Nonlinear parameter retrieval from three- and four-wave mixing in metamaterials

We present a generalized nonlinear susceptibility retrieval method for metamaterials based on transfer matrices and valid in the nondepleted pump approximation. We construct a general formalism to describe the transfer matrix method for nonlinear media and apply it to the processes of three- and four-wave mixing. The accuracy of this approach is verified via finite element simulations. The method is then reversed to give a set of equations for retrieving the nonlinear susceptibility. Finally, we apply the proposed retrieval operation to a three-wave mixing transmission experiment performed on a varactor loaded split ring resonator metamaterial sample and find quantitative agreement with an analytical effective medium theory model. © 2010 The American Physical Society.

Clinical Research Environment in India: Challenges and Proposed Solutions.

India has compelling need and keen aspirations for indigenous clinical research. Notwithstanding this need and previously reported growth the expected expansion of Indian clinical research has not materialized. We reviewed the scientific literature, lay press reports, and ClinicalTrials.gov data for information and commentary on projections, progress, and impediments associated with clinical trials in India. We also propose targeted solutions to identified challenges. The Indian clinical trial sector grew by (+) 20.3% CAGR (compound annual growth rate) between 2005 and 2010 and contracted by (-) 14.6% CAGR between 2010 and 2013. Phase-1 trials grew by (+) 43.5% CAGR from 2005-2013, phase-2 trials grew by (+) 19.8% CAGR from 2005-2009 and contracted by (-) 12.6% CAGR from 2009-2013, and phase-3 trials grew by (+) 13.0% CAGR from 2005-2010 and contracted by (-) 28.8% CAGR from 2010-2013. This was associated with a slowing of the regulatory approval process, increased media coverage and activist engagement, and accelerated development of regulatory guidelines and recuperative initiatives. We propose the following as potential targets for restorative interventions: Regulatory overhaul (leadership and enforcement of regulations, resolution of ambiguity in regulations, staffing, training, guidelines, and ethical principles [e.g., compensation]).Education and training of research professionals, clinicians, and regulators.Public awareness and empowerment. After a peak in 2009-2010, the clinical research sector in India appears to be experiencing a contraction. There are indications of challenges in regulatory enforcement of guidelines; training of clinical research professionals; and awareness, participation, partnership, and the general image amongst the non-professional media and public. Preventative and corrective principles and interventions are outlined with the goal of realizing the clinical research potential in India.

Recent national trends in Salvia divinorum use and substance-use disorders among recent and former Salvia divinorum users compared with nonusers.

CONTEXT: Media and scientific reports have indicated an increase in recreational use of Salvia divinorum. Epidemiological data are lacking on the trends, prevalence, and correlates of S. divinorum use in large representative samples, as well as the extent of substance use and mental health problems among S. divinorum users. OBJECTIVE: To examine the national trend in prevalence of S. divinorum use and to identify sociodemographic, behavioral, mental health, and substance-use profiles of recent (past-year) and former users of S. divinorum. DESIGN: Analyses of public-use data files from the 2006-2008 United States National Surveys on Drug Use and Health (N = 166,453). SETTING: Noninstitutionalized individuals aged 12 years or older were interviewed in their places of residence. MAIN MEASURES: Substance use, S. divinorum, self-reported substance use disorders, criminality, depression, and mental health treatment were assessed by standardized survey questions administered by the audio computer-assisted self-interviewing method. RESULTS: Among survey respondents, lifetime prevalence of S. divinorum use had increased from 0.7% in 2006 to 1.3% in 2008 (an 83% increase). S. divinorum use was associated with ages 18-25 years, male gender, white or multiple race, residence of large metropolitan areas, arrests for criminal activities, and depression. S. divinorum use was particularly common among recent drug users, including users of lysergic acid diethylamide (53.7%), ecstasy (30.1%), heroin (24.2%), phencyclidine (22.4%), and cocaine (17.5%). Adjusted multinomial logistic analyses indicated polydrug use as the strongest determinant for recent and former S. divinorum use. An estimated 43.0% of past-year S. divinorum users and 28.9% of former S. divinorum users had an illicit or nonmedical drug-use disorder compared with 2.5% of nonusers. Adjusted logistic regression analyses showed that recent and former S. divinorum users had greater odds of having past-year depression and a substance-use disorder (alcohol or drugs) than past-year alcohol or drug users who did not use S. divinorum. CONCLUSION: S. divinorum use is prevalent among recent or active drug users who have used other hallucinogens or stimulants. The high prevalence of substance use disorders among recent S. divinorum users emphasizes the need to study health risks of drug interactions.