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.
Metallic nanoparticles are known to enhance nonlinear optical processes due to a local enhancement of the optical field. This strategy has been proposed to enhance downconversion in thin film solar ...cells, but has various disadvantages, among which is the fact that the enhancement occurs only in a tiny volume close to the particles. We report on a very different physical mechanism that can lead to significant downconversion enhancement, namely, that of resonant light scattering, and which is a large volume effect. We show that only a tiny amount of resonantly scattering metallic (aluminum) nanoparticles is enough to create a significant enhancement of the fluorescence of dye molecules in the visible wavelength range. The strategy can be applied in general to increase the emission of UV-absorbing constituents, and is of particular use for solar energy.
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 (wavelength = 365 nm) exposure induces an extremely long-living giant PPC (GPPC) in monolayer MoS2 (ML-MoS2) 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 107. 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 unambiguously show that the GPPC arises mainly from the intrinsic properties of ML-MoS2 such as lattice defects that induce a large amount 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-MoS2 with scanning tunneling spectroscopy, high-resolution transmission electron microscopy, and photoluminescence measurements. The obtained results provide a basis towards the defect-based engineering of the electronic and optical properties of TMDs for device applications.
The addition of a tiny amount of Aluminum nanoparticles in dye solutions is shown to yield a significant enhancement of the down conversion of ultraviolet light while maintaining a high transparency ...at visible wavelengths.
CBCT is a widely applied imaging modality in dentistry. It enables the visualization of high-contrast structures of the oral region (bone, teeth, air cavities) at a high resolution. CBCT is now ...commonly used for the assessment of bone quality, primarily for pre-operative implant planning. Traditionally, bone quality parameters and classifications were primarily based on bone density, which could be estimated through the use of Hounsfield units derived from multidetector CT (MDCT) data sets. However, there are crucial differences between MDCT and CBCT, which complicates the use of quantitative gray values (GVs) for the latter. From experimental as well as clinical research, it can be seen that great variability of GVs can exist on CBCT images owing to various reasons that are inherently associated with this technique (i.e. the limited field size, relatively high amount of scattered radiation and limitations of currently applied reconstruction algorithms). Although attempts have been made to correct for GV variability, it can be postulated that the quantitative use of GVs in CBCT should be generally avoided at this time. In addition, recent research and clinical findings have shifted the paradigm of bone quality from a density-based analysis to a structural evaluation of the bone. The ever-improving image quality of CBCT allows it to display trabecular bone patterns, indicating that it may be possible to apply structural analysis methods that are commonly used in micro-CT and histology.
This case scenario shows the value of applying relevant imaging and the selection of appropriate antibiotic via culture and sensitivity before prescribing especially when dealing with a patient with ...type 1 Diabetes Mellitus. When confronted with a diagnosis of acute osteomyelitis, it is always better to refer the patient to a hospital for admission where the management and any other intervention is easily accomplished. Admission to the hospital, culture and sensitivity, and appropriate intravenous antibiotics may have limited the progress of the infection and ultimately may have prevented the sequestration in this patient, limiting the degree of morbidity. Monitoring and control of blood glucose levels is an important part of the management in a patient from this scenario.
Marine natural products offer an abundant source of pharmacologically active agents with great diversity and complexity, and the potential to produce valuable therapeutic entities. Indole alkaloids ...is one of the important class of marine-derived secondary metabolites, with wide occurrence amongst variety of marine sources such as sponges, tunicates, algae, worms and microorganisms and have been extensively studied for their biological activities. Among this chemical family, a sponge-derived bis-indole alkaloid fascaplysin (1) exhibited broad range of bioactivities including antibacterial, antifungal, antiviral, anti-HIV-1-RTase, p56 tyrosine kinase inhibition, antimalarial, anti-angiogenic, antiproliferative activity against numerous cancer cell lines, specific inhibition of cyclin-dependent kinase-4 (IC(50) 350 nM) and action as a DNA intercalator. In the present review, the chemical diversity of natural as well as synthetic analogues of fascaplysin has been reviewed with a detailed account on synthetic reports and pharmacological studies. Our analysis of the structure-activity relationships of this family of compounds highlights the existence of various potential leads for the development of novel anticancer agents.
Indole is a significant structural moiety and functionalization of the C−H bond in indole‐containing molecules expands their chemical space, and modifies their properties and/or activities. Indole ...prenyltransferases (IPTs) catalyze the direct regiospecific installation of prenyl moieties on indole‐derived compounds. IPTs have shown relaxed substrate flexibility enabling them to be used as tools for indole functionalization. However, the mechanism by which certain IPTs target a specific carbon position is not fully understood. Herein, we use structure‐guided site‐directed mutagenesis, in vitro enzymatic reactions, kinetics and structural‐elucidation of analogs to verify the key catalytic residues that control the regiospecificity of all characterized regiospecific C6 IPTs. The presented results also demonstrate that substitution of PriB_His312 to Tyr leads to the synthesis of analogs prenylated at different positions than C6. This work contributes to understanding of how certain IPTs can access a challenging position in indole‐derived compounds.
The functionalization of indole‐derived compounds modifies their physicochemical properties and/or pharmacological activities. Activation of the indole C6 position is challenging. Yet, certain indole prenyltransferases (IPTs) catalyze this reaction efficiently, regiospecifically and under physiological conditions. Through enzyme engineering, in vitro enzymatic reactions and NMR experiments, guided by protein structure analyses, the mechanism was verified by which C6 IPTs catalyze their reactions.
Temporomandibular Joint Imaging Singer, Steven R.; Mupparapu, Mel
The Dental clinics of North America,
April 2023, 2023-04-00, 20230401, Letnik:
67, Številka:
2
Journal Article
Recenzirano
Prescriptions for imaging studies for temporomandibular disorders are based on the patient’s complaint, history, and clinical findings. Appropriate selection criteria and justification for imaging ...examinations must be followed. Because the temporomandibular joint is composed of both hard and soft tissues, different studies are prescribed based on the clinically suspected condition. Current imaging modalities include panoramic radiographs, cone-beam computed tomography, and MRI. The entire examination must be interpreted, and the findings recorded in the patient record. No one imaging modalities is suitable for all patients. An oral and maxillofacial radiologist should be consulted when the interpretation of the study is beyond the scope of the practitioner.
OBJECTIVETo describe and report on the use of virtual clinical competency examinations (VCCEs) for D3 dental students in a radiology clinic during the COVID-19 pandemic and relate the technology to ...other clinical and educational applications. METHOD AND MATERIALSPaper-based clinical competency examinations (CCEs) were converted to three different VCCEs to closely replicate the CCEs. Existing grading rubrics were used to assess students' abilities to evaluate technical issues and interpret intraoral full-mouth series and panoramic radiographs. The grading rubrics were modified from their clinical versions to eliminate non-reproducible skills, such as patient management and application of selection criteria. Radiographs were selected from clinic records and anonymized. VCCEs were conducted via WebEx conferences that were scheduled via an appointment app. These experiences can be extended to virtual patient contacts, teleradiology, and telemedicine, as well as continuing dental education experiences. RESULTSApproximately 200 VCCEs were administered by four oral and maxillofacial radiology faculty over a 10-week period. Both students and faculty managed the technology well, with few missed appointments. All students were successful in challenging the examinations and appeared to be satisfied with the experience. CONCLUSIONSAlthough direct comparisons between the CCEs and the new VCCEs are difficult, as there was no time to pilot the VCCEs, students were successful in challenging the examinations and informally reported satisfaction with the experience. Although components of CCEs that could not be replicated on the VCEs could not be assessed, it is felt that the students had adequate experience in selection of radiographs and patient management prior to the COVID-19 lockdown. Additional benefits of the VCCEs included contact with students to check on their well-being. The experience indicates that VCCEs can be used in the future in hybrid models of oral & maxillofacial radiology education, clinical care, patient screening, and telemedicine. Moreover, the success of this demonstration points to potential for personalized distance learning in continuing dental education.
PDF
