Abstract
Monolayer transition metal dichalcogenides (TMD) have numerous potential applications in ultrathin electronics and photonics. The exposure of TMD-based devices to light generates ...photo-carriers resulting in an enhanced conductivity, which can be effectively used, e.g., in photodetectors. If the photo-enhanced conductivity persists after removal of the irradiation, the effect is known as persistent photoconductivity (PPC). Here we show that ultraviolet light (λ = 365 nm) exposure induces an extremely long-living giant PPC (GPPC) in monolayer MoS
2
(ML-MoS
2
) field-effect transistors (FET) with a time constant of ~30 days. Furthermore, this effect leads to a large enhancement of the conductivity up to a factor of 10
7
. In contrast to previous studies in which the origin of the PPC was attributed to extrinsic reasons such as trapped charges in the substrate or adsorbates, we show that the GPPC arises mainly from the intrinsic properties of ML-MoS
2
such as lattice defects that induce a large number of localized states in the forbidden gap. This finding is supported by a detailed experimental and theoretical study of the electric transport in TMD based FETs as well as by characterization of ML-MoS
2
with scanning tunneling spectroscopy, high-resolution transmission electron microscopy, and photoluminescence measurements. The obtained results provide a basis for the defect-based engineering of the electronic and optical properties of TMDs for device applications.
Summary Background Children with Down's syndrome have a greatly increased risk of acute megakaryoblastic and acute lymphoblastic leukaemias. Acute megakaryoblastic leukaemia in Down's syndrome is ...characterised by a somatic mutation in GATA1 . Constitutive activation of the JAK/STAT (Janus kinase and signal transducer and activator of transcription) pathway occurs in several haematopoietic malignant diseases. We tested the hypothesis that mutations in JAK2 might be a common molecular event in acute lymphoblastic leukaemia associated with Down's syndrome. Methods JAK2 DNA mutational analysis was done on diagnostic bone marrow samples obtained from 88 patients with Down's syndrome-associated acute lymphoblastic leukaemia; and 216 patients with sporadic acute lymphoblastic leukaemia, Down's syndrome-associated acute megakaryoblastic leukaemia, and essential thrombocythaemia. Functional consequences of identified mutations were studied in mouse haematopoietic progenitor cells. Findings Somatically acquired JAK2 mutations were identified in 16 (18%) patients with Down's syndrome-associated acute lymphoblastic leukaemia. The only patient with non-Down's syndrome-associated leukaemia but with a JAK2 mutation had an isochromosome 21q. Children with a JAK2 mutation were younger (mean SE age 4·5 years 0·86 vs 8·6 years 0·59, p<0·0001) at diagnosis. Five mutant alleles were identified, each affecting a highly conserved arginine residue (R683). These mutations immortalised primary mouse haematopoietic progenitor cells in vitro, and caused constitutive Jak/Stat activation and cytokine-independent growth of BaF3 cells, which was sensitive to pharmacological inhibition with JAK inhibitor I. In modelling studies of the JAK2 pseudokinase domain, R683 was situated in an exposed conserved region separated from the one implicated in myeloproliferative disorders. Interpretation A specific genotype-phenotype association exists between the type of somatic mutation within the JAK2 pseudokinase domain and the development of B-lymphoid or myeloid neoplasms. Somatically acquired R683 JAK2 mutations define a distinct acute lymphoblastic leukaemia subgroup that is uniquely associated with trisomy 21. JAK2 inhibitors could be useful for treatment of this leukaemia. Funding Israel Trade Ministry, Israel Science Ministry, Jewish National Fund UK, Sam Waxman Cancer Research Foundation, Israel Science Foundation, Israel Cancer Association, Curtis Katz, Constantiner Institute for Molecular Genetics, German–Israel Foundation, and European Commission FP6 Integrated Project EUROHEAR.
Model of boron movement in soils Shani, U. (Arava Research and Development, Heve, Israel); Dudley, L.M; Hanks, R.J
Soil Science Society of America journal,
September-October 1992, Letnik:
56, Številka:
5
Journal Article
Recenzirano
A model to predict B transport in calcareous soils is presented. The model considers one-dimensional, non-steady-state soil water flow, convective-dispersive solute transport of both noninteracting ...salt (i.e., Cl) and B. The model was designed to simulate field situations including infiltration, evaporation, transpiration, drainage, and water extraction by plant roots. Predictions were compared with field B profiles and column leaching studies. The model accurately simulated Bleaching from columns of B-contaminated soils under saturated and steady-state water flow conditions. Model simulations, Udder conditions of transient water flow and transient B concentrations in a column study, were in reasonable agreement with the measured values. Model predictions were also compared with evolving soil soluble-B profiles determined in a field study (5-7 yr) with repeated irrigation with saline, B-containing waters. Computed results of the B accumulation in the upper portion of the soil profile, and of the B front, were in good agreement with measured data
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