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