The predictive value of energy spectral CT parameters for assessing Ki-67 expression of lung cancer.

BACKGROUND: To investigate the predictive value of energy spectral CT parameters for Ki-67 expression in lung cancer. METHODS: In this retrospective analysis, 27 primary lung cancer patients confirmed by pathological examination were enrolled between December 2018 and February 2019. All patients underwent baseline arterial phase (AP) and venous phase (VP) energy spectral CT scanning followed by surgery in our institution. The iodine concentration (IC), normalized iodine concentration (NIC) and the slope of 40-80 keV energy spectrum curve (λHU) were derived from dual-energy virtual imaging on a Siemens postprocessed workstation. Immunohistochemical examination was performed to analyze Ki-67 expression. The ROC curves were used for predicting the performance of energy spectral parameters for Ki-67 expression. RESULTS: The tumors appeared larger in Ki-67 high expression group than the low expression group (P=0.046). The energy spectral parameters were higher in venous phase when compared to arterial phase, but only the venous phase NIC (vpNIC) was significantly different from that of the arterial phase NIC (apNIC) (P<0.01). There are significant differences in high and low Ki-67 expression groups for vpNIC and venous λHU (vpλHU), (P=0.033 and 0.037 for vpNIC and vpλHU, respectively). vpNIC ROC analysis showed borderline P value (P=0.056) with an AUC, sensitivity (SE), specificity (SP) and cut-off value (0.717, 92.86, 61.54 and ≤0.347), respectively. The AUC, SE, SP and cut-off value of vpλHU were 0.698, 92.86, 53.85 and ≤2.407, respectively. CONCLUSIONS: The energy spectral parameters (NIC and λHU) of venous phase might be used for predicting Ki-67 stratification. The venous phase energy spectral parameters were higher than the arterial phase. Furthermore, low expression Ki-67 group showed association with higher IC, NIC and λHU than high expression group.

Confocal laser scanning microscopy for rapid optical characterization of graphene.

Two-dimensional (2D) materials such as graphene have become the focus of extensive research efforts in condensed matter physics. They provide opportunities for both fundamental research and applications across a wide range of industries. Ideally, characterization of graphene requires non-invasive techniques with single-atomic-layer thickness resolution and nanometer lateral resolution. Moreover, commercial application of graphene requires fast and large-area scanning capability. We demonstrate the optimized balance of image resolution and acquisition time of non-invasive confocal laser scanning microscopy (CLSM), rendering it an indispensable tool for rapid analysis of mass-produced graphene. It is powerful for analysis of 1-5 layers of exfoliated graphene on Si/SiO2, and allows us to distinguish the interfacial layer and 1-3 layers of epitaxial graphene on SiC substrates. Furthermore, CLSM shows excellent correlation with conventional optical microscopy, atomic force microscopy, Kelvin probe force microscopy, conductive atomic force microscopy, scanning electron microscopy and Raman mapping.

Epitaxial graphene homogeneity and quantum Hall effect in millimeter-scale devices.

Quantized magnetotransport is observed in 5.6 × 5.6 mm2 epitaxial graphene devices, grown using highly constrained sublimation on the Si-face of SiC(0001) at high temperature (1900 °C). The precise quantized Hall resistance of [Formula: see text] is maintained up to record level of critical current Ixx = 0.72 mA at T = 3.1 K and 9 T in a device where Raman microscopy reveals low and homogeneous strain. Adsorption-induced molecular doping in a second device reduced the carrier concentration close to the Dirac point (n ≈ 1010 cm-2), where mobility of 18760 cm2/V is measured over an area of 10 mm2. Atomic force, confocal optical, and Raman microscopies are used to characterize the large-scale devices, and reveal improved SiC terrace topography and the structure of the graphene layer. Our results show that the structural uniformity of epitaxial graphene produced by face-to-graphite processing contributes to millimeter-scale transport homogeneity, and will prove useful for scientific and commercial applications.

Toward Clean Suspended CVD Graphene.

The application of suspended graphene as electron transparent supporting media in electron microscopy, vacuum electronics, and micromechanical devices requires the least destructive and maximally clean transfer from their original growth substrate to the target of interest. Here, we use thermally evaporated anthracene films as the sacrificial layer for graphene transfer onto an arbitrary substrate. We show that clean suspended graphene can be achieved via desorbing the anthracene layer at temperatures in the 100 °C to 150 °C range, followed by two sequential annealing steps for the final cleaning, using Pt catalyst and activated carbon. The cleanliness of the suspended graphene membranes was analyzed employing the high surface sensitivity of low energy scanning electron microscopy and x-ray photoelectron spectroscopy. A quantitative comparison with two other commonly used transfer methods revealed the superiority of the anthracene approach to obtain larger area of clean, suspended CVD graphene. Our graphene transfer method based on anthracene paves the way for integrating cleaner graphene in various types of complex devices, including the ones that are heat and humidity sensitive.

Fe-catalyzed etching of exfoliated graphite through carbon hydrogenation.

We present an investigation on Fe-catalyzed etching of graphite by dewetting Fe thin films on graphite in forming gas. Raman mapping of the etched graphite shows thickness variation in the etched channels and reveals that the edges are predominately terminated in zigzag configuration. X-ray diffraction and photoelectron spectroscopy measurements identify that the catalytic particles are Fe with the presence of iron carbide and iron oxides. The existence of iron carbide indicates that, in additional to carbon hydrogenation, carbon dissolution into Fe is also involved during etching. Furthermore, the catalytic particles can be re-activated upon a second annealing in forming gas.

Plate Versus Intramedullary Fixation Care of Displaced Midshaft Clavicular Fractures: A Meta-Analysis of Prospective Randomized Controlled Trials.

In recent decades, there has been a growing trend to the operative treatment of displaced midshaft clavicular fractures. Open reduction and internal plate fixation, and intramedullary nailing fixation are 2 of the widely used techniques for operative treatment, but the optimal fixation method for these types of fractures remains a topic of debate. The objective of this study was to determine the effectiveness of plate fixation versus intramedullary nailing fixation for displaced midshaft clavicle fractures by comparing their clinical results.Literature searches of the Pubmed, EMBASE, and Web of Science were performed from 1966 to April, 2015. Only randomized controlled clinical trials comparing plate and intramedullary nailing treatment for displaced midshaft clavicle fractures were included. Literature was screened, data were extracted, and methodological quality of the eligible trials was assessed by 2 independent reviewers accordingly.Seven randomized controlled trials involving 421 patients were included. Compared to intramedullary nailing fixation, plate fixation had a relatively longer mean surgical time and a trend towards a faster functional improvement during the first 6 months after surgery; apart from this, the pooled results revealed no significant differences in functional scores after 6 months postoperatively, complication rate and patients' satisfaction between plate fixation and intramedullary fixation.Our results demonstrated that these 2 methods were comparable and safe in the treatment of displaced midshaft clavicle fractures. We advocate both techniques for the treatment of displaced midshaft clavicle fractures, and the superior surgical technique was those that the surgeon was originally trained to perform.

Operative versus nonoperative treatment for displaced midshaft clavicle fractures: a meta-analysis based on current evidence.

Literature searches of the Cochrane Library, PubMed, EMBASE, Web of Science, LILACS, China National Knowledge Infrastructure, and Wanfang Data databases were performed from 1966 to September 2014. Only randomized and quasi-randomized controlled clinical trials comparing operative and nonoperative treatments for displaced midshaft clavicle fractures were included. Data collection and extraction, quality assessment, and data analyses were performed according to the Cochrane standards. Thirteen studies were considered in the meta-analysis. Constant scores and the Disabilities of the Arm, Shoulder and Hand scores were improved in the operative fixation group at a follow up of one year or more. The nonunion and symptomatic malunion rates were significantly lower in the operative group. Additionally, the nonoperative group had a higher likelihood of neurological symptoms compared with the operative group. A significantly higher risk of complications was found in patients treated conservatively than in those who underwent operative fixation. However, when patients with nonunion and symptomatic malunion were excluded from the analysis, no significant differences in the complication rate were found. We concluded that based on the current clinical reports, operative treatment is superior to nonoperative treatment in the management of displaced midshaft clavicle fractures. However, we do not support the routine use of primary operative fixation for all displaced midshaft clavicle fractures in adults.

Operative versus nonoperative treatment for displaced midshaft clavicle fractures: a meta-analysis based on current evidence

Literature searches of the Cochrane Library, PubMed, EMBASE, Web of Science, LILACS, China National Knowledge Infrastructure, and Wanfang Data databases were performed from 1966 to September 2014. Only randomized and quasi-randomized controlled clinical trials comparing operative and nonoperative treatments for displaced midshaft clavicle fractures were included. Data collection and extraction, quality assessment, and data analyses were performed according to the Cochrane standards. Thirteen studies were considered in the meta-analysis. Constant scores and the Disabilities of the Arm, Shoulder and Hand scores were improved in the operative fixation group at a follow up of one year or more. The nonunion and symptomatic malunion rates were significantly lower in the operative group. Additionally, the nonoperative group had a higher likelihood of neurological symptoms compared with the operative group. A significantly higher risk of complications was found in patients treated conservatively than in those who underwent operative fixation. However, when patients with nonunion and symptomatic malunion were excluded from the analysis, no significant differences in the complication rate were found. We concluded that based on the current clinical reports, operative treatment is superior to nonoperative treatment in the management of displaced midshaft clavicle fractures. However, we do not support the routine use of primary operative fixation for all displaced midshaft clavicle fractures in adults.

Influence of metal-MoS2 interface on MoS2 transistor performance: comparison of Ag and Ti contacts.

In this work, we compare the electrical characteristics of MoS2 field-effect transistors (FETs) with Ag source/drain contacts with those with Ti and demonstrate that the metal-MoS2 interface is crucial to the device performance. MoS2 FETs with Ag contacts show more than 60 times higher ON-state current than those with Ti contacts. In order to better understand the mechanism of the better performance with Ag contacts, 5 nm Au/5 nm Ag (contact layer) or 5 nm Au/5 nm Ti film was deposited onto MoS2 monolayers and few layers, and the topography of metal films was characterized using scanning electron microscopy and atomic force microscopy. The surface morphology shows that, while there exist pinholes in Au/Ti film on MoS2, Au/Ag forms a smoother and denser film. Raman spectroscopy was carried out to investigate the metal-MoS2 interface. The Raman spectra from MoS2 covered with Au/Ag or Au/Ti film reveal that Ag or Ti is in direct contact with MoS2. Our findings show that the smoother and denser Au/Ag contacts lead to higher carrier transport efficiency.

Toward clean and crackless transfer of graphene.

We present the results of a thorough study of wet chemical methods for transferring chemical vapor deposition grown graphene from the metal growth substrate to a device-compatible substrate. On the basis of these results, we have developed a "modified RCA clean" transfer method that has much better control of both contamination and crack formation and does not degrade the quality of the transferred graphene. Using this transfer method, high device yields, up to 97%, with a narrow device performance metrics distribution were achieved. This demonstration addresses an important step toward large-scale graphene-based electronic device applications.

Transmission electron microscopy characterization of colloidal copper nanoparticles and their chemical reactivity.

A colloidal synthesis method was developed to produce face centered cubic (fcc) Cu nanoparticles in the presence of surfactants in an organic solvent under an Ar environment. Various synthetic conditions were explored to control the size of the as-prepared nanoparticles by changing the precursor, varying the amount of surfactants, and tuning the reaction temperature. Transmission electron microscopy (TEM), selected-area electron diffraction, and high-resolution TEM were used as the main characterization tools. Upon exposure to air, these nanoparticles are oxidized at different levels depending on their sizes: (1) an inhomogeneous layer of fcc Cu(2)O forms at the surface of Cu nanoparticles (about 30 nm); (2) Cu nanoparticles (about 5 nm) are immediately oxidized into fcc Cu(2)O nanoparticles (about 6 nm). The occurrence of these different levels of oxidization demonstrates the reactive nature of Cu nanoparticles and the effect of size on their reactivity. Furthermore, utilization of their chemical reactivity and conversion of spherical Cu nanoparticles into CuS nanoplates through the nanoscale Kirkendall effect were demonstrated. The oxidization and sulfidation of Cu nanoparticles were compared. Different diffusion and growth behaviors were involved in these two chemical transformations, resulting in the formation of isotropic Cu(2)O nanoparticles during oxidization and anisotropic CuS nanoplates during sulfidation.

Influence of the colloidal environment on the magnetic behavior of cobalt nanoparticles.

The magnetic properties of 10 nm diameter surfactant-coated cobalt (Co) nanoparticles in 1,2-dichlorobenzene (DCB) are investigated by a series of sequential magnetic moment (m) vs temperature (T) measurements. A rapid rise in magnetic moment around 250 K during warming and an abrupt drop at 234 K during cooling are observed when a nonsaturating external magnetic field is applied. Differential scanning calorimetry (DSC) measurements demonstrate that the rapid rise and abrupt drop in magnetization are associated with the melting and freezing of the solvent. Magnetic measurements of these Co nanoparticles in DCB are also used to probe their aging over a period of 70 days. The saturation magnetic moment of Co nanoparticles in DCB stored in air at room temperature decreases by nearly 40% over 70 days. Transmission electron microscopy (TEM) characterizations are reported to show the time evolution in the size, shape, and crystalline structures of DCB-immersed nanoparticles.

Synthesis and self-assembled ring structures of Ni nanocrystals.

Narrow size distribution Ni nanocrystals with average diameters from 5 to 13 nm ( approximately 20% standard deviation) and a face-centered cubic (fcc) structure were synthesized via rapid thermo-decomposition in the presence of surfactants in solution. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize these nanocrystals. It was found that the solvent determined the rate of the decomposition of Ni precursors, while the surfactants controlled the size and shape of Ni nanocrystals. A three-step process was proposed to explain the synthesis. The purified Ni nanocrystals readily formed micrometer-sized ring structures on TEM grids after solvent evaporation (hexanes), and the magnetic field was found to increase the density of the rings.

Magnetic-field-induced assemblies of cobalt nanoparticles.

Under the influence of a 0.05 T magnetic field, 15-nm diameter cobalt nanoparticles covered with surfactants in a colloidal solution assemble into highly constrained linear chains along the direction of the magnetic field. The magnetic-field-induced (MFI) chains become floppy after removal of the field, folding into three-dimensional (3D) coiled structures upon gentle agitation. The 3D structures are broken into smaller units with vigorous agitation. The nanoparticles redisperse into the solvent upon ultrasonic agitation. Optical microscopy and transmission electron microscopy (TEM) are used to characterize the morphologies of the nanoparticle assemblies at various stages of this reversible process. The hysteresis loops and zero-field cooled/field cooled (ZFC/FC) curves reveal the interparticle coupling in the assemblies. MFI assembly provides a powerful tool to manipulate magnetic nanoparticles.

Compact 50-Hz terawatt Ti:sapphire laser for x-ray and nonlinear optical spectroscopy.

We report a high-repetition-rate, compact terawatt Ti:sapphire laser system. The oscillator produces an 82-MHz pulse train consisting of broad-bandwidth pulses of 0.5-nJ/pulse energy and of 9-fs pulse duration. The spectrally shaped, lambda/4 regenerative amplifier supports an 80-nm bandwidth. A single 50-Hz repetition-rate pump laser pumps both the regenerative amplifier and a multiple-pass amplifier. The final output from this laser is a 50-Hz pulse train made from pulses of 53 mJ/pulse energy and of 24-fs pulse duration. For generating ultrafast x-ray pulses, 90% of the energy from the final output of a 28-mm-diameter (1/e2) beam is focused onto an ultrafast x-ray wire target. The energy conversion efficiency from optical (800-nm central wavelength) to x-ray (characteristic lines of K(alpha) from Cu at 8 keV) pulses is estimated to be 7 x 10(-5). This laser system can also generate a lower-peak-power, dual-pulse output that can excite, simultaneously and coherently, Raman modes within an adjustable bandwidth (up to 700 cm(-1)) and at a tunable central vibrational frequency. Preliminary results for the generation of dual-pulse output and ultrafast x rays are presented.