1,205 research outputs found
Characterization of Fe-N nanocrystals and nitrogen–containing inclusions in (Ga,Fe)N thin films using transmission electron microscopy
Nanometric inclusions filled with nitrogen, located adjacent to FenN (n¼3 or 4) nanocrystals
within (Ga,Fe)N layers, are identified and characterized using scanning transmission electron
microscopy (STEM) and electron energy-loss spectroscopy (EELS). High-resolution STEM images reveal a truncation of the Fe-N nanocrystals at their boundaries with the nitrogen-containing inclusions. A controlled electron beam hole drilling experiment is used to release nitrogen gas from an inclusion in situ in the electron microscope. The density of nitrogen in an individual inclusion is measured to be 1.460.3 g/cm3. These observations provide an explanation for the location of surplus nitrogen in the (Ga,Fe)N layers, which is liberated by the nucleation of FenN (n>1) nanocrystals during growth
Islanding, growth mode and ordering in Si heteroepitaxy on Ge(001) substrates structured by thermal annealing
Si/Ge heteroepitaxial dots under tensile strain are grown on nanostructured
Ge substrates produced by high-temperature flash heating exploiting the
spontaneous faceting of the Ge(001) surface close to the onset of surface
melting. A very diverse growth mode is obtained depending on the specific
atomic structure and step density of nearby surface domains with different
vicinal crystallographic orientations. On highly-miscut areas of the Ge(001)
substrate, the critical thickness for islanding is lowered to about 5 ML, in
contrast to the 11 ML reported for the flat Ge(001) surface, while on
unreconstructed (1x1) domains the growth is Volmer-Weber driven. An explanation
is proposed considering the diverse relative contributions of step and surface
energies on misoriented substrates. In addition, we show that the bottom-up
pattern of the substrate naturally formed by thermal annealing determines a
spatial correlation for the dot sites
Role of traditional and new biomarkers in breast carcinogenesis
In recent decades, several biomarkers have been investigated as predictors of breast cancer risk, development, prognosis and treatment efficacy
Barriers to preventive therapy for breast and other major cancers and strategies to improve uptake.
The global cancer burden continues to rise and the war on cancer can only be won if improvements in treatment go hand in hand with therapeutic cancer prevention. Despite the availability of several efficacious agents, utilisation of preventive therapy has been poor due to various barriers, such as the lack of physician and patient awareness, fear of side effects, and licensing and indemnity issues. In this review, we discuss these barriers in detail and propose strategies to overcome them. These strategies include improving physician awareness and countering prejudices by highlighting the important differences between preventive therapy and cancer treatment. The importance of the agent-biomarker-cohort (ABC) paradigm to improve effectiveness of preventive therapy cannot be overemphasised. Future research to improve therapeutic cancer prevention needs to include improvements in the prediction of benefits and harms, and improvements in the safety profile of existing agents by experimentation with dose. We also highlight the role of drug repurposing for providing new agents as well as to address the current imbalance between therapeutic and preventive research. In order to move the field of therapeutic cancer prevention forwards, engagement with policymakers to correct research imbalance as well as to remove practical obstacles to implementation is also urgently needed.This study was partially supported by Gruppo Bancario Credito Valtellinese, and Cancer Research UK programme award (C569/A16891). Smith is supported by a Cancer Research UK Postdoctoral Fellowship (C42785/A17965)
Why vitamin D for cancer patients?
Several epidemiological, pre-clinical and clinical studies support Vitamin D as a preventive and therapeutic cancer agent
Element specific characterization of heterogeneous magnetism in (Ga,Fe)N films
We employ x-ray spectroscopy to characterize the distribution and magnetism
of particular alloy constituents in (Ga,Fe)N films grown by metal organic vapor
phase epitaxy. Furthermore, photoelectron microscopy gives direct evidence for
the aggregation of Fe ions, leading to the formation of Fe-rich nanoregions
adjacent to the samples surface. A sizable x-ray magnetic circular dichroism
(XMCD) signal at the Fe L-edges in remanence and at moderate magnetic fields at
300 K links the high temperature ferromagnetism with the Fe(3d) states. The
XMCD response at the N K-edge highlights that the N(2p) states carry
considerable spin polarization. We conclude that FeN{\delta} nanocrystals, with
\delta > 0.25, stabilize the ferromagnetic response of the films.Comment: 4 pages, 3 figures, 1 tabl
Reflectance anisotropy spectroscopy of strain-engineered GaAsBi alloys
In this paper, we present results obtained by an optical technique, namely, reflectance anisotropy spectroscopy (RAS), applied to a series of GaAs1-xBix samples grown by molecular beam epitaxy (MBE) under different strain conditions with the increasing concentration of Bi, up to the higher value of about 7%. The epitaxial buffer layers for the growing GaAs1-xBix layer were prepared with either a compressive strain (as it is commonly done) or a tensile strain: The latter case has been proven to be a strategy that allows us to obtain a better crystalline quality [Tisbi et al., Phys. Rev. Appl. 14, 014028 (2020)]. A characteristic, well defined anisotropy signal below 2.5 eV is demonstrated to be connected to the presence of Bi and, in particular, to the strain produced in the sub-surface region by the voluminous Bi atoms. The amplitude of this signal directly relates to the Bi quantity, while its sign gives information about the local clustering/ordering of Bi atoms in the grown sample. We conclude that the detailed interpretation of RAS signatures and the knowledge of their origin offer the opportunity to utilize this technique to follow in real time the GaAsBi growth either in MBE or in metal organic vapor phase epitaxy processes
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