{\phi}^4 Solitary Waves in a Parabolic Potential: Existence, Stability, and Collisional Dynamics

We explore a {\phi}^4 model with an added external parabolic potential term. This term dramatically alters the spectral properties of the system. We identify single and multiple kink solutions and examine their stability features; importantly, all of the stationary structures turn out to be unstable. We complement these with a dynamical study of the evolution of a single kink in the trap, as well as of the scattering of kink and anti-kink solutions of the model. We see that some of the key characteristics of kink-antikink collisions, such as the critical velocity and the multi-bounce windows, are sensitively dependent on the trap strength parameter, as well as the initial displacement of the kink and antikink

Dynamics of trimming the content of face representations for categorization in the brain

To understand visual cognition, it is imperative to determine when, how and with what information the human brain categorizes the visual input. Visual categorization consistently involves at least an early and a late stage: the occipito-temporal N170 event related potential related to stimulus encoding and the parietal P300 involved in perceptual decisions. Here we sought to understand how the brain globally transforms its representations of face categories from their early encoding to the later decision stage over the 400 ms time window encompassing the N170 and P300 brain events. We applied classification image techniques to the behavioral and electroencephalographic data of three observers who categorized seven facial expressions of emotion and report two main findings: (1) Over the 400 ms time course, processing of facial features initially spreads bilaterally across the left and right occipito-temporal regions to dynamically converge onto the centro-parietal region; (2) Concurrently, information processing gradually shifts from encoding common face features across all spatial scales (e.g. the eyes) to representing only the finer scales of the diagnostic features that are richer in useful information for behavior (e.g. the wide opened eyes in 'fear'; the detailed mouth in 'happy'). Our findings suggest that the brain refines its diagnostic representations of visual categories over the first 400 ms of processing by trimming a thorough encoding of features over the N170, to leave only the detailed information important for perceptual decisions over the P300

Two-neutron knockout from neutron-deficient 34^{34}Ar, 30^{30}S, and 26^{26}Si

Two-neutron knockout reactions from nuclei in the proximity of the proton dripline have been studied using intermediate-energy beams of neutron-deficient $^{34}$Ar, $^{30}$S, and $^{26}$Si. The inclusive cross sections, and also the partial cross sections for the population of individual bound final states of the $^{32}$Ar, $^{28}$S and $^{24}$Si knockout residues, have been determined using the combination of particle and $\gamma$-ray spectroscopy. Similar to the two-proton knockout mechanism on the neutron-rich side of the nuclear chart, these two-neutron removal reactions from already neutron-deficient nuclei are also shown to be consistent with a direct reaction mechanism.Comment: Phys. Rev. C, rapid communication, in pres

Synthesis, Structure and Stereodynamics of Atropisomeric <em>N</em>‑Chloroamides

Atropisomeric N-chloroamides were efficiently accessed by electrophilic halogenation of ortho-substituted secondary anilides. The stereodynamics of atropisomerism in these novel scaffolds was interrogated by detailed experimental and computational studies, revealing that racemization is correlated with amide isomerization. The stereoelectronic nature of the amide was shown to significantly influence racemization rates, with potentially important implications for other C-N atropisomeric scaffolds

Resident Memory T Cells (TRM) Are Abundant in Human Lung: Diversity, Function, and Antigen Specificity

Recent studies have shown that tissue resident memory T cells (TRM) are critical to antiviral host defense in peripheral tissues. This new appreciation of TRM that reside in epithelial tissues and mediate host defense has been studied most extensively in skin: adult human skin contains large numbers of functional TRM that express skin specific markers. Indeed, more than twice as many T cells reside in skin as in peripheral blood. This T cell population has a diverse T cell receptor repertoire, and can produce a broad array of cytokines. More recently, we have begun to examine other epithelial tissues for the presence of resident T cells. In the present study, we asked whether analogous populations of resident T cells could be found in human lung. We were able to demonstrate abundant resident T cells in human lung-more than 10 billion T cells were present. Lung T cells were largely of the effector memory T cell (TEM) phenotype, though small numbers of central memory T cells (TCM) and T regulatory cells (Treg) could be identified. Lung T cells had a diverse T cell receptor repertoire and subsets produced IL-17, IL-4, IFNγ, as well as TNFα. A significant number of lung TRM CD4+Th cells produced more than one cytokine, identifying them as “multifunctional” Th1 type cells. Finally, lung TRM, but not TRM resident to skin or T cells from blood, proliferated in response to influenza virus. This work suggests that normal human lung contains large numbers of TRM cells, and these cells are poised to respond to recall antigens previously encountered through lung mucosa. This population of T cells may contribute to the pathogenesis of asthma and other T cell mediated lung diseases

Age differences in conscious versus subconscious social perception: The influence of face age and valence on gaze following

© 2014 American Psychological Association. Gaze following is the primary means of establishing joint attention with others and is subject to age-related decline. In addition, young but not older adults experience an own-age bias in gaze following. The current research assessed the effects of subconscious processing on these age-related differences. Participants responded to targets that were either congruent or incongruent with the direction of gaze displayed in supraliminal and subliminal images of young and older faces. These faces displayed either neutral (Study 1) or happy and fearful (Study 2) expressions. In Studies 1 and 2, both age groups demonstrated gaze-directed attention by responding faster to targets that were congruent as opposed to incongruent with gaze-cues. In Study 1, subliminal stimuli did not attenuate the age-related decline in gaze-cuing, but did result in an own-age bias among older participants. In Study 2, gaze-cuing was reduced for older relative to young adults in response to supraliminal stimuli, and this could not be attributed to reduced visual acuity or age group differences in the perceived emotional intensity of the gaze-cue faces. Moreover, there were no age differences in gaze-cuing when responding to subliminal faces that were emotionally arousing. In addition, older adults demonstrated an own-age bias for both conscious and subconscious gaze- cuing when faces expressed happiness but not fear. We discuss growing evidence for age-related preservation of subconscious relative to conscious social perception, as well as an interaction between face age and valence in social perception

Rigorous engineering for hardware security: Formal modelling and proof in the CHERI design and implementation process

The root causes of many security vulnerabilities include a pernicious combination of two problems, often regarded as inescapable aspects of computing. First, the protection mechanisms provided by the mainstream processor architecture and C/C++ language abstractions, dating back to the 1970s and before, provide only coarse-grain virtual-memory-based protection. Second, mainstream system engineering relies almost exclusively on test-and-debug methods, with (at best) prose specifications. These methods have historically sufficed commercially for much of the computer industry, but they fail to prevent large numbers of exploitable bugs, and the security problems that this causes are becoming ever more acute. In this paper we show how more rigorous engineering methods can be applied to the development of a new security-enhanced processor architecture, with its accompanying hardware implementation and software stack. We use formal models of the complete instruction-set architecture (ISA) at the heart of the design and engineering process, both in lightweight ways that support and improve normal engineering practice -- as documentation, in emulators used as a test oracle for hardware and for running software, and for test generation -- and for formal verification. We formalise key intended security properties of the design, and establish that these hold with mechanised proof. This is for the same complete ISA models (complete enough to boot operating systems), without idealisation. We do this for CHERI, an architecture with \emph{hardware capabilities} that supports fine-grained memory protection and scalable secure compartmentalisation, while offering a smooth adoption path for existing software. CHERI is a maturing research architecture, developed since 2010, with work now underway on an Arm industrial prototype to explore its possible adoption in mass-market commercial processors. The rigorous engineering work described here has been an integral part of its development to date, enabling more rapid and confident experimentation, and boosting confidence in the design.This work was supported by EPSRC programme grant EP/K008528/1 (REMS: Rigorous Engineering for Mainstream Systems). This work was supported by a Gates studentship (Nienhuis). This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement 789108, ELVER). This work was supported by the Defense Advanced Research Projects Agency (DARPA) and the Air Force Research Laboratory (AFRL), under contracts FA8750-10-C-0237 (CTSRD), HR0011-18-C-0016 (ECATS), and FA8650-18-C-7809 (CIFV)

Continuous, Semi-discrete, and Fully Discretized Navier-Stokes Equations

The Navier--Stokes equations are commonly used to model and to simulate flow phenomena. We introduce the basic equations and discuss the standard methods for the spatial and temporal discretization. We analyse the semi-discrete equations -- a semi-explicit nonlinear DAE -- in terms of the strangeness index and quantify the numerical difficulties in the fully discrete schemes, that are induced by the strangeness of the system. By analyzing the Kronecker index of the difference-algebraic equations, that represent commonly and successfully used time stepping schemes for the Navier--Stokes equations, we show that those time-integration schemes factually remove the strangeness. The theoretical considerations are backed and illustrated by numerical examples.Comment: 28 pages, 2 figure, code available under DOI: 10.5281/zenodo.998909, https://doi.org/10.5281/zenodo.99890

Mesenchymal Stem Cell Alterations in Bone Marrow Lesions in Patients With Hip Osteoarthritis

Objective: In patients with osteoarthritis (OA), bone marrow lesions (BMLs) are intimately linked to disease progression. We hypothesized that aberrant multipotential stromal cell (also known as mesenchymal stem cell [MSC]) responses within bone tissue contributes to BML pathophysiology. The aim of this study was to investigate BML and non-BML native subchondral bone MSCs for numeric, topographic, in vitro functional, and gene expression differences. Methods: Ex vivo 3T magnetic resonance imaging (MRI) of the femoral heads of 20 patients with hip OA was performed. MRI-determined BML and non-BML regions were excised and enzymatically treated to extract cells and quantify MSCs using flow cytometry and colony-forming unit–fibroblast (CFU-F) assay. Immunohistochemical analysis was performed to determine in vivo CD271+ MSC distribution. Culture-expanded CD271+ cells were analyzed for tripotentiality and gene expression. Results: BML regions were associated with greater trabecular bone area and cartilage damage compared with non-BML regions. The proportion of CD45−CD271+ MSCs was higher in BML regions compared with non-BML regions (median difference 5.6-fold; P < 0.001); the CFU-F assay showed a similar trend (median difference 4.3-fold; P = 0.013). Immunohistochemistry revealed CD271+ cell accumulation in bone adjacent to cartilage defects and areas of osteochondral angiogenesis. BML MSCs had lower proliferation and mineralization capacities in vitro and altered expression of TNFSF11/RANKL and CXCR4/stromal cell–derived factor 1 receptor. OA MSCs showed up-regulated transcripts for CXCR1 and CCR6 compared with MSCs derived from healthy or osteoporotic bone. Conclusion: This study is the first to show numeric and topographic alterations in native MSCs in the diseased bone of patients with hip OA. Given the associated functional perturbation of MSCs, these data suggest that subchondral bone MSC manipulation may be an OA treatment target