243 research outputs found
An experimental study of the dual-fuel performance of a small compression ignition diesel engine operating with three gaseous fuels
A dual-fuel engine is a compression ignition (CI) engine where the primary gaseous fuel source is premixed with air as it enters the combustion chamber. This homogenous mixture is ignited by a small quantity of diesel, the âpilotâ, that is injected towards the end of the compression stroke. In the present study, a direct-injection CI engine, was fuelled with three different gaseous fuels: methane, propane, and butane. The engine performance at various gaseous concentrations was recorded at 1500 r/min and quarter, half, and three-quarters relative to full a load of 18.7 kW. In order to investigate the combustion performance, a novel three-zone heat release rate analysis was applied to the data. The resulting heat release rate data are used to aid understanding of the performance characteristics of the engine in dual-fuel mode.
Data are presented for the heat release rates, effects of engine load and speed, brake specific energy consumption of the engine, and combustion phasing of the three different primary gaseous fuels.
Methane permitted the maximum energy substitution, relative to diesel, and yielded the most significant reductions in CO2. However, propane also had significant reductions in CO2 but had an increased diffusional combustion stage which may lend itself to the modern high-speed direct-injection engine
Evaluation of mass spectrometric methods for detection of the anti-protozoal drug imidocarb
Imidocarb [N,N\u27-bis[3-(4,5-dihydro-1H-imidazol-2-yl)phenyl]urea, C19H20N6O1, m.w. 348.41] is a symmetrical carbanilide derivative used to treat disease caused by protozoans of the Babesia genus. Imidocarb, however, is also considered capable of suppressing Babesia-specific immune responses, allowing Babesia-positive horses to pass a complement fixation test (CFT) without eliminating the infection. This scenario could enable Babesia-infected horses to pass CFT-based importation tests. It is imperative to unequivocally identify and quantify equine tissue residues of imidocarb by mass spectrometry to address this issue. As a pretext to development of sensitive tissue assays, we have investigated possibilities of mass spectrometric (MS) detection of imidocarb. Our analyses disclosed that an unequivocal mass spectral analysis of imidocarb is challenging because of its rapid fragmentation under standard gas chromatography (GC)-MS conditions. In contrast, solution chemistry of imidocarb is more stable but involves distribution into mono- and dicationic species, m/z 349 and 175, respectively, in acid owing to the compound\u27s inherent symmetrical nature. Dicationic imidocarb was the preferred complex as viewed by either direct infusion-electrospray-MS or by liquid chromatography (LC)-MS. Dicationic imidocarb multiple reaction monitoring (MRM: m/z 175 â 162, 145, and 188) therefore offer the greatest opportunities for sensitive detection and LC-MS is more likely than GC-MS to yield a useful quantitative forensic analytical method for detecting imidocarb in horses
Clones of \u3cem\u3eStreptococcus zooepidemicus\u3c/em\u3e from Outbreaks of Hemorrhagic Canine Pneumonia and Associated Immune Responses
Acute hemorrhagic pneumonia caused by Streptococcus zooepidemicus has emerged as a major disease of shelter dogs and greyhounds. S. zooepidemicus strains differing in multilocus sequence typing (MLST), protective protein (SzP), and M-like protein (SzM) sequences were identified from 9 outbreaks in Texas, Kansas, Florida, Nevada, New Mexico, and Pennsylvania. Clonality based on 2 or more isolates was evident for 7 of these outbreaks. The Pennsylvania and Nevada outbreaks also involved cats. Goat antisera against acutely infected lung tissue as well as convalescent-phase sera reacted with a mucinase (Sz115), hyaluronidase (HylC), InlA domain-containing cell surface-anchored protein (INLA), membrane-anchored protein (MAP), SzP, SzM, and extracellular oligopeptide-binding protein (OppA). The amino acid sequences of SzP and SzM of the isolates varied greatly. The szp and szm alleles of the closely related Kansas clone (sequence type 129 [ST-129]) and United Kingdom isolate BHS5 (ST-123) were different, indicating that MLST was unreliable as a predictor of virulence phenotype. Combinations of conserved HylC and serine protease (ScpC) and variable SzM and SzP proteins of S. zooepidemicus strain NC78 were protectively immunogenic for mice challenged with a virulent canine strain. Thus, although canine pneumonia outbreaks are caused by different strains of S. zooepidemicus, protective immune responses were elicited in mice by combinations of conserved or variable S. zooepidemicus proteins from a single strain
Brewing of filter coffee
We report progress on mathematical modelling of coffee grounds in a drip filter coffee machine. The report focuses on the evolution of the shape of the bed of coffee grounds during extraction with some work also carried out on the chemistry of extraction. This work was sponsored by Philips who are interested in understanding an observed correlation between the final shape of the coffee grounds and the quality of the coffee. We used experimental data gathered by Philips and ourselves to identify regimes in the coffee brewing process and relevant regions of parameter space. Our work makes it clear that a number of separate processes define the shape of the coffee bed depending on the values of the parameters involved e.g. the size of the grains and the speed of fluid flow during extraction. We began work on constructing mathematical models of the redistribution of the coffee grounds specialised to each region and on a model of extraction. A variety of analytic and numerical tools were used. Furthermore our research has progressed far enough to allow us to begin to exploit connections between this problem and other areas of science, in particular the areas of sedimentology and geomorphology, where the processes we have observed in coffee brewing have been studied
Post-operative epiphora following the transcutaneous medial canthal incision
Purpose
The safety profile of the transcutaneous medial canthal incision for access to the medial orbit is assessed with a focus on the risk of post-operative iatrogenic epiphora.
Methods
A retrospective chart review of patients undergoing medial orbitotomy via the transcutaneous medial canthal incision was performed. Patients with a minimum of 3âŻmonths of follow-up were included and post-operative complications were assessed and characterized.
Results
One-hundred-fifty patients were included in the study. A total of 4 complications were identified, including one each of the following: nasolacrimal duct obstruction, hypertrophic scar, suture granuloma and soft tissue infection. Only the nasolacrimal duct obstruction required surgical intervention.
Discussion
Access to the medial orbit has been achieved through a variety of approaches, each with their own benefits and risk profile. The transcaruncular approach has increased in usage as a means to avoid a visible cutaneous scar and decrease the risk of iatrogenic epiphora, however, there are specific patients who may have relative contraindications to this approach. The current study demonstrates the low risk profile of the transcutaneous medial canthal incision, specifically the minimal risk of iatrogenic damage to the nasolacrimal outflow system. This approach is another useful tool which orbit surgeons should be familiar with to offer as an option to patients requiring medial orbitotomy
Individual addressing of trapped ions and coupling of motional and spin states using rf radiation
Individual electrodynamically trapped and laser cooled ions are addressed in
frequency space using radio-frequency radiation in the presence of a static
magnetic field gradient. In addition, an interaction between motional and spin
states induced by an rf field is demonstrated employing rf-optical double
resonance spectroscopy. These are two essential experimental steps towards
realizing a novel concept for implementing quantum simulations and quantum
computing with trapped ions.Comment: Replaced with published versio
Quantum Gates and Memory using Microwave Dressed States
Trapped atomic ions have been successfully used for demonstrating basic
elements of universal quantum information processing (QIP). Nevertheless,
scaling up of these methods and techniques to achieve large scale universal
QIP, or more specialized quantum simulations remains challenging. The use of
easily controllable and stable microwave sources instead of complex laser
systems on the other hand promises to remove obstacles to scalability.
Important remaining drawbacks in this approach are the use of magnetic field
sensitive states, which shorten coherence times considerably, and the
requirement to create large stable magnetic field gradients. Here, we present
theoretically a novel approach based on dressing magnetic field sensitive
states with microwave fields which addresses both issues and permits fast
quantum logic. We experimentally demonstrate basic building blocks of this
scheme to show that these dressed states are long-lived and coherence times are
increased by more than two orders of magnitude compared to bare magnetic field
sensitive states. This changes decisively the prospect of microwave-driven ion
trap QIP and offers a new route to extend coherence times for all systems that
suffer from magnetic noise such as neutral atoms, NV-centres, quantum dots, or
circuit-QED systems.Comment: 9 pages, 4 figure
An Elementary Quantum Network of Single Atoms in Optical Cavities
Quantum networks are distributed quantum many-body systems with tailored
topology and controlled information exchange. They are the backbone of
distributed quantum computing architectures and quantum communication. Here we
present a prototype of such a quantum network based on single atoms embedded in
optical cavities. We show that atom-cavity systems form universal nodes capable
of sending, receiving, storing and releasing photonic quantum information.
Quantum connectivity between nodes is achieved in the conceptually most
fundamental way: by the coherent exchange of a single photon. We demonstrate
the faithful transfer of an atomic quantum state and the creation of
entanglement between two identical nodes in independent laboratories. The
created nonlocal state is manipulated by local qubit rotation. This efficient
cavity-based approach to quantum networking is particularly promising as it
offers a clear perspective for scalability, thus paving the way towards
large-scale quantum networks and their applications.Comment: 8 pages, 5 figure
Semiempirical in-cylinder pressure based model for NOx prediction oriented to control applications
This work describes the development of a fast NO X predictive model oriented to engine control in diesel engines. The in-cylinder pressure is the only instantaneous input signal required, along with several mean variables that are available in the ECU during normal engine operation. The proposed model is based on the instantaneous evolution of the heat release rate and the adiabatic flame temperature (both obtained among other parameters from the in-cylinder pressure evolution). Corrections for considering the NO X reduction due to the re-burning mechanism are also included. Finally, the model is used for providing a model-based correction of tabulated values for the NO X emission at the reference conditions. The model exhibits a good behaviour when varying exhaust gas recirculation rate, boost pressure and intake temperature, while changes in the engine speed and injection settings are considered in the tabulated values. Concerning the calculation time, the model is optimised by proposing simplified sub-models to calculate the heat release and the adiabatic flame temperature. The final result is suitable for real time applications since it takes less than a cycle to complete the NO X prediction.Guardiola GarcĂa, C.; LĂłpez SĂĄnchez, JJ.; MartĂn DĂaz, J.; GarcĂa Sarmiento, D. (2011). Semiempirical in-cylinder pressure based model for NOx prediction oriented to control applications. Applied Thermal Engineering. 31(16):3275-3286. doi:10.1016/j.applthermaleng.2011.05.048S32753286311
Strong mechanical driving of a single electron spin
Quantum devices for sensing and computing applications require coherent
quantum systems which can be manipulated in a fast and robust way. Such quantum
control is typically achieved using external electric or magnetic fields which
drive the system's orbital or spin degrees of freedom. However, most of these
approaches require complex and unwieldy antenna or gate structures, and with
few exceptions are limited to the regime of weak driving. Here, we present a
novel approach to strongly and coherently drive a single electron spin in the
solid state using internal strain fields in an integrated quantum device.
Specifically, we study individual Nitrogen-Vacancy (NV) spins embedded in
diamond mechanical oscillators and exploit the intrinsic strain coupling
between spin and oscillator to strongly drive the spins. As hallmarks of the
strong driving regime, we directly observe the energy spectrum of the emerging
phonon-dressed states and employ our strong, continuous driving for enhancement
of the NV spin coherence time. Our results constitute a first step towards
strain-driven, integrated quantum devices and open new perspectives to
investigate unexplored regimes of strongly driven multi-level systems and to
study exotic spin dynamics in hybrid spin-oscillator devices.We gratefully acknowledge financial support from SNI; NCCR QSIT; SNF grants 200021_143697; and EU FP7 grant 611143 (DIADEMS). AN holds a University Research Fellowship from the Royal Society and acknowledges support from the Winton Programme for the Physics of Sustainability.This is the author accepted manuscript. The final version is available from NPG via http://dx.doi.org/10.1038/nphys341
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