594 research outputs found
Chain Formation by Spin Pentamers in eta-Na9V14O35
The nature of the gapped ground state in the quasi-one-dimensional compound
eta-Na9V14O35 cannot easily be understood, if one takes into account the odd
number of spins on each structural element. Combining the results of specific
heat, susceptibility and electron spin resonance measurements we show that
eta-Na9V14O35 exhibits a novel ground state where multi-spin objects build up a
linear chain. These objects - pentamers - consist of five antiferromagnetically
arranged spins with effective spin 1/2. Their spatial extent results in an
exchange constant along the chain direction comparable to the one in the
high-temperature state.Comment: 6 pages, 5 figure
Memory Effect and Triplet Pairing Generation in the Superconducting Exchange Biased Co/CoOx/Cu41Ni59/Nb/Cu41Ni59 Layered Heterostructure
We fabricated a nanolayered hybrid superconductor-ferromagnet spin-valve
structure, the resistive state of which depends on the preceding magnetic field
polarity. The effect is based on a strong exchange bias (about -2 kOe) on a
diluted ferromagnetic copper-nickel alloy and generation of a long range odd in
frequency triplet pairing component. The difference of high and low resistance
states at zero magnetic field is 90% of the normal state resistance for a
transport current of 250 {\mu}A and still around 42% for 10 {\mu}A. Both logic
states of the structure do not require biasing fields or currents in the idle
mode.Comment: 9 pages, 4 figures, Accepted to Applied Physics Letter
Provisional behavioral health licenses to full licenses: Analysis of Nebraska behavioral workforce data 2009–2019
There is a need to recruit and to retain behavioral health providers especially when providers are moving from the provisional licensing status to a full licensure status. This study estimated the rates of conversion of provisional licenses to full licenses among provisionally licensed psychologists, mental health practitioners, master social workers, and alcohol and drug counselors (ADCs) in Nebraska and examined potential associations among demographic characteristics and license conversion rates. Nebraska’s behavioral health licensure data (2009–2019) was obtained from the Health Professional Tracking Service (HPTS) program that was established as a joint effort between Nebraska Department of Health and Human Services, Human Services Office of Rural Health and University of Nebraska Medical Center. The rate of conversion from provisional to full license during the most recent years ranged from 44% for ADCs to 75% among social workers. Compared to individuals of older age, individuals of younger age are more likely to convert among ADCs (p = .0028). Moreover, compared to individuals living in urban areas, rural practitioners are more likely to convert among social workers (p \u3c .0001). With behavioral health problems on the rise across the country, it is urgent that behavioral health professional shortage areas begin to close the workforce gap. Increasing conversion rates from provisional to full licenses will be a part of this solution
Re-entrant superconductivity in Nb/Cu(1-x)Ni(x) bilayers
We report on the first observation of a pronounced re-entrant
superconductivity phenomenon in superconductor/ferromagnetic layered systems.
The results were obtained using a superconductor/ferromagnetic-alloy bilayer of
Nb/Cu(1-x)Ni(x). The superconducting transition temperature T_{c} drops sharply
with increasing thickness d_{CuNi} of the ferromagnetic layer, until complete
suppression of superconductivity is observed at d_{CuNi}= 4 nm. Increasing the
Cu(1-x)Ni(x) layer thickness further, superconductivity reappears at
d_{CuNi}=13 nm. Our experiments give evidence for the pairing function
oscillations associated with a realization of the quasi-one dimensional
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) like state in the ferromagnetic layer.Comment: 3 pages, 3 figures, REVTEX4/twocolum
Secondary Cosmic Ray Nuclei from Supernova Remnants and Constraints to the Propagation Parameters
The secondary-to-primary B/C ratio is widely used to study the cosmic ray
(CR) propagation processes in the Galaxy. It is usually assumed that secondary
nuclei such as Li-Be-B are entirely generated by collisions of heavier CR
nuclei with the interstellar medium (ISM). We study the CR propagation under a
scenario where secondary nuclei can also be produced or accelerated from
galactic sources. We consider the processes of hadronic interactions inside
supernova remnants (SNRs) and re-acceleration of background CRs in strong
shocks. Thus, we investigate their impact in the propagation parameter
determination within present and future data. The spectra of Li-Be-B nuclei
emitted from SNRs are harder than those due to CR collisions with the ISM. The
secondary-to-primary ratios flatten significantly at ~TeV/n energies, both from
spallation and re-acceleration in the sources. The two mechanisms are
complementary to each other and depend on the properties of the local ISM
around the expanding remnants. The secondary production in SNRs is significant
for dense background media, n ~1 cm^-3, while the amount of re-accelerated CRs
is relevant for SNRs expanding into rarefied media, n ~0.1 cm-3. Due to these
effects, the the diffusion parameter 'delta' may be misunderstood by a factor
of ~5-15%. Our estimations indicate that an experiment of the AMS-02 caliber
can constrain the key propagation parameters while breaking the
source-transport degeneracy, for a wide class of B/C-consistent models. Given
the precision of the data expected from on-going experiments, the SNR
production/acceleration of secondary nuclei should be considered, if any, to
prevent a possible mis-determination of the CR transport parameters.Comment: 13 pages, 9 figures; matches the published versio
New magnetic phase in metallic V_{2-y}O_3 close to the metal insulator transition
We have observed two spin density wave (SDW) phases in hole doped metallic
V_{2-y}O_3, one evolves from the other as a function of doping, pressure or
temperature. They differ in their response to an external magnetic field, which
can also induce a transition between them. The phase boundary between these two
states in the temperature-, doping-, and pressure-dependent phase diagram has
been determined by magnetization and magnetotransport measurements. One phase
exists at high doping level and has already been described in the literature.
The second phase is found in a small parameter range close to the boundary to
the antiferromagnetic insulating phase (AFI). The quantum phase transitions
between these states as a function of pressure and doping and the respective
metamagnetic behavior observed in these phases are discussed in the light of
structurally induced changes of the band structure.Comment: REVTeX, 8 pages, 12 EPS figures, submitted to PR
Paleoearthquake evidence in Tenerife (Canary Islands) and possible seismotectonic sources
Assessing the links between childhood trauma, C-reactive protein and response to antidepressant treatment in patients with affective disorders
Adverse Childhood Experiences (ACE) are a well-known risk-factor for depression. Additionally, (high-sensitive) C-reactive Protein (hsCRP) is elevated in subgroups of depressed patients and high following ACE. In this context the literature considers hsCRP and ACE to be associated with treatment resistant depression. With the data being heterogenous, this study aimed to explore the associations of ACE, hsCRP levels and response to antidepressant treatment in uni- and bipolar depression. N = 76 patients diagnosed with uni- or bipolar depression and N = 53 healthy controls were included. Treatment was over 6~weeks in an inpatient psychiatric setting within an observatory study design. Depressive symptoms were assessed by the Montgomery-Asberg Depression Rating Scale (MADRS), ACE were assessed by the Childhood Trauma Questionnaire (CTQ); the body-mass-index (BMI) and hsCRP were measured. HsCRP levels did not differ between the study population and the healthy controls. While the depressive symptoms decreased, the hsCRP levels increased. Sexual abuse was associated with significant higher and emotional abuse with lower levels of hsCRP after 6~weeks. The baseline hsCRP levels and the ACE subgroups did not~show significant associations with the treatment response in unipolar depressed patients. The long-lasting effects of specific forms of ACE may have relevant impact on inflammation, supporting hsCRP to be a suitable biomarker. With ACE and hsCRP not showing any significant associations with treatment response in the unipolar depressed subgroup, a more differentiate research concerning biomarkers and treatment regimens is needed when talking about treatment response
Land Cover Change in the Andes of Southern Ecuador — Patterns and Drivers
In the megadiverse tropical mountain forest in the Andes of southern Ecuador, a global biodiversity hotspot, the use of fire to clear land for cattle ranching is leading to the invasion of an aggressive weed, the bracken fern, which is threatening diversity and the provisioning of ecosystem services. To find sustainable land use options adapted to the local situation, a profound knowledge of the long-term spatiotemporal patterns of land cover change and its drivers is necessary, but hitherto lacking. The complex topography and the high cloud frequency make the use of remote sensing in this area a challenge. To deal with these conditions, we pursued specific pre-processing steps before classifying five Landsat scenes from 1975 to 2001. Then, we quantified land cover changes and habitat fragmentation, and we investigated landscape changes in relation to key spatial elements (altitude, slope, and distance from roads). Good classification results were obtained with overall accuracies ranging from 94.5% to 98.5% and Kappa statistics between 0.75 and 0.98. Forest was strongly fragmented due to the rapid expansion of the arable frontier and the even more rapid invasion by bracken. Unexpectedly, more bracken-infested areas were converted to pastures than vice versa, a practice that could alleviate pressure on forests if promoted. Road proximity was the most important spatial element determining forest loss, while for bracken the altitudinal range conditioned the degree of invasion in deforested areas. The annual deforestation rate changed notably between periods: ~1.5% from 1975 to 1987, ~0.8% from 1987 to 2000, and finally a very high rate of ~7.5% between 2000 and 2001. We explained these inconstant rates through some specific interrelated local and national political and socioeconomic drivers, namely land use policies, credit and tenure incentives, demography, and in particular, a severe national economic and bank crisis
Surface metal-insulator transition in the Hubbard model
The correlation-driven metal-insulator (Mott) transition at a solid surface
is studied within the Hubbard model for a semi-infinite lattice by means of the
dynamical mean-field theory. The transition takes place at a unique critical
strength of the interaction. Depending on the surface geometry, the interaction
strength and the wave vector, we find one-electron excitations in the coherent
part of the surface-projected metallic spectrum which are confined to two
dimensions.Comment: LaTeX, 9 pages, 5 eps figures included, Phys. Rev. B (in press
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