Treatment of vancomycin-resistant Enterococcus faecium infections with an investigational streptogramin antibiotic (quinupristin/dalfopristin): a report of fifteen cases

OBJECTIVE: Previous studies of surgical treatment for acromegaly have used varied criteria for 'cure', but elevated GH levels are considered to be associated with continuing disease activity. We wished to analyse the results of transsphenoidal pituitary surgery for acromegaly and assess the longer-term outcome for patients not offered further treatment when post-operative levels of GH < 5 mU/l were achieved. DESIGN: We studied a retrospective group of patients who underwent transsphenoidal surgery for acromegaly at St Bartholomew's Hospital between 1985 and 1993. PATIENTS: One hundred consecutive patients (53 male, mean age 46 years, range 18-68 years) undergoing transsphenoidal surgery for acromegaly were assessed. The patients were followed for a mean of 3.8 years (range 0.5-8 years) after operation. MEASUREMENTS: GH levels are represented as a mean value from a four-point day curve taken at 0830, 1300, 1700 and 1900 h. ACTH reserve was assessed basally and, if this was normal, with the insulin tolerance or glucagon tests. TSH, T4, PRL, LH, FSH, testosterone or oestradiol and plasma and urine osmolality were also measured. RESULTS: Post-operatively, 42% of patients achieved a mean GH level of < 5 mU/l. The success of surgery was related to the preoperative GH level; 65% of the patients with preoperative GH levels < 20 mU/l but only 18% of the patients with GH levels > 100 mU/l achieved post-operative GH values < 5 mU/l. In addition, tumour size influenced the outcome of surgery with 61% of patients with a microadenoma but only 23% of patients with a macroadenoma achieving post-operative GH levels of < 5 mU/l. Of the 42 patients considered in remission post-operatively (mean GH < 5 mU/l), 32 were available for long-term follow-up and were not offered any further treatment: only one of these has shown evidence of mild biochemical recurrence after a mean follow-up of 3.8 years (range 0.5-8). There were no peri-operative deaths. Two patients required surgical repair for CSF leaks and there were eight documented cases of meningitis. Permanent diabetes insipidus was noted in eight patients post-operatively. New anterior pituitary deficiency occurred in 21% of patients following surgery; 73% had unaltered pituitary function and in 6% recovery of partial hypopituitarism was noted. CONCLUSIONS: The stated outcome of surgery depends on the criteria adopted. Safe GH levels (mean levels < 5 mU/l) can be achieved in 42% of an unselected series of patients with acromegaly and if the tumour is a microadenoma this figure rises to 61%. Based on the current evidence it is safe not to offer further treatment to those patients in whom post-operative GH < 5 mU/l are achieved.     

Improving generalization capabilities of dynamic neural networks

This work addresses the problem of improving the generalization capabilities of continuous recurrent neural networks. The learning task is transformed into an optimal control framework in which the weights and the initial network state are treated as unknown controls. A new learning algorithm based on a variational formulation of Pontrayagin's maximum principle is proposed. Under reasonable assumptions, its convergence is discussed. Numerical examples are given that demonstrate an essential improvement of generalization capabilities after the learning process of a dynamic network.     

Numerical limit analysis of perforated plates

Full limit analysis is preseted of a thin plate under plane stress, perforated with circular holes arranged in a regular penetration pattern. The material is assumed to be elastic–perfectly plastic and to obey the Huber–Mises yield condition together with its associated flow law. The finite element tangential stiffness method is employed. Triangular constant-strain elements are used, the load being generated by means of constant edge displacements at the periphery of a suitably selected subregion. Load-displacement diagrams are obtained for various edge displacement programs and then an interaction curve is constructed for the perforated plate considered. Each computational step is associated with a certain plastic zone which develops until the limit state configuration is reached. The plate is provided with equilateral triangular configuration of holes with arbitrary cutout coefficients. The interaction curves are plotted against the Huber–Mises yield condition for the plate without openings.     

A model of the temperature distribution in an alumina coating during plasma spraying

An attempt to develop a theory for the calculation of the temperature distribution in a plasma-sprayed coating is presented. This theory takes into account both the physical properties of sprayed (not the bulk) material and the effect of thermal resistance between the coating and the substrate. The calculation procedure employed (finite differences) permits the theoretical prediction of the temperature distribution in samples of limited dimensions. The theory was used to determine the temperature distribution in alumina coatings plasma sprayed onto copper or mild steel substrates. A comparison between the theoretical predictions and experimentally determined surface coating temperatures is also presented. The experiments were carried out using IR thermography. For these measurements it was necessary to determine the emissivity of the sprayed alumina at the IR wavelength of interest. The influence of the spraying distance, the substrate material and cooling of the sprayed samples on the coating surface temperature was investigated. The predicted temperatures are within 20% of the experimental values.     

Polymerization of 2-hydroxyethyl acrylate and methacrylate <Emphasis Type="Italic">via</Emphasis> Michael-type addition

Summary 2-Hydroxyethyl acrylate was polymerized by use of few basic andlor nucleophilic initiators. The reactions proceeded via Michael-type addition of hydroxyl groups to carbon-carbon double bonds. The resulted polymers have an ether-ester chain structure and M_n values in order of up to 9000. The results were compared with those obtained previously for 2-hydroxyethyl methacrylate, where just oligomers having M_n of ca 1000 had been achieved.     

Thermische Ausdehnung,innere Spannungen und Porenverteilung in AlSiCp Metallmatrix‐ verbundwerkstoffen

Thermal expansion, internal stresses and porosity distribution in AlSiCp MMC AlSi7Mg/SiC/70p (AlSiC) is used for heat sinks because of its good thermal conductivity combined with a low coefficient of thermal expansion (CTE). These properties are important for power electronic devices where heat sinks have to provide efficient heat transfer to a cooling device. A low CTE is essential for a good surface bonding of the heat sink material to the isolating ceramics. Otherwise mismatch in thermal expansion would lead to damage of the bonding degrading the thermal contact within the electronic package. Therefore AlSiC replaces increasingly copper heat sinks. The CTE mismatch between isolation and a conventional metallic heat sink is transferred into the metal matrix composite (MMC). The stability of the external and internal interface bonding is essential for the heat sink function of AlSiC. In situ thermal cycling (RT – 400 °C) measurements of an AlSi7Mg/SiC/70p MMC are reported yielding the pore volume fraction and internal stresses between the matrix and the reinforcements in function of temperature. The changes in pore volume fractions are determined by synchrotron tomography and residual stresses by synchrotron diffraction at ESRF‐ID15A. The measurements show a relationship between thermal expansion, residual stresses and pore formation in the MMC. The results obtained from the in situ measurements reveal a thermo elastic range with inversion of the dominant tensile stresses in the matrix into compressive up to 200 °C followed by plastic matrix deformation reducing the volume of pores during heating. A reverse process takes place during cooling from 500 °C starting with elastic matrix strains converting into tensile stresses increasing the pore volume fraction again. Below 200 °C, the CTE behaves again according to thermo elastic calculations. Damage like in low cycle fatigue could be observed after multiple extreme cooling‐heating cycles between –100 °C and +400 °C, which increase the volume fraction and the size of the voids.     

Microstructural Changes in Wood Plastic Composites Due to Wetting and Re-drying Evaluated by X-ray Microtomography

An extruded wood polypropylene composite subjected to soaking-drying cycles in distilled water was investigated nondestructively using an X-ray microtomography. The representative elementary volumes of the material were examined and discussed using means/median of image intensity values and void contents in 3D XMT images. A 2 mm cube was determined as the representative elementary volume for this material. There were some differences for means in the dry, wet, and re-dried states. The specimen cutting position, i.e., surface or core, affects the results because there was a “resin rich/glazed” surface layer formed during extrusion and the WPPC material had a larger scale heterogeneity, which relates to the difference in flow rate between the core and face of a die. The void contents of re-dried specimens were higher than those of dry specimens.