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A capacitive-discharge spot welder is described which is primarily intended for making electrical connections between small (

A clearance‐sealed piston pump has been developed which can be used to move high pressure gases in a closed loop for the purpose of purification, mixing, or phase equilibration. It has been designed primarily with the former role in mind, so that inert gases may be used in the preparation of high purity intermetallic compounds to suppress the evaporation of volatile constituents without introducing contamination. To this end, the device is made in such a way as to minimize outgassing, leakage, the formation of dead volumes, and the creation of debris. The pump is intended for use at pressures of up to 200 bar. Its structural materials are highly resistant to corrosion, and this should enable the device to be used with a wide variety of reactive gases. Flow rates of between 4.3 and 0.043 l min−1 can be sustained without difficulty using realistic loads, although larger and smaller ones are possible. The pump is capable of producing a head of 0.23 bar. A novel system has been developed for sensing and controlling the position of the piston. This makes it possible to monitor and vary the instantaneous flow rate while minimizing wear and vibration. The arrangement does not require the presence of a transducer or any kind of feedthrough in the clean, high pressure environment. It may find applications in other areas where positioning is needed under hostile or demanding conditions, such as inside ultrahigh vacuum apparatus.

Introduction Generally, nearly all of the equipment, devices, substances, and software that are employed in scientific research are of commercial origin. It is clear from everyday experience that the reliability and usability of such products can range from superb to abysmal. (Usability has an impact on overall reliability through its effect on human error.) Low-quality items, coupled with poor documentation (e.g. operating instructions), and lack of after-sales technical support from the companies that made them, can have a very harmful effect on laboratory productivity. The purpose of this chapter is to provide ways of avoiding such problems. Using established technology and designs As was pointed out in a general context on page 4, if reliability is important, one should not normally employ devices or software that use a technology which has not previously been in commercial production. Most innovative things have unforeseen problems (sometimes in very significant numbers), which can be found and dealt with only after such things have been tested by many users over an extended period. This is a particularly serious issue with computer software (see page 504).

Summary: Azathioprine and cyclophosphamide in doses of 200 mg/day for a proposed duration of one year were compared as adjuncts to prednisolone in the treatment of systemic lupus erythematosus (SLE) in relapse, in a model trial designed to extract maximum information by using multiple indices in few patients. Neither drug proved clearly superior. The possibly greater effectiveness of cyclophosphamide was attributed to a relatively higher effective dosage; however this was offset by more frequent side effects, and in particular the planned 12 months' course of therapy was completed by only one of five cyclophosphamide-treated patients as compared with four of five azathioprine-treated patients. Continuing the trial by including more patients or prolonging treatment was not likely to have yielded additional information. This study on SLE in relapse indicated, at most, that azathioprine and cyclophosphamide may have an accessory role in therapy of this disease, for prednisolone-sparing effects.

The ac response at frequencies to 50 MHz of two thin‐film magnetic recording heads placed in mirror symmetry with respect to one another is measured as a function of relative position and applied dc fields. One driven head can be used to sense the presence of a second head even when the second head is not driven. An array of wires with current in alternating directions from wire to wire is used to obtain the absolute response of thin‐film heads. The efficiency of a head is found to be about 2/3.

Reduced platelet survival has been found in patients who have reccurrent VTE despite anticoagulant treatment, impaired fibrinolytic activity has been found in patients with recurrent VTE, and a reduced AT III level occurs in some families with VTE. This has led to the use of drugs which correct these abnormalities in patients with VTE. However, the incidence of these, and other, abnormalities of hemostasis in unselected patients with VTE is not known. We have measured 51 Cr-platelet survival, euglobulin lysis time (ELT) before and after venous tourniquet occlusion, antiplasmin activity, AT III level, and 125 I-fibrinogen survival in 57 patients documented by venography (49 patients) or lung scan (8 patients). All studies were done off treatment and at least 3 months after the most recent episode of VTE. The mean platelet half-time in patients was similar to the in 42 controls, but 7 patients with VTE (12%) had a reduced platelet half-time. The ELT was significantly longer (p < 0.005), before and after tourniquet occlusion, than in 89 controls. Thus, 40% of patients and only 10% of controls had a ELT longer than 240 minutes after tourniquet occlusion. AT III levels were normal, as was fibrinogen survival. An elevated antiplasmin level was found in one patient in this study and in two others studied while still under treatment with anticoagulants-all 3 had thromboembolic pulmonary hypertension. Abnormalities occurred with equal frequency in patients with idiopathic or secondary, and single episodes or recurrent VTE. These findings suggest that impaired fibrinolytic activity occurrs frequently in VTE, but that reduced platelet survival is uncommon. High antiplasmin levels may predispose to thromboembolic pulmonary hypertension.

Summary: A patient receiving cyclophosphamide suffered apnoea and respiratory insufficiency after two anaesthetics in which suxamethonium had been used whilst an anaesthetic without suxamethonium was uneventful; the plasma was found to have a lowered activity of plasma cholinesterase. Accordingly eight patients being treated with cyclophosphamide were tested for plasma cholinesterase activity; in seven there was a significantly depressed level, of the acquired type, as compared with control groups of healthy subjects and patients with comparable diseases not receiving cyclophosphamide. In two patients a fall in cholinesterase activity was demonstrable after cyclophosphamide was begun. Thus appropriate precautions should be taken with patients receiving cyclophosphamide and requiring general anaesthesia: withdrawal of cyclophosphamide, avoidance if possible of depolarising relaxant drugs, or the giving of fresh blood preoperatively to raise the level of plasma cholinesterase.

For experiments involving SQUID’s it is sometimes desirable to have a small source of confined magnetic field in order to provide a dc or rf flux bias. This has been done by closely winding ♯50 AWG copper wire on a 250‐μm‐diam optical fiber. The resulting solenoid is very small and has excellent mechanical and electrical properties at 4 K.