An alternative method to access diverse N,N′-diquaternised-3,3′-biquinoxalinium “biquinoxen” dications

An alternative synthetic route for the design of N,N′-diquaternised-3,3′-biquinoxalinium “biquinoxen” dications is reported, involving oxidative radical coupling of dithionite reduced quinoxaline quaternary salts. Although the reaction is not regioselective, leading to relatively modest yields (up to 32%), the advantages of this new synthetic protocol lie in a simple potentially gram scale synthesis using inexpensive easily accessible reagents with no metal catalysts and no purification steps. Thus whereas the method reported previously to access the N,N′-dimethyl-3,3′-biquinoxalinium, “methylbiquinoxen” precursor gave higher yield than the new method reported here, this new method avoids the limitation of using scarce oxonium reagents. Overall, the new protocol is a robust synthetic strategy which offers new design possibilities

Comparative Genomics of 9 Novel Paenibacillus Larvae Bacteriophages

American Foulbrood Disease, caused by the bacterium Paenibacillus larvae, is one of the most destructive diseases of the honeybee, Apis mellifera. Our group recently published the sequences of 9 new phages with the ability to infect and lyse P. larvae. Here, we characterize the genomes of these P. larvae phages, compare them to each other and to other sequenced P. larvae phages, and putatively identify protein function. The phage genomes are 38–45 kb in size and contain 68–86 genes, most of which appear to be unique to P. larvae phages. We classify P. larvae phages into 2 main clusters and one singleton based on nucleotide sequence identity. Three of the new phages show sequence similarity to other sequenced P. larvae phages, while the remaining 6 do not. We identified functions for roughly half of the P. larvae phage proteins, including structural, assembly, host lysis, DNA replication/metabolism, regulatory, and host-related functions. Structural and assembly proteins are highly conserved among our phages and are located at the start of the genome. DNA replication/metabolism, regulatory, and host-related proteins are located in the middle and end of the genome, and are not conserved, with many of these genes found in some of our phages but not others. All nine phages code for a conserved N-acetylmuramoyl-L-alanine amidase. Comparative analysis showed the phages use the “cohesive ends with 30 overhang” DNA packaging strategy. This work is the first in-depth study of P. larvae phage genomics, and serves as a marker for future work in this area

FARM MACHINERY INVESTMENT AND THE TAX REFORM ACT OF 1986

The Tax Reform Act of 1986 significantly changed incentives for investing. This analysis specifically examines how changes in marginal tax rates, depreciation schedules, and the investment tax credit altered the cost of capital and net investment in agriculture. A stochastic coefficients econometric methodology is used to estimate an investment function which is then used to simulate the effects of tax reform. Estimates indicated that relative to prior law, the Tax Reform Act will reduce the capital stock of farm machinery and equipment by nearly $4 billion.Agricultural Finance, Farm Management,

Signatures of Fermi surface reconstruction in Raman spectra of underdoped cuprates

We have calculated the Raman B$_{1g}$ and B$_{2g}$ spectra as a function of temperature, as well as doping, for the underdoped cuprates, using a model based on the resonating valence-bond spin-liquid. We discuss changes in intensity and peak position brought about by the presence of a pseudogap and the implied Fermi surface reconstruction, which are elements of this model. Signatures of Fermi surface reconstruction are evident as a sharp rise in the doping dependence of the antinodal to nodal peak ratio which occurs below the quantum critical point. The temperature dependence of the B$_{1g}$ polarization can be used to determine if the superconducting gap is limited to the Fermi pocket, as seen in angle resolved photoemission spectroscopy, or extends beyond. We find that the slope of the linear low energy B$_{2g}$ spectrum maintains its usual d-wave form, but with an effective gap which reflects the gap amplitude projected on the Fermi pocket. Our calculations capture the main qualitative features revealed in the extensive data set available on the HgBa$_2$CuO$_{4+\delta}$ (Hg-1201) cuprate.Comment: 13 pages, 14 figure

Effect of magnetic field on the phase transition in a dusty plasma

The formation of self-consistent crystalline structure is a well-known phenomenon in complex plasmas. In most experiments the pressure and rf power are the main controlling parameters in determining the phase of the system. We have studied the effect of externally applied magnetic field on the configuration of plasma crystals, suspended in the sheath of a radio-frequency discharge using the Magnetized Dusty Plasma Experiment (MDPX) device. Experiments are performed at a fixed pressure and rf power where a crystalline structure is formed within a confining ring. The magnetic field is then increased from 0 to 1.28 T. We report on the breakdown of the crystalline structure with increasing magnetic field. The magnetic field affects the dynamics of the plasma particles and first leads to a rotation of the crystal. At higher magnetic field, there is a radial variation (shear) in the angular velocity of the moving particles which we believe leads to the melting of the crystal. This melting is confirmed by evaluating the variation of the pair correlation function as a function of magnetic field.Comment: 9 pages, 5 figure

Approaching the limit of CuII/CuImixed valency in a CuIBr2–N-methylquinoxalinium hybrid compound

A novel 1D hybrid salt (MQ)[CuBr2]∞ (MQ = N-methylquinoxalinium) is reported. Structural, spectroscopic and magnetic investigations reveal a minimal CuII doping of less than 0.1%. However it is not possible to distinguish CuI and CuII. The unusually close packing of the organic moieties and the dark brown colour of the crystals suggest a defect electronic structure

A fascinating multifaceted redox-active chelating ligand: introducing the N,N′-dimethyl-3,3′-biquinoxalinium “methylbiquinoxen” platform

To intimately combine a chelating ligand function with the numerous properties of a viologen-like redox-active centre would offer a rare possibility to design controllable multi-redox states, whose properties arise from strongly correlated phenomena between the organic ligand as well as with any metalloid coordinated centres. Such a concept previously proved to be feasible, however is not widely applicable owing to challenges in terms of synthesis, isolation, and aerial sensitivity of both the ligand and its metal complexes. Here we report the first stable example of such a redox-active molecule, N,N′-dimethyl-3,3′-biquinoxalinium2+/˙+/0 “methylbiquinoxen, MBqn2+/˙+/0”, which shows a rich redox chemistry and chelates a metal ion in the case of the metal complex [CdCl2(MBqn0)]. This goes beyond what is possible to achieve using viologens, which are limited by not providing chelation as well as having no accessible biradicaloid state, corresponding to the neutral direduced MBqn0 open-shell behaviour we observe here