Experimental Approach for Development of a Powder Spreading Metric in Additive Manufacturing

The Powder Spreading is a Vital Step of Powder-Based Additive Manufacturing (AM) Processes. the Quality of Spread Powder Can Considerably Influence the Properties of Fabricated Parts. Poorly Packed Powder Beds with High Surface Roughness Result in Printed Part Layers with Large Porosity and Low Dimensional Accuracy, Leading to Poor Mechanical Properties. Therefore, the Powder Spread ability and its Dependence on Process Parameters and Powder Characteristics Should Be Quantified to Improve the Efficiency of Powder-Based AM Methods. This Study Proposes a Novel Dimensionless Powder Spread Ability Metric that Can Be Commonly Used in Different Powder-Based AM Processes. the Quality of Spread Powder in Terms of Powder Bed Density and Surface Roughness Was Evaluated by Adjusting the Process Parameters Including Recoating Velocity and Layer Thickness, and Powder Characteristics Including Particle Size Distribution. in Addition, the Dynamic Repose Angle Was Proposed and Examined as Another Powder Spread Ability Metric. the Results Showed that These Two Proposed Metrics Were Strongly Correlated and Lower Recoating Velocity and Larger Layer Thickness Led to Higher Spread ability and Lower Dynamic Repose Angle

Characterization of Virgin, Re-Used, and Oxygen-Reduced Copper Powders Processed by the Plasma Spheroidization Process

Fabrication of parts with high mechanical properties heavily depend on the quality of powder deployed in the fabrication process. Copper powder in three different powder types were spheroidized using radio-frequency inductively coupled plasma (ICP) spheroidization process (TekSphero-15 system). The characterized powders include virgin powder as purchased from the powder manufacturer, powder used in electron beam powder bed fusion (EB-PBF) process, and reconditioned powder, which was used powder that underwent an oxygen-reduction treatment. The goal of spheroidizing these powder types was to evaluate the change in powder morphology, the possibility of enhancing the powder properties back to their as-received conditions, and assess oxygen reduction of the powder lots given their initial oxygen contents. Also, to investigate the impact of re-spheroidization on powder properties, the second round of spheroidization was performed on the already used-spheroidized powder. The impact of powder type on powder sphericity and particle size distribution was evaluated using the image analysis of scanning electron microscope (SEM) micrographs and laser diffraction, respectively. The spheroidized powder showed higher sphericity and more uniform particle size distribution overall. Depending on the powder collection bin, second round of spheroidization affected the powder sphericity differently. The possibility of deploying the plasma spheroidization process as an alternative oxygen-reduction technique was also investigated through tracking the powders\u27 oxygen content using inert gas fusion method before and after the spheroidization. The plasma spheroidized powder showed less oxygen content than the hydrogen-treated powder. The second round of spheroidization caused no change in oxygen content. The correlation between oxygen-reduction and created cracks was discussed and compared between plasma spheroidization and hydrogen-treatment. The plasma spheroidization process created a powder with higher sphericity, uniform particle size, and less oxygen content

Investigation of Mechanical Properties of Parts Fabricated with Gas- and Water-Atomized 304L Stainless Steel Powder in the Laser Powder Bed Fusion Process

The use of gas-atomized powder as the feedstock material for the laser powder bed fusion (LPBF) process is common in the additive manufacturing (AM) community. Although gas-atomization produces powder with high sphericity, its relatively expensive production cost is a downside for application in AM processes. Water atomization of powder may overcome this limitation due to its low-cost relative to the gas-atomization process. In this work, gas- and water-atomized 304L stainless steel powders were morphologically characterized through scanning electron microscopy (SEM). The water-atomized powder had a wider particle size distribution and exhibited less sphericity. Measuring powder flowability using the Revolution Powder Analyzer (RPA) indicated that the water-atomized powder had less flowability than the gas-atomized powder. Through examining the mechanical properties of LPBF fabricated parts using tensile tests, the gas-atomized powder had significantly higher yield tensile strength and elongation than the water-atomized powder; however, their ultimate tensile strengths were not significantly different

Approach to diagnosis and pathological examination in bronchial Dieulafoy disease: a case series

<p>Abstract</p> <p>Background</p> <p>There are limited series concerning Dieulafoy disease of the bronchus. We describe the clinical presentation of a series of 7 patients diagnosed with Dieulafoy disease of the bronchus and provide information about the pathological diagnosis approach.</p> <p>Patients and methods</p> <p>A retrospective review of patients who underwent surgery for massive and unexplained recurrent hemoptysis in a referral center during a 11-year period.</p> <p>Results</p> <p>Seven heavy smoker (49 pack years) patients (5 males) mean aged 54 years experienced a massive hemoptysis (350–1000 ml) unrelated to a known lung disease and frequently recurrent. Bronchial contrast extravasation was observed in 3 patients, combining both CT scan and bronchial arteriography. Efficacy of bronchial artery embolization was achieved in 40% of cases before surgery. Pathological examination demonstrated a minute defect in 3 cases and a large and dysplasic superficial bronchial artery in the submucosa in all cases.</p> <p>Conclusion</p> <p>Dieulafoy disease should be suspected in patients with massive and unexplained episodes of recurrent hemoptysis, in order to avoid hazardous endoscopic biopsies and to alert the pathologist if surgery is performed.</p

Anti-inflammatory Effect of Sodium Valproate on Carrageenan-Induced Paw Edema in Male Rat

ABESTRACT: Introduction & objective: Inflammation is a body defensive response to the endogenous and exogenous stimulators such as chemical, radiation, trauma and invasive microorganism, which result pain and tissue necrosis. There are many natural and synthetic drugs for treatment of inflammation and lot of them are under investigation. Sodium valporate is an antiepileptic drug used particularly in the treatment of primary generalized seizure notably absence, myocolonic seizure, acute manic phase of bipolar disorder and prophylaxis of migraine. The previous observations showed sodium valporate increases level of gamma amino butyric acid (GABA) in the central and peripheral nervous system. In acute inflammation, GABA showed a significant attenuation of paw edema and nociception. The aim of this study was evaluation of anti-inflammatory effect of sodium valporate. Materials & Methods: In order to evaluated the anti-inflammatory and antiexudative of sodium valporate doses of 200,400 and 600 mg/kg were investigated on rat paw edema that induced by carrageenan. In addition, the plasma leakage in the inflamed tissue was evaluated by application of trypan blue as intravenous injection. Dexamethason was used as positive control. Results: Results showed sodium valporate doses of 400 and 600 mg/kg decreased inflammatory and exudative effect as compared to control group. Conclusion: Although the anti-inflammatory mechanisms of this drug were not evident but we can say sodium valporate in addition to already proved effects has anti-inflammatory effect

Comparing the effects of peritoneal and subcutaneous injections of Bupivacaine on post-appendectomy pain

Background: This study aimed to compare the effects of peritoneal and subcutaneous injections of bupivacaine 0.5% on post-appendectomy pain and also the efficacy of local anaesthetic injection for postoperative pain relief in peritoneal inflammation with subcutaneous injection. Materials and Methods: This randomized-clinical trial was conducted on 126 participants (age range, 15-45 years) underwent appendectomy for acute appendicitis in Kashan Shahid- Beheshti hospital. Participants were divided into three groups: bupivacaine (0.5%, ip), bupivacaine (0.5% s.c), and control (no injection). Pain intensity was evaluated using the visual analogue scale at 6, 12 and 24 hours after surgery. Results: There was no significant difference among the three groups in age, sex, the duration of anesthesia and surgery. Pain intensity (6 h post-surgery) was significantly higher in the subcutaneous group than the peritoneal group, but no significant difference was seen between the two groups at 12 and 24 h post-surgery. Moreover, pain intensity in the peritoneal and subcutaneous groups was significantly lower than the control group at 6 and 12 h post-surgery (P<0.05). There was a significant difference between the peritoneal and subcutaneous groups as well as between the peritoneal and control groups required analgesics, but the difference was not significant between the subcutaneous and control groups. Conclusion: Although both peritoneal and subcutaneous injections of bupivacaine can reduce postoperative pain in patients undergoing appendectomy, the peritoneal injection can significantly reduce the postoperative analgesic consumption

The Relationship between Maternal Environmental Tobacco Smoke Exposure during Pregnancy with Anthropometric Parameters of the Newborn

Background and ObjectivesMaternal environmental tobacco smoke exposure (ETS) or passive smoking would be a risk factor for maternal and new born morbidity. This study was conducted to determine this relationship with in pregnant woman referring to Shabihkhani Maternity Hospital of kashan, Iran, during 2006-2007 MethodsThe study was carried out on 150 Nonsmoking pregnant women who were exposed to ETS greater than or equal to 5 cigarettes per day smoked by others in the mother's presence in all of pregnancy period as exposed group and 150 Nonsmoking pregnant women who were not exposed to ETS as the non-exposed group. Birth weight, height and head circumference were compared in the two groups and analyzed by t- and X² tests.ResultsThe mean birth weights in the exposed group and non exposed group were and 3137.5±437.8 and 3270±499.5 grams respectively, the t- test showed this difference to be significant (p=0.015). The mean birth height and head circumference in the two groups were not significantly different.ConclusionNonsmoking pregnant women who were exposed to ETS gave 133 g reduction in birth weight compared to unexposed women. Further studies are needed to determine if ETS decreases birth height and birth head circumference Keywords: Birth Weight; Body Height; Birth Head Circumference; Tobacco Smoke Pollution; Pregnancy

Single-port video-assisted thoracoscopic surgery in the management of fibrinopurulent empyema: The experience of a single institution

BACKGROUND: Acute thoracic empyema requires appropriate diagnosis of the disease stage and on time management. The best time of surgical intervention and treatment options of the fibrinopurulent stage empyema is not precisely determined. This study aimed at assessing the effect of a single-port video-assisted thoracoscopic surgery (VATS), as the first option thorough previous chest tube incision, on management of acute thoracic empyema in the fibrinopurulent stage. METHODS: This cross-sectional, prospective, study was performed on 62 patients with fibrinopurulent empyema, who were non-responsive to chest tube drainage and antibiotic therapy, during February 2014 to September 2018. VATS was performed earlier than the course of medical management time (MMT), 12±3 days, thorough previously planned tube thoracostomy incision (5 th intercostal space) in majority of patients as the opening work. Then, the results were compared with possible published related studies at the same stage but in conventional (12-21 days) MMT time. RESULTS: From a total of 62 patients, 52 were males. The age range was 14-80 years. The median postoperative hospital stay was 6 days. The fever and dyspnea reduced after the operation. In majority of the patients, lung was expanded after the VATS but pleural thickening resolved during a follow-up period of 90±15 days. No intraoperative complications were observed. Morbidity rates were acceptable. Also, two conversions were performed, and two death cases occurred due to comorbidity. Pleural tissue diagnosis showed no malignancy, tuberculosis in two cases, and the necrotic tissue in remainder. CONCLUSIONS: The single-port VATS in the treatment of fibrinopurulent empyema as a first option is a highly effective approach and has better outcome in during 12±3days after MMT. Proper selected initial chest tube incision could be used as the opening work incision in VATS. © 2019 EDIZIONI MINERVA MEDIC

Development and Experimental Study of an Automated Laser-Foil-Printing Additive Manufacturing System

Purpose: This paper aims to present the development and experimental study of a fully automated system using a novel laser additive manufacturing technology called laser foil printing (LFP), to fabricate metal parts layer by layer. The mechanical properties of parts fabricated with this novel system are compared with those of comparable methodologies to emphasize the suitability of this process. Design/methodology/approach: Test specimens and parts with different geometries were fabricated from 304L stainless steel foil using an automated LFP system. The dimensions of the fabricated parts were measured, and the mechanical properties of the test specimens were characterized in terms of mechanical strength and elongation. Findings: The properties of parts fabricated with the automated LFP system were compared with those of parts fabricated with the powder bed fusion additive manufacturing methods. The mechanical strength is higher than those of parts fabricated by the laser powder bed fusion and directed energy deposition technologies. Originality/value: To the best knowledge of authors, this is the first time a fully automated LFP system has been developed and the properties of its fabricated parts were compared with other additive manufacturing methods for evaluation

Subduction-unrelated magmatism of southern periphery of Paleotethys: constraints from Late Paleozoic magmatism from the south of Masuleh, western Alborz

The Alborz Mountains in north of Iran correlates with the Paleotethyan Suture so preserves valuable clues for geodynamic clarifications and paleotectonic reconstructions. During life span of Paleotethys from Early Paleozoic to Late Triassic, major parts of Alborz appear as a continental margin in southern border of the oceanic basin. To test paleotectonic setting of Alborz during Late Paleozoic and its passive or active condition, geochemical data of magmatic rocks can provide useful clues. The Masuleh area (western Alborz) involves important exposures of Late Paleozoic volcanic associations. These volcanics are poorly studied and understood, so we intend to present new geochemical data about them. Field studies characterize various lithological units in tectonic and stratigraphic contact with volcanic units including Late Paleozoic low-grade metamorphics (slate-phyllite) and calcareous units of upper Devonian, Carboniferous to Permian. The whole rock geochemical data has been obtained by XRF and ICP-MS at Ferrara University, Italy. The volcanics mainly comprise basaltic to trachy-basaltic compositions. They show moderate to high alteration reflected in their LOI content (2.2 to 7.8 wt.%). Thus, for major element we used recalculated anhydrous values. The SiO2 abundances of 45.3 to 50.7 wt.% display basic nature of the studied rocks. Other major element components such as TiO2, Al2O3, CaO and MgO are in the ranges of 1-4.4, 13.7-18.3, 5-10.7 and 2.5-14.9 wt.%, respectively. Moreover, Mg# [MgO*100/(MgO+FeO*)] varies from 19-71. Wide range of major element variations likely corresponds to different modal mineralogy and also various extent of melt evolution and fractionation processes. Total alkali element abundance (Na2O+K2O) displays elevated values (1.95-7.9 wt.%) reflecting alkaline composition of the samples. Compatible elements such as Ni (2.2-213.7 ppm) and Cr (17-739 ppm) indicate highly varied amounts, as well, suggesting nearly primitive to extremely fractionated nature. In La/Sm vs. La plot, the compositional trend is consistent with fractional crystallization process. Chondrite-normalized REE patterns and primitive mantle -normalized spider diagrams are characterized by similar patterns suggesting genetic relationships of different samples. The spider diagrams display humped-shaped patterns in which the LILEs (Rb, Ba, Sr and K) and HFSEs (e.g. Th, Ta, Nb, Zr and REEs) show enrichment with increasing incompatibility and a slightly negative Nb anomaly. These patterns are consistent with typical intraplate alkaline magmatism (OIBs). REE patterns are characterized by pronounced negative slope reflecting high LREE/HREE enrichment ((La/Yb) N= 5-17). Moreover, La and Yb represent enrichment of 47-248 and 6.5-22 times chondrite abundances, respectively. Immobile trace elements (e.g. La, Y, Zr and Nb) discrimination diagrams suggest subduction unrelated within-plate mantle origin similar to OIB source. Furthermore, the mantle source nature and partial melting degrees are inferred from modeling based on incompatible element ratios (Sm/Yb vs. La/Yb plot) suggesting that parental melt derived from garnet-bearing lherzolite and partial melting of &lt;15%. Finally, we conclude that the area located to the southern margin of Paleotethys during Late Paleozoic was a passive margin (Gondwanian affinity) and the magmatic activity was related to thermal perturbation of mantle via hot spot/plume effects in an extensional tectonic regime