Experimental investigation of multimodal noise generation by ducted low Mach number flows through orifice plates.

Noise generation by low Mach number air flows through circular orifices in rectangular ducts is investigated. In particular, the influence of the number and position of the orifices maintaining a constant flow area is addressed. A review of the available theories suggests a certain importance of such parameters in the excitation of higher-order acoustic duct modes. A qualitative coefficient is proposed for a first characterization of the ability to enhance or lessen a given higher-order acoustic mode by the plate geometry. An experimental campaign is performed to measure the total emitted acoustic power by different plate geometries as well as its modal composition. It is found that the orifices' numbers and positions greatly influence the acoustic emissions while the flow pressure drop caused by the obstacles is similar. The proposed qualitative coefficient shows good agreement with the experimental results. A particle image velocimetry measurement campaign is performed to visualize the near-field average flow behavior upstream and downstream of the orifice plates. An increase in the turbulent velocity fluctuations in the vicinity of the orifices is observed on both sides, further validating previous studies on the subject.

Numerical investigation of the trapped modes in the presence of non-potential flow.

A calculation method is proposed to investigate trapped modes in a rigid waveguide with rigid obstacles in the presence of non-potential steady mean flow in a two-dimensional coordinate system. This method facilitates the investigation of trapped modes in the presence of non-potential flow. A coupled calculation method that combines computational fluid dynamics and computational aeroacoustics is used. Galbrun's equation of aeroacoustics is used and discretized by the finite element method. The boundary condition corresponding to the unbounded domain is modeled by the perfectly matched layer technique. The proposed approach facilitates the investigation of the trapped modes generated by obstacles with different geometrical shapes. The effects of both the dimensions of different geometrical shapes (e.g., thin plate, rectangular, and elliptical) and the presence of the non-potential flow on the trapped modes are studied. It is observed that the non-potential flow alters the pressure distribution around the obstacle and the frequencies of the trapped modes. The results show good agreement with the literature. Also, experimental investigations are performed to validate the model.

Experimental investigation of oscillating flow characteristics at the exit of a stacked mesh grid regenerator.

The aim of this study is to investigate the oscillating flow velocity field at the exit of different stacked mesh grid regenerators using Particle Image Velocimetry measurements. Twelve different experimental cases are discussed, yielding oscillating flow fields at the exit of four kinds of regenerators for different acoustic levels. The regenerators are classified according to the mesh wire size to viscous penetration depth ratio and according to the method of stacking the mesh grids. Based on the analysis of the vorticity fields at the exit of the regenerator, three groups of flow patterns are identified. This classification is correctly verified by using the Reynolds number (based on the acoustic amplitude and wire diameter) and the Strouhal number (based on the acoustic displacement amplitude and wire diameter). The characteristics of the fluctuating velocity components are investigated for these various flow patterns. The critical Reynolds number, past which the flow is highly dissipative, is determined. The dissipation timescale is investigated and the quasi-steady approximation is found to be valid for the analysis of the oscillating flow at the exit of the regenerator mesh.

Age and Tumor Location Predict Survival in Nonmetastatic Osteosarcoma in Upper Egypt.

AIM: The aims of this study were to assess survival outcome of pediatric patients with localized osteosarcoma of the extremities in Upper Egypt, identify factors of prognostic significance for survival, and to determine factors predictive of surgical methods used in these patients, as well as developing a clinical model for risk prediction. PATIENTS AND METHODS: A retrospective analysis of data assembled from medical records of 30 pediatric patients with a histologically verified nonmetastatic osteosarcoma of the extremities treated at South Egypt Cancer Institute with a unified chemotherapy protocol between January 2001 and December 2015 was carried out. Prognostic factors were determined using univariable and multivariable methods. A model for surgical outcomes in these patients based on the baseline clinical factors, and the parameters predictive of their tumor response to chemotherapy, was developed. RESULTS: With a median follow-up of 63 months for the study population, the estimates for event-free survival and overall survival (OS) at 3 and 5 years were 69.5% and 79% and 65.2% and 65.3%, respectively. Age 16 years or above was independently associated with both worse metastasis-free survival (hazard ratio [HR]=6.05, 95% confidence interval [CI]: 1.43-25.6, P=0.015) and OS (HR=7.9, 95% CI: 1.71-36.2, P=0.008). In the multivariable analysis, a proximal location within the limb gained a statistical significance to be independently associated with worse OS (HR=2.4, 95% CI: 1.13-22.1, P=0.003). Poor response to chemotherapy was marginally associated with worse metastasis-free survival (HR=4.9, 95% CI: 1.02-23.8, P=0.047) only in the univariable analysis. The patients found to be more likely to undergo an amputation surgery (odds ratio=14.1, 95% CI: 1.34-149.4, P=0.028) were those in whom a tumor was poorly responding to chemotherapy. CONCLUSION: In Upper Egypt, despite the reasonable survival outcomes in nonmetastatic osteosarcoma, a relatively high limb amputation rate has been encountered. The development of a clinical prediction model for future planning of possible outcome improvement in these patients, however, is still feasible.

Pediatric Osteosarcoma of Extremities: A 15-year Experience From a Tertiary Care Cancer Center in Upper Egypt.

AIM: To assess the outcome and determine predictors of survival in pediatric patients with osteosarcoma of the extremities treated with a unified chemotherapy protocol at a single institution over a 15-year period. MATERIALS AND METHODS: We performed a retrospective analysis of medical records of 48 pediatric patients with histologically verified osteosarcoma of the extremities diagnosed at South Egypt Cancer Institute and received treatment between January 2001 and December 2015. RESULTS: With a median follow-up of 61 months for the entire cohort, estimates of overall survival (OS) for 3- and 5-year were 50.9% and 42.1%, respectively. While the estimates of OS for 3- and 5-year in the nonmetastatic group were 79% and 65.2%, respectively. In the multivariable analysis, both metastatic disease at diagnosis and poor response to chemotherapy retained their statistical significance as independent predictors for event-free survival. Whereas for OS, a metastatic disease at diagnosis remained as the lone predictor of a dismal outcome, while a poor response to chemotherapy became marginally associated with an inferior outcome. CONCLUSIONS: In Upper Egypt, whereas slightly less than two thirds of children with localized osteosarcoma of extremities survives their disease, metastasis at presentation remains the key predictor of dismal survival outcomes.

Experimental investigation of the influence of natural convection and end-effects on Rayleigh streaming in a thermoacoustic engine.

The influence of both the natural convection and end-effects on Rayleigh streaming pattern in a simple standing-wave thermoacoustic engine is investigated experimentally at different acoustic levels. The axial mean velocity inside the engine is measured using both Laser Doppler Velocimetry and Particle Image Velocimetry. The mean flow patterns are categorized in three different regions referred to as "cold streaming" region, "hot streaming" region, and "end-effects" region. In the cold streaming region, the dominant phenomenon is Rayleigh streaming and the mean velocity measurements correspond well with the theoretical expectations of Rayleigh streaming at low acoustic levels. At higher acoustic levels, the measurements deviate from the theoretical expectations which complies with the literature. In the hot streaming region, temperature measurements reveal that the non-uniformity of the resonator wall temperature is the origin of natural convection flow. Velocity measurements show that natural convection flow superimposes on the Rayleigh streaming flow so that the measured mean velocity deviates from the theoretical expectations of Rayleigh streaming. In the last region, the measured mean velocity is very different from Rayleigh streaming due to the combined effects of both the flow disturbances generated near the extremity of the stack and the natural convection flow.

Does arthroscopic patellar denervation with high tibial osteotomy improve anterior knee pain?

PURPOSE: Patellofemoral (PF) joint osteoarthritis (OA) is a major cause of anterior knee pain. Combined PF and medial tibiofemoral (TF) OA is common in older adults. We evaluated the effect of arthroscopic patellar denervation (PD) in patients with combined TF and PFOA after malalignment correction. METHODS: Forty-five patients [females/males, 27/18; age, 30-59 years (45.5 ± 8.50); mean body mass index, 25.15 ± 3.04 kg/m2] were treated in our department from March 2017 to March 2019. The patients were randomised into 2 groups: group A included 22 patients who underwent open-wedge high tibial osteotomy (OWHTO) and arthroscopic PD and group B included 23 patients who underwent OWHTO without denervation. The effect of denervation was statistically and clinically evaluated using the Knee injury and Osteoarthritis Outcome Score (KOOS) and Kujala (anterior knee pain score) score. RESULTS: After 24 months, 40 patients were available for the final follow-up. The final values of KOOS and the Kujala score were significantly different between the groups (p < 0.001). For group A, the average KOOS improved from 42.73 to 72.38 (p < 0.001) and the Kujala score improved from 42 to 74.1 (p < 0.001), whereas in group B, the average KOOS improved from 39.22 to 56.84 (p < 0.001) and the Kujala score improved from 39.7 to 56.4 (p < 0.001). CONCLUSION: Adding arthroscopic PD to OWHTO relieves anterior knee pain in patients with combined TF and PFOA and improves knee joint function and quality of life. LEVEL OF EVIDENCE: Level I prospective randomised control clinical trial.

Ewing sarcoma outcomes in a country with limited resources: Egypt as an example.

As the scarcity of published research that comprehensively and meticulously analyzed the patient, disease, and treatment factors of prognostic significance in Ewing sarcoma (EWS) in Egypt; This study aimed at assessing survival outcomes of EWS in Upper Egypt, delineating factors of prognostic significance in comparison to other leading oncology centers in Egypt and internationally. By retrospectively reviewing medical records of 85 patients with a verified diagnosis of EWS in the period from 2001 to 2015 at Pediatric and Medical Oncology Departments at South Egypt Cancer Institute; We gathered data relevant to the patient, disease, and treatment variables of the study. Survival was estimated using the Kaplan Meier method and differences between various groups were determined by log rank test. Univariable and multivariable analyses were performed using Cox regression. With a median follow-up period of 62.7 months (95% CI 52.2-73.2, SE=5.4) for the study patients, the estimates of event-free survival (EFS) and overall survival (OS) at 3 and 5 years were 42.1% and 50.6%, and 40.8% and 48.5%, respectively. Metastatic disease at initial presentation (HR=8.91, 95% CI, 4.00-19.9; P<0.0001) stood as the most powerful predictor of OS in the multivariable analysis, followed by surgery used as a local modality (HR=0.16, 95% CI, 0.06-0.44; P=0.0004). Response to neoadjuvant chemotherapy (HR=2.61, 95% CI, 1.11-6.13; P=0.028), primary tumor size (HR=2.49, 95% CI, 1.03-6.03; P=0.044) were also shown to be significantly associated with OS. Radiotherapy as a local modality, whose effect, apparently shown to increase the hazard of events occurrence in the univariable analysis, an effect that was reversed to reveal EFS advantage (HR=0.41, 95% CI, 0.18-0.95; P=0.036) after control of other variables. With 5-year OS of 48.5%, our survival results were comparable to those previously published from Egypt; however, differences still exist between centers due to varied representative study samples. However, outcomes in Egypt in general are still inferior to internationally published studies.

Dexamethasone and Dexmedetomidine as an Adjuvant to Intraarticular Bupivacaine for Postoperative Pain Relief in Knee Arthroscopic Surgery: A Randomized Trial.

BACKGROUND: Knee arthroscopy causes minimal trauma, however, good analgesia is required for early rehabilitation and return to normal life in the patients. OBJECTIVE: We aimed to compare the analgesic effects of intraarticular dexamethasone and dexmedetomidine added to bupivacaine with those of bupivacaine alone. STUDY DESIGN: This study uses a double-blind, randomized, controlled design with allocation concealment in a 3-armed parallel group format among patients undergoing arthroscopic meniscal surgery. SETTING: The study was conducted at Assiut University Hospital in Asyut, Egypt. The study duration was from July 2016 to February 2017. METHODS: After the ethics committee approval, 60 patients, with the American Society of Anesthesiologists (ASA) physical status of I or II, 20 - 50 years old, and scheduled for arthroscopic meniscal surgery were randomized in a double-blind manner to receive 18 mL intraarticular bupivacaine 0.25% with either dexamethasone 8 mg (group I), dexmedetomidine 1 ug/kg (group II), or 2 mL of normal saline (group III). The total volume of injectate used in each group was 20 mL. All of the patients received spinal anesthesia. Postoperatively, oral paracetamol 1000 mg was given every 8 hours, and oral tramadol 50 mg was administered, as needed, for rescue analgesia. The visual analog scale (VAS) pain scores, time to first analgesic request, and total dose of postoperative analgesics were recorded for 3 days postoperatively. RESULTS: The VAS scores were lower in groups I and II compared with group III. The time to the first analgesic was significantly shorter in group III compared with groups I and II (P = 0.001). The total dose of rescue paracetamol was higher in group III compared with groups I and II (P = 0.001). No need for tramadol rescue analgesia was recorded in any of the groups. No significant differences between groups I and II were noticed. LIMITATIONS: The limitations of this study include the lack of previous research to compare the effect of both intraarticular dexamethasone and dexmedetomidine added to bupivacaine for postoperative analgesia in arthroscopic knee surgery. Additionally, there was a short observation period for the detection of chondrotoxicity, if occurred. CONCLUSION: The addition of dexamethasone or dexmedetomidine to a solution of bupivacaine 0.25% provided better analgesia than using bupivacaine alone. CLINICAL TRIAL REGISTRATION: NCT02818985. KEY WORDS: Intraarticular, knee arthroscopy, bupivacaine, dexmedetomidine, dexamethasone, postoperative pain.

Arthroscopic skills assessment and use of box model for training in arthroscopic surgery using Sawbones - "FAST" workstation.

PURPOSE: Arthroscopic skills training outside the operative room may decrease risks and errors by trainee surgeons. There is a need of simple objective method for evaluating proficiency and skill of arthroscopy trainees using simple bench model of arthroscopic simulator. The aim of this study is to correlate motor task performance to level of prior arthroscopic experience and establish benchmarks for training modules. METHODS: Twenty orthopaedic surgeons performed a set of tasks to assess a) arthroscopic triangulation, b) navigation, c) object handling and d) meniscus trimming using SAWBONES "FAST" arthroscopy skills workstation. Time to completion and the errors were computed. The subjects were divided into four levels; "Novice", "Beginner", "Intermediate" and "Advanced" based on previous arthroscopy experience, for analyses of performance. RESULTS: The task performance under transparent dome was not related to experience of the surgeon unlike opaque dome, highlighting the importance of hand-eye co-ordination required in arthroscopy. Median time to completion for each task improved as the level of experience increased and this was found to be statistically significant (p < .05) e.g. time for maze navigation (Novice - 166 s, Beginner - 135.5 s, Intermediate - 100 s, Advance - 97.5 s) and the similar results for all tasks. Majority (>85%) of subjects across all the levels reported improvement in performance with sequential tasks. CONCLUSION: Use of the arthroscope requires visuo-spatial coordination which is a skill that develops with practice. This simple box model can reliably differentiate the arthroscopic skills based on experience and can be used to monitor progression of skills of trainees in institutions.