Rectilinear Part Research Articles

Chemiluminescence determination of antibacterial drug trimethoprim by automated sequential injection technique with permanganate and hexametaphosphate as reagents

Antibacterial drug trimethoprim [2,4-diamino-5-(3,4,5-trimethoxybenzyl)-pyrimidine] ( I) was determined in pharmaceutical formulations by using a lab-made PC-controlled SIA analyser linked to conventional HPLC fluorimetric detector equipped with a chemiluminescence module. The chemical principle is the oxidation of I by KMnO 4 in acid medium; the reaction is accompanied by the emission of chemiluminescence, which is enhanced in the presence of hexametaphosphate (HMP). The optimum sequence and the flow parameters and concentrations and volumes of reagents aspirated optimised by a computer-aided simplex method were, 100 μl of 5 mM HMP, 40 μl of a test solution of I, 2 μl of 0.5 M H 2SO 4 and 20 μl of 1 mM KMnO 4; the luminescing zone was pushed into the detector at a flow rate of 49 μl s −1. The calibration graph relating the intensity of luminescence to concentration of I was parabolic ( r=0.9994) in the range 0.5–100 μg ml −1 of I with rectilinear part ( r=0.9999) in the range 20–100 μg ml −1 of I; the limit of detection was 0.1 μg ml −1 of I. The method was used for the assay of Triprim® tablets (with nominal content 100 or 200 mg of I) for the active substance as well as for content uniformity tests; the R.S.D. values did not exceed 1% ( n=5). The SIA results did not show statistical difference from those obtained by pharmacopoeial acidimetric titration in non-aqueous medium; the excipients such as microcrystalline cellulose, maze starch, povidone, talc, magnesium stearate and gelatin did not interfere.

Silver ultrathin layer growth on the Cu(1 1 1) face at temperatures from 130 to 570 K

The dependence of Auger peak heights of silver and copper at the time of silver deposition on the Cu(111) face (Auger peaks kinetics) was measured in the substrate temperature range 130K<T<570K. For T>280K, this dependence indicates the layer-by-layer growth (two succeeding rectilinear parts were observed with a bend between them for the value of the Cu peak height expected for the full silver monolayer). For lower temperatures, this bend appears earlier and earlier indicating the beginning of the second layer formation before completion of the first layer. When the evaporation was stopped after deposition of one-half monolayer and continued after about 45min, the copper Auger signal remained constant during the break in deposition but the slope of the Auger peak kinetics was smaller after this break than before it. The diminution of this slope was the smallest (and equal to about 20%) for 200K<T<280K. These results can be understood under supposition that the layer-by-layer growth is possible when silver islands are not too large (the critical size of islands depends on the substrate temperature and on the intensity of the silver flux). For large islands, silver atoms impinging on them are unable to reach the free copper surface (because of the potential barrier at the island edge) and they form the islands of the second layer. During the break in silver deposition the structure of the population of silver islands is modified owing to the silver atom diffusion, which leads to formation of larger islands. The second layer can grow on the largest islands.

Soritidés éocènes à costulation et/ou lames sous-épidermiques discrètes : les genres Spirolina, Praerhapydionina et Paraspirolina n. gen. dans le « Faciès à imperforés de l'Éocène moyen à supérieur de Grèce

In the Gavrovo-Tripolitza zone of Greece, the «Faciès à imperforés indicates a peculiar back-reef to lagoonal sedimentation episode succeeding a bauxitogenous emersion. The foraminiferal association comprises several arenaceous conical taxa, a lot of miliolids, a species close to Praebullalveolina afyonica, various Peneroplis and/or Dendritina, Spirolina and Praerhapydionina species, scarce small Orbitolites and Rhabdorites malatyaensis. The similarity of this association with others from various parts of the Tethyan area gives evidence for a generalized regressive episode linked to the terminal Middle Eocene tectonic phase. From this association, presence of a new taxon is emphasized : Paraspirolina gigantea n. gen., n. sp. is characterized by an external aspect of a large Spirolina, a single dendritic terminal aperture and the very unusual association of external ribs with sub-epidermal partitions. Both of these last features appearing as independent adaptive devices related to algal symbiosis, their conjunction seems to characterized a singular evolutionary grade in a particular lineage. A single terminal aperture, together with a common tendency to develop an uniserial evolute rectilinear final part (PRU) seems to show a link between the new taxon, several Eocene soritids of the Old World, namely various Spirolina species (devoid of sub-epidermal partitions) and various species assigned to Praerhapydionina (with sub-epidermal partitions, one of them, P. huberi, being reported as ribbed); they are thought to constitute a natural group (a plexus or a sub-family).

Comparison of the Ampère and Biot–Savart magnetostatic force laws in their line-current-element forms

The force laws of Ampère and Biot–Savart in magnetostatics are compared using the geometrical model of a closed curve to represent a current loop. The two laws give identical results when forces between separate current loops are considered and also for the force exerted by a current loop on a rectilinear part of itself. According to both laws, these self-forces diverge wherever the curvature of the curve representing the current loop is not equal to zero. Differences in the predictions of the two laws are shown to appear only as differences in diverging forces when evaluating forces of a current loop on a part of itself and to be entirely due to the oversimplified and unrealistic geometrical model used for the current loop.

A computer program for mathematical treatment of data in radioimmunoassay

A mathematical analysis of counting data obtained in hormone plasmatic radioimmunoassay is presented. A log-normal Galton distribution of the dose-effect type is assumed for the fitting of the experimental data. The special adopted procedure makes it possible to reproduce the total range of the sigmoid curve and not only the rectilinear part of it. Experimental data with iterations and the proper weights of the iterated counting rates are automatically taken into account and the statistical errors of the standard curve and of the sample`s dose evaluated from it are given by the code. A large number of analyses have been performed in order to test the affidability of the method and to explain the validity of the chemical-physical parameters of the calculated distribution. Some selected results are presented and a full description of the mathematical formalism is given.

Binding of adenosine diphosphate to human blood platelets and to isolated blood platelet membranes

The equilibrium binding of 14C-labeled ADP to intact washed human blood platelets and to platelet membranes was investigated. With both intact platelets and pletelet membranes a similar concentration dependence curve was found. It consisted of a curvilinear part below 20 μM and a rectilinear part above this concentration. At high ADP concentrations, the rectilinear part appeared to be saturable. Because of this, two classes of saturable ADP binding sites were proposed. ADP was partly converted to ATP and AMP with intact platelets while this conversion was virtually absent in isolated platelet membranes. ADP was bound to platelet membranes with the same type of curves found for intact platelets. The ADP binding to the high affinity system, which was stimulated by calcium ions, was nearly independent of temperature and had a pH optimum at 7.8. A number of agents were investigated for inhibiting properties. Of the sulfhydryl reagents only p-chloromercuribenzene sulfonate inhibited both high and low affinity binding systems while iodoacetamide and N-ethylmaleimide were without effect. Compounds acting via cyclic AMP on platelet aggregation, such as adenosine and cyclic AMP itself, had no influence on binding. Some nucleosidediphosphates and nucleotide analogs at a concentration of 100 μM had no, or only a slight, effect on high affinity ADP binding. For some other nucleotides inhibitor constants were determined for both platelet ADP aggregation and ADP binding. The inhibitor constants of ATP, adenyl-5′-yl-(β,γ-methylene)diphosphate, IDP, adenosine-5′-(2- O-thio)diphosphate, for aggregation and high affinity binding were in good correlation with each other. Exceptions formed fluorosulfonylbenzoyl adenosine and AMP. The ATP formation found with intact platelets could be attributed to a nucleosidediphosphate kinase. It was investigated in some detail. The enzymes was magnesium dependent. had a Q 10 value of 1.41, a pH optimum at 8.0, was competitively inhibited by AMP and reacted via a ping pong mechanism. All findings described in this paper indicate that platelets as well as platelet membranes bind ADP with the same characteristics and they suggest that the high affinity binding of ADP is involved in platelet aggregation induced by ADP. The results on nucleosidedphosphate kinase did not permit a firm conclusion ADP.

Evaluation of the strength of the compressed zone in a hollow gravity dam

1. The strength of a gravity dam of reduced mass with a facing is determined by the behavior of the compressed zone. 2. The most stressed part of the compressed zone is located between elevations 26 and 38 m at the linkage of the rectilinear and curvilinear parts of the downstream face. The principal compressive stresses produced by the acting loads reach 50–60 kgf/cm2 in this zone. 3. The structure falls when the principal compressive stresses in its most stressed part reach the prism strength of concrete. 4. At loads corresponding to normal operating conditions the safety factor, of a reduced-mass dam constructed of concrete grade 200 is 2.7–3 according to the data of testing brittle models. 5. When the construction joints are given high-quality treatment the compressive strength of the concrete is not reduced. 6. The safety factor of a reduced-mass dam with respect to shear along the construction joints treated according to the method used at the Toktogul station is higher than the safety factor of the most stressed zone.

Production and removal of lactate during exercise in man.

AbstractBlood lactate concentration (LA) was measured in 4 female and 3 male well‐trained subjects before and during 30 min of continuous treadmill running at 4 different speeds, demanding about 30, 60, 70 and 80% of the individuals' maximal oxygen uptake (Vo2 max). The same subjects also performed in another series of experiments where maximal intermittent exercise preceded 30 min of running at the same 4 speeds, or resting in a chair. During continuous running, starting from resting conditions, the blood LA increased only slightly up to a critical Ievel (i.e. 60—80%) of Vo2‐max. From then on, a pronounced lactate production may occur. During the maximal intermittent exercise, blood LA increased to 130—220 mg/100 ml. In the recovery period, i.e. continuous running at the same 4 speeds, or resting in a chair, blood LA decreased towards resting values. The lactate removal rate was calculated from the rectilinear part of the curves describing the changes in LA with time, and expressed as mg/100 ml X min. The lactate removal rate was higher during exercise than during rest, and increased with increasing work load up to the same critical level (i.e. 60—80% of Vo2 max), beyond which a reduction was observed. The highest removal rate was 8 mg lactate/100 ml x min at 63% of Vo2 max (average values). These results indicate that human skeletal muscle possesses a pronounced capacity to oxidize lactate. Therefore, a production of lactate is possible even with no increase in the blood LA. These results also indicate that the skeletal muscle, rather than the liver, may be regarded as the main site for lactate removal during exercise.

Ventilatory response to CO2 during work at normal and at low oxygen tensions.

Summary.The sensitivity of the respiratory center to CO2 during muscular work at normal and at low oxygen tensions has been studied in three human subjects.It was found that the rectilinear part of the stimulus‐response curves in normal air was displaced to the left of the resting curve and the more so the higher the work intensity. The steepness of the curves was in the majority of cases about the same. In low oxygen the stimulus‐response curves were displaced more to the left and were much steeper than for the same work intensity in normal air. The flattening of the stimulus‐response curves found at higher CO2 concentrations is assumed to be due mainly to a special depressant effect of high CO2 tensions on the respiratory center.

On Barbier's Solution of the Buffon Needle Problem

In the well known Buffon needle problem, a needle of length L is dropped on a board ruled with equidistant parallel lines of spacing D where D?L; it is required to determine the probability that the needle will intersect one of the lines. B3arbier's [1] elegant method was to let this problem depend on the following one: What is the mathematical expectation of the number of points of intersection when a polygonal line (convex or not) is thrown upon the board? The perimeter of the polygonal line can be subdivided into IV rectilinear parts a,, a2, ... , aN, all less than D. Associated with these IV parts are the variables x1, x2, , x, x,N such that