Ferromagnetic or antiferromagnetic spin ordering is governed by the exchange interaction, the strongest force in magnetism. Understanding spin dynamics in magnetic materials is an issue of crucial ...importance for progress in information processing and recording technology. Usually the dynamics are studied by observing the collective response of exchange-coupled spins, that is, spin resonances, after an external perturbation by a pulse of magnetic field, current or light. The periods of the corresponding resonances range from one nanosecond for ferromagnets down to one picosecond for antiferromagnets. However, virtually nothing is known about the behaviour of spins in a magnetic material after being excited on a timescale faster than that corresponding to the exchange interaction (10-100 fs), that is, in a non-adiabatic way. Here we use the element-specific technique X-ray magnetic circular dichroism to study spin reversal in GdFeCo that is optically excited on a timescale pertinent to the characteristic time of the exchange interaction between Gd and Fe spins. We unexpectedly find that the ultrafast spin reversal in this material, where spins are coupled antiferromagnetically, occurs by way of a transient ferromagnetic-like state. Following the optical excitation, the net magnetizations of the Gd and Fe sublattices rapidly collapse, switch their direction and rebuild their net magnetic moments at substantially different timescales; the net magnetic moment of the Gd sublattice is found to reverse within 1.5 picoseconds, which is substantially slower than the Fe reversal time of 300 femtoseconds. Consequently, a transient state characterized by a temporary parallel alignment of the net Gd and Fe moments emerges, despite their ground-state antiferromagnetic coupling. These surprising observations, supported by atomistic simulations, provide a concept for the possibility of manipulating magnetic order on the timescale of the exchange interaction.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Clinical legal education (CLE) is potentially the major disruptor of traditional law schools’ core functions. Good CLE challenges many central clichés of conventional learning in law—everything from ...case book method to the 50-minute lecture. And it can challenge a contemporary overemphasis on screen-based learning, particularly when those screens only provide information and require no interaction. Australian Clinical Legal Education comes out of a thorough research program and offers the essential guidebook for anyone seeking to design and redesign accountable legal education; that is, education that does not just transform the learner, but also inculcates in future lawyers a compassion for and service of those whom the law ought to serve. Established law teachers will come to grips with the power of clinical method. Law students struggling with overly dry conceptual content will experience the connections between skills, the law and real life. Regulators will look again at law curricula and ask law deans ‘when’?
The non-combustion based renewable electricity generation technologies were assessed against a range of sustainability indicators and using data obtained from the literature. The indicators used to ...assess each technology were price of generated electricity, greenhouse gas emissions during full life cycle of the technology, availability of renewable sources, efficiency of energy conversion, land requirements, water consumption and social impacts. The cost of electricity, greenhouse gas emissions and the efficiency of electricity generation were found to have a very wide range for each technology, mainly due to variations in technological options as well as geographical dependence of each renewable energy source. The social impacts were assessed qualitatively based on the major individual impacts discussed in literature. Renewable energy technologies were then ranked against each indicator assuming that indicators have equal importance for sustainable development. It was found that wind power is the most sustainable, followed by hydropower, photovoltaic and then geothermal. Wind power was identified with the lowest relative greenhouse gas emissions, the least water consumption demands and with the most favourable social impacts comparing to other technologies, but requires larger land and has high relative capital costs.
In a time when conservative politicians challenge the irrefutability of scientific findings such as climate change, it is more important than ever to understand the conflict at the heart of the ...“religion vs. science” debates unfolding in the public sphere. In this groundbreaking work, John H. Evans reveals that, with a few limited exceptions, even the most conservative religious Americans accept science’s ability to make factual claims about the world. However, many religious people take issue with the morality implicitly promoted by some forms of science. Using clear and engaging scholarship, Evans upends the prevailing notion that there is a fundamental conflict over the way that scientists and religious people make claims about nature and argues that only by properly understanding moral conflict between contemporary religion and science will we be able to contribute to a more productive interaction between these two great institutions.
Macro news can affect currency prices directly and indirectly via order flow. Past research shows that the direct effects of scheduled macro news account for less than 10% of daily price variance. ...This paper shows that the arrival of macro news can account for more than 30% of daily price variance. Two features of our analysis account for this finding: (1) We consider the broad spectrum of macro news items that market participants observe, not just scheduled announcements. (2) We allow the arrival of news to affect prices indirectly via its impact on the volatility of order flow. Our analysis shows that order flow variations contribute more to currency price dynamics following the arrival of public macro news than at other times. This is not consistent with news effects being common knowledge that is impounded in price directly. Roughly two-thirds of the total effect of macro news on the DM/$ exchange rate is transmitted via order flow.
Bureaucracy and Race overturns the common assumption that
apartheid in South Africa was enforced only through terror and
coercion. Without understating the role of violent intervention,
Ivan Evans ...shows that apartheid was sustained by a great and
ever-swelling bureaucracy. The Department of Native Affairs (DNA),
which had dwindled during the last years of the segregation regime,
unexpectedly revived and became the arrogant, authoritarian
fortress of apartheid after 1948. The DNA was a major player in the
prolonged exclusion of Africans from citizenship and the
establishment of a racially repressive labor market. Exploring the
connections between racial domination and bureaucratic growth in
South Africa, Evans points out that the DNA's transformation of
oppression into "civil administration" institutionalized and, for
whites, legitimized a vast, coercive bureaucratic culture, which
ensnared millions of Africans in its workings and corrupted the
entire state. Evans focuses on certain features of apartheid-the
pass system, the "racialization of space" in urban areas, and the
cooptation of African chiefs in the Bantustans-in order to make it
clear that the state's relentless administration, not its overtly
repressive institutions, was the most distinctive feature of South
Africa in the 1950s. All observers of South Africa past and present
and of totalitarian states in general will follow with interest the
story of how the Department of Native Affairs was crucial in
transforming "the idea of apartheid" into a persuasive-and all too
durable-practice.
Microfluidic-based chemical sensors take laboratory analytical protocols and miniaturize them into field-deployable systems for in situ monitoring of water chemistry. Here, we present a prototype ...nitrate/nitrite sensor based on droplet microfluidics that in contrast to standard (continuous phase) microfluidic sensors, treats water samples as discrete droplets contained within a flow of oil. The new sensor device can quantify the concentrations of nitrate and nitrite within each droplet and provides high measurement frequency and low fluid consumption. Reagent consumption is at a rate of 2.8 mL/day when measuring every ten seconds, orders of magnitude more efficient than those of the current state-of-the-art sensors. The sensor’s capabilities were demonstrated during a three-week deployment in a tidal river. The accurate and high frequency data (6% error relative to spot samples, measuring at 0.1 Hz) elucidated the influence of tidal variation, rain events, diurnal effects, and anthropogenic input on concentrations at the deployment site. This droplet microfluidic-based sensor is suitable for a wide range of applications such as monitoring of rivers, lakes, coastal waters, and industrial effluents.
A growing body of evidence supports the contention of scholarly culture theory that immersing children in book-oriented environments benefits their later educational achievement, attainment and ...occupational standing. These findings have been interpreted as suggesting that book-oriented socialization, indicated by home library size, equips youth with life-long tastes, skills and knowledge. However, to date, this has not been directly assessed. Here, we document advantageous effects of scholarly culture for adult literacy, adult numeracy, and adult technological problem solving. Growing up with home libraries boosts adult skills in these areas beyond the benefits accrued from parental education or own educational or occupational attainment. The effects are loglinear, with greatest returns to the growth in smaller libraries. Our evidence comes from regressions with balanced repeated replicate weights estimated on data from 31 societies which participated in the Programme for the International Assessment of Adult Competencies (PIAAC) between 2011 and 2015.
Vaccine Effectiveness Studies in the Field Evans, Stephen J.W; Jewell, Nicholas P
The New England journal of medicine,
08/2021, Letnik:
385, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The original trials of vaccines against infection with severe acute respiratory disease coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (Covid-19), have clearly shown ...vaccine efficacy. However, questions crucial to vaccination policy remain, at best, only partially answered. These include the effect of new virus variants, the timing between vaccine doses, the effect of vaccines on asymptomatic infection in contrast to severe disease, the waning of vaccine immunity, and the potentially enhanced effectiveness of mix-and-match strategies that might be used with booster shots. Wherever possible, vaccine efficacy should be assessed by means of randomized trials. Valid comparison is . . .
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