bluuebunny/crossref_metadata_2025 huggingface dataset:
Tailoring Mechanical Properties of Extruded Ti-6Al-4V Alloy from the Blended Elemental Route via Microstructure Control
Authors: Romero Villarreal Carlos , Yang Fei , Bolzoni Leandro
Published: August 2018

Vacuum-sintered billets of Ti-6Al-4V alloy from powder blend were extruded at two different temperatures: 1150 °C and 950 °C. The extruded material at 1150 °C was subjected to various heat treatments to obtain different microstructures: annealing in the β phase, β solution treatment and aging and α+β solution treatment and aging. The materials processed were characterised using scanning electron microscopy, X-ray diffraction and the mechanical properties were measured by tensile test. The microstructure of both extrusions are fairly similar, consisting of lamellar colonies, and the mechanical properties are also comparable, with yield strengths of about 1000 MPa, ultimate tensile strength of about 1100 MPa and elongation at fracture of 8-9%. The β annealing treatment, through coarsening the lamellar microstructure, reduces the strength of the alloy while keeping a high ductility. Both solution treatments and aging, which produces aged martensite and aged martensite and primary alpha, respectively, increases the strength and reduces the ductility. There is a trade-off between ductility and strength when it comes to tailoring the microstructure, and the as-extruded Ti-6Al-4V condition is the one with the best balance between strength and ductility.
The Effect of the Green Density on the Properties of Powder Metallurgy Ti Sintered by High Frequency Induction Heating
Authors: Raynova Stella , Collas Yann , Yang Fei , Bolzoni Leandro
Published: August 2018

Sintering is a vital technology used for consolidation of metal and ceramic powders. The process is generally long and energy consuming because of the way in which heat transfer happens in electrical and gas furnaces. This study focuses on optimizing the sintering process of metallic powders, in particular titanium, using high frequency induction heating as alternative sintering method. Using electromagnetic induction and the associated Eddy current effect, the heat is generated directly into the electrically conductive object. Consequently, faster heating rates and lower heat loses are achieved. The purpose of this study is to understand the effect of process parameters, such as the powder compact density, on the efficiency of the induction heating and the properties of the sintered materials. The average heating rates recorded while heating to 1300oC are in the range of 3.5o to 15.3o C per second. Significant densification and consolidation, evident by the amount of closed porosity and increase in tensile strength was found in spite of the short heating time. The results show that the powder compact density plays a crucial role on the heating efficiency as well on the properties of the sintered material such as final density, porosity distribution and tensile properties. The samples with higher initial density showed tensile strength and ductility values comparable to those of high vacuum sintered and those specified by international standards for powder metallurgy Ti products.
Yield of Binary Ti-Cu and Ti-Mn Alloys Produced via Powder Metallurgy
Authors: Alshammari Yousef , Yang Fei , Bolzoni Leandro
Published: August 2018

High strength, low density, good corrosion resistance and biocompatibility is the combination of properties that Ti and its alloys can provide for engineering applications. Its costs are the most important limiting factor for the widespread use of Ti. Cost reduction for Ti alloys can derive from the use of cheaper alloying elements as well as the use of alternative manufacturing techniques. In this study binary Ti-X alloys (where X = Cu or Mn) were formulated and produced using the conventional powder metallurgy route of pressing and sintering. These chemical elements were selected because they are β stabilisers and can be used to create α+β Ti alloys. The study shows that with the techniques and processing parameters used handable products without delamination can be pressed. Moreover, chemically homogenous materials with density and mechanical property values comparable to those of other wrought-equivalent Ti alloys produced via powder metallurgy were achieved.
Physical Properties and Rheological Characteristics of Activated Carbon Nanofluids with Varying Filler Fractions and Surfactants
Authors: Abdul Kaggwa , Carson James K. , Atkin Martin , Walmsley Michael
Published: August 2018

For the past fifteen years, there has been considerable interest in the use of nanofluids in various fields mainly in heat transfer applications. This paper investigated thermophysical properties of activated carbon nanofluids using hexane, water and ethylene glycol (EG) as base fluids. Experimental and qualitative observational tests were conducted to study the viscosity, specific heat capacity and stability of the nanofluids using arabinogalactan (ARB), sodium lauryl sulphate (SDS) and TritonX-114 as stabilising agents. The results revealed that the addition of ARB to activated carbon-water (C/H2O) nanofluids yielded nanofluid stability for up to 39 days. However, ARB decreased the heat capacity of C/H2O nanofluid. C/H2O nanofluid viscosity decreased with an increase in shear rate. On the other hand, results revealed that C/C6H14 viscosity increased with the increase in shear rate specifically for high shear rate values. C/H2O heat capacity was enhanced by 6.1% compared to C/EG that decreased by 6.3%. Keywords: Nanofluids; Viscosity; Specific heat capacity; Surfactant; Stability.
Overview of Sensor Technologies Used for 3D Localization of Asparagus Spears for Robotic Harvesting
Authors: Peebles Matthew , Lim Shen Hin , Duke Mike , Au Chi Kit
Published: August 2018

Advances in agricultural automation, coupled with a general decline of available labour hasgenerated interest in automated harvesting of various crops. Paramount to the success of such systemsis the development of accurate, robust detection technologies and localization strategies. This paperpresents an overview of sensor technologies used in the detection and localization of green aspara-gus spears for robotic harvesting. Tactile, photoelectric, machine vision and time-of-flight sensors areinvestigated and their applicability for use in robotic asparagus harvesting is evaluated. Investigationof previous asparagus harvesting devices has revealed that no such device has yet achieved commer-cial viability. It was identified that this is likely due to weaknesses in currently employed detectiontechnologies, namely slow response times, high sensitivity to changes in ambient lighting conditionsand requirement for frequent manual calibration. Of the sensor technologies investigated it was foundthat time-of-flight cameras, such as the Microsoft Kinect V2 are the most feasible for the detectionof asparagus spears for robotic harvesting. It was concluded that further research would be conductedinto the application of such sensors into a commercially viable harvester.
The Effect of Temperature and Time on the Formation of TiO2 (B) Nanowires via Hydrothermal Method
Authors: Nwe Thida San , Khangkhamano Matthana , Sikong Lek , Kooptanond Kalayanee
Published: August 2018

TiO2 (B) nanowires were prepared at 170 °C, 200 °C and 220 °C for 24 h via hydrothermal synthesis to evaluate the effect of temperature on phase composition and morphologies. The effect of reaction time: 24 and 72 h on the formation was also studied at 170 °C. All samples were calcined in air at 400 °C for 2 h. Phase identification was performed using X-ray diffraction (XRD) and morphologies was examined by a scanning electron microscope (SEM). It was found that hydrothermal temperature and time played an important role in defining TiO2 phase composition and its morphology. For 24 h hydrothermal synthesis, at low temperature of 170 °C, anatase TiO2 nanoparticles were formed, while at higher temperature of 200 and 220 °C, TiO2 (B) nanowires with averaged diameter of 49 nm and several micrometers in length were produced. Interestingly at 170 °C, by increasing reaction time to 72 h, anatase TiO2 nanoparticles were completely transformed to TiO2 (B) nanowires with averaged diameter of 74 nm and 2-4 micrometers in length.
Effect of Zn Additions on Thermal and Mechanical Properties of Sn-0.7Cu-xZn Solder Alloy
Authors: Ramli Mohd Izrul Izwan , Mohd Salleh Mohd Arif Anuar , Ibrahim I.N.A. , Said Rita Mohd
Published: August 2018

This research examines the influences of minor addition of Zn on the thermal and mechanical properties in Sn-0.7Cu solder alloy. The addition of 0.5, 1.0 and 1.5 wt.% of Zn were added into Sn-0.7Cu by using conventional casting method. It show that minor Zn addition has refined and promoted the nucleation of β-Sn phase. The vickers hardness show a increases the hardness of Sn-0.7Cu solder alloy with increasing amount of Zn. For thermal properties, with a small addition of Zn, it did not change the melting but has a slight decrease the undercooling of Sn-0.7Cu solder alloy.
Effect of Temperature on Oxide Growth Behaviour of Fe-33Ni-19Cr Alloy
Authors: Parimin Noraziana , Hamzah Esah , Amrin Astuty
Published: August 2018

The isothermal oxidation behaviour on two different temperature of Fe-33Ni-19Cr alloy was studied in this work. The present paper focuses on the isothermal oxidation behaviour at 700oC and 900oC. The oxidized samples were subjected to oxidation experiment under isothermal conditions for 500 hours. Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffraction (XRD) technique were employed in this study to analyse the oxidation behaviour of oxidized samples. The kinetics of oxidation followed the parabolic rate law which represent diffusion controlled oxide growth rate. Results indicate that Fe-33Ni-19Cr alloy oxidized at 700oC possess a better oxidation resistance with low Kp value of 2.39 x 10-7 mg2cm-4s-1. The oxide scale formed during oxidation were generally complex consists of several oxide phases. The samples morphologies of oxidized samples were influenced by the alloy structure and expose conditions. An elemental EDX line scan analysis of samples oxidized at 900oC indicated four different oxide layers composes of several oxide structure with evidence of internal oxide precipitates composed of Al-rich oxide phase.
Effect of Heat Treatment on the Isothermal Oxidation of Fe-33Ni-19Cr Alloy
Authors: Parimin Noraziana , Zulnuraini Zahraa , Sakdun S.A. Che
Published: August 2018

This research investigates the effect of heat treatment on the isothermal oxidation behaviour of Fe-33Ni-19Cr alloy. The samples were undergone heat treatment at three different temperatures namely, 1000oC, 1100oC and 1200oC for 120 minutes of soaking time followed by water quench to differ the grain size of alloy. The heat-treated sample was ground by using SiC paper atP600 finished. The samples were weighed using analytical balance and the surface area was measured before oxidation test. The heat-treated Fe-33Ni-19Cr alloys were isothermally oxidized at 850oC for 150 hours. The characterization on oxidized samples were carried out using scanning electron microscope equipped with energy dispersive x-ray (SEM-EDX) and x-ray diffraction (XRD). The result shows that, the average grain size increases as the heat treatment temperature increased. Fine grain size develops higher grain boundary area which acts as an ion diffusion path across the metal-gas interface during oxide formation. HT1000 sample with fine grain structure shows minimum weight gain and low oxidation rate compared to HT1100 and HT1200 samples. Uniform oxide layerformed on surface of the fine grain size sample. Whereas spallation of oxide scales was identified on the coarse grain size sample. Phase analysis shows that the oxidized sample formed several oxide phase.
Comparative Study on Microwave and Conventional Joining of Thermoplastic
Authors: Palanisamy C. , Selearajen S. Kumar , Siva K.
Published: August 2018

Industrialisation and the development of manufacturing process nowadays demand a more efficient and environmental friendly production. Microwave energy can be seen as the alternative heating application to meet the demands due to its ability to heat materials volumetrically. In this study, the usage of microwave energy to join thermoplastic is investigated. One of the key features of thermoplastic is the ability to shape when heated to their glass transition temperature and return to the moulded shape when it is cooled. Engineering thermoplastic Acrylonitrile-butadiene-styrene (ABS) was used as member while charcoal powder was used as susceptor material. The joining process was carried out with timing varying from 3 to 5 minutes, adhesive method and direct heating method. Upon the completion of joining, tensile test, 3 points test, hardness test and charpy impact test were conducted and compared to determine the strength of the joint.
Thermoelectric Transport Properties of SrTiO3 Doped with Pm
Authors: Adewale Akeem Adekunle , Chik Abdullah , Zaki Ruhiyuddin Mohd , Pa Faizul Che , Yeoh Cheow Keat , Jamil Noorina Hidayu
Published: August 2018

Thermoelectric properties of SrTiO3 doped with 8%Pm at Sr site were investigated using density functional theory and generalized gradient approximation. The transport properties were calculated based on BoltzTraP code at temperature range 300-1200K. In electronic properties study Fermi level were shifted to conduction band region due to high contribution 4f orbital in Pm. Present study thermoelectric figure of merit ZT result was 0.395 at 300K and 0.638 at 1200K. This shows a considerably good value of ZT for SrTiO3 as n-type oxide. Compared to previous work, ZT were at the range of 0.21 - 0.37 for temperature of 300-1000K in Pr, La, Ta and Ho.
Compressive Stress of Syntactic Foam: Effect of rNBR Particles Reinforced Epoxy Macrospheres (rNBR-EM)
Authors: Zakaria Zunaida , Yao C.Y.
Published: August 2018

This research focuses on the effect of rejected nitrile butadiene rubber (rNBR) gloves particles reinforced epoxy macrospheres (EM) on the physical properties and compressive stress of syntactic foam. Adding rNBR particles on the surface of macrospheres can increase the energy absorption as a result of improving the compressive properties of syntactic foam. Three types of macrospheres have been produced for the fabrication of syntactic foam, namely EM without rNBR, 1-layer rNBR-EM and 2-layer rNBR-EM. The results showed that increased rNBR particles layer on macrospheres has increased the wall thickness, and reduced the radius ratio of macrospheres as well as increased the density of syntactic foams. The compressive strength and modulus of syntactic foam with 2-rNBR-EM increased compared to the syntactic foams of 1-rNBR-EM and EM without rNBR. In addition, the toughness of the 2-rNBR-EM increased compared to the syntactic foams of 1-rNBR-EM and EM without rNBR.
Study of Mxene: Characterization and Radiation Properties of Two-Dimensional Titanium Carbide
Authors: OMAR MOHD FIRDAUS , Mohd Rasid Zarrul Azwan , A’ziz M.A. Abdul , Mohd Nazeri Muhammad Firdaus , Saidi S.A.
Published: August 2018

In this study, radon concentration of 2D Titanium Carbide MXene Ti3C2 was studied by using an established radon monitor. A layered MAX phase of Ti3AlC2 was synthesized through pressureless sintering (PLS) the initial powder of TiH2/Al/C without preliminary dehydrogenation under argon atmosphere at 1350 °C. An elegant exfoliation approach was used to eliminates Al from its precursor to form a layered-structure of Ti3C2. Morphological and structural properties of this 2D material also studied. SEM images shows two types of morphology which is a layer of Ti3C2 and the agglomerates Al2O3 with graphite. XRD pattern reveals three phases in this material which is a rhombohedral Al2O3, rhombohedral graphite and rhombohedral Ti3C2 phases. Radon concentration for this material for five consecutive days explains the radiation level of this material is under the suggestion value from US Environmental Protection Agency (EPA).
Effect of Modification Time of Kenaf Bast Fiber with Maleic Anhydride on Tensile Properties of Kenaf-Glass Hybrid Fiber Unsaturated Polyester Composites
Authors: Musa Luqman , Rozyanty A.R. , Zhafer S.F.
Published: August 2018

Natural fiber reinforced polymer composites are generally lower in mechanical performance compared to synthetic fiber reinforced polymer composites. However, this disadvantage can be improved via chemical modification of the natural fiber and hybridization with synthetic fiber. In this study, kenaf bast fiber was used as reinforcement in unsaturated polyester composites. It was subjected to chemical modification with maleic anhydride at various treatment time i.e. 60, 90 and 120 minutes prior to composites production. The untreated and MA treated kenaf bast fiber were hybridized with 10 weight percent of glass fiber to produce kenaf bast/glass fiber reinforced unsaturated polyester composites. The effect of treatment time on weight percent gain and functional group changes via infra-red spectra of kenaf bast fiber were investigated. The effect of treatment time on tensile properties of kenaf bast fiber and kenaf bast/glass fiber reinforced unsaturated polyester composites were also studied. It was revealed that the weight percent gain of kenaf bast fiber increased with the increasing of treatment time. The increasing of treatment time resulted in the enhancement of tensile strength and modulus of kenaf bast fiber and kenaf bast/glass fiber reinforced unsaturated polyester composites which were attributed to the presence of C=C bonds of maleic anhydride and has been proven through fourier transform infrared spectrum.
Simulation of the Heat-Insulating Sludge Waste Rubber Composite Brick by the Finite Element Method (FEM)
Authors: Namboonruang Weerapol , Suphadon Nutthanun
Published: August 2018

Recently, materials used to construct house or building wall are considered not only in the physical material behaviour but also energy conscious and economic factor. The possibility of utilization of the sludge waste obtained from the natural rubber manufacturing process as a raw material for producing composite brick was investigated. It has been widely known that the finite element method (FEM) is a tool used for finding accurate solutions of the heat transfer equation of materials including the composite bricks. In this work, study of the heat transfer of a composite brick containing rubber sludge waste (RSW) was showed and compared to results of finite element analysis (FEA) simulation. To determine the effect of rubber sludge waste to the heat transfer behaviour of composite brick with different volume fractions are varied by 10, 20, 30, 40 and 50%. It appeared that a FEA prediction showed good correspondence with the experimental results.
Effect of Limestone Powder in Self Consolidating Lightweight Foam Concrete
Authors: Mohd Ridzuan Ahmad Ruslan , Fauzi M.A. Mohd , Arshad Mohd Fadzil , Harun M.S. , Jasmi N.
Published: August 2018

Self-Consolidating Lightweight Foam Concrete (SCLFC) is known as a concrete which has no requirement towards vibration or compaction effort due to its flowability and capability in filling and achieving full compaction in reinforcement. The main component in SCLFC is cement. Cement is a basic component of concrete that used in construction industry. However, it is also the main source of Carbon Dioxide (CO2) emission. If this component of concrete is replaced with other materials, it surely can help in reducing the emission of CO2. Limestone powder can be replacement with the cement content in SCLFC. Therefore, the aim of this paper is to determine the effect of limestone powder on SCLFC in term of flowability and compressive strength. The specimens were tested for compressive strength at 3, 7, and 28 days. The result indicated the flowability of SCLFC increase with the increase of percentages of limestone powder replacement. Meanwhile, the highest compressive strength of SCLFC containing 10% limestone powder replacement give better performance than the normal SCLFC. Based on the finding, SCLFC containing 10% limestone powder replacement can be categorized same as a conventional concrete hence it can be utilized for construction purposes. Limestone powder can also acts as an alternative replacement in concrete for replacing the cement.
Investigation of Magnetoelectric Effect in the Bi-Layer Plate Structure
Authors: Saengow Treetep , Satitchantrakul Thanatcha , Silapunt Rardchawadee
Published: August 2018

Recently, the magnetoelectric (ME) effect is widely studied to apply in sensing applications. This paper proposes the investigation of ME effect in the bi-layer plate structure, which is the structure that allows deformation in the thickness direction. Mathematical models of the ME coefficients are developed using the constitutive equations of magnetostrictive and piezoelectric. Two modes of interest include longitudinal-transverse (L-T) and transverse-transverse (T-T) modes. Applying the models to the nanolayer of Terfenol-D/PZT in the assumingly low frequency regime yields the optimal thickness ratio of 0.34 for both modes. The maximum ME coefficients for 5, 10, and 10 nm thick structures are equal but occur at different resonant frequencies. They are approximately 480 and 240 mV/Oe cm for T-T and L-T modes, respectively. The maximum ME coefficients of the Terfenol-D/PZT plate structure are sufficiently high for nanoscale magnetic sensing applications.
Erosive Wear Characteristics of Laser Textured Alumina-Based Coatings for Marine Applications
Authors: Wahab Juyana A. , Ghazali Mariyam Jameelah , Derman Mohd Nazree B. , Otsuka Yuichi
Published: August 2018

Micro-groove textured surface of alumina-based ceramic coating is successfully fabricated via laser surface texturing (LST) method. The fabrication of textured surface is aimed to improve the resistivity of components against erosive wear. In this study, a slurry pot testing is conducted to investigate erosion damage on the surface of the textured alumina-based coating. The erosive wear rate of the specimens is determined and the surface morphology of the eroded surface is examined using an SEM. From the results, it is found that the erosion damage of textured coatings is dependent on the impact angles of SiO2 particles. The erosion wear mechanism is found to be varied with the formation of the micro-groove textured coatings. A significant decrease of 45 % in the erosion rate proved that the occurrence of an improved erosion resistance.
Cancer-related cognitive impairment in breast cancer survivors: An examination of conceptual and statistical cognitive domains using principal component analysis
Authors: Lambert Maude , Ouimet Lea Ann , Wan Cynthia , Stewart Angela , Collins Barbara , Vitoroulis Irene , Bielajew Catherine
Published: August 2018

There is a great deal of variability in the composition of neuropsychological test batteries used in the assessment of cancerrelated cognitive impairment (CRCI). Not only the development of a gold standard approach for CRCI assessment would allow for easier identification of women suffering from CRCI but it would also promote optimal care for survivors. As a first step towards the development of a valid and reliable unified test battery, the objective of this study was to verify whether the theoretical domains commonly used in CRCI assessment are statistically supported, before and after breast cancer treatment. Principal component analyses (PCA) were performed on the results from 23 neuropsychological tests grouped into eight conceptual domains. For baseline data, the Kaiser-Meyer-Olkin was .82 and Bartlett’s χ2(253, N=95) = 949.48, P<0.001. A five-component solution explained 60.94% of the common variance. For the post-treatment data, the Kaiser-Meyer-Olkin was .83 and Bartlett’s χ2(253, N=95) = 1007.21, P<0.001 and a five component solution explained 62.03% of the common variance. Although a visual comparison of the theoretical model with those determined via PCA indicated important overlap between conceptual domains and statistical components, significant dissimilarities were also observed.
An investigation into the changing relationship between the gold price and South African gold mining industry returns
Authors: Szczygielski Jan J. , Enslin Zack , Du Toit Elda
Published: August 2018

Background: It is accepted that the gold price impacts on the value of gold mining companies. Previous studies have shown that, in financial crises, gold is considered a ‘safe haven’ investment in developed markets. Aim: The aim of the study is to investigate whether an investment in gold mining stocks do provide gold price-linked safe haven benefits to investors in an emerging economy. An understanding of the possible safe haven benefits of their companies’ stocks and the variables that influence these benefits would be valuable to managers of gold companies when endeavouring to maximise shareholders’ wealth through hedging and investment decisions. Methods: Regression analysis is applied to investigate the relationship between gold mining returns, the gold price and the rand–dollar exchange rate within a multifactor model motivated by the arbitrage pricing theory. Results: The results indicate that there is a strong, yet changing, relationship between the gold price, the rand–dollar exchange rate and gold mining returns. Conclusion: This study extends the understanding of the changing South African gold mining industry in a world that is still recovering from the global financial crisis.
2-3 пути на графе-решетке. Случайные блуждания
Authors: Erusalimskyi Iakov Michailovich
Published: August 2018

В работе рассмотрен граф-решетка с 2-3 ограничениями на достижимость.
Он имеет вершины в точках плоскости с неотрицательными целочисленными
координатами. Из каждой вершины выходит две дуги: горизонтальная -
в ближайшую правую вершину и вертикальная - в ближайшую верхнюю вершину.
Допустимыми путями в случае 2-3 достижимости являются пути, удовлетворяющие
дополнительному условию делимости на 2 количества дуг в максимальных
по вложению отрезках путей, состоящих только из горизонтальных дуг
и делимости на 3 количеств дуг в максимальных по вложению отрезках путей,
состоящих только из вертикальных дуг. Это ограничение не распространяется
на заключительные отрезки путей. Получена формула для количества 2-3 путей,
ведущих из вершины в вершину. Рассмотрен процесс случайного блуждания
по 2-3 путям на графе-решетке. Показано, что он локально сводим
к Марковскому процессу на подграфах, определяемых типом начальной вершины.
Получены формулы для нахождения вероятностей перехода из вершины в вершину
по 2-3 путям.
Библиография: 22 названия.
О гранд-пространствах и малых пространствах Бергмана
Authors: Karapetyants Alexey Nikolaevich , Samko Stefan Grigor'evich
Published: August 2018

Вводятся гранд-пространства и малые пространства Бергмана голоморфных функций
на единичном диске. Доказана ограниченность проектора Бергмана в гранд-пространствах
Бергмана. Главный результат - оценки для функций в гранд- и малых пространствах
Бергмана вблизи границы, которые отличаются от оценок в случае классического
пространства Бергмана на логарифмический множитель с положительным
(для гранд-пространства) или отрицательным (для малого пространства)
показателем.
Библиография: 19 названий.
Итерационные интегральные операторы на конусе монотонных
функций
Authors: Stepanov Vladimir Dmitrievich , Shambilova Gul'dar'ya Ermakovna
Published: August 2018

В работе представлены критерии ограниченности сублинейных
интегральных двухъядерных операторов итерационного типа
на конусах монотонных функций пространств Лебега на
вещественной полуоси.
Библиография: 10 названий.
Malformações congênitas do sistema nervoso como causa de mortalidade infantil no estado do Pará no período de 2007 a 2016
Authors: Neves Dilma Costa de Oliveira , Pereira Angela Regina Rosa Correa , Melo Lorena Oliveira Silva de , Leandro Melissa Nunes
Published: August 2018

Objetivo: Analisar a ocorrência das malformações congênitas do sistema nervoso como causa de mortalidade infantil no Estado do Pará no período de 2007 a 2016. Método: Estudo descritivo-quantitativo-ecológico realizado no Departamento de Epidemiologia da Secretaria de Saúde do Estado do Pará. Foram incluídos os registros de crianças nascidas de mães residentes no Estado do Pará e que faleceram com menos de 1 ano, tendo como causa básica ou consequencial a malformação congênita do sistema nervoso. Resultados: Os óbitos por malformações congênitas, deformidades e anomalias cromossômicas representaram 17,3% (4.219) do total dos óbitos em menores de 1 ano e dentre estes aqueles decorrentes das malformações congênitas do sistema nervoso constituem 21,3% (900). A taxa média de mortalidade infantil para o período foi de 17,2 óbitos em cada 1000 nascidos vivos e a taxa por malformações congênitas do sistema nervoso contribuiu com aproximadamente 3,5%. Dentre as principais malformações congênitas do sistema nervoso encontrou-se a hidrocefalia congênita (32,5%), anencefalia e malformações similares (25,9%), outras malformações congênitas do cérebro (17,2%), e a microcefalia (6,4%). A sobrevida dessas crianças no primeiro ano de vida foi 10,2%. Conclusão: A análise das características do obituário por malformações congênitas do sistema nervoso no Estado do Pará permite identificar a fragilidade do planejamento reprodutivo e do pré-natal na prevenção dessas malformações, assim como a necessidade de implementar cuidados que possibilitem uma maior sobrevida dessas crianças e o apoio tanto para elas quanto para seus familiares.
Dilemas e frustrações do estudante de medicina
Authors: Feijó Daniel Haber , Mainardi Carolina Ribeiro , Valente André Lopes , Yamaki Vitor Nagai , Teixeira Renan Kleber Costa , Silva José Antônio Cordero da
Published: August 2018

Introdução: O período da graduação no curso de medicina é fundamental para a construção científica, psicológica e ética do futuro médico. O aluno passa por muitas mudanças, que podem ter consequências catastróficas se não houver adequada condução do aluno por parte da docência. Assim buscou-se identificar os dilemas e frustrações do estudante de medicina. Método: Foi realizado um estudo transversal nos estudantes de medicina do 1º o 4º ano da Universidade do Estado do Pará. Foram entrevistados 100 alunos divididos igualmente por cada ano do curso, por meio de questionário autoaplicável para avaliar os dilemas e frustações do estudante de medicina. Resultados: 95% dos alunos foram classificados com algum grau de frustração com o curso de medicina. Dentre as queixas mais comuns encontramos o desânimo com o curso (93%), decepção (76%), falta de orientação pelos professores (97%) e sobrecarga (97%). Foi encontrado um aumento do consumo de álcool e tabaco conforme os estudantes avançam no curso. Discussão: A frustração com o curso de medicina foi evidente nesta pesquisa, independente de fatores como sexo, idade, uso de drogas ou doenças, iniciando em períodos precoces do curso. O desânimo com a faculdade tem sido associado ao desenvolvimento de cinismo, pessimismo e burnout profissional. Conclusão: Os estudantes de medicina mostraram-se frustrados com o curso, sendo os principais dilemas a falta de orientação por parte dos professores e a sobrecarga de atividades acadêmicas
Evidence for pyrazine-based chromophores in cloud water mimics containing methylglyoxal and ammonium sulfate
Authors: Hawkins Lelia Nahid , Welsh Hannah G. , Alexander Matthew V.
Published: August 2018

Abstract. Simulating aqueous brown carbon (aqBrC) formation from small molecule amines and aldehydes in cloud water mimics provides insight into potential humic-like substance (HULIS) contributors and their effect on local and global aerosol radiative forcing. Previous work has shown that these (Maillard type) reactions generate products that are chemically, physically, and optically similar to atmospheric HULIS in many significant ways, including in their complexity. Despite numerous characterization studies, attribution of the intense brown color of many aqBrC systems to specific compounds remains incomplete. In this work, we present evidence of novel pyrazine-based chromophores (PBCs) in the product mixture of aqueous solutions containing methylglyoxal and ammonium sulfate. PBCs observed here include 2,5-dimethyl pyrazine (DMP) and products of methylglyoxal addition to the pyrazine ring. This finding is significant as the literature of Maillard reactions in food chemistry tightly links the formation of pyrazine (and related compounds) to browning in foods. We investigated the roles of both cloud processing (by bulk evaporation) and pH in absorptivity and product distribution in microliter samples to understand the contribution of these PBCs to aqBrC properties. In agreement with previous work, we observed elevated absorptivity across the entire UV–visible spectrum following simulated cloud processing as well as higher absorptivity in more basic samples. Absorptivity of the pH 2 sample, following evaporation over a period of days, exceeded that of the unevaporated pH 9 sample. In addition, mixtures of ammonium sulfate and methylglyoxal at pH 5 that were dried in under 1 h and analyzed 24 h later were as absorptive as pH 9 samples allowed to react for 7 days, indicating that evaporation occurring during cloud processing may provide a reaction pathway favorable for carbonyl–ammonia chemistry even under acidic conditions of aerosol and cloud water. The fraction of pyrazine compounds in the product mixture increased by up to a factor of 4 in response to drying with a maximum observed contribution of 16 % at pH 5. Therefore, cloud processing under acidic conditions may produce PBCs at the expense of imine- and imidazole-derived compounds. This finding has implications for further BrC reactivity and degradation pathways.
Cloud droplet activation of black carbon particles coated with organic compounds of varying solubility
Authors: Dalirian Maryam , Ylisirniö Arttu , Buchholz Angela , Schlesinger Daniel , Ström Johan , Virtanen Annele , Riipinen Ilona
Published: August 2018

Abstract. Atmospheric black carbon (BC) particles are a concern due to their impact on
air quality and climate. Their net climate effect is, however, still
uncertain. This uncertainty is partly related to the contribution of coated
BC particles to the global cloud condensation nuclei (CCN) budgets. In this study, laboratory
measurements were performed to investigate CCN
activity of BC (REGAL 400R pigment black) particles, in pure state or coated through
evaporating and subsequent condensation of glutaric acid, levoglucosan (both
water-soluble organics) or oleic acid (an organic compound with low
solubility). A combination of soot particle aerosol mass spectrometer
(SP-AMS) measurements and size distribution measurements with a scanning
mobility particle sizer (SMPS) showed that the studied BC particles were
nearly spherical agglomerates with a fractal dimension of 2.79 and that they
were coated evenly by the organic species. The CCN activity of BC particles
increased after coating with all the studied compounds and was governed by
the fraction of organic material. The CCN activation of the BC particles
coated by glutaric acid and levoglucosan were in good agreement with the
theoretical calculations using the shell-and-core model, which is based on a
combination of the CCN activities of the pure compounds. The oleic acid
coating enhanced the CCN activity of the BC particles, even though the pure
oleic acid particles were CCN inactive. The surprising effect of oleic acid
might be related to the arrangement of the oleic acid molecules on the
surface of the BC cores or other surface phenomena facilitating water
condensation onto the coated particles. Our results show that present
theories have potential for accurately predicting the CCN activity of
atmospheric BC coated with organic species, given that the identities and
amounts of the coating species are known. Furthermore, our results suggest
that even relatively thin soluble coatings (around 2 nm for the compounds
studied here) are enough to make the insoluble BC particles CCN active at
typical atmospheric supersaturations and thus be efficiently taken up by
cloud droplets. This highlights the need for an accurate description of the
composition of atmospheric particles containing BC to unravel their net
impact on climate.
Cloud-droplet growth due to supersaturation fluctuations in stratiform clouds
Authors: Li Xiang-Yu , Svensson Gunilla , Brandenburg Axel , Haugen Nils E. L.
Published: August 2018

Abstract. Condensational growth of cloud droplets due to supersaturation fluctuations is investigated by solving the hydrodynamic and thermodynamic equations using direct numerical simulations with droplets being modeled as Lagrangian particles. We find that the width of droplet size distributions increases with time, which is contrary to the classical theory without supersaturation fluctuations, where condensational growth leads to progressively narrower size distributions. Nevertheless, in agreement with earlier Lagrangian stochastic models of the condensational growth, the standard deviation of the surface area of droplets increases as t1/2. Also, we numerically confirm that the time evolution of the size distribution depends strongly on the Reynolds number and only weakly on the mean energy dissipation rate. This is shown to be due to the fact that temperature fluctuations and water vapor mixing ratio fluctuations increases with increasing Reynolds number, therefore the resulting supersaturation fluctuations are enhanced with increasing Reynolds number. Our simulations may explain the broadening of the size distribution in stratiform clouds qualitatively, where the updraft velocity is almost zero.
Evolutionary Characteristics of Lightning and Radar Echo Structure in Thunderstorms Based on the TRMM satellite
Authors: Wu Xueke , Yuan Tie , Jiang Rubin , Li Jinliang
Published: August 2018

Abstract. Based on the 16-years Tropical Rainfall Measuring Mission (TRMM) satellite observational data, the convective characteristics of thunderstorms over different topographic regions, as well as their radar echo structural and lightning activity, are analyzed. The results reveal that thunderstorms over the Tibetan Plateau have weak lightning frequency and small horizontal scale, but their occurrence frequency is the largest, accounting for ~ 20 % of total precipitation events, followed by 10 % over the adjacent foothills to the east and hilly land in southern China, with the lowest occurrence frequency (~ 3 %) over the ocean. The 30 dBZ echo top height is a good indicator to predict the occurrence probability of lightning in convective storm, which is more concise and intuitive than the 20 and 40 dBZ echo top heights. Integrating the ratio of convective rainfall to total rainfall and the three-dimensional radar echo structure features to identify thunderstorm life-cycle stages has been proved to be a useful method, and which can help us further explore and maximize the usage of the valuable convective event data from non-geostationary satellites. It is found that the development of dynamic process, which refers to radar echo vertical structure, precedes the lightning activity during the evolution of thunderstorms. Although both lightning activity and radar echo structure peaked at the mature stage, thunderstorms before reaching the mature stage are stronger in radar echo vertical structure while weaker in lightning activity, and vice versa after the mature stage. Even during the dissipating stage of thunderstorm, there still some lightning was observed.
Modelling of multi-lateral well geometries for geothermal applications
Authors: Peters Elisabeth , Blöcher Guido , Salimzadeh Saeed , Egberts Paul J. P. , Cacace Mauro
Published: August 2018

Abstract. Well inflow modelling in different numerical simulation
approaches are compared for a multi-lateral well. Specifically radial wells
will be investigated, which can be created using Radial Jet Drilling (RJD).
In this technique, powerful hydraulic jets are used to create small diameter
laterals (25–50 mm) of limited length (up to 100 m) from a well. The
laterals, also called radials, leave the backbone at a 90∘ angle. In
this study we compare three numerical simulators and a semi-analytical tool
for calculating inflow of a radial well. The numerical simulators are FE
approaches (CSMP and GOLEM) and an FV approach with explicit well model
(Eclipse®). A series of increasingly complex
well configurations is simulated, including one with inflow from a fault.
Although all simulators generally are reasonably close in terms of the total
well flow (deviations < 4 % for the homogeneous cases), the
distribution of the flow over the different parts of the well can vary
significantly. Also, the FE approaches are more sensitive to grid size when
the flow is dominated by radial flow to the well since they do not include a
dedicated well model. In the FE approaches, lower dimensional elements (1-D
for the well and 2-D for the faults) were superimposed into a 3-D space. In
case the flow is dominated by fracture flow, the results from the FV approach
in Eclipse deviates from the FE methods.
Spatial assessment of the distribution and potential of bioenergy resources in Kazakhstan
Authors: Koshim Asima , Karatayev Marat , Clarke Michèle L. , Nock William
Published: August 2018

Abstract. Kazakhstan is naturally rich in fossil fuels and its economy is strongly
linked to oil and gas exports. Significant coal reserves have led to an
energy mix that is dominated by aging and polluting thermal power plants. Yet
Kazakhstan comprises mainly grassland steppe where agriculture and livestock
pastoralism dominate offering the potential for cleaner, renewable energy
production from a range of agricultural and forestry wastes. Here we analyse
the spatial distribution and bioenergy generation potential of different
feedstocks using an ArcGIS platform and demonstrate a significant opportunity
for a range of bioenergy technologies. We recommend a number of policy
interventions to enable Kazakhstan to make a transition to cleaner, more
accessible and locally generated supply which is also sustainable and provide
a waste management solution.
A new scenario applying traffic flow analogy to poleward expansion of auroras
Authors: Saka Osuke
Published: August 2018

Abstract. An auroral ionosphere is generally incompressive and non-uniform medium with anisotropic conductivities. Compressibility may occur, however, following the onset of field line dipolarization. This behavior can happen when; (1) Westward directing electric fields transmitted from the dipolarization region accumulate both electrons and ions in equatorward latitudes in F region. (2) The mobility difference of electrons and ions in E region produces electrostatic potential in a quasi-neutral condition, positive in higher latitudes and negative in lower latitudes. (3) Density modulation in F region excites ion acoustic wave propagating along the field lines towards the magnetosphere. (4) The ion acoustic wave stops in the ionosphere for about 4 min because of a low phase velocity (~ 1.6 km/s). During this compressive interval, density accumulation in equatorward latitudes expands upstream to form a poleward expansion of auroras analogous to upstream propagation of a shock in traffic flow on crowded roads. Electrostatic potential produced in the E region generates field-aligned currents and closing Pedersen currents to retain electrostatic potential in a quasi-neutral ionosphere. The ion acoustic wave produces upward electric fields along the field lines in accordance with the Boltzmann relation which contributed to the ion upflow at topside ionosphere.
Basin-scale variability of microbial methanol uptake in the Atlantic Ocean
Authors: Sargeant Stephanie L. , Murrell J. Colin , Nightingale Philip D. , Dixon Joanna L.
Published: August 2018

Abstract. Methanol is a climate-active gas and the most abundant oxygenated volatile organic compound (OVOC) in the atmosphere and seawater. Marine methylotrophs are aerobic bacteria that utilise methanol from seawater as a source of carbon (assimilation) and/or energy (dissimilation). A few spatially limited studies have previously reported methanol oxidation rates in seawater; however, the basin-wide ubiquity of marine microbial methanol utilisation remains unknown. This study uniquely combines seawater 14C labelled methanol tracer studies with 16S rRNA pyrosequencing to investigate variability in microbial methanol dissimilation and known methanol-utilising bacteria throughout a meridional transect of the Atlantic Ocean between 47° N to 39° S. Microbial methanol dissimilation varied between 0.05 and 1.68 nmol L−1 h−1 in the top 200 m of the Atlantic Ocean and showed significant variability between biogeochemical provinces. The highest rates of methanol dissimilation were found in the northern subtropical gyre (average 0.99±0.41 nmol L−1 h−1), which were up to 8 times greater than other Atlantic regions. Microbial methanol dissimilation rates displayed a significant inverse correlation with heterotrophic bacterial production (determined using 3H-leucine). Despite significant depth stratification of bacterial communities, methanol dissimilation rates showed much greater variability between oceanic provinces compared to depth. There were no significant differences in rates between samples collected under light and dark environmental conditions. The variability in the numbers of SAR11 (16S rRNA gene sequences) were estimated to explain approximately 50 % of the changes in microbial methanol dissimilation rates. We estimate that SAR11 cells in the Atlantic Ocean account for between 0.3 % and 59 % of the rates of methanol dissimilation in Atlantic waters, compared to < 0.01 %–2.3 % for temperate coastal waters. These results make a substantial contribution to our current knowledge and understanding of the utilisation of methanol by marine microbial communities, but highlight the lack of understanding of in situ methanol production mechanisms.