Statistical Study of Aircraft Icing Probabilities at the 700- and 500- Millibar Levels over Ocean Areas in the Northern Hemisphere

A statistical study is made of icing data reported from weather reconnaissance aircraft flown by Air Weather Service (USAF). The weather missions studied were flown at fixed flight levels of 500 millibars (18,000 ft) and 700 millibars (10,000 ft) over wide areas of the Pacific, Atlantic, and Arctic Oceans. This report is presented as part of a program conducted by the NACA to obtain extensive icing statistics relevant to aircraft design and operation. The thousands of in-flight observations recorded over a 2- to 4-year period provide reliable statistics on icing encounters for the specific areas, altitudes, and seasons included in the data. The relative frequencies of icing occurrence are presented, together with the estimated icing probabilities and the relation of these probabilities to the frequencies of flight in clouds and cloud temperatures. The results show that aircraft operators can expect icing probabilities to vary widely throughout the year from near zero in the cold Arctic areas in winter up to 7 percent in areas where greater cloudiness and warmer temperatures prevail. The data also reveal a general tendency of colder cloud temperatures to reduce the probability of icing in equally cloudy conditions

LIGAND-INDUCED MOVEMENT OF LYMPHOCYTE MEMBRANE MACROMOLECULES : I. ANALYSIS BY IMMUNOFLUORESCENCE AND ULTRASTRUCTURAL RADIOAUTOGRAPHY

The fate of different complexes on the membrane of thymocytes and spleen lymphocytes was studied with the use of both immunofluorescence and ultrastructural radioautography. The complexes of anti-immunoglobulin (Ig) with the surface Ig of B lymphocytes were present all around the membrane at 4°C; an increase in temperature produced a rapid aggregation of the complex into a cap which was readily interiorized in vesicles. Ultrastructural details of this process were given. The movement of the complexes depended upon the amount of anti-Ig and the temperature. The complexes of anti-lymphocyte antibody with surface antigen(s) did not result in formation of a single large aggregate (or cap) unless an anti-antibody was brought into the reaction. The caps formed by this trilayered complex were not interiorized. Concanavalin A (Con A) bound to cell surface carbohydrate moieties and the complexes of Con A readily formed a cap and were interiorized. Finally, antibodies to H-2 determinants did not form in most instances a single cap aggregate even when anti-antibodies were used. With time the H-2 complexes tended to form several large aggregates with some endocytosis

AN ULTRASTRUCTURAL STUDY OF LYMPHOCYTES WITH SURFACE-BOUND IMMUNOGLOBULIN

This report is on a radioautographic study of lymphocytes exposed to 125I-labeled anti-Ig in an attempt to identify surface-bound Ig molecules. The results as studied by ultrastructural radioautography confirmed the presence of surface-bound Ig on a certain population of lymphocytes. The specificity of the anti-Ig was determined by using appropriate controls that included the use of an absorbed anti-Ig and anti-hemocyanin antibody. The labeling pattern resulting from the interaction of labeled anti-Ig and Ig was found to be specifically associated with the cell surface and random in its distribution. Morphological differences were not apparent between labeled and nonlabeled lymphocytes in the spleen and lymph nodes. In the thymus, most lymphocytes did not exhibit detectable Ig. The few thymic lymphocytes that were labeled had unique morphological characteristics that included fewer ribosomes, many of which were monoribosomes. Relative to the amount in their cytoplasmic organelles, plasma cells had surface Ig but to a lesser degree than lymphocytes. Finally, macrophages were nonspecifically labeled and contained antibody on their membranes as well as intracellularly

Somatosensory Deficits in Post-ACL Reconstruction Patients: A Case-Control Study

Introduction: Diminished cutaneous detection thresholds have been identified in patients with multiple orthopedic conditions, and these phenomena may occur in postanterior cruciate ligament reconstructed (ACLR) patients. The purpose of this study was to determine if differences in lower extremity cutaneous detection thresholds exist in post-ACLR patients when compared with healthy controls. Methods: Fifteen individuals who were post-ACLR and 15 individuals who had no history of knee injury participated. Light touch cutaneous detection thresholds were assessed at 4 locations on the foot and ankle (first metatarsal, fifth metatarsal, medial malleolus, and lateral malleolus). Nonparametric statistics examined group differences between the sites. Results: ACLR subjects had decreased cutaneous sensation at the first metatarsal and medial malleolus compared with healthy controls. Conclusions: Somatosensory deficits are present in post-ACLR patients. Future research should investigate these phenomena longitudinally in post-ACLR individuals along with somatosensory targeted interventions

The Generalized Hessenberg Representation, Near Aggregation, and Near Unobservability

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / N00014-84-C-014

Essential Parameters in Sensitivity Analysis

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / DAAB-07-67-C-0199Air Force Office of Scientific Research / AFOSR 931-6

Ternary Nitride Semiconductors in the Rocksalt Crystal Structure

Inorganic nitrides with wurtzite crystal structures are well-known semiconductors used in optoelectronic devices. In contrast, rocksalt-based nitrides are known for their metallic and refractory properties. Breaking this dichotomy, here we report on ternary nitride semiconductors with rocksalt crystal structures, remarkable optoelectronic properties, and the general chemical formula Mg$_{x}$TM$_{1-x}$N (TM=Ti, Zr, Hf, Nb). These compounds form over a broad metal composition range and our experiments show that Mg-rich compositions are nondegenerate semiconductors with visible-range optical absorption onsets (1.8-2.1 eV). Lattice parameters are compatible with growth on a variety of substrates, and epitaxially grown MgZrN$_{2}$ exhibits remarkable electron mobilities approaching 100 cm$^{2}$V$^{-1}$s$^{-1}$. Ab initio calculations reveal that these compounds have disorder-tunable optical properties, large dielectric constants and low carrier effective masses that are insensitive to disorder. Overall, these experimental and theoretical results highlight Mg$_{G-3}$TMN$_{G-2}$ rocksalts as a new class of semiconductor materials with promising properties for optoelectronic applications