2,441 research outputs found
Mechanical Properties of Epoxy Composites Containing Carbon Black and Graphene
Epoxy composite has been widely used in various industrial applications due to its high strength. Nevertheless, its high strength causes it to fracture easily. Fillers are often added to improve its fracture toughness and other properties. In this work, epoxy composites containing carbon black (CB) and graphene have been synthesized to assess their mechanical properties. Series of analysis have been performed on composites containing single filler (CB or graphene) of various loadings to evaluate the values of Young’s Modulus, yield strength, and KIC. The results demonstrate an improvement in Young’s Modulus, yield strength, and KIC values by adding different carbon fillers, compared to neat epoxy. Based on these results, composites containing dual fillers are fabricated to understand the resultant synergistic effects. The hy-brid fillers show an increment in both fracture toughness and yield strength test for the epoxy composite with an optimum improvement at (3.0 wt.% CB + 0.1 wt.% Graphene) loading which is an increase of 256% in the values of Young’s Modulus, compared to neat epoxy. The addition of carbon fillers enhances the mechanical properties of epoxy composites, with dual fillers demonstrate the highest improve-ment, which could be due to the improvement in the dispersion degree
Energy Absorption at High Strain Rate of Magnesium Alloy AZ31B
This paper presents the efficient energy absorption of magnesium alloy AZ31B with reinforcement carbon nanotubes (CNT) and lead (Pb). The high specific energy absorption demonstrated by CNT compared to metals is one of the criteria to improve the AZ31B performance against ballistic penetration. More ductility by adding Pb in the alloy also plays a vital role to increase the energy absorption capability. Four-cylinder shape AZ31B-based specimens are tested dynamically by using compression Split Hopkinson Pressure Bar (SHPB). The diameter and thickness of the specimen is 18 mm and 12.5 mm respectively. The striking velocity used in this work is 20 m/s. By equation of 1D wave propagation, stress-strain curve is plotted and the area under the curve is equivalent to energy absorption. The highest energy absorption is about 270 kJ with the increment of 47% compared to original AZ31B. This increment is consistent with the higher strain rate experienced by the specimen during the test. The strain rate determined from the study is 1300 per second compared to original AZ31B of 850 per second. The finding of this paper is the presence of CNT and lead could improve the energy absorption performance as the strain rate of the specimen also increased
The role of the cooperative Jahn-Teller effect in the charge ordered La1-xCaxMnO3 (0.5<=x<=0.87) manganites
Based on the magnetoresistance, magnetization, ultrasound, and
crystallographic data, we studied the role of the cooperative Jahn-Teller
effect in the charge ordered (CO) state for La1-xCaxMnO3. We found that, with
increasing the fraction of Q3 mode of Jahn-Teller distortion and decreasing
that of Q2 mode in the CO state, the magnetic structure evolves from CE-type to
C-type and the orbital ordering changes from 3d(x2-r2)/3d(y2-r2)-type to
3d(x2-z2)-type, with the strength of ferromagnetism and the phase separation
tendency being suppressed. At the same time, the stability of the CO state and
the cooperative Jahn-Teller lattice distortion increase. These effects imply
that the cooperative Jahn-Teller effect with different vibration modes is the
key ingredient in understanding the essential physics of the CO state.Comment: 10 pages, 2 figures. To appear on Applied Physics Letter
The non-coding landscape of head and neck squamous cell carcinoma.
Head and neck squamous cell carcinoma (HNSCC) is an aggressive disease marked by frequent recurrence and metastasis and stagnant survival rates. To enhance molecular knowledge of HNSCC and define a non-coding RNA (ncRNA) landscape of the disease, we profiled the transcriptome-wide dysregulation of long non-coding RNA (lncRNA), microRNA (miRNA), and PIWI-interacting RNA (piRNA) using RNA-sequencing data from 422 HNSCC patients in The Cancer Genome Atlas (TCGA). 307 non-coding transcripts differentially expressed in HNSCC were significantly correlated with patient survival, and associated with mutations in TP53, CDKN2A, CASP8, PRDM9, and FBXW7 and copy number variations in chromosomes 3, 5, 7, and 18. We also observed widespread ncRNA correlation to concurrent TP53 and chromosome 3p loss, a compelling predictor of poor prognosis in HNSCCs. Three selected ncRNAs were additionally associated with tumor stage, HPV status, and other clinical characteristics, and modulation of their expression in vitro reveals differential regulation of genes involved in epithelial-mesenchymal transition and apoptotic response. This comprehensive characterization of the HNSCC non-coding transcriptome introduces new layers of understanding for the disease, and nominates a novel panel of transcripts with potential utility as prognostic markers or therapeutic targets
High energy pseudogap and its evolution with doping in Fe-based superconductors as revealed by optical spectroscopy
We report optical spectroscopic measurements on electron- and hole-doped
BaFe2As2. We show that the compounds in the normal state are not simple metals.
The optical conductivity spectra contain, in addition to the free carrier
response at low frequency, a temperature-dependent gap-like suppression at
rather high energy scale near 0.6 eV. This suppression evolves with the
As-Fe-As bond angle induced by electron- or hole-doping. Furthermore, the
feature becomes much weaker in the Fe-chalcogenide compounds. We elaborate that
the feature is caused by the strong Hund's rule coupling effect between the
itinerant electrons and localized electron moment arising from the multiple Fe
3d orbitals. Our experiments demonstrate the coexistence of itinerant and
localized electrons in iron-based compounds, which would then lead to a more
comprehensive picture about the metallic magnetism in the materials.Comment: 6 pages, 7 figure
A kinematic study of the compact jet in quasar B3 1633+382
We present a study of the motion of compact jet components in quasar B3
1633+382. Through analyzing 14 epochs of VLBI observations of three components
(B1, B2, and B3) at 22 GHz, we find two different possibilities of component
classification. Thus two corresponding kinematical models can be adopted to
explain the evolutionary track of components. One is a linear motion, while
another is a helical model. Future observations are needed to provide new
kinematical constraints for the motion of these components in this source.Comment: 7 pages, 3 figures; Accepted for publication in A&
Molecular and Clinical Findings in Patients With Knobloch Syndrome
IMPORTANCE: Knobloch syndrome is a rare, recessively inherited disorder classically characterized by high myopia, retinal detachment, and occipital encephalocele, but it is now known to have an increasingly variable phenotype. There is a lack of reported electrophysiologic data, and some key clinical features have yet to be described. OBJECTIVE: To expand on current clinical, electrophysiologic, and molecular genetic findings in Knobloch syndrome. DESIGN, SETTING AND PARTICIPANTS: Twelve patients from 7 families underwent full ophthalmic examination and retinal imaging. Further investigations included electroretinography and neuroradiologic imaging. Bidirectional Sanger sequencing of COL18A1 was performed with segregation on available relatives. The study was conducted from July 4, 2013, to October 5, 2015. Data analysis was performed from May 20, 2014, to November 3, 2015. MAIN OUTCOMES AND MEASURES: Results of ophthalmic and neuroradiologic assessment and sequence analysis of COL18A1. RESULTS: Of the 12 patients (6 males; mean age at last review, 16 years [range, 2-38 years]), all had high myopia in at least 1 eye and severely reduced vision. A sibling pair had unilateral high myopia in their right eyes and near emmetropia in their left eyes from infancy. Anterior segment abnormalities included absent iris crypts, iris transillumination, lens subluxation, and cataract. Two patients with iris transillumination had glaucoma. Fundus characteristics included abnormal collapsed vitreous, macular atrophy, and a tesselated fundus. Five patients had previous retinal detachment. Electroretinography revealed a cone-rod pattern of dysfunction in 8 patients, was severely reduced or undetectable in 2 patients, and demonstrated cone-rod dysfunction in 1 eye with undetectable responses in the other eye in 2 patients. Radiologic imaging demonstrated occipital encephalocele or meningocele in 3 patients, occipital skull defects in 4 patients, minor occipital changes in 2 patients, and no abnormalities in 2 patients. Cutaneous scalp changes were present in 5 patients. Systemic associations were identified in 8 patients, including learning difficulties, epilepsy, and congenital renal abnormalities. Biallelic mutations including 2 likely novel mutations in COL18A1, were identified in 6 families that were consistent with autosomal recessive inheritance with a single mutation identified in a family with 2 affected children. CONCLUSIONS AND RELEVANCE: This report describes new features in patients with Knobloch syndrome, including pigment dispersion syndrome and glaucoma as well as cone-rod dysfunction on electroretinography. Two patients had normal neuroradiologic findings, emphasizing that some affected individuals have isolated ocular disease. Awareness of the ocular phenotype may aid early diagnosis, appropriate genetic counseling, and monitoring for potential complications
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