Nature-Inspired Interconnects for Self-Assembled Large-Scale Network-on-Chip Designs

Future nano-scale electronics built up from an Avogadro number of components needs efficient, highly scalable, and robust means of communication in order to be competitive with traditional silicon approaches. In recent years, the Networks-on-Chip (NoC) paradigm emerged as a promising solution to interconnect challenges in silicon-based electronics. Current NoC architectures are either highly regular or fully customized, both of which represent implausible assumptions for emerging bottom-up self-assembled molecular electronics that are generally assumed to have a high degree of irregularity and imperfection. Here, we pragmatically and experimentally investigate important design trade-offs and properties of an irregular, abstract, yet physically plausible 3D small-world interconnect fabric that is inspired by modern network-on-chip paradigms. We vary the framework's key parameters, such as the connectivity, the number of switch nodes, the distribution of long- versus short-range connections, and measure the network's relevant communication characteristics. We further explore the robustness against link failures and the ability and efficiency to solve a simple toy problem, the synchronization task. The results confirm that (1) computation in irregular assemblies is a promising and disruptive computing paradigm for self-assembled nano-scale electronics and (2) that 3D small-world interconnect fabrics with a power-law decaying distribution of shortcut lengths are physically plausible and have major advantages over local 2D and 3D regular topologies

On the prevalence of bridged macrocyclic pyrroloindolines formed in regiodivergent alkylations of tryptophan.

A Friedel-Crafts alkylation is described that efficiently transforms tryptophan-containing peptides into macrocycles of varying ring connectivity. Factors are surveyed that influence the distribution of regioisomers, with a focus on indole C3-alkylations leading to bridged endo-pyrroloindolines. We probe the stability and stereochemistry of these pyrroloindolines, study their rearrangement to C2-linked indolic macrocycles, and demonstrate a scalable, stereoselective synthesis of this compound class. Placing the macrocyclization in sequence with further template-initiated annulation leads to extraordinary polycyclic products and further demonstrates the potential for this chemistry to drive novel peptidomimetic lead discovery programs

Accelerated Test Development for Coil-coated Steel Building Panels

This paper discusses the experimental design and the preliminary findings of an ongoing project designed to establish an accelerated laboratory test that would rank coating system performance the same as their performance in atmospheric exposure. A total of ten materials are included in the program: four substrates each with two coating systems and one substrate with two additional coating systems. Samples were installed at four atmospheric exposure sites: Middletown, OH, Daytona Beach, FL, Monroeville, PA, and Halifax, NS, Canada. Three different orientations were utilized at each of the exposure sites and a variety of building panel features were included on the test panels (roll formed bends, laps, cut drip edges, standing seam closures, and scribes). The work discussed in this paper includes the program design and implementation and preliminary correlation\u27s of the three-year atmospheric exposure results to several standard accelerated test methods including: ASTM B117, ASTM G85, ASTM G87, and GM 9540

Stability of Fermi Surfaces and K-Theory

Nonrelativistic Fermi liquids in d+1 dimensions exhibit generalized Fermi surfaces: (d-p)-dimensional submanifolds in the momentum-frequency space supporting gapless excitations. We show that the universality classes of stable Fermi surfaces are classified by K-theory, with the pattern of stability determined by Bott periodicity. The Atiyah-Bott-Shapiro construction implies that the low-energy modes near a Fermi surface exhibit relativistic invariance in the transverse p+1 dimensions. This suggests an intriguing parallel between norelativistic Fermi liquids and D-branes of string theory.Comment: 4 pages, revte

Unveiling a Population of X-ray Non-Detected AGN

We define a sample of 27 radio-excess AGN in the Chandra Deep Field North by selecting galaxies that do not obey the radio/infrared correlation for radio-quiet AGN and star-forming galaxies. Approximately 60% of these radio-excess AGN are X-ray undetected in the 2 Ms Chandra catalog, even at exposures of > 1 Ms; 25% lack even 2-sigma X-ray detections. The absorbing columns to the faint X-ray-detected objects are 10^22 cm^-2 < N_H < 10^24 cm^-2, i.e., they are obscured but unlikely to be Compton thick. Using a local sample of radio-selected AGN, we show that a low ratio of X-ray to radio emission, as seen in the X-ray weakly- and non-detected samples, is correlated with the viewing angle of the central engine, and therefore with obscuration. Our technique can explore the proportion of obscured AGN in the distant Universe; the results reported here for radio-excess objects are consistent with but at the low end of the overall theoretical predictions for Compton-thick objects.Comment: Accepted for publication in the Astrophysical Journal, 15 pages, 10 figures, 4 table

Topological Defects and Gapless Modes in Insulators and Superconductors

We develop a unified framework to classify topological defects in insulators and superconductors described by spatially modulated Bloch and Bogoliubov de Gennes Hamiltonians. We consider Hamiltonians H(k,r) that vary slowly with adiabatic parameters r surrounding the defect and belong to any of the ten symmetry classes defined by time reversal symmetry and particle-hole symmetry. The topological classes for such defects are identified, and explicit formulas for the topological invariants are presented. We introduce a generalization of the bulk-boundary correspondence that relates the topological classes to defect Hamiltonians to the presence of protected gapless modes at the defect. Many examples of line and point defects in three dimensional systems will be discussed. These can host one dimensional chiral Dirac fermions, helical Dirac fermions, chiral Majorana fermions and helical Majorana fermions, as well as zero dimensional chiral and Majorana zero modes. This approach can also be used to classify temporal pumping cycles, such as the Thouless charge pump, as well as a fermion parity pump, which is related to the Ising non-Abelian statistics of defects that support Majorana zero modes.Comment: 27 pages, 15 figures, Published versio

Binarity as a key factor in protoplanetary disk evolution: Spitzer disk census of the eta Chamaeleontis cluster

The formation of planets is directly linked to the evolution of the circumstellar (CS) disk from which they are born. The dissipation timescales of CS disks are, therefore, of direct astrophysical importance in evaluating the time available for planet formation. We employ Spitzer Space Telescope spectra to complete the CS disk census for the late-type members of the ~8 Myr-old eta Chamaeleontis star cluster. Of the 15 K- and M-type members, eight show excess emission. We find that the presence of a CS disk is anti-correlated with binarity, with all but one disk associated with single stars. With nine single stars in total, about 80% retain a CS disk. Of the six known or suspected close binaries the only CS disk is associated with the primary of RECX 9. No circumbinary disks have been detected. We also find that stars with disks are slow rotators with surface values of specific angular momentum j = 2-15 j_sun. All high specific angular momentum systems with j = 20-30 j_sun are confined to the primary stars of binaries. This provides novel empirical evidence for rotational disk locking and again demonstrates the much shorter disk lifetimes in close binary systems compared to single star systems. We estimate the characteristic mean disk dissipation timescale to be ~5 Myr and ~9 Myr for the binary and single star systems, respectively.Comment: Accepted by ApJ

Research notes: Characterization of several abnormal nodulation reactions in soybeans

Several abnormal nodulation reactions in soybeans are known. These range from a complete lack of nodules, caused by the non-nodulating gene (Williams and Lynch, 1954) to plants with normal-appearing nodules (Vest et al., 1973), but low nitrogen fixation as exemplified by the \u27Peking\u27-strain T23 combination. The purpose of the study reported here was threefold

Research notes: Inheritance of abnormal nodulation between Rhizobium japonicum strain 62 and the soybean variety Amsoy 71

To date, four genes are known that result in abnormal nodulation in soybeans. The gene rj1 (Williams and Lynch, 1954; Caldwell, 1966) prevents nodulation with almost all Rhizobium japonicum strains. The genes Rj2 (Caldwell, 1966 ) in combination with strains b7 and bl4 of the 3-24-44 serogroup and bl22 of the 122 serogroup, Rj3 (Vest, 1970) in combination with strain 33, and Rj4 (Vest and Caldwell, 1972) in combination with strain 61 all result in chlorotic plants with abnormal nodulation