110 research outputs found
Information criteria determine the number of active sources
With the neuroelectromagnetic inverse problem, the optimal choice of the number of sources is a difficult problem, especially in the presence of correlated noise. In this paper we present a number of information criteria that help to solve this problem. They are based on the probability density function of the measurements or their eigenvalues. Make use of the Akaike or MDL (minimum description length) correction term and all employ some sort of noise information. By extensive simulations we investigated the conditions under which these criteria yield reliable estimations. We were able to quantify two major factors of influence: (1) the precision of the noise information and (2) the signal-to-noise ratio (SNR). Here defined as the ratio of the smallest signal eigenvalues and the average of the noise eigenvalues. Furthermore, we found that the Akaike correction term tends to overestimate, due to its greater sensibility to the precision of the noise informatio
The clinical use of drugs influencing neurotransmitters in the brain to promote motor recovery after stroke; a Cochrane systematic review\ud
The objective of this review was to compare and to discuss the results of studies that investigated the ability of drugs to improve motor recovery after stroke by influencing dopamine, norepinephrine, or serotonin concentrations in the brain. A systematic literature search up to January 2009 was conducted in MEDLINE, Pubmed, EMBASE and in the database of the Cochrane Stroke Group Trial Register. In addition, the literature reference lists of the relevant publications were checked. The literature search was conducted in order to identify randomized controlled trials focusing on the effects of drugs on motor recovery after stroke. In order to structure the data, motor recovery was sub-divided into motor control and motor function. The methodological quality of the studies was also assessed. Six studies, investigating the effects of 7 different kinds of drugs were included. Methodological scores varied between 10 and 14 (max 19). Motor control was not influenced by any of the drugs. Motor function improved in patients treated with methylphenidate, trazodone, and nortriptyline. Results for fluoxetine and levodopa were contradicting. There is insufficient evidence to conclude that neuromodulating drugs targeting serotonin, norepinephrine, or dopamine influence motor recovery after strok
Test of phi renormalization in nuclei through phi photoproduction
We propose an experimental procedure to find out the medium modifications of
the meson. The reaction is inclusive photoproduction in nuclei,
looking for pairs from the decay with total momentum smaller
than 100-150 , which are made possible at energies of present
laboratories from center of mass backward production and the help of
Fermi motion. We have conducted a many body calculation of the mass
distribution of the adapted to the experimental set up of a recent JLAB
experiment where the backwards photoproduction has been measured. Using
recent results for the in medium properties of the , we find that the
width of the invariant mass distribution for photoproduction on medium to heavy
nuclei is larger than the free width by a factor of two or more.Comment: 10 pages, 3 figure
Association between somatic cell count during the first lactation and the cumulative milk yield of cows in Irish dairy herds
Reduced potential milk yield is an important component of mastitis costs in dairy cows. The first aim of this study was to assess associations between somatic cell count (SCC) during the first lactation, and cumulative milk yield over the first lactation and subsequent lifetime of cows in Irish dairy herds. The second aim was to assess the association between SCC at 5 to 30 d in milk during parity 1 (SCC1), and SCC over the entire first lactation for cows in Irish dairy herds. The data set studied included records from 51,483 cows in 5,900 herds. Somatic cell count throughout the first lactation was summarized using the geometric mean and variance of SCC. Data were analyzed using linear models that included random effects to account for the lack of independence between observations, and herdlevel variation in coefficients. Models were developed in a Bayesian framework and parameters were estimated from 10,000 Markov chain Monte Carlo simulations. The final models were a good fit to the data. A 1-unit increase in mean natural logarithm SCC over the first lactation was associated with a median decrease in first lactation and lifetime milk yield of 135 and 1,663 kg, respectively. A 1-unit increase in the variance of natural logarithm SCC over the first lactation was associated with a median decrease in lifetime milk yield of 719 kg. To demonstrate the context of lifetime milk yield results, microsimulation was used to model the trajectory of individual cows and evaluate the expected outcomes for particular changes in herd-level geometric mean SCC over the first lactation. A 75% certainty of savings of at least €199/heifer in the herd was detected if herd-level geometric mean SCC over the first lactation was reduced from ≥120,000 to ≤72,000 cells/mL. The association between SCC1 and SCC over the remainder of the first lactation was highly herd dependent, indicating that control measures for heifer mastitis should be preferentially targeted on an individual-herd basis toward either the pre- and peripartum period, or the lactating period, to optimize the lifetime milk yield of dairy cows
Kaluza-Klein gravitino production with a single photon at e^+ e^- colliders
In a supersymmetric large extra dimension scenario, the production of
Kaluza-Klein gravitinos accompanied by a photino at e^+ e^- colliders is
studied. We assume that a bulk supersymmetry is softly broken on our brane such
that the low-energy theory resembles the MSSM. Low energy supersymmetry
breaking is further assumed as in GMSB, leading to sub-eV mass shift in each KK
mode of the gravitino from the corresponding graviton KK mode. Since the
photino decays within a detector due to its sufficiently large inclusive decay
rate into a photon and a gravitino, the process e^+ e^- -> photino + gravitino
yields single photon events with missing energy. Even if the total cross
section can be substantial at sqrt(s)=500 GeV, the KK graviton background of
e^+ e^- -> photon + graviton is kinematically advantageous and thus much
larger. It is shown that the observable, sigma(e^-_L)-sigma(e^-_R), can
completely eliminate the KK graviton background but retain most of the KK
gravitino signal, which provides a unique and robust method to probe the
supersymmetric bulk.Comment: Reference added and typos correcte
Search for lepton-flavor-violating decays at Belle
We have searched for neutrinoless lepton decays into and ,
where stands for an electron or muon, and for a vector meson
(, , , or ), using 543 fb
of data collected with the Belle detector at the KEKB asymmetric-energy
collider. No excess of signal events over the expected background has
been observed, and we set upper limits on the branching fractions in the range
at the 90% confidence level. These upper limits
include the first results for the mode as well as new limits that
are significantly more restrictive than our previous results for the , , and modes.Comment: 7 pages, 16 figure
Measurement of CP asymmetry in Cabibbo suppressed D0 decays
We measure the CP-violating asymmetries in decays to the D0 -> K+K- and D0 ->
pi+pi- CP eigenstates using 540 fb^{-1} of data collected with the Belle
detector at or near the Upsilon(4S) resonance. Cabibbo-favored D0 -> K-pi+
decays are used to correct for systematic detector effects. The results,
A_{CP}^{KK} = (-0.43 +- 0.30 +- 0.11)% and A_{CP}^{pipi} = (+0.43 +- 0.52 +-
0.12)%, are consistent with no CP violation.Comment: Submitted to Phys. Lett.
WW Production Cross Section and W Branching Fractions in e+e- Collisions at 189 GeV
From a data sample of 183 pb^-1 recorded at a center-of-mass energy of roots
= 189 GeV with the OPAL detector at LEP, 3068 W-pair candidate events are
selected. Assuming Standard Model W boson decay branching fractions, the W-pair
production cross section is measured to be sigmaWW = 16.30 +- 0.34(stat.) +-
0.18(syst.) pb. When combined with previous OPAL measurements, the W boson
branching fraction to hadrons is determined to be 68.32 +- 0.61(stat.) +-
0.28(syst.) % assuming lepton universality. These results are consistent with
Standard Model expectations.Comment: 22 pages, 5 figures, submitted to Phys. Lett.
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