Size effect on magnetism of Fe thin films in Fe/Ir superlattices

In ferromagnetic thin films, the Curie temperature variation with the thickness is always considered as continuous when the thickness is varied from $n$ to $n+1$ atomic planes. We show that it is not the case for Fe in Fe/Ir superlattices. For an integer number of atomic planes, a unique magnetic transition is observed by susceptibility measurements, whereas two magnetic transitions are observed for fractional numbers of planes. This behavior is attributed to successive transitions of areas with $n$ and $n+1$ atomic planes, for which the $T_c$'s are not the same. Indeed, the magnetic correlation length is presumably shorter than the average size of the terraces. Monte carlo simulations are performed to support this explanation.Comment: LaTeX file with Revtex, 5 pages, 5 eps figures, to appear in Phys. Rev. Let

Acclimatization of massive reef-building corals to consecutive heatwaves

Reef-building corals typically live close to the upper limits of their thermal tolerance and even small increases in summer water temperatures can lead to bleaching and mortality. Projections of coral reef futures based on forecasts of ocean temperatures indicate that by the end of this century, corals will experience their current thermal thresholds annually, which would lead to the widespread devastation of coral reef ecosystems. Here, we use skeletal cores of long-lived Porites corals collected from 14 reefs across the northern Great Barrier Reef, the Coral Sea, and New Caledonia to evaluate changes in their sensitivity to heat stress since 1815. High-density 'stress bands'-indicative of past bleaching-first appear during a strong pre-industrial El Nino event in 1877 but become significantly more frequent in the late twentieth and early twenty-first centuries in accordance with rising temperatures from anthropogenic global warming. However, the proportion of cores with stress bands declines following successive bleaching events in the twenty-first century despite increasing exposure to heat stress. Our findings demonstrate an increase in the thermal tolerance of reef-building corals and offer a glimmer of hope that at least some coral species can acclimatize fast enough to keep pace with global warming

Ferromagnetism above room temperature in Mn-Si-C alloy films

Mn-Si-C alloy films are prepared by e-beam coevaporation onto a Si substrate held at 600 °C. Ferromagnetism is observed below T = (360 +/- 5) K with SQUID magnetometry and magneto-optical Kerr effect. This is the highest Curie temperature T yet observed for a Mn-based alloy. Although the composition determined by Auger depth profiling varies appreciably for different films, their T is the same indicating that ferromagnetism is caused by an alloy of well-defined composition independent of precipitations

Development of Polish apparent steel consumption models for rebars 2004-2017 including the cement market and buildings category

Celem niniejszej publikacji jest opracowanie modeli ekonometrycznych określających zależności między zużyciem prętów żebrowanych (zmienna objaśniana) w krajowym budownictwie w latach 2004-2017 i materiałami substytucyjnymi (walcówka - również stosowana do zbrojenia betonu) oraz komplementarnymi (cement), które wpływają na wielkość zużycia prętów. W opracowanych modelach zmiennymi objaśniającymi były: zużycie cementu i produkcja budowlana. Budując model zużycia prętów żebrowanych w krajowym budownictwie ustalono także poziom zależności zużycia materiałów zbrojeniowych w różnych typach obiektów budowlanych o przeznaczeniu indywidualnym, np. budynki jednorodzinne, deweloperskim (np. budynki wielorodzinne), zbiorowym (np. budynki użytkowania zbiorowego) oraz o wykorzystaniu do celów przemysłowych, infrastrukturalnych i innych. Proces specyfikacji modelu zużycia prętów żebrowanych w krajowym budownictwie w latach 2004-2017 stanowi treść niniejszej publikacji.The purpose of this paper is to develop econometric models defining the relationship between the apparent consumption of rebars (dependent variable) in the domestic construction industry in 2004-2017 and substitutionary (ribbed wire rods) and complementary materials (cement) (independent variables), which affect the use of rebars. In the developed models, the independent variables were: cement consumption (material used for concrete production) and value of construction production. While building a model of the use of rebars in the domestic construction industry, the relations of consumption of individual materials in various types of construction facilities for individual use, e.g. singlefamily buildings, developers buildings (e.g. multi-family buildings), collective buildings (e.g. buildings for collective use) as well as industrial, infrastructural and other use, was also established. The process of model specification of the use rebars in the domestic construction industry in 2004-2017 is the content of this publication

Model map of the process of implementing a new platinum recovery technology from used car catalysts on the domestic market

The development of industry as well as competition and globalization entail the necessity to use new technologies, which largely affect the competitive advantage of enterprises. Analysis of the implementation process of new or modified technology is difficult to conduct due to the cost of the process, its complexity and the rate of changes on the global market in the field of implemented technological innovations. The paper presents an example map of implementation and organization of platinum recovery from used car catalysts in Poland, taking into account the expectations of participants in various segments of the car recycling network. During the construction of the map, the technical parameters were also taken into consideration, apart from economic and technological parameters. The proposed map consisted of several stages: technology project, market research, technology preparation, acquiring entities that taking over the technology, launch of technology, and sale and distribution of the product. The individual stages have been characterized in the aspect of technology of platinum recovery from used car catalysts. The number of these stages, however, depends on the situation on the market of end-of-life vehicles and interested economic entities forming the structure of the platinum recovery network. The publication is the basis for further discussion on the creation of a platinum recovery network (missing in Poland) from car catalysts

Scanning tunneling spectroscopy of rare-earth metals: Gadolinium on yttrium

Scanning tunneling microscopy images of ultrathin Gd films on Y(0001) show a strong chemical contrast depending on the tunneling voltage. For small voltages the tunneling spectra for Gd reveal pronounced features which are attributed to occupied and unoccupied electronic surface states as found previously in photoemission experiments. These Gd surface states give rise to a large tunneling current and the image contrast between Gd and Y is enhanced by a factor of two because low-energy surface states are absent in Y. On the other hand, for a high positive bias of $\rm +2\;V$ the contrast is reversed due to tunneling into unoccupied Y electronic states presumably originating from the Y 5d band. The corresponding current increase with respect to Gd exceeds the current increase induced by a monolayer step

Ferromagnetism above room temperature in Mn-Si-C alloy films

Mn-Si-C alloy films are prepared by e-beam coevaporation onto a Si substrate held at 600 °C. Ferromagnetism is observed below T = (360 +/- 5) K with SQUID magnetometry and magneto-optical Kerr effect. This is the highest Curie temperature T yet observed for a Mn-based alloy. Although the composition determined by Auger depth profiling varies appreciably for different films, their T is the same indicating that ferromagnetism is caused by an alloy of well-defined composition independent of precipitations

Decreased tourism during the COVID-19 pandemic positively affects reef fish in a high use marine protected area.

Humans alter ecosystems through both consumptive and non-consumptive effects. Consumptive effects occur through hunting, fishing and collecting, while non-consumptive effects occur due to the responses of wildlife to human presence. While marine conservation efforts have focused on reducing consumptive effects, managing human presence is also necessary to maintain and restore healthy ecosystems. Area closures and the tourism freeze related to the COVID-19 pandemic provided a unique natural experiment to measure the effects of decreased tourism on fish behavior in a high use no-take marine protected area (MPA) in Hawai`i. We found that when tourism shut down due to COVID restrictions in 2020, fish biomass increased and predatory species increased usage of shallow habitats, where tourists typically concentrate. When tourism resumed, fish biomass and habitat use returned to pre-pandemic levels. These displacement effects change fish community composition and biomass, which could affect key processes such as spawning, foraging and resting, and have knock-on effects that compromise ecosystem function and resilience. Managing non-consumptive uses, especially in heavily-visited MPAs, should be considered for sustainability of these ecosystems