Optically-excited simultaneous photoacoustic and ultrasound imaging based on aflexible gold-PDMS film

We constructed a flexible gold-polydimethylsiloxane(gold-PDMS)nanocomposites film with controllable thickness and light transmittance,to realize optically-excited simultaneous photo-acoustic(PA)and ultrasound(US)imaging under a single laser pulse irradiation.Benefiting from the excellent thermoelastic properties,the gold-PDMS film absorbs part of the incident laser energy and produces a high-intensity US,which is used to realize US imaging.Meanwhile,the partly transmitted light is used to excite samples for PA imaging.By controlling the thickness of the gold-PDMS,we can control the center frequency in the US imaging.We experimentally analyzed the frequency of the produced US signal by the gold-PDMSfilm and compared it with the finite element analysis(FEA)method,where the experiments agree with the FEA results.This method is demonstrated by the experiments on phantoms and a mouse model.Our work provides a cost-effective methodology for simultaneous PA and US imaging.

Collagen fiber anisotropy characterization by polarized photoacoustic imaging for just-in-time quantitative evaluation of burn severity

Just-in-time burn severity assessment plays a vital role in burn treatment and care.However,it is still difficult to quantitatively and promptly evaluate burn severity by existing medical imaging methods via initial burn depth measurement since burn wounds are usually dynamically developed.As an elastic skeleton of skin,the degree of conformational changes of collagen fibers caused by overheating can reflect the burn severity in a timelier manner.Herein,the polarized photoacoustic technique(PPAT)for just-in-time quantitative evaluation of burn severity via collagen fiber anisotropy assessment is proposed.First,phantom experiments demonstrate the ability of PPAT for deep imaging in a transport mean free path and accurately quantify changes in microstructural order by thermal damage.Then,the Pearson correlation coefficient of the PPAT in assessing burn severity is shown to be up to 0.95,validated by burn skin samples.The PPAT provides a just-in-time quantitative strategy for burn severity evaluation.

Surface reconstruction,doping and vacancy engineering to improve the overall water splitting of CoP nanoarrays

Development of a general regulatory strategy for efficient overall water splitting remains a challenging task.Herein,a simple,costfairness,and general fluorination strategy is developed to realize surface reconstruction,heteroatom doping,and vacancies engineering over cobalt phosphide(CoP)for acquiring high-performance bifunctional electrocatalysts.Specifically,the surface of CoP nanoarrays(NAs)becomes rougher,meanwhile F doped into CoP lattice and creating amounts of P vacancies by fluorination,which caused the increase of active sites and regulation of charge distribution,resulting the excellent electrocatalyst performance of F-CoP NAs/copper foam(CF).The optimized F-CoP NAs/CF delivers a lower overpotential of only 35 mV at 10 mA·cm^(−2)for hydrogen evolution reaction(HER)and 231 mV at 50 mA·cm^(−2)for oxygen evolution reaction(OER),and the corresponding overall water splitting requires only 1.48 V cell voltage at 10 mA·cm^(−2),which are superior to the most state-of-theart reported electrocatalysts.This work provides an innovative and feasible strategy to construct efficient electrocatalysts.

Polarization microwave-induced thermoacoustic imaging for quantitative characterization of deep biological tissue microstructures

Polarization optical imaging can be used to characterize anisotropy in biological tissue microstructures and has been demonstrated to be a powerful tool for clinical diagnosis. However, the approach is limited by an inability to image targets deeper than ~1 mm due to strong optical scattering in biological tissues. As such, we propose a novel polarization microwave-induced thermoacoustic imaging(P-MTAI) technique to noninvasively detect variations in deep tissue by exploiting the thermoacoustic signals induced by four pulsed microwaves of varying polarization orientations. The proposed P-MTAI method overcomes the penetration limits of conventional polarization optical imaging and provides submillimeter resolution over depths of several centimeters. As part of the paper, the structural characteristics of tissues were quantified using a new parameter, the degree of microwave absorption anisotropy. P-MTAI was also applied to the noninvasive detection of morphological changes in cardiomyocytes as they transitioned from ordered to disordered states, providing a potential indication of myocardial infarction.

Nonlinear photoacoustic imaging dedicated to thermal-nonlinearity characterization

We proposed a nonlinear photoacoustic(PA) technique as a new imaging contrast mechanism for tissue thermalnonlinearity characterization.When a sine-modulated Gaussian temperature field is introduced by a laser beam, in view of the temperature dependence of the thermal diffusivity, the nonlinear PA effect occurs, which leads to the production of second-harmonic PA(SHPA) signals.By extracting the fundamental frequency PA and SHPA signal amplitudes of samples through the lock-in technique, a parameter that only reflects nonlinear thermal-diffusivity characteristics of the sample then can be obtained.The feasibility of the technique for thermal-nonlinearity characterization has been studied on phantom samples.In vitro biological tissues have been studied by this method to demonstrate its medical imaging capability,prefiguring great potential of this new method in medical imaging applications.

Difference Analysis of Accumulated Degree-Day Samples in Different Regions of China

Background:Accumulated degree-days(ADD)refers to the temperature value and time within a certain period.More and more attention has been paid to the ADD in the study of postmortem interval(PMI)estimation.Aim and Objective:This study is to confirm whether ADD is applicable in China.Materials and Methods:We collected meteorological data of 10 different regions in China for 12 months,analyzed the distribution characteristics of ADD in different regions at different time periods,and tested the two ADD calculation methods(accumulated hourly temperature and accumulated daily average temperature),in an attempt to establish a more precise calculation method of ADD.Results:The results show that when the yearly or monthly effective temperature data is taken as the research object,the law of daily ADD mean value gradually decreases from south to north,and the average value of accumulated hourly temperature at each region is larger than the average value of accumulated daily average temperature(the difference was significant).In addition,in different periods of each day,ADD obtained at different regions is different,and the variation of its specific gravity also has a north-south difference.We take the daily average temperature as the independent variable and accumulated hourly temperature as the linear equation fitted by the dependent variable,showing a good linear relationship(0.992<R2<0.999).At the same time,we also identify that extra caution should be exercised when using ADD in some special regions(such as Lhasa)or during the cold season of some regions.It may be unrealistic to attempt divide daily ADD into equal parts and accurately estimate PMI to a certain hour on the day of the crime.However,accurate estimation of PMI can be improved by dividing ADD on the day of the crime according to proportion of different periods and checking the time period of the final ADD value.Conclusion:At present,the study results on ADD need to be further developed,our study provides a preliminary research basis for the future establishment of an unified,simple,accurate,and suitable for the ADD model in China.