Mitochondrial potassium channel opener diazoxide preserves neuronal-vascular function after cerebral ischemia in newborn pigs

Background and Purpose-N-Methyl-D-aspartate (NMDA) elicits neuronally mediated cerebral arteriolar vasodilation that is reduced by ischemia/reperfusion (I/R). This sequence has been preserved by pretreatment with the ATP-sensitive potassium (K-ATP) channel opener aprikalim, although the mechanism was unclear. In the heart, mitochondrial K-ATP channels (mitoK(ATP)) are involved in the ischemic preconditioning-like effect of K+ channel openers. We determined whether the selective mitoK(ATP) channel opener diazoxide preserves the vascular dilation to NMDA after I/R. Methods-Pial arteriolar diameters were determined with the use of closed cranial window/intravital microscopy in anesthetized piglets. Vascular responses to NMDA were assessed before and 1 hour after 10 minutes of global cerebral ischemia induced by raising intracranial pressure. Subgroups received 1 of the following pretreatments before I/R: vehicle; 1 to 10 mu mol/L diazoxide; and coapplication of 100 mu mol/L 5-hydroxydecanoic acid (5-HD), a K-ATP antagonist with diazoxide. Results-NMDA-induced dose-dependent pial arteriolar dilation was not affected by diazoxide treatment only but was severely attenuated by I/R, In contrast, diazoxide dose-dependently preserved the NMDA vascular response after I/R; at 10 mu mol/L, diazoxide arteriolar responses were unaltered by I/R. The effect of diazoxide was antagonized by coapplication of 5-HD with diazoxide. Percent preservation of 100 mu mol/L NMDA-induced vasodilation after I/R was 53 +/- 19% (mean +/- SEM, n = 8) in vehicle-treated controls versus 55 +/- 10%, 85 +/- 5%, and 99 +/- 15% in animals pretreated with 1, 5, and 10 mu mol/L diazoxide (n = 8, n = 8, and n = 12, respectively) and 60 +/- 15% in the group treated with 5-HD+diazoxide (n = 5). Conclusions-The mitoK(ATP) channel opener diazoxide in vivo preserves neuronal function after I/R, shown by pial arteriolar responses to NMDA, in a dose-dependent manner. Thus, activation of mitoK(ATP) channels may play a role in mediating the protective effect of other K+ channel openers

Ground state phases of the Half-Filled One-Dimensional Extended Hubbard Model

Using quantum Monte Carlo simulations, results of a strong-coupling expansion, and Luttinger liquid theory, we determine quantitatively the ground state phase diagram of the one-dimensional extended Hubbard model with on-site and nearest-neighbor repulsions U and V. We show that spin frustration stabilizes a bond-ordered (dimerized) state for U appr. V/2 up to U/t appr. 9, where t is the nearest-neighbor hopping. The transition from the dimerized state to the staggered charge-density-wave state for large V/U is continuous for U up to appr. 5.5 and first-order for higher U.Comment: 4 pages, 4 figure

Hiding relativistic degrees of freedom in the early universe

We quantify the extent to which extra relativistic energy density can be concealed by a neutrino asymmetry without conflicting with the baryon asymmetry measured by the Wilkinson Microwave Anisotropy Probe (WMAP). In the presence of a large electron neutrino asymmetry, slightly more than seven effective neutrinos are allowed by Big Bang Nucleosynthesis (BBN) and WMAP at 2\sigma. The same electron neutrino degeneracy that reconciles the BBN prediction for the primordial helium abundance with the observationally inferred value also reconciles the LSND neutrino with BBN by suppressing its thermalization prior to BBN.Comment: 5 pages, 5 figure

Diffractive Higgs Production from Intrinsic Heavy Flavors in the Proton

We propose a novel mechanism for exclusive diffractive Higgs production $pp \to p H p$ in which the Higgs boson carries a significant fraction of the projectile proton momentum. This mechanism will provide a clear experimental signal for Higgs production due to the small background in this kinematic region. The key assumption underlying our analysis is the presence of intrinsic heavy flavor components of the proton bound state, whose existence at high light-cone momentum fraction $x$ has growing experimental and theoretical support. We also discuss the implications of this picture for exclusive diffractive quarkonium and other channels.Comment: 30 pages, 5 figure

Non-thermal leptogenesis with strongly hierarchical right handed neutrinos

Assuming the Dirac-type neutrino masses m_D are related to quark or charged lepton masses, neutrino oscillation data indicate that right handed neutrino masses are in general strongly hierarchical. In particular, if m_D is similar to the up-type quark masses, the mass of the lightest right handed neutrino M_1<~10^6 GeV. We show that non-thermal leptogenesis by inflaton decay can yield sufficient baryon asymmetry despite this constraint, and discuss how the asymmetry is correlated with the low energy neutrino masses and CP-violating phases.Comment: 7 pages, 5 figures. v2: added some comments and references, v3: minor corrections and additions, v4: a typo corrected, published versio

First CNGS events detected by LVD

The CERN Neutrino to Gran Sasso (CNGS) project aims to produce a high energy, wide band $\nu_{\mu}$ beam at CERN and send it toward the INFN Gran Sasso National Laboratory (LNGS), 732 km away. Its main goal is the observation of the $\nu_{\tau}$ appearance, through neutrino flavour oscillation. The beam started its operation in August 2006 for about 12 days: a total amount of $7.6~10^{17}$ protons were delivered to the target. The LVD detector, installed in hall A of the LNGS and mainly dedicated to the study of supernova neutrinos, was fully operating during the whole CNGS running time. A total number of 569 events were detected in coincidence with the beam spill time. This is in good agreement with the expected number of events from Montecarlo simulations.Comment: Accepted for publication by the European Physical Journal C ; 7 pages, 11 figure

Prescriptions for the scaling variable of the nucleon structure function in nuclei

We tested several choices of the in-medium value of the Bjorken scaling variable assuming the nucleon structure function in nucleus to be the same as that of free nucleon. The results unambiguously show that it is different.Comment: 11 pages, 3 figures, 1 tabl

Exclusive and semi-inclusive strangeness and charm production in πN\pi N and NNNN reactions

Using the Quark-Gluon Strings Model (QGSM) combined with Regge phenomenology we consider the reactions $\pi^- p \to K^0 \Lambda$ and $\pi^- p \to D^- \Lambda_c^+$ which are dominated by the contributions of the $K^*$ and $D^*$ Regge trajectories, respectively. The spin structure of the amplitudes is described by introducing Reggeized Born terms. It is found that the existing data for the reaction $\pi^- p \to K^0 \Lambda$ are in reasonable agreement with the model predictions. To describe the absolute values of the cross sections it is necessary to introduce also suppression factors which can be related to absorption corrections. Furthermore, assuming the SU(4) symmetry to hold for Regge residues and the universality of absorption corrections we calculate the cross section of the reaction $\pi^- p \to D^- \Lambda_c^+$. Employing the latter results from $\pi^- p$ reactions we then estimate the contributions of the pion exchange mechanism to the cross sections of the reactions $NN \to NK\Lambda$ and $NN \to N\bar D \Lambda_c$ and compare them with the contributions of the $K$ and $D$ exchanges. We find that the $NN$ reactions are dominated not by pion exchange but by $K$ and $D$ exchanges, respectively. Moreover, assuming the SU(4) symmetry to hold approximately for the coupling constants $g_{ND \Lambda_c}$ = $g_{NK \Lambda}$ we analyze also the production of leading $\Lambda_c$ hyperons in the reaction $NN \to \Lambda_c X$. It is shown that the non-perturbative mechanism should give an essential contribution to the $\Lambda_c$ yield for $x \geq 0.5$.Comment: 3 pages, LaTeX, 4 postscript figures; contribution to QNP2002, Juelich, June 10-14, 200

Update on neutrino mixing in the early Universe

From the current cosmological observations of CMB and nuclear abundances we show, with an analytic procedure, that the total effective number of extra neutrino species $\Delta N_{\nu}^{\rm tot}< 0.3$. We also describe the possible signatures of non standard effects that could be revealed in future CMB observations. This cosmological information is then applied to neutrino mixing models. Taking into account the recent results from the SNO and SuperKamiokande experiments, disfavouring pure active to sterile neutrino oscillations, we show that all 4 neutrino mixing models, both of 2+2 and 3+1 type, lead to a full thermalization of the sterile neutrino flavor. Moreover such a sterile neutrino production excludes the possibility of an electron neutrino asymmetry generation and we conclude that $\Delta N_{\nu}^{\rm tot}\simeq 1$, in disagreement with the cosmological bound. This result is valid under the assumption that the initial neutrino asymmetries are small. We suggest the existence of a second sterile neutrino flavor, with mixing properties such to generate a large electron neutrino asymmetry, as a possible way out.Comment: 29 pages, 3 figures; to appear on Phys.Rev.D; added discussion (at page 19) and references; typos correcte

On-line recognition of supernova neutrino bursts in the LVD detector

In this paper we show the capabilities of the Large Volume Detector (INFN Gran Sasso National Laboratory) to identify a neutrino burst associated to a supernova explosion, in the absence of an "external trigger", e.g., an optical observation. We describe how the detector trigger and event selection have been optimized for this purpose, and we detail the algorithm used for the on-line burst recognition. The on-line sensitivity of the detector is defined and discussed in terms of supernova distance and electron anti-neutrino intensity at the source.Comment: Accepted for pubblication on Astroparticle Physics. 13 pages, 10 figure