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Abstract: The structural instability of a polymer crystal may be due to the involvement of various lattice vibrations in nonlinear resonance. The condition of this involvement is the prevalence of intramode anharmonicity over intermode interaction. A model of phase transitions in polymers of the PMMA type was constructed. Below transition points, coherent states of orientational vibrations of heavy side pendants are formed. The thermodynamic characteristics of these states were found. The structural instability of the polymer lattice is a second-order phase transition.

An integral equation for the representation of the response of a structure impinged by an incident wave field including soil–structure interaction is proposed. It requires the knowledge of the fundamental solution for the overall soil–structure domain when a unit load is applied to the structure. This fundamental solution is obtained by means of a substructuring technique and boundary integral equations using the Green tensors for homogeneous or horizontally stratified soil media. The effects of a non-stationary modulated random incident field are addressed in terms of the instantaneous power spectral density of the structural response of interest for a given coherency function of the free field. Several applications of the proposed procedure are presented. The first one considers kinematic interaction of a rigid circular foundation and is used to validate the numerical implementation. The second one considers a complex structure on a stiff stratified soil and the last one considers the pounding effect between two adjacent, identical structures resting on a thin soft soil layer. Copyright © 2002 John Wiley & Sons, Ltd.

We present a sub-structuring method for the coupling between a large elastic structure, and a stratified soil half-space exhibiting random heterogeneities over a bounded domain and impinged by incident waves. Both media are also weakly dissipative. The concept of interfaces classically used in sub-structuring methods is extended to ‘volume interfaces’ in the proposed approach. The random dimension of the stochastic fields modelling the heterogeneities in the soil is reduced by introducing a Karhunen–Loéve expansion of these stochastic fields. The coupled overall problem is solved by Monte-Carlo simulation techniques. A realistic example of a large industrial structure interacting with an uncertain stratified soil medium under earthquake is finally presented. This case study and others validate the presented methodology and its ability to handle complex mechanical systems. Copyright © 2002 John Wiley & Sons, Ltd.

Analytic expressions of the dynamic amplification factor and the characteristic response spectrum are derived for weakly damped beams with various boundary conditions subjected to point loads moving at constant speeds. These coefficients are given as functions of the ratio of the span length to the loads wavelength, and the loads wavelength respectively. They allow a rapid calculation of the vibration amplitudes induced by a succession of moving loads on a beam. These results are particularly useful in the context of railway bridges preliminary design and assessment of the expected maximum vibration levels under high-speed trains.

The rates of direct and concert passages of nuclei through a potential barrier in an external periodic field were determined within a generalized Slater model of thermal dissociation of multiatomic molecules. The external field accelerated direct and — to a much greater degree — concert passages. The curves of the efficiency of the concert mechanism of the chemical reaction as a function of the field amplitude were estimated.

We determined the compliance of the aortic “Windkessel using a non-invasive method. The occlusion of the lower extremities (5 min, 180 mm Hg) elicited reactive hyperemia. An abrupt change in pressure in the occluding cuffs from 180 to 60 mm Hg increased femoral blood flow (measured by pulsed Doppler) and decreased blood pressure (measured by Penaz continuous method). During abrupt decrease in blood pressure, the compliance was calculated as a ratio of the blood volume flowing out of the aorta via the femoral arteries to the decrease of blood pressure. The measurements were made repeatedly in eight healthy men, and in patients with essential hypertension (ten patients with essential hypertension, IInd degree – WHO without traitment and six patients with essential hypertension, IInd degree – WHO treated with slow released verapamil). Compliance in the first group was 1.18 ± 0.25 ml. mm Hg-1, in the second 0.96 ± 0.21 ml. mm Hg-1, and in the third group 0.90 ± 0.11 ml. mm Hg-1. We found a negative correlation between compliance and arterial blood pressure. However the relative large scatter requires repeated measurements.

Common carotid blood flow and middle cerebral artery velocities were determined simultaneously by using a range gated Doppler velocimeter and transcranial apparatus in ten subjects. Middle cerebral artery velocities were used as an index of cerebral resistance. Different gas mixture concentratrions were breathed in order to change cerebral haemodynamic conditions. In each condition there was a simultaneous modification of blood gases and cervicocerebral haemodynamics in common carotid blood flow and cerebral vascular resistance index. Carotid blood flow and the resistance index in middle cerebral artery changed also on opposite side. Acute hypercapnia in normoxia increases common carotid blood flow by 33% and simultaneously decreases cerebral resistance index by 11%. Normocapnic hyperoxia was associated with a fall in common carotid blood flow by 13% and with an increase in cerebral resistance index by 7%. There was a inter-subject statistically significant relation between common carotid blood flow and index of cerebral resistances (0.78

We determined middle cerebral artery, common carotid artery and temporal superficial artery Doppler derived flow velocities in ten subjects for 10 min after change in posture. Maximal changes were observed after about 3 min. The 10° head-down tilt position increased blood velocities in the common carotid artery by 13% (SD 4)% (P < 0.001), in the middle cerebral artery by,6% (SD 3)% (P < 0.001) and in the superficial temporal artery by 70% (SD 26)% (P < 0.001). In the standing position, there was an 18% (SD 9)% (P < 0.001) decrease in the common carotid blood velocities, with 14% (SD 6)% (P < 0.001) and 53% (SD 23)% (P < 0.001) reductions in the middle cerebral and superficial temporal artery velocities, respectively. At 9 min after the changes in posture, velocities in the middle cerebral artery were at the value of supine rest, whereas the common carotid blood velocity was not completely restored and deviations in the temporal artery velocity persisted. The data would suggest that cerebral blood flow is regulated with some delay and that such regulation is partially reflected in the common artery blood flow, since changes in a branch of the external carotid artery flow velocity remained.

The development of prenatal diagnosis in Italy was made difficult by the restrictions of the old abortion law and only in recent years has a consistent number of cases been investigated. We report the experience on prenatal chromosome diagnosis of ten Italian centers participating in a collaborative study on 4952 diagnoses performed from 1972 to 1980. The main indication groups were: advanced maternal age (2882 cases), previous child with chromosome anomaly from parents with normal karyotype (847 cases), and chromosome anomaly in one parent (97 cases). The other indications for amniocentesis, including cases without a cytogenetic risk, have been assembled into a “miscellaneous” group (1126 cases). We found 125 abnormal fetal karyotypes (2.5%) of which 89 were unbalanced (1.8%). The frequencies and types of chromosome anomalies are reported in detail for each indication group and are compared with the corresponding ones from the European Munich Conference. The great majority of these Italian data were not included in the Munich report.

The intra- and extracerebral Doppler artery blood velocity responses to a 10-mmHg abrupt blood pressure (BP) decrease in ten healthy men were studied. This decrease was obtained using two cuffs placed over both thighs. First, cuffs were inflated to pressures greater than the arterial BP for 5 min. Next, they were deflated to 60 mmHg in order to prevent venous return from the legs. We obtained a decrease in mean arterial BP of from 101 (10) to 90 (10) mmHg [mean (SD), P < 0.01] without modifications in the heart rate [HR, 88 (14) beats min -1]. Middle cerebral artery mean blood velocity (MCAmv) decreased immediately from 50 (10) to 42 (12) cm?s -1 ( P < 0.05). Simultaneously, temporal superficial artery mean blood velocity (TSAmv) decreased from 11 (3) to 7 (2) cm?s -1 ( P < 0.05) and common carotid artery blood flow (CCAbf?) decreased from 305 (23) to 233 (33) ml min -1 ( P < 0.05). After 5 s, MCAmv and CCAbf returned to baseline values, whereas TSAmv [8?(2) cm?s -1], mean arterial BP [86 (10) mmHg] remained low and HR increased [92 (12) beats min -1]. TSAmv, BP and HR returned to baseline values in 1 min. These data confirm that cerebral blood flow (CBF) is very rapidly regulated but that blood flow in extracranial territories is not and that it follows the arterial BP changes.

1.Deutero-exchange of cis-1, 2-dimethylcyclohexane and trans-1, 2-dimethylcyclohexane on atomized platinum films at temperatures up to 64°C proceeds at a rate no lower than the rate of configurational isomerization of these hydrocarbons.2.A comparison of the distribution curves of the molecular ions and fragment ions, corresponding to the loss of one methyl group by the molecule, reveals that in the deutero-exchange of 1,1-dimethylcyclohexane, there is no exchange in the side groups, in contrast to cis-1, 2-dimethylcyclohexane. This method may also be extended to other substituted cycloalkanes.

1.Cycloheptane and cyclooctane differ substantially from one another in their behavior in the reaction of deuteroexchange.2.The shape of the distribution curves of cycloheptane permits it to be added to the same group as cyclopentane and cyclohexane.

This paper is devoted to a study of the features of the nonlinear conversion of radiation in various types of optical fibers. It is found that, when a narrow-band radiation source is used, the spectrum of the converted radiation in a fiber-optic ring apparatus shows significant broadening, whose character depends on the type of optical fiber. It is shown that the broadening of the radiation spectrum results from partially degenerate four-wave mixing. Solutions are found in explicit form that satisfy boundary conditions that correspond to the experimental conditions.

The reaction of diphenyl sulfide with sulfuryl chloride was studied. Depending on the reaction conditions, it occurs either as chlorination of the aromatic ring or as oxidation to give sulfoxide.

Objective: To describe serotypes of Streptococcus pneumoniae from healthy children and paediatric patients < 5 years old.Study design: Multi-center microbiological and epidemiological study.Materials and Methods: 584 strains of pneumococci from 18 cities of Russian Federation were studied using PNEUMOTEST-LATEX test (Statens Serum Institut, Denmark). Among those 306 from healthy carriers, 14 from patients with invasive pneumococcal disease (IPD), 262 from non-invasive pneumococcal disease (NIPD). Population included children of day-care centers (163), orphanages (143) and paediatric hospitals (278).Results: In children of day-care centers predominant serotypes were as follows: 19 (28.8%), 6 (15.9%), 15 (10.4%), 23 (9.2%), 3 (6.7%) and 9 (6.7%). In orphanages serotype 19 was predominant (67.8%), followed by 6 (9.8%), 23 (9.2%), 14 (4.2%), 18 (2.1%). In 1.2% of cases serotype was not identified. Ten-valent vaccine coverage for healthy carriers was 80.7%. In paediatric patients with AOM serotype 19 was detected in 31.0%, 3 (10.2%), 14 (7.7%), 15 (5.1%), 23 (5.1%), 4 (5.1%), 6 (5.1%), 8 (2.5%), 9 (2.5%), 20 (2.5%), 22 (2.5%). Serotypes not included in vaccine composition, were detected in 20.7%. Vaccine coverage for AOM was 56.5%. In CAP patients, serotype 19 was detected in 33.6%, 6 (15.8%), 23 (8.9%) and 14 (7.2%). Vaccine coverage for CAP was 70.6%. Among strains from IPD, 50% were of 19 serotype.Conclusion: An average vaccine coverage in this study was 75.2%. All penicillin-resistant strains were covered by 10-valent vaccine.

This paper presents the response of an electrooptic modulator in the tonal region of frequencies for radiation reflected from the p-n junction of a germanium transistor that operates in the amplification regime. The modulator can be effectively used in fiber-optic communication, optical devices for quantum electronics, and devices for the recording, storage, and processing of optical information.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Femoral blood flow (FBF) was measured in seven dogs, simultaneously with both an electromagnetic perivascular probe and a transcutaneous range gated Doppler velocimeter. Measurements were made in basal conditions and during intraarterial infusions of noradrenaline (10 to 400 ng·kg–1min–1) and isoprenaline (10 to 400 ng·kg–1·min–1) thus allowing comparisons of ultrasonic (DBF) and electromagnetic (EMBF) blood flow at 91 different blood flow rates ranging from 5 to 300 cm3·min–1. The linear regression line through the data of ultrasonic and electromagnetic simultaneous measurements was:<$O_FD> /medium/19-11-700-si1.gif" ALT="Formula "<$INLINEFIG_ALIGN>><$C_FD>with a highly significant correlation (r = 0.96, p>0.001) but there was a wide scattering about the mean. Errors in DBF were mainly due to positioning of the probe and determination of arterial diameter.