Phenotypic Plasticity and Selection: Nonexclusive Mechanisms of Adaptation.

Selection and plasticity are two mechanisms that allow the adaptation of a population to a changing environment. Interaction between these nonexclusive mechanisms must be considered if we are to understand population survival. This review discusses the ways in which plasticity and selection can interact, based on a review of the literature on selection and phenotypic plasticity in the evolution of populations. The link between selection and phenotypic plasticity is analysed at the level of the individual. Plasticity can affect an individual's response to selection and so may modify the end result of genetic diversity evolution at population level. Genetic diversity increases the ability of populations or communities to adapt to new environmental conditions. Adaptive plasticity increases individual fitness. However this effect must be viewed from the perspective of the costs of plasticity, although these are not easy to estimate. It is becoming necessary to engage in new experimental research to demonstrate the combined effects of selection and plasticity for adaptation and their consequences on the evolution of genetic diversity.

A physically based trunk soft tissue modeling for scoliosis surgery planning systems.

One of the major concerns of scoliotic patients undergoing spinal correction surgery is the trunk's external appearance after the surgery. This paper presents a novel incremental approach for simulating postoperative trunk shape in scoliosis surgery. Preoperative and postoperative trunk shapes data were obtained using three-dimensional medical imaging techniques for seven patients with adolescent idiopathic scoliosis. Results of qualitative and quantitative evaluations, based on the comparison of the simulated and actual postoperative trunk surfaces, showed an adequate accuracy of the method. Our approach provides a candidate simulation tool to be used in a clinical environment for the surgery planning process.

Thigh muscles' responses caused by a single combined aerobic and resistance training session in healthy young men.

The aim of this study was to understand the amplitude and localization of neuromuscular response induced by a training session combining an aerobic and a resistance component. Ten healthy men completed a single session of combined (aerobic and resistance) and aerobic only training, in a randomized order. Surface electromyographic activity and torque obtained during maximal voluntary and electrically evoked contractions of the knee extensor muscles were analyzed to distinguish peripheral from central adaptations. The isometric torque developed by the knee extensor muscles during maximal voluntary contraction decreased significantly following a single session of both combined (-9.2%, p=0.043) and aerobic (-9.6%, p=0.005) training. This was accompanied by a decrease in central activation of the knee extensor muscles after each training session (respectively 2.9, p=0.005 and 1.8% p=0.040) as indicated by twitch interpolation technique. After the combined training protocol, the peak torque of the twitch significantly increased by 6.8% (p=0.046), whereas it decreased by 17.3% (p=0.016) after the aerobic training protocol. The present study demonstrates that the decrease in torque production is similar after a single combined training session or after an aerobic training session of the same duration. Both central and peripheral mechanisms could explain the decrease of torque.

Why vehicle design matters: Exploring the link between line-of-sight, driving posture and risk factors for injury.

Load haul dump (LHD) vehicles have been involved in workplace accidents resulting in fatal injuries and LHD operators also report high rates of musculoskeletal injury. Poor line-of-sight (LOS) and awkward postures adopted by the LHD operator increase the risk of driving related accidents and musculoskeletal injury. The purpose of this case study was to simultaneously measure point of regard (POR), driving posture and sitting position during the operation of a LHD in an underground mining environment in order to further understand the link between these variables and the design of the LHD vehicle. A 5.35 m3 bucket LHD vehicle was used and several driving tasks were analysed. The case study results showed that despite the driving task, the operator looked to the left side of the vehicle 65% of the time. Postural implications include extreme neck rotation (> 40 degrees) for 85% of the work cycle and the average peak compression at L4/L5 was 1843N. Despite changes in driving posture the average center of pressure location for the seated operator moved very little; however changes in peak pressure were observed. The design of the LHD vehicle dictated what the operator could see, which had a direct influence on driving postures adopted by the operator and resulted in several risk factors for musculoskeletal injury.

Predicting discomfort scores reported by LHD operators using whole-body vibration exposure values and musculoskeletal pain scores.

BACKGROUND: Laboratory studies have typically been used to establish a relationship between whole body vibration (WBV) magnitude, frequency, exposure duration and reported discomfort. However, the relationship between subjective reports of discomfort, and predicted comfort response according to International Standards Organization (ISO) 2631-1, predicted health risks according to ISO 2631-1 and reported musculoskeletal discomfort has not been examined. The purpose here was to compare discomfort values predicted by ISO 2631-1 with the subjective discomfort reported by nine Load-haul-dump (LHD) operators during typical operating conditions. METHODS: Vibration exposure at the operator/seat interface was measured and processed, for one-hour duration, according to criteria established in ISO 2631-1. Vibration total values were determined for 1-minute exposure periods and the LHD operators provided a discomfort score associated with the same vibration exposure period. A linear regression analysis and correlation was carried out to determine the strength of the relationship between the predicted subjective reports of discomfort, ISO 2631-1 discomfort, objectively measured acceleration levels and reported musculoskeletal discomfort. FINDINGS: Reported discomfort was poorly correlated to ISO discomfort scores (r=0.1799). Vibration exposure values and Musculo-Skeletal Disorder (MSD) variables were related to both ISO 2631-1 discomfort and to reported discomfort. The MSD scores produced stronger relationships with reported discomfort scores than did the vibration exposure values.

Molecular evolution within and between self-incompatibility specificities.

Genes under multiallelic balancing selection have sharply contrasted evolutionary dynamics across timescales, with much longer coalescence time among functionally distinct allelic lines but much shorter coalescence time among gene copies within allelic lines as compared with the genomic background. In this paper, we combine theoretical and empirical approaches to investigate patterns of molecular evolution within and between self-incompatibility (SI) specificities. We first use numerical simulations to investigate coalescence times within allelic lines in a subdivided population for a sporophytic SI system. We then report on a comprehensive analysis of nucleotide polymorphism among gene copies within five distinct allelic lines in the closely related Arabidopsis halleri and Arabidopsis lyrata. In line with our model predictions, we find that the observed level of polymorphism among gene copies was generally low but differed among allelic lines. The data provide compelling direct evidence for recombination and/or gene conversion not only within the two most recessive allelic lines but also between two closely related but distinct allelic lines, suggesting that recombination at the Arabidopsis SI locus is possible in the absence of large sequence divergence among haplotypes. We observed shared polymorphic sites between the two species in one allelic line and strikingly similar haplotypes in another allelic line. We discuss whether convergent evolution may have led to this pattern and suggest that these observations are consistent with ongoing or very recent introgression, as previously documented.

New model for magnetism in ultrathin fcc Fe on Cu(001).

Using soft-x-ray resonant magnetic scattering in combination with first-principles calculations for noncollinear magnetic configurations we present a new model of the magnetism in ultrathin fcc Fe films on Cu(001). We find the presence of blocks with robust magnetic structure, while the relative directions of the moments of different blocks are sensitive to the detailed atomic structure and temperature. The magnetic noncollinearity is directly demonstrated, which has not been possible so far.

Charge and orbital correlations at and above the Verwey phase transition in magnetite.

The subtle interplay among electronic degrees of freedom (charge and orbital orderings), spin and lattice distortion that conspire at the Verwey transition in magnetite (Fe3O4) is still a matter of controversy. Here, we provide compelling evidence that these electronic orderings are manifested as a continuous phase transition at the temperature where a spin reorientation takes place at around 130 K, i.e., well above TV approximately 121 K. The Verwey transition seems to leave the orbital ordering unaffected whereas the charge ordering development appears to be quenched at this temperature and the temperature dependence below TV is controlled by the lattice distortions. Finally, we show that the orbital ordering does not reach true long range (disorder), and the correlation length along the c-direction is limited to 100 angstroms.

When exposed to challenged ventilation, those with a history of LBP increase spine stability relatively more than healthy individuals.

OBJECTIVE: To determine if spine stability would be affected by the competing demands of simultaneous challenged ventilation and supporting a hand-held load. DESIGN: Subjects were their own controls in a repeated measures design where a single task was repeated, once in a different condition, in a random order. BACKGROUND: Muscle stiffness influences spine stability. The same muscles that contribute to spine stability assist in challenged breathing. We hypothesized that a challenged ventilation task would place low back pain (LBP) sufferers at risk of spine instability. METHODS: Subjects (14 normal; 14 with low back pain) performed two trials with a 22kg hand-held weight and the trunk angled forward at 30 degrees . One trial was of 60s duration while breathing ambient air, the other of 70s duration, while breathing 10% carbon dioxide. Spine stability and compression were quantified, using an EMG assisted optimization model in both trials. FINDINGS: Contrary to expectation, spine stability increased during the challenged breathing trials compared to the ambient air condition for subjects with a history of low back pain when abdominal muscle activity was accounted for as a covariate. INTERPRETATION: Subjects with a history of low back pain had higher stability in challenged breathing trials, indicating that some active mechanism protects the spine for the LBP groups in challenging situations. This may be to provide some margin of safety for damaged passive tissues but could be adversely affected by fatigue in the longer term.

Depth magnetization profile of a perpendicular exchange coupled system by soft-x-ray resonant magnetic reflectivity.

The magnetic profile across the interface of a perpendicular exchange coupled [NiO/CoO]3/Pt-Co/Pt(111) system is investigated. The magneto-optic Kerr effect reveals a strong coupling between the antiferromagnetic (AFM) oxide and the ferromagnetic (FM) Pt-Co layer, by an increasing coercivity and a rotation of the easy magnetization axis of the FM layer along the AFM spins. Soft x-ray resonant magnetic reflectivity is used to probe the spatial distribution of the out-of-plane magnetization inside the oxide above its ordering temperature. It extends over 1 nm and exhibits a change of sign.

Surface effects on the orbital order in the single-layered manganite La0.5Sr1.5MnO4.

The question of how bulk electronic order is terminated at a surface is an intriguing one, and one with possible practical implications--for example in nanoscaled systems that may be characterized by their surface behaviour. One example of such order is orbital order, and in principle it should be possible to probe the termination of this order with surface X-ray scattering. Here, we report the first observation of the scattering arising from the termination of bulk orbital order at the surface of a crystal--so-called 'orbital truncation rods'. The measurements, carried out on a cleaved perovskite, La(0.5)Sr(1.5)MnO(4), reveal that whereas the crystallographic surface is atomically smooth, the orbital 'surface', which is observed through the atomic displacements caused by the orbital order, is much rougher, with a typical scale of the surface roughness of approximately 7 degrees A. Interestingly, the temperature dependence of this scattering shows evidence of a surface-induced second-order transition.

Postural implications of obtaining line-of-sight for seated operators of underground mining load-haul-dump vehicles.

Operators of load-haul-dump (LHD) vehicles use awkward postures that may be held statically and at extreme ranges of motion for long shift periods to spot hazards in underground mining. This study examined postural variables associated with three amounts of seat rotation intended to maximize line-of-sight during forward driving. Three different models, representing the 1st, 50th and 99th percentile male for height and weight, were positioned with appropriate hand and foot constraints in the virtual LHD cab modelled in Classic JACK v4.0. A total of 15 virtual movement strategies were developed to model the postural behaviour of typical workers and each virtual subject was tested, first with the seat in a neutral 0 degrees position and then with it rotated counter-clockwise to 20 degrees and 45 degrees . Results revealed that reductions in trunk rotation, trunk lateral bend and neck rotation were associated with the seat rotation intervention. The general relationship observed was that as seat rotation increased, view of critical visual attention locations and visible line-of-sight area increased while postural load variables decreased. For the most part, 20 degres of seat rotation was beneficial but 45 dgrees produced significantly greater changes to postural load and visible visual attention locations.

Direct observation of oxygen superstructures in manganites.

We report the observation of superstructures associated with the oxygen 2p states in two prototypical manganites using x-ray diffraction at the oxygen K edge. In the stripe order system Bi0.31Ca0.69MnO3, hole-doped O states are orbitally ordered, at the same propagation vector as the Mn orbital ordering, but no oxygen charge stripes are found at this periodicity. In La7/8Sr1/8MnO3, we observe a 2p charge ordering described by alternating hole-poor and hole-rich MnO planes that is consistent with some of the recent predictions.

Cognitive behaviour therapy and medication in the treatment of obsessive-compulsive disorder.

OBJECTIVE: To compare cognitive behaviour therapy (CBT) with CBT plus medication; medication alone; and placebo in the treatment of adult obsessive-compulsive disorder (OCD). METHOD: Forty-eight participants (43 completers) were recruited into two protocols. In the first protocol, 21 people with OCD were randomly allocated to either a standard medication (fluvoxamine) or standard placebo condition for a 5-month period. Both these groups subsequently received CBT for a further 5 months. In the second protocol, 22 people with OCD received CBT, one group was already stabilized on an antidepressant of choice; the second group was drug naïve. RESULTS: All active treatments, but not the placebo, showed clinical improvement. There was no difference in treatment response to CBT regardless of whether participants had previously received medication or placebo. CONCLUSION: CBT has a more specific antiobsessional effect than medication but CBT plus medication shows greatest overall clinical improvement in mood.

Charge-transfer excitations in the model superconductor HgBa(2)CuO(4+delta).

We report a Cu -edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa(2)CuO(4+delta) at optimal doping (T(c)=96.5 K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly dispersive (<0.5 eV) electron-hole excitations, including a mode at 2 eV. The observation of this 2 eV excitation suggests the existence of a remnant charge-transfer gap deep in the superconducting phase. Quite generally, our results, which include additional data for the Mott insulator La(2)CuO(4), demonstrate the importance of exploring the incident photon-energy dependence of the RIXS cross section.

[3D cellular models: a powerful access to cutaneous physiology and to innovative developments of cosmetic active compounds]. / Les modèles cellulaires 3D: un accès puissant à la physiologie cutanée et aux développements innovants de principes actifs cosmétiques.

Two different anti-ageing cosmetic actives based respectively, on dermal compartment regeneration and on dermoepidermal reinforcement, have been developed using tissular engineering models. Conjointly use of different innovative three-dimensional models such as reconstructed dermis and skin built with human cells coming from variable aged donors allowed first, a better understanding of matrix modifications due to ageing and second, the screening of active ingredients highly targeted to reverse observed damages. The validity of such three-dimensional models has been then confirmed by in vivo studies on healthy volunteers.

d-d excitations in manganites probed by resonant inelastic x-ray scattering.

We report a study of electronic excitations in manganites exhibiting a range of ground states, using resonant inelastic x-ray scattering (RIXS) at the Mn K edge. Excitations with temperature dependent changes correlated with the magnetism were observed as high as 10 eV. By calculating Wannier functions, and finite-q response functions, we associate this dependence with intersite d-d excitations. The calculated dynamical structure factor is found to be similar to the RIXS spectra.

Soft x-ray resonant diffraction study of magnetic and orbital correlations in a manganite near half doping.

We have utilized resonant x-ray diffraction at the Mn L(II,III) edges in order to directly compare magnetic and orbital correlations in Pr0.6Ca0.4MnO3. Comparing the widths of the magnetic and orbital diffraction peaks, we find that the magnetic correlation length exceeds that of the orbital order by nearly a factor of 2. Furthermore, we observe a large (approximately 3 eV) spectral weight shift between the magnetic and orbital resonant line shapes, which cannot be explained within the classic Goodenough picture of a charge-ordered ground state. To explain the shift, we calculate the orbital and magnetic resonant diffraction line shapes based on a relaxed charge-ordered model.

On the implications of interpreting the stability index: a spine example.

Quantifying the stability of the spinal column offers a perspective on the effectiveness of the motor control strategy to ensure a stable spine--and minimize the risk of injury from experiencing an unstable event. There are essentially three energy based methods of calculating a stability index for the lumbar spine. All three methods involve mathematical manipulation of an 18 x 18 Hessian matrix. The purpose of this paper was to consider the mathematical implications for the three methods of determining a single stability index, and examine the effects of biological factors such as muscle activation in each of these methods. The first approach computes the Hessian's determinant and is thought to represent a more global or "average" perspective on stability. A second approach computes the smallest eigenvalue of the Hessian matrix to determine the weakest link of the spine. The final method determines an average critical stiffness difference for the spine and is intended to effectively determines how far a human spine is from instability, and allows comparison between tasks. This study shows that the same interpretation of stability is achieved via all three computational approaches--they agree as to whether the spine is stable or not. However they appear to differ in their sensitivity to the effect of muscle activation patterns.