Study of Silicon Cantilevers by the Photoacoustic Elastic Bending Method

Rectangular silicon cantilevers are studied by the photoacoustic (PA) elastic bending method. Experimental signals versus modulation frequency of the excitation optical beam are measured and analyzed in a frequency range from 20 Hz to 50 000 Hz. The procedure for experimental signal correction to eliminate the frequency characteristics of the measuring system is given. The corrected experimental signal shows a good correlation with theoretically calculated PA signal at frequencies below 32 000 Hz. The corrected experimental PA elastic bending signals for cantilevers with different thicknesses are analyzed. The experimental results allow identifying the resonant frequency (the first resonant mode) of the cantilever vibrations. These values are in good agreement with the theoretically computed values. A theoretical model of the optically excited Si cantilever is derived, taking into account plasmaelastic, thermoelastic, and thermodiffusion mechanisms. Dynamic relations for the amplitude and phase of electronic and thermal elastic vibrations in optically excited cantilevers are derived. The theoretical model is compared to the experimental results.     

Antimicrobial resistance and co-selection phenomenon in Listeria spp. recovered from food and food production environments

Antimicrobial resistance (AMR), co-selection phenomenon, and the relationship between reduced susceptibility (RSC) to ciprofloxacin (CIP) and resistance to other antimicrobials in Listeria spp. (n = 103) recovered from food processing environments (FPE) and food were investigated. Resistance of Listeria monocytogenes and other listeriae, respectively, to cefoxitin (FOX; 98% vs. 88%), CIP (7% vs. 4%), clindamycin (CLI; 33% vs. 59%) and tetracycline (6% vs. 8%) was observed, as was RSC to CIP (67% vs. 57%) and CLI (65% vs. 41%). L. monocytogenes also possessed RSC to linezolid (LZD; 6%), rifampicin (2%) and streptomycin (6%), with other listeriae displaying RSC to chloramphenicol (4%). L. monocytogenes serotype 1/2a (90%) isolates were more frequently resistant or possessed RSC to CIP compared to serotype 4b (55%) (p = 0.015). When eight strains were experimentally adapted to high concentrations of CIP, co-selection occurred as MICs to benzalkonium chloride (BAC) increased (n = 5), gentamicin MICs remained the same (n = 6) or increased 2-fold (n = 2), and led to RSC to LZD (n = 1) and resistance to CLI (n = 8). Overall, levels of resistance/RSC to CIP in food chain isolates, particularly 1/2a, are concerning. Further, reduced sensitivity to disparate antimicrobials following CIP exposure highlights the need for increased knowledge of co-selection phenomenon linked with antimicrobial agents.     

Biomass energy in Vojvodina: Market conditions,environment and food security

In this study, the policy, market conditions and food security of biomass energy sources are assessed for supplying the future needs of Vojvodina. The Autonomous Province of Vojvodina is an autonomous province in Serbia, containing about 27% of its total population according to the 2002 Census. It is located in the northern part of the country, in the Pannonia plain, in southeastern Europe.Vojvodina is an energy-deficient province. Vojvodina also has a large potential for renewable energy, especially energy from biomass (biodiesel and bio-ethanol). The lack of knowledge about renewable energy technologies by most policy-makers, potential consumers, and energy firm managers has played against renewable energy developments. The environmental impacts of programs that encourage biofuel production, farmland land requirements and the impacts on food production are also discussed, considering the life cycle analysis (LCA) as a tool.It is concluded that the rise in the use of biofuels is inevitable and that international cooperation, regulations and certification mechanisms must be established regarding the use of land, the mitigation of environmental and social impacts caused by biofuel production. It is also mandatory to establish appropriate working conditions and decent remuneration for workers of the biofuels production chain.     

Cleaner bioprocesses for promoting zero-emission biofuels production in Vojvodina

In this study, the policy, market conditions and food security of biomass energy sources are assessed for supplying the future needs of Vojvodina. The Autonomous Province of Vojvodina is an autonomous province in Serbia, containing about 27% of its total population according to the 2002 Census. It is located in the northern part of the country, in the Pannonia plain, in southeastern Europe. Vojvodina is an energy-deficient province. The incentives to invest human and financial resources in the research and development of cleaner bioprocesses are high, considering the benefits which might be achieved in terms of environment protection and manufacturing costs. In the near and medium tenu, the development of bioprocesses for waste recycling and resource recovery might be one of the most viable options, considering much research work has already been done. In Vojvodina, there are technological solutions that biofuels produced in a closed cycle, so that the quantity of waste reduced to a minimum. These solutions include the stillage (remainder after distillation) used for fattening cattle, and cattle excrement to produce biogas and manure as fertilizer. The energy required for the production of bioethanol is obtained combustion lignocelullose residual waste from the production of basic raw materials starch, or biogas. Ash from the burned biomass returned to soil as a source of minerals for plants and replacement of mineral fertilizer. Such a closed cycle is economical for small farms in Vojvodina.     

Artificial Antigen-Presenting Interfaces in the Service of Immunology

While the beneficial impact of modifying and/or targeting T lymphocytes is becoming increasingly accepted in the treatment of different diseases, the road towards cell-based immunotherapy is still long and winding. Major challenges that remain include, amongst others, the guidance and exquisite regulation of immune processes ex vivo. In part, this is due to the difficulties of simulating ex vivo the intimate cellular interactions that occur between T cells and antigen-presenting cells (APCs). The fate of T cells is not solely regulated by the presence of certain molecules on the surface of APCs but also by their density and spatial distribution on the micro- and nanometric scale. Moreover, mechanical properties of APCs and force-dependent conformational changes during the formation of an immunological synapse (IS; a highly organized supramolecular complex at the T cell APC interface), play a crucial role in T cell fate regulation. Various different technical means have been developed to create APC substitutes that are able to simulate ex vivo signals originating from naturally occurring APCs. Here, we review the performance of APC surrogates and discuss their contribution to understanding mechanisms underlying the ability of T cells to perform the “intelligent” mission of acquiring, processing and responding to environmental information.     

Characterization of native corticotropin-releasing factor receptor type 1 (CRFR1) in the rat and mouse central nervous system

Corticotropin releasing factor (CRF), the most important regulator of various responses to stress, acts through CRF receptors (CRFR). For their characterization in brain tissue of Sprague-Dawley rats and C57BL/6J mice, a recently described polyclonal antibody directed against the N-terminus of rat CRFR1 (rCRFR1) was used. The molecular weights of rat and mouse brain receptors were determined by Western blot analysis to be 80,000-76,000 and 83,000-79,000, respectively, whereas molecular weights of 72,000-59,000 were observed for CRFR1 from rat and mouse pituitary. Immunohistochemical analysis was performed with brain sections of naive rats and mice. Strong CRFR1 staining was detected in the cortex, cerebellum, mesencephalon and pons of both species, whereas weak staining was observed in amygdala and hippocampus. The striatum did not show immunoreactivity. The density of immunostaining was significantly lower in murine than in rat cortex. In contrast, in the pons and mesencephalon of mice, higher density of immunostaining was observed than in the same brain structures of rats. On the basis of the observed differences, it is suggested that CRFR1 is differentially processed in rats and mice. In addition, the density of CRFR1 staining differed between both species.     

Structure and enhanced antimicrobial activity of mechanically activated nano TiO2

Titanium dioxide is a photocatalyst, known not only for its ability to oxidize organic contaminants, but also for its antimicrobial properties. In this article, significant enhancement of the antimicrobial activity of TiO₂ (up to 32 times) was demonstrated after its activation by ball milling. The antimicrobial activity was analyzed for one fungal and 13 bacterial ATCC strains using the microdilution method and recording the minimum inhibitory concentration (MIC) values. In order to further investigate the correlation between the mechanical activation of TiO₂ and its antimicrobial activity, the structure, morphology and phase composition of the material were studied by means of Electron Microscopy, X-ray diffraction and nitrogen adsorption-desorption measurements. UV-Vis diffuse reflectance spectra were recorded and the Kubelka-Munk function was applied to convert reflectance into the equivalent band gap energy (E_g) and, consequently, to investigate changes in the E_g value. X-ray photoelectron spectroscopy was used to analyze the influence of mechanical activation on the Ti 2p and O 1s spectra. The presented results are expected to enable the development of more sustainable and effective advanced TiO₂-based materials with antimicrobial properties that could be used in numerous green technology applications.