Semi-quantitative Information Research Articles

A variational treatment of electron states in lattices with diagonal disorder

A variational method is applied to the partition function of an electron in a lattice with diagonal disorder. Apart from yielding band-tail densities of states the method yields semi-quantitative information on localisation. It is also suggested that critical temperatures will arise separating localised and delocalised regimes; this is a feature shared with attempts to relate the localisation problem with solutions of Ginzburg-Landau mean field theories.

Severity of mitral regurgitation assessed by echocardiography. Reliability and limitations.

To assess whether echocardiography may represent a useful mean to evaluate the degree mitral regurgitation (DR), left ventricular diastolic internal dimension (LVIDd), left atrial dimension (LAD), and velocity of circumferential fiber shortening (Vcf) were compared to DR assessed by left ventriculography in 48 patients with primary (n = 21) and cardiomyopathic (n = 27) valvular incompetence. In patients with good left ventricular contractility, i.e. with Vcf values above 1.02, a significant positive linear correlation was found between LVIDd and DR (LVIDd = 5.38 + 0.45DR; r = 0.72; p less than 0.001). In contrast, in patients with depressed left ventricular function, i.e. with Vcf values below 1.02, LVIDd did not correlate to DR. In either group LAD and Vcf did not correlate to DR. Thus, echocardiography may provide useful semiquantitative information concerning DR only in patients with preserved left ventricular performance.

Investigation of marine and terrestrial humic substances by 1H and 13C, nuclear magnetic resonance and infrared spectroscopy

Humic acids were isolated from 5 sediments in which the origin nature of the organic matter are both typical and different. The humic acids were characterized on the basis of elemental compositions, infrared spectra and 1H and 13C NMR. This last technique, especially 13C NMR, provides qualitative and semi-quantitative information regarding aromatic structure. Combined data from the three techniques permits differentiation of marine and terrestrial organic matter as well as identification of mixtures of humic acids from the two sources.

Syn–anti equilibrium of purine bases in dinucleoside monophosphates as studied by proton longitudinal relaxation

AbstractThe preferential orientations of the purine bases in dinucleoside monophosphates such as ApA, ApG, and GpA in 10−2M neutral aqueous solutions have been investigated by proton relaxation at 250 MHz. These orientations are deduced from computer simulations of the magnetization recovery curves following a 180° nonselective pulse. The distances between the H(8) proton of a base and the ribose ring protons which are used in these calculations are obtained by minimization as a function of the glycosyl torsion angle ϒ of the standard deviation between the isotropic reorientation correlation times τR derived from the relaxation rates of these protons. The average H(1′) – H(8) distance obtained by this procedure may be readily verified from the reduction of the H(1′) relaxation rate when H(8) is substituted by a deuteron. The limits of validity of the assumption of a single correlation time τR governing the proton relaxation have been estimated, taking into account several possible internal motions, e.g., the rotation of the base, of the methylene exocyclic group and the N ⇄ S interconversion of the ribose ring. For 10−10 < τR < 2 × 10−10 sec, it appears that the influence of these motions on the proton relaxation becomes perceptible when the jump rates among equilibrium positions exceed ca. 109 sec−1.The whole of the experimental results show that for the ribose ring N conformer, the orientation of the bases is found in the ranges 60° < ϒ < 80° (syn) and 180° < ϒ < 210° (anti). For ribose S conformer, it is observed that this orientation is mainly syn with 5° < ϒ < 90°. The average H(1′) – H(8) distance provides semiquantitative information on the overall syn or anti orientations of the base in each nucleoside moiety. At 298 K the population of the anti conformer is found to increase in the order A‐ pG < Ap‐G ∼ Gp‐A < Ap‐A < A‐pA < G‐pA. A more detailed analysis of relaxation data shows that the maximum possible fraction of the stacked form of dinucleotides, due to the occurrence of N‐anti conformers in both nucleoside moieties, is in the order ApG < GpA < ApA, in agreement with previous works, with however smaller values.Lastly the deuteron linewidth in position 8 of the bases indicates a syn–anti transition rate of the order of 109 sec−1 at room temperature, without noticeable effects therefore on the proton relaxation.

Measuring trace elements in semiconductors: Methods and pitfalls

A quantitative understanding of the electrical behavior of semiconductors requires quantitative knowledge of impurities at concentrations as small as one part per billion. Methods available for trace measurements at this level are few in number; for many constituents there are no routine, inexpensive and reliable accurate methods. If the sample of interest is a thin film on a substrate, the mass of sample is small and the difficulties of micro-analysis are added to those of trace analysis. Nearly all methods available for approaching this problem rely on physical rather than chemical reactions. The sample is probed with an external stimulus and the response to this stimulus is then detected. The probe and also the response may be photons (from microwaves to γ-rays), electrons, neutrons or other nuclear particles, or ions. Desirable properties of a method are high sensitivity to the signal from the component sought, insensitivityto the presence of uninteresting factors such as the matrix, and a response related to the stimulus by a known factor of proportionality. Although semiquantitative or relative information is sufficient to answer many questions, the analyst's goal is to produce measurements of high and known accuracy. The history of blind inter-laboratory comparisons of trace element measurements shows that agreement is seldom as good as expected a priori. The resolution of discrepancies is most efficiently done if one or more common lots of material is available for repeated analyses.

Detection of hyperlipidemia by semiquantitative fluorometric determinations of serum lipids on thin-layer chromatograms.

In one analytical procedure, semiquantitative information concerning the concentrations of triglycerides, free and esterified cholesterol were obtained. Twenty-five microlitres of serum were used and the concentrations were classified as high, borderline or normal compared to a lipid standard solution. Thirty-four patients were investigated and the results showed good agreement with the results from conventional screening for hyperlipidemia by separate quantitative analyses of total cholesterol and triglycerides.

A Non-Destructive Optical Method to Study De- and Remineralization of Enamel

The absorption and scattering of light in dental enamel or in a carious lesion have been studied quantitatively by using thin slabs. The method thus required destructive preparation techniques. In this paper we describe how the scattering by a bulk sample can be used to obtain semi-quantitative information.

Problèmes posés par l'insertion de la géochimie en méthodologie des recherches minières

The evolution of the geochemical methods, applied to mining exploration, has lead to a generalization of the geochemical approach and has created, and continues to create, for these comparatively new techniques, some problems of adaptation to the existing habits. The correct use of these techniques is hampered at different stages of the exploration programme: planning, execution, interpretation of results. We give a critical view of the problems involved, such as: inertia in decision-making and their inadequate knowledge of the exact conditions of application of the geochemical methods; the failure to properly appreciate the technical requirements, sometimes facilitated by the lack of esoterism of the method; the statistical ghetto in which some geochemists are confined; the lack of rigour which often leads to the use of semi-quantitative analytical information for multiple elements, instead of more tested methods; the inadequacy of geochemical maps with a lack of the necessary indications for an interpretation more connected with a good knowledge of geology, pedology, etc. This interpretation remains for the author the main approach.

Surface analysis of polysiloxane/metal oxide interfaces

The interfaces between various types of silane-based primers and abraded mild-steel surfaces have been investigated using two surface-specific techniques in an attempt to ascertain the bonding mechanism between primer and metal. The XPS technique gave semi-quantitative information about the relative concentrations of primer and exposed steel while the SSIMS technique enabled the chemical state of the first few monolayers of surface to be elucidated. From some primer/metal systems the presence of FeSiO+ radicals was detected by SSIMS and it was found that the environmental resistance of structural adhesive joints, employing the various silane-based primers, could be directly related to the presence or absence of this radical.

Conjugated polyene fatty acids as fluorescent probes: synthetic phospholipid membrane studies.

The preparation of polyene fatty acid membrane probes cis- and trans-parinaric acid and parinaroylphosphatidylcholines and their use in studies of several one- and two- component lipid systems are described. The fluorescence quantum yield of trans-parinaric acid in dipalmitoylphosphatidylcholine at 20 degrees C is approximately 0.3; the quantum yield in aqueous solution is negligibly small. Thermal-phase transitions in single-component phospholipid dispersions are monitored with absorption and fluorescence excitation peak position, fluorescence intensity, lifetime, and polarization. The transition temperatures observed are consistent with previous determinations. Shifts in the absorption peak position are related to the bilayer expansion as it undergoes the gel to liquid-crystalline transition, while fluorescence depolarization provides semiquantitative information concerning molecular motion of the probe in the bilayer. A long fluorescence lifetime component is observed for parinaric acid in the solid phase (up to 50 ns), and a short lifetime component is observed (ca. 5 ns) in the fluid phase of dipalmitoylphosphatidylcholine; both lifetime components are observed in the transition region. In most phospholipids, cis-parinaric acid detects the melting transition at about 1 degree C lower than trans-parinaric acid. Partitioning experiments involving mixed populations of phospholipid vesicles show that trans-parinaric acid preferentially associates with solid-phase lipids, while cis-parinaric acid shows a more equal distribution between solid and fluid lipids. The binding of cis-parinaric acid to dipalmitoylphosphatidylcholine at 25 degrees C is described as partitioning of parinaric acid between lipid vesicles and the aqueous phase with a partition coefficient of 5 X 10(5). Several rates are observed in the binding process which are interpreted as rapid outer monolayer uptake and a much slower process of interlamellar exchange. The phase diagram of the binary lipid mixture dipalmitoylphosphatidylcholine-dipalmitoylphosphatidylethanolamine has also been examined and found to be essentially identical to the one constructed using a nitroxide probe.

Instrumentation and Methods for Intraluminal Esophageal Manometry

Intraluminal manometry is a useful clinical and investigative method for the evaluation of esophageal motor function. If improperly performed, however, the examination yields only semiquantitative information. Notwithstanding, instrumentation and methods are now available that permit accurate quantitation of esophageal pressure activity. Esophageal pressure values are determined by several important factors: recording-system fidelity, recording technique, scoring method, and conditions existent during manometry.1All these factors must be considered and dealt with satisfactorily, in order to obtain precise esophageal pressure measurements. The purpose of this paper is to provide useful practical information relative to the performance and interpretation of clinical esophageal manometry. RECORDING ACCURACY Two major variables determine the recording fidelity of any pressure recording system: (1) character of the pressure event being recorded, and (2) recording-system performance.2For esophageal pressure waves, recording fidelity is inversely related to wave amplitude (Amp) and directly related to wave duration (Dur). On infusion

Ultrasound assessment of residual urine in children.

Ultrasound has been used to assess residual urine in children and found to have considerable advantages over other methods. Using a B-mode scan in the sagittal plane the presence or absence of residual urine can be confidently determined. Quantitative measurements of volume are subject to considerable error but semi-quantitative information in individual cases can be obtained by comparison of records made at subsequent examinations. More accurate quantitative values might be achieved by constructing an individual calibration curve. The advantages of ultrasound for assessing residual urine are that it is simple, quick, harmless and non-invasive. Because of these features the examination can be readily repeated, is suitable for out-patient use and is acceptable to children.

Colliding beam measurements of ICR collision processes between alkali ion–atom pairs

A colliding beam ion cyclotron resonance experiment has been developed and used to study rate constants for symmetric (resonant) and asymmetric charge exchange between potassium ion–atom pairs and between sodium ions and potassium atoms in the range of ionic energies from 0.1–2.0 eV. The results for symmetric charge exchange are in agreement with theory, but the rate constant for the exothermic process Na++K→Na+K+ at near thermal energies appears to be much larger than predicted. The changes in the ion cyclotron double resonance (ICDR) signals of ions A+, when ions B+ were heated using ICR methods, were found to be sensitive in magnitude and sign to the difference between the static field strength and the A+ ICR resonant field, as well as the intensity of the rf electric field used to heat the B+ ions. These results have been interpreted in terms of a previously published theory which takes into account explicitly the spatial distribution of ions in the ICR cell. Semiquantitative information is obtained on the energy dependence of asymmetric charge transfer between Na+ and K and resonant charge transfer between 39K+ and 41K at very low energies.

Perturbation theory for mixtures of polar fluids

The thermodynamic perturbation theory of Stell, Rasaiah and Narang is generalized to the case of multi-component Stockmayer fluids. The effects of polarization by the permanent dipoles is included to first order and the perturbation series is summed approximately to all orders in the dipole moments by means of two Pade approximants. The two-body and triplet terms in the expansion have been evaluated by Monte Carlo integration for a specific choice of the reference Lennard-Jones mixture and the results are used to study systematically the effect of dipolar interactions on excess thermodynamic properties. The utility of a one-fluid theory based on the van der Waals model is investigated and it is shown that the approach is useful for obtaining semi-quantitative information on mixtures of weakly polar fluids. The special case of mixtures of hydrogen chloride and xenon is considered and it is shown that the potential model used is inadequate to account for the large deviations from ideality which are observed...

Organic substances in potable water and in its precursor : III. The closed-loop stripping procedure compared with rapid liquid extraction

An attempt is made to define the role of gas chromatography in the investigation of organic substances in water, which is important because the handling of water samples before gas chromatographic (GC) analysis depends entirely on the information expected from the subsequent separation, identification and quantification. Practical long-term experience with the previously published closed-loop stripping procedure (with intermediate adsorption on activated carbon) is described and further refinements are reported. A rapid and simple liquid extraction method is described, based on shaking 11 of water with a small volume (0.5-1 ml) of solvent and subsequent high-resolution GC analysis of the extract. Qualitative and semi-quantitative information at the parts per 10 12 level is easily obtained. Further studies of recovery rates under conditions where the volatility and polarity of extracted organic substances are varied are described for both methods. The suitability of both methods for the analysis of different types of water samples is discussed.

Aerosol analysis by field desorption mass spectrometry combined with a new sampling technique

Analyses of inorganic and organic aerosols by Field Desorption Mass Spectrometry at high resolution are presented in this article. The method is unique in giving direct semi-quantitative information on intact inorganic salts, as they are present in the sample. Airborn polar organic compounds are also readily detected. Due to the high sensitivity of the method, sub-microgram quantities are sufficient for an analysis. Aerosols can therefore be collected by direct impaction on the field emitter which is subsequently transferred into the mass spectrometer. Advantages of this procedure are its relative simplicity and rapidity, providing information complementary to established methods of aerosols analysis.

Rotational and Segmental Motions in the Lipids of Human Plasma Lipoproteins

Abstract Natural abundance 13C NMR spectra of high density, low density, and very low density lipoproteins isolated from human plasma have been recorded and assigned, and the spin lattice relaxation times (T1) of some well resolved resonances have been determined. The 13C NMR spectra reflect differences in protein-lipid ratios and in lipid composition between the three classes of lipoproteins. All three lipoproteins yield numerous narrow 13C resonances assignable to the lipid component. The high density lipoprotein also yields several narrow peaks that arise from the protein moiety. All of the above narrow resonances must originate from liquid-like lipid and protein components. T1 values of lipid carbon resonances of lipoproteins and some model systems yielded semiquantitative information about rotational and segmental mobilities of the lipid components of lipoproteins. The T1 values of C6 of the cholesteryl moiety of high and low density lipoproteins revealed that the fused ring systems occupy regions of much higher microviscosity than that of the aqueous environment. T1 values of carbons of fatty acyl chains yielded information about segmental motions of these chains in the environment of the lipoprotein complex. Segmental mobilities of fatty acyl chains are identical, within experimental error, in high density and low density lipoproteins, despite marked compositional (and probably structural) differences. T1 values of fatty acyl chains of very low density lipoproteins are slightly longer than the corresponding values of the denser lipoproteins, a result that suggests somewhat greater segmental mobilities in very low density lipoproteins. Our 13C T1 values indicate that all or most of the lipid molecules of plasma lipoproteins, although in a liquid-like state, are significantly restricted in their rotational and segmental mobilities relative to lipids in organic solvents.

Thin layer electrofocusing followed by electrophoresis in antibody containing gel.

After thin layer electrofocusing in polyacrylamide gel electrophoresis was performed in antibody containing polyacrylamide agarose gel. The technique combines the high resolution of polyacrylamide gel electrofocusing with the high sensitivity of immunologic identification that gives semiquantitative information. The technique is demonstrated on multiple molecular forms of salivary amylase.

Application of thin-layer chromatography to hydrocarbon-type analysis

Thin-layer chromatography has been applied to the hydrocarbon-type separation of heavy oils, with emphasis on separation of petroleum resins. A three-stage discontinuous layer-gradient plate was employed and found to give better separation of hydrocarbon types than a single adsorbent plate. Various solvent combinations were utilized and placed in an eluotropic series as applied to petroleum resin separation. Semi-quantitative information was obtained from a completed chromatogram plate by measuring the size of the bands or spots with a ruler or photoelectric scanner.

Study of Structural Detail by X-rays of Wavelength Greater than 4Å

AbstractSome branches of structural research could benefit from supplemental information provided by “soft” x-rays. Little use is made of these wavelengths because they are difficult to generate at high intensity, hard to collimate, need vacuum for propagation, and are heavily absorbed in the sample. None of these difficulties is insurmountable, however, and it will be shown that the information to be gained is often worth the extra effort.A few theoretical and experimental examples with silver L-radiation (λ ≈ 4.15Å) and aluminum K-radiation (λ ≈ 8.34Å) demonstrate that valuable semiquantitative information on the size and number of aperiodic scatterers in solid samples can be extracted. Other examples show the superior sensitivity of these longer wavelengths to dimensional changes in periodic lattices. Applicability of long-wavelength diffraction is restricted to values of interplanar distance d > λ/2. Valuable information about lattice imperfection can be gained from broadening of the reflection at larger glancing angles. It is shown that the heavy absorption of these wavelengths in the sample is not necessarily prohibitive.The instrumentation used in these studies was designed for routine operation by laboratory personnel without special training. It consists of a demountable high-intensity x-ray source and a multipurpose highvacuum camera. Operation of the x-ray unit resembles that of commercial x-ray diffraction instruments. Because of its greater-flexibility, photographic recording has been practiced so far but could be replaced by electronic readout.