Diameter Irregularity Research Articles

Preparation and characterization of electrospun cellulose acetate sub-micro fibrous membranes

Electrospun sub-microfiber membrane of cellulose acetate (CA), with excellent biodegradability, high specific surface area and high porosity, has attracted wide attention in various research fields. Even so, the stable continuous electrospinning of CA sub-micro fibers is affected by the solution parameters and CA acetylation degree dramatically, which still remains challenging. In the present work, electrospun CA sub-micro fibrous membranes have been prepared from four distinct solvent systems, respectively, to explore the proper solution parameters for membrane fabrication. After hydrolysis and electrospinning, the produced CA sub-micro fibrous membranes were analyzed in terms of fiber size distribution, hydrophilicity and porosity. Current analysis has shown that the degree of substitution of CA sub-micro fibers decreases with the increase in hydrolysis time, resulting in increased diameter irregularity, decreased average porosity and increased hydrophilicity of the sub-micro fibrous membrane.

Molecular mechanism of amyloid formation by Ab peptide: review of own works

TA characteristic feature of amyloid structures is polymorphism. The study of amyloid structures and their formation process was carried out for synthetic and recombinant Ab(1-40) and Ab(1-42) peptide preparations. In the study of these peptides, we recognized fibrils of different morphologies. We observed fibrillar formations in the form of single fibrils, ribbons, bundles, bunches, and clusters. Polymorphism of fibrils was observed not only when the environmental conditions changed, but under the same conditions and this was a common characteristics of all amyloid formations. Fibrils of Ab(1-40) peptides tended to form aggregates of fibrils in the form of ribbons, while Ab(1-42) peptide under the same conditions polymerized in the form of rough fibrils of different diameters and tends to branch. We assume that the formation of fibrils of Ab(1-40) and Ab(1-42) peptides occurs according to a simplified scheme: a destabilized monomer ® a ring oligomer ® a mature fibril consisting of ring oligomers. Proceeding from the proposition that the ring oligomer is the main building block of amyloid fibril (similar to the cell in the body), it is easy to explain fibril polymorphism, as well as fragmentation of mature fibrils under various external influences, branching and irregularity of diameter (surface roughness) of fibrils. One aspect of the study of amyloidogenesis is the determination of the regions of the protein chain forming the core of the amyloid fibril. We theoretically predicted amyloidogenic regions for two isoforms of Ab peptides capable of forming an amyloid structure: 16-21 and 32-36 residues. Using the method of tandem mass spectrometry, these regions were determined experimentally. It was shown that the regions of Ab(1-40) peptide from 16 to 22 and from 28 to 40 residues were resistant to the action of proteases, i.e. its formed the core of the amyloid fibril. For Ab(1-42) peptide the whole sequence is not available for the action of proteases, which indicates a different way of associating ring oligomers in the formation of fibrils. Based on electron microscopy and mass spectrometry data we proposed a molecular model of the fibril formed by Ab(1-40) and Ab(1-42) peptides.

Vasculitic peripheral neuropathy

Article type Review article Article history Primary systemic vasculitis in pre-capillary arteries is associated with pe- ripheral neuropathy. In some types of systematic vasculitis about 60 % of patients have peripheral nervous system (PNS) involvement. In vasculitic peripheral neuropathies (VPN) a necrotizing and inflammatory process leads to narrowing of vasa nervorum lumen and eventually the appear- ance of ischemic lesions in peripheral nerves. Some features might be suggestive of VPN, like: axonal nerve degeneration, wallerian-like de- generation, and diameter irregularity of nerve. Peripheral nervous system (PNS) destruction during systemic vasculitides should be considered, due to its frequency and early occurrence in vasculitis progression. The first line treatment of non systematic VPNs is corticosteroid agents, but these drugs might worsen the VPNs or systemic vasculitis.

Relationship between angiographic graft vessel disease and microvascular reaction after heart transplantation

This study tests the correlation of coronary angiographic findings with the extent of microvascular reaction in right ventricular endomyocardial biopsies (EMBs) in transplanted hearts. In EMBs (n = 209) of 30 heart transplant patients (8 female, 22 male, mean age 48 years) microvascular reaction, i.e. endothelial cell swelling and vascular wall thickening (both grade 0-2), was graded by light microscopy at ×200. Patients' first and last coronary angiography (CA) (mean time after heart transplantation [HTx] 8 and 44 months) were graded according to the Stanford Classification and the presence of diameter irregularities was evaluated semi-quantitatively. We found a correlation of angiographic type B lesions with endothelial cell swelling during the first 5 months and vascular wall thickening during the fifth to fourteenth month after HTx (p <0.05). In patients with diameter irregularities and type B1 lesions in their first CA and type C lesions in their last CA, there was pronounced endothelial cell swelling in the early postoperative period (p <0.05). There was a tendency towards an increased vascular wall thickening in these patients during the later postoperative period. Graft vessel disease affects large and small coronary arteries and capillaries. Small vessel disease is characterized by architectural changes in blood vessel walls. Serial investigations of EMBs for diagnosis of small vessel disease complement the present diagnostic tools.

A mathematical method for constraint-based cluster analysis towards optimized constrictive diameter smoothing of saphenous vein grafts

This study was concerned with the cluster analysis of saphenous vein graft data to determine a minimum number of diameters, and their values, for the constrictive smoothing of diameter irregularities of a cohort of veins. Mathematical algorithms were developed for data selection, transformation and clustering. Constrictive diameter values were identified with interactive pattern evaluation and subsequently facilitated in decision-tree algorithms for the data clustering. The novel method proved feasible for the analysis of data of 118 veins grafts, identifying the minimum of two diameter classes. The results were compared to outcome of a statistical recursive partitioning analysis of the data set. The method can easily be implemented in computer-based intelligent systems for the analysis of larger data sets using the diameter classes identified as initial cluster structure.

Dimensional analysis of human saphenous vein grafts: Implications for external mesh support

Constrictive external mesh support of vein grafts was shown to mitigate intimal hyperplasia in animal experiments. To determine the degree of constriction required for the elimination of dimensional irregularities in clinically used vein grafts, a detailed anatomic study of human saphenous veins was conducted. In 200 consecutive patients having coronary artery bypass grafting, harvested saphenous veins (length 34.4 +/- 10.8 cm) were analyzed regarding diameter irregularities, side branch distribution, and microstructure. The mean outer diameter of surgically distended saphenous veins was 4.2 +/- 0.6 mm (men, 4.3 +/- 0.6 mm vs women, 3.9 +/- 0.5 mm; P < .0001). Although the outer diameter significantly decreased over the initial 18 cm (-7.6%; P < .0001), the overall increase between malleolus and thigh was not significant (+11.2%). Smaller-diameter veins (<3.5 mm) had more pronounced diameter fluctuations than larger veins (31.8% +/- 11.0% vs 21.2% +/- 8.8%; P < .0001), with more than 71% of all veins showing caliber changes of more than 20%. There was 1 side branch every 5.4 +/- 4.3 cm, with a significantly higher incidence between 20 and 32 cm from the malleolus (P < .0001 to distal, P < .0004 to proximal). Generally, women had more side branches than men (0.30 +/- 0.15 cm(-1) vs 0.25 +/- 0.12 cm(-1); P = .0190). Thick-walled veins (565.7 +/- 138.4 mum) had a significantly higher number of large side branches (P < .0001), and thin-walled veins (398.7 +/- 123.2 mum) had significantly more small side branches (P < .0001). Pronounced intimal thickening ("cushions") was found in 28% of vessels (119.8 +/- 28.0 mum vs 40.1 +/- 18.2 mum; P < .0001). Although the preferential location of side branches may be addressed by the deliberate discarding of infragenicular vein segments, a diameter constriction of 27% on average would eliminate diameter irregularities in 98% of vein grafts.

Bazex–Dupré–Christol Syndrome in a 1‐Year‐Old Boy and His Mother

Bazex-Dupré-Christol syndrome is a rare genodermatosis with cancer predisposition, characterized by follicular atrophoderma, multiple milia, congenital hypotrichosis, hypohidrosis and basal cell malformations that include nevoid basal cell carcinomas of early onset. We present two patients with this syndrome, a 1-year-old boy with diffuse scalp and eyebrows alopecia, milia papules on the face, ears, trunk, and limbs. Hypohidrosis was observed on his trunk and head. His 16-year-old mother had identical changes since childhood, with hair fragility, and multiple atrophic "ice pick" follicular depressions on the dorsa of her hands. She also had a basal cell carcinoma on her face. Microscopic examination of hairs from the mother revealed abnormalities such as diameter irregularities, broken shafts, trichorrexis nodosa and pili bifurcatti. Pili bifurcatti is an uncommon hair shaft dysplasia that has not before been observed in Bazex-Dupré-Christol syndrome.

Diameter variations of irregular fibers under different tensions

The cross-section area of animal fibers varies along the fiber length, and this geometrical irregularity has a major impact on the mechanical properties of those fibers. In practice fibers are often subjected to tensile stresses during processing and application, which may change fiber cross-section area. It is thus necessary to examine geometrical irregularity of fibers under tension. In this study, scoured animal fibers were subjected to different tensile loading using a Single Fiber Analyzer (SIFAN) instrument. The 3D images of the fiber specimens were first constructed, and then along-fiber diameter irregularities of the specimens were analyzed for different levels of tensile loading. The changes in effective fineness of the fiber specimens were also discussed. The results indicate that for the wool fibers examined, there is considerable discrepancy in the fiber diameter results obtained from the commonly used single scan along fiber length and that from multiple scans at different rotational angles, and that the diameter variation along fiber length increases as fiber tension increases. The results also show that when diameter reduction treatments are applied to wool by stretching, the reduced average fiber diameter is associated with an increase in both within-fiber and between-fiber diameter variations. So in terms of effective fineness, the change is much smaller than the difference between the average diameters of the parent and treated wool. These results have significant implications for improving the accuracy of fiber diameter measurement and evaluation.

Modeling the tensile behavior of fiber bundles with irregular constituent fibers

AbstractIn this article, the effect of fiber dimensional irregularities on the tensile behavior of fiber bundles is modeled with the finite element method. The fiber dimensional irregularities are simulated with sine waves of different magnitudes. The specific‐stress/strain curves of fiber bundles and their constituent single fibers are obtained and compared. The results indicate that fiber diameter irregularity along the fiber length has a significant effect on the tensile behavior of fiber bundles. For a bundle of uniform fibers of different diameters, all the constituent fibers will break simultaneously, regardless of the fiber diameter. Similarly, if fibers within a bundle have the same pattern and level of diameter irregularity along the fiber length, the fibers will break at the same time, also regardless of the difference in the average diameter of each fiber. In these cases, the specific‐stress/strain curve for the bundle overlaps with that of the constituent fibers. When a fiber bundle consists of single fibers with different levels of diameter irregularities, the specific‐stress/strain and load–elongation curves of the fiber bundle have a stepped or ladder shape. The fiber with the highest irregularity breaks first, even when the thinnest section of the fiber is still coarser than the diameter of a very thin but uniform fiber in the bundle. This study suggests that fiber diameter irregularity along the fiber length is a more important factor than the fiber diameter itself in determining the tensile behavior of a fiber bundle consisting of irregular fibers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2664–2668, 2004

Relationship between angiographic graft vessel disease and microvascular reaction after heart transplantation

This study tests the correlation of coronary angiographic findings with the extent of microvascular reaction in right ventricular endomyocardial biopsies (EMBs) in transplanted hearts. In EMBs (n = 209) of 30 heart transplant patients (8 female, 22 male, mean age 48 years) microvascular reaction, i.e. endothelial cell swelling and vascular wall thickening (both grade 0-2), was graded by light microscopy at ×200. Patients' first and last coronary angiography (CA) (mean time after heart transplantation [HTx] 8 and 44 months) were graded according to the Stanford Classification and the presence of diameter irregularities was evaluated semi-quantitatively. We found a correlation of angiographic type B lesions with endothelial cell swelling during the first 5 months and vascular wall thickening during the fifth to fourteenth month after HTx (p <0.05). In patients with diameter irregularities and type B1 lesions in their first CA and type C lesions in their last CA, there was pronounced endothelial cell swelling in the early postoperative period (p <0.05). There was a tendency towards an increased vascular wall thickening in these patients during the later postoperative period. Graft vessel disease affects large and small coronary arteries and capillaries. Small vessel disease is characterized by architectural changes in blood vessel walls. Serial investigations of EMBs for diagnosis of small vessel disease complement the present diagnostic tools.

The effect of early burn wound excision on regional gastric blood flow in rats

This study examined the effects of early burn wound excision on gastric blood flow and on morphologic changes in mucosal vessels. Wistar rats were given a 30% total body surface area burn and divided into four groups, consisting of control animals (group 1), animals with burn injury without and with fluid resuscitation (groups 2 and 3, respectively), and animals with both fluid resuscitation and early wound excision (group 4). Gastric mucosal blood flow (GMBF) was measured by the hydrogen gas clcarance method up to 24 h post-burn. Morphologic changes in mucosal vessels were examined by scanning electron microscopy (SEM) at 3 and 24 h post-burn. The GMBF sharply decreased in the acute period after the burn. In group 4, however, it recovered to the initial value by 6 h post-burn and there was no significant change throughout the experiment. Morphologically, although the mucosal capillaries revealed some changes such as irregularity in diameter in groups 2–4 at 3 h, most of mucosal capillaries retained their original appearance in group 4 at 24 h post-burn. These result suggest that early excision does not aggravate the state of gastric ischemia.

Processing and Mechanical Properties of Strands of Liquid Crystalline Copolyester and Copolyesteramide

Extrusion moulding behaviour, mechanical and morphological properties of thermotropic liquid crystalline copolyester (LCP-A) and copolyesteramide (LCP-B) strands were investigated using a co-rotating twin-screw extruder, tensile testing, x-ray diffraction measurements, and scanning electron microscopic observation. Extrusion pressure and torque of LCP-B strands were larger than those of LCP-A strands under the same extrusion conditions, reflecting a difference in the apparent melt viscosity of the two polymers. The LCP-B strands obtained in this study had more homogeneous diameters, as compared with the LCP-A strands. The irregularity in diameter of the LCP-A strands tended to become smaller with increasing the length-to-diameter ratio (l/D) and output flow rate. The molecular orientation of LCP-B strands rose rapidly with draw ratio and reached almost a plateau at a much lower one, whilst that of the LCP-A strands became slowly higher with draw ratio. The tensile modulus and strength of LCP-B strands increased gradually with a draw ratio, even after the molecular orientation of the strands levelled off. The effect of the draw ratio on the molecular orientation and the mechanical properties of the strands was discussed from a morphological point of view.

Processing and Mechanical Properties of Strands of Liquid Crystalline Copolyester and Copolyesteramide

Extrusion moulding behaviour, mechanical and morphological properties of thermotropic liquid crystalline copolyester (LCP-A) and copolyesteramide (LCP-B) strands were investigated using a co-rotating twin-screw extruder, tensile testing, x-ray diffraction measurements, and scanning electron microscopic observation. Extrusion pressure and torque of LCP-B strands were larger than those of LCP-A strands under the same extrusion conditions, reflecting a difference in the apparent melt viscosity of the two polymers. The LCP-B strands obtained in this study had more homogeneous diameters, as compared with the LCP-A strands. The irregularity in diameter of the LCP-A strands tended to become smaller with increasing the length-to-diameter ratio (l/D) and output flow rate. The molecular orientation of LCP-B strands rose rapidly with draw ratio and reached almost a plateau at a much lower one, whilst that of the LCP-A strands became slowly higher with draw ratio. The tensile modulus and strength of LCP-B strands increased gradually with a draw ratio, even after the molecular orientation of the strands levelled off. The effect of the draw ratio on the molecular orientation and the mechanical properties of the strands was discussed from a morphological point of view.

Reducing method of aerodynamic noise from high speed pantograph.

The aerodynamic noise from pantograph is one of the important external noise source of a high speed train as Shinkansen. The external noises of testing trains were measured using a linear-array type directional microphon and a full-scale pantograph was tested in a low noise wind tunnel. It is shown that the intensity of the pantograph aerodynamic noise is proportional to the 6th power of velocity and severe at the near place to the head of a train. A frequency analysis shows that the Aeolian tones from the bow and the oblique pipe of pantograph give main contributions. It is confirmed that an appropriate irregularity of diameter of cylinder or an air gap in the section of the bow are effective for reducing the Aeolian tones.

Utilization of Fiber Strength in Jute Yarns

From a study of the relationship between the breaking strength and the corresponding mass per unit length at thefracture zone of a yarn, the expected strength of a perfectly even yarn of identical fiber composition has been derived. The ratio between the observed strength and this estimated value has been taken as a measure of utilization of fiber strength in yarn. The dependence of this utilization factor on the diameter irregularity of yarn has been examined on the basis of test results obtained on a number of yarn samples of different qualities. The yarn tenacity at the fracture zone is also found to be related with its diameter irregularity; the causes of this are discussed

39—ANALYSIS OF YARN IRREGULARITY FOR PERFORMANCE EVALUATION IN JUTE-SPINNING

The diameter irregularity of jute yarns has been shown to be related with other yarn characteristics. A method has been developed for evaluating the component of yarn irregularity due to the fibre properties and random distribution of fibres in the yarns; the ratio between the observed irregularity of yarns and this component has then been used as an index to specify the over-all performance of the preparatory and spinning operations in a mill. The index values for yarn samples collected from different mills throughout the industry have been determined, and a suitable grading scheme in terms of the index is suggested. This should be of practical use for quality and process control in jute mills.