4,989 research outputs found
Elastic constants of nematic liquid crystalline Schiff’s bases
The three elastic constants of a number of structurally related nematic liquid crystalline Schiff’s bases have been measured as a function of temperature. The results are new in the sense that they exhibit a clear distinction in behavior between compounds with a rigid molecular structure and compounds with a molecular structure consisting of a rigid core and a flexible alkyl chain. In particular, it has been found that the ratio of the bend and splay elastic constants K3/K1 increases for compounds with a rigid molecular structure with increasing length to width ratio. This trend is the reverse of that observed wihin homologous series, for which K3/K1 has been found to decrease with increasing length of the alkyl chain. New is the experimental finding that the twist elastic constant K2 of the homologs studied is independent of the length of the alkyl chain. Finally, the experiments show that the average elastic constant K̄1+K2+K3)/3 is proportional to the smectic–isotropic transition temperature. The results can only be partly understood within the framework of existing theoretical models
Self Phase Modulation and Stimulated Raman Scattering due to High Power Femtosecond Pulse Propagation in Silicon-on-Insulator Waveguides.
Self Phase Modulation (SPM) and Stimulated Raman Scattering (SRS) in silicon waveguides have been observed and will be discussed theoretically using a modified Nonlinear Schrödinger Equation. The high optical peak powers needed for the experiments were obtained by coupling sub-picosecond (200fs) transform limited pulses with a spectral width of 12nm into a single mode silicon waveguide. Spectral broadening up to 50nm has been observed due to Self Phase Modulation. An intensity increase of the idler spectrum around 1650nm at the expense of the 1550nm pump signal has been observed as function of pump power, indicating the presence of Stimulated Raman Scattering
Self-organization of hydrophobic soil and granular surfaces
Soil can become extremely water repellent following forest fires or oil spillages, thus preventing penetration of water and increasing runoff and soil erosion. Here the authors show that evaporation of a droplet from the surface of a hydrophobic granular material can be an active process, lifting, self-coating, and selectively concentrating small solid grains. Droplet evaporation leads to the formation of temporary liquid marbles and, as droplet volume reduces, particles of different wettabilities compete for water-air interfacial surface area. This can result in a sorting effect with self-organization of a mixed hydrophobic-hydrophilic aggregate into a hydrophobic shell surrounding a hydrophilic core
First-principles study on dielectric properties of NaCl crystal and ultrathin NaCl films under finite external electric field
We present a first-principles study on the dielectric properties of an NaCl
crystal and ultrathin NaCl films under a finite external electric field. Our
results show that the high-frequency dielectric constant of the films is not
affected by the finite size effect from crystal surfaces and is close to that
of the crystal, whereas the static one is sensitive to the thickness of the
film due to the difference in the atomic configurations between the surface and
inside of the film.Comment: 11 pages and 4 figure
Narcissistic Personality Disorder: Are Psychodynamic Theories and the Alternative DSM-5 Model for Personality Disorders Finally Going to Meet?
Narcissistic Personality Disorder is the new borderline personality disorder of our current era. There have been recent developments on narcissism that are certainly worthwhile examining. Firstly, relational and intersubjective psychoanalysts have been rethinking the underlying concepts of narcissism, focusing on the development of self and relations to others. Secondly, in the DSM-5, the Alternative DSM-5 Model for Personality Disorders (AMPD) was presented for a dimensional evaluation of the severity of personality disorder pathology. The combined dimensional and trait conceptualization of NPD opened the door to new integrated diagnostic perspectives, including both internal and interpersonal functioning. Finally, Pincus and Lukowitsky encourage clinicians to use a hierarchical model of pathological narcissism, as it opens up opportunities for shared points of interest in empirical research from different scholarly perspectives. As for most non-psychodynamic clinicians and researchers the DSM-5 clearly bears dominant weight in their work, we will take the AMPD model for NPD as our point of reference. We will discuss the narcissist's unique pattern of self-impairments in identity and self-direction, and of interpersonal disfunctioning (evaluated by assessing empathy and intimacy). Subsequently, we will examine how contemporary psychodynamic theories and the hierarchical model of Pincus and Lukowitsky additionally inform or contradict the AMPD. For us, one of the big advantages of the AMPD is the use of structured clinical evaluations of disturbances of the self and interpersonal functioning and the dimensional evaluation of severity. As psychodynamically oriented therapists, we are enthusiastic about the opportunities for inclusion of psychodynamic concepts, but we also discuss a number of sticking points
Current-voltage scaling of a Josephson-junction array at irrational frustration
Numerical simulations of the current-voltage characteristics of an ordered
two-dimensional Josephson junction array at an irrational flux quantum per
plaquette are presented. The results are consistent with an scaling analysis
which assumes a zero temperature vortex glass transition. The thermal
correlation length exponent characterizing this transition is found to be
significantly different from the corresponding value for vortex-glass models in
disordered two-dimensional superconductors. This leads to a current scale where
nonlinearities appear in the current-voltage characteristics decreasing with
temperature roughly as in contrast with the behavior expected
for disordered models.Comment: RevTex 3.0, 12 pages with Latex figures, to appear in Phys. Rev. B
54, Rapid. Com
Competition between magnetic field dependent band structure and coherent backscattering in multiwall carbon nanotubes
Magnetotransport measurements in large diameter multiwall carbon nanotubes
(20-40 nm) demonstrate the competition of a magnetic-field dependent
bandstructure and Altshuler-Aronov-Spivak oscillations. By means of an
efficient capacitive coupling to a backgate electrode, the magnetoconductance
oscillations are explored as a function of Fermi level shift. Changing the
magnetic field orientation with respect to the tube axis and by ensemble
averaging, allows to identify the contributions of different Aharonov-Bohm
phases. The results are in qualitative agreement with numerical calculations of
the band structure and the conductance.Comment: 4 figures, 5 page
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