Delay of Rotating Stall in Compressors Using Plasma Actuation

RÉSUMÉ Le décrochage tournant est une instabilité aérodynamique des compresseurs qui est bien connue et qui limite l‘enveloppe d‘opération des turbines à gaz de moteurs d‘avion. Une méthode innovatrice avait été proposée pour supprimer le type d‘initiation le plus commun au décrochage tournant en utilisant un actionneur plasma DBD annulaire. Un actionneur plasma DBD est un dispositif simple sans pièces mobiles qui convertit l‘électricité directement en accélération de l‘écoulement via l‘ionisation partielle de l‘air. Cependant, le concept proposé n‘avait été évalué que de façon préliminaire via de simples simulations numériques d‘un rotor axial isolé avec un code CFD rudimentaire. Ce projet fait une évaluation expérimentale ainsi que numérique de ce concept pour un étage de compresseur axial et un étage de compresseur centrifuge, tous deux faisant partie d‘un banc d‘essai de compresseur bi-étagé axial-centrifuge à basse vitesse. Les deux configurations étudiées sont la configuration bi-étagé avec un actionneur plasma annulaire de 100 mN/m placé sur le carter juste en amont du bord d‘attaque du rotor axial, et une configuration avec un seul étage de compresseur centrifuge dans lequel le même actionneur est placé juste en amont du bord d‘attaque de l‘impulseur. Les configurations testées furent simulées avec un code RANS CFD commercial sophistiqué (ANSYS CFX) dans lequel furent intégrés le plus récent modèle d‘ingénierie de l‘actionneur DBD ainsi qu‘une condition de sortie dynamique, sur des domaines de calcul multi-étagé à un passage d‘aube. Les mesures expérimentales montrent que l‘actionneur plasma DBD annulaire sur le carter réduit le débit massique du dernier point d‘opération stable (point de décrochage tournant) de 19.28% pour l‘étage de compresseur axial et de 28.39% pour l‘étage de compresseur centrifuge pour lequel l‘impulseur était la source du décrochage tournant. Les simulations numériques indiquent que pour les deux types de compresseurs l‘actionneur retarde le décrochage tournant en poussant l‘interface entre l‘écoulement d‘entrée et l‘écoulement de jeu d‘aube en aval vers l‘intérieur du passage d‘aube. Dans chaque cas, le pourcentage prédit par CFD de la réduction du débit massique du point de décrochage tournant concorde assez bien avec la valeur mesurée.----------ABSTRACT Rotating stall is a well-known aerodynamic instability in compressors that limits the operating envelope of aircraft gas turbine engines. An innovative method for suppressing the most common form of rotating stall inception using an annular DBD plasma actuator had been proposed. A DBD plasma actuator is a simple solid-state device that converts electricity directly into flow acceleration through partial air ionization. However, the proposed concept had only been preliminarily evaluated with simple numerical simulations on an isolated axial rotor using a relatively basic CFD code. The current project provides both an experimental and a numerical assessment of this concept for an axial compressor stage as well as centrifugal compressor stage that are both part of a low-speed two-stage axial-centrifugal compressor test rig. The two configuration studied are the two-stage configuration with a 100 mN/m annular casing plasma actuator placed just upstream of the axial rotor leading edge, and the single-stage centrifugal compressor with the same actuator placed upstream of the impeller leading edge. The tested configuration were simulated with a sophisticated commercial RANS CFD code (ANSYS CFX) in which was implemented the latest engineering DBD plasma model and dynamic throttle boundary condition, using single-passage multiple blade row computational domains. The experiments show that the casing plasma actuator reduces the mass flow of the last stable point (stall point) by 19.28% for the axial compressor stage and 28.39% for the centrifugal compressor stage for which the impeller is the source of rotating stall. The CFD simulations indicate that in both types of compressors the actuator delays the stall inception by pushing the incoming/tip clearance flow interface downstream into the blade passage. In each case, the predicted percentage reduction in stalling mass flow matches the experimental value reasonably well. However, the CFD simulations over-predicts the mass flow of the stall point as well as the pressure rise of the centrifugal stage and under-predict the pressure rise of the axial stage. The main factors for the difference are likely slight discrepancies between the simulated and actual axial rotor blade geometry deformation and the inability of the simulation tool to accurately capture the total pressure loss in the hub region of the vaneless diffuser

Head Trauma as a Precipitating Factor for Late-onset Leigh Syndrome: a Case Report

Leigh syndrome is a severe progressive neurodegenerative disorder with different clinical presentationsthat usually becomes apparent in the first year of life and rarely in late childhood and elderly years. It is causedby failure of mitochondrial respiratory chain and often results in regression of both mental and motor skills and might even lead to death. In some of the inherited neurodegenerative diseases like Alexander disease, head trauma is reported as a trigger for onset of the disease. We present a late onset Leigh syndrome in a 14-year-old girl whose symptoms were initiating following head trauma

Association between Body Mass Index and Cognitive Performance.

Background: Because of well-established role of obesity in brain lesions, progressing cognitive deficits in obese patients has been recently suggested. In current study and for the first time, we aimed to assess cognition status in Iranian obese people and to compare it with non-obese individuals.Methods: One hundred and eighteen consecutive patients with the different cardiovascular and metabolic primary complaints were assigned to obese group (n = 25, 21.2%) and non-obese group (n = 93, 78.8%). Cognitive status was assessed at initial visiting using the Montreal Cognitive Assessment (MoCA) questionnaire.Results: Mean total cognitive score in obese patients was 20.04 ± 4.57 and in non-obese ones was 20.19 ± 5.32 with no difference (p = 0.886). In total, 8.0% of obese patients and 20.4% of non-obese patients had normal cognitive function (p = 0.149). No significant difference was also found in different subdomains of cognitive ability between obese and non-obese groups. None of the cognitive domains had significant association with BMI as the considered indicator for defining obesity. Based on multivariate linear regression modeling, obesity could not predict cognitive deficit (beta = 0.034, SE = 0.1.015, p = 0.973).Conclusion: Our survey could not demonstrate an association obesity and cognitive impairment in a sample of Iranian patients

Magnetic Resonance Spectroscopy Findings and Cognitive Function in Patients with Parkinson’s disease

Background and Purpose: Cognitive impairment (CI) is one of the most notable disabilities of Parkinson’s disease that is associated with lower quality of life. Early detection of CI is therefore very important for these patients. The purpose of this study was to examine the relationship between cognitive function and the metabolic data from magnetic resonance spectroscopy (MRS) of the patient suffering with Parkinson’s disease.Methods: Totally, 45 patients with Parkinson’s disease were used in this study. Subjects were divided into three groups based on scales for outcome from Parkinson cognition (SCOPA-COG) test. Patients were classified as non-cognitive impairment (NCI; n=15), mild cognitive impairment (MCI; n=15) and dementia (PDD; n=15). All subjects underwent MRI and 1H-MRS techniques and metabolic changes such as NAA/Cr and NAA/Cho ratios, which were measured in the left hippocampal area of the brain.Results: The mean and standard deviation of the NAA/Cr ratio in the three cognitive groups (NCI, MCI, PDD) were (2.51±0.037), (2.50±0.033) and (2.47±0.025), respectively. ANOVA test showed a significant difference in the three groups. Furthermore, the Scheffé test showed a significant difference between patients in the MCI and PDD groups (p=0.01). There was no significant difference between the non-cognitive impairment and mild cognitive impairment groups (p=0.54). No significant difference was found in NAA/Cho ratio (p=091). Conclusion: A decreasing NAA/Cr ratio has influence on cognitive function and the development of severe cognitive dysfunction in Parkinson suffering patients. Furthermore, 1H-MRS determinant can be useful to evaluate cognition in Parkinson patients

The Survey of Malnutrition Prevalence in Patients With Parkinson Disease In Tehran, Iran

Background: Parkinson disease (PD) introduced as the second most prevalent neurodegenerative disease following Alzheimer disease. A patient’s nutritional status may be compromising in PD. This study aimed to describe the outpatient nutritional status in patients with PD at a third-level hospital in Iran.Methods: The validated Persian version of the Mini-Nutritional Assessment (MNA) questionnaire was used to evaluate the nutritional status of 158 Iranian PD patients (age, 35-85 years). The exclusion criteria were as follows: chronic comorbidities affecting the nutritional status (e.g., diabetes and hypertension); adherence to special diets; and cognitive disorders. Based on the MNA questionnaire, a total score below 17 represented malnutrition, while scores 17-24 indicated a risk of malnutrition.Results: Based on the findings, 26% of the participants had low weight, 67% of whom were over 65 years. According to the MNA questionnaire, 14.3% of the participants showed malnutrition and 26.2% were at risk of malnutrition.Conclusion: Based on our findings, PD can contribute to reduced nutritional status. More than one-fourth of the PD population was at risk of malnutrition, which highlights the need for more attention towards nutritional assessment. Nutritional assessment is essential for the development of nutritional interventions and early detection of PD patients who are at risk of malnutrition

Association between Cognitive function and metabolic syndrome using Montreal Cognitive Assessment Test.

Background and Purpose: The increased risk for cognitive defects in individuals affected bymetabolic syndrome especially in those patients with cardiovascular disorders is now claimed.We aimed to assess the relationship between cognitive performance and the various componentsof metabolic syndrome.Methods: One hundred and eighteen consecutive individuals aged 30 to 86 years were includedinto this cross-sectional survey. The metabolic syndrome and its definitive components weredefined according to the definition described in the Framingham Heart Study by NCEP ATP IIIcriteria. The Montreal Cognitive Assessment (MOCA) questionnaire was employed to cognitivescreening.Results: Those patients with metabolic syndrome had significantly lower mean MOCA scorecompare to the group without metabolic syndrome (19.11 ± 5.49 versus 21.28 ± 4.56, p =0.021). Among all cognition sub domains, the mean attention score was significantly lower inthe group with metabolic syndrome than in another group. In a multivariate linear regressionmodel adjusting sex and age variables showed that the presence of metabolic syndrome couldeffectively predict cognitive impairment (beta = -2.202, SE = -0.214, p = 0.013).Conclusion: The presence of metabolic syndrome can be mainly related to damaging cognitionespecially impairing the power of attention

MRI Findings in Children with the First Unprovoked Seizure Presenting to the Emergency Department; Does Developmental Delay Suggest the Importance of Brain MRI Evaluation?

Introduction: The first unprovoked seizure (FUS) in children is a convulsive seizure with an unknown cause, which may be due to an underlying neurological disease or a manifestation of epilepsy. Objective: The aim of this study was to evaluate the findings of brain magnetic resonance imaging (MRI) in pediatric patients with FUS, presenting to the emergency department (ED). Methods: In this cross-sectional study, all children with FUS (age: >1month and<14 years), who were referred to the ED of Qaem Hospital, Mashhad, Iran from 2016 to 2019, were investigated. Medical records, brain MRI findings, electroencephalography (EEG) results, and developmental status of children were reviewed retrospectively. Results: The brain MRI findings of 56 children with FUS were reviewed. The mean age of children was 3.92±6.05 years, and the sex distribution was equal. Seventeen (30.4%) patients had abnormal EEG findings, while 13 (23.2%) patients’ had non-specific EEG findings. Neurological examination of 4 (7.1%) children was abnormal. Overall, 6 (10.7%) patients had non-specific abnormal brain MRI findings for seizure, while 3 (5.4%) patients had specific abnormal findings. A significant relationship was observed between the developmental status of children and abnormal MRI findings (P=0.04). However, MRI findings had no significant relationship with EEG or neurological findings (P>0.05). Conclusion: It may be useful to perform brain MRI for children with FUS presenting to ED, especially those who are suspected of developmental disorders

Cataract Surgical Coverage in Kurdistan, Iran

This is a Letter to the Editor and does not have an abstract. Please download the PDF or view the article HTML

MRI Findings in Children with the First Unprovoked Seizure Presenting to the Emergency Department; Does Developmental Delay Suggest the Importance of Brain MRI Evaluation?

Introduction: The first unprovoked seizure (FUS) in children is a convulsive seizure with an unknown cause, which may be due to an underlying neurological disease or a manifestation of epilepsy. Objective: The aim of this study was to evaluate the findings of brain magnetic resonance imaging (MRI) in pediatric patients with FUS, presenting to the emergency department (ED). Methods: In this cross-sectional study, all children with FUS (age: >1month and<14 years), who were referred to the ED of Qaem Hospital, Mashhad, Iran from 2016 to 2019, were investigated. Medical records, brain MRI findings, electroencephalography (EEG) results, and developmental status of children were reviewed retrospectively. Results: The brain MRI findings of 56 children with FUS were reviewed. The mean age of children was 3.92±6.05 years, and the sex distribution was equal. Seventeen (30.4%) patients had abnormal EEG findings, while 13 (23.2%) patients’ had non-specific EEG findings. Neurological examination of 4 (7.1%) children was abnormal. Overall, 6 (10.7%) patients had non-specific abnormal brain MRI findings for seizure, while 3 (5.4%) patients had specific abnormal findings. A significant relationship was observed between the developmental status of children and abnormal MRI findings (P=0.04). However, MRI findings had no significant relationship with EEG or neurological findings (P>0.05). Conclusion: It may be useful to perform brain MRI for children with FUS presenting to ED, especially those who are suspected of developmental disorders

MRI Findings of Primary CNS Lymphoma in 20 Patients of Stereotaxic Ward

PURPOSE: To record the MRI features of primary central nervous system lymphoma (PCNSL) and compare these properties in monofocal and multifocal disease.METHODS: Eleven cases of monofocal disease were compared to 9 cases of multifocal disease. All patients were examined by non-enhanced and contrast-enhanced MRI. Tumor location, signal intensity, enhancement characteristics, age distribution, peritumoral edema, cystic changes, and the presence of calcifications were assessed. The MRI features were compared between the monofocal and multifocal patients.RESULTS: There were 20 cases including both the monofocal and multifocal cases. Contrast-enhanced images showed variable enhancement patterns: homogeneous enhancement (14 patients), and hetrogenous enhancement (6 patients). One case of hemorrhage and two cases of cystic formation were observed. Intra-tumoral calcification was not detected. The frontal lobe, the corpus callosum and the basal ganglia were commonly involved in both the monofocal and multifocal lesion.CONCLUSION: Our data showed that PCNSL has a variable enhancement and edema pattern on MRI. Monofocal PCNSL cases typically have larger size tumors with mild or marked enhancement