In this review, the terminology that is used to describe the bioavailability and ileal digestibility of AA in pig feed ingredients is defined. Aspects of the methodology to establish bioavailability ...and ileal digestibility values also are discussed, and recommendations about the use of these values are provided. Two main factors can contribute to differences between bioavailability and ileal digestibility of AA. First, some AA, such as Lys, may be absorbed in chemical complexes that preclude their use for metabolism. Second, fermentation in the upper gut may result in a net loss or gain of AA to the animal. In addition, dietary effects on the efficiency of using bioavailable AA intake for tissue growth or milk production should be considered and may be attributed to endogenous AA losses in the hindgut and the metabolic costs associated with endogenous gut protein synthesis and losses. Ileal digestibility values may be expressed as apparent ileal digestibility (AID), standardized ileal digestibility (SID), or true ileal digestibility (TID). These terms are used to specify how ileal endogenous AA losses are reflected in digestibility values. Ileal endogenous AA losses may be separated into basal losses, which are not influenced by feed ingredient composition, and specific losses, which are induced by feed ingredient characteristics such as levels and types of fiber and antinutritional factors. Values for AID are established when total ileal outflow of AA (i.e., the sum of endogenous losses and nondigested dietary AA) is related to dietary AA intake. A concern with the use of AID values is that these are not additive in mixtures of feed ingredients. This concern may be overcome by correcting AID values for defined basal endogenous losses of AA, which yields SID values. Furthermore, if the AID values are corrected for basal and specific endogenous losses, then values for TID are calculated. However, reliable procedures to routinely measure specific endogenous losses are not yet available. It is recommended that basal ileal endogenous losses of AA should be measured in digestibility experiments using a defined protein-free diet and that these losses are reported with observed AID and SID values. It is suggested that SID values should be used for feed formulation, at least until more information on TID values becomes available.
Tuberculosis control relies on the identification and preventive treatment of individuals who are latently infected with Mycobacterium tuberculosis. However, direct identification of latent ...tuberculosis infection is not possible. The diagnostic tests used to identify individuals latently infected with M. tuberculosis, the in vivo tuberculin skin test and the ex vivo interferon-gamma release assays (IGRAs), are designed to identify an adaptive immune response against, but not necessarily a latent infection with, M. tuberculosis. The proportion of individuals who truly remain infected with M. tuberculosis after tuberculin skin test or IGRA conversion is unknown. It is also uncertain how long adaptive immune responses towards mycobacterial antigens persist in the absence of live mycobacteria. Clinical management and public healthcare policies for preventive chemotherapy against tuberculosis could be improved, if we were to gain a better understanding on M. tuberculosis latency and reactivation. This statement by the TBNET summarises knowledge and limitations of the currently available tests used in adults and children for the diagnosis of latent tuberculosis infection. In summary, the main issue regarding testing is to restrict it to those who are known to be at higher risk of developing tuberculosis and who are willing to accept preventive chemotherapy.
The third sector is becoming a growing provider of public, social, and health services. However, there is little evidence on the effectiveness of third sector organisations (TSOs), and their capacity ...to implement evidence-based interventions (EBIs). Understanding implementation aspects of service delivery remains an important issue in clinical practice, but is poorly understood in the context of TSOs. This is problematic, since implementation issues are known to be critical for effective intervention outcomes.
To identify and synthesise existing research on what barriers and facilitators influence the implementation process of TSOs delivering EBIs.
This review is reported according to PRISMA guidelines and was pre-registered in PROSPERO. Key databases were searched using relevant terms, experts in the field were contacted, and websites were reviewed. All identified studies were double-screened, and data were extracted independently by two authors. Included studies were synthesised using thematic analysis and were quality appraised.
Thirty-one studies were included, most of which were conducted in North America. The thematic synthesis identified resource limitations, in particular staff and finance, to be the most reported barrier to TSOs implementing EBIs. Organisational culture, including factors such as alignment between the mission of the TSO and EBI, and support/prioritisation of the implementation process were the most reported facilitators. These findings generalise across the included studies and are robust to study quality assessment.
While it is often assumed that good outcomes follow when implementing interventions that have been developed and tested according to best practice, little attention has been paid to how EBIs are best transported, contextualised, and implemented by third sector providers. This systematic review found that TSOs faced considerable challenges in implementing EBIs, which were primarily a lack of support and expertise, and unclear/insufficient guidelines on how to adapt EBIs to different populations. To address these challenges, it is important to engage with central stakeholders, such as funders, researchers, policymakers, and practitioners, to discuss how these needs can be met.
PROSPERO: CRD42017073090 .
Future information technology demands ever-faster, low-loss quantum control. Intense light fields have facilitated milestones along this way, including the induction of novel states of matter
, ...ballistic acceleration of electrons
and coherent flipping of the valley pseudospin
. These dynamics leave unique 'fingerprints', such as characteristic bandgaps or high-order harmonic radiation. The fastest and least dissipative way of switching the technologically most important quantum attribute-the spin-between two states separated by a potential barrier is to trigger an all-coherent precession. Experimental and theoretical studies with picosecond electric and magnetic fields have suggested this possibility
, yet observing the actual spin dynamics has remained out of reach. Here we show that terahertz electromagnetic pulses allow coherent steering of spins over a potential barrier, and we report the corresponding temporal and spectral fingerprints. This goal is achieved by coupling spins in antiferromagnetic TmFeO
(thulium orthoferrite) with the locally enhanced terahertz electric field of custom-tailored antennas. Within their duration of one picosecond, the intense terahertz pulses abruptly change the magnetic anisotropy and trigger a large-amplitude ballistic spin motion. A characteristic phase flip, an asymmetric splitting of the collective spin resonance and a long-lived offset of the Faraday signal are hallmarks of coherent spin switching into adjacent potential minima, in agreement with numerical simulations. The switchable states can be selected by an external magnetic bias. The low dissipation and the antenna's subwavelength spatial definition could facilitate scalable spin devices operating at terahertz rates.
How I do … ex vivo in vitro maturation? Neyroud, A-S; Guez-Loussouarn, C; Bales, D ...
Gynécologie, obstétrique, fertilité & sénologie
49, Številka:
4
Journal Article
Ultrafast charge transport in strongly biased semiconductors is at the heart of high-speed electronics, electro-optics and fundamental solid-state physics. Intense light pulses in the terahertz ...spectral range have opened fascinating vistas. Because terahertz photon energies are far below typical electronic interband resonances, a stable electromagnetic waveform may serve as a precisely adjustable bias. Novel quantum phenomena have been anticipated for terahertz amplitudes, reaching atomic field strengths. We exploit controlled (multi-)terahertz waveforms with peak fields of 72 MV cm-1 to drive coherent interband polarization combined with dynamical Bloch oscillations in semiconducting gallium selenide. These dynamics entail the emission of phase-stable high-harmonic transients, covering the entire terahertz-to-visible spectral domain between 0.1 and 675 THz. Quantum interference of different ionization paths of accelerated charge carriers is controlled via the waveform of the driving field and explained by a quantum theory of inter- and intraband dynamics. Our results pave the way towards all-coherent terahertz-rate electronics.
Harnessing the carrier wave of light as an alternating-current bias may enable electronics at optical clock rates
. Lightwave-driven currents have been assumed to be essential for high-harmonic ...generation in solids
, charge transport in nanostructures
, attosecond-streaking experiments
and atomic-resolution ultrafast microscopy
. However, in conventional semiconductors and dielectrics, the finite effective mass and ultrafast scattering of electrons limit their ballistic excursion and velocity. The Dirac-like, quasi-relativistic band structure of topological insulators
may allow these constraints to be lifted and may thus open a new era of lightwave electronics. To understand the associated, complex motion of electrons, comprehensive experimental access to carrier-wave-driven currents is crucial. Here we report angle-resolved photoemission spectroscopy with subcycle time resolution that enables us to observe directly how the carrier wave of a terahertz light pulse accelerates Dirac fermions in the band structure of the topological surface state of Bi
Te
. While terahertz streaking of photoemitted electrons traces the electromagnetic field at the surface, the acceleration of Dirac states leads to a strong redistribution of electrons in momentum space. The inertia-free surface currents are protected by spin-momentum locking and reach peak densities as large as two amps per centimetre, with ballistic mean free paths of several hundreds of nanometres, opening up a realistic parameter space for all-coherent lightwave-driven electronic devices. Furthermore, our subcycle-resolution analysis of the band structure may greatly improve our understanding of electron dynamics and strong-field interaction in solids.
PDF
