Home About us Contact
|
Home About us Contact | ||
|
|
||
Low Proportion (low + proportion)
Selected AbstractsLow proportion of whole exon deletions causing phenylketonuria in Denmark and Germany,,HUMAN MUTATION, Issue 2 2007Lisbeth Birk Møller Abstract Phenylketonuria (PKU) is an autosomal recessive genetic disorder caused by mutations of the gene encoding phenylalanine hydroxylase (PAH). More than 500 different PAH mutations have been identified and about 90% of these are single base mutations. Although the identification rate of the PAH mutations is generally very high, some variants remain unidentified. A fraction of these mutations are the result of genomic deletions or duplications, which are not recognized with standard PCR-based methods. Here we present the results of exon deletion or duplication analysis in a total of 34 families, in which two mutations had not been identified using conventional diagnostic screening techniques. Using multiplex ligation-dependent probe amplification (MLPA), we found a deletion covering exon 1 and exon 2 (c.1-?_168+?del) in one patient, a deletion of exon 3 (c.169-?_352+?del) in four patients, and a deletion of exon 5 (c.442-?_509+?del) in two patients. A deletion was thus detected in about 20% (7/34) of the families tested. Out of a combined cohort of 570 independent PKU patients from Denmark and Germany, exon deletions were identified in a total of four patients. The estimated allelic frequency of exon deletions in PKU patients in these two populations is therefore below 0.5%. © 2007 Wiley-Liss, Inc. [source] Population ecology of cave armoured catfish, Ancistrus cryptophthalmus Reis 1987, from central Brazil (Siluriformes: Loricariidae)ECOLOGY OF FRESHWATER FISH, Issue 2 2007E. Trajano Abstract,,, The population ecology of Ancistrus cryptophthalmus (Reis 1987) was studied by mark,recapture technique in caves from the São Domingos karst area, State of Goiás, northeastern Brazil. Total population sizes estimated for Angélica and Passa Três Caves were 20,000 and 1000 individuals, respectively. Densities around 1.0 individuals per m2 in Angélica, Bezerra and São Vicente I Streams, and 0.6 individuals per m2 in the smaller Passa Três Stream may be considered high for cavefish standards, as well as for epigean loricariids. As expected for benthic grazers, cave catfish are highly sedentary. The distribution of size classes did not differ among caves and within the same cave throughout the studied dry seasons; on the contrary, the condition factor decreased throughout this period probably because of the progressive depletion of organic matter available as food. Low proportions of mature individuals, low growth rates (average = 0.5 mm month,1) with cases of negative growth and high longevities (8,10 years) point to a precocial lifestyle, typical of troglobitic species. [source] Exotic plant species invade diversity hot spots: the alien flora of northwestern KenyaECOGRAPHY, Issue 2 2000J. Stadler We analysed the distribution of native and alien plant species across 20 ecogeographic zones of northwestern Kenya. The source pool for the majority of aliens was Europe and America. Thus, the source pool has a biogeographic bias which explains the low proportion of aliens in the tropics: most species in the European or American source pool are not well adapted to tropical conditions. As expected, native and alien plant species showed an area effect. Correcting for this area effect. species rich zones showed a higher proportion of alien plant species in their flora. At the analysed scale, species richness of native plant communities does not increase the resistance to invasions and alien plant species invade diversity hotspots. Compared to the other ecogeographic zone, the urban area around Nairobi showed an increased richness in alien and native plant species. This is very similar to findings in Europe, although the history of urbanisation is much shorter in Kenya. The species turnover between zones (,-diversity) shows a similar pattern in native and alien plant species. Within a very short time scale the alien plant species mapped the biogeographic patterns of natives, although the geography of human activities influences the propagule pressure. [source] A national stroke quality register: 12 years experience from a participating hospitalEUROPEAN JOURNAL OF NEUROLOGY, Issue 8 2007P. Appelros Registration of all hospitalized stroke patients is practiced in Sweden in order to assess care quality. Data in this register, Riks-Stroke (RS), may be biased due to incomplete registration. The purpose of this paper was to report changes in stroke outcome in relation to fluctuations in registration. Patients registered in RS at a hospital during the period 1994,2005 were analyzed. Case fatality at 28 days, living conditions, and activities of daily living (ADL) performance at 3 months were correlated to the number of patients registered and follow-up frequency. A total of 4994 stroke cases were registered during the period. A high annual registration rate was significantly correlated to a high case fatality ratio. A low annual follow-up rate was associated with a low proportion of patients living in their own home without any need of help. Quality parameters are sensible for selection bias, which make them difficult to compare over time and between hospitals. We suggest that by weighing outcome data against stroke severity, safer conclusions may be drawn. Additionally, hospitals considering setting up quality registers should make every effort to attain complete case ascertainment at all times, including patients managed outside the hospital, in order to avoid selection bias. [source] Reproduction of interspecific hybrids of Atlantic salmon and brown trout in a stream environmentFRESHWATER BIOLOGY, Issue 6 2003Eva Garcia-Vazquez SUMMARY 1.,Reproduction between Atlantic salmon males and interspecific hybrid Salmo salar × Salmo trutta females was monitored in a controlled flow channel diverted from a south European river located at the edge of Atlantic salmon natural geographic distribution in Europe. 2.,Post-F1 hybrids were viable and survived in the wild, at least until dispersal from redds. After transfer to hatchery conditions, 67% survived into the second year. 3.,The hybrids possessed 98 chromosomes: two sets of Atlantic salmon(2n = 58) and one set of brown trout (n = 40) chromosomes. 4.,The existence of a low proportion of allotriploid individuals can be expected in rivers where Atlantic salmon and brown trout populations coexist. [source] Sensory, chemical and microbiological assessment of farm-raised European sea bass (Dicentrarchus labrax) stored in melting iceINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 3 2002Vasiliki R. Kyrana Farm raised European sea bass (Dicentrarchus labrax) were stored in melting ice for a period up to 22 days from the time of harvest, and sensory, chemical, and microbiological assessments were made at intervals. The storage life of the ungutted fish, determined by sensory evaluation of the cooked flesh, was 19 days. Of the chemical tests, only k1 value provided a useful means of monitoring early storage change. Trimethylamine, total volatile bases and pH showed practically no change during the first half of the edible storage life of the fish. Changes in free fatty acid (FFA) content and thiobarbituric acid (TBA) value could not be used to determine loss of acceptability or end of storage life. Sulphide producing bacteria constituted a very low proportion of the total aerobic flora, suggesting that the common sulphide producer Shewanella putrefaciens was not a major spoiler of sea bass in this trial. [source] Matching of uncalibrated stereo images by elastic deformationINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 5 2004Wan-Chiu Li Abstract We propose a method for uncalibrated stereo matching. The method applies gradual elastic deformation to the line segments in a pair of images until they match with each other. By using an energy function and a neighborhood function, matching is performed in a coarse-to-fine manner. Our method gives point correspondences with a low proportion of outliers and is robust in the uncalibrated case (with no need to estimate the epipolar geometry). The computation complexity is proportional to the square of the number of line segments in the images, which is relatively efficient compared with other elaborate methods. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 14, 198,205, 2004; Published online in Wiley Inter-Science (www.interscience.wiley.com). DOI 10.1002/ima.20024 [source] Fatty acid status in captive and free-ranging black rhinoceroses (Diceros bicornis)*JOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 3 2008M. Clauss Summary The fatty acid (FA) patterns of plasma/serum triglycerides (TG), phospholipids (PL) and cholesteryl esters (CE) of captive and free-ranging black rhinoceroses (Diceros bicornis) were investigated. Free-ranging animals (n = 28) stemmed from four different regions. Captive animals sampled included specimens from North American (n = 11) and three different European facilities (n = 6). The European animals were tested on 1,4 different diets, resulting in a total of 15 blood samples. Regardless of differences between the free-ranging animals from different regions, differences between captive and free-ranging animals were relatively uniform: captive animals had higher overall proportions of polyunsaturated fatty acid (PUFA), due to levels of linoleic acid (LA, 18:2n6) that were drastically increased as compared to free-ranging animals. In contrast, levels of alpha-linolenic acid (ALA, 18:3n3) were consistently lower on conventional zoo diets. n6/n3 ratios for TG, PL and CE were 1.6, 10 and 8 in samples from free-ranging animals, respectively, as compared to 4.1,16.3, 16,148 and 40,277 in samples from captive animals. There was a distinct correlation between the proportion of grain-based products (commercial concentrates, plain grains and bread) in the diets of the European animals and the measured levels of n6 PUFA. An animal from a facility with a very low proportion of grain products in the diet nevertheless had high LA readings, most probably due to the use of sunflower oil as 2% (dry matter basis) of its diet. One animal that received a high proportion of grass meal pellets due to an oral disease had increased ALA contents after the diet change. These results allow conclusions on the suitability of diets fed in captivity: the black rhinoceros is prone to several uncommon diseases that have been suspected to be linked to oxidative damage, possibly due to the disposition of this species to excessive iron storage. An unnatural dietary loading with PUFAs would exacerbate this problem. Additionally, n6 FAs are known as precursors of pro-inflammatory mediators, and their overrepresentation could therefore exacerbate any inflammatory processes. Therefore, the current practice of using grain-based feeds as major ingredients in captive rhinoceros diets is discouraged. Diet items containing ALA (a precursor of anti-inflammatory mediators) such as, fresh grass, fresh browse, the respective silages should be included at higher levels in diets for captive black rhinoceroses. Grass meal pellets, although a good source of ALA and linked with high levels of ALA in an animal of this study, must be chosen with care for black rhinoceroses due to their particular proneness for high iron contents. [source] Population structure and establishment of the threatened long-lived perennial Scorzonera humilis in relation to environmentJOURNAL OF APPLIED ECOLOGY, Issue 2 2002Guy Colling Summary 1The intensification of agriculture has resulted in the decline of many plant species of nutrient-poor wet grasslands. At some sites local populations of long-lived characteristic species have persisted and might benefit from recent extensification schemes. However, little is known about the population biology of these plants, and the prospects for the populations are uncertain. 2We studied the population structure and establishment of the long-lived Scorzonera humilis in 23 populations in Luxembourg and neighbouring Belgium. Two types of populations could be distinguished according to their population structure: regenerating populations, with a high proportion of plants with only one or a few rosettes, and aged populations, with a low proportion of small, young plants but a high proportion of individuals with many rosettes. The total density of Scorzonera individuals was higher in regenerating than in aged populations. 3Within sites, S. humilis was restricted to more open and nutrient-poor patches. The composition of the vegetation in plots where S. humilis was present was significantly different from that of plots without the species, indicating that S. humilis is restricted to particular microhabitats. 4In multiple regression analyses, environmental variables explained a large part of the variation in the total density of genets, the density of genets of different size and the density of rosettes. The main variables of influence were site productivity and soil moisture. With increasing productivity and decreasing soil moisture the proportion of small genets decreased and that of large genets increased. Increased productivity had contrasting effects at the genet and ramet (rosette) levels. While genet density decreased, ramet density increased, indicating that if a site is fertilized, recruitment of new genets and survival of genets is reduced, but growth of surviving genets is increased. 5The results of a sowing experiment indicated that an aged population structure was due to a lack of recruitment. The number of seeds that germinated and the proportion of seedlings that survived until the next summer were positively correlated with soil moisture and negatively with productivity. Germination rate and establishment success were significantly higher in Molinion grassland than in the Calthion grasslands. 6The results suggest that for long-lived species the size and number of populations may not be good indicators of the status of a species. In S. humilis large populations (> 1000 genets) still exist, but all are of the aged type. In order to preserve existing populations of S. humilis, management should aim to reduce productivity and increase soil moisture. [source] Folivory in the white-tipped plantcutter Phytotoma rutila: seasonal variations in diet composition and qualityJOURNAL OF AVIAN BIOLOGY, Issue 2 2003Enrique H. Bucher Plantcutters (Phytotomidae) represent the only Passeriformes with a predominantly folivorous diet. Little is known however about their feeding habits and adaptations for leaf consumption. Here we analyze the relationship between diet composition and nutritional value in the white-tipped plantcutter Phytotoma rutila in a Chaco woodland in Córdoba, Argentina. The white-tipped plantcutter consumed mainly dicot leaves (91%), complemented with a small proportion of fruits (7%) and flowers (2%). Eleven plant species were utilized, of which five were strongly dominant: Lycium cestroides (38%), Prosopis alba and P. nigra (28%), Celtis tala (22%), and Schinus longifolius (8%). No animal food was consumed. The leaf material ingested by the white-tipped plantcutter had high protein content and low proportion of fibers and phenols. In multivariate analysis, leaf chemical properties accounted for over 81% of the variation in diet composition throughout the year. However, only protein and phenols content related significantly with diet composition in single regressions. The quality index that relates protein with lignin and phenols showed the highest correlation with diet composition. Availability of highly nutritive leaves of Lycium cestroides during the dry season seems to be a key factor for the occurrence of the white-tipped plantcutter in the study area. Our results confirm that plantcutters are truly folivorous passerine species, being able to obtain a highly nutritional diet throughout the year. [source] Population dynamics of fisheries stock enhancementJOURNAL OF FISH BIOLOGY, Issue 2004K. Lorenzen The population dynamics of fisheries stock enhancement, and its potential for generating benefits over and above those obtainable from optimal exploitation of wild stocks alone are poorly understood and highly controversial. I extend the dynamic pool theory of fishing to stock enhancement by unpacking recruitment, incorporating regulation in the recruited stock, and accounting for biological differences between wild and hatchery fish. I then analyse the dynamics of stock enhancement and its potential role in fisheries management, using the candidate stock of North Sea sole as an example. Enhancement through release of recruits or advanced juveniles is predicted to increase total yield and stock abundance, but reduce abundance of the naturally recruited stock component through compensatory responses or overfishing. Release of genetically maladapted fish reduces the effectiveness of enhancement, and is most detrimental overall if fitness of hatchery fish is only moderately compromised. As a temporary measure for rebuilding of depleted stocks, enhancement can not substitute for effort limitation, and is advantageous as an auxiliary measure only if the population has been reduced to a very low proportion of its unexploited biomass. Quantitative analysis of population dynamics is central to the responsible use of stock enhancement in fisheries management, and the necessary tools are available. [source] Estimating the Impact of the Minimum Wage Using Geographical Wage Variation,OXFORD BULLETIN OF ECONOMICS & STATISTICS, Issue 2002Mark B. Stewart Abstract This paper evaluates the impact on employment of the UK's introduction of a minimum wage in 1999 by exploiting the geographical variation in wages, which meant that the minimum wage's ,bite' into an area's wage distribution differed considerably across the country. The results indicate that, although the minimum wage had differential wage-distribution effects across the 140 areas of the country, employment growth after its introduction was not significantly lower in areas of the country with a high proportion of low-wage workers, whose wages had to be raised to comply, from that in areas with a low proportion of such workers. [source] Mesothelioma in blood related subjects: Report of 11 clusters among 1954 Italy cases and review of the literatureAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 5 2007Valeria Ascoli Abstract Background Malignant mesothelioma is a sporadic tumor related to asbestos. Its occurrence in blood relatives raises the question of potential contribution of predisposing factors. Methods The study analyses the features of mesothelioma in blood relatives that might explain the disease clustering. Data sources of familial clusters were three population-based Mesothelioma Registries in Italy (Veneto and Apulia Regions, Brescia province; 1978,2005) and Medline, Toxline, and Oshline/Hseline databases for a review of the literature (1968,2006). Results Eleven clusters (22 cases) were identified among 1954 Italy mesothelioma cases, and 51 clusters (120 cases) were extracted from 33 studies. The proportion of Italy familial cases was 1.4 per 100 mesothelioma cases; the ratio between the number of familial clusters and the number of non-familial mesothelioma cases was 1:148. The mesothelioma profile in consanguineous is the same as in non-consanguineous subjects (male prevalence; pleural site; age at diagnosis >50 years; asbestos exposure). Most clusters occurred in asbestos workers (shipyard, asbestos-cement production/processing, and insulation) and household-exposed blood relatives. Others were related to asbestos-cement factory pollution, asbestos-in-place, and handling asbestos-contaminated textiles. Two clusters were without any known exposure. Cancer family history revealed lung cancer cases in eight clusters. Conclusions Available data support asbestos exposure as the main risk factor in mesothelioma cases among blood relatives. Our finding of a low proportion of familial cases would not suggest the influence of a large genetic component for mesothelioma in blood relatives. Am. J. Ind. Med. 50:357,369, 2007. © 2007 Wiley-Liss, Inc. [source] Housing Markets And Regional Unemployment Flows In Great BritainTHE MANCHESTER SCHOOL, Issue 2 2003Martin T. Robson Over the past 20 years, there has been a great deal of interest from academic economists and policymakers in the UK in the contribution of the housing market to regional disparities in unemployment. However, despite a considerable body of research, there remains a great deal of uncertainty concerning the role played by different features of the housing market in shaping the regional pattern of unemployment. In this study, we aim to gain a deeper understanding of this issue by examining the relationship between housing market variables and the flows into and out of regional unemployment. Our findings indicate that both the level of regional house prices and the housing tenure mix have significant effects on the rate of flows into and out of regional unemployment and hence upon the equilibrium rate of unemployment in a region. In particular, we find that regions with a relatively high level of house prices and/or a low proportion of social rented housing will tend to have a relatively low equilibrium rate of unemployment, other things equal. [source] Fibonacci grids: A novel approach to global modellingTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 619 2006Richard Swinbank Abstract Recent years have seen a resurgence of interest in a variety of non-standard computational grids for global numerical prediction. The motivation has been to reduce problems associated with the converging meridians and the polar singularities of conventional regular latitude,longitude grids. A further impetus has come from the adoption of massively parallel computers, for which it is necessary to distribute work equitably across the processors; this is more practicable for some non-standard grids. Desirable attributes of a grid for high-order spatial finite differencing are: (i) geometrical regularity; (ii) a homogeneous and approximately isotropic spatial resolution; (iii) a low proportion of the grid points where the numerical procedures require special customization (such as near coordinate singularities or grid edges); (iv) ease of parallelization. One family of grid arrangements which, to our knowledge, has never before been applied to numerical weather prediction, but which appears to offer several technical advantages, are what we shall refer to as ,Fibonacci grids'. These grids possess virtually uniform and isotropic resolution, with an equal area for each grid point. There are only two compact singular regions on a sphere that require customized numerics. We demonstrate the practicality of this type of grid in shallow-water simulations, and discuss the prospects for efficiently using these frameworks in three-dimensional weather prediction or climate models. © Crown copyright, 2006. Royal Meteorological Society [source] Harm and Benefits of Primary Liver Resection and Salvage Transplantation for Hepatocellular CarcinomaAMERICAN JOURNAL OF TRANSPLANTATION, Issue 3 2010A. Cucchetti Primary transplantation offers longer life-expectancy in comparison to hepatic resection (HR) for hepatocellular carcinoma (HCC) followed by salvage transplantation; however, livers not used for primary transplantation can be reallocated to the remaining waiting-list patients, thus, the harm caused to resected patients could be balanced, or outweighed, by the benefit obtained from reallocation of livers originating from HCC patients first being resected. A Markov model was developed to investigate this issue based on literature data or estimated from the United Network for Organ Sharing database. Markov model shows that primary transplantation offers longer life-expectancy in comparison to HR and salvage transplantation if 5-year posttransplant survival remains higher than 60%. The balance between the harm for resected patients and the benefit for the remaining waiting list depends on (a) the proportion of HCC candidates, (b) the percentage shifted to HR and (c) the median expected time-to-transplant. Faced with a low proportion of HCC candidates, the harm caused to resected patients was higher than the benefit that could be obtained for the waiting-list population from re-allocation of extra livers. An increased proportion of HCC candidates and/or an increased median time-to-transplant could lead to a benefit for waiting-list patients that outweighs this harm. [source] Assessing the dominance of Phleum pratense cv. climax, a species commonly used for ski trail restorationAPPLIED VEGETATION SCIENCE, Issue 2 2009Francis Isselin-Nondedeu Abstract Questions: (1) Are some species used for ski trail restoration too dominant to allow native species to re-establish? (2) What plant traits can be used to predict which species are good competitors? We tested the hypothesis that limited native species establishment on ski trails is caused by (1) the dominance of Phleum pratense cv. climax (PPC) and (2) the asymmetry of competitive interactions. Location: Sub-alpine area in the northern French Alps. Methods: PPC was cultivated outdoors over 2 years with 15 alpine species in a systematic design with high- and low-nutrient soil conditions. For each species relative survival, competitive performance and relationships with plant traits were measured. Results: PPC exerted strong dominance on most of its neighbouring species. Survival performance of Anthyllis vulneraria, Luzula sudetica and Lotus alpinus were dramatically reduced. Results of above-ground competition showed that species were trapped in asymmetric competition. Festuca rubra, Trifolium repens, Alchemilla xanthochlora, Trifolium pratense and Plantago alpina best counteracted PPC. Below-ground competition was more symmetric, particularly at the high nutrient level. Plant traits such as biomass, canopy size and specific leaf area were positively correlated with competitive performance of the species. Conclusion: The study has implications for the management of restored ski trails since PPC may hinder the establishment of native sub-alpine species. Consequently, recommendations should focus on (1) maintaining a low proportion or decreasing the proportion of PPC seeds in the revegetation mix and (2) reducing soil fertilization. Plant traits and competition experiments can help to predict changes in restored grasslands. [source] Fatty acid composition and analysis of freshwater caridean shrimp Macrobrachium nipponense (De Haan) during spermiogenesisAQUACULTURE RESEARCH, Issue 8 2010Da-Hui Wang Abstract We analysed fatty acids (FAs) composition and the potential functions of FAs in hepatopancreas and testis of freshwater caridean shrimp Macrobrachium nipponense during testis development. The hepatopancreas presented a high unsaturated FA content of about 40%, whereas the testis showed a high level of saturated fatty acids (SFAs) with a decreasing content of 97,86% of total FAs during maturation. Several specific FAs in testis showed significant changes throughout maturation. Among SFAs, C14:0 contributed with a relatively constant high proportion of about 22%, whereas C16:0 and C18:0 contents were also at high levels but showed significant increases during maturation. Representatives of highly unsaturated fatty acids (HUFAs), such as C18:1n-9, C18:2n-6, C20:5n-3 (EPA), C20:4n-6 (AA) and C22:6n-3 (DHA) showed significant increases despite their low proportion in the gonad. These results suggest that a high content of HUFAs in hepatopancreas may represent a reservoir for sperm production. The FA C14:0 may provide a particular function. The variations of the FA profile in testis at different developmental stages reveals that C18:1n-9, C18:2n-6, C20:5n-3, C20:4n-6 and C22:6n-3 may play important roles in spermiogenesis. [source] Cell permeabilization by poliovirus 2B viroporin triggers bystander permeabilization in neighbouring cells through a mechanism involving gap junctionsCELLULAR MICROBIOLOGY, Issue 8 2010Vanesa Madan Summary Poliovirus 2B protein is a well-known viroporin implicated in plasma membrane permeabilization to ions and low-molecular-weight compounds during infection. Translation in mammalian cells expressing 2B protein is inhibited by hygromycin B (HB) but remains unaffected in mock cells, which are not permeable to the inhibitor. Here we describe a previously unreported bystander effect in which healthy baby hamster kidney (BHK) cells become sensitive to HB when co-cultured with a low proportion of cells expressing poliovirus 2B. Viroporins E from mouse hepatitis virus, 6K from Sindbis virus and NS4A protein from hepatitis C virus were also able to permeabilize neighbouring cells to different extents. Expression of 2B induced permeabilization of neighbouring cell lines other than BHK. We found that gap junctions are responsible mediating the observed bystander permeabilization. Gap junctional communication was confirmed in 2B-expressing co-cultures by fluorescent dye transfer. Moreover, the presence of connexin 43 was confirmed in both mock and 2B-transfected cells. Finally, inhibition of HB entry to neighbouring cells was observed with 18,-glycyrrhethinic acid, an inhibitor of gap junctions. Taken together, these findings support a mechanism involving gap junctional intercellular communication in the bystander permeabilization effect observed in healthy cells co-cultured with poliovirus 2B-expressing cells. [source] Strength Enhancement of Nanostructured Organogels through Inclusion of Phthalocyanine-Containing Complementary Organogelator Structures and In Situ Cross-Linking by Click ChemistryCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2008David, Díaz Díaz Dr. Abstract Stable photoactive organogels were successfully prepared by a two-step sequence involving: 1),formation of thermoreversible organogels by use of a combination of low-molecular-weight organogelators (LMOGs) and ZnII,phthalocyanine (ZnII,Pc) moieties containing complementary organogelator structures, and 2),strength enhancement of the gels by in situ cross-linking with the aid of CuI -catalysed azide,alkyne [3+2] cycloadditions (CuAACs). The optimum click reaction was carried out between a flexible C6 aliphatic diazide and a suitable dialkyne (molar ratio 1:1) added in a low proportion relative to the organogelator system [LMOG+ZnIIPc]. The dialkyne unit was incorporated into a molecule resembling the LMOGs structure in such a way that it could also participate in the self-assembly of [LMOG+ZnIIPc]. The significant compatibility of the multicomponent photoactive organogels towards this strengthening through CuAACs allowed their sol-to-gel transition temperatures (Tgel) to be enhanced by up to 15,°C. The Tgel values estimated by the "inverse flow method" were in good agreement with the values obtained by differential scanning calorimetry (DSC). Rheological measurements confirmed the viscoelastic, rigid, and brittle natures of all Pc-containing gels. Transmission and scanning electron microscopy (TEM, SEM) and atomic force microscopy (AFM) revealed the fibrilar nature of the gels and the morphological changes upon cross-linking by CuAAC. Emission of a red luminescence from the dry nanoscale fibrous structure,due to the self-assembly of the Pc-containing compounds in the organogel fibres,was directly observed by confocal laser scanning microscopy (CLSM). The optical properties were studied by UV/Vis and fluorescence spectroscopy. Fluorescence, Fourier-transform infrared (FTIR) and circular dichroism (CD) measurements were also carried out to complete the physicochemical characterization of selected gels. As a proof of concept, two different organogelators (cholesterol- and diamide-based LMOGs) were successfully used to validate the general strategy. [source] Determination of Total Organic Carbon Content and ,13C in Carbonate-Rich Detrital SedimentsGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 3 2007Valier Galy carbone organique; décarbonatation; solubilisation; sediment; carbonate The determination of total organic carbon content and composition in detrital sediments requires careful removal of their carbonate minerals. In detrital sediments containing large amounts of carbonates, including dolomite, this can only be achieved by liquid acid leaching that may solubilise a significant proportion of the organic carbon. For a set of detrital sediments from the Himalayan system and the Amazon River as well as five geological reference materials, we determined the proportion of organic carbon (Corg) solubilised during acid leaching. This proportion is significant for all analysed sediments and generally tends to increase with the organic carbon content. Compared to other types of sediments analysed, clay fractions extracted from river sediments and bed sediments with very low organic carbon content have high and low proportions of acid soluble Corg respectively. In Himalayan and Amazon river sediments, the proportion of Corg solubilised during acid leaching was relatively constant with average values of 14 and 19 % respectively. Thus, it is possible to correct the Corg content for the dissolved organic carbon content measured after decarbonation. Data presented here show that Corg dissolved during liquid acid leaching must be taken into account. After careful calibration, the method presented here should, therefore, be applied to any carbonate-rich detrital sediment. La détermination de la teneur totale en carbone organique et de sa composition dans des sédiments détritiques requiert leur décarbonatation préalable. l'élimination complète de carbonates tels que la dolomite ne peut être réalisée qu'au moyen d'une attaque avec un acide en phase liquide ce qui peut entrainer la solubilisation d'une partie du carbone organique. Pour un ensemble de sédiments détritiques provenant du système Himalayen et de l'Amazone ainsi que pour cinq matériaux géologiques de référence, nous avons déterminé la proportion de carbone organique (Corg) solubilisé lors de la décarbonatation. Celle-ci est significative pour l'ensemble des sédiments analysés et tend à augmenter avec la teneur en carbone organique. En comparaison avec les autres types de sédiments analysés, les fractions argileuses extraites de sédiments de rivière et les sédiments de fond très pauvres en Corg ont une proportion de Corg soluble dans l'acide respectivement élevée et faible. Dans les sédiments himalayens et amazoniens, la proportion de Corg solubilisé lors de la décarbonatation est plutôt constante avec des valeurs moyennes respectives de 14 et 19%. Nous pouvons donc calculer avec précision la teneur totale en carbone organique à partir de la teneur en Corg déterminée après décarbonatation. Nos données montrent que la solubilisation de Corg lors de la décarbonatation par un acide en solution est importante et doit être prise en compte lors de la détermination de la teneur en carbone organique. Moyennant une calibration minutieuse, la méthode que nous présentons devrait donc être utilisée pour l'analyse de sédiments détritiques riches en carbonates. [source] Diversity and distribution of gynogenetic hybrids between Fundulus diaphanus and Fundulus heteroclitus in Porter's Lake (Nova Scotia) in relation to salinityJOURNAL OF FISH BIOLOGY, Issue 5 2009D. Mérette Unisexual hybrids between Fundulus diaphanus and Fundulus heteroclitus were found in low proportions at intermediate salinity in Porter's Lake, Nova Scotia. One clone accounted for 72% of the hybrids, with most other hybrids being different at a single microsatellite allele. This clone thrives over a wide range of salinities, suggesting a general-purpose genotype. [source] Sterol Composition of Pneumocystis jirovecii with Blocked 14,-Demethylase ActivityTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 6 2004JOSÉ-LUIS GINER ABSTRACT Several drugs that interact with membrane sterols or inhibit their syntheses are effective in clearing a number of fungal infections. The AIDS-associated lung infection caused by Pneumocystis jirovecii is not cleared by many of these therapies. Pneumocystis normally synthesizes distinct C28 and C29 24-alkylsterols, but ergosterol, the major fungal sterol, is not among them. Two distinct sterol compositional phenotypes were previously observed in P. jirovecii. One was characterized by ,7 C28 and C29 24-alkylsterols with only low proportions of higher molecular mass components. In contrast, the other type was dominated by high C31 and C32 24-alkylsterols, especially pneumocysterol. In the present study, 28 molecular species were elucidated by nuclear magnetic resonance analysis of a human lung specimen containing P. jirovecii representing the latter sterol profile phenotype. Fifteen of the 28 had the methyl group at C-14 of the sterol nucleus and these represented 96% of the total sterol mass in the specimen (excluding cholesterol). These results strongly suggest that sterol 14,-demethylase was blocked in these organisms. Twenty-four of the 28 were 24-alkylsterols, indicating that methylation of the C-24 position of the sterol side chain by S-adenosyl-L-methionine:sterol C-24 methyl transferase was fully functional. [source] In search of the Pre- and Post-Neolithic Genetic Substrates in Iberia: Evidence from Y-Chromosome in Pyrenean PopulationsANNALS OF HUMAN GENETICS, Issue 1 2009A. M. López-Parra Summary The male-mediated genetic legacy of the Pyrenean population was assessed through the analysis of 12 Y-STR and 27 Y-SNP loci in a sample of 169 males from 5 main geographical areas in the Spanish Pyrenees: Cinco Villas (Western Pyrenees), Jacetania and Valle de Arán (Central Pyrenees) and Alto Urgel and Cerdaña (Eastern Pyrenees). In the Iberian context, the Pyrenean samples present some specificities, being characterizeded by a high proportion of chromosomes R1b1b2-M269 (including the usually uncommon R1b1b2d-SRY2627 and R1b1b2c-M153 types) or I2a2-M26 and low proportions of other haplogroups. Our results indicate that an old pre-Neolithic substrate is preponderant in populations of the whole Pyrenean fringe. However, AMOVA revealed a high level of substructure within Pyrenean populations, partially explained by drift effects as well as by the signature of an ancient genetic differentiation between Western and Eastern Pyrenees. [source] | ||||||||||||||||||||||