36 research outputs found
Composite quasiparticle formation and the low-energy effective Hamiltonians of the one- and two-dimensional Hubbard Model
We investigate the effect of hole doping on the strong-coupling Hubbard model
at half-filling in spatial dimensions . We start with an
antiferromagnetic mean-field description of the insulating state, and show that
doping creates solitons in the antiferromagnetic background. In one dimension,
the soliton is topological, spinless, and decoupled from the background
antiferromagnetic fluctuations at low energies. In two dimensions and above,
the soliton is non-topological, has spin quantum number 1/2, and is strongly
coupled to the antiferromagnetic fluctuations. We derive the effective action
governing the quasiparticle motion, study the properties of a single carrier,
and comment on a possible description at finite concentration.Comment: REVTEX 3.0, 22 pages with 14 figures in the PostScript format
compressed using uufile. Submitted to Phys. Rev. B. The complete PostScript
file including figures can be obtained via ftp at
ftp://serval.berkeley.edu/hubbard.ps . It is also available via www at
http://roemer.fys.ku.dk/recent.ht
Quasiparticle structure and coherent propagation in the model
Numerical studies, from variational calculation to exact diagonalization, all
indicate that the quasiparticle generated by introducing one hole into a
two-dimensional quantum antiferromagnet has the same nature as a string state
in the model. Based on this observation, we attempt to visualize the
quasiparticle formation and subsequent coherent propagation at low energy by
studying the generalized model in which we first
diagonalize the model and then perform a {\em degenerate}
perturbation in . We construct the quasiparticle state and derive an
effective Hamiltonian describing the coherent propagation of the quasiparticle
and its interaction with the spin wave excitations in the presence of the
N\'{e}el order. We expect that qualitative properties of the quasiparticle
remain intact when analytically continuing from the anisotropic
to the isotropic limit, despite the
fact that the spin wave excitations change from gapful to gapless.
Extrapolating to , our quasiparticle dispersion and spectral
weight compare well with the exact numerical results for small clusters.Comment: Revised with minor changes and references updated. To appear in Phys.
Rev. B., Jan. 1996. 10 pages, The complete PostScript file including figures
can be obtained via ftp at ftp://serval.berkeley.edu/tjzjp.ps . It is also
posted in the WEB site of Niels Bohr Institute at
http://roemer.fys.ku.dk/recent.ht
A global view of porcine transcriptome in three tissues from a full-sib pair with extreme phenotypes in growth and fat deposition by paired-end RNA sequencing
<p>Abstract</p> <p>Background</p> <p>Elucidation of the pig transcriptome is essential for interpreting functional elements of the genome and understanding the genetic architecture of complex traits such as fat deposition, metabolism and growth.</p> <p>Results</p> <p>Here we used massive parallel high-throughput RNA sequencing to generate a high-resolution map of the porcine mRNA and miRNA transcriptome in liver, longissimus dorsi and abdominal fat from two full-sib F<sub>2 </sub>hybrid pigs with segregated phenotypes on growth, blood physiological and biochemical parameters, and fat deposition. We obtained 8,508,418-10,219,332 uniquely mapped reads that covered 78.0% of the current annotated transcripts and identified 48,045-122,931 novel transcript fragments, which constituted 17,085-29,499 novel transcriptional active regions in six tested samples. We found that about 18.8% of the annotated genes showed alternative splicing patterns, and alternative 3' splicing is the most common type of alternative splicing events in pigs. Cross-tissue comparison revealed that many transcriptional events are tissue-differential and related to important biological functions in their corresponding tissues. We also detected a total of 164 potential novel miRNAs, most of which were tissue-specifically identified. Integrated analysis of genome-wide association study and differential gene expression revealed interesting candidate genes for complex traits, such as <it>IGF2, CYP1A1, CKM </it>and <it>CES1 </it>for heart weight, hemoglobin, pork pH value and serum cholesterol, respectively.</p> <p>Conclusions</p> <p>This study provides a global view of the complexity of the pig transcriptome, and gives an extensive new knowledge about alternative splicing, gene boundaries and miRNAs in pigs. Integrated analysis of genome wide association study and differential gene expression allows us to find important candidate genes for porcine complex traits.</p
A laboratory GTEM cell design for electromagnetic exposure study on biological system
International audienceIn this paper, a Gigaherz Transverse Electromagnetic (GTEM) cell is designed for laboratory use electromagnetic fields exposure study on biological system. Once the total volume and the area of exposure have been defined, a first calculation will be made to deduce the initial values of the parameters of the GTEM cell. The use of a fullwave electromagnetic simulation software will allow these parameters to be adjusted to obtain a low reflection on a frequency band around 915 MHz, and a fairly homogeneous electric field in the test zone... The effect of the biological medium on the distribution of the electromagnetic field will also be analyzed and the Specific Absorption Rate (SAR) estimation will be made with different parameters of the biological media
Les Lieux de Reverdy
Le concept de lieu intĂ©resse l analyse littĂ©raire non seulement dans une acception thĂ©matique mais aussi en ce qu il traduit et symbolise la relation du sujet lyrique au monde et au langage, que l Ćuvre de Reverdy reconstruit de maniĂšre originale. On se propose, dans une premiĂšre partie, de dĂ©crire la structuration du monde imaginaire de Reverdy, ce paysage au sens oĂč le dĂ©finit Michel Collot que son Ćuvre instaure, construit, recompose. S il est riche de lieux qui se distribuent de maniĂšre polysĂ©mique, il rend Ă©galement compte d une expĂ©rience originale de l existence, en traduit les donnĂ©es les plus personnelles, celles d un je poĂ©tique immergĂ© dans un monde qu il recompose par des lois imaginaires et dont il Ă©prouve l instabilitĂ© essentielle. Ce monde Ă©minemment subjectif nous sommes, rappelle Jean-Pierre Richard, en poĂ©sie et par lĂ -mĂȘme lacunaire et mouvant, prĂ©suppose une place du sujet ancrĂ© au monde, et donc lieu exclu du monde tel un point aveugle. Une seconde partie Ă©tudie le travail de l Ă©criture poĂ©tique reverdyenne qui conteste et subvertit cette relation. Sous l influence du cubisme, elle entre en lutte contre l unitĂ©/unicitĂ© d un sujet dont elle mine la vĂ©ritĂ©, dĂ©truit la cohĂ©sion, dont elle rĂȘve la diffraction et la dispersion dans un paysage qu elle investit de maniĂšre massive, jusqu Ă l y confondre. L Ă©criture poĂ©tique est donc un moyen privilĂ©giĂ© de repenser le lieu, ce Dasein qui concrĂ©tise l existence, et apparaĂźt ainsi comme un lieu de nouage, de fusion, un carrefour oĂč sujet et monde imaginaires se constituent en un lieu de l Ćuvre, vĂ©ritable figure du sujet lyrique, territoire au sens oĂč l entend Jean-Marie Gleize et dont une troisiĂšme partie expose l essence. C est lĂ l occasion de comprendre comment fonctionne l Ă©criture reverdyenne, quelles sont les grandes forces de l imaginaire qui s y met en Ćuvre, pour en tirer des conclusions sur sa spĂ©cificitĂ©.The concept of place is of special interest for literary analysis not only thematically but also in so far as it translates and symbolizes the relation of the lyrical subject to the world and to language, which is reconstructed by Reverdy s literary work in an original way. The first part of this thesis is devoted to the structuration of Reverdy s imaginary world, this landscape as defined by Michel Collot elaborated, built and recombined. This landscape, made of polysemous places, also translates an original existential experiment, through most personal data, the data of a poetical I submerged in a reconstructed world based on imaginary laws and experienced by the author as essentially unstable. This extremely subjective world we are, as Jean-Pierre Richard reminds us, in poesy thus on a land of gap and constant change, is based on the principle of a subject rooted in the world and thus a place excluded from the world like a blind spot. The second part studies the work of the Reverdian poetic writing that rejects and subverts this relation. Under the spell of Cubism, it fights against the unity/uniqueness of a subject by distorting reality, destructing coherence and dreaming of its diffraction and blurring into a landscape it massively invests in, till melting. Poetic writing is thus a privileged way of rethinking the concept of place, this Dasein materializing existence, and is revealed as a place of binding, of fusion, a crossroad where the subject and the imaginary world are intertwined in a place of the work, true self of the lyrical subject, territory as defined by Jean-Marie Gleize and whose third part presents the essence. We have the opportunity to understand the way the Reverdian writing works, the great forces of the imagination at work in it, so as to be able to conclude on its specificity.BORDEAUX3-Bib. Ă©lectronique (335229906) / SudocSudocFranceF
A test of empirical and semi-analytical algorithms for euphotic zone depth with SeaWifs data off southeastern China
This study employs SeaWiFS data over the waters off the southeastern China to evaluate a semi-analytical algorithm for euphotic zone depth (Ze). This algorithm is based on water's inherent optical properties (IOPs), which can be near-analytically calculated from spectral remote-sensing reflectance, where remote-sensing reflectance can be derived from the normalized water-leaving radiance provided by SeaWiFS. In the Taiwan Strait, compared with in situ Z(e) (+/- 3 hour within SeaWiFS collection), average error (c) is 15.0 % and root mean square error (RMSE) is 0.074, with Ze in a range of 14-34 in from field measurements. In the South China Sea, compared with in situ Ze ( 48 hour within SeaWiFS collection),epsilon is 5.1 % in summer and 22.6 in winter, while RMSE is 0.032 in summer and 0.129 in winter, with Z(e) in a range of 10-82 in from field measurements. For comparison, we also evaluate the performance of the empirical Ze algorithm that is based on chlorophyll concentration. It is found that the IOP-centered approach has higher accuracy, compared to the chlorophyll-a centered approach (e.g. in the South China Sea in winter, epsilon is 55.3 % and RMSE is 0.219). The new algorithm is thus found not only worked well with waters of the Gulf of Mexico, Monterey Bay and the Arabian Sea, but also worked well with waters of the China Sea