Unsupervised Spike Sorting for Large-Scale, High-Density Multielectrode Arrays

We present a method for automated spike sorting for recordings with high-density, large-scale multielectrode arrays. Exploiting the dense sampling of single neurons by multiple electrodes, an efficient, low-dimensional representation of detected spikes consisting of estimated spatial spike locations and dominant spike shape features is exploited for fast and reliable clustering into single units. Millions of events can be sorted in minutes, and the method is parallelized and scales better than quadratically with the number of detected spikes. Performance is demonstrated using recordings with a 4,096-channel array and validated using anatomical imaging, optogenetic stimulation, and model-based quality control. A comparison with semi-automated, shape-based spike sorting exposes significant limitations of conventional methods. Our approach demonstrates that it is feasible to reliably isolate the activity of up to thousands of neurons and that dense, multi-channel probes substantially aid reliable spike sorting

BLISS: an artificial language for learnability studies

To explore neurocognitive mechanisms underlying the human language faculty, cognitive scientists use artificial languages to control more precisely the language learning environment and to study selected aspects of natural languages. Artificial languages applied in cognitive studies are usually designed ad hoc, to only probe a specific hypothesis, and they include a miniature grammar and a very small vocabulary. The aim of the present study is the construction of an artificial language incorporating both syntax and semantics, BLISS. Of intermediate complexity, BLISS mimics natural languages by having a vocabulary, syntax, and some semantics, as defined by a degree of non-syntactic statistical dependence between words. We quantify, using information theoretical measures, dependencies between words in BLISS sentences as well as differences between the distinct models we introduce for semantics. While modeling English syntax in its basic version, BLISS can be easily varied in its internal parametric structure, thus allowing studies of the relative learnability of different parameter sets

An efficient spectrum decision scheme in opportunistic spectrum access networks

In this paper, we propose and compare two spectrum decision schemes namely; Adaptive Spectrum Decision (ASD) and Maximum Remaining Lifetime (MRL). The simulation results and performance analysis such as channel utilization, data delivery, and handoff rates are evaluated and compared

Deficit irrigation and nitrogen effects on nitrogen-use efficiency and grain protein of rice

To meet future food demand, world rice production must increase in the next few decades, which is possible only by effective use of soil and water resources and inputs. This research was conducted to investigate the effects of nitrogen, N, application and deficit irrigation treatments including a sprinkler, intermittent flooding and continuous flood irrigation, and their interaction with the N-use efficiency and grain protein of a local lowland rice cultivar. The results indicated that low (sprinkler irrigation) and high (continuous flood irrigation) applied water affected the plant and soil factors in N uptake and decreased N-use efficiency for rice. Therefore, optimum applied water was obtained in intermittent flooding (2-day interval). Reduction in nitrogen uptake at high applied water can be due to the effect of nitrate leaching in the root zone and the reduction in N uptake at low applied water can be due to the inability of the roots to absorb N and translocate it to the plant top. With respect to the relationship between N uptake and grain protein and leaf chlorophyll, these parameters can also be affected by applied water and N application. Appropriate linear models were proposed to show these relationships. At different times of soil nitrogen measurements and N application rates, maximum nitrogen leaching (about 50%) occurred in continuous flooding irrigation

Effect of Chitosan Coating on Increasing Postharvest Life and Maintaining Apple fruit Quality Cv “Soltani”

The advantage of coating agents is reducing transpiration and respiration, leading to maintaining the quality and extending the shelf life of the fruits. Chitosan, the most important coating agent, is used during the post-harvest process. In this research the effect of chitosan with different concentrations (0, 0.5, 1 and 2%) on the shelf-life of apple cv “Soltani” was studied. The study was conducted as a split plot in time within a complete randomized design in 3 replications and 4 tratments. After storage at 1°C and 90% RH, fruits were evaluated every 30 days in terms of some traits such as firmness, weight loss, soluble solids and titratable acid and vitamin C, total phenol, antioxidant capacity and pH. Results showed that the fruits treated with chitosan had significantly higher firmness, titratable acid (TA), soluble solids (TSS), vitamin C, total phenol, antioxidant capacity and lower weight loss and pH, compared to the control. There was no significant difference between 1 and 2% chitosan coating concentrations for most of the examined traits, though evidence indicated that the 2% chitosan may act better than the 1% for shelf life extension and quality maintaining