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791.
Poly-β-hydroxybuyrate (PHB) is a carbon—energy storage material which is accumulated as intracellular granule in variety of
microorganism under nutrient starved conditions. Solid PHB is a biodegradable thermoplastic polymer and is utilizable in various
ways similar to many conventional plastics. Ralstonia eutropha (Alcaligenes sp.), a gram negative bacteria accumulates PHB as insoluble granules inside the cells when nutrients other than carbon are
limited. In this report effort has been made to analyze PHB granule synthesis inside Alcaligenes sp. NCIM 5085 by transmission electron microscopy and qualitative estimation of PHB was carried out by fourier transform
infrared spectroscopy which provide better precision compared to other conventional techniques previously applied for PHB
determination. Maximum PHB concentration of 2.20 ± 0.40 g/L and cell biomass of 3.42 ± 0.20 g/L was obtained after 48.0 h
of fermentation. Leudking-Piret equation deduced mixed growth associated product formation which varies from earlier reports. 相似文献
792.
K. Abdel Tawab M. M. Magida Sayeda M. Ibrahim 《Journal of Polymers and the Environment》2011,19(2):440-446
Blends of water—soluble polymers based on Poly vinyl alcohol (PVA) and Polyethylene glycol (PEG) have been prepared by the
solution casting technique. The effect of various doses of γ-radiation on the structural properties of PVA/PEG polymer blends
with all its compositions has been investigated. From the visual observation of all the blend compositions, it was found that,
the best compatibility of the blend is up to 40% PVA/60%PEG. The structure–Property behavior of all the prepared blends before
and after γ-irradiation was investigated by IR Spectroscopy, thermogravimetric analysis (TGA), mechanical properties and Scanning
electron microscope (SEM). The gel content and the swelling behavior of the PVA/PEG blends were investigated. It was found
that the gel content increases with increasing irradiation dose and PVA concentration in the blend. Swelling percent increased
as the composition of PEG increased in the blend. The results obtained by FTIR analysis and SEM confirm the existence of possible
interaction between PVA and PEG homopolymers. TGA of PVA/PEG blend, before and after γ-irradiation, showed that the unirradiated
and irradiated PVA/PEG blends are more stable against thermal decomposition than pure PVA. Improvement in tensile mechanical
properties of PVA/PEG blends was occurred. 相似文献
793.
N. Mithil Kumar K. Varaprasad G. Ramachandra Reddy G. Siva Mohan Reddy Y. Sivabharathi G. Venkata Subba Reddy S. Venkata Naidu 《Journal of Polymers and the Environment》2011,19(1):225-229
Synthesis and characterization of novel biodegradable, water soluble and optically active DL-malic acid (DMA) and citric acid
(CA) copolymers were studied for possible use as antibacterial agents. The copolymers were synthesized by direct bulk melt
condensation in the absence of a catalyst above 150 °C. Characterization of obtained copolymers was carried out with the help
of infrared absorption spectra, differential scanning calorimetry and thermo gravimetric analysis. The antibacterial activity
of copolymers against bacteria was investigated. The results obtained shows the above copolymers possess a broad wound dressing
activity against different types of bacteria and may be useful as antibacterial agents. 相似文献
794.
Kevin A. Morin John A. Cherry Nand K. Dav Tjoe P. Lim Al J. Vivyurka 《Journal of contaminant hydrology》1988,2(4)
In this second paper of a series on groundwater seepage from uranium tailings, the general geochemical behavior of radionuclides is described and then applied to data from the field site, Seepage Area A of the Nordic Main impoundment near Elliot Lake, Ontario. The delineation of radionuclide behavior requires (1) the calculation of total element concentration by the summation of concentrations of each element's isotopes (the isotopic concentrations are calculated from the isotopes' radioactivities), (2) the evaluation of solid-liquid interactions using total element concentrations, and (3), for particular isotopes, the evaluation of the extent to which parental geochemical behavior causes a deviation in the isotope's behavior from that of its total element. A computerized speciation program, WATRAD, is used to evaluate aqueous complexation and mineral saturation indices of radium, actinium, thorium, and uranium. Data from Seepage Area A on isotopes of these four elements plus 210Pb show that the geochemical behavior of radionuclides can be best defined on an individual isotopic basis rather than on an elemental basis. 相似文献
795.
Mingxuan Mao Li Zhang Qichang Duan O.J.K Oghorada Pan Duan Bei Hu 《International Journal of Green Energy》2017,14(8):694-702
The power-voltage (P-V) characteristic curves of a PV array are nonlinear and have multiple peaks under partially shaded conditions (PSCs). This paper proposes a novel maximum power point tracking (MPPT) method for a PV system with reduced steady-state oscillation based on a two-stage particle swarm optimization (PSO) algorithm. The grouping method of the shuffled frog leaping algorithm (SFLA) is incorporated in the basic PSO algorithm (PSO-SFLA), ensuring fast and accurate searching of the global extremum. An adaptive speed factor is also introduced into the improved PSO to further enhance its convergence speed. Test results show that the proposed method converges in less than half the time taken by the conventional PSO method, and the power is improved by 33% under the worst PSCs, which confirms the superiority of the proposed method over the standard PSO algorithm in terms of tracking speed and steady-state oscillations under different PSCs. 相似文献
796.
Rudi Dungani Abdulwahab F. Owolabi Chaturbhuj K. Saurabh H. P. S. Abdul Khalil Paridah M. Tahir C. I. C. M. Hazwan Kamoldeen A. Ajijolakewu M. M. Masri E. Rosamah P. Aditiawati 《Journal of Polymers and the Environment》2017,25(3):692-700
The objective of this work was to isolate cellulose nanocrystal (CNC) from oil palm fronds (Elaeis guineensis) and its subsequent characterization. Isolation involves sodium hydroxide/anthraquinone pulping with mechanical refining followed by total chlorine free bleaching (includes oxygen delignification, hydrogen peroxide oxidation and peracetic acid treatment) before acid hydrolysis. Bleaching significantly decreased kappa number and increased α-cellulose percentage of fibers as confirmed by Technical Association of the Pulp and Paper Industry standards. Transmission electron microscopy (TEM), X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis revealed that acid hydrolysis along with bleaching improved crystallinity index and thermal stability of the extracted nanocrystals. It was observed that CNC maintained its cellulose 1 polymorph despite hydrolysis treatment. Mean diameter as observed by TEM and average fiber aspect ratio of obtained CNC was 7.44 ± 0.17 nm and 16.53 ± 3.52, respectively making it suitable as a reinforcing material for nanocomposite. 相似文献
797.
This paper presents a theoretical comparison between fuel cell (FC) power train and conventional petrol driven propulsion system. FC has potential to reduce the CO2-emissions from road. However, FC power trains require energy storing device, to meet the peak power during extreme drive situations and also able to recover the kinetic energy of the vehicle during break operation. The proposed system includes a polymer electrolyte membrane fuel cell (PEMFC) based drive train and a super capacitor connected in parallel. The system is designed and dimensioned for a conventional petrol driven propulsion system of the Mercedes B-Class160. The feasibility study also includes comparison between the existing conventional systems. It is shown that although FC power train is heavier compared to existing system, urban performance is better and produces no CO2 and other harmful emissions. 相似文献
798.
799.
A decision framework for possible remediation of contaminated sediments in the River Kymijoki, Finland 总被引:1,自引:1,他引:0
Verta M Kiviranta H Salo S Malve O Korhonen M Verkasalo PK Ruokojärvi P Rossi E Hanski A Päätalo K Vartiainen T 《Environmental science and pollution research international》2009,16(1):95-105
Background, aim, and scope The paper describes the spatial contamination of the River Kymijoki, South-Eastern Finland, and the coastal region of the
Gulf of Finland with PCDD/Fs and mercury. The findings of ecotoxicologial and human health studies are also reported, including
environmental and human risk assessments. Sediments from the River Kymijoki, draining into the Gulf of Finland, have been
heavily polluted by the pulp and paper industry and by chemical industries. A wood preservative, known as Ky-5, was manufactured
in the upper reaches of the river between 1940 and 1984 causing severe pollution of river sediments with polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF). Moreover, the sediments have been polluted with mercury (Hg) from chlor-alkali production
and the use of Hg as a slimicide in pulp and paper manufacturing.
Materials and methods An extensive sediment survey was conducted as well as sediment transport modeling, toxicity screening of sediment invertebrates,
and a survey of contaminant bioaccumulation in invertebrates and fish. Studies on human exposure to PCDD/Fs and the possible
effects on hypermineralization of teeth as well as an epidemiological study to reveal increased cancer risk were also conducted.
An assessment of the ecological and human health risks with a null hypothesis (no remediation) was undertaken.
Results The sediment survey revealed severe contamination of river and coastal sediments with PCDD/Fs and Hg. The total volume of
contaminated sediments was estimated to reach 5 × 106 m3 and hot spots with extremely high concentrations (max 292,000 ng g−1 or 1,060 ng I-TEQ g−1 d.w.) were located immediately downstream from the pollution source (approximately 90,000 m3). Sediment contamination was accompanied by changes in benthic assemblages, but direct effects were masked by many factors.
The fish showed only slightly elevated PCDD/F levels in muscle, but orders of magnitude higher in the liver compared with
reference freshwater sites and the Baltic Sea. The concentrations in human fat did not reveal high human exposure in the Kymijoki
area in general and was lower than in sea fishermen. The relative risk for total cancer among farmers was marginally higher
(RR = 1.13) among those living close to the river, compared with farmers living further away, and the possibility of increased
cancer risk cannot be ruled out. A conservative risk assessment revealed that the present probability of exceeding the WHO
upper exposure limit of 4 pg WHO-TEQ kg−1 d−1 for PCDD/Fs and DL-PCBs was 6%. The probability of exceeding the WHO limit value of 0.23 μg kg−1 d−1 for methyl mercury was estimated to be notably higher at 62%. Based on these studies and the estimated risks connected with
different remediation techniques a general remediation plan with cost benefit analysis was generated for several sub-regions
in the river. Dredging, on-site treatment, and a close disposal of the most contaminated sediments (90,000 m3) was suggested as the first phase of the remediation. The decision regarding the start of remediation will be made during
autumn 2008.
Conclusions The sediments in the River Kymijoki are heavily polluted with PCDD/Fs and mercury from earlier chlorophenol, chlor-alkali,
and pulp and paper manufacturing. A continuous transport of contaminants is taking place to the Gulf of Finland in the Baltic
Sea. The highly increased PCDD/F and Hg levels in river sediments pose an ecotoxicological risk to benthic fauna, to fish-eating
predators and probably to human health. The risks posed by mercury exceed those from PCDD/Fs and need to be evaluated for
(former) chlor-alkali sites and other mercury releasing industries as one basis for remediation decision making.
Recommendations and perspectives The studies form the basis of a risk management strategy and a plan for possible remediation of contaminated sediments currently
under consideration in the Southeast Finland Regional Environment Centre. It is recommended that a detailed restoration plan
for the most seriously contaminated areas should be undertaken. Based on current knowledge, the restoration of the whole river
is not feasible, considering the current risk caused by the contaminated sediment in the river and the costs of an extensive
restoration project. The experiences gained in the present case should be utilized in the evaluation of PCDD/F- and mercury-contaminated
sites in other countries. The case demonstrates that the historic reservoirs are of contemporary relevance and should be addressed,
e.g., in the national implementation plans of the Stockholm Convention.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
800.
Zusammenfassung
Hintergrund, Ziel und Zweck Borkenbewohnende (epiphytische) Flechten reagieren sehr empfindlich auf verschiedene Umwelteinflüsse wie Stoffgehalte in
der Atmosph?re und Temperaturen. Sie haben als Bioindikatoren für Luftverunreinigungen einen hohen Stellenwert bei Umweltuntersuchungen.
Basierend auf einer 1989 durchgeführten Kartierung borkenbewohnender (epiphytischer) Flechten in einem landwirtschaftlich
intensiv genutzten Raum Nordwestdeutschlands erfolgte 2007 eine Wiederholungsuntersuchung. Dabei galt es, m?gliche Ver?nderungen
der Immissionssituation und des Klimas zu erkennen.
Material und Methoden Die Studie basiert auf einer vergleichenden Kartierung epiphytischer Flechten von 355 Tr?gerb?umen an 45 Monitoringpunkten.
Die angewandte Methode orientiert sich an der 1989 angewandten halb-quantitativen Erfassung.
Ergebnisse Es stellten sich gravierende Ver?nderungen in der Vegetation rindenbewohnender Flechten heraus. Insgesamt war eine Erh?hung
der Artenzahl an nahezu allen Monitoringpunkten festzustellen. Es wurde eine sehr starke Abnahme s?uretoleranter Arten und
eine deutliche Zunahme basen- und n?hrstofffordernder Flechtenarten festgestellt. Darüber hinaus zeigte sich eine deutliche
Zunahme w?rmeliebender Flechtenarten mit einem Verbreitungsschwerpunkt in Südeuropa bei gleichzeitigem Rückgang von Arten
mit einem boreal-montanem Verbreitungsschwerpunkt.
Diskussion Die festgestellte Entwicklung steht im Einklang mit überregionalen Beobachtungen. Sie wird im Wesentlichen auf eine gro?r?umig
ver?nderte Immissionssituation, d. h. einer Abnahme der atmosph?rischen SO2-Belastung und Zunahme der Ammoniakbelastung zurückgeführt. Ebenso treten deutliche Auswirkungen der Klimaerw?rmung hervor.
Schlussfolgerungen Mit relativ geringem Untersuchungsaufwand lie?en sich Ver?nderungen bei den epiphytischen Flechten in den letzten 18 Jahren
aufzeigen. Diese sind relevant für die Beurteilung regional und kleinr?umig ver?nderter Umweltbedingungen, die auch für andere
Organismen und ?kosysteme l?ngerfristig von gro?er Bedeutung sind.
Empfehlungen und Ausblick Unter Verwendung standardisierter Methoden vermitteln epiphytische Flechten ein differenziertes Bild der Luftbelastungssituation
in Ballungsr?umen und in landwirtschaftlich genutzten Regionen. Darüber hinaus sind sie offensichtlich gute Indikatoren für
Temperatur?nderungen ihrer Umgebung. Weiterer Forschungsbedarf besteht für die Verwendung epiphytischer Flechten zum Biomonitoring
von Klimaver?nderungen.
相似文献