On the Degradation of Lubricating Grease

A comprehensive literature review on physical and chemical degradation monitoring and life estimation models for lubricating greases is presented in chapter one. Degradation mechanisms for lubricating grease are categorized and described, and an extensive survey of the available empirical and analytical grease life estimation models including degradation monitoring standards and methods are presented. In chapter two, irreversible thermodynamic theory is employed to study the mechanical degradation of lubricating grease. A correlation between the mechanical degradation and entropy generation is established and the results are verified experimentally using a rheometer, a journal bearing test rig, and a modified grease worker machine. It is shown that the degradation rate is linearly related to the entropy generation, and that it can be used for estimation of the mechanically degraded grease life. In chapter three, a model is presented that uses the principles of irreversible thermodynamics to predict the life of a lubricating grease undergoing mechanical shearing action. Here we restrict our attention to operating temperatures far below the initial activation energy needed to initiate chemical degradation or base oil evaporation. Thus, mechanical degradation is the dominant degradation process. The predictions of the model are validated using the experimental results obtained by testing three greases subjected to different shear rates and temperatures. In chapter four, mechanical life of grease in an elastohydrodynamic (EHL) line contact between two steel rollers is studied. Grease traction curves are measured and reported in different conditions. Three successive lubricating phases of “Fully grease covered rollers”, “Slippage and grease separation” and “Formation of liquid lubricant reservoir” are observed and their behaviors are examined. The traction of the grease is monitored during a long term mechanical degradation process. Our mechanical life prediction model is applied to the lubricating grease at the contact. In chapter five, chemical degradation is studied from an energy point of view. A theory is introduced based on acquired experimental results, and is verified using a roller tester rig. The theory is used to estimate the chemical life of a grease at different temperatures. Summary and conclusions are given in Chapter six along with recommendations for future studies

The Reliability of Ultrasound Imaging in measuring the Thickness of Lumbar Multifidus Muscle in Gymnastics Athletes with Sway-Back and Normal Posture

Introduction: Sway-Back Posture (SBP) is one of the most common poor postures especially among the female gymnastics athletes. It can result in multifidus muscles insufficiency and inability to support the spinal column. The aim of this study was to evaluate the intra-rater reliability of ultrasound imaging to measure the thickness of lumbar multifidus (LMM) muscle at different lumbar levels during both states of muscle at rest and contraction. Materials and Methods: The subjects of this study were 10 females’ gymnastics athletes among whom five had sway back posture. To have the posture assessed the plumb line and grid paper were used. The LMM thicknesses of all lumbar segments were measured thrice (with 1houre minutes interval) by the same examiner in both rest and contraction position simultaneous with arm lifts done by a real time Ultrasonography device. Results: The results of the relative and the absolute reliability of LMM thickness measurements at the state of rests were 0.97 < ICC < 0.99, 0.34 < SEM < 0.48 and 0.94 < MDC< 1.34 and at the state of contractions they were as: 0.95 < ICC < 0.98, 0.47< SEM < 0.71 and 1.31 < MDC< 1.98. The results of the Bland-Altman plotting indicated a good level of agreement between two measurements at all lumbar levels in both states of rest and contraction. Conclusion: The results of this study indicated that the method of ultrasonography had a high level of reliability and accuracy to measure the thickness of LMM in both states of muscle at rest and contraction. The method is highly recommended in physiotherapy and rehabilitation assessments.Key words: Gymnastic, Lumbar Multifidus Muscle, Reliability, Sway-Back Posture, Thickness, Ultrasound Imagin

Pennation Angle and Fascicle Length of Human Skeletal Muscles to Predict the Strength of an Individual Muscle Using Real-Time Ultrasonography: A Review of Literature

Introduction: Muscle fascicle length and pennation angle are two muscle structural parameters which can be non-invasively measured using methods like ultrasonography. The aim of the present literature review was to introduce fascicle length and pennation angle for the estimation of the force of an individual skeletal muscle using ultrasonography. Methods and Materials: The data for the current review study was obtained from Pubmed, Science Direct, Scopous, Google Scholar, Sprinter Link Database, and other authoritative references available on the Internet and in libraries between the years 1995-2015. A total number of 113 articles were obtained. In sum, 45 articles were collected and reviewed. Keywords such as muscle, fascicle, length, angle, force, and ultrasonography were searched to fulfill the purpose of the study. Results: Detailed information on the pennation angle and fascicle length is essential to predict the force of an individual muscle. It has been suggested that changes in muscle fascicle angle and length correlated variably with the muscles force production. Conclusions: Real-time ultrasonography has been introduced as a valuable measurement tool for estimation of the force individual muscle via measuring the muscle architecture parameters, such as pennation angle and fascicle length. However, factors like physiological, anatomical, and biomechanical properties have to be considered when predicting the force of an individual skeletal muscle.Key words: Muscle, Fascicle, Length, Pennation angle, Force, Ultrasonograph

Reliability of the Thickness Measurement and Histogram of Elbow Flexors by Ultrasonography in Patients with Fascioscapulohumoral Dystrophy and Healthy Subjects

Introduction: Ultrasonography is a non-invasive and available technique used to assess normal and pathological tissue in people with neuromuscular diseases. The aim of this study was to determine relative and absolute reliability of ultrasonography in evaluation of thickness and histogram of elbow flexor muscles in patients with facioscapulohumeral muscular dystrophy (FSHD and healthy subjects. Materials and Methods: The present study was carried out on an experimental group of six patients with FSHD and a control group comprising 6 healthy individuals. The thickness and histogram of elbow flexors were evaluated while subjects were in sitting position with knees bent, arms at 90 degrees abduction, elbows at 90 degrees flexion and forearms in neutral position. The probe was placed on the anterior surface of arm at 2/3 distance between the lateral tip of acromion and the lateral epicondyle of the humerus. Standard deviation of echogenicity based on histogram curve was also used to estimate the echogenic uniformity of muscle tissue (STDE), subsequently two parameters including L-mean and STDE were recorded. The intra-class correlation coefficient (ICC), standard error measurement (SEM) and minimal detectable changes (MDC) tests were applied to measure relative and absolute reliability and to estimate the measurement errors. Results: The values of the reliability of muscle thickness measurement were ICC=0.95, SEM=2.14 and MDC=5.94 and ICC=0.95, SEM=1.34 and MDC=3.72 in the experimental group and the control group respectively. Additionally, for L-mean measurements it appeared to be ICC=0.89, SEM=1.75 and MDC=4.86 among patients and ICC=0.66, SEM=1.04 and MDC=2.89 in healthy subjects. Finally, the reliability of STDE measurement was revealed to be ICC=0.98, SEM=0.18 and MDC=0.51 and (ICC=0.75, SEM=0.63 and MDC=1.74) among the participants of the experimental and the control groups. Conclusion: The results of this study showed that ultrasonography method used in this study had a high level of accuracy to measure the thickness and histogram of elbow flexors in both healthy subjects and patients with FSHD. The method can be recommended to compare or determine the effectiveness of different treatment methods in patients with FSHD.Key words: Elbow Flexors, Fascioscapulohumoral Dystrophy Histogram, Reliability; Thickness, Ultrasonograph

Rehabilitative Ultrasound Imaging to Study the Gastrocnemius Muscles Morphology in Patients with Genu Varum and Valgum Deformities

Introduction: Genu varum and genu valgum deformities are highly prevalent in Iran. These deformities bring about changes in the structure and function of muscles around the knees. The aim of the present investigation was to study the structure of medial and lateral gastrocnemius muscles in patients with primary genu varum and genu valgum deformities and individuals with normal knee alignment, using rehabilitative ultrasound imaging. Method and Materials: : A Honda 2100 (Honda Co., Japan) real time ultrasound scanner was used in the current the study. The dominant legs of 18 women, 6 with genu varum (mean age: 22.00±1.78 years), 6 with genu valgum (mean age: 21.67±1.03 years), and 6 with normal alignment (mean age: 21.83±1.72 years) were examined. The morphological parameters like muscle thickness, pennation angle and fascicle length of medial and lateral gastrocnemius muscle were compared among groups. Results: In participants with genu varum, the medial gastrocnemius was thinner, closer and shorter in terms of muscle thickness, pennation angle, and fascicle lengths when compared to the lateral gastrocnemius (P<0.05). However, in participants with genu valgum, it was the other way around (P<0.05). In participants with normal alignment, there was no statistically significant difference between the medial and lateral gastrocnemius muscle structures. Conclusions: The rehabilitative ultrasound imaging is highly recommended for studying the structure of gastrocnemius muscle. The structural differences between medial and lateral gastrocnemius muscles may be due to the long term neuromuscular adaptation to knee joint alignment in both genu varum and genu valgum deformities.Key words: Genu, Valgum, Varum, Rehabilitative, Ultrasound, Imagin

Reliability of Rehabilitative Ultrasound Imaging In Measuring Thickness of Levator Scapula Muscle in Asymptomatic Women

Introduction: Levator Scapula Muscle (LSM) is one of the stabilizers of the scapulae. Shortening of this muscle disrupts shoulder biomechanics and results in shoulder pain. Rehabilitative Ultrasound imaging (RUSI) has been introduced as a non-invasive method to measure muscle thickness. The present study aimed to determine the intra-rater reliability of RUSI to measure thickness of LSM in a group of asymptomatic women. Materials and method: Images of LSM were taken using RUSI at the level of the forth cervical vertebra in sitting position in 20 asymptomatic women aged 20-36 years. Images were obtained by one examiner on two separate days and muscle thickness was measured using RUSI. Intraclass Correlation Coefficients (ICC), Standard Error of Measurement (SEM), Smallest Detectable Difference (SDD), and Bland-Altman plot were used for the assessment of reliability. Results: The results of ICC (0.9), SEM (0.26 mm), and SDD (0.72 mm) values revealed an excellent intra-rater reliability and accuracy of RUSI to measure LSM thickness in asymptomatic women. Conclusion: The method of RUSI used in the current study is recommended to measure LSM thickness. It can be used to measure thickness of LSM in patients with shoulder pain where the thickness of the muscle varies according to the level of pain and spasm.Keywords: Levator Scapula; Ultrasonography; Muscle; Reliability; Shoulde

On Monitoring Physical and Chemical Degradation and Life Estimation Models for Lubricating Greases

Degradation mechanisms for lubricating grease are categorized and described. An extensive survey of the available empirical and analytical grease life estimation models including degradation monitoring standards and methods are presented. A summary of the important contributions on grease degradation is presented

On Monitoring Physical and Chemical Degradation and Life Estimation Models for Lubricating Greases

Degradation mechanisms for lubricating grease are categorized and described. An extensive survey of the available empirical and analytical grease life estimation models including degradation monitoring standards and methods are presented. A summary of the important contributions on grease degradation is presented

Genu varum deformity may increase postural sway and falling risk

Introduction: Any disturbance in balance control procedures may increase the risk of injury during sportactivities. Knee deformities such as genu valgum and genu varum may perturb the line of gravity passingthe lower limb joints and so disturb dynamic and static balance indices. This study was designed toinvestigate the effects of genu valgum and genu varum deformity on the static and dynamic balance indices.Material and Methods: A total of 90 non-athletic female university students were assigned in one of thethree experimental groups; normal knee (n=30), genu varum (n=30) and genu valgum (n=30), according totheir knee conditions. Static and dynamic overall stability index (OSI), anterior-posterior stability index(APSI), medial-lateral stability index (MLSI) and falling risk were evaluated three times by Biodex balancesystem, and the average of each index were recorded.Results: No significant difference was seen between groups in term of dynamic and static OSI and APSI,while significant lower stability was found in the genu varum group compared to normal groups in term ofdynamic and static MLSI (p<0.05). A significant increased in falling risk was also seen in genu varumgroup, compared to the normal group (p<0.05).Conclusion: The results showed that mechanical disturbance due to the genu varum deformity mayperturb the medial-lateral balance indices in both static and dynamic situations. This may indicate that genuvarum deformity may increase the normal postural sway in the medial lateral direction and increase fallingrisk as well