Searching and Stopping: An Analysis of Stopping Rules and Strategies

Searching naturally involves stopping points, both at a query level (how far down the ranked list should I go?) and at a session level (how many queries should I issue?). Understanding when searchers stop has been of much interest to the community because it is fundamental to how we evaluate search behaviour and performance. Research has shown that searchers find it difficult to formalise stopping criteria, and typically resort to their intuition of what is "good enough". While various heuristics and stopping criteria have been proposed, little work has investigated how well they perform, and whether searchers actually conform to any of these rules. In this paper, we undertake the first large scale study of stopping rules, investigating how they influence overall session performance, and which rules best match actual stopping behaviour. Our work is focused on stopping at the query level in the context of ad-hoc topic retrieval, where searchers undertake search tasks within a fixed time period. We show that stopping strategies based upon the disgust or frustration point rules - both of which capture a searcher's tolerance to non-relevance - typically result in (i) the best overall performance, and (ii) provide the closest approximation to actual searcher behaviour, although a fixed depth approach also performs remarkably well. Findings from this study have implications regarding how we build measures, and how we conduct simulations of search behaviours

Simulating Interactive Information Retrieval: SimIIR: A Framework for the Simulation of Interaction

Simulation provides a powerful and cost-effective approach to explore and evaluate how interactions between a searcher and system influence search behaviour and performance. With a growing interest in simulation and an increasing number of papers using such an approach, there is a need for a flexible framework for simulation. Thus, we present SimIIR, an open-source toolkit for building and conducting Interactive Information Retrieval (IIR) experiments. The framework consists of a number of high level components, including the simulation, the searcher and the system, all of which must be configured. The SimIIR framework provides a series of interchangeable components. Examples of these components include the querying strategies (how simulated queries are formulated) and stopping strategies (the depth to which a searcher will examine snippets and documents) that a simulated searcher will employ. We have implemented various existing strategies so that they can be used by other researchers to not only replicate and reproduce past experiments, but also create new experiments. This paper describes the SimIIR framework and the different components that can be configured and extended as required

The Influence of Taxation on Small Enterprise Development in Russia

Formation of adequate conditions in Russia market economy model requires the creation of a sound financial base. An important place in the mobilization of financial resources of society plays a tax system with its characteristic features of each state and the specifics of the tasks performed at a certain stage. In recent years, the negative effects of the transition period is expected to overcome through the development of small businesses, which determines the possibility of self-realization of the population in achieving the established preferences and values, as well as through the optimization of the tax system and, in particular, strengthening and stimulating social functions taxes. Formation and development of a market economy based on private property, accompanied by an expansion of business and the creation of small businesses, the activation of various financial and credit institutions, thus increasing the number of actual taxpayers. In connection with this problem is exacerbated relations between the state in the face of tax structures and small businesses as taxpayers

Astrocytes convert network excitation to tonic inhibition of neurons

<p>Abstract</p> <p>Background</p> <p>Glutamate and γ-aminobutyric acid (GABA) transporters play important roles in balancing excitatory and inhibitory signals in the brain. Increasing evidence suggest that they may act concertedly to regulate extracellular levels of the neurotransmitters.</p> <p>Results</p> <p>Here we present evidence that glutamate uptake-induced release of GABA from astrocytes has a direct impact on the excitability of pyramidal neurons in the hippocampus. We demonstrate that GABA, synthesized from the polyamine putrescine, is released from astrocytes by the reverse action of glial GABA transporter (GAT) subtypes GAT-2 or GAT-3. GABA release can be prevented by blocking glutamate uptake with the non-transportable inhibitor DHK, confirming that it is the glutamate transporter activity that triggers the reversal of GABA transporters, conceivably by elevating the intracellular Na⁺concentration in astrocytes. The released GABA significantly contributes to the tonic inhibition of neurons in a network activity-dependent manner. Blockade of the Glu/GABA exchange mechanism increases the duration of seizure-like events in the low-[Mg²⁺] <it>in vitro </it>model of epilepsy. Under <it>in vivo </it>conditions the increased GABA release modulates the power of gamma range oscillation in the CA1 region, suggesting that the Glu/GABA exchange mechanism is also functioning in the intact hippocampus under physiological conditions.</p> <p>Conclusions</p> <p>The results suggest the existence of a novel molecular mechanism by which astrocytes transform glutamat<it>ergic </it>excitation into GABA<it>ergic </it>inhibition providing an adjustable, <it>in situ </it>negative feedback on the excitability of neurons.</p

Experimental traumatic brain injury

Traumatic brain injury, a leading cause of death and disability, is a result of an outside force causing mechanical disruption of brain tissue and delayed pathogenic events which collectively exacerbate the injury. These pathogenic injury processes are poorly understood and accordingly no effective neuroprotective treatment is available so far. Experimental models are essential for further clarification of the highly complex pathology of traumatic brain injury towards the development of novel treatments. Among the rodent models of traumatic brain injury the most commonly used are the weight-drop, the fluid percussion, and the cortical contusion injury models. As the entire spectrum of events that might occur in traumatic brain injury cannot be covered by one single rodent model, the design and choice of a specific model represents a major challenge for neuroscientists. This review summarizes and evaluates the strengths and weaknesses of the currently available rodent models for traumatic brain injury

Phosphate uptake and release rates with different carbon sources in biological nutrient removal using a SBR

A three-step sequencing batch reactor (SBR) was used for nutrient removal from synthetic wastewater with different glucose-organic acid mixtures (1/1). Acetic. butyric. propionic and citric acids were used as organic acids along with glucose. The operation consisted of anaerobic. anoxic and oxic (An/Ax/Ox) phases with durations of 2/l/4.5 h. Sludge age was kept constant for 10 days. Phosphate release Pr and uptake rates were determined for different glucose-organic acid mixtures in the feed wastewater. Maximum phosphate uptake (8.1 mg PI-1 h(-1)) and release rates (2.23 Ing PI-1 h(-1)) were obtained with the glucose-citric acid mixture. The highest (96%) percent phosphate removal at the end of the nutrient removal cycle (7.5 h) was also obtained with the glucose-citric acid mixture while the glucose-acetic acid mixture resulted in comparable percent phosphate removal (95%). (c) 2005 Elsevier Ltd. All rights reserved

para-Chlorophenol inhibition on COD, nitrogen and phosphate removal from synthetic wastewater in a sequencing batch reactor

COD, nitrogen, phosphate and para-chlorophenol (4-chlorophenol, 4-CP) removal from synthetic wastewater was investigated using a four-step sequencing batch reactor (SBR) at different sludge ages and initial para-chlorophenol (4-CP) concentrations. The nutrient removal process consisted of anaerobic, oxic, anoxic and oxic phases with hydraulic residence times (HRT) of 1/3/1/1 h and a settling phase of 0.75 h. A Box-Wilson statistical experiment design was used considering the sludge age (5-25 days) and 4-CP concentration (0-400 mg l(-1)) as independent variables. Variations of percent COD, NH4-N, PO4-P and 4-CP removals with sludge age and initial 4-CP concentration were investigated. Percent nutrient removals increased with increasing sludge age and decreasing 4-CP concentrations. Low nutrient removals were obtained at high initial 4-CP concentrations especially at low sludge ages. However, high sludge ages partially overcome the adverse effects of 4-CP and resulted in high nutrient removals. COD, NH4-N, PO4-P and 4-CP removals were 76%, 72%, 26% and 34% at a sludge age of 25 days and initial 4-CP concentration of 200 mg l(-1). Sludge volume index (SVI) also decreased with increasing sludge age and decreasing 4-CP concentrations. An SVI value of 104 ml g(-1), was obtained at a sludge age of 25 days and initial 4-CP of 200 mg l(-1). (c) 2005 Elsevier Ltd. All rights reserved