Electrochemical Determination of Hydrogen in Steel

The electrochemical measurement of the permeation r·ate of hydrogen through metal foils consists of charging of the metal with hydrogen on one side of the foil and removal of hydrogen by electrochemical oxidation on the other side. The hydrogen diffusion coefficient can be determined by mathematical analysis of the time dependence of the oxidation current. This electrochemical technique can also be used to determine the hydrogen concentration in metals. For this purpose, an electrochemical cell is placed on the metal to be analyzed and a hydrogen concentration gradient is produced by oxidation of all hydrogen atoms which reach the surface. Under a contract with the Naval Air Development Center a portable barnacle cell system - so-called because of its magnetic attachment to steel surfaces - is developed for field use such as determination of hydrogen concentration in aircraft landing gears. The system consists of two parts: the measuring cell in a cylindrical magnet (1.5 inch diameter) and the electronic system which allows recording of the permeation current-time trace and integration of this trace over pre-set time intervals

Study program for encapsulation materials interface for low-cost solar array

The service integrity of the bonded interface in solar cell modules used in solar arrays is addressed. The development of AC impedance as a nondestructive evaluation (NDE) methodology for solar arrays is reported along with development of corrosion models and materials selection criteria for corrosion resistant interfaces

Study program for encapsulation materials interface for low cost silicon solar array

An atmospheric corrosion model was developed and verified by five months of corrosion rate and climatology data acquired at the Mead, Nebraska LSA test site. Atmospheric corrosion rate monitors (ACM) show that moisture condensation probability and ionic conduction at the corroding surface or interface are controlling factors in corrosion rate. Protection of the corroding surface by encapsulant was shown by the ACM recordings to be maintained, independent of climatology, over the five months outdoor exposure period. The macroscopic corrosion processes which occur at Mead are shown to be reproduced in the climatology simulator. Controlled experiments with identical moisture and temperature aging cycles show that UV radiation causes corrosion while UV shielding inhibits LSA corrosion

Polyethylene glycol as shape and size controller for the hydrothermal synthesis of SrTiO3 cubes and polyhedra

Understanding the correlation between the morphological and functional properties of particulate materials is crucial across all fields of physical and natural sciences. This manuscript reports on the investigation of the effect of polyethylene glycol (PEG) employed as a capping agent in the synthesis of SrTiO3 crystals. The crucial influence of PEG on both the shape and size of the strontium titanate particles is revealed, highlighting the effect on the photocurrents measured under UV–Vis irradiation

Efficient and gentle delivery of molecules into cells with different elasticity via Progressive Mechanoporation

Intracellular delivery of cargo molecules such as membrane-impermeable proteins or drugs is crucial for cell treatment in biological and medical applications. Recently, microfluidic mechanoporation techniques have enabled transfection of previously inaccessible cells. These techniques create transient pores in the cell membrane by shear-induced or constriction contact-based rapid cell deformation. However, cells deform and recover differently from a given extent of shear stress or compression and it is unclear how the underlying mechanical properties affect the delivery efficiency of molecules into cells. In this study, we identify cell elasticity as a key mechanical determinant of delivery efficiency leading to the development of “progressive mechanoporation” (PM), a novel mechanoporation method that improves delivery efficiency into cells of different elasticity. PM is based on a multistage cell deformation, through a combination of hydrodynamic forces that pre-deform cells followed by their contact-based compression inside a PDMS-based device controlled by a pressure-based microfluidic controller. PM allows processing of small sample volumes (about 20 μL) with high-throughput (>10 000 cells per s), while controlling both operating pressure and flow rate for a reliable and reproducible cell treatment. We find that uptake of molecules of different sizes is correlated with cell elasticity whereby delivery efficiency of small and big molecules is favoured in more compliant and stiffer cells, respectively. A possible explanation for this opposite trend is a different size, number and lifetime of opened pores. Our data demonstrates that PM reliably and reproducibly delivers impermeable cargo of the size of small molecule inhibitors such as 4 kDa FITC-dextran with >90% efficiency into cells of different mechanical properties without affecting their viability and proliferation rates. Importantly, also much larger cargos such as a >190 kDa Cas9 protein–sgRNA complex are efficiently delivered high-lighting the biological, biomedical and clinical applicability of our findings

Efficient and gentle delivery of molecules into cells with different elasticity via Progressive Mechanoporation.

Intracellular delivery of cargo molecules such as membrane-impermeable proteins or drugs is crucial for cell treatment in biological and medical applications. Recently, microfluidic mechanoporation techniques have enabled transfection of previously inaccessible cells. These techniques create transient pores in the cell membrane by shear-induced or constriction contact-based rapid cell deformation. However, cells deform and recover differently from a given extent of shear stress or compression and it is unclear how the underlying mechanical properties affect the delivery efficiency of molecules into cells. In this study, we identify cell elasticity as a key mechanical determinant of delivery efficiency leading to the development of "progressive mechanoporation" (PM), a novel mechanoporation method that improves delivery efficiency into cells of different elasticity. PM is based on a multistage cell deformation, through a combination of hydrodynamic forces that pre-deform cells followed by their contact-based compression inside a PDMS-based device controlled by a pressure-based microfluidic controller. PM allows processing of small sample volumes (about 20 μL) with high-throughput (>10 000 cells per s), while controlling both operating pressure and flow rate for a reliable and reproducible cell treatment. We find that uptake of molecules of different sizes is correlated with cell elasticity whereby delivery efficiency of small and big molecules is favoured in more compliant and stiffer cells, respectively. A possible explanation for this opposite trend is a different size, number and lifetime of opened pores. Our data demonstrates that PM reliably and reproducibly delivers impermeable cargo of the size of small molecule inhibitors such as 4 kDa FITC-dextran with >90% efficiency into cells of different mechanical properties without affecting their viability and proliferation rates. Importantly, also much larger cargos such as a >190 kDa Cas9 protein-sgRNA complex are efficiently delivered high-lighting the biological, biomedical and clinical applicability of our findings

Agroecology, Supply Chains, and COVID-19: Lessons on Food System Transitions from Ecuador

In cities, agroecological food consumption is often identified as an exclusive, middle-class practice. In this article, we examine changes in agroecological food circuits in urban Ecuador, amid COVID-19 breakdowns in conventional food systems. Through interviews with farmers, government officials, and NGO workers in 2020 and 2021, our research identifies three sets of experiences with distinct implications for agroecological transitions. First, some agroecological circuits could no longer function due to regulations on food circulation that favored the corporate food sector. Second, some circuits temporarily expanded to reach more urban middle-class consumers, using online platforms and government infrastructures. Third, urban collectives and neighborhood organizations re-appropriated urban spaces – from cultural centers to city streets – to facilitate the circulation of agroecological foods in low-income sectors. We highlight the spatial and social ‘re-localization’ practices of these urban groups that challenge the hegemony of conventional food circuits, as they drive agroecological food consumption beyond the middle-class

German Emigration and Remigration Panel Study (GERPS): Documentation of the Second Wave

International migration originating from highly developed countries is a crucial component of global migration flows. There are, however, surprisingly little data about the international mobility of the populations of affluent countries. The German Emigration and Remigration Panel Study (GERPS) aims to provide a resource that enables the analysis of individual consequences of international migration as well as the socio-structural consequences for the country of origin. GERPS is based on an origin-based multistage probability sample using the German population registers as a sampling frame. The second wave yields a net sample of roughly 7,000 persons who recently moved abroad from Germany and persons who returned from Germany after having lived abroad. The study follows a multidestination-country-design and enables the comparative analysis of migrants and nonmigrants, who stayed in the country of origin. GERPS is a panel study with at least four waves during a period of at least 24 months. This documentation presents the methods and data of the second wave. It provides information for researchers and invites them to use the new data infrastructure for their own research

On the Corrosion Resistance of Porous Electroplated Zinc Coatings in Different Corrosive Media

The corrosion resistance of an electroplated (EP) Zn coating whose surface was chemically etched to produce surface defects (pores) is investigated in this work. Impedance and DC polarisation measururements were employed to study the behaviour of such coating in various corrosive media (NaCl, NaOH and rain water). Four different faradaic relaxation processes were clearly revealed in different NaCl concentrations (from 0.1M to 1M). In the most concentrated solutions at least three relaxation processes at low frequencies (LF) appeared and were related to zinc deposition and dissolution. At lower concentrations and depending on the pH, only one process was observed. The charge transfer resistance (Rct) and the corrosion current (Icorr) were practically stable in the pH range 5 to 10. In deaerated NaCl 0.1M, the EIS diagrams showed two time-constants at very close frequencies. From the EIS diagrams the porous nature of the coating was highlighted and showed that the dissolution mechanisms occurred at the base of the pores