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Systematic Study (systematic + study)
Selected AbstractsA SYSTEMATIC STUDY OF GIGAR-TINACEAE FROM PACIFIC NORTH AMERICA BASED ON MOLECULAR AND MORPHOLOGICAL EVIDENCEJOURNAL OF PHYCOLOGY, Issue 2000J.R. Hughey Greater than 50 species of Gigartinaceae have been described from Pacific North America, about half of which are currently recognized. Although the family is treated extensively in the taxonomic literature, many of the species are still confused and a comprehensive revision is required. We sequenced the rbcL (RuBisCO) gene and ITS (Internal Transcribed Spacer) 1, 2, and 5.8S regions from a large number of recent collections and identified a discrete of number data sets. These were analysed in comparison with the morphological evidence for each of the taxa. Uncertain of the possibility that our operational taxonomic units may not correspond to the types, we developed a protocol for isolating PCR-friendly DNA from herbarium specimens, some reaching back as far as 1670. The DNA profiles of types and historically important specimens were compared to those for recently collected silica gel-dried and formalin-fixed material and assigned correct names. Species studied ranged from Alaska to Mexico and the Gulf of California and were compared to outgroup taxa from Pacific South America and the Southern Ocean. Particular attention was paid to variations in morphology as they relate to habitat with emphasis on the presence or absence of different morphological forms among sympatric and allopatric populations. We recognize 10 species in Chondracanthus (including one new combination and one new species) and 16 species in Mazzaella (including two new combinations and two new species). Finally, we tested a phylogenetic hypothesis inferred for the Gigartinaceae from rbcL sequences for congruence with one generated from ITS sequences. [source] The Immobilization of Rhodium-4-(diphenylphosphino)-2- (diphenylphosphinomethyl)-pyrrolidine (Rh-PPM) Complexes: A Systematic StudyADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 12-13 2006Benoît Pugin Abstract A modular toolbox for the immobilization of homogeneous catalysts to various supports is described. It consists of functionalized chiral diphosphines and three different linkers based on isocyanate chemistry and it is used to attach the 4-(diphenylphosphino)-2-(diphenylphosphinomethyl)-pyrrolidine (PPM) ligand to a large variety of soluble, swellable and non-swellable solid organic polymers and to silica gels. As model reaction the hydrogenation of acetamidocinnamic acid derivatives, catalyzed with high enantioselectivity was chosen. Besides information on the usefulness of a particular type of support for synthetic applications, the experiments were also designed to address the question how parameters such as solubility, swellability, cage or pore size and solvent affect the rate and enantioselectivity of an immobilized catalyst. Rhodium complexes of ligands attached to soluble polymers and inorganic supports achieved ees up to 95,% and turnover frequencies between 700 and 1400,h,1, very close to the values of the homogeneous Rh catalyst (ee 95,%, TOF 1320,h,1). Insoluble or strongly cross-linked organic polymers led to catalysts with lower enantioselectivity and activity. PPM ligands attached to water soluble dendrimer fragments allowed hydrogenation in water solution with ees up to 94,%, albeit with much lower activity compared to reactions in methanol with the homogeneous catalyst. [source] Systematic Study of Selected Diagonalization Methods for Configuration Interaction MatricesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2001Matthew L. Leininger Abstract Several modifications to the Davidson algorithm are systematically explored to establish their performance for an assortment of configuration interaction (CI) computations. The combination of a generalized Davidson method, a periodic two-vector subspace collapse, and a blocked Davidson approach for multiple roots is determined to retain the convergence characteristics of the full subspace method. This approach permits the efficient computation of wave functions for large-scale CI matrices by eliminating the need to ever store more than three expansion vectors (bi) and associated matrix-vector products (,i), thereby dramatically reducing the I/O requirements relative to the full subspace scheme. The minimal-storage, single-vector method of Olsen is found to be a reasonable alternative for obtaining energies of well-behaved systems to within ,Eh accuracy, although it typically requires around 50% more iterations and at times is too inefficient to yield high accuracy (ca. 10,10Eh) for very large CI problems. Several approximations to the diagonal elements of the CI Hamiltonian matrix are found to allow simple on-the-fly computation of the preconditioning matrix, to maintain the spin symmetry of the determinant-based wave function, and to preserve the convergence characteristics of the diagonalization procedure. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1574,1589, 2001 [source] ChemInform Abstract: A Systematic Study of the Crystal Structures of TlMX4 (M: Al, Ga; X: Cl, Br, I).CHEMINFORM, Issue 32 2009Tudor Timofte Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] How Post-Translational Modifications Influence Amyloid Formation: A Systematic Study of Phosphorylation and Glycosylation in Model PeptidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2010Malgorzata Broncel Abstract A reciprocal relationship between phosphorylation and O-glycosylation has been reported for many cellular processes and human diseases. The accumulated evidence points to the significant role these post-translational modifications play in aggregation and fibril formation. Simplified peptide model systems provide a means for investigating the molecular changes associated with protein aggregation. In this study, by using an amyloid-forming model peptide, we show that phosphorylation and glycosylation can affect folding and aggregation kinetics differently. Incorporation of phosphoserines, regardless of their quantity and position, turned out to be most efficient in preventing amyloid formation, whereas O-glycosylation has a more subtle effect. The introduction of a single ,-galactose does not change the folding behavior of the model peptide, but does alter the aggregation kinetics in a site-specific manner. The presence of multiple galactose residues has an effect similar to that of phosphorylation. [source] Synthesis, Microwave-Assisted Polymerization, and Polymer Properties of Fluorinated 2-Phenyl-2-oxazolines: A Systematic StudyCHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2008Matthias Lobert Dr. Abstract We present a detailed systematic study of the synthesis and ability of fluorinated 2-phenyl-2-oxazolines to undergo polymerization. The synthesis of these compounds is based on a two-step procedure that gives the desired 2-oxazolines in moderate-to-good yields. All the compounds were fully characterized by IR and NMR (1H, 13C, and 19F) spectroscopy, mass spectrometry, and elemental analysis. The 2-oxazolines were subsequently used as monomers for living cationic ring-opening polymerization (CROP) with microwave irradiation as the heat source (T=140,°C), nitromethane as the solvent, and methyl tosylate as the initiator. The linear first-order kinetic plots of the polymerizations accompanied by a linear increase of the molecular weight with conversion and low polydispersity index (PDI) values (generally below 1.30) indicate a living polymerization mechanism. The resulting polymerization rates reflect a strong sensitivity to the quantity of fluorine substituents in general and the presence or absence of ortho -fluoro substituents of the phenyl ring in particular. All the polymers were isolated and characterized by size-exclusion chromatography and MALDI-TOF mass spectrometry. Finally, a detailed investigation of selected polymer properties was performed by using differential scanning calorimetry, thermogravimetric analysis, and contact-angle measurements, thus resulting in structure,property relationships. Whereas the thermal properties of the polymers are mostly influenced by the presence of ortho -fluoro substituents, the surface properties are mainly determined by the presence of para - and/or meta -fluoro substituents. [source] A Promising Psychosocial Intervention: Next Steps Include Systematic Study and Creative ExtensionCLINICAL PSYCHOLOGY: SCIENCE AND PRACTICE, Issue 2 2004Cheryl A. King Sloan and Marx (this issue) provide a comprehensive and thoughtful review of the written exposure paradigm, noting that it is a promising psychosocial intervention. They focus on possible explanatory theories and close their review by advocating for research aimed at understanding mechanisms of action. While this critically important research is being conducted by some investigators, it will be important for others to consider modifications or enhancements that might improve the efficacy and effectiveness of the written exposure paradigm and still others to consider the myriad of related intervention possibilities raised by the promising findings. That is, the emerging data on the written exposure paradigm have substantial heuristic value. There is insufficient psychosocial intervention research being conducted, and we have barely scratched the surface of possibilities related to this strategy. [source] Systematic study of the genus Cyphononyx (Hymenoptera: Pompilidae) occurring in JapanENTOMOLOGICAL SCIENCE, Issue 2 2004Akira SHIMIZU Abstract Generic characteristics and phylogenetic relationships of the genus Cyphononyx are presented, together with a brief review of the biology of the genus. It is shown that only one species of the genus, C. fulvognathus (Rohwer), occurs in Japan. This species is distributed also in Taiwan and south China, and has hitherto been recognized under the name of C. dorsalis. In addition, two new combinations are presented: Cyphononyx hirtus (Haupt, 1935) (= Cryptochilus hirtus Haupt) and Cyphononyx plebejus (de Saussure, 1867) (= Agenia plebeja de Saussure), both of which were recorded from the Oriental Region. [source] Systematic study of interfacial interactions between clays and an ionomerJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Yan Gao Abstract To study the interfacial interactions between an ionomer [poly(ethylene- co -acrylic acid) neutralized by zinc salts (PI)] and clays, PI,clay nanocomposites were prepared using a solution method. Two types of commercially available montmorillonite clays respectively K10 and KSF were used, and were modified with organic modifiers with chain lengths of 12,18 carbons. The interactions between the PI, clays, and modifiers were evaluated through study of the structure, morphology, and properties of the PI,clay nanocomposites. We found that the modifiers were successfully intercalated into the clay layers (Fourier transform infrared spectroscopy). The clay modified with a long-chain agent showed an exfoliated nature in the nanocomposite. The thermal stability and storage modulus of PI were improved greatly by the addition of the clays, especially when the long-chain modifier was used (thermogravimetric analysis and dynamic mechanical analysis). The differential scanning calorimetry results show that clay layers are inserted into the clusters because of solvent-directed morphological evolution, so the transition of the ionic domains and the crystallinity of PI are changed. The interaction between PI, the modifier, and the silicate layer played an important role in the determination of the properties of the nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Systematic study on crystal-contact engineering of diphthine synthase: influence of mutations at crystal-packing regions on X-ray diffraction qualityACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2008Hisashi Mizutani It is well known that protein crystallizability can be influenced by site-directed mutagenesis of residues on the molecular surface of proteins, indicating that the intermolecular interactions in crystal-packing regions may play a crucial role in the structural regularity at atomic resolution of protein crystals. Here, a systematic examination was made of the improvement in the diffraction resolution of protein crystals on introducing a single mutation of a crystal-packing residue in order to provide more favourable packing interactions, using diphthine synthase from Pyrococcus horikoshii OT3 as a model system. All of a total of 21 designed mutants at 13 different crystal-packing residues yielded almost isomorphous crystals from the same crystallization conditions as those used for the wild-type crystals, which diffracted X-rays to 2.1,Å resolution. Of the 21 mutants, eight provided crystals with an improved resolution of 1.8,Å or better. Thus, it has been clarified that crystal quality can be improved by introducing a suitable single mutation of a crystal-packing residue. In the improved crystals, more intimate crystal-packing interactions than those in the wild-type crystal are observed. Notably, the mutants K49R and T146R yielded crystals with outstandingly improved resolutions of 1.5 and 1.6,Å, respectively, in which a large-scale rearrangement of packing interactions was unexpectedly observed despite the retention of the same isomorphous crystal form. In contrast, the mutants that provided results that were in good agreement with the designed putative structures tended to achieve only moderate improvements in resolution of up to 1.75,Å. These results suggest a difficulty in the rational prediction of highly effective mutations in crystal engineering. [source] Strategies in Human Nonmonotonic ReasoningCOMPUTATIONAL INTELLIGENCE, Issue 3 2000Marilyn Ford Although humans seem adept at drawing nonmonotonic conclusions, the nonmonotonic reasoning systems that researchers develop are complex and do not function with such ease. This paper explores people's reasoning processes in nonmonotonic problems. To avoid the problem of people's conclusions being based on knowledge rather than on some reasoning process, we developed a scenario about life on another planet. Problems were chosen to allow the systematic study of people's understanding of strict and nonstrict rules and their interactions. We found that people had great difficulty reasoning and we identified a number of negative factors influencing their reasoning. We also identified three positive factors which, if used consistently, would yield rational and coherent reasoning,but no subject achieved total consistency. (Another possible positive factor, specificity, was considered but we found no evidence for its use.) It is concluded that nonmonotonic reasoning is hard. When people need to reason in a domain where they have no preconceived ideas, the foundation for their reasoning is neither coherent nor rational. They do not use a nonmonotonic reasoning system that would work regardless of content. Thus, nonmonotonic reasoning systems that researchers develop are expected to do more reasoning than humans actually do! [source] Single-cell detection by gradient echo 9.4 T MRI: a parametric studyCONTRAST MEDIA & MOLECULAR IMAGING, Issue 4 2006P. Smirnov Abstract Recent studies have shown that cell migration can be monitored in vivo by magnetic resonance imaging after intracellular contrast agent incorporation. This is due to the dephasing effect on proton magnetization of the local magnetic field created by a labelled cell. Anionic iron oxide nanoparticles (AMNP) are among the most efficient and non-toxic contrast agents to be spontaneously taken up by a wide variety of cells. Here we measured the iron load and magnetization of HeLa tumour cells labelled with AMNP, as a function of the external magnetic field. High-resolution gradient echo 9.4,T MRI detected individual labelled cells, whereas spin echo sequences were poorly sensitive. We then conducted a systematic study in order to determine the gradient echo sequence parameters (echo time, cell magnetization and resolution) most suitable for in vivo identification of single cells. Copyright © 2006 John Wiley & Sons, Ltd. [source] National Adoption of International Accounting Standards: An Institutional PerspectiveCORPORATE GOVERNANCE, Issue 3 2010William Judge ABSTRACT Manuscript Type: Empirical Research Question/Issue: Effective corporate governance requires accurate and reliable financial information. Historically, each nation has developed and pursued its own financial standards; however, as financial markets consolidate into a global market, there is a need for a common set of financial standards. As a result, there is a movement towards harmonization of international financial reporting standards (IFRS) throughout the global economy. While there has been considerable research on the effects of IFRS adoption, there has been relatively little systematic study as to the antecedents of IFRS adoption. Consequently, this study seeks to understand why some economies have quickly embraced IFRS standards while others partially adopt IFRS and still others continue to resist. Research Findings/Results: After controlling for market capitalization and GDP growth, we find that foreign aid, import penetration, and level of education achieved within a national economy are all predictive of the degree to which IFRS standards are adopted across 132 developing, transitional and developed economies. Theoretical/Academic Implications: We found that all three forms of isomorphic pressures (i.e., coercive, mimetic, and normative) are predictive of IFRS adoption. Consequently, institutional theory with its emphasis on legitimacy-seeking by social actors was relatively well supported by our data. This suggests that the IFRS adoption process is driven more by social legitimization pressures, than it is by economic logic. Practitioner/Policy Implications: For policy makers, our findings suggest that the institutional pressures within an economy are the key drivers of IFRS adoption. Consequently, policy makers should seek to influence institutional pressures that thwart and/or enhance adoption of IFRS. For executives of multinational firms, our findings provide insights that can help to explain and predict future IFRS adoption within economies where their foreign subsidiaries operate. This ability could be useful for creating competitive advantages for foreign subsidiaries where IFRS adoption was resisted, or avoiding competitive disadvantages for foreign subsidiaries unfamiliar with IFRS standards. [source] Growth of ZnO crystals by vapour transport: Some ways to act on physical propertiesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2006R. Tena-Zaera Abstract Nowadays, the growth of ZnO by vapor transport in silica ampoules is generally made in presence of graphite. As it has been already shown, this means that the growth process is carried out in presence of a Zn excess. In order to control that and act, as a consequence, on the physical properties of crystals we have performed a systematic study of the growth process in a wide range of Zn excess compositions using well defined experimental conditions. As a preliminary characterization, optical absorption and electrical properties have been analyzed at room temperature. The results show how some physical properties of as-grown ZnO crystals can be changed in a controlled way by an adequate combination of different growth conditions such as graphite covering of inner ampoule walls, thermal difference between source material and crystallization zone and additional gas (composition and pressure). In this frame some post-growth annealing processes can be avoided reducing the time and cost of processes. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth of tin oxide nanocrystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005L. Zanotti Abstract Functional oxides are presently much investigated as regards not only their basic properties, but also their actual and potential applications. Tin oxides appear particularly interesting when grown in nanowire shape (SnO2 -NW) because of their electronic- and sensor-device applications. In this paper the results of a systematic study on nucleation and growth of SnO2 -NWs, when an open-tube vapor-transport technique is employed, are reported and discussed. The vapor transport conditions have been investigated in greater detail and for the first time a growth model is proposed. Functional tests at different temperatures and gaseous compositions have proved that the SnO2 -NW are suitable for the preparation of highly-sensitive and stable gas sensors. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Screen for genes differentially expressed during regeneration of the zebrafish caudal finDEVELOPMENTAL DYNAMICS, Issue 3 2004Bhaja K. Padhi Abstract The zebrafish caudal fin constitutes an important model for studying the molecular basis of tissue regeneration. The cascade of genes induced after amputation or injury, leading to restoration of the lost fin structures, include those responsible for wound healing, blastema formation, tissue outgrowth, and patterning. We carried out a systematic study to identify genes that are up-regulated during "initiation" (1 day) and "outgrowth and differentiation" (4 days) of fin regeneration by using two complementary methods, suppression subtraction hybridization (SSH) and differential display reverse transcriptase polymerase chain reaction (DDRT-PCR). We obtained 298 distinct genes/sequences from SSH libraries and 24 distinct genes/sequences by DDRT-PCR. We determined the expression of 54 of these genes using in situ hybridization. In parallel, gene expression analyses were done in zebrafish embryos and early larvae. The information gathered from the present study provides resources for further investigations into the molecular mechanisms of fin development and regeneration. Developmental Dynamics 231:527,541, 2004. © 2004 Wiley-Liss, Inc. [source] Defining and measuring braiding intensityEARTH SURFACE PROCESSES AND LANDFORMS, Issue 14 2008Roey Egozi Abstract Geomorphological studies of braided rivers still lack a consistent measurement of the complexity of the braided pattern. Several simple indices have been proposed and two (channel count and total sinuosity) are the most commonly applied. For none of these indices has there been an assessment of the sampling requirements and there has been no systematic study of the equivalence of the indices to each other and their sensitivity to river stage. Resolution of these issues is essential for progress in studies of braided morphology and dynamics at the scale of the channel network. A series of experiments was run using small-scale physical models of braided rivers in a 3 m , 20 m flume. Sampling criteria for braid indices and their comparability were assessed using constant-discharge experiments. Sample hydrographs were run to assess the effect of flow variability. Reach lengths of at least 10 times the average wetted width are needed to measure braid indices with precision of the order of 20% of the mean. Inherent variability in channel pattern makes it difficult to achieve greater precision. Channel count indices need a minimum of 10 cross-sections spaced no further apart than the average wetted width of the river. Several of the braid indices, including total sinuosity, give very similar numerical values but they differ substantially from channel-count index values. Consequently, functional relationships between channel pattern and, for example, discharge, are sensitive to the choice of braid index. Braid indices are sensitive to river stage and the highest values typically occur below peak flows of a diurnal (melt-water) hydrograph in pro-glacial rivers. There is no general relationship with stage that would allow data from rivers at different relative stage to be compared. At present, channel count indices give the best combination of rapid measurement, precision, and range of sources from which measurements can be reliably made. They can also be related directly to bar theory for braided pattern development. Copyright © 2008 John Wiley & Sons, Ltd. [source] 5 DIAGNOSTIC PITFALLS IN THE ECHOCARDIOGRAPHIC EVALUATION OF HYPERTROPHIC OBSTRUCTIVE CARDIOMYOPATHY (HOCM) REFERRED FOR CATHETER INTERVENTIONAL THERAPYECHOCARDIOGRAPHY, Issue 1 2004G. Beer Introduction: Generally, the diagnosis of typical HOCM with subaortic obstruction and a dynamic pressure gradient across the left ventricular outflow tract is made by noninvasive diagnostic procedures with great certainty by employing transthoracic (TTE) and/or transoesophageal (TEE) echocardiography. However, in patients with asymmetric septal hypertrophy pitfalls in echocardiographic examination may arise from several additional diseases as described in casuistic reports. To date systematic investigations in patients referred for catheter interventional therapy of HOCM are lacking. Patients and Methods: Therefore we investigated for the first time in a systematic study 200 symptomatic patients. (180 consecutive and 20 nonconsecutive patients; functional class 3 or 4 according to NYHA) with HOCM who were referred for this new catheter interventional therapy. In all patients TTE, bicycle exercise Doppler echocardiography and multiplane TEE were performed. Results: In 4 of 180 consecutive patients. (2.2%) discrete subvalvular membranous aortic stenosis (DSAS) (3 female patients and 1 male patient; age 20 to 58 years; mean septal diameter 19 mm; Sam-like motion in all 4 patients) was made. In all cases the diagnosis could be confirmed by surgical treatment. TEE evaluation was of crucial importance with demonstration of a typical subvalvular membrane that was situated a few millimeters below the aortic valve. In all cases a typical asymmetric septal hypertrophy mimicking HOCM was seen. Additionally, in 2 patients there was a conincidence of severe symptomatic valvular aortic stenosis and HOCM and in 1 patient a tunnel type of subvalvular aortic stenosis was present. Conclusion: These results show the potential pitfalls in echocardiographic diagnosis of HOCM. Especially, the frequency of DSAS in symptomatic patients referred for HOCM is unexpectedly high (2.2%). Especially in patients in whom TTE is of insufficient quality, investigation employing multiplane TEE with careful evaluation of the small poststenotic subvalvular area in HOCM is of crucial importance. This is of special significance prior to catheter interventional therapy, because in these patients surgical treatment is mandatory. [source] Emergency management of the morbidly obeseEMERGENCY MEDICINE AUSTRALASIA, Issue 4 2004Peter Grant Abstract Objectives: To identify the difficulties encountered with the emergency management of morbidly obese patients and formulate recommendations to streamline care. Methods: An English language literature search was undertaken using Medline (1966,2003) with key words ,morbid obesity',anaesthesia',imaging',obesity',emergency',transportation',retrieval',critical illness' and ,monitoring'. Potential articles were selected for content applicable to emergency medicine based on title and abstract and reviewed in detail. Reference lists were manually searched for further relevant articles. In view of the very limited systematic study in this area, all information deemed by the authors' to be of assistance to the emergency physician was included regardless of evidence level. Additional information was sought from standard critical care textbooks and their bibliographies and through personal communication with local ambulance and retrieval services. The authors' unpublished personal experience in providing emergency care to the morbidly obese was included for aspects of management not documented in medical literature. Results: Obesity levels and associated health problems are rapidly rising in Australia. Few studies were identified dealing with critical illness in the morbidly obese and none specifically addressing ED management. Problems identified included size related logistical issues, and limitations of physical assessment, monitoring and routine investigations. Invasive procedures, intubation and ventilation can be particularly problematic, and modified techniques may be required. Limited data indicates a poorer outcome from critical illness most marked in the case of blunt traumatic injury. Conclusion: Very obese patients present a variety of logistical and medical challenges for EDs. A series of recommendations are made based on available data. Further studies in this area would be desirable to more specifically address ED issues. [source] Micronuclei and chromatid buds are the result of related genotoxic eventsENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 1 2001Luis Serrano-García Abstract Chromatin buds (CHB), broken eggs, or budding cell nuclei are structures similar to micronuclei (MN) in shape, structure, and size, which are linked to the main nuclei of cells by a thread or stalks of chromatin. They have been observed in numerous cell types and there are reports of their existence relating them with MN or with genotoxic events. However, there is no systematic study reporting their frequency and no experiment has been done to ascertain whether they are really induced by genotoxins. Furthermore, they have been discarded as genotoxic events with the argument that they are not formed in dividing cells. Studies are presented here that indicate that CHB can be considered as genotoxic events and that their origin is comparable to that of MN. Bromodeoxyuridine (BrdU) was used to label proliferating lymphocytes, which were later identified by means of an immunohistochemical method, using the H2O2,DAB stain. The results show that CHB are consistently formed where MN are seen. CHB were induced by the clastogen mitomycin C (MMC) as well as by the aneuploidogen colcemid, with frequencies similar to MN in both cases, and to multinucleated cells in the case of colcemid. CHB occur in lymphocytes of smokers with frequencies similar to those of MN, and we found that the infection with Taenia solium metacestodes induced a comparable increase of both MN and CHB frequency in lymphocytes from pigs. Environ. Mol. Mutagen. 38:38,45, 2001 © 2001 Wiley-Liss, Inc. [source] Checking the Route to Cluster HelicatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2008Manuel R. Bermejo Abstract The aim of the work described here was to test the general applicability of our recently reported route to cluster helicates and to carry out a systematic study to relate the structural and coordinative properties of the organic strands with the microarchitectures of the resulting cluster helicates. Nine new ZnII, CuI and AgI complexes were prepared from three Schiff base ligands [H2La: bis(4-methyl-3-thiosemicarbazone)-2,6-diacetylpyridine; H2Lb: bis(4-methyl-3-thiosemicarbazone)-2,6-diacetylbenzene; H2Lc: bis(4-ethyl-3-thiosemicarbazone)-2,6-diacetylbenzene]. The experimental data confirm that AgI and CuI tetranuclear cluster helicates were obtained with a [M4(Lx)2] stoichiometry, and this finding demonstrates the general applicability of the synthetic route. The cluster helicates presented in this work were characterized for the first time in solution by NMR spectroscopy. In addition, six of the nine complexes were characterized by X-ray diffraction studies, and three of them were found to be tetranuclear cluster helicates. A detailed study of these three crystal structures leads us to state that the changes introduced in the organic strands do not prevent the assembly of the tetranuclear cluster dihelicates, but they do affect the microarchitectures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Population-based case,control study of morale in Parkinson's diseaseEUROPEAN JOURNAL OF NEUROLOGY, Issue 3 2009J. Benito-León Background:, Parkinson's disease (PD) is associated with cognitive, psychiatric, and motor features. Each could contribute to a poor sense of well-being and low morale. A systematic study of morale in community-dwelling PD cases has not been performed. Methods:, A total of 52 PD cases and 260 matched controls from three Spanish communities were assessed using the Philadelphia Geriatric Center Morale Scale (PGCMS) (range = 0[low morale],17). The PGCMS includes three dimensions of psychological well-being: agitation, lonely dissatisfaction, and attitude toward own aging. Results:, The PGCMS score was lower in PD cases than controls (8.71 ± 3.64 vs. 11.03 ± 2.77, P < 0.001), as were the agitation subscore (3.36 ± 1.91 vs. 4.07 ± 1.59, P < 0.05), lonely dissatisfaction subscore (3.48 ± 1.36 vs. 4.11 ± 1.12, P < 0.01), and attitude toward own aging subscore (1.86 ± 1.37 vs. 2.85 ± 1.13, P < 0.001). In a linear regression analysis that adjusted for depressive symptoms and other covariates, PD cases had a lower PGCMS score than controls (P < 0.001). Conclusions:, Morale was significantly lower in community-dwelling PD cases than matched controls. The detection and possible treatment of this problem may improve the psychological well-being of patients with this disease. [source] The Tautomerism of 5-Amino-3-oxo-1,2,4-thiadiazole: An Experimental and Theoretical StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 33 2007Arantxa Encinas Abstract The 1,2,4-thiadiazole system was the subject of our research as a consequence of the pharmacological activity of some derivatives as GSK3 inhibitors. Therefore, in order to explore the active form responsible for receptor interaction, a systematic study of the tautomerism in the 5-amino-3-oxo-1,2,4-thiadiazole system was performed by using experimental and theoretical methods. Thus, the relative stability of the possible tautomers was studied in the gas phase by density functional theory and local density functional methods. The theoretical study in solution was carried out by using severalcontinuum solvation models. Finally, experimental studies were carried out to unambiguously establish the tautomeric form.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Phenylphosphoric Acid as a New Additive to Inhibit Olefin Isomerisation in Ruthenium-Catalysed Metathesis ReactionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2007Nélida Gimeno Abstract A systematic study of the ruthenium-catalysed metathesis of alkenes containing hydrogen-bonding substituents (namely urea and thiourea groups) is presented. Under standard metathesis conditions, several of the substrates under study undergo alkene isomerisation instead of the targeted metathesis. However, in the course of these investigations it has been established that this unwanted isomerisation process can be suppressed by addition of phenylphosphoric acid to the reaction mixture. Some other potential isomerisation inhibitors (e.g. benzoic acid and salts of phosphoric acid) have been studied and their performance compared to that of phenylphosphoric acid. To extend the scope of phenylphosphoric acid, we also studied the metathesis of 1,3-diallylurea. Interestingly, not only did we observe the complete suppression of the isomerisation process, but also that it is possible to obtain instead of the ring-closing metathesis (RCM) product,ADMET oligomers resulting from the cross-metathesis of diallylurea at higher concentrations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] CD4 is expressed by epidermal Langerhans' cells predominantly as covalent dimersEXPERIMENTAL DERMATOLOGY, Issue 5 2003G. W. Lynch Abstract:, Langerhans' cells (LC) of skin are CD4 expressing, dendritic, antigen-presenting cells, that are essential for activation of primary immune responses and are productively infected by HIV. We have shown previously that lymphocytes and monocytes express CD4 both as monomers and covalently linked homodimers. In those cells the 55-kDa monomer structure predominates. LC in un-fractionated human epidermal cell (EC) suspension also expresses both forms of CD4, but in EC the dimer form is predominant. Because isolation of LC into single cell suspension by trypsin, as is routinely used for LC isolation, degrades CD4, a systematic study for an alternate procedure for LC isolation was performed. Thus it was found that collagenase blend F treatment can efficiently release LC into suspension, under conditions of only minimal degradation of control soluble recombinant CD4 or CEM-T4 or THP-1 cell CD4, or importantly of LC surface CD4. SDS,PAGE immunoblotting of purified LC extracted from EC by collagenase confirmed CD4 structure as predominantly 110-kDa dimers, with only minimal 55-kDa monomers. The suitability of LC prepared thus for functional studies was demonstrated with binding of functional ligand HIV gp120. It remains to be determined, however, why tissue embedded LC express mainly CD4 dimers, but single-celled blood lymphocytes and monocytes mainly monomers. [source] Single amino acid repeats in signal peptidesFEBS JOURNAL, Issue 15 2010abaj There has been an increasing interest in single amino acid repeats ever since it was shown that these are the cause of a variety of diseases. Although a systematic study of single amino acid repeats is challenging, they have subsequently been implicated in a number of functional roles. In general surveys, leucine runs were among the most frequent. In the present study, we present a detailed investigation of repeats in signal peptides of secreted and type I membrane proteins in comparison with their mature parts. We focus on eukaryotic species because single amino acid repeats are generally rather rare in archaea and bacteria. Our analysis of over 100 species shows that repeats of leucine (but not of other hydrophobic amino acids) are over-represented in signal peptides. This trend is most pronounced in higher eukaryotes, particularly in mammals. In the human proteome, although less than one-fifth of all proteins have a signal peptide, approximately two-thirds of all leucine repeats are located in these transient regions. Signal peptides are cleaved early from the growing polypeptide chain and then degraded rapidly. This may explain why leucine repeats, which can be toxic, are tolerated at such high frequencies. The substantial fraction of proteins affected by the strong enrichment of repeats in these transient segments highlights the bias that they can introduce for systematic analyses of protein sequences. In contrast to a general lack of conservation of single amino acid repeats, leucine repeats were found to be more conserved than the remaining signal peptide regions, indicating that they may have an as yet unknown functional role. [source] Amorphous Calcium Carbonate is Stabilized in ConfinementADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Christopher J. Stephens Abstract Biominerals typically form within localized volumes, affording organisms great control over the mineralization process. The influence of such confinement on crystallization is studied here by precipitating CaCO3 within the confines of an annular wedge, formed around the contact point of two crossed half-cylinders. The cylinders are functionalized with self-assembled monolayers of mercaptohexadecanoic acid on gold. This configuration enables a systematic study of the effects of confinement since the surface separation increases continuously from zero at the contact point to macroscopic (mm) separations. While oriented rhombohedral calcite crystals form at large (>10,µm) separations, particles with irregular morphologies and partial crystallinity are observed as the surface separation approaches the dimensions of the unconfined crystals (5,10,µm). Further increase in the confinement has a significant effect on the crystallization process with flattened amorphous CaCO3 (ACC) particles being formed at micrometer separations. These ACC particles show remarkable stability when maintained within the wedge but rapidly crystallize on separation of the cylinders. A comparison of bulk and surface free-energy terms shows that ACC cannot be thermodynamically stable at these large separations, and the stability is attributed to kinetic factors. This study therefore shows that the environment in which minerals form can have a significant effect on their stability and demonstrates that ACC can be stabilized with respect to the crystalline polymorphs of CaCO3 by confinement alone. That ACC was stabilized at such large (micrometer) separations is striking, and demonstrates the versatility of this strategy, and its potential value in biological systems. [source] Why does Kluyveromyces lactis not grow under anaerobic conditions?FEMS YEAST RESEARCH, Issue 3 2006Comparison of essential anaerobic genes of Saccharomyces cerevisiae with the Kluyveromyces lactis genome Abstract Although some yeast species, e.g. Saccharomyces cerevisiae, can grow under anaerobic conditions, Kluyveromyces lactis cannot. In a systematic study, we have determined which S. cerevisiae genes are required for growth without oxygen. This has been done by using the yeast deletion library. Both aerobically essential and nonessential genes have been tested for their necessity for anaerobic growth. Upon comparison of the K. lactis genome with the genes found to be anaerobically important in S. cerevisiae, which yielded 20 genes that are missing in K. lactis, we hypothesize that lack of import of sterols might be one of the more important reasons that K. lactis cannot grow in the absence of oxygen. [source] Hydrophilic Sparse Ionic Monolayer-Protected Metal Nanoparticles: Highly Concentrated Nano-Au and Nano-Ag "Inks" that can be Sintered to Near-Bulk Conductivity at 150,°CADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Bibin T. Anto Here, monolayer-protected gold and silver nanoparticles with extremely high solvent dispersibility (over 200,mg mL,1 in water and glycols) and low coalescence temperature (approximately 150,°C, measured by the percolation transition temperature Tp) are developed, to reach conductivities better than 1,×,105,S cm,1. These materials are suitable for inkjet and other forms of printing on substrates that may be solvent- and/or temperature-sensitive, such as for plastic electronics, and as bus lines for solar and lighting panels. This is achieved using a new concept of the sparse ionic protection monolayer. The metal nanoparticles are initially protected by a two-component mixed ligand shell comprising an ,-functionalized ionic ligand and a labile ligand. These are selectively desorbed to give a sparse shell of the ,-ionic ligands of ca. 25% coverage. Through a systematic study of different monolayer-protected Au nanoparticles using FTIR spectroscopy, supported by XPS and DSC, it is shown that Tp is not determined by thermodynamic size melting or by surface area effects, as previously thought, but by the temperature when ca. 80% of the dense monolayer is eliminated. Therefore, Tp depends on the thermal stability and packing density of the shell, rather than the size of the metal core, while the solubility characteristics depend strongly on the exposed terminal group. [source] The New Men's History and the Peculiar Absence of Gendered Power: Some Remedies from Early American Gender HistoryGENDER & HISTORY, Issue 1 2004Toby L. Ditz Historians with feminist commitments have expressed reservations about men's history and men's studies. This unease has existed more or less from the first appearance of men's history as a specialised area of inquiry, and shows no signs of abating. The first part of this article explores the sources of this unease. It discusses several guiding premises of men's history and shows that they tend to lead to the occlusion of men's gendered power over women. Nonetheless, the scrutiny of the gender of men is the logical outgrowth of several decades of theoretical and empirical work on gender,witness the many historians of women and gender who have recently turned their attention to the systematic study of manliness and masculinity. With the help of examples drawn from the scholarship on the history of the British colonies in America and the early United States, the second part of this article enumerates several strategies for successfully highlighting men's gendered power in histories of manliness and masculinity. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||