Unequal Absorption Research Articles

Study of the influence of fire retardants on the flammability of building materials made of pine and aspen wood

The results of the study of the effect of industrial fireproofing compositions on the weight loss of samples of solid pine and aspen wood during combustion are presented. Fireproofing compositions of different brands was introduced in the form of ready-made solutions (with a consumption of 500–600 g/m2) by impregnation of test samples of coniferous and deciduous wood. It has been established that, from the point of view of mass loss during combustion fireproofing compositions have different efficiency: the best of them provided I group of fire retardant efficiency. For a comparative assessment of the effectiveness of the use of various industrial flame retardants, the method of analysis of variance was used. The hypothesis about the effect of interaction between the type of wood and the grade of OS was tested, and the significance of the influence of factors on the weight loss of samples during combustion was assessed. It has been established that the effect of interaction between the type of wood and the type of fire retardant composition is 3.51 times greater than the effect of the type of wood, which is due to both the structural differences between aspen and pine wood, and the unequal absorption of OS of different operating principles into the outer layers of the wood material. It was determined that the degree of influence of the type of wood (aspen, pine) on the loss of mass of wood material during combustion is 62.3 times less than the influence of the type of fire retardant composition.

PH Sensitive Hydrogel: A Review

Hydrogels are three-dimensional cross-linked networks of polymer chains that can absorb and hold lots of water in the interstitial spaces between chains. Improving the safety efficacy ratio of existing drugs is a current challenge to be addressed rather than the development of novel drugs which involves much expense and time. The efficacy of drugs is affected by several factors such as their low aqueous solubility, unequal absorption along the gastrointestinal (GI) tract, risk of degradation in the acidic milieu of the stomach, low permeation of the drugs in the upper GI tract, systematic side effects, etc. This review aims to enlighten readers on the role of pH-sensitive hydrogels in drug delivery, their mechanism of action, swelling, and drug release as a function of pH change along the GI tract. The basis for the selection of materials, their structural features, physical and chemical properties, the presence of ionic pendant groups, and the influence of their pKavalues on the ionization, consequent swelling, and targeted drug release are also highlighted.

Impact of dosimeter size on energy dependence: An experimental study on glass TLDs

Practical Use of a dosimeter in a range of photon energies necessitates identification of radiation field as well as energy response of the dosimeter. Energy dependence of absorbed dose is caused by the unequal absorption properties of the material from various radiation energies, while the process of dosimeter response generation may also be energy dependent. The aim in this work is to measure the energy dependence of the response of sub-millimeter size glass silica fibre thermoluminescent dosimeters and to check whether there is a relation between energy dependence and the size of the dosimeter. Small size TLDs of capillary rod shape with the external/internal diameters of 870/544, 386/241 and 127/79 μm and 3 mm length prepared by a precision cutting process and appropriate preconditioning, were irradiated at various photon energies. Irradiations were performed in free-in-air condition at the secondary standard dosimetry laboratory (SSDL) of the Malaysian Nuclear Agency using X-ray narrow series spectra and gamma rays from a137Cs source as the reference photon energy. Theoretical energy dependence calculated by using the cavity theory was found in an acceptable agreement with the experimental results. The results show an increasing degree of energy dependence with the dosimeter size in the studied size range. This can be explained based on the low dimensions of the dosimeter that are comparable with the range of secondary electrons produced in the dosimeter, while luminescence efficiency may also play a role.

Unequal Absorption of Radiolabeled and Nonradiolabeled Drug from the Oral Dose Leads to Incorrect Estimates of Drug Absorption and Circulating Metabolites in a Mass Balance Study.

Mass balance studies conducted using radiolabeled material (14C or 3H) definitively characterize the Absorption, Metabolism, and Excretion (AME) of a drug. A critical aspect of these studies is that the radiotracer maintains its proportion to total drug from its administration to its complete elimination from the body. In the study of GDC-0276 in beagle dogs, we observed that the 14C radiotracer proportion (specific activity) varied through the study. High resolution-accurate mass spectrometric measurements of 12C and 14C isotopes of GDC- 0276 and its metabolites in plasma and excreta samples were used to determine the apparent specific activities, which were higher than the specific activity of the dosing formulation. Drug concentrations were adjusted to the observed specific activities to correct the readouts for GDC-0276 AME and PK. The enrichment of 14C, which resulted in higher specific activities, was consistent with faster and more extensive absorption of the radiotracer from the dosing formulation. This resulted in overestimating the dose absorbed, the extent of elimination in urine and bile, and the exposures to circulating metabolites. These biases were corrected by the specific activities determined for study samples by mass spectrometry. Assuming that the radiotracer was proportional to total drug throughout a radiolabeled study was not valid in a 14C study in beagle dogs. This presumably resulted from unequal absorption of the radiotracer and nonradiolabeled test articles from the oral dose due to inequivalent solid forms. We were able to provide a more accurate description of the AME of GDC-0276 in dogs by characterizing the differential absorption of the radiotracer.

PH Sensitive Hydrogels in Drug Delivery: Brief History, Properties, Swelling, and Release Mechanism, Material Selection and Applications.

Improving the safety efficacy ratio of existing drugs is a current challenge to be addressed rather than the development of novel drugs which involve much expense and time. The efficacy of drugs is affected by a number of factors such as their low aqueous solubility, unequal absorption along the gastrointestinal (GI) tract, risk of degradation in the acidic milieu of the stomach, low permeation of the drugs in the upper GI tract, systematic side effects, etc. This review aims to enlighten readers on the role of pH sensitive hydrogels in drug delivery, their mechanism of action, swelling, and drug release as a function of pH change along the GI tract. The basis for the selection of materials, their structural features, physical and chemical properties, the presence of ionic pendant groups, and the influence of their pKa and pKb values on the ionization, consequent swelling, and targeted drug release are also highlighted.

The coordination of C4 photosynthesis and the CO2-concentrating mechanism in maize and Miscanthus x giganteus in response to transient changes in light quality.

Unequal absorption of photons between photosystems I and II, and between bundle-sheath and mesophyll cells, are likely to affect the efficiency of the CO2-concentrating mechanism in C4 plants. Under steady-state conditions, it is expected that the biochemical distribution of energy (ATP and NADPH) and photosynthetic metabolite concentrations will adjust to maintain the efficiency of C4 photosynthesis through the coordination of the C3 (Calvin-Benson-Bassham) and C4 (CO2 pump) cycles. However, under transient conditions, changes in light quality will likely alter the coordination of the C3 and C4 cycles, influencing rates of CO2 assimilation and decreasing the efficiency of the CO2-concentrating mechanism. To test these hypotheses, we measured leaf gas exchange, leaf discrimination, chlorophyll fluorescence, electrochromatic shift, photosynthetic metabolite pools, and chloroplast movement in maize (Zea mays) and Miscanthus × giganteus following transitional changes in light quality. In both species, the rate of net CO2 assimilation responded quickly to changes in light treatments, with lower rates of net CO2 assimilation under blue light compared with red, green, and blue light, red light, and green light. Under steady state, the efficiency of CO2-concentrating mechanisms was similar; however, transient changes affected the coordination of C3 and C4 cycles in M. giganteus but to a lesser extent in maize. The species differences in the ability to coordinate the activities of C3 and C4 cycles appear to be related to differences in the response of cyclic electron flux around photosystem I and potentially chloroplast rearrangement in response to changes in light quality.

The impact of the Kasatochi eruption on the Moon's illumination during the August 2008 lunar eclipse

The Moon's changeable aspect during a lunar eclipse is largely attributable to variations in the refracted unscattered sunlight absorbed by the terrestrial atmosphere that occur as the satellite crosses the Earth's shadow. The contribution to the Moon's aspect from sunlight scattered at the Earth's terminator is generally deemed minor. However, our analysis of a published spectrum of the 16 August 2008 lunar eclipse shows that diffuse sunlight is a major component of the measured spectrum at wavelengths shorter than 600 nm. The conclusion is supported by two distinct features, namely the spectrum's tail at short wavelengths and the unequal absorption by an oxygen collisional complex at two nearby bands. Our findings are consistent with the presence of the volcanic cloud reported at high northern latitudes following the 7-8 August 2008 eruption in Alaska of the Kasatochi volcano. The cloud both attenuates the unscattered sunlight and enhances moderately the scattered component, thus modifying the contrast between the two contributions.

Disorder Influence on Linear Dichroism Analyses of Smectic Phases

Linear dichroism, the unequal absorption of parallel and perpendicular linear polarized light, is often used to determine the anisotropic ordering of rodlike polymers in a smectic phase, such as helices in a lipid bilayer. It is a measure of two properties of the sample: 1), orientation of the chromophore transition dipole moment (TDM) and 2), disorder. Since it is the orientation of the chromophore TDM that is needed for high resolution structural studies, it is imperative to either deconvolve sample disorder, or at a minimum, estimate its effect upon the calculated TDM orientation. Herein, a rigorous analysis of the effects of disorder is undertaken based on the recently developed Gaussian disorder model implemented in linear dichroism data. The calculation of both the rod tilt and rotational pitch angles as a function of the disorder and dichroism, yield the following conclusions: Disorders smaller than 5° have a vanishingly small effect on the calculated polymer orientation, whereas values smaller than 10° have a negligible effect on the calculated parameters. Disorders larger than 10° have an appreciable effect on the calculated orientational parameters and as such must be estimated before any structural characterization. Finally the theory is tested on the HIV vpu transmembrane domain, employing experimental mosaicity measurements from x-ray reflectivity rocking scans and linear dichroism.

Stimulated Brillouin scattering in Raman-pumped fibers: a theoretical approach

We develop a theoretical approach to describe stimulated Brillouin scattering (SBS) in Raman-pumped optical fibers. We derive the condition for the SBS threshold as a function of fiber parameters and the input power of forward and/or backward pump. A particular emphasis is given to the effect of the fiber length and unequal absorption coefficients for pump and signal wavelengths on the SBS threshold. Simple, yet accurate, analytical expressions for the SBS threshold in pumped fibers are also obtained. We show that in pumped fibers, the SBS threshold power is inversely proportional to the path-average integral of Raman gain. Validity ranges of derived formulas are considered in detail. The theoretical predictions are verified experimentally. The calculated values of the SBS threshold powers are in a good agreement with the measured threshold power in Raman-pumped dispersion-compensated fibers.

Radiative transfer in spectrally dissimilar absorbing-emitting-scattering adjacent mediums

Structure of radiation field in a cylindrical medium having two regions of different, but uniform absorption and scattering coefficients is analyzed. Fundamental aspects of the problem are elucidated by considering the case of a gray medium. It is shown for example that for unequal absorption coefficients in the two regions, both emission and absorption rates are discontinuous at the interface of the two regions, but the heat flux and incident radiation are continuous. As an application of the analysis, the influence on heat transfer of spatial distribution of particles in a coal-burning swirl combustor is investigated. In the example application, spectral calculations are performed spanning over the broad frequency range of the thermal radiation spectrum.

Electrostatic effects on conformational equilibria. Solvent dependence

The conformational equilibrium E ⇄ Z of methyl 2-fluorobenzoate was determined from the intensity of the carbonyl bands in 17 aprotic solvents of different polarity. The estimated values ΔG0 depend linearly on the reciprocal permittivity of the solvent as expected according to the electrostatic theory in combination with common cavity models. If a small correction is admitted for the unequal absorption coefficients of the two rotamers and/or for the steric effect of fluorine, the results agree very well with electrostatic calculations; the values extrapolated to vacuum agree also resonably with CNDO/2, INDO and PCILO, but not with STO-3G calculations. On the whole, the electrostatic theory seems to work better with conformational equilibria than with proton transfer reactions. This conclusion does not depend on the solvent used or on any particular cavity model.

A new Regge absorption model

The weak-cut Regge absorption model is generalized to allow for unequal absorption of the rotating (e − iπα ) and non-rotating (1) parts of the Regge-pole exchange amplitude. Some justification for this procedure is given in terms of duality and peripheral resonance dominance. Fits to data for πN charge-exchange cross section and polarization and cross sections for the line-reversed hypercharge-exchange reactions K N→πΣ and π N→ KΣ are obtained.

Duality-breaking effects in a model for meson-baryon scattering

Duality-violating effects are examined in the context of an exchange-degenerate multiple-scattering model incorporating strong EXD for poles,SU3 at the vertices ands-u crossing. Ten parameters. includingd/f ratios, are used to simultaneously fit cross-sections for K−p→π−Σ+, π+p→K+Σ+,\(K^ - p \to \bar K^0 n\), K+n→K0p, π−p→π0n and π−p→ηn. The qualitatively different energy dependences of the HCEX and CEX line-reversed cross-section differences arise naturally from the fact that the model requires equal absorption in CEX line-reversed reactions and unequal absorption in the HCEX reactions. The cross-section fits are excellent for the HCEX and reasonable for the CEX reactions; polarizations are correct in sign. Thed/f ratios obtained are close to the quark-modelSU6 values. The model is compared with other multireaction fits and their differences and relative successes are discussed.

Morphic effects-IV. Effects of an applied magnetic field on first-order photonoptical phonon interactions in non-magnetic crystals

We present a phenomenological treatment of the effect of an externally applied magnetic field on the first-order Raman and i.r. activity of q ≈ 0 optical phonons in non-magnetic crystals. We show that a contribution to the Raman tensor, linear in the applied field, can only be anti-symmetric, and exists only for those phonons which can exhibit symmetric and/or anti-symmetric Raman scattering. An explicit derivation of the magnetic-field-induced Raman tensor and effective charge is presented, based on simple group-theoretical arguments. By expressing the effective charge in circular coordinates, it is shown that the magnetic field in first order may cause unequal absorption of left- and right-polarized light by left- and right-polarized degenerate phonons respectively. The effect is described as circular dichroism of optical phonons.

Anionic and cationic exchange mechanisms in the skin of anurans, with special reference to leptodactylidae in vivo.

In several species of anurans, the in vivo skin has been shown to absorb Na + and Cl - independently from dilute external solutions. That the mechanism for sodium absorption is different from that of chloride absroption is born out by the following: (1) Either of these ions is absorbed without an accompanying ion when this latter is impermeant. (2) From NaCl solutions there can be an unequal absorption of sodium and chloride. (3) A selective inhibition of the absorption of one of the ions can be produced experimentally, while the net flux of the other remains unchanged. In all these situations, the absorbed ion has to be exchanged against an endogenous ion of the same charge. In Calyptocephalella gayi , H + and HCO - 3 are exchanged against sodium and chloride respectively. A comparison of the relationships between H + excretion and Na + absorption in vivo skins and shortcircuited in vitro skins shows that in the latter no H + excretion occurs, only the Na + transport being maintained under these experimental conditions. From this, one must conclude that the active Na + transport is the motive factor of the transport mechanism. H + excretion by the in vivo skin plays the role of physiologically short-circuiting the Na + transport.

The Radiographic Detection of Glass in Soft Tissue

The Physical basis of radiology rests on the unequal absorption of x rays as they pass through objects of different densities and effective atomic numbers. It is not generally appreciated that all types of commercial glass possess physical characteristics that are different from those of human tissues. The higher density and effective atomic number of glass compared to those of surrounding soft tissue cause it to be visible on the appropriately exposed radiograph. A review of the American radiologic literature uncovered only one reference concerning the radiopacity of glass, and that was written in 1932 (6). In 1958 two articles appeared, one in The Archives of Industrial Health (9) and the other in The British Journal of Surgery (4), reporting the radiopacity of glass and its detection in soft tissues. The German literature contains a report published in 1964 which concluded that all ordinary glass, when embedded in the tissues of the hand, could be detected radiographically (3). Information gained from consulting several of the standard texts is confusing and often inaccurate. Zatzkin states that ordinary glass used in windows and bottles usually can be demonstrated in soft tissues (12). He illustrates multiple varieties of glass that are radiopaque. Another text states that plate glass, glass utilized in lenses and chemical apparatus, and glass containing manganese may be faintly visible but that small pieces in thick parts of the body are not (10). Köhler and Zim-mer suggest that glass is either invisible or barely visible radiographically and do not include it among those objects that are easily visualized (5). Brodeur states that glass must contain iron, lead, or titanium in order to have a density greater than that of soft tissues and therefore cast a shadow (1). Caffey shows a picture of glass from a beer bottle in the hand. He concludes that, “The heavy density of this glass fragment is due to its lead content; glass free of lead is usually invisible in soft tissues because it has a density similar to that of soft tissues” (2). Other texts make no mention of the radiopacity of glass in soft tissue (7, 8, 11). The value of using a simple device such as an x ray to locate glass particles in the body should be apparent to all who treat glass-induced injuries. An informal survey of pediatric and surgical residents as well as some trained radiologists revealed that most did not consider all types of glass to be radiopaque. This is not surprising in view of the confusing information published in the standard radiology texts as well as the absence of any recent publication in the radiologic or pediatric literature. Contrary to general opinion, glass need not contain lead to be radiopaque. Ordinary machine-made glass contains no lead but is made of a mixture of soda-lime, silicates, and potash.2

Circular dichroism of biological macromolecules.

Circular dichroism, the unequal absorption of right and left circularly polarized light, is a manifestation of optical activity in the vicinity of absorption bands. To the experimental scientist interested in the conformation of macromolecules and in the sensitive response of optical activity to conformational alteration, it offers a relatively new and powerful means of understanding the environment of chromophoric residues. As a tool in the elucidation of electronic spectra, it should be useful to the theoretical scientist in identifying weakly allowed absorption bands as well as in providing rotational parameters which can be compared with the developing theory of optical activity. I have stressed application of circular dichroism, to experimental aspects of protein and nucleic acid conformation in solution. Much is still uncertain in particular quantitative details. However, even these early results shed new light and yield new information on the conformation of these molecules.

The intake and utilization of carbon by plant roots from C14-labeled urea Part I. The determination of radioactive carbon of plant materials and a preliminary seedling experiment utilizing C14-labeled urea

Abstract Utilizing radioactive carbon, A. Kursanov, A. Kuzin and co-workers1- 0 recently discovered a new function of the plant root; i.e. COs or carbonate can be absorbed by the plant root, transferred to green tissues and, in the presence of light, is transformed into sugar and protein. Absorption of carbon dioxide by roots is connected with ,β-carboxylation of keto acids and with the movement of dicarboxylic acid to leaves. Pot experiments with four crops where the cu-labeled sodium carbonate was used, showed that the carbon of soil carbonate can be taken up by crop plants only when the pH of the soil showed an alkaline reaction. Field experiments showed that; if carbonic acid was placed in the soil in the form of ammonium or potassium carbonate, the growth of sugar beet increased by 10 to 15 percents. In this new function of plant root, the amount of COs absorbed as well as its pathway to complicated carbon compounds should be discussed. Kursanov et al2,3 showed that the amount of CO2 taken up by roots was considerably large, while Overstreet et al7 obtained comparatively law values with barley root. More recently Poel8 observed a considerably large intake of CO2 by barley root, Cl being distributed in amino acids, amines and carboxylic acids of TCA cycle. Jacobson9 indicated that an unequal absorption of cations and anions by plant roots was reflected in gains or losses of inorganic ions and changes in organic acid content of the roots. Further, the same author10 investigated the relationship between CO2 fixation and malic acid metabolism in plant root, on the basis that among other organic acids particularly malic acid might directly or indirectly be implicated in the ion absorption. Young excised barley roots fixed from 1.18 to 7.02% of the C14Oa in three hours, when it was supplied as NaHC14Oa solution. When excess anion absorption occurred in CaBr2 solution, the lower figures were obtained, and higher figures when excess cation absorption occurred in KH3PO4 solution. The Cl14 accumulated in malate was 68 to 92%. He11,12 also suggested that the mechanism of CO2 fixation may be a reductive carboxylation of pyruvate with the help of malic enzyme, or an oxaloacetic acid carboxylase reduction followed by reduction to malate.

The development of the trigone of the bladder with a report of a case of ectopic ureter.

SUMMARYThe history of a patient suffering from incontinence of urine due to an ectopic ureter is presented. The embryology of this condition has been studied and the trigone of the bladder, together with the posterior part of the urethra, shown to be derived from the Wolffian ducts by gradual dilatation of the lower end of the latter. The subsequent alteration in relationship of the Wolffian ducts to the ureter is discussed, and it is suggested that the alteration of the orifices of the Wolffian ducts to the ureters during development is due to unequal absorption of the Wolffian duct and active growth at its upper and outer lip.The opening of the ectopic ureters may occur at any point on the outer edge of the area of bladder and urethra derived from the Wolffian duct. In the case presented an ectopic ureter was found to open into the urethra below the sphincters in conformity with the development outlined.It is a pleasure to acknowledge my indebtedness to Professor F. H. Bentley and Mr Fenton Braithwaite for their help, to Mr D. P. Hammersley for the diagrams used to illustrate this article, and to Mr A. L. Pegg of the Department of Photography, University of Durham, for the photomicrographs.

The Influence of Wavelength on the Biological Effectiveness of Radiation

At the request of the Joint Committee on Radiotherapy the following experiments have been undertaken as a contribution to the study of “the wavelength factor in radiotherapy.” Investigations of the influence of wavelength in determining the biological effectiveness of radiation have given results of a conflicting nature. The extreme claims of a highly selective action of certain wavelengths, made by Moppett17 for X radiation and Reiter20 for ultra-short wireless waves, have now been discredited. But differences of opinion still exist as to the relative effectiveness of soft and hard X radiation and of γ radiation. Packard19 in reviewing the evidence bearing on this problem, has critically analysed the experimental procedures of some workers who claim that the degree of biological response is determined by the quality of radiation used. Variable results by different workers may depend upon:— (a) Differences in the physiological condition of the test material, with concomitant alterations in radio-sensitivity. (b) Differences in the penetration of hard and soft radiation, which implies unequal absorption by unsuitable test objects. (c) Inaccuracies of the physical and biological measurements involved. Anyone acquainted with the literature on this subject will be aware that, even if we consider only those investigations in which these conditions appear to have been fulfilled, there does not emerge from the experimental results, taken together, any clear generalisation as to the relative effectiveness of different qualities of radiation on the various types of organisms and tissues which have been used as test objects.