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"Ivanov, Boris"
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Handbook of ripple effects in the supply chain
This book offers an introduction to the ripple effect in the supply chain for a broad audience comprising recent developments. The chapters of this handbook are written by leading experts in supply chain risk management and resilience. For the first time, the chapters present in their synergy a multiple-faceted view of the ripple effect in supply chains, while considering organization, optimization, and informatics perspectives. Ripple effect describes the impact of a disruption propagation on supply chain performance, structural designs and operational parameters. The ripple effect manifests when the impact of a disruption cannot be localized and cascades along the supply chain. The resulting structural dynamics can lead to capacity and demand fulfilment downscaling and negatively influence the firm's financial and operational performance. The book delineates major features of the ripple effect and methodologies to mitigate the adverse impact of supply chain disruption propagation and to recover in case of severe disruptions. The book provides fresh insights for supply chain management and engineering regarding the following questions: - In what circumstance does one failure cause other failures? - Which structures of the supply chain are especially susceptible to the ripple effect? - What are the typical ripple effect scenarios and what are the most efficient ways to respond them? Distinctive Features: It considers ripple effect in the supply chain from an multi-disciplinary perspective It offers an introduction to ripple effect mitigation and recovery policies in the framework of disruption risk management in supply chains for a broad audience It integrates management and engineering perspectives on disruption risk management in the supply chain It presents innovative optimization and simulation models for real-life management problems It considers examples from both industrial and service supply chains It reveals decision-making recommendations for tackling disruption risks in the supply chain in proactive and reactive domains.
Book
Antiferromagnetic THz-frequency Josephson-like Oscillator Driven by Spin Current
The development of compact and tunable room temperature sources of coherent THz-frequency signals would open a way for numerous new applications. The existing approaches to THz-frequency generation based on superconductor Josephson junctions (JJ), free electron lasers, and quantum cascades require cryogenic temperatures or/and complex setups, preventing the miniaturization and wide use of these devices. We demonstrate theoretically that a bi-layer of a heavy metal (Pt) and a bi-axial antiferromagnetic (AFM) dielectric (NiO) can be a source of a coherent THz signal. A spin-current flowing from a DC-current-driven Pt layer and polarized along the hard AFM anisotropy axis excites a non-uniform in time precession of magnetizations sublattices in the AFM, due to the presence of a weak easy-plane AFM anisotropy. The frequency of the AFM oscillations varies in the range of 0.1–2.0 THz with the driving current in the Pt layer from 10
8
A/cm
2
to 10
9
A/cm
2
. The THz-frequency signal from the AFM with the amplitude exceeding 1 V/cm is picked up by the inverse spin-Hall effect in Pt. The operation of a room-temperature AFM THz-frequency oscillator is similar to that of a cryogenic JJ oscillator, with the energy of the easy-plane magnetic anisotropy playing the role of the Josephson energy.
Journal Article
Directional control of spin-wave emission by spatially shaped light
In future spintronics it is anticipated that spin waves will function as unique information carriers that are free from Joule heating
1
,
2
,
3
,
4
,
5
,
6
,
7
. Directional control of spin-wave emission has been desired for the realization of switching devices. Here, we propose a promising technique that makes use of a spatially shaped light pulse with circular polarization. Focusing this light pulse on a magnet generates spin waves via the inverse Faraday effect. Moreover, the wavenumber distribution of the spin waves is determined by the spatial intensity distribution of the light spot. We demonstrate the principle of this technique both theoretically and experimentally. We successfully control the direction of the energy flow by shaping the light spot into an ellipse, with its major axis parallel or perpendicular to the magnetic field. Our findings will open up the possibility of fast and arbitrary synthesis of spin-wave patterns by using a more sophisticated light-shaping technique, for example using a computer-generated hologram
8
.
Researchers use spatially shaped light to control the direction of spin-wave emission from the ferrimagnetic insulator Gd
4/3
Yb
2/3
BiFe
5
O
12
. They capture the essential features of the observations by employing a simple model that maps the spatial profile of the pump pulse onto the dispersion relation of the spin wave.
Journal Article
Exceptional warming over the Barents area
In recent decades, surface air temperature (SAT) data from Global reanalyses points to maximum warming over the northern Barents area. However, a scarcity of observations hampers the confidence of reanalyses in this Arctic hotspot region. Here, we study the warming over the past 20–40 years based on new available SAT observations and a quality controlled comprehensive SAT dataset from the northern archipelagos in the Barents Sea. We identify a statistically significant record-high annual warming of up to 2.7 °C per decade, with a maximum in autumn of up to 4.0 °C per decade. Our results are compared with the most recent global and Arctic regional reanalysis data sets, as well as remote sensing data records of sea ice concentration (SIC), sea surface temperature (SST) and high-resolution ice charts. The warming pattern is primarily consistent with reductions in sea ice cover and confirms the general spatial and temporal patterns represented by reanalyses. However, our findings suggest even a stronger rate of warming and SIC-SAT relation than was known in this region until now.
Journal Article
Superoxide Anion Radical Generation in Photosynthetic Electron Transport Chain
This review analyzes data available in the literature on the rates, characteristics, and mechanisms of oxygen reduction to a superoxide anion radical at the sites of photosynthetic electron transport chain where this reduction has been established. The existing assumptions about the role of the components of these sites in this process are critically examined using thermodynamic approaches and results of the recent studies. The process of O2 reduction at the acceptor side of PSI, which is considered the main site of this process taking place in the photosynthetic chain, is described in detail. Evolution of photosynthetic apparatus in the context of controlling the leakage of electrons to O2 is explored. The reasons limiting application of the results obtained with the isolated segments of the photosynthetic chain to estimate the rates of O2 reduction at the corresponding sites in the intact thylakoid membrane are discussed.
Journal Article
Magnon-phonon Fermi resonance in antiferromagnetic CoF2
Understanding spin-lattice interactions in antiferromagnets is a critical element of the fields of antiferromagnetic spintronics and magnonics. Recently, coherent nonlinear phonon dynamics mediated by a magnon state were discovered in an antiferromagnet. Here, we suggest that a strongly coupled two-magnon-one phonon state in this prototypical system opens a novel pathway to coherently control magnon-phonon dynamics. Utilizing intense narrow-band terahertz (THz) pulses and tunable magnetic fields up to
μ
0
H
ext
= 7 T, we experimentally realize the conditions of magnon-phonon Fermi resonance in antiferromagnetic CoF
2
. These conditions imply that both the spin and the lattice anharmonicities harvest energy from the transfer between the subsystems if the magnon eigenfrequency
f
m
is half the frequency of the phonon 2
f
m
=
f
ph
. Performing THz pump-infrared probe spectroscopy in conjunction with simulations, we explore the coupled magnon-phonon dynamics in the vicinity of the Fermi-resonance and reveal the corresponding fingerprints of nonlinear interaction facilitating energy exchange between these subsystems.
Magnons offer a variety of attractive features for information processing: low dissipation, controllable non-linearity, short wavelengths at typical frequencies used in information technologies. Here, Metzger et al demonstrate control of a strongly coupled two-magnon-one-phonon state in antiferromagnetic CoF2.
Journal Article
Minimizing an Electron Flow to Molecular Oxygen in Photosynthetic Electron Transfer Chain: An Evolutionary View
Recruitment of H
O as the final donor of electrons for light-governed reactions in photosynthesis has been an utmost breakthrough, bursting the evolution of life and leading to the accumulation of O
molecules in the atmosphere. O
molecule has a great potential to accept electrons from the components of the photosynthetic electron transfer chain (PETC) (so-called the Mehler reaction). Here we overview the Mehler reaction mechanisms, specifying the changes in the structure of the PETC of oxygenic phototrophs that probably had occurred as the result of evolutionary pressure to minimize the electron flow to O
. These changes are warranted by the fact that the efficient electron flow to O
would decrease the quantum yield of photosynthesis. Moreover, the reduction of O
leads to the formation of reactive oxygen species (ROS), namely, the superoxide anion radical and hydrogen peroxide, which cause oxidative stress to plant cells if they are accumulated at a significant amount. From another side, hydrogen peroxide acts as a signaling molecule. We particularly zoom in into the role of photosystem I (PSI) and the plastoquinone (PQ) pool in the Mehler reaction.
Journal Article
Unsolved Problems of Carbonic Anhydrases Functioning in Photosynthetic Cells of Higher C3 Plants
The review presents current data on carbonic anhydrases found in various compartments of photosynthetic cells of higher plants. The available data on expression of genes some of carbonic anhydrases and its dependence on environmental factors and plant age are considered. The existing hypotheses on the functions of carbonic anhydrases of plasma membrane, cytoplasm, as well as of stroma and thylakoids of chloroplast, first of all, the hypothesis on participation of these enzymes in supplying carbon dioxide molecules to ribulose-bisphosphate carboxylase (Rubisco) are analyzed. Difficulties of establishing physiological role of the plant cell carbonic anhydrase are discussed in detail.
Journal Article
Warming of Atlantic Water in two west Spitsbergen fjords over the last century (1912-2009)
The recently observed warming of west Spitsbergen fjords has led to anomalous sea-ice conditions and has implications for the marine ecosystem. We investigated long-term trends of maximum temperature of Atlantic Water (AW) in two west Spitsbergen fjords. The data set is composed of more than 400 oceanographic stations for Isfjorden and Grønfjorden (78.1°N), spanning from 1876 to 2009. Trends throughout the last century (1912–2009) indicate an increase of 1.9°C and 2.1°C in the maximum temperature during autumn for Isfjorden and Grønfjorden, respectively. A recent warming event in the beginning of the 21st century is found to be more than 1°C higher than the second warmest period in the time series. Mean sea-level pressure (MSLP) data from ERA-40 and ERA-Interim data sets produced by the European Centre for Medium-Range Weather Forecasts and mean temperature in the core of the West Spitsbergen Current (WSC) at the Sørkapp Section along 76.3°N were used to explain the variability of the maximum temperature. A correlation analysis confirmed previous findings, showing that variability in the oceanography of the fjords can be explained mainly by two external factors: AW temperature variability in the WSC and regional patterns of the wind stress field. To take both processes into consideration, a multiple regression model accounting for temperature in the WSC core and MSLP over the area was developed. The predicted time series shows a reasonable agreement with observed maxima temperature in Isfjorden for the period 1977–2009 (N=24), with a statistically significant multiple correlation coefficient of 0.60 (R2=0.36) at P<0.05.
Journal Article
Mars/Moon Cratering Rate Ratio Estimates
This article presents a method to adapt the lunar production function, i.e. the frequency of impacts with a given size of a formed crater as discussed by Neukum et al. (2001), to Mars. This requires to study the nature of crater-forming projectiles, the impact rate difference, and the scaling laws for the impact crater formation. These old-standing questions are reviewed, and examples for the re-calculation of the production function from the moon to Mars are given.[PUBLICATION ABSTRACT]
Journal Article