String Interactions from Matrix String Theory

The Matrix String Theory, i.e. the two dimensional U(N) SYM with N=(8,8) supersymmetry, has classical BPS solutions that interpolate between an initial and a final string configuration via a bordered Riemann surface. The Matrix String Theory amplitudes around such a classical BPS background, in the strong Yang--Mills coupling, are therefore candidates to be interpreted in a stringy way as the transition amplitude between given initial and final string configurations. In this paper we calculate these amplitudes and show that the leading contribution is proportional to the factor g_s^{-\chi}, where \chi is the Euler characteristic of the interpolating Riemann surface and g_s is the string coupling. This is the factor one expects from perturbative string interaction theory.Comment: 15 pages, 2 eps figures, JHEP Latex class, misprints correcte

COVID-19 vaccination perceptions and intentions of maternity care consumers and providers in Australia.

IntroductionVaccination against COVID-19 is a key global public health strategy. Health professionals including midwives and doctors support and influence vaccination uptake by childbearing women. There is currently no evidence regarding the COVID-19 vaccination perceptions and intentions of those who receive or provide maternity care in Australia. The aim of this study was to address this gap in knowledge and explore the perceptions and intentions regarding COVID-19 vaccination from consumers and providers of maternity care in Australia.MethodsA national cross-sectional online study conducted in early 2021 in Australia, a country that has had a very low number of COVID-19 cases and deaths. Recruitment was undertaken through parenting and health professional social media sites and professional college distribution lists. A total of 853 completed responses, from women (n = 326), maternity care providers including doctors (n = 58), midwives (n = 391) and midwifery students (n = 78).FindingsPersonal intention to be vaccinated ranged from 48-89% with doctors most likely and women least likely. Doctors and midwifery students were significantly more likely to recommend the vaccine to pregnant women in their care than midwives (pConclusionThis is the first study to explore the perceptions and intentions regarding COVID-19 vaccination from the perspective of those who receive and provide maternity care in Australia. Findings have utility to support targeted public health messaging for these and other cohorts

Experiences of receiving and providing maternity care during the COVID-19 pandemic in Australia: A five-cohort cross-sectional comparison.

Introduction The global COVID-19 pandemic has radically changed the way health care is delivered in many countries around the world. Evidence on the experience of those receiving or providing maternity care is important to guide practice through this challenging time. Methods A cross-sectional study was conducted in Australia. Five key stakeholder cohorts were included to explore and compare the experiences of those receiving or providing care during the COVID-19 pandemic. Women, their partners, midwives, medical practitioners and midwifery students who had received or provided maternity care from March 2020 onwards in Australia were recruited via social media and invited to participate in an online survey released between 13th May and 24th June 2020; a total of 3701 completed responses were received. Findings While anxiety related to COVID-19 was high among all five cohorts, there were statistically significant differences between the responses from each cohort for most survey items. Women were more likely to indicate concern about their own and family’s health and safety in relation to COVID-19 whereas midwives, doctors and midwifery students were more likely to be concerned about occupational exposure to COVID-19 through working in a health setting than those receiving care through attending these environments. Midwifery students and women’s partners were more likely to respond that they felt isolated because of the changes to the way care was provided. Despite concerns about care received or provided not meeting expectations, most respondents were satisfied with the quality of care provided, although midwives and midwifery students were less likely to agree. Conclusion This paper provides a unique exploration and comparison of experiences of receiving and providing maternity care during the COVID-19 pandemic in Australia. Findings are useful to support further service changes and future service redesign. New evidence provided offers unique insight into key stakeholders’ experiences of the rapid changes to health services

Matrix Theory Interpretation of DLCQ String Worldsheets

We study the null compactification of type-IIA-string perturbation theory at finite temperature. We prove a theorem about Riemann surfaces establishing that the moduli spaces of infinite-momentum-frame superstring worldsheets are identical to those of branched-cover instantons in the matrix-string model conjectured to describe M-theory. This means that the identification of string degrees of freedom in the matrix model proposed by Dijkgraaf, Verlinde and Verlinde is correct and that its natural generalization produces the moduli space of Riemann surfaces at all orders in the genus expansion.Comment: 9 pages LaTeX. Changes in style, typos correcte

Fuzzy Spheres in pp Wave Matrix String Theory

The behaviour of matrix string theory in the background of a type IIA pp wave at small string coupling, g_s << 1, is determined by the combination M g_s where M is a dimensionless parameter proportional to the strength of the Ramond-Ramond background. For M g_s << 1, the matrix string theory is conventional; only the degrees of freedom in the Cartan subalgebra contribute, and the theory reduces to copies of the perturbative string. For M g_s >> 1, the theory admits degenerate vacua representing fundamental strings blown up into fuzzy spheres with nonzero lightcone momenta. We determine the spectrum of small fluctuations around these vacua. Around such a vacuum all N-squared degrees of freedom are excited with comparable energies. The spectrum of masses has a spacing which is independent of the radius of the fuzzy sphere, in agreement with expected behaviour of continuum giant gravitons. Furthermore, for fuzzy spheres characterized by reducible representations of SU(2) and vanishing Wilson lines, the boundary conditions on the field are characterized by a set of continuous angles which shows that generically the blown up strings do not ``close''.Comment: 45 pages REVTeX 4 and AMSLaTeX. 1 figure. v2: references added. Figure redrawn using LaTe

Scaffolding medical student knowledge and skills: team-based learning (TBL) and case-based learning (CBL)

Background Two established small-group learning paradigms in medical education include Case-based learning (CBL) and Team-based learning (TBL). Characteristics common to both pedagogies include the use of an authentic clinical case, active small-group learning, activation of existing knowledge and application of newly acquired knowledge. However, there are also variances between the two teaching methods, and a paucity of studies that consider how these approaches fit with curriculum design principles. In this paper we explore student and facilitator perceptions of the two teaching methods within a medical curriculum, using Experience based learning (ExBL) as a conceptual lens. Methods A total of 34/255 (13%) Year 2 medical students completed four CBLs during the 2019 Renal and Urology teaching block, concurrent to their usual curriculum activities, which included weekly TBLs. Questionnaires were distributed to all students (n = 34) and CBL facilitators (n = 13). In addition, all students were invited to attend focus groups. Data were analysed using descriptive statistics and thematic analysis. Results In total, 23/34 (71%) of students and 11/13 (85%) of facilitators completed the questionnaires. Twelve students (35%) participated in focus groups. Findings indicate their experience in CBL to be positive, with many favourable aspects that built on and complemented their TBL experience that provided an emphasis on the basic sciences. The learning environment was enriched by the CBL framework that allowed application of knowledge to solve clinical problems within the small groups with consistent facilitator guidance and feedback, their capacity to focus discussion, and associated efficiencies in learning. Conclusion While the TBL model was integral in developing students’ knowledge and understanding of basic science concepts, the CBL model was integral in developing students’ clinical reasoning skills. The strengths of CBL relative to TBL included the development of authentic clinical reasoning skills and guided facilitation of small group discussion. Our findings suggest that delivery of a medical curriculum may be enhanced through increased vertical integration, applying TBL in earlier phases of the medical program where the focus is on basic science principles, with CBL becoming more relevant as students move towards clinical immersion

The Color of Childhood: The Role of the Child/Human Binary in the Production of Anti-Black Racism

The binary between the figure of the child and the fully human being is invoked with regularity in analyses of race, yet its centrality to the conception of race has never been fully explored. For most commentators, the figure of the child operates as a metaphoric or rhetorical trope, a non-essential strategic tool in the perpetuation of White supremacy. As I show in the following, the child/human binary does not present a contingent or merely rhetorical construction but, rather, a central feature of racialization. Where Black peoples are situated as objects of violence it is often precisely because Blackness has been identified with childhood and childhood is historically identified as the archetypal site of naturalized violence and servitude. I proceed by offering a historical account of how Black peoples came to inherit the subordination and dehumanization of European childhood and how White youth were subsequently spared through their partial categorization as adults

Constraints on a Massive Dirac Neutrino Model

We examine constraints on a simple neutrino model in which there are three massless and three massive Dirac neutrinos and in which the left handed neutrinos are linear combinations of doublet and singlet neutrinos. We examine constraints from direct decays into heavy neutrinos, indirect effects on electroweak parameters, and flavor changing processes. We combine these constraints to examine the allowed mass range for the heavy neutrinos of each of the three generations.Comment: latex, 29 pages, 7 figures (not included), MIT-CTP-221

Letter to editor

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