Grain boundaries undergo thermally-activated, first-order transitions that result in discontinuous changes of interfacial properties. Importantly, grain boundary transitions lead to changes in bulk ...material properties (e.g., embrittlement) and/or behavior (e.g., abnormal grain growth). Numerous studies have been completed on the equilibrium states of grain boundaries and their transitions (i.e., complexion transitions), but there have been far fewer investigations of complexion transition kinetics; complexion transitions occur on the atomic-scale and are therefore challenging to detect experimentally. In this work, a 3D Potts grain growth model with stochastic complexion transitions was employed to investigate complexion transition kinetics. A Johnson-Mehl-Avrami-Kolmogorov (i.e., JMAK) approach was used to extract nucleation and growth rates (i.e., transformation rates), while point process analyses and correlation functions were used to infer complex interrelated nucleation and growth events. Time-temperature-transformation (TTT) diagrams, in particular grain-boundary complexion, transformed grain, and abnormal grain TTT diagrams, were constructed to summarize the progress of complexion-related transformations. Such diagrams relate complexion-induced grain growth to the underlying complexion transitions and, in the case of abnormal grain growth (AGG), permit one to assess the role of AGG as a temperature-dependent, time-displaced indicator of complexion transitions. Overall, this work details a theoretical framework that can be used to better understand complexion transition kinetics as well as to develop tools for the design of bulk microstructures.
Systems of N identical phase oscillators with global sinusoidal coupling are known to display low-dimensional dynamics. Although this phenomenon was first observed about 20 years ago, its underlying ...cause has remained a puzzle. Here we expose the structure working behind the scenes of these systems by proving that the governing equations are generated by the action of the Mobius group, a three-parameter subgroup of fractional linear transformations that map the unit disk to itself. When there are no auxiliary state variables, the group action partitions the N-dimensional state space into three-dimensional invariant manifolds (the group orbits). The N-3 constants of motion associated with this foliation are the N-3 functionally independent cross ratios of the oscillator phases. No further reduction is possible, in general; numerical experiments on models of Josephson junction arrays suggest that the invariant manifolds often contain three-dimensional regions of neutrally stable chaos.
We use resonant soft X-ray holography to image the insulator–metal phase transition in vanadium dioxide with element and polarization specificity and nanometer spatial resolution. We observe that ...nanoscale inhomogeneity in the film results in spatial-dependent transition pathways between the insulating and metallic states. Additional nanoscale phases form in the vicinity of defects which are not apparent in the initial or final states of the system, which would be missed in area-integrated X-ray absorption measurements. These intermediate phases are vital to understand the phase transition in VO2, and our results demonstrate how resonant imaging can be used to understand the electronic properties of phase-separated correlated materials obtained by X-ray absorption.
-dependent aqueous-phase rate constants were determined for the oxidation of the hydroxy aldehydes, glyceraldehyde, glycolaldehyde, and lactaldehyde, by the hydroxyl radicals (
OH), the sulfate ...radicals (SO
), and the nitrate radicals (NO
). The obtained Arrhenius expressions for the oxidation by the
OH radical are:
= (3.3 ± 0.1) × 10
× exp((-960 ± 80 K)/
)/L mol
s
,
= (4.3 ± 0.1) × 10
× exp((-1740 ± 50 K)/
)/L mol
s
,
= (1.6 ± 0.1) × 10
× exp((-1410 ± 180 K)/
)/L mol
s
; for the SO
radical:
= (4.3 ± 0.1) × 10
× exp((-1400 ± 50 K)/
)/L mol
s
,
= (10.3 ± 0.3) × 10
× exp((-1730 ± 190 K)/
)/L mol
s
,
= (2.2 ± 0.1) × 10
× exp((-1030 ± 230 K)/
)/L mol
s
; and for the NO
radical:
= (3.4 ± 0.2) × 10
× exp((-3470 ± 460 K)/
)/L mol
s
,
= (7.8 ± 0.2) × 10
× exp((-3820 ± 240 K)/
)/L mol
s
,
= (4.3 ± 0.2) × 10
× exp((-2750 ± 340 K)/
)/L mol
s
, respectively. Targeted simulations of multiphase chemistry reveal that the oxidation by OH radicals in cloud droplets is important under remote and wildfire influenced continental conditions due to enhanced partitioning. There, the modeled average aqueous
OH concentration is 2.6 × 10
and 1.8 × 10
mol L
, whereas it is 7.9 × 10
and 3.5 × 10
mol L
under wet particle conditions. During cloud periods, the aqueous-phase reactions by
OH contribute to the oxidation of glycolaldehyde, lactaldehyde, and glyceraldehyde by about 35 and 29%, 3 and 3%, and 47 and 37%, respectively.
STUDY QUESTION
What are the experiences of trans persons (i.e. those whose gender identity does not match the gender assigned to them at birth) who sought or accessed assisted reproduction (AR) ...services in Ontario, Canada, between 2007 and 2010?
SUMMARY ANSWER
The majority of trans persons report negative experiences with AR service providers.
WHAT IS KNOWN ALREADY
Apart from research examining desire to have children among trans people, most of the literature on this topic has debated the ethics of assisting trans persons to become parents. To-date, all of the published research concerning trans persons' experiences with AR services is solely from the perspective of service providers; no studies have examined the experiences of trans people themselves.
STUDY DESIGN, SIZE, DURATION
Secondary qualitative research study of data from nine trans-identified people and their partners (total n = 11) collected as part of a community-based study of access to AR services for sexual and gender minority people between 2010 and 2012.
PARTICIPANTS/MATERIALS, SETTING, METHODS
Trans-identified volunteers (and their partners, when applicable) who had used or attempted to access AR services since 2007 from across Ontario, Canada, participated in a 60–90 minute, semi-structured qualitative interview. Qualitative analysis was performed using a descriptive phenomenological approach. Emerging themes were continually checked against the data as part of an iterative process.
MAIN RESULTS AND THE ROLE OF CHANCE
The data highlight barriers to accessing AR services for trans people. Participant recommendations for improving AR service provision to better meet the needs of this population are presented. These recommendations address the following areas: (i) AR service provider education and training; (ii) service provider and clinic practices and (iii) clinic environment.
LIMITATIONS, REASONS FOR CAUTION
The majority of study participants were trans people who identified as men and who resided in major urban areas; those living in smaller communities may have different experiences that were not adequately captured in this analysis.
WIDER IMPLICATIONS OF THE FINDINGS
While existing literature debates the ethics of assisting trans people to become parents through the use of AR, our study demonstrates that they are already accessing or attempting to access these services. This reality necessitates a shift toward exploring the ways in which AR services can be improved to better meet the needs of this population, from the perspectives of both service users and service providers.
STUDY FUNDING/COMPETING INTEREST(S)
This project was supported by the Canadian Institutes of Health Research-Institute of Gender and Health, in partnership with the Assisted Human Reproduction Canada: Catalyst Grant: Psychosocial Issues Associated with Assisted Human Reproduction (FRN-103595). S.M. was supported by a Canada Graduate Scholarship from the Social Science and Humanities Research Council, as well as research funding from Osgoode Hall Law School, York University. S.J.-A. was supported by an Ontario Graduate Scholarship funded by the Province of Ontario and the University of Toronto.
TRIAL REGISTRATION NUMBER
N/A.
Developing a reliable and efficient fabrication method for phase-transition thin-film technology is critical for electronic and photonic applications. We demonstrate a novel method for fabricating ...polycrystalline, switchable vanadium dioxide thin films on glass and silicon substrates and show that the optical switching contrast is not strongly affected by post-processing annealing times. The method relies on electron-beam evaporation of a nominally stoichiometric powder, followed by fast annealing. As a result of the short annealing procedure we demonstrate that films deposited on silicon substrates appear to be smoother, in comparison to pulsed laser deposition and sputtering. However, optical performance of e-beam evaporated film on silicon is affected by annealing time, in contrast to glass.
Working memory (WM) involves the ability to maintain and manipulate information held in mind. Neuroimaging studies have shown that secondary motor areas activate during WM for verbal content (e.g., ...words or letters), in the absence of primary motor area activation. This activation pattern may reflect an inner speech mechanism supporting online phonological rehearsal. Here, we examined the causal relationship between motor system activity and WM processing by using transcranial magnetic stimulation (TMS) to manipulate motor system activity during WM rehearsal. We tested WM performance for verbalizable (words and pseudowords) and non-verbalizable (Chinese characters) visual information. We predicted that disruption of motor circuits would specifically affect WM processing of verbalizable information. We found that TMS targeting motor cortex slowed response times (RTs) on verbal WM trials with high (pseudoword) vs. low (real word) phonological load. However, non-verbal WM trials were also significantly slowed with motor TMS. WM performance was unaffected by sham stimulation or TMS over visual cortex (VC). Self-reported use of motor strategy predicted the degree of motor stimulation disruption on WM performance. These results provide evidence of the motor system's contributions to verbal and non-verbal WM processing. We speculate that the motor system supports WM by creating motor traces consistent with the type of information being rehearsed during maintenance.
Display omitted
The abrupt changes in structural, electronic and optical properties that accompany the vanadium dioxide (VO2) phase transition make it a promising material for a wide range of ...thin-film applications in electronics,photonics and plasmonics. Several physical vapor-deposition techniques are used by various research groups, but until now there has been no systematic comparison of the three most common methods – electron beam evaporation, pulsed-laser deposition and sputtering – covering the most common substrates. Here we explore the influence of substrate, deposition process and annealing time at 450°C on the phase transition properties and morphology of thin VO2 films. Films deposited by rf magnetron sputtering have the same structure on glass, silicon and sapphire substrates and are stable for 90min of annealing. In contrast, the structure of films deposited by electron beam evaporation and pulsed laser deposition depends heavily on the substrate. Dewetting plays a prominent role in the evolution of film structure and the phase transition properties for films deposited on silicon and glass are unstable for 90min annealing. The epitaxial relationship between VO2 and sapphire stabilizes the phase transition contrast for all deposition processes and annealing times. Performance as measured by switching contrast is maximized for all deposition processes with 10min of annealing.
We utilize near-infrared pump-mid-infrared probe spectroscopy to investigate the ultrafast electronic response of pressurized VO2. A clear anomaly in the linear mid-infrared response as well as in ...the fluence dependence of the pump-probe signal is observed around 8 GPa indicating a pressure-induced phase transition. Distinct pump-probe signals and a pumping threshold behavior typical for the insulating VO2 phase persist also in the high-pressure phase. Thus, in contrast to the temperature-induced rutile metallic state of VO2, the pressure-induced monoclinic phase preserves the energy gap. However, our results indicate the appearance and a gradual growth of additional intragap states upon increasing pressure above 8 GPa. These observations can be interpreted in terms of a bandwidth-controlled Mott-Hubbard transition.
PDF
