A Frequency Tuning Method for a Planar Inverted-F Antenna

A novel method is presented for electrically tuning the frequency of a planar inverted-F antenna (PIFA). A tuning circuit, comprising an RF switch and discrete passive components, has been completely integrated into the antenna element, which is thus free of dc wires. The proposed tuning method has been demonstrated with a dual-band PIFA capable of operating in four frequency bands. The antenna covers the GSM850, GSM900, GSM1800, PCS1900 and UNITS frequency ranges with over 40% total efficiency. The impact of the tuning circuit on the antenna's efficiency and radiation pattern have been experimentally studied through comparison with the performance of a reference antenna not incorporating the tuning circuit. The proposed frequency tuning concept can be extended to more complex PIFA structures as well as other types of antennas to give enhanced electrical performance.</p

Sexual health interventions delivered to participants by mobile technology: a systematic review and meta-analysis of randomised controlled trials

Background: The use of mobile technologies to prevent STIs is recognised as a promising approach worldwide; however, evidence has been inconclusive, and the field has developed rapidly. With about 1 million new STIs a day globally, up-to-date evidence is urgently needed. // Objective: To assess the effectiveness of mobile health interventions delivered to participants for preventing STIs and promoting preventive behaviour. // Methods: We searched seven databases and reference lists of 49 related reviews (January 1990–February 2020) and contacted experts in the field. We included randomised controlled trials of mobile interventions delivered to adolescents and adults to prevent sexual transmission of STIs. We conducted meta-analyses and assessed risk of bias and certainty of evidence following Cochrane guidance. // Results: After double screening 6683 records, we included 22 trials into the systematic review and 20 into meta-analyses; 18 trials used text messages, 3 used smartphone applications and 1 used Facebook messages as delivery modes. The certainty of evidence regarding intervention effects on STI/HIV occurrence and adverse events was low or very low. There was moderate certainty of evidence that in the short/medium-term text messaging interventions had little or no effect on condom use (standardised mean differences (SMD) 0.02, 95% CI −0.09 to 0.14, nine trials), but increased STI/HIV testing (OR 1.83, 95% CI 1.41 to 2.36, seven trials), although not if the standard-of-care control already contained an active text messaging component (OR 1.00, 95% CI 0.68 to 1.47, two trials). Smartphone application messages also increased STI/HIV testing (risk ratio 1.40, 95% CI 1.22 to 1.60, subgroup analysis, two trials). The effects on other outcomes or of social media or blended interventions is uncertain due to low or very low certainty evidence

A novel dual-ring multi-layer circular polarized antenna

A novel circular polarized antenna structure capable of high radiation efficiency, and suitable for use in multilayer microwave circuits is presented. The antenna uses dual ring feed system to enhance radiation. Data is provided for a prototype antenna working at 10 GHz.</p

Crop pollination management needs flower-visitor monitoring and target values

Despite the crucial importance of biotic pollination for many crops, land managers rarely monitor the levels of crop pollination needed to guide farming decisions. The few existing pollination recommendations focus on a particular number of honeybee or bumblebee hives per crop area, but these guidelines do not accurately predict the actual pollination services that crops receive. We argue that pollination management for pollinator-dependent crops should be based on direct measures of pollinator activity. We describe a protocol to quickly perform such a task by monitoring flower visitation rates. We provide target values of visitation rates for crop yield maximization for several important crops by considering the number of visits per flower needed to ensure full ovule fertilization. If visitation rates are well below or above these target values, corrective measures should be taken. Detailed additional data on visitation rates for different species, morpho-species, or groups of species and/or flower-visitor richness can improve pollination estimates. Synthesis and applications. We present target values of visitation rates for some globally important pollinator-dependent crops and provide guidance on why monitoring the number and diversity of pollinators is important, and how this information can be used for decision-making. The implementation of flower monitoring programmes will improve management in many aspects, including enhanced quality and quantity of crop yield and a more limited spillover of managed (often exotic) pollinators from crop areas into native habitats, reducing their many potential negative impacts.Fil: Garibaldi, Lucas Alejandro. Universidad Nacional de Río Negro. Sede Andina. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Sáez, Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Aizen, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Fijen, Thijs. University of Agriculture Wageningen; Países BajosFil: Bartomeus, Ignasi. Consejo Superior de Investigaciones Científicas. Estación Biológica de Doñana; Españ

Einstein equations in the null quasi-spherical gauge

The structure of the full Einstein equations in a coordinate gauge based on expanding null hypersurfaces foliated by metric 2-spheres is explored. The simple form of the resulting equations has many applications -- in the present paper we describe the structure of timelike boundary conditions; the matching problem across null hypersurfaces; and the propagation of gravitational shocks.Comment: 12 pages, LaTeX (revtex, amssymb), revision 18 pages, contains expanded discussion and explanations, updated references, to appear in CQ

Giant Shapiro Resonances in a Flux Driven Josephson Junction Necklace

We present a detailed study of the dynamic response of a ring of $N$ equally spaced Josephson junctions to a time-periodic external flux, including screening current effects. The dynamics are described by the resistively shunted Josephson junction model, appropriate for proximity effect junctions, and we include Faraday's law for the flux. We find that the time-averaged $I-V$ characteristics show novel {\em subharmonic giant Shapiro voltage resonances}, which strongly depend on having phase slips or not, on $N$, on the inductance and on the external drive frequency. We include an estimate of the possible experimental parameters needed to observe these quantized voltage spikes.Comment: 8 pages RevTeX, 3 figures available upon reques

Sexual health promotion for young people delivered via digital media: a scoping review

Background: Young people are at risk of poor sexual health and are, therefore, in need of comprehensive, effective sexual health education. Young people are confident and constant users of digital technology, such as the internet and mobile phones, and there are many innovative possibilities for sexual health education involving these technologies. Objectives: To summarise evidence on effectiveness, cost-effectiveness and mechanism of action of interactive digital interventions (IDIs) for sexual health; optimal practice for intervention development; contexts for successful implementation; research methods for digital intervention evaluation; and the future potential of sexual health promotion via digital media. Design: Literature review of evidence on digital interventions for sexual health for young people, integrating the findings with the views of young people, parents and experts in digital media/sexual health. IDIs are defined as digital media programmes that provide health information and tailored decision support, behaviour-change support and/or emotional support. We focus on sexual well-being for young people aged 13–24 years in the UK. Results: There are many imaginative IDIs for sexual health promotion, but few interventions address issues that are important to young people, such as sexual pleasure and relationships. It is vital to collaborate with young people and to use Behaviour-Change Theory in designing interventions. We located 19 randomised controlled trials of IDIs for sexual health promotion for young people, finding a moderate effect on sexual health knowledge [standardised mean difference (SMD) 0.54, 95% confidence interval (CI) 0.17 to 0.92], a small effect on confidence (self-efficacy) (SMD 0.11, 95% CI 0.02 to 0.20) and a positive effect on sexual behaviour (odds ratio 1.28, 95% CI 1.01 to 1.61), but no significant effects on safer sex intention or biological outcomes. One study suggests that IDIs may be as good as face-to-face interventions for sexual health knowledge and safer sex intention. There are no existing data on the cost-effectiveness of IDIs for sexual health promotion. The impact of an IDI will be determined by the proportion of the target population reached, intervention efficacy, adoption in a setting, how well it is delivered and maintenance/sustainability. All of these elements must be addressed for IDIs to be successful. More collaboration is needed to capitalise on the knowledge of users and stakeholders, the design and software skills of the commercial sector and the theoretical expertise and evaluation skills of academia. Conclusions: IDIs are effective for knowledge acquisition and sexual behaviour, and could usefully contribute to sexual health education in schools, in clinic settings and online; however, there are obstacles to overcome, such as access to information technology and ensuring the quality and safety of interventions