Optical detection of radio waves through a nanomechanical transducer.

Low-loss transmission and sensitive recovery of weak radio-frequency and microwave signals is a ubiquitous challenge, crucial in radio astronomy, medical imaging, navigation, and classical and quantum communication. Efficient up-conversion of radio-frequency signals to an optical carrier would enable their transmission through optical fibres instead of through copper wires, drastically reducing losses, and would give access to the set of established quantum optical techniques that are routinely used in quantum-limited signal detection. Research in cavity optomechanics has shown that nanomechanical oscillators can couple strongly to either microwave or optical fields. Here we demonstrate a room-temperature optoelectromechanical transducer with both these functionalities, following a recent proposal using a high-quality nanomembrane. A voltage bias of less than 10 V is sufficient to induce strong coupling between the voltage fluctuations in a radio-frequency resonance circuit and the membrane's displacement, which is simultaneously coupled to light reflected off its surface. The radio-frequency signals are detected as an optical phase shift with quantum-limited sensitivity. The corresponding half-wave voltage is in the microvolt range, orders of magnitude less than that of standard optical modulators. The noise of the transducer--beyond the measured 800 pV Hz-1/2 Johnson noise of the resonant circuit--consists of the quantum noise of light and thermal fluctuations of the membrane, dominating the noise floor in potential applications in radio astronomy and nuclear magnetic imaging. Each of these contributions is inferred to be 60 pV Hz-1/2 when balanced by choosing an electromechanical cooperativity of ~150 with an optical power of 1 mW. The noise temperature of the membrane is divided by the cooperativity. For the highest observed cooperativity of 6,800, this leads to a projected noise temperature of 40 mK and a sensitivity limit of 5 pV Hz-1/2. Our approach to all-optical, ultralow-noise detection of classical electronic signals sets the stage for coherent up-conversion of low-frequency quantum signals to the optical domain.

Autocrine semaphorin 3A signaling promotes glioblastoma dispersal.

Glioblastoma multiforme (GBM) is the most malignant glioma type with diffuse borders due to extensive tumor cell infiltration. Therefore, understanding the mechanism of GBM cell dispersal is critical for developing effective therapies to limit infiltration. We identified neuropilin-1 as a mediator of cancer cell invasion by a functional proteomic screen and showed its role in GBM cells. Neuropilin-1 is a receptor for semaphorin3A (Sema3A), a secreted chemorepellent that facilitates axon guidance during neural development. Although neuropilin-1 expression in GBMs was previously shown, its role as a Sema3A receptor remained elusive. Using fluorophore-assisted light inactivation and RNA interference , we showed that neuropilin-1 is required for GBM cell migration. We also showed that GBM cells secrete Sema3A endogenously, and RNA interference-mediated downregulation of Sema3A inhibits migration and alters cell morphology that is dependent on Rac1 activity. Sema3A depletion also reduces dispersal, which is recovered by supplying Sema3A exogenously. Extracellular application of Sema3A decreases cell-substrate adhesion in a neuropilin-1-dependent manner. Using immunohistochemistry, we showed that Sema3A is overexpressed in a subset of human GBMs compared with the non-neoplastic brain. Together, these findings implicate Sema3A as an autocrine signal for neuropilin-1 to promote GBM dispersal by modulating substrate adhesion and suggest that targeting Sema3A-neuropilin-1 signaling may limit GBM infiltration.

Urban CO exposure and its health effects on traffic policemen in Ankara.

Carbon monoxide (CO) is an important component of air pollution caused by traffic exhaust fumes. CO can cause chronic poisoning which shows its first symptoms as headaches, blurry vision, difficulty in concentration, and confusion. With the increasing number of vehicles in metropolitan areas of Turkey, the CO level has also increased in the city air as is the case in the capital city of Ankara, especially at certain locations. As far as the effects of CO on humans are concerned, traffic policemen are the population group under risk due to their inhalation of CO-rich air while on duty at the crowded cross-sections of the city. The traffic policemen on duty at these cross-sections are exposed to these high levels of CO for at least 6 h. This study was performed to investigate the traffic policemen (traffic organizers) who are exposed to high concentrations of CO at crowded cross-sections of Ankara City and to find out if chronic CO intoxication exits among this risk group. The CO levels in the ambient air at these cross-sections have also been compared to, and correlated with measurements of CO in the expired air of the target population. Additional factors like smoking, general health status, type of heating systems used at home, etc., have been taken into consideration by evaluating special questionnaires filled out by the policemen. A control group of clerk policemen, who were not engaged in street traffic activities was formed for comparative purposes.

Environmentally-induced malignant pleural mesothelioma and HLA distribution in Turkey.

SETTING: A large university hospital in Ankara, Turkey. OBJECTIVE: To investigate the potential links, if any, between the occurrence of malignant pleural mesothelioma (MPM) and the presence and distribution of human leukocyte antigens (HLA) in patients environmentally exposed to asbestos and erionite in rural Anatolia, Turkey. DESIGN: A case-control study design was used to compare the relative frequency and distribution of HLA among 31 MPM patients originating from the fibrous zeolite (erionite) and asbestos villages in central Anatolia, and two sets of controls. The cases represented all of the MPM cases diagnosed between 1995 and 1997 in our clinic at the Hacettepe University Hospital. One control group of 119 healthy individuals was drawn from Tuzköy, which has the largest population of three erionite villages, a very high prevalence of mesothelioma due to environmental exposure to erionite, and accounted for 16 of the MPM cases in the study. A second control group composed of 118 renal transplant donors was formed for external comparison. RESULTS: A significant relation was found with the HLA-B41 antigen in 19.4% of the patients compared to 0.8% of the Tuzköy inhabitants (odds ratio [OR] 28.3; 95% confidence interval [CI] 3.1-652.5) and 1.7% of the referent renal donor population (OR 13.9; 95% CI 2.3-106.7). The frequency of the HLA-B58 and -DR16 antigens was also observed to be significantly higher in patients with MPM compared to the two control groups. The odds ratios of MPM in those with HLA-B58 were 8.6 (95% CI 1.2-72.4) and 8.5 (95% CI 1.2-71.8), respectively, compared to those of the Tuzköy inhabitants and renal donors. CONCLUSION: The predictive role of the HLA antigens -B41, -B58 and -DR16 for MPM needs to be further investigated. This will help in screening the population at risk, and facilitate preventive measures such as family counselling and gene therapy.

Recognition of cigarette brand names and logos by primary schoolchildren in Ankara, Turkey.

OBJECTIVE: To assess the smoking behaviour of primary schoolchildren and their ability to recognise brand names and logos of widely advertised cigarettes, compared with other commercial products intended for children. DESIGN: Cross-sectional survey in classroom settings using a questionnaire designed to measure attitudes towards smoking and the recognition of brand names and logos for 16 food, beverage, cigarette, and toothpaste products. SETTING: Ankara, Turkey. SUBJECTS: 1093 children (54.6% boys, 44.4% girls) aged 7-13 years (mean = 10, SD = 1), from grades 2-5. The student sample was taken from three primary schools--one school in each of three residential districts representing high, middle, and low income populations. MAIN OUTCOME MEASURES: Prevalence of ever-smoking, recognition of brand names and logos. RESULTS: Prevalence of ever-smoking was 11.7% overall (13.9% among boys and 9.1% among girls; p < 0.05). Children aged eight years or less had a higher prevalence of ever-smoking (19.6%) than older children (p < 0.002). Ever-smoking prevalence did not differ significantly across the three school districts. Ever-smoking prevalence was higher among children with at least one parent who smoked (15.3%) than among those whose parents did not (4.8%) (p < 0.001). Brand recognition rates ranged from 58.1% for Chee-tos (a food product) to 95.2% for Samsun (a Turkish cigarette brand). Recognition rates for cigarette brand names and logos were 95.2% and 80.8%, respectively, for Samsun; 84.0% and 90.5%, respectively, for Camel; and 92.1% and 69.5%, respectively, for Marlboro. The Camel logo and the Samsun and Marlboro brand names were the most highly recognised of all product logos and brand names tested. CONCLUSIONS: The high recognition of cigarette brand names and logos is most likely the result of tobacco advertising and promotion. Our results indicate the need to implement comprehensive tobacco control measures in Turkey.