The effects of temperature on the interactions between volatile general anaesthetics and a neuronal nicotinic acetylcholine receptor

1. Completely isolated identified neurones from the right parietal ganglion of the pond snail Lymnaea stagnalis were investigated under two-electrode voltage clamp. Neuronal nicotinic acetylcholine receptor (AChR) currents were studied at low acetylcholine concentrations (< or = 200 nM). 2. Inhibition of the ACh-induced currents by three volatile general anaesthetics (halothane, isoflurane and methoxyflurane) and the specific inhibitor (+)-tubocurarine was studied as a function of temperature (over the range 4-25 degrees C). 3. The inhibition by the volatile anaesthetics increased (inhibition constants decreased) with decreasing temperature while the inhibition by (+)-tubocurarine did not change significantly near room temperature, but decreased at lower temperatures. The (+)-tubocurarine inhibition appeared to be competitive in nature and showed no significant voltage-dependence. 4. The van't Hoff plots (logarithms of the dissociation constants against reciprocal absolute temperature) were linear for the anaesthetics, but markedly non-linear for (+)-tubocurarine. From these plots, values for the changes in the standard Gibbs free energy delta G degrees water-->AChR, enthalpy delta H degree water-->AChR, entropy delta S degree water-->AChR and heat capacity delta Cp degree water-->AChR were determined. Tubocurarine was found to bind very much tighter to the receptor than the volatile anaesthetics due, entirely, to a favourable increase in entropy on binding. 5. A comparison between the temperature-dependence of the anaesthetic inhibition of the ACh receptor and that of general anaesthetic potencies in animals indicates that the temperature-dependence of animal potencies might be simply accounted for in terms of changes in anaesthetic/receptor binding.     

Perceived family criticism and primary care utilization: psychosocial and biomedical pathways

We explored the relationship of perceived family criticism to subsequent healthcare utilization in patients attending a family medicine center. We examined: a) the relationship of perceived criticism to subsequent utilization for biomedical and psychosocial/somatic problems; b) the mediating effects of self-rated mental health and physical function; and c) the mediating effects of social support. The analyses were adjusted for age, sex, race, education, health insurance, and martial status. Higher perceived criticism predicted more psychosocial/somatic and biomedical visits. The relationship of perceived criticism with psychosocial/somatic visits was entirely mediated through self-rated mental health. The relationship of perceived criticism with biomedical visits was partly mediated through self-rated physical function and, in part, independent. Social support played no role in explaining these relationships. Further research is needed to determine whether lowering perceived family criticism lowers primary care utilization.     

DEPOSITIONAL AND DIAGENETIC BARRIERS,BAFFLES AND CONDUITS: PERMIAN – CARBONIFEROUS UNAYZAH RESERVOIR,NUAYYIM FIELD,CENTRAL SAUDI ARABIA

The Unayzah Formation is one of the most important Palaeozoic reservoir systems in Saudi Arabia. In the Nuayyim field, Central Saudi Arabia, it produces light, sweet crude oil and consists of three main reservoir units, in descending stratigraphic order: Unayzah A, B and C. These reservoir units include a wide range of depositional facies deposited under a variety of climatic conditions, from high‐latitude glacio‐fluvial to more temperate playa/lacustrine, floodplain and braided‐fluvial to hot‐arid aeolian environments. Together with the diagenetic changes superimposed on the various depositional facies, this has produced complex reservoir heterogeneity. The effects of this diagenetic and sedimentologic complexity on reservoir quality and compartmentalization are the subject of this paper. Approximately 816 ft of core and 611 core plug samples were examined from three wells which penetrate, completely or in part, the Unayzah reservoir. We combine petrographic and scanning electron microscope analysis with porosity and permeability data and calculated pore throat dimensions to identify fluid conduits, barriers and baffles to fluid flow. A rock classification scheme is proposed which takes into account whether the pore‐level control on fluid flow is due to depositional or diagenetic processes and the composition of depositional or diagenetic phases within the pores. Distinguishing depositional versus diagenetic controls on fluid flow is important for predicting the three‐dimensional geometry of conduits, barriers and baffles, and a priori knowledge of potential reactions between injected fluids and reservoir rocks is important for designing enhanced oil recovery fluids. In the three wells studied, it appears that the Unayzah reservoir is compartmentalized vertically due to the occurrence of diagenetic and depositional barriers and baffles. There is insufficient data to assess the lateral or areal extent of the barriers, baffles and fluid conduits, but the understanding of pore‐level controls on reservoir quality and the rock classification schemes introduced here will provide a starting point for future studies. These studies should combine well logs, seismic and engineering data with data presented here to assist mapping conduits, barriers and baffles across the field. The proposed classification schemes may also prove to be useful for assessing reservoirs in other fields both within Saudi Arabia and elsewhere.     

Activities and well-being in older age: Effects of self-concept and educational attainment.

The positive effect of activities on well-being is proposed to be mediated by self-conceptualizations and facilitated by socioeconomic status. The hypothesized processes were estimated with LISREL VIII using data from a large cross-sectional survey with a sample of 679 adults aged 65 and older who were representative of older adults living in the Detroit area. Findings indicate that the frequency of performing both leisure and productive activities yields an effect on physical health and depression and that these effects are mediated in part by a sense of self as agentic, but less clearly by a sense of self as social. Furthermore, socioeconomic status, operationalized as formal educational attainment, facilitates the effect of leisure to a greater extent than that of productive activities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Realization of Finite Impulse Response Filters Using Coefficients +1, 0, and -1

New classes of nonrecursive linear digital filters are proposed as alternatives to conventional methods for digital signal processing devices. In fact, the traditional approach, where signal samples are represented by 8-15 bit words, can be very expensive to implement due to the complexity of multibit multipliers and adders. Filter structures consisting of a transversal filter with tap coefficients restricted to - 1, 0, or + 1 and cascaded with simple recursive sections are proposed. Using a mean square error criterion, dynamic programming methods to select optimum sets of coefficient values for the taps are presented and evaluated. It is shown that these structures lend themselves to very simple hardware implementations and offer a valid alternative to the conventional filtering approach. Designs for several example filters are presented, and their implementation complexity is examined.     

The Effect of Ionic Surfactant Adsorption on the Rheology of Ceramic Glaze Suspensions

The rheological behavior of ceramic glaze suspensions containing limestone, quartz, feldspar, and kaolin, has been improved by the addition of either a cationic (cetylpyridinium chloride, CPC) or an anionic (sodium dodecylbenzenesulfonate, SDBS) surfactant. Additional stability and lower viscosity can result from either electrical double layer repulsion or steric repulsion depending on the surfactant type, concentration, ionic strength, and pH. Underdosing may result in high viscosity due to charge neutrality and hydrophobic attraction between particles while overdosing may result in high viscosity possibly due to micelles in the solution. The situation is particularly complicated for glazes containing limestone and anionic surfactant at moderate to low pH where calcium carbonate is soluble. The anionic surfactant and calcium ions can form complexes that are poorly soluble and strongly adsorb to the surface of the particles. The resulting thick steric layer of complexes produces a significant repulsion and stable, low viscosity suspensions. ζ potential measurements and adsorption isotherms are used to interpret the rheological behavior.     

UV-responsive CCD image sensors with enhanced inorganic phosphor coatings

Typical polysilicon gate charge-coupled device (CCD) image sensors are unresponsive to ultraviolet (UV) light because of the high absorption of the radiation in polysilicon gate material, which leads to a short penetration depth (<2 nm), and absorption of the radiation in the gate material rather than within the channel of the CCD. An inorganic phosphor coating to convert the UV radiation to visible has been developed. Although the coating is similar to acrylics doped with organic laser dyes reported previously, in this work the organic dye has been replaced with a more robust inorganic phosphor. In addition, a new deposition method has been developed to improve the photoresponse nonuniformity (PRNU) of the coated sensor. The inorganic phosphor has been selected over organic laser dyes because organic molecules degrade rapidly upon exposure to UV radiation, with exponential degradation rates as high as 3% per hour at an illumination level of 1 /spl mu/W/cm/sup 2/. Inorganic phosphors exhibit reduced degradation with 90% of the degradation occurring within the first 2% of the material's lifetime. It is this stabilization that improves the viability of phosphor-coated CCD image sensors for commercial applications. The quantum efficiency observed was 12% at 265 nm. The improved deposition technique reduced the photoresponse nonuniformity degradation fourfold, so the observed PRNU was only 0.4 times greater than that of the uncoated sensor.