First quantized electrodynamics

The parametrized Dirac wave equation represents position and time as operators, and can be formulated for many particles. It thus provides, unlike field-theoretic Quantum Electrodynamics (QED), an elementary and unrestricted representation of electrons entangled in space or time. The parametrized formalism leads directly and without further conjecture to the Bethe–Salpeter equation for bound states. The formalism also yields the Uehling shift of the hydrogenic spectrum, the anomalous magnetic moment of the electron to leading order in the fine structure constant, the Lamb shift and the axial anomaly of QED.     

Cross section and parity-violating spin asymmetries of W± boson production in polarized p + p collisions at sqrt[s] = 500 GeV

Large parity-violating longitudinal single-spin asymmetries A(L)(e+) = -0.86(-0.14) (+0.30) and A(L)(e-) = 0.88(-0.71) (+0.12) are observed for inclusive high transverse momentum electrons and positrons in polarized p+p collisions at a center-of-mass energy of sqrt[s] = 500 GeV with the PHENIX detector at RHIC. These e± come mainly from the decay of W± and Z0 bosons, and their asymmetries directly demonstrate parity violation in the couplings of the W± to the light quarks. The observed electron and positron yields were used to estimate W± boson production cross sections for the e± channels of σ(pp → W+ X) × BR(W+ → e+ ν(e)) = 144.1 ± 21.2(stat)(-10.3) (+3.4) (syst) ± 21.6(norm) pb, and σ(pp → W- X) × BR(W- → e- ν[over ˉ](e)) = 31.7 ± 12.1(stat)(-8.2) (+10.1) (syst) ± 4.8(norm) pb.     

Reversible pressure-induced amorphization of a zeolitic imidazolate framework (ZIF-4)

We report the reversible pressure-induced amorphization of a zeolitic imidazolate framework (ZIF-4, [Zn(Im)(2)]). This occurs irrespective of pore occupancy and takes place via a novel high pressure phase (ZIF-4-I) when solvent molecules are present in the pores. A significant reduction in bulk modulus upon framework evacuation is also observed for both ZIF-4 and ZIF-4-I.     

OmniSpect: An Open MATLAB-Based Tool for Visualization and Analysis of Matrix-Assisted Laser Desorption/Ionization and Desorption Electrospray Ionization Mass Spectrometry Images

We present omniSpect, an open source web- and MATLAB-based software tool for both desorption electrospray ionization (DESI) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI) that performs computationally intensive functions on a remote server. These functions include converting data from a variety of file formats into a common format easily manipulated in MATLAB, transforming time-series mass spectra into mass spectrometry images based on a probe spatial raster path, and multivariate analysis. OmniSpect provides an extensible suite of tools to meet the computational requirements needed for visualizing open and proprietary format MSI data.      

Near-IR single fluorophore quenching system based on phthalocyanine (Pc) aggregation and its application for monitoring inhibitor/activator action on a therapeutic target: L1-EN

Controlled H-aggregation of single Pc-labeled oligonucleotides is utilized as a fluorescence quenching system to discern changes in enzyme activity for the discovery of inhibitors for Long Interspersed Element 1 endonuclease (L1-EN), which is involved in genome instability and implicated in many different diseases.     

J/psi production in sqrt s_NN=200 GeV Cu+Cu collisions

Yields for J/psi production in Cu+Cu collisions at sqrt s_NN=200 GeV have been measured over the rapidity range |y|<2.2 and compared with results in p+p and Au+Au collisions at the same energy. The Cu+Cu data offer greatly improved precision over existing Au+Au data for J/psi production in collisions with small to intermediate numbers of participants, in the range where the quark-gluon plasma transition threshold is predicted to lie. Cold nuclear matter estimates based on ad hoc fits to d+Au data describe the Cu+Cu data up to N_part approximately 50, corresponding to a Bjorken energy density of at least 1.5 GeV/fm(3).     

A semi-analytical approach using artificial neural network for dielectrophoresis generated by parallel electrodes

In this paper, we present a semi-analytical approach to obtain the DEP force generated by parallel electrodes. By solving the electric potential equation using the separation of variables method, a solution was found in the form of a Fourier series with unknown coefficients. The unknown coefficients were determined by training a linear artificial neural network with the appropriate data satisfied on the boundary. This results of calculated electric field and DEP force for both planar electrode system and 3D electrode system are validated by comparison with the numerical results obtained using the commercial software CFD-ACE+.     

The Synthesis, Crystal, and Molecular Structure of Two Mononuclear Arylimido Tungsten Tetrachloride Complexes, [WCl4(NC6H4I-p)(CH3CN)] and [WCl4(NC6H3-2,6-i-Pr 2)(CH3CN)]

Abstract We report two new crystal and molecular structures of the following monomeric arylimido tungsten tetrachloride complexes, [WCl₄(NC₆H₄I-p)(CH₃CN)] (1) and [WCl₄(NC₆H₃-2,6-i-Pr ₂)(CH₃CN)] (2), containing weakly coordinating acetonitrile ligands. Complex 1 crystallizes in the triclinic space group P-1 with lattice parameters a = 6.292(1) ?, b = 8.251(1) ?, c = 15.126(2) ?, α = 78.42(1)°, β = 82.33(2)°, γ = 77.89(1)°, V = 748.7(3) ?³, Z = 2. Complex 2 crystallizes in the monoclinic space group P2 ₁ /c with lattice parameters a = 9.629(1) ?, b = 16.790(2) ?, c = 24.155(2) ?, β = 95.42(1)°, V = 3888.7(6) ?³, Z = 8. Despite the different electronic/steric characteristics of the arylimido ligands, the structures show no significant differences in bond lengths or bond angles in the core {N–W(Cl)₄–N} fragment and are similar to those reported for other arylimido tungsten tetrachloride complexes. Index Abstract The Synthesis, Crystal, and Molecular Structure of Two Mononuclear Arylimido Tungsten Tetrachloride Complexes, [WCl ₄ (NC ₆ H ₄ I -p ) (CH ₃ CN)] and [WCl ₄ (NC ₆ H ₃ - 2,6- i-Pr ₂ )(CH ₃ CN)] Jeffrey C. Duhacek, Tasneem A. Siddiquee, Dennis W. Bennett, and Dean C. Duncan* The crystal and molecular structures of two new arylimido tungsten tetrachloride complexes are reported herein. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Native mass spectrometric studies of IscSU reveal a concerted,sulfur-initiated mechanism of iron–sulfur cluster assembly

Iron–sulfur (Fe–S) clusters are cofactors essential for life. Though the proteins that function in the assembly of Fe–S clusters are well known, details of the molecular mechanism are less well established. The Isc (iron–sulfur cluster) biogenesis apparatus is widespread in bacteria and is the closest homologue to the human system. Mutations in certain components of the human system lead to disease, and so further studies of this system could be important for developing strategies for medical treatments. We have studied two core components of the Isc biogenesis system: IscS, a cysteine desulfurase; and IscU, a scaffold protein on which clusters are built before subsequent transfer onto recipient apo-proteins. Fe²⁺-binding, sulfur transfer, and formation of a [2Fe–2S] was followed by a range of techniques, including time-resolved mass spectrometry, and intermediate and product species were unambiguously identified through isotopic substitution experiments using ⁵⁷Fe and ³⁴S. Under cluster synthesis conditions, sulfur adducts and the [2Fe–2S] cluster product readily accumulated on IscU, but iron adducts (other than the cluster itself) were not observed at physiologically relevant Fe²⁺ concentrations. Our data indicate that either Fe²⁺ or sulfur transfer can occur first, but that the transfer of sulfane sulfur (S⁰) to IscU must occur first if Zn²⁺ is bound to IscU, suggesting that it is the key step that initiates cluster assembly. Following this, [2Fe–2S] cluster formation is a largely concerted reaction once Fe²⁺ is introduced.

Time-resolved native mass spectrometry was used to investigate iron–sulfur cluster assembly on IscU. Data revealed a concerted assembly process in which sulfur (S⁰) transfer must occur first if IscU is in its Zn²⁺-bound form.     

Glass Formation in Hybrid Organic-Inorganic Perovskites

Crystalline materials have governed the development of hybrid organic-inorganic perovskites (HOIPs), giving rise to a variety of fascinating applications such as solar cells and optoelectronic devices. With increasing interest in non-crystalline systems, the glassy state of HOIPs has recently been identified. Here, the basic building blocks of crystalline HOIPs appear to be retained, though their glasses lack long-range periodic order. The emerging family of glasses formed from HOIPs exhibits diverse properties, complementary to their crystalline state. This mini review describes the chemical diversity of both three-dimensional and two-dimensional crystalline HOIPs and demonstrates how glasses are produced from these materials. Specifically, current achievements in melt-quenched glasses formed from HOIPs are highlighted. We conclude with our perspective on the future of this new family of materials.