Numerical and experimental investigations on the fatigue life of hot work tool steel X38CRMOV5-3 under forging process conditions

Hot forging dies experience during service excessive cyclic thermo-mechanical, tribological as well as chemical loads. These loads occur in a repeated manner and may cause premature fatigue failure of the forming tools and thus lead to an interruption of the production process. Die failures due to fatigue crack initiation constitute about 25 % of all failure types. The initiation and propagation of fatigue cracks can mainly be ascribed to high cyclic thermal and mechanical loads exerted on the tool material. Thus the hot work tool steel in service should combine a high red hardness with the ability to withstand heat checking at a high abrasion resistance. One of the most commonly used hot work tool steels for manufacturing high quality tools for hot forming operations like forging and casting is AISI H13 (X38CrMoV5-3), which also provides these properties. The numerical simulation based on the finite element method (FEM) has so far become an indispensable tool for the design and optimisation of hot forging processes. So far FE based process simulations are limited to obtaining accurate results related to the formability of the workpiece material and the necessary press force. Tool related aspects like the prediction of the tool life quantity and the estimation of abrasive wear is so far limited to cold forming tools. Due to the complex thermo-mechanical phenomena occurring in the interface layer between workpiece and forming tool it was so far not possible to give a reliable estimation on the tool life as current modelling approaches do not capture relevant influences in order to describe forging die fatigue and damage mechanisms in a realistic manner. For the prediction of the maximum cycles until fatigue failure it is still a common approach to resort to strain amplitude based models which neither take into account the transient temperature evolution nor the triaxiality of the local stress state. It is obvious that hot work tool steel materials need a more sophisticated modelling as severe thermo-mechanical loads are prevailing. In order to make a reliable estimation on the tool life quantity of forging dies it is therefore necessary to use advanced and sophisticated material models

The roles of intratumour heterogeneity in the biology and treatment of pancreatic ductal adenocarcinoma.

Intratumour heterogeneity (ITH) has become an important focus of cancer research in recent years. ITH describes the cellular variation that enables tumour evolution, including tumour progression, metastasis and resistance to treatment. The selection and expansion of genetically distinct treatment-resistant cancer cell clones provides one explanation for treatment failure. However, tumour cell variation need not be genetically encoded. In pancreatic ductal adenocarcinoma (PDAC) in particular, the complex tumour microenvironment as well as crosstalk between tumour and stromal cells result in exceptionally variable tumour cell phenotypes that are also highly adaptable. In this review we discuss four different types of phenotypic heterogeneity within PDAC, from morphological to metabolic heterogeneity. We suggest that these different types of ITH are not independent, but, rather, can inform one another. Lastly, we highlight recent findings that suggest how therapeutic efforts may halt PDAC progression by constraining cellular heterogeneity

Evaluation of uterine ultrasound imaging in cervical radiotherapy; a comparison of autoscan and conventional probe

OBJECTIVE: In cervical radiotherapy, it is essential that the uterine position is correctly determined prior to treatment delivery. The aim of this study was to evaluate an autoscan ultrasound (A-US) probe, a motorized transducer creating three-dimensional (3D) images by sweeping, by comparing it with a conventional ultrasound (C-US) probe, where manual scanning is required to acquire 3D images. METHODS: Nine healthy volunteers were scanned by seven operators, using the Clarity(®) system (Elekta, Stockholm, Sweden). In total, 72 scans, 36 scans from the C-US and 36 scans from the A-US probes, were acquired. Two observers delineated the uterine structure, using the software-assisted segmentation in the Clarity workstation. The data of uterine volume, uterine centre of mass (COM) and maximum uterine lengths, in three orthogonal directions, were analyzed. RESULTS: In 53% of the C-US scans, the whole uterus was captured, compared with 89% using the A-US. F-test on 36 scans demonstrated statistically significant differences in interobserver COM standard deviation (SD) when comparing the C-US with the A-US probe for the inferior–superior (p < 0.006), left–right (p < 0.012) and anteroposterior directions (p < 0.001). The median of the interobserver COM distance (Euclidean distance for 36 scans) was reduced from 8.5 (C-US) to 6.0 mm (A-US). An F-test on the 36 scans showed strong significant differences (p < 0.001) in the SD of the Euclidean interobserver distance when comparing the C-US with the A-US scans. The average Dice coefficient when comparing the two observers was 0.67 (C-US) and 0.75 (A-US). The predictive interval demonstrated better interobserver delineation concordance using the A-US probe. CONCLUSION: The A-US probe imaging might be a better choice of image-guided radiotherapy system for correcting for daily uterine positional changes in cervical radiotherapy. ADVANCES IN KNOWLEDGE: Using a novel A-US probe might reduce the uncertainty in interoperator variability during ultrasound scanning

A population-based case-control study on social factors and risk of testicular germ cell tumours

Objectives Incidence rates for testicular cancer have risen over the last few decades. Findings of an association between the risk of testicular cancer and social factors are controversial. The association of testicular cancer and different indicators of social factors were examined in this study.&lt;p&gt;&lt;/p&gt; Design Case–control study.&lt;p&gt;&lt;/p&gt; Setting Population-based multicentre study in four German regions (city states Bremen and Hamburg, the Saarland region and the city of Essen).&lt;p&gt;&lt;/p&gt; Participants The study included 797 control participants and 266 participants newly diagnosed with testicular cancer of which 167 cases were classified as seminoma and 99 as non-seminoma. The age of study participants ranged from 15 to 69 years.&lt;p&gt;&lt;/p&gt; Methods Social position was classified by educational attainment level, posteducational training, occupational sectors according to Erikson-Goldthorpe-Portocarrero (EGP) and the socioeconomic status (SES) on the basis of the International SocioEconomic Index of occupational status (ISEI). ORs and corresponding 95% CIs (95% CIs) were calculated for the whole study sample and for seminoma and non-seminoma separately.&lt;p&gt;&lt;/p&gt; Results Testicular cancer risk was modestly increased among participants with an apprenticeship (OR=1.7 (95% CI 1.0 to 2.8)) or a university degree (OR=1.6 (95% CI 0.9 to 2.8)) relative to those whose education was limited to school. Analysis of occupational sectors revealed an excess risk for farmers and farm-related occupations. No clear trend was observed for the analyses according to the ISEI-scale.&lt;p&gt;&lt;/p&gt; Conclusions Social factors based on occupational measures were not a risk factor for testicular cancer in this study. The elevated risk in farmers and farm-related occupations warrants further research including analysis of occupational exposures.&lt;p&gt;&lt;/p&gt

Entorhinal and ventromedial prefrontal cortices abstract and generalize the structure of reinforcement learning problems

Knowledge of the structure of a problem, such as relationships between stimuli, enables rapid learning and flexible inference. Humans and other animals can abstract this structural knowledge and generalize it to solve new problems. For example, in spatial reasoning, shortest-path inferences are immediate in new environments. Spatial structural transfer is mediated by cells in entorhinal and (in humans) medial prefrontal cortices, which maintain their co-activation structure across different environments and behavioral states. Here, using fMRI, we show that entorhinal and ventromedial prefrontal cortex (vmPFC) representations perform a much broader role in generalizing the structure of problems. We introduce a task-remapping paradigm, where subjects solve multiple reinforcement learning (RL) problems differing in structural or sensory properties. We show that, as with space, entorhinal representations are preserved across different RL problems only if task structure is preserved. In vmPFC and ventral striatum, representations of prediction error also depend on task structure

Wave conditions in the Baltic Proper and in the Gulf of Finland during windstorm Gudrun

International audienceWave conditions in the northern Baltic Proper during windstorm Erwin/Gudrun (January 2005) are analysed based on in situ measurements in three locations and output of operational wave models from the German Weather Forecast Service, the Danish Meteorological Institute and the Finnish Institute of Marine Research. The measured significant wave height reached 7.2 m in the northern Baltic Proper and 4.5 m in the Gulf of Finland. The roughest wave conditions, estimated from the comparison of the forecast and measured data, occurred remote from the sensors, off the coasts of Saaremaa and Latvia where the significant wave height was about 9.5 m. Peak periods exceeded 12 s in a large part of the northern Baltic Proper and in the central part of the Gulf of Finland

Spatially uniform calibration of a liquid xenon detector at low energies using 83m-Kr

A difficult task with many particle detectors focusing on interactions below ~100 keV is to perform a calibration in the appropriate energy range that adequately probes all regions of the detector. Because detector response can vary greatly in various locations within the device, a spatially uniform calibration is important. We present a new method for calibration of liquid xenon (LXe) detectors, using the short-lived 83m-Kr. This source has transitions at 9.4 and 32.1 keV, and as a noble gas like Xe, it disperses uniformly in all regions of the detector. Even for low source activities, the existence of the two transitions provides a method of identifying the decays that is free of background. We find that at decreasing energies, the LXe light yield increases, while the amount of electric field quenching is diminished. Additionally, we show that if any long-lived radioactive backgrounds are introduced by this method, they will present less than 67E-6 events/kg/day in the next generation of LXe dark matter direct detection searchesComment: 9 pages, 9 figures. Accepted to Review of Scientific Instrument