Towards the Modeling of Neuronal Firing by Gaussian Processes

This paper focuses on the outline of some computational methods for the approximate solution of the integral equations for the neuronal firing probability density and an algorithm for the generation of sample-paths in order to construct histograms estimating the firing densities. Our results originate from the study of non-Markov stationary Gaussian neuronal models with the aim to determine the neuron's firing probability density function. A parallel algorithm has been implemented in order to simulate large numbers of sample paths of Gaussian processes characterized by damped oscillatory covariances in the presence of time dependent boundaries. The analysis based on the simulation procedure provides an alternative research tool when closed-form results or analytic evaluation of the neuronal firing densities are not available.Comment: 10 pages, 3 figures, to be published in Scientiae Mathematicae Japonica

Role of the flat-designed surface in improving the cyclic fatigue resistance of endodontic NiTi rotary instruments

The aim of this study was to investigate the role of the flat-designed surface in improving the resistance to cyclic fatigue by comparing heat-treated F-One (Fanta Dental, Shanghai, China) nickel-titanium (NiTi) rotary instruments and similar prototypes, differing only by the absence of the flat side. The null hypothesis was that there were no differences between the two tested instruments in terms of cyclic fatigue lifespan. A total of 40 new NiTi instruments (20 F-One and 20 prototypes) were tested in the present study. The instruments were rotated with the same speed (500 rpm) and torque (2 N) using an endodontic motor (Elements Motor, Kerr, Orange, CA, USA) in the same stainless steel, artificial canal (90° angle of curvature and 5 mm radius). A Wilcoxon-Mann-Whitney test was performed to assess the differences in terms of time to fracture and the length of the fractured segment between the flat- and non-flat-sided instruments. Significance was set at p = 0.05. The differences in terms of time to fracture between non-flat and flat were statistically significant (p < 0.001). In addition, the differences in terms of fractured segment length were statistically significant (p = 0.034). The results of this study highlight the importance of flat-sided design in increasing the cyclic fatigue lifespan of NiTi rotary instruments

Fatigue resistance of new and used nickel-titanium rotary instruments: a comparative study

Aim of the present study was twofold. First, to evaluate in vitro, the performance of two different NiTi rotary instruments in one molar case; then, to evaluate their resistance to cyclic fatigue, compared to new ones

In vivo evaluation of operative torque generated by two Nickel-Titanium rotary instruments during root canal preparation

Objectives This in vivo study evaluated the operative torque and preparation time of ProTaper NEXT (Dentsply Maillefer; Ballaigues, Switzerland) and EdgeFile X7 (EdgeEndo; Albuquerque, New Mexico, United States) rotary systems during root canal preparation of maxillary premolars. Materials and Methods Ten double-rooted maxillary premolars with independent canals were selected. Each canal in each tooth was prepared with one of the rotary systems (n = 10), ProTaper NEXT or EdgeFile X7. The instruments were rotated at 300 rpm with maximum torque set at 2 N.cm using an electric motor (KaVo; Biberach, Germany) that automatically recorded torque values at every 1/10th of a second (ds). Statistical Analysis Operative torque (N.cm) and preparation time (s) of the first shaping instrument (size 17/.04) of both rotary systems were recorded and statistically compared using the Mann-Whiney U test with a significance level set at 5%. Results No instrument exhibited flute deformation or underwent intracanal failure. No differences were found between the instruments regarding the maximum (peak) torque values (p > 0.05). EdgeFile X7 17/.04 required significantly less preparation time (3.75 seconds interquartile range [IQR]: 3.2-9.0) than ProTaper NEXT X1 (15.45 seconds IQR: 8.35-21.1) (p < 0.05). The median operative torque values of ProTaper NEXT X1 (0.26 N.cm; IQR: 0.18-0.49) were significantly higher compared with EdgeFile X7 17/.04 (0.09 N.cm; IQR: 0.05-0.17) (p < 0.05). Conclusions Although no difference was found between the median peak torque values of ProTaper NEXT X1 and EdgeFile X7 17/.04 instruments, the operative torque and instrumentation time results were impacted by their different designs and alloys during clinical preparation of root canals

Vestibulo-Ocular Reflex Modification after Virtual Environment Exposure

Immersion in an illusory world is possible by means of virtual reality (VR), where environmental perception is modi bff c1c ed by artificial sensorial stimulation. The application of VR for the assessment and rehabilitation of pathologies affecting the vestibular system, in terms of both diagnosis and care, could represent an interesting new line of research. Our perception of reality is in fact based on static and dynamic spatial information perceived by our senses. During head movements in a virtual environment the images on the display and the labyrinthine information relative to the head angular accelerations differ and therefore a visuo-vestibular conflict is present. It is known that mismatches between visual and labyrinthine information may modify the vestibulo-oculomotor reflex (VOR) gain. We studied the post-immersion modifications in 20 healthy subjects (mean age 25 years) exposed to a virtual environment for 20 min by wearing a head-mounted display. VOR gain and phase were measured by means of harmonic sinusoidal stimulation in the dark before, at the end of and 30 min after VR exposure. A VOR gain reduction was observed in all subjects at the end of VR exposure which disappeared after 30 min. Our data show that exposure to a virtual environment can induce a temporary modi bff c1c cation of the VOR gain. This bff c1c nding can be employed to enable an artificial, instrumental modification of the VOR gain and therefore opens up new perspectives in the assessment and rehabilitation of vestibular diseases

Thermal Conductivity Enhancement of Al2O3 Nanofluid in Ethylene Glycol and Water Mixture

AbstractThe ability of nanofluids that exhibits enhanced thermal performance is acknowledged by researchers through studies since decades ago. However, the observation of thermal properties for nanofluids in water and ethylene glycol based is not fully explored yet. Hence, this paper presents the thermal conductivity of water and ethylene glycol (EG) based Al2O3 nanofluid. The 13 nm sized Al2O3 nanoparticles were dispersed into three different volume ratio of water: EG such as 40:60, 50:50 and 60:40 using a two-step method. The measurement of thermal conductivity was performed using KD2 Pro Thermal Properties Analyzer at working temperatures of 30 to 70 ̊C for volume concentration of 0.5 to 2.0%. The results indicate that the thermal conductivity increases with the increase of nanofluid concentration and temperature. While the percentage of ethylene glycol increase, the range of thermal conductivity decreases due to ethylene glycol properties. The measurement data of the nanofluids give maximum enhancement of thermal conductivity at condition 2.0% volume concentration, temperature of 70 ̊C and for all base fluid

Investigating feedforward neural regulation of circulation from analysis of spontaneous arterial pressure and heart rate fluctuations in conscious rats.

Investigating feedforward neural regulation of circulation from analysis of spontaneous arterial pressure and heart rate fluctuations in conscious rats. Am J Physiol Heart Circ Physiol 296: H202–H210, 2009. First published November 14, 2008; doi:10.1152/ajpheart.00358.2008.—It has been suggested in anesthetized animals that the occurrence of sequences of consecutive beats characterized by systolic arterial pressure (SAP) and RR or pulse interval (PI) changing in the opposite direction (SAP /RR and SAP /RR , nonbaroreflex sequences) might represent the expression of neural cardiovascular regulatory mechanisms operating with feedforward characteristics. The aim of the present study was to study nonbaroreflex sequences in a more physiological experimental model, i.e., in conscious freely moving rats. We studied conscious rats before and after 1) complete autonomic blockade (n 12), 2) sympathetic blockade (n 10), 3) (n 7)- and (n 8)-adrenergic blockade, and 4) parasympathetic blockade (n 10). Nonbaroreflex sequences were defined as three or more beats in which SAP and PI of the following beat changed in the opposite direction. Complete autonomic blockade reduced the number of nonbaroreflex sequences (95.6 9.0 vs. 45.2 4.1, P 0.001), as did sympathetic blockade (80.9 12.6 vs. 30.9 6.1, P 0.001). The selective -receptor blockade did not induce significant changes (80.9 12.5 in baseline vs. 79.0 14.7 after prazosin), whereas -receptor blockade significantly reduced nonbaroreflex sequence occurrence (80.9 12.5 in baseline vs. 48.9 15.3 after propranolol). Parasympathetic blockade produced a significant increase of nonbaroreflex sequences (95.1 6.9 vs. 136.0 12.4, P 0.01). These results demonstrate the physiological role of the nonbaroreflex sequences as an expression of a feedforward type of short-term cardiovascular regulation able to interact dynamically with the feedback mechanisms of baroreflex origin in the neural control of the sinus node