Zone Melting of Uranium

ABSTRACT A study was made of the possible application of the zone melting technique to the separation of u r a n i u m from fission products and other impurities. Bar specimens of U having various aRoying elements were zone purified in thoriacoated alumina boats. U r a n i u m bars previously irradiated in the Brookhaven pile were also zone melted. Zone melting has potential application in the removal of such impurities as B, Fe, Si, Ni, and Co from ordinary U. In the reprocessing of irradiated U, zone melting offers a method for removing such fission products as Zr, Nb, Ru. However, as employed here, it shows little promise as a method for complete decontamination of irradiated U from fission products, primarily because of concurrent slagging effects. Zone m e l t i n g is a purification t e c h n i q u e which has b e e n used to p r e p a r e v e r y p u r e Ge m e t a l in w h i c h the q u a n t i t y of i m p u r i t i e s p r e s e n t is of the order of parts per billion. The :;uccess of this t e c h n i q u e w i t h Ge suggested an i n v e s t i g a t i o n of its possible application to the purification of U f r o m fission products a n d other impurities. This r e p o r t p r e s e n t s the results of such a n investigation. In the zone m e l t i n g process a n a r r o w m o l t e n zone, p r o d u c e d b y i n d u c t i o n or resistance heating, is m a d e to t r a v e r s e t h e solid m e t a l by m o v e m e n t either of the heater or of the metal, as s h o w n in t i m a t e d i s t r i b u t i o n " is r e a c h e d after w h i c h a d d itional passes h a v e no effect. A m e a s u r e of the t e n d e n c y of the i m p u r i t y to m i g r a t e is given by the d i s t r i b u t i o n coefficient k, which is defined as the ratio of the solute c o n c e nt r a t i o n in the solid to that in the liquid at e q u il i b r i u m . The g r e a t e r the factor b y w h i c h k differs from unity, the m o r e r e a d i l y i m p u r i t i e s migrate. A simple t h e o r y of zone m e l t i n g has b e e n developed by P f a n n (1), in w h i c h it is a s s u m e d that solute diffusion in the liquid is sufficiently r a p i d that the i m p u r i t y c o n c e n t r a t i o n is u n i f o r m in the m o l t e n zone while diffusion in the solid phase is negligible. F r o m this theory it is possible to calculate the effect of repeated zone passes if the d i s t r i b u t i o n coefficient is k n o w n . In practice, one expects less m i g r a t i o n t h a n that calculated, because the a s s u m p t i o n s of complete e q u i l i b r i u m on which the c a l c u l a t i o n is based are not strictly true. In a n y case, the p u r ification a t t a i n e d depends on the n u m b e r of passes, the ratio of m o l t e n zone l e n g t h to b a r length, the e q u i l i b r i u m d i s t r i b u t i o n coefficient k, a n d the rate of zone travel. I n T a b l e I are given k v a l u e s for some metals in U, e s t i m a t e d f r o m the p a r t i c u l a r u r a n i u m -m e t a l phase d i a g r a m s (2). It should be n o t e d t h a t these k values are at best a p p r o x i m a t e since g e n e r a l l y the phase d i a g r a m s h a v e not b e e n a c c u r a t e l y d e t e r m i n e d in the region of low i m p u r i t y c o n c e n t r a t i o n . The theoretical ratio of i m p u r i t y c o n c e n t r a t i o n at the low c o n c e n t r a t i o n end of the b a r before a n d afte

A person-centered perspective on working with people who have experienced psychological trauma and helping them move forward to posttraumatic growth

Over the past decade posttraumatic growth (PTG) has become a major topic for theory, research and practice in mainstream trauma psychology. The aim of this paper is to discuss the implications of PTG for the person-centered approach. It is argued that PTG provides a new non-medical language for understanding psychological trauma that is consistent with the person-centered approach. Person-centered personality theory provides an explanation for how PTG arises and leads to new testable predictions for research into how person-centered therapy may be able to facilitate PTG

The Current State of Performance Appraisal Research and Practice: Concerns, Directions, and Implications

On the surface, it is not readily apparent how some performance appraisal research issues inform performance appraisal practice. Because performance appraisal is an applied topic, it is useful to periodically consider the current state of performance research and its relation to performance appraisal practice. This review examines the performance appraisal literature published in both academic and practitioner outlets between 1985 and 1990, briefly discusses the current state of performance appraisal practice, highlights the juxtaposition of research and practice, and suggests directions for further research

Diabetes and pancreatic cancer survival: A prospective cohort-based study

BACKGROUND: Diabetes is a risk factor for pancreatic cancer but its association with survival from pancreatic cancer is poorly understood. Our objective was to investigate the association of diabetes with survival among pancreatic cancer patients in a prospective cohort-based study where diabetes history was ascertained before pancreatic cancer diagnosis. METHODS: We evaluated survival by baseline (1993–2001) self-reported diabetes history (n=62) among 504 participants that developed exocrine pancreatic cancer within the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Hazard ratios (HRs) and 95% confidence intervals (CIs) for mortality were estimated using Cox proportional hazards model, adjusted for age, sex, body mass index, race, smoking, and tumour stage (local, locally advanced, and metastatic). RESULTS: The multivariable-adjusted HR for mortality comparing participants with diabetes to those without was 1.52 (95% CI=1.14–2.04, P-value <0.01). After excluding those diagnosed with pancreatic cancer within 3 years of study enrolment, HR for mortality among those with diabetes was 1.45 (95% CI=1.06–2.00, P-value=0.02). CONCLUSIONS: Using prospectively collected data, our findings indicate that diabetes is associated with worse survival among patients with pancreatic cancer

Efficacy and safety of non-pharmacological and non-biological pharmacological treatment: a systematic literature review informing the 2016 update of the ASAS/EULAR recommendations for the management of axial spondyloarthritis

To assess the efficacy and safety of non-biological therapies in patients with axial spondyloarthritis (axSpA) to inform the update of the Assessment of SpondyloArthritis international Society (ASAS)/European League Against Rheumatism (EULAR) recommendations for the management of axSpA. A systematic literature review (2009–2016) of all non-pharmacological treatments, non-biological drugs (except targeted synthetic disease-modifying antirheumatic drugs (DMARDs)) and surgical therapies was performed. Randomised controlled trials (RCTs) and clinical controlled trials were assessed for efficacy and safety, while observational studies with a comparator were assessed for safety. All relevant efficacy and safety outcomes were included. Study heterogeneity precluded data pooling. If possible, Cohen's effect size was calculated for non-pharmacological treatments. In total, 45 papers and 2 abstracts were included. Studies on non-pharmacological treatments were very heterogeneous but overall confirmed a benefit for regular exercises, with small improvements in disease activity, function and spinal mobility. New studies on non-steroidal anti-inflammatory drugs (NSAIDs) confirmed their efficacy and new safety signals were not found. NSAIDs used continuously compared with on-demand did not reduce the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) mean change over 2 years in patients with ankylosing spondylitis with normal C reactive protein (CRP; ≤5 mg/L) (1 ‘negative’ RCT (0.9 vs 0.8; p=0.62)), while for patients with high CRP, conflicting results were found (1 ‘positive’ RCT (0.2 vs 1.7; p=0.003), 1 ‘negative’ RCT (1.68 vs 0.96; p=0.28)). No new trials were found for conventional synthetic DMARDs (csDMARDs). Short-term high-dose systemic glucocorticoids showed limited efficacy. Regular exercises may improve several outcomes. Efficacy and safety of NSAIDs in axSpA are confirmed. Glucocorticoids are not proven to be effective in axSpA and new data on csDMARDs are lacking

Caveolin-1 protects B6129 mice against Helicobacter pylori gastritis.

Caveolin-1 (Cav1) is a scaffold protein and pathogen receptor in the mucosa of the gastrointestinal tract. Chronic infection of gastric epithelial cells by Helicobacter pylori (H. pylori) is a major risk factor for human gastric cancer (GC) where Cav1 is frequently down-regulated. However, the function of Cav1 in H. pylori infection and pathogenesis of GC remained unknown. We show here that Cav1-deficient mice, infected for 11 months with the CagA-delivery deficient H. pylori strain SS1, developed more severe gastritis and tissue damage, including loss of parietal cells and foveolar hyperplasia, and displayed lower colonisation of the gastric mucosa than wild-type B6129 littermates. Cav1-null mice showed enhanced infiltration of macrophages and B-cells and secretion of chemokines (RANTES) but had reduced levels of CD25+ regulatory T-cells. Cav1-deficient human GC cells (AGS), infected with the CagA-delivery proficient H. pylori strain G27, were more sensitive to CagA-related cytoskeletal stress morphologies ("humming bird") compared to AGS cells stably transfected with Cav1 (AGS/Cav1). Infection of AGS/Cav1 cells triggered the recruitment of p120 RhoGTPase-activating protein/deleted in liver cancer-1 (p120RhoGAP/DLC1) to Cav1 and counteracted CagA-induced cytoskeletal rearrangements. In human GC cell lines (MKN45, N87) and mouse stomach tissue, H. pylori down-regulated endogenous expression of Cav1 independently of CagA. Mechanistically, H. pylori activated sterol-responsive element-binding protein-1 (SREBP1) to repress transcription of the human Cav1 gene from sterol-responsive elements (SREs) in the proximal Cav1 promoter. These data suggested a protective role of Cav1 against H. pylori-induced inflammation and tissue damage. We propose that H. pylori exploits down-regulation of Cav1 to subvert the host's immune response and to promote signalling of its virulence factors in host cells

Magnetostimulated Chandges of Microhardness in Potassium Acid Phthalate Crystals

A decrease in microhardness along the (010) cleavage in potassium acid phthalate single crystals by 15--18% after the application of a permanent magnetic field was revealed for the first time. It is shown that the effect revealed is of the volume character. The role of interlayer water in the processes stimulated by a magnetic field is studied., Interlayer water plays does not cause the observed changes it only plays the part of an indicator of these changes in potassium acid phthalate crystals in a magnetic field. It is established that microhardness in the (100) plane of the crystal in an applied a magnetic field first increases by 12--15% and then remains constant in time within the accuracy of the experiment. The possibility of varying the crystal structure of potassium acid phthalate crystals by applying magnetic fields inducing rearrangement in the system of hydrogen bonds or in the defect structure is discussed.Comment: 6 pages, 7 figure

Understanding the mechanisms of cooperative physico-chemical treatment and mechanical disintegration of biomass as a route for enhancing enzyme saccharification

A novel chemico-kinetic disintegration model has been applied to study the cooperative relationship between physico-chemical treatment and supplementary wet-state milling of biomass, as an efficient process route to achieve high enzyme accessibility. Wheat straw, Miscanthus and short-rotation willow were studied as three contrasting biomass species, which were subjected to controlled hydrothermal pretreatment using a microwave reactor, followed by controlled wet-state ball-milling. Comparative particle disintegration behaviour and related enzyme digestibilities have been interpreted on the basis of model parameters and with evaluation of textural and chemical differences in tissue structures, aided by the application of specific material characterisation techniques. Supplementary milling led to a 1.3×, 1.6× and 3× enhancement in glucose saccharification yield after 24 h for straw, Miscanthus and willow, respectively, following a standardised 10-min hydrothermal treatment, with corresponding milling energy savings of 98, 97 and 91% predicted from the model, compared to the unmilled case. The results confirm the viability of pretreatment combined with supplementary wet-milling as an efficient process route. The results will be valuable in understanding the key parameters for process design and optimisation and also the key phenotypical parameters for feedstock breeding and selection for highest saccharification yield