1,836 research outputs found
The prediction of permanent deformation in flexible pavements
At the present time (1978) new roads in the United Kingdom are designed empirically. However, over approximately the last twenty years pavement technologists throughout the world have been advocating fundamentally based procedures. Such procedures, when applied to flexible pavements, require a detailed knowledge of the two main modes of failure, fatigue of the bituminous bound layers and excessive permanent deformation of the pavement as a whole.
The research described herein was aimed at improving knowledge of the permanent deformation behaviour of flexible pavements, and at developing a technique for predicting this deformation which could be incorporated in a fundamental design procedure. Three laboratory experimental pavements were trafficked with a rolling wheel facility under conditions of constant temperature, load and speed, and the resulting deformations were monitored. These deformations were compared with predictions using models developed from the results of repeated load characterisation tests on the pavement materials and utilising a digital computer.
A review of previous work is presented ill two parts, the first considering the resilient and permanent deformation response of pavement materials, the second considering proposals for the prediction of permanent deformation in pavements.
The development of the wheel loading facility, and the construction, instrumentation and measurements from the pavements are described briefly. More attention is given to the theoretical approach, materials characterisation testing and the prediction of resilient and permanent deformation response of the pavements.
The prediction techniques and their accuracy are assessed, the problems involved in the development of such procedures are discussed, and the conclusions which can be drawn from the work are presented. A number of suggestions regarding further work in this field are made.
Finally, an Appendix considers an alternative to the method of modelling permanent deformation presented in the main part of the text
The history of introduction of the African baobab (Adansonia digitata, Malvaceae: Bombacoideae) in the Indian subcontinent
To investigate the pathways of introduction of the African baobab, Adansonia digitata, to the Indian subcontinent, we examined 10 microsatellite loci in individuals from Africa, India, the Mascarenes and Malaysia, and matched this with historical evidence of human interactions between source and destination regions. Genetic analysis showed broad congruence of African clusters with biogeographic regions except along the Zambezi (Mozambique) and Kilwa (Tanzania), where populations included a mixture of individuals assigned to at least two different clusters. Individuals from West Africa, the Mascarenes, southeast India and Malaysia shared a cluster. Baobabs from western and central India clustered separately from Africa. Genetic diversity was lower in populations from the Indian subcontinent than in African populations, but the former contained private alleles. Phylogenetic analysis showed Indian populations were closest to those from the Mombasa-Dar es Salaam coast. The genetic results provide evidence of multiple introductions of African baobabs to the Indian subcontinent over a longer time period than previously assumed. Individuals belonging to different genetic clusters in Zambezi and Kilwa may reflect the history of trafficking captives from inland areas to supply the slave trade between the fifteenth and nineteenth centuries. Baobabs in the Mascarenes, southeast India and Malaysia indicate introduction from West Africa through eighteenth and nineteenth century European colonial networks
Meso-scale transboundary units for the management of coral reefs in the South China Sea area
Local communities and local government units are recognized as the primary stakeholders and participants in the management of coral reef resources and the primary beneficiaries of small-scale fishing activities in the nearshore areas of the coastal zone. The issues relating to the management of the coastal zone are multi-faceted and some issues are largely intertwined with national policy and development goals. Thus, national governments have jurisdiction over these nearshore coastal resources to harmonize policies, monitor resource use and provide incentives for sustainable use. However, the natural boundaries of these reef resources, the processes that support reef ecosystems, and the local or national affiliation of the people who benefit from them may transcend the boundaries of the local and national management units. Therefore, efforts to arrest the decline in fish catch and loss of biodiversity for reefs require management interventions and assessment activities to be carried out at varying scales. In Southeast Asia, some aspects of reef and reef resources management — particularly in deciding the allocation of catch among competing fisheries, development of sustainable harvest strategies, use of broodstock for restocking or stock enhancement programs, protection of nursery and spawning areas, designation of systems of marine protected areas, and the identification of representative, adequate and comprehensive areas for biodiversity conservation in the region — may require the definition of larger management units. At the regional level, multi-country initiatives will need to define units for the transboundary management of resources. The use of large marine ecosystems (LMEs) to identify and manage fisheries resources may be a starting point; however, given the relatively sedentary nature of coral reef-dwelling and reef-associated organisms compared with other pelagic and demersal species, meso-scale transboundary units within the LMEs have to be defined. This paper provides suggestions for transboundary management units for coral reef and reef-associated resources in Southeast Asia based on information from genetic structures of model organisms in the region. In addition, specific reef areas are identified, which may be important beyond their national boundaries, as potential sources of recruits.Coral reefs, Resource management, Large marine ecosystems, Population genetics, Reef fisheries, Fishery management, South China Sea,
The prediction of permanent deformation in flexible pavements
At the present time (1978) new roads in the United Kingdom are designed empirically. However, over approximately the last twenty years pavement technologists throughout the world have been advocating fundamentally based procedures. Such procedures, when applied to flexible pavements, require a detailed knowledge of the two main modes of failure, fatigue of the bituminous bound layers and excessive permanent deformation of the pavement as a whole.
The research described herein was aimed at improving knowledge of the permanent deformation behaviour of flexible pavements, and at developing a technique for predicting this deformation which could be incorporated in a fundamental design procedure. Three laboratory experimental pavements were trafficked with a rolling wheel facility under conditions of constant temperature, load and speed, and the resulting deformations were monitored. These deformations were compared with predictions using models developed from the results of repeated load characterisation tests on the pavement materials and utilising a digital computer.
A review of previous work is presented ill two parts, the first considering the resilient and permanent deformation response of pavement materials, the second considering proposals for the prediction of permanent deformation in pavements.
The development of the wheel loading facility, and the construction, instrumentation and measurements from the pavements are described briefly. More attention is given to the theoretical approach, materials characterisation testing and the prediction of resilient and permanent deformation response of the pavements.
The prediction techniques and their accuracy are assessed, the problems involved in the development of such procedures are discussed, and the conclusions which can be drawn from the work are presented. A number of suggestions regarding further work in this field are made.
Finally, an Appendix considers an alternative to the method of modelling permanent deformation presented in the main part of the text
Development and Validation of a Military Training Mental Toughness Inventory
Three studies were conducted in order to develop and validate a mental toughness instrument for use in military training environments. Study 1 (n = 435) focused on item generation and testing the structural integrity of the Military Training Mental Toughness Inventory (MTMTI). The measure assessed ability to maintain optimal performance under pressure from a range of different stressors experienced by recruits during infantry basic training. Study 2 (n = 104) examined the concurrent validity, predictive validity, and test-retest reliability of the measure. Study 3 (n = 106) confirmed the predictive validity of the measure with a sample of more specialized infantry recruits. Overall, the military training mental toughness inventory demonstrated sound psychometric properties and structural validity. Furthermore, it was found to possess good test-retest reliability, concurrent validity, and predicted performance in two different training contexts with two separate samples
Premature mortality in refractory partial epilepsy: does surgical treatment make a difference?
Background: Epilepsy carries an increased risk of premature death. For some people with intractable focal epilepsy, surgery offers hope for a seizure-free life. The authors aimed to see whether epilepsy surgery influenced mortality in people with intractable epilepsy. Methods: The authors audited survival status in two cohorts (those who had surgery and those who had presurgical assessment but did not have surgery). Results: There were 40 known deaths in the non-surgical group (3365 person years of follow-up) and 19 in the surgical group (3905 person-years of follow-up). Non-operated patients were 2.4 times (95% CI 1.4 to 4.2) as likely to die as those who had surgery. They were 4.5 times (95% CI 1.9 to 10.9) as likely to die a probable epilepsy-related death. In the surgical group, those with ongoing seizures 1 year after surgery were 4.0 (95% CI 1.2 to 13.7) times as likely to die as those who were seizure-free or who had only simple partial seizures. Time-dependent Cox analysis showed that the yearly outcome group did not significantly affect mortality (HR 1.3, 95% CI 0.9 to 1.8). Conclusion: Successful epilepsy surgery was associated with a reduced risk of premature mortality, compared with those with refractory focal epilepsy who did not have surgical treatment. To some extent, the reduced mortality is likely to be conferred by inducing freedom from seizures. It is not certain whether better survival is attributable only to surgery, as treatment decisions were not randomised, and there may be inherent differences between the groups.<br/
Genome-wide and Mendelian randomisation studies of liver MRI yield insights into the pathogenesis of steatohepatitis
Background
A non-invasive method to grade the severity of steatohepatitis and liver fibrosis is magnetic resonance imaging (MRI) based corrected T1 (cT1). We aimed to identify genetic variants influencing liver cT1 and use genetics to understand mechanisms underlying liver fibroinflammatory disease and its link with other metabolic traits and diseases.
Methods
First, we performed a genome-wide association study (GWAS) in 14,440 Europeans in UK Biobank with liver cT1 measures. Second, we explored the effects of the cT1 variants on liver blood tests, and a range of metabolic traits and diseases. Third, we used Mendelian randomisation to test the causal effects of 24 predominantly metabolic traits on liver cT1 measures.
Results
We identified six independent genetic variants associated with liver cT1 that reached GWAS significance threshold (p<5x10-8). Four of the variants (rs75935921 in SLC30A10, rs13107325 in SLC39A8, rs58542926 in TM6SF2, rs738409 in PNPLA3) were also associated with elevated transaminases and had variable effects on liver fat and other metabolic traits. Insulin resistance, type 2 diabetes, non-alcoholic fatty liver and BMI were causally associated with elevated cT1 whilst favourable adiposity (instrumented by variants associated with higher adiposity but lower risk of cardiometabolic disease and lower liver fat) was found to be protective.
Conclusion
The association between two metal ion transporters and cT1 indicates an important new mechanism in steatohepatitis. Future studies are needed to determine whether interventions targeting the identified transporters might prevent liver disease in at risk individuals
Non-local Realistic Theories and the Scope of the Bell Theorem
According to a widespread view, the Bell theorem establishes the untenability
of so-called 'local realism'. On the basis of this view, recent proposals by
Leggett, Zeilinger and others have been developed according to which it can be
proved that even some non-local realistic theories have to be ruled out. As a
consequence, within this view the Bell theorem allows one to establish that no
reasonable form of realism, be it local or non-local, can be made compatible
with the (experimentally tested) predictions of quantum mechanics. In the
present paper it is argued that the Bell theorem has demonstrably nothing to do
with the 'realism' as defined by these authors and that, as a consequence,
their conclusions about the foundational significance of the Bell theorem are
unjustified.Comment: Forthcoming in Foundations of Physic
Blurred femtoscopy in two-proton decay
We study the effects of final state interactions in two-proton emission by
nuclei. Our approach is based on the solution the time-dependent Schr\"odinger
equation. We show that the final relative energy between the protons is
substantially influenced by the final state interactions. We also show that
alternative correlation functions can be constructed showing large sensitivity
to the spin of the diproton system.Comment: 5 pages. 4 figures, accepted for publication in Phys. Lett.
Observations of 51 Ophiuchi with MIDI at the VLTI
We present interferometric observations of the Be star 51 Ophiuchi. These
observations were obtained during the science demonstration phase of the MIDI
instrument at the Very Large Telescope Interferometer (VLTI). Using MIDI, a
Michelson 2 beam combiner that operates at the N band (8 to 13 microns), we
obtained for the first time observations of 51 Oph in the mid-infrared at
high-angular resolution. It is currently known that this object presents a
circumstellar dust and gas disk that shows a very different composition from
other Herbig Ae disks. The nature of the 51 Oph system is still a mystery to be
solved. Does it have a companion? Is it a protoplanetary system? We still don't
know. Observations with MIDI at the VLTI allowed us to reach high-angular
resolution (20 mas).We have several uv points that allowed us to constrain the
disk model. We have modeled 51 Oph visibilities and were able to constrain the
size and geometry of the 51 Oph circumstellar disk.Comment: 5 pages, 3 figures, 2 tables, to be published in the proceedings of
"The Power of Optical / IR Interferometry: Recent Scientific Results and 2nd
Generation VLTI Instrumentation", Garching, April 4-8, 200
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