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Different Donors (different + donor)

Distribution by Scientific Domains

Medical Sciences	50%
Chemistry	20%

Selected Abstracts

Nanostructure and Optoelectronic Characterization of Small Molecule Bulk Heterojunction Solar Cells by Photoconductive Atomic Force Microscopy

ADVANCED FUNCTIONAL MATERIALS, Issue 19 2010
Xuan-Dung Dang
Abstract Photoconductive atomic force microscopy is employed to study the nanoscale morphology and optoelectronic properties of bulk heterojunction solar cells based on small molecules containing a benzofuran substituted diketopyrrolopyrrole (DPP) core (3,6-bis(5-(benzofuran-2-yl)thiophen-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione, DPP(TBFu)2, and [6,6],phenyl-C71 -butyric acid methyl ester (PC71BM), which were recently reported to have power conversion efficiencies of 4.4%. Electron and hole collection networks are visualized for blends with different donor:acceptor ratios. Formation of nanostructures in the blends leads to a higher interfacial area for charge dissociation, while maintaining bicontinuous collection networks; conditions that lead to the high efficiency observed in the devices. An excellent agreement between nanoscale and bulk open-circuit voltage measurements is achieved by surface modification of the indium tin oxide (ITO) substrate by using aminopropyltrimethoxysilane. The local open-circuit voltage is linearly dependent on the cathode work function. These results demonstrate that photoconductive atomic force microscopy coupled with surface modification of ITO substrate can be used to study nanoscale optoelectronic phenomena of organic solar cells. [source]

Nanostructure and Optoelectronic Characterization of Small Molecule Bulk Heterojunction Solar Cells by Photoconductive Atomic Force Microscopy

A computational study of the carboxylic acid of phloroglucinol in vacuo and in water solution

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2010
Liliana Mammino
Abstract 2,4,6-Trihydroxybenzoic acid (FA) is the carboxylic acid of phloroglucinol and, in turn, the parent compound of many biologically active compounds. The biological activities of FA are "extreme" among trihydroxybenzoic acids (e.g., lowest antioxidant activity, highest toxicity toward crustaceans). A complete MP2/6-31++G(d,p) conformational study in vacuo shows that the lowest energy conformers contain two intramolecular hydrogen bonds between the COOH function and the two ortho phenolic OH, with the Z form of COOH preferred over the E form. Comparisons with conformers in which the H-bonds are removed enable fairly reliable evaluations of their energy, because of an off-plane shift of COOH on H-bond removal, decreasing the effects of lone pair repulsion. Comparisons with the other hydroxybenzoic acids (extensively calculated in vacuo at the same level of theory) suggest that FA has the strongest intramolecular H-bonds. PCM calculations of FA in water solution show the same sequence of relative stabilities as in vacuo, with narrower differences because of the greater solvent stabilization of higher energy conformers. Calculations of adducts with water molecules H-bonded to different donor,acceptor centers of FA show the preferred arrangements of water molecules around the different regions of FA and confirm that the stronger intramolecular H-bonds are not broken on competition with the possibility of formation of intermolecular H-bonds. HF/6-31++G(d,p) calculations of adducts, in which the FA molecule is completely surrounded by water molecules, show that 14,16 water molecules (depending on the FA conformer geometry) realize arrangements corresponding to a presumable first solvation layer, with all the water molecules directly H-bonded to donor,acceptor centers of FA or bridging water molecules directly H-bonded to them. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source]

Comparative Sol,Hydro(Solvo)thermal Synthesis of TiO2 Nanocrystals

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2006
Xianfeng Yang
Abstract Three small inorganic compounds [acetic acid (CH3COOH), nitric acid (HNO3), and hydrochloric acid (HCl)] andfive small organic compounds [n -butyl alcohol (CH3CH2CH2CH2OH), 1,2-propanediol (CH2OHCHOHCH3), propane-1,3-dicarboxylic acid (HOOCCH2COOH), butane-1,4-dicarboxylic acid (HOOCCH2CH2COOH), and ethylenediamine (H2NCH2CH2NH2)] with different donors (Cl,, NO3,, OH, COO,, and NH2) are used respectively and comparatively in different reaction media for tailoring the sol,hydrothermal synthesis of TiO2 nanocrystals at a specific reaction temperature and/or for different reaction times. Both anatase and rutile with a variety of nanostructures such as nanocubes, nanorods, nanoneedles, and their self-assembled nanospheres are selectively grown. Well-defined and crystalline anatase nanocrystals with a narrow size distribution are prepared in the presence of n -butyl alcohol. With the use of HCl, nanoneedles and their assembled nanospheres of phase-pure rutile are obtained under much less drastic conditions, even at 100 °C and for only two hours. The effects of the reaction media, synthesis temperatures, and aging times on the structures and shapes of the products are investigated in detail by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

New Organic Nonlinear Optical Polyene Crystals and Their Unusual Phase Transitions,

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2007
O-P. Kwon
Abstract A series of new nonlinear optical chromophores based on configurationally locked polyenes (CLPs) with chiral pyrrolidine donors are synthesized. All CLP derivatives exhibit high thermal stability with decomposition temperatures Td at least > ,270,°C. Acentric single crystals of enantiopure D - and L -prolinol-based chromophores with a monoclinic space group P21 exhibit a macroscopic second-order nonlinearity that is twice as large than that of analogous dimethylamino-based crystal. This is attributed to a strong hydrogen-bonded polar polymer-like chain built by these molecules, which is aligned along the polar crystallographic b -axis. Five ,-phase CLP crystals with different donors grown from solution exhibit a reversible or irreversible thermally induced structural phase transition to a ,-phase. These phase transitions are unusual, changing the crystal symmetry from higher to lower at increasing temperatures, for example, from centrosymmetric to non-centrosymmetric, enhancing their macroscopic second-order nonlinear optical properties. [source]

A cornerstone for adequate supply of safe blood

ISBT SCIENCE SERIES: THE INTERNATIONAL JOURNAL OF INTRACELLULAR TRANSPORT, Issue 1 2006
M. Y. Zhu
Blood safety and timely adequate supply have significant impacts not only on healthcare service, but also the socio-economic development and political stability of a country. However, until a decade ago the importance has not been seriously taken in the country. Distinct blood programme and safety strategy were not always available. In certain regions of the country the supervision to establishments involved in blood collection, processing and transfusion was neither strict nor sufficient. During the early period of 1990, HIV was transmitted among plasma-apheresis donors in two central provinces. The relevant plasma-apheresis centres, in which plasma is collected solely as source materials for fractionation, were accused for wrongdoings including not performing HIV screening, and mixing red cells from different donors with same blood types before back infusion. [source]

Assessing levels of contaminants in breast milk: methodological issues and a framework for future research

PAEDIATRIC & PERINATAL EPIDEMIOLOGY, Issue 1 2008
Mary J. Renfrew
Summary To assess the scale of the possible exposure by the breast-fed infant to potentially harmful substances in breast milk, methodologically robust studies are essential. Many studies in this field, however, do not report details of crucial issues such as recruitment and milk sampling. The aims of the study reported here were to develop robust methods for the study of contaminants in breast milk, and to develop a framework for future research and population monitoring. Three cohorts of women and babies were recruited by midwives from five sites in northern England. Cohort 1 (cross-sectional, n = 322) were asked to provide two milk samples, one at one week following birth and one at a subsequent time point. Cohort 2 (longitudinal, n = 54) were asked to provide five samples at specified time points over the first 12,16 weeks after birth. Cohort 3 (convenience, n = 18), mothers of babies in the Special Care Unit, were asked to donate surplus breast milk. A novel method of analysing fat concentration in small volumes was developed and tested. A randomly selected set of samples from different donors and stages of lactation was screened for organochlorine pesticide residues, polychlorinated biphenyls, dioxins/furans, phthalates and heavy metals. A total of 453 samples were donated. Cohort 3 was the least successful route of recruitment. Cohorts 1 and 2 combined were most representative of the population. Sample collection, transport and storage procedures, and the collection of data on life style and diet, were robust and acceptable to women. Midwifery involvement in recruitment was an essential component. This study offers a framework both for the conduct of future research studies, and for the establishment of regional and national monitoring mechanisms for contaminants in breast milk. Similar work on contaminants in formula as fed to babies is needed to inform risk assessment methods. [source]

Coexpression of CD177 and membrane proteinase 3 on neutrophils in antineutrophil cytoplasmic autoantibody,associated systemic vasculitis: Anti,proteinase 3,mediated neutrophil activation is independent of the role of CD177-expressing neutrophils

ARTHRITIS & RHEUMATISM, Issue 5 2009
N. Hu
Objective Wegener's granulomatosis (WG) is strongly associated with antineutrophil cytoplasmic autoantibodies (ANCAs) directed against proteinase 3 (PR3). Recent studies have shown that membrane-bound PR3 (mPR3) is differentially expressed and colocalizes with CD177/NB1 on circulating neutrophils. We undertook this study to assess the differential expression of CD177 on neutrophils from patients with ANCA-associated systemic vasculitis (ASV) in comparison with patients with systemic lupus erythematosus (SLE), patients with rheumatoid arthritis (RA), and healthy individuals, and to investigate whether colocalization of mPR3 and CD177 affects anti-PR3,mediated neutrophil activation. Methods Expression of CD177 and mPR3 was analyzed by flow cytometry on isolated neutrophils from patients with ASV (n = 53), those with SLE (n = 30), those with RA (n = 26), and healthy controls (n = 31). Neutrophil activation mediated by anti-PR3 antibodies was assessed by measuring the oxidative burst with a dihydrorhodamine assay. Results Percentages of CD177-expressing neutrophils were significantly higher in patients with ASV and those with SLE than in healthy controls. In 3 healthy donors, CD177 expression was not detected. After priming with tumor necrosis factor ,, neutrophils remained negative for CD177 while mPR3 expression was induced. Neutrophils from CD177-negative donors or CD177, neutrophils sorted from donors with bimodal expression were susceptible to anti-PR3,mediated oxidative burst. Variation in the extent of anti-PR3,mediated neutrophil activation among different donors occurred independent of the percentage of CD177-expressing neutrophils. Conclusion Membrane expression of CD177 on circulating neutrophils is increased in patients with ASV and in those with SLE, but not in RA patients. However, primed neutrophils from CD177-negative individuals also express mPR3 and are susceptible to anti-PR3,mediated oxidative burst, suggesting that recruitment of CD177-independent mPR3 is involved in anti-PR3,induced neutrophil activation. [source]

Donor age and gestational age influence on growth factor levels in human amniotic membrane

ACTA OPHTHALMOLOGICA, Issue 6 2010
Maria J. López-Valladares
Acta Ophthalmol. 2010: 88: e211,e216 Abstract. Purpose:, Amniotic membrane (AM) is used as a biomaterial for reconstruction in ocular surface surgery. This study investigated the influence of interdonor variations and processing and preservation procedures applied to the AM on growth factors and protein levels. Methods:, Samples of human AM from thirteen donors were analysed. Collected donor data were age, parity and gestational age. Total protein amount was measured in extracts of intact AM nonpreserved, lyophilized and cryopreserved, at ,80°C and in liquid nitrogen. An enzyme-linked immunosorbent assay (ELISA) was used to assay growth factors protein levels for epidermal growth factor, basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), keratinocyte growth factor (KGF), transforming growth factor beta1 (TFG-,1) and nerve growth factor (NGF). Univariate and multivariate statistical analyses were used to study the influence of the preservation method applied and interdonor variations on growth factors levels. Results:, We detected important variations in growth factors and protein concentrations between samples from different donors. Total protein amount, bFGF, HGF, KGF and TGF-,1 showed lower levels in samples from donors with higher gestational ages and donor ages, for all groups. Conclusion:, The variability in the biochemical composition of AM from different donors is considerable, and it is related with donor factors as donor age and gestational age. As AM biochemical composition has a role in its therapeutic effects, these variations could affect the clinical results of amniotic membrane transplantation and must be taken into account in donor selection processes. [source]

Selective induction of nerve growth factor and brain-derived neurotrophic factor by LPS and allergen in dendritic cells

CLINICAL & EXPERIMENTAL ALLERGY, Issue 3 2008
O. Noga
Summary Background Neurotrophins are produced by various cells upon different stimuli and participate in the initiation and regulation of inflammation in various diseases including allergy and asthma, but little is known about the production and control of neurotrophins by dendritic cells (DCs). The aim of this study was to assess whether DCs produce the neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), and whether inflammatory stimuli or allergens are able to induce the production of neurotrophic factors. Methods Monocyte-derived dendritic cells (MoDCs) were generated from different donors. The neurotrophins NGF and BDNF were demonstrated by RT-PCR, Western blotting, flow cytometry analysis and fluorescence microscopy. MoDCs were cultured and stimulated with lipopolysaccharide (LPS) or allergen for 24 h. The supernatants and cells were collected. Measurement for NGF and BDNF was performed by ELISA. Results DCs express mRNA for the neurotrophins NGF and BDNF. Proteins were detectable by Western blot, FACS analysis and fluorescence microscopy. LPS led to an up-regulation of BDNF, while NGF was unaffected. Cell lysates demonstrated an increased amount of BDNF after stimulation with LPS or allergen, while NGF was not affected significantly. Conclusions DCs are a source of neurotrophins. LPS selectively regulates the production of BDNF. Allergen stimulation leads to an LPS-independent regulation. This contributes to a complex involvement of neurotrophins in allergic diseases. [source]