Search Results - (Author, Cooperation:R. M. White)

2018-04-17

The American Society for Microbiology (ASM)

0270-7306

1098-5549

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Medicine

2016-01-30

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

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Animals ; Animals, Genetically Modified ; Carcinogenesis/*genetics ; Embryonic Stem Cells/metabolism ; Enhancer Elements, Genetic ; *Gene Expression Regulation, Developmental ; *Gene Expression Regulation, Neoplastic ; Genes, Reporter ; Green Fluorescent Proteins/genetics ; Melanocytes/metabolism ; Melanoma/*genetics ; Melanoma, Experimental/*genetics ; Mutation ; Nerve Tissue Proteins/genetics ; Neural Crest/*metabolism ; Proto-Oncogene Proteins B-raf/genetics ; SOXE Transcription Factors/genetics ; Skin Neoplasms/*genetics ; Tumor Suppressor Protein p53/genetics ; *Zebrafish ; Zebrafish Proteins/genetics

2011-01-29

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

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*Awards and Prizes ; *Foundations ; *Science ; *Technology ; United States

2011-03-25

Nature Publishing Group (NPG)

0028-0836

1476-4687

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Physics

Amino Acid Substitution ; Animals ; Animals, Genetically Modified ; Cell Differentiation/drug effects ; Cell Line, Tumor ; Cell Lineage/drug effects ; Disease Models, Animal ; Gene Expression Regulation, Neoplastic ; Genes, p53/genetics ; Humans ; Isoxazoles/pharmacology/therapeutic use ; Melanoma/drug therapy/enzymology/*genetics/*pathology ; Mice ; Neural Crest/drug effects/*enzymology/metabolism/pathology ; Oxidoreductases Acting on CH-CH Group Donors/antagonists & inhibitors/*metabolism ; Proto-Oncogene Proteins B-raf/antagonists & ; inhibitors/chemistry/genetics/metabolism ; Rats ; Stem Cells/cytology/drug effects/pathology ; *Transcription, Genetic/drug effects/physiology ; Xenograft Model Antitumor Assays ; Zebrafish/embryology/genetics

1089-7550

AIP Digital Archive

Physics

Many physical systems exhibit a dynamic response referred to either as slow relaxation, a quasilogarithmic time dependence, or a stretched exponential response. Historically this time dependence has been attributed to the presence of disorder which creates a distribution of relaxation times. In two papers [D. K. Lottis, E. Dan Dahlberg, J. Christner, J. I. Lee, R. Peterson, and R. White, J. Appl. Phys. 63, 2920 (1988); D. K. Lottis, R. M. White, and E. Dan Dahlberg, Phys. Rev. Lett. 67, 362 (1991)], we have shown that this time dependence can alternatively be explained to be a consequence of interactions or couplings. In the model, the interactions between relaxing spins, the dipole–dipole couplings, drive the system from an initial state towards equilibrium. As the system relaxes, the dipolar energy is reduced and the driving force diminishes. This process gives rise to the observed slow relaxation-time dependence in a very natural manner. To guarantee the absence of disorder, the model considers the dipolar coupling or interaction between relaxing spins with a mean-field approximation, the demagnetization field. Another feature observed in physical systems which the model explains is the nonmonotonic temperature dependence of the logarithmic decay slope. In addition to a description of the model, measurements to determine the presence of interactions in some of the systems will be discussed.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The role of topological coupling, the magnetostatic coupling associated with interfacial roughness in magnetic sandwich/multilayer structures, was studied both analytically and experimentally. We report the first controlled measurements of such topological coupling. A coupling field of the order of 10 Oe between magnetic layers was observed in Co/Cu/Co sandwich structures fabricated with an artificially controlled in-phase roughness of variable amplitude with a fixed period of 3.5 μm. The coupling field was compared with the value predicted by a first-order approximation model and correlated with the geometry of the structure. Scale invariance of the coupling field allows the results to be extended to ultrathin giant magnetoresistance/spin valve structures. © 1996 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We describe the fluid loading of Lamb waves propagating in a 3 mm×9 mm composite membrane consisting of low-stress silicon nitride deposited by low-pressure chemical vapor deposition (2.0 μm thick) supporting an aluminum ground plane (0.3 μm), a piezoelectric zinc oxide layer (0.7 μm), and a pair of 100-μm-period interdigital Al transducers (0.5 μm). When this device is operated in air, the phase velocity of the lowest antisymmetric mode is 474 m/s; it changes to 304 and 322 m/s, respectively, when the membrane is loaded on one side with de-ionized water and with methanol. The large fluid-loading effect, in excellent agreement with theory, and the stability of an oscillator made with this membrane (stability better than 1 part in 106) suggest the utility of the device as a sensitive densitometer and pressure sensor.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We show that, for small added masses, the sensitivities of bulk-mode, surface-mode, and flexural plate-mode gravimetric ultrasonic sensors are respectively 2/ρλ, ≈1/ρλ, and 1/2ρd, where ρ is the density of the sensor substrate material, λ is the wavelength, and d is the plate thickness of the flexural-mode sensor.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The voltage dependence of magnetoresistance in spin dependent tunneling (SDT) junctions was studied experimentally and theoretically. Different magnetoresistance (MR)-V dependence in various patterned junctions was observed and correlated with other technologically important parameters, including the magnitude of the MR, linearity of the current–voltage characteristic, temperature dependence of the junction resistance, and the MR. A phenomenological model based on a spin-independent two-step tunneling via defect states in the barrier, in addition to the spin-dependent direct tunneling, is proposed to account for the MR-V dependence. The MR ratio is determined by the ratio of the two currents. The MR-V dependence results from a stronger voltage dependence of the two-step tunneling current compared to that of the direct tunneling current. The same model also satisfactorily predicts other properties of SDT junctions. A high quality barrier is required to minimize the MR-V dependence and improve other junction properties. The approach to achieving desirable junction impedance for data storage applications is discussed. © 1998 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

It was previously reported that multilayer samples of Co/GdCo2 annealed at 500 °C exhibited exchange anisotropy. One observes a B-H hysteresis loop centered at a finite field, the "exchange'' field. To identify the "hard'' magnetic phase(s) responsible for the shifted loops we have studied thin films of GdCox as well as multilayers of Co/GdCox, where x varies from 2 to 8.5. We saw shifted loops in two distinct groups of samples, neither of which is multilayered. The first group was GdCox in the composition range between GdCo3 and GdCo5. The loop displacement at room temperature is about 5 Oe. The coercivities of these samples are about 10 Oe. The second group of samples had a composition close to GdCo2. For these samples most of the B-H loop is centered at zero field with a coercivity of 1–2 Oe. However, at ±80 Oe there are small loops which account for about 20% of the total magnetization. X-ray measurements indicate that both groups of samples are microcrystalline or amorphous. The second set of samples discussed above exhibit a maximum in diffracted intensity at 2θ=36°, where GdCo2 has a strong (220) peak. The first group of samples have a broad maximum at 38°, where neither GdCo3 nor GdCo5 has peaks. Gd2Co7 has a very weak peak at this angle and Gd2Co17 has strong peaks but would have to be metastable.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We have studied the relaxation or decay of the perpendicular remanent magnetization of CoCr films after the removal of a saturating magnetic field. The films have a perpendicular anisotropy and are similar to those being studied for application as perpendicular recording media. The time dependence of the decay of the magnetization was determined by measuring the magnitude of the magnetization continuously for time periods up to a thousand minutes using a SQUID magnetometer. This time dependence was studied over a range of temperatures for each of the samples (10–300 K). The decays are found to be quasilogarithmic over at least three decades of time and have been compared to two phenomological models. A fit to one model's decay rate indicates the temperature dependence of the decay rate is nonmonotonic, i.e., the decay rate is a maximum in an intermediate temperature region for the films we have studied.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We have observed pumping of water induced by 4.7 MHz ultrasonic Lamb waves traveling in a 4-μm-thick composite membrane of silicon nitride and piezoelectric zinc oxide. The observed pumping speed is proportional to the square of the wave amplitude; the speed was 100 μm/s for a rf drive voltage of 8 V and a 6.5 nm wave amplitude. A nonlinear model based on acoustic streaming theory predicts velocities in good agreement with experiment.

Electronic Resource

1600-0560

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

We report a ease of distant cutaneous metastases in a 68-year-old patient with malignant ameloblastoma of the mandible. The metastatic lesions were first noted approximately 31 years after resection of the primary tumor. Metastases to lung, pleura, bone, and brain had also occurred. Histochemical findings differ from those described in adamantinoid basal cell carcinoma. Cutaneous metastasis probably resulted from hematogenous dissemination. To our knowledge, this is the first report of such an occurrence in English language literature.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Earlier this year the National Materials Advisory Board established a Committee on Magnetic Materials to assess the adequacy of U. S. research in magnetic materials and to identify opportunities for future research. The findings and recommendations of this Committee are presented here.

Electronic Resource