Stress on the wrist joint in semilunar bone necrosis--a morphologic study in vivo

Sn-mesoporphyrin (SnMP), a potent inhibitor of heme oxygenase (HO), controlled hyperbilirubinemia in rats of the mutant strain EHBR/Eis. This mutant strain displays pronounced conjugated hyperbilirubinuria and dark pigmentation of hepatocytes, characteristics of the Dubin-Johnson syndrome. SnMP administered at a dose of 10 mumol/kg body weight produced an immediate decrease in plasma bilirubin concentrations which could be maintained by weekly injections of this synthetic heme analogue. Marked inhibition of HO activity was demonstrated in liver, kidney and spleen but not in brain. These results demonstrate that SnMP can lower plasma bilirubin concentrations for extended periods in a new mutant rat model of Dubin-Johnson syndrome.     

Traumatic dislocations of the lesser toes

Meningiomas are common lesions in adults but unusual in infancy and meningiomas located in the posterior cranial fossa are even more rare. Metaplastic changes of meningothelial meningiomas can lead to the rarely observed xanthomatous form. We describe the case of a posterior pyramid xanthomatous meningioma in a 2-year-old girl. After detailed neuroradiological evaluation, the histological diagnosis was confirmed with the aid of immunohistochemical evaluation. A critical case evaluation in the light of the more recent literature, the surgical strategy and technique, and an immunohistological hypothesis are reported.     

Fractures and dislocations of the foot

The incidence and severity of fractures and dislocations vary depending on their location and on the direction of the forces responsible for the injury. The radiologist's role in evaluation of the injured foot is to recognize the types of injuries produced by particular forces. Because there is considerable overlap of fractures and dislocations of the foot and ankle, evaluation of one area to the neglect of the other can lead to significant oversights and failure to recognize additional injury patterns. For example, fractures of the talus, calcaneus, base of the fifth metatarsal, and to a lesser extent, the cuboid and navicular bones may masquerade as ankle sprains or malleolar injuries. The most important aspects to correct interpretation of traumatized foot radiographs are (1) pertinent clinical history, (2) a complete radiographic series, and (3) detection of soft-tissue swelling or injury.     

Bilateral transscapholunate dislocations

Irreversible hearing loss is a catastrophic complication of treatment with aminoglycoside antibiotics such as streptomycin, gentamycin, and kanamycin. Many kindreds showing a matrilineal pattern of inheritance of this trait have been described in China where the widespread use of aminoglycoside antibiotics accounts for approximately 25% of profound deafness in some districts. Because of the characteristic inheritance pattern, mitochondrial DNA (mtDNA) mutations were postulated to be the cause of the deafness in these pedigrees. In 1993 it was shown that an A to G substitution at base pair 1555 of the mitochondrial 12S ribosomal RNA gene was the only mutation common to all the families with aminoglycoside ototoxicity. We ascertained three Mongolian pedigrees from the School for the Deaf and Blind in Ulaanbaatar, all of which contained multiple affected subjects with streptomycin induced deafness in a pattern consistent with matrilineal transmission. Amplified mtDNA, obtained from transformed lymphoblastoid cell lines using previously described primers, showed the A to G point mutation in the 12S rRNA gene in two of the three families by restriction analysis as well as direct sequencing. No other example of this substitution was found among 400 control samples from Mongolians with normal hearing. We have thus confirmed the clinical relevance of the 1555 A to G mitochondrial mutation in the 12S rRNA gene by identifying it in affected subjects with familial aminoglycoside ototoxicity in another ethnic group. In countries where aminoglycosides are widely used, genetic counselling and screening of high risk families before the use of these drugs could have a dramatic effect on the incidence of deafness.     

Whither dislocations?

Some speculations are offered where dislocation theory may be headed. This paper is based on a presentation made at the symposium “50th Anniversary of the Introduction of Dislocations” held at the fall meeting of the TMS-AIME in Detroit, Michigan in October 1984 under the TMS-AIME Mechanical Metallurgy and Physical Metallurgy Committees.     

Fracture dislocations of the proximal interphalangeal joint

An expanded protection motivation model was used to investigate the intention to give up smoking. Because smoking has both physiological and social-psychological foundations, the model was expanded to include the social dimensions as well as the original disease dimensions as predictors of health behavior. The participants were 96 current smokers (35 male and 61 female) in Australia; 44 were young adults (age < 22 years), and 52 were adults (age > 34 years). Data were analyzed by multiple regression with hierarchical entry, first of disease dimensions, then of social dimensions. For both the young and the adult smokers, the disease dimensions contributed significantly to the results of the regression equations. Addition of the social dimensions yielded a significant F change only for young smokers and increased the amount of variance explained from 23% to 38%.     

The limiting speeds of dislocations

The purpose of this article is to show that the limiting speeds of moving dislocations are determined by inertial effects, or by viscous drag, at their cores. Simple expressions for the limiting speeds are derived. The standard idea that the speeds are limited by the inertia of the elastic fields, accompanied by Lorentz contractions, is shown to be flawed because it neglects the angular momentum of a moving dislocation; or, equivalently, because it assumes that the motion is steady if the velocity is constant, but this is not possible because the motion creates plastic deformation. Finally, the standard theory considers the dislocation to be moving in an infinite medium but this is not acceptable, because then both the energy and the mass would then be infinite. This article is based on a presentation given in the symposium entitled “Dynamic Behavior of Materials—Part II”, held during the 1998 Fall TMS/ASM Meeting and Materials Week, October 11–15, 1998, in Rosemont, Illinois, under the auspices of the TMS Mechanical Metallurgy and the ASM Flow and Fracture Committees.     

Hydrogen transport by dislocations

A kinetic model is presented for the transport of hydrogen, as Cottrell atmospheres on dislocation, at a rate appreciably in excess of that for lattice diffusion. The particular destinations for the hydrogen which are modeled here are ductile fracture initiation sites such as inclusions and microvoids. The functional predictions of the mechanism are shown to be consistent with available experimental evidence on ductile fracture behavior in the presence of hydrogen.     

The limiting speeds of dislocations

The purpose of this article is to show that the limiting speeds of moving dislocations are determined by inertial effects, or by viscous drag, at their cores. Simple expressions for the limiting speeds are derived. The standard idea that the speeds are limited by the inertia of the elastic fields, accompanied by Lorentz contractions, is shown to be flawed because it neglects the angular momentum of a moving dislocation; or, equivalently, because it assumes that the motion is steady if the velocity is constant, but this is not possible because the motion creates plastic deformation. Finally, the standard theory considers the dislocation to be moving in an infinite medium but this is not acceptable, because then both the energy and the mass would then be infinite. This article is based on a presentation given in the symposium entitled “Dynamic Behavior of Materials—Part II,” held during the 1998 Fall TMS/ASM Meeting and Materials Week, October 11–15, 1998, in Rosemont, Illinois, under the auspices of the TMS Mechanical Metallurgy and the ASM Flow and Fracture Committees.     

Hydrogen transport by dislocations

A kinetic model is presented for the transport of hydrogen, as Cottrell atmospheres on dislocation, at a rate appreciably in excess of that for lattice diffusion. The particular destinations for the hydrogen which are modeled here are ductile fracture initiation sites such as inclusions and microvoids. The functional predictions of the mechanism are shown to be consistent with available experimental evidence on ductile fracture behavior in the presence of hydrogen.     

Misfit dislocations in epitaxy

This article on epitaxy highlights the following: the definition and some historical milestones; the introduction by Frenkel and Kontorowa (FK) of a truncated Fourier series to model the periodic interaction at crystalline interfaces; the invention by Frank and van der Merwe (FvdM)—using the FK model—of (interfacial) misfit dislocations as an important mechanism in accommodating misfit at epilayer-substrate interfaces; the generalization of the FvdM theory to multilayers; the application of the parabolic model by Jesser and van der Merwe to describe, for growing multilayers and superlattices, the impact of Fourier coefficients in the realization of epitaxial orientations and the stability of modes of misfit accommodation; the involvement of intralayer interaction in the latter—all features that impact on the attainment of perfection in crystallinity of thin films, a property that is so vital in the fabrication of useful uniformly thick epilayers (uniformity being another technological requirement), which also depends on misfit accommodation through the interfacial energy that function strongly in the criterion for growth modes, proposed by Bauer; and the ingenious application of the Volterra model by Matthews and others to describe misfit accommodation by dislocations in growing epilayers. This article is based on a presentation in the symposium “Interfacial Dislocations: Symposium in Honor of J.H. van der Merwe on the 50th Anniversary of His Discovery,” as part of the 2000 TMS Fall Meeting, October 11–12, 2000, in St. Louis, Missouri, sponsored under the auspices of ASM International, Materials Science Critical Technology Sector, Structures.