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Granular flows occur in a wide range of situations of practical interest to industry, in our natural environment and in our everyday lives. This paper focuses on granular flow in the so-called inertial regime, when the rheology is independent of the very large particle stiffness. Such flows have been modelled with the
-rheology, which postulates that the bulk friction coefficient
(i.e. the ratio of the shear stress to the pressure) and the solids volume fraction
are functions of the inertial number
only. Although the
-rheology has been validated in steady state against both experiments and discrete particle simulations in several different geometries, it has recently been shown that this theory is mathematically ill-posed in time-dependent problems. As a direct result, computations using this rheology may blow up exponentially, with a growth rate that tends to infinity as the discretization length tends to zero, as explicitly demonstrated in this paper for the first time. Such catastrophic instability due to ill-posedness is a common issue when developing new mathematical models and implies that either some important physics is missing or the model has not been properly formulated. In this paper an alternative to the
-rheology that does not suffer from such defects is proposed. In the framework of compressible
-dependent rheology (CIDR), new constitutive laws for the inertial regime are introduced; these match the well-established
relations in the steady-state limit and at the same time are well-posed for all deformations and all packing densities. Time-dependent numerical solutions of the resultant equations are performed to demonstrate that the new inertial CIDR model leads to numerical convergence towards physically realistic solutions that are supported by discrete element method simulations.
Infants with prenatally diagnosed CHD are at high risk for adverse outcomes owing to multiple physiologic and psychosocial factors. Lack of immediate physical postnatal contact because of rapid initiation of medical therapy impairs maternal–infant bonding. On the basis of expected physiology, maternal–infant bonding may be safe for select cardiac diagnoses.
This is a single-centre study to assess safety of maternal–infant bonding in prenatal CHD.
In total, 157 fetuses with prenatally diagnosed CHD were reviewed. On the basis of cardiac diagnosis, 91 fetuses (58%) were prenatally approved for bonding and successfully bonded, 38 fetuses (24%) were prenatally approved but deemed not suitable for bonding at delivery, and 28 (18%) were not prenatally approved to bond. There were no complications attributable to bonding. Those who successfully bonded were larger in weight (3.26 versus 2.6 kg, p<0.001) and at later gestation (39 versus 38 weeks, p<0.001). Those unsuccessful at bonding were more likely to have been delivered via Caesarean section (74 versus 49%, p=0.011) and have additional non-cardiac diagnoses (53 versus 29%, p=0.014). There was no significant difference regarding the need for cardiac intervention before hospital discharge. Infants who bonded had shorter hospital (7 versus 26 days, p=0.02) and ICU lengths of stay (5 versus 23 days, p=0.002) and higher survival (98 versus 76%, p<0.001).
Fetal echocardiography combined with a structured bonding programme can permit mothers and infants with select types of CHD to successfully bond before ICU admission and intervention.
Terrestrial gastropods are problematical for radiocarbon (14C) measurement because they tend to incorporate carbon from ancient sources as a result of their dietary behavior. The 14C ecology of the pulmonate land snail, Helix melanostoma in Cyrenaica, northeastern Libya, was investigated as part of a wider study on the potential of using terrestrial mollusk shell for 14C dating of archaeological deposits. H. melanostoma was selected out of the species available in the region as it has the most predictable 14C ecology and also had a ubiquitous presence within the local archaeology. The ecological observations indicate that H. melanostoma has a very homogenous 14C ecology with consistent variations in F14C across sample sites controlled by availability of dietary vegetation. The majority of dated specimens from non-urbanized sample locations have only a small old-carbon effect, weighted mean of 476±48 14C yr, with between ~1% and 9% of dietary F14C from non-organic carbonate sources. Observed instabilities in the 14C ecology can all be attributed to the results of intense human activity not present before the Roman Period. Therefore, H. melanostoma and species with similar ecological behavior are suitable for 14C dating of archaeological and geological deposits with the use of a suitable offset.
Although repeatedly associated with white matter microstructural alterations, bipolar disorder (BD) has been relatively unexplored using complex network analysis. This method combines structural and diffusion magnetic resonance imaging (MRI) to model the brain as a network and evaluate its topological properties. A group of highly interconnected high-density structures, termed the ‘rich-club’, represents an important network for integration of brain functioning. This study aimed to assess structural and rich-club connectivity properties in BD through graph theory analyses.
We obtained structural and diffusion MRI scans from 42 euthymic patients with BD type I and 43 age- and gender-matched healthy volunteers. Weighted fractional anisotropy connections mapped between cortical and subcortical structures defined the neuroanatomical networks. Next, we examined between-group differences in features of graph properties and sub-networks.
Patients exhibited significantly reduced clustering coefficient and global efficiency, compared with controls globally and regionally in frontal and occipital regions. Additionally, patients displayed weaker sub-network connectivity in distributed regions. Rich-club analysis revealed subtly reduced density in patients, which did not withstand multiple comparison correction. However, hub identification in most participants indicated differentially affected rich-club membership in the BD group, with two hubs absent when compared with controls, namely the superior frontal gyrus and thalamus.
This graph theory analysis presents a thorough investigation of topological features of connectivity in euthymic BD. Abnormalities of global and local measures and network components provide further neuroanatomically specific evidence for distributed dysconnectivity as a trait feature of BD.
In light of the successes of the Navier–Stokes equations in the study of fluid flows, similar continuum treatment of granular materials is a long-standing ambition. This is due to their wide-ranging applications in the pharmaceutical and engineering industries as well as to geophysical phenomena such as avalanches and landslides. Historically this has been attempted through modification of the dissipation terms in the momentum balance equations, effectively introducing pressure and strain-rate dependence into the viscosity. Originally, a popular model for this granular viscosity, the Coulomb rheology, proposed rate-independent plastic behaviour scaled by a constant friction coefficient
. Unfortunately, the resultant equations are always ill-posed. Mathematically ill-posed problems suffer from unbounded growth of short-wavelength perturbations, which necessarily leads to grid-dependent numerical results that do not converge as the spatial resolution is enhanced. This is unrealistic as all physical systems are subject to noise and do not blow up catastrophically. It is therefore vital to seek well-posed equations to make realistic predictions. The recent
-rheology is a major step forward, which allows granular flows in chutes and shear cells to be predicted. This is achieved by introducing a dependence on the non-dimensional inertial number
in the friction coefficient
. In this paper it is shown that the
-rheology is well-posed for intermediate values of
, but that it is ill-posed for both high and low inertial numbers. This result is not obvious from casual inspection of the equations, and suggests that additional physics, such as enduring force chains and binary collisions, becomes important in these limits. The theoretical results are validated numerically using two implicit schemes for non-Newtonian flows. In particular, it is shown explicitly that at a given resolution a standard numerical scheme used to compute steady-uniform Bagnold flow is stable in the well-posed region of parameter space, but is unstable to small perturbations, which grow exponentially quickly, in the ill-posed domain.
Resilience is the capacity of individuals to resist mental disorders despite exposure to stress. Little is known about its neural underpinnings. The putative variation of white-matter microstructure with resilience in adolescence, a critical period for brain maturation and onset of high-prevalence mental disorders, has not been assessed by diffusion tensor imaging (DTI). Lower fractional anisotropy (FA) though, has been reported in the corpus callosum (CC), the brain's largest white-matter structure, in psychiatric and stress-related conditions. We hypothesized that higher FA in the CC would characterize stress-resilient adolescents.
Three groups of adolescents recruited from the community were compared: resilient with low risk of mental disorder despite high exposure to lifetime stress (n = 55), at-risk of mental disorder exposed to the same level of stress (n = 68), and controls (n = 123). Personality was assessed by the NEO-Five Factor Inventory (NEO-FFI). Voxelwise statistics of DTI values in CC were obtained using tract-based spatial statistics. Regional projections were identified by probabilistic tractography.
Higher FA values were detected in the anterior CC of resilient compared to both non-resilient and control adolescents. FA values varied according to resilience capacity. Seed regional changes in anterior CC projected onto anterior cingulate and frontal cortex. Neuroticism and three other NEO-FFI factor scores differentiated non-resilient participants from the other two groups.
High FA was detected in resilient adolescents in an anterior CC region projecting to frontal areas subserving cognitive resources. Psychiatric risk was associated with personality characteristics. Resilience in adolescence may be related to white-matter microstructure.
Two seasons of work have now been conducted by British and French survey teams, in conjunction with members of the Libyan Antiquities Department, under the charge of Dr. Abdullah Shaiboub. The objectives of the survey are to locate, survey and analyse the extensive remains of the ancient agricultural settlements that can be found in the wadis of the hinterlands of Tripolitania and the Sirtica. Within the framework established by the Department in cooperation with Unesco lies the archaeological aim of recording the evidence for periods when extensive areas of the pre-desert were, for whatever reasons, cultivated in ways that are not similarly practised today. In the longer term the programme is designed to locate those areas where modern farming might be re-established. Archaeology is thus brought into line with the aims of the modern world.
For the purposes of this report we intend to concentrate on the period which we call the Romano/Libyan in which the great majority of those farming settlements flourished. The prehistoric evidence is in any case mainly of the palaeolithic period, on which there is a separate section.
The preferred zone of settlement in Tripolitania has traditionally been the well watered coastal plain and the adjacent limestone hills of the Tarhuna Gebel as far south as the town of Beni Ulid, for these regions have more than 200 mm of rain a year, regarded as the threshold for settled farming without irrigation. Prehistoric settlement concentrated here, and mixed farming has probably characterised this zone from the fourth millennium b.c. In the Roman period the coastal cities like Sabratha and Leptis Magna were supported by prosperous farms on the plain and in the Gebel. In the Islamic period, too, the same region was densely settled.
The final season of the three-year programme to survey the central Tripolitanian pre-desert examined the region to the west of the regions of the Wadis Sofeggin and Zem Zem, casting important light on the route between the interior of Libya and the coast during the prehistoric and Roman periods. In particular, a detailed account is given of the archaeological sites of the Bir Scedua Basin and of the Severan fort at Gheriat el-Garbia.
A fourth season of work was carried out in the Spring of 1984. The centrepiece of the programme was the investigation of the well-preserved farm in the Wadi el-Amud (Lamout). The main farm buildings were excavated, faunal and botanical samples were collected systematically from within and between them, the field systems and sluices were examined in detail and investigations begun on the geomorphological and hydrological context. This report presents the basic description of the archaeological data resulting from excavation and survey; a second report will present the results of the various laboratory studies which were generated by the field work.
Digital image data from the Landsat satellite Multispectral scanner have been analysed using a Dipex Image Processor. The image data were classified by a clustering algorithm to produce a thematic map for trial use in areas of archaeological interest. The archaeological, pedological, geomorphic and geological importance of these new data are discussed in the context of ground data obtained during the UNESCO April 1984 field season.
This report presents the preliminary results of the final season of the UNESCO Libyan Valleys Survey, that took place in October 1989. The fieldwork was divided in two parts. The first part of the work concentrated on the settlements in the Wadi Buzra, a northern tributary of the Wadi Sofeggin, especially at Souk el Awty. The major monument here consists of a substantial church (published elsewhere by D. A. Welsby in this volume), which was investigated by architectural survey and limited excavation, as were the surrounding late Romano-Libyan farms. The modern name of the settlement suggests that it may have been an important centre in Islamic as well as the Romano-Libyan periods, but the excavation did not obtain conclusive chronological evidence. The second part of the fieldwork was in the Wadi Umm el-Kharab, a southern tributary of the Sofeggin. Here, the team carried out a detailed study of a series of fortified farms of the later Romano-Libyan period, to compare with the open farm of the earlier Romano-Libyan period in Wadi el Amud previously studied by the project. An analysis of the constructional details of the major farms was integrated with excavations to recover stratified dating evidence from within the farms and faunal and botanical evidence from associated middens, and with a survey of the water-control systems of walls down the length of the wadi. The study indicates that the wadi was settled by people living in open farms and nucleated settlements in the first four centuries AD, but that by the fifth and sixth centuries AD these were replaced by fortified farms. There is evidence that the occupants of the fortified farms cultivated the wadi within an integrated economic system characterised by centralised food storage, rather than as independent units.
This article describes the interdisciplinary methods developed by the UNESCO Libyan Valleys Survey in connection with the study of ancient agriculture. These methods combine the techniques of settlement archaeology with those of the earth sciences and palaeoeconomics. The interactive nature of the enquiry does not resolve all the questions, but it can help to re-shape those questions and suggest new lines of enquiry. The example of the Wadi Mansur is used here to demonstrate the application of both conventional and new techniques and the contribution this can make to our appreciation of ancient land use in an arid zone. This provisional statement of results describes the geomorphology of the wadi, the settlement archaeology, ceramic dating evidence, palaeoeconomic data (including palynological evidence), wadi wall technology and typology.
This paper describes the system architecture of a newly constructed radio telescope – the Boolardy engineering test array, which is a prototype of the Australian square kilometre array pathfinder telescope. Phased array feed technology is used to form multiple simultaneous beams per antenna, providing astronomers with unprecedented survey speed. The test array described here is a six-antenna interferometer, fitted with prototype signal processing hardware capable of forming at least nine dual-polarisation beams simultaneously, allowing several square degrees to be imaged in a single pointed observation. The main purpose of the test array is to develop beamforming and wide-field calibration methods for use with the full telescope, but it will also be capable of limited early science demonstrations.
Late preterm births constitute the majority of preterm births. However, most evidence suggesting that preterm birth predicts the risk of mental disorders comes from studies on earlier preterm births. We examined if late preterm birth predicts the risks of severe mental disorders from early to late adulthood. We also studied whether adulthood mental disorders are associated with post-term birth or with being born small (SGA) or large (LGA) for gestational age, which have been previously associated with psychopathology risk in younger ages.
Of 12 597 Helsinki Birth Cohort Study participants, born 1934–1944, 664 were born late preterm, 1221 post-term, 287 SGA, and 301 LGA. The diagnoses of mental disorders were identified from national hospital discharge and cause of death registers from 1969 to 2010. In total, 1660 (13.2%) participants had severe mental disorders.
Individuals born late preterm did not differ from term-born individuals in their risk of any severe mental disorder. However, men born late preterm had a significantly increased risk of suicide. Post-term birth predicted significantly increased risks of any mental disorder in general and particularly of substance use and anxiety disorders. Individuals born SGA had significantly increased risks of any mental and substance use disorders. Women born LGA had an increased risk of psychotic disorders.
Although men born late preterm had an increased suicide risk, late preterm birth did not exert widespread effects on adult psychopathology. In contrast, the risks of severe mental disorders across adulthood were increased among individuals born SGA and individuals born post-term.
Developmental or fetal programming has emerged as a major model for understanding the early and persisting effects of prenatal exposures on the health and development of the child and adult. We leverage the power of a 14-year prospective study to examine the persisting effects of prenatal anxiety, a key candidate in the developmental programming model, on symptoms of behavioral and emotional problems across five occasions of measurement from age 4 to 13 years. The study is based on the Avon Longitudinal Study of Parents and Children cohort, a prospective, longitudinal study of a large community sample in the west of England (n = 7,944). Potential confounders included psychosocial and obstetric risk, postnatal maternal mood, paternal pre- and postnatal mood, and parenting. Results indicated that maternal prenatal anxiety predicted persistently higher behavioral and emotional symptoms across childhood with no diminishment of effect into adolescence. Elevated prenatal anxiety (top 15%) was associated with a twofold increase in risk of a probable child mental disorder, 12.31% compared with 6.83%, after allowing for confounders. Results were similar with prenatal depression. These analyses provide some of the strongest evidence to date that prenatal maternal mood has a direct and persisting effect on her child's psychiatric symptoms and support an in utero programming hypothesis.
Excavations at the Easton Down long barrow were part of a wider programme of research into the Neolithic sequence and context of the Avebury area in north Wiltshire. The short barrow, on high chalk downland to the south-west of Avebury and the upper Kennet valley, and containing only a few inhumations according to Thurnam's 19th-century investigation, dates to the later 4th millennium BC. Test pits around the barrow produced very little struck flint, and virtually no colluvium in the adjacent dry valley to the west. The mound covered a thin calcareous turfline above a rubbly soil, probably formerly cultivated. The pre-barrow molluscan fauna, soil micromorphology and other environmental data indicate a clearance adjacent to woodland. In the secondary fill of the flanking ditches there is a succession from renewed woodland to open conditions in the Late Neolithic.
The Easton Down monument falls relatively late in the regional sequence of long barrow construction. Its setting was probably one of scattered, non-permanent clearances in woodland. Woodland was still widespread on the higher downland of the region in the middle of the Neolithic. Renewed and bigger-scale clearance towards the end of the Neolithic may be connected with the construction of very large monuments elsewhere in the region. The later prehistoric landscape became both more open and less diverse.
White matter (WM) abnormalities are proposed as potential endophenotypic markers of bipolar disorder (BD). In a diffusion tensor imaging (DTI) voxel-based analysis (VBA) study of families multiply affected with BD, we previously reported that widespread abnormalities of fractional anisotropy (FA) are associated with both BD and genetic liability for illness. In the present study, we further investigated the endophenotypic potential of WM abnormalities by applying DTI tractography to specifically investigate tracts implicated in the pathophysiology of BD.
Diffusion magnetic resonance imaging (MRI) data were acquired from 19 patients with BD type I from multiply affected families, 21 of their unaffected first-degree relatives and 18 healthy volunteers. DTI tractography was used to identify the cingulum, uncinate fasciculus (UF), arcuate portion of the superior longitudinal fasciculus (SLF), inferior longitudinal fasciculus (ILF), corpus callosum, and the anterior limb of the internal capsule (ALIC). Regression analyses were conducted to investigate the effect of participant group and genetic liability on FA and radial diffusivity (RD) in each tract.
We detected a significant effect of group on both FA and RD in the cingulum, SLF, callosal splenium and ILF driven by reduced FA and increased RD in patients compared to controls and relatives. Increasing genetic liability was associated with decreased FA and increased RD in the UF, and decreased FA in the SLF, among patients.
WM microstructural abnormalities in limbic, temporal and callosal pathways represent microstructural abnormalities associated with BD whereas alterations in the SLF and UF may represent potential markers of endophenotypic risk.
The UK has seen a significant transition from Defined Benefit (“DB”) to Defined Contribution (“DC”) for occupational pension saving. The planned automatic enrolment program starting in 2012 is expected to increase the use of DC. The main features of DC are that investment risk falls onto the individual during the pre-retirement phase and that there are no guarantees as to investment returns or the level of pension. In July 2012, Steve Webb, the Pensions Minister, challenged industry to think hard about meeting the need for more certainty about pension savings in DC plans and to consider providing an affordable ‘Money Safe’ guarantee where the member would get back at least the nominal value of their contributions (individual, employer and tax relief). This paper explores whether this is viable for the mass market.