Infinite Concentration Research Articles

Simultaneous intramolecular and intermolecular coupling of polar bond vibrations induced spectral splitting phenomenon

The positions of splitting bands resulting from simultaneous intramolecular (such as Fermi resonance) and intermolecular interactions were calculated by a variational method. Hamiltonian calculation model employed an antiparallel arrangement. Four nondegenerate energy solutions were obtained, which correspond exactly to the four peaks observed in polarized Raman spectroscopy and high resolution infrared spectroscopy: two in the VV component and two in the VH component. The intramolecular coupling constant W, unperturbed intensity ratios R, and unperturbed band difference X0 for vinylene carbonate (VC) were calculated from the derived equations and the experimental data at infinite dilution concentration. Additionally, the intermolecular interaction constants V of VC in different polar solvents (VC/CH3CN, VC/CHCl3 and VC/CH3OH binary mixtures) at varying concentrations were calculated. The curvature of V vs concentration was found to fit the Logan model very well.

Complete solution of the Einstein field equations for a spherical distribution of polytropic matter

We determine the complete solution of the Einstein field equations for the case of a spherically symmetric distribution of gaseous matter, characterized by a polytropic equation of state. We show that the field equations automatically generate two sharp boundaries for the gas, an inner one and an outer one, given by radial positions $$r_{1}$$ and $$r_{2}$$ , and thus define a shell of gaseous matter outside of which the energy density is exactly zero. Hence this shell is surrounded by an outer vacuum region, and surrounds an inner vacuum region. Therefore, the solution is given in three regions, one being the well-known analytical Schwarzschild exterior solution in the outer vacuum region, one being determined analytically in the inner vacuum region, and one being determined partially analytically and partially numerically, within the matter region, between the two boundary values $$r_{1}$$ and $$r_{2}$$ of the Schwarzschild radial coordinate r. This solution is therefore somewhat similar to the one previously found for a spherically symmetric shell of liquid fluid, and is in fact exactly the same in the cases of the inner and outer vacuum regions. The main difference is that here the boundary values $$r_{1}$$ and $$r_{2}$$ are not chosen arbitrarily, but are instead determined by the dynamics of the system. As was shown in the case of the liquid shell, also in this solution there is a singularity at the origin, that just as in that case does not correspond to an infinite concentration of matter, but in fact to zero matter energy density at the center. Also as in the case of the liquid shell, the spacetime within the spherical cavity is not flat, so that there is a non-trivial gravitational field there, in contrast with Newtonian gravitation. This inner gravitational field has the effect of repelling matter and energy away from the origin, thus avoiding a concentration of matter at that point.

Exact solution of the Einstein field equations for a spherical shell of fluid matter

We determine the exact solution of the Einstein field equations for the case of a spherically symmetric shell of liquid matter, characterized by an energy density which is constant with the Schwarzschild radial coordinate r between two values $$r_{1}$$ and $$r_{2}$$ . The solution is given in three regions, one being the well-known analytical Schwarzschild solution in the outer vacuum region, one being determined analytically in the inner vacuum region, and one being determined mostly analytically but partially numerically, within the matter region. The solutions for the temporal coefficient of the metric and for the pressure within this region are given in terms of a non-elementary but fairly straightforward real integral. For some values of the parameters this integral can be written in terms of elementary functions. We show that in this solution there is a singularity at the origin, and give the parameters of that singularity in terms of the geometrical and physical parameters of the shell. This does not correspond to an infinite concentration of matter, but in fact to zero energy density at the center. It does, however, imply that the spacetime within the spherical cavity is not flat, so that there is a non-trivial gravitational field there, in contrast with Newtonian gravitation. This gravitational field is repulsive with respect to the origin, and thus has the effect of stabilizing the geometrical configuration of the matter, since any particle of the matter that wanders out into either one of the vacuum regions tends to be brought back to the bulk of the matter by the gravitational field.

Purification of Xanthine Oxidase Enzyme and Investigation of Its Immobilization with Glutaraldehyde

In this study, the xanthine oxidase (XO) enzyme was purified by affinity chromatography technique using Sepharose-4B-L-tyrosine-4-aminobenzamidine gel and its immobilization with glutaraldehyde was investigated. Using ammonium sulfate precipitation and affinity gel, xanthine oxidase was purified 643.04-fold in an 11.5% yield. The purity of the enzyme was checked by SDS polyacrylamide gel electrophoresis and a single band around 150 kDa was observed. KM (the Michaelis constant) and VMax (the asymptotic reaction velocity at infinite substrate concentration) of the enzyme were determined at 1.67x10-4 M and 0.56 U/mL.min respectively by using a xanthine compound as a substrate. The in vitro effects of NH4F, NH4Cl, CaCl2, ZnCl2, HgCl2, Hg(NO3)2.H2O compounds and commercially named colchicum dispert, commonly used in the treatment of gout disease in the clinic, were investigated. The IC50 values of compounds showing inhibition effects were determined. Afterward, XO was immobilized with glutaraldehyde. The highest XO activity was observed in the sample of the immobilized enzyme at a rate of 6% glutaraldehyde. The kinetic constants (KM and VMax) of the immobilized enzyme were determined as 5.18x10-4 M and 0.73 U mL-1 min-1 respectively. These values revealed that the catalytic activity of the free enzyme was higher than the immobilized enzyme.

Thermophysical properties of 1-butyl-3-methylimidazolium octyl sulfate ionic liquid in aqueous and aqueous electrolyte solutions at different temperatures

Understanding the molecular interaction of 1-butyl-3-methylimidazolium octyl sulfate i.e., [Bmim][OcOSO3] in water and in aqueous NaCl solution is important for fabricating the new process. As it is already known that ionic liquids along with inorganic salt NaCl have significant potential in the tribology of lubricants and salting-out media for the separation of nicotine. It is known that ionic liquids exhibit characteristic behavior at solid−liquid interfaces. Although it is believed that the structure of ionic liquids at the interface contributes to the tribological properties in the region of boundary-mixed lubrication, this contribution has not been clarified yet. Thus, we study the molecular interaction of the ionic liquid in aqueous and ionic liquid in aqueous NaCl solutions through the thermodynamic approach. We have measured density as an important parameter for 1-butyl-3-methylimidazolium octyl sulfate i.e., [Bmim][OcOSO3] in water and in aqueous NaCl solution within the concentration range of 0.04-0.12 mol/kg at different temperatures i.e. 293.15, 298.15, 303.15, 308.15, and 313.15 K and atmospheric pressure by using a densitometer (DSA5000M Anton Paar). The density (ρ) data were employed to measure some derived parameters such as apparent molar volume of solute (Vϕ), limiting apparent molar volume of solute (Vϕ0), thermal expansion coefficient (α), apparent molar expansivity of solute at finite concentration (Eϕ) and at infinite concentration (Eϕ0) and transfer volume (ΔtrVϕ0). Results have been discussed in terms of all the possible molecular interactions in systems.

Use of coumarin derivatives as activators in the peroxyoxalate system in organic and aqueous media

The peroxyoxalate system – base catalyzed reaction of oxalic ester derivatives with hydrogen peroxide in the presence of a fluorescent activator – is one of the most efficient chemiluminescence transformations known and widely utilized in analytical and bioanalytical applications. Coumarin derivatives have found widespread application as fluorescent labels for the determination of enzymatic activity in biological fluids and in fluorescence immunoassays, among others. In this work, we show that coumarin derivatives can be utilized as activators in the peroxyoxalate reaction (with two oxalic esters, including a new, environmentally compatible derivative) in anhydrous and aqueous systems, leading to reproducible kinetic results and singlet quantum yields similar to that obtained with commonly utilized activators. Quantum yields are lower in aqueous than in anhydrous medium, however still considerably high to allow the application in analytical and bioanalytical assays. The chemiluminescence parameters (singlet quantum yields at infinite activator concentration and relative electron transfer rate constants) determined in the systems indicate the occurrence of electron or charge transfer steps according to the Chemically Initiated Electron Exchange Luminescence (CIEEL) mechanism.

The Uniqueness of a Correction to Interaction Parameter Formalism in a Thermodynamically Consistent Manner

Polynomial representation of partial excess Gibbs energy (i.e., activity coefficient) in multicomponent dilute solution has been widely used after Wagner. Although Wagner’s Interaction Parameter Formalism has been known to be only strictly valid at infinite dilute concentration, it has been used often, even at finite concentration, due to its mathematical simplicity. Nevertheless, several attempts have been made to correct the formalism to be thermodynamically consistent at finite concentration. Among those, Unified Interaction Parameter Formalism proposed by Pelton and Bale, which may be considered as an extension of Darken’s quadratic formalism, has obtained much attention. However, there have been much confusion and debate about the way of the correction. Recently, a thermodynamic analysis was reported that there are infinite numbers of ways to correct Wagner’s formalism to be thermodynamically consistent, which may prevent one from using the Unified Interaction Parameter Formalism with confidence. In the present article, the correction to the Wagner’s formalism is discussed by revisiting Darken’s condition of the thermodynamic consistency. It is shown that the correction to the Wagner’s formalism can be made uniquely. It is pointed out that to ensure the thermodynamic consistency among the activity coefficients of all components, Gibbs–Duhem relation and Maxwell relation among all components including solvent–solute, must be obeyed. Derived expressions for activity coefficients of all components by path-independent integration are also shown to be the same as those obtained by differentiating a corresponding integral excess partial Gibbs energy.

Preclinical Evaluation and Dosimetry of [111In]CHX-DTPA-scFv78-Fc Targeting Endosialin/Tumor Endothelial Marker 1 (TEM1)

PurposeEndosialin/tumor endothelial marker-1 (TEM1) is an attractive theranostic target expressed by the microenvironment of a wide range of tumors, as well as by sarcoma and neuroblastoma cells. We report on the radiolabeling and preclinical evaluation of the scFv78-Fc, a fully human TEM1-targeting antibody fragment cross-reactive with mouse TEM1.ProceduresThe scFv78-Fc was conjugated with the chelator p-SCN-Bn-CHX-A”-DTPA, followed by labeling with indium-111. The number of chelators per molecule was estimated by mass spectrometry. A conventional saturation assay, extrapolated to infinite antigen concentration, was used to determine the immunoreactive fraction of the radioimmunoconjugate. The radiopharmaceutical biodistribution was assessed in immunodeficient mice grafted with Ewing’s sarcoma RD-ES and neuroblastoma SK-N-AS human TEM1-positive tumors. The full biodistribution studies were preceded by a dose-escalation experiment based on the simultaneous administration of the radiopharmaceutical with increasing amounts of unlabeled scFv78-Fc. Radiation dosimetry extrapolations to human adults were obtained from mouse biodistribution data according to established methodologies and additional assumptions concerning the impact of the tumor antigenic sink in the cross-species translation.Results[111In]CHX-DTPA-scFv78-Fc was obtained with a radiochemical purity > 98 % after 1 h incubation at 42 °C and ultrafiltration. It showed good stability in human serum and > 70 % immunoreactive fraction. Biodistribution data acquired in tumor-bearing mice confirmed fast blood clearance and specific tumor targeting in both xenograft models. The radiopharmaceutical off-target uptake was predominantly abdominal. After a theoretical injection of [111In]CHX-DTPA-scFv78-Fc to the reference person, the organs receiving the highest absorbed dose would be the spleen (0.876 mGy/MBq), the liver (0.570 mGy/MBq) and the kidneys (0.298 mGy/MBq). The total body dose and the effective dose would be 0.058 mGy/MBq and 0.116 mSv/MBq, respectively.Conclusions[111In]CHX-DTPA-scFv78-Fc binds specifically to endosialin/TEM1 in vitro and in vivo. Dosimetry estimates are in the range of other monoclonal antibodies radiolabeled with indium-111. [111In]CHX-DTPA-scFv78-Fc could be potentially translated into clinic.

Rouse revisited: The bottom boundary condition for suspended sediment profiles

A linearly depth-dependent diffusivity is commonly used to model the vertical distribution of dilute, near-bed, suspended sediment in marine fluid environments, i.e., the Rouse model; this simplified form predicts unfortunately infinite concentration at the bed. That singularity causes problems in linking bed models to suspended sediment models. A common remedy to this problem is to assume a reference concentration and height above the bed, but some studies point to the arbitrariness of that procedure and suggest, instead, the existence of a residual eddy diffusion near the bed, which removes the singularity. In these past studies, the residual diffusion, εo, has been assigned a value based on the Nikuradse roughness height, ks=2.5ds, where ds is the (mean) equivalent sand-grain diameter. We examine this assumption by fitting a residual diffusion model to 14 time-averaged suspended-sediment profiles available in the literature, without assuming the Nikuradse length. This procedure produces εo values from 0.6 to 13cm2s−1, which are much greater than both the (molecular) kinematic viscosity of water and the expected Brownian diffusion coefficient of the sediment grains of the reported sizes. These residual diffusion coefficients indicate mixing scale heights at the bed, εo/κu∗, where κ is von Kármán's constant and u∗ is the shear velocity, are 7.4–56.0× greater than the Nikuradse height, ks. Although defined by only limited data, we also find that the residual diffusion correlates with grain size and the roughness Reynolds number but not with the Rouse parameter, nor with the shear and settling velocities. In addition, the residual diffusion coefficient correlates with van Rijn's roughness scale, again based on the same limited data, suggesting that bedforms influence residual diffusion near the bed.

When both Km and Vmax are altered, Is the enzyme inhibited or activated?

Enzyme activators lower Km (the Michaelis constant) and/or raise Vmax (the asymptotic reaction velocity at infinite substrate concentration); conversely, inhibitors raise Km and/or lower Vmax . But what if an effector moves both Km and Vmax in the same direction? Uncompetitive inhibitors, which decrease both Km and Vmax by the same factor, are the most common example of this. A less well-known example occurs often when crowding agents are added to the buffer in order to mimic the environment commonly encountered in vivo. Crowding agents tested on different enzymes have been shown to have every conceivable effect on Km or Vmax , causing them to rise, fall, or stay the same. In this article, a mathematical analysis is presented allowing biochemists to judge whether an effector that causes Km and Vmax to both move in the same direction serves as an inhibitor, an activator, or most surprising, as both. © 2019 International Union of Biochemistry and Molecular Biology, 47(4):446-449, 2019.

Floquet dynamics of classical and quantum cavity fields

We show that the time-dependence of electromagnetic field in a periodically modulated cavity can be effectively analyzed using a Floquet map. The map relates the field states separated by one period of the drive; iterative application of the map allows to determine field configuration after arbitrary number of drive periods. For resonant and near-resonant drives, the map has stable and unstable fixed points, which are the loci of infinite energy concentration in the long time limit. The Floquet map method can be applied both to classical and quantum massless field problems, including the dynamical Casimir effect. The stroboscopic time evolution implemented by the map can be interpreted in terms of the wave propagation in a curved space, with the fixed points of the map corresponding to the black hole and white hole horizons. More practically, the map can be used to design protocols for signal compression/decompression, cooling, and sensing.

On stress singularity at crack tip in elasticity

Abstract In order to gain a better understanding of the stress singularity at the crack tip in elasticity, the relevant solutions are investigated. Based on the rigorous solution of a plate containing a crack and its corresponding asymptotic expression, the stress singularity at the crack tip was described in details. The stress singularity at the crack tip is identified as: the infinite stress exists at the crack tip, and the stress components at the crack tip are multivalued. Besides, the rigorous solution of the infinite plate containing a crack may be derived from the rigorous solution of the infinite plate containing an elliptical hole, which is solved from Mushelishvili’s approach. As half minor-axial length approaches zero, the stress concentration field of a plate with an elliptical hole evolves into the stress singularity field of a plate with a crack. Thus, the stress intensity factor characterizing the stress singularity field near the crack tip may also be read as characterizing the infinite stress concentration field near the crack tip. Therefore, the mechanical concept of stress intensity factor can be identified as follows: stress intensity factor is a parameter characterizing the strength of infinite stress concentration field at the crack tip.

Multiple Doses of Rifabutin Reduce Exposure of Doravirine in Healthy Subjects

Doravirine is a nonnucleoside reverse transcriptase inhibitor in clinical development for the treatment of human immunodeficiency virus-1 infection in combination with other antiretroviral therapies. The cytochrome P450 (CYP)3A-dependent metabolism of doravirine makes it susceptible to interactions with modulators of this pathway, including the antituberculosis treatment rifampin. Rifabutin, an alternative antibiotic used to treat tuberculosis, may have a lower-magnitude effect on CYP3A. The aim of this trial was to determine the effect of steady-state rifabutin on doravirine single-dose pharmacokinetics and tolerability. In this open-label, 2-period, fixed-sequence, drug-drug interaction study, healthy subjects received a single dose of doravirine 100mg alone and coadministered on day 14 of once-daily administration of rifabutin 300mg for 16 days. Plasma samples were taken to determine doravirine pharmacokinetics, and safety was monitored throughout. Dose adjustment of doravirine in the presence of coadministered rifabutin was explored through nonparametric superposition analysis. Rifabutin reduced doravirine area under the concentration-time curve from time zero to infinite and plasma drug concentration 24 hours postdose with geometric mean ratios ([rifabutin+doravirine]/[doravirine alone]) (90%CIs) of 0.50 (0.45-0.55) and 0.32 (0.28-0.35), respectively. Doravirine apparent clearance increased from 5.9L/h without rifabutin to 12.2L/h when coadministered. Doravirine pharmacokinetics with and without coadministered rifabutin were not equivalent. Nonparametric superposition analysis projected that administration of doravirine 100mg twice daily with rifabutin will restore steady-state trough concentration values to efficacious levels associated with doravirine 100mg once daily in the absence of CYP3A inducers. Doravirine may be coadministered with rifabutin when the doravirine dose frequency is increased from 100mg once daily to 100mg twice daily.

Breaking the black-body limit with resonant surfaces

The speed with which electromagnetic energy can be wirelessly transferred from a source to the user is a crucial indicator for the performance of a large number of electronic and photonic devices. We expect that energy transfer can be enhanced using special materials. In this paper, we determine the constituent parameters of a medium which can support theoretically infinite energy concentration close to its boundary; such a material combines properties of Perfectly Matched Layers (PML) and Double-Negative (DNG) media. It realizes conjugate matching with free space for every possible mode including, most importantly, all evanescent modes; we call this medium Conjugate Matched Layer (CML). Sources located outside such layer deliver power to the conjugate-matched body exceptionally effectively, impressively overcoming the black-body absorption limit which takes into account only propagating waves. We also expand this near-field concept related to the infinitely fast absorption of energy along the air-medium interface to enhance the far-field radiation. This becomes possible with the use of small particles randomly placed along the boundary; the induced currents due to the extremely high-amplitude resonating fields can play the role of emission “vessels”, by sending part of the theoretically unlimited near-field energy far away from the CML structure.

On the uniqueness of solution to generalized Chaplygin gas

The main object of the paper is finding a unique solution to Riemann problem for generalized Chaplygin gas model. That is a model of the dark energy in Universe introduced in the last decade. It permits an infinite mass concentration so one has to consider solutions containing the Dirac delta function. Although it was easy to construct solution to any Riemann problem, the usual admissibility conditions, overcompressiveness, do not exclude unwanted delta-type waves when a classical solution exists. We are using Shadow Wave approach in order to solve that uniqueness problem since they are well adopted for using Lax entropy–entropy flux conditions and there is a rich family of convex entropies.

Partial molar enthalpies of organic solutes in the ionic liquid [EMIM][EtSO4

Partial molar excess enthalpies of mixing of the organic liquids methanol, acetonitrile, acetone and propan-1-ol in 1-ethyl-3-methylimidazolium ethyl sulfate ([EMIM][EtSO4]) have been measured using a titration calorimeter. Data have been obtained at 298K, in the case of methanol also at 308K, in the mole fraction range of the organic liquid x2 from 0.005 to 0.05. The results have been extrapolated to infinite dilution for determining enthalpies of dilution at infinite concentrations H¯2,∞E (x2=0). Alternatively values of H¯2,∞E can be obtained from measurements of activity coefficients γ2∞ at different temperatures using the gas chromatographic or the dilutor technique. However, according to our error analysis calorimetric results of H¯2E,∞ are by a factor 2–3 more reliable than the results obtained by the indirect methods.

Peroxyoxalate High-Energy Intermediate is Efficiently Decomposed by the Catalyst Imidazole.

The peroxyoxalate reaction is a highly efficient chemiluminescence system, its chemiexcitation process involving the intermolecular interaction between an activator (ACT) and the high-energy intermediate (HEI) of the reaction. Typically, the HEI is generated through the reaction of an oxalate ester with H2 O2 , in the presence of a basic/nucleophilic catalyst, such as imidazole (IMI-H). IMI-H, besides catalyzing the formation of the HEI, is also known to decompose this peroxidic intermediate. Despite that, up to now, no rate constant value has been determined for such significant interaction. Through kinetic measurements, we have observed that IMI-H is roughly four times more efficient than 9,10-diphenylanthracene (DPA), a classic ACT, in catalyzing the decomposition of the HEI by a bimolecular electron transfer reaction through a Chemically Initiated Electron Exchange Luminescence-like process. For instance, when IMI-H and DPA are at the same concentration, 78% of the generated HEI is actually consumed by the nonemissive bimolecular interaction with IMI-H. We have obtained an average singlet excited state formation quantum yield, at infinite ACT concentration, of (5.5±0.5)×10(-2) Emol(-1) , determined at five different IMI-H concentrations. This ultimately suggests that the yield of formation of HEI actually does not depend on the IMI-H concentration.

Inactivation of Human Cytochrome P450 3A4 and 3A5 by Dronedarone and N-Desbutyl Dronedarone.

Dronedarone is an antiarrhythmic agent approved in 2009 for the treatment of atrial fibrillation. An in-house preliminary study demonstrated that dronedarone inhibits cytochrome P450 (CYP) 3A4 and 3A5 in a time-dependent manner. This study aimed to investigate the inactivation of CYP450 by dronedarone. We demonstrated for the first time that both dronedarone and its main metabolite N-desbutyl dronedarone (NDBD) inactivate CYP3A4 and CYP3A5 in a time-, concentration-, and NADPH-dependent manner. For the inactivation of CYP3A4, the inactivator concentration at the half-maximum rate of inactivation and inactivation rate constant at an infinite inactivator concentration are 0.87 µM and 0.039 minute(-1), respectively, for dronedarone, and 6.24 µM and 0.099 minute(-1), respectively, for NDBD. For CYP3A5 inactivation, the inactivator concentration at the half-maximum rate of inactivation and inactivation rate constant at an infinite inactivator concentration are 2.19 µM and 0.0056 minute(-1) for dronedarone and 5.45 µM and 0.056 minute(-1) for NDBD. The partition ratios for the inactivation of CYP3A4 and CYP3A5 by dronedarone are 51.1 and 32.2, and the partition ratios for the inactivation of CYP3A4 and CYP3A5 by NDBD are 35.3 and 36.6. Testosterone protected both CYP3A4 and CYP3A5 from inactivation by dronedarone and NDBD. Although the presence of Soret peak confirmed the formation of a quasi-irreversible metabolite-intermediate complex between dronedarone/NDBD and CYP3A4/CYP3A5, partial recovery of enzyme activity by potassium ferricyanide illuminated an alternative irreversible mechanism-based inactivation (MBI). MBI of CYP3A4 and CYP3A5 was further supported by the discovery of glutathione adducts derived from the quinone oxime intermediates of dronedarone and NDBD. In conclusion, dronedarone and NDBD inactivate CYP3A4 and CYP3A5 via unique dual mechanisms of MBI and formation of the metabolite-intermediate complex. Our novel findings contribute new knowledge for future investigation of the underlying mechanisms associated with dronedarone-induced hepatotoxicity and clinical drug-drug interactions.

Hydrodynamic model of a self-gravitating optically thick gas and dust cloud

We propose an original mechanism of sustained turbulence generation in gas and dust clouds, the essence of which is the consistent provision of conditions for the emergence and maintenance of convective instability in the cloud. We considered a quasi-stationary one-dimensional model of a selfgravitating flat cloud with stellar radiation sources in its center. The material of the cloud is considered a two-component two-speed continuous medium, the first component of which, gas, is transparent for stellar radiation and is supposed to rest being in hydrostatic equilibrium, and the second one, dust, is optically dense and is swept out by the pressure of stellar radiation to the periphery of the cloud. The dust is specified as a set of spherical grains of a similar size (we made calculations for dust particles with radii of 0.05, 0.1, and 0.15 μm). The processes of scattering and absorption of UV radiation by dust particles followed by IR reradiation, with respect to which the medium is considered to be transparent, are taken into account. Dust-driven stellar wind sweeps gas outwards from the center of the cloud, forming a cocoon-like structure in the gas and dust. For the radiation flux corresponding to a concentration of one star with a luminosity of about 5 ×104L⊙ per square parsec on the plane of sources, sizes of the gas cocoon are equal to 0.2–0.4 pc, and for the dust one they vary from tenths of a parsec to six parsecs. Gas and dust in the center of the cavity are heated to temperatures of about 50–60 K in the model with graphite particles and up to 40 K in the model with silicate dust, while the background equilibrium temperature outside the cavity is set equal to 10 K. The characteristic dust expansion velocity is about 1–7 kms−1. Three structural elements define the hierarchy of scales in the dust cocoon. The sizes of the central rarefied cavity, the dense shell surrounding the cavity, and the thin layer inside the shell in which dust is settling provide the proportions 1 : {1–30} : {10−7–10−6}. The density differentials in the dust cocoon (cavity–shell) are much steeper than in the gas one, dust forms multiple flows in the shell so that the dust caustics in the turning points and in the accumulation layer have infinite dust concentration. We give arguments in favor of unstable character of the inverse gas density distribution in the settled dust flow that can power turbulence constantly sustained in the cloud. If this hypothesis is true, the proposed mechanism can explain turbulence in gas and dust clouds on a scale of parsecs and subparsecs.

Quantum yields for sacrificial hydrogen generation from saccharides over a Pt-loaded TiO2 photocatalyst

Much attention is paid to sacrificial hydrogen generation from saccharides over a Pt-loaded titanium oxide (Pt/TiO2) from the viewpoint of being a renewable energy alternative to petroleum-based fuels. Here, monosaccharides such as glucose, gluconic acid, galactose, sorbose, fructose, mannose, and disaccharides such as sucrose and cellobiose as well as related compounds such as ascorbic acid and sugar alcohols (xylitol and sorbitol) were used as sacrificial agents (R–H) in order to determine quantum yields (Φ) for hydrogen evolution. From double-reciprocal plots of Φ to the concentration of R–H, we obtained the limiting quantum yield in an infinite concentration of R–H. The limiting quantum yields were determined to be of similar values (0.058–0.168) for monosaccharides. Moreover, the rate constant (k R) for the hydrogen abstraction by hydroxyl radical from saccharides were obtained from the double reciprocal plots. It was found that the k R value of glucose was larger compared to galactose, mannose, sorbose, and fructose, which were the stereo and structural isomers of glucose.