703 research outputs found
On the Importance of Registers for Computability
All consensus hierarchies in the literature assume that we have, in addition
to copies of a given object, an unbounded number of registers. But why do we
really need these registers?
This paper considers what would happen if one attempts to solve consensus
using various objects but without any registers. We show that under a
reasonable assumption, objects like queues and stacks cannot emulate the
missing registers. We also show that, perhaps surprisingly, initialization,
shown to have no computational consequences when registers are readily
available, is crucial in determining the synchronization power of objects when
no registers are allowed. Finally, we show that without registers, the number
of available objects affects the level of consensus that can be solved.
Our work thus raises the question of whether consensus hierarchies which
assume an unbounded number of registers truly capture synchronization power,
and begins a line of research aimed at better understanding the interaction
between read-write memory and the powerful synchronization operations available
on modern architectures.Comment: 12 pages, 0 figure
How Equalization Techniques Affect the TCP Performance of MC-CDMA Systems in Correlated Fading Channels
This paper investigates the impact of several equalization techniques for multicarrier code division multiple access systems on the performance at both lower and upper layers (i.e., physical and TCP layers). Classical techniques such as maximal ratio combining, equal gain combining, orthogonality restoring combining, minimum mean square error, as well as a partial equalization (PE) are investigated in time- and frequency-correlated fading channels with various numbers of interferers. Their impact on the performance at upper level is then studied. The results are obtained through an integrated simulation platform carefully reproducing all main aspects affecting the quality of service perceived by the final user, allowing an investigation of the real gain produced by signal processing techniques at TCP level
A New Measurement of Kaonic Hydrogen X rays
The system at threshold is a sensitive testing ground for low
energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we
have measured the -series x rays of kaonic hydrogen atoms at the DANE
electron-positron collider of Laboratori Nazionali di Frascati, and have
determined the most precise values of the strong-interaction energy-level shift
and width of the atomic state. As x-ray detectors, we used large-area
silicon drift detectors having excellent energy and timing resolution, which
were developed especially for the SIDDHARTA experiment. The shift and width
were determined to be eV and
eV, respectively. The new
values will provide vital constraints on the theoretical description of the
low-energy interaction.Comment: 5 figures, submitted to Physics Letters
Shedding New Light on Kaon-Nucleon/Nuclei Interaction and Its Astrophysical Implications with the AMADEUS Experiment at DAFNE
The AMADEUS experiment deals with the investigation of the low-energy
kaon-nuclei hadronic interaction at the DA{\Phi}NE collider at LNF-INFN, which
is fundamental to respond longstanding questions in the non-perturbative QCD
strangeness sector. The antikaon-nucleon potential is investigated searching
for signals from possible bound kaonic clusters, which would open the
possibility for the formation of cold dense baryonic matter. The confirmation
of this scenario may imply a fundamental role of strangeness in astrophysics.
AMADEUS step 0 consisted in the reanalysis of 2004/2005 KLOE dataset,
exploiting K- absorptions in H, 4He, 9Be and 12C in the setup materials. In
this paper, together with a review on the multi-nucleon K- absorption and the
particle identification procedure, the first results on the {\Sigma}0-p channel
will be presented including a statistical analysis on the possible accomodation
of a deeply bound stateComment: 6 pages, 2 figure, 1 table, HADRON 2015 conferenc
Unprecedented studies of the low-energy negatively charged kaons interactions in nuclear matter by AMADEUS
The AMADEUS experiment aims to provide unique quality data of hadronic
interactions in light nuclear targets, in order to solve fundamental open
questions in the non-perturbative strangeness QCD sector, like the
controversial nature of the state, the yield of hyperon
formation below threshold, the yield and shape of multi-nucleon
absorption, processes which are intimately connected to the possible existence
of exotic antikaon multi-nucleon clusters. AMADEUS takes advantage of the
DANE collider, which provides a unique source of monochromatic
low-momentum kaons and exploits the KLOE detector as an active target, in order
to obtain excellent acceptance and resolution data for nuclear capture on
H, He, Be and C, both at-rest and in-flight. During the
second half of 2012 a successful data taking was performed with a dedicated
pure carbon target implemented in the central region of KLOE, providing a high
statistic sample of pure at-rest nuclear interactions. For the future
dedicated setups involving cryogenic gaseous targets are under preparation.Comment: 14 pages, 6 figure
The KAMEO proposal: Investigation of the E2 nuclear resonance effects in kaonic atoms
The E2 nuclear resonance effect is a phenomenon that occurs when the energy of an atomic de-excitation state closely matches that of a nuclear excitation state, resulting in the attenuation of certain atomic X-ray lines in the resonant
isotope target. The study of this effect in kaonic atoms can provide important insight into the mechanisms of the strong kaon-nucleus interaction. In 1975, Goldfrey, Lum, and Wiegand at Lawrence Berkeley Laboratory observed the effect in 98 42Mo, but they did not have enough data to reach a conclusive result. The E2 nuclear resonance effect is expected to occur in four kaonic molybdenum isotopes (94
42Mo, 96 42Mo, 98 42Mo, and 100 42 Mo) with similar energy values. The KAMEO (Kaonic Atoms Measuring Nuclear Resonance Effects Observables) proposal plans to study this effect in these isotopes at the DAΦNE Φ factory during the SIDDHARTA-2 experiment. KAMEO will use four solid strip targets, each enriched with a different molybdenum isotope, and expose them to negatively charged kaons produced by Φ meson decays. The X-ray transition measurements will be performed using a high-purity germanium detector, and an additional solid strip target of non-resonant 92 42Mo isotope will be
exposed and used as a reference for standard non-resonant transitions
Long-Term Survival Rates after Resection for Locally Advanced Kidney Cancer: Memorial Sloan Kettering Cancer Center 1989 to 2012 Experience
Purpose: We analyzed the 23-year Memorial Sloan Kettering Cancer Center experience with surgical resection, and concurrent adrenalectomy and lymphadenectomy for locally advanced nonmetastatic renal cell carcinoma. Materials and Methods: We retrospectively reviewed the records of 802 patients who underwent nephrectomy with or without concurrent adrenalectomy or lymphadenectomy for locally advanced renal cell carcinoma, defined as stage T3 or greater and M0. Patients who received adjuvant treatment within 3 months of surgery or had fewer than 3 months of followup or bilateral renal masses at presentation were excluded from analysis. Five and 10-year progression-free and overall survival was estimated by the Kaplan-Meier method. Differences between groups were analyzed by the log rank test. Results: A total of 596 (74%) and 206 patients (26%) underwent radical and partial nephrectomy, respectively. Renal cell carcinoma progressed in 189 patients and 104 died of the disease. Median followup in patients without progression was 4.6 years. Symptoms at presentation, ASA (R) classification, tumor stage, histological subtype, grade and lymph node status were significantly associated with progression-free and overall survival. On multivariate analysis adrenalectomy use decreased with time but lymphadenectomy use increased (OR 0.82 vs 1.16 per year). Larger tumors were associated with a higher likelihood of concurrent adrenalectomy and lymphadenectomy. Conclusions: In our series of patients with locally advanced nonmetastatic renal cell carcinoma survival was favorable in those in good health who were asymptomatic at presentation with T3 tumors and negative lymph nodes. Further, there has been a trend toward more selective use of adrenalectomy and increased use of lymphadenectomy
-series X-ray yield measurement of kaonic hydrogen atoms in a gaseous target
We measured the -series X-rays of the exotic atom in the
SIDDHARTA experiment with a gaseous hydrogen target of 1.3 g/l, which is about
15 times the of hydrogen gas. At this density, the absolute
yields of kaonic X-rays, when a negatively charged kaon stopped inside the
target, were determined to be 0.012 for and
0.043 for all the -series transitions . These
results, together with the KEK E228 experiment results, confirm for the first
time a target density dependence of the yield predicted by the cascade models,
and provide valuable information to refine the parameters used in the cascade
models for the kaonic atoms.Comment: 9 pages, 5 figures. Submitted to Nuclear Physics A, Special Issue on
Strangeness and Char
Strong interaction studies with kaonic atoms
The strong interaction of antikaons (K-) with nucleons and nuclei in the low
energy regime represents an active research field connected intrinsically with
few-body physics. There are important open questions like the question of
antikaon nuclear bound states - the prototype system being K-pp. A unique and
rather direct experimental access to the antikaon-nucleon scattering lengths is
provided by precision X-ray spectroscopy of transitions in low-lying states of
light kaonic atoms like kaonic hydrogen isotopes. In the SIDDHARTA experiment
at the electron-positron collider DA?NE of LNF-INFN we measured the most
precise values of the strong interaction observables, i.e. the strong
interaction on the 1s ground state of the electromagnetically bound K-p atom
leading to a hadronic shift and a hadronic broadening of the 1s state. The
SIDDHARTA result triggered new theoretical work which achieved major progress
in the understanding of the low-energy strong interaction with strangeness.
Antikaon-nucleon scattering lengths have been calculated constrained by the
SIDDHARTA data on kaonic hydrogen. For the extraction of the isospin-dependent
scattering lengths a measurement of the hadronic shift and width of kaonic
deuterium is necessary. Therefore, new X-ray studies with the focus on kaonic
deuterium are in preparation (SIDDHARTA2). Many improvements in the
experimental setup will allow to measure kaonic deuterium which is challenging
due to the anticipated low X-ray yield. Especially important are the data on
the X-ray yields of kaonic deuterium extracted from a exploratory experiment
within SIDDHARTA.Comment: Proc. Few Body 21, 4 pages, 2 figure
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