167 research outputs found

    Quantization of the elastic modes in an isotropic plate

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    We quantize the elastic modes in a plate. For this, we find a complete, orthogonal set of eigenfunctions of the elastic equations and we normalize them. These are the phonon modes in the plate and their specific forms and dispersion relations are manifested in low temperature experiments in ultra-thin membranes.Comment: 14 pages, 2 figure

    Inkluusioideologian ja koulutuspolitiikan jännitteitä 2000-luvun suomalaisessa peruskoulussa

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    This article examines the discrepancy between the ideology of inclusive education and the national education policy in the Finnish comprehensive school education. The study covers twenty years and is based on observations indicating that the change towards inclusive education ideals in comprehensive school education has been slow. This has been the case, even though in principle the Finland has committed to many international statements that promote inclusion ideology. The data consists primarily of statistics indicating the number of students in special education, and national and international research on the subject. The data confirmed our assumption, but it also gave support for the view that statistics are not only challenging but they are also capable of distorting reality. While examining the changes in student quantities over the last twenty years, we came to the conclusion that the fluctuation does not result from any real growth in student numbers. Changes in statistical methods, terminology used in the field, norms, education systems or even social phenomena can also cause distortion.Artikkelissa tarkastellaan inklusiivisen kasvatuksen ideologian ja kansallisen koulutuspolitiikan välistä ristiriitaa suomalaisessa peruskoulukasvatuksessa. Tarkastelun aikaperspektiivi on kaksi vuosikymmentä ja sen takaraja on vuosituhannen vaihde. Artikkelin taustalla ovat havainnot, joiden mukaan inklusiivisen kasvatuksen ihanteiden mukainen koulun muutos on Suomessa toteutunut varsin hitaasti, vaikka suomalainen koulutuspolitiikka on periaatteellisella tasolla sitoutunut moniin kansainvälisiin julkilausumiin edistääkseen osaltaan inkluusioideologian mukaista koulun kehittämistä

    Efficiency in nanostructured thermionic and thermoelectric devices

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    Advances in solid-state device design now allow the spectrum of transmitted electrons in thermionic and thermoelectric devices to be engineered in ways that were not previously possible. Here we show that the shape of the electron energy spectrum in these devices has a significant impact on their performance. We distinguish between traditional thermionic devices where electron momentum is filtered in the direction of transport only and a second type, in which the electron filtering occurs according to total electron momentum. Such 'total momentum filtered' kr thermionic devices could potentially be implemented in, for example, quantum dot superlattices. It is shown that whilst total momentum filtered thermionic devices may achieve efficiency equal to the Carnot value, traditional thermionic devices are limited to efficiency below this. Our second main result is that the electronic efficiency of a device is not only improved by reducing the width of the transmission filter as has previously been shown, but also strongly depends on whether the transmission probability rises sharply from zero to full transmission. The benefit of increasing efficiency through a sharply rising transmission probability is that it can be achieved without sacrificing device power, in contrast to the use of a narrow transmission filter which can greatly reduce power. We show that devices which have a sharply-rising transmission probability significantly outperform those which do not and it is shown such transmission probabilities may be achieved with practical single and multibarrier devices. Finally, we comment on the implications of the effect the shape of the electron energy spectrum on the efficiency of thermoelectric devices.Comment: 11 pages, 15 figure

    Calorimetric readout of a superconducting proximity-effect thermometer

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    A proximity-effect thermometer measures the temperature dependent critical supercurrent in a long superconductor - normal metal - superconductor (SNS) Josephson junction. Typically, the transition from the superconducting to the normal state is detected by monitoring the appearance of a voltage across the junction. We describe a new approach to detect the transition based on the temperature increase in the resistive state due to Joule heating. Our method increases the sensitivity and is especially applicable for temperatures below about 300 mK.Comment: 10 pages, 5 figures. To appear in the proceedings of the Conference on Micro- and Nanocryogenics (LT25 satellite) organized in Espoo, Finland (2008

    Expression of toll-like receptors in non-endemic nasopharyngeal carcinoma

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    BackgroundNasopharyngeal carcinoma (NPC) is a malignant disease with an enigmatic etiology. NPC associates with Epstein-Barr virus (EBV) and human papillomaviruses (HPVs), while immunological factors also play a role in carcinogenesis. Toll-like receptors (TLRs) are pattern recognition receptors that participate in the immunological defence against pathogens, but their functions are also linked to cancer.MethodsIn our whole population-based study, we retrieved 150 Finnish NPC cases and studied their tumour samples for TLR1, TLR2, TLR4, TLR5, TLR7, and TLR9 expressions by immunohistochemistry, and for the presence of EBV and high-risk HPVs with EBV RNA and HPV E6/E7 mRNA in situ hybridizations. In addition, we analyzed the TLR expression patterns according to age, tumour histology, EBV/HPV status, and outcome.ResultsWe found that all TLRs studied were highly expressed in NPC. Viral status of the tumours varied, and 62% of them were EBV-positive, 14% HPV-positive, and 24% virus-negative. The tumours with strong TLR2(nucl) or TLR5 expression were mostly virus-negative or HPV-positive keratinizing squamous cell carcinomas, and the patients with these tumours were significantly older than those with mild or negative TLR2(nucl)/TLR5 expression. In Kaplan-Meier analysis, the patients with strong TLR5 expression had worse survival compared to the patients with negative or mild TLR5 expression, but the results were linked to other patient and tumour characteristics. In multivariable-adjusted Cox regression analysis, the patients with positive TLR7 tumour expression had better overall survival than those with no TLR7 expression. The 5-year overall survival rates according to TLR7 expression were 66% (mild), 52% (moderate or strong), and 22% (negative).ConclusionsTLRs are highly expressed in non-endemic NPC. Intensity of TLR2 and TLR5 expressions correlate with viral status, and TLR7 seems to be an independent prognostic factor of non-endemic NPC.</p

    Learning Impact of a Virtual Brain Electrical Activity Simulator Among Neurophysiology Students: Mixed-Methods Intervention Study

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    Background:Virtual simulation is the re-creation of reality depicted on a computer screen. It offers the possibility to exercise motor and psychomotor skills. In biomedical and medical education, there is an attempt to find new ways to support students’ learning in neurophysiology. Traditionally, recording electroencephalography (EEG) has been learned through practical hands-on exercises. To date, virtual simulations of EEG measurements have not been used.Objective:This study aimed to examine the development of students’ theoretical knowledge and practical skills in the EEG measurement when using a virtual EEG simulator in biomedical laboratory science in the context of a neurophysiology course.Methods:A computer-based EEG simulator was created. The simulator allowed virtual electrode placement and EEG graph interpretation. The usefulness of the simulator for learning EEG measurement was tested with 35 participants randomly divided into three equal groups. Group 1 (experimental group 1) used the simulator with fuzzy feedback, group 2 (experimental group 2) used the simulator with exact feedback, and group 3 (control group) did not use a simulator. The study comprised pre- and posttests on theoretical knowledge and practical hands-on evaluation of EEG electrode placement.Results:The Wilcoxon signed-rank test indicated that the two groups that utilized a computer-based electrode placement simulator showed significant improvement in both theoretical knowledge (Z=1.79, P=.074) and observed practical skills compared with the group that studied without a simulator.Conclusions:Learning electrode placement using a simulator enhances students’ ability to place electrodes and, in combination with practical hands-on training, increases their understanding of EEG measurement.</p

    Extracellular Matrix Aggregates from Differentiating Embryoid Bodies as a Scaffold to Support ESC Proliferation and Differentiation

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    Embryonic stem cells (ESCs) have emerged as potential cell sources for tissue engineering and regeneration owing to its virtually unlimited replicative capacity and the potential to differentiate into a variety of cell types. Current differentiation strategies primarily involve various growth factor/inducer/repressor concoctions with less emphasis on the substrate. Developing biomaterials to promote stem cell proliferation and differentiation could aid in the realization of this goal. Extracellular matrix (ECM) components are important physiological regulators, and can provide cues to direct ESC expansion and differentiation. ECM undergoes constant remodeling with surrounding cells to accommodate specific developmental event. In this study, using ESC derived aggregates called embryoid bodies (EB) as a model, we characterized the biological nature of ECM in EB after exposure to different treatments: spontaneously differentiated and retinoic acid treated (denoted as SPT and RA, respectively). Next, we extracted this treatment-specific ECM by detergent decellularization methods (Triton X-100, DOC and SDS are compared). The resulting EB ECM scaffolds were seeded with undifferentiated ESCs using a novel cell seeding strategy, and the behavior of ESCs was studied. Our results showed that the optimized protocol efficiently removes cells while retaining crucial ECM and biochemical components. Decellularized ECM from SPT EB gave rise to a more favorable microenvironment for promoting ESC attachment, proliferation, and early differentiation, compared to native EB and decellularized ECM from RA EB. These findings suggest that various treatment conditions allow the formulation of unique ESC-ECM derived scaffolds to enhance ESC bioactivities, including proliferation and differentiation for tissue regeneration applications. © 2013 Goh et al

    Cell-in-cell phenomenon associates with aggressive characteristics and cancer-related mortality in early oral tongue cancer

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    BackgroundCell-in-cell structures (caused by cell cannibalistic activity) have been related to prognosis of many cancers. This is the first multi-institutional study to assess the prognostic impact of cell-in-cell structures in a large cohort of early oral tongue squamous cell carcinomas (OTSCC).MethodsA total of 308 cases from five Finnish University Hospitals and from the A.C. Camargo Cancer Center, SAo Paulo, Brazil, were included in this study. Cell-in-cell structures were evaluated on surgical postoperative sections that stained with hematoxylin and eosin staining.ResultsWe found that cell-in-cell structures associated with cancer-related mortality in univariable analysis with a hazard ratio (HR) of 2.99 (95%CI 1.52-5.88; P=0.001). This association was confirmed in multivariable analysis (HR 2.22, 95%CI 1.12-4.44; P=0.024). In addition, statistically significant associations were observed between the cell-in-cell structures and other adverse histopathologic characteristics including deep invasion (P< 0.001), high index of tumor budding (P=0.007), worst pattern of invasion (P< 0.001), perineural invasion (P=0.01), and stroma-rich pattern (P=0.001).ConclusionsOur findings demonstrate a significant relationship between cell-in-cell formation and aggressive characteristics of early OTSCC. Cell-in-cell structures have a distinct impact as a novel prognostic indicator in early OTSCC and they can be easily assessed during routine pathology practice
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