Vibrational modes of circular free plates under tension

The vibrational frequencies of a plate under tension are given by the eigenvalues $\omega$ of the equation $\Delta^2u-\tau\Delta u=\omega u$. This paper determines the eigenfunctions and eigenvalues of this bi-Laplace problem on the ball under natural (free) boundary conditions. In particular, the fundamental modes --- the eigenfunctions of the lowest nonzero eigenvalue --- are identified and found to have simple angular dependence.Comment: 17 pages. To be submitted for publication shortly

Non-adiabatic pressure loss boundary condition for modelling turbocharger turbine pulsating flow

This paper presents a simplified methodology of pulse flow turbine modelling, as an alternative over the meanline integrated methodology outlined in previous work, in order to make its application to engine cycle simulation codes much more straight forward. This is enabled through the development of a bespoke non-adiabatic pressure loss boundary to represent the turbine rotor. In this paper, turbocharger turbine pulse flow performance predictions are presented along with a comparison of computation duration against the previously established integrated meanline method. Plots of prediction deviation indicate that the mass flow rate and actual power predictions from both methods are highly comparable and are reasonably close to experimental data. However, the new boundary condition required significantly lower computational time and rotor geometrical inputs. In addition, the pressure wave propagation in this simplified unsteady turbine model at different pulse frequencies has also been found to be in agreement with data from the literature, thereby supporting the confidence in its ability to simulate the wave action encountered in turbine pulse flow operation

Primary photodynamic therapy with verteporfin for pigmented posterior pole cT1a choroidal melanoma: a 3-year retrospective analysis

AIMS: To investigate the outcomes of primary photodynamic therapy (PDT) for pigmented posterior pole cT1a choroidal melanoma. METHODS: Retrospective interventional consecutive case series of 26 patients (26 eyes) with pigmented posterior pole cT1a choroidal melanoma, who were treated with 3 sessions of PDT and followed-up thereafter. RESULTS: Included were 11 males and 15 females that presented at a median age of 66 years (mean: 64) with transformed naevi (n=11) or suspicious lesions (n=15) with ≥3 risk factors for growth, with lipofuscin in all. In all cases, diagnosis was clinically based (no tissue biopsy). Tumour control was achieved in 16 (62%) patients in a median follow-up time of 29 months (mean: 27). Ten patients failed treatment by form of radial expansion, diagnosed in a median time of 13 months (mean: 12) from last treatment. By Kaplan-Meier analysis, success rate after 1, 2 and 3 years was 85%, 59% and 51%, respectively. On statistical analysis, number of suspicious features was found to be the only risk factor predicting failure (P=0.046). One patient developed macula-sparing branch retinal artery occlusion after treatment. Following PDT, subretinal fluid resolved in all cases and visual acuity significantly improved in all treatment-success cases (P=0.043). There were no cases of metastatic spread. CONCLUSION: Primary PDT resulted in tumour regression of small, pigmented choroidal melanoma in 62% after a mean of 27 months. Treatment was more effective in tumours with three or less risk factors for growth, and resulted with fluid elimination and significant improvement in vision in treatment-success cases

Primary enucleation for group D retinoblastoma in the era of systemic and targeted chemotherapy: the price of retaining an eye

BACKGROUND: Chemotherapy is increasingly used as primary treatment for group D retinoblastoma, whereas primary enucleation is considered to have a diminishing role. This study aimed to compare the management course, including number of examinations under anaesthesia (EUAs), of group D patients treated by enucleation versus chemotherapy. METHODS: A retrospective analysis of 92 group D patients, of which 40 (37 unilateral) underwent primary enucleation and 52 (17 unilateral) were treated with intravenous chemotherapy. Number of EUAs was compared between the treatment groups with respect to the whole cohort, using univariate and multivariate analysis, and to unilateral cases only. RESULTS: Patients were followed up for a median of 61 months (mean: 66, range: 14-156), in which time primary enucleated patients had on average seven EUAs and chemotherapy-treated patients 21 EUAs (p<0.001). Chemotherapy, young age, bilateral disease, multifocal tumours, familial and germline retinoblastoma were found on univariate analysis to correlate with increased number of EUAs (p≤0.019). On multivariate analysis, however, only treatment type and presentation age were found significant (p≤0.001). On subanalysis of the unilateral cases, patients undergoing primary enucleation had in average seven EUAs, as compared with 16 in the chemotherapy group (p<0.001). Of the 55 unilateral-presenting patients, a new tumour developed in the fellow eye only in a single familial case. CONCLUSION: Group D patients' families should be counselled regarding the significant difference in number of EUAs following primary enucleation versus chemotherapy when deciding on a treatment strategy. In this regard, primary enucleation would be most beneficial for older patients with unilateral disease

The Incidence of Binocular Visual Impairment and Blindness in Children with Bilateral Retinoblastoma

Purpose: The study aimed to assess the incidence of and risk factors leading to visual impairment and legal blindness in children with retinoblastoma. Procedures: This is a singlecenter, retrospective case series of all patients with bilateral retinoblastoma presenting from 2010 to 2014. Results: A total of 44 patients were included in the study. Visual impairment was present in 14 (38%) children, legal blindness was present in 7 (19%) children. Bilateral macular tumors (BMT) were associated with visual impairment (12 of 18 patients with BMT, 2 of 19 patients without BMT, p = 0.0006) and legal blindness (7 of 18 patients with BMT, 0 of 19 patients without BMT, p = 0.003).The International Intraocular Retinoblastoma Classification (IIRC) of the better eye also predicted visual impairment (16% in IIRC Group A–C, 75% in IIRC Group D, E, p = 0.004) and blindness (3% eye in IIRC Group A–C, 50% in Group D, E, p = 0.005). Various non-Snellen visual acuity measures were able to predict visual impairment in pre-verbal children, providing them with early assistance. Conclusions: The rates of visual impairment and blindness reported in this paper can be used to counsel families regarding the risk of binocular visual impairment. Early detection and support for visually impaired infants are essential as d

Primary intravenous chemotherapy for group D retinoblastoma: a 13-year retrospective analysis.

BACKGROUND: Eye salvage rate for group D retinoblastoma using intravenous chemotherapy (IVC) as a primary modality is <50%. To report on 13 years' experience with the use of primary IVC for group D retinoblastoma. METHODS: A retrospective analysis of 64 group D eyes (52 patients) treated with primary IVC, from 2002 to 2014. RESULTS: The median age at presentation was 11.0 months (mean: 18.6, range: 0.6-144.0), 35 (67%) patients had bilateral disease, 38 (73%) germline disease and 8 (15%) cases were familial. In addition to IVC, patients received a median number of three treatments (mean: 6, range: 0-24), including thermotherapy/cryotherapy, plaque radiotherapy, intra-ophthalmic artery chemotherapy (IAC) and/or intravitreous chemotherapy. External beam radiotherapy (EBRT) was used in five eyes, all of which were eventually enucleated. In a median follow-up time of 55 months (mean: 64, range: 14-156), 63% of eyes were salvaged. By the Kaplan-Meier survival analysis, globe salvage rate was 83%, 70%, 59% and 45% at 1, 3, 5 and 10 years, respectively. There were no cases of metastatic spread from intraocular retinoblastoma and no deaths. IVC-related adverse events included febrile neutropenia in 21 (40%) patients and anaphylactic reaction to carboplatin in 2 (4%), all conservatively resolved. Of the patients receiving IAC, third and sixth nerve palsies were documented in two (10%) and one (5%) eyes, respectively. CONCLUSIONS: Primary IVC for group D eyes, with adjuvant treatments as required, was found to be a safe and efficient approach, achieving 63% eye salvage rate, no metastatic spread from intraocular retinoblastoma and no deaths. IAC has now replaced EBRT as a successful salvage treatment

A Cross-Sectional Survey of Anesthetic Airway Equipment and Airway Management Practices in Uganda.

BACKGROUND: Anesthesia-related causes contribute to a significant proportion of perioperative deaths, especially in low and middle-income countries (LMICs). There is evidence that complications related to failed airway management are a significant contributor to perioperative morbidity and mortality. While existing data have highlighted the magnitude of airway management complications in LMICs, there are inadequate data to understand their root causes. This study aimed to pilot an airway management capacity tool that evaluates airway management resources, provider practices, and experiences with difficult airways in an attempt to better understand potential contributing factors to airway management challenges. METHODS: We developed a novel airway management capacity assessment tool through a nonsystematic review of existing literature on anesthesia and airway management in LMICs, internationally recognized difficult airway algorithms, minimum standards for equipment, the safe practice of anesthesia, and the essential medicines and health supplies list of Uganda. We distributed the survey tool during conferences and workshops, to anesthesia care providers from across the spectrum of surgical care facilities in Uganda. The data were analyzed using descriptive methods. RESULTS: Between May 2017 and May 2018, 89 of 93 surveys were returned (17% of anesthesia providers in the country) from all levels of health facilities that provide surgical services in Uganda. Equipment for routine airway management was available to all anesthesia providers surveyed, but with a limited range of sizes. Pediatric airway equipment was always available 54% of the time. There was limited availability of capnography (15%), video laryngoscopes (4%), cricothyroidotomy kits (6%), and fiber-optic bronchoscopes (7%). Twenty-one percent (18/87) of respondents reported experiencing a "can't intubate, can't ventilate" (CICV) scenario in the 12 months preceding the survey, while 63% (54/86) reported experiencing at least 1 CICV during their career. Eighty-five percent (74/87) of respondents reported witnessing a severe airway management complication during their career, with 21% (19/89) witnessing a death as a result of a CICV scenario. CONCLUSIONS: We have developed and implemented an airway management capacity tool that describes airway management practices in Uganda. Using this tool, we have identified significant gaps in access to airway management resources. Gaps identified by the survey, along with advocacy by the Association of Anesthesiologists of Uganda, in partnership with the Ugandan Ministry of Health, have led to some progress in closing these gaps. Expanding the availability of airway management resources further, providing more airway management training, and identifying opportunities to support skilled workforce expansion have the potential to improve perioperative safety in Uganda

Solitary Iris Plasmacytoma With Anterior Chamber Crystalline Deposits

PURPOSE: To report a case of solitary iris plasmacytoma successfully treated with ruthenium plaque radiotherapy. METHODS: A 44-year-old white woman presented with pain in the right eye and raised intraocular pressure. Her medical history included breast cancer treated 11 years earlier with lumpectomy, lymph node clearance, chemotherapy, and radiotherapy. On examination, the right iris had a tan-colored mass with crystalline deposits visible on the mass surface and on the corneal endothelium. The fundus and left eye were normal. An anterior segment ultrasound scan showed a mass with mixed internal echogenicity and internal blood flow. RESULTS: An iris biopsy showed an infiltrate of plasma cells. Immunohistochemistry for kappa and lambda light chains demonstrated lambda light chain restriction. Systemic hematologic investigations including complete blood count, serum paraproteins, bone marrow biopsy, and full-body magnetic resonance image were normal. The monoclonal plasma cell infiltrate was consistent with a solitary iris plasmacytoma. The mass was treated with ruthenium plaque radiotherapy. After 4 years of follow-up, the mass remained regressed, and no systemic myeloma has developed. CONCLUSIONS: Iris plasmacytoma is rare and should prompt systemic evaluation to rule out multiple myeloma. Solitary iris plasmacytoma can be successfully treated with plaque radiotherapy