scholarly journals New tensorial estimates in Besov spaces for time-dependent (2 + 1)-dimensional problems

2014 ◽  
Vol 11 (04) ◽  
pp. 821-908
Author(s):  
Arick Shao
Keyword(s):  
Primary Objective ◽  
Null Cone ◽  
Trace Theorems ◽  
Einstein Vacuum ◽  
Bondi Mass ◽  
Vacuum Spacetime ◽  
Bondi Energy ◽  
Funct Anal ◽  
Invent Math ◽  
Causal Geometry

In this paper, we consider various tensorial estimates in geometric Besov-type norms on a one-parameter foliation of surfaces with evolving geometries. Moreover, we wish to accomplish this with only very weak control on these geometries. Several of these estimates were proved in [S. Klainerman and I. Rodnianski, Causal geometry of Einstein-vacuum spacetimes with finite curvature flux, Invent. Math. 159 (2005) 437–529; S. Klainerman and I. Rodnianski, Sharp trace theorems for null hypersurfaces on Einstein metrics with finite curvature flux, Geom. Funct. Anal. 16(3) (2006) 164–229], but in very specific settings. A primary objective of this paper is to significantly simplify and make more robust the proofs of the estimates. Another goal is to generalize these estimates to more abstract settings. In [S. Alexakis and A. Shao, On the geometry of null cones to infinity under curvature flux bounds, Class. Quantum Grav. 31 (2014) 195012], we will apply these estimates in order to consider a variant of the problem in [S. Klainerman and I. Rodnianski, Causal geometry of Einstein-vacuum spacetimes with finite curvature flux, Invent. Math. 159 (2005) 437–529], that of a truncated null cone in an Einstein-vacuum spacetime extending to infinity. This analysis will then be used in [S. Alexakis and A. Shao, Bounds on the Bondi energy by a flux of curvature, to appear in J. Eur. Math. Soc.] to study and to control the Bondi mass and the angular momentum under minimal conditions.

scholarly journals A new look at the Bondi-Sachs energy-momentum

2021 ◽  
Author(s):  
Jörg Frauendiener ◽  
Chris Stevens
Keyword(s):  
Unit Sphere ◽  
Gauss Curvature ◽  
Null Infinity ◽  
Conformally Invariant ◽  
Lorentzian Metric ◽  
Correct Definition ◽  
Ghp Formalism ◽  
Bondi Mass ◽  
Definition Of ◽  
Bondi Energy

Abstract How does one compute the Bondi mass on an arbitrary cut of null infinity I when it is not presented in a Bondi system? What then is the correct definition of the mass aspect? How does one normalise an asymptotic translation computed on a cut which is not equipped with the unit-sphere metric? These are questions which need to be answered if one wants to calculate the Bondi-Sachs energy-momentum for a space-time which has been determined numerically. Under such conditions there is not much control over the presentation of I so that most of the available formulations of the Bondi energy-momentum simply do not apply. The purpose of this article is to provide the necessary background for a manifestly conformally invariant and gauge independent formulation of the Bondi energy-momentum. To this end we introduce a conformally invariant version of the GHP formalism to rephrase all the well-known formulae. This leads us to natural definitions for the space of asymptotic translations with its Lorentzian metric, for the Bondi news and the mass-aspect. A major role in these developments is played by the “co-curvature”, a naturally appearing quantity closely related to the Gauß curvature on a cut of I.

scholarly journals Causal geometry of Einstein-Vacuum spacetimes with finite curvature flux

2004 ◽  
Vol 159 (3) ◽  
pp. 437-529 ◽  
Author(s):  
Sergiu Klainerman ◽  
Igor Rodnianski
Keyword(s):  
Einstein Vacuum ◽  
Causal Geometry

scholarly journals Null infinity as an open Hamiltonian system

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Wolfgang Wieland
Keyword(s):  
Free Energy ◽  
Phase Space ◽  
Hamiltonian Formulation ◽  
Time Dependent ◽  
Null Infinity ◽  
Null Tetrad ◽  
Bondi Mass ◽  
New Interpretation ◽  
Background Fields ◽  
Bondi Energy

Abstract When a system emits gravitational radiation, the Bondi mass decreases. If the Bondi energy is Hamiltonian, it can thus only be a time-dependent Hamiltonian. In this paper, we show that the Bondi energy can be understood as a time-dependent Hamiltonian on the covariant phase space. Our derivation starts from the Hamiltonian formulation in domains with boundaries that are null. We introduce the most general boundary conditions on a generic such null boundary, and compute quasi-local charges for boosts, energy and angular momentum. Initially, these domains are at finite distance, such that there is a natural IR regulator. To remove the IR regulator, we introduce a double null foliation together with an adapted Newman-Penrose null tetrad. Both null directions are surface orthogonal. We study the falloff conditions for such specific null foliations and take the limit to null infinity. At null infinity, we recover the Bondi mass and the usual covariant phase space for the two radiative modes at the full non-perturbative level. Apart from technical results, the framework gives two important physical insights. First of all, it explains the physical significance of the corner term that is added in the Wald-Zoupas framework to render the quasi-conserved charges integrable. The term to be added is simply the derivative of the Hamiltonian with respect to the background fields that drive the time-dependence of the Hamiltonian. Secondly, we propose a new interpretation of the Bondi mass as the thermodynamical free energy of gravitational edge modes at future null infinity. The Bondi mass law is then simply the statement that the free energy always decreases on its way towards thermal equilibrium.

Electron Microscopic Characterization and Quantitation of Air Borne Particulate Matter with Special Emphasis on Asbestos

1972 ◽  
Vol 30 ◽  
pp. 356-357
Author(s):  
Peter K. Mueller ◽  
Glenn R. Smith ◽  
Leslie M Carpenter ◽  
Ronald L. Stanley
Keyword(s):  
Electron Microscopy ◽  
Light And Electron Microscopy ◽  
Ambient Air ◽  
Quality Standard ◽  
Primary Objective ◽  
Cellulose Ester ◽  
Main Concept ◽  
Electron Microscopic ◽  
Air Samples ◽  
Diffraction Patterns

At the present time the primary objective of the electron microscopy group of the Air and Industrial Hygiene Laboratory is the development of a method suitable for use in establishing an air quality standard for asbestos in ambient air and for use in its surveillance. The main concept and thrust of our approach for the development of this method is to obtain a true picture of fiber occurrence as a function of particle size and asbestos type utilizing light and electron microscopy.We have now available an electron micrographic atlas of all asbestos types including selected area diffraction patterns and examples of fibers isolated from air samples. Several alternative approaches for measuring asbestos in ambient air have been developed and/or evaluated. Our experiences in this regard will be described. The most promising method involves: 1) taking air samples on cellulose ester membrane filters with a nominal pore size of 0.8 micron; 2) ashing in a low temperature oxygen plasma for several hours;

Ultrasturcture of cerebellar cells and neuropil in rats subjected to partial global cerebral ischemia

1986 ◽  
Vol 44 ◽  
pp. 126-127
Author(s):  
R.V.W. Dimlich ◽  
M.H. Biros
Keyword(s):  
Purkinje Cells ◽  
Glial Cells ◽  
Granule Cells ◽  
Molecular Layer ◽  
Cell Types ◽  
Primary Objective ◽  
Global Cerebral Ischemia ◽  
Forebrain Ischemia ◽  
Substantial Evidence ◽  
Cerebellar Cells

Although a previous study in this laboratory determined that Purkinje cells of the rat cerebellum did not appear to be damaged following 30 min of forebrain ischemia followed by 30 min of reperfusion, it was suggested that an increase in rough endoplasmic reticulum (RER) and/or polysomes had occurred in these cells. The primary objective of the present study was to morphometrically determine whether or not this increase had occurred. In addition, since there is substantial evidence that glial cells may be affected by ischemia earlier than other cell types, glial cells also were examined. To ascertain possible effects on other cerebellar components, granule cells and neuropil near Purkinje cells as well as neuropil in the molecular layer also were evaluated in this investigation.

Community Outreach Partnership Center (COPC)

2003 ◽  
Vol 1 (2) ◽  
pp. 44-51
Author(s):  
Kristine Brown ◽  
James Sturges
Keyword(s):  
Health Promotion ◽  
Los Angeles ◽  
Mexican Immigrants ◽  
Community Outreach ◽  
Well Being ◽  
Integrated Services ◽  
The United States ◽  
Primary Objective ◽  
Health Promotion Program ◽  
Federal Grant

With the continued influx of Mexican immigrants to the United States, especially to Southern California, health concerns and needs have increased among this population over the last several years. California State Polytechnic University, Pomona (Cal Poly Pomona) obtained a federal grant that provided resources to establish the Community Outreach Partnership Center (COPC). COPC consists of comprehensive efforts to improve the overall well-being of the Angela Chanslor area within the City of Pomona in East Los Angeles. Focus areas of the project include 1) Education and Integrated Services, 2) Community Planning and Capacity Building for Neighborhood Revitalization and Safety, and 3) Job Development and Training. The focus of this paper is health promotion activities within Education and Integrated Services. The primary objective of this portion of the program was to provide residents with physical examinations and health screenings, health education, and medical and social service referrals. Topics discussed are the target community, general overview of COPC, Family Services Information and Referral Program (i.e. health promotion program within Education and Integrated Services), program impact and results, and suggestions for continued implementation and future efforts. / Con la influencia continua de inmigrantes Mexicanos a los Estados Unidos, especialmente al sur de California, ciertas necesidades con respecto a la salud han incrementado en esta poblacion en los ultimos anos. California State Polytechnic University, Pomona (Cal Poly Pomona). Obtuvo ayuda Federal para establecer El Community Outreach Partnership Center (COPC). El centro COPC consiste de esfuerzos conprensivos para mejorar el bienestar del area Angela Chanslor que esta ubicado en la Ciudad de Pomona en la parte Este de Los Angeles. Las partes enfocadas del proyecto incluyen, 1) Educacion y servicios Integrados, 2) Plan para la Comunidad y un Edificio de Capacitacion para la comunidad que dara revitalizacion y seguridad, 3) Y habrira trabajos y entrenamientos. El enfoque de este proyecto es de actividades en Promocion de Salud aliadas con educacion y Servicios Integrados. El objetivo principal de esta porcion del programa era de proveer a los residentes con examinaciones fisicas, educacion para la salud, y eran referidas a servicios medicos y sociales. Los topicos que son tratados son: La comunidad que sera ayudada, El enfoque general de COPC, informacion del programa para referir a servicios familiares, el impacto del programa y resultados, y sugerencias para implementar futuros esfuerzos.

The Student Room Survey: Changes in the Post Graduate Study for Cardiothoracic Surgery

2020 ◽  
Vol 23 (2) ◽  
pp. 71-74
Author(s):  
Md Faizus Sazzad ◽  
Mohammed Moniruzzaman ◽  
Dewan Iftakher Raza Choudhury ◽  
Arif Ahmed Mohiuddin ◽  
Raafi Rahman ◽  
...  
Keyword(s):  
Thoracic Surgery ◽  
Retrospective Analysis ◽  
Primary Objective ◽  
Graduate Study ◽  
Postgraduate Students ◽  
Depth Interview ◽  
Secondary Objective ◽  
Cardio Vascular ◽  
The University ◽  
Day By Day

Background: The number of postgraduate students in Cardiac surgical discipline is increasing day by day with incremental proportion are measurably suffering from the unnecessary lingering of the present course curriculum. The primary objective of this study was to find out the last 5 years’ of results of Masters in Surgery course under the University of Dhaka from a student room survey. A secondary objective was to find out positive changes that could show us the way of a step toward up-gradation. Methods: It is a retrospective analysis of all examination results of Cardio-vascular & Thoracic Surgery published since January 2008 to January 2013 from the University of Dhaka with in depth interview of 11 participants. Results: 85.24% students failed to pass part-I of Masters in Surgery for Cardio-vascular & Thoracic Surgery course while, 82.18% in part-II and 71.28% failed to pass the final part. Average 2.51 attempts needed to complete each part of the designed course resulted into lingering of course duration for 42.18 months/student. In the thoracic surgery discipline the number of students alarmingly reduced up to 0% in the recent academic sessions. Conclusions: Masters in Surgery is resulting in unnecessary prolongation of the course. We should step forward to meet the next generation challenge. Journal of Surgical Sciences (2019) Vol. 23(2): 71-74

Epidemiology of pheochromocytoma and paraganglioma: population-based cohort study

2021 ◽  
Vol 184 (1) ◽  
pp. 19-28
Author(s):  
Alexander A Leung ◽  
Janice L Pasieka ◽  
Martin D Hyrcza ◽  
Danièle Pacaud ◽  
Yuan Dong ◽  
...  
Keyword(s):  
Cohort Study ◽  
Administrative Data ◽  
Laboratory Data ◽  
Population Based ◽  
Incidence Rates ◽  
Primary Objective ◽  
Administrative Databases ◽  
Secondary Objective ◽  
True Frequency ◽  
Clinical Records

Objective Despite the significant morbidity and mortality associated with pheochromocytoma and paraganglioma, little is known about their epidemiology. The primary objective was to determine the incidence of pheochromocytoma and paraganglioma in an ethnically diverse population. A secondary objective was to develop and validate algorithms for case detection using laboratory and administrative data. Design Population-based cohort study in Alberta, Canada from 2012 to 2019. Methods Patients with pheochromocytoma or paraganglioma were identified using linked administrative databases and clinical records. Annual incidence rates per 100 000 people were calculated and stratified according to age and sex. Algorithms to identify pheochromocytoma and paraganglioma, based on laboratory and administrative data, were evaluated. Results A total of 239 patients with pheochromocytoma or paraganglioma (collectively with 251 tumors) were identified from a population of 5 196 368 people over a period of 7 years. The overall incidence of pheochromocytoma or paraganglioma was 0.66 cases per 100 000 people per year. The frequency of pheochromocytoma and paraganglioma increased with age and was highest in individuals aged 60–79 years (8.85 and 14.68 cases per 100 000 people per year for males and females, respectively). An algorithm based on laboratory data (metanephrine >two-fold or normetanephrine >three-fold higher than the upper limit of normal) closely approximated the true frequency of pheochromocytoma and paraganglioma with an estimated incidence of 0.54 cases per 100 000 people per year. Conslusion The incidence of pheochromocytoma and paraganglioma in an unselected population of western Canada was unexpectedly higher than rates reported from other areas of the world.

Urban energetics applications and Geomatic technologies in a Smart City perspective

2015 ◽  
Vol 6 (1) ◽  
pp. 19-29 ◽  
Author(s):  
G. Bitelli ◽  
P. Conte ◽  
T. Csoknyai ◽  
E. Mandanici
Keyword(s):  
Smart City ◽  
Laser Scanning ◽  
Near Infrared ◽  
Three Dimensional ◽  
Energy Sector ◽  
Primary Objective ◽  
Airborne Lidar ◽  
City Management ◽  
Urban Context ◽  
Research Areas

The management of an urban context in a Smart City perspective requires the development of innovative projects, with new applications in multidisciplinary research areas. They can be related to many aspects of city life and urban management: fuel consumption monitoring, energy efficiency issues, environment, social organization, traffic, urban transformations, etc. Geomatics, the modern discipline of gathering, storing, processing, and delivering digital spatially referenced information, can play a fundamental role in many of these areas, providing new efficient and productive methods for a precise mapping of different phenomena by traditional cartographic representation or by new methods of data visualization and manipulation (e.g. three-dimensional modelling, data fusion, etc.). The technologies involved are based on airborne or satellite remote sensing (in visible, near infrared, thermal bands), laser scanning, digital photogrammetry, satellite positioning and, first of all, appropriate sensor integration (online or offline). The aim of this work is to present and analyse some new opportunities offered by Geomatics technologies for a Smart City management, with a specific interest towards the energy sector related to buildings. Reducing consumption and CO2 emissions is a primary objective to be pursued for a sustainable development and, in this direction, an accurate knowledge of energy consumptions and waste for heating of single houses, blocks or districts is needed. A synoptic information regarding a city or a portion of a city can be acquired through sensors on board of airplanes or satellite platforms, operating in the thermal band. A problem to be investigated at the scale A problem to be investigated at the scale of the whole urban context is the Urban Heat Island (UHI), a phenomenon known and studied in the last decades. UHI is related not only to sensible heat released by anthropic activities, but also to land use variations and evapotranspiration reduction. The availability of thermal satellite sensors is fundamental to carry out multi-temporal studies in order to evaluate the dynamic behaviour of the UHI for a city. Working with a greater detail, districts or single buildings can be analysed by specifically designed airborne surveys. The activity has been recently carried out in the EnergyCity project, developed in the framework of the Central Europe programme established by UE. As demonstrated by the project, such data can be successfully integrated in a GIS storing all relevant data about buildings and energy supply, in order to create a powerful geospatial database for a Decision Support System assisting to reduce energy losses and CO2 emissions. Today, aerial thermal mapping could be furthermore integrated by terrestrial 3D surveys realized with Mobile Mapping Systems through multisensor platforms comprising thermal camera/s, laser scanning, GPS, inertial systems, etc. In this way the product can be a true 3D thermal model with good geometric properties, enlarging the possibilities in respect to conventional qualitative 2D images with simple colour palettes. Finally, some applications in the energy sector could benefit from the availability of a true 3D City Model, where the buildings are carefully described through three-dimensional elements. The processing of airborne LiDAR datasets for automated and semi-automated extraction of 3D buildings can provide such new generation of 3D city models.

Linking fish and crustacean taxonomic composition with seasonal contrasts in the soft-bottom intertidal zone

2020 ◽  
Author(s):  
M. A. Gondal ◽  
S. Iqbal ◽  
U. Atique ◽  
N. U. Saher ◽  
N. A. Qureshi ◽  
...  
Keyword(s):  
Species Richness ◽  
Water Temperature ◽  
Fish Species ◽  
Diversity Index ◽  
Taxonomic Composition ◽  
Primary Objective ◽  
Negative Effect ◽  
Fish Species Composition ◽  
One Year ◽  
Sw Monsoon

Abstract The primary objective of this study was to investigate the seasonal fish and crustacean variations concerning taxonomic composition, species richness, and diversity in sandy beach habitat. For this purpose, we investigated the Sonmiani Hor lagoon area during four distinct seasons, i.e., northeast (NE) monsoon, pre-monsoon, south-west (SW) monsoon, and post-monsoon for one year. During each haul, the net was pulled about 100m along the beach in 0.5m depth. The results showed a strong linear correlation between the diversity index and equitability in fishes (r = 0.978). The diversity index was strong negatively correlated with the abundance and biomass (r = -0.978, -0.972, respectively). The physical attributes like sea surface water temperature and salinity showed a strong negative effect on species assemblages (r = -0.981 and -0.943, respectively). The mean air and water temperature illustrated approximately 3°C difference during NE and pre-monsoon seasons. However, salinity, pH, and electrical conductivity did not show any significant seasonal variabilities. Under the ecological indices, the fish species displayed higher diversity (H’ = 3.19) during SW monsoon, whereas the lowest diversity was observed during pre-monsoon (H’ = 1.58). The equitability and species richness, however, remained more noticeable during SW monsoon (J’ = 0.81). The total number of individuals of fish and crustaceans reached 4799 with 3813 fish individuals and 986 individuals of crustaceans. A total of 27 families of fish while five crustacean families comprising of 30 genera and 38 fish species while ten genera and 17 species of crustaceans were recorded. Liza subviridis displayed the highest abundance among the sampled fish species. In conclusion, fish species constituted a significant part of the coastal fauna in the study area. The seasonal variations displayed distinct variations in fish species composition and diversity.

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