Spin crossover in (Mg,Fe3+^{3+})(Si,Fe3+^{3+})O3_3 bridgmanite: effects of disorder, iron concentration, and temperature

The spin crossover of iron in Fe$^{3+}$-bearing bridgmanite, the most abundant mineral of the Earth's lower mantle, is by now a well-established phenomenon, though several aspects of this crossover remain unclear. Here we investigate effects of disorder, iron concentration, and temperature on this crossover using ab initio LDA + U$_{sc}$ calculations. The effect of concentration and disorder are addressed using complete statistical samplings of coupled substituted configurations in super-cells containing up to 80 atoms. Vibrational/thermal effects on the crossover are addressed within the quasiharmonic approximation. The effect of disorder seems quite small, while increasing iron concentration results in considerable increase in crossover pressure. Our calculated compression curves for iron-free, Fe$^{2+}$-, and Fe$^{3+}$-bearing bridgmanite compare well with the latest experimental measurements. The comparison also suggests that in a close system, Fe$^{2+}$ present in the sample may transform into Fe$^{3+}$ by introduction of Mg and O vacancies with increasing pressure. As in the spin crossover in ferropericlase, this crossover in bridgmanite is accompanied by a clear volume reduction and an anomalous softening of the bulk modulus throughout the crossover pressure range. These effects reduce significantly with increasing temperature. Though the concentration of [Fe$^{3+}$]$_{Si}$ in bridgmanite may be small, related elastic anomalies may impact the interpretation of radial and lateral velocity structures of the Earth's lower mantle.Comment: Under review with Earth and Planetary Science Letter

Bullen's parameter as a seismic observable for spin crossovers in the lower mantle

Elastic anomalies produced by the spin crossover in ferropericlase have been documented by both first principles calculations and high pressure-temperature experiments. The predicted signature of this spin crossover in the lower mantle is, however, subtle and difficult to geophysically observe within the mantle. Indeed, global seismic anomalies associated with spin transitions have not yet been recognized in seismologic studies of the deep mantle. A sensitive seismic parameter is needed to determine the presence and amplitude of such a spin crossover signature. The effects of spin crossovers on Bullen's parameter, $\eta$, are assessed here for a range of compositions, thermal profiles, and lateral variations in temperature within the lower mantle. Velocity anomalies associated with the spin crossover in ferropericlase span a depth range near 1,000 km for typical mantle temperatures. Positive excursions of Bullen's parameter with a maximum amplitude of $\sim$ 0.03 are calculated to be present over a broad depth range within the mid-to-deep lower mantle: these are largest for peridotitic and harzburgitic compositions. These excursions are highest in amplitude for model lower mantles with large lateral thermal variations, and with cold downwellings having longer lateral length-scales relative to hot upwellings. We conclude that predicted deviations in Bullen's parameter due to the spin crossover in ferropericlase for geophysically relevant compositions may be sufficiently large to resolve in accurate seismic inversions of this parameter, and could shed light on both the lateral variations in temperature at depth within the lower mantle, and the amount of ferropericlase at depth

Advanced Magnetic Resonance Imaging in Glioblastoma: A Review

INTRODUCTION In 2017, it is estimated that 26,070 patients will be diagnosed with a malignant primary brain tumor in the United States, with more than half having the diagnosis of glioblas- toma (GBM).1 Magnetic resonance imaging (MRI) is a widely utilized examination in the diagnosis and post-treatment management of patients with glioblastoma; standard modalities available from any clinical MRI scanner, including T1, T2, T2-FLAIR, and T1-contrast-enhanced (T1CE) sequences, provide critical clinical information. In the last decade, advanced imaging modalities are increasingly utilized to further charac- terize glioblastomas. These include multi-parametric MRI sequences, such as dynamic contrast enhancement (DCE), dynamic susceptibility contrast (DSC), diffusion tensor imaging (DTI), functional imaging, and spectroscopy (MRS), to further characterize glioblastomas, and significant efforts are ongoing to implement these advanced imaging modalities into improved clinical workflows and personalized therapy approaches. A contemporary review of standard and advanced MR imaging in clinical neuro-oncologic practice is presented

Thermoelasticity of Fe2+-bearing bridgmanite

We present LDA+U calculations of high temperature elastic properties of bridgmanite with composition (Mg$_{(1-x)}$Fe$_{x}^{2+}$)SiO$_3$ for $0\le{x}\le0.125$. Results of elastic moduli and acoustic velocities for the Mg-end member (x=0) agree very well with the latest high pressure and high temperature experimental measurements. In the iron-bearing system, we focus particularly on the change in thermoelastic parameters across the state change that occurs in ferrous iron above $\sim$30 GPa, often attributed to a high-spin (HS) to intermediate spin (IS) crossover but explained by first principles calculations as a lateral displacement of substitutional iron in the perovskite cage. We show that the measured effect of this change on the equation of state of this system can be explained by the lateral displacement of substitutional iron, not by the HS to IS crossover. The calculated elastic properties of (Mg$_{0.875}$Fe$_{0.125}^{2+}$)SiO$_3$ along an adiabatic mantle geotherm, somewhat overestimate longitudinal velocities but produce densities and shear velocities quite consistent with Preliminary Reference Earth Model data throughout most of the lower mantle.Comment: Accepted for Geophysical Research Letters (DOI: 10.1002/2014GL062888

Complexity of Scheduling in Synthesizing Hardware from Concurrent Action Oriented Specifications

Concurrent Action Oriented Specifications (CAOS) formalism such as Bluespec Inc.\u27s Bluespec System Verilog (BSV) has been recently shown to be effective for hardware modeling and synthesis. This formalism offers the benefits of automatic handling of concurrency issues in highly concurrent system descriptions, and the associated synthesis algorithms have been shown to produce efficient hardware comparable to those generated from hand-written Verilog/VHDL. These benefits which are inherent in such a synthesis process also aid in faster architectural exploration. This is because CAOS allows a high-level description (above RTL) of a design in terms of atomic transactions, where each transaction corresponds to a collection of operations. Optimal scheduling of such actions in CAOS-based synthesis process is crucial in order to generate hardware that is efficient in terms of area, latency and power. In this paper, we analyze the complexity of the scheduling problems associated with CAOS-based synthesis and discuss several heuristics for meeting the peak power goals of designs generated from CAOS. We also discuss approximability of these problems as appropriate

Beej Mantra Chikitsa and its impact on 48 students of PEC Chandigarh Pre & Post Meditation through Beej Mantra on Weight, BP, SPO2, BMI, BPS, BPD, BPP

In Ayurveda there is a description of 3 Aushadhi : 1. Daivavyapasraya Chikitsa [taking refuge of your Aatma (Soul)], 2. Yuktivyapasraya Chikitsa (taking refuge of device which is considered the fastest way to heal), 3. Sattavajaya Chikitsa (Purity of Thoughts). Here the Mantras are the sacred words having spiritual potency. Mantras are not merely sounds but thoughts which establish a connection between Divine and You. Later comes the sound of that Mantra and its impact is also affected if not done with full attention. Mantra instill confidence, improve concentration and Aatma (soul) therapy is the medicine of the future, soul as a creator of mind & body wave of consciousness protects us from several diseases and reforms the future. Aims & Objective: The aim of the present study was to know the effect of the beej mantra meditation on the student’s BP, Pulse, spo2, Weight and pulse rate. Methods: Manual and electronic search was done on Mantra Chikitsa, Beej Mantra in Charak Samhita, Susruta Samhita and Astanga Hridaya. Then 48 PEC Chandigarh Ist Yr students practised Beej Mantra meditation technique through a one hour lecture. Pre and post meditation measurements were recorded and analysed. Results: Significant number of students reported to be more attentive, comfortable, relaxed and had better memory and had significant reduction in mean pulse rate, Weight, BP. Students expressed a feeling of relaxation and of having a fun filled learning atmosphere after meditation. Conclusion: This simple and easy technique of Beej Mantra meditation could be adopted to enhance Stress reduction in students

Paleogene monsoons across India and South China: Drivers of biotic change

Monsoonal climates at low latitudes (2. Fossil leaf form reveals that under such 'hothouse' conditions megathermal early Eocene to earliest Miocene forests were exposed to strong monsoonal climates typical of those experienced today arising from annual migrations of the ITCZ, possibly enhanced by a lower equator-to-pole temperature gradient. Throughout the Paleogene an elevated Tibetan highland produced no discernable modification of this ITCZ monsoon, although rainfall seasonality similar to that of the modern South Asia Monsoon (SAM) is observed in northern India as early as the beginning of the Eocene, despite its near-equatorial palaeoposition. In South China rainfall seasonality increased progressively achieving modern monsoon-like wet season/dry season precipitation ratios by the early Oligocene. Despite evidencing weak rainfall seasonality overall, fossil leaves from South China have exhibited monsoon-adapted morphologies, comparable to those seen in today's Indonesia-Australia Monsoon, for at least 45 million years. Together, the Indian and South China fossil leaf assemblages show that the evolution of megathermal ecosystems across southern Asia has been influenced profoundly by monsoonal climates for at least the last 56 million years. The Paleogene ITCZ-driven monsoon system strongly impacted India as it transited the Equator likely eliminating Gondwanan taxa not able to adapt to seasonal precipitation extremes. Furthermore, powerful seasonally-reversing winds, and associated surface ocean currents, are likely to have facilitated two-way biotic transfer between India and Eurasia long before closure of the Tethys Ocean

Development and evaluation of a novel method for in-situ medical image display

Three-dimensional (3D) medical imaging, including computed tomography (CT) and magnetic resonance (MR), and other modalities, has become a standard of care for diagnosis of disease and guidance of interventional procedures. As the technology to acquire larger, more magnificent, and more informative medical images advances, so too must the technology to display, interact with, and interpret these data.This dissertation concerns the development and evaluation of a novel method for interaction with 3D medical images called "grab-a-slice," which is a movable, tracked stereo display. It is the latest in a series of displays developed in our laboratory that we describe as in-situ, meaning that the displayed image is embedded in a physical 3D coordinate system. As the display is moved through space, a continuously updated tomographic slice of a 3D medical image is shown on the screen, corresponding to the position and orientation of the display. The act of manipulating the display through a "virtual patient" preserves the perception of 3D anatomic relationships in a way that is not possible with conventional, fixed displays. The further addition of stereo display capabilities permits augmentation of the tomographic image data with out-of-plane structures using 3D graphical methods.In this dissertation we describe the research and clinical motivations for such a device. We describe the technical development of grab-a-slice as well as psychophysical experiments to evaluate the hypothesized perceptual and cognitive benefits. We speculate on the advantages and limitations of the grab-a-slice display and propose future directions for its use in psychophysical research, clinical settings, and image analysis