Dominant Morphology Research Articles

Surface topography of eroded Cu and Si cathodes in a PIG ion source

The surface topography development on a Cu sheet and a Si(111) wafer was studied after being sputtered in a Penning ionization gauge (PIG) ion source using Ar gas. In the case of Cu, a high density of conical structure was developed on the surface. The most striking feature was that the individual cones, relatively large in size, were often coated with impurity layers. Some cones were decorated with concentric ring-like patterns on their surfaces. The overlying coating was thought to be responsible for the initial growth of the cones and subsequent evolution of secondary protuberances on the surfaces of the cones. In the case of Si, though a few impurity-induced conical protrusions were formed, the dominant morphology was in the form of etch pits. In addition to usual single cones, Si surface developed cones of dimeric structure and cluster of cones.

Directional solidification of CoO-ZrO2 eutectics

The directional solidification of CoO-ZrO2 eutectic with and without Y2O3 has been investigated by the floating zone melting method. A directionally solidified structure without cell structure can be grown for both CoO-ZrO2 and CoO-ZrO2-Y2O3 eutectics. The dominant growth morphology in these eutectics was the lamellar structure. The interface of the lamella has the orientation relationship of (001)cubic ZrO2⌈(111)CoO and steps with periodic spacing. This relation at the interface was retained even if the ZrO2 phase was transformed to the monoclinic phase from the cubic phase through the tetragonal structure.

Faceted fatigue fracture and its relation to the crystallographic slip systems in Cu-16 at. Pct al single crystals

In order to explore the relationship between the characteristic linear marks on the fracture surfaces of fatigued planar slip materials and the activity of cross slip and secondary slip systems, fatigued single crystals of Cu-16 at. pct Al alloy with a common single slip orientation were examined by scanning electron microscopy (SEM). This paper documents and explains the fractographic details of stages I and II crack propagations as a function of crack depth, strain amplitude, and loading history in a planar slip metal. The linear marks on the fracture surfaces in stage I for the specimen cycled at low strain amplitude are found mostly parallel to the traces of the cross slip plane, which is the plane on which propagation occurs to link up closely parallel cracks on the primary slip plane. With increase of crack depth, the contribution of conjugate slip for the linking up of parallel primary cracks increases. By geometrical consideration of the secondary slip planes with respect to primary cracks, the cross slip plane was found to be the most favored for the linking up of parallel primary cracks. This linking-up phenomenon produces the dominant fracture surface morphology. The fracture surfaces in the final stages show the typical features of ductile fracture in striations or catastrophic rupture. This result indicates that the observation of crystallographic traces on the fracture surfaces in stages I and II need not be associated with a brittle cleavage mechanism of fatigue fracture. The present authors support a ductile, plastic mechanism of crack propagation in both stages I and II.

The formation of multi-domain precipitates in a Ni [sbnd]W alloy

The formation of twinned Ni 4W precipitates in a Ni W alloy has been studied. On prolonged aging the dominant morphology found is one where two perpendicular twin related variants of Ni 4W form plate-shaped precipitates with a near (100) Ni habit plane. The orientation relationship between the Ni 4W variants and the Ni matrix leads to a macroscopic shape change with the (100) habit plane interface nearly invariant. In addition each domain has a simple shear associated with it, which can be accomodated either elasticity or by arrays of screw dislocations. Elastic accommodation leads to a strain contrast effect which is similar to that observed at screw dislocations lying normal to the foil surface.

TEM in-situ investigations of the crystallization behaviour of amorphous silicon thin films

The crystallization of amorphous silicon thin films deposited on SiO 2 layers was in situ studied in a high-voltage electron microscope. The layers, grown by the LPCVD technique, were heated up to temperatures between 600 and 750°C for up to 70 minutes. The investigations have shown that the crystallization behaviour differs for undoped and phosphorus-doped layers. Amorphous deposited silicon layers contain small crystallites already after the doping process (implantation at room temperature) which grow parallel to 〈111〉 directions of the underlying silicon substrate. The most dominant morphology of the growing crystallites displays a needle-like shape; the ratio of the length (longitudinal axis) to the width is close to 2, independent of the doping. The pre-existing crystallites in the phosphorus-doped material influence the twin frequency in the crystallites. Respective reasons are discussed on the basis of the TEM results.

Comparison of QRS morphologies of spontaneous premature ventricular complexes and ventricular tachycardia induced by programmed stimulation

We addressed the hypothesis that premature ventricular complexes (PVCs) and sustained ventricular tachycardia (VT) have identical QRS morphologies in 20 patients with recurrent sustained VT. Continuous six-lead ECGs of PVCs and sustained VT induced with programmed stimulation were recorded. A computer program divided the PVCs and VT beats of each patient into distinct morphologic groups and a representative waveform was obtained by averaging the PVC and VT beats of the group members. A correlation coefficient was then derived between the QRS complexes of each PVC and VT morphology. The mean number of PVC morphologies was 12 +/- 8 per patient (range 1 to 26), the mean number of VT morphologies was 2 +/- 1 per patient (range 1 to 5). The correlation coefficient between the dominant PVC morphology and a VT morphology was greater than 0.7 in only three patients. The combined percent contribution of all PVCs with morphologies that were at least possibly identical to those of VT averaged only 13%. Thus PVCs with morphologies identical to those of VT are present in some patients with sustained VT, but these constitute a small proportion of all PVCs.

Echocardiographic spectrum of double inlet ventricle: Evaluation of the interventricular communication

To determine the spectrum and associated anomalies of double inlet ventricle (single ventricle), echocardiographic data of 50 patients with double inlet ventricle were reviewed and compared with the data obtained by cardiac catheterization, cardiac surgery and autopsy. Standard echocardiographic planes were used to determine the cardiac anatomy and the size of the interventricular communication. Double inlet by way of two perforate valves was found in 44 patients. In 42 of the 44 patients the dominant ventricular morphology was of the left ventricular type (double inlet left ventricle); in 13 of these 42 patients stenosis of one atrioventricular (AV) valve was found. Double inlet right ventricle and double inlet indeterminate ventricle were each found in one patient. Double inlet by way of a common AV valve was found in six patients, all of whom had atrial isomerism. The diagnosis of double inlet ventricle was accurate by two-dimensional echocardiography in all 44 patients. A restrictive interventricular communication was shown in 13 patients and a nonrestrictive communication in 17 patients by cardiac catheterization. Patients with a restrictive interventricular communication had a significantly smaller interventricular communication area normalized by the body surface area (mean +/- SD 1.21 +/- 0.53 cm2/m2) than did those with a nonrestrictive interventricular communication (2.33 +/- 0.71 cm2/m2) (p less than 0.01). Infants with an aortic anomaly had a significantly smaller interventricular communication area (1.35 +/- 0.65 cm2/m2) than did those without an aortic anomaly (2.57 +/- 0.76 cm2/m2) (p less than 0.05). Echocardiography provides an accurate noninvasive diagnosis in patients with double inlet ventricle, offering reliable information about the restrictive interventricular communication.

組合せ荷重を受ける純銅の環状切欠き材の疲労における微小き裂の成長挙動と寿命特性に関する研究

Fatigue tests were conducted using solid cylindrical specimens of pure copper with circumferential blunt notches subjected to combined axial-torsional loadings. The behavior of crack growth was observed by a plastic replication technique, and the property of fatigue life was investigated. The cracking at notch root was identified as an intergranular type. The dominant morphology of crack growth was found to be the coalescence of distributed small-cracks, while some difference was observed depending on the stress multiaxiality. The fatigue life was correlated with the equivalent stress of the Mises type and the maximum shear stress. The fatigue life for the same value of each stress parameter became longer as increasing shear component in the stress state at notch root.An analytical procedure for the crack growth at notch root was established by using a model based on the competition between the coalescence growth and the propagation of a dominant crack. Characteristics of intergranular cracking at the notch root and its dependence on the stress state were very well simulated by the present analytical model. Fatigue lives in several test conditions were statistically estimated by a simulation of the Monte Carlo type. The prediction with the simulated scatter-bands almost coincided with the experimental results.

Analytical transmission electron microscopy of La2O3-doped Y2O3

Analytical electron microscopy has been used to study the precipitation reactions in sintered samples of 9 mol% La2O3-Y2O3 samples upquenched from the single phase cubic region into the cubic and hexagonal phase field. Samples annealed just inside the two-phase cubic-cubic and hexagonal solvus exhibited predominantly grain boundary precipitation. Small La2O3 rich second phases formed within the first ten minutes and developed into strained, facetted precipitates after 300 min. Intergranular and intragranular precipitation occurred in samples annealed further into the two-phase field. Strained, lathlike La2O3-rich monoclinic precipitates, exhibiting a preferrred orientation in the matrix, appeared as the dominant morphology for long times at temperature. Chemical microanalyses of the strained structures obtained in samples annealed for 300 min revealed La2O3 matrix concentrations in agreement with phase diagram predictions. However, the La2O3 concentrations in the second-phase precipitates were found to be far in excess of the cubic and hexagonal-hexagonal solvus. This discrepancy is believed to arise from a re-equilibration of the second phase in the cubic and monoclinic phase field during quenching.

Medullary cystic disease: an inherited form of autoimmune interstitial nephritis?

I NHERITED KIDNEY lesions have historically been classified either by their dominant morphology or by a distinctive functional abnormality. This is because little is really known about their origins or pathophysiology. One consequence of a classification based on morphology is the inevitable tendency to regard diseases with common morphologic features as having shared pathogenic mechanisms, though this mayor may not be true. An enduring example of such a classification system is that of renal cystic diseases. Textbooks on the subject have traditionally grouped together inherited and acquired renal diseases having either macroscopic or microscopic cystS.1.2 Confusion regarding the descriptive nomenclature of cystic diseases is well appreciated, although in the last 10 to 15 years the terminology has become much more consistent. 3 The two most common inherited cystic diseases that typically progress to end-stage are adult polycystic kidney disease (APKD), and the medullary cystic disease-familial juvenile nephronophthisis complex (MCD-FJN). Their patterns of inheritance, natural histories, and associated clinical complications have all been well descibed in recent reports. 4,5 The inheritance of APKD seems to map to the short arm of chromosome 16.6 APKD is typically transmitted with autosomal dominant inheritance, whereas MCDFJN usually follows an autosomal recessive pattern. Together, they account for 10% to 12 % of all end-stage kidney diseases. Although meticulous management of hypertension and infections (especially in APKD) and volume depletion (especially in MCD-FJN) may prevent accelerated loss of renal function, there is no specific therapy for either disease.

Displacement reactions between Cr and MoO2 in a Ni-base alloy matrix

Displacement reactions at 1150 °C between Cr and MoO22 in a Ni-rich alloy matrix were studied. Depending on the Cr and Mo contents, three morphologies of the Cr2O3 product phase were observed: internal oxides, continuous scale, and aggregate product layer. Kinetic expressions were derived and fitted to the layer growth data. The reactions were found to be diffusion controlled and described well by quasi-steady-state fluxes. The selection by the system of the dominant product morphology was decided by the relative fluxes of chromium and oxygen solutes to the initial interface early in the reaction.

Nucleation of struvite (MgNH4PO4 · 6 H2O) single crystals and aggregates

AbstractThe conditions (concentration and pH) for preparation of single crystals of struvite at 25 °C from ammoniacal solutions equimolar with respect to magnesium and phosphate ions are given. The limits are found above which crystal aggregates (twins or dendrites) precipitate as dominant morphology. The mechanisms of nucleation are discussed and the interfacial tension between crystals and solution is evaluated.

Nucleation & Growth of Octahedral Oxide Particles in Silicon: Oxygen Ion Implantation

ABSTRACTCzochralski silicon was implanted with oxygen at 0.4 and 3.5MeV to obtain concentrations near 1020 oxygen/cm3 in the implanted region. Following implantation the wafers were aged at about 1000°C for 7 hours, and the resulting precipitates were examined by HREM. A high density of octahedral SiOx precipitates (∼1015/cm3) was the dominant morphology. Plate type precipitates and dislocations were also present at lower density. The data indicate octahedra grow from the plates.

Evaluation of propylene oxide for mutagenic activity in 3 in vivo test systems

Propylene oxide (CAS No. 75-56-9) was tested for mutagenic activity following vapor exposure using 3 in vivo test systems. Rat dominant lethal and mouse sperm-head morphology assays were conducted using males exposed to propylene oxide at 300 ppm in a dynamic exposure chamber for 7 h per day on 5 consecutive days. A sex-linked recessive lethal test in Drosophila melanogaster employed a 24-h static exposure to propylene oxide at 645 ppm. Male mice were killed 1, 3, 5, 7, and 9 weeks post-exposure for evaluation of sperm-head morphology. Propylene oxide exposure did not result in an increase in abnormal forms. Male rats were mated with 2 virgin females per week for 6 weeks following exposure. A statistically significant increase in preimplantation losses and a statistically significant reduction in the number of lving implants in the first post-exposure week did not appear to be treatment related. A highly significant increase in sex-linked recessive lethal mutations was observed in two germ cell stages (mature sperm and developing spermatocytes). These results warrant continued caution in potential human exposure to propylene oxide.

Recovery of plant communities on coastal sand-dunes disturbed by human trampling

The resilience of plant communities to disturbance can be characterized by the ability of species and life-forms to recover, provided that the desired degree of naturalness is present. Results of a case study in two ecological types of Danish sand dunes, the grey and the white dune, show that dominant growth morphology and initial pattern of recovery are inter-related. The propagation of above-ground organs leads to progressive lateral recovery, while subterranean proliferation by means of rhizomes leads to erratic recovery. Species behave in different ways depending on the environment, and patches of bare ground generally grow over slowly, unlike well-established patches of vegetation where environmental conditions are more suitable. Because of this change of structure, vegetation recovery is not assessable by traditional recording of individual factors such as number of species or percentage cover, and a list of the key factors involved is given. The erratic pattern of recovery of rare species stresses the importance of long-term recording of vegetation to assess recovery.

Bacteria Associated with the Gut Tract of Larval Stages of the Aquatic Cranefly Tipula abdominalis (Diptera; Tipulidae)

Scanning electron microscopy, light microscopy, and direct isolations were used to examine the distribution and diversity of bacteria in the gut tracts of larval stages of Tipula abdominalis. The animal had an enlarged hindgut which housed a diverse bacterial community in the lumen and directly attached to the gut wall. Distinct localization was noted, with the most dense and most diverse community anterior to the rectum. A distinct architecture of bacteria occurred in this region, characterized by a layering or a "weblike" array of filamentous bacteria overlying mats of bacteria closely associated with the gut wall. Although morphological diversity was high in the hindgut, filamentous bacteria were the dominant morphology observed. The attached microbiota, sloughed during ecdysis, recolonized to the same density and diversity observed before the molt. The majority of the isolatable bacterial types were facultatively anaerobic. The distinct localization and attached nature of the hindgut bacteria and the recolonization after each molt suggest they are indigenous to this region of the gut tract.

Organic chemistry of Protosalvinia (Foerstia) from the Chattanooga and New Albany Shales

Vertical samplings of Protosalvinia, a thalloid Upper Devonian alga from the Chattanooga and New Albany Shales, are chemically analyzed and correlated with the organic chemical constituents isolated from associated shale matrices. Normal, saturated acids ( n-C 8 to n-C 36 n-paraffins (C 10 to C 36), showing an odd carbon-number preference, branched-chain alkanes, and vanadyl porphyrins isolated from Protosalvinia vary in their concentrations with depth of burial and with the dominant associated morphology of Protosalvinia, i.e., P. arnoldii, P. ravenna, P. furcata. Organic constituents of shales, in general, reflect those detected in thalli; relative concentrations, molecular diversity, carbon chain-lengths and maxima of compounds extracted from both shale and fossil material are similar. Pristane, phytane and porphyrins are probably derived from a chlorophyllous organism, while δ 13C data corroborate a photosynthetic system operating in the primary biosynthesis of shale geochemistry. Crude-oil extracts of Protosalvinia-rich strata contain higher alkane and lower aromatic hydrocarbon concentrations than those of an average crude oil. Chemical variations among forms of Protosalvinia suggest biochemical differences in original plant composition rather than diagenetic transitions; field observations of morphological trends seen in vertical samplings may be used in crude extrapolations of the organic chemical compositions of shale strata.

Cystic kidneys as a cause of constant hypertension: Fahr, Th.: Deutsche med. Wchnschr. 55: 572, 1929

Diabetes mellitus (DM) is characterized by chronic hyperglycemia states and the development of specific microvascular disorders such as retinopathy and nephropathy. Conventional methods are used to study the vascular compromise of this entity, however, the use of capillaroscopy for the evaluation of capillary microarchitecture is not frequently used.Observational and descriptive study of 65 patients with an established diagnosis of DM and a control group that underwent an initial capillaroscopy examination. The parameters considered were: Capillary diameter (ectasia and giant capillaries), cross-linked, tortuous, arborified capillaries, avascular zones, haemorrhages, dominant morphology, visibility of the subpapillary venous plexus (SPVP), cuticulitis and SD pattern.Capillaroscopy was performed in 65 patients, the findings were: tortous capillaries (63%), crosslinked capillaries (59%), avascular areas (48%), ectasias (39%), giant capillaries (11%). The capillaroscopic findings were evident in the majority of the studied population, 83%, compared to 17% who did not have capillaroscopic alterations.Significant capillaroscopic changes were demonstrated in patients with DM, in turn, we described a specific pattern consisting of: capillary dilatation, avascular zones and tortuous capillaries. Patients with more comorbidities and evolution of the disease showed greater microvascular damage.