Abstract

Due to the high number of inflectional variations of Arabic words, empirical results suggest that stemming is essential for Arabic information retrieval. However, current light stemming algorithms do not extract the correct stem of irregular (so-called broken) plurals, which constitute ~10% of Arabic texts and ~41% of plurals. Although light stemming in particular has led to improvements in information retrieval [5, 6], the effects of broken plurals on the performance of information retrieval systems has not been examined.We propose a light stemmer that incorporates a broken plural recognition component, and evaluate it within the context of information retrieval. Our results show that identifying broken plurals and reducing them to their correct stems does result in a significant improvement in the performance of information retrieval systems.

после добавления токсиканта, во всем диапазоне концентраций фенола. Таким образом, зависимости, получаемые в таких случаях, являются сложными и фиксируют большое число факторов. Исключение в эксперименте одних факторов и изучение влияния других достигается в проточных реакторах полного перемешивания, когда один из факторов поддерживается постоянным (например, режим рН-стата). Построенные в работе зависимости позволяют разрабатывать методики эксперимента, служащих целям токсикологии, например, при разработке системы предельно допустимых концентраций по влиянию токсиканта на скорость дыхания тест-объекта. Природные фенольные соединения расщепляются почвенными микроорганизмами, использующими их в качестве источника углерода [29]. Микроорганизмы природных биоценозов приспособлены к низким концентрациям этих соединений. Для удаления фенолов при их высокой концентрации (например, промышленные сточные воды, аварийные ситуации, залповые выбросы) необходимо выделять формы, которые активно окисляют фенол, и адаптировать их к высоким концентрациям фенола как субстрата [30]. В связи с этим возникает круг задач оптимального сочетания концентраций основного субстрата, окислителя и косубстратов (азот в форме дрожжевого экстракта), которые могут быть решены в соответствии с подходом, представленным выше в форме задачи о конкуренции молекул субстрата и окислителя за активные центры поверхности клеточной мембраны. Круг подобного типа задач может быть расширен в зависимости от вопросов, которые ставит практика микробиологии.

Increased leukocyte-endothelial cell adhesion is a key early event in the development of retinopathy and atherogenesis in diabetic patients. We recently reported that raised activity of glycosylating enzyme [beta]1,6 acetylglucosaminyltransferase (core 2 GlcNAc-T) is responsible for increased leukocyte-endothelial cell adhesion and capillary occlusion in retinopathy. Here, we demonstrate that elevated glucose increases the activity of core 2 GlcNAc-T and adhesion of human leukocytes to retinal capillary endothelial cells, in a dose-dependent manner, through diabetes-activated serine/threonine protein kinase C beta2 (PKCbeta2)-dependent phosphorylation. This regulatory mechanism, involving phosphorylation of core 2 GlcNAc-T, is also present in polymorphonuclear leukocytes isolated from type 1 and type 2 diabetic patients. Inhibition of PKCbeta2 activation with the specific inhibitor, LY379196, attenuated serine phosphorylation of core 2 GlcNAc-T and prevented increased leukocyte-endothelial cell adhesion. Raised activity of core 2 GlcNAc-T was associated with a threefold increase in O-linked glycosylation of P-selectin glycoprotein ligand-1 on the surface of leukocytes of diabetic patients compared with age-matched control subjects. PKCbeta2-dependent phosphorylation of core 2 GlcNAc-T may thus represent a novel regulatory mechanism for activation of this key enzyme in mediating increased leukocyte-endothelial cell adhesion and capillary occlusion in diabetic retinopathy.

The preparation and characterization of a cobalt substituted ETS-10 titanosilicate are described. X-ray diffraction shows that cobalt incorporation causes an increase in unit cell dimensions. UV–VIS, EPR, Raman and Co K-edge XANES spectra all show that Co2+ occupies tetrahedral sites, substituting for silicon. The 29Si NMR spectra do not permit identification of which silicon sites in ETS-10 are substituted, but the Co K-edge EXAFS shows clearly that Co2+ substitutes at Si(3Si,1Ti) sites.

A review is given of recent work in the authors' laboratory on the characterization of different forms of nanostructured titania. It is shown that nanocrystalline anatase powders and nanocrystalline anatase thin films differ significantly in their optical properties, due primarily to differences in sintering behaviour on drying. It is argued that the electronic properties of these systems are determined by surface phenomena rather than quantum size effects. The novel titanosilicate zeolite ETS-10 which contains one dimensional “quantum wires” of titania provides an alternative system for studying quantum size effects which has considerable potential for photocatalysis.

The development of Language Engineering and Information Retrieval applications for Arabic require availability of sizeable, reliable corpora of modern Arabic text. These are not routinely available. This paper describes how we constructed an 18.5 million word corpus from Al-Hayat newspaper text, with articles tagged as belonging to one of 7 domains. We outline the profile of the data and how we assessed its representativeness. The literature suggests that the statistical profile of Arabic text is significantly different from that of English in ways that might affect the applicability of standard techniques. The corpus allowed us to verify a collection of experiments which had, so far, only been conducted on small, manually collected datasets. We draw some comparisons with English and conclude that there is evidence that Arabic data is much sparser than English for the same data size.

The exact mechanism for capillary occlusion in diabetic retinopathy is still unclear, but increased leukocyte-endothelial cell adhesion has been implicated. We examined the possibility that posttranslational modification of surface O-glycans by increased activity of core 2 transferase (UDP-Glc:Galbeta1-3GalNAcalphaRbeta-N-acetylglucoaminyltr ansferase) is responsible for increased adhesion of leukocytes to vascular endothelium in diabetes. The mean activity of core 2 transferase in polymorphonuclear leukocytes isolated from type 1 and type 2 diabetic patients was higher compared with age-matched control subjects (1,638 +/- 91 [n = 42] vs. 249 +/- 35 pmol x h(-1) x mg(-1) protein [n = 24], P = 0.00013; 1,459 +/- 194 [n = 58] vs. 334 +/- 86 [n = 11], P = 0.01). As a group, diabetic patients with retinopathy had significantly higher mean activity of core 2 transferase compared with individuals with no retinopathy. There was a significant association between enzyme activity and severity of retinopathy in type 1 and type 2 diabetic patients. There was a strong correlation between activity of core 2 transferase and extent of leukocyte adhesion to cultured retinal capillary endothelial cells for diabetic patients but not for age-matched control subjects. Results from transfection experiments using human myelocytic cell line (U937) demonstrated a direct relationship between increased activity of core 2 transferase and increased binding to cultured endothelial cells. There was no relationship between activity of core 2 transferase and HbA(1c) (P = 0.8314), serum advanced glycation end product levels (P = 0.4159), age of the patient (P = 0.7896), and duration of diabetes (P = 0.3307). On the basis that branched O-glycans formed by the action of core 2 transferase participate in leukocyte adhesion, the present data suggest the involvement of this enzyme in increased leukocyte-endothelial cell adhesion and the pathogenesis of capillary occlusion in diabetic retinopathy. 

The effect of Aldrich humic acid (HA) on the mobility of {sup 137}Cs, {sup 85}Sr, {sup 152}Eu and {sup 239}Pu radionuclides was studied in Ca-montmorillonite suspensions. Verified 2-sites-2-species (2s2s) models correspond to an intensive interaction of all elements with humificated surface, what is in a remarkable contrast with the weak complexation of cesium and even strontium in solutions - the neutral ligand interaction constants {beta} (l/mol) are log {beta} < -9.9 and 7.56 {+-} 0.21 for Cs and Sr, respectively. The result for europium complexation in solution, log {beta} = 12.49 {+-} 0.18 is in a good agreement with literature data. For plutonium(IV) not only high proton competitive constant in solution was obtained, log {beta} = (-0.67 {+-} 0.32)+3pH, but also a strong chemisorption, which at high concentrations of humic acid (above 0.05 g/l) indicates the formation of bridge humate complexes of plutonium on the humificated surface. Logarithms of heterogeneous interaction constants ({beta}{sub 10}, l/g) of the elements with surface humic acid are 4.47 {+-} 0.23, 4.39 {+-} 0.08, and 6.40 {+-} 0.33 for Cs, Sr, and Eu(III), respectively, and the logarithm of the proton competitive constant ({beta}{sub 24}, l/g) for Pu(IV) -3.80 {+-}0.72. Distribution coefficients of humic acid and metal humates between 0.01 g HA/l solution and montmorillonite were derived as log K{sub d}(AH) = -1.04 {+-} 0.11, log K{sub d}(EuA) = 1.56 {+-} 0.11 and log K{sub d}(PuA) = 2.25 {+-} 0.04, while the values for Cs and Sr were obtained with very high uncertainty. Speciation of the elements on montmorillonite surface is illustrated as a function of equilibrium concentration of humic acid in solution and of pH.

Abstract

The high-performance size-exclusion chromatography (HPSEC) and radiochromatography (HPSERC) was used for the identification of radiocesium and radiostrontium interaction with humic acid. It was found that the behavior of humic acid on size-exclusion chromatography is sensitive to the salt concentration and pH of the mobile phase. At lower ionic strength and in acidic region of pH, the Aldrich humic acid exhibited three main fraction within the ranges > 760 kDa, 25-100 kDa and < 5 kDa. Radiocesium was found in the low-molecular fractions (< 1 kDa) of humic acids but radiostrontium interacts preferably with the fractions of humic acid of molecular weight within the range 2-5 kDa. (author) 27 refs.

: This paper describes 29Si, 27Al, 207Pb and 113Cd NMR studies of Pb- and Cd-exchanged LTA zeolites. The 113Cd NMR spectra identify for the first time two different coordination states for Cd2C in hydrated CdLTA, consistent with x-ray single crystal diffraction data for this zeolite. The effects of Cd2C exchange on the 29Si NMR spectra of LTA are also consistent with the structural data. Cd2C exchange perturbs the 27Al NMR spectrum of the zeolite, as does Pb2C exchange. Changes in the 29Si NMR spectra on Pb2C exchange are explained in terms of structural distortion of the framework. 207Pb NMR spectra of Pb2C exchanged LTA show a single broad signal indicating that Pb2C cations are rigidly located in the zeolite at relatively long Pb—O distances in the hydrated zeolites.