Charge of a quasiparticle in a superconductor

Non-linear charge transport in SIS Josephson junctions has a unique signature in the shuttled charge quantum between the two superconductors. In the zero-bias limit Cooper pairs, each with twice the electron charge, carry the Josephson current. An applied bias $V_{SD}$ leads to multiple Andreev reflections (MAR), which in the limit of weak tunneling probability should lead to integer multiples of the electron charge $ne$ traversing the junction, with $n$ integer larger than $2{\Delta}/eV_{SD}$ and ${\Delta}$ the superconducting order parameter. Exceptionally, just above the gap, $eV_{SD}>2{\Delta}$, with Andreev reflections suppressed, one would expect the current to be carried by partitioned quasiparticles; each with energy dependent charge, being a superposition of an electron and a hole. Employing shot noise measurements in an SIS junction induced in an InAs nanowire (with noise proportional to the partitioned charge), we first observed quantization of the partitioned charge $q=e^*/e=n$, with $n=1-4$; thus reaffirming the validity of our charge interpretation. Concentrating next on the bias region $eV_{SD}{\approx}2{\Delta}$, we found a reproducible and clear dip in the extracted charge to $q{\approx}0.6$, which, after excluding other possibilities, we attribute to the partitioned quasiparticle charge. Such dip is supported by numerical simulations of our SIS structure

Designing a Nanotube Using Naturally Occurring Protein Building Blocks

Here our goal is to carry out nanotube design using naturally occurring protein building blocks. Inspection of the protein structural database reveals the richness of the conformations of proteins, their parts, and their chemistry. Given target functional protein nanotube geometry, our strategy involves scanning a library of candidate building blocks, combinatorially assembling them into the shape and testing its stability. Since self-assembly takes place on time scales not affordable for computations, here we propose a strategy for the very first step in protein nanotube design: we map the candidate building blocks onto a planar sheet and wrap the sheet around a cylinder with the target dimensions. We provide examples of three nanotubes, two peptide and one protein, in atomistic model detail for which there are experimental data. The nanotube models can be used to verify a nanostructure observed by low-resolution experiments, and to study the mechanism of tube formation

Governing Nanomedicine: Lessons from within, and for the EU medical technology regulatory framework.

Rapidly emerging technologies, such as nanotechnologies, are posing significant\ud challenges to regulatory governance due to the uncertainties of development\ud trajectories, product properties, and potential risk problems (Davies\ud 2009). While nanotechnology-based products and processes fall within the\ud scope of current regulatory instruments (European Commission 2008a;\ud Ludlow, Bowman, and Hodge 2007; van Calster 2006), there is increasing\ud concern that such frameworks may not be appropriate for adequately or\ud effectively regulating all dimensions of the technology (see, for example,\ud House of Lords Science and Technology Committee 2010; European Parliament\ud 2009a; Chaudhry et al. 2006; Taylor 2008, 2006; Royal Society and\ud Royal Academy of Engineering 2004). The traditional approach of evidencebased\ud regulation is not equipped to cope with myriad uncertainties surrounding\ud the development and commercialisation of nanotechnologies. This does\ud not mean that public policy can wait and see, however. Even in the case of\ud evidence deficiencies, public responsibility goes beyond a laissez-faire\ud approach to risk regulation. In the European Union and some other countries,\ud precautionary regulatory action is required when basic values like\ud human dignity, health, safety, environment, property, and privacy are at risk\ud (Fisher 2007; European Commission 2000)

High-energy resummation at the LHC: the case of Drell-Yan processes

We first review the general framework which enables one to resum high-energy logarithms in hadronic processes, both in the evolution of parton densities and in the coefficient functions. We then present an all-order calculation in perturbative QCD of the inclusive Drell Yan and vector boson production in hadron-hadron collisions, in the limit where centre of mass energy is much bigger than the invariant mass of the final state. Our calculation resums leading non-trivial logarithms in the ratio of these two scales. We also study the phenomenological relevance of the high-energy corrections for Drell-Yan processes at the LHC. We find that the resummation corrects the NNLO result by a few percent, for values of the invariant mass of the lepton pair below 100 GeV. Corrections to W, Z production are expected to be of the same order.Comment: 5 pages, Talk given at 10th DESY Workshop on Elementary Particle Theory: Loops and Legs 2010, Worlitz, Germany 25-30 April 201

A small molecule screen identifies novel inhibitors of mechanosensory nematocyst discharge in Hydra

Cnidarians are characterized by the possession of stinging organelles, called nematocysts, which they use for prey capture and defense. Nematocyst discharge is controlled by a mechanosensory apparatus with analogies to vertebrate hair cells. Members of the transient receptor potential (TRPN) ion channel family are supposed to be involved in the transduction of the mechanical stimulus. A small molecule screen was performed to identify compounds that affect nematocyst discharge in Hydra. We identified several [2.2]paracyclophanes that cause inhibition of nematocyst discharge in the low micro-molar range. Further structure–activity analyses within the compound class of [2.2]paracyclophanes showed common features that are required for the inhibitory activity of the [2.2]paracyclophane core motif. This study demonstrates that Hydra can serve as a model for small molecule screens targeting the mechanosensory apparatus in native tissues

The AMPK β2 subunit is required for energy homeostasis during metabolic stress

AMP activated protein kinase (AMPK) plays a key role in the regulatory network responsible for maintaining systemic energy homeostasis during exercise or nutrient deprivation. To understand the function of the regulatory β2 subunit of AMPK in systemic energy metabolism, we characterized β2 subunit-deficient mice. Using these mutant mice, we demonstrated that the β2 subunit plays an important role in regulating glucose, glycogen, and lipid metabolism during metabolic stress. The β2 mutant animals failed to maintain euglycemia and muscle ATP levels during fasting. In addition, β2-deficient animals showed classic symptoms of metabolic syndrome, including hyperglycemia, glucose intolerance, and insulin resistance when maintained on a high-fat diet (HFD), and were unable to maintain muscle ATP levels during exercise. Cell surface-associated glucose transporter levels were reduced in skeletal muscle from β2 mutant animals on an HFD. In addition, they displayed poor exercise performance and impaired muscle glycogen metabolism. These mutant mice had decreased activation of AMPK and deficits in PGC1α-mediated transcription in skeletal muscle. Our results highlight specific roles of AMPK complexes containing the β2 subunit and suggest the potential utility of AMPK isoform-specific pharmacological modulators for treatment of metabolic, cardiac, and neurological disorders

Moral Competence and Brain Connectivity: A Resting-State fMRI Study

Moral competence (MC) refers to the ability to apply certain moral orientations in a consistent and differentiated manner when judging moral issues. People greatly differ in terms of MC, however, little is known about how these differences are implemented in the brain. To investigate this question, we used functional magnetic resonance imaging and examined resting-state functional connectivity (RSFC) in n = 31 individuals with MC scores in the highest 15% of the population and n = 33 individuals with MC scores in the lowest 15%, selected from a large sample of 730 Master of Business Administration (MBA) students. Compared to individuals with lower MC, individuals with higher MC showed greater amygdala-ventromedial prefrontal connectivity, which may reflect better ability to cope with emotional conflicts elicited by moral dilemmas. Moreover, individuals with higher MC showed less inter-network connectivity between the amygdalar and fronto-parietal networks, suggesting a more independent operation of these networks. Our findings provide novel insights into how individual differences in moral judgment are associated with RSFC in brain circuits related to emotion processing and cognitive control