7,507 research outputs found
On the thermalization of a Luttinger liquid after a sequence of sudden interaction quenches
We present a comprehensive analysis of the relaxation dynamics of a Luttinger
liquid subject to a sequence of sudden interaction quenches. We express the
critical exponent governing the decay of the steady-state propagator as
an explicit functional of the switching protocol. At long distances
depends only on the initial state while at short distances it is also history
dependent. Continuous protocols of arbitrary complexity can be realized with
infinitely long sequences. For quenches of finite duration we prove that there
exist no protocol to bring the initial non-interacting system in the ground
state of the Luttinger liquid. Nevertheless memory effects are washed out at
short-distances. The adiabatic theorem is then investigated with
ramp-switchings of increasing duration, and several analytic results for both
the propagator and the excitation energy are derived.Comment: 7 pages, 4 figure
Knowledge and Prevention Practices Before Breast Cancer Diagnosis in a Cross-Sectional Study Among Survivors: Impact on Patients\u27 Involvement in the Decision Making Process
Disparities exist in breast cancer knowledge and education, which tend to influence symptom interpretation and decision to seek screening/care. The present project describes a cohort of women\u27s experiences, knowledge, and health behavior prior to and after a diagnosis of breast cancer. It also studies how knowledge and demographic factors are associated with level of involvement participants had in the treatment of their breast cancer. Women \u3e 18 years who have been diagnosed and treated for breast cancer within 10 years were recruited in Pittsburgh, PA, through the Healthy People Cohort Registry, a database of volunteers from the community, and Brooklyn, NY, through the American Cancer Society breast cancer survivor database. Subsequent to institutional ethics approval, a questionnaire was administered by mail and through an electronic interactive format. The study included 124 breast cancer survivors, one-quarter of whom were of African ancestry. Roughly half of the women indicated that their overall knowledge of breast cancer was limited before diagnosis; no significant association between overall knowledge before diagnosis and stage at diagnosis or an active role of the patient in treatment choices was observed. Two-third of the women reported using personal research on internet, books, and other media to increase knowledge on breast cancer after diagnosis; the improvement of knowledge was associated with an active role in therapy choice. White women\u27s self report of breast cancer knowledge prior to diagnosis was higher than that of women of African origin (p = 0.03); the latter experienced more delays in getting results about the diagnosis (p = 0.002), in starting treatment (p = 0.03), and in having treatment available at local facilities (p = 0.007) than white women. White women were more likely to improve their knowledge through their own research (p = 0.08) and through the contribution of their physician (p = 0.06) than women of African origin.There is still a need for addressing breast cancer knowledge among black women, and improvement in physician emotional support and in their contribution to the patient\u27s knowledge is necessary. These efforts may have a positive impact on breast cancer knowledge among black women in the US
Causes of prehospital misinterpretations of ST elevation myocardial infarction
Objectives: To determine the causes of software misinterpretation of ST elevation myocardial infarction (STEMI) compared to clinically identified STEMI to identify opportunities to improve prehospital STEMI identification. Methods: We compared ECGs acquired from July 2011 through June 2012 using the LIFEPAK 15 on adult patients transported by the Los Angeles Fire Department. Cases included patients ≥18 years who received a prehospital ECG. Software interpretation of the ECG (STEMI or not) was compared with data in the regional EMS registry to classify the interpretation as true positive (TP), true negative (TN), false positive (FP), or false negative (FN). For cases where classification was not possible using registry data, 3 blinded cardiologists interpreted the ECG. Each discordance was subsequently reviewed to determine the likely cause of misclassification. The cardiologists independently reviewed a sample of these discordant ECGs and the causes of misclassification were updated in an iterative fashion. Results: Of 44,611 cases, 50% were male (median age 65; inter-quartile range 52–80). Cases were classified as 482 (1.1%) TP, 711 (1.6%) FP, 43371 (97.2%) TN, and 47 (0.11%) FN. Of the 711 classified as FP, 126 (18%) were considered appropriate for, though did not undergo, emergent coronary angiography, because the ECG showed definite (52 cases) or borderline (65 cases) ischemic ST elevation, a STEMI equivalent (5 cases) or ST-elevation due to vasospasm (4 cases). The sensitivity was 92.8% [95% CI 90.6, 94.7%] and the specificity 98.7% [95% CI 98.6, 98.8%]. The leading causes of FP were ECG artifact (20%), early repolarization (16%), probable pericarditis/myocarditis (13%), indeterminate (12%), left ventricular hypertrophy (8%), and right bundle branch block (5%). There were 18 additional reasons for FP interpretation (<4% each). The leading causes of FN were borderline ST-segment elevations less than the algorithm threshold (40%) and tall T waves reducing the ST/T ratio below threshold (15%). There were 11 additional reasons for FN interpretation occurring ≤3 times each. Conclusion: The leading causes of FP automated interpretation of STEMI were ECG artifact and non-ischemic causes of ST-segment elevation. FN were rare and were related to ST-segment elevation or ST/T ratio that did not meet the software algorithm threshold
Observation of non-exponential magnetic penetration profiles in the Meissner state - A manifestation of non-local effects in superconductors
Implanting fully polarized low energy muons on the nanometer scale beneath
the surface of a superconductor in the Meissner state enabled us to probe the
evanescent magnetic field profile B(z)(0<z<=200nm measured from the surface).
All the investigated samples [Nb: kappa \simeq 0.7(2), Pb: kappa \simeq 0.6(1),
Ta: kappa \simeq 0.5(2)] show clear deviations from the simple exponential B(z)
expected in the London limit, thus revealing the non-local response of these
superconductors. From a quantitative analysis within the Pippard and BCS models
the London penetration depth lambda_L is extracted. In the case of Pb also the
clean limit coherence length xi0 is obtained. Furthermore we find that the
temperature dependence of the magnetic penetration depth follows closely the
two-fluid expectation 1/lambda^2 \propto 1-(T/T_c)^4. While B(z) for Nb and Pb
are rather well described within the Pippard and BCS models, for Ta this is
only true to a lesser degree. We attribute this discrepancy to the fact that
the superfluid density is decreased by approaching the surface on a length
scale xi0. This effect, which is not taken self-consistently into account in
the mentioned models, should be more pronounced in the lowest kappa regime
consistently with our findings.Comment: accepted in PRB 14 pages, 17 figure
Direct observation of non-local effects in a superconductor
We have used the technique of low energy muon spin rotation to measure the
local magnetic field profile B(z) beneath the surface of a lead film maintained
in the Meissner state (z depth from the surface, z <= 200 nm). The data
unambiguously show that B(z) clearly deviates from an exponential law and
represent the first direct, model independent proof for a non-local response in
a superconductor.Comment: 5 pages, 3 figure
Suppressed Magnetization at the Surfaces and Interfaces of Ferromagnetic Metallic Manganites
What happens to ferromagnetism at the surfaces and interfaces of manganites?
With the competition between charge, spin, and orbital degrees of freedom, it
is not surprising that the surface behavior may be profoundly different than
that of the bulk. Using a powerful combination of two surface probes, tunneling
and polarized x-ray interactions, this paper reviews our work on the nature of
the electronic and magnetic states at manganite surfaces and interfaces. The
general observation is that ferromagnetism is not the lowest energy state at
the surface or interface, which results in a suppression or even loss of
ferromagnetic order at the surface. Two cases will be discussed ranging from
the surface of the quasi-2D bilayer manganite
(LaSrMnO) to the 3D Perovskite
(LaSrMnO)/SrTiO interface. For the bilayer manganite,
that is, ferromagnetic and conducting in the bulk, these probes present clear
evidence for an intrinsic insulating non-ferromagnetic surface layer atop
adjacent subsurface layers that display the full bulk magnetization. This
abrupt intrinsic magnetic interface is attributed to the weak inter-bilayer
coupling native to these quasi-two-dimensional materials. This is in marked
contrast to the non-layered manganite system
(LaSrMnO/SrTiO), whose magnetization near the interface
is less than half the bulk value at low temperatures and decreases with
increasing temperature at a faster rate than the bulk.Comment: 15 pages, 13 figure
Mass detection on mammograms: signal variations and performance changes for human and model observers
We studied the influence of signal variability on human and model observer performances for a detection task with mammographic backgrounds and computer generated clustered lumpy backgrounds (CLB). We used synthetic yet realistic masses and backgrounds that have been validated by radiologists during previous studies, ensuring conditions close to the clinical situation. Four trained non-physician observers participated in two-alternative forced-choice (2-AFC) experiments. They were asked to detect synthetic masses superimposed on real mammographic backgrounds or CLB. Separate experiments were conducted with sets of benign and malignant masses. Results under the signal-known-exactly (SKE) paradigm were compared with signal-known-statistically (SKS) experiments. In the latter case, the signal was chosen randomly for each of the 1,400 2-AFC trials (image pairs) among a set of 50 masses with similar dimensions, and the observers did not know which signal was present. Human observers' results were then compared with model observers (channelized Hotelling with Difference-of-Gaussian and Gabor channels) in the same experimental conditions. Results show that the performance of the human observers does not differ significantly when benign masses are superimposed on real images or on CLB with locally matched gray level mean and standard deviation. For both benign and malignant masses, the performance does not differ significantly between SKE and SKS experiments, when the signals' dimensions do not vary throughout the experiment. However, there is a performance drop when the SKS signals' dimensions vary from 5.5 to 9.5 mm in the same experiment. Noise level in the model observers can be adjusted to reproduce human observers' proportion of correct answers in the 2-AFC task within 5% accuracy for most condition
Minimum joint space width and tibial cartilage morphology in the knees of healthy individuals: A cross-sectional study
<p>Abstract</p> <p>Background</p> <p>The clinical use of minimum joint space width (mJSW) and cartilage volume and thickness has been limited to the longitudinal measurement of disease progression (i.e. change over time) rather than the diagnosis of OA in which values are compared to a standard. This is primarily due to lack of establishment of normative values of joint space width and cartilage morphometry as has been done with bone density values in diagnosing osteoporosis. Thus, the purpose of this pilot study is to estimate reference values of medial joint space width and cartilage morphometry in healthy individuals of all ages using standard radiography and peripheral magnetic resonance imaging.</p> <p>Design</p> <p>For this cross-sectional study, healthy volunteers underwent a fixed-flexion knee X-ray and a peripheral MR (pMR) scan of the same knee using a 1T machine (ONI OrthOne™, Wilmington, MA). Radiographs were digitized and analyzed for medial mJSW using an automated algorithm. Only knees scoring ≤1 on the Kellgren-Lawrence scale (no radiographic evidence of knee OA) were included in the analyses. All 3D SPGRE fat-sat sagittal pMR scans were analyzed for medial tibial cartilage morphometry using a proprietary software program (Chondrometrics GmbH).</p> <p>Results</p> <p>Of 119 healthy participants, 73 were female and 47 were male; mean (SD) age 38.2 (13.2) years, mean BMI 25.0 (4.4) kg/m<sup>2</sup>. Minimum JSW values were calculated for each sex and decade of life. Analyses revealed mJSW did not significantly decrease with increasing decade (p > 0.05) in either sex. Females had a mean (SD) medial mJSW of 4.8 (0.7) mm compared to males with corresponding larger value of 5.7 (0.8) mm. Cartilage morphometry results showed similar trends with mean (SD) tibial cartilage volume and thickness in females of 1.50 (0.19) μL/mm<sup>2 </sup>and 1.45 (0.19) mm, respectively, and 1.77 (0.24) μL/mm<sup>2 </sup>and 1.71 (0.24) mm, respectively, in males.</p> <p>Conclusion</p> <p>These data suggest that medial mJSW values do not decrease with aging in healthy individuals but remain fairly constant throughout the lifespan with "healthy" values of 4.8 mm for females and 5.7 mm for males. Similar trends were seen for cartilage morphology. Results suggest there may be no need to differentiate a t-score and a z-score in OA diagnosis because cartilage thickness and JSW remain constant throughout life in the absence of OA.</p
Magnetism, superconductivity and coupling in cuprate heterostructures probed by low-energy muon-spin rotation
We present a low-energy muon-spin-rotation study of the magnetic and
superconducting properties of YBa2Cu3O7/PrBa2Cu3O7 trilayer and bilayer
heterostructures. By determining the magnetic-field profiles throughout these
structures we show that a finite superfluid density can be induced in otherwise
semiconducting PrBa2Cu3O7 layers when juxtaposed to YBa2Cu3O7 "electrodes"
while the intrinsic antiferromagnetic order is unaffected.Comment: 10 pages, 9 figures; figure 9 corrected in version
Design approaches in technology enhanced learning
Design is a critical to the successful development of any interactive learning environment (ILE). Moreover, in technology enhanced learning (TEL), the design process requires input from many diverse areas of expertise. As such, anyone undertaking tool development is required to directly address the design challenge from multiple perspectives. We provide a motivation and rationale for design approaches for learning technologies that draws upon Simon's seminal proposition of Design Science (Simon, 1969). We then review the application of Design Experiments (Brown, 1992) and Design Patterns (Alexander et al., 1977) and argue that a patterns approach has the potential to address many of the critical challenges faced by learning technologists
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