Experimental demonstration of a single-molecule electric motor

For molecules to be used as components in molecular machines, methods that couple individual molecules to external energy sources and that selectively excite motion in a given direction are required. Significant progress has been made in the construction of molecular motors powered by light and by chemical reactions, but electrically driven motors have not yet been built, despite several theoretical proposals for such motors. Here we report that a butyl methyl sulphide molecule adsorbed on a copper surface can be operated as a single-molecule electric motor. Electrons from a scanning tunnelling microscope are used to drive the directional motion of the molecule in a two-terminal setup. Moreover, the temperature and electron flux can be adjusted to allow each rotational event to be monitored at the molecular scale in real time. The direction and rate of the rotation are related to the chiralities of both the molecule and the tip of the microscope (which serves as the electrode), illustrating the importance of the symmetry of the metal contacts in atomic-scale electrical devices.     

Examining the relative effectiveness of different message framing strategies for child passenger safety: Recommendations for increased comprehension and compliance

Background

Age-appropriate child restraints and rear seating dramatically reduce injury in vehicle crashes. Yet parents and caregivers struggle to comply with child passenger safety (CPS) recommendations, and frequently make mistakes when choosing and installing restraints. The purpose of this research was to evaluate various methods of framing CPS recommendations, and to examine the relative effectiveness on parents’ knowledge, attitudes, and behavioral intentions related to best practices and proper use of child restraints. Emphasis framing is a persuasion technique that involves placing focus on specific aspects of the content in order to encourage or discourage certain interpretations of the content.

Method

A 5 (flyer group) X 2 (time) randomized experiment was conducted in which 300 parent participants answered a pre-survey, viewed one of four flyer versions or a no-education control version, and completed a post-survey. Surveys measured CPS knowledge, attitudes, perceptions of efficacy and risk, and behavioral intentions. The four flyers compared in this study all communicated the same CPS recommendations, but several versions were tested which each employed a different emphasis frame: (1) recommendations organized by the natural progression of seat types; (2) recommendations which focused on avoiding premature graduation; (3) recommendations which explained the risk-reduction rationale behind the information given; or (4) recommendations which were organized by age. In a fifth no-education (control) condition, participants viewed marketing materials.

Results

Analyses of covariance and pairwise comparisons indicated the risk-reduction rationale flyer outperformed other flyers for many subscales, and significantly differed from no-education control for the most subscales, including restraint selection, back seat knowledge, rear-facing knowledge and attitudes, total efficacy, overall attitudes, and stated intentions.

Conclusions

This research provides insight for increasing caregiver understanding and compliance with CPS information. Recommendations for the field include communicating the rationale behind the information given, using behavior-based directives in headers, avoiding age-based headers, and incorporating back-seat positioning directives throughout.     

Chemically Controlled Reversible and Irreversible Extraction Barriers Via Stable Interface Modification of Zinc Oxide Electron Collection Layer in Polycarbazole‐based Organic Solar Cells

A spin‐cast method is presented for the formation of phosphonic acid functionalized small molecule layers on solution‐processed ZnO substrates for use as electron collecting interlayers in organic photovoltaics. Phosphonic acid interlayers modify the ZnO work function and the charge carrier injection barrier at its interface, resulting in systematic control of V _OC in inverted bulk heterojunction solar cells. Surface modification is shown to moderate the need for UV light‐soaking of the ZnO contact layers. Lifetime studies (30 days) indicate stable and improved OPV performance over the unmodified ZnO contact, which show significant increases in charge extraction barriers and series resistance. Results suggest that enhanced stability using small molecule modifiers is due to partial passivation of the oxide surface to molecular oxygen adsorption. Surface passivation while maintaining work function control of a selective interlayer can be employed to improve net efficiency and lifetime of organic photovoltaic devices. The modified cathode work function modulates V _OC via static energetic barriers and modulates contact conductivity by creating reversible and irreversible S‐shape current‐voltage characteristics as a result of kinetic barriers to charge transport.     

Ductile tearing predictions with Wellman’s failure model

Predictions for the Sandia National Laboratories fracture challenge (Boyce et al. in Int J Fract 2013) were generated using a transient dynamic finite element code with a multi-linear elastic plastic failure model developed by Wellman (Simple approach to modeling ductile failure. Sandia National Laboratories, Albuquerque 2012). This model is a conventional, rate independent, von Mises plasticity model for metals with user-prescribed hardening as a function of equivalent plastic strain. In addition to conventional plasticity, this model has empirical criteria for crack initiation and growth. Ductile tearing predictions generated with this model were found to be in good agreement with experimental measurements and observations.     

Adaptation reveals multiple levels of representation in auditory stream segregation.

When presented with alternating low and high tones, listeners are more likely to perceive 2 separate streams of tones (“streaming”) than a single coherent stream when the frequency separation (Δ?) between tones is greater and the number of tone presentations is greater (“buildup”). However, the same large-Δ? sequence reduces streaming for subsequent patterns presented after a gap of up to several seconds. Buildup occurs at a level of neural representation with sharp frequency tuning. The authors used adaptation to demonstrate that the contextual effect of prior Δ? arose from a representation with broad frequency tuning, unlike buildup. Separate adaptation did not occur in a representation of Δ? independent of frequency range, suggesting that any frequency-shift detectors undergoing adaptation are also frequency specific. A separate effect of prior perception was observed, dissociating stimulus-related (i.e., Δ?) and perception-related (i.e., 1 stream vs. 2 streams) adaptation. Viewing a visual analogue to auditory streaming had no effect on subsequent perception of streaming, suggesting adaptation in auditory-specific brain circuits. These results, along with previous findings on buildup, suggest that processing in at least 3 levels of auditory neural representation underlies segregation and formation of auditory streams. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retrospective Study of Metastatic Melanoma and Renal Cell Carcinoma to the Brain with Multivariate Analysis of Prognostic Pre-Treatment Clinical Factors

Patients with brain metastasis from renal cell carcinoma (RCC) or melanoma have historically had very poor prognoses of less than one year. Stereotactic radiosurgery (SRS) can be an effective treatment for patients with these tumors. This study analyzes the effect of pretreatment prognostic factors on overall survival (OS) for RCC and melanoma patients with metastasis to the brain treated with SRS. A total of 122 patients with brain metastases from either RCC or melanoma were grouped by age at brain metastasis diagnosis, whether they received whole brain radiation therapy (WBRT) in addition to SRS, or they underwent surgical resection, Karnofsky Performance Score (KPS), number of brain metastases, and primary tumor. Median survival times for melanoma patients and RCC patients were 8.20 ± 3.06 and 12.70 ± 2.63 months, respectively. Patients with >5 metastases had a significantly shorter median survival time (6.60 ± 2.45 months) than the reference group (1 metastasis, 10.70 ± 13.40 months, p = 0.024). Patients with KPS ≤ 60 experienced significantly shorter survival than the reference group (KPS = 90–100), with median survival times of 5.80 ± 2.46 months (p < 0.001) and 45.20 ± 43.52 months, respectively. We found a median overall survival time of 12.7 and 8.2 months for RCC and melanoma, respectively. Our study determined that a higher number of brain metastases (>5) and lower KPS were statistically significant predictors of a lower OS prognosis.     

Fish living near two wastewater treatment plants have unaltered thermal tolerance but show changes in organ and tissue traits

Municipal wastewater treatment plants (WWTPs) are a significant source of anthropogenic pollutants and are a serious environmental stressor in Laurentian Great Lakes ecosystems. In this study, we examined whether three freshwater fish species (bluegill sunfish Lepomis macrochirus, green sunfish Lepomis cyanellus, and round goby Neogobius melanostomus) collected near two wastewater effluent outflows in Lake Ontario showed altered measures of somatic investment and thermal tolerance. Fish of all three species collected near the WWTPs were larger with 50–60% heavier body masses compared to those collected at reference sites. Green sunfish had higher body condition and increased haematocrit at wastewater-contaminated sites, and both round goby and bluegill sunfish had larger livers (controlling for body mass) at wastewater-contaminated sites. Thermal tolerance (critical thermal maximum, CT_max) differed between species (green sunfish > bluegill sunfish > round goby), but was similar in fish collected at wastewater-contaminated sites compared to cleaner reference sites. Wastewater-contaminated sites had poorer water quality, higher nutrient loadings, and higher concentrations of anthropogenic contaminants (measured via polar organic chemical integrative samplers, POCIS) than reference sites. Our results suggest that fish in the wild may have some capacity to cope with WWTP effluent and avoid any potential impairments in thermal tolerance. Our findings also suggest that treated wastewater is changing water quality locally in Great Lakes watersheds, and that many fish species may be able to access extra nutrients provided by such effluent outflows. However, if outflow areas become preferred foraging areas this will inadvertently increase exposure to anthropogenic stressors and pollutants.     

Three‐dimensional multiscale finite element models for in‐service performance assessment of bridges

Accurate representation of the structural performance of civil engineering structures, specifically complex bridge structures, may be achieved through an efficient multiscale finite element (FE) model. Multiscale FE modeling couples multiple dimensions of elements in a single model. In this study, the selected existing multipoint constraint equations applied in planar coupling conditions are modified and refined for out‐of‐plane coupling conditions in a single three‐dimensional FE model. Also, the optimum location for the interface points of different elements is determined to improve the model's accuracy and efficiency. The present case study, the Memorial Bridge in Portsmouth, NH, is a vertical lift bridge, which includes novel gusset‐less connections. These connections have complex geometries and therefore require finer dimension elements to represent the structural behavior, while the remainder of the structure is modeled with coarser dimension elements. To achieve an accurate and efficient multiscale model of the Memorial Bridge, multiple global FE models are developed and the predicted structural responses are verified with respect to the field‐collected structural responses of the bridge.     

Light‐Triggered Genome Editing: Cre Recombinase Mediated Gene Editing with Near‐Infrared Light

A light‐activated genome editing platform based on the release of enzymes from a plasmonic nanoparticle carrier when exposed to biocompatible near‐infrared light pulses is described. The platform relies on the robust affinity of polyhistidine tags to nitrilotriacetic acid in the presence of copper which is attached to double‐stranded nucleic acids self‐assembled on the gold nanoparticle surface. A protein fusion of the Cre recombinase containing a TAT internalization peptide sequence to achieve endosomal localization is also employed. High‐resolution gene knock‐in of a red fluorescent reporter is observed using a commercial two‐photon microscope. High‐throughput irradiation is described to generate useful quantities of edited cells.