10,475 research outputs found
Quantitative classification of breast fine needle aspirates using the AxioHOME system
Fine needle aspiration cytology is useful in the pre-operative assessment of patients with breast lumps. Lesions are reported as benign, suspicious or malignant. The number of suspicious categories is high in inexperienced hands thus limiting this useful diagnostic tool. The aim was to evaluate quantitative methods of classifying breast fine needle aspirates using the Highly Optimized Microscope Environment system. May- Grumwald Giemsa-stained archived slides were retrieved and smear quality assessed. Fifty epithelial cells corresponding to the cytological grading on each slide were measured using the system\'s general morphometry program. Generated data was exported to Microsoft Excel for analysis. A significant difference in the mean nuclear area, mean nuclear perimeter, mean largest nuclear diameter was found between the slides graded as benign, suspicious malignant and malignant. C2 & C4, D 1, P < 0.004. C4 & C5, Area P < 0.001. The means of
the number count of nucleoli was able to distinguish between FNAC Benign and Malignant category C2/C5, P = 00440 and suspicious benign and malignant C3/C5 P = 0.00486. Morphometry could be useful in situations where experienced cytopathologists are unavailable especially when this program can also measure the degree of dispersion between cells Keywords: Morphometric image analysis, aspiration cytology, breast. International Journal of Biological and Chemical Sciences Vol. 2 (2) 2008: pp. 139-14
Atomic Model of Susy Hubbard Operators
We apply the recently proposed susy Hubbard operators to an atomic model. In
the limiting case of free spins, we derive exact results for the entropy which
are compared with a mean field + gaussian corrections description. We show how
these results can be extended to the case of charge fluctuations and calculate
exact results for the partition function, free energy and heat capacity of an
atomic model for some simple examples. Wavefunctions of possible states are
listed. We compare the accuracy of large N expansions of the susy spin
operators with those obtained using `Schwinger bosons' and `Abrikosov
pseudo-fermions'. For the atomic model, we compare results of slave boson,
slave fermion, and susy Hubbard operator approximations in the physically
interesting but uncontrolled limiting case of N->2. For a mixed representation
of spins we estimate the accuracy of large N expansions of the atomic model. In
the single box limit, we find that the lowest energy saddle-point solution
reduces to simply either slave bosons or slave fermions, while for higher boxes
this is not the case. The highest energy saddle-point solution has the
interesting feature that it admits a small region of a mixed representation,
which bears a superficial resemblance to that seen experimentally close to an
antiferromagnetic quantum critical point.Comment: 17 pages + 7 pages Appendices, 14 figures. Substantial revision
Exponentially Large Probabilities in Quantum Gravity
The problem of topology change transitions in quantum gravity is investigated
from the Wheeler-de Witt wave function point of view. It is argued that for all
theories allowing wormhole effects the wave function of the universe is
exponentially large. If the wormhole action is positive, one can try to
overcome this difficulty by redefinition of the inner product, while for the
case of negative wormhole action the more serious problems arise.Comment: 9 pages in LaTeX, 4 figures in PostScript, the brief version of this
paper is to appear in Proceedings of the XXIV ITEP Winter School of Physic
Minority Becomes Majority in Social Networks
It is often observed that agents tend to imitate the behavior of their
neighbors in a social network. This imitating behavior might lead to the
strategic decision of adopting a public behavior that differs from what the
agent believes is the right one and this can subvert the behavior of the
population as a whole.
In this paper, we consider the case in which agents express preferences over
two alternatives and model social pressure with the majority dynamics: at each
step an agent is selected and its preference is replaced by the majority of the
preferences of her neighbors. In case of a tie, the agent does not change her
current preference. A profile of the agents' preferences is stable if the
preference of each agent coincides with the preference of at least half of the
neighbors (thus, the system is in equilibrium).
We ask whether there are network topologies that are robust to social
pressure. That is, we ask if there are graphs in which the majority of
preferences in an initial profile always coincides with the majority of the
preference in all stable profiles reachable from that profile. We completely
characterize the graphs with this robustness property by showing that this is
possible only if the graph has no edge or is a clique or very close to a
clique. In other words, except for this handful of graphs, every graph admits
at least one initial profile of preferences in which the majority dynamics can
subvert the initial majority. We also show that deciding whether a graph admits
a minority that becomes majority is NP-hard when the minority size is at most
1/4-th of the social network size.Comment: To appear in WINE 201
An Upper Bound on the Higgs Boson Mass from a Positivity Condition on the Mass Matrix
We impose the condition that the eigenvalues of the mass matrix in the
shifted Lagrangian density be positive at \phi=\phi_{0}, the vacuum expectation
value of the scalar field. Using the one-loop effective potential of the
standard model, this condition leads to an upper bound on the Higgs boson mass
m_{H}: m_{H}<230GeV, for a top quark mass of 175GeV.Comment: LaTex, 5 page
Fermionic Determinant of the Massive Schwinger Model
A representation for the fermionic determinant of the massive Schwinger
model, or , is obtained that makes a clean separation between the
Schwinger model and its massive counterpart. From this it is shown that the
index theorem for follows from gauge invariance, that the Schwinger
model's contribution to the determinant is canceled in the weak field limit,
and that the determinant vanishes when the field strength is sufficiently
strong to form a zero-energy bound state
Failure of Mean Field Theory at Large N
We study strongly coupled lattice QCD with colors of staggered fermions
in 3+1 dimensions. While mean field theory describes the low temperature
behavior of this theory at large , it fails in the scaling region close to
the finite temperature second order chiral phase transition. The universal
critical region close to the phase transition belongs to the 3d XY universality
class even when becomes large. This is in contrast to Gross-Neveu models
where the critical region shrinks as (the number of flavors) increases and
mean field theory is expected to describe the phase transition exactly in the
limit of infinite . Our work demonstrates that close to second order phase
transitions infrared fluctuations can sometimes be important even when is
strictly infinite.Comment: 4 pages, 3 figure
Co-operative Kondo Effect in the two-channel Kondo Lattice
We discuss the possibility of a co-operative Kondo effect driven by channel
interference in a Kondo lattice where local moments are coupled to a single
Fermi sea via two orthogonal scattering channels. In this situation, the
channel quantum number is not conserved. We argue that the absence of channel
conservation causes the Kondo effect in the two channels to constructively
interfere, giving rise to a superconducting condensate of composite pairs,
formed between the local moments and the conduction electrons. Our arguments
are based on the observation that a heavy Fermi surface gives rise to zero
modes for Kondo singlets to fluctuate between screening channels of different
symmetry, producing a divergent composite pair susceptibility. Secondary
screening channels couple to these divergent fluctuations, promoting an
instability into a state with long-range composite order. We present detailed a
detailed mean-field theory for this superconducting phase, and discuss the
possible implications for heavy fermion physics.Comment: 23 double column pages. 9 fig
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Can measurements of the near-infrared solar spectral irradiance be reconciled? A new ground-based assessment between 4000-10000 cm-1
The near-infrared solar spectral irradiance (SSI) is of vital importance for understanding the Earth’s radiation budget, and in Earth observation applications. Differences between previously published solar spectra (including the commonly-used ATLAS3 spectrum) reach up to 10% at the low-wavenumber end of the 4000-10000 cm-1 (2.5 – 1 μm) spectral region. The implications for the atmospheric sciences are significant, since this spectral region contains 25% of the incoming total solar irradiance. This work details an updated analysis of the CAVIAR SSI, featuring additional analysis techniques and an updated uncertainty budget using a Monte Carlo method. We report good consistency with ATLAS3 in the 7000-10000 cm-1 region where there is confidence in these results due to agreement with other spectra, but ~7% lower in the 4000-7000 cm-1 region, in general agreement with several other analyses
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