Prediction of gas hold-up and liquid velocity in airlift reactors using two-phase flow friction coefficients

The overall friction coefficient (K_f) of airlift reactors was estimated using equivalent lengths (L_eq) and friction factors ( f ). The friction factor was calculated taking into account the riser liquid velocity profile corresponding to the two-phase flow and using classical one-phase equations. A previously described model was used to obtain simultaneously both gas hold-up and liquid circulation velocity. The model simulates experimental data obtained in a wide range of configurations of internal (2 and 30 dm³ volume) and external (from 8 to 600 dm³ volume) airlift reactors with Newtonian (water and alcohol solutions) and non-Newtonian (carboxymethylcellulose (CMC) solutions) systems. Com-parison with other models from the literature yielded similar results.     

The influence of dietaryβ-carboline alkaloids on growth rate,food consumption,and food utilization of larvae ofSpodoptera exigua (Hubner)

-Carboline alkaloids are found worldwide in many plant families. Harman, harmine, and other simple -carboline alkaloids were tested for activity against a generalist phytophagous insect, the beet army worm [Spodoptera exigua (Hubner)]. Chronic dietary exposure tests (neonate to pupa) reveal potent antifeedant and possible toxic effects. Acute dietary exposure tests on fifth-instar larvae also demonstrate antifeedant activity.     

On‐Chip Self‐Assembly of a Smart Hybrid Nanocomposite for Antitumoral Applications

A hybrid nanocomposite comprised by porous silicon nanoparticles and a stimuli responsive polymeric material, polyethylene glycol‐block‐poly(L‐histidine), is spontaneously formed by nanoprecipitation in a flow‐focusing microfluidic chip. The nanocomposite presents a novel hybrid compound micelle structure with a great robustness for therapeutic applications. Therefore, the nanocomposite is developed and tested as a “smart” multistage drug delivery system (MDDS) in response to some of the current problems that cancer treatment presents. Based on the stimuli‐responsive behavior of the nanocomposite, a chemotherapeutic agent is successfully loaded into the nanosystem and released upon changes in the pH‐values. The nanocomposite demonstrates enhanced stability in plasma, narrow size distribution, improved surface smoothness, and high cytocompatibility. Furthermore, the nanocomposite presents reduced nanoparticle internalization by phagocytic macrophage cells and pH‐dependent cell growth inhibition capacity. Overall, the developed hybrid nanocomposite shows very promising features for its further development as a “smart” pH‐responsive MDDS.     

Fate of the chromene encecalin in the interaction ofEncelia farinosa and its specialized herbivoreTrirhabda geminata

Leaf beetles of the speciesTrirhabda geminata are specialized herbivores that are able to feed on the chemically well-protected foliage of the desert sunflowerEncelia farinosa, which contains the insecticidal chromene derivative encecalin. Chemical analysis of the beetles and their fecal excretions indicated that encecalin is present only in the alimentary canal and is not absorbed across the gut membrane, as previously shown for other herbivorous insects (e.g., the Egyptian armyworm,Spodoptera littoralis) that are susceptible to this chromene derivative. Further differences betweenT. geminata and nonadapted insects were observed with regard to the metabolism of encecalin. Whereas the encecalin-resistent leaf beetles metabolize encecalin mainly to encecalol by reduction of the acetyl group, susceptible insects, such as larvae ofS. littoralis, metabolize encecalin mainly by exoxidation of the 3,4 double bond, which creates a powerful alkylating agent and is responsible for the toxicity of encecalin. Reductive rather than oxidative metabolism of encecalin therefore seems important for the resistance ofT. geminata against the chemical defense of their host plantE. farinosa.     

In vitro evaluation of inflammatory cell response after CF4 plasma surface modification of poly(methyl methacrylate) intraocular lenses

Nasal intermittent positive pressure ventilation (NIPPV) provides effective ventilatory support in patients with nocturnal hypoventilation. Nasal pressure support ventilation (NPSV), which only provides ventilation in response to patient triggering, may also be effective, simpler, and cheaper, but has not been evaluated. NIPPV and NPSV were compared in 12 patients with nocturnal hypoventilation, requiring domiciliary ventilatory support. The patients were studied on three consecutive nights, in random order: a control night without ventilation and a night on each mode of ventilatory support using the bilevel positive airway pressure (BiPAP) ventilator. Both NIPPV and NPSV significantly increased mean arterial oxygen saturation (SaO2) compared to the control night (NIPPV mean increase 4.1%; 95% confidence interval (CI) 2.2 to 6.1, NPSV 4.4%; CI 2.1 to 6.6) with no significant difference between the two modes. The percentage of the study night spent below 90% SaO2 was significantly reduced by both ventilator modes compared to the control night (median reduction on NIPPV 37%; CI -54 to -10, reduction on NPSV 31%; CI -53 to -9, with no significant difference between NPSV and NIPPV. NPSV was as effective as NIPPV in patients with nocturnal hypoventilation, which suggests that these patients are able to trigger the ventilator adequately. The lower cost of NPSV will make it accessible to more patients with chronic lung disease.     

An event-triggered control approach for the leader-tracking problem with heterogeneous agents

This paper presents an event-triggered control and communication framework for the cooperative leader-tracking problem with communication constraints. Continuous communication among agents is not assumed in this work and decentralised event-based strategies are proposed for agents with heterogeneous linear dynamics. Also, the leader dynamics are unknown and only intermittent measurements of its states are obtained by a subset of the followers. The event-based method not only represents a way to restrict communication among agents, but it also provides a decentralised scheme for scheduling information broadcasts. Notably, each agent is able to determine its own broadcasting instants independently of any other agent in the network. In an extension, the case where transmission of information is affected by time-varying communication delays is addressed. Finally, positive lower-bounds on the inter-event time intervals are obtained in order to show that Zeno behaviour does not exist and, therefore, continuous exchange of information is never needed in this framework.     

Output feedback networked control with persistent disturbance attenuation

This paper presents a model-based control approach for output feedback stabilization and disturbance attenuation of continuous time systems that transmit measurements over a limited bandwidth communication network. Necessary and sufficient conditions for asymptotic stability of the networked system in the presence of persistent external disturbances are given. The results in this paper provide a significant improvement in the performance of the system and provide a considerably reduction of the necessary network bandwidth with respect to similar approaches in the literature.     

Efficiency of natural systems for removal of bacteria and pathogenic parasites from wastewater

A combined constructed wetland formed by a facultative pond (FP), a surface flow wetland (SF) and a subsurface flow wetland (SSF) was studied from December 2004 until September 2005 in north-western Spain in order to evaluate their efficiency in the removal of pathogenic and indicator microorganisms and to determine their relationships. Microbial removal ranged from 78% for coliphages to over 99% for helminth eggs, depending on the treatment system. The highest removal of indicator bacteria (total coliforms, E. coli, faecal streptococci and Clostridium perfringens) occurred in the stabilization pond, reaching 84%, 96%, 89% and 78%, respectively. However, the greatest removal of protozoan pathogens (Cryptosporidium and Giardia) and coliphages was found in the SSF wetland, 98%, 97% and 94%, respectively. In contrast, the SF wetland was most efficient in the removal of pathogenic parasites when considering superficial removal rates. Seasonal differences in organism removal were not statistically significant during the study period. First-order removal rate constants ranged from 0.0027 to 0.71 m/d depending on the microorganism and type of wetland. Significant correlations were found between pathogenic parasites and faecal indicators in the influent of the treatment system but not in the other sampling points suggesting that such relations varied along the system due to the different survival rates of the microorganisms.