Dynamic substructuring for shock spectrum analysis using component mode synthesis

Component mode synthesis was used to analyze different types of structures with MSC NASTRAN. The theory and technique of using Multipoint Constraint Equations (MPCs) to connect substructures to each other or to a common foundation is presented. Computation of the dynamic response of the system from shack spectrum inputs was automated using the DMAP programming language of the MSC NASTRAN finite element code

Comparison of Damage Path Predictions for Composite Laminates by Explicit and Standard Finite Element Analysis Tools

Splitting, ultimate failure load and the damage path in center notched composite specimens subjected to in-plane tension loading are predicted using progressive failure analysis methodology. A 2-D Hashin-Rotem failure criterion is used in determining intra-laminar fiber and matrix failures. This progressive failure methodology has been implemented in the Abaqus/Explicit and Abaqus/Standard finite element codes through user written subroutines "VUMAT" and "USDFLD" respectively. A 2-D finite element model is used for predicting the intra-laminar damages. Analysis results obtained from the Abaqus/Explicit and Abaqus/Standard code show good agreement with experimental results. The importance of modeling delamination in progressive failure analysis methodology is recognized for future studies. The use of an explicit integration dynamics code for simple specimen geometry and static loading establishes a foundation for future analyses where complex loading and nonlinear dynamic interactions of damage and structure will necessitate it

Influence of Shear Stiffness Degradation on Crack Paths in Uni-Directional Composite Laminates

Influence of shear stiffness degradation in an element, due to damage, on crack paths in uni-directional laminates has been demonstrated. A new shear stiffness degradation approach to improve crack path prediction has been developed and implemented in an ABAQUS/Explicit frame work using VUMAT. Three progressive failure analysis models, built-in ABAQUS (TradeMark), original COmplete STress Reduction (COSTR) and the modified COSTR damage models have been utilized in this study to simulate crack paths in five unidirectional notched laminates, 15deg, 30deg, 45deg, 60deg and 75deg under uniaxial tension load. Results such as crack paths and load vs. edge displacement curves are documented in this report. Modified COSTR damage model shows better accuracy in predicting crack paths in all the uni-directional laminates compared to the ABAQUS (TradeMark) and the original COSTR damage models

Community and genomic analysis of the human small intestine microbiota

Our intestinal tract is densely populated by different microbes, collectively called microbiota, of which the majority are bacteria. Research focusing on the intestinal microbiota often use fecal samples as a representative of the bacteria that inhabit the end of the large intestine. These studies revealed that the intestinal bacteria contribute to our health, which has stimulated the interest in understanding their dynamics and activities. However, bacterial communities in fecal samples are different compared to microbial communities at other locations in the intestinal tract, such as the small intestine. Despite that the small intestine is the first region where our food and intestinal microbiota meet, we know little about the bacteria in the small intestine and how they influence our overall well-being. This is mainly attributable to difficulties in obtaining samples with the small intestine being located between the stomach and the large intestine. Therefore, the work in this thesis aimed at providing a better understanding of the composition and dynamics of the human small intestinal microbiota and to provide insight in the metabolic potential as well as immunomodulatory properties of some of its typical commensal inhabitants. Small intestinal samples used in the work described in this thesis were collected from ileostomy subjects, individuals that had their large intestine surgically removed and the end of the small intestine connected to an abdominal stoma, providing access to luminal content of the small intestine. Considering the importance of molecular techniques in contemporary ecological surveys of microbial communities, first of all, two technologies, barcoded pyrosequencing and phylogenetic microarray analysis were compared in terms of their capacity to determine the bacterial composition in fecal and small intestinal samples from human individuals. As PCR remains a crucial step in sample preparation for both techniques, the use of different primer pairs in the amplification step was assessed in terms of its impact on the outcome of microbial profiling. The analyses revealed that the different primer pairs and the two profiling technologies provide overall similar results for samples of fecal and terminal ileum origin. In contrast, the microbial profiles obtained for small intestinal samples by barcoded pyrosequencing and phylogenetic microarray analysesdiffered considerably. This is most likely attributable to the constraints that are intrinsic to the use of the microarray to enable the detection of predefined microbiota members only, which is due to the probe design that is largely based on large intestinal microbiota communities. However, the pyrosequencing technology also allows for identification of bacteria that were not in advance known to inhabit our intestinal tract. The pyrosequencing technology was used as the method of choice to study the total and active small intestinal communities in ileostoma effluent samples from four different subjects through sequencing the 16S ribosomal RNA gene (rDNA) and ribosomal RNA (rRNA) contentcombined with metatranscriptome analysis by Illumina sequencing of cDNA derived from enriched mRNAof the same sample set to investigate the activities of the small intestinal bacteria. The composition of the small intestinal bacterial communities as assessed from rDNA, rRNA, and mRNA patterns appeared to be similar, indicating that the dominant bacteria in the small intestine are also highly active in this ecosystem. Streptococcusspp. were among the bacterial species that were detected in each ileostoma effluent sample, albeit that their abundance varied greatly between samples from the same subject as well as samples from different subjects. Veillonellaspp. frequently co-occurred with Streptococcus spp., indicating that the Streptococcusand Veillonellapopulations play a prominent role in the human small intestine ecosystem and their co-occurrence suggests a metabolic relation between these genera. Therefore, cultivation and molecular typing methodologies were employed to zoom-in on these groups, which revealed that the richness of the small intestinal streptococci strongly exceeded the diversity that could be estimated on basis of 16S rRNA analyses, and could be extended to the genomic lineage level (anticipated to resemble strain-level). From ileostoma samples 3 different Streptococcusspecies were recovered belonging to the S. mitisgroup, S. bovisgroup, and S. salivariusgroup, which could be further divided in 7 genomic lineages. Notably, the Streptococcuslineages that were isolated displayed distinct carbohydrate utilization capacities, which may imply that their growth and relative community composition may respond quite strongly to differences in the dietary intake of simple carbohydrates over time. This notion is in good agreement with the observation that the Streptococcuslineage populations fluctuated in time with only one Streptococcuslineage being cultivated from both ileostoma samples collected in a one-year time frame. Conversely, the cultivated Veillonellaisolates from samples during that same time-interval consistently encompassed a single lineage. Furthermore, this Veillonellalineage could be isolated from both the oral cavity as well as the ileostoma effluent. Analogously, three Streptococcuslineages that belong to a single phylotype also appeared to be present in bacterial communities from the oral cavity as well as the small intestine. These observations suggest the representatives of the Veillonellaand Streptococcusgenera that are encountered in the oral and small intestinal microbial ecosystems are closely related and indicate that the oral microbiota may serve as an inoculum for the upper GI tract. The metabolic capacity of 6 small intestinal Streptococcus lineages, that were obtained from a single ileostoma effluent sample, was further investigated through the determination of genomic sequences of these lineages. The small-intestinal Streptococcusgenomes were found to encode different carbohydrate transporters and the necessary enzymes to metabolize different sugars, which was in excellent agreement with what carbohydrates could be used by representative strains of the Streptococcuslineages. To further our understanding how the different streptococci as representatives of the dominant small intestinal bacterial populations may influence our immune system, human dendritic cells were stimulated with strains of the different Streptococcuslineages to study their immunomodulatory properties. The Streptococcuslineages differed significantly in their capacity to modulate cytokine responses of blood-monocyte derived immature dendritic cells. As Streptococcusand Veillonellafrequently co-occur in the small intestinal ecosystem, pair-wise combinations of strains of these two species were also tested for their combined immunomodulatory properties. This resulted in considerably different cytokine responses as those that could be predicted from the stimulations with either Streptococcusor Veillonella, indicating that it is not trivial to predict gut mucosal associated immune responses and thatthe composition of the intestinal microbiota as a whole may have a distinct influence on an individual’s immune status. In conclusion, the work described this thesis provides an expansion to the accumulating knowledge on the human intestine microbiota. Whereas most studies focus on the microbiota present in the distal regions of the intestinal tract, this study targeted the microbiota of the poorly proximal regions of the intestine and also addressed its capacity to interact with the local mucosal tissue. The data presented here can be exploited to guide the design of future studies that aim to elucidate the interplay between diet, microbiota and the mucosal tissues in the human small intestinal tract.</p

Effect of Gender on Lower Extremity Kinematics During Rapid Direction Changes: An Integrated Analysis of Three Sports Movements

Anterior cruciate ligament (ACL) injury is a common sports injury, particularly in females. Gender differences in knee kinematics have been observed for specific movements, but there is limited information on how these findings relate to other joints and other movements. Here we present an integrated analysis of hip, knee and ankle kinematics across three movements linked to non-contact ACL injury. It was hypothesised that there are gender differences in lower extremity kinematics, which are consistent across sports movements. Ten female and ten male NCAA basketball players had three-dimensional hip, knee and ankle kinematics quantified during the stance phase of sidestep, side-jump and shuttle-run tasks. For each joint angle, initial value at contact, peak value and between-trial variability was obtained and submitted to a two-way mixed design ANOVA (gender and movement), with movement condition treated as a repeated measure. Females had higher peak knee valgus and lower peak hip and knee flexion, with the same gender differences also existing at the beginning of stance (

Damage Simulation in Non-Crimp Fabric Composite Plates Subjected to Impact Loads

Progressive failure analysis (PFA) of non-crimp fabric (NCF) composite laminates subjected to low velocity impact loads was performed using the COmplete STress Reduction (COSTR) damage model implemented through VUMAT and UMAT41 user subroutines in the frame works of the commercial finite element programs ABAQUS/Explicit and LS-DYNA, respectively. To validate the model, low velocity experiments were conducted and detailed correlations between the predictions and measurements for both intra-laminar and inter-laminar failures were made. The developed material and damage model predicts the peak impact load and duration very close with the experimental results. Also, the simulation results of delamination damage between the ply interfaces, in-plane matrix damages and fiber damages were all in good agreement with the measurements from the non-destructive evaluation data

Three-Dimensional High Fidelity Progressive Failure Damage Modeling of NCF Composites

Performance prediction of off-axis laminates is of significant interest in designing composite structures for energy absorption. Phenomenological models available in most of the commercial programs, where the fiber and resin properties are smeared, are very efficient for large scale structural analysis, but lack the ability to model the complex nonlinear behavior of the resin and fail to capture the complex load transfer mechanisms between the fiber and the resin matrix. On the other hand, high fidelity mesoscale models, where the fiber tows and matrix regions are explicitly modeled, have the ability to account for the complex behavior in each of the constituents of the composite. However, creating a finite element model of a larger scale composite component could be very time consuming and computationally very expensive. In the present study, a three-dimensional mesoscale model of non-crimp composite laminates was developed for various laminate schemes. The resin material was modeled as an elastic-plastic material with nonlinear hardening. The fiber tows were modeled with an orthotropic material model with brittle failure. In parallel, new stress based failure criteria combined with several damage evolution laws for matrix stresses were proposed for a phenomenological model. The results from both the mesoscale and phenomenological models were compared with the experiments for a variety of off-axis laminates

Assessing Vaginal Surgical Skills Using Video Motion Analysis

OBJECTIVE: To demonstrate the feasibility of using video motion analysis to quantitate a key step of vaginal hysterectomy and define measurable differences between novice and experienced surgical trainees during vaginal hysterectomy. METHODS: Analyses focused on clamping, transecting, and suturing the left uterosacral ligament. Using a cutoff of 25, trainees were grouped as experienced (n=14) and novice (n=9) based on the total number of vaginal hysterectomies performed by each trainee. Contrasting-groups analysis was used to determine cutoff values that separated novices from experts. RESULTS: Novice trainees took longer (112 seconds compared with 84 seconds) and had greater cumulative translational motion (92 cm compared with 49 cm, P=.05) while performing the task. Experienced trainees placed the Heaney clamp closer to a right angle to the vertical axis (experienced 96° compared with novice 109°, P=.03) while passing the needle through the uterosacral ligament. Trainees move from novice to experts when the steps occur in 112 or fewer seconds, cumulative translational motion is at or less than 75 cm, and the angle between the clamp to bladder retractor is at or below 105°. CONCLUSION: Video motion analysis is a feasible technique to quantify and compare surgical skills objectively during vaginal surgery. There are measurable differences between novice and more experienced surgical trainees performing vaginal hysterectomy that can be quantified using motion analysis

The Influence of Foot Positioning on Ankle Sprains

The goal of this study was to examine the influence of changes in foot positioning at touch-down on ankle sprain occurrence. Muscle model driven computer simulations of 10 subjects performing the landing phase of a side-shuffle movement were performed. The relative subtalar joint and talocural joint angles at touchdown were varied, and each subject-specific simulation was exposed to a set of perturbed floor conditions. The touchdown subtalar joint angle was not found to have a considerable influence on sprain occurrence, while increased touchdown plantar flexion caused increased ankle sprain occurrences. Increased touchdown plantar flexion may be the mechanism which causes ankles with a history of ankle sprains to have an increased susceptibility to subsequent sprains. This finding may also reveal a mechanism by which taping of a sprained ankle or the application of an ankle brace leads to decreased ankle sprain susceptibility

Study of muons near shower cores at sea level using the E594 neutrino detector

The E594 neutrino detector has been used to study the lateral distribution of muons of energy 3 GeV near shower cores. The detector consists of a 340 ton fine grain calorimeter with 400,000 cells of flash chamber and dimensions of 3.7 m x 20 m x 3.7 m (height). The average density in the calorimeter is 1.4 gm/sq cm, and the average Z is 21. The detector was triggered by four 0.6 sq m scintillators placed immediately on the top of the calorimeter. The trigger required at least two of these four counters. The accompanying extensive air showers (EAS) was sampled by 14 scintillation counters located up to 15 m from the calorimeter. Several off line cuts have been applied to the data. Demanding five particles in at least two of the trigger detectors, a total of 20 particles in all of them together, and an arrival angle for the shower 450 deg reduced the data sample to 11053 events. Of these in 4869 cases, a computer algorithm found at least three muons in the calorimeter