Home About us Contact
|
Home About us Contact | ||
|
|
||
Uniform Size (uniform + size)
Selected AbstractsEffect of the pupal age of Calliphora erythrocephala (Diptera: Calliphoridae) on the reproductive biology of Melittobia acasta (Walker) (Hymenoptera: Chalcidoidea: Eulophidae)ENTOMOLOGICAL SCIENCE, Issue 1 2006Nyiutaha G. IMANDEH Abstract A laboratory experiment was conducted to determine the effect of the pupal age of Calliphora erythrocephala (Meigen) on the reproductive biology (in terms of number, size, developmental time and longevity of progeny) of the parasitoid Melittobia acasta Walker. Melittobia acasta females of uniform size were given five C. erythrocephala pupae from one of four experimental age groups: 17,24 h, 24,48 h, 48,72 h and 72,96 h, for parasitization. The mean number of progeny produced from the experimental age groups for a 24 h period were 2, 7.6, 15.6 and 13.6, respectively. The parasitoids preferred hosts that were 48,72 h old. There were no significant differences in the mean development time (18.2 days) and size of progeny (mean head width = 0.38 ± 0.01 mm) produced from the experimental host age groups. The longevity of progeny from the four host age groups varied (range: 4,39 days), with those from the 48,72 h group living longest (mean = 25 days). The F1 females from the 48,72 h group were reproductively more successful than those from the other groups, producing a mean F2 progeny of 912 individuals when compared with 867, 801 and 757 individuals from the 24,48 h, 72,96 h and 17,24 h age groups, respectively. These findings make significant contributions to our knowledge of the breeding and utilization of this parasitoid for the biological control of dipteran flies in pigsties and poultry houses. [source] Facile Fabrication and Superparamagnetism of Silica-Shielded Magnetite Nanoparticles on Carbon Nitride NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Jung Woo Lee Abstract Using conventional methods to synthesize magnetic nanoparticles (NPs) with uniform size is a challenging task. Moreover, the degradation of magnetic NPs is an obstacle to practical applications. The fabrication of silica-shielded magnetite NPs on carbon nitride nanotubes (CNNTs) provides a possible route to overcome these problems. While the nitrogen atoms of CNNTs provide selective nucleation sites for NPs of a particular size, the silica layer protects the NPs from oxidation. The morphology and crystal structure of NP,CNNT hybrid material is investigated by transmission electron microscopy (TEM) and X-ray diffraction. In addition, the atomic nature of the N atoms in the NP,CNNT system is studied by near-edge X-ray absorption fine structure spectroscopy (nitrogen K-edge) and calculations of the partial density of states based on first principles. The structure of the silica-shielded NP,CNNT system is analyzed by TEM and energy dispersive X-ray spectroscopy mapping, and their magnetism is measured by vibrating sample and superconducting quantum interference device magnetometers. The silica shielding helps maintain the superparamagnetism of the NPs; without the silica layer, the magnetic properties of NP,CNNT materials significantly degrade over time. [source] Array-MLPA: comprehensive detection of deletions and duplications and its application to DMD patients,HUMAN MUTATION, Issue 1 2008Fanyi Zeng Abstract Multiplex ligation-dependent probe amplification (MLPA) is widely used to screen genes of interest for deletions and duplications. Since MLPA is usually based on size-separation of the amplification products, the maximum number of target sequences that can be screened in parallel is usually limited to ,40. We report the design of a robust array-based MLPA format that uses amplification products of essentially uniform size (100,120,bp) and distinguishes between them by virtue of incorporated tag sequences. We were thus able to increase probe complexity to 124, with very uniform product yields and signals that have a low coefficient of variance. The assay designed was used to screen the largest set studied so far (249 patients) of unrelated Duchenne muscular dystrophy (DMD) cases from the Chinese population. In a blind study we correctly assigned 98% of the genotypes and detected rearrangements in 181 cases (73%); i.e., 163 deletions (65%), 13 duplications (5%), and five complex rearrangements (2%). Although this value is significantly higher for Chinese patients than previously reported, it is similar to that found for other populations. The location of the rearrangements (76% in the major deletion hotspot) is also in agreement with other findings. The 96-well flow-through microarray system used in this research provides high-throughput and speed; hybridization can be completed in 5 to 30,minutes. Since array processing and data analysis are fully automated, array-MLPA should be easy to implement in a standard diagnostic laboratory. The universal array can be used to analyze any tag-modified MLPA probe set. Hum Mutat 29(1), 190,197, 2008. © 2007 Wiley-Liss, Inc. [source] Oxide-Assisted Growth of Semiconducting Nanowires,ADVANCED MATERIALS, Issue 7-8 2003R.-Q. Zhang Abstract In this contribution, we outline oxide-assisted growth (OAG) (distinct from the conventional metal-catalytic vapor,liquid,solid (VLS) process) for the growth of nanostructured materials. This synthesis technique, in which oxides instead of metals play an important role in inducing the nucleation and growth of nanowires, is capable of producing large quantities of high-purity silicon nanowires with a preferential growth direction, uniform size, and long length, without the need for a metal catalyst. The OAG 1D nanomaterials synthesis is complementary to, and coexistent with, the conventional metal-catalyst VLS approach, and can be utilized to produce nanowires from a host of materials other than Si including Ge nanowires, carbon nanowires, silicon and SnO2 nanoribbons, and Group III,V and II,VI compound semiconductor nanowires. [source] Antibacterial effect of silver-zeolite containing root-canal filling materialJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Abstract The aim of this study was to determine the in vitro antibacterial effect of two experimental glass ionomer cements (GICs) on Streptococcus milleri, Staphylococcus aureus, and Enterococcus faecalis after 24 and 48 h incubation by using the agar diffusion inhibitory test. Silver zeolite (SZ) was added at 0.2 and 2% mass fraction concentration to GIC (Endion). The control group was Endion with no SZ. Each of them were prepared to uniform size using a custom-made Teflon mold, and the GIC materials were prepared to form disks (n = 5 per group). The effect of these materials on the growth of three bacteria associated with endodontic infections was determined using the agar diffusion inhibitory test. The amounts of silver ion release from these materials were measured with atomic absorption spectrophotometry at 10 min, 24- and 48-h periods. The pH of samples was measured with a pH-meter at 10 min, 24- and 48-h periods. After the incubation period, the agar plates were evaluated and the degrees of bacterial inhibition were measured in millimeters. A comparison of the mean of the test materials was statistically different in each group of specimens (p < 0.05). Between the two tested materials 2% SZ containing GIC showed the largest zone of inhibition on the agar plates of all the tested strains (p < 0.05). The most inhibition in bacterial growth occurred in E. faecalis. Adding 2% SZ to GIC resulted in a significant increase in the silver release into deionized water. This study demonstrated that GIC had an inhibitory affect on Streptococcus milleri, Staphylococcus aureus, and Enterococcus faecalis and that adding SZ increases that affect proportional to its concentration. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Arborescent polymers and other dendrigraft polymers: A journey into structural diversityJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2007Mario Gauthier Abstract Arborescent polymers are characterized by a dendritic, multilevel branched architecture derived from successive grafting reactions. In spite of their much larger size, these materials display properties analogous to dendrimers and hyperbranched polymers, the two other dendritic polymer families. The distinguishing features of arborescent polymers are their assembly from polymeric building blocks of uniform size and their very high molecular weights attained in few synthetic steps. This article offers an overview of the historical aspects of the development of dendrigraft polymers, starting from our initial efforts on the synthesis of arborescent polystyrenes. Major subsequent developments in the synthetic techniques from our and other research groups allowing the synthesis of dendrigraft copolymers, tailoring of the structural characteristics of the molecules, and further simplifications to their synthesis are also reviewed, with emphasis over the broad range of architectures attainable in these systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3803,3810, 2007 [source] Structure and Properties of CdS/Regenerated Cellulose NanocompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Dong Ruan Abstract Summary: Novel inorganic-organic hybrid materials composed of cadmium sulfide (CdS) semiconducting nanocrystals and regenerated cellulose (RC) were prepared by using in situ synthesizing method. Cellulose was dissolved in a 6 wt.-% NaOH/4 wt.-% urea/thiourea aqueous solution at low temperature followed by addition of cadmium chloride (CdCl2), resulting that the CdS nanocrystals were successfully grown in situ in the cellulose solution. Nanocomposite films containing homogeneous CdS nanoparticles were obtained by casting the resulting solution. Their structure and optical properties were characterized by X-ray photoelectron spectroscopy, wide-angle X-ray diffraction, thermogravimetry analysis, dynamic mechanical analysis, atomic force microscopy, transmittance electronic microscope, UV-vis spectroscopy, and photoluminescence spectroscopy. The experimental results confirmed that the CdS nanocrystalline existed in the composite films, and cellulose matrix provided a confined medium for CdS particle growth in uniform size. The CdS/RC composites showed narrow emission in photoluminescence spectra, and their optical absorbance in the UV range was higher than that of the cellulose film without CdS. This work provided a simple method to prepare cellulose functional materials in NaOH/urea aqueous solution. Photoluminescence of CdS/RC nanocomposites and TEM image of CdS nanocrystals dispersed in RC matrix. [source] The prion domain of yeast Ure2P induces autocatalytic formation of amyloid fibers by a recombinant fusion proteinPROTEIN SCIENCE, Issue 3 2000Martin Schlumpberger Abstract The Ure2 protein from Saccharomyces cerevisiae has been proposed to undergo a prion-like autocatalytic conformational change, which leads to inactivation of the protein, thereby generating the [URE3] phenotype. The first 65 amino acids, which are dispensable for the cellular function of Ure2p in nitrogen metabolism, are necessary and sufficient for [URE3] (Masison & Wickner, 1995), leading to designation of this domain as the Ure2 prion domain (UPD). We expressed both UPD and Ure2 as glutathione- S -transferase (GST) fusion proteins in Escherichia coli and observed both to be initially soluble. Upon cleavage of GST-UPD by thrombin, the released UPD formed ordered fibrils that displayed amyloid-like characteristics, such as Congo red dye binding and green-gold birefringence. The fibrils exhibited high ,-sheet content by Fourier transform infrared spectroscopy. Fiber formation proceeded in an autocatalytic manner. In contrast, the released, full-length Ure2p formed mostly amorphous aggregates; a small amount polymerized into fibrils of uniform size and morphology. Aggregation of Ure2p could be seeded by UPD fibrils. Our results provide biochemical support for the proposal that the [URE3] state is caused by a self-propagating inactive form of Ure2p. We also found that the uncleaved GST-UPD fusion protein could polymerize into amyloid fibrils by a strictly autocatalytic mechanism, forcing the GST moiety of the protein to adopt a new, ,-sheet-rich conformation. The findings on the GST-UPD fusion protein indicate that the ability of the prion domain to mediate a prion-like conversion process is not specific for or limited to the Ure2p. [source] Allometric growth relationships of East Africa highland bananas (Musa AAA-EAHB) cv. Kisansa and MbwazirumeANNALS OF APPLIED BIOLOGY, Issue 3 2009K. Nyombi Abstract Highland bananas are an important staple food in East Africa, but there is little information on their physiology and growth patterns. This makes it difficult to identify opportunities for yield improvement. We studied allometric relationships by evaluating different phenological stages of highland banana growth for use in growth assessment, understanding banana crop physiology and yield prediction. Pared corms of uniform size (cv. Kisansa) were planted in a pest-free field in Kawanda (central Uganda), supplied with fertilizers and irrigated during dry periods. In addition, tissue-cultured plants (cv. Kisansa) were planted in an adjacent field and in Ntungamo (southwest Uganda), with various nutrient addition treatments (of N, P, K, Mg, S, Zn, B and Mo). Plant height, girth at base, number of functional leaves and phenological stages were monitored monthly. Destructive sampling allowed derivation of allometric relationships to describe leaf area and biomass distribution in plants throughout the growth cycle. Individual leaf area was estimated as LA (m2) = length (m) × maximum lamina width (m) × 0.68. Total plant leaf area (TLA) was estimated as the product of the measured middle leaf area (MLA) and the number of functional leaves. MLA was estimated as MLA (m2) = ,0.404 + 0.381 height (m) + 0.411 girth (m). A light extinction coefficient (k = 0.7) was estimated from photosynthetically active radiation measurements in a 1.0 m grid over the entire day. The dominant dry matter (DM) sinks changed from leaves at 1118 °C days (47% of DM) and 1518 °C days (46% of DM), to the stem at 2125 °C days (43% of DM) and 3383 °C days (58% of DM), and finally to the bunch at harvest (4326 °C days) with 53% of DM. The allometric relationship between above-ground biomass (AGB in kg DM) and girth (cm) during the vegetative phase followed a power function, AGB = 0.0001 (girth)2.35 (R2 = 0.99), but followed exponential functions at flowering, AGB = 0.325 e0.036(girth) (R2 = 0.79) and at harvest, AGB = 0.069 e0.068(girth) (R2 = 0.96). Girth at flowering was a good parameter for predicting yields with R2 = 0.7 (cv. Mbwazirume) and R2 = 0.57 (cv. Kisansa) obtained between actual and predicted bunch weights. This article shows that allometric relationship can be derived and used to assess biomass production and for developing banana growth models, which can help breeders and agronomists to further exploit the crop's potential. [source] Do family farms really converge to a uniform size?AUSTRALIAN JOURNAL OF AGRICULTURAL & RESOURCE ECONOMICS, Issue 1 2010The role of unobserved farm efficiency We analyse the growth of family farms in Israeli cooperative villages during a period of economic turmoil. We use instrumental variables to account for the endogeneity of initial farm size, and correct for selectivity as a result of farm survival. We also include a technical efficiency index, derived from the estimation of a stochastic frontier production model, as an explanatory variable. Our aim is to check whether ignoring efficiency could have been the reason for convergence results obtained elsewhere in the literature. We found that technical efficiency is an important determinant of farm growth, and that not controlling for technical efficiency could seriously bias the results. In particular, larger farms are found to grow faster over time, while without controlling for technical efficiency the farm growth process seemed to be independent of initial farm size. The increasing polarisation of farm sizes in Israel has ramifications for the inefficiencies induced by the historical quota system, for the political power of the farm sector and for the social stability of farm communities. [source] Role of the Preparation Procedure in the Formation of Spherical and Monodisperse Surfactant/Polyelectrolyte ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2007Yuxia Luan Dr. Abstract Complexes formed by a double-tail cationic surfactant, didodecyldimethyl ammonium bromide, and an anionic polyelectrolyte, an alternating copolymer of poly(styrene-alt-maleic acid) in its sodium salt form, were investigated with respect to variation in the charge ratio (x) between the polyelectrolyte negative charges and the surfactant positive charges. The morphology and microstructure of the complexes were studied by light microscopy and small-angle X-ray scattering for different preparation conditions. Independent of the sample preparation procedure and the charge ratio x, the X-ray results show that the microscopic structure of the complexes is a condensed lamellar phase. By contrast, the morphology of the complexes changes dramatically with the preparation procedure. The complexes formed by mixing a surfactant solution and a polyelectrolyte solution strongly depend on x and are always extremely heterogeneous in size and shape. Surprisingly, we show that, when the two solutions interdiffuse slowly, spherical complexes of micrometric and rather uniform size are systematically obtained, independently on the initial relative amount of surfactant and polyelectrolyte. The mechanism for the formation of these peculiar complexes is discussed. [source] Stabilizer-free dispersion copolymerization of maleic anhydride and vinyl acetate.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2005Abstract A novel dispersion copolymerization of maleic anhydride (MAn) and vinyl acetate (VAc) without adding stabilizer is developed, which gives uniform copolymer microspheres with tunable sizes. Some principal factors affecting the microspheres, such as reaction time, monomer concentration and feed ratio, reaction media, and cosolvent, were investigated. It was found that the stabilizer-free dispersion copolymerization of MAn and VAc is a rapid process, and the particle size grows in accordance with the evolution of polymerization. The chemical composition of the copolymer microspheres was characterized by FT-IR and 13C NMR spectroscopies. Over a wide range of monomer concentrations, the microspheres can always be formed and stably dispersed, with uniform sizes ranging from 180 nm to 740 nm. The yield of copolymer microspheres reaches a maximum at 1:1 feed ratio of MAn to VAc, owing to the alternating copolymerization between the binary monomers by a known charge-transfer-complex mechanism. However, the diameter of microspheres drastically increases when MAn content is enhanced. Only some specific alkyl ester solvents, such as n -butyl acetate, isobutyl acetate, n -amyl acetate, are desirably fit for this unique stabilizer-free dispersion polymerization. Furthermore, we found that when some acetone is added as a cosolvent, the copolymer microspheres can still be formed, with much larger diameters. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3760,3770, 2005 [source] Recrystallization and Shape Control of Crystals of the Organic Dye Acid Green 27 in a Mixed SolventCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2007Huai-Ping Cong Abstract Recrystallization of the unstructured dye acid green 27 (AG27) in a mixed solvent of alcohol (ethanol or methanol) and water was systematically studied. The results demonstrated that AG27 crystals with uniform sizes and controllable shapes can be produced by simply changing the volume ratio of ethanol (or methanol) and deionized water (DIW). Rodlike and shuttlelike AG27 crystals can be selectively synthesized. The XRD analyses revealed the periodic structures of the organic crystals. Furthermore, crystallization in another mixed solvent of N,N -dimethylformamide (DMF) and DIW results in the formation of longer fibers with high aspect ratio, which further validates the remarkable effects of mixed solvent on the shape of the AG27 crystals. This method of recrystallization in a mixed solvent is expected to facilitate the synthesis of other functional organic crystals with unusual shapes. [source] | ||||||||||||||||||||||||||||