15,382 research outputs found
Density Functional Theory Study of the Oligomerization of Carboxylic Acids
D.D.T. thanks the U.K.’s Royal Society for the award of a Royal Society Industry Fellowship. This research utilized Queen Mary’s MidPlus computational facilities, supported by QMUL Research-IT and funded by EPSRC grant EP/K000128/1. Via our membership of the U.K.’s HPC Materials Chemistry Consortium, which is funded by EPSRC (EP/L000202), this work made use of the facilities of HECToR and ARCHER, the U.K.’s national high-performance computing service, which is funded by the Office of Science and Technology through EPSRC’s High End Computing Programme.publisher pdf not permitted, withdraw
A String Bit Hamiltonian Approach to Two-Dimensional Quantum Gravity
Motivated by the formalism of string bit models, or quantum matrix models, we
study a class of simple Hamiltonian models of quantum gravity type in two
space-time dimensions. These string bit models are special cases of a more
abstract class of models defined in terms of the sl(2) subalgebra of the
Virasoro algebra. They turn out to be solvable and their scaling limit
coincides in special cases with known transfer matrix models of two-dimensional
quantum gravity.Comment: 24 pages, no figure; LaTeX2
Possible polarisation and spin dependent aspects of quantum gravity
We argue that quantum gravity theories that carry a Lie algebraic
modification of the Poincare' and Heisenberg algebras inevitably provide
inhomogeneities that may serve as seeds for cosmological structure formation.
Furthermore, in this class of theories one must expect a strong polarisation
and spin dependence of various quantum-gravity effects.Comment: Awarded an "honourable mention" in the 2007 Gravity Research
Foundation Essay Competitio
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A Directory Service for the CERN PS/SL Java Programming Interface
The CERN PS and SL accelerator control groups developed a common application programming interface (API) in Java [1]. Part of this API is a directory service that provides information about the underlying hardware and software. With this information it is possible to write generic programs that do general actions on lists of devices without hard coding of device names. And, starting from a device name, full details about related devices, the device itself and its class and properties, can be obtained, including the meaning of bits and bitpatterns in status words. The interface definition is independent of any implementation but a reference implementation is provided using Java Database Connectivity (JDBC) against a set of tables in a relational database. Data from very different systems can be brought together and presented in a uniform way to the user. The full potential of the directory service is reached when it is used in software components (Java Beans)
Explicit Barenblatt Profiles for Fractional Porous Medium Equations
Several one-parameter families of explicit self-similar solutions are
constructed for the porous medium equations with fractional operators. The
corresponding self-similar profiles, also called \emph{Barenblatt profiles},
have the same forms as those of the classic porous medium equations. These new
exact solutions complement current theoretical analysis of the underlying
equations and are expected to provide insights for further quantitative
investigations
Accuracy of a New Wrist Cuff Oscillometric Blood Pressure Device: Comparisons with Intraarterial and Mercury Manometer Measurements
Accurate measurement of arterial blood pressure is of great importance for the diagnosis and treatment of hypertension. Because of the chronic nature of antihypertensive drug therapy, the involvement of the patient in blood pressure control is desirable. Such an involvement, however, is only feasible if simple, user-friendly, and precise blood pressure measurement devices are available. In this study we tested a new wrist cuff oscillometric blood pressure measurement device in 100 consecutive patients undergoing cardiac catheterization. Blood pressures were simultaneously taken intraarterially (axillary artery) and with a mercury manometer and stethoscope or noninvasive measurement device (OMRON R3). Intraarterial measurements were directly compared with two measurements taken in random order with either an arm cuff mercury manometer or the wrist cuff device. Systolic and diastolic blood pressure as assessed with the mercury manometer was higher, especially when compared with the intraarterial and the wrist cuff values, which were comparable. Correlations of blood pressure values with intraarterial measurement were 0.86 systolic and 0.75 diastolic (P < .01) for the wrist cuff and 0.84 systolic (P < .01) and 0.59 diastolic (P < .05) for the mercury manometer measurements. Reproducibility of both measurements was good for the wrist cuff device ([systolic/diastolic]: r = 0.94/0.92; P < .01) and the mercury manometer (r = 0.97/0.88; P < .01). Both methods overestimated high diastolic values, whereas only the wrist cuff underestimated high systolic values. Thus, the new oscillometric wrist cuff blood pressure measurement device measures arterial blood pressure with great accuracy and reproducibility. As compared with intraarterial values, the wrist cuff device overestimated high diastolic and underestimated high systolic blood pressure values. Blood pressure values as measured by the mercury manometer were higher than intraarterial values and those of the wrist cuff. Both noninvasive devices overestimated high diastolic value
The Extended Learning Curve for Laparoscopic Fundoplication: A Cohort Analysis Of 400 Consecutive Cases
Many studies have looked at the learning curve associated with laparoscopic Nissen fundoplication (LNF) in a given institution. This study looks at the learning curve of a single surgeon with a large cohort of patients over a 10-year period. Prospective data were collected on 400 patients undergoing laparoscopic fundoplication for over 10Â years. The patients were grouped consecutively into cohorts of 50 patients. The operating time, the length of postoperative hospital stay, the conversion rate to open operation, the postoperative dilatation rate, and the reoperation rate were analyzed. Results showed that the mean length of operative time decreased from 143Â min in the first 50 patients to 86Â min in the last 50 patients. The mean postoperative length of hospital stay decreased from 3.7Â days initially to 1.2Â days latterly. There was a 14% conversion to open operation rate in the first cohort compared with a 2% rate in the last cohort. Fourteen percent of patients required reoperation in the first cohort and 6% in the last cohort. Sixteen percent required postoperative dilatation in the first cohort. None of the last 150 patients required dilatation. In conclusion, laparoscopic fundoplication is a safe and effective operation for patients with gastroesophageal reflux disease. New techniques and better instrumentation were introduced in the early era of LNF. The learning curve, however, continues well beyond the first 20 patients
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