Explicit feedback synthesis for nonlinear robust model predictive control driven by quasi-interpolation

We present QuIFS (Quasi-Interpolation driven Feedback Synthesis): an offline feedback synthesis algorithm for explicit nonlinear robust minmax model predictive control (MPC) problems with guaranteed quality of approximation. The underlying technique is driven by a particular type of grid-based quasi-interpolation scheme. The QuIFS algorithm departs drastically from conventional approximation algorithms that are employed in the MPC industry (in particular, it is neither based on multi-parametric programming tools and nor does it involve kernel methods), and the essence of its point of departure is encoded in the following challenge-answer approach: Given an error margin $\varepsilon>0$, compute in a single stroke a feasible feedback policy that is uniformly $\varepsilon$-close to the optimal MPC feedback policy for a given nonlinear system subjected to constraints and bounded uncertainties. Closed-loop stability and recursive feasibility under the approximate feedback policy are also established. We provide a library of numerical examples to illustrate our results.Comment: 31 Page

Towards continuous-time MPC: a novel trajectory optimization algorithm

This article introduces a numerical algorithm that serves as a preliminary step toward solving continuous-time model predictive control (MPC) problems directly without explicit time-discretization. The chief ingredients of the underlying optimal control problem (OCP) are a linear time-invariant system, quadratic instantaneous and terminal cost functions, and convex path constraints. The thrust of the method involves finitely parameterizing the admissible space of control trajectories and solving the OCP satisfying the given constraints at every time instant in a tractable manner without explicit time-discretization. The ensuing OCP turns out to be a convex semi-infinite program (SIP), and some recently developed results are employed to obtain an optimal solution to this convex SIP. Numerical illustrations on some benchmark models are included to show the efficacy of the algorithm.Comment: Accepted in IEEE Conference on Decision and Control (CDC), 202

A discrete-time Pontryagin maximum principle under rate constraints

Limited bandwidth and limited saturation in actuators are practical concerns in control systems. Mathematically, these limitations manifest as constraints being imposed on the control actions, their rates of change, and more generally, the global behavior of their paths. While the problem of actuator saturation has been studied extensively, little attention has been devoted to the problem of actuators having limited bandwidth. While attempts have been made in the direction of incorporating frequency constraints on state-action trajectories before, rate constraints on the control at the design stage have not been studied extensively in the discrete-time regime. This article contributes toward filling this lacuna. In particular, we establish a new discrete-time Pontryagin maximum principle with rate constraints being imposed on the control trajectories, and derive first-order necessary conditions for optimality. A brief discussion on the existence of optimal control is included, and numerical examples are provided to illustrate the results

Characterization of adhesin variants in Indian isolates of enteroaggregative Escherichia coli

Enteroaggregative Escherichia coli (EAEC) are causative agents of diarrhea, being characterized by aggregative adherence to cultured epithelial cells. In this study, phenotypic properties of EAEC were analyzed with respect to AA, hemagglutination, clump and biofilm formation, all of which are mediated by aggregative adherence fimbriae (AAF). The strains were also screened for AAF types, AAF adhesin variants and Dr adhesin by PCR. Of the three known AAF types, AAF/I and AAF/II adhesin variants were identified. An association between the AAF/adhesin genotypes and the subtypes/scores of phenotypic properties was sought and it was observed that strains harboring same adhesins displayed different subtypes/scores and vice versa

Pancreatic neuroendocrine tumor in an individual with Von Hippel Lindau syndrome. A case report and review literature

Von Hippel Lindau (VHL) disease is a heritable cancer syndrome characterized by VHL gene mutation in 3p chromosome. Mutations occur at the exons. Rarely mutations at introns have been reported. It leads to accumulation of Hypoxic ischemic factor α (HIF α) which in turn leads to uncontrolled cellular proliferation. Few reports of pancreatic neuroendocrine tumors (PNETs) are there in the literature. Most of them are associated with a mutation in the exon of VHL gene. Association with intron mutation is not there. Here we are reporting a case of PNET in a patient who has a simultaneous mutation both at the exon and the intron

Tolerability and outcome of once weekly liposomal amphotericin B for the prevention of invasive fungal infections in hematopoietic stem cell transplant patients with graft-versus-host disease

BACKGROUND: Invasive fungal infections remain problematic in immunosuppressed allogeneic stem cell transplant recipients and the use of corticosteroids for the treatment of graft-versus-host-disease can increase the risk three-fold. Although antifungal prophylaxis has been shown to decrease the incidence of infection, the optimal antifungal prophylactic regimen in this patient population has yet to be identified. Since early diagnosis of fungal infections might not be possible and the treatment of established fungal infections might be difficult and associated with high infection related mortality, prevention has become an important strategy in reducing overall morbidity and mortality. While triazoles are the preferred agents, some patients are unable to tolerate them and an alternative drug is warranted. OBJECTIVES: To assess the tolerability of once weekly liposomal amphotericin B as a prophylactic strategy in patients undergoing stem cell transplantation by evaluating any adverse events leading to its discontinuation. In terms of efficacy, to also compare the outcome and incidence of invasive fungal infections in patients who received amphotericin B, triazoles, and echinocandins.RESULTS: A total of 101 allogeneic transplant recipients receiving corticosteroids for the treatment of graft-versus-host-disease and antifungal prophylaxis were evaluated from August 2009 to September 2012. Liposomal amphotericin B 3 mg/kg intravenous once weekly was found to be well-tolerated. The incidence of invasive fungal infections was 19%, 17%, and 7% in the liposomal amphotericin B, echinocandin, and triazole groups, respectively. Two deaths occurred in the liposomal amphotericin B group and one death occurred in the echinocandin group. None of the deaths were fungal infection-related. CONCLUSION: Antifungal prophylaxis with liposomal amphotericin B was well-tolerated but the incidence of invasive fungal infections in patients receiving liposomal amphotericin B was higher than other antifungal agents in this study. The optimal dose and schedule of liposomal amphotericin B for antifungal prophylaxis in this patient population is still not known and considering its broad spectrum activity, prospective trials in comparison to triazoles are warranted

“Waitlist mortality” is high for myeloma patients with limited access to BCMA therapy

BackgroundThe first-in-class approved BCMA CAR-T therapy was idecabtagene vicleucel (ide-cel), approved in March 2021, for RRMM patients who progressed after 4 or more lines of therapy. Despite the promising outcomes, there were limited apheresis/production slots for ide-cel. We report outcomes of patients at our institution who were on the “waitlist” to receive ide-cel in 2021 and who could not secure a slot.MethodsWe conducted a retrospective review of RRMM patients evaluated at the University of Kansas Cancer Center for ide-cel from 3/2021-7/2021. A retrospective chart review was performed to determine patient and disease characteristics. Descriptive statistics were reported using medians for continuous variables. Survival analysis from initial consult was performed using Kaplan-Meier Survival estimator.ResultsForty patients were eligible and were on the “waitlist” for CAR-T. The median follow-up was 14 months (2-25mo). Twenty-four patients (60%) secured a production slot and 16 (40%) did not. The median time from consult to collection was 38 days (8-703). The median time from collection to infusion was 42 days (34-132 days). The median overall survival was higher in the CAR-T group (NR vs 9 mo, p<0.001).Conclusion(s)Many patients who were eligible for ide-cel were not able to secure a timely slot in 2021. Mortality was higher in this group, due to a lack of comparable alternatives. Increasing alternate options as well as improvement in manufacturing and access is an area of high importance to improve RRMM outcomes

R-CHOP versus R-CVP in the treatment of follicular lymphoma: a meta-analysis and critical appraisal of current literature

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Purpose: R-CHOP (rituximab with cyclophosphamide, doxorubicin, vincristine and prednisone) and R-CVP (rituximab with cyclophosphamide, vincristine and prednisone) have both been used successfully in the treatment of patients with symptomatic follicular lymphoma (FL). No study has compared the efficacy of the two treatment modalities and attempted to evaluate the role of anthracyclines in the management of patients with FL. We conducted a meta-analysis of relevant literature comparing the two treatment arms for FL with response being the final endpoint. Patients and Methods: Two analyses were conducted: The first analysis compared R-CHOP to R-CVP as frontline agents for the treatment of FL, and the second analysis included both untreated and relapsed patients. Results: For both studies, R-CVP was superior to R-CHOP when evaluating for complete response (CR). Odds ratios were 2.86 (95 % CI, 1.81–4.51) in the first analysis and 1.48 (95 % CI, 0.991–2.22) in the second analysis. However for overall response (CR+Partial response, PR), R-CHOP was superior, with odds ratios of 5.45 (95 % CI: 2.51 – 11.83) and 5.54 (95 % CI: 2.69