折流板式外压管超滤器的传质研究

在外压管超滤器的管束上,设置了弓形和环形折流挡板,有效地提高了流体湍动程度。用α-淀粉酶为料液,测定了不同挡板型式时的蛋白凝胶层浓度和传质系数,并建立了传质准数方程。

Morphology Control of TiO_(2)Nanotubes towards High-Efficient Electrodes for Supercapacitor

This article studies the role of electrochemical parameters in controlling the morphology of oxidized TiO_(2)nanotubes and the electrochemical performance of modified TiO_(2)nanotubes.Humidity is a key factor for fabricating TiO_(2)nanotubes.When the relative humidity belows 70%,the TiO_(2)nanotubes can be successfully prepared.What's more,by changing the anodization voltage and time,the diameter and the length of TiO_(2)nanotubes can be adjusted.In addition,the TiO_(2)nanotubes are modified through electrochemical self-doping and loading Pt metal particles on the surface of the nanotubes,which promotes the performance of the supercapacitor.The sample anodized at 100 V for 3 h has a specific capacity of up to 2.576 mF/cm~2 at a scan rate of 100 mV/s after self-doping,and its capacity retention rate still remains at 89.55%after 5000 cycles,demonstrating excellent cycling stability.The Pt-modified sample has a specific capacity of up to 3.486 mF/cm~2 at the same scan rate,exhibiting more outstanding electrochemical performance.

前牙瘘孔一次性修复报道

笔者从门诊就诊的病历中选择58颗残冠残根牙齿(有瘘型)，行一次性根管超充术的同时用根管钉固位，冠部光固化树脂修复，经临床3年追踪观察，此疗法患者就诊次数少、费用极低，而且就诊一次就可得到牙冠外形的恢复，使患者在他人面前增强了自信心，不再因牙齿的残缺而羞色。达到了美学的标准，提高了疗效。

The Role of Transesophageal Echocardiography for Transcatheter Closure of Atrial Septal Defects with the Amplatzer Septal Occluder

Objective: To evaluate of the role of transesophageal echocardiography (TEE)in percutaneous closure of atrial septal defects (ASD) with the Amplatzer septal occluder. Methods:Sixty- two patients (10 to 55 years of age) were selected for percutaneous closure of ASD bytrans-esophageal echocardiography, which was also used to monitor the procedure, to select theappropriate size of the Amplatzer device, to verify its position, and to access the immediateresults of the procedure. During the follow-up, transthoracic echocardiography (TTE) or TEE was usedto evaluate the presence and magnitude of residual shunt (RS), device position, and right cardiacchamber diameters. Results: The mean ASD diameter by TTE ([19. 1 +- 5. 8] mm) was significantlysmaller (P< 0. 001) than the stretched diameter of the ASD (25. 1 +- 6. 4) mm. There are nosignificant differences between the TEE -measured value (23. 5+_6. 2) mm and the stretched diameterof the ASD (P > 0. 05). Due to proper patient selection all procedures were successful. There wasimmediate and complete closure in 61/62 patients, only one patients had trivial residual shunt.Follow- up was performed using TTE or TEE right after operation, 1 d, 1 month, 3 months, 6 monthsand yearly thereafter. Ail, patients remain asymptomatic without any clinical or technical problems.Conclusion: With the aid of TEE, percutaneous closure of ASD can be performed successfully, safely,and effectively.

Ultrastructural Studies on the Sieve Elements in Root Protophleom of Arabidopsis thaliana

The ultrastructures of the root protophleom sieve element at different developmental stages of Arabidopsis thaliana L. were investigated using the technique of high pressure freezing and freeze substitution fixing specimen. The results show that in the development of the sieve elements, the nuclei undergo typical characteristics of the programmed cell death (PCD): the nuclear envelopes form emboli, the chromatin condenses and aggregates towards the nuclear envelope, which degrades and fully disappears later. Before the nucleus degradation, neither the nuclear envelope undulation, nucleus lobe nor marked dilation (or bleb) of perinuclear space could be observed. In the cytoplasm of the mature sieve element, there are starch-like granules separately sheathed with a layer of membrane and usually with mitochondria around. These gnanules seem to provide substrates to mitochondria in their function. Small vacuoles originate from endoplasmic reticulum (ER), and no bigger vacuole was found.

A Novel Ultra-Thin Channel Poly-Si TFT Technology

A novel low temperature poly\|Si(LTPS) ultra\|thin channel thin film transistor (UTC\|TFT) technology is proposed. The UTC\|TFT has an ultra\|thin channel region (30nm) and a thick drain/source region (300nm). The ultra\|thin channel region that can result in a lower grain\|boundary trap density in the channel is connected to the heavily\|doped thick drain/source region through a lightly\|doped overlapped region. The overlapped lightly\|doped region provides an effective way for the electric field to spread in the channel near the drain at high drain biases, thereby reducing the electric field there significantly. Simulation results show the UTC\|TFT experiences a 50% reduction in peak lateral electric field compared to that of the conventional TFT. With the low grain\|boundary trap density and low drain electric field, excellent current saturation characteristics and high drain breakdown voltage are achieved in the UTC\|TFT. Moreover, this technology provides the complementary LTPS\|TFTs with more than 2 times increase in on\|current, 3.5 times reduction in off\|current compared to the conventional thick channel LTPS TFTs.

Fabrication and Simulation of an AlGaAs/GaAs Ultra-Thin Base NDR HBT

A novel mesa ultra-thin base AlGaAs/GaAs HBT is designed and fabricated with wet chemical selective etch technique and monitor electrode technique. It has a particular and obvious voltage-controlled NDR whose PVCR is larger than 120. By use of device simulation,the cause of NDR is that increasing collector voltage makes the ultrathin base reach through and the device transforms from a bipolar state to a bulk barrier state. In addition, the simulated cutoff frequency is about 60-80GHz.

Fabrication of superaligned carbon nanotubes reinforced copper matrix laminar composite by electrodeposition

A new kind of laminar metal matrix nanocomposite（MMC） was fabricated by an electrodeposition process with copper and superaligned carbon nanotubes film（SACNT film）.The SACNT film was put on a titanium plate and then a layer of copper was electrodeposited on it.By repeating the above process,the laminar Cu/SACNT composite which contains dozens or hundreds of layers of copper and SACNT films was obtained.The thickness of a single copper layer was controlled by adjusting the process parameter easily and the thinnest layer is less than 2 μm.The microscopic observation shows that the directional alignment structure of SACNT is retained in the composite perfectly.The mechanical and electrical properties testing results show that the tensile and yield strengths of composites are improved obviously compared with those of pure copper,and the high conductivity is retained.This technology is a potential method to make applicable MMC which characterizes high volume fraction and directional alignment of carbon nanotubes.

Seasonal Changes in the Ultrastructure of the Vascular Cambium in Shoots of Populus tomentosa

Wood is the product of cambial activity in trees, and the seasonal activity style of cambium directly influences wood biomass production, structures and properties. The seasonal changes in the ultrastructure of the vascular cambium activity of Populus tonientosa Carr. planted in Beijing area were examined in shoot tissues collected during 15 months by means of transmission electron microscopy. Before xylem mother cells reactivated completely, the dividing fusiform cells in cambium and new phloem cells had appeared at the same time. The initiation of cambial activity may be related to the bud sprouting and the young leaf growth in shoots. More details about the ultrastructural changes of cambial cells at the onset of cambial activity have been gained. When the large vacuole in active cambial cells divided into smaller ones during the dormant phase, proteinaceous material that disappeared in active cambial cells refilled many of these small vactioles. In addition, lipid droplets and starch granules had the same cycles as proteinaceous material. The plasmalemma invaginations of fusiform cells were observed not only in active phase but also in dormancy. The endomembrane system consisting of nuclear membrane, endoplasmic reticulum (ER), dictyosomes and their secretory vesicles, changed in form and distribution at different phases during a cycle and performed important roles at the onset of active cambium and during the wall formation process of secondary xylem cells. The tangential walls remained relatively thin throughout the year but the radial walls thickened markedly when the cambium was dormant. During the transition from dormancy to activity, a partial autolysis occurred in the radial walls of the cambial cells, especially at the cell wall junctions. A notable feature of the cells at the onset of cambial activity was the thinning of the radial walls.

灯光下的背影(外一首)

我走在灯光下的林荫小道。 夜风凉凉地吹，树叶“沙沙”作响。 一个背影在我前面，不远不近、不紧不慢地走着。

A Broadband Long-Wavelength Superluminescent Diode Based on Graded Composition Bulk InGaAs

A novel unselective regrowth buried heterostructure long-wavelength superluminescent diode （SLD） with a graded composition bulk InGaAs active region is developed by metalorganic vapor phase epitaxy （MOVPE）. At a 150mA injection current, the full width at half maximum of the emission spectrum of the SLD is about 72nm, ranging from 1602 to 1674nm. The emission spectrum is smooth and flat. The ripple of the spectrum is less than 0.3dB at any wavelength from 1550 to 1700nm. An output power of 4.3mW is obtained at a 200mA injection current under continuous-wave operation at room temperature. This device is suitable for the applications of light sources for gas detectors and L-band optical fiber communications.

Design considerations for the improved current-doubler-rectifier ZVS PWM full-bridge converter

The improved current-doubler-rectifier zero-voltage-switching PWM full-bridge converter (CDR ZVS PWM FB converter) achieves ZVS for the switches in a wide load range with the use of the energy stored in the output filter inductances, and the rectifier diodes commute naturally, therefore no oscillation and voltage spike occurs. The transformer needs no special manufacture method to limit the leakage inductance. The ZVS achievement and the design considerations for the output filter inductances and the blocking capacitor are discussed for the improved CDR ZVS PWM FB converter. A 540 W prototype converter is built in the lab to verify the operational principle and design considerations for the improved converter, the experimental results are also included.

Effects of Ultrasonication on Genetic Transformation via the Pollen-Tube Pathway in Chinese Cabbage

[Objective] This research aimed to explore the method to increase conversion rate of pollen-tub pathway in Chinese cabbage.[Method] Chinese cabbage varieties Yuqing and No.03 were used as materials for the selection of germination buffer and parameters for ultrasonication.[Result] The optimal buffer for pollen germination of Chinese cabbage was 200 g/L sucrose ＋ 100 mg/L boric acid ＋ 200 mg/L calcium nitrate,the preferred ultrasonic processing power was 150 W,processing time was 5 s,interval time was 5 s and processing frequency was 8.Three T1-generation plants were obtained through selection with 200 mg/L kanamycin.[Conclusion] This research laid foundation for the further genetic transformation of Chinese cabbage.

Review of endoscopic techniques in the diagnosis and management of cholangiocarcinoma

Cholangiocarcinoma is a rare malignancy of the biliary tract. Key factors in determining therapeutic options include knowledge of tumor extent, anatomy and obtaining tissue diagnosis. Endoscopically, there are three modalities available to make the diagnosis of cholangiocarcinoma. These include endoscopic retrograde cholangiopancreatography, endoscopic ultrasound with fine needle aspiration and cholangioscopy. Management of cholangiocarcinoma endoscopically is typically confined to stent placement for palliative purposes or as a bridge to surgery. In this article, we will review the endoscopic techniques available for the diagnosis and management of cholangiocarcinoma.

Prospective study of differential diagnosis of hepatic tumors by pattern-based classification of contrast-enhanced sonography

AIM: To prospectively evaluate the usefulness of a pattern-based classification of contrast-enhanced sonographic findings for differential diagnosis of hepatic tumors. METHODS: We evaluated the enhancement pattern of the contrast-enhanced sonography images in 586 patients with 586 hepatic lesions, consisting of 383 hepatocellular carcinomas, 89 metastases, and 114 hemangiomas. After injecting a galactose-palmitic acid contrast agent, lesions were scanned by contrast- enhanced harmonic gray-scale sonography in three phases: arterial, portal, and late. The enhancement patterns of the initial 303 lesions were classified retrospectively, and multiple logistic regression analysis was used to identify enhancement patterns that allowed differentiation between hepatic tumors. We then used the pattern-based classification of enhancement we had retrospectively devised to prospectively diagnose 283 liver tumors. RESULTS: Seven enhancement patterns were found to be significant predictors of different hepatic tumors. The presence of homogeneous or heterogeneous enhancement both in the arterial and portal phase was the typical enhancement pattern for hepatocellular carcinoma, while the presence of peritumoral vessels in the arterial phase and ring enhancement or a perfusion defect in the portal phase was the typical enhancement pattern for metastases, and the presence of peripheral nodular enhancement both in the arterial and portal phase was the typical enhancement pattern forhemangioma. The sensitivity, specificity, and accuracy of prospective diagnosis based on the combinations of enhancement patterns, respectively, were 93.2%, 96.2%, and 94.0% for hepatocellular carcinoma, 87.9%, 99.6%, and 98.2% for metastasis, and 95.6%, 94.1%, and 94.3% for hemangioma. CONCLUSION: The pattern-based classification of the contrast-enhanced sonographic findings is useful for differentiating among hepatic tumors.

Fabrication of carbon nanotubes reinforced AZ91D composites by ultrasonic processing

Magnesium matrix nanocomposite reinforced with carbon nanotubes(CNTs/AZ91D) was fabricated by mechanical stirring and high intensity ultrasonic dispersion processing.The microstructures and mechanical properties of the nanocomposite were investigated.The results show that CNTs are well dispersed in the matrix and combined with the matrix very well.As compared with AZ91D magnesium alloy matrix,the tensile strength,yield strength and elongation of the 1.5%CNTs/AZ91D nanocomposite are improved by 22%,21%and 42%respectively in permanent mold casting.The strength and ductility of the nanocomposite are improved simultaneously.The tensile fracture analysis shows that the damage mechanism of nanocomposite is still brittle fracture.But the CNTs can prevent the local crack propagation to some extent.

Ultrasonic diagnosis of biliary atresia: A retrospective analysis of 20 patients

AIM: To investigate the clinical value of ultrasono-graphic diagnosis of biliary atresia (BA), a retrospective analysis of the sonogram of 20 children with BA was undertaken. METHODS: Ultrasonography (US) was performed in 20 neonates and infants with BA, which was confirmed with cholangiography by operation or abdominoscopy. The presence of triangular cord, the size and echo of liver, the changes in empty stomach gallbladder and postprandial gallbladder were observed and recorded. RESULTS: The triangular cord could be observed at the porta hepatis (thickness: 0.3-0.6 cm) in 10 cases. Smaller triangular cord (0.2-0.26 cm) can be observed in 3 cases. The gallbladder was not observed in 2 cases, and 1 case showed a streak gallbladder without capsular space. The gallbladders of 15 cases were flat and small. The gallbladders of 2 cases were of normal size and appearance, however, there was no postprandial contraction. The livers of all cases showed hepatomegaly and hetreogeneous echogenicity. Statistical analysis was performed to compare the hepatomegaly and hetreogeneous echogenicity and the stage of hepatic fibrosis. CONCLUSION: The presence of the triangular cord atthe porta hepatis is specific. However, it is not the only diagnostic criterion, since flat and small gallbladder and poor contraction are also of important diagnostic and differential diagnostic significance. The degree of hepatomegaly and hetreogeneous echogenicity is proportional with liver fibrosis, and able to indicate the duration of course and prognosis.

Effect of thermal cycle on Ni-Cr based nanostructured thermal spray coating in boiler tubes

Ni-Cr based nanostructured feedstock powder was prepared by mechanical milling technique involving repeated welding, fracturing, and re-welding of powder particles in a planetary ball mill. The milled nanocrystalline powders were used to coat carbon steel tubes using high velocity oxygen fuel（HVOF） thermal spraying process. The characterization of the feedstock powder and HVOF coated substrates was performed using optical microscope, X-ray diffractometer（XRD）, scanning electron microscope（SEM）, high resolution transmission electron microscope（HR-TEM）, energy dispersive spectrometer（EDS） and microhardness tests. The coated and uncoated samples were subjected to different thermal cycles and characterized for their phase changes, metallurgical changes and microhardness variations. Ni-Cr nanostructured coated samples exhibited higher mechanical and metallurgical properties compared to their conventionally coated counter parts. The results showed that the nanostructured coating possessed a more uniform and denser microstructure than the conventional coating.

An anomaly in persistent right umbilical vein of portal vein diagnosed by ultrasonography

AIM: To detect the anomaly in the persistent right umbilical vein (PRUV) of portal vein (PV) with deviation of the ligamentum tere and left-sided gallbladder. METHODS: A total of 5783 candidates for routine analysis were evaluated for hepatic vascular abnormalities by ultrasonography. RESULTS: Ten candidates (0.17%) had a portal vein anomaly with a rightward-deviated ligamentum tere. The blood-flow velocity in the PRUV of the portal vein (17.7±3.0 cm/s) of the 10 cases was similar to that of the right anterior portal trunk (17.6±4.1 cm/s). However, the vessel diameter of the PRUV (φ12.4±4.4 mm) was larger than the right anterior portal trunk (φ6.1?.9 mm). Therefore, flow volume in the anomalous portion (0.97±0.30 L/min) was more than that in the right anterior portal trunk (0.18±0.05 L/min). CONCLUSION: The anomaly plays an important role in intra-hepatic PV flow.