Optimized Mix Design for Interlocking Concrete Blocks Using Quarry Dust for Roads in Sri Lanka

In an attempt to find a mix design where quarry dust incorporated, optimized combination of cementitious and aggregate materials has been developed which contains cement, sand, quarry dust and chips in intended for the production of interlocked concrete blocks paving in road pavement. The main purpose was to achieve optimized Concrete Blocks with fulfilling the requirements in road by using different aggregates, admixtures along with the economical production cost via materials. The analysis has indicated that the use of quarry dust instead of sand is more effective, since it is possible to include a higher percentage of quarry dust in the dosage (80% of the weight of fine aggregate) maintaining the required compressive strength in 28 days, higher than 50 N/mm2 (50 Mpa) for W/C of .30 while maintaining the shape and the surface texture. Therefore, non-conventional pre-cost block with the possibility of being extensively of being extensively used in urban and rural road networks represents contribution on standardization and economical aspects

Epicardial and microvascular coronary vasomotor dysfunction and its relation to myocardial ischemic burden in patients with non-obstructive coronary artery disease

5nononeAim: To assess the relative contribution of epicardial endothelium-dependent (EDD) and microvascular endothelium-independent (EIMVD) coronary vasomotor dysfunction to the extent of myocardial ischemia in patients with normal angiograms or non-obstructive coronary artery disease (NOCAD). Methods: Coronary vasomotion was evaluated by quantitative angiography and blood flow (CBF) measurements during intracoronary acetylcholine, nitroglycerine, and adenosine in 101 patients. Myocardial SPECT ischemic burden was evaluated by semi-quantitative scoring of summed stress (SSS) and summed ischemic (SDS) perfusion defect size. Results: Coronary vasomotor dysfunction was found in most patients (83; 77%) with a divergent behavior of EDD and EIMVD in one half of them (52.4%). There was no significant difference in SDS between patients with and without EIMVD, whereas SDS was significantly greater in subjects with EDD as compared to patients with normal response to acetylcholine (4.31 ± 2.44 vs 1.35 ± 1.45; P < .0001). Patients with EDD, either alone or in combination with EIMVD, had significantly higher SSS as compared to patients with lone EIMVD or normal vasomotor function (8.50 ± 5.32; 5.55 ± 3.21; 2.60 ± 2.14; and 1.74 ± 1.66, respectively; P < .0001). Acetylcholine CBF correlated inversely with both SDS (r = −0.545; P < .001) and SSS (r = 0.538; P < .001). Conclusions: In NOCAD patients with symptoms and signs of myocardial ischemia, vasomotor dysfunction is common. EDD is associated with greater extent of ischemia as compared to isolated EIMVD. Thus, assessment of both EIMVD and EDD is needed to recognize mechanisms of ischemia and identify patients with greater ischemic burden.Verna, Edoardo; Ghiringhelli, Sergio; Provasoli, Stefano; Scotti, Simone; Salerno-Uriarte, JorgeVerna, Edoardo; Ghiringhelli, Sergio; Provasoli, Stefano; Scotti, Simone; SALERNO URIARTE, JORGE ANTONI

Evaluating erosion performance of cold-sprayed coatings by Design of Experiments

Solid Particle Erosion (SPE) occurs when solid particles dragged by fluid means impinge on the surface of pneumatic or hydraulic systems resulting in loss of their mass. Multiple potential solutions to the problem have been investigated, including the modification of the machinery design and the use of filtration systems. From the perspective of materials engineering, the alleviation of SPE in metals has been widely encountered with the fabrication of coatings [1], using methods such as laser cladding, plasma spray, high-velocity oxyfuel and cold spray (CS) [2]. CS is a low-temperature particle deposition process in which microscale powder particles are accelerated to a high velocity (300 to 1200 m/s) through a De-Laval nozzle dragged by a high-pressure propelling gas (commonly nitrogen or helium) toward a target substrate [3]. The advantages of this powerful technique over other thermal spray processes include minimizing potential phase changes, preserving the original feedstock properties, and preventing coating defects, such as surface oxides and other inclusions. Amongst nickel-based superalloys, Inconel 718 (IN718) is commonly used in applications where stability at elevated temperatures, high long-time creep strength, and corrosion resistance in aggressive environments are required [3]. The complex nature of the SPE mechanism involves several variables related to the erodent properties (e.g., feed rate, velocity, size, hardness, impingement angle) and variables related to the intrinsic properties of the coating materials. As a result, identifying a standard method for predicting the erosion performance of coatings is extremely difficult. To this end, one of the most widely adopted techniques to assess the effect of control variables on coating erosion resistance is the Design of Experiments (DoE) [4], [5]. To date, few empirical studies have investigated the erosion performance of cold spray coatings through experimental design [6], which is a major innovative aspect of this study. The authors adopted a general full factorial design to investigate the SPE resistance of cold sprayed IN718-Ni composite coatings. The coatings were deposited onto substrates via high-pressure CS using nitrogen as the propulsive gas, with inlet pressure at 3.0 MPa and gas temperature at 1000 °C. The effect of the impingement angle (°), the erodent size (µm) and the erodent feed rate (g/min) on the erosion rate (mg/min) of the coating was investigated. Empirical results showed that the erodent feed rate and the impingement angle produced a statistically significant effect on the erosion rate, as well as the interaction between erodent size and impingement angle. Furthermore, a mathematical model relating such variables with the erosion rate was identified by stepwise regression analysis. This model effectively allows predicting the erosion performance of real components deposited with IN718-Ni coating under working conditions and properly designing the in-service conditions of new cold-sprayed components. The set of parameters optimizing the erosion rate was accordingly derived by performing an optimization, and then validated. Finally, the worn surfaces of the coatings were observed by SEM in order to understand the erosion mechanism

Cold Spraying of IN 718-Ni Composite Coatings: Microstructure Characterization and Tribological Performance

INCONEL 718 superalloy (IN 718) is frequently used in highly aggressive environments, such as aerospace and gas turbine engines, where excellent mechanical properties, creep-, fatigue- and oxidation-resistance performance at high and cryogenic temperatures are required. Recent studies have successfully cold sprayed IN 718, showing great potential mainly in maintenance and repairing fields. However, due to the low plastic deformation, the manufacture of IN 718 cold sprayed coatings often requires the use of expensive propulsive gases or high working parameters to enhance deposition efficiency, with a significant increase in production costs. This paper investigates for the first time the addition of Ni to IN 718 powders in order to increase plastic deformation and interparticle bonding strength. Four composite coatings were deposited via a high-pressure cold spray process using nitrogen as propulsive gas, considering different IN 718 mass fractions in the feedstock: C1 (0 wt%), C2 (25 wt%), C3 (50 wt%), C4 (75 wt%). The coatings are examined in terms of microstructural characteristics and tribological performance. The addition of IN 718 particles significantly improves the mechanical properties of the coatings, despite an increase in porosity, which however does not exceed 1%. The tribological performance of the four coatings is investigated using a pin-on-disk test, demonstrating that the coating wear resistance behaviour improved as the IN 718 content increased. Analysis of the wear mechanism shows that C4 coating has a different wear behaviour than the other coatings, thus achieving the best wear-resistance performance

Modeling of Erosion Response of Cold-Sprayed In718-Ni Composite Coating Using Full Factorial Design

In this work, the cold-spray technique was used to deposit Inconel 718–nickel (1:1) composite coatings on stainless steel substrate. A general full factorial design was adopted to identify the statistically significant operating variables, i.e., impingement angle, erodent size, and feed rate on the coating erosion response. Erodent feed rate, impingement angle, and the interaction between impingement angle and erodent size were identified as the highly significant variables on the erosion rate. Then, a model correlating the identified variables with the erosion rate was derived. The best combination of control variables for minimum erosion loss with respect to erodent feed rate, erodent size, and impingement angle was 2 mg/min, 60 μm, and 90°, respectively. To analyze the erosion mechanism, the erodent samples were finally observed using Scanning Electron Microscope (SEM)

Endothelial dysfunction versus early atherosclerosis: A study with high resolution imaging

no abstract availabl

Endothelial dysfunction versus early atherosclerosis: a study with high resolution imaging

Purpose: Endothelial dysfunction has been shown to be of prognostic significance in predicting major coronary events. Characterization of microstructural changes of the vessel wall in coronary segment with endothelial dysfunction may have potential prognostic importance for detection of ischemic heart disease (IHD). Methods: We studied 5 patients with IHD, found to have normal or near normal angiograms. These patients received graded doses of intracoronary acetylcholine (10-6, 10-5 and 10-4 mol/L over 3 minutes at 10 minutes intervals) to assess endothelial dysfunction. Epicardial endothelial dysfunction was defined as &gt;30% epicardial vessel diameter reduction during testing. An intracoronary bolus dose of 1000 μg of nitroglycerin was administered to relieve vasoconstriction; IVUS was performed 10 minutes after relief of vasoconstriction and OCT 20 minutes later. The OCT imaging wire was positioned at the site, and 1 cm proximal and distal to of the observed coronary vasomotor abnormality. Each OCT image was analyzed by two independent observers who were blinded to the results. Using OCT imaging, the intima is identified by a signal-rich layer near to the lumen, the media by a signal-poor middle layer, and the adventitia by a signal-rich outer layer. Loss of layered architecture reflects early sign of atherosclerosis. Results: A total of 7 coronary segments showed vasoconstriction. Wall morphology was evaluated by IVUS. Subjects with normal smooth coronaries exhibited a thickness of the coronary wall&lt;1mm. We obtained a total of 83 OCT images. There were 49 images of "dysfunctional" sites and 34 of the control segments. Of the 49 images of "dysfunctional" sites, 9 (19.4%) showed the usual layer structure of a normal artery (three-layer structure: intima, media and adventitia), and the remaining 40 (81.6%) showed early structural changes (single intimal thickened layer up to 380 micron). 16 of these 40 images revealed small signal-poor regions compatible with lipid deposits. Imaging of the control segments showed the usual three-layer structure in 5 (14.7%) images, small signal-poor regions in 14 (41.2%) images, and early structural changes in the remaining 15 (44.1%) images. Conclusions: Our findings indicate that endothelial dysfunction and early atherosclerosis, although related in many coronary segments, may exist separately. Functional alterations can be identified safely at a stage when atherosclerotic lesions are not detectable by any imaging technique. Acetylcholine testing may be useful in designing early effective interventions that restore endothelial function

A Mathematical Model for the Vessel Recruitment in Coronary Microcirculation In the Absence of Active Autoregulation

This paper proposes a mathematical model for vessel recruitment in the microvascular coronary network. The model is based on microvascular network units (MVNUs), where we define aMVNU as a portion of the microvascular network comprising seven generations of identical, parallel-arranged vessels (upstream arteries, large and small arterioles, capillaries, small and large venules, and downstream veins). The model implements a new mechanism to describe the variation in the number of MVNU in response to sudden variations of the local input pressure. In particular, it describes a recruitment mechanismdependent on distal pressure which operates in the coronary microcirculatory network even in maximally dilated conditions. Weapply the model to interpret data from 29 patients who underwent revascularization by percutaneous coronary intervention (PCI). Treated vessels were the left anterior descending coronary artery, the left circumflex and the right coronary artery in 26, 2 and 1 patients, respectively. Following intracoronary adenosine administration, distal coronary pressure and blood flow were 48 \ub1 18 mm Hg and 45 \ub1 30 ml/min before PCI, respectively, and significantly increased afterwards to 80\ub117mmHg and 68\ub132 ml/min (p b 0.001). The model predicts an increase inMVNU number in patients with preserved wall motion in the myocardial region which underwent PCI. On the contrary, a decrease in MVNU number is predicted by the model in patients with regional dysfunction and implies a relatively lower response of maximal flow to revascularization

Assessing MICRO-vascular resistances via IMR to predict outcome in STEMI patients with multivessel disease undergoing primary PCI (AMICRO): Rationale and design of a prospective multicenter clinical trial

BACKGROUND: In STEMI patients treated with primary percutaneous coronary angioplasty (PPCI) the evaluation of coronary microcirculatory resistance index (IMR) predict the extent of microvascular damage and left ventricular (LV) remodeling. However, the impact of IMR on the clinical outcome after PPCI in patients with multivessel disease (MVD) remains unsettled. AIM: We designed a prospective multicenter controlled clinical trial to evaluate the prognostic value of IMR in terms of clinical outcome and left ventricular remodeling in STEMI patients with MVD undergoing PPCI. METHODS AND DESIGN: The study will involve 242 patients with MVD defines as the presence of at least a non-culprit lesion of >50% stenosis at index coronary angiography. Both fractional flow reserve (FFR) and IMR will be measured in the infarct-related artery (IRA) after successful PPCI. Measurements of FFR and IMR will be repeated in the IRA and performed in the non-culprit vessels at staged angiography. The non-culprit vessel lesions will be treated only in the presence of a FFR<0.75. A 2D echocardiographic evaluation of the left ventricular (LV) volumes and ejection fraction will be performed before hospital discharge and at 1-year follow-up. The primary end-point of the study will be the composite of cardiovascular death, re-hospitalization for heart failure and resuscitation or appropriate ICD shock during 1-year of follow-up. Secondary end-points will be the impact of IMR in predicting LV remodeling during follow-up and correlations between IMR and ST-segment resolution. Other secondary endpoints will be need for new revascularization, stent thrombosis and re-infarction of the non-culprit vessels territory. IMPLICATIONS: If IMR significantly correlates with differences in outcome and LV remodeling, it will emerge as a potential prognostic index after PPCI in patients with MVD