Asymmetric Platform Research Articles

A Platform for the Synthesis of Corynantheine-Type Corynanthe Alkaloids.

Corynantheine-type alkaloids are major components of the Mitragyna speciosa, also known as kratom, that exhibit unique pharmacological activity. However, no universal method to prepare these alkaloids has been reported. Disclosed herein is a catalytic, asymmetric platform that enables rapid access to corynantheine alkaloids. The first enantioselective total synthesis of (-)-corynantheidine pseudoindoxyl is described. The first asymmetric syntheses of (+)-corynoxine and (-)-corynoxine B were also achieved, along with enantioselective syntheses of (-)-corynantheidol and (-)-corynantheidine. Through this work, all series of corynantheine alkaloids including indole, spirooxindole, and pseudoindoxyl can now be accessed in the laboratory, enabling comprehensive biological investigation of kratom alkaloids to be undertaken.

Exclusive Dealing in Asymmetric Platform Competition

Exclusive Dealing in Asymmetric Platform Competition

Design of Asymmetric Nanofibers-Membranes Based on Polyvinyl Alcohol and Wool-Keratin for Wound Healing Applications.

The development of asymmetric membranes—i.e., matching two fibrous layers with selected composition and morphological properties to mimic both the epidermis and dermis—currently represents one of the most promising strategies to support skin regeneration during the wound healing process. Herein, a new asymmetric platform fabricated by a sequential electrospinning process was investigated. The top layer comprises cross-linked polyvinylalcohol (PVA) nanofibers (NFs)—from water solution—to replicate the epidermis’s chemical stability and wettability features. Otherwise, the bottom layer is fabricated by integrating PVA with wool-keratin extracted via sulfitolysis. This protein is a biocompatibility polymer with excellent properties for dermis-like structures. Morphological characterization via SEM supported by image analysis showed that the asymmetric membrane exhibited average fiber size—max frequency diameter 450 nm, range 1.40 μm—and porosity suitable for the healing process. FTIR-spectrums confirmed the presence of keratin in the bottom layer and variations of keratin-secondary structures. Compared with pure PVA-NFs, keratin/PVA-NFs showed a significant improvement in cell adhesion in in vitro tests. In perspective, these asymmetric membranes could be promisingly used to confine active species (i.e., antioxidants, antimicrobials) to the bottom layer to support specific cell activities (i.e., proliferation, differentiation) in wound healing applications.

Asymmetric Platform Competition: Concentration vs Diversification Strategy in Ridesourcing Market

Asymmetric Platform Competition: Concentration vs Diversification Strategy in Ridesourcing Market

Asymmetric Platform Competition: Concentration VS Diversification Strategy in Ridesharing Market

Asymmetric Platform Competition: Concentration VS Diversification Strategy in Ridesharing Market

Augmented Virtual Teleportation for High-Fidelity Telecollaboration.

Telecollaboration involves the teleportation of a remote collaborator to another real-world environment where their partner is located. The fidelity of the environment plays an important role for allowing corresponding spatial references in remote collaboration. We present a novel asymmetric platform, Augmented Virtual Teleportation (AVT), which provides high-fidelity telepresence of a remote VR user (VR-Traveler) into a real-world collaboration space to interact with a local AR user (AR-Host). AVT uses a 360° video camera (360-camera) that captures and live-streams the omni-directional scenes over a network. The remote VR-Traveler watching the video in a VR headset experiences live presence and co-presence in the real-world collaboration space. The VR-Traveler's movements are captured and transmitted to a 3D avatar overlaid onto the 360-camera which can be seen in the AR-Host's display. The visual and audio cues for each collaborator are synchronized in the Mixed Reality Collaboration space (MRC-space), where they can interactively edit virtual objects and collaborate in the real environment using the real objects as a reference. High fidelity, real-time rendering of virtual objects and seamless blending into the real scene allows for unique mixed reality use-case scenarios. Our working prototype has been tested with a user study to evaluate spatial presence, co-presence, and user satisfaction during telecollaboration. Possible applications of AVT are identified and proposed to guide future usage.

Net neutrality and asymmetric platform competition

In this paper we analyze the interplay between access to the last-mile network and net neutrality in the market for Internet access. We consider two competing Internet service providers (ISPs), which act as platforms between Internet users and content providers (CPs). One of the ISPs is vertically integrated and provides the other (non-integrated) ISP with access to its last-mile network. We study the impact of the access price on the termination fees charged by the ISPs to CPs for carrying their traffic. First, we show that the termination fee set by the integrated ISP decreases with the access price, whereas the termination fee of the non-integrated ISP can either increase or decrease with it. Second, we show that there exists a negative relationship (“waterbed effect”) between the access price and the total termination fee paid by the CPs. As a consequence, it may be socially optimal for the regulator to set the access price above cost when termination fees are left to the market.

Multi-Sided Market

We study the equilibrium for symmetric competition between multi-sided platforms under utility competition and make equilibrium comparison for asymmetric platform competition. We consider the small-ticket effect where the price cap regulation of the large-ticket item leads to a rise of the price for the small-ticket item. We show that competitive price discrimination could lead to higher profits for firms. We build a model with general externality and demand function. We consider a partially covered market and show that the externality could be a bless for firms. Moreover, we conduct a merger analysis for the general demand and externality model.

Net Neutrality and Asymmetric Platform Competition

In this paper we analyze the interplay between access to the last-mile network and net neutrality in the market for Internet access. We consider two competing Internet service providers (ISPs), which act as platforms between Internet users and content providers (CPs). One of the ISPs is vertically integrated and provides the other (non-integrated) ISP with access to its last-mile network. We study the impact of the access price on the termination fees charged by the ISPs to CPs for carrying their traffic. First, we show that the termination fee set by the integrated ISP increases with the access price, whereas the termination fee of the non-integrated ISP can either increase or decrease with it. Second, we show that there is negative relationship (“waterbed effect”) between the access price and the total termination fee paid by the CPs. As a consequence, it may be socially optimal for the regulator to set the access price above cost when termination fees are left to the market.

Straight-line path following for asymmetric unmanned platform with disturbance estimation

The problem of straight-line path following for asymmetric unmanned platform exposed to unknown disturbances was addressed in this paper. The mathematical model of asymmetric unmanned platform was established and the inputs in sway and yaw directions were decoupled, which facilitated the establishment of control strategy of path following. The guidance law and the cross-track error were derived from the classical line-of-sight (LOS) guidance principle. And the equilibrium point of the cross-track error was proven to be uniformly semiglobally exponentially stable (USGES), which guaranteed the exponential convergence to zero. A new disturbance estimation law was developed by adding a linear item of the estimation error into the classical one, which improved the principle’s precision and sensitivity dramatically. The control strategy was developed based on the integrator backstepping technique and the new disturbance estimation law, which made the equilibrium system to be uniformly globally asymptotically stable (UGAS). Computer simulations were conducted to verify the effectiveness of the estimation and control laws during straight-line path following for asymmetric unmanned platform in the presence of unknown disturbances.

Synthesis of Au and Pt Hollow Capsules with Single Holes via Pickering Emulsion Strategy

Au and Pt hollow capsules with single holes were synthesized via a Pickering emulsion strategy. Pickering emulsions provided particles with oil–water interfaces as asymmetric platform for anisotropic structure sculpture. Reactive Cu2O particles were utilized not only as emulsifier to prepare Pickering emulsions but also as sacrificed hard template for the consequent asymmetric galvanic reaction at the oil–water interfaces, resulting in the formation of open-mouthed Au and Pt hollow capsules. The opened hollow structure can facilitate the diffusion of reactants to inner side of the shell wall, thus effectively activating the catalytic activity of the inner shell wall of the hollow capsules. The obtained open-mouthed Au hollow capsules show much higher catalytic performance than that of intact Au hollow capsules.

Structure of an Asymmetric Ternary Protein Complex Provides Insight for Membrane Interaction

Plasma membrane repair involves the coordinated effort of proteins and the inner phospholipid surface to mend the rupture and return the cell back to homeostasis. Here, we present the three-dimensional structure of a multiprotein complex that includes S100A10, annexin A2, and AHNAK, which along with dysferlin, functions in muscle and cardiac tissue repair. The 3.5Å resolution X-ray structure shows that a single region from the AHNAK Cterminus is recruited by an S100A10-annexin A2 heterotetramer, forming an asymmetric ternary complex. The AHNAK peptide adopts a coil conformation that arches across the heterotetramer contacting both annexin A2 and S100A10 protomers with tight affinity (∼30nM) and establishing a structural rationale whereby both S100A10 and annexin proteins are needed in AHNAK recruitment. The structure evokes a model whereby AHNAK is targeted to the membrane surface through sandwiching of the binding region between the S100A10/annexin A2 complex and the phospholipid membrane.

The S100A10-Annexin A2 Complex Provides a Novel Asymmetric Platform for Membrane Repair

Membrane repair is mediated by multiprotein complexes, such as that formed between the dimeric EF-hand protein S100A10, the calcium- and phospholipid-binding protein annexin A2, the enlargeosome protein AHNAK, and members of the transmembrane ferlin family. Although interactions between these proteins have been shown, little is known about their structural arrangement and mechanisms of formation. In this work, we used a non-covalent complex between S100A10 and the N terminus of annexin A2 (residues 1-15) and a designed hybrid protein (A10A2), where S100A10 is linked in tandem to the N-terminal region of annexin A2, to explore the binding region, stoichiometry, and affinity with a synthetic peptide from the C terminus of AHNAK. Using multiple biophysical methods, we identified a novel asymmetric arrangement between a single AHNAK peptide and the A10A2 dimer. The AHNAK peptide was shown to require the annexin A2 N terminus, indicating that the AHNAK binding site comprises regions on both S100A10 and annexin proteins. NMR spectroscopy was used to show that the AHNAK binding surface comprised residues from helix IV in S100A10 and the C-terminal portion from the annexin A2 peptide. This novel surface maps to the exposed side of helices IV and IV' of the S100 dimeric structure, a region not identified in any previous S100 target protein structures. The results provide the first structural details of the ternary S100A10 protein complex required for membrane repair.

Integrable cases in the dynamics of axial gyrostats and adiabatic invariants

This paper presents the study of axial gyrostats dynamics. The gyrostat is composed of two rigid bodies: an asymmetric platform and an axisymmetric rotor aligned with the platform principal axis. The paper discusses three types of gyrostats: oblate, prolate, and intermediate. Rotation of the rotor relative to the platform provides a source of small internal angular momentum and does not affect the moment of inertia tensor of the gyrostat. The dynamics of gyrostats without external torque is considered. The dynamics is described by using ordinary differential equations with Andoyer–Deprit canonical variables. For undisturbed motion, when the internal moment is equal to zero, the stationary solutions are found, and their stability is studied. General analytical solutions in terms of elliptic functions are also obtained. These results can be interpreted as the development of the classical Euler case for a solid, when to one degree of freedom—the relative rotation of bodies—is added. For disturbed motion of the gyrostats, when there is a system with slowly varying parameters, the adiabatic invariants are obtained in terms of complete elliptic integrals, which are approximately equal to the first integrals of the disturbed system. The adiabatic invariants remain approximately constant along a trajectory for long time intervals during which the parameter changes considerably. The results of the study can be useful for the analysis of dynamics of dual-spin spacecraft and for studying a chaotic behavior of the spacecraft.

Measurement and Statistical Analysis of Asymmetric Multipoint Videoconference Traffic in IP Networks

The paper contributes results on the modeling of videoconferencing traffic over IP networks. The study is based on extensive data, gathered by tracing the actual packet exchange during a comprehensive set of realistic teleconferencing sessions over an asymmetric platform, in which commercial H.261-compliant terminal clients were communicating through a Multipoint Control Unit (MCU) at `continuous presence' mode. Analysis of the data suggests that the video traffic from the client terminals can always be represented at the frame level as a stationary stochastic process with an autocorrelation function of exponentially fast decay and a marginal frame size distribution of approximately Gamma form. The video traffic from the MCU to the clients is again stationary and with exponentially decaying correlations, while the corresponding marginal frame-size PDF has the form of an appropriately weighted sum of Gamma components, the number of terms in the sum always being equal to the number of conferring terminals. The paper discusses methods for correctly matching the parameters of the modeling components to the data and for combining these components into complete traffic models that have been proposed in the literature.

Control of Chaotic Instability in a Dual-Spin Spacecraft with Dissipation Using Energy Methods

Control of chaotic instability in a rotating multibody system in the form of a dual-spin spacecraft with an axial nutational damper is achieved using an algorithm derived using energy methods. The control method is implemented on two realistic spacecraft parameter configurations which have been found to exhibit chaotic instability when a sinusoidally varying torque is applied to the spacecraft for a range of forcing amplitudes and frequencies. Such a torque, in practice, may arise under malfunction of the control system or from an unbalanced rotor. Chaotic instabilities arising from these torques could introduce uncertainties and irregularities into a spacecraft's attitude and consequently impair pointing accuracy. The control method is formulated from nutational stability results derived using an energy sink approximation for a dual-spin spacecraft with an asymmetric platform and axisymmetric rotor. The effectiveness of the control method is shown numerically and the results are studied by means of time history, phase space, Poincare map, Lyapunov characteristic exponents and Bifurcation diagrams.

QUANTIFICATION OF TRUNK MOTION IN RESPONSE TO COMPLEX PLATFORM PERTURBATIONS WHILE HOLDING WEIGHTS IN AN UPRIGHT POSTURE

This experiment investigated the role of the lumbar region in a simple load-holding situation for three asymmetric (0, 45 and 90 deg) platform perturbations for 18 normal, college age males. The platform perturbations included horizontal translation and rotation in addition to stable condition. The weight was 20% of the subjects' body weight. The Balance System (Chattecx Co.) was used to monitor balance performance while the Lumbar Motion Monitor was used to quantify low-back kinematics. The platform perturbation significantly affected both the lumbar motion parameters and the dispersion, an index of postural sway. The asymmetry of direction of perturbation also significantly affected both the postural sway and the lumbar motion involvement. Given the large mass of the spine, corrective/reactive fast movements to maintain the balance due to the unexpected perturbation to the base of support may lead to impulsive loading of the spine which is associated with the low back injuries. The study of postural stability, whilst an additional manual material handling task is being performed presents a more realistic and functional test than the traditional protocols used presently in Balance Clinics. This type of functional dual tasking is a rich paradigm that requires more research investigations.

Spinup dynamics of axial dual-spin spacecraft

We consider spinup dynamics of axial dual-spin spacecraft composed of two rigid bodies: an asymmetric platform and an axisymmetric rotor parallel to a principal axis of the platform. The system is free of external torques, and spinup of the rotor is effected by a small constant internal axial torque. The dynamics are described by four first-order differential equations. Conservation of angular momentum and the method of averaging are used to reduce the problem to a single first-order differential equation which is studied numerically. This reduction has a geometric counterpart that we use to simplify the investigation of spinup dynamics. In particular, a resonance condition due to platform asymmetry and associated with an instantaneous separatrix crossing is clearly identified using our approach.

Quantification of lumbar motion in response to asymmetric platform perturbations

Quantification of lumbar motion in response to asymmetric platform perturbations

Perturbation Solution for the Flat Spin Recovery of a Dual-§pin Spacecraft

Euler's differential equations for free-body attitude motion are solved for the constant bearing axis torque recovery maneuver of a spacecraft with a symmetric rotor and asymmetric platform. The rotor bearing axis coincides with the spacecraft's centroidal principal axis of least inertia. The recovery time and the residual nutation angle are algebraically related to the initial flat spin rate, the spacecraft inertia properties, and the bearing axis torque. The differential equations are solved by use of two asymptotic parameter expansions of the multiple time scale type, which are matched to a transition expansion with a limit process matching procedure.