Ranking academic impact of GIS research organizations in the United States: a bibliographic network analysis over 20 years

<div><p>In the United States, geographic information system (GIS) has been widely used and researched in thousands of organizations, including academic institutions, government agencies, and businesses. Few efforts have evaluated how much impact an organization has on the research community. To fill this gap, I established collaboration and citation networks among 2394 US organizations and calculated their impact scores based on quantity, diversity, and spread of scholarly activities. I reported top-ranking organizations between 1992 and 2011 and identified spatio-temporal patterns of GIS growth over the United States. The results are valuable for organizations to assess their strengths and weakness and find a path to broaden the impact.</p></div

Physicochemical Changes of Few-Layer Graphene in Peroxidase-Catalyzed Reactions: Characterization and Potential Ecological Effects

The environmental implications of graphene have received much attention, however, little is known about how graphene affects or may be affected by the enzymatic reactions that are critically involved in natural organic matter transformation processes. We conducted experiments to examine the role of few-layer graphene (FLG) in the reaction system of tetrabromobisphenol A (TBBPA) mediated by horseradish peroxidase (HRP). We found that TBBPA was transformed by HRP into two products that were likely formed from coupling of two TBBPA radicals via interaction of an oxygen atom on one radical and a propyl-substituted aromatic carbon atom on the other. Presence of FLG greatly increased the reaction rate by protecting HRP from inactivation. Direct reactions between TBBPA radicals and FLG were unequivocally evidenced using ¹⁴C labeling and the characteristic photoelectron response of bromine contained in TBBPA. The thickness, size, and aggregation profile of FLG was modified by the reaction as shown by multiple characterization tools. Assessment using <i>Daphnia magna</i> revealed a substantial decrease in the bioaccumulation and toxicity of the FLG after being modified. The data provides the first evidence that FLG can be modified in HRP-mediated reactions and indicates that such modifications may have strong implications in its ecological effects

Physicochemical Changes of Few-Layer Graphene in Peroxidase-Catalyzed Reactions: Characterization and Potential Ecological Effects

The environmental implications of graphene have received much attention, however, little is known about how graphene affects or may be affected by the enzymatic reactions that are critically involved in natural organic matter transformation processes. We conducted experiments to examine the role of few-layer graphene (FLG) in the reaction system of tetrabromobisphenol A (TBBPA) mediated by horseradish peroxidase (HRP). We found that TBBPA was transformed by HRP into two products that were likely formed from coupling of two TBBPA radicals via interaction of an oxygen atom on one radical and a propyl-substituted aromatic carbon atom on the other. Presence of FLG greatly increased the reaction rate by protecting HRP from inactivation. Direct reactions between TBBPA radicals and FLG were unequivocally evidenced using ¹⁴C labeling and the characteristic photoelectron response of bromine contained in TBBPA. The thickness, size, and aggregation profile of FLG was modified by the reaction as shown by multiple characterization tools. Assessment using <i>Daphnia magna</i> revealed a substantial decrease in the bioaccumulation and toxicity of the FLG after being modified. The data provides the first evidence that FLG can be modified in HRP-mediated reactions and indicates that such modifications may have strong implications in its ecological effects

Bioaccumulation of ¹⁴C‑Labeled Graphene in an Aquatic Food Chain through Direct Uptake or Trophic Transfer

The growing applications of graphene materials warrant a careful evaluation of their environmental fate in aquatic food webs. <i>Escherichia coli</i> (Bacteria), <i>Tetrahymena thermophila</i> (protozoa), <i>Daphnia magna</i> (zooplankton), and <i>Danio rerio</i> (vertebrate) were used to build aquatic food chains to investigate the waterborne uptake and trophic transfer of ¹⁴C-labeled graphene. Body burden factor (BBF) and trophic transfer factor (TTF) were analyzed for each organism and food chain to assess the bioaccumulation and biomagnification of graphene. The test organisms have high potential of accumulating graphene via direct uptake from culture medium with log-transformed BBF (log BBF) values of 3.66, 5.1, 3.9, and 1.62 for each organism, respectively. In the food chain from <i>E. coli</i> to <i>T. thermophila</i>, the calculated TTFs of 0.2 to 8.6 indicate the high trophic transfer potential in this aquatic food chain. However, the TTFs calculated for the food chain from <i>T. thermophila</i> to <i>D. magna</i> and from <i>D. magna</i> to <i>D. rerio</i> are much lower than 1, indicating that biomagnification was unlikely to occur in these food chains. Body burden measured for dietary uptake by <i>T. thermophila</i>, <i>D. magna</i>, and <i>D. rerio</i> are higher than that via waterborne exposure in a similar nominal concentration, respectively, indicating that trophic transfer is a nonnegligible route for the bioaccumulation of graphene in organisms

Ultrafast Charge Separation for Full Solar Spectrum-Activated Photocatalytic H₂ Generation in a Black Phosphorus–Au–CdS Heterostructure

Two-dimensional layered black phosphorus (BP) with a tunable band gap of 0.3–2.0 eV has received great interest in broad-spectrum-active photocatalysis, but rapid charge recombination limits its potential applications. Herein, we report that BP quantum dots (QDs) work as active photosensitizer in a ternary heterostructure consisting of BP QDs, Au nanorods (NRs), and CdS nanowires (NWs), which efficiently photocatalytically generates H₂ at full solar spectrum, especially in the near-infrared (NIR) region. The superior performance of the BP–Au–CdS heterostructure arises from the overall photoabsorption contribution, the dual role (electron relay and plasmonic electron donor) of Au NRs, as well as the appropriate band alignment and strong coupling between the three components. Tracking the electron and hole transfers via femtosecond transient absorption spectroscopy shows a unidirectional electron flow from BP to Au and then to CdS, which has been achieved by the high conduction band level of BP, the well-harnessed work function match in BP–Au, and the well-established Schottky barrier in Au–CdS heterojunction

Transformation and Removal of Tetrabromobisphenol A from Water in the Presence of Natural Organic Matter via Laccase-Catalyzed Reactions: Reaction Rates, Products, and Pathways

The widespread occurrence of the brominated flame retardant tetrabromobisphenol A (TBBPA) makes it a possible source of concern. Our experiments suggest that TBBPA can be effectively transformed by the naturally occurring laccase enzyme from <i>Trametes versicolor</i>. These reactions follow second-order kinetics, whereby apparent removal rate is a function of both substrate and enzyme concentrations. For reactions at different initial concentrations and with or without natural organic matter (NOM), reaction products are identified using liquid or gas chromatography with mass spectrometry. Detailed reaction pathways are proposed. It is postulated that two TBBPA radicals resulting from a laccase-mediated reaction are coupled together via interaction of an oxygen atom on one radical and a propyl-substituted aromatic carbon atom on the other. A 2,6-dibromo-4-isopropylphenol carbocation is then eliminated from the radical dimer. All but one of the detected products arise from either substitution or proton elimination of the 2,6-dibromo-4-isopropylphenol carbocation. Three additional products are identified for reactions in the presence of NOM, which suggests that reaction occurs between NOM and TBBPA radical. Data from acute immobilization tests with <i>Daphnia</i> confirm that TBBPA toxicity is effectively eliminated by laccase-catalyzed TBBPA removal. These findings are useful for understanding laccase-mediated TBBPA reactions and could eventually lead to development of novel methods to control TBBPA contamination

Tissue-Specific Accumulation, Depuration, and Transformation of Triphenyl Phosphate (TPHP) in Adult Zebrafish (Danio rerio)

Understanding bioaccumulation and metabolism is critical for evaluating the fate and potential toxicity of compounds in vivo. We recently investigated, for the first time, the bioconcentration and tissue distribution of triphenyl phosphate (TPHP) and its main metabolites in selected tissues of adult zebrafish. To further confirm the metabolites, deuterated TPHP (d₁₅-TPHP) was used in the exposure experiments at an environmentally relevant level (20 μg/L) and at 1/10 LC₅₀ (100 μg/L). After 11–14 days of exposure to 100 μg/L of d₁₅-TPHP, the accumulation and excretion of d₁₅-TPHP reached equilibrium, at which point the intestine contained the highest d₁₅-TPHP (μg/g wet weight, ww) concentration (3.12 ± 0.43), followed by the gills (2.76 ± 0.12) > brain (2.58 ± 0.19) > liver (2.30 ± 0.34) ≫ muscle (0.53 ± 0.04). The major metabolite of d₁₅-TPHP, d₁₀-diphenyl phosphate (d₁₀-DPHP), was detected at significantly higher contents in the liver and intestine, at levels up to 3.0–3.5 times those of d₁₅-TPHP. The metabolic pathways of TPHP were elucidated, including hydrolysis, hydroxylation, and glucuronic acid conjugation after hydroxylation. Finally, a physiologically based toxicokinetic (PBTK) model was used to explore the key factors influencing the bioaccumulation of d₁₅-TPHP in zebrafish. These results provide important information for the understanding of the metabolism, disposition, and toxicology of TPHP in aquatic organisms

Risk analysis and prediction of visceral leishmaniasis dispersion in São Paulo State, Brazil

<div><p>Visceral leishmaniasis (VL) is an important neglected disease caused by a protozoan parasite, and represents a serious public health problem in many parts of the world. It is zoonotic in Europe and Latin America, where infected dogs constitute the main domestic reservoir for the parasite and play a key role in VL transmission to humans. In Brazil this disease is caused by the protozoan <i>Leishmania infantum chagasi</i>, and is transmitted by the sand fly <i>Lutzomyia longipalpis</i>. Despite programs aimed at eliminating infection sources, the disease continues to spread throughout the Country. VL in São Paulo State, Brazil, first appeared in the northwestern region, spreading in a southeasterly direction over time. We integrate data on the VL vector, infected dogs and infected human dispersion from 1999 to 2013 through an innovative spatial temporal Bayesian model in conjunction with geographic information system. This model is used to infer the drivers of the invasion process and predict the future progression of VL through the State. We found that vector dispersion was influenced by vector presence in nearby municipalities at the previous time step, proximity to the Bolívia-Brazil gas pipeline, and high temperatures (i.e., annual average between 20 and 23°C). Key factors affecting infected dog dispersion included proximity to the Marechal Rondon Highway, high temperatures, and presence of the competent vector within the same municipality. Finally, vector presence, presence of infected dogs, and rainfall (approx. 270 to 540mm/year) drove the dispersion of human VL cases. Surprisingly, economic factors exhibited no noticeable influence on disease dispersion. Based on these drivers and stochastic simulations, we identified which municipalities are most likely to be invaded by vectors and infected hosts in the future. Prioritizing prevention and control strategies within the identified municipalities may help halt the spread of VL while reducing monitoring costs. Our results contribute important knowledge to public and animal health policy planning, and suggest that prevention and control strategies should focus on vector control and on blocking contact between vectors and hosts in the priority areas identified to be at risk.</p></div

Biological Uptake and Depuration of Radio-labeled Graphene by <i>Daphnia magna</i>

Graphene layers are potential candidates in a large number of applications. However, little is known about their ecotoxicological risks largely as a result of a lack of quantification techniques in complex environmental matrices. In this study, graphene was synthesized by means of graphitization and exfoliation of sandwich-like FePO₄/dodecylamine hybrid nanosheets, and ¹⁴C was incorporated in the synthesis. ¹⁴C-labeled graphene was spiked to artificial freshwater and the uptake and depuration of graphene by <i>Daphnia magna</i> were assessed. After exposure for 24 h to a 250 μg/L solution of graphene, the graphene concentration in the organism was nearly 1% of the organism dry mass. These organisms excreted the graphene to clean artificial freshwater and achieved roughly constant body burdens after 24 h depuration periods regardless of the initial graphene exposure concentration. Addition of algae and humic acid to water during the depuration period resulted in release of a significant fraction (>90%) of the accumulated graphene, but some still remained in the organism. Accumulated graphene in adult <i>Daphnia</i> was likely transferred to the neonates. The uptake and elimination results provided here support the environmental risk assessment of graphene and the graphene quantification method is a powerful tool for additional studies

Brazil and São Paulo State.

<p>Brazil and São Paulo State.</p