Mathematical modeling of the heat transfer process and protein denaturation during the thermal treatment of Patagonian marine crabs

Southern Ocean swimming crab Ovalipes trimaculatus and the Patagonian stone crab Platyxanthus patagonicus are fishing resources with commercial value. Thermal treatment of crabs is necessary to denature muscle proteins, facilitating meat detachment from the crab shell (picking procedure). The proximal composition, protein patterns of crab muscle, thermophysical properties and heat transfer coefficients were determined. Heat transfer during thermal processing of body (i.e., cephalothorax) and claws of both crab species was simulated using a finite element computational code; the simulations were experimentally validated. Color changes in crab muscle during the heating process were measured. Thermal denaturation kinetics of myofibrillar proteins was determined using Differential Scanning Calorimetry (DSC) in small samples previously heated in water under controlled conditions. DSC thermograms of raw crab muscle showed two peaks at 49.0 ± 0.4 and 77.5 ± 0.6 °C corresponding to myosin and actin respectively. Activation energies for the denaturation of myosin (145.70 kJ/mol) and actin (156.42 kJ/mol) were calculated from Arrhenius equation. The degree of denaturation achieved by the myofibrillar proteins at the coldest point of the muscle in body and claws during the heating process was established by considering the protein denaturation kinetics determined by DSC, the activation energies and the heat penetration curves. Adequate conditions for the detachment of meat from the crab exoskeleton were established. The obtained results may help in determining the optimal heating times during the industrialization of these crustaceans.     

Tribological properties of hardened high strength Boron steel at combined rolling and sliding condition

The use of hardened high strength steel is found in applications where high wear resistance is required. The wear properties of high strength Boron steel are well known in applications with abrasive wear from stones, ore and other hard material. A unique concept of wear protection of rails is newly presented, a wear resistant cap made of hardened high strength Boron steel.Reducing the wear of rails and wheels and controlling the frictional behavior in the wheel/rail contact are two key issues for railway owners in order to reduce the increasing costs related to higher axle loads, higher speeds, more frequent traffic, etc. Therefore, the aim of this work has been to investigate and compare the tribological properties of Boron steel and UIC 1100 rail steel in contact with Blue Light wheel steel (AAR Class C (69-JDG-8)) under dry and water lubricated conditions in a two-disc tribometer. Advanced analytical instruments including 3D optical surface profiler, micro-hardness indenter, light microscope and SEM/EDS were used to analyze the results.Results from the experiments show that the friction coefficient in tests with Boron steel is more stable both in dry and water lubricated conditions than tests including UIC 1100 rail steel used in todays application. Surface damages seen from water lubricated tests on UIC 1100 rail steel are not seen on the surface of the Boron steel discs. In all tests, the wear decreased when water was added in the contact and friction was slightly decreased.     

Tuning morphology of siloxane bond-based polybenzoxazines by controlling the sol–gel and curing processes

Novel polybenzoxazine/polysilsesquioxane nanocomposites were synthesized with uniform and reproducible structural morphology, high T_g, and good thermal stability. Polysilsesquioxane was oriented in a nanometer-size lamellar structure. Benzoxazine monomer based on silane (BA-3aptms) was synthesized by reaction between bisphenol A, 3-(trimethoxysilyl)propylamine, and paraformaldehyde in a 1:2:4 molar ratio. Four experimental conditions of the two stage sol–gel process for polysilsesquioxane were studied, and their effect on the material characteristics investigated. In the first stage, hydrolysis was favored, while the second stage mostly consisted of condensation. The reaction condition with the longest hydrolysis time allowed the increase of the concentration of silanol units and the selective condensation, favoring the formation of a higher amount of cage-like cyclic structures. In addition, this experimental procedure was well controlled so that the sol–gel and oxazine-ring opening reactions were extremely reproducible from batch to batch. All processes were monitored by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis and dynamic mechanical thermal analysis, scanning electron and transmission electron microscopies, and X-ray diffraction. A chemometric approach based on a multivariate curve resolution model was applied to the FTIR spectra, which allowed the identification of four reaction components associated with the sol–gel and the curing processes.     

Plants' entry and exit in Swedish municipalities

Plants' entry and exit behaviour in Swedish municipalities are studied within a fixed-effect, integer-valued autoregressive model. Based on eight industrial sectors, 1985–1993, and all municipalities, models are estimated by a generalized method of moment estimator. Influences on entry and exit are systematic and spatially as well as temporally variable. Responses to explanatory variables differ between sectors. Average income, local unemployment and higher education are found to be important determinants of both entry and exit across sectors. Received: August 1999/Accepted: January 2001     

Optimization of a HS-SPME-GC-MS Procedure for Beer Volatile Profiling Using Response Surface Methodology: Application to Follow Aroma Stability of Beers Under Different Storage Conditions

The optimization of the main experimental variables, such as extraction temperature, volume of sample and the extraction time of an HS-SPME/GC-MS procedure, for profiling beer volatile analysis was evaluated using response surface methodology. A central composite circumscribed design was employed to study the effect of the experimental variables on the extraction of 28 representative volatile compounds of beer flavour profile. The parameters of the models were estimated by multiple linear regressions. The strongest influence in the volatile extraction yield was the volume of the sample (V) and the extraction temperature (T), with a positive and a negative effect, respectively. The performance characteristics of the optimised method were also determined, showing adequate linear ranges, repeatability, detection and quantification limits. The optimised methodology was applied to the same beer sample stored during 5?months at three different temperature conditions (4, 20 and 40?°C). Sampling was performed monthly, and the results showed that the concentration of most volatile compounds decreased during beer storage, although the rate of decrease was clearly higher at room temperature (20?°C) compared with refrigeration conditions (4?°C). Accelerated ageing conditions (40?°C) showed the most different volatile profile. Sensory analysis also revealed large differences in the overall quality of the samples, showing that even at room temperature the aroma profile of beer is greatly modified during its shelf life.     

Can a knowledge‐based cluster be created? The case of the Barcelona 22@ district*

The aim of this paper is to evaluate the local policy that has promoted the formation of a cluster of knowledge‐based activities in the city of Barcelona. After decades of economic and industrial stagnation in a district called Poblenou, in the year 2000 the City Council of Barcelona implemented a plan to renew the area's urban and economic structure. Under the development plan, knowledge‐based firms were encouraged to set up in the area and thus to create a cluster of advanced activities. This paper examines the success of this local policy and aims to determine whether cluster amenities have played a part in attracting knowledge‐based firms. First, we evaluated the cluster implementation via a ‘difference‐in‐differences’ analysis, comparing the increase in the percentage of knowledge‐based firms in this specific area with the increase of these firms in other local areas. Second, to determine whether the cluster amenities are an important element in attracting knowledge‐based activities, we perform a multivariate regression to see if cluster amenities (as valued by firms in a survey) do have an effect on the decision of knowledge‐intensive firms to locate in the district. El propósito de este artículo es evaluar la política local que ha favorecido la formación de un conglomerado de actividades basadas en conocimiento en la ciudad de Barcelona. Después de décadas de estancamiento económico e industrial en un distrito llamado Poblenou, el Ayuntamiento de Barcelona implementó en el año 2000 un plan para renovar la estructura urbana y económica de la zona. Siguiendo el plan de desarrollo, se animó a las empresas de actividades basadas en conocimiento a que se establecieran en este área, creando con ello un conglomerado de actividades avanzadas. Este artículo examina el éxito de esta política local e intenta determinar si los servicios de conglomerado han jugado un papel a la hora de atraer a empresas de actividades basadas en conocimiento. Primero, evaluamos la implementación del conglomerado por medio de un análisis de diferencia en diferencias, al comparar el aumento del porcentaje de empresas de actividades basadas en conocimiento en este área específica con el aumento de estas empresas en otras áreas locales. Segundo, para determinar si las amenidades de conglomerado son un elemento importante a la hora de atraer actividades basadas en conocimiento, realizamos una regresión multivariante para observar si las amenidades de conglomerado (así valoradas por las empresas en una encuesta) afectan a la decisión de las empresas basadas en conocimiento de ubicarse en este distrito.      

On the interrelationship between hepatic carnitine, fatty acid oxidation, and triglyceride biosynthesis in nephrosis

The nephrotic syndrome is associated with disturbances in plasma lipid pattern and metabolism. However, the reason for these perturbations is poorly understood. In the present study, we have investigated hepatic triglyceride metabolism in puromycin aminonucleoside-induced nephrotic syndrome in rats. Nephrotic rats displayed a 70% increase in hepatic triglyceride levels compared to controls (16.9±1.6 vs. 9.8±0.6 μmol/g liver; means±SEM, P<0.01). The capacity for hepatic mitochondrial β-oxidation of fatty acids was substantially elevated (80%). This was associated with a rise in the liver content of the fatty acid carrier carnitine (1.24±0.06 vs. 0.85±0.07 μmol/g dry weight, P<0.05). A positive correlation between the levels of acetylcarnitine and acetyl-CoA was found in normal as well as in nephrotic rats, implying that carnitine plays an important role as an acetyl group acceptor in the liver under normo- and hyperlipidemic conditions. Changes in carnitine levels seem to be tightly coupled to the rate of fatty acid oxidation. There was a significant elevation in the activity of phosphatidate phosphohydrolase (E.C. 3.1.3.4) in liver microsomes from nephrotic rats (1.07±0.09 vs. 0.81±0.04 nmol/min·mg protein, P<0.02). Hepatic very low density lipoprotein (VLDL)-triglyceride secretion rate was 18% higher in nephrotic rats than in controls. The results demonstrate a deranged hepatic triglyceride metabolism in nephrosis, with an increased hepatic triglyceride biosynthesis, a sizable accumulation of hepatic triglycerides, and only a modest increase in VLDL triglyceride secretion. In addition, mitochondrial β-oxidation of fatty acids was enhanced, associated with an increased availability of carnitine.     

Intracellular Polysilicon Barcodes for Cell Tracking

During the past decade, diverse types of barcode have been designed in order to track living cells in vivo or in vitro, but none of them offer the possibility to follow an individual cell up to ten or more days. Using silicon microtechnologies a barcode sufficiently small to be introduced into a cell, yet visible and readily identifiable under an optical microscope, is designed. Cultured human macrophages are able to engulf the barcodes due to their phagocytic ability and their viability is not affected. The utility of the barcodes for cell tracking is demonstrated by following individual cells for up to ten days in culture and recording their locomotion. Interestingly, silicon microtechnology allows the mass production of reproducible codes at low cost with small features (bits) in the micrometer range that are additionally biocompatible.     

An hourly diffuse fraction model with correction for variability and surface albedo

The paper presents an improved version of a previously published model for the diffuse fraction of hourly global irradiance. In addition to hourly solar elevation and clearness index, an hour-to-hour variability index and regional surface albedo are included among the input parameters. Moreover, to prevent excessively high normal incidence beam irradiances at very low solar elevations, the model does not allow a solar elevation dependent maximum beam transmittance to be exceeded. This new model is tuned to 32 years of data from Bergen, Norway. Moreover, a test against independent data from four European stations showed that the model performs better than the models of Erbs et al. (1982), Maxwell (1987) and Perez et al. (1992).     

Children's performance on pseudoword repetition depends on auditory trace quality: Evidence from event-related potentials.

This study explored the relation between phonological short-term memory and auditory-sensory processing in 7–9-year-old children. Twenty-four participants performed a pseudoword repetition test. The mismatch-negativity (MMN) component of auditory event-related brain potentials was obtained from 9 participants with the highest and 9 participants with the lowest scores on the test. The MMN indexes short-term auditory-sensory memory, including auditory-sensory representations for speech. It was recorded to just perceptible /baga/–/baka/ bisyllabic and easily discriminable 1000/1100-Hz tone contrasts with interstimulus intervals of 350 and 2,000 ms. The high and low repeaters differed significantly in MMN amplitude to speech stimuli at the shorter interstimulus interval. Thus, the accuracy of auditory-sensory processing seems to affect phonological short-term representations in school-age children and therefore may play a role in vocabulary development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)