Free radical theory of aging: effect of dietary fat on central nervous system function

Free radical reactions have been implicated in aging. A rise in the level of random free radical reactions in a biologic system might have a greater effect on the central nervous system (CNS) than elsewhere, partly because of the presence of glial cells and the unique connections between neurons. To evaluate this possibility, some animal experiments were conducted. The initial experiment involved old male Sprague-Dawley rats fed (since shortly after weaning) with semisynthetic diets characterized by fat differing in amount or degree of unsaturation. The number of errors made in a Hebb-Williams maze was determined and found to be higher as the amount or degree of unsaturation of the fat was increased. Likewise rats aged 6 and 9 months, fed semisynthetic diets containing 20 percent by weight of lard, oleinate, or safflower oil +alpha-tocopherol performed significantly better in a discrimination learning situation (Skinner box) than did rats fed a diet containing 20 percent by weight of safflower oil. The diets employed in these studies did not have a significant effect on the mortality rates. These results are compatible with the possibility that enhancing the level of lipid peroxidation has an adverse effect on the CNS, out of proportion to the effect on the body as a whole, as measured by the mortality rate.     

Human, mouse, and rat calnexin cDNA cloning: identification of potential calcium binding motifs and gene localization to human chromosome 5

Calnexin is a 90-kDa integral membrane protein of the endoplasmic reticulum (ER). Calnexin binds Ca2+ and may function as a chaperone in the transition of proteins from the ER to the outer cellular membrane. We have purified human calnexin in association with the human interferon-gamma receptor and cloned calnexin cDNA from placenta. Fragments of calnexin have been prepared as glutathione S-transferase fusion proteins and analyzed for their abilities to bind 45Ca2+ and ruthenium red. A subdomain containing four internal repeats binds Ca2+ with the highest affinity. This sequence is highly conserved when compared to calreticulin (a luminal ER protein), an Onchocerca surface antigen, and yeast and plant calnexin homologues. Consequently, this sequence represents a conserved motif for the high-affinity binding of Ca2+, which is clearly distinct from the "E-F hand" motif. An adjacent subdomain, also highly conserved and containing four internal repeats, fails to bind Ca2+. The carboxyl-terminal, cytosolic domain is highly charged and binds Ca2+ with moderate affinity, presumably by electrostatic interactions. The calnexin amino-terminal domain (residues 1-253) also binds Ca2+, in contrast to the amino-terminal domain of calreticulin, which is relatively less acidic. We have also determined the cDNA sequences of mouse and rat calnexins. Comparison of the known mammalian calnexin sequences reveals very high conservation of sequence identity (93-98%), suggesting that calnexin performs important cellular functions. The gene for human calnexin is located on the distal end of the long arm of human chromosome 5, at 5q35.     

Modeling of oxy-fuel combustion for a western Canadian sub-bituminous coal

The motivation of this research is to develop practical oxy-coal combustion techniques in order to facilitate the conversion of coal-fired utility power plants so as to recover a CO₂ rich flue gas stream for use and/or sequestration. The objective of this study is to ascertain the applicability and accuracy of a modeling tool to assist with future pilot scale oxy-fuel combustion experiments and burner scale-up studies. Two modes of oxy-coal combustion, O₂ enriched air (OEA) and recycled flue gas (RFG), were experimentally tested in a 0.3 MW_th pilot-scale combustor using a western Canadian sub-bituminous coal. The computational fluid dynamic tool was utilized to model the combustion, heat transfer and pollutant formation characteristics of these test cases and to examine the impact due to changes in the combustion medium, burner swirl and burner configuration. The model provided insights for the observed variation in NO_x production among the test cases: the dramatic increase in the OEA mode, the drop at higher burner swirl settings and the surprisingly small reduction in the RFG mode. Overall the model results compared well with measured data in all test cases and established confidence in using the model to explore new design concepts for oxy-coal combustion.     

Ammonia borane-based reactive mixture for trapping and converting carbon dioxide

Ammonia borane (NH₃BH₃) is a reducing agent, able to trap and convert carbon dioxide. In the present work, we used a reactive solid consisting of a mixture of 90 wt.% of NH₃BH₃ and 10 wt.% of palladium chloride, because the mixture reacts in a fast and exothermic way while releasing H₂ and generating catalytic Pd⁰. We took advantage of such reactivity to trap and convert CO₂ (7 bar), knowing besides that Pd⁰ is a CO₂ hydrogenation catalyst. The operation (i.e. stage 1) was effective: BNH polymers, and B−O, C=O, C−O, and C−H bonds (like in BOCH₃ and BOOCH groups) were identified. We then (in stage 2) pyrolyzed the as-obtained solid at 1250 °C and washed it with water. In doing so, we isolated cyclotriboric acid H₃B₃O₆ (stemming from B₂O₃ formed at 1250 °C), hexagonal boron nitride, and graphitic carbon. In conclusion, the stage 1 showed that CO₂ can be ‘trapped’ and converted, resulting in the formation of BOCH₃ and BOOCH groups (possible sources of methanol and formic acid), and the stage 2 showed that CO₂ transforms into graphitic carbon.     

The composition and structure of depressive symptomatology in renal disease.

Renal disease is an increasingly common illness among middle-aged and older adults, and is often associated with depression. The Center for Epidemiologic Studies Depression Scale (CES–D) is a widely used self-report screening measure on which responses generally conform to a 4-factor structure, with each factor loading onto a higher-order Depression factor. The current study examines whether this structure is supported among individuals with renal disease (both predialysis and posttransplant kidney disease patients). Persons with renal disease (n = 225) and healthy control participants (n = 230) were recruited from Vancouver General Hospital and the community. Participants completed the CES–D as part of an extended assessment. Confirmatory factor analytic models were computed for the renal disease and healthy control groups. Results support a 4-factor structure for CES–D responses in persons with renal disease and healthy controls. The hierarchical structure of CES–D responses also appears invariant between groups. Factor structure was similar between groups; only for Depressive Affect was the strength of association with the second-order factor greater among the renal disease than healthy control participants. Findings support similarity of CES–D factor structures between patients with renal disease and healthy individuals. Results suggest that the CES–D's 4 factors contribute to measurement of a higher-order Depression factor in both groups; furthermore, 3 of 4 factors appear invariant between groups. As such, this measure can be used confidently to quantify depressive symptoms in individuals with renal disease. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

H2 production through oxide irradiation: Comparison of gamma rays and vacuum ultraviolet excitation

The production of molecular hydrogen by gamma radiolysis and vacuum ultra violet photolysis of dried and hydrated nanoporous titania and zirconia nanoparticles has been studied. The nanoparticles were prepared as free standing films using a surface sol-gel process on cellulose. A significant hydrogen production was observed for both TiO₂ and ZrO₂ in vacuum ultra violet or gamma irradiation. This production could be optimized by controlling the amount of water and by introducing hydroxyl radical scavengers in the irradiated systems. The mechanism underlying hydrogen production seems qualitatively different in gamma and in vacuum ultra violet (VUV) irradiation.     

Analog performance of standard and strained triple-gate silicon-on-insulator nFinFETs

This work shows a comparison between the analog performance of standard and strained Si n-type triple-gate FinFETs with high-κ dielectrics and TiN gate material. Different channel lengths and fin widths are studied. It is demonstrated that both standard and strained FinFETs with short channel length and narrow fins have similar analog properties, whereas the increase of the channel length degrades the early voltage of the strained devices, consequently decreasing the device intrinsic voltage gain with respect to standard ones. Narrow strained FinFETs with long channel show a degradation of the Early voltage if compared to standard ones suggesting that strained devices are more subjected to the channel length modulation effect.     

Harmonic distortion of 2-MOS structures for MOSFET-C filters implemented with n-type unstrained and strained FINFETS

This work investigates the harmonic distortion (HD) in 2-MOS balanced structures composed of triple gate FinFETs. HD has been evaluated through the determination of the third-order harmonic distortion (HD3), since this represents the major non-linearity source in balanced structures. The 2-MOS structures with devices of different channel lengths (L) and fin widths (W_fin) have been studied operating in the linear region as tunable resistors. The analysis was performed as a function of the gate voltage, aiming to verify the correlation between operation bias and HD3. The physical origins of the non-linearities have been investigated and are pointed out. Being a resistive circuit, the 2-MOS structure is generally projected for a targeted on-resistance, which has also been evaluated in terms of HD3. The impact of the application of biaxial strain has been studied for FinFETs of different dimensions. It has been noted that HD3 reduces with the increase of the gate bias for all the devices and this reduction is more pronounced both in narrower and in longer devices. Also, the presence of strain slightly diminishes the non-linearity at a similar bias. However, a drawback associated with the use of strain engineering consists in a significant reduction of the on-resistance with respect to unstrained devices.     

Test of a Method to Calculate Near-Bank Velocity and Boundary Shear Stress

Detailed knowledge of the flow and boundary shear stress fields near the banks of natural channels is essential for making accurate calculations of rates of near-bank sediment transport and geomorphic adjustment. This paper presents a high-resolution laboratory data set of velocity and boundary shear stress measurements and uses it to test a relatively simple, fully predictive, numerical method for determining these distributions across the cross-section of a straight channel. The measurements are made in a flume with a fairly complex cross-section that includes a simulated, cobble-roughened floodplain. The method tested is that reported by Kean and Smith in Riparian Vegetation and Fluvial Geomorphology in 2004, which is modified here to include the effects of drag on clasts located in the channel. The calculated patterns of velocity and boundary shear stress are shown to be in reasonable agreement with the measurements. The principal differences between the measured and calculated fields are the result of secondary circulations, which are not included in the calculation. Better agreement with the structure of the measured streamwise velocity field is obtained by distorting the calculated flow field with the measured secondary flow. Calculations for a variety of narrower and wider configurations of the original flume geometry are used to show how the width-to-depth ratio affects the distribution of velocity and boundary shear stress across the channel.