106 research outputs found

    Alfvenic waves in polar spicules

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    Context. For investigating spicules from the photosphere to coronal heights, the new Hinode/SOT long series of high resolution observations from Space taken in CaII H line emission offers an improved way to look at their remarkable dynamical behavior using images free of seeing effects. They should be put in the context of the huge amount of already accumulated material from ground-based instruments, including high- resolution spectra of off-limb spicules. Results. The surge-like behavior of solar polar region spicules supports the untwisting multi-component interpretation of spicules exhibiting helical dynamics. Several tall spicules are found with (i) upward and downward flows similar at lower and middle-levels, the rate of upward motion being slightly higher at high levels; (ii) the left and right-hand velocities are also increasing with height; (iii) a large number of multi-component spicules show shearing motion of both left-handed and right-handed senses occurring simultaneously, which might be understood as twisting (or untwisting) threads. The number of turns depends on the overall diameter of the structure made of components and changes from at least one turn for the smallest structure to at most two or three turns for surge-like broad structures; the curvature along the spicule corresponds to a low turn number similar to a transverse kink mode oscillation along the threads.Comment: 8 pages, 10 figures, Accepted in Astronomy and Astrophysic

    Effective Forchheimer Coefficient for Layered Porous Media

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    Inertial flow in porous media, governed by the Forchheimer equation, is affected by domain heterogeneity at the field scale. We propose a method to derive formulae of the effective Forchheimer coefficient with application to a perfectly stratified medium. Consider uniform flow under a constant pressure gradient Delta P/L in a layered permeability field with a given probability distribution. The local Forchheimer coefficient beta is related to the local permeability k via the relation beta = a/k(c), where a > 0 being a constant and c is an element of [0, 2]. Under ergodicity, an effective value of beta is derived for flow (i) perpendicular and (ii) parallel to layers. Expressions for effective Forchheimer coefficient, beta(e), generalize previous formulations for discrete permeability variations. Closed-form beta(e) expressions are derived for flow perpendicular to layers and under two limit cases, F << 1 and F >> 1, for flow parallel to layering, with F a Forchheimer number depending on the pressure gradient. For F of order unity, beta(e) is obtained numerically: when realistic values of Delta P/L and a are adopted, beta(e) approaches the results valid for the high Forchheimer approximation. Further, beta(e) increases with heterogeneity, with values always larger than those it would take if the beta - k relationship was applied to the mean permeability; it increases (decreases) with increasing (decreasing) exponent c for flow perpendicular (parallel) to layers. beta(e) is also moderately sensitive to the permeability distribution, and is larger for the gamma than for the lognormal distribution

    Thermal Hydraulic Modeling of Once-Through Steam Generator by Two-Fluid U-Tube Steam Generator Code

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    The THERMIT U-tube steam generator (THERMIT-UTSG) code was used for evaluation for the parametric study of a scaled once-through pressurized water reactor steam generator (OTSG) made by Babcock & Wilcox. The results of the code were compared to the experimental data of the 19-tube OTSG and a simple heat transfer code that was developed by Osakabe. The main calculated thermodynamic parameters were primary-secondary fluid temperatures, tube wall internal and external temperatures that were subjected to primary and the secondary fluid, and the secondary fluid vapor quality. The assessed code can be used for modeling the OTSGs with some modification. The results of THERMIT-UTSG were in agreement with the experimental results and the prediction of Osakabe’s numerical model

    Thermal Hydraulic Modeling of Once-Through Steam Generator by Two-Fluid U-Tube Steam Generator Code

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    The THERMIT U-tube steam generator (THERMIT-UTSG) code was used for evaluation for the parametric study of a scaled once-through pressurized water reactor steam generator (OTSG) made by Babcock & Wilcox. The results of the code were compared to the experimental data of the 19-tube OTSG and a simple heat transfer code that was developed by Osakabe. The main calculated thermodynamic parameters were primary-secondary fluid temperatures, tube wall internal and external temperatures that were subjected to primary and the secondary fluid, and the secondary fluid vapor quality. The assessed code can be used for modeling the OTSGs with some modification. The results of THERMIT-UTSG were in agreement with the experimental results and the prediction of Osakabe's numerical model

    Hemodynamic effect of atrioventricular and interventricular dyssynchrony in patients with biventricular pacing: Implications for the pacemaker syndrome

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    Background/Objectives: Pacemaker syndrome was mainly described as the sequel of atrioventricular (AV) dyssynchrony. The role of interventricular (VV) dyssynchrony has not been studied yet. The aims of this study were to noninvasively assess the hemodynamic effects of different ventricular pacing sites with and without AV and VV dyssynchrony and to observe the patients for clinical symptoms of the pacemaker syndrome during the AV sequential and ventricular-only pacing modes. Materials and Methods: Between March 2009 and February 2010, 40 patients (28 men; mean age, 61 ± 15 years) with biventricular (BiV) device were enrolled. Mean systolic and diastolic blood pressures (BP) of 5 beats were measured 5 minutes after each mode change using fingertip plethysmography. The patients were also observed for the occurrence of symptoms suggestive of the pacemaker syndrome, including dyspnea, palpitations, dizziness, presyncope, and syncope. Results: There was no difference in mean systolic BP among different ventricular-only pacing modes (all P = NS). However, mean systolic BP was significantly higher in AV sequential biventricular pacing (DDD-BiV) compared with ventricular-only pacing modes (all P0.05). Conclusions: The present study showed that the non-AV sequential BiV and LV pacing may have no significant benefit compared with RV pacing in terms of systolic blood pressure. However, there was marked hemodynamic improvement following mode change to AV sequential BiV pacing. This study may have important implications for pathogenesis of pacemaker syndrome

    Predictors of quality of life in breast cancer patients under chemotherapy

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    Background: Today, the quality of life studies has an important role in health care especially in chronic diseases. Breast cancer has third order among women\u2032s malignancies. Now, survival rate for this cancer is long. However breast cancer has several complications that affected the patient\u2032s life. Aims : The aim of this study was to assess the quality of life in Breast cancer patients under chemotherapy. Setting and Design: A cross-sectional study conducted on 119 breast cancer patients that were admitted and treated in chemotherapy ward of Namazi hospital in Shiraz city, south of Iran, between Jan and Feb 2006. Materials and Methods: The QLQ-C30 questionnaire was used to assess quality of life in these patients. Statistical Analysis: We used univariate methods. A multiple regression analysis was performed to identify predictors of quality of life. Results: Mean age of patients was 48.27\ub111.42 with quality of life total score 64.92\ub124.28. All symptoms scales had reverse association with quality of life except appetite loss (P>0.05) and diarrhea (P=0.752). The results of the regression analyses showed that only grade of tumor, occupational status, menopausal status, financial difficulties and dyspnea were statistically significant in predicting patients\u2032 quality of life. Conclusion: In conclusion, this study demonstrates the strength of the relationship between clinical and sociodemographical factors and breast cancer patients\u2032 quality of life. Psychological and financial support for women experiencing breast cancer diagnosis may improve quality of life

    Predictors of quality of life in breast cancer patients under chemotherapy

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    Background: Today, the quality of life studies has an important role in health care especially in chronic diseases. Breast cancer has third order among women′s malignancies. Now, survival rate for this cancer is long. However breast cancer has several complications that affected the patient′s life. Aims : The aim of this study was to assess the quality of life in Breast cancer patients under chemotherapy. Setting and Design: A cross-sectional study conducted on 119 breast cancer patients that were admitted and treated in chemotherapy ward of Namazi hospital in Shiraz city, south of Iran, between Jan and Feb 2006. Materials and Methods: The QLQ-C30 questionnaire was used to assess quality of life in these patients. Statistical Analysis: We used univariate methods. A multiple regression analysis was performed to identify predictors of quality of life. Results: Mean age of patients was 48.27±11.42 with quality of life total score 64.92±24.28. All symptoms scales had reverse association with quality of life except appetite loss (P>0.05) and diarrhea (P=0.752). The results of the regression analyses showed that only grade of tumor, occupational status, menopausal status, financial difficulties and dyspnea were statistically significant in predicting patients′ quality of life. Conclusion: In conclusion, this study demonstrates the strength of the relationship between clinical and sociodemographical factors and breast cancer patients′ quality of life. Psychological and financial support for women experiencing breast cancer diagnosis may improve quality of life

    Cardiogoniometry can predict positive response to cardiac resynchronization therapy � A proof of concept study

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    Background: According to American Heart Association guidelines, QRS duration and morphology are used to select patients for cardiac resynchronization therapy (CRT). But still there are some patients who are not responding to this device. We investigated whether the Cardiogoniometry (CGM) as a three-dimensional vectorcardiogram method can improve patient selection. Methods: Echocardiography and CGM were performed for 25 consecutive patients with Left bundle branch morphology who were candidate for CRT implantation and were in sinus rhythm. Patients re-evaluated by echocardiography after 6 months post CRT implantation. Results: The mean age of the patients was 63 ± 13 years and 17 (68) were males. The mean LVEF was 19.4 ± 7.4 and 24.2 ± 11.5 before and after CRT implantation respectively. Median of the duration of the R loop before the R maximum demonstrated a negative correlation with the increase in LVEF, (r = �0.36, P = 0.07) and mean of maximal spatial velocity of the T-loop for all measured showed a positive correlation (r = 0.39, p = 0.04). Other parameters didn't show any significant differences. Conclusions: Three-dimensional vectorcardiogram parameters can be helpful to predict the CRT response. Shorter duration of the R loop before the maximum R and smaller R loop area are predictors for responder patients. © 201

    Cardiogoniometry can predict positive response to cardiac resynchronization therapy � A proof of concept study

    Get PDF
    Background: According to American Heart Association guidelines, QRS duration and morphology are used to select patients for cardiac resynchronization therapy (CRT). But still there are some patients who are not responding to this device. We investigated whether the Cardiogoniometry (CGM) as a three-dimensional vectorcardiogram method can improve patient selection. Methods: Echocardiography and CGM were performed for 25 consecutive patients with Left bundle branch morphology who were candidate for CRT implantation and were in sinus rhythm. Patients re-evaluated by echocardiography after 6 months post CRT implantation. Results: The mean age of the patients was 63 ± 13 years and 17 (68) were males. The mean LVEF was 19.4 ± 7.4 and 24.2 ± 11.5 before and after CRT implantation respectively. Median of the duration of the R loop before the R maximum demonstrated a negative correlation with the increase in LVEF, (r = �0.36, P = 0.07) and mean of maximal spatial velocity of the T-loop for all measured showed a positive correlation (r = 0.39, p = 0.04). Other parameters didn't show any significant differences. Conclusions: Three-dimensional vectorcardiogram parameters can be helpful to predict the CRT response. Shorter duration of the R loop before the maximum R and smaller R loop area are predictors for responder patients. © 201
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