Subnanosecond spectral diffusion measurement using photon correlation

Spectral diffusion is a result of random spectral jumps of a narrow line as a result of a fluctuating environment. It is an important issue in spectroscopy, because the observed spectral broadening prevents access to the intrinsic line properties. However, its characteristic parameters provide local information on the environment of a light emitter embedded in a solid matrix, or moving within a fluid, leading to numerous applications in physics and biology. We present a new experimental technique for measuring spectral diffusion based on photon correlations within a spectral line. Autocorrelation on half of the line and cross-correlation between the two halves give a quantitative value of the spectral diffusion time, with a resolution only limited by the correlation set-up. We have measured spectral diffusion of the photoluminescence of a single light emitter with a time resolution of 90 ps, exceeding by four orders of magnitude the best resolution reported to date

Unconventional motional narrowing in the optical spectrum of a semiconductor quantum dot

Motional narrowing refers to the striking phenomenon where the resonance line of a system coupled to a reservoir becomes narrower when increasing the reservoir fluctuation. A textbook example is found in nuclear magnetic resonance, where the fluctuating local magnetic fields created by randomly oriented nuclear spins are averaged when the motion of the nuclei is thermally activated. The existence of a motional narrowing effect in the optical response of semiconductor quantum dots remains so far unexplored. This effect may be important in this instance since the decoherence dynamics is a central issue for the implementation of quantum information processing based on quantum dots. Here we report on the experimental evidence of motional narrowing in the optical spectrum of a semiconductor quantum dot broadened by the spectral diffusion phenomenon. Surprisingly, motional narrowing is achieved when decreasing incident power or temperature, in contrast with the standard phenomenology observed for nuclear magnetic resonance

A survey of pediatricians' attitudes regarding influenza immunization in children

<p>Abstract</p> <p>Background</p> <p>The Advisory Committee on Immunization Practices advocates that influenza immunization is the most effective method for prevention of illness due to influenza. Recommendations for vaccination of children against influenza have been revised several times since 2002, and as of 2008 include all children 6 months to 18 years of age. Nevertheless, influenza immunization rates have remained low.</p> <p>Methods</p> <p>We surveyed practicing pediatricians in Maryland in the spring of 2007 to determine their attitudes and practices toward childhood influenza immunization.</p> <p>Results</p> <p>The overall response to the survey was 21%. A total of 61% of respondents reported that immunization either is cost neutral or produces a loss, and 36.6% noted it was minimally profitable. Eighty-six percent of respondents were receptive to supporting school-based immunization programs, and 61% indicated that they would participate in such programs. Respondents reported higher rates of immunization of select patient groups than those noted by the Centers for Disease Control and Prevention</p> <p>Conclusion</p> <p>Vaccination was reported to occur at multiple types of patient encounters, as recommended. Survey respondents stated that practice-based immunization was not a profitable service. Pediatricians were supportive of school-based immunization programs, and more than half stated they would be actively involved in such programs. School-based programs may be critical to achieving high vaccination coverage in the school-aged population.</p

Entomological Surveillance of Behavioural Resilience and Resistance in Residual Malaria Vector Populations.

The most potent malaria vectors rely heavily upon human blood so they are vulnerable to attack with insecticide-treated nets (ITNs) and indoor residual spraying (IRS) within houses. Mosquito taxa that can avoid feeding or resting indoors, or by obtaining blood from animals, mediate a growing proportion of the dwindling transmission that persists as ITNs and IRS are scaled up. Increasing frequency of behavioural evasion traits within persisting residual vector systems usually reflect the successful suppression of the most potent and vulnerable vector taxa by IRS or ITNs, rather than their failure. Many of the commonly observed changes in mosquito behavioural patterns following intervention scale-up may well be explained by modified taxonomic composition and expression of phenotypically plastic behavioural preferences, rather than altered innate preferences of individuals or populations. Detailed review of the contemporary evidence base does not yet provide any clear-cut example of true behavioural resistance and is, therefore, consistent with the hypothesis presented. Caution should be exercised before over-interpreting most existing reports of increased frequency of behavioural traits which enable mosquitoes to evade fatal contact with insecticides: this may simply be the result of suppressing the most behaviourally vulnerable of the vector taxa that constituted the original transmission system. Mosquito taxa which have always exhibited such evasive traits may be more accurately described as behaviourally resilient, rather than resistant. Ongoing national or regional entomological monitoring surveys of physiological susceptibility to insecticides should be supplemented with biologically and epidemiologically meaningfully estimates of malaria vector population dynamics and the behavioural phenotypes that determine intervention impact, in order to design, select, evaluate and optimize the implementation of vector control measures

Does osteoporosis predispose falls? a study on obstacle avoidance and balance confidence

Contains fulltext : 96832.pdf (publisher's version ) (Open Access)BACKGROUND: Osteoporosis is associated with changes in balance and physical performance and has psychosocial consequences which increase the risk of falling. Most falls occur during walking; therefore an efficient obstacle avoidance performance might contribute to a reduction in fall risk. Since it was shown that persons with osteoporosis are unstable during obstacle crossing it was hypothesized that they more frequently hit obstacles, specifically under challenging conditions. METHODS: Obstacle avoidance performance was measured on a treadmill and compared between persons with osteoporosis (n = 85) and the comparison group (n = 99). The obstacle was released at different available response times (ART) to create different levels of difficulty by increasing time pressure. Furthermore, balance confidence, measured with the short ABC-questionnaire, was compared between the groups. RESULTS: No differences were found between the groups in success rates on the obstacle avoidance task (p = 0.173). Furthermore, the persons with osteoporosis had similar levels of balance confidence as the comparison group (p = 0.091). The level of balance confidence was not associated with the performance on the obstacle avoidance task (p = 0.145). CONCLUSION: Obstacle avoidance abilities were not impaired in persons with osteoporosis and they did not experience less balance confidence than the comparison group. These findings imply that persons with osteoporosis do not have an additional risk of falling because of poorer obstacle avoidance abilities

Single Molecule Analysis Research Tool (SMART): An Integrated Approach for Analyzing Single Molecule Data

Single molecule studies have expanded rapidly over the past decade and have the ability to provide an unprecedented level of understanding of biological systems. A common challenge upon introduction of novel, data-rich approaches is the management, processing, and analysis of the complex data sets that are generated. We provide a standardized approach for analyzing these data in the freely available software package SMART: Single Molecule Analysis Research Tool. SMART provides a format for organizing and easily accessing single molecule data, a general hidden Markov modeling algorithm for fitting an array of possible models specified by the user, a standardized data structure and graphical user interfaces to streamline the analysis and visualization of data. This approach guides experimental design, facilitating acquisition of the maximal information from single molecule experiments. SMART also provides a standardized format to allow dissemination of single molecule data and transparency in the analysis of reported data

Influenza H5 Hemagglutinin DNA Primes the Antibody Response Elicited by the Live Attenuated Influenza A/Vietnam/1203/2004 Vaccine in Ferrets

Priming immunization plays a key role in protecting individuals or populations to influenza viruses that are novel to humans. To identify the most promising vaccine priming strategy, we have evaluated different prime-boost regimens using inactivated, DNA and live attenuated vaccines in ferrets. Live attenuated influenza A/Vietnam/1203/2004 (H5N1) candidate vaccine (LAIV, VN04 ca) primed ferrets efficiently while inactivated H5N1 vaccine could not prime the immune response in seronegative ferrets unless an adjuvant was used. However, the H5 HA DNA vaccine alone was as successful as an adjuvanted inactivated VN04 vaccine in priming the immune response to VN04 ca virus. The serum antibody titers of ferrets primed with H5 HA DNA followed by intranasal vaccination of VN04 ca virus were comparable to that induced by two doses of VN04 ca virus. Both LAIV-LAIV and DNA-LAIV vaccine regimens could induce antibody responses that cross-neutralized antigenically distinct H5N1 virus isolates including A/HongKong/213/2003 (HK03) and prevented nasal infection of HK03 vaccine virus. Thus, H5 HA DNA vaccination may offer an alternative option for pandemic preparedness

Confirmed malaria cases among children under five with fever and history of fever in rural western Tanzania

The World Health Organization recommends that malaria treatment should begin with parasitological diagnosis. This will help to control misuse of anti-malarial drugs in areas with low transmission. The present study was conducted to assess the prevalence of parasitologically confirmed malaria among children under five years of age presenting with fever or history of fever in rural western Tanzania. A finger prick blood sample was obtained from each child, and thin and thick blood smears were prepared, stained with 10% Giemsa and examined under the light microscope. A structured questionnaire was used to collect each patient's demographic information, reasons for coming to the health center; and a physical examination was carried out on all patients. Fever was defined as axillary temperature ≥ 37.5°C. A total of 300 children with fever or a history of fever (1 or 2 weeks) were recruited, in which 54.3% (163/300, 95%CI, 48.7-59.9) were boys. A total of 76 (76/300, 25.3%, 95%CI, 22.8 - 27.8) of the children had fever. Based on a parasitological diagnosis of malaria, only 12% (36/300, 95%CI, 8.3-15.7) of the children had P. falciparum infection. Of the children with P. falciparum infection, 52.7% (19/36, 95%CI, 47.1-58.3) had fever and the remaining had no fever. The geometrical mean of the parasites was 708.62 (95%CI, 477.96-1050.62) parasites/μl and 25% (9/36, 95%CI, 10.9 -- 39.1) of the children with positive P. falciparum had ≥ 1001 parasites/μl. On Univariate (OR = 2.13, 95%CI, 1.02-4.43, P = 0.044) and multivariate (OR = 2.15, 95%CI, 1.03-4.49) analysis, only children above one year of age were associated with malaria infections. Only a small proportion of the children under the age of five with fever had malaria, and with a proportion of children having non-malaria fever. Improvement of malaria diagnostic and other causes of febrile illness may provide effective measure in management of febrile illness in malaria endemic areas

Increasing malaria hospital admissions in Uganda between 1999 and 2009

<p>Abstract</p> <p>Background</p> <p>Some areas of Africa are witnessing a malaria transition, in part due to escalated international donor support and intervention coverage. Areas where declining malaria rates have been observed are largely characterized by relatively low baseline transmission intensity and rapid scaling of interventions. Less well described are changing patterns of malaria burden in areas of high parasite transmission and slower increases in control and treatment access.</p> <p>Methods</p> <p>Uganda is a country predominantly characterized by intense, perennial malaria transmission. Monthly pediatric admission data from five Ugandan hospitals and their catchments have been assembled retrospectively across 11 years from January 1999 to December 2009. Malaria admission rates adjusted for changes in population density within defined catchment areas were computed across three time periods that correspond to periods where intervention coverage data exist and different treatment and prevention policies were operational. Time series models were developed adjusting for variations in rainfall and hospital use to examine changes in malaria hospitalization over 132 months. The temporal changes in factors that might explain changes in disease incidence were qualitatively examined sequentially for each hospital setting and compared between hospital settings</p> <p>Results</p> <p>In four out of five sites there was a significant increase in malaria admission rates. Results from time series models indicate a significant month-to-month increase in the mean malaria admission rates at four hospitals (trend <it>P </it>< 0.001). At all hospitals malaria admissions had increased from 1999 by 47% to 350%. Observed changes in intervention coverage within the catchments of each hospital showed a change in insecticide-treated net coverage from <1% in 2000 to 33% by 2009 but accompanied by increases in access to nationally recommended drugs at only two of the five hospital areas studied.</p> <p>Conclusions</p> <p>The declining malaria disease burden in some parts of Africa is not a universal phenomena across the continent. Despite moderate increases in the coverage of measures to reduce infection and disease without significant coincidental increasing access to effective medicines to treat disease may not lead to severe disease burden reductions in high transmission areas of Africa. More data is needed from a wider range of malaria settings to provide an honest tracking progress of the impact of scaled intervention coverage in Africa.</p