Probing the internal structure and morphology of fiber-like polythiophene-based block copolymer micelles

Dominic W HAYWARD,Robert R RICHARDSON,Ian MANNERS 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Gyroless Spin-Stabilization Controller and Deorbiting Algorithm for CubeSats

Jose E. Morales,김종래,Robert R. Richardson 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.2

CubeSats are becoming increasingly popular in the scientific community. While they provide a whole new range of opportunities for space exploration, they also come with their own challenges. One of the main concerns is the negative impact which they can have in the space debris problem. Commonly lacking from attitude determination and propulsion capabilities, it has been difficult to provide CubeSats with means for active deorbiting. While electric propulsion technology has been emerging for its application in CubeSats, little or no literature is available on methods to enable it to be used for deorbiting purposes, especially within the tight constraints faced by these nanosatellites. We present a new and simple algorithm for CubeSat deorbiting, which proposes the use of novel electric propulsion technology with minimum sensing and actuation capabilities. The algorithm is divided into two stages: a spin-stabilization control; and a deorbiting-phase detection. The spin-stabilization control is inspired by the B-dot controller. It does not require gyroscopes, but only requires magnetometers and magnetorquers as sensors and actuators, respectively. The deorbiting-phase detection is activated once the satellite is spin-stabilized. The algorithm can be easily implementable as it does not require any attitude information other than the orbital information, e.g., from the Global Positioning System receiver, which could be easily installed in CubeSats. The effectiveness of each part of the algorithms is validated through numerical simulations. The proposed algorithms outperform the existing approaches such as deorbiting sails, inflatable structures, and electrodynamic tethers in terms of deorbiting times. Stability and robustness analysis are also provided. The proposed algorithm is ready to be implemented with minimal effort and provides a robust solution to the space junk mitigation efforts.

Decreased Catalytic Subunit mRNA Levels and Altered Catalytic Subunit mRNA Structure in a cAMP-resistant Chinese Hamster Ovary Cell line

Howard, Paul,Day, Kathleen H.,Kim, Kyoon E.,Richardson, Jeanne,Thomas, James,Abraham,Irene,Fleischmann, Robert D.,Gottesman, Michael M.,Maurer, Richard A. 충남대학교부설 생명공학연구소 1992 생물공학연구지 Vol.2 No.-

The mechansims responsible for decreased levels of cAMP-dependent protein kinase activity in a mutant Chinese hamster ovary cell line have been examined. The cAMP-resistant Chinese hamster ovary 10260 cell line was found to possess only 20% of the cAMP-dependent protein kinase activity found in wild-type cells. The pressence of decreased concentrations of the catalytic subunit in these cells was confirmed through binding studies using a radiolabeled, heat-stable inhibitor of the kinase. Cloned Chinese hamster ovary catalytic subunit cDNAs were isolated, characterized, and used as hybridization probes to examine the relative concentrations of catalytic subunit mRNAs in the wild-type and 10260 cell lines. A 40-50% decrease in the concentration of the mRNA for the Cα isozyme of the catalytic subunit was observed in 10260 cells, as compared with wild-type. This decrease in catalytic subunit mRNA concentration probably accounts for a portion of the decreased kinase activity in the mutant cell. Further analysis of Cα mRNA by polymerase chain reaction confirmed the decreased expression of Cα mRNA in 10260 cells and further demonstrated the presence of two different species of Cα cDNAs was indistinguishable from the wild-type cDNA, but the other species was shorter. Nucleotide sequence analysis of the amplified cDNAs led to the identification of a 191-base pair deletion in the shorter cDNA. Gene transfer studies using wild-type and 10260 Cα cDNAs demonstrated wild-type activity, but the shorter cDNA was inactive. These studies suggest that at least two alternations in gene expression are responsible for decreased cAMP-dependent protein kinase activity in the 10260 cell line. One alteration results in an approximately 2-fold decrease in the concentrations of Cα mRNA in the cells.

MHz gravitational wave constraints with decameter Michelson interferometers

Chou, Aaron S.,Gustafson, Richard,Hogan, Craig,Kamai, Brittany,Kwon, Ohkyung,Lanza, Robert,Larson, Shane L.,McCuller, Lee,Meyer, Stephan S.,Richardson, Jonathan,Stoughton, Chris,Tomlin, Raymond,Weiss, American Physical Society 2017 Physical Review D Vol.95 No.6

<P>A new detector, the Fermilab Holometer, consists of separate yet identical 39-meter Michelson interferometers. Strain sensitivity achieved is better than 10(-21) / root Hz between 1 to 13 MHz from a 130-h data set. This measurement exceeds the sensitivity and frequency range made from previous high frequency gravitational wave experiments by many orders of magnitude. Constraints are placed on a stochastic background at 382 Hz resolution. The 3 sigma upper limit on Omega(GW), the gravitational wave energy density normalized to the closure density, ranges from 5.6 x 10(12) at 1 MHz to 8.4 x 10(15) at 13 MHz. Another result from the same data set is a search for nearby primordial black hole binaries (PBHB). There are no detectable monochromatic PBHBs in the mass range 0.83-3.5 x 10(21) g between the Earth and the Moon. Projections for a chirp search with the same data set increase the mass range to 0.59 - 2.5 x 10(25) g and distances out to Jupiter. This result presents a new method for placing limits on a poorly constrained mass range of primordial black holes. Additionally, solar system searches for PBHBs place limits on their contribution to the total dark matter fraction.</P>

Interferometric constraints on quantum geometrical shear noise correlations

Chou, Aaron,Glass, Henry,Richard Gustafson, H,Hogan, Craig J,Kamai, Brittany L,Kwon, Ohkyung,Lanza, Robert,McCuller, Lee,Meyer, Stephan S,Richardson, Jonathan W,Stoughton, Chris,Tomlin, Ray,Weiss, Rai IOP 2017 Classical and quantum gravity Vol.34 No.16

<P>Final measurements and analysis are reported from the first-generation Holometer, the first instrument capable of measuring correlated variations in space-time position at strain noise power spectral densities smaller than a Planck time. The apparatus consists of two co-located, but independent and isolated, 40 m power-recycled Michelson interferometers, whose outputs are cross-correlated to 25 MHz. The data are sensitive to correlations of differential position across the apparatus over a broad band of frequencies up to and exceeding the inverse light crossing time, 7.6 MHz. By measuring with Planck precision the correlation of position variations at spacelike separations, the Holometer searches for faint, irreducible correlated position noise backgrounds predicted by some models of quantum space-time geometry. The first-generation optical layout is sensitive to quantum geometrical noise correlations with shear symmetry—those that can be interpreted as a fundamental noncommutativity of space-time position in orthogonal directions. General experimental constraints are placed on parameters of a set of models of spatial shear noise correlations, with a sensitivity that exceeds the Planck-scale holographic information bound on position states by a large factor. This result significantly extends the upper limits placed on models of directional noncommutativity by currently operating gravitational wave observatories.</P>

The Holometer: an instrument to probe Planckian quantum geometry

Chou, Aaron,Glass, Henry,Gustafson, H Richard,Hogan, Craig,Kamai, Brittany L,Kwon, Ohkyung,Lanza, Robert,McCuller, Lee,Meyer, Stephan S,Richardson, Jonathan,Stoughton, Chris,Tomlin, Ray,Weiss, Rainer Institute of Physics 2017 Classical and quantum gravity Vol.34 No.6

<P>This paper describes the Fermilab Holometer, an instrument for measuring correlations of position variations over a four-dimensional volume of space-time. The apparatus consists of two co-located, but independent and isolated, 40 m power-recycled Michelson interferometers, whose outputs are cross-correlated to 25 MHz. The data are sensitive to correlations of differential position across the apparatus over a broad band of frequencies up to and exceeding the inverse light crossing time, 7.6 MHz. A noise model constrained by diagnostic and environmental data distinguishes among physical origins of measured correlations, and is used to verify shot-noise-limited performance. These features allow searches for exotic quantum correlations that depart from classical trajectories at spacelike separations, with a strain noise power spectral density sensitivity smaller than the Planck time. The Holometer in current and future configurations is projected to provide precision tests of a wide class of models of quantum geometry at the Planck scale, beyond those already constrained by currently operating gravitational wave observatories.</P>