BaFe12O19 single-particle-chain nanofibers : preparation, characterization, formation principle, and magnetization reversal mechanism

BaFe12O19 single-particle-chain nanofibers have been successfully prepared by an electrospinning method and calcination process, and their morphology, chemistry, and crystal structure have been characterized at the nanoscale. It is found that individual BaFe12O19 nanofibers consist of single nanoparticles which are found to stack along the nanofiber axis. The chemical analysis shows that the atomic ratio of Ba/Fe is 1:12, suggesting a BaFe12O19 composition. The crystal structure of the BaFe12O19 single-particle-chain nanofibers is proved to be M-type hexagonal. The single crystallites on each BaFe12O19 single-particlechain nanofibers have random orientations. A formation mechanism is proposed based on thermogravimetry/differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and transmission electron microscopy (TEM) at six temperatures, 250, 400, 500, 600, 650, and 800 �C. The magnetic measurement of the BaFe12O19 single-particle-chain nanofibers reveals that the coercivity reaches a maximum of 5943 Oe and the saturated magnetization is 71.5 emu/g at room temperature. Theoretical analysis at the micromagnetism level is adapted to describe the magnetic behavior of the BaFe12O19 single-particle-chain nanofibers

Challenges of diagnosing acute HIV-1 subtype C infection in African women: performance of a clinical algorithm and the need for point-of-care nucleic-acid based testing.

Background. Prompt diagnosis of acute HIV infection (AHI) benefits the individual and provides opportunities for public health intervention. The aim of this study was to describe most common signs and symptoms of AHI, correlate these with early disease progression and develop a clinical algorithm to identify acute HIV cases in resource limited setting. Methods. 245 South African women at high-risk of HIV-1 were assessed for AHI and received monthly HIV-1 antibody and RNA testing. Signs and symptoms at first HIV-positive visit were compared to HIV-negative visits. Logistic regression identified clinical predictors of AHI. A model-based score was assigned to each predictor to create a risk score for every woman. Results. Twenty-eight women seroconverted after a total of 390 person-years of follow-up with an HIV incidence of 7.2/100 person-years (95%CI 4.5–9.8). Fifty-seven percent reported ≥1 sign or symptom at the AHI visit. Factors predictive of AHI included age <25 years (OR = 3.2; 1.4–7.1), rash (OR = 6.1; 2.4–15.4), sore throat (OR = 2.7; 1.0–7.6), weight loss (OR = 4.4; 1.5–13.4), genital ulcers (OR = 8.0; 1.6–39.5) and vaginal discharge (OR = 5.4; 1.6–18.4). A risk score of 2 correctly predicted AHI in 50.0% of cases. The number of signs and symptoms correlated with higher HIV-1 RNA at diagnosis (r = 0.63; p<0.001). Conclusions. Accurate recognition of signs and symptoms of AHI is critical for early diagnosis of HIV infection. Our algorithm may assist in risk-stratifying individuals for AHI, especially in resource-limited settings where there is no routine testing for AHI. Independent validation of the algorithm on another cohort is needed to assess its utility further. Point-of-care antigen or viral load technology is required, however, to detect asymptomatic, antibody negative cases enabling early interventions and prevention of transmission

A visualized investigation at the atomic scale of the antitumor effect of magnetic nanomedicine on gastric cancer cells

Discovering which anticancer drugs attack which organelle(s) of cancer cells is essential and significant, not only for understanding their therapeutic and adverse effects, but also to enable the development of new-generation therapeutics. Here, we show that novel Fe3O4–carboxymethyl cellulose–5-fluorouracil (Fe3O4–CMC–5FU) nanomedicine can apparently enhance the antitumor effect on gastric cancer cells, and its mechanism of killing the SGC-7901 gastric cancer cells can be directly observed at the atomic scale. Materials & methods: The novel nanomedicine was prepared using the traditional antitumor drug 5FU to chemically bond onto the functionalized Fe3O4 nanoparticles (Fe3O4–CMC–5FU nanomedicine), and then was fed into SGC-7901 gastric cancer cells. The inorganic Fe3O4 nanoparticles were used to track the distribution and antitumor effect of the nanomedicine within individual SGC-7901 gastric cancer cells. Results & discussion: Atomic-level observation and tracking the elemental distribution inside individual cells proved that the magnetic nanomedicine killed the gastric cells mainly by attacking their mitochondria. The enhanced therapeutic efficacy derives from the localized high concentration and poor mobility of the aggregated Fe3O4–CMC–5FU nanomedicine in the cytoplasm. Conclusion: A brand new mechanism of Fe3O4–CMC–5FU nanomedicine killing SGC-7901 gastric cancer cells by attacking their mitochondria was discovered, which is different from the classical mechanism utilized by traditional medicine 5FU, which kills gastric cancer cells by damaging their DNA. Our work might provide a partial solution in nanomedicines or even modern anticancer medicine for the visualized investigation of their antitumor effect

BaFe₁₂O₁₉ Single-Particle-Chain Nanofibers: Preparation, Characterization, Formation Principle, and Magnetization Reversal Mechanism

BaFe₁₂O₁₉ single-particle-chain nanofibers have been successfully prepared by an electrospinning method and calcination process, and their morphology, chemistry, and crystal structure have been characterized at the nanoscale. It is found that individual BaFe₁₂O₁₉ nanofibers consist of single nanoparticles which are found to stack along the nanofiber axis. The chemical analysis shows that the atomic ratio of Ba/Fe is 1:12, suggesting a BaFe₁₂O₁₉ composition. The crystal structure of the BaFe₁₂O₁₉ single-particle-chain nanofibers is proved to be M-type hexagonal. The single crystallites on each BaFe₁₂O₁₉ single-particle-chain nanofibers have random orientations. A formation mechanism is proposed based on thermogravimetry/differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and transmission electron microscopy (TEM) at six temperatures, 250, 400, 500, 600, 650, and 800 °C. The magnetic measurement of the BaFe₁₂O₁₉ single-particle-chain nanofibers reveals that the coercivity reaches a maximum of 5943 Oe and the saturated magnetization is 71.5 emu/g at room temperature. Theoretical analysis at the micromagnetism level is adapted to describe the magnetic behavior of the BaFe₁₂O₁₉ single-particle-chain nanofibers

Overbank block-and-ash flow deposits and the impact of valley-derived, unconfined flows on populated areas at Merapi volcano, Java, Indonesia

Merapi, an andesitic volcanic complex in Central Java, is one of the most frequently erupting volcanoes in Indonesia and poses a permanent threat to the surrounding population of over 1 million people. With frequently recurring volcanic activity, the sixty or so reported eruptions since the mid-1500s have caused ~7,000 fatalities and destroyed numerous villages in the region. In June 2006, an eruption affected the densely populated area on the volcano’s southern and south-eastern flanks for the first time in almost a century. The resultant block-and-ash flows (BAFs) travelled down an incised river valley (Kali Gendol) to a distance of 7 km from the source, breaking out of the main channel at four main locations. Unconfined (overbank) BAFs were generated, which covered the interfluve regions on either side of the main valley and buried buildings and other infrastructure features in the village of Kaliadem, situated on the western bank of the Gendol valley ~5 km from the summit of Merapi. Using traditional volcanological field-based methods and non-invasive, high-resolution ground-penetrating radar techniques, the morphology and internal architecture of these overbank deposits were studied in detail in order to evaluate the destructive impact of these flows in a local context. The results show that complex, local-scale variations in flow dynamics and deposit architectures are apparent and that BAFs are capable of transporting significant numbers of large blocks (\u3e1–2 m) out of the valley confines. We propose a conceptual model for the escape of these channelised BAFs onto the interfluvial terrace at Kaliadem and show, through a stratigraphic analysis of the pyroclastic successions underlying the village and adjacent areas on the volcano’s southern flank, that the area has been affected repeatedly by overbank BAFs and explosive eruptions over the past few 100 years (and more)