Fireclay Refractories from Ugandan Kaolinitic Minerals

In the present work, two deposits, one of kaolin and the other of ball clay, located in Uganda were investigated for the possibility of manufacturing fireclay refractories. Kaolin from the Mutaka deposit was used as the main source of alumina while ball clay from Mukono was the main plasticizer and binder material. The formulated green body was consolidated by wet pressing and fired at 1350°C in a tunnel kiln. Characterization of the sintered articles was done by X‐ray diffraction, scanning electron microscopy, and chemical composition (ICP‐AES). In addition, technological properties related to thermal conductivity, thermal shock, alkali resistance, water absorption, porosity, shrinkage, permanent linear change, linear thermal expansion, refractoriness under load, and cold crushing strength were determined. The properties of the articles manufactured from these naturally occurring raw minerals reveal that they compare favorably with those of parallel types. Thus, the raw materials can be exploited for industrial production.     

Crystal structure and fluorescence spectrum of 3Y2O3, WO3: Eu3+

A structural study of the rhombohedral compound 3Y₂O₃, WO₃ doped with Europium was carried out. The fluorescence spectrum of Eu³⁺ was measured in the frequency range 12500–25000 cm^?1. Transitions from the excited state 5D₀ to the Stark components of the five lowest 7F_J (J=0,1,2,3,4) states were observed. The analysis revealed that the rare earth ion is within a crystal field of C₁ symmetry. We found values for the B^k_q parameters which give a good agreement between the observed and calculated levels.     

Characterization of fine grain Ba0.995Y0.005TiO3 ceramics obtained from gel-precursor nanopowder

Using an acetate-alkoxide sol-gel route in which the precursors are barium acetate, yttrium isopropoxide and titanium diisopropoxide bis-acetylacetonate, we prepared a ferroelectric material with the formula: Ba1-xYxTiO3, x = 0.005. SEM analysis showed a polymeric microstructure of the gel due to the chelated titanium alkoxide precursor used as starting materials. The evolution of the structure and microstructure of the precursor gel heated at temperatures up to 1000 degrees C was studied by various techniques. The powder obtained by heating the gel at 1100 degrees C presented a homogeneous structure consisting of submicronic particles (approximately 200 nm). XRD and SAED analyses revealed that Ba0.995Y0.005TiO3 nanocrystals of about 5-10 nm appeared at 600 degrees C, together with BaCO3. The presence of barium carbonate was identified also by IR spectroscopy and thermal analyses. The ceramics obtained from the as-prepared powder presented good dielectric properties (capacitance = 840 pF/dielectric constant = 3860 and dielectric loss (tandelta) = 0.078 at Curie temperatures of 120-121 degrees C).     

Revised procedures for yeast metabolites extraction: application to a glucose pulse to carbon-limited yeast cultures, which reveals a transient activation of the purine salvage pathway

In this study we have revised our original procedure of yeast metabolites extraction. We showed that: (a) less than 5% of intracellular metabolites leaks out during the step of rapid arrest of cellular metabolism by quenching yeast cells into a 60% methanol solution kept at -40 degrees C; and (b) with a few exception, the stability of metabolites were not altered during the 3 min boiling procedure in a buffered ethanol solution. However, there was a loss of external added metabolites of 5-30%, depending on the type of metabolites. This was mainly attributable to their retention on cellular debris after ethanol treatment, which prevented centrifugation of the cellular extracts before evaporation of ethanol. We further simplified our previous high-performance ionic chromatography (HPIC) techniques for easier, more reliable and robust quantitative measurements of organic acids, sugar phosphates and sugar nucleotides, and extended these techniques to purine and pyrimidine bases, using a variable wavelength detector set at 220 and 260 nm in tandem with a pulsed electrochemical or suppressed conductivity detector. These protocols were successfully applied to a glucose pulse to carbon-limited yeast cultures on purines metabolism. This study showed that glucose induced a fast activation of the purine salvage pathway, as indicated by a transient drop of ATP and ADP with a concomitant rise of IMP and inosine. This metabolic perturbation was accompanied by a rapid increase in the activity of the ISN1-encoded specific IMP-5'-nucleotidase. The mechanism of this activation remains to be determined.     

Tailored Silica Macrocellular Foams: Combining Limited Coalescence‐Based Pickering Emulsion and Sol–Gel Process

Solid‐sate monolithic macrocellular foams are synthesized by mineralizing the continuous phase of oil‐in‐water Pickering emulsions, used as templates, with the sol–gel process. For the first time, taking advantage of the limited coalescence phenomenon occurring in emulsions stabilized by solid particles, concentrated emulsions with calibrated drop size are produced, leading to the synthesis of monolithic foams with nearly monodisperse macroscopic voids. Such a strategy allows independent tuning of the macrocellular void diameters from 20 to 800 μm and the diameter of the windows connecting adjacent cells. The obtained macrocellular foams also bear micro‐ and mesoporosity, leading to Brunauer, Emmet and Teller (BET) surface area values between 700 and 900 m² g^?1 with a good mesopores monodispersity.     

Lignin/Carbohydrate Complex Isolated from Posidonia oceanica Sea Balls (Egagropili): Characterization and Antioxidant Reinforcement of Protein-Based Films

A lignin fraction (LF) was extracted from the sea balls of Posidonia oceanica (egagropili) and extensively dialyzed and characterized by FT-IR and NMR analyses. LF resulted water soluble and exhibited a brownish-to-black color with the highest absorbance in the range of 250–400 nm, attributed to the chromophore functional groups present in the phenylpropane-based polymer. LF high-performance size exclusion chromatography analysis showed a highly represented (98.77%) species of 34.75 kDa molecular weight with a polydispersity index of 1.10 and an intrinsic viscosity of 0.15. Quantitative analysis of carbohydrates indicated that they represented 28.3% of the dry weight of the untreated egagropili fibers and 72.5% of that of LF. In particular, eight different monosaccharides were detected (fucose, arabinose, rhamnose, galactose, glucose, xylose, glucosamine and glucuronic acid), glucuronic acid (46.6%) and rhamnose (29.6%) being the most present monosaccharides in the LF. Almost all the phenol content of LF (113.85 ± 5.87 mg gallic acid eq/g of extract) was water soluble, whereas around 22% of it consisted of flavonoids and only 10% of the flavonoids consisted of anthocyanins. Therefore, LF isolated from egagropili lignocellulosic material could be defined as a water-soluble lignin/carbohydrate complex (LCC) formed by a phenol polymeric chain covalently bound to hemicellulose fragments. LCC exhibited a remarkable antioxidant activity that remained quite stable during 6 months and could be easily incorporated into a protein-based film and released from the latter overtime. These findings suggest egagropili LCC as a suitable candidate as an antioxidant additive for the reinforcement of packaging of foods with high susceptibility to be deteriorated in aerobic conditions.     

Anticancer activity of Carica papaya: A review

Carica papaya is widely cultivated in tropical and subtropical countries and is used as food as well as traditional medicine to treat a range of diseases. Increasing anecdotal reports of its effects in cancer treatment and prevention, with many successful cases, have warranted that these pharmacological properties be scientifically validated. A bibliographic search was conducted using the key words “papaya”, “anticancer”, and “antitumor” along with cross‐referencing. No clinical or animal cancer studies were identified and only seven in vitro cell‐culture‐based studies were reported; these indicate that C. papaya extracts may alter the growth of several types of cancer cell lines. However, many studies focused on specific compounds in papaya and reported bioactivity including anticancer effects. This review summarizes the results of extract‐based or specific compound‐based investigations and emphasizes the aspects that warrant future research to explore the bioactives in C. papaya for their anticancer activities.     

Task switching: Interplay of reconfiguration and interference control.

The task-switching paradigm is being increasingly used as a tool for studying cognitive control and task coordination. Different procedural variations have been developed. They have in common that a comparison is made between transitions in which the previous task is repeated and transitions that involve a change toward another task. In general, a performance switch cost is observed such that switching to a new task results in a slower and more error-prone execution of the task. The present article reviews the theoretical explanations of the switch cost and the findings collected in support of those explanations. Resolution and protection from interference by previous events explain part of the switching cost, but processes related to task setting and task preparation also play a prominent role, as testified by faster execution and lower switch costs when the preparation time is longer. The authors discuss the evidence in favor of each of these sets of accounts and raise a number of questions that situate task switching in a broader context of cognitive control processes. The role of several aspects of the task set, including task variations, task-set overlap, and task-set structure, is addressed, as is the role of knowledge about probability of task changes and about the structure of task sequences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)