Abstract There are several stemming approaches that are applied to Arabic language, yet no a complete stemmer for this language is available. The existing stem-based stemmers for stemming Arabic text have a poor performance in terms of accuracy and error rates. In order to improve the accuracy rates of stemming, a hybrid method is proposed for stemming Arabic text to produce stems (not roots). The improvement of the accuracy of stemming will lead by necessity to the improvement of many applications very greatly, including: information retrieval, document classification, machine translation, text analysis and text compression. The proposed method integrates three different stemming techniques, including: morphological analysis, affix-removal and dictionaries. 

Diabetic retinopathy is one of the most common diabetic complications, and is a major cause of new blindness in the working-age population of developed countries. Progression of vascular abnormalities, including the selective loss of pericytes, formation of acellular capillaries, thickening of the basement membrane, and increased vascular permeability characterizes early nonproliferative diabetic retinopathy (NPDR). Capillary occlusion, as shown on fluorescein angiograms, is also one of the earliest clinically recognizable lesion of NPDR. In response to capillary non-perfusion, there is dilation of neighbouring capillaries, leading to early blood-retinal barrier breakdown, capillary non-perfusion, and endothelial cell injury and death. The resulting ischemia leads to increased production of growth factors, and the development of proliferative diabetic retinopathy (PDR), which is characterized by growth of new vessels and potential severe and irreversible visual loss. The exact pathogenic mechanism by which capillary non-perfusion occurs is still unclear but growing evidence now suggests that increased leukocyte-endothelial cell adhesion and entrapment (retinal leukostasis) in retinal capillaries is an early event associated with areas of vascular non-perfusion and the development of diabetic retinopathy. The leukocytes in diabetic patients are less deformable more activated, and demonstrate increased adhesion to the vascular endothelium. This review summarizes the current literature on the role of leukocytes in the pathogenesis of capillary occlusion, and discusses the potential of leukostasis as a new promising target in the treatment of diabetic retinopathy.

Aims/hypothesis: Increasing evidence suggests that chronic, subclinical inflammation plays an important role in the pathogenesis of diabetic retinopathy. We recently reported that a glycosylating enzyme, core 2 beta-1,6-N-acetylglucosaminyltransferase (core 2 GlcNAc-T), is implicated in increased leucocyte-endothelial cell adhesion in diabetic retinopathy via an upregulation mechanism controlled by TNF-alpha.

Subjects, materials and methods: We examined the functional link between circulating TNF-alpha and the activity and phosphorylation of core 2 GlcNAc-T in polymorphonuclear leucocytes of patients with type 1 and type 2 diabetes.

Results: Plasma levels of TNF-alpha, although similar in patients with type 1 and type 2 diabetes, were significantly higher than in age-matched healthy controls, and correlated well with the severity of retinopathy. Core 2 GlcNAc-T activity followed the same trend and was associated with phosphorylation of the enzyme. Finally, the observation that TNF-alpha levels are also linked to glycaemic values suggests that in patients, as well as in vitro, the glycosylation-mediated cell adhesion process that plays a role in diabetic retinopathy may involve glucose- and TNF-alpha-induced protein kinase beta2 activation, and subsequently raise activity of core 2 GlcNAc-T through increased enzyme phosphorylation.

Conclusions/interpretation: Our results reveal a novel rationale towards a specific treatment of diabetic retinopathy, based on the inhibition of core 2 GlcNAc-T activity and/or the blockage of cognate glycans.

A large body of evidence now implicates increased leukocyte-endothelial cell adhesion as a key early event in the development of diabetic retinopathy. We recently reported that raised activity of the glycosylating enzyme core 2 beta 1,6-N-acetylglucosaminyltransferase (GlcNAc-T) through protein kinase C (PKC)beta2-dependent phosphorylation plays a fundamental role in increased leukocyte-endothelial cell adhesion and capillary occlusion in retinopathy. In the present study, we demonstrate that following exposure to plasma from diabetic patients, the human promonocytic cell line U937 exhibits a significant elevation in core 2 GlcNAc-T activity and increased adherence to cultured retinal capillary endothelial cells. These effects of diabetic plasma on enzyme activity and cell adhesion, mediated by PKCbeta2-dependent phosphorylation of the core 2 GlcNAc-T protein, were found to be triggered by increased plasma levels of tumor necrosis factor (TNF)-alpha. Levels of enzyme activity in plasma-treated U937 cells were closely dependent on the severity of diabetic retinopathy, with the highest values observed upon treatment with plasma of patients affected by proliferative retinopathy. Furthermore, we noted much higher correlation, as compared with control subjects, between increased values of core 2 GlcNAc-T activity and cell adhesion properties. Based on the prominent role of TNF-alpha in the development of diabetic retinopathy, these observations further validate the significance of core 2 GlcNAc-T in the pathogenesis of capillary occlusion, thereby enhancing the therapeutic potential of specific enzyme inhibitors.

 carbon materials2 through their unique combination of excellent processability and high carbon yield. The enediyne functionality of the monomers undergo a thermal Bergman cycloaromatization reaction that yields reactive naphthalene diradicals which polymerize to form polynapthalene.(Figure 1) The tetrafunctionality of the monomers allows for both a higher processing window due to extensive branching and ultimately the formation of network polymers. The high carbon yield results in less shrinkage of the polymer upon pyrolysis to the glassy carbon state. This allows for the faithful templating of carbon structures from a polymeric precursor.

Hydrogen fuel cell electrodes require several properties for optimum performance. An ideal electrode would have as high a surface area as possible with an uniform dispersion of nano-scale catalyst particles attached to the surface. The electrode must be electrically conductive and have good mass transport for products and reactants. Carbon supported platinum is the best known catalyst for the oxidation of hydrogen at the anode and the reduction of oxygen at the cathode of a proton exchange membrane fuel cell (PEMFC) 3. The material also must have good compatibility with the material used for the proton exchange membrane in the membrane electrode assembly (MEA), usually a sulfonated fluoropolymer such as Nafion. We have undertaken a study to prepare a high surface area carbon material through a BODA templating method which can then be functionalized with both well dispersed platinum nanoparticles …

Irregular (so-called broken) plural identification in modern standard Arabic is a problematic issue for information retrieval (IR) and language engineering applications, but their effect on the performance of IR has never been examined. Broken plurals (BPs) are formed by altering the singular (as in English: tooth→ teeth) through an application of interdigitating patterns on stems, and singular words cannot be recovered by standard affix stripping stemming techniques. We developed several methods for BP detection, and evaluated them using an unseen test set. We incorporated the BP detection component into a new light-stemming algorithm that conflates both regular and broken plurals with their singular forms. We also evaluated the new light-stemming algorithm within the context of information retrieval, comparing its performance with other stemming algorithms.

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.