Fate of the Josephson effect in thin-film superconductors

The dc Josephson effect refers to the dissipationless electrical current -- the supercurrent -- that can be sustained across a weak link connecting two bulk superconductors. This effect is a probe of the fundamental nature of the superconducting state. Here, we analyze the case of two superconducting thin films connected by a point contact. Remarkably, the Josephson effect is absent at nonzero temperature, and the resistance across the contact is nonzero. Moreover, the point contact resistance is found to vary with temperature in a nearly activated fashion, with a UNIVERSAL energy barrier determined only by the superfluid stiffness characterizing the films, an angle characterizing the geometry, and whether or not the Coulomb interaction between Cooper pairs is screened. This behavior reflects the subtle nature of the superconductivity in two-dimensional thin films, and should be testable in detail by future experiments.Comment: 16 + 8 pages. 1 figure, 1 tabl

Medium and long-term adherence to postabortion contraception among women having experienced unsafe abortion in Dar es Salaam, Tanzania

<p>Abstract</p> <p>Background</p> <p>Postabortion contraceptive service is considered an effective means in addressing the problem of unsafe abortion; in spite this fact this component remains one of the weakest parts of postabortion care. In this context, the paper aims to describe the impact of a postabortion contraceptive service intervention among women admitted with complications from unsafe abortions and to explore the women's long-term contraceptive adherence.</p> <p>Methods</p> <p>392 women having experienced unsafe abortion were identified by an empathetic approach and offered postabortion contraceptive service, which included counselling on HIV and condom use. Questionnaire interviews about contraceptive use were conducted at the time of inclusion and 12 months after the abortion. Additionally, in-depth interviews were performed 6–12 months after the abortion.</p> <p>Results</p> <p>Eighty-nine percent of the women accepted postabortion contraception. Follow-up information was obtained 12 months after the abortion among 59 percent of the women. Among these, 79 percent of the married women and 84 percent of the single women stated they were using contraception at 12 months. Condom use among the single women increased significantly during the 12 months follow up.</p> <p>Conclusion</p> <p>Postabortion contraceptive services appear to be well accepted by women who are admitted with complications after an unsafe abortion and should thus be recognized as an important means in addressing the problem of unsafe abortion. In addition, counselling about HIV and condom use should be considered an essential aspect of postabortion care.</p

Understanding Outcomes in Behavior Change Interventions to Prevent Pediatric Obesity: The Role of Dose and Behavior Change Techniques

BACKGROUND: Behavioral interventions to prevent pediatric obesity have shown inconsistent results across the field. Studying what happens within the "black box" of these interventions and how differences in implementation lead to different outcomes will help researchers develop more effective interventions. AIM: To compare the implementation of three features of a phone-based intervention for parents (time spent discussing weight-related behaviors, behavior change techniques used in sessions, and intervention activities implemented by parents between sessions) with study outcomes. METHODS: A random selection of 100 parent-child dyads in the intervention arm of a phone-based obesity prevention trial was included in this analysis. Sessions were coded for overall session length, length of time spent discussing specific weight-related behaviors, number of behavior change techniques used during the sessions, and number of intervention-recommended activities implemented by the parents between sessions (e.g., parent-reported implementation of behavioral practice/rehearsal between sessions). The primary study outcome, prevention of unhealthy increase in child body mass index (BMI) percentile, was measured at baseline and 12 months. RESULTS: Overall session length was associated with decreases in child BMI percentile ( b = -0.02, p = .01). There was no association between the number of behavior change techniques used in the sessions and decreases in child BMI percentile ( b = -0.29, p = .27). The number of activities the parents reported implementing between sessions was associated with decreases in child BMI percentile ( b = -1.25, p = .02). DISCUSSION: To improve future interventions, greater attention should be paid to the intended and delivered session length, and efforts should be made to facilitate parents' implementation of intervention-recommended activities between sessions (ClinicalTrials.gov, No. NCT01084590)

Feasibility of standardized methods to specify behavioral pediatric obesity prevention interventions

Standardized methods are needed to evaluate what occurs within the 'black box' of behavioral interventions to prevent pediatric obesity. The purpose of this research is to evaluate methods to specify the behavior change techniques used and the amount of time spent discussing target weight-related behaviors in an intervention for parents of children at risk for becoming overweight or obese. Independent coders were trained to identify behavior change techniques and time spent discussing weight-related behaviors in audio recordings and transcripts of intervention sessions from 100 randomly selected participants. The behavior change technique taxonomy (BCTTv1) was used to code techniques present in sessions. A newly-developed tool was used to code time spent discussing each target weight-related behavior (e.g., physical activity, screen time). Sessions from a subset of these participants (N = 20) were double coded to evaluate inter-rater reliability. After revisions to coding protocols, coders reliably coded behavior change techniques used and time spent discussing target weight-related behaviors in sessions from the subset of 20 participants. The most commonly discussed target weight-related behavior was physical activity followed by energy intake and fruit and vegetable intake. On average, 13.9 (SD = 2.8) unique behavior change techniques were present across sessions for a given participant. These results offer reliable methods for systematically identifying behavior change techniques used and time spent discussing weight-related behaviors in a pediatric obesity prevention intervention. This work paves the way for future research to identify which specific target behaviors and techniques are most associated with the prevention of unhealthy weight gain in children

Decision-to-incision times and maternal and infant outcomes.

Journal ArticleOBJECTIVE: To measure decision-to-incision intervals and related maternal and neonatal outcomes in a cohort of women undergoing emergency cesarean deliveries at multiple university-based hospitals comprising the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. METHODS: All women undergoing a primary cesarean delivery at a Network center during a 2-year time span were prospectively ascertained. Emergency procedures were defined as those performed for umbilical cord prolapse, placental abruption, placenta previa with hemorrhage, nonreassuring fetal heart rate pattern, or uterine rupture. Detailed information regarding maternal and neonatal outcomes, including the interval from the decision time to perform cesarean delivery to the actual skin incision, was collected. RESULTS: Of the 11,481 primary cesarean deliveries, 2,808 were performed for an emergency indication. Of these, 1,814 (65%) began within 30 minutes of the decision to operate. Maternal complication rates, including endometritis, wound infection, and operative injury, were not related to the decision-to-incision interval. Measures of newborn compromise including umbilical artery pH less than 7 and intubation in the delivery room were significantly greater when the cesarean delivery was commenced within 30 minutes, likely attesting to the need for expedited delivery. Of the infants with indications for an emergency cesarean delivery who were delivered more than 30 minutes after the decision to operate, 95% did not experience a measure of newborn compromise. CONCLUSION: Approximately one third of primary cesarean deliveries performed for emergency indications are commenced more than 30 minutes after the decision to operate, and the majority were for nonreassuring heart rate tracings. In these cases, adverse neonatal outcomes were not increased. LEVEL OF EVIDENCE: II-2

Structural determinants of lipid specificity within Ups/PRELI lipid transfer proteins

Conserved lipid transfer proteins of the Ups/PRELI family regulate lipid accumulation in mitochondria by shuttling phospholipids in a lipid-specific manner across the intermembrane space. Here, we combine structural analysis, unbiased genetic approaches in yeast and molecular dynamics simulations to unravel determinants of lipid specificity within the conserved Ups/PRELI family. We present structures of human PRELID1–TRIAP1 and PRELID3b–TRIAP1 complexes, which exert lipid transfer activity for phosphatidic acid and phosphatidylserine, respectively. Reverse yeast genetic screens identify critical amino acid exchanges that broaden and swap their lipid specificities. We find that amino acids involved in head group recognition and the hydrophobicity of flexible loops regulate lipid entry into the binding cavity. Molecular dynamics simulations reveal different membrane orientations of PRELID1 and PRELID3b during the stepwise release of lipids. Our experiments thus define the structural determinants of lipid specificity and the dynamics of lipid interactions by Ups/PRELI proteins

Quantum Computing

Quantum mechanics---the theory describing the fundamental workings of nature---is famously counterintuitive: it predicts that a particle can be in two places at the same time, and that two remote particles can be inextricably and instantaneously linked. These predictions have been the topic of intense metaphysical debate ever since the theory's inception early last century. However, supreme predictive power combined with direct experimental observation of some of these unusual phenomena leave little doubt as to its fundamental correctness. In fact, without quantum mechanics we could not explain the workings of a laser, nor indeed how a fridge magnet operates. Over the last several decades quantum information science has emerged to seek answers to the question: can we gain some advantage by storing, transmitting and processing information encoded in systems that exhibit these unique quantum properties? Today it is understood that the answer is yes. Many research groups around the world are working towards one of the most ambitious goals humankind has ever embarked upon: a quantum computer that promises to exponentially improve computational power for particular tasks. A number of physical systems, spanning much of modern physics, are being developed for this task---ranging from single particles of light to superconducting circuits---and it is not yet clear which, if any, will ultimately prove successful. Here we describe the latest developments for each of the leading approaches and explain what the major challenges are for the future.Comment: 26 pages, 7 figures, 291 references. Early draft of Nature 464, 45-53 (4 March 2010). Published version is more up-to-date and has several corrections, but is half the length with far fewer reference

Transdermal microconduits by microscission for drug delivery and sample acquisition

BACKGROUND: Painless, rapid, controlled, minimally invasive molecular transport across human skin for drug delivery and analyte acquisition is of widespread interest. Creation of microconduits through the stratum corneum and epidermis is achieved by stochastic scissioning events localized to typically 250 μm diameter areas of human skin in vivo. METHODS: Microscissioning is achieved by a limited flux of accelerated gas: 25 μm inert particles passing through the aperture in a mask held against the stratum corneum. The particles scize (cut) tissue, which is removed by the gas flow with the sensation of a gentle stream of air against the skin. The resulting microconduit is fully open and may be between 50 and 200 μm deep. RESULTS: In vivo adult human tests show that microconduits reduce the electrical impedance between two ECG electrodes from approximately 4,000 Ω to 500 Ω. Drug delivery has been demonstrated in vivo by applying lidocaine to a microconduit from a cotton swab. Sharp point probing demonstrated full anaesthesia around the site within three minutes. Topical application without the microconduit required approximately 1.5 hours. Approximately 180 μm deep microconduits in vivo yielded blood sample volumes of several μl, with a faint pricking sensation as blood enters tissue. Blood glucose measurements were taken with two commercial monitoring systems. Microconduits are invisible to the unaided eye, developing a slight erythematous macule that disappears over days. CONCLUSION: Microscissioned microconduits may provide a minimally invasive basis for delivery of any size molecule, and for extraction of interstitial fluid and blood samples. Such microconduits reduce through-skin electrical impedance, have controllable diameter and depth, are fully open and, after healing, no foreign bodies were visible using through-skin confocal microscopy. In subjects to date, microscissioning is painless and rapid

Health plan administrative records versus birth certificate records: quality of race and ethnicity information in children

<p>Abstract</p> <p>Background</p> <p>To understand racial and ethnic disparities in health care utilization and their potential underlying causes, valid information on race and ethnicity is necessary. However, the validity of pediatric race and ethnicity information in administrative records from large integrated health care systems using electronic medical records is largely unknown.</p> <p>Methods</p> <p>Information on race and ethnicity of 325,810 children born between 1998-2008 was extracted from health plan administrative records and compared to birth certificate records. Positive predictive values (PPV) were calculated for correct classification of race and ethnicity in administrative records compared to birth certificate records.</p> <p>Results</p> <p>Misclassification of ethnicity and race in administrative records occurred in 23.1% and 33.6% children, respectively; the majority due to missing ethnicity (48.3%) and race (40.9%) information. Misclassification was most common in children of minority groups. PPV for White, Black, Asian/Pacific Islander, American Indian/Alaskan Native, multiple and other was 89.3%, 86.6%, 73.8%, 18.2%, 51.8% and 1.2%, respectively. PPV for Hispanic ethnicity was 95.6%. Racial and ethnic information improved with increasing number of medical visits. Subgroup analyses comparing racial classification between non-Hispanics and Hispanics showed White, Black and Asian race was more accurate among non-Hispanics than Hispanics.</p> <p>Conclusions</p> <p>In children, race and ethnicity information from administrative records has significant limitations in accurately identifying small minority groups. These results suggest that the quality of racial information obtained from administrative records may benefit from additional supplementation by birth certificate data.</p