Transoesophageal echocardiographic assessment of haemodynamic function during laparoscopic cholecystectomy

We have measured cardiovascular changes associated with insufflation of carbon dioxide and the reverse Trendelenburg position during laparoscopic cholecystectomy, using transoesophageal echocardiography in 13 healthy patients. End-tidal carbon dioxide values increased after insufflation of carbon dioxide, with values significantly (P < 0.05) increased after lateral tilt positioning. Creation of a pneumoperitoneum was associated with increases (P < 0.05) in left ventricular end-systolic wall stress, concomitant with increases (P < 0.01) in peak airway pressure and systemic arterial pressure. In addition, left ventricular end-diastolic area decreased (P < 0.05) after reverse Trendelenburg positioning. Left ventricular ejection fraction was maintained throughout the study.     

89-GHz fT room-temperature silicon MOSFETs

The authors report the implementation of deep-submicrometer Si MOSFETs that at room temperature have a unity-current-gain cutoff frequency (f_T) of 89 GHz, for a drain-to-source bias of 1.5 V, a gate-to-source bias of 1 V, a gate oxide thickness of 40 Å, and a channel length of 0.15 μm. The fabrication procedure is mostly conventional, except for the e-beam defined gates. The speed performance is achieved through an intrinsic transit time of only 1.8 ps across the active device region     

Measuring hospital performance: are we asking the right questions?

The aim of this randomized cross-over trial was to evaluate the dose effect and systemic absorption of epinephrine nebulized at 2 and 5 mg in comparison with salbutamol (5 mg). Thirteen asthmatic patients (29 +/- 15 years, 4 men and 9 women) were randomly assigned to receive one nebulization of each of the three treatment regimens at 24 h interval. The evaluation concerned forced expiratory volume in 1 second (FEV1), heart rate, respiratory rate and arterial pressure. All measurements were done at baseline, every 15 minutes during the first hour, and hourly thereafter until return to baseline FEV1. Serum potassium was measured at baseline (T0) and sixty minutes after (T60). Plasma levels of epinephrine were measured at T0, T20, T60. Fifteen minutes after the beginning of nebulization FEV1 improved significantly over baseline in the three groups. These changes were similar in the three groups until T45, while FEV1 improvement was significantly greater in A5 and S groups than A2 group (+640 +/- 470 ml, +721 +/- 349 ml, +406 +/- 306 ml in A5, S and A2 groups respectively, p < 0.01). Bronchodilation lasted significantly longer with salbutamol than with epinephrine (p < 0.05). No side effects were recorded in spite of substantial and dose-dependent systemic absorption of epinephrine. CONCLUSION: Increasing epinephrine doses produces greater bronchodilation without additional side effects. However this bronchodilation lasts shorter than with salbutamol.     

Electrical heat tracing: international harmonization-now and in thefuture

In the past, electrical heat tracing has been thought of as a minor addition to plant utilities. Today, it is recognized as a critical subsystem to be monitored and controlled. A marriage between process, mechanical, and electrical engineers must take place to ensure that optimum economic results are produced. The Internet, expert systems, and falling costs of instrumentation will all contribute to more reliable control systems and improved monitoring systems. There is a harmonization between Europe and North America that should facilitate design and installation using common components. The future holds many opportunities to optimize the design     

Ground antennas in NASA's deep space telecommunications

Ground antennas are the major visible components of NASA's Deep Space Network (DSN). The role, key characteristics, and performance of these antennas in deep-space telecommunications are described. The system analyses and tradeoffs to optimize the overall ground-to-spacecraft link and to define future missions are elaborated from an antenna perspective. Overall performance of receiving systems is compared using the widely accepted G/T figure-of-merit, i.e., net antenna gain divided by the operating system noise temperature. Performance of past, present, and future antennas and receiving systems is discussed, including the planned development of a world-wide network of 34-m diameter beam-waveguide antennas. The need for multifrequency operation, presently in the S- and X-bands, and in the future in the Ka-band, is discussed. The resulting requirements placed on antenna technology are highlighted. Beam-waveguide antenna performance to further improve performance and operational advantages is discussed     

Safety considerations for electrical heat tracing

Since the advent of electrical heat tracing over 50 years ago, many challenges have confronted industry to ensure safe and reliable heat tracing operation. Reliability of heat tracing systems can directly affect safety-related operations, such as fire protection and emergency eyewash and safety showers. As a good practice, the safety of process systems should not be dependent on the performance of a single component of the heat tracing system. The primary purpose of this article is to address the issue of high-impedance, low-current faults that have been reported in electrical heating cables. These faults usually initiate from phase to ground but have currents that are insufficient to trip the circuit protective device. However, the faults can dissipate enough energy to cause fires and other equipment damage     

An investigation into the amorphous phase separation characteristics of an ionomer glass series and a sodium-boro-silicate glass system

Amorphous phase separation of ionomer glasses, also known as fluoro-phospho-alumino-silicate glasses, of generic composition SiO₂-Al₂O₃-P₂O₅-CaO-CaF₂ were investigated. A sodium-boro-silicate glass system, which is known to undergo amorphous phase separation was also investigated. High Temperature Dynamic-Mechanical Thermal Analysis (DMTA), combined Differential Thermal Analysis/Thermo Gravimetric Analysis (DTA/TGA) and Scanning Electron Microscopy (SEM) were the principal analytical techniques used in this study. High temperature DMTA was used to measure the glass transition temperatures (T _g) of the original starting glass compositions, as well as being able to follow amorphous phase separation (APS) within the glass. High temperature DMTA traces of both the ionomer glasses and the sodium-boro-silicate glasses exhibited two maxima in tan , corresponding to two glass transition temperatures and demonstrating that amorphous phase separation of the parent glass into two glass phases had occurred. DTA/TGA of the ionomer glasses detected a glass transition and two crystallisation peaks for apatite and mullite, accompanied by a gradual weight loss of 1–3% on passing through the crystallisation region. The sodium-boro-silicate base glass showed no evidence of a glass transition, but a prominent glass transition was detected for a second sample which had undergone a heat-treatment of 240 min at 580°C. SEM analysis of the ionomer glass compositions revealed smooth spherical droplets of 2–15 nm while the background morphology appeared rough and speckled. A classic interconnected structure was observed for the sodium-boro-silicate glass.     

Cervical exploration for primary hyperparathyroidism--A 25 year experience

Parathyroidectomy should be considered in every patient with hypercalcaemia and primary hyperparathyroidism even if the symptoms are vague. Cervical exploration is a safe operation with very satisfactory results. Our experience in 214 patients over 25 years shows permanent postoperative normocalcaemia in 95% of cases with a complication rate of 2.8%. All patients with primary HPT, regardless of age or the severity of symptoms should be candidates for cervical exploration.     

Laboratory Measurements and a Theoretical Analysis of the TCT Fading Channel Radio System

This paper documents the laboratory and theoretical performance of a pilot-aided digital radio system. The technique considered transmits a midband pilot tone to improve the receiver data detection performance in a multipath fading channel and is referred to as the tone calibrated technique (TCT). We report on the performance of a 860 MHz prototype system carrying 2.4 kbit/s data under Rician fading conditions. Both experimental and analytical results show that the error floor experienced with nonpilot-aided transmission methods is effectively removed by the TCT scheme, resulting in significant performance gains at high signal-to-noise ratio (SNR) values. The paper also examines the TCT system performance under typical operating conditions and presents a new analysis of the TCT theoretical error probability.     

Inactivation of O6-alkylguanine-DNA alkyltransferase. 1. Novel O6-(hetarylmethyl)guanines having basic rings in the side chain

A number of novel guanine derivatives containing heterocyclic moieties at the O6-position have been synthesized using a purine quaternary salt which reacts with alkoxides under mild conditions. Initially O6-substituents were investigated in which the benzene ring of the known agent, O6-benzylguanine, was replaced by unsubstituted heterocyclic rings. The ability of these agents to inactivate the DNA repair protein O6-alkylguanine-DNA alkyltransferase (ATase), both as pure recombinant protein and in the human lymphoblastoid cell line Raji, has been compared with that of O6-benzylguanine. The present paper focuses on O6-substituents with basic rings, and under standard conditions several of them proved more effective than benzyl for inactivation of both recombinant and Raji ATase. Among the pyridine derivatives, the 2-picolyl compound 7 is not very active in contrast to the 3- and 4-picolyl compounds, and this influenced our choice of isomers of other basic ring systems for study. Since halogen substitution in the thiophene ring considerably increased the activity (17 versus 6), similar modifications in the pyridine series were examined. The more polar O6-substituents in this study are on the whole compatible with the stereochemical requirements of the ATase protein, and their pharmacological properties may be valuable in subsequent in vivo investigations, particularly the thenyl (6), 5-thiazolylmethyl (12), 5-bromothenyl (17), and 2-chloro-4-picolyl (21) derivatives.