An essential resource for learning about general relativity and much more, from four leading experts
Important and useful to every student of relativity, this book is a unique collection of some 475 ...problems--with solutions--in the fields of special and general relativity, gravitation, relativistic astrophysics, and cosmology. The problems are expressed in broad physical terms to enhance their pertinence to readers with diverse backgrounds.
In their solutions, the authors have attempted to convey a mode of approach to these kinds of problems, revealing procedures that can reduce the labor of calculations while avoiding the pitfall of too much or too powerful formalism. Although well suited for individual use, the volume may also be used with one of the modem textbooks in general relativity.
Beginning with a high schooler mesmerized by a stay on the Navajo and Hopi reservations and running through the founding of a major university department and the aftermath of a decision, a decade ...later, to forego permanent academic affiliations, Richard Price’s story is told with honesty, humor, and insight into the inner workings of academic politics from the 1960s to the present.
Inside/Outside relates his life as an anthropologist, historian, and Caribbeanist—from conducting predawn discussions with Maroon historians deep in the rainforest of Suriname to editing the world’s first book series on Atlantic history and culture; from weekly meetings with Claude Le´vi-Strauss in Paris to long-term collaboration with Sidney Mintz; from adventures at sea with Martiniquan fishermen to negotiating the ivory towers of Harvard, Yale, and Johns Hopkins; from explorations of the art of Romare Bearden to number crunching from the Trans-Atlantic Slave Trade Database. It is a tale of life experiences and often-unconventional life decisions, inside (and outside) the academic world. Readers look over Price’s shoulders—and those of his wife and research partner, Sally Price—as he developed the ideas for some of the twentieth- and twenty-first century’s most important books in the fields of history, anthropology, and Caribbean studies.
Abstract Objective To measure the localised irradiance and wavelength distributions from dental light curing units (LCUs) and establish a method to characterise their output. Methods Using a ...laboratory grade integrating sphere spectrometer system (Labsphere and Ocean Optics) the power, irradiance, and spectral emission were measured at the light tips of four LCUs: one plasma-arc (PAC) unit, one single peak blue light-emitting diode (blue-LED) unit, and two polywave LED (poly-LED) units. A beam profiler camera (Ophir Spiricon) was used to record the localised irradiance across the face of the light tips. The irradiance-calibrated beam profile images were then divided into 45 squares, each 1 mm2 . Each square contained the irradiance information received from approximately 3200 pixels. The mean irradiance value within each square was calculated, and the distribution of irradiance values among these 45 squares across the tip-ends was examined. Additionally, the spectral emission was recorded at various regions across each light tip using the integrating sphere with a 4 - mm diameter entrance aperture. Results The localised irradiance distribution was inhomogeneous in all four lights. The irradiance distribution was most uniformly distributed across the PAC tip. Both the irradiance and spectral emission from the poly-LED units were very unevenly distributed. Conclusions Reporting a single irradiance value or a single spectral range to describe the output from a curing light is both imprecise and inappropriate. Instead, an image of both the irradiance distribution and the distribution of the spectral emission across the light tip should be provided. Clinical significance The localised beam irradiance profile at the tip of dental LCUs is not uniform. Poly-LED units may deliver spectrally inhomogeneous irradiance profiles. Depending on the photoinitiator used in the RBC and the orientation of the LCU over the tooth, this non-uniformity may cause inadequate and inhomogeneous resin polymerisation, leading to poor physical properties, and premature failure of the restoration.
Modeling of gravitational waves from binary black hole inspiral has played an important role in the recent observations of such signals. The late-stage ringdown phase of the gravitational waveform is ...often associated with the null particle orbit (“light ring”) of the black hole spacetime. With simple models we show that this link between the light ring and spacetime ringing is based more on the history of specific models than on an actual constraining relationship. We also show, in particular, that a better understanding of the dissociation of the two may be relevant to the astrophysically interesting case of rotating (Kerr) black holes.
Human immunodeficiency virus type 1 (HIV-1) infection of the central nervous system (CNS) can lead to the development of HIV-1-associated dementia (HAD). We examined the virological characteristics ...of HIV-1 in the cerebrospinal fluid (CSF) of HAD subjects to explore the association between independent viral replication in the CNS and the development of overt dementia. We found that genetically compartmentalized CCR5-tropic (R5) T cell-tropic and macrophage-tropic HIV-1 populations were independently detected in the CSF of subjects diagnosed with HIV-1-associated dementia. Macrophage-tropic HIV-1 populations were genetically diverse, representing established CNS infections, while R5 T cell-tropic HIV-1 populations were clonally amplified and associated with pleocytosis. R5 T cell-tropic viruses required high levels of surface CD4 to enter cells, and their presence was correlated with rapid decay of virus in the CSF with therapy initiation (similar to virus in the blood that is replicating in activated T cells). Macrophage-tropic viruses could enter cells with low levels of CD4, and their presence was correlated with slow decay of virus in the CSF, demonstrating a separate long-lived cell as the source of the virus. These studies demonstrate two distinct virological states inferred from the CSF virus in subjects diagnosed with HAD. Finally, macrophage-tropic viruses were largely restricted to the CNS/CSF compartment and not the blood, and in one case we were able to identify the macrophage-tropic lineage as a minor variant nearly two years before its expansion in the CNS. These results suggest that HIV-1 variants in CSF can provide information about viral replication and evolution in the CNS, events that are likely to play an important role in HIV-associated neurocognitive disorders.
To test the hypothesis that coronavirus disease 2019 (COVID-19) has an impact on the CNS by measuring plasma biomarkers of CNS injury.
We recruited 47 patients with mild (n = 20), moderate (n = 9), ...or severe (n = 18) COVID-19 and measured 2 plasma biomarkers of CNS injury by single molecule array, neurofilament light chain protein (NfL; a marker of intra-axonal neuronal injury) and glial fibrillary acidic protein (GFAp; a marker of astrocytic activation/injury), in samples collected at presentation and again in a subset after a mean of 11.4 days. Cross-sectional results were compared with results from 33 age-matched controls derived from an independent cohort.
The patients with severe COVID-19 had higher plasma concentrations of GFAp (
= 0.001) and NfL (
< 0.001) than controls, while GFAp was also increased in patients with moderate disease (
= 0.03). In patients with severe disease, an early peak in plasma GFAp decreased on follow-up (
< 0.01), while NfL showed a sustained increase from first to last follow-up (
< 0.01), perhaps reflecting a sequence of early astrocytic response and more delayed axonal injury.
We show neurochemical evidence of neuronal injury and glial activation in patients with moderate and severe COVID-19. Further studies are needed to clarify the frequency and nature of COVID-19-related CNS damage and its relation to both clinically defined CNS events such as hypoxic and ischemic events and mechanisms more closely linked to systemic severe acute respiratory syndrome coronavirus 2 infection and consequent immune activation, as well as to evaluate the clinical utility of monitoring plasma NfL and GFAp in the management of this group of patients.
A substantial prevalence of mild neurocognitive disorders has been reported in HIV, also in patients treated with combination antiretroviral therapy (cART). This includes a new disorder that has been ...termed asymptomatic neurocognitive impairment (ANI).
ANI is identified by performance on formal neuropsychological testing that is at least 1 SD below the mean of normative scores in at least two cognitive domains out of at least five examined in patients without associated symptoms or evident functional impairment in daily living. While two tests are recommended to assess each domain, only one is required to fulfill this diagnostic criterion. Unfortunately, this definition necessitates that about 20% of the cognitively normal HIV-infected population is classified as suffering ANI. This liberal definition raises important ethical concerns and has as well diagnostic and therapeutic implications. Since neither its biological substrate, prognostic significance nor therapeutic implications are clearly established, we recommend that this diagnosis be modified or applied cautiously.
The diagnoses of less severe forms of neurocognitive disorders in HIV relies on the outcomes of neuropsychological testing, and a high proportion of HIV-infected patients with effective cART may be classified as neurocognitively abnormal using the current criteria. The definition of ANI is not stringent, and results in approximately 20% of the population being classified as abnormal. To us this seems an unacceptable false-positive rate.
The language of special responsibilities is ubiquitous in world politics, with policymakers and commentators alike speaking and acting as though particular states have, or ought to have, unique ...obligations in managing global problems. Surprisingly, scholars are yet to provide any in-depth analysis of this fascinating aspect of world politics. This path-breaking study examines the nature of special responsibilities, the complex politics that surround them and how they condition international social power. The argument is illustrated with detailed case-studies of nuclear proliferation, climate change and global finance. All three problems have been addressed by an allocation of special responsibilities, but while this has structured politics in these areas, it has also been the subject of ongoing contestation. With a focus on the United States, this book argues that power must be understood as a social phenomenon and that American power varies significantly across security, economic and environmental domains.
Solid tumor treatment relies heavily upon chemotherapies, radiation, surgical resection, and/or immunotherapies. Although many alternative non-invasive solid tumor therapies have been proposed ...through the years and continue to be tested in various contexts, tumor cell eradication remains a daunting task for the current cancer armamentarium. Indeed, solid tumors exhibit physically and biochemically heterogenous microenvironments, allowing them to easily acquire resistance mechanisms. Progress in sonodynamic therapy (SDT), a treatment modality capable of controlling tumor growth while limiting off-target effects and toxicities, has accelerated in recent years. SDT combines “sonosensitizing” agents with the non-invasive application of focused acoustic energy i.e. focused ultrasound (FUS) to drive highly localized formation of tumor cell-killing reactive oxygen species (ROS). Sonosensitizers selectively accumulate in tumor cells, after which FUS radiation eliminates the tumor by forcing the tumor cells to undergo cell death. In this article, we comprehensively review recent studies wherein SDT has been applied to treat primary and metastatic tumors. We discuss sonosensitizers, combination therapies with SDT, developments in defining the mechanism of SDT-induced cell cytotoxicity, and the promise SDT offers as a modulator of anti-tumor immunity.
•Sonodynamic therapy (SDT) elicits tumor cell death through ROS production.•ROS generation is the result of the activation of sonosensitizers with ultrasound.•SDT modulates the tumor immune landscape.•Solid tumor treatments may combine SDT with chemo- and/or immunotherapies.•Progress to date in sonodynamic therapy is comprehensively reviewed.
Highlights • Each light curing unit has an individual irradiance distribution. • The surface hardness map corresponds directly to the irradiance distribution. • Longer exposure times lift the ...hardness pattern to higher values. • Longer exposure times do not lead to more homogeneity of the hardness distribution.
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