838 research outputs found

    Deterministic and stochastic study for a microscopic angiogenesis model: applications to the Lewis lung carcinoma

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    Angiogenesis modelling is an important tool to understand the underlying mechanisms yielding tumour growth. Nevertheless, there is usually a gap between models and experimental data. We propose a model based on the intrinsic microscopic reactions defining the angiogenesis process to link experimental data with previous macroscopic models. The microscopic characterisation can describe the macroscopic behaviour of the tumour, which stability analysis reveals a set of predicted tumour states involving different morphologies. Additionally, the microscopic description also gives a framework to study the intrinsic stochasticity of the reactive system through the resulting Langevin equation. To follow the goal of the paper, we use available experimental information on the Lewis lung carcinoma to infer meaningful parameters for the model that are able to describe the different stages of the tumour growth. Finally we explore the predictive capabilities of the fitted model by showing that fluctuations are determinant for the survival of the tumour during the first week and that available treatments can give raise to new stable tumour dormant states with a reduced vascular network

    Mesoscopic scale modeling of concrete under triaxial loading using X-ray tomographic images

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    This paper focuses on the discrete modeling of triaxial behaviour of concrete. The originality of this work comes from two points. The first one concerns the predictive feature of the model developed for simulating the response of concrete specimens; the behaviour of mortar, rock, and their interaction being identified a priori or by means of experimental tests on the mortar and the rock. The second originality relates to the construction method of the discrete element assembly based on the 3D segmentation of tomographic images. Such a method allows modeling of concrete at the mesoscopic scale with an internal structure similar to the one of the concrete tested experimentally. The comparisons between numerical and experimental results show the model is capable to reproduce the triaxial behavior of concrete for confining pressure varying from 0 to 650 MPa

    An exploration of the experiences and utility of functional electrical stimulation for foot drop in people with multiple sclerosis

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    Purpose: Functional electrical stimulation (FES) is effective in improving walking in people with multiple sclerosis (MS) with foot drop. There is limited research exploring people’s experiences of using this device. This study aims to explore the utility, efficacy, acceptability, and impact on daily life of the device in people with MS. Methods: An interpretative phenomenological approach was employed. Ten participants who had used FES for 12 months were interviewed. Transcripts were analysed, and emergent themes identified. Results: Nine participants continued to use the device. Three relevant super-ordinate themes were identified; impact of functional electrical stimulation, sticking with functional electrical stimulation, and autonomy and control. Participants reported challenges using the device; however, all reported positive physical and psychological benefits. Intrinsic and external influences such as; access to professional help, the influence of others, an individual’s ability to adapt, and experiences using the device, influenced their decisions to continue with the device. A thematic model of these factors was developed. Conclusions: This study has contributed to our understanding of people with MS experiences of using the device and will help inform prescribing decisions and support the continued, appropriate use of FES over the longer term

    In-plane uniaxial anisotropy rotations in (Ga,Mn)As thin films

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    We show, by SQUID magnetometry, that in (Ga,Mn)As films the in-plane uniaxial magnetic easy axis is consistently associated with particular crystallographic directions and that it can be rotated from the [-110] direction to the [110] direction by low temperature annealing. We show that this behavior is hole-density-dependent and does not originate from surface anisotropy. The presence of uniaxial anisotropy as well its dependence on the hole-concentration and temperature can be explained in terms of the p-d Zener model of the ferromagnetism assuming a small trigonal distortion.Comment: 4 pages, 6 Postscript figures, uses revtex

    Configurations of the circle of Willis: a computed tomography angiography based study on a Polish population

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    The aim of the study was to investigate the distribution of the circle of Willis variants in Polish population by means of computed tomography angiography (CTA). The results were then analysed and compared with another study that used similar methods but that was carried out on an ethnically distinct population. Patients presenting with intracranial pathology were excluded from the initial study population. In total, 250 CTA belonging to 129 female and 121 male patients were reviewed. A modified classification system of the circle was proposed, which took into consideration the anterior and the posterior aspects of the circle individually. The typical variant of Willis’s circle occurred in 16.80% of cases. The anterior and the posterior portions of the circle were normal in 47.20% and 26.80% of the patients respectively. As forthe anterior part, lack of the anterior communicating artery was the most frequent abnormality (22.80%). Bilateral absence of posterior communicating arteries was the most common anomaly in the posterior part of the circle (29.20%). This type of anomaly was also the most common, when taking into consideration the entire circle (12.00%). There were statistically significant differences between the age groupsand genders when considering the occurrence of an incomplete circle. Overall, a substantial proportion of patients manifested clinically important variants that were incapable of providing collateral circulation. Comparison with other imaging-based and cadaveric studies revealed noticeable differences, that may have resulted from the variable technical features of other studies or other factors such as the ethnical origins of the studied populations

    Measurement of psychological entitlement in 28 countries

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    This article presents the cross-cultural validation of the Entitlement Attitudes Questionnaire, a tool designed to measure three facets of psychological entitlement: active, passive, and revenge entitlement. Active entitlement was defined as the tendency to protect individual rights based on self-worthiness. Passive entitlement was defined as the belief in obligations to and expectations toward other people and institutions for the fulfillment of the individual’s needs. Revenge entitlement was defined as the tendency to protect one’s individual rights when violated by others and the tendency to reciprocate insults. The 15-item EAQ was validated in a series of three studies: the first one on a general Polish sample (N = 1,900), the second one on a sample of Polish students (N = 199), and the third one on student samples from 28 countries (N = 5,979). A three-factor solution was confirmed across all samples. Examination of measurement equivalence indicated partial metric invariance of EAQ for all national samples. Discriminant and convergent validity of the EAQ was also confirmed

    Holocene carbon fluxes and palaeoproductivity in aquatic ecosystems: a multiproxy, palaeolimnological approach

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    Inland waters act as an important control on the global carbon cycle. Deep tectonic lakes may provide a key link between short‐term and long‐term carbon cycles as buried carbon is essentially locked away from the atmosphere over geological timescales. Here we investigate Holocene carbon dynamics in one of the world’s most important lake ecosystems, Lake Baikal, Siberia

    Reception Tests of the Cryogenic Distribution line for the Large Hadron Collider

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    The paper describes the thermo-mechanical validation of the first sector of cryogenic distribution line (QRL) [1]. The design of the line is recalled and the test methodology presented together with the main results of the reception test at cryogenic temperature
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