Generalized Weyl-Wigner map and Vey quantum mechanics

The Weyl-Wigner map yields the entire structure of Moyal quantum mechanics directly from the standard operator formulation. The covariant generalization of Moyal theory, also known as Vey quantum mechanics, was presented in the literature many years ago. However, a derivation of the formalism directly from standard operator quantum mechanics, clarifying the relation between the two formulations is still missing. In this paper we present a covariant generalization of the Weyl order prescription and of the Weyl-Wigner map and use them to derive Vey quantum mechanics directly from the standard operator formulation. The procedure displays some interesting features: it yields all the key ingredients and provides a more straightforward interpretation of the Vey theory including a direct implementation of unitary operator transformations as phase space coordinate transformations in the Vey idiom. These features are illustrated through a simple example.Comment: 15 pages, LaTe

Experimental evidence for the role of cantori as barriers in a quantum system

We investigate the effect of cantori on momentum diffusion in a quantum system. Ultracold caesium atoms are subjected to a specifically designed periodically pulsed standing wave. A cantorus separates two chaotic regions of the classical phase space. Diffusion through the cantorus is classically predicted. Quantum diffusion is only significant when the classical phase-space area escaping through the cantorus per period greatly exceeds Planck's constant. Experimental data and a quantum analysis confirm that the cantori act as barriers.Comment: 19 pages including 9 figures, Accepted for publication in Physical Review E in March 199

Time dependent transformations in deformation quantization

We study the action of time dependent canonical and coordinate transformations in phase space quantum mechanics. We extend the covariant formulation of the theory by providing a formalism that is fully invariant under both standard and time dependent coordinate transformations. This result considerably enlarges the set of possible phase space representations of quantum mechanics and makes it possible to construct a causal representation for the distributional sector of Wigner quantum mechanics.Comment: 16 pages, to appear in the J. Math. Phy

Chaos assisted instanton tunneling in one dimensional perturbed periodic potential

For the system with one-dimensional spatially periodic potential we demonstrate that small periodic in time perturbation results in appearance of chaotic instanton solutions. We estimate parameter of local instability, width of stochastic layer and correlator for perturbed instanton solutions. Application of the instanton technique enables to calculate the amplitude of the tunneling, the form of the spectrum and the lower bound for width of the ground quasienergy zone

Changes in Floquet state structure at avoided crossings: delocalization and harmonic generation

Avoided crossings are common in the quasienergy spectra of strongly driven nonlinear quantum wells. In this paper we examine the sinusoidally driven particle in a square potential well to show that avoided crossings can alter the structure of Floquet states in this system. Two types of avoided crossings are identified: on type leads only to temporary changes (as a function of driving field strength) in Floquet state structure while the second type can lead to permanent delocalization of the Floquet states. Radiation spectra from these latter states show significant increase in high harmonic generation as the system passes through the avoided crossing.Comment: 8 pages with 10 figures submitted to Physical Review

Engineered Phage Endolysin Eliminates Gardnerella Biofilm without Damaging Beneficial Bacteria in Bacterial Vaginosis Ex Vivo.

Bacterial vaginosis is characterized by an imbalance of the vaginal microbiome and a characteristic biofilm formed on the vaginal epithelium, which is initiated and dominated by Gardnerella bacteria, and is frequently refractory to antibiotic treatment. We investigated endolysins of the type 1,4-beta-N-acetylmuramidase encoded on Gardnerella prophages as an alternative treatment. When recombinantly expressed, these proteins demonstrated strong bactericidal activity against four different Gardnerella species. By domain shuffling, we generated several engineered endolysins with 10-fold higher bactericidal activity than any wild-type enzyme. When tested against a panel of 20 Gardnerella strains, the most active endolysin, called PM-477, showed minimum inhibitory concentrations of 0.13-8 µg/mL. PM-477 had no effect on beneficial lactobacilli or other species of vaginal bacteria. Furthermore, the efficacy of PM-477 was tested by fluorescence in situ hybridization on vaginal samples of fifteen patients with either first time or recurring bacterial vaginosis. In thirteen cases, PM-477 killed the Gardnerella bacteria and physically dissolved the biofilms without affecting the remaining vaginal microbiome. The high selectivity and effectiveness in eliminating Gardnerella, both in cultures of isolated strains as well as in clinically derived samples of natural polymicrobial biofilms, makes PM-477 a promising alternative to antibiotics for the treatment of bacterial vaginosis, especially in patients with frequent recurrence

What do South African adolescents want in a sexual health service Evidence from the South African Studies on HIV in Adolescents SASHA project

Background. Young people in sub-Saharan Africa (SSA) are disproportionately affected by HIV, sexually transmitted infections and unplanned pregnancies. The provision of accessible sexual and reproductive health services (SRHS) for young people in SSA is vital to reduce this burden.Objectives. To examine the needs of South African (SA) adolescents with regard to differentiated, accessible and adolescent-responsive SRHS.Methods. Data were drawn from a larger project examining the feasibility of conducting HIV vaccine trials in adolescents. Fifteen focus group discussions were conducted across five research sites in four SA provinces with 120 male and female adolescent human papillomavirus vaccine trial participants aged 12 - 19 years from low-income areas with a high incidence of HIV. Transcribed data were double-coded using framework analysis.Results. Three main themes emerged on how best to improve SRHS for adolescents in resource-limited settings: adolescent-friendly services, availability of developmentally appropriate and tailored information, and improved relationships between healthcare workers and clinic attendees. Participants wanted more flexible opening hours at SRHS to account for travel time to clinics from school and home. They suggested that services include contraception, counselling, educational materials, links to adoption services, emergency vehicles, pre- and postnatal care, and improved service quality from clinic staff.Conclusions. While dedicated adolescent SRHS might best meet the needs of young people in SA, the study suggests that failing this, existing SRHS should be more responsive to adolescent use. Innovations such as mobile outreach services, self-testing and flexible hours will help SRHS respond to adolescents’ needs.Â

What do South African adolescents want in a sexual health service? Evidence from the South African Studies on HIV in Adolescents (SASHA) project

Background. Young people in sub-Saharan Africa (SSA) are disproportionately affected by HIV, sexually transmitted infections and unplanned pregnancies. The provision of accessible sexual and reproductive health services (SRHS) for young people in SSA is vital to reduce this burden.Objectives. To examine the needs of South African (SA) adolescents with regard to differentiated, accessible and adolescent-responsive SRHS.Methods. Data were drawn from a larger project examining the feasibility of conducting HIV vaccine trials in adolescents. Fifteen focus group discussions were conducted across five research sites in four SA provinces with 120 male and female adolescent human papillomavirus vaccine trial participants aged 12 - 19 years from low-income areas with a high incidence of HIV. Transcribed data were double-coded using framework analysis.Results. Three main themes emerged on how best to improve SRHS for adolescents in resource-limited settings: adolescent-friendly services, availability of developmentally appropriate and tailored information, and improved relationships between healthcare workers and clinic attendees. Participants wanted more flexible opening hours at SRHS to account for travel time to clinics from school and home. They suggested that services include contraception, counselling, educational materials, links to adoption services, emergency vehicles, pre- and postnatal care, and improved service quality from clinic staff.Conclusions. While dedicated adolescent SRHS might best meet the needs of young people in SA, the study suggests that failing this, existing SRHS should be more responsive to adolescent use. Innovations such as mobile outreach services, self-testing and flexible hours will help SRHS respond to adolescents’ needs.