Existence of families of spacetimes with a Newtonian limit

J\"urgen Ehlers developed \emph{frame theory} to better understand the relationship between general relativity and Newtonian gravity. Frame theory contains a parameter $\lambda$, which can be thought of as $1/c^2$, where $c$ is the speed of light. By construction, frame theory is equivalent to general relativity for $\lambda >0$, and reduces to Newtonian gravity for $\lambda =0$. Moreover, by setting \ep=\sqrt{\lambda}, frame theory provides a framework to study the Newtonian limit \ep \searrow 0 (i.e. $c\to \infty$). A number of ideas relating to frame theory that were introduced by J\"urgen have subsequently found important applications to the rigorous study of both the Newtonian limit and post-Newtonian expansions. In this article, we review frame theory and discuss, in a non-technical fashion, some of the rigorous results on the Newtonian limit and post-Newtonian expansions that have followed from J\"urgen's work

Liver transplantation for type IV glycogen storage disease

TYPE IV glycogen storage disease is a rare autosomal recessive disorder (also called Andersen's disease1 or amylopectinosis) in which the activity of branching enzyme alpha-1, 4-glucan: alpha-1, 4-glucan 6-glucosyltransferase is deficient in the liver as well as in cultured skin fibroblasts and other tissues.2,3 This branching enzyme is responsible for creating branch points in the normal glycogen molecule. In the relative or absolute absence of this enzyme, an insoluble and irritating form of glycogen, an amylopectin-like polysaccharide that resembles plant starch, accumulates in the cells. The amylopectin-like form is less soluble than normal glycogen, with longer outer and inner chains. © 1991, Massachusetts Medical Society. All rights reserved

Standardized Laparoscopic Intracorporeal Right Colectomy for Cancer: Short-Term Outcome in 111 Unselected Patients

Purpose This study was designed to evaluate the impact of a standardized laparoscopic intracorporeal right colectomy on the short-term outcome of patients with neoplasia. Methods Consecutive patients with histologically proven right colon neoplasia underwent a standardized laparoscopic intracorporeal right colectomy with medial to lateral approach encompassing ten sequential steps: 1) ligation of ileocolic vessels, 2) identification of right ureter, 3) dissection along superior mesenteric vein, 4) division of omentum, 5) division of right branch of middle colic vessels, 6) transection of transverse colon, 7) mobilization of right colon, 8) transection of terminal ileum, 9) ileocolic anastomosis, 10) delivery of specimen. Values were medians (ranges). Results From July 2002 to June 2005, 111 laparoscopic intracorporeal right colectomies were attempted with a 5.4 percent conversion rate. There were 57 women and 54 men, aged 64.9 (range, 40–85) years, with body mass index of 33 (range, 20–43), American Society of Anesthesiology score of 2 (range, 2–4), 36.9 percent comorbidities, and 37.8 percent previous abdominal surgery. The indication for surgery was cancer in 109 patients. Operative time was 120 (range, 80–185) minutes. Estimated blood loss was 69 (range, 50–600) ml. Overall length of skin incisions was 66 (range, 60–66) mm; 29 (range, 2–41) lymph nodes were harvested. Length of stay was four (range, 2–30) days. Complication rate was 4.5 percent. Conclusions A standardized laparoscopic intracorporeal right colectomy resulted in a favorable short-term outcome in unselected patients with neoplasia of the right colon

Vanishing Viscosity Limits and Boundary Layers for Circularly Symmetric 2D Flows

We continue the work of Lopes Filho, Mazzucato and Nussenzveig Lopes [LMN], on the vanishing viscosity limit of circularly symmetric viscous flow in a disk with rotating boundary, shown there to converge to the inviscid limit in $L^2$-norm as long as the prescribed angular velocity $\alpha(t)$ of the boundary has bounded total variation. Here we establish convergence in stronger $L^2$ and $L^p$-Sobolev spaces, allow for more singular angular velocities $\alpha$, and address the issue of analyzing the behavior of the boundary layer. This includes an analysis of concentration of vorticity in the vanishing viscosity limit. We also consider such flows on an annulus, whose two boundary components rotate independently. [LMN] Lopes Filho, M. C., Mazzucato, A. L. and Nussenzveig Lopes, H. J., Vanishing viscosity limit for incompressible flow inside a rotating circle, preprint 2006

A Simple Separable Exact C*-Algebra not Anti-isomorphic to Itself

We give an example of an exact, stably finite, simple. separable C*-algebra D which is not isomorphic to its opposite algebra. Moreover, D has the following additional properties. It is stably finite, approximately divisible, has real rank zero and stable rank one, has a unique tracial state, and the order on projections over D is determined by traces. It also absorbs the Jiang-Su algebra Z, and in fact absorbs the 3^{\infty} UHF algebra. We can also explicitly compute the K-theory of D, namely K_0 (D) = Z[1/3] with the standard order, and K_1 (D) = 0, as well as the Cuntz semigroup of D.Comment: 16 pages; AMSLaTeX. The material on other possible K-groups for such an algebra has been moved to a separate paper (1309.4142 [math.OA]

Mental health, loneliness and stress of Asian, Black and White UK university students before and during the COVID-19 pandemic

The COVID-19 pandemic has negatively impacted the mental health of UK university students. However, the knowledge on the impact on students from different ethnic groups is limited. We investigated mental health, loneliness, and perceived stress in 656 university students with an Asian, Black and White ethnic background across three cohorts, before (2019-2020), during (2020-2021), and at the end of the pandemic (2021-2022). Students at City, University of London completed an online study, including the Counseling Center Assessment of Psychological Symptoms, the UCLA loneliness scale, the perceived stress scale, and questions about COVID-19. Substance-use concerns were highest before the pandemic compared to during the pandemic. Academic distress and loneliness were higher during the pandemic than before. COVID-19 related anxiety was significantly related with poor mental health across groups. Students with an Asian or Black ethnic background had slightly lower reported mental health difficulties than White students, which appeared to be partly driven by lower substance-use concerns. However, students from an Asian or Black ethnic background reported being more financially impacted by the pandemic and reported more loneliness than White students. The findings reflect pandemic-related changes in student life, characterized by reduced socializing with fellow students and suggest that overall students adapted well to these changes in terms of their mental health

Derivation of the Zakharov equations

This paper continues the study of the validity of the Zakharov model describing Langmuir turbulence. We give an existence theorem for a class of singular quasilinear equations. This theorem is valid for well-prepared initial data. We apply this result to the Euler-Maxwell equations describing laser-plasma interactions, to obtain, in a high-frequency limit, an asymptotic estimate that describes solutions of the Euler-Maxwell equations in terms of WKB approximate solutions which leading terms are solutions of the Zakharov equations. Because of transparency properties of the Euler-Maxwell equations, this study is led in a supercritical (highly nonlinear) regime. In such a regime, resonances between plasma waves, electromagnetric waves and acoustic waves could create instabilities in small time. The key of this work is the control of these resonances. The proof involves the techniques of geometric optics of Joly, M\'etivier and Rauch, recent results of Lannes on norms of pseudodifferential operators, and a semiclassical, paradifferential calculus

Using Administrative Data to Explore the Effect of Survey Nonresponse in the UK Employment Retention and Advancement Demonstration

Background: Even a well-designed randomized control trial (RCT) study can produce ambiguous results. This paper highlights a case in which full-sample results from a large-scale RCT in the United Kingdom (UK) differ from results for a sub-sample of survey respondents. Objectives: Our objective is to ascertain the source of the discrepancy in inferences across data sources and, in doing so, to highlight important threats to the reliability of the causal conclusions derived from even the strongest research designs. Research design: The study analyzes administrative data to shed light on the source of the differences between the estimates. We explore the extent to which heterogeneous treatment impacts and survey non-response might explain these differences. We suggest checks which assess the external validity of survey measured impacts, which in turn provides an opportunity to test the effectiveness of different weighting schemes to remove bias. The Subjects included 6,787 individuals who participated in a large-scale social policy experiment. Results: Our results were not definitive but suggest non-response bias is the main source of the inconsistent findings. Conclusions. The results caution against overconfidence in drawing conclusions from RCTs and highlight the need for great care to be taken in data collection and analysis. Particularly, given the modest size of impacts expected in most RCTs, small discrepancies in data sources can alter the results. Survey data remain important as a source of information on outcomes not recorded in administrative data. However, linking survey and administrative data is strongly recommended whenever possible

The geometry of a vorticity model equation

We provide rigorous evidence of the fact that the modified Constantin-Lax-Majda equation modeling vortex and quasi-geostrophic dynamics describes the geodesic flow on the subgroup of orientation-preserving diffeomorphisms fixing one point, with respect to right-invariant metric induced by the homogeneous Sobolev norm $H^{1/2}$ and show the local existence of the geodesics in the extended group of diffeomorphisms of Sobolev class $H^{k}$ with $k\ge 2$.Comment: 24 page