Graphene as an electronic membrane

Experiments are finally revealing intricate facts about graphene which go beyond the ideal picture of relativistic Dirac fermions in pristine two dimensional (2D) space, two years after its first isolation. While observations of rippling added another dimension to the richness of the physics of graphene, scanning single electron transistor images displayed prevalent charge inhomogeneity. The importance of understanding these non-ideal aspects cannot be overstated both from the fundamental research interest since graphene is a unique arena for their interplay, and from the device applications interest since the quality control is a key to applications. We investigate the membrane aspect of graphene and its impact on the electronic properties. We show that curvature generates spatially varying electrochemical potential. Further we show that the charge inhomogeneity in turn stabilizes ripple formation.Comment: 6 pages, 11 figures. Updated version with new results about the re-hybridization of the electronic orbitals due to rippling of the graphene sheet. The re-hybridization adds the next-to-nearest neighbor hopping effect discussed in the previous version. New reference to recent STM experiments that give support to our theor

Composition of exudates from meat drip loss and microbial spoilage differences between various pork quality classes

This study aimed at elucidating the differences in the composition of meat exudates and determining which constituents contribute the most to microbial growth between five pork quality classes (DFD=Dark, Firm, Dry; RFN=Reddish-pink, Firm and Non-exudative; RSE=Red, Soft and Exudative; PFN=Pale, Firm and Non-exudative and PSE=Pale, Soft and Exudative). A total of 65 Longissimus muscle samples (n=15/pork quality class; n=5 for DFD meat class) were analyzed in triplicate for glucose, glucose-6-phosphate, lactate and protein content, and microbial growth. Differences between pork quality classes were assessed using the MIXED procedure of SAS. Surprisingly, after storage at -80°C, the greatest pH value was observed in the purge of RFN pork (P0.05). Volume of drip loss was a major limit with the methods used. High throughput mass spectroscopy is currently under investigation as a more effective tool to study drip loss composition and effect on microbial growth

Aerobic biological treatment of wastewaters containing dichloromethane

BACKGROUND: Volatilization has been advanced as one of the predominant phenomena contributing to volatile organic carbon emissions from wastewater treatment plants (WWTPs). In this study, strategies for minimizing such air stripping losses when treating a liquid stream containing dichloromethane (DCM), aiming at decreasing the overall emission inventory from WWTPs, were investigated. RESULTS: System R1, consisting of a continuous flow stirred tank reactor (CSTR) treating a liquid stream containing DCM at a concentration of 12 mmol dm−3 presented a biodegradation efficiency (BE) of 68%, based upon chloride release, with 10% of measurable losses, mainly due to volatilization, and 22% of unmeasurable losses. System R2 introduced operational designs aiming at decreasing DCM volatilization. In Experiment R2.1, a biotrickling filter, through which the air stripped from the CSTR was driven, was introduced leading to a reduction from 10% to 7% on the measurable losses. In Experiment R2.2, the air stripped from the CSTR was recirculated at a flow rate of 2.4 dm3 h−1 through the reactormedium before entering the biotrickling filter. The BE was improved from 69% to 82% and the losses associated with air stripping were successfully reduced to 2%. The proposed design, including air recirculation and the biotrickling filter, increased the ratio between the biodegradation rate and the volatilization rate from 7 to 41. CONCLUSIONS: Recirculation of the gaseous effluent through the reactor medium, which allowed for higher residence time within the bioreactor, was shown to be a successful strategy for improving the treatment process, thus minimizing DCM volatilization losses

Bacterial community dynamics in horizontal flow constructed wetlands with different plants for high salinity industrial wastewater polishing

This study is focused on the diversity of bacterial communities from two series of horizontal subsurface flow constructed wetlands (CW) polishing high salinity tannery wastewater. Each series was planted with Arundo donax or Sarcocornia sp. in a substrate composed by expanded clay and sand. Chemical and biochemical oxygen demand removal efficiencies were similar in each series, varying between 58 and 67% (inlet COD 218 ± 28 mg L−1) and 60 and 77% (inlet BOD5 37 ± 6 mg L−1), respectively. High numbers of culturable bacteria were obtained from substrate and root samples – 5.75 × 106-3.95 × 108 CFU g−1 recovered on marine agar and 1.72 × 107-8.46 × 108 CFU g−1 on nutrient agar. Fifty bacterial isolates were retrieved from the CW, related phylogenetically to Firmicutes, Actinobacteria, Bacteroidetes, α-, β-, and γ-Proteobacteria. Changes in the bacterial communities, from roots and substrate of each series, related to the plant species, hydraulic loading rates and along CW operation were examined using denaturating gradient gel electrophoresis (DGGE). The clustering analysis suggested that a diverse and distinct bacterial community inhabits each series, which was related to the type of plant present in each CW.info:eu-repo/semantics/publishedVersio

Bacterial community dynamics in constructed wetlands with different plants for the polishing of high salinity industrial wastewater

info:eu-repo/semantics/publishedVersio

Isolation and identification of microbial populations from an odour treating biofilter

Complex odour emissions are normally associated to the operation of wastewater treatment plants, composting facilities and agro-industry activities. The most common contaminants are hydrogen sulfide (H2S), organic reduced sulfur compounds (e.g.,CH3SH), and volatile organic compounds (VOCs). These compounds can be treated using biological air treatment systems, such as biofilters. Five different types of material, including pieces of wood and polymeric material, were collected from different locations of a biofilter treating odours at an organic waste treatment plant and subjected to microbiological characterization. Colony forming units (CFU/g) ranged from 107 to 108 CFU/g from each different material analyzed. The different materials showed high heterogeneity of microbial colonization, being the diversity higher in a heather based material. After random amplification of polymorphic DNA (RAPD) analysis, a total of 22 different isolates were identified by 16S rRNA sequencing analysis. Ten isolates demonstrated capacity to grow on solid sulphur oxidizing medium. Their capacity to oxidize sulphur compounds in liquid medium is being further studied

Optimization of a multiple water-in-oil-in-water nanoemulsion encasing bacteriophages for inhalational antibiotherapy

Infectious bacterial diseases still remain the main cause of human premature deaths, especially in developing countries. The emergence and spread of pathogenic bacteria resistant to many chemical antibiotics (multidrugresistant strains) have created the need for the development of novel therapeutic agents. Bacteriophages have proven to be an interesting and effective alternative in the management of persistent bacterial infections where conventional chemical antibiotherapies fail. The lethality and specificity of bacteriophages for specific bacteria, their ability to replicate within bacterial hosts and safety of these human-friendly viruses makes them highly lethal antibacterial agents, besides being efficient and relatively cost-effective. Group A streptococci (GAS) are serious human pathogens that cause infections ranging from mild pharyngitis, tonsillitis, to chronic rheumatic heart disease and, in some cases, severe streptococcal toxic shock syndrome and necrotizing fasciitis. The frequency and severity of GAS infections has been increasing over the last decades, which has promoted extensive research on the improvement of naturally occurring antimicrobials as alternatives to their conventional chemical counterparts. In this research effort, development and optimization of a biotechnological process for the inhalational administration of a bacteriophage was pursued, using strategies of nanoencapsulation within lipid nanovesicles. This method of targeting may have a high potential for the treatment of bacterial infections of the respiratory tract, caused mainly by Streptococcus pyogenes. As a proof-of-concept for the nanoencapsulation strategy, and since there is not yet available a strictly lytic bacteriophage cocktail for Streptococcus pyogenes, a well-defined and characterized bacteriophage was utilized, viz. bacteriophage T4. Water-in-oil-in-water (W/O/W) multiple emulsions are nanosystems in which dispersions of small water droplets within larger oil droplets are themselves dispersed in a continuous aqueous phase. Due to their compartimentalized internal structure, multiple emulsions present important advantages over simple O/W emulsions for encapsulation of biomolecules, such as the ability to carry both polar and non-polar molecules, and a better control over releasing of therapeutic molecules. Bacteriophage T4 was accordingly entrapped within W/O/W multiple nanoemulsions, aiming at mimicking the multifunctional design of biology, optimized with several lipid matrices, poloxamers and stabilizing layer compositions. Physicochemical characterization of the optimized bacteriophage-encasing nanovesicle formulations encompassed determination of particle (hydrodynamic) size, size distribution and particle charge (Zeta potential), via Dynamic Light Scattering analysis, surface morphology via Cryo-SEM, and thermal analysis via DSC, whereas antimicrobial activity of the nanoemulsions produced were evaluated via the “spot-test” using appropriate bacterial cultures