bluuebunny/crossref_metadata_2025 huggingface dataset:
Predictors of Clinical Outcomes After Proximal Hamstring Repair
Authors: Bowman Eric N. , Marshall Nathan E. , Gerhardt Michael B. , Banffy Michael B.
Published: February 2019

Background:

Proximal hamstring avulsions cause considerable morbidity. Operative repair results in improved pain, function, and patient satisfaction; however, outcomes remain variable.

Purpose:

To evaluate the predictors of clinical outcomes after proximal hamstring repair.

Study Design:

Case series; Level of evidence, 4.

Methods:

We retrospectively reviewed proximal hamstring avulsions repaired between January 2014 and June 2017 with at least 1-year follow-up. Independent variables included patient demographics, medical comorbidities, tear characteristics, and repair technique. Primary outcome measures were the Single Assessment Numerical Evaluation (SANE), International Hip Outcome Tool–12 (iHOT-12), and Kerlan-Jobe Orthopaedic Clinic (KJOC) Athletic Hip score. Secondary outcome measures included satisfaction, visual analog scale for pain, Tegner score, and timing of return to sports.

Results:

Of 102 proximal hamstring repairs, 86 were eligible, 58 were enrolled and analyzed (67%), and patient-reported outcomes were available for 45 (52%), with a mean 29-month follow-up. The mean patient age was 51 years, and 57% were female. Acute tears accounted for 66%; 78% were complete avulsions. Open repair was performed on 90%. Overall satisfaction was 94%, although runners were less satisfied compared with other athletes ( P = .029). A majority of patients (88%) returned to sports by 7.6 months, on average, with 72% returning at the same level. Runners returned at 6.3 months, on average, but to the same level 50% of the time and at a decreased number of miles per week compared to nonrunners (15.7 vs 7.8, respectively; P < .001). Postoperatively, 78% had good/excellent SANE Activity scores, but the mean Tegner score decreased (from 5.5 to 5.1). Acute tears had higher SANE Activity scores. The mean iHOT-12 and KJOC scores were 99 and 77, respectively. Endoscopic repairs had equivalent outcome scores to open repairs, although conclusions were limited given the small number of patients in the endoscopic group. Greater satisfaction was noted in patients older than 50 years ( P = .024), although they were less likely to return to running ( P = .010).

Conclusion:

Overall, patient satisfaction and functionality were high. With the numbers available, we were unable to detect any significant differences in functional outcome scores based on patient age, sex, body mass index, smoking status, medical comorbidities, tear grade, activity level, or open versus endoscopic technique. Acute tears had better SANE Activity scores. Runners should be cautioned that they may be unable to return to the same preinjury activity level after proximal hamstring repair.

Clinical Relevance:

When counseling patients with proximal hamstring tears, runners and those with chronic tears should set appropriate expectations.
Who Counts as a Notable Sociologist on Wikipedia? Gender, Race, and the “Professor Test”
Authors: Adams Julia , Brückner Hannah , Naslund Cambria
Published: February 2019

This paper documents and estimates the extent of underrepresentation of women and people of color on the pages of Wikipedia devoted to contemporary American sociologists. In contrast to the demographic diversity of the discipline, sociologists represented on Wikipedia are largely white men. The gender and racial/ethnic gaps in likelihood of representation have exhibited little change over time. Using novel data, we estimate the “risk” of having a Wikipedia page for a sample of contemporary sociologists. We show that the observed differences (in academic rank, length of career, and notability measured with both H-index and departmental reputation) between men and women sociologists and whites and nonwhites, respectively, explain only about half of the differences in the likelihood of being represented on Wikipedia. The article also enumerates both supply- and demand-side mechanisms that may account for these continuing gaps in representation.
Randomized Trial of Silver Nitrate with Sodium Fluoride for Caries Arrest
Authors: Gao S.S. , Duangthip D. , Wong M.C.M. , Lo E.C.M. , Chu C.H.
Published: February 2019

Objectives:

The aim of this noninferiority double-blind randomized clinical trial was to compare the effectiveness of the topical semiannual application of a 25% silver nitrate (AgNO3) solution followed by a 5% sodium fluoride (NaF) varnish with that of a 38% silver diamine fluoride (SDF) solution in arresting caries among preschool children.

Methods:

Healthy 3-y-old children with active dentine carious lesions were randomly allocated to 2 groups via computer-generated random numbers. Lesions in group A received applications of a 25% AgNO3 solution followed by a 5% NaF varnish semiannually (every 6 mo). Lesions in group B received semiannual applications of a 38% SDF solution followed by a placebo varnish. A trained examiner recorded the status of caries and oral hygiene at baseline and during follow-up examinations. The examiner, children, and their caretakers were blinded to the intervention allocation. This study adopted an intention-to-treat analysis. A noninferiority test was conducted for the data analysis. Group A’s noninferiority was accepted if the lower limit of the 95% CI for the difference in the mean number of arrested surfaces was >−0.5.

Results:

A total of 1,070 children were recruited at baseline, with 535 children in each group. After 18 mo, the mean ± SD number of arrested surfaces was 3.3 ± 3.4 in group A (n = 484) and 3.2 ± 3.5 in group B (n = 476; P = 0.664). The difference in the mean number of arrested surfaces between the groups was 0.092 (95% CI, −0.322 to 0.505). Apart from black staining on the arrested lesions, no other significant side effect was observed.

Conclusion:

A semiannual application of 25% AgNO3 followed by 5% NaF is no worse than a 38% SDF in arresting dentine caries among preschool children over 18 mo. The Hong Kong Research Grants Council (GRF 17107315) funded this trial, which was registered at ClinicalTrials.gov (NCT02019160).

Knowledge Transfer Statement:

This randomized clinical trial found that silver nitrate solution followed by sodium fluoride varnish is effective in arresting dentine caries among preschool children. As silver nitrate followed by sodium fluoride is a noninvasive and simple protocol, it can be an alternative strategy to manage dental caries among young children, especially in countries where silver diamine fluoride is not available.
Is higher-quality land developed earlier?
Authors: Lopez Juan Carlos G , Arnott Richard J
Published: February 2019

Is higher-quality land developed earlier? To answer this question, the paper applies comparative static analysis to the Arnott–Lewis model of the transition of land from agricultural to urban use. It is shown that (i) an increase in agricultural fertility increases structural density and delays development; (ii) a decrease in land preparation cost reduces structural density and hastens development; and (iii) both an increase in amenities and a decrease in structure construction costs normally hasten but in anomalous cases can delay development.
A Comparison of the Types of Problems Encountered by Entrepreneurial Students and Successful Professional Entrepreneurs
Authors: Reeves Philip M. , Zappe Sarah E. , Follmer D. Jake
Published: February 2019

Research examining the similarities and differences between the types of problems that students enrolled in entrepreneurship courses encounter and the types of problems that successful entrepreneurs encounter when working on ventures is limited. Providing projects and activities that closely resemble real-world situations would likely increase the amount of knowledge and skills that students are able to transfer from school into the workforce. In this article, 7 successful professional entrepreneurs and 32 students enrolled in entrepreneurial classes were interviewed and asked to describe the problems that they encountered when working on projects. Fifteen different types of problems were classified based on the interviews. Entrepreneurs did not encounter three types of problems that students struggled with. Students encountered all but three of the same types of problems as entrepreneurs; but within these types of problems, there were some qualitative differences between the two groups. Implications and suggestions for improving courses and activities in entrepreneurship education are discussed.
Coexisting nanoscale phases of K-illite, NH4,K-illite and NH4-illite-smectite: an organic nitrogen contribution in the hydrothermal system of Harghita Bãi, East Carpathians, Romania
Authors: Bobos Iuliu
Published: February 2019

Nitrogen influx was identified in the Harghita Bãi area, where the mechanism of NH4+-fixation in illitic clays is relevant for the N-input budget estimation. The nanotextural features of K-illite (K-I), NH4,K-I and NH4-illite-smectite (NH4-I-S) mixed layers observed in argillic-altered andesitic rocks from the hydrothermal area of Harghita Bãi (East Carpathians) were studied by X-ray diffraction, infrared spectroscopy and transmission and analytical electron microscopy (TEM-AEM). The texture of undisturbed argillic-altered andesite rocks exhibits chaotic intergrowths of randomly oriented and curved illitic packets with abundant pore spaces and high porosity between packets. The TEM images of K-I and NH4,K-I intergrowths show subparallel packets with clear contacts, exhibiting a diffuse contrast across layers. The thicknesses of K-I and NH4,K-I packets range from 150 to 500 Å, and 1Md and 1M polytypes were identified by selected area electron diffraction patterns. Crystal chemistry of K-I, NH4,K-I and NH4-I-S was carried out by AEM. A third interlayer cation Na+ beside K+ was detected in several NH4,K-I packets. The NH4,Na,K-I packets interleaved with NH4,K-I or NH4-I-S (12% smectite layers) packets were also identified by TEM. The thicknesses of NH4,Na,K-I packets range from 300 to 1200 Å, with abundant lenses and lenticular layer separation along the boundaries between them. The 1Md polytype dominates the NH4,Na,K-I packets. Straight and parallel packets, continuous 00l layers and collapsed swelling layers at the boundary of individual NH4-I (5% smectite layers) packets with thicknesses ranging from 20 to 95 Å were observed. The nanotextural observations indicate direct crystallization of NH4-I crystals within a NH4-I-S series from a pore fluid, where NH4-I packets occupy void spaces previously occupied by fluids.
Characterization and treatment of congenital thrombotic thrombocytopenic purpura
Authors: Alwan Ferras , Vendramin Chiara , Liesner Ri , Clark Amanda , Lester William , Dutt Tina , Thomas William , Gooding Richard , Biss Tina , Watson H. G. , Cooper Nichola , Rayment Rachel , Cranfield Tanya , van Veen Joost J. , Hill Quentin A. , Davis Sarah , Motwani Jayashree , Bhatnagar Neha , Priddee Nicole , David Marianna , Crowley Maeve P. , Alamelu Jayanthi , Lyall Hamish , Westwood John-Paul , Thomas Mari , Scully Marie
Published: February 2019

Congenital thrombotic thrombocytopenic purpura (cTTP) is an ultra-rare thrombomicroangiopathy caused by an inherited deficiency of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13). There are limited data on genotype-phenotype correlation; there is no consensus on treatment. We reviewed the largest cohort of cTTP cases, diagnosed in the United Kingdom, over the past 15 years. Seventy-three cases of cTTP were diagnosed, confirmed by genetic analysis. Ninety-three percent were alive at the time of review. Thirty-six percent had homozygous mutations; 64% had compound heterozygous mutations. Two presentation peaks were seen: childhood (median diagnosis age, 3.5 years) and adulthood, typically related to pregnancy (median diagnosis age, 31 years). Genetic mutations differed by age of onset with prespacer mutations more likely to be associated with childhood onset (P = .0011). Sixty-nine percent of adult presentations were associated with pregnancy. Fresh-frozen plasma (FFP) and intermediate purity factor VIII concentrate were used as treatment. Eighty-eight percent of patients with normal blood counts, but with headaches, lethargy, or abdominal pain, reported symptom resolution with prophylactic therapy. The most common currently used regimen of 3-weekly FFP proved insufficient for 70% of patients and weekly or fortnightly infusions were required. Stroke incidence was significantly reduced in patients receiving prophylactic therapy (2% vs 17%; P = .04). Long-term, there is a risk of end-organ damage, seen in 75% of patients with late diagnosis of cTTP. In conclusion, prespacer mutations are associated with earlier development of cTTP symptoms. Prophylactic ADAMTS13 replacement decreases the risk of end-organ damage such as ischemic stroke and resolved previously unrecognized symptoms in patients with nonovert disease.
PD-L1 and tumor-associated macrophages in de novo DLBCL
Authors: McCord Ronald , Bolen Christopher R. , Koeppen Hartmut , Kadel Edward E. , Oestergaard Mikkel Z. , Nielsen Tina , Sehn Laurie H. , Venstrom Jeffrey M.
Published: February 2019

Programmed death-ligand 1 (PD-L1) and its receptor, programmed cell death-1 (PD-1), are important negative regulators of immune cell activation. Therapeutically targeting PD-1/PD-L1 in diffuse large B-cell lymphoma (DLBCL) patients with a single agent has limited activity, meriting a deeper understanding of this complex biology and of available PD-L1 clinical assays. In this study, we leveraged 2 large de novo DLBCL phase 3 trials (GOYA and MAIN) to better understand the biologic and clinical relevance of PD-L1 in de novo DLBCL. PD-L1 was expressed on myeloid cells in 85% to 95% of DLBCL patients (depending on staining procedure), compared with 10% on tumor cells, and correlated with macrophage gene expression. PD-L1 did not identify high-risk patients in de novo DLBCL; it correlated with STAT3, macrophage gene expression, and improved outcomes among a subset of patients. These results may help identify immunologically distinct DLBCL subsets relevant for checkpoint blockade. GOYA and MAIN trials were registered at www.clinicaltrials.gov as #NCT01287741 and #NCT00486759, respectively.
RETRACTED ARTICLE: Exosomes from glioma cells induce a
tumor-like phenotype in mesenchymal stem cells by activating glycolysis
Authors: Ma Zhanjun , Cui Xue , Lu Li , Chen Guohu , Yang Yang , Hu Yan , Lu Yubao , Cao Zhangqi , Wang Yan , Wang Xuexi
Published: February 2019

Background

Exosomes are nanoscale membrane vesicles secreted by both normal and
cancer cells, and cancer cell-derived exosomes play an important role in the
cross-talk between cancer cells and other cellular components in the tumor
microenvironment. Mesenchymal stem cells (MSCs) have tropism for tumors and have
been used as tumor-tropic vectors for tumor therapy; however, the safety of such
therapeutic use of MSCs is unknown. In this study, we investigated the role of
glioma cell-derived exosomes in the tumor-like phenotype transformation of human
bone marrow mesenchymal stem cells (hBMSCs) and explored the underlying molecular
mechanisms.

Methods

The effect of exosomes from U251 glioma cells on the growth of
hBMSCs was evaluated with the CCK-8 assay, KI67 staining, and a cell cycle
distribution assessment. The migration and invasion of hBMSCs were evaluated with
a Transwell assay. A proteomics and bioinformatics approach, together with Western
blotting and reverse transcriptase-polymerase chain reaction, was used to
investigate the effect of U251 cell-derived exosomes on the proteome of
hBMSCs.

Results

U251 cell-derived exosomes induced a tumor-like phenotype in hBMSCs
by enhancing their proliferation, migration, and invasion and altering the
production of proteins involved in the regulation of the cell cycle. Moreover,
U251 cell-derived exosomes promoted the production of the metastasis-related
proteins MMP-2 and MMP-9, glioma marker GFAP, and CSC markers (CD133 and Nestin).
The ten differentially expressed proteins identified participated in several
biological processes and exhibited various molecular functions, mainly related to
the inactivation of glycolysis. Western blotting showed that U251 cell-derived
exosomes upregulated the levels of Glut-1, HK-2, and PKM-2, leading to the
induction of glucose consumption and generation of lactate and ATP. Treatment with
2-deoxy-d-glucose significantly reversed
these effects of U251 cell-derived exosomes on hBMSCs.

Conclusions

Our data demonstrate that glioma cell-derived exosomes activate
glycolysis in hBMSCs, resulting in their tumor-like phenotype transformation. This
suggests that interfering with the interaction between exosomes and hBMSCs in the
tumor microenvironment has potential as a therapeutic approach for glioma.

Graphical abstract

ᅟ
Seismic vertical transversely isotropic parameter inversion from P- and S-wave cross-borehole measurements in an aquifer environment
Authors: von Ketelhodt Julius K. , Manzi Musa S. D. , Durrheim Raymond J. , Fechner Thomas
Published: February 2019

Joint P- and S-wave measurements for tomographic cross-borehole analysis can offer more reliable interpretational insight concerning lithologic and geotechnical parameter variations compared with P-wave measurements on their own. However, anisotropy can have a large influence on S-wave measurements, with the S-wave splitting into two modes. We have developed an inversion for parameters of transversely isotropic with a vertical symmetry axis (VTI) media. Our inversion is based on the traveltime perturbation equation, using cross-gradient constraints to ensure structural similarity for the resulting VTI parameters. We first determine the inversion on a synthetic data set consisting of P-waves and vertically and horizontally polarized S-waves. Subsequently, we evaluate inversion results for a data set comprising jointly measured P-waves and vertically and horizontally polarized S-waves that were acquired in a near-surface ([Formula: see text]) aquifer environment (the Safira research site, Germany). The inverted models indicate that the anisotropy parameters [Formula: see text] and [Formula: see text] are close to zero, with no P-wave anisotropy present. A high [Formula: see text] ratio of up to nine causes considerable SV-wave anisotropy despite the low magnitudes for [Formula: see text] and [Formula: see text]. The SH-wave anisotropy parameter [Formula: see text] is estimated to be between 0.05 and 0.15 in the clay and lignite seams. The S-wave splitting is confirmed by polarization analysis prior to the inversion. The results suggest that S-wave anisotropy may be more severe than P-wave anisotropy in near-surface environments and should be taken into account when interpreting cross-borehole S-wave data.
EPCI: A new tool for predicting absolute permeability from computed tomography images
Authors: Sun Huafeng , Al-Marzouqi Hasan , Vega Sandra
Published: February 2019

We have developed a new and fast MATLAB algorithm for predicting absolute permeability. The developed tool relies on measuring the connectivity of pores in a given 3D microcomputed tomography rock image. An index of pore connectivity is evaluated. After a calibration step, the developed index is used to estimate permeability in a variety of rocks with challenging pore structures (e.g., complex carbonate formations). The developed algorithm was tested on sandstone and carbonate rock samples. It offers large computational and memory savings when compared with algorithms based on the lattice Boltzmann method. Permeability estimates were, in general, in good agreement with laboratory measurements and numerical simulation results.
Application of Circulating Cell-Free Tumor DNA Profiles for Therapeutic Monitoring and Outcome Prediction in Genetically Heterogeneous Metastatic Melanoma
Authors: Váraljai Renáta , Wistuba-Hamprecht Kilian , Seremet Teofila , Diaz Joey Mark S. , Nsengimana Jérémie , Sucker Antje , Griewank Klaus , Placke Jan-Malte , Horn Peter A. , von Neuhoff Nils , Shannan Batool , Chauvistré Heike , Vogel Felix C. E. , Horn Susanne , Becker Jürgen C. , Newton-Bishop Julia , Stang Andreas , Neyns Bart , Weide Benjamin , Schadendorf Dirk , Roesch Alexander
Published: February 2019

PURPOSE

Circulating cell-free tumor DNA (ctDNA) reflects the heterogeneous spectrum of tumor-specific mutations, especially in systemic disease. We validated plasma-based assays that allow the dynamic quantitative detection of ctDNA as a prognostic biomarker for tumor load and prediction of therapy response in melanoma.

MATERIALS and METHODS

We analyzed plasma-derived ctDNA from a large training cohort (n = 96) of patients with advanced-stage melanoma, with assays for the BRAFV600Eand NRASQ61driver mutations as well as TERTC250Tand TERTC228Tpromoter mutations. An independent patient cohort (n = 35) was used to validate the utility of ctDNA monitoring under mitogen-activated protein kinase–targeted or immune checkpoint therapies.

RESULTS

Elevated plasma ctDNA level at baseline was an independent prognostic factor of disease progression when compared with serum S100 and lactate dehydrogenase levels in multivariable analyses (hazard ratio [HR], 7.43; 95% CI, 1.01 to 55.19; P = .05). The change in ctDNA levels during therapy correlated with treatment response, where increasing ctDNA was predictive for shorter progression-free survival (eg, for BRAFV600EctDNA, HR, 3.70; 95% CI, 1.86 to 7.34; P < .001). Increasing ctDNA levels predicted disease progression significantly earlier than did routine radiologic scans ( P < .05), with a mean lead time of 3.5 months. NRAS-mutant ctDNA was detected in a significant proportion of patients with BRAF-mutant tumors under therapy, but unexpectedly also at baseline. In vitro sensitivity studies suggested that this represents higher-than-expected intratumoral heterogeneity. The detection of NRASQ61ctDNA in baseline samples of patients with BRAFV600Emutation who were treated with mitogen-activated protein kinase inhibitors significantly correlated with shorter progression-free survival (HR, 3.18; 95% CI, 1.31 to 7.68; P = .03) and shorter overall survival (HR, 4.08; 95% CI, 1.57 to 10.58; P = .01).

CONCLUSION

Our results show the potential role of ctDNA measurement as a sensitive monitoring and prediction tool for the early assessment of disease progression and therapeutic response in patients with metastatic melanoma.
Computer Vision for Fault Detection in Aluminum Castings
Authors: Mery Domingo
Published: February 2019

Castings produced for the automotive industry are considered the important components for overall roadworthiness. To ensure the safety of construction, it is necessary to check every part thoroughly using nondestructive testing. X-ray testing rapidly became the accepted way for controlling the quality of die cast pieces. In this article, the fundamental principles of the automated detection of casting discontinuities are explained. A general computer vision inspection schema is presented, and several methods that have appeared in the literature in the past 30 years were explained showing the development of this sector in the areas of industry and academia.
Microstructure of Al-Cu, Al-Zn, Al-Ag-Zn, and Al-Zn-Mg Alloys
Authors: Skoko Željko , Popović Stanko
Published: February 2019

The precipitation phenomena and their connection with the microstructure of several Al alloys (Al-Cu, Al-Zn, Al-Ag-Zn, Al-Zn-Mg) are described with respect to the concentration and applied thermal treatment. The alloys were rapidly quenched or slowly cooled from a temperature higher than the solid solution temperature to room temperature. Both quenched-aged and slowly cooled alloys were heated from room temperature to the solid solution state and cooled back to room temperature, and their microstructure and precipitation phenomena were followed in situ by X-ray powder diffraction, e.g., anisotropy of thermal expansion, phase transitions, thermal hysteresis in phase transitions, change of precipitate shape, partial or complete dissolution of precipitates in the matrix, and formation of solid solution. It has been shown that the microstructure strongly depends on the previous thermal history of the alloys.
Precipitation in Al–Mg–Si Alloys: Modeling
Authors: Bahrami Abbas , Mehr Maryam Yazdan , Mousavi Anijdan Seyyed Hashem
Published: February 2019

Different approaches for modeling of precipitation in Al–Mg–Si alloys are reviewed. First of all, the importance of a precipitation modeling and its interrelations with other components in a process model are explained. Then the empirical, statistical, and physically based modeling, with each being a different modeling approach, are introduced. The Kampmann–Wagner numerical (KWN) model, which is a physically based finite difference method, is explained as a model that is able to capture simultaneous nucleation, growth, and coarsening reactions. The growth kinetics in the KWN model is based on the assumption of local equilibrium hypothesis, inferring that there is an immediate thermodynamic equilibrium as soon as two phases are in contact. This assumption implies the diffusion-controlled nature of the transformation. The other extreme approach is the assumption of interface-controlled growth, where the interface reaction (atom transport across the interface) controls the kinetics. In reality, neither of these scenarios can be absolutely true. A modified version of KWN model such that the growth can be treated with a mixed-mode nature (neither pure diffusion-controlled nor pure interface-controlled) is introduced. How the geometry of precipitates can be incorporated into the precipitation model is also explained.
Hipping Evaluation in Cast Aluminum Alloys: Quality Index-Based Approach
Authors: Nageswara Rao M. , Dhineshbabu G. , Sibal Prateek
Published: February 2019

Cast aluminum alloys find widespread application in the automotive and aircraft industries on account of their good castability, corrosion resistance, and high strength to weight ratio. Use of quality indices to rank cast aluminum alloys in terms of their quality has been in vogue since 1980s. Quality indices enable design engineers to select appropriate alloy condition by comparing the changes in quality with the changes in processing parameters like aging temperature and aging time. They also enable design engineers to select an appropriate alloy by way of comparing the quality obtainable with different alloy compositions. The present article highlights the effect of hot isostatic pressing (Hipping) on the quality of cast aluminum alloy 354 by using quality indices Q0, Q, and QC put forth in published literature. It has been observed that material in Hipped condition has higher value of these indices as compared to non-Hipped condition. This behavior is consistent across different aging conditions of the alloy. It is concluded that improvement accruing through Hipping of cast aluminum alloy 354 can be satisfactorily rated by using these quality indices.
Electrical Resistivity of Al-Cast Alloys in the Range of Solidification
Authors: Petri Mitja , Medved Jožef , Kastelic Sebastjan , Vončina Maja , Mrvar Primož
Published: February 2019

The aim of this paper is to explain the electrical resistivity change during solidification and connect it with the thermal analysis and solidification course. The problem at conducting the “in situ” measurement by four-point technique is the electrode material, which often oxidizes during measurements causing high contact resistance and providing incorrect results. Various materials were tested and aluminum electrodes chosen. The advantage of aluminum electrodes is that they melt within the specimen immediately after being poured and cause no interface resulting with any contact resistance. Pure aluminum, hypoeutectic alloy AlSi7Mg, and eutectic AlSi12 alloys were tested. Resistivity of Al–Si alloys is increasing with Si content. Grain refinement and modification of βSi were employed. Grain refinement has any effect on electrical resistivity. Modification of βSi phase causes decrease of electrical resistivity. The electrical resistivity curves give information similar as cooling curves from thermal analysis measurements.
Metallography of Aluminum Alloys: Atlas of Microstructures
Authors: Narayana Murty S.V.S. , Manwatkar Sushant K. , Narayanan P. Ramesh
Published: February 2019

Microstructure plays an important role in obtaining the desired properties in metallic materials in general and aluminum alloys in particular. Mechanical properties of aluminum alloys can be significantly altered by changing the microstructure. No other alloy system can boast of as many temper conditions as aluminum alloys. With the progress in the understanding of microstructure–mechanical property relationships in these materials, “tailor made” alloys to meet specific demands are being industrially developed. The broad spectrum of aluminum alloys in wide range of temper conditions offer materials with widely varying mechanical properties for structural designers. In order to select aluminum alloys with the desired properties for the intended application, it is essential to understand the role of microstructure under actual service conditions. It is in this context “Metallography of aluminum alloys” becomes very important. This chapter provides an insight in to the microstructural evolution of aluminum alloys from the as-cast condition to the final product. Typical examples of microstructural evolution in different aluminum alloys under various thermomechanical conditions are presented here. An atlas of microstructures of commercial and experimental wrought and cast aluminum alloys is presented in an appendix to this book. This appendix includes optical photomicrographs of both cast and wrought alloys and scanning electron micrographs of polished surfaces as well as fracture surfaces of various aluminum alloys as well as transmission electron micrographs as separate annexure. Readers are encouraged to go through the optical microstructures and fractographs along with this chapter for better understanding of the evolution of microstructure as a function of alloying additions, thermomechanical processing conditions, and fracture behavior under tension.
Welding Parameters for Aluminum Alloys
Authors: Meysam Haghshenas
Published: February 2019

With increasing application of aluminum and aluminum alloys, as the most commonly used nonferrous metallic alloys in industrial scales, joining and in particular welding of these alloys remains an important area for mechanical and welding engineers as well as manufacturers to gain broad and comprehensive knowledge of welding parameters of aluminum. This article presents a discussion about weldability and properties of different aluminum alloys before and after welding. To this end, welding of cast and wrought, and heat treatable and non-heat treatable aluminum alloys are assessed in detail in this article. Also, the challenges encountered with aluminum welding, different aluminum welding processes including conventional and solid-state welding techniques are discussed.
Ionic Liquids in Surface Protection of Aluminum and Its Alloys
Authors: Arias-Pardilla Joaquin , Espinosa Tulia , Sanes José , Jiménez Ana Eva , Martínez-Nicolás Ginés , Bérmudez María Dolores
Published: February 2019

Aluminum and its alloys are used in an increasing number of applications but the development of surface coatings and new techniques for corrosion resistance enhancement and for increasing wear resistance will be determinant for applications under aggressive environments. Ionic liquids have already found many industrial applications, including their use in surface protection. The present article will focus on the use of ionic liquids in aluminum and its alloys surface protection applications, including corrosion protection and inhibition, anodization and passivation processes, wear resistance, and potential applications of ionic liquid electrolytes in energy storage devices.
Tube Bending Forming Technologies: Advances and Trends
Authors: Heng Li , He Yang , Jun Ma
Published: February 2019

Bent tube parts have been widely used, as one kind of key components with enormous quantities and diversities, to satisfy the increasing demands for lightweight and high-performance products in broad industries such as aerospace, marine, automobile, energy, and health care. Tube bending is one of the key technologies used for manufacturing these lightweight products. The recent advances in tube bending are critically reviewed from four fundamental issues in tube bending, viz. characterization of tubular materials, prediction of multiple defects, bending formability, and innovative optimization design. Advantages and limitations of some recently developed innovative bending approaches are reviewed. Finally, considering the urgent requirements of more lightweight and high-performance bent tubes with hard-to-deform materials with complex structures, the development trends and corresponding challenges are thereafter presented for realizing the precision and high-efficiency tube bending.
Grain Refinement of Cast Aluminum by Heterogeneous Nucleation Sites
Authors: Watanabe Yoshimi , Sato Hisashi
Published: February 2019

Grain refinement plays a vital role in cast and wrought Al alloys. To achieve a grain refined cast microstructure, addition of Al-Ti, Al-Ti-B, and Al-Ti-C refiners has become a common industrial practice. The refiners introduce a large number of particles such as Al3Ti, TiB2, or TiC into the Al melt, and these particles act as heterogeneous nucleation sites for α-Al grains. In this article, some of the main theories of grain refining by refiners, and the crystal structure and shape of Al3Ti in Al-Ti refiner are briefly summarized to outline the physical aspects of grain refinement. Then, our results on grain refining performance of pure Al casts by equal-channel angular-pressed Al-11vol%Al3Ti refiner, cold-rolled Al-11vol%Al3Ti refiner, Al-10vol%Ti refiner, and Al-10vol% L12-type Al2.7Fe0.3Ti refiner will be described. Fragmentation behavior of Al3Ti platelets in Al-Ti refiner by friction stir processing is also presented.
Corrosion Protective Coatings: Fabrication of Sputtered CeO2-La2O3 and La2O3-CeO2 Bilayers
Authors: Miguel Antonio Domínguez-Crespo , Silvia Brachetti-Sibaja , Aidé Torres-Huerta , Edgar Onofre , Ana López-Oyama , Sandra Rodil
Published: February 2019

This entry provides a comparative study on the corrosion protection efficiency of Ce, La films as well as Ce/La- and La/Ce-bilayered coatings deposited onto AA7075 and AA6061 substrates by the radio frequency magnetron sputtering technique. The coating thickness ranged from ~12 to 835 nm, which changed with the deposition parameters and substrate composition. The relationship between microstructure, roughness, and electrochemical performance is examined. The reactivity and crystallinity of rare earth (RE) films can be tailored by adjusting the sputtering parameters. Sputtered La films with a thickness of ~390 nm and an average roughness of 66 nm showed the best corrosion protection properties in chloride medium as determined by potentiodynamic curves and electrochemical impedance spectroscopy. The method to obtain RE-bilayered coatings, i.e., La/Ce or Ce/La as well as the substrate composition and applied power, conditioned their inhibition properties. The RE-bilayered coatings displayed better barrier properties than Ce films, which were worser than those featured by La films.
Graphene-Reinforced Aluminum Matrix Nanocomposites: Structure and Properties
Authors: Yan S.J. , Chen Xiang , Hong Qihu , Wang Nan , Li Xiuhui , Zhao Shuangzan , Nan Wenzheng , Zhang Xiaoyan , Dai Shenglong , Lin Zuoming
Published: February 2019

Graphene materials with excellent mechanical and physical properties as well as two-dimensional flexible morphology are attractive reinforcement nanofillers for aluminum matrix nanocomposites. Rapid progress in graphene materials and nanocomposites fabricating technology promotes the development of advanced graphene-reinforced aluminum matrix nanocomposites for structural and functional applications. Nevertheless, the dispersion of graphene nanofillers within aluminum matrix and the interfacial controlling between them remain long-standing challenges in the fabrication of graphene-reinforced aluminum matrix nanocomposites. This article focuses on the recent development of the fabrication and characterization of graphene-reinforced aluminum matrix nanocomposites, including the dispersion and consolidation technology of graphene-reinforced aluminum matrix nanocomposites as well as their structural characters and mechanical behaviors.
Precipitation in AA2195 by Atom Probe Tomography and Transmission Electron Microscopy
Authors: Khushaim Muna
Published: February 2019

The transportation industries are constantly striving to achieve minimum weight to cut fuel consumption and improve overall performance. Different innovative design strategies have been placed and directed toward weight saving combined with good mechanical behavior. Among different materials, aluminum-based alloys play a key role in modern engineering and are widely used in construction components because of their lightweight and superior mechanical properties. Introduction of different nanostructure features can improve the service and the physical properties of such alloys. In this study, alloy AA2195 has been selected and characterized by means of transmission electron microscopy and atom probe tomography. Quantitative chemical analyses reveal that applying the rolling deformation on the specimen causes the uniform distribution of different platelet precipitates such as T1(Al2CuLi) and θ′(Al2Cu), which increases the hardening behavior of such alloys. Applying a plastic deformation on such alloys has been highlighted as an important engineering tool for the manipulation with second-phase precipitates in the microstructure. In this study, the findings of the characterization analysis were translated to construct a robust microstructure with an excellent hardness behavior (hardness value of 209 HV) by applying a low-energy consumption, cost-effective method.
Strength and Intergranular Corrosion of Aluminum Alloys: Effect of Cooling Rate
Authors: Kavalco Patricia Mariane , Canale Lauralice , Totten George
Published: February 2019

Although cooling rate and strength correlations for a wide range of quenching conditions are routinely discussed, cooling time–temperature data are shown less often. However, intergranular corrosion is also cooling rate and pathway dependent, but such data correlation is much less likely to be encountered, especially by commercial quenchant suppliers. Even cooling rate data, strength, intergranular corrosion, and either residual stress or distortion correlations are more rarely reported together. This entry discusses the mechanism of intergranular corrosion and provides an illustrative example of the dependence of intergranular corrosion on the cooling rate.
Microstructure and Yield Strength Evolution of Aluminum Alloys
Authors: Li Kai , Du Yong , Song Min
Published: February 2019

Aluminum alloys are light materials with high strength-to-weight ratio, corrosion resistance, and excellent formability. Due to these advantages, they are widely used in many industrial applications such as fabrication of aeroplanes, automobiles, ships, and architectural structures. Many fabrication parameters, such as alloy composition, casting and solidification conditions, strain rate, and ageing conditions, strongly affect the microstructural features such as morphology of phases, solute-dislocation interactions, as well as size and volume fraction of strengthening precipitates, and therefore determine the mechanical properties especially yield strength. This chapter probes microstructural optimization of aluminum alloys and the relationship between their microstructures and yield strength, with emphases on recent progress in microstructural modification of Al-Si alloys, yield strength modeling of dynamic strain ageing in Al-Mg alloys, and modeling of precipitate strengthening in Al-Mg-Si(-Cu) alloys.
Non-Heat Treatable Al-Alloys: Development of Intermetallic Particles during Solidification and Homogenization
Authors: Engler Olaf , Kuhnke Katrin , Hasenclever Jochen
Published: February 2019

The materials properties of Al-alloys are controlled by the added alloying elements and by the processing conditions through the resulting materials microstructure. An important aspect in the description of the microstructure is the constitution of the material in terms of alloying elements in solid solution and, in turn, volume, size, morphology, and species of second-phase particles. These constitutional characteristics, conveniently summarized as microchemistry, have an impact on physical properties like thermal or electrical conductivity and on mechanical properties including strength and formability of Al-alloys. In the present article, we summarize the phase selection upon solidification and the changes in microchemistry during subsequent homogenization annealing during conventional industrial processing of non-heat-treatable Al wrought alloys.
Microstructural Changes During Annealing of Aluminum Alloy: Modeling
Authors: Shabaniverki Soheila , Serajzadeh S.
Published: February 2019

Determination of microstructural events during heat treatment operations is an important task to obtain the desired microstructures and mechanical properties. Accordingly, during heat treatment of materials that have high stalking fault energy such as aluminum alloys, concurrent occurrence of recovery and recrystallization needs to be considered. On the other hand, the annealing processes may be performed under non-isothermal conditions in which a part of softening process is carried out during heating and/or cooling stage, particularly for the case of large-scale products. Thus, for estimation of softening fraction and microstructural events, different types of problems need to be taken into account such as the deformation analysis, the kinetics of metallurgical events, and heat conduction problem. In this entry, a combined analysis is discussed to manage the above-mentioned phenomena employing the finite element analysis together with cellular automata (CA) modeling. For this purpose, the distribution of plastic strain and the stored energy after cold rolling are determined utilizing finite element formulation, while they are considered as the initial conditions for the microstructural modeling. In the next stage, a two-dimensional CA coupled with a first-order equation is used to assess the softening rate, while a thermal finite element analysis is simultaneously employed to define temperature distribution during non-isothermal annealing. The model is then examined on softening behavior of cold-rolled AA1050 plate.
Extrudable Al-Si-Mg Alloys: Simulation of Microsegregation and Homogenization
Authors: Haidemenopoulos G.N. , Sarafoglou Panagiota
Published: February 2019

Extrudable Al-alloys of the 6xxx series are subjected to a homogenization treatment prior to extrusion in order to remove inhomogeneities generated during casting. Microsegregation of elements and phases is developed as a result of the solidification process. During homogenization, several phenomena take place such as the dissolution of various phases, the transformation of iron intermetallics, spheroidization of the remaining intermetallics, and reprecipitation during cooling. All these phenomena affect the extrudability of the material. An integrated simulation of microsegregation and homogenization is described. Microsegregation is simulated with the application of the Scheil-Gulliver model, employing computational thermodynamics. A Dual Grain Model has been developed for the simulation of homogenization, taking into account the variability of the grain size in the as-cast material. In this way, it is possible to simulate the dissolution of Mg2Si and the transformation of iron intermetallics concurrently. The results of the simulations provide a deeper understanding of the effects of processing on alloy microstructure and can be used toward the design of the homogenization process of extrudable Al-alloys.
Hot Stamping of Complex-Shaped High-Strength Aluminum Components
Authors: Wang Liliang , Liu Jun , Lin Jianguo
Published: February 2019

Aluminum alloy components are important contribution to lightweight transportations for improving energy efficiency. However, formability of aluminum alloys at room temperature often hinders their further applications in the automotive, rail, or aerospace industries. The solution heat treatment, forming, and in-die quenching (HFQ®) process is an advanced forming technology that performs both forming and heat treatment simultaneously in a single operation. Since its inception, a significant amount of research has been made on the process to develop it further and to assess the feasibility of using it to form components with increasingly complicated geometries, from a growing variety of alloys. This entry summarizes the HFQ® research work, with the emphasis on the development, modeling, and applications of the technology for stamping complex-shaped high-strength aluminum panel components.
Master Alloys for Grain Refinement
Authors: Wang Xiaoming
Published: February 2019

Master alloys are routinely added into aluminum melts before casting for grain refinement purposes. The widely used master alloys contain titanium and boron in the forms of Al3Ti and TiB2 particles in an aluminum matrix. Upon addition into aluminum melts, Al3Ti dissolves into the aluminum melts and promotes the heterogeneous nucleation of the α-Al grains while restricting the growth of α-Al grains through a constitutional cooling effect in solidification. Meanwhile, TiB2 is stable and acts as a substrate for the heterogeneous nucleation of α-Al grains through a layer of Al3Ti on the surface. Sharing these in common, different mechanisms for the grain refinement of aluminum by Al-Ti-B-type master alloys have been proposed. Another kind of popular master alloys is Al-Ti-C, which is used in a lesser extent for the grain refinement of Al alloys containing elements that are poisoning Al-Ti-B master alloys. Titanium and carbon exist as Al3Ti and TiC particles. TiC is not as stable as TiB2 and decomposes in aluminum melts. TiC in Al-Ti-C therefore acts as heterogeneous nucleation sites for α-Al grains similar to TiB2. However, the fading of Al-Ti-C master alloys is irreversible, which is the major disadvantage of Al-Ti-C master alloys. Al-Ti master alloys do not contain hard particles and are used industrially for products that are sensitive to hard TiB2 and TiC particles. There are also other master alloys that show high grain refinement potentials in lab tests but have never been used industrially for mainly low-volume production and high costs. This article gives an overview of the grain refinement of aluminum by master alloys with an emphasis on Al-Ti-B master alloys, from the production to the industrial applications of the master alloys.
Nanoparticle Aluminum Preparation
Authors: Venugopal Rao Soma , Muralidharan Krishnamurthi , Vargeese Anuj A.
Published: February 2019

An overview of recent developments in the synthesis of aluminum nanoparticles (Al NPs) and their applications in the field of energetic materials is presented. Various methods of preparing the Al NPs of different sizes including physical (laser ablation) and chemical methods are highlighted. Some of the results obtained by our group on the passivation of the Al NPs are highlighted. The laser ablation in liquids technique with ultrashort (picosecond and femtosecond) laser pulses is a green technique for preparing Al NPs devoid of any precursors, whereas the chemicals method yields passivated Al NPs. Among the various applications of the Al NPs, energetic applications are discussed in detail. This article is concluded by emphasizing the prospects of Al NPs in various energetic applications and the future of different techniques to synthesize them.