Dynamical Diffraction Theory for Wave Packet Propagation in Deformed Crystals

We develop a theory for the trajectory of an x ray in the presence of a crystal deformation. A set of equations of motion for an x-ray wave packet including the dynamical diffraction is derived, taking into account the Berry phase as a correction to geometrical optics. The trajectory of the wave packet has a shift of the center position due to a crystal deformation. Remarkably, in the vicinity of the Bragg condition, the shift is enhanced by a factor $\omega /\Delta \omega$ ($\omega$: frequency of an x ray, $\Delta\omega$: gap frequency induced by the Bragg reflection). Comparison with the conventional dynamical diffraction theory is also made.Comment: 4 pages, 2 figures. Title change

New Species and Host Associations of Commensal Leucothoid Amphipods from Coral Reefs in Florida and Belize (Crustacea:Amphipoda)

Six new amphipod species in the genus Leucothoe from the tropical western Atlantic Ocean are described and illustrated. Extensive field collecting and specialized underwater collecting techniques have documented 43 new invertebrate host records for these new taxa. Four of these new species inhabit interior canals of sponges; Leucothoe barana n.sp., Leucothoe garifunae n.sp., Leucothoe saron n.sp., and Leucothoe ubouhu n.sp. A remarkable new species, Leucothoe flammosa n.sp., nestles in the gills of seven species of bivalve mollusks. A single species, Leucothoe wuriti n.sp., appears restricted to the branchial chamber of two species of solitary ascidians. Detailed illustrations and scanning electron microscopy enables comparison of ultrastructure details. More precise taxonomic character morphologies are also presented thus allowing improved taxonomic precision within the family Leucothoidae

Leucothoidae

Four genera and 17 species of leucothoids, the majority of these belonging to the genus Leucothoe, are herein reported from the Great Barrier Reef. Fifteen species are new to science and only Anamixis bazimut has been previously reported from the Great Barrier Reef

Shear Strength of Lightly Reinforced T-Beams

Fifteen lightly reinforced concrete T-beams, 11 with stirrups and four without stirrups, were tested to failure. The major variables rit the study were the amounts of flexural and shear reinforcement. The flexural steel varied from 0.5 to 1 percent, and the shear reinforcement varied from 0 to 110 psi (0.75 MPa). The test results are analyzed and compared with the shear design provisions of "Building Code Requirements for Reinforced Concrete (AC1 318-77)" and the recommendations of AC1 Committee 426, Shear and Diagonal Tension. The test results confirmed the findings of other investigators, that the present AC1 equations for the shear cracking load are unconservative for beams without stirrups, having a longitudinal reinforcing ratio less than 1 percent. However, for beams with stirrups the web reinforcement was 1.5 times as effective as predicted by AC1 318-77 and compensated for the lower shear strength of the concrete. It is recommended that the shear design provisions of AC1 318-77 be retained in their current form

Penelitian Awal Tentang Pengaruh Penggunaan Consol Polymer Latex Sebagai Campuran Pada Balok Beton

Dalam dunia konstruksi, beton adalah barang yang sering kita jumpai. Seringkali beton yang kita dijumpai sudah dicampur dengan admixture untuk memperoleh hasil kekuatan beton yang maksimal. Salah satu jenis admixture yang ada yaitu latex. Oleh karena hal tersebut maka dilakukan penelitian. Penelitian ini untuk mengetahui pengaruh penggunaan consol polymer latex pada campuran beton. Consol polymer latex ini termasuk dalam jenis latex yaitu jenis latex emulsi. Dalam penelitian ini dilakukan 4 jenis percobaan, yaitu pengujian kuat tekan, kuat lentur, kuat tarik dan momen nominal beton. Semua tes dilakukan pengujian pada 7, 14, dan 28 hari, serta dilakukan juga tes pada saat 1 hari untuk beton yang telah dicampur dengan consol polymer latex