Arteriography of Cerebrovascular Disease

The importance of complete angiographic studies in patients suspected of extracranial vascular disease has been emphasized. Examples of a variety of lesions of the intracranial and extracranial circulation have been shown. It is important that the angiographer obtain adequate visualization of the circulation cephalad to the aortic arch with awareness of the type of lesion and technical problems that may be encountered. It is only in this way that further understanding of the stroke syndrome can be attained with appropriate therapy

Advances in Neuroradiology

The development of two new radiological techniques has significantly enhanced the performance of neuroradiological diagnostic procedures. The first of these was installed as the prototype unit at the Medical College of Virginia in November of 1972 and has marked advantages for the performance of encephalography, angiography, and air myelography. The present communication will relate the experiences of the author during the initial 15 months of clinical evaluation. The second technique is an entirely new concept of obtaining further information from the data provided by the penetration of x-ray photons. Each of these units will be discussed briefly with an outline of the principle indications and advantage of each system

Versatile spectral imaging with an algorithm-based spectrometer using highly tuneable quantum dot infrared photodetectors

We report on the implementation of an algorithm-based spectrometer capable of reconstructing the spectral shape of materials in the mid-wave infrared (MWIR) and long-wave infrared (LWIR) wavelengths using only experimental photocurrent measurements from quantum dot infrared photodetectors (QDIPs). The theory and implementation of the algorithm will be described, followed by an investigation into this algorithmic spectrometer's performance. Compared to the QDIPs utilized in an earlier implementation, the ones used here have highly varying spectral shapes and four spectral peaks across the MWIR and LWIR wavelengths. It has been found that the spectrometer is capable of reconstructing broad spectral features of a range of bandpass infrared filters between wavelengths of 4 and 12 mu m as well as identifying absorption features as narrow as 0.3 mu m in the IR spectrum of a polyethylene sheet

Journal Staff

The aluminum–zinc-vacancy (Al Zn −V Zn ) complex is identified as one of the dominant defects in Al-containing n -type ZnO after electron irradiation at room temperature with energies above 0.8 MeV. The complex is energetically favorable over the isolated V Zn , binding more than 90% of the stable V Zn ’s generated by the irradiation. It acts as a deep acceptor with the (0/− ) energy level located at approximately 1 eV above the valence band. Such a complex is concluded to be a defect of crucial and general importance that limits the n -type doping efficiency by complex formation with donors, thereby literally removing the donors, as well as by charge compensation

Bandgap narrowing in Mn doped GaAs probed by room-temperature photoluminescence

The electronic band structure of the (Ga,Mn)As system has been one of the most intriguing problems in solid state physics over the past two decades. Determination of the band structure evolution with increasing Mn concentration is a key issue to understand the origin of ferromagnetism. Here we present room temperature photoluminescence and ellipsometry measurements of Ga_{100%-x}Mn_{x}As alloy. The up-shift of the valence-band is proven by the red shift of the room temperature near band gap emission from the Ga_{100%-x}Mn_{x}As alloy with increasing Mn content. It is shown that even a doping by 0.02 at.% of Mn affects the valence-band edge and it merges with the impurity band for a Mn concentration as low as 0.6 at.%. Both X-ray diffraction pattern and high resolution cross-sectional TEM images confirmed full recrystallization of the implanted layer and GaMnAs alloy formation.Comment: 24 pages, 7 figures, accepted at Phys. Rev. B 201

Hydrogen induced optically-active defects in silicon photonic nanocavities

This work was supported by Era-NET NanoSci LECSIN project coordinated by F. Priolo, by the Italian Ministry of University and Research, FIRB contract No. RBAP06L4S5 and by the EPSRC UKSp project. Partial financial support by the Norwegian Research Council is also acknowledged.We demonstrate intense room temperature photoluminescence (PL) from optically active hydrogen- related defects incorporated into crystalline silicon. Hydrogen was incorporated into the device layer of a silicon on insulator (SOI) wafer by two methods: hydrogen plasma treatment and ion implantation. The room temperature PL spectra show two broad PL bands centered at 1300 and 1500 nm wavelengths: the first one relates to implanted defects while the other band mainly relates to the plasma treatment. Structural characterization reveals the presence of nanometric platelets and bubbles and we attribute different features of the emission spectrum to the presence of these different kind of defects. The emission is further enhanced by introducing defects into photonic crystal (PhC) nanocavities. Transmission electron microscopy analyses revealed that the isotropicity of plasma treatment causes the formation of a higher defects density around the whole cavity compared to the ion implantation technique, while ion implantation creates a lower density of defects embedded in the Si layer, resulting in a higher PL enhancement. These results further increase the understanding of the nature of optically active hydrogen defects and their relation with the observed photoluminescence, which will ultimately lead to the development of intense and tunable crystalline silicon light sources at room temperature.Publisher PDFPeer reviewe

Ab initio data-analytics study of carbon-dioxide activation on semiconductor oxide surfaces

The excessive emissions of carbon dioxide (CO2) into the atmosphere threaten to shift the CO2 cycle planet-wide and induce unpredictable climate changes. Using artificial intelligence (AI) trained on high-throughput first principles based data for a broad family of oxides, we develop a strategy for a rational design of catalytic materials for converting CO2 to fuels and other useful chemicals. We demonstrate that an electron transfer to the π-antibonding orbital of the adsorbed molecule and the associated bending of the initially linear molecule, previously proposed as the indicator of activation, are insufficient to account for the good catalytic performance of experimentally characterized oxide surfaces. Instead, our AI model identifies the common feature of these surfaces in the binding of a molecular O atom to a surface cation, which results in a strong elongation and therefore weakening of one molecular C-O bond. This finding suggests using the C-O bond elongation as an indicator of CO2 activation. Based on these findings, we propose a set of new promising oxide-based catalysts for CO2 conversion, and a recipe to find more

Experience of loneliness associated with being an informal caregiver: A qualitative investigation.

ArticleThis is the author accepted manuscript. The final version is available from Frontiers Media via the DOI in this record.Although providing care to a family member or friend may provide psychological benefits, informal (i.e. unpaid) caregivers also encounter difficulties which may negatively affect their quality of life as well as their mental and physical health. Loneliness is one important challenge that caregivers face, with this psychological state being associated with morbidity and premature mortality. Although previous research has identified loneliness as an issue associated with being an informal caregiver, there is a paucity of evidence that attempts to understand this phenomenon in depth. This study aimed to examine informal caregivers' reflections on, and accounts of, experiences of loneliness linked to their caregiving situation. A cross-sectional, qualitative study was designed. Sixteen semi-structured interviews were conducted with 8 spousal caregivers, 4 daughters caring for a parent, 3 mothers caring for a child (or children) and 1 woman looking after her partner. The cared-for persons were suffering from a range of mental and physical health conditions (e.g. dementia, frailty due to old age, multiple sclerosis, depression, autism). Data were analyzed using an inductive thematic analysis. Experiences of loneliness were described by reference to a context of shrunken personal space and diminished social interaction caused by the restrictions imposed by the caregiving role. Loneliness was also articulated against a background of relational deprivations and losses as well as sentiments of powerlessness, helplessness and a sense of sole responsibility. Social encounters were also seen to generate loneliness when they were characterized by some form of distancing. Though not all sources or circumstances of loneliness in caregivers are amenable to change, more opportunities for respite care services, as well as a heightened sensibility and social appreciation of caregivers' valued contributions could help caregivers manage some forms of loneliness.This study is part of a larger research project, titled Loneliness in the Digital Age (LiDA): Developing Strategies for Empathy and Trust. LiDA is financially supported from the Economic and Social Research Council (ESRC) ‘Empathy and Trust in Communicating Online’ (EMoTICON) program, with funding from the Arts and Humanities Research Council (AHRC), the Engineering and Physical Sciences Research Council (EPSRC), the Defence Science and Technology Laboratory (Dstl) and the Centre for the Protection of National Infrastructure (CPNI)

EMIC Waves in the Outer Magnetosphere: Observations of an Off-Equator Source Region.

Electromagnetic ion cyclotron (EMIC) waves at large L shells were observed away from the magnetic equator by the Magnetospheric MultiScale (MMS) mission nearly continuously for over four hours on 28 October 2015. During this event, the wave Poynting vector direction systematically changed from parallel to the magnetic field (toward the equator), to bidirectional, to antiparallel (away from the equator). These changes coincide with the shift in the location of the minimum in the magnetic field in the southern hemisphere from poleward to equatorward of MMS. The local plasma conditions measured with the EMIC waves also suggest that the outer magnetospheric region sampled during this event was generally unstable to EMIC wave growth. Together, these observations indicate that the bidirectionally propagating wave packets were not a result of reflection at high latitudes but that MMS passed through an off-equator EMIC wave source region associated with the local minimum in the magnetic field

The alternating least-squares algorithm for CDPCA

Clustering and Disjoint Principal Component Analysis (CDP CA) is a constrained principal component analysis recently proposed for clustering of objects and partitioning of variables, simultaneously, which we have implemented in R language. In this paper, we deal in detail with the alternating least-squares algorithm for CDPCA and highlight its algebraic features for constructing both interpretable principal components and clusters of objects. Two applications are given to illustrate the capabilities of this new methodology