Arbitrary Set Point Research Articles

Bayesian Optimization of a Laser-Plasma Accelerator.

Generating high-quality laser-plasma accelerated electron beams requires carefully balancing a plethora of physical effects and is therefore challenging-both conceptually and in experiments. Here, we use Bayesian optimization of key laser and plasma parameters to flatten the longitudinal phase space of an ionization-injected electron bunch via optimal beam loading. We first study the concept with particle-in-cell simulations and then demonstrate it in experiments. Starting from an arbitrary set point, the plasma accelerator autonomously tunes the beam energy spread to the subpercent level at 254MeV and 4.7 pC/MeV spectral density. Finally, we study a robust regime, which improves the stability of the laser-plasma accelerator and delivers sub-five-percent rms energy spread beams for 90% of all shots.

Glucose monitoring and adaptive feeding of mammalian cell culture in the presence of strong autofluorescence by near infrared Raman spectroscopy.

Raman spectroscopy offers an attractive platform for real-time monitoring and control of metabolites and feeds in cell culture processes, including mammalian cell culture for biopharmaceutical production. However, specific cell culture processes may generate substantial concentrations of chemical species and byproducts with high levels of autofluorescence when excited with the standard 785 nm wavelength. Shifting excitation further toward the near-infrared allows reduction or elimination of process autofluorescence. We demonstrate such a reduction in a highly autofluorescent mammalian cell culture process. Using the Kaiser RXN2-1000 platform, which utilizes excitation at 993 nm, we developed multivariate glucose models in a cell culture process which was previously impossible using 785 nm excitation. Additionally, the glucose level in the production bioreactor was controlled entirely by Raman adaptive feeding, allowing for maintenance of glucose levels at an arbitrary set point for the duration of the culture. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1574-1580, 2018.

Closed loop control of lactate concentration in mammalian cell culture by Raman spectroscopy leads to improved cell density, viability, and biopharmaceutical protein production.

Accumulation of lactate in mammalian cell culture often negatively impacts culture performance, impeding production of therapeutic proteins. Many efforts have been made to limit the accumulation of lactate in cell culture. Here, we describe a closed loop control scheme based on online spectroscopic measurements of glucose and lactate concentrations. A Raman spectroscopy probe was used to monitor a fed-batch mammalian cell culture and predict glucose and lactate concentrations via multivariate calibration using partial least squares regression (PLS). The PLS models had a root mean squared error of prediction (RMSEP) of 0.27 g/L for glucose and 0.20 g/L for lactate. All glucose feeding was controlled by the Raman PLS model predictions. Glucose was automatically fed when lactate levels were beneath a setpoint (either 4.0 or 2.5 g/L) and glucose was below its own setpoint (0.5 g/L). This control scheme was successful in maintaining lactate levels at an arbitrary setpoint throughout the culture, as compared to the eventual accumulate of lactate to 8.0 g/L in the historical process. Automated control of lactate by restricted glucose feeding led to improvements in culture duration, viability, productivity, and robustness. Culture duration was extended from 11 to 13 days, and harvest titer increased 85% over the historical process. Biotechnol. Bioeng. 2016;113: 2416-2424. © 2016 Wiley Periodicals, Inc.

Maremar, prevalence of chronic kidney disease, how to avoid over-diagnosis and under-diagnosis

Chronic kidney disease is considered as a major public health problem. Recent studies mention a prevalence rate between 8%–12%. Several editorials, comments, short reviews described the weaknesses (lack of confirmation of proteinuria, and of chronicity of decreased estimated glomerular filtration rate) of a substantial number of studies and the irrational of using a single arbitrary set point, i.e. diagnosis of chronic kidney disease whenever the estimated glomerular filtration rate is less than 60mL/min/1.73m2. Maremar (Maladies rénales chroniques au Maroc) is a prevalence study of chronic kidney disease, hypertension, diabetes and obesity in a randomized, representative, high response rate (85%), sample of the adult population of Morocco, strictly applying the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Compared to the vast majority of the available studies, Maremar has a low prevalence of chronic kidney disease (2.9% adjusted to the actual adult population of Morocco). The population pyramid, and particularly the confirmation of proteinuria and “chronicity” of the decreased estimated glomerular filtration rate are the main reasons for this low prevalence of chronic kidney disease. The choice of arbitrary single threshold of estimated glomerular filtration rate for classifying stage 3–5 chronic kidney disease inevitably leads to “over-diagnosis” (false positives) of the disease in the elderly, particularly those without proteinuria, hematuria or hypertension, and to “under-diagnosed” (false negatives) in younger individuals with an estimated glomerular filtration rate above 60mL/min/1.73m2 and below the 3rd percentile of their age/gender category. There is an urgent need for quality studies using in a correct way the recent KDIGO guidelines when investigating the prevalence of chronic kidney disease, in order to avoid a 50 to 100% overestimation of a disease state with potential dramatic consequences. The combination of the general population screening encompassing four different major health problems in the same screening procedure, using the correct methodologies and procedures, combined with a prevention/follow-up program results in a clinically/scientifically relevant program.

A simple approach to calculate active power of electrosurgical units

Introduction: Despite of more than a hundred years of electrosurgery, only a few electrosurgical equipment manufacturers have developed methods to regulate the active power delivered to the patient, usually around an arbitrary setpoint. In fact, no manufacturer has a method to measure the active power actually delivered to the load. Measuring the delivered power and computing it fast enough so as to avoid injury to the organic tissue is challenging. If voltage and current signals can be sampled in time and discretized in the frequency domain, a simple and very fast multiplication process can be used to determine the active power. Methods This paper presents an approach for measuring active power at the output power stage of electrosurgical units with mathematical shortcuts based on a simple multiplication procedure of discretized variables – frequency domain vectors – obtained through Discrete Fourier Transform (DFT) applied on time-sampled voltage and current vectors. Results Comparative results between simulations and a practical experiment are presented – all being in accordance with the requirements of the applicable industry standards. Conclusion An analysis is presented comparing the active power analytically obtained through well-known voltage and current signals against a computational methodology based on vector manipulation using DFT only for time-to-frequency domain transformation. The greatest advantage of this method is to determine the active power of noisy and phased out signals with neither complex DFT or ordinary transform methodologies nor sophisticated computing techniques such as convolution. All results presented errors substantially lower than the thresholds defined by the applicable standards.

A cryogenic tensile testing apparatus for micro-samples cooled by miniature pulse tube cryocooler

This paper introduces a cryogenic tensile testing apparatus for micro-samples cooled by a miniature pulse tube cryocooler. At present, tensile tests are widely applied to measure the mechanical properties of materials; most of the cryogenic tensile testing apparatus are designed for samples with standard sizes, while for non-standard size samples, especially for microsamples, the tensile testing cannot be conducted. The general approach to cool down the specimens for tensile testing is by using of liquid nitrogen or liquid helium, which is not convenient: it is difficult to keep the temperature of the specimens at an arbitrary set point precisely, besides, in some occasions, liquid nitrogen, especially liquid helium, is not easily available. To overcome these limitations, a cryogenic tensile testing apparatus cooled by a high frequency pulse tube cryocooler has been designed, built and tested. The operating temperatures of the developed tensile testing apparatus cover from 20 K to room temperature with a controlling precision of ±10 mK. The apparatus configurations, the methods of operation and some cooling performance will be described in this paper.

Long-Term Efficacy and Safety of Single-Agent Ibrutinib at 3 Years Follow-up in Patients With Chronic Lymphocytic Leukemia/Small Lymphocytic Leukemia (CLL/SLL)

S206 (21%) and 17pdel in 8 (12.9%) cases. The median time to first treatment was 22.8 months. We analyzed OS using 20 months as an arbitrary set point to stratify patients based on our calculated median time to treatment. The median OS for patients requiring treatment before 20 months vs. patients treated after 20 months were 7.8 and 12.1 years, respectively (p1⁄40.014). Chi square analysis revealed that NOTCH1 and trisomy 12 were associated with patients requiring treatment before 20 months (p1⁄40.028 and p1⁄40.015, respectively). There was no correlation among TP53 mutation (p1⁄40.52) and 17p deletion (p1⁄40.522) with requiring early treatment. Median OS of patients with mutated NOTCH1 vs. wild type NOTCH1 was 11 years and 15.7 years, respectively (p1⁄40.334). Conclusion: In our study, we showed the association of NOTCH1 mutations with earlier need for treatment (<20 months) and that time to first treatment did correlate with a statistically significant 35.5% reduction in OS. Independent of time to treatment, patients with mutated NOTCH1 had a shorter median OS; however this was not statistically significant. Prospective studies will be important to determine the impact of NOTCH1 in patients with high-risk CLL.

Activity and Tolerability of Ibrutinib in Combination With Ofatumumab in Patients With Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL/SLL)

S206 (21%) and 17pdel in 8 (12.9%) cases. The median time to first treatment was 22.8 months. We analyzed OS using 20 months as an arbitrary set point to stratify patients based on our calculated median time to treatment. The median OS for patients requiring treatment before 20 months vs. patients treated after 20 months were 7.8 and 12.1 years, respectively (p1⁄40.014). Chi square analysis revealed that NOTCH1 and trisomy 12 were associated with patients requiring treatment before 20 months (p1⁄40.028 and p1⁄40.015, respectively). There was no correlation among TP53 mutation (p1⁄40.52) and 17p deletion (p1⁄40.522) with requiring early treatment. Median OS of patients with mutated NOTCH1 vs. wild type NOTCH1 was 11 years and 15.7 years, respectively (p1⁄40.334). Conclusion: In our study, we showed the association of NOTCH1 mutations with earlier need for treatment (<20 months) and that time to first treatment did correlate with a statistically significant 35.5% reduction in OS. Independent of time to treatment, patients with mutated NOTCH1 had a shorter median OS; however this was not statistically significant. Prospective studies will be important to determine the impact of NOTCH1 in patients with high-risk CLL.

Decentralized Control of Cooperative Robotic Systems for Arbitrary Setpoint Tracking while Avoiding Collisions

Decentralized control strategies for multi-robot systems have been extensively studied in the literature, with the aim of regulating the overall state of the system to some desired configuration. Recently a few works have appeared that propose methodologies for solving more complex problems: in particular, partitioning of the multi-robot system into two subgroups can be exploited for cooperatively tracking arbitrarily defined setpoint functions. Specifically, a small number of independent robots can be exploited for controlling the overall state of the dependent robots. Based on this formulation, in this paper we exploit the null space based behavioral approach to obtain setpoint tracking for a multi-robot system, while avoiding inter-robot collisions.

Self-oscillating chaotic behavior and induced oscillations of a continuous stirred tank reactor with nonlinear control

We analyze the dynamical properties of a continuous stirred tank reactor (CSTR) to produce propylene glycol from propylene oxide with an excess of water containing sulfur acid and methanol assuming an exothermic pseudo-first order reaction. The self-oscillation behavior is briefly treated, and when this state is achieved, it is shown that a sinusoidal variation of the reactor coolant flow rate may produce chaotic behavior. The chaotic oscillations are researched from the bifurcation diagrams, whereas sensitive dependence, Lyapunov exponents and power spectral density and surrogate computations allow to corroborate the presence of chaos. The chaotic behavior is used in connection with a nonlinear control law (based on differential geometry methods) which is applied to reach an arbitrary set point with very small control signals, even in the presence of random noise. On the basis of the nonlinear control law, new control signals are deduced to obtain induced oscillations both in the concentration and reactor temperature. In this case two new dynamical behaviors have been obtained by means of two different strategies: choosing an oscillation frequency with arbitrary amplitude or choosing the amplitude with arbitrary frequency.

Set-point variation in learning schemes with applications to wafer scanners

This paper presents a finite impulse response strategy to deal with set-point variation in learning schemes. On the basis of converged learning forces obtained with learning control at a specific acceleration set-point profile, a finite impulse response mapping is derived to generalize the learned forces at a specific set-point toward arbitrary set-point profiles, thus relaxing the need for further learning. The above strategy is applied to the motion control systems of a wafer scanner in a multi-input multi-output feed-forward setting, where a variety of set-point profiles is used. Industrial potential is demonstrated via robustness to set-point variation and the improvements obtained in settling-time reduction.

Closed - Loop Identification of a Laboratory Chemical Reactor

This paper deals with temperature stabilisation of a laboratory continuous stirred tank reactor. In this paper, the modified iterative scheme of system identification and control design is combined. Based on identification, the feedback controller is designed, which stabilises the reactor at an arbitrary set point in spite of uncertainties on the kinetics.

Robust PI stabilization of a class of chemical reactors

The aim of this letter is to study the stabilization of a class of continuous-stirred tank reactors in the face of control input saturations and uncertain chemical kinetics. A first-order compensator with modeling error compensation is designed, and its ability to stabilize the reactor temperature at an arbitrary setpoint is proven. It is shown that the resulting controller is equivalent to a standard PI compensator with antireset windup scheme.

Robust PI stabilization of a class of continuously stirred‐tank reactors

AbstractThis article deals with the stabilization of continuously stirred‐tank reactors in the face of control input saturations and uncertain chemical kinetics. Using ideas from modeling‐error compensation techniques, a first‐order compensator is designed, and its ability to stabilize the reactor temperature at an arbitrary setpoint is shown. The dynamic part of the proposed controller is interpreted as a type of robust integral action to accommodate the modeling error.

Global attitude/position regulation for underwater vehicles

In this paper a nonlinear controller is designed for a 6 DOF model of an unmanned underwater vehicle (UUV) which includes both the kinematics and the dynamics. It is shown how the use of a Lyapunov function,consisting of aquadraticterm in the velocity (both linear and angular), a quadratic term in the position and a logarithmic term in the attitude leads to a design of a control law that achieves global asymptotic stabilization to an arbitrary set point in position/attitude. The control law is made linearly bounded by avoiding cancellation of some of the quadratic nonlinearities in the model. No information about the inertia matrix, thedamping,and the Coriolis/centripetal parameters is used in the controller, endowing it with a certain amount of parametric robustness. The control law is given in terms of the Modified Rodrigues parameters. An extensive simulation study shows that the proposed control law achieves excellent tracking for slowly changing trajectories, even though it is designed only for set point regulation. The nonlinear controller dramatically outperforms a liner controller.

Robust feedback stabilization of chemical reactors

This paper deals with the temperature stabilization of a large class of continuously stirred tank chemical reactors. We design state feedback controllers, and we show their ability to globally stabilize the temperature at an arbitrary set point in spite of uncertainties on the kinetics. Furthermore, it is also shown that these controllers can handle input constraints along the closed-loop trajectories in some instances. For the implementation purpose, we design a robust state observer for the case of partial state measurement, and we prove that its incorporation in the feedback loops does not impair the nominal stabilization properties of the controllers.