Maxwell-Boltzmann Distribution of M 3+-F− Interstitial Pairs in Fluorite-Type Lattices

Maxwell-Boltzmann distribution curves for M3+-F− interstitials in fluorite-type lattices have been calculated and compared with spectroscopic data. The dominant sites, in the order of their relative importance for low concentrations and T\u3c700 K, are the C4v(1, 0, 0), Cs(2, 1, 0), C3v(1, 1, 1), Cs(1, 2, 2), Cs(1, 1, 3), and Cs(2, 3, 0) sites. The dominant presence of the third-nearest-neighbor monoclinic Cs(2, 1, 0) pair, which has not been reported previously, is predicted by our calculations. In view of this result, the electron spin resonance data on U3+ in CaF2 reported by Mahlab, Volterra, Low, and Yariv, which these authors interpreted in terms of the fifth-nearest-neighbor site, have been shown to arise actually from the prominent presence of the third-nearest-neighbor Cs(2, 1, 0) site

Canonical Distribution Law and KCl: Sm2+ Fluorescence: The C2v Paradox

A combination of critical experiments has been carried out in order to elucidate the recent conclusions of Bradbury and Wong, who attributed all the dominant KCl: Sm2+ fluorescence lines to the nearest-neighbor C2v(1,1,0)Sm2+−K+ vacancy site. In an extensive investigation into the radiationless quenching, characteristic lifetimes, excitation spectra, and Zeeman polarization of KCl: Sm2+ fluorescence lines, all the prominent lines are unequivocally attributed to a distribution of three different Sm2+ - K+ vacancy sites. In addition, 18 weak lines are shown to originate from dimeric cluster and O2− compensated sites. The paradoxical C2v interpretations of Bradbury and Wong are shown to be based on incorrect premises, inadequate experimentation, and confusion in the identity of samples with different dopant concentrations

Crystalline ionic solutions

Systems of crystalline ionic solutions containing impurity cations and associated compensation defects are described. Interactions between aliovalent ions and compensation defects give rise to configuration partition functions which predict a distribution in ion-defect pair separation distances at low temperatures. At elevated temperatures such ion-defect pairs dissociate, and the concept of pair formation more appropriately gives way to the concept of pair correlation functions. The relative sizes of the aliovalent ion and the host ion which it replaces are seen to exert a pronounced effect on pair distribution. Salient features of the theory are applied to the KCl: Sr2+, NaCl: Mn2+, NaCl: Sr2+, LiCl: Mn2+ and (alkaline-earth halide): (rareearth)3+ systems. While the high-temperature treatment lends itself to comparisons with the Debye-Hückel theory for electrolytes, the low-temperature pair distribution theory is shown to be valid chiefly because of the specific nature of the crystalline ionic solutions

Zeeman Anisotropy Fluorescence Spectroscopy, Characteristic Radiative Lifetimes, and Novel Site Symmetries in KCl: Sm 2+

By means of Zeeman anisotropy fluorescence (ZAF) and its field dependence (up to 55.8 kG), the authors have investigated the 4.2 K narrow-line fluorescence of KCl:Sm2+ and identified some hitherto unreported Sm2+ sites. The strong no-field line at 7693.5 Å (5D0→7F3) and a very weak no-field line at 8742.8 Å (5D0→7F5) are shown to be of C3v symmetry origin. The 24.5-kG ZAF pattern observed in the 7696-7700-Å (5D0→7F3) region has been identified to originate from a type-II Cs site. The 26.5-kG ZAF patterns of the C3v no-field line at 7693.5 Å and the type-I Cs no-field line at 7694.5 Å overlap in the 7693-7695.3-Å region, and are elucidated through the field dependence of their Zeeman components. Characteristic radiative lifetimes of the 5D0 level in several Sm2+ symmetry types have been determined from dominant transitions to the 7FJ (J\u3c~4) levels. There are two distinct C4v sites: one with a lifetime of 9.5 msec, and the other 11.2 msec. C2v and type-I Cs sites have lifetimes of 10.5 and 10.8 msec, respectively, which are indistinguishable within the experimental error. The role of O2− compensation of Sm2+ in addition to K+ vacancy compensation in KCl is discussed in terms of these findings

Prognostic Significance of Vitamin D Receptor Polymorphisms in Head and Neck Squamous Cell Carcinoma

BACKGROUND:In patients with advanced non-small-cell lung cancer, vitamin D receptor (VDR) polymorphisms and haplotypes are reported to be associated with survival. We hypothesized that a similar association would be observed in patients with head and neck squamous-cell carcinoma (HNSCC). METHODS:In a post-hoc analysis of our previous prospective cohort study, VDR polymorphisms including Cdx2 G/A (rs11568820), FokI C/T (rs10735810), BsmI A/G (rs1544410), ApaI G/T (rs7976091), and TaqI T/C (rs731236) were genotyped by sequencing in 204 consecutive patients with HNSCC who underwent tumor resection. Progression-free survival was compared between VDR polymorphisms using Kaplan-Meier survival curves with log-rank tests and Cox proportional hazard models adjusting for age, gender, smoking status, primary tumor sites, postoperative stages, existence of residual tumor, and postoperative treatment with chemotherapy or radiotherapy. RESULTS:During a median follow-up of 1,047 days, tumor progression and death occurred in 76 (37.3%) and 27 (13.2%) patients, respectively. The FokI T/T genotype was associated with poor progression-free survival: median survival for T/T was 265 days compared with 1,127 days for C/C or C/T (log-rank test: P = 0.0004; adjusted hazard ratio, 3.03; 95% confidence interval, 1.62 to 5.67; P = 0.001). In contrast, the other polymorphisms (Cdx2, BsmI, ApaI, TaqI) showed no significant association with progression-free survival. The A-T-G (Cdx2-FokI-ApaI) haplotype demonstrated a significant association with a higher progression rate (P = 0.02). CONCLUSION:These results suggest that VDR polymorphisms and haplotypes may be associated with prognosis in patients with HNSCC, although the sample size is not large enough to draw definitive conclusions

Serum vitamin D levels and survival of patients with colorectal cancer: Post-hoc analysis of a prospective cohort study

<p>Abstract</p> <p>Background</p> <p>Recently, serum 25-hydroxyvitamin D (25OHD) levels were shown to be associated with the survival of patients with colorectal cancer. However, 25OHD levels were measured a median of 6 years before diagnosis or were predicted levels. In this study, we directly measured serum 25OHD levels at surgery and examined the association with survival among patients with colorectal cancer.</p> <p>Methods</p> <p>We started a prospective cohort study to find prognostic factors in patients with colorectal cancer from 2003 to 2008 and stored serum samples and clinical data. As part of a post-hoc analysis, serum 25OHD levels were measured by radioimmunoassay. Association between overall survival and serum 25OHD levels were computed using the Cox proportional hazard model adjusted for month of serum sampling as well as age at diagnosis, gender, cancer stage, residual tumor after surgery, time period of surgery, location of tumor, adjuvant chemotherapy and number of lymph nodes with metastasis at surgery. Unadjusted and adjusted hazard ratios (HR) and 95% confidence intervals (95% CI) were determined.</p> <p>Results</p> <p>Serum 25OHD levels were measured in 257 patients. Only 3% had sufficient levels (30 ng/ml and greater). Based on month of blood sampling, an annual oscillation of 25OHD levels was seen, with levels being lower in spring and higher in late summer. Higher 25OHD levels were associated with better overall survival under multi-variate analysis (HR, 0.91: 95% CI, 0.84 to 0.99, <it>P </it>= 0.027).</p> <p>Conclusions</p> <p>These results suggest that higher 25OHD levels at surgery may be associated with a better survival rate of patients with colorectal cancer.</p

A Streamlined DNA Tool for Global Identification of Heavily Exploited Coastal Shark Species (Genus Rhizoprionodon)

Obtaining accurate species-specific landings data is an essential step toward achieving sustainable shark fisheries. Globally distributed sharpnose sharks (genus Rhizoprionodon) exhibit life-history characteristics (rapid growth, early maturity, annual reproduction) that suggests that they could be fished in a sustainable manner assuming an investment in monitoring, assessment and careful management. However, obtaining species-specific landings data for sharpnose sharks is problematic because they are morphologically very similar to one another. Moreover, sharpnose sharks may also be confused with other small sharks (either small species or juveniles of large species) once they are processed (i.e., the head and fins are removed). Here we present a highly streamlined molecular genetics approach based on seven species-specific PCR primers in a multiplex format that can simultaneously discriminate body parts from the seven described sharpnose shark species commonly occurring in coastal fisheries worldwide. The species-specific primers are based on nucleotide sequence differences among species in the nuclear ribosomal internal transcribed spacer 2 locus (ITS2). This approach also distinguishes sharpnose sharks from a wide range of other sharks (52 species) and can therefore assist in the regulation of coastal shark fisheries around the world