IR-based System Research Articles

Opponent Learning with Different Representations in the Cortico-Basal Ganglia Circuits.

The direct and indirect pathways of the basal ganglia (BG) have been suggested to learn mainly from positive and negative feedbacks, respectively. Since these pathways unevenly receive inputs from different cortical neuron types and/or regions, they may preferentially use different state/action representations. We explored whether such a combined use of different representations, coupled with different learning rates from positive and negative reward prediction errors (RPEs), has computational benefits. We modeled animal as an agent equipped with two learning systems, each of which adopted individual representation (IR) or successor representation (SR) of states. With varying the combination of IR or SR and also the learning rates from positive and negative RPEs in each system, we examined how the agent performed in a dynamic reward navigation task. We found that combination of SR-based system learning mainly from positive RPEs and IR-based system learning mainly from negative RPEs could achieve a good performance in the task, as compared with other combinations. In such a combination of appetitive SR-based and aversive IR-based systems, both systems show activities of comparable magnitudes with opposite signs, consistent with the suggested profiles of the two BG pathways. Moreover, the architecture of such a combination provides a novel coherent explanation for the functional significance and underlying mechanism of diverse findings about the cortico-BG circuits. These results suggest that particularly combining different representations with appetitive and aversive learning could be an effective learning strategy in certain dynamic environments, and it might actually be implemented in the cortico-BG circuits.

Extracting Turnover Frequencies of Electron Transfer in Heterogeneous Catalysis: A Study of IrO2-TiO2 Anatase for Water Oxidation Using Ce4+ Cations

Within the context of electron transfer during the catalytic water oxidation reaction, the Ir-based system is among the most active. The reaction, mimicking photosynthesis II, requires the use of an electron acceptor such the Ce4+ cation. This complex reaction, involving adsorbed water at the interface of the metal cation and Ce4+, has mostly been studied in homogenous systems. To address the ambiguity regarding the gradual transformation of a homogenous system into a heterogeneous one, we prepared and studied a heterogeneous catalyst system composed of IrO2, with a mean particle size ranging from about 5 Å to 10 Å, dispersed on a TiO2 anatase support, with the objective of probing into the different parameters of the reaction, as well as the compositional changes and rates. The system was stable for many of the runs that were conducted (five consecutive runs with 0.18 M of Ce4+ showed the same reaction rate with TON > 56,000) and, equally importantly, was stable without induction periods. Extraction of the reaction rates from the set of catalysts, with an attempt to normalize them with respect to Ir loading and, therefore, to obtain turnover frequencies (TOF), was conducted. While, within reasonable deviations, the TOF numbers extracted from TPR and XPS Ir4f were close, those extracted from the particle shape (HR-STEM) were considerably larger. The difference indicates that bulk Ir atoms contribute to the electron transfer reaction, which may indicate that the reaction rate is dominated by the reorganization energy between the redox couples involved. Therefore, the normalization of reaction rates with surface atoms may lead to an overestimation of the site activity.

Design, Implementation and Evaluation of IR-Based Tagging System for RTLS

Real time location system (RTLS) technologies are being widely used to automatically identify and track the location of objects or people. Such technologies such as UWB tags, passive/active RFID tags, IR tags and WiFi tags are helpful in improving the accuracy and reducing the inspection time to automate the inventory control process. Since most of RTLS technologies make use of already crowded radio or microwave spectrum it is imperative to explore the use of infrared tags for such applications. IR tags offer many advantages like using simple technology, reducing false-positives due to their inherent room confinement features and electromagnetic interference free wide spectrum. In this paper a novel, effective and low cost real time location system utilizing IR tags for the application of inventory control is presented. The system is designed, tested and analysed keeping range, field angle, ambient light interference, time consumption and accuracy as performance metrics.

Kinetics of Photocatalytic Water Oxidation at Liposomes: Membrane Anchoring Stabilizes the Photosensitizer

A tris(bipyridine)ruthenium(II) photosensitizer (PS) was anchored to the lipid bilayer of liposomes together with Ru-, Co-, or Ir-based water-oxidation catalysts in order to study the effect of liposomes on photocatalytic water oxidation in the presence of Na2S2O8. The Ru-based and Co-based systems both showed O2 production upon light irradiation, whereas the Ir-based system did not. Membrane anchoring caused a large shift in the quantum yield of oxidative quenching of the photosensitizer excited state by peroxodisulfate, which decreased from 180% in homogeneous solution to 7.3% at the surface of liposomes. For the Ru-based system the electron-transfer rate between the photosensitizer PS+ and the water-oxidation catalyst was increased relative to oxidative quenching. Consequently, the rate-limiting step of the photocatalytic water oxidation reaction at liposomes was oxidative quenching, whereas previous work showed that in homogeneous solution it is the reduction of the oxidized photosensitizer PS+ by the...

Comparative Investigations of Cp*-Based Group 9 Metal-Catalyzed Direct C–H Amination of Benzamides

Key mechanistic features of the [Cp*MCl2]2 (M = Ir, Rh, Co; all are in group 9) catalyzed C–H amination of benzamides with organic azides were investigated with a strong emphasis on the metal effects on the reaction mechanism, revealing that the Rh- and Ir-catalyzed reactions follow a similar reaction profile, albeit with different individual kinetic and thermodynamic parameters. The observation that the Ir-based system was much superior in terms of the rates and efficiency in comparison to Rh was attributed to the intrinsically strong relativistic effects in iridium. While a cobalt system [Cp*CoIII] showed little catalytic activity for most azides examined, plausible [(BA)(Cp*)CoNR]+ intermediates of these reactions were characterized as a “Co(III)-nitrenoid radical” species with a weak (“one electron–two center type”) Co–NPh bond. Its Rh and Ir analogues are characterized as diamagnetic metal nitrenoids with a strong M═NR double bond. The provided experimental and computational investigations indicate t...

A kinect-based parking assistance system

This work presents an IR-based system for parking assistance and obstacle detection in the automotive field that employs the Microsoft Kinect camera for fast 3D point cloud reconstruction. In contrast to previous research that attempts to explicitly identify obstacles, the proposed system aims to detect "reachable regions" of the environment, i.e., those regions where the vehicle can drive to from its current position. A user-friendly 2D traversability grid of cells is generated and used as a visual aid for parking assistance. Given a raw 3D point cloud, first each point is mapped into individual cells, then, the elevation information is used within a graph-based algorithm to label a given cell as traversable or non-traversable. Following this rationale, positive and negative obstacles, as well as unknown regions can be implicitly detected. Additionally, no flat-world assumption is required. Experimental results, obtained from the system in typical parking scenarios, are presented showing its effectiveness for scene interpretation and detection of several types of obstacle.

A commercial V2O5-WO3/TiO2 catalyst used at an NH3-SCR deNOx process in an oil-fired power plant: cause of an increase in deNOxing and NH3 oxidation performances at low temperatures

The extent of both NOx removal and NH3 oxidation in the selective reduction of NOx by NH3 over a sample of a commercial V2O5-WO3/TiO2 catalyst that had been used for 20,000 h at an NH3-SCR deNOx process in a domestic heavy oil-fired power plant has been determined using an on-line IR-based system coupled with a modified White cell and the catalyst has been characterized to ascertain the reason why it possessed visibly different behaviors in the deNOx reaction, compared to a fresh sample. The on-site-used catalyst gave not only much higher deNOx activity at all temperatures less than 400 °C than that indicated for a fresh catalyst but also a greatly increased NH3 oxidation reaction. SEM-EDX measurements with samples of the used and fresh catalysts represented the presence of a huge amount of sulfur in the former sample, very consistent with sulfur amounts determined by a C/S analyzer; however, this did not create the measured enhancement in the low-temperature deNOx and NH3 oxidation performances. ICP measurements indicated a significant increase, by 1% as a basis of V2O5, in an amount of vanadium species after the on-site use and such vanadium species came from heavy oils used to generate electricity at the power plant and were in the form of polycrystalline V2O5 nanoparticles as acquired by XRD measurements. All these results propose that the increased V2O5 content might be associated with the noticeable difference in SCR activity and NH3 oxidation between both of the samples.

Semi-robotic 6 degree of freedom positioning for intracranial high precision radiotherapy; first phantom and clinical results

BackgroundTo introduce a novel method of patient positioning for high precision intracranial radiotherapy.MethodsAn infrared(IR)-array, reproducibly attached to the patient via a vacuum-mouthpiece(vMP) and connected to the table via a 6 degree-of-freedom(DoF) mechanical arm serves as positioning and fixation system. After IR-based manual prepositioning to rough treatment position and fixation of the mechanical arm, a cone-beam CT(CBCT) is performed. A robotic 6 DoF treatment couch (HexaPOD™) then automatically corrects all remaining translations and rotations. This absolute position of infrared markers at the first fraction acts as reference for the following fractions where patients are manually prepositioned to within ± 2 mm and ± 2° of this IR reference position prior to final HexaPOD-based correction; consequently CBCT imaging is only required once at the first treatment fraction.The preclinical feasibility and attainable repositioning accuracy of this method was evaluated on a phantom and human volunteers as was the clinical efficacy on 7 pilot study patients.ResultsPhantom and volunteer manual IR-based prepositioning to within ± 2 mm and ± 2° in 6DoF was possible within a mean(± SD) of 90 ± 31 and 56 ± 22 seconds respectively. Mean phantom translational and rotational precision after 6 DoF corrections by the HexaPOD was 0.2 ± 0.2 mm and 0.7 ± 0.8° respectively. For the actual patient collective, the mean 3D vector for inter-treatment repositioning accuracy (n = 102) was 1.6 ± 0.8 mm while intra-fraction movement (n = 110) was 0.6 ± 0.4 mm.ConclusionsThis novel semi-automatic 6DoF IR-based system has been shown to compare favourably with existing non-invasive intracranial repeat fixation systems with respect to handling, reproducibility and, more importantly, intra-fraction rigidity. Some advantages are full cranial positioning flexibility for single and fractionated IGRT treatments and possibly increased patient comfort.

Semplore: A Scalable IR Approach to Search the Web of Data

The Web of Data keeps growing rapidly. However, the full exploitation of this large amount of structured data faces numerous challenges like usability, scalability, imprecise information needs and data change. We present Semplore, an IR-based system that aims at addressing these issues. Semplore supports intuitive faceted search and complex queries both on text and structured data. It combines imprecise keyword search and precise structured query in a unified ranking scheme. Scalable query processing is supported by leveraging inverted indexes traditionally used in IR systems. This is combined with a novel block-based index structure to support efficient index update when data changes. The experimental results show that Semplore is an efficient and effective system for searching the Web of Data and can be used as a basic infrastructure for Web-scale Semantic Web search engines.

Semplore: A scalable IR approach to search the Web of Data

The Web of Data keeps growing rapidly. However, the full exploitation of this large amount of structured data faces numerous challenges like usability, scalability, imprecise information needs and data change. We present Semplore, an IR-based system that aims at addressing these issues. Semplore supports intuitive faceted search and complex queries both on text and structured data. It combines imprecise keyword search and precise structured query in a unified ranking scheme. Scalable query processing is supported by leveraging inverted indexes traditionally used in IR systems. This is combined with a novel block-based index structure to support efficient index update when data changes. The experimental results show that Semplore is an efficient and effective system for searching the Web of Data and can be used as a basic infrastructure for Web-scale Semantic Web search engines.

Mechanism of Ru(II)-catalyzed olefin insertion and C-H activation from quantum chemical studies.

The mechanism of catalytic hydroarylation of olefins by the homogeneous Ru(Tp)(CO)(Ph)(NCCH3) catalyst recently reported by Gunnoe et al. is characterized using quantum mechanics (density functional theory). The catalytic cycle features two key steps, 1,2-olefin insertion and C-H activation via an unusual mechanism, oxidative hydrogen migration. We find that these two key steps are competitive and that improving the rate of one step is detrimental to the rate of the other. The Ru catalyst has better balance and consequently higher activity than the previously explored Ir-based system.