The kelvin redefinition and its mise en pratique.

In 2018, it is expected that there will be a major revision of the International System of Units (SI) which will result in all of the seven base units being defined by fixing the values of certain atomic or fundamental constants. As part of this revision, the kelvin, unit of thermodynamic temperature, will be redefined by assigning a value to the Boltzmann constant k. This explicit-constant definition will define the kelvin in terms of the SI derived unit of energy, the joule. It is sufficiently wide to encompass any form of thermometry. The planned redefinition has motivated the creation of an extended mise en pratique ('practical realization') of the definition of the kelvin (MeP-K), which describes how the new definition can be put into practice. The MeP-K incorporates both of the defined International Temperature Scales (ITS-90 and PLTS-2000) in current use and approved primary-thermometry methods for determining thermodynamic temperature values. The MeP-K is a guide that provides or makes reference to the information needed to perform measurements of temperature in accord with the SI at the highest level. In this article, the background and the content of the extended second version of the MeP-K are presented.

Differences between ocular and generalized myasthenia gravis: binding characteristics of anti-acetylcholine receptor antibody against bovine muscles.

We studied the binding characteristics of anti-acetylcholine receptor antibody (AChR Ab) in sera of nine patients with myasthenia gravis (MG) using affinity-purified extraocular muscles (EOM) and foot muscles (FM) of bovine species. The titer of AChR Ab measured with EOM was the same as that measured with FM for both ocular and generalized MG. In patients with ocular MG, the affinity of AChR Ab, determined by Scatchard analysis, was higher for FM than for EOM (P less than 0.05), whereas it was the same for EOM and FM in those with generalized MG. On the other hand, the affinity of AChR Ab for FM was lower in generalized MG than in ocular MG (P less than 0.05), but that for EOM did not differ between the two types of MG. The affinity of AChR Ab did not change after passing the patients' sera through an EOM-affinity column. The EOM-affinity column treatment of the sera decreased the AChR Ab titer measured with EOM in all patients, but the AChR Ab titer measured with FM was decreased in only some of the patients. These data indicate that there are polyclonal or heterogeneous AChR Abs in the sera of MG patients, which does not help to explain the clinical difference between ocular and generalized MG.

Synthesis of (-)-aphanorphine using aryl radical cyclization.

[structure: see text] The synthesis of (-)-aphanorphine was achieved by using Bu(3)SnH-mediated aryl radical cyclization of 1-benzyloxycarbonyl-2-(2-bromo-4-methoxyphenylmethyl)-2-methoxycarbonyl-4-(phenylthiomethylene)pyrrolidine, leading to exclusive formation of the 6-exo cyclization product.

Regiochemistry in aryl radical cyclization onto methylenecycloalkanes

Bu(3)SnH-mediated aryl radical cyclization onto methylenecycloalkanes having a phenylthio, an ester, or a nitrile group at the terminus of the alkenic bond provides exclusively exo cyclization products. The results are in sharp contrast to those reported for nonsubstituted methylenecycloalkanes, which give exclusively endo cyclization products. Formation of endo cyclization products has been suggested to be a result of a consecutive 5-exo cyclization of an aryl radical and neophyl rearrangement. The exo-selective aryl radical cyclization offers a new method for synthesizing fused aromatic compounds containing a benzylic quaternary carbon atom.

The magician's forceps phenomenon in exotropia under general anaesthesia.

Prifinium bromide was administered for eight weeks to three patients with exotropia. Under general anaesthesia active discharges from the lateral rectus muscles were demonstrated by electromyography. When a slight adductive force was applied to the straight or the master eye, active discharge from the lateral rectus of the associate eye disappeared in all patients, and this eye moved in the direction of orthophorisation. The discharge reappeared when the master eye was released from the forced adduction. From these results the authors concluded that proprioception is involved in the magician's forceps phenomenon discovered by Mitsui in exotropic patients in 1978.

Proprioception and exodeviations.

When a slight adductive force is applied by forceps to the straight or master eye in exotropia, the exodeviated or slave eye assumes the straight position. The nature of this phenomenon was studied. The reflex occurred in an all-or-none form and showed little dose response, that is, the slave eye did not adduct beyond the straight position even if an extreme forced adduction was applied to the master eye. Once the slave eye assumed the straight position by the reflex it maintained this position, even when the master eye was covered, except when the master eye was released from the forced adduction. This reflex movement response occurred promptly on repeated forced adduction at 9 Hz on the master eye, while the visual movement of the eye was limited to follow 1 Hz movement of the target. The reflex occurred readily in the light but hardly at all in the dark. From these facts the authors conclude that the reflex is brought about as a result of interaction between the proprioceptive impulse and the visual input, where the former may chiefly constitute the signal, while the latter restricts the threshold of the reflex pathway.

An electromyographic study of esotropia.

Under general anaesthesia the eye position of esotropia generally moved divergently. When retrobulbar anaesthesia was added bilaterally, the eye position moved further in the same direction. In the electromyogram under general anaesthesia the 4 horizontal recti were silent in controls. In many cases of esotropia, however, both medial recti showed a considerable amount of discharge under general anaesthesia. When retrobulbar anaesthesia was superimposed on one eye, the discharge from its medial rectus tapered off and, reciprocally, that of the opposite eye increased. These facts may suggest that proprioception plays in the development of esotropia.

A test of K(+)-sensitive electrode responses to changes in K+ concentration.

Tests of K(+)-sensitive microelectrodes were made using a plastic chamber, which consisted of upper and lower compartments separated by a partition with a small opening in the center. After the upper and lower compartments were filled with 25 and 100 mM KCl respectively, the tip of a K(+)-sensitive electrode was moved up and down through the partition opening, while recording potential changes. Some hydrodynamic events associated with electrode movement and effects of gravity upon spherical diffusion are discussed.

The nature of reverse phase reflex eye movement.

The unusual phenomenon of reverse phase reflex eye movement was first described by Ishikawa. In this study the reflex frequency response was examined by electrooculography. In typical cases a reflex was observed by repeated forced duction up to 9 Hz. As a result it was postulated that proprioception is usually involved in reverse phase reflex eye movement, because visual eye movement cannot respond to a movement beyond 1 Hz. When the lag-times between the peaks of forced duction in one eye and those of the reflex movement in the other were measured, they were almost zero or even negative at high frequencies of forced duction as 6 and 9 Hz. This phase advance of the reflex movement was explained only when the receptor of the reflex had a dynamic response, because 90 degrees phase advance results in a reflex through such a receptor. The primary ending of muscle spindle represents such a receptor. The magician's forceps phenomenon as first discovered by Mitsui in exotropia is supposed to be a blocking reflex through the tendon organ. The transmission lag-times of both reflexes can be as short as 20 msec, but must be slightly longer to consider them to be monosynaptic.