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Search Results: 1 - 10 of 2783 matches for " variability "
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Resistance of Two Maize Landraces in Breeding Stage to the Attack of Sitophilus zeamais  [PDF]
Rejane Teixeira do Nascimento, Bruno Ettore Pavan, Luciana Barboza Silva, Gabriel dos Santos Carvalho, Alexandre Faria da Silva, Kellen Maggioni
American Journal of Plant Sciences (AJPS) , 2014, DOI: 10.4236/ajps.2014.520308
Abstract: This study aimed to assess the resistance of grain from two varieties of maize landraces in initial breeding in Bom Jesus-PI, with respect to S. zeamais attack. Seeds of two maize landraces were used: purple straw maize from two different origins (São Paulo (SP) and Espírito Santo (ES)) and Peruvian purple maize. The experimental design was completely randomized with four replications. The data for each response variable were subjected to analysis of variance, applying the F-test (p ≤ 0.05), and when significant differences were found, there was a comparison of means by Tukey test (p ≤ 0.05). The statistical analyses were performed using the software SAS®. In a free-choice test and bioassay for evaluating the nutritional index (no choice test), maize varieties differed significantly by Tukey test and the cultivar SP was considered resistant, while the cultivars purple and ES were considered susceptible.
Tropospheric Circulation Variability over Central and Southern South America  [PDF]
Oscar A. Frumento, Vicente R. Barros
Atmospheric and Climate Sciences (ACS) , 2014, DOI: 10.4236/acs.2014.45084
Abstract: Combined Empirical Orthogonal Function Analysis of low-level atmospheric circulation after filtering the synoptic scale was performed for the period 1981-2006 over Central and Southern South America. Modes with 40 and near 70 days frequency associated with swings in longitude of the South Pacific and South Atlantic Ocean heights were identified. Their extreme values were related to drought and to high anomalous precipitation associated to floods in South East South America (SESA). These modes were independent of other sources of variability of the Southern Hemisphere atmosphere, namely MJO (Madden-Julian Oscillation), ENSO (El Nino Southern Oscillation) and AAO (Antarctic Oscillation). Mode one, which in its positive phase has a circulation similar to the mean winter, has a trend that explains part of the winter warming observed since 1980’s in Central and Eastern Argentina. Variance was calculated for the intra-annual variability, the one associated to the inter-annual variability including trends and jumps, and that of the annual cycle. The partition of the total variance was roughly 70%, 10% and 20% respectively. This partition implies that predictability of the regional climate is more critically dependent on the predictability of the intra-annual variability than of the inter-annual variability.
Insurance Payer Status and Race Explains Much of the Variability in Colorectal Cancer Survival  [PDF]
Timothy L. Fitzgerald, Cary Suzanne Lea, Prashanti M. Atluri, Jason Brinkley, Emmanuel E. Zervos
Journal of Cancer Therapy (JCT) , 2014, DOI: 10.4236/jct.2014.513124
Abstract:

Health care inequalities exist for patients with colon cancer. We hypothesize that factors such as payers and medical comorbidities may explain much of this inequality. Methods: Patients with colon cancer in the NCDB from 2003-2010 were identified in this study. Results: 541,649 patients were identified. Median age and survival were 68.6 years and 62.5 months. A majority of them (80.2%) were non-Hispanic white (NHW). African American (AA) and Hispanic (HS) patients were more likely to have medicaid (MD) or be uninsured (UI) and reside in counties with lower socio-economic status (SES). From univariate analysis, it was found that private insurance (PI) had superior survival (98.7 months) compared to MD (46.0 months), medicare (MC) (50.4 months) and UI (54.4 months). Survival was highest for HS (70.9 months) followed by NHW (63.2 months) and AA (53.0 months). Also, survival was linked to comorbidity index (CI), SES, chemotherapy, gender and surgical resection. On multivariate analysis, it was found that male (RR 1.11), SES, surgery (RR 2.29), chemotherapy (RR 1.96), CI, and stage were associated with survival. Race was a predictor of survival, with a survival advantage for HS (RR 0.87) and others (0.87) compared to NHW (1) and AA (1.2). Insurance status was strongly linked to survival. Compared to PI all other groups had poorer survival: MC RR 1.11; MD RR 1.44; and NI RR 1.42.Conclusions: Inequality in outcomes for colon cancer patients is strongly associated with race and underinsurance.

Analysis of Bushfires Spatial and Temporal Variability in Guinea  [PDF]
Tamba Nicolas Millimono, Sa?dou Moustapha Sall, Daouda Badiane, Alassane Bah, Moussa Diakhate, Ibra Toure, Mamadou Ba?lo Barry, Diakaria Diallo, Idrissa Diaby
Atmospheric and Climate Sciences (ACS) , 2017, DOI: 10.4236/acs.2017.74034
Abstract: Guinea is confronted to the increasing risks of bushfires that destroy thousands of hectares of vegetation cover every year. Very little research is devoted to the variability of those fires, which makes it a serious threat to both wildlife and human habitats. The current study investigates the spatial and temporal distribution of bushfires in the period from 2003 to 2016. The method used is the geospatial technology: we first filter pixels corresponding with active light supplied by MODIS images (Moderate Resolution Imaging Spectroradiometer) and estimate their densities following the square meshing procedure. Burned areas are deducted from the estimated pixel densities by calculations. The results highlight great occurrence of fires: 4 to 48 pixels of active fire per year and per 100 km2 depending on the location; 2 to 5 million hectares per year of burned areas (20,000 to 50,000 sqkm). Almost 8 to 24% the size of the whole country. The prefectures of Beyla, Siguiri, Kouroussa, Kankan, Dinguiraye, Mali and Tougué are the most exposed areas. Every year, fire activities are observed as from October and between May and June. They are however mitigated according to the regions (or the geographical domains). Summits of bushfires activities are generally reached between December and January.
The Effect of Baroreflex Function on Blood Pressure Variability  [PDF]
Xiufang Wei, Xinhui Fang, Lina Ren, Yanyan Meng, Zixin Zhang, Yongquan Wang, Guoxian Qi
International Journal of Clinical Medicine (IJCM) , 2013, DOI: 10.4236/ijcm.2013.49068
Abstract: Objective: The aim of this study was to assess the relationship of blood pressure variability (BPV) and heart rate variability (HRV) to investigate the effect of baroreflex function on blood pressure variability. Methods: This study consisted of 111 subjects, including 32 normotensives and 79 hypertensives. All the subjects were given two concurrent tests: 24-hour Holter ECG and ambulatory blood pressure monitoring. According to standard deviation of normal-to-normal sinus RR intervals (SDNN) derived from the Holter ECG, the hypertensives were divided into two groups: an HRV normal group with SDNN > 100 ms and an HRV abnormal group with SDNN < 100 ms. HRV analysis used the time domain measure SDNN and two frequency domain analyses using low-frequency and high-frequency power. BPV analysis involved a formula correlated to each blood pressure value. Results: BPV was significantly higher in the HRV abnormal group compared with the HRV normal group in the hypertensives (0.018 ± 0.0033 vs 0.014 ± 0.0032, P < 0.05). In the HRV abnormal group, BPV value of the older hypertensive participants was higher than the younger participants (0.019 ± 0.0024 vs 0.017 ± 0.0037, P = 0.048). BPV and HRV were correlated in the younger hypertensives (r = ﹣0.314, P < 0.05) and older hypertensives (r = ﹣0.692, P < 0.001). Conclusions: Baroreflex function had effect on BPV. Factors like aging could cause damage to the baroreflex sensitivity, which in turn had influence on BPV. There may be benefits in restoration of baroreflex function to reduce BPV, especially in hypertensive patients.

 

Near-Field Variability of Residential Woodsmoke Concentrations  [PDF]
Tracy L. Thatcher, Thomas W. Kirchstetter, Stella H. Tan, Christopher J. Malejan, Courtney E. Ward
Atmospheric and Climate Sciences (ACS) , 2014, DOI: 10.4236/acs.2014.44055
Abstract: In many regions, wood combustion is a significant source of wintertime aerosols. However, since wood combustion sources are interspersed within neighborhoods, near-field concentration variability has the potential to cause large variations in the exposure levels between residents over a relatively small area. This field study compared filter samples and aethalometer measurements of black carbon concentration within a 1 km2 study region with no significant aerosol sources except wood combustion. Sampling occurred on 15 nights over two winter seasons in a small California coastal town. Even over the small distances in the study area, large spatial and temporal variations were observed. Measured black carbon concentrations varied by as much as a factor of 10 over a 12-hour night-time period. The spatial variability was non-random, with the highest location in the study area experiencing 4 times the average concentration within the neighborhood, when averaged over all sample periods. The results of this study indicate that within neighborhoods with residential wood combustion sources using an average concentration for a region to predict exposure may significantly undervalue the exposure of some residents and overvalue the exposure for others.
Winter-Spring Precipitation Variability in Pakistan  [PDF]
Iftikhar Ahmad, Romana Ambreen, Zhaobo Sun, Weitao Deng
American Journal of Climate Change (AJCC) , 2015, DOI: 10.4236/ajcc.2015.41010
Abstract: This study investigates the spatial-temporal variability of winter-spring (February-March-April) precipitation (WSP) in Pakistan over the period of 1961-2006 by making use of Empirical Orthogonal Function (EOF). The EOF analysis is based on ground observed data, reanalysis NCEP/NCAR of various geopotential heights and NOAA extended reconstructed sea surface temperatures (ERSST.v3). The significant modes are obviously variable at interannual time scale. The leading mode shows the node of maximum spatial variability anchored over the Peshawar Valley and Azad Kashmir (PVAK) axis. The pattern is associated with strong (weak) westerly jet over the Middle East. The pattern is also found closely associated with post monsoon and early winter El Nino. The Nino4 index can be an appropriate predictor for the first consistent single node pattern. The second significant mode represents a tripole pattern with areas of prominent variability over northwestern Pakistan, Quetta-Kalat region and northeastern Punjab. The pattern is found to be pro-NAO and in relation to this pattern, warm and stable SST anomalies appearing in the southern mid-latitudes of Indian and Atlantic basins.
Differences of Heart Rate Variability during Sevoflurane Anesthesia in Children by Age  [PDF]
Yong-Hee Park, Chang-Hoon Koo, Jin-Tae Kim, Hee-Soo Kim, Hyo-Jin Byon
Open Journal of Anesthesiology (OJAnes) , 2012, DOI: 10.4236/ojanes.2012.23018
Abstract: Background: The child’s central nervous system develops with aging, and heart rate variability (HRV), which is con-trolled by the brain, differs from that of adults. We investigated changes in HRV during sevoflurane anesthesia in children. Methods: One 138 children aged from 2 - 12 years without major underlying problems were enrolled. During maintenance with 2 - 2.5 vol% sevoflurane anesthesia, electrocardiographic data were obtained and power spectral analysis, approximate entropy (ApEn) or Hurst exponent were analyzed and compared in three groups (age 2 - 5 years, 6 - 9 and 10 - 12 years of age). Results: The RR interval increased with aging, but low-frequency powers did not. High- frequency power was greater in the oldest children (P < 0.05), while ApEn and Hurst exponents were lower (P < 0.05). Conclusion: Change in HRV is one of the characteristics of development in children.
Trends and Interannual Variability of Satellite-Based Wind and Sea Surface Temperature over the Southern Ocean in the Recent Decade  [PDF]
Shailesh Mohan Pednekar
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.62009
Abstract: Using satellite-based 10-m surface wind (SW), wind stress (WS) and sea surface temperature (SST) anomalies, trends and inter-annual variability during 1993 and 2008 over the Southern Ocean (SO) are addressed. The climatological mean (16 years average) indicates that negative wind stress curl diminished (enhanced) between 40°S and 60°S zonal strap region coincide with weak (strong) SW and warm (cold) SST anomaly during January (July). Annual climatology indicates that strong region of SW divides warmer waters northward with positive wind stress curl (WSCL) and colder waters southward with negative WSCL. The time series anomalies are smoothened with a 12-month running mean filter. The filtered area-mean time series anomalies of zonal and meridional component of SW and SST have linear trends of -0.0005 ± 0.0003 m/s/decade, 0.0012 ± 0.0002 m/s/decade and -0.00005°C ± 0.0001°C/decade, respectively. The SW anomalies show an increasing trend of 0.0013 ± 0.0002 m/s/decade, with the meridional (zonal) component exhibiting an increasing (decreasing) trend. The meridional component plays a critical role in heat transfer through atmospheric circulation. The WS and wind stress divergence exhibit increasing trends whereas wind stress curl shows a decreasing trend. The SST fluctuates close to zero with repeated high and low peaks at an interval of 2 - 3 years. We address the interannual variability by performing EOF analysis on SW, WS, WSCL and SST anomalies which have been passed through a 12-month running mean filter.
Variations in the Patterns of Precipitation in the Watershed of the Ambato River Associated with the Eruptive Process of the Tungurahua Volcano in Ecuador  [PDF]
Iván Ríos García, Abel Solera
Open Journal of Modern Hydrology (OJMH) , 2015, DOI: 10.4236/ojmh.2015.54011
Abstract: The Tungurahua, located in the Cordillera de los Andes, is the volcano with the most eruptive activity in Ecuador nowadays. 1993 records the eruptive initial process and in August of 1999, after almost 80 years of rest, the volcano begins an explosive eruptive period. This research examines the effects of the eruptive process of the volcano in the patterns of change in precipitation in the short term in a hydrographic watershed. Their results are intended to contribute to the studies carried out to understand the weather and the factors influencing its variability at local and global level. It aims also to contribute with technical data in the debate about experimenting with artificial volcanoes to weather modification. The analysis demonstrates a process of redistribution of rainfall, with significant increases in rainfall from 42.25% on December, and significant decreases of 40.03% on September, during the presence of the eruptive process.
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