1,916 research outputs found
Risk Factors of Stillbirth Among Women Who Gave Birth in Amhara Region Referral Hospitals, Ethiopia, in 2019: A Case-Control Study
No full textAtrsaw Dessie Liyew,1 Mihretu Molla,2 Zelalem Nigussie Azene3 1Department of Midwifery, College of Health Sciences, Dessie, Ethiopia; 2Department of Clinical Midwifery, School of Midwifery, College of Medicine and Health Sciences, University of Gondar, Gondar, Ethiopia; 3Department of Women’s and Family Health, School of Midwifery, College of Medicine and Health Sciences, University of Gondar, Gondar, EthiopiaCorrespondence: Zelalem Nigussie Azene Tel +251928446017Email [email protected]: Worldwide, 2.6 million stillbirths occur annually and more than three-quarters of them are recorded in South Asia and Sub-Saharan Africa. Thus, the aim of this study was to identify risk factors of stillbirth among women who gave birth in Amhara region referral hospitals found in northwest and northcentral, Ethiopia in 2019.Methods: A multi-center institution-based unmatched case-control study was conducted among 456 mothers who gave birth in Amhara region referral hospitals from October 1 to December 30, 2019. Consecutive and simple random sampling was used to select the cases and controls, respectively. A semi-structured, interviewer-administered questionnaire and patient chart reviews were used to collect the data. Epidemiological (Epi) data version 4.4.2.1 and Statistical Package for the Social Sciences (SPSS) version 25.0 were used for data entry and analysis, respectively. Binary logistic regression was employed. An adjusted odds ratio with a 95% confidence interval was used to declare statistically significant variables on the basis of p-value< 0.05 in the multivariable binary logistic regression model.Results: Alcohol drinking (adjusted odds ratio (AOR)=3.02, 95% confidence interval (CI)=1.24– 7.35), antepartum hemorrhage (AOR=5.74, 95% CI=2.67– 12.33), premature rupture of membrane (AOR=2.21, 95% CI=1.09– 4.44), meconium-stained amniotic fluid (AOR=8.18, 95% CI=4.29– 15.60), non-use of partograph for labor follow-up (AOR=3.89, 95% CI=2.12– 7.17), induction of labor (AOR=2.12, 95% CI=1.09– 4.11), previous history of stillbirth (AOR=2.15, 95% CI=1.08– 4.26), and birthweight less than 2,500 grams (AOR=7.36, 95% CI=3.43– 15.81) increase the odds of stillbirth.Conclusion: Stillbirth was higher among women who drank alcohol during their pregnancy, experienced antepartum hemorrhage, premature rupture of membrane, meconium-stained amniotic fluid, induction of labor, labor not followed by partograph, previous history of stillbirth, and birthweight less than 2,500 grams. As such, education to stop alcohol drinking during pregnancy, monitoring the progress of labor with partograph, and improving the quality of care for mothers and newborns at the time of pregnancy and childbirth will contribute to preventing stillbirth.Keywords: risk factors, stillbirth, delivered women, Ethiopi
Locating and Controlling the Zn Content in In(Zn)P Quantum Dots
No full textZinc is routinely employed in the synthesis of InP quantum dots (QDs) to improve the photoluminescence efficiency and carrier mobility of the resulting In(Zn)P alloy nanostructures. The exact location of Zn in the final structures and the mechanism by which it enhances the optoelectronic properties of the QDs are debated. We use synchrotron X-ray absorbance spectroscopy to show that the majority of Zn in In(Zn)P QDs is located at their surface as Zn carboxylates. However, a small amount of Zn is present inside the bulk of the QDs with the consequent contraction of their lattice, as confirmed by combining high-resolution high-angle annular dark-field imaging scanning transmission electron microscopy with statistical parameter estimation theory. We further demonstrate that the Zn content and its incorporation into the QDs can be tuned by the ligation of commonly employed Zn carboxylate precursors: the use of highly reactive Zn acetate leads to the formation of undesired Zn3P2 and the final nanostructures being characterized by broad optical features, whereas Zn carboxylates with longer carbon chains lead to InP crystals with much lower zinc content and narrow optical features. These results can explain the differences between structural and optical properties of In(Zn)P samples reported across the literature and provide a rational method to tune the amount of Zn in InP nanocrystals and to drive the incorporation of Zn either as surface Zn carboxylate, as a substitutional dopant inside the InP crystal lattice, or even predominantly as Zn3P2.ChemE/Opto-electronic Material
A uniform reduction equivalence for process calculi
No full textWe present a new uniform definition of reduction-based semantics for different process calculi, called indexed reduction equivalence (or congruence). We prove that early bisimulation coincides with indexed reduction equivalence for pi-calculus, context bisimulation coincides with indexed reduction equivalence for higher order pi-calculus and indexed reduction congruence is strictly finer than contextual barbed congruence for Safe Mobile Ambients.Computer Science, Software EngineeringComputer Science, Theory & MethodsSCI(E)CPCI-S(ISTP)
Rent - seeking trade policy : a time series approach
No full textUsing a time-series approach, the author analyzes the relationship between the extent of rent-seeking trade policy and both political and economic variables. For rent-seeking trade policy, the indicator he uses is the number of foreign-trade regulations passed each year for the benefit of a single firm or industry. The author uses data from Uruguay for 1925-83. Uruguay, which experienced an impressive economic decline, is an outstanding example of a rent-seeking society. After being a wealthy economy in midcentury, it suffered almost complete stagnation, which led to social and policital disintegration by the end of the 1960s. Three decades of restrictive regulations on foreign trade had created a nearly closed economy by the end of the 1960s. It was worth analyzing whether policymakers'great receptiveness to demands for protection could account for Uruguay's decline. Over the period 1925-83, the author finds almost 4,000 laws, decrees, and administrative resolutions that create, maintain, or modify a foreign-trade regulation for the benefit of a single firm or industry. About half of them explicitly identify the petitioner - usually a firm or guild. Since the size of the Uruguayan economy changed over the period studied, the author scales the annual number of regulations by output or exports to measure the extent of rent-seeking trade policy. The author shows that the extent of rent-seeking trade policy increased with discretionary policies and under dictatorship. (In the period studied, there were two stages of democracy - until 1932 and from 1943-72 - and two stages of dictatorship.) He also shows that rent-seeking trade restrictions increased under import-substitution strategies and, more unexpectedly, under active export promotion. This suggests that discretionary power leads to wasteful distribution, whether it is used to support inward- or outward-oriented policies. Finally, the author analyzes the correlation between innovations in the trade policy indicator and innovations in the growth rates of output and exports, with a lag of up to 20 years. Surprisingly, he finds a positive correlation with output growth rates after two or three years. But the correlation becomes negative some years later, particularly in the case of exports. The short-run positive impact on growth rates, together with the surprisingly long time lag before the negative impact, may account for policymakers'receptiveness to demands for protection.Trade Policy,Achieving Shared Growth,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Economic Theory&Research,Environmental Economics&Policies
Study on the Mg-Li-Zn ternary alloy system with improved mechanical properties, good degradation performance and different responses to cells
No full textNovel Mg-(3.5, 6.5wt%)Li-(0.5, 2, 4wt%)Zn ternary alloys were developed as new kinds of biodegradable metallic materials with potential for stent application. Their mechanical properties, degradation behavior, cytocompatibility and hemocompatibility were studied. These potential biomaterials showed higher ultimate tensile strength than previously reported binary Mg-Li alloys and ternary Mg-Li-X (X=Al, Y, Ce, Sc, Mn and Ag) alloys. Among the alloys studied, the Mg-3.5Li-2Zn and Mg-6.5Li-2Zn alloys exhibited comparable corrosion resistance in Hank's solution to pure magnesium and better corrosion resistance in a cell culture medium than pure magnesium. Corrosion products observed on the corroded surface were composed of Mg(OH)2, MgCO3 and Ca-free Mg/P inorganics and Ca/P inorganics. In vitro cytotoxicity assay revealed different behaviors of Human Umbilical Vein Endothelial Cells (HUVECs) and Human Aorta Vascular Smooth Muscle Cells (VSMCs) to material extracts. HUVECs showed increasing nitric oxide (NO) release and tolerable toxicity, whereas VSMCs exhibited limited decreasing viability with time. Platelet adhesion, hemolysis and coagulation tests of these Mg-Li-Zn alloys showed different degrees of activation behavior, in which the hemolysis of the Mg-3.5Li-2Zn alloy was lower than 5%. These results indicated the potential of the Mg-Li-Zn alloys as good candidate materials for cardiovascular stent applications. Statement of significance: Mg-Li alloys are promising as absorbable metallic biomaterials, which however have not received significant attention since the low strength, controversial corrosion performance and the doubts in Li toxicity. The Mg-Li-Zn alloy in the present study revealed much improved mechanical properties higher than most reported binary Mg-Li and ternary Mg-Li-X alloys, with superior corrosion resistance in cell culture media. Surprisingly, the addition of Li and Zn showed increased nitric oxide release. The present study indicates good potential of Mg-Li-Zn alloy as absorbable cardiovascular stent material.Accepted Author ManuscriptBiomaterials & Tissue Biomechanic
Extrusion-based additive manufacturing of Mg-Zn alloy scaffolds
No full textPorous biodegradable Mg and its alloys are considered to have a great potential to serve as ideal bone substitutes. The recent progress in additive manufacturing (AM) has prompted its application to fabricate Mg scaffolds with geometrically ordered porous structures. Extrusion-based AM, followed by debinding and sintering, has been recently demonstrated as a powerful approach to fabricating such Mg scaffolds, which can avoid some crucial problems encountered when applying powder bed fusion AM techniques. However, such pure Mg scaffolds exhibit a too high rate of in vitro biodegradation. In the present research, alloying through a pre-alloyed Mg-Zn powder was ultilized to enhance the corrosion resistance and mechanical properties of AM geometrically ordered Mg-Zn scaffolds simultaneously. The in vitro biodegradation behavior, mechanical properties, and electrochemical response of the fabricated Mg-Zn scaffolds were evaluated. Moreover, the response of preosteoblasts to these scaffolds was systematically evaluated and compared with their response to pure Mg scaffolds. The Mg-Zn scaffolds with a porosity of 50.3% and strut density of 93.1% were composed of the Mg matrix and MgZn2 second phase particles. The in vitro biodegradation rate of the Mg-Zn scaffolds decreased by 81% at day 1, as compared to pure Mg scaffolds. Over 28 days of static immersion in modified simulated body fluid, the corrosion rate of the Mg-Zn scaffolds decreased from 2.3 ± 0.9 mm/y to 0.7 ± 0.1 mm/y. The yield strength and Young's modulus of the Mg-Zn scaffolds were about 3 times as high as those of pure Mg scaffolds and remained within the range of those of trabecular bone throughout the biodegradation tests. Indirect culture of MC3T3-E1 preosteoblasts in Mg-Zn extracts indicated favorable cytocompatibility. In direct cell culture, some cells could spread and form filopodia on the surface of the Mg-Zn scaffolds. Overall, this study demonstrates the great potential of the extrusion-based AM Mg-Zn scaffolds to be further developed as biodegradable bone-substituting biomaterials.Biomaterials & Tissue BiomechanicsTeam Peyman TaheriTeam Arjan Mo
Ca-Mg-Zn-(Ag) bulk metallic glasses prepared by unidirectional quenching
No full textWe fabricated ternary Ca-Mg-Zn and quaternary Ca-Mg-Zn-Ag bulk metallic glasses with diameter of 7 mm by unidirectional quenching into water-cooled Ga-In-Sn liquid alloys. It was suggested that the electromagnetic stirring caused by induction eddy current facilitated the glass formation. Glass forming ability of Ca(62.5)Mg(17.5)Zn(20-x)Ag(x) (x = 0, 1, 3, 5, 7,9) system was dependent on Ag content. It was found that in the system the in-situ formed crystalline phases enhanced the second-stage crystallization, whereas there seemed no contribution to the third-stage crystallization. (C) 2011 Elsevier Ltd. All rights reserved
Origin of the low thermal conductivity of the thermoelectric material beta-Zn(4)Sb(3): An ab initio theoretical study
No full textBy modeling beta-Zn(4)Sb(3) material as a Zn(36)Sb(30) crystal with defects, the crystal structure and thermal properties of beta-Zn(4)Sb(3) are studied by ab initio method to explain its extremely low thermal conductivity at moderate temperature. The formation and migration energies of defects are calculated and used to explain the partial occupation of Zn at the lattice sites, the disordered local structures and the origin of the low thermal conductivity of beta-Zn(4)Sb(3). Our study also unravels the puzzling dependence of thermal conductivity on doping in beta-Zn(4)Sb(3). A doping strategy is proposed to improve the thermoelectric performance of beta-Zn(4)Sb(3). (C) 2011 American Institute of Physics. [doi:10.1063/1.3599483
Selective Dimerization of Ethene to 2-Butene on Zn<sup>2+</sup>-Modified ZSM-5 Zeolite
No full textSelective dimerization of ethene to 2-butene on Zn2+-containing ZSM-5 zeolite (Zn2+/ZSM-5) at 296-523 K has been discovered. The intermediate but-3-en-1-ylzinc species is identified with 13C CP/MAS NMR and Fourier transform infrared spectroscopy. The density functional theory study of two alternative dimerization pathways reveals that the intermediate is formed with the involvement of the saturated bridged dimeric Zn-(CH2)4-O species. It is also shown that ethene conversion to 2-butene increases with the increase in the quantity of Brønsted acid sites in Zn2+/ZSM-5 zeolite; however, the selectivity of the reaction decreases. The results obtained are of potential interest for developing industrially relevant Zn-containing zeolite catalysts for the selective conversion of ethene to 2-butene. Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ChemE/Inorganic Systems Engineerin
The delamination process of the dross build-up structure on submerged hardware in Zn-Al and Zn-Mg-Al baths: An empirical study
No full textHot-dip galvanizing is a well-known process to increase the corrosion resistance of steel. As a by-product dross is formed in the Zn-bath. The dross particles are composed of Fe, Al and Zn in the form of Fe2Al5Znx and interact with the hardware that is submerged in the Zn-bath and eventually accumulate on the surface of the hardware. This accumulation of dross on the hardware is known as dross build-up.Dross is formed in the Zn-bath as a result of the dissolution of Fe from the steel strip. This Fe reacts with Al present in the liquid Zn forming the Fe2Al5Znx dross particles. Once the hardware is submerged in the liquid Zn a thin compact Fe2Al5-layer is formed on top of the surface of the hardware, known as the diffusion layer. This diffusion layer acts as a barrier for Fe towards the Zn-bath and Zn towards the hardware surface. Once the diffusion layer is formed dross particles precipitate on top of this diffusion layer followed by a slow growth of the intermetallic dross particles. The diffusion layer and accumulated intermetallic dross particles are known as the dross build-up. The thickness of this dross build-up depends on immersion time, bath temperature and bath chemistry and varies typically between 90 μm up to several millimetres.The dross build-up is thought to be a critical factor in the bath hardware lifetime. The surface quality of the bath hardware directly influences the quality of products produced on the galvanizing line. More dross in the Zn-bath could lead to more defects in the coating, which could lead to failure when the steel strips are processed further, or giving the coating on the steel strip a bad appearance. Because of the dross build-up on the hardware, the bath hardware is changed every 4-6 weeks. By controlling the dross in the Zn-bath, the service lifetime of the hardware could possibly be extended. When the service lifetime of the hardware is extended the maintenance downtime and costs of the galvanizing lines are reduced.Recently, Tata Steel introduced a new type of Zn-coating: MagiZinc (MZ). This type of Zn-coating differs from the conventional Zn-coating: Conventional Zn-coating (GI) consists of Zn with 0,30 wt% Al whereas MagiZinc consists of Zn with 1,60 wt% Al and 1,60 wt% Mg. This difference in composition has an influence on the dross build-up formed on the hardware. At Tata Steel, there is some evidence that the dross build-up layer on the bath hardware created in the conventional Zn-bath is diminishing when the hardware is submerged in the MagiZinc-bath.This thesis project aims to identify the characteristics of this cleaning behaviour in MagiZinc of the dross build-up that is formed on bath hardware when submerged in conventional Zn.Based on the results obtained from experiments in this study it can be concluded that the delamination process of the intermetallic dross particles is a combination of intergranular diffusion of Zn and crack formation as a result of thermal shock.By changing the baths from conventional Zn to MagiZinc the composition of the bath changes. As a result the thermodynamic stability of the intermetallic Fe2Al5Znx dross particles change with respect to the liquid Zn-phase in such a way that the intermetallic dross particles partly dissolve in the liquid MagiZinc. As a result, the intermetallic dross particle/liquid Zn interface changes from a faceted to a curved interface. As a consequence of this change in structure intergranular diffusion can take place between the intermetallic dross particles. By the intergranular diffusion of Zn the cohesion of the grain boundaries of the intermetallic dross particles is reduced. This reduction in cohesion is probably the start of the delamination of the intermetallic dross particles, breaking into smaller pieces at the grain boundaries when enriched with Zn.The diffusion layer remains largely unaffected in the delamination process due to the better adhesion to the hardware surface compared with the adhesion of the intermetallic dross particles to the diffusion layer. The better adhesion of the diffusion layer to the hardware surface is the result of diffusion of Cr and Ni from the 316L SS substrate into the liquid Zn at time of immersion. The area from where Cr and Ni are dissolved, Al is diffusing into the 316L SS substrate forming the diffusion layer. Simultaneously the intermetallic dross particles form at the hardware surface. This layer is mainly formed from Fe and Al from the bath, not from the 316L SS substrate.Due to this limited bonding between the intermetallic dross particles and the diffusion layer the intermetallic dross particles are more prone to crack formation due to thermal shock.By changing the Zn-bath from conventional Zn to MagiZinc and vice versa the hardware and thus also the dross build-up rapidly cools down to room temperature. This thermal shock creates stresses within the intermetallic dross particle-layer. Due to a difference in thermal expansion between the 316L stainless steel matrix and the intermetallic dross particle-layer large cracks form in the intermetallic dross particle-layer. When the hardware is immersed again in liquid Zn the cracks still exist and these cracks accelerate the delamination process of the dross build-up structure. This observed mechanism is independent from the type of Zn-bath that the hardware is immersed in. The process also takes place when the hardware is taken out a conventional Zn-bath and placed back into a conventional Zn-bath.Materials Science and Engineerin
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