Analysis of the influence of surface roughness of various types of wood on the results of their hardness measured by the Leeb method

Determining the hardness in the Leeb scale consists in measuring the velocity of the impact mass before and after hitting the sample. The result is the speed of the impactor shall after the rebound divided by the speed before the rebound (multiplied by 1000). The measured hardness ranges from 0 to 1000 and is largely dependent on the Young's modulus of elasticity. The article presents the Leeb hardness measurement tests of six various species of wood. The samples were machining before testing in such a way that there were places with different surface roughness on its surface. The research showed the differentiation of the hardness test results for the same tree species depending on the roughness of the surface

Influence of lateral impact on reinforced concrete piers under drying-wetting cycle and chloride ion corrosion environment

In order to study the influence of lateral impact on reinforced concrete piers in marine environment, drop hammer impact tests were carried out on piers with different corrosion rates obtained from drying-wetting cycle and chloride ion corrosion experiment to study the crack propagation process and failure modes of piers. Then by numerical simulation, the influences of impact velocity, impact mass, compressive strength of concrete and impact number on the performance of corroded piers were studied. The results showed that the failure modes of piers with different corrosion rates under lateral impact were different. The non-corrosive and low corrosion rate piers were destroyed by the bending shear which was jointly controlled by the transverse bending crack and oblique shear crack. The medium corrosion rate pier was the bending shear failure caused by oblique shear crack. The high corrosion rate pier was the joint action of bending shear crack and rust expansion crack. The increase of impact velocity, impact mass and impact number will increase the maximum deflection and the damage of the corroded piers, but the increase degrees were different. The increase was largest when the impact number was increased. Increasing impact number from 1 to 5, the maximum deflection increased by 26.3 times and the number of damage element increased by 4.3 times. Increasing the compressive strength of concrete will decrease the damage of pier, but with less degree. Increasing the compressive strength from 25 to 45 MPa, the maximum deflection and number of damage element were decreased by 10.7% and 9.4% respectively.

Substituent Effects on EI-MS Fragmentation Patterns of 5-Allyloxy-1-aryl-tetrazoles and 4-Allyl-1-aryl-tetrazole-5-ones; Correlation with UV-Induced Fragmentation Channels

1,4- and 1,5-disubstituted tetrazoles possess enriched structures and versatile chemistry, representing a challenge for chemists. In the present work, we unravel the fragmentation patterns of a chemically diverse range of 5-allyloxy-1-aryl-tetrazoles and 4-allyl-1-aryl-tetrazolole-5-ones when subjected to electron impact mass spectrometry (EI-MS) and investigate the correlation with the UV-induced fragmentation channels of the matrix-isolated tetrazole derivatives. Our results indicate that the fragmentation pathways of the selected tetrazoles in EI-MS are highly influenced by the electronic effects induced by substitution. Multiple pathways can be envisaged to explain the mechanisms of fragmentation, frequently awarding common final species, namely arylisocyanate, arylazide, arylnitrene, isocyanic acid and hydrogen azide radical cations, as well as allyl/aryl cations. The identified fragments are consistent with those found in previous investigations concerning the photochemical stability of the same class of molecules. This parallelism showcases a similarity in the behaviour of tetrazoles under EI-MS and UV-irradiation in the inert environment of cryogenic matrices of noble gases, providing efficient tools for reactivity predictions, whether for analytical ends or more in-depth studies. Theoretical calculations provide complementary information to articulate predictions of resulting products.

Submersion of rubidium clusters in helium nanodroplets

Alkali atoms and small clusters are known to reside on the surface of a helium droplet rather than its inside as most other dopant species. A theoretical investigation suggested that alkali clusters (Li–Rb) exceeding a certain critical size can become submerged in the droplet, which was experimentally confirmed for sodium and potassium. Here, we report an analogous experimental study of rubidium cluster submersion by means of electron impact mass spectrometry. We recorded size distributions of Rb cluster ions at various electron energies between 8 and 160 eV. Our data suggest that Rb clusters attached to helium droplets undergo a gradual submersion transition similar to potassium, ultimately leading to the full submersion of clusters larger than $$\sim 100~\hbox {Rb}$$ ∼ 100 Rb atoms. Our findings are consistent with previous theoretical and experimental studies. Graphic abstract

Determination of Phosphodiesterase Type 5 Enzyme (PDE-5) Inhibitors and Analogues as Adulterants in Selected Herbal Products using Gas Chromatography–Electron Impact-Mass Spectrometer (GC-EI-MS)

Sildenafil, tadalafil, and vardenafil are phosphodiesterase type 5 enzyme (PDE-5) inhibitors used for the treatment of male erectile dysfunction. This present study aims to investigate 55 herbal products indicated for men’s sexual health from the Malaysian market for adulteration of PDE-5 inhibitors and analogues. The screening and identification of 20 PDE-5 inhibitors and analogues in herbal products of various forms (powder, capsules, tablets, and pastels) were conducted using gas chromatography–electron impact-mass spectrometer (GC-EI-MS). The analysis has shown that 19 herbal products were adulterated with PDE-5 inhibitors and analogues. Unique ion fragmentations and the presence of molecular ion serve as potential markers, and the limit of detection (LOD) was 0.1-5.0 µg/g. Ten PDE-5 inhibitors and analogues were randomly selected and successfully validated for simultaneous quantification, whereby the limit of quantitation (LOQ) was 5.0–50.0 µg/g with recoveries at 86.1-118.9%. The developed method of GC-EI-MS was shown to be simple, throughput, economical and had sufficient sensitivity to screen, identify and quantify PDE-5 inhibitors and analogues in herbal matrices.

On the mass spectrometric fragmentations of the bacterial sesterterpenes sestermobaraenes A–C

A 13C-labelling was introduced into each individual carbon of the recently discovered sestermobaraenes by the enzymatic conversion of the correspondingly 13C-labelled isoprenyl diphosphate precursors with the sestermobaraene synthase from Streptomyces mobaraensis. The main compounds sestermobaraenes A, B, and C were analysed by gas chromatography–mass spectrometry (GC–MS), allowing for a deep mechanistic investigation of the electron impact mass spectrometry (EIMS) fragmentation reactions of these sesterterpene hydrocarbons.

Mammalian exocrine secretions XIX. Chemical characterization of the interdigital secretion of the Black Wildebeest, Connochaetes gnou

Using gas chromatography (GC) in conjunction with electron impact mass spectrometry and retention-time comparison, 94 compounds, ranging from 2-methyl-2-propenal to octadecanoic acid, were identified in the interdigital secretions of male and female black wildebeests, Connochaetes gnou (also known as the white-tailed gnu). The constituents of these secretions belong to many different compound classes, including hydrocarbons, alcohols, aromatics and aliphatic carbonyl compounds including carboxylic acids as well as carboxylic acid esters. Relatively small quantitative differences were found between the male and female interdigital secretions. It was concluded that these compounds probably do not play a significant role in territorial marking or in chemical communication between males and females of the species, but they could be involved in preserving the remarkably strong attachment between members of social subgroups in black wildebeest populations.

Lessons from science fiction: Frederik Pohl and the robot prosumer

The diverse fields of business, management and marketing have long explored the concept of the ‘prosumer’ – the producer-consumer who not only consumes those products produced by industry, but also has some hand in their creation. But while the term itself is often credited to futurist Alvin Toffler , the concept he describes (and that which Ritzer et al. adapt) is a central concern of science fiction, which has much to offer our understanding of modern-day prosumption and is not limited by the language and limitations of purely scientific academic discourse. Indeed, one of the most important voices in this area is author and editor Frederik Pohl, with his co-authored novel The Space Merchants and short stories including ‘The Midas Plague’ and ‘The Man Who Ate the World’. In each of these works, Pohl seeks to satirise the mindless robot-like behaviour of human beings, while also posing a word of warning for the social, economic and ecological impact mass-prosumption. This is a particularly relevant message given the rise of ‘surveillance capitalism’ – the real world manifestation of the dystopias that Pohl and his contemporaries describe. In this paper, I argue that science fiction isn’t just a useful tool for social theorists, but rather, a vital resource, as it provides a speculative framework through which to interrogate the potential impacts and implications of new technology, and the links between production and consumption, technology and work. Furthermore, it provides the means through which to imagine possible futures and the lasting impacts of consumption that go beyond describing the world as it is, and move into the realms of what the world may become.