Investigation of laser milling process characteristics for micro tooling applications

Laser milling is a new application that is challenging for the power contained in the laser light. Due to its small unit of material removal, accuracy and repeatability, laser milling has found an application area in micro manufacturing, especially the manufacturing of microtools. There is a number of micro manufacturing and replication processes on the market at present. Their needs raise the requirements that have to be met by the microtool manufacturing process. Initially, the requirements of micro manufacturing processes, such as micro-injection moulding and hot-embossing, are identified and compared to what the laser milling process can achieve. An investigation is carried out to identify the capabilities of the laser milling process and match them to these requirements. The investigated process characteristics are surface finish, aspect ratio, accuracy and minimum feature size. Furthermore, as surface finish is identified to be a considerable constraint, an investigation is undertaken to improve the resulting surface finish obtained from the laser milling process. A two-dimensional theoretical model is developed to investigate the crater formation on a metal target by a microsecond laser pulse. The model takes into account the absorption of the laser light by the target, and simulates the heating and vaporisation of the material, including an adjustment to compensate for the change of state. A simple numerical technique is employed to describe the major physical processes taking part in the laser milling process. Experimental validation of the proposed model is provided for two common tooling materials. To investigate the formation of the material surface after laser milling, a complex 3D surface model is presented based on the single crater profiles of the 2D theoretical model together with a consideration for the overlapping of the craters. Additional factors, that are influential in the formation of the final material surface, are also considered and their effect on the surface roughness estimated. Finally, a number of techniques for reducing surface roughness are presented. Laser cleaning is a technique that utilises the de-focused laser beam to 'smooth out' the material surface irregularities. The other three techniques are applied after laser milling, and are ultrasonic cleaning bath, chemical pickling and electro-chemical polishing

Function and length scale integration in innovative products - technical solutions and new organisational models

This paper presents the issues typically occurring when integrating, into a single product, functions that can only be realised by employing different length scale features (macro, meso, micro and down to nano). The discussion is supported by the responses of a survey performed on 88 European research and development projects conducted by members of the multi-material micro manufacture (4M) community in Europe. Two main issues are highlighted as critical for a successful multi-scale integration. The first one relates to the concurrent design of materials properties and manufacturing processes. The second focuses on the need for new production approaches and organisational models applied by companies

Pollution of Varna Lake and possibilities of using the pollutants as resources

Varna Lake is of great social and economic importance for the city of Varna and the entire region. The urbanisation of the areas surrounding the Varna-Beloslav Lake complex and the accelerated industrialisation around the coastline of Varna Bay have significant anthropogenic pressure on the aquatic ecosystem. An essential aspect is that industrial development, maritime transport and urbanisation are substantial sources of large-scale inorganic and organic pollution with all the resulting negative consequences. Recent measurements show that the surface sediments, which are a source of nutrients for the water body of Varna Lake, are contaminated with heavy metals and oil products. In this paper, we present a quantitative assessment of the degree of contamination with heavy metals (Hg, As, Fe, Cu, Pb) and petroleum products in the upper sediments of Varna Lake and then discuss opportunities for using some of these pollutants as a resource. The exploitation of these resources would bring significant benefits for improving the ecological status of Varna Lake

Lanthanides as Calcium Mimetic Species in Calcium-Signaling/Buffering Proteins: The Effect of Lanthanide Type on the Ca²⁺/Ln³⁺ Competition

Lanthanides, the 14 4f-block elements plus Lanthanum, have been extensively used to study the structure and biochemical properties of metalloproteins. The characteristics of lanthanides within the lanthanide series are similar, but not identical. The present research offers a systematic investigation of the ability of the entire Ln3+ series to substitute for Ca2+ in biological systems. A well-calibrated DFT/PCM protocol is employed in studying the factors that control the metal selectivity in biological systems by modeling typical calcium signaling/buffering binding sites and elucidating the thermodynamic outcome of the competition between the “alien” La3+/Ln3+ and “native” Ca2+, and La3+ − Ln3+ within the lanthanide series. The calculations performed reveal that the major determinant of the Ca2+/Ln3+ selectivity in calcium proteins is the net charge of the calcium binding pocket; the more negative the charge, the higher the competitiveness of the trivalent Ln3+ with respect to its Ca2+ contender. Solvent exposure of the binding site also influences the process; buried active centers with net charge of −4 or −3 are characterized by higher Ln3+ over Ca2+ selectivity, whereas it is the opposite for sites with overall charge of −1. Within the series, the competition between La3+ and its fellow lanthanides is determined by the balance between two competing effects: electronic (favoring heavier lanthanides) and solvation (generally favoring the lighter lanthanides)

Metal-Assisted Complexation of Fluorogenic Dyes by Cucurbit[7]uril and Cucurbit[8]uril: A DFT Evaluation of the Key Factors Governing the Host–Guest Recognition

With the emergence of host-guest systems, a novel branch of complexation chemistry has found wide application in industries such as food, pharmacy, medicine, environmental protection and cosmetics. Along with the extensively studied cyclodextrins and calixarenes, the innovative cucurbiturils (CB) have enjoyed increased popularity among the scientific community as they possess even better qualities as cavitands as compared to the former molecules. Moreover, their complexation abilities could further be enhanced with the assistance of metal cations, which can interestingly exert a dual effect on the complexation process: either by competitively binding to the host entity or cooperatively associating with the CB@guest structures. In our previous work, two metal species (Mg2+ and Ga3+) have been found to bind to CB molecules in the strongest fashion upon the formation of host–guest complexes. The current study focuses on their role in the complex formation with three dye molecules: thiazole orange, neutral red, and thioflavin T. Various key factors influencing the process have been recognized, such as pH and the dielectric constant of the medium, the cavity size of the host, Mn+ charge, and the presence/absence of hydration shell around the metal cation. A well-calibrated DFT methodology, solidly based and validated and presented in the literature experimental data, is applied. The obtained results shed new light on several aspects of the cucurbituril complexation chemistry

Metal-Assisted Complexation of Fluorogenic Dyes by Cucurbit[7]uril and Cucurbit[8]uril: A DFT Evaluation of the Key Factors Governing the Host–Guest Recognition

With the emergence of host-guest systems, a novel branch of complexation chemistry has found wide application in industries such as food, pharmacy, medicine, environmental protection and cosmetics. Along with the extensively studied cyclodextrins and calixarenes, the innovative cucurbiturils (CB) have enjoyed increased popularity among the scientific community as they possess even better qualities as cavitands as compared to the former molecules. Moreover, their complexation abilities could further be enhanced with the assistance of metal cations, which can interestingly exert a dual effect on the complexation process: either by competitively binding to the host entity or cooperatively associating with the CB@guest structures. In our previous work, two metal species (Mg2+ and Ga3+) have been found to bind to CB molecules in the strongest fashion upon the formation of host–guest complexes. The current study focuses on their role in the complex formation with three dye molecules: thiazole orange, neutral red, and thioflavin T. Various key factors influencing the process have been recognized, such as pH and the dielectric constant of the medium, the cavity size of the host, Mn+ charge, and the presence/absence of hydration shell around the metal cation. A well-calibrated DFT methodology, solidly based and validated and presented in the literature experimental data, is applied. The obtained results shed new light on several aspects of the cucurbituril complexation chemistry

Cu⁺/Ag⁺ Competition in Type I Copper Proteins (T1Cu)

Due to the similarity in the basic coordination behavior of their mono-charged cations, silver biochemistry is known to be linked to that of copper in biological systems. Still, Cu+/2+ is an essential micronutrient in many organisms, while no known biological process requires silver. In human cells, copper regulation and trafficking is strictly controlled by complex systems including many cytosolic copper chaperones, whereas some bacteria exploit the so-called “blue copper” proteins. Therefore, evaluating the controlling factors of the competition between these two metal cations is of enormous interest. By employing the tools of computational chemistry, we aim to delineate the extent to which Ag+ might be able to compete with the endogenous copper in its Type I (T1Cu) proteins, and where and if, alternatively, it is handled uniquely. The effect of the surrounding media (dielectric constant) and the type, number, and composition of amino acid residues are taken into account when modelling the reactions in the present study. The obtained results clearly indicate the susceptibility of the T1Cu proteins to a silver attack due to the favorable composition and geometry of the metal-binding centers, along with the similarity between the Ag+/Cu+-containing structures. Furthermore, by exploring intriguing questions of both metals’ coordination chemistry, an important background for understanding the metabolism and biotransformation of silver in organisms is provided

Child abuse syndrome – a forensic case of fatal impulsive act of violence

Child abuse syndrome is a medico-social problem widely spread around the world, which includes a complex of clinically manifested forms of violence against children. This syndrome includes different forms of physical violence, sexual violence, neglect, and emotional violence against children. The main problem with this type of violence continues to be the large number of unregistered “hidden” cases. The consequences of violence against children are serious and have a lasting negative effect on the physical and mental health of the victims. Child abuse is often a result of impulsive violent behavior with minimal provocation and may have a fatal outcome. We present a case of a 3-year-old boy, admitted to the Emergency Department of the Municipal Hospital in Asenovgrad, Bulgaria, in a state of biological death. Case circumstances during the police investigation were unclear and the body was transported for forensic examination. During the forensic autopsy, many traumatic injuries were observed over the whole body – bruises of different ages, fractures of bones, abdominal trauma with bucket-handle tear of the mesentery, thoracic trauma with contusions and ruptures of the lungs, rupture of the diaphragm, and many other injuries that are specific predictors for this type of child physical abuse. The main aim of the present report is to enrich the knowledge of medical workers in their routine practical work in the identification and determination of child abuse syndrome. It could prevent the fatal outcome and reduce the mortality from this specific type of violence