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Erdei, Éva, Pál Pepó, János Csapó, Szilárd Tóth, and Béla Szabó. "Sweet sorghum (Sorghum dochna L.) restorer lines effects on nutritional parameters of stalk juice." Acta Agraria Debreceniensis, no. 36 (November 2, 2009): 51–56. http://dx.doi.org/10.34101/actaagrar/36/2792.
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Sweet sorghum can be utilized for bioethanol production because it has high sugar content (14-17%). We determined the most important nutritional values of 5 silo type sorghum lines in waxy and full maturation. The examined restorer lines were: RL 4, RL 9, RL 15, RL 18, K 1. The following nutritional parameters were examined: dry material content, refractometric total sugar content, reducing sugar content. In waxy maturation 73.85-87.37% of dry matter in stalk juice makes the total sugar. Dry material content, total and reducing sugar content of stalkdecreases from waxy mature to full maturation.There are differences between lines in dry matter (SzD5%=0.76), total sugar (SzD5%=0.79), reducing sugar content (SzD5%=0.30). RL 4 performed a decrease in total sugar content from 10.07% to 10.02% during this period, reducing sugar also decreased from 4.01% to 2.47%. RL 9 performed a decrease in total sugar content from 11.76% to 11.08% during this period. Reducing sugar also decreased from 3.17% to 2.01% in the waxymaturation. RL 15 showed a total sugar content decrease from 15.43 % to 15.36%. The reducing sugar also decreased from 3.23% to 1.71% in waxy maturation. In RL 18 total mean sugar content during waxy maturation was 13.78% which dropped to 13.26% approaching full maturation. Reducing sugar also decreased from 4.11% to 2.23% in waxy mature. K 1 performed a decrease in total sugar content from 9.35% to 6.15% during this period, while reducing sugar also decreased from 1.52% to 0.77%. These lines upcoming for experiments are perspectives since having excellent stalk juice nutritional parameters they are of great or very great height and their stalks are thick-very thick, stalk medullas are wet.
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Wang, Lei, Atsushi Sekimoto, Yuto Takehara, Yasunori Okano, Toru Ujihara, and Sadik Dost. "Optimal Control of SiC Crystal Growth in the RF-TSSG System Using Reinforcement Learning." Crystals 10, no. 9 (September 7, 2020): 791. http://dx.doi.org/10.3390/cryst10090791.
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We have developed a reinforcement learning (RL) model to control the melt flow in the radio frequency (RF) top-seeded solution growth (TSSG) process for growing more uniform SiC crystals with a higher growth rate. In the study, the electromagnetic field (EM) strength is controlled by the RL model to weaken the influence of Marangoni convection. The RL model is trained through a two-dimensional (2D) numerical simulation of the TSSG process. As a result, the growth rate under the control of the RL model is improved significantly. The optimized RF-coil parameters based on the control strategy for the 2D melt flow are used in a three-dimensional (3D) numerical simulation for model validation, which predicts a higher and more uniform growth rate. It is shown that the present RL model can significantly reduce the development cost and offers a useful means of finding the optimal RF-coil parameters.
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Moriyama, Takumi, Ryosuke Koishi, Kouhei Kimura, Satoru Kishida, and Kentaro Kinoshita. "Extraction of Filament Properties in Resistive Random Access Memory (ReRAM) Consisting of Binary-Transition-Metal-Oxides." Advances in Science and Technology 95 (October 2014): 84–90. http://dx.doi.org/10.4028/www.scientific.net/ast.95.84.
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Which parameter dominantly decides the value of time required to reset ReRAM (treset) among possible parameters, the value of a low resistance (RL), voltage to induce reset (Vreset), and temperature to induce reset (Treset)? Although to answer this question is important to achieve faster resistive switching, detailed correlations between the parameters are still unclear. In this paper, we extracted treset, Vreset, RL and Treset at the same time by combining two electrical measurements. As a result, we found a clear correlation between Vreset, RL, and Treset, meaning that each parameter can not be controlled independently. Tresetincreases not only with increasing Vresetbut also with increasing RL, which suggests the necessity of introducing ununiformly-shaped filamens and resistive switching takes place at the narrowing part of the filament.
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Khlebnikova, D. A., A. A. Lobova, O. N. Aladina, and M. Yu Cherednichenko. "The impact of light spectral composition on the in vitro growth of summer savory (Satureja hortensis L.) plants." Vegetable crops of Russia, no. 6 (December 18, 2019): 72–75. http://dx.doi.org/10.18619/2072-9146-2019-6-72-75.
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Relevance. Summer savory (Satureja hortensis L.) is an annual herbaceous plant whose essential oil and extracts are used in medicine, perfumery and the food industry.Methods. The article presents the results of studying the effect of the ratio of blue (BL) and red light (RL) in the total spectrum of LED lamps on the morphometric parameters of plants of summer savory varieties Gnom and Perechny aromat in vitro. For in vitro culture, seeds were sterilized with 5% NaCl solution for 10 minutes, placed in Petri dishes with Murashige and Skoog culture medium (MS). Aseptic seedlings at the age of 4-5 days were transplanted into tubes and transferred to racks with LED lamps (for 28 days): (1) from 1st day to 14th day 100% RL, from the 15th to the 28th day 60% RL, 40% BL; (2) 90% RL, 10% BL; (3) 60% RL and 40% BL; (4) 32% RL and 68% BL. The total illumination intensity in all variants was 175 μmol/m2 s.Results. It was found that a change in the RL:BL ratio in the total spectrum affects the morphometric parameters of the savory plants in an in vitro culture. When cultivated under 100% RL, tall plants with long internodes and small leaves are formed, a reduction in the share of RL to 60...32% results in more short-growing plants with large leaves. The results of this work can be used to develop the technology of clonal micropropagation of valuable breeding forms, as well as to create source material for breeding by in vitro culture methods.
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Lu, Chao, Jie Huang, and Jianwei Gong. "Reinforcement Learning for Ramp Control: An Analysis of Learning Parameters." PROMET - Traffic&Transportation 28, no. 4 (August 31, 2016): 371–81. http://dx.doi.org/10.7307/ptt.v28i4.1830.
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Reinforcement Learning (RL) has been proposed to deal with ramp control problems under dynamic traffic conditions; however, there is a lack of sufficient research on the behaviour and impacts of different learning parameters. This paper describes a ramp control agent based on the RL mechanism and thoroughly analyzed the influence of three learning parameters; namely, learning rate, discount rate and action selection parameter on the algorithm performance. Two indices for the learning speed and convergence stability were used to measure the algorithm performance, based on which a series of simulation-based experiments were designed and conducted by using a macroscopic traffic flow model. Simulation results showed that, compared with the discount rate, the learning rate and action selection parameter made more remarkable impacts on the algorithm performance. Based on the analysis, some suggestionsabout how to select suitable parameter values that can achieve a superior performance were provided.
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Pandit, Paresh B., Kee H. Pyon, Sherry E. Courtney, Sandra E. England, and Robert H. Habib. "Lung resistance and elastance in spontaneously breathing preterm infants: effects of breathing pattern and demographics." Journal of Applied Physiology 88, no. 3 (March 1, 2000): 997–1005. http://dx.doi.org/10.1152/jappl.2000.88.3.997.
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Reported values of lung resistance (Rl) and elastance (El) in spontaneously breathing preterm neonates vary widely. We hypothesized that this variability in lung properties can be largely explained by both inter- and intrasubject variability in breathing pattern and demographics. Thirty-three neonates receiving nasal continuous positive airway pressure [weight 606–1,792 g, gestational age (GA) of 25–33 wk, 2–49 days old] were studied. Transpulmonary pressure was measured by esophageal manometry and airway flow by face mask pneumotachography. Breath-to-breath changes in Rl and El in each infant were estimated by Fourier analysis of impedance (Z) and by multiple linear regression (MLR). Rl MLR (Rl MLR = 0.85 × Rl Z −0.43; r 2= 0.95) and El MLR(El MLR = 0.97 × El Z + 8.4; r 2 = 0.98) were highly correlated to Rl Z and El Z, respectively. Both Rl(mean ± SD; Rl Z = 70 ± 38, Rl MLR = 59 ± 36 cmH2O ⋅ s ⋅ l−1) and El (El Z = 434 ± 212, El MLR = 436 ± 210 cmH2O/l) exhibited wide intra- and intersubject variability. Regardless of computation method, Rl was found to decrease as a function of weight, age, respiratory rate (RR), and tidal volume (Vt) whereas it increased as a function of RR ⋅ Vt and inspiratory-to-expiratory time ratio (Ti/Te). El decreased with increasing weight, age, Vt and female gender and increased as RR and Ti/Te increased. We conclude that accounting for the effects of breathing pattern variability and demographic parameters on estimates of Rland El is essential if they are to be of clinical value. Multivariate statistical models of Rl and Elmay facilitate the interpretation of lung mechanics measurements in spontaneously breathing infants.
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Generoso, Tarcila N., Mauro A. Martinez, Genelício C. Rocha, and Paulo J. Hamakawa. "Water magnetization and phosphorus transport parameters in the soil." Revista Brasileira de Engenharia Agrícola e Ambiental 21, no. 1 (January 2017): 9–13. http://dx.doi.org/10.1590/1807-1929/agriambi.v21n1p9-13.
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ABSTRACT There are scientific studies describing changes in properties of the water when subjected to the action of a magnetic field, which may favor the availability of some nutrients in the soil solution. Some nutrients, although they are essential to the process of crop development, can be sources of pollution for watercourses and soil. The aim of this study was to evaluate the effect of water magnetization on transport parameters of the phosphate ion in a Red Latosol (RL) and in a Quartzarenic Neosol (QN). Saturated leaching columns were connected to bottles containing KH2PO4 solutions. In RL, there were significant differences in phosphorus (P) transport parameters, related to the retardation factor (R) and distribution coefficient (Kd). For the others, Peclet number (Pe), dispersive-diffusion coefficient (D) and dispersivity (λ), there were no significant differences in the comparison between the treatments with magnetized and non-magnetized water. In QN, there were statistical differences in R and Kd. For the other parameters, Pe, D and λ, there were no statistical differences between treatments.
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Kerger, H., A. G. Tsai, D. J. Saltzman, R. M. Winslow, and M. Intaglietta. "Fluid resuscitation with O2 vs. non-O2 carriers after 2 h of hemorrhagic shock in conscious hamsters." American Journal of Physiology-Heart and Circulatory Physiology 272, no. 1 (January 1, 1997): H525—H537. http://dx.doi.org/10.1152/ajpheart.1997.272.1.h525.
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Efficacy of a cell-free o-raffinose cross-linked and oligomerized hemoglobin (Hemo-link) solution in restoring macro- and microcirculatory conditions after 2 h of hemorrhagic shock (40 mmHg) was compared with conventional treatment with autologous whole blood, Ringer lactate (RL), and Dextran 70. Studies were conducted in the dorsal skinfold microcirculation of conscious hamsters. Initial infusion was equivalent to shed blood volume (SBV) for RL and 50% of SBV for remaining solutions. After 2 h all animals received blood at 50% of SBV. Vessel diameter, functional capillary density, microvascular red blood cell velocity, and flow were measured. Arteriolar, venular, and tissue PO2 were determined by phosphorescence decay. Systemic parameters included mean arterial blood pressure, heart rate, arterial blood gases, pH, and base excess. Autologous whole blood and Hemolink, but not Dextran 70 and RL, restored mean arterial blood pressure, systemic blood gas, and metabolic parameters. Tissue PO2 recovered to 40–50% with blood and Hemolink but remained significantly lower (10-15% of control) with Dextran 70 and RL. Initial volume replacement after shock with blood or Hemolink yields equivalent macro- and microhemodynamic improvements not attainable with non-O2-carrying plasma expanders.
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Al-Rawi, Hasan A. A., Kok-Lim Alvin Yau, Hafizal Mohamad, Nordin Ramli, and Wahidah Hashim. "Reinforcement Learning for Routing in Cognitive Radio Ad Hoc Networks." Scientific World Journal 2014 (2014): 1–22. http://dx.doi.org/10.1155/2014/960584.
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Cognitive radio (CR) enables unlicensed users (or secondary users, SUs) to sense for and exploit underutilized licensed spectrum owned by the licensed users (or primary users, PUs). Reinforcement learning (RL) is an artificial intelligence approach that enables a node to observe, learn, and make appropriate decisions on action selection in order to maximize network performance. Routing enables a source node to search for a least-cost route to its destination node. While there have been increasing efforts to enhance the traditional RL approach for routing in wireless networks, this research area remains largely unexplored in the domain of routing in CR networks. This paper applies RL in routing and investigates the effects of various features of RL (i.e., reward function, exploitation, and exploration, as well as learning rate) through simulation. New approaches and recommendations are proposed to enhance the features in order to improve the network performance brought about by RL to routing. Simulation results show that the RL parameters of the reward function, exploitation, and exploration, as well as learning rate, must be well regulated, and the new approaches proposed in this paper improves SUs’ network performance without significantly jeopardizing PUs’ network performance, specifically SUs’ interference to PUs.
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Wu, Kunlin, Ding Zhang, Minghua Liu, Qi Lin, and Bing-Chiuan Shiu. "A Study on the Improvement of Using Raw Lacquer and Electrospinning on Properties of PVP Nanofilms." Nanomaterials 10, no. 9 (August 31, 2020): 1723. http://dx.doi.org/10.3390/nano10091723.
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Raw lacquer (RL), ethanol being used as the solvent, was added to polyvinyl pyrrolidone (PVP) and then electrospun into RL/PVP nanofilms. Manufacturing parameters such as RL/PVP ratio, voltage, flow velocity, needle type, and the distance between syringe and the collection board were systematically investigated. A scanning electronic microscope (SEM) was used to observe the surface morphology of nanofilms; the block drop method was used to measure the water contact angle; the mechanical properties of RL/PVP nanofilms of different proportions were tested by universal material testing machine; and Fourier-transform infrared spectroscopy (FT-IR) was used to characterize the structure. Based on the water resistance and acid resistance measurements, the proposed nanofilms demonstrated to be water and acid resistant were successfully produced. The results show that PVP that melts in water becomes incompatible with water after adding raw lacquer, and the acid resistance is greatly improved. Furthermore, the smaller the fiber diameter, the better the mechanical properties of the nanofilms are under low ratio of RL/PVP. With a high proportion of RL/PVP, the inner structure of the nanofilm is denser, and the water resistance and acid resistance are better. The dense structure can protect the inner material of the nanofilms.
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Vieira, Jairo V., Giovani Olegario da Silva, and Leonardo S. Boiteux. "Genetic parameter and correlation estimates of processing traits in half-sib progenies of tropical-adapted carrot germplasm." Horticultura Brasileira 30, no. 1 (March 2012): 7–11. http://dx.doi.org/10.1590/s0102-05362012000100002.
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The estimate of the genetic parameters associated with processing (fresh-cut) traits, including root length (RL), is crucial for carrot breeding programs in tropical areas. The cultivar Alvorada is an important germplasm due to its resistance to nematodes, leaf blight, heat-tolerance, and high carotenoid content. Seventy-four 'Alvorada' half-sib progenies were evaluated during the summer of 2005 in the Federal District, Brazil, in a randomized complete block design with three replications. Thirteen competitive plants in each block were randomly selected and evaluated and/or classified for RL and for number of leaves (NL), leaf length (LL), root tip type (RT), root mass (RW), crown shape (CS), root diameter (RD), and xylem diameter (XD). The Pearson's correlation coefficients and the heritability values were estimated for all traits. The path analysis was also used considering the RL trait as dependent variable. The heritability for RL ranged from 12 to 44%. For the other traits, the values ranged from 3% (RD) to 79% (LL). Phenotypic and genotypic correlations among all traits were low to intermediate. Path analysis indicated positive direct relationship between RL and RW, whereas RD and XD displayed negative direct effect on RL. Longer roots had narrow diameter and narrow XD. Recurrent selection based upon either half-sib or S1 families would be more effective than mass phenotypic recurrent selection in increasing RL and to develop populations expressing multiple desirable processing traits in tropical-adapted carrot germplasm.
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Vaishnav, Avani S., Philip Saville, Steven McAnany, Sertac Kirnaz, Christoph Wipplinger, Rodrigo Navarro-Ramirez, Roger Hartl, Jingyan Yang, Catherine Himo Gang, and Sheeraz A. Qureshi. "Retrospective Review of Immediate Restoration of Lordosis in Single-Level Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Comparison of Static and Expandable Interbody Cages." Operative Neurosurgery 18, no. 5 (August 23, 2019): 518–23. http://dx.doi.org/10.1093/ons/opz240.
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Abstract BACKGROUND Sagittal alignment is an important consideration in spine surgery. The literature is conflicted regarding the effect of minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) on sagittal parameters and the role of expandable cage technology. OBJECTIVE To compare lordosis generated by static and expandable cages and to determine what factors affect postoperative sagittal parameters. METHODS Preoperative regional lordosis (RL), segmental lordosis (SL), and posterior disc height (PDH) were compared to postoperative values in single-level MI-TLIF performed using expandable or static cages. Patients were stratified based on preoperative SL: low lordosis (<15 degrees), moderate lordosis (15-25 degrees), and high lordosis (>25 degrees). Regression analyses were conducted to determine factors associated with postoperative SL and PDH. RESULTS Of the 171 patients included, 111 were in the static and 60 in the expandable cohorts. Patients with low preoperative lordosis experienced an increase in SL and maintained RL regardless of cage type. Those with moderate to high preoperative lordosis experienced a decrease in SL and RL with the static cage, but maintained SL and RL with the expandable cage. Although both cohorts showed an increase in PDH, the increase in the expandable cohort was greater. Preoperative SL was predictive of postoperative SL; preoperative SL, preoperative PDH, and cage type were predictive of postoperative PDH. CONCLUSION Expandable cages showed favorable results in restoring disc height and maintaining lordosis in the immediate postoperative period. Preoperative SL was the most significant predictor of postoperative SL. Thus, preoperative radiographic parameters and goals of surgery should be important considerations in surgical planning.
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Yasuda, Toshiyuki, Kousuke Araki, and Kazuhiro Ohkura. "Improving the Robustness of Instance-Based Reinforcement Learning Robots by Metalearning." Journal of Advanced Computational Intelligence and Intelligent Informatics 15, no. 8 (October 20, 2011): 1065–72. http://dx.doi.org/10.20965/jaciii.2011.p1065.
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Learning autonomous robots have been widely discussed in recent years. Reinforcement learning (RL) is a popular method in this domain. However, its performance is quite sensitive to the segmentation of state and action spaces. To overcome this problem, we developed the new technique Bayesian-discriminationfunction-based RL (BRL). BRL has proven to be more effective than other standard RL algorithms in dealing withmulti-robot system(MRS) problems. However, as in most learning systems, occasional overfitting problems occur in BRL. This paper introduces an extended BRL for improving the robustness of MRSs. Metalearning based on the information entropy of fired rules is adopted for adaptive modification of its learning parameters. Computer simulations are conducted to verify the effectiveness of our proposed method.
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Farnoosh, R., P. Nabati, and A. Hajirajabi. "Parameters estimation for RL electrical circuits based on least square and Bayesian approach." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 31, no. 6 (November 9, 2012): 1711–25. http://dx.doi.org/10.1108/03321641211267083.
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Farnoosh, Rahman, and Arezoo Hajrajabi. "Estimation of parameters in the state space model of stochastic RL electrical circuit." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 32, no. 3 (May 3, 2013): 1082–97. http://dx.doi.org/10.1108/03321641311306141.
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Pinto, Simone de Souza, and Mirabel Cerqueira Rezende. "Electromagnetic, Morphological, and Electrical Characterization of POMA/Carbon Nanotubes-Based Composites." Journal of Nanomaterials 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/1989785.
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This study involves the preparation of conducting composites based on poly(o-methoxyaniline) (POMA) and carbon nanotubes (CNT) and the evaluation of them as radar absorbing materials (RAM), in the frequency range of 8.2–12.4 GHz (X-band). The composites were obtained by synthesis in situ of POMA in the presence of CNT (0.1 and 0.5 wt% in relation to the o-methoxyaniline monomer). The resulting samples—POMA/CNT-0.1 wt% and POMA/CNT-0.5 wt%—were incorporated in an epoxy resin matrix in the proportion of 1 and 10 wt%. FT-IR analyses show that the POMA was successfully synthesized on the CNT surface. SEM analyses show that the synthesized POMA recovered all CNT surface. Electrical conductivity measurements show that the CNT contributed to increase the conductivity of POMA/CNT composites (1.5–6.7 S·cm−1) in relation to the neat POMA (5.4 × 10−1 S·cm−1). The electromagnetic characterization involved the measurements of complex parameters of electrical permittivity (ε) and magnetic permeability (µ), using a waveguide in the X-band. From these experimental data reflection loss (RL) simulations were performed for specimens with different thicknesses. The complex parameters show that the CNT in the composites increased ε and µ. These results are attributed to the CNT network formation into the composites. Simulated RL curves of neat POMA and POMA/CNT in epoxy resin show the preponderant influence of POMA on all RL curves. This behavior is attributed to the efficient CNT recovering by POMA. RL results show that the composite based on 10 wt% of POMA/CNT-0.5 wt% in epoxy resin (9 mm thickness) presents the best RL results (≈87% of attenuation at 12.4 GHz).
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Park, Jungyong, Haesang Yang, Woojae Seong, and Youngmin Choo. "Reverberation Level Modeling via Coupled Mode Approach in Shallow-Water Sound Channel with Internal Solitary Waves." Journal of Theoretical and Computational Acoustics 27, no. 04 (October 31, 2018): 1850045. http://dx.doi.org/10.1142/s2591728518500457.
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Reverberation level (RL) is modeled in a shallow water environment with an underwater sound channel and internal solitary wave (ISW) using the coupled mode method. Numerical RL result based on one-way coupled mode shows an abnormal increase when a source is located near the channel axis and the ISW is located far from the source. The abnormal increase is analyzed by using a two-mode approach (assuming a trapped mode and a bottom interacting mode). The two-mode approach explains the relation between the RL increase and the ISW location explicitly: the ISW transfers trapped mode energy to bottom interacting mode energy, and its increasing rate is a function of its modal attenuation and ISW location from the source. The sensitivity test according to several ISW parameters is also performed.
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Salmi, Abdelaziz, Lahbib Bousshine, and Khaled Lahlou. "Two unbound granular materials stiffness analysis with staged repeated load CBR test." MATEC Web of Conferences 286 (2019): 06003. http://dx.doi.org/10.1051/matecconf/201928606003.
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Design methods of flexible pavements in many countries are based on linear elastic behaviour model for Unbound Granular Materials (UGM). In this context, parameters required to characterize an UGM in structural analysis of pavements are Stiffness modulus and Poisson ratio (E and ν). This paper presents a study of two UGM stiffness. Finite element simulation of repeated load CBR (RL-CBR) test has allowed to derive equation used in calculation of materials equivalent modulus based on laboratory RL-CBR Outputs. The staged RL-CBR test is used to evaluate material stiffness for different stress states to highlight its influence on UGM stiffness and compare studied materials. Also, this paper shows that even if two materials are different according to the current road authority specifications, they can represent similar stiffness.
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Belhaj, Fatima Zahra, Hassan El Fadil, Zakariae El Idrissi, Abdessamad Intidam, Mohamed Koundi, and Fouad Giri. "New Equivalent Electrical Model of a Fuel Cell and Comparative Study of Several Existing Models with Experimental Data from the PEMFC Nexa 1200 W." Micromachines 12, no. 9 (August 30, 2021): 1047. http://dx.doi.org/10.3390/mi12091047.
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The present work investigates different models of polymer electrolyte membrane fuel cell. More specifically, three models are studied: a nonlinear state-space model, a generic dynamic model integrated into MATLAB/Simulink, and an equivalent RC electrical circuit. A new equivalent electrical RL model is proposed, and the methodology for determining its parameters is also given. An experimental test bench, based on a 1200-W commercial PEMFC, is built to compare the static and dynamic behaviour of the existing models and the proposed RL model with the experimental data. The comparative analysis highlights the advantages and drawbacks of each of these models. The major advantages of the proposed RL model lie in both its simplicity and its ability to provide a similar transitory behaviour compared to the commercially manufactured PEMFC employed in this research.
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Bauman, David R., Stephan Steckelbroeck, Michelle V. Williams, Donna M. Peehl, and Trevor M. Penning. "Identification of the Major Oxidative 3α-Hydroxysteroid Dehydrogenase in Human Prostate That Converts 5α-Androstane-3α,17β-diol to 5α-Dihydrotestosterone: A Potential Therapeutic Target for Androgen-Dependent Disease." Molecular Endocrinology 20, no. 2 (February 1, 2006): 444–58. http://dx.doi.org/10.1210/me.2005-0287.
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Abstract Androgen-dependent prostate diseases initially require 5α-dihydrotestosterone (DHT) for growth. The DHT product 5α-androstane-3α,17β-diol (3α-diol), is inactive at the androgen receptor (AR), but induces prostate growth, suggesting that an oxidative 3α-hydroxysteroid dehydrogenase (HSD) exists. Candidate enzymes that posses 3α-HSD activity are type 3 3α-HSD (AKR1C2), 11-cis retinol dehydrogenase (RODH 5), L-3-hydroxyacyl coenzyme A dehydrogenase , RODH like 3α-HSD (RL-HSD), novel type of human microsomal 3α-HSD, and retinol dehydrogenase 4 (RODH 4). In mammalian transfection studies all enzymes except AKR1C2 oxidized 3α-diol back to DHT where RODH 5, RODH 4, and RL-HSD were the most efficient. AKR1C2 catalyzed the reduction of DHT to 3α-diol, suggesting that its role is to eliminate DHT. Steady-state kinetic parameters indicated that RODH 4 and RL-HSD were high-affinity, low-capacity enzymes whereas RODH 5 was a low-affinity, high-capacity enzyme. AR-dependent reporter gene assays showed that RL-HSD, RODH 5, and RODH 4 shifted the dose-response curve for 3α-diol a 100-fold, yielding EC50 values of 2.5 × 10−9m, 1.5 × 10−9m, and 1.0 × 10−9m, respectively, when compared with the empty vector (EC50 = 1.9 × 10−7m). Real-time RT-PCR indicated that L-3-hydroxyacyl coenzyme A dehydrogenase and RL-HSD were expressed more than 15-fold higher compared with the other candidate oxidative enzymes in human prostate and that RL-HSD and AR were colocalized in primary prostate stromal cells. The data show that the major oxidative 3α-HSD in normal human prostate is RL-HSD and may be a new therapeutic target for treating prostate diseases.
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Schwarze, J., E. Hamelmann, and E. W. Gelfand. "Barometric whole body plethysmography in mice." Journal of Applied Physiology 98, no. 5 (May 2005): 1955–57. http://dx.doi.org/10.1152/japplphysiol.01279.2004.
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There has been significant utilization of the technique described by Hamelmann et al. ( Am J Respir Crit Care Med 156: 766–775, 1997) in which a parameter, enhanced pause (Penh), related to airways responsiveness is noninvasively measured by unrestrained plethysmography (UP). Investigating this technique, we sought to answer these questions: 1) How do changes in Penh compare with changes in traditional plethysmographic and lung mechanical parameters? 2) How do UP parameters perform in two different mouse strains? Awake immunized and control BALB/c ( n = 16) and C57BL/6 ( n = 14) mice were placed in the UP chamber and exposed to doses of aerosolized methacholine while the following parameters were measured at each concentration: inspiratory time (Ti), expiratory time (Te), total time (Ttot), Ti/Ttot, peak inspiratory pressure, peak expiratory pressure, Pause, Penh, tidal volume (Vt), Vt/Ti, Vt/Te, and Vt/Ttot. The next day, lung resistance (Rl) and compliance (Cl) were invasively measured in the same animals. For the BALB/c, the parameters with the highest magnitude of correlation coefficient vs. Rl are (in order) 1) Cl, 2) Pause and Penh, 3) parameters of breathing frequency (Te, Ttot, Ti), and 4) parameters related to Vt (inspiratory pressure, expiratory pressure). Flow parameters (Vt/Ttot, Vt/Te, Vt/Ti) and duty cycle parameters (Ti/Ttot) had insignificant correlations. This ordering is significantly different in C57BL/6 mice, in which the parameters with the largest correlations are 1) Cl, 2) parameters of breathing frequency, and 3) flow parameters. Pause, Penh, Vt, and duty cycle parameters had insignificant correlations. These data show that Penh is problematic in the sense that it is strain specific; it behaves very differently in BALB/c and C57BL/6 mice. We suggest that UP parameters largely originate as part of reflex control of breathing processes, rather than in the lung mechanics and conclude that it is inappropriate to use UP parameters in general, and Penh specifically, as substitute variables for invasive mechanical indexes such as Rl.
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Adler, Andy, Greg Cieslewicz, and Charles G. Irvin. "Unrestrained plethysmography is an unreliable measure of airway responsiveness in BALB/c and C57BL/6 mice." Journal of Applied Physiology 97, no. 1 (July 2004): 286–92. http://dx.doi.org/10.1152/japplphysiol.00821.2003.
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There has been significant utilization of the technique described by Hamelmann et al. ( Am J Respir Crit Care Med 156: 766–775, 1997) in which a parameter, enhanced pause (Penh), related to airways responsiveness is noninvasively measured by unrestrained plethysmography (UP). Investigating this technique, we sought to answer these questions: 1) How do changes in Penh compare with changes in traditional plethysmographic and lung mechanical parameters? 2) How do UP parameters perform in two different mouse strains? Awake immunized and control BALB/c ( n = 16) and C57BL/6 ( n = 14) mice were placed in the UP chamber and exposed to doses of aerosolized methacholine while the following parameters were measured at each concentration: inspiratory time (Ti), expiratory time (Te), total time (Ttot), Ti/Ttot, peak inspiratory pressure, peak expiratory pressure, Pause, Penh, tidal volume (Vt), Vt/Ti, Vt/Te, and Vt/Ttot. The next day, lung resistance (Rl) and compliance (Cl) were invasively measured in the same animals. For the BALB/c, the parameters with the highest magnitude of correlation coefficient vs. Rl are (in order) 1) Cl, 2) Pause and Penh, 3) parameters of breathing frequency (Te, Ttot, Ti), and 4) parameters related to Vt (inspiratory pressure, expiratory pressure). Flow parameters (Vt/Ttot, Vt/Te, Vt/Ti) and duty cycle parameters (Ti/Ttot) had insignificant correlations. This ordering is significantly different in C57BL/6 mice, in which the parameters with the largest correlations are 1) Cl, 2) parameters of breathing frequency, and 3) flow parameters. Pause, Penh, Vt, and duty cycle parameters had insignificant correlations. These data show that Penh is problematic in the sense that it is strain specific; it behaves very differently in BALB/c and C57BL/6 mice. We suggest that UP parameters largely originate as part of reflex control of breathing processes, rather than in the lung mechanics and conclude that it is inappropriate to use UP parameters in general, and Penh specifically, as substitute variables for invasive mechanical indexes such as Rl.
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Mousa, Abd Allah A., and Yousria Abo-Elnaga. "Stability of Solutions for Parametric Inverse Nonlinear Cost Transportation Problem." Mathematics 8, no. 11 (November 14, 2020): 2027. http://dx.doi.org/10.3390/math8112027.
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This paper investigates the solution for an inverse of a parametric nonlinear transportation problem, in which, for a certain values of the parameters, the cost of the unit transportation in the basic problem are adapted as little as possible so that the specific feasible alternative become an optimal solution. In addition, a solution stability set of these parameters was investigated to keep the new optimal solution (feasible one) is unchanged. The idea of this study based on using a tuning parameters λ∈Rm in the function of the objective and input parameters υ∈Rl in the set of constraint. The inverse parametric nonlinear cost transportation problem P(λ,υ), where the tuning parameters λ∈Rm in the objective function are tuned (adapted) as less as possible so that the specific feasible solution x∘ has been became the optimal ones for a certain values of υ∈Rl, then, a solution stability set of the parameters was investigated to keep the new optimal solution x∘ unchanged. The proposed method consists of three phases. Firstly, based on the optimality conditions, the parameter λ∈Rm are tuned as less as possible so that the initial feasible solution x∘ has been became new optimal solution. Secondly, using input parameters υ∈Rl resulting problem is reformulated in parametric form P(υ). Finally, based on the stability notions, the availability domain of the input parameters was detected to keep its optimal solution unchanged. Finally, to clarify the effectiveness of the proposed algorithm not only for the inverse transportation problems but also, for the nonlinear programming problems; numerical examples treating the inverse nonlinear programming problem and the inverse transportation problem of minimizing the nonlinear cost functions are presented.
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Liu, Xiongqing, and Yan Jin. "Reinforcement learning-based collision avoidance: impact of reward function and knowledge transfer." Artificial Intelligence for Engineering Design, Analysis and Manufacturing 34, no. 2 (March 16, 2020): 207–22. http://dx.doi.org/10.1017/s0890060420000141.
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AbstractCollision avoidance for robots and vehicles in unpredictable environments is a challenging task. Various control strategies have been developed for the agent (i.e., robots or vehicles) to sense the environment, assess the situation, and select the optimal actions to avoid collision and accomplish its mission. In our research on autonomous ships, we take a machine learning approach to collision avoidance. The lack of available ship steering data of human ship masters has made it necessary to acquire collision avoidance knowledge through reinforcement learning (RL). Given that the learned neural network tends to be a black box, it is desirable that a method is available which can be used to design an agent's behavior so that the desired knowledge can be captured. Furthermore, RL with complex tasks can be either time consuming or unfeasible. A multi-stage learning method is needed in which agents can learn from simple tasks and then transfer their learned knowledge to closely related but more complex tasks. In this paper, we explore the ways of designing agent behaviors through tuning reward functions and devise a transfer RL method for multi-stage knowledge acquisition. The computer simulation-based agent training results have shown that it is important to understand the roles of each component in a reward function and the various design parameters in transfer RL. The settings of these parameters are all dependent on the complexity of the tasks and the similarities between them.
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İlhan, Mustafa, Mete Kaan Ekmekçi, and İlker Çetin Keskin. "Judd–Ofelt parameters and X-ray irradiation results of MNb2O6:Eu3+ (M = Sr, Cd, Ni) phosphors synthesized via a molten salt method." RSC Advances 11, no. 18 (2021): 10451–62. http://dx.doi.org/10.1039/d0ra10834k.
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SHEIKH, NADEEM AHMAD, DENNIS LING CHUAN CHING, SAMI ULLAH, and ILYAS KHAN. "MATHEMATICAL AND STATISTICAL ANALYSIS OF RL AND RC FRACTIONAL-ORDER CIRCUITS." Fractals 28, no. 08 (July 10, 2020): 2040030. http://dx.doi.org/10.1142/s0218348x20400307.
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The RL and RC circuits are analyzed in this research paper. The classical model of these circuits is generalized using the modern concept of fractional derivative with Mittag-Leffler function in its kernel. The fractional differential equations are solved for exact solutions using the Laplace transform technique and the inverse transformation. The obtained solutions are plotted and presented in tables to show the effect of resistance, inductance and fractional parameter on current and voltage. Furthermore, the statistical analysis is presented to predict the seasonal of time and other parameters on the current flowing in the circuit. The statistical analysis shows that the variation in current is insignificant with respect to time and is more significant with respect to other parameters.
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Campos, Sergio, Teresa Cristina Tarle Pissarra, Favia Mazzer Rodrigues, Zacarias Xavier de Barros, and Fernada Leite Ribeiro. "ANÁLISE MULTIVARIADA DE MICROBACIAS EM RELAÇÃO AO TIPO DE SOLO." IRRIGA 15, no. 2 (June 17, 2010): 208–16. http://dx.doi.org/10.15809/irriga.2010v15n2p208.
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Este trabalho teve como objetivo analisar os parâmetros dimensionais da rede de drenagem através de 12 microbacias de 3a ordem de ramificação, sendo 4 microbacias por unidade de solo (LVA, RL e RQ). A distinção dos solos foi realizada através do teste "t" para verificação dos contrastes ortogonais entre as médias dos três solos e da análise de agrupamentos e de componentes principais. Os resultados permitiram concluir que a análise multivariada não foi eficiente na discriminação dos três solos através das variáveis dimensionais. Essas variáveis isoladamente através do teste "t" permitiram uma diferenciação entre o solo RQ e as unidades LVA e RL, porém não foram sensíveis para os solos LVA e RL. UNITERMOS: análise multivariada, agrupamentos, microbacia, solos. S. CAMPOS, S.; PISSARRA, T. C. T.; RODRIGUES, F. M.; BARROS, Z. X. de; RIBEIRO, F. L. WATERSHED MULTIVARIANCE ANALYSIS IN RELATION TO SOIL TYPE 2 ABSTRACT The objective of this work was to study the dimensional parameters of the drainage net using 12 third-order ramification hydrological watersheds: 4 watersheds per soil unit (LVA, RL and RQ). The soil distinction was realized using "t" test to verify the orthogonal contrast among three soil averages and the grouping analysis and mean components. The results showed that the multivariance analysis was not able to discriminate three soils using the dimensional analysis. The "t" test of this isolated variable allowed discriminating RQ soil from LVA and RL soil units; but it was not sensitive to discriminate the LVA soil and RL unit. KEYWORDS: multivariance analysis, grouping, watershed, soil.
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Hooshyar, Milad, S. Jamshid Mousavi, Masoud Mahootchi, and Kumaraswamy Ponnambalam. "Aggregation–Decomposition-Based Multi-Agent Reinforcement Learning for Multi-Reservoir Operations Optimization." Water 12, no. 10 (September 25, 2020): 2688. http://dx.doi.org/10.3390/w12102688.
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Stochastic dynamic programming (SDP) is a widely-used method for reservoir operations optimization under uncertainty but suffers from the dual curses of dimensionality and modeling. Reinforcement learning (RL), a simulation-based stochastic optimization approach, can nullify the curse of modeling that arises from the need for calculating a very large transition probability matrix. RL mitigates the curse of the dimensionality problem, but cannot solve it completely as it remains computationally intensive in complex multi-reservoir systems. This paper presents a multi-agent RL approach combined with an aggregation/decomposition (AD-RL) method for reducing the curse of dimensionality in multi-reservoir operation optimization problems. In this model, each reservoir is individually managed by a specific operator (agent) while co-operating with other agents systematically on finding a near-optimal operating policy for the whole system. Each agent makes a decision (release) based on its current state and the feedback it receives from the states of all upstream and downstream reservoirs. The method, along with an efficient artificial neural network-based robust procedure for the task of tuning Q-learning parameters, has been applied to a real-world five-reservoir problem, i.e., the Parambikulam–Aliyar Project (PAP) in India. We demonstrate that the proposed AD-RL approach helps to derive operating policies that are better than or comparable with the policies obtained by other stochastic optimization methods with less computational burden.
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Pietrzko, Stanislaw, and Qibo Mao. "Reduction of Structural Sound Radiation and Vibration Using Shunt Piezoelectric Materials." Solid State Phenomena 147-149 (January 2009): 882–89. http://dx.doi.org/10.4028/www.scientific.net/ssp.147-149.882.
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In this paper, structural sound and vibration control using passive and semi-active shunt piezoelectric damping circuits is presented. A piezoelectric patch with an electrical shunt circuit is bonded to a base structure. When the structure vibrates, the piezoelectric patch strains and transforms the mechanical energy of the structure into electrical energy, which can be effectively dissipated by the shunt circuit. Hence, the shunt circuit acts as a means of extracting mechanical energy from the base structure. First, different types of shunt circuits (such as RL series circuit, RL parallel circuit and RL-C circuit), employed in the passive damping arrangement, are analyzed and compared. By using the impedance method, the general modelling of different shunt piezoelectric damping techniques is presented. The piezoelectric shunt circuit can be seen as additional frequency-dependence damping of the system. One of the primary concerns in shunt damping is to choose the optimal parameters for shunt circuits. In past efforts most of the proposed tuning methods were based on modal properties of the structure. These methods are used to minimize the response of a particular structural mode whilst neglecting the contribution of the other modes. In this study, a design method based on minimization of the sound power of the structure is proposed. The optimal parameters for shunt circuits are obtained using linear quadratic optimal control theory. In general, the passive shunt circuit techniques are an effective method of modal damping. However, the main drawback of the passive shunt circuit is that the shunt piezoelectric is very sensitive to tuning errors and variations in the excitation frequency. To overcome this problem, the pulse-switching shunt circuit, a semi-active continuous switching technique in which a RL shunt circuit is periodically connected to a bonded piezoelectric patch, is introduced as structural damping. The switch law for pulse-switching circuit is discussed based on the energy dissipation technique. Compared with a standard passive piezoelectric shunt circuit, the advantages of the pulse-switching shunt circuit is a small required shunt inductance, a lower sensitivity to environmental changes and easier tuning. Very low external power for the switch controller is required so it may be possible to extract this energy directly from the vibration of the structure itself. Numerical simulations are performed for each of these shunts techniques focusing on minimizing radiated sound power from a clamped plate. It is found that the RL series, RL parallel and pulse-switching circuits have basically the same control performance. The RL–C parallel circuit allows us to reduce the value of the inductance L due to the insertion of an external capacity C. However, the control performance will be reduced simultaneously. The pulse-switching circuit is more stable than RL series circuit with regard to structural stiffness variations. Finally, experimental results are presented using an RL series/parallel shunt circuit, RL-C parallel shunt circuit and pulse-switching circuit. The experimental results have shown that the vibration and noise radiation of a structure can be reduced significantly by using these shunt circuits. The theoretical and experimental techniques presented in this study provide a valuable tool for effective shunt piezoelectric damping.
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Zaworska-Zakrzewska, Anita, Małgorzata Kasprowicz-Potocka, Robert Mikuła, Marcin Taciak, Ewa Pruszyńska-Oszmałek, and Andrzej Frankiewicz. "Growth Performance, Gut Environment and Physiology of the Gastrointestinal Tract in Weaned Piglets Fed a Diet Supplemented with Raw and Fermented Narrow-Leafed Lupine Seeds." Animals 10, no. 11 (November 10, 2020): 2084. http://dx.doi.org/10.3390/ani10112084.
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The aim of this study was to: (1) provide controlled fermentation of narrow-leafed lupine seeds; (2) monitor seed composition, and (3) determine the influence of fermentation on the performance, gut environment and physiology, and selected blood metabolic parameters, in young pigs. Firstly, the effect of 24 h lupine seed fermentation by bacteria and yeast on seed chemical composition was determined. It increased contents of crude protein, crude fiber and ash, but reduced nitrogen-free extractive levels. The amino acid profile of fermented lupine (FL) was similar to that of raw lupine (RL) seeds, whereas the contents of oligosaccharides and P-phytate decreased significantly, in contrast to alkaloids. In fermented feed, pH dropped from 5.5 to 3.9. In the 28-day experiment, 24 male pigs were divided into three groups. The control group was fed a soybean meal diet (SBM), whereas in the experimental diets, 50% of SBM protein was replaced by RL or FL. Afterwards, eight pigs from each group were euthanized and their digesta and blood samples were collected. The FL use did not affect pigs’ performance, nor their metabolic, microbial and most gastrointestinal tract parameters, but influenced crypt depth. Fermentation affected concentrations of short chain fatty acids and p-cresole in the proximal colon segment. In the small intestine, the levels of acetate and butyrate decreased, and, in the caecum, the propionate level decreased. Fermentation significantly lowered the pH of the middle colon digesta and ammonia contents compared to RL. A part of SBM may be successfully replaced by RL and FL in young pigs’ diets.
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Cyprych, Konrad, and Lech Sznitko. "Tailoring the Random Lasing Properties by Controlled Phase Separation Process in PMMA:PVK Dye-Doped Polymeric Blends." Polymers 13, no. 18 (September 19, 2021): 3182. http://dx.doi.org/10.3390/polym13183182.
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This article describes the random lasing (RL) phenomenon obtained in a dye-doped, polymeric double-phase system composed of PMMA and PVK polymers. It shows how relative concentrations between mentioned macromolecules can influence lasing parameters of the resulting blends, including obtained emission spectra and threshold conditions. We describe the influence of lasers’ composition on their morphologies and link them with particular RL properties. Our studies reveal that the disorder caused by phase separation can support the RL phenomenon both in the waveguiding and quasi-waveguiding regimes. Changing the relative concentration of polymers enables one to switch between both regimes, which significantly influences threshold conditions, spectral shift, number of lasing modes, and ability to support extended and/or localized modes. Finally, we show that a simple phase separation technique can be used to fabricate efficient materials for RL. Moreover, it enables the tailoring of lasing properties of materials in a relatively wide range at the stage of the laser material fabrication process in a simple way. Therefore, this technique can be seen as a fast, cheap, and easy to perform way of random lasers fabrication.
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Vuga, Rok, Bojan Nemec, and Aleš Ude. "Speed adaptation for self-improvement of skills learned from user demonstrations." Robotica 34, no. 12 (June 15, 2015): 2806–22. http://dx.doi.org/10.1017/s0263574715000405.
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SUMMARYThe paper addresses the problem of speed adaptation of movements subject to environmental constraints. Our approach relies on a novel formulation of velocity profiles as an extension of dynamic movement primitives (DMP). The framework allows for compact representation of non-uniformly accelerated motion as well as simple modulation of the movement parameters. In the paper, we evaluate two model free methods by which optimal parameters can be obtained: iterative learning control (ILC) and policy search based reinforcement learning (RL). The applicability of each method is discussed and evaluated on two distinct cases, which are hard to model using standard techniques. The first deals with hard contacts with the environment while the second process involves liquid dynamics. We find ILC to be very efficient in cases where task parameters can be easily described with an error function. On the other hand, RL has stronger convergence properties and can therefore provide a solution in the general case.
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Khairy, Sami, Ruslan Shaydulin, Lukasz Cincio, Yuri Alexeev, and Prasanna Balaprakash. "Learning to Optimize Variational Quantum Circuits to Solve Combinatorial Problems." Proceedings of the AAAI Conference on Artificial Intelligence 34, no. 03 (April 3, 2020): 2367–75. http://dx.doi.org/10.1609/aaai.v34i03.5616.
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Quantum computing is a computational paradigm with the potential to outperform classical methods for a variety of problems. Proposed recently, the Quantum Approximate Optimization Algorithm (QAOA) is considered as one of the leading candidates for demonstrating quantum advantage in the near term. QAOA is a variational hybrid quantum-classical algorithm for approximately solving combinatorial optimization problems. The quality of the solution obtained by QAOA for a given problem instance depends on the performance of the classical optimizer used to optimize the variational parameters. In this paper, we formulate the problem of finding optimal QAOA parameters as a learning task in which the knowledge gained from solving training instances can be leveraged to find high-quality solutions for unseen test instances. To this end, we develop two machine-learning-based approaches. Our first approach adopts a reinforcement learning (RL) framework to learn a policy network to optimize QAOA circuits. Our second approach adopts a kernel density estimation (KDE) technique to learn a generative model of optimal QAOA parameters. In both approaches, the training procedure is performed on small-sized problem instances that can be simulated on a classical computer; yet the learned RL policy and the generative model can be used to efficiently solve larger problems. Extensive simulations using the IBM Qiskit Aer quantum circuit simulator demonstrate that our proposed RL- and KDE-based approaches reduce the optimality gap by factors up to 30.15 when compared with other commonly used off-the-shelf optimizers.
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Kodikara, Iroshani, Dhanusha T. K. Gamage, Ganananda Nanayakkara, and Isurani Ilayperuma. "Diagnostic performance of renal ultrasonography in detecting chronic kidney disease of various severity." Asian Biomedicine 14, no. 5 (October 31, 2020): 195–202. http://dx.doi.org/10.1515/abm-2020-0028.
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AbstractBackgroundAssociation between early diagnosis of chronic kidney disease (CKD) and low morbidity and mortality rate has been proven. Thus, tools for early CKD diagnosis are vital. Ultrasonography has been widely used to diagnose and monitor the progression of CKD.ObjectivesTo determine the performance of selected renal ultrasonographic parameters for the diagnosis of early CKD.MethodsIn a cohort of patients diagnosed with CKD (n = 100), diagnostic performance of ultrasonographically measured renal length (RL), renal cortical thickness (RCT), and parenchymal thickness (PT) was determined using receiver operating curve analysis; correlation of each parameter with the associated comorbidities and serum creatinine (Scr) levels was also determined. Severity of CKD was graded with estimated glomerular filtration rates (eGFR).ResultsOf all patient participants, 85 had severity grades 2 or 3. Mean (standard deviation) Scr was 1.88 (0.60) mg/dL; eGFR was 43.3 (11.85) mL/min/1.73 m2. RL was 9.01 (0.83) cm, PT was 1.32 (0.22) cm, and RCT was 6.0 (0.10) mm. PT and RCT were positively correlated with eGFR (P = 0.01 and 0.002, respectively). Early CKD was better predicted by PT (area under the curve (AUC) 0.735; 82% sensitivity; 30% specificity; 68% positive predictive value (PPV)) and RCT (AUC 0.741; 82% sensitivity; 48% specificity; 51% PPV); severe CKD was better predicted by RL (AUC 0.809; 67% sensitivity; 26% specificity, 45% PPV; 13% negative predictive value).ConclusionIndex ultrasonic parameters show a diagnostic role in different stages of CKD. The index ultrasound and biochemical parameters showed a complementary role in predicting renal dysfunction.
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Hu, Dada, Zhongcai Pei, and Zhiyong Tang. "Single-Parameter-Tuned Attitude Control for Quadrotor with Unknown Disturbance." Applied Sciences 10, no. 16 (August 11, 2020): 5564. http://dx.doi.org/10.3390/app10165564.
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In this paper, methods are presented for designing a quadrotor attitude control system with disturbance rejection ability, wherein only one parameter needs to be tuned for each axis. The core difference between quadrotor platforms are extracted as critical gain parameters (CGPs). Reinforcement learning (RL) technology is introduced in order to automatically optimize the controlling law for quadrotors with different CGPs, and the CGPs are used to extend the RL state list. A deterministic policy gradient (DPG) algorithm that is based on an actor-critic structure in a model-free style is used as the learning algorithm. Mirror sampling and reward shaping methods are designed in order to eliminate the steady-state errors of the RL controller and accelerate the training process. Active disturbance rejection control (ADRC) is applied to reject unknown external disturbances. A set of extended state observers (ESOs) is designed to estimate the total disturbance to the roll and pitch axes. The covariance matrix adaptation evolution strategy (CMA-ES) algorithm is used to automatically tune the ESO parameters and improve the final performance. The complete controller is tested on an F550 quadrotor in both simulation and real flight environments. The quadrotor can hover and move around stably and accurately in the air, even with a severe disturbance.
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Militani, Davi Ribeiro, Hermes Pimenta de Moraes, Renata Lopes Rosa, Lunchakorn Wuttisittikulkij, Miguel Arjona Ramírez, and Demóstenes Zegarra Rodríguez. "Enhanced Routing Algorithm Based on Reinforcement Machine Learning—A Case of VoIP Service." Sensors 21, no. 2 (January 12, 2021): 504. http://dx.doi.org/10.3390/s21020504.
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The routing algorithm is one of the main factors that directly impact on network performance. However, conventional routing algorithms do not consider the network data history, for instances, overloaded paths or equipment faults. It is expected that routing algorithms based on machine learning present advantages using that network data. Nevertheless, in a routing algorithm based on reinforcement learning (RL) technique, additional control message headers could be required. In this context, this research presents an enhanced routing protocol based on RL, named e-RLRP, in which the overhead is reduced. Specifically, a dynamic adjustment in the Hello message interval is implemented to compensate the overhead generated by the use of RL. Different network scenarios with variable number of nodes, routes, traffic flows and degree of mobility are implemented, in which network parameters, such as packet loss, delay, throughput and overhead are obtained. Additionally, a Voice-over-IP (VoIP) communication scenario is implemented, in which the E-model algorithm is used to predict the communication quality. For performance comparison, the OLSR, BATMAN and RLRP protocols are used. Experimental results show that the e-RLRP reduces network overhead compared to RLRP, and overcomes in most cases all of these protocols, considering both network parameters and VoIP quality.
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Nowshiravan Rahatabad, Fereidoun. "Modeling and Control Human Arm With FuzzyGenetic Muscle Model Based on Reinforcement Learning: The Muscle Activation Method." International Clinical Neuroscience Journal 7, no. 3 (June 21, 2020): 138–46. http://dx.doi.org/10.34172/icnj.2020.15.
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Background: The central nervous system (CNS) is optimizing arm movements to reduce some kind of cost function. Simulating parts of the nervous system is one way of obtaining accurate information about the neurological and treatment of neuromuscular diseases. The primary purpose of this paper is to model and control the human arm in a reaching movement based on reinforcement learning (RL) theory. Methods: First, Zajac’s muscle model has improved by a fuzzy system. Second, the proposed muscle model applied to the 6 muscles, which are responsible for a two-link arm that moves in the horizontal plane. Third, the model parameters are approximated based on the genetic algorithm (GA). Experimental data recorded from healthy subjects for assessing the approach. At last, the RL algorithm has utilized to guide the arm for reaching tasks. Results: The results show that: (1) The proposed system is temporally similar to a real arm movement. (2) The RL algorithm can generate the motor commands obtained from electromyographies (EMGs). (3) The similarity of obtained activation function from the system has compared with the real data activation function, which may prove the possibility of RL in the CNS (basal ganglia). Finally, in order to have a graphical and effective representation of the arm model, the virtual reality environment of MATLAB has been used. Conclusion: Since the RL method is a representative of the brain’s control function, it has some features, such as better settling time, not having any peek overshoot, and robustness.
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Knap, P. W. "Time trends of Gompertz growth parameters in ‘meat-type’ pigs." Animal Science 70, no. 1 (February 2000): 39–49. http://dx.doi.org/10.1017/s1357729800051584.
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AbstractPreviously published data from serial slaughter trials on growing pigs of five genotypes were reanalysed. Gompertz curves were fitted to body protein and lipid mass in order to estimate mature protein and lipid mass (P∞,L∞) and the rate parameter (BGompJ that was presumed to be equal for the protein and lipid curves.L∞was expressed as its ratio toP∞, RL∞P∞. The maximum rate of protein deposition was derived as Pdep,max= P∞X BGomp/e. The analysed data encompass body weights of 10 to 133 kg, 13 to 217 kg, 18 to 106 kg, 20 to 110 kg and 11 to 145 kg. The Gompertz function fitted all data sets well, as judged by the standard deviations and distribution patterns of the residual terms. Autocorrelations among the residuals were non-significant.Averaged over sexes (females and entire and castrated males), the P estimates were all close to 31 kg; the RL∞/P∞estmates ranged from 1·4 to 4·7 kg/kg; the BGompestimates ranged from 0·009 to 0·017 kg/day per kg. The resulting Pdep,max estimates ranged from 110 to 193 g/day. The genotypes were placed in 1969, 1976, 1984, 1990 and 1993. Plotting the estimates against time (year) showed distinct time trends for all parameters except P∞. RL∞/P∞seems to gradually reach a plateau around unity, whereas BGompand Pdep/max increase linearly. These trends were confirmed by an analysis of body weight based on the same data plus data on three other genotypes that spanned the same time period. Analyses of the same protein and lipid data to fit a sigmoid growth function with a flexible point of inflexion did not change the apparently absent time trend of F. The estimates of the inflexion points of the fitted protein accretion curves, expressed as proportions ofF, were indistinguishable from the fixed 0·368 value of the Gompertz function for the earliest three genotypes and then showed a tendency to increase, up to 0·46 for the 1993 population. These time trends must be the consequence of a combination of changes in nutritional and other environmental factors and genetic changes. They cannot be the sole result of within-line selection for growth and body composition traits, since this should increase P∞. It seems as if pig breeders have repeatedly initiated their sire lines from genetic resources with small mature size, to subsequently increase this trait as an indirect result of within-line selection.
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Mosavi, Amirhosein, Yaser Faghan, Pedram Ghamisi, Puhong Duan, Sina Faizollahzadeh Ardabili, Ely Salwana, and Shahab S. Band. "Comprehensive Review of Deep Reinforcement Learning Methods and Applications in Economics." Mathematics 8, no. 10 (September 23, 2020): 1640. http://dx.doi.org/10.3390/math8101640.
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The popularity of deep reinforcement learning (DRL) applications in economics has increased exponentially. DRL, through a wide range of capabilities from reinforcement learning (RL) to deep learning (DL), offers vast opportunities for handling sophisticated dynamic economics systems. DRL is characterized by scalability with the potential to be applied to high-dimensional problems in conjunction with noisy and nonlinear patterns of economic data. In this paper, we initially consider a brief review of DL, RL, and deep RL methods in diverse applications in economics, providing an in-depth insight into the state-of-the-art. Furthermore, the architecture of DRL applied to economic applications is investigated in order to highlight the complexity, robustness, accuracy, performance, computational tasks, risk constraints, and profitability. The survey results indicate that DRL can provide better performance and higher efficiency as compared to the traditional algorithms while facing real economic problems in the presence of risk parameters and the ever-increasing uncertainties.
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Adams, Rick A., Michael Moutoussis, Matthew M. Nour, Tarik Dahoun, Declan Lewis, Benjamin Illingworth, Mattia Veronese, et al. "Variability in Action Selection Relates to Striatal Dopamine 2/3 Receptor Availability in Humans: A PET Neuroimaging Study Using Reinforcement Learning and Active Inference Models." Cerebral Cortex 30, no. 6 (February 21, 2020): 3573–89. http://dx.doi.org/10.1093/cercor/bhz327.
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Abstract Choosing actions that result in advantageous outcomes is a fundamental function of nervous systems. All computational decision-making models contain a mechanism that controls the variability of (or confidence in) action selection, but its neural implementation is unclear—especially in humans. We investigated this mechanism using two influential decision-making frameworks: active inference (AI) and reinforcement learning (RL). In AI, the precision (inverse variance) of beliefs about policies controls action selection variability—similar to decision ‘noise’ parameters in RL—and is thought to be encoded by striatal dopamine signaling. We tested this hypothesis by administering a ‘go/no-go’ task to 75 healthy participants, and measuring striatal dopamine 2/3 receptor (D2/3R) availability in a subset (n = 25) using [11C]-(+)-PHNO positron emission tomography. In behavioral model comparison, RL performed best across the whole group but AI performed best in participants performing above chance levels. Limbic striatal D2/3R availability had linear relationships with AI policy precision (P = 0.029) as well as with RL irreducible decision ‘noise’ (P = 0.020), and this relationship with D2/3R availability was confirmed with a ‘decision stochasticity’ factor that aggregated across both models (P = 0.0006). These findings are consistent with occupancy of inhibitory striatal D2/3Rs decreasing the variability of action selection in humans.
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Bennett, R. A., P. C. Colony, J. L. Addison, and D. E. Rannels. "Effects of prior adrenalectomy on postpneumonectomy lung growth in the rat." American Journal of Physiology-Endocrinology and Metabolism 248, no. 1 (January 1, 1985): E70—E74. http://dx.doi.org/10.1152/ajpendo.1985.248.1.e70.
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The effects of adrenalectomy, with and without subsequent glucocorticoid replacement therapy, on postpneumonectomy compensatory lung growth in the rat were investigated. Male Sprague-Dawley rats (200-230 g) were subjected to no operation (UNOP), left pneumonectomy (PNX), or PNX preceded by bilateral adrenalectomy 5 days earlier (ADX/PNX). At 14 days post-PNX, when compensatory lung growth is normally complete in 200-g rats, right lung (RL) dry weights of PNX (263 +/- 6 mg, n = 26) and ADX/PNX (334 +/- 13 mg, n = 25) rats were increased 58 and 101%, respectively, relative to UNOP controls (166 +/- 5 mg, n = 10). Increases in total DNA, RNA, and protein in the right lungs of PNX and ADX/PNX rats occurred in proportion to RL dry mass. The increase in all parameters examined in PNX and ADX/PNX rats at 7 days post-PNX was half that at 14 days, indicating linear lung growth in both treatment groups. The stimulatory effect of ADX on lung growth was blocked by hydrocortisone acetate (HCA), administered intraperitoneally in daily doses of 5 mg/kg, beginning on the day of PNX. The RL dry weights of HCA-treated ADX/PNX rats (241 +/- 7 mg, n = 10) did not differ significantly from the corresponding value in PNX rats (270 +/- 14 mg, n = 7). The lower RL weights in the HCA-treated rats resulted from an inhibition of cell division, as evidenced by the total RL DNA content, which was similar to that in PNX animals.(ABSTRACT TRUNCATED AT 250 WORDS)
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Baier, H., L. Yerger, R. Moas, and A. Wanner. "Vascular and airway effects of endogenous cyclooxygenase products during lung inflation." Journal of Applied Physiology 59, no. 3 (September 1, 1985): 884–89. http://dx.doi.org/10.1152/jappl.1985.59.3.884.
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The influence of lung inflation on lung elasticity and pulmonary resistance (RL) and on pulmonary and bronchial hemodynamics was examined in five anesthetized, mechanically ventilated adult sheep before and after treatment with the cyclooxygenase inhibitor indomethacin (2 mg/kg). Lung inflation was accomplished by increasing levels of positive end-expiratory pressure (PEEP). Measurements of pulmonary vascular resistance (PVR), bronchial blood flow (Qbr), and RL were obtained with a Swan-Ganz catheter, with an electromagnetic flow probe placed around the carinal artery, and by relating airflow to transpulmonary pressure (Ptp), respectively. Before indomethacin, increasing PEEP from 5 to 15 cmH2O increased mean lung volume (VL) to 135% (P less than 0.01), Ptp to 165% (P less than 0.005), and PVR to 132% (P less than 0.05) of base line and decreased mean Qbr (normalized for cardiac output) to 53% (P less than 0.05) of base line. Mean RL showed a tendency to decrease with a mean value of 67% of base line at 15 cmH2O PEEP. After indomethacin the corresponding values were 121% for VL, 155% for Ptp, 124% for PVR, 35% for Qbr, and 31% for RL. The PEEP-dependent changes were not different before and after indomethacin except for mean VL, which increased less (P less than 0.05) after indomethacin. The failure of indomethacin to modify PEEP-induced changes in RL, PVR, and Qbr was also present when these parameters were expressed as a function of Ptp. These findings suggest that the cyclooxygenase products elaborated during lung inflation reduce lung elasticity but fail to influence airflow resistance and pulmonary and bronchial hemodynamics.
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You, Ha Na, Myeong Ja Kwak, Sun Mi Je, Jong Kyu Lee, Yea Ji Lim, Handong Kim, Sanghee Park, Su Gyeong Jeong, Yun Soo Choi, and Su Young Woo. "Morpho-Physio-Biochemical Attributes of Roadside Trees as Potential Tools for Biomonitoring of Air Quality and Environmental Health in Urban Areas." Land 10, no. 3 (February 25, 2021): 236. http://dx.doi.org/10.3390/land10030236.
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Environmental pollution is an important issue in metropolitan areas, and roadside trees are directly affected by various sources of pollution to which they exhibit numerous responses. The aim of the present study was to identify morpho-physio-biochemical attributes of maidenhair tree (Ginkgo biloba L.) and American sycamore (Platanus occidentalis L.) growing under two different air quality conditions (roadside with high air pollution, RH and roadside with low air pollution, RL) and to assess the possibility of using their physiological and biochemical parameters as biomonitoring tools in urban areas. The results showed that the photosynthetic rate, photosynthetic nitrogen-use efficiencies, and photochromic contents were generally low in RH in both G. biloba and P. occidentalis. However, water-use efficiency and leaf temperature showed high values in RH trees. Among biochemical parameters, in G. biloba, the lipid peroxide content was higher in RH than in RL trees, but in P. occidentalis, this content was lower in RH than in RL trees. In both species, physiological activities were low in trees planted in areas with high levels of air pollution, whereas their biochemical and morphological variables showed different responses to air pollution. Thus, we concluded that it is possible to determine species-specific physiological variables affected by regional differences of air pollution in urban areas, and these findings may be helpful for monitoring air quality and environmental health using trees.
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Li, Xin, Chuan Zhi Zang, Xiao Ning Qin, Yang Zhang, and Dan Yu. "Hierarchical Simulated Annealing-Reinforcement Learning Energy Management for Smart Grids." Advanced Materials Research 805-806 (September 2013): 1206–9. http://dx.doi.org/10.4028/www.scientific.net/amr.805-806.1206.
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For energy management problems in smart grid, a hybrid intelligent hierarchical controller based on simulated annealing (SA) and reinforcement learning (RL) is proposed. The SA is used to adjust the parameters of the controller. The RL algorithm shows the particular superiority, which is independent of the mathematic model and just needs simple fuzzy information obtained through trial-and-error and interaction with the environment. By means of learning procedures, the proposed controller can learn to take the best actions to regulate the energy usage for equipments with the features of high comfortable for energy usage and low electric charge meanwhile. Simulation results show that the proposed load controller can promote the performance energy usage in smart grids.
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Li, Xin, Dan Yu, and Chuan Zhi Zang. "Genetic Based Reinforcement Learning Load Control for Smart Grids." Advanced Materials Research 860-863 (December 2013): 2423–26. http://dx.doi.org/10.4028/www.scientific.net/amr.860-863.2423.
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As the improvement of smart grids, the customer participation has reinvigorated interest in demand-side features such as load control for domestic users. A genetic based reinforcement learning (RL) load controller is proposed. The genetic is used to adjust the parameters of the controller. The RL algorithm, which is independent of the mathematic model, shows the particular superiority in load control. By means of learning procedures, the proposed controller can learn to take the best actions to regulate the energy usage for equipments with the features of high comfortable for energy usage and low electric charge meanwhile. Simulation results show that the proposed load controller can promote the performance energy usage in smart grids.
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RAHATABAD, FEREYDOON NOWSHIRAVAN, ALI FALLAH, and AMIR HOMAYOUN JAFARI. "A STUDY OF CHAOTIC PHENOMENA IN HUMAN-LIKE REACHING MOVEMENTS." International Journal of Bifurcation and Chaos 21, no. 11 (November 2011): 3293–303. http://dx.doi.org/10.1142/s0218127411030532.
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In this paper, the feasibility of observing chaotic behavior in the model of a human arm is discussed. Two-Link Arm driven by Six Muscles (TLASM) which is a well-known model of planar human arm reaching movements in the horizontal plane is investigated. Reinforcement learning (RL) that is considered as a model for Dopamine-based learning in the brain is used to control the TLSAM. Finally, the existence of chaos phenomena in the TLASM model controlled with RL is researched using tools like bifurcation maps, Lyapunov exponents, phase-plane trajectories, and spectral analysis using FFT. Results yield that chaos phenomena may occur in the overall system by changing some internal parameters of muscles that have a physiological explanation.
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Elkner, Timothy E., J. A. Barden, M. M. Kushad, and D. D. Wolf. "EFFECTS OF FRUIT AND GIRDLING ON GAS EXCHANGE, SPECIFIC LEAF WEIGHT, WATER POTENTIAL, AND CARBOHYDRATE CONTENT OF APPLE LEAVES." HortScience 25, no. 9 (September 1990): 1166a—1166. http://dx.doi.org/10.21273/hortsci.25.9.1166a.
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Fruiting spurs (`Red Prince Delicious') (RD) and shoots (`Sundale Spur Golden Delicious') (CD) with three leaf:fruit ratios and comparable nonfruiting spurs and shoots were girdled on 7 September 1988. An interaction between fruiting status and time existed for most parameters measured on both cultivars while there was no effect of leaf:fruit ratio. At 1 day after treatment (DAT) few differences existed due to fruiting status on either cultivar. At 8 DAT with RD and at 4 and 8 DAT with GD, Pn, transpiration (Tr), leaf water potential (ψ L), and nonreducing sugars were greater on fruiting than nonfruiting spurs and shoots while leaf resistance (RL), SLW, and starch were lower on fruiting spurs. In nonfruiting spurs and shoots Pn, Tr, and ψL tended to decrease while RL and SLW increased with time whereas m fruiting spurs and shoots most parameters remained constant. Total nonstructural carbohydrates, reducing sugars, and starch were greater in nonfruiting than fruiting spurs and shoots.
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Shan, Yan, Jun Li, Yongshi Wang, Boting Wu, Alex J. Barker, Michael Markl, Chunsheng Wang, Xiaolin Wang, and Xianhong Shu. "Aortic stenosis exacerbates flow aberrations related to the bicuspid aortic valve fusion pattern and the aortopathy phenotype." European Journal of Cardio-Thoracic Surgery 55, no. 3 (September 11, 2018): 534–42. http://dx.doi.org/10.1093/ejcts/ezy308.
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Abstract OBJECTIVES A bicuspid aortic valve (BAV) is characterized by variable phenotypic manifestations, as well as longitudinal evolution of valve dysfunction and ascending aorta dilatation. The present study investigated the impact of severe aortic stenosis (AS) on the flow patterns and wall shear stress (WSS) distribution in BAV patients with right–left (RL) and right-non-coronary (RN) cusp fusion types, and the study aimed to reveal whether aortic dysfunction could further alter intrinsic aortic haemodynamic aberrations generated by abnormal BAV cusp fusion patterns. METHODS Four-dimensional flow magnetic resonance imaging was performed in 120 BAV subjects and 20 tricuspid aortic valve controls. BAV patients were evenly categorized into 4 cohorts, including RL and RN BAV with no more than mild aortic dysfunction as well as RL and RN BAV-AS with isolated severe AS. RESULTS BAV subjects exhibited eccentric outflow jets resulting in regional WSS elevation at the right-anterior position of the ascending aorta in the RL group and the right-posterior location in the RN group (P < 0.005). The presence of severe AS resulted in accelerated outflow jets and more prominent flow and WSS eccentricity (P < 0.005) by marked helical (P = 0.014) and vortical flow formation (P < 0.005), as well as increased prevalence of tubular and transverse arch dilatation. The changes to the flow jet in BAV-AS subjects blurred the differences in peak flow velocity and WSS distribution between RL and RN BAV. Differences in the phenotypes of aortopathy were associated with changes in functional haemodynamic parameters such as flow displacement and WSS eccentricity. CONCLUSIONS Severe AS markedly exacerbated aortic flow aberrations in BAV patients and masked the existing distinct flow features deriving from RL and RN fusion types. Longitudinal studies are needed to investigate the evolution of ascending aortic dilatation relative to the interaction between intrinsic cusp fusion types and acquired severe valve dysfunction.
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Perez, Christian, Felipe Petroski Such, and Theofanis Karaletsos. "Generalized Hidden Parameter MDPs:Transferable Model-Based RL in a Handful of Trials." Proceedings of the AAAI Conference on Artificial Intelligence 34, no. 04 (April 3, 2020): 5403–11. http://dx.doi.org/10.1609/aaai.v34i04.5989.
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There is broad interest in creating RL agents that can solve many (related) tasks and adapt to new tasks and environments after initial training. Model-based RL leverages learned surrogate models that describe dynamics and rewards of individual tasks, such that planning in a good surrogate can lead to good control of the true system. Rather than solving each task individually from scratch, hierarchical models can exploit the fact that tasks are often related by (unobserved) causal factors of variation in order to achieve efficient generalization, as in learning how the mass of an item affects the force required to lift it can generalize to previously unobserved masses. We propose Generalized Hidden Parameter MDPs (GHP-MDPs) that describe a family of MDPs where both dynamics and reward can change as a function of hidden parameters that vary across tasks. The GHP-MDP augments model-based RL with latent variables that capture these hidden parameters, facilitating transfer across tasks. We also explore a variant of the model that incorporates explicit latent structure mirroring the causal factors of variation across tasks (for instance: agent properties, environmental factors, and goals). We experimentally demonstrate state-of-the-art performance and sample-efficiency on a new challenging MuJoCo task using reward and dynamics latent spaces, while beating a previous state-of-the-art baseline with > 10× less data. Using test-time inference of the latent variables, our approach generalizes in a single episode to novel combinations of dynamics and reward, and to novel rewards.
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Kolesnikov, Evgeniy N., Elena Alekseevna Nikipelova, Elena Mikhaylovna Frantsiyants, Larisa Kozlova, Valeria Bandovkina, Irina V. Kaplieva, Lidia K. Trepitaki, et al. "Differences in plasminogen activation in primary rectal adenocarcinoma with and without liver metastasis." Journal of Clinical Oncology 35, no. 15_suppl (May 20, 2017): e15111-e15111. http://dx.doi.org/10.1200/jco.2017.35.15_suppl.e15111.
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e15111 Background: Plasminogen activators play a key role in the cascade fibrinolytic system as they catalyze plasmin formation from plasminogen (PG). Plasminogen activators together with plasmin are directly or indirectly involved in tumor growth. The purpose of the study was to compare the plasminogen activation system in primary adenocarcinomas (РА) of the rectum (R) with and without liver metastases (LM). Methods: Tissues of tumors (РА, st. III, G2, 38-74 years) and their perifocal zone (PZ) with LM (T2-3NхM1, n = 24) and without them (T2-3N0M0, n = 32) were studied by ELISA. Results: The studied parameters did not differ in apparently intact R tissues in the resection line (RL) with and without LM. Plasmin-α2-antiplasmin complex (PAP) was 1.4 times higher in PA with LM than without LM (p < 0.05). Prourokinase and urokinase levels (uPA-Ag and uPA-act) were 12.4 and 3.7 higher than in RL. uPA-Ag and uPA-act in PA+LM were higher than without LM by 1.4 and 1.6 times. PG levels and α2-macroglobulin (α2M) activity in PA+LM were lower by 1.5 and 2.7 times than in PA without LM and lower than in RL (p < 0.01). All studied parameters, except α2M, in PA+LM were activated more than in PA without LM. Low α2M content supposed realization of effects of uPA and plasmin in insufficient inhibitory control. Most parameters in PZ+LM were between the levels in PA and RL being significantly different from both and significantly exceeding the values in PZ of PA without LM. α2М was an exception being 1.8 times lower in PZ of PA+LM than in PZ of PA without LM. The results demonstrated higher uPA and РАР levels in PA and its PZ with LM than without them, with increased PG consumption and decreased α2M activity in these parts of the rectum. Activation of plasminogen system in tissues of PA+LM and in PA without LM was unidirectional. Conclusions: Levels of uPA and PAP, as well as low α2M content in PA and PZ with LM can be used as an indicator of tumor metastatic activity.