Predicting Phase Stability at Interfaces

We present the RAFFLE methodology for structural prediction of the interface between two materials and demonstrate its effectiveness by applying it to MgO encapsulated by two layers of graphene. To address the challenge of interface structure prediction, our methodology combines physical insights derived from morphological features observed in related systems with an iterative machine learning technique. This employs physical-based methods, including void-filling and n-body distribution functions to predict interface structures. For the carbon-MgO encapsulated system, we have shown the rocksalt and hexagonal phases of MgO to be the two most energetically stable in the few-layer regime. We demonstrate that monolayer rocksalt is heavily stabilized by interfacing with graphene, becoming more energetically favorable than the graphenelike monolayer hexagonal MgO. The RAFFLE methodology provides valuable insights into interface behavior, and a route to finding new materials at interfaces.

Phase Stability and Electronic Properties of Hybrid Organic-Inorganic Perovskite Solid Solution (CH(NH2)2) x (CH3NH3)1-x Pb(Br y I1-y )3 as a Function of Composition

Compositional mixing provides the means to maintain the structural stability of a hybrid organic-inorganic perovskite for efficient and robust photovoltaic applications. Here we present a theoretical, first-principles study of the electronic and energetic properties of the solid solution (CH(NH₂)₂) _x (CH₃NH₃)_1-x PbBr _y I_1-y , the mixing of two organic molecules with various orientations, formamidinium and methylammonium, and two halides, bromide and iodide. Our results show the variation in the band gap as a function of composition (x and y) provides several candidates that exceed the 27.5% Schockley-Queisser efficiency. The variation in the composition of hybrid perovskite shows specific regions where either the hexagonal or cubic phase dominates. We discuss the balance between the band gap and phase stability and indicate regions where the phase transition temperature between cubic and hexagonal phases is far from room temperature, indicating that these compositions are more robust at room temperature against phase transitions.

A survey of mental health care provider's and managed care organization attitudes toward, familiarity with, and use of group interventions

Managed Care has had a significant impact on delivery systems for mental health services. Direct and indirect persuasion to provide more cost-effective treatments has been one consequence. The cost-saving qualities and the effectiveness of group interventions have produced clear expectations for an increased use of therapy groups. This study compared perceptions and uses of group treatments on a national sample of managed care organizations and mental health providers. Because group psychotherapy encompasses such a broad definition, five specific types of group interventions were defined: problem-focused homogenous, process-oriented heterogeneous, psycho-educational, self-help, and short-term groups. Implications of differences and similarities between directors of managed care organizations and treatment providers are examined and discussed across five response categories (familiarity/training, perceived effectiveness, likelihood of reimbursement/referral, daily use, and expectation for future use).

The prevalence of vitiligo and poliosis in patients with uveitis

Vitiligo is a disease of cutaneous pigment cells. Recently we reported that one third of patients with vitiligo had destructive lesions in the retinal pigment epithelium and/or the choroid which were visible by ophthalmologic examination. To determine whether abnormalities of the pigment system of the eye and skin are in fact associated, we examined for vitiligo the skin and hair of 107 patients with active uveitis. Thirty-four patients had an infectious or a known cause for their uveitis and none of these had vitiligo. In contrast, six of seventy-three patients (8%) with idiopathic uveitis had vitiligo or early graying of the hair. Seven other patients with active inflammatory diseases of the ocular pigment system were referred for evaluation of white spots on the skin. One of these patients was legally blind (correlated visual acuity less than 20/200 in both eyes) due to chorioretinal scars in the fovea. The finding that vitiligo is more common than expected in patients with uveitis is significant biologically and statistically. This observation supports our hypothesis that the same systemic factors, probably immunologic, are responsible for destroying pigment cells in the skin (vitiligo) and the eye (uveitis).