Discrete solvent effects on the effective interaction between charged colloids

Using computer simulations of two charged colloidal spheres with their counterions in a hard sphere solvent, we show that the granular nature of the solvent significantly influences the effective colloidal interaction. For divalent counterions, the total effective force can become attractive generated by counterion hydration, while for monovalent counterions the forces are repulsive and well-described by a solvent-induced colloidal charge renormalization. Both effects are not contained in the traditional "primitive" approaches but can be accounted for in a solvent-averaged primitive model.Comment: 4 pages, 3 figure

Physical activity and healthy ageing: A systematic review and meta-analysis of longitudinal cohort studies.

BACKGROUND: Older people constitute a significant proportion of the total population and their number is projected to increase by more than half by 2030. This increasing probability of late survival comes with considerable individual, economic and social impact. Physical activity (PA) can influence the ageing process but the specific relationship with healthy ageing (HA) is unclear. METHODS: We conducted a systematic review and meta-analysis of longitudinal studies examining the associations of PA with HA. Studies were identified from a systematic search across major electronic databases from inception as January 2017. Random-effect meta-analysis was performed to calculate a pooled effect size (ES) and 95% CIs. Studies were assessed for methodological quality. RESULTS: Overall, 23 studies were identified including 174,114 participants (30% men) with age ranges from 20 to 87 years old. There was considerable heterogeneity in the definition and measurement of HA and PA. Most of the identified studies reported a significant positive association of PA with HA, six reported a non-significant. Meta-analysis revealed that PA is positively associated with HA (ES: 1.39, 95% CI=1.23-1.57, n=17) even if adjusted for publication bias (ES: 1.27, 95% CI=1.11-1.45, n=20). CONCLUSIONS: There is consistent evidence from longitudinal observational studies that PA is positively associated with HA, regardless of definition and measurement. Future research should focus on the implementation of a single metric of HA, on the use of objective measures for PA assessment and on a full-range of confounding adjustment. In addition, our research indicated the limited research on ageing in low-and-middle income countries

Hearing damage of nontraumatic and nonacoustic genesis in relation to normal audiogram

Iznijeti su osnovni elementi osjetnog sustava koji igraju ulogu u percepciji zvuka. Sustavno su prikazani različiti poremećaji uslijed kojih dolazi do oštećenja funkcije sluha te je izložen mehanizam zavisnosti funkcionalnih poremećaja sluha i uzroka tih poremećaja. Raspravlja se o značenju odstupanja normalne audiometrijske krivulje.The essential elements of the hearing system which are involved in the perception of sound are presented. Various disturbances which may damage hearing function are systematically dealt with; so is the dependence of functional impairments of hearing on their causes. The significance of deviation of the normal audiometric curve is discussed

Inhibition of ache by malathion and some structuraly similar compounds

Inhibition of bovine serum acetylcholinesterase by in vitro exposure to malathion, malaoxon, isomalathion and diethyl maleate was investigated to elucidate the mechanism of the enzyme interaction with structurally similar organophosphorus compounds. IC50 (half maximum inhibitory concentrations) were determined by Hill analysis of experimentally obtained inhibition curves. The values (2.87 ± 0.24)x10-6 M, (2.65±0.61)x10-6M, (3.01±0.36)x10-4 M and (5.69 ±0.7)x10-2 M were obtained for malaoxon, isomalathion, malathion and their hydrolysis product diethyl maleate, respectively. The relationship between the structure of the compounds and their potency to inhibit the enzyme activity was discussed.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Palladium(II) complexes of quinolinylaminophosphonates: synthesis, structural characterization, antitumor and antimicrobial activity

Three types of palladium(II) halide complexes of quinolinylaminophosphonates have been synthesized and studied. Diethyl and dibutyl [alpha-anilino-(quinolin-2-ylmethyl)]phosphonates (L1, 12) act as N,N-chelate ligands through the quinoline and aniline nitrogens giving complexes cis-[Pd(L1/12)X-2] (X Cl, Br) (1-4). Their 3-substituted analogues [alpha-anilino-(quinolin-3-ylmethyl)]phosphonates (L3, L4) form dihalidopalladium complexes trans-[Pd(L3/L4)(2)X-2] (5-8), with trans N-bonded ligand molecules only through the quinoline nitrogen. Dialkyl [alpha-(quinolin-3-ylamino)-N-benzyl]phosphonates (L5, L6) give tetrahalidodipalladium complexes [Pd-2(L5/L6)(3)X-4] (9-12), containing one bridging and two terminal ligand molecules. The bridging molecule is bonded to the both palladium atoms, one through the quinoline and the other through the aminoquinoline nitrogen, whereas terminal ligand molecules are coordinated each only to one palladium via the quinoline nitrogen. Each palladium ion is also bonded to two halide ions in a trans square-planar fashion. The new complexes were identified and characterized by elemental analyses and by IR, UV-visible, H-1, C-13 and P-31 nuclear magnetic resonance and ESI-mass spectroscopic studies. The crystal structures of complexes 1-4 and 6 were determined by X-ray structure analysis. The antitumor activity of complexes in vitro was investigated on several human tumor cell lines and the highest activity with cell growth inhibitory effects in the low micromolar range was observed for dipalladium complexes 11 and 12 derived from dibutyl ester L6. The antimicrobial properties in vitro of ligands and their complexes were studied using a wide spectrum of bacterial and fungal strains. No specific activity was noted. Only ligands L3 and L4 and tetrahalidodipalladium complexes 9 and 11 show poor activities against some Gram positive bacteria

Interaction and flocculation of spherical colloids wetted by a surface-induced corona of paranematic order

Particles dispersed in a liquid crystal above the nematic-isotropic phase transition are wetted by a surface-induced corona of paranematic order. Such coronas give rise to pronounced two-particle interactions. In this article, we report details on the analytical and numerical study of these interactions published recently [Phys. Rev. Lett. 86, 3915 (2001)]. We especially demonstrate how for large particle separations the asymptotic form of a Yukawa potential arises. We show that the Yukawa potential is a surprisingly good description for the two-particle interactions down to distances of the order of the nematic coherence length. Based on this fact, we extend earlier studies on a temperature induced flocculation transition in electrostatically stabilized colloidal dispersions [Phys. Rev. E 61, 2831 (2000)]. We employ the Yukawa potential to establish a flocculation diagram for a much larger range of the electrostatic parameters, namely the surface charge density and the Debye screening length. As a new feature, a kinetically stabilized dispersion close to the nematic-isotropic phase transition is found.Comment: Revtex v4.0, 16 pages, 12 Postscript figures. Accepted for publication in Phys. Rev.

Nematic-Wetted Colloids in the Isotropic Phase: Pairwise Interaction, Biaxiality and Defects

We calculate the interaction between two spherical colloidal particles embedded in the isotropic phase of a nematogenic liquid. The surface of the particles induces wetting nematic coronas that mediate an elastic interaction. In the weak wetting regime, we obtain exact results for the interaction energy and the texture, showing that defects and biaxiality arise, although they are not topologically required. We evidence rich behaviors, including the possibility of reversible colloidal aggregation and dispersion. Complex anisotropic self-assembled phases might be formed in dense suspensions.Comment: 4 pages, 6 figure

Role of disclinations in determining the morphology of deformable fluid interfaces

We study the equilibrium shapes of vesicles, with an in-plane nematic order, using a Monte-Carlo scheme and show that highly curved shapes, like tubes and discs, with a striking similarity to the structures engendered by certain curvature sensing peripheral membrane proteins, can be spontaneously generated by anisotropic directional curvature with nematic disclinations playing and important role. We show that the coupling between nematic order and local curvature could lead to like defects moving towards each other and unlike defects moving away, in turn leading to tube formation. Thermally induced defect pair production lead to branched tubular structures. It is also shown that helical arrangement of the membrane tubes, with nematic field spiraling around it, is a dominant soft mode of the system.Comment: 6 Figures; Soft Matter, Advance Article 201

The Mass and Ion Kinetic Energy Spectra of Fluoro-Chloro Substituted Norbornanes and Nortricyclanes

The mass and ion kinetic energy spectra of difluoro- and fluoro- chloro-norbornanes and fluoro-chloro-nortricyclanes have been examined. In several instances the similarity of the mass spectra makes it impossible to distinguish the diastereoisomers from each other. In contrast, however, their ion kinetic energy spectra differ clearly and allow unambiguous differentiation of the stereoisomers

Annihilation of edge dislocations in smectic A liquid crystals

This paper presents a theoretical study of the annihilation of edge dislocations in the same smectic plane in a bulk smectic-A phase. We use a time-dependent Landau-Ginzburg approach where the smectic ordering is described by the complex order parameter psi( r--> ,t) =eta e(iphi) . This quantity allows both the degree of layering and the position of the layers to be monitored. We are able to follow both precollision and postcollision regimes, and distinguish different early and late behaviors within these regimes. The early precollision regime is driven by changes in the phi ( r--> ) configuration. The relative velocity of the defects is approximately inversely proportional to the interdefect separation distance. In the late precollision regime the symmetry changes within the cores of defects also become influential. Following the defect collision, in the early postcollision stage, bulk layer order is approached exponentially in time. At very late times, however, there seems to be a long-time power-law tail in the order parameter fluctuation relaxation