Ultrasonic backscatter from mammalian tissues

Ultrasonic B-mode images are formed from echoes backscattered from tissue structures in the body. Quantitative analysis of this signal from tissues may provide additional information about the tissues which may be valuable for clinical diagnosis. Results on measurements of backscatter properties of tissues such as heart, liver, and blood have been reported by a number of investigators. Data on other tissues such as spleen, kidney, and pancreas, however, are still very scanty. In this paper, results on ultrasonic backscattering properties of bovine heart, liver, kidney, spleen, pancreas, and rat myocardium, recently obtained in our laboratory utilizing a computerized system over the frequency range of 2-7 MHz, are presented. The results show that for all the tissues investigated, backscatter from liver is the highest, while that from spleen is the lowest. Liver and pancreas exhibit frequency dependence distinctively different from other tissues. Moreover, backscatter from bovine myocardium is found to be higher than that from rat myocardium. The significance of these findings in relation to the histological composition of these tissues is discussed.     

An approach for measuring ultrasonic backscattering from biologicaltissues with focused transducers

When the standard substitution method is used with a focused transducer to measure the backscattering coefficient from biological tissues including blood, it yields erroneous results. Extending the backscattering measurements to frequencies beyond 15 MHz necessitates the use of focused transducers because of the worsened signal-to-noise ratio-caused by the increased attenuation and the smaller transducer aperture size-in order to make the measurements close to the transducer. An approach which allows the use of focused transducers in backscattering measurements has been developed. It has been used to measure the backscattering coefficient of red cell suspensions of hematocrit ranging from a few percent to 30% in the frequency range from 5 MHz to 30 MHz. The results at hematocrits below 20% agree well with those obtained with the standard substitution method, although they differ as the hematocrit is increased beyond 20%. The experimental results also show that the fourth-power dependence of backscatter on frequency is in general approximately valid for suspended erythrocytes of hematocrit between 6% and 30%     

A neural fuzzy resource manager for hierarchical cellular systems supporting multimedia services

Using intelligent techniques to perform radio resource management is an effective method. The paper proposes neural fuzzy control for radio resource management in hierarchical cellular systems supporting multimedia services. A neural fuzzy resource manager (NFRM) is designed, which mainly contains a neural fuzzy channel allocation processor (NFCAP). The NFCAP has a two-layer architecture: a fuzzy cell selector (FCS) in the first layer and a neural fuzzy call-admission and rate controller (NFCRC) in the second layer. The FCS chooses not only the handoff failure probabilities and the resource availabilities in both microcell and macrocell, but also the user mobility, as input linguistic variables. The NFCRC takes the handoff failure probability and the resource availability of the selected cell as input variables to perform call admission control and rate control for the call. Simulation results show that the NFRM can always guarantee the quality of service (QoS) requirement for handoff failure probability for all traffic loads. Also, the NFRM improves the system utilization by 31.1% while increasing the handoff rate by 2% over the overflow channel allocation (OCA) scheme; it enhances the system utilization by 6.3% and 1.4%, and still reduces the handoff rate by 14.9% and 6.8%, as compared to the combined channel allocation (CCA) and fuzzy channel allocation control (FCAC) schemes, respectively, under a predefined QoS constraint.     

Polypeptides with High Zwitterion Density for Safe and Effective Therapeutics

The commonly used “stealth material” poly(ethylene glycol) (PEG) effectively promotes the pharmacokinetics of therapeutic cargos while reducing their immune response. However, recent studies have suggested that PEG could induce adverse reactions, including the emergence of anti‐PEG antibodies and tissue histologic changes. An alternative stealth material with no or less immunogenicity and organ toxicity is thus urgently needed. We designed a polypeptide with high zwitterion density (PepCB) as a stealth material for therapeutics. Neither tissue histological changes in liver, kidney, or spleen, nor abnormal behavior, sickness or death was induced by the synthesized polymer after high‐dosage administration for three months in rats. When conjugated to a therapeutic protein uricase, the uricase–PepCB bioconjugate showed significantly improved pharmacokinetics and immunological properties compared with uricase–PEG conjugates.     

Origin of Open‐Circuit Voltage Enhancements in Planar Perovskite Solar Cells Induced by Addition of Bulky Organic Cations

The origin of performance enhancements in p‐i‐n perovskite solar cells (PSCs) when incorporating low concentrations of the bulky cation 1‐naphthylmethylamine (NMA) are discussed. A 0.25 vol % addition of NMA increases the open circuit voltage (V_oc) of methylammonium lead iodide (MAPbI₃) PSCs from 1.06 to 1.16 V and their power conversion efficiency (PCE) from 18.7% to 20.1%. X‐ray photoelectron spectroscopy and low energy ion scattering data show NMA is located at grain surfaces, not the bulk. Scanning electron microscopy shows combining NMA addition with solvent assisted annealing creates large grains that span the active layer. Steady state and transient photoluminescence data show NMA suppresses non‐radiative recombination resulting from charge trapping, consistent with passivation of grain surfaces. Increasing the NMA concentration reduces device short‐circuit current density and PCE, also suppressing photoluminescence quenching at charge transport layers. Both V_oc and PCE enhancements are observed when bulky cations (phenyl(ethyl/methyl)ammonium) are incorporated, but not smaller cations (Cs/MA)—indicating size is a key parameter. Finally, it demonstrates that NMA also enhances mixed iodide/bromide wide bandgap PSCs (V_oc of 1.22 V with a 1.68 eV bandgap). The results demonstrate a facile approach to maximizing V_oc and provide insights into morphological control and charge carrier dynamics induced by bulky cations in PSCs.     

Ultrasound‐Induced Wireless Energy Harvesting for Potential Retinal Electrical Stimulation Application

Retinal electrical stimulation for people with neurodegenerative diseases has shown to be feasible for direct excitation of neurons as a means of restoring vision. In this work, a new electrical stimulation strategy is proposed using ultrasound‐driven wireless energy harvesting technology to convert acoustic energy to electricity through the piezoelectric effect. The design, fabrication, and performance of a millimeter‐scale flexible ultrasound patch that utilizes an environment‐friendly lead‐free piezocomposite are described. A modified dice‐and‐fill technique is used to manufacture the microstructure of the piezocomposite and to generate improved electrical and acoustic properties. The as‐developed device can be attached on a complex surface and be driven by ultrasound to produce adjustable electrical outputs, reaching a maximum output power of 45 mW cm^?2. Potential applications for charging energy storage devices and powering commercial electronics using the device are demonstrated. The considerable current signals (e.g., current >72 µA and current density >9.2 nA µm^?2) that are higher than the average thresholds of retinal stimulation are also obtained in the ex vivo experiment of an implanted environment, showing great potential to be integrated on implanted biomedical devices for electrical stimulation application.     

Strong Facet Effects on Interfacial Charge Transfer Revealed through the Examination of Photocatalytic Activities of Various Cu2O–ZnO Heterostructures

Confirming the photocatalytic inactivity of Cu₂O nanocubes through the formation of Au‐decorated–Cu₂O heterostructures, spiky ZnO nanostructures are grown on Cu₂O cubes, octahedra, and rhombic dodecahedra to demonstrate that charge transfer across semiconductor heterojunctions is also strongly facet dependent. Unintended CuO formation in the growth of ZnO on perfect Cu₂O cubes makes them slightly active toward methyl orange photodegradation. Under optimal ZnO growth conditions without CuO presence, Cu₂O cubes remain inactive, while rhombic dodecahedra show an enhanced photocatalytic activity due to better charge transfer according to normal Cu₂O–ZnO band alignment. Surprisingly, photocatalytically active Cu₂O octahedra become inactive after ZnO deposition. An extensive interfacial microscopic examination reveals preferential formation of the ZnO (101) planes on the {111} surfaces of Cu₂O octahedra, while different ZnO lattice planes are observed to deposit on Cu₂O cubes and rhombic dodecahedra. The photocatalytic inactivity of ZnO‐decorated Cu₂O octahedra is explained in terms of an unfavorable band alignment arising from an unusual degree of band bending for the ZnO {101} face relative to the band energy of the Cu₂O {111} surface. The efficiency of charge transfer across semiconductor heterojunctions strongly depends on the band edge energies of the contacting planes.     

Studies of Photon Correlation Spectroscopy of the Microemulsion of H2O/Tween 80/Benzene Derivative

The microemulsion of the H₂O/Tween 80/benzene derivative (C₆H₆, CH₃C₆H₅, NO₂C₆H₅ and NH₂C₆H₅) was investigated by the technique of Photon correlation spectroscopy. Autocorrelation data were measured at 90 scattering angle and were analyzed by using a quadratic fit and linear fit. The quadratic fit was found to describe all Properties better than the linear fit, and thus the linear fit was limited to the region of very short sampling time. When the amount of benzene derivative added to the sample solution was lower than V_max, the Z-average mean radius, <r>_z, and the polydispersit Y, μ2/Γ², increased as the amount of benzene derivative was increased. When the amount of benzene derivative was larger than V_max, the aqueous and organic phases separated and the <r> z, and μ₂/Γ² of all phases remained constant. Emulsification did not occur in the organic phase of the H₂O/Tween 80/aniline system. When we adjusted the Tween 80 concentration, it was found that <r>z and μ₂/Γ² decreased as the Tween 80 concentration increased.