Optical absorption of circularly polarized light is well known to yield an electron spin polarization in direct band gap semiconductors. We demonstrate that electron spins can even be generated with high efficiency by absorption of linearly polarized light in In x Ga 1−x As. By changing the incident linear polarization direction we can selectively excite spins both in polar and transverse directions.These directions can be identified by the phase during spin precession using time-resolved Faraday rotation. We show that the spin orientations do not depend on the crystal axes suggesting an extrinsic excitation mechanism.
We report on lateral spin-caloric transport (LSCT) of electron spin packets which are optically generated by ps laser pulses in the non-magnetic semiconductor n-GaAs at T ≤ 35 K. LSCT is driven by a local temperature gradient induced by an additional cw heating laser. The spatio-temporal evolution of the spin packets is probed using time-resolved Faraday rotation. We demonstrate that the local temperature-gradient induced spin diffusion is solely driven by a non-equilibrium hot spin distribution, i.e. without involvement of phonon drag effects. Additional electric field-driven spin drift experiments are used to verify directly the validity of the non-classical Einstein relation for moderately doped semiconductors at low temperatures for near band-gap excitation.
Introduction:The world is facing the devastating impact a biological event can have on human health, economies, and political stability. COVID-19 has revealed that national governments and the international community are woefully unprepared to respond to pandemics—underscoring our shared vulnerability to future catastrophic biological threats that could meet or exceed the severe consequences of the current pandemic. This study examines potential threats related to deliberate Russian military use and misuse of the tools of modern biology or an accident caused by a CBRN event evolving rapidly in the highly volatile political environment in and around Ukraine and other conflicts.Method:A participatory foresight, co-creative, future and transformation-oriented methodology was used to structure a transformative model for a disciplined exploration of scenarios to confront complex challenges and facilitate improved outcomes. Foresight helps to evaluate current policy priorities and potential new policy directions; see how the impact of possible policy decisions may combine with other developments; inform, support and link policy-making in and across a range of sectors; identify future directions, emerging technologies, new societal demands and challenges; and anticipate future developments, disruptive events, risks and opportunities.Results:The study found that the “mitigation scenarios” are based on the “Confront, Regulate, Overcome” metamodel combined with the “Security, Rescue, Care” response modalities. These require the cooperation/coordination of law enforcement forces along with military forces, fire departments and civil security resources, hospital and first-line responder teams, in order to appropriately address populations, assets and territories issues elicited by the identified threat, which drives key decision makers’ tasks at the strategic level.Conclusion:The participatory foresight exercise demonstrated gaps in national and international biosecurity and pandemic preparedness architectures highlighted by the challenges of the Ukraine war—exploring opportunities for better cooperation to improve prevention and response capabilities for high-consequence biological events, and generate actionable recommendations for the international community.
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