Preparation and antibacterial properties of hybrid-zirconia films with silver nanoparticles

The antimicrobial effect of incorporating silver nanoparticles (AgNps) into zirconia matrix–polyether glycol was studied. AgNps of 4–6 nm in size were synthesized using the inverse micelles method, and different doses of metallic nanoparticles were incorporated into zirconia–polyether glycol mixtures during the ageing procedure. Atomic force microscopy (AFM) of the modified hybrid film showed a homogenous distribution of 20–80 nm diameter AgNps, indicating agglomeration of these structures during film modification; such agglomerations were greater when increasing the dosage of the colloidal system. The AgNps-hybrid films showed higher antimicrobial activity against Gram-positive bacteria than for Gram-negative bacteria. Hybrid films prepared with dioctyl sodium sulfosuccinate (AOT) stabilized AgNps presented enhanced antibacterial activity compared to that obtained through the addition of a high AgNO₃ concentration (0.3 wt%).     

Rapid determination of sanitizer concentration using impedance-based methods

Chlorine, iodophor, and quaternary ammonium solutions of various concentrations were assayed with rapid test kits and with three Bactometer impedimetric test codes (the impedance, conductance, and capacitance test codes). An initial study was conducted to determine which test code was most suitable for each sanitizer. Impedance was shown to be the best for sodium hypochlorite solutions, conductance for iodophor solutions, and capacitance for quaternary ammonium solutions. When Bactometer results were compared with test kit results, linear regression revealed strong correlations for all three sanitizer solutions. For sodium hypochlorite concentrations of 0 to 100 ppm and 100 to 1,000 ppm, R2 values of 0.87 and 0.99, respectively, were obtained. For iodophor concentrations between 25 to 150 ppm, an R2 value of 0.95 was obtained. For quaternary ammonium compound concentrations of 100 to 1,000 ppm, an R2 value of 0.94 was obtained. The impedimetric methods proved to be simple and rapid (6 min) alternatives for measuring concentrations of the sanitizer solutions with a high level of certainty (P < 0.0002). The Bactometer will save time when multiple samples are tested.     

Corrosion Protection of Stainless Steel by Poly(Carbazole-co-pyrrole) Films Deposited on TiO2 Sol–Gel Film

The poly(carbazole-co-pyrrole) copolymer was synthesized on TiO₂ sol–gel precoated 304 stainless steel (TiO₂) by cyclic voltammetry in tetrabutylammonium perchlorate containing acetonitrile solution. The synthesized coating was characterized by attenuated total reflectance–Fourier transform infrared spectroscopy, scanning electron microscopy, and solid-state conductivity measurements. Corrosion protection behavior of the TiO₂/poly(carbazole-co-pyrrole)-coated steel was evaluated by open circuit potential–time curves, potentiodynamic polarization, and electrochemical impedance spectroscopy methods. Corrosion test results showed that TiO₂/poly(carbazole-co-pyrrole) composite film enhanced corrosion resistance of stainless steel up to 50 days of immersion in 0.1M HCl corrosive medium.     

Dielectric and electromechanical properties of Mn-doped 0.2875 Pb(Mg1/3Nb2/3)O3–0.2875 Pb(Yb1/2Nb1/2)O3–0.425 PbTiO3 ceramics

In this study, 0.2875 Pb(Mg_1/3Nb_2/3)O₃–0.2875 Pb(Yb_1/2Nb_1/2)O₃–0.425 PbTiO₃ (0.2875PMN–0.2875PYbN–0.425PT) ternary ceramic composition was doped with 1 mol% MnCO₃ in order to induce hard character for potential high-power applications. Dense 0.2875PMN–0.2875PYbN–0.425PT ceramics with 1 mol% MnCO₃ addition were fabricated after sintering at 1100 °C. ε _r = 1728, tanδ = 0.35 %, d ₃₃ = 320 pC/N, d ₃₁ = ?103 pC/N, Q _m = 467, k _p = 0.40, k ₃₁ = 0.24, k ₃₃ = 0.49, and T _c = 280 °C were measured for Mn-doped ceramics. However, undoped ceramics had ε _r = 2380, tanδ = 1.95 %, d ₃₃ = 433 pC/N, d ₃₁ = ?145 pC/N, Q _m = 60, k _p = 0.43, k ₃₁ = 0.27, k ₃₃ = 0.48, and T _c = 285 °C. Acceptor Mn²⁺/Mn³⁺ ions presumably substituted B-site ions in the perovskite structure and formed defect dipole pairs. The electrically “hard” character was induced as a result of the domain wall pinning due to the existing defect pairs. Particularly, increasing Q _m from 60 to 467 and decreasing tanδ from 1.95 to 0.35 % after Mn doping showed that Mn-doped 0.2875PMN–0.2875PYbN–0.425PT ceramics with “hard” character are potential candidates for high-power projector and transducer applications.     

Deletion of the H19 differentially methylated domain results in loss of imprinted expression of H19 and Igf2

Differentially methylated sequences associated with imprinted genes are proposed to control genomic imprinting. A 2-kb region located 5' to the imprinted mouse H19 gene is hypermethylated on the inactive paternal allele throughout development. To determine whether this differentially methylated domain (DMD) is required for imprinted expression at the endogenous locus, we have generated mice harboring a 1.6-kb targeted deletion of the DMD and assayed for allelic expression of H19 and the linked, oppositely imprinted Igf2 gene. H19 is activated and Igf2 expression is reduced when the DMD deletion is paternally inherited; conversely, upon maternal transmission of the mutation, H19 expression is reduced and Igf2 is activated. Consistent with the DMD's hypothesized role of setting up the methylation imprint, the mutation also perturbs allele-specific methylation of the remaining H19 sequences. In conclusion, these experiments show that the H19 hypermethylated 5' flanking sequences are required to silence paternally derived H19. Additionally, these experiments demonstrate a novel role for the DMD on the maternal chromosome where it is required for the maximal expression of H19 and the silencing of Igf2. Thus, the H19 differentially methylated sequences are required for both H19 and Igf2 imprinting.     

Preparation of nanometric titanium hydrous oxide particles by vapour phase hydrolysis of titanium tetrabutoxide

Spherical titanium nanoparticles in the range of 60 to 500 nm have been obtained by a vapour-phase hydrolysis procedure using titanium tetrabutoxide as raw material. In this work, different parameters such as alkoxide temperature, water temperature, carrier gas flow rate, inlet pressure, vacuum and dilution of the raw material were tested. The most important parameters in order to obtain nanoparticles of low mean size were the flow rate, the alkoxide temperature and the inlet pressure. When the temperature decreases the mean size decreases obtaining nanoparticles below 100 nm when the temperature is set up to 125°C. On the other hand, as the flow rate that pass through the alkoxide increases the particle size decreases. Same behaviour is observed when the pressure inlet is increased. In all cases, these results are attributed to a minor concentration of the alkoxide (low amount of alkoxide molecules) in the gas stream. The other parameters, vacuum, water temperature and dilution of the alkoxide did not show any important influence in the particle size as the other ones. Polydispersity (broad or narrow particle size distribution) has the same trend. The alkoxide temperature and carrier flow rate generate narrow distributions while the other parameters produces broad distributions. FT-IR analysis of these nanoparticles showed that for sizes below 100 nm the alkoxide is fully hydrolysed and as the particle size increases the nanoparticle has more alkoxide or alcohol retained inside. The heat treatment of these nanoparticles produces a decreasing in the particle size and in all cases, the spherical shape is retained and no blackening in the nanoparticles of higher size is observed.     

Phase formation and texture development in mullite/zirconia composites fabricated by templated grain growth

Mullite is a promising candidate for advanced ceramic applications but its low fracture toughness and difficulties in sintering are the main limitations for more widespread industrial applications. Therefore, mullite/zirconia composites were prepared from a reactive mixture of alumina and zircon powders. Additives, TiO₂ and MgO, were used to modify aluminosilicate glass to increase densification and <001> aluminum borate templates were incorporated to texture mullite in [001] by templated grain growth. Mullite/zirconia phase formation was complete at 1450°C in the presence of both templates and additives, as compared to 1500°C for the samples with only additives and to 1600°C for the samples with only templates. Dense mullite/zirconia composites with highly <001>-textured mullite grains (Lotgering factor ∼1) and a retention of ∼13% tetragonal ZrO₂ were fabricated after sintering at 1450°C for 2 h. A high quality of mullite texture with a degree of orientation parameter of 0.22 and a narrow distribution of elongated mullite grains within 8.8° around [001] were successfully obtained in the composites.     

Extragenital malignant mixed mesodermal tumor: case report and review of the literature

The hypothesis is presented that our life span is genetically programmed and that it is possible that a defect in produced proteins encoded by the 'longevity' gene is a cause of aging. A study of correlations between defective enzyme activity in two diseases characterized by premature aging (progeria and Werner's syndrome) could assist in elucidating the common mechanism for all aging processes.     

Rural american indians' perspectives of obstacles in the mental health treatment process in three treatment sectors.

This study sought to identify obstacles associated with alcohol, drug, and mental (ADM) health care utilization in three treatment sectors for residents on three reservations in the United States. Participants (N = 224) disclosed that they had sought treatment for ADM problems in the past year and identified obstacles they faced during this process. Four obstacles were identified: (a) self-reliance, (b) privacy issues, (c) quality of care, and (d) communication/trust. A vast majority (71%) of participants reported at least one of these obstacles during treatment, and 61% faced two or more obstacles. There were no differences in the type or number of obstacles by treatment sector. Privacy and communication/trust obstacles were more likely to occur in emotional treatment compared to alcohol/drug treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)