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1.
Nanoscale ; 12(15): 8268-8276, 2020 Apr 21.
Article in English | MEDLINE | ID: mdl-32236177

ABSTRACT

We report on the phosphonic acid route for the grafting of functional molecules, optical switch (dithienylethene diphosphonic acid, DDA), on La0.7Sr0.3MnO3 (LSMO). Compact self-assembled monolayers (SAMs) of DDA are formed on LSMO as studied by topographic atomic force microscopy (AFM), ellipsometry, water contact angle measurements and X-ray photoemission spectroscopy (XPS). The conducting AFM measurements show that the electrical conductance of LSMO/DDA is about 3 decades below that of a bare LSMO substrate. Moreover, the presence of the DDA SAM suppresses the known conductance switching of the LSMO substrate that is induced by mechanical and/or bias constraints during C-AFM measurements. A partial light-induced conductance switching between the open and closed forms of the DDA is observed for the LSMO/DDA/C-AFM tip molecular junctions (closed/open conductance ratio of about 8). We show that, in the case of long-time exposure to UV light, this feature can be masked by a non-reversible decrease (a factor of about 15) of the conductance of the LSMO electrode.

2.
Langmuir ; 33(10): 2677-2687, 2017 03 14.
Article in English | MEDLINE | ID: mdl-28221811

ABSTRACT

The localized deformation of molecular monolayers constrained between the spherical surfaces of Au nanoparticles is studied by means of molecular dynamics simulations. Alkyl or polyethylene glycol long-chain molecules were homogeneously distributed over the curved Au surface, pushed against each other by repeated cycles of force relaxation and constant-volume equilibration at temperatures increasing from 50 to 300 K before being slowly quenched to near-zero temperature. Plots of minimum configurational energy can be obtained as a function of the nanoparticle distance, according to different directions of approach; therefore, such simulations describe a range of deformations, from perfectly uniaxial compression to a combination of compression and shear. Despite the relative rigidity of molecular backbones, the deformation is always found to be localized at the interface between the opposing molecular monolayers. We find that shorter ligands can be more densely packed on the surface but do no interdigitate upon compression; they respond to the applied force by bending and twisting, thus changing their conformation while remaining disjointed. On the contrary, longer ligands attain lower surface densities and can interprenetrate when the nanoparticles are compressed against each other; such molecules remain rather straight and benefit from the increased overlap to maximize the adhesion by dispersion forces. The apparent Young's and shear moduli of a dense nanostructure, composed of a triangular arrangement of identical MUDA-decorated Au nanoparticles, are found to be smaller than estimates indirectly deduced by atomic-force experiments but quite close to previous computer simulations of molecular monolayers on flat surfaces and of bulk nanoparticle assemblies.

3.
Rev Sci Instrum ; 82(3): 036101, 2011 Mar.
Article in English | MEDLINE | ID: mdl-21456803

ABSTRACT

The measurement of local surface potentials by Kelvin force microscopy (KFM) can be sensitive to external perturbations which lead to artifacts such as strong dependences of experimental results (typically in a ∼1 V range) with KFM internal parameters (cantilever excitation frequency and/or the projection phase of the KFM feedback-loop). We analyze and demonstrate a correction of such effects on a KFM implementation in ambient air. Artifact-free KFM measurements, i.e., truly quantitative surface potential measurements, are obtained with a ∼30 mV accuracy.

4.
Water Sci Technol ; 63(4): 733-40, 2011.
Article in English | MEDLINE | ID: mdl-21330721

ABSTRACT

The potential of membrane bioreactor (MBR) systems to remove organic micropollutants was investigated at different scales, operational conditions, and locations. The effluent quality of the MBR system was compared with that of a plant combining conventional activated sludge (CAS) followed by ultrafiltration (UF). The MBR and CAS-UF systems were operated and tested in parallel. An MBR pilot plant in Israel was operated for over a year at a mixed liquor suspended solids (MLSS) range of 2.8-10.6 g/L. The MBR achieved removal rates comparable to those of a CAS-UF plant at the Tel-Aviv wastewater treatment plant (WWTP) for macrolide antibiotics such as roxythromycin, clarithromycin, and erythromycin and slightly higher removal rates than the CAS-UF for sulfonamides. A laboratory scale MBR unit in Berlin - at an MLSS of 6-9 g/L - showed better removal rates for macrolide antibiotics, trimethoprim, and 5-tolyltriazole compared to the CAS process of the Ruhleben sewage treatment plant (STP) in Berlin when both were fed with identical quality raw wastewater. The Berlin CAS exhibited significantly better benzotriazole removal and slightly better sulfamethoxazole and 4-tolyltriazole removal than its MBR counterpart. Pilot MBR tests (MLSS of 12 g/L) in Aachen, Germany, showed that operating flux significantly affected the resulting membrane fouling rate, but the removal rates of dissolved organic matter and of bisphenol A were not affected.


Subject(s)
Bioreactors , Environmental Pollutants/isolation & purification , Membranes, Artificial , Organic Chemicals/isolation & purification , Sewage , Ultrafiltration/methods , Waste Management/methods , Anti-Bacterial Agents/isolation & purification , Carbon/chemistry , Cities , Environmental Pollutants/chemistry , Organic Chemicals/chemistry , Solubility
5.
Aliment Pharmacol Ther ; 32(9): 1154-62, 2010 Nov.
Article in English | MEDLINE | ID: mdl-21039677

ABSTRACT

BACKGROUND: Reliable epidemiological data for portal vein thrombosis are lacking. AIMS: To investigate the incidence, prevalence and survival rates for patients with portal vein thrombosis. METHODS: Retrospective multicentre study of all patients registered with the diagnosis of portal vein thrombosis between 1995 and 2004. RESULTS: A total of 173 patients (median age 57 years, 93 men) with portal vein thrombosis were identified and followed up for a median of 2.5 years (range 0-9.7). The mean age-standardized incidence and prevalence rates were 0.7 per 100,000 per year and 3.7 per 100,000 inhabitants, respectively. Liver disease was present in 70 patients (40%), malignancy in 27%, thrombophilic factors in 22% and myeloproliferative disorders in 11%. Two or more risk factors were identified in 80 patients (46%). At diagnosis, 65% were put on anticoagulant therapy. Thrombolysis, TIPS, surgical shunting and liver transplantation were performed in 6, 3, 2 and 8 patients, respectively. The overall survival at 1 year and 5 years was 69% and 54%. In the absence of malignancy and cirrhosis, the survival was 92% and 76%, respectively. CONCLUSIONS: The incidence and prevalence rates of portal vein thrombosis were 0.7 per 100,000 inhabitants per year and 3.7 per 100,000 inhabitants, respectively. Concurrent prothrombotic risk factors are common. The prognosis is variable and highly dependent on underlying disease.


Subject(s)
Portal Vein , Venous Thrombosis/epidemiology , Adolescent , Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Multivariate Analysis , Prevalence , Retrospective Studies , Sweden/epidemiology , Venous Thrombosis/physiopathology , Venous Thrombosis/therapy , Young Adult
6.
Water Sci Technol ; 62(6): 1265-73, 2010.
Article in English | MEDLINE | ID: mdl-20861539

ABSTRACT

Managed Aquifer Recharge (MAR) with reclaimed water plays a particular role in water stress mitigation, due to both the large potential benefits achieved in terms of sustainable water resources management as well as the complexity of the planning and implementation. This paper focuses on the role of policy in establishing water quality related legal frameworks that are crucial for MAR development. It analyses and compares the current practice of shaping boundary conditions, particularly in a European context but with some international comparison. The work reports on the legal aspects considered most relevant for MAR in the European Union and summarises issues addressed in aquifer recharge regulations and guidelines. Some potential actions are proposed to develop a suitable guidance framework for further exploitation of MAR benefits.


Subject(s)
Conservation of Natural Resources , Fresh Water/analysis , Government Regulation , Water Purification/methods , Conservation of Natural Resources/legislation & jurisprudence , Conservation of Natural Resources/methods , Europe , Guidelines as Topic , Water Purification/legislation & jurisprudence , Water Purification/standards , Water Supply/analysis , Water Supply/legislation & jurisprudence , Water Supply/standards
7.
Talanta ; 82(1): 92-8, 2010 Jun 30.
Article in English | MEDLINE | ID: mdl-20685441

ABSTRACT

Landfill or digester gas can contain man-made volatile methylsiloxanes (VMS), usually in the range of a few milligrams per normal cubic metre (Nm(3)). Until now, no standard method for siloxane quantification exists and there is controversy with respect to which sampling procedure is most suitable. This paper presents an analytical and a sampling procedure for the quantification of common VMS in biogas via GC-MS and polyvinyl fluoride (Tedlar) bags. Two commercially available Tedlar bag models are studied. One is equipped with a polypropylene valve with integrated septum, the other with a dual port fitting made from stainless steel. Siloxane recovery in landfill gas samples is investigated as a function of storage time, temperature, surface-to-volume ratio and background gas. Recovery was found to depend on the type of fitting employed. The siloxanes sampled in the bag with the polypropylene valve show high and stable recovery, even after more than 30 days. Sufficiently low detection limits below 10 microg Nm(-3) and good reproducibility can be achieved. The method is therefore well applicable to biogas, greatly facilitating sampling in comparison with other common techniques involving siloxane enrichment using sorption media.


Subject(s)
Gases/chemistry , Polyethylene Glycols/chemistry , Siloxanes/analysis , Limit of Detection , Polyethylene Terephthalates , Reproducibility of Results , Temperature , Time Factors , Volatilization , Waste Management , Water/chemistry
8.
Water Sci Technol ; 62(4): 915-9, 2010.
Article in English | MEDLINE | ID: mdl-20729596

ABSTRACT

Many phenolic compounds show high boiling points, low molecular weights, moderate polarities or high toxicities. Therefore, conventional wastewater treatment is limited or expensive. Recycling of the separated compounds is often not possible. But, if liquid-liquid reactive extraction is linked to a non-porous membrane, some or all of the above mentioned limitations may be overcome. The key element is a composite membrane with a dense, hydrophobic top layer which avoids the mixing of the two aqueous fluid streams. The dilute phenol stream is one of them, the other is caustic soda as stripping solvent. Since the basics of this technology have been discussed before, the scope of this study is to facilitate process implementation and integration. To this end, a life cycle assessment framework is used to identify the optimal equipment size for the treatment of wastewater that may, for example, originate from the production of polycarbonate. Limiting for this application is not the environmental performance though, but most likely process economics.


Subject(s)
Life Cycle Stages , Phenols/isolation & purification , Animals , Ecosystem , Environmental Monitoring/methods , Global Warming , Membranes, Artificial , Oxygen Consumption , Polycarboxylate Cement , Silicon , Sodium Hydroxide , Solvents , Water/analysis
9.
Nanotechnology ; 21(22): 225706, 2010 Jun 04.
Article in English | MEDLINE | ID: mdl-20453285

ABSTRACT

Electrostatic nanopatterning of electret thin films by atomic force microscopy (AFM) has emerged as an alternative efficient tool for the directed assembly of nano-objects on surfaces. High-resolution charge imaging of such charge patterns can be performed by AFM-based Kelvin force microscopy (KFM). Nevertheless, quantitative analysis of KFM surface potential mappings is not trivial because of side-capacitance effects induced by the tip cone and the cantilever of the scanning probe. In this paper, we developed numerical simulations of KFM measurements taking into account these artifacts, so as to estimate the actual surface charge density of square charge patterns (nominal sizes ranging from 100 nm to 10 microm) written by AFM into polymethylmethacrylate (PMMA) thin films. This work revealed that, under our conditions, such charge patterns exhibit a surface charge density between 1.5 x 10(-3) and 3.8 x 10(-3) C m(-2), depending on the assumed depth of injected charges. These results are crucial to quantify the actual electric field generated by such charge patterns and thus the electrostatic forces responsible for the directed assembly of nano-objects onto these electrostatic traps.

10.
Bioresour Technol ; 101(9): 2913-23, 2010 May.
Article in English | MEDLINE | ID: mdl-20061140

ABSTRACT

This paper reviews technologies for the removal of volatile methyl siloxanes (VMS) from biogas. More than 20 years after identifying silicon dioxide in gas engines running on landfill and sewage gas, three technologies are commercially available to remove siloxanes today: adsorption, absorption and deep chilling. Newer concepts based on technologies other than sorption or condensation have not yet gained access to commercial biogas purification. These emerging siloxane removal concepts include biotrickling filters, catalysts, membranes, and in the case of sewage gas, sludge stripping, peroxidation and filtration at point inlet source. This work introduces the main principles of commercial siloxane removal systems and reviews scientific progress in the field over the last decade.


Subject(s)
Gases/chemistry , Siloxanes/isolation & purification , Waste Disposal, Fluid/methods , Water Pollutants, Chemical/isolation & purification , Biodegradation, Environmental , Catalysis , Siloxanes/chemistry
11.
Ultramicroscopy ; 110(2): 162-9, 2010 Jan.
Article in English | MEDLINE | ID: mdl-19939564

ABSTRACT

The acquisition rate of all scanning probe imaging techniques with feedback control is limited by the dynamic response of the control loops. Performance criteria are the control loop bandwidth and the output signal noise power spectral density. Depending on the acceptable noise level, it may be necessary to reduce the sampling frequency below the bandwidth of the control loop. In this work, the frequency response of a vacuum Kelvin force microscope with amplitude detection (AM-KFM) using a digital signal processing (DSP) controller is characterized and optimized. Then, the main noise source and its impact on the output signal is identified. A discussion follows on how the system design can be optimized with respect to output noise. Furthermore, the interaction between Kelvin and distance control loop is studied, confirming the beneficial effect of KFM on topography artefact reduction in the frequency domain. The experimental procedure described here can be generalized to other systems and allows to locate the performance limitations.

12.
Water Sci Technol ; 60(1): 251-9, 2009.
Article in English | MEDLINE | ID: mdl-19587422

ABSTRACT

Direct capillary nanofiltration was tested for reclamation of tertiary effluent from a municipal wastewater treatment plant. This process can be regarded as a promising treatment alternative for high quality water reuse applications when combined with powdered activated carbon for enhanced removal of organic compounds. The nanofiltration was operated at flux levels between 20 and 25 L/(m2 h) at a transmembrane pressure difference of 2-3 bar for approximately 4,000 operating hours. The study was conducted with PAC doses in the range from 0 to 50 mg/L. The plant removal for DOC ranged from 88-98%. The sulfate retention of the membrane filtration process was between 87 and 96%. The process provided a consistently high permeate quality with respect to organic and inorganic key parameters.


Subject(s)
Charcoal/chemistry , Filtration/methods , Water Purification/methods , Adsorption , Reproducibility of Results
13.
Water Sci Technol ; 58(9): 1849-55, 2008.
Article in English | MEDLINE | ID: mdl-19029728

ABSTRACT

Soluble organic macromolecules are ubiquitous in activated sludge supernatant. For the operation of membrane bioreactors (MBR) this group of substances is considered as the dominant factor causing severe membrane fouling due to the concentration polarisation phenomenon. The well established critical flux concept for the characterisation of membrane bioreactor's operation limits is based on filtration data only. As there is an cause-and-effect relation between the partial retention of organic compounds and the limited flux according the critical flux concept the aim of this study was to draw a comparison between different permeate fluxes on the retention of organic macromolecules. Thus, a municipal pilot-scale MBR with three capillary hollow fibre membrane modules was operated in sub critical, critical and supercritical flux mode, respectively and the retention of macromolecules was quantified by size exclusion chromatography. Three permeate extraction pumps allow a simultaneous operation with different operational conditions for each membrane module and proved the crucial impact of permeate flux on the fouling rate. The interchange of these conditions gave evidence of an optimised start-up procedure for MBRs characterised by higher permeate fluxes. An increased flux causes both a higher retention of soluble macromolecules and subsequent a higher fouling rate.


Subject(s)
Bioreactors , Membranes, Artificial , Polymers/chemistry , Chromatography, Gel , Pilot Projects , Sewage
14.
Water Sci Technol ; 58(8): 1699-706, 2008.
Article in English | MEDLINE | ID: mdl-19001728

ABSTRACT

Direct capillary nanofiltration also in combination with an upstream powdered activated carbon treatment was tested for high quality water reuse of tertiary effluent from a municipal wastewater treatment plant. Two endocrine disruptors (BPA and EE2) and two cytostatics (CytR and 5-FU) were spiked in concentrations of 1 to 2 microg/L to evaluate the process performance. In direct NF the real total removal of the micropollutants was between 5 and 40%. Adsorption to the membrane played a major role leading to a seemingly total removal between 35 and 70%. Addition of powdered activated carbon and lignite coke dust largely reduced the influence from adsorption to the membrane and increased the total removal to >95 to 99.9% depending on the PAC type and dose. The cytostatics showed already in direct NF a very high removal due to unspecified losses. Further investigations are ongoing to understand the underlying mechanism. The PAC/NF process provided a consistently high permeate quality with respect to bulk and trace organics.


Subject(s)
Carbon/chemistry , Endocrine Disruptors/isolation & purification , Filtration/methods , Water Pollutants, Chemical/isolation & purification , Adsorption , Powders
15.
Water Sci Technol ; 57(5): 707-14, 2008.
Article in English | MEDLINE | ID: mdl-18401142

ABSTRACT

Due to the depletion of mineral phosphorus resources there is an increasing demand for efficient phosphorus recovery technologies. In this study the potential of nanofiltration to recover phosphorus from pre-treated sewage sludge is investigated. The efficiency of three commercial nanofiltration membranes (Desal 5DK, NP030; MPF34) was tested using model solutions. Desal 5DK showed the best selectivity for phosphorus. A pH of lower than 1.5 was found to be most suitable. Desal 5DK was used on four different sewage sludge ash eluates and on one sewage sludge. In these experiments it was shown that a separation of phosphorus from undesired components such as heavy metals was possible with significant variations in the efficiency for the different ash and sludge types. Additionally the achievable product recovery was investigated with model solutions. A product recovery of 57.1% was attained for pH 1 and 41.4% for pH 1.5.


Subject(s)
Nanotechnology/methods , Phosphorus/isolation & purification , Sewage/analysis , Filtration/methods , Hydrogen-Ion Concentration
16.
Water Sci Technol ; 57(6): 821-7, 2008.
Article in English | MEDLINE | ID: mdl-18413940

ABSTRACT

Direct nanofiltration and nanofiltration combined with powdered activated carbon known as the PAC/NF process were tested regarding the removal of effluent organic matter for reclamation of tertiary effluent from a municipal wastewater treatment plant. They can be regarded as a promising treatment alternative for high quality water reuse applications, especially for direct injection. The total removal for DOC was above 90% with permeate concentrations below 0.5 mg/l. Size exclusion chromatography and fluorescence EEM proved to trace origin of the organic matter even in low concentration ranges. The type and dosage of adsorbent influences the process performance significantly and allows process optimization.


Subject(s)
Conservation of Natural Resources/methods , Organic Chemicals/isolation & purification , Waste Disposal, Fluid/methods , Filtration/instrumentation , Filtration/methods , Nanotechnology/instrumentation , Nanotechnology/methods , Organic Chemicals/chemistry , Waste Disposal, Fluid/instrumentation , Water Purification/instrumentation , Water Purification/methods , Water Supply/analysis
17.
Ultramicroscopy ; 108(8): 773-81, 2008 Jul.
Article in English | MEDLINE | ID: mdl-18342448

ABSTRACT

We investigate the gap-voltage control loop in a Kelvin force microscopy setup with simultaneous non-contact topography imaging. The Kelvin controller electrostatically excites the second resonance of the cantilever at about 6.3 times the first resonance frequency and adjusts the DC component of the gap voltage to cancel the oscillation amplitude at this frequency, while the non-contact topography imaging is based on a frequency control loop that maintains a constant frequency of the mechanically excited first resonance of the cantilever by adjusting the tip-sample separation. Due to the self-excitation of the first resonance in our setup, it has to be considered that the electrostatic excitation at the second resonance frequency is applied to a closed feedback loop and cannot be considered as a simple superposition to the oscillation at the first resonance frequency. In particular, special care has to be taken about internal capacitive crosstalk between the tip bias and the cantilever deflection output signal. It is shown that such a coupling cannot be corrected by subtraction of a constant offset at the demodulator output since the crosstalk is sent into the self-excitation loop and is multiplied by the closed loop transfer function. We present a circuit that actively compensates, outside the vacuum environment, the internal crosstalk by adding to the deflection output a dephased fraction of the electrostatic excitation signal.

18.
Water Sci Technol ; 57(1): 99-107, 2008.
Article in English | MEDLINE | ID: mdl-18192746

ABSTRACT

Solutions to global water stress problems are urgently needed yet must be sustainable, economical and safe. The utilisation of alternative water sources like reclaimed municipal wastewater is one of the most obvious and promising options in integrated water resources management. Among the various beneficial uses of reclaimed wastewater Aquifer Recharge (AR) receives growing attention because it features advantages such as additional natural treatment, storage capacity to buffer seasonal variations of supply and demand as well as mixing with natural water bodies which promotes the acceptance of further uses, particularly indirect potable use. Major concerns about the safety of this exploitation route of an alternative water source are connected to microbial and chemical contaminants occurring in wastewater, among which are emerging trace organics like endocrine disrupters and pharmaceuticals. This paper reviews the current international debate about the relevance of emerging contaminants and technical mitigation options in water recycling for indirect potable use.


Subject(s)
Water Movements , Water Pollutants, Chemical/analysis , Water Purification/methods , Water Supply/analysis , Conservation of Natural Resources/methods
19.
Water Sci Technol ; 56(5): 175-82, 2007.
Article in English | MEDLINE | ID: mdl-17881851

ABSTRACT

The reuse of upgraded wastewater for beneficial uses is increasingly adopted and accepted as a tool in water management. However, funding of schemes is still a critical issue. The focus of this paper is on economic considerations of water reuse planning. A survey of pricing mechanisms for reclaimed water revealed that most schemes are subsidised to a great extent. In order to minimise these state contributions to the implementation and operation of reuse projects, their planning should identify a least cost design option. This also has to take into account the established pricing structure for conventional water resources and the possibility of gaining revenues from reclaimed water pricing. The paper presents a case study which takes into account these aspects. It evaluates different scheme designs with regard to their Net Present Value (NPV). It could be demonstrated that for the same charging level, quite different amounts of reclaimed water can be delivered while still producing an overall positive NPV. Moreover, the economic feasibility and competitiveness of a reuse scheme is highly determined by the cost structure of the conventional water market.


Subject(s)
Conservation of Natural Resources/economics , Decision Support Techniques , Waste Disposal, Fluid/economics , Water Purification/economics , Costs and Cost Analysis , Waste Disposal, Fluid/methods , Water Purification/methods
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