A critical literature review on biohydrogen production by pure cultures

Global research is moving forward in developing hydrogen as a renewable energy source in order to alleviate concerns related to carbon dioxide emissions and depleting fossil fuels resources. Biohydrogen has the potential to replace current hydrogen production technologies relying heavily on fossil fuels. Batch and continuous systems employing pure mesophiles and thermophiles isolates and co-cultures of isolates have been investigated. The co-cultures of the isolates achieved better results than mono-cultures of the isolates with respect to different parameters. This paper presents a critical review of the literature reporting on fermentative biohydrogen production by pure cultures of bacteria in different systems. Synergies between different types of bacteria, i.e. strict and facultative, and a comparison between mono- and co-cultures, types of feedstocks, and preferred feedstocks for mono- and cultures are outlined.     

On the interdependence between kinetics of friction-released thermal energy and the transition in wear mechanisms during sliding of metallic pairs

Sliding of complying solids is often associated with the release of thermal energy. This energy accumulates within the mechanically affected zone (MAZ) of the rubbing pair. The accumulation of thermal energy within the MAZ tends to maximize the potential energy at the interface. Now, since a maximized potential energy renders the sliding system unstable, one (or both) materials will respond in a manner that consumes (dissipates) part or all of the accumulated energy in order to re-establish system stability or at least equilibrium. The material response may be in many forms: oxidation, crack initiation, wear debris generation, transition in wear mechanism, etc. As such, one may consider that these processes are intrinsic responses by the material to dissipate energy. Moreover, many of these responses are triggered at different stages of rubbing according to the balance between the rate of external thermal energy release (which is a factor of the nominal operation parameters) and the rate of thermal energy accumulation—RTEA (which is mainly a function of thermal transport properties of the rubbing pair). An interesting feature of this view is that the later quantity—RTEA—is directly related to the ability of the particular solid to dissipate thermal loads. This quantity, which is termed here as the heat dissipation capacity (HDC), is directly related to the state of blockage of energy dissipation paths within the rubbing solid. The objective of this paper is therefore to study the relation between the change in the HDC of a sliding solid and the transition in the mechanism of wear. It is shown that there exists an inverse correlation between the change in the HDC and the transition in the mechanism of wear. Moreover, it is also shown that a so-called ratio of residual heat (RRH, representing the ratio between the actual thermal load and the part of that load that is not dissipated by the solid) is a significant parameter that influences the magnitude and mechanism of wear. The findings are applied to explain the wear behavior of two tribo systems: a titanium (Ti-6Al-4V) sliding on itself and sliding on a steel (AISI M2) counterpart.     

BOT Viability Model for Large-Scale Infrastructure Projects

The key to a successful implementation of a build-operate-transfer (BOT) infrastructure project is in-depth analysis of all aspects related to economic, environmental, social, political, legal, and financial feasibility of the project. For these reasons, the analysis of the project feasibility decision needs a technique to include the qualitative decision factors that have a strong impact on the project. This paper aims to introduce a decomposed evaluation model developed to assess the most common significant decision factors that strongly affect the feasibility of BOT projects. The paper describes the viability decision factors that were identified and screened with the assistance of a group of industry experts. This analysis yielded 21 significant factors that would have a certain impact on the feasibility of any BOT project. These factors were classified into three relative categories forming the structure of the suggested project viability model. This model presents a new approach, based on the analytical hierarchy process technique, to evaluate the relationships between decision factors related to project feasibility determination. The new approach has been validated by information obtained from three case studies of BOT projects. The proposed approach to project feasibility evaluation aims to increase the decision maker’s ability to determine the factors contributing the most to the viability to the BOT project at hand.     

Total dissolved solids removal by electrochemical ion exchange (EIX) process

In the present investigation, synthetic wastewater was prepared by the addition of required amount of salts into deionized water. Their performance, on removal of Cl⁻, SO₄²⁻, PO₄³⁻, Ca²⁺, Fe²⁺ and Mg²⁺ in laboratory scale plate and frame type electrochemical ion exchange (EIX) cells, were evaluated under varying operating conditions. Ruthenium dioxide coated titanium plates (RuO₂/Ti) were used as anode and stainless steel plates as cathode in all the four different EIX cells used in the present investigation. All the four EIX cells were run for a maximum of 7 h. Almost complete removal of all the above ionic solids were observed within 4.5-7 h under one or more test conditions.     

In-cylinder fluid flow,turbulence and spray models—A review

This article is a literature review of use of computational fluid dynamics (CFD) codes to model the in-cylinder fluid flow, turbulence and spray characteristics. This study is based on the reports of about 60 scientists, who published their results between 1978 and 2008. Most of the scientists and researchers used CFD codes to analyze the models under simulation conditions and compared these simulated results with experimental results. Some scientists reported that different engines exhibit different behaviors with similar fuel sprays and Re-Normalized Group (RNG) k-? model is the best applicable turbulence model for engine simulation. The KIVA code is widely used for model development in academia due to the availability of the source. However, its capability for resolving complex geometries is limited. On the other hand, other commercial CFD codes such as STAR-CD, FIRE, VECTIS and FLUENT are frequently used by the industry due to their superior mesh generation interfaces and because of their available user support. Some scientists combined STAR-CD and KIVA code for the engine simulations but they concluded that, it would be preferable to implement the advanced submodels directly into one commercial code for engine simulations.     

Hybridization of kaolinite by consecutive intercalation: Preparation and characterization of hyperbranched poly(amidoamine)–kaolinite nanocomposites

Different nanocomposites based on virgin as well as treated kaolinites, as dispersed phases, and hyperbranched poly(amidoamine) (PAMAM) as a continuous phase were formulated using aqueous dispersion method. The interactive forces between the phases were evidenced using different techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscope (TEM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed that intercalation of PAMAM took place in pre-expanded kaolinite to give exfoliated nanocomposite. However, virgin kaolinite was successfully intercalated with PAMAM without pretreatment to give a nanocomposite of intercalated type with a basal space of about 47 Å. All samples exhibited lower Tg values along with worsened thermal stability compared to the parent polymer.     

On multistage ranked set sampling for distribution and median estimation

A variation of ranked set sampling (RSS), multistage RSS (MSRSS), is investigated for the estimation of the distribution function and some of its quantiles, in particular the median. It is shown that this method is significantly more efficient than simple random sampling (SRS). The method becomes more and more effective as the number of stages r increases. Two estimators of the median based on MSRSS are proposed and compared to the sample median obtained by SRS.     

Developing Flexible Software Using Agent-Oriented Software Engineering

Software agents are associated with modern industrial software. In various application fields such as e-business, telecommunications, logistics, and industrial automation, software based on agents seems to make the challenges in modern applications easier to overcome. However, it's often unclear what a software agent is and why problems can be better solved with it. Is it concerning a technology, an architecture, or a programming concept? This article presents a general introduction to software agent concepts from the software engineer's perspective, explaining the theoretical basis and clarifying to which type of problem software agents might represent a reasonable approach.     

Nrf2 Activation Attenuates Acrylamide-Induced Neuropathy in Mice

Acrylamide is a well characterized neurotoxicant known to cause neuropathy and encephalopathy in humans and experimental animals. To investigate the role of nuclear factor erythroid 2-related factor 2 (Nrf2) in acrylamide-induced neuropathy, male C57Bl/6JJcl adult mice were exposed to acrylamide at 0, 200 or 300 ppm in drinking water and co-administered with subcutaneous injections of sulforaphane, a known activator of the Nrf2 signaling pathway at 0 or 25 mg/kg body weight daily for 4 weeks. Assessments for neurotoxicity, hepatotoxicity, oxidative stress as well as messenger RNA-expression analysis for Nrf2-antioxidant and pro-inflammatory cytokine genes were conducted. Relative to mice exposed only to acrylamide, co-administration of sulforaphane protected against acrylamide-induced neurotoxic effects such as increase in landing foot spread or decrease in density of noradrenergic axons as well as hepatic necrosis and hemorrhage. Moreover, co-administration of sulforaphane enhanced acrylamide-induced mRNA upregulation of Nrf2 and its downstream antioxidant proteins and suppressed acrylamide-induced mRNA upregulation of tumor necrosis factor alpha (TNF-α) and inducible nitric oxide synthase (iNOS) in the cerebral cortex. The results demonstrate that activation of the Nrf2 signaling pathway by co-treatment of sulforaphane provides protection against acrylamide-induced neurotoxicity through suppression of oxidative stress and inflammation. Nrf2 remains an important target for the strategic prevention of acrylamide-induced neurotoxicity.     

Poly(amidoamine) dendritic structures,bearing different end groups,as adhesion promoters for urea–formaldehyde wood adhesive system

A series of core‐shell poly(amidoamine) (PAMAM) dendritic compounds bearing different end groups such as  OH, NH₂, and NH₃⁺⁻Cl up to the third generation were prepared via successive Michael addition of a nucleophilic core (ethylenediamine) to methylacrylate followed by amination steps using ethylenediamine for the amine‐terminated while ethanolamine for the hydroxyl‐terminated compounds, also the protonated ammonium salt terminated form was obtained by cationization of the amine‐terminated form using hydrochloric acid solution. The Surface activity and aggregation behavior of the corresponding aqueous solutions of the prepared generations with their different end groups were studied and confirmed by surface tension measurements using ring method technique. The prepared dendrimers showed high surface activity and the measurements revealed their ability to self aggregate in water at very low concentrations, critical aggregation concentrations (CACs). The CACs were found to decrease with increasing the generation number, which implies that molecular weight and structure play important rules in controlling the surface activity and CAC. The dendritic compounds proved to be effective as adhesion promoters for urea formaldehyde (UF) resins when applied as wood adhesive systems, which was ascribed in partial to the improved wetting over the substrate, a role that is fundamentally related to the huge number of function groups present at the interface. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011