Closed-loop Experimental Setup Research Articles

Physical reservoir computing with FORCE learning in a living neuronal culture

Rich dynamics in a living neuronal system can be considered as a computational resource for physical reservoir computing (PRC). However, PRC that generates a coherent signal output from a spontaneously active neuronal system is still challenging. To overcome this difficulty, we here constructed a closed-loop experimental setup for PRC of a living neuronal culture, where neural activities were recorded with a microelectrode array and stimulated optically using caged compounds. The system was equipped with first-order reduced and controlled error learning to generate a coherent signal output from a living neuronal culture. Our embodiment experiments with a vehicle robot demonstrated that the coherent output served as a homeostasis-like property of the embodied system from which a maze-solving ability could be generated. Such a homeostatic property generated from the internal feedback loop in a system can play an important role in task solving in biological systems and enable the use of computational resources without any additional learning.

Open Hardware for neuro-prosthesis research: A study about a closed-loop multi-channel system for electrical surface stimulations and measurements

Abstract Recent progress in neuro-prosthetic technology gives rise to the hope that in the future blind people might regain some degree of visual perception. It was shown that electrically stimulating the brain can be used to produce simple visual impressions of light blobs (phosphenes). This technology, using electrodes placed on top of the visual cortex, was successfully used to give blind people some degree of visual impression of their surrounding. However, this perception is very far away from natural sight. For developing the next generation of visual prostheses, real-time closed-loop stimulators are required. Such a stimulator measures the actual neuronal activities and on this basis determines the required stimulation pattern. In addition, there is a desire to shrink the diameter of the applied electrodes and increase their spatial density. This leads to the challenge of designing a system that can produce arbitrary stimulation-patterns with up to ± 70 V and with up to 25 mA while measuring neuronal signals with amplitudes in the order of mV. Furthermore, interruptions of the measurements during stimulation should be as short as possible and the system needs to scale to hundreds of electrodes. We discuss how such a system and especially its current pumps and input protection need to be designed and which problems arise. We condense our findings into an example design for which we provide all design files (boards, firmwares and software) as open-source. This is a first step in taking the existing open-source www.open-ephys.org recording system and converting it into a closed-loop experimental setup for neuro-prosthetic research.

The Development and Validation of a Closed-Loop Experimental Setup for Investigating CO2 and H2O Coadsorption Kinetics under Conditions Relevant to Direct Air Capture

A closed-loop experimental setup was developed to investigate the kinetics of CO2 and H2O coadsorption onto a differential bed comprising amine-functionalized nanofibrillated cellulose (NFC) under conditions relevant to direct air capture. The temporal sorbate uptake profiles were determined in the absence of external heat and mass transfer intrusion based on the mass balance in the constant-volume gas phase. The uncertainty of the mass balance calculations caused by the inherent nonuniform gas pressure and temperature within the tubing, valves, and instrumentation was decreased 4-fold with incorporation of a large perfectly mixed gas tank that occupied 94% of the total volume of the closed loop. The preliminary results have revealed the half-times for H2O and CO2 adsorptions of the order of tens of seconds and tens of minutes, respectively. This finding implies that coadsorption on amine-functionalized NFC can be investigated by considering that the H2O loading on the sorbent is at any instance in the eq...

First on-sky demonstration of the piezoelectric adaptive secondary mirror.

We propose using a piezoelectric adaptive secondary mirror (PASM) in the medium-sized adaptive telescopes with a 2-4m aperture for structure and control simplification by utilizing the piezoelectric actuators in contrast with the voice-coil adaptive secondary mirror. A closed-loop experimental setup was built for on-sky demonstration of the 73-element PASM developed by our laboratory. In this Letter, the PASM and the closed-loop adaptive optics system are introduced. High-resolution stellar images were obtained by using the PASM to correct high-order wavefront errors in May 2016. To the best of our knowledge, this is the first successful on-sky demonstration of the PASM. The results show that with the PASM as the deformable mirror, the angular resolution of the 1.8m telescope can be effectively improved.

Self-induced intracerebral gamma oscillations in the human cortex.

Gamma oscillations play a pivotal role in multiple cognitive functions. They enable coordinated activity and communication of local assemblies, while abnormalities in gamma oscillations exist in different neurological and psychiatric diseases. Thus, a specific rectification of gamma synchronization could potentially compensate the deficits in pathological conditions. Previous experiments have shown that animals can voluntarily modulate their gamma power through operant conditioning. Using a closed-loop experimental setup, we show in six intracerebrally recorded epileptic patients undergoing presurgical evaluation that intracerebral power spectrum can be increased in the gamma frequency range (30-80 Hz) at different fronto-temporal cortical sites in human subjects. Successful gamma training was accompanied by increased gamma power at other cortical locations and progressively enhanced cross-frequency coupling between gamma and slow oscillations (3-12 Hz). Finally, using microelectrode targets in two subjects, we report that upregulation of gamma activities is possible also in spatial micro-domains, without the spread to macroelectrodes. Overall, our findings indicate that intracerebral gamma modulation can be achieved rapidly, beyond the motor system and with high spatial specificity, when using micro targets. These results are especially significant because they pave the way for use of high-resolution therapeutic approaches for future clinical applications.

Experimental study of heat transfer enhancement in automobile radiator using Al2O3/water–ethylene glycol nanofluid coolants

An experimental study on heat transfer enhancement in an automobile radiator using Al2O3/water–ethylene glycol (EG) nanofluids is carried out. Heat transfer enhancement studies can help in the design of lighter and more compact radiators for the same given load, which in turn can improve the fuel economy of the automobile. A closed loop experimental setup is designed using a commercial automobile radiator for the study. The effect of adding EG to water on the overall heat conductance (UA) is studied using two mixtures of water–EG proportions, 90:10 and 80:20 (by volume). They showed a reduction in UA by 20% and 25% respectively. Experiments have also been done using Al2O3/water–EG nanofluids. The nanofluid was prepared using an 80:20 mixture and 0.1% (vol.) of Al2O3 nanoparticles. The addition of nanoparticles enhanced the heat transfer performance by 37 %. All the experiments have been conducted at a constant coolant flow rate and coolant inlet temperatures varying from 40 C to 70 C. The results showed that the heat transfer performance of the radiator reduced with the addition of EG and increased with the addition of nanoparticles to the water–EG mixture.

Confined jet array impingement boiling of subcooled aqueous ethylene glycol solution

A closed-loop experimental setup was built to study the confined jet array impingement boiling of 43% mass concentration aqueous ethylene glycol solution at low jet velocities and large degree of subcoolings. A 20mm×40mm rectangular thin metal film with thickness of 0.03mm was used as the heating surface. The in-line jet array had an orifice diameter d=1mm, a dimensionless jet-to-jet spacing S/d=5 or 4, and a dimensionless jet-to-target spacing H/d=1, 1.5 or 3. Experiments were performed at atmospheric pressure with the saturation temperature of 106°C, jet velocities of 0.2m/s, 0.31m/s and 0.5m/s, and liquid subcoolings of 36°C, 46°C and 56°C. It is found that the heat transfer coefficient in the nucleate boiling regime at first increases with the increase of heat flux and then starts to decrease before the critical heat flux (CHF). Jet velocity and jet-to-target spacing have little effects on heat transfer coefficient in the nucleate boiling dominant regime, while subcooling and jet-to-jet spacing play important roles. Not only the jet velocity but also the liquid subcooling has great influences on the boiling inception and CHF. There exists an optimal jet-to-target spacing to achieve the maximum CHF because of the tradeoff between the breakup and confinement (or expel) of vapor bubbles. For the same flow rate, S/d=5 has a higher heat transfer coefficient and CHF than S/d=4.

Experimental Dipole Moments for Nonisolatable Acetic Acid Structures in a Nonpolar Medium. A Combined Spectroscopic, Dielectric, and DFT Study for Self-Association in Solution

Acetic acid can exist in many possible structural forms depending on its surrounding medium. A recently developed inverse problem methodology (J. Phys. Chem. B 2007, 111, 13064-13074) was utilized in order to elucidate acetic acid structures in a dilute nonpolar medium. In this regard, simultaneous and stopped-flow measurements of the bulk solution densities, refractive indices, relative permittivities, and IR spectra of acetic acid in toluene were performed at several different concentrations in a semibatch closed-loop experimental setup at 298.15 K and 0.1013 MPa. This combined IR spectroscopic and dielectric, density, and refractive index analysis was employed in order to distinguish acetic acid structures and to further determine the dipole moments of the monomer, cyclic dimer, and "lumped-sum" open dimers. The infrared spectra were first analyzed to provide qualitative understanding as well as quantitative estimates for each acetic acid species. Subsequently, the dipole moments of these species were calculated using a direct approach which was primarily based on response surface models. The present method allows the determination of individual dipole moments not only for the monomer but also for the cyclic dimer and the open dimer. The results obtained from this study experimentally show that the cyclic dimer with centrosymmetric structure has a dipole moment approximately 0 D. The results also suggest that the linear dimers are present as mixtures of linear dimers structures. The existence of the linear dimers mixture was also indicated by the experimental infrared analysis of the OH-stretching region (particularly for measurements in n-hexane as solvent) and comparison of these spectra with DFT predictions. Finally, the present methodology which incorporates simultaneous physicochemical and spectroscopic analysis is undoubtedly useful for physicochemical characterization for other nonisolatable solute species and self-associated structures in solution.