scholarly journals Effective Null Raychaudhuri Equation

Particles ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 230-237 ◽  
Author(s):  
Alessandro Pesci
Keyword(s):  
Focal Point ◽  
Effective Rate ◽  
Rate Of Change ◽  
Point Of View ◽  
Small Scale ◽  
Generic Point ◽  
Cross Sectional ◽  
Effective Expansion ◽  
Continuous Description ◽  
Particle Nature

The effects on Raychaudhuri’s equation of an intrinsically-discrete or particle nature of spacetime are investigated. This is done through the consideration of null congruences emerging from, or converging to, a generic point of spacetime, i.e., in geometric circumstances somehow prototypical of singularity issues. We do this from an effective point of view, that is through a (continuous) description of spacetime modified to embody the existence of an intrinsic discreteness on the small scale, this adding to previous results for non-null congruences. Various expressions for the effective rate of change of expansion are derived. They in particular provide finite values for the limiting effective expansion and its rate of variation when approaching the focal point. Further, this results in a non-vanishing of the limiting cross-sectional area itself of the congruence.

scholarly journals Effective Null Raychaudhuri Equation

2018 ◽  
Author(s):  
Alessandro Pesci
Keyword(s):  
Focal Point ◽  
Effective Rate ◽  
Rate Of Change ◽  
Point Of View ◽  
Small Scale ◽  
Generic Point ◽  
Cross Sectional ◽  
Effective Expansion ◽  
Continuous Description ◽  
Particle Nature

The effects on Raychaudhuri's equation of an intrinsically discrete or particle nature of spacetime are investigated, through consideration of null congruences emerging from, or converging to, a generic point of spacetime, i.e. in geometric circumstances somehow prototypical of singularity issues. This is done from an effective point of view, meaning through a (continuous) description of spacetime modified to embody the existence of an intrinsic discreteness on the small scale, adding to previous results for non-null congruences. Various expressions for the effective rate of change of expansion are derived. They in particular provide finite values for the limiting effective expansion and its rate of variation when approaching the focal point; this on top of resulting non vanishing the limiting cross-sectional area itself of the congruence.

A walking bout reveals altered foot thermodynamics associated with unilateral transtibial amputation among individuals with type 2 diabetes

2020 ◽  
pp. 030936462096864
Author(s):  
Kyle R Leister ◽  
Shane R Wurdeman
Keyword(s):  
Type 2 Diabetes ◽  
Temperature Change ◽  
Foot Ulcer ◽  
Diabetic Foot Ulcer ◽  
Rate Of Change ◽  
Peak Temperature ◽  
Cross Sectional ◽  
Contralateral Limb ◽  
Transtibial Amputation

Background: Increased foot temperature among individuals with type 2 diabetes can be predictive of diabetic foot ulcer development. A combination of physiological and mechanical deficiencies may contribute to elevations in intact foot temperature during gait for individuals with type 2 diabetes and transtibial amputation. Objective: This study evaluated plantar foot temperature differences between individuals with type 2 diabetes with and without transtibial amputation. We hypothesized that individuals with transtibial amputation maintain increased foot temperature compared to those without amputation. Study Design: Cross-sectional, case control. Methods: A sample of 16 participants with type 2 diabetes and transtibial amputation, and 16 age- and sex-matched participants with type 2 diabetes without amputation were recruited. Foot temperatures were measured during resting, walking, and cooldown periods. Peak temperature, mean temperature, and rate of temperature change were analyzed for each period, and compared between cohorts. Results: Participants with amputation exhibited increased mean foot temperature while at rest and during walking. Participants without amputation exhibited increased rate of change of foot temperature during walking. No differences in peak temperature or rate of temperature change were observed during the baseline or cooldown periods. Conclusion: The current findings of altered foot temperature for individuals with transtibial amputation and type 2 diabetes suggest a possible reason for the high rates of contralateral limb ulceration and amputation among this population.

scholarly journals Engineering students’ attitudinal beliefs by gender and student division: a methodological comparison of changes over time

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Madison E. Andrews ◽  
Anita D. Patrick ◽  
Maura Borrego
Keyword(s):  
Self Efficacy ◽  
Engineering Students ◽  
Focal Point ◽  
Value Engineering ◽  
Longitudinal Analyses ◽  
Utility Value ◽  
Cross Sectional ◽  
Targeted Interventions ◽  
Significant Difference ◽  
Over Time

Abstract Background Students’ attitudinal beliefs related to how they see themselves in STEM have been a focal point of recent research, given their well-documented links to retention and persistence. These beliefs are most often assessed cross-sectionally, and as such, we lack a thorough understanding of how they may fluctuate over time. Using matched survey responses from undergraduate engineering students (n = 278), we evaluate if, and to what extent, students’ engineering attitudinal beliefs (attainment value, utility value, self-efficacy, interest, and identity) change over a 1-year period. Further, we examine whether there are differences based on gender and student division, and then compare results between cross-sectional and longitudinal analyses to illustrate weaknesses in our current understanding of these constructs. Results Our study revealed inconsistencies between cross-sectional and longitudinal analyses of the same dataset. Cross-sectional analyses indicated a significant difference by student division for engineering utility value and engineering interest, but no significant differences by gender for any variable. However, longitudinal analyses revealed statistically significant decreases in engineering utility value, engineering self-efficacy, and engineering interest for lower division students and significant decreases in engineering attainment value for upper division students over a one-year period. Further, longitudinal analyses revealed a gender gap in engineering self-efficacy for upper division students, where men reported higher means than women. Conclusions Our analyses make several contributions. First, we explore attitudinal differences by student division not previously documented. Second, by comparing across methodologies, we illustrate that different conclusions can be drawn from the same data. Since the literature around these variables is largely cross-sectional, our understanding of students’ engineering attitudes is limited. Our longitudinal analyses show variation in engineering attitudinal beliefs that are obscured when data is only examined cross-sectionally. These analyses revealed an overall downward trend within students for all beliefs that changed significantly—losses which may foreshadow attrition out of engineering. These findings provide an opportunity to introduce targeted interventions to build engineering utility value, engineering self-efficacy, and engineering interest for student groups whose means were lower than average.

Dilatation of Vascular Prostheses in Ascending Aortic Position: A Long-Term Follow-Up Computed Tomography Study with Comparison of Different Measurement Methods

2016 ◽  
Vol 66 (03) ◽  
pp. 206-214
Author(s):  
Matthias Endlich ◽  
Christian Krämer ◽  
Chris Probst ◽  
Armin Welz ◽  
Kai Wilhelm ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Measurement Methods ◽  
Point Of View ◽  
Cross Sectional ◽  
Vascular Prostheses ◽  
Aortic Replacement ◽  
Ascending Aortic Replacement ◽  
Long Term Follow Up ◽  
Methods Of Measurement

Background The aim of this study was to evaluate long-term dilatation of Hemashield Gold and Hemashield Platinum vascular prostheses in ascending aortic position using different measurement methods to obtain precise results. Methods Between 1999 and 2007, 73 patients with Stanford type A dissection received ascending aortic replacement with Hemashield Gold and Hemashield Platinum prostheses. Measurements were performed using multiplanar reconstruction mode of electrocardiogram (ECG)-gated, multislice spiral computed tomography (MSCT) in strictly orthogonal cross-sectional planes. Different methods of measurement were compared and maximum dilatation was estimated for different time spans. Results Diameters calculated from the measured circumference showed a significant (p = 0.037) but clinically not relevant difference (0.1 mm) to the mean between the largest and the shortest cross-sectional diameter of the prosthesis. Dilatation after 24.2 ± 10.2 months was 8.5 ± 4.5%. Long-term dilatation after 91.8 ± 34 months amounted to 11.8 ± 4.2%. Conclusion Based on ECG-gated MSCT images, the presented methods of measurement provided reliable results. Long-term analysis shows low dilatation rates for Hemashield prostheses, which therefore can be considered as safe from this point of view. Nevertheless, a maximal dilatation of 20% could be relevant in valve sparing root replacement. It remains unclear if a dilatation like this contributes to the formation of suture aneurysms.

scholarly journals Caregiver Status and Diet Quality in Community-Dwelling Adults

Nutrients ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1803
Author(s):  
Sharmin Hossain ◽  
May A. Beydoun ◽  
Michele K. Evans ◽  
Alan B. Zonderman ◽  
Marie F. Kuczmarski
Keyword(s):  
Diet Quality ◽  
Healthy Aging ◽  
Healthy Eating Index ◽  
Community Dwelling ◽  
Rate Of Change ◽  
Least Square ◽  
Inverse Association ◽  
Linear Regression Models ◽  
Middle Aged ◽  
Cross Sectional

Objective: We investigated cross-sectional and longitudinal associations of diet quality with middle-aged caregiver status. Methods: Caregiving in the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study (57.7% women, 62% African American (AA)) was measured at waves 3 (2009–2013) and 4 (2013–2017) (mean follow-up time 4.1 years). Diet quality was assessed by the Healthy Eating Index 2010 (HEI-2010) derived from two separate 24 h diet recalls. Multivariable ordinary least square regression was performed for cross-sectional analyses of the association of wave 4 caregiving with wave 4 HEI-2010. Wave 3 caregiving was examined both cross-sectionally and with annual rate of change in HEI using mixed-effects linear regression Models. Multivariable models were adjusted for age, sex, and poverty status. Results: Cross-sectional analyses at wave 4 demonstrate an inverse association of frequent caregiving (“Daily or Weekly” vs. “Never”) for grandchildren with HEI-2010 total score (i.e., lower diet quality) among Whites (β = −2.83 ± 1.19, p = 0.03, Model 2) and AAs (β = −1.84 ± 0.79, p = 0.02,). The “cross-sectional” analysis pertaining to grandchildren caregiving frequency suggested that frequent caregiving (i.e., “Daily or Weekly” vs. “Never” (β = −2.90 ± 1.17, p = 0.04)) only among Whites was inversely related to HEI-2010 total score. Total HEI-2010 score was also related to caring (Model 1), for the elderly over “5 years vs. Never” among Whites (−7.31 ± 3.54, p = 0.04, Model 2). Longitudinally, we found slight potential improvement in diet quality over time (“Daily or Weekly” vs. Never by TIME interaction: +0.88 ± 0.38, p = 0.02) with frequent caregiving among Whites, but not so among AAs. Conclusions: Frequent caring for grandchildren had an inverse relationship with the diet quality of White and AA urban middle-aged caregivers, while caring for elderly was inversely linked to diet quality among Whites only. Longitudinal studies should address the paucity of research on caregivers’ nutritional quality.

SUBMERGED CITRIC ACID FERMENTATION OF SUGAR BEET MOLASSES: INCREASE IN SCALE

1955 ◽  
Vol 1 (5) ◽  
pp. 299-311 ◽  
Author(s):  
R. Steel ◽  
C. P. Lentz ◽  
S. M. Martin
Keyword(s):  
Citric Acid ◽  
Scale Up ◽  
Aeration Rate ◽  
Small Scale ◽  
Acid Fermentation ◽  
Inoculum Level ◽  
Cross Sectional ◽  
Factors Affecting ◽  
Beet Molasses ◽  
Initial Ph

Factors affecting the production of citric acid in the submerged fermentation of ferrocyanide-treated beet molasses by Aspergillus niger were studied in 2.5 and 36 liter fermenters. The small fermenters were used to determine the effects of changes in sterilization technique, phosphate supplement, ferrocyanide treatment, inoculum level, initial pH, fermentation temperature, and aeration rate. The relation between ferrocyanide concentration and inoculum level was also studied. Four different samples of molasses were fermented successfully. An average yield of 8.2% citric acid (64% conversion) was obtained from 51 small-scale fermentations. Comparable yields were obtained in the large fermenters under comparable conditions. Most of the information obtained with the small fermenters was applicable to the larger-scale fermenters, but in the latter the fermentation was significantly more stable. Aeration was the main problem in the scale-up and aeration rates approximately double those calculated on a fermenter cross-sectional area basis were required for comparable results in the large fermenters.

Error Estimation for Known Marker Position Retrieval by Ideal Pinhole Camera Direct Observation

2016 ◽  
Vol 841 ◽  
pp. 192-197
Author(s):  
Constantin Radu Mirescu ◽  
Gabriela Roșca
Keyword(s):  
Gait Analysis ◽  
Error Estimation ◽  
Motion Capture ◽  
Direct Observation ◽  
Focal Point ◽  
Pinhole Camera ◽  
Point Of View ◽  
Direct Approach ◽  
Marker Position

For Motion Capture in Gait Analysis using Known Spherical Markers one simple direct approach is to compute the projection of the Marker Center using its projection in the Pixel Plane and based on it to find the location of the Marker on the line that connects the Marker Center Projection and the camera Focal Point. For various positions of the Marker in the workspace the exact image of the marker is computed using a genuine approach and compute back the approximation of the position based on the generated image. Various algorithms are taken in consideration and finally the results are assessed from the point of view of Gait Analysis and two directions for calculus improvement are identified.

Towards a New Model of Conversion Careers: the Impact of Personality and Contingency Factors

Exchange ◽  
2005 ◽  
Vol 34 (2) ◽  
pp. 149-166 ◽  
Author(s):  
Henri Gooren
Keyword(s):  
Religious Conversion ◽  
Religious Affiliation ◽  
Point Of View ◽  
Small Scale ◽  
Central Question ◽  
Roman Catholicism ◽  
Guatemala City ◽  
Practical Point ◽  
The Poor ◽  
The Impact

AbstractThe central question of this article — why people may change their religious affiliation or become disaffiliated — is relevant from both an academic and a practical point of view. The article makes first an inventory of existing literature on religious conversion. Next I sketch the contours of the new conversion careers approach I am currently working on. I make some comparisons with a region that is not usually mentioned in the literature on conversion: Latin America. These comparisons are based on my earlier fieldwork on Roman Catholicism, Pentecostalism, and Mormonism in Costa Rica and Guatemala (H. Gooren, Rich among the Poor: Church, Firm, and Household among Small-scale Entrepreneurs in Guatemala City, Amsterdam: Thela Thesis 1999).

Evaluation of health system in Iraq from people's point of view: a comparative study of two different eras

2021 ◽  
Vol 4 (2) ◽  
pp. 380-387
Author(s):  
Saad Ahmed Ali Jadoo ◽  
Adil H. Alhusseiny ◽  
Shukr Mahmood Yaseen ◽  
Mustafa Ali Mustafa Al-Samarrai ◽  
Anmar Shukur Mahmood
Keyword(s):  
Health System ◽  
Health Sector ◽  
Health Resources ◽  
Sampling Technique ◽  
Point Of View ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Current Health ◽  
Multi Stage ◽  
Geographical Regions

Background: Since the 2003 United States–British Coalition military invasion, Iraq has been in a state of continuous deterioration at all levels, including the health sector. This study aimed to elicit the viewpoints of the Iraqi people on the current health system, focusing on many provided health services and assessing whether the public prefers the current health system or that was provided before the invasion. Methods: A cross-sectional survey designed to explore the Iraqi people’s opinions on their health system. A self-administered questionnaire using a multi-stage sampling technique was distributed in five geographical regions in Iraq to collect the data from the head of household between 1st October and 31st of December 2019. Multiple logistic regressions were recruited to determine the significant contributing variables in this study. Results: A total of 365 heads of households (response rate: 71.7%) with the mean age of 48.36 + 11.92 years (ranged 35-78) included in the study. Most of the respondents (61.4%) complained of healthcare inaccessibility, 59.7% believed that health resources were not available, 53.7% claimed a deterioration in the quality of care, and 62.2% believed that the political / media position did not contribute to positive changes during the past two decades. Indeed, most respondents (66.0%) believe that the current healthcare system is worse than before. In the multivariate analysis, there was a statistically significant relationship between the characteristics and opinions of the respondents. Young age group (p = 0.003), men (p = < 0.001), unmarried (p = 0.001), high educated (p = < 0.001), rural resident (p = < 0.001), unemployed (p = 0.003), monthly income of less than USD 400 (p = < 0.001), consider themselves to be unhealthy (p = 0.001),  and those who think that people are unhappy now than two decades ago (p = 0.012) have a more negative opinion of the health system. Conclusions: Most Iraqis surveyed expressed disappointment from the health system after the 2003 US-led invasion. The current health system is faltering at all levels and does not meet the citizens' basic needs. Health Transformation Program (HTP) has become inevitable to develop an accessible, affordable, high-quality, efficient, and effective health system.

A new age-period-cohort model for cancer surveillance research

2018 ◽  
Vol 28 (10-11) ◽  
pp. 3363-3391 ◽  
Author(s):  
Philip S Rosenberg
Keyword(s):  
Group Versus ◽  
R Package ◽  
New Age ◽  
Variable Number ◽  
Rate Of Change ◽  
Cancer Surveillance ◽  
Cohort Model ◽  
Cross Sectional ◽  
New Model ◽  
Regression Parameters

We develop a new age-period-cohort model for cancer surveillance research; the theory and methods are broadly applicable. In the new model, cohort deviations are weighted to account for the variable number of periods that each cohort is observed. Weighting ensures that the fitted rates can be naturally expressed as a function of age × a function of period × a function of cohort. Furthermore, the age, period, and cohort deviations are split into orthogonal quadratic components plus higher-order terms. These decompositions enable powerful combination significance tests of first- and second-order age, period, and cohort effects. The regression parameters of the orthogonal quadratic polynomials (global curvatures) quantify how fast on average the trends in the rates are changing. Importantly, the global curvature for cohort determines the least squares slope of the expected annual percentage changes by age group versus age (local drifts), thereby providing a powerful one-degree-of-freedom test of age-period interactions. We introduce new estimable functions, including age gradients that quantify the rate of change of the longitudinal and cross-sectional age curves at each attained age, and gradient shifts that quantify how the cross-sectional age trend varies by period. We illustrate the new model using nationally representative multiple myeloma incidence. Comprehensive proofs are given in technical appendices. We provide an R package.

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