1,634 research outputs found
Electronic and optical properties of beryllium chalcogenides/silicon heterostructures
We have calculated electronic and optical properties of
Si/BeSeTe heterostructures by a semiempirical
tight-binding method. Tight-binding parameters and band bowing of
BeSeTe are considered through a recent model for highly
mismatched semiconductor alloys. The band bowing and the measurements of
conduction band offset lead to a type II heterostucture for
Si/BeSeTe with conduction band minimum in the Si layer and
valence band maximum in the BeSeTe layer. The electronic
structure and optical properties of various (Si/(BeSeTe [001] superlattices have been considered. Two
bands of interface states were found within the bandgap of bulk Si. Our
calculations indicate that the optical edges are below the fundamental bandgap
of bulk Si and the transitions are optically allowed.Comment: 16 pager, 7 figure
Spin tunneling through an indirect barrier
Spin-dependent tunneling through an indirect bandgap barrier like the
GaAs/AlAs/GaAs heterostructure along [001] direction is studied by the
tight-binding method. The tunneling is characterized by the proportionality of
the Dresselhaus Hamiltonians at and points in the barrier and by
Fano resonances. The present results suggest that large spin polarization can
be obtained for energy windows that exceed significantly the spin splitting. We
also formulate two conditions that are necessary for the existence of energy
windows with large polarization.Comment: 19 pages, 7 figure
A blended electronic illness management and recovery program for people with severe mental illness : qualitative process evaluation alongside a randomized controlled trial
Background: We conducted a trial to test the electronic Illness Management and Recovery (e-IMR) intervention to provide conclusions on the potential efficacy of eHealth for people with severe mental illness (SMI). In the e-IMR intervention, we used the standard IMR program content and methodology and combined face-to-face sessions with internet-based strategies on the constructed e-IMR internet platform. During the trial, the e-IMR platform was sparsely used.
Objective: This study aimed to evaluate the added value of the e-IMR intervention and the barriers and facilitators that can explain the low use of the e-IMR platform.
Methods: This process evaluation was designed alongside a multicenter, cluster randomized controlled trial. In this study, we included all available participants and trainers from the intervention arm of the trial. Baseline characteristics were used to compare users with nonusers. Qualitative data were gathered at the end of the semistructured interviews. Using theoretical thematic analyses, the data were analyzed deductively using a pre-existing coding frame.
Results: Out of 41 eligible participants and 14 trainers, 27 participants and 11 trainers were interviewed. Of the 27 participants, 10 were identified as users. eHealth components that had added value were the persuasive nature of the goal-tracking sheets, monitoring, and the peer testimonials, which had the potential to enhance group discussions and disclosure by participants. The low use of the e-IMR platform was influenced by the inflexibility of the platform, the lack of information technology (IT) resources, the group context, participants' low computer skills and disabilities, and the hesitant eHealth attitude of the trainers.
Conclusions: The extent of eHealth readiness and correlations with vulnerabilities in persons with SMI need further investigation. This study shows that flexible options were needed for the use of e-IMR components and that options should be provided only in response to a participant's need. Use of the e-IMR intervention in the future is preconditioned by checking the available IT resources (such as tablets for participants) providing computer or internet guidance to participants outside the group sessions, evaluating the eHealth attitude and skills of trainers, and tailoring eHealth training to increase the skills of future e-IMR trainers
State and local governments plan for development of most land vulnerable to rising sea level along the US Atlantic coast
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of IOP Publishing for personal use, not for redistribution. The definitive version was published in
Environmental Research Letters 4 (2009): 044008, doi:10.1088/1748-9326/4/4/044008.Rising sea level threatens existing coastal wetlands. Overall ecosystems could often survive by migrating
inland, if adjacent lands remained vacant. On the basis of 131 state and local land use plans, we estimate that
almost 60% of the land below 1 m along the US Atlantic coast is expected to be developed and thus unavailable
for the inland migration of wetlands. Less than 10% of the land below 1 m has been set aside for conservation.
Environmental regulators routinely grant permits for shore protection structures (which block wetland migration)
on the basis of a federal finding that these structures have no cumulative environmental impact. Our results
suggest that shore protection does have a cumulative impact. If sea level rise is taken into account, wetland
policies that previously seemed to comply with federal law probably violate the Clean Water Act
NASA Planetary Mission Concept Study: Assessing: Dwarf Planet Ceres' past and Present Habitability Potential
The Dawn mission revolutionized our understanding of Ceres during the same decade that has also witnessed the rise of ocean worlds as a research and exploration focus. We will report progress on the Planetary Mission Concept Study (PMCS) on the future exploration of Ceres under the New Frontiers or Flagship program that was selected for NASA funding in October 2019. At the time this writing, the study was just kicked off, hence this abstract reports the study plan as presented in the proposal
Switchable chiral transport in charge-ordered kagome metal CsV3Sb5
When electric conductors differ from their mirror image, unusual chiral transport coefficients appear that are forbidden in achiral metals, such as a non-linear electric response known as electronic magnetochiral anisotropy (eMChA). Although chiral transport signatures are allowed by symmetry in many conductors without a centre of inversion, they reach appreciable levels only in rare cases in which an exceptionally strong chiral coupling to the itinerant electrons is present. So far, observations of chiral transport have been limited to materials in which the atomic positions strongly break mirror symmetries. Here, we report chiral transport in the centrosymmetric layered kagome metal CsVSb observed via second-harmonic generation under an in-plane magnetic field. The eMChA signal becomes significant only at temperatures below 35 K, deep within the charge-ordered state of CsVSb (T ≈ 94 K). This temperature dependence reveals a direct correspondence between electronic chirality, unidirectional charge order and spontaneous time-reversal symmetry breaking due to putative orbital loop currents. We show that the chirality is set by the out-of-plane field component and that a transition from left- to right-handed transport can be induced by changing the field sign. CsVSb is the first material in which strong chiral transport can be controlled and switched by small magnetic field changes, in stark contrast to structurally chiral materials, which is a prerequisite for applications in chiral electronics
Switchable chiral transport in charge-ordered kagome metal CsV3Sb5
When electric conductors differ from their mirror image, unusual chiral transport
coefficients appear that are forbidden in achiral metals, such as a non-linear electric
response known as electronic magnetochiral anisotropy (eMChA)1–6
. Although chiral
transport signatures are allowed by symmetry in many conductors without a centre of
inversion, they reach appreciable levels only in rare cases in which an exceptionally
strong chiral coupling to the itinerant electrons is present. So far, observations of
chiral transport have been limited to materials in which the atomic positions strongly
break mirror symmetries. Here, we report chiral transport in the centrosymmetric
layered kagome metal CsV3Sb5 observed via second-harmonic generation under an
in-plane magnetic field. The eMChA signal becomes significant only at temperatures
below T′≈ 35 K, deep within the charge-ordered state of CsV 3Sb5 (TCDW ≈ 94 K). This
temperature dependence reveals a direct correspondence between electronic
chirality, unidirectional charge order7 and spontaneous time-reversal symmetry
breaking due to putative orbital loop currents8–10
. We show that the chirality is set by
the out-of-plane field component and that a transition from left- to right-handed
transport can be induced by changing the field sign. CsV3Sb5 is the first material in
which strong chiral transport can be controlled and switched by small magnetic field
changes, in stark contrast to structurally chiral materials, which is a prerequisite for
applications in chiral electronics.This work was funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (MiTopMat, grant agreement no. 715730, and PARATOP, grant agreement no. 757867). This project received funding by the Swiss National Science Foundation (grant no. PP00P2_176789). M.G.V., I.E. and M.G.-A. acknowledge the Spanish Ministerio de Ciencia e Innovacion (grant PID2019-109905GB-C21). M.G.V., C.F. and T.N. acknowledge support from FOR 5249 (QUAST) lead by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation). This work has been supported in part by Basque Government grant IT979-16. This work was also supported by the European Research Council Advanced Grant (no. 742068) ‘TOPMAT’, the Deutsche Forschungsgemeinschaft (Project-ID no. 247310070) ‘SFB 1143’ and the DFG through the Würzburg–Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter ct.qmat (EXC 2147, Project-ID no. 390858490).
Open access funding provided by Max Planck Society
ANTIMICROBIAL ACTIVITY OF ESSENTIAL OILS OF OCIMUM GRATISSIMUM L. FROM DIFFERENT POPULATIONS OF KENYA
Hydro-distilled volatile oils from the leaves of Ocimum gratissimum L. (Lamiaceae) of 13 populations of different silvicultural zones were evaluated for antimicrobial activity against Gram positive (Staphylococcus aereus, Bacillus spp.) and Gram negative (Escherichia coli, Pseudomonas aeruginosa, Samonella typhi, Klebisiella pneumoniae, Proteus mirabilis) bacteria and a pathogenic fungus, Candida albicans. All the essential oils are active to the tested microbiles with different strength. The highest antimicrobial activity against Gram positive bacteria (Staphylococcus aureus) and Gram negative bacteria (Pseudomonas aeruginosae and Proteus mirabilis) was observed from the eastern Kenya (Meru) oil. Meru oil was the best and its effectiveness was consistent on nearly all the microbes tested. The oil from the plant growing in the coastal region of Kenya (Mombasa) showed the best effect only on Gram negative bacteria (Escherichia coli and Proteus mirabilis). Both oils (Meru and Mombasa) were dominated by monoterpenes accounting for 92.48 % and 81.37 % respectively. The monoterpene fraction was characterized by a high percentage of eugenol (68.8 %) for Meru oil and 74.10 % for Mombasa oil. The other major monoterpene was methyl eugenol (13.21 %). Camphor (0.95 %) was observed only in the Meru oil. (Cis)-Ocimene, (trans)-ocimene and β-pinene were present in both Meru and Mombasa oils. The sesquiterpenes present in fairly good amounts in both oils were germacrene D and (trans)-caryophyllene. The minor sesquiterpenes were α-farnesene (0.85 %) and β-bisabolene (0.74 %) which were present in the Meru oil only
The influence of tumor regression, solar elastosis, and patient age on pathologists\u27 interpretation of melanocytic skin lesions.
It is not known whether patient age or tumor characteristics such as tumor regression or solar elastosis influence pathologists\u27 interpretation of melanocytic skin lesions (MSLs). We undertook a study to determine the influence of these factors, and to explore pathologist\u27s characteristics associated with the direction of diagnosis. To meet our objective, we designed a cross-sectional survey study of pathologists\u27 clinical practices and perceptions. Pathologists were recruited from diverse practices in 10 states in the United States. We enrolled 207 pathologist participants whose practice included the interpretation of MSLs. Our findings indicated that the majority of pathologists (54.6%) were influenced toward a less severe diagnosis when patients were70 years of age, or by the presence of tumor regression or solar elastosis (58.5%, 71.0%, and 57.0%, respectively). Generally, pathologists with dermatopathology board certification and/or a high caseload of MSLs were more likely to be influenced, whereas those with more years\u27 experience interpreting MSL were less likely to be influenced. Our findings indicate that the interpretation of MSLs is influenced by patient age, tumor regression, and solar elastosis; such influence is associated with dermatopathology training and higher caseload, consistent with expertise and an appreciation of lesion complexity
Distinct switching of chiral transport in the kagome metals KVSb and CsVSb
The kagome metals AVSb (A=K,Rb,Cs) present an ideal sandbox to study
the interrelation between multiple coexisting correlated phases such as charge
order and superconductivity. So far, no consensus on the microscopic nature of
these states has been reached as the proposals struggle to explain all their
exotic physical properties. Among these, field-switchable electric
magneto-chiral anisotropy (eMChA) in CsVSb provides intriguing evidence
for a rewindable electronic chirality, yet the other family members have not
been likewise investigated. Here, we present a comparative study of
magneto-chiral transport between CsVSb and KVSb. Despite their
similar electronic structure, KVSb displays negligible eMChA, if any,
and with no field switchability. This is in stark contrast to the
non-saturating eMChA in CsVSb even in high fields up to 35 T. In light
of their similar band structures, the stark difference in eMChA suggests its
origin in the correlated states. Clearly, the V kagome nets alone are not
sufficient to describe the physics and the interactions with their environment
are crucial in determining the nature of their low-temperature state
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