Effect of 20 mph speed limits on traffic injuries in Edinburgh, UK: a natural experiment and modelling study.

INTRODUCTION: There is limited research evaluating 20 mph speed limit interventions, and long-term assessments are seldom conducted either globally or within the UK. This study evaluated the impact of the phased 20 mph speed limit implementation on road traffic collisions and casualties in the City of Edinburgh, UK over approximately 3 years post implementation. METHODS: We used four sets of complementary analyses for collision and casualty rates. First, we compared rates for road segments changing to 20 mph against those at 30 mph. Second, we compared rates for the seven implementation zones in the city against paired control zones. Third, we investigated citywide casualty rate trends using generalised additive model. Finally, we used simulation modelling to predict casualty rate changes based on changes in observed speeds. RESULTS: We found a 10% (95% CI -19% to 0%) greater reduction in casualties (8% for collisions) for streets that changed to 20 mph compared with those staying at 30 mph. However, the reduction was similar, 8% (95% CI -22% to 5%) for casualties (10% collisions), in streets that were already at 20 mph. In the implementation zones, we found a 20% (95% CI -22% to -8%) citywide reduction in casualties (22% for collisions) compared with control zones; this compared with a predicted 10% (95% CI -18% to -2%) reduction in injuries based on the changes in speed and traffic volume. Citywide casualties dropped 17% (95% CI 13% to 22%) 3 years post implementation, accounting for trend. CONCLUSION: Our results indicate that the introduction of 20 mph limits resulted in a reduction in collisions and casualties 3 years post implementation. However, the effect exceeded expectations from changes in speed alone, possibly due to a wider network effect.

Effect of Indentation Depth on Friction Coefficient in Adhesive Contacts: Experiment and Simulation.

The quasi-static regime of friction between a rigid steel indenter and a soft elastomer with high adhesion is studied experimentally. An analysis of the formally calculated dependencies of a friction coefficient on an external load (normal force) shows that the friction coefficient monotonically decreases with an increase in the load, following a power law relationship. Over the entire range of contact loads, a friction mode is realized in which constant shear stresses are maintained in the tangential contact, which corresponds to the "adhesive" friction mode. In this mode, Amonton's law is inapplicable, and the friction coefficient loses its original meaning. Some classical works, which show the existence of a transition between "adhesive" and "normal" friction, were analyzed. It is shown that, in fact, there is no such transition. A computer simulation of the indentation process was carried out within the framework of the boundary element method, which confirmed the experimental results.

Behavioural responses of fin whales to military mid-frequency active sonar.

The effect of active sonars on marine mammal behaviour is a topic of considerable interest and scientific investigation. Some whales, including the largest species (blue whales, Balaenoptera musculus), can be impacted by mid-frequency (1-10 kHz) military sonars. Here we apply complementary experimental methods to provide the first experimentally controlled measurements of behavioural responses to military sonar and similar stimuli for a related endangered species, fin whales (Balaenoptera physalus). Analytical methods include: (i) principal component analysis paired with generalized additive mixed models; (ii) hidden Markov models; and (iii) structured expert elicitation using response severity metrics. These approaches provide complementary perspectives on the nature of potential changes within and across individuals. Behavioural changes were detected in five of 15 whales during controlled exposure experiments using mid-frequency active sonar or pseudorandom noise of similar frequency, duration and source and received level. No changes were detected during six control (no noise) sequences. Overall responses were more limited in occurrence, severity and duration than in blue whales and were less dependent upon contextual aspects of exposure and more contingent upon exposure received level. Quantifying the factors influencing marine mammal responses to sonar is critical in assessing and mitigating future impacts.

Indentation and Detachment in Adhesive Contacts between Soft Elastomer and Rigid Indenter at Simultaneous Motion in Normal and Tangential Direction: Experiments and Simulations.

In reported experiments, a steel indenter was pressed into a soft elastomer layer under varying inclination angles and subsequently was detached under various inclination angles too. The processes of indentation and detachment were recorded with a video camera, and the time dependences of the normal and tangential components of the contact force and the contact area, as well as the average contact pressure and average tangential stresses, were measured as functions of the inclination angle. Based on experimental results, a simple theoretical model of the indentation process is proposed, in which tangential and normal contacts are considered independently. Both experimental and theoretical results show that at small indentation angles (when the direction of motion is close to tangential), a mode with elastomer slippage relative to the indenter is observed, which leads to complex dynamic processes-the rearrangement of the contact boundary and the propagation of elastic waves (similar to Schallamach waves). If the angle is close to the normal angle, there is no slipping in the contact plane during the entire indentation (detachment) phase.

Thermal Stability and Melting Dynamics of Bimetallic Au@Pt@Au Core-Shell Nanoparticles.

Thermal stability is an important feature of the materials used as components and parts of sensors and other devices of nanoelectronics. Here we report the results of the computational study of the thermal stability of the triple layered Au@Pt@Au core-shell nanoparticles, which are promising materials for H2O2 bi-directional sensing. A distinct feature of the considered sample is the raspberry-like shape, due to the presence of Au nanoprotuberances on its surface. The thermal stability and melting of the samples were studied within classical molecular dynamics simulations. Interatomic forces were computed within the embedded atom method. To investigate the thermal properties of Au@Pt@Au nanoparticles, structural parameters such as Lindemann indexes, radial distribution functions, linear distributions of concentration, and atomistic configurations were calculated. As the performed simulations showed, the raspberry-like structure of the nanoparticle was preserved up to approximately 600 K, while the general core-shell structure was maintained up to approximately 900 K. At higher temperatures, the destruction of the initial fcc crystal structure and core-shell composition was observed for both considered samples. As Au@Pt@Au nanoparticles demonstrated high sensing performance due to their unique structure, the obtained results may be useful for the further design and fabrication of the nanoelectronic devices that are required to work within a certain range of temperatures.

In silico evaluation of the mechanical stimulation effect on the regenerative rehabilitation for the articular cartilage local defects.

Osteoarthritis is one of the most severe diseases of the human musculoskeletal system, and therefore, for many years, special attention has been paid to the search for effective methods of its treatment. However, even the most modern methods only in a limited number of cases in the early or intermediate stages of osteoarthritis lead to positive treatment results. In the later stages of development, osteoarthritis is practically incurable and most often ends with disability or the need for joint replacement for a large number of people. One of the main reasons hindering the development of osteoarthritis treatment methods is the peculiarities of articular cartilage, in which there is practically no vascular network and tissue homeostasis is carried out mainly due to the diffusion of nutrients present in the synovial fluid. In modern medicine, for the treatment of osteoarthritis, tissue engineering strategies have been developed based on the implantation of scaffolds populated with chondrogenic cells into the area of the defect. In vitro studies have established that these cells are highly mechanosensitive and, under the influence of mechanical stimuli of a certain type and intensity, their ability to proliferate and chondrogenesis increases. This property can be used to improve the efficiency of regenerative rehabilitation technologies based on the synergistic combination of cellular technologies, tissue engineering strategies, and mechanical tissue stimulation. In this work, using a regenerative rehabilitation mathematical model of local articular cartilage defects, numerical experiments were performed, the results of which indicate that the micro-and macro environment of the restored tissue, which changes during mechanical stimulation, has a significant effect on the formation of the extracellular matrix, and, consequently, cartilage tissue generally. The results obtained can be used to plan strategies for mechanical stimulation, based on the analysis of the results of cell proliferation experimental assessment after each stimulation procedure in vivo.

High-Precision Tribometer for Studies of Adhesive Contacts.

Herein, we describe the design of a laboratory setup operating as a high-precision tribometer. The whole design procedure is presented, starting with a concept, followed by the creation of an exact 3D model and final assembly of all functional parts. The functional idea of the setup is based on a previously designed device that was used to perform more simple tasks. A series of experiments revealed certain disadvantages of the initial setup, for which pertinent solutions were found and implemented. Processing and correction of the data obtained from the device are demonstrated with an example involving backlash and signal drift errors. Correction of both linear and non-linear signal drift errors is considered. We also show that, depending on the research interests, the developed equipment can be further modified by alternating its peripheral parts without changing the main frame of the device.

Efficient Inner-to-Outer Wall Energy Transfer in Highly Pure Double-Wall Carbon Nanotubes Revealed by Detailed Spectroscopy.

The coaxial stacking of two single-wall carbon nanotubes (SWCNTs) into a double-wall carbon nanotube (DWCNT), forming a so-called one-dimensional van der Waals structure, leads to synergetic effects that dramatically affect the optical and electronic properties of both layers. In this work, we explore these effects in purified DWCNT samples by combining absorption, wavelength-dependent infrared fluorescence-excitation (PLE), and wavelength-dependent resonant Raman scattering (RRS) spectroscopy. Purified DWCNTs are obtained by careful solubilization that strictly avoids ultrasonication or by electronic-type sorting, both followed by a density gradient ultracentrifugation to remove unwanted SWCNTs that could obscure the DWCNT characterization. Chirality-dependent shifts of the radial breathing mode vibrational frequencies and transition energies of the inner and outer DWCNT walls with respect to their SWCNT analogues are determined by advanced two-dimensional fitting of RRS and PLE data of DWCNT and their reference SWCNT samples. This exhaustive data set verifies that fluorescence from the inner DWCNT walls of well-purified samples is severely quenched through efficient energy transfer from the inner to the outer DWCNT walls. Combined analysis of the PLE and RRS results further reveals that this transfer is dependent on the inner and outer wall chirality, and we identify the specific combinations dominant in our DWCNT samples. These obtained results demonstrate the necessity and value of a combined structural characterization approach including PLE and RRS spectroscopy for bulk DWCNT samples.

Preparation of Micro-Pit-Textured PCD Tools and Micro-Turning Experiment on SiCp/Al Composites.

Serious tool wear occurs very often during machining due to the reinforcing phases in the workpiece. In this study, micro-pit-textures were prepared on the surfaces of PCD tools with a nanosecond laser to improve their cutting performance on SiCp/Al composites. The micro-pits were designed with rounded corners to improve the chip flow. The location and size of the texture were determined by analyzing the tool-chip contact area of the non-textured tool. The cutting performance of these textured PCD tools was investigated through orthogonal cutting experiments. It was found that the optimal cutting performance of the textured tools was achieved with the proper distance of the texture from the main cutting edge (35 µm) and the pit spacing (60 µm), aa a result of which the main cutting force reduced by about 14%, and the tool wear and surface adhesion significantly reduced. This texture was then applied in the micro-turning experiments of the PCD tool on the SiCp/Al composites. The cutting force in this experiment reduced by 22%, and the textured tool provided better chip transfer and tool anti-tipping. In this study, the role of SiC particles as a third body between the tool and the chip surface is discussed.

Electroluminescence from Single-Walled Carbon Nanotubes with Quantum Defects.

Individual single-walled carbon nanotubes with covalent sidewall defects have emerged as a class of photon sources whose photoluminescence spectra can be tailored by the carbon nanotube chirality and the attached functional group/molecule. Here we present electroluminescence spectroscopy data from single-tube devices based on (7, 5) carbon nanotubes, functionalized with dichlorobenzene molecules, and wired to graphene electrodes. We observe electrically generated, defect-induced emissions that are controllable by electrostatic gating and strongly red-shifted compared to emissions from pristine nanotubes. The defect-induced emissions are assigned to excitonic and trionic recombination processes by correlating electroluminescence excitation maps with electrical transport and photoluminescence data. At cryogenic conditions, additional gate-dependent emission lines appear, which are assigned to phonon-assisted hot-exciton electroluminescence from quasi-levels. Similar results were obtained with functionalized (6, 5) nanotubes. We also compare functionalized (7, 5) electroluminescence data with photoluminescence of pristine and functionalized (7, 5) nanotubes redox-doped using gold(III) chloride solution. This work shows that electroluminescence excitation is selective toward neutral defect-state configurations with the lowest transition energy, which in combination with gate-control over neutral versus charged defect-state emission leads to high spectral purity.

Pallidal neuron activity determines responsiveness to deep brain stimulation in cervical dystonia.

OBJECTIVE: In patients with cervical dystonia we sought for the differences in neuronal behavior of pallidal regions where deep brain stimulation resulted in favorable therapeutic response compared to those where the response was absent. METHODS: We compared single-unit activity of 564 neurons recorded from deep brain stimulation sensitive and non-sensitive regions in 17 cervical dystonia patients. RESULTS: Globus pallidus internus regions responsive to the deep brain stimulation had lower firing rates and bursting compared to non-responsive areas. The differences were robust in locations where neuronal responses correlated with neck movements. Per the effects of deep brain stimulation, the pallidal regions were classified in weak, intermediate, and excellent responsive. Pallidal regions with weak response to deep brain stimulation had fewer burst neurons and higher firing rate compared to neurons in areas with excellent response. The burst index was significantly decreased in excellent response regions. There was a significant decrease in the alpha band oscillation score but a substantial increase in the gamma band in excellent response neurons. CONCLUSION: The pallidal region that would be responsive to deep brain stimulation has distinct physiology compared to the non-responsive region. SIGNIFICANCE: These results provide novel insights into globus pallidus interna neurons' physiology in cervical dystonia.

Pallidal 1/f asymmetry in patients with cervical dystonia.

Lateralized differences in pallidal outflow are putatively linked to asymmetric tonic contractions of the neck muscles in cervical dystonia (CD). At the population level, the interhemispheric asymmetry has been traditionally studied for the estimation of the spectral power in specified frequency bands. Broadband spectral features, however, were not taken into consideration. The contemporary analysis revealed that the aperiodic (1/f) broadband activity could be a neurophysiological marker of the excitation/inhibition ratio. During deep brain stimulation (DBS) surgery, we measured bilateral pallidal local field potentials (LFP) in nine CD patients, examining the effects of lateralized asymmetry on 1/f broadband activity. All patients showed a trend towards an asymmetric difference in the 1/f broadband activity. The ipsilateral 1/f slope was significantly higher in internal (GPi) segment of the globus pallidus that is on the contralateral side of the direction of the dystonia. We also found lateralized differences in the beta oscillations for GPi and in the alpha oscillations for GPe. Our findings emphasize the importance of mainstreaming broadband activity in the estimation of LFP spectral features together with periodic features and provide further evidence for the pallidal asymmetry in CD patients.

Feedback-dependent neuronal properties make focal dystonias so focal.

Focal dystonia, by definition, affects a specific body part; however, it may have a widespread neural substrate. We tested this hypothesis by examining the intrinsic behaviour and the neuronal properties that are modulated by changes in the physiological behaviour of their connections, that is feedback dependence, of the isolated pallidal neurons. During deep brain stimulation surgery in 12 patients with isolated cervical dystonia (without hand involvement), we measured spontaneous as well as evoked single-unit properties in response to fist making (hand movement) or shoulder shrug (neck movements). We measured the activity of isolated neurons that were only sensitive to the neck movements, hand movement, or not responsive to hand or neck movements. The spontaneous firing behaviour, such as the instantaneous firing rate and its regularity, was comparable in all three types of neurons. The neck movement-sensitive neurons had prominent bursting behaviour in comparison with the hand neurons. The feedback dependence of the neck movement-sensitive neurons was also significantly impaired when compared to hand movement-sensitive neurons. Motor-evoked change in firing rate of neck movement-sensitive neurons rapidly declined; the decay time constant was much shorter compared to hand movement-sensitive neurons. These results suggest that in isolated cervical dystonia, at the resolution of single neurons, the deficits are much widespread, affecting the neurons that drive the neck movement as well as the hand movements. We speculate that clinically discernable dystonia occurs when additional abnormality is added to baseline dysfunctional network, and one source of such abnormality may involve feedback.

Role of Adhesion Stress in Controlling Transition between Plastic, Grinding and Breakaway Regimes of Adhesive Wear.

A discrete-element based model of elastic-plastic materials with non-ideal plasticity and with an account of both cohesive and adhesive interactions inside the material is developed and verified. Based on this model, a detailed study of factors controlling the modes of adhesive wear is performed. Depending on the material and loading parameters, we observed three main modes of wear: slipping, plastic grinding, cleavage, and breakaway. We find that occurrence of a particular mode is determined by the combination of two dimensionless material parameters: (1) the ratio of the adhesive stress to the pure shear strength of the material, and (2) sensitivity parameter of material shear strength to local pressure. The case study map of asperity wear modes in the space of these parameters has been constructed. Results of this study further develop the findings of the widely discussed studies by the groups of J.-F. Molinari and L. Pastewka.

Dynamic stiction without static friction: The role of friction vector rotation.

In the textbook formulation of dry friction laws, static and dynamic friction (stick and slip) are qualitatively different and sharply separated phenomena. However, accurate measurements of stick-slip motion generally show that static friction is not truly static but characterized by a slow creep that, upon increasing tangential load, smoothly accelerates into bulk sliding. Microscopic, contact-mechanical, and phenomenological models have been previously developed to account for this behavior. In the present work, we show that it may instead be a systemic property of the measurement apparatus. Using a mechanical model that exhibits the characteristics of typical setups of measuring friction forces-which usually have very high transverse stiffness-and assuming a small but nonzero misalignment angle in the contact plane, we observe some fairly counterintuitive behavior: Under increasing longitudinal loading, the system almost immediately starts sliding perpendicularly to the pulling direction. Then the friction force vector begins to rotate in the plane, gradually approaching the pulling direction. When the angle between the two becomes small, bulk sliding sets in quickly. Although the system is sliding the entire time, macroscopic stick-slip behavior is reproduced very well, as is the accelerated creep during the "stick" phase. The misalignment angle is identified as a key parameter governing the stick-to-slip transition. Numerical results and theoretical considerations also reveal the presence of high-frequency transverse oscillations during the "static" phase, which are also transmitted into the longitudinal direction by nonlinear processes. Stability analysis is carried out and suggests dynamic probing methods for the approaching moment of bulk slip and the possibility of suppressing stick-slip instabilities by changing the misalignment angle and other system parameters.

Hyperactivity of Basal Ganglia in Patients With Parkinson's Disease During Internally Guided Voluntary Movements.

The contribution of different brain areas to internally guided (IG) and externally triggered (ET) movements has been a topic of debate. It has been hypothesized that IG movements are performed mainly through the basal ganglia-thalamocortical loop while ET movements are through the cerebello-thalamocortical pathway. We hypothesized that basal ganglia activity would be modified in patients with Parkinson's disease during IG movement as compared with normal subjects. We used functional MRI (fMRI) to investigate the differences between IG and ET motor tasks. Twenty healthy participants and 20 Parkinson's disease patients (OFF-state) were asked to perform hand movements in response to sound stimuli (ET) and in advance of the stimuli (IG). We showed that ET movements evoked activation of a few large clusters in the contralateral motor areas: the sensorimotor and premotor cortex, supplementary motor area (SMA), insula, putamen, motor thalamus and ipsilateral cerebellum. IG movements additionally evoked activation of a large number of small clusters distributed in different brain areas including the parietal and frontal lobes. Comparison between the activity of Parkinson's disease patients and healthy volunteers showed few important differences. We observed that along with the activity of the posterior areas, an activation of the anterior areas of putamen was observed during IG movements. We also found hyperactivity of the ventral thalamus for both movements. These results showed that IG movements in PD patients were made with the involvement of both sensorimotor and associative basal ganglia-thalamocortical loops.

Effect of elastic grading on fretting wear.

We consider fretting wear in elastic frictional contact under influence of oscillations of small amplitude and investigate the question, how wear damage can be influenced by the introduction of material gradients. To achieve a general understanding we restrict our consideration to media with a power-law dependency of the elastic modulus on depth. In this case, a complete analytical solution can be found for the final worn shape. In the limiting case of small fretting oscillations we obtain a simple, closed-form asymptotic solution of the problem. We find that the optimum grading depends on the oscillation amplitude: for large amplitudes, the use of materials with a positive exponent decreases the wear volume whilst for very small amplitudes the use of graded materials with slightly negative exponent is beneficial. Especially interesting is the case of the Gibson-medium which may help avoiding both fretting wear and fretting fatigue.

Modelling reassurances of clinicians with hidden Markov models.

BACKGROUND: A key element in the interaction between clinicians and patients with cancer is reassurance giving. Learning about the stochastic nature of reassurances as well as making inferential statements about the influence of covariates such as patient response and time spent on previous reassurances are of particular importance. METHODS: We fit Hidden Markov Models (HMMs) to reassurance type from multiple time series of clinicians' reassurances, decoded from audio files of review consultations between patients with breast cancer and their therapeutic radiographer. Assuming a latent state process driving the observations process, HMMs naturally accommodate serial dependence in the data. Extensions to the baseline model such as including covariates as well as allowing for fixed effects for the different clinicians are straightforward to implement. RESULTS: We found that clinicians undergo different states, in which they are more or less inclined to provide a particular type of reassurance. The states are very persistent, however switches occasionally occur. The lengthier the previous reassurance, the more likely the clinician is to stay in the current state. CONCLUSIONS: HMMs prove to be a valuable tool and provide important insights for practitioners. TRIAL REGISTRATION: Trial Registration number: ClinicalTrials.gov: NCT02599506. Prospectively registered on 11th March 2015.

Heterogeneity of material structure determines the stationary surface topography and friction.

The character of surface roughness and the force of friction in the stationary state after a sufficiently long run-in process are of key importance for numerous applications, e.g. for friction between road and tire. In the present paper, we study theoretically and experimentally the asymptotic worn state of a bi-phasic material that is arbitrarily heterogeneous in the contact plane, but homogeneous in the direction of the surface normal. Under the assumption of Archard's wear law in its local formulation, the asymptotic shape is found in the closed integral form. Given the surface profile, the coefficient of friction can be estimated, since the coefficient of friction is known to be strongly correlated with the mean square root value of the surface slope. The limiting surface profiles and the corresponding coefficient of friction are determined as functions of size, relative concentration and wear ratio of the phases. The results of numerical calculations are compared to and validated by experiments carried out on simplified model systems. The main conclusion is that the rms value of the surface slope is not influenced by the characteristic linear size of inclusions and depends solely on the relative concentration of phases, as well as the ratio of their wear coefficients.

Adhesive contact of rough brushes.

The adhesive contact between a rough brush-like structure and an elastic half-space is numerically simulated using the fast Fourier transform (FFT)-based boundary element method and the mesh-dependent detachment criterion of Pohrt and Popov. The problem is of interest in light of the discussion of the role of contact splitting in the adhesion strength of gecko feet and structured biomimetic materials. For rigid brushes, the contact splitting does not enhance adhesion even if all pillars of the brush are positioned at the same height. Introducing statistical scatter of height leads to a further decrease of the maximum adhesive strength. At the same time, the pull-off force becomes dependent on the previously applied compression force and disappears completely at some critical roughness. For roughness with a subcritical value, the pressure dependence of the pull-off force qualitatively follows the known theory of Fuller and Tabor with moderate modification due to finite size effect of the brush.