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 $\phi/\phi_m$ only, where $\phi_m$ is the estimated random loose packing, the yield stress is a function of both the volume fraction $\phi$ 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 $\phi_c$. 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 ($\phi_1 < \phi < \phi_2$). The fragile state separates the two conditions that define $\phi_c$ with an exponential rise in pressure starting at $\phi_1$ and an exponential fall in disk displacements ending at $\phi_2$. 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 $E$ and friction coefficients $\mu$, 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 $\phi_c$ on $\mu$. Under repetitive loading (compression), the system exhibits hysteresis in pressure, and the onset $\phi_c$ 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 $\Delta \phi$ which provides the only perturbative mechanism in the experimental protocol, and the friction coefficient $\mu$ which acts to stabilize the pack.Comment: 12 pages, 10 figure

The Roles of Knowledge and Organizational Form on Opportunity Evaluation

What influences an individual to pursue one type of entrepreneurial opportunity versus another? Knowledge is central to the concept of opportunity identification and evaluation.  Using conjoint analysis to capture underlying decision policies, we explore the roles of both knowledge and organizational form in the evaluation of entrepreneurial opportunities.  Our findings suggest that, among respondents who considered entering a franchise agreement a viable alternative to founding an independent business, franchise versus independent form alone did not play a specific and significant role in the evaluation of the attractiveness of entrepreneurial opportunities.  Rather, organizational form appears to influence the impact of both human capital relatedness and the inimitability of resources attributes on opportunity attractiveness. 

Mathematics of random growing interfaces

We establish a thermodynamic limit and Gaussian fluctuations for the height and surface width of the random interface formed by the deposition of particles on surfaces. The results hold for the standard ballistic deposition model as well as the surface relaxation model in the off-lattice setting. The results are proved with the aid of general limit theorems for stabilizing functionals of marked Poisson point processes.Comment: 12 page

Laser refractive surgery in the UK Biobank study: Frequency, distribution by sociodemographic factors, and general health, happiness, and social participation outcomes

PURPOSE: To evaluate the frequency and distribution of laser refractive surgery in the United Kingdom by sociodemographic factors and outcomes of social participation and well-being. SETTING: Six regional recruitment centers in England and Wales. DESIGN: Cross-sectional epidemiological study. METHODS: Data were collected on sociodemographic factors and medical history; self-report on eyes/vision included reason for wearing optical correction, eye diseases, and treatment received (including refractive laser surgery). Mean spherical equivalent was used to categorize individuals as myopic (+1.0 diopter). RESULTS: Between 2009 and 2010, 117 281 subjects recruited by UK Biobank undertook an ophthalmic assessment, including autorefraction. Of those with refractive error within a range eligible for laser refractive surgery (n = 60 352), 1892 (3.1%) reported having bilateral refractive surgery and 549 (0.9%) unilateral surgery. Frequency of bilateral surgery decreased with increasing age and was higher in women. Frequency did not vary with educational attainment or accommodation status but increased with income among working age adults. Social participation, for example, regular visits to a pub or social club, was more common among those who underwent surgery. Other eye conditions were reported by 28% of those reporting refractive surgery compared with 11% of those eligible for treatment but not reporting surgery. CONCLUSION: This study provides information not available routinely on the frequency and distribution of laser refractive surgery in an adult UK population. A high frequency of ocular conditions conventionally considered contraindications to laser refractive surgery raises the possibility that extant guidance on patient selection may not be followed

UK & Ireland observational study of outcomes following congenital / infantile cataract surgery: IoLunder2 five year follow up

PURPOSE: To investigate outcomes following cataract surgery with and without primary intraocular lens implantation in children aged under 2 years with congenital or infantile cataract. METHODS: A bi-national prospective longitudinal cohort study undertaken through a collaborative research network, with case ascertainment through active surveillance, and standardised data collection on children who underwent cataract surgery with and without IoL implantation between Jan ‘09 and Dec ’10. Multivariable multilevel regression modelling was undertaken to interrogate the association between IoL implantation and outcomes of interest. RESULTS: 256 children were recruited into the study following informed parental consent. For 242 (95%) children, 5 year post–operative follow up data were available. Overall, median age at surgery was 7 weeks (IQR 5 weeks-7 months). Significant ocular co-morbidity (horizontal corneal diameter<10mm, axial length<16mm, complex persistent fetal vasculature, other structural anomaly) was present in 42% of BCC eyes, 39% of UCC eyes. Primary IoL implantation was undertaken in 58/149 children with bilateral congenital/infantile cataract (BCC) and 45/93 with unilateral disease (UCC). Children who underwent IoL implantation were older at surgery, less likely to have an ocular comorbidity, and less likely to live in relative socioeconomic deprivation. At 5 years following surgery, median acuity in eyes of children with BCC was 0.5 logMAR (interquartile range 0.2-0.9), and with both eyes open 0.38. Median acuity in operated eyes of children with UCC was 0.8 logMAR (IQR 0.4-1.5). Secondary glaucoma had been diagnosed in 24% of BCC children (13% of eyes), and 12% of children with UCC. Following adjustment for age at surgery and presence of co-existent anomalies, IoLs were not associated with better visual outcome, and did not reduce odds of secondary glaucoma. CONCLUSIONS: Based on the findings that IoLs do not confer visual benefit or protective effect against glaucoma (as previously postulated), and previous findings of a higher risk of re-operation, routine use of IoLs in children under 2 years is not advocated. IoLunder2 is also able to provide data on the associations of visual outcomes and glaucoma risk with age at surgery, peri-operative management and post-operative rehabilitation, in order to inform policy and practice