Differential hydrogen exchange during the biosynthesis of fatty acids in Anacystisnidulans: the incorporation of [2,2,2-2H3, 2-13Co;1] acetate

¹³C NMR studies (with $\text{simultaneous}$¹H, ²H-decoupling) of ¹³C, ²H-labelled methyl palmitate showed a gradation of ²H-retention along the acyl chain. The results are rationalized within the known steps of fatty acid biosynthesis.     

Space-charge-limited insulated-gate surface-channel transistor (s.c.l. i.g.f.e.t.)

Preliminary experimental results are reported on insulated-gate field-effect transistors made in high-resistivity (near-intrinsic silicon substrates. Operation occurs under space-charge-limited conditions, and maximum transconductance and minimum parasitic capacitances for this kind of device are thus obtained. Some implications for integrated monolithic microelectronics are discussed.     

Studies on 5-benzoyl-3-isothiazolinones

5-Benzoyl-3-isothiazolinones are obtained when β-benzoylpropionamides are heated with thionyl chloride. Some reactions of 5-benzoyl-2-phenyl-3-isothiazolinone are described, the most interesting being that with dimethyl and diethyl malonate carbanions, in which ring opening, loss of sulphur, and subsequent ring closure occur, leading to maleimide derivatives.     

Simple method for improving fringe contrast when testing mirror surfaces in the Fizeau interferoscope

The low contrast of fringes used to examine aluminized optical flats is a problem. An inexpensive and simple solution is suggested.     

The structure of quartz at 25 and 590°C determined by neutron diffraction

Analysis of single-crystal data on the α to β transformation in quartz, which takes place at 573°C, showed that the model which, till now, has best agreed with available X-ray data, does not hold for the neutron data. In an earlier model both oxygen and silicon atoms move to special positions (6j and 3c in the space group P6₂22). The new data for β-quartz were best explained by assuming a disorder for the oxygen atom around the 6j position, and in order to keep regular SiO₄ tetrahedra, a corresponding small disorder in the silicon atom is assumed.     

Charged multiplicities in K−p interactions at 100 GeV/c

The charged multiplicity distribution is presented for K^?p interactions produced in the hydrogen bubble chamber, BEBC, using an r.f. separated, tagged K^? beam of 110 GeV/c momentum. A comparison with K⁺p, πp and pp data at lower energies shows that the main features of the multiplicity distributions depend on energy and charge of the incident particles, but not on their strangeness. At high energies, only the energy is important.     

Electronic structure of excimer molecular lasers

The electronic structure, potential energy curves, and radiative transition probabilities of excimer systems have been examined using quantum mechanical methods. These molecules are characterized by repulsive or weakly bound ground state potential curves and by bound, strongly ionic, or Rydberg, excited states. They constitute a very interesting class of molecules which offer the possibility for high power, high efficiency UV laser operation. Calculations have been carried out using the density functional SCF -X_α method, modified extensively to correct for well known errors arising from approximations to the potential and exchange terms. A limited number of ab initio calculations were also carried out for comparison purposes. For the ArF system we find that the lowest excited ionic state has symmetry ²∑${}_{\text{½}}^{\text{+}}$ , and that the dominant laser transition observed at 1933 Å should be assigned to B ²∑${}_{\text{½}}^{\text{+}}$ → X ²∑${}_{\text{½}}^{\text{+}}$ . The C ²Π_3/2 → X ²∑${}_{\text{½}}^{\text{+}}$ transition is calculated to be two orders of magnitude smaller in emission intensity than the dominant transition, thus ruling out this assignment for the observed laser line in ArF. Preliminary calculations carried out for Ar₂F indicate that the bound upper ionic state has ²B₂ symmetry and that the most probable ground state also has ²B₂ symmetry. This polyatomic system is predicted to exhibit a broadband emission spectrum with a relatively long radiative lifetime.     

Creating permanent 3D arrangements of isolated cells using holographic optical tweezers

We report the creation of permanent 3D configurations of cells, at predefined positions, within a gelatin matrix. The technique used holographic optical tweezers to manipulate individual E. coli within a solution comprising monomer precursors. The matrix was then set and after the laser beam was removed, we were able to demonstrate that the structures remained intact for many days. We were also able to demonstrate that, in the presence of appropriate nutrients, the E. coli survived within the gelatin matrix for several days. The technique could have a number of potential future applications, including the arrangement of a variety of different cell types in complex architectures, as motifs for promoting tissue differentiation and growth within the field of cell engineering.     

Oxabicyclo[3.2.1]octane derivatives as highly reactive dienophiles: synthesis of bicyclo[5.n.0] systems

[reaction: see text] We have developed highly versatile, homochiral oxabicyclo[3.2.1]octadiene building blocks for the synthesis of natural products. We have found that these bridged alkenes undergo exceptionally facile Diels-Alder reactions and react faster than several well studied bicyclo[2.2.1]heptene dienophiles. The reaction proceeds with high levels of stereochemical control and in very good to excellent yields, providing access to bicyclo[5.4.0]undecane and bicyclo[5.3.0]decane systems. This reactivity is attributed to strain and homoconjugation effects.