593 research outputs found
Dissipation, Lorentz metric and information: a phenomenological calculus of bilinear forms
AbstractThe geometry and physics of three symmetric bilinear forms on the description space, which in our phenomenological calculus underlies the representation of complex systems, are discussed. These three bilinear forms represent dissipation, Lorentz metric and information, and their mathematical connections model a variety of physical and biological concepts, such as space and time, communication, causality, aging, discrimination and measurement. The phenomenological calculus of bilinear forms thus provides a unified theory of thermodynamics, relativity and quantum mechanics
Pulmicort® turbohaler® once daily as initial prophylactic therapy for asthma
AbstractIn a double-blind, randomized, parallel-group clinical trial, 340 asthmatic patients aged 12–70 years received budesonide 400 μg once daily in the morning, budesonide 400 μg once daily in the evening, budesonide 200 μg twice daily or placebo, for 12 weeks in addition to inhaled short-acting β2-agonists used as required (p.r.n.). Budesonide was given as Pulmicort Turbohaler.Peak expiratory flow rate (PEFR) increased by 20 to 30 1 min−1 in each of the active treatment groups, significantly more than in the placebo group (P<0·01). There were no significant differences between the active treatment groups. Symptom improvement and decreased β2-agonist use reflected the PEFR data. Incidences of adverse events in the active treatment groups were similar to those observed in the placebo group.Budesonide 400 μg given once daily morning or evening is equieffective with the same total daily dose given twice daily in the treatment of mild to moderate stable asthmatics
Vale of York 3-D borehole interpretation and cross-sections study
The Vale of York between Doncaster and Scunthorpe in the south and York and Bugthorpe in
the north is largely underlain by bedrock of the Sherwood Sandstone Group – one of the regions
principal aquifers. Significant superficial deposits of Quaternary age overlie the Sherwood
Sandstone. This study aims to investigate the nature of these superficial deposits with respect to
their relationship with the underlying aquifer.
The Vale of York project area represents a varied glaciated terrain, consisting of pro-glacial finegrained
sediments, coarser glaciofluvilal sediments and extensive glacial tills. These diverse
superficial units vary in thickness throughout the project area. The hydrogeological nature of the
natural superficial sequence is consequently highly variable. Units may be considered as
aquitards, while others may act as aquifers, providing a potential pathway to the underlying
sandstone. The classification of lithologies as aquifer or aquitard is described in detail in this
report.
To investigate the hydrogeological nature of the superficial sequence, six east-west and three
north-south lithostratigraphical cross-sections were constructed. A range of geoscientific
information was considered, including existing geological mapping and over 3000 fully
attributed and coded boreholes. The cross-sections show a subdivision of the superficial
sequence into lithostratigraphical units. Each unit is described in detail in this report.
In addition, a series of thematic maps were generated from the lithological component of the
digital borehole data. Total superficial aquifer and superficial aquitard maps show how the
lithological nature of the superficial sequence varies across the area. Rockhead elevation and
superficial thickness maps indicate where the sandstone aquifer outcrops at the ground surface.
In summary, four main lithostratigraphical units overlie the Sherwood Sandstone Group aquifer
in the project area: a basal sequence of glaciofluvial sand and gravel (interpreted as a superficial
aquifer), glaciolacustrine laminated silt & clay (aquitard), glacial till comprising sandy gravelly
clay (aquitard), and a cover sequence of fluvial and aeolian sand, clay and peat (aquifer /
aquitard). The correlations illustrate that in certain areas, superficial deposits are thin or absent
and that in these areas the Sherwood Sandstone aquifer comes directly to ground surface
Theory of band gap bowing of disordered substitutional II-VI and III-V semiconductor alloys
For a wide class of technologically relevant compound III-V and II-VI
semiconductor materials AC and BC mixed crystals (alloys) of the type
A(x)B(1-x)C can be realized. As the electronic properties like the bulk band
gap vary continuously with x, any band gap in between that of the pure AC and
BC systems can be obtained by choosing the appropriate concentration x, granted
that the respective ratio is miscible and thermodynamically stable. In most
cases the band gap does not vary linearly with x, but a pronounced bowing
behavior as a function of the concentration is observed. In this paper we show
that the electronic properties of such A(x)B(1-x)C semiconductors and, in
particular, the band gap bowing can well be described and understood starting
from empirical tight binding models for the pure AC and BC systems. The
electronic properties of the A(x)B(1-x)C system can be described by choosing
the tight-binding parameters of the AC or BC system with probabilities x and
1-x, respectively. We demonstrate this by exact diagonalization of finite but
large supercells and by means of calculations within the established coherent
potential approximation (CPA). We apply this treatment to the II-VI system
Cd(x)Zn(1-x)Se, to the III-V system In(x)Ga(1-x)As and to the III-nitride
system Ga(x)Al(1-x)N.Comment: 14 pages, 10 figure
The First High-Precision Radial Velocity Search for Extra-Solar Planets
In the late 1970s and early 1980s, the introduction of solid-state,
signal-generating detectors and absorption cells to impose wavelength fiducials
directly on the starlight, the errors in stellar radial velocity (RV)
measurements were reduced to the point where Doppler searches for planets
became feasible. In 1980 we began to use a hydrogen fluoride gas cell with the
CFHT coud\'{e} spectrograph and, for 12 years, monitored RVs of some 29
solar-type stars. Since extra-solar planets were expected to resemble Jupiter
in both mass and orbit, we were awarded only three or four two-night observing
runs each year. In 1988 we highlighted a potential planetary companion to
Cep (K1 IV), in 1993 one to Gem (K0 III), and another to
Eri (K2 V) in 1992. The putative planets all resembled Jovian
systems with periods and masses of 2.5 yr and 1.4 , 1.6 yr and 2.6
, and 6.9 yr and 0.9 , respectively. All three were subsequently
confirmed from more extensive data by the Texas group led by Cochran and Hatzes
who derived the currently accepted orbital elements. None of the systems is
simple and some still question Eri b.Comment: 23 pages, 7 figure
Multiband tight-binding theory of disordered ABC semiconductor quantum dots: Application to the optical properties of alloyed CdZnSe nanocrystals
Zero-dimensional nanocrystals, as obtained by chemical synthesis, offer a
broad range of applications, as their spectrum and thus their excitation gap
can be tailored by variation of their size. Additionally, nanocrystals of the
type ABC can be realized by alloying of two pure compound semiconductor
materials AC and BC, which allows for a continuous tuning of their absorption
and emission spectrum with the concentration x. We use the single-particle
energies and wave functions calculated from a multiband sp^3 empirical
tight-binding model in combination with the configuration interaction scheme to
calculate the optical properties of CdZnSe nanocrystals with a spherical shape.
In contrast to common mean-field approaches like the virtual crystal
approximation (VCA), we treat the disorder on a microscopic level by taking
into account a finite number of realizations for each size and concentration.
We then compare the results for the optical properties with recent experimental
data and calculate the optical bowing coefficient for further sizes
On the isoperimetric problem for the Laplacian with Robin and Wentzell boundary conditions
Doctor of PhilosophyWe consider the problem of minimising the eigenvalues of the Laplacian with Robin boundary conditions and generalised Wentzell boundary conditions with respect to the domain on which the problem is defined. For the Robin problem, when we extend the Faber-Krahn inequality of Daners [Math. Ann. 335 (2006), 767--785], which states that the ball minimises the first eigenvalue, to prove that the minimiser is unique amongst domains of class . The method of proof uses a functional of the level sets to estimate the first eigenvalue from below, together with a rearrangement of the ball's eigenfunction onto the domain and the usual isoperimetric inequality.
We then prove that the second eigenvalue attains its minimum only on the disjoint union of two equal balls, and set the proof up so it works for the Robin -Laplacian. For the higher eigenvalues, we show that it is in general impossible for a minimiser to exist independently of . When , we prove that every eigenvalue behaves like as , provided only that is bounded with boundary. This generalises a result of Lou and Zhu [Pacific J. Math. 214 (2004), 323--334] for the first eigenvalue.
For the Wentzell problem, we (re-)prove general operator properties, including for the less-studied case establish a type of equivalence property between the Wentzell and Robin minimisers for all eigenvalues. This yields a minimiser of the second Wentzell eigenvalue. We also prove a Cheeger-type inequality for the first eigenvalue in this case
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