90 research outputs found
Supplemental Material—Cross-sectional analysis of whole-brain microstructural changes in adult patients with bipolar and unipolar depression by diffusion kurtosis imaging
No full textSupplemental Material for Cross-sectional analysis of whole-brain microstructural changes in adult patients with bipolar and unipolar depression by diffusion kurtosis imaging by Muniraju Maralakunte, Vivek Gupta, Sandeep Grover, Chirag Kamal Ahuja, Swapnajeet Sahoo, Kamal Kishore, Sameer Vyas, Gaurav Sharma, Paramjeet Singh, and Varan Govind in The Neuroradiology Journal.</p
MRS in Motor Neuron Diseases
No full textUpper motor neurons (UMN) in the motor cortex and/or lower motor neurons (LMN) in the brainstem and spinal cord are affected in a heterogeneous group of related or pathologically similar adult-onset diseases, collectively termed as motor neuron diseases (MND). Amyotrophic lateral sclerosis (ALS) is the most predominant (85 %) among MND in which both UMN and LMN progressively degenerate. The etiology of ALS is not known in approximately 90 % of patients; however, inheritance of genetic mutations underlies in about 10 % of them. To date, neither conventional neuroimaging techniques nor laboratory tests of body fluids or biopsy samples yielded definitive biomarkers for ALS. Furthermore, molecular and cellular mechanisms involved in this disease remain poorly understood. Proton MRS is well suited to quantify metabolite alterations in the brain, and it has been used on patients with ALS in an effort to gain insight into the pathophysiology of ALS. A brief description on MND and their subtypes, limitations of clinical neuroimaging methods to diagnose ALS, a number of brain metabolites that can be quantified by in vivo MRS and their relevance to MND, and MRS techniques and their limitations are provided. Use of a whole-brain MRSI approach to fully characterize changes within the brain due to disease is described with a sample dataset obtained in a patient with ALS. Changes in the concentration or ratio of brain metabolites in patients with ALS and their pathophysiological significances are described. Finally, the use of MRS methods for longitudinal and therapeutic evaluation studies and future perspectives are discussed
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1H‐NMR Chemical Shifts and Coupling Constants for Brain Metabolites
No full textA detailed compilation of
1
H‐NMR chemical shift (
δ
) and coupling constant (
J
) values of 38 low‐molecular‐weight metabolites, found in mammalian brain at physiological or pathological conditions, is presented. These metabolites are detectable using in vivo
1
H magnetic resonance spectroscopy techniques and include energy metabolites (sources, intermediaries, and products), essential and nonessential amino acids, excitatory and inhibitory neurotransmitters, neuro‐modulators, and phospholipid membrane precursors and break‐down products. The values of
δ
and
J
were measured from high‐field NMR data of aqueous solutions of each metabolite acquired at typical physiological temperature and pH conditions. The spectral parameter values (
δ
,
J
) may be used to identify metabolites from their resonances in in vivo spectra, to simulate metabolite spectra or to generate basis functions (i.e., amplitude, frequency, and phase) for spectral fitting, and to optimize parameters in data acquisition sequences in order to improve metabolite quantitation or selectively edit different spectral components
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Evaluation of Pain, Brain Tissue Metabolite and Structural Alterations in Individuals with TBI-related Chronic Pain
No full textTraumatic brain injury (TBI) can lead to chronic pain; however, the underlying pathophysiological mechanisms of this condition are not fully understood. Chronic pain significantly impacts quality of life and psychosocial function in affected individuals. Therefore, a multimodal evaluation of pain can provide information important for optimal pain management. Thus, the first aim of the present study was to evaluate chronic pain, somatosensory, psychological, and psychosocial function to identify and profile pain phenotypes among adults with closed-head TBI during the chronic injury stage. In addition, we evaluated brain tissue metabolite levels, including N-Acetyl Aspartate, Myo-Inositol, total Choline, and glutamate plus glutamine using whole-brain proton magnetic resonance spectroscopic imaging (1H-MRSI). We then compared metabolite levels among healthy control and within the TBI group (pain vs. without pain); and assessed associations between metabolites and clinical variables. Finally, we evaluated microstructural integrity in pain-related brain regions and white matter tracts using diffusion tensor imaging (DTI), and compared DTI metrics between groups. Our findings indicate the presence of two multidimensional pain phenotypes based on neuropathic pain and anxiety-associated symptoms. Additionally, metabolite and microstructural alterations in pain-related brain regions and neuro-axonal tracts (i.e., frontal region, cingulum, and corticothalamic tract) suggest a combination of pathological conditions, including neuronal and glial alterations in individuals with TBI. However, brain tissue metabolite dysfunction and microstructural alterations seem to be necessary but not sufficient for developing chronic pain.</p
Mathematical model for the performance measures of Dynamic Channel Selection in a bounded DECT system
No full textDECT is an ETSI standard for digital wireless communications, and uses a Dynamic Channel Selection algorithm for the allocation of channels at run-time. Contrary to Fixed Channel Allocation, where the channels are allocated according to location, the channels are allocated according to channel quality at the time of use. A previous study was made on a mathematical model for an infinite area using Dynamic Channel Selection as defined in the DECT standard. This model was used to make a model for areas of limited size, in order to calculate with boundary effects. Channel availability, desired signal power and interfering signal power has been calculated, as well as call blocking probabilities. The results were compared to results from previous models and simulations.Applied SciencesElectrical EngineeringTelecommunications and Traffic Control Systems Grou
Indigenous terrains and the threat of cultural erosion
No full textThe author explores the conflict between indigenous and academic discourse, noting the extent to which the former continues to perceive television as culturally intrusive while the later discounts this threat on the basis of a wide range of studies which have empirically examined the issue. The author revisits these studies to demonstrate that while the arguments in each study refuting any significant transcultural effects related to television have been consolidated to form a meta-argument discounting this threat, those findings documenting effects have been left in isolation. The author proposes a new model of cultural erosion which, he maintains, better accommodates previous findings by framing the question with geological constructs associated with erosion. Four specific processes associated with such ‘cultural erosion’ are explored: Cultural abrasion, resulting from friction between the contrasting values reflected in a cultural terrain and a foreign media agent; cultural deflation, whereby those facets which are least consolidated within a culture are most vulnerable to foreign influence — a process facilitated by agents of displacement which can weaken consolidating factors within a terrain; cultural deposition in which foreign beliefs, practices and artifacts supplement the local cultural landscape potentially, at times, providing for cross-cultural fertilization; and cultural saltation, where social practices appropriate communication systems in response to the perceived threat of a foreign media agent. the author concludes with a brief discussion of potential policy implications associated with the new model
Enhancement of a Simulation of Dynamic Channel Selection as implemented in the DECT standard
No full textThe DECT standard developed by ETSI is based upon so-called Dynamic Channel Selection. DCS is a flexible and adoptive algorithm for efficiently allocating channels in a mobile wireless environment. A simulation program has been enhanced to confirm a mathematical model for DCS, developed by Jan Punt [6]. Results from the simulation program have been compared to theoretically calculated results, with respect to channel availability, carrier power, interference power and carrier to interference ratio.Applied SciencesElectrical EngineeringTelecommunications and Traffic Control Systems Grou
Geochemical constraints on Eocene–Miocene geodynamic and magmatic evolution of the Varan-Naragh area, Urumieh-Dokhtar Magmatic Arc, Iran
No full textTwo different types of igneous rock formed during separate Cenozoic magmatic phases in the Varan-Naragh area in the central part of the Urumieh-Dokhtar Magmatic Arc (UDMA) of Iran as a part of the Alpine-Himalayan system. The first phase comprises late Eocene – early Oligocene Naragh gabbroic rocks (Ns), and the second phase is characterized by the emplacement of both volcanic and plutonic rocks of the early Miocene. Both phases display moderate enrichment of large rare earth elements and depletion of high field strength elements coupled with negative Nb, Ti, and P anomalies, indicative of subduction-related magmatic events within an active continental margin. Initial values of 87Sr/86Sr and εNdT are 0.70684 and +0.15 and 0.70560–0.70654 and +2.55 to +3.49 for Ns and early Miocene intrusive and volcanic rocks, respectively. Comparisons of rare earth element patterns and mantle-like isotopic ratios suggest that Ns mafic and early Miocene magmatic rocks were derived from partial melting of a common subcontinental lithospheric mantle. Geochemical and isotopic ratios of Ns gabbroic rocks, in combination with the data related to other coeval and proximal mafic-intermediate intrusions (such as Nashalj), suggest enrichment of the lithospheric mantle by slab-derived fluids with a minor subducted sediment melt. The low εNdT of Ns gabbroic rocks can reflect involvement of slab-derived components. The geochemical similarity and the close spatial and temporal association of Varan intrusive and volcanic rocks suggest a common petrogenetic relationship. Geochemical, isotopic, and geochronological evidence from the region indicate three major phases of igneous activity in the Kashan magmatic segment of the central UDMA during late Eocene to Miocene, resulting in complex tectonic regime transition from compressional subduction to extensional post-collisional settings. Integrated with published studies, the new results support a model suggesting that subduction-related magmatic activity was still influencing the central UDMA in the early Miocene time and are also consistent with the notion of oblique and diachronous collision along the northeast margin of the Arabia plate.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
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