The sub-luminal phase velocity of electromagnetic waves in free space is generally unobtainable, being closely linked to forbidden faster than light group velocities. The requirement of sub-luminal ...phase-velocity in laser-driven particle acceleration schemes imposes a limit on the total acceleration achievable in free space, and necessitates the use of dispersive structures or waveguides for extending the field-particle interaction. We demonstrate a travelling source approach that overcomes the sub-luminal propagation limits. The approach exploits ultrafast optical sources with slow group velocity propagation, and a group-to-phase front conversion through nonlinear optical interaction. The concept is demonstrated with two terahertz generation processes, nonlinear optical rectification and current-surge rectification. We report measurements of longitudinally polarised single-cycle electric fields with phase and group velocity between 0.77c and 1.75c. The ability to scale to multi-megawatt-per-metre field strengths is demonstrated. Our approach paves the way towards the realisation of cheap and compact particle accelerators with femtosecond scale control of particles.Controlled generation of terahertz radiation with subluminal phase velocities is a key issue in laser-driven particle acceleration. Here, the authors demonstrate a travelling-source approach utilizing the group-to-phase front conversion to overcome the sub-luminal propagation limit.
Size at birth, postnatal weight gain, and adult risk for type 2 diabetes may reflect environmental exposures during developmental plasticity and may be mediated by epigenetics. Both low birth weight ...(BW), as a marker of fetal growth restraint, and high birth weight (BW), especially after gestational diabetes mellitus (GDM), have been linked to increased risk of adult type 2 diabetes. We assessed DNA methylation patterns using a bead chip in cord blood samples from infants of mothers with GDM (group 1) and infants with prenatal growth restraint indicated by rapid postnatal catch‐up growth (group 2), compared with infants with normal postnatal growth (group 3). Seventy‐five CpG loci were differentially methylated in groups 1 and 2 compared with the controls (group 3), representing 72 genes, many relevant to growth and diabetes. In replication studies using similar methodology, many of these differentially methylated regions were associated with levels of maternal glucose exposure below that defined by GDM the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study or were identified as changes observed after randomized periconceptional nutritional supplementation in a Gambian cohort characterized by maternal deprivation. These studies provide support for the concept that similar epigenetic modifications may underpin different prenatal exposures and potentially increase long‐term risk for diseases such as type 2 diabetes.—Quilter, C. R., Cooper, W. N., Cliffe, K. M., Skinner, B. M., Prentice, P. M., Nelson, L., Bauer, J., Ong, K. K., Constância, M., Lowe, W. L., Affara, N. A., Dunger, D. B., Impact on offspring methylation patterns of maternal gestational diabetes mellitus and intrauterine growth restraint suggest common genes and pathways linked to subsequent type 2 diabetes risk. FASEB J. 28, 4868–4879 (2014). www.fasebj.org
The structure of a glass obtained by the melt quenching of a two-dimensional (2D) coordination network was examined. X-ray analyses disclosed a 2D-to-0D structural transformation before and after ...glass formation. The mechanism is unique to coordination compounds, as it is characterized by labile and flexible coordination bonds.
The original version of this Article contained an error in the abstract, referring to "multi-megawatt-per-metre" instead of "multi-megavolt-per-metre". This has now been corrected in both the PDF and ...HTML versions of the Article.
A general description of electro-optic detection including non-collinear phase matching and finite transverse beam profiles is presented. It is shown theoretically and experimentally that ...non-collinear phase matching in ZnTe (and similar materials) produces an angular chirp in the χ(2)-generated optical signal. Due to this, in non-collinear THz and probe arrangements such as single-shot THz measurements or through accidental misalignment, measurement of an undistorted THz signal is critically dependent on having sufficient angular acceptance in the optical probe path. The associated spatial walk-off can also preclude the phase retardation approximation used in THz-TDS. The rate of misalignment-induced chirping in commonly used ZnTe and GaP schemes is tabulated, allowing ready analysis of a detection system.
Sequences from 20 amplicons representing nine different loci and 11369bp from the short arm of the pig Y chromosome were compared using pools of DNA from different European and Chinese breeds. A ...total of 33 polymorphic sites were identified, including five indels and 28 single nucleotide polymorphisms (SNPs). Three high frequency SNPs within the coding regions of SRY were further analysed across 889 males representing 25 European and 25 Asian breeds or Lines, plus a European Line of Meishan. Two haplotypes seen to be associated with ‘European' or ‘Chinese' origin in the initial SNP discovery phase were found to be the most common in their respective groups of breeds in a more detailed genotyping study. Two further SRY haplotypes are relatively rare. One was found exclusively within Tamworth, at low frequency in Retinto, and in three Chinese breeds (Huai, Sahwutou and Xiaomeishan). The other uncommon haplotype is found exclusively in Bamajiang, two further Chinese breeds (Hangjiang Black and Longling) and two European rare breeds (Mangalica and Linderödssvin), but appears based on comparison with other suids to represent an ancestral sequence.
Background: A 35‐year‐old postpartum woman presented with myocardial infarction (MI) due to spontaneous coronary artery dissection (SCAD). In addition to conventional medical therapy, she was treated ...with immunosuppressive agents (prednisone and cytoxan) because of five noncontiguous coronary dissections, surgical inoperability, and postinfarction angina. Repeat angiography 94 days later demonstrated angiographically normal vessels.
Methods: A literature review of 42 additional cases of peripartum SCAD was performed, and the results were compared with this patient.
Results: Mortality was 48.8% (21/43). Sudden cardiac death was the initial presentation in 27.9% (12/43) of cases. The left coronary artery was involved in 78.6% (44/56) of dissections with left main segment dissection in 10 cases. In women who survived > 24 h post infarction, recurrent MI, usually due to a second coronary dissection, occurred in 20.8% (5/24). Histopathologic studies have often shown periadventitial inflammation (80%, 16/20), in which eosinophils predominate (68.8%, 11/16), and may be linked to the medial degeneration often found in these cases.
Conclusions: The common observation of eosinophilic periadventitial inflammation suggests a role in the pathophysiology of this rare, yet serious condition. Aggressive immunosuppressive therapy in this case of multivessel dissection resulted in spontaneous angiographic healing of all lesions.
The ELFIN Mission Angelopoulos, V.; Tsai, E.; Bingley, L. ...
Space science reviews,
2020/8, Letnik:
216, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The Electron Loss and Fields Investigation with a Spatio-Temporal Ambiguity-Resolving option (ELFIN-STAR, or heretoforth simply: ELFIN) mission comprises two identical 3-Unit (3U) CubeSats on a polar ...(∼93
∘
inclination), nearly circular, low-Earth (∼450 km altitude) orbit. Launched on September 15, 2018, ELFIN is expected to have a >2.5 year lifetime. Its primary science objective is to resolve the mechanism of storm-time relativistic electron precipitation, for which electromagnetic ion cyclotron (EMIC) waves are a prime candidate. From its ionospheric vantage point, ELFIN uses its unique pitch-angle-resolving capability to determine whether measured relativistic electron pitch-angle and energy spectra within the loss cone bear the characteristic signatures of scattering by EMIC waves or whether such scattering may be due to other processes. Pairing identical ELFIN satellites with slowly-variable along-track separation allows disambiguation of spatial and temporal evolution of the precipitation over minutes-to-tens-of-minutes timescales, faster than the orbit period of a single low-altitude satellite (T
orbit
∼ 90 min). Each satellite carries an energetic particle detector for electrons (EPDE) that measures 50 keV to 5 MeV electrons with
Δ
E/E < 40% and a fluxgate magnetometer (FGM) on a ∼72 cm boom that measures magnetic field waves (e.g., EMIC waves) in the range from DC to 5 Hz Nyquist (nominally) with <0.3 nT/sqrt(Hz) noise at 1 Hz. The spinning satellites (T
spin
∼
3 s) are equipped with magnetorquers (air coils) that permit spin-up or -down and reorientation maneuvers. Using those, the spin axis is placed normal to the orbit plane (nominally), allowing full pitch-angle resolution twice per spin. An energetic particle detector for ions (EPDI) measures 250 keV – 5 MeV ions, addressing secondary science. Funded initially by CalSpace and the University Nanosat Program, ELFIN was selected for flight with joint support from NSF and NASA between 2014 and 2018 and launched by the ELaNa XVIII program on a Delta II rocket (with IceSatII as the primary). Mission operations are currently funded by NASA. Working under experienced UCLA mentors, with advice from The Aerospace Corporation and NASA personnel, more than 250 undergraduates have matured the ELFIN implementation strategy; developed the instruments, satellite, and ground systems and operate the two satellites. ELFIN’s already high potential for cutting-edge science return is compounded by concurrent equatorial Heliophysics missions (THEMIS, Arase, Van Allen Probes, MMS) and ground stations. ELFIN’s integrated data analysis approach, rapid dissemination strategies via the SPace Environment Data Analysis System (SPEDAS), and data coordination with the Heliophysics/Geospace System Observatory (H/GSO) optimize science yield, enabling the widest community benefits. Several storm-time events have already been captured and are presented herein to demonstrate ELFIN’s data analysis methods and potential. These form the basis of on-going studies to resolve the primary mission science objective. Broad energy precipitation events, precipitation bands, and microbursts, clearly seen both at dawn and dusk, extend from tens of keV to >1 MeV. This broad energy range of precipitation indicates that multiple waves are providing scattering concurrently. Many observed events show significant backscattered fluxes, which in the past were hard to resolve by equatorial spacecraft or non-pitch-angle-resolving ionospheric missions. These observations suggest that the ionosphere plays a significant role in modifying magnetospheric electron fluxes and wave-particle interactions. Routine data captures starting in February 2020 and lasting for at least another year, approximately the remainder of the mission lifetime, are expected to provide a very rich dataset to address questions even beyond the primary mission science objective.
Understanding spin textures in frustrated magnets Paddison, J. A. M.; Zhang, H.; Rai, B. ...
Acta crystallographica. Section A, Foundations and advances,
08/2023, Letnik:
79, Številka:
a2
Journal Article
PDF
