R Leoni | PubMed Health

PubMed1991

A planar second-order DC SQUID gradiometer.

In this work we describe a DC SQUID gradiometer, sensitive to the second spatial derivative of the magnetic field. The sensitive area of the gradiometer is the inductive body of the DC SQUID itself. The isoflux line distribution generated by a dipolar source, obtained by performing magnetic measurements with an array of such detectors, is relatively complicated, but its localisation capability is similar to that one usually achieves with axial detector arrays. Planar gradiometers also show a better resolution for near sources and a stronger rejection of far disturbances. The final device is expected to have an inductance of a few hundreds of pH in order to obtain performances typical of a low noise DC SQUID. The pick-up coils will be the combination of four square holes of 500 microns side with a 1.05 cm baseline. Due to the magnetic field concentration (in the final device it can be a factor 10) the gradiometer will have a sensitivity of 10(-11) T m-2 Hz-1/2 and a field sensitivity of about 2 fT Hz-1/2. Some preliminary results, obtained on detectors with an intermediate area between the prototype and final device, are reported here. The process used to fabricate this second-order gradiometer is based on Nb-NbO chi-PbAuIn Josephson tunnel junctions. Some possible improvements will also be described.

Equipment Design↗

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[Reinterpretation of the hepatic abscess, a new dimension in abdominal digestive surgery].

Pyogenic abscess of the liver is viewed here as a surgical disease, which appears to raise doubts as to its actual identity. Though located in a given abdominal organ, such abscesses find it hard to recognize this as their exclusive setting and attempt to shrug off these traditional confines. They aspire, rightly or wrongly perhaps, to symbolize a splanchnic context, though, in actual fact, the latter--at least for contingent, doctrinal reasons--is confined to the bipolar liver-bowel system. This context presents its candidacy as playing a leading role in a disease of such importance as to be regarded almost as the "Caudine Forks" of the very process of "surgical" dying. Liver abscess and multiorganic or multisystemic organ failure (MOF or MSOF) might thus be viewed as the two opposite poles (taxonomically definable) of a single clinical condition, which fans out over a broad area and for the most part is only barely known to us. Though is characterized by its abdominal location, it would be all too simple to define the condition as abdominal. In this case, in fact, the abdomen speaks an unusual language, not the habitual, traditional, "spatial" language of location, but the as yet uncertainly articulated "biological" or, why not, even "biosurgical" language of mediation. Is this then a turning point in the pathological field? No, if by that we mean a new concept of the problem. In effect, the concept dates back several centuries and, moreover, darries a heavy burden of responsibility, such as, for instance, having induced the Nobel Prize-winner Elie Metcknicoff (Metcknicoff E., The prolongation of life. London, Heinemann, 1907) to come up with theories appropriated and implemented surgically by Sir William Arbutnot Lane, gaining him nothing but sad notoriety (Gordon R., Great Medical Disasters, Hutchinson, London-Melbourne, 1983). "Concept" is a euphenism, and a more appropriate term might be simply "intuition". The real innovation lies in reviving this old intuition, reinterpreting it now, in fact, as a "concept". The code for this modern interpretation has barely been sketched out in its essentials, but is daily going from strength to strength.(ABSTRACT TRUNCATED AT 400 WORDS)

Endotoxins↗