284 research outputs found
Radiation back-reaction in relativistically strong and QED-strong laser fields
The emission from an electron in the field of a relativistically strong laser
pulse is analyzed. At the pulse intensities of \ge 10^{22} W/cm^2 the emission
from counter-propagating electrons is modified by the effects of Quantum
ElectroDynamics (QED), as long as the electron energy is sufficiently high: E
\ge 1 GeV. The radiation force experienced by an electron is for the first time
derived from the QED principles and its applicability range is extended towards
the QED-strong fields.Comment: 4 pages, 4 figure
Emission and its back-reaction accompanying electron motion in relativistically strong and QED-strong pulsed laser fields
The emission from an electron in the field of a relativistically strong laser
pulse is analyzed. At pulse intensities of J > 2 10^22 W/cm2 the emission from
counter-propagating electrons is modified by the effects of Quantum
ElectroDynamics (QED), as long as the electron energy is sufficiently high: E >
1 GeV. The radiation force experienced by an electron is for the first time
derived from the QED principles and its applicability range is extended towards
the QED-strong fields.Comment: 14 pages, 5 figures. Submitted to Phys.Rev.
Coherent control of plasma dynamics
Coherent control of a system involves steering an interaction to a final
coherent state by controlling the phase of an applied field. Plasmas support
coherent wave structures that can be generated by intense laser fields. Here,
we demonstrate the coherent control of plasma dynamics in a laser wakefield
electron acceleration experiment. A genetic algorithm is implemented using a
deformable mirror with the electron beam signal as feedback, which allows a
heuristic search for the optimal wavefront under laser-plasma conditions that
is not known a priori. We are able to improve both the electron beam charge and
angular distribution by an order of magnitude. These improvements do not simply
correlate with having the `best' focal spot, since the highest quality vacuum
focal spot produces a greatly inferior electron beam, but instead correspond to
the particular laser phase that steers the plasma wave to a final state with
optimal accelerating fields
Frizzled-8 integrates Wnt-11 and transforming growth factor-β signaling in prostate cancer
Wnt-11 promotes cancer cell migration and invasion independently of β-catenin but the receptors involved remain unknown. Here, we provide evidence that FZD8 is a major Wnt-11 receptor in prostate cancer that integrates Wnt-11 and TGF-β signals to promote EMT. FZD8 mRNA is upregulated in multiple prostate cancer datasets and in metastatic cancer cell lines in vitro and in vivo. Analysis of patient samples reveals increased levels of FZD8 in cancer, correlating with Wnt-11. FZD8 co-localizes and co-immunoprecipitates with Wnt-11 and potentiates Wnt-11 activation of ATF2-dependent transcription. FZD8 silencing reduces prostate cancer cell migration, invasion, three-dimensional (3D) organotypic cell growth, expression of EMT-related genes, and TGF-β/Smad-dependent signaling. Mechanistically, FZD8 forms a TGF-β-regulated complex with TGF-β receptors that is mediated by the extracellular domains of FZD8 and TGFBR1. Targeting FZD8 may therefore inhibit aberrant activation of both Wnt and TGF-β signals in prostate cancer
Multiple colliding electromagnetic pulses: a way to lower the threshold of pair production from vacuum
The scheme of simultaneous multiple pulse focusing on one spot naturally
arises from the structural features of projected new laser systems, such as ELI
and HiPER. It is shown that the multiple pulse configuration is beneficial for
observing pair production from vacuum under the action of sufficiently
strong electromagnetic fields. The field of the focused pulses is described
using a realistic three-dimensional model based on an exact solution of the
Maxwell equations. The pair production threshold in terms of
electromagnetic field energy can be substantially lowered if, instead of one or
even two colliding pulses, multiple pulses focused on one spot are used. The
multiple pulse interaction geometry gives rise to subwavelength field features
in the focal region. These features result in the production of extremely short
bunches.Comment: 10 pages, 4 figure
High Flux Femtosecond X-ray Emission from the Electron-Hose Instability in Laser Wakefield Accelerators
Bright and ultrashort duration X-ray pulses can be produced by through
betatron oscillations of electrons during Laser Wakefield Acceleration (LWFA).
Our experimental measurements using the \textsc{Hercules} laser system
demonstrate a dramatic increase in X-ray flux for interaction distances beyond
the depletion/dephasing lengths, where the initial electron bunch injected into
the first wake bucket catches up with the laser pulse front and the laser pulse
depletes. A transition from an LWFA regime to a beam-driven plasma wakefield
acceleration (PWFA) regime consequently occurs. The drive electron bunch is
susceptible to the electron-hose instability and rapidly develops large
amplitude oscillations in its tail, which leads to greatly enhanced X-ray
radiation emission. We measure the X-ray flux as a function of acceleration
length using a variable length gas cell. 3D particle-in-cell (PIC) simulations
using a Monte Carlo synchrotron X-ray emission algorithm elucidate the
time-dependent variations in the radiation emission processes.Comment: 6 pages, 4 figures, accepted for publication in Phys. Rev. Accel.
Beam
Outcome of Men Presenting with Clinical Breast Problems: The Role of Mammography and Ultrasound
The purpose of this study was to determine the outcome of men presenting with clinical breast problems for breast imaging and to evaluate the role of mammography and ultrasound in the diagnosis of benign and malignant breast problems. We retrospectively reviewed clinical, radiographic, and pathologic records of 165 consecutive symptomatic men presenting to Breast Imaging over a 4 year period. We assessed the clinical indication for referral, mammographic findings, sonographic findings, histologic results, and clinical outcomes. Patients ranged in age from 22 to 96 years. Breast Imaging Reporting and Data System (BI-RADS) category 4 and 5 mammograms and solid sonographic masses were considered suspicious for malignancy. Six of 165 men (4%) had primary breast carcinoma, which were mammographically suspicious in all 6 (100%). Five were invasive ductal carcinoma and one was ductal carcinoma in situ (DCIS). Of 164 mammograms, 20 (12%) were suspicious. Six were cancer and 14 were benign. Clinical follow-up for 2 years or biopsy results were available for 138 of the 165 men (84%). Twelve with benign mammographic findings had benign biopsies. All men with benign mammography not undergoing biopsy were cancer free. Sensitivity for cancer detection (mammography) was 100% and specificity was 90%. Positive predictive value (mammography) was 32% (6 of 19) and the negative predictive value was 100%. Sonography was performed in 68 of the 165 men (41%). Three of three cancers (100%) were solid sonographic masses. There were 9 of 68 false-positive examinations (13%). Sensitivity and negative predictive value for cancer detection (ultrasound) was 100% and specificity was 74%. The most common clinical indication for referral was mass/thickening (56%). Mammography had excellent sensitivity and specificity for breast cancer detection and should be included as the initial imaging examination of men with clinical breast problems. The negative predictive value of 100% for mammography suggests that mammograms read as normal or negative need no further examination if the clinical findings are not suspicious. A normal ultrasound in these men confirms the negative predictive value of a normal mammogram.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74705/1/j.1075-122X.2006.00298.x.pd
Online effects of beta-tACS over the left prefrontal cortex on phonological decisions
The left posterior inferior frontal gyrus in the prefrontal cortex is a key region for phonological aspects of language processing. A previous study has shown that alpha-tACS over the prefrontal cortex applied before task processing facilitated phonological decision-making and increased task-related theta power. However, it is unclear how alpha-tACS affects phonological processing when applied directly during the task. Moreover, the frequency specificity of this effect is also unclear since the majority of neurostimulation studies tested a single frequency only. The present study addressed the question whether and how 10 Hz online tACS affects phonological decisions. To this end, 24 healthy participants received tACS at 10 Hz or 16.18 Hz (control frequency) or sham stimulation over the left prefrontal cortex during task processing in three sessions. As an unexpected finding, 16.18 Hz significantly impaired task accuracy relative to sham stimulation, without affecting response speed. There was no significant difference in phonological task performance between 10 Hz and 16.18 Hz tACS or between 10 Hz and sham stimulation. Our results support the functional relevance of the left prefrontal cortex for phonological decisions and suggest that online beta-tACS may modulate language comprehension
Muon pair creation from positronium in a circularly polarized laser field
We study elementary particle reactions that result from the interaction of an
atomic system with a very intense laser wave of circular polarization. As a
specific example, we calculate the rate for the laser-driven reaction , where the electron and positron originate from a positronium
atom or, alternatively, from a nonrelativistic plasma. We distinguish
accordingly between the coherent and incoherent channels of the process. Apart
from numerical calculations, we derive by analytical means compact formulas for
the corresponding reaction rates. The rate for the coherent channel in a laser
field of circular polarization is shown to be damped because of the destructive
interference of the partial waves that constitute the positronium ground-state
wave packet. Conditions for the observation of the process via the dominant
incoherent channel in a circularly polarized field are pointed out
Patient‐friendly pathology reports for patients with breast atypias
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146318/1/tbj13061_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146318/2/tbj13061.pd
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