15,762 research outputs found
A Sub-block Based Image Retrieval Using Modified Integrated Region Matching
This paper proposes a content based image retrieval (CBIR) system using the
local colour and texture features of selected image sub-blocks and global
colour and shape features of the image. The image sub-blocks are roughly
identified by segmenting the image into partitions of different configuration,
finding the edge density in each partition using edge thresholding followed by
morphological dilation. The colour and texture features of the identified
regions are computed from the histograms of the quantized HSV colour space and
Gray Level Co- occurrence Matrix (GLCM) respectively. The colour and texture
feature vectors is computed for each region. The shape features are computed
from the Edge Histogram Descriptor (EHD). A modified Integrated Region Matching
(IRM) algorithm is used for finding the minimum distance between the sub-blocks
of the query and target image. Experimental results show that the proposed
method provides better retrieving result than retrieval using some of the
existing methods.Comment: 7 page
Nickel-catalyzed transamidation of aliphatic amide derivatives.
Transamidation, or the conversion of one amide to another, is a long-standing challenge in organic synthesis. Although notable progress has been made in the transamidation of primary amides, the transamidation of secondary amides has remained underdeveloped, especially when considering aliphatic substrates. Herein, we report a two-step approach to achieve the transamidation of secondary aliphatic amides, which relies on non-precious metal catalysis. The method involves initial Boc-functionalization of secondary amide substrates to weaken the amide C-N bond. Subsequent treatment with a nickel catalyst, in the presence of an appropriate amine coupling partner, then delivers the net transamidated products. The transformation proceeds in synthetically useful yields across a range of substrates. A series of competition experiments delineate selectivity patterns that should influence future synthetic design. Moreover, the transamidation of Boc-activated secondary amide derivatives bearing epimerizable stereocenters underscores the mildness and synthetic utility of this methodology. This study provides the most general solution to the classic problem of secondary amide transamidation reported to date
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Measuring ligand efficacy at the mu-opioid receptor using a conformational biosensor.
The intrinsic efficacy of orthosteric ligands acting at G-protein-coupled receptors (GPCRs) reflects their ability to stabilize active receptor states (R*) and is a major determinant of their physiological effects. Here, we present a direct way to quantify the efficacy of ligands by measuring the binding of a R*-specific biosensor to purified receptor employing interferometry. As an example, we use the mu-opioid receptor (µ-OR), a prototypic class A GPCR, and its active state sensor, nanobody-39 (Nb39). We demonstrate that ligands vary in their ability to recruit Nb39 to µ-OR and describe methadone, loperamide, and PZM21 as ligands that support unique R* conformation(s) of µ-OR. We further show that positive allosteric modulators of µ-OR promote formation of R* in addition to enhancing promotion by orthosteric agonists. Finally, we demonstrate that the technique can be utilized with heterotrimeric G protein. The method is cell-free, signal transduction-independent and is generally applicable to GPCRs
Novel type of phase transition in a system of self-driven particles
A simple model with a novel type of dynamics is introduced in order to
investigate the emergence of self-ordered motion in systems of particles with
biologically motivated interaction. In our model particles are driven with a
constant absolute velocity and at each time step assume the average direction
of motion of the particles in their neighborhood with some random perturbation
() added. We present numerical evidence that this model results in a
kinetic phase transition from no transport (zero average velocity, ) to finite net transport through spontaneous symmetry breaking of the
rotational symmetry. The transition is continuous since is
found to scale as with
Theory of pressure acoustics with boundary layers and streaming in curved elastic cavities
The acoustic fields and streaming in a confined fluid depend strongly on the
acoustic boundary layer forming near the wall. The width of this layer is
typically much smaller than the bulk length scale set by the geometry or the
acoustic wavelength, which makes direct numerical simulations challenging.
Based on this separation in length scales, we extend the classical theory of
pressure acoustics by deriving a boundary condition for the acoustic pressure
that takes boundary-layer effects fully into account. Using the same
length-scale separation for the steady second-order streaming, and combining it
with time-averaged short-range products of first-order fields, we replace the
usual limiting-velocity theory with an analytical slip-velocity condition on
the long-range streaming field at the wall. The derived boundary conditions are
valid for oscillating cavities of arbitrary shape and wall motion as long as
the wall curvature and displacement amplitude are both sufficiently small.
Finally, we validate our theory by comparison with direct numerical simulation
in two examples of two-dimensional water-filled cavities: The well-studied
rectangular cavity with prescribed wall actuation, and the more generic
elliptical cavity embedded in an externally actuated rectangular elastic glass
block.Comment: 18 pages, 5 figures, pdfLatex, RevTe
Evidence for CO2-rich fluids in rocks from the type charnockite area near Pallavaram, Tamil Nadu
Fluid inclusion and mineral chemistry data was presented for samples from the type charnockite area near Pallavaram (Tamil Nadu, India). The results indicate the presence of a dense CO2 fluid phase, but the data cannot distinguish between influx of this fluid from elsewhere or localized migration of CO2-rich fluids associated with dehydration melting
The Use of DISC Behavioral Profiling and Training: An Innovative Pedagogical Strategy to Enhance Learning and Future Career Opportunities in Sport Management and Sport Coaching Higher Education Classrooms
Implementing effective training and education programs is of critical importance for sport management and sport coaching academic education programs. This exploratory research examined the implementation and effectiveness of DISC behavioral profiling in sport management and sport coaching classrooms at the university level. Over four academic years (eight semesters), pre- and post-tests were collected from multiple samples of sport management and sport coaching students (N = 216) at two universities in the United States. Students received a personalized DISC behavioral profile and educational activities were used to enhance the value of the behavioral profiling initiatives. Using pre- and post-activity surveys of the knowledge and skills gained during in-course activities, paired sample t-test showed positive and significant results for 11 of 16 measured areas. The findings suggest that behavioral profiling tools and activities within sport management and sport coaching curricula can enhance student’s self-awareness and help develop leadership skills which will prepare for future career opportunities. Limitations and opportunities for future research are also presented
Lubricating Bacteria Model for Branching growth of Bacterial Colonies
Various bacterial strains (e.g. strains belonging to the genera Bacillus,
Paenibacillus, Serratia and Salmonella) exhibit colonial branching patterns
during growth on poor semi-solid substrates. These patterns reflect the
bacterial cooperative self-organization. Central part of the cooperation is the
collective formation of lubricant on top of the agar which enables the bacteria
to swim. Hence it provides the colony means to advance towards the food. One
method of modeling the colonial development is via coupled reaction-diffusion
equations which describe the time evolution of the bacterial density and the
concentrations of the relevant chemical fields. This idea has been pursued by a
number of groups. Here we present an additional model which specifically
includes an evolution equation for the lubricant excreted by the bacteria. We
show that when the diffusion of the fluid is governed by nonlinear diffusion
coefficient branching patterns evolves. We study the effect of the rates of
emission and decomposition of the lubricant fluid on the observed patterns. The
results are compared with experimental observations. We also include fields of
chemotactic agents and food chemotaxis and conclude that these features are
needed in order to explain the observations.Comment: 1 latex file, 16 jpeg files, submitted to Phys. Rev.
Hierarchical population model with a carrying capacity distribution
A time- and space-discrete model for the growth of a rapidly saturating local
biological population is derived from a hierarchical random deposition
process previously studied in statistical physics. Two biologically relevant
parameters, the probabilities of birth, , and of death, , determine the
carrying capacity . Due to the randomness the population depends strongly on
position, , and there is a distribution of carrying capacities, .
This distribution has self-similar character owing to the imposed hierarchy.
The most probable carrying capacity and its probability are studied as a
function of and . The effective growth rate decreases with time, roughly
as in a Verhulst process. The model is possibly applicable, for example, to
bacteria forming a "towering pillar" biofilm. The bacteria divide on randomly
distributed nutrient-rich regions and are exposed to random local bactericidal
agent (antibiotic spray). A gradual overall temperature change away from
optimal growth conditions, for instance, reduces bacterial reproduction, while
biofilm development degrades antimicrobial susceptibility, causing stagnation
into a stationary state.Comment: 25 pages, 11 (9+2) figure
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