160 research outputs found
Aqua and Terra MODIS RSB Calibration Comparison Using BRDF Modeled Reflectance
The inter-comparison of MODIS reflective solar bands onboard Aqua and Terra is very important for assessment of each instrument's calibration. One of the limitations is the lack of simultaneous nadir overpasses. Their measurements over a selected Earth view target have significant differences in solar and view angles, which magnify the effects of atmospheric scattering and Bidirectional Reflectance Distribution Function (BRDF). In this work, an intercomparison technique is formulated after correction for site's BRDF and atmospheric effects. The reflectance measurements over Libya desert sites 1, 2, and 4 from both the Aqua and Terra MODIS are regressed to a BRDF model with an adjustable coefficient accounting for calibration difference. The ratio between Aqua and Terra reflectance measurements are derived for bands 1 to 9 and the results from different sites show good agreement. For year 2003, the ratios are in the range of 0.985 to1.010 for band 1 to 9. Band 3 shows the lowest ratio 0.985 and band 1 shows the highest ratio 1.010. For the year 2014, the ratio ranges from approximately 0.983 for bands 2 and 1.012 for band 8. The BRDF corrected reflectance for the two instruments are also derived for every year from 2003 to 2014 for stability assessment. Bands 1 and 2 show greater than 1 differences between the two instruments. Aqua bands 1 and 2 show downward trends while Terra bands 1 and 2 show upward trends. Bands 8 and 9 of both Aqua and Terra show large variations of reflectance measurement over time
In-situ strain tuning of the Dirac surface states in Bi2Se3 films
Elastic strain has the potential for a controlled manipulation of the band
gap and spin-polarized Dirac states of topological materials, which can lead to
pseudo-magnetic-field effects, helical flat bands and topological phase
transitions. However, practical realization of these exotic phenomena is
challenging and yet to be achieved. Here, we show that the Dirac surface states
of the topological insulator Bi2Se3 can be reversibly tuned by an externally
applied elastic strain. Performing in-situ x-ray diffraction and in-situ
angle-resolved photoemission spectroscopy measurements during tensile testing
of epitaxial Bi2Se3 films bonded onto a flexible substrate, we demonstrate
elastic strains of up to 2.1% and quantify the resulting reversible changes in
the topological surface state. Our study establishes the functional
relationship between the lattice and electronic structures of Bi2Se3 and, more
generally, demonstrates a new route toward momentum-resolved mapping of
strain-induced band structure changes
Synergistic Catalysis of Ruthenium Nanoparticles and Polyoxometalate Integrated Within Single UiO−66 Microcrystals for Boosting the Efficiency of Methyl Levulinate to γ-Valerolactone
The synthesis of heterogeneous cooperative catalysts in which two or more catalytically active components are spatially separated within a single material has generated considerable research efforts. The multiple functionalities of catalysts can significantly improve the efficiency of existing organic chemical transformations. Herein, we introduce ruthenium (Ru) nanoparticles (NPs) on the surfaces of a metal–organic framework pre-encapsulated with polyoxometalate silicotungstic acid (SiW) UiO−66 (University of Oslo [UiO]) and prepared a 2.0% Ru/11.7% SiW@UiO−66 porous hybrid using the impregnation method. The close synergistic effect of metal Ru NPs, SiW, and UiO-66 endow 2.0% Ru/11.7% SiW@UiO-66 with increased activity and stability for complete methyl levulinate (ML) conversion and exclusive γ-valerolactone (GVL) selectivity at mild conditions of 80°C and at a H2 pressure of 0.5 MPa. Effectively, this serves as a model reaction for the upgrading of biomass and outperforms the performances of the constituent parts and that of the physical mixture (SiW + Ru/UiO−66). The highly dispersed Ru NPs act as active centers for hydrogenation, while the SiW molecules possess Brønsted acidic sites that cooperatively promote the subsequent lactonization of MHV to generate GVL, and the UiO−66 crystal accelerates the mass transportation facilitated by its own porous structure with a large surface area
On-Orbit Performance and Calibration Improvements For the Reflective Solar Bands of Terra and Aqua MODIS
Moderate Resolution Imaging Spectroradiometer (MODIS) is the keystone instrument for NASAs EOS Terra and Aqua missions, designed to extend and improve heritage sensor measurements and data records of the land, oceans and atmosphere. The reflective solar bands (RSB) of MODIS covering wavelengths from 0.41 micrometers to 2.2 micrometers, are calibrated on-orbit using a solar diffuser (SD), with its on-orbit bi-directional reflectance factor (BRF) changes tracked using a solar diffuser stability monitor (SDSM). MODIS is a scanning radiometer using a two-sided paddle-wheel mirror to collect earth view (EV) data over a range of (+/-)55 deg. off instrument nadir. In addition to the solar calibration provided by the SD and SDSM system, lunar observations at nearly constant phase angles are regularly scheduled to monitor the RSB calibration stability. For both Terra and Aqua MODIS, the SD and lunar observations are used together to track the on-orbit changes of RSB response versus scan angle (RVS) as the SD and SV port are viewed at different angles of incidence (AOI) on the scan mirror. The MODIS Level 1B (L1B) Collection 6 (C6) algorithm incorporated several enhancements over its predecessor Collection 5 (C5) algorithm. A notable improvement was the use of the earth-view (EV) response trends from pseudo-invariant desert targets to characterize the on-orbit RVS for select RSB (Terra bands 1-4, 8, 9 and Aqua bands 8, 9) and the time, AOI, and wavelength-dependent uncertainty. The MODIS Characterization Support Team (MCST) has been maintaining and enhancing the C6 algorithm since its first update in November, 2011 for Aqua MODIS, and February, 2012 for Terra MODIS. Several calibration improvements have been incorporated that include extending the EV-based RVS approach to other RSB, additional correction for SD degradation at SWIR wavelengths, and alternative approaches for on-orbit RVS characterization. In addition to the on-orbit performance of the MODIS RSB, this paper also discusses in detail the recent calibration improvements implemented in the MODIS L1B C6
Tumor Mutation Burden Predicts Relapse in Papillary Thyroid Carcinoma With Changes in Genes and Immune Microenvironment
BackgroundThe risk factors of papillary thyroid carcinoma (PTC) recurrence are meaningful for patients and clinicians. Tumor mutation burden (TMB) has been a biomarker for the effectiveness of immune checkpoint inhibitor (ICI) and prognosis in cancer. However, the role of TMB and its latent significance with immune cell infiltration in PTC are still unclear. Herein, we aimed to explore the effect of TMB on PTC prognosis.Material and MethodsRNA-seq and DNA-seq datasets of PTC patients were downloaded from The Cancer Genome Atlas (TCGA) database. The Gene Ontology (GO) and gene set enrichment analysis (GSEA 4.0.1) were applied further to explore potential differences in PTC patients’ biological functions. The differentially expressed genes (DEGs) and immune microenvironment between the high and low TMB groups were determined.ResultsTMB had the highest AUC score than other clinical indicators in ROC analysis on recurrence-free survival, and a higher TMB score was related to a worse prognosis. Further, GSEA showed a higher level of oxidative phosphorylation (OXPHOS) in the high TMB group, and four genes correlated with recurrence-free survival rate were identified. The abundance of CD8+ T cells and M1 macrophages in the high TMB group was significantly lower than that in the low TMB group.ConclusionsOur study found that TMB was a better predictor variable at evaluating the risk of PTC recurrence. Moreover, TMB-related genes conferred dramatically correlated prognosis, which was worth exploring in guiding postoperative follow-up and predicting recurrence for PTC patients
Experimental and Theoretical Electronic Structure and Symmetry Effects in Ultrathin NbSe2 Films
Layered quasi-two-dimensional transition metal dichalcogenides (TMDCs), which
can be readily made in ultrathin films, offer excellent opportunities for
studying how dimensionality affects electronic structure and physical
properties. Among all TMDCs, NbSe2 is of special interest; bulk NbSe2 hosts a
charge-density-wave phase at low temperatures and has the highest known
superconducting transition temperature, and these properties can be
substantially modified in the ultrathin film limit. Motivated by these effects,
we report herein a study of few-layer NbSe2 films, with a well-defined
single-domain orientation, epitaxially grown on Gallium Arsenide (GaAs).
Angle-resolved photoemission spectroscopy (ARPES) was used to determine the
electronic band structure and the Fermi surface as a function of layer
thickness; first-principles band structure calculations were performed for
comparison. The results show interesting changes as the film thickness
increases from a monolayer (ML) to several layers. The most notable changes
occur between a ML and a bilayer, where the inversion symmetry in bulk NbSe2 is
preserved in the bilayer but not in the ML. The results illustrate some basic
dimensional effects and provide a basis for further exploring and understanding
the properties of NbSe2.Comment: 15 pages, 4 figure
Gapped Electronic Structure of Epitaxial Stanene on InSb(111)
Stanene (single-layer grey tin), with an electronic structure akin to that of
graphene but exhibiting a much larger spin-orbit gap, offers a promising
platform for room-temperature electronics based on the quantum spin Hall (QSH)
effect. This material has received much theoretical attention, but a suitable
substrate for stanene growth that results in an overall gapped electronic
structure has been elusive; a sizable gap is necessary for room-temperature
applications. Here, we report a study of stanene epitaxially grown on the
(111)B-face of indium antimonide (InSb). Angle-resolved photoemission
spectroscopy (ARPES) measurements reveal a gap of 0.44 eV, in agreement with
our first-principles calculations. The results indicate that stanene on
InSb(111) is a strong contender for electronic QSH applications.Comment: 15 pages, 4 figure
Efficacy evaluation of surgery combined with chemotherapy for stage IIIA small cell lung cancer patients: a retrospective analysis
Background: The efficacy of surgery in combination of chemotherapy for stage IIIA small cell lung cancer (IIIA-SCLC) is controversial. The aim of the present study was to analyze the efficacy of surgery combined with chemotherapy, especially in the setting of neoadjuvant chemotherapy (NAC) followed by surgery for IIIA-SCLC.Methods: Between 2004 and 2015, we reviewed 2,199 chemotherapy-treated stage IIIA (N1/2) SCLC cases in the Surveillance, Epidemiology, and End Results (SEER) database, and 32 NAC + intentional radical resection treated, centrally-located IIIA-SCLC cases at Shanghai Pulmonary Hospital (SPH). Outcomes were compared between surgically and non-surgically treated patients from the SEER database after propensity score matching (PSM), and comparing lobectomy/bi-lobectomy and pneumonectomy patients from SPH. Prognostic factors were evaluated by Kaplan-Meier method and the Cox proportional hazards regression model.Results: There was significantly higher overall survival (OS) in surgically treated IIIA-SCLC patients (OS, 44.8 vs. 21.2 months, P=0.048), and similar efficacy was observed between sub-lobectomy and lobectomy/ bi-lobectomy patients (OS: 55.6 vs. 30.3 months, P=0.167) in SEER database. At SPH, significantly higher OS was associated with T1 stage (before NAC: T1 vs. T2-4, 48.7 vs. 32.2 months, P=0.025; after NAC: T1 vs. T2-4, 42.7 vs. 21.3 months, P=0.048). Female sex [hazard ratio (HR): 0.078, P=0.009], T1 stage (HR: 13.048, P=0.026), and pneumonectomy (HR: 0.095, P=0.009) were independent prognostic factors for IIIASCLC patients who received NAC + intentional radical resection.Conclusions: For stage IIIA SCLC patients, complete resection combined with chemotherapy might improve the prognosis than patients without surgery. Post-NAC lobectomy was not found to be superior to sub-lobectomy, while pneumonectomy was considered suitable for central-type IIIA-SCLC patients after NAC treatment
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