Field dependence of currents

Arguments are presented to show that in a theory with spin , vector and axial-vector fields, the vector current in general depends upon the axial-vector field also in addition to the dependence on the vector field. The exact dependence is worked out on quite general grounds. We point out, however, that there are inconsistencies in the approach in which use is made of the definition of field dependent current and the usual canonical commutation relations of vector and axial-vector fields.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32804/1/0000177.pd

Use of contingency management incentives to improve completion of hepatitis B vaccination in people undergoing treatment for heroin dependence: a cluster randomised trial

Background: Poor adherence to treatment diminishes its individual and public health benefit. Financial incentives, provided on the condition of treatment attendance, could address this problem. Injecting drug users are a high-risk group for hepatitis B virus (HBV) infection and transmission, but adherence to vaccination programmes is poor. We aimed to assess whether contingency management delivered in routine clinical practice increased the completion of HBV vaccination in individuals receiving opioid substitution therapy. Methods: In our cluster randomised controlled trial, we enrolled participants at 12 National Health Service drug treatment services in the UK that provided opioid substitution therapy and nurse-led HBV vaccination with a super-accelerated schedule (vaccination days 0, 7, and 21). Clusters were randomly allocated 1:1:1 to provide vaccination without incentive (treatment as usual), with fixed value contingency management (three £10 vouchers), or escalating value contingency management (£5, £10, and £15 vouchers). Both contingency management schedules rewarded on-time attendance at appointments. The primary outcome was completion of clinically appropriate HBV vaccination within 28 days. We also did sensitivity analyses that examined vaccination completion with full adherence to appointment times and within a 3 month window. The trial is registered with Current Controlled Trials, number ISRCTN72794493. Findings: Between March 16, 2011, and April 26, 2012, we enrolled 210 eligible participants. Compared with six (9%) of 67 participants treated as usual, 35 (45%) of 78 participants in the fixed value contingency management group met the primary outcome measure (odds ratio 12·1, 95% CI 3·7–39·9; p<0·0001), as did 32 (49%) of 65 participants in the escalating value contingency management group (14·0, 4·2–46·2; p<0·0001). These differences remained significant with sensitivity analyses. Interpretation: Modest financial incentives delivered in routine clinical practice significantly improve adherence to, and completion of, HBV vaccination programmes in patients receiving opioid substitution therapy. Achievement of this improvement in routine clinical practice should now prompt actual implementation. Drug treatment providers should employ contingency management to promote adherence to vaccination programmes. The effectiveness of routine use of contingency management to achieve long-term behaviour change remains unknown

Barriers to Pharmacy-Based Syringe Purchase Among Injection Drug Users in Tijuana, Mexico: A Mixed Methods Study

Injection drug users (IDUs) may be denied purchase of sterile syringes even where purchase without a prescription is legal. This study examined barriers to over-the-counter (OTC) syringe purchase among IDUs in Tijuana, Mexico. A quantitative survey and subsequent focus groups were used to quantify barriers to purchase, identify their correlates and provide in-depth exploration of syringe purchase experiences. Of 627 IDUs, 81% purchased a syringe in the past 6 months and 16% were refused or overcharged. Factors independently associated with refusal/overcharging were homelessness, receptive syringe sharing, >5 uses per syringe, and number of lifetime abscesses. Few pharmacies sold syringes to IDUs, who adapted by limiting purchase attempts to pharmacies known to sell syringes consistently. Failed purchases occurred when drug withdrawal required purchase at unusual times or locations, often following release from jail. IDUs reported syringe sharing, syringe reuse, and searching through unsecured medical waste for syringes in response to failed purchase attempts. Interventions to expand OTC syringe sales to IDUs, particularly near detention facilities, will facilitate safer injection practices

Hepatitis Vaccination of Men Who Have Sex with Men at Gay Pride Events

Prevention researchers have advocated primary prevention such as vaccination in alternative venues. However, there have been major questions about both the attendance of, and the ability to, vaccinate high-risk individuals in such settings. The current study seeks to assess the feasibility of vaccinating high-risk men who have sex with men (MSM) at Gay Pride events. The research questions are: Do gay men who are sampled at Gay Pride events engage in more or less risky behavior than gay men sampled at other venues? Do the gay men who receive hepatitis vaccinations at Gay Pride engage in more or less risky behavior than gay men at Gay Pride who do not receive hepatitis vaccination? Of the 3689 MSM that completed the Field Risk Assessment (FRA), 1095/3689 = 29.68% were recruited at either the 2006 or 2007 Long Beach, California Gay Pride events. The remaining, 2594/3689 = 70.32% were recruited at Long Beach gay bars, gay community organizations and institutions, and through street recruitment in various gay enclaves in the Long Beach area. Logistic regression analysis yielded eight factors that were associated with non-attendance of Gay Pride: Age, had sex while high in the last 12 months, had unprotected anal intercourse (UAI) in the last 12 months, had sex for drugs/money in the last 12 months, been diagnosed with a sexually transmitted infection (STI) in the last 12 months, used nitrites (poppers) in the last 12 months, and used methamphetamine in the last 12 months. Identifying as White, Asian, or African American compared to Hispanic was also associated with non-attendance. Bivariate analysis indicated that, of the MSM sampled at Gay Pride, 280/1095 = 25.57% received a hepatitis vaccination there. The MSM sampled at Gay Pride who reported engaging in UAI or having used any stimulant (cocaine, crack-cocaine, or methamphetamine) in the last 12 months were more likely to receive hepatitis vaccination on-site. The results provide evidence for the viability of successfully vaccinating high-risk MSM at Gay Pride events. However, it is vital that no-cost vaccinations are also funded in other community settings such as STI clinics, drug treatment programs, prisons, universities, and other community resource centers in order to reach those additional high-risk MSM who do not attend Gay Pride

Multi-Component NLS Equation with NZBCs

The Inverse Scattering Transform (IST) for the defocusing vector nonlinear Schr¨ odinger equations (NLS), with an arbitrary number of components and nonvanishing boundary conditions at space infinities, is formulated by adapting and generalizing the approach used by Beals, Deift, and Tomei in the development of the IST for the N-wave interaction equations. Specifically, a complete set of sectionally meromorphic eigenfunctions is obtained from a family of analytic forms that are constructed for this purpose. As in the scalar and two-component defocusing NLS, the direct and inverse problems are formulated on a two-sheeted, genus-zero Riemann surface, which is then transformed into the complex plane by means of an appropriate uniformization variable. The inverse problem is formulated as a matrix Riemann-Hilbert problem with prescribed poles, jumps, and symmetry conditions. In contrast to traditional formulations of the IST, the analytic forms and eigenfunctions are first defined for complex values of the scattering parameter, and extended to the continuous spectrum a posteriori

Teaching Modeling with Partial Differential Equations: Several Successful Approaches

We discuss the introduction and teaching of partial differential equations (heat and wave equations) via modeling physical phenomena, using a new approach that encompasses constructing difference equations and implementing these in a spreadsheet, numerically solving the partial differential equations using the numerical differential equation solver in Mathematica, and analytically constructing solutions from reasoned building blocks. We obtain graphical feedback as soon as possible in each approach and permit “what if” modeling wherever possible. This approach is contrasted with the usual Fourier series development and series solution using boundary value solution strategies

Integrable Nonlinear Schrodinger Systems and their SolitonDynamics

Nonlinear Schrodinger (NLS) systems are important examples of physically-significant nonlinear evolution equations that can be solved by the inverse scattering transform (IST) method. In fact, the IST for discrete and continuous, as well as scalar and vector, NLS systems all fit into the same framework, which is reviewed here. The parallel presentation of the IST for each of these systems not only clarifies the common structure of the IST, but also highlights the key variations. Importantly, these variations manifest themselves in the dynamics of the solutions. With the IST approach, one can explicitly construct the soliton solutions of each of these systems, as well as formulas from which one can determine the dynamics of soliton interaction. In particular, vector solitons, both continuous and discrete, are partially characterized by a polarization vector, which is shifted by soliton interaction. Here, we give a complete account of the nature of this polarization shift. The polarization vector can be used to encode the value of a binary digit (“bit”) and the soliton interaction arranged so as to effect logical computations

Sequential Events in Bacterial Colony Morphogenesis

Bacterial colonies are organized, differentiated multicellular communities expressing genetically controlled patterns. These patterns can be seen in mature colonies by staining for differential gene expression, by visualization of surface textures, and by microscopic examination of cellular morphologies and multicellular arrays. Colony morphogenesis involves many sequential processes of cellular growth, differentiation and movement which are regulated, at least in part, by cell-cell interactions and communication between groups of cells. These morphogenetic processes can be followed by periodic microscopic examination of developing colonies and by time-lapse video recordings. Since the final colony structure is the integrated product of many steps, pattern formation cannot realistically be explained by assumptions about autonomous cell behaviors. Instead, colony growth is best viewed as a developmental process in which the cells interact and adjust their individual and collective behaviors as morphogenesis proceeds

Discrete Vector Solitons: Composite Solitons, Yang–Baxter Maps and Computation

Collisions of solitons for an integrable discretization of the coupled nonlinear Schrodinger equation are investigated. By a generalization of Manakov’s well-known formulas for the polarization shift of interacting vector solitons, it is shown that the multisoliton interaction process is equivalent to a sequence pairwise interactions and, moreover, the net result of the interaction is independent of the order in which such collisions occur. Further, the order-invariance is shown to be related to the fact that the map that determines the interaction of two such solitons satisfies the Yang–Baxter relation. The associated matrix factorization problem is discussed in detail and the notion of fundamental and composite solitons is elucidated. Moreover, it is shown that, in analogy with the continuous case, collisions of fundamental solitons can be described by explicit fractional linear transformations of a complex-valued scalar polarization state. Because the parameters controlling the energy switching between the two components exhibit nontrivial information transformation, they can, in principle, be used to implement logic operations