Assessing freeze–thaw and high pressure low temperature induced damage to Bacillus subtilis cells with flow cytometry

The effect of high pressure low temperature (HPLT) treatment of Bacillus subtilis PS832 in the domain of Ice I–III was studied. Flow cytometry (FCM) forward and sideward scatter measurements gave no indication for HPLT induced complete rupture of cells. The single cell population was gated using FCM in combination with propidium iodide (PI) and carboxyfluorescein diacetate. Results show that membrane damage was inflicted upon a significant subpopulation of cells. Of the remaining cells an increase in severely stressed and ghost cells was found. Positive PI staining was indicative for nearly complete loss of viability, while impaired esterase activity was not indicative for absence of viability. We confirmed that Ice I–Ice III phase transition, characteristic for a ? 25 °C/250 MPa treatment led to a > 4 log inactivation of vegetative B. subtilis. However, such a treatment did not influence the robustness of survivors. Finally, cells that survived either freeze–thaw or HPLT did not sporulate upon entry into stationary phase.Industrial relevanceThe single cell physiology data represented here, underpin that industrial application of this preservation technology is best done at conditions where Ice I–Ice III phase transitions occur. Importantly, the data also shows that compared to (just) a freeze–thaw cycle at ? 25 °C, such treatment does not lead to less robustness (outgrowth capability) of survivors.     

Effects of long-term heavy metal contamination on soil microbial characteristics

In this study, total heavy metal content and its effects on soil microbiological characteristics were investigated in soil samples from an area with known long-term pollution problems. The total heavy metal concentrations of contaminated soil samples were 109 and 1,558 mg/kg for Hg and As, respectively. Key microbiological parameters measured included dehydrogenase activity, ATP content and number of culturable aerobic bacteria, actinomycetes, fungi and asymbiotic nitrogen-fixers. Quantitative analysis of soil microbial populations shows a marked decrease in total culturable numbers of the different microbial groups of the contaminated soil samples. Certain groups of soil microbes were particularly sensitive to long-term contamination (asymbiotic nitrogen-fixers and heterotrophic bacteria). Dehydrogenase activity was found to be a sensitive assay for determining the effect of heavy metals on physiologically active soil microbial biomass and sustains the high applicability of this parameter for soil ecotoxicological testing as reported by other authors.     

Ab initio study of phosphorus donors acting as quantum bits in silicon nanowires

A phosphorus (P) donor has been extensively studied in bulk Si to realize the concept of Kane quantum computers. In most cases the quantum bit was realized as an entanglement between the donor electron spin and the nonzero nuclei spin of the donor impurity mediated by the hyperfine coupling between them. The donor ionization energies and the spin-lattice relaxation time limited the temperatures to a few kelvin in these experiments. Here, we demonstrate by means of ab initio density functional theory calculations that quantum confinement in thin Si nanowires (SiNWs) results in (i) larger excitation energies of donor impurity and (ii) a sensitive manipulation of the hyperfine coupling by external electric field. We propose that these features may allow to realize the quantum bit (qubit) experiments at elevated temperatures with a strength of electric fields applicable in current field-effect transistor technology. We also show that the strength of quantum confinement and the presence of strain induced by the surface termination may significantly affect the ground and excited states of the donors in thin SiNWs, possibly allowing an optical read-out of the electron spin.     

Alkyd resins: From down and out to alive and kicking

Alkyd resins have been introduced in the 1930s as binders for paints. Their compatibility with many polymers and the extremely wide formulating latitude made them suitable for the production of a very broad range of coating materials. This includes do-it-yourself paints and varnishes for wood and metal, road marking paints, anticorrosive paints, nitrocellulose lacquers, two-component isocyanate curing coatings, acid curing coatings, stoving enamels, etc. Except for phthalic anhydride, being of petrochemical origin, the other raw materials used in the synthesis of the alkyds are from biologically renewable sources. This, combined with their biological degradability, makes them very interesting binders from an ecological point of view. Solvents which are used to reduce and adjust the paint viscosity are the only concern with respect to the ecological aspects of the alkyd paints. In recent years, however, we witness quite an activity in designing alkyd emulsions and high solids alkyds which can serve as binders for environmentally friendly coatings.     

Spatial and temporal variation in indicator microbe sampling is influential in beach management decisions

Fecal indicator microbes, such as enterococci, are often used to assess potential health risks caused by pathogens at recreational beaches. Microbe levels often vary based on collection time and sampling location. The primary goal of this study was to assess how spatial and temporal variations in sample collection, which are driven by environmental parameters, impact enterococci measurements and beach management decisions. A secondary goal was to assess whether enterococci levels can be predictive of the presence of Staphylococcus aureus, a skin pathogen. Over a ten-day period, hydrometeorologic data, hydrodynamic data, bather densities, enterococci levels, and S. aureus levels including methicillin-resistant S. aureus (MRSA) were measured in both water and sand. Samples were collected hourly for both water and sediment at knee-depth, and every 6 h for water at waist-depth, supratidal sand, intertidal sand, and waterline sand. Results showed that solar radiation, tides, and rainfall events were major environmental factors that impacted enterococci levels. S. aureus levels were associated with bathing load, but did not correlate with enterococci levels or any other measured parameters. The results imply that frequencies of advisories depend heavily upon sample collection policies due to spatial and temporal variation of enterococci levels in response to environmental parameters. Thus, sampling at different times of the day and at different depths can significantly impact beach management decisions. Additionally, the lack of correlation between S. aureus and enterococci suggests that use of fecal indicators may not accurately assess risk for some pathogens.     

Synthesis,morphology and properties of segmented poly(ether ester amide)s comprising uniform glycine or β-alanine extended bisoxalamide hard segments

Segmented poly(ether ester amide)s comprising glycine or β-alanine extended bisoxalamide hard segments are highly phase separated thermoplastic elastomers with a broad temperature independent rubber plateau. These materials with molecular weights, M_n, exceeding 30 × 10³ g mol^?1 are conveniently prepared by polycondensation of preformed bisester–bisoxalamides and commercially available PTHF diols. FT-IR revealed strongly hydrogen bonded and highly ordered bisoxalamide hard segments with degrees of ordering between 73 and 99%. The morphology consists of fiber-like nano-crystals randomly dispersed in the soft polymer matrix. The micro-structural parameters of the copolymers were addressed by simultaneous small- and wide-angle X-ray scattering. It is shown that the crystals have strictly identical thickness, which is close to the contour length of the hard segment. The long dimension of the crystals is identified with the direction of the hydrogen bonds. The melting transitions of the hard segments are sharp, with temperatures up to 170 °C. The studied polymers have an elastic modulus in the range of 139–170 MPa, a stress at break in the range of 19–31 MPa combined with strains at break of higher than 800%. The segmented copolymer comprising the β-alanine based bisoxalamide hard segment with a spacer of 6 methylene groups has a melting transition of 141 °C which is higher than the melting transition of its glycine analogue of 119 °C. Likewise, the fracture stress increased from 22 to 31 MPa when the glycine ester group in the hard segment was replaced with β-alanine. The improved thermal and mechanical properties of the latter polymers is related to the crystal packing of the β-alanine based hard segments in the copolymer compared to the packing of the hard segments comprising glycine ester groups.     

In Situ analysis of CO2 laser irradiation on controlling progression of erosive lesions on dental enamel

The present study aimed to evaluate in situ the effect of CO₂ laser irradiation to control the progression of enamel erosive lesions. Fifty‐six slabs of bovine incisors enamel (5 × 3 × 2.5 mm³) were divided in four distinct areas: (1) sound (reference area), (2) initial erosion, (3) treatment (irradiated or nonirradiated with CO₂ laser), (4) final erosion (after in situ phase). The initial erosive challenge was performed with 1% citric acid (pH = 2.3), for 5 min, 2×/day, for 2 days. The slabs were divided in two groups according to surface treatment: irradiated with CO₂ laser (λ = 10.6 µm; 0.5 W) and nonirradiate. After a 2‐day lead‐in period, 14 volunteers wore an intraoral palatal appliance containing two slabs (irradiated and nonirradiated), in two intraoral phases of 5 days each. Following a cross‐over design during the first intraoral phase, half of the volunteers immersed the appliance in 100 mL of citric acid for 5 min, 3×/day, while other half of the volunteers used deionized water (control). The volunteers were crossed over in the second phase. Enamel wear was determined by an optical 3D profilometer. Three‐way ANOVA for repeated measures revealed that there was no significant interaction between erosive challenge and CO₂ laser irradiation (P = 0.419). Erosive challenge significantly increased enamel wear (P = 0.001), regardless whether or not CO₂ laser irradiation was performed. There was no difference in enamel wear between specimens CO₂‐laser irradiated and non‐irradiated (P = 0.513). Under intraoral conditions, CO₂ laser irradiation did not control the progression of erosive lesions in enamel caused by citric acid. Microsc. Res. Tech. 77:586–593, 2014. © 2014 Wiley Periodicals, Inc.     

Synthesis and characterisation of biologically compatible TiO2 nanoparticles

We describe for the first time the synthesis of biocompatible TiO2 nanoparticles containing a functional NH2 group which are easily dispersible in water. The synthesis of water dispersible TiO2 nanoparticles coated with mercaptosuccinic acid is also reported. We show that it is possible to exchange the stearic acid from pre-synthesised fatty acid-coated anatase 5-nm nanoparticles with a range of organic ligands with no change in the size or morphology. With further organic functionalisation, these nanoparticles could be used for medical imaging or to carry cytotoxic radionuclides for radioimmunotherapy where ultrasmall nanoparticles will be essential for rapid renal clearance.     

Modeling of the FCC Gasoline Desulfurization Process by Liquid Extraction with Sulfolane

Abstract

Extractive desulfurization of fluid catalytic cracking (FCC) gasoline with sulfolane was studied in a batch apparatus. The influence of three inlet parameters (temperature, inlet sulfur content, and solvent ratio) on the process response, that is, desulfurization efficiency, was investigated with the use of a Box-Behnken experimental design by response surface methodology. A mathematical model that can be used for predicting sulfur content in raffinate after extractive batch processing with sulfolane was statistically developed and proven with analysis of variance. Statistical analysis showed that the largest influence on desulfurization efficiency was solvent ratio, the second most significant influence was inlet sulfur content, followed by temperature, and last the interaction between solvent ratio and inlet sulfur content. The obtained second-order polynomial model shows that maximum desulfurization efficiency of 65.34% can be achieved at temperature of 50°C and higher values of inlet sulfur content and solver ratio in the researched range of inlet parameter values.     

What's in a name: Implicit self-esteem and the automatic self.

This article explores the links between implicit self-esteem and the automatic self (D. L. Paulhus, 1993). Across 4 studies, name letter evaluations were positively biased, confirming that implicit self-esteem is generally positive (A. G. Greenwald & M. R. Banaji, 1995). Study 1 found that this name letter bias was stable over a 4-week period. Study 2 found that positive bias for name letters and positive bias for birth date numbers were correlated and that both biases became inhibited when participants were induced to respond in a deliberative manner. Studies 3–4 found that implicit self-evaluations corresponded with self-reported self-evaluations, but only when participants were evaluating themselves very quickly (Study 3) or under cognitive load (Study 4). Together, these findings support the notion that implicit self-esteem phenomena are driven by self-evaluations that are activated automatically and without conscious self-reflection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)