6,295 research outputs found
Feasibility study of an Integrated Program for Aerospace vehicle Design (IPAD). Volume 3: Support of the design process
The user requirements for computer support of the IPAD design process are identified. The user-system interface, language, equipment, and computational requirements are considered
Analytical solutions of the Schr\"{o}dinger equation with the Woods-Saxon potential for arbitrary state
In this work, the analytical solution of the radial Schr\"{o}dinger equation
for the Woods-Saxon potential is presented. In our calculations, we have
applied the Nikiforov-Uvarov method by using the Pekeris approximation to the
centrifugal potential for arbitrary states. The bound state energy
eigenvalues and corresponding eigenfunctions are obtained for various values of
and quantum numbers.Comment: 14 page
Mortality study of 18 000 patients treated with omeprazole.
Background: The long term safety of potent gastric acid suppressive therapy has yet to be established.
Method: General practice record review at a median interval of 26 months followed by retrieval of details of all deaths within four years using the UK National Health Service Central Registers in 17 936 patients prescribed omeprazole in 1993–1995. Death rates were compared with general population rates.
Results: Records of 17 489 patients (97.5%) were examined. A total of 12 703 patients received further scripts for antisecretory drugs, 8097 for omeprazole only (65.6%): 3097 patients have died. All cause mortality was higher in the first year (observed/expected (O/E) 1.44 (95% confidence intervals (CI) 1.34–1.55); p<0.0001) but had fallen to population expectation by the fourth year. There were significant mortality increases in the first year, falling to or below population expectation by the fourth year, for deaths ascribed to neoplasms (1.82 (95% CI 1.58–2.08); p<0.0001), circulatory diseases (1.27 (95% CI 1.13–1.43); p<0.0001), and respiratory diseases (1.37 (95% CI 1.12–1.64); p<0.001). Increased mortality ascribed to digestive diseases (2.56 (95% CI 1.87–3.43); p<0.0001) persisted, although reduced. Increased mortality rates for cancers of the stomach (4.06 (95% CI 2.60–6.04); p<0.0001), colon and rectum (1.40 (95% CI 0.84–2.18); p=0.075), and trachea, bronchus, and lung (1.64 (95% CI 1.19–2.19); p<0.01) seen in the first year had disappeared by the fourth year but that for cancer of the oesophagus had not (O/E 7.35 (95% CI 5.20–10.09) (p<0.0001) in year 1; 2.88 (95% CI 1.62–4.79) (p<0.001) in year 4). Forty of 78 patients dying of oesophageal cancer had the disease present at registration. Twenty seven of those remaining cases had clinical evidence of Barrett’s disease, stricture, ulcer, or oesophagitis at registration (O/E 3.30 (95% CI 2.17–4.80)). Six deaths occurred in patients with hiatal hernia or reflux only (O/E 1.02 (95% CI 0.37–2.22)) and five in patients without oesophageal disease (O/E 0.77 (95% CI 0.25–1.80)). No relationships were detected with numbers of omeprazole scripts received.
Conclusions: Increases in mortality associated with treatment are due to pre- existing illness, including pre-existing severe oesophageal disease. There was no evidence of an increased risk of oesophageal adenocarcinoma in those without oesophageal mucosal damage recorded at registration
Asymptotic behavior of the least common multiple of consecutive arithmetic progression terms
Let and be two integers with , and let and be
integers with and . In this paper, we prove that , where is a constant depending on and .Comment: 8 pages. To appear in Archiv der Mathemati
Helical, Angular and Radial Ordering in Narrow Capillaries
To enlighten the nature of the order-disorder and order-order transitions in
block copolymer melts confined in narrow capillaries we analyze peculiarities
of the conventional Landau weak crystallization theory of systems confined to
cylindrical geometry. This phenomenological approach provides a quantitative
classification of the cylindrical ordered morphologies by expansion of the
order parameter spatial distribution into the eigenfunctions of the Laplace
operator. The symmetry of the resulting ordered morphologies is shown to
strongly depend both on the boundary conditions (wall preference) and the ratio
of the cylinder radius and the wave length of the critical order parameter
fluctuations, which determine the bulk ordering of the system under
consideration. In particular, occurrence of the helical morphologies is a
rather general consequence of the imposed cylindrical symmetry for narrow
enough capillaries. We discuss also the ODT and OOT involving some other
simplest morphologies. The presented results are relevant also to other
ordering systems as charge-density waves appearing under addition of an ionic
solute to a solvent in its critical region, weakly charged polyelectrolyte
solutions in poor solvent, microemulsions etc.Comment: 6 pages, 3 figure
Mass as a Relativistic Quantum Observable
A field state containing photons propagating in different directions has a
non vanishing mass which is a quantum observable. We interpret the shift of
this mass under transformations to accelerated frames as defining space-time
observables canonically conjugated to energy-momentum observables. Shifts of
quantum observables differ from the predictions of classical relativity theory
in the presence of a non vanishing spin. In particular, quantum redshift of
energy-momentum is affected by spin. Shifts of position and energy-momentum
observables however obey simple universal rules derived from invariance of
canonical commutators.Comment: 5 pages, revised versio
Closed form representation for a projection onto infinitely dimensional subspace spanned by Coulomb bound states
The closed form integral representation for the projection onto the subspace
spanned by bound states of the two-body Coulomb Hamiltonian is obtained. The
projection operator onto the dimensional subspace corresponding to the
-th eigenvalue in the Coulomb discrete spectrum is also represented as the
combination of Laguerre polynomials of -th and -th order. The latter
allows us to derive an analog of the Christoffel-Darboux summation formula for
the Laguerre polynomials. The representations obtained are believed to be
helpful in solving the breakup problem in a system of three charged particles
where the correct treatment of infinitely many bound states in two body
subsystems is one of the most difficult technical problems.Comment: 7 page
Dynamic properties of the spin-1/2 XY chain with three-site interactions
We consider a spin-1/2 XY chain in a transverse (z) field with multi-site
interactions. The additional terms introduced into the Hamiltonian involve
products of spin components related to three adjacent sites. A Jordan-Wigner
transformation leads to a simple bilinear Fermi form for the resulting
Hamiltonian and hence the spin model admits a rigorous analysis. We point out
the close relationships between several variants of the model which were
discussed separately in previous studies. The ground-state phases (ferromagnet
and two kinds of spin liquid) of the model are reflected in the dynamic
structure factors of the spin chains, which are the main focus in this study.
First we consider the zz dynamic structure factor reporting for this quantity a
closed-form expression and analyzing the properties of the two-fermion
(particle-hole) excitation continuum which governs the dynamics of transverse
spin component fluctuations and of some other local operator fluctuations. Then
we examine the xx dynamic structure factor which is governed by many-fermion
excitations, reporting both analytical and numerical results. We discuss some
easily recognized features of the dynamic structure factors which are
signatures for the presence of the three-site interactions.Comment: 28 pages, 10 fugure
Microbiological influences on fracture surfaces of intact mudstone and the implications for geological disposal of radioactive waste
The significance of the potential impacts of microbial activity on the transport properties of host rocks for geological repositories is an area of active research. Most recent work has focused on granitic environments. This paper describes pilot studies investigating changes in transport properties that are produced by microbial activity in sedimentary rock environments in northern Japan. For the first time, these short experiments (39 days maximum) have shown that the denitrifying bacteria, Pseudomonas denitrificans, can survive and thrive when injected into flow-through column experiments containing fractured diatomaceous mudstone and synthetic groundwater under pressurized conditions. Although there were few significant changes in the fluid chemistry, changes in the permeability of the biotic column, which can be explained by the observed biofilm formation, were quantitatively monitored. These same methodologies could also be adapted to obtain information from cores originating from a variety of geological environments including oil reservoirs, aquifers and toxic waste disposal sites to provide an understanding of the impact of microbial activity on the transport of a range of solutes, such as groundwater contaminants and gases (e.g. injected carbon dioxide)
The least common multiple of a sequence of products of linear polynomials
Let be the product of several linear polynomials with integer
coefficients. In this paper, we obtain the estimate: as , where is a constant depending on
.Comment: To appear in Acta Mathematica Hungaric
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