Bayesian inference of the crust–core transition density via the neutron-star radius and neutron-skin thickness data

In this work,we perform a Bayesian inference of the crust-core transition density ρ_(t) of neutron stars based on the neutron-star radius and neutron-skin thickness data using a thermodynamical method.Uniform and Gaussian distributions for the ρ_(t) prior were adopted in the Bayesian approach.It has a larger probability of having values higher than 0.1 fm^(−3) for ρ_(t) as the uniform prior and neutron-star radius data were used.This was found to be controlled by the curvature K_(sym) of the nuclear symmetry energy.This phenomenon did not occur if K_(sym) was not extremely negative,namely,K_(sym)>−200 MeV.The value ofρ_(t) obtained was 0.075_(−0.01)^(+0.005) fm^(−3) at a confidence level of 68%when both the neutron-star radius and neutron-skin thickness data were considered.Strong anti-correlations were observed between ρ_(t),slope L,and curvature of the nuclear symmetry energy.The dependence of the three L-K_(sym) correlations predicted in the literature on crust-core density and pressure was quantitatively investigated.The most probable value of 0.08 fm^(−3) for ρ_(t) was obtained from the L-K_(sym) relationship proposed by Holt et al.while larger values were preferred for the other two relationships.

Retinal thickness and fundus blood flow density changes in chest pain subjects with dyslipidemia

AIM:To assess the retinal thickness and fundus blood flow density changes in chest pain patients with dyslipidemia using optical coherence tomography angiography(OCTA).METHODS:All subjects with chest pain as the main symptom accepted a comprehensive ophthalmological examination.According to the serum lipid levels,the participants were divided into the control group and the dyslipidemia group.The retina thickness and fundus blood flow density were determined using OCTA.RESULTS:The study enrolled 87 left eyes from 87 adults with dyslipidemia and 87 left eyes from age-and sexmatched participants without dyslipidemia.The retina of dyslipidemia subjects was significantly thinner than that of the controls in the inferior(P=0.004 and P=0.014,respectively)and temporal(P=0.015 and P=0.019,respectively)regions,both inner and outer layers.In terms of blood flow density in the macula or optic disk,there was a decreasing trend in the dyslipidemia group compared with the control group,especially in the inferior and temporal regions.CONCLUSION:Dyslipidemia may contribute to the decrease in retinal thickness and fundus blood flow density.Further validation of the association between abnormal lipid metabolism and fundus microcirculation alterations needs to be carried out in chest pain patients.

Visual acuity and endothelial cell density with respect to the graft thickness in Descemet's stripping automated endothelial keratoplasty: one year results

AIM: To evaluate the visual acuity and endothelial cell density according to the thickness in Descemet’s stripping automated endothelial keratoplasty(DSAEK)one year after surgery.METHODS: DSAEK patients’ data were reviewed. Thirty seven eyes of 37 patients who underwent DSAEK for pseudophakic bullous keratopathy(PBK) were included in this study. Graft thickness was measured with optical coherence tomography(OCT) 12 mo after DSAEK. Eyes were divided into 3 groups based on the graft thickness:thick(】200 μm), medium-thick(150-200 μm) and thin(【150 μm). Best corrected visual acuity(BCVA),endothelial cells density(ECD) and complications were assessed and comparisons were done between groups.RESULTS: Median thickness of postoperative grafts was 188(range 73-317 μm). There was no significant difference in age, sex, preoperative BCVA, or follow-up period between DSAEK groups. At postoperative 12 mo,mean BCVA was 0.28±0.10 in thick graft group, 0.52±0.08 in medium-thick graft group, and 0.72 ±0.06 in thin graft group. Thin grafts showed better postoperative BCVA as compared with the medium-thick and thick grafts(P =0.001). Thick graft group had 1637.44 ±88.19-mm2,medium thick graft had 1764.50±34.28-mm2 and thin graft group had 1845.30 ±65.62-mm2. Thin graft group had better ECD at 12 mo after surgery(P =0.001).CONCLUSION: Thin grafts after DSAEK ensure better visual rehabilitation. Eyes with thin grafts had significantly lesser loss of ECD compared to eyes withmedium-thick and thick grafts one year after surgery.

Variations in bark thickness and sapwood density of Calophyllum inophyllum provenances in Australia and in Sri Lanka

Sapwood density and bark thickness of Calophyllum inophyllum L. （a multipurpose durable timber species） were studied in various locations in Northern Australia and in Sri Lanka. Measurements were taken non-destructively by using core sampling and bark gauge. From each provenance, 4–15 mature trees having girth at breast height over bark （GBHOB） at 100–150 cm were selected on the basis of the population size. Significant （p0.05） hemispheric and provenance variations in bark thickness were found. Variations in the bark thickness are influenced by environmental variables. Variations in sapwood density were less pronounced compared to that of bark thickness. Variations in sapwood density are likely to be governed by genotypic variations.

Corneal endothelial cell density and morphology and central corneal thickness in Guangxi Maonan and Han adolescent students of China

AIM: To investigate the corneal endothelial cell density and morphology and central corneal thickness in the Guangxi Maonan and Han adolescent students of China.METHODS: Noncontact specular microscope(Topcon SP3000 P, Tokyo, Japan) was performed in 133 adolescent students of Maonan ethnic group(M:F 54:79)and 105 adolescent students of Han ethnic group(M:F 50:55),5 to 20 y of age, who were randomly selected from 3schools in Huanjiang Maonan Autonomous County of Guangxi Zhuang Autonomous Region of China.Parameters studied included endothelial cell density,mean cell area, coefficient of variation in cell size,percentage hexagonality and central corneal thickness. RESULTS: Endothelial cell density, mean cell area,coefficient of variation in cell size, percentage hexagonality and central corneal thickness in the study population were(2969.50 ±253.93) cells/mm2,(339.23 ±29.44) μm2,(29.96 ±4.07) %,(64.58 ±9.41) % and(523.71 ±32.82) μm in Maonan and(2998.26 ±262.65) cells/mm2,(336.11±30.07) μm2,(29.89±5.03) %,(64.91±11.64) % and(524.39 ±33.15) μm in Han, respectively. No significant differences were observed in endothelial cell density,mean cell area, coefficient of variation in cell size,percentage hexagonality and central corneal thickness between Maonan and Han(P =0.615, 0.659, 0.528, 0.551,0.999). In Maonan and Han, we found age was negatively correlated with endothelial cell density and percentagehexagonality and positively correlated with mean cell area and coefficient of variation in cell size. Negative correlation was also found between central corneal thickness and age in Han, whereas no correlation was found in Maonan. CONCLUSION: There were no differences between Maonan and Han in corneal endothelial cell density and morphology and central corneal thickness. In these two ethnic groups, there were statistically significant decrease in endothelial cell density and percentage hexagonality with increasing age and statistically significant increase in cell area and coefficient of variation in cell size with increasing age. Central corneal thinned with increasing age in Han, whereas difference did not attain statistical significance in Maonan.

Changes of peripapillary vascular density and its correlation with nerve fiber layer thickness in patients with unilateral retinal vein occlusion

Objective:To observe the changes of peripapillary vascular density(VD)and its correlation with retinal nerve fiber layer(RNFL)thickness in patients with unilateral retinal vein occlusion(RVO)by optical coherence tomography angiography(OCTA).Methods:Prospective case-control study.Thirty-two patients(32 eyes)with RVO diagnosed at the Eye Hospital of China Academy of Chinese Medical Sciences from September 2020 to June 2021 were selected.Another 32 outpatients(32 eyes)with normal ocular examination were selected as the normal control group.Optic disc blood flow imaging was performed in all subjects using the OCTA to measure peripapillary RNFL thickness,peripapillary vessel density,optic disc area,and disc rim area.The correlation between peripapillary vascular density and RNFL,optic disc area and disc rim area in eyes with unilateral RVO was analyzed.Results:Compared with the normal control group,the prevalence of hypertension was higher in the unilateral RVO group,and the difference was statistically significant(P<0.05).Compared with the normal control group,the overall,inferior and temporal RNFL thickness around the optic disc was thinner in patients with unilateral RVO,and the difference was statistically significant(P<005).Compared with the normal control group,the overall VD,internal ring,external ring and inferior VD around the optic disc were slightly decreased in patients with unilateral RVO,and the differences were statistically significant(P<0.05).The results of Pearson correlation analysis indicated that RNFL thickness was positively correlated with peripapillary global VD(r=0.648,P<0.001),RNFL thickness was positively correlated with intrapapillary ring VD(r=0.427,P=0.015),and RNFL thickness was positively correlated with peripapillary VD(r=0.666,P<0.001).Conclusion:The results showed that the RNFL thickness around the optic disc was thinner in patients with unilateral RVO,especially in the inferior and temporal area,and the full area VD around the optic disc was decreased,especially in the internal ring,external ring and inferior area.In patients with unilateral RVO,peripapillary RNFL was positively correlated with peripapillary global,internal ring and external ring VD.

Thickness Method for Measuring Hair Density of Rex Rabbit

[Objective] The paper was to characterize hair density by changes in hair thickness under certain pressure.[Method] Tile effects of weight of thickness tester and wafer urea at the hottom of presser foot on measurement results were studied, and the optimal measuring weight and wafer diameter was determined. The measurement results of hair thickness under the ahove condition were compared with the results of manual counting. Meanwhile, the effects of hair length and hair fineness on hair density were analyzed.[Result] The hair density obtained by manual count- ing had consistent change trend with the hair thickness measured under certain conditions. If the length and fineness of hairs were introduced for modification, the correlation between hair thickness and hair density would be better. There were little changes in hair length and finelless of rex rabbit, and their effects on hair thickness could be ignored under general condition. [Conclusion] It is completely feasible to characterize hair den- sity of rex rabbit by hair thickness under pressure.

Identification of retinal thickness and blood flow in agerelated macular degeneration with reticular pseudodrusen

AIM:To investigate thickness characteristics and vascular plexuses in retinas with reticular pseudodrusen(RPD)as an early detection strategy for age-related macular degeneration(AMD).METHODS:This retrospective study included 24 subjects(33 eyes)with RPD and 25 heathy control subjects(34 eyes).The superficial capillary plexus(SCP)and the deep capillary plexus(DCP)of the retinal posterior poles were investigated with optical coherence tomography angiography(OCTA).Retinal thicknesses and vessel densities were analyzed statistically.RESULTS:The general retinal thicknesses of RPD eyes were significantly decreased(95%CI-14.080,-0.655;P=0.032).The vessel densities of DCP in RPD eyes were significantly increased in the global(95%CI 1.067,7.312;P=0.027),parafoveal(95%CI 0.417,5.241;P=0.022),and perifoveal(95%CI 0.181,6.842;P=0.039)quadrants.However,the vessel densities of the SCP were rarely increased in the eyes with RPD.CONCLUSION:The thinning of retinas in the RPD group suggests a reduction in the number of cells.Additionally,the increased vessel density of the DCP in retinas with RPD indicates a greater demand for blood supply,possibly due to the hypoxia induced RPD compensation caused by RPD in the outer retina.This study highlights the pathological risks associated with RPD and emphasizes the importance of early intervention to retard the progression of AMD.

Age-related changes of lens thickness and density in different age phases

AIM: To explore the changes in lens thickness and density with age.METHODS: A Chinese population-based retrospective study was performed. A total of 497 individuals(490 right eyes and 495 left eyes), ranging from 3 to 69 years old were included. Lens images obtained from IOL Master 700 were used to measure lens thickness and density. Piecewise regression model was chosen to illustrate the relationship of lens thickness and density with age.RESULTS: The proportion of people aged 3-18, 19-40, over 40 was 38.6%, 50.9% and 10.5% respectively. The whole lens thickness decreased with age during the first 7 years of life, kept stable from 8 to 16 years old, and then increased at the rate of about 27 μm per year. The thickness of the lens cortex and nucleus tended to decrease first and then increase with age, which was dependent on age stages. The whole lens density also decreased with age until 7 years old. The increasing rate of lens density was different in different age groups. The whole lens density increased rapidly from 7 to 22 years old and slowed down after 22 years old. Similarly, the changing tendency of lens cortical and nuclear density differed in different age phases. CONCLUSION: Both lens thickness and density are significantly associated with age, whereas they do not change linearly with age. Moreover, it is necessary to increase the population over 40 years old and conduct further research.

Effect of layer thickness and voxel size inversion on leaf area density based on the voxel-based canopy profiling method

Voxel-based canopy profiling is commonly used to determine small-scale leaf area.Layer thickness and voxel size impact accuracy when using this method.Here,we determined the optimal combination of layer thickness and voxel size to estimate leaf area density accurately.Terrestrial LiDAR Stonex X300 was used to generate point cloud data for Masson pines(Pinus massoniana).The canopy layer was stratified into 0.10-1.00-m-thick layers,while voxel size was 0.01-0.10 m.The leaf area density of individual trees was estimated using leaf area indices for the upper,middle,and lower canopy and the overall canopy.The true leaf area index,obtained by layered harvesting,was used to verify the inversion results.Leaf area density was inverted by nine combinations of layer thickness and voxel size.The average relative accuracy and mean estimated accuracy of these combined inversion results exceeded 80%.When layer thickness was 1.00 m and voxel size 0.05 m,inversion was closest to the true value.The average relative accuracy was 92.58%,mean estimated accuracy 98.00%,and root mean square error 0.17.The combination of leaf area density and index was accurately retrieved.In conclusion,nondestructive voxel-based canopy profiling proved suitable for inverting the leaf area density of Masson pine in Hetian Town,Fujian Province.

Improved Retrieval of Sea Ice Thickness and Density from Laser Altimeter

The sensitivity of weather and climate system to sea ice thickness (SIT) in the Arctic is recognised from various studies. Decrease of SIT will affect atmospheric circulation, temperature, precipitation and wind speed in the Arctic and remotely. Ice thermodynamics and dynamic properties depend strongly on ice and snow thickness. The heat transfer through ice critically depends on ice thickness. Long term accurate SIT records with corresponding uncertainties are required for improved seasonal weather forecast and estimate of the sea ice mass balance. Satellite radar and Laser Altimeter (LA) provide long term records of sea ice freeboard. Assuming isostatic equilibrium, SIT is retrieved from the freeboard, extracted from radar altimeter (RA) or LA, where the snow depth, density, ice and water density are input variables in the equation for hydrostatic equilibrium to derive SIT from LA or RA. Different input variables (snow depth, density, ice and water density) with unknown accuracy have been applied from various authors to retrieve SIT and Sea Ice Draft (SID) from RA or LA, leading to not comparative results. Sea ice density dependence on ice type, thermodynamic properties and freeboard is confirmed with different studies. Sensitivity analyses confirm the great impact of sea ice density, snow depth and density on accuracy of the retrieved SIT and the importance of inserting variable ice density (VID) in the equation for hydrostatic equilibrium for more accurate SIT retrieval, weather and climate forecast. The impact of sea ice density and snow depth and density on retrieved SIT from the freeboard derived from LA and RA have been analyzed in this study using the equation for hydrostatic equilibrium, statistical and sensitivity analyses. An algorithm is developed to convert the freeboard, derived from LA in SIT, inserting VID in the equation for hydrostatic equilibrium. The algorithm is validated with field, laboratory studies and collocated SIT retrieved from RA on board Envisat. The accuracy of the developed algorithm is analyzed, using statistical and uncertainty analyses. It is found that the uncertainty of the retrieved SIT from LA is decreased 7.6 times (from rhi = 59 cm for fixed ice density) if variable ice density is inserted in the equation for hydrostatic equilibrium. The SIT, which has been retrieved from the freeboard derived from LA is validated with collocated SIT derived from RA2 on Envisat, using variable ice density. The bias of the mean SIT derived from LA and RA has been reduced from -1.1 m to about one millimeter when VID is applied to retrieve SIT from LA and RA. The results and algorithms, discussed in this paper are essential contribution to SIT and SID retrieval, satellite remote sensing, cryosphere, meteorology and improved weather and climate forecast.

Selection of Thickness of High Density Polyethylene Film for Mulching in Paddy Rice

In water deficit area, judicious use of water is essential for increasing area under crop production with limited water supply. Film Mulching has been advocated as an effective means for conserving soil moisture in rice production. The effects of high density polyethylene (HDPE) film on increasing rice production, controlling weeds and residue amount of plastic were studied under five treatments, including 5, 10, 15 and 20 μm thickness as well as bare cultivation (CK). The results indicated that the HDPE film mulching mode had significant effects on weed control, soil temperature, soil moisture, photosynthetic rate, seedling biomass, yield and residues of plastic film. Combined with economic effect, it showed that the HDPE film of 10 μm is the best option for rice production.

Retinal thickness and vascular parameters using optical coherence tomography in Alzheimer's disease:a meta-analysis

Examining the retinal tissue has the potential to provide a unique method and technique to quantify Alzheimer’s disease-related changes in participants at various stages of the disease.In this metaanalysis,we aimed to investigate the association of various optical coherence tomography parameters with Alzheimer’s disease and whether retinal measurements can be used to diffe rentiate between Alzheimer’s disease and control subjects.Scientific databases including Google Schola r,Web of Science,and PubMed were systematically searched for published articles that evaluated retinal nerve fiber layer thickness and retinal microvascular network in Alzheimer’s disease and control subjects.Seventy-three studies(5850 participants,including 2249 Alzheimer’s disease patients and 3601controls) were included in this meta-analysis.Relative to controls,Alzheimer’s disease patients had a significantly lower global retinal nerve fiber layer thickness(standardized mean difference [SMD]=-0.79,95% confidence intervals [CI]:-1.03 to-0.54,P <0.00001) as well as each quadrant being thinner in Alzheimer’s disease versus controls.Regarding macular paramete rs,values measured by optical coherence tomography were significantly lower in Alzheimer’s disease than controls for macular thickness(pooled SMD:-0.44,95% CI:-0.67 to-0.20,P=0.0003),foveal thickness(pooled SMD=-0.39,95% CI:-0.58 to-0.19,P <0.0001),ganglion cell inner plexiform layer(SMD=-1.26,95% CI:-2.24 to-0.27,P=0.01) and macular volume(pooled SMD=-0.41,95% CI-0.76 to-0.07,P=0.02).Analysis using optical coherence tomography angiography parameters revealed mixed results between Alzheimer’s disease and controls.Superficial vessel density(pooled SMD=-0.42,95% CI:-0.68 to-0.17,P=0.0001) and deep vessel density(pooled SMD=-0.46,95% CI:-0.75 to-0.18,P=0.001) were found to be thinner in Alzheimer’s disease patients whereas the foveal avascular zone(SMD=0.84,95% CI:0.17-1.51,P=0.01) was larger in controls.Vascular density and thickness of various retinal laye rs were decreased in Alzheimer’s disease patients compared to controls.Our results provide evidence for optical coherence tomography technology having the potential to detect retinal and microvascular changes in patients diagnosed with Alzheimer’s disease and aid in monito ring and early diagnosis methods.

常规体检指标对颈动脉硬化发生的预测价值

目的探讨常规体检指标如性别、年龄、血压、血脂、同型半胱氨酸等在颈动脉硬化发生的预测价值。方法采用回顾性研究方法。选取2016年1月至2021年12月连续6年在我院接受健康体检人群985例作为研究对象。收集受试者一般资料、体格检查指标、实验室检查指标、颈动脉超声结果等信息。受试者在随访中经颈动脉超声诊断为颈动脉内中膜厚度(cIMT)>1mm或有颈动脉斑块形成则被认为出现颈动脉粥样硬化进展并结束随访。受试者若未出现颈动脉粥样硬化进展,则直至2021年12月随访结束。将研究对象按随访过程中cIMT是否增加分为硬化组、进展组和对照组。分析颈动脉硬化发生的影响因素,并采用受试者操作特征曲线分析体检指标对颈动脉硬化的诊断效能。结果进展组在颈动脉硬化发病后TC、LDL-C、FBG、UA、Hcy和SBP均高于发生前,HDL-C低于发病前,差异有统计学意义(P<0.05);硬化组除HDL-C和Hcy指标差异没有统计学意义外,其他指标如男性比例、年龄、TC、TG、LDL-C、FBG、UA、SBP、DBP、BMI指标均高于对照组,差异有统计学意义(P<0.05);其中FBG、LDL-C和SBP为颈动脉硬化发生的独立风险因素(OR=5.505、4.222、1.071,P<0.05),以上指标联合诊断颈动脉硬化的曲线下面积高于各项单独检测,差异有统计学意义(P<0.01)。结论FBG、LDL-C和BMP与颈动脉硬化的发生密切相关,联合检测对颈动脉硬化有较好的诊断效能。

雷珠单抗两种给药策略对糖尿病黄斑水肿视觉功能、中心凹视网膜厚度、角膜内皮细胞密度的影响

目的探讨雷珠单抗不同给药策略对糖尿病黄斑水肿(DME)视觉功能、中心凹视网膜厚度(FT)、角膜内皮细胞密度的影响。方法选取2020年6月至2022年6月郑州市第二人民医院眼科收治的60例DME患者作为研究对象,采用随机数表法分为常规组(30例39眼)和强化组(30例42眼),所有患者均予以玻璃体内注射雷珠单抗治疗,常规组患者予以3+按需治疗(PRN)给药方案,强化组予以5+PRN给药方案,两组患者均随访12个月观察疗效。比较两组患者PRN治疗期间患眼注射次数、补救性光凝次数,以及治疗3个月、6个月、9个月、12个月后的最佳矫正视力(BCVA)较基线提高字母数、黄斑中心凹厚度(FT)和治疗3个月、6个月、12个月后的角膜内皮细胞密度、六角形细胞比例、角膜神经变化,同时比较两组患者治疗期间的不良反应发生情况。结果强化组患者PRN治疗期间患眼注射次数、补救性光凝次数分别为(2.40±0.80)次、(1.12±0.30)次,明显少于常规组的(4.10±1.00)次、(1.97±0.64)次,差异均有统计学意义(P<0.05);强化组患者治疗6个月、9个月、12个月后患眼BCVA较基线提高字母数分别为(5.06±0.82)个、(7.83±1.21)个、(10.20±3.14)个,明显高于常规组的(4.30±0.77)个、(5.64±1.30)个、(8.96±2.55)个,差异均有统计学意义(P<0.05);强化组患者治疗12个月后患眼BCVA提高>10个字母患眼占66.67%,明显多于常规组的43.59%,差异均有统计学意义(P<0.05);强化组治疗9个月、12个月后患眼FT分别为(276.25±83.40)μm、(242.34±77.59)μm,明显低于常规组的(325.86±56.04)μm、(296.27±53.00)μm,差异均有统计学意义(P<0.05);两组患者治疗前后患眼角膜内皮细胞密度、六角形细胞比例、神经纤维长度、神经纤维密度比较差异均无统计学意义(P>0.05);两组患者治疗期间均未观察到不良反应发生。结论雷珠单抗3+PRN、5+PRN给药方案可安全治疗DME,且对角膜内皮细胞密度无明显影响,而在视觉功能、中心凹视网膜厚度、给药次数、药物经济性方面,5+PRN给药方案作用效果更优。

皮质骨厚度及颌骨骨密度对种植术中疼痛的影响

目的:探讨种植位点不同皮质骨厚度及颌骨骨密度对种植手术术中疼痛的影响。方法:选择2021年8月—2022年8月南昌大学第四附属医院接受种植体植入手术的患者187例(种植位点数263个),分析种植位点不同皮质骨厚度及颌骨密度HU值对麻醉效果的影响。采用SPSS 26.0软件包对数据进行统计学分析。结果:疼痛位点的皮质骨平均厚度为(3.90±1.36)mm,显著大于非疼痛位点的(2.24±0.66)mm(P<0.05)。下颌前牙、前磨牙、磨牙区皮质骨厚度在疼痛及非疼痛位点的比较中,差异有统计学意义。疼痛位点的骨密度平均HU值为(764.46±239.75),非疼痛位点的平均HU值为(612.23±235.31),差异有统计学意义(P<0.05)。下颌前牙及前磨牙区疼痛位点与非疼痛位点HU值相比,差异无统计学意义(P>0.05),下颌磨牙区疼痛与非疼痛位点的HU值相比较,差异有统计学意义(P<0.05)。结论:皮质骨厚度大的位点,阻挡浸润麻药渗透的作用较大,种植过程中更易发生术中疼痛。在下颌前牙及前磨牙区,种植位点HU值对浸润麻药的渗透作用影响较小,在下颌磨牙区的影响较大,下颌磨牙区HU值高的种植位点更易发生术中疼痛。当计划种植位点的皮质骨厚度大于3.9 mm以及在下颌磨牙区骨密度均值大于665 HU时,若有足够的备洞安全距离,建议在术前施加下颌神经阻滞麻醉联合阿替卡因浸润麻醉,以避免患者发生术中疼痛。

熔融石英陶瓷材料介电性能影响因素分析

采用凝胶注模成型工艺制备熔融石英陶瓷,通过XRD、SEM和电性能网络分析仪对陶瓷样品的晶体结构、微观形貌、介电性能进行分析,研究了熔融石英陶瓷介电性能的影响因素,为筛选制备石英陶瓷材料最优工艺方案提供依据。研究结果表明:材料制备工艺一定时,制备不同厚度的石英陶瓷板,平铺烧结,同一块方板沿垂直方向自上而下,密度逐渐下降,密度与介电常数呈正相关,密度每上升0.01 g/cm^(3),介电常数对应上升0.01~0.02,密度对损耗角正切数值影响不大;同一块板同样厚度位置,边角与中间位置的密度几乎没有变化;同一块板,同样厚度方向,介电常数变化不大;石英陶瓷板中引入松香导致试样更致密,密度升高,介电常数随之增大;相同密度的试样,采用不同的介电测试方式计算所得的介电常数有约0.03的偏差。

成年正畸患者颧牙槽嵴区微种植钉植入的位点选择

目的 对成年男性及女性正畸患者颧牙槽嵴区的骨皮质密度、骨皮质厚度及颊侧可利用的有效骨量进行分析,为微种植钉植入时的位点选择提供参考。方法 采集200例年龄20~30岁患者(男女比例为1∶1)的锥形束CT扫描数据,从近中至远中依次将矢状面上右侧上颌后牙区分为6个层面,每个层面在垂直距离为颊侧骨皮质距离釉牙骨质界8、10、12 mm处分别设置3个测量位点,共计18个测量位点,测量其骨皮质密度、厚度及有效骨量,并进行统计分析。结果 成年男性与女性正畸患者的骨皮质密度、厚度及有效骨量的最高值均位于平分第二前磨牙与第一磨牙根间区,其中骨皮质密度、厚度随着垂直高度增加而增大,而有效骨量随着垂直高度增加而减少。成年男性与女性患者之间的骨皮质密度、骨皮质厚度和颊侧有效骨量存在一定的差异。结论成年男性与女性正畸患者颧牙槽嵴区微种植钉的最佳植入位点均位于第二前磨牙与第一磨牙根间区,其中男性最佳植入位点的垂直高度可以适当高于女性。

电镀参数对电沉积Sn-Ag-Cu合金镀层的影响

采用自主研发的甲磺酸锡银铜电镀液在黄铜基体上制备了Sn-Ag-Cu合金镀层。通过扫描电子显微镜(SEM)及其自带的能谱仪(EDS)分析了电镀工艺参数对Sn-Ag-Cu合金镀层的成分、表面形貌以及镀层厚度产生的影响。结果表明,当电流密度为4 A/dm^(2)、温度为25℃及pH为5.5时,可获得结晶较细且致密,表面平整光亮且厚度均匀的Sn-Ag-Cu合金镀层。

高密度电法在河北省青龙满族自治县某花岗岩矿区地质勘查中的应用

介绍了应用高密度电法在河北省青龙满族自治县青龙镇某花岗岩矿区工程勘察的案例。为指导该矿区开采,需查明矿区风化层厚度、基覆面分布、破碎裂隙情况等地质条件。在1号、2号、3号矿区分别开展了高密度电法测量,结合部分钻探地质资料,认为:1)矿区浅地表大部分基岩出露,土石层覆盖部分少、厚度小;2)山脊部位风化层总体较薄(3~10 m),沟谷部位风化层总体较厚(6~50 m);3)通过明显的低阻异常圈定了多处可能的基岩裂隙或破碎区,推测为后期岩浆岩侵入挤压所致。研究成果为该区下一步的安全开采提供了重要地质依据。