Magnetic Properties of Pr0.7Ca0.3MnO3/SrRuO3 Superlattices

High-quality Pr0.7Ca0.3MnO3/SrRuO3 superlattices were fabricated by pulsed laser deposition and were investigated by high-resolution transmission electron microscopy and SQUID magnetometry. Superlattices with orthorhombic and tetragonal SrRuO3 layers were investigated. The superlattices grew coherently; in the growth direction Pr0.7Ca0.3MnO3 layers were terminated by MnO2- and SrRuO3 layers by RuO2-planes. All superlattices showed antiferromagnetic interlayer coupling in low magnetic fields. The coupling strength was significantly higher for orthorhombic than for tetragonal symmetry of the SrRuO3 layers. The strong interlayer exchange coupling in the superlattice with orthorhombic SrRuO3 layers led to a magnetization reversal mechanism with a partially inverted hysteresis loop.Comment: 12 pages, 4 figure

Operationally Efficient Propulsion System Study (OEPSS) data book. Volume 4: OEPSS design concepts

This study was initiated to identify operations problems and cost drivers for current propulsion systems and to identify technology and design approaches to increase the operational efficiency and reduce operations costs for future propulsion systems. To provide readily usable data for the Advanced Launch System (ALS) program, the results of the OEPSS study have been organized into a series of OEPSS Data Books. This volume describes three propulsion concepts that will simplify the propulsion system design and significantly reduce operational requirements. The concepts include: (1) a fully integrated, booster propulsion module concept for the ALS that avoids the complex system created by using autonomous engines with numerous artificial interfaces; (2) an LOX tank aft concept which avoids potentially dangerous geysering in long LOX propellant lines; and (3) an air augmented, rocket engine nozzle afterburning propulsion concept that will significantly reduce LOX propellant requirements, reduce vehicle size and simplify ground operations and ground support equipment and facilities

The Early Bronze Age Ceramic Assemblage from Tell Ta\u27annek, Palestine

The problem Greenberg has recently stated that isolating temporal ceramic indicators for the Early Bronze II-III periods is one of the thorniest issues in the archaeology of Palestine (2000: 183). Part of theproblem stems from the homogenous nature of ceramic assemblages from Early Bronze Age Palestine; part of it stems from a continued lack of published information. Both of these issues are addressed by this study. Excavations at Tell Ta`annek between 1963 and 1967 unearthed the remains of a multi-period site, including the residues of an Early Bronze II-III fortified settlement. It is purposed here to isolate that portion of the site in the collected records and residues in order to produce a ceramic sample that is stratigraphically derived. From this sample, inferences may be drawn concerning chronology, technology, and trade. Method On the basis of data drawn from field records, a relative chronology of the settlement was built by square and locus. This sequence was tested by the retrieval and analysis of saved ceramic sherds. Index forms forced alterations in the sequence, that, in turn, prompted additional stratigraphic work. This cycle produced approximately 400 isolated loci and a working sample of some 2,000 sherds. This assemblage was then analyzed internally, in typological and technological terms, and externally, through comparison with other published assemblages from North Palestine. Results Deposition from Tell Ta`annek suggests three distinct Early Bronze Age strata and a corresponding ceramic sequence stretching from EB I (Stratum 1), through EB II (Stratum 2), and early EB III (Stratum 3). While the presence of fortification and destruction debris is indicative of destabilization and armed conflict, the ceramic record of Common Ware is stable and fairly homogenous, interrupted only by the presence of Metallic Ware and Khirbet Kerak Ware. Conclusion Using Metallic Ware and Khirbet Kerak Ware as reference points, select Common Ware features may be isolated. These contribute to a growing set of knowledge that offers promise for isolating temporal ceramic indicators for the Early Bronze II-III periods. In addition, it is suggested that most residents of Tell Ta`annek were removed from--or resistant to-- imported potting traditions that left a powerful imprint elsewhere in North Palestine. A preference for local wares over more expensive or exotic forms underlines a rural conservatism that is consistent with the site\u27s location

Operationally efficient propulsion system study (OEPSS) data book

A design tool of figure of merit was developed that allows the operability of a propulsion system design to be measured. This Launch Operations Index (LOI) relates Operations Efficiency to System Complexity. The figure of Merit can be used by conceptual designers to compare different propulsion system designs based on their impact on launch operations. The LOI will improve the design process by making sure direct launch operations experience is a necessary feedback to the design process

Evidence of defect-induced ferromagnetism in ZnFe2_{2}O4_{4} thin films

X-ray absorption near-edge and grazing incidence X-ray fluorescence spectroscopy are employed to investigate the electronic structure of ZnFe$_{2}$O$_{4}$ thin films. The spectroscopy techniques are used to determine the non-equilibrium cation site occupancy as a function of depth and oxygen pressure during deposition and its effects on the magnetic properties. It is found that low deposition pressures below 10$^{-3}$ mbar cause iron superoccupation of tetrahedral sites without Zn$^{2+}$ inversion, resulting in an ordered magnetic phase with high room temperature magnetic moment.Comment: Accepted for publication in Phys. Rev.

Logatome Discrimination in Cochlear Implant Users: Subjective Tests Compared to the Mismatch Negativity

This paper describes a logatome discrimination test for the assessment of speech perception in cochlear implant users (CI users), based on a multilingual speech database, the Oldenburg Logatome Corpus, which was originally recorded for the comparison of human and automated speech recognition. The logatome discrimination task is based on the presentation of 100 logatome pairs (i.e., nonsense syllables) with balanced representations of alternating “vowel-replacement” and “consonant-replacement” paradigms in order to assess phoneme confusions. Thirteen adult normal hearing listeners and eight adult CI users, including both good and poor performers, were included in the study and completed the test after their speech intelligibility abilities were evaluated with an established sentence test in noise. Furthermore, the discrimination abilities were measured electrophysiologically by recording the mismatch negativity (MMN) as a component of auditory event-related potentials. The results show a clear MMN response only for normal hearing listeners and CI users with good performance, correlating with their logatome discrimination abilities. Higher discrimination scores for vowel-replacement paradigms than for the consonant-replacement paradigms were found. We conclude that the logatome discrimination test is well suited to monitor the speech perception skills of CI users. Due to the large number of available spoken logatome items, the Oldenburg Logatome Corpus appears to provide a useful and powerful basis for further development of speech perception tests for CI users

Direct correlation between 1/f magnetonoise and magnetoresistance in La<SUB>0.7</SUB>Sr<SUB>0.3</SUB>MnO<SUB>3</SUB> and (La<SUB>0.5</SUB>Pr<SUB>0.2</SUB>)Ba<SUB>0.3</SUB>MnO<SUB>3</SUB> manganites

Temperature- and magnetic-field-dependent electrical noise and electrical resistivity measurements were carried out on epitaxial thin films of a large bandwidth La0.7Sr0.3MnO3 and a disordered intermediate bandwidth (La0.5Pr0.2)Ba0.3MnO3 manganite system. The power spectral density was dominated by 1/f noise. This 1/f noise was observed to follow the overall temperature dependence of the resistivity. Moreover, in these compounds the magnetonoise effect was found to be of nearly the same magnitude as the magnetoresistance. This direct correlation between magnetonoise and magnetoresistance suggests that the enhanced 1/f noise has its origin in intrinsic charge-carrier density fluctuations