6,160 research outputs found
Analytical BER Performance of DS-CDMA Ad Hoc Networks using Large Area Synchronized Spreading Codes
The family of operational CDMA systems is interference-limited owing to the Inter Symbol Interference (ISI) and the Multiple Access Interference (MAI) encountered. They are interference-limited, because the orthogonality of the spreading codes is typically destroyed by the frequency-selective fading channel and hence complex multiuser detectors have to be used for mitigating these impairments. By contrast, the family of Large Area Synchronous (LAS) codes exhibits an Interference Free Window (IFW), which renders them attractive for employment in cost-efficient quasi-synchronous ad hoc networks dispensing with power control. In this contribution we investigate the performance of LAS DS-CDMA assisted ad hoc networks in the context of a simple infinite mesh of rectilinear node topology and benchmark it against classic DS-CDMA using both random spreading sequences as well as Walsh-Hadamard and Orthogonal Gold codes. It is demonstrated that LAS DS-CDMA exhibits a significantly better performance than the family of classic DS-CDMA systems operating in a quasi-synchronous scenario associated with a high node density, a low number of resolvable paths and a sufficiently high number of RAKE receiver branches
First Subleading Power Resummation for Event Shapes
We derive and analytically solve renormalization group (RG) equations of
gauge invariant non-local Wilson line operators which resum logarithms for
event shape observables at subleading power in the
expansion. These equations involve a class of universal jet and soft functions
arising through operator mixing, which we call -jet and -soft
functions. An illustrative example involving these operators is introduced
which captures the generic features of subleading power resummation, allowing
us to derive the structure of the RG to all orders in , and provide
field theory definitions of all ingredients. As a simple application, we use
this to obtain an analytic leading logarithmic result for the subleading power
resummed thrust spectrum for in pure glue QCD. This resummation
determines the nature of the double logarithmic series at subleading power,
which we find is still governed by the cusp anomalous dimension. We check our
result by performing an analytic calculation up to .
Consistency of the subleading power RG relates subleading power anomalous
dimensions, constrains the form of the -soft and -jet
functions, and implies an exponentiation of higher order loop corrections in
the subleading power collinear limit. Our results provide a path for carrying
out systematic resummation at subleading power for collider observables.Comment: 39 pages + 2 Appendices, 2 figures. v2: journal versio
Cystic benign prostatic hyperplasia in a dog
Old intact male dogs are often predisposed to benign prostatic hyperplasia. Both hypertrophy and hyperplasia of prostate gland occur due to hormonal influences. Clinical signs such as haematuria, stranguria and tenesmus are often associated with benign prostatic hyperplasia. A seven year-old local breed intact male dog was presented with a primary complaint of haematuria and stranguria. Diagnostic work-up conducted inclusive of complete blood count, serum biochemistry, urinalysis, abdominal radiograph, cystourethrography and abdominal ultrasonography. The dog was diagnosed with cystic benign prostatic hyperplasia. Prostatic omentalisation and castration were performed in this case
A possible disk mechanism for the 23d QPO in Mkn~501
Optically thin two-temperature accretion flows may be thermally and viscously
stable, but acoustically unstable. Here we propose that the O-mode instability
of a cooling-dominated optically thin two-temperature inner disk may explain
the 23-day quasi-periodic oscillation (QPO) period observed in the TeV and
X-ray light curves of Mkn~501 during its 1997 high state. In our model the
relativistic jet electrons Compton upscatter the disk soft X-ray photons to TeV
energies, so that the instability-driven X-ray periodicity will lead to a
corresponding quasi-periodicity in the TeV light curve and produce correlated
variability. We analyse the dependence of the instability-driven
quasi-periodicity on the mass (M) of the central black hole, the accretion rate
() and the viscous parameter () of the inner disk. We
show that in the case of Mkn~501 the first two parameters are constrained by
various observational results, so that for the instability occurring within a
two-temperature disk where , the quasi-period is expected to
lie within the range of 8 to 100 days, as indeed the case. In particular, for
the observed 23-day QPO period our model implies a viscosity coefficient
, a sub-Eddington accretion rate and a transition radius to the outer standard disk of , and predicts a period variation due to the
motion of the instability region.Comment: 18 pages, 1 figure, accepted by AP
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