921 resultados para Central point
Resumo:
We study transport across a point contact separating two line junctions in a nu = 5/2 quantum Hall system. We analyze the effect of inter-edge Coulomb interactions between the chiral bosonic edge modes of the half-filled Landau level (assuming a Pfaffian wave function for the half-filled state) and of the two fully filled Landau levels. In the presence of inter-edge Coulomb interactions between all the six edges participating in the line junction, we show that the stable fixed point corresponds to a point contact that is neither fully opaque nor fully transparent. Remarkably, this fixed point represents a situation where the half-filled level is fully transmitting, while the two filled levels are completely backscattered; hence the fixed point Hall conductance is given by G(H) = 1/2e(2)/h. We predict the non-universal temperature power laws by which the system approaches the stable fixed point from the two unstable fixed points corresponding to the fully connected case (G(H) = 5/2e(2)/h) and the fully disconnected case (G(H) = 0).
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This paper reports on the collection of S. australiensis from the continental shelf off southern Queensland, easter Australia, in the western Central Pacific, documenting for the first time the occurrence of the species outside of eastern Bass Strait.
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A semi-similar solution of an unsteady laminar compressible three-dimensional stagnation point boundary layer flow with massive blowing has been obtained when the free stream velocity varies arbitrarily with time. The resulting partial differential equations governing the flow have been solved numerically using an implicit finite-difference scheme with a quasi-linearization technique in the nodal point region and an implicit finite-difference scheme with a parametric differentiation technique in the saddle point region. The results have been obtained for two particular unsteady free stream velocity distributions: (i) an accelerating stream and (ii) a fluctuating stream. Results show that the skin-friction and heat-transfer parameters respond significantly to the time dependent arbitrary free stream velocity. Velocity and enthalpy profiles approach their free stream values faster as time increases. There is a reverse flow in the y-wise velocity profile, and overshoot in the x-wise velocity and enthalpy profiles in the saddle point region, which increase as injection and wall temperature increase. Location of the dividing streamline increases as injection increases, but as the wall temperature and time increase, it decreases.
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Quantifying the local crop response to irrigation is important for establishing adequate irrigation management strategies. This study evaluated the effect of irrigation applied with subsurface drip irrigation on field corn (Zea mays L.) evapotranspiration (ETc), yield, water use efficiencies (WUE = yield/ETc, and IWUE = yield/irrigation), and dry matter production in the semiarid climate of west central Nebraska. Eight treatments were imposed with irrigation amounts ranging from 53 to 356 mm in 2005 and from 22 to 226 mm in 2006. A soil water balance approach (based on FAO-56) was used to estimate daily soil water and ETc. Treatments resulted in seasonal ETc of 580-663 mm and 466-656 mm in 2005 and 2006, respectively. Yields among treatments differed by as much as 22% in 2005 and 52% in 2006. In both seasons, irrigation significantly affected yields, which increased with irrigation up to a point where irrigation became excessive. Distinct relationships were obtained each season. Yields increased linearly with seasonal ETc (R 2 = 0.89) and ETc/ETp (R 2 = 0.87) (ETp = ETc with no water stress). The yield response factor (ky), which indicates the relative reduction in yield to relative reduction in ETc, averaged 1.58 over the two seasons. WUE increased non-linearly with seasonal ETc and with yield. WUE was more sensitive to irrigation during the drier 2006 season, compared with 2005. Both seasons, IWUE decreased sharply with irrigation. Irrigation significantly affected dry matter production and partitioning into the different plant components (grain, cob, and stover). On average, the grain accounted for the majority of the above-ground plant dry mass (≈59%), followed by the stover (≈33%) and the cob (≈8%). The dry mass of the plant and that of each plant component tended to increase with seasonal ETc. The good relationships obtained in the study between crop performance indicators and seasonal ETc demonstrate that accurate estimates of ETc on a daily and seasonal basis can be valuable for making tactical in-season irrigation management decisions and for strategic irrigation planning and management.
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The genetic population structure of red snapper Lutjanus malabaricus and Lutjanus erythropterus in eastern Indonesia and northern Australia was investigated by allozyme electrophoresis and sequence variation in the control region of mtDNA. Samples were collected from eight sites in Indonesia and four sites in northern Australia for both species. A total of 13 allozyme loci were scored. More variable loci were observed in L. malabaricus than in L. erythropterus. Sequence variation in the control region (left domain) of the mitochondrial genome was assessed by RFLP and direct sequencing. MtDNA haplotype diversity was high (L. erythropterus, 0.95 and L. malabaricus, 0.97), as was intraspecific sequence divergence, (L. erythropterus, 0.0-12.5% and L. malabaricus, 0.0-9.5%). The pattern of mtDNA haplotype frequencies grouped both species into two broad fisheries stocks with a genetic boundary either between Kupang and Sape (L. malabaricus) or between Kupang and Australian Timor Sea (L. erythropertus). The allozyme analyses revealed similar boundaries for L. erythropterus. Seven allozymes stocks compared to two mtDNA stocks of L. malabaricus including Ambon, which was not sampled with mtDNA, however, were reported. Possible reasons for differences in discrimination between the methods include: i) increased power of multiple allozyme loci over the single mtDNA locus, ii) insufficient gene sampling in the mtDNA control region and iii) relative evolutionary dynamics of nuclear (allozyme loci) and mitochondrial DNA in these taxa. Allozyme and haplotype data did not distinguish separate stocks among the four Australian locations nor the central Indonesian (Bali and Sape locations) for both L. malabaricus and L. erythropterus.
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Tove Jansson (1914--2001) was a Finnish illustrator, author, artist, caricaturist and comic artist. She is best known for her Moomin Books, written in Swedish, which she illustrated herself, and published between 1945 and 1977. My study focuses on the interweaving of images and words in Jansson s picturebooks, novels and short stories situated in the fantasy world of Moomin Valley. In particular, it concentrates on Jansson s development of a special kind of aesthetics of movement and stasis, based upon both illustration and text. The conventions of picturebook art and illustration are significant to both Jansson s visual art and her writing, and she was acutely conscious of them. My analysis of Jansson s work begins by discussing her first published picturebooks and less familiar illustrations (before she began her Moomin books) and I then proceed to discuss her three Moomin picturebooks, The Book about Moomin, Mymble and Little My; Who Will Comfort Toffle?, and The Dangerous Journey. The discussion moves from images to words and from words to images: Barthes s (1982) concept of anchoring and, in particular, what he calls relaying , form a point of reading and viewing Moomin texts and illustrations in a complementary relation, in which the message s unity occurs on a higher level: that of the story, the anecdote, the diegesis . The eight illustrated Moomin novels and one collection of short stories are analysed in a similar manner, taking into account the academic discourse about picturebooks which was developed in the last decade of the 20th century and beginning of the 21st century by, among others, scholars such as Nodelman, Rhedin, Doonan, Thiele, Stephens, Lewis, Nikolajeva and Scott. In her Moomin books, Jansson uses a wide variety of narrative and illustrative styles which are complementary to each other. Each book is different and unique in its own way, but a certain development or progression of mood and representation can be seen when assessing the series as a whole. Jansson s early stories are happy and adventurous but her later Moomin novels, beginning from Moominland Midwinter, focus more on the interiority of the characters, placing them in difficult situations which approximate social reality. This orientation is also reflected in the representation of movement and space. The books which were published first include more obviously descriptive passages, exemplifying the tradition of literary pictorialism. Whereas in Jansson s later work, the space develops into something that is alive which can have an enduring effect on the characters personalities and behaviour. This study shows how the idea of an image a dynamic image -- forms a holistic foundation for Jansson s imagination and work. The idea of central perspective, or frame, for instance, provided inspiration for whole stories or in the way that she developed her characters, as in the case of the Fillyjonk, who is a complex female figure, simultaneously frantic and prim. The idea of movement is central to the narrative art of picturebooks and illustrated texts, particularly in relation to the way that action is depicted. Jansson, however, also develops a specific choreography of characters in which poses and postures signify action, feelings and relationships. Here, I use two ideas from modern dance, contraction and release (Graham), to characterise the language of movement which is evident in Jansson s words and images. In Jansson s final Moomin novels and short stories, the idea of space becomes more and more dynamic and closely linked with characterisation. My study also examines a number of Jansson s early sketches for her Moomin novels, in which movement is performed much more dramatically than in those illustrations which appeared in the last novels to be published.
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The unsteady free convection boundary layer hydromagnectic flow near a stagnation point of a three-dimensional body with applied magnetic field and time-dependent wall temperature has been studied. Both semi-semilar and self-similar cases have been considered. The equations governing the above flow have been solved numerically using an implicit finite-difference scheme due to Keller. The magnetic field is found to reduce both the heat transfer and skin friction. The effect of the variation of the wall temperature with time and of mass transfer is found to be more pronounced on the heat transfer than on the skin friction. In self-similar case, for decelerating flow, there is temperature overshoot in the presence of fmagnetic field, but in semi-similar case overshoot occurs even without magnetic field due to the unsteadiness
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The unsteadely laminar incompressible second-order boundary-layer flow at the stagnation point of a three-dimensional body has been studied for both nodal and saddle point regions. The effects of mass transfer and Prandtl number have been taken into account. The equations governing the flow have been solved numerically using an implicit finite-difference scheme. It has been found that the parameter characterizing the unsteadiness in the velocity of the free stream, the nature of the stagnation point, the mass transfer and Prandtl number strongly affect the second-order skin friction and heat transfer. The overall skin friction becomes less due to second-order effects but the heat transfer has the opposite behaviour. For large injection, the second-order skin-friction and heat-transfer results prevail over the first-order boundary layer results whereas for the case of large suction the behaviour is just the opposite.
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The heat and mass transfer for unsteady laminar compressible boundary-layer flow, which is asymmetric with respect to a 3-dimensional stagnation point (i.e. for a jet incident at an angle on the body), have been studied. It is assumed that the free-stream velocity, wall temperature, and surface mass transfer vary arbitrarily with time and also that the gas has variable properties. The solution in the neighbourhood of the stagnation point has been obtained by series expansion in the longitudinal distance. The resulting partial differential equations have been solved numerically using an implicit finite-difference scheme. The results show that, in contrast with the symmetric flow, the maximum heat transfer does not occur at the stagnation point. The skin-friction and heat-transfer components due to asymmetric flow are only weakly affected by the mass transfer as compared to those components associated with symmetric flow. The variation of the wall temperature with time has a strong effect on the heat transfer component associated with the symmetric part of the flow. The skin friction and heat transfer are strongly affected by the variation of the density-viscosity product across the boundary layer. The skin friction responds more to the fluctuations of the free stream oscillating velocities than the heat transfer. The results have been compared with the available results and they are found to be in excellent agreement.
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The sequential nature of gel-based marker systems entails low throughput and high costs per assay. Commonly used marker systems such as SSR and SNP are also dependent on sequence information. These limitations result in high cost per data point and significantly limit the capacity of breeding programs to obtain sufficient return on investment to justify the routine use of marker-assisted breeding for many traits and particularly quantitative traits. Diversity Arrays Technology (DArT™) is a cost effective hybridisation-based marker technology that offers a high multiplexing level while being independent of sequence information. This technology offers sorghum breeding programs an alternative approach to whole-genome profiling. We report on the development, application, mapping and utility of DArT™ markers for sorghum germplasm. Results: A genotyping array was developed representing approximately 12,000 genomic clones using PstI+BanII complexity with a subset of clones obtained through the suppression subtractive hybridisation (SSH) method. The genotyping array was used to analyse a diverse set of sorghum genotypes and screening a Recombinant Inbred Lines (RIL) mapping population. Over 500 markers detected variation among 90 accessions used in a diversity analysis. Cluster analysis discriminated well between all 90 genotypes. To confirm that the sorghum DArT markers behave in a Mendelian manner, we constructed a genetic linkage map for a cross between R931945-2-2 and IS 8525 integrating DArT and other marker types. In total, 596 markers could be placed on the integrated linkage map, which spanned 1431.6 cM. The genetic linkage map had an average marker density of 1/2.39 cM, with an average DArT marker density of 1/3.9 cM. Conclusion: We have successfully developed DArT markers for Sorghum bicolor and have demonstrated that DArT provides high quality markers that can be used for diversity analyses and to construct medium-density genetic linkage maps. The high number of DArT markers generated in a single assay not only provides a precise estimate of genetic relationships among genotypes, but also their even distribution over the genome offers real advantages for a range of molecular breeding and genomics applications.
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A switched DC voltage three level NPC is proposed in this paper to eliminate capacitor balancing problems in conventional three-level Neutral Point Clamped (NPC) inverter. The proposed configuration requires only one DC link with a voltage V-dc/2, where V-dc is the DC link voltage in a onventional NPC inverter. To get rated DC link voltage (V-dc), the voltage source is alternately onnected in parallel to one of the two series capacitors using two switches and two diodes with device voltage rating of V-dc/2. The frequency at which the voltage source is switched is independent and will not affect the operation of NPC inverter. The switched voltage source in this configuration balances the capacitors automatically. The proposed configuration can also be used as a conventional two level inverter in lower modulation range, thereby increases the reliability of the drive system. A space vector based PWM scheme is used to verify this proposed topology.
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The unsteady laminar compressible boundary-layer flow over two-dimensional and axisymmetric bodies at the stagnation point with mass transfer has been studied for all second-order boundary layer effects when the basic potential flow admits selfsimilarity. The solutions for the governing equations are obtained by using an implicit finite-difference scheme. Computations have been carried out for different values of the parameters characterizing the unsteadiness in the free stream velocity, wall temperature, mass transfer rate and variable gas properties. The results are found to be strongly affected by the unsteadiness in the free stream velocity. For large injection rates the second-orderboundary layer effects may prevail over the first-order boundary layer, but reverse is true for suction. The wall temperature and the variation of the density-viscosity product across the boundary layer appreciably change the skin-friction and heat-transfer rates due to second-order boundary-layer effects.
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The study examines the dissertation process. The thesis is based on twenty-three autobiographical stories. They were collected from PhDs who had taken their doctoral degrees at the University of Helsinki. The purpose is to investigate the experiences of these PhD recipients and find out what they recall of the events, traditions, and meanings associated with their PhD studies. An anthology collected from PhDs in the historical sciences, which was published in 1998, was used as reference material. This study begins with a general presentation of the history and values of the university and the traditions of the academic community in Finland. Thereafter, the data and the methodological framework of the study are presented. Attention is paid to the discipline background, sex and age of these PhDs, which may have affected their storytelling. The former studies concerning the academic life together with the experiences of the writers revealed that the process of becoming a PhD graduate is generally considered as an academic rite of passage. The change from student status to becoming a fully accepted professional member of one’s field is real, transforming and at certain points, ritualized. The finding of an inner logic to the doctoral process, which included meaningful turning points, was central to the narrative analysis approach. During the process there were different kinds of struggles and highlights. The family background, university studies and time in employment had directed the doctoral studies of some PhD students enormously. But generally the most memorable and value laden were the phases of actually writing the dissertation, the public examination, and the celebration party in the evening called “karonkka”. The picture that emerged from these various life-stories demonstrated that there was no ivory tower where doctoral candidates live an isolated existence. Everyday cares in ordinary life and tasks in academic life are both demanding and rewarding at the same time. The main point is that the academic community in general and PhD supervisors in particular should concentrate not only on the thesis-writing process their students but also on the doctoral students´ wider life situation. Doctoral students need scientific, financial, and mental support. Somebody must be available to inspire and offer encouragement otherwise the process will be disturbed. The successful completion of the PhD ritual gives the PhD graduate self-confidence and respect but its’ influence on the doctors’ subsequent academic career is diverse. The dissertation process is a personal and unique experience. The aim of the PhD graduation is that this traditional ritual leads to a successful completion and ensures a positive reward for the PhD graduate and the academic community. Keywords: autobiography, narratives, academic traditions, PhD graduates.
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The self-similar solution of the unsteady laminar compressible boundary-layer flow with variable properties at a three-dimensional stagnation point with mass transfer has been obtained when the free-stream velocity varies inversely as a linear function of time. The resulting ordinary differential equations have been solved numerically using an implicit finite-difference scheme. The results are found to be strongly dependent on the parameter characterizing the unsteadiness in the free-stream velocity. The velocity profiles show some features not encountered in steady flows.