Superphénix Benchmark Part II: Transient Results

The paper presents a transient simulation phase of the new benchmark on a large sodium fast reactor (SFR). This phase of the benchmark is devoted to the modeling of selected operational transients performed during startup tests of the French SFR Superphénix. Six operational transients were selected for the analysis. The specifications of a simplified thermal hydraulic model equipped with point kinetics reactivity data and boundary conditions for the selected transients are given in the paper. The developed model contains a necessary thermal hydraulic description of the primary system components, assumptions to account for thermal expansion reactivity feedback from out-of-core structures, neutron kinetics parameters, power distribution, and reactivity coefficients. The neutronic input parameters were obtained with the help of the Monte Carlo code serpent during the first phase of the benchmark related to the static neutronic characterization of the core. In this study, the solution of the transient benchmark was obtained with three thermal hydraulic system codes, namely, TRACE, SIM-SFR, and ATHLET. The numerical results, compared to the available experimental data, exhibit a reasonable mutual agreement. Particular discrepancies between calculations and experiments could not be fully resolved. Therefore, a set of recommendations for achieving an improved agreement was proposed. In general, the proposed transient benchmark can be seen as an effective tool for validation and cross comparisons of system codes applied for safety analyses of SFRs, including approbation and comparison of different modeling features for thermal expansion of the out-of-core structures.

NEUTRONIC MODELLING OF THE FFTF CONTROL ROD WORTH MEASUREMENTS WITH DIFFUSION CODES

This paper presents an assessment of three deterministic core simulators with the focus on the neutronic performance in steady-state calculations of small Sodium cooled Fast Reactor cores. The selected codes are DYN3D, PARCS and the novel multi-physics solver GeN-Foam. By using these codes, the multi-group diffusion solutions are obtained for the selected twenty control rod worth measurements performed during the isothermal physics tests of the Fast Flux Test Facility (FFTF). The identical set of homogenized few-group cross sections applied in the calculations is generated with the Serpent Monte Carlo code. The numerical results are compared with each other as well as with the measured values. The obtained numerical results, such as the multiplication factors and control rod worth values, are in good agreement as compared to the experimental data. Furthermore, a comparison of the radial power distributions is presented between DYN3D, PARCS and GeN-Foam. Ultimately, the power distributions are compared to the full core Serpent solution, demonstrating an adequate performance of the selected deterministic tools. In overall, this study presents a verification and validation of the neutronic solvers applied by DYN3D, PARCS and GeN-Foam to steady-state calculations of SFR cores.

Positive surgical margin following radical nephrectomy is an independent predictor of local recurrence and disease-specific survival

Background

Positive surgical margins (PSM) are recognized as an adverse prognostic sign and are often associated with higher rates of local and systemic disease recurrence. The data regarding the oncological outcome for PSM following radical nephrectomy (RN) is limited. We examined the predictive factors for PSM and its influence on survival and site of recurrence in patients treated with RN for renal cell carcinoma (RCC).

Methods

Clinical, pathologic and follow-up data on 714 patients undergoing RN for kidney cancer were analyzed. Secondary analysis included 44 patients with metastatic RCC upon diagnosis who underwent cytoreductive nephrectomy (CRN). Univariate and multivariable logistic regression models were fit to determine clinicopathologic features associated with PSM. A Cox proportional-hazards regression model was used to test the independent effects of clinical and pathologic variables on survival.

Results

PSM was documented in 17 cases (2.4%). PSM were associated with tumour size, advanced pathologic stage (pT3 vs. ≤ pT2) and presence of necrosis. On multivariate analysis, cancer-specific survival (CSS) was associated with tumour stage, size, presence of necrosis and PSM. PSM was also associated with local recurrence but not distant metastasis or overall survival (OS). CSS and OS were comparable between the PSM and metastatic RCC groups, but significantly lower than the negative margin group.

Conclusions

The prevalence of PSM following RN is rare. Pathological data, including advanced stage (> pT2), tumour necrosis and tumour size, are associated with the presence of PSM. PSM is associated with tumour recurrence and CSS. Patients with PSM are a potential group for adjuvant therapy or for more careful and thorough follow-up following surgery.

New version of the reactor dynamics code DYN3D for Sodium cooled Fast Reactor analyses

The reactor dynamics code DYN3D being developed at the Helmholtz-Zentrum Dresden-Rossendorf is currently under extension for Sodium cooled Fast Reactor analyses. This paper provides an overview on the new version of DYN3D to be used for SFR core calculations. The current article shortly describes the newly implemented thermal mechanical models, which can account for thermal expansion effects of the reactor core. Furthermore, the methodology used in Sodium cooled Fast Reactor analyses to generate homogenized few-group cross sections is summarized. The conducted and planned verification and validation studies are briefly presented. Related publications containing more detailed descriptions are outlined for the completeness of this overview.

Upregulation of RET induces perineurial invasion of pancreatic adenocarcinoma

Tumor spread along nerves, a phenomenon known as perineurial invasion, is common in various cancers including pancreatic ductal adenocarcinoma (PDAC). Neural invasion is associated with poor outcome, yet its mechanism remains unclear. Using the transgenic Pdx-1-Cre/KrasG12D /p53R172H (KPC) mouse model, we investigated the mechanism of neural invasion in PDAC. To detect tissue-specific factors that influence neural invasion by cancer cells, we characterized the perineurial microenvironment using a series of bone marrow transplantation (BMT) experiments in transgenic mice expressing single mutations in the Cx3cr1, GDNF and CCR2 genes. Immunolabeling of tumors in KPC mice of different ages and analysis of human cancer specimens revealed that RET expression is upregulated during PDAC tumorigenesis. BMT experiments revealed that BM-derived macrophages expressing the RET ligand GDNF are highly abundant around nerves invaded by cancer. Inhibition of perineurial macrophage recruitment, using the CSF-1R antagonist GW2580 or BMT from CCR2-deficient donors, reduced perineurial invasion. Deletion of GDNF expression by perineurial macrophages, or inhibition of RET with shRNA or a small-molecule inhibitor, reduced perineurial invasion in KPC mice with PDAC. Taken together, our findings show that RET is upregulated during pancreas tumorigenesis and its activation induces cancer perineurial invasion. Trafficking of BM-derived macrophages to the perineurial microenvironment and secretion of GDNF are essential for pancreatic cancer neural spread.

The reactor dynamics code DYN3D

The article provides an overview on the code DYN3D which is a three-dimensional core model for steady-state, dynamic and depletion calculations in reactor cores with quadratic or hexagonal fuel assembly geometry being developed by the Helmholtz-Zentrum Dresden-Rossendorf for more than 20 years. The current paper gives an overview on the basic DYN3D models and the available code couplings. The verification and validation status is shortly outlined. The paper concludes with the current developments of the DYN3D code. For more detailed information the reader is referred to the publications cited in the corresponding chapters.

Extensive heterosis in growth of yeast hybrids is explained by a combination of genetic models

Heterosis, also known as hybrid vigor, is the superior performance of a heterozygous hybrid relative to its homozygous parents. Despite the scientific curiosity of this phenotypic phenomenon and its significance for food production in agriculture, its genetic basis is insufficiently understood. Studying heterosis in yeast can potentially yield insights into its genetic basis, can allow one to test the different hypotheses that have been proposed to explain the phenomenon and allows better understanding of how to take advantage of this phenomenon to enhance food production. We therefore crossed 16 parental yeast strains to form 120 yeast hybrids, and measured their growth rates under five environmental conditions. A considerable amount of dominant genetic variation was found in growth performance, and heterosis was measured in 35% of the hybrid-condition combinations. Despite previous reports of correlations between heterosis and measures of sequence divergence between parents, we detected no such relationship. We used several analyses to examine which genetic model might explain heterosis. We found that dominance complementation of recessive alleles, overdominant interactions within loci and epistatic interactions among loci each contribute to heterosis. We concluded that in yeast heterosis is a complex phenotype created by the combined contribution of different genetic interactions.

Macrosomic newborns of non-diabetic mothers: anthropometric measurements and neonatal complications

OBJECTIVE

To assess the association of anthropometric measurements with neonatal complications in macrosomic newborns of non-diabetic mothers.

DESIGN

Retrospective cohort study.

PATIENTS

All liveborn, singleton, full term newborns with birth weight ≥4000 g born to non-diabetic mothers at a tertiary medical centre in 1995-2005 (n=2766, study group) were matched to the next born, healthy, full term infant with a birth weight of 3000-4000 g (control group). Exclusion criteria were multiple birth, congenital infection, major malformations and pregnancy complications.

INTERVENTION

Data collection by file review.

OUTCOME MEASURES

Complication rates were compared between study and control groups and between symmetric and asymmetric macrosomic newborns, defined by weight/length ratio (WLR), Body Mass Index and Ponderal Index.

RESULTS

The 2766 non-diabetic macrosomic infants identified were matched to 2766 control infants. The macrosomic group had higher rates of hypoglycaemia (1.2% vs 0.5%, p=0.008), transient tachypnoea of the newborn (1.5% vs 0.5%, p<0.001), hyperthermia (0.6% vs 0.1%, p=0.012), and birth trauma (2% vs 0.7%, p<0.001), with no cases of symptomatic polycythaemia, and only one case of hypoglycaemia. Hypoglycaemia was positively associated with birth weight. It was significantly higher in the asymmetric than the symmetric macrosomic newborns, defined by WLR (1.7% vs 0.3%, p<0.001).

CONCLUSIONS

Macrosomic infants of non-diabetic mothers are at increased risk of neonatal complications. However, routine measurements of haematocrit and calcium may not be necessary. Symmetric macrosomic infants (by WLR) have a similar rate of hypoglycaemia as normal-weight infants. Thus, repeat glucose measurements in symmetric macrosomic infants are not justified.

The simplified P3 approach on a trigonal geometry of the nodal reactor code DYN3D

DYN3D is a three-dimensional nodal code for steady-state and transient analyses of Light Water Reactors applicable for square and hexagonal fuel assembly geometries. Several versions of the DYN3D code are available including a multigroup diffusion and a simplified P3 (SP3) neutron transport option. The multi-group SP3 method based on a trigonal geometry was developed recently. This method is applicable to the analysis of reactor cores with hexagonal fuel assemblies and allows flexible mesh refinement. In this paper, the theoretical background for the SP3 method is briefly described. The consistency of the implementation of the trigonal SP3 methodology in DYN3D is demonstrated by means of a simplified VVER-440 core test example. The corresponding few-group homogenized cross sections and reference solutions were produced by the Monte Carlo code Serpent. The DYN3D results are in good agreement with the reference solutions.

Phenotypic landscapes: phenological patterns in wild and cultivated barley

Phenotypic variation in natural populations is the outcome of the joint effects of environmentally induced adaptations and neutral processes on the genetic architecture of quantitative traits. In this study, we examined the role of adaptation in shaping wild barley phenotypic variation along different environmental gradients. Detailed phenotyping of 164 wild barley (Hordeum spontaneum) accessions from Israel (of the Barley1K collection) and 18 cultivated barley (H. vulgare) varieties was conducted in common garden field trials. Cluster analysis based on phenotypic data indicated that wild barley in this region can be differentiated into three ecotypes in accordance with their ecogeographical distribution: north, coast and desert. Population differentiation (Q(ST) ) for each trait was estimated using a hierarchical Bayesian model and compared to neutral differentiation (F(ST) ) based on 42 microsatellite markers. This analysis indicated that the three clusters diverged in morphological but not in reproductive characteristics. To address the issue of phenotypic variation along environmental gradients, climatic and soil gradients were compared with each of the measured traits given the geographical distance between sampling sites using a partial Mantel test. Flowering time and plant growth were found to be differentially correlated with climatic and soil characteristic gradients, respectively. The H. vulgare varieties were superior to the H. spontaneum accessions in yield components, yet resembled the Mediterranean types in vegetative characteristics and flowering time, which may indicate the geographical origin of domesticated barley.

Detection of prostate cancer by radio-frequency near-field spectroscopy in radical prostatectomy ex vivo specimens

BACKGROUND

The aim of radical prostatectomy (RP) is the complete removal of the prostate gland with negative surgical margins. The presence of cancer at the surgical margin is associated with higher probability of disease progression. Current methods of intraoperative margin assessment are inaccurate or time-consuming.The study goal was to evaluate the ability of a novel device (Dune Medical Devices) to differentiate between cancer and BPH.

METHODS

A total of 49 patients undergoing RP in four medical centers between November 2007 and May 2008 were enrolled in this study.The device was applied to numerous intra- and extra-capsular sites of freshly excised RP specimens. Measurement sites were accurately marked and analyzed histologically. The ability of the device to differentiate between malignant and nonmalignant sites was assessed.

RESULTS

A total of 15,156 measurements from 45 patients were analyzed. Differentiation of the intra-capsular malignant sites from extra-capsular nonmalignant sites (bladder neck and apex regions) depends on the cancer feature size. Differentiation was achieved with sensitivity and specificity of 93.6 (95% confidence interval (CI): 88-98) and 94.1 (95% CI: 93-95), respectively, at feature sizes at or >0.8 mm in diameter. The device was able to discriminate between all intra-capsular malignant (with feature sizes down to a few cells) and nonmalignant measurement sites, with sensitivity and specificity of 80.8 (95% CI: 73-87) and 68.4 (95% CI: 67-69), respectively.

CONCLUSIONS

First results from a radio-frequency near-field spectroscopy sensor look promising for differentiation between cancer and benign prostate tissue. The sensor's dimensions (radius of ~ 1 mm) and design enable use in open, laparoscopic and robotic RP to evaluate the surgical margins intraoperatively.

Development of the coupled 3D neutron kinetics/thermal-hydraulics code DYN3D-HTR for the simulation of transients in block-type HTGR

The Light Water Reactor (LWR) dynamics code DYN3D is extended and adopted for the application to block-type High Temperature Gas-Cooled Reactor (HTGR). A procedure for the cross section generation for the HTGR core calculations was developed. The modified Reactivity-Equivalent Physical Transformation (RPT) approach is applied in order to eliminate the double-heterogeneity of HTGR fuel elements in the deterministic lattice calculations. A full core analysis of the reference simplified HTGR core is performed with DYN3D using macroscopic nodal cross sections provided by HELIOS.

The SP3 transport approximation is integrated into the multi-group DYN3D code to take anisotropy of the neutron flux and heterogeneity of the core more precisely into account. The SP3 method was developed for hexagonal geometry of the graphite blocks, where the hexagons are subdivided into triangular nodes.

A 3D heat conduction module coupled with a channel-type coolant flow model is implemented into the code. It is shown that there is significant redistribution of the produced heat by heat conduction between the graphite blocks.

New prospective for non-invasive detection, grading, size evaluation, and tumor location of prostate cancer

BACKGROUND

PSA blood test and other present screening tools fail to provide the required sensitivity and specificity and, at early stages, lack correlation with tumor grade, volume, and location. Thus alternative approaches are highly desired. We present and assess a novel method for PCa detection, grading, volume evaluation and tumor location, based on non-invasive zinc concentration mapping in the gland by means of a dedicated rectal probe.

METHODS

Zinc-concentration values measured in histologically examined tissue fragments from needle biopsy of 598 patients were analyzed. They were used to generate computer simulated zinc-concentration maps, further analyzed with image-processing tools. The tumor detection performances versus Gleason grade were assessed.

RESULTS

A significant increase of zinc depletion with increasing Gleason pattern (grade) classification was established. Tumor detection performance in zinc-concentration maps progressively improves with the cancer's first component score. Reliable information on the location, size and Gleason-grade combination of the lesion can be extracted for clinically relevant volumes.

CONCLUSIONS

Zinc depletion in the prostate peripheral zone is the basis for a novel, non-invasive PCa detection, localization, volume evaluation and grading method. Its realization and application as a pre-biopsy and pre-treatment examination, or a follow-up tool, relies on the development of a dedicated transrectal probe. It should have significant impact on biopsy effectiveness, point at a possible extraprostatic extension and provide critical data for focal treatment. The information on tumor grade and distribution may have an important impact on disease management.

Strong correlation of wild barley (Hordeum spontaneum) population structure with temperature and precipitation variation

In this study, we present the genetic analysis of a new collection of wild barley (Hordeum spontaneum) using 42 simple sequence repeat (SSR) markers that represent the seven chromosomes. The Barley1K (B1K) infrastructure consists of 1020 accessions collected in a hierarchical sampling mode (HSM) from 51 sites across Israel and represents the wide adaptive niche of the modern barley's ancestor. According to the genetic structure analysis, the sampled sites can be divided into seven groups, and sampled microsites located on opposing slopes or in different soil types did not show significant genetic differentiation. Although the genetic analysis indicates a simple isolation-by-distance model among the populations, examination of the genetic populations' structure with abiotic parameters in an ordination analysis revealed that the combination of elevation, mid-day temperature and rainfall explains a high proportion of the variance in the principal components analysis. Our findings demonstrate that the current populations have therefore been shaped and distinguished by non-selective forces such as migration; however, we suggest that aridity and temperature gradients played major roles as selective forces in the adaptation of wild barley in this part of the Fertile Crescent. This unique collection is a prelude for the investigation of the molecular basis underlying plant adaptation and responsiveness to harsh environments.