Offset prism for optical waveguide coupling

High refractive index prisms have been used to couple optical beams into the thin film waveguides. To scan through various propagating modes normally requires rotating and repositioning of the prism-waveguide assembly. We have found that the required adjustment of the prism-position can be eliminated during the scanning of the various modes if the prism is properly offset with respect to the rotational axis. An analysis and a computer program are given for the calculation of this prism offset position on the basis of minimum deviation within the specified limits of the prism rotational angle.

Subnanosecond Laser Recording on MnBi Thin Films

Thermomagnetic writing and erasure of binary information in MnBi thin films using 250-psec pulses are described. The ability to write with such short pulses could greatly improve data rates in optical memories. Repeated cycling of a single spot gave inconclusive results concerning possible retardation or inhibition of phase change in MnBi for very short heating pulses.

Magnetic materials for optical recording

Optical digital data storage using magnetic materials offers the combined advantages of magnetic recording and beam addressable technique. Recent progress in this technology is reviewed.

Deoxyribonucleic Acid polymerase from wheat embryos

A soluble DNA-dependent DNA polymerase was extracted from wheat embryos. In vitro, the incorporation of radioactive thymidine triphosphate into acid-insoluble material is dependent upon the presence of the enzyme, all four deoxyribonucleotide triphosphates, Mg(2+), and a DNA template. Incorporation occurs on native, alkali-denatured, and strictly double-stranded DNA. The in vitro synthesized product is a polydeoxynucleotide with a chain length shorter than the template; it has the same buoyant density as wheat embryo DNA when this DNA is used as template; and it forms a double-stranded complex with the DNA template. These data suggest that the in vitro DNA synthesis catalyzed by proteins extracted from wheat embryos occurs in a semiconservative way.

The antibody response to sporozoites of simian and human malaria parasites: its stage and species specificity and strain cross-reactivity

Attempts to vaccinate against malaria are currently being pursued in both simian hosts and human volunteers, using X-irradiated sporozoites as antigen. The present experiments provide information on the developmental stage during which simian malaria sporozoites acquire certain antigen(s) and become infective, and on the antigenic similarities between sporozoites of different strains and species of simian and human malaria parasites. Such knowledge should prove of value in the choice of sporozoite preparations for future attempts at vaccination.

Antibodies against Sporozoites of Human and Simian Malaria Produced in Rats

The various methods commonly used for the detection of antimalarial antibodies employ, in nearly all instances, the erythrocytic stages of these parasites as antigen source (1). The antigenic components of the different stages of development of the malaria parasites, however, differ considerably, in spite of the existence of some shared or common antigens (2, 3). Furthermore, the common antigens do not account for all of the antigenic components of the parasites, nor do they include the functional, i.e., protective, antigens of the various developmental stages. This is suggested by the finding that rodents immunized with attenuated sporozoites become totally resistant to an otherwise lethal sporozoite inoculum, but remain fully susceptible to challenge with erythrocytic stages of the same parasite strain (4).

Anti-sporozoite antibodies, i.e., antibodies directed against the infective stages of all malaria parasites, have previously been shown to occur in avian and rodent malaria. In both instances, these antibodies were observed upon immunization of the animals with attenuated, irradiated sporozoites.

Advanced optical storage techniques for computers

The growing demand for data storage in computing systems has stimulated the investigation of optical memory techniques because they offer a potential improvement in packing density of about two orders of magnitude over the apparent limits of conventional magnetic storage techniques. Physical properties and optical memory characteristics of magnetooptic thin-films of manganese bismuth have been investigated with regard to both bit-oriented and holographic memories. All the required technology for design of a bit-oriented memory appears to be available, but several key components required for a holographic memory still remain to be developed.

Onset of deoxyribonucleic Acid synthesis in germinating wheat embryos

Germinating wheat embryos (Triticum vulgare var. Florence) synthesize proteins before the onset of DNA synthesis. The onset of DNA replication occurs at about 15 hours of germination and was shown to depend on proteins synthesized before 9 hours of germination with the use of blasticidin S, a specific inhibitor of protein synthesis. A 10-fold increase in the activity of DNA-dependent DNA polymerase was found in extracts derived from germinated embryos, as compared to the activity found in extracts from ungerminated embryos.

Hormones in the Translational Control of Early Germination in Wheat Embryos

Gibberellic and abscisic acid seem to exert their effects on germination by acting in some way at the level of translation. The two hormones may act at different sites.

Naphthoquinone biosynthesis in higher plants. I. Studies on 2-hydroxy-1,4-naphthoquinone in Impatiens balsamina L

The biosynthesis of 2-hydroxy-1,4-naphthoquinone in aerial portions of Impatiens balsamina L. (Balsaminaceae) has been studied. Phenylalanine-U-14C and sodium acetate-1-14C did not label the quinone. Shikimic acid-U-14C, however, was incorporated into the quinone with a dilution of 15.7. The conversion of shikimic acid to ferulic acid in these experiments was accomplished with a dilution of 39.6. GIucose-U-14C was incorporated into the naphthoquinone and ferulic acid molecules with dilutions of 9230 and 29,500 respectively. Administration of an excess of cold p-hydroxybenzoic acid along with labeled shikimic acid resulted in no incorporation of label into the quinone. Degradation of labeled 2-hydroxy-1,4-naphthoquinone yielded phthalic acid with 68.5% of the label originally in the quinone. This agrees well with the theoretical value of 67% calculated on the basis that the shikimic acid ring is incorporated intact into the quinone ring of 2-hydroxy-1,4-naphthoquinone.

THERMOGRAVIMETRY OF THE DEHYDRATION OF Mg(OH)2

The DTG curves for the dehydration of a number of preparations of Mg(OH)2 were determined. Equations necessary to calculate energies of activation and rate constants from these curves were derived on the basis of a two-thirds-order process for dehydration. It was found that the energy of activation was about 5 kcal greater for naturally occurring than for precipitated Mg(OH)2. This was interpreted to mean that there was a difference in the energy levels of the two preparations, and therefore a difference in their apparent solubility products. Differences obtained in the DTG curves for four different preparations of Mg(OH)2 indicated the probability of a series of energy levels for Mg(OH)2.