6,914 research outputs found
Tunable Balun Low-Noise Amplifier in 65nm CMOS Technology
The presented paper includes the design and implementation of a 65 nm CMOS low-noise amplifier (LNA) based on inductive source degeneration. The amplifier is realized with an active balun enabling a single-ended input which is an important requirement for low-cost system on chip implementations. The LNA has a tunable bandpass characteristics from 4.7 GHz up to 5.6 GHz and a continuously tunable gain from 22 dB down to 0 dB, which enables the required flexibility for multi-standard, multi-band receiver architectures. The gain and band tuning is realized with an optimized tunable active resistor in parallel to a tunable L-C tank amplifier load. The amplifier achieves an IIP3 linearity of -8dBm and a noise figure of 2.7 dB at the highest gain and frequency setting with a low power consumption of 10 mW. The high flexibility of the proposed LNA structure together with the overall good performance makes it well suited for future multi-standard low-cost receiver front-ends
Matching factors for Delta S=1 four-quark operators in RI/SMOM schemes
The non-perturbative renormalization of four-quark operators plays a
significant role in lattice studies of flavor physics. For this purpose, we
define regularization-independent symmetric momentum-subtraction (RI/SMOM)
schemes for Delta S=1 flavor-changing four-quark operators and provide one-loop
matching factors to the MS-bar scheme in naive dimensional regularization. The
mixing of two-quark operators is discussed in terms of two different classes of
schemes. We provide a compact expression for the finite one-loop amplitudes
which allows for a straightforward definition of further RI/SMOM schemes.Comment: 22 pages, 5 figure
Deep brain stimulation in schizophrenia
Deep brain stimulation (DBS) has successfully advanced treatment options of putative therapy-resistant
neuropsychiatric diseases. Building on this strong foundation more and more mental disorders in the
stadium of therapy-resistance are considered as possible indications for DBS. Especially schizophrenia
with its associated severe and difficult to treat symptoms is gaining attention. This attention demands
critical questions regarding the assumed mechanisms of DBS and its possible influence on the supposed
pathophysiology of schizophrenia. Here we synoptically compare current approaches and theories of
DBS and discuss the feasibility of DBS in schizophrenia as well as the transferability from other
psychiatric disorders successfully treated with DBS. For this we consider recent advances in animal
models of schizophrenic symptoms, results regarding the influence of DBS on dopaminergic
transmission as well as data concerning neural oscillation and synchronization. In conclusion the use of
DBS for some symptoms of schizophrenia seems to be a promising approach, but the lack of a
comprehensive theory of the mechanisms of DBS as well as its impact on schizophrenia might void the
use of DBS in schizophrenia at this point
How Sensitive are Di-Leptons from Rho Mesons to the High Baryon Density Region?
We show that the measurement of di-leptons might provide only a restricted
view into the most dense stages of heavy ion reactions. Thus, possible studies
of meson and baryon properties at high baryon densities, as e.g. done at
GSI-HADES and envisioned for FAIR-CBM, might observe weaker effects than
currently expected in certain approaches. We argue that the strong absorption
of resonances in the high baryon density region of the heavy ion collision
masks information from the early hot and dense phase due to a strong increase
of the total decay width because of collisional broadening. To obtain
additional information, we also compare the currently used approaches to
extract di-leptons from transport simulations - i.e. shining, only vector
mesons from final baryon resonance decays and instant emission of di-leptons
and find a strong sensitivity on the method employed in particular at FAIR and
SPS energies. It is shown explicitly that a restriction to rho meson (and
therefore di-lepton) production only in final state baryon resonance decays
provide a strong bias towards rather low baryon densities. The results
presented are obtained from UrQMD v2.3 calculations using the standard set-up.Comment: 8 pages, 6 figures, expanded versio
Subtropical Real Root Finding
We describe a new incomplete but terminating method for real root finding for
large multivariate polynomials. We take an abstract view of the polynomial as
the set of exponent vectors associated with sign information on the
coefficients. Then we employ linear programming to heuristically find roots.
There is a specialized variant for roots with exclusively positive coordinates,
which is of considerable interest for applications in chemistry and systems
biology. An implementation of our method combining the computer algebra system
Reduce with the linear programming solver Gurobi has been successfully applied
to input data originating from established mathematical models used in these
areas. We have solved several hundred problems with up to more than 800000
monomials in up to 10 variables with degrees up to 12. Our method has failed
due to its incompleteness in less than 8 percent of the cases
Swift J053041.9-665426, a new Be/X-ray binary pulsar in the Large Magellanic Cloud
We observed the newly discovered X-ray source Swift J053041.9-665426 in the
X-ray and optical regime to confirm its proposed nature as a high mass X-ray
binary. We obtained XMM-Newton and Swift X-ray data, along with optical
observations with the ESO Faint Object Spectrograph, to investigate the
spectral and temporal characteristics of Swift J053041.9-665426. The XMM-Newton
data show coherent X-ray pulsations with a period of 28.77521(10) s (1 sigma).
The X-ray spectrum can be modelled by an absorbed power law with photon index
within the range 0.76 to 0.87. The addition of a black body component increases
the quality of the fit but also leads to strong dependences of the photon
index, black-body temperature and absorption column density. We identified the
only optical counterpart within the error circle of XMM-Newton at an angular
distance of ~0.8 arcsec, which is 2MASS J05304215-6654303. We performed optical
spectroscopy from which we classify the companion as a B0-1.5Ve star. The X-ray
pulsations and long-term variability, as well as the properties of the optical
counterpart, confirm that Swift J053041.9-665426 is a new Be/X-ray binary
pulsar in the Large Magellanic Cloud.Comment: 10 pages, 8 figures, accepted for publication in A&
Imaging density disturbances in water with 41.3 attosecond time resolution
We show that the momentum flexibility of inelastic x-ray scattering may be
exploited to invert its loss function, alowing real time imaging of density
disturbances in a medium. We show the disturbance arising from a point source
in liquid water, with a resolution of 41.3 attoseconds (
sec) and 1.27 ( cm). This result is used to
determine the structure of the electron cloud around a photoexcited molecule in
solution, as well as the wake generated in water by a 9 MeV gold ion. We draw
an analogy with pump-probe techniques and suggest that energy-loss scattering
may be applied more generally to the study of attosecond phenomena.Comment: 4 pages, 4 color figure
Discovery of a 168.8 s X-ray pulsar transiting in front of its Be companion star in the Large Magellanic Cloud
We report the discovery of LXP169, a new high-mass X-ray binary (XRB) in the
LMC. The optical counterpart has been identified and appears to exhibit an
eclipsing light curve. We performed follow-up observations to clarify the
eclipsing nature of the system. Energy spectra and time series were extracted
from two XMM-Newton observations to search for pulsations, characterise the
spectrum, and measure spectral and timing changes. Long-term X-ray variability
was studied using archival ROSAT data. The XMM positions were used to identify
the optical counterpart. We obtained UV to NIR photometry to characterise the
companion, along with its 4000 d long I-band light curve. We observed LXP169
with Swift at two predicted eclipse times. We found a spin period of 168.8 s
that did not change between two XMM observations. The X-ray spectrum, well
characterised by a power law, was harder when the source was brighter. The
X-ray flux of LXP169 is found to be variable by a factor of at least 10. The
counterpart is highly variable on short and long timescales, and its photometry
is that of an early-type star with a NIR excess. This classifies the source as
a BeXRB pulsar. We observed a transit in the UV, thereby confirming that the
companion star itself is eclipsed. We give an ephemeris for the transit of MJD
56203.877 + N*24.329. We propose and discuss the scenario where the matter
captured from the companion's equatorial disc creates an extended region of
high density around the neutron star (NS), which partially eclipses the
companion as the NS transits in front of it. This is most likely the first time
the compact object in an XRB is observed to eclipse its companion star. LXP169
would be the first eclipsing BeXRB, and a wealth of important information might
be gained from additional observations, such as a measure of the possible Be
disc/orbital plane misalignment, or the mass of the NS.Comment: Updated version of arXiv 1302.4665v1, accepted for publication in
Astronomy and Astrophysics. 11 pages, 8 figures, 3 table
Monomer dynamics of a wormlike chain
We derive the stochastic equations of motion for a tracer that is tightly
attached to a semiflexible polymer and confined or agitated by an externally
controlled potential. The generalised Langevin equation, the power spectrum,
and the mean-square displacement for the tracer dynamics are explicitly
constructed from the microscopic equations of motion for a weakly bending
wormlike chain by a systematic coarse-graining procedure. Our accurate
analytical expressions should provide a convenient starting point for further
theoretical developments and for the analysis of various single-molecule
experiments and of protein shape fluctuations.Comment: 6 pages, 4 figure
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