6,612 research outputs found
Numerical analysis of a nonlocal parabolic problem resulting from thermistor problem
We analyze the spatially semidiscrete piecewise linear finite element method
for a nonlocal parabolic equation resulting from thermistor problem. Our
approach is based on the properties of the elliptic projection defined by the
bilinear form associated with the variational formulation of the finite element
method. We assume minimal regularity of the exact solution that yields optimal
order error estimate. The full discrete backward Euler method and the
Crank-Nicolson-Galerkin scheme are also considered. Finally, a simple algorithm
for solving the fully discrete problem is proposed
An Exploration of Early Work Packaging in Construction Manager/General Contractor Highway Projects
Recently, state agencies have been successfully implementing construction manager/general contractor (CM/GC) delivery on highway projects. While early work packaging is frequently cited in the literature as a primary benefit of CM/GC, there is limited to substantiate or refute these benefits. Additionally, agencies need a better understanding of the current state-of-practice of early work packing in CM/GC to help with effective implementation. In an ongoing Federal Highway Agency research project, 12 of 34 completed CM/GC projects reported the use early work packaging, and will be the focus of this study. Research methods used within this paper include: literature review, content review of agency manuals/instructions, project surveys, agency interviews, and case studies. Triangulated findings suggest that early work packaging can contribute to expediting project completion, mitigating project risks, reducing project cost, and minimizing public impacts. To achieve these outcomes, agencies must perform detailed planning to generate severable/independent packages that take into account all potential impacts to the project. Trends in data indicate that early work packages can lead to cost savings, yet the sample size does not provide statistical significance. Future research should explore the performance of a larger data set of CM/GC projects with and without early work packaging along with a cost/benefit analysis of early work packages
String compactifications on Calabi-Yau stacks
In this paper we study string compactifications on Deligne-Mumford stacks.
The basic idea is that all such stacks have presentations to which one can
associate gauged sigma models, where the group gauged need be neither finite
nor effectively-acting. Such presentations are not unique, and lead to
physically distinct gauged sigma models; stacks classify universality classes
of gauged sigma models, not gauged sigma models themselves. We begin by
defining and justifying a notion of ``Calabi-Yau stack,'' recall how one
defines sigma models on (presentations of) stacks, and calculate of physical
properties of such sigma models, such as closed and open string spectra. We
describe how the boundary states in the open string B model on a Calabi-Yau
stack are counted by derived categories of coherent sheaves on the stack. Along
the way, we describe numerous tests that IR physics is
presentation-independent, justifying the claim that stacks classify
universality classes. String orbifolds are one special case of these
compactifications, a subject which has proven controversial in the past;
however we resolve the objections to this description of which we are aware. In
particular, we discuss the apparent mismatch between stack moduli and physical
moduli, and how that discrepancy is resolved.Comment: 85 pages, LaTeX; v2: typos fixe
Failure of Standard Thermodynamics in Planck Scale Black Hole System
The final stage of the black hole evaporation is a matter of debates in the
existing literature. In this paper, we consider this problem within two
alternative approaches: noncommutative geometry(NCG) and the generalized
uncertainty principle(GUP). We compare the results of two scenarios to find a
relation between parameters of these approaches. Our results show some
extraordinary thermodynamical behavior for Planck size black hole evaporation.
These extraordinary behavior may reflect the need for a fractal nonextensive
thermodynamics for Planck size black hole evaporation process.Comment: 26 Pages, 10 Figures, Revised and References adde
Experimental and theoretical study of benzene (acetonitrile)(n) clusters, n=1-4
Well-resolved spectra of benzene–acetonitrile binary clustersBAn, with n=1–4 have been obtained by the (one-color) resonant two-photonionization technique using the benzene’s B2u←A1g 000 and 610 resonances. The spectra reveal a rapid increase in complexity with the number of acetonitrile molecules in the cluster, associated with van der Waal modes and isomeric forms. While only single cluster origins are found for the benzene–acetonitrile (BA) and the BA2clusters, two and four distinct isomers are identified for the BA3 and BA4clusters, respectively. The origins of the BA and BA2clusters are blueshifted with respect to the free benzene molecule by 38 cm−1 and 26 cm−1, respectively. Monte Carlo(MC) simulations reveal two types of isomeric structures of the BAnclusters. The clusters containing an even number of the acetonitrile molecules (BA2, BA4, and BA6) are dominated by acetonitrile anti-parallel paired dimers. The BA3cluster consists of a cyclic acetonitrile trimer parallel to the benzene ring. In the BA5clusters, the acetonitrile molecules are assembled in a cyclic trimer + a paired dimer configuration or in two paired dimers + a single monomer structure. The R2PI spectra, in conjunction with the MC structural models and simple energetic arguments, provide a reasonably compelling picture of the spectroscopic and dynamical phenomena associated with dipole pairing molecular cluster systems
Governing biological material at the intersection of care and research: the use of dried blood spots for biobanking
A series of governance issues currently surrounds the multiple uses and multiple users of dried blood spots (DBS) for research purposes. Internationally there is a discussion on storing DBS resulting from newborn screening for public health and using them as the basis for large biobank-like collections to facilitate biomedical research. If such a transformation were to be formalized, then DBS would sit at the intersection of care (ie, public health) and research, with the mechanisms through which such a collection could be managed not totally self-evident. What is more, a DBS collection raises questions about the fuzzy boundaries between privacy and anonymity; how to control or define quality control uses of DBS; medical vs nonmedical uses; as well as benefit sharing and stakeholder involvement. Our goal here is to explore some of the key questions relating to DBS governance by way of the bio-objects and bio-objectification concepts. By embracing – rather than resisting to – the blurring of boundaries and problems in categorization that have come to characterize bio-objects and bio-objectification processes recently described in this journal, we attempt to highlight some issues that might not be currently considered, and to point to some possible directions to go (or avoid). Building from our knowledge of the current DBS situation in the Netherlands, we outline questions concerning the uses, management, collection, and storage of DBS
Mesenchymal adenomatous polyposis coli plays critical and diverse roles in regulating lung development.
BackgroundAdenomatous polyposis coli (Apc) is a tumor suppressor that inhibits Wnt/Ctnnb1. Mutations of Apc will not only lead to familial adenomatous polyposis with associated epithelial lesions, but will also cause aggressive fibromatosis in mesenchymal cells. However, the roles of Apc in regulating mesenchymal cell biology and organogenesis during development are unknown.ResultsWe have specifically deleted the Apc gene in lung mesenchymal cells during early lung development in mice. Loss of Apc function resulted in immediate mesenchymal cell hyperproliferation through abnormal activation of Wnt/Ctnnb1, followed by a subsequent inhibition of cell proliferation due to cell cycle arrest at G0/G1, which was caused by a mechanism independent of Wnt/Ctnnb1. Meanwhile, abrogation of Apc also disrupted lung mesenchymal cell differentiation, including decreased airway and vascular smooth muscle cells, the presence of Sox9-positive mesenchymal cells in the peripheral lung, and excessive versican production. Moreover, lung epithelial branching morphogenesis was drastically inhibited due to disrupted Bmp4-Fgf10 morphogen production and regulation in surrounding lung mesenchyme. Lastly, lung mesenchyme-specific Apc conditional knockout also resulted in altered lung vasculogenesis and disrupted pulmonary vascular continuity through a paracrine mechanism, leading to massive pulmonary hemorrhage and lethality at mid-gestation when the pulmonary circulation should have started.ConclusionsOur study suggests that Apc in lung mesenchyme plays central roles in coordinating the proper development of several quite different cellular compartments including lung epithelial branching and pulmonary vascular circulation during lung organogenesis
Metastasis occurring eleven years after diagnosis of human papilloma virus-related oropharyngeal squamous cell carcinoma
Human papilloma virus (HPV)-related oropharyngeal squamous cell carcinoma (OPSCC) is associated with a favourable prognosis, although approximately 20–25% of patients ultimately develop recurrent cancer. Most disease recurrence events appear within 3 years; however, long-term follow-up of reported studies are limited, and the risk of late recurrence is unknown. We present a case report of a patient who developed distant metastases of HPV-related SCC 11 years after initial diagnosis and treatment of HPV-related OPSCC. Late disease recurrence may occur after initial diagnosis of HPV-related OPSCC. This observation has implications on the appropriate duration of follow-up and surveillance of these patients
The Application of Building Modifications and their Effects on Energy Consumption in Buildings
A huge amount of energy is used for air-conditioning in residential buildings in hot climates. Passive design features such as shading and advanced glazing can help to reduce energy use and carbon emissions, and thus mitigate the impact on climate change. This paper aimed at demonstrating how the application of selected modification devices such as solar films and shading devices affects the energy consumption patterns and levels in a residential building. A model of a building was constructed with VE using “Model IT” module, which was then analysed in a variety of different ways. A Virtual Integrated Environmental Solutions (IES-VE) was used to assess the energy gain and consumption parameters such as solar gains, shading devices, solar cloud and chilli clouds in residential buildings in Tripoli, Libya. The findings indicate that the best way to control and reduce the energy gains pattern in a building is to introduce energy modification devices such as shading device, solar films, emissivity paints and roof slab absorbers among others. In specific terms, the best device would be the application of external solar film, follow by shading device and internal solar film. An application of emissivity paints and roof slab absorbers does not contribute significantly to the energy reduction in the building. The study concludes that the application of modification devices in buildings can reduces the heat gain significantly. This study underscores the need and importance of the applications of energy modification devices in buildings in order to reduce their energy gains in the context of tropical regions. Though the climatological characteristics of tropical regions are similar, the generalisation of the findings in this study requires caution since the findings are limited in geographical context. Future research should also explore the impact of urban forms, street layout and orientation on solar penetration and energy use in buildings. Keywords: Architecture, Buildings, Climate change, Energy consumption, Energy gains, Liby
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