Morphology of the poly(vinyl alcohol)–poly(vinyl acetate) copolymer in macrodefect-free composites: a 13C magic-angle-spinning nuclear magnetic resonance and 1H spin-diffusion study

A study was made of the macrodefect-free (MDF) composite based on aluminate cement and a poly(vinyl alcohol)–poly(vinyl acetate) (PVAc) copolymer by ¹³C cross-polarization magic-angle-spinning nuclear magnetic resonance. The spectra were run on both the copolymer and the MDF composite in order to observe the atomic environments of the carbon nuclei. An analysis of the intramolecular hydrogen bonds showed a stronger modification in the sample containing CaAl₂O₄ (CA) than in that containing Ca₃Al₂O₆ (C₃A). From the spectra, it was seen that deacetylation had occurred, and that there was interaction between acetate groups and the calcium and aluminium ions. Proton relaxation times both in the laboratory frame, T ₁(H), and in the rotating frame, T1ρ(H), were exploited for the study of the dimension of the polymer matrix in MDF composites. An extended interphase was identified in the composite containing CA. A comparison with the behaviour of the composite based on silicates Ca₃SiO₅–PVAc highlights the better mixing of the phases in the MDF composites containing CA. This revised version was published online in November 2006 with corrections to the Cover Date.     

Analysis of the interface conditions during drying of rice

The influence of the relative air humidity on the surface conditions of rice grain during drying was investigated. It was found that the equilibrium condition given by the desorption isotherm of the product is not valid over the whole range of relative humidity analysed. While this condition was verified with air of high relative humidity (between 43 and 59% for drying temperatures ranging from 40 to 70°C), the experimental results indicated that the surface moisture approaches the monolayer value given by the Brunauer, Emmett and Teller (BET) desorption isotherm when drying takes place with air of low relative humidity (7 and 14% for the same temperature range). An explanation of these facts is suggested taking into account the high value of the heat of desorption associated with the monolayer moisture content of the product under investigation. Finally, a method based on the Fick's second law solution when the time of drying becomes large enough is proposed to evaluate the surface moisture content of the grain independently of the conditions of the air drying.     

Performance of a Scraped-Surface Heat Exchanger Under Ultra High Temperature Conditions: A Dimensional Analysis

Performance characteristics of a pilot-scale scraped-surface heat exchanger (Contherm Model 6 × 2) under UHT operating conditions were evaluated. Outlet temperature and overall heat transfer coefficient (U) were significantly affected by rotational speed of the blades, mass flow rate of feed, feed inlet temperature, steam pressure and solids content of the model low-acid liquid food (soy extracts). The scraping action of the blades greatly improved the performance up to about 350 rpm; higher blade speeds had little or no effect and sometimes decreased U values. Application of dimensionless models showed that the effect of axial Reynolds number (Re_A) on the Nusselt number was more significant in the turbulent regime (Re_A > 1800), while rotational Reynolds number above 10⁵ had a significant effect at all values of Re_A between 1200 and 3700. At very high values of the Taylor number (> 10¹⁰) when laminar axial flow conditions prevailed, Nusselt number decreased with increase in rotational Reynolds number.     

PURIFICATION AND CHARACTERIZATION OF THREEISOZYMES OF PECTIN METHYLESTERASE FROM TOMATO FRUIT

Three isozymes of pectin methylesterase (EC 3.1.1.11) have been purified to homogeneity from tomato (var. S. marzano). The isozymes were separated by affinity chromatography on Heparin-Sepharose column. They exhibited a molecular mass of 31 kDa when analyzed in sodium dodecyl sulfate gel electrophoresis and of 35 kDa in gel-filtration chromatography in native conditions. The isoelectric points of all three isozymes were found to be higher than 9.3. The K_ms calculated for the three isozymes were different toward citrus pectin used as substrate; one had a K_m of 9.7 mM (by expressing the pectin concentration as mmoles/L of methoxy groups) and the other two had similar K_ms of 3.0 and 2.6 mM, respectively. The isozyme having the higher K_m for substrate was inhibited by citrus pectin (which had a degree of methylation of 70%) at concentrations higher than 5 mM, but no inhibition was found using a pectin with a degree of methylation of 30% at concentrations up to 13 mM (i.e. 9 mg/ml) with a K_m of 14.7 mM. Furthermore, this isozyme showed a more broad range of activity in a pH range 5–10 with respect to that exhibited by the other two isozymes. All three isozymes were found to be glycosylated, although to different extents.     

Adaptive checkpointing in message passing distributed systems

Determining consistent global checkpoints is common to many distributed problems such as fault-tolerance, distributed debugging, properties detection, etc. Uncoordinated and coordinated checkpointing algorithms have been traditionally used for such determinations. This paper addresses a third technique, namely adaptive checkpointing, that has recently emerged. This technique assumes processes take local checkpoints independently and requires them to take additional local checkpoints in order that all local checkpoints be members of some consistent global checkpoint. We first study the characteristics of such adaptive algorithms. Then, a general adaptive checkpointing algorithm is designed from a condition, first stated by Netzer and Xu, that answers the following question: ‘does a given local checkpoint belong to a consistent global checkpoint’' (such a local checkpoint is not useless). The resulting algorithm has the nice property to reduce the number of additional local checkpoints taken to ensure the property ‘no local checkpoint is useless’. Futhermore, it provides each local checkpoint with a consistent global checkpoint to which it belongs. Compared to uncoordinated and coordinated checkpointing algorithms, this algorithm combines the advantages of both without inheriting their drawbacks.     

AN EFFICIENT DNA-EXTRACTION PROTOCOL FOR NUT SEEDS

Establishing genetic origin of food products allows verification of the authenticity of valuable foods and discourages adulteration with material of lower cost and value. This is particularly important for food products that have obtained European recognition. The use of molecular markers could be a solution for species and cultivar identification and for the genetic traceability. The development of efficient DNA-extraction protocols is an essential step for the procedure. In this work, a method for total DNA isolation was developed for hazelnut, almond and walnut seeds. The efficiency and reliability of the method was tested by assessing quantity and quality of the extracted DNA, and by Polymerase Chain Reaction (PCR) amplification, using two decamer primers and three universal primer pairs designed on the chloroplast DNA. The success of amplifications confirmed the presence of both nuclear and chloroplast DNA in the extracted sample.

PRACTICAL APPLICATIONS

Cultivar identification of nuts, based on morphological traits only, is often difficult, and adulterations with seeds of lower cost and quality are easy, above all when they are sold as shelled kernel, as is common for hazelnut. The genetic identification of cultivars is nowadays a routine practice, because of the development of DNA-typing techniques based on molecular markers. An efficient DNA-extraction procedure for hazelnut, almond and walnut seeds is a preliminary step required for enabling the recognition of the cultivar of origin of the nuts and fighting commercial frauds. It will also be useful in marker-assisted selection, applied in breeding.     

REMARKS ON THERMODYNAMIC DIAGRAMS WITH SPECIFIC CONSIDERATIONS FOR “ INVARIANT” PROPERTIES

When the aim is a qualitative examination of thermodynamic phenomena and processes of two independent variable systems, the various state diagrams ( p vs. v; T vs. s; i vs. s; p vs. i, etc.) are very useful. Every one of these diagrams is suitable to put in evidence some topics, whereas other ones cannot be displayed. That is unavoidable since all topics can be displayed only by means of a three-dimension representation

The several diagrams, even if very different among them, have some common properties. The main aim of this paper is that of examining one property which seems interesting for the analysis of such diagrams: the order, according to which the different processes ( isobaric, isothermal, isentropic, isenthalpic, isochoric) depart from a given point, is invariable, even if this order is different in the various zones of the diagrams. In addition, other properties of some diagrams are considered