Computer simulation of interfacial packing in concrete

Computer simulation of particle packing against an aggregate surface was undertaken to show the effects of four variables on interfacial porosity profiles. The variables in order of significance and their assumed physical meaning are: sticking probability (tendency of cement particles to flocculate), amplitude of particle motion (energy of mixing), travel distance of particle to surface (thickness of water film surrounding aggregate), and original particle density (roughly related to water/cement ratio). In all cases, simulations demonstrated that interface porosity decreased from nearly 100% directly at the interface to that of the bulk paste at two to three particle diameters. Flocculation (sticking probability) was found to be the single most-significant variable. Highly flocculated systems produced very porous interfaces. When flocculation was reduced, packing became more efficient. It was also found that energy of mixing (amplitude of motion), was not an entirely independent variable. The simulation showed that, if the tendency to flocculate was high, gentle mixing (low amplitude of motion) was found to result in better packing and a less porous interfacial zone. If, on the other hand, flocculation was low, then vigorous mixing (high amplitude of motion) promoted better packing near the interface. The thickness of the water film surrounding the aggregate (travel distance) was found to have only a minor effect on the outcome of simulations, while original packing density (w/c) resulted in no significant differences at all.     

Bidirectional single-mode Er-doped fiber-ring laser

A Faraday rotator is used in a laser cavity to eliminate spatial hole burning in a bidirectional Er-doped fiber-ring laser. A stable operation is achieved in single longitudinal mode with comparable intensities for both clockwise and counter-clockwise directions. A beat signal between the clockwise and the counter-clockwise laser outputs of 40 dB above noise and of about 30% fringe visibility is observed.     

Doctors who perform operations. A study on in-hospital surgery in four diverse geographic areas (second of two parts)

To facilitate manpower planning in the surgical field, a study was c onducted into the work loads of surgeons in various specialities in 4 different geographical areas. Surgeons in group practice and surgeons who were Board-certified specialists carried a statistically significant larger work load of surgery. The certified surgeons performed more and more complex operations. The mean operative work load increased steeply with age, reaching a maximum at 40-44 years, and fell linearly after that age. Approximately 18 years following medical school graduation were needed for a surgeon to achieve his maximum work load. The geographic factor had no appreciable effect on work loads. Tables which broke down frequencies for each major type of operation for each type of surgical specialist indicated that even commonplace operations were not frequent events on the average for any individual surgeon. It is concluded from the study that work loads are relatively low due to excessive supply of surgeons. This is of concern because there is some doubt about maintenance of surgical skills by those doctors who perform infrequent operations. The widest variation in practice was evident between ophthalmologists and thoracic surgeons, indicating that manpower planning in this field would have to be done on a specialty-by-specialty basis. 3 plans for redistributing the operative work load and reducing the number of specialist surgeons are considered.     

Verhalten von Holo-, Apo- und Coenzym der Peroxidase beim Erhitzen

Zusammenfassung Das thermische Verhalten der beiden Komponenten von Meerrettich-Peroxidase — des Apoenzyms und der prosthetischen Gruppe — wurde mit dem des Holoenzyms verglichen. Daraus wird geschlossen, daß die thermische Inaktivierung der Peroxidase in wäßriger Lösung nicht nur als Resultat einer Veränderung des Apoproteins angesehen werden kann. Vielmehr muß die gesamte dreidimensionale Struktur unter Einschluß der prosthetischen Gruppe in Betracht gezogen werden. Die Inaktivierungsvorgänge beim Holoenzym werden spektralphotometrisch verfolgt, wobei beobachtet wurde, daß die Extinktionsänderung der Soret-Bande mit der Verminderung der Enzymaktivität beim Erhitzen parallel geht. Da ein Wiederanstieg der Soret-Absorption im Verlaufe der Lagerung festgestellt und gleichzeitig eine Regenerierung der Enzymaktivität beobachtet wurde, ist die Änderung der Soret-Absorption beim Erhitzen die Folge sowohl reversibler als auch irreversibler Denaturierungsprozesse.

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The reaction of holo-, apo- and coenzyme of the peroxidase to heating

Summary The thermal reaction of the two components of the horseradish peroxidase—the apoenzyme and the prosthetic group—with that of the holoenzyme were compared. From this we conclude that the thermal inactivation of the peroxidase in aqueous solution is not caused by a change of the apoprotein alone, but rather by participation of the entire three-dimensional structure including the prosthetic group. Spectrophotometric studies of the inactivation process in the holoenzyme revealed that the absorbance of the Soret band changes parallely to a reduction of the enzyme activity during heating. Since it has been found that the Soret absorption increases again during storage and simultaneously the enzyme activity regenerates, the change of the Soret absorption during heating can be regarded as the result of both reversible and irreversible denaturation processes.

     

Seroepidemiologic investigations of human hepatitis caused by A, B, and a possible third virus

The results of magnet implantation in the upper and lower eyelids of 29 patients suffering from Keratopathia due to lagophthalmos due to facial palsy as well as the surgical techniques involved are described. Contrary to a lateral tarsorrhaphy - still popular today - this method does not alter the form or the size of the palpebral fissure nor does it hinder the visual field. It is technically simple to perform and easily reversible should nerve function recover. The subjective results were also good.     

An adaptive notch-filter-based frequency-difference detector andits applications

A frequency-difference detector (FDD) based on an adaptive notch filter is proposed. Frequency detectors are useful in decreasing acquisition times in phase-locked-loop and Costas-loop-based clock and carrier-recovery systems. To avoid certain drawbacks associated with signal down-conversion to baseband, the input is initially processed in the bandpass domain. In applications where limits on acquisition time demand a wide closed-loop tracking bandwidth, the output of the proposed FDD has less inherent ripple and bias when compared with a quadricorrelator, a commonly used FDD. Two applications of the proposed FDD in the demodulation of BPSK data are presented