In this paper, Zr
2
SB ceramic with purity of 82.95 wt% (containing 8.96 wt% ZrB
2
and 8.09 wt% zirconium) and high relative density (99.03%) was successfully synthesized from ZrH
2
, sublimated ...sulfur, and boron powders by spark plasma sintering (SPS) at 1300 °C. The reaction process, microstructure, and physical and mechanical properties of Zr
2
SB ceramic were systematically studied. The results show that the optimum molar ratio to synthesize Zr
2
SB is
n
(ZrH
2
):
n
(S):
n
(B) = 1.4:1.6:0.7. The average grain size of Zr
2
SB is 12.46 µm in length and 5.12 µm in width, and the mean grain sizes of ZrB
2
and zirconium impurities are about 300 nm. In terms of physical properties, the measured thermal expansion coefficient (TEC) is 7.64×10
−6
K
−1
from room temperature to 1200 °C, and the thermal capacity and thermal conductivity at room temperature are 0.39 J·g
−1
·K
−1
and 12.01 W·m
−1
·K
−1
, respectively. The room temperature electrical conductivity of Zr
2
SB ceramic is measured to be 1.74×10
6
Ω
−1
·m
−1
. In terms of mechanical properties, Vickers hardness is 9.86±0.63 GPa under 200 N load, and the measured flexural strength, fracture toughness, and compressive strength are 269±12.7 MPa, 3.94±0.63 MPa·m
1/2
, and 2166.74±291.34 MPa, respectively.
MAX phases have great research value and application prospects, but it is challenging to synthesize the MAX phases containing Cd and Sb for the time being. In this paper, we confirmed the existence ...of the 312 MAX phases of Zr3CdC2 and Zr3SbC2, both from theoretical calculations and experimental synthesis. The Zr3AC2 (A = Cd, Sb) phase was predicted by the first-principles calculations, and the two MAX phases were confirmed to meet the requests of thermal, thermodynamic, and mechanical stabilities using formation energy, phonon dispersion, and the Born–Huang criteria. Their theoretical mechanical properties were also systematically investigated. It was found that the elastic moduli of Zr3CdC2 and Zr3SbC2 were 162.8 GPa and 164.3 GPa, respectively. Then, differences in the mechanical properties of Zr3AC2 (A = Cd, In, Sn, and Sb) were explained using bond layouts and charge transfers. The low theoretical Vickers hardness of the Zr3CdC2 (5.4 GPa) and Zr3SbC2 (4.3 GPa) phases exhibited excellent machinability. Subsequently, through spark plasma sintering, composites containing Zr3CdC2 and Zr3SbC2 phases were successfully synthesized at the temperatures of 850 °C and 1300 °C, respectively. The optimal molar ratio of Zr:Cd/Sb:C was determined as 3:1.5:1.5. SEM and the EDS results analysis confirmed the typical layered microstructure of Zr3CdC2 and Zr3SbC2 grains.
The ternary or quaternary layered compounds called MAB phases are frequently mentioned recently together with the well-known MAX phases. However, MAB phases are generally referred to layered ...transition metal borides, while MAX phases are layered transition metal carbides and nitrides with different types of crystal structure although they share the common nano-laminated structure characteristics. In order to prove that MAB phases can share the same type of crystal structure with MAX phases and extend the composition window of MAX phases from carbides and nitrides to borides, two new MAB phase compounds Zr
2
SeB and Hf
2
SeB with the Cr
2
AlC-type MAX phase (211 phase) crystal structure were discovered by a combination of first-principles calculations and experimental verification in this work. First-principles calculations predicted the stability and lattice parameters of the two new MAB phase compounds Zr
2
SeB and Hf
2
SeB. Then they were successfully synthesized by using a thermal explosion method in a spark plasma sintering (SPS) furnace. The crystal structures of Zr
2
SeB and Hf
2
SeB were determined by a combination of the X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The lattice parameters of Zr
2
SeB and Hf
2
SeB are
a
= 3.64398 Å,
c
= 12.63223 Å and
a
= 3.52280 Å,
c
= 12.47804 Å, respectively. And the atomic positions are M at 4f (1/3, 2/3, 0.60288 Zr or 0.59889 Hf), Se at 2c (1/3, 2/3, 1/4), and B at 2a (0, 0, 0). And the atomic stacking sequences follow those of the Cr
2
AlC-type MAX phases. This work opens up the composition window for the MAB phases and MAX phases and will trigger the interests of material scientists and physicists to explore new compounds and properties in this new family of materials.
Pemetrexed, a new generation antifolate drug, has been approved for the treatment of locally advanced or metastatic breast cancer. However, factors affecting its efficacy and resistance have not been ...fully elucidated yet. ATP-binding cassette (ABC) transporters are predictors of prognosis as well as of adverse effects of several xenobiotics. This study was designed to explore whether ABC transporters affect pemetrexed resistance and can contribute to the optimization of breast cancer treatment regimen.
First, we measured the expression levels of ABC transporter family members in cell lines. Subsequently, we assessed the potential role of ABC transporters in conferring resistance to pemetrexed in primary breast cancer cells isolated from 34 breast cancer patients and the role of ABCC5 in mediating pemetrexed transport and apoptotic pathways in MCF-7 cells. Finally, the influence of ABCC5 expression on the therapeutic effect of pemetrexed was evaluated in an in vivo xenograft mouse model of breast cancer.
The expression levels of ABCC2, ABCC4, ABCC5, and ABCG2 significantly increased in the pan-resistant cell line, and the ABCC5 level in the MCF-7-ADR cell line was 5.21 times higher than that in the control group. ABCC5 expression was inversely correlated with pemetrexed sensitivity (IC
, r = 0.741; p < 0.001) in breast cancer cells derived from 34 patients. Furthermore, we found that the expression level of ABCC5 influenced the efflux and cytotoxicity of pemetrexed in MCF-7 cells, with IC
values of 0.06 and 0.20 μg/mL in ABCC5 knockout and over-expression cells, respectively. In the in vivo study, we observed that ABCC5 affected the sensitivity of pemetrexed in breast tumor-bearing mice, and the tumor volume was much larger in the ABCC5-overexpressing group than in the control group when compared with their own initial volumes (2.7-fold vs. 1.3-fold).
Our results indicated that ABCC5 expression was associated with pemetrexed resistance in vitro and in vivo, and it may serve as a target or biomarker for the optimization of pemetrexed regimen in breast cancer treatment.
To assess the feasibility and effectiveness of total laparoscopic nephroureterectomy for upper urinary tract urothelial carcinoma (UUTUC) under a single surgical position.
The medical data of 89 ...UUTUC patients were collected, who were treated in our institution from Jan 2016 to Jun 2018. The 45 cases that underwent total laparoscopic nephroureterectomy with a single position were allocated in the test group, while the 44 patients who received retroperitoneal laparoscopy combined with hypogastric oblique incision were assigned in the control group. We compared the two groups in perioperative indicators and tumor recurrence rate and analyzed the clinical effect of the new surgical treatment of UUTUC.
All 89 operations for UUTUC were successful and had no conversion to open surgery. No obvious complications occurred during the perioperative period. The test group had significantly shorter average operation time (96.58 ± 8.56 min versus 147.45 ± 9.16 min), less blood loss (39.58 ± 4.15 ml versus 46.50 ± 4.58 ml), earlier ambulation (7.47 ± 1.01 h versus 11.39 ± 1.82 h), and shorter length of stay in hospital (6.98 ± 1.14 days versus 9.89 ± 1.51 days) (P < 0.05). The visual analogue scale (VAS) scores of the test group at 1 h, 12 h, and 24 h after operation were lower compared with those of the control group (P < 0.05). No significant difference was found in the tumor stage, tumor grade, postoperative gastrointestinal function recovery time, follow-up time, and tumor recurrence rate between the two groups.
Compared with the traditional surgical methods, the total laparoscopic treatment of UUTUC under a single surgical position had advantages of shorter operation time, less blood loss, and early postoperative ambulation. The new operative method could shorten the length of stay and accelerate recovery of patients, and it is a viable surgical procedure which deserved clinical application and promotion.
Our trial was approved and has been registered in the ethics committee of the Yantai Yuhuangding Hospital (Approval NO.2015171) .
Cell is the basic unit of structure and function of all living bodies. The study of intracellular drug concentration distribution is helpful to understand the drug efficacy of target site. Pemetrexed ...is a new multitarget folate antagonist with pyrrolidine group as its core structure. An ultra high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed for rapid quantification of pemetrexed concentration in human breast cancer cells (MCF-7). Sample pretreatment was completed by protein precipitation using methanol. The optimized chromatographic separation was achieved on a ZORBAX SB-C18 column (2.1 × 150 mm, 3.5 μm). The column was equilibrated with initial mobile phase and eluted under gradient phases containing 0.1% formic acid in water (phase A) and in acetonitrile (phase B). The gradient program started at 5% B, increased to 95% B in 2 min, and then held at 95% B for 1.5 min. The linear range of pemetrexed in cells and nucleus was 2.0–200.0 ng/mL, while in the medium sample it was 50.0–5000.0 ng/ml, and the correlation coefficients were all greater than 0.99. The recovery was 47.50–67.55% (2.0–200.0 ng/mL) and 82.72–97.15% (50.0–5000.0 ng/mL), and the matrix effect was 98.10–100.62% (2.0–200.0 ng/mL) and 89.78–97.65% (50.0–5000.0 ng/mL). Interday precision and intraday precision (RSD%) were less than 15.0% (for LLOQ, less than 20%), and accuracy (RE%) was within ±15%; the deviation of stability was within ±15%, all meeting the requirements of biological sample analysis. The results of intracellular samples showed that the concentration of pemetrexed reached its peak at 3 h after administration. The concentration of pemetrexed in the nucleus continued to increase 2 h after administration and may have reached the maximum concentration at 6 h.
Bearing faults are the main contributors to the failures of induction motors, which are widely used in industrial field. In this paper, 8 embedded coils are firstly proposed for air gap sensing. With ...the 8 coils, 6 differential signals are generated, which are sensitive indicators to the bearing faults. Then, PCA is introduced for fault detection. Experiments with an oil pump fault detection are carried out to verify our approach. The results convince the validity and effectiveness of the embedded coils and PCA based method.
Packet loss is of great importance as a metric that characterizes the network’s performance, and is crucial for video applications, congestion control and routing. Most of existing measurement tools ...can indicate the packet loss of network links instead of the actual packet loss of individual application. On the other hand, because occurrence of packet loss behavior is relatively rare and its duration is short, active measuring methods need to inject a large number of packets and run for a long time for reporting accurate estimates, which would introduce additional intrusiveness to the network and perturb user traffic. In this paper, we present a new packet loss estimation technique by making use of user_data field of video, which is less intrusive since it does not affect video playing and does not need to inject extra probing stream. It can also provide the packet loss detailed information of I,P,B frames. The accuracy of the algorithm has been evaluated with both simulations and experiments over real-world Internet paths. In addition, we analyze the video quality distortion caused by packet loss of different frame types, and a real-time video quality monitoring system is built.
PDF
