A conceptual framework for discrete inverse problems in geophysics

In geophysics, inverse modelling can be applied to a wide range of goals, including, for instance, mapping the distribution of rock physical parameters in applied geophysics and calibrating models to forecast the behaviour of natural systems in hydrology, meteorology and climatology. A common, thorough conceptual framework to define inverse problems and to discuss their basic properties in a complete way is still lacking. The main goal of this paper is to propose a step forward toward such a framework, focussing on the discrete inverse problems, that are used in practical applications. The relevance of information and measurements (real world data) for the definition of the calibration target and of the objective function is discussed, in particular with reference to the Bayesian approach. Identifiability of model parameters, posedness (uniqueness and stability) and conditioning of the inverse problems are formally defined. The proposed framework is so general as to permit rigorous definitions and treatment of sensitivity analysis, adjoint-state approach, multi-objective optimization

Systemic Chemotherapy as Salvage Treatment for Locally Advanced Rectal Cancer Patients Who Fail to Respond to Standard Neoadjuvant Chemoradiotherapy.

Background The potential of chemotherapy as salvage treatment after failure of neoadjuvant chemoradiotherapy for locally advanced rectal cancer (LARC) has never been explored. We conducted a single-center, retrospective analysis to address this question.Patients and methods Patients with newly diagnosed LARC who were inoperable or candidates for extensive (i.e., beyond total mesorectal excision [TME]) surgery after long-course chemoradiotherapy and who received salvage chemotherapy were included. The primary objective was to estimate the proportion of patients who became suitable for TME after chemotherapy.Results Forty-five patients were eligible (39 candidates for extensive surgery and 6 unresectable). Previous radiotherapy was given concurrently with chemotherapy in 43 cases (median dose: 54.0 Gy). Oxaliplatin- and irinotecan-based salvage chemotherapy was administered in 40 (88.9%) and 5 (11.1%) cases, respectively. Eight patients (17.8%) became suitable for TME after chemotherapy, 10 (22.2%) ultimately underwent TME with clear margins, and 2 (4.4%) were managed with a watch and wait approach. Additionally, 13 patients had extensive surgery with curative intent. Three-year progression-free survival and 5-year overall survival in the entire population were 30.0% (95% confidence interval [CI]: 15.0-46.0) and 44.0% (95% CI: 26.0-61.0), respectively. For the curatively resected and "watch and wait" patients, these figures were 52.0% (95% CI: 27.0-73.0) and 67.0% (95% CI: 40.0-84.0), respectively.Conclusion Systemic chemotherapy may be an effective salvage strategy for LARC patients who fail to respond to chemoradiotherapy and are inoperable or candidates for beyond TME surgery. According to our study, one out of five patients may become resectable or be spared from an extensive surgery after systemic chemotherapy.Implications for practice High-quality evidence to inform the optimal management of rectal cancer patients who are inoperable or candidates for beyond total mesorectal excision surgery following standard chemoradiotherapy is lacking. We show for the first time that systemic chemotherapy may be beneficial and result in one out of five poor prognosis patients becoming resectable or being spared from an extensive surgical approach. Although mores studies are needed to confirm these data, administering salvage systemic chemotherapy in this setting may have the potential to minimize morbidity associated with extensive surgical procedures and improve long-term oncological outcome

Multi-laboratory efforts for the standardization of performance assessment of diffuse optics instruments - The BitMap Exercise

A multi-laboratory exercise, involving 29 diffuse optical instruments, aimed at performance assessment of diffuse optics instruments on standardized protocols is presented. The overarching methodology and future actions will also be discussed

A multi-laboratory comparison of photon migration instruments and their performances – the BitMap Exercise

Performance assessment and standardization are indispensable for instruments of clinical relevance in general and clinical instrumentation based on photon migration/diffuse optics in particular. In this direction, a multi-laboratory exercise was initiated with the aim of assessing and comparing their performances. 29 diffuse optical instruments belonging to 11 partner institutions of a European level Marie Curie Consortium BitMap1 were considered for this exercise. The enrolled instruments covered different approaches (continuous wave, CW; frequency domain, FD; time domain, TD and spatial frequency domain imaging, SFDI) and applications (e.g. mammography, oximetry, functional imaging, tissue spectroscopy). 10 different tests from 3 well-accepted protocols, namely, the MEDPHOT2, the BIP3, and the nEUROPt4 protocols were chosen for the exercise and the necessary phantoms kits were circulated across labs and institutions enrolled in the study. A brief outline of the methodology of the exercise is presented here. Mainly, the design of some of the synthetic descriptors, (single numeric values used to summarize the result of a test and facilitate comparison between instruments) for some of the tests will be discussed.. Future actions of the exercise aim at deploying these measurements onto an open data repository and investigating common analysis tools for the whole dataset

Performances Modelling of a Twin Fluid Internal Mixing Nozzles for Industrial Burners

At the Centro Combustione Ambiente facility, within the “BE4GreenS” R&D project, sponsored by Regione Puglia using European founds, a series of test is being performed to analyze the performances of different Heavy Fuel Oil burner guns and injection nozzles, by varying the operative conditions and some design parameters. With the aim of improving the parameters design, semi-empirical models are being developed to predict the system performance. The emission of NOx and CO are measured and displayed as a function O2, the residual oxygen content in the exhaust gasses, that depends on the tunable air excess being varied for each test series. The CO content data are then interpolated by an hyperbolic function under some hypotheses and simplifications, the first one being that air excess is always guaranteed, otherwise for an under-stoichiometric combustion the CO asymptote should be backward inclined instead of vertical but. So two parameters should be determined experimentally for each test series i: the position of each vertical asymptote O2lim,i, and the curvature of each hyperbole defined by the parameter Ki, in the function (O2 - O2lim,i) × CO = Ki . By assuming also that for similar combustion systems, e.g. the same furnace and the same gun with similar flame asset and burned fuel, the parameters Ki, specific for each test series i can be replaced by a unique parameter K for that set-up, only the specific O2Lim,i have to be determined for each series. This can help in reducing the total number of tests, and furthermore it allows to reverse the function, for example to calculate the air excess that will keep the CO content under a given limit. A similar linear model for the NOx can then be used to complete the simulation and help in tuning-up the system operative parameter

Single- and Dual-domain Models of Solute Transport in Alluvial Sediments: the Effects of Heterogeneity Structure and Spatial Scale

Fine-scale heterogeneity of alluvial aquifers controls solute transport in groundwater at the scales relevant for practical applications: the architecture of sedimentary structures might create preferential flow paths (PFPs) or hydraulic barriers, which affect the breakthrough curves (BTCs). Objective of this paper was the assessment of the relevance of single- and dual-domain models for different heterogeneity patterns and scale lengths in alluvial sediments. Three case studies have been analysed with a classical single-domain model (SDM) and with three dual-domain models (DDMs): a dual-porosity model (DPorM) and two dual-permeability models (DPerM), which differ for the presence or the absence of solute exchange between the two domains. The first case study includes numerical tracer tests in metre-scale blocks of alluvial sediments; the second is a laboratory experiment of tracer injection in a decimetre-scale column of homogeneous sand; the third is a field tracer test performed at hectometre scale at the Cape Cod site. The relevance of the solute exchange in the DDMs is analysed with the characteristic advection and exchange times and with the P\ue9clet and Damk\uf6hler numbers. The SDM is satisfactory for alluvial sediments with unstructured heterogeneity. The uncoupled DPerM is shown to be a better approach than the DPorM in sediments with PFPs; in this case, the coupled DPerM does not improve significantly the results of the uncoupled DPerM. A minor difference between the results of the three DDMs is observed for sediments in which the non-Fickian behaviour is not clearly determined by the presence of PFPs