Search results for "Vibration"

Conformational substates of the Fe2+-His F8 linkage in deoxymyoglobin and hemoglobin probed in parallel by the Raman band of the Fe-His stretching vi…

1996

Liver stiffness measurement by vibration-controlled transient elastography improves outcome prediction in primary biliary cholangitis

2022

BACKGROUND & AIMS: Liver stiffness measurement (LSM) by vibration-controlled transient elastography (VCTE) has been shown to predict outcomes of patients with primary biliary cholangitis (PBC) in small-size studies. We aimed to validate the prognostic value of LSM in a large cohort study. METHODS: We performed an international, multicentre, retrospective follow-up study of 3,985 patients with PBC seen at 23 centres in 12 countries. Eligibility criteria included at least 1 reliable LSM by VCTE and a follow-up ≥ 1 year. Independent derivation (n = 2,740) and validation (n = 568) cohorts were built. The primary endpoint was time to poor clinical outcomes defined as liver-related complications,…

DOSE–RESPONSE RELATIONSHIPS BETWEEN WHOLE-BODY VIBRATION AND LUMBAR DISK DISEASE—A FIELD STUDY ON 388 DRIVERS OF DIFFERENT VEHICLES

1998

Abstract In a longitudinal study, the dose–response relationships between long term occupational exposure to whole-body vibration and degenerative processes in the lumbar spine caused by the lumbar disks were examined. From 1990 to 1992, 388 vibration-exposed workers from different driving jobs were examined medically and by lumbar X-ray. For each individual, a history of all exposure conditions was recorded, and a cumulative vibration dose was calculated allowing comparisons between groups of low, middle, and high intensity of exposure. 310 subjects were selected for a follow-up four years later, of whom 90·6% (n=281) agreed to participate. In comparing the exposure groups, the results ind…

Vibration control of base-isolated structures using mixed H2/H∞ output-feedback control

2009

A mixed H2/ H∞ output-feedback control design methodology for vibration reduction of base-isolated building structures modelled in the form of second-order linear systems is presented. Sufficient conditions for the design of a desired control are given in terms of linear matrix inequalities. A controller that guarantees asymptotic stability and a mixed H2/ H∞ performance for the closed-loop system of the structure is developed, based on a Lyapunov function. The performance of the controller is evaluated by means of simulations in MATLAB/Simulink.

An LMI approach to vibration control of base-isolated building structures with delayed measurements

2010

In this article, we address a convex optimisation approach to the problem of state-feedback H∞ control design for vibration reduction of base-isolated building structures with delayed measurements, where the delays are time-varying and bounded. An appropriate Lyapunov-Krasovskii functional and some free-weighting matrices are utilised to establish some delay-range-dependent sufficient conditions for the design of desired controllers in terms of linear matrix inequalities. The controller, which guarantees asymptotic stability and an H∞ performance, simultaneously, for the closed-loop system of the structure, is then developed. The performance of the controller is evaluated by means of simula…

Control of Flow Rate in Pipeline Using PID Controller

2019

In this paper a PID controller is utilized in order to control the flow rate of the heavy-oil in pipelines by controlling the vibration in motor-pump. A torsional actuator is placed on the motor-pump in order to control the vibration on motor and consequently controlling the flow rates in pipelines. The necessary conditions for asymptotic stability of the proposed controller is validated by implementing the Lyapunov stability theorem. The theoretical concepts are validated utilizing numerical simulations and analysis, which proves the effectiveness of the PID controller in the control of flow rates in pipelines.

Optical magnetic circular dichroism in threshold photoemission from a magnetite thin film

2011

Threshold photoemission excited by polarization-modulated ultraviolet femtosecond laser light is exploited for phase-sensitive detection of magnetic circular dichroism (MCD) for a magnetite thin film. Magnetite (Fe(3)O(4)) shows a magnetic circular dichroism of ∼(4.5 ± 0.3) × 10(-3) for perpendicularly incident circularly polarized light and a magnetization vector switched parallel and antiparallel to the helicity vector by an external magnetic field. The asymmetry in threshold photoemission is discussed in comparison to the magneto-optical Kerr effect. The optical MCD contrast in threshold photoemission will provide a basis for future laboratory photoemission studies on magnetic surfaces.

Serotonin modulates a depression-like state in Drosophila responsive to lithium treatment

2016

Major depressive disorder (MDD) affects millions of patients; however, the pathophysiology is poorly understood. Rodent models have been developed using chronic mild stress or unavoidable punishment (learned helplessness) to induce features of depression, like general inactivity and anhedonia. Here we report a three-day vibration-stress protocol for Drosophila that reduces voluntary behavioural activity. As in many MDD patients, lithium-chloride treatment can suppress this depression-like state in flies. The behavioural changes correlate with reduced serotonin (5-HT) release at the mushroom body (MB) and can be relieved by feeding the antidepressant 5-hydroxy-L-tryptophan or sucrose, which …

Comparison of the Prolonged Effects of Foam Rolling and Vibration Foam Rolling Interventions on Passive Properties of Knee Extensors

2022

Foam rolling (FR) and vibration foam rolling (VFR) interventions have received attention as pre-exercise warm-ups because they maintain performance and increase range of motion (ROM). However, the immediate and prolonged effects and the comparisons between FR and VFR interventions are unknown. Therefore, this study was designed to compare the effects of FR and VFR interventions on passive properties of knee extensors over time (up to 30 min after interventions). A crossover, random allocation design was used with 14 male college students (22.1 ± 1.0 years old) in the control, FR, and VFR conditions. The knee flexion ROM, pain pressure threshold (PPT), and tissue hardness were measured befor…

Long-term effects on motor cortical excitability induced by repeated muscle vibration during contraction in healthy subjects

2008

article i nfo Objective: The effects of a novel repeated muscle vibration intervention (rMV; 100 Hz, 90 min over 3 consecutive days) on corticomotor excitability were studied in healthy subjects. Methods: rMV was applied over the flexor carpi radialis (FCR) during voluntary contraction (experiment 1), during relaxation and during contraction without vibration (experiment 2). Focal transcranial magnetic stimulation (TMS) was applied before rMV and one hour, and one, two and three weeks after the last muscle vibration intervention. At each of these time points, we assessed the motor map area and volume in the FCR, extensor digitorum communis (EDC) and abductor digiti minimi (ADM). Short-inter…