Acrylamide Production Using Encapsulated Nitrile Hydratase from \u3cem\u3ePseudonocardia thermophila\u3c/em\u3e in a Sol–gel Matrix

The cobalt-type nitrile hydratase from Pseudonocardia thermophila JCM 3095 (PtNHase) was successfully encapsulated in tetramethyl orthosilicate sol–gel matrices to produce a PtNHase:sol–gel biomaterial. The PtNHase:sol–gel biomaterial catalyzed the conversion of 600 mM acrylonitrile to acrylamide in 60 min at 35 °C with a yields of \u3e90%. Treatment of the biomaterial with proteases confirmed that the catalytic activity is due to the encapsulated enzyme and not surface bound NHase. The biomaterial retained 50% of its activity after being used for a total of 13 consecutive reactions for the conversion of acrylonitrile to acrylamide. The thermostability and long-term storage of the PtNHase:sol–gel are substantially improved compared to the soluble NHase. Additionally, the biomaterial is significantly more stable at high concentrations of methanol (50% and 70%, v/v) as a co-solvent for the hydration of acrylonitrile than native PtNHase. These data indicate that PtNHase:sol–gel biomaterials can be used to develop new synthetic avenues involving nitriles as starting materials given that the conversion of the nitrile moiety to the corresponding amide occurs under mild temperature and pH conditions

Strongly Secure and Efficient Data Shuffle On Hardware Enclaves

Mitigating memory-access attacks on the Intel SGX architecture is an important and open research problem. A natural notion of the mitigation is cache-miss obliviousness which requires the cache-misses emitted during an enclave execution are oblivious to sensitive data. This work realizes the cache-miss obliviousness for the computation of data shuffling. The proposed approach is to software-engineer the oblivious algorithm of Melbourne shuffle on the Intel SGX/TSX architecture, where the Transaction Synchronization eXtension (TSX) is (ab)used to detect the occurrence of cache misses. In the system building, we propose software techniques to prefetch memory data prior to the TSX transaction to defend the physical bus-tapping attacks. Our evaluation based on real implementation shows that our system achieves superior performance and lower transaction abort rate than the related work in the existing literature.Comment: Systex'1

Towards an improved understanding of eta --> gamma^* gamma^*

We argue that high-quality data on the reaction $e^+e^-\to \pi^+\pi^-\eta$ will allow one to determine the double off-shell form factor $\eta \to \gamma^*\gamma^*$ in a model-independent way with controlled accuracy. This is an important step towards a reliable evaluation of the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. When analyzing the existing data for $e^+e^- \to \pi^+\pi^-\eta$ in the range of total energies $1\text{GeV}^2<Q_2^2<(4.5\text{GeV})^2$, we demonstrate that the double off-shell form factor $F_{\eta\gamma^*\gamma^*}(Q_1^2,Q_2^2)$ is consistent with the commonly employed factorization ansatz at least for $Q_1^2<1\text{GeV}^2$, if the effect of the $a_2$ meson is taken into account. However, better data are needed to draw firm conclusions.Comment: 7 pages, 3 figure

Double Compact Objects III: Gravitational Wave Detection Rates

The unprecedented range of second-generation gravitational-wave (GW) observatories calls for refining the predictions of potential sources and detection rates. The coalescence of double compact objects (DCOs)---i.e., neutron star-neutron star (NS-NS), black hole-neutron star (BH-NS), and black hole-black hole (BH-BH) binary systems---is the most promising source of GWs for these detectors. We compute detection rates of coalescing DCOs in second-generation GW detectors using the latest models for their cosmological evolution, and implementing inspiral-merger-ringdown (IMR) gravitational waveform models in our signal-to-noise ratio calculations. We find that: (1) the inclusion of the merger/ringdown portion of the signal does not significantly affect rates for NS-NS and BH-NS systems, but it boosts rates by a factor $\sim 1.5$ for BH-BH systems; (2) in almost all of our models BH-BH systems yield by far the largest rates, followed by NS-NS and BH-NS systems, respectively, and (3) a majority of the detectable BH-BH systems were formed in the early Universe in low-metallicity environments. We make predictions for the distributions of detected binaries and discuss what the first GW detections will teach us about the astrophysics underlying binary formation and evolution.Comment: published in ApJ, 19 pages, 11 figure

Habitat distribution modeling reveals vegetation flammability and land use as drivers of wildfire in SW Patagonia

Despite important recent advances in modeling current and future global fire activity in relation to biophysical predictors there remain important uncertainties about finer-scale spatial heterogeneity of fire and especially about human influences which are typically assessed at coarse-spatial resolutions. The purpose of the current study is to quantify the influence of biophysical and anthropogenic variables on the spatial distribution of wildfire activity between 1984 and 2010 over an extensive southern Patagonian-Andean region from ca. 43° to 53° S extending from coastal rainforests to xeric woodland and steppe. We used satellite imagery to map all detectable fires > 5 ha from 1984 to 2010 in four study areas (each of 13,100 to 36,635 km2) and field checked 65 of these burns for accuracy of burned vegetation class and fire perimeters. Then, we used the MaxEnt modeling technique to assess the relationships of wildfire distributions to biophysical and human environmental variables in each of the four regions. The 232 fires > 5 ha mapped in the four study areas accounted for an area of 1,314 km2 indicating that at least 1.8% of the total area burned between 1984 and 2010. In general, areas with intermediate productivity levels (e.g. shrublands) have higher fire probability compared with areas of low and high productivity levels, such as steppe and wet forests, respectively. There is a marked contrast in the flammability of broad vegetation classes in determining fire activity at a regional scale, as well as a strong spatial relationship of wildfires to anthropogenic variables. The juxtaposition of fire-resistant tall forests with fire-prone shrublands and woodlands creates the potential for positive feedbacks from human-set fires to gradually increase the flammability of extensive landscapes through repeated burning. Distance to roads and settlements were also strong predictors, suggesting that fire in all regions is ignition-limited. However, these anthropogenic predictors influenced probability of fire differently among study regions depending on their main land-use practices and their past and present socioeconomic contexts.Fil: Paritsis, Juan. State University Of Colorado-boulder; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Holz, Andrés. State University Of Colorado-boulder; Estados UnidosFil: Veblen, Thomas T.. State University Of Colorado-boulder; Estados UnidosFil: Kitzberger, Thomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentin

Two-Dimensional \u3csup\u3e1\u3c/sup\u3eH NMR Studies on Octahedral Nickel(II) Complexes

The dinucleating ligand ethylene glycol−bis(β-aminoethyl ether) N,N,N‘,N‘-tetrakis[(2-(1-ethylbenzimidazoyl)] (EGTB-Et; 1) was used to synthesize the dinuclear Ni(II) tetraacetonitrile complex cation [Ni2(EGTB-Et)(CH3CN)4]2+ (2):  triclinic space group P1̄ (a = 12.273(5) Å, b = 12.358(7) Å, c = 12.561(6) Å, α = 90.43(4)°, β = 110.26(3)°, γ = 99.21 (4)°, and Z = 1). The structure shows two identical octahedral Ni(II) centers each bound to two benzimidazole ring nitrogen atoms, one amine nitrogen atom, an ether oxygen atom, and two acetonitrile nitrogen atoms. The Ni(II) ions are tethered together by a diethyl ether linkage with a crystallographic center of inversion between the methylene carbons of this bridge. The Ni--Ni separation in 2 is 7.072 Å. The mononuclear Ni(II) complex cation [Ni(Bipy)2(OAc)]+ (3) (Bipy = bipyridine) was synthesized and crystallographically characterized:  monoclinic space group P21/c (a = 9.269(4) Å, b = 8.348(4) Å, c = 14.623(7) Å, and β = 102.46(4)°, Z = 2). The Ni(II) ions in 3 adopts a distorted octahedral geometry and is bound to four bipyridine ring nitrogen atoms and two carboxylate oxygen atoms. The average Ni−N and Ni−O distances are 2.062 and 2.110 Å. The electronic absorption spectra of both 2 and 3 were recorded in acetonitrile solution and are consistent with octahedral coordination geometries about the Ni(II) ions with Racah parameters of 840 and 820 cm-1, respectively. Both one- and two-dimensional 1H NMR techniques were used to assign the observed hyperfine shifted 1H NMR resonances of 2 and 3 in acetonitrile solution. Clear COSY cross signals are observed between the aromatic protons of both the benzimidazole and pyridine protons of 2 and 3, respectively. The use of 2D NMR methods to assign inequivalent aromatic protons rather than synthetic methods such as substitution or deuteration are discussed

Apparent horizons in simplicial Brill wave initial data

We construct initial data for a particular class of Brill wave metrics using Regge calculus, and compare the results to a corresponding continuum solution, finding excellent agreement. We then search for trapped surfaces in both sets of initial data, and provide an independent verification of the existence of an apparent horizon once a critical gravitational wave amplitude is passed. Our estimate of this critical value, using both the Regge and continuum solutions, supports other recent findings.Comment: 7 pages, 6 EPS figures, LaTeX 2e. Submitted to Class. Quant. Gra

Torsion Degrees of Freedom in the Regge Calculus as Dislocations on the Simplicial Lattice

Using the notion of a general conical defect, the Regge Calculus is generalized by allowing for dislocations on the simplicial lattice in addition to the usual disclinations. Since disclinations and dislocations correspond to curvature and torsion singularities, respectively, the method we propose provides a natural way of discretizing gravitational theories with torsion degrees of freedom like the Einstein-Cartan theory. A discrete version of the Einstein-Cartan action is given and field equations are derived, demanding stationarity of the action with respect to the discrete variables of the theory

Regge Calculus in Teleparallel Gravity

In the context of the teleparallel equivalent of general relativity, the Weitzenbock manifold is considered as the limit of a suitable sequence of discrete lattices composed of an increasing number of smaller an smaller simplices, where the interior of each simplex (Delaunay lattice) is assumed to be flat. The link lengths between any pair of vertices serve as independent variables, so that torsion turns out to be localized in the two dimensional hypersurfaces (dislocation triangle, or hinge) of the lattice. Assuming that a vector undergoes a dislocation in relation to its initial position as it is parallel transported along the perimeter of the dual lattice (Voronoi polygon), we obtain the discrete analogue of the teleparallel action, as well as the corresponding simplicial vacuum field equations.Comment: Latex, 10 pages, 2 eps figures, to appear in Class. Quant. Gra