Synthesis and characterization of biodegradable lignin nanoparticles with tunable surface properties

Lignin nanoparticles can serve as biodegradable carriers of biocidal actives with minimal environmental footprint. Here we describe the colloidal synthesis and interfacial design of nanoparticles with tunable surface properties using two different lignin precursors, Kraft (Indulin AT) lignin and Organosolv (high-purity lignin). The green synthesis process is based on flash precipitation of dissolved lignin polymer, which enabled the formation of nanoparticles in the size range of 45–250 nm. The size evolution of the two types of lignin particles is fitted on the basis of modified diffusive growth kinetics and mass balance dependencies. The surface properties of the nanoparticles are fine-tuned by coating them with a cationic polyelectrolyte, poly(diallyldimethylammonium chloride). We analyze how the colloidal stability and dispersion properties of these two types of nanoparticles vary as a function of pH and salinities. The data show that the properties of the nanoparticles are governed by the type of lignin used and the presence of polyelectrolyte surface coating. The coating allows the control of the nanoparticles’ surface charge and the extension of their stability into strongly basic regimes, facilitating their potential application at extreme pH conditions

Controlled adhesion, membrane pinning and vesicle transport by Janus particles

The interactions between biomembranes and particles are key to many applications, but the lack of controllable model systems to study them limits the progress in their research. Here, we describe how Janus polystyrene microparticles, half coated with iron, can be partially engulfed by artificial cells, namely giant vesicles, with the goals to control and investigate their adhesion and degree of encapsulation. The interaction between the Janus particles and these model cell membrane systems is mediated by electrostatic charge, offering a further mode of modulation in addition to the iron patches. The ferromagnetic particle coatings also enable the ability to manipulate and transport the vesicles by magnetic fields

Direct measurements of the effects of salt and surfactant on interaction forces between colloidal particles at water-oil interfaces

The forces between colloidal particles at a decane-water interface, in the presence of low concentrations of a monovalent salt (NaCl) and of the surfactant sodium dodecylsulfate (SDS) in the aqueous subphase, have been studied using laser tweezers. In the absence of electrolyte and surfactant, particle interactions exhibit a long-range repulsion, yet the variation of the interaction for different particle pairs is found to be considerable. Averaging over several particle pairs was hence found to be necessary to obtain reliable assessment of the effects of salt and surfactant. It has previously been suggested that the repulsion is consistent with electrostatic interactions between a small number of dissociated charges in the oil phase, leading to a decay with distance to the power -4 and an absence of any effect of electrolyte concentration. However, the present work demonstrates that increasing the electrolyte concentration does yield, on average, a reduction of the magnitude of the interaction force with electrolyte concentration. This implies that charges on the water side also contribute significantly to the electrostatic interactions. An increase in the concentration of SDS leads to a similar decrease of the interaction force. Moreover the repulsion at fixed SDS concentrations decreases over longer times. Finally, measurements of three-body interactions provide insight into the anisotropic nature of the interactions. The unique time-dependent and anisotropic interactions between particles at the oil-water interface allow tailoring of the aggregation kinetics and structure of the suspension structure.Comment: Submitted to Langmui

Direct Observation of the Dynamics of Latex Particles Confined inside Thinning Water-Air Films

The dynamics of micrometer-size polystyrene latex particles confined in thinning foam films was investigated by microscopic interferometric observation. The behavior of the entrapped particles depends on the mobility of the film surfaces, the particle concentration, hydrophobicity, and rate of film formation. When the films were stabilized by sodium dodecyl sulfate, no entrapment of particles between the surfaces was possible. When protein was used as a stabilizer, a limited number of particles were caught inside the film area due to the decreased mobility of the interfaces. In this case, extraordinary long-ranged (>100 Ìm) capillary attraction leads to two-dimensional (2D) particle aggregation. A major change occurs when the microspheres are partially hydrophobized by the presence of cationic surfactant. After the foam films are opened and closed a few times, a layer of particles simultaneously adsorbed to the two interfaces is formed, which sterically inhibits any further film opening and thinning. The particles within this layer show an excellent 2D hexagonal ordering. The experimental data are relevant to the dynamics of defects in coating films, Pickering emulsions, and particle assembly into 2D arrays

Field Quality Measurements in a Single-Aperture 11 T Nb3Sn Demonstrator Dipole for LHC Upgrades

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Tunneling electroresistance effect in ferroelectric tunnel junctions at the nanoscale

Stable and switchable polarization of ferroelectric materials opens a possibility to electrically control their functional behavior. A particularly promising approach is to employ ferroelectric tunnel junctions where the polarization reversal in a ferroelectric barrier changes the tunneling current across the junction. Here, we demonstrate the reproducible tunneling electroresistance effect using a combination of Piezoresponse Force Microscopy (PFM) and Conducting Atomic Force Microscopy (C-AFM) techniques on nanometer-thick epitaxial BaTiO3 single crystal thin films on SrRuO3 bottom electrodes. Correlation between ferroelectric and electronic transport properties is established by the direct nanoscale visualization and control of polarization and tunneling current in BaTiO3 films. The obtained results show a change in resistance by about two orders of magnitude upon polarization reversal on a lateral scale of 20 nm at room temperature. These results are promising for employing ferroelectric tunnel junctions in non-volatile memory and logic devices, not involving charge as a state variable.Comment: 18 pages, 4 figure

A review of selected topics in physics based modeling for tunnel field-effect transistors

The research field on tunnel-FETs (TFETs) has been rapidly developing in the last ten years, driven by the quest for a new electronic switch operating at a supply voltage well below 1 V and thus delivering substantial improvements in the energy efficiency of integrated circuits. This paper reviews several aspects related to physics based modeling in TFETs, and shows how the description of these transistors implies a remarkable innovation and poses new challenges compared to conventional MOSFETs. A hierarchy of numerical models exist for TFETs covering a wide range of predictive capabilities and computational complexities. We start by reviewing seminal contributions on direct and indirect band-to-band tunneling (BTBT) modeling in semiconductors, from which most TCAD models have been actually derived. Then we move to the features and limitations of TCAD models themselves and to the discussion of what we define non-self-consistent quantum models, where BTBT is computed with rigorous quantum-mechanical models starting from frozen potential profiles and closed-boundary Schr\uf6dinger equation problems. We will then address models that solve the open-boundary Schr\uf6dinger equation problem, based either on the non-equilibrium Green's function NEGF or on the quantum-transmitting-boundary formalism, and show how the computational burden of these models may vary in a wide range depending on the Hamiltonian employed in the calculations. A specific section is devoted to TFETs based on 2D crystals and van der Waals hetero-structures. The main goal of this paper is to provide the reader with an introduction to the most important physics based models for TFETs, and with a possible guidance to the wide and rapidly developing literature in this exciting research field

Living with Landslides: Perceptions of Risk and Resilience in Far West Nepal

This study presents an analysis of risk and resilience perceptions in two villages of Far West Nepal, Sunkuda and Bajedi, located in the upper Karnali River Basin. The area has been affected by deep-seated and shallow landslides, which have had a devastating impact on many rural lives and livelihoods. While both villages are exposed to landslides, Bajedi is situated in a higher risk zone. Using structured surveys, semi-structured interviews and insights from stakeholder workshops, the risk and resilience perceptions of household residents of the two villages are elicited. The objectives of the study are 1) to understand how residents perceive their risk and resilience to landslides, and 2) to provide evidence and insights on the factors that influence risk perception. Results show that landslides are perceived as an existential risk in both villages, although risks are perceived as more serious in Bajedi. The higher risk perception in Bajedi is shown to be mainly driven by households' ability to cope, including their energy sources, whether they know whom to call in case of a landslides, as well as household savings and income sources. In Sunkuda, risk perception is shown to be influenced by households' access to and status of community forests, expenditure on medication, the seasonality and types of water sources, and ethnicity. In both villages, additional drivers of risk perception include households' social networks, their perceived triggers of landslides, their outstanding loans, and who collects the water. The results demonstrate the interconnectedness of risk perception and indicators of resilience. By elucidating the risk perception of Sunkuda and Bajedi, this study has important implications for local risk management strategies and policies

Bulgarian sport policy 1945-1989: A strategic relation perspective

The 2008 Beijing Olympic Games have stimulated discussions about the success of different sport systems and the Chinese model in particular. Revisiting explanations of sport in the former communist countries of Eastern Europe during the Cold War seems timely, as the current Chinese model of sport was largely designed after the Soviet example established in this period. This paper examines Bulgarian sport policy between 1945 and 1989. It employs a Strategic Relation approach (Jessop, 1990) to analyse sport policy making as a strategic relation closely linked to the dominant state project of building a new stateness. It goes beyond ideological interpretations and argues that the state represents a strategic terrain where these relations have to be established in struggles, the outcomes of which are always uncertain. Furthermore, past and present struggles and their outcomes create various socio-political environments that presuppose the forms of state selectivity and intervention in sport. The process of constructing sport policy was influenced by two main categories of strategic relations: intra-state, including political, organisational and personal relations between the Party, state apparatus and various sport and non-sport organisations and their managers, and transnational, concerning ideological, political, economic and organisational relations with both communist and western countries and international sport organisations