752 research outputs found

    A General Approach of Quasi-Exactly Solvable Schroedinger Equations with Three Known Eigenstates

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    We propose a general method for constructing quasi-exactly solvable potentials with three analytic eigenstates. These potentials can be real or complex functions but the spectrum is real. A comparison with other methods is also performed

    Performance evaluation of humidity controlled ventilation strategies in residential buildings

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    Occupational burden of disease in the Netherlands

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    Ongunstige arbeidsomstandigheden veroorzaken 2 tot 4% van de totale ziektelast in Nederland. Het begrip ziektelast is een maatstaf om de gevolgen van ziekte uit te drukken. Het combineert gezondheidsverlies door verminderde kwaliteit van leven en door vroegtijdig overlijden. Hoge werkdruk, blootstelling aan schadelijke stoffen (inclusief passief roken) en beeldschermwerk zijn de ongunstigste arbeidsomstandigheden. Zij zorgen voor veel ziektelast door burn-out, de chronische luchtwegaandoening COPD, longkanker en klachten van arm, nek en schouder (KANS). In het rapport is de positieve invloed van arbeid op de gezondheid niet meegenomen. Het RIVM laat voor het eerst zien welke arbeidsgerelateerde aandoeningen veel ziektelast in Nederland veroorzaken. Deze gegevens bieden aanknopingspunten voor verder onderzoek en voor maatregelen om de ziektelast door deze aandoeningen te verminderen. Dat is niet alleen goed voor werknemers en werkgevers, maar ook voor de volksgezondheid en de samenleving in haar geheel: health is wealth. In eerdere ziektelastberekeningen van de wereldgezondheidsorganisatie (WHO) is de arbeidsgerelateerde ziektelast in Nederland sterk onderschat. In Nederland veroorzaken niet zozeer de 'klassieke' risico's en aandoeningen, zoals arbeidsongevallen en slechthorendheid door lawaai, de meeste ziektelast. Juist 'nieuwe' aandoeningen, zoals burn-out en KANS, leiden hiertoe, en die zijn niet meegenomen in de WHO-schattingen. Behalve negatieve effecten op de gezondheid hebben ongunstige arbeidsomstandigheden een nadelig effect op de arbeidsproductiviteit, het ziekteverzuim en arbeidsongeschiktheid. In theorie blijkt het mogelijk om deze effecten te berekenen. Het is aan te bevelen om uit te zoeken of dit in de praktijk haalbaar is.Occupational health risks cause 2 to 4% of the total burden of disease in the Netherlands. The concept of burden of disease is a criterion to express the consequences of disease. It combines the time lived with disability and the time lost due to premature mortality. A high workload, exposure to harmful chemicals (including environmental tobacco smoke) and working with a computer are the most unfavourable working conditions. They contribute most to the occupational burden of disease caused by: burn-out, chronic obstructive pulmonary disease, lung cancer and complaints of arm, neck and shoulder (CANS). The health benefits of work were not included in this report. For the first time, the RIVM shows in this study which occupational diseases contribute most to the burden of disease in the Netherlands. The data offer starting points for further research and measures to reduce the burden of disease caused by these complaints. This is good not only for employers and employees but also for public health and society as a whole: health is wealth. The World Health Organization (WHO) underestimated the occupational burden of disease in the Netherlands in its earlier burden of disease assessments. In the Netherlands, most of the burden of disease is not caused by the 'classical' risks and diseases like accidents and hearing impairment caused by noise. Rather 'new' diseases like burn-out and CANS cause considerable loss of health and were not taken into account in the assessments of the WHO. Unfavourable working conditions do not only have negative effects on health, but also have a disadvantageous effect on productivity, absenteeism and incapacity for work. In theory it is possible to estimate these adverse effects. We therefore advise to study whether estimating them is feasible in practice.SZ

    A General Approach of Quasi-Exactly Solvable Schroedinger Equations

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    We construct a general algorithm generating the analytic eigenfunctions as well as eigenvalues of one-dimensional stationary Schroedinger Hamiltonians. Both exact and quasi-exact Hamiltonians enter our formalism but we focus on quasi-exact interactions for which no such general approach has been considered before. In particular we concentrate on a generalized sextic oscillator but also on the Lame and the screened Coulomb potentials.Comment: 23 pages, no figur

    Darboux transformations for quasi-exactly solvable Hamiltonians

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    We construct new quasi-exactly solvable one-dimensional potentials through Darboux transformations. Three directions are investigated: Reducible and two types of irreducible second-order transformations. The irreducible transformations of the first type give singular intermediate potentials and the ones of the second type give complex-valued intermediate potentials while final potentials are meaningful in all cases. These developments are illustrated on the so-called radial sextic oscillator.Comment: 11 pages, Late

    Effects of non-local exchange on core level shifts for gas-phase and adsorbed molecules

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    Density functional theory calculations are often used to interpret experimental shifts in core level binding energies. Calculations based on gradient-corrected (GC) exchange-correlation functionals are known to reproduce measured core level shifts (CLS) of isolated molecules and metal surfaces with reasonable accuracy. In the present study, we discuss a series of examples where the shifts calculated within a GC-functional significantly deviate from the experimental values, namely the CLS of C 1s in ethyl trifluoroacetate, Pd 3d in PdO and the O 1s shift for CO adsorbed on PdO(101). The deviations are traced to effects of the electronic self-interaction error with GC-functionals and substantially better agreements between calculated and measured CLS are obtained when a fraction of exact exchange is used in the exchange-correlation functional

    N\'eel and Spin-Peierls ground states of two-dimensional SU(N) quantum antiferromagnets

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    The two-dimensional SU(N) quantum antiferromagnet, a generalization of the quantum Heisenberg model, is investigated by quantum Monte Carlo simulations. The ground state for N‚ȧ4N\le 4 is found to be of the N\'eel type with broken SU(N) symmetry, whereas it is of the Spin-Peierls type for N‚Č•5N\ge 5 with broken lattice translational invariance. No intermediate spin-liquid phase was observed in contrast to previous numerical simulations on smaller lattices [Santoro et al., Phys. Rev. Lett. {\bf 83} 3065 (1999)].Comment: 4 pages, 4 figure

    Cost-effectiveness study of early versus late parenteral nutrition in critically ill children (PEPaNIC)

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    __Background:__ The multicentre randomised controlled PEPaNIC trial showed that withholding parenteral nutrition (PN) during the first week of critical illness in children was clinically superior to providing early PN. This study describes the cost-effectiveness of this new nutritional strategy. __Methods:__ Direct medical costs were calculated with use of a micro-costing approach. We compared the costs of late versus early initiation of PN (n = 673 versus n = 670 pa
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