This study explores the extent to which a bilingual advantage can be observed for three tasks in an established population of fully fluent bilinguals from childhood through adulthood. Welsh-English simultaneous and early sequential bilinguals, as well as English monolinguals, aged 3 years through older adults, were tested on three sets of cognitive and executive function tasks. Bilinguals were Welsh-dominant, balanced, or English-dominant, with only Welsh, Welsh and English, or only English at home. Card sorting, Simon, and a metalinguistic judgment task (650, 557, and 354 participants, respectively) reveal little support for a bilingual advantage, either in relation to control or globally. Primarily there is no difference in performance across groups, but there is occasionally better performance by monolinguals or persons dominant in the language being tested, and in one case-in one condition and in one age group-lower performance by the monolinguals. The lack of evidence for a bilingual advantage in these simultaneous and early sequential bilinguals suggests the need for much closer scrutiny of what type of bilingual might demonstrate the reported effects, under what conditions, and why.
Transition metal
carbides (TMCs) have demonstrated outstanding
potential for utilization in a wide range of catalytic applications
because of their inherent multifunctionality and tunable composition.
However, the harsh conditions required to prepare these materials
have limited the scope of synthetic control over their physical properties.
The development of low-temperature, carburization-free routes to prepare
TMCs would unlock the versatility of this class of materials, enhance
our understanding of their physical properties, and enable their cost-effective
production at industrial scales. Here, we report an exceptionally
mild and scalable solution-phase synthesis route to phase-pure molybdenum
carbide (α-MoC1–x
) nanoparticles
(NPs) in a continuous flow millifluidic reactor. We exploit the thermolytic
decomposition of Mo(CO)6 in the presence of a surface-stabilizing
ligand and a high boiling point solvent to yield MoC1–x
NPs that are colloidally stable and resistant to
bulk oxidation in air. To demonstrate the utility of this synthetic
route to prepare catalytically active TMC NPs, we evaluated the thermochemical
CO2 hydrogenation performance of α-MoC1–x
NPs dispersed on an inert carbon support. The α-MoC1–x
/C catalyst exhibited a 2-fold increase
in both activity on a per-site basis and selectivity to C2+ products as compared to the bulk α-MoC1–x
analogue.
The translation of batch chemistries onto continuous flow platforms requires addressing the issues of consistent fluidic behaviour, channel fouling and high-throughput processing. Droplet microfluidic technologies reduce channel fouling and provide an improved level of control over heat and mass transfer to control reaction kinetics. However, in conventional geometries, the droplet size is sensitive to changes in flow rates. Here we report a three-dimensional droplet generating device that exhibits flow invariant behaviour and is robust to fluctuations in flow rate. In addition, the droplet generator is capable of producing droplet volumes spanning four orders of magnitude. We apply this device in a parallel network to synthesize platinum nanoparticles using an ionic liquid solvent, demonstrate reproducible synthesis after recycling the ionic liquid, and double the reaction yield compared with an analogous batch synthesis.
The photovoltage onset reveals the energetics of the donor states, while photovoltage size and reversibility provide information on the charge transfer dynamics of the dopants and their ability to oxidize methanol.
The
translation of batch chemistries to high-throughput flow methods
addresses scaling concerns associated with the implementation of colloidal
nanoparticle (NP) catalysts for industrial processes. A literature
procedure for the synthesis of Ni-NPs was adapted to a continuous
millifluidic (mF) flow method, achieving yields >60%. Conversely,
NPs prepared in a batch (B) reaction under conditions analogous to
the continuous flow conditions gave only a 45% yield. Both mF- and
B-Ni-NP catalysts were supported on SiO2 and compared to
a Ni/SiO2 catalyst prepared by traditional incipient wetness
(IW) impregnation for the hydrodeoxygenation (HDO) of guaiacol under ex situ catalytic fast pyrolysis conditions (350 °C,
0.5 MPa). Compared to the IW method, both colloidal NPs displayed
increased morphological control and narrowed size distributions, and
the NPs prepared by both methods showed similar size, shape, and crystallinity.
The Ni-NP catalyst synthesized by the continuous flow method exhibited
similar H-adsorption site densities, site-time yields, and selectivities
toward deoxygenated products compared to the analogous batch-prepared
catalyst, and it outperformed the IW catalyst with respect to higher
selectivity to lower oxygen content products and a 31-fold decrease
in deactivation rate. These results demonstrate the utility of synthesizing
colloidal Ni-NP catalysts using flow methods that can produce >27
g/day of Ni-NPs (equivalent to >0.5 kg of 5 wt % Ni/SiO2), while maintaining the catalytic properties displayed by the batch
equivalent.
The pursuit of scalable
methods for the preparation of well-defined
metallic nanoparticles (MNPs) is addressed in this work via a novel
microwave-assisted continuous flow synthesis technique. It is shown
that single- and two-phase flow synthesis methods provide access to
morphologically well-defined and near-monodisperse RhNPs. The RhNPs
can be prepared in shorter reaction times and at lower temperatures
than are commonly required in conventional batch reactions. Under
single-phase flow conditions, in which Rh(III) is reduced in ethylene
glycol, near-monodisperse cuboctahedral RhNPs are obtained; the average
NP size can be controlled as a function of the residence time of the
reactant stream within the microwave cavity. In contrast, a two-phase
microfluidic droplet flow method leads to the highly selective formation
of Rh multipods. When compared to cuboctahedral RhNPs of comparable
size, the Rh multipods are found to exhibit significantly higher catalytic
activity in the vapor-phase hydrogenation of cyclohexene. The potential
versatility of this new two-phase flow method coupled with microwave-assisted
heating is further demonstrated in the synthesis of well-defined isotropic
NPs comprised of classically immiscible RhAg random alloys.
An
ionic liquid (IL) solvent was used to synthesize small, phase-pure
nickel phosphide (Ni2P) nanocrystals. In contrast, under
analogous reaction conditions, substitution of the IL for the common
high-boiling organic solvent 1-octadecene (ODE) results in phase-impure
nanocrystals. The 5 nm Ni2P nanocrystals prepared in IL
were electrocatalytically active toward the hydrogen evolution reaction.
The synthesis in IL was also extended to alloyed Ni2–x
Co
x
P nanocrystals,
where 0.5 ≤ x ≤ 1.5.
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