Wideband digital phase comparator for high current shunts

A wideband phase comparator for precise measurements of phase difference of high current shunts has been developed at INRIM. The two-input digital phase detector is realized with a precision wideband digitizer connected through a pair of symmetric active guarded transformers to the outputs of the shunts under comparison. Data are first acquired asynchronously, and then transferred from on-board memory to host memory. Because of the large amount of data collected the filtering process and the analysis algorithms are performed outside the acquisition routine. Most of the systematic errors can be compensated by a proper inversion procedure. The system is suitable for comparing shunts in a wide range of currents, from several hundred of milliampere up to 100 A, and frequencies ranging between 500 Hz and 100 kHz. Expanded uncertainty (k=2) less than 0.05 mrad, for frequency up to 100 kHz, is obtained in the measurement of the phase difference of a group of 10 A shunts, provided by some European NMIs, using a digitizer with sampling frequency up to 1 MHz. An enhanced version of the phase comparator employs a new digital phase detector with higher sampling frequency and vertical resolution. This permits to decrease the contribution to the uncertainty budget of the phase detector of a factor two from 20 kHz to 100 kHz. Theories and experiments show that the phase difference between two high precision wideband digitizers, coupled as phase detector, depends on multiple factors derived from both analog and digital imprint of each sampling system.Comment: 20 pages, 9 figure

A tricky start: The first decade of ethnographic cinema

The earliest encounters between cinema and anthropology occurred while the former was taking its first steps and the latter was trying to better define its disciplinary profile. Among the first to be involved was the Frenchman Félix Regnault, an investigator of many topics and a lifelong supporter of the importance of ethnographic cinema. Racial differences were at the center of his interests, although attempts to highlight them yielded contradictory results. Some years later, the Britain Alfred C. Haddon brought a camera with him on the legendary Cambridge expedition to the Torres Strait (1898) and recorded a few films. The third example discussed here is that of Baldwin Spencer, who, together with Francis Gillen, included the filming of native ceremonies in his studies on the indigenous populations of Central Australia. Not only did technical and logistical problems trouble the start of ethnographic cinema. The theoretical framework of social evolutionism was weakening and anthropology was turning more and more to the study of language, kinship and belief systems. Here the contribution that cinema could make seemed temporarily to be in question

Eugenistas, pero con prudencia

Thinking that one could not describe eugenics like a unique movement, since numerous bound varians took place related to the geographical and cultural context, this article tries to demostrate the peculiarity of the Italian case. If already in 1889 Giuseppe Sergi wanted that the artificial selection take it to end what should make the natural, avoiding the risk of the so called «degeneration», only in the face of the First World War seems to grow the alarm for the decadent quality of the population, finding a more and more wide echo. In 1919 the Siges was born (Società italiana de genetica ed eugenica) shocked under the impression of the difusse fear about the butcher the war had caused. From there from now on fastens a «nazional» direction closely related to the traditional thought and also with the new political temper. A «moderate» direction, Fascist, Catholic, that was built in consonance with the pronatalism of the regime and in rough polemic with the presumed Anglo-Saxon eugenics aberration

Bistable forespore engulfment in Bacillus subtilis by a zipper mechanism in absence of the cell wall

To survive starvation, the bacterium Bacillus subtilis forms durable spores. The initial step of sporulation is asymmetric cell division, leading to a large mother-cell and a small forespore compartment. After division is completed and the dividing septum is thinned, the mother cell engulfs the forespore in a slow process based on cell-wall degradation and synthesis. However, recently a new cell-wall independent mechanism was shown to significantly contribute, which can even lead to fast engulfment in $\sim$ 60 $$ of the cases when the cell wall is completely removed. In this backup mechanism, strong ligand-receptor binding between mother-cell protein SpoIIIAH and forespore-protein SpoIIQ leads to zipper-like engulfment, but quantitative understanding is missing. In our work, we combined fluorescence image analysis and stochastic Langevin simulations of the fluctuating membrane to investigate the origin of fast bistable engulfment in absence of the cell wall. Our cell morphologies compare favorably with experimental time-lapse microscopy, with engulfment sensitive to the number of SpoIIQ-SpoIIIAH bonds in a threshold-like manner. By systematic exploration of model parameters, we predict regions of osmotic pressure and membrane-surface tension that produce successful engulfment. Indeed, decreasing the medium osmolarity in experiments prevents engulfment in line with our predictions. Forespore engulfment may thus not only be an ideal model system to study decision-making in single cells, but its biophysical principles are likely applicable to engulfment in other cell types, e.g. during phagocytosis in eukaryotes

Lucky Triune Brain. Chronicles of Paul D. MacLean's Neuro-Catchword

The triune brain idea has been rated as the most influential in post-war neuroscience. The first part of this article seeks to retrace its genesis and development through the vicissitudes of the research conducted by Paul D. MacLean (1913-2007). Ten years have passed since his death: despite the loss of scientific credit, the apparent simplicity of his tripartite theory continues to exert a certain popular appeal. In the second part of the article an attempt is made to figure out how the transfer from the laboratory to public fruition could happen. The man initially responsible for the operation was MacLean himself, then aided by a few followers who had the means to spread his message of slavation. Against the background of the Cold War, and while Western culture started to realize the threat posed by overpopulation, pollution, exhaustion of critical resources, they deluded themselves that “knowing the brain” might suggest new and more effective approaches to the troubles of the oncoming end of the century. Consulting MacLean’s papers in the archives at the National Library of Medicine (Bethesda, MD) has been essential to this historical reconstruction

A Voltage Calibration Chain for Meters Used in Measurements of EV Inductive Power Charging

The inductive charging of electric vehicles requires specific measurement and calibration systems. In fact, the measurement of power on board involves DC signals, which are superimposed to a significant AC ripple up to or over 150 kHz, depending on the type of charging system. A calibration method that makes use of a phantom power, based on two independent but synchronized circuits, is considered, simulating the charging voltage and current. This paper describes in detail a solution in the realization of the voltage calibration chain, based on the use of a DC voltage calibrator, an injector and a voltage divider.Comment: 2 pages, Conference on Precision Electromagnetic Measurements (CPEM 2018), Paris

Science and Race: Images, Objects, Maps

Introduction to the special issue Science and rac

Forespore Engulfment Mediated by a Ratchet-Like Mechanism

SummaryA key step in bacterial endospore formation is engulfment, during which one bacterial cell engulfs another in a phagocytosis-like process that normally requires SpoIID, SpoIIM, and SpoIIP (DMP). We here describe a second mechanism involving the zipper-like interaction between the forespore protein SpoIIQ and its mother cell ligand SpoIIIAH, which are essential for engulfment when DMP activity is reduced or SpoIIB is absent. They are also required for the rapid engulfment observed during the enzymatic removal of peptidoglycan, a process that does not require DMP. These results suggest the existence of two separate engulfment machineries that compensate for one another in intact cells, thereby rendering engulfment robust. Photobleaching analysis demonstrates that SpoIIQ assembles a stationary structure, suggesting that SpoIIQ and SpoIIIAH function as a ratchet that renders forward membrane movement irreversible. We suggest that ratchet-mediated engulfment minimizes the utilization of chemical energy during this dramatic cellular reorganization, which occurs during starvation

Impact of level densities and γ\gamma-strength functions on rr-process simulations

Studies attempting to quantify the sensitivity of the $r$-process abundances to nuclear input have to cope with the fact that the theoretical models they rely on, rarely come with confidence intervals. This problem has been dealt with by either estimating these intervals and propagating them statistically to the final abundances using reaction networks within simplified astrophysical models, or by running more realistic astrophysical simulations using different nuclear-physics models consistently for all the involved nuclei. Both of these approaches have their strengths and weaknesses. In this work, we use the reaction network code SkyNet to run $r$-process calculations for five trajectories using 49 different neutron-capture rate models. Our results shed light on the importance of taking into account shell effects and pairing correlations in the network calculations.Comment: 11 pages, 7 figure

Asynchronous Phase Comparator for Characterization of Devices for PMUs Calibrator

This paper reports recent progress in developing a new asynchronous digital phase comparator for the precision measurement of phase difference of voltage ratio devices and calibration of functional elements of phasor measurement units (PMUs) calibrator. The phase error of the proposed digital comparator is below 300 nrad at 50 Hz and 100 μrad at 100 kHz with applied voltages ranging between 500 mV and 3 V, whereas the phase error of cables and connectors was estimated to be 4 μrad at 1 MHz. Besides resistive dividers, the phase comparator has been employed for the characterization of frequency behavior of phase difference between the output and input of voltage and transconductance amplifiers for a PMUs calibrator. The system can also be an important tool for phase-frequency characterization of devices employed for specific wideband power measurements