Current viewpoints on oxide adherence mechanisms

Additional hot stage Auger experiments have provided surface segregation data for NiCrAl + or - Y or Zr alloys in agreement with other investigations. This data, combined with experimental and theoretical evidence of the Al2O3-metal bond strength, is presented in support of a chemical mechanism of Al2O3 scale adhesion. Both the detrimental effects of sulfur segregation and the beneficial effects of dopant segregation may be important. Chemical features of the dopants are compared in light of these proposed mechanisms, namely delta H sub f (sulfide), delta H sub f (oxide), electron orbital configuration, and insolubility in Ni

X-ray photoemission characterization of La_{0.67}(Ca_{x}Sr_{1-x})_{0.33}MnO_{3} films

The Curie temperature and x-ray photoemission spectra of thin films of La_{0.67}(Ca_{x}Sr_{1-x})_{0.33}MnO_{3} (LCSMO) have been studied as a function of the Ca/Sr ratio. The films were grown by off-axis cosputtering from individual targets of La_{0.67}Ca_{0.33}MnO_{3} (LCMO) and La_{0.67}Sr_{0.33}MnO_{3} (LSMO) onto (100) oriented NdGaO_{3} substrates. The films grow with a (100) orientation, with no other orientations observed by x-ray diffraction. For the alloy mixtures, the Curie temperature, T_C, varies slowly as the Ca/Sr is decreased, remaining $\approx$ 300 K, while for the LCMO and LSMO films T_C is 260 and 330 K, respectively. The Mn-O valence structure is composed of two dominant peaks, whose positions undergo a change as the Ca fraction is decreased. The core lines behave as linear combinations of lines from pure LCMO and LSMO.Comment: 3 pages, 5 eps figures. To be published in Journal of Applied Physics (Proceedings of MMM'98

Lithospheric layering beneath northern Central Africa by S-to-P receiver functions

Using a total of 4520 S-to-P receiver functions (SRFs) recorded by 19 broadband seismic stations belonging to the Libyan Center for Remote Sensing and Space Science and the Incorporated Research Institutions for Seismology Data Management Center, we imaged the depth of the lithosphere–asthenosphere boundary (LAB) beneath northern Central Africa. This boundary occurs over the depth range of 57–124 km which we imaged in consecutive circular bins (radius of 2°) using a high number of receiver functions. The mean depth of the discontinuity is 80 ± 17 km, which is significantly shallower than the global average of ~250 km, commonly found beneath ancient cratons. The SRFs in the study area produced 156 bins with observable arrivals from the LAB. All the stacked traces were plotted along eight latitudinal profiles from 20°N to 35°N. The observed depth of the LAB increases systematically toward the northern central part of the study area from approximately 67 km–120 km. The apparent depth of the LAB increases from 70 to 90 km from 21°N to 28°N and then further increases to 120 km from 28°N to 34°N. These depth variations are extreme beneath the northern central part of Libya. The LAB depth beneath the Hoggar volcanic province area is relatively low (~57 km) compared to other areas. This study provides new constraints on regional-scale tectonic processes such as lithospheric stretching or thinning, due to partial melting beneath the study region that may be an effect of the LAB topography in this part of northern Central Africa

New Multiline Oats - Designed to Breeak the Chain of Crown Rust

Until now, oat breeders have been in a race to keep ahead of new strains of crown rust. Now multiline oats show promise of outdistancing the disease. Here\u27s the full story on development and early results with the first multiline oats in the world

Breeding Multiline Oat Varieties for Iowa

To stay ahead of oat rust races that can multiply 50 percent per day in late June, oat breeders at the Iowa Experiment Station are breeding in earlier maturity and adding extra genetic resistance to oat diseases

Characterization of transport and magnetic properties in thin film La(0.67)(Ca(x)Sr(1-x))(0.33)MnO(3) mixtures

We have grown thin films of (100) oriented La_{0.67}(Ca_{x}Sr_{1-x})_{0.33}MnO_{3} on (100) NdGaO_{3} substrates by off-axis sputtering. We have looked at the changes in the resistivity and magnetoresistance of the samples as the Ca/Sr ratio was varied. We find that as the calcium fraction is decreased, the lattice match to the substrate decreases, and the films become more disordered, as observed in transport measurements and the variation in Curie and peak resistance temperatures. We find a correlation between the temperature independent and T^2 terms to the low temperature resistivity. The room temperature magnetoresistance exhibits a maximum as the peak temperature is increased by the substitution of Sr for Ca, and a change in the field dependence to the resistivity at room temperature is observed.Comment: 5 pages, 6 eps figures, to be published in Journal of Applied Physic

Nonlinear Instability of kink oscillations due to shear motions

First results from a high-resolution three-dimensional nonlinear numerical study of the kink oscillation are presented. We show in detail the development of a shear instability in an untwisted line-tied magnetic flux tube. The instability produces significant deformations of the tube boundary. An extended transition layer may naturally evolve as a result of the shear instability at a sharp transition between the flux tube and the external medium. We also discuss the possible effects of the instability on the process of resonant absorption when an inhomogeneous layer is included in the model. One of the implications of these results is that the azimuthal component of the magnetic field of a stable flux tube in the solar corona, needed to prevent the shear instability, is probably constrained to be in a very specific range

The Bristol ‘OA500 study’: progression and impact of the disease after 8 years

AbstractObjective To study the natural history of peripheral joint osteoarthritis (OA) and assess its impact over eight years in a prospective study of 500 patients.Methods 500 consecutive patients with peripheral joint OA were recruited from a hospital-based rheumatology clinic. All were invited for review 3 and 8 years after entry. Joint sites involved, pain severity, change in index joints, global change in the condition, use of medication, surgery and walking aids were all recorded at each visit, and after eight years disability was assessed by the health assessment questionnaire (HAQ) and anxiety and depression by the Hospital anxiety and depression scale (HAD).Results At eight-year review, 349 patients were seen: 90% of those remaining alive. Outcome was heterogeneous. Sixty patients (17.2%) reported worsening in all three subjective parameters (pain, index joint and global change) compared with 22 (6.3%) who improved in all three parameters. Using this definition of worsening or improvement, strong baseline predictors of clinical outcome did not emerge. For further description, the group was split according to the index joint sites involved at entry to the study, there being 111 with knee OA alone, 87 with hand and knee OA, 72 with hand disease alone, and 29 with hip disease alone. Forty-four percent of those with lone hand disease at entry had acquired significant knee or hip OA 8 years later. The mean HAQ and HAD scores at 8 years were high, especially in those with knee disease, indicating significant disability as a result of the disease. Those with knee or knee and hand disease had the worst outcome in all parameters recorded. The data showed a general decrease in use of NSAIDs over the eight years, but an increase in utilization of analgesics, surgery (especially for hip disease) and walking aids.Conclusions Patients with peripheral joint OA of sufficient severity to lead to hospital referral have a heterogeneous, but generally bad outcome over 8 years, the disease resulting in high levels of physical disability, anxiety and depression, with a high level of utilization of healthcare resources, including joint replacement, drugs and walking aids. The results were consistent with previous suggestions that peripheral joint OA in older people is characterized by the slow acquisition of new joint sites. Progression and outcome may depend on a complex set of psychosocial factors, as well as biological ones

Natural resources of Lake Earl and Smith River Delta

The Lake Earl/Smith River Delta area is a key coastal wetland situated in northern California. The Lake and Delta have retained much of their value to wildlife and serve as an important link in a chain of such wetlands that extend southward along the Pacific Ocean from Alaska to South America. Millions of water-associated birds of the Pacific Flyway utilize these areas as feeding and resting stops along their migration paths. In California, these wetlands also serve as a significant portion of the available wintering grounds for a major share of the birds within the flyway. The Smith River is also one of the State's most productive salmon and steelhead streams. Anadromous fish produced here provide thousands of angler use days to sport fishermen and contribute substantially to the commercial fishing catch off the northern coast. Because of the importance of coastal wetlands to the fish and wildlife of California, the Department of Fish and Game has initiated a high priority statewide inventory and assessment of these wetlands. This publication is an integral part of that program. This report identifies specific resources and uses; directs attention to problems; and recommends courses of action needed to insure resource protection. It is intended as a guide for citizens, planners, administrators and other interested in the use and development of California's coastal land and waters. (132pp.

Implications of longitudinal ridges for the mechanics of ice-free long runout landslides

The emplacement mechanisms of long runout landslides across the Solar System and the formation mechanisms of longitudinal ridges associated with their deposits remain subjects of debate. The similarity of longitudinal ridges in martian long runout landslides and terrestrial landslides emplaced on ice suggests that an icy surface could explain both the reduction of friction associated with the deposition of long runout landslides and the development of longitudinal ridges. However, laboratory experiments on rapid granular flows show that ice is not a necessary requirement for the development of longitudinal ridges, which instead may form from convective cells within high-speed flows. These experiments have shown that the wavelength (S) of the ridges is 2-3 times the thickness (T) of the flow, which has also been demonstrated at field scale on a tens-of-kilometre martian long runout landslide. Here, we present the case study of the 4-km-long, ice-free El Magnifico landslide in Northern Chile which exhibits clear longitudinal ridges, and show for the first time on a terrestrial landslide that the S/T ratio is in agreement with the scaling relationship found for both laboratory rapid granular flows and a previously measured martian long runout landslide. Several outcrops within the landslide allow us to study internal sections of the landslide deposit and their relationship with the longitudinal ridges in order to shed light on the emplacement mechanism. Our observations include interactions without chaotic mixing between different lithologies and the presence of meters-sized blocks that exhibit preserved original bedding discontinuities. We associate these observations with fluctuations in stress, as they are qualitatively similar to numerically modelled rapid granular slides, which were suggested, to some degree, to be associated with acoustic fluidization. Our results suggest that 1) the mechanism responsible for the formation of longitudinal ridges is scale- and environment-independent; 2) while the internal structures observed do not necessarily support a mechanism of convective-style motion, their interpretation could also point to a mechanism of internal deformation of the sliding mass derived from pattern-forming vibrations. Our novel observations and analysis provide important insights for the interpretation of similar features on Earth and Mars and for discerning the underlying mechanisms responsible for the emplacement of long run out landslides