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Consider an input–output system where the output is the tracking error given some desired reference signal. It is natural to consider under what conditions the problem has an exact solution, that is, the tracking error is exactly the zero function. If the system has a well defined relative degree and the zero function is in the range of the input–output map, then it is well known that the system is locally left invertible, and thus, the problem has a unique exact solution. A system will fail to have relative degree when more than one exact solution exists. The general goal of this paper is to describe a decomposition of an input–output system having a Chen-Fliess series representation into a parallel product of subsystems in order to identify possible solutions to the problem of zeroing the output. For computational purposes, the focus is on systems whose generating series are polynomials. It is shown that the shuffle algebra on the set of generating polynomials is a unique factorization domain so that any polynomial can be uniquely factored modulo a permutation into its irreducible elements for the purpose of identifying the subsystems in a parallel product decomposition. This is achieved using the fact that this shuffle algebra is isomorphic to the symmetric algebra over the vector space spanned by Lyndon words. A specific algorithm for factoring generating polynomials into its irreducible factors is presented based on the Chen-Fox-Lyndon factorization of words. [ABSTRACT FROM AUTHOR]

Background: Esophagectomy carries a high risk of morbidity and mortality compared to other major surgeries. With the aim of creating an easy-to-use clinical preoperative risk assessment tool and to validate previously described risk factors for major complications following surgery, esophagectomies at two tertiary medical centers were analyzed. Methods: A total of 450 patients who underwent esophagectomy for esophageal carcinoma at the University Medical Centre, Hamburg, or at the Medical Center University Duisburg-Essen, Germany (January 2008 to January 2020) were retrospectively analyzed. Epidemiological and perioperative data were analyzed to identify the risk factors that impact major complication rates. The primary endpoint of this study was to determine the incidence of major complications. Results: The mean age of the patients was 63 years with a bimodal distribution. There was a male predominance across the cohort (81% vs. 19%, respectively). Alcohol abuse (p = 0.0341), chronic obstructive pulmonary disease (p = 0.0264), and cardiac comorbidity (p = 0.0367) were associated with a significantly higher risk of major complications in the multivariate analysis. Neoadjuvant chemotherapy significantly reduced the risk of major postoperative complications (p < 0.0001). Conclusions: Various patient-related risk factors increased the rate of major complications following esophagectomy. Patient-tailored prehabilitation programs before esophagectomy that focus on minimizing these risk factors may lead to better surgical outcomes and should be analyzed in further studies. [ABSTRACT FROM AUTHOR]

Background: Intraoperative blood loss has an unfavorable impact on the outcome of patients undergoing liver surgery. Today, the use of devices capable of minimizing this risk with high technical performance becomes mandatory. Into this scenario fits the CUSA® Clarity Ultrasonic Surgical Aspirator System. This prospective survey involving five liver surgery centers had the objective of investigating whether this innovative ultrasonic surgical aspirator is safe and effective in the transection of the liver parenchyma. Materials and Methods: This clinical study was a prospective, multicenter, single-arm Post-Market Clinical Follow-up study investigating 100 subjects who underwent liver surgery using the CUSA Clarity Ultrasonic Surgical Aspirator System at five centers during a period of 1 year and 8 months. After collecting all the patient's clinical information and instrument usage details, surgeons completed a brief survey giving their opinions on the performance of CUSA. Therefore, safety and efficacy outcomes were evaluated. Results: Surgeons had a 95% success rate in complete removal of the mass with an average overall operative time of 4 hours and 34 minutes. Overall, there were no complications or device deficiencies. Conclusion: The CUSA Clarity Ultrasonic Surgical Aspirator System performs well during liver surgery with a low complication rate. ClinicalTrials.gov Identifier: NCT04298268. [ABSTRACT FROM AUTHOR]

Background: The recurrence of hepatitis C virus (HCV) after liver transplantation (OLT) leads to recurrent cirrhosis in up to 40% of patients.Aims: To identify patients who profit the most from antiviral therapy and to delineate whether early treatment after OLT is effective to reach sustained virological response (SVR), we analyzed factors associated to SVR during pegylated interferon/ribavirin (PegIFN/RBV) therapy.Methods: A retrospective analysis of efficiency and viral decline kinetics in 83 HCV-infected liver transplant recipients who received therapy with PegIFN/RBV was carried out.Results: Forty-one of 83 (49.4%) patients became HCV RNA-negative. SVR was achieved in 26/83 (31.3%) patients. Viral decline of at least 2 log 10 (n = 47) at week 12 was significantly associated with an end-of-treatment (EOT) response. Eleven early viral response patients were not able to clear HCV RNA, whereas five patients without a 2 log decline achieved SVR. The highest predictive value for SVR was an undetectable viremia at week 24 (92%).Conclusions: The outcome of antiviral combination therapy for HCV reinfection after OLT can be best predicted by week-24 virologic response. The high SVR rates in patients with detectable HCV RNA at week 12 might suggest a prolonged treatment protocol in liver transplant recipients. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to evaluate annual direct medical costs of adult SLE patients with active autoantibody positive disease on medication in Germany., Methods: A multicentre, observational, retrospective European study with German sub-analysis was performed. Costs were assessed according to national tariffs., Results: 10 German centres included 77 patients. The mean (SD) annual direct medical costs of patients were € 3 452.21 (3 777.07), and were 3.4 times higher in severe than non-severe patients (€ 5 291.07 vs. 1 564.97; p<0.001). Cost of medication (€ 2 349.40) represented 68.1% of the total cost. Flares, especially severe flares, were identified as cost predictors. Each flare increased the annual total cost by € 2 164,01 (p<0,001)., Conclusion: The annual direct medical cost of SLE patients in Germany is linked to disease severity. Medical treatments and severe flares were identified as the cost predictors and drivers, respectively., (© Georg Thieme Verlag KG Stuttgart · New York.)

Background: While much discussion has been placed on the problem of poor compliance in the treatment of schizophrenia, there has been little discussion on the concordance between patients and psychiatrists, an important contributing factor to patient-centred care., Objective: To estimate the concordance between patients' and psychiatrists' (ordinal and cardinal) valuations of multiple goals for schizophrenia treatment and to illustrate the utility of the self-explicated method in valuing a large number of treatment goals., Design: Twenty treatment goals were identified during focus groups and literature review and were presented to patients and psychiatrists during structured interviews. Respondents were asked to rank the multiple treatment goals and rate them on a 5-point Likert scale. Three scores were calculated based on the ranking (1-20), rating (Likert scale) (1-5) and a self-explicated method estimated as the product of rating and ranking score (1-100). Concordance was tested using Spearman's rho for overall ordinal rankings and via anova and F-test for the cardinal values assigned to a specific treatment goal., Participants: A total of 105 outpatients diagnosed with schizophrenia and 160 psychiatrists in Germany., Results: Patient and psychiatrist values were concordant when the ordinal properties of their valuations were assessed by rating (ρ = 0.63; P = 0.002), ranking (ρ = 0.51; P = 0.02) and self-explicated methods (ρ = 0.54; P = 0.01). Significant discordances were found when comparing the cardinal value placed on any given treatment goal using all three approaches, but the self-explicated method produced a more discerning statistic. Relative to patients, psychiatrists significantly (P < 0.05) overvalued reduced lack of emotion, improved sexual pleasure and improved communication while undervaluing reuptake of activities of daily living, improved satisfaction and recovered capacity for work., Conclusions: While there is an overall concordance between patients' and psychiatrists' valuation, significantly different valuations on specific goals can be identified. Here, psychiatrists tend to focus on 'textbook' outcomes, while patients are more concerned with functioning and living a normal life. This study also demonstrates the importance of comparing the concordance in treatment goals and the importance of preference-based methods, such as the self-explicated method, in the study of concordance., (© 2011 John Wiley & Sons Ltd.)

Background: Schizophrenia is a severe mental illness associated with hallucinations, delusions, apathy, poor social functioning, and impaired cognition. Researchers and funders have been hesitant to focus efforts on treatment preferences of patients with schizophrenia because of the perceived cognitive burden that research methods, such as conjoint analysis, place on them., Objective: The objective of this study was to test if patients diagnosed with schizophrenia were able to complete a choice-based conjoint analysis (often referred to as discrete-choice experiments) and to test if meaningful trade-offs were being made., Methods: German outpatients diagnosed with schizophrenia were eligible to participate in this study if they were aged 18-65 years, had received treatment for at least 1 year and were not experiencing acute symptoms. Conjoint analysis tasks were based on six attributes, each with two levels, which were identified via a literature review and focus groups. A psychologist in a professional interview facility presented each respondent with the eight tasks with little explanation. All interviews were recorded, transcribed, and analyzed to verify that respondents understood the tasks. Preferences were assessed using logistic regression, with a correction for clustering., Results: We found evidence that the 21 patients diagnosed with schizophrenia participating in the study could complete conjoint analysis tasks in a meaningful way. Patients not only related to the scenarios presented in conjoint tasks, but explicitly stated that they used their own preferences to judge which scenarios were better. Statistical analysis confirmed all hypotheses about the attributes (i.e. all attributes had the expected sign). Having a supportive physician, not feeling slowed, and improvements in stressful situations (p < 0.01) were the most important attributes., Conclusions: We found that patients diagnosed with schizophrenia can complete conjoint analysis tasks, that they base their decisions on their own preferences, and that patients make trade-offs between attributes.

Solely on the basis of Raman spectra and quantum chemical calculations, the previously unknown cluster anion Si 9 (structure shown) was characterized and its structure determined. The anion is formed as a component of solid phases by the thermal decomposition of alkali metal monosilicides.4- (structure shown) was characterized and its structure determined. The anion is formed as a component of solid phases by the thermal decomposition of alkali metal monosilicides., (© 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)