The Smallest Particles in Saturn's A and C Rings

Radio occultations of Saturn's main rings by spacecraft suggest a power law particle size-distribution down to sizes of the order of 1 cm (Marouf et al., 1983), (Zebker et al., 1985). The lack of optical depth variations between ultraviolet and near-IR wavelengths indicate a lack of micron-sized particles. Between these two regimes, the particle-size distribution is largely unknown. A cutoff where the particle-size distribution turns over must exist, but the position and shape of it is not clear from existing studies. Using a series of solar occultations performed by the VIMS instrument on-board Cassini in the near-infrared, we are able to measure light forward scattered by particles in the A and C rings. With a model of diffraction by ring particles, and the previous radio work as a constraint on the slope of the particle size distribution, we estimate the minimum particle size using a truncated power-law size distribution. The C Ring shows a minimum particle size of $4.1^{+3.8}_{-1.3}$ mm, with an assumed power law index of q=3.1 and a maximum particle size of 10 m. The A Ring signal shows a similar level of scattered flux, but modeling is complicated by the presence of self-gravity wakes and higher optical depths. If q<3, our A Ring model requires a minimum particle size below one millimeter (< 0.34 mm for an assumed q=2.75, or $0.56^{+0.35}_{-0.16}$ mm for a steeper q=2.9) to be consistent with VIMS observations. These results might seem to contradict previous optical(Dones et al., 1993) and infrared (French and Nicholson, 2000) work, which implied that there were few particles in the A Ring smaller than 1 cm. But, because of the shallow power law, relatively little optical depth (between 0.03 and 0.16 in extinction, or 0.015 - 0.08 in absorption) is provided by these particles.Comment: 47 pages, 16 figures, 3 Table

Alien Registration- Harbison, James M. (Monticello, Aroostook County)

https://digitalmaine.com/alien_docs/33895/thumbnail.jp

Formation of Low Threshold Voltage Microlasers

Vertical cavity surface emitting lasers (VCSELs) with threshold voltages of 1.7V have been fabricated. The resistance-area product in these new vertical cavity lasers is comparable to that of edge-emitting lasers, and threshold currents as low as 3 mA have been measured. Molecular beam epitaxy was used to grow n-type mirrors, a quantum well active region, and a heavily Be-doped p-contact. After contact definition and alloying, passive high-reflectivity mirrors were deposited by reactive sputter deposition of SiO2/Si3N4 to complete the laser cavity

Ultranarrow conducting channels defined in GaAs-AlGaAs by low-energy ion damage

We have laterally patterned the narrowest conducting wires of two-dimensional electron gas (2DEG) material reported to date. The depletion induced by low-energy ion etching of GaAs-AlGaAs 2DEG structures was used to define narrow conducting channels. We employed high voltage electron beam lithography to create a range of channel geometries with widths as small as 75 nm. Using ion beam assisted etching by Cl2 gas and Ar ions with energies as low as 150 eV, conducting channels were defined by etching only through the thin GaAs cap layer. This slight etching is sufficient to entirely deplete the underlying material without necessitating exposure of the sidewalls that results in long lateral depletion lengths. At 4.2 K, without illumination, our narrowest wires retain a carrier density and mobility at least as high as that of the bulk 2DEG and exhibit quantized Hall effects. Aharonov–Bohm oscillations are seen in rings defined by this controlled etch-damage patterning. This patterning technique holds promise for creating one-dimensional conducting wires of even smaller sizes

Trends in the Use of Extrinsic Aids in Statutory Interpretation

As evidenced by the increasing numbers of court decisions which involve statutes,\u27 and by the large and continually growing literature in the field, the subject of statutory interpretation is one of the most important in modern law. Although it is a field in which exact rules of automatic application can very seldom be formulated, only recently a member of the Supreme Court pointed out the great need for a set of consistently accepted principles of interpretation. Since the primary purpose of all statutory interpretation is to ascertain the meaning and to effectuate the purposes of the legislature, and since words are merely symbols without inherent meaning, every statute upon which a court is required to rule must, in some sense, be construed and interpreted

Trends in the Use of Extrinsic Aids in Statutory Interpretation

As evidenced by the increasing numbers of court decisions which involve statutes,\u27 and by the large and continually growing literature in the field, the subject of statutory interpretation is one of the most important in modern law. Although it is a field in which exact rules of automatic application can very seldom be formulated, only recently a member of the Supreme Court pointed out the great need for a set of consistently accepted principles of interpretation. Since the primary purpose of all statutory interpretation is to ascertain the meaning and to effectuate the purposes of the legislature, and since words are merely symbols without inherent meaning, every statute upon which a court is required to rule must, in some sense, be construed and interpreted

Non-Volatile Memory Characteristics of Submicrometre Hall Structures Fabricated in Epitaxial Ferromagnetic MnAl Films on GaAs

Hall-effect structures with submicrometre linewidths (<0.3pm) have been fabricated in ferromagnetic thin films of Mn[sub 0.60]Al[sub 0.40] which are epitaxially grown on a GaAs substrate. The MnAl thin films exhibit a perpendicular remanent magnetisation and an extraordinary Hall effect with square hysteretic behaviour. The presence of two distinct stable readout states demonstrates the potential of using ultrasmall ferromagnetic volumes for electrically addressable, nonvolatile storage of digital information

Epitaxial-tau(Mn,Ni)Al/(Al,Ga)As heterostructures: Magnetic and magneto-optic properties

Ferromagnetic Perpendicularly magnetized epitaxial thin films of tau (Mn,Ni)AI have been successfully grown on AlAs/GaAs heterostructures by molecular beam epitaxy. We have investigated the polar Kerr rotation and magnetization of tau MnAl and (Mn,Ni) Al as a function of Mn and Ni concentration. The largest polar Kerr rotation and remnant magnetization were obtained for Mn0.5Al0.5 thin films with values of 0.16-degrees and 224 emu/cm3, respectively. We observed that the Kerr rotation and magnetization remained constant with Ni additions up to about 12 at. % and subsequently decreased with further Ni additions. We discuss these results and one possible method of enhancing the Kerr rotation

Emerging out of the “blur”: exploration, evaluation and significance of 3D N-glycans’ structure through molecular dynamic studies

Glycosylation is the most abundant and diverse post-translational modification of proteins, contributing to protein folding, trafficking, structural stability and dynamics, and function. Complex N-glycans are a class of glycans found in eukaryotes, sharing a common pentasaccharide core structure. The functionalization of the arms and the branching patterns are specific to different species, while the complexity of the cellular biosynthetic pathways contribute to the broad variety and to the heterogeneity of N-glycan sequences. By understanding at an atomistic level of detail the structural implications of glycan sequence, we can relate the glycan sequence to its function in a given glycoprotein environment. With this ultimate goal in mind I conducted, through conventional and enhanced molecular dynamics (MD) methods, a series of systematic studies of mammalian, plant and invertebrate glycosylation patterns, in order to characterize the intrinsic 3D architecture of different sets of commonly found and synthetic (non-natural) glycan structures. From these results, we were able to disentangle the complexity of N-glycans structure and dynamics through a new 3D representation, which describes N- glycans not only in terms of the monosaccharides sequence, but that also includes anomeric configurations and linkage specificity. Within this framework, we defined N-glycans as structured by specific groups of monosaccharide units, named “glycoblocks”. This formulation incorporates 3D structural information and uniquely dictates the overall conformational landscape of any given N - glycan. With this expanded viewpoint of sequence-to-structure dependencies in complex N-glycans, we applie d this knowledge to glycoproteins, where variation of glycan composition affects its functiona l capabilities. In the two cases presented in this thesis, we determined how changes in the sequence of the N-glycans in the Fc region of IgG1 antibodies affect its effector function, and discovered for the first time a unique functional role of the glycan shield in the SARS-CoV-2 spike protein. In both cases, we observed that the conformational equilibria of complex N-glycans change to promote conformers that can accommodate interactions with the glycoprotein environment, but this adaption does not interfere with the intrinsic 3D glycan architecture, shifting a paradigm commonly assumed in structural biology, where the protein dictates the glycan conformation by actively morphing it. The work presented in this thesis shows an alternative atomistic perspective of N-glycans structure and dynamics, where glycans play a starring role rather than a cameo as a simple protein “decoration”, while the knowledge and insight gained could inform the ad-hoc design and modulation of sequence-to- structure-to-function relationships of complex N-glycans, with applications in glycoengineering and therapeutic and diagnostic strategies