Breakdown

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Breakdown

  • barrier breakdown
  • collagen breakdown
  • electrical breakdown
  • glycogen breakdown
  • hybrid breakdown
  • leaf breakdown
  • leaf litter breakdown
  • litter breakdown
  • membrane breakdown
  • periodontal breakdown
  • protein breakdown
  • rapid breakdown
  • starch breakdown
  • structural breakdown
  • wound breakdown

  • Terms modified by Breakdown

  • breakdown curve
  • breakdown field
  • breakdown product
  • breakdown products
  • breakdown rate
  • breakdown spectroscopy
  • breakdown threshold
  • breakdown voltage

  • Selected Abstracts


    SLI and Deficits in the Computational Syntactic System: A Comment on W. Frawley's "Control and Cross-Domain Mental Computation: Evidence from Language Breakdown"

    COMPUTATIONAL INTELLIGENCE, Issue 1 2002
    Heather K. J. Van Der Lely
    [source]


    Screening Breakdown in a Plasma by Two Laser Fields and Strong DC Magnetic Field

    CONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005
    D. F. Miranda
    Abstract The effective static dielectric constant of an electron plasma system in the simultaneous presence of two electromagnetic waves and a strong DC magnetic field is calculated. It is found that as the difference ,, of the two electromagnetic wave frequencies matches the plasma frequency ,, a breakdown in screening occurs thereby increasing the plasma heating rate via the external fields due to inverse Bremmstrahlung. An application is made by considering the typical parameters of a hot plasma. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Protective role of pigment epithelium-derived factor (PEDF) in early phase of experimental diabetic retinopathy

    DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 7 2009
    Yumiko Yoshida
    Abstract Background Pigment epithelium-derived factor (PEDF) is the most potent inhibitor of angiogenesis in the mammalian eye, thus suggesting that PEDF may protect against proliferative diabetic retinopathy. However, a role for PEDF in early diabetic retinopathy remains to be elucidated. We investigated here whether and how PEDF could prevent the development of diabetic retinopathy. Methods Streptozotocin-induced diabetic rats were treated with or without intravenous injection of PEDF for 4 weeks. Early neuronal derangements were evaluated by electroretinogram (ERG) and immunofluorescent staining of glial fibrillary acidic protein (GFAP). Expression of PEDF and 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative stress, was localized by immunofluorescence. Vascular endothelial growth factor (VEGF) and p22phox expression were evaluated with western blots. Breakdown of blood retinal barrier (BRB) was quantified with fluorescein isothiocynate (FITC)-conjugated dextran. NADPH oxidase activity was measured with lucigenin luminescence. Results Retinal PEDF levels were reduced, and amplitudes of a- and b-wave in the ERG were decreased in diabetic rats, which were in parallel with GFAP overexpression in the Müller cells. Further, retinal 8-OHdG, p22phox and VEGF levels and NADPH oxidase activity were increased, and BRB was broken in diabetic rats. Administration of PEDF ameliorated all of the characteristic changes in early diabetic retinopathy. Conclusions Results suggest that PEDF could prevent neuronal derangements and vascular hyperpermeability in early diabetic retinopathy via inhibition of NADPH oxidase-driven oxidative stress generation. Substitution of PEDF may offer a promising strategy for halting the development of diabetic retinopathy. Copyright © 2009 John Wiley & Sons, Ltd. [source]


    Experimental frost weathering of sandstone by various combinations of salts

    EARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2001
    R. B. G. Williams
    Abstract Weathering experiments are reported combining frost and a range of salts that occur naturally on rock faces in western and central Europe. Potassium and ammonium alums enhanced frost weathering quite considerably, both singly and in combination, though they were less potent than halite, the destructiveness of which, at sub-zero temperatures, was again confirmed. By contrast, alunogen and gypsum had little or no effect on rates of frost weathering either singly or in combination. Combining halite and gypsum produced breakdown that was intermediate between that of the two salts individually, as did the combination of gypsum and potassium alum. Breakdown in solutions of ammonium alum and gypsum, and in a combination of potassium and ammonium alum with gypsum, caused greater breakdown over 25 cycles of freeze,thaw than was recorded with the salts singly. The results extend the range of salts known to enhance frost weathering, and show that it is difficult to predict the aggressiveness of combinations of salts by experimenting with each salt separately. Copyright © 2001 John Wiley & Sons, Ltd. [source]


    Breakdown of wood in the Agüera stream

    FRESHWATER BIOLOGY, Issue 11 2002
    Joserra Díez
    SUMMARY 1. Breakdown of wood was compared at three sites of the Agüera catchment (Iberian Peninsula): two oligotrophic first-order reaches (one under deciduous forest, the other under Eucalyptus globulus plantations) and one third-order reach under mixed forest, where concentration of dissolved nutrients was higher. 2. Branches (diameter = 3 cm, length = 10 cm) of oak (Quercus robur), alder (Alnus glutinosa), pine (Pinus radiata) and eucalyptus, plus prisms (2.5 × 2.5 × 10 cm) of alder heartwood were enclosed in mesh bags (1 cm mesh size) and placed in the streams. Mass loss was determined over 4.5 years, whereas nutrient, lignin and ergosterol were determined over 3 years. In order to describe fungal dynamics, ergosterol was also determined separately on the outer and inner parts of some branches. 3. Breakdown rates ranged from 0.0159 to 0.2706 year,1 with the third-order reach having the highest values whatever the species considered. The most rapid breakdown occurred in alder heartwood and the slowest in pine branches; breakdown rates of oak, eucalyptus and alder branches did not differ significantly. 4. The highest nitrogen and phosphorus contents were found in alder, followed by oak, while pine and eucalyptus had low values. During breakdown, all materials rapidly lost phosphorus, but nitrogen content remained constant or slightly increased. Lignin content remained similar. 5. Peaks of ergosterol ranged from 0.023 to 0.139 mg g,1 and were higher in alder than in other species in two of the three sites. The third-order reach generally had the greatest increase in ergosterol, especially in alder branches, eucalyptus and alder heartwood. The overall species/site pattern of fungal biomass was thus consistent with the observed differences in breakdown. 6. When compared with leaves of the same species decomposing at these sites, wood breakdown appeared to be less sensitive to the tree species but more sensitive to stream water chemistry. Although wood breakdown is slower and its inputs are lower than those of leaf litter, its higher resistance to downstream transport results in a relatively high standing stock and a significant contribution to the energy flux. [source]


    Going Against the Historical Grain: Perspectives on Gendered Occupational Identity and Resistance to the Breakdown of Occupational Segregation in Two Manufacturing Firms

    GENDER, WORK & ORGANISATION, Issue 3 2002
    Anne-marie Greene
    This article discusses a process of restructuring of working practices within two manufacturing firms with respect to its implications for gendered occupational segregation. A contextualized, historically situated analysis is presented, which is cast within debates on the nature of gendered occupational identity, equality initiatives and arenas of power and influence for women and men, within what were traditionally male-dominated organizational contexts. Such an analysis serves to highlight the significance of the new restructuring in sweeping away 150 years of practice and embedded ,ways of doing things' and offers explanations for the actions of contemporary men and women in opposing what were seen by management and the trade union as emancipatory changes. [source]


    Space Charge Measurement in MgO/LDPE Nanocomposite up to Breakdown under DC Ramp Voltage

    IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2010
    Yoshinobu Murakami Member
    Abstract To understand the basic electric properties of nanosized magnesium oxide (MgO)/low-density polyethylene (LDPE) nanocomposites under an applied DC voltage, the DC breakdown strength and space charge up to the breakdown under a DC ramp voltage were investigated. Compared to that of the LDPE sample, the sample containing a MgO nanofiller (hereafter, called a nanocomposite) had a higher DC breakdown strength. In the case of the LDPE sample, the homo charges, which contained a large negative charge and a small positive charge, were only observed near the electrodes just prior to breakdown. However, in the case of the nanocomposite sample, the positive charge increased as the average field increased until the average field reached a certain value. After that, the positive charge decreased as the average field increased until breakdown occurred. The field enhancement rate (=maximum field/average field) of the nanocomposite sample increased with the average field, until it became saturated. After peaking, the field enhancement rate of the nanocomposite sample decreased as the average field increased. These observations suggest that, instead of the MgO nanofiller suppressing the electronic avalanche, it suppresses the conduction current, which was determined by the space charge, leading to the higher DC breakdown strength. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]


    Flow Velocity Effect on Leaf Litter Breakdown in Tufa Depositing System (Plitvice Lakes, Croatia)

    INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 4 2009
    Anita Belan
    Abstract Considerable amount of riparian leaf litter is annually supplied to the cascade Plitvice Lakes and trapped on tufa barriers where it decays together with aquatic macrophytes. These barriers are the sites of heavy calcite precipitation that can widely differ in terms of current velocity. We conducted a leafbag experiment at sites differing in flow velocity and tufa deposition rate. Decomposition of Petasites spp. and Fagus sylvatica was higher under high current (0.80 m/s) and high tufa deposition areas than in low current (< 0.20 m/s) and low tufa deposition areas (k = 0.085 vs. 0.021 for Petasites spp. and 0.009 vs. 0.002 for Fagus sylvatica). We concluded that although tufa deposition could interfere with decomposition by obstructing physical abrasion and also restricting microbial conditioning, thin calcite crusts developed on the surface of the leaves made them more fragile and thus accelerated their decomposition. High current velocity probably magnified this effect by supporting higher tufa deposition and coarser type of tufa fabrics. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Leaf Breakdown in a Tropical Stream

    INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2006
    José Francisco Gonçalves Jr.
    Abstract The objectives of this study were to investigate leaf breakdown in two reaches of different magnitudes, one of a 3rd (closed riparian vegetation) order and the other of a 4th (open riparian vegetation) order, in a tropical stream and to assess the colonization of invertebrates and microorganisms during the processing of detritus. We observed that the detritus in a reach of 4th order decomposed 2.4 times faster than the detritus in a reach of 3rd order, in which, we observed that nitrate concentration and water velocity were greater. This study showed that the chemical composition of detritus does not appear to be important in evaluating leaf breakdown. However, it was shown to be important to biological colonization. The invertebrate community appeared not to have been structured by the decomposition process, but instead by the degradative ecological succession process. With regards to biological colonization, we observed that the density of bacteria in the initial stages was more important while fungi appeared more in the intermediate and final stages. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Breakdown of the brown trout evolutionary history due to hybridization between native and cultivated fish

    JOURNAL OF FISH BIOLOGY, Issue 2004
    R. M. Araguas
    Genetic changes in the population structure of brown trout Salmo trutta in the eastern Pyrenees were monitored during the 1990s. Stocking with cultivated exogenous fish has resulted in introgressed populations where those with higher introgression coefficients also have the highest values of heterozygosity. Nevertheless, this increase of local diversity reflects a decrease of genetic differentiation between populations and loss of native alleles. These changes obscure native gene pools and modify evolutionary distinctions among native brown trout populations. [source]


    ,-Galactosidase Activity and Cell Wall Breakdown in Apricots

    JOURNAL OF FOOD SCIENCE, Issue 6 2002
    E. Kovács
    ABSTRACT: Apricots (Prunus armeniaca L., cultivars Magyar and Bergeron) were harvested 3 d apart (1st, 2nd and 3rd harvest). Fruits were stored at 4 to 6 °C, 90 % relative humidity, for 3 to 25 d. (,-Galactosidase activity, pectin degradation, and softening were studied as a function of harvest and storage time. (,-Galactosidase activity increased as a function of harvest; it increased continuously during storage in the case of cv. Bergeron. With Magyar enzyme activity reached a maximum value during storage in the case of 2nd and 3rd harvest fruits, then it declined. Total pectin and that solubilized neutral carbohydrate contents decreased as a function of storage. Solubilized pectin quantity did not depend either on harvest or on storage. [source]


    Salmonella Enteritidis Risk Assessment: A Kinetic Analysis

    JOURNAL OF FOOD SCIENCE, Issue 3 2002
    S. Almonacid
    ABSTRACT: Egg and egg preparations are important vehicles for Salmonella enteritidis infections. The influence of time-temperature becomes important when the presence of this microorganism is found in commercial shell eggs, particularly in countries where refrigeration is not mandatory as in Chile. The objective of this research was to develop a mathematical model to analyze the Salmonella enteritidis risk under variable ambient temperatures. Breakdown of vitelline egg membrane was assumed to be required for initiation of bacterial growth. When the critical factor concerning safety is the vitelline membrane breakdown, 15 °C was found to be the storage threshold temperature for a 30-d shelf life. This computer based tool can be used as a contribution in current regulation adjustments or modifications. [source]


    COOKING BEHAVIOR OF RICE AND BLACK GRAM IN THE PREPARATION OF IDLI, A TRADITIONAL FERMENTED PRODUCT OF INDIAN ORIGIN, BY VISCOGRAPHY

    JOURNAL OF TEXTURE STUDIES, Issue 1 2009
    BONG KYUNG KOH
    ABSTRACT Pasting profile of coarse rice, fine rice as well as black gram was carried out individually, in combination, in flour as well as in batter form, before and after fermentation by Brabender Viscoamylograph. Lowest gelatinization temperature was seen in black gram among the three commodities studied. Coarse rice registered a peak viscosity (PV) of 1,300 BU, fine rice 1,030 BU and black gram 1,080 BU. Cold paste viscosity (CPV) was highest in fine rice, lowest in black gram and intermediate in coarse rice. Breakdown (BD) was least in fine rice, highest in coarse rice and black gram lay in between. Values of total setback indicated the strong reason for use of coarse rice in parboiling as well as in idli and dosa preparations. Physical combination of black gram, with fine as well as coarse rice, reduced PV on an average to an extent of 26,30%. CPV was highest in fine rice and black gram combination compared with that of coarse rice and black gram. BD was high in the physical mix of coarse rice and black gram. In comparison with physical mix of fine rice and black gram, in the batter form before fermentation, the PV and CPV reduced by 23 and 34%, respectively, but there was no BD in this mix, indicating restricted swelling behavior in the batter before fermentation. Almost all viscographic parameters reduced before fermentation in coarse rice and black gram compared with their physical combination. Highest relative BD (BDr) was noticed in the pasting profile of black gram alone, probably because of the presence of mucilaginous principle. BDr values increased in batter form to various extents, before and after fermentation, compared with physical combination of rice and black gram. After fermentation, in coarse rice and black gram, the BDr value was low compared with that in fine rice and black gram. PRACTICAL APPLICATIONS Fermented products are commonly ingested in India, especially in the southern states. Nowadays, batter is sold in public for the sake of convenience, as it is a common breakfast preparation. The practice is to use coarse rice for the preparation of idli, a steamed fermented product. It is generally not known how the rice behaves before and after fermentation while cooking. Hence, this work was planned, and results indicated the scientific basis for the usage of coarse rice in the preparation of rice products. The behavior of batter prepared from fine rice has also been described, although it is not an economically viable option. [source]


    Breakdown of adenine nucleotide pool in fatiguing skeletal muscle in McArdle's disease: A noninvasive 31P-MRS and EMG study

    MUSCLE AND NERVE, Issue 6 2003
    Jochen Zange PhD
    Abstract Energy metabolism and electrical muscle activity were studied in the calf muscles of 19 patients with proven McArdle's disease and in 25 healthy subjects. Phosphorus magnetic resonance spectroscopy and surface electromyography (S-EMG) were performed during two isometric muscle contractions of 3 min at 30% maximum voluntary contraction, one performed during normal perfusion and the other during applied ischemia. After about 1 min of ischemic muscle contraction in diseased muscle a significant acceleration in phosphocreatine breakdown was observed, along with a significant decrease in adenosine triphosphate. During both contractions the absence of glycolysis was shown by a significant alkalinization. Furthermore, in patients we observed a greater increase in the S-EMG amplitude than in control subjects. We conclude that early on during moderate exercise, a small number of muscle fibers reach metabolic depletion, indicated by a reduction in the adenine nucleotide pool. An increasing number of motor units, which are still in a high-energy state, are continuously recruited to compensate for muscle fatigue. This functional compartmentation may contribute to the pathophysiology of exercise intolerance in McArdle's disease. Muscle Nerve 27: 728,736, 2003 [source]


    The Relevance of Reconciliation Actions in the Breakdown of Israeli,Palestinian Negotiations, 2000

    PEACE & CHANGE, Issue 4 2002
    Louis Kriesberg
    The breakdown of Israeli,Palestinian negotiations toward a final status agreement and the subsequent eruption of violence stunned many partisans of the conflict as well as intermediaries and observers. Although some partisans on each side had argued from the outset that successful negotiations were impossible, leaders of the Palestinians and the Israelis had negotiated directly for several years as if they were possible. The Israeli,Palestinian conflict had become partially transformed but perhaps insufficiently so to support a negotiated agreement acceptable to both sides. The possible role of what might be regarded as reconciliation actions in that partial transformation of the conflict is examined here. The negotiation and mediation processes prior to the breakdown are reviewed, and then different views of the impact of reconciliation actions, or their absence, are assessed. [source]


    Alteration Patterns Related to Hydrothermal Gold Mineralizaition in Meta-andesites at Dungash Area, Eastern Desert, Egypt

    RESOURCE GEOLOGY, Issue 1 2001
    Hossam A. Helba
    Abstract: The hydrothermal alteration patterns associating with the gold prospect hosted by metavolcanics in the Dungash area, Eastern Desert of Egypt, were investigated in order to assign their relationship to mineralization. The metavolcanics of andesitic composition are generated by regional metamorphism of greenschist facies superimposed by hydrothermal activity. Epidote and chlorite are metamorphic minerals, whereas sericite, carbonates, and chlorite are hydrothermal alteration minerals. The auriferous quartz vein is of NEE-SWW trend and cuts mainly the andesitic metavolcanics, but sometimes extends to the neighbouring metapyroclastics and metasediments. Quartz-sericite, sericite, carbonate-sericite, and chlorite-sericite constitute four distinctive alteration zones which extend outwards from the mineralized quartz vein. The quartz-sericite and sericite zones are characterized by high contents of SiO2, K2O, Rb, and As, the carbonate-sericite zone is by high contents of CaO, Au, Cu, Cr, Ni, and Y, and the chlorite-sericite zone is by high contents of MgO, Na2O, Zn, Ba, and Co. Gold and sulphide minerals are relatively more abundant in the carbonate-sericite zone followed by the sericite one. The geochemistry of the alteration system was investigated using volume-composition and mass balance calculations. The volume factors obtained for the different alteration zones, mentioned above (being 1.64, 1.19, 1.17, and 1.07, respectively), indicate that replacement had taken place with a volume gain. The mass balance calculations revealed addition of SiO2, K2O, As, Cu, Rb, Ba, Ni, and Y to the system as a whole and subtraction of Fe2O3 from the system. Initial high aK+ and aH+ for the invading fluids is suggested. As the fluids migrated into wallrocks, they became more concentrated in Mg, Ca, and Na with increasing activities of CO2 and S. The calculated loss-gain data are in agreement with the microscopic observations. Breakdown of ferromagnesian minerals and feldspars in the quartz-sericite, sericite, and chlorite-sericite zones accompanied by loss in Mg, Fe, Ca, and Na under acidic conditions and low CO2/H2O ratio may obstruct the formation of carbonates and sulphides, and the precipitation of gold in these zones. The role of metamorphic fluids in the area is expected to be restricted to the liberation of Au and some associated elements from their hosts. [source]


    Breakdown of Casimir invariance in curved space-time

    ANNALEN DER PHYSIK, Issue 8 2010
    D. Singh
    Abstract It is shown that the commonly accepted definition for the Casimir scalar operators of the Poincaré group does not satisfy the properties of Casimir invariance when applied to the non-inertial motion of particles while in the presence of external gravitational and electromagnetic fields, where general curvilinear co-ordinates are used to describe the momentum generators within a Fermi normal co-ordinate framework. Specific expressions of the Casimir scalar properties are presented. While the Casimir scalar for linear momentum remains Lorentz invariant in the absence of external fields, this is no longer true for the spin Casimir scalar. Potential implications are considered for the propagation of photons, gravitons, and gravitinos as described by the spin-3/2 Rarita-Schwinger vector-spinor field. In particular, it is shown that non-inertial motion introduces a frame-based effective mass to the spin interaction, with interesting physical consequences that are explored in detail. [source]


    Into adulthood: a follow-up study of 718 young people who were placed in out-of-home care during their teens

    CHILD & FAMILY SOCIAL WORK, Issue 2 2008
    Bo Vinnerljung
    ABSTRACT In this study, national register data were used to analyse long-term outcomes at age 25 for around 700 Swedish young people placed in out-of-home care during their teens. The sample consisted of 70% of all 13- to 16-year olds who entered out-of-home care in 1991. Results revealed a dividing line between young people placed in care for behavioural problems and those placed for other reasons. Young woman and men from the first group had , in comparison with peers who did not enter care , very high rates of premature death, serious involvement in crime, hospitalizations for mental-health problems, teenage parenthood, self-support problems and low educational attainment. Young people who were placed for other reasons had better outcomes, but still considerably worse than non-care peers. Young women tended to do better than young men, regardless of reasons for placement. Very high rates of hospitalizations for mental health problems were found among young people placed for behavioural problems. Breakdown of placement was found to be a robust indicator of poor long-term prognosis. [source]


    Breakdown of teenage placements in Swedish foster and residential care

    CHILD & FAMILY SOCIAL WORK, Issue 2 2004
    Marie Sallnäs
    ABSTRACT This article deals with the problem of breakdown in different types of out-of-home care (foster care/residential care) for Swedish teenagers. How often are such placements prematurely terminated against the wishes and intentions of child welfare authorities? Which factors appear to increase or decrease the risk of placement breakdown? The sample consists of a national cohort of 776 youths who started 922 placements during 1991. Every placement was followed in municipal case files for a maximum period of five years. Between 30 and 37% of all placements were prematurely terminated, the exact figure depending on whether a narrow or wide definition of breakdown was applied. The lowest rates of breakdown were found in kinship care and secure units, the highest in non-kinship foster homes. Teenagers who display antisocial behaviour and/or have mental health problems constitute a high-risk category for most types of out-of-home care, but especially in non-kinship foster homes. Risk factors in relation to breakdown were analysed in the four main forms of Swedish out-of-home care separately (foster homes, privately/publicly run residential care and secure units). The analysis pointed out that risk factors are not the same in all types of care, but antisocial behaviour at time of placement increased the risk in most forms of care. Prior research indicates that placement breakdown is a major problem of child welfare in other countries, and this study found that Sweden is no exception. [source]


    Effects of pharmacological adrenergic and vagal modulation on fractal heart rate dynamics

    CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2001
    Mikko P. Tulppo
    Breakdown of short-term fractal-like behaviour of HR indicates an increased risk for adverse cardiovascular events and mortality, but the pathophysiological background for altered fractal HR dynamics is not known. Our aim was to study the effects of pharmacological modulation of autonomic function on fractal correlation properties of heart rate (HR) variability in healthy subjects. Short-term fractal scaling exponent (,1) along with spectral components of HR variability were analysed during the following pharmacological interventions in healthy subjects: (i) noradrenaline (NE) infusion (n=22), (ii) NE infusion after phentolamine (PHE) (n=8), (iii) combined NE + adrenaline (EPI) infusion (n=12), (iv) vagal blockade with high dose of atropine (n=10), (v) and vagal activation by low dose of atropine (n=10). Then ,1 decreased progressively during the incremental doses of NE (from 0·85 ± 0·250 to 0.55 ± 0·23, P<0·0001). NE also decreased the average HR (P<0·001) and increased the high frequency spectral power (P<0·001). Vagal blockade with atropine increased the ,1 value (from 0·82 ± 0·22 to 1·24 ± 0·41, P<0·05). Combined NE + EPI infusion and vagal activation with a low dose atropine did not result in any changes in ,1, and ,-adrenergic blockade by PHE did not completely reverse the effects of NE on ,1. Increased levels of circulating NE result in reduction of short-term correlation properties of HR dynamics. The results suggest that coactivation of cardiac vagal outflow at the time of high levels of a circulating sympathetic transmitter explains the breakdown of fractal-like behaviour of human HR dynamics. [source]


    Breakdown of the Camassa-Holm equation

    COMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 3 2004
    Henry P. McKean
    No abstract is available for this article. [source]


    A qualitative study examining tensions in interdoctor telephone consultations

    MEDICAL EDUCATION, Issue 8 2006
    Anupma Wadhwa
    Objective, Communication skills have gained increasing attention in medical education. Much of the existing literature and medical curricula addresses issues of doctor,patient communication. The critical importance of communication between health professionals, however, is now coming under the spotlight. The interdoctor telephone consultation is a common health care setting in which health professional communication skills are exercised. Breakdowns in this communication commonly occur and, surprisingly, this skill is not formally addressed in medical training. This study sought to clarify the communication issues that can occur during interdoctor telephone consultations in order to inform future educational initiatives in this domain. Methods, Data were collected and triangulated among 3 sources: documentation of 129 telephone consults received; 51 hours of field observations of consultants, and semi-structured interviews of 12 callers and 12 consultants. Analysis was performed using grounded theory methodology. Results, Overwhelmingly, participants described tensions with telephone consultation communication. Recurrent theme analysis revealed 5 key sources of tension: discursive features; context; fragmented clinical process; reason for call, and responsibility. Often, callers and consultants viewed similar instances in different and opposite manners, contributing to difficulties in the exchange. Further, a vicious cycle in which a participant's strategies to mitigate tension actually increased tension for the other participant was identified. Conclusions, Interdoctor telephone consultation has become an integral part of medical practice; however, tensions within this exchange can undermine its effectiveness. The results of this study provide a preliminary theory upon which an educational intervention to improve this communication skill can be based. [source]


    Further examining the triangle tip: Improving support for students with emotional and behavioral needs

    PSYCHOLOGY IN THE SCHOOLS, Issue 1 2009
    Lee Kern
    Students identified as having emotional and behavioral disorders (EBD) experience the poorest educational outcomes among any disability group. Although models of intervention and corresponding evidence-based practices continue to advance, the promise of new approaches has failed to reach the general population of students with EBD. In this artice, we visit possible explanations for these continued poor outcomes. Breakdowns along several systems are discussed, including placement and related practices as well as the absence of individualized approaches. In addition, we offer suggestions for improvement. © 2008 Wiley Periodicals, Inc. [source]


    Regional variations in action potential alternans in isolated murine Scn5a+/, hearts during dynamic pacing

    ACTA PHYSIOLOGICA, Issue 2 2010
    G. D. K. Matthews
    Abstract Aim:, Clinical observations suggest that alternans in action potential (AP) characteristics presages breakdown of normal ordered cardiac electrical activity culminating in ventricular arrhythmogenesis. We compared such temporal nonuniformities in monophasic action potential (MAP) waveforms in left (LV) and right ventricular (RV) epicardia and endocardia of Langendorff-perfused murine wild-type (WT), and Scn5a+/, hearts modelling Brugada syndrome (BrS) for the first time. Methods:, A dynamic pacing protocol imposed successively incremented steady pacing rates between 5.5 and 33 Hz. A signal analysis algorithm detected sequences of >10 beats showing alternans. Results were compared before and following the introduction of flecainide (10 ,m) and quinidine (5 ,m) known to exert pro- and anti-arrhythmic effects in BrS. Results:, Sustained and transient amplitude and duration alternans were both frequently followed by ventricular ectopic beats and ventricular tachycardia or fibrillation. Diastolic intervals (DIs) that coincided with onsets of transient (tr) or sustained (ss) alternans in MAP duration (DI*) and amplitude (DI,) were determined. Kruskal,Wallis tests followed by Bonferroni-corrected Mann,Whitney U -tests were applied to these DI results sorted by recording site, pharmacological conditions or experimental populations. WT hearts showed no significant heterogeneities in any DI. Untreated Scn5a+/, hearts showed earlier onsets of transient but not sustained duration alternans in LV endocardium compared with RV endocardium or LV epicardium. Flecainide administration caused earlier onsets of both transient and sustained duration alternans selectively in the RV epicardium in the Scn5a+/, hearts. Conclusion:, These findings in a genetic model thus implicate RV epicardial changes in the arrhythmogenicity produced by flecainide challenge in previously asymptomatic clinical BrS. [source]


    Caffeine and theophylline block insulin-stimulated glucose uptake and PKB phosphorylation in rat skeletal muscles

    ACTA PHYSIOLOGICA, Issue 1 2010
    A. J. Kolnes
    Abstract Aim:, Caffeine and theophylline inhibit phosphatidylinositol 3-kinase (PI3-kinase) activity and insulin-stimulated protein kinase B (PKB) phosphorylation. Insulin-stimulated glucose uptake involves PI3-kinase/PKB, and the aim of the present study was to test the hypothesis that caffeine and theophylline inhibit insulin-stimulated glucose uptake in skeletal muscles. Methods:, Rat epitrochlearis muscles and soleus strips were incubated with insulin and different concentrations of caffeine and theophylline for measurement of glucose uptake, force development and PKB phosphorylation. The effect of caffeine was also investigated in muscles stimulated electrically. Results:, Caffeine and theophylline completely blocked insulin-stimulated glucose uptake in both soleus and epitrochlearis muscles at 10 mm. Furthermore, insulin-stimulated PKB Ser473 and Thr308 and GSK-3, Ser9 phosphorylation were blocked by caffeine and theophylline. Caffeine reduced and theophylline blocked insulin-stimulated glycogen synthase activation. Caffeine stimulates Ca2+ release and force development increased rapidly to 10,20% of maximal tetanic contraction. Dantrolene (25 ,m), a well-known inhibitor of Ca2+ -release, prevented caffeine-induced force development, but caffeine inhibited insulin-stimulated glucose uptake in the presence of dantrolene. Contraction, like insulin, stimulates glucose uptake via translocation of glucose transporter-4 (GLUT4). Caffeine and theophylline reduced contraction-stimulated glucose uptake by about 50%, whereas contraction-stimulated glycogen breakdown was normal. Conclusion:, Caffeine and theophylline block insulin-stimulated glucose uptake independently of Ca2+ release, and the likely mechanism is via blockade of insulin-stimulated PI3-kinase/PKB activation. Caffeine and theophylline also reduced contraction-stimulated glucose uptake, which occurs independently of PI3-kinase/PKB, and we hypothesize that caffeine and theophylline also inhibit glucose uptake in skeletal muscles via an additional and hitherto unknown molecule involved in GLUT4 translocation. [source]


    Forearm and leg amino acid metabolism in the basal state and during combined insulin and amino acid stimulation after a 3-day fast

    ACTA PHYSIOLOGICA, Issue 3 2009
    J. Gjedsted
    Abstract Aim:, Fasting is characterized by a progressive loss of protein, but data on protein kinetics are unclear and few have studied the effects of re-feeding. The present study was designed to test the hypothesis that a combined infusion of insulin and amino acids after fasting would induce compensatory increases in protein synthesis and reductions in protein breakdown at the whole body level and in muscle. Methods:, We included 10 healthy male volunteers and studied them twice: (1) in the post-absorptive state and (2) after 72 h of fasting. Amino acid kinetics was measured using labelled phenylalanine and tyrosine, whole body energy expenditure was assessed and urea nitrogen synthesis rates were calculated. Results:, After fasting we observed an increase in arterial blood concentration of branched chain amino acids and a decrease in gluconeogenic amino acids (P < 0.05). Isotopically determined whole body, forearm and leg phenylalanine fluxes were unaltered apart from a 30% decrease in phenylalanine-to-tyrosine conversion (2.0 vs. 1.4 ,mol kg,1 h,1, P < 0.01). During infusion of insulin and amino acids, amino acid concentrations increased. Conclusion:, Our data indicate that after a 72-h fast basal and insulin/amino acid-stimulated regional phenylalanine fluxes in leg and forearm muscle are unaltered. During fasting concentrations of gluconeogenic amino acids decrease and hepatic and/or renal phenylalanine-to-tyrosine conversion decreases. Thus, as opposed to glucose and lipid metabolism, fasting does not induce insulin resistance as regards amino acid metabolism. [source]


    Stochastic and Relaxation Processes in Argon by Measurements of Dynamic Breakdown Voltages

    CONTRIBUTIONS TO PLASMA PHYSICS, Issue 7 2005
    V. Lj.
    Abstract Statistically based measurements of breakdown voltages Ub and breakdown delay times td and their variations in transient regimes of establishment and relaxation of discharges are a convenient method to study stochastic processes of electrical breakdown of gases, as well as relaxation kinetics in afterglow. In this paper the measurements and statistical analysis of the dynamic breakdown voltages Ub for linearly rising (ramp) pulses in argon at 1.33 mbar and the rates of voltage rise k up to 800 V s,1 are presented. It was found that electrical breakdowns by linearly rising (ramp) pulses is an inhomogeneous Poisson process caused by primary and secondary ionization coefficients , , , and electron yield Y variations on the voltage (time). The experimental breakdown voltage distributions were fitted by theoretical distributions by applying approximate analytical and numerical models. The afterglow kinetics in argon was studied based on the dependence of the initial electron yield on the relaxation time Y0 (, ) derived from fitting of distributions. The space charge decay was explained by the surface recombination of nitrogen atoms present as impurities. The afterglow kinetics and the surface recombination coefficients on the gas tube and cathode were determined from a gas-phase model. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Screening Breakdown in a Plasma by Two Laser Fields and Strong DC Magnetic Field

    CONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005
    D. F. Miranda
    Abstract The effective static dielectric constant of an electron plasma system in the simultaneous presence of two electromagnetic waves and a strong DC magnetic field is calculated. It is found that as the difference ,, of the two electromagnetic wave frequencies matches the plasma frequency ,, a breakdown in screening occurs thereby increasing the plasma heating rate via the external fields due to inverse Bremmstrahlung. An application is made by considering the typical parameters of a hot plasma. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Limited LCAs of pharmaceutical products: merits and limitations of an environmental management tool

    CORPORATE SOCIAL RESPONSIBILITY AND ENVIRONMENTAL MANAGEMENT, Issue 2 2003
    Anne Marie de Jonge
    This article explores both the merits and the limitations of life cycle analysis (LCA) as an environmental management tool in the framework of the pharmaceutical industry. In this study, limited LCAs in the form of product lifecycle-oriented energy balances were established for two rather different pharmaceutical products. Primary energy requirements served as the single indicator for the products' direct and indirect environmental impacts. The functional units of the products were defined as the one year treatments of average patients. The results of the case studies indicate that the portion of the active substance in the pharmaceutical end product is an important predictor for the breakdown of energy requirements and thus environmental impacts over the life cycle. Despite its limitations, the energy balances provide first-hand indications of where eco-efficiency measures should be taken. In this sense, the limited LCAs served as a useful environmental management tool. Copyright © 2003 John Wiley & Sons, Ltd. and ERP Environment [source]


    The Impact of Imperfect Processes on Production Run Times

    DECISION SCIENCES, Issue 4 2000
    Tonya Boone
    ABSTRACT This paper investigates the interaction between the economics of production and imperfections in the production process. Specifically, this paper is the first to devise a model in an attempt to provide managers with guidelines to choose the appropriate production run times to buffer against both the production of defective items and stoppages occurring due to machine breakdowns. In addition to providing several structural properties of the model, we show that a manager will always incur a cost penalty when (s)he uses the results of two oft-cited models-the EMQ (Economic Order/Manufacturing Quantity) and the NR-E (No-Resumption, Exponential machine breakdown)-to determine production run times. [source]