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In this paper, we describe the design, fabrication and functional principle of microfluidic diodes – devices for directional liquid transport. They are passive (i.e., need no external energy input) and are capable of unidirectional water transport even vertically against gravity, i.e. they prevent backflow of liquid. In designing the devices with an area of several cm2, we used a capillary channel network that was bio-inspired by the skin of the Texas horned lizard (Phrynosoma cornutum). By means of a CO2 laser, we engraved the microfluidic structures into plates made of poly(methyl methacrylate) (PMMA), a low-cost technical polymer commonly used in disposable microfluidics. We then characterized the topography of the fabricated 3D structures by optical coherence tomography (OCT). Theoretical analysis of the OCT data enabled us to determine their working principle which differs from that presented previously in the literature. We accessed the fluid transport properties of the device by measuring distance, velocity, wetted area and flow asymmetry. Biomimetic abstraction led to a simplified structure which was validated experimentally. All tested devices allowed unidirectional liquid transport at velocities in the range of a few mm/s in the forward direction while preventing backflow of volumes of about 0.5 ml in the backward direction on an area of approximately 28 mm x 14 mm. The transport velocity of about 1 mm/s was found to be nearly constant for a distance of approximately 2 cm, beyond which it decreased. The application spectrum ranges from biomedical microfluidics, lab-on-a-chip and micro-analysis devices to filtration, lubrication, cooling of electronics and e-ink displays.

A dielectric elastomer transducer is a deformable capacitor, and is under development as a sensor, actuator, or generator. Among various geometric configurations, laterally-constrained transducer, also known as pure-shear transducer, is easy to implement and effective to couple mechanical force and electrical voltage. This analytical study reveals that lateral pre-stretch enhances actuation, far exceeding previously reported actuation strokes. Laterally-constrained transducers exhibit complex electromechanical behavior. As voltage increases, an actuator may undergo electromechanical instability, or form wrinkles, or suffer electrical breakdown. We survey the behavior of actuators under all possible states of pre-stretches, and identify five modes of actuation. Our analysis predicts that laterally-constrained actuators can achieve actuation stroke of 1000% for an acrylic elastomer, and 230% for natural rubber. This analysis opens the door to design actuators of simple geometry capable of a very large range of electromechanical actuation.

The volume of literature recognizing the importance of rural credit in developing countries has grown significantly in recent years. However, previous studies have mainly assumed that credit has a homogeneous impact on recipients. This paper contributes to the literature by further examining the impacts of credit on different groups of accessed households categorized by relative poverty, loan volumes, access to agricultural extension services and ethnicity in Vietnam. This paper uses data of 1338 households collected from the Vietnam Access Resources Household Survey in 2012. To increase the reliability of estimation measures, the distribution for the impact estimator is further constructed by applying the bootstrapping approach to the Propensity Score Matching. Results show that credit access affects recipient groups heterogeneously. Although there is strong evidence of positive impacts on non-farm income, credit has no effect on farm income, even for recipients with more annual visits to agricultural extension. While credit significantly increases total income, per capita income, and nonfarm income of the Kinh majority, it has little to no impact on those income components of ethnic minorities. Credit tends to have significantly positive impacts on household income of the better-off, the richest and those receiving larger credit volumes. Results imply that households with favorable economic conditions tend to benefit from accessing rural credit.

Engineered wood, a high-tech material of the 21st century demonstrates the revival of timber for the construction of green urban eco-buildings. However, the testing of wood-based materials is still based on destructive methods known for centuries. In-situ monitoring of curing, cross-linking, and aging is essential for the optimisation of glues, resins and coatings. For press moulding, impedance spectroscopy is the only practical way for in-line detection of the crosslinking. Flat sensors that can be integrated into glue joints are known, but the substrate material of these sensors weakens the glue joint as they do not interact with the commonly used wood glues. Sensors printed on porous paper and wood can solve this problem. We show that although almost every tested paper is printable but not all of them are suitable for the detection of cross-linking analysis, since paper additives can catalyse or inhibit the cross-linking of glues or resins. Printed impedance sensors on pH-neutral porous papers allow an unaltered in-situ analysis of the cross-linking in complex glue joints. The porous papers allow the glue or resin to penetrate the paper and bridge it. Integrated sensors can provide valuable information about the state (aging, moisture) of bonding throughout the life cycle of the engineered wood. With the help of paper-based sensors, wood can be equipped integratively, network-compatible and communicative. Damage in the glue joints can be detected on time. With this innovative sensor technology, wood is not only an ingenious material, but also an intelligent one.

The anodization behaviour of Hf/Al stacked thin films, sequentially deposited from vapour phase without breaking vacuum, was investigated using scanning droplet cell microscopy. Surface microstructure and crystallographic analysis revealed the formation of highly textured and compact hexagonal Hf films for thicknesses above 7.5 nm. Cyclic voltammetry suggested the formation of discrete anodic layers starting with pure HfO 2 on the surface, a mixture of HfO 2 and Al 2 O 3 as an intermediate layer and pure Al 2 O 3 in depth of the films. Coulometric investigations revealed oxide formation factors of 2.2 nm V −1 for HfO 2 while for pure Al 2 O 3 a maximum of 1.4 nm V −1 was measured. Electrochemical impedance spectroscopy performed for various Hf thicknesses and different final anodization potentials revealed almost ideal dielectrics formed from mixed HfO 2 /Al 2 O 3 , permittivities up to 26 being measured for the anodized Hf/Al films. Surface analytical investigations and depth profiling as well as high resolution transmission electron microscopy confirmed the discrete anodic layer growth and the mixing of both anodic oxides. The significant thickness values found for the mixed oxide layer must redefine the general expectations for the use of anodized superimposed layers in various applications.

Low density energy sources, like wind and solar energy, are widely available and they are increasingly used for electricity conversion worldwide. Ambient energy sources with even lower energy densities are universally available and could equally be converted into electricity with large scale special purpose converter systems. This work discusses a simple concept for an electret-based electrostatic converter suitable for large scale conversion of ambient low density energy sources. The converter is a capacitive charge pump capable of working at low frequencies ( ≤ 1 Hz ) with a very low mechanical input energy and a high conversion efficiency. With a charged electret-like elastomer membrane the converter can operate without an initial bias voltage supply. First tests with a simple proof-of-concept demonstrator resulted in a mechanical input energy of 332 μJ (9.1 μJ/cm 2 ) and a converted electrical output energy of 206 μJ (5.7 μJ/cm 2 ) per conversion cycle. This gives a total conversion efficiency of 63%.

Summary This study evaluates the effect of certified organic production on poverty in smallholder production systems. Data was collected from cross sectional survey of local market-oriented peri-urban vegetable and rural honey producers in Kenya. Poverty was measured using the multidimensional poverty methodology and endogenous switching probit model used to assess the effect of certified organic production on multidimensional poverty. Findings were that certified producers were less likely to be multidimensional poor compared to their counterfactual case of not participating in organic certification schemes. Additionally, noncertified producers would be less likely to be poor if they were to participate in organic certification production.

The Texas Horned lizard has the ability to harvest moisture from ambience with its skin and to transport water directionally to its snout; at the same time water is hindered to flow in opposite direction. We present a passive microfluidic device for directional liquid transport which is inspired by this natural role model. To this end, we deduce a subnatural capillary network from the measurement data of the Texas Horned lizard's skin. We adapt the network to various liquid-polymer combinations with the help of a mathematical model. Applying a CO 2 laser we engrave the structures into poly(methyl methacrylate) (PMMA). By distance measurements we verify that our devices transport liquids of different contact angles in a preferential direction, while stopping it in opposite direction. The applied network of interconnected capillary channels is advantageous, when it comes to defects during production or when particles block part of the capillary channels. The proposed concept is thought to be useful for micro-analysis devices and lubrication.

The major attempt of this paper is to examine the factors affecting the biogas technology adoption in rural areas in Bangladesh. The study was conducted by a survey method on respondents. Stratified random and purposive sampling techniques were applied for selecting 150 biogas users and 150 non-users. Data were collected through individual interviews by using structural questionnaire. A qualitative response model (Logistic regression model) was applied for examining the main factors influencing the biogas adoption. As a result, socio-economic factors play an important role in the respondents' behaviors toward biogas adoption. The empirical results indeed highlighted that year of education, income level, number of cattle, and women headed family have significant influences on the decision of biogas plant installation. Subsequently, increasing the level of education, empowering women, enhancing the yearly income and number of cattle are strategies likely to increase the adoption rate of biogas plants. Environmental, economic, social, and technological benefits were considered by the respondents while engaging in the biogas plant adoption. Households are also motivated toward biogas plant installation by Non Governmental Organizations (NGOs). A tiny motivation comes from Governmental Organizations (GOs), local government, electronic and print media. Therefore, raising the population awareness on the benefits of biogas plant installation through the existing channels of communication campaigns, provision of financial incentive, participation of print media and active attendances of Government institutions could extend the biogas technology in Bangladesh.

Functional materials such as piezoelectric and pyroelectric polymers or organic photodiodes are promising candidates for flexible sensor surfaces; combining thin films of these materials with large-area resistive electrodes leads to position-sensitivity for passive touch- or light-point localization, respectively. However, this type of large-area sensors for passive stimulus-localization lacks a general theoretical description, which is necessary to understand the physics underlying the sensor concept. To this end we present a one-dimensional, theoretical model for these sensors; the model is based on the solutions of the telegrapher's equations under the appropriate boundary conditions. We specify the applied boundary conditions, list approximate solutions for certain parameter ranges and present two model-based normalization procedures. These normalization procedures allow for stimulus localization independently of its magnitude and significantly increase the quality of the measurement signals. Experimental results agree well with theoretical findings, proving the suitability of the presented theoretical models.

Dielectric elastomers are capable of large voltage-induced deformation, but achieving such large deformation in practice has been a major challenge due to electromechanical instability and electric breakdown. The complex nonlinear behavior suggests an important opportunity: electromechanical instability can be harnessed to achieve giant voltage-induced deformation. We introduce the following principle of operation: place a dielectric elastomer near the verge of snap-through instability, trigger the instability with voltage, and bend the snap-through path to avert electric breakdown. We demonstrate this principle of operation with a commonly used experimental setup—a dielectric membrane mounted on a chamber of air. The behavior of the membrane can be changed dramatically by varying parameters such as the initial pressure in the chamber, the volume of the chamber, and the prestretch of the membrane. We use a computational model to analyze inhomogeneous deformation and map out bifurcation diagrams to guide the experiment. With suitable values of the parameters, we obtain giant voltage-induced expansion of area by 1692%, far beyond the largest value reported in the literature.

We report on the fabrication and performance of vacuum-processed organic field effect transistors utilizing evaporated low-density polyethylene (LD-PE) as a dielectric layer. With C60 as the organic semiconductor, we demonstrate low operating voltage transistors with field effect mobilities in excess of 4 cm2/Vs. Devices with pentacene showed a mobility of 0.16 cm2/Vs. Devices using tyrian Purple as semiconductor show low-voltage ambipolar operation with equal electron and hole mobilities of ~0.3 cm 2/Vs. These devices demonstrate low hysteresis and operational stability over at least several months. Grazing-angle infrared spectroscopy of evaporated thin films shows that the structure of the polyethylene is similar to solution-cast films. We report also on the morphological and dielectric properties of these films. Our experiments demonstrate that polyethylene is a stable dielectric supporting both hole and electron channels. © 2012 Elsevier B.V. All rights reserved., P20772-N20, S09712-N08, S9711-N08, S09706-N08 BAP-08-11-DPT2002K120510, The work was financially funded by Turkish Grant BAP-08-11-DPT2002K120510 and by the Austrian Science Foundation “FWF” within the National Research Network NFN on Interfaced Controlled and Functionalized Organic Films ( P20772-N20 , S09712-N08 , S09706-N08 and S9711-N08 ). Financial support of the corresponding author from the city of Linz and the Land Oberösterreich is highly appreciated. We thank Philipp Stadler and Gebhard Matt for stimulating discussions and suggestions.

Soil degradation is a major threat to agricultural sustainability in Nepal. Increased anthropogenic activities in the inherently fragile ecosystem of unstable geology, steep slopes and intense monsoon rains have accelerated the loss of soil and its fertility in the Nepalese hills. This paper assesses soil conservation technologies from biophysical and economic perspectives using the integrated bio-economic analysis. The study applied a biophysical model, Soil Change Under Agroforestry (SCUAF), to project effects of the conservation technologies on soil erosion control as well as on crop yields over a thirty-year period. The technologies considered are hedgerow intercropping and minimum tillage. The outcome of the biophysical model was integrated into a cost-benefit analysis to examine the economic viability of the technologies. The results showed that these technologies are effective in reducing a substantial rate of soil erosion prevailing in the conventional system of maize cultivation. They have a variable impact on yield maintenance and the farmers’ economic return over time. The hedgerow intercropping sustained crop yields in the long-term although yield was reduced in the short-term. Likewise, high costs for establishing and maintaining the hedgerow intercropping significantly reduced farmers’ economic returns in the short-term. Minimum tillage technology, while better than the conventional farming system, was not able to sustain crop yield in the long-term. Yet, it provided positive returns for a longer period than the conventional system. The study concludes that though the evaluated technological options are effective in reducing the high rate of erosion resulting from the conventional maize cropping system, economically they are not viable for farmers in the short-term. Therefore, to expedite the wider adoption of these technologies and to halt and reverse soil degradation, it is suggested that farmers initially be supported with economic incentives to compensate their short-term economic loss.

The potential risk for livestock breeding is much higher than other agricultural producer which affects income stability and welfare of households. Agricultural insurance is developed slowly in China. This paper analyzes farmers’ Willingness to pay (WTP) for cow insurance and factors influencing farmers’ participation in and WTP. It shows that the current premium is in the range that famers can accept. The acceptance of premium and farmers’ knowledge of allowance significantly influenced both of their participation and WTP. Policy makers should encourage farmers to enlarge their scale and make the premium as low as possible through subsidy farmers.

We present a flexible polymer sensor for light point localization based on the pyroelectric polymer poly(vinylidene fluoride) (PVDF) in combination with large area resistive electrodes. This large area sensor is simple in design; a division of the sensor surface into an array of individual sensor elements as used in active matrix technology is avoided. Electronic circuitry is placed only at the edges of the device. We have fabricated a flexible sensor strip with a length of 12 cm and a width of 1.6 cm according to the proposed concept. The position sensitive output signals of the sensor strip have been measured in response to the intensity-modulated light of a red laser diode. Two model-based normalization procedures have been developed in order to increase the quality of the measurement signals. The results indicate that the sensor strip can be treated mathematically analogous to a transmission line. Calculations based on the solutions of the telegrapher's equations under the appropriate boundary conditions are in good agreement with the experimental results, proving the suitability of the proposed concept for position sensitive detection.

We demonstrate the operation of a digital microfluidic lab-on-a-chip system utilizing Electro Wetting on Dielectrics (EWOD) as the actuation principle and a High Fundamental Frequency (HFF; 50MHz) quartz crystal microbalance (QCM) resonator as a mass-sensitive sensor. In a first experiment we have tested the reversible formation of a phosphor-lipid monolayer of phospholipid vesicles out of an aqueous buffer suspension onto a bio-functionalized integrated QCM sensor. A binding of bio-molecules results in an altered mass load of the resonant sensor and a shift of the resonance frequency can be measured. In the second part of the experiment, the formation of a protein multilayer composed of the biomolecule streptavidin and biotinylated immunoglobulin G was monitored. Additionally, the macroscopic contact angle was optically measured in order to verify the bio-specific binding and to test the implications onto the balance of the surface tensions. Using these sample applications, we were able to demonstrate and to verify the feasibility of integrating a mass-sensitive QCM sensor into a digital microfluidic chip.

The effect of oxygen on the degradation of inverted bulk heterojunction solar cells based on poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) blends has been investigated by monitoring current–voltage (jV)-curves, impedance spectra and charge extraction by linearly increasing voltage (CELIV) traces during the degradation process. The use of gas permeable top electrodes allows monitoring the kinetics of degradation without being limited by the diffusion through a compact metal electrode. A computational model is used to provide a phenomenological explanation of the experimental results. The charge distribution inside the device is modeled by solving the fully coupled set of nonlinear differential equations for the quasi-one-dimensional transport of electrons and holes. Degradation of the cells in the presence of oxygen results mainly in the reduction of short circuit current (jsc), while the concomitant loss in light absorption is negligible. The rate of degradation is enhanced significantly by illumination. A significant part of the loss in jsc is reversible upon annealing under nitrogen or in vacuum. The irreversible part of the degradation is assigned to the photochemical formation of carbonyl and carboxylic groups, which act as traps for electrons. The reversible component of degradation is due to p-doping of the photoactive layer by oxygen, which results in the formation of mobile holes and immobile superoxide anions. This leads to the formation of a space charge region in front of the electron extracting electrode whose width depends on the doping level as well as on the applied bias. The space charge region shields the electric field inside the photoactive layer and hence hampers charge carrier extraction, which leads to the observed loss in short circuit current.

Environmentally sustainable systems for the design, production, and handling of electronic devices should be developed to solve the dramatic increase in electronic waste. Sustainability in plastic electronics may be the production of electronic devices from natural materials, or materials found in common commodity products accepted by society. Thereby biodegradable, biocompatible, bioresorbable, or even metabolizable electronics may become reality. Transistors with an operational voltage as low as 6 V, a source drain current of up to 0.5 lA and an on–off ratio up to four orders of magnitude, with saturated field effect mobilities in the range of 1.5 10 4

Poverty and deforestation are critical issues in a number of developing countries where the policy framework is in many cases insufficient to provide rural people an incentive to afforest. This paper analyzes both the impact of land privatization on afforestation efforts of rural farm households in the Northern Uplands of Vietnam and the economic incentive of farm households on afforestation efforts. The determinants of afforestation by farm households were analyzed. Empirical findings were used to derive relevant policy implications for promoting forest rehabilitation in a country where the majority of forestland had been in State control prior to land privatization in 1994.

Two different position sensitive devices for large-area detection of light points and objects are presented. The core of the system consists of a luminescent foil, where impinging laser light is absorbed and the fluorescence light is coupled out via attached silicon photodiodes. Due to a direct relation between the signal amplitude and the distance to the photodiodes, this detector can be used for pinpointing laser spots over large areas. When clamping small stripes of the detector inside a rectangular frame, the foil can be used for object tracing over large-areas as well.

Ferroelectrets are flexible and conformable polymer transducer materials with a dominant longitudinal piezoelectric effect. They can be used in a wide range of transient pressure sensing applications. We present concepts for thin, flexible ferroelectret-keyboards (and advanced pressure sensors) based on ternary coded polarization patterns in a multilayer configuration. The decoration of a cellular polypropylene ferroelectret with a heteropolar polarization pattern of high resolution is a technical challenge. We discuss several concepts for achieving such polarization patterns and demonstrate a flexible 300 μm thin 3-layer keyboard where the combined signals of every single layer allow to encode and detect a total number of 26 keys.

We demonstrate the operation of an Electro Wetting on Dielectrics (EWOD) hybrid lab-on-a-chip system by utilizing a High Fundamental Frequency (HFF; 50MHz) Quartz Crystal Microbalance (QCM) resonator as masssensitive sensor. In a first experiment we have tested the reversible formation of a phosphor-lipid monolayer out of an aqueous buffer suspension of phospholipid vesicles onto the integrated sensor, coated by a Self-Assembled Monolayer (SAM) of 1-octadecanethiol on a gold-covered surface. The altered mass load resulted in a shift of the resonance frequencies. In the second experiment, the formation of a protein multilayer composed of streptavidin and biotinylated immunoglobulin G was monitored. The original resonance frequency was recovered by the complete lipid removal by the detergent octyl-D-glucopyranoside. Using these sample applications, we were able to demonstrate and verify the feasibility of our prototype combining a mass-sensitive QCM sensor with digital microfluidics based on EWOD.

The transfer of benchtop knowledge into large scale industrial production processes represents a challenge in the field of organic electronics. Large scale industrial production of organic electronics is envisioned as roll to roll (R2R) processing which nowadays comprises usually solution-based large area printing steps. The search for a fast and reliable fabrication process able to accommodate the deposition of both insulator and semiconductor layers in a single step is still under way. Here we report on the fabrication of organic field effect transistors comprising only evaporable small molecules. Moreover, both the gate dielectric (melamine) and the semiconductor (C60) are deposited in successive steps without breaking the vacuum in the evaporation chamber. The material characteristics of evaporated melamine thin films as well as their dielectric properties are investigated, suggesting the applicability of vacuum processed melamine for gate dielectric layer in OFETs. The transistor fabrication and its transfer and output characteristics are presented along with observations that lead to the fabrication of stable and virtually hysteresis-free transistors. The extremely low price of precursor materials and the ease of fabrication recommend the evaporation processes as alternative methods for a large scale, R2R production of organic field effect transistors.

For the application of high fundamental frequency (HFF) quartz crystal resonators as ultra sensitive acoustic biosensors, a tailor-made quartz crystal microbalance (QCM) flow cell has been fabricated and tested. The cell permits an equally fast and easy installation and replacement of small and fragile HFF sensors. Usability and simple fabrication are two central features of the HFF-QCM flow cell. Mechanical, thermal, electrical and chemical requirements are considered. The design of the cell combines these, partially contradictory, requirements within a simple device. Central design concepts are discussed and a brief description of the fabrication, with a special focus on the preparation of crucial parts, is provided. For test measurements, the cell was equipped with a standard 50 MHz HFF resonator which had been surface-functionalised with a self-assembled monolayer of 1-octadecanethiol. The reliable performance is demonstrated with two types of experiments: the real time monitoring of phospholipid monolayer formation and its removal with detergent, as well as step-wise growth of a protein multilayer system by an alternating immobilisation of streptavidin and biotinylated immunoglobulin G.

Deoxyribonucleic acid (DNA) bio-polymers derived from fish waste products are employed as gate dielectric in n-type methanofullerene as well as p-type pentacene based organic field-effect transistors working at low voltage levels and low gate leakage currents. Based on the large hysteresis in the transfer characteristics, operation of the transistor as a non-volatile memory element is shown. Practically hysteresis free operation of DNA based transistors is obtained at low voltage levels by adding an additional aluminium oxide blocking layer between the organic semiconductor and the DNA gate dielectric.

Results on photoresponsive organic field-effect transistors (photOFETs) based on conjugated polymer/fullerene solid-state mixtures as active semiconductor layer and poly-vinyl-alcohol (PVA) or divinyltetramethyldisiloxane-bis(benzocyclobutene) (BCB) as gate dielectrics are presented. With LiF/Al top source–drain contacts all devices show dominantly n-type transistor behaviour. Devices fabricated with PVA as gate insulator reveal gate voltage induced saturation upon illumination but low photostability. Contrary, devices fabricated with BCB as gate insulator show transistor amplification in a wide range of illumination intensities. The increase of the drain–source current by more than two orders of magnitudes upon illumination is explained by the generation of a large carrier concentration due to photoinduced charge transfer at the conjugated polymer/fullerene bulk heterojunction upon illumination (photodoping). After illumination, a change of the dark transfer characteristics with respect to the initial transfer characteristics was observed. The initial dark state is achieved either by applying a large negative gate bias or by annealing.

Temperature-dependent spectra of the linear, second- and third-order nonlinear dielectric permittivities are reported for an amorphous polymethylmethacrylate/Disperse Red 1 guest–host polymer and a poly(styrene maleic anhydride)-Disperse Red 1 side-chain polymer glass. Both polymer systems contain Disperse Red 1 chromophores, a very strong molecular dipole. In guest–host polymers with low dye loading, the dipole density and dipole moment of the chromophores can be determined from the linear and third-order nonlinear dielectric relaxation strength, associated with the micro-Brownian motion of the chromophore dipoles. The second-order nonlinear dielectric permittivity is non-vanishing in the glassy state only in poled polymers. Contributions to the second-order dielectric permittivity arise from piezoelectricity and from the elasto-optical and electronic electro-optical Pockels effect. In poled polymer dipole glasses with nonlinear optically active chromophores, the electronic electro-optical response is the dominant source for the second-order nonlinear dielectric permittivity. Therefore, electrical current versus voltage measurements enable a measurement of the electro-optical Pockels effect in poled polymer chromophore dipole glasses.

We present C60-based n-channel organic field-effect transistors with mobility in the range of 0.4–1 cm2 V−1 s−1. A solution-processed organic dielectric divinyltetramethyldisiloxane-bis(benzocyclobutene) (BCB) was used as a gate dielectric and C60 films were grown on top by hot wall epitaxy. Devices characterised in inert atmosphere conditions show high stability with an on/off ratio >104. The determined mobility values are nearly gate voltage independent.

Martian neutral gas temperatures estimated from topside plasma scale heights of electron density distributions and Lyman-a dayglow observations obtained by several Mars missions yield an exospheric temperature in the order of 350 � 100 K. However, this value would imply a much higher dependence on the F10:7 radio flux than found for Venus and does not appear to be consistent with the observed solar cycle dependence of the Martian ionospheric peak plasma densities. On the other hand, observations on Venus indicate that photochemically produced very low energetic H atoms, as well as part of the solar wind protons and accelerated planetary H þ ions, which can be transformed into energetic H atoms (ENAs) may also contribute to the observed neutral H atoms. By calculating the flux of solar wind ENAs we find that they may give rise to an increase of the exospheric temperature of up to

The evolution of the martian atmosphere with regard to its H 2 O inventory is influenced by thermal loss processes of H, H 2 , nonthermal atmospheric loss processes of H + , H 2 + , O, O + , CO 2 , and O 2 + into space, as well as by chemical weathering of the surface soil. The evolution of thermal and nonthermal escape processes depend on the history of the intensity of the solar XUV radiation and the solar wind density. Thus, we use actual data from the observation of solar proxies with different ages from the Sun in Time program for reconstructing the Sun's radiation and particle environment from the present to 3.5 Gyr ago. The correlation between mass loss and X-ray surface flux of solar proxies follows a power law relationship, which indicates a solar wind density up to 1000 times higher at the beginning of the Sun's main sequence lifetime. For the study of various atmospheric escape processes we used a gas dynamic test particle model for the estimation of the pick up ion loss rates and considered pick up ion sputtering, as well as dissociative recombination. The loss of H 2 O from Mars over the last 3.5 Gyr was estimated to be equivalent to a global martian H 2 O ocean with a depth of about 12 m, which is smaller than the values reported by previous studies. If ion momentum transport, a process studied in detail by Mars Express is significant on Mars, the water loss may be enhanced by a factor of about 2. In our investigation we found that the sum of thermal and nonthermal atmospheric loss rates of H and all nonthermal escape processes of O to space are not compatible with a ratio of 2:1, and is currently close to about 20:1. Escape to space cannot therefore be the only sink for oxygen on Mars. Our results suggest that the missing oxygen (needed for the validation of the 2:1 ratio between H and O) can be explained by the incorporation into the martian surface by chemical weathering processes since the onset of intense oxidation about 2 Gyr ago. Based on the evolution of the atmosphere-surface-interaction on Mars, an overall global surface sink of about 2×10 42 oxygen particles in the regolith can be expected. Because of the intense oxidation of inorganic matter, this process may have led to the formation of considerable amounts of sulfates and ferric oxides on Mars. To model this effect we consider several factors: (1) the amount of incorporated oxygen, (2) the inorganic composition of the martian soil and (3) meteoritic gardening. We show that the oxygen incorporation has also implications for the oxidant extinction depth, which is an important parameter to determine required sampling depths on Mars aimed at finding putative organic material. We found that the oxidant extinction depth is expected to lie in a range between 2 and 5 m for global mean values.

We report on the deposition of parylene-like films by plasma polymerization, starting from the sublimation of the di-para-xylylene precursor. The experiments were performed in a 13.56 MHz RF plasma set-up consisting of a tubular reactor with external electrodes. Deposition rates in the range of 4–250 nm min−1 were obtained. Depending on the RF power and precursor mass flow values, layers with various morphology and composition can be obtained, ranging from rough semi-crystalline to smooth amorphous and from polymer-like to hydrogenated carbon-like films. The electrical properties of the layers studied by means of dielectric spectroscopy and charge stability measurements correlate to the structural film properties.

Toxicological and genotoxicological investigation of complex mixtures is one of the main focus of the recent research in toxicology. Testing complex mixtures present a formidable scientific problem since most recently available toxicological data has been obtained from single substance studies and is not simply transferable to mixtures of chemicals. Although there are no special strategies and standard protocols available for determining toxic and genotoxic effects of complex mixtures, the fundamental concepts of evaluation are the same as those for single substances [1] . The focus of interest of the submitted paper is the genotoxicological characterisation of a complex mixture of mostly perhalogenated hydrocarbons which is generated as a waste product from the plasma etching process in the semiconductor industry. By use of several in vitro test systems (comet assay and micronucleus test), the clastogenic potency of the mixture was tested in various human cell types (lymphocytes and normal bronchial epithelial cells) and in rat hepatocytes. Results demonstrated that the complex perhalogenated hydrocarbons mixture causes DNA single-strand breaks and micronuclei formation, and direct concentration-to-effect correlations were proved in all experiments. The presence of an external metabolising system (S9 mix from rat hepatocytes) in human cell culture systems did not cause any change of the observed effects when compared to experiments performed in the absence of the S9 mix. Therefore, we conclude that the mixture acts as direct genotoxicant and that there is no detoxification by the external enzyme system. Further, convincing and reproducible results of the in vitro comet assay and the micronucleus assay in primary human cell cultures indicated these tests may be utilized for the genotoxicological analyses of complex mixtures with concern to human health hazard.

We investigate the contribution of the radial component of the magnetic field in the solar wind interaction with Mars. We use Mars Global Surveyor Magnetometer and Electron Reflectometer data during the Science Phasing Orbits to gain a qualitative understanding of the magnitude of the radial magnetic field from the solar wind draping around the dayside of Mars. Using only data far away from the strong crustal magnetic sources, we find that the angle the magnetic field makes to the horizontal within the martian ionosphere has an average closer to zero than that outside the ionosphere. However, we find a much larger spread in angles inside the ionosphere. In addition, we find that the angle of inclination increases with increasing altitude and local time, but more spatial coverage is needed to quantify these relationships.

The first determination of the 15N/14N ratio in Titan’s atmosphere comes from Earth-based millimetric wavelength spectroscopic observations of HC15N/HC14N. These measurements indicate that the bulk nitrogen is enriched in the heavy isotope 15N by about 4.5 times relative to the Earth value. A 15N/14N anomaly on Mars of about 1.6 times the terrestrial value has been established previously resulting from nonthermal atmospheric escape processes (e.g. dissociative recombination of N+2 ions). We investigated electron dissociative recombination of N+2 ions, electron impact dissociation of N2 molecules, nonthermal exothermic ionosphere-related photochemical reactions, atmospheric sputtering via solar wind and magnetospheric particles, solar wind pick-up and the loss of 14N to 14C via cosmic rays as possible sources of nitrogen isotope fractionation in Titan’s atmosphere where this molecule is the principal constituent. Using a Monte Carlo method we have shown that electron impact dissociation and dissociative recombination in the low energy range of molecular nitrogen and N+2 ions could lead to an isotope fractionation since the energy of the newly released 15N isotope is slightly smaller than the necessary escape energy, or in the case of dissociative recombination, close to Titan’s escape energy. We show that the isotope fractionation for the other more efficient escape processes like atmospheric sputtering is negligibly small, since the energy of both newly released nitrogen isotopes is much greater than Titan’s escape energy. We found that diffusive separation of 15N/14N according to their atomic mass is very important in the solution of this isotope anomaly. Further indications of a much greater particle output or much higher solar wind mass flux of the early Sun during the first half billion years are presented which could explain the observed enrichment of 15N. We found that atmospheric sputtering and pick-up caused by a high solar wind particle outflow during a Post T-Tauri phase could be responsible for the observed nitrogen anomaly. Our study indicates that the mass of Titan’s early atmosphere was at least 30 times greater than the present value. An explanation of this anomaly is important for enabling us to estimate the total nitrogen reservoir required to produce the present Titan atmosphere. In situ measurements and confirmation of the Earth-based 15N/14N isotope anomaly observations will be possible with the Gas Chromatograph and Mass Spectrometer (GCMS) instrument on board of the Huygens probe. They will be of great importance for understanding the formation and evolution of atmospheres around bodies in the solar system.

The MGS MAG/ER investigation provides vector measurements of the magnetic field and the ionospheric electron density near periapsis. The instrumentation consists of twin triaxial fluxgate magnetometers and a “top hat” electrostatic analyzer of electrons in the energy range of 1 eV to 20 keV. Results include extensive mapping of the detached bow shock wave in the solar wind, the nature and structure of the ionopause and magnetic pile-up boundaries. The most surprising result is the discovery of localized magnetic fields of planetary origin, presumably due to remanent crustal magnetization. Maximum fields measured while below the ionosphere exceed 300 nT. We present an initial study of one of these very localized fields and extrapolations to the Martian surface in the Acidalia planitia.

The existence of gaseous species H, He, O, Na and K, established by euv spectroscopic observations on Mariner 10 for the first three and groundbased observations for the last two species with column contents of the order of 1012 cm−2 or less, qualify the gaseous envelope of Mercury as an exosphere (column content per definition ≤ 1014 cm−2). Whereas H and He seem to have its origin in the direct supply from the solar wind, the heavier constituents can arise from particle and photon interactions with surface materials. Some observations have suggested that Na extends to 700 km above the surface at the subsolar point, implying the existence of non-thermal atomic velocities of at least 2 km s−1. Although Mercury has a small intrinsic magnetic field, solar wind protons have access to parts of its surface. Since particle sputtering liberates volatiles from the surface at energies greater than the mean thermal energy, the sputtered particle profile is governed by a scale height much larger than the barometric scale height. The surface densities of these sputtered volatiles then exhibit a lower exponential decay than would be expected from a barometric law using the exospheric (surface) temperature. Mercury's exosphere is a low attenuation medium for solar euv radiation which therefore can penetrate to its surface. Under these circumstances no ionospheric “layer” can be formed. The ionization of exospheric species leads to electron-ion pair formation which is balanced by chemical loss and transport processes. Since radiative recombination is an extremely slow loss process for atomic ions, plasma diffusion under gravity, which has a short time constant, controls the ionized species. Thus, the densities of the ionized exospheric component do not exceed a few electrons/ions cm−3. This yields an extremely low height-integrated Pedersen conductivity, which must be taken into account in the understanding of convection processes in the magnetosphere.

A comparative investigation of the thermal dipole-orientation stability in a guest-host and a cross-linked non-linear optical polymer with similar structures of the polymer backbone is reported. Cross-linking yields a rigid polymer network with two types of dipoles: those already cross-linked and therefore thermally stable and those not as yet cross-linked and therefore fast relaxing. The combination of isothermal and thermally stimulated measurements allows for a complete characterization of dipole relaxation in the two sample polymers.

In this popular engineering science book the world of materials that make our life in developed economies comfortable is illustrated; looking at steel, cement, plastic, paper, and aluminum, which account for more than 50 % of the annual industrial carbon dioxide emissions. Their impact on the environment is steadily growing and if we continue to use them without “both eyes open” for a sustainable future our children may not have the chance to live as well as we do. We are used to distinguishing different periods in the development of mankind according to the materials predominantly used – the stone age, bronze age, and iron age are common to everyone. The last and current century is often called the electronic materials age, dominated by silicon, an electronic material that dramatically changed our life in an unforeseen manner – mobile appliances being an illustrative example. But are these the materials that largely account for global annual industrial emissions? No, rather simple materials we do not often talk about are important in this respect, and they are covered in this book. Five popular materials in construction and packaging, steel, cement, plastic, paper, and aluminum have been selected by the authors in their survey of a sustainable materials future. It is a popular engineering book, it is very well written, easy to read and with a fine sense of humor.The book is divided into five parts, starting with the world of materials, concentrating on our current use of metals, followed by suggestions for a sustainable material future – with one eye open it becomes clear that the materials industry is already quite efficient in production, so there is not much hope for significant improvements. The authors propose looking at the problem with two eyes open – suggesting a bundle of new options by using materials wisely – using less material, using materials longer, and re-using them by recycling. A very simple and illustrative example is the use of a single aluminum alloy in the fabrication of beverage cans – allowing for a significant simplification in aluminum recycling. There are many more such options presented, and these options for change may have a significant impact on future energy use and emissions. The major part of the book is devoted to metals, in total 19 of 25 chapters, while the other materials are discussed in part four, part five is devoted to the creation of a sustainable material future.The book contains a lot of highly useful graphical illustrations and diagrams which makes it especially useful for teachers and students in materials engineering. There is also an excellent webpage for the book, with free downloadable text (so you need not buy the book to save paper) and supplementary material. There are lines of music on different pages –funny and original, but I am not sure if this is really a great idea or not.It may appear disappointing that the book is limited to five materials only, largely used in construction and packaging, though our society relies on most of the elements in the periodic table – especially when looking at our current “electronic materials age”. Electronic waste is a major concern as well, and it is steadily growing. Many modern electronic materials are also highly questionable in terms of their sustainability – but it would have been impossible to cover all these in a single book. So, hopefully this book will be only the first in a series of attempts to describe ways for developing a sustainable materials future – and electronic materials, products, and waste is a fine set of examples worth considering.At the end of the book there is a list of useful references for further reading and a rather extensive, mostly useful index that helps find relevant information quickly. The topic of the book is highly timely, and the authors have done an excellent job in making science reading enjoyable to the general public, while still keeping the book as a very valuable reference for teachers and students of materials science, physics, chemistry, and engineering at all levels.

In order to achieve the maximal sensitivity of a thermal IR sensor, the incident light must be efficiently absorbed. This may be done either by the sensor material with its own electrodes or by an additional absorber structure. Freely suspended thin metal films are known to act as wide-band absorbers for IR radiation. Prepared on the solid surface of the sensor, the absorbing properties of the metal layer are, however, strongly influenced by the dielectric function of the sensor material. Results are presented for thermoelectric and pyroelectric sensors. For the thermoelectric sensor, a 400 nm thick silicon layer is used as a support for the absorbing silver film with a sheet resistance of 150 Ω/□, evaporated onto the rear side of the silicon layer. This absorber has an absorbance of nearly 50% independent of the wavelength over the whole IR range. For pyroelectric sensors two examples of absorbers on PVDF are presented. The first is a broad-band absorber and has an absorbance of about 50% within the wavelength region 3–200 μm. The other is a selective absorber and has an absorbance of about 90% within the region 7–15 μm. The selective absorber is completely opaque and can be realized by means of a PVDF film with a thickness of about 2 μm, covered on both sides by metal films. This structure may serve as an excellent absorber for a crystalline pyroelectric sensor.

Recently, Zenobi, Hahn and Zare introduced thin-film resistance sensors for the surface temperature measurement of dielectric materials heated by pulsed laser radiation. They concluded that absorption or reflection by their thin-film sensor is in any case negligible, thus causing no systematic errors. We show theoretically and experimentally that the thin-film sensors can be very effective absorbers for the infrared radiation used by Zenobi . The absorptance of the thin-film sensor is negligible only if its square resistance is greater than 10 kΩ.

The pyroelectric element in an integrated IR sensor is usually in good thermal contact with the silicon chip. To characterize materials for these applications, heat sink figures of merit are introduced and various materials are compared. Integrated arrays with the materials poly(vinylidene fluoride) (PVDF) and LiTaO 3 are realized. The measured specific detectivity of arrays with 40 μm thick PVDF is D * = 1.4 × 10 7 cm √Hz/W.

This paper examines the basic problems of the mathematical programming models used for agricultural sector and policy analysis. Experience with traditional programming models shows that a considerable improvement in performance is possible by adequately incorporating non-linear relationships. Particular emphasis will be given to the calibration and validation problems involved in this type of model. With the help of the Turkish agricultural sector model it will be demonstrated that an empirical specification of a non-linear programming model for the agricultural sector is possible even with poor statistical data and that an operational model version can be handled on a PC.

In-situ measurements of the ion composition and concentration of the ionosphere of Venus are obtained with the Bennett RF ion mass spectrometer (OIMS) on the Pioneer Venus Orbiter (PVO). Dayside ion profiles exhibit considerable variability in the height of the ionopause as well as the scale heights of the ion constituents, which reflect the compression and expansion of the ionosphere in response to solar wind variations. Near the dayside upper boundary of the thermal O+ distribution, super-thermal ions are detected by the OIMS, presenting a complication for identifying the ion signature of the ionopause. Correlated with the presence of the superthermal ions, the ac electric field detector (OEFD) detects regions of intensified signals, with peak response in the 100 Hz frequency channel. It is expected that further analysis of the superthermal ion-electric field signatures will contribute to a clearer understanding of the physical processes underlying the formation of the ionopause.

The distributions of several ion species in a data base obtained by in situ measurements of the thermal ion composition of the ionosphere of Venus by the Pioneer Venus Orbiter have been sorted to identify temporal and spatial variations and determine the feasibility of an analytical representation of the experimental results. The first results from the sorting of several prominent ions including O(+), O2(+), and H(+) and several minor ions including CO2(+), C(+), and H2(+) reveal significant diurnal variations which consist of strong day to night contrast in the ion concentrations, with differences of one to two orders of magnitude, depending upon ion mass and altitude. It is suggested that repeatable day to night gradients in the ion distribution are adaptable to parametric modeling.

Across the nightside of Venus, daily measurements from the PV Orbiter Ion Mass Spectrometer often indicate an ionosphere of relatively abundant concentration, with a composition characteristic of the dayside ionosphere. Such conditions are interspersed by other days on which the ionosphere appears to largely 'disappear' down to about 200 km, with ion concentrations at lower heights also much reduced. These characteristics, coupled with observations of strong day to night flows of O(+) in the upper ionosphere, support arguments that ion transport from the dayside is important for the maintenance of the nightside ionosphere. In the range 140-160 km, strong concentrations of O2(+) and NO(+) indicate that the ionization peak is at times composed of at least two prominent ion species. Nightside concentrations of O2(+) and NO(+) as large as 100,000 and 10,000/cu cm, respectively, appear to require sources in addition to that provided by transport. The most probable sources are considered briefly, and no satisfactory explanation is yet found for the observed NO(+) concentrations.

An outline is given of the theory of the ionospheric Faraday effect (the rotation of the plane of polarization of radio waves by the ionosphere). Measurements of ionospheric characteristics by means of lunar radio reflections and radio transmissions from artificial satellites utilizing this effect are discussed. The rate of fading of satellite signals due to the Faraday effect is found to depend upon both the integrated electron density up to the height of the satellite and the local electron density at the satellite. Thus, a possibility exists of determining both quantities provided the satellite transmissions are received simultaneously by two or more stations. Expressions for the fading rate are derived and the effects of orbital parameters on the determination of ionospheric characteristics are discussed.

Ionic and thermal structure model of daytime Venus ionosphere with solar wind heating based on Mariner 5 flyby mission