A correlation noise spectrometer for flicker noise measurement in graphene samples

We present a high-resolution digital correlation spectrum analyzer for the measurement of low frequency resistance fluctuations in graphene samples. The system exploits the cross-correlation method to reject the amplifiers' noise. The graphene sample is excited with a low-noise DC current. The output voltage is fed to two two-stage low-noise amplifiers connected in parallel; the DC signal component is filtered by a high-pass filter with a cutoff frequency of 34 mHz. The amplified signals are digitized by a two-channel synchronous ADC board; the cross-periodogram, which rejects uncorrelated amplifiers' noise components, is computed in real time. As a practical example, we measured the noise cross-spectrum of graphene samples in the frequency range from 0.153 Hz to 10 kHz, both in two- and four-wire configurations, and for different bias currents. We report here the measurement setup, the data analysis and the error sources

Targeting kinases with anilinopyrimidines: Discovery of N-phenyl-N'-[4-(pyrimidin-4-ylamino)phenyl]urea derivatives as selective inhibitors of class III receptor tyrosine kinase subfamily

Kinase inhibitors are attractive drugs/drug candidates for the treatment of cancer. The most recent literature has highlighted the importance of multi target kinase inhibitors, although a correct balance between specificity and non-specificity is required. In this view, the discovery of multityrosine kinase inhibitors with subfamily selectivity is a challenging goal. Herein we present the synthesis and the preliminary kinase profiling of a set of novel 4-anilinopyrimidines. Among the synthesized compounds, the N-phenyl-N\u2019-[4-(pyrimidin-4-ylamino)phenyl]urea derivatives selectively targeted some members of class III receptor tyrosine kinase family. Starting from the structure of hit compound 19 we synthesized a further compound with an improved affinity toward the class III receptor tyrosine kinase members and endowed with a promising antitumor activity both in vitro and in vivo in a murine solid tumor model. Molecular modeling simulations were used in order to rationalize the behavior of the title compounds

Primary Realization of Inductance and Capacitance Scales With a Fully Digital Bridge

This article describes an automated electronic fully digital bridge for the comparison of four-terminal-pair (4TP) impedance standards in the audio frequency range. The bridge relative accuracy, which is on the order of 10-6, makes it suitable as a reference bridge for the realization of primary scales of inductance and capacitance in metrology institutes and calibration laboratories. The performances of this bridge were validated by comparing the results of the calibrations of inductance and capacitance standards with those obtained from an existing analog reference system based on the three-voltage method. The article also reports the results of this validation

A fully digital bridge towards the realization of the farad from the quantum Hall effect

This paper presents the implementation of an electronic fully-digital impedance bridge optimized for RC comparisons with equal impedance magnitudes, together with an evaluation of the uncertainty. This bridge has been designed with the goal of realizing the farad directly from the quantum Hall effect with a bridge uncertainty component at the 1E-7 level. Thanks to its simple design, ease of operation and affordability, this bridge is suitable to be industrially manufactured. Together with the increasing availability of graphene quantum Hall resistance standards, this can provide an affordable quantum realization of the unit farad for metrology institutes and calibration centres. In this paper we present the uncertainty budget of an example measurement and the results of the validation of the bridge against a suitably modified version of the traceability chain of the Italian national standard of capacitance. The combined uncertainty of the bridge resulted from repeated measurements (overall measurement time of about 200 min) is 9.2 × 10^−8, suitable for the primary realization of the unit of capacitance from a quantized Hall resistance standard. The crosstalk among the channels of the electrical generator is the most significant uncertainty component, possibly reducible with internal shielding and filtering of the electronic generator

An international comparison of phase angle standards between the novel impedance bridges of CMI, INRIM and METAS

We report here the results of a comparison of electrical impedance standards aimed at evaluating four novel digital impedance bridges developed by the national metrology institutes CMI, INRIM and METAS. This comparison, which is the first of its kind, involved phase angle impedance standards developed by TÜBITAK UME with phase angles of  ± 30° and  ± 60°, and magnitudes ranging from about 100 Ω to 1 MΩ. The comparison demonstrated agreement among the measurement results obtained with the different bridges, and allowed us to gather information on the stability of the phase standards and on more critical aspects related to the characterization of the bridges

Novel digital impedance bridges for the realization of the farad from graphene quantum standards

In the International System of Units, a realization of the impedance units is the quantum Hall effect, a macroscopic quantum phenomenon that produces quantized resistance values. Established experiments employ individual GaAs devices [1], but research is ongoing on novel materials such as graphene, which allows the realization of the units with relaxed experimental conditions. Furthermore, novel digital impedance bridges allow the implementation of simple traceability chains. In the framework of the European EMPIR project 18SIB07 GIQS (Graphene Impedance Quantum Standards), an affordable and easy-to-operate impedance standard combining novel digital impedance bridges and graphene quantum standards has been developed. An onsite comparison of an electronic and a Josephson impedance bridges developed at INRIM (Istituto Nazionale di Ricerca Metrologica, Italy) and PTB (Physikalisch-Technische Bundesanstalt, Germany), respectively, were organized for their mutual validation and to assess their performance in the realization of the farad.Measurements of temperature-controlled impedance standards and of a graphene quantized Hall resistance standard in the AC regime were performed with both INRIM’s and PTB’s bridges. The result of the comparison and the last progresses of the GIQS project are here presented

Next-generation crossover-free quantum Hall arrays with superconducting interconnections

This work presents precision measurements of quantized Hall array resistance devices using superconducting, crossover-free and multiple interconnections as well as graphene split contacts. These new techniques successfully eliminate the accumulation of internal resistances and leakage currents that typically occur at interconnections and crossing leads between interconnected devices. As a result, a scalable quantized Hall resistance array is obtained with a nominal value that is as precise and stable as that from single-element quantized Hall resistance standards

A coaxial cryogenic probe for quantum Hall effect measurements in the AC regime

open9sìThe quantum Hall effect is the basis for the realisation of the resistance and impedance units in the revised International System of units of 2019. This paper describes a cryogenic probe that allows to set graphene Hall devices in quantisation conditions in a helium bath (4.2 K) and magnetic fields up to 6 T, to perform precision measurements in the ac regime with impedance bridges. The probe has a full coaxial wiring, isolated from the probe structure, and holds the device in a TO-8 socket. First characterisation experiments are reported on a GaAs device which shows quantisation at 5.5 T.openMartina Marzano, Ngoc Thanh Mai Tran, Vincenzo D’Elia, Danilo Serazio, Emanuele Enrico, Massimo Ortolano, Klaus Pierz, Jan Kučera, Luca CallegaroMarzano, Martina; Thanh Mai Tran, Ngoc; D'Elia, Vincenzo; Serazio, Danilo; Enrico, Emanuele; Ortolano, Massimo; Pierz, Klaus; Kučera, Jan; Callegaro, Luc

Virtual Training Laboratory for Primary Impedance Metrology

This article presents the concept and some aspects of the physical implementation of a virtual training laboratory (VTL) in the field of primary impedance metrology. The creation of a VTL provides a novel method of disseminating metrological knowledge and expertise in a practical way and at a low cost. It will expose new users to the live experience of operating a digital impedance bridge thus helping to encourage the uptake of this novel and useful impedance measurement technology. The VTL was developed as part of the EMPIR projects VersICal 17RPT04, A versatile electrical impedance calibration laboratory based on digital impedance bridges, and GIQS 18SIB07, Graphene impedance quantum standard