1,521 research outputs found
Fuels characterization studies
Current analytical techniques used in the characterization of broadened properties fuels are briefly described. Included are liquid chromatography, gas chromatography, and nuclear magnetic resonance spectroscopy. High performance liquid chromatographic ground-type methods development is being approached from several directions, including aromatic fraction standards development and the elimination of standards through removal or partial removal of the alkene and aromatic fractions or through the use of whole fuel refractive index values. More sensitive methods for alkene determinations using an ultraviolet-visible detector are also being pursued. Some of the more successful gas chromatographic physical property determinations for petroleum derived fuels are the distillation curve (simulated distillation), heat of combustion, hydrogen content, API gravity, viscosity, flash point, and (to a lesser extent) freezing point
Detailed investigation of a vaporising fuel spray. Part 1: Experimental investigation of time averaged spray
A laser tomographic light scattering technique provides rapid and accurate high resolution measurements of droplet sizes, concentrations, and vaporization. Measurements using a computer interfaced thermocouple are presented and it is found that the potential exists for separating gas and liquid temperature measurements and diagnosing local spray density by in situ analysis of the response characteristics of the thermocouple. The thermocouple technique provides a convenient means for measuring mean gas velocity in both hot and cold two phase flows. The experimental spray is axisymmetric and has carefully controlled initial and boundary conditions. The flow is designed to give relatively insignificant transfer of momentum and mass from spray to air flow. The effects of (1) size-dependent droplet dispersion by the turbulence, (2) the initial spatial segregation of droplet sizes during atomization, and (3) the interaction between droplets and coherent large eddies are diagnosed
Electrically pumped semiconductor laser with low spatial coherence and directional emission
We design and fabricate an on-chip laser source that produces a directional
beam with low spatial coherence. The lasing modes are based on the axial orbit
in a stable cavity and have good directionality. To reduce the spatial
coherence of emission, the number of transverse lasing modes is maximized by
fine-tuning the cavity geometry. Decoherence is reached in a few nanoseconds.
Such rapid decoherence will facilitate applications in ultrafast speckle-free
full-field imaging
Tunable spin-selective loading of a silicon spin qubit
The remarkable properties of silicon have made it the central material for
the fabrication of current microelectronic devices. Silicon's fundamental
properties also make it an attractive option for the development of devices for
spintronics and quantum information processing. The ability to manipulate and
measure spins of single electrons is crucial for these applications. Here we
report the manipulation and measurement of a single spin in a quantum dot
fabricated in a silicon/silicon-germanium heterostructure. We demonstrate that
the rate of loading of electrons into the device can be tuned over an order of
magnitude using a gate voltage, that the spin state of the loaded electron
depends systematically on the loading voltage level, and that this tunability
arises because electron spins can be loaded through excited orbital states of
the quantum dot. The longitudinal spin relaxation time T1 is measured using
single-shot pulsed techniques and found to be ~3 seconds at a field of 1.85
Tesla. The demonstration of single spin measurement as well as a long spin
relaxation time and tunability of the loading are all favorable properties for
spintronics and quantum information processing applications.Comment: 4 pages, 3 figures, Supplemental Informatio
Response of low-strength phenol-acclimated activated sludge to shock loading of high phenol concentrations
(ii) investigate the degradation pathways and (iii) model the growth and biodegradation kinetics, all under the condition of increasingly higher phenol concentrations (step-up shock loading). With the use of activated sludge acclimated to phenol concentration of 140 mg∙ℓ−1 (low-strength phenol-acclimated activated sludge), complete degradation of phenol with a COD removal efficiency of more than 95% was achieved up to 1 050 mg∙ℓ−1 of initial phenol concentration. At low initial phenol concentrations, the experimental results were indicative of the meta-cleavage pathway for phenol degradation. When the initial phenol concentration was above 630 mg∙ℓ−1, the degradation results were indicative of both meta- and ortho-cleavage pathways. The values of the Haldane kinetic parameters indicated a low degree of inhibition exerted by the presence of increasing phenol concentration. This was substantiated by the observation that the rate constant of phenol removal decreased by only 33% even though the initial phenol concentration was increased by 15 times from 70 to 1 050 mg∙ℓ−1.Thus, the activated sludge acclimated to only 140 mg∙ℓ−1 of phenol could successfully treat up to 1 050 mg∙ℓ−1 of phenol without experiencing complete inhibition during the degradation process.Keywords: Phenol removal, low-strength phenol-acclimated activated sludge, degradation pathway, Haldane kinetic paramete
Quantum control and process tomography of a semiconductor quantum dot hybrid qubit
The similarities between gated quantum dots and the transistors in modern
microelectronics - in fabrication methods, physical structure, and voltage
scales for manipulation - have led to great interest in the development of
quantum bits (qubits) in semiconductor quantum dots. While quantum dot spin
qubits have demonstrated long coherence times, their manipulation is often
slower than desired for important future applications, such as factoring.
Further, scalability and manufacturability are enhanced when qubits are as
simple as possible. Previous work has increased the speed of spin qubit
rotations by making use of integrated micromagnets, dynamic pumping of nuclear
spins, or the addition of a third quantum dot. Here we demonstrate a new qubit
that offers both simplicity - it requires no special preparation and lives in a
double quantum dot with no added complexity - and is very fast: we demonstrate
full control on the Bloch sphere with -rotation times less than 100 ps in
two orthogonal directions. We report full process tomography, extracting high
fidelities equal to or greater than 85% for X-rotations and 94% for
Z-rotations. We discuss a path forward to fidelities better than the threshold
for quantum error correction.Comment: 6 pages, excluding Appendi
Pauli spin blockade and lifetime-enhanced transport in a Si/SiGe double quantum dot
We analyze electron transport data through a Si/SiGe double quantum dot in
terms of spin blockade and lifetime-enhanced transport (LET), which is
transport through excited states that is enabled by long spin relaxation times.
We present a series of low-bias voltage measurements showing the sudden
appearance of a strong tail of current that we argue is an unambiguous
signature of LET appearing when the bias voltage becomes greater than the
singlet-triplet splitting for the (2,0) electron state. We present eight
independent data sets, four in the forward bias (spin-blockade) regime and four
in the reverse bias (lifetime-enhanced transport) regime, and show that all
eight data sets can be fit to one consistent set of parameters. We also perform
a detailed analysis of the reverse bias (LET) regime, using transport rate
equations that include both singlet and triplet transport channels. The model
also includes the energy dependent tunneling of electrons across the quantum
barriers, and resonant and inelastic tunneling effects. In this way, we obtain
excellent fits to the experimental data, and we obtain quantitative estimates
for the tunneling rates and transport currents throughout the reverse bias
regime. We provide a physical understanding of the different blockade regimes
and present detailed predictions for the conditions under which LET may be
observed.Comment: published version, 18 page
The effects of PTSD treatment during pregnancy: systematic review and case study
Background: PTSD in pregnant women is associated with adverse outcomes for mothers and their children. It is unknown whether pregnant women with PTSD, or symptoms of
PTSD, can receive targeted treatment that is safe and effective.
Objective: The purpose of the present paper was to assess the effectiveness and safety of treatment for (symptoms of) PTSD in pregnant women.
Method: A systematic review was conducted in accordance with the PRISMA guidelines in Pubmed, Embase, PsychINFO, and Cochrane. In addition, a case is presented of a pregnant woman with PTSD who received eye-movement desensitization and reprocessing (EMDR) therapy aimed at processing the memories of a previous distressing childbirth.
Results: In total, 13 studies were included, involving eight types of interventions (i.e. trauma-focused cognitive behavioural therapy, exposure therapy, EMDR therapy, interpersonal psychotherapy, explorative therapy, self-hypnosis and relaxation, Survivor Moms
Companion, and Seeking Safety Intervention). In three studies, the traumatic event pertained to a previous childbirth. Five studies reported obstetrical outcomes. After requesting additional information, authors of five studies indicated an absence of serious adverse
events. PTSD symptoms improved in 10 studies. However, most studies carried a high risk of bias. In our case study, a pregnant woman with a PTSD diagnosis based on DSM-5 no longer fulfilled the criteria of PTSD after three sessions of EMDR therapy. She had an uncomplicated pregnancy and delivery.
Conclusion: Despite the fact that case studies as the one presented here report no adverse events, and treatment is likely safe, due to the poor methodological quality of most studies it is impossible to allow inferences on the effects of any particular treatment of PTSD (symptoms) during pregnancy. Yet, given the elevated maternal stress and cortisol levels in pregnant women with PTSD, and the fact that so far no adverse effects on the unborn child have been reported associated with the application of trauma-focused therapy, treatment of PTSD during pregnancy is most likely safe
The Role of Training Variables in Effective Dissemination of Evidence-Based Parenting Interventions
From a public health perspective, mental health in parents and children can be promoted through population-based dissemination of parenting and family support interventions. However, it is critical that service providers who are acquiring evidence-based parenting interventions complete the training regimen to optimize dissemination and impact. This article examines training completion and its relationship to individual service provider characteristics, barriers to program use and subsequent implementation of an evidence-based program, the Triple P - Positive Parenting Program. In this study, 83.7% of the service providers completed the two-part training. Individual-level variables did not predict training completion. Service providers from diverse backgrounds were equally likely to complete training, were highly satisfied with the training provided and reported relatively few barriers to implementation. The majority of those who completed training (67.6%) went on to deliver the program with families in the community, whereas only 37.8% of those who did not complete training used the program subsequently. Implications are discussed for fidelity in delivery, cost-effectiveness in dissemination efforts, and population-wide health promotion
State/Operator Correspondence in Higher-Spin dS/CFT
A recently conjectured microscopic realization of the dS/CFT
correspondence relating Vasiliev's higher-spin gravity on dS to a Euclidean
CFT is used to illuminate some previously inaccessible aspects of
the dS/CFT dictionary. In particular it is argued that states of the boundary
CFT on are holographically dual to bulk states on geodesically
complete, spacelike slices which terminate on an at future
infinity. The dictionary is described in detail for the case of free scalar
excitations. The ground states of the free or critical model are dual
to dS-invariant plane-wave type vacua, while the bulk Euclidean vacuum is dual
to a certain mixed state in the CFT. CFT states created by operator
insertions are found to be dual to (anti) quasinormal modes in the bulk. A norm
is defined on the bulk Hilbert space and shown for the scalar case to be
equivalent to both the Zamolodchikov and pseudounitary C-norm of the
CFT.Comment: 24 page
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