Representation as a fluent: an AI challenge for the next half century

The authors argued that AI systems must be able to manipulate their own internal representations automatically to deal with an infinitely complex and ever-changing world and to scale up to rich, complex applications. Such manipulation must go beyond changing beliefs and learning new concepts in terms of old concepts; it must be able to change ontology's underlying syntax and semantics. Initial progress has been made, but further progress is urgently needed owing to the demands of autonomous multiagent systems. Understanding and implementing this ability must be a major focus of AI for the next 50 years.     

Quantifying the benefits of enhanced filter selectivity

Today's mobile communications market is very competitive, with wireless service providers making every effort to improve the performance of their network to retain subscribers. Coupled with the proliferation of radio-frequency signals in the environment due to the growth of all forms of wireless communication, this leads to a very challenging task - namely, to provide ubiquitous high-quality service in spite of ever-increasing interference levels. One of the tools at the disposal of the network operator to provide such service is a cryogenically cooled receiver front end for base stations, wherein each receive path consists of a high-temperature superconducting (HTS) bandpass filter followed by a cryogenically cooled low-noise amplifier. There are two primary benefits achieved by the use of this front end. The first is improved receiver sensitivity through the reduction of electrical noise generated by the front end itself. The second is the significant reduction in the effects of out-of-band interference through the highly selective filtering made possible by the use of HTS materials. While this paper addresses both receiver-sensitivity and filter-selectivity benefits, the focus is on improved out-of-band interference rejection through enhanced filter selectivity.     

Herd immunity to filarial infection is a function of vector biting rate

Despite the existence of an impressive body of work on human immune responses against filarial infections, the occurrence of a protective response to infection remains unclear. Here, we use a combined modelling and comparative data analysis framework to address this issue for human infections with the filarial parasite, Wuchereria bancrofti. By analogy with previous work, the analysis involves the comparison of observed field patterns of infection with epidemiological patterns predicted by a mathematical model of parasite immunity. Unlike most other human helminths, which are transmitted by ingestion or dermal penetration, exposure to infection with lymphatic filariasis can be measured explicitly in terms of vector mosquito biting rates, thereby also allowing, probably for the first time, examination of the suggested role of exposure in generating herd immunity to macroparasites. Observed field patterns in this study were derived from 19 different published studies, which gave parallel estimates of community exposure rates and the corresponding age--prevalence patterns of infection, while predictions of the epidemiological impact of herd immunity were obtained using a catalytic model framework. The results provide the first conclusive evidence to date that variations in the observed age--prevalence patterns of infection in filariasis can be effectively explained by the occurrence of an exposure-driven acquisition of herd immunity. We discuss this result in terms of implications for the new World Health Organization-led initiative for the global control of this parasitic disease.     

Metabolic profile biomarkers of metal contamination in a sentinel terrestrial species are applicable across multiple sites

In this study, we addressed the question of whether an omic approach could genuinely be useful for biomarker profile analysis across different field sites with different physicochemical characteristics. We collected earthworms (Lumbricus rubellus) from seven sites with very different levels of metal contamination and prevailing soil type and analyzed tissue extracts by 1H nuclear magnetic resonance spectroscopy. Pattern recognition analysis of the data showed that both site- and contaminant-specific effects on the metabolic profiles could be discerned. Zinc was identified as the probable major contaminant causing a metabolic change in the earthworms. Individual sites could be resolved on the basis of NMR spectral profiles by principal component analysis; these site differences may also have been caused by additional abiotic factors such as soil pH. Despite an inevitable degree of confounding between site and contaminant concentrations, it was possible to identify metabolites which were correlated with zinc across all different sites. This study therefore acts as a proof of principle for the use of NMR-based metabolic profiling as a diagnostic tool for ecotoxicological research in polluted field soils.     

Oligonucleotide mixture analysis via electrospray and ion/ion reactions in a quadrupole ion trap

Electrospray ionization combined with ion/ion reactions in a quadrupole ion trap can be used for the direct analysis of oligonucleotide mixtures. Elements to the success of this approach include factors related to ionization, ion/ion reactions, and mass analysis. This paper deals with issues regarding the ion polarity combination, viz., positive oligonucleotides/negative charge-transfer agent versus negative oligonucleotides/positive charge-transfer agent. Anions derived from perfluorocarbons appear to be directly applicable to mixtures of positive ions derived from electrospray of oligonucleotides, in direct analogy with positive protein ions. Conditions for forming positive oligonucleotide ions devoid of adducts were more difficult to establish than for forming relatively clean negative oligonucleotide ions. A new approach for manipulating negative ion charge states in the ion trap is described and is based on use of the electric field of the positive charge-transfer agent for storage of high-mass negative ions formed during the ion/ion reaction period. Oxygen cations are shown to be acceptable for charge-state manipulation of mixed-base oligomers but induce fragmentation in polyadenylate homopolymers. Protonated isobutylene (C4H9+), on the other hand, is shown to induce significantly less fragmentation of polyadenylate homopolymers.     

Microjet impingement followed by scanning electron microscopy as a qualitative technique to compare cellular adhesion to various biomaterials

Adhesion of cells to biomaterial surfaces is one of the major factors which mediates their biocompatibility. Quantitative or qualitative cell adhesion measurements would be useful for screening new implant materials. Microjet impingement has been evaluated by scanning electron microscopy, to determine to what extent it measures cell adhesion. The shear forces of the impingement, on the materials tested here, are seen to be greater than the cohesive strength of the cells in the impinged area, causing their rupture. The cell bodies are removed during impingement, leaving the sites of adhesion and other cellular material behind. Thus the method is shown not to provide quantification of cell adhesion forces for the metals and culture plastic tested. It is suggested that with highly adherent biomaterials, the distribution and patterns of these adhesion sites could be used for qualitative comparisons for screening of implant surfaces.     

Anthelmintic treatment improves the hemoglobin and serum ferritin concentrations of Tanzanian schoolchildren

To investigate the relationships between helminth infections and iron status among school-aged children, 1,115 Tanzanian children in grades 2 through 5 were randomly assigned to treatment or control groups. The children in the treatment group were screened for infection with Schistosoma haematobium and hookworm at baseline, 3 months, and 15 months; infected children were given albendazole against hookworm and praziquantel against schistosomiasis. The control group received a placebo and did not undergo parasitological screening until 15 months after the baseline. Hematological variables were compared between the treatment and control groups. The main results were, first, that the hemoglobin concentration significantly improved after treatment for hookworm (p < .001) by 9.3 g/L in children treated for hookworm only and by 8.8 g/L in children treated for hookworm and schistosomiasis. The ferritin concentration also improved in children treated for schistosomiasis (p = .001) or hookworm (p = .019). Second, a longitudinal analysis of the data from the children in the control group showed that hookworm and schistosomiasis loads were negatively associated with hemoglobin and ferritin concentrations. Moreover, ferritin concentrations increased as C-reactive protein levels increased. Overall, the results showed that anthelmintic treatment is a useful tool for reducing anemia in areas with high hookworm and schistosomiasis endemicity. The empirical relationship between ferritin and C-reactive protein indicated that simple procedures for adjusting cutoff points for the use of ferritin as an indicator of low iron stores were unlikely to be useful in this population.     

Lectin and carbohydrate affinity capture surfaces for mass spectrometric analysis of microorganisms

In a preliminary report (Bundy, J. L.; Fenselau, C. Anal. Chem 1999, 71, 1460-1463), we demonstrated the use of lectin-derivatized surfaces to capture and concentrate complex carbohydrates as well as microorganisms from sample matrixes unamenable to direct MALDI mass spectrometry. Here, we extend the work to include samples representative of a wider variety of microorganisms of importance to human health and of enveloped viruses. In this study, lectins were immobilized directly to a membrane surface via primary amines. A complementary approach was also explored, using immobilized carbohydrates to capture bacteria via microbial lectins expressed on their surfaces. The carbohydrate-based surfaces were constructed by first immobilizing streptavidin to the membrane, followed by attachment of a commercially produced biotin/carbohydrate polymer. Acid treatment of the sample prior to mass spectrometric analysis permits the observation of protein biomarkers from the captured microbial samples in the 5-20 kDa mass range. Bacteria samples were detected from physiological buffers, urine, milk, and processed chicken samples using the biocapture probes. Viral samples were detected from culture based on glycoprotein moieties desorbed directly from the surface. The carbohydrate-based system provided greater sensitivity than the lectin system, possibly due to the larger number of accessible saccharide ligands on the polymer.     

Correctness criteria of some algorithms for uncertain reasoning using Incidence Calculus

Incidence Calculus is a technique for associating uncertainty values with logical sentences. These uncertainty values are called incidences and they are sets of points, which may be thought of as representing equivalence classes of situations, Tarskian models, or possible worlds. Incidence Calculus was originally introduced in [1]. Incidence Calculus was designed to overcome various inherent problems with purely numeric mechanisms for uncertain reasoning [2]. In particular, incidences can represent the dependence between sentences, which numbers cannot, and hence Incidence Calculus can provide genuine, probabilistic reasoning. In this paper we prove soundness and completeness results for some algorithms introduced in [1] and hence satisfy some of the correctness criteria for Incidence Calculus. These algorithms can be used for probabilistic reasoning and to check the consistency of the subjective probabilities of sentences.     

Between-person comparison of metabolite fitting for NMR-based quantitative metabolomics

Nuclear magnetic resonance (NMR) spectroscopy is widely used as an analytical platform for metabolomics. Many studies make use of 1D spectra, which have the advantages of relative simplicity and rapid acquisition times. The spectral data can then be analyzed either with a chemometric workflow or by an initial deconvolution or fitting step to generate a list of identified metabolites and associated sample concentrations. Various software tools exist to simplify the fitting process, but at least for 1D spectra, this still requires a degree of skilled operator input. It is of critical importance that we know how much person-to-person variability affects the results, in order to be able to judge between different studies. Here we tested a commercially available software package (Chenomx' NMR Suite) for fitting metabolites to a set of NMR spectra of yeast extracts and compared the output of five different people for both metabolite identification and quantitation. An initial comparison showed good agreement for a restricted set of common metabolites with characteristic well-resolved resonances but wide divergence in the overall identities and number of compounds fitted; refitting according to an agreed set of metabolites and spectral processing approach increased the total number of metabolites fitted but did not dramatically increase the quality of the metabolites that could be fitted without prior knowledge about peak identity. Hence, robust peak assignments are required in advance of manual deconvolution, when the widest range of metabolites is desired. However, very low concentration metabolites still had high coefficients of variation even with shared information on peak assignment. Overall, the effect of the person was less than the experimental group (in this case, sampling method) for almost all of the metabolites.