Back Reaction of Hawking Radiation on Black Hole Geometry

We propose a model for the geometry of a dynamical spherical shell in which the metric is asymptotically Schwarzschild, but deviates from Ricci-flatness in a finite neighbourhood of the shell. Hence, the geometry corresponds to a `hairy' black hole, with the hair originating on the shell. The metric is regular for an infalling shell, but it bifurcates, leading to two disconnected Schwarzschild-like spacetime geometries. The shell is interpreted as either collapsing matter or as Hawking radiation, depending on whether or not the shell is infalling or outgoing. In this model, the Hawking radiation results from tunnelling between the two geometries. Using this model, the back reaction correction from Hawking radiation is calculated.Comment: Latex file, 15 pages, 4 figures enclosed, uses eps

Quantum Bubble Dynamics in 2+1 Dimensional Gravity I: Geometrodynamic Approach

The Dirac quantization of a 2+1 dimensional bubble is performed. The bubble consists of a string forming a boundary between two regions of space-time with distinct geometries. The ADM constraints are solved and the coupling to the string is introduced through the boundary conditions. The wave functional is obtained and the quantum uncertainty in the radius of the ring is calculated; this uncertainty becomes large at the Planck scale.Comment: 14 pages, Latex (\cite typos corrected

New Tetra-dentate Schiff Base Ligand N2O2 and Its Complexes with Some of Metal Ions: Preparation, Identification, and Studying Their Enzymatic and Biological Activities

في هذا البحث، تم تحضير ليجند جديد رباعي المخلب، بعنوان 5و3-بس (5- برومو-2-هايدروكسي بنزالدين امينو) حمض البنزويك (H3L) ، من خلال عملية التكثيف المحفز بالحامض. تم أيضًا تحضير أربعة معقدات فلزية جديدة مع أيونات Co (II) و Ni (II) و Cu (II) و Zn (II) ، من مفاعلة مولات مكافئة. تركيب الليكاند ومعقداته تم تأكيدها من خلال العديد من طرائق التوصيف، بما في ذلك الأشعة فوق البنفسجية المرئية، الأشعة تحت الحمراء، مطياف الكتلة، أطياف الرنين المغناطيسي النووي للبروتون والكاربون، الامتصاص الذري اللهبي، الحساسية المغناطيسية، وقياسات التوصيلية المولارية. أثبتت نتائج التحاليل الطيفية أن الليكاند المحضر يعمل كرابط رباعي المخلب ثنائي الشحنة السالبة ويرتبط مع ألايونات الفلزية بواسطة ذرتين من النيتروجين من مجموعتي الآزوميثين وبواسطة ذرتين من الأوكسجين من مجموعتي هيدروكسيل الفينول بعد فقدانهما لبروتونيهما. تم اقتراح بنية ثماني السطوح لجميع المعقدات المحضرة. تم فحص النشاطات (المضادة للبكتيريا) و (المضادة للفطريات) لهذه المركبات ضد بكتريا (E. coli) ، (S. aureus)، (Klebsiella spp.)، (S. epidermidis)، وفطر ال (Candida albicans). أشارت النتائج إلى أن هذه المركبات لها سلوك تثبيط معتدل. كما تمت دراسة نشاط المركبات المحضرة ضد إنزيم أستيل كولين استيراز (AChE) وتشير البيانات التي تم الحصول عليها إلى وجود سلوك تثبيط مختلف.In present work, new tetra-dentate ligand, titled 3,5-bis ((E)-5-Bromo-2-hydroxy benzylidene amino) benzoic acid (H3L), was prepared via an acid-catalyzed condensation process. New four metallic ligand complexes with Co(II), Ni(II), Cu(II) and Zn(II) ions, were also prepared from the refluxing of equivalent moles. Ligand's structure and its complexes; were confirmed by numerous characterization methods, including Ultraviolet-Visible, Infrared, Mass Spectrometer, 1H and 13C Nuclear Magnetic Resonance spectra, atomic absorption, magnetic moments, and molar conductivity measurements. The results of the spectroscopic analyzes proved that the prepared ligand acts as tetradentate bi-ionic ligand and it was bonded to the metal ions by two nitrogen atoms of the two azomethine groups and by two oxygen atoms of the two phenolic hydroxyl groups after losing their two protons. Octahedral structure proposed to all prepared complexes. The (anti-bacterial) and (anti-fungal) activities of these compound were screened against (E. coli, S. aureus, Klebsiella spp., S. epidermidis,), and (Candida albicans). The results indicated that these compounds have moderated inhibition behavior. The activity of the prepared compounds against Acetyl Choline Esterase Enzyme (AChE) have also studied and the obtained data indicated the presence of different inhibition behavior

Cancer Patterns in Karachi Division (1998-1999)

Objective: A minimal cancer incidence data for Karachi, the largest city of Pakistan, is being presented here, for the years 1998-1999. The city has a population of 9,802,134; males 5,261,712 (52.6%) and females 4,540,422 (47.4%); census 19981. Methodology: A predominantly mixed (passive and active) registration system has evolved in Karachi, the data sources being the hospitals within the Karachi Division. The reported/retrieved cancer data sets at the Karachi Cancer Registry are checked, coded, computerised in an analytical format and analysed. Results: The incident cancer cases registered in Karachi, during the 2-year period, 1st January 1998 to 31st December 1999 were analysed. The age-standardised incidence rate (ASR) of cancer, all sites was 132.4/100,000 for the males. Cancer of the lung 10.8%; ASR 17.3 was the most frequently recorded malignancy, followed by oral cavity 10.5%; ASR 13.2 and larynx 5.0%; ASR 7.4. The age-standardised incidence rate (ASR) of cancer, all sites was 133.0/100,000 in the females. Cancer of the breast, 32.0%; ASR 40.7 was the most frequently recorded malignancy, followed by oral cavity 8.1%; ASR 11.7 and gall bladder 3.6%; ASR 5.5. Conclusion: The present data has been calculated with an estimated 15-20% probable under ascertainment. Tobacco-associated cancers in Karachi were responsible for 38.3% of the tumours diagnosed amongst the males. Two principal cancers, breast and oral cavity were responsible for 40.1% of the cancers in females. A rare finding was the high incidence of gall bladder cancer in the females. At present it is difficult to determine whether this indicates a genuine high risk or a selection bias. A continuous process of cancer registration to study the trends in the incidence and an adequate cancer control program are possible and essential for Pakistan and can be based on the pattern being practiced in Karachi

Microclustering: When the Cluster Sizes Grow Sublinearly with the Size of the Data Set

Most generative models for clustering implicitly assume that the number of data points in each cluster grows linearly with the total number of data points. Finite mixture models, Dirichlet process mixture models, and Pitman--Yor process mixture models make this assumption, as do all other infinitely exchangeable clustering models. However, for some tasks, this assumption is undesirable. For example, when performing entity resolution, the size of each cluster is often unrelated to the size of the data set. Consequently, each cluster contains a negligible fraction of the total number of data points. Such tasks therefore require models that yield clusters whose sizes grow sublinearly with the size of the data set. We address this requirement by defining the \emph{microclustering property} and introducing a new model that exhibits this property. We compare this model to several commonly used clustering models by checking model fit using real and simulated data sets

Comparative methods for PET image segmentation in pharyngolaryngeal squamous cell carcinoma

Several methods have been proposed for the segmentation of ¹⁸F-FDG uptake in PET. In this study, we assessed the performance of four categories of ¹⁸F-FDG PET image segmentation techniques in pharyngolaryngeal squamous cell carcinoma using clinical studies where the surgical specimen served as the benchmark

Templated Control of Au nanospheres in Silica Nanowires

The formation of regularly-spaced metal nanostructures in selectively-placed insulating nanowires is an important step toward realization of a wide range of nano-scale electronic and opto-electronic devices. Here we report templated synthesis of Au nanospheres embedded in silica nanowires, with nanospheres consistently spaced with a period equal to three times their diameter. Under appropriate conditions, nanowires form exclusively on Si nanostructures because of enhanced local oxidation and reduced melting temperatures relative to templates with larger dimensions. We explain the spacing of the nanospheres with a general model based on a vapor-liquid-solid mechanism, in which an Au/Si alloy dendrite remains liquid in the nanotube until a critical Si concentration is achieved locally by silicon oxide-generated nanowire growth. Additional Si oxidation then locally reduces the surface energy of the Au-rich alloy by creating a new surface with minimum area inside of the nanotube. The isolated liquid domain subsequently evolves to become an Au nanosphere, and the process is repeated

Advanced Silicon Space Solar Cells Using Nanotechnology

Application of nanotechnology and advanced optical structures offer new possibilities for improved radiation tolerance in silicon solar cells. We describe the application of subwavelength diffractive structures to enhance optical absorption near the surface, and thereby improve the radiation tolerance

Identity work and the `unemployed' worker: age, disability and the lived experience of the older unemployed

This article seeks to explore how older individuals negotiate and manage their self-identity in relation to work while situated without paid employment. After reviewing the current positions of the older unemployed in the UK, noting the substantial overlap between age and disability, we turn our attention to conceptualizing the lived experiences of individuals through exploring `identity work' as a means of understanding a non-working work identity. Based upon focus group interviews, our empirical analysis focuses on key dimensions of participants' identity practice and how they sought to manage the following social processes: imposed identities; crafting working identities; and contesting unfavourable working identities.The conclusion contextualizes the findings against a backdrop of increasing individualistic discourses underpinning approaches to employability, closes with the policy implications arising from this study, and makes suggestions for future research agendas. </jats:p