Gossypol mediated DNA degradation

Gossypol, a polyphenolic compound isolated from cotton plant was found to degrade pBR322 DNA Image in a reaction which required the presence of a metal ion, a reducing agent (2-mercaptoethanol) and oxygen as revealed after agarose gel electrophoresis. Fe3+ and Co2+ showed maximum degradation whereas addition of Ca2+ and Mg2+ prevented the gossypol mediated DNA damage. Gossypol caused degradation of rat liver DNA incubated Image even in the absence of added metal ions and 2-mercaptoethanol. Incubation of intact rat liver nuclei with gossypol reveled DNA degradation and nuclei isolated from rats treated with gossypol Image showed higher succestibility to DNA fragmentation when incubated with gossypol Image than control nuclei. EcoRl and AIuI digestion of DNA isolated from gossypol treated rats gave clear cut evidence for DNA degradation. These observations indicate that gossypol is genotoxic and considereable care has to be exercised in its use. SDS, sodium dodecayl sulphate; TE buffer, Tris-HCL-EDTA buffer.

The risk of pollen-mediated gene flow from exotic Corymbia plantations into native Corymbia populations in Australia

Sectors of the forest plantation industry in Australia are set to expand in the near future using species or hybrids of the spotted gums (Corymbia, Section Politaria). Plantations of these taxa have already been introduced across temperate and subtropical Australia, representing locally exotic introductions from native stands in Queensland and New South Wales. A literature review was undertaken to provide insights into the potential for pollen-mediated gene flow from these plantations into native populations. Three factors suggest that such gene flow is likely; (1) interspecific hybridisation within the genus has frequently been recorded, including between distantly related species from different sections, (2) apparent high levels of vertebrate pollinator activity may result in plantation pollen being moved over hundreds of kilometres, (3) much of the plantation estate is being established among closely related taxa and therefore few barriers to gene flow are expected. Across Australia, 20 of the 100 native Corymbia taxa were found to have regional level co-occurrence with plantations. These were located most notably within regions of north-east New South Wales and south-east Queensland, however, co-occurrence was also found in south-west Western Australia and eastern Victoria. The native species found to have co-occurrence were then assessed for the presence of reproductive barriers at each step in the process of gene flow that may reduce the number of species at risk even further. The available data suggest three risk categories exist for Corymbia. The highest risk was for gene flow from plantations of spotted gums to native populations of spotted gums. This was based on the expected limited existence of pre- and post-zygotic barriers, substantial long-distance pollen dispersal and an apparent broad period of flowering in Corymbia citriodora subsp. variegata plantations. The following risk category focussed on gene flow from Corymbia torelliana × C. c. variegata hybrid plantations into native C. c. variegata, as the barriers associated with the production and establishment of F1 hybrids have been circumvented. For the lowest risk category, Corymbia plantations may present a risk to other non-spotted gum species, however, further investigation of the particular cross-combinations is required. A list of research directions is provided to better quantify these risks. Empirical data will need to be combined within a risk assessment framework that will not only estimate the likelihood of exotic gene flow, but also consider the conservation status/value of the native populations. In addition, the potential impacts of pollen flow from plantations will need to be weighed up against their various economic and environmental benefits.

Effects of particle size distribution in the response of model granular materials in multi-ring shear

Rail track undergoes complex loading patterns under moving traffic conditions compared to roads due to its continued and discontinued multi-layered structure, including rail, sleepers, ballast layer, sub-ballast layer, and subgrade. Particle size distributions (PSDs) of ballast, subballast, and subgrade layers can be critical in cyclic plastic deformation of rail track under moving traffic on frequent track degradation of rail tracks, especially at bridge transition zones. Conventional test approaches: static shear and cyclic single-point load tests are however unable to replicate actual loading patterns of moving train. Multi-ring shear apparatus; a new type of torsional simple shear apparatus, which can reproduce moving traffic conditions, was used in this study to investigate influence of particle size distribution of rail track layers on cyclic plastic deformation. Three particle size distributions, using glass beads were examined under different loading patterns: cyclic sin-gle-point load, and cyclic moving wheel load to evaluate cyclic plastic deformation of rail track under different loading methods. The results of these tests suggest that particle size distributions of rail track structural layers have significant impacts on cyclic plastic deformation under moving train load. Further, the limitations in con-ventional test methods used in laboratories to estimate the plastic deformation of rail track materials lead to underestimate the plastic deformation of rail tracks.

New initiators for the ring-opening thermal polymerization of hexachlorocyclotriphosphazene: synthesis of linear poly(dichlorophosphazene) in high yields

Ring-opening thermal polymerization of hexachlorocyclotriphosphazene (N3P3C&h)a s been investigated at 250 "C and at 1.333-Pa pressure using chlorocyclotriphosphazenes N3P3C15(N=PPh3) and N3P3Cl,.,(NMe2), (n = 2-4), salt hydrates, triphenylphosphine, and benzoic acid as initiators. The linear poly (dich1orophosphazene) products are phenoxylated, and the phenoxy polymers are characterized by gel permeation chromatography and dilute solution viscometry. Among the various initiators investigated, CaS04.2H20b rings about a high conversion (>60%) of N3P3C&to the linear [NPC12], polymer which possesses a high molecular weight (>5 X lo6). The rationale for the choice of the initiators and possible mechanism(s) of polymerization is discussed. Several mixed substituent polymers, [NP(OPh),(OC6H4Me-p)2,1, and [NP(OPh),(OCHzCF3)2,]nh, ave been prepared and their thermal properties evaluated.

Transmission loss analysis of rectangular expansion chamber with arbitrary location of inlet/outlet by means of Green's functions

Transmission loss of a rectangular expansion chamber, the inlet and outlet of which are situated at arbitrary locations of the chamber, i.e., the side wall or the face of the chamber, are analyzed here based on the Green's function of a rectangular cavity with homogeneous boundary conditions. The rectangular chamber Green's function is expressed in terms of a finite number of rigid rectangular cavity mode shapes. The inlet and outlet ports are modeled as uniform velocity pistons. If the size of the piston is small compared to wavelength, then the plane wave excitation is a valid assumption. The velocity potential inside the chamber is expressed by superimposing the velocity potentials of two different configurations. The first configuration is a piston source at the inlet port and a rigid termination at the outlet, and the second one is a piston at the outlet with a rigid termination at the inlet. Pressure inside the chamber is derived from velocity potentials using linear momentum equation. The average pressure acting on the pistons at the inlet and outlet locations is estimated by integrating the acoustic pressure over the piston area in the two constituent configurations. The transfer matrix is derived from the average pressure values and thence the transmission loss is calculated. The results are verified against those in the literature where use has been made of modal expansions and also numerical models (FEM fluid). The transfer matrix formulation for yielding wall rectangular chambers has been derived incorporating the structural–acoustic coupling. Parametric studies are conducted for different inlet and outlet configurations, and the various phenomena occurring in the TL curves that cannot be explained by the classical plane wave theory, are discussed.

Conserved water-mediated H-bonding dynamics of catalytic Asn 175 in plant thiol protease

The role of invariant water molecules in the activity of plant cysteine protease is ubiquitous in nature. On analysing the 11 different Protein DataBank (PDB) structures of plant thiol proteases, the two invariant water molecules W I and W2 (W220 and W222 in the template 1PPN structure) were observed to form H-bonds with the Ob atom of Asn 175. Extensive energy minimization and molecular dynamics simulation studies up to 2 ns on all the PDB and solvated structures clearly revealed the involvement of the H-bonding association of the two water molecules in fixing the orientation of the asparagine residue of the catalytic triad. From this study, it is suggested that H-bonding of the water molecule at the W1 invariant site better stabilizes the Asn residue at the active site of the catalytic triad.

Modelling the potential spread of Solenopsis invicta Buren (Hymenoptera: Formicidae) (red imported fire ant) in Australia

Quantifying the potential spread and density of an invading organism enables decision-makers to determine the most appropriate response to incursions. We present two linked models that estimate the spread of Solenopsis invicta Buren (red imported fire ant) in Australia based on limited data gathered after its discovery in Brisbane in 2001. A stochastic cellular automaton determines spread within a location (100 km by 100 km) and this is coupled with a model that simulates human-mediated movement of S. invicta to new locations. In the absence of any control measures, the models predict that S. invicta could cover 763 000–4 066 000 km2 by the year 2035 and be found at 200 separate locations around Australia by 2017–2027, depending on the rate of spread. These estimated rates of expansion (assuming no control efforts were in place) are higher than those experienced in the USA in the 1940s during the early invasion phases in that country. Active control efforts and quarantine controls in the USA (including a concerted eradication attempt in the 1960s) may have slowed spread. Further, milder winters, the presence of the polygynous social form, increased trade and human mobility in Australia in 2000s compared with the USA in 1940s could contribute to faster range expansion.

Phosphorus nutrition and tolerance of cotton to water stress: II. Water relations, free and bound water and leaf expansion rate

In previous experiments, increased leaf-Phosphorus (P) content with increasing P supply enhanced the individual leaf expansion and water content of fresh cotton leaves in a severely drying soil. In this paper, we report on the bulk water content of leaves and its components, free and bound water, along with other measures of plant water status, in expanding cotton leaves of various ages in a drying soil with different P concentrations. The bound water in living tissue is more likely to play a major role in tolerance to abiotic stresses by maintaining the structural integrity and/or cell wall extensibility of the leaves, whilst an increased amount of free water might be able to enhance solute accumulation, leading to better osmotic adjustment and tolerance to water stress, and maintenance of the volumes of sub-cellular compartments for expansive leaf growth. There were strong correlations between leaf-P%, leaf water (total, free and bound water) and leaf expansion rate (LER) under water stress conditions in a severely drying soil. Increased soil-P enhanced the uptake of P from a drying soil, leading to increased supply of osmotically active inorganic solutes to the cells in growing leaves. This appears to have led to the accumulation of free water and more bound water, ultimately leading to increased leaf expansion rates as compared to plants in low P soil under similar water stress conditions. The greater amount of bound and free water in the high-P plants was not necessarily associated with changes in cell turgor, and appears to have maintained the cell-wall properties and extensibility under water stressed conditions in soils that are nutritionally P-deficient.

Strong-coupling expansion for the momentum distribution of the Bose-Hubbard model with benchmarking against exact numerical results

A strong-coupling expansion for the Green's functions, self-energies, and correlation functions of the Bose-Hubbard model is developed. We illustrate the general formalism, which includes all possible (normal-phase) inhomogeneous effects in the formalism, such as disorder or a trap potential, as well as effects of thermal excitations. The expansion is then employed to calculate the momentum distribution of the bosons in the Mott phase for an infinite homogeneous periodic system at zero temperature through third order in the hopping. By using scaling theory for the critical behavior at zero momentum and at the critical value of the hopping for the Mott insulator–to–superfluid transition along with a generalization of the random-phase-approximation-like form for the momentum distribution, we are able to extrapolate the series to infinite order and produce very accurate quantitative results for the momentum distribution in a simple functional form for one, two, and three dimensions. The accuracy is better in higher dimensions and is on the order of a few percent relative error everywhere except close to the critical value of the hopping divided by the on-site repulsion. In addition, we find simple phenomenological expressions for the Mott-phase lobes in two and three dimensions which are much more accurate than the truncated strong-coupling expansions and any other analytic approximation we are aware of. The strong-coupling expansions and scaling-theory results are benchmarked against numerically exact quantum Monte Carlo simulations in two and three dimensions and against density-matrix renormalization-group calculations in one dimension. These analytic expressions will be useful for quick comparison of experimental results to theory and in many cases can bypass the need for expensive numerical simulations.

Perennial grassland dynamics on fertile plains: Is coexistence mediated by disturbance?

The response of grasslands to disturbance varies with the nature of the disturbance and the productivity of the landscape. In highly productive grasslands, competitive exclusion often results in decreased species richness and grazing may allow more species to coexist. Once widespread, grasslands dominated by Dichanthium sericeum (Queensland bluegrass) and Astrebla spp. (Mitchell grass) occur on fertile plains but have been reduced in extent by cultivation. We tested the effects of exclusion of livestock grazing on these grasslands by comparing the floristic composition of sites in a nature reserve with an adjacent stock reserve. In addition, sites that had been cultivated within the nature reserve were compared with those where grazing but no cultivation had occurred. To partition the effects of temporal variation from spatial variation we sampled sites in three different years (1998, 2002 and 2004). Some 194 taxa were recorded at the nature reserve and surrounding stock routes. Sampling time, the occurrence of past cultivation and livestock grazing all influenced species composition. Species richness varied greatly between sampling periods relating to highly variable rainfall and water availability on heavy clay soils. Native species richness was significantly lower at previously cultivated sites (13-22 years after cultivation), but was not significantly influenced by grazing exclusion. After 8 years it appears that reintroducing disturbance in the form of livestock grazing is not necessary to maintain plant species richness in the reserve. The highly variable climate (e.g. droughts) probably plays an important role in the coexistence of species by negating competitive exclusion and allowing interstitial species to persist.

Personality and social psychological studies on computer-mediated communication in school settings

The present study examined how personality and social psychological factors affect third and fourth graders' computer-mediated communication. Personality was analysed in terms of the following strategies: optimism, pessimism and defensive pessimism. Students worked either individually or in dyads which were paired homogeneously or heterogeneously according to the strategies. Moreover, the present study compared horizontal and vertical interaction. The study also examined the role that popularity plays, and students were divided into groups based on their popularity level. The results show that an optimistic strategy is useful. Optimism was found to be related to the active production and processing of ideas. Although previous research has identified drawbacks to pessimism in achievement settings, this study shows that the pessimistic strategy is not as debilitating a strategy as is usually assumed. Pessimistic students were able to process their ideas. However, defensive pessimists were somewhat cautious in introducing or changing ideas. Heterogeneous dyads were not beneficial configurations with respect to producing, introducing, or changing ideas. Moreover, many differences were found to exist between the horizontal and vertical interaction; specifically, the students expressed more opinions and feelings when teachers took no part in the discussions. Strong emotions were observed especially in the horizontal interaction. Further, group working skills were found to be more important for boys than for girls, while rejected students were not at a disadvantage compared to popular ones. Schools can encourage emotional and social learning. The present study shows that students can use computers to express their feelings. In addition, students who are unpopular in non-computer contexts or students who use pessimism can benefit from computers. Participation in computer discussions can give unpopular children a chance to develop confidence when relating to peers.

Oppimisen kohteen ja oppijan vastavuoroinen kehitys : Teleyrityksen asiakaspalvelun työyhteisöjen oppimiskäytäntöjen uudistaminen osana teknologis-taloudellista kumousta

Reciprocal development of the object and subject of learning. The renewal of the learning practices of front-line communities in a telecommunications company as part of the techno-economical paradigm change. Current changes in production have been seen as an indication of a shift from the techno-economical paradigm of a mass-production era to a new paradigm of the information and communication technological era. The rise of knowledge management in the late 1990s can be seen as one aspect of this paradigm shift, as knowledge creation and customer responsiveness were recognized as the prime factors in business competition. However, paradoxical conceptions concerning learning and agency have been presented in the discussion of knowledge management. One prevalent notion in the literature is that learning is based on individuals’ voluntary actions and this has now become incompatible with the growing interest in knowledge-management systems. Furthermore, commonly held view of learning as a general process that is independent of the object of learning contradicts the observation that the current need for new knowledge and new competences are caused by ongoing techno-economic changes. Even though the current view acknowledges that individuals and communities have key roles in knowledge creation, this conception defies the idea of the individuals’ and communities’ agency in developing the practices through which they learn. This research therefore presents a new theoretical interpretation of learning and agency based on Cultural-Historical Activity Theory. This approach overcomes the paradoxes in knowledge-management theory and offers means for understanding and analyzing changes in the ways of learning within work communities. This research is also an evaluation of the Competence-Laboratory method which was developed as part of the study as a special application of Developmental Work Research methodology. The research data comprises the videotaped competence-laboratory processes of four front-line work communities in a telecommunications company. The findings reported in the five articles included in this thesis are based on the analyses of this data. The new theoretical interpretation offered here is based on the assessment that the findings reported in the articles represent one of the front lines of the ongoing historical transformation of work-related learning since the research site represents one of the key industries of the new “knowledge society”. The research can be characterized as elaboration of a hypothesis concerning the development of work related learning. According to the new theoretical interpretation, the object of activity is also the object of distributed learning in work communities. The historical socialization of production has increased the number of actors involved in an activity, which has also increased the number of mutual interdependencies as well as the need for communication. Learning practices and organizational systems of learning are historically developed forms of distributed learning mediated by specific forms of division of labor, specific tools, and specific rules. However, the learning practices of the mass production era become increasingly inadequate to accommodate the conditions in the new economy. This was manifested in the front-line work communities in the research site as an aggravating contradiction between the new objects of learning and the prevailing learning practices. The constituent element of this new theoretical interpretation is the idea of a work community’s learning as part of its collaborative mastery of the developing business activity. The development of the business activity is at the same time a practical and an epistemic object for the community. This kind of changing object cannot be mastered by using learning practices designed for the stable conditions of mass production, because learning has to change along the changes in business. According to the model introduced in this thesis, the transformation of learning proceeds through specific stages: predefined learning tasks are first transformed into learning through re-conceptualizing the object of the activity and of the joint learning and then, as the new object becomes stabilized, into the creation of new kinds of learning practices to master the re-defined object of the activity. This transformation of the form of learning is realized through a stepwise expansion of the work community’s agency. To summarize, the conceptual model developed in this study sets the tool-mediated co-development of the subject and the object of learning as the theoretical starting point for developing new, second-generation knowledge management methods. Key words: knowledge management, learning practice, organizational system of learning, agency

Tree-ring based hydroclimate reconstruction over northern Vietnam from Fokienia hodginsii: eighteenth century mega-drought and tropical Pacific influence

We present here the first statistically calibrated and verified tree-ring reconstruction of climate from continental Southeast Asia.The reconstructed variable is March-May (MAM) Palmer Drought Severity Index (PDSI) based on ring widths from 22 trees (42 radial cores) of rare and long-lived conifer, Fokienia hodginsii (Po Mu as locally called) from northern Vietnam. This is the first published tree ring chronology from Vietnam as well as the first for this species. Spanning 535 years, this is the longest cross-dated tree-ring series yet produced from continental Southeast Asia. Response analysis revealed that the annual growth of Fokienia at this site was mostly governed by soil moisture in the pre-monsoon season. The reconstruction passed the calibration-verification tests commonly used in dendroclimatology, and revealed two prominent periods of drought in the mid-eighteenth and late-nineteenth enturies. The former lasted nearly 30 years and was concurrent with a similar drought over northwestern Thailand inferred from teak rings, suggesting a ``mega-drought'' extending across Indochina in the eighteenth century. Both of our reconstructed droughts are consistent with the periods of warm sea surface temperature (SST)anomalies in the tropical Pacific. Spatial correlation analyses with global SST indicated that ENSO-like anomalies might play a role in modulating droughts over the region, with El Nio (warm) phases resulting in reduced rainfall. However, significant correlation was also seen with SST over the Indian Ocean and the north Pacific,suggesting that ENSO is not the only factor affecting the climate of the area. Spectral analyses revealed significant peaks in the range of 53.9-78.8 years as well as in the ENSO-variability range of 2.0 to 3.2 years.

Packed bed bioreactor for the isolation and expansion of placental-derived Mesenchymal Stromal Cells

Large numbers of Mesenchymal stem/stromal cells (MSCs) are required for clinical relevant doses to treat a number of diseases. To economically manufacture these MSCs, an automated bioreactor system will be required. Herein we describe the development of a scalable closed-system, packed bed bioreactor suitable for large-scale MSCs expansion. The packed bed was formed from fused polystyrene pellets that were air plasma treated to endow them with a surface chemistry similar to traditional tissue culture plastic. The packed bed was encased within a gas permeable shell to decouple the medium nutrient supply and gas exchange. This enabled a significant reduction in medium flow rates, thus reducing shear and even facilitating single pass medium exchange. The system was optimised in a small-scale bioreactor format (160 cm2) with murine-derived green fluorescent protein-expressing MSCs, and then scaled-up to a 2800 cm2 format. We demonstrated that placental derived MSCs could be isolated directly within the bioreactor and subsequently expanded. Our results demonstrate that the closed system large-scale packed bed bioreactor is an effective and scalable tool for large-scale isolation and expansion of MSCs.

Proline ring conformations corresponding to a bistable jump model from 13C spin-lattice relaxation times

A formalism for extracting the conformations of a proline ring based on the bistable jump model of R. E. London [(1978) J. Am. Chem. Soc. 100, 2678-2685] from 13C spin-lattice relaxation times (T1) is given. The method is such that the relaxation data are only partially used to generate the conformations; these conformations are constrained to satisfy the rest of the relaxation data and to yield acceptable ring geometry. An alternate equation for T1 of 13C nuclei to that of London is given. The formalism is illustrated through an example.