Decentralized Estimation over Orthogonal Multiple-access Fading Channels in Wireless Sensor Networks - Optimal and Suboptimal Estimators

Optimal and suboptimal decentralized estimators in wireless sensor networks (WSNs) over orthogonal multiple-access fading channels are studied in this paper. Considering multiple-bit quantization before digital transmission, we develop maximum likelihood estimators (MLEs) with both known and unknown channel state information (CSI). When training symbols are available, we derive a MLE that is a special case of the MLE with unknown CSI. It implicitly uses the training symbols to estimate the channel coefficients and exploits the estimated CSI in an optimal way. To reduce the computational complexity, we propose suboptimal estimators. These estimators exploit both signal and data level redundant information to improve the estimation performance. The proposed MLEs reduce to traditional fusion based or diversity based estimators when communications or observations are perfect. By introducing a general message function, the proposed estimators can be applied when various analog or digital transmission schemes are used. The simulations show that the estimators using digital communications with multiple-bit quantization outperform the estimator using analog-and-forwarding transmission in fading channels. When considering the total bandwidth and energy constraints, the MLE using multiple-bit quantization is superior to that using binary quantization at medium and high observation signal-to-noise ratio levels

Electronic transitions of iron in almandine-composition glass to 91 GPa

Valence and spin states of Fe were investigated in a glass of almandine (Fe$_3$Al$_2$Si$_3$O$_{12}$) composition to 91 GPa by X-ray emission spectroscopy and energy- and time-domain synchrotron Mössbauer spectroscopy in the diamond-anvil cell. Changes in optical properties, total spin moment and Mössbauer parameters all occur predominantly between 1 bar and ~30 GPa. Over this pressure range, the glass changes from translucent brown to opaque and black. The total spin moment of the glass derived from X-ray emission spectroscopy decreases by ~20%. The complementary Mössbauer spectroscopy approaches reveal consistent changes in sites corresponding to 80–90% Fe$^{2+}$ and 10–20% Fe$^{3+}$. The high-spin Fe$^{2+}$ doublet exhibits a continuous decrease in isomer shift and increase in line width and asymmetry. A high-spin Fe$^{3+}$ doublet with quadrupole splitting of ~1.2 mm/s is replaced by a doublet with quadrupole splitting of ~1.9 mm/s, a value higher than all previous measurements of high-spin Fe$^{3+}$ and consistent with low-spin Fe$^{3+}$. These observations suggest that Fe$^{3+}$ in the glass undergoes a continual transition from a high-spin to a low-spin state between 1 bar and ~30 GPa. Almandine glass is not expected to undergo any abrupt transitions in electronic state at deep mantle pressures.National Science FoundationThis is the author accepted manuscript. The final version is available from the Mineralogical Society of America via http://dx.doi.org/10.2138/am-2016-560

A 10-year study reveals clinical and laboratory evidence for the 'semi-invasive' properties of chronic pulmonary aspergillosis

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Phase structure of black branes in grand canonical ensemble

This is a companion paper of our previous work [1] where we studied the thermodynamics and phase structure of asymptotically flat black $p$-branes in a cavity in arbitrary dimensions $D$ in a canonical ensemble. In this work we study the thermodynamics and phase structure of the same in a grand canonical ensemble. Since the boundary data in two cases are different (for the grand canonical ensemble boundary potential is fixed instead of the charge as in canonical ensemble) the stability analysis and the phase structure in the two cases are quite different. In particular, we find that there exists an analog of one-variable analysis as in canonical ensemble, which gives the same stability condition as the rather complicated known (but generalized from black holes to the present case) two-variable analysis. When certain condition for the fixed potential is satisfied, the phase structure of charged black $p$-branes is in some sense similar to that of the zero charge black $p$-branes in canonical ensemble up to a certain temperature. The new feature in the present case is that above this temperature, unlike the zero-charge case, the stable brane phase no longer exists and `hot flat space' is the stable phase here. In the grand canonical ensemble there is an analog of Hawking-Page transition, even for the charged black $p$-brane, as opposed to the canonical ensemble. Our study applies to non-dilatonic as well as dilatonic black $p$-branes in $D$ space-time dimensions.Comment: 32 pages, 2 figures, various points refined, discussion expanded, references updated, typos corrected, published in JHEP 1105:091,201

Combined acoustic radiation force impulse, aminotransferase to platelet ratio index and Forns index assessment for hepatic fibrosis grading in hepatitis B

published_or_final_versio

In the Shadow of the Transiting Disk: Imaging epsilon Aurigae in Eclipse

Eclipses of the single-line spectroscopic binary star, epsilon Aurigae, provide an opportunity to study the poorly-defined companion. We used the MIRC beam combiner on the CHARA array to create interferometric images during eclipse ingress. Our results demonstrate that the eclipsing body is a dark disk that is opaque and tilted, and therefore exclude alternative models for the system. These data constrain the geometry and masses of the components, providing evidence that the F-star is not a massive supergiant star.Comment: As submitted to Nature. Published in Nature April 8, 2010

Iron force constants of bridgmanite at high pressure: Implications for iron isotope fractionation in the deep mantle

The isotopic compositions of iron in major mantle minerals may record chemical exchange between deep-Earth reservoirs as a result of early differentiation and ongoing plate tectonics processes. Bridgmanite (Bdg), the most abundant mineral in the Earth’s lower mantle, can incorporate not only Al but also Fe with different oxidation states and spin states, which in turn can influence the distribution of Fe isotopes between Bdg and ferropericlase (Fp) and between the lower mantle and the core. In this study, we combined first-principles calculations with high-pressure nuclear resonant inelastic X-ray scattering measurements to evaluate the effects of Fe site occupancy, valence, and spin states at lower-mantle conditions on the reduced Fe partition function ratio (β-factor) of Bdg. Our results show that the spin transition of octahedral-site (B-site) Fe3+ in Bdg under mid-lower-mantle conditions generates a +0.09‰ increase in its β-factor, which is the most significant effect compared to Fe site occupancy and valence. Fe2+-bearing Bdg varieties have smaller β-factors relative to Fe3+-bearing varieties, especially those containing B-site Fe3+. Our models suggest that Fe isotopic fractionation between Bdg and Fp is only significant in the lowermost mantle due to the occurrence of low-spin Fe2+ in Fp. Assuming early segregation of an iron core from a deep magma ocean, we find that neither core formation nor magma ocean crystallization would have resulted in resolvable Fe isotope fractionation. In contrast, Fe isotopic fractionation between low-spin Fe3+-bearing Bdg/Fe2+-bearing Fp and metallic iron at the core-mantle boundary may have enriched the lowermost mantle in heavy Fe isotopes by up to +0.20‰

Artesunate potentiates antibiotics by inactivating heme-harbouring bacterial nitric oxide synthase and catalase

<p>Abstract</p> <p>Background</p> <p>A current challenge of coping with bacterial infection is that bacterial pathogens are becoming less susceptible to or more tolerant of commonly used antibiotics. It is urgent to work out a practical solution to combat the multidrug resistant bacterial pathogens.</p> <p>Findings</p> <p>Oxidative stress-acclimatized bacteria thrive in rifampicin by generating antibiotic-detoxifying nitric oxide (NO), which can be repressed by artesunate or an inhibitor of nitric oxide synthase (NOS). Suppressed bacterial proliferation correlates with mitigated NO production upon the combined treatment of bacteria by artesunate with antibiotics. Detection of the heme-artesunate conjugate and accordingly declined activities of heme-harbouring bacterial NOS and catalase indicates that artesunate renders bacteria susceptible to antibiotics by alkylating the prosthetic heme group of hemo-enzymes.</p> <p>Conclusions</p> <p>By compromising NO-mediated protection from antibiotics and triggering harmful hydrogen peroxide burst, artesunate may serve as a promising antibiotic synergist for killing the multidrug resistant pathogenic bacteria.</p