Neutron scattering characterization of homopolymers and graft-copolymer micelles in supercritical carbon dioxide

1996

Abstract Superficial fluids (SCF) are becoming an attractive alternative to the liquid solvents traditionally used as polymerization media [1]. As the synthesis proceeds, a wide range of colloidal aggregates form, but there has hitherto been no way to measure such structures directly. We have applied small-angle neutron scattering (SANS) to characterize such systems, and although SCF polymerizations are carried out at high pressures, the penetrating power of the neutron beam means that typical cell windows are virtually transparent. Systems studied include polymers soluble in CO 2 such as poly(1,1-dihydroperfluorooctyl acrylate) (PFOA), poly(hexafluoropropylene oxide) (PHFPO) and poly(dimet…

Cationic Iron Aminocarbene Complexes as Dienophiles in Diels‐Alder Reaction with Cyclopentadiene

1996

The cationic iron (alkynyl)aminocarbene complexes [Cp(CO)2Fe(C(NHR)CCSiMe3][PF6], (R C6H5, p-CH3C6H4) 1 derived from aromatic amines smoothly react with cyclopentadiene in dichloromethane to yield the cycloadducts 2. No reaction was observed for complexes derived from sterically demanding aliphatic amines, like L-alanine tert-butyl ester. For comparison, the alkynyl-substituted acyl iron compounds Cp(CO)2Fe(CO)CC (R SiMe3, C6H5) 3 were investigated, requiring TiCl4 catalysis to undergo the cycloaddition reaction. The structures of the cycloadducts 4 were determined by X-ray crystallography.

Influence of the quadratic term in the alongwind stochastic response of SDOF structures

1996

A parametric study, regarding the influence of the quadratic pressure term, which is often neglected in the literature, on the stochastic alongwind response of a single-degree-of-freedom (SDOF) structure subjected to wind action, is presented. The results are reported in terms of percentages of difference in the evaluation of the response, by considering and neglecting the quadratic pressure term. The changing parameters considered are: the terrain drag coefficient, the structure height, the structure natural radian frequency, the structure damping coefficient and the wind reference mean velocity. The response stochastic analysis has been carried out in the time domain, by means of the mome…

INDUCTIVE INFERENCE OF LIMITING PROGRAMS WITH BOUNDED NUMBER OF MIND CHANGES

1996

We consider inductive inference of total recursive functions in the case, when produced hypotheses are allowed some finite number of times to change “their mind” about each value of identifiable function. Such type of identification, which we call inductive inference of limiting programs with bounded number of mind changes, by its power lies somewhere between the traditional criteria of inductive inference and recently introduced inference of limiting programs. We consider such model of inductive inference for EX and BC types of identification, and we study • tradeoffs between the number of allowed mind changes and the number of anomalies, and • relations between classes of functions ident…

Decremental 2- and 3-connectivity on planar graphs

1996

We study the problem of maintaining the 2-edge-, 2-vertex-, and 3-edge-connected components of a dynamic planar graph subject to edge deletions. The 2-edge-connected components can be maintained in a total ofO(n logn) time under any sequence of at mostO(n) deletions. This givesO(logn) amortized time per deletion. The 2-vertex- and 3-edge-connected components can be maintained in a total ofO(n log2n) time. This givesO(log2n) amortized time per deletion. The space required by all our data structures isO(n). All our time bounds improve previous bounds.

Metal speciation in biological fluids — a review

1996

The literature on the speciation of metal ions in biological fluids is comprehensively reviewed. Critical examination on this subject reveals that major work has been done in blood and urine. Speciation in materials like milk has not yet been widely studied. On the other hand, only few references could be found on sweat, saliva, cell lysate, cerebrospinal, seminal, tear and bronchoalveolar fluids. The topics studied for these fluids were mainly the speciation of arsenic, mercury, aluminium and selenium. Work on the speciation of other elements like zinc, chromium, cadmium, lead, copper, iron etc. have also been carried out in such matrices. The present literature survey includes also a crit…

A Monte Carlo Study of Living Polymers in 2D: Effect of Small Chains on Static Properties

1996

A slithering snake algorithm is combined with a binding and breaking chain algorithm to simulate the static behavior of living polymers according to Cates' description. It is shown that this simple two-dimensional simulation on a square lattice gives good agreement with the mean field theory. However, the large amount of small contour length chains for small values of the mean average length 〈L 〉 appears to be one of the reasons for the discrepancies observed between the simulated results and the mean field theory. This finding could explain disagreements between experimental observation and theory. Also, the results are not in favor of a swelling of the greater chains by the smaller one.

Prospects for the microbial production of food flavours

1996

The microbial production of natural flavours has been extensively studied during the past decade, and some processes are currently being exploited commercially. However, in the case of flavour compounds such as lactones and some aromatic compounds, the lack of basic information on their metabolism, as well as their high toxicity, are two main barriers to industrial production. The development of novel and cheap production processes, such as solid-state fermentation, may help overcome some of the current limitations of microbial flavour production, as well as widening the spectrum of biotechnologically accessible compounds.

Sealing ability of five different retrograde filling materials.

1996

The sealing ability of Amalgam, Harvard-Cement, Diaket, gold-leaf, and Ketac-Endo as retrofilling materials was investigated. Paper cones were fixed with Harvard-Cement in the instrumented roots of 100 extracted human incisors. Apicectomy was performed and a 2-mm-deep retrograde cavity was prepared. Teeth were assigned to five groups (n = 20); each group received a different filling material. Surfaces of the roots were isolated with nail polish. Teeth, were stored in 1% methylene blue dye for 72 h. Roots were sectioned, and the depth of dye penetration was evaluated through a stereomicroscope. Retrofills with Ketac-Endo showed significantly less leakage compared with amalgam. There was no s…

Self-organization of amphiphilic N-acylated linear polyethyleneimines: investigation of a reversible monolayer collapse

1996

Abstract Poly-N-4-decyloxybenzoylethyleneimine, highly crystalline in bulk, forms a stable monolayer at the air-water interface which undergoes a reversible collapse into a probable bilayer structure at higher surface pressures. We achieved transfer both from the monolayer and “bilayer” region of the polymer film at the water surface onto hydrophilic and hydrophobized quartz supports. Based on X-ray investigations on the deposited Langmuir-Blodgett films, a possible mechanism for the reversible collapse is proposed.

Diversity of denitrifying community in three soils and ability to reduce nitrous oxide

1996

International audience

On the nature of phase separation in a commercial aluminium-lithium alloy

1996

Abstract The formation of lithium-rich precipitate particles, known as δ′ phase, is responsible for the particularly desirable mechanical properties which make aluminium-lithium alloys interesting for different industrial applications. The structure and the kinetics of the phase separation process are conveniently studied by small-angle X-ray scattering, though uncertainties remain on the actual shape of the phase diagram of the system, particularly in the region of interest. In this paper are reported small-angle X-ray scattering measurements on a commercial AlLi (8.49% Li atoms) both in the region of formation of the precipitate and during its successive growth. Modelling of the experime…

Effects of SCA40 on human isolated bronchus and human polymorphonuclear leukocytes: comparison with rolipram, SKF94120 and levcromakalim

1996

1. SCA40 (0.1 nM-0.1 mM) produced concentration-dependent suppression of the spontaneous tone of human isolated bronchus (-log EC50 = 6.85 +/- 0.09; n = 10) and reached a maximal relaxation similar to that of theophylline (3 mM). The potency (-log EC50 values) of SCA40 compared to other relaxants was rolipram (7.44 +/- 0.12; n = 9) > SCA40 > or = levcromakalim (6.49 +/- 0.04; n = 6) > SKF94120 (5.87 +/- 0.10; n = 9). 2. When tested against the activity of the isoenzymes of cyclic nucleotide phosphodiesterase (PDE) isolated from human bronchus, SCA40 proved highly potent against PDE III (-log IC50 = 6.47 +/- 0.16; n = 4). It was markedly less potent against PDE IV (4.82 +/- 0.18; n = 4) and …

Intracytoplasmic sperm injection: a treatment for extreme oligospermia.

1996

AbstractPurpose: We evaluated the efficacy of intracytoplasmic sperm injection in patients with extreme oligospermia.Materials and Methods: A total of 67 intracytoplasmic sperm injection cycles was attempted in 58 infertile couples in which the husbands had extreme oligospermia (less than 100,000 spermatozoa per ml. ejaculate).Results: Fertilization was achieved in 65 of 67 cycles. Mean fertilization rate per cycle was 66.4 percent. A total of 18 clinical pregnancies was obtained, for a pregnancy rate of 26.8 percent per started cycle. There were 4 miscarriages and 8 live births from 5 deliveries. Nine pregnancies are ongoing.Conclusions: Intracytoplasmic sperm injection in patients with ex…

Intrusion age of Pan-African augen gneisses in the southern Menderes Massif and the age of cooling after Alpine ductile extensional deformation

1996

AbstractPb–Pb single zircon ages of 546.2 ± 1.2 Ma demonstrate that the augen gneisses in the southern Menderes Massif were generated from Pan-African intrusions. During the Alpine orogenic evolution of the Menderes Massif these granites were metamorphosed and transformed into augen gneiss in an extensional top-to-the-south shear zone, located between augen gneisses and overlying schists. Quartz fabrics suggest a pronounced static recrystallization that post-dates the ductile deformation in the shear zone. Ar–Ar muscovite ages of 43–37 Ma from augen gneisses and schists suggest that ductile deformation and subsequent cooling occurred in the Eocene. These results contradict previous models t…

Small angle scattering study of the structure of isotactic polypropylene-hydrogenated oligo(cyclopentadiene) blends

1996

Abstract Blends of isotactic polypropylene ( i PP) and hydrogenated oligo cyclopentadiene (HOCP) have been studied by means of small angle X-ray scattering in the temperature range 70–160°C. The structure of blends containing less than 25% HOCP is very similar to the one of plain i PP, i.e. lamellae whose thickness increases by increasing the temperature. Blends containing more than 25% HOCP are characterized by two kinds of lamellae formed by layers of i PP and amorphous material rich in i PP and in HOCP, respectively. The crystallizable i PP present in both phases crystallizes from the melt, in analogy to what happens in HDPE/HOCP blends and in agreement with the values of the crystallini…

Towards higher accuracy with the ISOLTRAP mass spectrometer

1996

To now the masses of more than hundred unstable isotopes have been determined with the ISOLTRAP mass spectrometer installed at ISOLDE/CERN. Typically a resolving power of mΔm ≈ 1 × 106 was used and the mass determinations were assigned an accuracy of δmm ≈ 1 × 10−7. We show that with improvements to ISOLTRAP and refinements of the experimental technique an accuracy of δmm ≈ 3 × 10−8 can be obtained.

IS ALR SUGGESTING A LEFT–RIGHT SYMMETRIC SOLUTION?

1996

The implications of the recent measurement of the left–right asymmetry ALR by the SLD collaboration for the left–right symmetric theory are examined. We show that it is possible to arrange for a large, negative value of S, without serious side effects for other observables within this model. We also consider a restricted model with specified Higgs structure, where limits on MZ2 can be obtained.

The sunset diagram in SU(3) chiral perturbation theory

1996

A general procedure for the calculation of a class of two-loop Feynman diagrams is described. These are two-point functions containing three massive propagators, raised to integer powers, in the denominator, and arbitrary polynomials of the loop momenta in the numerator. The ultraviolet divergent parts are calculated analytically, while the remaining finite parts are obtained by a one-dimensional numerical integration, both below and above the threshold. Integrals of this type occur, for example, in chiral perturbation theory at order p^6.

Spontaneous CP violation in the left-right model and the kaon system

1996

A left-right model with spontaneous $CP$ breakdown, consistent with the particle physics phenomenology, is presented. Constraints on free parameters of the model: mass of the new right handed gauge boson $M_2$ and ratio $r$ of the two vacuum expectation values of the bidoublet, are found from the measurement of $\epsilon$ in the kaon system. For most of the parameter space, $M_2$ is restricted to be below 10 TeV. Higher masses can be achieved only by fine tuning of Kobayashi-Maskawa matrix elements, quark masses, $r$ and the phase $\alpha$ which is the unique source of $CP$-violation in the model. Large number of combinations of signs of quark masses, which are observables of the model, are…

Learning from observations of the microwave background at small angular scales

1996

In this paper, we focus our attention on the following question: How well can we recover the power spectrum of the cosmic microwave background from the maps of a given experiment?. Each experiment is described by a a pixelization scale, a beam size, a noise level and a sky coverage. We use accurate numerical simulations of the microwave sky and a cold dark matter model for structure formation in the universe. Angular scales smaller than those of previous simulations are included. The spectrum obtained from the simulated maps is appropriately compared with the theoretical one. Relative deviations between these spectra are estimated. Various contributions to these deviations are analyzed. The…

The influence of the label on, the perceived familiarity, complexity and liking of flavoured yoghurts

1996

International audience

bcl-2 expression and prognosis in squamous-cell carcinomas of the esophagus

1996

The bcl-2 proto-oncogene is a known inhibitor of apoptosis and may be an important regulator of tumor growth. In the present study, bcl-2-protein expression was investigated by immunohistochemistry and correlated with prognosis in a series of 150 potentially curatively resected squamous-cell carcinomas of the esophagus. For comparison, bcl-2-protein expression was analyzed in normal esophageal mucosa, severe squamous dysplasias and carcinomas in situ. bcl-2 immunoreactivity was found in 40 out of 150 invasive squamous-cell carcinomas; the remaining carcinomas were completely negative. bcl-2-protein expression was found more frequently among poorly differentiated than among well-differentiat…

Non-perturbative renormalization in kaon decays

1996

We discuss the application of the MPSTV non-perturbative method \cite{NPM} to the operators relevant to kaon decays. This enables us to reappraise the long-standing question of the $\Delta I=1/2$ rule, which involves power-divergent subtractions that cannot be evaluated in perturbation theory. We also study the mixing with dimension-six operators and discuss its implications to the chiral behaviour of the $B_K$ parameter.

Virtual Compton scattering off the nucleon in chiral perturbation theory

1996

We investigate the spin-independent part of the virtual Compton scattering (VCS) amplitude off the nucleon within the framework of chiral perturbation theory. We perform a consistent calculation to third order in external momenta according to Weinberg's power counting. With this calculation we can determine the second- and fourth-order structure-dependent coefficients of the general low-energy expansion of the spin-averaged VCS amplitude based on gauge invariance, crossing symmetry and the discrete symmetries. We discuss the kinematical regime to which our calculation can be applied and compare our expansion with the multipole expansion by Guichon, Liu and Thomas. We establish the connectio…

Photo fragmentation of metal clusters stored in a penning trap

1996

Photo fragmentation studies of stored mass selected metal cluster ions of a large size range are reported. The experimental method and the data evaluation are described in detail. Gold cluster ions were produced by laser vaporization and stored in a Penning trap. After size selection they were electronically excited by irradiation with a pulsed laser beam. Relaxation by evaporation of neutral atoms and dimers was observed as a function of photon energy. From these data upper and lower limits for dissociation energies are determined for Aun + (n=3 to 23).

Azido- und 2,2′-Bipyrimidin-Liganden als nützliche Werkzeuge zur Synthese zwei- und dreidimensionaler Mangan(II)-Netzwerke

1996

Components and connections of the circadian timing system in mammals

1996

The circadian timing system is a neural network consisting of the hypothalamic suprachiasmatic nucleus, aided by the retina, other hypothalamic nuclei, autonomic regions of the spinal cord, sympathetic ganglia and the pineal gland. Extensive studies conducted over the last two decades have unravelled the principal items of its functional neuroanatomy. The system is responsible for the generation of the circadian rhythm, its synchronization by environmental factors such as light, and its mediation with respect to morphological, physiological and biochemical parameters of mammals that exhibit distinct alterations throughout the 24-h cycle. This review characterizes the brain sites involved an…

J. Robert Oppenheimer. Schöpfer der ersten Atombombe. VonK. Hoffmann. Springer, Berlin, 1995. 307 S., geb. 48.00 DM. – ISBN 3–540–59330–6

1996

Degradation features of BaF2 scintillators under radiation and magnetic fields

1996

Degradation features of BaF2 scintillators have been examined in combined γ- and n-radiation and strong magnetic fields. Created radiation defects have been investigated by optical magnetooptical, and ODMR techniques. It is shown that the magnetic field has no selective action on defects of different structure. The magnetic field slightly diminishes the efficiency of creation of impurity color centers. The decrease of the creation rate at a magnetic field of B = 1 T does not exceed 10%. The nature of these radiation defects in BaF2 scintillators obtained by different technologies is discussed. Degradations-Eigenschaften von BaF2-Szintillatoren wurden in kombinierter γ- und Neutronen-Strahlu…

Dependence of the lattice parameters and the energy gap of zinc-blende-type semiconductors on isotopic masses.

1996

The dependence of the ${\mathit{E}}_{0}$ direct gap of Ge, GaAs, and ZnSe on isotopic masses at low temperatures has been investigated. Contributions of the variation of the lattice parameter to the gap shift of the binary compounds have been evaluated by using a volume-dependent lattice dynamics, while local empirical pseudopotential techniques have been employed to calculate gap shifts due to electron-phonon interaction. The dependence of these terms on the lattice-dynamical model and on the q\ensuremath{\rightarrow}0 extrapolation of the pseudopotential form factors has been investigated. The contributions of the optical and acoustical modes to the isotopic shift are analyzed. The result…

Stability of opiates in hair fibers after exposure to cosmetic treatment.

1996

Abstract The stability of opiates in clipped natural human hair was investigated. Hair fibers were incubated with defined solutions of morphine, codeine and dihydrocodeine (pH 7.4) until saturated. Original opiate-positive hair samples collected from drug addicts also were examined. Commercially available bleaching as well as perming formulas (Poly Blonde Ultra®, Poly Lock®; Henkel, Dusseldorf, Germany) were applied in vitro to the hair strands of both groups under investigation. After these treatments, the drug concentration had decreased for both bleaching and permanent waving. In the spiked hair, only 2–18% of the starting solution could be found after bleaching. About 20–30% of the drug…

Expression of the fibrinogen binding mannoprotein and the laminin receptor of Candida albicans in vitro and in infected tissues.

1996

We have previously reported a 37 kDa laminin-binding protein (p37) and a 58 kDa fibrinogen-binding mannoprotein (mp58) on the surface of Candida albicans. A few yeast cells expressed both functional receptors at the surface while germ tubes expressed a functional mp58 fibrinogen but not a functional p37 laminin receptor. These receptors were heterogeneously dispersed at the surface as shown by binding of rabbit antiserum to mp58 (PAb anti-mp58) and antiserum to the human high affinity laminin receptor. In this report we have used a dual fluorescence technique to determine if the two receptors colocalize, perhaps as part of a receptor complex. Fibrinogen was used as a probe for mp58 and poly…

Gravitational violation of R parity and its cosmological signatures

1996

The discrete R-parity ($R_P$) usually imposed on the Supersymmetric (SUSY) models is expected to be broken at least gravitationally. If the neutralino is a dark matter particle its decay channels into positrons, antiprotons and neutrinos are severely constrained from astrophysical observations. These constraints are shown to be violated even for Planck-mass-suppressed dimension-five interactions arising from gravitational effects. We perform a general analysis of gravitationally induced $R_P$ violation and identify two plausible and astrophysically consistent scenarios for achieving the required suppression.

Validation of the SOS/umu test using test results of 486 chemicals and comparison with the Ames test and carcinogenicity data

1996

The present study gives a comprehensive update of all umu genotoxicity assay results published so far. The available data of 486 chemicals investigated with the umu test are compared with the Ames test (274 compounds) as well as rodent carcinogenicity data (179 compounds). On the whole, there is good agreement between the umu test and the Ames test results, with a concordance of about 90%. The umu test was able to detect 86% of the Ames mutagens, while the Ames test (using at least 5 strains) detected 97% of the umu positive compounds. The elimination of TA102 from the set of Ames tester strains reduced the percentage of detectable umu genotoxins from 97 to 86%. The agreement between carcin…

Fragile-X carrier females: evidence for a distinct psychopathological phenotype?

1996

The present study examined 35 mothers (29 premutation carriers) of children with fragile-X syndrome in measures of intelligence and psychiatric disorders by comparing them with two control groups: a) 30 mothers of children in the general population and b) 17 mothers of non-fra-X retarded children with autism. Premutation carriers had a higher frequency of affective disorders than mothers from the general population. Preliminary data indicate that normally intelligent premutation carriers of the fra-X genetic abnormality have a similar frequency of affective disorders (DSM-III-R criteria [APA, 1987]) than mothers of autistic children. Neither carriers of the premutation nor carriers of the f…