[Nondestructive Measurement of RDX Grain's Internal Pressure by Using Raman Spectrum Method].

RDX is a most widely used military explosive. As the development of new warheads, there are more and more applications of RDX with abnormal grain shapes. To ensure the operational effectiveness of the new warheads, it is necessary to find an on-line nondestructive methods that can measure the RDX grain's internal pressure. In this paper, we use Raman spectrum and first-principles methods to determine the characteristic spectral line of the RDX samples and have studied the shift of the Raman spectral lines under various pressures. In particular, we measured the RDX samples under the pressures of 10, 20 and 30 MPa, respectively, and checked the fitting errors by measuring the RDX samples under the pressures of 15, 25 and 35 MPa, respectively. It is found that the shift of the characteristic Raman spectral line has a good linear dependence on the external pressures. Therefore, we can at first calibrate the linear relation between the shift of the Raman spectral line of regular RDX and the pressures in laboratory and then measure the Raman spectral line shift of the RDX with abnormal shapes. Based on the calibrated linear relation and the measurement of Raman spectra, one can determine the internal pressure in RDX. In this way, we can realize the nondestructive detection of the internal pressure of RDX. The experiment results show that this method has the advantage of good sensitivity and reproducibility. The Raman spectrum method has been successfully tested in the warhead production line.

Rapid Focused Ion Beam Milling Based Fabrication of Plasmonic Nanoparticles and Assemblies via "Sketch and Peel" Strategy.

Focused ion beam (FIB) milling is a versatile maskless and resistless patterning technique and has been widely used for the fabrication of inverse plasmonic structures such as nanoholes and nanoslits for various applications. However, due to its subtractive milling nature, it is an impractical method to fabricate isolated plasmonic nanoparticles and assemblies which are more commonly adopted in applications. In this work, we propose and demonstrate an approach to reliably and rapidly define plasmonic nanoparticles and their assemblies using FIB milling via a simple "sketch and peel" strategy. Systematic experimental investigations and mechanism studies reveal that the high reliability of this fabrication approach is enabled by a conformally formed sidewall coating due to the ion-milling-induced redeposition. Particularly, we demonstrated that this strategy is also applicable to the state-of-the-art helium ion beam milling technology, with which high-fidelity plasmonic dimers with tiny gaps could be directly and rapidly prototyped. Because the proposed approach enables rapid and reliable patterning of arbitrary plasmonic nanostructures that are not feasible to fabricate via conventional FIB milling process, our work provides the FIB milling technology an additional nanopatterning capability and thus could greatly increase its popularity for utilization in fundamental research and device prototyping.

In Situ Fabrication and Characterization of Graphene Electronic Device Based on Dual Beam System.

The graphene, as a one atomic-layer material, is very sensitive to the environment and easy to be polluted. Here, we propose an in situ fabrication and characterization method for graphene electronic devices using the Dual Beam system. Instead of the conventional photo/e-beam lithography, plasma etching and lift-off techniques, the focused ion beam (FIB) is employed to pattern the graphene and the e-beam induced deposition of platinum (Pt) is adopted to fabricate the electrodes. Using the nano-probes in the specimen chamber, we obtained the typical electronic bipolar behavior of graphene in situ both with the Pt/graphene contact and the nano-probes/graphene direct contact. In the whole process of the fabrication and characterization, the graphene sample is kept in high vacuum condition all the time.

A novel route for the removal of bodily heavy metal lead (II).

The lead ion concentration in bile is considerably higher than in blood, and bile is released into the alimentary tract. Thiol-modified SBA-15 administered orally can combine with lead ions in the alimentary tract. In this paper, the in vitro lead absorption of bile was investigated. This thiol-modified SBA-15 material was used in pharmacodynamics studies on rabbits. The result that the lead content in faeces was notably higher indicates that thiol-modified SBA-15 can efficiently remove lead. The mechanism could include the following: thiol-modified SBA-15 material cuts off the heavy metal lead recirculation in the process of bile enterohepatic circulation by chelating the lead in the alimentary tract, causing a certain proportion of lead to be removed by the thiol mesoporous material, and the lead is subsequently egested out of the body in faeces. The results indicate that this material might be a potential non-injection material for the removal bodily heavy metal lead in the alimentary tract. This material may also be a useful means of lead removal, especially for non-acute sub-poisoning symptoms.

[Study on Raman spectra of multi-walled carbon nanotubes with different parameters].

In order to study the influencing factors on Raman spectroscopy, we research a series of comparative Raman spectroscopy of multi-walled carbon nanotubes (MWCNT) with different tube diameter and length. The results suggest that the G peak and D peak of MWCNT are all red-shifted as compared to that of polycrystalline graphite; In the same conditions, the peak intensity (G peak and D peak) is directly proportional to the diameter of the MWCNT, and inversely proportional to the length of the MWCNT; G peak frequency shift is closely related to the MWCNT diameter and length, which are inversely proportional to the diameter (with identical results of the single-walled carbon nanotube radial breathing modes) and direct proportional to the length. While, the influences of the diameter and length on D peak frequency shift are weak, and future analysis for the reason of this kind of phenomenon is as follows. Subsequently, we investigated the relation between D peak frequency shift and MWCNT aspect ratio, the relationship between G peak frequency shift and aspect ratio is nearly linear increase. Using the same analysis method, we plotted the different graphs of G peak and D peak intensity vs the aspect ratio of MWCNT, respectively. As the expected, the linear degression relation are existent in the two relationships.

Growth of millimeter-size single crystal graphene on Cu foils by circumfluence chemical vapor deposition.

A simply and reproducible way is proposed to significantly suppress the nucleation density of graphene on the copper foil during the chemical vapor deposition process. By inserting a copper foil into a tube with one close end, the nucleation density on the copper foils can be reduced by more than five orders of magnitude and an ultra-low nucleation density of ~10 nucleus/cm(2) has been achieved. The structural analyses demonstrate that single crystal monolayer graphene with a lateral size of 1.9 mm can be grown on the copper foils under the optimized growth condition. The electrical transport studies show that the mobility of such single crystal graphene is around 2400 cm(2)/Vs.

Position-addressable digital laser scanning point fluorescence microscopy with a Blu-ray disk pickup head.

A compact and position-addressable blue ray scanning microscope (BSM) based on a commercially available Blu-ray disk pickup head (PUH) is developed for cell imaging with high resolution and low cost. The BSM comprises two objective lenses with numerical apertures (NAs) of 0.85 and 0.6 for focusing blue and red laser beams, respectively, on the sample slide. The blue and red laser beams are co-located adjacent to each other and move synchronously. A specially designed sample slide is used with a sample area and an address-patterned area for sample holding and address recognition, respectively. The blue laser beam is focused on the sample area and is used for fluorescent excitation and image capturing, whereas the red laser beam is focused on the address-patterned area and is used for address recognition and dynamic focusing. The address-patterned area is divided into 310 sectors. The cell image of each sector of the sampling area has a corresponding address pattern. Fluorescence images of monkey-derived kidney epithelial cells and fibroblast cells in which the F-actin is stained with fluorophore phalloidin CF 405 are measured by the BSM, with results comparable to those measured by a Leica TCS CP2 confocal microscope. The cell image of an area of interest can be easily tracked based on the coded address, and a large-area sample image can be accurately reconstructed from the sector images.

Study on the heterodyning scattering of retroreflective free-space optical communication with optical heterodyning.

Retroreflective free-space optical communication is important because of advantages such as small volume, low weight, and low power consumption. Link failure caused by bad weather conditions will occur because of the attenuated retroreflective signal and the increased scattering of the transmitted light. The scattering effect can be reduced because the physical properties (including polarization, wavefront, and phase) of the scattering signal are different from those of the retroreflective signal. The physical properties of the scattering signal are obtained using a polarization-sensitive Monte Carlo model, and the heterodyning scattering signal is obtained using heterodyning theory. Results show that, with optical heterodyning, the scattering effect is efficiently reduced, and advantages such as better adaptability to bad weather conditions, longer communication range, more compact transceiver design, larger covering area of the optical receiver, and easier target acquisition for the retromodulator than before can also be obtained.

Electric-induced oxide breakdown of a charge-coupled device under femtosecond laser irradiation.

A femtosecond laser provides an ideal source to investigate the laser-induced damage of a charge-coupled device (CCD) owing to its thermal-free and localized damage properties. For conventional damage mechanisms in the nanosecond laser regime, a leakage current and degradation of a point spread function or modulation transfer function of the CCD are caused by the thermal damages to the oxide and adjacent electrodes. However, the damage mechanisms are quite different for a femtosecond laser. In this paper, an area CCD was subjected to Ti: sapphire laser irradiation at 800 nm by 100 fs single pulses. Electric-induced oxide breakdown is considered to be the primary mechanism to cause a leakage current, and the injured oxide is between the gate and source in the metal-oxide semiconductor field-effect transistor (MOSFET) structure for one CCD pixel. Optical microscopy and scanning electron microscopy are used to investigate the damaged areas and the results show that the electrodes and the oxide underneath are not directly affected by the femtosecond laser, which helps to get rid of the conventional damage mechanisms. For the primary damage mechanism, direct damage by hot carriers, anode hole injection, and an enlarged electric field in the insulating layer are three possible ways to cause oxide breakdown. The leakage current is proved by the decrease of the resistance of electrodes to the substrate. The output saturated images and the dynamics of an area CCD indicate that the leakage current is from an electrode to a light sensing area (or gate to source for a MOSFET), which proves the oxide breakdown mechanism.

Adsorption of gas molecules on monolayer MoS2 and effect of applied electric field.

: Using first-principles calculations, we investigate the adsorption of various gas molecules (H2, O2, H2O, NH3, NO, NO2, and CO) on monolayer MoS2. The most stable adsorption configuration, adsorption energy, and charge transfer are obtained. It is shown that all the molecules are weakly adsorbed on the monolayer MoS2 surface and act as charge acceptors for the monolayer, except NH3 which is found to be a charge donor. Furthermore, we show that charge transfer between the adsorbed molecule and MoS2 can be significantly modulated by a perpendicular electric field. Our theoretical results are consistent with the recent experiments and suggest MoS2 as a potential material for gas sensing application.

Photocurrent imaging of CdS/Al interfaces based on microscopic analysis.

We investigate the lateral variations of photocurrent on CdS/Al interfaces, with a combination of a semiconductor characterization system and scanning near-field optical microscopy, in which the near-field probe is used to locally induce photocurrent on the CdS/Al interfaces with high spatial resolution. By analyzing the spatially resolved photoresponse, we find that the resolution is worsened in the photocurrent images by the lateral diffusion of the photoexcited electrons and that the photoelectric properties of the CdS/Al interfaces are strongly affected by the bias voltage. Furthermore, in a complementary experiment, we also demonstrate that the photocurrent measurements can reveal structures that are not present in the case of shear-force data. The analysis demonstrates the band structure and microscopic mechanism of CdS/Al heterostructures, which provide an effective approach for developing CdS-based photoelectronic devices.

Charge transport property of mesoporous silica thin films incorporated with gold nanoparticles.

Highly ordered mesoporous silica thin films (MSTFs) were spin-coated on Si wafers by self-assemble of water-soluble nanocrystal micelles with soluble silica. The gold nanoparticles (GNPs) were assembled within the silica matrix. Based on this nanocomposite, nanoscale electrodes were fabricated to form single electron devices. Two main transport behaviors of resemblant Coulomb blockage were demonstrated in the current-voltage measurements. The Coulomb island size calculated from the current-voltage data was close to the real size of the GNPs. The random loading positions of GNPs in the MSTF, which lead to uncertain tunneling resistances, might be response for the conductive differences.

Fabrication and characterization of single electron tunneling device on Au/SiO2 nanocomposite films.

Amino-functionalized mesoporous silica thin films (AF-MSTFs) have been directly dip-coated on silica wafers by co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) in the presence of Brij56 (C16H33(OCH2CH2)10OH) under acidic condition. Using the AF-MSTFs as templates, gold nanoparticles (GNPs) are well formed within the mesopores. The transmission electron microscope images and X-ray diffraction patterns demonstrate that the MSTFs are consistent with well ordered mesostructures and the GNPs are well crystallized in the templates. A single electron tunneling device based on self-assembled GNPs of the Au/SiO2 nanocomposite film has been fabricated by using nanolithographic definitions. The device shows Coulomb stair-cases at 77 K. The data are interpreted as single electron tunneling through the GNP which served as a Coulomb island between the source and drain electrodes. The charging energy is estimated to be much larger than the thermal energy at 77 K. The Coulomb island size calculated from the experimental data is -3.8 nm, which is consistent with the size of the GNPs self-assembled in the MSTFs.

Histological complete response after neoadjuvant XELOX in advanced gastric carcinoma.

We report on a case of a 65-year-old Chinese male with locally advanced gastric adenocarcinoma achieving pathological complete response after neoadjuvant chemotherapy with capecitabine and oxaliplatin (XELOX) regimen. He underwent esophagogastroduodenoscopy, which revealed a 6x5cm gastric ulcer. Biopsy of gastric ulcer revealed adenocarcinoma. Further workups with abdominal enhancement computed tomography (CT) staged his cancer as T4N2M0. He received 2 cycles of neoadjuvant chemotherapy with XELOX without severe toxicity. Afterwards, he underwent curative surgery consisting of total gastrectomy with extended D2 lymph node dissections and a Roux-en-Y esophagojejunostomy. On microscopic examination, no tumor cells were detected in the ulcer scar of the resected stomach and in the regional lymph nodes. The benefit of XELOX regimen as neoadjuvant chemotherapy in gastric cancer is worth further investigation.

Characteristics of non-line-of-sight polarization ultraviolet communication channels.

This paper investigates characteristics of polarization in non-line-of-sight (NLOS) ultraviolet (UV) communication channels based on a vectorized polarization-sensitive model of NLOS multiple-scatter propagation. The degree of polarization has been analyzed from the following factors: elevation angles, beam angle, field-of-view, off-axis angles, and baseline distance, etc. We draw conclusions that will guide the design of polarization multiplexing technology in NLOS UV communication systems. Outdoor experimentation has validated that this technology is useful to improve the data rate.

Bandgap tuning in armchair MoS2 nanoribbon.

We report on the first-principles calculations of bandgap modulation in armchair MoS(2) nanoribbon (AMoS(2)NR) by transverse and perpendicular electric fields respectively. In the monolayer AMoS(2)NR case, it is shown that the bandgap can be significantly reduced and be closed by transverse field, whereas the bandgap modulation is absent under perpendicular field. The critical strength of transverse field for gap closure decreases as ribbon width increases. In the multilayer AMoS(2)NR case, in contrast, it is shown that the bandgap can be effectively reduced by both transverse and perpendicular fields. Nevertheless, it seems that the two fields exhibit different modulation effects on the gap. The critical strength of perpendicular field for gap closure decreases with increasing number of layers, while the critical strength of transverse field is almost independent of it.

Magnetic and electronic properties of α-graphyne nanoribbons.

Based on the first-principles calculations, we investigate the magnetic and electronic properties of α-graphyne nanoribbons (NRs). We show that all the armchair α-graphyne NRs are nonmagnetic semiconductors with band gaps as a function of ribbon widths. The zigzag α-graphyne NRs are found to have magnetic semiconducting ground state with ferromagnetic ordering at each edge and opposite spin orientation between the two edges. Under the application of transverse electric field, we further predict the existence of half-metallicity in the zigzag NRs which strongly depends on the width of the ribbon.

Theoretical evaluation of scattering effect on retroreflective free-space optical communication.

Retroreflective free-space optical (RFSO) communication is a new concept of optical communication; it consists of an optical transceiver and a retromodulator and has advantages such as light weight, small volume, and low power consumption. The power captured by the receiver consists of two parts: retroreflective and scattering. The retroreflective characteristics are obtained using an analytical formula, the scattering characteristics using a Monte Carlo model. Results show that the scattering power plays an important role in a RFSO communication link, especially when the communication range is long or the meteorological range is short. Some rules are also obtained for the sake of system design, which include increasing the range from the transmitter and the receiver properly, increasing the area of the retromodulator, limiting the field of view of the receiver, and limiting the beam divergence of the transmitter.

Study of effects of obstacle on non-line-of-sight ultraviolet communication links.

This paper studies the effects of the obstacle on non-line-of-sight ultraviolet communication links using multiple-scatter model based on a Monte Carlo method. On the condition that transmitter beam and receiver FOV just pass the top of the obstacle, and ranges is fixed, the received energy density is at its maximum. The path loss increases when the transmitter or the receiver is much near to the obstacle, because the nearby common scattering volumes decrease intensively. The optimal received range decreases with the increasing of the distance between transmitter and obstacle. The predictions are validated with experimental measurements. This work can be used for the guidance of UV system design and network technology to apply in complex surroundings, such as mountain, buildings, etc.

Vectorized polarization-sensitive model of non-line-of-sight multiple-scatter propagation.

The existing Monte-Carlo-based non-line-of-sight (NLOS) multiple-scatter propagation model is extended to include polarization and also vectorized to improve the simulation speed by about 500 times. This model is validated by the noncoplanar single-scatter model; the results show a perfect match. Numerical examples for various polarization setups are obtained, and results show that the single-scatter and multiple-scatter signals are all polarization dependent. Therefore, NLOS polarized UV communication with a high data rate is achievable--the polarizing information is coded by a time-dependent polarizer, influenced by the atmospheric channel, and decoded according to the distribution characteristics of the scattered signals after the time-independent analyzers.