The association of antihypertensives with postural blood pressure and falls among seniors residing in the community : a case control study

Date of Acceptance: 22/07/2015 This article is protected by copyright. All rights reserved.

The association of antihypertensives with postural blood pressure and falls among seniors residing in the community : a case control study

Date of Acceptance: 22/07/2015 This article is protected by copyright. All rights reserved.

Physical Insights, Steady Aerodynamic Effects, and a Design Tool for Low-Pressure Turbine Flutter

The successful, efficient, and safe turbine design requires a thorough understanding of the underlying physical phenomena. This research investigates the physical understanding and parameters highly correlated to flutter, an aeroelastic instability prevalent among low pressure turbine (LPT) blades in both aircraft engines and power turbines. The modern way of determining whether a certain cascade of LPT blades is susceptible to flutter is through time-expensive computational fluid dynamics (CFD) codes. These codes converge to solution satisfying the Eulerian conservation equations subject to the boundary conditions of a nodal domain consisting fluid and solid wall particles. Most detailed CFD codes are accompanied by cryptic turbulence models, meticulous grid constructions, and elegant boundary condition enforcements all with one goal in mind: determine the sign (and therefore stability) of the aerodynamic damping. The main question being asked by the aeroelastician, ``is it positive or negative?'' This type of thought-process eventually gives rise to a black-box effect, leaving physical understanding behind. Therefore, the first part of this research aims to understand and reveal the physics behind LPT flutter in addition to several related topics including acoustic resonance effects. A percentage of this initial numerical investigation is completed using an influence coefficient approach to study the variation the work-per-cycle contributions of neighboring cascade blades to a reference airfoil. The second part of this research introduces new discoveries regarding the relationship between steady aerodynamic loading and negative aerodynamic damping. Using validated CFD codes as computational wind tunnels, a multitude of low-pressure turbine flutter parameters, such as reduced frequency, mode shape, and interblade phase angle, will be scrutinized across various airfoil geometries and steady operating conditions to reach new design guidelines regarding the influence of steady aerodynamic loading and LPT flutter. Many pressing topics influencing LPT flutter including shocks, their nonlinearity, and three-dimensionality are also addressed along the way. The work is concluded by introducing a useful preliminary design tool that can estimate within seconds the entire aerodynamic damping versus nodal diameter curve for a given three-dimensional cascade.

Influence of Outlet Boundary Conditions on Cerebrovascular Aneurysm Hemodynamics

Computational fluid dynamic (CFD) studies of blood flow in cerebrovascular aneurysms have potential to improve patient treatment planning by enabling clinicians and engineers to model patient-specific geometries and compute predictors and risks prior to neurovascular intervention. However, the use of patient-specific computational models in clinical settings is unfeasible due to their complexity, computationally intensive and time-consuming nature. An important factor contributing to this challenge is the choice of outlet boundary conditions, which often involves a trade-off between physiological accuracy, patient-specificity, simplicity and speed. In this study, we analyze how resistance and impedance outlet boundary conditions affect blood flow velocities, wall shear stresses and pressure distributions in a patient-specific model of a cerebrovascular aneurysm. We also use geometrical manipulation techniques to obtain a model of the patient’s vasculature prior to aneurysm development, and study how forces and stresses may have been involved in the initiation of aneurysm growth. Our CFD results show that the nature of the prescribed outlet boundary conditions is not as important as the relative distributions of blood flow through each outlet branch. As long as the appropriate parameters are chosen to keep these flow distributions consistent with physiology, resistance boundary conditions, which are simpler, easier to use and more practical than their impedance counterparts, are sufficient to study aneurysm pathophysiology, since they predict very similar wall shear stresses, time-averaged wall shear stresses, time-averaged pressures, and blood flow patterns and velocities. The only situations where the use of impedance boundary conditions should be prioritized is if pressure waveforms are being analyzed, or if local pressure distributions are being evaluated at specific time points, especially at peak systole, where the use of resistance boundary conditions leads to unnaturally large pressure pulses. In addition, we show that in this specific patient, the region of the blood vessel where the neck of the aneurysm developed was subject to abnormally high wall shear stresses, and that regions surrounding blebs on the aneurysmal surface were subject to low, oscillatory wall shear stresses. Computational models using resistance outlet boundary conditions may be suitable to study patient-specific aneurysm progression in a clinical setting, although several other challenges must be addressed before these tools can be applied clinically.

Effect of road quality in structural health monitoring under operational conditions

The effect of unevenness in a bridge deck for the purpose of Structural Health Monitoring (SHM) under operational conditions is studied in this paper. The moving vehicle is modelled as a single degree of freedom system traversing the damaged beam at a constant speed. The bridge is modelled as an Euler-Bernoulli beam with a breathing crack, simply supported at both ends. The breathing crack is treated as a nonlinear system with bilinear stiffness characteristics related to the opening and closing of crack. The unevenness in the bridge deck considered is modelled using road classification according to ISO 8606:1995(E). Numerical simulations are conducted considering the effects of changing road surface classes from class A - very good to class E - very poor. Cumulant based statistical parameters, based on a new algorithm are computed on stochastic responses of the damaged beam due to passages of the load in order to calibrate the damage. Possibilities of damage detection and calibration under benchmarked and non-benchmarked cases are considered. The findings of this paper are important for establishing the expectations from different types of road roughness on a bridge for damage detection purposes using bridge-vehicle interaction where the bridge does not need to be closed for monitoring.

Effects of vehicle speed in structural health monitoring from operational conditions of bridges

The effects of vehicle speed for Structural Health Monitoring (SHM) of bridges under operational conditions are studied in this paper. The moving vehicle is modelled as a single degree oscillator traversing a damaged beam at a constant speed. The bridge is modelled as simply supported Euler-Bernoulli beam with a breathing crack. The breathing crack is treated as a nonlinear system with bilinear stiffness characteristics related to the opening and closing of crack. The unevenness of the bridge deck is modelled using road classification according to ISO 8606:1995(E). The stochastic description of the unevenness of the road surface is used as an aid to monitor the health of the structure in its operational condition. Numerical simulations are conducted considering the effects of changing vehicle speed with regards to cumulant based statistical damage detection parameters. The detection and calibration of damage at different levels is based on an algorithm dependent on responses of the damaged beam due to passages of the load. Possibilities of damage detection and calibration under benchmarked and non-benchmarked cases are considered. Sensitivity of calibration values is studied. The findings of this paper are important for establishing the expectations from different vehicle speeds on a bridge for damage detection purposes using bridge-vehicle interaction where the bridge does not need to be closed for monitoring. The identification of bunching of these speed ranges provides guidelines for using the methodology developed in the paper.

A Novel Method for Rapid and Selective Extraction of Male DNA from Rape Kits using Alkaline Lysis and Pressure Cycling Technology (PCT)

There is an increasing demand for DNA analysis because of the sensitivity of the method and the ability to uniquely identify and distinguish individuals with a high degree of certainty. But this demand has led to huge backlogs in evidence lockers since the current DNA extraction protocols require long processing time. The DNA analysis procedure becomes more complicated when analyzing sexual assault casework samples where the evidence contains more than one contributor. Additional processing to separate different cell types in order to simplify the final data interpretation further contributes to the existing cumbersome protocols. The goal of the present project is to develop a rapid and efficient extraction method that permits selective digestion of mixtures. Selective recovery of male DNA was achieved with as little as 15 minutes lysis time upon exposure to high pressure under alkaline conditions. Pressure cycling technology (PCT) is carried out in a barocycler that has a small footprint and is semi-automated. Typically less than 10% male DNA is recovered using the standard extraction protocol for rape kits, almost seven times more male DNA was recovered from swabs using this novel method. Various parameters including instrument setting and buffer composition were optimized to achieve selective recovery of sperm DNA. Some developmental validation studies were also done to determine the efficiency of this method in processing samples exposed to various conditions that can affect the quality of the extraction and the final DNA profile. Easy to use interface, minimal manual interference and the ability to achieve high yields with simple reagents in a relatively short time make this an ideal method for potential application in analyzing sexual assault samples.

The impact of fluctuating light on the dinoflagellate Prorocentrum micans depends on NO3- and CO2 availability

Increasing atmospheric pCO2 and its dissolution into oceans leads to ocean acidification and warming, which reduces the thickness of upper mixing layer (UML) and upward nutrient supply from deeper layers. These events may alter the nutritional conditions and the light regime to which primary producers are exposed in the UML. In order to better understand the physiology behind the responses to the concomitant climate changes factors, we examined the impact of light fluctuation on the dinoflagellate Prorocentrum micans grown at low (1 µmol/L) or high (800 µmol/L) [NO3(-)] and at high (1000 µatm) or low (390 µatm, ambient) pCO2. The light regimes to which the algal cells were subjected were (1) constant light at a photon flux density (PFD) of either 100 (C100) or 500 (C500) µmol/m**2/s or (2) fluctuating light between 100 or 500 µmol photons/m**2/s with a frequency of either 15 (F15) or 60 (F60) min. Under continuous light, the initial portion of the light phase required the concomitant presence of high CO2 and NO3(-) concentrations for maximum growth. After exposure to light for 3h, high CO2 exerted a negative effect on growth and effective quantum yield of photosystem II (F'(v)/F'(m)). Fluctuating light ameliorated growth in the first period of illumination. In the second 3h of treatment, higher frequency (F15) of fluctuations afforded high growth rates, whereas the F60 treatment had detrimental consequences, especially when NO3(-) concentration was lower. F'(v)/F'(m) respondent differently from growth to fluctuating light: the fluorescence yield was always lower than at continuous light at 100 µmol/m**2/s, and always higher at 500 µmol/m**2/s. Our data show that the impact of atmospheric pCO2 increase on primary production of dinoflagellate depends on the availability of nitrate and the irradiance (intensity and the frequency of irradiance fluctuations) to which the cells are exposed. The impact of global change on oceanic primary producers would therefore be different in waters with different chemical and physical (mixing) properties.

High-pressure experiments on a natural olivine gabbro from ODP Hole 176-735B

We have conducted high-pressure experiments on a natural oceanic gabbro composition (Gb108). Our aim was to test recent proposals that Sr-enrichment in rare primitive melt inclusions from Mauna Loa, Hawaii, may have resulted from melting of garnet pyroxenite formed in the magma source regions by reaction of peridotite with siliceous, Sr-enriched partial melts of eclogite of gabbroic composition. Gb108 is a natural, Sr-enriched olivine gabbro, which has a strong positive Sr anomaly superimposed on an overall depleted incompatible trace element pattern, reflecting its origin as a plagioclase-rich cumulate. At high pressures it crystallises as a coesite eclogite assemblage, with the solidus between 1,300 and 1,350°C at 3.5 GPa and 1,450 and 1,500°C at 4.5 GPa. Clinopyroxenes contain 4-9% Ca-eskolaite component, which varies systematically with pressure and temperature. Garnets are almandine and grossular-rich. Low degree partial melts are highly siliceous in composition, resembling dacites. Coesite is eliminated between 50 and 100°C above the solidus. The whole-rock Sr-enrichment is primarily hosted by clinopyroxene. This phase dominates the mode (>75 wt%) at all investigated PT conditions, and is the major contributor to partial melts of this eclogite composition. Hence the partial melts have trace element patterns sub-parallel to those of clinopyroxene with ~10* greater overall abundances and with strong positive Sr anomalies. Recent studies of primitive Hawaiian volcanics have suggested the incorporation into their source regions of eclogite, formerly gabbroic material recycled through the mantle at subduction zones. The models suggest that formerly gabbroic material, present as eclogite in the Hawaiian plume, partially melted earlier than surrounding peridotite (i.e. at higher pressure) because of the lower solidus temperature of eclogite compared with peridotite. This produced highly siliceous melts which reacted with surrounding peridotite producing hybrid pyroxene + garnet lithologies. The Sr-enriched nature of the formerly plagioclase-rich gabbro was present in the siliceous partial melts, as demonstrated by these experiments, and was transferred to the reactive pyroxenite. These in turn partially melted, producing Sr-enriched picritic liquids which mixed with normal picritic partial melts of peridotite before eruption. On rare occasions these mixed, relatively Sr-rich melts were trapped as melt inclusions in primitive olivine phenocrysts.Yaxley-Sobolev

Seawater carbonate chemistry and biological processes of Amphisorus hemprichii, Amphisorus kudakajimensis and Calcarina gaudichaudii during experiments, 2011

Ocean acidification, which like global warming is an outcome of anthropogenic CO2emissions, severely impacts marine calcifying organisms, especially those living in coral reef ecosystems. However, knowledge about the responses of reef calcifiers to ocean acidification is quite limited, although coral responses are known to be generally negative. In a culture experiment with two algal symbiont-bearing, reef-dwelling foraminifers, Amphisorus kudakajimensis and Calcarina gaudichaudii, in seawater under five different pCO2 conditions, 245, 375, 588, 763 and 907 µatm, maintained with a precise pCO2-controlling technique, net calcification of A. kudakajimensis was reduced under higher pCO2, whereas calcification of C. gaudichaudii generally increased with increased pCO2. In another culture experiment conducted in seawater in which bicarbonate ion concentrations were varied under a constant carbonate ion concentration, calcification was not significantly different between treatments in Amphisorus hemprichii, a species closely related to A. kudakajimensis, or in C. gaudichaudii. From these results, we concluded that carbonate ion and CO2 were the carbonate species that most affected growth ofAmphisorus and Calcarina, respectively. The opposite responses of these two foraminifer genera probably reflect different sensitivities to these carbonate species, which may be due to their different symbiotic algae.

Seawater carbonate chemistry and hydrogen ions and carbonate chemistry in calcifying fluid of coral Astrangia poculata during experiments, 2011

A generalized physicochemical model of the response of marine organisms' calcifying fluids to CO2-induced ocean acidification is proposed. The model is based upon the hypothesis that some marine calcifiers induce calcification by elevating pH, and thus Omega aragonite, of their calcifying fluid by removing protons (H+). The model is explored through two end-member scenarios: one in which a fixed number of H+ is removed from their calcifying fluid, regardless of atmospheric pCO2, and another in which a fixed external-internal proton ratio ([H+]E/[H+]I) is maintained. The model is able to generate the full range of calcification response patterns observed in prior ocean acidification experiments and is consistent with the assertion that organisms' calcification response to ocean acidification is more negative for marine calcifiers that exert weaker control over their calcifying fluid pH. The model is empirically evaluated for the temperate scleractinian coral Astrangia poculata with in situ pH microelectrode measurements of the coral's calcifying fluid under control and acidified conditions. These measurements reveal that (1) the pH of the coral's calcifying fluid is substantially elevated relative to its external seawater under both control and acidified conditions, (2) the coral's [H+]E/[H+]I remains constant under control and acidified conditions, and (3) the coral removes fewer H+ from its calcifying fluid under acidified conditions than under control conditions. Thus, the carbonate system dynamics of A. poculata's calcifying fluid appear to be most consistent with the fixed [H+]E/[H+]I end-member scenario. Similar microelectrode experiments performed on additional taxa are required to assess the model's general applicability.

Seawater carbonate chemistry, chlorophyll a and phosphate during experiments with Trichodesmium erythraeum IMS101 (CCMP1985), 2010

In this laboratory study, we monitored the buildup of biomass and concomitant shift in seawater carbonate chemistry over the course of a Trichodesmium bloom under different phosphorus (P) availability. During exponential growth, dissolved inorganic carbon (DIC) decreased, while pH increased until maximum cell densities were reached. Once P became depleted, DIC decreased even further and total alkalinity (TA) dropped, accompanied by precipitation of aragonite. Under P-replete conditions, DIC increased and TA remained constant in the postbloom phase. A diffusion-reaction model was employed to estimate changes in carbonate chemistry of the diffusive boundary layer. This study demonstrates that Trichodesmium can induce precipitation of aragonite from seawater and further provides possible explanations about underlying mechanisms.

Seawater carbonate chemistry and biological processes of coccolithophore (Gephyrocapsa oceanica and Coccolithus pelagicus ssp. braarudii) during experiments, 2011

All species of coccolithophore appear to respond to perturbations of carbonate chemistry in a different way. Here, we show that the degree of malformation, growth rate and stable isotopic composition of organic matter and carbonate produced by two contrasting species of coccolithophore (Gephyrocapsa oceanica and Coccolithus pelagicus ssp. braarudii) are indicative of differences between their photosynthetic and calcification response to changing DIC levels (ranging from ~1100 to ~7800 µmol/kg) at constant pH (8.13 ± 0.02). Gephyrocapsa oceanica thrived under all conditions of DIC, showing evidence of increased growth rates at higher DIC, but C. braarudii was detrimentally affected at high DIC showing signs of malformation, and decreased growth rates. The carbon isotopic fractionation into organic matter and the coccoliths suggests that C. braarudii utilises a common internal pool of carbon for calcification and photosynthesis but G. oceanica relies on independent supplies for each process. All coccolithophores appear to utilize bicarbonate as their ultimate source of carbon for calcification resulting in the release of a proton. But, we suggest that this proton can be harnessed to enhance the supply of CO2(aq) for photosynthesis either from a large internal HCO3- pool which acts as a pH buffer (C. braarudii), or pumped externally to aid the diffusive supply of CO2 across the membrane from the abundant HCO3- (G. oceanica), likely mediated by an internal and external carbonic anhydrase respectively. Our simplified hypothetical spectrum of physiologies may provide a context to understand different species response to changing pH and DIC, the species-specific delta p and calcite "vital effects", as well as accounting for geological trends in coccolithophore cell size.

Seawater carbonate chemistry and community metabolism during an experiment with a coral reef, 2003

The effect of elevated pCO2 on the metabolism of a coral reef community dominated by macroalgae has been investigated utilizing the large 2650 m3 coral reef mesocosm at the Biosphere-2 facility near Tucson, Arizona. The carbonate chemistry of the water was manipulated to simulate present-day and a doubled CO2 future condition. Each experiment consisted of a 1-2 month preconditioning period followed by a 7-9 day observational period. The pCO2 was 404 ± 63 ?atm during the present-day pCO2 experiment and 658 ± 59 ?atm during the elevated pCO2 experiment. Nutrient levels were low and typical of natural reefs waters (NO3? 0.5-0.9 ?M, NH4+ 0.4 ?M, PO43? 0.07-0.09 ?M). The temperature and salinity of the water were held constant at 26.5 ± 0.2°C and 34.4 ± 0.2 ppt. Photosynthetically available irradiance was 10 ± 2 during the present-day experiment and 7.4 ± 0.5 mol photons m?2 d?1 during the elevated pCO2 experiment. The primary producer biomass in the mesocosm was dominated by four species of macroalgae; Haptilon cubense, Amphiroa fragillisima, Gelidiopsis intricata and Chondria dasyphylla. Algal biomass was 10.4 mol C m?2 during the present-day and 8.7 mol C m?2 and during the elevated pCO2 experiments. As previously observed, the increase in pCO2 resulted in a decrease in calcification from 0.041 ± 0.007 to 0.006 ± 0.003 mol CaCO3 m?2 d?1. Net community production (NCP) and dark respiration did not change in response to elevated pCO2. Light respiration measured by a new radiocarbon isotope dilution method exceeded dark respiration by a factor of 1.2 ± 0.3 to 2.1 ± 0.4 on a daily basis and by 2.2 ± 0.6 to 3.9 ± 0.8 on an hourly basis. The 1.8-fold increase with increasing pCO2 indicates that the enhanced respiration in the light was not due to photorespiration. Gross production (GPP) computed as the sum of NCP plus daily respiration (light + dark) increased significantly (0.24 ± 0.03 vs. 0.32 ± 0.04 mol C m?2 d?1). However, the conventional calculation of GPP based on the assumption that respiration in the light proceeds at the same rate as the dark underestimated the true rate of GPP by 41-100% and completely missed the increased rate of carbon cycling due to elevated pCO2. We conclude that under natural, undisturbed, nutrient-limited conditions elevated CO2 depresses calcification, stimulates the rate of turnover of organic carbon, particularly in the light, but has no effect on net organic production. The hypothesis that an increase pCO2 would produce an increase in net production that would counterbalance the effect of decreasing saturation state on calcification is not supported by these data.

Time series of seawater carbonate chemistry calculated throughout incubation periods of Boreogadus saida and Gadus morhua during exposure to different CO2 and temperature conditions

Oceans are experiencing increasing acidification in parallel to a distinct warming trend in consequence of ongoing climate change. Rising seawater temperatures are mediating a northward shift in distribution of Atlantic cod (Gadus morhua), into the habitat of polar cod (Boreogadus saida), that is associated with retreating cold water masses. This study investigates the competitive strength of the co-occurring gadoids under ocean acidification and warming (OAW) scenarios. Therefore, we incubated specimens of both species in individual tanks for 4 months, under different control and projected temperatures (polar cod: 0, 3, 6, 8 °C, Atlantic cod: 3, 8, 12, 16 °C) and PCO2 conditions (390 and 1170 µatm) and monitored growth, feed consumption and standard metabolic rate. Our results revealed distinct temperature effects on both species. While hypercapnia by itself had no effect, combined drivers caused nonsignificant trends. The feed conversion efficiency of normocapnic polar cod was highest at 0 °C, while optimum growth performance was attained at 6 °C; the long-term upper thermal tolerance limit was reached at 8 °C. OAW caused only slight impairments in growth performance. Under normocapnic conditions, Atlantic cod consumed progressively increasing amounts of feed than individuals under hypercapnia despite maintaining similar growth rates during warming. The low feed conversion efficiency at 3 °C may relate to the lower thermal limit of Atlantic cod. In conclusion, Atlantic cod displayed increased performance in the warming Arctic such that the competitive strength of polar cod is expected to decrease under future OAW conditions.