Distribution by Scientific Domains
Distribution within Life Sciences

Terms modified by FM

  • fm level
  • fm patient
  • fm protein
  • fm ratio

  • Selected Abstracts


    JOURNAL OF PHYCOLOGY, Issue 4 2001
    Jean-Paul Parkhill
    In biological oceanography, it has been widely accepted that the maximum quantum yield of photosynthesis is influenced by nutrient stress. A closely related parameter, the maximum quantum yield for stable charge separation of PSII, (,PSII)m, can be estimated by measuring the increase in fluorescence yield from dark-adapted minimal fluorescence (Fo) to maximal fluorescence (Fm) associated with the closing of photosynthetic reaction centers with saturating light or with a photosynthetic inhibitor such as 3,-(3,4-dichlorophenyl)-1,,1,-dimethyl urea (DCMU). The ratio Fv/Fm (= (Fm, Fo)/Fm) is thus used as a diagnostic of nutrient stress. Published results indicate that Fv/Fm is depressed for nutrient-stressed phytoplankton, both during nutrient starvation (unbalanced growth) and acclimated nutrient limitation (steady-state or balanced growth). In contrast to published results, fluorescence measurements from our laboratory indicate that Fv/Fm is high and insensitive to nutrient limitation for cultures in steady state under a wide range of relative growth rates and irradiance levels. This discrepancy between results could be attributed to differences in measurement systems or to differences in growth conditions. To resolve the uncertainty about Fv/Fm as a diagnostic of nutrient stress, we grew the neritic diatom Thalassiosira pseudonana (Hustedt) Hasle et Heimdal under nutrient-replete and nutrient-stressed conditions, using replicate semicontinuous, batch, and continuous cultures. Fv/Fm was determined using a conventional fluorometer and DCMU and with a pulse amplitude modulated (PAM) fluorometer. Reduction of excitation irradiance in the conventional fluorometer eliminated overestimation of Fo in the DCMU methodology for cultures grown at lower light levels, and for a large range of growth conditions there was a strong correlation between the measurements of Fv/Fm with DCMU and PAM (r2 = 0.77, n = 460). Consistent with the literature, nutrient-replete cultures showed consistently high Fv/Fm (,0.65), independent of growth irradiance. Under nutrient-starved (batch culture and perturbed steady state) conditions, Fv/Fm was significantly correlated to time without the limiting nutrient and to nutrient-limited growth rate before starvation. In contrast to published results, our continuous culture experiments showed that Fv/Fm was not a good measure of nutrient limitation under balanced growth conditions and remained constant (,0.65) and independent of nutrient-limited growth rate under different irradiance levels. Because variable fluorescence can only be used as a diagnostic for nutrient-starved unbalanced growth conditions, a robust measure of nutrient stressed oceanic waters is still required. [source]

    Is a short, sharp shock equivalent to long-term punishment?

    PLANT CELL & ENVIRONMENT, Issue 4 2009
    Contrasting the spatial pattern of acute, chronic ozone damage to soybean leaves via chlorophyll fluorescence imaging
    ABSTRACT Experimental investigations of ozone (O3) effects on plants have commonly used short, acute [O3] exposure (>100 ppb, on the order of hours), while in field crops damage is more likely caused by chronic exposure (<100 ppb, on the order of weeks). How different are the O3 effects induced by these two fumigation regimes? The leaf-level photosynthetic response of soybean to acute [O3] (400 ppb, 6 h) and chronic [O3] (90 ppb, 8 h d,1, 28 d) was contrasted via simultaneous in vivo measurements of chlorophyll a fluorescence imaging (CFI) and gas exchange. Both exposure regimes lowered leaf photosynthetic CO2 uptake about 40% and photosystem II (PSII) efficiency (Fq,/Fm,) by 20% compared with controls, but this decrease was far more spatially heterogeneous in the acute treatment. Decline in Fq,/Fm, in the acute treatment resulted equally from decreases in the maximum efficiency of PSII (Fv,/Fm,) and the proportion of open PSII centres (Fq,/Fv,), but in the chronic treatment decline in Fq,/Fm, resulted only from decrease in Fq,/Fv,. Findings suggest that acute and chronic [O3] exposures do not induce identical mechanisms of O3 damage within the leaf, and using one fumigation method alone is not sufficient for understanding the full range of mechanisms of O3 damage to photosynthetic production in the field. [source]

    Chlorophyll fluorescence, predawn water potential and photosynthesis in precipitation pulse-driven ecosystems , implications for ecological studies

    FUNCTIONAL ECOLOGY, Issue 3 2008
    V. Resco
    Summary 1A major research focus in population and community ecology is to establish a mechanistic understanding of plant interactions and demographic responses. The first step towards this mechanistic approach relies on understanding the differences in stress caused by different environmental conditions. Leaf-level photosynthetic rate (A) within and among plant populations provides important insight into population and community processes, but is difficult to acquire with sufficient replication under field conditions. Instead, chlorophyll fluorescence (Fv/Fm) and predawn water potential (,pd) are often used in arid and semi-arid ecosystems. 2Fv/Fm reflects the photoactivation status of photosystem II (PSII), whereas ,pd indicates water availability in the rhizosphere. Here we compare these indices with A in two perennial C4 grasses (native Heteropogon contortus and invasive Eragrostis lehmanniana) and in seedlings of the C3 shrub Prosopis velutina growing on highly contrasting sandy loam and loamy clay soils in experimental plots. Measurements were made the day prior to and up to 7 days following a 39-mm rainfall pulse after 2 months of drought. 3A was more sensitive across a broad range of environmental conditions, whereas Fv/Fm and ,pd only responded to periods of protracted drought. The use of these measures was further complicated because their values varied daily and we observed different time-lags in their response to precipitation pulses. 4We suggest sampling schemes and a priori measurements to capture the value that is representative for the question of interest, and that match the pulsed biological activity in these ecosystems. Finally, we suggest the use of these measures in combination with measurements providing integration over longer time periods, such as ,13C, ,18O and N concentration in bulk leaf tissue. [source]

    Stress-induced dynamic adjustments of reproduction differentially affect fitness components of a semi-arid plant

    JOURNAL OF ECOLOGY, Issue 1 2008
    Cristina F. Aragón
    Summary 1Summer drought stress is considered the primary constraint to plant performance in Mediterranean ecosystems. However, little is known about the implications of summer stress for plant reproduction under real field conditions and, particularly, for the regulatory mechanisms of maternal investment in reproduction. 2The relationship between plant physiological status at different reproductive stages over the course of the summer drought period and final reproductive output was modelled in the Mediterranean semi-arid specialist Helianthemum squamatum. 3Plant physiological status, assessed by the chlorophyll fluorescence-based parameter Fv/Fm, and soil moisture content beneath each plant, were determined in the field at five key phenological moments in a total of 88 plants. We used Generalized Linear Mixed Models to evaluate the effect of plant physiological status at those different dates on several components of reproduction (number of flowers and seeds per plant, fruit-set and intra-fruit seed abortion). We included soil moisture as an additional predictor to statistically control its potential effect on reproduction. 4Fv/Fm measured at midday was a significant predictor of reproductive output, but its significance varied over time and with the specific reproductive response variable. Fv/Fm measured at the onset of flowering was positively related to the number of flowers and seeds per plant, whereas Fv/Fm at the fruiting peak positively affected fruit-set. Soil moisture content was only significant when measured before flowering, being positively related to total flowers and seeds. The effect of stress on reproductive output acted either at an early stage of the reproductive season, by varying the number of flowers produced and seed primordia initiated, or at a later stage, by adjusting the number or ripe fruits. 5Synthesis. Our results show a direct relationship between physiological status and reproduction, and highlight the importance of the timing of stress for reproductive success. They also show that small departures from the physiological optimum at specific reproductive stages may cause significant decreases in the reproductive output. We suggest that the dynamic adjustment of reproduction in response to stress is adaptive in fluctuating and unpredictable Mediterranean semi-arid environments, where an adequate temporal distribution of maternal resources determines the species' ability to withstand severe environmental conditions. [source]

    Population pharmacokinetic and pharmacodynamic modelling of the antimalarial chemotherapy chlorproguanil/dapsone

    Julie A. Simpson
    Aims To determine the population pharmacokinetics of chlorproguanil, dapsone and the active metabolite of chlorproguanil, chlorcycloguanil; and to estimate the duration of parasitocidal activity for chlorpoguanil/dapsone against Plasmodium falciparum isolates of varying sensitivity. Methods Rich and sparse pharmacokinetic data were collected prospectively from: healthy volunteers (n = 48) and adults (n = 65) and children (n = 68) suffering from P. falciparum malaria. All subjects received 2.0 mg kg,1 of chlorproguanil and 2.5 mg kg,1 of dapsone. Results The population pharmacokinetic parameter estimates for chlorproguanil were ka = 00.09 h,1 (intersubject variability was 44%), CL/F = 51.53 l h,1 (57%), CLD/F = 54.67 l h,1, V1/F = 234.40 l (50%) and V2/F = 1612.75 l; for dapsone were ka = 00.93 h,1, CL/F = 1.99 l h,1 (72%) and V/F = 76.96 l (48%); and for chlorcycloguanil were CLm/Fm = 3.72 l h,1 kg,1 (67%) and Vm/Fm = 12.76 l kg,1 (64%). For dapsone, CL/F and V/F were both significantly positively correlated with body weight. For a 10-kg child, the mean duration of parasitocidal activity for chlorproguanil/dapsone against the three most susceptible P. falciparum strains was 4.5 days [5th and 95th percentiles 2.4, 7.3] for W282; 5.9 days (3.6, 9.7) for ItG2F6; and 6.1 days (3.7, 10.1) for K39. For an isolate with the ile-164-leu mutation, V1/S, activity ranged from 0.8 days (0.0, 3.3) for a 10-kg child to 1.8 days (0.0, 4.0) for a 60-kg adult. Conclusions Plasmodium falciparum malaria has no effect on the pharmacokinetic parameters for chlorproguanil, dapsone or chlorcycloguanil. Chlorproguanil/dapsone will probably prove to be ineffective against parasite strains with the mutation ile-164-leu, were these to become prevalent in Africa. [source]

    Oxygen evolution and respiration of the cyanobacterium Synechocystis sp.

    PCC 6803 under two different light regimes applying light/dark intervals in the time scale of minutes
    The photosynthetic performance of the cyanobacterium Synechocystis sp. PCC 6803 exposed to intermittent light was studied by measuring oxygen evolution, respiration and the fluorescence parameters for maximum efficiency of excitation energy capture by photosystem II (PSII) reaction centres (Fv/Fm), PSII quantum yield (,F/Fm1) and non-photochemical quenching (NPQ). Cultures were pre-acclimated to constant light conditions. Block and sinusoidal light regimes were tested using four photon-flux densities (PFDs) applied in light/dark intervals of 1:1, 5:5 and 10:10 min. Light use was higher under the sinusoidal light regime compared with the block regime. The accumulated gross photosynthesis of the cyanobacterium was lower under intermittent light conditions compared with predictions from the photosynthesis-irradiance curve (PI curve). The respiration rates were similar for all light/dark intervals tested. However, the respiration slightly increased with increasing oxygen production for both block and sinusoidal light regime. NPQ, ,F/Fm, and Fv/Fm depended on the PFD rather than on the duration of the light/dark intervals tested, and there was no detected influence of the two applied light regimes. [source]

    DNA damage and photosynthesis in Antarctic and Arctic Sanionia uncinata (Hedw.) Loeske under ambient and enhanced levels of UV-B radiation

    PLANT CELL & ENVIRONMENT, Issue 12 2002
    D. LUD
    Abstract The response of the bipolar moss Sanionia uncinata (Hedw.) Loeske to ambient and enhanced UV-B radiation was investigated at an Antarctic (Léonie Island, 67°35, S, 68°20, W) and an Arctic (Ny-Alesund, 78°55, N, 11°56, E) site, which differed in ambient UV-B radiation (UV-BR: 280,320 nm) levels. The UV-BR effects on DNA damage and photosynthesis were investigated in two types of outdoor experiments. First of all, sections of turf of S. uncinata were collected in an Arctic and Antarctic field site and exposed outdoors to ambient and enhanced UV-BR for 2 d using UV-B Mini-lamps. During these experiments, chlorophyll a fluorescence, chlorophyll concentration and cyclobutyl pyrimidine dimer (CPD) formation were measured. Secondly, at the Antarctic site, a long-term filter experiment was conducted to study the effect of ambient UV-BR on growth and biomass production. Additionally, sections of moss turf collected at both the Antarctic and the Arctic site were exposed to UV-BR in a growth chamber to study induction and repair of CPDs under controlled conditions. At the Antarctic site, a summer midday maximum of 2·1 W m,2 of UV-BR did not significantly affect effective quantum yield (,F/Fm,) and the ratio of variable to maximal fluorescence (Fv/Fm). The same was found for samples of S. uncinata exposed at the Arctic site, where summer midday maxima of UV-BR were about 50% lower than at the Antarctic site. Exposure to natural UV-BR in summer did not increase CPD values significantly at both sites. Although the photosynthetic activity remained largely unaffected by UV-B enhancement, DNA damage clearly increased as a result of UV-B enhancement at both sites. However, DNA damage induced during the day by UV-B enhancement was repaired overnight at both sites. Results from the long-term filter experiment at the Antarctic site indicated that branching of S. uncinata was reduced by reduction of ambient summer levels of UV-BR, whereas biomass production was not affected. Exposure of specimens collected from both sites to UV-BR in a growth chamber indicated that Antarctic and Arctic S. uncinata did not differ in UV-BR-induced DNA damage. It was concluded that S. uncinata from both the Antarctic and the Arctic site is well adapted to ambient levels of UV-BR. [source]

    Evaluation of instant light-response curves of chlorophyll fluorescence parameters obtained with a portable chlorophyll fluorometer on site in the field

    PLANT CELL & ENVIRONMENT, Issue 12 2000
    U. Rascher
    ABSTRACT Miniaturized pulse-amplitude modulated photosynthesis yield analysers are primarily designed for measuring effective quantum yield (,F/Fm,) of photosystem II under momentary ambient light conditions in the field. Although this provides important ecophysiological information, it is often necessary to learn more about the potential intrinsic capacities of leaves by measuring light-response curves. Thus, instruments provide light-curve programmes, where light intensities are increased in short intervals and instant light-response curves are recorded within a few minutes. This method can be criticized because photosynthesis will most likely not be in steady state. This technical report shows that with the appropriate precautions instant light curves can nevertheless provide reliable information about cardinal points of photosynthesis. First, the geometry of the light source of the instrument in relation to the quantum sensor must be considered and quantum sensor readings must be corrected. Second, the measurements of the light-response curves must be compared with readings of effective quantum yield of photosystem II under ambient light conditions where photosynthesis is in steady state. This may show that in the critical range of the light curves either both measurements perfectly coincide or are offset against each other by a constant value (examples are given here). In the first case results of light curves can be taken at face values, and in the second case a simple correction can be applied. With these precautions and careful interpretations instant light-response curves can be an enormous advantage in ecophysiological field work. [source]

    Contributions of diffusional limitation, photoinhibition and photorespiration to midday depression of photosynthesis in Arisaema heterophyllum in natural high light

    PLANT CELL & ENVIRONMENT, Issue 3 2000
    Hiroyuki Muraoka
    ABSTRACT Diurnal changes in photosynthetic gas exchange and chlorophyll fluorescence were measured under full sunlight to reveal diffusional and non-diffusional limitations to diurnal assimilation in leaves of Arisaema heterophyllum Blume plants grown either in a riparian forest understorey (shade leaves) or in an adjacent deforested open site (sun leaves). Midday depressions of assimilation rate (A) and leaf conductance of water vapour were remarkably deeper in shade leaves than in sun leaves. To evaluate the diffusional (i.e. stomatal and leaf internal) limitation to assimilation, we used an index [1,A/A350], in which A350 is A at a chloroplast CO2 concentration of 350 ,mol mol,1. A350 was estimated from the electron transport rate (JT), determined fluorometrically, and the specificity factor of Rubisco (S), determined by gas exchange techniques. In sun leaves under saturating light, the index obtained after the ,peak' of diurnal assimilation was 70% greater than that obtained before the ,peak', but in shade leaves, it was only 20% greater. The photochemical efficiency of photosystem II (,F/Fm,) and thus JT was considerably lower in shade leaves than in sun leaves, especially after the ,peak'. In shade leaves but not in sun leaves, A at a photosynthetically active photon flux density (PPFD) > 500 ,mol m,2 s,1 depended positively on JT throughout the day. Electron flows used by the carboxylation and oxygenation (JO) of RuBP were estimated from A and JT. In sun leaves, the JO/JT ratio was significantly higher after the ,peak', but little difference was found in shade leaves. Photorespiratory CO2 efflux in the absence of atmospheric CO2 was about three times higher in sun leaves than in shade leaves. We attribute the midday depression of assimilation in sun leaves to the increased rate of photorespiration caused by stomatal closure, and that in shade leaves to severe photoinhibition. Thus, for sun leaves, increased capacities for photorespiration and non-photochemical quenching are essential to avoid photoinhibitory damage and to tolerate high leaf temperatures and water stress under excess light. The increased Rubisco content in sun leaves, which has been recognized as raising photosynthetic assimilation capacity, also contributes to increase in the capacity for photorespiration. [source]

    Contact allergy to farnesol in 2021 consecutively patch tested patients.

    CONTACT DERMATITIS, Issue 3 2004
    Results of the IVDK
    Farnesol is one of the fragrances considered to be a significant contact allergen. Therefore, it was decided by the European Union to label products containing farnesol. Farnesol was tested [5% petrolatum (pet.)] together with the standard series between 1 January 2003 and 30 June 2003 in 2021 consecutive patients, 1243 females and 778 males. Of these, 22 [1.1%, 95% confidence interval (CI): 0.7,1.6%] had a positive reaction to farnesol. 147 (8.1%) of those 1825 tested to Myroxylon pereirae resin (balsam of Peru, 25% pet.) at the same time reacted positively, 143 (7.8%) of those 1823 tested to the fragrance mix (FM) (8% pet.) and 34 (1.9%) of 1831 tested to propolis (10% pet.). With regard to concomitant reactions in farnesol-positive patients, 5 of 22 reacted additionally to the FM [odds ratio (OR): 4.3; CI: 1.53,12.15] and 2 (of these 5) additionally to M. pereirae resin (OR: 1.27; CI: 0.29,5.54). The strongest association was seen to propolis (OR: 6.2; 95% CI: 1.4,27.7). Compared to those with negative reactions to farnesol, the group of patients allergic to farnesol was characterized by a higher proportion of young females and office workers, and the hand and the face were more often affected. In conclusion, farnesol is an important allergen. We recommend that farnesol should be included in a fragrance patch-test preparation and that its use should be regulated for consumer safety reasons. Furthermore, the extent of exposure to farnesol should be further studied. [source]

    Multicentre study of fragrance allergy in Hungary

    CONTACT DERMATITIS, Issue 6 2002
    Immediate, late type reactions
    The authors followed the frequency of fragrance contact sensitization in Hungary in a multicentre study in the years 1998 and 1999. A total of 3604 patients were tested with fragrance mix (FM), and positive reactions were observed in 294 (8.2%). In 160 FM hypersensitive patients, the study was continued with patch testing of the mix constituents (cinnamic alcohol, cinnamic aldehyde, eugenol, amyl cinnamic aldehyde, hydroxycitronellal, geraniol, isoeugenol, oak moss absolute). Of the patients tested, 70.6% produced positive reactions to the constituents. FM contact sensitization was mainly observed in female patients (74.4%). The incidence of contact urticaria in FM hypersensitive patients was 6.1%. Simultaneous patch test trials of other environmental contact allergens, in both early and late evaluations, mainly confirmed hypersensitivity reactions to balsams. Female dominance of hypersensitivity reactions observed during testing the individual components of the mix was striking (82.4%). In positive skin reactions, cinnamic alcohol, isoeugenol and oak moss provoked skin symptoms most frequently. We also tested the 104 patients who produced negative reactions to FM with the constituent individual allergens, with 11.9% positive incidence. The clinical symptoms of the patients were above all manifest in the form of contact eczema, located on the hands, face, eyelids and axillae. With this study, the authors, members of the Hungarian Contact Dermatitis Research Group, call attention to one of the most frequent allergens in the environment. [source]

    Minor long-term changes in weight have beneficial effects on insulin sensitivity and ,-cell function in obese subjects

    A. M. Rosenfalck
    SUMMARY Aim To evaluate the long-term effect of changes in body composition induced by weight loss on insulin sensitivity (SI), non-insulin mediated glucose disposal, glucose effectiveness (SG) and ,-cell function. Design Glucose metabolism was evaluated before and after participation in a two-year weight loss trial of Orlistat vs. placebo, combined with an energy and fat restricted diet. Subjects Twelve obese patients (11 women, 1 man), age 45.8 ± 10.5 years, body weight (BW) 99.7 ± 13.3 kg, BMI 35.3 ± 2.8 kg/m2. Measurements At inclusion and 2 years later an oral glucose tolerance test (OGTT) and a frequently sampled intravenous glucose tolerance test (FSIGT) were performed. Body composition was estimated by a dual-energy X-ray absorptiometry (DXA) whole body scanning. Results The patients obtained varying changes in BW ranging from a weight loss of 17.8 kg to a weight gain of 6.0 kg. Corresponding changes in fat mass (FM) varied from a 40% reduction to a 19% increase. A significant decrease in both fasting (p =,0.038) and 2 h (p =,0.047) blood glucose at OGTT was found. The improvement in insulin sensitivity (SI) estimated by means of Bergmans Minimal Model, was significantly and linearly correlated to change in total FM (r = , 0.83, p =,0.0026). A multiple regression analysis showed that changes in truncal FM was the strongest predictor of change in SI explaining 67% of the variation. First phase insulin response (AIRg) remained unchanged whereas insulin disposition index increased significantly (p =,0.044). At inclusion five patients had impaired glucose tolerance of which four, who lost weight, were normalized at the retest 2 years later. Conclusion In obese subjects long-term minimal or moderate changes in weight were found to be linearly associated with changes in insulin sensitivity. In obese subjects with impaired glucose tolerance even a minor weight loss was able to normalize glucose tolerance. [source]

    Risk factors for suicide attempts in patients with alcohol dependence or abuse and a history of depressive symptoms: A subgroup analysis from the WHO/ISBRA study

    Abstract Introduction and Aims. Alcoholism, depression and suicide attempts (SA) are strongly interrelated. The aims were to determine risk factors and develop a prognostic predictor model for SA in a subgroup of patients with a history of alcohol dependence or abuse and depressive symptoms. Design and Methods. A subgroup analysis from the data of the World Health Organisation (WHO)/the International Society for Biomedical Research on Alcoholism (ISBRA)-collaborative study on biological state and trait marker of alcohol use and dependence, an international multi-centre study with a cross-sectional design, based on a standardised questionnaire. We analysed from 1314 variables 43 factors,including demographic characteristics, dependence variables, comorbid disorders, personality trait markers and family history,that were supposed to be most predictive for SA according to the literature. Correlation analyses by the ,2 -test and Mann,Whitney U -test were performed to obtain statistical meaningful parameters for logistic regression analysis. Results. Of the 1863 persons included in the WHO/ISBRA study, 292 had both a history of depressive symptoms and alcohol dependence or abuse and were included in the subgroup analysis. In the logistic regression analysis, drinking status, depressive symptoms, adverse drinking experiences during alcohol consumption, bad experiences from drug abuse and antidepressant therapy were found to be independent risk factors for SA. Positive family history of alcoholism was a model-improving co-factor. This predictive model explains approximately 60% of the variance (Nagelkerkes' square). Discussion and Conclusions. This prognostic model derived from data of the WHO/ISBRA collaborative study shows important risk factors for SA in patients with history of alcohol abuse or dependence and depressive symptoms. [ Yaldizli Ö, Kuhl HC, Graf M, Wiesbeck GA, Wurst FM. Risk factors for suicide attempts in patients with alcohol dependence or abuse and a history of depressive symptoms: A subgroup analysis from the WHO/ISBRA study. Drug Alcohol Rev 2009] [source]

    The magnocellular theory of developmental dyslexia

    DYSLEXIA, Issue 1 2001
    John Stein
    Abstract Low literacy is termed ,developmental dyslexia' when reading is significantly behind that expected from the intelligence quotient (IQ) in the presence of other symptoms,incoordination, left,right confusions, poor sequencing,that characterize it as a neurological syndrome. 5,10% of children, particularly boys, are found to be dyslexic. Reading requires the acquisition of good orthographic skills for recognising the visual form of words which allows one to access their meaning directly. It also requires the development of good phonological skills for sounding out unfamiliar words using knowledge of letter sound conversion rules. In the dyslexic brain, temporoparietal language areas on the two sides are symmetrical without the normal left-sided advantage. Also brain ,warts' (ectopias) are found, particularly clustered round the left temporoparietal language areas. The visual magnocellular system is responsible for timing visual events when reading. It therefore signals any visual motion that occurs if unintended movements lead to images moving off the fovea (,retinal slip'). These signals are then used to bring the eyes back on target. Thus, sensitivity to visual motion seems to help determine how well orthographic skill can develop in both good and bad readers. In dyslexics, the development of the visual magnocellular system is impaired: development of the magnocellular layers of the dyslexic lateral geniculate nucleus (LGN) is abnormal; their motion sensitivity is reduced; many dyslexics show unsteady binocular fixation; hence poor visual localization, particularly on the left side (left neglect). Dyslexics' binocular instability and visual perceptual instability, therefore, can cause the letters they are trying to read to appear to move around and cross over each other. Hence, blanking one eye (monocular occlusion) can improve reading. Thus, good magnocellular function is essential for high motion sensitivity and stable binocular fixation, hence proper development of orthographic skills. Many dyslexics also have auditory/phonological problems. Distinguishing letter sounds depends on picking up the changes in sound frequency and amplitude that characterize them. Thus, high frequency (FM) and amplitude modulation (AM) sensitivity helps the development of good phonological skill, and low sensitivity impedes the acquisition of these skills. Thus dyslexics' sensitivity to FM and AM is significantly lower than that of good readers and this explains their problems with phonology. The cerebellum is the head ganglion of magnocellular systems; it contributes to binocular fixation and to inner speech for sounding out words, and it is clearly defective in dyslexics. Thus, there is evidence that most reading problems have a fundamental sensorimotor cause. But why do magnocellular systems fail to develop properly? There is a clear genetic basis for impaired development of magnocells throughout the brain. The best understood linkage is to the region of the Major Histocompatibility Complex (MHC) Class 1 on the short arm of chromosome 6 which helps to control the production of antibodies. The development of magnocells may be impaired by autoantibodies affecting the developing brain. Magnocells also need high amounts of polyunsaturated fatty acids to preserve the membrane flexibility that permits the rapid conformational changes of channel proteins which underlie their transient sensitivity. But the genes that underlie magnocellular weakness would not be so common unless there were compensating advantages to dyslexia. In developmental dyslexics there may be heightened development of parvocellular systems that underlie their holistic, artistic, ,seeing the whole picture' and entrepreneurial talents. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Diagnosis Clusters for Emergency Medicine

    Debbie A. Travers RN
    Objectives: Aggregated emergency department (ED) data are useful for research, ED operations, and public health surveillance. Diagnosis data are widely available as The International Classification of Diseases, version, 9, Clinical Modification (ICD-9-CM) codes; however, there are over 24,000 ICD-9-CM code-descriptor pairs. Standardized groupings (clusters) of ICD-9-CM codes have been developed by other disciplines, including family medicine (FM), internal medicine (IM), inpatient care (Agency for Healthcare Research and Quality [AHRQ]), and vital statistics (NCHS). The purpose of this study was to evaluate the coverage of four existing ICD-9-CM cluster systems for emergency medicine. Methods: In this descriptive study, four cluster systems were used to group ICD-9-CM final diagnosis data from a southeastern university tertiary referral center. Included were diagnoses for all ED visits in July 2000 and January 2001. In the comparative analysis, the authors determined the coverage in the four cluster systems, defined as the proportion of final diagnosis codes that were placed into clusters and the frequencies of diagnosis codes in each cluster. Results: The final sample included 7,543 visits with 19,530 diagnoses. Coverage of the ICD-9-CM codes in the ED sample was: AHRQ, 99%; NCHS, 88%; FM, 71%; IM, 68%. Seventy-six percent of the AHRQ clusters were small, defined as grouping <1% of the diagnosis codes in the sample. Conclusions: The AHRQ system provided the best coverage of ED ICD-9-CM codes. However, most of the clusters were small and not significantly different from the raw data. [source]

    Accumulation and DNA damage in fathead minnows (Pimephales promelas) exposed to 2 brominated flame-retardant mixtures, Firemaster® 550 and Firemaster® BZ-54

    Jonathan S. Bearr
    Abstract Firemaster® 550 and Firemaster® BZ-54 are two brominated formulations that are in use as replacements for polybrominated diphenyl ether (PBDE) flame retardants. Two major components of these mixtures are 2,3,4,5-tetrabromo-ethylhexylbenzoate (TBB) and 2,3,4,5-tetrabromo-bis(2-ethylhexyl) phthalate (TBPH). Both have been measured in environmental matrices; however, scant toxicological information exists. The present study aimed to determine if these brominated flame-retardant formulations are bioavailable and adversely affect DNA integrity in fish. Fathead minnows (Pimephales promelas) were orally exposed to either FM 550, FM BZ54, or the nonbrominated form of TBPH, di-(2-ethylhexyl) phthalate (DEHP) for 56 d and depurated (e.g., fed clean food) for 22 d. At several time points, liver and blood cells were collected and assessed for DNA damage. Homogenized fish tissues were extracted and analyzed on day 0 and day 56 to determine the residue of TBB and TBPH and the appearance of any metabolites using gas chromatography-electron-capture negative ion mass spectrometry (GC/ECNI-MS). Significant increases (p,<,0.05) in DNA strand breaks from liver cells (but not blood cells) were observed during the exposure period compared with controls, although during depuration these levels returned to control. Both parent compounds, TBB and TBPH, were detected in tissues at approximately 1% of daily dosage along with brominated metabolites. The present study provides evidence for accumulation, metabolism, and genotoxicity of these new formulation flame retardants in fish and highlights the potential adverse effects of TBB- and TBPH-formulated fire retardants to aquatic species. Environ. Toxicol. Chem. 2010;29:722,729. © 2009 SETAC [source]

    Body composition in young Standardbreds in training: relationships to body condition score, physiological and locomotor variables during exercise

    C. LELEU
    Summary Reasons for performing study: Body composition is an essential factor in athletic performance of human sprinters and long distance runners. However, in horses, many questions remain concerning relationships between body composition and performance in the different equine activities. Objectives: To determine relationships between body composition, body score, physiological and locomotor variables in a population of young Standardbreds in training. Methods: Twenty-four 2-year-old Standardbreds were studied, body condition on a scale 0,5 and bodyweight recorded, and height at withers measured. Percentage of fat (%F), fat mass (FM) and fat free mass (FFM) were estimated echographically. During a standardised exercise test on the track, velocity, heart rate, respiratory frequency and blood lactate concentrations were measured. V4 and V200 (velocity for a blood lactate concentration of 4 mmol/1 and velocity of 200 beats/min) calculated. Basic gait variables were measured at 3 different speeds with an accelerometric device. Results: Body composition variables: %F and FM were significantly related to body condition score and physiological variables. Body score was highly correlated to %F (r=0.64) and FM (r = 0.71). V4 was negatively correlated to %V (r=-0.59) and FM (r = -0.60), P<0.05. V200 was also negatively related to %F and FM, (r=-0.39 and r = -0.37, respectively, P<0.1). No relationships were found between body composition and gait characteristics. Conclusions: Body composition was closely related to indirect measurements of aerobic capacity, which is a major factor of athletic performance in middle distance running horses. Potential relevance: As in human athletes, trainers should take special note to evaluate optimal bodyweight and body composition of race horses to optimise performance. [source]

    Impact of body fat mass extent on cardiac autonomic alterations in women

    J. Sztajzel
    Abstract Background, Obesity has been associated with significant abnormalities of the cardiac autonomic regulation. However, the precise impact of increasing body weight on cardiac autonomic function and the metabolic and hormonal contributors to these changes are presently unclear. The aim of our study was to explore in subjects with increasing values of body mass index (BMI) the alterations of cardiac autonomic function and to establish the potential role of various metabolic and hormonal contributors to these alterations. Materials and methods, We investigated time and frequency domain heart rate variability (HRV) parameters taken from 24-h Holter recordings, and several anthropometric, metabolic and hormonal parameters (plasma glucose, insulin, triglycerides, free fatty acids, leptin and adiponectin) in 68 normoglycaemic and normotensive women (mean age of 40 ± 3 years), subdivided according to their BMI into 15 normal body weight (controls), 15 overweight, 18 obese and 20 morbidly obese. Results, Heart rate was increased and HRV was decreased in the morbidly obese group as compared with controls. In overall population, a negative association linked body fat mass (FM) to HRV indices. None of the metabolic and hormonal parameters were significantly related to the HRV indices, after they were adjusted for the body FM. Conclusions, Morbidly obese, normoglycaemic and normotensive young women have increased HR and low HRV, indicating an abnormal cardiac autonomic function and representing a risk factor for adverse cardiovascular events. A decrease of HRV parameters is associated with a progressive increase of body FM. Other metabolic and hormonal factors, characterising obesity, do not show an independent influence on these HRV alterations. [source]

    Two Cobalt Compounds Based on Azide/Methoxy and Isonicotinate N -Oxide Ligands Exhibiting Ferromagnetic and Antiferromagnetic Interactions

    Fu-Chen Liu
    Abstract Two new CoII complexes, [Co(OCH3)L] (1) and [Co3(N3)4(OCH3)2L2] (2) (L = isonicotinate N -oxide), were synthesized by solvothermal reaction and magnetically characterized. The cobalt ions in 1 and 2 all exhibit distorted octahedral coordination geometry. In 1, there is a ,11 -methoxy/syn,syn -carboxylate mixed coordinated cobalt chain with mixed coordination, and a 3D structure is formed by the chains linked through the L ligands. In 2, the alternating CoII chains that are formed by linking the double end-on azide-bridged trimers are connected by the L ligands to form a 2D layer. Magnetic studies revealed that ferromagnetic coupling exists between the CoII ions in 1, and 1 undergoes a ferromagnetic transition at 2.5 K, whereas alternating ferromagnetic (FM) and antiferromagnetic (AFM) interactions exist in the chain of 2. [source]

    CLINICAL STUDY: A comparison of exposure to carcinogens among roll-your-own and factory-made cigarette smokers

    ADDICTION BIOLOGY, Issue 3 2009
    Lion Shahab
    ABSTRACT Consumption of roll-your-own (RYO) tobacco is rising, but little is known about its in vivo delivery of toxins relative to factory-made (FM) cigarettes. To start to address this issue, this study compared the concentrations of metabolites of recognized human carcinogens in smokers of RYO tobacco and FM cigarettes. We opportunistically recruited 127 FM and 28 RYO cigarette smokers in central London and collected saliva and urine samples. Saliva samples were assayed for cotinine while urinary samples were assayed for 1-hydroxypyrene (1-HOP) and total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), metabolic markers of polycyclic aromatic hydrocarbons and tobacco-specific N -nitrosamines, respectively. Data on socio-demographic, anthropometric and puffing characteristics were also obtained. Both unadjusted and adjusted analyses (controlling for age, sex, body mass index, puff flow, puff duration and cotinine) showed no difference in metabolic markers between RYO and FM cigarette smokers. However, significant main effects for cotinine levels and sex were observed in adjusted analyses. Greater levels of cotinine were associated with a greater concentration of both 1-HOP (B = 0.002, P = 0.037) and NNAL (B = 0.002, P < 0.001). In addition, women had significantly greater concentrations of urinary 1-HOP (B = 0.679, P = 0.004) and total NNAL metabolites (B = 0.117, P = 0.024) than men, irrespective of the type of cigarettes smoked. More research is now needed to confirm these findings and gender-specific effects in a larger, representative sample. However, results do not support the common belief that RYO cigarettes are less harmful than manufactured cigarettes. [source]

    Color vision and macular recovery time in epileptic adolescents treated with valproate and carbamazepine

    A. Verrotti
    Visual dysfunction has been reported in patients diagnosed with epilepsy. Some of these visual disturbances may be attributable to either the disease process, or the anticonvulsant therapy prescribed to control the seizures. The aims of our study were to evaluate whether color vision and macular function are impaired in epileptic adolescents, to study if the monotherapy with valproic acid (VPA) and carbamazepine (CBZ) can affect color vision and macular function and to determine the possible relationship between color vision, retinal function and antiepileptic drugs (AEDs) dosage and their serum concentrations. We examined 45 (16 male and 29 female, mean age ± SD, 15.71 ± 2.01 years) Caucasian epileptic patients suffering from various types of cryptogenic epilepsy before the beginning of therapy and after 1 year of VPA or CBZ monotherapy and 40 sex- and age-matched healthy controls. Color vision was assessed by Farnsworth Munsell (FM) 100-hue test and total error score (TES) was evaluated. This test consists of colored caps: the testee has to arrange the caps according to their colors macular function was assessed by nyctometry evaluating initial recovery time (IRT) and summation method (SM). This test evaluates visual acuity after a period of intense illumination of macula. Analysis of variance was used to evaluate the difference between controls and patients; moreover, Pearson's correlation test have been performed. Before the beginning of therapy, there were no differences in color vision and macular function between controls and epileptic patients. After 1 year, the patients, treated with VPA or CBZ, showed a deficit in FM 100-hue test. At nyctometry, all patients showed no significant variation of macular function between baseline evaluation and second evaluation at end of the follow-up. Our study demonstrates that, in our group of epileptic patients, epilepsy per se does not affect color vision and retinal function. In contrast, after 1 years of therapy with VPA and CBZ these patients showed a deficit in FM 100-hue test although nyctometry evaluation continued to be normal allowing to exclude an impairment in macular function. Further investigations are required to determine the pathophysiological alteration(s) that are at the basis of color perception defects. [source]

    L-type calcium channels are involved in fast endocytosis at the mouse neuromuscular junction

    Paula P. Perissinotti
    Abstract We used fluorescence microscopy of FM dyes-labeled synaptic vesicles and electrophysiological recordings to examine the functional characteristics of vesicle recycling and study how different types of voltage-dependent Ca2+ channels (VDCCs) regulate the coupling of exocytosis and endocytosis at mouse neuromuscular junction. Our results demonstrate the presence of at least two different pools of recycling vesicles: a high-probability release pool (i.e. a fast destaining vesicle pool), which is preferentially loaded during the first 5 s (250 action potentials) at 50 Hz; and a low-probability release pool (i.e. a slow destaining vesicle pool), which is loaded during prolonged stimulation and keeps on refilling after end of stimulation. Our results suggest that a fast recycling pool mediates neurotransmitter release when vesicle use is minimal (i.e. during brief high-frequency stimulation), while vesicle mobilization from a reserve pool is the prevailing mechanism when the level of synaptic activity increases. We observed that specific N- and L -type VDCC blockers had no effect on evoked transmitter release upon low-frequency stimulation (5 Hz). However, at high-frequency stimulation (50 Hz), L -type Ca2+ channel blocker increased FM2-10 destaining and at the same time diminished quantal release. Furthermore, when L -type channels were blocked, FM2-10 loading during stimulation was diminished, while the amount of endocytosis after stimulation was increased. Our experiments suggest that L -type VDCCs promote endocytosis of synaptic vesicles, directing the newly formed vesicles to a high-probability release pool where they compete against unused vesicles. [source]

    Effect of auditory cortex lesions on the discrimination of frequency-modulated tones in rats

    Natalia Rybalko
    Abstract The lateralization of functions to individual hemispheres of the mammalian brain remains, with the exception of the human brain, unresolved. The aim of this work was to investigate the ability to discriminate between falling and rising frequency-modulated (FM) stimuli in rats with unilateral or bilateral lesions of the auditory cortex (AC). Using an avoidance conditioning procedure, thirsty rats were trained to drink in the presence of a rising FM tone and to stop drinking when a falling FM tone was presented. Rats with a lesion of the AC were able to learn to discriminate between rising and falling FM tones; however, they performed significantly worse than did control rats. A greater deficit in the ability to discriminate the direction of frequency modulation was observed in rats with a right or bilateral AC lesion. The discrimination performance (DP) in these rats was significantly worse than the DP in rats with a left AC lesion. Animals with a right or bilateral AC lesion improved their DP mainly by recognizing the pitch at the beginning of the stimuli. The lesioning of the AC in trained animals caused a significant decrease in DP, down to chance levels. Retraining resulted in a significant increase in DP in rats with a left AC lesion; animals with a right lesion improved only slightly. The results demonstrate a hemispheric asymmetry of the rat AC in the recognition of FM stimuli and indicate the dominance of the right AC in the discrimination of the direction of frequency modulation. [source]

    A Gene Therapy Technology-Based Biomaterial for the Trigger-Inducible Release of Biopharmaceuticals in Mice

    Michael M. Kämpf
    Abstract Gene therapy scientists have developed expression systems for therapeutic transgenes within patients, which must be seamlessly integrated into the patient's physiology by developing sophisticated control mechanisms to titrate expression levels of the transgenes into the therapeutic window. However, despite these efforts, gene-based medicine still faces security concerns related to the administration of the therapeutic transgene vector. Here, molecular tools developed for therapeutic transgene expression can readily be transferred to materials science to design a humanized drug depot that can be implanted into mice and enables the trigger-inducible release of a therapeutic protein in response to a small-molecule inducer. The drug depot is constructed by embedding the vascular endothelial growth factor (VEGF121) as model therapeutic protein into a hydrogel consisting of linear polyacrylamide crosslinked with a homodimeric variant of the human FK-binding protein 12 (FM), originally developed for gene therapeutic applications, as well as with dimethylsuberimidate. Administrating increasing concentrations of the inducer molecule FK506 triggers the dissociation of FM thereby loosening the hydrogel structure and releasing the VEGF121 payload in a dose-adjustable manner. Subcutaneous implantation of the drug depot into mice and subsequent administration of the inducer by injection or by oral intake triggers the release of VEGF121 as monitored in the mouse serum. This study is the first demonstration of a stimuli-responsive hydrogel that can be used in mammals to release a therapeutic protein on demand by the application of a small-molecule stimulus. This trigger-inducible release is a starting point for the further development of externally controlled drug depots for patient-compliant administration of biopharmaceuticals. [source]

    Does contact dermatitis to fragrances influence the quality of life?

    A descriptive study measuring, comparing the quality of life, skin involvement in patients with contact dermatitis to fragrances
    Abstract The study of the impact of diseases on individuals' quality of life is an important and useful tool for clinicians, particularly for an efficient follow-up and for the good management of patients suffering from chronic diseases. Contact dermatitis is a common condition in dermatological patients. However, despite efficient screening, the understanding and acceptance of contact allergy remain difficult and avoidance of these allergens is not always possible. The aim of this study was to determine whether contact dermatitis to fragrances affects quality of life and to define whether there is a relationship between the severity of skin involvement and quality of life. To measure the quality of life, we chose the VQ-Dermato (VQ-d) questionnaire, the only valid and reliable questionnaire in French, to which we added 10 non-validated specific questions regarding fragrances. We included patients with pertinent positive patch test reactions to fragrances attending the contact clinic between 1 January 1998 and 30 September 2004. During this time, 2814 patients were patch tested and 310 had positive reactions to the fragrance mix 8% (FM) of the standard series. We recruited non-atopic individuals, exclusively allergic to fragrance mix, with patch test reactions scored ++ and +++; the only additional positive reactions accepted were to balsam of Peru and the patient's own perfumes; 52 patients met these criteria, but only 33 participated. To evaluate the severity of skin involvement, we used the severity scoring of atopic dermatitis (SCORAD index). The quality of life of individuals allergic to fragrances was mostly moderately affected. Patients were more affected psychologically during the first year after the diagnosis of fragrance allergy. Skin reaction during the acute stage of contact allergy to fragrances can be severe. No correlation between VQ-d and SCORAD could be established. It was concluded that there was no severe impact on quality of life because of fragrance contact allergy, but that psychological issues and depression may play an important role in determining the way skin disease affects people. Patch testing improves the quality of life. Lack of correlation between VQ-d and SCORAD demonstrates that an objective measure such as SCORAD may not fully capture the impact of the disease. These results cannot be generalized because of the low response rate and limited sample size. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Silage quality when Moringa oleifera is ensiled in mixtures with Elephant grass, sugar cane and molasses

    GRASS & FORAGE SCIENCE, Issue 4 2009
    B. Mendieta-Araica
    Abstract Fourteen different silages were prepared using mixtures of Moringa (Moringa oleifera), Elephant grass (Pennisetum purpureum cv Taiwan) or sugar cane (Saccharum officinarum). Molasses from sugar cane was used in the amounts of either 10 or 50 g kg,1 fresh matter (FM) in treatments without sugar cane. A completely randomized design with three replicates of each treatment was used. The silages were prepared in 1800 mL micro silos and opened after 120 d. The presence of Moringa and Elephant grass in the silage changed the pH by ,0·8 and +0·7, respectively (P < 0·001), indicating a favourable effect of Moringa on silage pH. Overall differences were found among treatments for dry matter content, crude protein and acetic acid concentrations, weight loss, CO2 production and silage pH after spoilage (P < 0·001). Weight loss was proportionately 0·034 and 0·014 in silages with and without sugar cane respectively (P < 0·001). Overall, differences (P < 0·05) were also found for neutral-detergent fibre and lactic acid concentrations, lactic acid bacteria counts, clostridial counts and time to spoilage of the silages. Treatments containing Moringa had higher lactic acid concentrations (+16 g kg,1 DM; P < 0·01) compared to treatments without but the presence of Moringa decreased time to spoilage by 67 h (P < 0·05). No differences were found in propionic acid concentration or fungal growth of the silages. It is concluded that Moringa can be used as a component of high quality silages which also contain high concentrations of crude protein. [source]

    Direct Spectroscopic Evidence that the Photochemical Outcome of Flutamide in a Protein Environment is Tuned by Modification of the Molecular Geometry: A Comparison with the Photobehavior in Cyclodextrin and Vesicles

    Salvatore Sortino
    The photoreactivity of the phototoxic anticancer drug flutamide (FM) in the presence of bovine serum albumin (BSA) has been investigated. The presence of BSA induces a remarkable modification of the photochemical outcome of the drug with respect to that observed in aqueous solution. Induced circular dichroism (ICD) measurements combined with theoretical calculations provide strong evidence that the new photochemical scenario is tuned by changes of the molecular geometry of FM when incorporated in the protein microenvironment. This behavior presents close analogies to that found in the presence of either cyclodextrin or phospholipid vesicles, chosen as models for biological systems, and delineates a quite general photochemical picture that can be useful for a more appropriate understanding of the adverse phototoxic effects induced by this drug. [source]

    The health status burden of people with fibromyalgia: a review of studies that assessed health status with the SF-36 or the SF-12

    D. L. Hoffman
    Summary Objective:, The current review describes how the health status profile of people with fibromyalgia (FM) compares to that of people in the general population and patients with other health conditions. Methods:, A review of 37 studies of FM that measured health status with the 36-item Medical Outcomes Study Short-Form Health Survey (SF-36) or the 12-item Short-Form Health Survey (SF-12). Results:, Studies performed worldwide showed that FM groups were significantly more impaired than people in the general population on all eight health status domains assessed. These domains include physical functioning, role functioning difficulties caused by physical problems, bodily pain, general health, vitality (energy vs. fatigue), social functioning, role functioning difficulties caused by emotional problems and mental health. FM groups had mental health summary scores that fell 1 standard deviation (SD) below the general population mean, and physical health summary scores that fell 2 SD below the general population mean. FM groups also had a poorer overall health status compared to those with other specific pain conditions. FM groups had similar or significantly lower (poorer) physical and mental health status scores compared to those with rheumatoid arthritis, osteoarthritis, osteoporosis, systemic lupus erythematosus, myofacial pain syndrome, primary Sjögren's syndrome and others. FM groups scored significantly lower than the pain condition groups mentioned above on domains of bodily pain and vitality. Health status impairments in pain and vitality are consistent with core features of FM. Conclusions:, People with FM had an overall health status burden that was greater in magnitude compared to people with other specific pain conditions that are widely accepted as impairing. [source]

    Understanding postorganic fresh fruit and vegetable consumers at participatory farmers' markets in Ireland: reflexivity, trust and social movements

    Oliver Moore
    Abstract This paper examines how trusting relations between consumers and vendors of organic fresh fruits and vegetables (FFVs) in a particular type of farmers' market (FM) in Ireland are established and maintained, and what the implications of this are. First, the food system is outlined, and then its attendant problems. These problems have led to various solutions, two of which are organic food and FMs. Then, the growth in these two areas is outlined, as is the accompanying growth in the academic literature on these two areas, some of which overlaps. Various pressures, including in particular the increasing distance food travels and disconnected stallholders and products at the FM, are suggested. In light of this, a need to apply an understanding of the reflexive consumer, trust and social movements is suggested. It is found that the consumers interviewed act reflexively by choosing to go to these FMs. They prioritize the trusting relationships built up through repeated personal contact at these FMs over and above organic certification. Along with and as part of this, they prioritize local, fresh, seasonal ,chemical-free' FFVs over and above imported certified organic produce. Various aspects of collective identity formation, including modes of behaviour, objects and stories, and language, are involved in this process. These elements, to some extent, act as a buffer against the pressures of distance and disconnection. Along with this, the essential meaning of the word organic is, in this particular context, reconstructed to include various socio-environmental values missing from some certified organic produce. The word postorganic is suggested. The main methodologies used are semistructured in-depth interviews and participant observation. [source]

    Satellite image segmentation using hybrid variable genetic algorithm

    Mohamad M. Awad
    Abstract Image segmentation is an important task in image processing and analysis. Many segmentation methods have been used to segment satellite images. The success of each method depends on the characteristics of the acquired image such as resolution limitations and on the percentage of imperfections in the process of image acquisition due to noise. Many of these methods require a priori knowledge which is difficult to obtain. Some of them are parametric statistical methods that use many parameters which are dependent on image property. In this article, a new unsupervised nonparametric method is developed to segment satellite images into homogeneous regions without any a priori knowledge. The new method is called hybrid variable genetic algorithm (HVGA). The variability is found in the variable number of cluster centers and in the changeable mutation rate. In addition, this new method uses different heuristic processes to increase the efficiency of genetic algorithm in avoiding local optimal solutions. Experiments performed on two different satellite images (Landsat and Spot) proved the high accuracy and efficiency of HVGA compared with another two unsupervised and nonparametric segmentation methods genetic algorithm (GA) and self-organizing map (SOM). The verification of the results included stability and accuracy measurements using an evaluation method implemented from the functional model (FM) and field surveys. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 199,207, 2009 [source]