Subtropical forest vegetation development and climate change in Baishanzu area of Zhejiang Province, China, since the Holocene

Human activities and climate change pose major challenges for the sustainable development of terrestrial biological forests. The modern vegetation in the Baishanzu area is typical mixed subtropical evergreen broad-leaved, coniferous, and deciduous broad-leaved forest, with a vegetation combination sensitive to climate change. Higher resolution pollen records from the Shangyang Lake Wetland, located in the subtropical monsoon climate of the Baishanzu area in Zhejiang, China, were combined with environmental proxy data, such as data on loss on ignition and charcoal, to reconstruct the vegetation and climate changes since the Holocene. The results show that the climate was cool and dry during the early Holocene (11660-6580 cal. aBP), when the zonal vegetation changed from evergreen deciduous broad-leaved mixed forests dominated by evergreen Quercus (Quercus(E)), Castanopsis, deciduous Quercus (Quercus(D)), and Castanea to coniferous and broad-leaved mixed forests with rich Cryptomeria. Abies pollen spread to lower altitudes during the period 9620-8020 cal. aBP with Abies beshanzuensis covering large areas of land. The increased in the East Asian summer monsoon from 6580 to 2040 cal. aBP led to the Holocene Climate Optimum, when the climate was particularly warm and humid. The zonal vegetation was middle subtropical evergreen broad-leaved forest dominated by Quercus(E), Castanopsis, and Cyclobalanopsis with particularly high forest coverage and few fire events. For the last 2000 years, coniferous and broad-leaved mixed forests, mainly Pinus taiwanensis, have dominated the vegetation in the area. Sharp increase in such flora was observed after the year 980. Decreased temperature, cold climate, and increased anthropogenic disturbances have resulted in a substantial reduction in the arboreal pollen content, including Quercus, Castanopsis, Castanea, and Ilex, and an increase in Pinus and Poaceae. The results of this study will play a positive role in fully understanding the historical background and internal mechanisms of subtropical forest changes

Femoral neck fracture after femoral head necrosis: a case report and review of the literature

Abstract Introduction Pathological fractures of the femoral neck caused by necrosis of the femoral head are extremely rare. Here, we report a rare case of bilateral femoral head osteonecrosis extending to the femoral neck, with bilateral pathological fractures of the femoral neck occurring within a short period of time. Case report A 65-year-old male with a 25-year history of daily consumption of 750 ml of liquor, presented with right hip pain after labor for 1 month. He subsequently sustained a right femoral neck fracture without trauma and underwent a right total hip arthroplasty. Two months later, he suffered a non-traumatic left femoral neck fracture and underwent a left total hip arthroplasty. Histopathological examination revealed osteonecrosis of the femoral head and neck, along with the presence of osteoclasts and granulomatous inflammation. Bone mineral density testing also showed osteoporosis. The bilateral femoral neck fractures were ruled out to be caused by any other pathological factors. Discussion This is the first report of pathological fractures of the bilateral femoral neck caused by femoral head necrosis. During the literature review process, we found that this case conforms to the histological characteristics of rapidly destructive hip disease and analyzed the etiology of femoral head necrosis and the pathogenesis of femoral neck fractures

A Preliminary Study on Pollen Distribution in the Surface Soil of the Baishanzu Area in Qingyuan County, Zhejiang Province, China

Baishanzu area in Qingyuan, Zhejiang Province, which is famous for the discovery of Abies beshanzuensis, has the most typical mid-subtropical evergreen broad-leaved forest and complete vertical zones of mountain ecosystems in China, and this provides good natural conditions for paleoclimatic reconstruction using surface soil and airborne pollen data. Based on the pollen spectra of nine surface soil pollen samples collected at 300-1,700 m altitude, the relationship between vegetation and surface soil pollen in this area was preliminarily studied. The results show that surface soil pollen in this area can be divided into three assemblage zones from top to bottom according to altitude and ratios of coniferous pollen/broad-leaved pollen and arboreal pollen/non-arboreal pollen, which correspond to the evergreen deciduous broad-leaved mixed forest and temperate coniferous forest, evergreen broad-leaved forest and warm coniferous forest, secondary forest, and farmland (caused by human interference) zones. The surface pollen assemblages were dominated by the evergreen coniferous tree species Pinus, with an average pollen content of 67.5%. The pollen of Castanopsis (6.2%), Quercus (3.4%), Betula (1.4%), and Corylus (1.4%) is common. In contrast, Cyclobalanopsis, Liquidambar, Symplocos, Tsuga, Oleaceae, and Ericaceae had lower contents. Herbaceous plants are dominated by Poaceae (11.2%), including Artemisia, Chenopodiaceae, Apiaceae, Asteraceae, etc. The spore content of fern vegetation was high, mainly Hicriopteris (38.2%) and Polypodiaceae (7.4%). Pinus pollen appeared in all samples, with the highest average content. With increasing altitude, the mean percentage gradually increased from 54.8% to 77.3%, and it is an overly represented pollen with a low sedimentation rate that is easily preserved and transported to the area. Abies pollen is only observed in the samples under the A. beshanzuensis tree at an altitude of 1,700 m. Its percentage is lower than 1%, which may be related to low pollen yield and the relatively narrow distribution range of A. beshanzuensis in this area. In addition, the pollen diversity analysis results based on Simpson's index show that human interference factors prevent the surface soil pollen at lower altitudes in this area from reflecting the regional zonal vegetation. With decreasing altitude, the deciduous component of arboreal pollen in the pollen assemblage increased from 13.2% in Zone I to 40.9% in Zone III. Zone III shows a coniferous and broad-leaved mixed forest zone caused by human factors. The content of the evergreen component in zone I is high, which is related to the high humidity at higher altitudes. This study selects Baishanzu National Park to study the surface soil pollen and preliminarily discusses the characteristics of the surface soil pollen assemblage and its relationship with vegetation, which provide research materials and the basis for Quaternary paleovegetation and paleoclimate reconstructions in the Baishanzu area, Qingyuan County, China. However, due to a lack of surface soil samples and modern vegetation investigation data, the reliability of the research results is affected. In future research, sampling and density quadrat surveys of surface sampling sites will be increased to cover as many vegetation zones as possible

A nomogram for predicting the risk of new vertebral compression fracture after percutaneous kyphoplasty

Abstract Background New vertebral compression fractures (NVCFs) are common adverse events in percutaneous kyphoplasty (PKP). The present study aimed to investigate the risk factors for NVCFs in patients after PKP and to construct a nomogram for the prediction of the risk of re-fracture. Methods We retrospectively analyzed the medical records of patients after PKP surgery between January 2017 and December 2020. Patients were divided into an NVCF group (n = 225) and a control group (n = 94) based on the presence or absence of NVCFs, respectively, at follow-up within 2 years after surgery. Lasso regression was used to screen for risk factors for re-fracture. Based on the results, a Lasso-logistic regression model was developed, and its prediction performance was evaluated using receiver operating characteristic curves, calibration, and decision curve analysis. The model was visualized, and a nomogram was constructed. Results A total of eight potential predictors were obtained from Lasso screening. Advanced age, low body mass index, low bone mineral density, lack of anti-osteoporosis treatment, low preoperative vertebral body height, vertebral body height recovery ≥ 2, cement leakage, and shape D (lack of simultaneous contact of bone cement with the upper and lower plates) were included in the logistic regression model. Conclusions A nomogram for predicting postoperative NVCF in PKP was developed and validated. This model can be used for rational assessment of the magnitude of the risk of developing NVCFs after PKP, and can help orthopedic surgeons make clinical decisions aimed at reducing the occurrence of NVCFs

Temperature-dependent magnetization in (Mn, N)-codoped ZnO-based diluted magnetic semiconductors

The influences of Mn doping on the structural quality of the ZnxMn1-xO:N alloy films have been investigated by XRD. Chemical compositions of the samples (Zn and Mn content) and their valence states were determined by X-ray photoelectron spectrometry (XPS). Hall effect measurements versus temperature for ZnxMn1-xO:N samples have been designed and studied in detail. The ferromagnetic transitions happened at different TC should explain that the magnetic transition in field-cooled magnetization of Zn1-xMnxO:N films at low temperature is caused by the strong pd exchange interactions besides magnetic transition at 46 K resulting from Mn oxide, and that the room temperature ferromagnetic signatures are attributed to the uncompensated spins at the surface of anti-ferromagnetic nano-crystal of Mn-related Zn(Mn)O

Influences of the type of dopant and substrate on ferromagnetism in ZnO:Mn

ZnO:Mn films doped with indium (In) and nitrogen (N) have been grown on sapphire and ZnO template substrates, respectively by the metal-organic chemical vapor deposition method. All these samples show clear hysteresis loops and saturation magnetizations