Piecewise affine systems approach to control of biological networks

In terms of a piecewise affine system representation, which is a kind of hybrid system model, this article discusses a series of approaches to modelling, analysing and synthesizing a biological network such as a gene-regulatory network. First, the input assignment problem, the controllable state set problem (CSP) and the input trajectory generation problem are emphasized as control problems to be addressed for biological networks. Subsequently, after the modelling issue on biological networks developed in the systems and control community is briefly explained, the CSP is described in detail with reference to control of the quorum-sensing system in the pathogen Pseudomonas aeruginosa. Finally, an optimal control design method to the quorum-sensing system is proposed as a solution to the input trajectory generation problem.     

Composition,Taste, Aroma,and Antioxidant Activity of Solidified Noncentrifugal Brown Sugars Prepared from Whole Stalk and Separated Pith of Sugarcane (Saccharum officinarum L.)

In this study, 2 types of solidified noncentrifugal brown sugars (W‐NCS and P‐NCS) were prepared from the whole stalk and separated pith, respectively, of raw sugarcane (Saccharum officinarum L.). These products were discriminated in terms of their quality attributes, including color, sugars and minerals composition, taste, aroma, and antioxidant activity. The brown color of P‐NCS was clearly different compared with that of W‐NCS with a color difference value (ΔE^*) of 9.36. There was no difference in the sugars and minerals composition between the 2 types of sugar, which led to very similar taste profiles. However, P‐NCS had a weaker aroma intensity than W‐NCS did. Moreover, P‐NCS retained more than 60% of the antioxidant activity of W‐NCS. The information gleaned from this study might be used to select appropriate end‐uses for these 2 types of sugars.     

Dynamic Analysis of Phorbol Esters in the Manufacturing Process of Fatty Acid Methyl Esters from <Emphasis Type="Italic">Jatropha curcas</Emphasis> Seed Oil

Jatropha curcas seed oil, which is unsuitable as an edible oil but has received attention as a novel vegetable fat and oil resource, contains tumor-promoting phorbol esters. Currently, six types of derivatives of 12-deoxy-16-hydroxyphorbol (DHPEs) in J. curcas oil have been identified, and their toxicological safety for humans is being discussed. However, it is reported that most DHPEs disappear during the transesterification process. We investigated the dynamics of phorbol esters in the manufacturing process of fatty acid methyl esters from J. curcas seed oil. With the assumption that the precursor ion was the fragment ion (m/z = 311) from the frame unit of phorbol esters and their derivatives, we developed an LC–MS method for detecting the product ion (m/z = 165), which was obtained by cleavage of the fragment ion. The derivatives generated from the structural changes of the phorbol esters existed in fractions of glycerine–water in the manufacturing process; however, phorbol esters and their derivatives were not detected in the fatty acid methyl esters that were produced via a high-vacuum distillation process. Investigation into the dynamics of phorbol esters confirmed that the contents of phorbol esters, including DHPEs, in the fatty acid methyl esters were under detection limits.     

Intercalated Polycarbonate/Clay Nanocomposites: Nanostructure Control and Foam Processing

Intercalated polycarbonate (PC)/clay nanocomposites (PCCN)s have been prepared successfully through the melt intercalation method in the presence of a compatibilizer. The internal structure and morphology of the PCCNs has been established by using wide‐angle X‐ray diffraction (WAXD) analyses and transmission electron microscopic (TEM) observations. The morphology of these nanocomposites and degradation of the PC matrix after nanocomposites preparation can be controlled by varying surfactants used for the modification of clay and compatibilizer. The intercalated PCCNs exhibited remarkable improvements of mechanical properties when compared with PC without clay. We also discuss foam processing of one representative PCCN using supercritical CO₂ as a foaming agent.

TEM bright field image of intercalated polycarbonate/synthetic fluorohectorite nanocomposite.     

Control of Biodegradability of Polylactide via Nanocomposite Technology

Polymer/layered silicate nanocomposite technology is not only suitable for the significant improvement of mechanical and various other materials properties of virgin polymers, it is also suitable to enhance the rate of biodegradation of biodegradable polymers such as polylactide. The biodegradability of polylactide in nanocomposites completely depends upon both the nature of pristine layered silicates and surfactants used for the modification of layered silicate, and we can control the biodegradability of polylactide via judicious choice of organically modified layered silicate.

Biodegradation of neat PLA and various PLA/OMLS nanocomposites recovered from compost with time.     

Studies on metabolism of linoleic-1-14C acid in testes of hypophysectomized rats

Studies are reported on the influence of hypophysectomy and pituitary gonadotrophins on the interconversion and incorporation of linoleic-1-¹⁴C acid into lipid classes of mature rat testis. Linoleic 1-¹⁴C acid was injected into the testes of mature rats 3 weeks after hypophysectomy. Groups of animals were killed at 0.25, 0.50, 1, 3, 12, 24, 36 and 48 hr after injection of the radioactive linoleic acid, and the incorporation of radio-activity into the fatty acids and lipid classes of the testicular lipids was determined. Similar experiments were carried out with hypophysectomized animals injected intramuscularly with luteinizing or follicle stimulating hormones, or both. The specific activitties of the triglyverides and phospholipids of the testicular lipid increased to a maximum ca. 1 hr after the injection of the radioactive linoleic acid, then decreased sharply. The general pattern of changes in the specific activities of these compounds indicated that the rate of fatty acid catabolism was greatly increased by hypophysectomy. In contrast, the specific activities of the cholesteryl esters and glyceryl ether diesters changed slowly after reaching a maximum at approximately the same time. This pattern, their accumulation in the lipid, and an increase in the constituent 22∶5 indicated that the turnover of these compounds was impaired by hypophysectomy. The conversion of linoleic acid to arachidonic acid was also impaired by hypophysectomy, as evidenced by an increase in the percentage and the high specific activity of 20∶3 compared to 20∶4. The administration of gonadotrophins partially prevented the effects of hypophysectomy, indicating that some of the enzymes in the testes involved in the metabolism of the lipids are hormone sensitive.     

Esterification of cholesterol and hydrolysis of cholesteryl ester in alcohol induced fatty liver of rats

Repeated oral administrations of ethanol to rats induced accumulation of cholesteryl ester, as well as triglyceride in the livers. The contents of free cholesterol and phospholipid in the livers were not changed significantly in the present experiment in which ethanol ingestions were repeated four times. Although in vitro esterification of cholesterol by particle fractions of the alcoholic fatty liver was not affected, hydrolysis of cholesteryl palmitate by the supernatant fraction of the liver homogenate was reduced when compared with those of the control group which was given water or isocaloric glucose. The results of in vitro esterification of cholesterol and hydrolysis of cholesteryl palmitate in the liver of the rats which were ingested with glucose were larger than those of the control rats which were given water.     

Syringic Acid Alleviates Cesium-Induced Growth Defect in Arabidopsis

Syringic acid, a phenolic compound, serves a variety of beneficial functions in cells. Syringic acid increases in plants in response to cesium, and exogenous application of syringic acid resulted in a significant attenuation of cesium-induced growth defects in Arabidopsis. In addition, cesium or syringic acid application to plants also resulted in increased lignin deposition in interfascicular fibers. To better understand the role of lignin and syringic acid in attenuating cesium-induced growth defects, two mutants for Arabidopsis REDUCED EPIDERMAL FLUORESCENE 4 (REF4) and fourteen laccase mutants, some of which have lower levels of lignin, were evaluated for their response to cesium. These mutants responded differently to cesium stress, compared to control plants, and the application of syringic acid alleviated cesium-induced growth defects in the laccase mutants but not in the ref4 mutants. These findings imply that lignin plays a role in cesium signaling but the attenuation of cesium stress defects by syringic acid is mediated by regulatory components of lignin biosynthesis and not lignin biosynthesis itself. In contrast, syringic acid did not alleviate any low potassium-induced growth defects. Collectively, our findings provide the first established link between lignin and cesium stress via syringic acid in plants.     

Amidation of alcohols with nitriles under solvent-free conditions using molecular iodine as a catalyst

The reactions of alcohols with nitriles under solvent-free conditions, using molecular iodine as a catalyst, were investigated. The reaction of 1-phenylethanol with propanenitrile produced the amide N-(1-phenylethyl)propanamide, by dehydration and tautomerization, in 71% yield, under the following conditions: temperature=90°C, alcohol:iodine molar ratio=1:0.2, alcohol:nitrile molar ratio=1:5, and reaction time=5 h. The amidation reactivity depended on the stability of the cationic intermediate formed from the alcohol. The reaction of (-)-borneol with benzonitrile produced a racemic amide in 83% yield.