Istituto Nazionale di Ricerca Metrologica
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Self‐organized Criticality in Neuromorphic Nanowire Networks With Tunable and Local Dynamics
Full text linkSelf-organized criticality (SOC) has attracted large interest as a key property for the optimization of information processing in biological neural systems. Inspired by this synergy, nanoscale self-organizing devices are demonstrated to emulate critical dynamics due to their complex nature, proving to be ideal candidates for the hardware implementation of brain-inspired unconventional computing paradigms. However, controlling the emerging critical dynamics and understanding its relationship with computing capabilities remains a challenge. Here, it is shown that memristive nanowire networks (NWNs) can be programmed in a critical state through appropriate electrical stimulation. Furthermore, multiterminal electrical characterization reveals that network areas can establish spatial interactions endowing local critical dynamics. The impact of such tunable and local dynamics versus the information processing in the network is experimentally analyzed through in materia implementation of nonlinear transformation (NLT) tasks, in the framework of reservoir computing. As for brain where cortical areas are specialized for a certain function, it is demonstrated that the computing performance of nanowire networks rely on the response of reduced subsets of outputs, which may show critical dynamics or not, depending on the specificity of the task. Such brain-like behavior can lead to neuromorphic systems based on self-organizing networks with reduced hardware complexity by exploiting their local and specialized behavior
Neuromorphic Light‐Responsive Organic Matter for in Materia Reservoir Computing
Full text linkMaterials able to sense and respond to external stimuli by adapting their internal state to process and store information, represent promising candidates for implementing neuromorphic functionalities and brain-inspired computing paradigms. In this context, neuromorphic systems based on light-responsive materials enable the use of light as information carrier, allowing to emulate basic functions of the human retina. In this work it is demonstrated that optically-induced molecular dynamics in azopolymers can be exploited for neuromorphic-type of data processing in the analog domain and for computing at the matter level (i.e., in materia). Besides showing that azopolymers can be exploited for data storage, it is demonstrated that the adaptiveness of these materials enables the implementation of synaptic functionalities including short-term memory, long-term memory, and visual memory. Results show that azopolymers allow event detection and motion perception, enabling physical implementation of information processing schemes requiring real-time analysis of spatio-temporal inputs. Furthermore, it is shown that light-induced dynamics can be exploited for the in materia implementation of the unconventional computing paradigm denoted as reservoir computing. This work underscores the potential of azopolymers as promising materials for developing adaptive, intelligent photo-responsive systems that mimic some of the complex processing abilities of biological systems
Establishment of good practices for the usage of machine-actionable core metrological terminology
No full textWith progressing digitalisation of scientific research and metrological services, the exchange and reuse of data benefits from the usage of standard metadata schemas and controlled terminologies as a “common language” to describe, search and filter data. However, no framework yet unifies metrology-related endeavours to rigorously deal with machine-actionable data. Normative terminology documents often lack machine-readability, while community-driven machine-readable terminologies lack both metrological rigour and comprehensiveness. The resulting fragmented landscape makes it difficult for end users to adopt a good practice in registering data. Our contribution takes a step to cover this gap, by providing a unified overview of all relevant recommendations in a comprehensive and accessible way, in agreement with authoritative regulation bodies, current good practices, and existing digital-object validation platforms. Our activity will focus on a machine-readable version of the International Vocabulary of Metrology (VIM)
Uncertainty Evaluation of a Supercapacitor Equivalent Circuit Parameters
No full textThe accurate simulation of the behavior of a supercapacitor (SC) and its control in an electronic system, cannot be achieved by a simple one-branch circuit. A correct simulation requires the use of more complex equivalent circuits, with at least two or three branches. These equivalent circuits guarantee a good reproduction of the device’s behavior. The effectiveness of an equivalent circuit is linked to the limits of the circuit parameter identification, which is commonly achieved by means of the voltage and current measurement of charge and self-discharge cycles. The uncertainty in the identification of these circuit parameters, is dependent on the accuracy of the measurement instrumentation and on the repeatability of the SC. A cycle for determining the parameters can extend over a few hours for larger SCs, also considering the time needed by the software algorithm for the parameter identification. Therefore, having a large set of cycles including the parameters determination is a time-consuming procedure. In this study, an efficient method for the repeatability and uncertainty assessment of the equivalent circuit parameters is proposed; this approach relies on a limited set of experimental data and on a single parameter identification process. The analysis presented in this paper highlights how the limited repeatability of the device is an important source of uncertainty for the identification of the equivalent circuit parameters, but it is not the main one for all parameters
Mitotane activates ATF4/ATF3 axis triggering endoplasmic reticulum stress in adrenocortical carcinoma cells
No full textAssignment of IR spectra of ethanol at Brønsted sites of H-ZSM-5 to monomer adsorption using a Fermi resonance model
Full text linkUnderstanding how alcohol molecules interact with the Brønsted acid sites (BAS) of zeolites is a prerequisite to the design of zeolite catalysts and catalytic processes. Here, we report IR spectra for the adsorption of ethanol on a highly crystalline sample of H-ZSM-5 zeolites exposed to ethanol gas at increasing pressure. We use density functional theory in combination with a FERMI resonance model to assign the measured spectra to a single adsorbed ethanol molecule per BAS. Specifically, we assign the bands at 2450 cm−1 and 1670 cm−1 to a FERMI resonance between the fundamental (Z)O-H stretching band of a single-ethanol-loaded BAS and the first overtone of the (Z)O-H out-of-plane bending. We conclude that adsorbed dimers do not contribute in a noticeable way up to a concentration of almost one ethanol molecule per BAS site. We further show that hybrid functionals (B3LYP) are required to get a close match between the predicted and experimental spectra, whereas commonly used generalized gradient type functionals such as PBE incorrectly describe the potential energy surface. They overestimate the redshift of the OH stretching band on hydrogen bond formation which results in an erroneous assignment of the IR bands
Metrological traceability of moisture/water content measurements
No full textThis paper explains advantages and disadvantages of the measurement methods for moisture and water content
determinations in plant-based materials, in order to identify the method providing the best metrological features.
The term “moisture” is generic and it does not identify a specific measurand. In this sense, to declare proper
Calibration and Measurement Capabilities (CMCs) and to develop Certified Reference Materials (CRMs), a better
specification of the measurand should be given. Currently, no CMCs for moisture or water content measurements
in the plant-origin bulk materials, as well as respective CRMs, are available in the Key Comparison Database
(KCDB) published on the website of the Bureau International del Poids et Mesures (BIPM). Undoubtedly, those
CMCs and CRMs, characterised for water content, are crucial and essential to provide metrological traceability of
measurement results for the quality assessment of plant-origin bulk materials in the agricultural sector
Comparison between an optical pressure standard based on multi-reflection interferometric technique and conventional primary standards
Full text linkAn optical pressure standard, based on a multi-reflection interferometric technique, has been recently developed. This quantum-based standard realizes the pascal through the measurement of the refractive index of a gas by an unbalanced homodyne interferometer and it is currently capable of measuring gas pressure with a relative uncertainty of 10 ppm at 100 kPa. The performance of such optical-based standard have been preliminary evaluated by comparing it with two conventional primary pressure standards, namely a force balanced piston gauge and a pressure balance, in the range from 400 Pa to 120 kPa. This work describes the performed study and discusses the results, which demonstrated the agreement between the optical pressure standard and the conventional standards in the considered range, within their related uncertainties (k = 1)
Impact of simultaneous exposure to RF and gradient electromagnetic fields on implant MR safety labeling
Full text linkPurpose: To investigate whether heating contributions produced by radiofrequency (RF) and gradient fields superpose sufficiently at the worst-case locations to justify their simultaneous consideration in magnetic resonance imaging (MRI) implant safety labeling. Theory and methods: Six implant models were positioned in an ASTM phantom and realistically implanted in two anatomical human models, and exposed to gradient and RF fields at 64 MHz and 128 MHz. The simulations with the anatomical body models considered different axial exposure landmarks inside the RF and gradient body coils. The exposures were scaled to represent two sets of scenarios: either limited by the implant's MR conditional labeling to a fixed peak temperature rise, or representing an EPI or TrueFISP examination with clinically relevant parameters, where the implant label is not limiting. Results: The temperature enhancement due to the combined RF and gradient sources, evaluated with respect to the maximum values obtained separately, depends on the implant, pulse sequence, and exposure landmark. A maximum relative enhancement of about 65% was found in the ASTM phantom, and maximum absolute enhancements above 0.3 K were found in anatomical models with realistic pulse sequences. Conclusion: There are clinically relevant MR examination scenarios where the maximum heating contributions produced by RF and gradient fields combine, enhancing the local peak temperature increase beyond that obtained from either assessment alone. The results prove to be useful for defining safety margins on the maximum allowable temperature increase, avoiding the requirement of a combined gradient coil and RF test
An Approach for Reliable Calibrations of Ultra-high Value Resistors with the Dual Source Bridge
Full text linkAt the Istituto Nazionale di Ricerca Metrologica (INRiM), an approach for reliably calibrating ultra-high-value resistors with the dual source bridge (DSB) is proposed as part of the INRiM knowledge transfer task. This approach is particularly suitable for commercial DSBs, which can be used by electrical calibration laboratories for their activities for external clients. The approach is based on ratio measurements, metrological triangulation rule and measurement compatibility. The proposed reliable calibration value is the corrected weighted mean of three intermediate calibration values which must satisfy a strict triangulation rule and be compatible within small uncertainties. This approach helps to reduce systematic errors or to include them into the uncertainty of the corrected weighted mean. For this paper the method was applied to three high value resistors using a commercial DSB to obtain a reliable calibration value of a 1 PX resistor. This technique meets the requirements of the EN 17025 standard for risk assessment of calibration activities