4,188 research outputs found
Identification of neutral tumor evolution across cancer types
A.S. is supported by The Chris Rokos Fellowship in Evolution and Cancer.
B.W. is supported by the Geoffrey W. Lewis Post-Doctoral Training fellowship.
This work was supported by the Wellcome Trust (105104/Z/14/Z). C.P.B.
acknowledges funding from the Wellcome Trust through a Research Career
Development Fellowship (097319/Z/11/Z). This work was supported by a
Cancer Research UK Career Development Award to T.A.G. M.J.W. is supported
by a UK Medical Research Council student fellowship
Toward quantitative super-resolution microscopy: molecular maps with statistical guarantees
Quantifying the number of molecules from fluorescence microscopy measurements is an important topic in cell biology and medical research. In this work, we present a consecutive algorithm for super-resolution (stimulated emission depletion (STED)) scanning microscopy that provides molecule counts in automatically generated image segments and offers statistical guarantees in form of asymptotic confidence intervals. To this end, we first apply a multiscale scanning procedure on STED microscopy measurements of the sample to obtain a system of significant regions, each of which contains at least one molecule with prescribed uniform probability. This system of regions will typically be highly redundant and consists of rectangular building blocks. To choose an informative but non-redundant subset of more naturally shaped regions, we hybridize our system with the result of a generic segmentation algorithm. The diameter of the segments can be of the order of the resolution of the microscope. Using multiple photon coincidence measurements of the same sample in confocal mode, we are then able to estimate the brightness and number of molecules and give uniform confidence intervals on the molecule counts for each previously constructed segment. In other words, we establish a so-called molecular map with uniform error control. The performance of the algorithm is investigated on simulated and real data
Quantum-Classical Correspondence of Dynamical Observables, Quantization and the Time of Arrival Correspondence Problem
We raise the problem of constructing quantum observables that have classical
counterparts without quantization. Specifically we seek to define and motivate
a solution to the quantum-classical correspondence problem independent from
quantization and discuss the general insufficiency of prescriptive
quantization, particularly the Weyl quantization. We demonstrate our points by
constructing time of arrival operators without quantization and from these
recover their classical counterparts
Entanglement generation in continuously coupled parametric generators
We investigate a compact source of entanglement. This device is composed of a
pair of linearly coupled nonlinear waveguides operating by means of degenerate
parametric downconversion. For the vacuum state at the input the generalized
squeeze variance and logarithmic negativity are used to quantify the amount of
nonclassicality and entanglement of output beams. Squeezing and entanglement
generation for various dynamical regimes of the device are discussed.Comment: 6 pages, 7 figure
Eccrine porocarcinoma of the head: An important differential diagnosis in the elderly patient
Background: Eccrine porocarcinoma is a rare malignant tumor of the sweat gland, characterized by a broad spectrum of clinicopathologic presentations. Surprisingly, unlike its benign counterpart eccrine poroma, eccrine porocarcinoma is seldom found in areas with a high density of eccrine sweat glands, like the palms or soles. Instead, eccrine porocarcinoma frequently occurs on the lower extremities, trunk and abdomen, but also on the head, resembling various other skin tumors, as illustrated in the patients described herein. Observations: We report 5 cases of eccrine porocarcinoma of the head. All patients were initially diagnosed as having epidermal or melanocytic skin tumors. Only after histopathologic examination were they classified as eccrine porocarcinoma, showing features of epithelial tumors with abortive ductal differentiation. Characteristic clinical, histopathologic and immunohistochemical findings of eccrine porocarcinomas are illustrated. Conclusion: Eccrine porocarcinomas are potentially fatal adnexal malignancies, in which extensive metastatic dissemination may occur. Porocarcinomas are commonly overlooked, or misinterpreted as squamous or basal cell carcinomas as well as other common malignant and even benign skin tumors. Knowledge of the clinical pattern and histologic findings, therefore, is crucial for an early therapeutic intervention, which can reduce the risk of tumor recurrence and serious complications. Copyright (c) 2008 S. Karger AG, Basel
Theory of Photon Blockade by an Optical Cavity with One Trapped Atom
In our recent paper [1], we reported observations of photon blockade by one
atom strongly coupled to an optical cavity. In support of these measurements,
here we provide an expanded discussion of the general phenomenology of photon
blockade as well as of the theoretical model and results that were presented in
Ref. [1]. We describe the general condition for photon blockade in terms of the
transmission coefficients for photon number states. For the atom-cavity system
of Ref. [1], we present the model Hamiltonian and examine the relationship of
the eigenvalues to the predicted intensity correlation function. We explore the
effect of different driving mechanisms on the photon statistics. We also
present additional corrections to the model to describe cavity birefringence
and ac-Stark shifts. [1] K. M. Birnbaum, A. Boca, R. Miller, A. D. Boozer, T.
E. Northup, and H. J. Kimble, Nature 436, 87 (2005).Comment: 10 pages, 6 figure
An Explicit Strategy Prevails When the Cerebellum Fails to Compute Movement Errors
In sensorimotor adaptation, explicit cognitive strategies are thought to be unnecessary because the motor system implicitly corrects performance throughout training. This seemingly automatic process involves computing an error between the planned movement and actual feedback of the movement. When explicitly provided with an effective strategy to overcome an experimentally induced visual perturbation, people are immediately successful and regain good task performance. However, as training continues, their accuracy gets worse over time. This counterintuitive result has been attributed to the independence of implicit motor processes and explicit cognitive strategies. The cerebellum has been hypothesized to be critical for the computation of the motor error signals that are necessary for implicit adaptation. We explored this hypothesis by testing patients with cerebellar degeneration on a motor learning task that puts the explicit and implicit systems in conflict. Given this, we predicted that the patients would be better than controls in maintaining an effective strategy assuming strategic and adaptive processes are functionally and neurally independent. Consistent with this prediction, the patients were easily able to implement an explicit cognitive strategy and showed minimal interference from undesirable motor adaptation throughout training. These results further reveal the critical role of the cerebellum in an implicit adaptive process based on movement errors and suggest an asymmetrical interaction of implicit and explicit processes
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