Periodic Orbits and Spectral Statistics of Pseudointegrable Billiards

We demonstrate for a generic pseudointegrable billiard that the number of periodic orbit families with length less than $l$ increases as $\pi b_0l^2/\langle a(l) \rangle$, where $b_0$ is a constant and $\langle a(l) \rangle$ is the average area occupied by these families. We also find that $\langle a(l) \rangle$ increases with $l$ before saturating. Finally, we show that periodic orbits provide a good estimate of spectral correlations in the corresponding quantum spectrum and thus conclude that diffraction effects are not as significant in such studies.Comment: 13 pages in RevTex including 5 figure

Disclosure of non-recent (historic) childhood sexual abuse: What should researchers do?

Non-recent (historic) childhood sexual abuse is an important issue to research, though often regarded as taboo and frequently met with caution, avoidance or even opposition from research ethics committees. Sensitive research, such as that which asks victim-survivors to recount experiences of abuse or harm, has the propensity to be emotionally challenging for both the participant and the researcher. However, most research suggests that any distress experienced is usually momentary and not of any clinical significance. Moreover, this type of research offers a platform for voices which have often been silenced, and many participants report the cathartic effect of recounting their experiences in a safe, non-judgemental space. With regard to the course of such research, lines of inquiry which ask adult participants to discuss their experiences of childhood sexual abuse may result in a first-time disclosure of that abuse by the victim-survivor to the researcher. Guidance about how researchers should respond to first-time disclosure is lacking. In this article, we discuss our response to one research ethics committee which had suggested that for a qualitative study for which we were seeking ethical approval (investigating experiences of pregnancy and childbirth having previously survived childhood sexual abuse), any disclosure of non-recent (historic) childhood sexual abuse which had not been previously reported would result in the researcher being obliged to report it to relevant authorities. We assess this to be inconsistent with both law and professional guidance in the United Kingdom; and provide information and recommendations for researchers and research ethics committees to consider

Disclosure of non-recent (historic) childhood sexual abuse: What should researchers do?

Non-recent (historic) childhood sexual abuse is an important issue to research, though often regarded as taboo and frequently met with caution, avoidance or even opposition from research ethics committees. Sensitive research, such as that which asks victim-survivors to recount experiences of abuse or harm, has the propensity to be emotionally challenging for both the participant and the researcher. However, most research suggests that any distress experienced is usually momentary and not of any clinical significance. Moreover, this type of research offers a platform for voices which have often been silenced, and many participants report the cathartic effect of recounting their experiences in a safe, non-judgemental space. With regard to the course of such research, lines of inquiry which ask adult participants to discuss their experiences of childhood sexual abuse may result in a first-time disclosure of that abuse by the victim-survivor to the researcher. Guidance about how researchers should respond to first-time disclosure is lacking. In this article, we discuss our response to one research ethics committee which had suggested that for a qualitative study for which we were seeking ethical approval (investigating experiences of pregnancy and childbirth having previously survived childhood sexual abuse), any disclosure of non-recent (historic) childhood sexual abuse which had not been previously reported would result in the researcher being obliged to report it to relevant authorities. We assess this to be inconsistent with both law and professional guidance in the United Kingdom; and provide information and recommendations for researchers and research ethics committees to consider

(Re)activation of survival strategies during pregnancy and childbirth following experiences of childhood sexual abuse

Objectives: To explore the pregnancy and childbearing experiences of women-survivors of childhood sexual abuse [CSA]. We aimed to generate a theory explaining those experiences for this population (women), this phenomenon (pregnancy and childbirth), and this context (those who have survived CSA). Method: Participants (N=6) were recruited to semi-structured interviews about their experiences of CSA and subsequent pregnancy and childbirth. Data saturated early, and were analysed using Grounded Theory (appropriate to cross-disciplinary health research). Coding was inductive and iterative, to ensure rigour and achieve thematic saturation. Results: Open and focused coding led to the generation of super-categories, which in-turn were collapsed into three distinct, but related themes. These themes were: Chronicity of Childhood (Sexual) Abuse; Pregnancy and Childbirth as Paradoxically (Un)safe Experiences; Enduring Nature of Survival Strategies. The relationship between these themes was explained as the theory of: (Re)activation of Survival Strategies during Pregnancy and Childbirth following Experiences of Childhood Sexual Abuse. Conclusion: Pregnancy and childbirth can be triggering for women-survivors of CSA. Survival strategies learnt during experiences of CSA can be (re)activated as a way of not only coping, but surviving (the sometimes unconsented) procedures, such as monitoring and physical examinations, as well as the feelings of lack of control and bodily agency

Distribution of Husimi Zeroes in Polygonal Billiards

The zeroes of the Husimi function provide a minimal description of individual quantum eigenstates and their distribution is of considerable interest. We provide here a numerical study for pseudo- integrable billiards which suggests that the zeroes tend to diffuse over phase space in a manner reminiscent of chaotic systems but nevertheless contain a subtle signature of pseudo-integrability. We also find that the zeroes depend sensitively on the position and momentum uncertainties with the classical correspondence best when the position and momentum uncertainties are equal. Finally, short range correlations seem to be well described by the Ginibre ensemble of complex matrices.Comment: includes 13 ps figures; Phys. Rev. E (in press

Mode structure and ray dynamics of a parabolic dome microcavity

We consider the wave and ray dynamics of the electromagnetic field in a parabolic dome microcavity. The structure of the fundamental s-wave involves a main lobe in which the electromagnetic field is confined around the focal point in an effective volume of the order of a cubic wavelength, while the modes with finite angular momentum have a structure that avoids the focal area and have correspondingly larger effective volume. The ray dynamics indicates that the fundamental s-wave is robust with respect to small geometrical deformations of the cavity, while the higher order modes are associated with ray chaos and short-lived. We discuss the incidence of these results on the modification of the spontaneous emission dynamics of an emitter placed in such a parabolic dome microcavity.Comment: 50 pages, 17 figure

Level statistics and eigenfunctions of pseudointegrable systems: dependence on energy and genus number

We study the level statistics (second half moment $I_0$ and rigidity $\Delta_3$) and the eigenfunctions of pseudointegrable systems with rough boundaries of different genus numbers $g$. We find that the levels form energy intervals with a characteristic behavior of the level statistics and the eigenfunctions in each interval. At low enough energies, the boundary roughness is not resolved and accordingly, the eigenfunctions are quite regular functions and the level statistics shows Poisson-like behavior. At higher energies, the level statistics of most systems moves from Poisson-like towards Wigner-like behavior with increasing $g$. Investigating the wavefunctions, we find many chaotic functions that can be described as a random superposition of regular wavefunctions. The amplitude distribution $P(\psi)$ of these chaotic functions was found to be Gaussian with the typical value of the localization volume $V_{\rm{loc}}\approx 0.33$. For systems with periodic boundaries we find several additional energy regimes, where $I_0$ is relatively close to the Poisson-limit. In these regimes, the eigenfunctions are either regular or localized functions, where $P(\psi)$ is close to the distribution of a sine or cosine function in the first case and strongly peaked in the second case. Also an interesting intermediate case between chaotic and localized eigenfunctions appears

Gfi1aa and Gfi1b set the pace for primitive erythroblast differentiation from hemangioblasts in the zebrafish embryo

The transcriptional repressors G fi 1(a) and G fi 1b are epigenetic regulators with unique and overlapping roles in hematopoiesis. In different contexts, G fi 1 and G fi 1b restrict or promote cell proliferation, prevent apoptosis, in fl uence cell fate decisions, and are essential for terminal differentiation. Here, we show in primitive red blood cells (prRBCs) that they can also set the pace for cellular differentiation. In zebra fi sh, prRBCs express 2 of 3 zebra fi sh G fi 1/ 1bparalogs,G fi 1aaandG fi 1b.Therecentlyidenti fi edzebra fi sh gfi1aa gene trap allele qmc551 drives erythroid green fl uorescent protein (GFP) instead of G fi 1aa expression, yet homozygous carriers have normal prRBCs. prRBCs display a maturation defect only after splice morpholino-mediated knockdown of G fi 1b in gfi1aa qmc551 homozygous embryos. To study the transcriptome of the G fi 1aa/1b double-depleted cells, we performed an RNA-Seq experi- ment on GFP-positive prRBCs sorted from 20-h our-old embryos that were heterozygous or homozygous for gfi1aa qmc551 ,aswellas wt or morphant for gfi1b .Wesubsequentlycon fi rmed and extended these data in whole-mount in situ hybridization experiments on newly generated single- and double-mutant embryos. Combi ned, the data showed that in the absence of G fi 1aa, the synchronously developing prRBCs were delayed in activating late erythr oid differentiation, as they struggled to suppress early erythroid and endothelial transcripti on programs. The latter highlighted the bipotent natu re of the progenitors from which prRBCs arise. In the absence of G fi 1aa, G fi 1b promoted erythroid differentiation as stepwise loss of wt gfi1b copies progressively delayed G fi 1aa-depleted prRBCs even further, showing that G fi 1aa and G fi 1b together set the pace for prRBC diffe rentiation from hemangioblasts

Prevalence and Predictors of Urinary Tract Infection and Severe Malaria Among Febrile Children Attending Makongoro Health Centre in Mwanza City, North-Western Tanzania.

In malaria endemic areas, fever has been used as an entry point for presumptive treatment of malaria. At present, the decrease in malaria transmission in Africa implies an increase in febrile illnesses related to other causes among underfives. Moreover, it is estimated that more than half of the children presenting with fever to public clinics in Africa do not have a malaria infection. Thus, for a better management of all febrile illnesses among under-fives, it becomes relevant to understand the underlying aetiology of the illness. The present study was conducted to determine the relative prevalence and predictors of P. falciparum malaria, urinary tract infections and bacteremia among under-fives presenting with a febrile illness at the Makongoro Primary Health Centre, North-Western Tanzania. From February to June 2011, a cross-sectional analytical survey was conducted among febrile children less than five years of age. Demographic and clinical data were collected using a standardized pre-tested questionnaire. Blood and urine culture was done, followed by the identification of isolates using in-house biochemical methods. Susceptibility patterns to commonly used antibiotics were investigated using the disc diffusion method. Giemsa stained thin and thick blood smears were examined for any malaria parasites stages. A total of 231 febrile under-fives were enrolled in the study. Of all the children, 20.3% (47/231, 95%CI, 15.10-25.48), 9.5% (22/231, 95%CI, 5.72-13.28) and 7.4% (17/231, 95%CI, 4.00-10.8) had urinary tract infections, P. falciparum malaria and bacteremia respectively. In general, 11.5% (10/87, 95%CI, 8.10-14.90) of the children had two infections and only one child had all three infections. Predictors of urinary tract infections (UTI) were dysuria (OR = 12.51, 95% CI, 4.28-36.57, P < 0.001) and body temperature (40-41 C) (OR = 12.54, 95% CI, 4.28-36.73, P < 0.001). Predictors of P. falciparum severe malaria were pallor (OR = 4.66 95%CI, 1.21-17.8, P = 0.025) and convulsion (OR = 102, 95% CI, 10-996, P = 0.001). Escherichia coli were the common gram negative isolates from urine (72.3%, 95% CI, 66.50-78.10) and blood (40%, 95%CI, and 33.70-46.30). Escherichia coli from urine were 100% resistant to ampicillin, 97% resistant to co-trimoxazole, 85% resistant to augmentin and 32.4% resistant to gentamicin; and they were 100%, 91.2% and 73.5% sensitive to meropenem, ciprofloxacin and ceftriaxone respectively. Urinary tract infection caused by multi drug resistant Escherichia coli was the common cause of febrile illness in our setting. Improvement of malaria diagnosis and its differential diagnosis from other causes of febrile illnesses may provide effective management of febrile illnesses among children in Tanzania