SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Material

380

Plastic debris litters aquatic habitats globally, the majority of which is microscopic (< 1 mm), and is ingested by a large range of species. Risks associated with such small fragments come from the material itself and from chemical pollutants that sorb to it from surrounding water. Hazards associated with the complex mixture of plastic and accumulated pollutants are largely unknown. Here, we show that fish, exposed to a mixture of polyethylene with chemical pollutants sorbed from the marine environment, bioaccumulate these chemical pollutants and suffer liver toxicity and pathology. Fish fed virgin polyethylene fragments also show signs of stress, although less severe than fish fed marine polyethylene fragments. We provide baseline information regarding the bioaccumulation of chemicals and associated health effects from plastic ingestion in fish and demonstrate that future assessments should consider the complex mixture of the plastic material and their associated chemical pollutants.

Concepts: Chemical substance, Mixture, Toxicology, Pollution, Plastic, Chemical compound, Material, Ocean

168

Agro-industrial wastes are generated during the industrial processing of agricultural products. These wastes are generated in large amounts throughout the year, and are the most abundant renewable resources on earth. Due to the large availability and composition rich in compounds that could be used in other processes, there is a great interest on the reuse of these wastes, both from economical and environmental view points. The economic aspect is based on the fact that such wastes may be used as low-cost raw materials for the production of other value-added compounds, with the expectancy of reducing the production costs. The environmental concern is because most of the agro-industrial wastes contain phenolic compounds and/or other compounds of toxic potential; which may cause deterioration of the environment when the waste is discharged to the nature. Although the production of bioethanol offers many benefits, more research is needed in the aspects like feedstock preparation, fermentation technology modification, etc., to make bioethanol more economically viable.

Concepts: Environment, Natural environment, Natural resource, Material, Recycling, Habitat conservation, Environmentalism, Ethanol fuel

152

Recent research suggests that variation exists among and between Oldowan stone tool assemblages. Oldowan variation might represent differential constraints on raw materials used to produce these stone implements. Alternatively, variation among Oldowan assemblages could represent different methods that Oldowan producing hominins utilized to produce these lithic implements. Identifying differential patterns of stone tool production within the Oldowan has implications for assessing how stone tool technology evolved, how traditions of lithic production might have been culturally transmitted, and for defining the timing and scope of these evolutionary events. At present there is no null model to predict what morphological variation in the Oldowan should look like. Without such a model, quantifying whether Oldowan assemblages vary due to raw material constraints or whether they vary due to differences in production technique is not possible. This research establishes a null model for Oldowan lithic artifact morphological variation. To establish these expectations this research 1) models the expected range of variation through large scale reduction experiments, 2) develops an algorithm to categorize archaeological flakes based on how they are produced, and 3) statistically assesses the methods of production behavior used by Oldowan producing hominins at the site of DK from Olduvai Gorge, Tanzania via the experimental model. Results indicate that a subset of quartzite flakes deviate from the null expectations in a manner that demonstrates efficiency in flake manufacture, while some basalt flakes deviate from null expectations in a manner that demonstrates inefficiency in flake manufacture. The simultaneous presence of efficiency in stone tool production for one raw material (quartzite) and inefficiency in stone tool production for another raw material (basalt) suggests that Oldowan producing hominins at DK were able to mediate the economic costs associated with stone tool procurement by utilizing high-cost materials more efficiently than is expected and low-cost materials in an inefficient manner.

Concepts: Material, Materials, Economic efficiency, Stone Age, Raw material, Stone tool, Oldowan, Olduvai Gorge

146

In this study, chlorhexidine hexametaphosphate (CHX-HMP) is investigated as a persistent antimicrobial coating for wound care materials.

Concepts: Wound healing, Effectiveness, Materials science, Material

38

For aerial robots, maintaining a high vantage point for an extended time is crucial in many applications. However, available on-board power and mechanical fatigue constrain their flight time, especially for smaller, battery-powered aircraft. Perching on elevated structures is a biologically inspired approach to overcome these limitations. Previous perching robots have required specific material properties for the landing sites, such as surface asperities for spines, or ferromagnetism. We describe a switchable electroadhesive that enables controlled perching and detachment on nearly any material while requiring approximately three orders of magnitude less power than required to sustain flight. These electroadhesives are designed, characterized, and used to demonstrate a flying robotic insect able to robustly perch on a wide range of materials, including glass, wood, and a natural leaf.

Concepts: Fundamental physics concepts, Materials science, Material, Flight, Takeoff

34

Chemical warfare agents containing phosphonate ester bonds are among the most toxic chemicals known to mankind. Recent global military events, such as the conflict and disarmament in Syria, have brought into focus the need to find effective strategies for the rapid destruction of these banned chemicals. Solutions are needed for immediate personal protection (for example, the filtration and catalytic destruction of airborne versions of agents), bulk destruction of chemical weapon stockpiles, protection (via coating) of clothing, equipment and buildings, and containment of agent spills. Solid heterogeneous materials such as modified activated carbon or metal oxides exhibit many desirable characteristics for the destruction of chemical warfare agents. However, low sorptive capacities, low effective active site loadings, deactivation of the active site, slow degradation kinetics, and/or a lack of tailorability offer significant room for improvement in these materials. Here, we report a carefully chosen metal-organic framework (MOF) material featuring high porosity and exceptional chemical stability that is extraordinarily effective for the degradation of nerve agents and their simulants. Experimental and computational evidence points to Lewis-acidic Zr(IV) ions as the active sites and to their superb accessibility as a defining element of their efficacy.

Concepts: Chemistry, Chemical substance, Chemical element, Material, Nerve agent, Chemical warfare

29

Abstract -  Aim: Experimental materials incorporating fiberglass cloth were used to develop a thin and lightweight face guard (FG). This study aims to evaluate the effect of fiberglass reinforcement on the flexural and shock absorption properties compared with conventional thermoplastic materials. Material and Method: Four commercial 3.2-mm and 1.6-mm medical splint materials (Aquaplast, Polyform, Co-polymer, and Erkodur) and two experimental materials were examined for use in FGs. The experimental materials were prepared by embedding two or four sheets of a plain woven fiberglass cloth on both surfaces of 1.5-mm Aquaplast. The flexural strength and flexural modulus were determined using a three-point bending test. The shock absorption properties were evaluated for a 5200-N impact load using the first peak intensity with a load cell system and the maximum stress with a film sensor system. Results and Conclusions: The flexural strength (74.6 MPa) and flexural modulus (6.3 GPa) of the experimental material with four sheets were significantly greater than those of the 3.2-mm commercial specimens, except for the flexural strength of one product. The first peak intensity (515 N) and maximum stress (2.2 MPa) of the experimental material with four sheets were significantly lower than those of the commercial 3.2-mm specimens, except for one product for each property. These results suggest that the thickness and weight of the FG can be reduced using the experimental fiber-reinforced material.

Concepts: Shock, Materials science, Tensile strength, Material, Pascal, Young's modulus, Thermoplastic, Shock absorber

28

Zn(II) complexes of the following new, fluorine-containing, benzothiazole-derived ligands have been synthesized and characterized crystallographically: 2-(3,3,3-trifluoro-2-oxopropyl)benzothiazole (3), 4,5,6,7-tetrafluoro-2-(3,3,3-trifluoro-2-oxopropyl)benzothiazole (4), 4,5,6,7-tetrafluoro-2-(2-hydroxyphenyl)benzothiazole (12), 2-(3,4,5,6-tetrafluoro-2-hydroxyphenyl)-4,5,6,7-tetrafluorobenzothiazole (13), and 2-(3,4,5,6-tetrafluoro-2-hydroxyphenyl)benzothiazole (16); the Cu(II) complex of ligand 4 is also reported. These are analogs of the important photo- and electroluminescent material [Zn(BTZ)(2)](2), where H-BTZ = 2-(2-hydroxyphenyl)benzothiazole. DFT calculations indicate that HOMO and LUMO energy levels in these materials are substantially lowered by fluorination. The fluorinated ZnL(2) complexes are mononuclear (in contrast to the dinuclear, nonfluorinated material [Zn(BTZ)(2)](2)). They easily sublime and show broad visible photoluminescence. A common crystallographic feature is the existence of pairs of fluorinated ZnL(2) molecules related by inversion centers, with their π systems facing one another.

Concepts: Following, Benzene, Ligand, Complex, Luminescence, Material, HOMO/LUMO, Electroluminescence

28

The exciting area of invisibility cloaking is reviewed by Andrea Alù and co-workers on page OP281. Various solutions for invisibility cloaking using metamaterials, metasurfaces, graphene and plasmonic materials in different spectral ranges are discussed. Particular focus is placed on scattering-cancellation approaches, highlighting material challenges, venues and opportunities for plasmonicand mantle-cloaking techniques, in various frequency windows, and for several devices and applications.

Concepts: Optics, Materials science, Material, Cloak of invisibility, Cloaking device

28

Thermoelectric materials transform temperature gradients to voltages and vise versa. Despite their many advantages, devices based on thermoelectric materials are used today only in a few applications, due to their low efficiency, which is described by the figure of merit ZT. Theoretical studies predict that scaling down these materials to the nanometric scale should enhance their efficiency partially due to a decrease in their lattice thermal conductivity. In this work we determine for the first time the lattice thermal conductivity of 40 nm bismuth (Bi) nanowires (NWs), i.e. NWs with a diameter comparable to the Fermi wavelength of charge carriers in this material. We find a surprisingly low lattice thermal conductivity of 0.13 ± 0.05 W K(-1) m(-1) at 77 K. A quantitative argument, which takes into account several unique properties of Bi, is given to explain this unusual finding.

Concepts: Scientific method, Thermodynamics, Heat, Physical quantities, Material, Electrical conductivity, Thermoelectric effect, Fermi paradox