Performance Limits and Geometric Properties of Array Localization

Location-aware networks are of great importance and interest in both civil and military applications. This paper determines the localization accuracy of an agent, which is equipped with an antenna array and localizes itself using wireless measurements with anchor nodes, in a far-field environment. In view of the Cram\'er-Rao bound, we first derive the localization information for static scenarios and demonstrate that such information is a weighed sum of Fisher information matrices from each anchor-antenna measurement pair. Each matrix can be further decomposed into two parts: a distance part with intensity proportional to the squared baseband effective bandwidth of the transmitted signal and a direction part with intensity associated with the normalized anchor-antenna visual angle. Moreover, in dynamic scenarios, we show that the Doppler shift contributes additional direction information, with intensity determined by the agent velocity and the root mean squared time duration of the transmitted signal. In addition, two measures are proposed to evaluate the localization performance of wireless networks with different anchor-agent and array-antenna geometries, and both formulae and simulations are provided for typical anchor deployments and antenna arrays.Comment: to appear in IEEE Transactions on Information Theor

Diaqua­(5,5,7,12,12,14-hexa­methyl-1,4,8,11-tetra­azacyclo­tetra­deca­ne)nickel(II) tetra­cyanidonickelate(II)

In the title complex, [Ni(C16H36N4)(H2O)2][Ni(CN)4], the [Ni(teta)(H2O)2]2+ cations (teta = 5,5,7,12,12,14-hexa­methyl-1,4,8,11-tetra­azacyclo­tetra­deca­ne) and [Ni(CN)4]2− anions are arranged in an alternating fashion through electrostatic and N—H⋯N and O—H⋯N hydrogen-bonding inter­actions, forming a two-dimensional layered structure. Adjacent layers are linked through weak van der Waals inter­actions, resulting in a three-dimensional supra­molecular network

Entry- and Sunk-Cost Spillovers from the Rival: Evidence from Entry and Expansion of KFC and McDonald\u27s in Chinese Cities

We model the entry and expansion of KFC and McDonald\u27s in Chinese cities as a dynamic game. We assume that the observed entry and expansion decisions are equilibrium outcomes. This allows us to recover the structural parameters of the game without solving for equilibrium. We use the estimated model to study the entry- and sunk-cost spillovers from the rival. Our estimates suggest substantial spillovers to the cost of entering a new city. For example, if the rival is not present in the city in which the chain is entering and the distance from the nearest city where the rival is present decreases by 100 kilometers, the cost of entry into the city decreases by 1.22 standard deviations for KFC and 1.52 standard deviations for McDonald\u27s. If the rival is already present in the city, a one-unit increase in the number of rival\u27s outlets decreases the cost of entry by 0.59 standard deviations for McDonald\u27s but increases it by 1.49 standard deviations for KFC. We also find that the spillovers to the sunk cost of opening a new outlet are much smaller. Hence the expansion within a city is not as much influenced by the presence of the rival as is the entry into a new city

Geometric bionics: Lotus effect helps polystyrene nanotube films get good blood compatibility

Various biomaterials have been widely used for manufacturing biomedical applications including artificial organs, medical devices and disposable clinical apparatus, such as vascular prostheses, blood pumps, artificial kidney, artificial hearts, dialyzers and plasma separators, which could be used in contact with blood^1^. However, the research tasks of improving hemocompatibility of biomaterials have been carrying out with the development of biomedical requirements^2^. Since the interactions that lead to surface-induced thrombosis occurring at the blood-biomaterial interface become a reason of familiar current complications with grafts therapy, improvement of the blood compatibility of artificial polymer surfaces is, therefore a major issue in biomaterials science^3^. After decades of focused research, various approaches of modifying biomaterial surfaces through chemical or biochemical methods to improve their hemocompatibility were obtained^1^. In this article, we report that polystyrene nanotube films with morphology similar to the papilla on lotus leaf can be used as blood-contacted biomaterials by virtue of Lotus effect^4^. Clearly, this idea, resulting from geometric bionics that mimicking the structure design of lotus leaf, is very novel technique for preparation of hemocompatible biomaterials

Improving accuracy of protein contact prediction using balanced network deconvolution

Residue contact map is essential for protein three‐dimensional structure determination. But most of the current contact prediction methods based on residue co‐evolution suffer from high false‐positives as introduced by indirect and transitive contacts (i.e., residues A–B and B–C are in contact, but A–C are not). Built on the work by Feizi et al. (Nat Biotechnol 2013; 31:726–733), which demonstrated a general network model to distinguish direct dependencies by network deconvolution, this study presents a new balanced network deconvolution (BND) algorithm to identify optimized dependency matrix without limit on the eigenvalue range in the applied network systems. The algorithm was used to filter contact predictions of five widely used co‐evolution methods. On the test of proteins from three benchmark datasets of the 9th critical assessment of protein structure prediction (CASP9), CASP10, and PSICOV (precise structural contact prediction using sparse inverse covariance estimation) database experiments, the BND can improve the medium‐ and long‐range contact predictions at the L/5 cutoff by 55.59% and 47.68%, respectively, without additional central processing unit cost. The improvement is statistically significant, with a P‐value < 5.93 × 10−3 in the Student's t‐test. A further comparison with the ab initio structure predictions in CASPs showed that the usefulness of the current co‐evolution‐based contact prediction to the three‐dimensional structure modeling relies on the number of homologous sequences existing in the sequence databases. BND can be used as a general contact refinement method, which is freely available at: http://www.csbio.sjtu.edu.cn/bioinf/BND/. Proteins 2015; 83:485–496. © 2014 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110720/1/prot24744.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/110720/2/prot24744-sup-0001-suppinfo.pd

Optimal input potential functions in the interacting particle system method

The assessment of the probability of a rare event with a naive Monte-Carlo method is computationally intensive, so faster estimation methods, such as variance reduction methods, are needed. We focus on one of these methods which is the interacting particle (IPS) system method. The method requires to specify a set of potential functions. The choice of these functions is crucial, because it determines the magnitude of the variance reduction. So far, little information was available on how to choose the potential functions. To remedy this, we provide the expression of the optimal potential functions minimizing the asymptotic variance of the estimator of the IPS method

High prevalence of a globally disseminated hypervirulent clone, Staphylococcus aureus CC121, with reduced vancomycin susceptibility in community settings in China

Objectives: Most vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA) are derived from hospital-associated MRSA due to treatment failure; however, the prevalence of hVISA/VISA in community settings remains unclear. Methods: Four hundred and seventy-six community-associated isolates were collected between 2010 and 2011 during national surveillance for antimicrobial resistance in 31 county hospitals across China. Drug susceptibility evaluation and mecA detection were performed by using broth microdilution and PCR analysis, respectively. hVISA/VISA were identified by using macro-Etest and a modified population analysis profile (PAP)-AUC method. The genetic features of all hVISA/VISA isolates were genotyped. Results: Among 476 isolates, MRSA and MSSA accounted for 19.7% (n = 94) and 80.3% (n = 382), respectively. Two VISA and 36 hVISA isolates were identified by PAP-AUC testing. The VISA isolates and 29 of the hVISA isolates were MRSA. The proportion of hVISA/VISA was significantly higher in MRSA (30.9%) than in MSSA (1.8%). The hVISA/VISA isolates were assigned to 18 STs classified into seven clonal complexes (CCs). CC121 (n = 12) followed by ST239 (n = 11) was the most prevalent hVISA/VISA clone. All ST239-hVISA/VISA were MRSA, while 12 CC121-hVISA isolates included 6 MSSA and 6 MRSA isolates. SCCmec III was predominant among MRSA-hVISA/VISA isolates. agr I and agr IV were detected in ST239 and CC121, respectively. All except two strains were positive for Panton-Valentine leucocidin genes. Conclusions: To the best of our knowledge, this is the first report of CC121 as a prevalent hVISA clone in community settings, highlighting the necessity of surveillance and stricter infection control measures for this globally disseminated lineage

Neutron star phase transition as the origin for the fast radio bursts and soft gamma-ray repeaters of SGR J1935+2154

Magnetars are believed as neutron stars (NSs) with strong magnetic fields. X-ray flares and fast radio bursts (FRBs) have been observed from the magnetar (soft gamma-ray repeater, SGR J1935+2154). We propose that the phase transition of the NS can power the FRBs and SGRs.Based on the equation of state provided by the MIT bag model and the mean field approximation, we solve the Tolman-Oppenheimer-Volkoff equations to get the NS structure. With spin-down of the NS, the hadronic shell gradually transfers to the quark shell.The gravitational potential energy released by one time of the phase transition can be achieved. The released energy, time interval between two successive phase transitions, and glitch are all consistent with the observations of the FRBs and the X-ray flares from SGR J1935+2154. We conclude that the phase transition of an NS is a plausible mechanism to power the SGRs as well as the repeating FRBs.Comment: 11 pages, 3 figure