Browse Articles

High printing quality of banknotes and the variety of security features implemented in banknotes make a big difference between the genuine notes and high-quality forgeries. The counterfeiter cannot reproduce or imitate the printing quality and all security features embedded in every banknote, such as Optically Variable Ink, Optically Variable Diffractive Images, or intaglio printing. The present research focused on the examination of optically variable devices embedded on 50Îbanknotes. The altered banknotes were examined using different techniques.

The paper describes an innovative method of production of non-ferrous drop forgings, a manufacturing method based on closed die forging without flash. From economic point of view, this method is very interesting for production, due to small quantity of lost material. The research was verified using DEFORM 3D software. In this way can be better understood the principles of forging process and can be analyzed the plastic flow of the material into the die cavity. This experiment was successfully performed at laboratory conditions and the results will be applied in practice.

In order to evaluate the durability of paint layers exposed to simultaneous action of climatic and electrical stresses, the influence of 50 Hz electrical field and of aging by thermal cycling on the resistance to the action of molds of some painting materials was evaluated by specific microbiological determinations. Comparative measurements were carried out on initial paint samples and samples aged by applying of 1000 successive thermal cycles (between –38oC and 85oC, with the duration of a cycle of 90 min), exposed to Czapek-Dox culture media (with and without sucrose), inoculated with a salt solution containing approximately 106 mold spores (of 10 different species), and incubated at 30±2oC and RH 90±5%. It was found that for the samples exposed to a controlled field of 5V/cm and 50Hz the resistance to the action of molds is almost two times less than in the absence of the disruptive electric field. Also, it was noticed that the field of 5V/cm and 50Hz stimulates the growth of Aspergillus niger, but completely inhibit those of Trichoderma viride and Aspergillus flavus.

On a total of 150 renal corrosion casts were examined the posterior branch and the artery of renal posterior segment. For the origin of the posterior branch, there have been highlighted three morphological types, namely: Type I, bifurcation in anterior and posterior branches (92.67% of cases); Type II, trifurcation in anterior, posterior and superior or inferior branches (6.00% of cases); Type III, quadrifurcation in anterior, posterior, superior and inferior branches (1.33% of cases). Depending on the relations between this path and those with the posterior aspect of the renal pelvis, we highlighted four morphological types: Type I (62.67% of cases) with large extension of the posterior segmental artery, convex downward path and multiple subsegmentary branches; Type II (34.00% of cases) with large extension of the posterior segmental artery, that bifurcates or trifurcates in segmental branches and convex downward path; Type III (2.00% of cases) with small extension of the posterior segmental artery, with downward path in relation to the upper portion of the posterior surface of the renal pelvis upper portion; Type IV (1.33% of the cases) with small extension of the posterior segmental artery, with upward trajectory in relation to the lower portion of the renal pelvis. Knowledge of these aspects is important both to investigate morphological imaging and for performing partial resection of the renal parenchyma.

The goal of this paper was to study the modification of porous clay heterostructures (PCHs) with various silane coupling agents. Two commercial coupling agents (3-aminopropyl-triethoxysilane (APTES) and 3-glycidoxypropyl-trimethoxysilane (GPTMS)) with different functional groups (amine and epoxy groups) were used as modifying agents for the PCHs functionalization. The functionalization of PCH with APTES and GPTMS was evaluated by Fourier transform infrared (FTIR) spectrometry, thermogravimetric analysis (TGA), X-Ray Diffractions (XRD) and BET Analysis. FTIR spectra of modified PCHs confirmed the presence of characteristic peaks of silane coupling agents. TGA results highlighted an increase of weight loss for the modified PCHs that was assigned to the degradation of silane coupling agents (APTES and GPTMS) attached to the PCHs. The XRD results showed that the structure of modified PCHs was influenced by the type of the silane coupling agent. The functionalization of PCHs with silane coupling agents was also confirmed by BET analysis. Textural parameters (specific surface area (SBET), total pore volume (Vt )) suggested that the modified PCHs exhibit lower values of SBET and a significant decrease of total pore volume than unmodified PCHs.

According to titanium’s much higher hardness and strength compared with the bone, if correctly applied, mini-screws will suffer no damage. Reusing orthodontic mini-screws would reduce treatment cost and lead to more use of mini-screws and improvement of orthodontic treatments. In this study, scanning electron microscopy (SEM) was used to assess structural variations of retrieved orthodontic implants and to evaluate the mechanical properties that may adversely affect stability of orthodontic implants. For analisys 10 self-drilling mini-implants retrieved after treatment, made from commercially pure (CP) alpha-titanium from two brands Leone™, Italy and ForestaDent™, Germany were analised using SEM according to the degree of morphological deformation of the head, transmucosal neck, threaded body, and tip of the implant at up to 10,000 x light magnification. The mini-implants did not present any defects such as bubbles, imperfections or fissures in their internal microstructure. No significant marks resulting from the manufacturing process were observed. Surface irregularities in the threaded body and tip (fig. 5-7) were observed and significant tip deformation was evident in the majority (80%) of retrieved mini-implants.

Antibacterial gels offer an efficient hygiene in the absence of soap and water. The most part of these products are based on mixtures of different antibacterial and fungicide substances dissolved in an alcohol. Unfortunately, all cosmetic products containing alcohols wash the sebum and dry the skin. In the present study, alcohol-free antibacterial hydrogels were obtained through the synthesis of polyurethane (PU) microstructures with an increased amount of surfactant; 5-mercapto-1,2,4-triazole derivatives were used as active compounds inside the PU microstructures as antibacterial agents. There were studied: the pH of samples, the size and stability of PU microstructures, the skin irritation, sebum level and the hydration of stratum corneum using the mouse model and their efficiency against Escherichia coli. The results indicate that were obtained hydrogels with a slightly acid pH, PU microstructures with sizes between 185 and 265 nm and with a medium stability. It was found that these new antibacterial hydrogels do not produce an important modification of skin parameters (erythema, melanin, sebum and hydration of stratum corneum) and are efficient against E. coli.

In this paper, were study the pervaporation of mono-nitrophenols in a laboratory installation of the Membrane, Materials, and Membrane Processes Group of the Polytechnic University of Bucharest, from aqueous synthetic solutions, to composite membranes with polysulfone matrix (PSf) and nanometric inclusions: Polyaniline (PANI), carbon nanotubes (CNT), magnetic nanoparticles (MNP) and sulfonated polyetheretherketone (PEEK-S). Tests carried out over 144 h at a pressure of 100 mm Hg or 5 L / min air flow at 25oC and pH 7 of the feed solution show that vacuum pervaporation is better than vacuum. The more advanced composite membranes are those with sulfonated polyether-ether cellulose (PSf-PEEK-S) and polyaniline (PSf-PANI) ionizers. The results of airborne pervaporation show that composite membranes (PSf-PEEK-S and PSf-PANI) present a marked difference in flux for the mono-mono-nitrophenol isomers, which could also be found in a technically exploitable selectivity. Thus, in the case of the PSf-PEEK-S composite membrane, the mono-nitro-phenol streams decrease in the order: m-C6H5NO3] o-C6H5NO3] p-C6H5NO3, while for the PSf-PANI composite membrane the order is o-C6H5NO3] m-C6H5NO3] p-C6H5NO3. At the same time, it is noted that the PSf-PEEK-S composite membrane performance is superior during operation, but shows the opposite of the more pronounced drop.

Collagen is an important natural biopolymer, found in mammal’s body. It is the main structural protein in the extracellular space in the various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals. Its importance increased in last decades. Collagen has many applications in medicine and cosmetics. The work presented in this paper shows one method to obtain collagen films from collagen solutions. These collagen solutions were characterized by rheological measurements. The preparation of the collagen films was performed in the presence of calcium and silicium salts, using glycerin as plasticizer. The collagen was first solubilized and reconstituted, in order to maintain its initial properties.

Due their various applications the fabric reinforced polymer composites are subject of a large number of researches especially for aero- and automotive industry. Regarding the last domain there are huge interests in designing and forming composites with controllable strengthens for car bodies able to protect both the driver and passengers inside and pedestrians in case of unfortunate events. In this regard, based on previous studies developed at the Research and Development Centre for Thermoset Matrix Composites, our proposal is to design the bending behaviour of a fabric reinforced materials by means of changing the bending strength of the polymer matrix using a solvent. 1-Methyl, 2- pyrrolidinone is a well-known polymer solvent that had been used in previous studies as vector to transfer various organic agents into epoxy resins. During those studies it had been noticed that the presence of above mentioned solvent is changing the bending behaviour of polymer samples and induces some properties that are belonging to memory-shape materials. The present study is related to mechanical analysis of a multi-layered material (fabric layers) immersed into an epoxy resin having a graded bending strength.