Aims: This study investigates the effects of physical fatigue, mental fatigue and their combinations on the ability of rugby players to produce force during rugby scrummaging. Method: 10 male subjects (Mean age = 27.4 ± 3.92, Weight =102.9kg ± 10.96) were recruited from local rugby union football clubs in the Stockholm area. Scrummaging force measurements were collected following and before treatments (control), after a 30-min mental task and after a physical fatigue protocol. The mean peak force was calculated by averaging the force data 1 second around the highest peak of force during a 5 second sustained push. Results: Mean force decreased significantly after the physical fatigue (PF) protocol compared to the control (CON) (PF = 1740 ± 342 N vs. CON = 2007.5 ± 359 N. P= 0.0009) and combinations of physical and mental fatigue (PMF) or mental and physical fatigue (MPF) were also found to significantly decrease compared to the control (PMF = 1750 ± 348N vs. CON = 2007.5 ± 359N. P=0.0014 and MPF = 1818 ± 335N vs. CON = 2007.5 ± 359N. P=0.026). Mental fatigue did not significantly decrease mean peak force during the sustained push of a rugby scrum (MF = 1912 ± 321N vs. CON = 2007.5 ± 359N. P=0.52). Conclusion: Physical fatigue reduces the ability of rugby players to produce force during rugby scrummaging, however mental fatigue does not. Furthermore, mental fatigue does not exacerbate the effects of physical fatigue on scrummaging performance.

Computational simulations of chemical systems play an ever-increasing role in many areas of biochemical research from rational drug design to probing fundamental physiological processes. Depending on the method, a vast array of properties are able to be predicted. Here we report the design and implementation of two methods for investigating diverse problems in protein biochemistry. In order to better understand protein–metal interactions—most importantly for the difficult to model transition metal ions— empirical force field parameters were developed for Pt(II), cisplatin, and other Pt(II) coordination compounds. Two force field frameworks were used: a modified version of the fixed- charge OPLS-AA and the polarizable POSSIM force field. A seven-site model was used for the Pt(II) ion. The produced parameters are compatible with the OPLS-AA and POSSIM force fields and can be used in protein–metal binding simulations in which—contrary to the common treatment of metal ions in such simulations—the position or even coordination of the ion does not have to be constrained using preexisting knowledge. It has been demonstrated that the produced models are capable of reproducing key properties of relevant Pt(II) complexes but that the POSSIM formalism yields more accurate values for energies of formation than the OPLS-AA model. This Pt(II) model was employed—along with previously developed Cu(I) parameters—to investigate the binding of platinum to the protein Atox1, a human copper chaperone implicated in the resistance mechanism of cisplatin and other platinum antitumor compounds. In collaboration with the Dmitriev and Bernholc groups, we used our models to inform and refine spectroscopic experiments as well as to serve as starting points for high-performance quantum calculations. It was shown that under physiological redox conditions, copper(I) and cisplatin can form large polymers with glutathione. These polymers were capable of transferring copper(I) to apo-Atox1 or to platinum(II) to copper-loaded Atox1. Analysis of the simultaneous binding of copper(I) and platinum(II) to Atox1 was found to occur through the formation of copper–sulfur–platinum bridges, where copper is coordinated by three sulfur atoms and platinum by four sulfur atoms. With the goal of using a simple model to be able to quickly estimate the acid disassociation constants of proteins, PKA17 has been developed and tested. PKA17 is a coarse-grain grid-based method and software tool for accurately and rapidly calculating protein pKa values given an input PDB structure file. During development, parameter fitting was carried out using a compilation of 442 Asp, Glu, His, and Lys residues that had both high-resolution PDB structures and published experimental pKa values available. Applying our PKA17 model, the calculated average unsigned error and RMSD for the residue set were found to be 0.628 and 0.831 pH units, respectively. As a benchmark for comparison, the same residue set was evaluated with the PROPKA software package which resulted in an average unsigned error of 0.761 pH units and an RMSD of 1.063 pH units. Finally, a web interface for the PKA17 software was developed and deployed (http://users.wpi.edu/~jpcvitkovic/pka_calc.html) to make PKA17 available to the wider scientific community.

This thesis explores the British government’s approach to international negotiations concerning nuclear weapons during Harold Wilson’s first two terms of office (1964-1970). It focuses on three distinct but interrelated strands of British nuclear diplomacy: ‘hardware solutions’, the sharing of nuclear weapons between states in the form of a multilateral force; ‘software solutions’, non-physical measures of cooperation, such as consultative and planning arrangements, between alliance members; and a global non-proliferation treaty. In looking at how and why these interrelated policies evolved, this thesis considers party, domestic and international influences on decision-making within the government. It pays particular attention to political and economic events, building on existing diplomatic and strategic accounts of the period.

Tissue cells exhibit varying responses according to the stiffness of their extracellular matrix (ECM). The mechanism of this stiffness sensing is not fully understood; however, it is known that cells probe stiffness by applying intracellular force to the ECM via integrin-mediated focal adhesions. The bonds between integrins and ECM have been described as “catch bonds�, and it is unclear how ECM viscoelasticity affects these bonds. We have observed the effects of ECM stiffness on the binding strength of integrins to ECM ligands by measuring the dissociation force of individual integrin-ligand bonds of 3T3 fibroblasts on collagen-coated polyacrylamide gels using atomic force microscopy. Results show that integrins exhibit higher rates of activation on stiff substrates. Furthermore, increased matrix stiffness results in the occurrence of larger, multi-bond dissociation events, which suggests that substrate stiffness may affect the cellular response by promoting integrin clustering as well as by modulating the maximum possible force between individual integrins and the ECM.

"In this thesis, a cell traction force microscopy method is developed for measuring traction forces of connective tissue cells. This method includes an improved methodology in traction force microscopy of live cells cultured on an elastic substrate. Tissue cells, such as skin and muscle cells respond to the mechanical stimuli of their microenvironment by adhering to their substrate and exerting forces on the proteins of the extracellular matrix (ECM). These forces are called cell traction forces. Fibroblasts are grown on polyacrylamide (PA) gels embedded with fluorescent beads and coated with different types of ECM ligands. Traction forces of NIH 3T3 fibroblasts are calculated from the measured deformations of PA gels by using a 3-D finite element method. The advantages of this method compared to the traditional methods of cell traction force microscopy (CTFM) are that this method takes into account the finite thickness of the substrate by applying a 3-D FEM analysis to reduce the errors of using an infinite half space approximation for a substrate with a finite thickness and that it uses a novel method for embedding the substrate with fluorescent markers that decreases the measurement uncertainties. In our approach fluorescent beads were embedded on the top of substrate instead of getting mixed with the gel. This decreases the effect of out-of-focus fluorescent beads on the measured deformation fields which enhances the accuracy of cell traction force measurements."

Thesis (M.S.)--Boston University

Various traumatic events such as automobile accidents, structure fires, or terrorist attacks result in traumatic and thermal injury. Fire is a destructive force that can alter or destroy evidence, and thermal alterations have negative effects on forensic and anthropological recovery and analysis. Blunt force trauma is particularly difficult to analyze because of the multiple ways in which this trauma appears on a body and the variety of objects that can impact and fracture a bone or the variety of ways a body can impact a blunt surface. As fire is a common way to cover up a crime and blunt force trauma is used as a means to kill or injure an individual, it is necessary to understand the differences between these two types of fractures that can present together on bone. The present study was performed to determine the amount of survivability of traumatic fracture patterns in remains that have been exposed to a burning event. The sample used for this investigation was composed of twenty limbs (forty long bones) from five full-grown, domestic, female sheep (Ovis aries) obtained from a farm in Connecticut. Thirty specimens were traumatized with the head of an Estwing ball peen hammer and ten were left as controls. After specimens were subjected to blunt force trauma, each was radiographed using Computed Tomography. They were then placed in a small structure, 8' x 8', that was constructed to simulate the conditions of a house fire. Each post-burn bone was analyzed based on a number of characteristics. A trauma score of "1" no trauma, "2" ambiguous, and "3" traumatic fractures were given based on these observations. CT scans were examined after bone samples had been analyzed. Again, each specimen's CT scan was given a trauma score ("1" no trauma, "2" ambiguous, and "3" traumatic fractures). Results from the bone analysis on the 30 traumatized and burned specimens revealed that 15 did not have trauma, 2 were ambiguous (i.e., they may have trauma but traumatic characteristics were not distinct), and 13 presented with distinguishable traumatic injury. Comminuted was the most prominent type of fracture, and the next most common fracture was oblique. The majority of traumatic injury was found on the middle portion of the bone. CT examination showed that 12 specimens had suffered traumatic injury. The two analyses were compared and showed an agreement of 83.3% between the trauma scores. Results show that differentiation of traumatic and thermally induced fractures is possible using various fracture characteristics as well as taphonomic indicators to determine the sequence of events.

Thesis (M.S.)--Boston University

Les foldamères sont des architectures moléculaires synthétiques repliées, inspirées par les structures et les fonctions des biopolymères naturels. Le repliement est un processus sélectionné par la nature pour contrôler la conformation de sa machinerie moléculaire afin de réaliser des tâches chimiques ou mécaniques. Durant les dix dernières années de recherche sur les foldamères, des oligomères synthétiques, capables d'adopter des conformations repliées bien définies et prévisibles, comme des hélices, ont été proposés. Les progrès récents ont montré que la synthèse chimique par étapes et le design moléculaire basé sur un squelette oligoamide aromatique permettaient de produire des architectures moléculaires repliées de manière hélicoïdale. La forme du squelette et sa rigidité, des préférences conformationnelles locales, des interactions spécifiques entre monomères éloignés dans une séquence, ainsi que l'action de paramètres externes comme le solvant, ou la présence d'ions peuvent être combinés pour induire une tendance au repliement. Ces architectures sont remarquables car elles peuvent donner lieu à des motifs de repliement qui n'ont pas d'équivalent dans les structures des biopolymères naturels. Par exemple, des hélices dont le diamètre varie le long de la séquence, ou des hélices possédant un centre d'inversion du pas, des hélices en chevrons,... ont été rapportées. Alors que les structures de ces molécules hélicoïdales ont été abondamment caractérisées à l'état solide par cristallographie des rayons X, leur comportement en solution, et surtout le comportement dynamique, est très peu connu. Leurs propriétés mécano-chimiques sont quant à elles inconnues à ce jour. L'objectif du projet est de synthétiser différentes molécules synthétiques hélicoïdales de type oligoamide aromatique et d'obtenir une description détaillée de leur conformation dynamique en solution, ainsi que de leurs propriétés mécano-chimiques, par spectroscopie de force sur molécule unique basée sur l'AFM. / Foldamers are artificial folded molecular architectures inspired by the structures and functions of natural biopolymers. Folding is the process selected by nature to control the conformation of its molecular machinery to carry out chemical functions and mechanical tasks, such as en-zyme catalysis, duplication in nucleic acids, force generation,... During the last decade of research on foldamers, synthetic oligomers able to adopt well- defined and predictable folded conformations, such as helices, have been proposed. Recent progress has shown that stepwise chemical synthesis and molecular design based on aromatic oligoamide backbones enable to produce large helically folded molecular architectures. The shape and stiffness of the backbone, local conformational preferences, specific interactions between distant monomers in sequences, as well as the action of external parameters such as the solvent or the presence of ions, can be combine to induce folding tendency. A remarkable aspect of these architectures is that they can give rise to folded patterns that have no in natural counterparts biopolymer structures. For instance, helices whose diameter varies along the se-quence, helices possessing a handedness inversion centre, herringbone helices have been reported. While the structures of these helical molecules have been well characterized in the solid state by X-ray crystallography, much less is known about their dynamic behavior in solution. Their mechanochemical properties are unknown. The objective of the project is to synthesize various helical nanorchitectures based on an oli-goamide aromatic backbone and to obtain a detailed picture of their dynamical conformation in solution, as well as, their mechanochemical properties, by AFM-based single molecule force spectroscopy.

A question which has arisen clinically is the inability to generate adequate vertical force during the second half of the stance phase in cerebral palsy gait. Neither the mechanism nor the consequences of this inability are understood. It implies that the centre of mass (CoM) is inadequately supported with the potential for collapse of the limb in single support. Normal walking is achieved by the sophisticated control of the neuromuscular and skeletal systems with the purpose of advancing the body with minimum energy expenditure. These control systems are affected by damage to the brain in children with cerebral palsy and result in a multitude of problems which affect their gait making it difficult to determine cause and effect. This study aimed to improve the understanding of the ground reaction forces and motion of the CoM. Objectives The principle objectives were to analyse the supporting forces of the CoM during gait in normal adults, children, and children with diplegic cerebral palsy, by examining the inter-relationships of the vertical and horizontal components of the ground reaction force with the vertical component of motion and temporal parameters of the CoM. Design The study of adults and children’s data was both prospective and retrospective. The study of cerebral palsy data was retrospective. A new software programme was developed to extract specific gait parameters from both normal and cerebral palsy gait patterns. A novel approach to analyse the interaction of motion and force data in normal walking was subsequently developed. Background In normal gait, the vertical component of the ground reaction force forms a double hump where both humps are equal in magnitude and greater than body weight. It is widely accepted that the first hump (FZ1) is associated with deceleration of the downward motion of the CoM as the foot “impacts” the ground and the second hump (FZ2) is the action of “push off” as the body is propelled upwards and forwards. Walking requires force contributions from both legs but traditionally computed three-dimensional (3D) gait analysis packages presents the force data with both legs superimposed, rather than sequentially in time. This gives the impression that there is no period of overlap of the forces and thus ignores the critically important period where the CoM is transferred from one leg to the other during double support. By changing the presentation to view it sequentially in time, plus superimposing the CoM kinematics onto the same scale allowed their interactions to be observed and objectively measured. Methods The kinematic and kinetic data of 53 normal adults, 33 normal children, and 57 diplegic cerebral palsy children were acquired for the study. A new gait cycle, based on CoM motion, was defined to allow analysis of the forces in relation to CoM motion. Software was developed to extract specified parameters from the gait data. Impulse calculations over specific periods (based on the vertical motion of the CoM) allowed analysis of the vertical force contribution of each leg to the vertical support of the CoM. Results The results showed that inadequate generation of vertical force in children with diplegic cerebral palsy was widespread. In approximately 40% of such children there was a reduced ability to generate an adequate FZ2, which resulted in a reduced ability to control of the descent velocity of the CoM. The mean reduction in descent velocity in cerebral palsy was only 54% compared to 86% in adults. Integration of the vertical force and motion of the CoM showed that FZ2 was associated with controlling the descent velocity of the CoM. This reverses the traditionally accepted concept of “impact” and is contrary to the belief that FZ2 is associated with ‘push off’. Conclusions and Relevance This study emphasises the importance of the role of the supporting leg in the second half of stance. Failure to generate an adequate FZ2, which is currently ignored in clinical practice, should be given priority in patient management. This new knowledge has significant implications from a clinical perspective, not only in diplegic cerebral palsy, but in pathologies such as amputees, spina-bifida, and other neuro-muscular conditions.