Coupled modeling for investigation of blast induced traumatic brain injury

Modeling of human body biomechanics resulting from blast exposure is very challenging because of the complex geometry and the substantially different materials involved. We have developed anatomy based high-fidelity finite element model (FEM) of the human body and finite volume model (FVM) of air around the human. The FEM model was used to accurately simulate the stress wave propagation in the human body under blast loading. The blast loading was generated by simulating C4 explosions, via a combination of 1-D and 3-D computational fluid dynamics (CFD) formulations. By employing the coupled Eulerian-Lagrangian fluid structure interaction (FSI) approach we obtained the parametric response of the human brain by the blast wave impact. We also developed the methodology to solve the strong interaction between cerebrospinal fluids (CSF) and the surrounding tissue for the closed-head impact. We presented both the arbitrary Lagrangian Eulerian (ALE) method and a new unified approach based on the material point method (MPM) to solve fluid dynamics and solid mechanics simultaneously. The accuracy and efficiency of ALE and MPM solvers for the skull-CSF-brain coupling problem was compared. The presented results suggest that the developed coupled models and techniques could be used to predict human biomechanical responses in blast events, and help design the protection against the blast induced TBI

Analysis of Combat Helmet Performance Integrating Blast Loading and Blunt Impact through Simulation

The mild traumatic brain injury (mTBI) is one of the most common injuries to service members in recent conflicts. Combat helmets have been designed and evaluated to perform against ballistic and blunt impact threats, but not blast threats. An optimal design of combat helmet considering blunt, ballistic impacts and blast effects is a key requirement to improve the head protection against mTBI. Combat helmets are usually designed based on costly and time consuming laboratory tests. Computational models can offer insights in understanding the force transmission through the head-helmet system into the brain and underlying mechanism of brain injury, and help the development of effective protective design. We developed a design approach integrating the effect of both blast and blunt threats to a helmet system by utilizing multi-physics computational tools and representative human head and helmet models. The high-fidelity computational models were used to capture the dynamic response of the composite shell, suspension pads, retention straps and head. Multiple helmet system configurations subjected to blast and blunt loadings with a combination of loading magnitude and orientation were considered to quantify their influence on brain biomechanical response. Parametric studies were carried out to assess energy absorption for different suspension geometry and material morphology for different loadings. The resulting brain responses in terms of pressure, stress, strain, and strain rate as well as the head acceleration were used with published injury criteria to characterize the helmet system performance through a single metric for each threat type. Approaches to combine single-threat metrics to allow aggregating performance against multiple threats were discussed

Multiscale Modelling of Blast-Induced TBI Mechanobiology - From Body to Neuron to Molecule

Blast induced Traumatic Brain Injury (bTBI) has become a signature wound of the recent military operations and is becoming a significant factor of recent civilian blast explosion events. In spite of significant clinical and preclinical research on TBI, current understanding of injury mechanisms is limited and little is known about the short and long-term outcomes. Mathematical models of bTBI may provide capabilities to study brain injury mechanisms, perhaps accelerating the development of neuroprotective strategies and aiding in the development of improved personal protective equipment. The paper presents a novel multiscale simulation framework that couples the body/brain scale biomechanics with micro-scale mechanobiology to study the effects of “primary” micro-damage to neuro-axonal structures with the “secondary” injury and repair mechanisms. Our results show that oligodendrocyte myelinating processes distribute strains among neighbor axons and cause their off-axis deformations. Similar effects have been observed at the finer scale for the Tau-Microtubule interaction. The paper also discusses the need for coupled modeling of primary injury biomechanics, secondary injury mechanobiology and model based assessment of injury severity scores. A new integrated computational and experimental approach is described coupling micro-scale injury criteria for the primary micro-mechanical damage to brain tissue/cells as well as to investigate various secondary injury mechanisms.

Comportamento alimentar do peixe recifal Sargentinho (Abudefduf saxatilis) em Santa Catarina

TCC(graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Biológicas. Biologia.Estudos da ecologia alimentar de peixes recifais são essenciais para compreender o fluxo energético nestes ecossistemas. Diversos estudos abordam o comportamento alimentar das espécies, porém, são poucos os estudos que avaliam esse comportamento ao longo do dia. Visto isso, este estudo busca observar e quantificar o comportamento alimentar do peixe recifal Sargentinho (Abudefduf saxatilis) no litoral de Santa Catarina, Brasil. Foram realizados mergulhos livres e autônomos, nos quais empregou-se busca ativa por indivíduos de A. saxatilis. Utilizando o método de animal focal, um indivíduo era seguido de cada vez por um minuto ou até sua primeira mordida, quando era anotado em qual substrato o mesmo estava mordendo, seu comprimento total e o horário. Para verificar se [1] há diferenças no substrato de forrageio ao longo do dia; e se [2] há diferença no substrato de forrageio entre classes de tamanho, foram utilizados teste-G. Sete substratos foram utilizados pela espécie para forrageio, sendo a coluna d’água o predominante (79,7% dos indivíduos observados), seguido pelos substratos bentônicos: matriz algal epilítica (16,6%), Sargassum sp. (3,3%), alga calcária (0,22%), Palythoa sp. (0,12%) e desova de A. saxatilis (0,06%). As análises sugerem A. saxatilis prefere forragear na coluna d’água durante toda a manhã e no final da tarde, com maior intensidade antes do meio dia, enquanto no começo da tarde preferem o componente bentônico. Estas diferenças podem ser explicadas pelo comportamento oportunista da espécie, que o permite explorar diferentes substratos para forrageio. Também foi demonstrado que as classes de tamanho utilizam diferentes substratos de forrageio, indicando diferenças nas demandas energéticas ao longo de sua ontogenia. Por fim este trabalho revela a grande importância do comportamento alimentar na compreensão geral da ecologia alimentar para a espécie.Reef fish feeding ecology is essential for understating the energy flow of these ecosystems. Many studies approach feeding behaviour, although those approaching the variation of feeding behaviours during the day are scarce. This study aims to observe the feeding behaviour of the reef fish Sargeant major (Abudefduf saxatilis) on the coast of Santa Catarina state, Brazil. For this, free and SCUBA dives were conducted, in which active search for A. saxatilis was performed. Using the focal animal method, an individual was followed each time for one minute or until it’s first bite, when the bitten substrate, total length and time was recorded. To verify if [1] there are differences among the foraging substratum during the day; and if [2] there are differences among foraging substratum between different size classes, a G-test was used. Seven substrata were utilized, being the water column predominant (79,7% of observed individuals), followed by the benthic substrata: epilitic algal matrix (16,6%), Sargassum sp. (3,3%), calcareous algae (0,22%), Palythoa sp. (0,12%) and A. saxatilis eggs (0,06%). The analysis suggests that A. saxatilis prefer to forage on the water column during the morning and end of the evening, with a higher intensity of bites before midday, while at the beginning of the evening benthic substrata are preferred. These differences can be explained by the opportunistic behaviour of the species, that allows the exploration of different substrata. It was also demonstrated that individual size classes use different foraging substrata, indicating different energetic demands according to the species different ontogeny. Lastly, this study verified the important role of feeding behaviour in the general understanding of the species feeding ecology

Longitudinal Association Between Physical Activity and Frailty Among Community-Dwelling Older Adults

OBJECTIVES: To examine the longitudinal association between frequency of moderate physical activity (PA) and overall, physical, psychological, and social frailty among community-dwelling older adults older than 70 years. Second, we assessed the association between a 12-month change in frequency of moderate PA and frailty. DESIGN: Longitudinal cohort study. SETTING: Community settings in Spain, Greece, Croatia, the Netherlands, and the United Kingdom. PARTICIPANTS: A total of 1735 participants (61.1% female; mean age = 79.6 years; SD = 5.5 years). MEASUREMENTS: The frequency of self-reported moderate PA was measured and classified into two categories: “regular frequency” and “low frequency.” The 12-month change in frequency of moderate PA between baseline and follow-up was classified into four categories: “continued regular frequency,” “decreased frequency,” “continued low frequency,” and “increased frequency.” The 15-item Tilburg Frailty Indicato

Search for the W-exchange decays B0 --> Ds(*)- Ds(*)+

We report a search for the decays $B^{0} \to D_{s}^{-} D_{s}^{+}$, $B^{0} \to D_{s}^{*-} D_{s}^{+}$, $B^{0} \to D_{s}^{*-} D_{s}^{*+}$ in a sample of 232 million $\Upsilon(4S)$ decays to \BBb ~pairs collected with the \babar detector at the PEP-II asymmetric-energy $e^+ e^-$ storage ring. We find no significant signal and set upper bounds for the branching fractions: ${\cal B}(B^{0} \to D_{s}^{-} D_{s}^{+}) < 1.0 \times 10^{-4}, {\cal B}(B^{0} \to D_{s}^{*-} D_{s}^{+}) < 1.3 \times 10^{-4}$ and ${\cal B}(B^{0} \to D_{s}^{*-} D_{s}^{*+}) < 2.4 \times 10^{-4}$ at 90% confidence level.Comment: 8 pages, 2 figures, submitted to PRD-R

A Functional Polymorphism in Renalase (Glu37Asp) Is Associated with Cardiac Hypertrophy, Dysfunction, and Ischemia: Data from the Heart and Soul Study

Renalase is a soluble enzyme that metabolizes circulating catecholamines. A common missense polymorphism in the flavin-adenine dinucleotide-binding domain of human renalase (Glu37Asp) has recently been described. The association of this polymorphism with cardiac structure, function, and ischemia has not previously been reported.We genotyped the rs2296545 single-nucleotide polymorphism (Glu37Asp) in 590 Caucasian individuals and performed resting and stress echocardiography. Logistic regression was used to examine the associations of the Glu37Asp polymorphism (C allele) with cardiac hypertrophy (LV mass>100 g/m2), systolic dysfunction (LVEF<50%), diastolic dysfunction, poor treadmill exercise capacity (METS<5) and inducible ischemia.Compared with the 406 participants who had GG or CG genotypes, the 184 participants with the CC genotype had increased odds of left ventricular hypertrophy (OR = 1.43; 95% CI 0.99-2.06), systolic dysfunction (OR = 1.72; 95% CI 1.01-2.94), diastolic dysfunction (OR = 1.75; 95% CI 1.05-2.93), poor exercise capacity (OR = 1.61; 95% CI 1.05-2.47), and inducible ischemia (OR = 1.49, 95% CI 0.99-2.24). The Glu37Asp (CC genotype) caused a 24-fold decrease in affinity for NADH and a 2.3-fold reduction in maximal renalase enzymatic activity.A functional missense polymorphism in renalase (Glu37Asp) is associated with cardiac hypertrophy, ventricular dysfunction, poor exercise capacity, and inducible ischemia in persons with stable coronary artery disease. Further studies investigating the therapeutic implications of this polymorphism should be considered

Measurement of Branching Fraction and Dalitz Distribution for B0->D(*)+/- K0 pi-/+ Decays

We present measurements of the branching fractions for the three-body decays B0 -> D(*)-/+ K0 pi^+/-$and their resonant submodes$B0 -> D(*)-/+ K*+/- using a sample of approximately 88 million BBbar pairs collected by the BABAR detector at the PEP-II asymmetric energy storage ring. We measure: B(B0->D-/+ K0 pi+/-)=(4.9 +/- 0.7(stat) +/- 0.5 (syst)) 10^{-4} B(B0->D*-/+ K0 pi+/-)=(3.0 +/- 0.7(stat) +/- 0.3 (syst)) 10^{-4} B(B0->D-/+ K*+/-)=(4.6 +/- 0.6(stat) +/- 0.5 (syst)) 10^{-4} B(B0->D*-/+ K*+/-)=(3.2 +/- 0.6(stat) +/- 0.3 (syst)) 10^{-4} From these measurements we determine the fractions of resonant events to be : f(B0-> D-/+ K*+/-) = 0.63 +/- 0.08(stat) +/- 0.04(syst) f(B0-> D*-/+ K*+/-) = 0.72 +/- 0.14(stat) +/- 0.05(syst)Comment: 7 pages, 3 figures submitted to Phys. Rev. Let

Measurement of the B+ --> p pbar K+ Branching Fraction and Study of the Decay Dynamics

With a sample of 232x10^6 Upsilon(4S) --> BBbar events collected with the BaBar detector, we study the decay B+ --> p pbar K+ excluding charmonium decays to ppbar. We measure a branching fraction Br(B+ --> p pbar K+)=(6.7+/-0.5+/-0.4)x10^{-6}. An enhancement at low ppbar mass is observed and the Dalitz plot asymmetry suggests dominance of the penguin amplitude in this B decay. We search for a pentaquark candidate Theta*++ decaying into pK+ in the mass range 1.43 to 2.00 GeV/c2 and set limits on Br(B+ --> Theta*++pbar)xBr(Theta*++ --> pK+) at the 10^{-7} level.Comment: 8 pages, 7 postscript figures, submitted to Phys. Rev. D (Rapid Communications

Measurement of the quasi-elastic axial vector mass in neutrino-oxygen interactions

The weak nucleon axial-vector form factor for quasi-elastic interactions is determined using neutrino interaction data from the K2K Scintillating Fiber detector in the neutrino beam at KEK. More than 12,000 events are analyzed, of which half are charged-current quasi-elastic interactions nu-mu n to mu- p occurring primarily in oxygen nuclei. We use a relativistic Fermi gas model for oxygen and assume the form factor is approximately a dipole with one parameter, the axial vector mass M_A, and fit to the shape of the distribution of the square of the momentum transfer from the nucleon to the nucleus. Our best fit result for M_A = 1.20 \pm 0.12 GeV. Furthermore, this analysis includes updated vector form factors from recent electron scattering experiments and a discussion of the effects of the nucleon momentum on the shape of the fitted distributions.Comment: 14 pages, 10 figures, 6 table