A possibility to measure elastic photon--photon scattering in vacuum

Photon--photon scattering in vacuum due to the interaction with virtual electron-positron pairs is a consequence of quantum electrodynamics. A way for detecting this phenomenon has been devised based on interacting modes generated in microwave waveguides or cavities [G. Brodin, M. Marklund and L. Stenflo, Phys. Rev. Lett. \textbf{87} 171801 (2001)]. Here we materialize these ideas, suggest a concrete cavity geometry, make quantitative estimates and propose experimental details. It is found that detection of photon-photon scattering can be within the reach of present day technology.Comment: 7 pages, 3 figure

Beyond viral suppression: the quality of life of people living with HIV in Sweden

Sweden has one of the best HIV treatment outcomes in the world and an estimated 95% of all diagnosed people living with HIV are virally suppressed, but the quality of life (QoL) is understudied. The aim of this study was to examine the associations between variables within sociodemographic, behavioural, clinical, psychological, sexual life, social support and personal resource component and the QoL of people living with HIV in Sweden. Data were derived from a cross-sectional, nation-wide survey completed by 15% (n = 1096) of all people living with HIV and collected at 15 infectious disease clinics and 2 needle exchange sites during 2014. Ordinal univariate and multivariate logistic regression analyses were used to examine associations between potential contributors and QoL. Respondents reported high QoL: 63% rated their QoL 7 or higher on a scale ranging from 0 to 10. QoL was independent of gender, age, mode of HIV transmission and country of origin. Lower QoL was associated with recent homelessness, hazardous alcohol consumption, comorbidities, treatment side-effects, HIV-related physical symptoms, hopelessness, negative self-image, sexual dissatisfaction, and negative changes in sex life after HIV. The QoL of people living with HIV in Sweden was high overall, but still significantly influenced by HIV

Second Harmonic Coherent Driving of a Spin Qubit in a Si/SiGe Quantum Dot

We demonstrate coherent driving of a single electron spin using second harmonic excitation in a Si/SiGe quantum dot. Our estimates suggest that the anharmonic dot confining potential combined with a gradient in the transverse magnetic field dominates the second harmonic response. As expected, the Rabi frequency depends quadratically on the driving amplitude and the periodicity with respect to the phase of the drive is twice that of the fundamental harmonic. The maximum Rabi frequency observed for the second harmonic is just a factor of two lower than that achieved for the first harmonic when driving at the same power. Combined with the lower demands on microwave circuitry when operating at half the qubit frequency, these observations indicate that second harmonic driving can be a useful technique for future quantum computation architectures.Comment: 9 pages, 9 figure

Correlates of ever had sex among perinatally HIV-infected adolescents in Uganda

Background: The objective of this study was to explore the correlates of ever had sex among perinatally HIV-infected PHIV) adolescents. Methods: A cross-sectional survey of sexual behaviour was conducted with 624 PHIV adolescents living three regions 12 districts) of Uganda. Data was collected on socio demographic characteristics (age, sex, occupation, religion and education status), sexual practices and behaviours (Intimate relationships, sexual intercourse, age of sexual debut, condom use, multiple and concurrent sexual partners), consequences of sexual behaviours (pregnancy and STI’s) and life style factors (use of alcohol, psychoactive substances and peer influence). Multivariable logistic-regression was used to ascertain the determinants of sexual activity. Results: The majority of PHIV were female (59.3 %) and the mean age of the sample was 16.2 (±2.1) years. The mean age of sexual debut was 15.8 years; 16.2 % (101/624) reported symptoms for sexually transmitted infections (STI) and more than a third (213/624) reported ever had sex. Of these 76.5 % (165/213) used condoms inconsistently; and 49.3 % (105/213) had been pregnant or made someone pregnant. Of those in relationships, 56.3 % (223/396) did not disclose and were not aware of their partners’ HIV status. Adolescents aged 15–19 years were more likely to have ever been sexually active (Adjusted odds ratio (AOR) 6.28, 95 % Confidence interval (CI): 2.63-14.99) compared to those aged 10–14 years. Adolescents who were living alone were more likely to have ever been sexually active compared to those living with one or both parents (AOR 4.33, 95 % CI: 1.13-16.62). The odds of being sexually active were lower among adolescents in school compared to those out of school (AOR 0.2, 95 % CI:0.13-0.30), who had never been treated for STI (compared to those who had never been treated for STI) (AOR 0.19, 95 % 0.11-0.32) and adolescents who never drank alcohol (AOR 0.49, 95 % CI 0.28-0.87). Conclusion: PHIV adolescents have risky sexual behaviours charac terized by being sexually active, inconsistent condom use, and having partners of unknown status. Risk reduction interventions are required to minimize unplanned pregnancies, STI, and HIV transmission by PHIV adolescents