Efficient tree construction for the multicast problem

A new heuristic for the Steiner Minimal Tree problem is presented here. The method described is based on the detection of particular sets of nodes in networks, the “Hot Spot” sets, which are used to obtain better approximations of the optimal solutions. An algorithm is also proposed which is capable of improving the solutions obtained by classical heuristics, by means of a stirring process of the nodes in solution trees. Classical heuristics and an enumerative method are used CIS comparison terms in the experimental analysis which demonstrates the goodness of the heuristic discussed in this paper.

Efficient tree construction for the multicast problem

A new heuristic for the Steiner minimal tree problem is presented. The method described is based on the detection of particular sets of nodes in networks, the “hot spot” sets, which are used to obtain better approximations of the optimal solutions. An algorithm is also proposed which is capable of improving the solutions obtained by classical heuristics, by means of a stirring process of the nodes in solution trees. Classical heuristics and an enumerative method are used as comparison terms in the experimental analysis which demonstrates the capability of the heuristic discussed

Norepinephrine ignites local hot spots of neuronal excitation: how arousal amplifies selectivity in perception and memory

Arousal sometimes enhances and sometimes impairs perception and memory. In our Glutamate Amplifies Noradrenergic Effects (GANE) model, glutamate at active synapses interacts with norepinephrine released by the locus coeruleus to create local ‘hot spots’ of activity that enable the selective effects of arousal. This hot spot mechanism allows local cortical regions to self-regulate norepinephrine release based on current activation levels. In turn, hot spots bias global energetic delivery and functional network connectivity to enhance processing of high priority representations and impair processing of lower priority representations.

Fatigue apparatus for geometrically complex non-standardized specimens

Standard Test Methods (e.g. ASTM, DIN) for materials characterization in general, and for fatigue in particular, do not contemplate specimens with complex geometries, as well as the combination of axial and in-plane bending loads in their methodologies. The present study refers to some patents and the new configuration or configurations of specimens (non-standardized by the status quo of test methods) and a device developed to induce axial and bending combined forces resultants from axial loads applied by any one test equipment (dynamic or monotonic) which possesses such limitation, towards obtaining more realistic results on the fatigue behavior, or even basic mechanical properties, from geometrically complex structures. Motivated by a specific and geometrically complex aeronautic structure (motor-cradle), non-standardized welded tubular specimens made from AISI 4130 steel were fatigue-tested at room temperature, by using a constant amplitude sinusoidal load of 20 Hz frequency, load ratio R = 0.1 with and without the above referred auxiliary fatigue apparatus. The results showed the fatigue apparatus was efficient for introducing higher stress concentration factor at the welded specimen joints, consequently reducing the fatigue strength when compared to other conditions. From the obtained results it is possible to infer that with small modifications the proposed apparatus will be capable to test a great variety of specimen configurations such as: squared tubes and plates with welded or melted junctions, as well as other materials such as aluminum, titanium, composites, polymeric, plastics, etc. © 2009 Bentham Science Publishers Ltd.

Hot spots, hot moments, and spatio-temporal controls on soil CO2 efflux in a water-limited ecosystem

Soil CO2 efflux is the primary source of CO2 emissions from terrestrial ecosystems to the atmosphere. The rates of this flux vary in time and space producing hot moments (sudden temporal high fluxes) and hot spots (spatially defined high fluxes), but these high reaction rates are rarely studied in conjunction with each other. We studied temporal and spatial variation of soil CO2 efflux in a water-limited Mediterranean ecosystem in Baja California, Mexico. Soil CO2 efflux increased 522% during a hot moment after rewetting of soils following dry summer months. Monthly precipitation was the primary driver of the seasonal trend of soil CO2 efflux (including the hot moment) and through changes in soil volumetric water content (VWC) it influenced the relationship between CO2 efflux and soil temperature. Geostatistical analyses showed that the spatial dependence of soil CO2 efflux changed between two contrasting seasons (dry and wet). During the dry season high soil VWC was associated with high soil CO2 efflux, and during the wet season the emergence of a hot spot of soil CO2 efflux was associated with higher root biomass and leaf area index. These results suggest that sampling designs should accommodate for changes in spatial dependence of measured variables. The spatio-temporal relationships identified in this study are arguably different from temperate ecosystems where the majority of soil CO2 efflux research has been done. This study provides evidence of the complexity of the mechanisms controlling the spatio-temporal variability of soil CO2 efflux in water-limited ecosystems. (C) 2014 Elsevier Ltd. All rights reserved.

Arctic Report Card 2007: Tracking Recent Environmental Changes

Collectively, the observations indicate that the overall warming of the Arctic system continued in 2007. There are some elements that are stabilizing or returning to climatological norms. These mixed tendencies illustrate the sensitivity and complexity of the Arctic System. Atmosphere: Hot spot shifts toward Europe Ocean: North Pole Temperatures at depth returning to 1990s values Sea Ice: Summer extent at record minimum Greenland: Recent warm temperatures associated with net ice loss Biology: increasing tundra shrub cover and variable treeline advance; up to 80% declines in some caribou herds while goose populations double Land: Increase in permafrost temperatures The Arctic Report Card 2007 is introduced as a means of presenting clear, reliable and concise information on recent observations of environmental conditions in the Arctic, relative to historical time series records. It provides a method of updating and expanding the content of the State of the Arctic Report, published in fall 2006, to reflect current conditions. Material presented in the Report Card is prepared by an international team of scientists and is peer-reviewed by topical experts nominated by the US Polar Research Board. The audience for the Arctic Report Card is wide, including scientists, students, teachers, decision makers and the general public interested in Arctic environment and science. The web-based format will facilitate future timely updates of the content.

Development of analytical methodologies for iodine species in gaseous and particulate phases of the coastal atmosphere

It has been demonstrated that iodine does have an important influence on atmospheric chemistry, especially the formation of new particles and the enrichment of iodine in marine aerosols. It was pointed out that the most probable chemical species involved in the production or growth of these particles are iodine oxides, produced photochemically from biogenic halocarbon emissions and/or iodine emission from the sea surface. However, the iodine chemistry from gaseous to particulate phase in the coastal atmosphere and the chemical nature of the condensing iodine species are still not understood. A Tenax / Carbotrap adsorption sampling technique and a thermo-desorption / cryo-trap / GC-MS system has been further developed and improved for the volatile organic iodine species in the gas phase. Several iodo-hydrocarbons such as CH3I, C2H5I, CH2ICl, CH2IBr and CH2I2 etc., have been measured in samples from a calibration test gas source (standards), real air samples and samples from seaweeds / macro-algae emission experiments. A denuder sampling technique has been developed to characterise potential precursor compounds of coastal particle formation processes, such as molecular iodine in the gas phase. Starch, TMAH (TetraMethylAmmonium Hydroxide) and TBAH (TetraButylAmmonium Hydroxide) coated denuders were tested for their efficiencies to collect I2 at the inner surface, followed by a TMAH extraction and ICP/MS determination, adding tellurium as an internal standard. The developed method has been proved to be an effective, accurate and suitable process for I2 measurement in the field, with the estimated detection limit of ~0.10 ng∙L-1 for a sampling volume of 15 L. An H2O/TMAH-Extraction-ICP/MS method has been developed for the accurate and sensitive determination of iodine species in tropospheric aerosol particles. The particle samples were collected on cellulose-nitrate filters using conventional filter holders or on cellulose nitrate/tedlar-foils using a 5-stage Berner impactor for size-segregated particle analysis. The water soluble species as IO3- and I- were separated by anion exchanging process after water extraction. Non-water soluble species including iodine oxide and organic iodine were digested and extracted by TMAH. Afterwards the triple samples were analysed by ICP/MS. The detection limit for particulate iodine was determined to be 0.10~0.20 ng•m-3 for sampling volumes of 40~100 m3. The developed methods have been used in two field measurements in May 2002 and September 2003, at and around the Mace Head Atmospheric Research Station (MHARS) located at the west coast of Ireland. Elemental iodine as a precursor of the iodine chemistry in the coastal atmosphere, was determined in the gas phase at a seaweed hot-spot around the MHARS, showing I2 concentrations were in the range of 0~1.6 ng∙L-1 and indicating a positive correlation with the ozone concentration. A seaweed-chamber experiment performed at the field measurement station showed that the I2 emission rate from macro-algae was in the range of 0.019~0.022 ng•min-1•kg-1. During these experiments, nanometer-particle concentrations were obtained from the Scanning Mobility Particle Sizer (SMPS) measurements. Particle number concentrations were found to have a linear correlation with elemental iodine in the gas phase of the seaweeds chamber, showing that gaseous I2 is one of the important precursors of the new particle formation in the coastal atmosphere. Iodine contents in the particle phase were measured in both field campaigns at and around the field measurement station. Total iodine concentrations were found to be in the range of 1.0 ~ 21.0 ng∙m-3 in the PM2.5 samples. A significant correlation between the total iodine concentrations and the nanometer-particle number concentrations was observed. The particulate iodine species analysis indicated that iodide contents are usually higher than those of iodate in all samples, with ratios in the range of 2~5:1. It is possible that those water soluble iodine species are transferred through the sea-air interface into the particle phase. The ratio of water soluble (iodate + iodide) and non-water soluble species (probably iodine oxide and organic iodine compounds) was observed to be in the range of 1:1 to 1:2. It appears that higher concentrated non-water soluble species, as the products of the photolysis from the gas phase into the particle phase, can be obtained in those samples while the nucleation events occur. That supports the idea that iodine chemistry in the coastal boundary layer is linked with new particle formation events. Furthermore, artificial aerosol particles were formed from gaseous iodine sources (e.g. CH2I2) using a laboratory reaction-chamber experiment, in which the reaction constant of the CH2I2 photolysis was calculated to be based upon the first order reaction kinetic. The end products of iodine chemistry in the particle phase were identified and quantified.

An integrative transcranial magnetic stimulation mapping technique using non-linear curve fitting

The aim of this study is to develop a new simple method for analyzing one-dimensional transcranial magnetic stimulation (TMS) mapping studies in humans. Motor evoked potentials (MEP) were recorded from the abductor pollicis brevis (APB) muscle during stimulation at nine different positions on the scalp along a line passing through the APB hot spot and the vertex. Non-linear curve fitting according to the Levenberg-Marquardt algorithm was performed on the averaged amplitude values obtained at all points to find the best-fitting symmetrical and asymmetrical peak functions. Several peak functions could be fitted to the experimental data. Across all subjects, a symmetric, bell-shaped curve, the complementary error function (erfc) gave the best results. This function is characterized by three parameters giving its amplitude, position, and width. None of the mathematical functions tested with less or more than three parameters fitted better. The amplitude and position parameters of the erfc were highly correlated with the amplitude at the hot spot and with the location of the center of gravity of the TMS curve. In conclusion, non-linear curve fitting is an accurate method for the mathematical characterization of one-dimensional TMS curves. This is the first method that provides information on amplitude, position and width simultaneously.

Heat transfer in microwave heating

Heat transfer is considered as one of the most critical issues for design and implement of large-scale microwave heating systems, in which improvement of the microwave absorption of materials and suppression of uneven temperature distribution are the two main objectives. The present work focuses on the analysis of heat transfer in microwave heating for achieving highly efficient microwave assisted steelmaking through the investigations on the following aspects: (1) characterization of microwave dissipation using the derived equations, (2) quantification of magnetic loss, (3) determination of microwave absorption properties of materials, (4) modeling of microwave propagation, (5) simulation of heat transfer, and (6) improvement of microwave absorption and heating uniformity. Microwave heating is attributed to the heat generation in materials, which depends on the microwave dissipation. To theoretically characterize microwave heating, simplified equations for determining the transverse electromagnetic mode (TEM) power penetration depth, microwave field attenuation length, and half-power depth of microwaves in materials having both magnetic and dielectric responses were derived. It was followed by developing a simplified equation for quantifying magnetic loss in materials under microwave irradiation to demonstrate the importance of magnetic loss in microwave heating. The permittivity and permeability measurements of various materials, namely, hematite, magnetite concentrate, wüstite, and coal were performed. Microwave loss calculations for these materials were carried out. It is suggested that magnetic loss can play a major role in the heating of magnetic dielectrics. Microwave propagation in various media was predicted using the finite-difference time-domain method. For lossy magnetic dielectrics, the dissipation of microwaves in the medium is ascribed to the decay of both electric and magnetic fields. The heat transfer process in microwave heating of magnetite, which is a typical magnetic dielectric, was simulated by using an explicit finite-difference approach. It is demonstrated that the heat generation due to microwave irradiation dominates the initial temperature rise in the heating and the heat radiation heavily affects the temperature distribution, giving rise to a hot spot in the predicted temperature profile. Microwave heating at 915 MHz exhibits better heating homogeneity than that at 2450 MHz due to larger microwave penetration depth. To minimize/avoid temperature nonuniformity during microwave heating the optimization of object dimension should be considered. The calculated reflection loss over the temperature range of heating is found to be useful for obtaining a rapid optimization of absorber dimension, which increases microwave absorption and achieves relatively uniform heating. To further improve the heating effectiveness, a function for evaluating absorber impedance matching in microwave heating was proposed. It is found that the maximum absorption is associated with perfect impedance matching, which can be achieved by either selecting a reasonable sample dimension or modifying the microwave parameters of the sample.

Impact of coil position and electrophysiological monitoring on determination of motor thresholds to transcranial magnetic stimulation

OBJECTIVE: We compared motor and movement thresholds to transcranial magnetic stimulation (TMS) in healthy subjects and investigated the effect of different coil positions on thresholds and MEP (motor-evoked potential) amplitudes. METHODS: The abductor pollicis brevis (APB) 'hot spot' and a standard scalp position were stimulated. APB resting motor threshold (APB MEP-MT) defined by the '5/10' electrophysiological method was compared with movement threshold (MOV-MT), defined by visualization of movements. Additionally, APB MEP-MTs were evaluated with the '3/6 method,' and MEPs were recorded at a stimulation intensity of 120% APB MEP-MT at each position. RESULTS: APB MEP-MTs were significantly lower by stimulation of the 'hot spot' than of the standard position, and significantly lower than MOV-MTs (n=15). There were no significant differences between the '3/6' and the '5/10' methods, or between APB MEP amplitudes by stimulating each position at 120% APB MEP-MT. CONCLUSIONS: Coil position and electrophysiological monitoring influenced motor threshold determinations. Performing 6 instead of 10 trials did not produce different threshold measurements. Adjustment of intensity according to APB MEP-MT at the stimulated position did not influence APB MEP amplitudes. SIGNIFICANCE: Standardization of stimulation positions, nomenclature and criteria for threshold measurements should be considered in design and comparison of TMS protocols.

Hotshots, hot spots, and female preference: exploring lek formation models with a bower-building cichlid fish

In many animals, males congregate in leks that females visit for the sole purpose of mating. We observed male and female behavior on 3 different-sized leks of the bower-building cichlid fish Nyassachromis cf. microcephalus to test predictions of 3 prominent lek models: the "hotshot," "hot spot," and "female preference" models. In this system, we were able to refine these predictions by distinguishing between indirect mate choice, by which females restrict their set of potential mates in the absence of individual male assessment, and direct mate choice, by which females assess males and their territories through dyadic behavioral interactions. On no lek were males holding central territories favored by indirect or direct mate choice, contrary to the prediction of the hotshot model that leks form because inferior males establish territories surrounding hotshot males preferred by females. Average female encounter rate of males increased with lek size, a pattern typically interpreted as evidence that leks form through female preference for lekking males, rather than because males congregate in hot spots of high female density. Female propensity to engage in premating behavior once courted did not increase with lek size, suggesting female preference for males on larger leks operated through indirect choice rather than direct choice based on individual assessment. The frequency of male-male competitive interactions increased with lek size, whereas their foraging rate decreased, implying a cost to males maintaining territories on larger leks. Together these data most strongly support the female preference model, where females may benefit through indirect mate choice for males able to meet the competitive cost of occupying larger leks.

Systematic interpretation of molecular beacon polymerase chain reaction for identifying rpoB mutations in Mycobacterium tuberculosis isolates with mixed resistant and susceptible bacteria

Detection of multidrug-resistant tuberculosis (MDR-TB), a frequent cause of treatment failure, takes 2 or more weeks to identify by culture. RIF-resistance is a hallmark of MDR-TB, and detection of mutations in the rpoB gene of Mycobacterium tuberculosis using molecular beacon probes with real-time quantitative polymerase chain reaction (qPCR) is a novel approach that takes ≤2 days. However, qPCR identification of resistant isolates, particularly for isolates with mixed RIF-susceptible and RIF-resistant bacteria, is reader dependent and limits its clinical use. The aim of this study was to develop an objective, reader-independent method to define rpoB mutants using beacon qPCR. This would facilitate the transition from a research protocol to the clinical setting, where high-throughput methods with objective interpretation are required. For this, DNAs from 107 M. tuberculosis clinical isolates with known susceptibility to RIF by culture-based methods were obtained from 2 regions where isolates have not previously been subjected to evaluation using molecular beacon qPCR: the Texas–Mexico border and Colombia. Using coded DNA specimens, mutations within an 81-bp hot spot region of rpoB were established by qPCR with 5 beacons spanning this region. Visual and mathematical approaches were used to establish whether the qPCR cycle threshold of the experimental isolate was significantly higher (mutant) compared to a reference wild-type isolate. Visual classification of the beacon qPCR required reader training for strains with a mixture of RIF-susceptible and RIF-resistant bacteria. Only then had the visual interpretation by an experienced reader had 100% sensitivity and 94.6% specificity versus RIF-resistance by culture phenotype and 98.1% sensitivity and 100% specificity versus mutations based on DNA sequence. The mathematical approach was 98% sensitive and 94.5% specific versus culture and 96.2% sensitive and 100% specific versus DNA sequence. Our findings indicate the mathematical approach has advantages over the visual reading, in that it uses a Microsoft Excel template to eliminate reader bias or inexperience, and allows objective interpretation from high-throughput analyses even in the presence of a mixture of RIF-resistant and RIF-susceptible isolates without the need for reader training.^

Targeting TRAF6 for Cancer Therapeutical Development

Tumor necrosis factor (TNF)-Receptor Associated Factors (TRAFs) are a family of signal transducer proteins. TRAF6 is a unique member of this family in that it is involved in not only the TNF superfamily, but the toll-like receptor (TLR)/IL-1R (TIR) superfamily. The formation of the complex consisting of Receptor Activator of Nuclear Factor κ B (RANK), with its ligand (RANKL) results in the recruitment of TRAF6, which activates NF-κB, JNK and MAP kinase pathways. TRAF6 is critical in signaling with leading to release of various growth factors in bone, and promotes osteoclastogenesis. TRAF6 has also been implicated as an oncogene in lung cancer and as a target in multiple myeloma. In the hopes of developing small molecule inhibitors of the TRAF6-RANK interaction, multiple steps were carried out. Computational prediction of hot spot residues on the protein-protein interaction of TRAF6 and RANK were examined. Three methods were used: Robetta, KFC2, and HotPoint, each of which uses a different methodology to determine if a residue is a hot spot. These hot spot predictions were considered the basis for resolving the binding site for in silico high-throughput screening using GOLD and the MyriaScreen database of drug/lead-like compounds. Computationally intensive molecular dynamics simulations highlighted the binding mechanism and TRAF6 structural changes upon hit binding. Compounds identified as hits were verified using a GST-pull down assay, comparing inhibition to a RANK decoy peptide. Since many drugs fail due to lack of efficacy and toxicity, predictive models for the evaluation of the LD50 and bioavailability of our TRAF6 hits, and these models can be used towards other drugs and small molecule therapeutics as well. Datasets of compounds and their corresponding bioavailability and LD50 values were curated based, and QSAR models were built using molecular descriptors of these compounds using the k-nearest neighbor (k-NN) method, and quality of these models were cross-validated.

Isotope geochemistry of Ninetyeast Ridge basalts

The Ninetyeast Ridge lavas have Sr and Nd isotopic ratios intermediate between those of Indian Ocean MORBs and those of the very enriched Kerguelen hot spot. In an Nd-Sr isotope diagram, they also plot close to the fields of St. Paul Island lavas and of the early magmatism on Kerguelen Archipelago. The Ninetyeast Ridge lavas were generated by mixing among at least three components: a depleted, MORB-type component, such as the one erupted today on the Southeast Indian Ridge; a very enriched, high- Sr/ Sr, low-epsilon-Nd, OIB-type component (the Kerguelen hot spot); and an OIB-type component comparable to that sampled from the St. Paul (and Amsterdam) lavas. The Ninetyeast Ridge lavas show a typical Dupal anomaly signature and Pb, Sr, and Nd isotopic systematics indicate that the Kerguelen hot spot was involved in the ridge's formation as the Indian plate moved northward. The different sites cored during ODP Leg 121 show a trend in their isotopic compositions, from less radiogenic Pb/ Pb ratios and intermediate 87Sr/86Sr and 143Nd/**Nd ratios in the oldest lavas (Site 758) toward more radiogenic 206Pb/204Pb, higher epsilon-Nd, and lower 87Sr/86Sr values in the youngest lavas (Site 756). The lavas from Site 757 have 206Pb/204Pb ratios intermediate between those of the lavas from Sites 756 and 758 and higher 87Sr/86Sr and lower epsilon-Nd values. The relative proportions of the hot spot(s) and MORB component have evolved with time, reflecting differences of tectonic setting: the relative proportion of the Kerguelen hot spot component appears lower in the younger Site 756 lavas than in the older lavas from Sites 757 and 758. Site 756 coincides with the beginning of rifting at the Southeast Indian Ridge, about 43 Ma ago. The formation of the early Kerguelen Archipelago lavas may have drained most of the plume-derived material toward the Antarctic plate. Alternatively, the proximity of the spreading-ridge axis may account for the isotopic similarity of the Site 756 lavas to young lavas erupted on the Southeast Indian Ridge, from 33? to 37?S. The older lavas of Ninetyeast Ridge may have formed when the hot spot and ridge axis did not exactly coincide. The involvement of the third component, a St. Paul hot spot, in the genesis of the Ninetyeast Ridge lavas, especially for the Site 756 lavas, is clearly indicated by Sr, Pb, and Nd isotope systematics and also by trace element ratios. These data, together with those from the Kerguelen Plateau, indicate that the Kerguelen hot spot has been active more or less continuously in the South Indian Ocean for at least 115 Ma. This could indicate that the plume, and by inference the Dupal anomaly, is deep seated in origin.