Revolution analysis of three-dimensional arbitrary cloaks

We extend the design of radially symmetric three-dimensional invisibility cloaks through transformation optics to cloaks with a surface of revolution. We derive the expression of the transformation matrix and show that one of its eigenvalues vanishes on the inner boundary of the cloaks, while the other two remain strictly positive and bounded. The validity of our approach is confirmed by finite edge-elements computations for a non-convex cloak of varying thickness.Comment: 6 pages, 4 figure

Experimental and guided theoretical investigation of complex reaction mechanisms in a prins reaction of glyoxylic acid and isobutene

(Chemical Equation Presented) A laboratory experiment was designed for undergraduate students, in which the outcome of an easy single-step organic synthesis with well-defined conditions was not elucidated until the end of the exercise. In class, students predict and discuss the possible products using their knowledge of reaction mechanisms. In the laboratory, they learn how to carry out a reaction safely with gaseous isobutene, and to isolate and identify the two main products. The class and the laboratory components are completed in 10 h, including laboratory time of 6 to 7 h, divided in two sessions. The class-component could also be implemented independently as a theoretical exercise in a "virtual experiment" simply by presenting the methods and results to students using a guided-inquiry approach, appropriate for a standard 3 h undergraduate class. The finding that the simple reaction leads to a largely unexpected product, together with open discussions with students covering several theoretical aspects applicable to this reaction, helps to promote critical thinking and to provide an effective educational tool to better understand the process of scientific research in chemistry

Electrically conducting ternary amorphous fully oxidized materials and their application

Electrically active devices are formed using a special conducting material of the form Tm--Ox mixed with SiO2 where the materials are immiscible. The immiscible materials are forced together by using high energy process to form an amorphous phase of the two materials. The amorphous combination of the two materials is electrically conducting but forms an effective barrier

Zinc-selective inhibition of the promiscuous bacterial amide-hydrolase DapE: implications of metal heterogeneity for evolution and antibiotic drug design

The development of resistance to virtually all current antibiotics makes the discovery of new antimicrobial compounds with novel protein targets an urgent challenge. The dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) is an essential metallo-enzyme for growth and proliferation in many bacteria, acting in the desuccinylation of N-succinyl-l,l-diaminopimelic acid (SDAP) in a late stage of the anabolic pathway towards both lysine and a crucial building block of the peptidoglycan cell wall. l-Captopril, which has been shown to exhibit very promising inhibitory activity in vitro against DapE and has attractive drug-like properties, nevertheless does not target DapE in bacteria effectively. Here we show that l-captopril targets only the Zn(2+)-metallo-isoform of the enzyme, whereas the Mn(2+)-enzyme, which is also a physiologically relevant isoform in bacteria, is not inhibited. Our finding provides a rationale for the failure of this promising lead-compound to exhibit any significant antibiotic activity in bacteria and underlines the importance of addressing metallo-isoform heterogeneity in future drug design. Moreover, to our knowledge, this is the first example of metallo-isoform heterogeneity in vivo that provides an evolutionary advantage to bacteria upon drug-challenge

Pair bond endurance promotes cooperative food defense and inhibits conflict in coral reef butterflyfish

Pair bonding is generally linked to monogamous mating systems, where the reproductive benefits of extended mate guarding and/or of bi-parental care are considered key adaptive functions. However, in some species, including coral reef butterflyfishes (f. Chaetodonitidae), pair bonding occurs in sexually immature and homosexual partners, and in the absence of parental care, suggesting there must be non-reproductive adaptive benefits of pair bonding. Here, we examined whether pair bonding butterflyfishes cooperate in defense of food, conferring direct benefits to one or both partners. We found that pairs of Chaetodon lunulatus and C. baronessa use contrasting cooperative strategies. In C. lunulatus, both partners mutually defend their territory, while in C. baronessa, males prioritize territory defence; conferring improvements in feeding and energy reserves in both sexes relative to solitary counterparts. We further demonstrate that partner fidelity contributes to this function by showing that re-pairing invokes intra-pair conflict and inhibits cooperatively-derived feeding benefits, and that partner endurance is required for these costs to abate. Overall, our results suggest that in butterflyfishes, pair bonding enhances cooperative defense of prey resources, ultimately benefiting both partners by improving food resource acquisition and energy reserves

Quantum Yield Measurement of Fluorescent Zeolite Nanopigments

Organic fluorescent molecules are infiltrated in the channels of zeolite L nanocrystals, thus creating organic-inorganic fluorescent nanoparticles. Combined with dielectric matrices, these fluorescent nanopigments open the way to the realization of novel optical devices. In this paper, the optical measurement of the quantum yield of fluorescent zeolites by means of a precise and reliable diffuse reflectance technique is presented. Several possible factors that may affect the fluorescence quantum yield are also investigated

Hybridization of a RoR HPP with a BESS—The XFLEX HYDRO Vogelgrun Demonstrator

In the XFLEX HYDRO Vogelgrun demonstrator, a run-of-river hydropower plant, the hybridization of one turbine-generator unit with a battery energy storage system is being investigated. This paper describes the integration methodology of the hybrid control algorithm without replacing the existing speed governor of the unit. Furthermore, the comparison of the performances of a non-hybrid and hybrid unit is discussed, and first experiences gained during the operation and monitoring of the hybrid operating mode are presented.This work has been realized with the participation of INES.2S. David Valentín and Alexandre Presas acknowledge the Serra Húnter program. The corresponding author would like to express his gratitude to Nicolas Ruchonnet for his contributions during the revision.Postprint (published version

Coil 2 of intermediate filaments: its complete structure and impact of desminopathy-related mutations.

The eukaryotic cytoskeleton consists of three major filamentous networks. The thinnest filament network of about 6 nm diameter is made up of globular actin subunits, whereas the thicker microtubule network of about 22 nm diameter contains 13 protofilament subunits of globular [alpha]- and [beta]-tubulin arranged in a helical manner. This thesis deals with intermediate filaments (IFs) of about 15 nm diameter. IFs have a long [alpha]-helical rod domain flanked by variable in length and non-helical N-terminal ‘head’ and C-terminal ‘tail’ domains. The elementary dimer forming the rod domain has an underlying heptad repeat sequence characteristic for left-handed coiled-coils. This heptad repeat, however, discontinues at three positions called linker L1, L12 and L2. The linker L1 divides the coil 1 into 1A and 1B subdomains and the linker L2 the coil 2 into 2A and 2B. The linker L12 is found between coil 1 and coil 2. In contrast to microfilaments and microtubules, IFs like vimentin build up from elongated fibrous protein dimers. These dimers laterally assemble into tetramers and further into unit-length filaments (ULFs). ULFs then anneal longitudinally, and after a radial compaction step form mature IFs filaments. Within this thesis, the dimer structure of vimentin was further investigated using a ‘divide-and-conquer’ approach (Strelkov, 2001). For this, seven different vimentin (D1-D7) fragments covering the predicted linkers L12 and L2 were expressed in E. coli and screened towards crystallization. One of them, the fragment D3, yields crystals suitable for X-ray diffraction. The resulting 2.4Å structure covers the regions of the vimentin molecule formerly designated as coil 2A, linker L2 and the beginning of coil 2B. We show that this region forms a single, contiguous [alpha]-helix and thus, there is no linker L2. Further, the N-terminal part of this fragment starting with Pro263 and ending with Ala302 is not twisted and should be designated as a parallel [alpha]-helical bundle rather than a coiled-coil. The rest of coil 2 is a regular left-handed coiled-coil with the exception of a small unwound region, the stutter, at position 351. The considerable overall sequence similarity of D3 to other IFs (80% for NFL and 60% for keratin types and nuclear lamins) clearly suggests a conserved structural feature to all IF proteins. We also investigate the impact of some myopathic point mutations in the IF desmin. For this, desmin wild-type (wt) and six mutant fragments (L345P, A360P, L370P, L385P, deltaN366 and E401S) homologous to the previously crystallized vimentin cys2 and lamin A lam1 fragments were expressed in E. coli. With analytical ultracentrifugation and gel-filtration profiles, we show that wt and L345P mutant fragment form dimers in solution, whereas the mutant fragments A360P and E401S are mostly monomeric. Further, we show by circular dichroism that all our fragments were [alpha]-helical. Since our attempts to crystallize these fragments were unsuccessful, we decided to investigate the desmin wt assembly versus desmin myopathic mutants by small angle X-ray scattering (SAXS). For this, we triggered full-length desmin assembly by adding salts to a low ionic strength buffer known to prevent desmin polymerization. Our SAXS measurements in low ionic strength buffer show that almost all mutants are similar to desmin wt, but exhibit more variability with increased ionic strength buffers. In high ionic strength buffer, about half of our samples turned into gel and could not be analyzed by SAXS. Based on SAXS measurements, we were able to classify our mutant into three groups; one group of desmin mutants (L345P, R406W, R350P, A360P, deltaN366, A377P, N342D) behaves as the wt, a second mutant group (E413K, A357P, deltaE359-S361, L385P, E245D, A213V, D399Y, I451M) has an increased assembly upon ionic strength compared to desmin wt and a third group is composed of two outlier mutants (Q389P forming a gel in a low ionic strength buffer and L370P having a broader cross-section diameter than wt already in tetramer buffer)

Atomic structure of vimentin coil 2

Intermediate filaments (IFS) are essential cytoskeletal components in metazoan cells. They assemble from elementary dimers that are built around the central alpha-helical coiled-coil rod domain representing the IF 'signature'. The rod consists of two similarly-sized parts, coil 1 and coil 2, connected by a non-alpha-helical linker L12. Coil 2 is absolutely conserved in length across all IF types and was initially predicted to consist of a short coiled-coil segment 2A based on a heptad pattern of hydrophobic residues, another linker L2 and a coiled-coil segment 2B. Here we present the crystal structure of human vimentin fragment including residues 261-335 i.e. approximately the first half of coil 2. The N-terminal part of this fragment reveals a parallel alpha-helical bundle characterized by 3.5 consecutive hendecad repeats. It is immediately followed by a regular left-handed coiled coil. The distinct non-helical linker L2 is therefore not observed. Together with the previously determined crystal structure of the major part of segment 2B (Strelkov et al., 2002), we can now build a complete atomic model of the 21 nm long vimentin coil 2 dimer being a relatively rigid rod. (C) 2010 Elsevier Inc. All rights reserved.status: publishe

Atomic structure of vimentin coil 2

Intermediate filaments (IFs) are essential cytoskeletal components in metazoan cells. They assemble from elementary dimers that are built around the central alpha-helical coiled-coil rod domain representing the IF 'signature'. The rod consists of two similarly-sized parts, coil 1 and coil 2, connected by a non-alpha-helical linker L12. Coil 2 is absolutely conserved in length across all IF types and was initially predicted to consist of a short coiled-coil segment 2A based on a heptad pattern of hydrophobic residues, another linker L2 and a coiled-coil segment 2B. Here we present the crystal structure of human vimentin fragment including residues 261-335 i.e. approximately the first half of coil 2. The N-terminal part of this fragment reveals a parallel alpha-helical bundle characterized by 3.5 consecutive hendecad repeats. It is immediately followed by a regular left-handed coiled coil. The distinct non-helical linker L2 is therefore not observed. Together with the previously determined crystal structure of the major part of segment 2B (Strelkov et al., 2001), we can now build a complete atomic model of the 21nm long vimentin coil 2 dimer being a relatively rigid rod