Mechanistic identification of specific force coefficients for a general end mill

The paper presents expressions for semi-empirical mechanistic identification of specific cutting and edge force coefficients for a general helical end mill from milling tests at an arbitrary radial immersion. The expressions are derived for a mechanistic force model in which the total cutting force is described as a sum of the cutting and edge forces. Outer geometry of the end mill is described by a generalized mathematical model valid for a variety of end mill shapes, such as cylindrical, taper, ball, bull nose, etc. The derivations follow a procedure originally proposed for a cylindrical end mill. The procedure itself is improved by including the helix angle in evaluation of the average edge forces. The resulting expressions for the specific force coefficients are verified by simulations and experiments.     

Intracellular Trafficking of Cationic Carbon Dots in Cancer Cell Lines MCF-7 and HeLa—Time Lapse Microscopy,Concentration-Dependent Uptake,Viability, DNA Damage,and Cell Cycle Profile

Fluorescent carbon dots (CDs) are potential tools for the labeling of cells with many advantages such as photostability, multicolor emission, small size, rapid uptake, biocompatibility, and easy preparation. Affinity towards organelles can be influenced by the surface properties of CDs which affect the interaction with the cell and cytoplasmic distribution. Organelle targeting by carbon dots is promising for anticancer treatment; thus, intracellular trafficking and cytotoxicity of cationic CDs was investigated. Based on our previous study, we used quaternized carbon dots (QCDs) for treatment and monitoring the behavior of two human cancer cell MCF-7 and HeLa lines. We found similarities between human cancer cells and mouse fibroblasts in the case of QCDs uptake. Time lapse microscopy of QCDs-labeled MCF-7 cells showed that cells are dying during the first two hours, faster at lower doses than at higher ones. QCDs at a concentration of 100 µg/mL entered into the nucleus before cellular death; however, at a dose of 200 µg/mL, blebbing of the cellular membrane occurred, with a subsequent penetration of QCDs into the nuclear area. In the case of HeLa cells, the dose-depended effect did not happen; however, the labeled cells were also dying in mitosis and genotoxicity occurred nearly at all doses. Moreover, contrasted intracellular compartments, probably mitochondria, were obvious after 24 h incubation with 100 µg/mL of QCDs. The levels of reactive oxygen species (ROS) slightly increased after 24 h, depending on the concentration, thus the genotoxicity was likely evoked by the nanomaterial. A decrease in viability did not reach IC 50 as the DNA damage was probably partly repaired in the prolonged G0/G1 phase of the cell cycle. Thus, the defects in the G2/M phase may have allowed a damaged cell to enter mitosis and undergo apoptosis. The anticancer effect in both cell lines was manifested mainly through genotoxicity.     

Why Monoamine Oxidase B Preferably Metabolizes N-Methylhistamine over Histamine: Evidence from the Multiscale Simulation of the Rate-Limiting Step

Histamine levels in the human brain are controlled by rather peculiar metabolic pathways. In the first step, histamine is enzymatically methylated at its imidazole N^τ atom, and the produced N-methylhistamine undergoes an oxidative deamination catalyzed by monoamine oxidase B (MAO-B), as is common with other monoaminergic neurotransmitters and neuromodulators of the central nervous system. The fact that histamine requires such a conversion prior to oxidative deamination is intriguing since MAO-B is known to be relatively promiscuous towards monoaminergic substrates; its in-vitro oxidation of N-methylhistamine is about 10 times faster than that for histamine, yet this rather subtle difference appears to be governing the decomposition pathway. This work clarifies the MAO-B selectivity toward histamine and N-methylhistamine by multiscale simulations of the rate-limiting hydride abstraction step for both compounds in the gas phase, in aqueous solution, and in the enzyme, using the established empirical valence bond methodology, assisted by gas-phase density functional theory (DFT) calculations. The computed barriers are in very good agreement with experimental kinetic data, especially for relative trends among systems, thereby reproducing the observed MAO-B selectivity. Simulations clearly demonstrate that solvation effects govern the reactivity, both in aqueous solution as well as in the enzyme although with an opposing effect on the free energy barrier. In the aqueous solution, the transition-state structure involving histamine is better solvated than its methylated analog, leading to a lower barrier for histamine oxidation. In the enzyme, the higher hydrophobicity of N-methylhistamine results in a decreased number of water molecules at the active side, leading to decreased dielectric shielding of the preorganized catalytic electrostatic environment provided by the enzyme. This renders the catalytic environment more efficient for N-methylhistamine, giving rise to a lower barrier relative to histamine. In addition, the transition state involving N-methylhistamine appears to be stabilized by the surrounding nonpolar residues to a larger extent than with unsubstituted histamine, contributing to a lower barrier with the former.     

A numerical model for the analyses of heat transfer and leakages in a rotary air preheater

Air preheaters make a considerable contribution to the improved overall efficiency of fossil-fuel-fired power plants. In this study we used a combination of fluid dynamics and a newly developed three-dimensional numerical model for heat transfer as the basis for a theoretical analysis of a rotary air preheater. The model enables studies of the flue-gas flow through the preheater and the adjoining channels as well as the regenerative heat transfer and the resulting temperature distribution in the matrix of the preheater. Special attention was focused on the influences of leakages on the flue-gas parameters in the preheater. The numerical analysis and the experimental results showed an obvious dependence of the flue-gas parameters on various seal settings. Based on the results a method for online monitoring of the tightness of the radial seals is proposed.     

Zero—a blend of static typing and dynamic metaprogramming

Zero is an experimental statically typed, fully object-oriented reflective programming language. Reflective features cover introspection as well as structural and behavioural reflection. The reflective facilities include safe method and class replacements and detailed modification of methods. These enable Zero programs to quickly accommodate to run-time requirements. Behavioural reflection is realised using handlers (hooks), which may be attached to all language constructs based on closures. Zero provides an efficient static typing system with run-time extensions. Methods are first class values and are represented as objects when such representation is required. By using such representation, Zero provides elegant use of statically typed higher-order methods.     

Deformation of specimen during laser surface remelting

During laser surface remelting, thermal expansion in heating, and contraction of material in cooling, and due to microstructure changes in the heated surface layer, the specimen deforms. This induces volume changes during the process of remelting the thin surface layer and causes internal stresses. By measuring the deformation of the specimen during the remelting process as well as after the laser beam interaction, i.e., to the moment when the specimen cools down to the ambient temperature, it is possible to follow the progress of deformation in the specimen material. Detailed information on the deformation events in the specimen material during the laser remelting process of a thin surface layer enables the engineer to optimize the process variables in terms of amount of deformation or magnitude of residual stresses on completion of cooling.     

Comparison of two micromechanical models for predicting elasto-plastic response of wood–plastic composites

The mechanical response of wood- and cellulose-filled polymers and its comparison to analytical models is studied in this article. To model the elasto-plastic response of the wood–plastic composite (WPC), two explicit semi-analytical micromechanical methods were used: Mori–Tanaka Method (MTM) and Generalised Method of Cells (GMC). For experimental purpose, several test specimens composed of matrix polypropylene (PP) or polystyrene (PS) and filled with wood or cellulose short fibres of different length to width aspect ratio and various volume fractions were injection moulded. Tensile testing was then used to gain experimental data, which were then compared to the calculated prediction of proposed micromechanical models to test their applicability. The comparison of results show that both methods can accurately predict the response of the composite in the elastic area; however Mori–Tanaka Method can achieve better results when forecasting plastic deformations of wood–plastic composites.     

User-centred app design for speech sound disorders interventions with tablet computers

Traditional speech and language pathology practice (SLPP) faces challenges delivering effective and timely therapy due to long waiting lists, the need for regular practice outside the clinic and a lack of children’s motivation to engage in persistent practice. Technology has untapped potential to address these issues and improve SLPP. This paper describes the design of a tablet app for delivering technology-enhanced therapy for children with speech sound disorders and investigates the impact of the use of apps on SLPP. The initial design was informed by a nation-wide survey of speech-language pathologists (SLPs). The quantitative analysis disclosed that even though SLPs positively perceive mobile technology, they do not currently fully exploit it in their practice due to a lack of apps in their native language and the limited usefulness of apps in foreign languages. Using a user-centred design process, a multidisciplinary team created three prototypes and a final version of an app that has been tested in real therapeutic sessions during everyday practice and informed by feedback from SLPs and children. The observation analysis is presented based on an adaptation of Koole’s FRAME model. The qualitative findings indicate that SLPs identify mobile apps as enabling greater mobility, allowing new therapeutic approaches, creating possibilities for practice outside the therapeutic setting and increasing children’s motivation, supporting greater persistence to practise in the context of the therapy.     

Overheating in residential passive house: Solution strategies revealed and confirmed through data analysis and simulations

Energy efficiency and living comfort certainly contribute to popularity of the passive house concept. Since these houses are weakly coupled to an environment, any internal energy gains are difficult to be released against small temperature gradients, i.e. in a typical situation occurring in hot summer months. In such a case already a small energy input raises the internal temperature significantly and dramatically affects the living comfort. To provide more information on this problem, we collected and analyzed data from a single family Slovenian passive house. Our goal was to estimate the general house response under real conditions and to investigate overheating in hot summer periods. Different energy gains were identified and explored with respect to their influence on the overheating of this passive house. Results show that windows-opening during the nights in hot summer days, strict shading of the southern and western windows as well as minimization of internal energy sources are necessary and sufficient to keep internal temperature on the comfort level.