Biomimetic Sonar for Electrical Activation of the Auditory Pathway

Relying on the mechanism of bat’s echolocation system, a bioinspired electronic device has been developed to investigate the cortical activity of mammals in response to auditory sensorial stimuli. By means of implanted electrodes, acoustical information about the external environment generated by a biomimetic system and converted in electrical signals was delivered to anatomically selected structures of the auditory pathway. Electrocorticographic recordings showed that cerebral activity response is highly dependent on the information carried out by ultrasounds and is frequency-locked with the signal repetition rate. Frequency analysis reveals that delta and beta rhythm content increases, suggesting that sensorial information is successfully transferred and integrated. In addition, principal component analysis highlights how all the stimuli generate patterns of neural activity which can be clearly classified. The results show that brain response is modulated by echo signal features suggesting that spatial information sent by biomimetic sonar is efficiently interpreted and encoded by the auditory system. Consequently, these results give new perspective in artificial environmental perception, which could be used for developing new techniques useful in treating pathological conditions or influencing our perception of the surroundings

Influence of the fabrication accuracy of hot-embossed PCL scaffolds on cell growths

Polycaprolactone (PCL) is a biocompatible and biodegradable polymer widely used for the realization of 3D scaffold for tissue engineering applications. The hot embossing technique (HE) allows the obtainment of PCL scaffolds with a regular array of micro pillars on their surface. The main drawback affecting this kind of micro fabrication process is that such structural superficial details can be damaged when detaching the replica from the mold. Therefore, the present study has focused on the optimization of the HE processes through the development of an analytical model for the prediction of the demolding force as a function of temperature. This model allowed calculating the minimum demolding force to obtain regular micropillars without defects. We demonstrated that the results obtained by the analytical model agree with the experimental data. To address the importance of controlling accurately the fabricated microstructures, we seeded on the PCL scaffolds human stromal cell line (HS-5) and monocytic leukemia cell line (THP-1) to evaluate how the presence of regular or deformed pillars affect cells viability. In vitro viability results, scanning electron and fluorescence microscope imaging analysis show that the HS-5 preferentially grows on regular microstructured surfaces, while the THP-1 on irregular microstructured ones

Noise measurements in multiloop superconducting interferometers

Noise measurements on multiloop dc SQUIDs, fabricated with Nb‐NbOx‐PbAuIn and Pb‐alloy Josephson tunnel junctions and well coupled with the external world by an input coil, we performed in flux locked loop mode. To achieve this task, we built a reliable low‐cost control electronics to detect the voltage output of the SQUID. The results show that for multiloop dc SQUIDs with single‐junction critical currents larger than 20 μA and an inductive parameter βL less than 4.5, an intrinsic white‐energy spectral density of about 100h can be obtained independently of the technology used to fabricate the junctions. Furthermore, the Nb‐NbOx‐PbAuIn dc SQUIDs have a lower 1/f  noise than the Pb‐alloy ones

A planar second-order DC SQUID gradiometer

In this work we describe a DC SQUID gradiometer, sensitive to the second spatial derivative of the magnetic field. The sensitive area of the gradiometer is the inductive body of the DC SQUID itself. The isoflux line distribution-generated by a dipolar source, obtained by performing magnetic measurements with an array of such detectors, is relatively complicated, but its localisation capability is similar to that one usually achieves with axial detector arrays. Planar gradiometers also show a better resolution for near sources and a stronger rejection of far disturbances. The final device is expected to have an inductance of a few hundreds of pH in order to obtain performances typical of a low noise DC SQUID. The pick-up coils will be the combination of four square holes of 500 μm side with a 1.05 cm baseline. Due to the magnetic field concentration (in the final device it can be a factor 10) the gradiometer will have a sensitivity of 10 -11 T m -2 Hz - 1/2 and a field sensitivity of about 2 fT Hz - 1/2 . Some preliminary results, obtained on detectors with an intermediate area between the prototype and final device, are reported here. The process used to fabricate this second-order gradiometer is based on Nb-NbO(x)-PbAuIn Josephson tunnel junctions. Some possible improvements will also be described. In this work we describe a DC SQUID gradiometer, sensitive to the second spatial derivative of the magnetic field. The sensitive area of the gradiometer is the inductive body of the DC SQUID itself. The isoflux line distribution generated by a dipolar source, obtained by performing magnetic measurements with an array of such detectors, is relatively complicated, but its localization capability is similar to that usually achieved with axial detector arrays. Planar gradiometers also show a better resolution for near sources and a stronger rejection of far disturbances. The final device is expected to have an inductance of a few hundred pH in order to obtain performances typical of a low noise DC SQUID. The pick-up coils will be a combination of four square holes of 500 μm side with a 1.05 cm baseline. Due to the magnetic field concentration (in the final device it can be a factor of 10) the gradiometer will have a sensitivity of 10 -11 T m -2 Hz - 1/2 and a field sensitivity of about 2 fT Hz - 1/2. Some preliminary results, obtained on detectors with an intermediate area between the prototype and final device, are reported here. The process used to fabricate this second-order gradiometer is based on Nb-NbO x-PbAuIn Josephson tunnel junctions. Some possible improvements are also described

Mobile TV with long time interleaving and fast zapping

The main challenge for provisioning of Mobile TV services is to overcome long burst errors as are often found in mobile reception conditions. Long time interleaving can be implemented by means of Application Layer FEC (AL-FEC) to increase the time diversity of the signal and thereby its robustness against burst errors. The main obstacle of long time interleaving for streaming services is the increase in service tune-in time, which significantly decreases the Quality of Experience (QoE) of end users. That is why today's Mobile TV systems are provisioned in a way to minimize the time interleaving length to provide an acceptable tune-in time, though the service robustness would significantly benefit from a longer interleaving length. This paper presents a new way of service provisioning that marries fast zapping and long time interleaving by combining Layer-Aware FEC and layered media codecs with unequal time interleaving and an appropriate transmission scheduling. The effect of the proposed scheme on the QoE as well as the service tune-in time is analyzed. Simulation results within a Gilbert-Elliot channel report the benefit of the proposed scheme, which for the first time enables broadcast services with fast tune-in and at the same time long time interleaving

Nature Inspired Plasmonic Structures: Influence of Structural Characteristics on Sensing Capability

Surface enhanced Raman scattering (SERS) is a powerful analytical technique that allows the enhancement of a Raman signal in a molecule or molecular assemblies placed in the proximity of nanostructured metallic surfaces, due to plasmonic effects. However, laboratory methods to obtain of these prototypes are time-consuming, expensive and they do not always lead to the desired result. In this work, we analyse structures existing in nature that show, on a nanoscale, characteristic conformations of photonic crystals. We demonstrate that these structures, if covered with gold, change into plasmonic nanostructures and are able to sustain the SERS effect. We study three different structures with this property: opal, a hydrated amorphous form of silica (SiO2 center dot nH(2)O); diatoms, a kind of unicellular alga; and peacock tail feather. Rhodamine 6G (down to 10(-12) M) is used to evaluate their capability to increase the Raman signal. These results allow us to define an alternative way to obtain a high sensitivity in Raman spectroscopy, currently achieved by a long and expensive technique, and to fabricate inexpensive nanoplasmonic structures which could be integrated into optical sensors

Tracing and analysis of 288 early SARS-CoV-2 infections outside China: A modeling study

Background In the early months of 2020, a novel coronavirus disease (COVID-19) spread rapidly from China across multiple countries worldwide. As of March 17, 2020, COVID-19 was officially declared a pandemic by the World Health Organization. We collected data on COVID-19 cases outside China during the early phase of the pandemic and used them to predict trends in importations and quantify the proportion of undetected imported cases. Methods and findings Two hundred and eighty-eight cases have been confirmed out of China from January 3 to February 13, 2020. We collected and synthesized all available information on these cases from official sources and media. We analyzed importations that were successfully isolated and those leading to onward transmission. We modeled their number over time, in relation to the origin of travel (Hubei province, other Chinese provinces, other countries) and interventions. We characterized the importation timeline to assess the rapidity of isolation and epidemiologically linked clusters to estimate the rate of detection. We found a rapid exponential growth of importations from Hubei, corresponding to a doubling time of 2.8 days, combined with a slower growth from the other areas. We predicted a rebound of importations from South East Asia in the successive weeks. Time from travel to detection has considerably decreased since first importation, from 14.5 +/- 5.5 days on January 5, 2020, to 6 +/- 3.5 days on February 1, 2020. However, we estimated 36% of detection of imported cases. This study is restricted to the early phase of the pandemic, when China was the only large epicenter and foreign countries had not discovered extensive local transmission yet. Missing information in case history was accounted for through modeling and imputation. Conclusions Our findings indicate that travel bans and containment strategies adopted in China were effective in reducing the exportation growth rate. However, the risk of importation was estimated to increase again from other sources in South East Asia. Surveillance and management of traveling cases represented a priority in the early phase of the epidemic. With the majority of imported cases going undetected (6 out of 10), countries experienced several undetected clusters of chains of local transmissions, fueling silent epidemics in the community. These findings become again critical to prevent second waves, now that countries have reduced their epidemic activity and progressively phase out lockdown.Author summaryWhy was this study done? Originating from China, COVID-19 outbreak has now become a global pandemic, with more than 4 million cases reported across all continents. Underdetection of imported cases from China in the early phase of the epidemic played a crucial role in the spreading of the virus across and within countries. We quantified importations over time in light of the implemented travel ban in China and assessed delay and rate of detection of the first imported cases responsible for seeding the epidemic across multiple countries. What did the researchers do and find? We collected information on all international cases outside China officially confirmed in the period from January 3 to February 13, 2020. We developed a statistical model to predict trends in importations and predicted a rebound effect in importations from South East Asia. By analyzing clusters of local transmission, we estimated the detection rate at 36%. What do these findings mean? Travel bans adopted in China contributed to reducing the growth rate of exportations; however, they did not prevent international seeding. The majority of imported cases went undetected, generating extensive chains of local transmission in countries outside China. This led to silently spreading epidemics in seeded countries

Preparedness and vulnerability of African countries against importations of COVID-19: a modelling study

Background The novel coronavirus disease 2019 (COVID-19) epidemic has spread from China to 25 countries. Local cycles of transmission have already occurred in 12 countries after case importation. In Africa, Egypt has so far confirmed one case. The management and control of COVID-19 importations heavily rely on a country's health capacity. Here we evaluate the preparedness and vulnerability of African countries against their risk of importation of COVID-19.Methods We used data on the volume of air travel departing from airports in the infected provinces in China and directed to Africa to estimate the risk of importation per country. We determined the country's capacity to detect and respond to cases with two indicators: preparedness, using the WHO International Health Regulations Monitoring and Evaluation Framework; and vulnerability, using the Infectious Disease Vulnerability Index. Countries were clustered according to the Chinese regions contributing most to their risk.Findings Countries with the highest importation risk (ie, Egypt, Algeria, and South Africa) have moderate to high capacity to respond to outbreaks. Countries at moderate risk (ie, Nigeria, Ethiopia, Sudan, Angola, Tanzania, Ghana, and Kenya) have variable capacity and high vulnerability. We identified three clusters of countries that share the same exposure to the risk originating from the provinces of Guangdong, Fujian, and the city of Beijing, respectively.Interpretation Many countries in Africa are stepping up their preparedness to detect and cope with COVID-19 importations. Resources, intensified surveillance, and capacity building should be urgently prioritised in countries with moderate risk that might be ill-prepared to detect imported cases and to limit onward transmission. Funding EU Framework Programme for Research and Innovation Horizon 2020, Agence Nationale de la Recherche. Copyright (C) 2020 Elsevier Ltd. All rights reserved