Introduction: The Winding Road to Quantum Gravity Abhay Ashtekar Traveler, there are no paths; Paths are made by walking. ...

Logarithmic ambiguities in the choice of asymptotically Cartesian coordinates at spatial infinity are discussed. It is shown that they do not affect the definitions of energy-momentum and angular momentum at i°. Thus, from a physical viewpoint, the ambiguities are “pure gauge.” A prescription is given for fixed this gauge freedom for the class of space-times in which the leading-order part of the Weyl tensor satisfies a certain reflection symmetry. This class admits, in all (relatively boosted) rest frames at infinity, a (...) one-parameter family of asymptotically distinct 3-surfaces (generalized 3-planes) on which the trace of the extrinsic curvature falls off faster than usual. (shrink)

This book is for physicists, historians and philosophers of physics as well as students seeking an introduction to ongoing debates in relativistic and quantum physics. This title covers the recent debates on the emergence of relativity and quantum theory. It includes chapters with an introductory character, comprehensible to students and science teachers. It strengthens the bonds between the communities of scientists, historians, and philosophers.

This white paper outlines the plans of the History Philosophy Culture Working Group of the Next Generation Event Horizon Telescope Collaboration.

The right to health is enshrined in the constitution of the World Health Organization and numerous other international agreements. Yet today, an estimated 5.7 million people die each year from treatable infectious diseases, most of which are susceptible to existing antimicrobials if they were accessible. These deaths occur predominantly among populations living in poverty in low- and middle-income countries, and they greatly exceed the estimated 700,000 annual deaths worldwide currently attributed to antimicrobial resistance. Ensuring universal appropriate access to antimicrobials is (...) not only a critical part of realizing the right to health, it is necessary for mobilizing effective collective action against the development and spread of AMR. (shrink)

This paper discusses the utilization of pilots' physiological indications such as electroencephalographic signals, ocular parameters, and pilot performance-based quantitative metrics to estimate cognitive workload. The study aims to derive a non-invasive technique to estimate pilot's cognitive workload and study their correlation with standard physiological parameters. Initially, we conducted a set of user trials using well-established psychometric tests for evaluating the effectiveness of pupil and gaze-based ocular metrics for estimating cognitive workload at different levels of task difficulty and lighting conditions. Later, (...) we conducted user trials with the NALSim flight simulator using a business class Learjet aircraft model. We analyzed participants' ocular parameters, power levels of different EEG frequency bands, and flight parameters for estimating variations in cognitive workload. Results indicate that introduction of secondary task increases pilot's cognitive workload significantly. The beta frequency band of EEG, nearest neighborhood index specifying distribution of gaze fixation, L1 Norm of power spectral density of pupil diameter, and the duty cycle metric indicated variations in cognitive workload. (shrink)

Background: Maximum safe resection of infiltrative brain tumors in eloquent area is the primary objective in surgical neuro-oncology. This goal can be achieved with direct electrical stimulation to perform a functional mapping of the brain in patients awake intraoperatively. When awake surgery is not possible, we propose a pipeline procedure that combines advanced techniques aiming at performing a dissection that respects the anatomo-functional connectivity of the peritumoral region. This procedure can benefit from intraoperative monitoring with computerized tomography scan and brain (...) shift correction. Associated with this intraoperative monitoring, the additional value of preoperative investigation combining brain mapping by navigated transcranial magnetic stimulation with various neuroimaging modalities has not yet been reported.Case Report: A 42-year-old left-handed man had increased intracranial pressure, left hand muscle deficit, and dysarthria, related to an infiltrative tumor of the right frontal lobe with large mass effect and circumscribed contrast enhancement in motor and premotor cortical areas. Spectroscopy profile and intratumoral calcifications on CT-scan suggested an WHO grade III glioma, later confirmed by histology. The aforementioned surgical procedure was considered, since standard awake surgery was not appropriate for this patient. In preoperative time, nTMS mapping of motor function was performed, combined with magnetic resonance imaging -based tractography reconstruction of 6 neural tracts and resting-state functional MRI connectivity of sensorimotor and language networks. In intraoperative time, DES mapping was performed with motor evoked response recording and tumor resection was optimized using non-rigid image transformation of the preoperative data to iCT data. Image guidance was updated with correction for brain shift and tissue deformation using biomechanical modeling taking into account brain elastic properties. This correction was done at crucial surgical steps, i.e., when tumor bulged through the craniotomy after dura mater opening and when approaching the presumed eloquent brain regions. This procedure allowed a total resection of the tumor region with contrast enhancement as well as a complete regression of IICP and dysarthria. Hand paresis remained stable with no additional deficit. Postoperative nTMS mapping confirmed the good functional outcome.Conclusion: This case report and technical note highlights the value of preoperative functional evaluation by nTMS updated intraoperatively with correction of brain deformation by iCT. This multimodal approach may become the optimized technique of reference for patients with brain tumors in eloquent areas that are unsuitable for awake brain surgery. (shrink)

This is a substantially expanded version of a chapter-contribution to "The Springer Handbook of Spacetime", edited by Abhay Ashtekar and Vesselin Petkov, published by Springer Verlag in 2014. This contribution introduces the reader to the reformulation of Einstein's field equations of General Relativity as a constrained evolutionary system of Hamiltonian type and discusses some of its uses,together with some technical and conceptual aspects. Attempts were made to keep the presentation self contained and accessible to first-year graduate students. This (...) implies a certain degree of explicitness and occasional reviews of background material. (shrink)

Ashtekar has illustrated that two of the available roads to testing for time asymmetry can be generalized beyond the structure of quantum theory, to much more general formulations of mechanics. The purpose of this note is to show that a third road to T-violation, which I have called "Wigner's Principle," can be generalized in this way as well.

Complaints about the state of medical care are increasing in today s India; whether it s unnecessary investigations, botched operations or expensive, sometimes even harmful, medication. But while the unease is widespread, few outside the profession understand the extent to which the medical system is being distorted. Dr Arun Gadre and Dr Abhay Shukla have gathered evidence from seventy-eight practising doctors, in both the private and public medical sectors, to expose the ways in which vulnerable patients are exploited by (...) a system that promotes unscrupulous medical practices. At a time when the medical sector is growing rapidly, especially in urban areas, with the proliferation of multi-specialty hospitals and the adoption of ever-more sophisticated technologies, rational and ethical medical care is becoming increasingly rare. Honest doctors feel under siege, professional bodies meant to regulate the medical sector fail to do so, and the influence of the powerful pharmaceutical industry becomes even more pervasive. Drawing on the frank and courageous statements of these seventy-eight doctors dismayed at the state of their profession, Dissenting Diagnosis lays bare the corruption afflicting the medical sector in India and sets out solutions for a healthier future. (shrink)