Early treatment of acute biliary pancreatitis by endoscopic papillotomy

Background. Most patients with acute biliary pancreatitis have stones in the biliary tract or ampulla of Vater. Because these stones may be passed spontaneously soon after a patient is admitted to the hospital, the importance of early operative removal is not known. We tested the hypothesis that endoscopic papillotomy within 24 hours of admission decreased the incidence of complications in patients with acute biliary pancreatitis. Methods. We studied 195 patients with acute pancreatitis who were randomly assigned to one of two groups: 97 patients underwent within 24 hours after admission emergency endoscopic retrograde cholangiopancreatography (ERCP) followed by endoscopic papillotomy for ampullary and common-bile-duct stones, and 98 patients received initial conservative treatment and selective ERCP with or without endoscopic papillotomy only if their condition deteriorated. Results. One hundred twenty-seven patients ultimately proved to have biliary stones. Emergency ERCP with or without endoscopic papillotomy resulted in a reduction in biliary sepsis as compared with conservative treatment (0 of 97 patients vs. 12 of 98 patients, P = 0.001). The decrease in biliary sepsis occurred both in patients predicted to have mild pancreatitis (0 of 56 patients in the group that received emergency ERCP vs. 4 of 58 patients in the conservative-treatment group, P = 0.14) and in patients predicted to have severe pancreatitis (0 of 41 patients vs. 8 of 40 patients, P = 0.008). In all patients who had unrelenting biliary sepsis, persistent ampullary or common-bile-duct stones were identified. There were no major differences in the incidence of local complications (10 patients in the group that received emergency ERCP vs. 12 patients in the conservative-treatment group) or systemic complications (10 patients vs. 14 patients) of acute pancreatitis between the two groups, but the hospital mortality rate was slightly lower in the group undergoing emergency ERCP with or without endoscopic papillotomy (5 patients vs. 9 patients, P = 0.4). Conclusions. Emergency ERCP with or without endoscopic papillotomy is indicated in the treatment of patients with acute pancreatitis.published_or_final_versio

Temperature dependent distinct coupling and dispersions of heavy- and light-hole excitonic polaritons in ZnO

Distinct coupling behavior of heavy- and light-hole excitonic polaritons in ZnO was unveiled by investigating the optical reflectance spectra of a high quality ZnO single crystal as a function of temperature both experimentally and theoretically. A resonance like coupling region was found at a temperature of around 50 K at which several relevant physical quantities such as the transverse exciton transition energy, polarizability, and damping parameters of the two kinds of excitonic polaritons were revealed to overturn. Calculated dispersions correctly reflect the nature of coupled photon and exciton and reproduce the spectral structures of the interacting polaritons. © 2012 American Institute of Physics.published_or_final_versio

Experimental investigation of multi-step stress-relaxation-ageing of 7050 aluminium alloy for different pre-strained conditions

A novel insight into the whole two-step stress relaxation ageing process during T74 multi–step ageing treatment (120 °C for 6 h and subsequently 177 °C for 7 h), which is typically experienced by extra-large aircraft components that contain high residual stresses, has been established. Stress relaxation ageing (SRA) tests, tensile tests and transmission electron microscopy (TEM) were performed on AA7050 samples to determine the relationship between internal microstructure and macroscopic behaviour during the stress relaxation and precipitate evolution process. Samples were subjected to SRA at different initial stresses (220–360 MPa) after being pre-strained to different extents (i.e. 0%, 1%, 3%). Room temperature tensile tests were then performed on interrupted SRA test specimens to examine the corresponding strengthening phenomenon. TEM was performed on a selection of peak–aged and T74 over–aged samples to study the precipitate distribution. At 120 °C typical stress relaxation behaviour was observed and the data follow ed a logarithmic curve. Subsequently at 177 °C, dislocation–creep dominated stress relaxation behaviour, with no apparent threshold stress, was observed. The absence of a threshold stress at 177 °C may be attributed to the continuous over-ageing phenomenon. The effect of pre-deformation levels and initial stresses on SRA has also been investigated. Pre-stretching, which creates uniformly distributed dislocations, promotes stress relaxation and ageing. No significant influence of initial stress level on SRA was observed at 120 °C, but noticeable effects were seen at 177 °C. The calculated stress exponent n at 177 °C is found independent of the initial stresses. These findings provide clear scientific guidance for residual stress reduction during the multi-step ageing process of AA7050 and provide the basis for residual stress prediction models

Can interference patterns in the reflectance spectra of GaN epilayers give important information of carrier concentration?

Low-temperature reflectance spectra of a series of Si-doped GaN epilayers with different doping concentrations grown on sapphire by metal-organic chemical vapour deposition were measured. In addition to the excitonic polariton resonance structures at the band edge, interference oscillating patterns were observed in the energy region well below the band gap. The amplitudes of these oscillation patterns show a distinct dependence on the doping concentrations of the samples. From the thin-film optical interference principle, an approach connecting the amplitude of the interference oscillations and the impurity scattering was established. Good agreement between experiment and theory is achieved. © 2012 American Institute of Physics.published_or_final_versio

Inner surface enhanced femtosecond second harmonic generation in thin ZnO crystal tubes

2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Field-Effect Ferroelectric-Semiconductor Solar Cells

Traditional photovoltaic devices employ limited semiconductor materials largely due to the P-N junction structure. We have developed a new kind of field-effect ferroelectric semiconductor solar cells. Prototype cells have been demonstrated successfully. Substantial photovoltaic effect and rectifying behavior were experimentally observed. In addition, simulation study was conducted to indicate that the induced electric field due to the bound surface changes of the ferroelectric could be extended into the semiconductor. The simulation results are consistent with experimental observations. This unique device structure offers a promising alternative to achieve novel solar cells. The new cells are not P-N junction based, and in principle offer more flexibility in materials selection and optimizing charge generation, separation and collection for achieving high performance solar cells.published_or_final_versio

Field-effect BaTiO3-Si solar cells

published_or_final_versio

Liver grafts for transplantation from donors with diabetes: an analysis of the Scientific Registry of Transplant Recipients database

published_or_final_versio

Water-wax behaviour in porous silica at low temperature Fischer-Tropsch conditions

© 2018 Water is a major product of Fischer-Tropsch synthesis, and hence the behaviour of water within Fischer-Tropsch synthesis catalysts and its potential influence on catalyst rate and selectivity are questions of long-standing interest. The present work applies three different magnetic resonance techniques to study how water interacts with a model wax, n-octacosane, within the pore space of a porous silica of mean pore size ∼18 nm. 1H magnetic resonance spectroscopy, spin-lattice relaxation time and pulsed-field gradient measurements were performed at 195 °C, and for water pressure in the range 3–13.6 bar, conditions relevant to low temperature Fischer-Tropsch synthesis. The uptake of water within this system is shown to be very similar to that observed for capillary condensation of water within the empty pore space of the same porous silica under the same experimental conditions; suggesting that capillary condensation of water within the wax-saturated pores is occurring. The behaviour of water is characterised by two regimes. At low water relative pressures of ∼0.3 ≤ P/P0 ≤ ∼0.8 water moves into the pore space, displacing wax from the pore surface and existing as a water-rich layer between the pore surface and an oil-rich phase in the centre of the pore; the strong interaction with the pore surface is evidenced by the short nuclear spin relaxation time values of water at the lowest pressures which then increase slightly as multi-layer adsorption at the pore surface occurs with increase in pressure. In the water relative pressure range ∼0.8 ≤ P/P0 ≤ ∼0.97, condensation of water within the pores is observed, characterised by increases in both spin-lattice relaxation time and molecular diffusivity. Analysis of the data suggests that as much as ∼40% of the pore surface is occupied by condensed water after condensation has occurred. It is suggested that these two regimes of water behaviour inside initially wax-filled pores might explain previously reported aspects of the behaviour of Fischer-Tropsch catalyst performance as a function of pore size and amount of co-fed water

Contribution of the cyclic nucleotide gated channel subunit, CNG-3, to olfactory plasticity in Caenorhabditis elegans.

In Caenorhabditis elegans, the AWC neurons are thought to deploy a cGMP signaling cascade in the detection of and response to AWC sensed odors. Prolonged exposure to an AWC sensed odor in the absence of food leads to reversible decreases in the animal's attraction to that odor. This adaptation exhibits two stages referred to as short-term and long-term adaptation. Previously, the protein kinase G (PKG), EGL-4/PKG-1, was shown necessary for both stages of adaptation and phosphorylation of its target, the beta-type cyclic nucleotide gated (CNG) channel subunit, TAX-2, was implicated in the short term stage. Here we uncover a novel role for the CNG channel subunit, CNG-3, in short term adaptation. We demonstrate that CNG-3 is required in the AWC for adaptation to short (thirty minute) exposures of odor, and contains a candidate PKG phosphorylation site required to tune odor sensitivity. We also provide in vivo data suggesting that CNG-3 forms a complex with both TAX-2 and TAX-4 CNG channel subunits in AWC. Finally, we examine the physiology of different CNG channel subunit combinations