Varying constants, Gravitation and Cosmology

Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. It is thus of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We thus detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, Solar system observations, meteorites dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.Comment: 145 pages, 10 figures, Review for Living Reviews in Relativit

Engineering of microfabricated ion traps and integration of advanced on-chip features

Atomic ions trapped in electromagnetic potentials have long been used for fundamental studies in quantum physics. Over the past two decades, trapped ions have been successfully used to implement technologies such as quantum computing, quantum simulation, atomic clocks, mass spectrometers and quantum sensors. Advanced fabrication techniques, taken from other established or emerging disciplines, are used to create new, reliable ion-trap devices aimed at large-scale integration and compatibility with commercial fabrication. This Technical Review covers the fundamentals of ion trapping before discussing the design of ion traps for the aforementioned applications. We overview the current microfabrication techniques and the various considerations behind the choice of materials and processes. Finally, we discuss current efforts to include advanced, on-chip features in next-generation ion traps

Relationship Characteristics Differ Based on Use of Substances with Sex among an Urban Internet Sample of HIV-Discordant and HIV-Positive Male Couples

Previous research with men who have sex with men (MSM) has found that substance use with sex is strongly associated with HIV acquisition and poor adherence to HIV treatments. Although some studies have assessed male couples’ use of substances with unprotected anal sex, little is known on whether differences in their relationship dynamics are associated with their usage. Current HIV prevention initiatives underscore the importance of studying male couples’ relationship dynamics. Using dyadic data from 28 HIV-positive and 58 HIV-discordant male couples, this analysis sought to: (1) describe, by substance type, whether neither, one, or both partners in the couple used a particular substance with sex within their relationship or outside of the relationship, respectively, and (2) assess, by substance type, whether relationship characteristic differences existed between these three groups of couples with respect to substance use with sex within and outside the relationship. Data from 86 dyads came from a cross-sectional, Internet study. Multivariate multinomial regression models were employed to achieve the aims. Except for alcohol, most did not use substances with sex. Within the relationship, those who used with sex varied by substance type; outside the relationship, most couples had only one partner who used with sex regardless of substance type. Several relationship characteristic differences were noted between the groups of couples. Within the relationship, marijuana and erectile dysfunction medication (EDM) use with sex was associated with having less tangible resources; for outside the relationship, these were associated with perceiving to have greater quality of alternatives. In general, amyl nitrates and party drug use with sex were associated with viewing the main partner as being less dependable for trustworthiness. Marijuana and party drug use with sex within the relationship and EDM use with sex outside the relationship were negatively associated with being able to communicate constructively. Mixed results were noted for relationship satisfaction. Additional research is urgently needed for prevention and promotion of healthy relationships for male couples who use substances with sex

Gender difference in the characteristics of and high-risk behaviours among non-injecting heterosexual methamphetamine users in Qingdao, Shandong Province, China

<p>Abstract</p> <p>Background</p> <p>Despite the increasing risk of HIV infections, few studies concerning the characteristics of non-injecting heterosexual methamphetamine (MA) users and related risk behaviours have been conducted in China.</p> <p>Methods</p> <p>Gender differences in socio-demographic characteristics, perception of MA and STD/HIV, MA use practices, and sexual behaviours related to MA use were examined among 398 non-injecting heterosexual MA users (288 males, 110 females).</p> <p>Results</p> <p>Male MA users were more likely to be married, local, and self-employed; female MA users were more likely to be young, single, engaged in commercial service or unemployed. Female MA users usually start MA use at an earlier age than males (24.3 vs. 31.3 years old), with shorter abuse durations (2.6 vs. 2.9 years), higher frequency of MA use (3.6 vs. 2.4 times per week), and higher likelihood of using MA with heterosexual partners (100% vs. 78.1%). More male MA users have had multiple sex partners (96.9% vs. 77.3%) and sex exchanges (72.9% vs. 46.4%). Among 277 males who had had sex with commercial sex workers (CSW), 69.4% never used condoms, and among 77 males who had had sex with multiple partners who are commercial sex workers and always or usually used condoms, 87.0% never changed condoms when changing partners.</p> <p>Conclusion</p> <p>There may be gender difference in the characteristics of high-risk behaviours among non-injecting heterosexual MA users. The findings suggest the integration of specific risk reduction strategies into intervention programs for non-injecting heterosexual MA user populations may significantly improve program goals.</p