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PubMed1987

On the damped frequency response of a finite-element model of the cat eardrum.

This article presents frequency responses calculated using a three-dimensional finite-element model of the cat eardrum that includes damping. The damping is represented by both mass-proportional and stiffness-proportional terms. With light damping, the frequency responses of points on the eardrum away from the manubrium display numerous narrow minima and maxima, the frequencies and amplitudes of which are different for different positions on the eardrum. The frequency response on the manubrium is smoother than that on the eardrum away from the manubrium. Increasing the degree of damping smooths the frequency responses both on the manubrium and on the eardrum away from the manubrium. The overall displacement magnitudes are not significantly reduced even when the damping is heavy enough to smooth out all but the largest variations. Experimentally observed frequency responses of the cat eardrum are presented for comparison with the model results.

Acoustics↗

PubMed2003

Compost-induced suppression of Pythium damping-off is mediated by fatty-acid-metabolizing seed-colonizing microbial communities.

Leaf composts were studied for their suppressive effects on Pythium ultimum sporangium germination, cottonseed colonization, and the severity of Pythium damping-off of cotton. A focus of the work was to assess the role of fatty-acid-metabolizing microbial communities in disease suppression. Suppressiveness was expressed within the first few hours of seed germination as revealed by reduced P. ultimum sporangium germination, reduced seed colonization, and reduced damping-off in transplant experiments. These reductions were not observed when cottonseeds were sown in a conducive leaf compost. Microbial consortia recovered from the surface of cottonseeds during the first few hours of germination in suppressive compost (suppressive consortia) induced significant levels of damping-off suppression, whereas no suppression was induced by microbial consortia recovered from cottonseeds germinated in conducive compost (conducive consortia). Suppressive consortia rapidly metabolized linoleic acid, whereas conducive consortia did not. Furthermore, populations of fatty-acid-metabolizing bacteria and actinobacteria were higher in suppressive consortia than in conducive consortia. Individual bacterial isolates varied in their ability to metabolize linoleic acid and protect seedlings from damping-off. Results indicate that communities of compost-inhabiting microorganisms colonizing cottonseeds within the first few hours after sowing in a Pythium-suppressive compost play a major role in the suppression of P. ultimum sporangium germination, seed colonization, and damping-off. Results further indicate that fatty acid metabolism by these seed-colonizing bacterial consortia can explain the Pythium suppression observed.

Antibiosis↗

PubMed1994

Damp housing and adult health: results from a lifestyle study in Worcester, England.

STUDY OBJECTIVE: To explore the relationship between damp housing and adult health using two separate measures of ill health and taking into account the confounding effects of health related lifestyles and social factors. DESIGN AND SETTING: Analysis of responses gathered in a cross sectional, postal questionnaire survey of a randomly selected sample of 5347 residents of Worcester. PARTICIPANTS: Altogether 2353 people aged 16 to 64 years responded to the survey (adjusted response 52%). RESULTS: Nine per cent of respondents lived in housing which they reported to be damp. Rates were highest among young women. People who lived in damp housing were more likely to report long standing illness, disability, or infirmity; the increased prevalence could not be attributed to any particular medical condition. Perceived ill health, as measured by the sleep, energy, and social isolation dimensions of the Nottingham Health Profile, was also more common in this group. These associations could not be explained by lifestyle factors; the relationship proved strongest among people in non-manual social classes living in owner occupied housing. The prevalence of ill health increased as the severity of dampness increased. CONCLUSION: Self reported damp housing and ill health in adults were strongly associated, most noticeably among people in non-manual social classes living in owner occupied housing. The association met many of the epidemiological criteria necessary for suggesting causality: alternative explanations are discussed.

Adolescent↗

PubMed1998

Effect of dampness at home in childhood on bronchial hyperreactivity in adolescence.

BACKGROUND: Relatively little is known about risk factors for the persistence of asthma and respiratory symptoms from childhood into adolescence, and few studies have included objective measurements to assess outcomes and exposure. METHODS: From a large cross sectional study of all 4th grade school children in Munich (mean age 10.2 years), 234 children (5%) with active asthma were identified. Of these, 155 (66%) were reinvestigated with lung function measurements and bronchial provocation three years later (mean age 13.5 years). RESULTS: At follow up 35.5% still had active asthma. Risk factors for persisting asthma symptoms in adolescence were more severe asthma (OR 4.94; CI 1.65 to 14.76; p = 0.004) or allergic triggers (OR 3.54; CI 1.41 to 8.92; p = 0.007) in childhood. Dampness was associated with increased night time wheeze and shortness of breath but not with persisting asthma. Risk factors for bronchial hyperreactivity in adolescence were bronchial hyperreactivity in childhood (p = 0.004), symptoms triggered by allergen exposure (OR 5.47; CI 1.91 to 25.20; p = 0.029), and damp housing conditions (OR 16.14; CI 3.53 to 73.73; p < 0.001). In a subgroup in whom house dust mite antigen levels in the bed were measured (70% of the sample), higher mite antigen levels were associated with bronchial hyperreactivity (OR per quartile of mite antigen 2.30; CI 1.03 to 5.12; p = 0.042). Mite antigen levels were also significantly correlated with dampness (p = 0.05). However, the effect of dampness on bronchial hyperreactivity remained significant when adjusting for mite allergen levels (OR 5.77; CI 1.17 to 28.44; p = 0.031). CONCLUSION: Dampness at home is a significant risk factor for the persistence of bronchial hyperreactivity and respiratory symptoms in children with asthma. This risk is only partly explained by exposure to house dust mite antigen.

Adolescent↗

PubMed2004

Temporal damping in response to broadband noise. I. Inferior colliculus.

Many cells in the inferior colliculus (IC) are sensitive to interaural time differences (ITDs), in the form of an oscillatory dependency of average firing rate on ITD. We studied the degree of damping in such binaural responses, recording from neurons in the inferior colliculus of pentobarbital-anesthetized cats to binaural broadband noise and tones. Noise-delay functions and composite curves were characterized by computing the difference between responses to correlated and anticorrelated stimuli. We use a new metric, based on the envelope of this difference, to quantify damping. There is a clear relationship between damping and characteristic frequency (CF), but even neurons of the same CF can differ in their damping. For individual cells, damping can be stronger to tones or to noise; at the population level the two are positively correlated and are scarcely affected by SPL. The frequencies that dominate ITD sensitivity are near the CF in response to noise, but are often below CF in response to tones. These findings qualify conclusions from earlier reports but overall they support the conclusion that, at a population level, basic aspects of binaural responses to wideband noise are consistent with summed responses to pure tones.

Acoustic Stimulation↗

PubMed1998

Damping in reflexively active and areflexive lengthening muscle evaluated with inertial loads.

Damping in reflexively active and areflexive lengthening muscle evaluated with inertial loads. J. Neurophysiol. 80: 3369-3372, 1998. Studies of active areflexive muscle have shown that during a constant velocity stretch the increment in force elicited by an incremental length change falls dramatically after a few hundred micrometers of stretch, a finding labeled as "muscle yield." The mechanical behavior after the yield was like a viscous damper, in that force varied only with velocity. In light of these observations, our aims were to determine whether viscous properties are also evident under more physiological conditions, specifically under inertial loading, and to evaluate the damping action of reflexively intact compared with that of deafferented muscle. The active soleus muscle in a decerebrate cat was forcibly stretched by a simulated inertia with a specified initial velocity. We compared muscle length changes when afferent pathways were intact with those recorded after cutting the dorsal roots. Our findings were that areflexive muscle showed highly damped responses, with large changes in mean muscle length, indicative of high viscosity relative to stiffness. In contrast, reflexively active muscle produced lightly damped oscillations, with minimal changes in mean length, reflecting low viscosity and high stiffness. It appears that the stretch reflect modifies the relative contributions of elastic and viscous-like forces, maintaining elasticity, which in turn sustains oscillations. These differences highlight tradeoffs between positional and velocity regulation, in that elastic properties of reflexively active muscle promote oscillations with modest change in mean muscle length, whereas viscous-like properties of areflexive muscle produce damped responses, with poor positional regulation.

Algorithms↗

PubMed2006

Smart damping modulation of carotid wall energetics in human hypertension: effects of angiotensin-converting enzyme inhibition.

Damping is the conversion of mechanical energy of a structure into thermal energy, and it is related to the material viscous behavior. To evaluate the role of damping in the common carotid artery (CCA) wall in human hypertension and the possible improvement of angiotensin-converting enzyme (ACE) inhibition, we used noninvasive CCA pressure (tonometry) and diameter (B-mode echography) waveforms in normotensive subjects (NT group; n=12) and in hypertensive patients (HT group; n=22) single-blind randomized into HT-placebo (n=10) or HT-treated (ramipril, 5 to 10 mg/d during 3 months; n=12). Vascular smooth muscle (VSM) null tonus condition was achieved from in vitro pressure and diameter waveforms (Konigsberg microtransducer and sonomicrometry) measured in explanted human CCA (n=14). Arterial wall dynamics was described by viscous (eta), inertial (M), and compliance (C) parameters, mean circumferential wall stress, viscous energy dissipation (WD), peak strain energy (WSt), damping ratio (xi=WD/WSt), and modeling isobaric indexes CIso and WSt(Iso). The lack of VSM tonus isobarically increased wall stress and reduced eta, CIso, and damping (P<0.01). Wall stress, eta, and WD were greater in HT than in NT (P<0.015) and arrived near normal in HT-treated (P<0.032 respect to HT), with no changes in HT-placebo. Whereas CIso increased in HT-treated (P<0.01) approaching the NT level, xi did not vary among groups. During hypertension, because of the WSt increase, the arterial wall reacts increasing WD to maintain xi. ACE inhibition modulates VSM activation and vessel wall remodeling, significantly improving wall energetics and wall stress. This protective vascular action reduces extra load to the heart and maintains enhanced arterial wall damping.

Adult↗

PubMed1998

Residential dampness problems and symptoms and signs of bronchial obstruction in young Norwegian children.

To assess the role of dampness problems and house dust mite exposure in the development of bronchial obstruction in early life, a cohort of 3,754 children born in Oslo during 1992 and 1993 was followed for 2 yr. Bronchial obstruction was defined as two or more episodes with symptoms and signs of obstruction or one lasting 1 mo or more. A matched case-control study was carried out in 251 cases of bronchial obstruction (response rate: 98%) and their 251 paired controls. Information on home dampness problem(s), house dust mite exposure, and potential confounders was collected during home visits and by questionnaires. Dampness problems were confirmed in the homes of 27% of the cases and 14% of the controls, while a concentration of Dermatophagoides pteronyssinus allergens > 2 microg/g dust was found in the beds of 11 (4.5%) cases and three (1.2%) controls. In conditional logistic regression analysis controlling for potential confounders, confirmed dampness problems increased the risk of bronchial obstruction (adjusted odds ratio: 3.8; 95% confidence interval: 2.0-7.2). Exposure to D. pteronyssinus allergens > 2 microg/g dust increased the risk of bronchial obstruction (adjusted odds ratio: 2.8; 95% confidence interval: 0.7-11.7). Residential dampness problems in Oslo dwellings seem to increase symptoms and signs of bronchial obstruction in young children, apparently without increasing their exposure to house dust mites.

Airway Obstruction↗

PubMed1997

A dynamic and harmonic damped finite element analysis model of stapedotomy.

This study was undertaken in an attempt to better understand the mechanics of sound transmission at the footplate following stapedotomy. The insertion of a Teflon (polytetrafluoroethylene) stapes prosthesis introduces new constraints within the reconstructed ossicular chain which have an effect on the normal vibration patterns of the tympanic membrane. In a finite element model of the ear, constraints have been reproduced as a series of spring constants in the incus/prosthesis/footplate interfaces incorporating damping to simulate the impedance of the inner ear. At zero damping, the frequency response at the pseudo stapes footplate exhibit several maxima and minima between 800 Hz and 2.5 Hz. At higher damping values, these maxima and minima become smoothened out with two or three naturals occurring over the same frequency range. Severe ankylosis of a diseased footplate is reproduced by over-damped conditions. The umbo, incus and stapes footplate vibrate in phase with similar frequencies at light damping levels. The movement of the prosthesis at the pseudo-footplate can be large in the out of plane axis of the ossicular chain, unless sufficient support is provided at the reconstructed footplate. Clinically, this would suggest the vein graft interposed between the piston and stapedotomy hole should endow resistance and elasticity to the system.

Acoustics↗

PubMed2000

Fast repairing of oxidized OH radical adducts of dAMP and dGMP by phenylpropanoid glycosides from Scrophularia ningpoensis Hemsl.

AIM: To investigate the antioxidative activity of the constituents of the roots of Scrophularia ningpoensis (Chinese name: Xuanshen). METHODS: The main compounds from the roots of Scrophularia ningpoensis were isolated and identified by chromatography and FABMS, NMR etc. Using the techniques of pulse radiolysis, the electron transfers from iridoid glycosides (IG) or phenylpropanoid glycosides (PG) to oxidized OH radical adducts of 2'-deoxyadenosine-5'-monophosphate acid (dAMP) or 2'-deoxyguanosine-5'-monophosphate acid (dGMP) were observed. RESULTS: Two IG: harpagoside and harpagide, two PG: angoroside C and acteoside were obtained as the main hydrophilic constituents of the plant. At 0.1 mmol/L concentration, angoroside C and acteoside were able to repair the oxidized OH adducts dAMP and dGMP significantly. However, harpagoside and harpagide had no such effect. The electron transfer rate constants of angoroside C with dAMP and dGMP were 4.2 x 10(8) and 10.3 x 10(8) L.mol-1.s-1; the electron transfer rate constants of acteoside with dAMP and dGMP were 5.3 x 10(8) and 20.2 x 10(8) L.mol-1.s-1. CONCLUSION: PG from Scrophularia ningpoensis have a potent antioxidative activity for reducing of the oxidized OH adducts of dAMP and dGMP.

Antioxidants↗

PubMed2003

Problems with damp and cold housing among Pacific families in New Zealand.

AIMS: To describe reported problems with damp and cold housing among Pacific families in New Zealand and their associations with two facets of maternal health, namely postnatal depression and asthma. METHODS: The data were gathered as part of the Pacific Islands Families: First Two Years of Life (PIF) Study in which 1376 mothers were interviewed when their infants were six weeks old. Mothers were questioned with regard to problems with dampness or mould and cold housing, facets of maternal health (assessed using the Edinburgh Postnatal Depression Scale), and asthma. RESULTS: Over one third of the mothers (37%) reported that their homes had dampness/mould problems, and over half reported problems with cold housing (53.8%). Damp and cold housing were significantly associated with a number of variables including large household size, state rental housing, and financial difficulty with housing costs. Damp and cold housing were also both significantly related to maternal depression and incidence of asthma. CONCLUSIONS: Efforts to reduce problems with damp and cold housing are needed to improve maternal health. To this end, advice regarding the importance of home heating and ventilation may be beneficial.

Adult↗

PubMed1993

Kinetics of activation and in vivo muscarinic receptor binding of N-(2-bromoethyl)-4-piperidinyl diphenylacetate: an analog of 4-DAMP mustard.

4-DAMP mustard (N-2-chloroethyl)-4-piperidinyl diphenylacetate) has been shown to selectively and irreversibly inhibit muscarinic receptors. In an attempt to increase the rate of formation and peak concentration of the reactive intermediate, an analog [N-(2-bromoethyl)-4-piperidinyl diphenylacetate (4-DAMP bromo mustard)] was synthesized and the molecular formula confirmed by mass analysis. The 4-DAMP bromo mustard was shown to cyclize in phosphate buffer (pH 7.4) to the corresponding aziridinium ion with a first-order rate constant (k1) of 0.071 min-1 at 0 degrees C. At 25 degrees C and 37 degrees C, the formation of the aziridinium ion was nearly instantaneous (100% cyclized within 15 sec) at neutral pH. The rate constants (k2) for the hydrolysis of the aziridinium ion at 25 degrees C and 37 degrees C (pH 7.4) were 0.0027 and 0.010 min-1, respectively, in excellent agreement with the published rate constants for the hydrolysis of the aziridinium ion formed from 4-DAMP mustard. In vivo treatment with 4-DAMP bromo mustard in rats resulted in irreversible inhibition of muscarinic receptor binding in peripheral, but not central nervous system, tissues, suggesting that the quickly formed aziridinium ion does not penetrate the blood-brain barrier.

Animals↗

PubMed1993

Material damping for monitoring of density and strength of bones.

The aim of this work was a preliminary assessment of the feasibility of using in vivo measurements of mechanical properties of bones to detect mineral loss and further to relate them to the tendency of the bone to fracture in the case of loss of minerals, such as in osteoporosis. Previous studies of bone strength in vitro have demonstrated that the decrease in bone strength in both the spine and the femur has strong correlation with the mineral content (BMC) measured with bone densitometry. It was demonstrated that loss of mineral in the bone is accompanied by substantial change of the main mechanical properties, decrease of the Young's modulus, and increase of the damping factor. The change in those properties is one order of magnitude greater than the change in bone density. Moreover, increase of bone density, by way of training, resulted in decrease of the damping factor that also was substantially greater than the change in density. The tests showed clearly that the change in mechanical properties was much greater than the change in bone mass density. This offers an attractive new alternative to the detection of bone mass loss as it appears that the change of the bone mass is well correlated to the change in these mechanical properties. In particular, the change in the damping factor of the material was found to be much more substantial than the bone density change. Therefore, the damping mechanism offers the vehicle for a direct assessment of the bone tendency to fracture due to the loss of mass, as tendency to fracture and mass loss are known to be related.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1989

Understanding natural frequency and damping and how they relate to the measurement of blood pressure.

The model that describes the physical behavior of a fluid-filled catheter-transducer blood pressure monitoring system is a simple mass-spring system. When the mass is displaced and then released, there results a characteristic motion called simple harmonic motion. The full description of this motion requires defining the concepts of undamped and damped natural frequency, as well as of damping itself. Once these concepts are defined and the mass-spring system clearly understood, their relevance to recording blood pressure measurement by fluid-filled catheters is explained. The apparent paradox of how damping can affect undamped natural frequency is clarified. Finally, impedance matching is explained in the context of how some damping devices work. Detailed mathematical proofs are relegated to an appendix.

Blood Pressure Determination↗

PubMed1992

Contribution of damped passive recoil to the measured shortening velocity of skinned rabbit and sheep muscle fibres.

Maximum shortening velocities of skinned fibres from rabbit psoas and sheep extensor digitorum longus muscles were measured by the slack test and by extrapolating force-velocity curves to zero load. Both overall muscle velocity and sarcomere velocity were measured with each method. Maximum sarcomere velocity measured by the slack test was not significantly different from that assessed from the force-velocity curves (p greater than 0.1). Maximum overall muscle velocity measured from the slack test was significantly (p greater than 0.001) and substantially (62% rabbit, 83% sheep) greater than maximum sarcomere velocity. The difference is attributed to damped recoil of the series elastic elements contributing to the overall muscle velocity. The extent and time course of this damped recoil in isotonic steps was assessed from comparisons of overall muscle length and sarcomere length records during isotonic steps. When the records were shifted and scaled so that they superposed during the late stages of isotonic shortening, there was a substantial difference between the early parts of the records. This difference was reduced by about half in association with the step and the remaining half declined at a diminishing rate following the step, lasting longer with lower loads. This result is explained by about half of the series elastic element behaving as a viscoelastic element and half being undamped. With steps to the lowest isotonic loads, which averaged 6.7% of isometric force in sheep and 9.5% in rabbit, the total series elastic element recoil (both damped and undamped) averaged 3.4% and 2.7% of fibre segment length, respectively, in sheep and rabbit. The rapid series elastic element recoil at zero load, assessed from the slack test, was approximately 50% higher, indicating a substantial series compliance at low forces. The contribution of an additional, longer lasting, damped series elastic element recoil to the overall muscle velocity can explain the greater maximum velocity that is frequently found with the slack test.

Animals↗

PubMed2006

Rhizosphere Pseudomonas sp. strains reduce occurrence of pre- and post-emergence damping-off in chile and tomato in Central Himalayan region.

Based on in vitro screening for PGP and anti-mycelial activity against three zoosporic pathogenic oomycetes, Pythium aphanidermatum 123, P. aphanidermatum 4746, and Phytophthora nicotianae 4747, seven bacterial isolates were selected for field trials on tomato and chile to test for plant growth promotion under natural and artificial disease-infested field sites in both winter and wet seasons. The effectiveness of isolates in the field trials correlated with the in vitro antagonism screening data. Pseudomonas sp. FQP PB-3, FQA PB-3 and GRP(3) showed substantial beneficial effects on plant growth promotion and lowered considerably the incidence of pre- and post-emergence damping-off in both the crops under various disease scenarios. For example, seed bacterization with these bacterial strains reduced pre-emergence-damping off by ca. 60-70% in the two natural sites, with and without histories of fungicide use in the winter season, and to a lesser extent, ca. 20-40%, in the warmer wet (high humidity; 85-92%) season. The suppression efficacy for post-emergence damping-off was less compared to pre-emergence damping-off although still significant (P > 0.05). Our data unambiguously show that screening of a large number of bacterial pool identifies promising isolates that show beneficial effects on all stages of plant growth in natural oomycete-infested regimes.

Antibiosis↗

PubMed1985

Modification of spastic gait through mechanical damping.

The effect of dissipative mechanical loads on spastic gait has been studied, to evaluate the feasibility of using mechanically damped orthoses to effect functional improvements in the gait of spastic patients. This concept is based on a hypothesis citing uninhibited, velocity-dependent stretch reflexes as a possible causal factor in spastic gait abnormalities, such as equinus and back-kneeing. In order to screen potential experimental subjects and to quantify velocity-dependent reflex behaviour, ankle rotation experiments and filmed gait analysis were performed. The results supported the existence of a velocity threshold. Orthosis simulation experiments were performed with one spastic subject, using a wearable, computer-controlled, electromechanical, below-knee orthosis simulator to apply a variety of damping loads to the ankle as the subject walked. Results indicated that appropriate damping can improve local joint kinematics. The damping causes a reduction in muscle stretch velocity which apparently results in reduced spastic reflex activity.

Adult↗

PubMed1992

Associations between questionnaire reports of home dampness and childhood respiratory symptoms.

The relationship between home dampness and respiratory health was studied in two populations of children of 6-12 years old, living in the south east of the Netherlands. In one study, lung function was measured at the schools, and in both studies, information on respiratory symptoms was collected from a self-administered questionnaire completed by the parents of the children. Information on home dampness was collected by questionnaire. Information on other potential indoor determinants of respiratory health, like (sources of) nitrogen dioxide and smoking in the home was collected by questionnaire as well. Respiratory symptoms were found to be associated with home dampness. There was a weak, negative association between MMEF and reporting of mould in the home. Several potential biases were evaluated. It was not considered likely that the results could be explained by information, selection or confounding bias. However, further work is needed to conclusively exclude these biases, and to develop objective measures of home dampness for use in epidemiologic studies.

Asthma↗