A global long-term (1981–2000) land surface temperature product for NOAA AVHRR

Land surface temperature (LST) plays an important role in the research of climate change and various land surface processes. Before 2000, global LST products with relatively high temporal and spatial resolutions are scarce, despite a variety of operational satellite LST products. In this study, a global 0.05∘×0.05∘ historical LST product is generated from NOAA advanced very-high-resolution radiometer (AVHRR) data (1981–2000), which includes three data layers: (1) instantaneous LST, a product generated by integrating several split-window algorithms with a random forest (RF-SWA); (2) orbital-drift-corrected (ODC) LST, a drift-corrected version of RF-SWA LST; and (3) monthly averages of ODC LST. For an assumed maximum uncertainty in emissivity and column water vapor content of 0.04 and 1.0 g cm−2, respectively, evaluated against the simulation dataset, the RF-SWA method has a mean bias error (MBE) of less than 0.10 K and a standard deviation (SD) of 1.10 K. To compensate for the influence of orbital drift on LST, the retrieved RF-SWA LST was normalized with an improved ODC method. The RF-SWA LST were validated with in situ LST from Surface Radiation Budget (SURFRAD) sites and water temperatures obtained from the National Data Buoy Center (NDBC). Against the in situ LST, the RF-SWA LST has a MBE of 0.03 K with a range of −1.59–2.71 K, and SD is 1.18 K with a range of 0.84–2.76 K. Since water temperature only changes slowly, the validation of ODC LST was limited to SURFRAD sites, for which the MBE is 0.54 K with a range of −1.05 to 3.01 K and SD is 3.57 K with a range of 2.34 to 3.69 K, indicating good product accuracy. As global historical datasets, the new AVHRR LST products are useful for filling the gaps in long-term LST data. Furthermore, the new LST products can be used as input to related land surface models and environmental applications. Furthermore, in support of the scientific research community, the datasets are freely available at https://doi.org/10.5281/zenodo.3934354 for RF-SWA LST (Ma et al., 2020a), https://doi.org/10.5281/zenodo.3936627 for ODC LST (Ma et al., 2020c), and https://doi.org/10.5281/zenodo.3936641 for monthly averaged LST (Ma et al., 2020b)

Creating two-dimensional solid helium via diamond lattice confinement

The universe abounds with solid helium in polymorphic forms. Therefore, exploring the allotropes of helium remains vital to our understanding of nature. However, it is challenging to produce, observe and utilize solid helium on the earth because high-pressure techniques are required to solidify helium. Here we report the discovery of room-temperature two-dimensional solid helium through the diamond lattice confinement effect. Controllable ion implantation enables the self-assembly of monolayer helium atoms between {100} diamond lattice planes. Using state-of-the-art integrated differential phase contrast microscopy, we decipher the buckled tetragonal arrangement of solid helium monolayers with an anisotropic nature compressed by the robust diamond lattice. These distinctive helium monolayers, in turn, produce substantial compressive strains to the surrounded diamond lattice, resulting in a large-scale bandgap narrowing up to ~2.2 electron volts. This approach opens up new avenues for steerable manipulation of solid helium for achieving intrinsic strain doping with profound applications

Chemistry and Biology of DNA-protein cross-links

University of Minnesota Ph.D. dissertation. February 2019. Major: Chemistry. Advisor: Natalia Tretyakova. 1 computer file (PDF); xxxvii, 373 pages.DNA-protein cross-links (DPCs) are ubiquitous DNA lesions formed when proteins become covalently trapped on DNA strands upon exposure to various endogenous, environmental and chemotherapeutic agents. Because of their considerable size, DPCs interfere with the progression of replication and transcription machineries, potentially contributing to mutagenesis and carcinogenesis. However, unlike small DNA lesions of which the biological consequences and repair mechanisms have been well characterized, biological effects and repair mechanism of DPC lesions remain to be established. A significant challenge in the field is the structural diversity of DPC lesions and the scarcity of experimental mythologies to create site-specific DNA-protein conjugates. The main objective of this thesis was to synthesize model DPC and to investigate their biological consequences and repair mechanisms. In Chapter II, we discovered, characterized and quantified 5-formylcytosine(5fC) mediated DNA-histone conjugates in human cells. 5-Formylcytosine (5fC) is an endogenous DNA modification enzymatically generated in the genome as an oxidation product of 5-methyl-dC (5mC). While 5mC is known to be an epigenetic mark that controls the levels of gene expression, the biological functions of 5fC are incompletely understood. In this chapter, we discovered that 5fC bases in DNA readily form Schiff base conjugates with Lys side chains of nuclear proteins such as histones, forming covalent DNA-protein conjugates. Isotope dilution nanoLC-ESI-MS/MS methodology was employed to detect and quantify 5fC-lys conjugate in human cells. We hypothesize that reversible 5fC-histone cross-linking contributes to epigenetic signaling, transcriptional regulations and chromatin remodeling. After the discovery of 5fC-mediated DNA-histone crosslinks in mammalian cells, we investigated their effects on DNA replication in Chapter III. DNA substrates containing site-specific DPCs were subjected to in vitro translesion synthesis (TLS) in the presence of TLS DNA polymerases. We found that DPCs containing various full-length proteins conjugated to DNA via the C-5 position of cytosine completely blocked human DNA polymerases, while the corresponding lesions containing shorter peptides were bypassed by translesion synthesis (TLS) polymerases. These results are consistent with the proposed DPC repair pathway in the literature, in which full-length DPCs are subjected to proteolytic degradation to generate short DNA-peptide cross-links, which may serve as substrates for translesion synthesis. In addition, our steady-state kinetics analysis and mass- spectrometry-based sequencing and quantification revealed that the bypass of DNA- peptide cross-links by human TLS polymerases was highly error-prone, introducing significant amounts of C to T and deletion mutations. In Chapter IV, we investigated the effects of DPCs on transcription using two model DPCs where the proteins are conjugated to the C5 position of cytosine or the C7 position of 7-deazaguanine. The latter serves as a hydrolytically stable model of the N7- guanine lesions, which commonly form upon exposure to bis-electrophiles such antitumor agents. We found that full-length proteins cross-linked to either 5fC or 7-deazaguanine completely blocked T7 RNA polymerase, while relatively short peptide cross-links were bypassed, although with low efficiency. Interestingly, the two model DPCs exhibited completely different mutagenic patterns are revealed by PCR and mass spectrometry based assays. While the bypass of peptide cross-linked to 7-deaza-G by T7 RNA polymerases induced very small numbers of mutations, transcription past peptide lesions conjugated to C-5 of C induced significant amounts of C to T transcriptional mutations. In Chapter V, we investigated the effects of 5fC-mediated DNA-peptide/protein cross-links on transcription and its potential repair by nucleotide excision repair (NER) in living cells. To accomplish this goal, structurally defined DPCs were site-specifically incorporated into plasmid molecules, which was then transfected into wild type cells or cells deficient in NER. RT-PCR and LC-MS/MS based strategy was then employed to quantitatively study the effects of DPC lesions on efficiency and fidelity of transcription in mammalian cells. We found that the presence of peptide cross-links conjugated to C-5 of cytosine significantly inhibited DNA transcription in human embryonic kidney cells. However, in contrast to our in vitro results, no transcriptional mutagenesis was observed. In addition, we compared the transcription bypass efficiencies of DpC lesions in wild-type and NER-deficient cell-lines, and also conducted the in vitro NER assays using cell-free extracts from human HeLa cells. Collectively, our data suggested that 5fC-mediated DNA- peptide cross-links are poor NER substrates, requiring a different pathway for their repair. Recent studies suggested that the bulky DPCs in cells are proteolytically processed to shorter DNA-peptide cross-links before they can be tolerated by translation synthesis mechanism or removed by nucleotide excision repair. DPCs can block DNA replication, signaling for recruitment of specialized metalloprotease (Spartan). However, the mechanisms of protease-mediated DPC digestion in the absence of DNA replication are incompletely understood. In Chapter VI, we employed an immunoprecipitation(IP)-PCR methodology to demonstrate that DPCs present on non-replicating plasmids are rapidly ubiquitinylated in mammalian cells, which likely serves as a signal for the proteasome- mediated DPC processing or other ubiquitin-mediated pathways to facilitate the DPC repair

Episcleritis in a patient with mucosal melanoma treated with interferon alfa-2b and radiotherapy: a case report

Abstract Background Mucosal melanoma of the head and neck is a rare malignant tumor associated with a poor prognosis. Surgery, chemotherapy, radiotherapy, and biotherapy are common strategies for treating mucosal melanoma of the head and neck. Episcleritis is an idiopathic, immune-mediated disease, and is classified into two types: simple episcleritis and nodular episcleritis. Case presentation In this case report we describe ocular changes involving simple episcleritis in a 65-year-old Chinese man with mucosal melanoma of the head and neck after treatment with interferon alfa-2b and radiotherapy. On the third day of interferon alfa-2b treatment, he began to develop simple episcleritis in his left eye. Moreover, the percentage of CD3+ T cells in lymphocytes from blood was increased after interferon alfa-2b treatment. After approximately 6 days, the symptoms of eye pain, hyperemia, and edema disappeared gradually. Then, after radiotherapy was performed three times, he again developed episcleritis in his left eye. The same symptoms of hyperemia and edema occurred again; CD3+ T cell frequency was also at a higher level. After approximately a week, all the symptoms disappeared completely. Simple treatment involving topical ofloxacin and phenylephrine was administered during the two periods of episcleritis. Conclusion Episcleritis in this patient might have been due to the treatment with interferon alfa-2b and radiotherapy, leading to an increase in the level of CD3+ T cells and activation of immune system cells, which provides the guide for clinical clinicians

On the Improvement of the Poor Heat Transfer Lee-Side Regions of Square Cross-Section Ribbed Channels.

Heat transfer and flow characteristics of six ribbed channels of square cross section having different rib structure are computed with the objective of improving heat transfer in the lee-side of the ribs. Six ribs are installed on the bottom walls of each channel. The rib pitch-to-height ratio (P/e) is 10. Details of the turbulent flow structure, temperature fields, local heat transfer coefficients, flow friction coefficients, normalized heat transfer rates, and normalized friction factors are reported. The simulations use the v(2)f turbulence model and inlet Reynolds number range of 8,000 to 24,000. A uniform heat flux is appropriately applied on all surfaces. The heat transfer performances features of the ribbed channels of various designs are evaluated and compared. A case with an inclined lee-side structure having an inclination angle of 160 degrees yields the highest Nusselt number and friction factor, about 4.6%-6.4% higher than those with rectangular ribs, and 7.1%-9.0% higher heat transfer when the heated-surface area is considered. Increased pressure drop is kept within certain limits when considering the balance between cooling effectiveness and pressure loss for the comparisons. Though having the best heat transfer, the case with the inclined back-wall geometry of the ribs does not present the better overall thermal performance due to the higher friction. The heat transfer enhancement is more prominent when improvements of the poor heat transfer regions downstream of the rib are computed with the surface area change excluded. A conclusion to be drawn is that lee-side improvement of heat transfer can be effected with suitable design of the rib downstream side. This finding can be applied to improvement of turbine airfoil cooling

Data from: Population size and time since island isolation determine genetic diversity loss in insular frog populations

Understanding the factors that contribute to loss of genetic diversity in fragmented populations is crucial for conservation measurements. Land-bridge archipelagoes offer ideal model systems for identifying the long-term effects of these factors on genetic variations in wild populations. In this study, we used 9 microsatellite markers to quantify genetic diversity and differentiation of 810 pond frogs (Pelophylax nigromaculataus) from 24 islands of the Zhoushan Archipelago and 3 sites on nearby mainland China and estimated the effects of the island area, population size, time since island isolation, distance to the mainland and distance to the nearest larger island on reduced genetic diversity of insular populations. The mainland populations displayed higher genetic diversity than insular populations. Genetic differentiations and no obvious gene flow were detected among the frog populations on the islands. Hierarchical partitioning analysis showed that only time since island isolation (square root transformed) and population size (log transformed) significantly contributed to insular genetic diversity. These results suggest that decreased genetic diversity and genetic differentiations among insular populations may have been caused by random genetic drift following isolation by rising sea levels during the Holocene. The results provide strong evidence for a relationship between retained genetic diversity and population size and time since island isolation for pond frogs on the islands, consistent with the prediction of the neutral theory for finite populations. Our study highlights the importance of the size and estimated isolation time of populations in understanding the mechanisms of genetic diversity loss and differentiation in fragmented wild populations

Estimating Land Surface Temperature from Satellite Passive Microwave Observations with the Traditional Neural Network, Deep Belief Network, and Convolutional Neural Network

Neural networks, especially the latest deep learning, have exhibited good ability in estimating surface parameters from satellite remote sensing. However, thorough examinations of neural networks in the estimation of land surface temperature (LST) from satellite passive microwave (MW) observations are still lacking. Here, we examined the performances of the traditional neural network (NN), deep belief network (DBN), and convolutional neural network (CNN) in estimating LST from the AMSR-E and AMSR2 data over the Chinese landmass. The examinations were based on the same training set, validation set, and test set extracted from 2003, 2004, and 2009, respectively, for AMSR-E with a spatial resolution of 0.25°. For AMSR2, the three sets were extracted from 2013, 2014, and 2016 with a spatial resolution of 0.1°, respectively. MODIS LST played the role of “ground truth” in the training, validation, and testing. The examination results show that CNN is better than NN and DBN by 0.1–0.4 K. Different combinations of input parameters were examined to get the best combinations for the daytime and nighttime conditions. The best combinations are the brightness temperatures (BTs), NDVI, air temperature, and day of the year (DOY) for the daytime and BTs and air temperature for the nighttime. By adding three and one easily obtained parameters on the basis of BTs, the accuracies of LST estimates can be improved by 0.8 K and 0.3 K for the daytime and nighttime conditions, respectively. Compared with the MODIS LST, the CNN LST estimates yielded root-mean-square differences (RMSDs) of 2.19–3.58 K for the daytime and 1.43–2.14 K for the nighttime for diverse land cover types for AMSR-E. Validation against the in-situ LSTs showed that the CNN LSTs yielded root-mean-square errors of 2.10–4.72 K for forest and cropland sites. Further intercomparison indicated that ~50% of the CNN LSTs were closer to the MODIS LSTs than ESA’s GlobTemperature AMSR-E LSTs, and the average RMSDs of the CNN LSTs were less than 3 K over dense vegetation compared to NASA’s global land parameter data record air temperatures. This study helps better the understanding of the use of neural networks for estimating LST from satellite MW observations

Speeding Up Velocity Consensus Control with Small World Communication Topology for Unmanned Aerial Vehicle Swarms

This study addressed a problem of rapid velocity consensus within a swarm of unmanned aerial vehicles. Our analytical framework was based on tools using matrix theory and algebraic graph theory. We established connections between algebraic connectivity and the speed of converging on a velocity. The relationship between algebraic connectivity and communication cost was established. To deal with the trade-off among algebraic connectivity, convergence speed and communication cost, we propose a distributed small world network construction method. The small world network characteristics expedite the convergence speed toward consensus in the unmanned aerial vehicle swarm. Eventually, our method greatly sped up the consensus velocities in the unmanned aerial vehicle swarms at a lower communication cost than other methods required

Mutagenicity of a Model DNA-Peptide Cross-Link in Human Cells: Roles of Translesion Synthesis DNA Polymerases

DNA protein cross-links are formed upon exposure of cellular DNA to various agents, including antitumor drugs, UV light, transition metals, and reactive oxygen species. They are thought to contribute to cancer, aging, and neurodegenerative diseases. It has been proposed that DNA protein cross-links formed in cells are subject to proteolytic degradation to the corresponding DNA-peptide T cross-links (DpCs). To investigate the effects of DpCs on DNA replication, we have constructed plasmid DNA containing a 10-mer Myc peptide covalently linked to C7 of 7-deaza-dG, a hydrolytically stable mimic of N7-dG lesions. Following transfection in human embryonic kidney cells (HEK 293T), progeny plasmids were recovered and sequenced. Translesion synthesis (TLS) past DpC was 76% compared to that of the unmodified control. The DpC induced 20% targeted G -> A and G -> T plus 15% semitargeted mutations, notably at a guanine (G(5)) five bases 3' to the lesion site. Proteolytic digestion of the DpC reduced the mutation frequency considerably, indicating that the covalently attached 10-mer peptide was responsible for the observed mutations. TLS efficiency and targeted mutations were reduced upon siRNA knockdown of pol eta, pol kappa, or pol zeta, indicating that they participate in error-prone bypass of the DpC lesion. However, the semitargeted mutation at G(5) was only reduced upon knockdown of pol zeta, suggesting its critical role in this type of mutations. Our results indicate that DpCs formed at the N7 position of guanine can induce both targeted and semitargeted mutations in human cells and that the TLS polymerases play a critical role in their error-prone bypass