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)     

The production-location problem revisited

This paper reconsiders the production-location problem (PLP) initiated by Moses. The PLP is extended to allow for the geographical substitution between input sources, which is likely to occur in an integrated market. An algorithm is then proposed to solve this problem. Finally, using numerical examples, it is shown that small variations in the elasticity of substitution of the production function may lead to substantial jumps in the optimal firm location. Received: 2 December 1997 / Accepted: 5 October 1999     

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.     

Modification of wheat gluten with citric acid to produce superabsorbent materials

Wheat gluten was reacted with citric acid to produce natural superabsorbent materials able to absorb up to 78 times its weight in water. The properties of the modified gluten samples were characterized using Fourier Transform Infra‐red (FTIR) spectroscopy, thermogravimetric analysis, and water uptake. The reaction between gluten and citric acid was examined for gluten : citric acid ratios of 0.38 : 1 to 0.75 : 1 at temperatures from 100 to 130°C. More citric acid reacted for samples containing higher citric acid concentrations and at higher temperatures. FTIR analyses indicated the presence of carboxylate groups on the modified gluten samples, which resulted in modified samples having higher water uptake values than neat gluten. The sample with a gluten:citric acid ratio of 0.5 : 1 and reaction temperature of 120°C had the largest water uptake value. Also, all modified gluten samples had lower thermal stability than neat gluten. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Water absorbance and thermal properties of sulfated wheat gluten films

Wheat gluten films of various thicknesses formed at 30–70°C were treated with cold sulfuric acid to produce sulfated gluten films. Chemical, thermal, thermal stability, and water uptake properties were characterized for neat and sulfated films. The sulfated gluten films were able to absorb up to 30 times their weight in deionized water. However, this value dropped to 3.5 when the film was soaked in a 0.9% (w/w) NaCl solution. The films were also soaked 4 times in deionized water, and each soaking resulted in a reduced water uptake capacity. The temperature of film formation had no effect on the final water uptake properties. Also, thinner films had higher concentrations of sulfate groups than thicker films; this resulted in higher water uptake values. In addition, sulfated gluten films had comparable glass‐transition temperatures but lower thermal stabilities than the neat gluten films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010