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Determinants of day-night difference in blood pressure in subjects of African ancestryMaseko, Joseph Muzi 25 May 2009 (has links)
Hypertension is a major risk factor for cardiovascular disease in both developed
and developing countries. Blood pressure normally decreases at night and a number of
studies have indicated that a reduced nocturnal decline in blood pressure (BP) increases
the risk for cardiovascular disease. Nocturnal decreases in BP are attenuated in subjects
of African as compared to European descent, but the mechanisms of this effect require
clarity. In the present study I attempted to identify potentially modifiable factors that
contribute toward nocturnal decreases in BP in a random sample of 171 nuclear families
comprising 438 black South Africans living in Soweto.
Prior studies have suggested that adiposity and salt intake may determine
nocturnal decreases in BP. Adiposity and salt intake were considered to be potentially
important factors to consider in the present study as 67% of the group studied were either
overweight or obese and in 291 subjects that had complete 24-hour urine collections
(used to assess salt intake) and BP measurements, Na+ and K+ intake was noted to be
considerably higher and lower respectively than the recommended daily allowance in the
majority of people. Moreover, a lack of relationship between either hypertension
awareness and treatment and Na+ and K+ intake suggested that current recommendations
for a reduced Na+ intake and increased K+ intake in hypertensives do not translate into
clinical practice in this community.
In order to assess whether adiposity or salt intake are associated with nocturnal
decreases in BP in this community, ambulatory BP monitoring was performed using
Spacelabs model 90207 oscillometric monitors. Of the 438 subjects recruited, 314 had
ambulatory BP measurements that met pre-specified quality criteria (more than 20 hours
of recordings and more than 10 and 5 readings for the computation of daytime and nighttime
means respectively). To identify whether adiposity or salt intake are associated with
a reduced nocturnal decline in BP, non-linear regression analysis was employed with
indices of adiposity and urinary Na+ and K+ excretion rates and urine Na+: K+ ratios
included in the regression model with adjustments for potential confounders. Neither
body mass index, skin-fold thickness, waist circumference, waist-to hip ratio, urinary Na+
and K+ excretion rates, nor urine Na+: K+ ratios were associated with nocturnal decreases
in systolic and diastolic BP. Indices of adiposity were however associated with 24 hour
ambulatory systolic and diastolic BP. Unexpectedly, female gender was associated with
an attenuated nocturnal decrease in BP.
In conclusion, in the first random, community-based sample with large sample
sizes conducted with ambulatory BP monitoring in Africa, I found that neither adiposity
nor salt intake are associated with a reduced nocturnal decline in BP. The lack of
association between either salt intake or adiposity and nocturnal decreases in BP was
despite a high prevalence of excessive adiposity in the community, as well as clear
evidence that current recommendations for a reduced Na+ intake and increased K+ intake
do not translate into clinical practice in this community. Thus, based on this study, the
question arises as to whether primordial prevention programs targeting excess adiposity
or inappropriate salt intake are likely to modify nocturnal decreases in BP, in urban,
developing communities of African ancestry in South Africa. However, unexpectedly I
noted that females were more likely to have an attenuated nocturnal decrease in BP. Thus
further work is required to explain this finding.
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A Comparison of Vehicle Speed at Day and Night Rural Horizontal CurvesQuaium, Ridwan B. 2010 May 1900 (has links)
This thesis documents the linear mixed model developed for vehicle speed along two-lane two-way rural horizontal curves in the outside lane. Speed data at each curve was collected at four points along the curve including the midpoint of the curve for a minimum of 48 hours during weekdays. Vehicle speed was analyzed separately for day and night conditions. The horizontal curves were categorized into different groups using different methods using side friction demand, radius and pavement edgeline marking retroreflectivity.
In the speed prediction model, radius, superelevation at the midpoint of the curve, deflection angle, posted speed limit and pavement edgeline marking retroreflectivity were used to predict the vehicle speed at the midpoint of the horizontal curve. The regression analysis indicates that all of these variables are statistically significant in predicting the vehicle speed at the midpoint of horizontal curves with a 95 percent confidence interval. The linear model determined that the vehicle speed has a positive relation with the radius of the curve, superelevation and posted speed limit but has a negative relation with the deflection angle and pavement edgeline marking retroreflectivity.
Curves were categorized based on side friction demand or radius and retroreflectivity of pavement edgeline marking. ANOVA was used to compare the day and night time speed. The comparisons reveal that vehicle speed at the horizontal curves decreases as the side friction demand value of the curves increases. Another finding of this research was that even though the posted speed limit is incorporated into the calculation of side friction demand, it may be necessary to analyze the impact of posted speed limit on vehicle speed for both daytime and nighttime. Previous literature determined that drivers may drive at an unsafe speed during nighttime at high levels of retroreflectivity. The results of this study could not confirm this statement as data from this study suggests that for curves with pavement edgeline marking retroreflectivity greater than 90 mcd/m2/lx, the effects of retroreflectivity on speed was determined to be minimal. This is based on the finding that the daytime and nighttime speeda were basically the same as the daytime and nighttime speed difference was both statistically and practically insignificant.
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Weight, Corticosterone and Glucose: Changes With Time of Day After Food DeprivationSommerville, Sheri, Perez, Vernon J., Elias, Jeffrey W., Smith, Constance J. 01 January 1988 (has links)
The effects of constant food deprivation, terminated at different times of day were examined with respect to percent body weight loss (%BWL), plasma corticosterone (PC) and plasma glucose (PG). A 19-hour food deprivation paradigm schedule staggered around varying times of the day-night cycle was used. Patterns of %BWL related to nocturnal lipogenesis and diurnal lipolysis showed the greatest loss (10%) occurring at 0700 hr, while in evening hours, there was an increasing pattern of weight loss, with the greatest amount (7%) occurring at 2200 hr. A pattern suggestive of neuroregulatory cycles of glucocorticoid release was evident for PC levels; maximum levels for PC (23.2 μg%) were reported at 0700 hr and at 1900 hr (16.6 μg%). Similar patterns were also noted in PG levels, with respective maximum levels of 138.0 mg% and 125.8 mg% occurring at 0700 hr and 1900 hr. These results indicate that the time of day that a deprivation schedule is initiated and terminated is an important consideration due to the impact of circadian photoperiodism. Time of day should be an essential consideration when utilizing deprivation paradigms.
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Barns föreställningar om dag- och nattcykeln : Har eleverna uppnått målen för år 5?Martinsson, Lisbeth January 2006 (has links)
<p>Syftet med detta examensarbete är att ta reda på hur elevers uppfattningar om de rörelser som sker i vårt solsystem stämmer överens med de vetenskapliga fakta som finns. I våra vardagliga situationer refererar vi till det vi med ögats hjälp kan uppfatta i fråga om vad som rör sig eller ej. Hur påverkas eleverna av de dagliga uttryck som de får höra sedan de är mycket små, och har de en möjlighet att med skolans hjälp förändra dessa tankesätt?</p><p>Undersökningen genomfördes med hjälp av kvalitativa intervjuer av elever i skolår 1 respektive 5. Detta för att se hur stor skillnaden är mellan de elever som inte har erhållit någon undervisning om solsystemet och de elever som ska ha uppnått de mål för fysik som skolverket har ställt upp.</p><p>Eleverna som deltog i studien valdes slumpmässigt ur respektive klasser. De fick besvara 14 frågor, var och en för sig. De besvarade frågorna olika utförligt, vissa var mycket fåordiga. Ibland var jag tvungen att ställa följdfrågor, eftersom jag ville förstå eleverna på ett bra sätt.</p><p>Resultatet av undersökningen visar att elevernas kunskaper inom området har en stor variation, även inom samma åldrar. Detta kan härledas till elevernas eget intresse av vårt solsystem. Den slutsats som jag har dragit av undersökningen är att det är viktigt att ta reda på vilka föreställningar som eleverna har inför arbetet med arbetsområdet.</p> / <p>The purpose of this degree project is to find pupils´ understanding about the movements which occur in our solar system and compare them with the scientific facts we know about. In our daily life we refer to what we can see with the help from our eyes whether something moves or not. How do the pupils´ get affected by these daily expressions they hear from early ages, and do they have an opportunity with the help from the school to change these ways of thinking?</p><p>The survey was carried out with help of qualitative interviews of pupils´ in class 1 and 5. This because to see how large the difference is between pupils´ who hasn’t received any education about the solar system and the pupils´ who are supposed to have reached the goals compiled by The National Agency for Education.</p><p>The pupils´ who took part in this study were chosen by random from both classes. They answered to 14 questions, each and everyone on their own. They answered the questions with various details, some were very taciturn. Sometimes I had to ask resulting questions, since I wanted to understand the pupils´ properly.</p><p>The result of the survey shows that the pupils´ knowledge within the area have a large variation, even within the same ages. This can be deduced to the interest of the pupils´ in our solar system. The conclusion I have maid from this survey are that it is important to find out which understandings the pupils´ have before the work with the subject area.</p>
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Barns föreställningar om dag- och nattcykeln : Har eleverna uppnått målen för år 5?Martinsson, Lisbeth January 2006 (has links)
Syftet med detta examensarbete är att ta reda på hur elevers uppfattningar om de rörelser som sker i vårt solsystem stämmer överens med de vetenskapliga fakta som finns. I våra vardagliga situationer refererar vi till det vi med ögats hjälp kan uppfatta i fråga om vad som rör sig eller ej. Hur påverkas eleverna av de dagliga uttryck som de får höra sedan de är mycket små, och har de en möjlighet att med skolans hjälp förändra dessa tankesätt? Undersökningen genomfördes med hjälp av kvalitativa intervjuer av elever i skolår 1 respektive 5. Detta för att se hur stor skillnaden är mellan de elever som inte har erhållit någon undervisning om solsystemet och de elever som ska ha uppnått de mål för fysik som skolverket har ställt upp. Eleverna som deltog i studien valdes slumpmässigt ur respektive klasser. De fick besvara 14 frågor, var och en för sig. De besvarade frågorna olika utförligt, vissa var mycket fåordiga. Ibland var jag tvungen att ställa följdfrågor, eftersom jag ville förstå eleverna på ett bra sätt. Resultatet av undersökningen visar att elevernas kunskaper inom området har en stor variation, även inom samma åldrar. Detta kan härledas till elevernas eget intresse av vårt solsystem. Den slutsats som jag har dragit av undersökningen är att det är viktigt att ta reda på vilka föreställningar som eleverna har inför arbetet med arbetsområdet. / The purpose of this degree project is to find pupils´ understanding about the movements which occur in our solar system and compare them with the scientific facts we know about. In our daily life we refer to what we can see with the help from our eyes whether something moves or not. How do the pupils´ get affected by these daily expressions they hear from early ages, and do they have an opportunity with the help from the school to change these ways of thinking? The survey was carried out with help of qualitative interviews of pupils´ in class 1 and 5. This because to see how large the difference is between pupils´ who hasn’t received any education about the solar system and the pupils´ who are supposed to have reached the goals compiled by The National Agency for Education. The pupils´ who took part in this study were chosen by random from both classes. They answered to 14 questions, each and everyone on their own. They answered the questions with various details, some were very taciturn. Sometimes I had to ask resulting questions, since I wanted to understand the pupils´ properly. The result of the survey shows that the pupils´ knowledge within the area have a large variation, even within the same ages. This can be deduced to the interest of the pupils´ in our solar system. The conclusion I have maid from this survey are that it is important to find out which understandings the pupils´ have before the work with the subject area.
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Detecting nighttime fire combustion phase by hybrid application of visible and infrared radiation from Suomi NPP VIIRSRoudini, Sepehr 01 August 2019 (has links)
An accurate estimation of biomass burning emissions is in part limited by the lack of knowledge of fire burning phase (smoldering/flaming). In recent years, several fire detection products have been developed to provide information of fire radiative power (FRP), location, size, and temperature of fire pixels, but no information regarding fire burning phase is retrieved. The Day-Night band (DNB) aboard Visible Infrared Imaging Radiometer Suite (VIIRS) is sensitive to visible light from flaming fires in the night. In contrast, VIIRS 4 µm moderate resolution band #13 (M13), though capable to detect fires at all phases, has no direct sensitivity for discerning fire phase. However, the hybrid usage of VIIRS DNB and M-bands data is hampered due to their different scanning technology and spatial resolution. In this study, we present a novel method to rapidly and accurately resample DNB pixel radiances to M-band pixels’ footprint that is based on DNB and M-band’s respective characteristics in their onboard schemes for detector aggregation and bow-tie effect removals. Subsequently, the visible energy fraction (VEF) as an indicator of fire burning phase is introduced and is calculated as the ratio of visible light power (VLP) and FRP for each fire pixel retrieved from VIIRS 750 m active fire product. A global distribution of VEF values, and thereby the fire phase, is quantitatively obtained, showing mostly smoldering wildfires such as peatland fires (with smaller VEF values) in Indonesia, flaming wildfires (with larger VEF values) over grasslands and savannahs in sub-Sahel region, and gas fares with largest VEF values in the Middle East. VEF is highly correlated with modified combustion efficiency (MCE) for different land cover types or regions. These results together with a case study of the 2018 California Campfire show that the VEF has the potential to be an indicator of fire combustion phase for each fire pixel, appropriate for estimating emission factors at the satellite pixel level.
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Matter and damping effects in neutrino mixing and oscillationsBlennow, Mattias January 2005 (has links)
<p>This thesis is devoted to the study of neutrino physics in general and the study of neutrino mixing and oscillations in particular. In the standard model of particle physics, neutrinos are massless, and as a result, they do not mix or oscillate. However, many experimental results now seem to give evidence for neutrino oscillations, and thus, the standard model has to be extended in order to incorporate neutrino masses and mixing among different neutrino flavors.</p><p>When neutrinos propagate through matter, the neutrino mixing, and thus, also the neutrino oscillations, may be significantly altered. While the matter effects may be easily studied in a framework with only two neutrino flavors and constant matter density, we know that there exists (at least) three neutrino flavors and that the matter density of the Universe is far from constant. This thesis includes studies of three-flavor effects and a solution to the two-flavor neutrino oscillation problem in matter with an arbitrary density profile.</p><p>Furthermore, there have historically been attempts to describe the neutrino flavor transitions by other effects than neutrino oscillations. Even if these effects now seem to be disfavored as the leading mechanism, they may still give small corrections to the neutrino oscillation formulas. These effects may lead to erroneous determination of the fundamental neutrino oscillation parameters and are also studied in this thesis in form of damping factors.</p>
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Barns tankar och idéer om himlakropparnas rörelse : Vanliga astronomiska missförstånd / Children’s Thoughts and Ideas About Celestial Motion : Common astronomical misconceptionsJohansson, Elin January 2014 (has links)
Sammanfattning De flesta barn fängslas och visar intresse för temat rymden och finner vanligtvis att det är ett mycket intressant ämne. Fokusgruppen har varit elever i årskurs 4-6 och efter några större bortfall var det slutligen elever ifrån 8 klasser som deltog, totalt 94 elever. Eleverna fick svara på en enkät där eleverna i både text och bild bland annat fick förklara hur de trodde att objekten i sol–jord–månsystemet samverkade och rörde sig i förhållande till varandra, vad de placerade i centrum för detta system, hur de såg på orsaken till årstider samt varför vi har dag och natt. De två pedagogerna som undervisade klasserna fick svara på några frågor om hur de såg på undervisningen om astronomi, om den undervisningsmetod de använde sig av och på elevernas lärande och förståelse för ämnet astronomi. I denna undersökning kunde samma typer av missuppfattningar ses hos dessa elever, som de missuppfattningar som har dykt upp i en rad olika undersökningar som genomförts tidigare år med andra barn ifrån olika länder. Några av de missuppfattningar som fanns hos eleverna i denna undersökning var bland annat att jorden var mittpunkten, något som en femtedel av eleverna visade. Att sol och måne låg i samma omloppsbana runt jorden, årstiderna orsakas av att avståndet till solen förändras och att dag/natt beror på jordens omloppsbana runt solen var några andra missuppfattningar som rådde bland eleverna. Användandet av konkret material och 3D-modeller i undervisningen om rymden tycks vara en viktig del för elevernas förståelse av området. Nyckelord: undervisning om rymden – astronomiska missförstånd – årstider – dag/natt – omloppsbanor i sol–jord–månsystemet / Abstract Most children find astronomy an interesting subject and usually show an interest during lessons about the subject. The focus group in this paper is Swedish students in school year 4-6. In total there were 94 students from eight classes who answered the survey with simple drawings and explanations about for example how they thought the objects Sun–Earth–Moon orbit each other, which object they placed as the center in this system, what causes season and the reason behind day and night. Two teachers whom educate the students answered some questions about their teaching method, their thoughts about the subject in question and the students learning and understanding of astronomy. In the study that are presented in this paper the same types of astronomical misconceptions can be seen amongst these students, that has been shown in similar studies of children all over the world. 20 % of the children in this study showed an earth centered Sun–Earth–Moon system. Other misconceptions that were shown was: the sun and the moon shares the same orbit around the earth, that the seasons are caused by the distance to the sun changing and that day and night happens because the earth orbits the sun. The use of concrete material and 3D-models in the education seemed to be important for the students understanding of the subject. Keywords: Astronomy education – astronomy misconceptions – seasons – day/night – Celestial Motion in the Sun–Earth–Moon system
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Matter and damping effects in neutrino mixing and oscillationsBlennow, Mattias January 2005 (has links)
This thesis is devoted to the study of neutrino physics in general and the study of neutrino mixing and oscillations in particular. In the standard model of particle physics, neutrinos are massless, and as a result, they do not mix or oscillate. However, many experimental results now seem to give evidence for neutrino oscillations, and thus, the standard model has to be extended in order to incorporate neutrino masses and mixing among different neutrino flavors. When neutrinos propagate through matter, the neutrino mixing, and thus, also the neutrino oscillations, may be significantly altered. While the matter effects may be easily studied in a framework with only two neutrino flavors and constant matter density, we know that there exists (at least) three neutrino flavors and that the matter density of the Universe is far from constant. This thesis includes studies of three-flavor effects and a solution to the two-flavor neutrino oscillation problem in matter with an arbitrary density profile. Furthermore, there have historically been attempts to describe the neutrino flavor transitions by other effects than neutrino oscillations. Even if these effects now seem to be disfavored as the leading mechanism, they may still give small corrections to the neutrino oscillation formulas. These effects may lead to erroneous determination of the fundamental neutrino oscillation parameters and are also studied in this thesis in form of damping factors. / QC 20101124
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Theoretical and Phenomenological Studies of Neutrino PhysicsBlennow, Mattias January 2007 (has links)
This thesis is devoted to the theory and phenomenology of neutrino physics. While the standard model of particle physics has been extremely successful, it fails to account for massive neutrinos, which are necessary to describe the observations of neutrino oscillations made by several different experiments. Thus, neutrino physics is a possible window for exploring the physics beyond the standard model, making it both interesting and important for our fundamental understanding of Nature. Throughout this thesis, we will discuss different aspects of neutrino physics, ranging from taking all three types of neutrinos into account in neutrino oscillation experiments to exploring the possibilities of neutrino mass models to produce a viable source of the baryon asymmetry of the Universe. The emphasis of the thesis is on neutrino oscillations which, given their implication of neutrino masses, is a phenomenon where other results that are not describable in the standard model could be found, such as new interactions between neutrinos and fermions. / QC 20100630
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