[Ultrasonographic assessment and differentiation of spontaneous degenerating cystic thyroid nodules and papillary thyroid carcinomas].

Objective: To analyze the features of degenerating cystic thyroid nodules (DCTN) on conventional ultrasound and contrast-enhanced ultrasound (CEUS), and to explore the differentiation between DCTN and papillary thyroid carcinomas (PTC). Methods: A total of 46 DCTN (39 cases, including 12 males and 27 females, with an age range of 25 to 76 years) and 36 PTC (32 cases, including 8 males and 24 females, with an age range of 23 to 68 years) diagnosed via fine- needle aspiration (FNA) or surgery from February 2019 to January 2020 in the First Affiliated Hospital of Nanchang University were enrolled. The size, shape, margin, echogenicity, presence of shadowing, calcification and vascularity of DCTN and PTC were retrospectively evaluated, and 28 DCTN and 30 PTC underwent CEUS were separately analyzed and compared.The t test, χ² test or Fisher's exact test were implemented to compare the features of ultrasound among the two groups. The binary Logistic regression test was performed to determine whether the feature whose difference was statistically significant was an independent predictive risk factor. Results: A univariate analysis indicated that DCTN more frequently showed wider-than-tall shapes, marked hypoechogenicity, well-defined margin and no or dot-lined enhancement (wider-than-tall shapes: 36 vs. 17, χ2=8.511; well-defined margin: 30 vs. 15, χ2=4.523; marked hypoechogenicity: 27 vs. 9, χ2=9.310; no or dot-lined enhancement: 24 vs. 3, χ2=33.369; all P＜0.05). A multivariate analysis demonstrated that wider-than-tall shapes, well-defined margin and marked hypoechogenicity were independent predictors for DCTN (OR values were 5.204, 3.134 and 5.042, P values were 0.003, 0.031, and 0.003, respectively). Among 28 DCTN, 15 showed a decrease in mean maximum diameter (24.3±11.4 mm) with a mean time span of (18.6±10.5) months between the presence and absence of suspicious ultrasound features. Conclusions: Compared with PTC, DCTN shows the ultrasound characteristics of wider-than-tall shapes, well-defined margin, marked hypoechogenicity and no or dot-lined enhancement pattern. Ultrasound follow-up can help to identify spontaneous DCTN.

Mapping the near-field spin angular momenta in the structured surface plasmon polariton field.

Optical spin angular momenta in a confined electromagnetic field exhibit a remarkable difference with their free space counterparts; in particular, the optical transverse spin that is locked with the energy propagating direction lays the foundation for many intriguing physical effects such as unidirectional transportation, quantum spin Hall effects, photonic Skyrmions, etc. In order to investigate the underlying physics behind the spin-orbit interactions as well as to develop the optical spin-based applications, it is crucial to uncover the spin texture in a confined field, yet it faces challenges due to their chiral and near-field vectorial features. Here, we propose a scanning imaging technique which can map the near-field distributions of the optical spin angular momenta with an achiral dielectric nanosphere. The spin angular momentum component normal to the interface can be uncovered experimentally by employing the proposed scanning imaging technique and the three-dimensional spin vector can be reconstructed theoretically with the experimental results. The experiment is demonstrated on the example of surface plasmon polaritons excited with various vector vortex beams under a tight-focusing configuration, where the spin-orbit interaction emerges clearly. The proposed method, which can be utilized to reconstruct the photonic Skyrmion and other photonic topological structures, is straightforward and of high precision, and hence it is expected to be valuable for the study of near-field spin optics and topological photonics.

Optical transverse spin coupling through a plasmonic nanoparticle for particle-identification and field-mapping.

Electromagnetic fields at near-field exhibit distinctive properties with respect to their free-space counterparts. In particular, an optical transverse spin appearing in a confined electromagnetic field provides the foundation for many intriguing physical effects and applications. We present a transverse spin coupling configuration where plasmonic nanoparticles are employed to couple the transverse spin in a focused beam to that of a surface plasmon polariton. The plasmonic resonance of nanoparticles on a metal film plays a significant role in transverse spin coupling. We demonstrate in experiments that Ag and Au nanoparticles yield distinct imaging patterns when scanned over a focused field, because of their different plasmonic responses to the transverse and longitudinal electric fields. Such resonance-dependent spin-coupling enables the identification of nanoparticles using a focused field, as well as electric field mapping of a specific field component of a focused beam using a plasmonic nanoparticle. These interesting findings regarding the transverse spin coupling with a plasmonic nanoparticle may find valuable applications in near-field and nano-optics.

Effects of melatonin on spinal cord injury-induced oxidative damage in mice testis.

This study evaluated the effects of melatonin on spinal cord injury (SCI)-induced oxidative damage in testes. Adult male C57BL/6 mice were randomly divided into sham-, SCI- or melatonin (10 mg/kg, i.p.)-treated SCI groups. To induce SCI, a standard weight-drop method that induced a contusion injury at T10 was used. After 1 week, testicular blood flow velocity was measured using the Laser Doppler Line Scanner. Malondialdehyde (MDA), glutathione (GSH), oxidised glutathione (GSSG) and myeloperoxidase (MPO) were measured in testis homogenates. Microvascular permeability of the testes to Evan's Blue was examined by spectrophotometric and fluorescence microscopic quantitation. The tight junction protein zonula occludens-1 (ZO-1) and occludin in testes were assessed by immunoblot analysis. Melatonin increased the reduced blood flow and decreased SCI-induced permeability of capillaries. MDA levels and MPO activity were elevated in the SCI group compared with shams, which was reversed by melatonin. In contrast, SCI-induced reductions in GSH/GSSG ratio were restored by melatonin. Decreased expression of ZO-1 and occludin was observed, which was attenuated by melatonin. Overall, melatonin treatment protects the testes against oxidative stress damage caused by SCI.

Investigation of an SPR biosensor for determining the influence of connexin 43 expression on the cytotoxicity of cisplatin.

The real-time and label free detection abilities of surface plasmon resonance (SPR) biosensors provide a way of evaluating the influence of some genes' expression on anti-tumor drug cytotoxicity. However, studies in this field are lacking. Connexin 43 is a tumor suppressor gene and the mechanism of its effect in cisplatin cytotoxicity is still unclear. A phase SPR biosensor was used to determine the influence of connexin 43 expression on cisplatin cytotoxicity in three cancer cell lines. The results showed that the SPR signal curves have two stages. In the first hour, the SPR signal shows dramatic changes which are related to connexin 43 expression. In the subsequent stage, the SPR signal slowly declines and is related to apoptosis. Comparison of SPR measurements from several conventional biological assays showed that connexin 43 expression can affect cellular response to cisplatin in the period of oxidative stress, and results in the cells being more sensitive to cisplatin. The conclusion is further confirmed by long-term SPR measurement results and cellular morphological changes.

Generation and detection of broadband multi-channel orbital angular momentum by micrometer-scale meta-reflectarray.

We theoretically demonstrate the generation and detection of broadband multi-channel Orbital Angular Momentum(OAM) by a micrometer-scale meta-reflectarray. The meta-reflectarray composed of patterned silicon bars on a silver ground plane can be designed to realize phase modulation and work as chip-level OAM devices. Compared to traditional methods of OAM generation and detection, our approach shows superiorities of very compact structure size, broadband working wavelength (1250-1750 nm), high diffraction efficiency (~70%), simultaneously handling multiplex OAMs, and tunable reflection angle (0-45°). These fascinating advantages provides great potential applications in photonic integrated devices and systems for high-capacity and multi-channel OAM communication.

Sub-100nm resolution PSIM by utilizing modified optical vortices with fractional topological charges for precise phase shifting.

We demonstrate an all-optical plasmonic structured illumination microscopy (PSIM) technique. A set of plasmonic standing-wave patterns is excited by amplitude-modified optical vortices (OVs), which have fractional topological charges for precise phase shift of {-2π/3, 0, 2π/3}. A specially designed optical aperture is introduced to modify the OVs in order to improve the uniformity of interference patterns. The imaging results of fluorescent beads reveal a sub-100nm resolving capability in aqueous environment. This PSIM technique as a structure-free, wide-field and super-resolved imaging technique is of great potential for low-cost biological dynamic imaging applications.

Dynamic cosine-Gauss plasmonic beam through phase control.

We carry out an approach to dynamic manipulation of a nondiffracting cosine-Gauss plasmonic beam (CGPB) illuminated with an incident phase modulation within nanostructures by a spatial light modulator (SLM). By changing the hologram addressed on the SLM, dynamic control on the lobe width and the propagating direction of the CGPB is experimentally verified. Finally, we demonstrate an application example of this dynamic CGPB in routing optical signals to multichannel subwavelength wave guides through numerical simulation.

Scattering coefficients of mice organs categorized pathologically by spectral domain optical coherence tomography.

Differences in tissue density cause a variety of scattering coefficients. To quantify optical coherence tomography (OCT) images for diagnosis, the tissue's scattering coefficient is estimated by curve fitting the OCT signals to a confocal single backscattering mode. The results from a group of 30 mice show that the scattering coefficients of bone, skin, liver, brain, testis, and spleen can be categorized into three groups: a scattering coefficient between 1.947 and 2.134 mm(-1): bone and skin; a scattering coefficient between 1.303 and 1.461 mm(-1): liver and brain; a scattering coefficient between 0.523 and 0.634 mm(-1): testis and spleen. The results indicate that the scattering coefficient is tissue specific and could be used in tissue diagnosis.

Quantitative diagnosis of colorectal polyps by spectral domain optical coherence tomography.

The principal aim of this study is to investigate the scattering coefficient of colorectal polyp tissues using an optical coherence tomography (OCT) technique. It combines the existing scattering coefficient model and spectral domain OCT to achieve method of early diagnosis of colorectal polyp in hospitals. Seventeen patients were studied, and a total of 1456 data points were extracted by curve-fitting the OCT signals into a confocal single-backscattering model. The results show that the mean scattering coefficient value for colorectal polyps is 1.91 mm(-1) (std: ± 0.54 mm(-1)), which is between the values for normal and malignant tissues. In addition, we studied the difference between adenomatous polyps (n = 15) and inflammatory polyps (n = 2) quantitatively and found that the adenomatous tissues had lower scattering coefficients than the inflammatory ones. The quantitative measurements confirmed that OCT can be used in primary diagnosis to compensate for the deficiencies in methods of pathological diagnosis, with a great potential for early diagnosis of tissues.

Phase-stepping technique for highly sensitive microscopic surface plasmon resonance biosensor.

In this paper, the phase-stepping technique is applied to improve a phase-sensitive surface plasmon resonance biosensor based on differential interferometry between focused radially polarized and azimuthally polarized cylindrical vector beams. Detailed analysis is presented for the phase-stepping method, and the least squares unwrapping algorithm is employed to detect the phase distribution in correspondence to the refractive index of sample. Benefiting from the phase-stepping technique, both the measurement speed and sensitivity are improved significantly. The proposed sensor maintains high sensitivity of 9.4×10-7 RIU/1° and a wide dynamic range of 0.35 RIU simultaneously. Furthermore, the real-time binding reaction process of bovine serum albumin with antibody is monitored to verify the system for potential biological applications.

Tight focusing of quasi-cylindrically polarized beams.

Based on vectorial diffraction theory, tight focusing properties of quasi-cylindrical polarized beams (QCPBs) composed of equal fan-shaped sectors with linear polarization are investigated. We find that, for quasi-radially polarized illumination, a weak azimuthal component emerges and the circular symmetry of focus is traded in when the total number of sector N is small, but when N≥8 it is approaching that of a perfect radially polarized beam with a deviation smaller than 5.3% and a ratio of maximum total intensity larger than 95.5%. Meanwhile, for quasi-azimuthal polarized illumination, although weak radial and longitudinal components emerge, it is also close to that of the perfect azimuthally polarized beam when N≥8 with deviation smaller than 5.3% and a ratio larger than 95.0%. These results not only reveal a deep understanding of the focusing properties of QCPBs, but also provide an important contribution toward optimization of the monolithic methods for generating vector beams.

Enhanced matrix metalloproteinases-2 activates aortic endothelial hypermeability, apoptosis and vascular rarefaction in spontaneously hypertensive rat.

Microvascular rarefaction with endothelial cells apoptosis is a common characteristic of various microvascular complications in the spontaneously hypertensive rat (SHR). Elevated levels of proteolytic (e.g. matrix metalloproteinase, MMPs) activity and apoptosis in aortic endothelial cells of SHR were found when compared to its normotensive control. However, the exact mechanisms of microvascular rarefaction and the role of MMPs in this process remain poorly understood. Besides cleavage of VEGFR2 via unbalanced MMPs, we hypothesize that selected cleavage of Beta-Catenin and VE-cadherin by MMPs could induce apoptosis of rat aortic endothelial cells (RAECs) and rarefaction. Primary RAECs were isolated, identified and used in a in-vitro model. Transwell system was used to analyze the permeability of Wistar RAECs, SHR RAECs and SHR RAECs with pretreatment by doxycycline. Qualitative and semi-quantitative analysis of major endothelial adhesion molecules were detected by immunofluorescence technique and Western blot, respectively. MMP-2 activity of SHR RAECs was increased significantly and doxycycline (50 µM) effectively reduced the level of MMP-2 and hyper-permeability in SHR RAECs. SHR RAECs showed enhanced cleavage of VEGFR2, VE-cadherin and B-catenin, which could be prevented by doxycycline (50 µM). Doxycycline (50 µM) attenuated hyper-permeability via decreased MMP-2 by protecting VEGFR2, VE-cadherin, Beta-catenin from cleavage and inhibited the reduction of mitochondrial transmembrane potential (MTP), thus prevented mitochondria-mediated apoptotic signaling and capillary rarefaction in the SHR. It might be a novel insight into the mechanisms of SHR microvascular rarefaction that is independent of pressure but relevant to MMP-2.

Measurement of the microscopic viscosities of microfluids with a dynamic optical tweezers system.

Viscosity coefficients of microfluids-Newtonian and non-Newtonian-were explored through the rotational motion of a particle trapped by optical tweezers in a microflute. Unlike conventional methods based on viscometers, our microfluidic system employs samples of less than 30 µl to complete a measurement. Viscosity coefficients of ethanol and fetal bovine serum, as typical examples of Newtonian and non-Newtonian fluids, were obtained experimentally, and found to be in excellent agreement with theoretical predictions. Additionally, a practical application to a DNA solution with incremental ethidium bromide content was employed and the results are consistent with clinical data, indicating that our system provides a potentially important complementary tool for use in such biological and medical applications.

Plasmonic petal-shaped beam for microscopic phase-sensitive SPR biosensor with ultrahigh sensitivity.

Differential phase measurement between radially polarized (RP) and azimuthally polarized (AP) beams is an important technique in microscopic surface plasmon resonance (SPR) biosensors as reported in our earlier works [Opt. Lett.37, 2091 (2012); Appl. Phys. Lett.102, 011114 (2013)]. However, such a technique suffers complex beam splitting, detection, and data processing procedures for RP and AP beams which may lower the accuracy of phase measurement. In this Letter, a novel plasmonic petal-shaped vector beam is proposed instead of RP and AP beams, greatly simplifying the sensor system and enabling single measurement in differential interferometry. Moreover, an improved ultrahigh sensitivity on the order of 10(-7) refractive index units (RIUs) is experimentally verified in the proposed system.

Sidelobe-modulated optical vortices for free-space communication.

We propose and experimentally demonstrate a new method for free-space optical (FSO) communication, where the transmitter encodes data into a composite computer-generated hologram and the receiver decodes through a retrieved array of sidelobe-modulated optical vortices (SMOVs). By employing the SMOV generation and detection technique, the usual stringent alignment and phase-matching requirement of the detection of optical vortices is released. In transmitting a gray-scale picture with 180×180 pixels, a bit error rate as low as 3.01×10(-3) has been achieved. Due to the orbital angular momentum multiplexing and spatial paralleling, this FSO communication method possesses the ability to greatly increase the capacity of data transmission.

Visualizing orbital angular momentum of plasmonic vortices.

Plasmonic vortices (PVs) are generated by focusing a radially polarized optical vortex (OV) beam onto a metal surface. The intensity distribution of the PV is registered with a near-field scanning optical microscopy and agrees well with a theoretical prediction as well as numerical calculation. Beside the dark central spot, the numerical calculation also shows an azimuthal Poynting vector belonging to the PV, implying that the orbital angular momentum (OAM) was transferred from the radially polarized OV. To directly verify the OAM, plasmonic trapping experiments with gold micrometer particles are performed and the particle rotation is visualized. Further experiments by varying the topological charge of radially polarized OVs show the corresponding changes in rotation in terms of speed and radius.

Optically stitched arbitrary fan-sectors with selective polarization states for dynamic manipulation of surface plasmon polaritons.

Novel hybrid-polarized vector beams with radial and azimuthal polarization states in arbitrary fan-sectors are generated and studied for manipulating surface plasmon polaritons (SPPs). The method has high energy conversion efficiency based on an interferometric arrangement with a Dammann vortex phase grating. The polarization states of generated beams are measured by a linear polarizer and show excellent agreement with theoretical predictions. The manipulation properties of the hybrid-polarized beams on SPPs excitation and distribution are demonstrated by both experiments and simulations. The results show that focusing or standing wave patterns of SPPs can be obtained depending on the polarization of the beams.

Improved sinusoidal phase plate to extend depth of field in incoherent hybrid imaging systems.

An improved sinusoidal phase plate is proposed by adding a new parameter to the conventional sinusoidal phase plate. A series of performance comparisons are made among various phase plates, including sinusoidal, cubic phase, and the modified logarithmic phase. The results demonstrate that the improved sinusoidal phase plate can further extend the depth of field in incoherent hybrid imaging systems, with lower surface relief phase structures fabricated in photoresist (AR-N 4340, ALL Resist, Germany).

A dynamic plasmonic manipulation technique assisted by phase modulation of an incident optical vortex beam.

A novel phase modulation method for dynamic manipulation of surface plasmon polaritons (SPPs) with a phase engineered optical vortex (OV) beam illuminating on nanoslits is experimentally demonstrated. Because of the unique helical phase carried by an OV beam, dynamic control of SPP multiple focusing and standing wave generation is realized by changing the OV beam's topological charge constituent with the help of a liquid-crystal spatial light modulator. Measurement of SPP distributions with near-field scanning optical microscopy showed an excellent agreement with numerical predictions. The proposed phase modulation technique for manipulating SPPs features has seemingly dynamic and reconfigurable advantages, with profound potential for development of SPP coupling, routing, multiplexing and high-resolution imaging devices on plasmonic chips.