Step Ladder Research Articles

Stochastic model for triplet yields

A stochastic model of triplet yields is considered where the singlet S 1 is initially excited and subsequently feeds the triplet T 1. Both S 1 and T 1 have Montroll—Shuler step ladder vibrational relaxation mechanisms and radiative and non-radiative decay rates that vary linearly with increasing vibrational energy. Assuming the S 1 → T 1 rates also have this linear variation, the kinetic model is exactly solved in terms of integrals of simple functions of hyperbolic functions. The predictions of the model are illustrated by application to naphthalene. The model parameters are chosen; wherever possible, from experimental data. The predictions are in gross qualitative agreement with available experiments on triplet yields, and they indicate more detailed future experiments to separate the S 1 → T 1 and S 1 → S 0 (ground singlet) decays (and their energy dependence) in aromatic hydrocarbons.

THE MECHANISM OF TARSO-METATARSAL JOINT INJURIES

1. Twenty cases of tarso-metatarsal joint injury have been studied with regard to the mechanism of injury, and experiments have been done on cadavers to confirm clinical impressions. 2. Injuries of the tarso-metatarsal joints occur by direct and indirect mechanisms, the latter being more common. 3. Indirect injuries occur in at least two ways-namely, acute abduction of the forefoot and plantar-flexion of the forefoot. 4. Most of the indirect injuries occur when the ankle joint is in a plantar-flexed position. 5. Whereas this foot injury once gained prominence on the field of battle amongst cavalrymen, it is currently associated with the motor car, the step ladder, the toboggan, the joy-rider, and commonly the simple misguided step.

Interferometric studies of domain structures in potassium niobate single crystals

Interferometric studies of domain structures in KNbO3 single crystals, grown by using excess of K2CO3 as a flux are reported. The surface deformations produced on the pseudocubic (001) planes by the stable patterns of 90°, 60° and 180° domains have been studied and discussed. If the observed plane is not the plane of the shear, the 90° domains are inclined at 30prime. The angle between the 60° domains is 57prime for the domain line, parallel to a pseudocubic edge. The head to tail coupling of dipoles across the 60° domain walls gives a step ladder structure on the surface. The nature of dipole coupling in a step ladder due to 90° domains cannot, however, be distinguished. The wedges are all 60° wedges, with the wedge angle 57prime. The theoretical formulae have been derived, and the values found to agree closely with the experimental values.The angles between the planes and the other surface angles are all temperature dependent as they are functions of the lattice parameters. In the tetragonal phase, the domain behaviour is found to be quite similar to that of BaTiO3. The domain patterns are seen at times to have a memory indicating the presence of traps in the crystals for these domain walls.

Collisional Quenching of Competitive Unimolecular Reactions. Vibrational Energy Transfer

Two competitive–consecutive unimolecular reaction systems were investigated. An H+olefin chemical activation technique was used to produce highly vibrationally excited polyatomic alkyl radicals (Rp*) in a narrow, nonequilibrium distribution of energy states centered near 45 kcal mole−1. The radicals studied, 3,3-dimethylhexyl-2·* and 3-methylhexyl-2·*, each decompose unimolecularly by several competitive C–C rupture reaction channels to stable olefins and smaller radical fragments; also, isomerization by H-atom transfer to secondary radicals, 4,4-dimethylhexyl-2·* and 4-methylhexyl-2·*, respectively, competes with C–C rupture. The isomerized species retain the vibrational excitation and undergo further consecutive unimolecular reactions including C–C rupture and H-atom isomerization. The spectrum of competitive reactions of Rp* via various paths, each characterized by a different energy threshold, provides a type of competitive chemical reaction “spectroscopy” wherein the amounts of the various decomposition events associated with each threshold act as transducers of the steady-state energy level populations of the reactive species. The competition between collisional stabilization and reaction via the several reaction paths of Rp* was measured for H2 and CF4 heat-bath molecules. The experimental results are compared with calculations made on a stochastic basis. Various collisional transition probability models characterized by different distributions of vibrational energy jump sizes were examined. Based on a step ladder model of transition probabilities, H2 transfers ∼ 400 cm−1 per collision and CF4 >̃ 1600 cm−1 per collision; for an exponential distribution of transition probabilities, a larger amount of vibration energy, e.g., ∼ 500 cm−1 for H2, is appropriate. The conclusions obtained by this technique are independent of information on the magnitudes of the collision cross sections. Some of the more important aspects of the radical chemistry are considered and several disproportionation–recombination ratios were obtained.

STUDIES ON ELECTRIC PRESSURE TRACING OF ESOPHAGUS AND CARDIAC PORTION OF THE STOMACH

The physiology of motility of the esophago-cardiac junction, pathophysiological changes of this area due to various esophageal diseases and their clinical applications were studied by our new method of obtaining electric internal pressure curve and several interesting findings were obtained. These examinations were carried out on 91 clicnial cases (including several controls).(1) Order of food passage through the normal esophago-cardiac junction is usually controlled and carried out mainly by pressure of the esophagocardiac junction at rest, positive pressure of the esophagus, and negative and positive waves of the gastric cardia which arise simultaneously.(2) Failure in presence of this negative pressure at the gastric cardia, is noted in all 17 cases of achalasia patients. By various values of the internal pressure at rest, this disease could be divided into two groups; the flaccid type (type A) and accelerated type (type B).(3) As to the surgical indications, cardioplasty type of surgery for group A, and esophago-gastrostomy type for group B, are better suited and effective.(4) Very specific inconsistent internal pressure was obtained in 8 out of 9 clinical patients with carcinoma of the gastric cardia. These specific curves were divided into three groups; the serrated type, step ladder type and canopy type.We have concluded therefore that this method has a certain advantage in utilizing diagnostic measure for various esophageal diseases.

Interferometric study of domain structure in barium titanate

The surface microtopography arising out of the 90° domain walls in single crystals of Barium Titanate in the ferroelectric tetragonal state has been studied in detail employing optical and multiple beam interferometric techniques. The domain walls mark a change in level at the crystal surface and it is shown that the change in level is proportional to the distance between the domain walls. A step ladder structure is often found on the crystal surface which indicates, beyond doubt, the head to tail coupling of the dipoles. In a few cases, however, 90° wall configuration with head to head or tail to tail orientation has been observed. These laminae frequently advance in groups in the two perpendicular directions parallel to the edges of the crystal. As a result of the intersection of these groups the crystal surface becomes highly complicated with a step ladder structure in mutually perpendicular directions, terminating in a square base or at times in a point. In many cases, the multiple beam interferometric techniques have shown that the crystal surface is deformed with a cylindrical curvature: the axis of a cylinder being parallel to the edge of the crystal. Some times one observes the crystal having cylindrical curvatures in perpendicular directions.

Determination of the Potency of X-Ray Developer

Deterioration of x-ray developer is nearly-proportional to the number of square inches of film developed. A simple method for estimating this deterioration is to keep account of the amount of film developed. Charts to be used in the dark room for this purpose are available and the method is recommended by photographic material manufacturers. R. B. Wilsey (1) recommends a method which makes use of the fact that the time of development bears a definite ratio to the time required for the image to appear after the film is first immersed in the developer. This ratio is known as the Watkins' factor. Pieces of film which have been exposed over part of their surfaces are developed in a tray, measuring the seconds to the first appearance of the image. Multiplication of this appearance time by the Watkins' factor gives proper development. Chamberlain and Newell (2) have worked out and described a method of adjusting for changes in the speed of the film as well as for the weakening of the developer with use. Their method is an exact one but since the test films are made with the aid of an accurately controlled therapy machine, it is not available to many roentgenologists. Thanks to the ingenuity of Dr. Robert S. Stone (3), a method is here described in which the test films are exposed with a radiographic machine, such as most roentgenologists have in their laboratories. Because radiographic apparatus is not equipped with instruments to insure constancy of output from time to time, special precautions are necessary in order that the process of calibrating the developer may be carried over from one test film to the next. Directions for Determining the Potency of the X-Ray Developer with Radiographi-Cally Exposed Film Place a fresh 8 × 10-inch film in an exposure holder (no intensifying screens) under an aluminum step ladder: the ladder we use is made of aluminum sheets 1 mm. thick × 10 inches wide arranged in a staircase running from one to seven thicknesses (Fig. 1). A radiographic tube is placed so that its focal spot is 60 inches above the center of the 8 × 10-inch film. Then, place 2 mm. of aluminum in the filter slots of the tube stand, and expose for 14 seconds at 70 K.V.P., 10 milliamperes. This film holder is opened in the dark room and about an inch is cut off one of the 8-inch ends of the film. Place this strip horizontally in one-day-old developer at 65° F. for five minutes. (Absolutely fresh developer has been found somewhat variable in our experience.) After being fixed, washed, dried, and labeled, this strip is set aside as the “standard strip” with which subsequent calibration strips are to be compared (Fig. 2). From one to three days later, depending upon the size of the tank in relation to the volume of work, another strip, approximately an inch wide, is cut from the film (which in the meantime has been carefully protected from light and x-rays). This is developed for 5 minutes, placed horizontally in the developer.

Efficiency Engineering in the Dark Room

Most of the problems connected with roentgen diagnosis are of such a nature as to require individual solutions. If we are to get the most out of every examination, no two cases can be handled exactly alike. Individual treatment of every case results in more intelligent search, and overstandardization is to be avoided. But there is one element in the chain of procedures between the radiographic room and the final interpretation of the films which will bear standardization, and even “efficiency engineering.” Fixed time development, in calibrated developer, at a fixed and appropriate temperature, produces results, especially in a large, busy hospital department, which are so far superior to the erratic performances with variable factors, that more than passing comment on this subject is superfluous. The “dark room” here described has been in service for two years, and has justified our fondest expectations. In our former dark room, which was of the conventional type, and of a size quite up to the average in large, busy departments, we had an excellent drier, but films were delayed in the wash tank (the washing operation being frequently prolonged when the technician did not know which of the films had had sufficient time), the congestion backed up into the hypo bath, and even farther, at times, onto the loading shelf. The average time from radiographic room to viewing room was four hours. With our present arrangement it is one and a half hours. And formerly the films were in the dark room during the entire four-hour period, whereas with the present system the films stay in the dark room for only from twenty to twenty-five minutes. One of the chief causes of delay in the old days was the shutting-down of the dark room routine while lights were turned on, to find and examine an unfinished film. It is hardly necessary to point out that removal of washing and drying operations from the dark room, and shortening the time between radiographic room and viewing room to one and a half hours, have reduced dark room intrusions to an absolute minimum. In the design of this installation, attention was paid to Temperature Regulation A twenty-gallon developer tank, of enameled steel, is immersed in a 65° F. water bath, with a large clear-vision dial thermometer on the wall over the tank, with supplies of hot, cold, and ice water for convenient regulation. Ventilation In addition to an open light-proof entrance maze, there are light-proof open air vents. Daily Calibration of Developer Films which have been exposed under a thin copper “step ladder,” to exactly 0.33 r-units of 200 K.V., copper-filtered X-ray, from a specially calibrated machine, are developed, and then compared with a standard. Changes in developer strength, thus discovered, are compensated for by changing the time factor.

A CASE OF CEREBRAL CLOT; LOSS OF VISION FOLLOWING INJURY; TREPHINING; RECOVERY.

In November, 1893, Dr. Julia Holmes Smith, of Chicago, brought a patient to my service at the Chicago Policlinic with the following history: Sister Adele, of the Benedictine order, aged 20, strong and healthy, was injured in Canon City, Colorado, June 18, 1893. At the time of injury was on a step ladder unscrewing one of the fastenings of a chandelier in the Academy St. Scholastica. A staple or hook fell, striking her on the top of the head, just posterior to the Rolandic fissure on fhe right side. Had great pain, but no wound of the scalp; severe headache which has never entirely disappeared. Vision in right eye gradually failed, and could not see; totally blind in right eye. Deafness of right ear began almost immediately after the accident and continued. There was no motor paralysis, no loss of sense of taste or of smell. Vision and hearing apparently