University of Haifa

About: University of Haifa is a education organization based out in Haifa, Israel. It is known for research contribution in the topics: Population & Poison control. The organization has 7558 authors who have published 27141 publications receiving 711629 citations. The organization is also known as: Haifa University & Universiṭat Ḥefah.

A multiprojection algorithm using Bregman projections in a product space

Abstract: Generalized distances give rise to generalized projections into convex sets. An important question is whether or not one can use within the same projection algorithm different types of such generalized projections. This question has practical consequences in the area of signal detection and image recovery in situations that can be formulated mathematically as a convex feasibility problem. Using an extension of Pierra's product space formalism, we show here that a multiprojection algorithm converges. Our algorithm is fully simultaneous, i.e., it uses in each iterative stepall sets of the convex feasibility problem. Different multiprojection algorithms can be derived from our algorithmic scheme by a judicious choice of the Bregman functions which govern the process. As a by-product of our investigation we also obtain blockiterative schemes for certain kinds of linearly constraned optimization problems.

Non-local Image Dehazing

Abstract: Haze limits visibility and reduces image contrast in outdoor images. The degradation is different for every pixel and depends on the distance of the scene point from the camera. This dependency is expressed in the transmission coefficients, that control the scene attenuation and amount of haze in every pixel. Previous methods solve the single image dehazing problem using various patch-based priors. We, on the other hand, propose an algorithm based on a new, non-local prior. The algorithm relies on the assumption that colors of a haze-free image are well approximated by a few hundred distinct colors, that form tight clusters in RGB space. Our key observation is that pixels in a given cluster are often non-local, i.e., they are spread over the entire image plane and are located at different distances from the camera. In the presence of haze these varying distances translate to different transmission coefficients. Therefore, each color cluster in the clear image becomes a line in RGB space, that we term a haze-line. Using these haze-lines, our algorithm recovers both the distance map and the haze-free image. The algorithm is linear in the size of the image, deterministic and requires no training. It performs well on a wide variety of images and is competitive with other stateof-the-art methods.

Microsatellites: genomic distribution, putative functions and mutational mechanisms: a review.

Abstract: Microsatellites, or tandem simple sequence repeats (SSR), are abundant across genomes and show high levels of polymorphism. SSR genetic and evolutionary mechanisms remain controversial. Here we attempt to summarize the available data related to SSR distribution in coding and noncoding regions of genomes and SSR functional importance. Numerous lines of evidence demonstrate that SSR genomic distribution is nonrandom. Random expansions or contractions appear to be selected against for at least part of SSR loci, presumably because of their effect on chromatin organization, regulation of gene activity, recombination, DNA replication, cell cycle, mismatch repair system, etc. This review also discusses the role of two putative mutational mechanisms, replication slippage and recombination, and their interaction in SSR variation.

Vocabulary size and use: lexical richness in L2 written production

Abstract: This article shows that if there is some control over genre then there will be a close correspondence between the vocabulary size of intermediate learners as reflected in their writing and a more direct measure of vocabulary size The study proposes a new measure of lexical richness, the Lexical Frequency Profile, which looks at the proportion of high frequency general service and academic words in learners' writing The study shows that it is possible to obtain a reliable measure of lexical richness which is stable across two pieces of writing by the same learners It also discriminates between learners of different proficiency levels For learners of English as a second language, the Lexical Frequency Profile is seen as being a measure of how vocabulary size is reflected in use In this study, it was found that the Lexical Frequency Profile correlates well with an independent measure of vocabulary size This reliable and valid measure of lexical richness in writing will be useful for determining the factors that affect judgements of quality in writing and will be useful for examining how vocabulary growth is related to vocabulary use. © 1995 Oxford University Press.

Microsatellites Within Genes: Structure, Function, and Evolution

Abstract: Recently, increasingly more microsatellites, or simple sequence repeats (SSRs) have been found and characterized within protein-coding genes and their untranslated regions (UTRs). These data provide useful information to study possible SSR functions. Here, we review SSR distributions within expressed sequence tags (ESTs) and genes including protein-coding, 3'-UTRs and 5'-UTRs, and introns; and discuss the consequences of SSR repeat-number changes in those regions of both prokaryotes and eukaryotes. Strong evidence shows that SSRs are nonrandomly distributed across protein-coding regions, UTRs, and introns. Substantial data indicates that SSR expansions and/or contractions in protein-coding regions can lead to a gain or loss of gene function via frameshift mutation or expanded toxic mRNA. SSR variations in 5'-UTRs could regulate gene expression by affecting transcription and translation. The SSR expansions in the 3'-UTRs cause transcription slippage and produce expanded mRNA, which can be accumulated as nuclear foci, and which can disrupt splicing and, possibly, disrupt other cellular function. Intronic SSRs can affect gene transcription, mRNA splicing, or export to cytoplasm. Triplet SSRs located in the UTRs or intron can also induce heterochromatin-mediated-like gene silencing. All these effects caused by SSR expansions or contractions within genes can eventually lead to phenotypic changes. SSRs within genes evolve through mutational processes similar to those for SSRs located in other genomic regions including replication slippage, point mutation, and recombination. These mutational processes generate DNA changes that should be connected by DNA mismatch repair (MMR) system. Mutation that has escaped from the MMR system correction would become new alleles at the SSR loci, and then regulate and/or change gene products, and eventually lead to phenotype changes. Therefore, SSRs within genes should be subjected to stronger selective pressure than other genomic regions because of their functional importance. These SSRs may provide a molecular basis for fast adaptation to environmental changes in both prokaryotes and eukaryotes.