463 research outputs found

    Quasi-exactly solvable quartic: real algebraic spectral locus

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    We describe the real quasi-exactly solvable spectral locus of the PT-symmetric quartic using the Nevanlinna parametrization.Comment: 17 pages, 11 figure

    On eigenvalues of the Schr\"odinger operator with an even complex-valued polynomial potential

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    In this paper, we generalize several results of the article "Analytic continuation of eigenvalues of a quartic oscillator" of A. Eremenko and A. Gabrielov. We consider a family of eigenvalue problems for a Schr\"odinger equation with even polynomial potentials of arbitrary degree d with complex coefficients, and k<(d+2)/2 boundary conditions. We show that the spectral determinant in this case consists of two components, containing even and odd eigenvalues respectively. In the case with k=(d+2)/2 boundary conditions, we show that the corresponding parameter space consists of infinitely many connected components

    Quasi-exactly solvable quartic: elementary integrals and asymptotics

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    We study elementary eigenfunctions y=p exp(h) of operators L(y)=y"+Py, where p, h and P are polynomials in one variable. For the case when h is an odd cubic polynomial, we found an interesting identity which is used to describe the spectral locus. We also establish some asymptotic properties of the QES spectral locus.Comment: 20 pages, 1 figure. Added Introduction and several references, corrected misprint

    Transport and Environment Database System (TRENDS): Maritime Air Pollutant Emission Modelling

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    This paper reports the development of the maritime module within the framework of the Transport and Environment Database System (TRENDS) project. A detailed database has been constructed for the calculation of energy consumption and air pollutant emissions. Based on an in-house database of commercial vessels kept at the Technical University of Denmark, relationships between the fuel consumption and size of different vessels have been developed, taking into account the fleet's age and service speed. The technical assumptions and factors incorporated in the database are presented, including changes from findings reported in Methodologies for Estimating air pollutant Emissions from Transport (MEET). The database operates on statistical data provided by Eurostat, which describe vessel and freight movements from and towards EU 15 major ports. Data are at port to Maritime Coastal Area (MCA) level, so a bottom-up approach is used. A port to MCA distance database has also been constructed for the purpose of the study. This was the first attempt to use Eurostat maritime statistics for emission modelling; and the problems encountered, since the statistical data collection was not undertaken with a view to this purpose, are mentioned. Examples of the results obtained by the database are presented. These include detailed air pollutant emission calculations for bulk carriers entering the port of Helsinki, as an example of the database operation, and aggregate results for different types of movements for France. Overall estimates of SOx and NOx emission caused by shipping traffic between the EU 15 countries are in the area of 1 and 1.5 million tonnes, respectively

    An impairment-specific hip exoskeleton assistance for gait training in subjects with acquired brain injury: a feasibility study

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    This study was designed to investigate the feasibility and the potential effects on walking performance of a short gait training with a novel impairment-specific hip assistance (iHA) through a bilateral active pelvis orthosis (APO) in patients with acquired brain injury (ABI). Fourteen subjects capable of independent gait and exhibiting mild-to-moderate gait deficits, due to an ABI, were enrolled. Subjects presenting deficit in hip flexion and/or extension were included and divided into two groups based on the presence (group A, n = 6) or absence (group B, n = 8) of knee hyperextension during stance phase of walking. Two iHA-based profiles were developed for the groups. The protocol included two overground gait training sessions using APO, and two evaluation sessions, pre and post training. Primary outcomes were pre vs. post-training walking distance and steady-state speed in the 6-min walking test. Secondary outcomes were self-selected speed, joint kinematics and kinetics, gait symmetry and forward propulsion, assessed through 3D gait analysis. Following the training, study participants significantly increased the walked distance and average steady-state speed in the 6-min walking tests, both when walking with and without the APO. The increased walked distance surpassed the minimal clinically important difference for groups A and B, (respectively, 42 and 57&nbsp;m &gt; 34&nbsp;m). In group A, five out of six subjects had decreased knee hyperextension at the post-training session (on average the peak of the knee extension angle was reduced by 36%). Knee flexion during swing phase increased, by 16% and 31%, for A and B groups respectively. Two-day gait training with APO providing iHA was effective and safe in improving walking performance and knee kinematics in ABI survivors. These preliminary findings suggest that this strategy may be viable for subject-specific post-ABI gait rehabilitation

    Technology experience café - enabling technology - driven social innovation for an ageing society

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    Effective technology innovation process management in the context of active healthy ageing has the potential to improve older adults’ quality of life, allowing them to maintain their independence and age in their own homes for longer. But as older adults significantly differ from the general population in technology use and its impact on their quality of life, tools are needed that (1) involve this target group into the innovation process, as well as (2) capture the diverse needs of technology for various stakeholders involved in this process. This paper presents the framework called Technology Experience Café (TEC), developed within the European project SIforAGE, answering exactly this need. Detailed information on the methodology and its implementation in five sites, in four different countries across Europe, focusing on participating stakeholders, general design of the TEC, and used evaluation tools, is provided. Preliminary results show, that (1) the target group’s perception of the TEC as a framework was thoroughly positive and TECs had a positive impact on older adults’ technology related attitudes and (2) that stakeholders’ benefits affiliated with their involvement in the TECs are manifold. Implications and limitations are discussed

    Transcriptome and metabolome profiling identify factors potentially involved in pro-vitamin A accumulation in cassava landraces

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    Open Access ArticleCassava (Manihot esculenta Crantz) is a predominant food security crop in several developing countries. Its storage roots, rich in carbohydrate, are deficient in essential micronutrients, including provitamin A carotenoids. Increasing carotenoid content in cassava storage roots is important to reduce the incidence of vitamin A deficiency, a public health problem in sub-Saharan Africa. However, cassava improvement advances slowly, mainly due to limited information on the molecular factors influencing β-carotene accumulation in cassava. To address this problem, we performed comparative transcriptomic and untargeted metabolic analyses of roots and leaves of eleven African cassava landraces ranging from white to deep yellow colour, to uncover regulators of carotenoid biosynthesis and accumulation with conserved function in yellow cassava roots. Sequence analysis confirmed the presence of a mutation, known to influence β-carotene content, in PSY transcripts of deep yellow but not of pale yellow genotypes. We identified genes and metabolites with expression and accumulation levels significantly associated with β-carotene content. Particularly an increased activity of the abscisic acid catabolism pathway together with a reduced amount of L-carnitine, may be related to the carotenoid pathway flux, higher in yellow than in white storage roots. In fact, NCED_3.1 was specifically expressed at a lower level in all yellow genotypes suggesting that it could be a potential target for increasing carotenoid accumulation in cassava. These results expand the knowledge on metabolite compositions and molecular mechanisms influencing carotenoid biosynthesis and accumulation in cassava and provide novel information for biotechnological applications and genetic improvement of cassava with high nutritional values
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