Chronic Exposure to Altered Gravity During the Pregnancy-to-Lactation Transition Affects Abundance of Cytoskeletal Proteins in the Rat Mammary Gland

The mammogenic, lactogenic, and lactopoetic effects of prolactin (PRL) in the mammary gland are mediated through a specific cytokine receptor, the PRL-receptor (PRLR). PRLR is anchored to the cytoskeleton and its activation, and subsequent signal transduction, is dependent on an integral/intact cytoskeletal organization. Previous studies revealed a down-regulation of PRLR and reduced metabolic output in the mammary gland of rats exposed to hypergravity (HG). Therefore, the objective of this study was to use quantitative immunohistochemistry to determine the effects of HG exposure during pregnancy on the pre- and postpartum abundance of the cytoskeletal proteins in the rat mammary gland. Pregnant rats were exposed to either 2xg [HG] or 1xg [Stationary control (SC)] from days 11 to 20 of gestation (G20) through postpartum days 1 (P1) and 3 (P3). Spectral characterization and quantitation of each antigen (actin, tubulin, cytokeratin, and vimentin) per lobule (n=3–7 lobules/micrograph; 4 micrographs/slide) was computed using the CRi Nuance multispectral system. At G20 and P3, increased (p<0.001) amounts of actin, tubulin, cytokeratin, and vimentin were detected in HG rats. Tubulin, cytokeratin, and vimentin were overexpressed (p<0.01) in HG group compared to SC at P1. These results suggest that atypical composition of cytoskeletal proteins contribute to the aberrant lactogenic signal transduction and associated reduced postpartum mammary metabolic output in rats exposed to altered inertial environment.

Suppression of Cross-Well Oscillations for Bistable Composites Through Potential Well Elimination

Although there have been numerous efforts into harnessing the snap through dynamics of bistable structures with piezoelectric transducers to achieve large energy conversion, these same dynamics are undesirable under morphing applications where stationary control of the structure’s configuration is paramount. To suppress cross-well vibrations that primarily result from periodic excitation at low frequencies, a novel control strategy is proposed and implemented on the piezoelectrically generated bistable laminate, which consists of only macro fiber composites (MFCs) in a [0MFC/90MFC]T layup. While under cross-well regimes such as subharmonic, chaotic, or limit cycle oscillations, a single MFC is actuated to the laminate’s limit voltage to eliminate one of its potential wells and force it into the remaining stable state. Simultaneously, a positive position feedback (PPF) controller suppresses the resulting single-well oscillations through the other MFC. This dual control strategy is numerically and experimentally demonstrated through the suppression of various cross-well regimes and results in significant reduction of amplitude. The active control capability of the laminate prevents snap through instability when under large enough external vibrations.

Identification of Linear Time-Varying Parameters of Nonstationary Systems

The paper considers the identification algorithm for unknown parameters of linear non-stationary control objects. It is assumed that only the object output variable and the control signal are measured (but not their derivatives or state variables) and unknown parameters are linear functions or their derivatives are piecewise constant signals. The derivatives of non-stationary parameters are supposed to be unknown constant numbers on some time interval. This assumption for unknown parameters is not mathematical abstraction because in most electromechanical systems parameters are changing during the operation. For example, the resistance of the rotor is linearly changing, because the resistance of the rotor depends on the temperature changes of the electric motor in operation mode. This paper proposes an iterative algorithm for parameterization of the linear non-stationary control object using stable LTI filters. The algorithm leads to a linear regression model, which includes time-varying and constant (at a certain time interval) unknown parameters. For this model, the dynamic regressor extension and mixing (DREM) procedure is applied. If the persistent excitation condition holds, then, in the case the derivative of each parameter is constant on the whole time interval, DREM provides the convergence of the estimates of configurable parameters to their true values. In the case of a finite time interval, the estimates convergence in a certain region. Unlike well-known gradient approaches, using the method of dynamic regressor extension and mixing allows to improve the convergence speed and accuracy of the estimates to their true values by increasing the coefficients of the algorithm. Additionally, the method of dynamic regressor extension and mixing ensures the monotony of the processes, and this can be useful for many technical problems.

Suppression of Cross-Well Oscillations With Active Control of a Bistable Laminate

Although there have been numerous efforts into harnessing the snap through dynamics of bistable structures with piezoelectric transducers to achieve large energy conversion, these same dynamics are undesirable under morphing applications where stationary control of the structure’s configuration is paramount. To suppress cross-well vibrations that primarily result from periodic excitation at low frequencies, a novel control strategy is proposed and implemented on the piezoelectrically generated bistable laminate, which consists of only Macro Fiber Composites (MFC) in a [0MFC/90MFC]T layup. While under cross-well regimes such as chaotic or limit cycle oscillations, a single MFC is actuated past the laminate’s limit voltage to eliminate one of its potential wells and force it into the remaining stable state. Simultaneously, a Positive Position Feedback (PPF) controller suppresses the resulting single-well oscillations through the other MFC. This dual control strategy is demonstrated with an electromechanical model through the suppression of various cross-well regimes, and results in significant reduction of amplitude. The active control capability of the laminate prevents snap through instability when under large enough external vibrations and adds to its multifunctionality along with morphing and broadband energy harvesting.