1,104 research outputs found
Worsening of cerebral hyperemia by the administration of terlipressin in acute liver failure with severe hepatic encephalopathy
There is increasing evidence that terlipressin is useful in patients with cirrhosis and
hepatorenal syndrome, but there are no data of its use in patients with acute liver
failure (ALF) in whom hepatorenal syndrome is common. Although terlipressin
produces systemic vasoconstriction, it produces cerebral vasodilatation and may
increase cerebral blood flow (CBF). Increased CBF contributes to intracranial
hypertension in patients with ALF. The aim of this study was to evaluate the safety of
terlipressin in patients with ALF with respect to cerebral haemodynamics. Six
successive patients with ALF were electively ventilated for grade IV hepatic
encephalopathy. Patients were monitored invasively and CBF was measured (Kety-
Schmidt technique). Measurements were made before, at 1, 3 hour and 5 hours after
intravenous (single bolus) administration of terlipressin (0.005 mg/kg) )intravenously
(single bolus), median 0.25mg (range 0.2-0.3). There was no significant change in
heart rate, mean arterial pressure or cardiac output. CBF and jugular venous oxygen
saturation both increased significantly at 1 hour (p<0.0=0.016) respectively.
Intracranial pressure increased significantly at 21 hours (p<0=.0.031), returning back
to baseline values at 42 hours. This study shows that administration of terlipressin, at
a dose that did not alter systemic haemodynamicshemodynamics, resulted in
worsening of cerebral hyperemia and intracranial hypertension in patients with ALF
and severe hepatic encephalopathy. These data suggest the need to exercise extreme
caution in the use of terlipressin in these patients in view of its potentially deleterious
consequences on cerebral haemodynamics
Clinicopathological evidence that neovascularisation is a cause of recurrent varicose veins
Objectives:Recurrent varicose veins may result from poor initial surgical technique or progression of varicosities in collateral veins. In some cases new veins may develop at the saphenofemoral junction (neovascularisation) and cause recurrent saphenofemoral incompetence. This was a histological study of recurrent varicose veins.Design:This clinicopathological study included 20 patients (median age 55 years) who had surgery for recurrent saphenofemoral incompetence.Materials and methods:A total of 28 legs had groin re-exploration with repeat flush saphenofemoral ligation. The venous tissue block from the saphenofemoral region (including the proximal thigh varicosity) was excised and orientated for histological analysis. Evidence of neovascularisation was sought using routine histological sections and S100 immunohistochemistry.Results:At operation, thin-walled, serpentine neovascular veins were detected clinically as the principal cause of recurrence in 19 groins. In five groins recurrence was due to a residual missed vein at the saphenofemoral junction, and in four recurrence was caused by cross groin collaterals. On histological sections, evidence of neovascularisation was present in 27 of 28 groins. In eight it co-existed with the veins missed at the original operation but it was the sole identified cause of recurrent saphenofemoral incompetence in 19 (68%) groins.Conclusions:Neovascularisation was the principal cause of recurrent saphenofemoral incompetence in this series
Exciton swapping in a twisted graphene bilayer as a solid-state realization of a two-brane model
It is shown that exciton swapping between two graphene sheets may occur under
specific conditions. A magnetically tunable optical filter is described to
demonstrate this new effect. Mathematically, it is shown that two turbostratic
graphene layers can be described as a "noncommutative" two-sheeted
(2+1)-spacetime thanks to a formalism previously introduced for the study of
braneworlds in high energy physics. The Hamiltonian of the model contains a
coupling term connecting the two layers which is similar to the coupling
existing between two braneworlds at a quantum level. In the present case, this
term is related to a K-K' intervalley coupling. In addition, the experimental
observation of this effect could be a way to assess the relevance of some
theoretical concepts of the braneworld hypothesis.Comment: 15 pages, 3 figures, final version published in European Physical
Journal
Effective Functional Form of Regge Trajectories
We present theoretical arguments and strong phenomenological evidence that
hadronic Regge trajectories are essentially nonlinear and can be well
approximated, for phenomenological purposes, by a specific square-root form.Comment: 29 pages, LaTeX. Published versio
Ultraviolet cut off, black hole-radiation equilibrium and big bang
In the presence of a minimal uncertainty in length, there exists a critical
temperature above which the thermodynamics of a gas of radiation changes
drastically.
We find that the equilibrium temperature of a system composed of a
Schwarzschild black hole surrounded by radiation is unaffected by these
modifications. This is in agreement with works related to the robustness of the
Hawking evaporation. The only change the deformation introduces concerns the
critical volume at which the system ceases to be stable.
On the contrary, the evolution of the very early universe is sensitive to the
new behavior. We readdress the shortcomings of the standard big bang
model(flatness, entropy and horizon problems) in this context, assuming a
minimal coupling to general relativity. Although they are not solved, some
qualitative differences set in.Comment: 10 pages revtex, 1 figur
Quantum gates with neutral atoms: Controlling collisional interactions in time dependent traps
We theoretically study specific schemes for performing a fundamental
two-qubit quantum gate via controlled atomic collisions by switching
microscopic potentials. In particular we calculate the fidelity of a gate
operation for a configuration where a potential barrier between two atoms is
instantaneously removed and restored after a certain time. Possible
implementations could be based on microtraps created by magnetic and electric
fields, or potentials induced by laser light.Comment: 10 pages, 3 figure
Low-cost hyperspectral imaging with a smartphone
Recent advances in smartphone technologies have opened the door to the development of accessible, highly portable sensing tools capable of accurate and reliable data collection in a range of environmental settings. In this article, we introduce a low-cost smartphone-based hyperspectral imaging system that can convert a standard smartphone camera into a visible wavelength hyperspectral sensor for ca. £100. To the best of our knowledge, this represents the first smartphone capable of hyperspectral data collection without the need for extensive post processing. The Hyperspectral Smartphone’s abilities are tested in a variety of environmental applications and its capabilities directly compared to the laboratory-based analogue from our previous research, as well as the wider existing literature. The Hyperspectral Smartphone is capable of accurate, laboratory- and field-based hyperspectral data collection, demonstrating the significant promise of both this device and smartphone-based hyperspectral imaging as a whole
Adjoint "quarks" on coarse anisotropic lattices: Implications for string breaking in full QCD
A detailed study is made of four dimensional SU(2) gauge theory with static
adjoint ``quarks'' in the context of string breaking. A tadpole-improved action
is used to do simulations on lattices with coarse spatial spacings ,
allowing the static potential to be probed at large separations at a
dramatically reduced computational cost. Highly anisotropic lattices are used,
with fine temporal spacings , in order to assess the behavior of the
time-dependent effective potentials. The lattice spacings are determined from
the potentials for quarks in the fundamental representation. Simulations of the
Wilson loop in the adjoint representation are done, and the energies of
magnetic and electric ``gluelumps'' (adjoint quark-gluon bound states) are
calculated, which set the energy scale for string breaking. Correlators of
gauge-fixed static quark propagators, without a connecting string of spatial
links, are analyzed. Correlation functions of gluelump pairs are also
considered; similar correlators have recently been proposed for observing
string breaking in full QCD and other models. A thorough discussion of the
relevance of Wilson loops over other operators for studies of string breaking
is presented, using the simulation results presented here to support a number
of new arguments.Comment: 22 pages, 14 figure
Binding Energy of Charged Excitons in ZnSe-based Quantum Wells
Excitons and charged excitons (trions) are investigated in ZnSe-based quantum
well structures with (Zn,Be,Mg)Se and (Zn,Mg)(S,Se) barriers by means of
magneto-optical spectroscopy. Binding energies of negatively () and positively
(X+) charged excitons are measured as functions of quantum well width, free
carrier density and in external magnetic fields up to 47 T. The binding energy
of shows a strong increase from 1.4 to 8.9 meV with decreasing quantum well
width from 190 to 29 A. The binding energies of X+ are about 25% smaller than
the binding energy in the same structures. The magnetic field behavior of and
X+ binding energies differ qualitatively. With growing magnetic field strength,
increases its binding energy by 35-150%, while for X+ it decreases by 25%.
Zeeman spin splittings and oscillator strengths of excitons and trions are
measured and discussed
Revisiting the agro-climatic zones of Ghana: a re-classification in conformity with climate change and variability
The Ghana Meteorological Agency delineated Ghana’s geographical space into four agro-climatic zones namely the north, transition, forest and coastal zones. Since the demarcation in the 1960s, previous studies have rarely provided a more dis-aggregated agro-climatic zone map in tandem with contemporary climate change and variability. The continued use of this age-old classified zones is a disservice to the public. In this study, therefore, we evaluated the existing agro-climatic zone map of Ghana and reconstructed it to a more appropriate and dis-aggregated map that reflect current climate change and variability impact. This was achieved by quantifying the contrast in rainfall and temperature amount over a 30 year period for different climate windows and mapped out areas with similar rainfall and temperature regimes. Our findings revealed significant changes in the existing agro-climatic zones especially in terms of number, the boundary size and geographical orientation of the zones. The newly proposed map consist of five distinctive climate zones namely: the Sudan Savannah, Guinea Savannah, Transition, Forest and Coastal zones. The Sudan and Guinea Savannah zones showed a southerly expansion. The transition zone shriveled in size as the Guinea Savannah zone took over most of it, notably in the southeast. The forest zone shrank in size with a northwest shift while the coastal belt grew to encompass the whole coast of Ghana. These changes are strong evidence of climate change and possible food production changes. These findings are useful to agriculture sector in planning their activities, the health sector in predicting specific diseases caused by changes in weather and climate, Ghana Meteorological Agency for weather forecasting purposes, and the National Disaster Management in identifying disaster prone zones
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