Investigation of Deep Defects Due to -Particle Irradiation in n-Silicon

Electrical properties of deep defects induced in n-silicon by -particles of about 10 MeV energy at a dose of 1014 and 1015 cm-2 are studied by DLTS. The levels at Ec -0.18 eV, Ec -0.26 eV, and Ec -0.48 eV are identified as A center, V2 (=/-) and V2 (-/0) on the basis of activation energy, electron capture cross section, and annealing behavior. Two other irradiation related levels at Ec -0.28 eV and Ec -0.51 eV could not be related to any known center.

Impact of Stem Defect Agent Defects on Hardwood Wood Quality

Queensland's hardwood plantation industry is producing increasing volumes of sawlog, veneer and poles. Wood quality can sometimes be impaired in some plantation hardwoods when the growing trees are attacked by insect borers. Susceptibility to borer damage varies with the species as well as site conditions or location. The risk model developed from this project will enable the plantation industry to match tree species with appropriate growing conditions in Queensland.

Surface-enhanced Raman scattering of molecules adsorbed on nanocrystalline Au and Ag films formed at the organic-aqueous interface

Surface-enhanced Raman scattering (SERS) of pyridine adsorbed on ultrathin nanocrystalline Au and Ag films generated at the liquid-liquid interface has been investigated. The shifts and intensification of bands formed with these films comprising metal nanoparticles are comparable to those found with other types of Au and Ag substrates. SERS of rhodamine 6G adsorbed on Ag films has also been studied. The results demonstrate that nanocrystalline metal films prepared by the simple method involving the organic-aqueous interface can be used effectively for SERS investigations.

Phase field study of precipitate growth: Effect of misfit strain and interface curvature

We have used phase field simulations to study the effect of misfit and interfacial curvature on diffusion-controlled growth of an isolated precipitate in a supersaturated matrix. Treating our simulations as computer experiments, we compare our simulation results with those based on the Zener–Frank and Laraia–Johnson–Voorhees theories for the growth of non-misfitting and misfitting precipitates, respectively. The agreement between simulations and the Zener–Frank theory is very good in one-dimensional systems. In two-dimensional systems with interfacial curvature (with and without misfit), we find good agreement between theory and simulations, but only at large supersaturations, where we find that the Gibbs–Thomson effect is less completely realized. At small supersaturations, the convergence of instantaneous growth coefficient in simulations towards its theoretical value could not be tracked to completion, because the diffusional field reached the system boundary. Also at small supersaturations, the elevation in precipitate composition matches well with the theoretically predicted Gibbs–Thomson effect in both misfitting and non-misfitting systems.

Barley Grains Defects (Blackpoint, Pre-harvest sprouting, Kernal staining)

Screening new and existing breeding germplasm and cultivars for grain defect tolerance for breeding programs, evaluate new methods and technologies to screen more effectively for the barley grains defects - pre-harvest sprouting, blackpoint, kernel discolouration, and investigate genetic mechanisms involved in controlling barley grain defect tolerance.

Defects in tricarboxylic acid cycle enzymes Fumarate hydratase and Succinate dehydrogenase in cancer

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a recently characterized cancer syndrome which predisposes to cutaneous and uterine leiomyomas as well as renal cell carcinoma (RCC). Uterine leiomyosarcoma (ULMS) has also been observed in certain Finnish HLRCC families. The predisposing gene for this syndrome, fumarate hydratase (FH), was identified in 2002. The well-known function of FH is in the tricarboxylic acid cycle (TCAC) in the energy metabolism of cells. As FH is a novel cancer gene, the role of FH mutations in tumours is in general unknown. Similarly, the mechanisms through which defective FH is associated with tumourigenesis are unclear. The loss of a wild type allele has been observed in virtually all HLRCC patients tumours and the FH enzyme activities are either totally lost or remarkably reduced in the tissues of mutation carrier patients. Therefore, FH is assumed to function as a tumour suppressor. Mutations in genes encoding subunits of other TCAC enzyme SDH have also been reported recently in tumours: mutations in SDHB, SDHC, and SDHD genes predispose to paraganglioma and pheochromocytoma. In the present study, mutations in the SDHB gene were observed to predispose to RCC. This was the first time that mutations in SDHB have been detected in extra-paraganglial tumours. Two different SDHB mutations were observed in two unrelated families. In the first family, the index patient was diagnosed with RCC at the age of 24 years. Additionally, his mother with a paraganglioma (PGL) of the heart and his maternal uncle with lung cancer were both carriers of the mutation. The RCC of the index patient and the PGL of his mother showed LOH. In the other family, an SDHB mutation was detected in two siblings who were both diagnosed with RCC at the ages of 24 and 26 years. Both of the siblings also suffered PGL. All these tumours showed LOH. Therefore, we concluded that mutations in SDHB predispose also for RCC in certain families. Several tumour types were analysed for FH mutations to define the role of FH mutations in these tumour types. In addition, patients with a putative cancer phenotype were analysed to identify new HLRCC families. Three FH variants were detected, of which two were novel. One of the variants was observed in a patient diagnosed with ULMS at the age of 41 years. However, LOH was not detected in the tumour tissue. The FH enzyme activity of the mutated protein was clearly reduced, being 43% of the activity of the normal protein. Together with the results from an earlier study we calculated that the prevalence of FH mutations in Finnish non-syndromic ULMS is around 2.4%. Therefore, FH mutations seem to have a minor role in the pathogenesis on non-syndromic ULMS. Two other germline variants were detected in a novel tumour type, ovarian mucinous cystadenoma. However, tumour tissues of the patients were not available for LOH studies and therefore LOH status remained unclear. Therefore, it is possible that FH mutations predispose also for ovarian tumours but further studies are needed to verify this result. A novel variant form of the FH gene (FHv) was identified and characterized in more detail. FHv contains an alternative first exon (1b), which appeared to function as 5 UTR sequence. The translation of FHv is initiated in vitro from exons two and three. The localization of FHv is both cytosolic and nuclear, in contrast to the localization of FH in mitochondria. FHv is expressed at low levels in all human tissues. Interestingly, the expression was induced after heat shock treatment and in chronic hypoxia. Therefore, FHv might have a role e.g. in the adaptation to unfavourable growth conditions. However, this remains to be elucidated.

National screening for barley grain defects

Three defects on barley grain can impact on the price paid to grain growers. Black point (BP), kernel staining (KS) and pre-harvest sprouting (PHS) can result in malting barley being downgraded to feed. Resistance to these defects is the best option, and in this project hundreds of breeding lines grown over three years were screened for these traits. A number of lines exhibited resistance to each defect but very few had resistance to all defects. The results from the screening program have been provided to the Australian barley breeders through the Barley Breeding Australia (BBA) program.

Dynamic structure factor across the liquid-solid interface: appearance of a delta-function elastic peak

We present a theoretical calculation of the dynamic structure factor, S(k, ω), at the liquid-solid interface for large values of the wavevector k. An analytic expression is derived which shows the evolution of the elastic peak as the solid surface is approached from the liquid side.

Biaxial-load effects on isopachics for a crack at the interface of dissimilar media

The plane problem of two dissimilar materials, bonded together and containing a crack along their common interface, which were subjected to a biaxial load at infinity, is examined by giving a closed-form expression for the first stress invariant of the normal stresses, which is equally valid everywhere, near to, and far from, the crack-tip region. This exact expression for the first-stress invariant is compared by constructing the respective isopachic-fringe patterns, to the approximate expression with non-singular terms, due to the biaxiality factor, for the same quantity. Significant differences between respective isopachic-patterns were found and their dependence on the elastic properties of both materials and the applied loads was demonstrated. The relative errors between the computedK I - andK II -components by using the approximate expression for the first stress-invariant and the accurate one, derived from closed-form solution along either isopachic-fringes or along circles and radii from the crack-tip have been given, indicating in some cases large discrepancies between exact and approximate solutions.

On the non-existence of hydrodynamic solution of surface plasmons at the bimetallic interface

It is shown that for an abrupt bimetallic interface a hydrodynamic solution for interface plasmons does not exist. It appears that this result is valid irrespective of the choice of of the additional boundary condition, thereby suggesting a careful look at the use of usual hydrodynamic equations for a bimetallic interface.

Line tension of a two dimensional gas-liquid interface

In two dimensional (2D) gas-liquid systems, the reported simulation values of line tension are known to disagree with the existing theoretical estimates. We find that while the simulation erred in truncating the range of the interaction potential, and as a result grossly underestimated the actual value, the earlier theoretical calculation was also limited by several approximations. When both the simulation and the theory are improved, we find that the estimate of line tension is in better agreement with each other. The small value of surface tension suggests increased influence of noncircular clusters in 2D gas-liquid nucleation, as indeed observed in a recent simulation.

Viscoelastic Properties of Nanocrystalline Films of Semiconducting Chalcogenides at Liquid/Liquid Interface

The interfacial shear rheological properties of a continuous single-crystalline film of CuS and a 3D particulate gel of CdS nanoparticles (3−5 nm in diameter) formed at toluene−water interfaces have been studied. The ultrathin films (50 nm in thickness) are formed in situ in the shear cell through a reaction at the toluene−water interface between a metal−organic compound in the organic layer and an appropriate reagent for sulfidation in the aqueous layer. Linear viscoelastic spectra of the nanofilms reveal solid-like rheological behavior with the storage modulus higher than the loss modulus over the range of angular frequencies probed. Large strain amplitude sweep measurements on the CdS nanofilms formed at different reactant concentrations suggest that they form a weakly flocculated gel. Under steady shear, the films exhibit a yield stress, followed by a steady shear thinning at high shear rates. The viscoelastic and flow behavior of these films that are in common with those of many 3D “soft” materials like gels, foams, and concentrated colloidal suspensions can be described by the “soft” glassy rheology model.

Optic-phonon-magnetoplasmons at the interface of two polar semiconductors semiconductors

An interface between two polar semiconductors can support a whole new family of seven type of optic-phonon magnetoplasmons. Six of these arise due to nonequivalence property of propagation introduced by the magnetic field in Voigt configuration and one mainly due to finite plasma density ratio at the interface.