Real Interference Alignment and Degrees of Freedom Region of Wireless X Networks

Abstract-We consider a single hop wireless X network with K transmitters and J receivers, all with single antenna. Each transmitter conveys for each receiver an independent message. The channel is assumed to have constant coefficients. We develop interference alignment scheme for this setup and derived several achievable degrees of freedom regions. We show that in some cases, the derived region meets a previous outer bound and are hence the DoF region. For our achievability schemes, we divide each message into streams and use real interference alignment on the streams. Several previous results on the DoF region and total DoF for various special cases can be recovered from our result. Index Terms-real interference alignment, degrees of freedom region, wireless X network, stream alignmen

Mechanistic insights into allosteric regulation of the A2A adenosine G protein-coupled receptor by physiological cations.

Cations play key roles in regulating G-protein-coupled receptors (GPCRs), although their mechanisms are poorly understood. Here, 19F NMR is used to delineate the effects of cations on functional states of the adenosine A2A GPCR. While Na+ reinforces an inactive ensemble and a partial-agonist stabilized state, Ca2+ and Mg2+ shift the equilibrium toward active states. Positive allosteric effects of divalent cations are more pronounced with agonist and a G-protein-derived peptide. In cell membranes, divalent cations enhance both the affinity and fraction of the high affinity agonist-bound state. Molecular dynamics simulations suggest high concentrations of divalent cations bridge specific extracellular acidic residues, bringing TM5 and TM6 together at the extracellular surface and allosterically driving open the G-protein-binding cleft as shown by rigidity-transmission allostery theory. An understanding of cation allostery should enable the design of allosteric agents and enhance our understanding of GPCR regulation in the cellular milieu

Doctor of Philosophy

dissertationPlatelet-surface interactions are a key mediator in a host's response to vascular biomaterials. Directly after implantation, a wide variety of serum proteins are adsorbed onto the surface of vascular devices, many of which activate platelets. Serving as the first step in the coagulation cascade, the local activation of platelets sets off a chain of events that can ultimately determine the fate of implanted vascular devices. Many material engineering approaches have been taken in an effort to reduce this activation; however, the most successful method to date remains the systemic delivery of antiplatelet and anticoagulant agents. The prevalence of antiplatelet pharmaceutics, coupled with a variation in efficacy across a diverse population, has led to an industry focused on the personalized assessment of platelet function. In this dissertation, methods were developed to address a deficiency in the current approach to platelet function testing. No current assays take into account the transient interactions of platelets with agonist surfaces, interactions that have the capability to prime a platelet population for enhanced adhesion and activation downstream of a stimulus. This phenomenon was leveraged here to create a flow cell in which the upstream priming of a platelet population by a surface-bound agonist could be assessed by downstream capture assay. It was demonstrated that this device is capable of determining the response of a platelet population to a variable priming stimulus, both alone and in the presence of common antiplatelet agents. To further investigate the priming response of platelets, it was of interest to develop a method by which to pattern multiple proteins on the same surface, thus enabling the measurement of the platelet population response to multiple surface bound agonists. Taking advantage of advances in microcontact printing and modern light microscopy, a new method by which to deposit multiple aligned patterns of agonists on a single substrate was developed. This patterning method was then used to investigate the ability of multiple agonists to prime platelets in flowing blood and observe the synergistic response that platelets exhibit when primed by multiple pathways. Taken collectively, these experiments contribute to the field of platelet activation by providing a controlled environment in which to study the priming response of platelets following transient exposure to surface bound agonists. This assay provides a platform in which the platelet response to a variety of surface coatings, biomaterials, and antiplatelet agents can be explored, and establishes a foundation for the further investigation of priming pathways in platelets

Autonomous support for microorganism research in space

A preliminary design for performing on orbit, autonomous research on microorganisms and cultured cells/tissues is presented. An understanding of gravity and its effects on cells is crucial for space exploration as well as for terrestrial applications. The payload is designed to be compatible with the Commercial Experiment Transporter (COMET) launch vehicle, an orbiter middeck locker interface, and with Space Station Freedom. Uplink/downlink capabilities and sample return through controlled reentry are available for all carriers. Autonomous testing activities are preprogrammed with in-flight reprogrammability. Sensors for monitoring temperature, pH, light, gravity levels, vibrations, and radiation are provided for environmental regulation and experimental data collection. Additional experimental data acquisition includes optical density measurement, microscopy, video, and film photography. On-board full data storage capabilities are provided. A fluid transfer mechanism is utilized for inoculation, sampling, and nutrient replenishment of experiment cultures. In addition to payload design, representative experiments were developed to ensure scientific objectives remained compatible with hardware capabilities. The project is defined to provide biological data pertinent to extended duration crewed space flight including crew health issues and development of a Controlled Ecological Life Support System (CELSS). In addition, opportunities are opened for investigations leading to commercial applications of space, such as pharmaceutical development, modeling of terrestrial diseases, and material processing

Spacecraft design project: Low Earth orbit communications satellite

This is the final product of the spacecraft design project completed to fulfill the academic requirements of the Spacecraft Design and Integration 2 course (AE-4871) taught at the U.S. Naval Postgraduate School. The Spacecraft Design and Integration 2 course is intended to provide students detailed design experience in selection and design of both satellite system and subsystem components, and their location and integration into a final spacecraft configuration. The design team pursued a design to support a Low Earth Orbiting (LEO) communications system (GLOBALSTAR) currently under development by the Loral Cellular Systems Corporation. Each of the 14 team members was assigned both primary and secondary duties in program management or system design. Hardware selection, spacecraft component design, analysis, and integration were accomplished within the constraints imposed by the 11 week academic schedule and the available design facilities

Super-resolution and super-localization microscopy: a novel tool for imaging chemical and biological processes

Optical microscopy imaging of single molecules and single particles is an essential method for studying fundamental biological and chemical processes at the molecular and nanometer scale. The best spatial resolution (~ λ/2) achievable in traditional optical microscopy is governed by the diffraction of light. However, single molecule-based super-localization and super-resolution microscopy imaging techniques have emerged in the past decade. Individual molecules can be localized with nanometer scale accuracy and precision for studying of biological and chemical processes. The obtained spatial resolution for plant cell imaging is not yet as good as that achieved in mammalian cell imaging. Numerous technical challenges, including the generally high fluorescence background due to significant autofluorescence of endogenous components, and the presence of the cell wall (\u3e 250 nm thickness) limit the potential of super-resolution imaging in studying the cellular processes in plants. Here variable-angle epi-fluorescence microscopy (VAEM) was combined with localization based super-resolution imaging, direct stochastic optical reconstruction microscopy (dSTORM), to demonstrate imaging of cortical microtubule (CMT) network in the Arabidopsis thaliana root cells with 20 – 40 nm spatial resolution for the first time. With such high spatial resolution, the subcellular organizations of CMTs within single cells, and different cells in many regions along the root, were analyzed quantitatively. Nearly all of these technical advances in super-localization and super-resolution microscopy imaging were originally developed for biological studies. More recently, however, efforts in super-resolution chemical imaging started to gain momentum. New discoveries that were previously unattainable with conventional diffraction-limited techniques have been made, such as a) super-resolution mapping of catalytic reactions on single nanocatalysts and b) mechanistic insight into protein ion-exchange adsorptive separations. Furthermore, single molecules and single particles were localized with nanometer precision for resolving the dynamic behavior of single molecules in porous materials. This work uncovered the heterogeneous properties of the pore structures. In this dissertation, the coupling of molecular transport and catalytic reaction at the single molecule and single particle level in multilayer mesoporous nanocatalysts was elucidated. Most previous studies dealt with these two important phenomena separately. A fluorogenic oxidation reaction of non-fluorescent amplex red to highly fluorescent resorufin was tested. The diffusion behavior of single resorufin molecules in aligned nanopores was studied using total internal reflection fluorescence microscopy (TIRFM). To fully understand the working mechanisms of biological processes such as stepping of motor proteins requires resolving both the translational movement and the rotational motions of biological molecules or molecular complexes. Nanoparticle optical probes have been widely used to study biological processes such as membrane diffusion, endocytosis, and so on. The greatly enhanced absorption and scattering cross sections at the surface plasmon resonance (SPR) wavelength make nanoparticles an ideal probe for high precision tracking. Furthermore, gold nanorods (AuNRs) were used for resolving orientation changes in all three dimensions. The translational and rotational motions of AuNRs in glycerol solutions were tracked with fast imaging rate up to 500 frames per second (fps) in reflected light sheet microscopy (RLSM). The effect of imaging rates on resolving details of single AuNR motions was studied