InGaAs/InP中离子注入和新型HPT

北京市基金,国家自然科学基金

Phase transition temperature of HPT(2,3,6,7,10,11-hexa-n-pentyloxytriphenylene) from molecule dynamic simulation

Molecule dynamics simulation was used on HPT(2,3,6,7,10,11-hexa-n-pentyloxytriphenylene), which is a discotic Liquid crystal. From analyzing the energy and displacement varying with the temperature, the phase transition temperature of PM6MPP can be predicted. The deviations of T-g, T-m and T-i due to the MD time scale are small enough that it should be possibly used to predict the material properties especially when more powerful computers are available.

The role of cognitive and visual abilities as predictors in the Multifactorial Model of Driving Safety

Objective The current study evaluated part of the Multifactorial Model of Driving Safety to elucidate the relative importance of cognitive function and a limited range of standard measures of visual function in relation to the Capacity to Drive Safely. Capacity to Drive Safely was operationalized using three validated screening measures for older drivers. These included an adaptation of the well validated Useful Field of View (UFOV) and two newer measures, namely a Hazard Perception Test (HPT), and a Hazard Change Detection Task (HCDT). Method Community dwelling drivers (n = 297) aged 65–96 were assessed using a battery of measures of cognitive and visual function. Results Factor analysis of these predictor variables yielded factors including Executive/Speed, Vision (measured by visual acuity and contrast sensitivity), Spatial, Visual Closure, and Working Memory. Cognitive and Vision factors explained 83–95% of age-related variance in the Capacity to Drive Safely. Spatial and Working Memory were associated with UFOV, HPT and HCDT, Executive/Speed was associated with UFOV and HCDT and Vision was associated with HPT. Conclusion The Capacity to Drive Safely declines with chronological age, and this decline is associated with age-related declines in several higher order cognitive abilities involving manipulation and storage of visuospatial information under speeded conditions. There are also age-independent effects of cognitive function and vision that determine driving safety.

Agrobacterium-mediated transformation of indica rice cultivars using binary and superbinary vectors

The Agrobacterium-mediated transformation system was extended to two indica cultivars: a widely cultivated breeding line IR-64 and an elite basmati cultivar Karnal Local. Root tips and shoot tips of seedlings, and scutellar-calli derived from mature seeds showed high-efficiency Agrobacterium tumefaciens infection and stable transformation. In addition to the superbinary vector pTOK233 in Agrobacterium strain LBA4404, almost equally high levels of transformation were achieved with a relatively much smaller (13.1 kb) binary vector (pCAMBIA1301) in a supervirulent host strain AGL1. In both cases, as well as in both cultivars, while 60–90% of the infected explants produced calli resistant to the selectable agent hygromycin, 59–75% of such calli tested positive for GUS. A high level (400 μM) of acetosyringone in the preinduction medium for Agrobacterium and a higher level (500 μM) in the cocultivation medium was necessary for an enhancement in transformation frequency of the binary vector to levels comparable to a superbinary. Hygromycin-resistant calli could be produced from all the explants used. Transformants could be regenerated for both cultivars using the superbinary and binary vector, but only for calli of scutellar origin. In addition to the molecular confirmation of hpt and gus gene transfer and transcription, absence of gene sequences outside the transferred DNA (T-DNA) region confirmed absence of any long T-DNA transfer.

Visual motion perception predicts driving hazard perception ability

PURPOSE: To examine the basis of previous findings of an association between indices of driving safety and visual motion sensitivity and to examine whether this association could be explained by low-level changes in visual function. METHODS: 36 visually normal participants (aged 19 – 80 years), completed a battery of standard vision tests including visual acuity, contrast sensitivity and automated visual fields. and two tests of motion perception including sensitivity for movement of a drifting Gabor stimulus, and sensitivity for displacement in a random-dot kinematogram (Dmin). Participants also completed a hazard perception test (HPT) which measured participants’ response times to hazards embedded in video recordings of real world driving which has been shown to be linked to crash risk. RESULTS: Dmin for the random-dot stimulus ranged from -0.88 to -0.12 log minutes of arc, and the minimum drift rate for the Gabor stimulus ranged from 0.01 to 0.35 cycles per second. Both measures of motion sensitivity significantly predicted response times on the HPT. In addition, while the relationship involving the HPT and motion sensitivity for the random-dot kinematogram was partially explained by the other visual function measures, the relationship with sensitivity for detection of the drifting Gabor stimulus remained significant even after controlling for these variables. CONCLUSION: These findings suggest that motion perception plays an important role in the visual perception of driving-relevant hazards independent of other areas of visual function and should be further explored as a predictive test of driving safety. Future research should explore the causes of reduced motion perception in order to develop better interventions to improve road safety.

Agrobacterium tumefaciens-mediated transformation of an elite Australian barley cultivar with virus resistance and reporter genes

Efficient transformation of barley cv. Schooner was achieved using Agrobacterium delivery, hygromycin or bialaphos selection and embryogenic callus. Using this system, transgenic plants were generated that contained either the green fluorescent protein gene, or transgenes derived from barley yellow dwarf (BYDV) and cereal yellow dwarf (CYDV) viruses. Many of these plants contained 1-3 transgene copies that were inherited in a simple Mendelian manner. Some plants containing BYDV and/or CYDV derived transgenes showed reduced virus symptoms and rates of viral replication when challenged with the appropriate virus. The ability to transform Schooner is a significant advance for the Australian barley industry, as this elite malting variety is, and has for the last 15 years been, the most widely grown barley variety in eastern Australia.

Age-related changes in perception of movement in driving scenes

Purpose Age-related changes in motion sensitivity have been found to relate to reductions in various indices of driving performance and safety. The aim of this study was to investigate the basis of this relationship in terms of determining which aspects of motion perception are most relevant to driving. Methods Participants included 61 regular drivers (age range 22–87 years). Visual performance was measured binocularly. Measures included visual acuity, contrast sensitivity and motion sensitivity assessed using four different approaches: (1) threshold minimum drift rate for a drifting Gabor patch, (2) Dmin from a random dot display, (3) threshold coherence from a random dot display, and (4) threshold drift rate for a second-order (contrast modulated) sinusoidal grating. Participants then completed the Hazard Perception Test (HPT) in which they were required to identify moving hazards in videos of real driving scenes, and also a Direction of Heading task (DOH) in which they identified deviations from normal lane keeping in brief videos of driving filmed from the interior of a vehicle. Results In bivariate correlation analyses, all motion sensitivity measures significantly declined with age. Motion coherence thresholds, and minimum drift rate threshold for the first-order stimulus (Gabor patch) both significantly predicted HPT performance even after controlling for age, visual acuity and contrast sensitivity. Bootstrap mediation analysis showed that individual differences in DOH accuracy partly explained these relationships, where those individuals with poorer motion sensitivity on the coherence and Gabor tests showed decreased ability to perceive deviations in motion in the driving videos, which related in turn to their ability to detect the moving hazards. Conclusions The ability to detect subtle movements in the driving environment (as determined by the DOH task) may be an important contributor to effective hazard perception, and is associated with age, and an individuals' performance on tests of motion sensitivity. The locus of the processing deficits appears to lie in first-order, rather than second-order motion pathways.

Non-finite constructions in Old English : with special reference to syntactic borrowing from Latin

My dissertation is a corpus-based study of non-finite constructions in Old English (OE). It revisits the question of Latin influence on the OE syntax, offering a new evaluation of syntactic interference between Latin and OE, and, more generally, of the contact situation in the OE period, drawing on methods used in studying grammaticalization and language contact. I address three non-finite constructions: absolute participial construction, accusative-and-infinitive construction, and nominative-and-infinitive construction, exemplified respectively in present-day English as - She looked like a pixie sometimes, her eyes darting here and there, forever watchful (BNC CCM 98); - My first acquaintance with her was when I heard her sing (BNC CFY 2215); - Charles the Bald was said to resemble his grandfather physically (BNC HPT 175). This study compares data from translated texts against the background of original OE writings, establishing dependencies and differences between the two. Although the contrastive analysis of source and target texts is one of the major methods employed in the study, translation and translation strategies as such are only my secondary foci. The emphasis is rather on what source/target comparison can tell us about the OE non-finite syntax and the typological differences between Latin and OE in this domain, and on whether contact-induced change can originate in translation. In terms of theoretical framework, I have adopted functional-typological approach, which rests on the principles of iconicity and event integration, and to the best of my knowledge, has not been applied systematically to OE non-finite constructions. Therefore one more aim of the dissertation is to test this framework and to see how OE fits into the cross-linguistic picture of non-finites. My research corpus consists of two samples: 1) written OE closely dependent on the Latin originals, based on editions of two gloss texts, five translations, and Latin originals of these texts, representing four text types: hymns, religious regulations, homily/life narrative, and biblical narrative (180,622 words); and 2) written OE as far independent from Latin as possible, based on a selection from the York-Toronto-Helsinki Parsed Corpus of Old English Prose (YCOE) and representing five text types: laws, charters, correspondence, chronicle narrative, and homily/life narrative (274,757 words).

Cytokinin signalling in the regulation of cambial development

Secondary growth of plants is of pivotal importance in terrestrial ecosystems, providing a significant carbon sink in the form of wood. As plant biomass accumulation results largely from the cambial growth, it is surprising that quite little is known about the hormonal or genetic control of this important process in any plant species. The central aim of my thesis studies was to explore the function of cytokinin in the regulation of cambial development. Since their discovery as regulators of plant cell divisions, cytokinins have been assumed to participate in the control of cambial development. Evidence for this action was deduced from hormone treatment experiments, where exogenously applied cytokinin was shown to enhance cambial cell divisions in diverse plant organs and species. In my thesis work, the conservation of cytokinin signalling and homeostasis genes between a herbaceous plant, Arabidopsis, and a hardwood tree species, Populus trichocarpa. Presumably reflecting the ancient origin of cytokinin signalling system, the Populus genome contains orthologs for all Arabidopsis cytokinin signalling and homeostasis genes. Thus, genes belonging to five main families of isopentenyl transferases (IPTs), cytokinin oxidases (CKXs), two-component receptors, histidine containing phosphotransmitters (HPts) and response regulators (RRs) were identified from the Populus genome. Three subfamilies associated with cytokinin signal transduction, the CKI1-like family of two-component receptors, the AHP4-like HPts, and the ARR22-like atypical RRs, were significantly larger in Populus genome than in Arabidopsis. Potential contribution to the extensive secondary development of Populus by the members of these considerably expanded gene families will be discussed. Representatives of all cytokinin signal transduction elements were expressed in the Populus cambial zone, and most of the expressed genes appeared to be slightly more abundant on the phloem side of the meristem. The abundance of cytokinin related genes in the cambium emphasizes the important role of this hormone in the regulation of the extensive secondary growth characteristic of tree species. The function of the pseudo HPts in primary vascular development was studied in Arabidopsis root vasculature. It was demonstrated that the pseudo HPt AHP6 has a role in locally inhibiting cytokinin signalling in the protoxylem position in the Arabidopsis root, thus enabling differentiation of the protoxylem cell file. The possible role of pseudo HPts in cambial development will be discussed. The expression peak of cytokinin signalling genes in the tree cambial zone strongly indicates that cytokinin has a role in the regulation of this meristem function. To address whether cytokinin signalling is required for cambial activity, transgenic Populus trees with modified cytokinin signalling were produced. These trees were expressing a cytokinin catabolic gene from Arabidopsis, CYTOKININ OXIDASE 2, (AtCKX2) under the promoter of a Betula CYTOKININ RECEPTOR 1 (BpCRE1). The pBpCRE1::CKX2 transgenic Populus trees showed a reduced concentration of a biologically active cytokinin, correlating with their impaired cytokinin response. Furthermore, the radial growth of these trees was compromised, as illustrated by a smaller stem diameter than in wild-type trees of the same height. Moreover, the level of cambial cytokinin signalling was down-regulated in these thin-stemmed trees. The reduced signalling correlated with a decreased number of meristematic cambial cells, implicating cytokinin activity as a direct regulator of cambial cell division activity. Together, the results of my study indicate that cytokinins are major hormonal regulators required for cambial development.

Eye movements and road hazard detection: Effects of blur and distractors

Purpose To examine the effects of optical blur, auditory distractors and age on eye movement patterns while performing a driving hazard perception test (HPT). Methods Twenty young (mean age 27.1 ± 4.6 years) and 20 older (73.3 ± 5.7 years) drivers with normal vision completed a HPT in a repeated-measures counterbalanced design while their eye movements were recorded. Testing was performed under two visual (best-corrected vision and with +2.00DS blur) and two distractor (with and without auditory distraction) conditions. Participants were required to respond to road hazards appearing in the HPT videos of real-world driving scenes and their hazard response times were recorded. Results Blur and distractors each significantly delayed hazard response time, by 0.42 and 0.76s respectively (p<0.05). A significant interaction between age and distractors indicated that older drivers were more affected by distractors than young drivers (response with distractors delayed by 0.96 and 0.60s respectively). There were no other two- or three-way interaction effect on response time. With blur, both groups fixated significantly longer on hazards before responding compared to best-corrected vision. In the presence of distractors, both groups exhibited delayed first fixation on the hazards and spent less time fixating on the hazards. There were also significant differences in eye movement characteristics between groups, where older drivers exhibited smaller saccades, delayed first fixation on hazards, and shorter fixation duration on hazards compared to the young drivers. Conclusions Collectively, the findings of delayed hazard response times and alterations in eye movement patterns with blur and distractors provide further evidence that visual impairment and distractors are independently detrimental to driving safety given that delayed hazard response times are linked to increased crash risk.

Evolution of microhardness and microstructure in a cast Al–7 % Si alloy during high-pressure torsion

Disks of a cast Al-7 % Si alloy were processed through high-pressure torsion (HPT) for 1/4, 1/2, 1, 5, and 10 revolutions under a pressure of 6.0 GPa and at temperatures of 298 and 445 K. The hardness of the samples after processing was significantly higher than in the cast sample, and the hardness profiles across the samples became more uniform with increasing numbers of turns. Processing at higher temperature gave lower hardness values. Experiments were conducted to examine the effects of HPT processing on various microstructural aspects of the cast Al-7 % Si alloy such as the grain size, the Taylor factor, and the fraction of high-angle grain boundaries. The results demonstrate that there is a correlation between trends in the microhardness values and the observed microstructures.

Effect of High-Pressure Torsion on Texture, Microstructure, and Raman Spectroscopy: Case Study of Fe- and Te-Substituted CoSb3

Fe0.05Co0.95Sb2.875Te0.125, a double-element-substituted skutterudite, was prepared by induction melting, annealing, and hot pressing (HP). The hot-pressed sample was subjected to high-pressure torsion (HPT) with 4 GPa pressure at 673 K. X-ray diffraction was performed before and after HPT processing of the sample; the skutterudite phase was observed as a main phase, but an additional impurity phase (CoSb2) was observed in the HPT-processed sample. Surface morphology was determined by high-resolution scanning electron microscopy. In the HP sample, coarse grains with sizes in the range of approximately 100 nm to 300 nm were obtained. They changed to fine grains with a reduction in grain size to 75 nm to 125 nm after HPT due to severe plastic deformation. Crystallographic texture, as measured by x-ray diffraction, indicated strengthening of (112), (102) poles and weakening of the (123) pole of the HPT-processed sample. Raman-active vibrational modes showed a peak position shift towards the lower energy side, indicating softening of the modes after HPT. The distortion of the rectangular Sb-Sb rings leads to broadening of Sb-Sb vibrational modes due to local strain fluctuation. In the HPT process, a significant effect on the shorter Sb-Sb bond was observed as compared with the longer Sb-Sb bond.

A critical examination of the paradox of strength and ductility in ultrafine-grained metals

The paradox of strength and ductility is now well established and denotes the difficulty of simultaneously achieving both high strength and high ductility. This paradox was critically examined using a cast Al-7% Si alloy processed by high-pressure torsion (HPT) for up to 10 turns at a temperature of either 298 or 445 K. This processing reduces the grain size to a minimum of similar to 0.4 mu m and also decreases the average size of the Si particles. The results show that samples processed to high numbers of HPT turns exhibit both high strength and high ductility when tested at relatively low strain rates and the strain rate sensitivity under these conditions is similar to 0.14 which suggests that flow occurs by some limited grain boundary sliding and crystallographic slip. The results are also displayed on the traditional diagram for strength and ductility and they demonstrate the potential for achieving high strength and high ductility by increasing the number of turns in HPT.

The contribution of grain boundary sliding in tensile deformation of an ultrafine-grained aluminum alloy having high strength and high ductility

An as-cast Al-7 % Si alloy was processed by high-pressure torsion (HPT) for up to 10 turns at temperatures of 298 or 445 K. The HPT-processed samples had ultrafine-grained structures and they were tested in tension at room temperature at various strain rates in the range from 1.0 x 10(-4) to 1.0 x 10(-2) s(-1). The contributions of grain boundary sliding (GBS) to the total strain were measured directly using atomic force microscopy. Samples simultaneously showing both high strength and high ductility contained the highest fractions of high-angle grain boundaries (HAGB) and exhibited the highest contributions from GBS, whereas samples showing high strength but low ductility gave negligible values for the sliding contributions. It is concluded that high strength and high ductility require both an ultrafine grain size and a high fraction of HAGB.