610 research outputs found
Solid-liquid equilibria for the dimethyl ether plus carbon dioxide binary system
A recently built experimental setup was employed for the estimation of the solid-liquid equilibria of alternative refrigerants systems. The behavior of dimethyl ether (DME) + carbon dioxide was measured down to temperatures of 131.6 K. To confirm the reliability of the apparatus, the triple point of the DME was measured. The triple point data measured revealed a good consistency with the literature. The results obtained for the mixtures were corrected by the Rossini method and interpreted by means of the Schröder equation. © 2010 Akadémiai Kiadó, Budapest, Hungary
Combinatorial synthesis and high-throughput photopotential and photocurrent screening of mixed-metal oxides for photoelectrochemical water splitting
A high-throughput method has been developed using a commercial piezoelectric inkjet printer for synthesis and characterization of mixed-metal oxide photoelectrode materials for water splitting. The printer was used to deposit metal nitrate solutions onto a conductive glass substrate. The deposited metal nitrate solutions were then pyrolyzed to yield mixed-metal oxides that contained up to eight distinct metals. The stoichiometry of the metal oxides was controlled quantitatively, allowing for the creation of vast libraries of novel materials. Automated methods were developed to measure the open-circuit potentials (Eoc), short-circuit photocurrent densities (Jsc), and current density vs. applied potential (JâE) behavior under visible light irradiation. The high-throughput measurement of Eoc is particularly significant because open-circuit potential measurements allow the interfacial energetics to be probed regardless of whether the band edges of the materials of concern are above, close to, or below the values needed to sustain water electrolysis under standard conditions. The Eoc measurements allow high-throughput compilation of a suite of data that can be associated with the composition of the various materials in the library, to thereby aid in the development of additional screens and to form a basis for development of theoretical guidance in the prediction of additional potentially promising photoelectrode compositions
Conversion of neutral nitrogen-vacancy centers to negatively-charged nitrogen-vacancy centers through selective oxidation
The conversion of neutral nitrogen-vacancy centers to negatively charged
nitrogen-vacancy centers is demonstrated for centers created by ion
implantation and annealing in high-purity diamond. Conversion occurs with
surface exposure to an oxygen atmosphere at 465 C. The spectral properties of
the charge-converted centers are investigated. Charge state control of
nitrogen-vacancy centers close to the diamond surface is an important step
toward the integration of these centers into devices for quantum information
and magnetic sensing applications.Comment: 4 pages, 3 figure
Low-temperature tapered-fiber probing of diamond NV ensembles coupled to GaP microcavities
In this work we present a platform for testing the device performance of a
cavity-emitter system, using an ensemble of emitters and a tapered optical
fiber. This method provides high-contrast spectra of the cavity modes,
selective detection of emitters coupled to the cavity, and an estimate of the
device performance in the single- emitter case. Using nitrogen-vacancy (NV)
centers in diamond and a GaP optical microcavity, we are able to tune the
cavity onto the NV resonance at 10 K, couple the cavity-coupled emission to a
tapered fiber, and measure the fiber-coupled NV spontaneous emission decay.
Theoretically we show that the fiber-coupled average Purcell factor is 2-3
times greater than that of free-space collection; although due to ensemble
averaging it is still a factor of 3 less than the Purcell factor of a single,
ideally placed center.Comment: 15 pages, 6 figure
Secure self-calibrating quantum random bit generator
Random bit generators (RBGs) are key components of a variety of information
processing applications ranging from simulations to cryptography. In
particular, cryptographic systems require "strong" RBGs that produce
high-entropy bit sequences, but traditional software pseudo-RBGs have very low
entropy content and therefore are relatively weak for cryptography. Hardware
RBGs yield entropy from chaotic or quantum physical systems and therefore are
expected to exhibit high entropy, but in current implementations their exact
entropy content is unknown. Here we report a quantum random bit generator
(QRBG) that harvests entropy by measuring single-photon and entangled
two-photon polarization states. We introduce and implement a quantum
tomographic method to measure a lower bound on the "min-entropy" of the system,
and we employ this value to distill a truly random bit sequence. This approach
is secure: even if an attacker takes control of the source of optical states, a
secure random sequence can be distilled.Comment: 5 pages, 2 figure
Properties of implanted and CVD incorporated nitrogen-vacancy centers: preferential charge state and preferential orientation
The combination of the long electron state spin coherence time and the optical coupling of the ground electronic states to an excited state manifold makes the nitrogen-vacancy (NV) center in diamond an attractive candidate for quantum information processing. To date the best spin and optical properties have been found in centers deep within the diamond crystal. For useful devices it will be necessary to engineer NVs with similar properties close to the diamond surface. We report on properties including charge state control and preferential orientation for near surface NVs formed either in CVD growth or through implantation and annealing
Coupling of nitrogen-vacancy centers in diamond to a GaP waveguide
The optical coupling of guided modes in a GaP waveguide to nitrogen-vacancy
(NV) centers in diamond is demonstrated. The electric field penetration into
diamond and the loss of the guided mode are measured. The results indicate that
the GaP-diamond system could be useful for realizing coupled microcavity-NV
devices for quantum information processing in diamond.Comment: 4 pages 4 figure
Development and optimization of a method for analyzing biodiesel mixtures with non-aqueous reversed phase liquid chromatography
Biodiesel (a mixture of fatty acid esters) is normally analyzed using gas chromatography/ïŹame ionization
detection, as speciïŹed by the ASTM D6584 and EN14105 standards. This paper proposes a binary gradient
method for analyzing biodiesel mixtures using non-aqueous reverse phase HPLC with a UV detector
capable of overcoming the drawbacks of the gas chromatographic technique normally used. The new analytical
method was developed by means of a statistical sensitivity analysis applied to the main parameters
inïŹuencing the recording, using the full factorial design method combined with the Yates algorithm and
the steepest ascent optimization procedure. The present study shows the inïŹuence of the main biodiesel
mixture separation analysis parameters. The resulting tool proved valid for analyzing not only biodiesel
but also any traces of unreacted oil
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