AFM-based dynamic single-molecule force spectroscopy was used to stretch carboxymethylated amylose (CMA) polymers, which have been covalently tethered between a silanized glass substrate and a silanized AFM tip via acid-catalyzed ester condensation at pH 2.0. Rupture forces were measured as a function of temperature and force loading rate in the force-ramp mode. The data exhibit significant statistical scattering, which is fitted with a maximum likelihood estimation (MLE) algorithm. Bond rupture is described with a Morse potential based Arrhenius kinetics model. The fit yields a bond dissociation energy De = 35 kJ mol−1 and an Arrhenius pre-factor A = 6.6 × 104 s−1. The bond dissociation energy is consistent with previous experiments under identical conditions, where the force-clamp mode was employed. However, the bi-exponential decay kinetics, which the force-clamp results unambiguously revealed, are not evident in the force-ramp data. While it is possible to fit the force-ramp data with a bi-exponential model, the fit parameters differ from the force-clamp experiments. Overall, single-molecule force spectroscopy in the force-ramp mode yields data whose information content is more limited than force-clamp data. It may, however, still be necessary and advantageous to perform force-ramp experiments. The number of successful events is often higher in the force-ramp mode, and competing reaction pathways may make force-clamp experiments impossible.

Micro-patterned surfaces are frequently used in high-throughput single-cell studies, as they allow one to image isolated cells in defined geometries. Commonly, cells are seeded in excess onto the entire chip, and non-adherent cells are removed from the unpatterned sectors by rinsing. Here, we report on the phenomenon of cellular self-organization, which allows for autonomous positioning of cells on micro-patterned surfaces over time. We prepared substrates with a regular lattice of protein-coated adhesion sites surrounded by PLL-g-PEG passivated areas, and studied the time course of cell ordering. After seeding, cells randomly migrate over the passivated surface until they find and permanently attach to adhesion sites. Efficient cellular self-organization was observed for three commonly used cell lines (HuH7, A549, and MDA-MB-436), with occupancy levels typically reaching 40-60% after 3-5 h. The time required for sorting was found to increase with increasing distance between adhesion sites, and is well described by the time-to-capture in a random-search model. Our approach thus paves the way for automated filling of cell arrays, enabling high-throughput single-cell analysis of cell samples without losses.

The photo-physical properties of 2-(1-ethynylpyrene)-adenosine (PyA), a fluorescent probe for RNA dynamics, were examined by solvation studies. The excited-state dynamics display the influence of the vicinity on the spectral features. Combining improved transient absorption and streak camera measurements along with a new analysis method provide a detailed molecular picture of the photophysics. After intramolecular vibrational energy redistribution (IVR), two distinct states are observed. Solvent class (protic/aprotic) and permittivity strongly affect the properties of these states and their population ratio. As a result their emission spectrum is altered, while the fluorescence quantum yield and the overall lifetime remain nearly unchanged. Consequently, the hitherto existing model of the photophysics is herein refined and extended. The findings can serve as basis for improving the information content of measurements with PyA as a label in RNA.

The nu g(9/2), d(5/2), s(1/2) orbitals are assumed to be responsible for the swift onset of collectivity observed in the region below Ni-68. Especially the single-particle energies and strengths of these orbitals are of importance. We studied such properties in the nearby Ni-67 nucleus, by performing a (d, p)-experiment in inverse kinematics employing a post-accelerated radioactive ion beam (RIB) at the REX-ISOLDE facility. The experiment was performed at an energy of 2.95 MeV/u using a combination of the T-REX particle detectors, the Miniball gamma-detection array and a newly-developed delayed-correlation technique as to investigate mu s-isomers. Angular distributions of the ground state and multiple excited states in 67Ni were obtained and compared with DWBA cross-section calculations, leading to the identification of positive-parity states with substantial nu g(9/2) (1007keV) and nu d(5/2) (2207 keV and 3277 keV) single-particle strengths up to an excitation energy of 5.8 MeV. 50 of the nu d(5/2) single-particle strength relative to the nu g(9/2)-orbital is concentrated in and shared between the first two observed 5/2(+) levels. A comparison with extended Shell Model calculations and equivalent (He-3, d) studies in the region around Zr-90(40)50 highlights similarities for the strength of the negative-parity pf and positive-parity g(9/2) state, but differences are observed for the d(5/2) single-particle strength. (C) 2014 The Authors. Published by Elsevier B.V.

Motivated by the construction of spectral manifolds in noncommutative geometry, we introduce a higher degree Heisenberg commutation relation involving the Dirac operator and the Feynman slash of scalar fields. This commutation relation appears in two versions, one sided and two sided. It implies the quantization of the volume. In the one-sided case it implies that the manifold decomposes into a disconnected sum of spheres which will represent quanta of geometry. The two sided version in dimension 4 predicts the two algebras M 2(ℍ) and M 4(ℂ) which are the algebraic constituents of the Standard Model of particle physics. This taken together with the non-commutative algebra of functions allows one to reconstruct, using the spectral action, the Lagrangian of gravity coupled with the Standard Model. We show that any connected Riemannian Spin 4-manifold with quantized volume > 4 (in suitable units) appears as an irreducible representation of the two-sided commutation relations in dimension 4 and that these representations give a seductive model of the “particle picture” for a theory of quantum gravity in which both the Einstein geometric standpoint and the Standard Model emerge from Quantum Mechanics. Physical applications of this quantization scheme will follow in a separate publication.

If electroweak symmetry breaking is driven by a new strongly coupled dynamical sector, one expects the bound states to appear at the TeV scale or slightly below. However, electroweak precision data imposes severe constraints on most of the existing models, putting them under strain. Conventional models require the newcomposite states to come in pairs of rather heavy, close to degenerate spin-1 resonances. In this paper I argue that spin-1 states can actually be lighter without clashing with experimental bounds. As an example, I consider a composite model with a light pseudovector resonance that couples to the Standard Model gauge boson, fermion, and scalar fields. I show how such a resonance leaves basically no imprint on the NLO corrections to the Standard Model. This happens not through parameter tuning, but rather as a consequence of generic properties of realistic UV completions. This pseudovector is mostly unconstrained by existing data and could be as light as 600 GeV. In the last part of the paper I briefly discuss its most characteristic signatures for direct detection at colliders.

We discuss the systematics of power counting in general effective field theories, focusing on those that are nonrenormalizable at leading order. As an illuminating example we consider chiral perturbation theory gauged under the electromagnetic U(1) symmetry. This theory describes the low-energy interactions of the octet of pseudo-Goldstone bosons in QCD with photons and has been discussed extensively in the literature. Peculiarities of the standard approach are pointed out and it is shown how these are resolved within our scheme. The presentation follows closely our recent discussion of power counting for the electroweak chiral Lagrangian. The systematics of the latter is reviewed and shown to be consistent with the concept of chiral dimensions. The results imply that naive dimensional analysis (NDA) is incomplete in general effective field theories, while still reproducing the correct counting in special cases.

We consider the Standard Model, including a light scalar boson h, as an effective theory at the weak scale v = 246 GeV of some unknown dynamics of electroweak symmetry breaking. This dynamics may be strong, with h emerging as a pseudo-Goldstone boson. The symmetry breaking scale Λ is taken to be at 4 π v or above. We review the leading-order Lagrangian within this framework, which is nonrenormalizable in general. A chiral Lagrangian can then be constructed based on a loop expansion. A systematic power counting is derived and used to identify the classes of counterterms that appear at one loop order. With this result the complete Lagrangian is constructed at next-to-leading order, O ( v 2 / Λ 2 ) . This Lagrangian is the most general effective description of the Standard Model containing a light scalar boson, in general with strong dynamics of electroweak symmetry breaking. Scenarios such as the {SILH} ansatz or the dimension-6 Lagrangian of a linearly realized Higgs sector can be recovered as special cases.

We compute the fully differential rate for the Higgs-boson decay h→Zℓ+ℓ− , with Z→ℓ′+ℓ′− . For these processes we assume the most general matrix elements within an effective Lagrangian framework. The electroweak chiral Lagrangian we employ assumes minimal particle content and Standard Model gauge symmetries, but it is otherwise completely general. We discuss how information on new physics in the decay form factors may be obtained that is inaccessible in the dilepton-mass spectrum integrated over angular variables. The form factors are related to the coefficients of the effective Lagrangian, which are used to estimate the potential size of new-physics effects.