Linear Interval Approximation of Sensor Characteristics with Inflection Points.

The popularity of smart sensors and the Internet of Things (IoT) is growing in various fields and applications. Both collect and transfer data to networks. However, due to limited resources, deploying IoT in real-world applications can be challenging. Most of the algorithmic solutions proposed so far to address these challenges were based on linear interval approximations and were developed for resource-constrained microcontroller architectures, i.e., they need buffering of the sensor data and either have a runtime dependency on the segment length or require the sensor inverse response to be analytically known in advance. Our present work proposed a new algorithm for the piecewise-linear approximation of differentiable sensor characteristics with varying algebraic curvature, maintaining the low fixed computational complexity as well as reduced memory requirements, as demonstrated in a test concerning the linearization of the inverse sensor characteristic of type K thermocouple. As before, our error-minimization approach solved the two problems of finding the inverse sensor characteristic and its linearization simultaneously while minimizing the number of points needed to support the characteristic.

Analysis of Polarization Images in the Microphysical Blood Parameters Research for the Hematocrit Diagnostics.

The development of non-invasive optoelectronic technologies for human blood monitoring is one of the important research areas for medicine. A critical analysis of optoelectronic methods of blood research and the micromechanical systems based on them is carried out in this article. A design realization of a polarizing portable system for non-invasive monitoring of hematocrit as one of the basic homeostatic constants of the human body containing information about the microphysical parameters of blood cells has been substantiated. A physical model of polarized radiation conversion in a video information system of laser sensing of a biological research object has been formed. Visual and quantitative differences in the spatial distribution of polarization parameters of the scattered radiation for the states of the body with different hematocrit levels have been revealed. A scheme of a multichannel imaging portable system, based on a smartphone using miniature optical and microelectronic components of information conversion for non-invasive monitoring of microphysical blood parameters, has been created. The system implements the principle of polarimetric blood photometry and a multiparametric analysis of the polarization properties of the laser radiation scattered by blood. The developed portable optoelectronic system, based on a smartphone, can be used for rapid blood diagnostics in disaster medicine and the presence of clinical contraindications to the formation of invasive tests. The proposed polarization-based approach is a promising automated alternative to traditional devices and systems for the research of microphysical blood parameters.

Linear Interval Approximation for Smart Sensors and IoT Devices.

In this work, we introduce and use an innovative approach for adaptive piecewise linear interval approximation of sensor characteristics, which are differentiable functions. The aim is to obtain a discreet type of inverse sensor characteristic, with a predefined maximum approximation error, with minimization of the number of points defining the characteristic, which in turn is related to the possibilities for using microcontrollers with limited energy and memory resources. In this context, the results from the study indicate that to overcome the problems arising from the resource constraints of smart devices, appropriate "lightweight" algorithms are needed that allow efficient connectivity and intelligent management of the measurement processes. The method has two benefits: first, low-cost microcontrollers could be used for hardware implementation of the industrial sensor devices; second, the optimal subdivision of the measurement range reduces the space in the memory of the microcontroller necessary for storage of the parameters of the linearized characteristic. Although the discussed computational examples are aimed at building adaptive approximations for temperature sensors, the algorithm can easily be extended to many other sensor types and can improve the performance of resource-constrained devices. For prescribed maximum approximation error, the inverse sensor characteristic is found directly in the linearized form. Further advantages of the proposed approach are: (i) the maximum error under linearization of the inverse sensor characteristic at all intervals, except in the general case of the last one, is the same; (ii) the approach allows non-uniform distribution of maximum approximation error, i.e., different maximum approximation errors could be assigned to particular intervals; (iii) the approach allows the application to the general type of differentiable sensor characteristics with piecewise concave/convex properties.

Review of Microfluidic Methods for Cellular Lysis.

Cell lysis is a process in which the outer cell membrane is broken to release intracellular constituents in a way that important information about the DNA or RNA of an organism can be obtained. This article is a thorough review of reported methods for the achievement of effective cellular boundaries disintegration, together with their technological peculiarities and instrumental requirements. The different approaches are summarized in six categories: chemical, mechanical, electrical methods, thermal, laser, and other lysis methods. Based on the results derived from each of the investigated reports, we outline the advantages and disadvantages of those techniques. Although the choice of a suitable method is highly dependent on the particular requirements of the specific scientific problem, we conclude with a concise table where the benefits of every approach are compared, based on criteria such as cost, efficiency, and difficulty.

Effect of the type of image study (CT or MRI) on some parameters of neuronavigation-assisted procedures.

AIM: The aim of this study was to determine the effect of the applied method of image investigation (CT or MRI) on the following parameters of the neuronavigation (NN) assisted procedure: "number of attempts for registration", "duration of registration" and "registration accuracy". PATIENTS AND METHODS: A total of 195 patients with various cranial pathological lesions underwent neuronavigation-assisted surgery between March 2003 and December 2005 at the Clinic of Neurosurgery of St. I. Rilsky University Hospital, Medical University, Sofia. All of them were included in our study. CT based registration was realized in 81 patients of our series and MR based registration--in 114 patients. The patients were examined and followed up in a standardized manner. We conducted a prospective study on the effect of the type of image investigation (either CT or MRI) on the parameters registration accuracy, number of attempts for registration and duration of registration. Statistical analysis was performed using a one-factor non-parametric rank analysis (Friedman ANOVA) with a factor "type of image study" which had four sublevels: "MR I", "CT", MRI+MRI Angiography" and "MRI+CT". Multiple Hotelling F-contrasts were applied; the level of statistical significance was 95% (Statistica 6.0, 2001, Statsoft, Tulsa, USA). RESULTS: In the series, the best (the lowest digital expression) mean registration accuracy was demonstrated in MRI based neuronavigation (1.6 mm). Besides that, in MRI-NN the number of attempts for registration was smaller and the time necessary for registration was shorter in comparison with CT-NN. In the "MR I+CT" subgroup the mean values of the investigated parameters were lower in comparison with the other three subgroups. Nevertheless, the differences were not statistically significant because of the wide statistical dispersions of the obtained results and the small number of patients investigated in this subgroup. ANOVA did not show statistically significant difference between the number of attempts for registration, the duration of registration and the registration accuracy in CT and MR-based neuronavigation-assisted procedures. CONCLUSION: We did not found any statistically significant differences between CT- and MRI-based neuronavigation with respect to the accuracy and reliability of the methods. The type of image study that should be used for neuronavigation depends on the specific characteristics of the corresponding pathological lesion.

Neuronavigated surgery of intracranial cavernomas--enthusiasm for high technologies or a gold standard?

AIM: The aim of this study was to investigate the effect of neuronavigation on the following parameters: "skin incision", "craniotomy", "intraoperative anatomical orientation", "dissection guiding", "localization of the pathological formation", "assessment of the degree of resection" and "duration of surgical procedure" in resections of intracranial cavernomas and to specify the indications for neuronavigation in their surgical treatment. PATIENTS AND METHODS: The present prospective study included 20 patients with intracranial cavernomas who underwent neuronavigated surgery between March 2003 and December 2005 at the Clinic of Neurosurgery of the "St. I. Rilsky" University Hospital, Medical University, Sofia. The female/male ratio in the series was 9/11 (45%-55%). The patients' mean age was 27.96 +/- 11.61 years (age range 1.2 to 44 years). The patients were examined and followed up in a standard manner. RESULTS: Cavernous malformations were totally removed in 19 patients. One patient with thalamic cavernoma underwent navigated endoscopic biopsy. There was no morbidity or mortality associated with the method. Neuronavigation allowed precise localization and individual design of the skin incision and craniotomy. Neuronavigated intraoperative anatomical orientation, dissection guiding, localization of the pathological formation, and assessment of degree of resection were evaluated as markedly useful. They resulted in excellent surgery results and reduced operation time in comparison with the conventional surgery. CONCLUSION: In intracranial cavernomas frameless stereotaxy provides the surgeon with useful feedback in the preoperative anatomical orientation, the planning and simulation of surgical approach, the intraoperative navigation, in avoiding vital neurovascular structures, in the assessment of the degree of resection and the identification of possible residual parts. That is why cavernous malformations are among the most common indications for cranial neuronavigation.

Cranial neuronavigation--a step forward or a step aside in modern neurosurgery.

Neuronavigation is a result of the introduction and integration of high technologies into modern neurosurgery. The method is becoming increasingly available, and more than ever, its "fashionable", ungrounded application (literally, in each neurosurgical procedure) requires objective evaluation of its real usefulness. The aim of the present survey was to analyze the use of neuronavigation in the general fields of modern cranial neurosurgery. The reliability of the classical method of brain lesion localization was compared to neuronavigated localization. We studied the neuronavigation assisted interventions in tumor surgery, skull-base surgery, biopsies, neuroendoscopy, functional neurosurgery, vascular neurosurgery and surgical procedures in the proximity of functionally important cortical zones. We showed the modern tendencies in neuronavigation and outlined the social and economic aspects of neuronavigation-assisted neurosurgery. A summary of the advantages and disadvantages of frameless stereotaxy is made.

Role of neuronavigation in the resection of intracranial arteriovenous malformations.

AIM: The aim of this study was to investigate the effect of neuronavigation on the following parameters: "skin incision", "craniotomy", "intraoperative anatomical orientation", "dissection guiding", "localization of the pathological formation", "assessment of the degree of resection" and "duration of surgical procedure" in the resection of intracranial arteriovenous malformations (AVMs) and to specify the indications for application of neuronavigation in the surgical treatment of AVMs. METHODS: Five neuronavigation-assisted resections of intracranial AVMs were performed between March 2003 and December 2005 at the Clinic of Neurosurgery of St. I. Rilsky University Hospital, Medical University, Sofia. The female/male ratio in the series was 2:3 (40%:60%). The patients' mean age was 28.2 +/- 18.27 (range 10 to 56) years. The study was prospective in design. Patients were examined and followed in a standardized manner. RESULTS: Arteriovenous malformations were totally removed in all 5 cases of neuronavigation-assisted resections. We did not observe any morbidity or mortality associated with the method. Neuronavigation allowed precise localization and individual design of the skin incision and craniotomy. Neuronavigation facilitated the surgeon during intraoperative anatomical orientation. Dissection guiding, localization of the formation and assessment of the degree of resection were assessed as markedly useful. This resulted in reduced duration of surgery compared to conventional neurosurgery. CONCLUSIONS: In AVMs resection neuronavigation optimizes surgical approach by visualizing the relationship ofAVMs to the skull and various critical anatomical structures. Deep vessel components and nidus margins, especially in the vicinity of the ventricles can be identified precisely. Neuronavigation can improve the early post-operative results in cerebral AVMs reducing operating time and blood loss.