Metal Stick Research Articles

New discoveries of stress fluctuations at the tool-chip interface and sticking tool tendency in metal cutting processes

Addressing the issue of sticking tools during the metal cutting process is crucial for enhancing cutting efficiency and ensuring industrial safety. This study employs molecular dynamics (MD) simulations to investigate single-crystal SiC tools and 27 different grain orientations of single-crystal pure metal workpieces (Ni, Cu, Co, and Fe). MD models were established to simulate the nanocutting and tool retraction processes. This study revealed a new phenomenon of stress fluctuations at tool-chip interfaces and proposed a new theory on the relationship between stress fluctuations and metal sticking tool tendencies. Research indicates that during nanocutting, the normal stress distribution at the tool-chip interface of different materials exhibits the same periodic fluctuation (T=0.5a, where a is the tool lattice constant). The greater the stress fluctuation is, the greater the sticking tool tendency. By fitting the results for 27 workpieces, an approximate relationship was established. For metals with the same lattice type, such as FCC-structured Ni and Cu, the stress fluctuation and sticking tool tendency are both greater when the cutting orientation is 11111¯0, and the chip morphology and temperature distribution are similar. Through the analysis of lattice transformation, atomic shear strain, and temperature field, this study explored the microscopic mechanisms and thermomechanical theories underlying the new findings of stress fluctuations and sticking tool tendencies. The stress fluctuation distribution at the tool-chip interface is a new discovery that differentiates nanocutting from traditional processing models. Future research can further investigate the cutting behavior of complex materials under complex conditions, which will help to further elucidate the mechanism of sticking tools during processing.

СПОСІБ ВЧИНЕННЯ ВБИВСТВ З ОСОБЛИВОЮ ЖОРСТОКІСТЮ ЯК ЕЛЕМЕНТ КРИМІНАЛІСТИЧНОЇ... ХАРАКТЕРИСТИКИ ЦИХ ЗЛОЧИНІВ

The article is devoted to the study of the method of committing murders with particular brutality as one of the most important elements of the forensic characteristics of these crimes. On the basis of a systematic analysis of scientific forensic literature, criminal, criminal procedural legislation and the results of investigative and judicial practice, as well as the results of a survey of practical workers (investigators, prosecutors), it was concluded that the method of committing the crime as an element of the forensic characteristics has a significant impact on the qualification, as well as on the methodology of the investigation of the specified criminal offense. The method of committing murders with particular brutality has been considered by us from the point of view of its classic in criminology system of interrelated actions of preparation, direct commission and concealment of traces of the crime. The results of the systematic analysis of criminal proceedings opened on the grounds of the crime provided for in Clause 4, Part 2, Art. 115 of the Criminal Code of Ukraine, convincingly testifies that murders with particular brutality are almost never committed with preliminary preparation for the commission of the crime. As a rule, the criminal immediately implements the criminal intent that has arisen. It has been established that the only preparatory action carried out by a criminal and which can be considered preparation for the commission of a murder committed with particular cruelty is the selection and bringing to the scene of the crime of the instrument of its commission. In isolated cases, there was also a place for the criminal to wait for a favorable moment to start his criminal activity, namely the moment when the criminal and the victim (or victims) were alone. It has been established that murders with particular brutality are most often committed in the following ways: striking with hands and feet, jumping with feet on the victim’s body and head; inflicting barbed-cutting blows with a knife, including a hunting knife that belongs to cold weapons, with another sharp object (screwdriver, etc.); an object of chopping action (axe, shovel, etc.); amputation of body parts with a knife; striking with a blunt object (hammer, metal stick, etc.); strangulation with hands, object (wire, rope, etc.); arson of the victim and others. There have been several cases where various methods of committing murder with particular brutality are consistently used. The correlations between the elements of forensic characteristics are established: the way the crime was committed and the person of the criminal, the place of the crime and the victim.

Burn wound healing effects of the root hydroethanolic extract of Cochlospermum planchonii in mice

Cochlospermum planchonii is a plant traditionally used in Togo to treat burn wounds. The present study aimed at evaluating the effect of the root hydroethanolic extract of Cochlospermum planchonii on the skin burn wounds. Burns were induced in ICR mice by applying on the skin of the dorsal region with a metal stick (0.7 cm diameter) preheated at 100 °C for 10 seconds. Four (4) groups of 8 mice were formed, Control Group (I); Group II, III and IV treated respectively with C. planchonii gel 2.5%, 5%, and Brulex® (Zinc oxide 15% cream). The surfaces of the wounds were evaluated daily by the ImageJ software. Biopsies were performed on day six and twelve for hydroxyproline assays and histological examinations. On the 12th day, wound contraction rates were 44.12%, 67.82%, 66.68% and 69.32% respectively for Group I, Group II, Group III and Group IV. Hydroxyproline levels on day 12 were significantly higher in samples of animals treated with C. planchonii 2.5% and 5% (+114,93 ± 1,61 and +120,54 ± 7,22 of augmentation respectively, P<0.01 when compared to the control group). Histological examination confirmed these observations. C. planchonii root hydroethanolic extract could be a potentially natural remedy for burn wound.

Aggression of Carcharhinus leucas and Carcharhinus amblyrhynchos towards humans

An important step in combating shark endangerment is lowering the stigma surrounding the species; one way to do so is to publish data on shark aggression. This paper presents findings on Carcharhinus leucas (bull shark) and Carcharhinus amblyrhynchos (grey reef shark) aggression towards humans at Beqa Adventure Divers in Shark Reef Marine Reserve, Fiji. We collected data on the number of sharks present and prods delivered - a method to redirect sharks away from tourist divers using a 2.5-meter metal stick by dive masters - during nine shark feeds. We hypothesized that grey reef sharks would receive more prods than bull sharks because grey reef sharks are typically more aggressive than bull sharks. The results supported our hypothesis, as an individual grey reef shark received 2.44 prods on average per feed, while a bull shark had an average of 0.61. Furthermore, grey reef sharks showed signs of aggression, including pectoral depressions and exaggerated swimming, throughout the feeds, while bull sharks showed none. These findings are meaningful not only to the world’s general understanding of shark aggression, but also to human protection against grey reef sharks as well as public education on bull sharks and the conservation of the species.

Improving the technology of part machining by surface plastic deformation

The purpose of this work is to study the technological process of strengthening hollow cylindrical parts of tractor engines using surface plastic deformation.Experimental studies in a wide range of changes in various factors have been preliminary performed on models. The data obtained were recalculated from the model to specific parts – piston fingers and bushings of the top heads of connecting rods in automotive tractor engines. The study was aimed at determining the efforts, stresses, changes in shape, the properties and structure of a parts' material. In the course of our study, the law of similarity was maintained, whereby the sample models were geometrically similar and physically identical to parts. The rational shape of machining tools was experimentally established – conical; as well as its optimum dimensions: angle of inclination, 10°30'; magnitude of the calibration belt, 6–7 mm, which provide for the magnitude of strengthening and surface quality of the machined material. We have experimentally established the effect of angle of inclination of the machining tool on the amount of a metal sticking to its working surface. The dependence of the amount of a sticking metal on its hardness and the elasticity module has been established. We have determined the impact of height of the calibration part of a machining tool on the roughness of a part's machined surface.The empirical dependence of machining allowance with a residual deformation along the outer diameter of a piston finger has been derived based on the laboratory data obtained. It has been found that the most dangerous are the tangential stresses along the outer surface of piston fingers, which were determined in the process of deformation by a strain gauge method. We have experimentally established the value of machining allowance over a single run of the working tool at vibration deformation of piston fingers, which ensures a reduction in tensile residual stresses. Our study into the static strength of piston fingers has found that the magnitude of wear depends on the following basic factors: a machining method, the material and time of operation.The research into the weight wear of piston fingers and bushings of the top heads of connecting rods has established that at vibration deformation the amount of wear is less compared to regular expansion. The magnitude of wear of the piston fingers restored by a vibration method is 1.13 times less than that in those restored by regular expansion

The application of hybrid operation suite in the management of cerebral and spinal vascular diseases and intracranial hypervascular tumors

Objective: To evaluate the effect of hybrid operation suite in the treatment of cerebral and spinal vascular diseases and intracranial hypervascular tumors. Methods: A retrospective study was conducted on 132 patients with various cerebral and spinal vascular diseases and intracranial hypervascular tumors who were treated by hybrid surgery at Department of Neurosurgery, Huashan Hospital from October 2016 to December 2017.There were 70 male and 62 female patients with a mean age of 48.33 years (range: 14-78 years), including 64 cases of intracranial aneurysm (41 complicated aneurysm cases), 28 cases of brain arteriovenous malformation (BAVM), 12 cases of hypervascular tumor, 12 cases of dural arteriovenous fistula (DAVF), 6 cases of carotid artery stenosis, 5 cases of Moyamoya disease, 3 cases of intracranial aneurysm or BAVM combined with tumor, 1 case of scalp arteriovenous fistula and 1 case of critical brain trauma in which a foreign metal stick approached the basal vascular circuit.Abnormalities were found in 16 cases in intraoperative angiography. The clinical data of all patients was collected as a perspective cohort. The success rate of hybrid surgery, intra-operative and post-operative complications, morbidity, mortality, rate of infection, the length of hospital stay were all analyzed to illustrate the effect of hybrid operation mode to traditional surgical pattern. Results: For 64 cases with intracranial aneurysms, the immediate complete occlusion rate was 90.5%, with a mortality of 4.7% and a morbidity of 14.0%. For 28 cases of BAVM and 12 cases of DAVF, all patients achieved total obliteration and favorable social independent outcomes after hybrid surgery, with no complication.For 6 cases of carotid artery stenosis and 5 cases of Moyamoya, intra-operative confirmed good cerebral reperfusion without any new post-operative neurologic deficits. After tumor vessels embolization, 4 out of 12 cases of hypervascular tumor needed intra-operative blood transfusion, and all patients achieved total tumor resection in a single stage. Only one patient with medulla oblongata hemangioblastoma died 6 months after operation due to respiratory deficit related pneumonia. Compared to traditional surgeries, the hybrid operation pattern did not significantly increase the total infection rate, central nervous system infection rate, hospital stay days and post-operative hospital stay days (all P>0.05) while the in-patient cost increased mildly (119 332 yuan vs.98 215 yuan, t=2.38, P=0.02). Conclusions: The operations of complex cerebral and spinal vascular diseases and intracranial hypervascular tumors can be performed in hybrid operation suite safely.This surgical mode can ensure the quality of operation and promote the development of innovative and complicated surgical procedures.

Mechanical oscillations in the technological processes of restoration of machine parts

The paper addresses the issues of increasing the durability of piston pins of automotive and tractor engines through the use of vibration oscillations during their restoration. Experimentally found the optimal values of the angle of inclination of the machined tool – punch and its effect on the amount of metal sticking to the working surface of the punch, which reduces the quality of the processed surface of the piston pins and increases the non-uniformity of deformation in the radial direction and length. The change of the residual strain along the outer and inner diameter of the piston pin during vibratory deformation is shown. The obtained mathematical dependences of the change in residual strain on the outer diameter on the value of the allowance for processing. Experimentally found a relationship that associates residual deformation with the wear of piston pins. The results of the work will be used for the development of technological processes for the restoration of piston pins and bushings of the top heads of connecting rods of various autotractor engines by the method of vibration deformation.

Effect of chemical composition on the performance of centrifugally cast indefinite chilled cast iron rolls

Problem Statement (Relevance): An urgent task of rolling mill operators includes minimizing the cost of manufactured products while ensuring the required quality. To accomplish the task, measures are being taken to optimize the rolling process aimed at increasing the duration of the rolling campaigns and reducing the number of roll regrinds. The performance of the rolls is influenced by the properties of the working layer material which determine wear resistance, formation and development of fire cracks, as well as resistance to metal sticking. Finishing mill rolls dictate the surface quality of the rolled steel. That is why it is important to make timely regrinds in order to completely remove the fire crack layer. The removal depth and the acceptable duration of the campaigns depend on the properties of the roll working layer material. To improve the properties of the rolls, the roll manufacturers need the actual roll operation data to be able to analyze how the chemical composition and the structure of the roll working layer is related to the roll performance. Such analysis will help improve the structure and properties of the materials used, as well as develop new ones. Objectives: The objective of this research is to understand how the chemical composition of the working layer of indefinite chilled cast iron rolls used in finishing mills dictates the roll performance, to evaluate the effect of each chemical element, and to determine what concentrations of the chemical elements could most effectively benefit the performance of indefinite chilled cast iron rolls. Methods Applied: The methods applied include building a database of the finishing mill indefinite chilled cast iron rolls and using artificial neural networks based on a dual-function algorithm. Originality: The authors built a neuromodel which can help understand the effect of the chemical composition of the roll working layer and predict the performance of indefinite chilled cast iron rolls. The authors studied the effect of carbon, silicon, manganese, chromium, nickel, molybdenum, vanadium, niobium and boron on the performance of indefinite chilled cast iron rolls. Findings: Graphic diagrams were built which demonstrate the effect of each chemical element on the performance of indefinite chilled cast iron rolls at constant concentrations of the remaining elements. The authors looked at the relationship between the chemical elements and the roll performance in terms of the impact of the former on the structure of indefinite chilled cast iron rolls. The effective concentrations of the chemical elements were also determined. Practical Relevance: The authors developed a new chemical composition of indefinite chilled cast iron to be used for the working layer of finishing mill rolls. As a result, a 12–14% increase in the roll performance was achieved.

Melyssa's Story.

Melyssa's Story.

APPLICATION OF COATINGS MADE BY PLASMA SPRAY AND PVD METHODS FOR PROTECTION OF GRAPHITE MOULDS

The results of our research on the application of coatings for protecting industrial casting molds are presented. Tests were carried out on graphite molds with deposited Al2O3 coatings containing the addition of glassy carbon and with W/Zr/DLC coatings, both examined after the process of pouring molds with molten aluminum bronze. The coatings were applied by two different methods; i.e., plasma spraying in the case of Al2O3 + glassy carbon coating and PVD in the case of W/Zr/DLC coating. Reference tests were also conducted on graphite molds without coating. The use of protective coatings on graphite molds seems to be an effective solution. Studies have shown that coatings have good resistance during the casting process. The liquid metal sticking to the surface did not penetrate deep inside the graphite mold. The use of coating technology reduces the amount of downtime necessary to replace worn molds and increases the efficiency of the casting process. Application of coatings made by plasma spray and PVD methods for protection of graphite moulds Normal 0 21 false false false PL X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Standardowy; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:8.0pt; mso-para-margin-left:0cm; line-height:107%; mso-pagination:widow-orphan; font-size:10.0pt; mso-bidi-font-size:12.0pt; font-family:Verdana,sans-serif; mso-fareast-language:EN-US;}

Interoception Sensitivity and Autonomic Regulation During Social Interaction in Schizophrenia

Introduction The awareness of one's body constitutes a basic experience of Self which modulates the individual engagement in social interactions. Indeed, Interoception Sensitivity (IS), an index of individual ability to represent one’s own internal body states, is implicated in the autonomic regulation in interpersonal context. Schizophrenia deficits in Self-experience and awareness, which frequently entail anomalies in self-other relationship, capture the ever-growing attention of researchers. Nevertheless, IS and autonomic regulation of schizophrenic patients in social context are completely new and not yet investigated aspects of Schizophrenia. Aim To investigate whether Schizophrenia could be associated with lower IS and with a dysfunctional autonomic regulation during social interaction. Methods 24 chronic schizophrenia patients, and a matched group of healthy controls, performed a Social and a Non-social task while respiratory sinus arrhythmia (an index of autonomic regulation) was measured. In the Social task participants viewed an experimenter performing a caress-like movement at different distances from their hand. In the Non-social task a metal stick was moved at the same distances from the participants’ hand. As measure of IS, a cardiac Mental Tacking Task was performed. Results Comparing to controls, Schizophrenia patients presented lower IS, absence of relation between IS and autonomic regulation, and an anomalous autonomic regulation in social and non-social contexts. Conclusions Deficits in Self-experience, associated with Schizophrenia, could be extended to patients’ sensitivity to internal bodily signals. Moreover, the observed altered autonomic regulation will be part of interpersonal interaction deficit frequently associated to Schizophrenia.

A conservative approach in a child with haematuria after accidental rectal impalement trauma

We present a case of an 11-year-old boy with haematuria after traumatic rectal insertion of a sharp metal stick. It demonstrates that an expectative management with close observation can be considered in patients with rectal impalement trauma presenting with haematuria and stable vital parameters without significant injury on abdominal ultrasound.

Closing the gap between the inside and the outside: interoceptive sensitivity and social distances.

Humans’ ability to represent their body state from within through interoception has been proposed to predict different aspects of human cognition and behaviour. We focused on the possible contribution of interoceptive sensitivity to social behaviour as mediated by adaptive modulation of autonomic response. We, thus, investigated whether interoceptive sensitivity to one's heartbeat predicts participants' autonomic response at different social distances. We measured respiratory sinus arrhythmia (RSA) during either a Social or a Non-social task. In the Social task each participant viewed an experimenter performing a caress-like movement at different distances from their hand. In the Non-social task a metal stick was moved at the same distances from the participant's hand. We found a positive association between interoceptive sensitivity and autonomic response only for the social setting. Moreover, only good heartbeat perceivers showed higher autonomic response 1) in the social compared to the non-social setting, 2) specifically, when the experimenter's hand was moving at boundary of their peripersonal space (20 cm from the participant's hand). Our findings suggest that interoceptive sensitivity might contribute to interindividual differences concerning social attitudes and interpersonal space representation via recruitment of different adaptive autonomic response strategies.

Immunohistochemical Expression of Stem Cell Markers during the Wound Healing Process of Cutaneous Burn

Purpose: A cutaneous wound healing requires a well-orchestrated integration of the complex biological and molecular events of cell migration and proliferation, extracellular matrix deposition, angiogenesis and remodeling. Finally, skin regeneration is the main goal. Stem cells are self-renewing multipotent progenitors with the broadest developmental potential in a given tissue at a given time. The aim of this study was to examine the role of stem cells during the wound healing process of cutaneous burn in hairless mice by using immunohistochemical stainings (nestin, cytokeratin 15 and CD31). Methods: Each mouse received 2 burns at the dorsal area by applying a metal stick heated in boiling water. Burn wound sites were dressed with duoderm. The mice were sacrificed at 0, 2, 7, 14 and 21 days after burn. Histological findings and immunohistochemical expression for stem cell markers were observed. Results: Nestin was expressed in the stromal cells beneath the epidermis, hair follices, dermal cysts and endothelial cells. Cytokeratin 15 was expressed in the epidermis except in basal cells. On 7 and 14 days after burn, the regenerated epidermis didn't express cytokeratin 15. CD31 was expressed in the endothelial cells on 7 and 14 days after burn. The amount of nestin expression was the highest. Conclusion: Our results showed that nestin may have various effects on burn wound healing. Cytokeratin 15 was expressed before burn and after burn. It is likely that other cytokeratin may stimulate epithelial regeneration. CD31 may act in vascular regeneration during burn healing. (J Korean Surg Soc 2010;79:1-7)

My Summer of ‘68

You can always get warm, but it's hard to stay cool. My mother's words, muttered every summer since I can remember, rang like a mantra in my head as I stood in the uncut grass of a football field (the 20-yard line, to be precise), knees locked and eyes forward, arms akimbo, to balance a 28-inch-long metal stick at a 45-degree angle, just so. Perspira tion trickled down my temples and collected under my jaw, but I held still. Since reaching my teens, I'd come to dread the wasteland of summer vacation: heat and more heat, the sodden press of humidity that forced my painfully coifed pageboy to retract its hooks, sun that turned my caramel complexion to burnt umber if I forgot to wear a hat. It was the 19th of August, 1968, four days until the Soap Box Derby Parade and nine days before my 16th birthday, and I still hadn't figured out how to keep my minimalist emergency 'do (French twist with bangs pinned to the side) from shrinking to that fine corona of frizz usually found in the National Geographic photographs of ostrich heads. Why, oh why was I standing here at attention like a tin soldier, ankle-deep in crabgrass in the middle of a sweltering Midwestern summer, sweating out all the good sense Mom had pressed into the curls on my head? Four months earlier, in April, a week or so after Martin Luther King Jr.'s murder, I was packing up my cello one afternoon after orchestra practice when Rhonda bounded up, flute propped on her shoulder like a baseball bat, and clapped me on the back. Rhonda was always doing things like that; copper-skinned and confident (even in glasses!) to the point of being uncomfortably gung-ho, she was what my grandmother would call, wrinkling her nose, sturdy. I started to straighten up, but she couldn't wait. Rita, she whispered, I've got a terrific idea. Let's try out for the majorette squad! Funny thing is, even though I gulped and felt my heart pound into my throat, I thought it was a great idea, too. In the Byzantine hierarchy of high school, majorettes and cheerleaders were the Cream. Cheerleaders enjoyed a noisy devotion from the masses, but majorettes were the serene wizards, the silvery circumferences of their batons humming before them like horizontal pirouettes. If I said yes, if I tried out and actually made the squad, maybe I could finally be?I closed my eyes to savor the possibility?popular. Just thinking the word sent a shiver of longing through me. What was it like? Ever since junior high, I'd been called brainier. I thought I was used to it, but sometimes, on pale green spring mornings or glimpsing the tentative expression on my face reflected in a store window, I'd wonder. Although I'd never been exactly reviled, had never borne the brunt of schoolyard taunts or classroom pranks, I'd also never been pursued by a boy,

A fatal search for worms—a peculiar electrical accident

A 32-year-old man used a self-made electrical instrument to collect earthworms for fishing. It consisted of a metal stick with a plastic handle. The stick was connected to a 10 m long wire which ended in a single-phase plug. After watering the lawn and connecting the plug to one phase of a socket (AC 220 V), he touched both the handle and the metal stick, presumably while trying to push it deeper into the soil. Through this procedure he closed the electrical circuit from his left hand to his bare feet standing on the wet lawn and was killed instantly. The autopsy revealed burn marks only on the left palm. Petechiae were found in the facial skin and the mucous membranes. The inner organs showed intensive signs of blood congestion. Toxicological analysis of blood, urine, gastric contents, liver and bile was negative. The calculated current of about 111 mA flowing through the body exceeded the range of 80–100 mA generally considered to be lethal.

Synthesis of Cr3C2 coatings for tribological applications

PVD coatings such as TiN and CrN have been successfully applied to metal forming industries for their advanced wear resistance. Metal pick-up and sticking problems in certain deep drawing and plastic injection molding processes, however, demand more sophisticated tribological thin films. In this study, we evaluated chromium carbide coatings synthesized by PVD processes for potential applications in forming and molding operations. We deposited Cr3C2 thin films of 3 μm thickness using both cathodic arc evaporation and unbalanced magnetron sputtering to ensure superior adhesion strength at the film–substrate interface. Using X-ray diffraction (XRD), scanning electron microscopy (SEM)/electron desorption spectroscopy (EDS), Vicker's microhardness, and wear tests, we studied the influences of deposition parameters on microstructure and mechanical properties. Our results indicated that Cr3C2 outperforms hard chrome plating and CrN coatings in measures of sliding wear resistance and ease of mold release. We attributed Cr3C2's performance to its process-improved microhardness and low surface energy. In sum, we found Cr3C2 coatings to be highly promising for tribological applications at low-to-medium temperatures.

Materials for Sports

The interplay between materials science and sports equipment takes many forms. Certainly a broad cross section of materials is used in sporting equipment to improve performance and safety, and to reduce cost. The new materials used in sports equipment originate from a long history of innovation, drawing from and contributing to other technologies. Amateurs and professionals play sports, so rules on the use of new technology vary immensely. This allows for a short circuit of new technology into the market-place in some cases and restriction or prohibition of opportunities in others. Also materials selection and development for sports equipment must stretch beyond consideration of the object itself to include the human interface and design of a system that best makes use of the materials. Sports after all are about human capability and interaction. The equipment is just a facilitator. Certainly more efficient ways exist of placing a ball into a hole than hitting it with a long metal stick from hundreds of yards away. This is perhaps the most unique element of materials development for sports. The rules governing materials development are not just laws of science and of government but rules put into place just for “sport.” Because of the connection of sports to the lives of so many people, either as participants or spectators, materials science of sporting equipment is also a great platform for educating students about materials selection and behavior.

The effect of photo-oxidation on the sticking and reactivity of Ag on amorphous

Photo-oxidation of amorphous films illuminated by band-gap radiation drastically alters the growth mode and reactivity of subsequently deposited Ag. In the former case (monolayer/simultaneous multilayer growth) the Ag reacts with both Ge and S sites. In the latter case (Stranski - Krastanov growth) Ge sites are selectively oxidized and film growth proceeds by Ag nucleation at the unoxidized S sites. The behaviour is very different from that reported earlier for Zn deposition on , where photo-oxidation results in very large changes in metal sticking probability. XPS, XAES and EXAFS data provide the basis for understanding both this phenomenon and the very different photodiffusion behaviour of Zn and Ag in .

Up-Regulation of Endothelin-B Receptors in Atherosclerotic Human Coronary Arteries

Both endothelin-A (ETA) and endothelin-B (ETB) receptors are known to be present in human coronary arteries. However, their absolute and relative amounts, functional roles, and the influence of pathology are uncertain. The goal of the present study was to characterize endothelin receptors mediating constriction in human coronary arteries and to assess the influence of cardiomyopathy (CMP) and coronary artery disease (CAD) on ET receptors in human tissue. For comparison, porcine coronary arteries were evaluated in parallel. Competition binding experiments using [125I]ET-1 and different selective and nonselective ETA- and ETB-receptor agonists or antagonists revealed similar relative densities (relative Bmax) of ETA and ETB receptors in coronary arteries from human cardiomyopathic hearts (83% ETA and 17% ETB; n = 5) and porcine hearts (78% ETA and 22% ETB; n = 5). In marked contrast, the relative Bmax of ETB receptors were significantly higher in coronary arteries from human atherosclerotic hearts (51% ETA and 49% ETB; n = 3). Total receptor density (Bmax; fmol/mg protein) was highest in porcine (385 +/- 29) arteries, followed by human CAD (253 +/- 41) and CMP (174 +/- 20) coronary arteries. The relative and absolute Bmax values for ETA and ETB receptors in coronary arteries from a donor heart were similar to those obtained in CMP hearts. There were no significant differences in affinity constants (KD) values for ET-1, ET-3, Sarafotoxin S6c (SRTX S6c), BQ-123, and bosentan (Ro 47-0203) between tissues. In human coronary arteries from CMP hearts, ET-induced constriction seemed to be solely mediated via ETA receptors. In contrast, in porcine coronary arteries 20% of the maximal effect mediated by ET-1 could be attributed to ETB receptors, in agreement with the binding data. The functional role of ETB receptors in CAD tissue could not be evaluated because of the occurrence of spontaneous phasic contractions. We conclude that ETB receptors are up-regulated in human atherosclerotic coronary arteries. Further studies are needed to determine the pathophysiological importance of these receptors.