A diminished role for hydrogen bonds in antifreeze protein binding to ice

The most abundant isoform (HPLC-6) of type I antifreeze protein (AFP1) in winter flounder is a 37-amino-acid-long, alanine-rich, alpha-helical peptide, containing four Thr spaced 11 amino acids apart. It is generally assumed that HPLC-6 binds ice through a hydrogen-bonding match between the Thr and neighboring Asx residues to oxygens atoms on the {2021} plane of the ice lattice. The result is a lowering of the nonequilibrium freezing point below the melting point (thermal hysteresis). HPLC-6, and two variants in which the central two Thr were replaced with either Ser or Val, were synthesized. The Ser variant was virtually inactive, while only a minor loss of activity was observed in the Val variant. CD, ultracentrifugation, and NMR studies indicated no significant structural changes or aggregation of the variants compared to HPLC-6. These results call into question the role of hydrogen bonds and suggest a much more significant role for entropic effects and van der Waals interactions in binding AFP to ice.     

Problems with the mass spectrometric determination of tritium from cold fusion

Among the attempts to measure particles produced in the cold fusion of deuterium in palladium metal is the mass spectrometric observation of tritium. An experiment which has been reported in the popular press involves attaching a hollow Pd electrode to a vacuum chamber and measuring the tritium produced during electrolysis using a mass spectrometer. We present data demonstrating that mass 5 and 6, which could be mistaken for the ions DT⁺ and T₂ ⁺, can arise from ion-molecule reactions in the ionizer of the mass spectrometer giving the ions HD₂ ⁺ and D₃ ⁺. With H₂ and D₂ present in the vacuum chamber, there are at least eight reactions which lead to these triatomic species, and these may contribute to a complex time and pressure dependence of the signals.     

Skin surface microflora of the saddle-back tamarin monkey,Saguinus fuscicollis

The resident skin surface microflora of 12 male and three femaleSaguinus fuscicollis was studied. The suprapubic-circumgenital gland surface and the perirectal area were most heavily colonized (10⁶–10⁸ colony forming units/cm²), but high numbers of organisms were also present on the abdomen, the sternal gland surface, and palms and plantar surfaces. Bacteria were also recovered from hair clippings as well as from shaven skin surface, although at much lower densities (10²–10⁴ colony forming units/cm²). Coagulase negative staphylococci, gram-negative bacteria,Streptococcus species and coryneform bacteria were most dominant.Staphylococcus aureus and species ofBacillus were also present. Fungi, yeast, and dermatophytes were infrequently recovered or completely absent. The microbial flora of these tamarins appears to be closely associated with the secretions of the circumgenital scent gland and would therefore be ideally situated to participate in the generation or modification of chemical signals.     

Fuß‐ und Radwegbrücke aus Carbonbeton in Albstadt‐Ebingen

Pedestrian bridge made from carbon‐concrete in Albstadt‐Ebingen – First entirely carbon‐reinforced concrete bridge worldwide The bridge erected in Albstadt‐Ebingen in October 2015 is realized without any steel reinforcement or pre‐tensioning, making it the world's first entirely carbon‐reinforced concrete bicycle and pedestrian‐bridge. The trough section with material thicknesses of 70 mm (trough walls) and 90 mm (slab) respectively has been fabricated as monolithic pre‐cast element. With a span length of 15 m and a width of 3 m, the bridge‐deck requires no further coating and has a total weight of just 14 tons (approximately 310 kg/m2); this is about 50 % of comparable conventional reinforced concrete bridge‐decks. Besides material and weight savings, an exceptionally long service life with minimal maintenance can be expected, as the steel corrosion that is typical in reinforced concrete structures can be entirely avoided. Since the use of carbon‐reinforced concrete (carbon concrete) is not yet approved in Germany, the client had to obtain approval based on individual cases (ZiE).     

Rat behavior in go/no-go and two-alternative choice odor discrimination: Differences and similarities.

To elucidate the cognitive structures of animals, neuroscientists use several behavioral tasks. Therefore, it is imperative to have a firm understanding of each task's behavioral parameters in order to parse out possible task effects. We compare two operant discrimination tasks (Go/No-Go: GNG; Two-Alternative Choice: TAC) that are commonly used in olfactory research. Past research has suggested that solving the two tasks requires divergent cognitive strategies. One hypothesis is that the two tasks differ in how an animal optimizes reward rate by means of a speed–accuracy trade-off (SAT). If this is true, then changing tasks could give researchers an additional tool to understand animal cognition. However, no study has systematically analyzed the two tasks in parallel using odor stimuli. Using standardized training protocols, we test GNG and TAC in parallel. Our protocols allow us to isolate the stimulus sampling period from a general reaction time period. We find that the two tasks do not differ with regard to the stimulus sampling period and conclude that the two tasks do not differ in the amount of time it takes an animal to perform a discrimination. Instead, tasks differ in the time it takes to make an overt behavioral response, with GNG showing shorter periods than TAC. We also find no evidence of rats using either task-specific or intertrial interval-dependent SAT schema in order to optimize reward rate. We show that similarities between dependent variables, with the possible exception of response delay, appear to be under experimenter control. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Are We Prepared? Using Reliability Analysis to Evaluate Emergency Response Systems

The evaluation of government programmes designed to prepare for future contingencies is an ongoing challenge for analysts and public managers. Despite significant focus in emergency management, the existing approaches have difficulty linking preparedness inputs to their effect on performance at future response operations. Adapting techniques from the analysis of technical systems, an approach for assessing response reliability – the likelihood that a response system will be able to deliver response capabilities at or above a specific level at a future incident – is described. The approach bases evaluation on the systematic assessment of the likelihood and consequences of events that would disrupt operations and reduce response performance. By doing so, it provides a clearer method for assessing the cost effectiveness of different preparedness policies and evaluating the performance of past investments in preparedness programmes.     

Preventing discoloration of squalene-soiled cotton fabrics with antioxidants

Removal of discoloration caused by aged oily soils is difficult because oily soils undergo autoxidation, which results in polymerization and formation of chromophores. Use of antioxidants and a reducing agent was investigated for their impact on appearance retention and soil removal. The effect of a reducing agent, sodium dithionite, on the removal of aged squalene from cotton fabrics was studied as a pretreatment to laundering, which enhanced the removal of squalene as well as whiteness restoration. Increases in treatment concentration and time increased color removal. However, no significant increase was found in oil removal, suggesting that the role of the reducing agent is mainly a reductive bleaching action. Thus, the color will probably reverse by oxidation over time making this approach a not-so-promising laundry treatment. As a method of preventing discoloration of oily soiled textile materials, antioxidants Irganox^® 1010, t-butylhydroxyanisole and α-tocopherol were examined; they were found to be effective antioxidants for this purpose by preventing the discoloration of squalene upon aging. With Irganox^® 1010, this prevention occurred without decreasing the detergency of the oil. Most importantly, these antioxidants either did not stain the substrate or showed very low levels of staining upon usage. The biggest barrier to applying antioxidants on textiles is their hydrophobic nature. A search for water-soluble antioxidants with nonstaining and good oxidation inhibiting properties is necessary.     

Particle-induced network formation in linear PDMS filled with silica

We study the formation of permanent elastomers from linear PDMS chains by solution blending with up to 25 wt% fumed silica. The physical networks are characterized by time-domain multiple-quantum NMR. Based upon dynamic parameters measured for the linear precursor polymer, we develop a reliable strategy for component separation in this complex heterogeneous system, providing information on the amount of monomers involved in network-like material, in elastically inactive yet entangled linear chains, and isotropically mobile chain ends, as well as on the effective network chain length as measured via the average residual dipolar coupling constant. The use of untreated silica leads to permanent networks, for which the NMR results correlate well with macroscopic determinations of the relaxed Young modulus and the degree of swelling. Surface-modified silicas do not lead to percolated network structures, but still lead to the formation of 20–40% network-like material, with effective network chain lengths that depend on the surface functionalization and thus on the nanoparticle dispersion. Characteristic changes in the mobile chain end fraction with temperature, in particular its decrease with increasing degree of filling are interpreted as a consequence of altered contour-length fluctuations. An aging experiment conducted on a sample prepared by melt blending reveals the microscopic changes in the network structure occurring over many months.