Hexatic-Herringbone Coupling at the Hexatic Transition in Smectic Liquid Crystals: 4-ϵ\epsilon Renormalization Group Calculations Revisited

Simple symmetry considerations would suggest that the transition from the smectic-A phase to the long-range bond orientationally ordered hexatic smectic-B phase should belong to the XY universality class. However, a number of experimental studies have constantly reported over the past twenty years "novel" critical behavior with non-XY critical exponents for this transition. Bruinsma and Aeppli argued in Physical Review Letters {\bf 48}, 1625 (1982), using a $4-\epsilon$ renormalization-group calculation, that short-range molecular herringbone correlations coupled to the hexatic ordering drive this transition first order via thermal fluctuations, and that the critical behavior observed in real systems is controlled by a `nearby' tricritical point. We have revisited the model of Bruinsma and Aeppli and present here the results of our study. We have found two nontrivial strongly-coupled herringbone-hexatic fixed points apparently missed by those authors. Yet, those two new nontrivial fixed-points are unstable, and we obtain the same final conclusion as the one reached by Bruinsma and Aeppli, namely that of a fluctuation-driven first order transition. We also discuss the effect of local two-fold distortion of the bond order as a possible missing order parameter in the Hamiltonian.Comment: 1 B/W eps figure included. Submitted to Physical Review E. Contact: [email protected]

An open ocean record of the Toarcian oceanic anoxic event

Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic matter-rich sediments (black shales) and significant perturbations in the global carbon cycle. These perturbations are globally recorded in sediments as carbon isotope excursions irrespective of lithology and depositional environment. During the early Toarcian, black shales were deposited on the epi- and pericontinental shelves of Pangaea, and these sedimentary rocks are associated with a pronounced (ca. 7 ‰) negative (organic) carbon isotope excursion (CIE) which is thought to be the result of a major perturbation in the global carbon cycle. For this reason, the lower Toarcian is thought to represent an oceanic anoxic event (the T-OAE). If the T-OAE was indeed a global event, an isotopic expression of this event should be found beyond the epi- and pericontinental Pangaean localities. To address this issue, the carbon isotope composition of organic matter (δ13Corg of lower Toarcian organic matter-rich cherts from Japan, deposited in the open Panthalassa Ocean, was analysed. The results show the presence of a major (>6 ‰) negative excursion in δ13Corg that, based on radiolarian biostratigraphy, is a correlative of the lower Toarcian negative CIE known from Pangaean epi- and pericontinental strata. A smaller negative excursion in δ13Corg (ca. 2 ‰) is recognized lower in the studied succession. This excursion may, within the current biostratigraphic resolution, represent the excursion recorded in European epicontinental successions close to the Pliensbachian/Toarcian boundary. These results from the open ocean realm suggest, in conjunction with other previously published datasets, that these Early Jurassic carbon cycle perturbations affected the active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric)

Job searching with a history of drugs and crime

This article explores the experiences and aspirations of offenders with histories of substance misuse in job searching. The analysis is based upon qualitative data from a localised study of 27 men and two women who were undertaking community-based court orders in Scotland. Their perspectives on job searching, job-readiness and aspirations for sustained employment including the role of self-employment are presented. The article concludes that with adequate support, greater tolerance and flexibility by employers and job searchers could contribute to reducing the vicious cycle of suspicion and dishonesty. Policy action needs to be sustained and possibly augmented to include enterprise training

The size, structure and efficiency of Mongolian flocks and herds on degraded grasslands

Since 1990, the number of livestock in Mongolia has more than doubled. In large areas of Mongolia, grassland degradation is now a problem of national concern. A survey was done of 10 herders in two Soums (Altanbulag and Khashaat; heavily and moderately degraded, respectively) to measure the animals (sheep, goats, cattle and horse numbers, sex and weights) and grasslands (species and biomass) every 3 months from April 2017 to December 2018. Rainfall is mostly in summer and mean monthly temperatures vary from –20 to 20°C. Throughout the study, the grassland herbage mass in summer was less than 0.5 t dry matter/ha, below that considered sustainable for the steppe. Herders had 200–1000 sheep equivalents (SE, 50 kg base weight), moved camps 2–4 times each year and stocking rates varied from 0.5–1 SE/ha. Female animals reached their mature weights by 4 years of age (sheep 50 kg, goats 40 kg, cattle 350 kg, horses 300 kg). Animals only grew over summer, but a significant part of that was compensatory gain in animals >1 year old. Over winter, sheep and goats lost 21–29% of their liveweight, cattle and horses 15–30%. The weaning rate was 43–48% across species. The male:female ratio (>2 years old) was sheep 63%, goats 72%, cattle 27% and horses 106%. All animals are managed in common mobs with no particular control of breeding. Areas where the efficiency of livestock production and grassland productivity could be improved are discussed

Chemical dissociation of human awareness: focus on non-competitive NMDA receptor antagonists

Since the mid-1950s the pharmaceutical industry has developed a number of chemicals, including phencyclidine, ketamine and related arylcyclohexylamines (PCE and TCP), dizocilpine (MK-801), N-allylnormetazocine [ NANM, (±)SKF-10,047], etoxadrol, dioxadrol and its enantiomers dexoxadrol and levoxadrol, which produce a constellation of unusual behavioral effects in animals and man. The compounds best studied in humans are phencyclidine and ketamine. They produce a remarkable dose-dependent dissociation of awareness. All of these substances are now known to be non-competitive antagonists of NMDA receptors of glutamic acid. They act in the NMDA receptor ion channel. One can conclude, on the basis of the effects observed with these agents, that glutamic acid and related excitatory amino acids are extremely important in the maintenance of human awareness.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68872/2/10.1177_026988119200600312.pd

Chinese degraded grasslands – pathways for sustainability

The 400 m ha of grazing lands in China, mainly across the north and west of the country, have similar problems to those throughout the steppe of Mongolia, Central Asia and neighbouring countries. The grasslands are in drier regions (50–500 mm) across mainly Inner Mongolia, Xinjiang, Tibet, Qinghai, Gansu and Sichuan, often at higher altitudes on the Tibetan, Mongolian and Loess Plateaus, and have for millennia supported the livelihoods of millions of herders. By 2002, surveys were classifying 90% of the grasslands as degraded. Less than 10% were considered desertified to the extent that replanting was the only option to restore some plant cover. The majority of the grasslands were considered capable of being rehabilitated to some degree through changing management practices. In the 1980s the first Grassland Laws were promulgated, initiating a series of programs aimed at rehabilitating the grasslands. These programs included the establishment of individual ‘user rights’ to herders to use a defined area of grassland and the imposition of grazing bans, often for five years, to rehabilitate degraded areas. These were often applied at a regional level. At the same time, herders were encouraged to have more livestock as that was seen as a pathway to lift them from poverty. The sheep equivalent of grazing animals for the whole of China, has increased 4-fold since 1949, often by greater amounts in some regions. But there was very limited work done on how best to manage grazing livestock in ways that could aid grassland rehabilitation. In the early 2000s a collaborative program was started between several Australian and Chinese Institutes, to investigate better ways of rehabilitating the grasslands and to improve herder incomes from livestock. This work involved the development of four models that could use the limited data available, to help guide a series of research programs. These models indicated that halving stocking rates could maintain or increase herder net incomes. Farm demonstrations showed this result applied in practice and grasslands did improve. A series of grazing experiments found that halving the current stocking rates was needed to enable the survival of the better plant species within the grassland. A model that estimated the net value of each animal indicated that often half the animals were generating marginal or negative incomes, and could be culled without affecting the household income, again substantiated in farm demonstrations. In this paper, the causes of degradation, which can be traced back to the progressive changes that have occurred in China since 1949, are discussed together with the practice changes that have come from a large collaborative research program between Australia and China. Efficient markets and land tenure reform are needed to help create the incentives for herders to change in sustainable ways

Effects of watershed land use on nitrogen concentrations and δ15 Nitrogen in groundwater

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 77 (2006): 199-215, doi:10.1007/s10533-005-1036-2.Eutrophication is a major agent of change affecting freshwater, estuarine, and marine systems. It is largely driven by transportation of nitrogen from natural and anthropogenic sources. Research is needed to quantify this nitrogen delivery and to link the delivery to specific land-derived sources. In this study we measured nitrogen concentrations and δ15N values in seepage water entering three freshwater ponds and six estuaries on Cape Cod, Massachusetts and assessed how they varied with different types of land use. Nitrate concentrations and δ15N values in groundwater reflected land use in developed and pristine watersheds. In particular, watersheds with larger populations delivered larger nitrate loads with higher δ15N values to receiving waters. The enriched δ15N values confirmed nitrogen loading model results identifying wastewater contributions from septic tanks as the major N source. Furthermore, it was apparent that N coastal sources had a relatively larger impact on the N loads and isotopic signatures than did inland N sources further upstream in the watersheds. This finding suggests that management priorities could focus on coastal sources as a first course of action. This would require management constraints on a much smaller population.This work was supported by funds from the Woods Hole Oceanographic Institution Sea Grant Program, from the Cooperative Institute for Coastal and Estuarine Environmental Technology, from Massachusetts Department of Environmental Protection to Applied Science Associates, Narragansett, RI, as well as from Palmer/McLeod and NOAA National Estuarine Research Reserve Fellowships to Kevin Kroeger. This work is the result of research sponsored by NOAA National Sea Grant College Program Office, Department of Commerce, under Grant No. NA86RG0075, Woods Hole Oceanographic Institution Sea Grant Project No. R/M-40

Re-creation of site-specific multi-directional waves with non-collinear current

Site-specific wave data can be used to improve the realism of tank test conditions and resulting outputs. If this data is recorded in the presence of a current, then the combined conditions must be re-created to ensure wave power, wavelength and steepness are correctly represented in a tank. In this paper we explore the impacts of currents on the wave field and demonstrate a simple, effective methodology for re-creating combined wave-current scenarios. Regular waves, a parametric unidirectional spectrum, and a complex site-specific directional sea state were re-created with current velocities representing 0.25, 0.5, and 1.0 m/s full scale. Waves were generated at a number of angles relative to the current, providing observations of both collinear and non-collinear wave-current interactions. Wave amplitudes transformed by the current were measured and corrected linearly, ensuring desired frequency and wavenumber spectra in the presence of current were obtained. This empirical method proved effective after a single iteration. Frequency spectra were within 3% of desired and wave heights normally within 1%. The generation-measurement-correction procedure presented enables effective re-creation of complex wave-current scenarios. This capability will increase the realism of tank testing, and help de-risk devices prior to deployment at sea

Espalhamento e secagem de filme de amido-glicerol-fibra preparado por "tape-casting"

O objetivo deste trabalho foi avaliar processos de espalhamento e secagem de filme de amido-glicerol-fibras de celulose, preparado por "tape-casting". O espalhamento da suspensão foi avaliado a 50, 150 e 250 cm min-1, seguido de secagem em estufa com circulação forçada de ar, a 40 ou 70ºC; avaliou-se também o espalhamento da suspensão a 150 cm min-1, seguido da secagem do filme sobre suporte de "tape-casting" a 22ºC e 60% de umidade relativa, com velocidades do ar de 4, 6 e 8 m s-1 no túnel de secagem. Ensaios reológicos mostraram que o espalhamento das suspensões a temperaturas inferiores a 50ºC apresentou módulo de elasticidade superior ao módulo viscoso, em todo o espectro de frequências de oscilação. As microscopias mostraram filmes secos a 40 e 70ºC sem defeitos de formação, e cujas propriedades mecânicas não diferiam. A velocidade de espalhamento e a do ar não modificam o tempo de secagem nem as propriedades dos filmes. O tempo de secagem pode ser reduzido para aproximadamente duas horas, o que é importante para a produção dos filmes em larga escala