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Kosmos
Astronomia Astrofizyka
Inne

Kultura
Sztuka dawna i współczesna, muzea i kolekcje

Metoda
Metodologia nauk, Matematyka, Filozofia, Miary i wagi, Pomiary

Materia
Substancje, reakcje, energia
Fizyka, chemia i inżynieria materiałowa

Człowiek
Antropologia kulturowa Socjologia Psychologia Zdrowie i medycyna

Wizje
Przewidywania Kosmologia Religie Ideologia Polityka

Ziemia
Geologia, geofizyka, geochemia, środowisko przyrodnicze

Życie
Biologia, biologia molekularna i genetyka

Cyberprzestrzeń
Technologia cyberprzestrzeni, cyberkultura, media i komunikacja

Działalność
Wiadomości | Gospodarka, biznes, zarządzanie, ekonomia

Technologie
Budownictwo, energetyka, transport, wytwarzanie, technologie informacyjne

Kolekcje IOP - REVIEWS

Reviews

Half-Heusler thermoelectrics first attracted interest in the late-1990s and are currently undergoing
a renaissance. This has been driven by improved synthesis, processing and characterisation methods,
leading to increases in the thermoelectric figure of merit and the observation of novel phenomena
such as carrier filtering in nanocomposite samples. The difficulty in extracting good thermoelectric
performance is at first glance surprising given the relative simplicity of the ideal crystal
structure with only site occupancies and lattice parameter as crystallographic variables. However,
the observed thermoelectric properties are found to depend sensitively on sample processing. Recent
work has shown that prepared ingots can contain a range of inhomogeneities, including interstitials,
nano- and micron sized Heusler inclusions and multiple half-Heusler phases. For this reason, the
prepared materials are far more complex than initially appreciated and this may offer opportunities
to e...

http://iopscience.iop.org/0953-8984/26/43/433201 2014/10/03 - 11:41

For many applications of semiconductor quantum dots in quantum technology, well-controlled state
preparation of the quantum dot states is mandatory. Since quantum dots are embedded in the
semiconductor matrix, their interaction with phonons often plays a major role in the preparation
process. In this review, we discuss the influence of phonons on three basically different optical
excitation schemes that can be used for the preparation of exciton, biexciton and superposition
states: a resonant excitation leading to Rabi rotations in the excitonic system, an excitation with
chirped pulses exploiting the effect of adiabatic rapid passage and an off-resonant excitation
giving rise to a phonon-assisted state preparation. We give an overview of experimental and
theoretical results, showing the role of phonons and compare the performance of the schemes for
state preparation.

http://iopscience.iop.org/0953-8984/26/42/423203 2014/10/03 - 11:41

Basal-plane stacking faults are an important class of optically active structural defects in
wurtzite semiconductors. The local deviation from the 2H stacking of the wurtzite matrix to a 3C
zinc-blende stacking induces a bound state in the gap of the host crystal, resulting in the
localization of excitons. Due to the two-dimensional nature of these planar defects, stacking faults
act as quantum wells, giving rise to radiative transitions of excitons with characteristic energies.
Luminescence spectroscopy is thus capable of detecting even a single stacking fault in an otherwise
perfect wurtzite crystal. This review draws a comprehensive picture of the luminescence properties
related to stacking faults in GaN. The emission energies associated with different types of stacking
faults as well as factors that can shift these energies are discussed. In this context, the
importance of the quantum-confined Stark effect in these zinc-blende/wurtzite heterostructures,
which results from the...

http://iopscience.iop.org/0022-3727/47/42/423001 2014/10/01 - 22:59

A comprehensive investigation of quantum confinement in nanowires has been carried out. Though
applied to silicon nanowires (SiNWs), it is general and applicable to all nanowires. Fundamentals
and applications of quantum confinement in nanowires and possible laws obeyed by these nanowires,
have been investigated. These laws may serve as backbones of nanowire science and technology. The
relationship between energy band gap and nanowire diameter has been studied. This relationship
appears to be universal. A thorough review indicates that the first principles results for quantum
confinement vary widely. The possible cause of this variation has been examined. Surface passivation
and surface reconstruction of nanowires have been elucidated. It has been found that quantum
confinement owes its origin to surface strain resulting from surface passivation and surface
reconstruction and hence thin nanowires may actually be crystalline-core/amorphous-shell (c-Si/a-Si)
nanowires. Experimental...

http://iopscience.iop.org/0953-8984/26/42/423202 2014/09/25 - 13:04

A highly unconventional superconducting state with a spin-singlet ##IMG##
[http://ej.iop.org/images/0953-8984/26/42/423201/cm501389ieqn001.gif] {$d_{x^2-y^2}\pm {\rm
i}d_{xy}$} -wave, or chiral d -wave symmetry has recently been suggested to emerge from
electron–electron interactions in doped graphene. It has been argued that graphene doped to the van
Hove singularity at 1/4 doping, where the density of states diverge, is particularly likely to be a
chiral d -wave superconductor. In this review we summarize the currently mounting theoretical
evidence for the existence of a chiral d -wave superconducting state in graphene, obtained with
methods ranging from mean-field studies of effective Hamiltonians to angle-resolved renormalization
group calculations. We further discuss the multiple distinctive properties of the chiral d -wave
superconducting state in graphene, as well as its stability in the presence of disorder. We also
review the...

http://iopscience.iop.org/0953-8984/26/42/423201 2014/09/20 - 12:51

The enormous advances in the understanding of human anatomy, physiology and pathology in recent
decades have led to ever-improving methods of disease prevention, diagnosis and treatment. Many of
these achievements have been enabled, at least in part, by advances in ionizing radiation detectors.
Radiology has been transformed by the implementation of multi-slice CT and digital x-ray imaging
systems, with silver halide films now largely obsolete for many applications. Nuclear medicine has
benefited from more sensitive, faster and higher-resolution detectors delivering ever-higher SPECT
and PET image quality. PET/MR systems have been enabled by the development of gamma ray detectors
that can operate in high magnetic fields. These huge advances in imaging have enabled equally
impressive steps forward in radiotherapy delivery accuracy, with 4DCT, PET and MRI routinely used in
treatment planning and online image guidance provided by cone-beam CT. The challenge of ensuring
safe, a...

http://iopscience.iop.org/0031-9155/59/20/R303 2014/09/20 - 12:51

Over the past ten years, the all-atom molecular dynamics method has grown in the scale of both
systems and processes amenable to it and in its ability to make quantitative predictions about the
behavior of experimental systems. The field of computational DNA research is no exception,
witnessing a dramatic increase in the size of systems simulated with atomic resolution, the duration
of individual simulations and the realism of the simulation outcomes. In this topical review, we
describe the hallmark physical properties of DNA from the perspective of all-atom simulations. We
demonstrate the amazing ability of such simulations to reveal the microscopic physical origins of
experimentally observed phenomena. We also discuss the frustrating limitations associated with
imperfections of present atomic force fields and inadequate sampling. The review is focused on the
following four physical properties of DNA: effective electric charge, response to an external
mechanical force, interacti...

http://iopscience.iop.org/0953-8984/26/41/413101 2014/09/20 - 12:51

We review our achievements in exploring the high resolution imaging of scanning tunneling microscopy
(STM) on the surface and adsorbates in a ultra-high vacuum system, by modifying the STM tip or
introducing a decoupled layer onto the substrate. With an ultra-sharp tip, the highest resolution of
Si(1 1 1)-7 × 7 reconstruction can be achieved, in which all the rest atoms and adatoms are observed
simultaneously with high contrast. Further functionalization of STM tips can realize selective
imaging of inherent molecular states. The electronic states of perylene and metal–phthalocyanine
molecules are resolved with special decorated tips on metal substrates at low temperature. Moreover,
we present two kinds of buffer layer: an organic molecular layer and epitaxially grown graphene to
decouple the molecular electronic structure from the influence of the underlying metallic substrate
and allow the direct imaging of the intrinsic orbitals of the adsorbed molecules. Theoretical
calculatio...

http://iopscience.iop.org/0953-8984/26/39/394001 2014/09/12 - 21:27

The spin textures of ultra-thin magnetic layers exhibit surprising variety. The loss of inversion
symmetry at the interface of the magnetic layer and substrate gives rise to the so-called
Dzyaloshinskii–Moriya interaction which favors non-collinear spin arrangements with unique
rotational sense. Here we review the application of spin-polarized scanning tunneling microscopy to
such systems, which has led to the discovery of interface-induced chiral domain walls and spin
spirals. Recently, different interface-driven skyrmion lattices have been found, and the writing as
well as the deleting of individual skyrmions based on local spin-polarized current injection has
been demonstrated. These interface-induced non-collinear magnetic states offer new exciting
possibilities to study fundamental magnetic interactions and to tailor material properties for
spintronic applications.

http://iopscience.iop.org/0953-8984/26/39/394002 2014/09/12 - 21:27

Geophysical methodologies have been implemented, tested and validated as diagnostic and /or
monitoring tools in artworks or historical monuments. They are non-destructive and can give an image
of internal structure of investigated medium. This paper is a review about the main geophysical
techniques applied to the study of cultural built heritage (excluding the archaeology field). A
brief description of the used methodologies is presented, the main investigations done in this field
are showed, the method or methods most appropriate to answer each problem (moisture detection,
characterization of the materials, study of the structural continuity of the material, assessment of
intervention’s effectiveness) are indicated and the main advances and gaps and future developments
are also pointed out.

http://iopscience.iop.org/1742-2140/11/5/053001 2014/09/12 - 21:27

The semiconductor oxides SnO 2 , HfO 2 , ZrO 2 , TiO 2 and SrTiO 3 are interesting materials for
applications as high- K dielectric gate materials in silicon-based devices and spintronics, among
others. Here we review our theoretical work about the structural, electronic and vibrational
properties of these oxides in their most stable structural phases, including dielectric properties
as derived from the electronic structure taking into account the lattice contribution. Finally, we
address the recent role played by the presence of transition metal atoms in semiconductor oxides,
considering in particular SnO 2 as an example in forming diluted magnetic alloys.

http://iopscience.iop.org/0022-3727/47/41/413001 2014/09/11 - 16:34

Axial magnetic field (AMF) technology is a most important control method of vacuum arc, particularly
for high-current vacuum arcs in vacuum interrupters. In this paper, a review of the state of current
research on vacuum arcs under AMF is presented. The major aspects of vacuum arc in an AMF such as
arc voltage, the motion of cathode spots, and anode activities are discussed, and the most recent
progress both of experimental and simulation research is presented.

http://iopscience.iop.org/0022-3727/47/40/403001 2014/09/11 - 16:34

Incorporation of nanostructures is a recent trend in the photovoltaic community, aimed at improving
light absorption and consequently cell efficiency. In this regard, semiconductor nanowires provide
an attractive research platform for a new generation of cost-effective and efficient solar cells.
Thanks to their unique geometry, silicon nanowires enhance light trapping and anti-reflection
effects by means of multiple scattering between individual nanowires, and by coupling the light into
confined eigenmodes over a broad range of the solar spectrum. Moreover, radial junction solar cells
built around nanowires decouple the light absorption and carrier collection directions, which allows
for a higher internal field and better carrier collection. Thus, arrays of radial junction solar
cells bring advantages of high efficiency with reduced material amount. This is particularly
attractive for devices based on hydrogenated amorphous and microcrystalline silicon thin films. In
this paper, ...

http://iopscience.iop.org/0022-3727/47/39/393001 2014/09/11 - 16:34

Turbulence has been studied in laboratory plasmas for decades. Magnetic and electrostatic turbulence
fluctuations have been implicated in degraded confinement in fusion devices so understanding
turbulent transport is critical for those devices. The externally applied magnetic field in most
laboratory plasmas has a strong effect on the character of the turbulence (particularly parallel and
perpendicular to the applied field). A new turbulent plasma source is described with several unique
features. First, the magnetohydrodynamic (MHD) wind tunnel configuration has no applied magnetic
field and has no net axial magnetic flux. Second, the plasma flow speed is on the order of the local
sound speed ( M = 1), so flow energy is comparable to thermal energy. Third, the plasma β (ratio of
thermal to magnetic pressure) is of order unity so thermal energy is comparable to magnetic energy.
We will review sources of magnetic turbulence in laboratory plasmas and discuss the main an...

http://iopscience.iop.org/0963-0252/23/6/063001 2014/09/09 - 00:44

The measured properties of the recently discovered Higgs boson are in good agreement with
predictions from the Standard Model. However, small deviations in the Higgs couplings may manifest
themselves once the currently large uncertainties will be improved as part of the LHC program and at
a future Higgs factory. We review typical new physics scenarios that lead to observable
modifications of the Higgs interactions. They can be divided into two broad categories: mixing
effects as in portal models or extended Higgs sectors, and vertex loop effects from new matter or
gauge fields. In each model we relate coupling deviations to their effective new physics scale. It
turns out that with percent level precision the Higgs couplings will be sensitive to the multi-TeV
regime.

http://iopscience.iop.org/0954-3899/41/11/113001 2014/09/09 - 00:44

Myoelectric control is filled with potential to significantly change human–robot interaction due to
the ability to non-invasively measure human motion intent. However, current control schemes have
struggled to achieve the robust performance that is necessary for use in commercial applications. As
demands in myoelectric control trend toward simultaneous multifunctional control, multi-muscle
coordinations, or synergies, play larger roles in the success of the control scheme. Detecting and
refining patterns in muscle activations robust to the high variance and transient changes associated
with surface electromyography is essential for efficient, user-friendly control. This article
reviews the role of muscle synergies in myoelectric control schemes by dissecting each component of
the scheme with respect to associated challenges for achieving robust simultaneous control of
myoelectric interfaces. Electromyography recording details, signal feature extraction, pattern
recognition and m...

http://iopscience.iop.org/1741-2552/11/5/051001 2014/09/06 - 14:19

The field of squeezed states for gravitational-wave (GW) detector enhancement is rapidly maturing.
In this review paper, we provide an analysis of the field circa 2013. We begin by outlining the
concept and description of quantum squeezed states. This is followed by an overview of how quantum
squeezed states can improve GW detection, and the requirements on squeezed states to achieve such
enhancement. Next, an overview of current technology for producing squeezed states, using atoms,
optomechanical methods and nonlinear crystals, is provided. We finally highlight the milestone
squeezing implementation experiments at the GEO600 and LIGO GW detectors.

http://iopscience.iop.org/0264-9381/31/18/183001 2014/09/06 - 14:19

We summarize recent theoretical and experimental work in the field of magnetic small-angle neutron
scattering (SANS) of bulk ferromagnets. The response of the magnetization to spatially inhomogeneous
magnetic anisotropy and magnetostatic stray fields is computed using linearized micromagnetic
theory, and the ensuing spin-misalignment SANS is deduced. Analysis of experimental
magnetic-field-dependent SANS data of various nanocrystalline ferromagnets corroborates the
usefulness of the approach, which provides important quantitative information on the
magnetic-interaction parameters such as the exchange-stiffness constant, the mean magnetic
anisotropy field, and the mean magnetostatic field due to jumps Δ M of the magnetization at internal
interfaces. Besides the value of the applied magnetic field, it turns out to be the ratio of the
magnetic anisotropy field H p to Δ M , which determines the properties of the magnetic SANS
cross-section of bulk f...

http://iopscience.iop.org/0953-8984/26/38/383201 2014/09/03 - 20:01

Image-potential states of graphene on various substrates have been investigated by two-photon
photoemission and scanning tunneling spectroscopy. They are used as a probe for the
graphene-substrate interaction and resulting changes in the (local) work function. The latter is
driven by the work function difference between graphene and the substrate. This results in a charge
transfer which also contributes to core-level shifts in x-ray photoemission. In this review article,
we give an overview over the theoretical models and the experimental data for image-potential states
and work function of graphene on various substrates.

http://iopscience.iop.org/0953-8984/26/39/393001 2014/08/29 - 01:46

Lasers have been used extensively to manipulate matter in a controlled way – from single atoms and
molecules up to macroscopic materials. They are particularly valuable for the analysis and control
of mesoscopic systems such as few-particle clusters. Here we report on recent work on finite size
complex (dusty) plasma systems. These are unusual types of clusters with a very strong
inter-particle interaction so that, at room temperature, they are practically in their ground state.
Lasers are employed as a tool to achieve excited states and phase transitions. The most attractive
feature of dusty plasmas is that they allow for a precise diagnostic with single-particle
resolution. From such measurements, the structural properties of finite two-dimensional (2D)
clusters and three-dimensional (3D) spherical crystals in nearly harmonic traps—so-called Yukawa
balls—have been explored in great detail. Their structural features—the shell compositions and the
order within the shells—ha...

http://iopscience.iop.org/0022-3727/47/38/383001 2014/08/29 - 01:46

The fundamentals of neuronal membrane excitability are globally described using the Hodgkin-Huxley
(HH) model. The HH model, however, does not account for a number of biophysical phenomena associated
with action potentials or propagating nerve impulses. Physical mechanisms underlying these
processes, such as reversible heat transfer and axonal swelling, have been compartmentalized and
separately investigated to reveal neuronal activity is not solely influenced by electrical or
biochemical factors. Instead, mechanical forces and thermodynamics also govern neuronal excitability
and signaling. To advance our understanding of neuronal function and dysfunction, compartmentalized
analyses of electrical, chemical, and mechanical processes need to be revaluated and integrated into
more comprehensive theories. The present perspective is intended to provide a broad overview of
biophysical forces that can influence neural function, but which have been traditionally
underappreciated in neuro...

http://iopscience.iop.org/1478-3975/11/5/051001 2014/08/26 - 18:09

Progress in metal-organic chemical vapor deposition of high quality ##IMG##
[http://ej.iop.org/images/0268-1242/29/11/113001/sst499638ieqn2.gif] {$\left( 000\bar{1} \right)$}
N-polar (Al, Ga, In)N films on sapphire, silicon carbide and silicon substrates is reviewed with
focus on key process components such as utilization of vicinal substrates, conditions ensuring a
high surface mobility of species participating in the growth process, and low impurity
incorporation. The high quality of the fabricated films enabled the demonstration of N-polar (Al,
Ga, In)N based devices with excellent performance for transistor applications. Challenges related to
the growth of high quality N-polar InGaN films are also presented.

http://iopscience.iop.org/0268-1242/29/11/113001 2014/08/22 - 19:33

Radiation dose calculation using models of the human anatomy has been a subject of great interest to
radiation protection, medical imaging, and radiotherapy. However, early pioneers of this field did
not foresee the exponential growth of research activity as observed today. This review article walks
the reader through the history of the research and development in this field of study which started
some 50 years ago. This review identifies a clear progression of computational phantom complexity
which can be denoted by three distinct generations. The first generation of stylized phantoms,
representing a grouping of less than dozen models, was initially developed in the 1960s at Oak Ridge
National Laboratory to calculate internal doses from nuclear medicine procedures. Despite their
anatomical simplicity, these computational phantoms were the best tools available at the time for
internal/external dosimetry, image evaluation, and treatment dose evaluations. A second generation
of a l...

http://iopscience.iop.org/0031-9155/59/18/R233 2014/08/22 - 19:33

We provide a summary of both seminal and recent results on typical entanglement. By ‘typical’ values
of entanglement, we refer here to values of entanglement quantifiers that (given a reasonable
measure on the manifold of states) appear with arbitrarily high probability for quantum systems of
sufficiently high dimensionality. We shall focus on pure states and work within the Haar measure
framework for discrete quantum variables, where we report on results concerning the average von
Neumann and linear entropies as well as arguments implying the typicality of such values in the
asymptotic limit. We then proceed to discuss the generation of typical quantum states with random
circuitry. Different phases of entanglement, and the connection between typical entanglement and
thermodynamics are discussed. We also cover approaches to measures on the non-compact set of
Gaussian states of continuous variable quantum systems.

http://iopscience.iop.org/1751-8121/47/36/363001 2014/08/22 - 19:33

If transport of a given (classical, fermionic, or bosonic) particle species in media is described by
a Boltzmann transport equation (BTE), it is often expedient to solve this BTE in the framework of a
moment expansion of the particle distribution function, while an exact solution or simulation of the
problem with real material properties and complex geometries is unpractical or even unfeasible.
Whereas for local thermal equilibrium (LTE) the well-known hydrodynamic equations for the densities
of the conserved quantities are derived from the BTE, for non-LTE it is not obvious how to define
moments and to close the truncated hierarchy of partial differential equations for these moments.
This paper reviews a closure based on entropy production rate minimization, which is applicable to
incoherent transport of independent particles in non-LTE interacting with an LTE-medium. The BTE is
then linear, includes emission-absorption and elastic scattering processes, and is equivalent to
radi...

http://iopscience.iop.org/0022-3727/47/36/363001 2014/08/22 - 19:33

Linearized augmented planewave methods are known as the most precise numerical schemes for solving
the Kohn–Sham equations of density-functional theory (DFT). In this review, we describe how this
method is realized in the all-electron full-potential computer package, exciting. We emphasize the
variety of different related basis sets, subsumed as (linearized) augmented planewave plus local
orbital methods, discussing their pros and cons and we show that extremely high accuracy
(microhartrees) can be achieved if the basis is chosen carefully. As the name of the code suggests,
exciting is not restricted to ground-state calculations, but has a major focus on excited-state
properties. It includes time-dependent DFT in the linear-response regime with various static and
dynamical exchange-correlation kernels. These are preferably used to compute optical and
electron-loss spectra for metals, molecules and semiconductors with weak electron–hole interactions.
exciting makes use of many-bod...

http://iopscience.iop.org/0953-8984/26/36/363202 2014/08/22 - 19:33

The endeavor of exploiting arrays of vertical one-dimensional (1D) nanostructures (NSs) for cellular
applications has recently been experiencing a pronounced surge of activity. The interest is rooted
in the intrinsic properties of high-aspect-ratio NSs. With a height comparable to a mammalian cell,
and a diameter 100–1000 times smaller, NSs should intuitively reach far into a cell and, due to
their small diameter, do so without compromising cell health. Single NSs would thus be expedient for
measuring and modifying cell response. Further organization of these structures into arrays can
provide up-scaled and detailed spatiotemporal information on cell activity, an achievement that
would entail a massive leap forward in disease understanding and drug discovery. Numerous
proofs-of-principle published recently have expanded the large toolbox that is currently being
established in this rapidly advancing field of research. Encouragingly, despite the diversity of NS
platforms and experi...

http://iopscience.iop.org/0957-4484/25/36/362001 2014/08/18 - 22:08

Recent advances in the theory of complex symmetric operators are presented and related to current
studies in non-Hermitian quantum mechanics. The main themes of the survey are: the structure of
complex symmetric operators, C -selfadjoint extensions of C -symmetric unbounded operators,
resolvent estimates, reality of spectrum, bases of C -orthonormal vectors and conjugate-linear
symmetric operators. The main results are complemented by a variety of natural examples arising in
field theory, quantum physics and complex variables.

http://iopscience.iop.org/1751-8121/47/35/353001 2014/08/18 - 22:08

This review covers the results obtained in the period 2006–2014 in the field of plasma-assisted
combustion, and in particular the results on ignition and combustion triggered or sustained by
pulsed nanosecond discharges in different geometries. Some benefits of pulsed high voltage
discharges for kinetic study and for applications are demonstrated. The necessity of and the
possibility of building a particular kinetic mechanism of plasma-assisted ignition and combustion
are discussed. The most sensitive regions of parameters for plasma–combustion kinetic mechanisms are
selected. A map of the pressure and temperature parameters ( P – T diagram) is suggested, to unify
the available data on ignition delay times, ignition lengths and densities of intermediate species
reported by different authors.

http://iopscience.iop.org/0022-3727/47/35/353001 2014/08/16 - 18:07

We review the status of flavour physics in spring 2014. The numerous accurate new measurements of
flavour experiments have enabled us to test our theoretical understanding of flavour processes with
an unprecedented precision. At first sight the dominant amount of measurements seems to be standard
model like. Having a closer look one finds, however, that in most of the observables there is still
some considerable space for new effects. In addition many discrepancies are still not yet settled.
For further investigations and definite conclusions an improvement of the theoretical precision as
well as the experimental one is mandatory. Communicated by Professor Alan Martin

http://iopscience.iop.org/0954-3899/41/10/103001 2014/08/15 - 08:17

Measuring the magnetic configuration at complex buried layers and interfaces is an important task,
which requires especially a non-destructive probing technique. X-ray resonant magnetic reflectometry
(XRMR) combines the non-destructive depth profiling potential of x-ray reflectometry with the
excellent sensitivity for magnetic phenomena, utilizing the x-ray magnetic circular dichroism
effect. It provides the magnetic spatial distribution with a precision down to the angstrom scale,
combined with element and symmetry specificity, sub-monolayer sensitivity, and the possible
separation of spin and orbital magnetic moments. This review provides an overview to the XRMR
technique in a tutorial way. We focus on the introduction to the theory, measurement types, and data
simulation. We provide related experimental examples and show selected applications.

http://iopscience.iop.org/0953-8984/26/36/363201 2014/08/15 - 08:17

Functional MRI (fMRI) has grown to be the neuroimaging technique of choice for investigating brain
function. This topical review provides an outline of fMRI methods and applications, with a
particular emphasis on the recent advances provided by ultra-high field (UHF) scanners to allow
functional mapping with greater sensitivity and improved spatial specificity. A short outline of the
origin of the blood oxygenation level dependent (BOLD) contrast is provided, followed by a review of
BOLD fMRI methods based on gradient-echo (GE) and spin-echo (SE) contrast. Phase based fMRI
measures, as well as perfusion contrast obtained with the technique of arterial spin labelling
(ASL), are also discussed. An overview of 7 T based functional neuroimaging is provided, outlining
the potential advances to be made and technical challenges to be addressed.

http://iopscience.iop.org/0967-3334/35/9/R167 2014/08/15 - 08:17

Energy applications employing high-temperature superconductors (HTS), such as motors/generators,
transformers, transmission lines and fault current limiters, are usually operated in the alternate
current (ac) regime. In order to be efficient, the HTS devices need to have a sufficiently low value
of ac loss, in addition to the necessary current-carrying capacity. Most applications are operated
with currents beyond the current capacity of single conductors and consequently require cabled
conductor solutions with much higher current carrying capacity, from a few kA up to 20–30 kA for
large hydro-generators. A century ago, in 1914, Ludwig Roebel invented a low-loss cable design for
copper cables, which was successively named after him. The main idea behind Roebel cables is to
separate the current in different strands and to provide a full transposition of the strands along
the cable direction. Nowadays, these cables are commonly used in the stator of large generators.
Based on the sa...

http://iopscience.iop.org/0953-2048/27/9/093001 2014/08/15 - 08:17

The electrocatalysis of borohydride oxidation is a complex, up-to-eight-electron transfer process,
which is essential for development of efficient direct borohydride fuel cells. Here we review the
progress achieved by density functional theory (DFT) calculations in explaining the adsorption of BH
4 − on various catalyst surfaces, with implications for electrocatalyst screening and selection.
Wherever possible, we correlate the theoretical predictions with experimental findings, in order to
validate the proposed models and to identify potential directions for further advancements.

http://iopscience.iop.org/0953-8984/26/35/353001 2014/08/12 - 05:26

Origami, the ancient art of paper folding, has inspired the design of engineering devices and
structures for decades. The underlying principles of origami are very general, which has led to
applications ranging from cardboard containers to deployable space structures. More recently,
researchers have become interested in the use of active materials (i.e., those that convert various
forms of energy into mechanical work) to effect the desired folding behavior. When used in a
suitable geometry, active materials allow engineers to create self-folding structures. Such
structures are capable of performing folding and/or unfolding operations without being kinematically
manipulated by external forces or moments. This is advantageous for many applications including
space systems, underwater robotics, small scale devices, and self-assembling systems. This article
is a survey and analysis of prior work on active self-folding structures as well as methods and
tools available for the de...

http://iopscience.iop.org/0964-1726/23/9/094001 2014/08/12 - 05:26

We briefly review a history of the impact of the famous 1963 paper by E Lorenz on hydrodynamics,
physics and mathematics communities on both sides of the iron curtain. This paper was an attempt to
apply the ideas and methods of dynamical systems theory to the problem of weather forecast. Its
major discovery was the phenomenon of chaos in dissipative dynamical systems which makes such
forecasts rather problematic, if at all possible. In this connection we present some recent results
which demonstrate that both a short-term and a long-term forecast are actually possible for the most
chaotic dynamical (as well as for the most random, like IID and Markov chain) systems. Moreover,
there is a sharp transition between the time interval where one may use a short-term forecast and
the times where a long-term forecast is applicable. Finally we discuss how these findings could be
incorporated into the forecast strategy outlined in the Lorenz's paper.

http://iopscience.iop.org/0951-7715/27/9/R51 2014/08/06 - 21:14

In this paper we discuss properties of the Korteweg–de Vries (KdV) equation under periodic boundary
conditions, especially those which are important for studying perturbations of the equation. We then
review what is known about the long-time behaviour of solutions for perturbed KdV equations.

http://iopscience.iop.org/0951-7715/27/9/R61 2014/08/06 - 21:14

Taylor–Couette (TC) flow and Rayleigh–Bénard (RB) convection are two systems in hydrodynamics, which
have been widely used to investigate the primary instabilities, pattern formation, and transitions
from laminar to turbulent flow. These two systems are known to have an elegant mathematical
similarity. Both TC and RB flows are closed systems, i.e. the total energy dissipation rate exactly
follows from the global energy balances. From an experimental point of view, the inherent simple
geometry and symmetry in these two systems permits the construction of high precision experimental
setups. These systems allow for quantitative measurements of many different variables, and provide a
rich source of data to test theories and numerical simulations. We review the various experimental
techniques in these two systems in fully developed turbulent states.

http://iopscience.iop.org/0951-7715/27/9/R89 2014/08/06 - 21:14

Thin-film based novel magnetic and electronic devices have entered a new era in which the film
crystallography, structural coherence, and epitaxy play important roles in determining their
functional properties. The capabilities of controlling such structural and functional properties are
being continuously developed by various physical deposition technologies. Epitaxial patterning
strategies further allow the miniaturization of such novel devices, which incorporates thin-film
components into nanoscale architectures while keeping their functional properties unmodified from
their ideal single-crystal values. In the past decade, epitaxial patterning methods on the
laboratory scale have been reported to meet distinct scientific inquires, in which the techniques
and processes used differ from one to the other. In this review we summarize many of these
pioneering endeavors in epitaxial patterning of thin-film devices that use both conventional and
novel lithography techniques. These me...

http://iopscience.iop.org/0960-1317/24/9/093001 2014/08/01 - 16:44

Fiber lasers, which consist of ideal waveguides of optical fibers, work as stable, practical, and
maintenance-free lasers. A passively mode-locked ultrashort pulse fiber laser using the
intensity-dependent absorption element has made great progress using a new type of saturable
absorber with a nanocarbon material. The techniques of ultrashort pulse amplification and pulse
compression were also developed. Using a combination of specialty fibers, ultrawideband pulse
sources, such as wavelength tunable ultrashort pulses and supercontinuum, can be demonstrated. These
new light sources are useful for laser applications, especially for optical metrology. In this
paper, the progress of highly functional ultrashort pulse fiber laser sources and their applications
are reviewed mainly on the basis of the works of this author.

http://iopscience.iop.org/1347-4065/53/9/090101 2014/08/01 - 16:44