Terahertz bistatic three-dimensional computational imaging of hidden objects through random media.

Random media pose limitations on the imaging capability of photoelectric detection devices. Currently, imaging techniques employed through random media primarily operate within the laser wavelength range, leaving the imaging potential of terahertz waves unexplored. In this study, we present an approach for terahertz bistatic three-dimensional imaging (TBTCI) of hidden objects through random media. By deducing the field distribution of bistatic terahertz time-domain spectroscopy system, and proposing an explicit point spread function of the random media, we conducted three-dimensional imaging of hidden objects obscured by the random media. Our proposed method exhibits promising applications in imaging scenarios with millimeter-wave radar, including non-invasive testing and biological imaging.

Flexible Metamaterial Quarter-Wave Plate and Its Application in Blocking the Backward Reflection of Terahertz Waves.

A terahertz flexible metamaterial quarter-wave plate (QWP) is designed and fabricated using polyimide as the substrate in this paper, with a 3 dB axial ratio bandwidth of 0.51 THz and high polarization conversion efficiency and transmittance. The effect of the incidence angle on the polarization conversion performance of the QWP is discussed by measuring the transmissions at multiple incidence angles. The blocking effect of this QWP combined with a polarizer on the backward reflection of terahertz waves is investigated by terahertz time-domain spectral transmission experiments. By adjusting the angle of the QWP and polarizer with respect to the incident light in the optical path, a blocking efficiency of 20 dB can be achieved at a 20° incidence angle, with a bandwidth of 0.25 THz, a maximum blocking efficiency of 58 dB at 1.73 THz, and an insertion loss of only 1.4 dB. Flexible terahertz metamaterial QWPs and polarizers can effectively block harmful reflected waves in terahertz communication and other systems. They have the advantages of a simple structure, ultra-thinness and flexibility, easy integration, no external magnetic field, and no low-temperature and other environmental requirements, thus having broad application prospects for terahertz on-chip integrated systems.

Computational imaging of moving objects obscured by a random corridor via speckle correlations.

Computational imaging makes it possible to reconstruct hidden objects through random media and around corners, which is of fundamental importance in various fields. Despite recent advances, computational imaging has not been studied in certain types of random scenarios, such as tortuous corridors filled with random media. We refer to this category of complex environment as a 'random corridor', and propose a reduced spatial- and ensemble-speckle intensity correlation (RSESIC) method to image a moving object obscured by a random corridor. Experimental results show that the method can reconstruct the image of a centimeter-sized hidden object with a sub-millimeter resolution by a low-cost digital camera. The imaging capability depends on three system parameters and can be characterized by the correlation fidelity (CF). Furthermore, the RSESIC method is able to recover the image of objects even for a single pixel containing the contribution of about 102 speckle grains, which overcomes the theoretical limitation of traditional speckle imaging methods. Last but not least, when the power attenuation of speckle intensity leads to serious deterioration of CF, the image of hidden objects can still be reconstructed by the corrected intensity correlation.

Local pressure calibration method of inductively coupled plasma generator based on laser Thomson scattering measurement.

Based on laser Thomson scattering (TS) measurements and finite element method (FEM) simulations of electron density in inductively coupled plasma (ICP), the simulated local pressure calibration curves of ICP generator are obtained by comparing the experimental and simulated electron density distributions and maxima. The equation coefficients of theoretical model associated with the ICP generator experimental system can be obtained by fitting the simulation curve with the least square method, and the theoretical pressure calibration curves under different absorbed powers can be further obtained. Combined with the vacuum gauge measurements, both the simulated and theoretical pressure calibration curves can give the true local pressure in the plasma. The results of the local pressure calibration at the different absorbed powers show that the density gradient from the vacuum gauge sensor to the center of the coil in ICP generator cavity becomes larger with the increase of electron density, resulting in a larger gap between the measured value and the pressure calibration value. This calibration method helps to grasp the local pressure of ICP as an external control factor and helps to study the physicochemical mechanism of ICP in order to achieve higher performance in ICP etching, material modification, etc.

Propagation characteristics of terahertz wave in inductively coupled plasma.

Firstly, the electron density distribution of inductively coupled plasma (ICP) is measured by laser Thomson scattering (TS) method and the features of the ICP under the same experimental conditions are simulated by finite element method (FEM). The simulated results are in good agreement with the experimental results, which verifies the accuracy of the ICP generation simulation model. Secondly, the propagation characteristics of terahertz wave in ICP are measured by terahertz time domain spectroscopy (THz-TDS) and calculated by FEM according to the electron density distribution of ICP simulated in the first step above. The high consistency between the experimental and simulation results of terahertz wave propagation characteristics in ICP further proves the accuracy of terahertz wave transmission model in plasma and the feasibility of joint simulation with ICP generation simulation model.

High energy and tunable mid-infrared source based on BaGa4Se7 crystal by single-pass difference-frequency generation.

A high-energy and tunable mid-infrared source based on BaGa4Se7 crystal was demonstrated by single-pass difference-frequency generation (DFG). Orthogonally polarized wave at 1064 nm (λ1) and tunable idler wave (λ2) generated by KTP-OPO, which could be tuned in the wavelength range of 1360-1600 nm, were used as the DFG dual-wavelength pump. The pump parameters including total pump energy and energy ratio were studied. Maximum pulse energy of 5.72 mJ at 3.58 µm was obtained at the dual-wavelength pump energy of 58.4 mJ/pulse. The wavelength tuning range was 3.36-4.27 µm with a flat tunability. Moreover, a saturation phenomenon of DFG output was observed and experimentally inferred to be related to the input energy of λ2 in the BaGa4Se7 crystal.

The numerical and experimental analysis of upward flame spread over the flat surface and the wavy surface.

The corrugated cardboards have been widely used in warehouse where flame spread over its surface consisting of the flat layer and the wavy layer contributes more hazards once fire disaster happens. This paper therefore performs a numerical investigation to study upward flame spread over the cardboards with wavy structures. Comparisons between upward flame spread over the flat surface and the wavy surface of corrugated cardboards were made on the flame characteristics, flame spread rate, standoff distance, local burning rate and flame splitting. It is found that the flame gets closer to the wavy surface and a larger averaged temperature gradient is exerted on the surface, which causes the fuel to burn with a higher rate. The wavy structure is the main reason that causes a distinct difference between the flat surface and the corrugated surface, and it promotes the flame to split into more small flames, thus leading the flame to move faster. To validate the model results, experiments on the flame spreading over the fuel with wavy structure were conducted, which were in good agreement with the simulation. The results can provide a solid basis on which to guide the stacking of goods in warehouse in the future.

Inhibitory effects of TNP-470 in combination with BCNU on tumor growth of human glioblastoma xenografts.

This study investigated the effect of TNP-470 in combination with carmustine (BCNU) on the growth of subcutaneously implanted human glioblastoma xenografts in nude mice. Human glioblastoma U-251 cells (1×10(7)) were injected into 24 nude mice subcutaneously. The tumor-bearing mice were randomly divided into 4 groups on the seventh day following tumor implantation: TNP-470 group, in which TNP-470 was given 30 mg/kg subcutaneously every other day 7 times; BCNU group, in which 20 mg/kg BCNU were injected into peritoneal cavity per 4 days 3 times; TNP-470 plus BCNU group, in which TNP-470 and BCNU were coadministered in the same manner as in the TNP-470 group and the BCNU group; control group, in which the mice were given 0.2 mL of the mixture including 3% ethanol, 5% acacia and 0.9% saline subcutaneously every other day 7 times. The tumor size and weights were measured. The tumor microvessel density (MVD) was determined by immunostaining by using goat-anti-mouse polyclonal antibody CD105. The results showed that on the 21th day following treatment, the volume of xenografts in the TNP-470 plus BCNU group was (108.93±17.63)mm(3), markedly lower than that in the TNP-470 group [(576.10±114.29)mm(3)] and the BCNU group [(473.01±48.04)mm(3)] (both P<0.01). And the xenograft volume in these 3 treatment groups was even much lower than that in the control group [(1512.61±470.25) mm(3)] (all P<0.01). There was no significant difference in the volume of xenografts between the TNP-470 group and the BCNU group (P>0.05). The inhibition rate of the tumor growth in the TNP-470 plus BCNU group was (92.80±11.37)%, notably higher than that in the TNP-470 group [(61.91±6.29)%] and the BCNU group [(68.73±9.65)%] (both P<0.01) on the 21th day following treatment. There was no significant difference in the inhibition rate of tumor growth between the TNP-470 group and the BCNU group (P>0.05). The MVD of xenografts in the TNP-470 plus BCNU group was decreased significantly as compared with that in the TNP-470 group or the BCNU group (both P<0.05). The MVD of xenografts in the 3 treatment groups was markedly reduced as compared with that in the control group (all P<0.05). No significant changes in weights were observed before and after the treatment in each group (all P>0.05). It was concluded that the combination of TNP-470 and BCNU can significantly inhibit the growth of human glioblastoma xenografts in nude mice without evident side effects.

[Effect of wt p53 gene transfection on sensitivity of hyperthermia in C6 glioma cells].

OBJECTIVE: To investigate the effect of wt p53 gene transfection on the sensitivity of hyperthermia in C6 glioma. METHODS: The recombinant eukaryotic expressive vector pCMV-p53 plasmids were extracted, identified and transmitted to C6 glioma cells by stable transfection. The biological characteristics were compared among C6/p53 (+) cells, thermo-treated C6/p53 (+) cells, thermo-treated C6 cells, thermotolerance C6 cells and control C6 cells. Transplanted glioma was treated by laser interstitial thermotherapy (LITT) in tumor-bearing nude mice. RESULT: The wt p53 gene segments were extracted and correctly identified by restriction enzyme (Hind and EcoR). The optimal transfection concentration of plasmid to liposome was 1:6, neo gene expressed stably in C6 cells transfected with positive and blank plasmid. Thermotolerance C6 cell growth was normal in vitro, growth of C6/p53 (+) cells was inhibited. Growth of hyperthermia treated C6 cells was inhibited significantly 12 h after thermal treatment, cell proliferation activity of C6/p53 (+) cells was suppressed significantly 6 h after hyperthermia treatment. Apoptosis was observed in C6/p53 (+), thermo-treat C6 and thermo-treat C6/p53 (+) cells. The apoptosis ratio of hyperthermia treated C6/p53(+) cells was increased by 30 folds compared with that of control groups. Study in nude mouse model demonstrated lower positive inoculation rate in groups of C6/p53 (+) cells (57 %), hyperthermia treated C6 cells (75 %) and hyperthermia treated C6/p53(+) cells (20 %). C6/p53(+) LITT group showed the highest antitumor effect, compared with C6 LITT group(P<0.05). However, thermotolerance C6 LITT group had the lowest effect. CONCLUSION: Transfection of wt p53 gene can increase the sensitivity of hyperthermia in glioma cells.

Cranial arachnoid membranes: some aspects of microsurgical anatomy.

Although the arachnoid membranes have been known for more than 300 years, the anatomy of the arachnoid membranes has not been studied in detail. This study was performed to explore the microanatomical features of the cranial arachnoid membranes. The arachnoid membranes and cisterns were observed in eight Han Chinese adult human cadaveric brains with an operating microscope, without staining of intracranial structures or injection of colored material into blood vessels. Twenty seven arachnoid membranes and 21 subarachnoid cisterns were identified. The topographical features of each arachnoid membrane were described. On the basis of the arachnoid membranes we identified, the arachnoidal limits of the cisterns were discussed. The microsurgical anatomical research on the arachnoid membranes is a supplement to the anatomical study of the subarachnoid cisterns. The understanding of the topographical features of the arachnoid membranes is valuable to the reasonable dissection of the cisterns and the minimally invasive manipulations during microsurgical procedures.

Magnetic resonance imaging of transplanted neural stem cells in Parkinson disease rats.

In this study we implanted magnetically labeled neural stem cells (NSCs) in PD rats and then monitored their survival and migration in the host brain by magnetic resonance imaging (MRI). The mesencephalic NSCs were obtained from the brain of SD rats. Superparamagnetic iron oxide (SPIO) was transferred to NSCs by Lipofectamine transfection. Eighteen PD lesioned rats were selected for transplantation by evaluation of their rotational behavior in response to amphetamine and randomly assigned to 3 groups, i.e., sham group, PBS group and NSCs transplanted group, with 6 rats in each group. MR scanning was performed at 1, 2, 4, 6, 8 and 10 week(s) following transplantation. At the meantime, rotational behavior was assessed in each group. Our results showed that SPIO particles were clearly visible with Prissian blue staining in neurospheres and cells derived from NSCs. The rotational behavior of the NSCs transplanted group was remarkably improved compared with that of sham group and PBS group (P < 0.05). In vivo MR tracking of NSCs showed that SPIO labeling led to a strong susceptibility change of signal 1 week after transplantation on T2 weighted images. And a large circular hypointense signal appeared in the transplanted area on T2* gradient echo images. Ten weeks following transplantation, the hypointense signal on T2 weighted and T2* gradient echo images was still displayed. It is concluded that SPIO particles could label NSCs effectively, and MRI detection of SPIO labeled cells is a promising method and novel approach to analyzing the NSCs following transplantation in the treatment of PD.

Effect of wild-type p53 gene transfection on the growth and radiotherapeutic sensitivity of human glioma cells.

To evaluate the effect of wild-type p53 gene on the growth and radiotherapeutic sensitivity of human glioma cells, plasmid PC53-SN3 carrying wild-type p53 gene was transfected into U251 cells. p53 gene expression in transfected cells was detected by RT-PCR, and the cell growth inhibition and apoptosis in the absence or presence of irradiation were assessed by MTT and flow cytometry. The transfection of p53 gene into U251 cells was confirmed by RT-PCR. MTT showed that p53 gene alone induced strong inhibitory effect on the growth of U251 cells (inhibition rate (IR), (79.60 +/- 5.69)%). The killing effect of irradiation alone on U251 cells was not strong (IR: (17.06 +/- 4.35)% (17.39 +/- 1.67)% (18.73 +/- 4.68)%) and increased with the irradiation doses (3, 6, 9 Gy). When combined treatment of wild-type p53 gene transfection and irradiation was used, the effect was significantly increased (IR:(80.60 +/- 5.35)%. (90.30 +/- 1.67)%, (91.30 +/- 2.01)%). The apoptosis rate of U251 cells induced by p53 gene transfection was 17.38%. The rate induced by irradiation increased (4.61%, 4.84%, 5.40%) with the irradiation doses (3, 6, 9 Gy). The apoptosis rate was also significantly increased (17.80%, 20.03%, 22.34%) after combined treatment of p53 and irradiation with different doses (3, 6, 9 Gy). It is concluded that wild-type p53 gene and irradiation could result in synergistic inhibitory effect on the growth of human glioma cells.

Microsurgical anatomy of the interpeduncular cistern and related arachnoid membranes.

OBJECT: The goal of this study was to investigate the microsurgical anatomy of the interpeduncular cistern and related arachnoid membranes. METHODS: The interpeduncular cistern and related arachnoid membranes were studied in eight Han Chinese adult human cadaveric brains with the aid of an operating microscope. The interpeduncular cistern is one area in the cranial cavity in which the arachnoid membranes and trabeculae are extremely luxuriant and complicated. The Liliequist membrane, the medial pontomesencephalic membrane, and the lateral pontomesencephalic membranes form the walls of the interpeduncular cisterns. The basilar artery (BA) bifurcation membrane, posterior perforated membrane, and arachnoid trabeculae fill the cistern. These arachnoid membranes and trabeculae adhere to the hypothalamus, brainstem, and oculomotor nerves, and bind the bifurcation of the BA, posterior cerebral arteries, superior cerebellar arteries, posterior communicating arteries, and their perforating branches. CONCLUSIONS: Arachnoid membranes and trabeculae complicate the exposure and dissection of lesions within the interpeduncular cistern. All arachnoid membranes and trabeculae should be dissected and incised sharply during surgical procedures. The BA bifurcation membrane and the posterior perforated membrane must be incised after opening the Liliequist membrane for sufficient exposure of deep structures within the interpeduncular cistern.

[Electrophysiological influences of gamma knife at different doses on the compressed cat optic nerve].

OBJECTIVE: To investigate the electrophysiological influences of gamma knife at different doses on the compressed cat optic nerve. METHODS: Model of compressed optic nerve was established in 20 cats. Two months later, the 20 cats were randomly divided into 5 equal groups. Four groups accepted the irradiation of gamma knife at the dose of 10, 11, 12, and 13 Gy respectively. One group was used as controls. Pattern visual evoked potential examination was used 3 days, 1 week, half a month, and 1, 2, 3, 4, and 5 months after the beginning of irradiation. RESULTS: Electrophysiological changes could be observed 1 week later began to recover half a month later and then gradually recovered to normal with the lapse of time. Irreversible electrophysiological changes were observed in the groups undergoing gamma knife at the doses of 11 Gy and over, and these changes aggravated with the lapse of time. CONCLUSION: 10 Gy is the minimum dose of gamma knife that cause beneficial electrophysiological changes in the compressed cat optic nerves. The minimum dose that causes irreversible damage is 11 Gy.

The effects of wild-type p53 gene transfection on the growth and chemotherapeutic sensitivity of human glioma cells.

To evaluate the effects of wild-type p53 gene on the growth and chemotherapeutic sensitivity of human glioma cells, plasmid PC53-SN3 carrying wild-type p53 gene was transfected into U251 cells. p53 gene expression in transfected cells was detected by RT-PCR, the cell growth inhibition and apoptosis in either the absence or the presence of cisplatin was assessed by MTT and flow cytometry. The transfection of p53 gene into U251 cells was confirmed by RT-PCR. MTT showed that p53 gene by itself induced strong inhibition effect on the growth of U251 cells [inhibition rate, IR (79.60 +/- 5.69)%]. The killing effects of cisplatin by itself on U251 cells was not strong [IR (19.40 +/- 6.69)%, (24.41 +/- 2.68)%, (51.84 +/- 13.38)%, (66.22 +/- 5.02)%] and increased with the increase of cisplatin concentration (1, 2, 4, 8 micrograms/ml). When combined treatment of wild-type p53 gene transfection and cisplatin was used, that was significantly increased [IR (91.64 +/- 1.00)%, (94.98 +/- 1.67)%, (95.32 +/- 2.01)%, (95.65 +/- 1.00)%]. The apoptosis rate of U251 cells induced by p53 gene transfection was 17.38%. That induced by cisplatin increased (5.71%, 5.93%, 6.27%, and 6.81%) with the increase of cisplatin concentration (1, 2, 4, 8 micrograms/ml). The apoptosis rate was also significantly increased (23.50%, 23.54%, 23.89%, and 28.88%) after combined treatment of p53 and cisplatin with different concentration (1, 2, 4, 8 micrograms/ml). It is concluded that wild-type p53 gene and cisplatin could result in synergistic inhibition effects on the growth of human glioma cells.