Imaging Nucleation and Propagation of Pinned Domains in Few-Layer Fe5-xGeTe2.

Engineering nontrivial spin textures in magnetic van der Waals materials is highly desirable for spintronic applications based on hybrid heterostructures. The recent observation of labyrinth and bubble domains in the near room-temperature ferromagnet Fe5-xGeTe2 down to a bilayer thickness was thus a significant advancement toward van der Waals-based many-body physics. However, the physical mechanism responsible for stabilizing these domains remains unclear and requires further investigation. Here, we combine cryogenic scanning diamond quantum magnetometry and field reversal techniques to elucidate the high-field propagation and nucleation of bubble domains in trilayer Fe5-xGeTe2. We provide evidence of pinning-induced nucleation of magnetic bubbles and further show an unexpectedly high layer-dependent coercive field. These measurements can be easily extended to a wide range of magnetic materials to provide valuable nanoscale insight into domain processes critical for spintronic applications.

Robust Weak Antilocalization Effect Up to ∼120 K in the van der Waals Crystal Fe5-xGeTe2 with Near-Room-Temperature Ferromagnetism.

The van der Waals Fe5-xGeTe2 is a 3d ferromagnetic metal with a high Curie temperature of 275 K. We report herein the observation of an exceptional weak antilocalization (WAL) effect that can persist up to 120 K in an Fe5-xGeTe2 nanoflake, indicating the dual nature with both itinerant and localized magnetism of 3d electrons. The WAL behavior is characterized by the magnetoconductance peak around zero magnetic field and is supported by the calculated localized nondispersive flat band around the Fermi level. The peak to dip crossover starting around 60 K in magnetoconductance is visible, which could be ascribed to temperature-induced changes in Fe magnetic moments and the coupled electronic band structure as revealed by angle-resolved photoemission spectroscopy and first-principles calculations. Our findings would be instructive for understanding the magnetic exchanges in transition metal magnets as well as for the design of next-generation room-temperature spintronic devices.

Layer-Dependent Magnetic Domains in Atomically Thin Fe5GeTe2.

Magnetic domain formation in two-dimensional (2D) materials gives perspectives into the fundamental origins of 2D magnetism and also motivates the development of advanced spintronics devices. However, the characterization of magnetic domains in atomically thin van der Waals (vdW) flakes remains challenging. Here, we employ X-ray photoemission electron microscopy (XPEEM) to perform layer-resolved imaging of the domain structures in the itinerant vdW ferromagnet Fe5GeTe2 which shows near room temperature bulk ferromagnetism and a weak perpendicular magnetic anisotropy (PMA). In the bulk limit, we observe the well-known labyrinth-type domains. Thinner flakes, on the other hand, are characterized by increasingly fragmented domains. While PMA is a characteristic property of Fe5GeTe2, we observe a spin-reorientation transition with the spins canting in-plane for flakes thinner than six layers. Notably, a bubble phase emerges in four-layer flakes. This thickness dependence, which clearly deviates from the single-domain behavior observed in other 2D magnetic materials, demonstrates the exciting prospect of stabilizing complex spin textures in 2D vdW magnets at relatively high temperatures.

Effect of (NH4)2ZrF6, Voltage and Treating Time on Corrosion Resistance of Micro-Arc Oxidation Coatings Applied on ZK61M Magnesium Alloys.

The effects of (NH4)2ZrF6 concentration, voltage and treating time on the corrosion resistance of ZK61M magnesium alloy micro-arc oxidation coatings were studied by orthogonal experiments. The SEM result shows that the surface roughness and porosity of MAO coatings increased with (NH4)2ZrF6 concentration, voltage and treating time as a whole, except the porosity decreased with treating time. EDS, XRD and XPS analysis show that (NH4)2ZrF6 was successfully incorporated into coatings by reactive incorporation, coatings are dominantly composed of ZrO2, MgO, MgF2 and amorphous phase Mg phosphate. Potentiodynamic polarization was used to evaluate the corrosion property of coatings. When the concentration of (NH4)2ZrF6 is 6 g/L, the voltage is 450 V, and the treating time is 15 min, the coating exhibits the best corrosion resistance which corrosion current density is four magnitudes lower than substrate attributed to the incorporation of ZrO2 and the deposition of MgF2 in the micropores.

Magnetic critical behavior of the van der Waals Fe5GeTe2 crystal with near room temperature ferromagnetism.

The van der Waals ferromagnet Fe5GeTe2 has a Curie temperature TC of about 270 K, which is tunable through controlling the Fe deficiency content and can even reach above room temperature. To achieve insights into its ferromagnetic exchange that gives the high TC, the critical behavior has been investigated by measuring the magnetization in Fe5GeTe2 crystal around the ferromagnetic ordering temperature. The analysis of the measured magnetization by using various techniques harmonically reached to a set of reliable critical exponents with TC = 273.7 K, ß = 0.3457 ± 0.001, γ = 1.40617 ± 0.003, and δ = 5.021 ± 0.001. By comparing these critical exponents with those predicted by various models, it seems that the magnetic properties of Fe5GeTe2 could be interpreted by a three-dimensional magnetic exchange with the exchange distance decaying as J(r) ≈ r-4.916, close to that of a three-dimensional Heisenberg model with long-range magnetic coupling.

Effect of Diffusion Annealing Temperature on the Formation Process and Properties of a Carbon-Aluminum Composite Layer on Pure Titanium.

A carbon-aluminum composite layer was prepared on the surface of pure titanium by double glow plasma carburizing, magnetron sputtering aluminizing, and vacuum-diffusional annealing treatment. The microstructure, phase composition, and properties of the composite layer obtained at different annealing temperatures were investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and the ball-on-disc wear method. Results showed that the layer contained a mixture of TiAl3, Ti2Al5, and TiC phases at 650 °C for 6 h, which can significantly enhance the hardness and wear resistance of pure titanium. The layer exhibited a higher hardness of around 1231 HV0.1, a lower friction coefficient of 0.33, and lower wear volumes of 0.018 mm3 than those of the titanium substrate.

Morphology and Wear Resistance of Composite Coatings Formed on a TA2 Substrate Using Hot-Dip Aluminising and Micro-Arc Oxidation Technologies.

Aluminium layers were coated onto the surface of pure titanium using hot-dip aluminising technology, and then the aluminium layers were in situ oxidised to form oxide ceramic coatings, using the micro-arc oxidation (MAO) technique. The microstructure and composition distribution of the hot-dip aluminium coatings and ceramic layers were studied by using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The phase structure of the MAO layers was studied using X-ray diffraction. The surface composition of the MAO layer was studied by X-ray photoelectron spectroscopy. The wear resistance of the pure titanium substrate and the ceramic layers coated on its surface were evaluated by using the ball-on-disc wear method. Therefore, aluminising coatings, which consist of a diffusion layer and a pure aluminium layer, could be formed on pure titanium substrates using the hot-dip aluminising method. The MAO method enabled the in-situ oxidation of hot-dip pure aluminium layers, which subsequently led to the formation of ceramic layers. Moreover, the wear resistance values of the ceramic layers were significantly higher than that of the pure titanium substrate.

Parity-time symmetry in periodically curved optical waveguides.

The coupling strength between two parity-time (PT) symmetric resonators determines whether the PT phase is broken or not. Here we investigate the scenario that two optical waveguides are spatially curved so that they switch periodically between unbroken and broken PT phases. We show that the existence of locally broken PT phase does not necessarily render a broken phase to waves propagating inside. Criteria are proposed to characterize the collective dynamics of wave near the Brillouin zone (BZ) edge, toward the cases of a totally broken phase, a partially broken phase, or a totally unbroken phase. We also discuss the characteristics of two special kinds of exceptional points (EPs) at the BZ edge, and show that their field patterns are displaced by half a period with each other. Full-wave numerical simulation proves our analysis. Potential applications especially these associated with EPs are discussed. This study helps us to understand how the locally PT-symmetric related eigenstate influences the globally collective dynamics of wave in spatially periodic configuration.

Influence of KMnO4 Concentrationon Infrared Emissivity of Coatings Formed on TC4 Alloys by Micro-Arc Oxidation.

Ceramic coatings with high emissivity were fabricated on TC4 alloys by micro-arc oxidation technique (MAO) in mixed silicate and phosphate electrolytes with varying KMnO4 addition. The microstructure, phase and chemical composition were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and the infrared emissivity of the MAO coatings was measured in a waveband of 5-20 µm. The results show that the thickness of the coatings increased with the addition of KMnO4, but the roughness of the coatings first decreased and then increased slightly due to the inhibitory effect of KMnO4 on Na2SiO3 deposition. The main phase composition of the coatings was anatase and rutile TiO2, amorphous form of SiO2 and MnO2. The infrared emissivity value of the coatings strongly depended on KMnO4 concentration, the coating formed at the concentration of 0.8 g/L KMnO4 reached the highest and an average of up to 0.87 was observed.

[Time of salvage treatment on sudden sensorineural hearing loss].

OBJECTIVE: To explore the best time of intratympanic dexamethasone injection to treat sudden sensorineural hearing loss (SSNHL) as salvage therapy so that to improve the curative efficacy on sudden deafness at the utmost. METHOD: A total of 192 patients with SSNHL were included in this study, among whom 63 cases received the systemic steroid therapy throughout the study, while the other ones were treated with systemic steroid as initial treatment and were given intratympanic steroid administration as salvage treatment starting at different time point. The salvage treatment started on the 3rd day after the beginning of the initial treatment for 29 cases, on the 7th day for 38 cases, on the 14th day for 43 cases, and 1 month later for 19 cases. All the patients were followed up for 2 months. RESULT: The recovery rates and total effective rates showed no statistically significant difference between the patients received only systemic steroid therapy and the ones received intratympanic steroid administration on the 3rd, 7th day and 1 month later after the initial treatment. The recovery rate and total effective rate exhibited statistically significant difference between the patients received intratympanic steroid administration since the 14th day after the initial treatment and the ones received only systemic steroid therapy, with the numerical value of P 0. 037 and 0. 034, respectively. CONCLUSION: (1) As an initial management plan, the curative effects. between the intratympanic steroid administration and the systemic steroid therapy were not significantly different. (2) As a salvage treatment, intratympanic steroid was a better choice for patients who have not completely recover from ISSNHL after failure of initial management with systemic steroid only. (3) The best time point of salvage treatment with intratympanic steroid was about 2 weeks after initial management with systemic steroid.

[The effect of hyperbaric oxygen therapy to different degree of hearing loss and types of threshold curve in sudden deafness patients].

OBJECTIVE: To investigate the effect of hyperbaric oxygen therapy to different degrees of hearing loss and different types of threshold curve in sudden deafness patients, and establish a personalized therapy, so as to promote clinical effect to sudden deafness. METHOD: One hundred and twenty cases were divided into two groups respectively (each group 60 cases). Drug treatment had been used in group A for two weeks. The patients in group B received drug treatment combined with hyperbaric oxygen therapy for two weeks. According to the different degrees of hearing loss and the types of audiogram in two groups, the statistical analysis to the difference of hyperbaric oxygen therapeutic effect was done. RESULT: The effective rates was statistically different (chi2 = 8.044, P < 0.01) between group A (60.00%, 36/60) and group B (83.33%, 50/60). There was no statistical difference between two treatment program in mild and the profound deafness patients. The statistical difference could been found between moderate and the severe deafness, the value of chi2 and p were 4.969, 5.560 and 0.040, 0.035, respectively. In group A, the statistical difference could only been found between mild and the profound deafness patients (chi2 = 6.739, P < 0.05). In group B, the statistical difference could been found in mild and the profound deafness, the moderate and the profound deafness, the severe and the profound deafness patients. The value of chi2 were 11.500, 15.058,10.221 and P < 0.01 respectively. The effective rates was no statistical difference in two treatment programs in the upsloping audiogram and the profound deafness. The statistical difference could been found between the downsloping and the flat audiogram, with the value of chi2 and p were 5.144 and 5.969, P < 0.05, respectively. In group A, the statistical difference could been found between the ascending and descending audiogram, the ascending and the flat audiogram,the ascending type and the profound deafness. The value of chi2 were 6.188, 7.247, 8.082 and P < 0.05, respectively. No statistical difference could been found among the other types of audiogram. In group B, no statistical difference could been found among all types of audiogram. CONCLUSION: The effect of hyperbaric oxygen therapy varies with degree of hearing loss and audiogram type. Drug treatment combined with HBOT can promote clinical effect for patients in moderate deafness and severe deafness, the descending and flat type of audiogram.

[Choice of treatment plan and operation time on pediatric chronic sinusitis].

OBJECTIVE: To explore the curative effect of pediatric chronic sinusitis and analyze its relative factors, so that the best treatment plan and operation time can be choose. METHOD: Two hundred and twenty cases of pediatric chronic sinusitis were divided into 4 groups: group A with only simple chronic sinusitis, group B accompanied adenoid hypertrophy. Among group B, group B1 with no nasal cavity structural abnormalities but group B2 on the contrary. Group C accompanied only nasal cavity structural abnormalities. According to the documents, all patients were administered with standard and systematical three-stage treatment. The curative effect of each group was calculated and analyzed in each treated stage. RESULT: After the first stage treated in 220 pediatric chronic sinusitis, a statistical significance of curative effect could be observed between group A and B, A and B1, A and B2, A and C (P < 0.01), but none between group B and C, B1 and B2, B1 and C, B2 and C (P > 0.01). Ninety-four patients in group B were accepted the second stage treated: adenoidectomy after first treatment failed. There was a statistical significance of curative effect between group B1 and B2 (P < 0.01). Once the above management both failed, endoscopic sinus surgery (FESS) was carried out. The total effective rate of FESS was 89.65%. CONCLUSION: The systemic, disciplinary medical management has some referred value in the treatment for children with chronic sinusitis. Adenoid hypertrophy and nasal cavity structural abnormalities are two relative factors of the curative effect in pediatric chronic sinusitis. The time and cost of therapy can be saved if adenoidectomy and FESS are done for cases with adenoid hypertrophy or (and) nasal cavity structural abnormalities with the systemic, disciplinary medical management simultaneously.

[The value of cyclooxygenase-2 to predict the effect of radiotherapy in nasopharyngeal carcinoma].

OBJECTIVE: To investigate the relation between the expression of COX-2 protein and the effect of radiotherapy, estimate the value of COX-2 in predicting the effect of radiotherapy in patients with nasopharyngeal carcinoma,provide theoretical basement for establishing characteristic project of treatment and raising curative effect and life quantity. METHOD: The expression of COX-2 protein was examined in 30 radiosensitive and 30 radioresistant poorly differentiated NPC by immunohistochemical staining (SP method) before radiotherapy. The relation between the expression of COX-2 and the effect of radiotherapy was analyzed. RESULT: The positive rate of COX-2 protein expression was 61. 67% in NPC tissues, there was statistical difference( P <0. 01) of the positive rate between the 86. 67 % of 30 radioresistant and 36. 67 % of radiosensitive NPC tissues. The intensity of COX-2 protein expressions showed statistical difference( P <0. 05),too. Based on the expression of COX-2, the effect of radiotherapy, sensitivity, specificity, accuracy, positive predictive value, negative predictive value, false positive and false negative were predicted as follows: 86. 67Y, 63. 33% ,75. 00%, 70. 27% ,82. 61% ,36. 67% and 13. 33 , respectively. CONCLUSION: COX-2 expression may serve as a marker in predicting the response to radiotherapy in NPC. According to the expression of COX-2, the sound treatment scheme can be selected.

[Blood vessel multiply and significance of expression of Cox-2, VEGF in pterygium].

OBJECTIVE: To investigate the role of cyclooxygenases-2 (Cox-2) and vascular endothelial growth factor (VEGF) in the occurrence and development of human pterygium. METHODS: The immunohistochemical elivision method was used to examine the expressions of Cox-2 and VEGF in 30 cases of pterygium and 15 cases with normal conjunctiva. RESULTS: The positive rate of Cox-2 was 42.8% in resting stage, 84.6% in active stage, 90.0% in recurrent pterygium and 6.6% in normal conjunctiva. The positive rate of VEGF was 57.1% in resting stage, 69.2% in active stage, 100.0% in recurrent pterygium and 13.3% in the normal conjunctiva. There was significant difference in the expressions of Cox-2 and VEGF between the pterygium and normal conjunctiva (P < 0.05, P < 0.001). CONCLUSIONS: There are high Cox-2 and VEGF expressions in pterygium, which suggests that there is abnormal blood vessel multiply in pterygium, and the Cox-2 and VEGF plays an important role in the incidence and development of pterygium. Specific Cox-2 and VEGF inhibitor become a new target for the therapy of pterygium. Specific Cox-2 and VEGF inhibitor become a new target for the therapy of pterygium.

[Evidence-based treatment of secretory otitis media in patients with nasopharyngeal carcinoma after radiotherapy].

OBJECTIVE: According to the principle of Evidence-Based Medicine (EBM), to analyse the cause of SOM in patients with nasopharyngeal carcinoma (NPC) after radiotherapy and to explore the effective treatment methods of SOM in patients with NPC after radiotherapy. METHOD: One hundred and six cases (112 ears) of SOM in patients with NPC after radiotherapy were treated with comprehensive management,e. g application of general and local antibiotics,nerves nutrition medicine, blood vessel dilating drugs and hormone, reinforced clearance of nasal cavities and nasopharynx and treatment of the disease of nasal cavities and sinuses, in addition to inserting catheter into the tympanum and intratympanic application of medicine through the eustachian tube. RESULT: Before the comprehensive treatment, all patients had hearing impairment, tinnitus and/or the feeling of ear blocked. Acoustic immittance test showed 112 ears(100%) had Type B tympanogram. After the treatment, tinnitus (ears) disappeared in 81 ears (72.32%), relieved in 25 ears (22.32%) and no effect was seen in 6 ears (5.36%). The total efficiency was 94.64. The feeling of ear blocked disappeared in 92 ears (82.14%), relieved in 18 ears (16.07%) and no effect was found in 2 ears (1.79%). The total efficiency was 98.21%. Acoustic immittance test showed 56 ears (50%) had Type A tympanogram, 42 ears had Type As (37.50%), 2 ears had Type B (1.79%) and, 12 ear had Type Cs (10.71%). The mean hearing threshold of 0.5,1,2 kHz of pure-tone was (28.5 +/- 3.0) dBHL after the treatment, which was (47.0 +/- 5.0) dBHL prior to it. No otorrhea, or permanent scar obstruction in the eustachian tube was found after the treatment. CONCLUSION: It is very effective and practicable to treat SOM in patients with NPC after radiotherapy according to the principle of EBM and to aim directly at the cause of SOM in patients with NPC after radiotherapy. It is very significant to improve the life quality of patients with NPC after radiotherapy.

[The features of auditory brainstem response in patients with obstructive sleep apnea-hypopnea syndrome].

OBJECTIVE: To investigate the effects and causes of obstructive sleep apnea-hypopnea syndrome (OSAHS) on auditory pathway, the changes of auditory brainstem response (ABR) were analyzed. METHOD: With the use of polysomnography,72 snorers were examined and divided into OSAHS and non- OSAHS groups. These two groups patients and a group of normal person were underwent ABR measuring. RESULT: There were statistically significant difference between the group of OSAHS and the non-OSAHS or the group of OSAHS and the normals on the delayed latency of wave I and wave V, the response liminal value of wave V rised. CONCLUSION: The results suggest that cochlear function may be affected in patient with OSAHS, the effected of brain stem is unknown.

[Association between the shape alteration of pharyngeal ostium of eustachian tube and secretory otitis media].

OBJECTIVE: To investigate the association between the shape alteration of pharyngeal ostium of eustachian tube and secretory otitis media (SOM). METHOD: Two hundred and twelve pharyngeal ostiums of eustachian tube were observed by using rhinopharyngoscope and divided into two groups: the contrast's and the secretory otitis media's, and all the shape of pharyngeal ostium of eustachian tube were divided into triangular type, cravice type, elliptical type and bell type. RESULT: The shape of pharyngeal ostium of eustachian tube are remarkablely difference with the normal group and the diseased group. There are 84 cases triangular type (73%), 4 cases cravice type (3.5%), 17 cases bell type (8.7%) and 10 cases elliptical type (14.8%) in the former. There are 13 cases triangular type (13.4%), 68 cases cravice type (3.5%), 5 cases elliptical type (5.2%) and 11 cases bell type (11.3%) in the SOM group. CONCLUSION: The study suggest that there is a close association between the shape alteration of pharyngeal ostium of eustachian tube and secretory otitis media, meanwhile it offer a new index for exploring the new methods to cure the adult secretory otitis media how to resume the normal shape and the function of pharyngeal ostium of eustachian tube as soon as possible early.

[Relationship between adenoids hypertrophy and secretory otitis media].

OBJECTIVE: To investigae the cause of secretory otitis media resulting from adenoids hypertrophy and the relationship between adenoids hypertrophy and secretory otitis media. METHOD: According to the grades of adenoids hypertrophy, 140 children were divided into two groups: the group of middle-grade and the group of pathological hypertrophy. The effect about the degree of adenoids hypertrophy resulted in the descendent of middle ear function and the difference of incidence of secretory otitis media were analyzed. RESULT: The incidence of secretory otitis media and the pattern of tympanic press were distinct difference in two groups. CONCLUSION: The results suggested that there was a positive correlation among the grades of adenoids hypertrophy, the descendent degree of middle ear function and the incidence of secretory otitis media.

[Implantation of complex tissue flap for atrophic rhinitis].

OBJECTIVE: To improve the treatment effect of atrophic rhinitis. METHOD: Twenty-one cases (thirty-one sides) of atrophic rhinitis were treated by implantation of complex tissue flap to narrow the nasal cavity. RESULT: Short-term effective treatment results were 100% (21/21), long-term effective treatment results were 90.5% (19/21). CONCLUSION: Implantation of complex tissue flap offers a simple and effective way and can be recommended for the treatment of atrophic rhinitis.