8,260 research outputs found
Systematic trends in beta-delayed particle emitting nuclei: The case of beta-p-alpha emission from 21Mg
We have observed beta+-delayed alpha and p-alpha emission from the
proton-rich nucleus 21Mg produced at the ISOLDE facility at CERN. The
assignments were cross-checked with a time distribution analysis. This is the
third identified case of beta-p-alpha emission. We discuss the systematic of
beta-delayed particle emission decays, show that our observed decays fit
naturally into the existing pattern, and argue that the patterns are to a large
extent caused by odd-even effects.Comment: 6 pages, 5 figure
Rational sequences for the conductance in quantum wires from affine Toda field theories
We analyse the expression for the conductance of a quantum wire which is
decribed by an integrable quantum field theory. In the high temperature regime
we derive a simple formula for the filling fraction. This expression involves
only the inverse of a matrix which contains the information of the asymptotic
phases of the scattering matrix and the solutions of the constant thermodynamic
Bethe ansatz equations. Evaluating these expressions for minimal affine Toda
field theory we recover several sequences of rational numbers, which are
multiples of the famous Jain sequence for the filling fraction occurring in the
context of the fractional quantum Hall effect. For instance we obtain for -minimal affine Toda field theory. The matrices
involved have in general non-rational entries and are not part of previous
classification schemes based on integral lattices.Comment: 9 pages Latex, version to appear in Journal of Physics
Customer Focused Price Optimisation
Tesco want to better understand how to set online prices for their general merchandise (i.e. not groceries or clothes) in the UK. Because customers can easily compare prices from different retailers we expect they will be very sensitive to price, so it is important to get it right. There are four aspects of the problem.
âą Forecasting: Estimating the customer demand as a function of the price chosen (especially hard for products with no sales history or infrequent sales).
âą Objective function: What exactly should Tesco aim to optimise? Sales volume? Profit? Profit margin? Conversion rates?
âą Optimisation: How to choose prices for many related products to optimise the chosen objective function.
âą Evalution: How to demonstrate that the chosen prices are optimal, especially to people without a mathematical background.
Aggregate sales data was provided for about 400 products over about 2 years so that quantitive approaches could be tested. For some products competitorsâ prices were also provided
Team i kommunal sektor
Tema for prosjektoppgaven er teamorganisering i kommunal sektor. I oppgaven har vi tatt for oss en teammodell i en kommunal enhet som bĂ„de er demokratisk og kostnadseffektiv. Ved Ă„ se nĂŠrmere pĂ„ hvilke suksesskriterier som ligger til grunn for teammodellen, har mĂ„let vĂŠrt Ă„ finne ut om den kan overfĂžres til andre kommunale enheter. Resultatene viser at teammodellen krever gode rammebetingelser for at den skal fungere optimalt. SĂŠrlig strukturell myndiggjĂžring er av stor betydning, det vil si en flatere organisering som gir medbestemmelse og ansvar til teamene. Av resultatene ser vi at teamlederen har en sentral rolle i teammodellen. Teamlederen er operativ, det vil si at han bĂ„de har personalansvar og deltar i produksjonen pĂ„ linje med Ăžvrige teammedlemmer. Ăkt motivasjon, trivsel og lĂŠring er effekter av teammodellen, i tillegg til hĂžy kvalitet pĂ„ tjenesteproduksjonen. Sammen med relevant teori har informasjon fra ni dybdeintervju gitt svar pĂ„ vĂ„r problemstilling. Prosjektoppgaven konkluderer med at teammodellen er veien Ă„ gĂ„ for flere kommunale enheter
Approximating k-Forest with Resource Augmentation: A Primal-Dual Approach
In this paper, we study the -forest problem in the model of resource
augmentation. In the -forest problem, given an edge-weighted graph ,
a parameter , and a set of demand pairs , the
objective is to construct a minimum-cost subgraph that connects at least
demands. The problem is hard to approximate---the best-known approximation
ratio is . Furthermore, -forest is as hard to
approximate as the notoriously-hard densest -subgraph problem.
While the -forest problem is hard to approximate in the worst-case, we
show that with the use of resource augmentation, we can efficiently approximate
it up to a constant factor.
First, we restate the problem in terms of the number of demands that are {\em
not} connected. In particular, the objective of the -forest problem can be
viewed as to remove at most demands and find a minimum-cost subgraph that
connects the remaining demands. We use this perspective of the problem to
explain the performance of our algorithm (in terms of the augmentation) in a
more intuitive way.
Specifically, we present a polynomial-time algorithm for the -forest
problem that, for every , removes at most demands and has
cost no more than times the cost of an optimal algorithm
that removes at most demands
Deltagardriven forskning â VĂ€xtodlingsgruppen, resultat och utvĂ€rdering av arbetet under 1998 till 2001
DÄ arbetet i vÀxtodlingsgruppen pÄbörjades var förvÀntningarna pÄ deltagardriven forskning att den sammanlagda erfarenheten hos lantbrukare, forskare och rÄdgivare skulle bidra till utförandet av relevanta gÄrdsförsök. Lantbrukarna önskade dessutom strÀva efter att öka och vidarebefordra den kunskap som fanns i gruppen, samt att fÄ etablerade forskare att undersöka omrÄden som praktikerna upplever som viktiga och svÄra.
Redan i initialskedet slog vÀxtodlingsgruppen fast att arbeta för att gemensamt identifiera problem och anvÀnda relevanta forskningsmetoder pÄ gÄrdsnivÄ. Syftet var att genom olika odlingsÄtgÀrder kunna förbÀttra förutsÀttningarna för ekologisk vÀxtodling. Ett mÄl var att finna effektiva metoder för optimal vÀxtnÀringstillförsel i ekologisk produktion pÄ lerjordar i MÀlardalen. För nÀrvarande saknas bra underlag för hur kvÀveleveransen varierar under sÀsongen framförallt till strÄsÀd. Detta pÄverkar i sin tur bÄde skördeutfall, proteinhalt, miljöbelastning och ekonomi. Ett annat mÄl var att kunna reglera ogrÀsförekomsten, frÀmst kvickrot och tistel, pÄ ett effektivt sÀtt i vÀxtföljden.
Motivationen för lantbrukarna har under projektets gÄng varit att frÀmja det ekologiska lantbruket som helhet. Detta har möjliggjorts genom erfarenhetsutbyte pÄ grupptrÀffar kombinerat med gÄrdsbesök dÀr lantbrukarnas intressen och frÄgestÀllningar har varit drivande. VÀxtodlingsgruppen har pÄ sÄ vis initialt bidragit till ett lokalt utvecklingsarbete och en uppbyggnad av ökat kunnande inom ekologiskt vÀxtodling
Plasma cell-free DNA methylation marks for episodic memory impairment : a pilot twin study
Decline in episodic memory performance usually causes the first clinical symptoms of Alzheimer's disease. At present, Alzheimer's disease can only be diagnosed at a very late stage when neurodegeneration and cognitive impairment is already irreversible. New early disease markers are needed for earlier and more efficient Alzheimer's disease intervention. To identify early disease markers, we implemented a genome-wide bisulphite sequencing method for the analysis of plasma cell-free DNA methylation profiles and compared differences associated with episodic memory performance in Finnish twin pairs. A noticeable amount of cell-free DNA was present in plasma, however, the amounts as well as the genomic coverage of these fragments varied substantially between individuals. We found no significant markers associated with episodic memory performance in the twins' plasma cell-free DNA methylation profiles. Furthermore, our results indicate that due to the low genomic coverage of cell-free DNA fragments and the variety in these fragments between individuals, the implemented genome-wide bisulphite sequencing method is not optimal for comparing cell-free DNA methylation differences between large groups of individuals.Peer reviewe
(Total) Vector Domination for Graphs with Bounded Branchwidth
Given a graph of order and an -dimensional non-negative
vector , called demand vector, the vector domination
(resp., total vector domination) is the problem of finding a minimum
such that every vertex in (resp., in ) has
at least neighbors in . The (total) vector domination is a
generalization of many dominating set type problems, e.g., the dominating set
problem, the -tuple dominating set problem (this is different from the
solution size), and so on, and its approximability and inapproximability have
been studied under this general framework. In this paper, we show that a
(total) vector domination of graphs with bounded branchwidth can be solved in
polynomial time. This implies that the problem is polynomially solvable also
for graphs with bounded treewidth. Consequently, the (total) vector domination
problem for a planar graph is subexponential fixed-parameter tractable with
respectto , where is the size of solution.Comment: 16 page
Development of an analogue optical link for the front-end read-out of the ATLAS electromagnetic calorimeter
We have developed an analogue optical data transmission system intended to meet the read-out requirements of the ATLAS liquid argon electromagnetic calorimeter. Eight-way demonstrators have been built and tested. The link uses arrays of VCSEL diodes as the optical emitters, coupled to a 70 m long fibre ribbon to simulate the distance between the detector and the control room. The receiver is based around a custom-designed PIN photodiode array. We describe here the final results of laboratory tests on a demonstrator, laying stress on the VCSEL-to-fibre coupling issues, and the overall performance of the full link. A 9-bit dynamic range is achieved, with a 5on-linearity
- âŠ