Quartz forming conditions in secant veins in granodiorites of the Andean intrusive complex of the Barchans Islands (Аrgentine Islands, West Antarctic)

It is established that the growth of quartz in veins in granodiorites of the Andean intrusive complex (the Barchans Islands, West Antarctic) happened in rock crystalbearing veins of steep falling, in which the temperature difference necessary for the dissolution of massive quartz and crystallization of its transparent variety in the shape of perfectly cut crystals in central parts of secant veins was reached. The discovered enrichment of the fluid medium of the quartz crystallization with СО₂, NaCl, and ÊCl indicates a carbonatehaloid composition of quartzforming fluids, which favoured the formation of jewelry and technologically perfect crystals, possibly having piezoelectric properties similar to crystals of quartz both from rockcrystalbearing veins of the Nearpolar Ural and those synthesized under laboratory conditions. As a conclusion, the connection of quartzforming fluids and the postmagmatic processes in a granodiorite intrusion is justified, and the view of investigated quartz veins as formations of posttectonic hydrothermal stage is confirmed and expanded.Bстановлено, що ріст жильного кварцу в гранодіоритах андського інтрузивного комплексу (острови Бархани, Західна Антарктида) здійснювався у кришталеносних жилах крутого падіння, в яких досягався перепад температури, необхідний для розчинення масивного кварцу і кристалізації його прозорого різновиду у вигляді прекрасно огранених кристалів у центральних частинах січних жил. Виявлена збагаченість флюїдного середовища кристалізації кварцу СО₂, NaCl і КCl вказує на карбонатно-галоїдний склад кварцутворювальних флюїдів, що сприяло формуванню ювелірно і технологічно досконалих кристалів, можливо, з п'єзоелектричними властивостями, подібно до кристалів кварцу, як кришталеносних жил Приполярного Уралу, так і синтезованих у лабораторних умовах. У підсумку обгрунтовано зв'язок кварцутворювальних флюїдів та постмагматичних процесів у гранодіоритовій інтрузії і підтверджено та розвинено точку зору на вивчені кварцові жили як на утворення посттектонічної гідротермальної стадії.Установлено, что рост жильного кварца в гранодиоритах андского интрузивного комплекса (острова Барханы, Западная Антарктида) осуществлялся в хрусталеносных жилах крутого падения, в которых достигался перепад температуры, необходимый для растворения массивного кварца и кристаллизации его прозрачной разновидности в виде прекрасно ограненных кристаллов в центральных частях секущих жил. Выявленнoe обогащениe флюидной среды кристаллизации кварца СО₂, NaCl и КCl указывает на карбонатно-галоидный состав кварцобразующих флюидов, что способствовало формированию ювелирно и технологически совершенных кристаллов, возможно, с пьезоэлектрическими свойствами, подобно кристаллам кварца, как хрусталеносных жил Приполярного Урала, так и синтезированных в лабораторных условиях. В итоге обоснована связь кварцобразующих флюидов и постмагматических процессов в гранодиоритовой интрузии и подтверждена и развита точка зрения на изученные кварцевые жилы как на образования посттектонической гидротермальной стадии

Dark Energy Content of Nonlinear Electromagnetism

Quasi-constant external fields in nonlinear electromagnetism generate a contribution to the energy-momentum tensor with the form of dark energy. To provide a thorough understanding of the origin and strength of the effects, we undertake a complete theoretical and numerical study of the energy-momentum tensor $T^{\mu\nu}$ for nonlinear electromagnetism. The Euler-Heisenberg nonlinearity due to quantum fluctuations of spinor and scalar matter fields is considered and contrasted with the properties of classical nonlinear Born-Infeld electromagnetism. We also address modifications of charged particle kinematics by strong background fields.Comment: 16 pages, 12 figures; reorganized introduction and sections 4 and 5, added further numerical results and discussion, updated references, fixed typo

Next-to-Next-to-Leading Order QCD Analysis of DIS Structure Functions

It is performed for the first time a next-to-next-to-leading order analysis of deep inelastic structure functions $F_2$ and $F_L$ using the recently determined first moments of the non-singlet anomalous dimensions and the corresponding Wilson coefficients. {}From a comparison to BCDMS data we found a slight decrease in the energy scale of perturbative QCD with respect to the next-to-leading order analysis, which brings the scale closer to the value predicted from a scheme invariant approach.Comment: Latex 12 pages, 2 figures available on request, preprint UCI-TR/94-

Prediction with expert advice by following the perturbed leader for general weights

When applying aggregating strategies to Prediction with Expert Advice, the learning rate must be adaptively tuned. The natural choice of � complexity/current loss renders the analysis of Weighted Majority derivatives quite complicated. In particular, for arbitrary weights there have been no results proven so far. The analysis of the alternative “Follow the Perturbed Leader ” (FPL) algorithm from [KV03] (based on Hannan’s algorithm) is easier. We derive loss bounds for adaptive learning rate and both finite expert classes with uniform weights and countable expert classes with arbitrary weights. For the former setup, our loss bounds match the best known results so far, while for the latter our results are new

Tracking a Small Set of Experts by Mixing Past Posteriors

In this paper, we examine on-line learning problems in which the target concept is allowed to change over time. In each trial a master algorithm receives predictions from a large set of n experts. Its goal is to predict almost as well as the best sequence of such experts chosen off-line by partitioning the training sequence into k + 1 sections and then choosing the best expert for each section. We build on methods developed by Herbster and Warmuth and consider an open problem posed by Freund where the experts in the best partition are from a small pool of size m. Since k >> m, the best expert shifts back and forth between the experts of the small pool. We propose algorithms that solve this open problem by mixing the past posteriors maintained by the master algorithm. We relate the number of bits needed for encoding the best partition to the loss bounds of the algorithms. Instead of paying log n for choosing the best expert in each section we first pay log bits in the bounds for identifying the pool of m experts and then log m bits per new section. In the bounds we also pay twice for encoding the boundaries of the sections

Introduction: racialization in theory and practice

Racialization has become one of the central concepts in the study of race and racism. It is widely used in both theoretical and empirical studies of racial situations. There has been a proliferation of texts that use this notion in quite diverse ways. It is used broadly to refer to ways of thinking about race as well as to institutional processes that give expression to forms of ethno-racial categorization. An important issue in the work of writers such as Robert Miles, for example, concerns the ways in which the construction of race is shaped historically and how the usage of that idea forms a basis for exclusionary practices. The concept therefore refers both to cultural or political processes or situations where race is invoked as an explanation, as well as to specific ideological practices in which race is deployed. It is evident, however, that despite the increasing popularity of the concept of racialization there has been relatively little critical analysis exploring its theoretical and empirical usages. It is with this underlying concern in mind that Racialization: Studies in Theory and Practice brings together leading international scholars in the field of race and ethnicity in order to explore both the utility of the concept and its limitations

Applications of Effective Probability Theory to Martin-Löf Randomness

The original publication is available at www.springerlink.comInternational audienceWe pursue the study of the framework of layerwise computability introduced in a preceding paper and give three applications. (i) We prove a general version of Birkhoff's ergodic theorem for random points, where the transformation and the observable are supposed to be effectively measurable instead of computable. This result significantly improves V'yugin and Nandakumar's ones. (ii) We provide a general framework for deriving sharper theorems for random points, sensitive to the speed of convergence. This offers a systematic approach to obtain results in the spirit of Davie's ones. (iii) Proving an effective version of Prokhorov theorem, we positively answer a question recently raised by Fouché: can random Brownian paths reach any random number? All this shows that layerwise computability is a powerful framework to study Martin-Löf randomness, with a wide range of applications

On the Existence and Convergence of Computable Universal Priors

Solomonoff unified Occam's razor and Epicurus' principle of multiple explanations to one elegant, formal, universal theory of inductive inference, which initiated the field of algorithmic information theory. His central result is that the posterior of his universal semimeasure M converges rapidly to the true sequence generating posterior μ, if the latter is computable. Hence, M is eligible as a universal predictor in case of unknown μ. We investigate the existence and convergence of computable universal (semi)measures for a hierarchy of computability classes: finitely computable, estimable, enumerable, and approximable. For instance, M is known..