Superconductors with Magnetic Impurities: Instantons and Sub-gap States

When subject to a weak magnetic impurity potential, the order parameter and quasi-particle energy gap of a bulk singlet superconductor are suppressed. According to the conventional mean-field theory of Abrikosov and Gor'kov, the integrity of the energy gap is maintained up to a critical concentration of magnetic impurities. In this paper, a field theoretic approach is developed to critically analyze the validity of the mean field theory. Using the supersymmetry technique we find a spatially homogeneous saddle-point that reproduces the Abrikosov-Gor'kov theory, and identify instanton contributions to the density of states that render the quasi-particle energy gap soft at any non-zero magnetic impurity concentration. The sub-gap states are associated with supersymmetry broken field configurations of the action. An analysis of fluctuations around these configurations shows how the underlying supersymmetry of the action is restored by zero modes. An estimate of the density of states is given for all dimensionalities. To illustrate the universality of the present scheme we apply the same method to study `gap fluctuations' in a normal quantum dot coupled to a superconducting terminal. Using the same instanton approach, we recover the universal result recently proposed by Vavilov et al. Finally, we emphasize the universality of the present scheme for the description of gap fluctuations in d-dimensional superconducting/normal structures.Comment: 18 pages, 9 eps figure

(Non)Existence of Pleated Folds: How Paper Folds Between Creases

We prove that the pleated hyperbolic paraboloid, a familiar origami model known since 1927, in fact cannot be folded with the standard crease pattern in the standard mathematical model of zero-thickness paper. In contrast, we show that the model can be folded with additional creases, suggesting that real paper “folds” into this model via small such creases. We conjecture that the circular version of this model, consisting simply of concentric circular creases, also folds without extra creases. At the heart of our results is a new structural theorem characterizing uncreased intrinsically flat surfaces—the portions of paper between the creases. Differential geometry has much to say about the local behavior of such surfaces when they are sufficiently smooth, e.g., that they are torsal ruled. But this classic result is simply false in the context of the whole surface. Our structural characterization tells the whole story, and even applies to surfaces with discontinuities in the second derivative. We use our theorem to prove fundamental properties about how paper folds, for example, that straight creases on the piece of paper must remain piecewise-straight (polygonal) by folding.National Science Foundation (U.S.) (CAREER Award CCF-0347776

‘We’ are more likely to endorse than ‘I’: the effects of self-construal and brand symbolism on consumers’ online brand endorsements

Recent research increasingly highlights that consumers engage in online brand endorsements (e.g. Facebook likes) to signal their identity, but has failed to explain why different consumers use this type of signaling to differing degrees. This paper addresses this gap by looking at a culturally constructed individual difference variable, namely self-construal. Self-construal, which can be independent or interdependent, refers to the extent that people define themselves in terms of the relations they have with others. In four studies, this research shows that consumers’ self-construal is related to their intention to endorse brands online. In particular, high levels of interdependent self-construal positively affect consumers’ intention to endorse brands online (Studies 1A & 1B). This effect is mediated by an increased perception of brands’ symbolic value (Study 2). Moreover, this positivity bias toward symbolic brand cues is conditional upon consumers’ brand attitude (Study 3). These findings demonstrate that consumers’ identity plays a central role in their brand perception and brand-related social media use

Design and analysis of a 20 MW propulsion power train

The electric ship research program at the University of Texas at Austin focuses on the development of power system technology for future electric ships. The main goal of the on-going research activity is to identify critical, high pay-off technology development needed to enable major improvement, in size and functionality, of navy ships power systems. Initial efforts were directed towards the establishment of a baseline power train which highlights various constraints and provides a basis for later optimization efforts. A 20 MW power train system was chosen for such a baseline, and all components, from fuel to propulsion motor, were considered and their impact on the whole power system assessed. The baseline design consists of a 25 MVA/3600 rpm radial flux permanent magnet generator, a 22 MVA PWM converter, and a 20 MW/150 rpm radial flux permanent magnet motor, along with the amount of fuel sized for an assumed mission profile, and the widely used LM2500 gas turbine. The analysis shows that fuel is by far the dominant component contributing to weight and volume and, consequently, overall efficiency of power train components is the most relevant parameter to reduce weight and volume. The 3600 rpm generator is the smallest component. The 150 rpm motor is the heaviest component, other than fuel, weighing close to 100 tonnes.Center for Electromechanic

Coping with the effects of fear of failure in young elite athletes

Coping with stress is an important element in effective functioning at the elite level in sports, and fear of failure (FF) is an example of a stressor that athletes experience. Three issues underpin the present preliminary study. First, the prevalence of problems attributed to FF in achievement settings. Second, sport is a popular and significant achievement domain for children and adolescents. Third, there is a lack of research on FF in sport among this population. Therefore, the objectives of the study were to examine the effects of FF on young athletes and to find out their coping responses to the effects of FF. Interviews were conducted individually with nine young elite ath­letes (5 males, 4 females; ages 14-17 years). It was inferred from the data that FF affected the athletes' well-being, interpersonal behavior, sport performance, and schoolwork. The athletes employed a combination of problem-focused, emotion-fo­cused, and avoidance-focused coping strategies, with avoidance strategies being the most frequently reported

Effects of breast cancer adjuvant chemotherapy regimens on expression of the aging biomarker, p16ink4a

Background: Although chemotherapy saves lives, increasing evidence shows that chemotherapy accelerates aging. We previously demonstrated that mRNA expression of p16INK4a, a biomarker of senescence and molecular aging, increased early and dramatically after beginning adjuvant anthracycline-based regimens in early stage breast cancer patients. Here, we determined if changes in p16INK4a expression vary by chemotherapy regimen among early stage breast cancer patients. Methods: We conducted a study of stage I-III breast cancer patients receiving adjuvant or neoadjuvant chemotherapy. p16INK4a expression was analyzed prechemotherapy and postchemotherapy (median 6.2 months after the last chemotherapy) in peripheral blood T lymphocytes. Chemotherapy-induced change in p16INK4a expression was compared among regimens. All statistical tests were 2-sided. Results: In 146 women, chemotherapy was associated with a statistically significant increase in p16INK4a expression (accelerated aging of 17 years; P < .001). Anthracycline-based regimens were associated with the largest increases (accelerated aging of 23 to 26 years; P ≤ .008). Nonanthracycline-based regimens demonstrated a much smaller increase (accelerated aging of 9 to 11 years; P ≤ .15). In addition to the type of chemotherapy regimen, baseline p16INK4a levels, but not chronologic age or race, were also associated with the magnitude of increases in p16INK4a. Patients with lower p16INK4a levels at baseline were more likely to experience larger increases. Conclusions: Our findings suggest that the aging effects of chemotherapy may be influenced by both chemotherapy type and the patient's baseline p16INK4a level. Measurement of p16INK4a expression is not currently available in the clinic, but nonanthracycline regimens offering similar efficacy as anthracycline regimens might be favored

Titan's cold case files - Outstanding questions after Cassini-Huygens

Abstract The entry of the Cassini-Huygens spacecraft into orbit around Saturn in July 2004 marked the start of a golden era in the exploration of Titan, Saturn's giant moon. During the Prime Mission (2004–2008), ground-breaking discoveries were made by the Cassini orbiter including the equatorial dune fields (flyby T3, 2005), northern lakes and seas (T16, 2006), and the large positive and negative ions (T16 & T18, 2006), to name a few. In 2005 the Huygens probe descended through Titan's atmosphere, taking the first close-up pictures of the surface, including large networks of dendritic channels leading to a dried-up seabed, and also obtaining detailed profiles of temperature and gas composition during the atmospheric descent. The discoveries continued through the Equinox Mission (2008–2010) and Solstice Mission (2010–2017) totaling 127 targeted flybys of Titan in all. Now at the end of the mission, we are able to look back on the high-level scientific questions from the start of the mission, and assess the progress that has been made towards answering these. At the same time, new scientific questions regarding Titan have emerged from the discoveries that have been made. In this paper we review a cross-section of important scientific questions that remain partially or completely unanswered, ranging from Titan's deep interior to the exosphere. Our intention is to help formulate the science goals for the next generation of planetary missions to Titan, and to stimulate new experimental, observational and theoretical investigations in the interim

Patient-reported symptom severity, interference with daily activities, and adverse events in older and younger women receiving chemotherapy for early breast cancer

Background: To the authors' knowledge, it is unknown whether patient-reported symptom severity and symptom interference with daily activities differ between younger (aged <65 years) and older (aged ≥65 years) women receiving similar chemotherapy regimens for early breast cancer (EBC). Methods: Study participants rated 17 side effects of chemotherapy regimens currently in use in clinical practice (2014-2019). Results: Of 284 women with EBC (stage I-III), approximately 57% were aged <65 years and 43% were aged ≥65 years. For anthracycline-based regimens, a higher percentage of younger women reported moderate, severe, or very severe (MSVS) hot flashes (49% vs 18%) (P <.001). For nonanthracycline regimens, a higher percentage of younger women reported MSVS hot flashes (38% vs 19%) (P =.009) and a lower percentage reported MSVS arthralgia (28% vs 49%) (P =.005). With regard to symptom interference with daily activities, a higher percentage of younger women being treated with anthracycline-based regimens reported MSVS hot flashes (32% vs 7%) (P =.001) and myalgia (38% vs 18%) (P =.02). For nonanthracycline chemotherapy, a higher percentage of younger women reported MSVS interference for hot flashes (26% vs 9%) (P =.006) and lower percentages reported abdominal pain (13% vs 28%) (P =.02). Overall, there were no significant differences noted among younger versus older patients with regard to hospitalizations (19% vs 12%; P =.19), dose reductions (34% vs 31%; P =.50), dose delays (22% vs 25%; P =.59), or early treatment discontinuation (16% vs 16%; P =.9546). Conclusions: Older and younger women with EBC who were treated with identical chemotherapy regimens generally experienced similar levels of symptom severity, symptom-related interference with daily activities, and adverse events. Lay Summary: In this study, women receiving chemotherapy for early breast cancer rated the severity of 17 symptoms and symptom interference with their activities of daily living. Older (aged ≥65 years) and younger (aged <65 years) women who received identical chemotherapy regimens generally experienced similar levels of symptom severity, symptom-related interference with daily activities, and adverse events

Congruence of patient- and clinician-reported toxicity in women receiving chemotherapy for early breast cancer

Background: The National Cancer Institute's Patient-Reported Outcomes Version of the Common Terminology Criteria for Adverse Events, collected alongside the clinician-reported Common Terminology Criteria for Adverse Events, enables comparisons of patient and clinician reports on treatment toxicity. Methods: In a multisite study of women receiving chemotherapy for early-stage breast cancer, symptom reports were collected on the same day from patients and their clinicians for 17 symptoms; their data were not shared with each other. The proportions of moderate, severe, or very severe patient-reported symptom severity were compared with the proportions of clinician-rated grade 2, 3, or 4 toxicity. Patient-clinician agreement was assessed via κ statistics. Chi-square tests investigated whether patient characteristics were associated with patient-clinician agreement. Results: Among 267 women, the median age was 58 years (range, 24-83 years), and 26% were nonwhite. There was moderate scoring agreement (κ = 0.413-0.570) for 53% of symptoms, fair agreement for 41% (κ = 0.220-0.378), and slight agreement for 6% (κ = 0.188). For example, patient-reported and clinician-rated percentages were 22% and 8% for severe or very severe fatigue, 41% and 46% for moderate fatigue, 32% and 39% for mild fatigue, and 6% and 7% for none. Clinician severity scores were lower for nonwhite patients in comparison with white patients for peripheral neuropathy, nausea, arthralgia, and dyspnea. Conclusions: Although clinician reporting of symptoms is common practice in oncology, there is suboptimal agreement with the gold standard of patient self-reporting. These data provide further evidence supporting the integration of patient-reported outcomes into oncological clinical research and clinical practice to improve monitoring of symptoms as well as timely interventions for symptoms