Psychophysics with children: Evaluating the use of maximum likelihood estimators in children aged 4-15 years (QUEST plus )

Maximum Likelihood (ML) estimators such as QUEST+ allow complex psychophysical measurements to be made more quickly and precisely than traditional staircase techniques. They could therefore be useful for quantifying sensory function in populations with limited attention spans, such as children. To test this, the present study empirically evaluated the performance of an ML estimator (QUEST+) versus a traditional Up-Down Weighted Staircase in children and adults. Seventy-one children (4.7–14.7 years) and 43 adults (18.1–29.6 years) completed a typical psychophysical procedure: Contrast Sensitivity Function (CSF) determination. Some participants were tested twice with the same method (QUEST+ or Staircase), allowing test-retest repeatability to be quantified. Others were tested once each with either method (QUEST+ and Staircase), allowing accuracy to be quantified. The results showed that QUEST+ was more efficient: In both children and adults, approximately half the number of ML trials were required to attain comparable levels of accuracy and reliability as a traditional Staircase paradigm, and plausible CSF estimates could be made in even the youngest children. The ML procedure was also as robust as the Staircase to lapses in concentration, and its performance did not depend on prespecifying correct model priors. The results show that ML estimators could greatly improve our ability to study sensory processes and detect impairments in children, although important practical considerations for-and-against their use are discussed

Transmission Power Adjustment Scheme for Mobile Beacon-Assisted Sensor Localization

© 2005-2012 IEEE. Localization, as a crucial service for sensor networks, is an energy-demanding process for both indoor and outdoor scenarios. GPS-based localization schemes are infeasible in remote, indoor areas, and it is not a cost-effective solution for large-scale networks. Single mobile-beacon architecture is recently considered to localize sensor networks with the aim of removing numerous GPS-equipped nodes. The critical issue for the mobile beacon-Assisted localization is to preserve the consumed power to increase the lifetime. This paper presents a novel power control scheme, namely 'Z-power,' for mobile beacon traveling along a predefined path. The proposed scheme takes the advantage of deterministic path traveled by the single beacon to efficiently adjust the transmission power. Based on the extensive results, the proposed power control scheme could successfully improve the beacon and sensors energy consumption about 25.37% and 34.09%, respectively. A significant energy-Accuracy tradeoff was achieved using Z-power, which could successfully keep the same level of accuracy while providing lower energy consumption. Another group of results collected when obstacle-handling algorithm was applied at the presence of obstacles. In this scenario, Z-power improves energy consumption and localization accuracy with the same level of success

Indoor navigation systems based on data mining techniques in internet of things: a survey

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. Internet of Things (IoT) is turning into an essential part of daily life, and numerous IoT-based scenarios will be seen in future of modern cities ranging from small indoor situations to huge outdoor environments. In this era, navigation continues to be a crucial element in both outdoor and indoor environments, and many solutions have been provided in both cases. On the other side, recent smart objects have produced a substantial amount of various data which demands sophisticated data mining solutions to cope with them. This paper presents a detailed review of previous studies on using data mining techniques in indoor navigation systems for the loT scenarios. We aim to understand what type of navigation problems exist in different IoT scenarios with a focus on indoor environments and later on we investigate how data mining solutions can provide solutions on those challenges

Depression and social anxiety in children: Differential links with coping strategies

Background: Strategies that children use for coping with stressors are known to be related to emotional adjustment, but not enough is understood about specific links with social anxiety and depression. The present investigation tested differentiated associations of social anxiety and depression with specific types of coping strategies, and evaluated the direction of these associations over time. Methods: In Study 1, 404 children aged 8-13 years completed a coping scale modified from Kochenderfer-Ladd and Skinner (2002) in order to evaluate factor structure and subscale internal consistency. In Study 2, 270 8-11-year-old children completed depression and social anxiety scales, a sociometric survey, and the coping scale from Study 1, with a follow-up timepoint 9 months later. Results: In Study 1, factor analysis revealed six internally consistent coping subscales. In Study 2, social anxiety and depression were found to have distinctive longitudinal associations with subsequent coping strategies. Decreased problem-solving, social support-seeking, and distraction were uniquely predicted by depression but not by social anxiety. Internalising coping was a stronger outcome of social anxiety, and increased externalising was uniquely predicted by depression. There was also some evidence for a moderating role of peer relations. However, none of the coping strategies predicted changes in depression or social anxiety over the two timepoints. Conclusions: These results highlight the impact that emotional adjustment may have on childrens coping strategies, and clarify important distinctions between social anxiety and depression in relation to coping. Keywords: social anxiety, depression, coping, peer relations, longitudina

How far is Facebook from me? Facebook network infrastructure analysis

Facebook is today the most popular social network with more than one billion subscribers worldwide. To provide good quality of service (e.g., low access delay) to their clients, FB relies on Akamai, which provides a worldwide content distribution network with a large number of edge servers that are much closer to FB subscribers. In this article we aim to depict a global picture of the current FB network infrastructure deployment taking into account both native FB servers and Akamai nodes. Toward this end, we have performed a measurement-based analysis during a period of two weeks using 463 Planet-Lab nodes distributed across 41 countries. Based on the obtained data we compare the average access delay that nodes in different countries experience accessing both native FB servers and Akamai nodes. In addition, we obtain a wide view of the deployment of Akamai nodes serving FB users worldwide. Finally, we analyze the geographical coverage of those nodes, and demonstrate that in most of the cases Akamai nodes located in a particular country service not only local FB subscribers, but also FB users located in nearby countries.This works is partially supported by the European Celtic-Plus project CONVINcE and eCOUSIN (EUFP7-318398). This work is also funded by the Ministerio de Economía y Competitividad of SPAIN through the project BigDatAAM (FIS2013-47532-C3-3-P)

Antibiotic resistance pattern and distribution of psla gene among biofilm producing pseudomonas aeruginosa isolated from waste water of a burn center

Background: Pseudomonas aeruginosa is considered as a major cause of hospital-acquired infections due to its high antibacterial resistance. Biofilm formation is a well-known pathogenic mechanism in P. aeruginosa infections, since sessile bacteria are protected in an extracellular matrix of exopolysaccharide. The expression of polysaccharide synthesis locus (pslA gene) can be important for biofilm formation by P. aeruginosa. Objectives: The purpose of this research was to evaluate the antibiotic resistance pattern and distribution of the pslA gene among biofilm-producing P. aeruginosa isolates obtained from waste water of Burn Centre in Guilan, Iran. Materials and Methods: Fifty isolates of P. aeruginosa were obtained from waste water of a burn center. The P. aeruginosa isolates were identified using standard bacteriological procedures. Drug susceptibility test was performed by disk diffusion method for all the isolates against nine antimicrobial agents. Biofilm formation was measured by microtiter plate assay. Polymerase chain reaction (PCR) was used to identify the presence of the pslA gene among the isolates. Results: Biofilm formation was observed in 70 of the P. aeruginosa isolates. The potential formation of biofilm was significantly associated with resistance to gentamicin, imipenem, tobramycin and piperacillin. In addition, the pslA gene only existed in biofilm-producing isolates with a frequency of 42.9 (n = 15).Conclusions: The findings of the present study well demonstrated that the P. aeruginosa biofilm-producing isolates were more resistant to the tested antibiotics. Furthermore, because of wide distribution, it seems that the pslA gene is associated with biofilm formation. � 2015, Ahvaz Jundishapur University of Medical Sciences

Development of the spatial contrast sensitivity function (CSF) during childhood: Analysis of previous findings and new psychophysical data

While the contrast sensitivity function (CSF) changes markedly during infancy, there is no consensus regarding whether, how, and why it continues to develop in later childhood. Here we analyzed previously published data (N = 1,928 CSFs), and present new psychophysical findings from 98 children (4.7–14.8 years) and 50 adults (18.1–29.7 years), in order to establish: (1) Does the CSF change during childhood? (2) How large is the developmental effect size? (3) Are any changes uniform across the CSF, or frequency-specific? (4) Can some or all of the changes be explained by ‘non-visual’ (i.e., procedural/cognitive) factors, such as boredom or inattentiveness? The new data were collected using a four-alternative forced-choice [4AFC] Gabor-detection task, with two different psychophysical procedures (Weighted Staircase; QUEST+), and suprathreshold (false-negative) catch trials to quantify lapse rates. It is shown that from 4—18 years, the CSF improves (at an exponentially decaying rate) by approximately 0.3 log10 units (a doubling of CS), with 90% of this change complete by 12 years. The size of the effect was small relative to individual variability, with age alone explaining less than one sixth of variability (16%), and most children performing as well as some adults (i.e., falling within the 90% population limits for adults). Development was frequency-specific, with changes occurring primarily around or below the CSF peak (≤ 4 cpd). At least half --- and potentially all --- of the changes observed could be explained by ‘non-visual’ factors (e.g., lapses in concentration), though possible biological mechanisms are discussed

Cohort study of electroencephalography markers of amyloid-tau-neurodegeneration pathology

Electroencephalography signatures of amyloid-β, tau and neurodegenerative pathologies would aid in screening for, tracking progression of, and critically, understanding the pathogenesis of dementia. We hypothesized that slowing of the alpha peak frequency, as a signature of hyperpolarization-activated cyclic nucleotide gated ‘pacemaker’ channel activity, would correlate with amyloid and tau pathology burden measured by amyloid (Pittsburgh Compound B) and tau (MK-6240) positron emission tomography or CSF biomarkers. We also hypothesized that EEG power would be associated with neurodegeneration (CSF neurofilament light and hippocampal volume). Wakeful high-density EEG data were collected from 53 subjects. Both amyloid-β and tau pathology were associated with slowing in the alpha peak frequency [Pittsburgh Compound B (+) vs. Pittsburgh Compound B (−) subjects, P = 0.039 and MK-6240 (+) vs. MK-6240 (−) subjects, P = 0.019]. Furthermore, slowing in the peak alpha frequency correlated with CSF Aβ42/40 ratio (r2 = 0.270; P = 0.003), phosphoTau (pTau181, r2 = 0.290; P = 0.001) and pTau181/Aβ42 (r2 = 0.343; P < 0.001). Alpha peak frequency was not associated with neurodegeneration. Higher CSF neurofilament light was associated with lower total EEG power (r2 = 0.136; P = 0.018), theta power (r2 = 0.148; P = 0.014) and beta power (r2 = 0.216; P = 0.002); the latter was also associated with normalized hippocampal volume (r2 = 0.196; P = 0.002). Amyloid-tau and neurodegenerative pathologies are associated with distinct electrophysiological signatures that may be useful as mechanistic tools and diagnostic/treatment effect biomarkers in clinical trials