A Variational Formulation of Dissipative Quasicontinuum Methods

Lattice systems and discrete networks with dissipative interactions are successfully employed as meso-scale models of heterogeneous solids. As the application scale generally is much larger than that of the discrete links, physically relevant simulations are computationally expensive. The QuasiContinuum (QC) method is a multiscale approach that reduces the computational cost of direct numerical simulations by fully resolving complex phenomena only in regions of interest while coarsening elsewhere. In previous work (Beex et al., J. Mech. Phys. Solids 64, 154-169, 2014), the originally conservative QC methodology was generalized to a virtual-power-based QC approach that includes local dissipative mechanisms. In this contribution, the virtual-power-based QC method is reformulated from a variational point of view, by employing the energy-based variational framework for rate-independent processes (Mielke and Roub\'i\v{c}ek, Rate-Independent Systems: Theory and Application, Springer-Verlag, 2015). By construction it is shown that the QC method with dissipative interactions can be expressed as a minimization problem of a properly built energy potential, providing solutions equivalent to those of the virtual-power-based QC formulation. The theoretical considerations are demonstrated on three simple examples. For them we verify energy consistency, quantify relative errors in energies, and discuss errors in internal variables obtained for different meshes and two summation rules.Comment: 38 pages, 21 figures, 4 tables; moderate revision after review, one example in Section 5.3 adde

Novel anisotropic continuum-discrete damage model capable of representing localized failure of massive structures. Part II: identification from tests under heterogeneous stress field

In Part I of this paper we have presented a simple model capable of describing the localized failure of a massive structure. In this part, we discuss the identification of the model parameters from two kinds of experiments: a uniaxial tensile test and a three-point bending test. The former is used only for illustration of material parameter response dependence, and we focus mostly upon the latter, discussing the inverse optimization problem for which the specimen is subjected to a heterogeneous stress field.Comment: 18 pages, 12 figures, 6 table

Dyspraxia in a patient with corticobasal degeneration: the role of visual and tactile inputs to action

Objectives-To investigate the roles of visual and tactile information in a dyspraxic patient with corticobasal degeneration (CBD) who showed dramatic facilitation in miming the use of a tool or object when he was given a tool to manipulate; and to study the nature of the praxic and neuropsychological deficits in CBD. Methods-The subject had clinically diagnosed CBD, and exhibited alien limb behaviour and striking ideomotor dyspraxia. General neuropsychological evaluation focused on constructional and visuospatial abilities, calculation, verbal fluency, episodic and semantic memory, plus spelling and writing because impairments in this domain were presenting complaints. Four experiments assessed the roles of visual and tactile information in the facilitation of motor performance by tools. Experiment I evaluated the patient's performance of six limb transitive actions under six conditions: (1) after he described the relevant tool from memory, (2) after he was shown a Line drawing of the tool, (3) after he was shown a real exemplar of the tool, (4) after he watched the experimenter perform the action, (5) while he was holding the tool, and (6) immediately after he had performed the action with the tool but with the tool removed from his grasp. Experiment 2 evaluated the use of the same six tools when the patient had tactile but no visual information (while he was blindfolded). Experiments 3 and 4 assessed performance of actions appropriate to the same six tools when the patient had either neutral or inappropriate tactile feedback-that is, while he was holding a non-tool object or a different tool. Results-Miming of tool use was not facilitated by visual input; moreover, lack of visual information in the blindfolded condition did not reduce performance. The principal positive finding was a dramatic facilitation of the patient's ability to demonstrate object use when he was holding either the appropriate tool or a neutral object. Tools inappropriate to the requested action produced involuntary performance of the stimulus relevant action. Conclusions-Tactile stimulation was paramount in the facilitation of motor performance in tool use by this patient with CBD. This outcome suggests that tactile information should be included in models which hypothesise modality specific inputs to the action production system. Significant impairments in spelling and letter production that have not previously been reported in CBD have also been documented

Prescribing sodium oxybate for narcolepsy: Demanding that a patient's need is "exceptional" is irrational and should be abandoned

PublishedEditorialJournalEditorial

Checkpoint Inhibitors in Nonsmall Cell Lung Cancer

Lung cancer remains the leading cause of cancer‐related deaths worldwide. The majority of NSCLC patients present with advanced stage disease. Lung cancer was once thought of as a low antigenicity cancer unlikely to benefit from immunotherapy, but has recently been found to have a high level of antigenicity. Moreover, a large body of research now exists to support both the safety and efficacy of immunotherapy in advanced stage NSCLC. The checkpoint inhibitors nivolumab, pembrolizumab, and atezolizumab are now approved by the U.S. Federal Drug Administration for second‐line treatment in advanced stage NSCLC. In addition to being efficacious, checkpoint inhibitors have a superior safety profile compared to previous standard of care, chemotherapy. Further trials are needed to investigate the checkpoint inhibitors’ role in combination treatment, first‐line treatment, and early stage disease

Effects of turbulence compressibility and unsteadiness in compression corner flow

The structure of the separated flow region over a 20 degree compression corner at a free-stream Mach number of 2.84 is investigated computationally using a Reynolds averaged Navier Stokes (R.A.N.S.) solver and kappa-epsilon model. At this Mach number and ramp angle, a steady-state recirculation region of order delta(sub o) is observed, with onset of a 'plateau' in the wall pressure distribution near the corner. At lower ramp angles, separation is negligible, while at an angle of 24 degrees, separation regions of length 2 delta(sub o) are expected. Of interest here is the response of the mathematical model to inclusion of the pressure dilatation term for turbulent kinetic energy. Compared with the experimental data of Smits and Muck (1987), steady-state computations show improvement when the pressure dilatation term is included. Unsteady computations, using both unforced and then forced inlet conditions, did not predict the oscillatory motion of the separation bubble as observed in laboratory experiments. An analysis of the separation bubble oscillation and the turbulent boundary layer (T.B.L.) frequencies for this flow suggests that the bubble oscillations are of nearly the same order as the turbulent frequencies, and therefore difficult for the model to separate and resolve

The Eye's mind - Visual imagination, neuroscience and the humanities

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordThis work was supported by funding from the Arts and Humanities Research Council through a Science in Culture Innovation Award: The Eye's Mind – a study of the neural basis of visual imagination and of its role in culture (Reference AH/M002756/1)

Investigation of the dilatational dissipation in compressible homogeneous shear flow

The dilatational dissipation rate within compressible homogeneous turbulent shear flow is studied using data from direct numerical simulations. It is found that the dilatational dissipation rate is mainly associated with large scale acoustic waves. Eddy shocklets are observed; however, they have little contribution to the average dissipation rate. A mechanism for the generation of eddy shocklets is shown to be the focusing of acoustic waves. Turbulence models for the dilatational dissipation rate are compared with data from the simulations. It is found that the formulation of Zeman used by Viegas & Rubesin to calculate a compressible mixing layer agrees well with the numerical simulation results for turbulent Mach numbers less than 0.3. However, it is also found that, for the Mach number range occurring in mixing layers, the model does not accurately represent the theory upon which it is based