The group of causal automorphisms

The group of causal automorphisms on Minkowski space-time is given and its structure is analyzed

Quantitative prediction of 3D solution shape and flexibility of nucleic acid nanostructures

DNA nanotechnology enables the programmed synthesis of intricate nanometer-scale structures for diverse applications in materials and biological science. Precise control over the 3D solution shape and mechanical flexibility of target designs is important to achieve desired functionality. Because experimental validation of designed nanostructures is time-consuming and cost-intensive, predictive physical models of nanostructure shape and flexibility have the capacity to enhance dramatically the design process. Here, we significantly extend and experimentally validate a computational modeling framework for DNA origami previously presented as CanDo [Castro,C.E., Kilchherr,F., Kim,D.-N., Shiao,E.L., Wauer,T., Wortmann,P., Bathe,M., Dietz,H. (2011) A primer to scaffolded DNA origami. Nat. Meth., 8, 221–229.]. 3D solution shape and flexibility are predicted from basepair connectivity maps now accounting for nicks in the DNA double helix, entropic elasticity of single-stranded DNA, and distant crossovers required to model wireframe structures, in addition to previous modeling (Castro,C.E., et al.) that accounted only for the canonical twist, bend and stretch stiffness of double-helical DNA domains. Systematic experimental validation of nanostructure flexibility mediated by internal crossover density probed using a 32-helix DNA bundle demonstrates for the first time that our model not only predicts the 3D solution shape of complex DNA nanostructures but also their mechanical flexibility. Thus, our model represents an important advance in the quantitative understanding of DNA-based nanostructure shape and flexibility, and we anticipate that this model will increase significantly the number and variety of synthetic nanostructures designed using nucleic acids.MIT Faculty Start-up Fun

Computed terahertz near-field mapping of molecular resonances of lactose stereo-isomer impurities with sub-attomole sensitivity

Terahertz near-field microscopy (THz-NFM) could locally probe low-energy molecular vibration dynamics below diffraction limits, showing promise to decipher intermolecular interactions of biomolecules and quantum matters with unique THz vibrational fingerprints. However, its realization has been impeded by low spatial and spectral resolutions and lack of theoretical models to quantitatively analyze near-field imaging. Here, we show that THz scattering-type scanning near-field optical microscopy (THz s-SNOM) with a theoretical model can quantitatively measure and image such low-energy molecular interactions, permitting computed spectroscopic near-field mapping of THz molecular resonance spectra. Using crystalline-lactose stereo-isomer (anomer) mixtures (i.e., alpha-lactose (>= 95%, w/w) and beta-lactose (<= 4%, w/w)), THz s-SNOM resolved local intermolecular vibrations of both anomers with enhanced spatial and spectral resolutions, yielding strong resonances to decipher conformational fingerprint of the trace beta-anomer impurity. Its estimated sensitivity was similar to 0.147 attomoles in similar to 8 x 10(-4) mu m(3) interaction volume. Our THz s-SNOM platform offers a new path for ultrasensitive molecular fingerprinting of complex mixtures of biomolecules or organic crystals with markedly enhanced spatio-spectral resolutions. This could open up significant possibilities of THz technology in many fields, including biology, chemistry and condensed matter physics as well as semiconductor industries where accurate quantitative mappings of trace isomer impurities are critical but still challenging.11Ysciescopu

Core-Level X-Ray Photoemission Satellites in Ruthenates: A New Mechanism Revealing the Mott Transition

Ru 3d core-level x-ray photoemission spectra of various ruthenates are examined. They show in general two-peak structures, which can be assigned as the screened and unscreened peaks. The screened peak is absent in a Mott insulator, but develops into a main peak in the metallic regime. This spectral behavior is well explained by the dynamical mean-field theory calculation for the single-band Hubbard model with on-site core-hole potential using the exact diagonalization method. The new mechanism of the core-level photoemission satellite can be utilized to reveal the Mott transition phenomenon in various strongly correlated electron systems, especially in nano-scale devices and phase-separated materials.Comment: 4 pages, 5 figures, submitted to PR

Haemodynamic and Clinical Assessment of Lateral Marginal Vein Excision in Patients with a Predominantly Venous Malformation of the Lower Extremity

ObjectiveThe purpose of the present study was to determine the effects of the surgical excision of lateral marginal veins (LMVs) in patients with a venous malformation (VM) affecting the lower extremity.MethodsPreoperative and postoperative air plethysmography (APG), CEAP classification C scores, and venous clinical severity scores (VCSS) of the 25 VM patients who underwent LMV excision were compared.ResultsAfter LMV excision, venous haemodynamic parameters revealed significantly increased ejection fraction (EF, 33.2 S.D.18.5% vs. 39.7 S.D.21.2%, P=.020), and reduced venous volume (VV, 235.0 S.D.141.8ml vs. 198.0 S.D.114.1ml, P=.016) and residual venous fraction (RVF, 62.4 S.D. 26.6% vs. 56.9 S.D. 25.3%, P=.046). Clinical assessments of affected limbs revealed significantly improved mean CEAP C scores and VCSS (preoperative score, 4.4 S.D.1.7 vs. postoperative score 2.4 S.D.1.7, P=.026) after LMV excision versus preoperative data.ConclusionHaemodynamic and clinical improvements were observed in patients with lower extremity VM after LMV excision

Gaugino mass in AdS space

We study supersymmetric QED in AdS4 with massless matter. At 1-loop the ultra-violet regulator of the theory generates a contribution to the gaugino mass that is naively inconsistent with unbroken supersymmetry. We show that this effect, known in flat space as anomaly mediated supersymmetry breaking, is required to cancel an infra-red contribution arising from the boundary conditions in AdS space, which necessarily break chiral symmetry. We also discuss an analogous UV/IR cancellation that is independent of supersymmetry.Comment: 20 pages, 1 figur