How red is a quantum black hole?

Radiating black holes pose a number of puzzles for semiclassical and quantum gravity. These include the transplanckian problem -- the nearly infinite energies of Hawking particles created near the horizon, and the final state of evaporation. A definitive resolution of these questions likely requires robust inputs from quantum gravity. We argue that one such input is a quantum bound on curvature. We show how this leads to an upper limit on the redshift of a Hawking emitted particle, to a maximum temperature for a black hole, and to the prediction of a Planck scale remnant.Comment: 3 pages, essay for the Gravity Research Foundatio

Pengaruh Pajanan Gelombang Telepon Seluler Terhadap Struktur Histologi Limpa Pada Mencit (Mus Musculus)

Radiasi elektromagnetik yang dihasilkan oleh gelombang telepon seluler dapat berpotensi menimbulkan gangguan kesehatan apabila seseorang terpajan melampaui ambang batas pemajanan. Penelitian ini bertujuan untuk mengetahui pengaruh pajanan radiasi gelombang telepon seluler terhadap sistem imunitas mencit (Mus musculus) dengan mengukur diameter pulpa putih limpa. Jenis penelitian adalah eksperimental menggunakan mencit (Mus musculus) jantan, berat badan 30 gram, selama 30 hari perlakuan. Perlakuan dibagi menjadi empat kelompok, yaitu kelompok kontrol, kelompok perlakuan dengan telepon seluler GSM jenis monophonic, kelompok perlakuan dengan telepon seluler GSM jenis polyphonic dan kelompok perlakuan dengan telepon seluler CDMA, masing-masing terdiri dari lima ekor mencit. Dengan Lama pemajanan 120 menit selama 30 hari. Pada hari ke-31dilakukan dekapitasi pada mencit, organ limpa diambil, dibuat preparat histologi dengan teknik pewarnaan HE dan diukur diameter pulpa putih limpa. Hasil penelitian menunjukkan bahwa diameter pulpa putih limpa pada mencit yang diberi perlakuan tampak lebih besar bila dibandingkan dengan mencit kontrol secara bermakna(p<0,05). Hal ini menunjukkan bahwa antara kelompok perlakuan radiasi gelombang telepon seluler dan kelompok kontrol berbeda secara bermakna, khususnya pada kelompok CDMA. Disimpulkan bahwa radiasi elektromagnetik mempunyai efek mengaktivasi sistem imun di daerah perifer

Flat slice Hamiltonian formalism for dynamical black holes

We give a Hamiltonian analysis of the asymptotically flat spherically symmetric system of gravity coupled to a scalar field. This 1+1 dimensional field theory may be viewed as the "standard model" for studying black hole physics. Our analysis is adapted to the flat slice Painleve-Gullstrand coordinates. We give a Hamiltonian action principle for this system, which yields an asymptotic mass formula. We then perform a time gauge fixing that gives a Hamiltonian as the integral of a local density. The Hamiltonian takes a relatively simple form compared to earlier work in Schwarzschild gauge, and therefore provides a setting amenable to full quantisation.Comment: 11 pages, refererences added, discussions clarified, version to appear in PR

Semiclassical states for quantum cosmology

In a metric variable based Hamiltonian quantization, we give a prescription for constructing semiclassical matter-geometry states for homogeneous and isotropic cosmological models. These "collective" states arise as infinite linear combinations of fundamental excitations in an unconventional "polymer" quantization. They satisfy a number of properties characteristic of semiclassicality, such as peaking on classical phase space configurations. We describe how these states can be used to determine quantum corrections to the classical evolution equations, and to compute the initial state of the universe by a backward time evolution.Comment: 13 page

Constants of motion for vacuum general relativity

The 3+1 Hamiltonian Einstein equations, reduced by imposing two commuting spacelike Killing vector fields, may be written as the equations of the $SL(2,R)$ principal chiral model with certain `source' terms. Using this formulation, we give a procedure for generating an infinite number of non-local constants of motion for this sector of the Einstein equations. The constants of motion arise as explicit functionals on the phase space of Einstein gravity, and are labelled by sl(2,R) indices.Comment: 10 pages, latex, version to appear in Phys. Rev. D

Dynamic Updating of Working Memory Resources for Visual Objects

Recent neurophysiological and imaging studies have investigated how neural representations underlying working memory (WM) are dynamically updated for objects presented sequentially. Although such studies implicate information encoded in oscillatory activity across distributed brain networks, interpretation of findings depends crucially on the underlying conceptual model of how memory resources are distributed.Here, we quantify the fidelity of human memory for sequences of colored stimuli of different orientation. The precision with which each orientation was recalled declined with increases in total memory load, but also depended on when in the sequence it appeared. When one item was prioritized, its recall was enhanced, but with corresponding decrements in precision for other objects. Comparison with the same number of items presented simultaneously revealed an additional performance cost for sequential display that could not be explained by temporal decay. Memory precision was lower for sequential compared with simultaneous presentation, even when each item in the sequence was presented at a different location.Importantly, stochastic modeling established this cost for sequential display was due to misbinding object features (color and orientation). These results support the view that WM resources can be dynamically and flexibly updated as new items have to be stored, but redistribution of resources with the addition of new items is associated with misbinding object features, providing important constraints and a framework for interpreting neural data

New Solution for ICT/ELV Infrastructure Project Reporting Using Datalink Technique System

In infrastructure project, a failure on reliable project reporting will lead to Variation Order (VO) and Project Delay issues. It is now a normal phenomenon, which leads to many negative effects such as lawsuits, claims, loss of productivity and revenue, which may also lead to contract termination. Hence, the research aims to develop a new solution system program, called Datalink Technique System (DTS) to solve the problems that occur in an infrastructure project. The objective is to eliminate the loss and reduce the project cost. However, it is not limited to that as in future it can also be applied to others. DTS introduces the new advanced technologies system solution and reliable, yet it is still consistent with the current approach to manage the project. The program produces data/information correctly and precisely

A Clinicopathological Study of Urinary Bladder Neoplasms in Patients at Three Centers in Khartoum, Sudan

OBJECTIVES: To present the histopathological pattern of urinary bladder neoplasms using the WHO/ISUP classification system and relate it to the outcome.METHODS: This study was conducted in the period from January 2004 through December 2005 at three centres in Khartoum, Sudan. One hundred and six patients with urinary bladder neoplasms were included in the study.RESULTS: The commonest affected age group was 60-80 years with male to female ratio 4.6:1. Urothelial neoplasms were found in 72 (67.9%), Squamous cell carcinoma (SCC) in 26 (24.5%), urothelial neoplasms with Squamous differentiation in 3 (2.8%), and other types in 5 (4.7%) of thepatients. There were 43.4% of the urothelial neoplasms graded as papillary carcinoma of high grade, 52.6% papillary carcinoma of low grade, 1.3% papillary neoplasm of low malignant potential, 1.3% papilloma, and 1.3% was graded as flat neoplasm. Of the SCCs, twelve (42.9%)were poorly differentiated SCCs, nine (32.1%) moderately differentiated, and seven (25%) cases were well differentiated SCCs. Follow-up information was available in 32 patients. At last followup, fifteen (46.9%) patients were dead of the disease, twelve (35.5%) were alive with no evidence of disease, four (12.5%) were alive with disease, and one (3.1%) was alive and terminally ill. CONCLUSION: Histological grade (P: 0.006), and muscle invasion (P: 0.002) were significantly associated with survival. A subset of the cases could not be assessed for muscle invasion due toinadequate sampling; we thus recommend proper trans-urethral bladder biopsy (TUBP) sampling.Key words: Urinary bladder neoplasm; Papillary carcinoma; Squamous cell carcinoma; WHO/ISUP classification system