Chromosome studies in "preleukemia". III. Myelofibrosis

Cytogenetic studies were done on 18 patients with myelofibrosis or the closely related syndrome, undifferentiated myeloproliferative disorder (MPD). Clones of cells with chromosome abnormalities were demonstrated in the blood of eight individuals, including two with a history of radiation therapy and two with "acute myelofibrosis". Trisomy 8 was present in the latter two patients, but otherwise, there was no consistent cytogenetic pattern or correlation with specific hematologic findings. Sixteen of these patients have been followed for more than 1 year or until death; none has progressed to leukemia. The results indicate that chromosome abnormalities are relatively common in this disorder, but as with polycythemia vera, and unlike some other "preleukemic" states, the aberrant clones in myelofibrosis do not appear to indicate that clinical leukemia is imminent.     

Cancer genetics, cytogenetics--defining the enemy within

BACKGROUND/AIMS: International comparisons of clinical practice may help in assessing the magnitude and possible causes of variation in cross national healthcare utilisation. With this aim, the indications for cataract surgery in the United States, Denmark, the province of Manitoba (Canada), and the city of Barcelona (Spain) were compared. METHODS: In a prospective multicentre study, patients scheduled for first eye cataract surgery and aged 50 years or older were enrolled consecutively. From the United States 766 patients were enrolled; from Denmark 291; from Manitoba 152; and from Barcelona 200. Indication for surgery was measured as preoperative visual status of patients enlisted for cataract surgery. Main variables were preoperative visual acuity in operative eye, the VF-14 score (an index of functional impairment in patients with cataract) and ocular comorbidity. RESULTS: Mean visual acuity were 0.23 (USA), 0.17 (Denmark), 0.15 (Manitoba), and 0.07 (Barcelona) (p < 0.001). When restricting the sample to eyes with normal retina and macula, no significant difference between United States and Denmark was observed (p > 0.05). Mean VF-14 scores were 76 (USA), 76 (Denmark), 71 (Manitoba), and 64 (Barcelona) (p < 0.001). CONCLUSION: Similar indications for cataract surgery were found in the United States and Denmark. Significantly more restricted indications were observed in Manitoba and Barcelona. Possible explanations for the results are discussed, including differences in sociodemographic characteristics, access to care, surgeons' willingness to operate, and patient demand.     

Three-dimensional cracks with Dugdale-type plastic zones

A general method for the determination of three-dimensional crack-front plastic zones is presented. The crack-model utilised is of the Dugdale-type, that is a plastic zone is assumed to spread in front of the crack, in the plane of the crack. The solution method relies on the eigenstrain approach to crack-problem solving. Using this approach, the elastic and plastic regions of the crack are first discretised into triangular elements and the stress arising over the crack due to a constant or linear crack-surface displacement in each element is obtained. The stresses are given in terms of hyper-singular integrals, which may be solved numerically. The boundary conditions in the elastic portion (traction-free) and in the plastic zones (Tresca or some other yield condition) are encompassed in an object function in such a way that the boundary conditions are satisfied if and only if the object function is zero. The resulting quadratic programming problem is solved numerically, and hence the crack displacements, and other important quantities, are obtained. Results agree well with some known analytic results regarding the penny shaped crack in tension.     

Composition, distribution, and potential toxicity of organochlorine mixtures in bed sediments of streams

Mixtures of organochlorine compounds have the potential for additive or interactive toxicity to organisms exposed in the stream. This study uses a variety of methods to identify mixtures and a modified concentration-addition approach to estimate their potential toxicity at 845 stream sites across the United States sampled between 1992 and 2001 for organochlorine pesticides and polychlorinated biphenyls (PCBs) in bed sediment. Principal-component (PC) analysis identified five PCs that account for 77% of the total variance in 14 organochlorine compounds in the original dataset. The five PCs represent: (1) chlordane-related compounds and dieldrin; (2) p,p′-DDT and its degradates; (3) o,p′-DDT and its degradates; (4) the pesticide degradates oxychlordane and heptachlor epoxide; and (5) PCBs. The PC analysis grouped compounds that have similar chemical structure (such as parent compound and degradate), common origin (in the same technical pesticide mixture), and(or) similar relation of concentrations to land use. For example, the highest concentrations of chlordane compounds and dieldrin occurred at urban sites, reflecting past use of parent pesticides for termite control. Two approaches to characterizing mixtures—PC-based mixtures and unique mixtures—were applied to all 299 samples with a detection of two or more organochlorine compounds. PC-based mixtures are defined by the presence (in the sample) of one or more compounds associated with that PC. Unique mixtures are defined as a specific combination of two or more compounds detected in a sample, regardless of how many other compounds were also detected in that sample. The simplest PC-based mixtures (containing compounds from 1 or 2 PCs) commonly occurred in a variety of land use settings. Complex mixtures (containing compounds from 3 or more PCs) were most common in samples from urban and mixed/urban sites, especially in the Northeast, reflecting high concentrations of multiple chlordane, dieldrin, DDT-related compounds, and(or) PCBs. The most commonly occurring unique mixture (p,p′-DDE, p,p′-DDD) occurred in both simple and complex PC-based mixtures, and at both urban and agricultural sites. Mean Probable Effect Concentration Quotients (PEC-Q) values, which estimate the potential toxicity of organochlorine contaminant mixtures, were highest for complex mixtures. Mean PEC-Q values were highest for urban sites in the Northeast, followed by mixed/urban sites in the Northeast and agricultural sites in cotton growing areas. These results demonstrate that the PEC-Q approach can be used in combination with PC-based and unique mixture analyses to relate potential aquatic toxicity of contaminant mixtures to mixture complexity, land use, and other surrogates for contaminant sources.     

Effect of film thickness on the evolution of annealing texture in sputtered copper films

Microstructural evolution during elevated temperature annealing of sputter deposited copper (Cu) films was investigated by electron backscatter diffraction (EBSD). Analysis of films was performed both in situ using a heating stage, and by ex-situ observation of microstructural evolution. It was noted that not only is the Cu film texture and grain size a function of film thickness, but also that the fraction of twin boundaries present in the material is strongly dependent upon film thickness. This is explained by means of a simple model that considers the energy of the system. Surface and interface energies, as well as grain boundary energies for random high angle boundaries and for twin boundaries (both coherent and incoherent planes) are used in the determination. The model was shown to accurately predict the twin boundary size in self-annealed films. This type of analysis also results in a texture map similar to that presented by Thompson,¹² but incorporates the development and effect of twin boundaries, so that additional texture components (in addition to 111 and 100 fibers) are included.     

ANALYSIS OF CRACK INITIATION AND PROPAGATION IN FRETTING FATIGUE: THE EFFECTIVE INITIAL FLAW SIZE METHODOLOGY

Abstract— A number of fretting fatigue tests were carried out on CMV steel and INCO 718 alloys under closely controlled experimental conditions. A fracture mechanics-based lifing model was developed and the Paris Law employed to predict fatigue lives under a range of experimental conditions. An effective initial flaw size was used to describe initiation and early propagation of cracks. This approach was found to give good predictions of fatigue life of specimens for different values of bulk stress under the same fretting load.     

An elastic-plastic asperity interaction model for sliding friction

A finite-element model of the interaction of an elastic-plastic asperity junction based on cylindrical or spherical asperities is used to predict sliding friction coefficients. The modelling differs from previous work by permitting greater asperity overlaps, enforcing an interface adhesional shear strength, and allowing material failure. The results of the modelling were also used to predict friction coefficients for a stochastic rough surface. The asperities were based on the titanium alloy Ti-6Al-4V, and the magnitudes of the predicted friction coefficients were generally representative of experimental measurements of sliding friction. The results suggest that friction arises from both plasticity and tangential interface adhesion.