A new approach to bond valence parameters for Pb(II)-halide bonds

The values of bond valence parameters R-0 for the bonds of main group metal halides are usually obtained by systematic analysis of the crystal structure data by assuming B=0.037 nm. In this work, conversely, the values of B were proposed to be fitted with crystal structure data on assuming the values of R-0 equal to the bond lengths of r(g) accurately determined by gaseous electron diffraction. As an example, the new sets of R-0/B for the Pb(II)-X (X=F, Cl, Br, I) bonds were obtained and fitted as 0.2036/0.0382, 0.2447/0.040, 0.2598/0.040, and 0.2804/0.0386, respectively. Compared with the values of R-0=0.203, 0.253, 0.264, and 0.278 nm based on B=0.037nm for Pb(II)-X bonds reported in the literature, these new parameters were not only accurate and reliable for bond valence calculations, but also revealed the physical meaning inherent in every R-0 as unit valence bond length

The correlation between metal oxidation state and bond valence parameters for M-O bonds (M = V, Fe and Cu). A simple method to search for the metal oxidation-state independent parameter pairs

Based on the latest available crystal data and the reported bond valence parameters, the linear correlation between the bond valence parameter R-0 with B = 0.37A for M-O bonds (M = V, Fe and Cu) and the metal oxidation state n is shown for the first time. For V-O bonds, a linear equation of R-0 similar to n is perfectly established as R-0 = 0.0250n + 1.674 (n = 2-5). Similarly, a linear equation for Fe-O bonds is fitted as R-0 = 0.0335n + 1.648 (n = 2-4), as well as R-0 = 0.0855n + 1.482 (n = 1-3) for Cu-O bonds fitted properly. In addition, the linear correlation between R-0 and n within certain range of B values for V-O and Fe-O bonds is also established. Consequently, the oxidation-state independent parameters (R-0, B) of (1.788, 0.32 A) for V-O bonds and (1.795, 0.30 A) for Fe-O bonds can be derived from the zero slope of the R-0 similar to n straight lines. However, a similar parameter pair for Cu-O bonds cannot be found using this unique approach

Solar microwave millisecond spike at 2.84 GHz

Using the high time resolution of 1 ms, the data of solar microwave millisecond spike (MMS) event was recorded more than two hundred times at the frequency of 2.84 GHz at Beijing (Peking) Observatory since May 1981. A preliminary analysis was made. It can be seen from the data that the MMS-events have a variety of the fast activities such as the dispersed and isolated spikes, the clusters of the crowded spikes, the weak spikes superimposed on the noise background, and the phenomena of absorption. The marked differences from that observed with lower time resolution are presented. Using the data, a valuable statistical analysis was made. There are close correlations between MMS-events and hard X-ray bursts, and fast drifting bursts. The MMS events are highly dependent on the type of active regions and the magnetic field configuration. It seems to be crucial to find out the accurate positions on the active region where the MMS-events happen and to make co-operative observations at different bands during the special period when specific active regions appear on the solar disk

The quasar SDSS J142507.32+323137.4 : dual AGNs?

We analyze the optical spectrum of type 1 QSO SDSS J1425+3231. This ob- ject is interesting since its narrow emission lines such as [O III]{\lambda}{\lambda}4959, 5007 are double- peaked, and the line structure can be modeled well by three Gaussian components: two components for the two peaks (we refer the peaks at low/high redshift as "the blue/red component") and another one for the line wing which has the same line center as that of the blue component, but ~ 3 times broader. The separation between the blue and red components is ~ 500 km/s with blue component ~ 2 times broader than the red one. The H{\beta} emission can be separated into four components: two for the double-peaked narrow line and two for the broad line which comes from the broad line region (BLRs). The black hole mass estimated from the broad H{\beta} emission line using the typical reverberation map- ping relation is 0.85 \times 108M\odot, which is consistent with that derived from parameters of [O III]{\lambda} 5007 of the blue component. We suggest this QSO might be a dual AGN system, the broad H{\beta} emission line is mainly contributed by the primary black hole (traced by the blue component) while the broad H{\beta} component of the secondary black hole (traced by the red component) is hard to be separated out considering a resolution of ~2000 of SDSS spectra or it is totally obscured by the dusty torus.Comment: 9 pages, 2 figures, accepted for publication in RA

Enhanced surface acceleration of fast electrons by using sub-wavelength grating targets

Surface acceleration of fast electrons in intense laser-plasma interaction is improved by using sub-wavelength grating targets. The fast electron beam emitted along the target surface was enhanced by more than three times relative to that by using planar target. The total number of the fast electrons ejected from the front side of target was also increased by about one time. The method to enhance the surface acceleration of fast electron is effective for various targets with sub-wavelength structured surface, and can be applied widely in the cone-guided fast ignition, energetic ion acceleration, plasma device, and other high energy density physics experiments.Comment: 14 pages, 4figure

Protein tyrosine kinase 6 is associated with nasopharyngeal carcinoma poor prognosis and metastasis

BACKGROUND: The aim of this study was to analyze the expression of protein tyrosine kinase 6 (PTK6) in nasopharyngeal carcinoma (NPC) samples, and to identify whether PTK6 can serve as a biomarker for the diagnosis and prognosis of NPC. METHODS: We used quantitative RT-PCR and Western blotting analysis to detect mRNA and protein expression of PTK6 in NPC cell lines and immortalized nasopharyngeal epithelial cell lines. 31 NPC and 16 non-tumorous nasopharyngeal mucosa biopsies were collected to detect the difference in the expression of mRNA level of PTK6 by quantitative RT-PCR. We also collected 178 NPC and 10 normal nasopharyngeal epithelial cases with clinical follow-up data to investigate the expression of PTK6 by immunohistochemistry staining (IHC). PTK6 overexpression on cell growth and colony formation ability were measured by the method of cell proliferation assay and colony formation assay. RESULTS: The expression of PTK6 was higher in most of NPC cell lines at both mRNA and protein levels than in immortalized nasopharyngeal epithelial cell lines (NPECs) induced by Bmi-1 (Bmi-1/NPEC1, and Bmi-1/NPEC2). The mRNA level of PTK6 was high in NPC biopsies compared to non-tumorous nasopharyngeal mucosa biopsies. IHC results showed the expression of PTK6 was significantly correlated to tumor size (P<0.001), clinical stage (P<0.001), and metastasis (P=0.016). The patients with high-expression of PTK6 had a significantly poor prognosis compared to those of low-expression (47.8% versus 80.0%, P<0.001), especially in the patients at the advanced stages (42.2% versus 79.1%, P<0.001). Multivariate analysis indicated that the level of PTK6 expression was an independent prognostic factor for the overall survival of patients with NPC (P <0.001). Overexpression of PTK6 in HNE1 cells enhanced the ability of cell proliferation and colony formation. CONCLUSIONS: Our results suggest that high-expression of PTK6 is an independent factor for NPC patients and it might serve as a potential prognostic biomarker for patients with NPC

Optimization of fermentation conditions for pristinamycin production by immobilized Streptomyces pristinaespiralis using response surface methodology

Abstract Response surface methodology was used to optimize the fermentation conditions for the production of pristinamycin by immobilization of Streptomyces pristinaespiralis F213 in shaking flask cultivation. Seed medium volume, fermentation medium volume and shaking speed of seed culture were found to have significant effects on pristinamycin production by the Plackett-Burman design. The steepest ascent method was adopted to approach the vicinity of optimum space, followed by central composite design for further optimization. A quadratic model was built to fit the pristinamycin production. The optimum conditions were found to be seed medium volume of 29.5 ml, fermentation medium volume of 28.8 ml, and shaking speed of seed culture at 204 rpm. At the optimum conditions, a production of 213 mg/l was obtained, which was in agreement with the maximum predicted pristinamycin yield of 209 mg/l. This is the first report on pristinamycins production by immobilized S. pristinaespiralis using response surface methodology