Evaluation of problematic indigenous phosphate deposits for phosphoric acid manufacture

To examine the possible utilization of indigenous phosphate reserves, bench scale studies were under-taken to assess their suitability for phosphoric acid manufacture.It was found out that in spite of few problems, the Silicious phosphate reserves of 2–3 million tons could be utilized for phosphoric acid manufacture, because low sulphuric acid consumption 2.52 ton acid/ton P₂O₅ and better P₂O₅ recovery yield (94.71) was achieved. The dolomitic phosphate reserves of 4–5 million tons (having 5–6% MgO) remained problematic, giving low P₂O₅ recovery yield (89.25) and higher sulphuric acid consumption 4.08 tons acid/ton P₂O₅.Product acid from the dolomitic reserves upon concentration became paste like at 36–38% P₂O₅ and therefore, these indigenous dolomitic phosphate reserves could not be utilized for the production of phosphoric acid.     

An adaptive controller design for linear state-delay systems with actuator failures

In this paper, an adaptive fault tolerant controller is developed for a class of linear state delay systems against actuator failures. To design the controller, all parameters of the system are considered to be unknown, but the time delay value is assumed to be known. Actuator failures are characterized by some unknown system inputs are stuck at some unknown fixed values and at unknown time instants. The adaptive controller is designed based on SPR-Lyapunov approach for the cases with the relative degrees of one and two. Closed-loop system stability and asymptotic output tracking are proved using a suitable Lyapunov-Krasovskii functional for each case and the effectiveness of the proposed results has been illustrated through simulation studies.     

Insights into the enhancement of the ASB benthal solids digestion rate

Aerated stabilization basins (ASB) accumulate benthal solids as they provide biotreatment to wastewaters. The accumulated solids must digest at a rate that matches the rate of settling of fresh solids in order to maintain the water column depth at the design value. In practice, however, the deposited solids digest at rates much slower than the fresh deposition rates, resulting in solids accumulation in the system. Excessive build-up of solids warrants dredging or abandoning the solids-filled cells in favour of opening new ones, often due to prohibitive dredging costs. An investigating study on factors affecting digestion rate was carried out using benthal solids from a pulp and paper ASB. The rate of digestion was not limited by the lack of macronutrients N, P, and S in the system or by toxicity due to ammonia or sulphide. Oxidation-reduction potential and pH were found conducive to anaerobic digestion throughout the 1120-day study. However, the generation of volatile organic acids from liquefaction/fermentation of solid substrate appeared to be a major factor limiting the digestion rate. Based on laboratory data, operating an ASB in the optimal mesophilic temperature range could be a practical way of enhancing the benthal solids digestion rate.     

Elastic/piezoelectric solids with electro-mechanical singular surfaces

When a tensor-valued function is continuous in regions Σ₀ and Σ₁, but has a finite jump across the interface Γ₀₁ between Σ₀ and Σ₁, then Γ₀₁ is referred to as singular surface relative to the field . In this paper, it is intended to give a general treatment of three-dimensional static and free vibration analysis of bodies composed of multi-phase elastic and/or piezoelectric bodies with electro-mechanical singular surfaces. The geometry of the medium, boundary conditions, and the geometry of the singular surfaces may be arbitrary. The displacement field and the electric potential in each region are expressed in terms of functions composed of 3-D series and special 3-D functions. The composite functions are selected in such a way that they satisfy exactly: (1) the continuity of the displacement and the electric potential across the singular surfaces; and (2) the homogeneous and inhomogeneous kinematical boundary conditions. This methodology leads to remarkable accuracies in computation of the field quantities, including the quantities, which are discontinuous across the singular surfaces. Taking advantage of any symmetry that may be present in the problem, will substantially increase the convergence rate. For illustrations several examples are examined. Comparisons with the exact solutions, whenever available, established the remarkable accuracy and robustness of the present methodology.     

Anoxic sulfide biooxidation using nitrite as electron acceptor

Biotechnology can be used to assess the well being of ecosystems, transform pollutants into benign substances, generate biodegradable materials from renewable sources, and develop environmentally safe manufacturing and disposal processes. Simultaneous elimination of sulfide and nitrite from synthetic wastewaters was investigated using a bioreactor. A laboratory scale anoxic sulfide-oxidizing (ASO) reactor was operated for 135 days to evaluate the potential for volumetric loading rates, effect of hydraulic retention time (HRT) and substrate concentration on the process performance. The maximal sulfide and nitrite removal rates were achieved to be 13.82 and 16.311 kg/(m3 day), respectively, at 0.10 day HRT. The process can endure high sulfide concentrations, as the sulfide removal percentage always remained higher than 88.97% with influent concentration up to 1920 mg/L. Incomplete sulfide oxidation took place due to lower consumed nitrite to sulfide ratios of 0.93. It also tolerated high nitrite concentration up to 2265.25mg/L. The potential achieved by decreasing HRT at fixed substrate concentration is higher than that by increasing substrate concentration at fixed HRT. The process can bear short HRT of 0.10 day but careful operation is needed. Nitrite conversion was more sensitive to HRT than sulfide conversion when HRT was decreased from 1.50 to 0.08 day. Stoichiometric analyses and results of batch experiments show that major part of sulfide (89-90%) was reduced by nitrite while some autooxidation (10-11%) was resulted from presence of small quantities of dissolved oxygen in the influent wastewater. There was ammonia amassing in considerably high amounts in the bioreactor when the influent nitrite concentration reached above 2265.25mg/L. High ammonia concentrations (200-550 mg/L) in the bioreactor contributed towards the overall inhibition of the process. Present biotechnology exhibits practical value with a high potential for simultaneous removal of nitrite and sulfide from concentrated wastewaters at shorter HRT.     

Osmotic stress on nitrification in an airlift bioreactor

The effect of osmotic pressure on nitrification was studied in a lab-scale internal-loop airlift-nitrifying reactor. The reactor slowly adapted to the escalating osmotic pressure during 270 days operation. The conditions were reversed to the initial stage upon full inhibition of the process. Keeping influent ammonium concentration constant at 420 mg N L(-1) and hydraulic retention time at 20.7h, with gradual increase in osmotic pressure from 4.3 to 18.8x10(5) Pa by adding sodium sulphate, the ammonium removal efficiencies of the nitrifying bioreactor were maintained at 93-100%. Further increase in osmotic pressure up to 19.2x10(5) Pa resulted in drop of the ammonium conversion to 69.2%. The osmotic pressure caused abrupt inhibition of nitrification without any alarm and the critical osmotic pressure value causing inhibition remained between 18.8 and 19.2x10(5) Pa. Nitrite oxidizers were found more sensitive to osmotic stress as compared with ammonia oxidizers, leading to nitrite accumulation up to 61.7% in the reactor. The performance of bioreactor recovered gradually upon lowering the osmotic pressure. Scanning and transmission electron microscopy indicated that osmotic stress resulted in simplification of the nitrifying bacterial populations in the activated sludge as the cellular size reduced; the inner membrane became thinner and some unknown inclusions appeared within the cells. The microbial morphology and cellular structure restored upon relieving the osmotic pressure. Addition of potassium relieved the effect of osmotic pressure upon nitrification. Results demonstrate that the nitrifying reactor possesses the potential to treat ammonium-rich brines after acclimatization.     

Nutritional and therapeutic potentials of rambutan fruit (<Emphasis Type="Italic">Nephelium lappaceum</Emphasis> L.) and the by-products: a review

The progressive development of functional foods and herbal medicine has enthused many researchers to explore novel plant sources. In this regard, the rambutan fruit (Nephelium lappaceum L.) appears to be a promising candidate primarily due to its nutritional and bioactive compositions. With that, this particular review presents a systematic depiction of chemical composition and bioactivities of the rambutan fruit peel, pulp, and seed. Numerous reports do not provide sufficient data pertaining to cultivar, stage of maturity or the environment of fruit, yet the summarized data suggest a myriad of therapeutic potentials derived from the rambutan fruit. In fact, the rambutan fruit has been proven to possess phytochemicals that demonstrate anticancer, anti-allergic, anti-obesity, antidiabetic, anti-HIV, antimicrobial, anti-dengue, anti-hypercholesterolemic, and antihyperglycemic effects in varied in-vitro and in-vivo models. Nonetheless, advance studies are indispensable to further highlight the therapeutic mechanisms involved. In addition, a phytochemical analysis would further establish the rambutan fruit as a sustainable candidate in developing functional foods and pharmaceuticals.     

Development of the γ′ Stability in Co–Al–W Alloys at 800 °C by Alloying with Carbon

Metallurgical and Materials Transactions A - The microstructures and hardnesses of Co–10Al–9W–1C, Co–7Al–5W–1C, and Co–7Al–5W (at. pct) alloys are...     

Functional modeling of astrocytes in epilepsy: a feedback system perspective

Astrocytes, a subtype of glial cells, in the brain provide structural and metabolic supports to the nervous system. They are also active partners in synaptic transmission and neuronal activities. In the present study, a biologically plausible thalamocortical neural population model (TCM) originally proposed by Suffczynski et al. (Neuroscience 126(2):467–484, 2004) is extended by integrating the functional role of astrocytes in the regulation of synaptic transmission. Therefore, the original TCM is modified to consider neuron-astrocyte interactions. Using the modified model, it is demonstrated that the healthy astrocytes are capable to compensate the variation of cortical excitatory input by increasing their firing frequency. In this way, they can preserve the attractor corresponding to the normal activity. Furthermore, the performance of the pathological astrocytes is also investigated. It is hypothesized that one of the plausible causes of seizures is the malfunction of astrocytes in the regulatory feedback loop. That is, pathologic astrocytes are not any more able to regulate and/or compensate the excessive increase of the cortical input. Therefore, pathologic astrocytes lead to the emergence of paroxysmal attractor. Results demonstrate that disruption of the homeostatic or signaling function of astrocytes can initiate the synchronous firing of neurons, suggesting that astrocytes might be one of the potential targets for the treatment of epilepsy.