Degenerate multi-solitons in the sine-Gordon equation

We construct various types of degenerate multi-soliton and multi-breather solutions for the sine-Gordon equation based on Bäcklund transformations, Darboux–Crum transformations and Hirota's direct method. We compare the different solution procedures and study the properties of the solutions. Many of them exhibit a compound like behaviour on a small timescale, but their individual one-soliton constituents separate for large time. Exceptions are degenerate cnoidal kink solutions that we construct via inverse scattering from shifted Lamé potentials. These type of solutions have constant speed and do not display any time-delay. We analyse the asymptotic behaviour of the solutions and compute explicit analytic expressions for time-dependent displacements between the individual one-soliton constituents for any number of degeneracies. When expressed in terms of the soliton speed and spectral parameter the expression found is of the same generic form as the one formerly found for the Korteweg–de-Vries equation

Quantum dynamics of non-Hermitian many-body Landau-Zener systems

We develop a framework to solve a large class of linearly driven non-Hermitian quantum systems. Such a class of models in the Hermitian scenario is commonly known as multi-state Landau-Zener models. The non-hermiticity is due to the anti-Hermitian couplings between the diabatic levels. We find that there exists a new conservation law, unique to this class of models, that describes the simultaneous growth of the unnormalized wavefunctions. These models have practical applications in Bose-Einstein condensates, and they can describe the dynamics of multi-species bosonic systems. The conservation law relates to a pair-production mechanism that explains the dissociation of diatomic molecules into atoms. We provide a general framework for both solvable and semiclassically solvable non-Hermitian Landau-Zener models. Our findings will open new avenues for a number of diverse emergent phenomena in explicitly time-dependent non-Hermitian quantum systems

Tobacco cues in India: An ecological momentary assessment

Funding for Open Access provided by the UMD Libraries Open Access Publishing Fund.Background: Tobacco use in India is a major health concern; however, little is known about the influence of tobacco-related social and environmental cues on tobacco use. This study uses ecological momentary assessment (EMA) to examine real-time tobacco use and exposure to social and environmental cues. Methods: In Hyderabad and Kolkata, participants were recruited, and an EMA application was installed on their mobile phones. Momentary prompts (MP) were randomly used to collect real-time information and end-of-day (EOD) prompts gathered retrospective information on daily basis. Besides personal tobacco use, the surveys asked about exposure to social (e.g., presence of others using tobacco) and environmental cues (e.g., visual and olfactory stimuli). Using the data aggregation approach, bivariate and multivariate analyses were performed to examine the association of tobacco use and cue exposure. Moderating roles of participants’ socio-demographic characteristics were also tested to gain an in-depth understanding of the relationship. Results: Among the 205 participants, around a third (MP, 33.7 %; EOD, 37.6 %) used tobacco at least once during the study period. Tobacco-related social and environmental cues related were commonly reported. In the bivariate models, tobacco use was associated with gender, age, and all the examined social and environmental cues except for seeing restrictions on tobacco use. In the multivariate models, tobacco use was associated with age, gender, seeing others using tobacco, and seeing restrictions on tobacco use. Seeing others in one’s immediate group using tobacco was the strongest predictor of tobacco use in both MP and EOD assessments. Gender and age did not moderate the relationship between cue exposure and tobacco use, although males reported higher tobacco use and cue exposure in general. Conclusions: This research provides data on the ubiquity of social and environmental tobacco cues in India. The EMA approach was feasible and informative. Future cessation interventions and advocacy efforts should address the high prevalence of tobacco use and exposure to pro-tobacco use cues especially among Indian males. Health education campaigns for promoting tobacco use restrictions in private places as well as changing the norms of tobacco use in social settings are recommended

Integrable nonlocal Hirota equations

We construct several new integrable systems corresponding to nonlocal ver-sions of the Hirota equation, which is a particular example of higher order nonlinearSchrödinger equations. The integrability of the new models is established by providingtheir explicit forms of Lax pairs or zero curvature conditions.The two compatibility equa-tions arising in this construction are found to be related to each other either by a paritytransformationP, by a time reversalTor aPT-transformation possibly combined with aconjugation. We construct explicit multi-soliton solutions forthese models by employingHirota’s direct method as well as Darboux-Crum transformations.The nonlocal natureof these models allows for a modification of these solution procedures as the new systemsalso possess new types of solutions with different parameter dependence and differentqualitative behaviour. The multi-soliton solutions are of varied type, being for instancenonlocal in space, nonlocal in time of time crystal type, regular with local structureseither in time/space or of rogues wave type

Complex solitons with real energies

Using Hirota’s direct method and Bäcklund transformations we construct explicit complex one and two-soliton solutions to the complex Korteweg-de Vries equation, the complex modified Korteweg-de Vries equation and the complex sine-Gordon equation. The one-soliton solutions of trigonometric and elliptic type turn out to be PT -symmetric when a constant of integration is chosen to be purely imaginary with one special choice corresponding to solutions recently found by Khare and Saxena. We show that alternatively complex PT -symmetric solutions to the Korteweg-de Vries equation may also be constructed alternatively from real solutions to the modified Korteweg-de Vries by means of Miura transformations. The multi-soliton solutions obtained from Hirota’s method break the PT -symmetric, whereas those obtained from Bäcklund transformations are PT -invariant under certain conditions. Despite the fact that some of the Hamiltonian densities are non-Hermitian, the total energy is found to be positive in all cases, that is irrespective of whether they are PT -symmetric or not. The reason is that the symmetry can be restored by suitable shifts in space-time and the fact that any of our N-soliton solutions may be decomposed into N separate PT -symmetrizable one-soliton solutions

Generation and characterization of a defective HIV-1 Virus as an immunogen for a therapeutic vaccine

BACKGROUND: The generation of new immunogens able to elicit strong specific immune responses remains a major challenge in the attempts to obtain a prophylactic or therapeutic vaccine against HIV/AIDS. We designed and constructed a defective recombinant virus based on the HIV-1 genome generating infective but non-replicative virions able to elicit broad and strong cellular immune responses in HIV-1 seropositive individuals. RESULTS: Viral particles were generated through transient transfection in producer cells (293-T) of a full length HIV-1 DNA carrying a deletion of 892 base pairs (bp) in the pol gene encompassing the sequence that codes for the reverse transcriptase (NL4-3/ΔRT clone). The viral particles generated were able to enter target cells, but due to the absence of reverse transcriptase no replication was detected. The immunogenic capacity of these particles was assessed by ELISPOT to determine γ-interferon production in a cohort of 69 chronic asymptomatic HIV-1 seropositive individuals. Surprisingly, defective particles produced from NL4-3/ΔRT triggered stronger cellular responses than wild-type HIV-1 viruses inactivated with Aldrithiol-2 (AT-2) and in a larger proportion of individuals (55% versus 23% seropositive individuals tested). Electron microscopy showed that NL4-3/ΔRT virions display immature morphology. Interestingly, wild-type viruses treated with Amprenavir (APV) to induce defective core maturation also induced stronger responses than the same viral particles generated in the absence of protease inhibitors. CONCLUSIONS: We propose that immature HIV-1 virions generated from NL4-3/ΔRT viral clones may represent new prototypes of immunogens with a safer profile and stronger capacity to induce cellular immune responses than wild-type inactivated viral particles.This study was supported by grants FIS PI050265, FIS PI040503, FIS PI070291, FIS Intrasalud 080752, FIS PS09/01297, FIS PI10/02984, SAF2006-26667-E, FIT 09-010-205-9, FIPSE 36780/08, Fundación Mútua Madrileña, TRA-094, EC10-153, ISCIII-RETIC RD06/0006, HIVACAT–HIV Development Program in Catalonia, FIPSE 36630/07, UE Program Health 2009 CHAARM. Spanish Health Institute Carlos III (ISCIII) and the Health Department of the Catalan Government (Generalitat de Catalunya). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.S

Stability of PT and anti-PT-symmetric Hamiltonians with multiple harmonics

Hermitian Hamiltonians with time-periodic coefficients can be analyzed via Floquet theory, and have been extensively used for engineering Floquet Hamiltonians in standard quantum simulators. Generalized to non-Hermitian Hamiltonians, time periodicity offers avenues to engineer the landscape of Floquet quasienergies across the complex plane. We investigate two-level non-Hermitian PT and anti-PT-symmetric Hamiltonians with coefficients that have multiple harmonics using Floquet theory. By analytical and numerical calculations, we obtain their regions of stability, defined by real Floquet quasienergies, and contours of exceptional point (EP) degeneracies. We extend our analysis to study the phases that accompany these cyclic changes with the biorthogonality approach. Our results demonstrate that these time-periodic Hamiltonians generate a rich landscape of stable (real) and unstable (complex) regions

Perceived ease of flavored e-cigarette use and e-cigarette use progression among youth never tobacco users.

BACKGROUND:There is an increased need to understand how e-cigarette flavors may contribute to e-cigarette uptake and use among youth. We examined the relationship between perceived ease of flavored e-cigarette use and e-cigarette use susceptibility and progression among a nationally representative sample of U.S. youth never tobacco users. METHODS:The wave 1 (2013-2014) and wave 2 (2014-2015) surveys of PATH Study were used. Youth never tobacco users (ages 12-17) who reported whether flavored e-cigarettes were easier to use than unflavored e-cigarettes at wave 1 (n = 6,983) were included in the study. Multivariable logistic regressions were used to examine the associations between perceived ease of using flavored e-cigarettes (wave 1) and e-cigarette use outcomes including e-cigarette use susceptibility (wave 1) and e-cigarette initiation and past-30-day use (wave 2). RESULTS:Overall, 21.2% of the sample perceived flavored e-cigarettes easier to use than unflavored e-cigarettes; and 28.9% of the sample were susceptible to using e-cigarettes at wave 1, and 7.5% and 2.0% initiated e-cigarettes and used e-cigarettes in the past 30 days at wave 2, respectively. Among those who perceived flavored e-cigarettes easier to use, 41.0% were susceptible to using e-cigarettes at wave 1, and 10.6% and 3.4% initiated and used e-cigarettes in the past 30 days at wave 2, respectively. Perceiving flavored e-cigarettes as easier to use than unflavored e-cigarettes at wave 1 was positively associated with e-cigarette use susceptibility at wave 1 (AOR = 1.43, CI = 1.21, 1.69), and e-cigarette initiation (AOR = 1.32, CI = 1.12, 1.67) and past-30-day use (AOR = 1.25, CI = 1.10, 2.47) at wave 2. CONCLUSIONS:Perceiving flavored e-cigarettes as easier to use than unflavored e-cigarettes may lead to e-cigarette use progression among youth never tobacco users. Determining the factors (including e-cigarette marketing and specific e-cigarette flavors) that lead to perceived ease of using flavored e-cigarettes would inform efforts to prevent and curb youth e-cigarette use