Contemporaneous relationship between substance abuse treatment and poly-substance use: evidence from the Persistent Effect of Treatment Studies.

Data from the Persistent Effect of Treatment Studies (PETS) are used to explore the relationship between duration of substance use treatment and simultaneous poly-substance using behaviors. Studying such contemporaneous relationships is especially important given the chronic nature of the substance-using population (McLellan, 2002) in the PETS study. Data were collected at intake to treatment programs and follow-up interviews were performed periodically at treatment program sites. One of the features of the analysis was the development of a poly-substance scale to measure multiple substance use. Multilevel models were implemented to examine the relationship between three levels of care (i.e., intensive outpatient, outpatient, and residential) and simultaneous poly-substance use. Contemporaneous effects of treatment were obtained such that higher duration of treatment was associated with drops in substance-using behaviors. This result supports the need for sustaining treatment for a population of chronic substance abusers.

Experimental realization of ultrathin, double-sided metamaterial perfect absorber at terahertz gap through stochastic design process.

We design and demonstrate a flexible, ultrathin and double-sided metamaterial perfect absorber (MPA) at 2.39 terahertz (THz), which enables excellent light absorbance under incidences from two opposite sides. Herein, the MPA is fabricated on a λ0/10.1-thick flexible polyethylene terephthalate substrate of εr = 2.75 × (1 + 0.12i), sandwiched by two identical randomized metallic patterns by our stochastic design process. Such an MPA provides tailored permittivity and permeability to approach the impedance of free space for minimizing reflectance and a great imaginary part of the refractive index for reducing transmittance and finally results in high absorbance. Both experimental measurement and numerical simulation are in a good agreement. The flexible, ultrathin and double-sided MPA significantly differs from traditional quarter-wavelength absorbers and other single-sided perfect absorbers, paving a way toward practical THz applications in thermal emission, sensing and imaging, communications, stealth technique, and even energy harvesting.