Magnetic Sensors Based on Long Josephson Tunnel Junctions - An Alternative to SQUIDs

The properties of Josephson devices are strongly affected by geometrical effects. A loop-shaped superconducting electrode tightly couples a long Josephson tunnel junction with the surrounding electromagnetic field. Due to the fluxoid conservation, any change of the magnetic flux linked to the loop results in a variation of the shielding current circulating around the loop, which, in turn, affects the critical current of the Josephson junction. This method allows the realization of a novel family of robust superconducting devices (not based on the quantum interference) which can function as a general-purpose magnetic sensors. The best performance is accomplished without compromising the noise performance by employing an in-line-type junction few times longer than its Josephson penetration length. The linear (rather than periodic) response to magnetic flux changes over a wide range is just one of its several advantages compared to the most sensitive magnetic detectors currently available, namely the Superconducting Quantum Interference Devices (SQUID). We will also comment on the drawbacks of the proposed system and speculate on its noise properties.Comment: 13 pages, 4 figure

Multigraded Hilbert Series of noncommutative modules

In this paper, we propose methods for computing the Hilbert series of multigraded right modules over the free associative algebra. In particular, we compute such series for noncommutative multigraded algebras. Using results from the theory of regular languages, we provide conditions when the methods are effective and hence the sum of the Hilbert series is a rational function. Moreover, a characterization of finite-dimensional algebras is obtained in terms of the nilpotency of a key matrix involved in the computations. Using this result, efficient variants of the methods are also developed for the computation of Hilbert series of truncated infinite-dimensional algebras whose (non-truncated) Hilbert series may not be rational functions. We consider some applications of the computation of multigraded Hilbert series to algebras that are invariant under the action of the general linear group. In fact, in this case such series are symmetric functions which can be decomposed in terms of Schur functions. Finally, we present an efficient and complete implementation of (standard) graded and multigraded Hilbert series that has been developed in the kernel of the computer algebra system Singular. A large set of tests provides a comprehensive experimentation for the proposed algorithms and their implementations.Comment: 28 pages, to appear in Journal of Algebr

Continual reproduction of self-assembling oligotriazole peptide nanomaterials.

Autocatalytic chemical reactions, whereby a molecule is able to catalyze its own formation from a set of precursors, mimic nature's ability to generate identical copies of relevant biomolecules, and are thought to have been crucial for the origin of life. While several molecular autocatalysts have been previously reported, coupling autocatalytic behavior to macromolecular self-assembly has been challenging. Here, we report a non-enzymatic and chemoselective methodology capable of autocatalytically producing triskelion peptides that self-associate into spherical bioinspired nanostructures. Serial transfer experiments demonstrate that oligotriazole autocatalysis successfully leads to continual self-assembly of three-dimensional nanospheres. Triskelion-based spherical architectures offer an opportunity to organize biomolecules and chemical reactions in unique, nanoscale compartments. The use of peptide-based autocatalysts that are capable of self-assembly represents a promising method for the development of self-synthesizing biomaterials, and may shed light on understanding life's chemical origins.Molecules that act as both autocatalysts and material precursors offer exciting prospects for self-synthesizing materials. Here, the authors design a triazole peptide that self-replicates and then self-assembles into nanostructures, coupling autocatalytic and assembly pathways to realize a reproducing supramolecular system

Resonance at 125 GeV: Higgs or Dilaton/Radion?

We consider the possibility that the new particle that has been observed at 125 GeV is not the Standard Model (SM) Higgs, but instead the dilaton associated with an approximate conformal symmetry that has been spontaneously broken. We focus on dilatons that arise from theories of technicolor, or from theories of the Higgs as a pseudo-Nambu-Goldstone boson (pNGB), that involve strong conformal dynamics in the ultraviolet. In the pNGB case, we are considering a framework where the Higgs particle is significantly heavier than the dilaton and has therefore not yet been observed. In each of the technicolor and pNGB scenarios, we study both the case when the SM fermions and gauge bosons are elementary, and the case when they are composites of the strongly interacting sector. Our analysis incorporates conformal symmetry violating effects, which are necessarily present since the dilaton is not massless, and is directly applicable to a broad class of models that stabilize the weak scale and involve strong conformal dynamics. Since the AdS/CFT correspondence relates the radion in Randall-Sundrum (RS) models to the dilaton, our results also apply to RS models with the SM fields localized on the infrared brane, or in the bulk. We identify the parameters that can be used to distinguish the dilatons associated with the several different classes of theories being considered from each other, and from the SM Higgs. We perform a fit to all the available data from several experiments and highlight the key observations to extract these parameters. We find that at present, both the technicolor and pNGB dilaton scenarios provide a good fit to the data, comparable to the SM Higgs. We indicate the future observations that will help to corroborate or falsify each scenario.Comment: 41 pages, 4 figures. Analysis updated using current theoretical limits on dimensions of CFT operators. References added. Version to appear on JHE

Preferred Suppliers in Auction Markets

In a procurement setting, this paper examines agreements between a buyer and one of the suppliers which would increase their joint surplus. The provisions of such agreements depend on the buyer's ability to design the rules of the final procurement auction. When the buyer has no such ability, their joint surplus can be increased by an agreement which grants to the preferred supplier a right-of-first-refusal on the lowest price offer from the other suppliers. When the buyer does have this ability, one agreement which maximizes their joint surplus includes a revelation game for the cost of the preferred supplier and a reserve price in the procurement auction based on that cost.procurement auctions, bilateral agreements

Fast multi-image matching via density-based clustering

We consider the problem of finding consistent matches across multiple images. Previous state-of-the-art solutions use constraints on cycles of matches together with convex optimization, leading to computationally intensive iterative algorithms. In this paper, we propose a clustering-based formulation. We first rigorously show its equivalence with the previous one, and then propose QuickMatch, a novel algorithm that identifies multi-image matches from a density function in feature space. We use the density to order the points in a tree, and then extract the matches by breaking this tree using feature distances and measures of distinctiveness. Our algorithm outperforms previous state-of-the-art methods (such as MatchALS) in accuracy, and it is significantly faster (up to 62 times faster on some bechmarks), and can scale to large datasets (with more than twenty thousands features).Accepted manuscriptSupporting documentatio

De novo vesicle formation and growth: an integrative approach to artificial cells.

The assembly of artificial cells provides a novel strategy to reconstruct life's functions and shed light on how life emerged on Earth and possibly elsewhere. A major challenge to the development of artificial cells is the establishment of simple methodologies to mimic native membrane generation. An ambitious strategy is the bottom-up approach, which aims to systematically control the assembly of highly ordered membrane architectures with defined functionality. This perspective will cover recent advances and the current state-of-the-art of minimal lipid architectures that can faithfully reconstruct the structure and function of living cells. Specifically, we will overview work related to the de novo formation and growth of biomimetic membranes. These studies give us a deeper understanding of the nature of living systems and bring new insights into the origin of cellular life

Heterozygous deletion of both sclerostin (Sost) and connexin43 (Gja1) genes in mice is not sufficient to impair cortical bone modeling

Connexin43 (Cx43) is the main gap junction protein expressed in bone forming cells, where it modulates peak bone mass acquisition and cortical modeling. Genetic ablation of the Cx43 gene (Gja1) results in cortical expansion with accentuated periosteal bone formation associated with decreased expression of the Wnt inhibitor sclerostin. To determine whether sclerostin (Sost) down-regulation might contribute to periosteal expansion in Gja1 deficient bones, we took a gene interaction approach and crossed mice harboring germline null alleles for Gja1 or Sost to generate single Gja1+/-and Sost+/-and double Gja1+/-;Sost+/-heterozygous mice. In vivo μCT analysis of cortical bone at age 1 and 3 months confirmed increased thickness in Sost-/-mice, but revealed no cortical abnormalities in single Gja1+/-or Sost+/-mice. Double heterozygous Gja1+/-Sost+/-also showed no differences in mineral density, cortical thickness, width or geometry relative to wild type control mice. Likewise, 3-point bending measurement of bone strength revealed no significant differences between double Gja1+/-;Sost+/-or single heterozygous and wild type mice. Although these data do not exclude a contribution of reduced sclerostin in the cortical expansion seen in Gja1 deficient bones, they are not consistent with a strong genetic interaction between Sost and Gja1 dictating cortical modeling

Black hole masses and accretion states in ULXs

We summarize indirect empirical arguments used for estimating black hole (BH) masses in ultraluminous X-ray sources (ULXs). The interpretation of the X-ray data is still too model-dependent to provide tight constraints, but masses <~ 100 Msun seem the most likely. It is getting clearer that ULXs do not show the same evolutionary sequence between canonical spectral states as stellar-mass BHs, nor the same timescale for state transitions. Most ULX spectra are consistent either with a power-law-dominated state (apparently identical to the canonical low/hard state), or with a very high state (or slim-disk state). Despite often showing luminosity variability, there is little evidence of ULXs settling into a canonical high/soft state, dominated by a standard disk (disk-blackbody spectrum). It is possible that the mass accretion rate (but not necessarily the luminosity) is always higher than Eddington; but there may be additional physical differences between stellar-mass BHs and ULXs, which disfavour transitions to the standard-disk, radio-quiet state in the latter class. We speculate that the hard state in ULXs is associated with jet or magnetic processes rather than an ADAF, can persist up to accretion rates ~ Eddington, and can lead directly to the very high state.Comment: 8 pages; to appear in the proceedings of the conference "Observational Evidence of Black Holes", Kolkata, February 200