Interferometric detection of spin-polarized transport in the depletion layer of a metal-GaAs Schottky barrier

It is shown that the Kerr rotation of spin-polarized electrons is modulated by the distance of the electrons from the sample surface. Time-resolved Kerr rotation of optically-excited spin-polarized electrons in the depletion layer of n-doped GaAs displays fast oscillations that originate from an interference between the light reflected from the semiconductor surface and from the front of the electron distribution moving into the semiconductor. Using this effect, the dynamics of the photogenerated charge carriers in the depletion layer of the biased Schottky barrier is measured.Comment: 10 pages, 4 figure

Energy relaxation of an excited electron gas in quantum wires: many-body electron LO-phonon coupling

We theoretically study energy relaxation via LO-phonon emission in an excited one-dimensional electron gas confined in a GaAs quantum wire structure. We find that the inclusion of phonon renormalization effects in the theory extends the LO-phonon dominated loss regime down to substantially lower temperatures. We show that a simple plasmon-pole approximation works well for this problem, and discuss implications of our results for low temperature electron heating experiments in quantum wires.Comment: 10 pages, RevTex, 4 figures included. Also available at http://www-cmg.physics.umd.edu/~lzheng

Cataract How Important Is Age of Intervention?

Purpose: To study effect of age of intervention on visual outcome following treatment of pediatric patients with cataract. Setting: Tertiary eye care centre in Dahod at the trijunction of Gujarat, Madhya Pradesh, and Rajasthan states in central western India. Participants: 705 eyes of 1047 patients Methods: This is a prospective cohort study. We studied a consecutive series of pediatric patients with congenital, developing, or COMPLICATED cataracts who underwent surgery between January, 1999 and April, 2012 at our center. Patient demographics, cataract type, presenting symptoms, surgical intervention, postoperative visual acuity, and follow-up refractive changes were recorded. Primary Outcome measures: vision. Results: In total, 1305 eyes of 1047 children were included: unilateral cataracts were present in 786 (60.2%) eyes. There were 600 (46.7%) traumatic and 705 (53.3%) non-traumatic cases. Ages at surgery ranged from 1 to 215 months. Eyes were grouped by the age of surgical intervention performed: Group 1,</= 5 years including 177 (25.1%) eyes, and Group 2, >5 years, including 528 (74.9%) eyes either by anterior or pars plana route ± IOL placement. The mean follow-up time was 117 days. Ultimately, 128 (18.2%) Group 1 and 213 (30.2%) Group 2 patients achieved a visual acuity better than 20/80 (P < 0.001). Age at intervention was significantly related (all P < 0.001) to visual outcome. Conclusions: Age of intervention affects visual outcome significantly (p<0.001)

Compassionate Use of Experimental Therapies: Who Should Decide?

In addition to being an example of unsubstantiated hype about regenerative medicine, the controversy around the Italy-based Stamina Foundation\u27s unproven stem cell therapy represents another chapter in a continuing debate about how to balance patients\u27 requests for early access to experimental medicines with requirements for demonstrating safety and effectiveness. Compassionate use of the Stamina therapy arguably should not have been permitted under Italy\u27s laws, but public pressure was intense and judges ultimately granted access. One lesson from these events is that expert regulatory agencies may be the institutions most competent to make compassionate use decisions and that policies should include more specific criteria for authorizing compassionate use. But even where regulatory agencies make decisions based on clear rules, difficult questions will arise

Balancing Local Order and Long-Ranged Interactions in the Molecular Theory of Liquid Water

A molecular theory of liquid water is identified and studied on the basis of computer simulation of the TIP3P model of liquid water. This theory would be exact for models of liquid water in which the intermolecular interactions vanish outside a finite spatial range, and therefore provides a precise analysis tool for investigating the effects of longer-ranged intermolecular interactions. We show how local order can be introduced through quasi-chemical theory. Long-ranged interactions are characterized generally by a conditional distribution of binding energies, and this formulation is interpreted as a regularization of the primitive statistical thermodynamic problem. These binding-energy distributions for liquid water are observed to be unimodal. The gaussian approximation proposed is remarkably successful in predicting the Gibbs free energy and the molar entropy of liquid water, as judged by comparison with numerically exact results. The remaining discrepancies are subtle quantitative problems that do have significant consequences for the thermodynamic properties that distinguish water from many other liquids. The basic subtlety of liquid water is found then in the competition of several effects which must be quantitatively balanced for realistic results.Comment: 8 pages, 6 figure

Three-coordinate iron(II) expanded ring N-heterocyclic carbene complexes

A sterically demanding seven-membered expanded ring N-heterocyclic carbene (NHC) ligand allows access to rare examples of three-coordinate iron(II)-NHC complexes incorporating only halide coligands of the general formula [Fe(NHC)X 2 ] (NHC = 7-DiPP; X = Br (1) Cl (2)). Reducing the steric influence of the ancillary NHC ligand through modulation of the N-aryl substituents leads to either four- or three-coordinate complexes of the general formula [Fe(NHC)Br 2 (THF)] (3) or [Fe(NHC)Br 2 ] (4) (NHC = 7-Mes), dependent upon the solvent of recrystallization. The further reduction of NHC steric influence results in four-coordinate geometries at iron in the form of the dimeric species [Fe(NHC)Br(μ-Br)] 2 (5) or [Fe(NHC)Br 2 (THF)] (6) (NHC = SDiPP), again dependent upon the solvent of recrystallization. Compounds 1-6 have been analyzed by 1 H NMR spectroscopy, X-ray crystallography, elemental microanalysis, Mössbauer spectroscopy (for 1 and 3-5), and Evans method magnetic susceptibility. In addition to these measurements the three-coordinate species 1 and 4 have been further analyzed by SQUID magnetometry and CASSCF calculations, which show significant magnetic anisotropy that is extremely sensitive to the coordination geometry

Physician Executive Leadership: Assessing a Student-Led Approach to Healthcare Leadership Education in Medical School

Poster presented at: 14th Annual AMA Research Symposium in Orlando, Fl Objective: To investigate the effectiveness of Physican Leadership, an open access, student-led healthcare leadership program at Sidney Kimmel Medical College, in preparing to face five key emerging topics in medical practice: healthcare economics, health policy, care and quality and safety, law and medicine, and patient experience. The Problem: Gaps in Medical Education Healthcare in the US continues to evolve, and topics such as health policy, health finance, and patient experience are not central to the practice of medicine. However, the sheer volume of material students are required to learn in the preclinical years makes it challenging to introduce new subjects into traditional medical school curricula. As a result, these topics in healthcare leadership are often left out. Indeed, only 40-50% of medical student report appropriate training in the practice of medicine, including subjects as medical economics, healthcare systems, and managed care.https://jdc.jefferson.edu/pel/1002/thumbnail.jp