Terahertz radiation of a butterfly-shaped photoconductive antenna(invited)

The terahertz(THz) far-field radiation properties of a butterfly-shaped photoconductive antenna(PCA) were experimentally studied using a home-built THz time-domain spectroscopy(THz-TDS) setup.To distinguish the contribution of in-gap photocurrent and antenna structure to far-field radiation,polarization-dependent THz field was measured and quantified as the illuminating laser beam moved along the bias field within the gap region of electrodes. The result suggests that, although the far-field THz radiation originates from the in-gap photocurrent, the antenna structure of butterfly-shaped PCA dominates the overall THz radiation. In addition, to explore the impact of photoconductive material,radiation properties of butterfly-shaped PCAs fabricated on both low-temperature-grown GaAs(LT-GaAs) and semi-insulating GaAs(Si-GaAs) were characterized and compared. Consistent with previous experiments, it is observed that while Si-GaAs-based PCA can emit higher THz field than LT-GaAs-based PCA at low laser power, it would saturate more severely as laser power increased and eventually be surpassed by LT-GaAs-based PCA. Beyond that, it is found the severe saturation effect of Si-GaAs was due to the longer carrier lifetime and higher carrier mobility, which was confirmed by the numerical simulation.

Optical coherence tomography of the living human kidney

Acute tubular necrosis(ATN)induced by ischemia is the most common insult to donor kidneysdestined for trarsplantation.ATN results from sweling and subsequent damage to cells lining thelkidney tubules.In this study,we demonstrate the capability of optical coherence tomography(OcT)to image the renal microst ructures of living human donor kidneys and potentially providea measure to det ermine the extent of A TN.We also found that Doppler-based OCT(i.e.,DOCT)reveals renal blood flow dynamics that is another major factor which could relate to post-transplant renal finction.All OCT/DoCT oberva tions were performed in a noninvasive,sterileand timely manner on intact human kidneys both prior to(er vivo)and following(in vivo)theirtransplantation.Our results indicate that this imaging model provides transplant surgeons withan objective visualization of the transplant lidneys prior and immediately post transplantation.

Intravital imaging of adriamycin-induced renal pathology using two-photon microscopy and optical coherence tomography

Adriamycin(doxorubicin),a common cancer chemotherapeutic drug,can be used to induce a model of chronic progressive glomerular disease in rodents.In our studies,we evahuated renal changes in a rat model after Adriamydin injection using two photon microscopy(TPM),optical coherence tomography(OCT)and Doppler OCT(DOCT).Taking advantage of deep penetra-tion and fast scanning speed for three dimensional(3D)label-free imaging,OCT/DOCT system was able to reveal glomerular and tubular pathology noninvasively and in real time.By imaging renal pathology following the infusion of fAuorophore-labeled dextrans of different molecular weights,TPM can provide direct views of glomerular and tubular flow dynamics with the onset and progression of renal disease.Specifically,glomerular permeability and filtration,proximal and distal tubular flow dynamics can be revealed.6-8 weeks after injection of Adriamycin,TPM and OCT/DOCT imaging revealed glomerular sclerosis,compromised flow across the glomerular wall,tubular atrophy,tubular dilation,and variable intra-tubular flow dynamics.Our results indicate that TPM and OCT/DOCT provide real-time imaging of renal pathology in vivo that has not been previously available using conventional microscopic procedures.

OPTIMIZATION OF DESIGN PARAMETERS FOR FLUORESCENCE LAMINAR OPTICAL TOMOGRAPHY

Laminar optical tomography(LOT)is a mesoscopic tomographic imaging technique ranging between confocal microscopy and diffuse optical tomography(DOT).Fluorescence LOT(FLOT)provides depth-resolved molecular information with 100-200μm resolution over 2-3mm depth.In this study,we use Monte Carlo simulation and singular-value analysis(SVA)to optimize the source-detector configurations for potential enhancement of FLOT imaging performance.The effects of different design parameters,including source incidence and detector collection angles,detector number,and sampling density,are presented.The results indicate that angled incidence/detection configuration might improve the imaging resolution and depth sensitivity,especially for low-scattering medium.Increasing the number of detectors and the number of scanning steps will also result in enhanced imaging performance.We also demonstrate that the optimal imaging performance depends upon the background scattering coe±cient.Our result might provide an optimization strategy for FLOT or LOT experimental setup.

DEVELOPMENT OF NEEDLE-BASED MICROENDOSCOPY FOR FLUORESCENCE MOLECULAR IMAGING OF BREAST TUMOR MODELS

Fluorescence molecular imaging enables the visualization of basic molecular processes such as gene expression,enzyme activity,and disease-specific molecular interactions in vivo using targeted contrast agents,and therefore,is being developed for early detection and in situ characterization of breast cancers.Recent advances in developing near-infrared fluorescent imaging contrast agents have enabled the specific labeling of human breast cancer cells in mouse model systems.In synergy with contrast agent development,this paper describes a needle-based fluorescence molecular imaging device that has the strong potential to be translated into clinical breast biopsy procedures.This microendoscopy probe is based on a gradient-index(GRIN)lens interfaced with a laser scanning microscope.Specifications of the imaging performance,including the field-of-view,transverse resolution,and focus tracking characteristics were calibrated.Orthotopic MDA-MB-231 breast cancer xenografts stably expressing the tdTomato red fluorescent protein(RFP)were used to detect the tumor cells in this tumor model as a proof of principle study.With further development,this technology,in conjunction with the development of clinically applicable,injectable fluorescent molecular imaging agents,promises to perform fluorescence molecular imaging of breast cancers in vivo for breast biopsy guidance.

Improving localization precision of Brillouin measurements using spectral autocorre lation analysis

Brillouin spectroscopy is a powerful tool for measuring the mechanical properties of materials without contact.The sensitivity to mechanical changes that a Brillouin spectrometer can detect is determined by the precision to which a spectral peak can be localized.The localization precision is however fundamentally limited by the low mumber of photons within a Brillouin measurement,as wel as by intrinsic noise of the setup.Here,we present a method to improve the spectral sensitivity of Brillouin measurements by exploiting the autocorelation function of the spectrum.We show that by performing a localization process on the autocorrelation function nearly 20%increase in localizat ion precision can be obtained.This result is consistent bet ween our theoretical treatment,numerical simulation and experimental results.We further study the efect of back-ground noise on the precision im provement for realistic scenarios.

Ecological and Chemotypic Analysis for Improved Growth and Management of Naturally Occurring Black Cohosh (<i>Actaea racemosa</i>L.) Populations in Western Maryland

Black cohosh (Actaea racemosa L.) is a perennial herb native to deciduous woodlands in eastern North America with an extensive history of traditional use, most commonly for rheumatoid arthritis and female reproductive issues. Modern clinical research has maintained this herb’s relevance into the 21st century with a majority of authentic black cohosh raw material still harvested from naturally occurring populations in Appalachian woodlands for use in botanical supplements. Increased use and interest in black cohosh have led to increased wild harvesting, reports of adulteration, and stress on this important natural resource. In an effort to study this significant medicinal plant as part of an ecosystem, and to understand factors that would contribute to the more effective growth and maintenance of black cohosh, key chemical, physiological, and ecological aspects of two occurring populations in western Maryland were surveyed. Rhizomes were harvested from six populations of naturally occurring black cohosh in two state forests located in the Allegheny Plateau and Ridge and Valley physiogeographic provinces of Maryland. The concentrations of five medicinal compounds found in black cohosh extracts, actein, 23-epi-26-deoxyactein, cafeic acid, ferulicacid, and N-methylserotonin, were compared with plant reproductive status as well as accompanying overstory and under story species, soil moisture, and soil pH at each site. Compound levels showed a complex dependence on physiography but were independent of reproductive state. The findings provide clues to guide efforts at effective growth and management of wild populations of black cohosh and other threatened medicinal plants.

Editorial--The centennial celebration of Dr.Britton Chance

To celebrate the scientific legacy and spirit of the late Dr.Brtton Chance(1913-2010)and his 100thbir thday,t he Brit ton Chance International Symposium on Metabolic Imaging and Spectroscopy was heldat the Perelman School of Medicine,University of Pennsylvania on June 18-19th,2013.The symposium brought toget her over 200 physicists,engineers,biologists and clinicians from all over the world includingEurope,Asia and North America.The latest research innovations and clinical progresses by optical,nuclear magnetic resonance(NMR)and nuclear medicine methods were presented and discussed extensively.

Effect of Induced Anxiety on Respiratory Resistance Using Virtual Reality Simulation

Background: The purpose of this research was to identify significant changes to respiratory resistance resulting from anxiety inducing simulations presented through the medium of virtual reality (VR) goggles. The tested hypothesis was that a virtual reality simulation would produce anxiety in the wearer, and, with it, a statistically significant change in subject respiratory resistance. It was also suggested that there may be a significant difference in the levels of respiratory resistance responses of males and females. The Oculus Rift DK2 VR goggles with video software designed for the Rift were used to induce anxiety in the wearers. Methods: Respiratory resistances in both inhalation and exhalation directions were measured with the Airflow Perturbation Device (APD), a medical instrument used noninvasively. Two groups of subjects were tested: the test group watched a simulation deemed to be anxiety inducing, and the Control group watched a simulation determined to be non-anxiety inducing. Anxiety levels and respiratory resistance were measured before and during the simulation with two anxiety measures, the State Trait Anxiety Inventory (STAI) and the Subjective Units of Distress Scale (SUDS). Results: Statistically significant increases in anxiety level and respiratory resistance were found in the Test group, but no significant differences in anxiety and respiratory resistance levels were found in the control group. Anxiety affected both breathing phases similarly. For the gender hypothesis, we found that one of the tests used to measure anxiety, (the SUDS difference) was statistically significant, while the other test and the difference in respiratory resistance were not statistically significant. Conclusion: Results from this experiment show that anxiety level can be a significant contributor to the physiological measurement of respiratory resistance, and this can have implications for pulmonary function test environments and the psychological conditions of the patients being tested.

Assessment of Bronchodilator Response in Children with Asthma Exacerbation Using the Respiratory Resistance Values

Sixty-four pediatric patients with asthma exacerbation were studied. The children were subjected to respiratory resistance evaluation using the Airflow Perturbation Device (APD) and spirometry evaluation. They were then administered albuterol and 15 minutes later the APD and spirometry evaluations were repeated. Eleven of the children could not perform spirometry. The APD results demonstrated that respiratory resistance of the patients decreased by about 20%, indicating that the APD could detect the expected response to bronchodilator. However, no similar conclusion could be made with the spirometry parameters (FVC, FEV1, FEV1/FVC, and FEF25% - 75%) performed on the same patients. The differences on the spirometry parameters did not change significantly before and after bronchodilator administration. Furthermore, these differences were negligibly increased or decreased for some with no consistency between the FVC, FEV1, FEV1/FVC, and FEF25% - 75%. Even though all the children were clinically improved after albuterol administration and discharged home, this could not be demonstrated by spirometry data. This study validates previous reports that spirometry is not a reliable pulmonary diagnostic tool for young children, as spirometry is highly effort-dependent and requires a substantial degree of patient cooperation. APD on the other hand is a reliable, simple, effortless diagnostic tool that can be utilized in evaluation and management of children with asthma symptoms and exacerbation.

Immediate Respiratory Response to Electronic Cigarette Use

Background: Electronic cigarettes were originally designed to reduce adult dependency on normal cigarettes and as a tobacco cessation tool to substitute traditional cigarettes. But it has become the most popular among teenagers. Rationale: To investigate the immediate adverse respiratory effect of short-term electronic cigarette vapor inhalation. Method: Twenty-five subjects were randomly selected and used in this study. The respiratory resistance values were evaluated and used for comparison. The subjects were asked to breathe into the Airflow Perturbation Device (APD) for evaluation of their respiratory resistance before vaping (in triplicate). The same subjects, a minute later, were then asked to use one poke (3 seconds) of the e-Cigarette device to inhale e-Cigarette vapor with nicotine from a pod with 59 mg/ml nicotine. Immediately following the e-Cigarette use, their respiratory resistance was measured again (in triplicate). Results: Comparing the respiratory resistance values before and immediately after exposure to e-Cigarette vapor showed that their respiratory resistance increased almost immediately. Conclusion: Although there are long-term studies showing that the e-Cigarette is as harmful as regular cigarettes, this study showed a nearly immediate effect of using the e-Cigarette that significantly increased the respiratory resistance of the user. Very short exposure time to e-Cigarette vapor (3 seconds only), caused an immediate adverse physiologic effect in respiratory resistance.

时变动态贝叶斯网络模型及其在皮层脑电网络连接中的应用

大脑执行语言的发音需要顶叶、颞叶、额叶等多个脑区协同完成.皮层脑电具有高时间分辨率、较高空间分辨率和高信噪比等优势,为研究大脑的电生理特性提供了重要的技术手段.为了探索大脑对语言的动态处理过程,利用多尺度皮层脑电(标准电极与微电极)分析了被试在执行音节朗读任务时的皮层脑电信号的高频gamma段特征,提出采用时变动态贝叶斯网络构建单次实验任务的有向网络.结果显示该方法能够快速有效地构建语言任务过程中标准电极、微电极以及二者之间的有向网络连接,且反映了大规模网络(标准电极之间的连接)、局部网络(微电极之间的连接)以及大规模网络与局部网络之间的连接(标准电极与微电极之间的连接)随语言任务发生的动态改变.研究还发现,发音时刻之前与之后的网络连接存在显著性差异,且发音方式不同的音节网络间也存在明显差异.该研究将有助于癫痫等神经疾病的术前临床评估以及理解大脑对语言加工的实时处理过程.

Axial strain enhances osteotomy repair with a concomitant increase in connexin43 expression

The mechanical environment is known to influence fracture healing. We speculated that connexin43 （Cx43） gap junctions, which impact skeletal homeostasis, fracture healing and the osteogenic response to mechanical load, may play a role in mediating the response of the healing bone to mechanical strain. Here, we used an established rat fracture model, which uses a 2 mm osteotomy gap stabilized by an external fixator, to examine the impact of various cyclical axial loading protocols （2%, 10%, and 30% strain） on osteotomy healing. We examined the presence of Cx43 in the osteotomy-healing environment and assessed how mechanical strain modulates Cx43 expression patterns in the callus. We demonstrated that increased cyclical axial strain results in increased radiographic and histologic bone formation. In addition, we show by immunohistochemistry that Cx43 is abundantly expressed in the healing callus, with the expression most robust in samples exposed to increased cyclical axial strain. These data are consistent with the concept that an increase in Cx43 expression by mechanical load may be part of the mechanisms by which mechanical forces enhances fracture healing.

Introduction to the special iss ue on optics in elastography and cell mechanics

The mechanical properties of tissues and cells have proven to be of great importance in biology andmedicine,spawning major research efforts and commercial outcomes,The interplay bet ween mechanical andbiochemical cues and the mechanical properties of subellar and cellular constituents has come to beappreciated as key to umnderstanding many fundamental aspects of biology as well as the geneis andprogression of disease.

Efficient, Season-Independent Seed Germination in Black Cohosh (<i>Actaea racemosa</i>L.)

Seed germination in black cohosh was systematically examined in eighteen populations including 15 USDA accessions with an effective protocol for the consistent, season independent germination of this valuable alternative specialty crop. Two in vitro approaches were investigated for breaking the complex double dormancy of black cohosh seeds for yearround germination of plants for increased cultivation and laboratory studies. The first approach was a two-step alternating temperature stratification in which surface sterilized seeds were incubated in darkness at 25?C for two weeks followed by incubation at alternating temperatures of 20?C and 8?C for 12-hour periods with a 16-hour photoperiod for 12 months. The second was a three-step-approach that involved initial stratification of seeds in darkness at 25?C for two weeks, followed by incubation at 4?C in darkness for 3 -4 months and then cultivation at 25?C with a 16-hour photoperiod to generate seedlings. Although both approaches broke double dormancy for black cohosh seed germination, the three-step-stratification technique yielded higher percentage seed germination in less time when compared to the two-step scheme, including for seeds stored over two years. Additional factors of critical importance for efficient germination included the selection of healthy and viable seeds, as well as thorough but non-excessive surface sterilization to control bacterial and fungal contamination. The in vitro approach for black cohosh germination allowed year-round cultivation and culture of a number of different genotypic accessions to enable laboratory based studies on cell culture and transformation approaches to aid in deciphering gene-metabolite relationships in this important medicinal plant.

A PERSONAL REFLECTION ON MY PH.D. ADVISOR DR. BRITTON CHANCE

This article briefly reflects some of my interactions with Dr.Britton Chance(BC),from a perspective of his graduate student.

Resistance Measured by Airflow Perturbation Compared with Standard Pulmonary Function Measures

Background: Routine lung function testing requires expensive equipment, or requires maximum expiratory effort. The airflow perturbation device (APD) is a light handheld device, allowing for serial measures of respiratory resistance noninvasively and effortlessly. Methods: In a convenience sample of 398 patients undergoing pulmonary function testing, we compared routine spirometric indices (forced expired volume in 1 second (FEV1), peak expiratory flow (PEF)), and airways resistance (Raw-272 patients), to measures of respiratory resistance measured with the APD including inspiratory (IR), expiratory (ER) and averaged (AR) resistance. Results: Measures of lung function were significantly correlated (p 0.001). On regression analysis, between 7% - 17% of the variance (R2) for FEV1, PEF, and Raw was explained by APD measurements. Approximately 2/3 of the variance in FEV1 was explained by PEF measurements. Conclusions: APD measurements of lung function correlate with conventional measures. Future studies should be directed at exploring the use of the APD device in serial measures of lung function in patients with lung disease.

Compound muscle action potential(CMAP)scan examination of paretic and contralateral muscles reveals motor unit alterations after stroke

This study presents a novel compound muscle action potential(CMAP)examination of motor unit changes in paretic muscle post stroke.CMAP scan of the first dorsal interosseous(FDI)muscle was performed bilaterally in 16 chronic stroke subjects.Various parameters were derived from the CMAP scan to examine paretic muscle changes,including CMAP amplitude,D50,step index(STEPIX)and amplitude index(AMPIX).A significant decrease in CMAP amplitude and STEPIX was observed in paretic muscles compared with contralateral muscles(CMAP amplitude:paretic(9.0±0.5)mV,contralateral(11.3±0.9)mV,P=0.024;STEPIX:paretic 101.2±7.6,contralateral 121.9±6.5,P=0.020).No significant difference in D50 and AMPIX was observed between the paretic and contralateral sides(P>0.05).The findings revealed complex paretic muscle changes including motor unit degeneration,muscle fiber denervation,reinnervation and atrophy,providing useful insights to help understand neuromuscular mechanisms associated with weakness and other functional deterioration post stroke.The CMAP scan experimental protocols and the applied processing methods are noninvasive,convenient,and automated,offering practical benefits for clinical application.

Erratum to:Compound muscle action potential(CMAP)scan examination of paretic and contralateral muscles reveals motor unit alterations after stroke

The article“Compound muscle action potential(CMAP)scan examination of paretic and contralateral muscles reveals motor unit alterations after stroke”was originally published Online First without Open Access.After online first publication,the authors decided to opt for Open Choice and to make the article an Open Access publication.Therefore,the copyright of the article has been changed to©The Author(s)2023 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License(http://creativecommons.org/licenses/by/4.0/),which permits use,duplication,adaptation,distribution and reproduction in any medium or format,as long as you give appropriate credit to the original author(s)and the source,provide a link to the Creative Commons license,and indicate if changes were made.