Ground movements generated by sequential Twin-tunnelling in over-consolidated clay

The expansion of urban populations comes with an associated demand for increased public transport. An often utilised solution is to construct a rapid transit system within tunnels. Generally, a pair of tunnels are constructed within relative close proximity. The construction of these tunnels will generate ground movements which have the potential to cause damage to existing surface and subsurface structures. Modern tunnelling practice aims to reduce these movements to a minimum; however there is still a requirement for accurate assessment of settlements. For tunnels driven in clay, superposition of settlement predictions made by considering a single tunnel is an accepted method used to estimate movements around pairs of tunnels. This presumes that the movements generated from the construction of the second tunnel are not influenced in any way by the presence of the first tunnel. A series of plane strain centrifuge model tests have been conducted to explore the validity of superposition as a prediction method. The tests consisted of a sequential twin-tunnel construction with varied centre-to-centre spacing in over-consolidated clay. Relatively complex apparatus facilitated a predefined volume loss whilst monitoring surface settlement, tunnel support pressures and pore-water pressures. The measured data were assessed against superposition for surface vertical settlements in the plane perpendicular to an advancing tunnel face. The results highlight some inconsistencies with the superposition method

Explanation for twin tunnelling-induced surface settlements by changes in soil stiffness on account of stress history

In this article, a group of representative centrifuge tests were selected for numerical modelling to explain the surface settlements induced by sequential twin tunnelling. Both Modified Cam Clay model (MCC) and Three-Surface Kinematic Hardening model (3-SKH) were adopted in the simulation, which indicated the use of 3-SKH model conduced to mimicking more closely centrifuge model response. Via performing more contrastive numerical analyses with 3-SKH model, the influence of the first tunnel event on the stiffness of the soil around the second tunnel was quantitatively investigated, whereby the mechanism behind the observed surface settlements was finally made clear

Do the severity of Intellectual Disability and /or the presence of neurodevelopmental disorders influence the onset of dementia in people with Down syndrome?

Introduction: Having a diagnosis of Down syndrome (DS) is associated with intellectual disability (ID), pervasive developmental disorders and Alzheimer’s dementia (AD). The association between these conditions has not been well evaluated. This paper looks to examine the current evidence pertaining to the relationship between dementia in people with DS and severity of ID and the presence of pervasive developmental disorders. Methods: A scoping review using PRISMA guidance was undertaken. Medline, Cochrane database, NHS evidence, Trial registers and Open Grey were searched in December 2018 and an updated search was completed in July 2020. Three search strategies were used to retrieve articles relating to DS, dementia, pervasive developmental disorders (including autism, autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD)) and severity of ID. Studies were included if they met the pre-defined inclusion criteria of investigating an association between autism/ASD, ADHD, or severity of ID and the development of dementia in people with DS. Studies were excluded if they did not include primary data, if the population included non-Down causes of ID, or if no specific outcome measure related to comorbid autism/ASD, ADHD, or severity of ID and dementia in people with a diagnosis of DS were reported. There were no exclusions related to study design. Papers were assessed for quality using the Mixed Methods Appraisal Tool (MMAT). Results: The search identified 15 papers, publishing results from 12 studies, relating to severity of ID, DS and dementia. No papers were identified relating to pervasive developmental disorders, DS and dementia. There is limited evidence on how severity of ID impacts on the presentation, diagnosis, management or prognosis of dementia in people with DS. However, no evidence was found on comorbid pervasive developmental disorders, DS and dementia. Conclusion: This paper has identified multiple areas for future research. There is an urgent need for longitudinal studies into the presentation, development and progression of dementia in people with DS ensuring the severity of ID and comorbid pervasive developmental conditions are captured regularly to understand their influence on the dementia etiology and outcome

Centrifuge Modelling of Long-term Tunnelling Ground Movements

The increasing demand for public transport provision in cities has resulted in a requirement for enlarged public transport infrastructure. Where underground railways represent an important component of these systems, tunnel construction will inevitably lead to some degree of ground movement that can cause damage to surface structures and buried structures and services. It is important, therefore, that in the design of tunnels in urban environments these ground movements are predicted reliably. Predicting short-term ground movements resulting from tunnelling is standard when assessing the potential for damage to adjacent infrastructure. However, long-term tunnelling-induced ground movements and how these develop are understood less well and a research programme, based on geotechnical centrifuge modelling, is being conducted to improve our fundamental scientific understanding of this. The first stage of the programme has been to develop an apparatus that simulates the construction of a tunnel with a lining of known stiffness and permeability and allows construction ground loss to be replicated correctly. This paper describes the initial development of the apparatus along with results and analysis that demonstrates the suitability of the technique for the proposed study. The results obtained were observed to represent the short-term settlements that might be expected above a tunnel excavated in clay. The results also prove the modelling technique suitable for application in a full parametric study in which the geometry and boundary conditions of the model will be varied together with the permeability of the tunnel liner

A Microchip CD4 Counting Method for HIV Monitoring in Resource-Poor Settings

BACKGROUND: More than 35 million people in developing countries are living with HIV infection. An enormous global effort is now underway to bring antiretroviral treatment to at least 3 million of those infected. While drug prices have dropped considerably, the cost and technical complexity of laboratory tests essential for the management of HIV disease, such as CD4 cell counts, remain prohibitive. New, simple, and affordable methods for measuring CD4 cells that can be implemented in resource-scarce settings are urgently needed. METHODS AND FINDINGS: Here we describe the development of a prototype for a simple, rapid, and affordable method for counting CD4 lymphocytes. Microliter volumes of blood without further sample preparation are stained with fluorescent antibodies, captured on a membrane within a miniaturized flow cell and imaged through microscope optics with the type of charge-coupled device developed for digital camera technology. An associated computer algorithm converts the raw digital image into absolute CD4 counts and CD4 percentages in real time. The accuracy of this prototype system was validated through testing in the United States and Botswana, and showed close agreement with standard flow cytometry (r = 0.95) over a range of absolute CD4 counts, and the ability to discriminate clinically relevant CD4 count thresholds with high sensitivity and specificity. CONCLUSION: Advances in the adaptation of new technologies to biomedical detection systems, such as the one described here, promise to make complex diagnostics for HIV and other infectious diseases a practical global reality

Halophilanema prolata n. gen., n. sp. (Nematoda: Allantonematidae), a parasite of the intertidal bug, Saldula laticollis (Reuter)(Hemiptera: Saldidae) on the Oregon coast

This is the publisher’s final pdf. The published article is copyrighted by BioMed Central and can be found at: http://www.biomedcentral.com/.Background: It is rare to find terrestrial nematode lineages parasitizing arthropods inhabiting the intertidal or\ud littoral zone of the oceans. During an ecological study along the Oregon dunes, an allantonematid nematode\ud (Tylenchomorpha: Allantonematidae) was discovered parasitizing the intertidal shore bug, Saldula laticollis (Reuter)\ud (Hemiptera: Saldidae). This shore bug is adapted to an intertidal environment and can survive short periods of\ud submergence during high tides. The present study describes the nematode parasite and discusses aspects of its\ud development, ecology and evolution.\ud Methods: Adults and last instar nymphs of S. laticollis (Hemiptera: Saldidae) were collected from the high intertidal\ud zone among clumps of Juncus L. (Juncaceae) plants at Waldport, Oregon on October 3, 2011. The bugs were\ud dissected in 1% saline solution and the nematodes killed in 1% Ringers solution and immediately fixed in 5%\ud formalin (at 20°C). Third stage juveniles removed from infected hosts were maintained in 1% saline solution until\ud they matured to the adult stage, molted and mated.\ud Results: Halophilanema prolata n. gen., n. sp. (Nematoda: Allantonematidae) is described from last instar nymphs\ud and adults of the intertidal bug, Saldula laticollis on the Oregon coast. The new genus can be distinguished from\ud other genera in the Allantonematidae by a stylet lacking basal knobs in both sexes, an excretory pore located\ud behind the nerve ring, ribbed spicules, a gubernaculum, the absence of a bursa and the elongate-tubular shape of\ud the ovoviviparous parasitic females. Studies of the organogenesis of Halophilanema showed development to third\ud stage juveniles in the uterus of parasitic females. Maturation to the free-living adults and mating occurred in the\ud environment. The incidence of infection of S. laticollis ranged from 0% to 85% depending on the microhabitat in\ud the intertidal zone.\ud Conclusions: Based on the habitat and morphological characters, it is proposed that Halophilanema adapted a\ud parasitic existence fairly recently, evolutionarily speaking. It was probably a free-living intertidal or shore nematode\ud that fed on microorganisms, especially fungi, in the intertidal habitat and became parasitic after saldids entered the\ud environment. Halophilanema represents the first described nematode parasite of an intertidal insect

An update on the Hirsch conjecture

The Hirsch conjecture was posed in 1957 in a letter from Warren M. Hirsch to George Dantzig. It states that the graph of a d-dimensional polytope with n facets cannot have diameter greater than n - d. Despite being one of the most fundamental, basic and old problems in polytope theory, what we know is quite scarce. Most notably, no polynomial upper bound is known for the diameters that are conjectured to be linear. In contrast, very few polytopes are known where the bound $n-d$ is attained. This paper collects known results and remarks both on the positive and on the negative side of the conjecture. Some proofs are included, but only those that we hope are accessible to a general mathematical audience without introducing too many technicalities.Comment: 28 pages, 6 figures. Many proofs have been taken out from version 2 and put into the appendix arXiv:0912.423

Intergroup struggles over victimhood in violent conflict: The victim-perpetrator paradigm

Most groups in violent, intergroup conflict perceive themselves to be the primary or sole victims of that conflict. This often results in contention over who may claim victim status and complicates a central aim of post-conflict processes, which is to acknowledge and address harms experienced by the victims. Drawing from victimology scholarship and intergroup relations theory, this article proposes the victim-perpetrator paradigm as a framework to analyse how, why and to what end groups in conflict construct and maintain their claims to the moral status of victim. This interdisciplinary paradigm builds on the knowledge that groups utilise the ‘ideal victim’ construction to exemplify their own innocence and blamelessness in contrast to the wickedness of the perpetrator, setting the two categories as separate and mutually exclusive even where experiences of violence have been complex. Additionally, this construction provides for a core intergroup need to achieve positive social identity, which groups may enhance by demonstrating a maximum differentiation between the in-group as victims and those out-groups identified as perpetrators. The paradigm contributes greater knowledge on the social roots of victim contention in conflict, as well as how groups legitimise their violence against out-groups during and after conflict

Calibration of Traffic Simulation Models using SPSA

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Γεωπληροφορική