636 research outputs found
The Significance of the -Numerical Range and the Local -Numerical Range in Quantum Control and Quantum Information
This paper shows how C-numerical-range related new strucures may arise from
practical problems in quantum control--and vice versa, how an understanding of
these structures helps to tackle hot topics in quantum information.
We start out with an overview on the role of C-numerical ranges in current
research problems in quantum theory: the quantum mechanical task of maximising
the projection of a point on the unitary orbit of an initial state onto a
target state C relates to the C-numerical radius of A via maximising the trace
function |\tr \{C^\dagger UAU^\dagger\}|. In quantum control of n qubits one
may be interested (i) in having U\in SU(2^n) for the entire dynamics, or (ii)
in restricting the dynamics to {\em local} operations on each qubit, i.e. to
the n-fold tensor product SU(2)\otimes SU(2)\otimes >...\otimes SU(2).
Interestingly, the latter then leads to a novel entity, the {\em local}
C-numerical range W_{\rm loc}(C,A), whose intricate geometry is neither
star-shaped nor simply connected in contrast to the conventional C-numerical
range. This is shown in the accompanying paper (math-ph/0702005).
We present novel applications of the C-numerical range in quantum control
assisted by gradient flows on the local unitary group: (1) they serve as
powerful tools for deciding whether a quantum interaction can be inverted in
time (in a sense generalising Hahn's famous spin echo); (2) they allow for
optimising witnesses of quantum entanglement. We conclude by relating the
relative C-numerical range to problems of constrained quantum optimisation, for
which we also give Lagrange-type gradient flow algorithms.Comment: update relating to math-ph/070200
Prevalence of Self-Reported Diabetes and Exposure to Organochlorine Pesticides among Mexican Americans: Hispanic Health and Nutrition Examination Survey, 1982–1984
Country differences in the diagnosis and management of coronary heart disease : a comparison between the US, the UK and Germany
Background
The way patients with coronary heart disease (CHD) are treated is partly determined by non-medical factors. There is a solid body of evidence that patient and physician characteristics influence doctors' management decisions. Relatively little is known about the role of structural issues in the decision making process. This study focuses on the question whether doctors' diagnostic and therapeutic decisions are influenced by the health care system in which they take place. This non-medical determinant of medical decision-making was investigated in an international research project in the US, the UK and Germany.
Methods
Videotaped patients within an experimental study design were used. Experienced actors played the role of patients with symptoms of CHD. Several alternative versions were taped featuring the same script with patients of different sex, age and social status. The videotapes were shown to 384 randomly selected primary care physicians in the three countries under study. The sample was stratified on gender and duration of professional experience. Physicians were asked how they would diagnose and manage the patient after watching the video vignette using a questionnaire with standardised and open-ended questions.
Results
Results show only small differences in decision making between British and American physicians in essential aspects of care. About 90% of the UK and US doctors identified CHD as one of the possible diagnoses. Further similarities were found in test ordering and lifestyle advice. Some differences between the US and UK were found in the certainty of the diagnoses, prescribed medications and referral behaviour. There are numerous significant differences between Germany and the other two countries. German physicians would ask fewer questions, they would order fewer tests, prescribe fewer medications and give less lifestyle advice.
Conclusion
Although all physicians in the three countries under study were presented exactly the same patient, some disparities in the diagnostic and patient management decisions were evident. Since other possible influences on doctors treatment decisions are controlled within the experimental design, characteristics of the health care system seem to be a crucial factor within the decision making process
Predictors of Recovery from Prenatal Depressive Symptoms from Pregnancy Through Postpartum
Abstract Background: Identifying predictors of the course of depressive symptoms from pregnancy through postpartum is important to inform clinical interventions. Methods: This longitudinal study investigated predictors of recovery from prenatal elevated depressive symptoms in the postpartum period. Forty-one pregnant women completed demographic, interpersonal, and psychosocial self-report assessment measures at 32 weeks of gestation and again 12 weeks postpartum. Results: Of those with elevated depressive symptoms, defined as a Beck Depression Inventory-II (BDI-II) score ≥10, at the prenatal baseline, 39% (n=16) recovered to nonelevated symptom levels postpartum, whereas 61% (n=25) experienced sustained elevated symptoms. Women who recovered evidenced significantly lower baseline depression severity and more frequent engagement in physical activity and cohabitated with a romantic partner. In multiparous women (n=25), history of past postpartum depression (PPD) differentiated between those with transient and those with persisting symptoms, although history of lifetime depression did not. None of the additional demographic, interpersonal, or psychosocial variables investigated differentiated between groups. Logistic regression analysis showed prenatal depression severity and exercise frequency as predictors of recovery postpartum. Conclusions: Results suggest most women will not experience spontaneous recovery. Women with prenatal heightened symptom severity and previous experiences with PPD are acutely vulnerable to experience sustained symptoms. In contrast, having a cohabitating partner and engagement in prenatal exercise predicted symptom improvement. Physical exercise may be an important clinical recommendation, as it may improve mood. Given the small sample size, these results are preliminary. Implications and future research recommendations are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98461/1/jwh%2E2010%2E2266.pd
Gate-controlled Guiding of Electrons in Graphene
Ballistic semiconductor structures have allowed the realization of
optics-like phenomena in electronics, including magnetic focusing and lensing.
An extension that appears unique to graphene is to use both n and p carrier
types to create electronic analogs of optical devices having both positive and
negative indices of refraction. Here, we use gate-controlled density with both
p and n carrier types to demonstrate the analog of the fiber-optic guiding in
graphene. Two basic effects are investigated: (1) bipolar p-n junction guiding,
based on the principle of angle-selective transmission though the graphene p-n
interface, and (2) unipolar fiber-optic guiding, using total internal
reflection controlled by carrier density. Modulation of guiding efficiency
through gating is demonstrated and compared to numerical simulations, which
indicates that interface roughness limits guiding performance, with
few-nanometer effective roughness extracted. The development of p-n and
fiber-optic guiding in graphene may lead to electrically reconfigurable wiring
in high-mobility devices.Comment: supplementary materal at
http://marcuslab.harvard.edu/papers/OG_SI.pd
Manipulating infrared photons using plasmons in transparent graphene superlattices
Superlattices are artificial periodic nanostructures which can control the
flow of electrons. Their operation typically relies on the periodic modulation
of the electric potential in the direction of electron wave propagation. Here
we demonstrate transparent graphene superlattices which can manipulate infrared
photons utilizing the collective oscillations of carriers, i.e., plasmons of
the ensemble of multiple graphene layers. The superlattice is formed by
depositing alternating wafer-scale graphene sheets and thin insulating layers,
followed by patterning them all together into 3-dimensional
photonic-crystal-like structures. We demonstrate experimentally that the
collective oscillation of Dirac fermions in such graphene superlattices is
unambiguously nonclassical: compared to doping single layer graphene,
distributing carriers into multiple graphene layers strongly enhances the
plasmonic resonance frequency and magnitude, which is fundamentally different
from that in a conventional semiconductor superlattice. This property allows us
to construct widely tunable far-infrared notch filters with 8.2 dB rejection
ratio and terahertz linear polarizers with 9.5 dB extinction ratio, using a
superlattice with merely five graphene atomic layers. Moreover, an unpatterned
superlattice shields up to 97.5% of the electromagnetic radiations below 1.2
terahertz. This demonstration also opens an avenue for the realization of other
transparent mid- and far-infrared photonic devices such as detectors,
modulators, and 3-dimensional meta-material systems.Comment: under revie
A novel malaria vaccine candidate antigen expressed in Tetrahymena thermophila
Development of effective malaria vaccines is hampered by the problem of producing correctly folded Plasmodium proteins for use as vaccine components. We have investigated the use of a novel ciliate expression system, Tetrahymena thermophila, as a P. falciparum vaccine antigen platform. A synthetic vaccine antigen composed of N-terminal and C-terminal regions of merozoite surface protein-1 (MSP-1) was expressed in Tetrahymena thermophila. The recombinant antigen was secreted into the culture medium and purified by monoclonal antibody (mAb) affinity chromatography. The vaccine was immunogenic in MF1 mice, eliciting high antibody titers against both N- and C-terminal components. Sera from immunized animals reacted strongly with P. falciparum parasites from three antigenically different strains by immunofluorescence assays, confirming that the antibodies produced are able to recognize parasite antigens in their native form. Epitope mapping of serum reactivity with a peptide library derived from all three MSP-1 Block 2 serotypes confirmed that the MSP-1 Block 2 hybrid component of the vaccine had effectively targeted all three serotypes of this polymorphic region of MSP-1. This study has successfully demonstrated the use of Tetrahymena thermophila as a recombinant protein expression platform for the production of malaria vaccine antigens
Generating natural language tags for video information management
This exploratory work is concerned with generation of natural language descriptions that can be used for video retrieval applications. It is a step ahead of keyword-based tagging as it captures relations between keywords associated with videos. Firstly, we prepare hand annotations consisting of descriptions for video segments crafted from a TREC Video dataset. Analysis of this data presents insights into human’s interests on video contents. Secondly, we develop a framework for creating smooth and coherent description of video streams. It builds on conventional image processing techniques that extract high-level features from individual video frames. Natural language description is then produced based on high-level features. Although feature extraction processes are erroneous at various levels, we explore approaches to putting them together to produce a coherent, smooth and well-phrased description by incorporating spatial and temporal information. Evaluation is made by calculating ROUGE scores between human-annotated and machine-generated descriptions. Further, we introduce a task-based evaluation by human subjects which provides qualitative evaluation of generated descriptions
The Pap smear screening as an occasion for smoking cessation and physical activity counselling: baseline characteristics of women involved in the SPRINT randomized controlled trial
<p>Abstract</p> <p>Background</p> <p>Gender-specific smoking cessation strategies have rarely been developed. Evidence of effectiveness of physical activity (PA) promotion and intervention in adjunct to smoking cessation programs is not strong. SPRINT study is a randomized controlled trial (RCT) designed to evaluate a counselling intervention on smoking cessation and PA delivered to women attending the Italian National Health System Cervical Cancer Screening Program. This paper presents study design and baseline characteristics of the study population.</p> <p>Methods/Design</p> <p>Among women undergoing the Pap examination in three study centres (Florence, Turin, Mantua), participants were randomized to the smoking cessation counselling [S], the smoking cessation + PA counselling [S + PA], or the control [C] groups. The program under evaluation is a standard brief counselling on smoking cessation combined with a brief counselling on increasing PA, and was delivered in 2010. A questionnaire, administered before, after 6 months and 1 year from the intervention, was used to track behavioural changes in tobacco use and PA, and to record cessation rates in participants.</p> <p>Discussion</p> <p>Out of the 5,657 women undergoing the Pap examination, 1,100 participants (55% of smokers) were randomized in 1 of the 3 study groups (363 in the S, 366 in the S + PA and 371 in the C groups). The three arms did not differ on any demographic, PA, or tobacco-use characteristics. Recruited smokers were older, less educated than non-participant women, more motivated to quit (33% vs.9% in the Preparation stage, <it>p </it>< 0.001), smoked more cigarettes per day (12 vs.9, <it>p </it>< 0.001), and were more likely to have already done 1 or more quit attempts (64% vs.50%, <it>p </it>< 0.001). The approach of SPRINT study appeared suitable to enrol less educated women who usually smoke more and have more difficulties to quit.</p> <p>Trial registration number</p> <p>ISRCTN: <a href="http://www.controlled-trials.com/ISRCTN52660565">ISRCTN52660565</a></p
- …