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PubMedDate not supplied

[Ecological study of Pyroglyphides mites in house dust in the Grenoble area. A qualitative approach and incidence of various parameters: seasons, altitude, temperature and relative dampness in their multiplication].

This study concerns the analysis of 70 samples of dust mites taken periodically from 13 sample areas or mattresses at different altitudes. It shows the presence of Pyroglyphid mites in all the mattresses studied. Four species were found: Dermatophagoides pteronyssinus, Dermatophagoides farinae, Euroglyphus maynei and Dermatophagoides evansi. From a quantitative point of view, the statistical analysis of the results obtained allows the following conclusions to be drawn: -- All the Pyroglyphids (adults and young) undergo seasonal fluctuations at low, middle and high altitude. In the plains and at middle altitude these mites have a seasonal maximum and minimum. At high altitude only the seasonal maximum can be determined. -- The number of Pyroglyphids found is much higher in the plaine than at middle altitude and at middle altitude than at high altitude. The influence of altitude can be demonstrated with certitude. -- The conditions of temperature and relative dampness most favourable to the multiplication of mites are found in the plaine. At middle and high altitude these conditions are only met in summer. In flat country the statistical analysis allows us to show the existance of a correlation between the rate of dampness and the number of Pyroglyphids, and more specially, between the dampness rate and Dermatophagoides farinae, a predominant species at this sampling area. At middle and high altitude such a correlation cannot be shown clearly. At the three altitudes considered, no correlation can be established between the temperature and the number of Pyroglyphid mites found.

Altitude↗

PubMed1995

A method for assessing the damping characteristics of periodontal tissues: goals and limitations.

The Periotest method, an objective, noninvasive clinical diagnostic method, is a dynamic procedure that measures the resistance of the periodontium to a defined impact load. It has been reported that Periotest values depend to some extent on tooth mobility, but mainly on the damping characteristics of the periodontium. Nevertheless, the real clinical meaning of the measurements and some important limitations of the Periotest measuring principle still seem to be poorly understood. In the present study, the relationship between damping characteristics of periodontal tissues and tooth mobility was investigated. The best correlations between tooth deflection and Periotest values were found for teeth showing a certain degree of clinical mobility (R2 from .79 to .91). Nevertheless, this correlation was clearly lower when only healthy subjects were examined (R2 from .43 to .54). The better correlation found for forces greater than 1.0 N indicates that the damping characteristics assessed with the Periotest method are related to secondary tooth movement. The Periotest methodology, measuring principle, and limitations are critically reviewed.

Adult↗

PubMed1979

Regulation of IgE antibody production by serum molecules. V. Evidence that coincidental sensitization and imbalance in the normal damping mechanism results in "allergic breakthrough".

Experiments presented in this paper were designed to test a new concept concerning the possible pathogenesis of the allergic phenotype. This concept, termed "allergic breakthrough" considers that one of the avenues toward the allergic phenotype involves coincidental sensitization combined with an imbalance in the normal damping mechanism that serves to limit IgE antibody production. The three predictions of this concept that can be tested experimentally are: 1) manipulations that are effective in heightening or re-establishing the damping mechanism should manifest persistence insofar as IgE antibody synthesis to the relevant allergen is concerned; 2) once allergic breakthrough has occurred, the height of production of IgE antibodies specific for the sensitizing agent should remain elevated at levels characteristic of the allergic phenotype, even after the threshold of damping activity has returned to a normal level; and 3) allergic breakthrough should display specificity in that breakthrough would occur in response to subsequent exposure to the specific antigen to which coincidental sensitization initially occurred, but not for other unrelated antigens. The studies presented herein confirm each one of these predictions, thereby providing substantial support for the validity of this concept as one possible distinguishing feature between individuals manifesting the nonallergic and allergic phenotypes, respectively.

Animals↗

PubMed2006

Fingerprints of damped quantum rotation observed in solid-state proton NMR spectra.

(1)H NMR spectra of the methyl group in an oriented crystal sample of methylmalonic acid with all three non-methyl protons replaced by deuterons are interpreted in terms of the damped quantum rotation (DQR) theory of NMR line shapes. The DQR approach offers a perfect theoretical reproduction of the observed spectra while the conventional Alexander-Binsch line-shape model shows evident defects in the present case. The temperature trends of the quantities characterizing the coherent and incoherent dynamics of the methyl group in the DQR approach (the effective tunnelling frequency and two coherence-damping rates) derived from the spectra are fairly reproduced using a model reported previously. The present findings provide further evidence of limitations to the validity of the common belief that molecular rate processes in condensed phases are necessarily classical.

Computer Simulation↗

PubMed1991

A coupled resonator model of the detection of nuclear magnetic resonance: radiation damping, frequency pushing, spin noise, and the signal-to-noise ratio.

Magnetic resonance involves two coupled resonating systems: the spins and the tuned receiver coil. We simulate the spin system by an equivalent electrical resonator. An analysis of coupled resonators leads to a straightforward derivation of properties such as radiation damping, frequency pushing, and spin noise. The theory is applied to recent experiments (M. Guéron and J. L. Leroy, J. Magn. Reson. 85, 209-215 (1989]. The sensitivity of the spin noise experiment is shown to be T2/tau 0, where 1/tau 0 is the rate of radiation damping. This result leads directly to a fundamental formulation of the usual signal-to-noise ratio, (SNR)2 = (m0 B/tau 0)/(4Fk theta delta v), where m0 is the equilibrium magnetic moment, theta is the temperature, and F is the noise figure of the receiver. An equivalent electrical resonator can also be used to describe the active medium of masers.

Computer Simulation↗

PubMed1998

Measurement of Chemical Exchange Rate Constants with Solvent Protons Using Radiation Damping

When chemical exchange occurs between a concentrated and a diluted species like the proton exchange between water and proteins in biochemical systems, it is difficult to use the conventional methods for a quantitative dynamical study. In this paper, a new approach which utilizes radiation damping of the strong water magnetization exchanging with the weak resonance of the mobile protons in biomolecules is proposed. It is demonstrated with a dilute guanidine solution, using the simple inversion-recovery pulse sequence, that the exchange rate constants between water and guanidine protons are evaluated by solving the Bloch equations modified with both the radiation damping and the chemical exchange effects. Copyright 1998 Academic Press.

Journal Article↗

PubMed1999

Suppression of radiation damping in high-resolution NMR.

The radiation damping field induced by an intense NMR line can be counterbalanced by a DANTE sequence of small flip angle pulses of opposite phase applied during the free induction decay. The transient NMR signal is acquired, one complex data point at a time, in the intervals between these DANTE pulses. As the intense signal decays, reducing the radiation damping field, the flip angles of the DANTE pulses are reduced at a matching rate. An experimental test on an aqueous solution of d-glucose demonstrates a reduction in linewidth at half height from 13.5 to 0.8 Hz, revealing a weak doublet response previously hidden under the broad water line.

Glucose↗

PubMed1998

Slowly reverting enzyme inactivation: a mechanism for generating long-lived damped oscillations

Single-enzyme systems can undergo weakly damped concentration oscillations if the enzyme can be converted to an inactive form which only slowly reverts to the active form. Inactivation can take many forms, including a simple (hysteretic) conformational change of the enzyme. This observation may provide an explanation for the damped oscillations seen in photosynthetic activity following a sudden disturbance since rubisco, the enzyme responsible for fixing carbon, is a hysteretic enzyme with appropriate kinetic constants for oscillation. Copyright 1998 Academic Press

Journal Article↗

PubMed1975

Antagonistic effects of Trichoderma harzianum on Pythium aphanidermatum causing the damping-off disease of tobacco in Nigeria.

Culture filtrates of Trichoderma harzianum Rifai have been found to inhibit zoospore germination, germ tube elongation and mycelial growth of Pythium aphanidermatum causing the damping-off disease of tobacco in Nigeria. Further, the invasion of the hyphae of P. aphanidermatum by hyphae of T. harzianum has been demonstrated in mixed cultures of the two fungi. The results of investigations on the role of T. harzianum as an agent of biological control of the damping-off disease in sterilized and unsterilzed soils are reported and discussed.

Antibiosis↗

PubMed1975

A new method for the simultaneous measurement of the movement of inertia, the damping coefficient and the location of the centre of mass of a body segment in situ.

A new method which permits, in a single measurement, the determination of the moment of inertia, the angular damping coefficient of the joint and the location of the centre of mass of a body segment in situ is presented. The underlying principle is the theory of small, damped oscillations of a system about its equilibrium position. The fact that the oscillogram contains information about certain parameters of the oscillating system is used to find these parameters. The application of the method is simple and does not require highly sophisticated instrumentation. The results are very reproducable and immediately available.

Biomechanical Phenomena↗

PubMed2001

Serum IgE specific to indoor moulds, measured by basophil histamine release, is associated with building-related symptoms in damp buildings.

OBJECTIVE: To study the relationship between basophil histamine release (HRT) to indoor moulds, indicating specific IgE, and building-related symptoms (BRS), asthma, and hay fever in individuals working in damp and mouldy buildings. METHODS: A cross-sectional study was performed among 86 school staff members, who on average had worked 143 months (range: 3-396) in moist buildings with mould growth in the constructions. A questionnaire concerning mucous membrane symptoms, facial skin symptoms, central nervous system symptoms, hay fever, and asthma was fulfilled by the participants, and blood samples were taken. Eight mould species growing on building constructions were identified and cultivated to obtain allergenic materials for testing. The presence in serum of IgE specific to moulds was verified by histamine release test (HRT) based on passive sensitization of basophil leukocytes. The validity of the method was confirmed by parallel testing of patients allergic to grass- and birch pollen and by the shift from positive to negative response after removal of serum IgE and by using sham sensitization. RESULTS: The prevalence of most BRS was between 32% and 62%. Positive HRT, showing serum IgE specific to one or more of the moulds, was observed in 37% of the individuals. The highest frequency of positive HRT was found to Penicillium chrysogenum and then to Aspergillus species, Cladosporium sphaerospermum and Stachybotrys chartarum. A significant association was found between most BRS and positive HRT, whereas no association was observed between positive HRT to moulds and self reported hay fever or asthma. CONCLUSION: Positive HRT to indoor moulds, showing the presence in serum of IgE specific to the fungi, was found to be related to BRS in individuals working in damp and mouldy buildings. Whether the association is of causal character is a question for further studies. The test may be useful in the evaluation and study of possible mould induced BRS.

Adult↗

PubMed2001

Pseudomonas fluorescens DR54 Reduces Sclerotia Formation, Biomass Development, and Disease Incidence of Rhizoctonia solani Causing Damping-Off in Sugar Beet.

Effects of the biocontrol strain, Pseudomonas fluorescens DR54, on growth and disease development by Rhizoctonia solani causing damping-off in sugar beet were studied in soil microcosms and in pot experiments with natural, clay-type soil. In pot experiments with P. fluorescens DR54-treated seeds, significantly fewer Rhizoctonia-challenged seedlings showed damping-off symptoms than when not inoculated with the biocontrol agent. In the rhizosphere of P. fluorescens DR54 inoculated seeds, the bacterial inoculant was present in high numbers as shown by dilution plating and immunoblotting. By the ELISA antibody technique and direct microscopy of the fungal pathogen grown in soil microcosms, it was shown that the presence of P. fluorescens DR54 on the inoculated seeds had a strong inhibitory effect on development of both mycelium biomass and sclerotia formation by R. solani. In the field experiment, plant emergence was increased by treatment with P. fluorescens DR54 and the inoculant was found to be the dominating rhizosphere colonizing pseudomonad immediately after seedling emergence.

Journal Article↗

PubMed2003

Dynamic stiffness and damping of human intervertebral disc using axial oscillatory displacement under a free mass system.

The aim of this study was to analyse the dynamic response of the human intervertebral disc to vibration in a physiologically relevant frequency spectrum. Eight lumbar intervertebral discs were harvested. After preparation, each sample was subjected to a pre-loading and then dynamic compression (from 5 to 30 Hz). The dynamic compression was applied using an experimental set-up comprising a free weight loading from above and a driving oscillatory displacement from below (closest to the in vivo loading). A viscoelastic model enabled the calculation of stiffness and damping from the transfer function. From 5 Hz to 30 Hz the stiffness values are between 0.19 and 3.66 (MN/m) and the damping values between 32 and 2094 (Ns/m). The mean resonant frequency was found at 8.7 Hz. These dynamic characteristics of the intervertebral disc could be used in a three-dimensional finite elements model of the human body to study its response to vibration in the driving position.

Aged↗

PubMed1979

Electrocardiographic and serum enzymic alterations associated with cardiac alterations induced in dogs by single transthoracic damped sinusoidal defibrillator shocks of various strengths.

The safety margin between the strength of shock needed to defibrillate the ventricle and shocks which produce cardiac damage has not previously been reported. This study quantitates the shock intensity required to produce ECG alterations, serum alpha-1LDH and MB CPK isoenzyme elevation and myocardial damage using single transchest damped sinusoidal defibrillator shocks. Shocks of 1 to 20 amperes per Kg. of body weight were applied. Fifty-six dog weighing 2.4 to 15 kilograms were shocked with defibrillator pulses via 10 centimeter diameter electrodes applied to the thorax. Electrocardiograms were taken to be analyzed for arrhythmias, S-T segment changes, and T wave changes. Serum enzyme levels were determined in 25 dogs. Macroscopic and histopathologic studies were conducted on the hearts. Transchest single damped sine wave shocks did not produce microscopically detectable cardiac damage until at least a threefold current overdose was applied. No macroscopic morphologic alterations were observed until at least a sixfold current overdose was applied and no deaths occurred until a twelvefold or greater current overdose was delivered. Incidence and severity of ECG changes, increase in serum enzyme activity, incidence and severity of cardiac damage, and incidence of mortality all correlated positively with shock strength. However, these four adverse effects did not correlate well with each other. Transient ECG changes were very frequent following shock application regardless of the morphologic damage produced, and hence the transient changes have little value as indicators or predictors of damage. Persistent ECG changes were predictive of morphologic changes but were not sensitive enough to detect damage in mildly injured hearts. Likewise, elevated serum cardiac isoenzyme activity was a reliable but insensitive indicator of damage.

Animals↗

PubMed1992

Phosphorylation of 9-(2-phosphonomethoxyethyl)adenine and 9-(S)-(3-hydroxy-2-phosphonomethoxypropyl)adenine by AMP(dAMP) kinase from L1210 cells.

Acyclic nucleotide analogues 9-(2-phosphonomethoxyethyl)adenine (PMEA) and 9-(S)-(3-hydroxy-2-phosphonomethoxypropyl)adenine ((S)-HPMPA) which display potent antiviral activity are transformed in the cells to their mono- and disphosphoryl derivatives. We purified from mouse L1210 cells the enzyme that in two steps phosphorylates PMEA and (S)-HPMPA to their diphosphoryl derivatives and found that it co-purifies with AMP(dAMP) kinase activity; the best substrates of this enzyme were AMP, ADP and dAMP. Other nucleoside 5'-triphosphates or creatine phosphate could not be substituted for ATP as a phosphate donor. Our results also indicated that at least one other enzyme (creatine kinase) is capable of transforming the monophosphoryl derivatives of the studied compounds to their respective diphosphates.

Adenine↗

PubMed1987

Effect of material damping on bone remodelling.

This paper considers the effect of internal material damping on the stresses, strains, and surface and internal remodelling behaviour in a section of axisymmetrical bone with a force-fitted axially oriented medullary pin. The bone response to several loading situations is modelled using visco-elastic equations. An approximate method is developed to analyse the proposed mathematical model. By considering a numerical example, the effect of material damping on the remodelling stresses is quantified.

Adaptation, Physiological↗

PubMed1989

Odor volatiles associated with microflora in damp ventilated and non-ventilated bin-stored bulk wheat.

Western hard red spring wheat, stored at 20 and 25% moisture contents for 10 months during 1985-86, was monitored for biotic and abiotic variables in 10 unheated bins in Winnipeg, Manitoba. The major odor volatiles identified were 3-methyl-1-butanol, 3-octanone and 1-octen-3-ol. The production of these volatiles was associated and correlated with microfloral infection. Ventilation, used for cooling and drying of grain, disrupted microfloral growth patterns and production of volatiles. The highest levels of 3-methyl-1-butanol occurred in 25% moisture content wheat infected with bacteria, Penicillium spp. and Fusarium spp. In non-ventilated (control) bins with 20% moisture content wheat, 3-methyl-1-butanol was correlated with infection by members of the Aspergillus glaucus group and bacteria. In control bins, 1-octen-3-ol production was correlated with infection of wheat of both moisture contents by Penicillium spp. The fungal species, isolated from damp bin-stored wheat and tested for production of odor volatiles on wheat substrate, included Alternaria alternata (Fr.) Keissler, Aspergillus repens (Corda) Saccardo, A. flavus Link ex Fries, A. versicolor (Vuill.) Tiraboschi, Penicillium chrysogenum Thom, P. cyclopium Westling, Fusarium moniliforme Sheldon, F. semitectum (Cooke) Sacc. In the laboratory, fungus-inoculated wheat produced 3-methyl-1-butanol; 3-octanone and 1-octen-3-ol were also produced, but less frequently. Two unidentified bacterial species isolated from damp wheat and inoculated on agar produced 3-methyl-1-butanol.

Alcohols↗

PubMed1986

Some failings of pulsatility index and damping factor.

Pulsatility index (PI) is a commonly used method of objective assessment of the Doppler waveform. PI falls with increasing proximal stenosis and is raised by increasing peripheral resistance. Damping factor (DF) for an arterial segment is calculated by dividing the proximal by the distal PI. DF rises with increasing severity of disease of the arterial segment. DF is not, however, sufficiently accurate to be used alone but is usually combined with transit time measurements to provide information of diagnostic use. Both PI and DF have been examined in a canine model of combined segment disease. With increasing stenosis, distal PI falls as expected but so also does proximal PI. Such a stenosis is, in effect, a flow-throttling resistance so that although the characteristics of blood flow are altered by its presence, similar changes are observed both above and below the stenosis. The reduction of PI by a stenosis distal to the insonation site may result in the false interpretation of a low PI as indicating disease proximal to the insonation site. The observed similarity between PI proximal and distal to a stenosis reduces the usefulness of pulsatility index damping factor, particularly in the assessment of the femoro-popliteal segment in combined segment disease.

Animals↗