Size-dependent absorption and defect states in CdSe nanocrystals in various multilayer structures

GeS2-CdSe superlattices and composite films are prepared by consecutive thermal evaporation of CdSe and GeS2 in vacuum. CdSe layer thickness varies between 1 and 10 nm, while the thickness of GeS2 layers is either equal (in superlattices) to or 20 times greater (in composite films) than that of CdSe layers. Standard spectral photocurrent measurements and various constant photocurrent methods are used to study optical absorption of all samples. An overall blueshift is observed with decreasing CdSe layer thickness of superlattices. This shift is related to a size-induced increase of the optical band gap of CdSe due to one-dimensional carrier confinement in the continuous nanocrystalline CdSe layers. A number of features are observed in the absorption spectra of composite films containing CdSe nanocrystals with average radii of approximately 2.5 and approximately 3.3 nm. They are discussed in terms of three-dimensional carrier confinement and are considered a manifestation of excited electron states in CdSe nanocrystals embedded in GeS2 thin film matrix. In addition to these discrete features, the exponential dependence of the optical absorption (Urbach) edge indicates a distribution of "valence band" tail states associated with disorder. Transient photoconductivity measurements made on similarly prepared SiOx-CdSe superlattices exhibit a rapid fall in photocurrent by a power law decay over several orders of magnitude of time, which is consistent with multi-pletrapping transport via an extensive distribution of deep defects.     

Can Reconstructed Se-Deficient Line Defects in Monolayer VSe2 Induce Magnetism?

There have been several recent conflicting reports on the ferromagnetism of clean monolayer VSe₂. Herein, the controllable formation of 1D defect line patterns in vanadium diselenide (VSe₂) monolayers initiated by thermal annealing is presented. Using scanning tunneling microscopy and q-plus atomic force microscopy techniques, the 1D line features are determined to be 8-member-ring arrays, formed via a Se deficient reconstruction process. The reconstructed VSe₂ monolayer with Se-deficient line defects displays room-temperature ferromagnetism under X-ray magnetic circular dichroism and magnetic force microscopy, consistent with the density functional theory calculations. This study possibly resolves the controversy on whether ferromagnetism is intrinsic in monolayer VSe₂, and highlights the importance of controlling and understanding the atomic structures of surface defects in 2D crystals, which could play key roles in the material properties and hence potential device applications.     

Enhanced multi-spectral imaging of live breast cancer cells using immunotargeted gold nanoshells and two-photon excitation microscopy

We demonstrate the capability of using immunotargeted gold nanoshells as contrast agents for in vitro two-photon microscopy. The two-photon luminescence properties of different-sized gold nanoshells are first validated using near-infrared excitation at 780?nm. The utility of two-photon microscopy as a tool for imaging live HER2-overexpressing breast cancer cells labeled with anti-HER2-conjugated nanoshells is then explored and imaging results are compared to normal breast cells. Five different imaging channels are simultaneously examined within the emission wavelength range of 451-644?nm. Our results indicate that under near-infrared excitation, superior contrast of SK-BR-3 cancer cells labeled with immunotargeted nanoshells occurs at an emission wavelength ranging from 590 to 644?nm. Luminescence from labeled normal breast cells and autofluorescence from unlabeled cancer and normal cells remain imperceptible under the same conditions.     

Clinical assessment of attachment patterns and personality disorder in adolescents and adults.

The relevance of attachment theory and research for practice has become increasingly clear. The authors describe a series of studies with 3 aims: (a) to validate measures of attachment for use by clinicians with adolescents and adults, (b) to examine the relation between attachment and personality pathology, and (c) to ascertain whether factor analysis can recover dimensions of attachment reflecting both interpersonal and narrative style. In 3 studies, experienced clinicians provided psychometric data using 1 of 4 attachment questionnaires (2 adolescent and 2 adult samples). Attachment dimensions predicted both personality pathology and developmental experiences in predictable ways. Factor analysis identified 4 dimensions that replicated across adolescent and adult samples on the basis of a combination of interpersonal and narrative indicators: secure, dismissing, preoccupied, and incoherent/disorganized. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

(In)visible men: Emerging research on low-income, unmarried, and minority fathers.

The author aims to help make low-income, unmarried, and minority fathers more visible by reviewing the emerging literature base on this population and addressing important conceptual, methodological, and policy issues. Recent evidence is reviewed concerning patterns of fatherhood, factors that support or prohibit fathers' active involvement with their children, and the impact of paternal involvement on children's development. To move the field forward, advances are needed in methodology (increased use of father reports, multiple methods, and longitudinal studies), measurement (greater diversity and depth, multiple reporters), and theoretical and conceptual definitions (family systems perspectives, new and inclusive definitions of fatherhood). In particular, a multidisciplinary and contextualized perspective is an imperative aid to significantly increase understanding of the lives and impact of low-income, unmarried, and minority fathers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pain drawings in the assessment of nerve root compression: a comparative study with lumbar spine magnetic resonance imaging

STUDY DESIGN: Prospective comparative study of pain drawings with findings on lumbar spine magnetic resonance imaging. OBJECTIVES: To assess the ability of the pain drawing to predict the presence of nerve root compression. SUMMARY OF BACKGROUND DATA: Most research work has concentrated on the ability of the pain drawing to act as a screening method for psychological distress with less work directed at the influence the anatomic abnormality has on the pain drawing. METHODS: One hundred thirty-four consecutive outpatients attending for lumbar magnetic resonance imaging in the investigation of back and leg pain completed pain drawings and psychological testing immediately before the examination. The pain drawing was analyzed by previously reported criteria, and the magnetic resonance imaging was assessed independently for the presence of nerve compression by three radiologists. Multivariate stepwise discriminant analysis was used to identify patients with nerve compression on the basis of their pain drawing. RESULTS: Nerve compression was predicted by numbness in the anterolateral aspect of the foot. There was considerable overlap in the appearances of the pain drawings between patients with and without nerve compression, and the pain drawing correctly classified only 58% of patients with nerve compression. CONCLUSIONS: The pain drawing is not a good predictor of nerve compression on magnetic resonance imaging in a group of patients investigated for back and leg pain. It should be interpreted with caution and in light of the full clinical picture.     

Therapists' experiences treating Asian American women with eating disorders.

How do psychologists treat eating disorders (EDs) and subclinical issues in Asian American women in a culturally competent manner? Disordered eating and body dissatisfaction are so common in women that most therapists work with the issues to some degree, and it is increasingly likely they will see women of color. Asian American women are at significant risk and yet little treatment literature exists. Twelve therapists with experience in ED treatment were interviewed about their work with Asian American women. Grounded theory and consensual qualitative analysis methods were used to analyze the data, resulting in two central domains of conceptualization within the cultural context and treatment approach. Therapists reported that their clients were mostly first- and second-generation Americans who experienced acculturation stress and cultural conflict, particularly with elders. Other results suggested therapists perceived a strong connection between clients' desires to be thin and successful, and clients' efforts to conform to traditional Asian cultural values and fit in with U.S. mainstream culture. Therapists emphasized the cultural contextualization of family dynamics, developmental processes (e.g., individuation), and intergenerational conflicts. They viewed EDs as providing clients with culturally congruent coping strategies to affectively disconnect and to express distress. Treatment themes centered on psychoeducation and the importance of including parents in the treatment of their adult daughters. Helping clients navigate autonomy within the family and cultural context, and challenging clients and parents on the cultural (both Asian and mainstream U.S.) pressures regarding achievement and beauty were particularly important. Implications for therapy are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Evidence suggesting the role of specific genetic factors in cigarette smoking.

Twin studies suggest that propensity to smoke and ability to quit smoking are influenced by genetic factors. As a means of investigating the risk of smoking associated with genetic polymorphisms in the dopamine transporter (SLC6A3) and the D? dopamine receptor (DRD2) genes, a case-control study of 289 smokers and 233 nonsmoking controls and a case series analysis of smokers were conducted. A significant effect for SLC6A3 and a significant gene-gene interaction were found in a logistic regression model, indicating that individuals with SLC6A3-9 genotypes were significantly less likely to be smokers, especially if they also had DRD2-A2 genotypes. Smokers with SLC6A3-9 genotypes were also significantly less likely to have started smoking before 16 years of age and had prior smoking histories indicating a longer period of prior smoking cessation. This study provides preliminary evidence that the SLC6A3 gene may influence smoking initiation and nicotine dependence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Children's understanding of the knowledge prerequisites of drawing and pretending.

Many young children will claim that someone is pretending to be something even when the person does not know what that something is. To examine whether children's failure to take knowledge prerequisites into account is part of a more fundamental problem in recognizing how mental representations constrain external ones, the authors asked children whether an artist who did not know what something was, yet whose drawing bore resemblance to it, was drawing it. The same questions were asked regarding pretending. Children performed similarly on pretending and drawing questions, and performance on both questions improved when the protagonists' point of view was emphasized. Performance for drawing improved somewhat when alternative goals were stated. Further, cross-sectional data indicated that understanding how knowledge relates to producing external representations increases gradually from age 4 to age 8, suggesting that experiential factors may be crucial to this understanding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)