111 research outputs found
Predicting the optoelectronic properties of nanowire films based on control of length polydispersity
We demonstrate that the optoelectronic properties of percolating thin films of silver nanowires (AgNWs) are predominantly dependent upon the length distribution of the constituent AgNWs. A generalized expression is derived to describe the dependence of both sheet resistance and optical transmission on this distribution. We experimentally validate the relationship using ultrasonication to controllably vary the length distribution. These results have major implications where nanowire-based films are a desirable material for transparent conductor applications; in particular when application specific performance criteria must be met. It is of particular interest to have a simple method to generalize the properties of bulk films from an understanding of the base material, as this will speed up the optimisation process. It is anticipated that these results may aid in the adoption of nanowire films in industry, for applications such as touch sensors or photovoltaic electrode structures
A Triple Protostar System Formed via Fragmentation of a Gravitationally Unstable Disk
Binary and multiple star systems are a frequent outcome of the star formation
process, and as a result, almost half of all sun-like stars have at least one
companion star. Theoretical studies indicate that there are two main pathways
that can operate concurrently to form binary/multiple star systems: large scale
fragmentation of turbulent gas cores and filaments or smaller scale
fragmentation of a massive protostellar disk due to gravitational instability.
Observational evidence for turbulent fragmentation on scales of 1000~AU has
recently emerged. Previous evidence for disk fragmentation was limited to
inferences based on the separations of more-evolved pre-main sequence and
protostellar multiple systems. The triple protostar system L1448 IRS3B is an
ideal candidate to search for evidence of disk fragmentation. L1448 IRS3B is in
an early phase of the star formation process, likely less than 150,000 years in
age, and all protostars in the system are separated by 200~AU. Here we
report observations of dust and molecular gas emission that reveal a disk with
spiral structure surrounding the three protostars. Two protostars near the
center of the disk are separated by 61 AU, and a tertiary protostar is
coincident with a spiral arm in the outer disk at a 183 AU separation. The
inferred mass of the central pair of protostellar objects is 1 M,
while the disk surrounding the three protostars has a total mass of 0.30
M_{\sun}. The tertiary protostar itself has a minimum mass of 0.085
M. We demonstrate that the disk around L1448 IRS3B appears susceptible
to disk fragmentation at radii between 150~AU and 320~AU, overlapping with the
location of the tertiary protostar. This is consistent with models for a
protostellar disk that has recently undergone gravitational instability,
spawning one or two companion stars.Comment: Published in Nature on Oct. 27th. 24 pages, 8 figure
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A Qualitative Analysis of Experiential Challenges Associated with Meditation Practice
Although empirical interest in meditation has flourished in recent years, few studies have addressed possible downsides of meditation practice, particularly in community populations. In-depth interviews were conducted with 30 male meditators in London, UK, recruited using principles of maximum variation sampling, and analysed using a modified constant comparison approach. Having originally set out simply to inquire about the impact of various meditation practices (including but not limited to mindfulness) on menâs wellbeing, we uncovered psychological challenges associated with its practice. While meditation was generally reported to be conducive to wellbeing, substantial difficulties accounted for approximately one quarter of the interview data. Our paper focuses specifically on these issues in order to alert health professionals to potential challenges associated with meditation. Four main problems of increasing severity were uncovered: Meditation was a difficult skill to learn and practise; participants encountered troubling thoughts and feelings which were hard to manage; meditation reportedly exacerbated mental health issues, such as depression and anxiety; and in a few cases, meditation was associated with psychotic episodes. Our paper raises important issues around safeguarding those who practise meditation, both within therapeutic settings and in the community
The Interplay Between Post-Critical Beliefs and Anxiety: An Exploratory Study in a Polish Sample
The present research investigates the relationship between anxiety and the religiosity dimensions that Wulff (Psychology of religion: classic and contemporary views, Wiley, New York, 1991; Psychology of religion. Classic and contemporary views, Wiley, New York, 1997; Psychologia religii. Klasyczna i wspĂłĹczesna, Wydawnictwo Szkolne i Pedagogiczne, Warszawa, 1999) described as Exclusion vs. Inclusion of Transcendence and Literal vs. Symbolic. The researchers used the Post-Critical Belief scale (Hutsebaut in J Empir Theol 9(2):48â66, 1996; J Empir Theol 10(1):39â54, 1997) to measure Wulffâs religiosity dimensions and the IPAT scale (Krug et al. 1967) to measure anxiety. Results from an adult sample (N = 83) suggest that three dimensions show significant relations with anxiety. Orthodoxy correlated negatively with suspiciousness (L) and positively with guilt proneness (O) factorâin the whole sample. Among women, Historical Relativism negatively correlated with suspiciousness (L), lack of integration (Q3), general anxiety and covert anxiety. Among men, Historical Relativism positively correlated with tension (Q4) and emotional instability (C), general anxiety, covert anxiety and overt anxiety. External Critique was correlated with suspiciousness (L) by men
Connecting Planetary Composition with Formation
The rapid advances in observations of the different populations of
exoplanets, the characterization of their host stars and the links to the
properties of their planetary systems, the detailed studies of protoplanetary
disks, and the experimental study of the interiors and composition of the
massive planets in our solar system provide a firm basis for the next big
question in planet formation theory. How do the elemental and chemical
compositions of planets connect with their formation? The answer to this
requires that the various pieces of planet formation theory be linked together
in an end-to-end picture that is capable of addressing these large data sets.
In this review, we discuss the critical elements of such a picture and how they
affect the chemical and elemental make up of forming planets. Important issues
here include the initial state of forming and evolving disks, chemical and dust
processes within them, the migration of planets and the importance of planet
traps, the nature of angular momentum transport processes involving turbulence
and/or MHD disk winds, planet formation theory, and advanced treatments of disk
astrochemistry. All of these issues affect, and are affected by the chemistry
of disks which is driven by X-ray ionization of the host stars. We discuss how
these processes lead to a coherent end-to-end model and how this may address
the basic question.Comment: Invited review, accepted for publication in the 'Handbook of
Exoplanets', eds. H.J. Deeg and J.A. Belmonte, Springer (2018). 46 pages, 10
figure
Edible bio-based nanostructures: delivery, absorption and potential toxicity
The development of bio-based nanostructures as nanocarriers of bioactive compounds to specific body sites has been presented as a hot topic in food, pharmaceutical and nanotechnology fields. Food and pharmaceutical industries seek to explore the huge potential of these nanostructures, once they can be entirely composed of biocompatible and non-toxic materials. At the same time, they allow the incorporation of lipophilic and hydrophilic bioactive compounds protecting them against degradation, maintaining its active and functional performance. Nevertheless, the physicochemical properties of such structures (e.g., size and charge) could change significantly their behavior in the gastrointestinal (GI) tract. The main challenges in the development of these nanostructures are the proper characterization and understanding of the processes occurring at their surface, when in contact with living systems. This is crucial to understand their delivery and absorption behavior as well as to recognize potential toxicological effects. This review will provide an insight into the recent innovations and challenges in the field of delivery via GI tract using bio-based nanostructures. Also, an overview of the approaches followed to ensure an effective deliver (e.g., avoiding physiological barriers) and to enhance stability and absorptive intestinal uptake of bioactive compounds will be provided. Information about nanostructures potential toxicity and a concise description of the in vitro and in vivo toxicity studies will also be given.Joana T. Martins, Oscar L. Ramos, Ana C. Pinheiro, Ana I. Bourbon, Helder D. Silva and Miguel A. Cerqueira (SFRH/BPD/89992/2012, SFRH/BPD/80766/2011, SFRH/BPD/101181/2014, SFRH/BD/73178/2010, SFRH/BD/81288/2011, and SFRH/BPD/72753/2010, respectively) are the recipients of a fellowship from the Fundacao para a Ciencia e Tecnologia (FCT, POPH-QREN and FSE, Portugal). The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013 and the project "BioInd-Biotechnology and Bioengineering for improved Industrial and Agro-Food processes," REF.NORTE-07-0124-FEDER-000028, co-funded by the Programa Operacional Regional do Norte (ON.2-O Novo Norte), QREN, FEDER. We also thank to the European Commission: BIOCAPS (316265, FP7/REGPOT-2012-2013.1) and Xunta de Galicia: Agrupamento INBIOMED (2012/273) and Grupo con potencial de crecimiento. The support of EU Cost Action FA1001 is gratefully acknowledged
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