The identification of ancient worked materials is one of the fundamental goals of lithic use wear analysis and one of the most important parts of understanding how stone tools were used in the past. ...Given the documented overlaps in wear patterns generated by different materials, it is imperative to understand how individual materials’ mechanical properties might influence wear formation. Because isolating physical parameters and measuring their change is necessary for such an endeavor, controlled (rather than replicative) experiments combined with objective measurements of surface topography are necessary to better grasp how surface modifications formed on stone tools. Therefore, we used a tribometer to wear natural flint surfaces against five materials (bone, antler, beech wood, spruce wood, and ivory) under the same force, and speed, over one, three, and five hours. The study aimed to test if there is a correlation between surface modifications and the hardness of the worked material. We measured each raw material’s hardness using a nano-indentation test, and we compared the surface texture of the flint bits using a 3D optical profilometer. The interfacial detritus powder was analyzed with a scanning electron microscope to look for abraded flint particles. We demonstrate that, contrary to expectation, softer materials, such as wood, create a smoother surface than hard ones, such as ivory.
Graphene-reinforced aluminum (Gr-Al) matrix nanocomposites (NCs) have attracted strong interest from both research and industry in high-performance weight-sensitive applications. Due to the vastly ...different bonding characteristics of the Al matrix (metallic) and graphene (in-plane covalent + inter-plane van der Waals), the graphene phase has a general tendency to agglomerate and phase separate in the metal matrix, which is detrimental for the mechanical and chemical properties of the composite. Thus, synthesis of Gr-Al NCs is extremely challenging. This review summarizes the different methods available to synthesize Gr-Al NCs and the resulting properties achieved in these NCs. Understanding the effect of processing parameters on the realized properties opens up the possibility of tailoring the synthesis methods to achieve the desired properties for a given application.
Polished edges of archaeological stone tools are commonly investigated to obtain information on the tools' uses in prehistory. Yet to this day, it remains unclear what exactly such polishes are and ...how they form. Answering these questions should allow the elaboration of new interpretative methods based on objective measurements. Two major competing hypotheses of polish formation have been proposed: abrasion and the formation of a thin amorphous film on the chert or flint surface. We employ reflectance infrared spectroscopy, a technique particularly sensitive to thin amorphous films, to investigate these two hypotheses. We found no added amorphous layer that would have formed upon friction against bone, antler, ivory or wood. Our observations suggest polish formation by abrasion, notwithstanding previous claims of added amorphous surface structures. This has implications for our understanding of the physical processes taking place during friction of chert and flint against different materials. Our results also open the possibility to propose new pathways for identifying different use-wear processes, based on the degree of abrasion.
Thorium dioxide (ThO(2)) is of great interest to energy research as thorium-based nuclear fuel offers the promise of increased proliferation resistance, longer fuel cycles, higher burn-up and ...improved wasteform characteristics in the generation of nuclear power. However, understanding of ThO(2) as a nuclear fuel is not as comprehensive as UO(2). In order to improve the atomic level understanding of thorium-based fuels, we have developed eight interatomic potential descriptions of ThO(2) by fitting the experimental lattice parameter, elastic constants and static dielectric constants. Using these interatomic potentials, we have calculated the structural and elastic properties, phase stability, defect formation energies, defect binding energies and complexes as well as the energetics of low-index surfaces. A critical assessment of all the potentials is performed by comparing the predicted properties with available experimental and first-principles calculations.
In the era of climate change, the overall productivity of pea (
L.) is being threatened by several abiotic stresses including heat stress (HS). HS causes severe yield losses by adversely affecting ...several traits in peas. A reduction in pod yield has been reported from 11.1% to 17.5% when mean daily temperature increase from 1.4 to 2.2°C. High-temperature stress (30.5-33°C) especially during reproductive phase is known to drastically reduce both seed yield and germination. HS during germination and early vegetative stage resulted in poor emergence and stunted plant growth along with detrimental effects on physiological functions of the pea plant. To combat HS and continue its life cycle, plants use various defense strategies including heat escape, avoidance or tolerance mechanisms. Ironically, the threshold temperatures for pea plant and its responses are inconsistent and not yet clearly identified. Trait discovery through traditional breeding such as semi leaflessness (
), upright growing habit, lodging tolerance, lower canopy temperature and small seeded nature has highlighted their utility for greater adaptation under HS in pea. Screening of crop gene pool and landraces for HS tolerance in a targeted environment is a simple approach to identify HS tolerant genotypes. Thus, precise phenotyping using modern phenomics tools could lead to increased breeding efficiency. The NGS (next generation sequencing) data can be associated to find the candidate genes responsible for the HS tolerance in pea. In addition, genomic selection, genome wide association studies (GWAS) and marker assisted selection (MAS) can be used for the development of HS tolerant pea genotypes. Additionally, development of transgenics could be an alternative strategy for the development of HS tolerant pea genotypes. This review comprehensively covers the various aspects of HS tolerance mechanisms in the pea plant, screening protocols, omic advances, and future challenges for the development of HS tolerant genotypes.
Wild edible flowers used as indigenous food and improve remarkably to the nutritional security of several tribal people of Koraput. However, systematic study on nutritional and nutraceutical ...potential of these wild edible flowers is meager. Present study evaluated the proximate compositions, vitamins, phenol, flavonoid and antioxidant capacity in selected wild flowers of Koraput. The protein, fat and carbohydrates of the wild flowers are varied from 3.36 to 5.38, 2.29 to 5.51% and 0.89 to 5.59%, respectively. The wild flowers are rich in energy content which varied from 49.49 to 80.64 kcal100g
−1
. The energy content was highest in
Sesbania grandiflora
followed by >
Gliricidia sepium
>
Bauhinia variegata
>
Indigofera tinctoria
>
Woodfordia fruticosa.
The flowers are rich in vitamin C (1.97–5.12 mg 100 g
−1
) and vitamin E (0.25–1.34 mg 100 g
−1
)
.
The studied wild flowers contain antioxidant, flavonoid and phenol which were varied from 92.3 to 238.86%, 7.19 to 14.47 mg 100 g
−1
dry weight and 32.47 to 111.93 mg 100 g
−1
dry weight, respectively. Antioxidant capacity showed significant positive relation with vitamin C, vitamin E and flavonoid. Based on the results, some wild flowers rich in antioxidants should be promoted for the sources of natural antioxidants and beneficial for health.
...this topic includes an experimental investigation by Vasanth Chakravarthy Shunmugasamy and Bilal Mansoor. From a three-point bend test experiment, the failure mechanism of the sandwich is reported ...to be core shear in nature, which matches well with the failure mode map established using Gibson's model. ...this article uses both experimental and theoretical approaches to justify the failure mechanism obtained in the sandwichstructured composite. To read or download any of the papers, follow the URL<http://link.springer.com/journal/11837/71/11/p age/1> to the table of contents page for the November 2019 issue (vol. 71, no. 11). * "Computational Modeling of the Mechanical Behavior of 3D Hybrid Organic-Inorganic Nanocomposites" by Mohammad MaghsoudiGanjeh, Liqiang Lin, Xiaodu Wang, Xianqiao Wang, and Xiaowei Zeng * "Establishment of Constitutive Relationships for Laminated Composites Considering the Variation of the Microhardness with the Strain of the Heterostructure Layers and Bonding Regions" by Tao Huang, Mei Zhan, Yanbo Pei, Nan Xiang, Fangfang Yang, Yanyang Li, Junqing Guo, Xuewen Chen, and Fuxiao Chen * "Effect of Nickel Doping on Adsorption of SF6 Decomposition Products over MoS2 Surface" by Yingang Gui, Hao Sun, Huangli Wei, Shukai Duan, Chao Tang, and Xiaoxing Zhang * "Evaluation of the Tensile Strength in Carbon Nanotubes-Reinforced Nanocomposites Using the Expanded Takayanagi Model" by Yasser Zare and Kyong Yop Rhee * "A Simulation Work for the Influences of Aggregation/Agglomeration of Clay Layers on the Tensile Properties of Nanocomposites" by Yasser Zare and Kyong Yop Rhee * "Inverse Simulation of Fracture Parameters for Cement-Bonded Corundum Refractories" by Li Ping Pan, Zhu He, Yawei Li, Baokuan Li, and Shengli Jin * "Describing the Effective Conductivity of TwoPhase and Multiphase Materials via Weighted Means of Bounds and General Power Means" by Willi Pabst and Soha Hnbalova * "Artificial Neural Network Approach to Determine Elastic Modulus of Carbon Fiber-Reinforced Laminates" by Xianbo Xu and Nikhil Gupta * "Flexural Response of an Aluminum Foam Core/ Stainless Steel Facesheet Sandwich Composite" by Vasanth Chakravarthy Shunmugasamy and Bilal Mansoor While individual length-scale and time-scale computational approaches provide extremely useful information, there is a need for an integrated multi-scale simulation approach to investigate existing and novel composite materials.
Recent efforts towards developing novel lead electrodes involving carbon and lead composites have shown potential for increasing the cycle life of lead–acid (LA) batteries used to store energy in ...various applications. In this study, first-principles calculations are used to examine the structural stability, defect formation energy, and migration barrier of C in Pb for LA batteries. Density functional theory with the GGA-PBE functional performed the best out of various functionals used for structural stability calculations. Furthermore, with the complete incorporation of C in the Pb matrix, the results show that C is energetically preferred to be at the octahedral interstitial (CiOcta) site in the FCC structure of Pb. Additionally, climbing-image nudged elastic band calculations show a minimum energy pathway for C diffusing from a stable octahedral site to the adjacent octahedral site assisted by a tetrahedral intermediate site. Therefore, the minimum energy pathway for C migration is envisioned to be CiOcta→ CiTetra→CiOcta, where the total energy barrier is observed to be ~90% and more than 100% lower than the CiTetra→CiTetra and CiOcta→CiOcta barriers, respectively.
Globally powdery mildew (PM) is one of the major diseases of the pea caused by
Besides, two other species
.
and
have also been identified to infect the pea plant. To date, three resistant genes, ...namely
,
and
located on linkage groups VI, III and IV respectively were identified. Studies have shown the
gene to be a
'
' homologue and subsequent analysis has identified eleven alleles namely
to
. Despite reports mentioning the breakdown of
gene-mediated PM resistance by
and
it is still the most widely deployed gene in PM resistance breeding programmes across the world. Several linked DNA markers have been reported in different mapping populations with varying linkage distances and effectiveness, which were used by breeders to develop PM-resistant pea cultivars through marker assisted selection. This review summarizes the genetics of PM resistance and its mechanism, allelic variations of the
gene, marker linkage and future strategies to exploit this information for targeted PM resistance breeding in
.
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