Diatoms are single cell microalgae enclosed in silica exoskeletons (frustules) that provide inspiration for advanced hybrid nanostructure designs mimicking multi-scale porosity to achieve outstanding ...mechanical and optical properties. Interrogating the structure and properties of diatoms down to nanometer scale leads to breakthrough advances reported here in the nanomechanical characterization of Coscinodiscus oculus-iridis diatom pure silica frustules, as well as of air-dried and wet cells with organic content. Static and dynamic mode Atomic Force Microscopy (AFM) and in-SEM nanoindentation revealed the peculiarities of diatom response with separate contributions from material nanoscale behavior and membrane deformation of the entire valve. Significant differences in the nanomechanical properties of the different frustule layers were observed. Furthermore, the deformation response depends strongly on silica hydration and on the support from the internal organic content. The cyclic loading revealed that the average compliance of the silica frustule is 0.019 m/N and increases with increasing number of cycles. The structure-mechanical properties relationship has a direct impact on the vibrational properties of the frustule as a complex micrometer-sized mechanical system. Lessons from Nature's nanostructuring of diatoms open up pathways to new generations of nano- and microdevices for electronic, electromechanical, photonic, liquid, energy storage, and other applications.
We report on the results of the first search for the production of axion-like particles (ALPs) via Primakoff production on nuclear targets, γA→aA, in the “SRC-CT” experiment using the GlueX detector ...at Jefferson Lab. This search uses an integrated luminosity of 100 pb⋅−1nucleon on a 12C target with a real photon beam of energies 6<Eγ<10.8 GeV, and explores the mass region of 200<ma<450 MeV via the decay a→γγ. This mass range is between the π0 and η meson masses, which enables the use of the measured η meson production rate to obtain absolute bounds on the ALP production with reduced sensitivity to experimental luminosity and detection efficiency. We find no evidence for an ALP, consistent with previous searches in the quoted mass range, and present limits on the effective photon coupling scale of O(1TeV−1). We further find that the ALP production limit we obtain is hindered by the peaking structure of the non-target-related dominant background the in GlueX spectrometer, which we treat by using data on 4He to estimate and subtract it. We comment on how this search can be improved in a future higher-statistics dedicated measurement.
The western Bering Sea is an important region that is used by many nekton species for feeding. From the seasonal aspect, these waters are characterized by pronounced dynamics of the abundance and ...structure of the nekton community. The pattern of seasonal variations in the total biomass, composition, and structure of nekton in the upper epipelagic layer (0–50 m) of this region are considered based on the data of the complex studies conducted by the Pacific Research Fisheries Center (TINRO Center) in the deep-sea basins of the western Bering Sea and the Navarin area in June–October, 2003–2015. During June–October, the total nekton biomass changed by more than an order of magnitude: from 100 kg/km
2
in early June it increased to a maximum of 2700 kg/km
2
in the middle of August and then declined significantly, to 200 kg/km
2
, in late October. The major contribution to the nekton biomass was made by Pacific salmon (
Oncorhynchus
spp.), mainly
O. keta
, as well as by the boreopacific gonate squid (
Boreoteuthis borealis
) and the shortarm gonate squid (
Gonatus kamtschaticus
). As well, walleye pollock (
Theragra chalcogramma
), Pacific herring (
Clupea pallasii
), and capelin (
Mallotus villosus
) were abundant in waters near the shelf. The dynamics of the species structure can be divided into three periods: (1)
early summer
, from June to the second 10 days of July, when pre-anadromous pink (
O. gorbuscha
) and chum salmon predominate and the species diversity is at a medium level (the polydominance index is 3.5–4.0); (2)
summer
, from the third 10 days of July to the second 10 days of September, when chum salmon becomes dominant (more than 70% of the biomass) and the species diversity is at a minimum (1.5–2.0); and (3)
autumn
, from the third 10 days of September to October, when common species such as chum salmon, sockeye salmon, and boreopacific gonate squid have relatively equal proportions, the proportion of pink salmon underyearlings is also high, and the species diversity is at a maximum (4.5). The pattern of the spatial distribution in the
early summer
period is characterized by active formation of the nekton community due to the large-scale migrations from the central and eastern Bering Sea and from the Pacific Ocean. In the
summer
period, the concentration of the nekton in the western Bering Sea, particularly in the Aleutian Basin, reaches the maximum level and the migratory activity decreases. Reverse migration processes are observed in the
autumn
period: a major portion of the nekton biomass redistributes to the southeastern Commander Basin for further movement to the ocean and the central Bering Sea.
Studies of the structure and properties of pressed strips made of a promising V-1977 highly doped aluminum alloy of the Al–Zn–Mg–Cu system with the addition of Zr after two-step aging are conducted. ...It is found that a characteristic feature of the microstructure of the V-1977 alloy after two-step aging is the uniform distribution of the platelike nanoparticles of the main strengthening metastable hexagonal η' phase throughout the grain body and larger particles of the stable η phase along the grain boundaries. It is shown that, at a high level of the strength characteristics, the values of the fracture toughness exceed the level of the values of high-strength aluminum alloys, which is achieved owing to the chemical composition of the V-1977 alloy balanced with respect to the doping elements and impurities as well as the chosen temperature–time parameters of two-step aging.
In the last decade, perovskite photovoltaics gained popularity as a potential rival for crystalline silicon solar cells, which provide comparable efficiency for lower fabrication costs. However, ...insufficient stability is still a bottleneck for technology commercialization. One of the key aspects for improving the stability of perovskite solar cells (PSCs) is encapsulating the photoactive material with the hole-transport layer (HTL) with low gas permeability. Recently, it was shown that the double HTL comprising organic and inorganic parts can perform the protective function. Herein, a systematic investigation and comparison of four double HTLs incorporating polytriarylamine and thermally evaporated transition metal oxides in the highest oxidation state are presented. In particular, it was shown that MoOx, WOx, and VOx-based double HTLs provided stable performance of PSCs for 1250 h, while devices with NbOx lost 30% of their initial efficiency after 1000 h. Additionally, the encapsulating properties of all four double HTLs were studied in trilayer stacks with HTL covering perovskite, and insignificant changes in the absorber composition were registered after 1000 h under illumination. Finally, it was demonstrated using ToF-SIMS that the double HTL prevented the migration of perovskite volatile components within the structure. Our findings pave the way towards improved PSC design that ensures their long-term operational stability.
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•Two types of MSNs are created using the associates of targeted antiseptics as templates.•Both types of MSNs are characterized by extra high content of encapsulated antiseptics.•The ...release of encapsulated drugs is controlled by medium pH.•Both types of MSNs show high activity against Staphylococcus aureus.
The possibility of one-step creating of pH-sensitive mesostructured silica-based nanocontainers with exceptionally high payload using associates of two antiseptics (including hydrolyzable one) as templates is demonstrated. The effects of the template nature and the conditions of the sol-gel process on the porous structure of silica nanocontainers are studied and discussed. The kinetics of the templating drug release from such containers is studied and some features of this process are analyzed. It is shown that the drug release rate can be tuned by varying the medium pH. The bactericidal activity of two encapsulated antiseptics against the Staphylococcus aureus is evaluated in vitro by agar diffusion method with replacement of agar with agarose. The diameters of the inhibition zones for silica-based containers loaded with antiseptics increased with the pre-diffusion time at 4 °C. At the same time, empty containers (after elimination of antiseptics by etching) did not reveal any bactericidal properties.
We have carried out complex studies of the structure and properties after thermal hardening by the T1 mode of pressed shapes 20–40 mm thick from a new promising high aluminum alloy V-1977 based on ...the Al–Zn–Mg–Cu system with the addition of Zr. It has been found that, after aging according to the T1 mode, in the pressed shapes of alloy V-1977, a homogeneous structure and a uniform distribution of finely dispersed nanocrystalline particles of the η' phase and dispersoids of the β' phase (ZrAl
3
) with spherical shape are observed. Owing to this, the required level of mechanical, corrosion, and resource characteristics for parts of modern aviation and missile technology is achieved. Thus, the V-1977 alloy is shown to be competitive in comparison with the widespread serial alloy V95och and a domestic analog of alloy V96ts-3pch.
The influence of one-stage and two-stage artificial aging on the structure and properties of pressed strips from V-1977 aluminum superalloy is studied. The grain size and the distribution of the ...phase components, the tensile mechanical properties, the electrical conductivity, the fracture toughness, and the corrosion resistance of the alloy are determined. It is shown that the one-stage and two-stage modes of artificial aging of pressed strips from V-1977 provide a combination of high strength (over 650 MPa) and elevated fracture toughness (over 35 MPa · m
1/2
) required for advanced new-generation aerospace structures. This combination of properties renders the articles manufactured from alloy V-1977 competitive to the Russian and foreign counterparts for heavy-duty airframe components, the internal power set in particular.
The main goal of the pair spectrometer of the GlueX experiment at Jefferson Lab is to determine the photon beam flux and to measure beam polarization. We present the design of the pair spectrometer ...and the performance results during fist commissioning runs of the GlueX experiment.
The description of the pair spectrometer of the GlueX detector at Jefferson Lab and its performance during the first beam commissioning runs are presented. We measured the amount of light collected ...from each channel of the pair spectrometer hodoscopes and the time resolution of the pair spectrometer counters.
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