104,846 research outputs found
Determination of Propranolol Hydrochloride in Pharmaceutical Preparations Using Near Infrared Spectrometry with Fiber Optic Probe and Multivariate Calibration Methods
A method for determination of propranolol hydrochloride in pharmaceutical preparation using near infrared spectrometry with fiber optic probe (FTNIR/PROBE) and combined with chemometric methods was developed. Calibration models were developed using two variable selection models: interval partial least squares (iPLS) and synergy interval partial least squares (siPLS). The treatments based on the mean centered data and multiplicative scatter correction (MSC) were selected for models construction. A root mean square error of prediction (RMSEP) of 8.2 mg g −1 was achieved using siPLS (s2i20PLS) algorithm with spectra divided into 20 intervals and combination of 2 intervals (8501 to 8801 and 5201 to 5501 cm −1 ). Results obtained by the proposed method were compared with those using the pharmacopoeia reference method and significant difference was not observed. Therefore, proposed method allowed a fast, precise, and accurate determination of propranolol hydrochloride in pharmaceutical preparations. Furthermore, it is possible to carry out on-line analysis of this active principle in pharmaceutical formulations with use of fiber optic probe
Anatomy of a Duality
The nature of M-theory on K3 X I, where I is a line interval, is considered,
with a view towards formulating a `matrix theory' representation of that
situation. Various limits of this compactification of M-theory yield a number
of well known N=1 six dimensional compactifications of the heterotic and type I
string theories. Geometrical relations between these limits give rise to
string/string dualities between some of these compactifications. At a special
point in the moduli space of compactifications, this motivates a partial
definition of the matrix theory representation of the M-theory on K3 X I as the
large N limit of a certain type IA orientifold model probed by a conglomerate
of N D-branes. Such a definition in terms of D-branes and orientifold planes is
suggestive, but necessarily incomplete, due to the low amount of superymmetry.
It is proposed - following hints from the orientifold model - that the complete
matrix theory representation of the K3 X I compactified M-theory is given by
the large N limit of compactification - on a suitable `dual' surface - of the
`little heterotic string' N = 1 six dimensional quantum theories.Comment: 55 pages, harvmac.tex (`b' mode), epsf.tex for 3 figures, (Some
references were corrected. Small adjustments to text and abstract. Physics
unchanged
Orientifold dual for stuck NS5 branes
We establish T-duality between NS5 branes stuck on an orientifold 8-plane in
type I' and an orientifold construction in type IIB with D7 branes intersecting
at angles. Two applications are discussed. For one we obtain new brane
constructions, realizing field theories with gauge group a product of
symplectic factors, giving rise to a large new class of conformal N=1 theories
embedded in string theory. Second, by studying a D2 brane probe in the type I'
background, we get some information on the still elusive (0,4) linear sigma
model describing a perturbative heterotic string on an ADE singularity.Comment: 24 pages, LaTeX, references adde
Calabi-Yau mirror symmetry as a gauge theory duality
Using brane set-ups we construct dual gauge theories in two dimensions with calN = (2,2) supersymmetry. Two different dualities are realized. One is basically a consequence of three-dimensional mirror symmetry. The nonlinear sigma model with a Calabi-Yau target space on the Higgs branch of the gauge theory is mapped into an equivalent non-linear sigma model on the Coulomb branch on the dual, realizing a T-dual target space with torsion. The second dual is genuine to two dimensions. In addition to swapping Higgs and Coulomb branches it trades twisted for untwisted multiplets, implying a sign flip of the left-moving U (1)R charge. Successive application of both dualities leads to geometric mirror symmetry for the Calabi-Yau target space
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Validation of data analysis routines for a thermal probe apparatus using numerical data sets
Most thermal properties of construction materials used in the analysis of building performance have been measured under laboratory conditions, using a guarded hot box or hot plate apparatus. As a consequence, these properties seldom reflect the impact of actual conditions (especially moisture content) on the values of conductivity and diffusivity. Hence there is a need to develop techniques that allow to take into account local conditions, and measure building material properties in situ. One option available is the use of a thermal probe. The thermal probe technique is based on creating a line source in a material sample, and measuring the temperature rise in the sample in reaction to heat being applied. Obviously the data analysis routines used to calculate thermal conductivity and thermal diffusivity based on the temperature rise observed are crucial to the success of the technique. Transient thermal simulation of a of a model representing a line source in an infinite material sample has been used to generate a set of numerical data sets to validate analysis routines in conjunction with an experimental thermal probe apparatus. Findings show that by careful application of these routines, a close agreement with simulation input values can be achieved, with errors of less than one percent. This validates the analysis routines and provides a deeper appreciation of the theoretical behaviour of a thermal probe
2.5D multi-view gait recognition based on point cloud registration
This paper presents a method for modeling a 2.5-dimensional (2.5D) human body and extracting the gait features for identifying the human subject. To achieve view-invariant gait recognition, a multi-view synthesizing method based on point cloud registration (MVSM) to generate multi-view training galleries is proposed. The concept of a density and curvature-based Color Gait Curvature Image is introduced to map 2.5D data onto a 2D space to enable data dimension reduction by discrete cosine transform and 2D principle component analysis. Gait recognition is achieved via a 2.5D view-invariant gait recognition method based on point cloud registration. Experimental results on the in-house database captured by a Microsoft Kinect camera show a significant performance gain when using MVSM
Observational bounds on the cosmic radiation density
We consider the inference of the cosmic radiation density, traditionally
parameterised as the effective number of neutrino species N_eff, from precision
cosmological data. Paying particular attention to systematic effects, notably
scale-dependent biasing in the galaxy power spectrum, we find no evidence for a
significant deviation of N_eff from the standard value of N_eff^0=3.046 in any
combination of cosmological data sets, in contrast to some recent conclusions
of other authors. The combination of all available data in the linear regime
prefers, in the context of a ``vanilla+N_eff'' cosmological model,
1.1<N_eff<4.8 (95% C.L.) with a best-fit value of 2.6. Adding data at smaller
scales, notably the Lyman-alpha forest, we find 2.2<N_eff<5.8 (95% C.L.) with
3.8 as the best fit. Inclusion of the Lyman-alpha data shifts the preferred
N_eff upwards because the sigma_8 value derived from the SDSS Lyman-alpha data
is inconsistent with that inferred from CMB. In an extended cosmological model
that includes a nonzero mass for N_eff neutrino flavours, a running scalar
spectral index and a w parameter for the dark energy, we find 0.8<N_eff<6.1
(95% C.L.) with 3.0 as the best fit.Comment: 23 pages, 3 figures, uses iopart.cls; v2: 1 new figure, references
added, matches published versio
Optimal change-point estimation from indirect observations
We study nonparametric change-point estimation from indirect noisy
observations. Focusing on the white noise convolution model, we consider two
classes of functions that are smooth apart from the change-point. We establish
lower bounds on the minimax risk in estimating the change-point and develop
rate optimal estimation procedures. The results demonstrate that the best
achievable rates of convergence are determined both by smoothness of the
function away from the change-point and by the degree of ill-posedness of the
convolution operator. Optimality is obtained by introducing a new technique
that involves, as a key element, detection of zero crossings of an estimate of
the properly smoothed second derivative of the underlying function.Comment: Published at http://dx.doi.org/10.1214/009053605000000750 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
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