The Little Book of Viruses

Michael Emerman reviews science writer Carl Zimmer's latest book

Copper phosphoramidite-catalyzed enantioselective desymmetrization of meso-cyclic allylic bisdiethyl phosphates

A highly regio-, diastereo-, and enantioselective desymmetrization of five-, six-, and seven-membered meso-cyclic allylic bis-diethyl phosphates (2a, 2b, and 2c, respectively) was obtained with diethylzinc, using catalytic amounts of [Cu(OTf)](2).C6H6 and phosphoramidite ligands 5. Enantiomeric excesses of up to 87, 94, and >98% were obtained for the addition of diethylzinc to cyclopentene, cyclohexene, and cycloheptene bis-diethyl phosphates, respectively

A self-consistent perturbative evaluation of ground state energies: application to cohesive energies of spin lattices

The work presents a simple formalism which proposes an estimate of the ground state energy from a single reference function. It is based on a perturbative expansion but leads to non linear coupled equations. It can be viewed as well as a modified coupled cluster formulation. Applied to a series of spin lattices governed by model Hamiltonians the method leads to simple analytic solutions. The so-calculated cohesive energies are surprisingly accurate. Two examples illustrate its applicability to locate phase transition.Comment: Accepted by Phys. Rev.

Field evaluation of rigid and flexible scarifier shanks

Se llevaron a cabo ensayos en campo con el objeto de evaluar parámetros de prestación de arcos de escarificador rígidos y flexibles. Se empleó un tractor de diseño convencional de 73 kW de potencia y un bastidor de tracción libre, registrándose los esfuerzos traccionales mediante una celda de carga interpuesta entre ambos, determinándose el área removida mediante un perfilómetro y obteniéndose los valores de resistencia específica. Los arcos rígidos produjeron un frente de labor significativamente mayor que los arcos flexibles. Los arcos rígidos son energéticamente más eficientes que los arcos flexiblesField tests were carried out with the aim to evaluate both rigid and flexible scarifier shanks performance parameters. A 2WD, 73 kW tractor and a pull type implement were used. The draft force was measured with a force transducer with strain gauges. The loosening area was recorded through a profilometer and, from this data, the specific resistance was calculated. The rigid shanks produced a significantly greather working area than the flexible shanks. The rigid shanks shows higher efficiency than the flexible shanksFacultad de Ciencias Agrarias y Forestale

Field evaluation of rigid and flexible scarifier shanks

Se llevaron a cabo ensayos en campo con el objeto de evaluar parámetros de prestación de arcos de escarificador rígidos y flexibles. Se empleó un tractor de diseño convencional de 73 kW de potencia y un bastidor de tracción libre, registrándose los esfuerzos traccionales mediante una celda de carga interpuesta entre ambos, determinándose el área removida mediante un perfilómetro y obteniéndose los valores de resistencia específica. Los arcos rígidos produjeron un frente de labor significativamente mayor que los arcos flexibles. Los arcos rígidos son energéticamente más eficientes que los arcos flexiblesField tests were carried out with the aim to evaluate both rigid and flexible scarifier shanks performance parameters. A 2WD, 73 kW tractor and a pull type implement were used. The draft force was measured with a force transducer with strain gauges. The loosening area was recorded through a profilometer and, from this data, the specific resistance was calculated. The rigid shanks produced a significantly greather working area than the flexible shanks. The rigid shanks shows higher efficiency than the flexible shanksFacultad de Ciencias Agrarias y Forestale

Mimivirus Gene Promoters Exhibit an Unprecedented Conservation among all Eukaryotes

The initial analysis of the recently sequenced genome of Acanthamoeba polyphaga Mimivirus, the largest known double-stranded DNA virus, predicted a proteome of size and complexity more akin to small parasitic bacteria than to other nucleo-cytoplasmic large DNA viruses, and identified numerous functions never before described in a virus. It has been proposed that the Mimivirus lineage could have emerged before the individualization of cellular organisms from the 3 domains of life. An exhaustive in silico analysis of the non-coding moiety of all known viral genomes, now uncovers the unprecedented perfect conservation of a AAAATTGA motif in close to 50% of the Mimivirus genes. This motif preferentially occurs in genes transcribed from the predicted leading strand and is associated with functions required early in the viral infectious cycle, such as transcription and protein translation. A comparison with the known promoter of unicellular eukaryotes, in particular amoebal protists, strongly suggests that the AAAATTGA motif is the structural equivalent of the TATA box core promoter element. This element is specific to the Mimivirus lineage, and may correspond to an ancestral promoter structure predating the radiation of the eukaryotic kingdoms. This unprecedented conservation of core promoter regions is another exceptional features of Mimivirus, that again raises the question of its evolutionary origin

Charge Transfer from Regularized Symmetry-Adapted Perturbation Theory

16 pages, 16 figure

Low energy measurement of the 7Be(p,gamma)8B cross section

We have measured the cross section of the 7Be(p,gamma)8B reaction for E_cm = 185.8 keV, 134.7 keV and 111.7 keV using a radioactive 7Be target (132 mCi). Single and coincidence spectra of beta^+ and alpha particles from 8B and 8Be^* decay, respectively, were measured using a large acceptance spectrometer. The zero energy S factor inferred from these data is 18.5 +/- 2.4 eV b and a weighted mean value of 18.8 +/- 1.7 eV b (theoretical uncertainty included) is deduced when combining this value with our previous results at higher energies.Comment: Accepted for publication in Phys. Rev. Let