Evidence of striped electronic phases in a structurally modulated superlattice.

The electronic properties of crystals can be manipulated by superimposing spatially periodic electric, magnetic or structural modulations. Long-wavelength modulations incommensurate with the atomic lattice are particularly interesting1, exemplified by recent advances in two-dimensional (2D) moiré materials2,3. Bulk van der Waals (vdW) superlattices4-8 hosting 2D interfaces between minimally disordered layers represent scalable bulk analogues of artificial vdW heterostructures and present a complementary venue to explore incommensurately modulated 2D states. Here we report the bulk vdW superlattice SrTa2S5 realizing an incommensurate one-dimensional (1D) structural modulation of 2D transition metal dichalcogenide (TMD) H-TaS2 layers. High-quality electronic transport in the H-TaS2 layers, evidenced by quantum oscillations, is made anisotropic by the modulation and exhibits commensurability oscillations paralleling lithographically modulated 2D systems9-11. We also find unconventional, clean-limit superconductivity in SrTa2S5 with a pronounced suppression of interlayer relative to intralayer coherence. The in-plane magnetic field dependence of interlayer critical current, together with electron diffraction from the structural modulation, suggests superconductivity12-14 in SrTa2S5 is spatially modulated and mismatched between adjacent TMD layers. With phenomenology suggestive of pair-density wave superconductivity15-17, SrTa2S5 may present a pathway for microscopic evaluation of this unconventional order18-21. More broadly, SrTa2S5 establishes bulk vdW superlattices as versatile platforms to address long-standing predictions surrounding modulated electronic phases in the form of nanoscale vdW devices12,13 to macroscopic crystals22,23.

Clean 2D superconductivity in a bulk van der Waals superlattice.

Advances in low-dimensional superconductivity are often realized through improvements in material quality. Apart from a small group of organic materials, there is a near absence of clean-limit two-dimensional (2D) superconductors, which presents an impediment to the pursuit of numerous long-standing predictions for exotic superconductivity with fragile pairing symmetries. We developed a bulk superlattice consisting of the transition metal dichalcogenide (TMD) superconductor 2H-niobium disulfide (2H-NbS2) and a commensurate block layer that yields enhanced two-dimensionality, high electronic quality, and clean-limit inorganic 2D superconductivity. The structure of this material may naturally be extended to generate a distinct family of 2D superconductors, topological insulators, and excitonic systems based on TMDs with improved material properties.

Precision cutting and patterning of graphene with helium ions.

We report nanoscale patterning of graphene using a helium ion microscope configured for lithography. Helium ion lithography is a direct-write lithography process, comparable to conventional focused ion beam patterning, with no resist or other material contacting the sample surface. In the present application, graphene samples on Si/SiO2 substrates are cut using helium ions, with computer controlled alignment, patterning, and exposure. Once suitable beam doses are determined, sharp edge profiles and clean etching are obtained, with little evident damage or doping to the sample. This technique provides fast lithography compatible with graphene, with approximately 15 nm feature sizes.

New approaches to nanoparticle sample fabrication for atom probe tomography.

Due to their unique properties, nano-sized materials such as nanoparticles and nanowires are receiving considerable attention. However, little data is available about their chemical makeup at the atomic scale, especially in three dimensions (3D). Atom probe tomography is able to answer many important questions about these materials if the challenge of producing a suitable sample can be overcome. In order to achieve this, the nanomaterial needs to be positioned within the end of a tip and fixed there so the sample possesses sufficient structural integrity for analysis. Here we provide a detailed description of various techniques that have been used to position nanoparticles on substrates for atom probe analysis. In some of the approaches, this is combined with deposition techniques to incorporate the particles into a solid matrix, and focused ion beam processing is then used to fabricate atom probe samples from this composite. Using these approaches, data has been achieved from 10-20 nm core-shell nanoparticles that were extracted directly from suspension (i.e. with no chemical modification) with a resolution of better than ± 1 nm.

Omega-conotoxin MVIIC reversibly inhibits a human N-type calcium channel and calcium influx into chick synaptosomes.

We have investigated the effects of omega-CmTX MVIIC on the recombinant alpha 1B-mediated calcium channel expressed in HEK 293 cells and on the predominantly N-type calcium channel in chick synaptosomes. omega-CmTX MVIIC potently and reversibly inhibited the calcium current through alpha 1B-mediated calcium channels and inhibited KCl-evoked increases in [Ca2+]i in chick synaptosomes in a concentration-dependent manner.

Normative influence on condom use in the personal networks of female cocaine smokers.

Attitudes-norms research (the theories of planned behavior and reasoned action) has been successful in accounting for many types of behavior change. One of the strengths of this approach has been to combine individual beliefs and normative influences in the explanation of behavior change. However, the conceptualization of normative influence in these theories makes very strong assumptions about self-awareness in the selection of normative referents. These assumptions are particularly problematic when applied to female cocaine smokers, who report frequent sex while under duress or while cognitively impaired. In this study the original conceptualization of normative influence and two alternatives (assuming emotion-based and interaction-based selection of normative referents) are operationalized to evaluate stage of change for condom use among women who are heavy crack cocaine users with multiple sex partners. Results show that stage of change for use of condoms with nonmain partners is best accounted for by interaction-based selection of normative referents.

Barriers to social services for HIV-infected urban migrators.

Anecdotal accounts suggest that residency requirements often lead to denial of services at a time when HIV positive migrators are most in need of these services. However, this suspicion has never been empirically tested. Using needs assessment data collected for Harris County, Texas, this article examines eligibility and knowledge barriers faced by HIV positive recent migrators into Harris County. Results indicated that migration into the county was a significant predictor of failure to receive government-administered basic services such as food services but was not a significant predictor of failure to receive community based organization (CBO)-administered "specialized" services targeted specifically to HIV positive individuals. Results also indicated that migration was associated with knowledge barriers for all types of services.

The trajectory of client progress. A longitudinal pilot study.

Successful nonchemical drug treatment is a transformative experience: client change is the goal of treatment. Two domains in which programs intend to facilitate change are emotional well-being and the therapeutic relationship. Little previous research has addressed the question of what changes clients in drug treatment actually undergo while in treatment. This article presents results from a pilot longitudinal study of clients in two short-term drug treatment programs in Houston, TX. Results showed measurable increases in self-esteem and connection to counselor and decreases in anxiety and depression over the course of treatment for clients who completed treatment. Program graduates and early withdrawals showed distinctly different patterns of progress as measured by emotional and relationship scales.

Mediators of drug treatment outcomes.

Treatment for drug use, like the process by which a person comes to use illicit drugs, may be seen to be at least in part a psychosocial process involving emotional, cognitive, and relationship domains. Treatment programs attempt to improve the psychosocial functioning of clients with the ultimate goal of effecting change in drug-use behaviors. In a longitudinal study of clients in an intensive outpatient treatment program using a cognitive behavioral model to treat crack cocaine use, it was found that length of treatment was directly associated with improvement in emotional well-being, cognitive functioning, and relationships. Of the three psychosocial domains, improvement in relationships had the strongest effect on self-reported decreases in cocaine usage, verified by urinalysis. Improvement in cognitive functioning had a small impact on cocaine use, whereas improvement in emotional well-being had almost no independent effect in this cognitive behavioral treatment program.

An analysis of unmet need for HIV services: The Houston Study.

HIV/AIDS is indicative of general institutional neglect that disproportionately affects minorities, poor, and underserved populations. Among women and minorities, HIV infection is associated with preexisting economic distress. Moreover, socioeconomic resources, gender, and race/ethnicity may determine access to medical and nonmedical services that affect disease progression. An analysis of data collected for the Ryan White Care Act needs assessment in Houston, Texas, was performed to assess the effects of socioeconomic and demographic factors on unmet needs for existing medical, social, and counseling services, adjusting for the effects of illness and substance abuse. Results indicated that lower income and Hispanic ethnicity were associated with the unmet need for medical services. Higher income was positively associated and African American ethnicity was negatively associated with the unmet need for social services. Also, higher income and private insurance were negatively associated with counseling services. The authors suggest that these latter findings may result from program eligibility requirements and respondents' hierarchy of needs, respectively.

A pilot study of client progress in short-term drug abuse treatment.

This paper is a pilot study of client progress in two short-term (23-day) drug abuse treatment programs. Client progress is defined as those changes in cognitive functioning, emotional well-being, and social support resources that are th proximate goals of drug abuse treatment. In this study, client progress was measured by changes in cognitive functioning, emotional well-being, and social support domains over the course of treatment. This pilot study showed that client progress can be detected in short-term treatment and can be related to indicators of the quantity and quality of treatment. In general, results showed that both relationships and emotional well-being changed over the course of treatment. Cognitive functioning variables did not generally change over time, nor were they related to indicators of treatment quality. Evidence in this pilot study suggests that more attention needs to be given to the relational and emotional aspects of the drug abuse treatment process.

Epitaxial Catalyst-Free Growth of InN Nanorods on c-Plane Sapphire.

We report observation of catalyst-free hydride vapor phase epitaxy growth of InN nanorods. Characterization of the nanorods with transmission electron microscopy, and X-ray diffraction show that the nanorods are stoichiometric 2H-InN single crystals growing in the [0001] orientation. The InN rods are uniform, showing very little variation in both diameter and length. Surprisingly, the rods show clear epitaxial relations with the c-plane sapphire substrate, despite about 29% of lattice mismatch. Comparing catalyst-free with Ni-catalyzed growth, the only difference observed is in the density of nucleation sites, suggesting that Ni does not work like the typical vapor-liquid-solid catalyst, but rather functions as a nucleation promoter by catalyzing the decomposition of ammonia. No conclusive photoluminescence was observed from single nanorods, while integrating over a large area showed weak wide emissions centered at 0.78 and at 1.9 eV.

Connection in therapeutic communities.

The success of therapeutic community treatment is based on trust. Trust underlies the willingness of residents to endorse and profit from confrontations of their denial. Lack of trust can be seen to underlie the high dropout rate of many therapeutic communities. Social learning theory, which is usually cited as a theoretical foundation for therapeutic communities, does not explain the role of trust. Instead, we need an explanation of trust based on a logic of emotion rather than the cognitive, calculating logic of social learning. This logic can be found in the process of connection. Trust, in the theoretical orientation of connection, grows out of the resident's perception that community members care. This caring is revealed in their empathy for the resident, their willingness to take responsibility for helping the resident, and their nurturance. The resident's level of trust determines his (her) willingness to be open and responsive to the community. The implications of the connection process for the development of trust between new residents and old residents and between residents and staff are developed.

Implications of managed care in a publicly funded health care delivery system.

In the light of federal cuts in the Medicaid budget, the Medicaid-funded health delivery system is under severe cost pressures, especially in publicly funded institutions. In the private health insurance industry, managed care innovations have successfully restrained costs. For publicly funded institutions to remain viable, managed care contracts must be implemented for the Medicaid system as well. Managed care holds promise for reducing costs as well as reducing many of the current barriers to quality health care for the indigent.

Modeling HIV risk.

OBJECTIVE: To provide HIV risk estimates for specific local population subgroups using an HIV risk index combining HIV risk behaviors, prevalence rates, and transmission probabilities. METHODS: A sample of 270 individuals was studied. Respondents described sexual and injection risk behaviors and partners in the previous 30 days. An HIV risk index was computed for each individual, combining reported sexual and injecting risk behaviors, HIV prevalence estimates for partners and HIV transmission probabilities for each of the risk behaviors. Partner HIV prevalence rates were estimated from a national sample, and HIV transmission probabilities were obtained from previously published studies. RESULTS: Projected risk estimates were found to differ a great deal within major demographic categories. Highest 10-year risk was found among African-American male gay injectors (72%) and the lowest among white male heterosexual noninjectors (<.01%). CONCLUSIONS: The method used here for estimating HIV risk can be calculated for specific at-risk population subgroups of any size and composition, including individuals. By understanding which specific subpopulations are at risk, specific interventions and public health campaigns may be better targeted.