bluuebunny/crossref_metadata_2025 huggingface dataset:
Bone Morphogenic Protein‐2 Induces Apoptosis and Cytotoxicity in Periodontal Ligament Cells
Authors: Muthukuru Manoj
Published: July 2012

Background: Periodontal ligament (PDL) expresses endogenous growth factors, such as bone morphogenic proteins (BMPs), which facilitate maintenance of tissue homeostasis. Inflammatory conditions, such as chronic periodontitis, could disrupt this homeostasis, and physiologic levels of growth factors may be insufficient to maintain tissue homeostasis. BMPs facilitate periodontal bone regeneration but also are implicated in causing tooth ankylosis and root resorption. The underlying mechanism of tooth ankylosis is unclear. However, there is evidence that BMPs induce apoptosis in progenitor cells. Little is known about BMP‐induced cytotoxicity in PDL cells, which contain a population of progenitor cells. The aim of this study is to determine BMP2‐induced osteogenic mediators and cytotoxic effects in PDL cells and compare these cells to osteoblasts.

Methods: Human PDL cells and primary osteoblasts were stimulated with doses of 1 to 200 ng/mL BMP2. Expression of alkaline phosphatase (ALP), in vitro mineralization along with osteonectin expression, induction of apoptosis, and cytotoxicity assays were performed.

Results: PDL cells and osteoblasts upregulated ALP and in vitro mineralization in a dose‐dependent manner with BMP2 stimulation. However, at BMP2 concentrations >10 ng/mL, ALP, in vitro mineralization, and osteonectin were downregulated in PDL cells. Relative to osteoblasts, PDL cells were susceptible to apoptosis and cytotoxicity with 10 times lower concentration of BMP2.

Conclusions: Relative to osteoblasts, PDL cells are susceptible to BMP2‐induced cytotoxicity. BMP‐induced tooth ankylosis is controversial and is poorly understood. Disruption of PDL homeostasis by BMP‐induced apoptosis could play a role in tooth ankylosis.
Influence of Mutations in the Hepatitis B Virus Genome on Virus Replication and Drug Resistance - Implications for Novel Antiviral Strategies
Authors: Tacke Frank , Manns Michael P. , Trautwein Christian
Published: July 2012

Persistent infection with the hepatitis B virus (HBV) represents a major health problem worldwide with over 350 million patients at risk of developing liver cirrhosis or hepatocellular carcinoma. HBV is a small, partially double-stranded DNA virus with four overlapping genes and a unique life cycle, creating an intracellular pool of covalently closed circular DNA molecules for persistence and an RNA template for replication via reverse transcription. Mutations occur frequently, and particular selection pressures, both endogenous (host immune clearance) and exogenous (vaccines and antivirals), readily select escape mutants. For example, HBeAg-negative chronic HBV infection with either basal core promoter or precore mutations is predominant in many parts of the world. Therapy of HBV infection with the nucleoside analogue lamivudine frequently leads to the selection of drug-resistant strains with polymerase mutations. Treatment options for chronic HBV infection include at present either interferon-alpha or the oral nucleos(t)ide analogues lamivudine or adefovir. However, these drugs have drawbacks, including possible serious side effects and low response rates in HBeAg-negative patients in the case of interferon or recurrence of viremia after cessation of therapy and development of escape mutants after a long period of treatment with nucleoside inhibitors. Recent advances of in vitro and in vivo models allow to study new antiviral strategies, including novel nucleoside analogues, nucleocapsid inhibitors or small interfering RNA. This review summarises the impact of clinically relevant mutations in the HBV genome on viral replication and drug sensitivity, the current status of therapy and promising future perspectives on novel drug regimens.
Intracellular Location of KATP Channels and Sulphonylurea Receptors in the Pancreatic β-cell: New Targets for Oral Antidiabetic Agents
Authors: Quesada I. , Soria B.
Published: July 2012

Diabetes Mellitus is by far one of the most propagated chronic diseases, affecting 150 million people worldwide. This affliction is caused by a malfunction of pancreatic endocrine cells, which provokes a failure in the insulin release and glucose homeostasis. Plasma membrane KATP channels have a key role in the stimulus-secretion coupling of pancreatic β-cells. Consequently, many investigations have developed efficient drugs for the treatment of diabetes, such as sulphonylureas, which specifically close KATP channels leading to an enhanced insulin secretion. Recent studies show that, in addition to its well-known plasma membrane location, sulphonylurea receptors and sulphonylurea-sensitive KATP channels are also present in various intracellular sites including secretory granules, mitochondria, endoplasmic reticulum and more recently, the nucleus. What roles do they play in these organelles? Intracellular KATP channels and sulphonylurea receptors, which operate in conjunction with classical pathways, can provide specific signaling circuits to establish direct links between extracellular signals and different cell functions, such as secretion or gene expression. The study of these intracellular channels provides novel perspectives in the signal transduction of the pancreatic β-cell, and may offer clues for the development of new strategies in diabetes therapy. In this review we will address this topic with special emphasis on the biophysical basis and functional implications in the pancreatic β-cell.
Supporting heterogeneous agent mobility with ALAS
Authors: Mitrovic Dejan , Ivanovic Mirjana , Budimac Zoran , Vidakovic Milan
Published: July 2012

Networks of multi-agent systems are considered to be heterogeneous if they
include systems with different sets of APIs, running on different virtual
machines. Developing an agent that can operate in this kind of a setting is a
difficult task, because the process requires regeneration of the agent?s
executable code, as well as modifications in the way it communicates with the
environment. With the main goal of providing an effective solution to the
heterogeneous agent mobility problem, a novel agent-oriented programming
language, named ALAS, is proposed. The new language also provides a set of
programming constructs that effectively hide the complexity of the overall
agent development process. The design of the ALAS platform and an experiment
presented in this paper will show that an agent written in ALAS is able to
work in truly heterogeneous networks of multi-agent systems.
Hybrid dynamic stabilization: a biomechanical assessment of adjacent and supraadjacent levels of the lumbar spine
Authors: Mageswaran Prasath , Techy Fernando , Colbrunn Robb W. , Bonner Tara F. , McLain Robert F.
Published: July 2012

Object

The object of this study was to evaluate the effect of hybrid dynamic stabilization on adjacent levels of the lumbar spine.

Methods

Seven human spine specimens from T-12 to the sacrum were used. The following conditions were implemented: 1) intact spine; 2) fusion of L4–5 with bilateral pedicle screws and titanium rods; and 3) supplementation of the L4–5 fusion with pedicle screw dynamic stabilization constructs at L3–4, with the purpose of protecting the L3–4 level from excessive range of motion (ROM) and to create a smoother motion transition to the rest of the lumbar spine. An industrial robot was used to apply continuous pure moment (± 2 Nm) in flexion-extension with and without a follower load, lateral bending, and axial rotation. Intersegmental rotations of the fused, dynamically stabilized, and adjacent levels were measured and compared.

Results

In flexion-extension only, the rigid instrumentation at L4–5 caused a 78% decrease in the segment's ROM when compared with the intact specimen. To compensate, it caused an increase in motion at adjacent levels L1–2 (45.6%) and L2–3 (23.2%) only. The placement of the dynamic construct at L3–4 decreased the operated level's ROM by 80.4% (similar stability as the fusion at L4–5), when compared with the intact specimen, and caused a significant increase in motion at all tested adjacent levels. In flexion-extension with a follower load, instrumentation at L4–5 affected only a subadjacent level, L5–sacrum (52.0%), while causing a reduction in motion at the operated level (L4–5, −76.4%). The dynamic construct caused a significant increase in motion at the adjacent levels T12–L1 (44.9%), L1–2 (57.3%), and L5–sacrum (83.9%), while motion at the operated level (L3–4) was reduced by 76.7%. In lateral bending, instrumentation at L4–5 increased motion at only T12–L1 (22.8%). The dynamic construct at L3–4 caused an increase in motion at T12–L1 (69.9%), L1–2 (59.4%), L2–3 (44.7%), and L5–sacrum (43.7%). In axial rotation, only the placement of the dynamic construct at L3–4 caused a significant increase in motion of the adjacent levels L2–3 (25.1%) and L5–sacrum (31.4%).

Conclusions

The dynamic stabilization system displayed stability characteristics similar to a solid, all-metal construct. Its addition of the supraadjacent level (L3–4) to the fusion (L4–5) did protect the adjacent level from excessive motion. However, it essentially transformed a 1-level lumbar fusion into a 2-level lumbar fusion, with exponential transfer of motion to the fewer remaining discs.
Parakeratotic-like cells in effusions — A clue to diagnosis of malignant mesothelioma
Authors: Gao Ling , Reeves Ward , DeMay Richard M.
Published: July 2012

Background:

Malignant mesothelioma (MM) is an aggressive neoplasm with a poor prognosis. Its incidence has been increasing worldwide. Cytological examination of an effusion is often the first opportunity to diagnose MM. However, the cytological diagnosis of MM can be difficult. We have noticed that parakeratotic-like cells, with orange cytoplasm and pyknotic nuclei, are present in many cases of mesothelioma on Papanicolaou-stained cytology slides. Although this cytological finding has been described previously, to our knowledge, there has been no systematic study of this finding. Our study is to determine whether the presence of small parakeratotic / orangeophilic cells (PK-like cells) is specific for the cytodiagnosis of mesothelioma.

Materials and Methods:

A total of 90 body fluid cases were selected from our archived specimens in the Cytology Section at the University of Chicago Hospital accessioned between January 2000 to November 2011. They included 30 cases of mesothelioma, 30 cases of adenocarcinoma, and 30 cases of reactive mesothelial cells.

Results:

PK-like cells were present in 83% of the mesothelioma cases, 13% of the adenocarcinoma cases, and 7% of the reactive cases. Our data showed that the presence of PK-like cells has a specificity of 90%, sensitivity of 83%, positive predictive value of 81%, and negative predictive value of 84% for the diagnosis of malignant mesothelioma in body cavity fluids.

Conclusion:

The presence of PK-like cells in the effusion specimen, especially in pleural effusions, is a highly specific and moderately sensitive cytological feature for diagnosis of mesothelioma.
De novo microdeletion of 5q14.3 excluding MEF2C in a patient with infantile spasms, microcephaly, and agenesis of the corpus callosum
Authors: Shimojima Keiko , Okumura Akihisa , Mori Harushi , Abe Shinpei , Ikeno Mitsuru , Shimizu Toshiaki , Yamamoto Toshiyuki
Published: July 2012

The 5q14.3 microdeletion syndrome has recently been recognized as a clinical entity manifesting as severe intellectual disability, epilepsy, and brain malformations. Analysis of the shortest region of overlap among patients with this syndrome and subsequent identification of nucleotide alterations in the coding region of myocyte enhancer factor 2C gene (MEF2C) have suggested MEF2C as the gene responsible for the 5q14.3 microdeletion syndrome. We identified a de novo 3.4‐Mb deletion of 5q14.3 in a patient with infantile spasms, microcephaly, and brain malformation. The deleted region in the present patient was positional toward the centromere, and MEF2C was not included in the deleted region. However the neurological and dysmorphic features of the present patient resembled those of patients with the 5q14.3 microdeletion syndrome. We consider that a positional effect is the likely explanation for this evidence. To study the precise mechanism of this positional effect, further information is required on patients showing atypical deletions neighboring MEF2C. © 2012 Wiley Periodicals, Inc.
Partial duplication of 13q31.3–q34 and deletion of 13q34 associated with diaphragmatic hernia as a sole malformation in a fetus
Authors: Jønch Aia E. , Larsen Lise G. , Pouplier Susanne , Nielsen Kate , Brøndum‐Nielsen Karen , Tümer Zeynep
Published: July 2012

Partial duplications and deletions of chromosome 13 are rare and the phenotypic expressions of both aneuploidies are highly variable. Here we report on a fetus diagnosed prenatally with partial trisomy of 13q and a diaphragmatic hernia as a sole malformation. The parents had decided to terminate the pregnancy after the finding of diaphragmatic hernia by ultrasound scan, which was also confirmed by autopsy of the fetus. Subsequently chromosome analysis, fluorescence in situ hybridization (FISH), and array comparative genomic hybridization (array CGH) was carried out on fetal tissue. The chromosome analysis revealed additional material on chromosome 13, which was shown to be from the same chromosome, by FISH analysis. Array CGH demonstrated a partial duplication and a small deletion at the distal long arm of chromosome 13. The parents had normal karyotypes. This is the first case of a de novo pure partial duplication of 13q31.3–q34 and distal deletion of 13q34 with a phenotype apparently only involving a diaphragmatic hernia and three lung lobes on both sides. Microarray analysis was useful in refining the chromosomal imbalance and suggesting a candidate region for diaphragmatic hernia. © 2012 Wiley Periodicals, Inc.
A general template for synthesis of hollow microsphere with well‐defined structure
Authors: Gao Ke‐Jing , Yi Jianjun , Mao Jing , Li Guangtao , Xu Bo‐Qing
Published: July 2012

Using chitooligosaccharides (COS) as the backbones and polycaprolactones (PCL) as the branches, a novel type of amphiphilic graft copolymers with a large amount of free OH and NH2 groups remained on the COS backbones was synthesized. The obtained Chitooligosaccharide‐graft‐poly(ε‐caprolactone)(COS‐g‐PCL) was self‐assembled into giant vesicles which served as templates for the preparation of hollow spheres of a series of metals(Au, Ag, Cu, Pt, and Pd). The method involved the initial mixing of COS‐g‐PCL and metal‐containing groups or metal ions to generate corresponding complex, followed by adding the selective solvent of water to induce the self‐assembly of the graft copolymers into giant vesicles; Metal ions were reduced and crosslinked by a subsequent calcination procedure to form metal hollow spheres. In addition, hybrid hollow spheres with fluorescent quantum dots and silica hollow spheres were also prepared by slightly modified procedures. A preliminary study on the trinitrotoluene sensor of CdS/vesicle hybrid hollow spheres revealed a considerable sensitivity, which exemplifies the distinct properties imparted by the hybrid hollow structure. All of the results demonstrate that the giant vesicles self‐assembled from COS‐g‐PCL could be utilized as effective templates for the synthesis of various hollow spheres. Using Chitooligosaccharide‐graft‐poly(ε‐caprolactone) vesicles as general templates, the hollow spheres of a series of metals such as Au, Ag, Cu, and Pt were produced. The method involved the initial absorption of metal ions from solution into the functional surface layer of the graft copolymer giant vesicles. Metal ions were reduced and crosslinked by a subsequent calcination procedure to form metal hollow spheres. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Statistical Mechanics of Non‐Spherical Molecules: Spherical Harmonic Expansions on Non‐Spherical Surfaces
Authors: Kabadi Vinayak N. , Steele William A.
Published: July 2012

Simple pseudo‐spherical harmonic expansions over non‐spherical surfaces are proposed for two body functions such as pair potentials and pair correlation functions of anisotropic fluids. It is shown that the thermodynamics of fluids with Gaussian overlap potential with constant well depth (GOCE fluids) can be calculated from only the leading terms in the expansions over equipotential surfaces. Resummation of the individual terms in the expansions of pair correlation functions over equipotential surfaces give molecular correlations for specific orientations which agreed very well with the same functions calculated directly during the simulations. These functions are used to bring out some significant differences in the structures of GOCE fluids and equivalent site‐site fluids. Support for this work by a grant from the Chemistry Division of the National Science Foundation is gratefully acknowledged.
Depolarized Rayleigh Scattering from CO2: An Experimental and Molecular Dynamics Investigation
Authors: Murthy C. S. , Vallauri R. , Versmold H. , Zimmermann U. , Singer K.
Published: July 2012

A direct comparison of experimental depolarized Rayleigh spectra of CO2 with those obtained by molecular dynamics (MD) simulations at two different statepoints are reported. For the MD simulations a three Lennard‐Jones centres and central point quadrupole moment (3LJC + Q) interaction model has been used. Total depolarized spectra as well as their constituents (a) orientational, (b) collision induced, and (c) cross spectra were calculated for two polarizability models: In the first centre‐centre (C‐C) model the molecular polarizability is placed in the centre of the molecules whereas in the second site‐site (S‐S) model two partial polarizabilities are placed on the O atom sites. At the lower density the spectra resulting from both polarizability models compare well with the experimental spectrum. At the high density both model spectra noticeably deviate from the experimental one: the C‐C model spectrum giving the better description. This result is in contradiction to a previous investigation based on a two Lennard‐Jones centres potential. Thus any assessment of the relative merits of the two polarizability models seem to be premature at this stage since the role played by the interaction potential is not fully understood.
Sorption of Strontium by Graphitic Materials
Authors: Hilpert K. , Gerads H. , Kobertz D.
Published: July 2012

The sorption of Sr by graphitic materials used in high‐temperature gas‐cooled reactors was studied by applying high‐temperature mass spectro‐metry with a Knudsen cell and the isopiestic method. Sorption isotherms were determined for matrix graphite with Sr concentrations between 3.88 · 10−5 and 8.85 · 10−2 mol kg−1. The sorption enthalpies and partial pressures determined for concentrations greater than 1.5 · 10−4 mol kg−1 showed many properties of Freundlich isotherms. The evaluated vaporization enthalpies of Sr(e.g. ΔvH01660 = 447. 8 ± 7.7 kj mol−1 for a Sr concentration of 3.42 · 10−4 mol kg−1) indicate a strong chemisorption of Sr by graphite. An exceptionally high sorption capacity for Sr has been observed for nongraphitized coked resin binder.
Interlamellar Liquid Sorption on Hydrophobic Silicates
Authors: Dékány I. , Szántó F. , Weiss Armin , Lagaly G.
Published: July 2012

A particular advantage of adsorption measurements on layer silicates is that the adsorption between the silicate layers can be followed by X‐ray measurements. — When the external and internal surface of the silicate montmorillonite is modified by increasing amounts of hexadecylpyridinium cations, the surface character changes from hydrophilicity to hydrophobicity. The changes are evaluated from the excess adsorption isotherms for methanol‐benzene mixtures. The volume Vs of the adsorption phase derived from the isotherms is compared with the free interlayer volume Vf from X‐ray measurements. — On sodium montmorillonite methanol is preferentially adsorbed and the volume increase observed by X‐ray measurements coincides with Vs. If the sodium cations are progressively displaced by hexadecylpyridinium ions the azeotropic point of the type IV isotherms is shifted to lower mole fractions of methanol. The methanol molecules are increasingly displaced from the adsorption phase by benzene molecules. Vf becomes strikingly larger than Vs. — It is concluded that the adsorption layer is not homogeneous in the interlayer space: the methanol molecules are adsorbed on the silicate layers and the benzene molecules are in the vicinity of the hexadecylpyridinium ions. In addition to this adsorption layer the remaining volume is filled with methanol‐benzene mixtures having a composition different from the adsorbed phase and more similar to the bulk phase.
Photoelectrochemistry of CdSe in Sulfite Electrolyte
Authors: Tenne R. , Hodes G.
Published: July 2012

Cyclic voltammetry is used to discriminate between two light induced reactions occurring on the surface of CdSe electrodes: Oxidation of the sulfite solution and self oxidation of the crystal itself. The latter reaction (photoetching) can be used to improve the performance of any photoelectrochemical cell based on CdSe as is shown here. The charge transfer of holes to the SO2‐3 electrolyte appears to be the rate determining step with photogenerated Se dissolution in the electrolyte playing an appreciable, but lesser, role. SO2‐3 ions are shown to adsorb weakly onto the surface of CdSe — a conclusion that supports a previous study. Thus, sulfite solutions are less favorable for use in a photoelectrochemical cells with CdSe but they can be used to carry out controlled photoetching of the CdSe electrode which leads to a reduction of the density of defects on the surface of that electrode and increases its surface area considerably.
The Effect of Ionic Strength and Pressure on the Hydrolysis Equilibrium of Aquated Iron(III) Ions
Authors: Martinez P. , van Eldik R. , Kelm H.
Published: July 2012

The ionic strength dependence of the hydrolysis constant of Fe(H2O)3+6 was studied at 25°C over the range 0 to 2.0 M as a function of pressure up to 120 MPa in perchlorate medium. The data are well described by the equation

where A and B are constants taken from the literature and K0 and α (quoted in brackets) have the values 6.46 · 10−3 (0.90), 5.85 · 10−3 (0.95), 5.52 · 10−3 (0.97) and 5.08 · 10−3 M (1.00 nm) at ambient, 40, 80 and 120 MPa pressure, respectively. The reaction volume, ΔṼ, for the hydrolysis process exhibits a significant increase with decreasing ionic strength, and has a limiting value of +4.8 ± 0.3 cm3 mol−1 at infinite dilution.
Cobaltous Oxide in an Oxygen Potential Gradient: Morphological Stability of the Phase Boundaries
Authors: Martin M. , Schmalzried H.
Published: July 2012

If the binary transition metal oxide Co1‐δO is exposed to an oxygen potential gradient, a steady state flux of cation vacancies from the high to the low potential and a corresponding flux of cobalt cations in the opposite direction are induced. Thereby, the crystal as a whole moves to the side of the higher oxygen activity. By solving the diffusion equation for the vacancy transport, the following results are obtained: At the reducing side, the Co1‐δO‐surface is morphologically unstable. At the oxidizing side, the surface is morphologically stable. In addition, the influence of surface tension, surface diffusion, phase boundary reaction and concentration dependence of the chemical diffusion coefficient on the movement of the crystal and the morphological stability of the gas/solid interfaces is analysed. The theoretical results are verified experimentally by exposing Co1‐δ O‐discs to oxygen potential gradients in various gas mixtures.
High Temperature Reaction Rate for H + O2 = OH + O and OH + H2 = H2O + H
Authors: Frank P. , Just Th.
Published: July 2012

Shock heating together with atomic resonance absorption spectrometry (ARAS) was used to record simultaneously H‐ and O‐atom concentration profiles in the post‐shock region behind reflected shocks. The dissociation of N2O together with the reaction O + H2 = OH + H was used as a source of H and OH for the reactions H + O2 = OH + O and OH + H2 = H2O + H. The test gas mixtures consisted of argon with relative concentrations of a few ppm N2O and 100 to 500 ppm H2 and O2. The experiments were conducted in the temperature range of 1700 to 2500 K at total densities of 6 · 10−6 to 1.3 · 10−5 mol cm−3. The following rate coefficients were deduced:

For temperatures below 2500 K nearly complete agreement with the value for the rate coefficient of reaction R1 as recommended by Baulch [1] was obtained. For reaction R2 a rate coefficient was deduced which is close to the value as given by Gardiner et al. [23].
Diffusion Controlled Atom Recombination and Photolytic Cage Effect of Halogens in Compressed Gases and Liquids
Authors: Hippler H. , Otto B. , Schroeder J. , Schubert V. , Troe J.
Published: July 2012

Photolysis quantum yields and atom recombination rate constants were measured for iodine and bromine at pressures of up to 7 kbar in both the dense gas and liquid phase employing a variety of solvents. The results are analyzed in terms of a simple model which uses empirical parameters to describe cage break‐out, competition between diffusive separation of atom pairs and cage energy relaxation, and stabilization in halogen molecule‐solvent clusters. This enables us to single out the dominant processes governing escape versus recombination efficiencies in the different density regimes.
Kinetics of OH(v = 0 and 1) and OD(v = 0 and 1) Studied by Time‐Resolved Laser‐Induced Fluorescence
Authors: Smith Ian W. M. , Williams Martin D.
Published: July 2012

Coupled with pulsed photochemical generation of OH (and OD), laser‐induced fluorescence has been used to study the kinetics of OH(v = 0 and 1) and OD(v = 0 and 1) with HCI, DCI and CO.
Study of OH Reactions at High Pressures by Excimer Laser Photolysis — Dye Laser Fluorescence
Authors: Schmidt V. , Zhu G. Y. , Becker K. H. , Fink E. H.
Published: July 2012

Reactions of hydroxyl radicals have been studied up to total pressures of 1 atm and in the presence of strongly quenching gases by using excimer laser photolysis of H2O2 or HNO3 for the generation and pulsed dye laser fluorescence for monitoring the concentration of the radicals as a function of reaction time. Results are reported of a study of the effects of molecular oxygen on the reactions of OH with acetylene and with some sulfur containing compounds (e.g. CS2).
The Reaction of OH with C2H2 at Atmospheric Conditions Investigated by CW‐UV‐Laser‐Longpath‐Absorption of OH
Authors: Wahner Andreas , Zetzsch Cornelius
Published: July 2012

A sensitive CW‐UV‐laser absorption method at 308 nm has been used to investigate the pressure dependence of the kinetics of OH reactions with C2H2. OH radicals are generated by excimer laser photolysis of H2O at 193 nm or of H2O2 at 248 nm. Using an absorption light path of 151 m and accumulating 50 decay curves, OH concentrations in the range from 1010 down to 107 cm−3 can be detected in the presence of N2 at 10–1000 mbar. The experimental data on the pressure dependence of the rate constant for the reaction of OH with C2H2 in N2 yield the limiting values (at room temperature):

.
The Study of Reactions of HO2 Radicals by Mid‐Infrared Laser Spectroscopy
Authors: Salmon T. M. F. , Thrush B. A. , Tyndall G. S.
Published: July 2012

In principle, infrared lasers provide specific methods for detecting all reactive species in the gas phase, except for free atoms. This paper compares the use of tunable diode lasers and mid‐infrared laser magnetic resonance in the study of reactions of HO2 using its v3 band at 1100 cm−1.
Laser Induced Fluorescence Studies on C2O and CH Radicals
Authors: Bauer W. , Becker K. H. , Meuser R.
Published: July 2012

C2O and CH radicals were quantitatively analysed by LIF in the reaction systems C3O2 + O + H and C2H2 + O + H. The measurements of rate constants and products of the reaction C2O + O as well as C2O + H have been carried out by excimer laser pulse photolysis for the production and by LIF for the detection of the radicals. The results give a basis of a new interpretation of the C2H2 + O + H atom flame system.
A Direct Study of the Reactions of CH2 (X̃ 3B1)‐Radicals with Selected Hydrocarbons in the Temperature Range 296 K ≤ T ≤ 705 K
Authors: Dóbé S. , Böhland T. , Temps F. , Wagner H. Gg.
Published: July 2012

The kinetics of the reactions of CH2 (X̃ 3B1)‐radicals with five selected organic compounds has been studied in an isothermal discharge flow system in the temperature range 296 K ≤ T ≤ 705 K. Ground state CH2‐radicals have been generated via the reaction O + CH2CO and monitored with a far infrared laser magnetic resonance spectrometer. The experimental results are described by the following Arrhenius expressions:

Two basic reaction mechanisms, either direct H‐atom abstraction by 3CH2 or thermal excitation of 3CH2 to the low lying ã 1A1 state followed by consecutive reactions of 1CH2, are of importance. For acetaldehyde, isobutane, and propane direct H‐atom abstraction by 3CH2 predominates. After separation of the small contribution attributed to the singlet reaction the following rate constants for the reactions of CH2 (X̃3B1) with acetaldehyde, isobutane, and propane are obtained:

Presuming the reactions of 1CH2 with hydrocarbons are fast the thermal excitation mechanism dominates the reaction system in the cases of methane and ethane. The activation energy of EA (CH4) = 40 ± 8 kJ/mol measured for methane is concluded to he determined by the singlet‐triplet energy splitting in CH2.
p,T,c‐Dependence of 2H Spin‐Lattice Relaxation Rates in Supercooled LiCl‐D2O Solutions
Authors: Lang E. W. , Lüdemann H.‐D.
Published: July 2012

Long‐ranged structural correlations develop within the random, transient hydrogen‐bonded network of liquid water at low temperatures and cause characteristic anomalies in the physical properties of supercooled water. Hydrostatic pressure suppresses these anomalies and turns liquid water into a normal viscous liquid. The addition of salt‐is considered another mean to suppress long‐ranged density‐density correlations, hence the pressure‐, temperature and composition dependence of deuterium (2H) spin‐lattice relaxation times (T1) is reported for supercooled LiCl‐D2O solutions over a large range of concentration (c ≤ 11 molal), pressure (p ≤ 226 MPa) and temperature (180 K ≤ T ≤ 283 K). The anomalous pressure dependence of the spin‐lattice relaxation times becomes weaker with increasing salt concentration
Dispersed Systems ‐ Recent Developments
Authors: Ottewill R. H.
Published: July 2012

Direct methods for determining the electrostatic force of interaction between molecularly smooth mica plates are compared with a less direct method (osmotic pressure) of determining the forces between particles (flat plates) in a colloidal dispersion. It is shown that macroscopic surfaces and particles exhibit similar behaviour the common link being the range of the interaction forces; the range is very large in low salt concentrations compared with atomic size. For concentrated dispersions of spherical particles small angle neutron scattering can be used to determine the nature of the interaction forces. In addition this enables the structure of the system to be determined in terms of the pair distribution function g(r). From the latter and the interaction pair potential it becomes possible to predict the bulk properties of the system.
Morphology of Complex Boundaries
Authors: Richter Peter H. , Peitgen Heinz‐Otto
Published: July 2012

The dynamics of physical or mathematical systems may follow simple rules and yet unfold in enormous complexity. Thanks to computer graphical experimentation we are beginning to detect universal scenarios some of which are reviewed here. The emphasis is on the formation of boundaries between different modes of behavior, or between basins of attraction in systems with competitive dynamics.
Visualization of Organized Structures in Buoyant Diffusion Flames
Authors: Schönbucher A. , Brötz W. , Balluff Ch. , Riedel G. , Kettler A. , Schieß N.
Published: July 2012

In pool fires of liquid hydrocarbons static equidensitometric structures (2 types) and dynamic radiance structures (18 types) are obtained from flame photograms evaluated with an image analysis computer system. A third kind of structures, the dynamic synchronous structures (9 types) are visualized with a holographic real‐time interferometry method. ‐ The control parameters of the observed structures are the pool diameter, the height above the fuel surface, the density of the fuel vapor and the volumetric fuel flow rate. ‐ The dynamic radiance structures have 4 monoperiodic subprocesses with a frequency of 12 Hz (n‐hexane pool fire, d = 4.6 cm) which depend strongly on the pool diameter and show 18 statistical characteristics. The dynamic synchronous structures of the same pool fire show a quasiperiodic region I with 7 sub‐processes at 11, 13 and 3 Hz. In a quasiperiodic region II, 8 sub‐processes exist at the frequencies 11, 12, 13, 39 and 41 Hz. In addition there are 17 statistical characteristics. ‐ The effects of the observed dynamic structures on turbulent exchange processes in pool fires are calculated and lead to turbulent Prandtl‐, Schmidt‐ and Lewis‐numbers between 0.3 and 1.
Non‐Linearities in Chemical Reactions. Temporal and Spatial Structures; Efficiency
Authors: Ross John
Published: July 2012

Experiments and theory are reviewed on systems with multiple stable states, stabilization of unstable stationary states, oscillations, inverted Hopf bifurcations, the velocity and structure of chemical fronts and waves including the constancy of the profile in time, and structure formation in precipitation processes. Reduction of dissipation is shown possible in nonlinear systems compared to stationary state operation, by means of external periodic perturbations or oscillatory conditions, and is illustrated with thermal and biochemical engines (glycolysis).
Effects of Global Constraints on Permissible Local Behavior
Authors: Noyes Richard M.
Published: July 2012

If two composition variables X and Y are sufficient to define both the thermodynamic and dynamic states of a system with acceptable accuracy, any such state can be represented by a point in a bounded region of the positive quadrant of the X‐Y plane. Any stationary state within that region must belong to one of seven behavior classes, one of which is a double degeneracy that will probably never the encountered. The other six behavior classes are illustrated by well established models. Assignment of behavior class for a specific system can be made from the dynamic parameters for local behavior by using the signs and relative magnitudes of the trace and determinant of the secular equation. An entirely equivalent assignment can be made if two of the rate constants are replaced by the directions of the X and Y nullclines at the intersection which generates the stationary state. Although the secular equation is based solely on local behavior, the use of nullcline directions permits that local behavior to be impacted by global thermodynamic constraints. Such considerations show that the Lotka model with irreversible steps does not satisfy the thermodynamic constraints for a real chemical system, and only a very fortuitous combination of rate constants would permit the steady state to become the conservative center generated by the irreversible mechanism. The irreversible Brusselator model also fails to satisfy the thermodynamic constraints on a real chemical system, but the difficulty can be resolved by inclusion of reversibility. The irreversible Oregonator and Berlinator models satisfy the global constraints even with virtually no attention to reversibility.
The Development of a Model for the Cooperative Behavior of Palladium Crystallites During the Catalytic Oxidation of CO
Authors: Jaeger N. I. , Möller K. , Plath P. J.
Published: July 2012

The complex product oscillations in the catalytic oxidation of carbon monoxide on a zeolite supported palladium catalyst are analyzed by reconstructing the time series in 3‐dimensional phase space. A mathematical model is proposed based on a cellular automaton corresponding to a discrete version of the Sierpinsky‐gasket.
Slow Fluctuations between Attractors in a Forced Chemical Oscillator: The Belousov‐Zhabotinsky Reaction in the CSTR
Authors: Freund A. , Buchholtz F. , Schneider F. W.
Published: July 2012

Longtime measurements in a isothermal CSTR over 25–30 residence times (100 oscillations) showed that at least two oscillators (attractors) exist together with their combination bands in the Fourier spectrum of the unperturbed (constant in‐flow) Belousov‐Zhabotinsky (BZ) oscillations. Slow and large fluctuations in successive power spectra were observed. They are due to transitions between attractors and do not represent chaos. Such slow fluctuations were also observed in the quasi‐periodic region but not in the entrained state of the sinusoidally perturbed BZ reaction. From previous experiments we show entrainment of order 2 (superharmonic) and 1/2 (subharmonic) as examples. The extreme sensitivity of the Fourier spectra with respect to slight changes in the forcing period (0.2–0.3%) is noteworthy.
The Diversity of Biochemical Time Patterns
Authors: Hess Benno , Markus Mario
Published: July 2012

The effects of coupling of oscillating glycolysis and oscillating substrate supply are investigated with a two‐enzyme model using detailed two‐substrate rate laws for both enzymes. Under a sinusoidal substrate supply rate, a profusion of entrained, quasiperiodic and chaotic regimes is obtained. Periodic modulation of the sinusoidal supply rate may lead to a considerable enhancement of the degree of randomness in the chaotic regime. Up to four coexisting attractors are found in phase space for a given set of control parameters, having complicatedly interleaved basins of attraction. Switching between such coexisting attractors is accomplished by pulsed substrate fluctuations that drive the system from one basin of attraction to the other. The effect of a series of substrate fluctuations with randomly distributed amplitudes is investigated, allowing the following distinction of cases: 1. For small fluctuations, the system stays within a given basin thus preserving the initial time pattern. 2. For larger fluctuations, an evolution takes place by which the system reaches a basin that cannot be left, thus displaying a time pattern that is fittest to withstand the external stochasticity. 3. For even larger fluctuations, the system is driven back and forth between the basins, displaying an intermittent switching between time patterns. 4. For still larger fluctuations, the system is switched between the basins, staying always so far from the attractors that it can be considered as an amplifier of random fluctuations.
Dynamics of Evolutionary Optimization
Authors: Schuster Peter , Sigmund Karl
Published: July 2012

General criteria of selection are derived from the kinetic equations of polynucleotide replication. As an illustrative example we discuss replication in the continuously stirred tank reactor (CSTR). The total rate of RNA synthesis is optimized during selection. The conjecture that the rate of approach towards the stable steady state is a maximum can be easily disproved. It is possible, nevertheless, to derive a potential function for polynucleotide replication in the CSTR. Following a method first introduced by Shahshahani we define a non Euclidean metric on the space of polynucleotide concentrations. In this space with a Riemannian metric the systems follows the corresponding generalized gradient during the process of selection and, therefore, the rate of ascent is now maximum. Potential functions can be derived also for some second order autocatalytic systems which are of interest in evolution, for a multidimensional Schloegl model in the CSTR and, as originally has been shown by Shahshahani, for the Fisher‐Haldane‐Wright equation of population genetics. In the general case, however, second order autocatalysis is not compatible with the existence of a potential. The elementary hypercycle is discussed as one simple example of a reaction network whose dynamics cannot be described by means of a generalized gradient system. Finite population size introduces a stochastic element into the selection process. Under certain conditions fluctuations in particle numbers become extremely important for the dynamics of selection. Two examples of this kind are: kinetic degeneracy of rate constants and low accuracy of replication.
Dielectric Properties of Polyelectrolyte Solutions Behaviour of Aqueous Solutions of Carboxymethylcellulose with Different Univalent Counterions
Authors: Bordi F. , Cametti C.
Published: July 2012

The dielectric properties of Carboxymethylcellulose in various uni‐univalent electrolyte solutions in the frequency range from 1 KHz to 10 MHz have been measured by means of a conventional impedance bridge technique. — Two contiguous dielectric dispersions, due to different molecular mechanisms, have been observed, in accordance with the usual behaviour of linear, high‐charged polyelectrolytes. — The influence of the molecular weight, polyion concentration and different monovalent counterions (Na+, K+, Li+) has been examinated. — The results are analyzed in terms of rod‐like polyelectrolyte dielectric models taking into account the polarization due to the fluctuation in the counterion concentration.
The H2O/D2O Exchange Across Vesicular Lipid Bilayers. Lecithins and Binary Mixtures of Lecithins
Authors: Engelbert H.‐P. , Lawaczeck R.
Published: July 2012

A new method to measure the water (D2O/H2O) permeation across vesicular lipid bilayers is described. The method is based on the solvent isotope effect of the light scattering which is a consequence of the different indices of refraction of D2O and H2O. Unilamellar lipid vesicles in excess of H2O are rapidly mixed with D2O or vice versa. As result of the H2O/D2O exchange across the vesicular bilayer the light scattering signal has a time dependent, almost single exponential component allowing the deduction of the exchange relaxation rate kex and, at known size, of the permeability coefficient, Pd. The experimental results are in accord with calculations from the Mie theory of light scattering for coated spheres. The method is applicable for large vesicles where the permeation is the rate‐limiting step. Size separations are performed by a flow dialysis through a sequence of pore‐membrane‐filters. For dimyristoyl‐lecithin bilayers the water permeability‐coefficient is 1.9 · 10−5 cm/s in the crystalline phase and increases by a factor of 10–100 in the liquid‐crystalline state. The temperature dependence of the permeation exhibits a sharp change at the phase transition. For binary mixtures of lecithins this sharp change follows the solidus curve of the non‐ideal phase diagram determined by spectroscopic techniques.
UCl4 Compound: Determination of High Temperature Phase Transitions from Electrical Conductivity and Calorimetric Measurements
Authors: Fouque Y. , Bros J. P. , Gaune‐Escard M. , Wisaniowski M. , Bogacz A.
Published: July 2012

In the course of a systematic investigation of some compounds of uranium (IV), several physico‐chemical methods have been applied to the salts of the series UX4 and M2UX6 (with X = Cl, Br, I and M = Li, Na, K, Rb, Cs). ‐ The results obtained in the present work refer to UCl4; they have been obtained by electrical conductivity measurements, by differential thermal analysis and by differential enthalpic analysis.
Ternary Diffusion of Carbon Dioxide in Alkaline Solutions of Aqueous Sodium Hydroxide and Aqueous Sodium Carbonate
Authors: Leaist Derek G.
Published: July 2012

Carbon dioxide dissolved in alkaline solutions diffuses as bicarbonate and carbonate ions produced by the reactions CO2 + OH− = HCO−3 and CO2 + 2OH− = CO2‐3 + H2O. Ternary diffusion coefficients of the systems NaHCO3 + Na2CO3 + H2O and Na2CO3 + NaOH + H2O have been measured by a conductimetric technique at 298.15 K. The mixed electrolyte data are transformed by use of the solution equilibria to ternary diffusion coefficients of the systems CO2 + Na2CO3 + H2O and CO2 + NaOH + H2O. Unlike the binary diffusivity of CO2 in water (1.9 · 10−9 m2 s−1), the ternary diffusivity of CO2 in alkaline solutions is sensitive to concentration and varies from 0.9 · 10−9 to 3.5 · 10−9 m2 s−1 at 298.15 K. Expressions are derived to estimate the transport coefficients of the components from the concentrations and diffusion coefficients of the constituent ions. At high pH values hydroxide‐coupled transport leads to rapid diffusion of CO2 as CO2‐3. The results are consistent with the Onsager reciprocal relation for isothermal ternary diffusion.
Excess Molar Heat Capacity of (1,2‐Dichloroethane + Benzene) Revisited
Authors: Lainez A. , Grolier J.‐P. E. , Wilhelm Emmerich
Published: July 2012

Excess molar heat capacities CEP at constant pressure were measured, as a function of mole fraction x1 at 298.15 K, for {x1 1,2‐C2H4Cl2 + x2C6H6}. Determinations in the regions x1 < 0.1 and x1 > 0.9 were emphasized. The instrument used was a Picker flow calorimeter. The new data corroborate our results of 1977 [2]: CEP shows only one minimum at about x1,min = 0.4595, and CEP (x1,min) = ‐ 1.165 J K−1 mol−1. The “inverted” W‐shaped composition dependence of CEP, as inferred by Baños et al. [9] from their measurements of excess enthalpies between 288.15 and 318.15 K, is thus shown to be untenable.
Aggregation of an Azo Dye in Aqueous Solution
Authors: Hamada Kunihiro , Kubota Hiroyuki , Ichimura Ayako , Lijima Toshiro , Amiya Shigetoshi
Published: July 2012

The investigation of the aggregation of a simple monoazo dye carrying fluorine atoms was performed by means of 19F nuclear magnetic resonance Spectroscopy. — As the concentration of the dye increased, the signals of the fluorine showed progressive shifts to the higher field. From the changes in shift it is concluded that the fluorine atoms are oriented above an adjacent aromatic nucleus. The results of the visible absorption Spectroscopy indicate that the dye solutions are a polydispersed system. The equilibrium constant of the aggregation was estimated dn the basis of an isodesmic model. A molecular model of the aggregates was proposed.
Picosecond‐Absorption Study of the Photoisomerization of Trans‐Stilbene in Compressed Gases and Liquids
Authors: Maneke G. , Schroeder J. , Troe J. , Voß F.
Published: July 2012

The photoisomerization of trans‐stilbene after picosecond excitation at 308 nm has been studied by picosecond absorption at 500 or 616 nm in ethane and propane. Experiments were performed in gaseous ethane (30–54 bar), liquid ethane (42–6000 bar), and liquid propane (9–4050 bar). The pressure dependence of the reaction is modelled from isolated molecule conditions in low pressure gases up to diffusion control in high pressure liquids. In dense media marked solvent shifts of the reaction threshold energy are postulated which can be described by simple cluster — and cage — solvent shift models. UV spectra show similar solvent shifts as isomerization rates.
Collective Translational Motions in Binary Mixtures of Hexafluorobenzene with Benzene and Cyclohexane as Studied by Self and Mutal Diffusion Measurements
Authors: Weingärtner Hermann , Braun Bernd M.
Published: July 2012

Mutual and self‐diffusion coefficients have been measured for binary mixtures of hexafluorobenzene with benzene and cyclohexane at 25°C. The results have been used to calculate velocity correlation coefficients which characterize collective translational motions among the various interaction partners. For comparison, velocity correlation coefficients have also been calculated from literature data on benzene‐cyclohexane mixtures. The resulting coefficients are compared with predictions for ideal reference systems. While the C6H6C6H12 system exhibits fairly ideal behaviour, correlated motions between like molecules in C6F6C6H12 mixtures in excess to those expected for an ideal system indicate self association of the components. Correlated motions between unlike molecules in C6F6C6H6 mixtures indicate preferred mutual association of C6F6C6H6. The results are in agreement with the conclusions drawn from the behaviour of the thermodynamic excess functions.