Size-Dependent Electrochemical Performance Mediated by Stress-Induced Cracking in Zn2SnO4 Electrodes.

Correlating the microscopic structural characteristics with the macroscopic electrochemical performance in electrode materials is critical for developing excellent-performance lithium-ion batteries, which however remains largely unexplored. Here, we show that the Zn2SnO4 (ZTO) nanowires (NWs) with smaller diameters (d < 5 nm) exhibit slower capacity fade rate and better cycling stability, as compared with the NWs with larger diameters ranging from tens to hundreds of nanometers. By applying in situ transmission electron microscopy (TEM), we discover a strong correlation of cracking behavior with the NW diameter. Upon the first lithiation, there exists a critical diameter of ∼80 nm, below which the NWs neither crack nor fracture, and above which the cracks could easily nucleate and propagate along the specific planes, resulting in the deteriorated cycling stability in larger sized electrodes. Further theoretical calculations based on the finite element model and the climbing image nudged elastic band method faithfully predict the size-dependent cracking behaviors, which may result from the synergistic effect of axial stress evolution as well as preferential Li-ion migration directions during the first lithiation. This work provides a real-time tracking of the tempo-spatial structural evolution of a single ZTO NW, which facilitates a fundamental understanding of how the sample size affects the electrochemical behavior and thus offers a reference for future battery design and application strategy.

Unexpected Two-Dimensional Polarons Induced by Oxygen Vacancies in Layered Structure MoO3-x.

Unveiling the effects of oxygen vacancies on the structural stability of layered α-MoO3 is critical for optimizing its physical and chemical properties. Herein, we present experimental evidence regarding the phase stability of α-MoO3 with ∼2% oxygen vacancy concentrations. Interestingly, we report a previously ignored oxygen-deficient orthorhombic MoO3-x phase in space group Cmcm. Further density functional theory calculations reveal a detailed phase transition mechanism from α-MoO3 to MoO3-x. More importantly, we demonstrate that two-dimensional (2D) large polarons must exist to stabilize the MoO3-x crystal structure. 2D large polarons are suspected to exist in numerous quasi-2D systems but have never been found in layered α-MoO3 or other molybdenum oxides. Our work contributes to a basic understanding of the polaronic behavior in MoO3-x and may broaden the application realm of molybdenum oxides.

Size-Dependent Phase Transition in Ultrathin Ga2O3 Nanowires.

Gallium oxide (Ga2O3) has attracted extensive attention as a potential candidate for low-dimensional metal-oxide-semiconductor field-effect transistors (MOSFETs) due to its wide bandgap, controllable doping, and low cost. The structural stability of nanoscale Ga2O3 is the key parameter for designing and constructing a MOSFET, which however remains unexplored. Using in situ transmission electron microscopy, we reveal the size-dependent phase transition of sub-2 nm Ga2O3 nanowires. Based on theoretical calculations, the transformation pathways from the initial monoclinic ß-phase to an intermediate cubic γ-phase and then back to the ß-phase have been mapped and identified as a sequence of Ga cation migrations. Our results provide fundamental insights into the Ga2O3 phase stability within the nanoscale, which is crucial for advancing the miniaturization, light weight, and integration of wide-bandgap semiconductor devices.

Na+ Migration Mediated Phase Transitions Induced by Electric Field in the Framework Structured Tungsten Bronze.

Framework structured tungsten bronzes serve as promising candidates for electrode materials in sodium-ion batteries (SIBs). However, the tungsten bronze framework structure changes drastically as mediated by the sodium ion concentration at high temperatures. While the three-dimensional ion channels facilitate fast ion storage and transport capabilities, the structural instability induced by Na+ migration is a big concern regarding the battery performance and safety, which unfortunately remains elusive. Here, we show the real-time experimental evidence of the phase transitions in framework structured Na0.36WO3.14 (triclinic phase) by applying different external voltages. The Na+-rich (Na0.48WO3, tetragonal phase) or -deficient (NaxWO3, x < 0.36, hexagonal phase) phase nucleates under the positive or negative bias, respectively. Combined with the theoretical calculations, the atomistic phase transition mechanisms associated with the Na+ migration are directly uncovered. Our work sheds light on the phase instability in sodium tungsten bronzes and paves the way for designing advanced SIBs with high-stability.

Pushing detectability and sensitivity for subtle force to new limits with shrinkable nanochannel structured aerogel.

There is an urgent need for developing electromechanical sensor with both ultralow detection limits and ultrahigh sensitivity to promote the progress of intelligent technology. Here we propose a strategy for fabricating a soft polysiloxane crosslinked MXene aerogel with multilevel nanochannels inside its cellular walls for ultrasensitive pressure detection. The easily shrinkable nanochannels and optimized material synergism endow the piezoresistive aerogel with an ultralow Young's modulus (140 Pa), numerous variable conductive pathways, and mechanical robustness. This aerogel can detect extremely subtle pressure signals of 0.0063 Pa, deliver a high pressure sensitivity over 1900 kPa-1, and exhibit extraordinarily sensing robustness. These sensing properties make the MXene aerogel feasible for monitoring ultra-weak force signals arising from a human's deep-lying internal jugular venous pulses in a non-invasive manner, detecting the dynamic impacts associated with the landing and take-off of a mosquito, and performing static pressure mapping of a hair.

Long-term effect of active parenteral nutrition support regimen in preterm infants with a gestational age of <34 weeks. / ç§¯æžè‚ å¤–è¥å »æ”¯æŒæ–¹æ¡ˆåœ¨èƒŽé¾„å°äºŽ34å‘¨æ—©äº§å„¿ä¸­çš„è¿œæœŸæ•ˆæžœç ”ç©¶.

OBJECTIVES: To study the long-term effect of active parenteral nutrition support regimen in preterm infants with a gestational age of <34 weeks. METHODS: According to the different doses of fat emulsion and amino acids used in the early stage, the preterm infants with a gestational age of <34 weeks, who were admitted to the hospital within 24 hours after birth from May to December 2019, were divided into an active parenteral nutrition group and a conventional parenteral nutrition group (n=50). Physical indices and the measurements of the Gesell Development Scale were collected at the age of 6 months and 13 months. RESULTS: At the age of 6 months, the active parenteral nutrition group (n=46) had higher developmental quotients of gross motor, fine motor, and personal-social behavior than the conventional parenteral nutrition group (n=34) (P<0.05). At the age of 13 months, the active parenteral nutrition group (n=25) had higher developmental quotients of adaptive behavior, gross motor, and personal-social behavior than the conventional parenteral nutrition group (n=19) (P<0.05). There were no significant differences in the physical development indices such as body weight, body height, and head circumference between the two groups during follow-up (P>0.05). CONCLUSIONS: For preterm infants with a gestational age of <34 weeks, an active parenteral nutrition support strategy with high doses of fat emulsion and amino acids within 24 hours after birth can improve their long-term neurodevelopment.

Cation Defect Mediated Phase Transition in Potassium Tungsten Bronze.

Applying in situ transmission electron microscopy, the phase instability in potassium tungsten bronze (KxWO3, 0.18 < x < 0.57) induced by heating was investigated. The atomistic phase transition pathway of monoclinic K0.20WO3 → hexagonal KmWO3 (0.18 < m < 0.20) → cubic WO3 induced by cationic defects (K and W vacancies) was directly revealed. Unexpectedly, a K+-rich tetragonal KnWO3 (0.40 < n < 0.57) phase would nucleate as well, which may result from the blockage of K+ diffusion at the grain boundaries. Our results point out the critical role of the cationic defects in mediating the crystal structures in KxWO3, which provide reference to rational structural design for extensive high-temperature applications.

Atomistic Observation of Desodiation-Induced Phase Transition in Sodium Tungsten Bronze.

The phase instability in layered-structure Na0.5WO3.25 induced by the extraction of Na ions was investigated by applying transmission electron microscopy. Real-time atomic-scale observation reveals the phase transition pathway: Na0.5WO3.25 (triclinic) → NaxWO3 (cubic) → WO3 (monoclinic) with specific orientation relationships. The dynamic evolution of Na0.5WO3.25/NaxWO3 phase boundaries shows that Na0.5WO3.25 will cleave along the (100)T and (010)T and recrystallize as (101)C and (010)C of NaxWO3, respectively. The phase transition pathway can be well-explained according to the structural characteristics in the three phases. By better understanding of the phase instability induced by the extraction of Na ions in possible layered-structure cathode materials, this work provides a reference for the design of sophisticated strategies toward high-performance Na-ion batteries.

Ultrathin high-κ antimony oxide single crystals.

Ultrathin oxides have been reported to possess excellent properties in electronic, magnetic, optical, and catalytic fields. However, the current and primary approaches toward the preparation of ultrathin oxides are only applicable to amorphous or polycrystalline oxide nanosheets or films. Here, we successfully synthesize high-quality ultrathin antimony oxide single crystals via a substrate-buffer-controlled chemical vapor deposition strategy. The as-obtained ultrathin antimony oxide single crystals exhibit high dielectric constant (~100) and large breakdown voltage (~5.7 GV m-1). Such a strategy can also be utilized to fabricate other ultrathin oxides, opening up an avenue in broadening the applicaitons of ultrathin oxides in many emerging fields.

Atomistic and dynamic structural characterizations in low-dimensional materials: recent applications of in situ transmission electron microscopy.

In situ transmission electron microscopy has achieved remarkable advances for atomic-scale dynamic analysis in low-dimensional materials and become an indispensable tool in view of linking a material's microstructure to its properties and performance. Here, accompanied with some cutting-edge researches worldwide, we briefly review our recent progress in dynamic atomistic characterization of low-dimensional materials under external mechanical stress, thermal excitations and electrical field. The electron beam irradiation effects in metals and metal oxides are also discussed. We conclude by discussing the likely future developments in this area.

[70 degrees recumbent position transperitoneal laparoscopy for treatment of upper urinary tract transitional cell carcinoma].

OBJECTIVE: To study the effect of 70 degrees recumbent position transperitoneal laparoscopy for treatment of upper urinary tract transitional cell carcinoma (TCC). METHODS: From May 2004 to January 2007, 70 degrees recumbent position transperitoneal laparoscopy combined with urethral resectoscope was used to treat 31 cases of upper urinary tract transitional cell carcinoma. At the same time titanium clip to occlude the two extremities of ureter tumor was used, extracting specimen by oblique incision of lower quadrant. RESULTS: All operations were finished successfully, no one was turned to open surgery; mean operation time was 140 min, mean blood loss 80 ml, mean hospital stay time 8 d, without complications of urine leakage and intestinal fistula and so on. CONCLUSIONS: 70 degrees recumbent position transperitoneal laparoscopy for resection of whole kidney and ureter is worth of general clinical application because it could provide large space for operation, simplify the treatment of renal pedicle vessels, decrease operation risk, reduce operation trauma and offer early recovery. But its effect on tumor spread and recurrence will still need long term follow-up.

[Laparoscopic aid in upper urinary reconstructive operation].

OBJECTIVE: To evaluate the efficacy and feasibility of laparoscopic aid in upper urinary reconstructive operation. METHODS: Fifty-eight patients with ureteropelvic junction obstruction, 5 patients with upper ureter polypous, 2 patients with upper ureter stenosis, and 13 patients with upper ureter lithiasis underwent upper urinary reconstructive operation with laparoscopic aid described as follows:an incision 1 cm long was made, a 10 mm trocar and a 30 degrees laparoscope were wt in, the part with lesion was isolated and resected, and then pyeloplasty or end-to-end anastomosis of ureter was performed. RESULTS: The mean operative time was 33 minutes (25-45 minutes). The mean blood loss was 20 ml (15-25 ml). Complications such as urinary leakage and infection were observed. The double J stent was removed at 1 month after the operation. Follow-up for 3 to 15 months in 20 cases showed alleviation of hydronephrosis. CONCLUSION: An effective and safe method with less wound and operative time, combination of laparoscopic aid and open surgery in upper urinary reconstructive operation helps avoid difficult laparoscopic operation, does not increase trauma of the abdominal wall, and is worth promoting clinically.