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\"Grace in All Simplicity narrates the saga of how we have prospected for some of Nature's most tightly held secrets, the basic constituents of matter and the fundamental forces that rule them. Our current understanding of the world (and universe) we inhabit is the result of curiosity, diligence, and daring, of abstraction and synthesis, and of an abiding faith in the value of exploration. In these pages we will meet scientists of both past and present. These men and women are professional scientists and amateurs, the eccentric and the conventional, performers and introverts\"-- Provided by publisher.

We have observed both superluminal and ultraslow light propagation in an alexandrite crystal at room temperature. Group velocities as slow as 91 meters per second to as fast as -800 meters per second were measured and attributed to the influence of coherent population oscillations involving chromium ions in either mirror or inversion sites within the crystal lattice. Namely, ions in mirror sites are inversely saturable and cause superluminal light propagation, whereas ions in inversion sites experience conventional saturable absorption and produce slow light. This technique for producing large group indices is considerably easier than the existing methods to implement and is therefore suitable for diverse applications.

The enhanced reversibility (stable transition temperature even at high strain under a solid-to-solid phase transition), low hysteresis and unusual riverine microstructure (ranging through thermal cycles) of the martensitic material Zn 45 Au 30 Cu 25 makes it attractive for applications from eco-friendly fridges to medical sensors. A boost for martensitic alloys Martensitic transformations are diffusionless, solid-to-solid phase transformations characterized by a change of crystal structure that can often be very useful. Applications include medical sensors, eco-friendly refrigerators and energy conversion devices. Repeated transformation cycles, however, can cause thermal hysteresis that modifies the material's properties and can cause permanent damage. Here Richard James and colleagues report the development of a martensitic alloy of zinc, gold and copper that maintains near-reproducible macroscopic properties despite drastic changes in its microstructure during each cycle. As well as providing a system that throws new light on the effects of hysteresis on reversible martensitic phase transformations, this work could help to extend applications for the materials in new areas — towards shape memory alloys for instance. Materials undergoing reversible solid-to-solid martensitic phase transformations are desirable for applications in medical sensors and actuators 1 , eco-friendly refrigerators 2 , 3 and energy conversion devices 4 . The ability to pass back and forth through the phase transformation many times without degradation of properties (termed ‘reversibility’) is critical for these applications. Materials tuned to satisfy a certain geometric compatibility condition have been shown 2 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 to exhibit high reversibility, measured by low hysteresis and small migration of transformation temperature under cycling 6 , 9 , 12 , 15 . Recently, stronger compatibility conditions called the ‘cofactor conditions’ 5 , 15 have been proposed theoretically to achieve even better reversibility. Here we report the enhanced reversibility and unusual microstructure of the first martensitic material, Zn 45 Au 30 Cu 25 , that closely satisfies the cofactor conditions. We observe four striking properties of this material. (1) Despite a transformation strain of 8%, the transformation temperature shifts less than 0.5 °C after more than 16,000 thermal cycles. For comparison, the transformation temperature of the ubiquitous NiTi alloy shifts up to 20 °C in the first 20 cycles 9 , 16 . (2) The hysteresis remains approximately 2 °C during this cycling. For comparison, the hysteresis of the NiTi alloy is up to 70 °C (refs 9 , 12 ). (3) The alloy exhibits an unusual riverine microstructure of martensite not seen in other martensites. (4) Unlike that of typical polycrystal martensites, its microstructure changes drastically in consecutive transformation cycles, whereas macroscopic properties such as transformation temperature and latent heat are nearly reproducible. These results promise a concrete strategy for seeking ultra-reliable martensitic materials.

Spin dissection The magnetism produced by electrons in a solid can have two components — spin and orbital moments — that are interchangeable on femtosecond timescales. Christine Boeglin and colleagues have used ultrashort pulses of light to modify the orbital angular momentum of electrons in a magnetic material and to observe, with X-ray pulses, how rapidly this momentum is transferred to the spins. By disentangling the changes in these two components in this way, it is possible to obtain insights into the underlying dynamical processes that could be of value for ultrafast magnetic recording. The magnetism produced by electrons in a solid can have two components — the spin and orbital moments — that are interchangeable on femtosecond timescales. Here it is shown how rapid changes in these two components can be disentangled, providing insights into the underlying dynamical processes that could be of value for the ultrafast control of information in magnetic recording media. For an isolated quantum particle, such as an electron, the orbital ( L ) and spin ( S ) magnetic moments can change provided that the total angular momentum of the particle is conserved. In condensed matter, an efficient transfer between L and S can occur owing to the spin–orbit interaction, which originates in the relativistic motion of electrons 1 . Disentangling the absolute contributions of the orbital and spin angular momenta is challenging, however, as any transfer between the two occurs on femtosecond timescales. Here we investigate such phenomena by using ultrashort optical laser pulses to change the magnetization of a ferromagnetic film 2 , 3 , 4 , 5 , 6 , 7 and then probe its dynamics with circularly polarized femtosecond X-ray pulses 8 . Our measurements enable us to disentangle the spin and orbital components of the magnetic moment, revealing different dynamics for L and S . We highlight the important role played by the spin–orbit interaction in the ultrafast laser-induced demagnetization of ferromagnetic films, and show also that the magneto-crystalline anisotropy energy is an important quantity to consider in such processes. Our study provides insights into the dynamics in magnetic systems 9 as well as perspectives for the ultrafast control of information in magnetic recording media 10 .

Spectrally resolved scattering of ultrafast K-α x-rays has provided experimental validation of the modeling of the compression and heating of shocked matter. The elastic scattering component has characterized the evolution and coalescence of two shocks launched by a nanosecond laser pulse into lithium hydride with an unprecedented temporal resolution of 10 picoseconds. At shock coalescence, we observed rapid heating to temperatures of 25,000 kelvin when the scattering spectra show the collective plasmon oscillations that indicate the transition to the dense metallic plasma state. The plasmon frequency determines the material compression, which is found to be a factor of 3, thereby reaching conditions in the laboratory relevant for studying the physics of planetary formation.

Travelling through the chaos The ease with which waves can travel through a disordered system is theoretically encapsulated in the separation and width of the energy levels — or modes — describing that system. But extracting this information is experimentally challenging because of the spectral overlap of these modes. Jing Wang and Azriel Genack now show how these modal properties can be reconstructed from measurements of the 'speckle' pattern of radiation transmitted through a disordered medium. The ease with which waves can travel through a disordered system is theoretically encapsulated in the separation and width of the energy levels, or modes, describing that system. However, extracting this information is experimentally challenging due to the spectral overlap of these modes. Here it is shown how these modal properties can be reconstructed from measurements of the 'speckle' pattern of radiation transmitted through a disordered medium. Excitations in complex media are superpositions of eigenstates that are referred to as ‘levels’ for quantum systems and ‘modes’ for classical waves. Although the Hamiltonian of a complex system may not be known or solvable, Wigner conjectured 1 that the statistics of energy level spacings would be the same as for the eigenvalues of large random matrices. This has explained key characteristics of neutron scattering spectra 2 . Subsequently, Thouless and co-workers argued 3 , 4 that the metal–insulator transition in disordered systems 4 , 5 , 6 could be described by a single parameter, the ratio of the average width and spacing of electronic energy levels: when this dimensionless ratio falls below unity, conductivity is suppressed by Anderson localization 5 of the electronic wavefunction. However, because of spectral congestion due to the overlap of modes 7 , 8 , 9 , even for localized waves, a comprehensive modal description of wave propagation has not been realized. Here we show that the field speckle pattern 10 of transmitted radiation—in this case, a microwave field transmitted through randomly packed alumina spheres—can be decomposed into a sum of the patterns of the individual modes of the medium and the central frequency and linewidth of each mode can be found. We find strong correlation between modal field speckle patterns, which leads to destructive interference between modes. This allows us to explain complexities of steady state and pulsed transmission of localized waves and to harmonize wave and particle descriptions of diffusion.

We compute the time variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine-structure constant and Newton’s constant) within the context of the so-called running vacuum models (RVMs) of the cosmic evolution. Recently, compelling evidence has been provided that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance Λ CDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level ≳ 3 σ . Here we use such remarkable status of the RVMs to make definite predictions on the cosmic time variation of the fundamental constants. It turns out that the predicted variations are close to the present observational limits. Furthermore, we find that the time evolution of the dark matter particle masses should be crucially involved in the total mass variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the “micro–macro connection” (viz. the dynamical feedback between the evolution of the cosmological parameters and the time variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS).

PurposeThe purpose of this research is to address the existing gap in the study of construction and demolition waste (C&DW) by focusing on its impact on human health throughout the entire life cycle. And this research provides a comprehensive assessment model that incorporates the release of gaseous pollutants and particulate matter during the whole life cycle of C&DW, thereby contributing to a more holistic understanding of its impact on human health.Design/methodology/approachThe research was conducted in two stages. Firstly, the quantitative model framework of pollutants emitted by C&DW was established. Three types of pollutants were considered, namely nitrogen dioxide (NO2), sulfur dioxide (SO2) and inhalable particulate matter (PM10). Second, disability-adjusted life year (DALY) and willingness to pay (WTP) assessments were used to provide a monetary quantified health impact for pollutants released by C&DW.FindingsThe results show that the WTP value of PM10 is the highest among all pollutants and 8.68E+07 dollars/a, while the WTP value in the disposal stage accounts for the largest proportion compared to the generation and transportation stage. These findings emphasize the importance of PM10 and C&DW treatment stage for pollutant treatment.Originality/valueThe results of this study are of great significance for the management department to optimize the construction management scheme to reduce the total amount of pollutants produced by C&DW and its harm to human health. Meanwhile, this study fills the gap in existing research on the impact assessment of C&DW on human health throughout the whole life cycle, and provides reference and basis for future research and policy formulation.

Background A recent epidemiological study showed that air pollution is closely involved in the prognosis of ischemic stroke. We and others have reported that microglial activation in ischemic stroke plays an important role in neuronal damage. In this study, we investigated the effects of urban aerosol exposure on neuroinflammation and the prognosis of ischemic stroke using a mouse photothrombotic model. Results When mice were intranasally exposed to CRM28, urban aerosols collected in Beijing, China, for 7 days, microglial activation was observed in the olfactory bulb and cerebral cortex. Mice exposed to CRM28 showed increased microglial activity and exacerbation of movement disorder after ischemic stroke induction. Administration of core particles stripped of attached chemicals from CRM28 by washing showed less microglial activation and suppression of movement disorder compared with CRM28-treated groups. CRM28 exposure did not affect the prognosis of ischemic stroke in null mice for aryl hydrocarbon receptor, a polycyclic aromatic hydrocarbon (PAH) receptor. Exposure to PM2.5 collected at Yokohama, Japan also exacerbated movement disorder after ischemic stroke. Conclusion Particle matter in the air is involved in neuroinflammation and aggravation of the prognosis of ischemic stroke; furthermore, PAHs in the particle matter could be responsible for the prognosis exacerbation.

A shining example of doping Many technological materials are intentionally 'doped' by the introduction of trace amounts of foreign elements to impart new and useful properties — a classic example is the doping of semiconductors. Feng Wang et al . describe a system in which lanthanide doping can be used to control the growth of NaYF 4 nanocrystals, making it possible to simultaneously tune the size, crystallographic phase and optical properties of the resulting materials. These findings increase our understanding of doping-induced structural transformations, and provide a straightforward route for the controlled synthesis of luminescent nanocrystals for many applications. Many technological materials are intentionally 'doped' with foreign elements to impart new and desirable properties, a classic example being the doping of semiconductors to tune their electronic behaviour. Here lanthanide doping is used to control the growth of nanocrystals, allowing for simultaneous tuning of the size, crystallographic phase and optical properties of the hybrid material. Doping is a widely applied technological process in materials science that involves incorporating atoms or ions of appropriate elements into host lattices to yield hybrid materials with desirable properties and functions. For nanocrystalline materials, doping is of fundamental importance in stabilizing a specific crystallographic phase 1 , modifying electronic properties 2 , 3 , 4 , modulating magnetism 5 as well as tuning emission properties 6 , 7 , 8 , 9 . Here we describe a material system in which doping influences the growth process to give simultaneous control over the crystallographic phase, size and optical emission properties of the resulting nanocrystals. We show that NaYF 4 nanocrystals can be rationally tuned in size (down to ten nanometres), phase (cubic or hexagonal) and upconversion 10 , 11 , 12 emission colour (green to blue) through use of trivalent lanthanide dopant ions introduced at precisely defined concentrations. We use first-principles calculations to confirm that the influence of lanthanide doping on crystal phase and size arises from a strong dependence on the size and dipole polarizability of the substitutional dopant ion. Our results suggest that the doping-induced structural and size transition, demonstrated here in NaYF 4 upconversion nanocrystals, could be extended to other lanthanide-doped nanocrystal systems for applications ranging from luminescent biological labels 12 to volumetric three-dimensional displays 13 .