Recently, the perpendicular magnetic tunnel junctions (p-MTJs) arouse great interest because of its unique features in the application of spin-transfer-torque magnetoresistive random access memory ...(STT-MRAM), such as low switching current density, good thermal stability and high access speed. In this paper, we investigated current induced switching (CIS) in ultrathin MgO barrier p-MTJs with dimension down to 50 nm. We obtained a CIS perpendicular tunnel magnetoresistance (p-TMR) of 123.9% and 7.0 Ω·μm2 resistance area product (RA) with a critical switching density of 1.4×1010 A/m2 in a 300 nm diameter junction. We observe that the extrinsic breakdown mechanism dominates, since the resistance of our p-MTJs decreases gradually with the increasing current. From the statistical analysis of differently sized p-MTJs, we observe that the breakdown voltage (V
b) of 1.4 V is 2 times the switching voltage (V
s) of 0.7 V and the breakdown process exhibits two different breakdown states, unsteady and steady state. Using Simmons’ model, we find that the steady state is related with the barrier height of the MgO layer. Furthermore, our study suggests a more efficient method to evaluate the MTJ stability under high bias rather than measuring V
b. In conclusion, we developed well performant p-MTJs for the use in STT-MRAM and demonstrate the mechanism and control of breakdown in nano-scale ultrathin MgO barrier p-MTJs.
Atmospheric deposition of metals originating from a variety of sources, including bitumen upgrading facilities and blowing dusts from landscape disturbances, is of concern in the Athabasca oil sands ...region of northern Alberta, Canada. Mercury (Hg) is of particular interest as methylmercury (MeHg), a neurotoxin which bioaccumulates through foodwebs, can reach levels in fish and wildlife that may pose health risks to human consumers. We used spring-time sampling of the accumulated snowpack at sites located varying distances from the major developments to estimate winter 2012 Hg loadings to a ∼20 000 km2 area of the Athabasca oil sands region. Total Hg (THg; all forms of Hg in a sample) loads were predominantly particulate-bound (79 ± 12%) and increased with proximity to major developments, reaching up to 1000 ng m–2. MeHg loads increased in a similar fashion, reaching up to 19 ng m–2 and suggesting that oil sands developments are a direct source of MeHg to local landscapes and water bodies. Deposition maps, created by interpolation of measured Hg loads using geostatistical software, demonstrated that deposition resembled a bullseye pattern on the landscape, with areas of maximum THg and MeHg loadings located primarily between the Muskeg and Steepbank rivers. Snowpack concentrations of THg and MeHg were significantly correlated (r = 0.45–0.88, p < 0.01) with numerous parameters, including total suspended solids (TSS), metals known to be emitted in high quantities from the upgraders (vanadium, nickel, and zinc), and crustal elements (aluminum, iron, and lanthanum), which were also elevated in this region. Our results suggest that at snowmelt, a complex mixture of chemicals enters aquatic ecosystems that could impact biological communities of the oil sands region.
Abstrakt Inżynieria tkankowa to interdyscyplinarna dziedzina badań, która stosuje zasady inżynierii i nauk przyrodniczych do opracowywania substytutów biologicznych, przywracania, utrzymywania lub ...poprawy funkcji tkanek. Łączy medycy-nę kliniczną, inżynierię mechaniczną, materiałoznawstwo i biologię molekularną. Chitozan jest związkiem, który może być stosowany na szeroką skalę w biomedycynie, m.in. jako nośnik leków, nici chirurgiczne, materiały opatrunkowe przeznaczone do przyspieszonego gojenia ran oraz rusztowania komórkowe w inżynierii tkankowej. Chitozon spełnia najważniejsze kryteria dla biomateriałów, m.in. kompatybilność, odpowiednie właściwości mechaniczne, morfologia i porowatość, nietoksyczność i biodegradowalność. Rusztowania chitozanowe mogą sprzyjać adhezji, różnicowaniu i proliferacji na powierzchni komórek. Z chitozanu można tworzyć różne formy funkcjonalne w zależności od potrzeb i wymagań, w tym: hydrożele 3D, gąbki 3D, folie i membrany oraz nanowłókna. Ze względu na unikalne właściwości fizykochemiczne biopolimer ten może być również wykorzystany do oczyszczania białek terapeutycznych z endotoksyn bakteryjnych, co jest dziś istotnym problemem w oczyszczaniu produktu końcowego w zastosowaniach medycznych. Obecnie terapie oparte na białkach rekombinowanych znajdują szerokie zastosowanie w terapiach celowanych, inżynierii tkankowej oraz szeroko pojętej medycynie regeneracyjnej. Dlatego tak ważny jest współistniejący, dobrze zapro-jektowany system oczyszczania produktu białkowego, który nie zmieni swoich zasadniczych właściwości. Artykuł jest przeglądem aktualnych badań nad zastosowaniem materiałów bioaktywnych na bazie chitozanu w medycynie regene-racyjnej różnych tkanek i narządów (m.in. tkanki chrzęstnej i kostnej, tkanki skórnej czy tkanki nerwowej).
Abstract Tissue engineering is an interdisciplinary field of research that applies the principles of engineering and the natural sciences to the development of biological substitutes, restoring, maintaining, or improving tissue functions. It combines clinical medicine, mechanical engineering, materials science and molecular biology. Chitosan is a very promising compound that can be used on a large scale in biomedicine as a carrier of drugs, surgical threads, dressing materials dedicated to accelerating wound healing and cell scaffolding in tissue engineering. It meets the most important criteria for biomaterials, such as compatibility, adequate mechanical properties, morphology and porosity, non-toxicity and biodegradability. Chitosan scaffolds can promote cell surface adhesion, differentiation and proliferation. It can be used to create various functional forms depending on the needs and requirements, including 3D hydrogels, 3D sponges, films and membranes and nanofibers. Due to its unique physicochemical properties, this biopolymer also has the potential to purify therapeutic proteins from bacterial endotoxins, which is currently an important problem in the purification of the end product in the context of medical applications. Currently, recombinant protein therapeutics are widely used in targeted therapies, tissue engineering and broadly understood regenerative medicine. That is why the coexisting, well-designed purification system of a protein product, which will not change its essential properties, is so important. This article is a review of current research on the use of bioactive materials based on chitosan in regenerative medicine of various tissues and organs (including cartilage and bone tissues, skin tissues or nervous tissue).
In order to achieve sustainable food production, non-chemical weed management practices need to be developed for fruit growing. Tailor-made floor management systems enable efficient weed regulation, ...but they also affect the soil quality in an orchard. In this article, the effects of various floor management systems in a ‘Red Jonaprince’ apple (Malus × domestica Borkh.) orchard on the soil properties and the trees’ nutritional status and initial development during the first two years after the orchard’s establishment were assessed. The experiment was set up in the spring of 2017 in the Experimental Orchard of WULS. ‘Red Jonaprince’ cv. trees grafted on M.9 rootstock were planted with 3.5 × 1 m spacing between them. Different floor management systems were applied to the rows, including the selected organic mulches: Miscanthus × giganteus straw (MG1 and MG2), spent mushroom substrates (SMS1 and SMS2), herbicide strip (HS), clear mechanical soil cultivation (MC), and synthetic black mulch (BC). The organic mulches affected the soil properties significantly. Spent mushroom substrates (SMS1, SMS2) increased the P and K contents in the soil, increased the salinity 10-fold, and retarded the growth in terms of the trunk cross-section area (TCSA) and its increment compared with other systems. Miscanthus × giganteus straw mulch (MG1, MG2) was associated with a more vigorous shoot growth compared with other combinations in the first year of the study as it provided a better tree nitrogen nutritional status. The floor management system affected the generative development of the trees. Mulching with a spent mushroom substrate boosted the flower bud formation intensity, but it did not affect the yielding quantity. Moreover, due to the poor fruit set, the trees mulched with a spent mushroom substrate (SMS2) gave a low initial bearing. High crop loads were noted for the trees treated with black synthetic mulch (BC) and the trees mulched with Miscanthus × giganteus straw (MG1). This was an effect of the tree size rather than the blooming intensity, while there were no differences in the cropping efficiency index (CEI) parameter.
In current management research, a variety of different activities are summarized under the generic term “nonmarket strategy”. Simultaneously, “sub-categories” of nonmarket strategies such as ...political or social strategies are treated as isolated activities, making it difficult to realize cross-concept relations or commonalities. This article bundles, maps and critically evaluates the rising number of publications in the field of nonmarket strategy research. Based on an integrative framework, we work up insights that have been developed since Baron’s (Manag Rev 37:47–65,
1995
) seminal publication. Doing so, our analysis extends previous studies by including internal and external antecedents that influence the development of nonmarket strategies, by analyzing the impact of nonmarket strategies on firm performance and the possibility of strategy integration, on a national as well as multinational level. Key empirical and conceptual papers are reviewed and major findings, relationships, patterns and contradictions are revealed. By consolidating and synthesizing dispersed knowledge, we identify implications for nonmarket strategy elaboration as well as several directions for future research.
Aging is a biological event that influences many organs and systems. Both sarcopenia and frailty syndrome refer to geriatric conditions with overlapping phenotypes. Many mechanisms are involved in ...the aging process such as DNA methylation telomeres which are susceptible to oxidative stress, and inflammations which result in telomere shortening, leading to chromosomal instability. The study aimed to determine the associations between these processes, frailty and sarcopenia syndrome. Global DNA methylation was analyzed using the ELISA method. Telomere length was analyzed using qPCR. Total oxidative status (TOS) was analyzed using a colorimetric method. The present study revealed that the main factor affecting methylation, telomeres length and level of total oxidant stress was age.
The aim of this paper is to further develop the original method proposed by the authors in their previous publications and submitted as a patent to shape frequency response of a vibrating plate ...according to precisely defined demands. The method is based on modeling the plate together with additional masses and ribs, and applying a sophisticated optimization algorithm, which issues arrangement of the masses and ribs. It has a very high practical potential. It can be used to improve acoustic radiation of the plate for required frequencies or enhance acoustic isolation of noise barriers and device casings. It can be utilized for both passive and active control. For the latter case it allows at the same time to optimally arrange actuators and sensors.
In the paper there are presented, compared and discussed simulation results of the method for a plate with different boundary conditions: simply supported, fully-clamped and elastically restrained against rotation (corresponding to a mounting in a real device casing). Proposed optimization criteria are followed from practical scenarios, where precise modification of a vibrating plate frequency response is desired. The application of the proposed method for active control is also shown. The important additional outcome of the paper are guidelines on designing device casings in terms of rigidity in order to obtain their required vibration and noise isolation features.
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