Single cell DNA damage/repair assay using HaloChip

The molecular level damage to DNA is important due to DNA's susceptibility to free radical attacks and crucial roles in maintaining cell functions. Although a panel of techniques can be used to detect DNA damages, most of them are limited due to low sensitivity, low throughput, incompatibility for automated data analysis, and labor-intensive operations. We have developed a cell array based DNA damage assay in which mammalian cells are attached on an array of microfabricated patterns through electrostatic interactions. After trapping patterned cells inside gels, damaged DNA fragment can diffuse out of the nucleus and form a halo around each cell inside gels. The halo array can be observed fluorescently after labeling DNA with ethidium bromide. DNA damages can be determined sensitively at the single cell level, accurately due to the symmetric shape of the halo, and automatically due to the spatial registry of each cell and the nonoverlapping halos surrounding cells. The HaloChip can be used to detect DNA damages caused by chemicals and ultraviolet and X-ray irradiations with high efficiency. A major advantage of HaloChip is the ability to increase throughout by spatially encoding multiple dosing conditions on the same chip. Most importantly, the method can be used to measure variations in response to DNA damaging agents within the same cell population. Compared with halo assay or comet assay alone, this method allows automated analysis of a million cells without an overlapping issue. Compared with the microwell array based comet assay, this method can selectively capture and analyze cells, and the results can be easily analyzed to provide precise information on DNA damage. This method can be used in a broad range of clinical, epidemiological, and experimental settings.     

Rapid Determination of Technetium-99 in Large Volume Seawater Samples Using Sequential Injection Extraction Chromatographic Separation and ICP-MS Measurement

An automated method was developed for rapid determination of (99)Tc in large volume seawater samples. The analytical procedure involves preconcentration of technetium with coprecipitation, online separation using extraction chromatography (two TEVA columns) implemented in a sequential injection setup, and measurement of (99)Tc by inductively coupled plasma mass spectrometry (ICP-MS). Chromatographic behaviors of technetium, molybdenum, and ruthenium were investigated, and the mechanism of adsorption and elution of TcO(4)(-) on a TEVA column using HNO(3) was explored. The results show that not only NO(3)(-) but also acidity (or concentration of H(+)) of the loading or eluting solution affect the adsorption and desorption of TcO(4)(-) on TEVA resin. Decontamination factors of more than 1 × 10(6) for ruthenium and 5 × 10(5) for molybdenum are achieved. Chemical yields of technetium in the overall procedure range from 60% to 75% depending on the sample volumes, and a detection limit of 7.5 mBq/m(3) (or 11.5 pg/m(3)) for 200 L of seawater was obtained. Compared with the conventional analytical procedure, the developed method significantly reduces analytical time. A batch of samples (n > 4) can be analyzed within 24 h. The method has been successfully applied for rapid and automated determination of low level (99)Tc in large volume seawater samples. The analytical results of seawater samples collected in Denmark show a good agreement with the values obtained using the conventional method.     

Acetylcholinesterase liquid crystal biosensor based on modulated growth of gold nanoparticles for amplified detection of acetylcholine and inhibitor

A novel acetylcholinesterase (AChE) liquid crystal (LC) biosensor based on enzymatic growth of gold nanoparticles (Au NPs) has been developed for amplified detection of acetylcholine (ACh) and AChE inhibitor. In this method, AChE mediates the hydrolysis of acetylthiocholine (ATCl) to form thiocholine, and the latter further reduces AuCl(4)(-) to Au NPs without Au nanoseeds. This process, termed biometallization, leads to a great enhancement in the optical signal of the LC biosensor due to the large size of Au NPs, which can greatly disrupt the orientational arrangement of LCs. On the other hand, the hydrolysis of ATCl is inhibited in the presence of ACh or organophosphate pesticides (OPs, a AChE inhibitor), which will decrease the catalytic growth of Au NPs and, as a result, reduce the orientational response of LCs. On the basis of such an inhibition mechanism, the AChE LC biosensor can be used as an effective way to realize the detection of ACh and AChE inhibitors. The results showed that the AChE LC biosensor was highly sensitive to ACh with a detection limit of 15 μmol/L and OPs with a detection limit of 0.3 nmol/L. This study provides a simple and sensitive AChE LC biosensing approach and offers effective signal enhanced strategies for the development of enzyme LC biosensors.     

In situ high-pressure and high-temperature experiments on n-heptane

The Raman spectroscopy of n-heptane was investigated in a moissanite anvil cell at ambient temperatures and a diamond anvil cell under pressures of up to ~2000 MPa and at temperature range from 298 to 588 K. The results show that at room temperature the vibration modes, assigned to the symmetric and antisymmetric stretching of CH(3) and CH(2) stretching, shifted to higher frequency according to quasi-linearity with increasing pressure, and a liquid-solid phase transition occurred at near 1150 MPa. The high-temperature solidus line of n-heptane follows a quadratic function of P = 0.00737T(2) + 5.27977T - 1195.76556. Upon phase change, fitting the experimental data obtained in the temperature range of 183～412 K to the Clausius-Clapeyron equation allows one to define the thermodynamic parameters of n-heptane of dP/dT = 0.01474T + 5.27977.     

Fe(3)O(4) nanobelts: one-pot and template-free synthesis, magnetic property, and application for lithium storage

We report on the synthesis of Fe(3)O(4) nanobelts with good magnetic properties and lithium storage performances by using a one-pot and template-free hydrothermal method with Na(2)CO(3) and FeCl(2) as the reactants. By controlling the amount of Na(2)CO(3), we obtained pure Fe(3)O(4) nanobelts with widths of 0.1-2?μm, thicknesses of about 10 nm and lengths of 20-30?μm, showing a high aspect ratio. XRD and SAED patterns of the obtained sample demonstrated that the Fe(3)O(4) nanobelts were well crystallized. Nitrogen adsorption/desorption measurements showed that Fe(3)O(4) nanobelts manifested a BET surface area of 25.04?m(2)?g(-1). Further experiments demonstrated that the amount of Na(2)CO(3) played an important role in controlling both the morphologies and crystal structures of the products. The formation mechanism of Fe(3)O(4) nanobelts was also studied. More importantly, we found that the Fe(3)O(4) nanobelts showed magnetic properties with a magnetic saturation value of 77.0?emu?g(-1) and lithium storage performances with a high initial discharge capacity of 1090?mAh?g(-1) at a current rate of 500?mA?g(-1), and a reversible capacity of 404?mAh?g(-1) retained after 60 charge/discharge cycles. These results suggest that the Fe(3)O(4) nanobelts might be promising for magnetic and lithium battery applications.     

Broadband enhancement in thin-film amorphous silicon solar cells enabled by nucleated silver nanoparticles

Recently plasmonic effects have gained tremendous interest in solar cell research because they are deemed to be able to dramatically boost the efficiency of thin-film solar cells. However, despite of the intensive efforts, the desired broadband enhancement, which is critical for real device performance improvement, has yet been achieved with simple fabrication and integration methods appreciated by the solar industry. We propose in this paper a novel idea of using nucleated silver nanoparticles to effectively scatter light in a broadband wavelength range to realize pronounced absorption enhancement in the silicon absorbing layer. Since it does not require critical patterning, experimentally these tailored nanoparticles were achieved by the simple, low-cost and upscalable wet chemical synthesis method and integrated before the back contact layer of the amorphous silicon thin-film solar cells. The solar cells incorporated with 200 nm nucleated silver nanoparticles at 10% coverage density clearly demonstrate a broadband absorption enhancement and significant superior performance including a 14.3% enhancement in the short-circuit photocurrent density and a 23% enhancement in the energy conversion efficiency, compared with the randomly textured reference cells without nanoparticles. Among the measured plasmonic solar cells the highest efficiency achieved was 8.1%. The significant enhancement is mainly attributed to the broadband light scattering arising from the integration of the tailored nucleated silver nanoparticles.     

Experimental Investigation of Second Interface Cement Bond Evaluation

Cement bond model wells (1:10 scaled-down) were made with a gradually degrading cement annulus for cement bond evaluation of the first interface (between the casing and the cement annulus) and the second interface (between the cement annulus and the formation). Experimental simulation on cement bond logging was carried out with these model wells. The correlation of acoustic waveforms, casing wave energy and free casing area before and after cement bonding of the second interface was established. The experimental results showed that the arrival of the casing waves had no relationship with the cement bonding of the second interface, but the amplitude of the casing head wave decreased obviously after the second interface was bonded. So, cement bonding of the second interface had little effect on the evaluation of the cement bond quality of the first interface by using casing head wave arrivals. Strong cement annulus waves with early arrivals were observed before the second interface was bonded, while obvious "formation waves" instead of cement annulus waves were observed after the second interface was bonded.     

井间地震地质分辨能力浅析

井间地震无低速带干扰,具有高信噪比、高采样率等特点,能够识别单砂体、韵律层和层内夹层,在沉积微相划分、微构造研究、低序级断层识别、储层精细描述等方面具有明显的优势。文章从频谱特征、反射系数、分层能力等方面讨论了井间地震的地质分辨能力,希望为井间地震的进一步应用提供一个借鉴尺度。研究认为井间地震能够表征地层横向的变化,其垂向分辨能力可以达到1-5m,是描述剩余油“总体分散、局部集中”分布的重要技术手段。     

Microstructure and Mechanical Properties of X80 HTP Pipeline Steel Produced by Steckel Mill

The demand for energy becomes a bottleneck in development of China. Economically delivering natural gas and oil through pipeline is an urgent problem to be solved. In the present work, X80 pipeline steel with high toughness and thickness 21.0 mm was produced through HTP (High Temperature Processing) by Steckel mill rolling. And the microstructure and mechanical properties of the X80 pipeline steel, which produced by different processing parameters such as reheating temperature of slabs, resume temperature, finishing temperature, accelerated cooling exit temperature and cooling rate, were analyzed. The results show that finishing temperature of 800-820℃ and cooling rate above 20℃/s are necessary to obtain fine and uniform acicular ferrite with high solute niobium in X80 pipeline steel.