Orbital frustration in the S = ½ kagome magnet vesignieite, BaCu3V2O8(OH)2

Here we report crystallographic and magnetic studies on high quality samples of the magnetically frustrated S = ½ kagome antiferromagnet vesignieite, BaCu3V2O8(OD)2. Powder neutron diffraction data collected from samples obtained by a new hydrothermal synthetic route reveal a previously unobserved trigonal P3121 structure, similar to the isoelectronic mineral SrCu3V2O8(OH)2. The refined structure is consistent with orbital frustration of the eg d-orbitals in a sublattice of the Cu2+ kagome network due to a dynamic Jahn–Teller effect, which persists below the magnetic transition at TN = 9 K and makes the material an interesting candidate for exploring concomitant spin and orbital frustration. A combination of crystallographic strain analysis and magnetisation measurements indicate strong magnetostructural coupling which may explain the varied magnetic behaviour between samples of vesignieite in the literature. The revised orbital structure is similar to that found in volborthite, rather than the quantum spin liquid herbertsmithite, and provides a convincing argument for the differing magnetic properties found in these frustrated magnets

A Novel Anthropomorphic Flow Phantom for the Quantitative Evaluation of Prostate DCE-MRI Acquisition Techniques

A novel anthropomorphic flow phantom device has been developed which can be used for quantitatively assessing the ability of MRI scanners to accurately measure signal / concentration time-intensity curves (CTCs) associated with dynamic contrast-enhanced (DCE) MRI. Modelling of the complex pharmacokinetics of contrast agents as they perfuse through the tumour capillary network has shown great promise for cancer diagnosis and therapy monitoring. However, clinical adoption has been hindered by methodological problems, resulting in a lack of consensus regarding the most appropriate acquisition and modelling methodology to use and a consequent wide discrepancy in published data. A heretofore overlooked source of such discrepancy may arise from measurement errors of tumour CTCs deriving from the imaging pulse sequence itself, while the effects on the fidelity of CTC measurement of using rapidly-accelerated sequences such as parallel imaging and compressed sensing remain unknown. The present work aimed to investigate these features by developing a test device in which „ground truth‟ CTCs were generated and presented to the MRI scanner for measurement, thereby allowing for an assessment of the DCE-MRI protocol to accurately measure this curve-shape. The device comprised of a 4-pump flow system wherein CTCs derived from prior patient prostate data were produced in measurement chambers placed within the imaged volume. The ground truth was determined as the mean of repeat measurements using an MRI-independent, custom-built optical imaging system. In DCE-MRI experiments, significant discrepancies between the ground truth and measured CTCs were found for both tumorous and healthy tissue-mimicking curve shapes. Pharmacokinetic modelling revealed errors in measured Ktrans, ve and kep values of up to 42%, 31%, and 50% respectively, following a simple variation of the parallel imaging factor and number of signal averages in the acquisition protocol The device allows for the quantitative assessment and standardisation of DCE-MRI protocols (both existing and emerging)

Outcome Expectations and Environmental Factors Associated with Engineering College-Going: A Case Study

Family, school, and community contexts each link to secondary school enrollment, yet these factors have been comparatively examined only in limited ways. A holistic examination of contextual factors will be particularly important for engineering where college enrollment patterns vary by demographics. To begin explaining patterns of engineering college-going at different high schools across the Commonwealth of Virginia, we answered the following research questions: Within a single school system and from a socializer’s perspective, what outcome expectations and environmental factors influence students’ engineering-related postsecondary educational plans? How are these factors the same and different between high schools within a school district? Using a single-case-study approach and in-depth interviews with socializers (teachers, administrators, and counselors), we examined similarities and differences in outcome expectations and environmental factors at three high schools within a single school district. By integrating the results regarding outcome expectations and environmental factors, three important findings emerged: (1) relationships between outcome expectations and environmental factors vary across schools within the same system, (2) proximity to a postsecondary institution is not just about physical distance, and (3) messaging regarding career pathways matters. Each of these has practical implications but can also set the foundation for future research

Demineralization enables reeling of wild Silkmoth cocoons

Wild Silkmoth cocoons are difficult or impossible to reel under conditions that work well for cocoons of the Mulberry silkmoth, Bombyx mori. Here we report evidence that this is caused by mineral reinforcement of Wild Silkmoth cocoons and that washing these minerals out allows for the reeling of commercial lengths of good quality fibers with implications for the development of the “Wild Silk” industry. We show that in the Lasiocampid silkmoth Gonometa postica, the mineral is whewellite (calcium oxalate monohydrate). Evidence is presented that its selective removal by ethylenediaminetetraacetic acid (EDTA) leaves the gum substantially intact, preventing collapse and entanglement of the network of fibroin brins, enabling wet reeling. Therefore, this method clearly differs from the standard “degumming” and should be referred to as “demineralizing”. Mechanical testing shows that such preparation results in reeled silks with markedly improved breaking load and extension to break by avoiding the damage produced by the rather harsh degumming, carding, or dry reeling methods currently in use, what may be important for the development of the silk industries not only in Asia but also in Africa and South America

Effect of Particle Damping on an Acoustically Excited Curved Vehicle Panel Structure with varied Equipment Assemblies

Particle dampers provide a mechanism for diverting energy away from resonant structural vibrations. This experimental study provides data from trials to determine how effective use of these dampers might be for equipment mounted to a curved orthogrid vehicle panel. Trends for damping are examined for variations in damper fill level, component mass, and excitation energy. A significant response reduction at the component level would suggest that comparatively small, thoughtfully placed, particle dampers might be advantageously used in vehicle design. The results of this test will be compared with baseline acoustic response tests and other follow-on testing involving a range of isolation and damping methods. Instrumentation consisting of accelerometers, microphones, and still photography data will be collected to correlate with the analytical results

Barriers to Entry into the Specialty Red Meat Sector: The Role of Food Safety Regulation

Historically, the rules governing red meat food safety in the U.S. were driven as much by global trade and industry rationalization as by food safety. Contemporary and historical documents, statutes, and regulations; a survey of producer and farmers’ market representatives; and key informant interviews show that these rules, and their implementation, have affected the current development of niche marketing opportunities. Three significant issues arise from this research: a) the elimination of the state meat inspections limits producer access to slaughter; b) the Hazard Analysis and Critical Control Points (HACCP) rule limits producer access to processing; and c) uncertainty at the local level limits producer access to direct markets. We conclude that the accumulated rules affect producers’ quality of life; and they raise several issues about the relationship between sustainability and policy including barrier mitigation, balancing competing qualities, and the effects of the broader policy context

Nanolaminate Mirrors With "Piston" Figure-Control Actuators

Efforts are under way to develop a special class of thin-shell curved mirrors for high-resolution imaging in visible and infrared light in a variety of terrestrial or extraterrestrial applications. These mirrors can have diameters of the order of a meter and include metallic film reflectors on nanolaminate substrates supported by multiple distributed piezoceramic gpiston h-type actuators for micron-level figure control. Whereas conventional glass mirrors of equivalent size and precision have areal mass densities between 50 and 150 kg/sq m, the nanolaminate mirrors, including not only the reflector/ shell portions but also the actuators and the backing structures needed to react the actuation forces, would have areal mass densities that may approach .5 kg/m2. Moreover, whereas fabrication of a conventional glass mirror of equivalent precision takes several years, the reflector/shell portion of a nanolaminate mirror can be fabricated in less than a week, and its actuation system can be fabricated in 1 to 2 months. The engineering of these mirrors involves a fusion of the technological heritage of multisegmented adaptive optics and deformable mirrors with more recent advances in metallic nanolaminates and in mathematical modeling of the deflections of thin, curved shells in response to displacements by multiple, distributed actuators. Because a nanolaminate shell is of the order of 10 times as strong as an otherwise identical shell made of a single, high-strength, non-nanolaminate metal suitable for mirror use, a nanolaminate mirror can be made very thin (typically between 100 and 150 m from the back of the nanolaminate substrate to the front reflecting surface). The thinness and strength of the nanolaminate are what make it possible to use distributed gpiston h-type actuators for surface figure control with minimal local concentrated distortion (called print-through in the art) at the actuation points

Evaluating Attenuation of Vibration Response using Particle Impact Damping for a Range of Equipment Assemblies

Particle dampers provide a mechanism for diverting energy away from resonant structural vibrations. This experimental study provides data from a series of acoustically excited tests to determine the effectiveness of these dampers for equipment mounted to a curved orthogrid panel for a launch vehicle application. Vibration attenuation trends are examined for variations in particle damper fill level, component mass, and excitation energy. A significant response reduction at the component level was achieved, suggesting that comparatively small, strategically placed, particle damper devices might be advantageously used in launch vehicle design. These test results were compared to baseline acoustic response tests without particle damping devices, over a range of isolation and damping parameters. Instrumentation consisting of accelerometers, microphones, and still photography data will be collected to correlate with the analytical results

The professionals' perspective on the causes of project delay in the construction industry

Purpose: Construction project delays are described as a universal problem, which has led to many empirical studies. However, most of these studies were based on the rankings by respondents, and they were rarely verified. Therefore, the purpose of this paper is to explore professional perspectives on the causes of delay in the construction industry, where there has been little explicit consideration on this subject in recent decades. Design/methodology/approach: A critical literature review and a qualitative approach was considered for a deeper and fresh understanding of the causes of delays, rather than recycling the existing themes and the risk of a statistically biased approach. A total of 41 interviews were undertaken which included the London Olympic 2012 project team. Findings: In all, 32 themes were identified, which were categorised into 15 categories of causes of delay in the construction projects. Almost two-thirds of the main themes are not ranked top 15 causes of delay. These include knowledge and competence shortage, poor commercial decisions, unnecessary health and safety restrictions, poor risk management and poor space and logistics management. Research limitations/implications: Due to the qualitative nature of the study, the findings might not be considered as representative. Practical implications: The findings provide consideration of the causes of delay in the construction industry as seen by practitioners, which should provide guidance to enhance performance. Originality/value: The study contributes to the better understanding of the causes of delays by using qualitative research strategy which is limited in the construction management literature. This study is an empirical investigation into the causes of delay in the twenty-first century and it represents an important edition to the body of knowledge within the subject area