Biomechanical construction principles of the human hip joint in frontal plane

The prognosis of hip joint function is only to determine unsatisfactory on the base of the knowledges of anatomy by means of inspection or angles and distances from X-rays as well as on the base of models known for the biomechanic of hip. The term "normal anatomical" hip structure is analysed with respect to functional biomechanical influences on its macroscopic design in frontal plane. It is shown to interpret the macroscopic hip design as result of an effective arrangement of centre of rotation and muscle forces which a minimum on energy needing for its function. A mathematical equation describes the skeleton-muscle-system hip biomechanically. This new connection between angles and distances as well as first easy consequences are proofed on a-p-hip radiographs of 53 normal adults.     

Of pubs and platforms

This article argues for a more explicit concern with sociality in anthropology, illustrated through a study of one of the oldest English platforms for sociality: the English pub. Using an approach derived from the study of social media, the pub is analysed in terms of the balance between structural (mainly commercial) forces and agency (mainly the desire for particular kinds of sociality). Following an introduction to the English pub, the article considers how pubs exert control over which population they serve. The next section, shows how groups of people colonize pubs, regardless of the pub's intentions. This is followed by a discussion of the various responses by pubs to this colonization. The final section, ‘Scalable sociality’, demonstrates how these processes combine to produce a phenomenon called scalable sociality, which is also a definition of social media: a series of platforms that can be sited along various scales and parameters of sociality. This is important because a similar tension between, on the one hand, commercial or state forces and, on the other hand, the development of new forms of sociality is increasingly common within many topics studied by anthropologists.     

The mechanical environment of chondrocytes in articular cartilage

There is a growing literature concerning chondrocyte responses to mechanical loading, but relatively little is known about the mechanical environment these cells experience in a living joint. Calculations indicate that high forces are applied to limb joints whenever the joints are flexed, because flexion can cause body weight to act on long lever arms compared to the joint centre, whereas the muscles which extend the joint act on much shorter lever arms. As a result, joint reaction forces (which compress the cartilage) can rise to 3-6 times body weight during activities such as stair climbing. Articular cartilage tends to spread this load evenly over the joint surface, but is too thin to do this well, and compressive stresses can rise to 10-20 MPa. Within cartilage, matrix stresses vary locally, possibly as a result of variation in composition or undulations in the subchondral bone, and further modifications of stress occur within each chondron. Articular cartilage is a fibrous solid and cells within it are deformed by mechanical loading rather than subjected to a hydrostatic pressure. The mechanical environment of chondrocytes can best be reproduced in vitro by direct compression of the articular surface of cartilage which is supported naturally by adjacent cartilage and subchondral bone.     

Photolysis of alpha-xylyl chlorides: an efficient deep-UV photoinitiating system for radical and cationic polymerization.

Photoacid generators (PAG) are chemical systems where light absorption renders strong acid formation, typically with quantum yields greater than one. Many compounds bearing halogen atoms are reported to produce hydrogen halides upon photolysis. Here, alpha-chloroxylene derivatives (ortho, meta and para) were subject of a photolysis study in order to: (i) determine the operative mechanism, (ii) identify the products formed and (iii) quantify the amount of HCl formed. Product structure and quantum yields of HCl formation where determined for the photolysis of alpha-chloro-o-xylene (1), alpha-chloro-m-xylene (2), alpha-chloro-p-xylene (3), alpha, alpha'-dichloro-o-xylene (4), alpha, alpha'-dichloro-m-xylene (5) and alpha, alpha'-dichloro-p-xylene (6) in apolar (benzene, cumene, ethylbenzene, toluene and isooctane) and polar (methanol, n-propanol, isopropyl alcohol) solvents. Some of these compounds were analysed by laser flash photolysis in argon-purged isooctane as solvent to examine the possible reaction intermediates involved. The observed products are derived from typical radical reactions like recombination, dimerization and hydrogen abstraction from the starting compound or from solvents. The formation of HCl is expected as the result of C-Cl homolysis followed by hydrogen abstraction by chlorine atom. The results showed yields ranging from 1.2 to 18, depending on the conditions used. These numbers indicate the potential use of these compounds as PAG systems for the deep UV region.     

The SpoMBe pathway drives membrane bending necessary for cytokinesis and spore formation in yeast meiosis

Precise control over organelle shapes is essential for cellular organization and morphogenesis. During yeast meiosis, prospore membranes (PSMs) constitute bell-shaped organelles that enwrap the postmeiotic nuclei leading to the cellularization of the mother cell's cytoplasm and to spore formation. Here, we analysed how the PSMs acquire their curved bell-shaped structure. We discovered that two antagonizing forces ensure PSM shaping and proper closure during cytokinesis. The Ssp1p-containing coat at the leading edge of the PSM generates a pushing force, which is counteracted by a novel pathway, the spore membrane-bending pathway (SpoMBe). Using genetics, we found that Sma2p and Spo1p, a phospholipase, as well as several GPI-anchored proteins belong to the SpoMBe pathway. They exert a force all along the membrane, responsible for membrane bending during PSM biogenesis and for PSM closure during cytokinesis. We showed that the SpoMBe pathway involves asymmetric distribution of Sma2p and does not involve a GPI-protein-containing matrix. Rather, repulsive forces generated by asymmetrically distributed and dynamically moving GPI-proteins are suggested as the membrane-bending principle.     

The Isomerization of Δ5-Androstene-3,17-dione by the Human Glutathione Transferase A3-3 Proceeds via a Conjugated Heteroannular Diene Intermediate

The seemingly simple proton abstraction reactions underpin many chemical transformations, including isomerization reactions, and are thus of immense biological significance. Despite the energetic cost, enzyme-catalyzed proton abstraction reactions show remarkable rate enhancements. The pathways leading to these accelerated rates are numerous and on occasion partly enigmatic. The isomerization of the steroid Δ⁵-androstene-3,17-dione by the glutathione transferase A3-3 in mammals was investigated to gain insight into the mechanism. Particular emphasis was placed on the nature of the transition state, the intermediate suspected of aiding this process, and the hydrogen bonds postulated to be the stabilizing forces of these transient species. The UV-visible detection of the intermediate places this species in the catalytic pathway, whereas fluorescence spectroscopy is used to obtain the binding constant of the analog intermediate, equilenin. Solvent isotope exchange reveals that proton abstraction from the substrate to form the intermediate is rate-limiting. Analysis of the data in terms of the Marcus formalism indicates that the human glutathione transferase A3-3 lowers the intrinsic kinetic barrier by 3 kcal/mol. The results lead to the conclusion that this reaction proceeds through an enforced concerted mechanism in which the barrier to product formation is kinetically insignificant.     

Action understanding and active inference

We have suggested that the mirror-neuron system might be usefully understood as implementing Bayes-optimal perception of actions emitted by oneself or others. To substantiate this claim, we present neuronal simulations that show the same representations can prescribe motor behavior and encode motor intentions during action?Cobservation. These simulations are based on the free-energy formulation of active inference, which is formally related to predictive coding. In this scheme, (generalised) states of the world are represented as trajectories. When these states include motor trajectories they implicitly entail intentions (future motor states). Optimizing the representation of these intentions enables predictive coding in a prospective sense. Crucially, the same generative models used to make predictions can be deployed to predict the actions of self or others by simply changing the bias or precision (i.e. attention) afforded to proprioceptive signals. We illustrate these points using simulations of handwriting to illustrate neuronally plausible generation and recognition of itinerant (wandering) motor trajectories. We then use the same simulations to produce synthetic electrophysiological responses to violations of intentional expectations. Our results affirm that a Bayes-optimal approach provides a principled framework, which accommodates current thinking about the mirror-neuron system. Furthermore, it endorses the general formulation of action as active inference.     

Elegant‐crested Tinamous Eudromia elegans do not synchronize head and leg movements during head‐bobbing

Head‐bobbing is the fore–aft movement of the head relative to the body during terrestrial locomotion in birds. It is considered to be a behaviour that helps to stabilize images on the retina during locomotion, yet some studies have suggested biomechanical links between the movements of the head and legs. This study analysed terrestrial locomotion and head‐bobbing in the Elegant‐crested Tinamou Eudromia elegans at a range of speeds by synchronously recording high‐speed video and ground reaction forces in a laboratory setting. The results indicate that the timing of head and leg movements are dissociated from one another. Nonetheless, head and neck movements do affect stance duration, ground reaction forces and body pitch and, as a result, the movement of the centre of mass in head‐bobbing birds. This study does not support the hypothesis that head‐bobbing is itself constrained by terrestrial locomotion. Instead, it suggests that visual cues are the primary trigger for head‐bobbing in birds, and locomotion is, in turn, constrained by a need for image stabilization and depth perception.     

Cancer during adolescence: negative and positive consequences reported three and four years after diagnosis

Persons diagnosed with cancer during adolescence have reported negative and positive cancer-related consequences two years after diagnosis. The overall aim was to longitudinally describe negative and positive cancer-related consequences reported by the same persons three and four years after diagnosis. A secondary aim was to explore whether reports of using vs. not using certain coping strategies shortly after diagnosis are related to reporting or not reporting certain consequences four years after diagnosis. Thirty-two participants answered questions about coping strategies shortly after diagnosis and negative and positive consequences three and four years after diagnosis. Answers about consequences were analysed with content analysis, potential relations between coping strategies and consequences were analysed by Fisher's exact test. The great majority reported negative and positive consequences three and four years after diagnosis and the findings indicate stability over time with regard to perceived consequences during the extended phase of survival. Findings reveal a potential relation between seeking information shortly after diagnosis and reporting a more positive view of life four years after diagnosis and not using fighting spirit shortly after diagnosis and not reporting good self-esteem and good relations four years after diagnosis. It is concluded that concomitant negative and positive cancer-related consequences appear stable over time in the extended phase of survival and that dialectical forces of negative and positive as well as distress and growth often go hand-in-hand after a trauma such as cancer during adolescence.     

Investigating physical cognition in rooks, Corvus frugilegus

Although animals (particularly tool-users) are capable of solving physical tasks in the laboratory , the degree to which they understand them in terms of their underlying physical forces is a matter of contention. Here, using a new paradigm, the two-trap tube task, we report the performance of non-tool-using rooks. In contrast to the low success rates of previous studies using trap-tube problems , seven out of eight rooks solved the initial task, and did so rapidly. Instead of the usual, conceptually flawed control, we used a series of novel transfer tasks to test for understanding. All seven transferred their solution across a change in stimuli. However, six out of seven were unable to transfer to two further tasks, which did not share any one visual constant. One female was able to solve these further transfer tasks. Her result is suggestive evidence that rooks are capable of sophisticated physical cognition, if not through an understanding of unobservable forces , perhaps through rule abstraction. Our results highlight the need to investigate cognitive mechanisms other than causal understanding in studying animal physical cognition.     

Variation of reaction dynamics for OH hydrogen abstraction from glycine between ab initio levels of theory

The variation in reaction dynamics of OH hydrogen abstraction from glycine between HF, MP2, CCSD(T), M05-2X, BHandHLYP, and B3LYP levels was demonstrated. The abstraction mode shows distinct patterns between these five levels and determines the barrier height, and the spin density transfer between OH radical and glycine. These differences are mainly resulted from the spin density distribution and geometry of the alpha carbon during the abstraction. The captodative effect which is commonly believed as one of the major factors to stabilize the caron-centered radical can only be observed in DFT levels but not in HF and MP2 levels. Difference in the abstraction energy were found in these calculation levels, by using the result of CCSD(T) as reference, B3LYP, BHandHLYP, and M05-2X underestimated the reaction barrier about 5.1, 0.1, and 2.4 kcal mol^-1, while HF and MP2 overestimated 19.1 kcal mol^-1 and 1.6 kcal mol^-1, respectively. These differences can be characterized by the vibration mode of imaginary frequency of transition states, which indicates the topology around transition states and determines reaction barrier height. In this model system, BHandHLYP provides the best prediction of the energy barrier among those tested methods.     

Stability threshold of a tissue system

Studies of changes in the cells adhesive force during spontaneous and induced cancerogenesis, as well as under the effect of cancerogenesis promotors permits to reveal the cells adhesion forces critical values which separate tissue states stable and unstable to blastomogenesis. These data are analysed proceeding from the concepts on generalized cooperative transitions in the membranes and their role in the control over biological systems. It is taken into account that the membranes and cytoskeleton elements are the most important systems of the tissue mechanical integration, and phase transitions proceeding in them must be reflected in the tissue mechanical properties.     

Does substrate quality influence take-off decisions in Common Starlings?

1. An instrumented perch was used to measure the reaction forces during take-off of starlings from perches of three thicknesses. There was no significant decrease in reaction force with decreasing perch thickness; however, over the range of perch sizes there was a 10-fold decrease in safety factor and a 400-fold increase in the energy of deflection of the thinnest perch.
2. The implications of these results are that birds do not change their take-off strategy when faced with perches of variable thickness and that, as a result, leaps from thin perches are very much less efficient than those from thicker perches. Birds appear not to adjust their leaping behaviour to minimize the risk of substrate failure during take-offs.     

MECHANICAL PROPERTIES OF SEA URCHIN EGGS III. VISCO-ELASTICITY OF THE CELL SURFACE

When a sea urchin egg was compressed between two parallel plates, the force required to keep the distance between the plates constant gradually decreased with time. The contours of the compressed egg were different from the contours expected from the assumption that the surface forces are uniform over the entire surface. The surface forces of the egg without deformation computed from the area of the cell surface in contact with the substratum, the density of the egg and its size were 0.02–0.04 dynes/cm in Hemicentrotus pulcherrimus. Larger values were obtained in eggs during compression. Surface forces, which were computed from measurements of the form of the egg and the applied force when the egg was deformed by a rod and a plate supporting the egg, increased as the deformation increased.
From these results, it was concluded that the cell surface is visco-elastic in sea urchin eggs.     

Actomyosin-mediated statolith positioning in gravisensing plant cells studied in microgravity

The positioning and gravity-induced sedimentation of statoliths is crucial for gravisensing in most higher and lower plants. In positively gravitropic rhizoids and, for the first time, in negatively gravitropic protonemata of characean green algae, statolith positioning by actomyosin forces was investigated in microgravity (<10(-4) g) during parabolic flights of rockets (TEXUS/MAXUS) and during the Space-Shuttle flight STS 65. In both cell types, the natural position of statoliths is the result of actomyosin forces which compensate the statoliths' weight in this position. When this balance of forces was disturbed in microgravity or on the fast-rotating clinostat (FRC), a basipetal displacement of the statoliths was observed in rhizoids. After several hours in microgravity, the statoliths were loosely arranged over an area whose apical border was in the same range as in 1 g, whereas the basal border had increased its distance from the tip. In protonemata, the actomyosin forces act net-acropetally. Thus, statoliths were transported towards the tip when protonemata were exposed to microgravity or rotated on the FRC. In preinverted protonemata, statoliths were transported away from the tip to a dynamically stable resting position. Experiments in microgravity and on the FRC gave similar results and allowed us to distinguish between active and passive forces acting on statoliths. The results indicate that actomyosin forces act differently on statoliths in the different regions of both cell types in order to keep the statoliths in a position where they function as susceptors and initiate gravitropic reorientation, even in cells that had never experienced gravity during their growth and development.     

A Force Balance Model of Early Spindle Pole Separation in Drosophila Embryos

The formation and function of the mitotic spindle depends upon force generation by multiple molecular motors and by the dynamics of microtubules, but how these force-generating mechanisms relate to one another is unclear. To address this issue we have modeled the separation of spindle poles as a function of time during the early stages of spindle morphogenesis in Drosophila embryos. We propose that the outward forces that drive the separation of the spindle poles depend upon forces exerted by cortical dynein and by microtubule polymerization, and that these forces are antagonized by a C-terminal kinesin, Ncd, which generates an inward force on the poles. We computed the sum of the forces generated by dynein, microtubule polymerization, and Ncd, as a function of the extent of spindle pole separation and solved an equation relating the rate of pole separation to the net force. As a result, we obtained graphs of the time course of spindle pole separation during interphase and prophase that display a reasonable fit to the experimental data for wild-type and motor-inhibited embryos. Among the novel contributions of the model are an explanation of pole separation after simultaneous loss of Ncd and dynein function, and the prediction of a large value for the effective centrosomal drag that is needed to fit the experimental data. The results demonstrate the utility of force balance models for explaining certain mitotic movements because they explain semiquantitatively how the force generators drive a rapid initial burst of pole separation when the net force is great, how pole separation slows down as the force decreases, and how a stable separation of the spindle poles characteristic of the prophase steady state is achieved when the force reaches zero.     

Patterns of natural selection on morphology of male and female collared flycatchers (Ficedula albicollis)

Natural selection may act in different directions among years, life stages, or classes of individuals. Fluctuating selection of this kind is potentially an important mechanism by which additive genetic variation for quantitative traits is maintained, and can prevent populations reaching local adaptive peaks. We analysed natural selection acting on three morphological traits of male and female collared flycatchers via both fecundity and survival, using 15 years' data from a large isolated population on Godand, Sweden. We particularly investigated variation in the direction and magnitude of selection acting: (1) among years over the study period; (2) on different life stages and (3) the consistency of observed patterns of selection with sexual size dimorphism (SSD) in this population. We found little evidence of natural selection on these traits over the study period. Evidence for directional, stabilizing and disruptive selection was found for some year-trait combinations, but these patterns were inconsistent with respect to both the magnitude and form of selection found. Consequently, our results, based on the detailed analysis of natural selection in a large wild population over a period of 15 years, provide evidence for the common assumption that forces of selection acting on quantitative traits are generally weak. They are also consistent with the suggestion that environmental stability is an important determinant of the degree to which organisms fit their environment.     

Study of micromotion in modular acetabular components during gait and subluxation: a finite element investigation

Polyethylene wear after total hip arthroplasty may occur as a result of normal gait and as a result of subluxation and relocation with impact. Relocation of a subluxed hip may impart a moment to the cup creating sliding as well as compression at the cup liner interface. The purpose of the current study is to quantify, by a validated finite element model, the forces generated in a hip arthroplasty as a result of subluxation relocation and compare them to the forces generated during normal gait. The micromotion between the liner and acetabular shell was quantified by computing the sliding track and the deformation at several points of the interface. A finite element analysis of polyethylene liner stress and liner/cup micromotion in total hip arthroplasty was performed under two dynamic profiles. The first profile was a gait loading profile simulating the force vectors developed in the hip arthroplasty during normal gait. The second profile is generated during subluxation and subsequent relocation of the femoral head. The forces generated by subluxation relocation of a total hip arthroplasty can exceed those forces generated during normal gait. The induced micromotion at the cup polyethylene interface as a result of subluxation can exceed micromotion as a result of the normal gait cycle. This may play a significant role in the generation of backsided wear. Minimizing joint subluxation by restoring balance to the hip joint after arthroplasty should be explored as a strategy to minimize backsided wear.