Pneumococcal infections: penicillin resistance and therapeutic implications]

OBJECTIVE: We studied the prevalence of viral hepatitis B, C and D markers in chronic hepatopathies from Cluj. MATERIAL AND METHODS: Sera of 297 patients with chronic hepatopathies (236 adults and 61 children) have been tested for viral hepatitis markers: HBsAg, anti-HBc, anti-HBs, HBeAg, anti-HBe, anti-HDV, anti-HCV, by automated ELISA. RESULTS: HBV infection markers in 32% (adults) and 4.9% (children), and HDV infection markers in 11.8% (adults) and 26.3% (children). Double (HBV and HCV) and triple infection (HBV, HDV and HCV) were observed in 28.4% (adults), 4.9% (children), and 3.4% (adults), 0% (children), respectively. CONCLUSIONS: Hepatitis virus infection markers, especially HBV and HCV play an important role in the determinism of chronic hepatopathies from Cluj area, both in children and adults.     

Nonlinear structural behavior of a size-dependent MEMS gyroscope assuming a non-trivial shaped proof mass

In this paper, a size-dependent based non-classical mechanics model for the structural behavior of a MEMS (micro-electro-mechanical systems) gyroscope is investigated. The micro-cantilever based gyroscope is possessing a proof mass at its free end, assumed to hold a non-negligible length as compared to the micro-cantilever’s length. The proof mass is triggered through an actuating electrode and at the same time is assuming a sensing electrode together assuming parallel-plates capacitive arrangements. The governing equations of the micro-gyroscope system are derived within the framework of a modified couple stress non-classical mechanics theory. Based on the resulting equations, the static and dynamic analyses of the system are performed to estimate the pull-in instability voltages, natural frequency, and dynamic responses of the sensing electrodes near primary resonance that are caused by the use of point mass assumption and classical theory. A mixed based method involving both the Galerkin modal expansion procedure along with the method of multiple scales (MMS) technique is utilized to carry out the micro-gyroscope primary resonance analysis through plotting its respective frequency responses near its fundamental mode. Simulated results show that the proof mass dimension and its respective size effects play a substantial role in drastically changing the initiation of the system pull-in instability along its actuation direction, its fundamental natural frequency, and accordingly its dynamic amplitude along its corresponding sensing direction.

     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles coated by new functionalized tetraaza-2,3 dialdehyde micro-crystalline cellulose: synthesis,characterization, and catalytic application for degradation of Acid Yellow 17

In this study, we developed an original approach for preparing cellulose-coated magnetite nanoparticles (NPs). Two novel Schiff bases (PDA-g-DAC) and [Bz-(PDA-g-DAC)] were synthesized via condensation reactions of periodate oxidized micro-crystalline cellulose (DAC) with o-phenylene diamine (PDA) to obtain its azomethine derivative with 85% yield. Subsequently, the functionalization of (PDA-g-DAC) with benzil (Bz) yields the tetraaza macrocycle [Bz-(PDA-g-DAC)]. The physicochemical characterization of the condensation products was performed using ¹³CNMR, FTIR, ATG, DSC, and X-ray diffraction techniques. Magnetic nanomaterial-based Schiff base cellulose was successfully prepared using in situ chemical co-precipitation of coordinated ferric and ferrous ions in cellulose Schiff base matrix under optimized conditions, and then, its magnetic properties were characterized. The results demonstrated that the Fe₃O₄ NPs coated with [Bz-(PDA-g-DAC)] were homogeneously coated in the matrix under ultrasonic irradiation with the saturation magnetization of 69.50 emu g^?1. In addition, XRD line broadening analysis showed that the average particle size of the NPs was 37.3 nm. Furthermore, FTIR spectra demonstrated that [Bz-(PDA-g-DAC)] concavity was anchored to magnetite Fe₃O₄ NPs through azomethine groups. Vibrating sample magnetometry (VSM) of [Bz-(PDA-g-DAC)@Fe₃O₄] magnetic nanocomposite samples showed the typical behavior of ferromagnetism. This study provided a green and facile method to inhibit magnetic nanoparticle aggregation. Activity results revealed that the prepared [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst shows the maximum activity for degradation of Acid Yellow 17 (AY17) compared to other prepared catalysts. After degradation reaction, the [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst was recovered from the reaction mixture via an external magnet and used for further five consecutive cycles with excellent catalytic activity, successively, which was comparable to the fresh catalyst. The catalyst degradation efficiency and its easy separation exhibited that [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst is a promising material for the removal of AY17 from aqueous solutions in green chemistry perspectives.     

Hydric,morphological and thermo-physical characterization of glass wools: From macroscopic to microscopic approach

In this paper, experiments to investigate fibrous insulating materials used in buildings have been performed. Two kinds of glass fibers based products were studied. Scanning electron microscopy (SEM) coupled with an EDX detector, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction diagnostic method were used to assess materials properties. Through the coupling of thermal analyses with morphological and structural characterization techniques, a fast and safer comparison between the insulators becomes possible. So, after being tested at various rates of humidities, it is shown that the aim cause of ageing in the glass wools studied is mainly due to their binders. In fact, the alteration of glass constituting fibers comes much later. Besides, there is no preferential orientation for the vapor transfer inside glass wools.     

Experimental and theoretical investigations of the lateral vibrations of an unbalanced Jeffcott rotor

The current work experimentally explores and then theoretically examines the lateral vibrations of an unbalanced Jeffcott rotor-system working at several unbalance conditions. To this end, three conditions of eccentric masses are considered by using a Bently Nevada RK-4 rotor kit. Measurements of the steady-state as well as the startup data at rigid and flexible rotor states are captured by conducting a setup that mimics the vibration monitoring industrial practices. The linear governing equation of the considered rotor is extracted by adopting the Lagrange method on the basis of rigid rotor assumptions to theoretically predict the lateral vibrations. The dynamic features of the rotor system such as the linearized bearing induced stiffness are exclusively acquired from startup data. It is demonstrated that, with an error of less than 5%, the proposed two-degrees-of-freedom model can predict the flexural vibrations at rigid condition. While at flexible condition, it fails to accurately predict the dynamic response. In contrast to the other works where nonlinear mathematical models with some complexities are proposed to mathematically model the real systems, the present study illustrates the applicability of employing simple models to predict the dynamic response of a real rotor-system with an acceptable accuracy.     

Controlled synthesis of crosslinked polyamide 6 using a bis-monomer derived from cyclized lysine

The controlled synthesis of polyamide 6 chemical networks by anionic ring-opening copolymerization of ε-caprolactam (CL) with synthesized bis-ε-caprolactam derived from α-amino-ε-caprolactam, i.e. N-functionalized α-amino-ε-caprolactam bis-monomers, using sodium ε-caprolactamate as an initiator and hexamethylene-1,6-dicarbamoylcaprolactam as di-functional fast activator was examined in bulk at 140 °C. An urea-based bis-monomer and CL were first shown to copolymerize with a decreasing polymerization rate due to side reactions. On the contrary, quantitative copolymerization of CL with various amounts of bis-N(2-oxo-3-azepanyl)-1,6-tetramethylenediamide, an amide-based bis-monomer, leads to fast kinetics similar to the homopolymerization of CL. Crosslinked PA6 with network exhibiting elastic or viscoelastic behaviors, depending on the amount of crosslinker, were observed and characterized by swelling in hexafluoroisopropanol, dynamic mechanical analysis and rheology measurements. Crystallinity and swelling were shown to decrease with the increasing content of the crosslinking agent.