Mechanisms for the Oxonolysis of Ethene and Propene: Reliability of Quantum Chemical Predictions

Reactions of ozone with ethene and propene leading to primary ozonide (concerted and stepwise ozonolysis) or epoxide and singlet molecular oxygen (partial ozonolysis) are studied theoretically. The mechanism of concerted ozonolysis proceeds via a single transition structure which is a partial diradical. The transition structures and intermediates in the stepwise ozonolysis and partial ozonolysis mechanisms are singlet diradicals. Spin-restricted and unrestricted density functional methods are employed to calculate the structures of the closed-shell and diradical species. Although the partial diradicals exhibit moderate to pronounced instability in their RDFT and RHF solutions, RDFT is required to locate the transition structure for concerted ozonolysis. Spin projected fourth-order Møller–Plesset theory (PMP4) was used to correct the DFT energies. The calculated pre-exponential factors and activation energies for the concerted ozonolysis of ethene and propene are in good agreement with experimental values. However, the PMP4//DFT procedure incorrectly predicts the stepwise mechanism as the favored channel. UCCSD(T) predicts the concerted mechanism as the favored channel but significantly overestimates the activation energies. RCCSD(T) is found to be more accurate than UCCSD(T) for the calculation of the concerted mechanism but is not applicable to the diradical intermediates. The major difficulty in accurate prediction of the rate constant data for these reactions is the wide range of spin contamination for the reference UHF wave functions and UDFT solutions across the potential energy surface. The possibility of the partial ozonolysis mechanism being the source of epoxide observed in some experiments is discussed

Microscopic Investigation of Vortex Breakdown in a Dividing T-Junction Flow

3D-printed microfluidic devices offer new ways to study fluid dynamics. We present the first clear visualization of vortex breakdown in a dividing T-junction flow. By individual control of the inflow and two outflows, we decouple the effects of swirl and rate of vorticity decay. We show that even slight outflow imbalances can greatly alter the structure of vortex breakdown, by creating a net pressure difference across the junction. Our results are summarized in a dimensionless phase diagram, which will guide the use of vortex breakdown in T-junctions to achieve specific flow manipulation.Comment: 5 pages, 5 figure

Gender preselection

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Nonmigratory online deadline scheduling on multiprocessors

In this paper we consider multiprocessor scheduling with hard deadlines and investigate the cost of eliminating migration in the online setting. Let I be any set of jobs that can be completed by some migratory offline schedule on m processors. We show that I can also be completed by a nonmigratory online schedule using m speed-5.828 processors (i.e., processors 5.828 times faster). This result supplements the previous results that I can also be completed by a non-migratory offline schedule using 6m unit-speed processors [B. Kalyanasundaram and K. R. Pruhs, J. Algorithms, 38 (2001), pp. 2-24] or a migratory online schedule using m speed-2 processors [C. A. Phillips et al., Algorithmica. 32 (2002), pp. 163-200]. Our result is based on a simple conservative scheduling algorithm called PARK, which commits a processor to a job only when the processor has zero commitment before its deadline. A careful analysis of PARK further shows that the processor speed can be reduced arbitrarily close to 1 by exploiting more processors (say, using 16m speed-1.8 processors). PARK also finds application in overloaded systems; it gives the first online nonmigratory algorithm that can exploit moderately faster processors to match the performance of any migratory offline algorithm. © 2005 Society for Industrial and Applied Mathematics.published_or_final_versio

Review of salivary gland neoplasms

Salivary gland tumours most often present as painless enlarging masses.Most are located in the parotid glands andmost are benign. The principal hurdle in their management lies in the difficulty in distinguishing benign from malignant tumours. Investigations such as fine needle aspiration cytology and MRI scans provide some useful information, but most cases will require surgical excision as ameans of coming to a definitive diagnosis. Benign tumours and early low-grademalignancies can be adequately treated with surgery alone, while more advanced and high-grade tumours with regional lymph node metastasis will require postoperative radiotherapy. The role of chemotherapy remains largely palliative. This paper highlights some of the more important aspects in the management of salivary gland tumours.published_or_final_versio

Unexpectedly Higher Morbidity and Mortality of Hospitalized Elderly Patients Associated with Rhinovirus Compared with Influenza Virus Respiratory Tract Infection

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Severe macrolide-resistant Mycoplasma pneumoniae pneumonia associated with macrolide failure

We investigated differences in outcomes between 68 children hospitalized with macrolide-sensitive Mycoplasma pneumoniae pneumonia (MSMP group) and 25 children hospitalized with macrolide-resistant M. pneumoniae pneumonia (MRMP group). In the MRMP group, 19 children received macrolides and clinical failure occurred in six of which five had pneumonia progression during therapy.published_or_final_versio

Prevalence of antibiotic-resistant intestinal flora in patients undergoing transrectal ultrasonography-guided prostate biopsy (TRUS-Bx) and its implication for clinical practice: preliminary results

Oral (Free Paper) Session I - Prostate Cancer: Diagnosis to Treatment: OP.1-2香港泌尿外科學會OBJECTIVE: An important factor determining the choice of antibiotic for TRUS-Bx prophylaxis and treatment of post-biopsy infection is the prevalence of quinolone-resistant and ESBL-producing organisms in the rectum of patients undergoing this procedure. We aim to determine these prevalence values in patients undergoing TRUS-Bx and to study their correlation with the microbiological data of patients ...published_or_final_versionThe 17th Annual Scientific Meeting of the Hong Kong Urological Association, Hong Kong, 6 November 2011. In Program Book, 2011, p. 3

LED Traffic Light as Communication Device

The visible light from an LED (light emitting diode) traffic light can be modulated and encoded with information. Hence, it can be used for the broadcasting of audio messages or any traffic or road information. Essentially all LED traffic lights can be used as communications devices. The paper focuses on the description of an audio information system made up of high brightness, visible light emitting diodes (LEDs) in which one or more LEDs are modulated and encoded with audio messages. The system also comprises a receiver combined with a speaker which is located at a distance from the LED traffic light. The receiver is designed to demodulate the optically transmitted audio information and broadcast the messages with the speaker. The optical link employs intensity modulation with direct detection. The audio information system implemented on an LED traffic light can provide the function of open space, wireless broadcasting of audio messages.published_or_final_versio

Subcapsular hematoma after ureteroscopy and laser lithotripsy

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