Effect of Gyroscopic Couple on Aircraft Landing Gear Shimmy

This article presents the effect of gyroscopic couples on the shimmy response of landing gear. The gyroscopic effect between the rotational motions of the aircraft’s longitudinal and vertical axes may be one of the causes of shimmy. The vertical load acting on the wheel axle plays a significant role in a tire’s dynamic characteristics, which may influence shimmy oscillation. So, vertical dynamics also need to be considered for shimmy analysis along with lateral and torsional modes. Suitable mathematical models are required to study the system’s shimmy oscillation and stability nature. The mathematical model was developed by introducing a gyroscopic couple with 5 degrees of freedom (DOF). A numeric analysis was made to investigate the influence of gyroscopic couples on the landing gear model. The simulation results of the model with and without gyroscopic couple are compared and the effect of each parameter on shimmy is studied

A study of myocardial injury in organophosphorous poisoning.

Organophosphorous (OP) pesticide self-poisoning is estimated to kill around two lakhs population per year, largely in pacific asian region , majority of incidences takes place in rural populations and is mostly due to impulsion. In western population the scenario is different that is more incidence of poisoning with drugs takes place. In India the mortality is around one fourth to one fifth; but in western it is only less than one percent(1). Even developed countries are prone to military or terrorist attacks with nerve agent OP compounds. The main mechanism of action of all OPs is that they inhibit the enzyme acetyl cholinesterase. Majority of the mortality is due to cardiorespiratory compromise. But the clinical manifestations vary with type of insecticide and amount of insecticide consumed. In a clinical study 38 percent of patients require intubation for respiratory compromise following that the death rate was also high (2). If cardiac complications are not recognised early it can be fatal. 1 The exact pathogenesis of cardiac complications has not yet been defined. A few important studies have been carried out both in India and abroad to study the cardiac complications and electrocardiographic changes in organophosphorous poisoning. The current study was carried out to understand the cardiac manifestations of organophosphorous poisoning with special reference to cardiac enzymes and ECG changes

Shimmy analysis of light weight aircraft nose wheel landing gear

This paper presents mathematical modeling and analysis of shimmy oscillations for a light weight airplane single wheel nose landing gear. Shimmy is a self-excited oscillation which occurs usually on the nose wheel landing gear assembly during ground maneuvers which is governed by the dynamic characteristics of the landing gear and tires. Shimmy oscillation may lead to reduce the fatigue life of the landing gear and fuselage structure. So, the study of dynamic response and stability boundaries of landing gear plays crucial role while designing of airplanes. In earlier studies of vehicle shimmy only 3 degrees of freedom (DOF) considered such as torsional mode, lateral bending mode and tire lateral deformation. In this work along with above mentioned DOF, two more additional DOF introduced such as axial vibration of strut and tire in order to include the effect of vertical dynamics on shimmy model. Gyroscopic coupling effect also included in the model to study its influence on shimmy. Analysis carried out to determine critical velocity region for occurrence of shimmy and to investigate the effectiveness of ground unevenness on the landing gear system for two different runway conditions such as flat runway and random roughness runway. The results are more helpful to study significant interaction between the different parameters of landing gear and to represent stability boundaries

Clinical Evidence of Human Pathogens Implicated in Alzheimer’s Disease Pathology and the Therapeutic Efficacy of Antimicrobials: An Overview

A wealth of pre-clinical reports and data derived from human subjects and brain autopsies suggest that microbial infections are relevant to Alzheimer\u27s disease (AD). This has inspired the hypothesis that microbial infections increase the risk or even trigger the onset of AD. Multiple models have been developed to explain the increase in pathogenic microbes in AD patients. Although this hypothesis is well accepted in the field, it is not yet clear whether microbial neuroinvasion is a cause of AD or a consequence of the pathological changes experienced by the demented brain. Along the same line, the gut microbiome has also been proposed as a modulator of AD. In this review, we focus on human-based evidence demonstrating the elevated abundance of microbes and microbe-derived molecules in AD hosts as well as their interactions with AD hallmarks. Further, the direct-purpose and potential off-target effects underpinning the efficacy of anti-microbial treatments in AD are also addressed

A neutron diffraction study of the oxygen diffusion in molybdenum doped Ba2InO5

International audienceThe structures of molybdenum doped Ba2In2O5 were refined using X-ray and neutron diffraction data at room and high temperature with the aim to derive preferred oxygen diffusion pathways. At room temperature, refinement of composition Ba2In2-xMoxO5+3x/2 with x=0.1 revealed molybdenum atoms are preferentially located in the tetrahedral layers of the brownmillerite. At 700°C, the structure can be viewed as the stacking of alternating In and In/Mo octahedral layers. The conduction process occurs preferentially in the later which is highly oxygen deficient. Preferred oxygen diffusion pathways were deduced from Joint Probability Density Function (JPDF) and energy barriers were derived. It was in good agreement with the activation energy deduced from impedance spectroscopy for composition x=0.1 at 950°C. However, calculation of energy barrier assumes a dynamic disorder of oxide ions which is unlikely to occur at lower temperature and for sample containing a larger amount of molybdenum. Composition x=0.5 is cubic on the whole range of temperature. At room temperature, JPDF revealed a static disorder of the oxygen atoms, which is likely due to the solution of molybdenum into the barium indium perovskite. When temperature increases the disorder becomes more and more dynamic

Neurochemical Effects of Sepsis on the Brain

Sepsis is a life-threatening organ dysfunction triggered by a dysregulated host immune response to eliminate an infection. After the host immune response is activated, a complex, dynamic, and time-dependent process is triggered. This process promotes the production of inflammatory mediators, including acute-phase proteins, complement system proteins, cytokines, chemokines, and antimicrobial peptides, which are required to initiate an inflammatory environment for eliminating the invading pathogen. The physiological response of this sepsis-induced systemic inflammation can affect blood-brain barrier (BBB) function; subsequently, endothelial cells produce inflammatory mediators, including cytokines, chemokines, and matrix metalloproteinases (MMPs) that degrade tight junction (TJ) proteins and decrease BBB function. The resulting BBB permeability allows peripheral immune cells from the bloodstream to enter the brain, which then release a range of inflammatory mediators and activate glial cells. The activated microglia and astrocytes release reactive oxygen species (ROS), cytokines, chemokines, and neurochemicals, initiate mitochondrial dysfunction and neuronal damage, and exacerbate the inflammatory milieu in the brain. These changes trigger sepsis-associated encephalopathy (SAE), which has the potential to increase cognitive deterioration and susceptibility to cognitive decline later in life

Clinical Significance and Potential Role of Trimethylamine N-Oxide in Neurological and Neuropsychiatric Disorders

Research in the last three decades has attracted the attention of many scientists and industrialists on the gut microbiome and its metabolites. Among many of these metabolites, trimethylamine oxide. Dietary choline, phosphatidylcholine, carnitine, and betaine produces TMAO that with other gut metabolites such as TMA (trimethylamine), and short-chain fatty acids (SCFA) enter the circulation. Finally they reach the brain through the blood-brain barrier (BBB) where they are involved in several physiological functions such as brain development, neurogenesis, and behavior. Gut-microbiota composition is influenced by diet, lifestyle, antibiotics, and age resulting in dysbiosis. Several studies have confirmed that altered TMAO levels can be harmful, contributing to several metabolic, vascular, psychiatric and neurodegenerative disorders. This review focuses on how altered TMAO levels impact oxidative stress, microglial activation, and apoptosis of neurons that subsequently lead to the development of psychiatric, cognitive, and behavioral disorders. In addition, possible therapeutic strategies targeting TMAO are discussed