Coherence creation in an optically thick medium by matched propagation of a chirped laser pulse pair

We consider the simultaneous propagation of a pair of Raman-resonant, frequency-modulated (chirped) laser pulses in an optically thick medium, modeled by an ensemble of $\Lambda$-atoms. A self-organization ('matching`) effect is shown for the chirped pulse pair, which leads to a quasi-lossless propagation. Furthermore, we demonstrate that a well-defined coherent superposition of the atomic ground states and, correspondingly, a coherence is robustly created in the medium that can be controlled by amplitudes of the laser pulses. The proposed scheme can be applied to substantially increase the efficiency of the optical wave mixing processes, as well as in other nonlinear processes where the initial preparation of a spatially extended medium in a coherent superposition state is required

Pattern forming instability induced by light in pure and dye-doped nematic liquid crystals

We study theoretically the instabilities induced by a linearly polarized ordinary light wave incident at a small oblique angle on a thin layer of homeotropically oriented nematic liquid crystal with special emphasis on the dye-doped case. The spatially periodic Hopf bifurcation that occurs as the secondary instability after the stationary Freedericksz transition is analyzed.Comment: 8 pages, 7 figures, LaTeX, accepted to Phys. Rev.

Miniaturization of molecular conjugated systems for organic solar cells: towards pigmy donors

Organic solar cells with short-circuit current densities and conversion efficiencies of ca. 7.0 mA cm(-2) and 2.0%, respectively, have been fabricated with a very small molecular donor based on substituted triarylamines

Organic dye for dye-sensitized solar cell

Organic dye for a dye-sensitized solar cell (DSSC) comprising at least one electron-acceptor unit and at least one π-conjugated unit. Said organic dye is particularly useful in a dye-sensitized photoelectric transformation element which, in its turn, can be used in a dye-sensitized solar cell (DSSC)

Strain induced pressure effect in pulsed laser deposited thin films of the strongly correlated oxide V2O3

V2O3 thin films about 10 nm thick were grown on Al2O3 (0001) by pulsed laser deposition. The XRD analysis is in agreement with R-3c space group. Some of them exhibit the metal / insulator transition characteristic of V2O3 bulk material and others samples exhibit a metallic behavior. For the latter, the XPS analysis indicates an oxidation state of +III for vanadium. There is no metal / insulator transition around 150 K in this sample and a strongly correlated Fermi liquid rho = AT2 behavior of the resistivity at low temperature is observed, with a value of A of 1.2 10-4 ohm cm, 3 times larger than the bulk value at 25 kbar

Poly(thiophenes) derivatized with linear and macrocyclic polyethers: from cation detection to molecular actuation

The association of linear or macrocyclic polyethers with the electronic properties of the π-conjugated polythiophene backbone leads to functional conducting polymers that exhibit metal cation dependent electronic properties. Based on this concept, various classes of cation sensors have been proposed and investigated for almost two decades. The interactions of metal cations with linear or macrocyclic polyether functional groups lead to modifications of the electronic properties of the π-conjugated backbone through various mechanisms including direct electronic effects on a single conjugated chain, collective electrochemical processes, or conformational changes. Conjugated polymers and oligomers representative of these various processes are discussed with an emphasis on recent examples of derivatized conjugated systems in which the interactions between metal cations and polyether groups serve as driving force to create molecular motion in conjugated systems

Organic dye for dye-sensitized solar cells

Organic dye for a dye-sensitized solar cell (DSSC) comprising at least one electron-acceptor unit and at least one π-conjugated unit. Said organic dye is particularly useful in a dye-sensitized photoelectric transformation element which, in its turn, can be used in a dye-sensitized solar cell (DSSC)

The situation of horticultural family farms in Hajdu-Bihar County

The main aim of this research work is to study horticultural farms in Hajdú-Bihar County, that mobilize labour and capital for thesake of agricultural production, namely family farms. During this study work we tried to chart the main characters, the conditions offunctioning, their profitability and its use possibilities, their external contacts and the resource of information of these farms, beside this toinvestigate the relationships between these parameters. Parallel to this we tried to compensate the relatively high deficiency of information byempirical research work. This deficiency is the characterization of farmers and the inducement of farming and its conditions both on the levelof county and state. By our empirical research work we have made a comprehensive position paper that shows the conditions of farms andfarmer populations, as well. Two hundred questionnaires were evaluated. The percentages of horticultural farms were 25% from allquestionnaires. Above all this paper is looking for the answer to the following questions: How and by which sources do farmers develop andextent their farms? How do farmers see their own future, what kind of aims do they have?Who will stop and who will go on producing? Thecollected information on the whole may help to make much more flexible legislatives and administrative regulations, although the surveycovered only one county

Variation in heart rate influences the assessment of transient ischemic dilation in myocardial perfusion scintigraphy

BACKGROUND: Transient arrhythmias can affect transient ischemic dilation (TID) ratios. This study was initiated to evaluate the frequency and effect of normal heart rate change on TID measures in routine clinical practice. METHODS: Consecutive patients undergoing stress/rest sestamibi gated myocardial perfusion scintigraphy were studied (N = 407). Heart rate at the time of stress and rest imaging were recorded. TID ratios were analyzed in relation to absolute change in heart rate (stress minus rest) for subjects with normal perfusion and systolic function (Group 1, N = 169) and those with abnormalities in perfusion and/or function (Group 2, N = 238). RESULTS: In Group 1, mean TID ratio was inversely correlated with the change in heart rate (r = -0.47, P < 0.0001). For every increase of 10 BPM in heart rate change, the TID ratio decreased by approximately 0.06 (95% confidence interval 0.04–0.07). In Group 2, multiple linear regression demonstrated that the change in heart rate (beta = -0.25, P < 0.0001) and the summed difference score (beta = 0.36, P < 0.0001) were independent predictors of the TID ratio. CONCLUSION: Normal variation in heart rate between the stress and rest components of myocardial perfusion scans is common and can influence TID ratios in patients with normal and abnormal cardiac scans