Information transmission without energy exchange.

We show that it is possible to use a massless field in the vacuum to communicate in such a way that the signal travels arbitrarily slower than the speed of light and such that no energy is transmitted from the sender to the receiver. Instead, the receiver has to supply a signal-dependent amount of work to switch his detector on and off. This type of communication is related to Casimir-like interactions, and it is made possible by dimension-and curvature-dependent subtleties of Huygens' principle.

The decline in visual acuity in elderly people with healthy eyes or eyes with early age-related maculopathy in two Scandinavian population samples.

PURPOSE: This study aimed to analyse the decline in visual acuity (VA) during normal ageing in two Scandinavian population samples of subjects aged ≥ 70 years and to study the age-specific decline in VA in eyes with early age-related maculopathy (ARM). METHODS: We carried out a cross-sectional analysis of data pertaining to VA in the better eye in one population sample from Oulu (OU), Finland (aged 70-82 years) and a second population sample from Gothenburg (GG), Sweden (aged 82 or 88 years). The change in VA with age was evaluated in healthy eyes (OU, n = 119; GG, n = 40) and in eyes with early ARM (OU-ARM, n = 22; GG-ARM, n = 114) using linear regression or logistic regression. The results were compared with those of previous reports. RESULTS: Our population samples showed a significant decrease with age in VA in healthy eyes in subjects aged ≥ 44 years using both statistical models. Comparisons with previous reports demonstrated a homogeneity in the decline in VA with age. On average, 0.3 logMAR are lost from middle age up to 88 years, presumably as a result of physiological ageing. In early ARM, the rate of age-specific decline in VA more than doubled and the prevalence of VA < 0.5 markedly increased. CONCLUSIONS: Visual acuity in healthy eyes declines with age from middle age onwards. The decrease in VA possibly accelerates in subjects aged > 70 years, although no significant evidence for this was found. An age-specific decline in VA is shown in eyes with early ARM. These results are important for the evaluation of age-specific treatment results.

Stability of visual outcome from 7 years in children treated surgically for bilateral dense congenital cataracts before 37 weeks of age.

PURPOSE: To study the long-term visual outcome and the age at which final visual acuity can be predicted in a population sample of children treated surgically for bilateral dense congenital cataract before 37 weeks of age. In addition, we assessed the influence of associated risk factors and compared the visual development of these aphakic children with presumably blocked visual input before early surgery to that of normal children in Sweden. METHODS: The 18 patients included were followed for at least 10 years postoperatively. The median age at last visit was 15.5 years (range 10-18). The best-corrected visual acuity (BCVA) was tested monocularly with a logarithmically scaled letter acuity test from 4 years of age to late teens. Other registered postoperative data were presence of manifest nystagmus, strabismus and complications. RESULTS: The BCVA of the better-seeing eye reached a plateau at 7 years of age. Age at surgery of 80 days or less characterized the majority of cases with a logMAR ≤ 0.3 with a threshold effect between 80 and 130 days of age. Compared to normal children in Sweden, the long-term visual outcome showed a deficit of 0.5-0.6 logMAR. CONCLUSION: In spite of optimized care and surgery before 9 months, the BCVA was subnormal in our population compared to healthy children. The long-term visual outcome can be predicted at 7 years of age. Screening with early detection followed by surgery before the end of the third month is important to decrease the risk of marked acuity loss.

Final pH affects the interference capacity of naturally occurring oral Lactobacillus strains against mutans streptococci.

OBJECTIVES: To establish the effects of three factors: previous caries experience; colonization of Streptococcus mutans; and final pH on autologous lactobacilli-mediated inhibition against a panel of mutans streptococci in young subjects with different caries experiences. DESIGN: The inhibition capacity was determined by the use of the agar overlay method and the final pH in culture medium was measured after 20 h. Using a logistic regression model, the risk of having an incomplete lactobacilli-mediated inhibition was calculated. RESULTS: All three factors significantly influenced the interference outcome in the order; final pH of the Lactobacillus strains, oral colonization of autologous S. mutans and caries experience. A high risk occurred at a lower pH and at a wider pH range for individuals with previous caries experience and autologous colonization of S. mutans compared with caries-free subjects who were not colonized. At a final pH of 4.0, this risk was approximately eight times higher than that of the latter group. Two mutans Streptococcus strains in the test panel demonstrated high individual predictive values of inhibition mediated by oral lactobacilli. CONCLUSIONS: Generation of a low pH either directly via organic acid production and/or production of bacteriocins or metabolites at a low pH may promote mutans Streptococcus growth inhibition, in vitro. Furthermore, a shift of pH range for the risk of incomplete inhibition of mutans streptococci suggests a less effective inhibition at a wider pH range for naturally occurring lactobacilli from individuals with earlier caries experience containing own S. mutans.

Predictors for work ability and disability in men and women with low-back or neck problems.

In many countries back and neck problems are the most common reason for work incapacity. Numerous studies have looked for reliable predictors of return to work (RTW) or not return to work (NRTW) for those incapacitated, but with few exceptions their predictive and detective ability has been limited. We aimed to perform a comparative study of various commonly used health measures ability to predict RTW or NRTW in a cohort of men and women sick-listed for more than 28 days due to low-back pain (LBP) or neck pain (NP). A cohort of 1,575 men and women sick-listed more than 28 days due to back or neck problems was asked to answer ten different health measures (scales) about various aspects of health status (health related quality of life, pain, back function and depressivity) at four occasions during a 2-year period. A statistical diagnostic test was used to study how well the subject's values on these scales would serve as a predictor for work resumption. There was an improvement from day 28 up until 2 years, reflected by the different scales, more pronounced for LBP than for NP patients and for men with LBP compared with women with LBP. For all separately tested scales EuroQol (EQ-5D) had the highest overall ability to predict RTW or NRTW irrespective of gender, diagnoses or duration of the problems. When RTW or NRTW were predicted in a cohort of sick-listed low-back or neck patients, EQ-5D had outstanding properties in this respect irrespective of gender, diagnosis or elapsed time during this 2-year study.