Origin of the unusual dependence of Raman D band on excitation wavelength in graphite-like materials

We have revisited the still unresolved puzzle of the dispersion of the Raman disordered-induced D band as a function of laser excitation photon energy E$_L$ in graphite-like materials. We propose that the D-mode is a combination of an optic phonon at the K-point in the Brillioun zone and an acoustic phonon whose momentum is determined uniquely by the double resonance condition. The fit of the experimental data with the double-resonance model yields the reduced effective mass of 0.025m$_{e}$ for the electron-hole pairs corresponding to the A$_{2}$ transition, in agreement with other experiments. The model can also explain the difference between $\omega_S$ and $\omega_{AS}$ for D and D$^{\star}$ modes, and predicts its dependence on the Raman excitation frequency.Comment: 4 figures in eps forma

Covariant quantum measurements may not be optimal

Quantum particles, such as spins, can be used for communicating spatial directions to observers who share no common coordinate frame. We show that if the emitter's signals are the orbit of a group, then the optimal detection method may not be a covariant measurement (contrary to widespread belief). It may be advantageous for the receiver to use a different group and an indirect estimation method: first, an ordinary measurement supplies redundant numerical parameters; the latter are then used for a nonlinear optimal identification of the signal.Comment: minor corrections, to appear in J. Mod. Opt. (proc. of Gdansk conf.

Parabolic Focal Conics and Polygonal Textures in Lipid Liquid Crystals

Polygonal defect arrays in lipid liquid crystals prepared from dipalmitoyl-, dimyristoyl-, and dilaurylphosphatidylcholine with various concentrations of water have been observed and characterized using optical microscopy. These arrays appear similar to the polygonal arrays previously observed in thermotropic smectic and cholesteric liquid crystals. The parabolic focal conic model proposed by Rosenblatt, Pindak, Clark and Meyer for the polygonal arrays in thermotropic smectic liquid crystals also describes the observed properties in the smectic A phase of lipid liquid crystals. The polygonal arrays become progressively more birefringent as the strains inducing them are increased. The parabolic focal conic model does not completely describe the details of the more birefringent polygonal arrays.Engineering and Applied Science

Alignment and Defect Structures in Oriented Phosphatidylcholine Multilayers

The alignment of dilauryl-, dimyristoyl-, and dipalmitoylphosphatidylcholine at various water concentrations into large oriented monodomain multilayers by annealing at elevated temperatures (Powers and Clark, 1975, Proc. Natl. Acad. Sci. U.S.A. 72:840; Powers and Pershan. 1977. Biophys. J. 20:137) is accompanied by the formation and subsequent dissolution of various defect structures. Some of these defects appear similar to those observed in thermotropic and other lyotropic liquid crystals, reflecting the lamellar structure of these materials. The formation and evolution of defects during the alignment of the lipids into the defect-free, monodomain, multilamellar geometry is studied using polarized microscopy. A combination of polarized and dark-field microscopy facilitated characterization of the defects; specific structural models are proposed. A new alignment technique involving compression and dilation of the lipid, which effects sample alignment at temperatures that are lower than those required by the Powers technique, is described. Lower temperature alignment avoids thermal decomposition that will sometimes occur if the lipid is maintained at elevated temperatures for prolonged periods. With this technique, samples $(80 \mu m thick)$ of dilaurylphosphatidylcholine with 20% water by weight were aligned at room temperature.Engineering and Applied Science

Hydration of Single Crystals of Dipalmitoylphosphatidylcholine

Optical birefringence and x-ray measurements are reported for single crystals $(0.5 mm \times 2 mm \times 5 \mu m)$ of dipalmitoylphosphatidylcholine as a function of temperature and relative humidity. Large single crystals grown in $CHCl_3$/acetone at a low water concentration undergo an irreversible phase transformation at $20^{\circ}C$ and 70% relative humidity or at $60^{\circ}C$ and 65% relative humidity. After this transformation occurs, the crystals can be made to undergo a reversible transformation into and out of the $L_{\alpha}$ phase. The x-ray-determined mosaic spread in the hydrated crystal is less than $\approx 0.04^{\circ}$ both above and below the main transition.Engineering and Applied Science

Pengaruh Model Pembelajaran Inkuiriterhadap Kemampuan Menulis Teks Prosedur Kompleks Oleh Siswa Kelas X Smk Negeri 1 Siantar Kabupaten Simalungun Tahun Pembelajaran 2014/2015

Penelitian ini bertujuan untuk mengetahui pengaruh model pembelajaran inkuiri terhadap kemampuan menulis teks prosedurkompleks pada siswa kelas X SMK N 1 SiantarKabupatenSimalungunTahun Pembelajaran 2014/2015. Populasi penelitian ini adalah siswa kelas X SMK N 1 Siantaryang terdiri dari 6 kelas dengan jumlah siswa sebanyak 181 orang. Dari jumlah tersebut ditetapkan sampel sebanyak 25 orang siswa. Metode yang digunakan dalam penelitian ini adalah metode eksprimen dengan modelone-group pre-test posttest design.Instrumen yang digunakan untuk menjaring data adalah tes penugasan hasil karya (tertulis). Pengujian hipotesis dilakukan dengan menggunakan uji “t”. Hasil penelitian menunjukkan bahwa kemampuan siswa dalam menulis teks prosedurkompleksdengan menerapkan model pembelajaran inkuiri termasuk kategori baik dengan rata-rata 80,2, sedangkan kemampuan siswa dalam menulisteks prosedurkompleks sebelum menerapkan model pembelajaran inkuiritermasuk dalam kategori cukup dengan nilai rata-rata 73,2. Dengan demikian dapat disimpulkan bahwa nilai rata-rata menulis teksprosedurkomplekssiswa setelah perlakuan lebih tinggi daripada nilai sebelum perlakuan. Pengujian hipotesis thitung = 3,30 kemudian dikonsultasikan dengan ttabel pada taraf signifikan 5% = 2,06. Karena thitung = 3,30> ttabel = 2,06, maka hipoteis nihil (H0) ditolak. Hal ini membuktikan bahwa model pembelajaran inkuiri berpengaruh positifterhadapkemampuan menulis teksprosedurkompleksoleh siswa kelas X SMK N 1 SiantarKabupatenSimalungun

Lorentz transformations of open systems

We consider open dynamical systems, subject to external interventions by agents that are not completely described by the theory (classical or quantal). These interventions are localized in regions that are relatively spacelike. Under these circumstances, no relativistic transformation law exists that relates the descriptions of the physical system by observers in relative motion. Still, physical laws are the same in all Lorentz frames.Comment: Final version submitted to J. Mod. Opt. (Proc. of Gdansk conference

Fission yeast sec3 bridges the exocyst complex to the actin cytoskeleton.

The exocyst complex tethers post-Golgi secretory vesicles to the plasma membrane prior to docking and fusion. In this study, we identify Sec3, the missing component of the Schizosaccharomyces pombe exocyst complex (SpSec3). SpSec3 shares many properties with its orthologs, and its mutants are rescued by human Sec3/EXOC1. Although involved in exocytosis, SpSec3 does not appear to mark the site of exocyst complex assembly at the plasma membrane. It does, however, mark the sites of actin cytoskeleton recruitment and controls the organization of all three yeast actin structures: the actin cables, endocytic actin patches and actomyosin ring. Specifically, SpSec3 physically interacts with For3 and sec3 mutants have no actin cables as a result of a failure to polarize this nucleating formin. SpSec3 also interacts with actin patch components and sec3 mutants have depolarized actin patches of reduced endocytic capacity. Finally, the constriction and disassembly of the cytokinetic actomyosin ring is compromised in these sec3 mutant cells. We propose that a role of SpSec3 is to spatially couple actin machineries and their independently polarized regulators. As a consequence of its dual role in secretion and actin organization, Sec3 appears as a major co-ordinator of cell morphology in fission yeast.This work was supported by Cancer Research UK (T. T.)

Developing a corpus of strategic conversation in The Settlers of Catan

International audienceWe describe a dialogue model and an implemented annotation scheme for a pilot corpus of annotated online chats concerning bargaining negotiations in the game The Settlers of Catan. We will use this model and data to analyze how conversations proceed in the absence of strong forms of cooperativity, where agents have diverging motives. Here we concentrate on the description of our annotation scheme for negotiation dialogues, illustrated with our pilot data, and some perspectives for future research on the issue

Nonlocal effects in Fock space

If a physical system contains a single particle, and if two distant detectors test the presence of linear superpositions of one-particle and vacuum states, a violation of classical locality can occur. It is due to the creation of a two-particle component by the detecting process itself.Comment: final version in PRL 74 (1995) 4571; 76 (1996) 2205 (erratum