NMDA receptor complex blockade by oral administration of magnesium: comparison with MK-801

The ion channel of the N-methyl-D-aspartate (NMDA) receptor complex is subject to a voltage-dependent regulation by Mg2+ cations. Under physiological conditions, this channel is supposed to be blocked by a high concentration of magnesium in extracellular fluids. A single dose of magnesium organic salts (i.e., aspartate, pyroglutamate, and lactate) given orally to normal mice rapidly increases the plasma Mg2+ level and reveals a significant dose-dependent antagonist effect of magnesium on the latency of NMDA-induced convulsions; this effect is similar to that seen after administration of the dizocilpine (MK-801) channel blocker. An anticonvulsant effect of Mg2+ treatment is also observed with strychnine-induced convulsions but not with bicuculline-, picrotoxin-, or pentylenetetrazol-induced convulsions. In the forced swimming test, Mg2+ salts reduce the immobility time in a way similar to imipramine and thus resemble the antidepressant-like activity of MK-801. This activity is masked at high doses of magnesium by a myorelaxant effect that is comparable to MK-801-induced ataxia. Potentiation of yohimbine fatal toxicity is another test commonly used to evaluate putative antidepressant drugs. Administration of Mg2+ salts, like administration of imipramine strongly potentiates yohimbine lethality in contrast to MK-801, which is only poorly active in this test. Neither Mg2+ nor MK-801 treatment can prevent reserpine-induced hypothermia. These data demonstrate that oral administration of magnesium to normal animals can antagonize NMDA-mediated responses and lead to antidepressant-like effects that are comparable to those of MK-801. This important regulatory role of Mg2+ in the central nervous system needs further investigation to evaluate the potential therapeutic advantages of magnesium supplementation in psychiatric disorders.     

Linear pseudosystolic array for partitioned matrix algorithms

We describe a class-specific linear pseudosystolic array, withK processing elements, suitable for partitioned execution of matrix algorithms. This array achieves high efficiency, exploits pipelining within cells in a simple manner, has off-cells communication rate lower than computation rate, a small storage inside each cell (whose size is independent of the size of problems), and external storage. This array has been derived from the application of the multimesh graph (MMG) method to a large class of matrix algorithms.Processing elements (cells) use the decoupled access/execute model of computation, which requires two programs in each cell: one controlling the execution of operations and the other the data transfers. All storage modules in the array are accessed as FIFO queues, without the need for addressing mechanisms. We describe the proposed instruction set, which includes single-instruction loops with no overhead, and block-loops with just one extra instruction. Moreover, cells can nest up to three loops with no added overhead. These features are needed for mapping algorithms with the MMG method.Mapping onto this array is illustrated using the LU-decomposition algorithm, and results obtained with other algorithms are also given. Estimates of performance indicate that it is possible to achieve over 85% efficiency, with low requirements in communication bandwidth and storage.This research has been supported in part by Universidad de Concepción (Grant DI-20.92.21, Linear array for matrix algorithms) and by NSF (Grant MIP-8813340, Composite operations using on-line arithmetic in application-specific parallel architectures).     

Effects of Co−Cr corrosion products and corresponding separate metal ions on human osteoblast-like cell cultures

The cytocompatibility of the degradation products of a Co–Cr orthopaedic alloy was investigated with particular focus on the dose-effect of an electrochemically dissolved alloy extract and of the corresponding separate metal ions on human osteogenic bone marrow derived cells. The extract solution contained 15 ppm of Co and 8ppm of Cr as analysed by atomic absorption spectroscopy. Stock salt solutions of CoCl₂·6H₂O, CrCl₃·6H₂O and Na₂CrO₄ at corresponding concentrations were also prepared. Several dilutions of the above metallic solutions were tested for a period of 21 days on cells (third subculture) cultured in -minimal essential medium containing foetal govine serum and supplemented with antibiotics, dexamethasone ascorbic acid and -glycerophosphate. The osteoblast response to the presence of metal ions was evaluated by several biochemical parameters: cell viability (MTT reduction by intracellular enzymes), alkaline phosphatase activity (an osteoblast marker) and protein production (both intracellular and extracellur). Co–Cr corrosion products showed opposite effects to their respective metal salts only on day 1. With time the different metal solutions presented a similar pattern of inhibition. These results suggest that impaired bone formation in vitro can occur in the presence of Co–Cr corrosion products.This paper was accepted for publication after the 1995 Conference of the European Society of Biomaterials, Oporto, Portugal, 10–13 September.     

From Faces to Outdoor Light Probes

Image‐based lighting has allowed the creation of photo‐realistic computer‐generated content. However, it requires the accurate capture of the illumination conditions, a task neither easy nor intuitive, especially to the average digital photography enthusiast. This paper presents an approach to directly estimate an HDR light probe from a single LDR photograph, shot outdoors with a consumer camera, without specialized calibration targets or equipment. Our insight is to use a person's face as an outdoor light probe. To estimate HDR light probes from LDR faces we use an inverse rendering approach which employs data‐driven priors to guide the estimation of realistic, HDR lighting. We build compact, realistic representations of outdoor lighting both parametrically and in a data‐driven way, by training a deep convolutional autoencoder on a large dataset of HDR sky environment maps. Our approach can recover high‐frequency, extremely high dynamic range lighting environments. For quantitative evaluation of lighting estimation accuracy and relighting accuracy, we also contribute a new database of face photographs with corresponding HDR light probes. We show that relighting objects with HDR light probes estimated by our method yields realistic results in a wide variety of settings.     

Shrinkage reduction and morphological characterization of PP reinforced with glass fiber and nanoclay using functionalized PP as compatibilizer

This work presents results of shrinkage and structure characteristics of reinforced PP using combinations of glass fiber and nanoclay with functionalized PP as compatibilizer during injection molding. Shrinkage, warpage and structure characteristics of clay-fiber reinforced nanocomposites using PP grafted with 2-[2- (Dimethylamino) ethoxy] ethanol (DMAE) to obtain PPgDMAE as compatibilizer, were analyzed. The glass fiber-nanoclay combinations decrease the PP shrinkage as well as the warpage tendency. Functionalized PP facilitates glass fiber and clay dispersion and intercalation. The crystallization temperature, Tc, increases slightly with respect to pure PP and the degree of crystallinity, Xc, was reduced with the clay content.     

Bayesian Reliability of Gas Network Under Varying Incident Registration Criteria

Gas transmission pipeline network is of great importance to any country using natural gases in its various technological processes. However, the usefulness cannot overshadow the threat posed to people and property by the grid failures. In order to quantify the reliability of the grid, se veral widely recognized pipeline incident databases have been established. However, each database contains data about pipelines operated in remote geographical regions with varying soil types, under different incident registration criterion. For a longer time period even in single database, there is variation of these incident registration criteria. Therefore, analysis of an entire sample without regard to the incident criteria change raises suspicions about the validity of resulting inferences. Authors move beyond the qualitative pipeline incident database comparison and provide a methodology for quantitative integration of all available statistical information to improve gas pipeline network reliability evaluation. We develop a new model called Criteria‐dependent Poisson model, which takes into account various incident data collection criteria and extend it to the hierarchical (Bayesian) case when different databases with differing incident registration criteria can be joined in the same analysis. With the real data examples, we demonstrate the applicability of our method, which unfolds itself to be of great usefulness in reliability prediction. The Lithuanian pipeline network failure rate assessment shows the advantages of hierarchical structuring of Criteria‐dependent Poisson model in small sample problems. Copyright © 2015 John Wiley & Sons, Ltd.     

Accurate micro-computed tomography imaging of pore spaces in collagen-based scaffold

In this work we have used X-ray micro-computed tomography (μCT) as a method to observe the morphology of 3D porous pure collagen and collagen-composite scaffolds useful in tissue engineering. Two aspects of visualizations were taken into consideration: improvement of the scan and investigation of its sensitivity to the scan parameters. Due to the low material density some parts of collagen scaffolds are invisible in a μCT scan. Therefore, here we present different contrast agents, which increase the contrast of the scanned biopolymeric sample for μCT visualization. The increase of contrast of collagenous scaffolds was performed with ceramic hydroxyapatite microparticles (HAp), silver ions (Ag⁺) and silver nanoparticles (Ag-NPs). Since a relatively small change in imaging parameters (e.g. in 3D volume rendering, threshold value and μCT acquisition conditions) leads to a completely different visualized pattern, we have optimized these parameters to obtain the most realistic picture for visual and qualitative evaluation of the biopolymeric scaffold. Moreover, scaffold images were stereoscopically visualized in order to better see the 3D biopolymer composite scaffold morphology. However, the optimized visualization has some discontinuities in zoomed view, which can be problematic for further analysis of interconnected pores by commonly used numerical methods. Therefore, we applied the locally adaptive method to solve discontinuities issue. The combination of contrast agent and imaging techniques presented in this paper help us to better understand the structure and morphology of the biopolymeric scaffold that is crucial in the design of new biomaterials useful in tissue engineering.     

Demonstrating Improved Fuel Economy Using Subsystem Specific Lubricants on a Modified Diesel Engine

Fuel economy performance in modern internal combustion engines is of increasing importance to lubricant formulators due to regulations targeting global greenhouse gas emissions. Engines typically employ a single lubricant, with a common sump, to service all components. As a result, base oil and additive selection for fuel economy performance is a compromise among competing demands for different engine subsystems. Opportunities for significant fuel economy improvement through targeted formulation of lubricants for specific engine subsystems are presented, with specific emphasis on segregating the lubricant supplies for the valve train and the power cylinder subsystems. A working prototype was developed in a lab environment by modifying a commercially available twin-cylinder diesel engine. Motored valve train and whole-engine fired test results were obtained and compared to model data. Fuel economy benefits were demonstrated using market representative heavy-duty diesel lubricants, including mineral oil and polyalphaolefin (PAO) blends. The fuel economy benefits of a dual-loop lubricant system are demonstrated through significant viscosity reduction in the power cylinder subsystem, achieving overall engine friction reductions of up to 8% for the investigated operating condition. Results suggest that additional gains may be realized through targeted base oil and additive formulation. Implications for incorporation in larger diesel engines are also considered.     

On the syntheses of branched saturated fatty acids

In order to investigate the relation between the structure of mono-branched saturated fatty acids and their physical properties, a three-factor central composite design was constructed. For this purpose sixteen different fatty acids were prepared. The synthetic strategy was to use if possible, a few common starting materials for the preparation of most of the acids. Thus alkylation and hydrolysis of oxazolines were used for the preparation of 2-butylhexanoic acid, 2-methyloctadecanoic acid, 2-hexadecyloctadecanoic acid and 2-pentyloctadecanoic acid. A number of acids were prepared from thiophene derivatives followed by desulfurization with Raney-Nickel alloy under alkaline conditions. Thus, starting from 3-ethylthiophene, 4-ethyl-2-thiophenecarboxylic acid and 4-ethyl-2-methyl-5-thiophenecarboxylic acid were prepared, which upon desulfurization gave the desired 4-methylhexanoic acid. From 3-bromo-2-methylthiophene, 3-ethyl-2-methyl-5-thiophenecarboxylic acid was preparedvia 3-acetyl-2-methylthiophene and 3-ethyl-2-methylthiophene. Desulfurization gave 4-ethylhexanoic acid. Another approach started with 2-acylthiophenes, which were reacted with Grignard reagent to yield the appropriate olefins. By metalation and reaction with carbon dioxide, these were transformed to the corresponding 2-thiophenecarboxylic acids. Upon desulfurization, the desired fatty acids were obtained. In this way 6-propyldecanoic acid, 6-hexyldodecanoic acid, 6-methyldodecanoic acid and 6-pentylpentadecanoic acid were prepared. The remaining four acids were prepared from some of the branched acids described above through Kolbe reactions of dioic acids. Thus 16-methyloctadecanoic acid and 10-methyl-dodecanoic acid were obtained from 4-methylhexanoic acid, 16-ethyloctadecanoic acid from 4-ethylhexanoic acid and 9-pentyloctadecanoic acid from 6-pentylpentadecanoic acid.     

Quantifying the predatory effect of round goby on Saginaw Bay dreissenids

Invasive dreissenid mussels (D. polymorpha and D. r. bugensis) have fundamentally altered Laurentian Great Lake ecosystems, however in many areas their abundances have declined since the mid-1990s. Another invader, the benthic fish round goby (Neogobius melanostomus), is morphologically adapted to feed on dreissenids and likely affects dreissenid populations; however, the degree of this predatory effect is variable. In 2009 and 2010, we examined round goby abundances, size distributions, diet contents, and diet selectivity in Saginaw Bay, Lake Huron; a shallow bay that has been subjected to numerous anthropogenic stressors. We further used a consumption model to estimate dreissenid consumption by three different size classes of round goby. Round gobies were found throughout the bay and most were smaller than 80 mm total length. Round gobies of all sizes consumed dreissenids (including fish as small as 30 mm total length), though dreissenids were rarely preferred. The relative proportion of dreissenids (by biomass) present in diets of round gobies increased with fish size, but also throughout the year for all size classes. Despite this, overall consumptive effects of round gobies on dreissenids in Saginaw Bay were low. Many dreissenids present in the bay were larger than those consumed by round gobies. Bioenergetics-based model estimates suggest that the smallest round gobies are responsible for the majority of dreissenid consumption. While our findings are limited to soft substrates and influenced by sampling restrictions, our study design allowed us to put bounds on our estimates based upon these multiple sources of uncertainty.