Search

The TAROGE-M radio observatory is a self-triggered antenna array on top of the ∼2700 m high Mt. Melbourne in Antarctica, designed to detect impulsive geomagnetic emission from extensive air showers induced by ultra-high energy (UHE) particles beyond 1017 eV, including cosmic rays, Earth-skimming tau neutrinos, and particularly, the “ANITA anomalous events” (AAE) from near and below the horizon. The six AAE discovered by the ANITA experiment have signal features similar to tau neutrinos but that hypothesis is in tension either with the interaction length predicted by Standard Model or with the flux limits set by other experiments. Their origin remains uncertain, requiring more experimental inputs for clarification. The detection concept of TAROGE-M takes advantage of a high altitude with synoptic view toward the horizon as an efficient signal collector, and the radio quietness as well as strong and near vertical geomagnetic field in Antarctica, enhancing the relative radio signal strength. This approach has a low energy threshold, high duty cycle, and is easy to extend for quickly enlarging statistics. Here we report experimental results from the first TAROGE-M station deployed in January 2020, corresponding to approximately one month of livetime. The station consists of six receiving antennas operating at 180–450 MHz, and can reconstruct source directions of impulsive events with an angular resolution of ∼0.3°, calibrated in situ with a drone-borne pulser system. To demonstrate TAROGE-M's ability to detect UHE air showers, a search for cosmic ray signals in 25.3-days of data together with the detection simulation were conducted, resulting in seven identified candidates. The detected events have a mean reconstructed energy of 0.95-0.31 +0.46 EeV and zenith angles ranging from 25° to 82°, with both distributions agreeing with the simulations, indicating an energy threshold at about 0.3 EeV. The estimated cosmic ray flux at that energy is 1.2-0.9 +0.7 × 10-16 eV-1 km-2 yr-1 sr-1, also consistent with results of other experiments. The TAROGE-M sensitivity to AAEs is approximated by the tau neutrino exposure with simulations, which suggests comparable sensitivity as ANITA's at around 1 EeV energy with a few station-years of operation. These first results verified the station design and performance in a polar and high-altitude environment, and are promising for further discovery of tau neutrinos and AAEs after an extension in the near future.

We present a portable calibration pulser system applied to radio antennas in order to detect ultra-high energy cosmic rays and neutrinos. The system consists of a solid-state high-voltage impulse generator, a digital attenuator, a wide band (150-350 MHz) bi-cone antenna, and a differential GPS. Taking an advantage of light weight of each component (less than $1.4$ kg), we developed an airborne calibration system by attaching them on a commercial drone. This system will be used for TAROGE experiment in high mountains as well as in Antarctica. We will report on its design, construction, performance, and potential applications for future radio experiments.

During the transition phase from a prestellar to a protostellar cloud core, one or several protostars can form within a single gas core. The detailed physical processes of this transition, however, remain unclear. We present 1.3 mm dust continuum and molecular line observations with the Atacama Large Millimeter/submillimeter Array toward 43 protostellar cores in the Orion molecular cloud complex (λ Orionis, Orion B, and Orion A) with an angular resolution of ∼0.″35 (∼140 au). In total, we detect 13 binary/multiple systems. We derive an overall multiplicity frequency (MF) of 28% ± 4% and a companion star fraction (CSF) of 51% ± 6%, over a separation range of 300-8900 au. The median separation of companions is about 2100 au. The occurrence of stellar multiplicity may depend on the physical characteristics of the dense cores. Notably, those containing binary/multiple systems tend to show a higher gas density and Mach number than cores forming single stars. The integral-shaped filament of the Orion A giant molecular cloud (GMC), which has the highest gas density and hosts high-mass star formation in its central region (the Orion Nebula cluster), shows the highest MF and CSF among the Orion GMCs. In contrast, the λ Orionis GMC has a lower MF and CSF than the Orion B and Orion A GMCs, indicating that feedback from H ii regions may suppress the formation of multiple systems. We also find that the protostars comprising a binary/multiple system are usually at different evolutionary stages., T.L. acknowledges support from the National Natural Science Foundation of China (NSFC) through grants No. 12073061 and No. 12122307, the International Partnership Program of the Chinese Academy of Sciences (CAS) through grant No. 114231KYSB20200009, the Shanghai Pujiang Program (20PJ1415500), and science research grants from the China Manned Space Project with no. CMS-CSST-2021-B06. K.T. was supported by Japan Society for the Promotion of Science (JSPS) KAKENHI (grant No. 20H05645). D.J. and J.d.F. are supported by NRC Canada and by NSERC Discovery Grants. C.-F.L. acknowledge grants from the Ministry of Science and Technology of Taiwan (MoST 107-2119-M-001-040-MY3 and 110-2112-M-001-021-MY3) and Academia Sinica (Investigator Award AS-IA-108-M01). This research was carried out in part at the Jet Propulsion Laboratory, which is operated by the California Institute of Technology under a contract with the National Aeronautics and Space Administration (80NM0018D0004). J.-E.L. was supported by a National Research Foundation of Korea grant funded by the Korean government (MSIT) (grant No. 2021R1A2C1011718). J.H. acknowledges the support of NSFC projects 11873086 and U1631237. This work is sponsored (in part) by the CAS, through a grant to the CAS South America Center for Astronomy in Santiago, Chile. S.-L.Q. is supported by the NSFC with grant No. 12033005. S.Z. acknowledges the support of the China Postdoctoral Science Foundation through grant No. 2021M700248. L.B. gratefully acknowledges support by the ANID BASAL projects ACE210002 and FB210003. P.S. was supported by a Grant-in-Aid for Scientific Research (KAKENHI No. 18H01259) of JSPS. V.-M.P. acknowledges support by the grant PID2020-115892GB-I00 funded by MCIN/AEI/10.13039/501100011033.

Prestellar cores are self-gravitating dense and cold structures within molecular clouds where future stars are born. They are expected, at the stage of transitioning to the protostellar phase, to harbor centrally concentrated dense (sub)structures that will seed the formation of a new star or the binary/multiple stellar systems. Characterizing this critical stage of evolution is key to our understanding of star formation. In this work, we report the detection of high-density (sub)structures on the thousand-astronomical-unit (au) scale in a sample of dense prestellar cores. Through our recent ALMA observations toward the Orion Planck Galactic Cold Clumps, we have found five extremely dense prestellar cores, which have centrally concentrated regions of ∼2000 au in size, and several 107 cm-3 in average density. Masses of these centrally dense regions are in the range of 0.30 to 6.89M⊙. For the first time, our higher resolution observations (0.8' ∼ 320 au) further reveal that one of the cores shows clear signatures of fragmentation; such individual substructures/fragments have sizes of 800-1700 au, masses of 0.08 to 0.84M⊙, densities of 2 - 8 × 107 cm-3, and separations of ∼1200 au. The substructures are massive enough (≳0.1M⊙) to form young stellar objects and are likely examples of the earliest stage of stellar embryos that can lead to widely (∼1200 au) separated multiple systems., L. acknowledges the support from the international partnership program of the Chinese Academy of Sciences through grant No.114231KYSB20200009, National Natural Science Foundation of China (NSFC) through grant NSFC No.12073061, and Shanghai Pujiang Program 20PJ1415500. N.H. acknowledges MoST 108-2112-M-001-017 and MoST 109-2112-M-001-023 grants. G.G. acknowledges support from ANID project AFB 170002. L.B. acknowledges support from ANID project AFB-170002. S.L.Q. is supported by the National Natural Science Foundation of China under grant No. U1631237. D.J. is supported by NRC Canada and by an NSERC Discovery Grant. V.M.P. acknowledges support by the Spanish MINECO under project AYA2017-88754-P, and financial support from the State Agency for Research of the Spanish Ministry of Science and Innovation through the “Unit of Excellence María de Maeztu 2020-2023” award to the Institute of Cosmos Sciences (CEX2019-000918-M). C.W.L. is supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2019R1A2C1010851). A.S. acknowledges financial support from the NSF through grant AST-1715876. The research was carried out in part at the Jet Propulsion Laboratory, which is operated for NASA by the California Institute of Technology. D. L. acknowledges support from NSFC No. 11911530226 and 11725313. K.T. was supported by JSPS KAKENHI grant No. 20H05645. J.H. thanks the NSFC grant No. 11873086 and Yunnan Province of China (No. 2017HC018).This work is sponsored (in part) by the Chinese Academy of Sciences (CAS), through a grant to the CAS South America Center for Astronomy (CASSACA) in Santiago, Chile.

Gas at high Galactic latitude is a relatively little-noticed component of the interstellar medium. In an effort to address this, forty-one Planck Galactic Cold Clumps at high Galactic latitude (HGal; $|b|>25^{\circ}$) were observed in $^{12}$CO, $^{13}$CO and C$^{18}$O J=1-0 lines, using the Purple Mountain Observatory 13.7-m telescope. $^{12}$CO (1-0) and $^{13}$CO (1-0) emission was detected in all clumps while C$^{18}$O (1-0) emission was only seen in sixteen clumps. The highest and average latitudes are $71.4^{\circ}$ and $37.8^{\circ}$, respectively. Fifty-one velocity components were obtained and then each was identified as a single clump. Thirty-three clumps were further mapped at 1$^\prime$ resolution and 54 dense cores were extracted. Among dense cores, the average excitation temperature $T_{\mathrm{ex}}$ of $^{12}$CO is 10.3 K. The average line widths of thermal and non-thermal velocity dispersions are $0.19$ km s$^{-1}$ and $0.46$ km s$^{-1}$ respectively, suggesting that these cores are dominated by turbulence. Distances of the HGal clumps given by Gaia dust reddening are about $120-360$ pc. The ratio of $X_{13}$/$X_{18}$ is significantly higher than that in the solar neighbourhood, implying that HGal gas has a different star formation history compared to the gas in the Galactic disk. HGal cores with sizes from $0.01-0.1$ pc show no notable Larson's relation and the turbulence remains supersonic down to a scale of slightly below $0.1$ pc. None of the HGal cores which bear masses from 0.01-1 $M_{\odot}$ are gravitationally bound and all appear to be confined by outer pressure., 35 pages, 13 figures

We have selected six sources (G209.55–19.68S2, G205.46–14.56S1-A, G203.21–11.20W2, G191.90–11.21S, G205.46–14.56S3, and G206.93–16.61W2) from the Atacama Large Millimeter/submillimeter Array Survey of Orion Planck Galactic Cold Clumps (ALMASOP), in which these sources have been mapped in the CO (J = 2−1), SiO (J = 5−4), and C18O (J = 2−1) lines. These sources have high-velocity SiO jets surrounded by low-velocity CO outflows. The SiO jets consist of a chain of knots. These knots have been thought to be produced by semiperiodic variations in jet velocity. Therefore, we adopt a shock-forming model, which uses such variations to estimate the inclination angle and velocity of the jets. We also derive the inclination angle of the CO outflows using the wide-angle wind-driven shell model and find it to be broadly consistent with that of the associated SiO jets. In addition, we apply this shock-forming model to another three protostellar sources with SiO jets in the literature—HH 211, HH 212, and L1448C(N)—and find that their inclination angle and jet velocity are consistent with those previously estimated from proper-motion and radial-velocity studies.

The presence of complex organic molecules (COMs) in the interstellar medium (ISM) is of great interest since it may link to the origin and prevalence of life in the universe. Aiming to investigate the occurrence of COMs and their possible origins, we conducted a chemical census toward a sample of protostellar cores as part of the ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP) project. We report the detection of 11 hot corino sources, which exhibit compact emissions from warm and abundant COMs, among 56 Class 0/I protostellar cores. All the hot corino sources discovered are likely Class 0 and their sizes of the warm region ($>$ 100 K) are comparable to 100 au. The luminosity of the hot corino sources exhibits positive correlations with the total number of methanol and the extent of its emissions. Such correlations are consistent with the thermal desorption picture for the presence of hot corino and suggest that the lower luminosity (Class 0) sources likely have a smaller region with COMs emissions. With the same sample selection method and detection criteria being applied, the detection rates of the warm methanol in the Orion cloud (15/37) and the Perseus cloud (28/50) are statistically similar when the cloud distances and the limited sample size are considered. Observing the same set of COM transitions will bring a more informative comparison between the cloud properties., 34 pages. 14 figures. 1 figure set. 1 machine-readable table. Accepted for publication in ApJ

Introduction Leadership has long been suggested as an attribute essential to the pharmacy profession. Academic pharmacy has identified and addressed the need for leadership development among student pharmacists. The objective of this study is to assess differences in learning styles, critical thinking skills, and peer-perceived leadership skill evaluations between those with vs. without student leadership engagement (SLE). Methods Four cohorts of pharmacy students were included in the analysis. Each student completed the Kolb Learning Style Inventory and Health Science Reasoning Test (HSRT) during pharmacy school orientation. Student-peer evaluation scores were derived from three courses and assessed important leadership skills such as communication, critical thinking, teamwork, and professionalism. Descriptive analysis was performed; group difference was tested using independent group t-tests on continuous variables and Fisher exact tests on categorical variables. Results This study included 205 pharmacy students from the Classes of 2018 to 2021; 63 students (31%) displayed SLE. No significant differences were found in the peer evaluation scores between students with and without SLE. Students with SLE showed significantly higher scores in domains of the HSRT and the overall HSRT score. Conclusions The study results showed that HSRT assessment of critical thinking skills was significantly higher in students engaging in leadership, suggesting that HSRT should be explored as a possible predictor for SLE in future studies.

Jets and outflows trace the accretion history of protostars. High-velocity molecular jets have been observed from several protostars in the early Class 0 phase of star formation, detected with the high-density tracer SiO. Until now, no clear jet has been detected with SiO emission from isolated evolved Class I protostellar systems. We report a prominent dense SiO jet from a Class I source G205S3 (HOPS-315: T bol ∼ 180 K, spectral index ∼0.417), with a moderately high mass-loss rate (∼0.59 × 10−6 M ⊙ yr−1) estimated from CO emission. Together, these features suggest that G205S3 is still in a high-accretion phase, similar to that expected of Class 0 objects. We compare G205S3 to a representative Class 0 system G206W2 (HOPS-399) and literature Class 0/I sources to explore the possible explanations behind the SiO emission seen at the later phase. We estimate a high inclination angle (∼40°) for G205S3 from CO emission, which may expose the infrared emission from the central core and mislead the spectral classification. However, the compact 1.3 mm continuum, C18O emission, location in the bolometric luminosity to submillimeter fluxes diagram, outflow force (∼3.26 × 10−5 M ⊙ km s−1 yr−1) are also analogous to that of Class I systems. We thus consider G205S3 to be at the very early phase of Class I, and in the late phase of high accretion. The episodic ejection could be due to the presence of an unknown binary, a planetary companion, or dense clumps, where the required mass for such high accretion could be supplied by a massive circumbinary disk.

Background and Purpose To describe implementation and lessons learned from use of a mock trial as a teaching-learning and assessment activity in a required evidence-based practice course. This innovative self-directed learning strategy reinforced evidence-based skills and affective domain competencies in Center for the Advancement of Pharmaceutical Education (CAPE) 2013 Outcomes and Accreditation Council for Pharmacy Education (ACPE) Standards 2016. Educational Activity and Setting During spring semesters 2015 and 2016, first professional year (P1) cohorts were divided into teams and assigned controversial topics to research and debate in mock trials. The activity provided opportunities for teaching-learning and assessment. Statistical analysis included inter-rater reliability (IRR), comparison of faculty-judge and student-juror evaluation of trial performance. Findings Two cohorts were divided into eight teams (four per cohort) to debate four issues. Students within each team were assigned individual scores. Mean individual scores are reported by trial/topic. Faculty-judges and student-jurors rated eight criteria including content/knowledge, critical thinking, application/discussion of federal/state law, citations/references, visual aids, delivery/style, and active listening. Analysis indicated students met competency expectations with overall judges’ and jurors’ mean scores above 54/60 points (90%) in 2015 and above 51/60 points (85%) in 2016. Judges’ scores showed a wider distribution than jurors’ scores. Peer evaluation mean scores were above 55/60 points in all four trials. Intra-class correlation was calculated. Judges’ scores had excellent IRR in two trials, and good IRR in a third trial, whereas jurors had good IRR in one trial. Summary Evaluation scores demonstrated students successfully applied knowledge and skills from this and prior P1 courses, and met competency expectations for the mock trial.

We report the detection of four new hot corino sources, G211.47-19.27S, G208.68-19.20N1, G210.49-19.79W and G192.12-11.10 from a survey study of Planck Galactic Cold Clumps in the Orion Molecular Cloud Complex with the Atacama Compact Array (ACA). Three sources had been identified as low mass Class 0 protostars in the Herschel Orion Protostar Survey (HOPS). One source in the lambda Orionis region is firstly reported as a protostellar core. We have observed abundant complex organic molecules (COMs), primarily methanol but also other oxygen-bearing COMs (in G211.47-19.27S and G208.68-19.20N1) and the molecule of prebiotic interest NH2CHO (in G211.47-19.27S), signifying the presence of hot corinos. While our spatial resolution is not sufficient for resolving most of the molecular emission structure, the large linewidth and high rotational temperature of COMs suggest that they likely reside in the hotter and innermost region immediately surrounding the protostar. In G211.47-19.27S, the D/H ratio of methanol ([CH2DOH]/[CH3OH]) and the 12C/13C ratio of methanol ([CH3OH]/[13CH3OH]) are comparable to those of other hot corinos. Hydrocarbons and long carbon-chain molecules such as c-C3H2 and HCCCN are also detected in the four sources, likely tracing the outer and cooler molecular envelopes., 37 pages, 51 figures, to be published in ApJ

This study examines how best to present information in an antidepressant print DTCA. The objectives of this study are to: (1) modify an antidepressant print advertisement to enhance consumers’ understanding of the presented information, (2) create a questionnaire to measure consumers’ recall of the information presented in an antidepressant print advertisement and (3) pilot test the study instruments by comparing consumers’ recall of the information in the antidepressant print advertisement between those who view the original advertisement and those who view the modified advertisement. Modifications of the advertisement were based on the Explanatory Structure Building Model, findings from previous studies, and literature pertaining to the enhancement of the readability and comprehension of written health information. Data collection was conducted in three stages using mixed methods. This study details potential techniques that can be used to enhance the presentation of information in print DTCA in order to improve consumers’ recall of the information. Furthermore, this study shows that strategies to improve the presentation of information in print DTCA exist and that the strategies are feasible to apply. Conflict of Interest This research study was supported by the University of Wisconsin-Madison Population Health Dissertation Grants sponsored by the Robert Wood Johnson Foundation and the Sonderegger Research Center Dissertation Research Grants. Type: Original Research

The influence of the antiferromagnetic layer of cobalt oxide on the magnetization reversal of a submicron cobalt planar wire was studied using the magneto-transport measurements. For pure Cobalt (Co) planar wires of width less than 1.2 μm, length of 30 μm, and thickness of 30 nm, the shape anisotropy dominates the magnetic behavior revealing all characteristics of a single domain structure. With oxidation, there is a thin layer of CoO on top of the Co layer and the exchange coupling between the CoO (antiferromagnet) and Co (ferromagnetic) layers may suppress the shape anisotropy induced single domain structure and the typical switching behavior of magnetization reversal. The magnetic configuration and magnetization reversal are determined by the competition of unidirectional anisotropy and exchange coupling constant.

Despite the explosion of new, innovative technologies in the area of multiple identification and subsequent attenuation, their applicability is mostly limited to marine environments especially in deep water. In land seismic data sets however, the application of such multiple-elimination methodologies is not always straightforward and in many cases poor results are obtained. The unique characteristics of land seismic data (i.e., noise, statics and coupling) are major obstacles in multiple estimation and subsequent elimination. The well-defined surface multiples present in marine data are rarely identifiable in land data. Particularly in desert terrains with a complex near surface and low-relief structures, surface multiples hardly exist. In most cases, we are dealing with so called “near-surface-related multiples.” These are primarily internal multiples generated within the complex near surface.

Multiple removal is a longstanding problem in exploration seismology. Although methods for removing multiples have advanced and have become more effective, the concomitant industry trend toward more complex exploration areas and difficult plays has often outpaced advances in multiple-attenuation technology. The topic of multiples, and developing ever more effective methods for their removal, remains high in terms of industry interest, priority and research investment. The question as to whether today, in 2011, multiples or multiple removal is winning is a way of describing what we are about to discuss. This paper focuses on recent advances, progress and strengths and limitations of current capability and a prioritized list of open issues that need to be addressed.

The world of petroleum exploration constantly demands higher efficacy at every link in the data processing chain, from preconditioning to imaging and inversion. Within that chain, the removal of internal multiples constitutes a particularly resilient problem, whose resolution has only partially benefited from the advent of the data-driven technologies which have transformed the practice of free-surface multiple elimination.

A direct determination of the interfacial transparency on the basis of current-perpendicular-to-plane (CPP) resistances for Cu0.5Ni0.5/Nb layered system is presented. This particular realization has substantial significance for understanding the interfacial transport in such heterostructures. The unexpected large critical thickness for this weak ferromagnetic containing system can be attributed to the strong pair-breaking effect as a result of the high interfacial transparency. Besides, the strong pair-breaking also plays a decisive role in the occurrence of the dimensionality crossover of the temperature dependent upper critical magnetic field.

We have measured the electric transport of double quantum point contacts in series at low temperatures. Two pairs of metal gates are placed longitudinally and sequentially with an edge-to-edge distance of 600 nm. They are used to form two quantum point contacts in a GaAs / Al x Ga 1 ‐ x As heterostructure. Isolating from an insulating layer, a top gate is also fabricated on top of the quantum point contacts to modify the electron densities in the quantum point contacts and the two dimensional electron gas as well. The transport is characterized by the direct transmission probability T d which represents the portions of electrons travelling ballistically from one quantum point contact to the other. Our results show that the parameter T d decreases with decreasing carrier density. The transport is partially adiabatic in high 2D electron densities and transits to completely ohmic regimes in low densities. Because of the correlation between the coherence length and transmission probability, we attribute the result to the reduction of the coherence length and mean free path in the unconstricted electron gas between quantum point contacts.

Statistics for 2002 to 2012 show that the percentage of women among graduates in physics and astronomy has not changed much in the Republic of China in Taiwan. Women comprise about 15% of graduates with bachelor’s degrees in physics and astronomy, 17% of those with master’s degrees, and 12% of doctorates. The number of female faculty members has increased slightly during this time frame but overall has stayed at approximately 11%.

Magnetoconductance (MC) measurements have been performed on a 2140 A thick tungsten carbide film at temperatures very close to the superconducting transition temperature Tc of the film. The data are dominated by superconducting fluctuations. A novel three-dimensional phenomenological model is proposed to explain the MC data, yielding good fits. The Larkin beta factor, βLarkin, appeared as a fitting parameter. An expression proposed by Larkin for βLarkin failed badly for temperatures extremely close to Tc. But at intermediate and high temperatures compared to Tc, Larkin's expression gave very good agreement in fits to the MC data. At temperatures very close to Tc, a crossover from three dimensions to two dimensions was observed in the behaviour of the MC of the film.

We have measured the low-temperature resistivities of a series of bulk crystalline disordered Ti 73− x Al 27 Sn x alloys ( x ≲5) as well as the sheet resistances of a number of thin ferromagnetic Ni films (≈120 A thick) sandwiching an ultrathin Ag or Au (≲5 A) layer. The level of impurities (concentration of Sn in the former case, and thickness of Ag or Au in the latter case) is progressively increased in order to enhance the spin–orbit scattering in a controllable manner. The influence of the spin–orbit scattering on the electron–electron interaction effects is studied from the temperature dependence of resistivities (sheet resistance) at low temperatures. We find that the electron–electron interaction contribution to the resistivities (sheet resistances) increases slightly with increasing spin–orbit scattering. Our observation is discussed in terms of the current theoretical concept for the electron–electron interactions in disordered metals.

We have performed electronic tunneling density of states and resistivity measurements in three-dimensional CuxGe100−x films spanning the weakly and strongly localized regimes. We found that the Coulomb anomaly in tunneling density of states in the strongly disordered regime is very profound and grows in strength with resistivity. However, when the system becomes less disorderly and approaches the weakly disordered regime, this anomaly weakens rapidly. The data suggest that the disorder enhanced electron–electron interaction effects can drive the crossover from weak disorder to strong disorder in CuGe alloy system.

We present magnetoresistance measurements aimed at answering several open questions in the understanding of giant magnetoresistance (GMR). Our measurements are performed on $(F1/N/F2/N)$ multilayers in which N is a nonmagnetic metal (Cu or Cr), and $F1$ and $F2$ are various ferromagnetic metals or alloys. In current perpendicular to the plane (CPP) measurements on $(F1/\mathrm{Cu}/\mathrm{Co}/\mathrm{Cu})$ multilayers, where $F1$ is Fe, Co, or Ni doped with impurities, we observe an inversion of the GMR for V or Cr impurities; this demonstrates, first the importance of the extrinsic effects in GMR and secondly the possibility of obtaining negative as well as positive values of the bulk spin asymmetry coefficient $\ensuremath{\beta}.$ A compensation thickness with zero GMR is found when the bulk and interface spin asymmetry have opposite signs in the same layer. We interpret the sign of $\ensuremath{\beta}$ in models of electronic structure. Measurements on other series of multilayers allow us to show that the interface spin asymmetry coefficient $\ensuremath{\gamma}$ can also be positive (interfaces with Cu) or negative (interfaces with Cr). Finally, the comparison between CPP and CIP data obtained on the same samples sheds light on the different role of the interface intrinsic potential in the two geometries.

The transition temperature T c and upper critical field H c2 of sputtered Fe/Nb trilayers and multilayers have been determined by measurement of electrical resistivity. For a fixed Fe layer thickness, T c decreases with decreasing Nb thickness up to a critical thickness d Nb crit ≈ 34 nm below which superconductivity vanishes. When the superconducting layers are thin ( d Nb 140 nm ) and decoupled by pair breaking in the ferromagnetic layers, the parallel critical field exhibits nonlinear temperature dependence, revealing a change in the superconducting dimensionality. The strong decrease of T c with decreasing Nb thickness as well as the temperature dependence of H c2 can be well described by theoretical model.

We present the first measurements of giant magnetoresistance with current perpendicular to the layer planes (CPP-MR) of an exchange-biased spin-valve (EBSV) - a controllable spin-switch. Interpreted with the theory of Valet and Fert, data on EBSVs of permalloy (Py) with Cu yield an unexpectedly short spin-diffusion length in Py − l sf Py =5.5± nm. Such a short length has implications for the interpretation of Johnson's data on a Py/Au/Py spin-switch.

From data on $({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{V}}_{x}/\mathrm{Cu}/\mathrm{Co}/\mathrm{Cu}{)}_{N}$ multilayers, we show that Fe doped with V gains a negative spin asymmetry for bulk scattering $(\ensuremath{\beta}l0)$, which, combined with the positive asymmetry of Co, accounts for the inverse current perpendicular to the plane (CPP) giant magnetoresistance (GMR) we observe. More precisely, the competition between positive and negative asymmetries for interface and bulk scatterings in FeV leads to inverse (normal) GMR for layers thicker (thinner) than a compensation thickness. The negative $\ensuremath{\beta}$ of FeV is consistent with theoretical predictions and bulk alloy data. The current in the plane (CIP) GMR is not reversed, which illustrates the role of channeling in CIP.

Spin-relaxation effects are generally believed to have a strong influence on giant magnetoresistance of ferromagnetic/noble-metal multilayers. We have measured current perpendicular to plane magnetoresistances (CPP MR's) of sputtered Co/${\mathrm{Cu}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ni}}_{\mathit{x}}$ multilayers with x=0.06, 0.10, 0.14, and 0.23. Our results indicate that the spin-diffusion length of CuNi is reduced as the concentration of Ni increases. Spin-diffusion lengths obtained from fitting the CPP MR to Valet-Fert theory are in a good agreement with theoretical calculations from spin-orbit scattering. Assuming that the permalloy(Py)-Cu interface in Py/Cu multilayers resembles a CuNi alloy, we can conclude that there will be spin-flip scattering at a Py-Cu interface, but we expect its effect on the MR to be small. \textcopyright{} 1996 The American Physical Society.

Superconducting YBa2Cu3O7−x films having smooth surfaces were successfully synthesized by a microwave plasma‐enhanced pulsed laser deposition (PEPLD) process. Particulates that frequently occurred in filmsgrown by the conventional PLD process were effectively eliminated. The films were epitaxial‐like. The c‐axis was perpendicular to the films’ surface, the a and b axes were aligned in the films’ plane, and the onset and zero of the transition temperature were at T c =90 K and T c0=86 K, respectively. Optical emission spectroscopy indicated that the presence of oxygen plasma not only reexcited the laser‐induced species via the collision process, but also produced abundant atomic oxygen in PEPLD process. The surface reaction kinetics for the formation of the thin‐film process was thus greatly enhanced, which substantially improved the thin‐film quality.

We have measured the low temperature $T\ensuremath{\le}20\mathrm{K}$ magnetoconductance (MC) of ultrathin films that have strong spin-orbit interactions and conductances $G$ spanning the weakly $G\ensuremath{\gg}{G}_{00}{\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}e}^{2}/2{\ensuremath{\pi}}^{2}\ensuremath{\Elzxh}$ and strongly localized $G\ensuremath{\ll}{G}_{00}$ regimes. For $G\ensuremath{\gg}{G}_{00}$, the MC is negative in agreement with weak localization theory, and for $G\ensuremath{\ll}{G}_{00}$, it is positive in accord with theories of electron hopping transport. The MC changes sign when $G\ensuremath{\approx}{G}_{00}$, independent of material and temperature. The data suggest that a well defined conductance separates the weak and strong localization regimes in two dimensions.

Electron tunneling measurements on ultrathin quench-condensed films near the superconductor-to-insulator (SI) transition reveal that the superconducting state degrades with increasing normal state sheet resistance, R□, in a manner that depends strongly on film morphology. In homogeneously disordered films, the superconducting energy gap Δo decreases continuously and appears to go to zero at the SI transition. In granular films the transport properties degrade while Δo remains constant. Measurements in the normal state reveal disorder enhanced e- -e- interaction corrections to the density of states. These effects are strong and depend on morphology in a manner that is consistent with their playing an important role in driving the SI transition.

We have measured the tunneling density of states in ultrathin high-sheet-resistance, 16 {Omega}{lt}{ital R}{sub {ital N}}{lt}17 k{Omega}, granular Pb films in perpendicular magnetic fields, {ital H}. At the lowest {ital R}{sub {ital N}}, states appear within the superconducting energy gap at low fields ({ital H}{lt}0.1 T) indicating the presence of vortex cores. At the highest {ital R}{sub {ital N}}, no states appear in the gap in fields as high as 2 T indicating that the field-induced vortices do not have cores. A simple model implies that the average Josephson coupling energy between the grains of the film is comparable to the condensation energy of a single grain at the {ital R}{sub {ital N}} separating these two regimes.

To share data with other parties in computer collaboration is an important issue of data security. k-anonymity and l-diversity are used to protect privacy and secure data sharing. It was proved that optimal k-anonymity are NP hard for k ≥ 3 and that there is a polynomial algorithm for optimal 2-anonymity. This paper proves that an optimal 2-diversity is NP hard. Since l-diversity must be l-anonymity, it follows that the l-diversity is NP hard for l ≥ 2. The result shows that finding polynomial algorithm for efficient (but not optimal) l-diversity is important.

We utilize theoretical concepts from the Inverse Scattering Series (ISS) formulation to develop internal multiple elimination algorithms for land seismic data. ISS-based methods are fully data-driven, therefore, they do not require any subsurface knowledge. Internal multiples from all possible generators are computed and adaptively subtracted from the input data. These methods are equally well suited for pre- and post-stack applications, and are effective even when there is little or no moveout difference between primary reflections and multiples. The performance of the ISS approach is demonstrated using realistic synthetic and field datasets from the Arabian Peninsula.

We have measured the perpendicular upper critical field, ${\mathit{H}}_{\mathit{c}2}$(T), in ultrathin granular Pb films with normal-state sheet resistances, ${\mathit{R}}_{\mathit{N}}$, that range from 10 \ensuremath{\Omega} to 11 k\ensuremath{\Omega}. The films with the highest ${\mathit{R}}_{\mathit{N}}$ are near the threshold for the superconductor-to-insulator (S-I) transition. We compare our results to calculations for granular superconductors and obtain values for the grain size and coherence length characteristic of a single grain. In addition, we present a measurement of the ratio of the intergrain Josephson-coupling energy to the single-grain condensation energy near the S-I transition in these films. The small value of this ratio, 0.05, at ${\mathit{R}}_{\mathit{N}}$=11 k\ensuremath{\Omega} is consistent with the picture that fluctuations in the phase of the order parameter dominate the S-I transition in these films.

We present a systematic study on the zero-bias conductance peak and its dependences on the carrier density and structural geometry in quasi-one-dimensional quantum wires (QWs). This zero-bias anomaly (ZBA) is suppressed by either decreasing the carrier density or increasing the QW length. The differential conductance at zero bias decreases with increasing temperature in accordance with a thermal-activation model up to a well-defined cut-off temperature. We demonstrate that the activation energy, cut-off temperature, and width of the ZBA are correlated, and suggest that these features are controlled by electron scattering in QWs.

The estimation and subsequent elimination of internal multiples in land seismic data is one of the most challenging steps in data processing. Although marine multiple elimination techniques, such as the SRME technology, are well established, in land their implementation is not straightforward and in many cases poor results are obtained. In this paper we use theoretical concepts from the Inverse Scattering Series (ISS) formulation and develop computer algorithms for land internal multiple elimination. The key characteristic of the ISS-based methods is that they do not require any information about the subsurface, i.e., they are fully data driven. Internal multiples from all possible generators are computed and adaptively subtracted from the input data. These methodologies can be applied preand post-stack and their performance is demonstrated using realistic synthetic and field datasets from the Arabian Peninsula. These are the first published results of the application of the ISS internal multiple attenuation method to the daunting challenge of land internal multiples.

Removal of multiples from seismic reflection data is an important preprocessing step before conventional seismic imaging and inversion in most onshore and offshore environments. While many methods have been developed and successfully used to remove free-surface multiples, internal multiple attenuation remains a challenge when working in land and complex marine environments. The inverse scattering series (ISS) internal multiple algorithm is a data-driven tool to predict all orders of internal multiples for all horizons at once, without requiring subsurface information. However, use of the multidimensional version of this algorithm has been limited due to high computational cost, which increases with the maximum output frequency in the prediction. Even with the recent advances in computer hardware, the cost of the multidimensional algorithm remains expensive. To overcome this problem, we use the quasi-Monte Carlo integration technique that can significantly improve the computational efficiency of the multidimensional ISS internal multiple algorithm. The efficiency is improved by reducing the number of samples being evaluated and combining multiple integrals into a single summation.

We present measurements of the temperature dependence of the tunneling density of states near the Fermi energy, G 0 (T) , and resistive transitions, R(T) , of ultrathin PbBi films. Both R(T) and G 0 (T) broaden substantially near the superconductor to insulator transition (SIT). The broadening in R(T) is not affected by the proximity of a ground plane suggesting that long range Coulomb interactions are not important to the SIT. The results suggest that the transport properties of films near the SIT are influenced by fluctuations in both the phase and the amplitude of the order parameter. We discuss the data in terms of recent theories of the superconducting transition in low superfluid density systems.

Granular Pb thin films on the insulating side of the two-dimensional superconductor-insulator transition are observed to exhibit a large negative magnetoresistance and electroresistance (change in resistance with electric field) at low temperatures. At high measurement voltages and low temperatures, the film resistances become temperature independent creating a ``metallic'' state. These phenomena are explained as manifestations of transport due to intergranular quasiparticle tunneling. This explanation might also provide insights into the similar behavior observed in other superconductors.

We present CPP-GMR experiments on a series of multilayers of the type (A/Cu/Co/Cu)×N where A is a layer of NiCr, FeCr, or FeV alloys with concentrations of Cr or V between 2.5 and 30 at. %. The inverse GMR effects we observe can be accounted for by the opposite scattering spin asymmetries in Co (positive spin asymmetry) and A (negative spin asymmetry). As the spin asymmetry in A is positive for interface scattering and negative for bulk scattering, the inverse GMR is observed only for thicknesses greater than one at which interface and bulk scattering compensate. We determine the magnitude and sign of the spin asymmetry coefficients, and we notice the agreement with previous data on dilute alloys and with theoretical calculations.

Na x CoO 2 ( x ∼0.68) thin films were fabricated on sapphire (0 0 0 1) substrates via the lateral diffusion of sodium into Co 3 O 4 (1 1 1) films, which were grown by pulsed-laser deposition. From the results of X-ray diffraction and in-plane resistivity ρ ab , the single phase and the metallic behaviors of these Na x CoO 2 films can be identified. For the same sodium content x , ρ ab is consistent with that of single crystals. In addition, the O 1 s X-ray absorption near edge spectra of thin films are measured and compared with those of single crystals.

Metal-graphene contact recently attracts much attention because of its effects on the performance and the operational speed of graphene field-effect transistor. Simple two-probe graphene devices on mechanically exfoliated graphene flakes are fabricated and the temperature behavior of resistance is measured from room temperature down to liquid helium temperature for the study of electron transport in the interface. Comparing experimental data with several different transport theories, it is confirmed that the model of fluctuation-induced tunneling conduction describes precisely the electron transport and indicates the existence of a thin insulating layer in the metal-graphene interface. Through the interface probing by electron transport measurements, the way to reduce the contact resistance is suggested.

Bulk nanostructured materials are made from the assembly of octahedral PbSe nanocrystals. After thermal annealing, the artificial bulk demonstrates a large difference in behavior depending on the temperature, and a large variation of room-temperature resistivity of up to seven orders of magnitude. This variation originates from the high-indexed sharp edges of the octahedral nanocrystals. As the nanocrystals are arranged in the edge-to-edge configuration, which was observed in scanning electron microscopy images, the inter-nanocrystal capacitance is small due to the small parallel area between the nanocrystals. The small capacitance results in a high thermal fluctuation voltage and drives electron transport. The temperature-dependent resistivity and the electric field-dependent current are highly in agreement with the model of fluctuation-induced tunneling conduction. Thermal annealing reduces the inter-nanocrystal separation distance, creating a large variation in the electrical properties. Specifically, octahedral-shaped PbSe nanocrystals are employed in tailoring the electron transport in bulk nanostructured materials.