Dynamic forces and acoustic energy dissipation in conical bubble luminescence

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.The dynamics and acoustics of conical bubble collapse occurring in a U-Tube device are studied. Two conical shapes are used, one with a smooth interior and another with a stepped interior in order to understand their associated phenomena such as: luminescence, bubble cloud formation, and emission of strong rebound pressures. High-speed video frames, waveforms from piezoelectric transducers and photomultipliers were acquired during the experimental runs. All data are synchronized on the same timeline. To explore the details of the acoustic energy dissipation, the piezoelectric waveforms were analyzed by means of Fourier transform and wavelets. Results show (I) with to respect to the frustum cone that: a) two mean flow structures are formed, one of them is a gas pocket and the other is a bubble cloud. The bubble cloud is produced when the concave meniscus is folded inwards due to fluid flow surrounding that divides the initial gas pocket in two, one remains trapped inside of meniscus area and the other is pushed towards to the cone end. These structures are the main location where the light emission occurs; (II) for the stepped cone that: a) asymmetrical counter-current flows are produced by the stepped boundaries, which generate several stagnation points. From the detailed analysis of the signals acquired, two issues were found: the frequencies and scales associated with the shock waves emission onset and its propagation, as well as frequency bands in which there is an absence of energy. The detailed flow structures as jets and splashing effects also are considered.cf201

Pheochromocytomas/Paragangliomas and two cases

Pheochromocytomas are catecholamine-producing neuroendocrine tumours that arise from the adrenal medulla or extramedullary pheochromoblasts with highly variable clinical presentation, including episodes of headache, sweating, palpitations and hypertension. Due to the non-specificity of the symptoms there is usually a delay between the onset of symptoms and the final diagnosis. To make a firm diagnosis, biochemical testing of the blood (catecholamines) or urine (metanephrines and VMA) are mandatory. Many stimuli increase circulating catecholamines and metabolites and must receive due attention to prevent false-positive results. Therapeutically, surgery is the gold standard. To minimise complications during and post surgery the lesion(s) should be carefully localised via imaging studies. Adequate pre- and postoperative medical treatment is important. The history, diagnosis and therapy of two patients - the one with a paraganglioma of the organ of Zuckerkandl, the other with a intra thoracic paraganglioma are presented. South African Family Practice Vol. 49 (5) 2007: pp. 42-4

Comparisons between dynamics of SBSL and an encapsulated bubble in spherical resonator

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Single bubble sonoluminescence (SBSL) and ultrasound agent contrast (UAC), each one levitating in a standing wave field (30~70 kHz) inside of a spherical resonator filled with sterile water, are compared in order to understand their radial dynamics. Light scattering technique is employed to measure the radial pulsations of individual/cloud microbubbles. Waves emitted by bubble (shock wave) and the intensity of the acoustic field applied are measured through a needle hydrophone. UAC is highly diluted Polyson® microbubbles. Waveforms are processed by means of Fourier and time-frequency analysis. The experimental data and the main parameters involved (T, , Pa, Re and De) are analyzed as a function of short and long regimen. Linear and nonlinear oscillations were observed and associated with time-frequency spectra. Parametric instabilities are inferred from the light-scattered signal. The resting diameter and temperature are shown as principal parameters in the prediction of microbubble behavior.cf201

Supportive networks among companies: Key factors of success and failure

The role of entrepreneurial networks in the development of Small and Medium-sized Enterprises (SMEs) and the associated entrepreneurial activities are a core topic in both the networks and IMP literature. However the effectiveness of these networks remains little understood. This paper investigates a specific form of formal entrepreneurial network: the supportive networks among companies. More precisely, it seeks to identify the key factors of success and failure of these networks in their actions to support small and new business development by focusing on the interactions between the three categories of actors embedded in these networks. Eleven case studies were undertaken focusing on three French supportive networks between companies. The results showed that convergent interests - altruistic as well as economic - shared both between and within companies is the overarching reason why supportive action succeeds. We also found that interactions driven by non-trading interests contribute favourably to the development of the dynamics of these networks

Chaotic oscillations of a single cavitating bubble immersed in a maxwell liquid

In the present work we develop a mathematical model for a bubble immersed in a Maxwell fluid insonified by an ultrasonic field. As in previous works we wanted to see the effect of the viscoelasiticy in the overall behavior of the bubble in time. With a modified Rayleigh-Plesset equation we obtain the evolution of radius in time, for different Deborah and Reynolds Numbers. Of interest the phase space graphs that show the chaotic oscillations for different values of the parameters, and how these parameters can be used as controllers of the oscillations. For a more complete analysis we perform a Perturbation Multiple Scale technique to get a frequency analysis, which can demonstrate how the parameters might modulate the resonance.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

Serum prostate-specific antigen as surrogate for the Histological diagnosis of Prostate cancer

Introduction. To determine whether there is a cut-off value of serum prostate-specific antigen (PSA) which can be used confidently to make the diagnosis of prostate cancer, thereby obviating the need for biopsy.Patients and methods. During the period October 1991 to March 1998 the Department of Chemical Pathology at Tygerberg Hospital performed a total of 6 733 serum PSA assays on 3960 patients. The histopathological and clinical diagnoses of these patients were obtained from records in the departments of Anatomical Pathology, Urological Oncology and Radiation Oncology. The serum PSA levels were correlated with the histopathology reports, using different PSA cut-off values ranging from 5 to 500 ng/ ml, to calculate the sensitivity, specificity, and positive and negative predictive values of each cut-off value of PSA in predicting the presence of prostate cancer.Results. In total, 3 837 (57%) of the 6 733 serum PSA assays were ≤ 4 ng/ ml, 1 045 (15.5%) of the assays were ≥50 ng/ ml, and 798 (11.9%) were~ 100 ng/ ml. Of the total of 3 960 individual patients, 531 (13.4%) had a serum PSA ≥50 ng/ ml and 423 (10.7%) had a PSA ≥ 100 ng/ ml. A serum PSA of ≥ 30 ng/ml had a positive predictive value (PPV) of 90% at a specificity of 87% and sensitivity of 78%, while a PSA ≥ 60 ng/ ml had a PPV of 98% at a specificity of 98% and sensitivity of 65% for the presence of prostate cancer. The PPV reached 99% at a PSA ≥ 100 ng/ ml and 100% at a PSA ≥ 500 ng/ ml, with a specificity of 99% and 100%, but sensitivity of only 53% and 19%, respectively.Conclusions. A serum PSA ≥ 60 ng/ ml has a PPV of 98% for the presence of adenocarcinoma of the prostate, and may be used as a surrogate for histological diagnosis where facilities for obtaining prostatic biopsies are not readily available, thus decreasing costs and patient morbidity

Collaboration Towards a More Inclusive Society: The Case of South African ICT4D Researchers

In this study, research collaboration in the context of South African Information and Communication for Development (ICT4D) researchers was investigated using a mixed methods approach. South Africa, a country with stark development challenges and on the other hand a well-established ICT infrastructure, provides an appropriate context for ICT4D research. Firstly, a quantitative analysis of South African research collaboration between 2003 and 2016 was conducted to determine the existing research collaboration patterns of South African ICT4D researchers. This is based on the publications in three top ICT4D journals namely the Electronic Journal of Information Systems in Developing Countries (EJISDC), Information Technologies & International Development (ITID), and Information Technology for Development (ITD). The results show that most co-authored papers were intra-institutional collaborations, with limited inter-institutional collaboration between South African authors or between South African and other African authors. Secondly, interviews were conducted with South African researchers who emerged as inter- and intra-institutional collaborators to gain insight into the technology, drivers and barriers affecting South African research collaboration. We report our findings and discuss the implications for employing research collaboration as a mechanism for addressing inequality and supporting inclusion.School of Computin

Early diagnosis of prostate cancer in the Western Cape

Background. Early stage prostate cancer does not cause symptoms, and even metastatic disease may exist for years without causing symptoms or signs. Whereas early stage prostate cancer can be cured with radical prostatectomy or radiotherapy, the prognosis of patients with locally advanced or metastatic cancer is significantly poorer.Objectives. ln view of the high incidence of advanced and therefore incurable prostate cancer seen at the oncology clinic of the Department of Urology, Tygerberg Hospital, we started a prostate clinic with the aim of detecting early stage prostate cancer which is potentially curable. A secondary objective was to investigate the question whether there is a higher incidence of prostate cancer among black African men.Patients and methods. Men aged 50 - 70 years were invited by means of media communications (newspaper and radio) to attend our prostate clinic for a free physical examination, including a digital rectal examination (DRE) and serum prostate specific antigen (PSA) assay. If the DRE was clinically suspicious of malignancy and/ or the serum PSA was > 4 ng/ ml, the patient was appropriately counselled and referred for transrectal ultrasound (TRUS)-guided sextant prostate biopsy.Results. In the period June 1997- September 1999 a total of 1056 men attended the prostate clinic. Biopsies were indicated in 160 cases, and were obtained in 114 (71.3%, i.e. 10.8% of the entire cohort). Prostate cancer was detected on first biopsy in 3.5% of the entire group of men (in 35.9% of those with a clinically abnormal DRE, in 41.3% of those with a serum PSA > 4 ng/ ml and in 88.6% of those with an abnormal DRE and serum PSA > 4 ng/ ml. In the 37 men with prostate cancer, the clinical tumour stage was T1 - 2 in 83.8% and T3- 4 in 16.2%. ln the group of patients with clinical stage T1 - 2 tumours, the treatment was watchful waiting in 62.5% of cases, radiotherapy in 20.8% and radical prostatectomy in 16.7%. Analysis of the data according to race showed that in the group of 47 black men there was a higher percentage of clinically abnormal DRE, PSA > 4 .0 ng/ ml and biopsies showing malignancy, and a higher overall prostate cancer detection rate (8.5%).Conclusions. Our prostate cancer detection rate of 3.5% is slightly lower than that reported in larger studies (4.7%), which may be due to the fact that prostate biopsy was performed in only 71% of those who had an indication for biopsy. ln the men diagnosed with clinically localised prostate cancer, potentially curative treatment was given in only 37.5% of cases. This compares unfavourably with the historical cohort of men seen at our oncology clinic, where 53% received potentially curative treatment, and a large European study where potentially curative treatment was given in 89% of cases. Our finding that black men had a higher percentage of clinically abnormal DRE, PSA > 4.0 ng/ ml and biopsies showing malignancy and a higher overall detection rate of prostate cancer should be interpreted with caution, since black men comprised only 4.5% of our overall study cohort.

Differential criterion of a bubble collapse in viscous liquids

The present work is devoted to a model of bubble collapse in a Newtonian viscous liquid caused by an initial bubble wall motion. The obtained bubble dynamics described by an analytic solution significantly depends on the liquid and bubble parameters. The theory gives two types of bubble behavior: collapse and viscous damping. This results in a general collapse condition proposed as the sufficient differential criterion. The suggested criterion is discussed and successfully applied to the analysis of the void and gas bubble collapses.Comment: 5 pages, 3 figure