On the Mathematical and Geometrical Structure of the Determining Equations for Shear Waves in Nonlinear Isotropic Incompressible Elastodynamics

Using the theory of $1+1$ hyperbolic systems we put in perspective the mathematical and geometrical structure of the celebrated circularly polarized waves solutions for isotropic hyperelastic materials determined by Carroll in Acta Mechanica 3 (1967) 167--181. We show that a natural generalization of this class of solutions yields an infinite family of \emph{linear} solutions for the equations of isotropic elastodynamics. Moreover, we determine a huge class of hyperbolic partial differential equations having the same property of the shear wave system. Restricting the attention to the usual first order asymptotic approximation of the equations determining transverse waves we provide the complete integration of this system using generalized symmetries.Comment: 19 page

An exact fluid model for relativistic electron beams: The many moments case

An interesting and satisfactory fluid model has been proposed in literature for the the description of relativistic electron beams. It was obtained with 14 independent variables by imposing the entropy principle and the relativity principle. Here the case is considered with an arbitrary number of independent variables, still satisfying the above mentioned two principles; these lead to conditions whose general solution is here found. We think that the results satisfy also a certain ordering with respect to a smallness parameter $\epsilon$ measuring the dispersion of the velocity about the mean; this ordering generalizes that appearing in literature for the 14 moments case

Born-Infeld Theory and Stringy Causality

Fluctuations around a non-trivial solution of Born-Infeld theory have a limiting speed given not by the Einstein metric but the Boillat metric. The Boillat metric is S-duality invariant and conformal to the open string metric. It also governs the propagation of scalars and spinors in Born-Infeld theory. We discuss the potential clash between causality determined by the closed string and open string light cones and find that the latter never lie outside the former. Both cones touch along the principal null directions of the background Born-Infeld field. We consider black hole solutions in situations in which the distinction between bulk and brane is not sharp such as space filling branes and find that the location of the event horizon and the thermodynamic properties do not depend on whether one uses the closed or open string metric. Analogous statements hold in the more general context of non-linear electrodynamics or effective quantum-corrected metrics. We show how Born-Infeld action to second order might be obtained from higher-curvature gravity in Kaluza-Klein theory. Finally we point out some intriguing analogies with Einstein-Schr\"odinger theory.Comment: 31 pages, 4 figures, LaTex; Some comments and references adde

High voltage pulser for ion shutters in ion mobility spectrometry based on an optocoupler

A novel high voltage pulser for an ion shutter used in drift-tube ion-mobility spectrometers is described. The simple design suitable for the in-house construction of these spectrometers relies on a special optocoupler to isolate the triggering circuitry from the high voltage at the ion shutter. The device was tested with an electrospray-ionization ion-mobility device with a 10 cm drift tube operated at 4 kV into which a standard test mixture of four tetraalkylamines was injected with a negative going gating pulse of about 50 V on top of 4 kV. A fall time of 15.7 µs and a rise time of 2.0 µs were determined for the pulse, which was adequate for the required injection pulse width of 450 µs. Resolving powers between 61 and 81 were determined for the four quaternary amines, which were found to be comparable to the performance obtained with a previously reported pulser circuitry of a different design used as a reference

From Paper-Based to Mobile Checklists - A Reference Model

Checklists are cognitive tools that ensure quality, safety and reduce human errors when executing working routines. Besides their popularity in practice, checklists increasingly receive attention from academics, who have even called for a "science of checklists". According to prior studies, mobile checklists are more effective than their paper-based alternatives, but research in this domain is still limited. It focuses on mobile checklists' use and benefits, ra- ther than on their characteristics and design. Our study aims at developing a reference model for conceptualizing mobile checklists. The suggested reference model has been constructed by following design science principles, based on an extensive analysis of paper-based and mobile checklists from the literature and from the practical world. Its main contribution is a shared understanding of the domain knowledge between users and developers, which helps to communicate innovative ideas about mobile checklist application

Entering the World of Individual Routines: The Affordances of Mobile Applications

The IS discipline has a long tradition in investigating how new technologies affect work practices, but has mostly focused on the organizational level. With mobile applications, we are facing a new technology wave that is centered on the individual users. Despite their popularity, mobile applications' possibilities to enhance an individual's knowledge, skills, and competence in daily work practices have not been studied in a systematic way. Building on the concept of routines from organizational theory and insights from two field studies, we investigate mobile applications acting as material artifacts and their possibilities of goal-oriented actions in individual routines. Our main contributions are the extension of Pentland & Feldman's generative system model and a set of affordances that mobile applications bring to individual routines. Our findings complement recent studies on routines at the organizational level and contribute to enhance artifact design knowledge for mobile applications beyond "interaction design"

When Sales Meet Process Mining: A Scientific Approach to Sales Process and Performance Management

Selling has long been considered as an “art” driven by personal intuition and native sales talent. However, significant changes have occurred over the past 30 years, as a result of technological advances and changing customer expectations. As one answer to these changes, practitioners and scholars have promoted the idea of “sales as a science”, relying on documented, repeatable ways of selling that reflect scientific methods. We argue that process mining is a relevant candidate f or empowering “sales as a science” via its capacity to analyze, discover, and enhance end-to-end processes. Through a design science approach, we propose a framework for applying process mining to sales, comprising a refined notation and seven process min ing analysis scenarios. Our study represents a first step towards gaining a better un derstanding of real-world sales processes based on digital traces from operational systems e.g., customer relationship management (CRM) systems, or emerging technologies e.g., smart watches

Born-Infeld-Einstein Actions?

We present some obvious physical requirements on gravitational avatars of non-linear electrodynamics and illustrate them with explicit determinantal Born-Infeld-Einstein models. A related procedure, using compensating Weyl scalars, permits us to formulate conformally invariant versions of these systems as well.Comment: 7 page

Differential Role of the Lectin Pathway of Complement Activation in Susceptibility to Neonatal Sepsis

Background. The incidence of bacterial sepsis during the neonatal period is high. Mannan-binding lectin (MBL), L-ficolin, and H-ficolin recognize microorganisms and activate the complement system viaMBL-associated serine proteases (MASPs). This study investigated whether cord blood concentrations of the lectin pathway proteins are associated with neonatal sepsis. >Methods. This was a case-control study including 47 infants with culture-proven sepsis during the first month of life and 94 matched controls. MBL, L-ficolin, H-ficolin, MASP-2, and MASP-3 levels were measured in cord blood with use of enzyme-linked immunosorbent assay and time-resolved immunofluorometric assay. Multivariate logistic regression was performed. Results. Infants with gram-positive sepsis had significantly lower H-ficolin cord blood concentrations than controls (multivariate odds ratio [OR], 4.00; 95% confidence interval [CI], 1.51-10.56; P=.005), whereas infants with gram-negative sepsis had lower MBL cord blood concentrations (OR, 2.99; 95% CI, 0.86-10.33; P=.084). When excluding patients with postoperative sepsis, multivariate analysis confirmed that low H-ficolin was associated with a significantly higher risk of gram-positive sepsis (OR, 3.71; 95% CI, 1.26-10.92; P=.017) and late-onset sepsis (OR, 3.14; 95% CI, 1.07-9.21; P=.037). In contrast, low MBL was associated with a significantly higher risk of gram-negative sepsis (OR, 4.39; 95% CI, 1.10-17.45; P=.036) and early-onset sepsis (OR, 3.87; 95% CI, 1.05-14.29; P=.042). The concentrations of all the lectin pathway proteins increased with gestational age (P<.01). Conclusions. These preliminary results indicate that low MBL concentrations are a susceptibility factor for gram-negative sepsis, and low H-ficolin concentrations indicate susceptibility to gram-positive sepsis. The decreased expression of lectin pathway proteins in neonates must be considered to be an additional form of neonatal immunodeficienc

Intracellular Zinc Activates KCNQ Channels by Reducing their Dependence on Phosphatidylinositol 4,5-bisphosphate

M-type (Kv7, KCNQ) potassium channels are proteins that control the excitability of neurons and muscle cells. Many physiological and pathological mechanisms of excitation operate via the suppression of M channel activity or expression. Conversely, pharmacological augmentation of M channel activity is a recognized strategy for the treatment of hyperexcitability disorders such as pain and epilepsy. However, physiological mechanisms resulting in M channel potentiation are rare. Here we report that intracellular free zinc directly and reversibly augments the activity of recombinant and native M channels. This effect is mechanistically distinct from the known redox-dependent KCNQ channel potentiation. Interestingly, the effect of zinc cannot be attributed to a single histidine- or cysteine-containing zinc-binding site within KCNQ channels. Instead, zinc dramatically reduces KCNQ channel dependence on its obligatory physiological activator, phosphatidylinositol 4,5-bisphosphate (PIP2). We hypothesize that zinc facilitates interactions of the lipid-facing interface of a KCNQ protein with the inner leaflet of the plasma membrane in a way similar to that promoted by PIP2. Because zinc is increasingly recognized as a ubiquitous intracellular second messenger, this discovery might represent a hitherto unknown native pathway of M channel modulation and provide a fresh strategy for the design of M channel activators for therapeutic purposes