On the fundamental equations of piezoelasticity of quasicrystal media

AbstractThe three-dimensional fundamental equations of elasticity of quasicrystals with extension to quasi-static electric effect are expresses in both differential and variational invariant forms for a regular region of quasicrystal material. The principle of conservation of energy is stated for the regular region and the constitutive relations are obtained for the piezoelasticity of material. A theorem is proved for the uniqueness in solutions of the fundamental equations by means of the energy argument. The sufficient boundary and initial conditions are enumerated for the uniqueness. Hamilton’s principle is stated for the regular region and a three-field variational principle is obtained under some constraint conditions. The constraint conditions, which are generally undesirable in computation, are removed by applying an involutory transformation. Then, a unified variational principle is obtained for the regular region, with one or more fixed internal surface of discontinuity. The variational principle operating on all the field variables generates all the fundamental equations of piezoelasticity of quasicrystals under the symmetry conditions of the phonon stress tensor and the initial conditions. The resulting equations, which are expressible in any system of coordinates and may be used through simultaneous approximation upon all the field variables in a direct method of solutions, pave the way to the study of important dislocation, fracture and interface problems of both elasticity and piezoelasticity of quasicrystal materials

On the fundamental equations of electromagnetoelastic media in variational form with an application to shell/laminae equations

AbstractThe fundamental equations of elasticity with extensions to electromagnetic effects are expressed in differential form for a regular region of materials, and the uniqueness of solutions is examined. Alternatively, the fundamental equations are stated as the Euler–Lagrange equations of a unified variational principle, which operates on all the field variables. The variational principle is deduced from a general principle of physics by modifying it through an involutory transformation. Then, a system of two-dimensional shear deformation equations is derived in differential and fully variational forms for the high frequency waves and vibrations of a functionally graded shell. Also, a theorem is given, which states the conditions sufficient for the uniqueness in solutions of the shell equations. On the basis of a discrete layer modeling, the governing equations are obtained for the motions of a curved laminae made of any numbers of functionally graded distinct layers, whenever the displacements and the electric and magnetic potentials of a layer are taken to vary linearly across its thickness. The resulting equations in differential and fully variational, invariant forms account for various types of waves and coupled vibrations of one and two dimensional structural elements as well. The invariant form makes it possible to express the equations in a particular coordinate system most suitable to the geometry of shell (plate) or laminae. The results are shown to be compatible with and to recover some of earlier equations of plane and curved elements for special material, geometry and/or effects

Sellar and Parasellar Metastatic Tumors

The sellar and parasellar (SPS) region is a complex area rich in vital neurovascular structures and as such may be the location of first manifestation of a systemic malignancy. Metastases to this region are rare; breast cancer is the most common source among those that metastasize to the SPS region. Ophthalmoplegia, headache, retroorbital or facial pain, diabetes insipidus, and visual field defects are the most commonly reported symptoms. Lack of specific clinical and radiological features renders SPS metastases difficult to differentiate from the other frequently encountered lesions in this area, especially when there is no known history of a primary disease. Currently accepted management is multimodality therapy that includes biopsy and/or palliative surgical resection, radiation, and chemotherapy. Although no significant survival benefits have been shown by the surgical series, surgical resection may improve quality of life. Here we review the relevant literature and present six illustrative cases from our own institution

Optimal multi-period consumption and investment with short-sale constraints

Cataloged from PDF version of article.This article examines agents’ consumption-investment problem in a multi-period pure exchange economy where agents are constrained with the short-sale of state-dependent risky contingent claims. In equilibrum, agents hold options written on aggregate consumption in their optimal portfolios. Furthermore, under the specific case of quadratic utility, the optimal risk-sharing rule derived for the pricing agent leads to a multifactor conditional consumption-based capital asset pricing model (CCAPM), where excess option returns appear as factors. 2013 Elsevier Inc. All rights reserved

Improving Disaster Response Efforts With Decision Support Systems

As evidenced by Hurricane Katrina in August, 2005, disaster response efforts are hindered by a lack of coordination, poor information flows, and the inability of disaster response managers to validate and process relevant information and make decisions in a timely fashion. A number of factors contribute to current lackluster response efforts. Some are inherent to the complex, rapidly changing decision-making environments that characterize most disaster response settings. Others reflect systematic flaws in how decisions are made within the organizational hierarchies of the many agencies involved in a disaster response. Slow, ineffective strategies for gathering, processing, and analyzing data can also play a role. Information technology, specifically decision support systems, can be used to reduce the time needed to make crucial decisions regarding task assignment and resource allocation. Decision support systems can also be used to guide longer-term decisions involving resource acquisition as well as for training and the evaluation of command and control capability

Autekologi dan Fisiologi Percambahan Centaurea kilaea Boiss. dari Turki

In this study germination requirements, plant-soil interactions and population biology of Centaurea kilaea was studied. The plant and soil samples were collected from Sofular Village (Sile District) and shore of Çatalca District (Istanbul) in Turkey by using standard methods. Methods like Scheibler, Wetdigestion, Kjeldahl and Olsen were employed for measurement of soil texture, structure and other physical and chemical characteristics (pH, total protein and electrical conductivity) using spectrophotometer, flame photometer, calcimeter and ICP. The results showed that ranges of different elements in the soil were 0.007-0.2% for N, 0.0007-0.001% for P, 0.001-0.01% for K, 0.0001-0.0002 % for Na. N, P, K and Na values in the plants were 2.17, 0.005, 0.1 and 0.006%, respectively. The data revealed that germination success of the seeds was influenced by the environmental factors such as pH, germination season and temperature.Dalam kajian ini keperluan percambahan, saling tindakan tumbuhan-tanih dan biologi populasi Centaurea kilaea telah dilakukan. Sampel tumbuhan dan tanih telah dikumpul dari Kampung Sofular (Daerah Şile) dan pantai Daerah Çatalca (Istanbul) di Turki dengan menggunakan kaedah piawai. Kaedah seperti Scheibler, Wetdigestion, Kjeldahl dan Olsen telah digunakan bagi pengukuran tekstur tanih, struktur dan sifat fizikal dan kimia lain (pH, jumlah protein dan kekonduksian elektrik) menggunakan spektrofotometer, fotometer api, kalsimeter dan ICP. Hasil menunjukkan bahawa julat unsur berbeza dalam tanih ialah 0.007-0.2% bagi N, 0.0007-0.001% bagi P, 0.001-0.01% bagi K, 0.0001-0.0002% bagi Na. N, P, K dan nilai Na dalam tumbuhan ialah masing-masing 2.17, 0.005, 0.1 dan 0.006%. Data menunjukkan kejayaan percambahan bagi biji benih telah dipengaruhi faktor persekitaran seperti pH, musim percambahan dan suhu

Predictive Factors Of One-year Mortality In A Cohort Of Patients Undergoing Urgent-start Hemodialysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Chronic kidney disease (CKD) affects 10-15% of adult population worldwide. Incident patients on hemodialysis, mainly those on urgent-start dialysis at the emergency room, have a high mortality risk, which may reflect the absence of nephrology care. A lack of data exists regarding the influence of Baseline factors on the mortality of these patients. The aim of this study was to evaluate the clinical and laboratory characteristics of this population and identify risk factors that contribute to their mortality. Patients and methods We studied 424 patients who were admitted to our service between 01/2006 and 12/2012 and were followed for 1 year. We analyzed vascular access, risk factors linked to cardiovascular disease (CVD) and mineral and bone disease associated with CKD (CKD-MBD), and clinical events that occurred during the follow-up period. Factors that influenced patient survival were evaluated by Cox regression analysis. Results The patient mean age was 50 18 years, and 58.7% of them were male. Hypertension was the main cause of primary CKD (31.8%). Major risk factors were smoking (19.6%), dyslipidemia (48.8%), and CVD (41%). Upon admission, most patients had no vascular access for hemodialysis (89.4%). Biochemical results showed that most patients were anemic with high C-reactive protein levels, hypocalcemia, hyperphosphatemia, elevated parathyroid hormone and decreased 25-hydroxy vitamin D. At the end of one year, 60 patients died (14.1%). These patients were significantly older, had a lower percentage of arteriovenous fistula in one year, and low levels of 25-hydroxy vitamin D. Conclusions The combined evaluation of clinical and biochemical parameters and risk factors revealed that the mortality in urgent-start dialysis is associated with older age and low levels of vitamin D deficiency. A lack of a permanent hemodialysis access after one year was also a risk factor for mortality in this population.121Sao Paulo Research Foundation (FAPESP) [2010/03867-7]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Misinformation on Misinformation: Conceptual and Methodological Challenges

Copyright © 2021 The Author(s). Alarmist narratives about online misinformation continue to gain traction despite evidence that its prevalence and impact are overstated. Drawing on research questioning the use of big data in social science and reception studies, we identify six misconceptions about misinformation and examine the conceptual and methodological challenges they raise. The first three misconceptions concern the prevalence and circulation of misinformation. First, the internet is not rife with misinformation or news, but with memes and entertaining content. Second, scientists focus on social media because it is methodologically convenient, but misinformation is not just a social media problem. Third, falsehoods do not spread faster than the truth; how we define (mis)information influences our results and their practical implications. The second three misconceptions concern the impact and the reception of misinformation. First, people do not believe everything they see on the internet: sheer volume of engagement should not be conflated with belief. Second, the influence of misinformation on people’s behavior is overblown since it often ‘preaches to the choir’. Third, people are more likely to be uninformed than misinformed; surveys overestimate misperceptions and say little about the causal influence of misinformation. To appropriately understand and fight misinformation, future research needs to address these challenges

How high is the inter-observer reproducibility in the LIRADS reporting system?

Purpose: To investigate the reproducibility of LIRADS v2014 and contribute to its widespread use in clinical practice. Material and methods: This retrospective, single-centre study was conducted between January 2010 and October 2015. A total of 132 patients who had dynamic magnetic resonance imaging (MRI)/computed tomography (CT) images in the Picture Archiving and Communication Systems (PACS) with liver nodule were included in the study, 37 of whom had histopathology results. Five radiologists who participated in the study, interpreted liver nodules independently on different PACS stations according to the LIRADS reporting system and its main parameters. Results: We determined that level of inter-observer agreement in the LR-1, LR-5, and LR-5V categories was higher than in the LR-2, LR-3, and LR-4 categories (κ = 0.522, 0.442, and 0.600 in the LR-1, LR-5, and LR-5V categories, respectively; κ = 0.082, 0.298, and 0.143 in the LR-2, LR-3, and LR-4 categories, respectively). The parameter that we observed to have the highest level of inter-observer agreement was venous thrombus (κ = 0.600). Conclusions: Our study showed that LIRADS achieves an acceptable inter-observer reproducibility in terms of clinical practice although it is insufficient at intermediate risk levels. We think that the prevalence of its use will be further increased with training related to the subject and the assignment of numerical values that express the probability of malignancy for each category and including the ancillary features in the algorithm according to clearer rules