Accuracy, detail reproduction, and hardness of gypsum casts produced from silicone impressions treated with glow discharge

Plasma treatment has been reported to improve the wettability of silicone impression materials. This study investigated whether plasma treatment of silicone impressions influenced the linear dimensional accuracy, detail reproducibility, and surface hardness of models produced from a type IV dental die stone. Five silicone impressions materials were used in this study. Linear dimensional accuracy and detail reproduction were tested according to ISO standards. Surface hardness was evaluated with a Vickers hardness test. The results indicated that plasma-treated impressions from Xantopren and Provil silicone impression materials had significantly smaller dimensional change than their respective controls, and the other materials were not influenced. The detail reproduction was superior in casts produced from plasma-treated impressions from President silicone. Surface hardness was not influenced by the treatment. Plasma treatment of silicone impressions has no negative influence on the tested physical properties of die stone models.     

Early morphological and immunological alterations in the spleen during magnesium deficiency in the rat

PURPOSE: Materials used to fabricate the most dimensionally accurate implant casts have not been identified experimentally. The purpose of this investigation was to examine the dimensional accuracy of implant casts fabricated with different materials. Measurements of linear horizontal dimensional change and strain produced on a master framework were evaluated and correlated. MATERIALS AND METHODS: A master framework was fabricated to fit an aluminum five-implant model. Forty polyether implant impressions of the aluminium model were randomly grouped and poured in either Vel-mix, Die Keen, Resin Rock, or Low Fusing Alloy. A digital veneer caliper was used to measure linear distance between the most distal abutments on each of the experimental implant casts and the master model. In addition, strain values were recorded from strain gauges bonded in the mesiodistal axis of the framework, which was secured by prosthetic retaining screws torqued to 10 Ncm. RESULTS: A one-way ANOVA showed a significant difference among the four die materials in dimensional change of the experimental casts (p = .0001). A post-hoc Duncan's multiple-range test (p < .05) showed that casts fabricated with Low Fusing Alloy had the least linear dimensional change from the master cast, but the material exhibited the greatest dimensional variability. A MANOVA (Wilks' Lambda) showed significant differences in strain on the framework based upon die material (p = .015). A post-hoc Duncan's multiple-range test (p < .05) showed that Resin Rock casts induced significantly less strain on the framework than the other materials. Negligible correlation was found between the linear horizontal dimensional change and the total absolute strain on the framework. CONCLUSION: Experimental implant casts made of Resin Rock minimized strain on the master framework and decreased the amount of framework distortion on casts of this material. Low Fusing Alloy yielded accurate casts, but highly variable linear dimensional changes in the horizontal dimension may preclude its clinical benefit.     

Neonatal nucleated red blood cell and lymphocyte counts in fetal brain injury

STATEMENT OF PROBLEM: Flexible die materials have been introduced to facilitate the fabrication of indirect provisional or definitive restorations in 1 appointment. PURPOSE: This study compared the surface detail reproduction of 7 potential flexible die materials when used in combination with 7 elastomeric impression materials. METHODS: Surface detail reproduction of 17 impression material/flexible die material systems was compared with a control system containing an elastomeric impression material and a Type IV dental stone. Test dies of each system were prepared in a random order with the American Dental Association apparatus for testing detail reproduction, compatibility, and dimensional stability. RESULTS: One flexible die system had better surface detail reproduction than the control stone die, other systems had similar or worse reproduction. Surface detail reproduction was adversely affected when a separator was required between the impression and flexible die material. CONCLUSIONS: Impregum F die material with Extrude Light impression material produced better surface detail reproduction than the control dies. Impregum F impressions were incompatible with Blu-Mousse, Impregum F, or Imprint die materials. Polyvinyl siloxane impressions were incompatible with polyvinyl siloxane dies unless a separator was used. When a separator was used, the surface detail reproduction was not as good as the control die system or the Extrude Light impression material/Impregum F die material combination.     

Clinical significance of surface activation of silicone impression materials

OBJECTIVES: Surface activation of silicone impression materials enhances impression accuracy as well as the quality of stone casts. This study examined the relation between impression quality and the hydrophilicity of silicone impression materials used in a two-stage putty and wash technique. METHODS: The study included 14 silicone impression materials with and without surface activation. The contact angles of the light body materials were measured using deionised water. Free surface energies were calculated. A total of 140 impressions of wet intact permanent molar teeth were examined for definition of the gingival sulcus reproduction and then classified in a quality ranking. The percentage of the sulcus reproduction ability of each material was calculated from the sulcus depths of cross-sectioned resin casts from the impressions and clinically measured sulcus depths. RESULTS: Free surface energies (mJ/m2) of hydrophobic materials (contact angle > 90 degrees) ranged from 16.8 to 26.8 mJ/m2. Surface activated materials (contact angle < 90 degrees) exhibited free surface energies from 38.1 to 55.7 mJ/m2. Not all materials described as surface activated showed hydrophilic properties. Medians of impression quality ranking ranged from 1.75 (best) to 13.25 (worst), mean sulcus reproduction ranged from 30 to 52%. Significant differences (P < 0.05) in quality ranking and sulcus reproduction were found between certain materials but correlations were found neither between sulcus reproduction and free surface energy nor between quality ranking and free surface energy. CONCLUSIONS: For clinical impression recording, surface activation seems to be of minor relevance, at least in the two-stage putty and wash technique investigated and is superimposed by other material properties.     

Preparation of void-free casts from vinyl polysiloxane impressions

PURPOSE: To investigate two techniques to produce void-free casts from vinyl polysiloxane impressions. MATERIALS AND METHODS: Thirty casts prepared using a conventional technique were compared with 30 casts prepared using a technique involving syringing of stone in terms of numbers of surface voids. RESULTS: Significantly fewer surface voids were observed in the casts prepared using syringing technique. CONCLUSION: The syringing technique investigated is considered to have advantages over the conventional technique for the production of casts from vinyl polysiloxane impressions.     

Surface Modification of AISI 1045 Carbon Steel by the Electrolytic Plasma Process

The electrolytic plasma process (EEP) was employed for surface modification of 1045 carbon steel for the first time, which resulted in a harder surface. Surface composition of the samples at different depths was evaluated by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), which revealed diffusion of Cr from the bath to ~15 μm beneath the surface of the samples during the test time of 10 minutes. The effects of applied voltage, test duration, and electrolyte concentration on the hardness and microstructure of the samples were investigated by microhardness measurements and optical microscopy. It was concluded that surface hardness as well as depth hardness of the samples increased with the applied voltage, test duration, and electrolyte concentration.     

Investigation of surface roughness of aluminium solid mould investment castings

Solid investment moulds are used for precious or non-precious metals and alloys castings, the most common application areas are dental prosthesis and jewellery fabrications. Investment casting is known for high dimensional accuracy and smooth surface finish. Casting of ultra-thin sections and small complex parts require vacuum assisted or centrifugal filling. In this study, solid investment casting of aluminium has been tried and surface quality of the castings was investigated. Specially designed steppedwedge surface roughness specimens were produced with A413 aluminium alloy casting into gypsum bonded solid moulds. Casting operations were carried out in two ways; the first only with gravitational force and the second with vacuum assistance. Surface roughness of as cast specimens were measured, effects of section thickness, vacuum assistance and location of the pattern on the wax tree were determined.     

Kinetics of VO2 and VCO2 in the horse and comparison of five methods for determination of maximum oxygen uptake

To determine whether maximum oxygen uptake (VO2max) in the horse in influenced by type of exercise test, five different protocols were evaluated in eight untrained Thoroughbreds exercised on a treadmill. With all protocols, horses were given a 5 min warm-up on a 10 per cent treadmill slope. Three protocols were at a 10 per cent slope and included: 1) increasing the running speed by 1 to 2 m/sec every 60 secs from 4 m/sec to a maximum of 12 m/sec; 2) running at 12 m/sec until fatigue; and 3) running for 3 to 4 mins at speeds ranging from 6 to 12 m/sec with rest pauses between exercise bouts. The fourth protocol employed a 24 per cent slope where animals exercised for 5 mins at 2 m/sec followed by 3 mins at 5 m/sec, and 2 mins at 6 m/sec. The fifth test involved running at 11 m/sec while the slope of the surface was increased every 2 mins until the horses could not maintain the pace. A plateau in VO2 occurred in all protocols except when exercise was performed on a 24 per cent slope. Slow speed exercise at a steep grade (24 per cent) produced the highest VO2 (P < 0.05) even though there was no plateau in the VO2. A steady state for VO2 and VCO2 existed 90 secs after the onset of exercise with all protocols which involved 2 mins or more at each speed. The VO2 and VCO2 values at all speeds of the rapid incremental exercise test were not different to those found at steady state in the third exercise protocol.     

车轮表面硬度不合格原因分析及对策

根据断面硬度值的分布,对车轮表面硬度不合格品进行分类,寻找影响表面硬度不合格的主要原因,认为轧前加热导致的车轮表面脱碳是导致车轮表面硬度不合格的主要因素,并制定了对策。     

Mechanical Properties of a Ni–Cr–Mo Steel Subjected to Room Temperature Carburizing Using Surface Mechano-Chemical Carburizing Treatment (SMCT)

Surface mechano-chemical carburizing treatment (SMCT) is a modified version of surface mechanical attrition treatment and it is one of the cutting-edge technologies for producing hard nano-crystalline surface in metallic materials. In the present study, a case carburized surface layer is achieved in 1.75 Ni–Cr–Mo steel at room temperature using SMCT. Activated charcoal powder is continuously fed during the process so as to achieve the carbon diffusion into the surface layer. The SMCT process has been carried out for different periods say 15, 30, 45 and 60 min respectively. The microstructure and surface chemical composition is investigated by using TEM and XRF analysis. The mechanical properties such as yield strength (YS), ultimate tensile strength (UTS), fracture toughness and surface hardness of SMCT samples have been investigated using universal testing machine, Plain strain fracture toughness test and Microvickers hardness test respectively. The surface carbon content has been found to increase linearly and grain size reduces continuously with processing time. A 60 min SMCT samples reveal 0.8% C and about 10 nm grains over the surface. The SMCT samples show significant improvement in mechanical properties. The surface hardness increases from 180 HV_0.1 to ~ 878 HV_0.1 by 60 min of treatment. About 55% increment in the YS and 30% increment in UTS is achieved by 60 min of SMCT. It is also interesting to note that the fracture toughness of the samples enhances from 24 to 47 MPa \( \sqrt m \) after 60 min of SMCT.     

Surface hardening of nickel alloys by means of plasma nitriding

Surface hardening of Ni alloys by plasma nitriding was investigated by using tentative Ni binary alloys contained nitride forming elements such as Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, Mn, Fe, Al, or Si at the nitriding temperature from 673 to 1073 K. Surface hardness was different depending on the types of alloying elements, their contents, and their nitriding temperatures. Higher hardness than HV500 was obtained in Ti, V, Nb, and Cr containing alloys at 823 to 873 K, but other alloys showed lower surface hardness than HV400. The elements Ti, V, Nb, and Cr were the effective alloying elements for the surface hardening of nitrided Ni alloys. From transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis, the nitrided layer was composed of fine precipitate particles in the matrix of the nitrided layer. At the lower nitriding temperature, these particles were metastable fine particles or Ginier-Preston (GP) zone having coherency with the matrix, and these fine particles induced large microstrain in the matrix. However, at the higher nitriding temperature, equilibrium nitride particles were precipitated and coherency with the matrix was decreased. Therefore, the hardening of Ni alloys by plasma nitriding was due to the microstrain induced in the nitrided layer by the precipitation of metastable particles or GP.     

Low-frequency vibrations in the treatment of patients with acute maxillary sinusitis and ethmoiditis. Non-specific resistance and immunity

Effect of sodium hypochlorite disinfection of impressions on the size and quality of plaster models is studied. Twenty-minute submerging of silicone impressions in 0.5% sodium hypochlorite solution did not change their size and did not deteriorate the quality of surface and hardness of plaster models. Stomalgin impressions cannot be disinfected by sodium hypochlorite solution because of expressed destructive effect of this disinfectant on the impressions.     

S355海洋钢表面微弧氧化复合膜层耐蚀性能

采用激光熔覆与微弧氧化技术相结合在海洋钢表面制备了复合膜层.运用扫描电子显微镜（SEM）、能谱仪（EDS）和X射线衍射仪（XRD）表征复合膜层的微观结构,采用极化曲线、电化学阻抗谱、腐蚀磨损实验和浸泡腐蚀实验等测试方法研究膜层在质量分数3.5%的NaCl水溶液中腐蚀行为,并与熔覆涂层和基体进行对比.结果表明:复合膜层主要分为内致密层和外疏松层,疏松层主要由γ-Al₂O₃组成,致密层主要由α-Al₂O₃组成,与基底层结合较好,复合膜层表面硬度最大能达到HV_0.2 1423.3,比熔覆涂层高47.6%,其硬度较S355海洋钢有显著提升.基体在腐蚀和磨损交互作用中主要以腐蚀加速磨损为主,涂层在交互作用中主要以磨损加速腐蚀为主,在经过微弧氧化处理后,膜层的自腐蚀电位负移,钝态电流密度上升,抗磨蚀性能明显提高.熔覆涂层的浸泡腐蚀方式以点蚀为主,复合膜层腐蚀较轻微,阻抗模值最大能达到105.3 Ω·cm2,比熔覆层提高两个数量级,这表明复合处理可进一步提高涂层的耐腐蚀性.      

WC-10Co-4Cr粉末及涂层性能研究

采用北京矿冶研究总院生产的WC-10Co-4Cr复合粉末作为喷涂材料,对该粉末的流动性、松装密度、表面形貌、元素分布等物理性能进行了分析。采用HVOF喷涂法制备WC-10Co-4Cr涂层,测试了涂层的结合强度和显微硬度,并利用HITACHIS-3500型扫描电子显微镜对涂层的显微组织进行了分析。研究结果表明:北京矿冶研究总院生产的WC-10Co-4Cr复合粉末具有良好的物理性能。采用HVOF喷涂制备的WC-10Co-4Cr涂层的连续性和致密度良好,且具有高硬度和结合强度,涂层中各组分分布均匀,没有明显的偏析现象。     

250 mm铸坯红送工艺生产Nb-V-Ti微合金钢板表面裂纹分析

利用金相观察、能谱分析、连铸坯红送与冷送工艺的对比试验等手段,对红送工艺生产微合金钢板出现的表面裂纹进行了分析研究。结果表明,红送工艺生产微合金钢板表面裂纹并不是因为连铸坯本身存在裂纹缺陷,而是由于铸坯在凝固后的冷却过程中,大量细小的C、N化合物在奥氏体晶界析出,降低了晶界强度,导致钢板表面裂纹形成。     

Examination of the relationship between true halo and halo error in performance ratings.

The purpose of this study was to test competing theories regarding the relationship between true halo (actual dimensional correlations) and halo rater error (effects of raters' general impressions on specific ratee qualities) at both the individual and group level of analysis. Consistent with the prevailing general impression model of halo rater error, results at both the individual and group level analyses indicated a null (vs. positive or negative) true halo-halo rater error relationship. Results support the ideas that (a) the influence of raters' general impressions is homogeneous across rating dimensions despite wide variability in levels of true halo; (b) in assigning ratings, raters rely both on recalled observations of actual ratee behaviors and on general impressions of ratees in assigning dimensional ratings; and (c) these 2 processes occur independently of one another. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Surface Characteristics and Distortion Analysis of the Case-Hardened Helical Gears: A Comparison of Different Case-Hardening Treatments

In this study, the effect of different case-hardening treatments on microstructure, hardness distribution, surface roughness parameters, and dimensional changes was investigated for helical-toothed gears made of 16MnCr5 and 21NiCrMo2 steels. Gas carburizing, gas carburizing–double quenching, low-pressure carburizing, and plasma-nitriding treatments were performed as case-hardening processes. The surface characteristics and distortion analyses of the case-hardened helical gears were examined using an optical microscope, hardness tester, profilometer, and micrometer. In order to ensure adequate pitting and bending strength, the required minimum effective case depth and minimum total case depth values were provided by the performed case-hardening treatments. In the gears, the largest dimensional increase after the heat treatments occurred at the end of the gas carburizing due to the long treatment times at high processing temperatures. The surface roughness values obtained through all performed case-hardening treatments necessitated the finishing processes.     

Acute hypercapnia increases the oxygen-carrying capacity of the blood in ventilated dogs

OBJECTIVE: To test the hypothesis that PaCO2 levels generated during permissive hypercapnia may enhance arterial oxygenation, when ventilation is maintained. DESIGN: Prospective study. SETTING: Research laboratory in a hospital. SUBJECTS: One group of eight mongrel dogs (four male; four female). INTERVENTIONS: The dogs were anesthetized (30 mg/kg iv pentobarbital), intubated, and cannulated in one femoral artery and vein. While paralyzed with 0.1 mg/kg/hr iv vecouronium bromide, all subjects were ventilated with room air. Anesthesia was maintained, using 2 to 3 mg/kg/hr iv pentobarbital. Arterial hypercapnia at the levels generated during permissive hypercapnia was produced by stepwise increases in the dry, inspired Pco2 (PiCO2) (0, 30, 45, 60 and 75 torr [0, 4, 6, 8, and 10 kPa]; 15 mins each). MEASUREMENTS AND MAIN RESULTS: Blood gas profiles were determined at each level of hypercapnia. The minute volume was maintained at the baseline level during all exposures. Arterial hypercapnia produced gradual and significant increases in the hemoglobin concentration. These increases were approximately 6%, 7%, 11%, and 14% at PiCO2 of 30, 45, 60, and 75 torr (4, 6, 8, and 10 kPa), respectively (p < .05; repeated analysis of variance followed by Dunnett multiple comparisons test). In parallel, the oxygen content increased by approximately 6%, 7%, 11%, and 13%, respectively. During hypercapnic trials, the PaO2 remained at the normal range, whereas the dry, inspired PO2 (PiO2) was reduced from 150 to 138 torr (20 to 18.4 kPa). The average PaO2 at the highest investigated level of arterial hypercapnia was at a normal range. The hemoglobin concentration and oxygen content returned to baseline values 30 mins after hypercapnic trials. The PaCO2 and pH became normalized 15 mins after hypercapnic trials. Indirect evidence for a similar response to hypercapnia in humans is presented. CONCLUSIONS: Permissive hypercapnia due to inhaled CO2 increases oxygen-carrying capacity in dogs. The PaO2 remains at normal range even at a PiCO2 of 75 torr (10 kPa). The benefits of these effects during permissive hypercapnia, due to controlled hypoventilation, warrants investigation.     

Simultaneous co-deposition of SiC and CNT into the Ni coating

Various researches are carried out to investigate the properties of Ni-SiC and Ni-CNT composite coatings. The simultaneous effect of carbon nanotube (CNT) and silicon carbide (SiC) is not addressed in the literature. Hence, Ni-SiC and Ni-SiC-CNT nanocomposite coatings were electrodeposited on aluminium substrate in this paper. Surface hardness and elastic modulus of the coatings were measured by atomic force microscope, and X-ray diffraction technique was used to evaluate the grain size of the coatings. Pin-on-disk wear test was carried out and the frictional surfaces along with the morphology of the coatings were investigated using scanning electron microscope. Both hardness and elastic modulus of the coating increased after CNT was introduced. The results indicate that CNT improved the wear behaviour of the coating by preventing the detachment of strengthening particles from the coating and consequently decreasing its abrasive wear.     

Self-knowledge and social inference: II. The diagnosticity of cognitive/affective and behavioral data.

Explored the social perceptions of 60 undergraduate observers exposed to tape-recorded interviews in which 20 undergraduate speakers described themselves, either emphasizing past thoughts and feelings, past behaviors, or whatever mix of these speakers perceived as appropriate. Observers' subsequent impressions of speakers were measured using Q-sort ratings and various affective and behavioral predictions, which both speakers and speakers' close friends (n?=?20) had previously completed. It was found that the cognitive/affective interviews produced more accurate social impressions, or at least impressions that were more in accord with speakers' self-assessments prior to the interviews and with the assessments made by their close friends, than did the behavioral or the mixed interviews. This greater congruence was shown to result both from real and from stereotyped accuracy. The relevance of these findings to theory and research on self-perception is discussed. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)