Stochastic pumping of heat: Approaching the Carnot efficiency

Random noise can generate a unidirectional heat current across asymmetric nano objects in the absence (or against) a temperature gradient. We present a minimal model for a molecular-level stochastic heat pump that may operate arbitrarily close to the Carnot efficiency. The model consists a fluctuating molecular unit coupled to two solids characterized by distinct phonon spectral properties. Heat pumping persists for a broad range of system and bath parameters. Furthermore, by filtering the reservoirs' phonons the pump efficiency can approach the Carnot limit

Quantum Hall Effect on the Hyperbolic Plane

In this paper, we study both the continuous model and the discrete model of the Quantum Hall Effect (QHE) on the hyperbolic plane. The Hall conductivity is identified as a geometric invariant associated to an imprimitivity algebra of observables. We define a twisted analogue of the Kasparov map, which enables us to use the pairing between $K$-theory and cyclic cohomology theory, to identify this geometric invariant with a topological index, thereby proving the integrality of the Hall conductivity in this case.Comment: AMS-LaTeX, 28 page

Twisted K-theory and K-theory of bundle gerbes

In this note we introduce the notion of bundle gerbe K-theory and investigate the relation to twisted K-theory. We provide some examples. Possible applications of bundle gerbe K-theory to the classification of D-brane charges in non-trivial backgrounds are discussed.Comment: 29 pages, corrected typos, added references, included new section on twisted Chern character in non-torsion cas

Cyclic cocycles on twisted convolution algebras

We give a construction of cyclic cocycles on convolution algebras twisted by gerbes over discrete translation groupoids. For proper \'etale groupoids, Tu and Xu provide a map between the periodic cyclic cohomology of a gerbe-twisted convolution algebra and twisted cohomology groups which is similar to a construction of Mathai and Stevenson. When the groupoid is not proper, we cannot construct an invariant connection on the gerbe; therefore to study this algebra, we instead develop simplicial techniques to construct a simplicial curvature 3-form representing the class of the gerbe. Then by using a JLO formula we define a morphism from a simplicial complex twisted by this simplicial curvature 3-form to the mixed bicomplex computing the periodic cyclic cohomology of the twisted convolution algebras. The results in this article were originally published in the author's Ph.D. thesis.Comment: 39 page

Screening for sexually transmitted infections at a DeAddictions service in South India

Objectives To estimate the lifetime prevalence of four sexually transmitted infections (STIs) and to identify correlates of these infections among patients seeking care for a substance use disorder at a specialized DeAddictions Unit in southern India. Methods Consecutive inpatients (n = 361; 98% male; M age = 36.7 years) admitted to DeAddictions Unit of the National Institute of Mental Health and Neuro Sciences in Bangalore, India, participated in a structured interview to obtain demographic, psychiatric, sexual behavior, and substance use data; each patient also provided a blood sample for serologic testing for HIV, chlamydia, syphilis, and hepatitis B. Results One-quarter of all patients tested positive for at least one STI. Lifetime seroprevalence rates were 12.9% for syphilis, 10.3% for chlamydia, 3.1% for hepatitis B, and 1.1% for HIV. Analyses did not reveal any consistent pattern of associations between STI status and sociodemographic, psychiatric, and sexual behavioral characteristics. Conclusions All patients should receive a comprehensive sexual assessment during standard care; for those patients who report risky sexual practices, we recommend voluntary counseling and testing for STIs. Although we do not recommend universal testing for STIs at this time, this should be revisited based upon national surveillance data

Collective efficacy and HIV Prevention in South African Townships

South African townships have high HIV prevalence and a strong need for collective action to change normative sexual risk behaviors. This study investigated the relationship between perceptions of individuals about collective efficacy in the community’s ability to prevent HIV and their personal HIV risk behaviors. Men (n=1581) and women (n=718) completed anonymous surveys within four Black African Townships in Cape Town, South Africa from June 2008 to December 2010. Measures included demographics, alcohol use, attitudinal and behavioral norms, sexual health communications, and sexual risk behaviors. In multivariate logistic regressions, men were more likely to endorse collective efficacy if they were married, drank less often in alcohol serving establishments, believed that fewer men approve of HIV risk behaviors, talk more with others about HIV/AIDS, and had more sex partners in the past month. Women were more likely to endorse collective efficacy if they drank alcohol less often, talked more with others about HIV/ AIDS, had more sex partners in the past month, but reported fewer unprotected sex acts in the past month. Community level interventions that strengthen collective efficacy beliefs will have to consider both protective and risk behaviors associated with believing that the community is ready and capable of preventing HIV.Department of HE and Training approved lis

Nonresonant hyper‐Raman and hyper‐Rayleigh scattering in benzene and pyridine

This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/90/9/10.1063/1.456592.Nonresonant hyper‐Raman and hyper‐Rayleigh spectra excited at 1064 nm are reported for neat benzene and pyridine. The theory of Herzberg–Teller vibronic coupling in nonresonant and preresonant hyper‐Raman scattering is developed. Nonresonant hyper‐Raman scattering is shown to be vibronically induced by modes that efficiently couple strongly allowed one‐photon and two‐photon transitions. A weak and broad (55 cm− 1) hyper‐Rayleigh band was observed in benzene and attributed to collective scattering, while in pyridine, a much more intense and much narrower hyper‐Rayleigh band was observed. Only the a 2u vibration (ν1 1) was observed in the hyper‐Raman spectrum of benzene, while several strong bands were observed in pyridine. Possible vibronic‐coupling pathways are discussed for these modes. In addition, the observed hyper‐Raman spectrum of pyridine is compared to a recent calculation