Search

Two hundred and ninety F9recombinant inbred lines (RILs) derived from the bread wheat cultivar Gaocheng 8901 and the waxy wheat cultivar Nuomai 1 were used in determining the high-molecular-weight glutenin subunit (HMW-GS) and waxy protein subunit combinations and their effects on the dough quality and texture profile analysis (TPA) of cooked Chinese noodles. Seven alleles were detected at Glu-1 loci. There were two alleles found at each of the Wx-A1, Wx-B1 and Wx-D1 loci. Eight allelic combinations were observed for HMW-GS, LMW-GS and waxy proteins, respectively. Both the 1/7+8/5+10 and 1/7+8/5+12 combinations contributed to dough elasticity, and the 1/7+8/5+10 combination also provided better TPA characteristics. Compared to Wx protein, HMW-GS was more important on dough alveogram properties. LMW-GS significantly affected springiness and cohesiveness; HMW-GS mainly affected the hardness; Wx×LMW-GS significantly affected the springiness, cohesiveness and chewiness; HMW-GS×Wx×LMW-GS mainly influenced the springiness and chewiness. But HMW-GS×LMW-GS only affected the spinginess. These indicated the TPA of noodles was significantly affected by the interactions between glutenin and Wx proteins.

A 2-hydroxyl pendant group was anchored on the N-alkyl chain of imidazolium ionic liquid crystals. This hydroxyl group enhanced the hydrogen bonding interactions between neighboring compounds and, therefore, widened the temperature range of the mesophase, as compared to those without the hydroxyl group. Many room temperature ionic liquid crystals were formed. Polarized optical microscopy, differential scanning calorimetry, X-ray diffraction and infrared spectroscopy were used to study the properties of these materials. The molecular structure of one of the compounds was determined by single crystal X-ray diffraction, in order to have a better understanding of the structure relation between the solid and liquid crystal.

The onset of instability in a liquid annular jet enclosing another fluid, and surrounded by a gas in a pipe is analysed by use of a spectra-collocation method. The dynamic responses to the variation of different flow parameters are elucidated by use of numerical results. Two linearly independent convectively unstable interfacial modes of disturbances are found. In general, the para-sinuous mode has a larger amplification rate than the para-varicose mode. It is shown that to initiate encapsulation of core fluid with a uniform shell fluid, the growth of the para-sinuous mode must be promoted and the para-varicose mode must be suppressed. Suppression of the paravaricose mode in a finite range of wavenumbers is possible by varying the flow parameters. The effects of ten relevant parameters on instability are discussed. In certain parameter space, the annular jet becomes absolutely unstable with respect to the sinuous mode. The transition Weber number below which the flow is absolutely unstable and above which the flow is convectively unstable is found as a function of the Reynolds number when the rest of flow parameters are given. A successful encapsulation of core fluid with a uniform shell fluid is possible if the process is carried out outside of the parameter space of absolute instability, and if an external forcing is introduced at a frequency within a band in which the para-varicose mode is stable but the para-sinuous mode is convectively unstable.

All internal organs are asymmetric along the left-right axis. Here we report a genetic screen to discover mutations which perturb organ laterality. Our particular focus is upon whether, and how, organs are linked to each other as they achieve their laterally asymmetric positions. We generated mutations by ENU mutagenesis and examined F3 progeny using a cocktail of probes that reveal early primordia of heart, gut, liver and pancreas. From the 750 genomes examined, we isolated seven recessive mutations which affect the earliest left-right positioning of one or all of the organs. None of these mutations caused discernable defects elsewhere in the embryo at the stages examined. This is in contrast to those mutations we reported previously (Chen et al., 1997) which, along with left-right abnormalities, cause marked perturbation in gastrulation, body form or midline structures. We find that the mutations can be classified on the basis of whether they perturb relationships among organ laterality. In Class 1 mutations, none of the organs manifest any left-right asymmetry. The heart does not jog to the left and normally left-predominant BMP4 in the early heart tube remains symmetric. The gut tends to remain midline. There frequently is a remarkable bilateral duplication of liver and pancreas. Embryos with Class 2 mutations have organotypic asymmetry but, in any given embryo, organ positions can be normal, reversed or randomized. Class 3 reveals a hitherto unsuspected gene that selectively affects laterality of heart. We find that visceral organ positions are predicted by the direction of the preceding cardiac jog. We interpret this as suggesting that normally there is linkage between cardiac and visceral organ laterality. Class 1 mutations, we suggest, effectively remove the global laterality signals, with the consequence that organ positions are effectively symmetrical. Embryos with Class 2 mutations do manifest linkage among organs, but it may be reversed, suggesting that the global signals may be present but incorrectly orientated in some of the embryos. That laterality decisions of organs may be independently perturbed, as in the Class 3 mutation, indicates that there are distinctive pathways for reception and organotypic interpretation of the global signals. Copyright © 2001 John Wiley & Sons, Ltd.

A theoretic analysis employing the film model for the isothermal absorption of ozone in aqueous solutions with self-decomposition of general orders (not necessarily integers) is performed. A closed-form solution has been obtained. The effects of system parameters on the ozone mass transfer rate are examined. These parameters include the self-decomposition reaction rate parameters (Mm05, Mn05), the reaction orders (m, n), the pH value of solution, and the liquid-phase mass transfer coefficient (kL°). The results indicate that Mm and Mn significantly enhance the absorption rate of ozone. In favor of the direct use of molecular ozone, either the liquid phase should be maintained in the neutral or acidic conditions, or the gas-liquid contactors operated with higher values of kL° if the liquid phase is in the strong basic conditions. The reverse choices, on the other hand, would favor the formation of self-decomposition specices of ozone such as free radicals. This analysis is of importance for the efficient use of ozone in the water/wastewater treatment processes. For some known special cases (for example, Mm=O for any n), the present solution reduces to the previous works of other investigators.

The linear instability of a viscous liquid flowing in a vertical sheet sandwiched between two viscous gases bounded externally by two vertical walls is investigated. The critical Weber number below which the flow is absolutely unstable and above which the flow is convectively unstable is found to be approximately equal to one and is weakly dependent on the rest of the parameters. The Weber number is defined as We ≡ ρ1 U20d/S where S is the surface tension, ρ1 is the liquid density, U0 is the centre-line velocity of the liquid sheet, and d is the half-thickness of the uniform liquid sheet. The sinuous mode is found to have a greater amplification rate than the varicose mode in the convective instability regime. While absolute instability is caused by the surface tension, convective instability is caused by the amplification of disturbances near the liquid–gas interface. The surface tension, and viscosities of liquids and gases all suppress the amplification of the convectively unstable disturbances. An increase in the gravitational force or the gas density results in an enhancement of the amplification rate.

The role of interfacial shear in the onset of instability of a cylindrical viscous liquid jet in a viscous gas surrounded by a coaxial circular pipe is elucidated by use of an energy budget associated with the disturbance. It is shown that the shear force at the liquid–gas interface retards the Rayleigh-mode instability which leads to the breakup of the liquid jet into drops of diameter comparable to the jet diameter, due to capillary force. On the other hand the interfacial shear and pressure work in concert to cause the Taylor-mode instability which leads the jet to break up into droplets of diameter much smaller than the jet diameter. While the interfacial pressure plays a slightly more important role than the interfacial shear in amplifying the longer-wave spectrum in the Taylor mode, the shear stress plays the main role of generating the disturbances of shorter wavelength.

A theoretical analysis is performed employing the film model for the isothermal absorption and self-decomposition of ozone in aqueous solutions with interfacial resistance, which is inversely proportional to the interfacial mass transfer coefficient ks. A closed-form solution has been obtained. The effects of system parameters on the ozone mass transfer rate are examined. These parameters include the interfacial resistance (1/ks), the acidic and basic self-decomposition reaction rate parameters (Mm0.5, Mn0.5.; Mm = [2DAkmCAim-1/(m+1)]/(kL0)2, Mn=(2DAknCAin-1/(n+1))/(kL0)2, the reaction orders (m,n), the pH value of solution, and the liquid-phase mass transfer coefficient (kL0). The results indicate that the reduction effect of the interfacial resistance on the absorption rate is most significant for the situation with the larger values of Mm and Mn as well as with higher pH values. Also, for any particular finite value of kL0/ks, the reduction effect encountered is greater for a gas liquid contactor with a lower kL0. The reduction effect should be avoided in order to maintain a higher mass transfer rate of ozone in aqueous solution. This analysis is of importance for the efficient use of ozone in water/wastewater treatment processes in the presence of interfacial resistance substances such as surface active agents. For some known special cases (for example, cases with no interfacial resistance), the present solution reduces to the previous works of other investigators.

In a screen for early developmental mutants of the zebrafish, we have identified mutations specifically affecting the internal organs. We identified 53 mutations affecting the cardiovascular system. Nine of them affect specific landmarks of heart morphogenesis. Mutations in four genes cause a failure in the fusion of the bilateral heart primordia, resulting in cardia bifida. In lonely atrium, no heart venticle is visible and the atrium is directly fused to the outflow tract. In the overlooped mutant, the relative position of the two heart chambers is distorted. The heart is enormously enlarged in the santa mutant. In two mutants, scotch tape and superglue, the cardiac jelly between the two layers of the heart is significantly reduced. We also identified a number of mutations affecting the function of the heart. The mutations affecting heart function can be subdivided into two groups, one affecting heart contraction and another affecting the rhythm of the heart beat. Among the contractility group of mutants are 5 with no heart beat at all and 15 with a reduced heart beat of one or both chambers. 6 mutations are in the rhythmicity group and specifically affect the beating pattern of the heart. Mutations in two genes, bypass and kurzschluss, cause specific defects in the circulatory system. In addition to the heart mutants, we identified 23 mutations affecting the integrity of the liver, the intestine or the kidney. In this report, we demonstrate that it is feasible to screen for genes specific for the patterning or function of certain internal organs in the zebrafish. The mutations presented here could serve as an entry point to the establishment of a genetic hierarchy underlying organogenesis.

As part of a large-scale mutagenesis screen of the zebrafish genome, we have identified 58 mutations that affect the formation and function of the cardiovascular system. The cardiovascular system is particularly amenable for screening in the transparent zebrafish embryo because the heart and blood vessels are prominent and their function easily examined. We have classified the mutations affecting the heart into those that affect primarily either morphogenesis or function. Nine mutations clearly disrupt the formation of the heart. cloche deletes the endocardium. In cloche mutants, the myocardial layer forms in the absence of the endocardium but is dysmorphic and exhibits a weak contractility. Two loci, miles apart and bonnie and clyde, play a critical role in the fusion of the bilateral tubular primordia. Three mutations lead to an abnormally large heart and one to the formation of a diminutive, dysmorphic heart. We have found no mutation that deletes the myocardial cells altogether, but one, pandora, appears to eliminate the ventricle selectively. Seven mutations interfere with vascular integrity, as indicated by hemorrhage at particular sites. In terms of cardiac function, one large group exhibits a weak beat. In this group, five loci affect both chambers and seven a specific chamber (the atrium or ventricle). For example, the weak atrium mutation exhibits an atrium that becomes silent but has a normally beating ventricle. Seven mutations affect the rhythm of the heart causing, for example, a slow rate, a fibrillating pattern or an apparent block to conduction. In several other mutants, regurgitation of blood flow from ventricle to atrium is the most prominent abnormality, due either to the absence of valves or to poor coordination between the chambers with regard to the timing of contraction. The mutations identified in this screen point to discrete and critical steps in the formation and function of the heart and vasculature.

The fashioning of a vertebrate organ requires integration of decisions of cell fate by individual cells with those that regulate organotypic form. Logical candidates for this role, in an organ such as the heart, are genes that initiate the differentiation process leading to heart muscle and those that define the earliest embryonic heart field, but for neither class are genes defined. We cloned zebrafish Nkx2.5, a homolog of the tinman homeodomain gene needed for visceral and cardiac mesoderm formation in Drosophila. In the zebrafish, its expression is associated with cardiac precursor cells throughout development, even in the early gastrula, where the level of zebrafish Nkx2.5 is in a gradient which spatially matches the regional propensity of ventral-marginal cells to become heart. Overexpression of Nkx2.5 causes formation of disproportionally larger hearts in otherwise apparently normal embryos. Transplanted cell expressing high levels of Nkx2.5 express cardiac genes even in ectopic locales. Fibroblasts transfected with myc-tagged Nkx2.5 express cardiac genes. These effects require the homeodomain. Thus, Nkx2.5 appears to mark the earliest embryonic heart field and to be capable of initiating the cardiogenic differentiation program. Because ectopic cells or transfected fibroblasts do not beat, Nkx2.5 is likely to be but one step in the determination of cardiac myocyte cell fate. Its overexpression increases heart size, perhaps by bringing cells on the edge of the field to a threshold level for initiation of cardiac differentiation.

The first evident break in left-right symmetry of the primitive zebrafish heart tube is the shift in pattern of BMP4 expression from radially symmetric to left-predominant. The midline heart tube then 'jogs' to the left and subsequently loops to the right. We examined 279 mutations, affecting more than 200 genes, and found 21 mutations that perturb this process. Some cause BMP4 to remain radially symmetric. Others randomize the asymmetric BMP4 pattern. Retention of BMP4 symmetry is associated with failure to jog: right-predominance of the BMP4 pattern is associated with reversal of the direction of jogging and looping. Raising BMP4 diffusely throughout the heart, via sonic hedgehog injection, or the blocking of its action by injection of a dominant negative BMP4 receptor, prevent directional jogging or looping. The genes crucial to directing cardiac asymmetry include a subset of those needed for patterning the dorsoventral axis and for notochord and ventral spinal cord development. Thus, the pattern of cardiac BMP4 appears to be in the pathway by which the heart interprets lateralizing signals from the midline.

In many vertebrates, removal of early embryonic heart precursors can be repaired, leaving the heart and embryo without visible deficit. One possibility is that this 'regulation' involves a cell fate switch whereby cells, perhaps in regions surrounding normal progenitors, are redirected to the heart cell fate. However, the lineage and spatial relationships between cells that are normal heart progenitors and those that can assume that role after injury are not known, nor are their molecular distinctions. We have adapted a laser-activated technique to label single or small patches of cells in the lateral plate mesoderm of the zebrafish and to track their subsequent lineage. We find that the heart precursor cells are clustered in a region adjacent to the prechordal plate, just anterior to the notochord tip. Complete unilateral ablation of all heart precursors with a laser does not disrupt heart development, if performed before the 18-somite stage. By combining extirpation of the heart precursors with cell labeling, we find that cells anterior to the normal cardiogenic compartments constitute the source of regulatory cells that compensate for the loss of the progenitors. One of the earliest embryonic markers of the premyocardial cells is the divergent homeodomain gene, Nkx2.5. Interestingly, normal cardiogenic progenitors derive from only the anterior half of the Nkx2.5-expressing region in the lateral plate mesoderm. The posterior half, adjacent to the notochord, does not include cardiac progenitors and the posterior Nkx2.5-expressing cells do not contribute to the heart, even after ablation of the normal cardiogenic region. The cells that can acquire a cardiac cell fate after injury to the normal progenitors also reside near the prechordal plate, but anterior to the Nkx2.5-expressing domain. Normally they give rise to head mesenchyme. They share with cardiac progenitors early expression of GATA 4. The location of the different elements of the cardiac field, and their response to injury, suggests that the prechordal plate supports and/or the notochord suppresses the cardiac fate.

A theoretical analysis is performed employing the film model for the isothermal absorption and decomposition of ozone in aqueous solution with ultraviolet (UV) radiation, which exhibits catalytic effect on the ozone decomposition. A closed-form solution with the ozone decomposition of general orders (not necessarily integers) has been obtained. The effects of major system parameters on the ozone mass transfer rate are examined by using the rate expression of ozone decomposition with UV radiation reported by Huang and Chen. These parameters include the intensity of UV radiation ([I]), the pH value of solution, and the physical liquid-phase mass transfer coefficient (kL0). The results indicate that the combined enhancing effect of self-decomposition reaction (r) and UV radiation (u) on the ozone absorption rate in terms of NAru/NA (ratio of mass flux with to that without r and u) is most significant for the situation with larger values of [I], as well as with smaller values of kL0. Also, for any particular finite value of [I] the enhancing effect due to UV radiation alone in terms of NAro/NAr reaches a local maximum at some pH value. The utilization of UV in addition to self-decomposition reaction is thus most efficient at this specific pH value. The present study is of importance for the efficient use of ozone with UV radiation in addition to self-decomposition reaction in favor of the formation of free radicals in water/waste water treatment processss. For some known special cases (for example, cases with no UV radiation), the present solution reduces to the previous works of other investigators.

The catalytic decomposition of ozone was investigated by using a tubular fixed-bed reactor. The performance tests and reaction kinetic studies were conducted for two catalysts, i.e., MnO2 and Pt/γ -Al2O3 (symbolized as Dash-220). The experiments were carried out at various constant reaction temperatures (288-338 K) and space velocities (24,000 - 68,000 hr-1). The decomposition efficiencies of ozone with values higher than 99 % can be achieved at low temperatures (e.g., 338 K) and moderate space velocities (e.g., 38,000 hr-1). The results indicated that the Dash-220 catalyst gave higher decomposition performance than MnO2 catalyst at the same reaction conditions. For the reaction kinetics, it was found that the pseudo-first-order chemical reaction kinetic equation was appropriate for the catalytic decomposition of ozone investigated in this study. The apparent activation energies for MnO2 and Dash-220 catalysts are 53.2 and 51.1 kJ mol-1, respectively. The corresponding pre-exponential factors are 1,863 and 3,681 mol (s g-cat. (mol m-3))-1, respectively.

A novel technique (direct recoil spectrometry = DRS) for monitoring surface kinetics which provides direct time‐resolved compositions of surface constituents is presented.

A qualitative model for describing a specific type of secondary particle emission, i.e., atoms which are directly recoiled (DR) from a surface as a result of a single primary ion collision, is developed and used for the interpretation of ion fractions of DR atoms from surfaces with differing chemical environments.