An Open-Source Virtual Reality System for the Measurement of Spatial Learning in Head-Restrained Mice.

Head-restrained behavioral experiments in mice allow neuroscientists to observe neural circuit activity with high-resolution electrophysiological and optical imaging tools while delivering precise sensory stimuli to a behaving animal. Recently, human and rodent studies using virtual reality (VR) environments have shown VR to be an important tool for uncovering the neural mechanisms underlying spatial learning in the hippocampus and cortex, due to the extremely precise control over parameters such as spatial and contextual cues. Setting up virtual environments for rodent spatial behaviors can, however, be costly and require an extensive background in engineering and computer programming. Here, we present a simple yet powerful system based upon inexpensive, modular, open-source hardware and software that enables researchers to study spatial learning in head-restrained mice using a VR environment. This system uses coupled microcontrollers to measure locomotion and deliver behavioral stimuli while head-restrained mice run on a wheel in concert with a virtual linear track environment rendered by a graphical software package running on a single-board computer. The emphasis on distributed processing allows researchers to design flexible, modular systems to elicit and measure complex spatial behaviors in mice in order to determine the connection between neural circuit activity and spatial learning in the mammalian brain.

An Improved TDOA Method for Land-Based Long-Range HF Skywave Source Geolocation and Experimental Results.

The real-time information of the unknown ionospheric environments is difficult to obtain, plaguing the timely and accurate geolocation of high frequency (HF) sources. In this paper, we propose an improved HF skywave source geolocation method based on the time-difference-of-arrival (TDOA) with the semidefinite programming (SDP), and model HF signal propagation paths as paths with significant non-line-of-sight (NLOS) biases. With this method, no priori information about the ionosphere, especially the priori ionospheric virtual heights of reflection, is necessary while timely and accurately geolocating the HF sources. Furthermore, we use the ray tracing technique and build a 3D ionospheric electron density gridded matrix model to simulate realistic HF signal propagation paths. In the simulations, the proposed method is compared with existing methods, and detailed geolocation error distribution maps are given. In the experiments, HF I/Q data captured from different types of HF transmitters are located by six receivers with time synchronization. Simulated and experimental results show that the proposed method improves the positioning accuracy by about 50% compared with existing methods under the same conditions, and the average relative positioning error is less than 2.7%.

Tuning the Light Response of Strong Polyelectrolyte Brushes with Counterions.

In this work, a negatively charged poly(3-sulfopropyl methacrylate potassium) (PSPMA) brush has been employed as a model system to demonstrate the tuning of the light response of strong polyelectrolyte brushes (SPBs) with counterions. The substitution of K+ counterions by azobenzene-containing counterions (Azo-N+) renders the PSPMA brush light-responsive in aqueous solutions. Nevertheless, the strength of the light response of the PSPMA brush is weak due to the inefficient disassembly of the micelle-like aggregates in the brush upon irradiation with ultraviolet light. Counterion mixtures of Azo-N+ and K+ are employed to realize a strong light response of the PSPMA brush by incorporating a reasonable amount of Azo-N+ counterions into the brush. The strength of the light response of the PSPMA brush can be tuned by the mole ratio of Azo-N+ to K+. Furthermore, properties including the hydration and conformation of the PSPMA brush can be reversibly switched via alternating ultraviolet and visible light irradiation. This work opens up the opportunities available for the use of counterions to tune the light response of SPBs.

The diagnostic value of magnetic resonance urography for detecting ureteric obstruction: a systematic review and meta-analysis.

OBJECTIVE: To evaluate the diagnostic accuracy of magnetic resonance urography (MRU) and determine its value for detecting ureteric obstruction. METHODS: The electronic databases, including PubMed, Embase and the Cochrane library, were systematically searched for studies published throughout September 2018. The summary of sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR) and receiver operating characteristic (ROC) curves was assessed to evaluate the diagnostic accuracy of MRU. Subgroup analyses were conducted based on the mean age of the included patients (adults or children). RESULTS: Eight studies with a total of 594 patients were included. The summary of the sensitivity and specificity of MRU for diagnosing ureteric obstruction was 0.94 and 0.87, respectively. Furthermore, the pooled PLR and NLR were 7.33 and 0.07, respectively. The DOR of MRU for detecting ureteric obstruction was 95.12. In addition, the summary of the area under the ROC of MRU was 0.96. Finally, the specificity, PLR and area under the ROC of MRU for diagnosing ureteric obstruction in adults were higher than children, while the sensitivity of MRU in adults was lower than children. CONCLUSIONS: These findings suggested a relatively high diagnostic value of MRU for detecting ureteric obstruction. Moreover, the diagnostic accuracy of MRU in adults was higher than in children. KEY MESSAGE Magnetic resonance urography (MRU) in detecting ureteric obstruction has relatively better sensitivity, specificity, PLR, NLR, DOR and AUC. The diagnostic value, including specificity, PLR and AUC of MRU in adults, was higher than in children, while the sensitivity of MRU in adults was lower than in children.

Counterion-Tunable Thermosensitivity of Strong Polyelectrolyte Brushes.

In this work, poly(sodium styrene sulfonate) brushes have been employed as a precursor to prepare thermosensitive strong polyelectrolyte brushes (SPBs) through a counterion exchange strategy. The substitution of hydrophilic Na+ counterions by hydrophobic tetraalkylphosphonium counterions leads to a thermoresponsivity of the SPBs. The thermosensitive properties including hydration, stiffness, and surface water wettability of the SPBs can be modulated by the type of the tetraalkylphosphonium counterions. Nevertheless, the wet thickness of the SPBs with tetraalkylphosphonium counterions does not exhibit an obvious temperature dependency due to the high steric barrier in the crowded environment of SPBs generated by the large tetraalkylphosphonium counterions. The mixtures of small Na+ counterions and large tetraalkylphosphonium counterions are employed to realize the thermosensitive wet thickness without sacrificing other thermoresponsive properties of the SPBs because the mixed counterions can bring both a certain hydrophobicity and some free space to the brushes. This work opens up the opportunities available for the use of counterions to tune the thermosensitivity of SPBs.

Controlling Hydrogel Properties by the Cooperative Harvesting of the Components of Sunlight.

The utilization of the full spectrum of sunlight from ultraviolet to infrared to cooperatively control the properties of hydrogels is the key to developing efficient sunlight-responsive hydrogels, but there are significant challenges. The photoresponsive hydrogel developed here formed by azobenzene-containing polyzwitterionic chains possesses capabilities for simultaneously utilizing light from the ultraviolet to the infrared to cooperatively facilitate the gel-to-sol transitions. The ultraviolet and visible light can be converted into mechanical energy simultaneously to synergistically power the dynamic wagging of azobenzene groups, while the infrared light can be converted into kinetic energy of the zwitterionic groups to promote the wagging of the azobenzene groups. Cooperative action between the major components of sunlight can be applied to control a range of important properties of the hydrogel including wettability, adhesion, molecular release, self-healing, and mineralization. The work presented here demonstrates a novel strategy for harvesting all the major components of sunlight to control the properties of photoresponsive materials.

Tuning the pH Response of Weak Polyelectrolyte Brushes with Specific Anion Effects.

The positively charged poly( N, N'-dimethylaminoethyl methacrylate) (PDMAEMA) brushes have been employed as model weak polyelectrolyte brushes (WPBs) to demonstrate the tuning of the pH response of WPBs with specific anion effects. The charge density of PDMAEMA brushes can be modulated by specific ion-pairing interactions between counterions and the protonated dimethylamino group; as a result, the strength of the pH response of PDMAEMA brushes can be tuned by specific anion effects. A more chaotropic counterion can more strongly interact with the protonated dimethylamino group, thereby more effectively neutralizing the positively charged group associated with the grafted weak polyelectrolyte chains and more remarkably suppressing the pH response of PDMAEMA brushes. Although the pH response of PDMAEMA brushes is insensitive to the anion identity at a low salt concentration, it can be tuned by specific anion effects at relatively high salt concentrations. Our study demonstrates that the pH-responsive properties of PDMAEMA brushes including hydration, conformation, oil wettability, and adhesion can be tuned by specific anion effects. The work presented here provides a method to tune the pH response of WPBs by the anion identity.