Dynamics of Spontaneous Magnetization Reversal in Exchange Biased Heterostructures

The dependence of thermally induced spontaneous magnetization reversal on time-dependent cooling protocols was studied. Slower cooling and longer waiting close to the N\`{e}el temperature of the antiferromagnet ($T_N$) enhances the magnetization reversal. Cycling the temperature around $T_N$ leads to a thermal training effect under which the reversal magnitude increases with each cycle. These results suggest that spontaneous magnetization reversal is energetically favored, contrary to our present understanding of positive exchange bias

Dynamic Spin-Polarized Resonant Tunneling in Magnetic Tunnel Junctions

Precisely engineered tunnel junctions exhibit a long sought effect that occurs when the energy of the electron is comparable to the potential energy of the tunneling barrier. The resistance of metal-insulator-metal tunnel junctions oscillates with an applied voltage when electrons that tunnel directly into the barrier's conduction band interfere upon reflection at the classical turning points: the insulator-metal interface, and the dynamic point where the incident electron energy equals the potential barrier inside the insulator. A model of tunneling between free electron bands using the exact solution of the Schroedinger equation for a trapezoidal tunnel barrier qualitatively agrees with experiment.Comment: 4pgs, 3 fig

Anomalous Spontaneous Reversal in Magnetic Heterostructures

We observe a thermally induced spontaneous magnetization reversal of epitaxial ferromagnet/antiferromagnet heterostructures under a constant applied magnetic field. Unlike any other magnetic system, the magnetization spontaneously reverses, aligning anti-parallel to an applied field with decreasing temperature. We show that this unusual phenomenon is caused by the interfacial antiferromagnetic coupling overcoming the Zeeman energy of the ferromagnet. A significant temperature hysteresis exists, whose height and width can be tuned by the field applied during thermal cycling. The hysteresis originates from the intrinsic magnetic anisotropy in the system. The observation of this phenomenon leads to open questions in the general understanding of magnetic heterostructures. Moreover, this shows that in general heterogeneous nanostructured materials may exhibit unexpected phenomena absent in the bulk.Comment: 14 pages, 4 figure

575 UNITED STATES DEPARTMENT OF THE INTERIOR 'GEOLOGICAL SURVEY GEOLOGIC SETTING AND CHEMICAL CHARACTERISITICS OF HOT SPRINGS IN CENTRAL AND WESTERN ALASKA

ABSTRACT Numerous hot springs occur in a variety of geologic provinces in central and western Alaska. Granitic plutons are common to all the provinces and the hot springs are spatially associated with the contacts of these plutons. Of 23 hot springs whose bedrock geology is known, all occur within 3 miles of a granitic pluton. The occurrence of hot springs, however, appears to be independent of the age, composition, or magmatic history of the pluton. Preliminary chemical and isotopic analyses suggest the hot springs waters belong to two groups. Most of the analyzed hot springs appear to have chemical and Isotopic compositions indicating they were derived from deeply circulating meteoric water. About 25 percent of the analyzed hot springs show a distinct saline character with high concentrations of chloride, sodium, potassium, and calcium indicating either much more complex water rock reactions than occurred in the other hot springs or the addition of another type of water. The present chemical and isotopic data are insufficient to determine the source of the constituents of the saline hot springs. Chemical geothermometers suggest subsurface temperatures in the general range of 100°C to 160°C. If the hot spring waters have derived their heat solely from deep circulation, the waters must have reached depths of 9,000 to 15,000 feet, assuming geothermal gradients of 30°C to 50°C/km. If hot magmatic water has been added to the geothermal systems or if dilution or mixing has occurred, temperatures of 100°C to 160°C may be reached at shallower depths. The geologic and chemical data are too preliminary to make an estimate of the potential of the hot springs as a geothermal resource. The data suggest, however, that most of the hot springs of central and western Alaska have relatively low subsurface temperatures and limited reservoir capacities in comparison with geothermal areas presently being utilized for electrical power generation

The treatment of psychotic major depression: is there a role for adjunctive psychotherapy?

Psychotherapy and Psychosomatics, 76(5): pp. 271-277.Background: Psychotic depression is a relatively prevalent mood disorder associated with greater symptom severity, a poorer course of illness and higher levels of functional impairment compared with nonpsychotic depression. Separate lines of investigation suggest that various forms of cognitive- behavioral therapy are efficacious for treating severe forms of nonpsychotic depression as well as primary psychotic disorders. However, there currently are no empirically supported psychotherapies specifically designed for treating psychotic depression. Method: We review the efficacy of current somatic treatments for the disorder and discuss the limited data to date on potentially useful psychotherapeutic approaches. In particular, we describe the clinical improvement observed in a subgroup of hospitalized patients with psychotic depression treated with Acceptance and Commitment Therapy as part of a larger clinical trial. Results: Pilot results demonstrated that Acceptance and Commitment Therapy was associated with clinically significant reductions in acute symptom severity and impairment compared with treatment as usual. Conclusion: The findings suggest that patients with psychotic depression can benefit from psychotherapy. Clinical and research recommendations in this area are presented

Computer Administered Safety Planning for Individuals at Risk for Suicide: Development and Usability Testing

BACKGROUND: Safety planning is a brief intervention that has become an accepted practice in many clinical settings to help prevent suicide. Even though it is quick compared to other approaches, it frequently requires 20 min or more to complete, which can impede adoption. A self-administered, Web-based safety planning application could potentially reduce clinician time, help promote standardization and quality, and provide enhanced ability to share the created plan. OBJECTIVE: The aim of this study was to design, build, and test the usability of a Web-based, self-administered safety planning application. METHODS: We employed a user-centered software design strategy led by a multidisciplinary team. The application was tested for usability with a target sample of suicidal patients. Detailed observations, structured usability ratings, and Think Aloud procedures were used. Suicidal ideation intensity and perceived ability to cope were assessed pre-post engagement with the Web application. RESULTS: A total of 30 participants were enrolled. Usability ratings were generally strong, and all patients successfully built a safety plan. However, the completeness of the safety plan varied. The mean number of steps completed was 5.5 (SD 0.9) out of 6, with 90% (27/30) of participants completing at least 5 steps and 67% (20/30) completing all 6 steps. Some safety planning steps were viewed as inapplicable to some individuals. Some confusion in instructions led to modifications to improve understandability of each step. Ratings of suicide intensity after completion of the application were significantly lower than preratings, pre: mean 5.11 (SD 2.9) versus post: mean 4.46 (SD 3.0), t27=2.49, P=.02. Ratings of ability to cope with suicidal thoughts after completion of the application were higher than preratings, with the difference approaching statistical significance, pre: mean 5.93 (SD 2.9), post: mean 6.64 (SD 2.4), t27=-2.03, P=.05. CONCLUSIONS: We have taken the first step toward identifying the components needed to maximize usability of a self-administered, Web-based safety planning application. Results support initial consideration of the application as an adjunct to clinical contact. This allows for the clinician or other personnel to provide clarification, when needed, to help the patient build the plan, and to help review and revise the draft

Measurement of the Ratio of Double-to-Single Photoionization of Helium at 2.8 keV Using Synchrotron Radiation

We report the first measurement of the ratio of double-to-single photoionization of helium well above the double-ionization threshold. Using a time-of-flight technique, we find He++/He+=1.6±0.3% at hν=2.8 keV. This value lies between calculations by Amusia (2.3%) and by Samson, who predicts 1.2% by analogy with electron-impact ionization cross sections of singly charged ions. Good agreement is obtained with older shake calculations of Byron and Joachain, and of Åberg, who predict 1.7%

A Paul Trap Mass Analyzer Consisting of Two Microfabricated Electrode Plates

We report the design and performance of a novel radiofrequency (RF) ion trap mass analyzer, the planar Paul trap, in which a quadrupolar potential distribution is made between two electrode plates. Each plate consists of a series of concentric, lithographically deposited 100-micrometer-wide metal rings, overlaid with a thin resistive layer. To each ring is applied a different RF amplitude, such that the trapping field produced is similar to that of the conventional Paul trap. The accuracy and shape of the electric fields in this trap are not limited by electrode geometry nor machining precision, as is the case in traps made with metal electrodes. The use of two microfabricated plates for ion trap construction presents a lower-cost alternative to conventional ion traps, with additional advantages in electrode alignment, electric field optimization, and ion trap miniaturization. Experiments demonstrate the effects of ion ejection mode and scan rate on mass resolution for several small organic compounds. The current instrument has a mass range up to ~180 Thompsons (Th), with better than unit mass resolution over the whole range

High-energy Behavior of the Double Photoionization of Helium from 2 to 12 keV

We report the ratio of double-to-single photoionization of He at several photon energies from 2 to 12 keV. By time-of-Aight methods, we find a ratio consistent with an asymptote at 1.5%±0.2%, essentially reached by h v≈4 keV. Fair agreement is obtained with older shake calculations of Byron and Joachain [Phys. Rev. 164, 1 (1967)], of Aberg [Phys. Rev. A 2, 1726 (1970)], and with recent many-body perturbation theory (MBPT) of Ishihara, Hino, and McGuire [Phys. Rev. A 44, 6980 (1991)]. The result lies below earlier MPBT calculations by Amusia et al. [J. Phys. B 8, 1248 (1975)] (2.3%), and well above semiempirical predictions of Samson [Phys. Rev. Lett. 65, 2861 (1990)], who expects no asymptote and predicts ơ(He2+)/ơ (He+) =0.3% at 12 keV