Hypersensitivity and chaos signatures in the quantum baker's maps

Classical chaotic systems are distinguished by their sensitive dependence on initial conditions. The absence of this property in quantum systems has lead to a number of proposals for perturbation-based characterizations of quantum chaos, including linear growth of entropy, exponential decay of fidelity, and hypersensitivity to perturbation. All of these accurately predict chaos in the classical limit, but it is not clear that they behave the same far from the classical realm. We investigate the dynamics of a family of quantizations of the baker's map, which range from a highly entangling unitary transformation to an essentially trivial shift map. Linear entropy growth and fidelity decay are exhibited by this entire family of maps, but hypersensitivity distinguishes between the simple dynamics of the trivial shift map and the more complicated dynamics of the other quantizations. This conclusion is supported by an analytical argument for short times and numerical evidence at later times.Comment: 32 pages, 6 figure

Distribution of resonances for open quantum maps

We analyze simple models of classical chaotic open systems and of their quantizations (open quantum maps on the torus). Our models are similar to models recently studied in atomic and mesoscopic physics. They provide a numerical confirmation of the fractal Weyl law for the density of quantum resonances of such systems. The exponent in that law is related to the dimension of the classical repeller (or trapped set) of the system. In a simplified model, a rigorous argument gives the full resonance spectrum, which satisfies the fractal Weyl law. For this model, we can also compute a quantity characterizing the fluctuations of conductance through the system, namely the shot noise power: the value we obtain is close to the prediction of random matrix theory.Comment: 60 pages, no figures (numerical results are shown in other references

Evaluation of Fetuses in the Preventive IVIG Therapy for Congenital Heart Block (PITCH) study

The recurrence rate of anti-SSA/Ro associated congenital heart block (CHB) is 17%. Reversal of 3rd degree block has never been achieved. Based on potential reduction of maternal autoantibody titers as well as fetal inflammatory responses, IVIG was evaluated as a preventative therapy for CHB

The timing of delivery of infants with gastroschisis influences outcome

The delayed onset of intestinal function in children with gastroschisis may be because of the injurious effects of amniotic fluid on the exposed bowel. This has led to consideration of early delivery to minimize intestinal damage and improve outcome, although this has not been carefully evaluated. The authors hypothesized that timing of delivery influences outcome in children with gastroschisis, and sought to evaluate the relative impact of factors that predict outcome in this disease. All consecutive patients with gastroschisis (1992-2002) were divided into those delivered before ("early") or after ("late") 36 weeks. Bowel peel was described as "thin" or "thick," based on operative reports. Individual measures were analyzed by univariate analyses (chi2 /Student's t test), and logistic regression was used to identify significant factors for the length of stay (LOS) longer than the population average of 55 days. In 75 patients, 53.4% were "early" and 46.6% were "late." Groups were similar with respect to maternal age, birth weight, delivery mode, sex, and associated anomalies. Thickness of bowel peel was not affected by delivery time, yet "early" patients had significantly longer LOS and time to enteral feeds. Significant predictors of LOS more than 55 days included gestational age of 36 weeks or younger, time to enteral feeds of more than 26 days, and associated anomalies. Nonsignificant predictors included size of the defect, thickness of bowel peel, and need for silo. Delivery before 36 weeks is associated with longer hospitalization and increased tune to attainment of full feeds compared with later delivery. Fetal well-being should thus be the primary determinant of delivery for gastroschisis, as opposed to considerations regarding possible injurious effects to the bowel of prolonged gestation