Level Crossing Probabilities II: Polygonal Recurrence of Multidimensional Random Walks

In part I (math.PR/0406392) we proved for an arbitrary one-dimensional random walk with independent increments that the probability of crossing a level at a given time n is of the maximal order square root of n. In higher dimensions we call a random walk 'polygonally recurrent' (resp. transient) if a.s. infinitely many (resp. finitely many) of the straight lines between two consecutive sites hit a given bounded set. The above estimate implies that three-dimensional random walks with independent components are polygonally transient. Similarly a directionally reinforced random walk on Z^3 in the sense of Mauldin, Monticino and v.Weizsaecker [1] is transient. On the other hand we construct an example of a transient but polygonally recurrent random walk with independent components on Z^2.Comment: 23 pages, errors and typos corrected, references adde

Representation of Quantum Field Theory by Elementary Quantum Information

In this paper is considered relativistic quantum field theory expressed by elementary units of quantum information as they are considered as fundamental entity of nature by Carl Friedrich von Weizsaecker. Through quantization of a Weyl spinor describing an elementary unit of quantum information and consisting of four real components one obtains four pairs of creation and annihilation operators acting in a tensor space of states containing many units of quantum information. There can be constructed position and momentum operators from the creation and annihilation operators and based on these operators the Poincare group can be represented in this abstract tensor space of quantum information. A general state in the tensor space can be mapped to a state in Minkowski space-time by using the position representation of the eigenstates of the occupation number operators which correspond to the eigenstates of the harmonic oscillator. This yields a description of relativistic quantum mechanics. Quantization of the coefficients of a general state in the tensor space leads to many particle theory and thus to quantum field theory.Comment: 7 page

Chernoff's Theorem and Discrete Time Approximations of Brownian Motion on Manifolds

Let (S(t)) be a one-parameter family S = (S(t)) of positive integral operators on a locally compact space L. For a possibly non-uniform partition of [0,1] define a measure on the path space C([0,1],L) by using a) S(dt) for the transition between cosecutive partition times of distance dt, and b) a suitable continuous interpolation scheme (e.g. Brownian bridges or geodesics). If necessary normalize to get a probability measure. We prove a version of Chernoff's theorem of semigroup theory and tighness results which together yield convergence in law of such measures as the partition gets finer. In particular let L be a closed smooth submanifold of a Riemannian manifold M. We prove convergence of Brownian motion on M, conditioned to visit L at all partition times, to a process on L whose law has a Radon-Nikodym density with repect to Brownian motion on L which contains scalar, mean and sectional curvature terms. Various approximation schemes for Brownian motion are also given. These results substantially extend earlier work by the authors and by Andersson and Driver.Comment: 35 pages, revised version for publication, more detailed expositio

Ein Tiger im Schildkrötenpanzer?

Vorliegende Diplomarbeit beschäftigt sich mit der so genannten Eingewöhnung von Kleinkindern in die Kinderkrippe, im Besonderen mit der eines in seinem Verhalten auffallend stillen Jungen namens Jakob. Dieser wurde im Rahmen der Wiener Kinderkrippenstudie mittels der Young Child Observation über mehrere Monate hinweg beobachtet. Das dadurch gewonnene Beobachtungsmaterial diente als Grundstock dieser Arbeit. Jakob, bei Eintritt in die Kinderkrippe gerade mal zwei Jahre und zwei Monate alt, erschien anfangs als munterer neugieriger Junge, der jedoch im weiteren Verlauf seines Aufenthalts während der Beobachtungen größtenteils stilles und zurückgezogenes Verhalten an den Tag legte. Im Zentrum dieser Diplomarbeit steht daher die Frage, welche Bedeutung Jakobs vornehmlich stilles und zurückgezogenes Verhalten im Hinblick auf den Prozess der Bewältigung von Trennung und des Getrennt-Seins von seinen primären Bezugspersonen hatte. Als Einzelfallstudie konzipiert, gibt diese Arbeit einen differenzierten Einblick in die innere Erlebniswelt des Jungen und wie diese in engem Zusammenhang mit dem Prozess von Bewältigung steht. Dazu wurde das Erleben des Jungen hinsichtlich seines Affektausdrucks, seines Interesses und seines dynamischen Austauschs mit den anwesenden Personen während der ersten vier Monate seines Krippenaufenthalts in differenzierter Weise untersucht, analysiert und mit bestehenden psychoanalytischen Konzepten in Bezug gesetzt. Eine der bedeutsamsten Schlussfolgerungen der vorliegenden Einzelfallstudie ist, dass komplexe Verstrickungen der Begebenheiten in einer Kinderkrippe im Umgang mit einem auffallend stillen Kind dazu führen können, dass stilles Verhalten nicht nur als Hinweis auf Schwierigkeiten beim Bewältigen, sondern gleichzeitig auch als Ausdruck und Folge davon verstanden werden kann. Die Ergebnisse geben dazu unter anderem Aufschluss darüber, welch bedeutende Rolle der Beziehung zwischen Kind und PädagogInnen für den Bewältigungsprozess von Trennung und Getrennt-Sein innewohnt und welch positiven, aber möglicherweise auch negativen Einfluss die jeweiligen Beziehungserfahrungen auf das Erleben des Kindes und somit auf die vom Kind zu leistende Bewältigung haben können. Abschließend wird auf den Ergebnissen der Fallanalyse basierend, unter Bezugnahme bereits bestehender Forschungsergebnisse der Krippenforschung, diskutiert, welche möglichen Konsequenzen für die Konzeption der Aus- und Weiterbildung von KrippenpädagogInnen hinsichtlich stiller und dadurch unauffälliger Kinder berücksichtigt werden sollten.The present thesis deals with the so-called familiarization of toddlers in day care centres, in particular with the acclimatization of a remarkably silent little child named Jakob. He had been observed for several months in line with the ‘Wiener Kinderkrippenstudie’ (research project ‘Toddlers’ Adjustment to Out-of-Home Care’) by means of Young Child Observation research conducted at the University of Vienna. The thereby won observation material has served as basis for this paper. The two years and two months old Jakob, who seemed to be a lively and curious boy at his entry at the day care centre, however developed a silent and secluded behaviour during his stay. Therefore at the focus of the present thesis stands the meaning of Jakob’s silent and secluded behaviour as to the process of coping with separation and the experience of being separated from his parents, his primary attachment figures. Conceived as single case study this paper delivers insight into the realm of experience of the little boy and how his inner world copes with the process of accomplishment. The boy´s experience was oberved concerning his affective expression, interests and dynamic approach to the others during his first four months stay at the day care centre. It was intensively analysed and connected with existing psychoanalytic concepts. One of the most significant conclusions of the present single case study is the following: complex mechanisms of occurrence at a day care centre handling with a remarkably silent child demonstrate that silent behaviour is not only an indication of the toddler’s difficulties of accomplishment, but at the same time may also be an expression or a result of all this. The results indicate the prominent role of the relationship between the toddler and the caregivers as to the process of accomplishment of separation and being separated and the positive but also potentially negative effects of this experience on the toddler and the coping of separation itself. Finally on the results of this single case study and referring to existing research results of the Child Care Observation, the present thesis discusses, which possible consequences of the conception of the caregivers’ further education should be taken into consideration concerning silent and therefore inconspicuous children

High seroprevalence of human herpes virus 8 (HHV-8) antibodies among vertically HIV-infected pediatric patients living in Germany

Background: Human herpes virus 8 (HHV-8), a gamma herpes virus, is the etiological agent for Kaposi sarcoma (KS). HIV-infected adults with advanced immunodeficiency are at risk. Prevalence data of HHV-8 infection in HIV-infected children living in non-endemic areas are limited. Serologic studies indicate low seroprevalence rates of 3–4% for healthy children living in United States and Germany [1]. Purpose of the study: The aim of the study was to determine the seroprevalence of HHV-8 antibodies among vertically HIV-infected pediatric patients in Germany and to evaluate their association with age, gender, ethnicity, and other demographic factors. Methods: In 2012, a multi-center cross-sectional study was conducted in four University Hospitals in Germany. Stored frozen serum specimens obtained from vertically HIV-infected children and adolescents were tested for antibodies against lytic and latent HHV-8 antigens. Data on patients' demographic characteristics and medical history were recorded. Results: A total of 214 HIV-infected children and adolescents (105 males, 109 females) were included. The median age was 10.2 years (range 1 months–22.6 years). A high proportion of these children (62%) was born in Western Europe, whereas 65% (139/214) of their mothers were born in countries outside Western Europe. The majoritiy (91%) of the children had been treated with highly active antiretroviral therapy and 55.2% (116/210) had a HIV-viral load<50 copies/mL. The median CD4 cell count was 1000/L (range 3–4400). The overall seroprevalence of HHV-8 antibodies was 23.8% (51/214). Seroprevalence rates did not show significant differences between age or gender. In the group of young children aged 1 month to 35 months, 19.4% (46/31) had HHV-8 antibodies, compared to 25% (25/100) in children aged 36 months to 11 years, and 24.1% (20/83) children 12 years and older. In the study group, seroprevalence rates were significantly lower in children who were born in Western Europe (p <0.01) compared to those born in Africa, Asia, or Eastern Europe. Clinical symptoms of HHV-8 infection were reported to be uncommon; only one child had a history of KS at 2 years of age. Conclusions: Vertically HIV-infected pediatric patients living in Germany showed a high HHV-8 seroprevalence of 23.8%. These rates were higher as expected in the normal pediatric population. The findings suggest that HHV-8 infection occurred already in the first years of life

Simplicial quantum dynamics

Present-day quantum field theory can be regularized by a decomposition into quantum simplices. This replaces the infinite-dimensional Hilbert space by a high-dimensional spinor space and singular canonical Lie groups by regular spin groups. It radically changes the uncertainty principle for small distances. Gaugeons, including the gravitational, are represented as bound fermion-pairs, and space-time curvature as a singular organized limit of quantum non-commutativity. Keywords: Quantum logic, quantum set theory, quantum gravity, quantum topology, simplicial quantization.Comment: 25 pages. 1 table. Conference of the International Association for Relativistic Dynamics, Taiwan, 201

“Till the muddle in my mind have cleared awa”: can we help shape policy using systems modelling?

This paper considers how some well-documented deficiencies of mental models make it difficult to create effective policies, and suggests that systems modelling can begin to address this issue. To illustrate the argument three short cases are presented. These relate to specific domains but demonstrate how systems modelling can illuminate different general phenomena: effects on labour costs (unintended consequences and feedback); fishery management (accumulation and non-linearity) and child protection (worldviews and sense-making). Six levers for increasing the use of systems modelling in the policy arena are then discussed. The paper closes by emphasising the opportunities for systems modellers in the Anthropocene Era

Association of peripartum management and high maternal blood loss at cesarean delivery for placenta accreta spectrum (PAS) : A multinational database study

Introduction Placenta accreta spectrum (PAS) carries a high burden of adverse maternal outcomes, especially significant blood loss, which can be life-threatening. Different management strategies have been proposed but the association of clinical risk factors and surgical management options during cesarean delivery with high blood loss is not clear. Material and methods In this international multicenter study, 338 women with PAS undergoing cesarean delivery were included. Fourteen European and one non-European center (USA) provided cases treated retrospectively between 2008 and 2014 and prospectively from 2014 to 2019. Peripartum blood loss was estimated visually and/or by weighing and measuring of volume. Participants were grouped based on blood loss above or below the 75th percentile (>3500 ml) and the 90th percentile (>5500 ml). Results Placenta percreta was found in 58% of cases. Median blood loss was 2000 ml (range: 150-20 000 ml). Unplanned hysterectomy was associated with an increased risk of blood loss >3500 ml when compared with planned hysterectomy (adjusted OR [aOR] 3.7 [1.5-9.4], p = 0.01). Focal resection was associated with blood loss comparable to that of planned hysterectomy (crude OR 0.7 [0.2-2.1], p = 0.49). Blood loss >3500 ml was less common in patients undergoing successful conservative management (placenta left in situ, aOR 0.1 [0.0-0.6], p = 0.02) but was more common in patients who required delayed hysterectomy (aOR 6.5 [1.7-24.4], p = 0.001). Arterial occlusion methods (uterine or iliac artery ligation, embolization or intravascular balloons), application of uterotonic medication or tranexamic acid showed no significant effect on blood loss >3500 ml. Patients delivered by surgeons without experience in PAS were more likely to experience blood loss >3500 ml (aOR 3.0 [1.4-6.4], p = 0.01). Conclusions In pregnant women with PAS, the likelihood of blood loss >3500 ml was reduced in planned vs unplanned cesarean delivery, and when the surgery was performed by a specialist experienced in the management of PAS. This reinforces the necessity of delivery by an expert team. Conservative management was also associated with less blood loss, but only if successful. Therefore, careful patient selection is of great importance. Our study showed no consistent benefit of other adjunct measures such as arterial occlusion techniques, uterotonics or tranexamic acid.Peer reviewe