770 research outputs found
Feasibility of MRI-guided large-core-needle biopsy of suspiscious breast lesions at 3 T
The feasibility of large-core-needle magnetic resonance imaging (MRI)-guided breast biopsy at 3 T was assessed. Thirty-one suspicious breast lesions shown only by MRI were detected in 30 patients. Biopsy procedures were performed in a closed-bore 3-T clinical MR system on a dedicated phased-array breast coil with a commercially available add-on stereotactic biopsy device. Tissue sampling was technically successful in 29/31 (94%) lesions. Median lesion size (n = 29) was 9 mm. Histopathological analysis showed 19 benign lesions (66%) and one inconclusive biopsy result (3%). At follow-up of these lesions, 15 lesions showed no malignancy, no information was available in three patients and two lesions turned out to be malignant (one lesion at surgical excision 1 month after biopsy and one lesion at a second biopsy because of a more malignant enhancement curve at 12-months follow-up MRI). Nine biopsy results showed a malignant lesion (31%) which were all surgically removed. No complications occurred. MRI-guided biopsy at 3 T is a safe and effective method for breast biopsy in lesions that are occult on mammography and ultrasound. Follow-up MRI at 6 months after the biopsy should be performed in case of a benign biopsy result
An Evolutionary Reduction Principle for Mutation Rates at Multiple Loci
A model of mutation rate evolution for multiple loci under arbitrary
selection is analyzed. Results are obtained using techniques from Karlin (1982)
that overcome the weak selection constraints needed for tractability in prior
studies of multilocus event models. A multivariate form of the reduction
principle is found: reduction results at individual loci combine topologically
to produce a surface of mutation rate alterations that are neutral for a new
modifier allele. New mutation rates survive if and only if they fall below this
surface - a generalization of the hyperplane found by Zhivotovsky et al. (1994)
for a multilocus recombination modifier. Increases in mutation rates at some
loci may evolve if compensated for by decreases at other loci. The strength of
selection on the modifier scales in proportion to the number of germline cell
divisions, and increases with the number of loci affected. Loci that do not
make a difference to marginal fitnesses at equilibrium are not subject to the
reduction principle, and under fine tuning of mutation rates would be expected
to have higher mutation rates than loci in mutation-selection balance. Other
results include the nonexistence of 'viability analogous, Hardy-Weinberg'
modifier polymorphisms under multiplicative mutation, and the sufficiency of
average transmission rates to encapsulate the effect of modifier polymorphisms
on the transmission of loci under selection. A conjecture is offered regarding
situations, like recombination in the presence of mutation, that exhibit
departures from the reduction principle. Constraints for tractability are:
tight linkage of all loci, initial fixation at the modifier locus, and mutation
distributions comprising transition probabilities of reversible Markov chains.Comment: v3: Final corrections. v2: Revised title, reworked and expanded
introductory and discussion sections, added corollaries, new results on
modifier polymorphisms, minor corrections. 49 pages, 64 reference
Lateral Gene Expression in Drosophila Early Embryos Is Supported by Grainyhead-Mediated Activation and Tiers of Dorsally-Localized Repression
The general consensus in the field is that limiting amounts of the transcription factor Dorsal establish dorsal boundaries of genes expressed along the dorsal-ventral (DV) axis of early Drosophila embryos, while repressors establish ventral boundaries. Yet recent studies have provided evidence that repressors act to specify the dorsal boundary of intermediate neuroblasts defective (ind), a gene expressed in a stripe along the DV axis in lateral regions of the embryo. Here we show that a short 12 base pair sequence (“the A-box”) present twice within the ind CRM is both necessary and sufficient to support transcriptional repression in dorsal regions of embryos. To identify binding factors, we conducted affinity chromatography using the A-box element and found a number of DNA-binding proteins and chromatin-associated factors using mass spectroscopy. Only Grainyhead (Grh), a CP2 transcription factor with a unique DNA-binding domain, was found to bind the A-box sequence. Our results suggest that Grh acts as an activator to support expression of ind, which was surprising as we identified this factor using an element that mediates dorsally-localized repression. Grh and Dorsal both contribute to ind transcriptional activation. However, another recent study found that the repressor Capicua (Cic) also binds to the A-box sequence. While Cic was not identified through our A-box affinity chromatography, utilization of the same site, the A-box, by both factors Grh (activator) and Cic (repressor) may also support a “switch-like” response that helps to sharpen the ind dorsal boundary. Furthermore, our results also demonstrate that TGF-β signaling acts to refine ind CRM expression in an A-box independent manner in dorsal-most regions, suggesting that tiers of repression act in dorsal regions of the embryo
The UN in the lab
We consider two alternatives to inaction for governments combating terrorism, which we term Defense and Prevention. Defense consists of investing in resources that reduce the impact of an attack, and generates a negative externality to other governments, making their countries a more attractive objective for terrorists. In contrast, Prevention, which consists of investing in resources that reduce the ability of the terrorist organization to mount an attack, creates a positive externality by reducing the overall threat of terrorism for all. This interaction is captured using a simple 3×3 “Nested Prisoner’s Dilemma” game, with a single Nash equilibrium where both countries choose Defense. Due to the structure of this interaction, countries can benefit from coordination of policy choices, and international institutions (such as the UN) can be utilized to facilitate coordination by implementing agreements to share the burden of Prevention. We introduce an institution that implements a burden-sharing policy for Prevention, and investigate experimentally whether subjects coordinate on a cooperative strategy more frequently under different levels of cost sharing. In all treatments, burden sharing leaves the Prisoner’s Dilemma structure and Nash equilibrium of the game unchanged. We compare three levels of burden sharing to a baseline in a between-subjects design, and find that burden sharing generates a non-linear effect on the choice of the efficient Prevention strategy and overall performance. Only an institution supporting a high level of mandatory burden sharing generates a significant improvement in the use of the Prevention strategy
Effect of Electron Energy Distribution Function on Power Deposition and Plasma Density in an Inductively Coupled Discharge at Very Low Pressures
A self-consistent 1-D model was developed to study the effect of the electron
energy distribution function (EEDF) on power deposition and plasma density
profiles in a planar inductively coupled plasma (ICP) in the non-local regime
(pressure < 10 mTorr). The model consisted of three modules: (1) an electron
energy distribution function (EEDF) module to compute the non-Maxwellian EEDF,
(2) a non-local electron kinetics module to predict the non-local electron
conductivity, RF current, electric field and power deposition profiles in the
non-uniform plasma, and (3) a heavy species transport module to solve for the
ion density and velocity profiles as well as the metastable density. Results
using the non-Maxwellian EEDF model were compared with predictions using a
Maxwellian EEDF, under otherwise identical conditions. The RF electric field,
current, and power deposition profiles were different, especially at 1mTorr,
for which the electron effective mean free path was larger than the skin depth.
The plasma density predicted by the Maxwellian EEDF was up to 93% larger for
the conditions examined. Thus, the non-Maxwellian EEDF must be accounted for in
modeling ICPs at very low pressures.Comment: 19 pages submitted to Plasma Sources Sci. Techno
A neural oscillations perspective on phonological development and phonological processing in developmental dyslexia
Children’s ability to reflect upon and manipulate the sounds in words (’phonological awareness’) develops as part of natural language acquisition, supports reading acquisition, and develops further as reading and spelling are learned. Children with developmental dyslexia typically have impairments in phonological awareness. Many developmental factors contribute to individual differences in phonological development. One important source of individual differences may be the child’s sensory/neural processing of the speech signal from an amplitude modulation (~ energy or intensity variation) perspective, which may affect the quality of the sensory/neural representations (’phonological representations’) that support phonological awareness. During speech encoding, brain electrical rhythms (oscillations, rhythmic variations in neural excitability) re-calibrate their temporal activity to be in time with rhythmic energy variations in the speech signal. The accuracy of this neural alignment or ’entrainment’ process is related to speech intelligibility. Recent neural studies demonstrate atypical oscillatory function at slower rates in children with developmental dyslexia. Potential relations with the development of phonological awareness by children with dyslexia are discussed.Medical Research Council, G0400574 and G090237
Is zero underestimation feasible? Extended Vacuum-assisted breast biopsy in solid lesions – a blind study
This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
Meson-Meson Scattering in the Quark Model: Spin Dependence and Exotic Channels
We apply a quark interchange model to spin-dependent and exotic meson-meson
scattering. The model includes the complete set of standard quark model forces,
including OGE spin-orbit and tensor and scalar confinement spin-orbit.
Scattering amplitudes derived assuming SHO and Coulomb plus linear plus
hyperfine meson wavefunctions are compared. In I=2 pi pi we find approximate
agreement with the S-wave phase shift from threshold to 1.5 GeV, where we
predict an extremum that is supported by the data. Near threshold we find rapid
energy dependence that may reconcile theoretical estimates of small scattering
lengths with experimental indications of larger ones based on extrapolation of
measurements at moderate kpi^2. In PsV scattering we find that the quark-quark
L*S and T forces map into L*S and T meson-meson interactions, and the P-wave
L*S force is large. Finally we consider scattering in J^PC-exotic channels, and
note that some of the Deck effect mechanisms suggested as possible nonresonant
origins of the pi_1(1400) signal are not viable in this model.Comment: 51 pages, 10 figures, uses epsf.sty epsfig.st
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