Nonselectivity, reflection

In Surface Analysis by Laser Ionization (SALI), a probe beam such as an ion beam, electron beam, or laser is directed onto a surfiice to remove a sample of material. An untuned, high-intensity laser beam passes parallel and close to but above the sur-fiice. The laser has sufficient intensity to induce a high degree of nonresonant, and hence nonselective, photoionization of the vaporized sample of material within the laser beam. The nonselectively ionized sample is then subjected to mass spectral analysis to determine the nature of the unknown species. SALI spectra accurately reflect the surface composition, and the use of time-of-flight mass spectrometers provides fast, efficient and extremely sensitive analysis. 

A comprehensive, randomized, placebo-controlled trial of infused bolus L-arg and its enantiomer (D-arg) included healthy subjects, non-insulin dependent diabetics, hypertensive subjects, and normotensives with primary hypercholesterolemia [147]. A blood-pressure drop and an acute inhibition of ADP-induced aggregation in platelet-rich plasma were observed in all subjects after L-arg administration (<5 g). Both responses to L-arg infusion closely correlated in magnitude, were weaker in noninsulin dependent diabetics and hypercholesterolemics, and declined with increasing age. Notably, D-arg did not elicit any of the L-arg effects, which were reduced by some 70% when superimposed upon ongoing, nonselective NOS inhibition with infused L-N-monomethyl-arginine (L-NMMA). Since D-arg is not a NOS substrate, and L-NMMA is a substrate-competitive NOS inhibitor, the L-arg effects observed in this study were theorized to reflect a rise in vascular NO production by eNOS. In contrast, the inhibition of platelet aggregation observed in vitro after a 5 min L-arg infusion (160 mg total dose) into healthy subjects and patients with angiographic... 

Local anesthetic action, also known as "membrane-stabilizing" action, is a prominent effect of several 3 blockers (Table 10-2). This action is the result of typical local anesthetic blockade of sodium channels (see Chapter 26) and can be demonstrated experimentally in isolated neurons, heart muscle, and skeletal muscle membrane. However, it is unlikely that this effect is important after systemic administration of these drugs, since the concentration in plasma usually achieved by these routes is too low for the anesthetic effects to be evident. These membrane-stabilizing 3 blockers are not used topically on the eye, where local anesthesia of the cornea would be highly undesirable. Sotalol is a nonselective 3-receptor antagonist that lacks local anesthetic action but has marked class III antiarrhythmic effects, reflecting potassium channel blockade (see Chapter 14). 

These equations correspond, respectively, to the set of Eq. (10.87) for the case of dilute solutions. The value of reflection coefficient cr must depend on the nature of both the solute and the membrane. For the case of volume flow in the absence of the concentration gradient in the permeant solute (AIIS = 0), we see that the quantity (1 - cr) is a direct measure of the extent of coupling between the solute flow and the volume flow. If the membrane is completely nonselective, then a = 0 if the membrane is perfectly selective, permeable only to the solvent, then cr = 1. In most cases, a will lie between 0 and 1. 

A reflection coefficient characterizes some particular solute interacting with a specific membrane. In addition, oy depends on the solvent on either side of the membrane — water is the only solvent that we will consider. Two extreme conditions can describe the passage of solutes impermeability, which leads to the maximum value of 1 for the reflection coefficient, and nonselectivity, where ay is 0. A reflection coefficient of zero may describe the movement of a solute across a very coarse barrier (one with large pores) that cannot distinguish or select between solute and solvent molecules also, it may refer to the passage through a membrane of a molecule very similar in size and structure to water. Impermeability describes the limiting case in which water can cross some membrane but the solute cannot. 

The following sections review new insights from KO models on cardiac biology of oq-ARs, as summarized in Table 4 for male mice. The focus is on the double AB KO, highlighting the requirement for cq-AR signaling in the heart. The KO results suggest that adverse clinical consequences of nonselective oq-antagonists reflect loss of adaptive oq-AR functions in the heart. 

Similar results have been noted by other workers, but when the selenoacetals (19) are treated with either tributyltin hydride, or tris(trimethylsilyl)silicon hydride, in the presence of AIBN, nonselective ring opening occurs (Equation (1)). Some preference for equatorial attack is observed for the silicon hydride, but this most likely reflects the large size of the reagent <93TL8517>. 

Three methods have been described for three halogens, two based on fluorescence and one on absorption. In the first [87], the fluorescence of rubrene in polystyrene is quenched by traces of iodine. This method is nonselective and the optode is also sensitive to oxygen. In another sensor, naphthoflavone in solution in a material of the silicone or PVC type serves as a sensitive layer for free halides [88]. The absorption technique uses a fiber with a liquid CS2 core [89] to detect 10 ng of iodide using a S m long capillary cell with sample circulation. The Hber itself constitutes the active optode (total reflection in the liquid core). A comparison of optodes based on dynamic quenching of absorbed Rhodamine 6G by iodide was reported [90]. Three solid supports for immobilization were used PTFE tape, XAD resin beads and crushed XAD-4 resin. The limits of detection are 0.18-0.30 and 1.1 mM respectively. Some anions (eg. Cl , Br , CN ) interfere at the 1-M level. 

Only the as-deposited and/or annealed (T = 300°C) Ti films show wide absorption bands near 3000 cm [275]. At different stages of the silicidation reaction, the films reveal different nonselective absorption curves in the 400-4000-cm range. Thus, it was shown that the absorption at 4000 cm increases monotonically as the annealing temperature of the sample increases and the absorption at 400 cm increases monotonically with increasing sample conductivity. Thus the composition of a silicide may be deduced however, in calculations of absorbance it is necessary to take into account the strong dependence of the reflectance on both the frequency (/ = 95% at 400 cm , R = 60% at 4000 cm ) and the silicide composition [275]. 

Flour is opaque and its whiteness is due to nonselective diffuse surface reflectance. There has not been such interest, internationally, tince the world market is for the whole grain, rather than flour. Thus the professional group in the United States (American Association of Cereal Chemists) has no committee on the measurement of flour color, although collaborative studies have been made on methods for determining the yellow pigment content—chiefly carotenoid in nature—of wheat flour. This lies outside the realm of the present review. Four main factors determine flour color, according to Kent-Jones (1952) ... 

W. Erb of the Physikalisch-Techniche Bundesanstalt has characterized an ideal standard as having the following properties It is (1) transportable or, if not transportable, then easily reproduced with high reliability (2) stable with respect to time, radiation, temperature, atmosphere, etc. (3) homogeneous, with a smooth surface (4) diffusely reflecting (5) spectrally nonselective (6) nontransparent (not translucent) (7) nonfluorescent and (8) easy to handle. 

The differential response to gastrin in terms of secretion and DNA synthesis may reflect different intracellular coupling or transduction mechanisms that follow ligand binding. Genistein, a nonselective protein tyrosine kinase inhibitor, inhibits both cytoplasmic and membrane-assodated tyrosine kinases. At 10- M, genistein failed to inhibit histamine secretion but blocked gastrin-stimulated DNA synthesis. 

---