1,006 research outputs found
Realizing a Superconducting Square-Lattice Bismuth Monolayer
Interplay of crystal symmetry, strong spinorbit coupling (SOC), and
many-body interactions in low dimensional materials provides a fertile ground
for the discovery of unconventional electronic and magnetic properties and
versatile functionalities. Two-dimensional (2D) allotropes of group 15 elements
are appealing due to their structures and controllability over symmetries and
topology under strong SOC. Here, we report the heteroepitaxial growth of a
proximity-induced superconducting 2D square-lattice bismuth monolayer on
superconducting Pb films. The square lattice of monolayer bismuth films in a
symmetry together with a stripey moir\'e structure is clearly resolved by
our scanning tunneling microscopy and its atomic structure is revealed by
density functional theory (DFT) calculations. A Rashba-type spin-split Dirac
band is predicted by DFT calculations to exist at the Fermi level and becomes
superconducting through the proximity effect from the Pb substrate. We suggest
the possibility of a topological superconducting state in this system with
magnetic dopants/field. This work introduces an intriguing material platform
with 2D Dirac bands, strong SOC, topological superconductivity, and the moir\'e
superstructure.Comment: 21 pages, 4 figure
Charge Transfer Induced Molecular Hole Doping into Thin Film of Metal-Organic-Frameworks
Despite the highly porous nature with significantly large surface area, metal
organic frameworks (MOFs) can be hardly used in electronic, and optoelectronic
devices due to their extremely poor electrical conductivity. Therefore, the
study of MOF thin films that require electron transport or conductivity in
combination with the everlasting porosity is highly desirable. In the present
work, thin films of Co3(NDC)3DMF4 MOFs with improved electronic conductivity
are synthesized using layer-by-layer and doctor blade coating techniques
followed by iodine doping. The as-prepared and doped films are characterized
using FE-SEM, EDX, UV/Visible spectroscopy, XPS, current-voltage measurement,
photoluminescence spectroscopy, cyclic voltammetry, and incident photon to
current efficiency measurements. In addition, the electronic and semiconductor
property of the MOF films are characterized using Hall Effect measurement,
which reveals that in contrast to the insulator behavior of the as-prepared
MOFs, the iodine doped MOFs behave as a p-type semiconductor. This is caused by
charge transfer induced hole doping into the frameworks. The observed charge
transfer induced hole doping phenomenon is also confirmed by calculating the
densities of states of the as-prepared and iodine doped MOFs based on density
functional theory. Photoluminescence spectroscopy demonstrate an efficient
interfacial charge transfer between TiO2 and iodine doped MOFs, which can be
applied to harvest solar radiations.Comment: Main paper (19 pages, 6 figures) and supplementary information (15
pages, 10 figures), accepted in ACS Appl. Materials & Interface
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High frequency transformation of cottonwoods (genus Populus) by Agrobacterium rhizogene
Many species of Populus, particularly cottonwoods of sections Aigeiros and Tacamahaca, remain recalcitrant to genetic transformation. We demonstrate that transgenic trees can be readily produced in several poplar genotypes using wild-type Agrobacterium rhizogenes. Hairy roots were produced in a variety of clones that included Populus trichocarpa Torr. & A. Gray, Populus deltoides Bartr. ex Marsh., P. trichocarpa x P. deltoides hybrids, and Populus alba L. x Populus grandidentata Michx., some of which were otherwise recalcitrant to regeneration or transformation. The frequency of hairy roots ranged from 17 to 92%; nearly all hairy roots could be regenerated into transgenic plants. Among 18 transgenic lines that were confirmed by Southern analysis and grown into small trees, 5 showed severe dwarfism and other phenotypic abnormalities, while the majority grew normally. Agrobacterium rhizogenes appears to be an effective means for transformation of diverse poplar genotypes and may be useful in genotypes where disarmed strains of Agrobacterium or regeneration protocols are inadequate to produce transgenic plants.Keywords: genetic transformation, rhizogenes, Agrobacterium, transgenic, poplar (Populus
Expression of GA733-Fc Fusion Protein as a Vaccine Candidate for Colorectal Cancer in Transgenic Plants
The tumor-associated antigen GA733 is a cell-surface glycoprotein highly expressed in colorectal carcinomas. In this study, 3 recombinant genes were constructed as follows: GA733 tagged to the ER retention sequence KDEL (GA733K), GA733 fused to the immunoglobulin Fc fragment (GA733-Fc), and GA733-Fc fused to the ER retention sequence (GA733-FcK). Agrobacterium-mediated transformation was used to generate transgenic plants expressing recombinant genes. The presence of transgenes was confirmed by genomic PCR. Western blot, confocal immunofluorescence, and sandwich ELISA showed the expression of recombinant proteins. The stability, flexibility, and bioactivity of recombinant proteins were analyzed and demonstrated through N-glycosylation analysis, animal trials, and sera ELISA. Our results suggest that the KDEL retained proteins in ER with oligomannose glycan structure and enhanced protein accumulation level. The sera of mice immunized with GA733-FcK purified from plants contained immunoglobulins which were at least as efficient as the mammalian-derived GA733-Fc at recognizing human colorectal cancer cell lines. Thus, a plant system can be used to express the KDEL fusion protein with oligomannose glycosylation, and this protein induces an immune response which is comparable to non-KDEL-tagged, mammalian-derived proteins
Association between Workplace Risk Factor Exposure and Sleep Disturbance: Analysis of the 2nd Korean Working Conditions Survey
OBJECTIVES: Sleep is essential for human beings to live and work properly. This study was conducted to investigate the relationship between occupational exposures to workplace risk factors and sleep disturbance in Korean workers. METHODS: The data were drawn from the second Korean Working Conditions Survey (KWCS); a total of 7,112 paid workers were analyzed. The independent variables were occupational exposures such as physical, chemical, biological, and psychosocial risk factor in the workplace, and psychosocial risk factor was divided into five categories (job demand, job control, social support, job insecurity, lack of reward). We estimated the relationship between various occupational exposures and sleep disturbance using multivariate logistic regression analysis. RESULTS: The results showed that people who exposed to physical, chemical, biological, and psychosocial (high job demand, inadequate social support, lack of reward) risk factors were more likely to increase the risk of sleep disturbance. Furthermore, after adjusting for general and occupational characteristics, we found significant positive associations between exposures to physical (odds ratios [OR] 1.47, 95% confidence interval [CI] 1.05-2.07) and psychosocial (high job demand (OR 2.93, 95% CI 2.16-3.98), inadequate social support (OR 1.57, 95% CI 1.14-2.15), lack of reward (OR 1.45, 95% CI 1.08-1.96)) risk factors and sleep disturbance. CONCLUSION: These results suggest that occupational exposures to physical and psychosocial workplace risk factors are significantly related to sleep disturbance
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