Design of a nature-like fractal celebrating warp-knitting

In earlier work we created a new textile pattern which was derived from the well-known houndstooth pattern which originates from weaving with twill binding. The new pattern became interesting, both mathematically and aesthetically because it was a fractal. Now we are turning our attention to another basic fabric construction method: warp-knitting. We develop a recursive algorithm and explore the properties of the result. We also develop an attractive fashion item based on the new pattern, to be presented at Bridges

Design of a nature-like fractal celebrating warp-knitting

In earlier work we created a new textile pattern which was derived from the well-known houndstooth pattern which originates from weaving with twill binding. The new pattern became interesting, both mathematically and aesthetically because it was a fractal. Now we are turning our attention to another basic fabric construction method: warp-knitting. We develop a recursive algorithm and explore the properties of the result. We also develop an attractive fashion item based on the new pattern, to be presented at Bridges

Self-avoiding fractional Brownian motion - The Edwards model

In this work we extend Varadhan's construction of the Edwards polymer model to the case of fractional Brownian motions in $\R^d$, for any dimension $d\geq 2$, with arbitrary Hurst parameters $H\leq 1/d$.Comment: 14 page

Energy efficiency trade-offs drive nucleotide usage in transcribed regions

Efficient nutrient usage is a trait under universal selection. A substantial part of cellular resources is spent on making nucleotides. We thus expect preferential use of cheaper nucleotides especially in transcribed sequences, which are often amplified thousand-fold compared with genomic sequences. To test this hypothesis, we derive a mutation-selection-drift equilibrium model for nucleotide skews (strand-specific usage of 'A' versus 'T' and 'G' versus 'C'), which explains nucleotide skews across 1,550 prokaryotic genomes as a consequence of selection on efficient resource usage. Transcription-related selection generally favours the cheaper nucleotides 'U' and 'C' at synonymous sites. However, the information encoded in mRNA is further amplified through translation. Due to unexpected trade-offs in the codon table, cheaper nucleotides encode on average energetically more expensive amino acids. These trade-offs apply to both strand-specific nucleotide usage and GC content, causing a universal bias towards the more expensive nucleotides 'A' and 'G' at non-synonymous coding sites

FIRI - a Far-Infrared Interferometer

Half of the energy ever emitted by stars and accreting objects comes to us in the FIR waveband and has yet to be properly explored. We propose a powerful Far-InfraRed Interferometer mission, FIRI, to carry out high-resolution imaging spectroscopy in the FIR. This key observational capability is essential to reveal how gas and dust evolve into stars and planets, how the first luminous objects in the Universe ignited, how galaxies formed, and when super-massive black holes grew. FIRI will disentangle the cosmic histories of star formation and accretion onto black holes and will trace the assembly and evolution of quiescent galaxies like our Milky Way. Perhaps most importantly, FIRI will observe all stages of planetary system formation and recognise Earth-like planets that may harbour life, via its ability to image the dust structures in planetary systems. It will thus address directly questions fundamental to our understanding of how the Universe has developed and evolved - the very questions posed by ESA's Cosmic Vision.Comment: Proposal developed by a large team of astronomers from Europe, USA and Canada and submitted to the European Space Agency as part of "Cosmic Vision 2015-2025

Finite temperature effects on the collapse of trapped Bose-Fermi mixtures

By using the self-consistent Hartree-Fock-Bogoliubov-Popov theory, we present a detailed study of the mean-field stability of spherically trapped Bose-Fermi mixtures at finite temperature. We find that, by increasing the temperature, the critical particle number of bosons (or fermions) and the critical attractive Bose-Fermi scattering length increase, leading to a significant stabilization of the mixture.Comment: 5 pages, 4 figures; minor changes, proof version, to appear in Phys. Rev. A (Nov. 1, 2003

Polarizing Bubble Collisions

We predict the polarization of cosmic microwave background (CMB) photons that results from a cosmic bubble collision. The polarization is purely E-mode, symmetric around the axis pointing towards the collision bubble, and has several salient features in its radial dependence that can help distinguish it from a more conventional explanation for unusually cold or hot features in the CMB sky. The anomalous "cold spot" detected by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite is a candidate for a feature produced by such a collision, and the Planck satellite and other proposed surveys will measure the polarization on it in the near future. The detection of such a collision would provide compelling evidence for the string theory landscape.Comment: Published version. 15 pages, 8 figure

Notes on contributors

The gas-phase complex UO2(TMOGA)(2)(2+) (TMOGA = tetramethyl-3-oxa-glutaramide) prepared by electrospray ionization was characterized by infrared multiphoton dissociation (IRMPD) spectroscopy. The IRMPD spectrum from 700-1800 cm(-1) was interpreted using a computational study based on density functional theory. The predicted vibrational frequencies are in good agreement with the measured values, with an average deviation of only 8 cm(-1) (<1%) and a maximum deviation of 21 cm(-1) (<2%). The only IR peak assigned to the linear uranyl moiety was the asymmetric v(3) mode, which appeared at 965 cm(-1) and was predicted by DFT as 953 cm(-1). This v(3) frequency is red-shifted relative to bare uranyl, UO22+, by ca. 150 cm(-1) due to electron donation from the TMOGA ligands. Based on the degree of red-shifting, it is inferred that two TMOGA oxygen-donor ligands have a greater effective gas basicity than the four monodentate acetone ligands in UO2(acetone)(4)(2+). The uranyl v(3) frequency was also computed for uranyl coordinated by two TMGA ligands, in which the central O-ether, of TMOGA has been replaced by CH2. The computed v(3) for UO2(TMGA)(2)(2+), 950 cm(-1), is essentially the same as that for UO2(TMOGA)(2)(2+), suggesting that electron donation to uranyl from the ether of TMOGA is minor. The computed v(3) asymmetric stretching frequencies for the three actinyl complexes, UO2(TMOGA)(2)(2+), NpO2(TMOGA)(2)(2+) and PuO2(TMOGA)(2)(2+), are comparable. This similarity is discussed in the context of the relationship between v(3) and intrinsic actinide-oxygen bond energies in actinyl complexes

Dislocation Density-Dependent Quality Factors in InGaN Quantum Dot Containing Microdisks

Microdisks incorporating InGaN quantum dots were fabricated using SiO2 microspheres as a hard mask in conjunction with a photoelectrochemical etch step from a structure containing a sacrificial InGaN/InGaN superlattice. Formation of microdisks from two near-identical structures with differing dislocation densities was carried out and investigated using microphotoluminescence. This confirmed the existence of quantum dots through the presence of resolution limited spectral lines and showed a clear correlation between the resulting modes quality factors and the dislocation densities within the disks. The disks with higher dislocation densities showed up to 80% lower quality factors than the low dislocation density disks.Engineering and Applied Science