323 research outputs found
Nucleation and growth of a quasicrystalline monolayer: Bi adsorption on the five-fold surface of i-Al70Pd21Mn9
Scanning tunnelling microscopy has been used to study the formation of a Bi
monolayer deposited on the five-fold surface of i-Al70Pd21Mn9. Upon deposition
of low sub-monolayer coverages, the nucleation of pentagonal clusters of Bi
adatoms of edge length 4.9 A is observed. The clusters have a common
orientation leading to a film with five-fold symmetry. By inspection of images
where both the underlying surface and the Bi atoms are resolved, the pentagonal
clusters are found to nucleate on pseudo-Mackay clusters truncated such that a
Mn atom lies centrally in the surface plane. The density of these sites is
sufficient to form a quasiperiodic framework, and subsequent adsorption of Bi
atoms ultimately leads to the formation of a quasicrystalline monolayer. The
initial nucleation site is different to that proposed on the basis of recent
density functional theory calculations.Comment: 6 pages, 5 figure
Formation of a quasicrystalline Pb monolayer on the ten-fold surface of the decagonal Al-Ni-Co quasicrystal
Lead has been deposited on the ten-fold surface of decagonal Al72Ni11Co17 to
form an epitaxial quasicrystalline single-element monolayer. The overlayer
grows through nucleation of nanometer-sized irregular islands and the coverage
saturates at 1 ML. The overlayer is well-ordered quasiperiodically as evidenced
by LEED and Fourier transforms of STM images. Annealing the film to 600 K
improves the structural quality, but causes the evaporation of some material
such that the film develops pores. Electronic structure measurements using
X-ray photoemission spectroscopy indicate that the chemical interaction of the
Pb atoms with the substrate is weak.Comment: 12 pages, 5 figure
UK and US Physician Assistant Student Performance on an International Test of Core Biomedical Science Knowledge
Physician assistants (PAs) have provided cost effective, high quality care in the United States for more than 40 years. There is a growing international interest in utilizing PAs for a variety of pressing health care needs. This pilot study compared the performance of PA students trained in the United States to those trained in the United Kingdom on a core biomedical science knowledge examination using multiple choice questions developed by the National Commission on Certification of Physician Assistants (NCCPA). The study found that despite differing educational models and health systems, the students performed similarly. While rigorous statistical analyses were not possible given the small sample sizes, the study provides a promising indication that there is an international common core of biomedical science knowledge. Repeated studies and the expansion of the pilot to other countries will provide more generalizability and statistical support to establish whether there is an assessable, global core of PA biomedical science knowledge that could become one component of locally determined national standards for PAs
C60 adsorption on an aperiodically modulated Cu surface
Copper deposited on the ve-fold surface of icosahedral Al-Pd-Mn forms domains of a structure whose surface has a one-dimensional aperiodic modulation. It is shown that C60
deposited on this aperiodic film has highly reduced mobility as compared to C60 deposited on periodic Cu surfaces. This fnding is explained in terms of the recently proposed structural model of this system
What is the contribution of physician associates in hospital care in England? A mixed methods, multiple case study.
OBJECTIVES: To investigate the deployment of physician associates (PAs); the factors supporting and inhibiting their employment and their contribution and impact on patients' experience and outcomes and the organisation of services. DESIGN: Mixed methods within a case study design, using interviews, observations, work diaries and documentary analysis. SETTING: Six acute care hospitals in three regions of England in 2016-2017. PARTICIPANTS: 43 PAs, 77 other health professionals, 28 managers, 28 patients and relatives. RESULTS: A key influencing factor supporting the employment of PAs in all settings was a shortage of doctors. PAs were found to be acceptable, appropriate and safe members of the medical/surgical teams by the majority of doctors, managers and nurses. They were mainly deployed to undertake inpatient ward work in the medical/surgical team during core weekday hours. They were reported to positively contribute to: continuity within their medical/surgical team, patient experience and flow, inducting new junior doctors, supporting the medical/surgical teams' workload, which released doctors for more complex patients and their training. The lack of regulation and attendant lack of authority to prescribe was seen as a problem in many but not all specialties. The contribution of PAs to productivity and patient outcomes was not quantifiable separately from other members of the team and wider service organisation. Patients and relatives described PAs positively but most did not understand who and what a PA was, often mistaking them for doctors. CONCLUSIONS: This study offers new insights concerning the deployment and contribution of PAs in medical and surgical specialties in English hospitals. PAs provided a flexible addition to the secondary care workforce without drawing from existing professions. Their utility in the hospital setting is unlikely to be completely realised without the appropriate level of regulation and authority to prescribe medicines and order ionising radiation within their scope of practice
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Nilotinib, an approved leukemia drug, inhibits smoothened signaling in Hedgehog-dependent medulloblastoma.
Dysregulation of the seven-transmembrane (7TM) receptor Smoothened (SMO) and other components of the Hedgehog (Hh) signaling pathway contributes to the development of cancers including basal cell carcinoma (BCC) and medulloblastoma (MB). However, SMO-specific antagonists produced mixed results in clinical trials, marked by limited efficacy and high rate of acquired resistance in tumors. Here we discovered that Nilotinib, an approved inhibitor of several kinases, possesses an anti-Hh activity, at clinically achievable concentrations, due to direct binding to SMO and inhibition of SMO signaling. Nilotinib was more efficacious than the SMO-specific antagonist Vismodegib in inhibiting growth of two Hh-dependent MB cell lines. It also reduced tumor growth in subcutaneous MB mouse xenograft model. These results indicate that in addition to its known activity against several tyrosine-kinase-mediated proliferative pathways, Nilotinib is a direct inhibitor of the Hh pathway. The newly discovered extension of Nilotinib's target profile holds promise for the treatment of Hh-dependent cancers
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