937 research outputs found
The Photophysical Properties Investigation of Hybrid Associates of Methylene Blue Molecules with Colloidal CdS Quantum Dots and CdS / Cd(OH)2 "Core-Shell" Systems
The spectral properties of associates of methylene blue molecules with colloidal CdS quantum dots and
CdS / Cd(OH)2 «core-shell» systems were investigated. It is shown that according to env ironment
methylene blue changes its photophysical properties during association. These properties are due to
changes of MB structure as a result of oxidation-reduction reactions.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3527
Spectral Manifestation of Hybrid Association of Zn0.7Sd0.3S Colloidal Quantum Dots with J-Aggregates of Thiacarbocyanine Dye
Spectral properties of mixtures of Zn0.7Sd0.3S colloidal quantum dots with mean diameter value of
3.5 nm with the molecules of 3,3'-di(γ-sulfopropil)-9-ethyl-4,5,4',5'-dibenzo-thiacarbocyanine betaine pyridine
salt (DEC), prepared in gelatin were investigated. The obtained data indicated that the formation of
well-luminescent trans-J-aggregates and spectral tuning in the position of the absorption band of DEC and
the luminescence band of quantum dots, providing requirements for resonant energy transfer in the hybrid
associate are the determinant factors in the increase of the luminescent emission of DEC molecules, interacting
with Zn0.7Cd0.3S colloidal quantum dots.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3532
Alexithymia and Emotional Ambivalence as Predictors of College Adjustment
The current study evaluated the constructs alexithymia and emotional ambivalence, regarding their impact on adjustment to college. Alexithymia is an emotional processing concept which is defined as difficulty identifying and describing feelings, externally oriented thought, and limited imaginal ability. Emotional ambivalence is the ongoing internal conflict about the desire to hide emotions, despite external circumstances that demand disclosure, and/or regret over decisions to disclose feelings. These were both looked at as predictors of college adjustment, with the inclusion of chronic pain and psychiatric distress as physical and mental health components of the transition
Energy levels and lifetimes of Gd IV and enhancement of the electron dipole moment
We have calculated energy levels and lifetimes of 4f7 and 4f6 5d
configurations of Gd IV using Hartree-Fock and configuration interaction
methods. This allows us to reduce significantly the uncertainty of the
theoretical determination of the electron electric dipole moment (EDM)
enhancement factor in this ion and, correspondingly, in gadolinium-containing
garnets for which such measurements were recently proposed. Our new value for
the EDM enhancement factor of Gd+3 is -2.2 +- 0.5. Calculations of energy
levels and lifetimes for Eu~III are used to control the accuracy.Comment: Submitted to Phys. Rev. A 6 pages, 0 figures, 3 table
Kohn Anomalies in Superconductors
I present the detailed behavior of phonon dispersion curves near momenta
which span the electronic Fermi sea in a superconductor. I demonstrate that an
anomaly, similar to the metallic Kohn anomaly, exists in a superconductor's
dispersion curves when the frequency of the phonon spanning the Fermi sea
exceeds twice the superconducting energy gap. This anomaly occurs at
approximately the same momentum but is {\it stronger} than the normal-state
Kohn anomaly. It also survives at finite temperature, unlike the metallic
anomaly. Determination of Fermi surface diameters from the location of these
anomalies, therefore, may be more successful in the superconducting phase than
in the normal state. However, the superconductor's anomaly fades rapidly with
increased phonon frequency and becomes unobservable when the phonon frequency
greatly exceeds the gap. This constraint makes these anomalies useful only in
high-temperature superconductors such as .Comment: 18 pages (revtex) + 11 figures (upon request), NSF-ITP-93-7
Measuring the elements of the optical density matrix
Most methods for experimentally reconstructing the quantum state of light
involve determining a quasiprobability distribution such as the Wigner
function. In this paper we present a scheme for measuring individual density
matrix elements in the photon number state representation. Remarkably, the
scheme is simple, involving two beam splitters and a reference field in a
coherent state.Comment: 6 pages and 1 figur
Method for Measuring the Momentum-Dependent Relative Phase of the Superconducting Gap of High-Temperature Superconductors
The phase variation of the superconducting gap over the (normal) Fermi
surface of the high-temperature superconductors remains a significant
unresolved question. Is the phase of the gap constant, does it change sign, or
is it perhaps complex? A detailed answer to this question would provide
important constraints on various pairing mechanisms. Here we propose a new
method for measuring the relative gap PHASE on the Fermi surface which is
direct, is angle-resolved, and probes the bulk. The required experiments
involve measuring phonon linewidths in the normal and superconducting state,
with resolution available in current facilities. We primarily address the
La_1.85Sr_.15CuO_4 material, but also propose a more detailed study of a
specific phonon in Bi_2Sr_2CaCu_2O_8.Comment: 13 pages (revtex) + 5 figures (postscript-included), NSF-ITP-93-2
Preparation of facilities for fundamental research with ultracold neutrons at PNPI
The WWR-M reactor of PNPI offers a unique opportunity to prepare a source for
ultracold neutrons (UCN) in an environment of high neutron flux (about 3*10^12
n/cm^2/s) at still acceptable radiation heat release (about 4*10^-3 W/g). It
can be realized within the reactor thermal column situated close to the reactor
core. With its large diameter of 1 m, this channel allows to install a 15 cm
thick bismuth shielding, a graphite premoderator (300 dm^3 at 20 K), and a
superfluid helium converter (35 dm^3). At a temperature of 1.2 K it is possible
to remove the heat release power of about 20 W. Using the 4pi flux of cold
neutrons within the reactor column can bring more than a factor 100 of cold
neutron flux incident on the superfluid helium with respect to the present cold
neutron beam conditions at the ILL reactor. The storage lifetime for UCN in
superfluid He at 1.2 K is about 30 s, which is sufficient when feeding
experiments requiring a similar filling time. The calculated density of UCN
with energy between 50 neV and 250 neV in an experimental volume of 40 liters
is about 10^4 n/cm^3. Technical solutions for realization of the project are
discussed.Comment: 10 pages, more detail
Bayesian Analysis and Constraints on Kinematic Models from Union SNIa
The kinematic expansion history of the universe is investigated by using the
307 supernovae type Ia from the Union Compilation set. Three simple model
parameterizations for the deceleration parameter (constant, linear and abrupt
transition) and two different models that are explicitly parametrized by the
cosmic jerk parameter (constant and variable) are considered. Likelihood and
Bayesian analyses are employed to find best fit parameters and compare models
among themselves and with the flat CDM model. Analytical expressions
and estimates for the deceleration and cosmic jerk parameters today ( and
) and for the transition redshift () between a past phase of cosmic
deceleration to a current phase of acceleration are given. All models
characterize an accelerated expansion for the universe today and largely
indicate that it was decelerating in the past, having a transition redshift
around 0.5. The cosmic jerk is not strongly constrained by the present
supernovae data. For the most realistic kinematic models the
confidence limits imply the following ranges of values: ,
and , which are compatible with the
CDM predictions, , and .
We find that even very simple kinematic models are equally good to describe the
data compared to the concordance CDM model, and that the current
observations are not powerful enough to discriminate among all of them.Comment: 13 pages. Matches published versio
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