Chemical nano-gardens: growth of salt nanowires from supramolecular self-assembly gels.

In this article, we examine the phenomenon of single-crystal halide salt wire growth at the surface of porous materials. We report the use of a single-step casting technique with a supramolecular self-assembly gel matrix that upon drying leads to the growth of single-crystal halide (e.g., NaCl, KCl, and KI) nanowires with diameters ~130-200 nm. We demonstrate their formation using electron microscopy and electron-dispersive X-ray spectroscopy, showing that the supramolecular gel stabilizes the growth of these wires by facilitating a diffusion-driven base growth mechanism. Critically, we show that standard non-supramolecular gels are unable to facilitate nanowire growth. We further show that these nanowires can be grown by seeding, forming nanocrystal gardens. This study helps understand the possible prefunctionalization of membranes to stimulate ion-specific filters or salt efflorescence suppressors, while also providing a novel route to nanomaterial growth.

Analysis and retrofitting design of a single-span R.C. bridge

This paper deals with the case history of a damaged one-span prestressed concrete bridge on a crucial artery near the city of Cagliari (Sardinia), along the sea-side. After being involved in a disastrous flood, attention has arisen on the worrying safety state of the deck, submitted to an intense daily traffic load. Evident signs of this severe condition were the deterioration of the beams concrete and the corrosion, the lack of tension and even the rupture of the prestressing cables. After performing a limited in situ test campaign, consisting of sclerometer, pull out and carbonation depth tests, a first evaluation of the safety of the structure was performed. After collecting the data of dynamic and static load tests as well, a comprehensive analysis have been carried out, also by means of a properly calibrated F.E. model. Finally the retrofitting design is presented, consisting of the reparation and thickening of the concrete cover, providing flexural and shear FRP external reinforcements and an external prestressing system, capable of restoring a satisfactory bearing capacity, according to the current national codes. The intervention has been calibrated by the former F.E. model with respect to transversal effects and influence of local and overall deformation of reinforced elements. © 2012 Taylor & Francis Group.

Seasonal pattern of reproduction of Hizikia fusiformis (Sargassaceae, Phaeophyta) from Nanao Island, Shantou, China

The maturation pattern of sexual reproduction in Hizikia fusiformis (Harvey) Okamura (Sargassaceae, Phaeaophyta) was examined in 2003 at Yunao Bay, Nanao Island, Shantou, China. Maturation began in mid-April (seawater temperature 19-21 degrees C), reached the peak in mid-May (maturation rate ca. 70%, and seawater temperature 23.5-25 degrees C) and finished in late-June (seawater temperature 27.5-30 degrees C). The Hizikia plants continued to gain the length from the beginning of maturation season to reach a maximum mean length of 34.8 cm in mid-May, after which the mean length was reduced drastically due to the senescence and rupture of the larger plants in size. The major portion of the mature plants belonged to the larger plants between April and May, but to the smaller ones in June. It is suggested that the plant must achieve a critical size before reproductive maturation occurred. There was a positive relationship between the number of receptacles (NR), as well as the reproductive allocation (RA), and the plant size of Hizikia population, with the recorded maximum values of NR and RA being 1220 and 64.3% respectively, for a single plant.

Polyamide thin film composite membranes prepared from 3,4',5-biphenyl triacyl chloride, 3,3',5,5'-biphenyl tetraacyl chloride and m-phenylenediamine

Two novel of tri- and tetra-functional biphenyl acid chloride: 3,4',5-biphenyl triacyl chloride (BTRC) and 3,3',5,5'-biphenyl tetraacyl chloride (BTEC), were synthesized, and used as new monomers for the preparations of the thin film composite (TFC) reverse osmosis (RO) membranes. The TFC RO membranes were prepared on a polysulfone supporting film through interfacial polymerization with the two new monomers and m-phenylenediamine (MPD). The membranes were characterized for the permeation properties, chemical composition, d-space between polymer chains, hydrophilicity, membrane morphology including top surface and cross-section. Permeation experiment was employed to evaluate the membranes performance including salt rejection and water flux. The surface structure and chemical composition of membranes were analyzed by attenuated total reflectance infrared (ATR-IR) and X-ray photoelectronic spectroscopy (XPS). The results revealed that the active layer of membranes was composed of highly cross-linked aromatic polyamide with the functional acylamide (-CONH-) bonds. The TFC membranes prepared from biphenyl acid chloride exhibit higher salt rejection compared with that prepared from trimesoyl chloride (TMC) at the expanse of some flux.

Solvent-induced crystallization of spherical micelles formed by copolymer blends

We have followed the morphological evolution and crystallization process of spherical micelles formed by the mixture of polystyrene-b-poly(acrylic acid) (PS-b-PAA) and polystyrene-b-poly(2-vinylpyridine)b-poly(ethylene oxide) (PS-b-P2VP-b-PEO) (the core of the spherical micelles was made of P2VP and PAA blocks through hydrogen bonding in neutral solvent N,N-dimethylformamide, DMF) via DMF vapor treatment. Different phenomena, such as rupture of the film, formation of cylinder aggregates and regular square lamellae, were observed when the micelle film was treated in DMF for different times. At the early stage of annealing in DMF vapor, the micelle film became unstable and ruptured. Cylinder aggregates, within which the PEO blocks achieved the association and primary chain folding, formed as the mesophases before the nucleation of the PEO single crystals at this stage. Further treatment in DMF vapor resulted in the nucleation of the PEO blocks at the corners of quasi-square lamellae. Then a quite regular "sandwich" lamellar structure, constructed by a PEO single-crystal layer covered by two tethered layers of other amorphous blocks on the top and bottom crystal basal surfaces, formed when the film of micelles was annealed in DMF vapor for sufficient times.

Synthesis of poly(ether ether ketone)s with high content of sodium sulfonate groups as gas dehumidification membrane materials

Sodium sulfonate-functionalized polyether ether ketone)s derived from Bisphenol A with a degree of sulfonation up to 2.0 were synthesized by aromatic nucleophilic polycondensation of various amounts of 5,5-carbonylbis(2-fluorobenzenesulfonate) (1), 4,4'-diflurobenzophenone (2) and Bisphenol A (2). Copolymers showed excellent thermal stability and good mechanical properties. The selectivity of water vapor over nitrogen of membranes prepared from copolymers 3a and 3h was determined to be 3.43 x 10(6) and 1.05 x 10(7), respectively.

VOLTAMMETRY OF CYTOCHROME-C ENTRAPPED IN HYDROGEL MEMBRANE ON GRAPHITE ELECTRODE

The voltammetric behavior of cytochrome c entrapped in hydrogel membranes at paraffin wax-impregnated spectroscopic graphite electrodes (WISGE) was studied in this paper. A pair of well-defined peaks appeared at +70 mV (vs. Ag/AgCl). Beside these two peaks, another pair of peaks emerged at around +225 mV. Further investigations suggested that at least three states of cytochrome c existed in the membranes due to the special structure of the hydrogel. The native conformation of cytochrome c molecules was stabilized by the hydrophilic environment that was formed by the hydroxyl structure of the membranes and facilitated the cytochrome c electron transfer reaction at +70 mV. The molecules directly adsorbed on the surface of the graphite electrode were responsible for the redox peaks at around +225 mV. Whether the adsorption peaks were detectable or not was related to the thickness of membranes and the pre-retaining time before the formation of membranes.

SURFACE-MODIFIED HYDROPHILIC MEMBRANES IN MEMBRANE DISTILLATION

The porosity and the hydrophobicity of membranes are two essential requirements for membrane distillation (MD) of aqueous solutions. So far, the hydrophobic porous membranes used in MD studies have been prepared from hydrophobic materials. In this work, hydrophilic cellulose acetate and cellulose nitrate membranes were modified into hydrophobic membranes by radiation grafting polymerization and plasma polymerization, and used in MD studies successfully. The results indicated that modified membranes with good performance in MD can be obtained if the modifying conditions are controlled appropriately. Especially plasma polymerization, in which many particular kinds of monomer could be polymerized onto the surface of porous materials, has become an efficient method to prepare hydrophobic porous membrane with high performance from hydrophilic membranes. It will stimulate the development and practical application of MD.

Flow cytometry and ultrastructure of cryopreserved red seabream (Pagrus major) sperm

The objectives were to assess motility, fertilizing capacity, structural integrity, and mitochondrial function in fresh versus frozen-thawed (15% DMSO was used as a cryoprotectant) sperm from red seabrearn (Pagrus major). Mean (+/- S.D.) rates of motility, fertilization and hatching of frozen-thawed sperm were 81.0 +/- 5.4, 92.8 +/- 1.9, and 91.8 +/- 5.2%, respectively; for fresh sperm, they were 87.5 +/- 7.7, 95.8 +/- 2.4, and 93.8 +/- 4.2%. Although motility was lower in frozen-thawed versus fresh sperm (P < 0.05), there was no effect (P > 0.05) of cryopreservation on fertilization or hatching. Based on scanning and transmission electron microscopy, 77.8 +/- 5.6% of fresh sperm had normal morphology, whereas for frozen-thawed sperm, 63.0 +/- 7.2% had normal morphology, 20.6 +/- 3.1% were slightly damaged (e.g. swelling or rupture of head, mid-piece and tail region as well as mitochondria), and 16.4 +/- 4.2% were severely damaged. Sperm were stained with propidium iodide and Rhodamine 123 to assess plasma membrane integrity and mitochondrial function, respectively, and examined with flow cytometry. For fresh sperm, 83.9% had an intact membrane and functional mitochondria, whereas for frozen-thawed sperm, 74.8% had an intact membrane and functional mitochondria, 12.7% had a damaged membrane, 9.9% had nonfunctional mitochondria, and 2.6% had both a damaged membrane and nonfunctional mitochondria. In conclusion, ultrastructure and flow cytometry were valuable for assessment of frozen-thawed sperm quality; cryopreservation damaged the sperm but fertilizing ability was not significantly decreased. (c) 2007 Elsevier Inc. All rights reserved.

Alkaline treatment of the cellulose fiber affecting membrane column behaviour for high-performance immunoaffinity chromatography

The original cellulose fibers and those treated by alkaline solution were both used to prepare the acrylic membranes. The two kinds of membranes were packed into the columns for high-performance immunoaffinity chromatography by the immobilization of protein A on them. It was observed that the alkaline treatment of the cellulose fiber decreased the pressure resistance of the membrane to the mobile phases and greatly increased the accessible volume to the proteins, but affected the adsorption capacity of human IgG on the protein A membrane columns less. There is little difference between those two kinds of membranes on the adsorption capacities of HIgG, which means that the alkaline treatment of the cellulose fiber only significantly changes the void volume inter-membrane, and the porosity and surface area of membrane less. Alkaline treatment of the cellulose fiber reduced the membrane-column efficiency significantly. Some typical examples for the immunoaffinity analysis of IgG from human and dog plasma on the protein A membrane columns are illustrated. Copyright (C) 2000 John Wiley & Sons, Ltd.

Premature ovarian aging in mice deficient for Gpr3

After becoming competent for resuming meiosis, fully developed mammalian oocytes are maintained arrested in prophase I until ovulation is triggered by the luteotropin surge. Meiotic pause has been shown to depend critically on maintenance of cAMP level in the oocyte and was recently attributed to the constitutive Gs (the heterotrimeric GTP-binding protein that activates adenylyl cyclase) signaling activity of the G protein-coupled receptor GPR3. Here we show that mice deficient for Gpr3 are unexpectedly fertile but display progressive reduction in litter size despite stable age-independent alteration of meiotic pause. Detailed analysis of the phenotype confirms premature resumption of meiosis, in vivo, in about one-third of antral follicles from Gpr3-/- females, independently of their age. In contrast, in aging mice, absence of GPR3 leads to severe reduction of fertility, which manifests by production of an increasing number of nondeveloping early embryos upon spontaneous ovulation and massive amounts of fragmented oocytes after superovulation. Severe worsening of the phenotype in older animals points to an additional role of GPR3 related to protection (or rescue) of oocytes from aging. Gpr3-defective mice may constitute a relevant model of premature ovarian failure due to early oocyte aging.

Evaporation-induced evolution of the capillary force between two grains

© 2014, Springer-Verlag Berlin Heidelberg.The evolution of capillary forces during evaporation and the corresponding changes in the geometrical characteristics of liquid (water) bridges between two glass spheres with constant separation are examined experimentally. For comparison, the liquid bridges were also tested for mechanical extension (at constant volume). The obtained results reveal substantial differences between the evolution of capillary force due to evaporation and the evolution due to extension of the liquid bridges. During both evaporation and extension, the change of interparticle capillary forces consists in a force decrease to zero either gradually or via rupture of the bridge. At small separations between the grains (short & wide bridges) during evaporation and at large volumes during extension, there is a slight initial increase of force. During evaporation, the capillary force decreases slowly at the beginning of the process and quickly at the end of the process; during extension, the capillary force decreases quickly at the beginning and slowly at the end of the process. Rupture during evaporation of the bridges occurs most abruptly for bridges with wider separations (tall and thin), sometimes occurring after only 25% of the water volume was evaporated. The evolution (pinning/depinning) of two geometrical characteristics of the bridge, the diameter of the three-phase contact line and the “apparent” contact angle at the solid/liquid/gas interface, seem to control the capillary force evolution. The findings are of relevance to the mechanics of unsaturated granular media in the final phase of drying.

Simple models of complex aggregation: Vesicle formation by soft repulsive spheres with dipolelike interactions

Structural and thermodynamic properties of spherical particles carrying classical spins are investigated by Monte Carlo simulations. The potential energy is the sum of short range, purely repulsive pair contributions, and spin-spin interactions. These last are of the dipole-dipole form, with however, a crucial change of sign. At low density and high temperature the system is a homogeneous fluid of weakly interacting particles and short range spin correlations. With decreasing temperature particles condense into an equilibrium population of free floating vesicles. The comparison with the electrostatic case, giving rise to predominantly one-dimensional aggregates under similar conditions, is discussed. In both cases condensation is a continuous transformation, provided the isotropic part of the interatomic potential is purely repulsive. At low temperature the model allows us to investigate thermal and mechanical properties of membranes. At intermediate temperatures it provides a simple model to investigate equilibrium polymerization in a system giving rise to predominantly two-dimensional aggregates.

The Pleiotropic Effects of Simvastatin on Retinal Microvascular Endothelium Has Important Implications for Ischaemic Retinopathies

Background: Current guidelines encourage the use of statins to reduce the risk of cardiovascular disease in diabetic patients; however the impact of these drugs on diabetic retinopathy is not well defined. Moreover, pleiotropic effects of statins on the highly specialised retinal microvascular endothelium remain largely unknown. The objective of this study was to investigate the effects of clinically relevant concentrations of simvastatin on retinal endothelium in vitro and in vivo.

Methods and Findings: Retinal microvascular endothelial cells (RMECs) were treated with 0.01–10 µM simvastatin and a biphasic dose-related response was observed. Low concentrations enhanced microvascular repair with 0.1 µM simvastatin significantly increasing proliferation (p<0.05), and 0.01 µM simvastatin significantly promoting migration (p<0.05), sprouting (p<0.001), and tubulogenesis (p<0.001). High concentration of simvastatin (10 µM) had the opposite effect, significantly inhibiting proliferation (p<0.01), migration (p<0.01), sprouting (p<0.001), and tubulogenesis (p<0.05). Furthermore, simvastatin concentrations higher than 1 µM induced cell death. The mouse model of oxygen-induced retinopathy was used to investigate the possible effects of simvastatin treatment on ischaemic retinopathy. Low dose simvastatin(0.2 mg/Kg) promoted retinal microvascular repair in response to ischaemia by promoting intra-retinal re-vascularisation (p<0.01). By contrast, high dose simvastatin(20 mg/Kg) significantly prevented re-vascularisation (p<0.01) and concomitantly increased pathological neovascularisation (p<0.01). We also demonstrated that the pro-vascular repair mechanism of simvastatin involves VEGF stimulation, Akt phosphorylation, and nitric oxide production; and the anti-vascular repair mechanism is driven by marked intracellular cholesterol depletion and related disorganisation of key intracellular structures.

Conclusions: A beneficial effect of low-dose simvastatin on ischaemic retinopathy is linked to angiogenic repair reducing ischaemia, thereby preventing pathological neovascularisation. High-dose simvastatin may be harmful by inhibiting reparative processes and inducing premature death of retinal microvascular endothelium which increases ischaemia-induced neovascular pathology. Statin dosage should be judiciously monitored in patients who are diabetic or are at risk of developing other forms of proliferative retinopathy.

Systematic review of reviews of risk factors for intracranial aneurysms

Systematic reviews of systematic reviews identify good quality reviews of earlier studies of medical conditions. This article describes a systematic review of systematic reviews performed to investigate factors that might influence the risk of rupture of an intracranial aneurysm. It exemplifies the technique of this type of research and reports the finding of a specific study. The annual incidence of subarachnoid haemorrhage resulting from the rupture of intracranial aneurysms is estimated to be nine per 100,000. A large proportion of people who have this bleed, will die or remain dependent on the care of others for some time. Reliable knowledge about the risks of subarachnoid haemorrhage in different populations will help in planning, screening and prevention strategies and in predicting the prognosis of individual patients. If the necessary data were available in the identified reviews, an estimate for the numerical relationship between a particular characteristic and the risk of subarachnoid haemorrhage was included in this report. The identification of eligible systematic reviews relied mainly on the two major bibliographic databases of the biomedical literature: PubMed and EMBASE. These were searched in 2006, using specially designed search strategies. Approximately 2,000 records were retrieved and each of these was checked carefully against the eligibility criteria for this systematic review. These criteria required that the report be a systematic review of studies assessing the risk of subarachnoid haemorrhage in patients known to have an unruptured intracranial aneurysm or of studies that had investigated the characteristics of people who experienced a subarachnoid haemorrhage without previously being known to have an unruptured aneurysm. Reports which included more than one systematic review were eligible and each of these reviews was potentially eligible. The quality of each systematic review was assessed. In this review, 16 separate reports were identified, including a total of 46 eligible systematic reviews. These brought together research studies for 24 different risk factors. This has shown that the following factors appear to be associated with a higher risk of subarachnoid haemorrhage: being a woman, older age, posterior circulation aneurysms, larger aneurysms, previous symptoms,