A computationally efficient alternative to the Buckingham potential for molecular mechanics calculations.

This paper describes a (6-8) variant of the Lennard-Jones (6-12) potential, for computing the energy of non-bonded interactions in molecular mechanics calculations, which combines the overall precision of the Buckingham (6-exp) potential with the computational efficiency of the standard Lennard-Jones (6-12) potential. There is also a note on the radius of convergence of the full matrix Newton-Raphson optimization procedure.

Parallel pattern search energy minimization.

This article describes the adaptation of a pattern search algorithm, for the computational optimization of model molecular structures, to run on a parallel computer. The parallel efficiency (speedup) of the algorithm is discussed, and the rate of convergence of the parallel procedure is compared to that of the sequential implementation. More generally, the article also illustrates how inherently nonparallelizable stochastic procedures may be successfully parallelized by rearrangement of the algorithm.

Sequential and parallel molecular mechanics calculations.

This article describes a gradient algorithm for the computational optimization of model molecular structures, and discusses the various compromises inherent in the practical expression of the algorithm in a Fortran computer program (VULCAN) for both sequential and parallel computers. Details are given of some previously undiscussed properties of gradient algorithms; various acceleration techniques are compared; and some traps for the unwary are highlighted.

Interfacing electrochromic spectacles to computer IO ports.

Many important properties of molecules depend on their precise three-dimensional (3D) structure. It is therefore useful to be able to view a molecule in 3D on a 2D computer screen when manipulating it. An inexpensive method for viewing in 3D using liquid crystal glasses and a PC is presented. The methodology used is easily extended to other computers and workstations.

The early development of neurosonology: I. Echoencephalography in adults.

The discovery of Midline Echoencephalography is usually attributed to Leksell in 1956. While this was the first time that the examination had been used clinically, it had been preceded by work in England where the echo from the midline of the head appears first to have been demonstrated but its clinical usefulness not recognised. The clinical need for such an examination was so great that, until 1968, more papers were published about echoencephalography than any other medical ultrasonic technique. It only slowly became appreciated how subjective was the technique which, for highest accuracy, had to be performed by a skilled neurologist or neurosurgeon with an intimate knowledge of the patient's cerebral status. The development of more objective automatic techniques, which did not involve the expenditure of a skilled clinician's time, was vociferously opposed by established echoencephalographers who appeared to believe that the demonstration that the examination depended, for accuracy, upon clinical bias by both operator and interpreter, reflected upon their honesty. It was demonstrated that it was the gross attenuation of the acoustic beam by scattering while propagating through the diploic layer of the skull that was responsible for the very variable displays made by echoencephalography. It was for the same reason that two-dimensional B-mode examinations were equally unsatisfactory and none of the ingenious attempts to overcome the obscuring effect of the skull have, after 35 years, been successful. It is only when the skull is removed that the techniques of transdural and intracerebral ultrasonic encephalography can provide useful images from the brain within the skull. It was fortuitous that the realization that ultrasonic encephalography in adults was largely useless coincided with the development of more sophisticated radiological and magnetic techniques which were much more successful in imaging the brain.

The early development of neurosonology: III. Pulsatile echoencephalography and Doppler techniques.

From the earliest days of echoencephalography, it was noted that echoes from intracerebral interfaces showed systolic pulsations both in amplitude and range. Recordings of larger pulsations in range could also be obtained from the walls of intracranial arteries. It was hoped that clinical information might be obtained from recording and measuring these pulsations. Since it was easier to build equipment that recorded pulsations in amplitude, most work was confined to the recording of amplitude pulsations. However, such recordings of both amplitude and range pulsations usually used range gates in order to isolate the echo of interest and movement of the echoes within the gates introduced artefact in the recordings. Such artefact was more easily identified in recordings of range rather than amplitude. None of these types of recordings resulted in the development of a clinically useful examination in either the living or dying patient. However, the recordings of range fluctuations were able to demonstrate the presence of Traube-Hering waves in the blood vessels of the brain, thus suggesting that these vessels received an autonomic innervation in addition to their chemical sensitivity. Such range recordings also showed that, as a result of the increase in cerebral volume with the arrival of each systolic pulse wave, the brain moved centripetally to compress the cerebral ventricles and downwards to compress the basal cisterns and venous sinuses. The volume increase in the brain was accomodated by displacing cerebrospinal fluid and venous blood outside the rigid skull. When such a venting mechanism was over-taxed, as may result from increased intracranial pressure, it was postulated that the systolic pulse pressure wave, which could no longer be adequately attenuated by the compensatory venting of blood and cerebrospinal fluid outside the rigid skull, gave rise to shock waves which damaged the periventricular ependymal interface and the underlying brain with the production of progressive hydrocephalus. The development of ultrasonic Doppler techniques was quite a different matter and led to a number of clinically useful examinations as the technology became increasingly developed. The Doppler frequency shifts were displayed in various forms culminating in the display of their whole spectrum. Directional displays added further information and the ability to use short pulses enabled the Doppler shift and velocity of blood flowing in small regions of blood vessels to be recorded. Two-dimensional displays of the Doppler frequencies present in blood flowing in vessels were developed concurrently with duplex techniques which made B-mode displays of the blood vessel of interest in a tomogram of the surrounding tissues.(ABSTRACT TRUNCATED AT 400 WORDS)

The early development of neurosonology: II. Fetal and neonatal echoencephalography.

The obscuring effect of the diploe in the skull for attempts to use ultrasonic energy to image the brain is not present in the fetus, neonate or infant prior to ossification of the skull. Initially, however, the fetal examination was largely confined to a single measurement of the size of the skull, usually in the bi-parietal plane, just prior to labour. In this way it became possible to identify immature fetuses where delivery should be delayed as long as possible, as well as cases of cephalo-pelvic disproportion where the large size of the fetal head would make vaginal delivery difficult. Measurements made earlier in pregnancy, in order to predict the gestational age and estimated date of delivery, would only be accurate if all fetal heads were the same size at every gestational age. Similarly, attempts to predict birthweight from the size of the fetal head at any given gestational age foundered both upon the uncertainty of determining the gestational age from the menstrual history and upon the variations in the size of fetuses for various gestational ages. By making serial measurements of fetal head size, the rate of fetal growth can be measured. In this way, it is possible to separate the normal fetus which appeared to be small for its gestational age because the gestational age had been erroneously calculated from the menstrual history, from two clinically important groups. In the first group, the fetus is small and grows abnormally slowly throughout the whole pregnancy because of some congenital defect; and in the second the rate of growth becomes slowed towards the end of pregnancy because the placenta is no longer able to supply the increased nutritional needs of the mature fetus. Where it is not possible to make serial measurements throughout pregnancy, they can often be restricted to two measurements. The first is made in mid-pregnancy and, if the size of the fetal head agrees with that predicted from the menstrual history, it is assumed that the fetus is not abnormally small due to some congenital defect. In such cases the only other examination that needs to be made is another measurement near term to identify cases of placental insufficiency. If the first measurement does not coincide with that expected from the menstrual history, then more frequent measurements should be made in order to separate those normal fetuses in which the gestational age was wrongly calculated from the menstrual history from those fetuses with growth retardation throughout pregnancy due to some abnormality.(ABSTRACT TRUNCATED AT 400 WORDS)

YAG laser resection of complicated hemangiomas of the hand and upper extremity.

Complicated hemangiomas of the hand or upper extremity have been resected in eight patients with use of the YAG laser with sapphire scalpels. This laser allows excellent hemostasis and precise surgery, thus allowing resection of complicated problems. Many of the patients have had preoperative arteriography with selective embolization, which has aided in hemostasis. Almost complete but subtotal resection of hemangioma was possible in four of the eight patients with well localized lesions. Three patients had only partial resections of hemangiomas and one lesion was considered unresectable.

Benefits of contact and noncontact YAG laser for periorbital hemangiomas.

Twenty patients with capillary/cavernous hemangiomas of the periorbital area (eyelid, eyebrow, nose extending to canthus) have been treated with a variety of techniques. Six patients were treated by yttrium-aluminum-garnet (YAG) laser photocoagulation and direct injection of steroids. Rapid shrinkage of the hemangiomas occurred in all patients, and 2 infants whose eye was totally occluded by the hemangioma had their eyes rapidly opened. YAG laser excision with or without previous photocoagulation plus injection and with arteriogram plus superselective embolization was performed in the other 14 patients. Results were satisfactory in all patients.

Combination treatment for massive cavernous hemangioma of the face: YAG laser photocoagulation plus direct steroid injection followed by YAG laser resection with sapphire scalpel tips, aided by superselective embolization.

A massive cavernous hemangioma of the face in an 11 month old child has been successfully resected utilizing a combination of laser and non-laser techniques. The hemangioma was initially treated twice with YAG laser photocoagulation plus direct injection of steroids. This treatment promptly stopped the rapid growth and induced blanching as well as a 25% shrinkage with each treatment. Arteriogram with superselective embolization produced a further shrinkage of the hemangioma. Finally, the contact YAG laser with sapphire scalpel tips was utilized for complete and cosmetically satisfactory hemangioma resection. The treatment of a massive cavernous hemangioma by a combination of modalities is discussed.

High- and low-technology solutions for massive cavernous hemangioma of the face: lasers and leeches to the rescue.

A massive cavernous hemangioma of the face has been resected using a combination of old and new techniques. The ability of the neodymium: YAG laser to cut with excellent hemostasis formed the basis for the resection. Adjuncts to the surgical excision included such high-technology modalities as laser Doppler flowmeters and tissue expanders. Flap viability was salvaged by the lowly but essential common leech. This case is presented to illustrate the fantastic array of modalities available to plastic surgeons for major resections and reconstructions.

Sapphire tip technology for YAG laser excisions in plastic surgery.

Thirty-two patients with a variety of vascular and nonvascular lesions have been resected over a 3-year period with the neodymium:YAG laser utilizing sapphire peripheral scalpel devices. These innovative peripheral devices concentrate the YAG laser energy to a small area at the end of the scalpel, providing precise incisions with excellent hemostasis. In addition, the tactile sensation of the scalpel contacting tissue is more comfortable and familiar than the "no touch" aspect of other lasers that are held away from the surface and depend on laser light transmission to approach the skin. Total excision with excellent hemostasis was achieved in 17 patients, while 15 patients had subtotal resection. The YAG laser with sapphire scalpels has allowed resection of very difficult and massive hemangiomas previously considered unresectable by standard techniques.

Benefits of the CO2 laser for verruca resistant to other modalities of treatment.

The benefits of the carbon dioxide (CO2) laser in the treatment of verruca resistant to other forms of treatment have been studied. Twenty-five patients with warts unsuccessfully treated from one to five times previously were treated with the laser, followed for a minimum of 6 months, and evaluated. Eight of these patients (32%) gained a total permanent cure. An additional five treatments resulted in a subtotal (over 75%) cure but some warts remained. Thus, 13 of 25 patients (52%) experienced complete or partially successful treatment. The CO2 laser is a valuable modality in the treatment of recalcitrant warts but cannot be expected to cure all such warts.

A preliminary study of the combined effect of neodymium: YAG laser photocoagulation and direct steroid instillation in the treatment of capillary/cavernous hemangiomas of infancy.

Thirteen patients with capillary/cavernous hemangiomas of infancy have been treated with a combination of neodymium: YAG laser photocoagulation plus direct local instillation of steroids. In all cases, rapid growth immediately ceased and blanching started. Shrinkage of the lesions then occurred spontaneously over the ensuing months; any plateau in shrinkage was retreated. Five of 13 patients experienced dramatic blanching and shrinkage with one treatment. Six experienced mild to moderate shrinkage. Complications occurred in 2 patients.

Failure of carbon dioxide laser excision of keloids.

Seven patients with nine keloids have been treated by excision with the carbon dioxide laser. Eight of the nine keloids have recurred to their original or close to original size as early as 10 months following treatment and as late as 22 months. Keloids included in this study were located on the trunk, nuchal region, back, and earlobe. Only one patient (who underwent earlobe keloid excision) has greatly improved keloids after only 9 months follow-up, but this patient needs to wear pressure earrings continuously. The long-term benefits of keloid excision with the carbon dioxide laser is not demonstrated in this case study series.

Computerized suction lipectomy aspirator monitor for improved results in suction lipectomy.

A new computerized suction aspirator monitor is described. This device offers the benefits of instantaneous and concurrent scientifically accurate readout of aspirate contents in five separate bodily areas. Thus knowledge of amounts of blood versus fat can be immediately known without resorting to guess, estimate, or cumbersome lipocrit determination by centrifuging. Advantages of such a device include better accuracy in determination of fat removal from each area, with improvement of symmetrical fat removal. More exact determination of blood loss with improved hemodynamic replacement is also more easily and safely accomplished. In an area of mystique, experience, artistry, and aesthetic appreciation which has cloaked the initial enthusiasm for suction lipectomy, a new generation of scientific accuracy is now possible. Thus accurate determination of aspirate content vis-a-vis fat and blood can now transform this procedure into a more sophisticated and scientifically accurate operation which traditionally is desired by most practitioners of suction lipectomy.