969 resultados para AC IMPEDANCE


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BACKGROUND: Little information is available on the validity of simple and indirect body-composition methods in non-Western populations. Equations for predicting body composition are population-specific, and body composition differs between blacks and whites. OBJECTIVE: We tested the hypothesis that the validity of equations for predicting total body water (TBW) from bioelectrical impedance analysis measurements is likely to depend on the racial background of the group from which the equations were derived. DESIGN: The hypothesis was tested by comparing, in 36 African women, TBW values measured by deuterium dilution with those predicted by 23 equations developed in white, African American, or African subjects. These cross-validations in our African sample were also compared, whenever possible, with results from other studies in black subjects. RESULTS: Errors in predicting TBW showed acceptable values (1.3-1.9 kg) in all cases, whereas a large range of bias (0.2-6.1 kg) was observed independently of the ethnic origin of the sample from which the equations were derived. Three equations (2 from whites and 1 from blacks) showed nonsignificant bias and could be used in Africans. In all other cases, we observed either an overestimation or underestimation of TBW with variable bias values, regardless of racial background, yielding no clear trend for validity as a function of ethnic origin. CONCLUSIONS: The findings of this cross-validation study emphasize the need for further fundamental research to explore the causes of the poor validity of TBW prediction equations across populations rather than the need to develop new prediction equations for use in Africa.

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Red blood cell (RBC) parameters such as morphology, volume, refractive index, and hemoglobin content are of great importance for diagnostic purposes. Existing approaches require complicated calibration procedures and robust cell perturbation. As a result, reference values for normal RBC differ depending on the method used. We present a way for measuring parameters of intact individual RBCs by using digital holographic microscopy (DHM), a new interferometric and label-free technique with nanometric axial sensitivity. The results are compared with values achieved by conventional techniques for RBC of the same donor and previously published figures. A DHM equipped with a laser diode (lambda = 663 nm) was used to record holograms in an off-axis geometry. Measurements of both RBC refractive indices and volumes were achieved via monitoring the quantitative phase map of RBC by means of a sequential perfusion of two isotonic solutions with different refractive indices obtained by the use of Nycodenz (decoupling procedure). Volume of RBCs labeled by membrane dye Dil was analyzed by confocal microscopy. The mean cell volume (MCV), red blood cell distribution width (RDW), and mean cell hemoglobin concentration (MCHC) were also measured with an impedance volume analyzer. DHM yielded RBC refractive index n = 1.418 +/- 0.012, volume 83 +/- 14 fl, MCH = 29.9 pg, and MCHC 362 +/- 40 g/l. Erythrocyte MCV, MCH, and MCHC achieved by an impedance volume analyzer were 82 fl, 28.6 pg, and 349 g/l, respectively. Confocal microscopy yielded 91 +/- 17 fl for RBC volume. In conclusion, DHM in combination with a decoupling procedure allows measuring noninvasively volume, refractive index, and hemoglobin content of single-living RBCs with a high accuracy.

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L'histoire du jugement de Dieu sur Ananias et Saphira (Ac 5.1-11) compte parmi les épisodes les plus pathétiques du livre des Actes. L'art lucanien de la dramatisation atteint ici un sommet. La fin tragique d'Ananias foudroyé par la parole dénonciatrice de Pierre, son enterrement hâtif, puis la venue de Saphira ignorante du drame, son mensonge public suivi de sa mort annoncée sur un ton d'humour noir (5.9b): l'effet pragmatique cherché par le narrateur est programmé par le scénario; il s'inscrit aussi dans le texte lui-même: 'un grand effroi saisit ceux qui l'entendaient' (5.5, 11). L'histoire est destinée à provoquer la crainte.

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OBJECTIVES: Perioperative fluid accumulation determination is a challenge for the clinician. Bioelectrical impedance analysis (BIA) is a noninvasive method based on the electrical properties of tissues, which can assess body fluid compartments. The study aimed at assessing their changes in three types of surgery (thoracic, abdominal, and intracranial) requiring various regimens of fluid administration. DESIGN: Prospective descriptive trial. PATIENTS: A total of 26 patients scheduled for elective surgery were separated into three groups according to site of surgery: thoracic (n = 8), abdominal aortic (n = 8), and brain surgery (n = 10). SETTING: University teaching hospital. INTERVENTION: None. MEASUREMENTS: Whole body, segmental (arm, trunk, and legs) BIA at multiple frequency (0.5, 50, 100 kHz) was used to assess perioperative fluid accumulation after surgery. The fluid balances were calculated from the charts. RESULTS: The patients were aged 62+/-4 yrs. Fluid balances were 4.8+/-1.0 L, 4.1+/-0.5 L, and 1.9+/-0.3 L, respectively, in the three groups. In trunk surgery patients, fluid accumulation was detected as a drop in impedance in the operated area at all frequencies. In the operated area, there was an expansion of both intra- and extracellular compartments. A reduction in high frequencies' impedance in the legs was only detected after aortic surgery. Fluid accumulation and trunk impedance changes were strongly correlated. Neurosurgery only induced minor body fluid changes. CONCLUSIONS: Segmental BIA is able to detect and localize perioperative fluid accumulation. It may become a bedside tool to quantify and to localize fluid accumulation.

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Aquest estudi presenta els diferents àmbits d’actuació que composen el Programa CA/AC així com l’explicació de les etapes d’implementació d’aquest programa en la seva modalitat B. Aquesta modalitat ha estat aplicada en diversos centres escolars pertanyents als Berritzegunes (Serveis Educatius) de la província de Guipúscoa durant el curs 2010/11. A partir d’aquesta pràctica, s’ha realitzat l’anàlisi quantitativa de les diferents actuacions dels àmbits A i B de manera que se’n poden analitzar a partir de gràfics, quines han estat les freqüències i el grau d’aplicació de les dinàmiques i de les estructures cooperatives que conformen el programa aplicat.

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Projecte de recerca elaborat a partir d’una estada a l’Oriental Institute de la University of Oxford, Regne Unit, entre juliol i octubre de 2007. Durant l’estada s’ha analitzat la documentació demòtica datada del regnat d’Alexandre el Gran com a faraó d’Egipte (332-323 aC). El conjunt de fonts que examinat està constituït per sis papirs (actes notarials que recullen diversos tipus de contractes o acords entre dues parts), un òstrakon fragmentari i una sèrie d’esteles provinents de la Necròpolis d’Animals de Saqqara Nord, en concret de la Catacumba de les Mares d’Apis. Aquesta documentació és fonamental perquè permet extreure conclusions importants sobre diversos aspectes relacionats amb l’administració i la religiositat egípcies en els moments inicials de la dominació grega d'Egipte. Cadascun d’aquests documents ha estat traduït, analitzat en profunditat i degudament contextualitzat històricament. D’una banda, en l’àmbit de l’administració, he pogut constatar la continuïtat existent amb el període històric immediatament anterior, és a dir, amb la Segona Dominació Persa del país; mentre que de l'altra, des del punt de vista religiós, l’anàlisi d’aquestes fonts m’ha permès verificar l'existència de tota una sèrie de canvis substancials, estretament vinculats a la voluntat expressa de la nova elit dirigent d'origen grec de distanciar-se dels seus predecessors aquemènides i de marcar amb força l’obertura d’una nova era que es caracteritzarà pel respecte a les tradicions autòctones i per la potenciació dels cultes nacionals.

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L’objectiu d’aquest projecte ha estat identificar i analitzar els rituals funeraris a celebrats als suburbis de Tàrraco i el seu territorium. Per tal d’assolir-lo hem revisat col•leccions de museus, arxius i informes arqueològics arribant a documentar 721 enterraments. A través de la recerca, hem estudiat les peculiaritats i els elements d’aixovar que les tombes presenten amb el suport de les fonts escrites. Hem detectat pràctiques rituals com ara libacions, sacrificis i objectes relacionats amb ofrenes funeràries a l’exterior de les tombes. Hem documentat certa una uniformitat general i repetiva pel que fa a la selecció dels aixovars funerari. No obstant això, hi ha algunes diferències sobretot en aixovars que provenen de les tombes d’individus morts prematurament (individus no casats, infants). També s’ha constatat una diferència sexual entre dones i homes pel que fa als objectes d’aixovar. Hem utilitzat l’evidència arqueològica i literària per tal de trobar el significat d’aquests artefactes quotidians que canvien de significat quan entren en contacte amb els morts. En revisar la informació procedent d’excavacions hem identificat espais rituals específics dins de la necròpolis com jardins funeraris i ustrina. Aquest estudi ha explorat la manera com l’arqueologia ens permeten identificar les pràctiques rituals dins les àrees funeràries. L’estudi de materials arqueològics documentats als estrats de freqüentació de les necròpolis ens ha permès detectar l’evidència material de la ritualitat.

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BACKGROUND AND AIMS: little is known regarding the reproducibility of body fat measuring devices; hence, we assessed the between and within-device reproducibility, and the within-day variability of body fat measurements. METHODS: body fat percentage was measured twice on seventeen female students aged between 18 and 20 with a body mass index of 21.9 ± 2.5 kg/m2 (mean ± SD) using seven bipolar bioelectrical impedance devices. Each participant was also measured each hour between 7:00 and 22:00. RESULTS: the correlation between first and second measurements was very high (Spearman r between 0.985 and 1.000, p<0.001), as well as between devices (Spearman r between 0.916 and 0.991, p<0.001). Repeated measurements analysis showed no differences were between devices (p=0.59) or readings (first vs. second: p=0.74). Conversely, significant differences were found between assessment periods throughout the day, measurements made in the morning being lower than those made in the afternoon (F test for repeated values= 6.58, p<0.001). CONCLUSIONS: the between and within-device reproducibility for measuring body fat is high, enabling the use of multiple devices in a single study. Conversely, small but significant changes in body fat measurements occur during the day, urging body fat measurements to be performed at fixed times.

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The present study assessed the relative contribution of each body segment to whole body fat-free mass (FFM) and impedance and explored the use of segmental bioelectrical impedance analysis to estimate segmental tissue composition. Multiple frequencies of whole body and segmental impedances were measured in 51 normal and overweight women. Segmental tissue composition was independently assessed by dual-energy X-ray absorptiometry. The sum of the segmental impedance values corresponded to the whole body value (100.5 +/- 1.9% at 50 kHz). The arms and legs contributed to 47.6 and 43.0%, respectively, of whole body impedance at 50 kHz, whereas they represented only 10.6 and 34.8% of total FFM, as determined by dual-energy X-ray absorptiometry. The trunk averaged 10.0% of total impedance but represented 48.2% of FFM. For each segment, there was an excellent correlation between the specific impedance index (length2/impedance) and FFM (r = 0.55, 0.62, and 0.64 for arm, trunk, and leg, respectively). The specific resistivity was in a similar range for the limbs (159 +/- 23 cm for the arm and 193 +/- 39 cm for the leg at 50 kHz) but was higher for the trunk (457 +/- 71 cm). This study shows the potential interest of segmental body composition by bioelectrical impedance analysis and provides specific segmental body composition equations for use in normal and overweight women.