48 research outputs found
Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides
Motivated by the triumph and limitation of graphene for electronic
applications, atomically thin layers of group VI transition metal
dichalcogenides are attracting extensive interest as a class of graphene-like
semiconductors with a desired band-gap in the visible frequency range. The
monolayers feature a valence band spin splitting with opposite sign in the two
valleys located at corners of 1st Brillouin zone. This spin-valley coupling,
particularly pronounced in tungsten dichalcogenides, can benefit potential
spintronics and valleytronics with the important consequences of spin-valley
interplay and the suppression of spin and valley relaxations. Here we report
the first optical studies of WS2 and WSe2 monolayers and multilayers. The
efficiency of second harmonic generation shows a dramatic even-odd oscillation
with the number of layers, consistent with the presence (absence) of inversion
symmetry in even-layer (odd-layer). Photoluminescence (PL) measurements show
the crossover from an indirect band gap semiconductor at mutilayers to a
direct-gap one at monolayers. The PL spectra and first-principle calculations
consistently reveal a spin-valley coupling of 0.4 eV which suppresses
interlayer hopping and manifests as a thickness independent splitting pattern
at valence band edge near K points. This giant spin-valley coupling, together
with the valley dependent physical properties, may lead to rich possibilities
for manipulating spin and valley degrees of freedom in these atomically thin 2D
materials
Spin-half paramagnetism in graphene induced by point defects
Using magnetization measurements, we show that point defects in graphene -
fluorine adatoms and irradiation defects (vacancies) - carry magnetic moments
with spin 1/2. Both types of defects lead to notable paramagnetism but no
magnetic ordering could be detected down to liquid helium temperatures. The
induced paramagnetism dominates graphene's low-temperature magnetic properties
despite the fact that maximum response we could achieve was limited to one
moment per approximately 1000 carbon atoms. This limitation is explained by
clustering of adatoms and, for the case of vacancies, by losing graphene's
structural stability.Comment: 14 pages, 14 figure
EGF functionalized polymer-coated gold nanoparticles promote EGF photostability and EGFR internalization for photothermal therapy
The application of functionalized nanocarriers on photothermal therapy for cancer ablation has wide interest. The success of this application depends on the therapeutic efficiency and biocompatibility of the system, but also on the stability and biorecognition of the conjugated protein. This study aims at investigating the hypothesis that EGF functionalized polymer -coated gold nanoparticles promote EGF photostability and EGFR internalization, making these conjugated particles suitable for photothermal therapy. The conjugated gold nanoparticles (100-200 nm) showed a plasmon absorption band located within the near infrared range (650-900 nm), optimal for photothermal therapy applications. The effects of temperature, of polymer-coated gold nanoparticles and of UVB light (295nm) on the fluorescence properties of EGF have been investigated with steady-state and time-resolved fluorescence spectroscopy. The fluorescence properties of EGF, including the formation of Trp and Tyr photoproducts, is modulated by temperature and by the intensity of the excitation light. The presence of polymeric-coated gold nanoparticles reduced or even avoided the formation of Trp and Tyr photoproducts when EGF is exposed to UVB light, protecting this way the structure and function of EGF. Cytotoxicity studies of conjugated nanoparticles carried out in normal-like human keratinocytes showed small, concentration dependent decreases in cell viability (0-25%). Moreover, conjugated nanoparticles could activate and induce the internalization of overexpressed Epidermal Growth Factor Receptor in human lung carcinoma cells. In conclusion, the gold nanoparticles conjugated with Epidermal Growth Factor and coated with biopolymers developed in this work, show a potential application for near infrared photothermal therapy, which may efficiently destroy solid tumours, reducing the damage of the healthy tissue.Support was provided by: Fundacao para a Ciencia e Tecnologia (FCT) for the financial support under the project reference PTDC/BBB-BMC/0611/2012 [https://www.fct.pt/apoios/projectos)]. The work at CBMA was supported by the strategic programme UID/BIA/04050/2013 (POCI-01-0145-FEDER-007569) funded by national funds through the FCT I.P. and by the ERDF through the COMPETE2020 - Programa Operacional Competitividade e Internacionalizacao (POCI) [https://www.fct.pt/apoios/projectos]; European Commission through the project H2020-644242-SAPHELY (https://saphely.eu/project.php) and the project H2020-634013-2-PHOCNOSIS [http://cordis.europa.eu/project/rcn/193268_en.html].The authors would like to thank Fundacao para a Ciencia e Tecnologia (FCT) for the financial support under the project reference PTDC/BBB-BMC/0611/2012. The work at CBMA was supported by the strategic programme UID/BIA/04050/2013 (POCI-01-0145-FEDER-007569) funded by national funds through the FCT I.P. and by the ERDF through the COMPETE2020 - Programa Operacional Competitividade e Internacionalizacao (POCI). The authors acknowledge the funding from the European Commission through the project H2020-644242-SAPHELY and the project H2020-634013-2-PHOCNOSIS. Finally, the authors would also like to thank the master student Joao Lopes from Universidade Lusofona (Portugal) for the help with in vitro cytotoxic assays. Isabel Correia acknowledges FCT for Investigator FCT contract.info:eu-repo/semantics/publishedVersio
SPARC 2018 Internationalisation and collaboration : Salford postgraduate annual research conference book of abstracts
Welcome to the Book of Abstracts for the 2018 SPARC conference. This year we not only celebrate the work of our PGRs but also the launch of our Doctoral School, which makes this yearâs conference extra special. Once again we have received a tremendous contribution from our postgraduate research community; with over 100 presenters, the conference truly showcases a vibrant PGR community at Salford. These abstracts provide a taster of the research strengths of their works, and provide delegates with a reference point for networking and initiating critical debate. With such wide-ranging topics being showcased, we encourage you to take up this great opportunity to engage with researchers working in different subject areas from your own. To meet global challenges, high impact research inevitably requires interdisciplinary collaboration. This is recognised by all major research funders. Therefore engaging with the work of others and forging collaborations across subject areas is an essential skill for the next generation of researchers
Understanding the retinal basis of vision across species
The vertebrate retina first evolved some 500 million years ago in ancestral marine chordates. Since then, the eyes of different species have been tuned to best support their unique visuoecological lifestyles. Visual specializations in eye designs, large-scale inhomogeneities across the retinal surface and local circuit motifs mean that all species' retinas are unique. Computational theories, such as the efficient coding hypothesis, have come a long way towards an explanation of the basic features of retinal organization and function; however, they cannot explain the full extent of retinal diversity within and across species. To build a truly general understanding of vertebrate vision and the retina's computational purpose, it is therefore important to more quantitatively relate different species' retinal functions to their specific natural environments and behavioural requirements. Ultimately, the goal of such efforts should be to build up to a more general theory of vision
Carbohydrate and torpor duration in hibernating golden-mantled ground squirrels ( Citellus lateralis )
Plasma glucose concentrations were increased in torpid Citellus lateralis to test the hypothesis that plasma glucose depletion stimulates periodic arousals from torpor during hibernation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47127/1/360_2004_Article_BF00689301.pd
Healing through culturally embedded practice: an investigation of counsellorsâ and clientsâ experiences of Buddhist Counselling in Thailand
This thesis is concerned with an exploration of counsellorsâ and clientsâ lived experiences of
Buddhist Counselling, an indigenous Buddhist-based counselling approach in Thailand. Over
the past decade, Buddhist Counselling has received a growing interest from Thai counselling
trainees and practitioners, and it has also expanded to serve Thai people in various settings.
Research on Buddhist Counselling is very limited and most of the existing studies in the
field have focused on measuring the effectiveness of the approach. While these studies have
consistently indicated the positive effects of Buddhist Counselling on psychological
improvement across several population groups, the significant questions of how Buddhist
Counselling brings about such outcome and how it is experienced are still largely
unanswered. Moreover, existing research is concentrated much more on clientsâ views than
counsellorsâ views, although counsellorsâ views of their counselling practice can also serve as
a knowledge base of the field. This thesis thus sets out to contribute to rectifying this
omission by exploring Buddhist Counselling from the perspectives of both counsellors and
clients.
The thesis is based on two qualitative studies. The first study addressed Buddhist
Counselling from the perspective of five counsellors through a focus group and semi-structured
interviews. The second study explored Buddhist Counselling from the perspective
of three clients, using two semi-structured interviews with each of them. All data received
were analysed using interpretative phenomenological analysis (IPA).
The study reveals counsellorsâ and clientsâ overall positive experience of engaging in
Buddhist Counselling. Central to the accounts of the counsellors are the following
perceptions: that their practice of Buddhist Counselling is culturally congruent with the
existing values and beliefs of both themselves and their clients; that their personal and
professional congruence is key to their therapeutic efficacy; and that they enhance such
congruence through their application of Buddhist ideas and practices in their daily lives. Key
to the clientsâ accounts is their emphasis on the significant roles of the counsellorsâ Buddhist
ideas and personal qualities, and of their religious practices in facilitating healing and change.
Key shared findings from both studies reveal that the participantsâ accounts of their cultural
background and their experiences of Buddhist Counselling are intertwined. Adopting
hermeneutics to address this intertwinement, I reveal the cultural and moral dimensions
underlying the practice of Buddhist Counselling. Based on such revelation, I suggest that
Buddhist Counselling in particular, as well as psychotherapy in general, should be better
understood as a historically situated, culturally bound, and morally constituted activity of
people who are concerned with improving the quality of their lives and their community,
rather than the transcultural and merely relational work of morally-neutral practitioners