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  • Chemistry  (408,534)
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  • 1
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    North Pacific Marine Science Organization (PICES)
    Publication Date: 2020-01-28
    Description: PICES science in 2019: Notes from the Science Board Chair. 2019 PICES awards. Working Group 37 organizes Phase 2 of a Practical Workshop. Communicating science. Integrating biological research, fisheries science and management of Pacific halibut and other widely distributed fish species across the North Pacific. Two decades of the North Pacific CPR program. PICES calendar of events for 2020. PICES/ICES collaborative research initiative. PICES/NPFC collaborative research. The 2019 International Gulf of Alaska Expedition. GlobalHAB: Evaluating, reducing and mitigating the cost of Harmful Algal Blooms. PICES on the cloud. New leadership in PICES. PICES Interns. PICES Special Project: Sea turtle ecology in relation to environmental stressors in North Pacific regions. Regional Consultative and Planning Workshop towards the UN Decade of Ocean Science for Sustainable Development. Towards an integrated approach to understanding ecosystem predictability in the North Pacific. Shellfish –Resources and invaders of the North. Highlights of the 2019 FAO International Symposium on Fisheries Sustainability. The Bering Sea: Current status and recent trends. Copepod responses to, and recovery from, the recent marine heatwave in the Northeast Pacific . The western North Pacific during the 2019 warm season. Northeast Pacific juvenile salmon summer surveys in 2019.
    Keywords: Biology ; Chemistry ; Ecology ; Environment ; Oceanography
    Repository Name: Aquatic Commons
    Type: Monograph or Serial Issue , NonPeerReviewed
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  • 2
    Publication Date: 2020-08-06
    Description: Ciguatera Fish Poisoning (CFP) is primarily caused by ingesting reef fishes contaminated with ciguatoxins (CTX) produced by the Gambierdiscus species. The unpredictability of this type of food poisoning poses risks to public health and adversely affecting the fish trade industry. This study aimed to provide useful information on ciguatera in the Philippines. Different reef fish species and host-macroalgae for benthic dinoflagellates were collected in Visayan and Sibuyan Seas. Ciguatoxins were extracted from reef fish samples, and toxicity was determined qualitatively using mouse bioassay. Meanwhile, cell density estimation of toxic benthic dinoflagellates isolated from the host-macroalgae was done through microscopy. It was observed that 4.46% of the total reef fish samples were positive with ciguatoxins. Spatially, Carles, Iloilo in Visayan sea had the highest number of toxic specimens belonging to Epinephelus merra, Lethrinus lentjan, Lutjanus campechanus, Scarus quoyi, Siganus guttatus, and Sphyraena barracuda. Based on data gathered from three sampling sites, fish toxin occurrence is observed to be site-specific. Geographical conditions affect the frequency of toxic samples. Moreover, fish weight is not a good predictor of fish toxicity. For toxic benthic dinoflagellates, Gambierdiscus spp. were observed to have the lowest cell density count among other dinoflagellates averaging 7-115 cells per 100 g macroalgae. On the other hand, Ostreopsis spp. had the highest average cell density of 118-1,455 cells per 100 g macroalgae, followed by Prorocentrum spp. (207-594 cells per 100 g macroalgae). Fish toxicity is directly proportional to the occurrence of benthic dinoflagellates in areas as seen during dry season. Monitoring and management of CFP on identified reef fish vectors and its causative benthic dinoflagellates in the area are necessary to promote food safety and fair trade practice.
    Keywords: Chemistry ; Ecology ; Fisheries ; Health
    Repository Name: Aquatic Commons
    Type: Article , PeerReviewed
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  • 3
    Publication Date: 2020-08-21
    Description: Waste from aquaculture is considered as one of the possible causes of water quality deterioration in Manila Bay. Aquaculture in the area accounts for almost 30% of the total production in the Philippines. This high production entails intensified application of inputs that could possibly contribute to the nutrient (nitrogen, N and phosphorus, P) load in the bay. Thus, estimation of the N, P and SO4 loaded from aquaculture farms is necessary to develop more responsive intervention to reduce nutrient load in Manila Bay. Water samples were collected throughout the rearing period from different aquaculture systems in Cavite, Bulacan, Pampanga, and Bataan. The annual estimated N and P loaded from aquaculture farms were 12, 696.66 MT and 2, 363.01 MT, respectively. Fish pens/cages recorded the highest contribution accounting for 88% N and 86% P of the total load. It can be attributed to the direct release of uneaten feeds into the bodies of water. Roughly, 12% N and 14% P were obtained from the fishponds. Furthermore, the annual SO4 loaded from fishponds was estimated at 36,917.54 MT. Results of the study suggested that there should be an extensive monitoring of the environmental impacts and annual load of aquaculture farms for the sustainable regulations and management of aquaculture activities to reduce nutrient load and improve the aquaculture production as well. Finally, strict compliance to the regulatory guidelines and ordinances must be imposed to achieve the effluent quality standards.
    Keywords: Aquaculture ; Chemistry ; Ecology ; Environment ; Pollution
    Repository Name: Aquatic Commons
    Type: Article , PeerReviewed
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  • 4
    Publication Date: 2019-05-06
    Description: This study aimed to evaluate the nutritional value (proximate composition, fatty acid profiles, vitamins and minerals) contents and also nutritional quality indices (NQI)) of grass carp (Ctenopharyngodon idella) prepared according to common consumer techniques: raw, poached, steamed, microwaved, pan-fried and deep-fried (in olive oil). In comparison to raw fish fillets, when grass carp was cooked there was an increase in protein, lipid and ash contents. Cooking methods had no significant effect on total n-3 fatty acids except for frying fillets. Lowest and highest content of n-3 was shown in deep-fried and pan-fried samples, respectively. Total n-6 fatty acid of cooked samples increased in comparison to raw samples. Na, K, Mg, P and Zn contents of boiled fish fillets significantly decreased. None of cooking methods had a significant effect a vitamin D. However, vitamin A, B_1 and B_3 contents of cooked fish significantly decreased.
    Keywords: Aquaculture ; Biology ; Chemistry
    Repository Name: Aquatic Commons
    Type: Article , PeerReviewed
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  • 5
    Publication Date: 2019-05-06
    Description: Skin cancer has been reported as a contemporary malignant cancer. Here, anti-cancer effects of sea cucumber extract (SCE) from Holothuria arenicola have been examined on melanoma cells and compared with imidazole carboxamide (Dacarbazine) as a chemotherapy medication against melanoma and Hodgkin's lymphoma. MTT assay and morphological analysis were performed to evaluate cytotoxic effects of H. arenicola extract. Also, several methods were exerted to detect cell dying by SCE and imidazole carboxamide. The MTT assay showed that B16F10 cells proliferation was blocked by SCE (IC_50=31µg ml ^-1) and imidazole carboxamide (IC_50=1600 µg ml ^-1) in a dose and time dependent manner. Apoptosis induction yield treatment occurred at IC50 concentration of SCE and imidazole carboxamide using DAPI staining, Acridine orange/Propodium iodide, PI flow cytometry and annexin/PI assay. The caspase colorimetric kit indicated that SCE and imidazole carboxamide could induce apoptosis through an intrinsic pathway. Collectively, our findings suggested that the methanolic SCE has more efficient cytotoxicity efficiency compared to imidazole carboxamide. Therefore, SCE may be considered as a futuristic marine natural product regarding prevention or treatment of melanoma malignancy.
    Keywords: Biology ; Chemistry
    Repository Name: Aquatic Commons
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2019-05-06
    Description: The present study was conducted to examine different dietary levels of iron (FeSO4) on some haematological parameters of ship sturgeon, Acipenser nudiventris including red blood cells (RBC), white blood cells (WBCs), differential WBCs, hematocrit (Hct), Hemoglobin (Hb), the mean corpuscular hemoglobin (MCH) and the mean corpuscular hemoglobin concentration (MCHC), the mean corpuscular volume (MCV), immunoglobulin (IgM), ferritin, transferrin and plasma Fe^2+. Four experimental treatments and one control group with three replicates were considered for the experiment. The experimental treatments were fish fed experimental diets containing different levels of FeSO_4 i.e. 100, 200, 250, and 300 mg kg. diet^-1. After 60 days, there were significant differences between experimental groups in terms of WBCs, lymphocytes, neutrophils, monocytes, eosinophils, MCH and MCHC, MCV, total plasma protein, IgM, ferritin, transferrin and plasma Fe^2+ (p〈0.05). In the treatment fed 100 mg. iron kg. diet^-1, more levels of IgM and total plasma protein were observed compared to other experimental groups (p〈0.05). The highest values of neutrophils, monocytes and MCHC were found in control fish whereas MCV, MCH and eosinophils values were higher in the treatment fed 200 mg. iron kg. diet^-1 (p〈0.05). Also, more WBCs were observed in 250 mg. iron kg. diet^-1 treatment than in other groups (p〈0.05). The values of lymphocytes, RBC, Hct, Hb, ferritin, transferrin and plasma Fe^2+ were higher in fish fed 300 mg. iron kg. diet^-1 compared to other experimental groups (p〈0.05). In conclusion, our results showed that the supplementation of ship sturgeon diets with high levels of iron enhances the RBC, Hct, Hb, ferritin, transferrin and plasma iron.
    Keywords: Aquaculture ; Biology ; Chemistry
    Repository Name: Aquatic Commons
    Type: Article , PeerReviewed
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  • 7
    Publication Date: 2019-05-06
    Description: The effects of chitosan (2%) coating combined with green tea extract (GTE) (1%) on the quality of tiger-tooth croaker (Otolithes ruber) fillets including chemical, microbiological, texture, color and sensory properties during 16 days of refrigerated storage was investigated. The color changes were significantly retared, and the texture parameteres and sensory scores were significantly improved in tiger- tooth croaker coated by chitosan, GTE and chitosan combined with GTE, compared with the control. The coincidental lowered rate of increase total volatile base (TVB) content, thiobarbitoric acid (TBA), peroxide value (POV) and free fatty acids (FFA) were obtained in tiger-tooth croaker coated chitosan+GTE. Chitosan in combination with GTE had higher inhibition on microbial growth and yielded the tigertooth croaker with higher likeness, compared with the other treatments. Therefore, fish coated with chitosan+GTE had the lowest losses in quality during refrigerated storage.
    Keywords: Biology ; Chemistry ; Fisheries
    Repository Name: Aquatic Commons
    Type: Article , PeerReviewed
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  • 8
    Publication Date: 2019-05-06
    Description: Hand cream is used for rehydrating and improving skin properties. The skin is the first point of contact with the environment. Thus having healthy skin with proper barrier properties is quite important. The beneficial effects of fish oil on skin make it a favorable ingredient to be used in hand care products. In the present study, the efficacy and stability of various hand cream formulations using 0, 1.0, 2.5 and 5.0% of fish oil were investigated and compared. The appearance, odor, texture, and pH of formulations containing 1 and 2.5% of fish oil remained stable in very good qualities during the storage, whereas the related values to the appearance and texture of formulation containing 5.0% of fish oil at the end of 6 months of storage at 45°C were significantly (p〈0.05) lower than other formulations and previous evaluations of this formulation. Weight loss was not observed in all formulations under study.
    Keywords: Biology ; Chemistry ; Fisheries
    Repository Name: Aquatic Commons
    Type: Article , PeerReviewed
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  • 9
    Publication Date: 2019-05-06
    Description: Research on eliminating organic pollutants in water by using heterogeneous photocatalysts such as nano-TiO_2 abound. However, the question is whether metabolites, resulting from optical dispersion of environmental pollutants, are still toxic to aquatic organisms. Therefore, this study was designed to evaluate the effect of a co-exposure to paraquat and TiO_2-NPs on blood biochemical indices of common carp. Fish were exposed to 0.2 and 0.4 mg L^-1 paraquat with 0.125 mg L^-1 TiO_2-NPs for 21 days under different light conditions, including natural photoperiod (16 L 8h^-1 D) and complete darkness. No significant alterations in the Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Lactate dehydrogenase (LDH), Alkaline phosphatase (ALP) and Creatine phosphokinase (CPK), activities and total protein, albumin, globulin, glucose, cholesterol and triglyceride levels were observed in fish exposed to TiO_2-NPs and 0.2 mg L^-1 paraquat under normal lighting conditions. However, a significant change in blood biochemical indices in fish exposed to TiO2-NPs with 0.4 mg L^-1 paraquat (16 L 8h^-1 D) and in fish exposed to TiO_2-NPs and paraquat (under darkness). A significant decrease in the activity of Gamma-glutamyltransferase (GGT) and a significant increase in creatinine level were observed in all groups which were exposed to TiO_2-NPs and paraquat. The results of this study indicate that using 0.125 mg L^-1 nano-TiO2 in order to remove paraquat (0.2 mg L^-1) under lighting conditions can minimize the adverse effects of paraquat and its metabolites on blood biochemical indices of fish. So, using nano-TiO_2 (0.125 mg L^-1) to remove paraquat under lighting conditions can significantly reduce its toxic effects.
    Keywords: Biology ; Chemistry ; Environment ; Pollution
    Repository Name: Aquatic Commons
    Type: Article , PeerReviewed
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  • 10
    Publication Date: 2019-05-06
    Description: To investigate the effects of carvacrol supplementation in rainbow trout induced by lipopolysaccharide (LPS), relative gene expressions levels of some pro-inflammatory cytokines and apoptosis markers in kidney and liver were measured. Fish with a mean weight of 44.71±1.33 g were studied using four different treatments with three replicates each. Inflammation and apoptosis were performed using LPS of Escherichia coli (25 µg ml ^-1) except in the control group and only carvacrol (100 µg ml ^-1 diet) containing diets were fed to this group (CAR). The last group was the infected fish fed carvacrol supplemented diet (+CAR). Kidney and liver tissues were removed 3 days after to determine the levels of interleukin-1β (IL-1β), interferon gamma (INF-γ), caspase 3 (Cas 3), caspase 8 (Cas 8) using Real-Time PCR analyses. IL-1β expressions of both kidney and liver was significantly decreased (12.9 and 2.14 fold, respectively) in LPS treated cells (p〈0.05). While IFN-γ expression was up regulated in kidney, it had down regulation in liver. LPS decreased both Cas 3 and 8 expressions in kidney but increased in liver. +CAR increased expressions of IL-1β and IFN-γ compared with the control (up to 2-3 fold) in all tissues except caspase gene expressions that were similar in the control. In all tissues, IL-1β and IFN-γ expressions increased in +CAR group, expect IFN-γ in the kidney. However, Cas 3 and 8 expressions including apoptosis was induced by up-down regulations in all tissues compared to LPS-injected fish. The results showed that carvacrol had pro-inflammatory and apoptotic effects especially on liver tissue of LPS-induced inflammation model of Oncorhynchus mykiss.
    Keywords: Aquaculture ; Biology ; Chemistry ; Fisheries
    Repository Name: Aquatic Commons
    Type: Article , PeerReviewed
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  • 11
    Publication Date: 2019-05-06
    Description: The study on physicochemical factors and primary production of the aquatic ecosystems is important to know the characteristics of the environment and capacity of recharge. Mahshahr Creeks are the most important creeks in the Northwest Persian Gulf, Iran. In this study, variations in physicochemical factors, chl-a, and primary production in creeks of Mahshahr, Zangi, and Moussa were evaluated for 2 months of every season of 2014. The following variables were analyzed: nitrate, phosphate, nitrite, silicate, temperature, salinity, DO, pH, conductivity, turbidity, light, chl-a, primary production and phytoplankton abundance. The maximum amount of chl-a (1.6 mg m^3) was observed in Moussa Creek in April while the minimum amount (0.1 mg m ^-3) was seen in Moussa in July. The highest (1.19 gc m^-2 day^-1) and lowest (0.1gc m^-2 day^-1) amount of primary production were observed at the entrance of Moussa Creek in April and in Zangi Creek in November, respectively. The maximum and minimum abundance of phytoplankton was observed in April and October, respectively in all study areas. The results of correlation test between the studied factors revealed that primary production has a significant relationship with nitrite, chl-a, phytoplankton abundance and light. Primary production in these creeks is relatively high in April and is attributed to the uptake of nutrients including nitrate and phosphate from shallow waters entering these creeks, sufficient light and suitable temperature, but in other months the production is low.
    Keywords: Biology ; Chemistry
    Repository Name: Aquatic Commons
    Type: Article , PeerReviewed
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  • 12
    Publication Date: 2019-05-06
    Description: Concentrations of heavy metals (Cd, Ni and Pb) were determined in soft and hard tissues (three separated shell sections) of gastropod Bufonaria echinata as well as surficial sediments collected in October 2015 from two sampling sites located in the sub-littoral zone of Qeshm Island, Persian Gulf. There were significant differences between the sampling sites for concentrations of all the three elements in the shells and sediments. But in terms of the soft tissues, in the case of Ni and Pb significant differences between the sites could be observed. In all the cases, higher levels were observed in the samples from Suza site, which may be mainly due to the proximity of this site to the relevant anthropogenic sources. Comparison of the gained data from this study with the other relevant researches shows that in most cases the levels of the elements in the soft tissues and shells either fell within the range for other world areas or were lower. The observed increasing trends of metals accumulation in the shell sections (from older to younger sections) could be mainly attributed to the gradual increase of relevant anthropogenic pollutants in the study area, especially in Suza pier, during the recent years. Generally, it can be concluded that the shells of B.echinata could be possibly employed as a biomonitoring tool for historic metals contamination in northeastern part of the Persian Gulf.
    Keywords: Biology ; Chemistry ; Pollution
    Repository Name: Aquatic Commons
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  • 13
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    North Pacific Marine Science Organization (PICES)
    Publication Date: 2020-01-27
    Keywords: Atmospheric Sciences ; Chemistry ; Earth Sciences ; Environment ; Oceanography
    Repository Name: Aquatic Commons
    Type: Monograph or Serial Issue , NonPeerReviewed
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  • 14
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    North Pacific Marine Science Organization (PICES)
    Publication Date: 2020-01-28
    Description: PICES science in 2017: Notes from the Science Board Chair. 2018 PICES awards. ECCWO-4 Workshop on “Intercomparison of fisheries and marine ecosystem models”. The PICES–MAFF-sponsored Project on “Building capacity for coastal monitoring by local small-scale fishers”. Northeast Pacific juvenile salmon summer surveys in 2018. 2018 PICES Summer School on “Coastal ocean observatory science”. Working Group 37 organizes a Practical Workshop on “Production methodologies and measurements for in situ zooplankton”. PICES in Ireland: ADRIFT marine bioinvasions study presented at NEOBIOTA 2018. The Bering Sea: Current status and recent trends. The Northeast Pacific: Current status and recent trends. The western North Pacific during the 2018 warm season. In memory of Boris Kotenev. New leadership in PICES.
    Keywords: Biology ; Chemistry ; Fisheries ; Oceanography
    Repository Name: Aquatic Commons
    Type: Monograph or Serial Issue , NonPeerReviewed
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  • 15
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    North Pacific Marine Science Organization (PICES)
    Publication Date: 2020-01-28
    Description: 2019 Inter-sessional Science Board Meeting. 2019 Pacific Ecology and Evolution Conference. Highlights from the FUTURE SSC’s 5th Inter-sessional Meeting. Working together at the 4th GOA-ON International Workshop. Scientific dialogue between the ocean and the atmosphere. SOLAS Early-Career Scientist Day. FishGIS: Incorporating community-based research principles. Future Oceans2 IMBeR Open Science Conference. First global planning meeting for the United Nations Decade of Ocean Science for Sustainable Development. In memoriam: Dr. Olga Nikolaevna Lukyanova. Topic sessions and workshops at PICES-2019. Upcoming Shellfish – Resources and Invaders of the North symposium. The Northeast Pacific: Current status and recent trends. The Bering Sea: Current status and recent trends. The western North Pacific during the 2018/2019 cold season.
    Keywords: Biology ; Chemistry ; Ecology ; Environment ; Oceanography
    Repository Name: Aquatic Commons
    Type: Monograph or Serial Issue , NonPeerReviewed
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  • 16
    Publication Date: 2020-03-05
    Description: A pre-column derivatization-ultra high performance liquid chromatographic (UHPLC) method is described for the determination of histamine in fish and fishery products. The homogenized samples were extracted with trichloroacetic acid (TCA) solution and derivatized with o-phthaldialdehyde. Histamine was separated using reversed-phase column and determined using UHPLC with fluorescence detection. The linear calibration range was 10 to 60 µg/mL with a correlation coefficient of 0.9993. Good recoveries were observed for the histamine under investigation at all spiking levels, and average recoveries were higher than 89% with a precision smaller than 8.46%. The detection and quantification limit were 2.7 and 8.3 µg/g, respectively. The uncertainty was estimated to be ± 0.45. The performance of the proposed method was checked with a proficiency test sample from the Food Analysis Performance Assessment Scheme (FAPAS) as external quality control; the resulting z-score was -0.2, which was found within acceptable range of -2 ≤ z ≤ 2. The results indicated that this HPLC method was reliable, sensitive, reproducible, and practical for the routine analysis of histamine in fish and fishery products.
    Keywords: Chemistry ; Environment ; Fisheries
    Repository Name: Aquatic Commons
    Type: Article , PeerReviewed
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  • 17
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    UNSAM EDITA
    Publication Date: 2019-02-10
    Description: Este libro contiene las presentaciones de las conferencias invitadas de expertos y las realizadas en formato “poster” por los estudiantes participantes en el Workshop “Aguas + Humedales”, realizado en San Martín entre el 17 y el 22 de octubre de 2016 en la Universidad Nacional de San Martín, San Martín, Argentina. Con el objeto de brindar a los estudiantes de posgrado un panorama amplio del problema del agua y su proyección hacia el futuro, el material que aquí se presenta se ocupa de temas tales como el agua como fuente segura para consumo humano y su vida cotidiana, como recurso fundamental para la actividad agropecuaria, como fuente de alimentos, como fluido de proceso y de transporte de calor, como vía de comunicación y transporte. Se plantean interrogantes sobre la disponibilidad del recurso, sobre la intervención humana en el ciclo hidrológico y en el clima. También se analizan problemas relacionados con tecnologías para el tratamiento de aguas, tanto para consumo humano como tratamiento de efluentes de diverso tipo. Se presta especial atención a la dimensión social del tema: derecho y economía del agua, estudios vinculados con las decisiones sobre el uso del recurso y el desarrollo de legislaciones y regulaciones.
    Keywords: Agriculture ; Aquaculture ; Biology ; Chemistry ; Conservation ; Earth Sciences ; Ecology ; Engineering ; Environment ; Fisheries ; Limnology ; Policies ; Pollution
    Repository Name: Aquatic Commons
    Type: Book , PeerReviewed
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  • 18
    Publication Date: 2018-11-15
    Description: In this study, the removal of congo red and erythrosine as anionic dyes were investigated by using the cucurbit[6]uril nonporous as a new adsorbent. In the proposed mythology, the batch removal method was applied. In order to obtain maximum removal efficiency, the effects of acidity of solution, adsorbent dosage and contacting time were investigated and optimized. Adsorption experimental data were analyzed using Langmuir and Freundlich isotherm models and the best-fitted data was obtained with the Langmuir model. The maximum adsorption capacity was 128.2 mg g^-1 and 95.9 mg g^-1 for congo red and erythrosine, respectively. This method was successfully applied for the removal of congo red and erythrosine dyes from Karron and Bahmanshir water river and Persian Gulf water samples.
    Keywords: Biology ; Chemistry ; Pollution
    Repository Name: Aquatic Commons
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  • 19
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    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publication Date: 2018-11-02
    Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2018
    Description: Many chemical constituents are removed from the ocean by attachment to settling particles, a process referred to as “scavenging.” Radioisotopes of thorium, a highly particle-reactive element, have been used extensively to study scavenging in the ocean. However, this process is complicated by the highly variable chemical composition and concentration of particles in oceanic waters. This thesis focuses on understanding the cycling of thorium as affected by particle concentration and particle composition in the North Atlantic. This objective is addressed using (i) the distributions 228,230,234Th, their radioactive parents, particle composition, and bulk particle concentration, as measured or estimated along the GEOTRACES North Atlantic Transect (GA03) and (ii) a model for the reversible exchange of thorium with particles. Model parameters are either estimated by inversion (chapter 2-4), or prescribed in order to simulate 230Th in a circulation model (chapter 5). The major findings of this thesis follow. In chapters 2 and 3, I find that the rate parameters of the reversible exchange model show systematic variations along GA03. In particular, 𝑘1, the apparent first-order rate "constant" of Th adsorption onto particles, generally presents maxima in the mesopelagic zone and minima below. A positive correlation between 𝑘1 and bulk particle concentration is found, consistent with the notion that the specific rate at which a metal in solution attaches to particles increases with the number of surface sites available for adsorption. In chapter 4, I show that Mn (oxyhydr)oxides and biogenic particles most strongly influence 𝑘1 west of the Mauritanian upwelling, but that biogenic particles dominate 𝑘1 in this region. In chapter 5, I find that dissolved 230Th data are best represented by a model that assumes enhanced values of 𝑘1 near the seafloor. Collectively, my findings suggest that spatial variations in Th radioisotope activities observed in the North Atlantic reflect at least partly variations in the rate at which Th is removed from the water column.
    Description: This work was supported by the US National Science Foundation. Two US NSF grants have supported the research in this thesis (OCE-1232578 and OCE-155644).
    Keywords: Thorium ; Chemistry
    Repository Name: Woods Hole Open Access Server
    Type: Thesis
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  • 20
    Publication Date: 2019-06-05
    Description: In this study alginate was extracted for the first time from few species of Phaeophycota (Cystoseira indica, Padina tetrastromatica and Jolyna laminarioides) whereas Spatoglossum variabile and Sargassum tenerrimum, has been reported earlier from Karachi coast. Chemical bonding of extracted alginate was examined by using FTIR spectroscopy. Furthermore in pre-extraction step seaweeds were treated with diluted sulfuric acid solution for two different time intervals, all the selected alginophytes showed increased yield of alginate at 12 hrs treatment as compare to 5 hrs treatment.
    Keywords: Biology ; Chemistry
    Repository Name: Aquatic Commons
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  • 21
    Publication Date: 2019-06-05
    Description: In this research a comparative study was made between biodegradable films obtained from two different indigenous red seaweeds collected from Karachi coast. Gracilaria corticata and Melanothamnus afaqhussainii were collected from the Buleji coast of Karachi, Pakistan (24o50’N, 66o48’E). Agar extracted from both the seaweeds was used and incorporated as raw material for the formulation of biodegradable films. Sorbitol was used as plasticizer to increase the tensile strength and elasticity of the films. The results showed that the solubility of M. afaqhussainii was higher than G. corticata. The soil burial test showed that the biodegradability percent of M. afaqhussainii (60%) was higher as compared to G. corticata (40%). The tensile strength and elongation break of G. corticata (9.79±1.21 MPa and 28.72±5.13%) was stronger than the M. afaqhussainii (3.98±1.08 MPa and 16.32±3.80). Results of current study showed that the G. corticata has stronger gelling property as compared to M. afaqhussainii.
    Keywords: Biology ; Chemistry
    Repository Name: Aquatic Commons
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  • 22
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    North Pacific Marine Science Organization (PICES)
    Publication Date: 2020-01-27
    Keywords: Atmospheric Sciences ; Chemistry ; Ecology ; Environment ; Oceanography
    Repository Name: Aquatic Commons
    Type: Monograph or Serial Issue , NonPeerReviewed
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  • 23
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    North Pacific Marine Science Organization (PICES)
    Publication Date: 2020-01-28
    Description: 2018 Inter-sessional Science Board Meeting. 2018 Pacific Ecology and Evolution Conference. Applying global experiences to regional assessments: A workshop on the Protection of Vulnerable Marine Ecosystems. Activities of the joint PICES/ICES/PAME WG on an Integrated Ecosystem Assessment for the Central Arctic Ocean. In memoriam: Dr. Mary N. Arai. Highlights from the FUTURE SSC’s 4th Inter-sessional Meeting. PICES Interns. A new PICES MAFF-sponsored project: Building capacity for coastal monitoring by small-scale fishers. Scientists from PICES and Mexico meet to discuss closer ties in North Pacific research. An International Symposium on “Understanding changes in transitional areas of the Pacific”. The 4th International Symposium on “The effects of climate change on the world’s oceans”. ECCWO-4 Workshop on “Communicating and responding to climate change”. ECCWO-4 Workshop on “Advances in Earth System Models (ESMs) for marine applications”. ECCWO-4 Workshop on “Exploring potential ocean-based solutions to climate change impacts on marine biodiversity and ecosystem services”. ECCWO-4 Workshop on “Climate change adaptation of fisheries and aquaculture: examples of field projects supporting countries and communities”. ECCWO-4 Workshop on “Climate change and fishing communities: Interactions with environmental conservation, sustainable livelihoods and food security”. ECCWO-4 Workshop on “Utilizing bioenergetics measurements and modeling to evaluate climate change effects on marine species and ecosystems”. ECCWO-4 Workshop on “What do seabirds reveal about the effects of climate change on the world’s oceans?”. ECCWO-4 Workshop on “Connecting climate, ocean and ecosystem observation – Ocean observation futures”. ECCWO-4 Workshop on “Vulnerability of Low Elevated Coastal Zones (LECZ) to SLR in changing oceans”. ECCWO-4 Workshop on “Quantifying thresholds in driver-response relationships to identify reference points”. The Bering Sea: Current status and recent trends. The Northeast Pacific: Current status and recent trends. The western North Pacific during the 2017/2018 cold season. Topic sessions and workshops at PICES-2018. Progress in Oceanography Special Commemorative Issue.
    Keywords: Biology ; Chemistry ; Fisheries ; Oceanography
    Repository Name: Aquatic Commons
    Type: Monograph or Serial Issue , NonPeerReviewed
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    North Pacific Marine Science Organization (PICES)
    Publication Date: 2020-01-28
    Description: PICES science in 2017: A note from the Science Board Chair. 2017 PICES awards. Capacity building: PICES scientists reach out to the next generation of oceanographers in Vladivostok. A MONITOR/TCODE Workshop on “The role of the northern Bering Sea in modulating the Arctic II”. New leadership in PICES. PICES Interns. An unusual gelatinous plankton event in the NE Pacific: The Great Pyrosome Bloom of 2017. Building international partnerships to enhance science-based ecosystem approaches. The Bering Sea: Current status and recent trends. The state of the western North Pacific during the 2017 warm season. Ocean acidification and carbon dioxide uptake in the global ocean. In remembrance of Dr. William T. Peterson. Call for Papers - William Peterson Commemorative Issue. Global Ocean Observing System – Biology and Ecosystems Panel report. OceanObs’19 call for Community White Paper abstracts. Calendar of events.
    Keywords: Biology ; Chemistry ; Environment ; Fisheries ; Oceanography
    Repository Name: Aquatic Commons
    Type: Monograph or Serial Issue , NonPeerReviewed
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  • 25
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-01-19
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 26
    Publication Date: 2018-01-26
    Description: The scarcity of complex intermediates in pharmaceutical research motivates the pursuit of reaction optimization protocols on submilligram scales. We report here the development of an automated flow-based synthesis platform, designed from commercially available components, that integrates both rapid nanomole-scale reaction screening and micromole-scale synthesis into a single modular unit. This system was validated by exploring a diverse range of reaction variables in a Suzuki-Miyaura coupling on nanomole scale at elevated temperatures, generating liquid chromatography–mass spectrometry data points for 5760 reactions at a rate of 〉1500 reactions per 24 hours. Through multiple injections of the same segment, the system directly produced micromole quantities of desired material. The optimal conditions were also replicated in traditional flow and batch mode at 50- to 200-milligram scale to provide good to excellent yields.
    Keywords: Chemistry
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  • 27
    Publication Date: 2018-01-26
    Description: Since the discovery by Ullmann and Bielecki in 1901, reductive dimerization (or homocoupling) of aryl halides has been extensively exploited for the generation of a range of biaryl-based functional molecules. In contrast to the single-point connection in these products, edge-sharing fused aromatic systems have not generally been accessible from simple aryl halides via annulation cascades. Here we report a single-step synthesis of fused aromatics with a triphenylene core by the palladium-catalyzed annulative dimerization of structurally and functionally diverse chlorophenylenes through double carbon-hydrogen bond activation. The partially fused polyaromatics can be transformed into fully fused, small graphene nanoribbons, which are otherwise difficult to synthesize. This simple, yet powerful, method allows access to functional -systems of interest in optoelectronics research.
    Keywords: Chemistry
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  • 28
    Publication Date: 2018-12-21
    Description: Single-molecule magnets (SMMs) containing only one metal center may represent the lower size limit for molecule-based magnetic information storage materials. Their current drawback is that all SMMs require liquid-helium cooling to show magnetic memory effects. We now report a chemical strategy to access the dysprosium metallocene cation [(Cp i Pr5 )Dy(Cp*)] + (Cp i Pr5 , penta-iso-propylcyclopentadienyl; Cp *, pentamethylcyclopentadienyl), which displays magnetic hysteresis above liquid-nitrogen temperatures. An effective energy barrier to reversal of the magnetization of U eff = 1541 wave number is also measured. The magnetic blocking temperature of T B = 80 kelvin for this cation overcomes an essential barrier toward the development of nanomagnet devices that function at practical temperatures.
    Keywords: Chemistry
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  • 29
    Publication Date: 2018-12-14
    Description: Theory has established the importance of geometric phase (GP) effects in the adiabatic dynamics of molecular systems with a conical intersection connecting the ground- and excited-state potential energy surfaces, but direct observation of their manifestation in chemical reactions remains a major challenge. Here, we report a high-resolution crossed molecular beams study of the H + HD -〉 H 2 + D reaction at a collision energy slightly above the conical intersection. Velocity map ion imaging revealed fast angular oscillations in product quantum state–resolved differential cross sections in the forward scattering direction for H 2 products at specific rovibrational levels. The experimental results agree with adiabatic quantum dynamical calculations only when the GP effect is included.
    Keywords: Chemistry
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  • 30
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-19
    Keywords: Chemistry
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  • 31
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-02
    Description: Exploration of intermediates that enable chemoselective cycloaddition reactions and expeditious construction of fused- or bridged-ring systems is a continuous challenge for organic synthesis. As an intermediate of interest, the oxyallyl cation has been harnessed to synthesize architectures containing seven-membered rings via (4+3) cycloaddition. However, its potential to access five-membered skeletons is underdeveloped, largely due to the thermally forbidden (3+2) pathway. Here, the combination of a tailored precursor and a Pd(0) catalyst generates a Pd-oxyallyl intermediate that cyclizes with conjugated dienes to produce a diverse array of tetrahydrofuran skeletons. The cycloaddition overrides conventional (4+3) selectivity by proceeding through a stepwise pathway involving a Pd-allyl transfer and ring closure sequence. Subsequent treatment of the (3+2) adducts with a palladium catalyst converts the heterocycles to the carbocyclic cyclopentanones.
    Keywords: Chemistry
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  • 32
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-09
    Keywords: Chemistry
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  • 33
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-12-14
    Keywords: Chemistry
    Print ISSN: 0036-8075
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  • 34
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-12-21
    Keywords: Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 35
    Publication Date: 2018-09-28
    Description: Some of the simplest and most powerful carbon-carbon bond forming strategies take advantage of readily accessible ubiquitous motifs: carbonyls and olefins. Here we report a fundamentally distinct mode of reactivity between carbonyls and olefins that differs from established acid-catalyzed carbonyl-ene, Prins, and carbonyl-olefin metathesis reaction paths. A range of epsilon, zeta-unsaturated ketones undergo Brønsted acid–catalyzed intramolecular cyclization to provide tetrahydrofluorene products via the formation of two new carbon-carbon bonds. Theoretical calculations and accompanying mechanistic studies suggest that this carbocyclization reaction proceeds through the intermediacy of a transient oxetane formed by oxygen atom transfer. The complex polycyclic frameworks in this product class appear as common substructures in organic materials, bioactive natural products, and recently developed pharmaceuticals.
    Keywords: Chemistry
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  • 36
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-05
    Keywords: Chemistry
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  • 37
    Publication Date: 2018-10-05
    Description: Photocatalysis based on optically active, "plasmonic" metal nanoparticles has emerged as a promising approach to facilitate light-driven chemical conversions under far milder conditions than thermal catalysis. However, an understanding of the relation between thermal and electronic excitations has been lacking. We report the substantial light-induced reduction of the thermal activation barrier for ammonia decomposition on a plasmonic photocatalyst. We introduce the concept of a light-dependent activation barrier to account for the effect of light illumination on electronic and thermal excitations in a single unified picture. This framework provides insight into the specific role of hot carriers in plasmon-mediated photochemistry, which is critically important for designing energy-efficient plasmonic photocatalysts.
    Keywords: Chemistry
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  • 38
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Keywords: Chemistry
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  • 39
    Publication Date: 2018-10-12
    Description: Reactions that form a product with the same reactive functionality as that of one of the starting compounds frequently end in oligomerization. As a salient example, selective aldol coupling of the smallest, though arguably most useful, enolizable aldehyde, acetaldehyde, with just one partner substrate has proven to be extremely challenging. Here, we report a highly enantioselective Mukaiyama aldol reaction with the simple triethylsilyl (TES) and tert -butyldimethylsilyl (TBS) enolates of acetaldehyde and various aliphatic and aromatic acceptor aldehydes. The reaction is catalyzed by recently developed, strongly acidic imidodiphosphorimidates (IDPi), which, like enzymes, display a confined active site but, like small-molecule catalysts, have a broad substrate scope. The process is scalable, fast, efficient (0.5 to 1.5 mole % catalyst loading), and greatly simplifies access to highly valuable silylated acetaldehyde aldols.
    Keywords: Chemistry
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  • 40
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-02
    Keywords: Chemistry
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  • 41
    Publication Date: 2018-11-16
    Description: Heterobiaryls composed of pyridine and diazine rings are key components of pharmaceuticals and are often central to pharmacological function. We present an alternative approach to metal-catalyzed cross-coupling to make heterobiaryls using contractive phosphorus C–C couplings, also termed phosphorus ligand coupling reactions. The process starts by regioselective phosphorus substitution of the C–H bonds para to nitrogen in two successive heterocycles; ligand coupling is then triggered via acidic alcohol solutions to form the heterobiaryl bond. Mechanistic studies imply that ligand coupling is an asynchronous process involving migration of one heterocycle to the ipso position of the other around a central pentacoordinate P(V) atom. The strategy can be applied to complex drug-like molecules containing multiple reactive sites and polar functional groups, and also enables convergent coupling of drug fragments and late-stage heteroarylation of pharmaceuticals.
    Keywords: Chemistry
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  • 42
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-16
    Keywords: Chemistry
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  • 43
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-03-16
    Description: Zhang et al . (Reports, 27 January 2017, p. 374) reported synthesis of a cyclo -N 5 – ion putatively stabilized in a solid-state salt by hydrogen bonding from surrounding counterions. We performed theoretical calculations suggesting that HN 5 would be favored over the anion in the reported pentazolate salt via proton transfer.
    Keywords: Chemistry
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  • 44
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-03-23
    Keywords: Chemistry
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  • 45
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-03-30
    Keywords: Chemistry
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  • 46
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-06
    Keywords: Chemistry
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  • 47
    Publication Date: 2018-04-06
    Description: Cross-coupling chemistry is widely applied to carbon-carbon bond formation in the synthesis of medicines, agrochemicals, and other functional materials. Recently, single-electron–induced variants of this reaction class have proven particularly useful in the formation of C(sp 2 )–C(sp 3 ) linkages, although certain compound classes have remained a challenge. Here, we report the use of sulfones to activate the alkyl coupling partner in nickel-catalyzed radical cross-coupling with aryl zinc reagents. This method’s tolerance of fluoroalkyl substituents proved particularly advantageous for the streamlined preparation of pharmaceutically oriented fluorinated scaffolds that previously required multiple steps, toxic reagents, and nonmodular retrosynthetic blueprints. Five specific sulfone reagents facilitate the rapid assembly of a vast set of compounds, many of which contain challenging fluorination patterns.
    Keywords: Chemistry
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  • 48
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-27
    Keywords: Chemistry
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  • 49
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-27
    Keywords: Chemistry
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  • 50
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-05-04
    Keywords: Chemistry
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  • 51
    Publication Date: 2018-05-04
    Description: Plasmon-induced chemical reactions of molecules adsorbed on metal nanostructures are attracting increased attention for photocatalytic reactions. However, the mechanism remains controversial because of the difficulty of direct observation of the chemical reactions in the plasmonic field, which is strongly localized near the metal surface. We used a scanning tunneling microscope (STM) to achieve real-space and real-time observation of a plasmon-induced chemical reaction at the single-molecule level. A single dimethyl disulfide molecule on silver and copper surfaces was dissociated by the optically excited plasmon at the STM junction. The STM study combined with theoretical calculations shows that this plasmon-induced chemical reaction occurred by a direct intramolecular excitation mechanism.
    Keywords: Chemistry
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  • 52
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-03-06
    Keywords: Chemistry
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  • 53
    Publication Date: 2018-02-16
    Description: Labinger argues that stepwise reaction of methane with water to produce methanol and hydrogen will never be commercially feasible because of its substoichiometric basis with respect to the active site and the requirement of a large temperature swing. This comment is not touching any new ground, beyond describing the thermodynamic feasibility, thermal cycling, and the role of water as discussed previously. Most important, it does not have a solid numerical basis.
    Keywords: Chemistry
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  • 54
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-16
    Keywords: Chemistry
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  • 55
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-01-26
    Keywords: Chemistry
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  • 56
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-23
    Keywords: Chemistry
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  • 57
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-23
    Keywords: Chemistry
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  • 58
    Publication Date: 2018-02-23
    Description: Currently, the only compounds known to support fixation and functionalization of dinitrogen (N 2 ) under nonmatrix conditions are based on metals. Here we present the observation of N 2 binding and reduction by a nonmetal, specifically a dicoordinate borylene. Depending on the reaction conditions under which potassium graphite is introduced as a reductant, N 2 binding to two borylene units results in either neutral (B 2 N 2 ) or dianionic ([B 2 N 2 ] 2– ) products that can be interconverted by respective exposure to further reductant or to air. The 15 N isotopologues of the neutral and dianionic molecules were prepared with 15 N-labeled dinitrogen, allowing observation of the nitrogen nuclei by 15 N nuclear magnetic resonance spectroscopy. Protonation of the dianionic compound with distilled water furnishes a diradical product with a central hydrazido B 2 N 2 H 2 unit. All three products were characterized spectroscopically and crystallographically.
    Keywords: Chemistry
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  • 59
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-13
    Keywords: Chemistry
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  • 60
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-03-23
    Keywords: Chemistry
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  • 61
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-23
    Keywords: Chemistry
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  • 62
    Publication Date: 2018-03-06
    Description: Intramolecular insertion of metal nitrenes into carbon-hydrogen bonds to form -lactam rings has traditionally been hindered by competing isocyanate formation. We report the application of theory and mechanism studies to optimize a class of pentamethylcyclopentadienyl iridium(III) catalysts for suppression of this competing pathway. Modulation of the stereoelectronic properties of the auxiliary bidentate ligands to be more electron-donating was suggested by density functional theory calculations to lower the C–H insertion barrier favoring the desired reaction. These catalysts transform a wide range of 1,4,2-dioxazol-5-ones, carbonylnitrene precursors easily accessible from carboxylic acids, into the corresponding -lactams via sp 3 and sp 2 C–H amidation with exceptional selectivity. The power of this method was further demonstrated by the successful late-stage functionalization of amino acid derivatives and other bioactive molecules.
    Keywords: Chemistry
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  • 63
    Publication Date: 2018-01-19
    Description: Chemical manufacturing is often done at large facilities that require a sizable capital investment and then produce key compounds for a finite period. We present an approach to the manufacturing of fine chemicals and pharmaceuticals in a self-contained plastic reactionware device. The device was designed and constructed by using a chemical to computer-automated design (ChemCAD) approach that enables the translation of traditional bench-scale synthesis into a platform-independent digital code. This in turn guides production of a three-dimensional printed device that encloses the entire synthetic route internally via simple operations. We demonstrate the approach for the -aminobutyric acid receptor agonist, (±)-baclofen, establishing a concept that paves the way for the local manufacture of drugs outside of specialist facilities.
    Keywords: Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-01-26
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 65
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-16
    Description: The comment and response concerning the report of oxidation of methane to methanol by water (Reports, 5 May 2017, p. 523) do not fully capture the implications of thermodynamic limitations. A nonisothermal process in which each cycle requires a large temperature swing and permits only substoichiometric methane conversion surely could not be carried out on any practical scale.
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 66
    Publication Date: 2018-03-16
    Description: Single adatoms are expected to participate in many processes occurring at solid surfaces, such as the growth of graphene on metals. We demonstrate, both experimentally and theoretically, the catalytic role played by single metal adatoms during the technologically relevant process of graphene growth on nickel (Ni). The catalytic action of individual Ni atoms at the edges of a growing graphene flake was directly captured by scanning tunneling microscopy imaging at the millisecond time scale, while force field molecular dynamics and density functional theory calculations rationalize the experimental observations. Our results unveil the mechanism governing the activity of a single-atom catalyst at work.
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences ,