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Although patients with alpha-fetoprotein-negative hepatocellular carcinoma (AFPNHCC) have a favorable prognosis, a high risk of postoperative recurrence remains. We developed and validated a novel liver fibrosis assessment index, the direct bilirubin-gamma-glutamyl transpeptidase-to-platelet ratio (DGPRI). DGPRI was calculated for each of the 378 patients with AFPNHCC who underwent hepatic resection. The patients were divided into high- and low-score groups using the optimal cutoff value. The Lasso-Cox method was used to identify the characteristics of postoperative recurrence, followed by multivariate Cox regression analysis to determine the independent risk factors associated with recurrence. A nomogram model incorporating the DGPRI was developed and validated. High DGPRI was identified as an independent risk factor (hazard ratio = 2.086) for postoperative recurrence in patients with AFPNHCC. DGPRI exhibited better predictive ability for recurrence 1–5 years after surgery than direct bilirubin and the gamma-glutamyl transpeptidase-to-platelet ratio. The DGPRI-nomogram model demonstrated good predictive ability, with a C-index of 0.674 (95% CI 0.621–0.727). The calibration curves and clinical decision analysis demonstrated its clinical utility. The DGPRI nomogram model performed better than the TNM and BCLC staging systems for predicting recurrence-free survival. DGPRI is a novel and effective predictor of postoperative recurrence in patients with AFPNHCC and provides a superior assessment of preoperative liver fibrosis. [ABSTRACT FROM AUTHOR]

This work demonstrates high-performance AlN/GaN double-barrier resonant tunneling diodes (RTDs) with high peak current density grown by plasma-assisted molecular beam epitaxy on c-plane free-standing GaN substrates, featuring stable and repeatable negative differential resistance (NDR) characteristics at room temperature. By scaling down the barrier thickness of AlN barrier and the lateral mesa size of collector, the record peak current density of 1551 kA/cm2 is achieved along with a peak-to-valley current ratio (PVCR) of 1.24, which is attributed to the reduced resonant tunneling time under thinner AlN barrier and the suppressed external incoherent valley current by reducing the dislocation number contained in the RTD device with the smaller size of collector. By statistically analyzing the NDR performance of RTD devices with different thicknesses of AlN barrier, the average peak current density increases from 145.7 to 1215.1 kA/cm2, while the average PVCR decreases from 1.45 to 1.1, correspondingly, accompanying with a decreased peak voltage from 6.89 to 5.49 V, with downscaling the AlN barrier thickness from 1.5 to 1.25 nm. The peak current density obtained in this work is the highest value among all the reported nitride-based RTDs up until now while maintaining high PVCR value simultaneously, which illustrates that ultra-scaled RTD based on vertical quantum-well structure and lateral collector size is a valuable approach for the development of nitride-based RTDs with excellent NDR characteristics and reveals their great potential applications in high-frequency oscillation sources and high-speed switch circuits. [ABSTRACT FROM AUTHOR]

Here, we present a systematical investigation of AlN/GaN double-barrier resonant tunneling diodes (RTDs) grown by plasma-assisted molecular beam epitaxy on metal-organic chemical vapor deposition GaN-on-sapphire templates. The processed devices featured an active region composed of 2.5 nm GaN quantum well sandwiched by two 1.5 nm AlN barriers and RTD mesa diameter ranging from 1 to 20 μm. Room temperature current–voltage characteristics exhibited a repeatable negative differential resistance (NDR) free of degradation and hysteresis after 1000 times subsequently up-to-down voltage sweeps across different sizes. High peak-to-valley current ratios of 1.93 and 1.58 were obtained at room temperature for 1 and 12 μm diameter devices, respectively, along with peak current densities of 48 and 36 kA/cm2 corresponding to peak voltages of 4.65 and 5.9 V. The peak current density decreased quickly initially and then was less susceptible to this averaging effect with increasing the device diameter. Temperature-dependent measurements revealed that the valley current density displayed a positive relationship to the temperature, and an abruptly increasement was observed for the devices with a diameter of 20 μm when the temperature rose over 230 K. We attributed this abnormal phenomenon to the increased contribution from acoustic and longitudinal optical (LO) phonon scattering, especially for the LO phonon scattering. The area dependence of electrical performance suggested that the leakage pathway through dislocations played a vital role for charge transport and there existed a threshold of dislocation density for NDR characteristics. These results promote further study for future implementation of III-nitride-based RTD oscillators into high-frequency and high-power terahertz radiation. [ABSTRACT FROM AUTHOR]

Mesenchymal stromal/stem cells (MSCs) have the ability of self-renewal, the potential of multipotent differentiation, and a strong paracrine capacity, which are mainly used in the field of clinical medicine including dentistry and orthopedics. Therefore, tissue engineering research using MSCs as seed cells is a current trending directions. However, the healing effect of direct cell transplantation is unstable, and the paracrine/autocrine effects of MSCs cannot be effectively elicited. Tumorigenicity and heterogeneity are also concerns. The combination of MSCs as seed cells and appropriate vector materials can form a stable cell growth environment, maximize the secretory features of stem cells, and improve the biocompatibility and mechanical properties of vector materials that facilitate the delivery of drugs and various secretory factors. There are numerous studies on tissue engineering and inflammation of various biomaterials, mainly involving bioceramics, alginate, chitosan, hydrogels, cell sheets, nanoparticles, and three-dimensional printing. The combination of bioceramics, hydrogels and cell sheets with stem cells has demonstrated good therapeutic effects in clinical applications. The application of alginate, chitosan, and nanoparticles in animal models has also shown good prospects for clinical applications. Three-dimensional printing technology can circumvent the shortage of biomaterials, greatly improve the properties of vector materials, and facilitate the transplantation of MSCs. The purpose of this narrative review is to briefly discuss the current use of MSC-based carrier biomaterials to provide a useful resource for future tissue engineering and inflammation research using stem cells as seed cells. [ABSTRACT FROM AUTHOR]

Background: Most studies to date have focused on predicting the risk of venous thromboembolism (VTE), but prediction models about mortality risk in VTE are rarely reported. We sought to develop and validate a multivariable model to predict the all-cause mortality risk in patients with acute VTE in emergency settings. Methods: A total of 700 patients were included from Qilu Hospital of Shandong University and were randomly assigned into training set (n=490) and validation set (n=210) in an 7:3 ratio. Multivariate logistics regression analysis was performed to identify independent variables and develop a prediction model, which was validated internally using bootstrap method. The discrimination, calibration and clinical utility were evaluated by receiver operating characteristic curve (ROC) analysis, Hosmer-Lemeshow (HL) test, Kaplan-meier (KM) analysis and decision curve analysis (DCA). Results: There were 52 patients (10.6%) dying and 437 (89.4%) surviving in training set. Age (odds ratio [OR]: 4.158, 95% confidence interval [CI]: 2.426– 7.127), pulmonary embolism (OR: 1.779, 95% CI: 1.124– 2.814), platelet count (OR: 0.507, 95% CI: 0.310– 0.830), D-dimer (OR: 1.826, 95% CI: 1.133– 2.942) and platelet/lymphocyte ratio (OR: 2.166, 95% CI: 1.259– 3.727) were independent risk variables associated with all-cause mortality. The model had good predictive capability with an AUC of 0.746 (95% CI: 0.668,0.825), a sensitivity of 0.769 (95% CI: 0.607,0.889), a specificity of 0.672 (95% CI: 0.634,0.707). The validation model had an AUC of 0.739 (95% CI: 0.685,0.793), a sensitivity of 0.690 (95% CI: 0.580,0.787), a specificity of 0.693 (95% CI: 0.655,0.729). The model is well calibrated and the HL test showed a good fit (χ2=5.291, p=0.726, Nagelkerke R2=0.137). KM analysis and DCA showed a good clinical utility of the nomogram. Conclusion: This study identified independent variables affecting all-cause mortality in patients with acute VTE, and developed a prediction model and provided a nomogram with good prediction capability and clinical utility. [ABSTRACT FROM AUTHOR]

Background: Idiopathic hypereosinophilic syndrome (IHES) often causes inflammatory damage to multiple organs. However, whether immune/inflammatory indicators and other factors are associated with mortality in patients with IHES remains unclear. Patients and Methods: The clinical data and follow-up results of 167 patients with IHES were retrospectively analyzed using Cox regression analysis and receiver operating characteristic curve (ROC). Results: Of 167 patients, 120 were men (71.9%) and 47 were women (28.1%). The median age was 52 (36.0, 68.0) years. The median follow-up period was 42.8 (18.5, 75.1) months, during which all-cause mortality occurred in 26 patients (15.6%). Age (HR: 1.041, 95% CI: 1.015– 1.068; p = 0.002), lymphocyte counts (109/L, HR: 0.866, 95% CI: 0.816– 0.907; p = 0.013), platelet counts (109/L, HR: 0.994, 95% CI: 0.989– 0.999; p = 0.012) and NLR (HR: 1.161, 95% CI: 1.054– 1.280; p = 0.003) were independent risk factors for all-cause mortality. There was no relationship between PLR, and SII and all-cause mortality (p = 0.181 and 0.202, respectively). ROC analysis showed that the AUCs of age, lymphocyte count (109/L), platelet count (109/L) and NLR were 0.712 (95% CI: 0.601– 0.824), 0.584 (95% CI: 0.448– 0.719), 0.686 (95% CI: 0.560– 0.812), and 0.797 (95% CI: 0.695– 0.899), respectively, with sensitivities of 0.5, 0.462, 0.769, and 0.792, respectively, and specificities of 0.765, 0.745, 0.617, and 0.845, respectively. Kaplan–Meier analysis (Log rank test) showed that patients with age ≥ 73.5 years, lymphocyte count (109/L) < 1.45, platelet count (109/L) < 225 and NLR ≥ 2.54 had high mortality. Patients with high NLR (≥ 2.54) usually have multiorgan involvement, with cardiac involvement and skin involvement being the most common. Patients with NLR ≥ 2.54 had significantly higher absolute eosinophil counts (p = 0.047) and percentages (p = 0.041). Conclusion: We identified NLR for the first time as an independent predictive factor for all-cause mortality in patients with IHES, necessitating its further application in clinical practice. [ABSTRACT FROM AUTHOR]

In this Letter, we present the excellent negative differential resistance (NDR) characteristics of AlN/GaN double-barrier resonant tunneling diodes (RTDs) in which the active layers are grown by molecular beam epitaxy on thick GaN-on-sapphire templates manufactured by metal-organic chemical vapor deposition. Here, indium flux is introduced as surfactant to reduce the interface roughness and improve the sharpness of heterointerface during epitaxial growth of AlN/GaN/AlN quantum well. The processed device with a top collector diameter of 1 μm size demonstrates a record peak current density of 1039 kA/cm2 while simultaneously featuring a peak-to-valley current ratio of 1.23 at room temperature, excellent achievements among all the reported GaN-based RTDs on any substrates. In addition, no degradation of device performance together with free of hysteresis is observed for the 1000 times consecutive up-to-down voltage sweeps under forward bias. These remarkable achievements are attributed to the marked improvement in heterointerface quality of AlN/GaN/AlN double-barrier quantum well by adopting indium as surfactant during epitaxial growth as clarified by transmission electron microscopy analysis, which dramatically suppresses the interface roughness scattering and elements interdiffusion, thus significantly improving the NDR signatures in current–voltage curves. The obtained results in this work illustrate that indium-surfactant added epitaxy technique turns out to be a promising approach for the modulation of vertical electron resonant tunneling in III-nitride heterostructures and realization of highly reproducible and reliable AlN/GaN double-barrier RTDs, in favor of implementation for future high-power solid-state electronics operating in terahertz spectra. [ABSTRACT FROM AUTHOR]

Venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), has been an important cause of sudden in-hospital death. Studies have shown that the immune/inflammatory response plays an important role in the pathogenesis of vascular disease, with representative markers in the blood including the neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), monocyte/lymphocyte ratio (MLR), systemic immune/inflammatory index (SII), etc. However, there is a variety of immune/inflammatory indicators. Moreover, most previous studies have been single-center investigations involving one or two indicators, with varying nature of cases, number of cases and study objectives, thereby making it difficult to reach consensus conclusions with good clinical guidelines. This article reviews the clinical value of immunoinflammatory indicators for VTE based on previous studies, including the diagnostic and prognostic capabilities. In conclusion, NLR provides promising predictive capability for the onset and prognosis of VTE and deserves extensive application in clinical practice. PLR also has certain diagnostic and prognostic value, but further studies are warranted to identify its reliability and stability. Monocytes, eosinophils and platelet-related indicators show some clinical association with VTE, although the predictive capabilities are mediocre. SII is of promising potential value for VTE and deserves further investigations. This review will provide new clues and valuable clinical guidance for the diagnosis and therapy of VTE. [ABSTRACT FROM AUTHOR]

The N-polar GaN high-electron mobility transistors (HEMTs) have demonstrated a powerful performance as the Ga-polar GaN HEMTs. This investigation aims to show the direct current performance and cutoff frequency (${f}_{\text {T}}$) of the planar N-polar GaN HEMTs with gate lengths downscaling from $4~\mu \text{m}$ to 50 nm by 2-D device simulation. The impacts of traps and gate dielectrics and the roles of the field-dependent mobility and the source and drain series resistances are investigated. For our central-gated device with a 10-nm top GaN channel layer, a 30-nm Al0.3Ga0.7N barrier layer, and a 3-nm Al2O3 gate dielectric, the gate length (${L}_{\text {G}}$) as the transition point from the long-channel behavior to the short-channel one is found to be 200 nm. For ${L}_{\text {G}} < {200}$ nm, a linear ${f}_{\text {T}}^{-{1}}$ versus ${L}_{\text {G}}$ relation shows up, and notable short-channel effects appear, i.e., the negative shift of the threshold voltage, the increase of the drain-induced barrier lowering, and the almost ${L}_{\text {G}}$ -independent constant maximum transconductance in the saturation region. The degradation of the ${f}_{\text {T}}\times {L}_{\text {G}}$ product with the decrease in the aspect ratio between ${L}_{\text {G}}$ and the equivalent gate-channel distance (${t}_{t}$) is shown to be quite small. The ${L}_{\text {G}}/{t}_{t}$ ratio for 15% degradation of the ${f}_{\text {T}}\times {L}_{\text {G}}$ product from its upper limit ($19.23~\text {GHz}\cdot \mu \text {m}$) is 5.5. This small degradation of the frequency characteristics in short-channel devices is attributed to the quite small fringing capacitance of the gate. [ABSTRACT FROM AUTHOR]

The AlGaN‐channel III‐N heterostructure effect transistor (HFET) devices with high breakdown voltage and acceptable on‐resistance has shown great potential for next generation of power switching. The electronic transport property of two‐dimensional electron gases (2DEGs) in AlInGaN/AlGaN heterostructures is investigated for the first time, and the effects of the alloy disorder scattering from both the barrier layer and the channel layer are analyzed. The quaternary alloy composition dependences of the 2DEG density and mobility and the sheet resistance (positively proportional to the device on‐resistance) are studied in nearly lattice matched AlInGaN/Al0.2Ga0.8N heterostructures. The alloy composition ranges of the AlxInyGa1−x−yN barrier layer of 0.58 ≤ x ≤ 0.76 and 0 ≤ y ≤ 0.14 is found to be optimal in all aspects, which corresponds to the threshold voltage of −1.55 ∼ −6.24 V for an AlInGaN/Al0.2Ga0.8N HFET with a nickel gate. Moreover, the temperature dependence of 2DEG mobility in lattice‐matched AlInGaN/AlGaN heterostructures is discussed with various scattering models. The results show that the magnitudes of the mobility in the sample Al0.3In0.05Ga0.65N/Al0.05Ga0.95N, Al0.5In0.06Ga0.44N/Al0.2Ga0.8N, and Al0.8In0.06Ga0.14N/Al0.5Ga0.5N heterostructures reduces by 61%, 47%, and 37% with the temperature increasing from 300 to 600 K. Our research may provide some instructions for the application of AlInGaN/AlGaN heterojunction to high voltage power devices. [ABSTRACT FROM AUTHOR]

As a promising group III-nitride semiconductor material, InAlN ternary alloy has been attracted increasing interest and widespread research efforts for optoelectronic and electronic applications in the last 5 years. Following a literature survey of current status and progress of InAlN-related studies, this paper provides a brief review of some recent developments in InAlN-related III-nitride research in Xidian University, which focuses on innovation of the material growth approach and device structure for electronic applications. A novel pulsed metal organic chemical vapor deposition (PMOCVD) was first adopted to epitaxy of InAlN-related heterostructures, and excellent crystalline and electrical properties were obtained. Furthermore, the first domestic InAlN-based high-electron mobility transistor (HEMT) was fabricated. Relying on the PMOCVD in combination with special GaN channel growth approach, high-quality InAlN/GaN double-channel HEMTs were successfully achieved for the first time. Additionally, other potentiality regarding to AlGaN channel was demonstrated through the successful realization of nearly lattice-matched InAlN/AlGaN heterostructures suitable for high-voltage switching applications. Finally, some advanced device structures and technologies including excellent work from several research groups around the world are summarized based on recent publications, showing the promising prospect of InAlN alloy to push group III-nitride electronic device performance even further. [ABSTRACT FROM AUTHOR]

The electrical properties of two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures using high temperature (HT) AlN interlayers (ITs) grown on c-plane sapphire substrate by metal organic chemical vapor deposition (MOCVD) have been investigated. It is found that the electrical properties (electron mobility and sheet carrier density) are improved compared with those in the conventional AlGaN/GaN heterostructures without HT AlN ITs, and the improved 2DEG properties result in the reduction of the sheet resistance. The results from high resolution X-ray diffraction (HRXRD) and Raman spectroscopy measurements show that HT AlN ITs increase the in-plane compressive strain in the upper GaN layer, which enhances the piezoelectric polarization in it and consequently causes increasing of 2DEG density at the AlGaN/GaN interface. Meanwhile, the compressive strain induced by HT AlN ITs leads to a less tensile strain in AlGaN barrier layer and causes positive and negative effects on the sheet carrier density of 2DEG, which counteract each other. The HT AlN ITs reduce the lattice mismatch between the GaN and AlGaN layers and smooth the interface between them, thus increasing the electric mobility of 2DEG by weakening the alloy-related interface roughness and scattering. In addition, the surface morphology of AlGaN/GaN heterostructures is improved by the insertion of HT AlN ITs. The reason for the improved properties is discussed in this paper. [ABSTRACT FROM AUTHOR]

High quality, nearly lattice-matched InAlN/GaN/InAlN/GaN double-channel heterostructures were grown on sapphire by pulsed-metal-organic-chemical-vapor-deposition (PMOCVD). High electron mobility of 1414 cm2/Vs was achieved along with a two-dimensional-electron-gas density of 2.55 × 1013 cm-2. We attribute it to the high quality PMOCVD-grown InAlN barriers and, additionally, to the novel GaN layer growth between two InAlN barriers, which consists of a thin GaN spacer to prevent indium-redistribution and indium-cluster formation during the subsequent growth and a relatively thick GaN channel to enhance electron mobility. High-electron-mobility-transistors fabricated on these heterostructures with 0.8-μm-length gate exhibit a maximum drain current of 906 mA/mm and a transconductance of 186 mS/mm. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of trap states in InAlN/AlN/GaN double-channel high electron mobility transistors grown by pulsed metal organic chemical vapor deposition. By frequency dependent conductance measurements, trap densities and time constants at both InAlN/AlN/GaN interfaces were determined. Two types of traps, with a high density of up to ∼1014 cm-2 eV-1, were observed existing at the higher InAlN/AlN/GaN interface. On the other hand, the density dramatically decreased to ∼1012 cm-2 eV-1 for traps located at lower InAlN/AlN/GaN interface on which a low-temperature grown GaN (LT-GaN) layer was deposited. Additionally, photo-assisted capacitance-voltage measurements were performed to estimate deep-level defects, yielding a low density of 1.79 × 1011 cm-2 acting as negative fixed charges at the LT-GaN and lower InAlN interface. [ABSTRACT FROM AUTHOR]

AlGaN/GaN superlattices (SLs) with and without Si doping exhibit very different properties. Because of the difference between the dielectric constants of AlGaN and GaN, the wells of the SL are depleted in the undoped structure. With increased Si doping in the GaN wells, the depletion effect will vanish, and the accumulation of electrons will compensate for the polarization-induced internal electric field (PIIEF) in the AlGaN barrier, which is followed by disturbance of the PIIEF in the GaN wells due to electron overflow from the ground state E0 to the first excited state E1. This leads to a decrease in E1-E0. [ABSTRACT FROM AUTHOR]

We report on a growth of nearly lattice-matched InAlN/GaN heterostructures on 4H-SiC substrates by pulsed metal organic chemical vapor deposition, and an excellent device characteristic of high electron mobility transistors (HEMTs) fabricated on these InAlN/GaN heterostructures. The electron mobility is 1032 cm2/V s together with a high two-dimensional-electron-gas density of 1.59×1013 cm-2 for the In0.17Al0.83N/AlN heterostructures. HEMTs with gate dimensions of 0.5×50 μm2 and 3 μm source-drain distance exhibits a maximum drain current of 1 A/mm, a maximum extrinsic transconductance of 310 mS/mm, and current gain and maximum oscillation cutoff frequencies of 18 GHz and 39 GHz, respectively. [ABSTRACT FROM AUTHOR]

The AlGaN/GaN/AlGaN double heterostructure (DH) with high electron mobility of 1862 cm2/Vs at room temperature and 478 cm2/Vs at 573 K high temperature was obtained by a combination of optimization schemes considering scattering mechanisms. First, a composite buffer layer structure, including GaN and AlGaN layer, was used to improve the crystal quality of the AlGaN/GaN/AlGaN DH. Second, interface roughness scattering was reduced by increasing the channel thickness, thus the two-dimensional electron gas mobility was further improved. Moreover, an ultrathin AlN interlayer was inserted between the GaN channel layer and the AlGaN buffer layer to decrease the alloy disorder scattering. The Hall effect measurements showed that the DH had better transport characteristics at high temperatures, and an electron mobility of 478 cm2/Vs was achieved at 573 K, which is twice larger than that of the conventional single heterostructure (∼200 cm2/Vs at 573 K). Therefore, AlGaN/GaN/AlGaN DH is more suitable for the applications in high temperature electronic devices. [ABSTRACT FROM AUTHOR]

In our previous work [J. S. Xue et al., Appl. Phys. Lett. 100, 013507 (2012)], superior electron-transport properties are obtained in InAlN/GaN/InAlN/GaN double-channel (DC) heterostructures grown by pulsed metal organic chemical vapor deposition (PMOCVD). In this paper, we present a detailed fabrication and systematic characterization of high electron mobility transistors (HEMTs) fabricated on these heterostructures. The device exhibits distinct DC behavior concerning with both static-output and small-signal performance, demonstrating an improved maximum drain current density of 1059 mA/mm and an enhanced transconductance of 223 mS/mm. Such enhancement of device performance is attributed to the achieved low Ohmic contact resistance as low as 0.33 ± 0.05 Ω·mm. Moreover, very low gate diode reverse leakage current is observed due to the high quality of InAlN barrier layer deposited by PMOCVD. A current gain frequency of 10 GHz and a maximum oscillation frequency 21 GHz are also observed, which are comparable to the state-of-the-art AlGaN/GaN-based DC HEMT found in the literature. The results demonstrate the great potential of PMOCVD for application in InAlN-related device's epitaxy. [ABSTRACT FROM AUTHOR]

The authors report the effects of growth temperature on the structural and electrical properties of InAlN/GaN heterostructures, which were grown on c-plane sapphire substrates by pulsed metal organic chemical vapor deposition (PMOCVD). High resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM) measurements indicate that the quality of InAlN barrier is strongly dependent on the growth temperature. It is observed that the indium composition and surface root-mean-square (rms) roughness value of InAlN barrier decrease with increasing the growth temperature, and a nearly lattice-matched InAlN/GaN heterostructure with a smooth surface is obtained at 710 °C. As a consequence, the variation of structural properties of InAlN barrier influences the electrical properties of InAlN/GaN heterostructures, and high electron mobility in excess of 1400 cm2 V-1 s-1 is achieved at an optimized growth temperature window of InAlN barrier layer between 710 and 730 °C. [ABSTRACT FROM AUTHOR]