The Sample Complexity of Dictionary Learning

A large set of signals can sometimes be described sparsely using a dictionary, that is, every element can be represented as a linear combination of few elements from the dictionary. Algorithms for various signal processing applications, including classification, denoising and signal separation, learn a dictionary from a set of signals to be represented. Can we expect that the representation found by such a dictionary for a previously unseen example from the same source will have L_2 error of the same magnitude as those for the given examples? We assume signals are generated from a fixed distribution, and study this questions from a statistical learning theory perspective. We develop generalization bounds on the quality of the learned dictionary for two types of constraints on the coefficient selection, as measured by the expected L_2 error in representation when the dictionary is used. For the case of l_1 regularized coefficient selection we provide a generalization bound of the order of O(sqrt(np log(m lambda)/m)), where n is the dimension, p is the number of elements in the dictionary, lambda is a bound on the l_1 norm of the coefficient vector and m is the number of samples, which complements existing results. For the case of representing a new signal as a combination of at most k dictionary elements, we provide a bound of the order O(sqrt(np log(m k)/m)) under an assumption on the level of orthogonality of the dictionary (low Babel function). We further show that this assumption holds for most dictionaries in high dimensions in a strong probabilistic sense. Our results further yield fast rates of order 1/m as opposed to 1/sqrt(m) using localized Rademacher complexity. We provide similar results in a general setting using kernels with weak smoothness requirements

Advancing the Science of Natural and Enhanced Attenuation for Chlorinated Solvents

This report summarizes the results of a three-year program that addressed key scientific and technical aspects related to natural and enhanced attenuation of chlorinated organics. The results from this coordinated three-year program support a variety of technical and regulatory advancements. Scientists, regulators, engineers, end-users and stakeholders participated in the program, which was supported by the U.S. Department of Energy (DOE) and the Interstate Technology and Regulatory Council (ITRC). The overarching objective of the effort was to examine environmental remedies that are based on natural processes--remedies such as Monitored Natural Attenuation (MNA) or Enhanced Attenuation (EA). A key result of the recent effort was the general affirmation of the approaches and guidance in the original U.S. Environmental Protection Agency (EPA) chlorinated solvent MNA protocols and directives from 1998 and 1999, respectively. The research program did identify several specific opportunities for advances based on: (1) mass balance as the central framework for attenuation based remedies, (2) scientific advancements and achievements during the past ten years, (3) regulatory and policy development and real-world experience using MNA, and (4) exploration of various ideas for integrating attenuation remedies into a systematic set of ''combined remedies'' for contaminated sites. These opportunities are summarized herein and are addressed in more detail in referenced project documents and journal articles, as well as in the technical and regulatory documents being developed within the ITRC. Natural attenuation processes occur in all soil and groundwater systems and act, to varying degrees, on all contaminants. Thus, a decision to rely on natural attenuation processes as part of a site-remediation strategy does not depend on the occurrence of natural attenuation, but on its effectiveness in meeting site-specific remediation goals. Meeting these goals typically requires low risk, plume stability, and documentation of accepted and sustainable attenuation processes. Plume stability and sustainability depend on the balance between contaminant loading into the plume and contaminant attenuation within the plume. This ''mass balance'' is a simple and powerful idea that developed into the central framework for all aspects of the DOE MNA/EA program. The centrality of mass balance has been advocated by Chapelle and others (e.g., 1995) for several years, and the concepts proved to be critical to conceptualizing natural attenuation remedies, designing enhancements, developing characterization and monitoring strategies, and developing regulatory decision frameworks that encourage broader use of MNA/EA with clarified technical responsibility

Short-Term Outcomes of Secondary Liver Surgery for Initially Unresectable Colorectal Liver Metastases following Modern Induction Systemic Therapy in the Dutch CAIRO5 Trial

Objective: To present short-term outcomes of liver surgery in patients with initially unresectable colorectal liver metastases (CRLM) downsized by chemotherapy plus targeted agents. Background: The increase of complex hepatic resections of CRLM, technical innovations pushing boundaries of respectability, and use of intensified induction systemic regimens warrant for safety data in a homogeneous multicenter prospective cohort. Methods: Patients with initially unresectable CRLM, who underwent complete resection after induction systemic regimens with doublet or triplet chemotherapy, both plus targeted therapy, were selected from the ongoing phase III CAIRO5 study (NCT02162563). Short-term outcomes and risk factors for severe postoperative morbidity (Clavien Dindo grade ≥ 3) were analyzed using logistic regression analysis. Results: A total of 173 patients underwent resection of CRLM after induction systemic therapy. The median number of metastases was 9 and 161 (93%) patients had bilobar disease. Thirty-six (20.8%) 2-stage resections and 88 (51%) major resections (>3 liver segments) were performed. Severe postoperative morbidity and 90-day mortality was 15.6% and 2.9%, respectively. After multivariable analysis, blood transfusion (odds ratio [OR] 2.9 [95% confidence interval (CI) 1.1-6.4], P = 0.03), major resection (OR 2.9 [95% CI 1.1-7.5], P = 0.03), and triplet chemotherapy (OR 2.6 [95% CI 1.1-7.5], P = 0.03) were independently correlated with severe postoperative complications. No association was found between number of cycles of systemic therapy and severe complications (r = -0.038, P = 0.31). Conclusion: In patients with initially unresectable CRLM undergoing modern induction systemic therapy and extensive liver surgery, severe postoperative morbidity and 90-day mortality were 15.6% and 2.7%, respectively. Triplet chemotherapy, blood transfusion, and major resections were associated with severe postoperative morbidity

Reactivity tests for supplementary cementitious materials: RILEM TC 267-TRM phase 1

A primary aim of RILEM TC 267-TRM: “Tests for Reactivity of Supplementary Cementitious Materials (SCMs)” is to compare and evaluate the performance of conventional and novel SCM reactivity test methods across a wide range of SCMs. To this purpose, a round robin campaign was organized to investigate 10 different tests for reactivity and 11 SCMs covering the main classes of materials in use, such as granulated blast furnace slag, fly ash, natural pozzolan and calcined clays. The methods were evaluated based on the correlation to the 28 days relative compressive strength of standard mortar bars containing 30% of SCM as cement replacement and the interlaboratory reproducibility of the test results. It was found that only a few test methods showed acceptable correlation to the 28 days relative strength over the whole range of SCMs. The methods that showed the best reproducibility and gave good correlations used the R3 model system of the SCM and Ca(OH)2, supplemented with alkali sulfate/carbonate. The use of this simplified model system isolates the reaction of the SCM and the reactivity can be easily quantified from the heat release or bound water content. Later age (90 days) strength results also correlated well with the results of the IS 1727 (Indian standard) reactivity test, an accelerated strength test using an SCM/Ca(OH)2-based model system. The current standardized tests did not show acceptable correlations across all SCMs, although they performed better when latently hydraulic materials (blast furnace slag) were excluded. However, the Frattini test, Chapelle and modified Chapelle test showed poor interlaboratory reproducibility, demonstrating experimental difficulties. The TC 267-TRM will pursue the development of test protocols based on the R3 model systems. Acceleration and improvement of the reproducibility of the IS 1727 test will be attempted as well

Intersurgeon Variability in Local Treatment Planning for Patients with Initially Unresectable Colorectal Cancer Liver Metastases: Analysis of the Liver Expert Panel of the Dutch Colorectal Cancer Group

Background: Consensus on resectability criteria for colorectal cancer liver metastases (CRLM) is lacking, resulting in differences in therapeutic strategies. This study evaluated variability of resectability assessments and local treatment plans for patients with initially unresectable CRLM by the liver expert panel from the randomised phase III CAIRO5 study. Methods: The liver panel, comprising surgeons and radiologists, evaluated resectability by predefined criteria at baseline and 2-monthly thereafter. If surgeons judged CRLM as resectable, detailed local treatment plans were provided. The panel chair determined the conclusion of resectability status and local treatment advice, and forwarded it to local surgeons. Results: A total of 1149 panel evaluations of 496 patients were included. Intersurgeon disagreement was observed in 50% of evaluations and was lower at baseline than follow-up (36% vs. 60%, p < 0.001). Among surgeons in general, votes for resectable CRLM at baseline and follow-up ranged between 0–12% and 27–62%, and for permanently unresectable CRLM between 3–40% and 6–47%, respectively. Surgeons proposed different local treatment plans in 77% of patients. The most pronounced intersurgeon differences concerned the advice to proceed with hemihepatectomy versus parenchymal-preserving approaches. Eighty-four percent of patients judged by the panel as having resectable CRLM indeed received local treatment. Local surgeons followed the technical plan proposed by the panel in 40% of patients. Conclusion: Considerable variability exists among expert liver surgeons in assessing resectability and local treatment planning of initially unresectable CRLM. This stresses the value of panel-based decisions, and the need for consensus guidelines on resectability criteria and technical approach to prevent unwarranted variability in clinical practice

Osteosarcoma of the maxilla

Background: A 25-year-old male patient presented with tooth pain and progressive swelling of his left cheek. Dental examination was unremarkable

Converting the legend of the soil map of Belgium to world reference base for soil resources: case studies of the Flemish region

Within the European Union, there is a general interest to prepare joint soil maps at a 1:250,000 scale in order to harmonise agricultural and environmental policies and for which the World Reference Base for Soil Resources ( WRB ) has been adopted as the common soil classification system. As soil surveys in most member states were conducted independently, the challenge is now to convert the national legends into a common WRB legend. In Belgium, soils were mapped between 1947 and 1991 and maps were published at a 1:20,000 scale. These maps have proven useful in e.g. land consolidation projects and for assessing soils’ vulnerability to erosion and pollution. The legend of the soil map of Belgium is based on soil texture, drainage status and profile development. The WRB classification is based on diagnostic features defined by morphological, physical and chemical properties. A key and a software programme have been developed to convert the Belgian units into WRB units. However, as many Belgian soil units could not unequivocally be translated into WRB units, additional guidelines had to be derived based on soil profile data that were classified according to WRB. To overcome resulting ambiguities it is proposed to establish a national database of reference soil profiles. By using WRB Reference Soil Groups with one or two qualifiers expressing morphologic properties, the salient soil information of the original 1:20,000 scale soil map of Belgium can be represented; it is proposed to present the information on texture, drainage and substrate as separate inset maps. In this way, the legend allows for greater flexibility when adjusting large to small scale maps (e.g. 1:20,000 to 1:250,000). Keeping information on soil texture, drainage and occurrence of lithologic discontinuities in separate data fields conforms the logic of working with geographical information systems and allows making compromise between the Belgian and the WRB classification systems. Inevitably the conversion to WRB leads to some loss of information as some details get generalised into broader categories in WRB. This generalisation however can be neatly represented on 1:50,000 scale maps. Being less complex than the original maps, these maps have the advantage to provide a wider insight into the regional soil geography. These maps have also proven to provide a good base for deriving maps at a 1:250,000 scale. Whereas, overall WRB is satisfactory for classifying soils at national level, the experience also shows that some WRB concepts may benefit from revisions to facilitate its correlation with national soil survey data.Bestek nr. BOD/STUD/2009/05nrpages: 121status: publishe