427 research outputs found
A cohort study of the effectiveness of influenza vaccine in older people, performed using the United Kingdom general practice research database.
BACKGROUND: The effectiveness of influenza vaccination against hospitalization and death can only ethically be assessed in observational studies. A concern is that individuals who are vaccinated are healthier than individuals who are not vaccinated, potentially biasing estimates of effectiveness upward. METHODS: We conducted a historical cohort study of individuals >64 years of age, for whom there were data available in the General Practice Research Database for 1989 to 1999 in England and Wales. Rates of admissions for acute respiratory diseases and rates of death due to respiratory disease were compared over 692,819 person-years in vaccine recipients and 1,534,280 person-years in vaccine nonrecipients. RESULTS: The pooled effectiveness of vaccine against hospitalizations for acute respiratory disease was 21% (95% confidence interval [CI], 17%-26%). The rate reduction attributable to vaccination was 4.15 hospitalizations/100,000 person-weeks in the influenza season. Among vaccine recipients, no important reduction in the number of admissions to the hospital was seen outside influenza seasons. The pooled effectiveness of vaccine against deaths due to respiratory disease was 12% (95% CI, 8%-16%). A greater proportionate reduction was seen among people without medical disorders, but absolute rate reduction was higher in individuals with medical disorders, compared with individuals without such disorders (6.14 deaths due to respiratory disease/100,000 person-weeks vs. 3.12 deaths due to respiratory disease/100,000 person-weeks). Clear protection against death due to all causes was not seen. CONCLUSIONS: Influenza vaccination reduces the number of hospitalizations and deaths due to respiratory disease, after correction for confounding in individuals >64 years of age who had a high risk or a low risk for influenza. For elderly people, untargeted influenza vaccination is of confirmed benefit against serious outcomes
Macroscopic behavior of bidisperse suspensions of noncolloidal particles in yield stress fluids
We study both experimentally and theoretically the rheological behavior of
isotropic bidisperse suspensions of noncolloidal particles in yield stress
fluids. We focus on materials in which noncolloidal particles interact with the
suspending fluid only through hydrodynamical interactions. We observe that both
the elastic modulus and yield stress of bidisperse suspensions are lower than
those of monodisperse suspensions of same solid volume fraction. Moreover, we
show that the dimensionless yield stress of such suspensions is linked to their
dimensionless elastic modulus and to their solid volume fraction through the
simple equation of Chateau et al.[J. rheol. 52, 489-506 (2008)]. We also show
that the effect of the particle size heterogeneity can be described by means of
a packing model developed to estimate random loose packing of assemblies of dry
particles. All these observations finally allow us to propose simple closed
form estimates for both the elastic modulus and the yield stress of bidisperse
suspensions: while the elastic modulus is a function of the reduced volume
fraction only, where is the estimated random loose
packing, the yield stress is a function of both the volume fraction and
the reduced volume fraction
Fragility and hysteretic creep in frictional granular jamming
The granular jamming transition is experimentally investigated in a
two-dimensional system of frictional, bi-dispersed disks subject to
quasi-static, uniaxial compression at zero granular temperature. Currently
accepted results show the jamming transition occurs at a critical packing
fraction . In contrast, we observe the first compression cycle exhibits
{\it fragility} - metastable configuration with simultaneous jammed and
un-jammed clusters - over a small interval in packing fraction (). The fragile state separates the two conditions that define
with an exponential rise in pressure starting at and an exponential
fall in disk displacements ending at . The results are explained
through a percolation mechanism of stressed contacts where cluster growth
exhibits strong spatial correlation with disk displacements. Measurements with
several disk materials of varying elastic moduli and friction coefficients
, show friction directly controls the start of the fragile state, but
indirectly controls the exponential slope. Additionally, we experimentally
confirm recent predictions relating the dependence of on . Under
repetitive loading (compression), the system exhibits hysteresis in pressure,
and the onset increases slowly with repetition number. This friction
induced hysteretic creep is interpreted as the granular pack's evolution from a
metastable to an eventual structurally stable configuration. It is shown to
depend upon the quasi-static step size which provides the only
perturbative mechanism in the experimental protocol, and the friction
coefficient which acts to stabilize the pack.Comment: 12 pages, 10 figure
Bioavailability of nanoscale metal oxides TiO(2), CeO(2), and ZnO to fish
addresses: The Hatherly Laboratories, University of Exeter, Prince of Wales Road, Exeter EX4 4PS, UK.types: Journal Article; Research Support, Non-U.S. Gov'tCopyright © 2010 American Chemical Society. Post print version of article deposited. The final published version is available from: http://dx.doi.org/10.1021/es901971aNanoparticles (NPs) are reported to be a potential environmental health hazard. For organisms living in the aquatic environment, there is uncertainty on exposure because of a lack of understanding and data regarding the fate, behavior, and bioavailability of the nanomaterials in the water column. This paper reports on a series of integrative biological and physicochemical studies on the uptake of unmodified commercial nanoscale metal oxides, zinc oxide (ZnO), cerium dioxide (CeO(2)), and titanium dioxide (TiO(2)), from the water and diet to determine their potential ecotoxicological impacts on fish as a function of concentration. Particle characterizations were performed and tissue concentrations were measured by a wide range of analytical methods. Definitive uptake from the water column and localization of TiO(2) NPs in gills was demonstrated for the first time by use of coherent anti-Stokes Raman scattering (CARS) microscopy. Significant uptake of nanomaterials was found only for cerium in the liver of zebrafish exposed via the water and ionic titanium in the gut of trout exposed via the diet. For the aqueous exposures undertaken, formation of large NP aggregates (up to 3 mum) occurred and it is likely that this resulted in limited bioavailability of the unmodified metal oxide NPs in fish
Recommended from our members
A Method for Monitoring Deposition at a Solid Cathode in an Electrorefiner for a Two-Species System Using Electrode Potentials
Currently, process monitoring of spent nuclear fuel electrorefining relies upon sampling and destructive analysis methods coupled with extrapolative thermodynamic process models for non-interrupted operations. Corrections to those models are performed infrequently, jeopardizing both the control of the process and safeguarding of nuclear material. Furthermore, the timeliness of obtaining the results is inadequate for application of international safeguards protocol. Alternatively, a system that dynamically utilizes electrical data such as electrode potentials and cell current can hypothetically be used to achieve real-time process monitoring and more robust control as well as improved safeguards. Efforts to develop an advanced model of the electrorefiner to date have focused on a forward modeling approach by using feed and salt compositions to determine the product composition, cell current and electrode potential response. Alternatively, an inverse model was developed, and reported here, to predict the product deposition rates on a cathode using the cell current, cathode potential, and fundamental relations of electrochemistry. The model was applied to the following cases: pure uranium deposition, co-deposition of uranium and plutonium, and co-deposition of uranium and zirconium. The deposition rates predicted by the inverse model were compared to those of a forward model, ERAD
Internal states of model isotropic granular packings. I. Assembling process, geometry and contact networks
This is the first paper of a series of three, reporting on numerical
simulation studies of geometric and mechanical properties of static assemblies
of spherical beads under an isotropic pressure. Frictionless systems assemble
in the unique random close packing (RCP) state in the low pressure limit if the
compression process is fast enough, slower processes inducing traces of
crystallization, and exhibit specific properties directly related to
isostaticity of the force-carrying structure. The different structures of
frictional packings assembled by various methods cannot be classified by the
sole density. While lubricated systems approach RCP densities and coordination
number z^*~=6 on the backbone in the rigid limit, an idealized "vibration"
procedure results in equally dense configurations with z^*~=4.5. Near neighbor
correlations on various scales are computed and compared to available
laboratory data, although z^* values remain experimentally inaccessible. Low
coordination packings have many rattlers (more than 10% of the grains carry no
force), which should be accounted for on studying position correlations, and a
small proportion of harmless "floppy modes" associated with divalent grains.
Frictional packings, however slowly assembled under low pressure, retain a
finite level of force indeterminacy, except in the limit of infinite friction.Comment: 29 pages. Published in Physical Review
Internal states of model isotropic granular packings. III. Elastic properties
In this third and final paper of a series, elastic properties of numerically
simulated isotropic packings of spherical beads assembled by different
procedures and subjected to a varying confining pressure P are investigated. In
addition P, which determines the stiffness of contacts by Hertz's law, elastic
moduli are chiefly sensitive to the coordination number, the possible values of
which are not necessarily correlated with the density. Comparisons of numerical
and experimental results for glass beads in the 10kPa-10MPa range reveal
similar differences between dry samples compacted by vibrations and lubricated
packings. The greater stiffness of the latter, in spite of their lower density,
can hence be attributed to a larger coordination number. Voigt and Reuss bounds
bracket bulk modulus B accurately, but simple estimation schemes fail for shear
modulus G, especially in poorly coordinated configurations under low P.
Tenuous, fragile networks respond differently to changes in load direction, as
compared to load intensity. The shear modulus, in poorly coordinated packings,
tends to vary proportionally to the degree of force indeterminacy per unit
volume. The elastic range extends to small strain intervals, in agreement with
experimental observations. The origins of nonelastic response are discussed. We
conclude that elastic moduli provide access to mechanically important
information about coordination numbers, which escape direct measurement
techniques, and indicate further perspectives.Comment: Published in Physical Review E 25 page
Associations with photoreceptor thickness measures in the UK Biobank.
Spectral-domain OCT (SD-OCT) provides high resolution images enabling identification of individual retinal layers. We included 32,923 participants aged 40-69 years old from UK Biobank. Questionnaires, physical examination, and eye examination including SD-OCT imaging were performed. SD OCT measured photoreceptor layer thickness includes photoreceptor layer thickness: inner nuclear layer-retinal pigment epithelium (INL-RPE) and the specific sublayers of the photoreceptor: inner nuclear layer-external limiting membrane (INL-ELM); external limiting membrane-inner segment outer segment (ELM-ISOS); and inner segment outer segment-retinal pigment epithelium (ISOS-RPE). In multivariate regression models, the total average INL-RPE was observed to be thinner in older aged, females, Black ethnicity, smokers, participants with higher systolic blood pressure, more negative refractive error, lower IOPcc and lower corneal hysteresis. The overall INL-ELM, ELM-ISOS and ISOS-RPE thickness was significantly associated with sex and race. Total average of INL-ELM thickness was additionally associated with age and refractive error, while ELM-ISOS was additionally associated with age, smoking status, SBP and refractive error; and ISOS-RPE was additionally associated with smoking status, IOPcc and corneal hysteresis. Hence, we found novel associations of ethnicity, smoking, systolic blood pressure, refraction, IOPcc and corneal hysteresis with photoreceptor thickness
- …