1,166 research outputs found
Safety of clonidine used for long-term sedation in paediatric intensive care: A systematic review
AIM:
Although not approved, the α-adrenoceptor agonist clonidine is considered an option for long-term sedation protocols in paediatric intensive care. We reviewed adverse effects of clonidine occurring in this indication.
METHODS:
Relevant literature was systematically identified from PubMed and Embase. We included interventional and observational studies on paediatric patients admitted to intensive care units and systemically long-term sedated with clonidine-containing regimes. In duplicates, we conducted standardised and independent full-text assessment and extraction of safety data.
RESULTS:
Data from 11 studies with 909 patients were analysed. The studies were heterogeneous regarding patient characteristics (age groups, comorbidity, or comedication) and sedation regimes (dosage, route, duration, or concomitant sedatives). Just four randomised controlled trials (RCTs) and one observational study had comparison groups, using placebo or midazolam. For safety outcomes, our validity evaluation showed low risk of bias only in three studies. All studies focused on haemodynamic problems, particularly bradycardia and hypotension. Observed incidences or subsequent interventions never caused concerns. However, only two RCTs allowed meaningful comparisons with control groups. Odds ratios showed no significant difference between the groups, but small sample sizes (50 and 125 patients) must be considered; pooled analyses were not reasonable.
CONCLUSION:
All evaluated studies concluded that the use of clonidine in paediatric intensive care units is safe. However, a valid characterisation of the safety profile remains challenging due to limited, biased and heterogeneous data and missing investigation of long-term effects. This evaluation demonstrates the lack of data, which prevents reliable conclusions on the safety of clonidine for long-term sedation in critically ill children. For an evidence-based use, further studies are needed
Black Hole - Neutron Star Mergers as Central Engines of Gamma-Ray Bursts
Hydrodynamic simulations of the merger of stellar mass black hole - neutron
star binaries (BH/NS) are compared with mergers of binary neutron stars
(NS/NS). The simulations are Newtonian, but take into account the emission and
backreaction of gravitational waves. The use of a physical nuclear equation of
state allows us to include the effects of neutrino emission. For low neutron
star to black hole mass ratios the neutron star transfers mass to the black
hole during a few cycles of orbital decay and subsequent widening before
finally being disrupted, whereas for ratios near unity the neutron star is
already distroyed during its first approach. A gas mass between about 0.3 and
about 0.7 solar masses is left in an accretion torus around the black hole and
radiates neutrinos at a luminosity of several 10^{53} erg/s during an estimated
accretion time scale of about 0.1 s. The emitted neutrinos and antineutrinos
annihilate into electron-positron pairs with efficiencies of 1-3% percent and
rates of up to 2*10^{52} erg/s, thus depositing an energy of up to 10^{51} erg
above the poles of the black hole in a region which contains less than 10^{-5}
solar masses of baryonic matter. This could allow for relativistic expansion
with Lorentz factors around 100 and is sufficient to explain apparent burst
luminosities of up to several 10^{53} erg/s for burst durations of
approximately 0.1-1 s, if the gamma emission is collimated in two moderately
focussed jets in a fraction of about 1/100-1/10 of the sky.Comment: 8 pages, LaTex, 4 postscript figures, 2 tables. ApJ Letters,
accepted; revised and shortened version, Fig. 2 change
Magneto-optical evidence of the percolation nature of the metal-insulator transition in the 2D electron system
We compare the results of the transport and time-resolved
magneto-luminescence measurements in disordered 2D electron systems in
GaAs-AlGaAs heterostructures in the extreme quantum limit, in particular, in
the vicinity of the metal-insulator transition (MIT). At filling factors , the optical signal has two components: the single-rate exponentially
decaying part attributed to a uniform liquid and a power-law long-living tail
specific to a microscopically inhomogeneous state of electrons. We interprete
this result as a separation of the 2D electron system into a liquid and
localized phases, especially because the MIT occurs strikingly close to those
filling factors where the liquid occupies of the sample area (the
percollation threshold condition in two-component media).Comment: 5 pages RevTex + 4 fig., to appear in PRB, Rapid Com
Sfermion Pair Production in Polarized and Unpolarized Collisions
We calculate total and differential cross sections for the production of
sfermion pairs in photon-photon collisions, including contributions from
resolved photons and arbitrary photon polarization. Sfermion production in
photon collisions depends only on the sfermion mass and charge. It is thus
independent of the details of the SUSY breaking mechanism, but highly sensitive
to the sfermion charge. We compare the total cross sections for bremsstrahlung,
beamstrahlung, and laser backscattering photons to those in
annihilation. We find that the total cross section at a polarized photon
collider is larger than the annihilation cross section up to the
kinematic limit of the photon collider.Comment: 19 pages, Latex, 18 (e)ps-figure
Quantum Hall Effect induced by electron-electron interaction in disordered GaAs layers with 3D spectrum
It is shown that the observed Quantum Hall Effect in epitaxial layers of
heavily doped n-type GaAs with thickness (50-140 nm) larger the mean free path
of the conduction electrons (15-30 nm) and, therefore, with a three-dimensional
single-particle spectrum is induced by the electron-electron interaction. The
Hall resistance R_xy of the thinnest sample reveals a wide plateau at small
activation energy E_a=0.4 K found in the temperature dependence of the
transverse resistance R_xx. The different minima in the transverse conductance
G_xx of the different samples show a universal temperature dependence
(logarithmic in a large range of rescaled temperatures T/T_0) which is
reminiscent of electron-electron-interaction effects in coherent diffusive
transport.Comment: 6 pages, 3 figures, 1 tabl
Sfermion Pair Production at Colliders
We discuss pair production of stops, sbottoms, staus and tau--sneutrinos at a
collider. We present the formulae for the production cross
sections and perform a detailed numerical analysis within the Minimal
Supersymmetric Standard Model. In particular, we consider sfermion production
near and .Comment: 21 pages, Latex, uses Revtex (included), 8 figures (included as
PS-files
Human neutrophil clearance of bacterial pathogens triggers anti-microbial gamma delta T cell responses in early infection
Human blood Vc9/Vd2 T cells, monocytes and neutrophils share a responsiveness toward inflammatory chemokines and are rapidly recruited to sites of infection. Studying their interaction in vitro and relating these findings to in vivo observations in patients may therefore provide crucial insight into inflammatory events. Our present data demonstrate that Vc9/Vd2 T cells provide potent survival signals resulting in neutrophil activation and the release of the neutrophil chemoattractant CXCL8 (IL-8). In turn, Vc9/Vd2 T cells readily respond to neutrophils harboring phagocytosed bacteria, as evidenced by expression of CD69, interferon (IFN)-c and tumor necrosis factor (TNF)-a. This response is dependent on the ability of these bacteria to produce the microbial metabolite (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP), requires cell-cell contact of Vc9/Vd2 T cells with accessory monocytes through lymphocyte function-associated antigen-1 (LFA-1), and results in a TNF-a dependent proliferation of Vc9/Vd2 T cells. The antibiotic fosmidomycin, which targets the HMB-PP biosynthesis pathway, not only has a direct antibacterial effect on most HMB-PP producing bacteria but also possesses rapid anti-inflammatory properties by inhibiting cd T cell responses in vitro. Patients with acute peritoneal-dialysis (PD)-associated bacterial peritonitis – characterized by an excessive influx of neutrophils and monocytes into the peritoneal cavity – show a selective activation of local Vc9/Vd2 T cells by HMB-PP producing but not by HMB-PP deficient bacterial pathogens. The cd T celldriven perpetuation of inflammatory responses during acute peritonitis is associated with elevated peritoneal levels of cd T cells and TNF-a and detrimental clinical outcomes in infections caused by HMB-PP positive microorganisms. Taken together, our findings indicate a direct link between invading pathogens, neutrophils, monocytes and microbe-responsive cd T cells in early infection and suggest novel diagnostic and therapeutic approaches.Martin S. Davey, Chan-Yu Lin, Gareth W. Roberts, Sinéad Heuston, Amanda C. Brown, James A. Chess, Mark A. Toleman, Cormac G.M. Gahan, Colin Hill, Tanya Parish, John D. Williams, Simon J. Davies, David W. Johnson, Nicholas Topley, Bernhard Moser and Matthias Eber
Supersymmetric Higgs production in gluon fusion at next-to-leading order
The next-to-leading order (NLO) QCD corrections to the production and decay
rate of a Higgs boson are computed within the framework of the Minimal
Supersymmetric Standard Model (MSSM). The calculation is based on an effective
theory for light and intermediate mass Higgs bosons. We provide a Fortran
routine for the numerical evaluation of the coefficient function. For most of
the MSSM parameter space, the relative size of the NLO corrections is typically
of the order of 5% smaller than the Standard Model value. We exemplify the
numerical results for two scenarios: the benchmark point SPS1a, and a parameter
region where the gluon-Higgs coupling at leading order is very small due to a
cancellation of the squark and quark contributions.Comment: 27 pages, LaTeX, 31 embedded PostScript-files; v2: typos corrected,
reformatted in JHEP style; accepted for publication in JHE
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