Magnetoresistance of nanobridges of lanthanum-strontium manganite

Nanobridges are fabricated from lanthanum-strontium anganite deposited on Si₃N₄ membranes perforated by a focused ion beam. The magnetoresistance is ≈9% in fields of ∼ kOe. Nonlinearity of the current-voltage characteristic of the bridges is observed, and it is found that the maximum of the resistance is shifted to lower temperatures from that of a control film sample of composition La_0.8Sr_0.2MnO₃. Pis’ma Zh. Tekh. Fiz. 25, 42–50 (May 26, 1999)     

Integral equation method for solution of boundary value problems of structural mechanics,Part II. Elliptic partial diffeerential equations

The method presented in Part I of this paper¹ is extended to problems governed by a system of partial differential equations. The basic clarity and simplicity of the method is preserved. The domain of integration is covered by a net of orthogonal (not necessarily equidistant) straight lines. Choosing again highest derivatives with respect to each of the co-ordinates as unknowns, it is possible to reduce the problem to a system of integral equations along the lines of the adopted net. The subsequent procedure is basically the same as in Part I. The results prove to be of remarkable accuracy even for very coarse nets.     

Capturing the high-risk environment of the transition economy in Bulgaria—a simulation-based DSS

Eastern European countries have undergone a transition from centralized economic planning to more open economic systems. Hard data based upon past experience are inappropriate for decision making in this radically changed environment. A team of Bulgarian and U.S. researchers utilized system dynamics simulation to model the microeconomic environment of a Bulgarian winery expanding into regional and international markets. Expert opinion was provided for both micro- and macroeconomic factors. Given the uncertainty of the data and the ambiguity in the experts' opinions, fuzzy logic was used to model the transitional economic firm's decision making.     

Cellular Control of Protein Turnover via the Modification of the Amino Terminus

The first amino acid of a protein has an important influence on its metabolic stability. A number of ubiquitin ligases contain binding domains for different amino-terminal residues of their substrates, also known as N-degrons, thereby mediating turnover. This review summarizes, in an exemplary way, both older and more recent findings that unveil how destabilizing amino termini are generated. In most cases, a step of proteolytic cleavage is involved. Among the over 500 proteases encoded in the genome of higher eukaryotes, only a few are known to contribute to the generation of N-degrons. It can, therefore, be expected that many processing paths remain to be discovered.     

New-generation of cryogenic sapphire microwave oscillators for space, metrology, and scientific applications

This article reports on the characterization of cryogenic sapphire oscillators (CSOs), and on the first test of a CSO in a real field installation, where ultimate frequency stability and continuous operation are critical issues, with no survey. Thanks to low-vibration liquid-He cryocooler design, Internet monitoring, and a significant effort of engineering, these oscillators could bridge the gap from an experiment to a fully reliable machine. The cryocooler needs scheduled maintenance every 2 years, which is usual for these devices. The direct comparison of two CSOs demonstrates a frequency stability of 5 × 10(-16) for 30 s ≤ τ ≤ 300 s integration time, and 4.5 × 10(-15) at 1 day (1 × 10(-14) typical). Two prototypes are fully operational, codenamed ELISA and ULISS. ELISA has been permanently installed the new deep space antenna station of the European Space Agency in Malargu?e, Argentina, in May 2012. ULISS is a transportable version of ELISA, modified to fit in a small van (8.5 m(2) footprint). Installation requires a few hours manpower and 1 day of operation to attain full stability. ULISS, intended for off-site experiments and as a technology demonstrator, and has successfully completed two long-distance travels.     

SERR Spectroelectrochemistry as a Guide for Rational Design of DyP-Based Bioelectronics Devices

Immobilised dye-decolorizing peroxidases (DyPs) are promising biocatalysts for the development of biotechnological devices such as biosensors for the detection of H₂O₂. To this end, these enzymes have to preserve native, solution properties upon immobilisation on the electrode surface. In this work, DyPs from Cellulomonas bogoriensis (CboDyP), Streptomyces coelicolor (ScoDyP) and Thermobifida fusca (TfuDyP) are immobilised on biocompatible silver electrodes functionalized with alkanethiols. Their structural, redox and catalytic properties upon immobilisation are evaluated by surface-enhanced resonance Raman (SERR) spectroelectrochemistry and cyclic voltammetry. Among the studied electrode/DyP constructs, only CboDyP shows preserved native structure upon attachment to the electrode. However, a comparison of the redox potentials of the enzyme in solution and immobilised states reveals a large discrepancy, and the enzyme shows no electrocatalytic activity in the presence of H₂O₂. While some immobilised DyPs outperform existing peroxidase-based biosensors, others fail to fulfil the essential requirements that guarantee their applicability in the immobilised state. The capacity of SERR spectroelectrochemistry for fast screening of the performance of immobilised heme enzymes places it in the front-line of experimental approaches that can advance the search for promising DyP candidates.     

Effect of gamma‐irradiation on the electret properties of poly(L‐lactide)

Electret stability of poly(L ‐lactide) (PLA) films, gamma‐irradiated up to 100 kGy has been investigated by measuring the surface potential during the storage period. PLA samples—40‐μm thick films—were prepared by the casting method and then irradiated in a ⁶⁰Co radiation facility at a dose rate of 0.25 kGy/h. The structural changes during the irradiation were estimated by viscometric, differential scanning calorimetry and scanning electron microscope measurements. Random chain scission and appearance of end radicals are the most probable results of the irradiation process. After irradiation, the samples were charged in a corona discharge system and surface potential was measured by the method of the vibrating electrode with compensation. The values of the surface potential of the irradiated samples were higher in comparison with the non‐irradiated samples. This effect could be related to the degradation of the macromolecules and changes in the crystal state of PLA during the irradiation. Both of the mentioned factors lead to structural defects that increase the number of discrete trapping levels. The effect of low pressure on the surface potential drop was also investigated. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Application of modified Kalina cycle in biomass chp plants

This paper presents alternatives to Kalina cycles typically used in place of the organic Rankine cycle in biomass power plants. Overviews of both Rankine and Kalina cycles are given alongside the possibilities of using biomass as a viable energy source and recommended guidelines from the engineering practice for selection and management of these cycles. Benefits of Kalina novel bottoming cycle (and the alternative cycles presented herewith) over the Rankine cycle are the higher thermodynamic cycle efficiency and lower capital expenditures combined with the possibility of using low-grade heat sources, such as biomass or waste heat from exhaust gases. Analysis of ammonia-water binary system under various operating conditions has been performed for all the proposed cycles based on the published references and it has been shown that the proposed alternative models prove to be simpler and to have similar or even greater thermodynamic efficiency compared with the Kalina novel bottoming cycle.     

Antimicrobial nanoparticles and biodegradable polymer composites for active food packaging applications

The food industry faces numerous challenges to assure provision of tasty and convenient food that possesses extended shelf life and shows long-term high-quality preservation. Research and development of antimicrobial materials for food applications have provided active antibacterial packaging technologies that are able to meet these challenges. Furthermore, consumers expect and demand sustainable packaging materials that would reduce environmental problems associated with plastic waste. In this review, we discuss antimicrobial composite materials for active food packaging applications that combine highly efficient antibacterial nanoparticles (i.e., metal, metal oxide, mesoporous silica and graphene-based nanomaterials) with biodegradable and environmentally friendly green polymers (i.e., gelatin, alginate, cellulose, and chitosan) obtained from plants, bacteria, and animals. In addition, innovative syntheses and processing techniques used to obtain active and safe packaging are showcased. Implementation of such green active packaging can significantly reduce the risk of foodborne pathogen outbreaks, improve food safety and quality, and minimize product losses, while reducing waste and maintaining sustainability.