2,802 research outputs found
Crystallization of medium length 1-alcohols in mesoporous silicon: An X-ray diffraction study
The linear 1-alcohols n-C16H33OH, n-C17H35OH, n-C19H37OH have been imbibed
and solidified in lined up, tubular mesopores of silicon with 10 nm and 15 nm
mean diameters, respectively. X-ray diffraction measurements reveal a set of
six discrete orientation states (''domains'') characterized by a perpendicular
alignment of the molecules with respect to the long axis of the pores and by a
four-fold symmetry about this direction, which coincides with the crystalline
symmetry of the Si host. A Bragg peak series characteristic of the formation of
bilayers indicates a lamellar structure of the spatially confined alcohol
crystals in 15 nm pores. By contrast, no layering reflections could be detected
for 10 nm pores. The growth mechanism responsible for the peculiar orientation
states is attributed to a nano-scale version of the Bridgman technique of
single-crystal growth, where the dominant growth direction is aligned
parallelly to the long pore axes. Our observations are analogous to the growth
phenomenology encountered for medium length n-alkanes confined in mesoporous
silicon (Phys. Rev. E 75, 021607 (2007)) and may further elucidate why porous
silicon matrices act as an effective nucleation-inducing material for protein
solution crystallization.Comment: 4 pages, 4 figures, to appear as a Brief Report in Physical Review
Structure and diffusion in amorphous aluminium silicate: A molecular dynamics computer simulation
The amorphous aluminium silicate (Al2O3)2(SiO2) [AS2] is investigated by
means of large scale molecular dynamics computer simulations. We consider fully
equilibrated melts in the temperature range 6100K >= T >= 2300K as well as
glass configurations that were obtained from cooling runs from T=2300K to 300K
with a cooling rate of about 10^12K/s. Already at temperatures as high as
4000K, most of the Al and Si atoms are four-fold coordinated by oxygen atoms.
Thus, the structure of AS2 is that of a disordered tetrahedral network. The
packing of AlO4 tetrahedra is very different from that of SiO4 tetrahedra in
that Al is involved with a relatively high probability in small-membered rings
and in triclusters in which an O atom is surrounded by four cations. We find as
typical configurations two-membered rings with two Al atoms in which the shared
O atoms form a tricluster. On larger length scales, the system shows a
microphase separation in which the Al-rich network structure percolates through
the SiO2 network. The latter structure gives rise to a prepeak in the static
structure factor at a wavenumber q=0.5\AA^{-1}. The comparison of experimental
X-ray data with the results from the simulation shows a good agreement for the
structure function. The diffusion dynamics in AS2 is found to be much faster
than in SiO2. We show that the self-diffusion constants for O and Al are very
similar and that they are by a factor of 2-3 larger than the one for Si.Comment: 30 pages of Latex, 13 figure
Preferred orientation of n-hexane crystallized in silicon nanochannels: A combined x-ray diffraction and sorption isotherm study
We present an x-ray diffraction study on n-hexane in tubular silicon channels
of approximately 10 nm diameter both as a function of the filling fraction f of
the channels and as a function of temperature. Upon cooling, confined n-hexane
crystallizes in a triclinic phase typical of the bulk crystalline state.
However, the anisotropic spatial confinement leads to a preferred orientation
of the confined crystallites, where the crystallographic direction
coincides with the long axis of the channels. The magnitude of this preferred
orientation increases with the filling fraction, which corroborates the
assumption of a Bridgman-type crystallization process being responsible for the
peculiar crystalline texture. This growth process predicts for a channel-like
confinement an alignment of the fastest crystallization direction parallel to
the long channel axis. It is expected to be increasingly effective with the
length of solidifying liquid parcels and thus with increasing f. In fact, the
fastest solidification front is expected to sweep over the full silicon
nanochannel for f=1, in agreement with our observation of a practically perfect
texture for entirely filled nanochannels
Yes-associated protein (YAP) is a negative regulator of chondrogenesis in mesenchymal stem cells
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Acknowledgements The authors would like to thank Dr Marius Sudol for the hYAP plasmids (obtained through Addgene), Dr Pete Zammit for the pMSCV-IRES-eGFP plasmid, Dr Robert Judson for subcloning the hYAP cDNAs into the pMSCV-IRES-eGFP plasmid, Dr Lynda Erskine for the provision of mouse embryo samples, and Professor Jimmy Hutchison and the Orthopaedics Department at the Aberdeen Royal Infirmary for the provision of human tissue samples. The authors are also grateful to Denise Tosh and Susan Clark for excellent technical support. This work was funded by Arthritis Research UK (grant 19429).Peer reviewedPublisher PD
White-light OLEDs using liquid crystal polymer networks
We have mixed nematic light-emitting liquid crystals and incorporated them as insoluble cross-linked polymer networks in a liquid crystal white-light organic light-emitting diode (LC-WOLED). The light emission is not voltage-dependent and polarized white light emission is also demonstrated. This wet-chemistry approach to WOLEDs is compatible with patterning by photolithography as well as by inkjet printing at room temperature on plastic substrates by roll-to-roll manufacturing
Advertising Effect on Consumer Emotions, Judgements, and Purchase Intent
Advertising has been found to induce consumer reactions, including emotions and judgements, which in turn are believed to relate to important outcomes, such as purchase intents. Marketing researches seek to understand these consumer reactions and their decision-making processes to influence purchase intents. This study focuses on the information role of emotion in understanding advertising effects and influencing consumer choices. Individuals use affective responses to evaluate information and to form judgements, which are critical in the decision-making process. This research further expands the Informative Strategy Model by adding judgement as a mediator. The results of a multiple mediation analysis provide support that consumersâ positive emotions directly influence their purchase intent, while consumer judgements partially mediate the effect of individualsâ emotions on purchase intents. Research findings benefit marketing and advertising professionals by providing empirical evidence for the effect of advertising, including controversial advertising on consumer purchase intent. The challenge with controversial advertising is that if individuals experience negative emotions and judgements, advertisers may have limited or potentially negative influence on consumer purchase intents
Negative Social Cognitions in Socially Anxious Youth: Distorted Reality or a Kernel of Truth?
We review studies that investigate negative social cognitions of socially anxious youth in relation to two specific domains: interpretation of ambiguous social situations and self-evaluation of social performance, including social skills and nervous behaviors. In this review, we address the question whether socially anxious youthâs negative perceptions are distortions of reality or reflect a kernel of truth as compared to other sources of information including independent adult observers and age peers. Studies key to this question are those that investigate not only the social perceptions themselves but also the social behavior of socially anxious youth. Hence the selection of studies for the review was based on this criterion. From the relevant literature it is, as yet, unclear whether the negative interpretations of ambiguous social situations shown by socially anxious youth are distorted or a reflection of reality. Socially anxious youthâs self-evaluations of social skills appear partly distorted and partly true, depending on the person judging the social skills. In contrast, self-evaluations of nervous behaviors appear distorted. The studies reviewed indicate that research would benefit from including a wider range of perceptions from persons relevant to the socially anxious youthâs daily social environment, not only parents and teachers but also their age peers
Emergence of a Dynamic Super-Structural Order Integrating Antiferroelectric and Antiferrodistortive Competing Instabilities in EuTiO3
Microscopic structural instabilities of EuTiO3 single crystal were
investigated by synchrotron x-ray diffraction. Antiferrodistortive (AFD) oxygen
octahedral rotational order was observed alongside Ti derived antiferroelectric
(AFE) distortions. The competition between the two instabilities is reconciled
through a cooperatively modulated structure allowing both to coexist. The
electric and magnetic field effect on the modulated AFD order shows that the
origin of large magnetoelectric coupling is based upon the dynamic equilibrium
between the AFD - antiferromagnetic interactions versus the electric
polarization - ferromagnetic interactions
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