Proximal Bellman mappings for reinforcement learning and their application to robust adaptive filtering

This paper aims at the algorithmic/theoretical core of reinforcement learning (RL) by introducing the novel class of proximal Bellman mappings. These mappings are defined in reproducing kernel Hilbert spaces (RKHSs), to benefit from the rich approximation properties and inner product of RKHSs, they are shown to belong to the powerful Hilbertian family of (firmly) nonexpansive mappings, regardless of the values of their discount factors, and possess ample degrees of design freedom to even reproduce attributes of the classical Bellman mappings and to pave the way for novel RL designs. An approximate policy-iteration scheme is built on the proposed class of mappings to solve the problem of selecting online, at every time instance, the "optimal" exponent $p$ in a $p$-norm loss to combat outliers in linear adaptive filtering, without training data and any knowledge on the statistical properties of the outliers. Numerical tests on synthetic data showcase the superior performance of the proposed framework over several non-RL and kernel-based RL schemes.Comment: arXiv admin note: text overlap with arXiv:2210.1175

Carrier transport properties of the Group-IV ferromagnetic semiconductor Ge1-xFex with and without boron doping

We have investigated the transport and magnetic properties of group-IV ferromagnetic semiconductor Ge1-xFex films (x = 1.0 and 2.3 %) with and without boron doping grown by molecular beam epitaxy (MBE). In order to accurately measure the transport properties of 100-nm-thick Ge1-xFex films, (001)-oriented silicon-on-insulator (SOI) wafers with an ultra-thin Si body layer (~5 nm) were used as substrates. Owing to the low Fe content, the hole concentration and mobility in the Ge1-xFex films were exactly estimated by Hall measurements because the anomalous Hall effect in these films was found to be negligibly small. By boron doping, we increased the hole concentration in Ge1-xFex from ~1018 cm-3 to ~1020 cm-3 (x = 1.0%) and to ~1019 cm-3 (x = 2.3%), but no correlation was observed between the hole concentration and magnetic properties. This result presents a contrast to the hole-induced ferromagnetism in III-V ferromagnetic semiconductors

Metabolic Profiling of the Cerebrospinal Fluid in Pediatric Epilepsy

To characterize metabolic profiles within the central nervous system in epilepsy, we performed gas chromatography-tandem mass spectrometry (GC-MS/MS)-based metabolome analysis of the cerebrospinal fluid (CSF) in pediatric patients with and without epilepsy. The CSF samples obtained from 64 patients were analyzed by GC-MS/MS. Multivariate analyses were performed for two age groups, 0-5 years of age and 6-17 years of age, to elucidate the effects of epilepsy and antiepileptic drugs on the metabolites. In patients aged 0-5 years (22 patients with epilepsy, 13 without epilepsy), epilepsy patients had reduced 2-ketoglutaric acid and elevated pyridoxamine and tyrosine. In patients aged 6-17 years (12 with epilepsy, 17 without epilepsy), epilepsy patients had reduced 1,5-anhydroglucitol. Valproic acid was associated with elevated 2-aminobutyric acid, 2-ketoisocaproic acid, 4-hydroxyproline, acetylglycine, methionine, N-acetylserine, and serine. Reduced energy metabolism and alteration of vitamin B6 metabolism may play a role in epilepsy in young children. The roles of 1,5-anhydroglucitol in epilepsy in older children and in levetiracetam and zonisamide treatment remain to be explained. Valproic acid influenced the levels of amino acids and related metabolites involved in the metabolism of serine, methionine, and leucine

Vitamin B6 in acute encephalopathy with biphasic seizures and late reduced diffusion

Background The initial presentation of acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is indistinguishable from that of complex febrile seizures (FS), which poses a great diagnostic challenge for clinicians. Excitotoxicity is speculated to be the pathogenesis of AESD. Vitamin B6 (VB6) is essential for the biosynthesis of gamma-aminobutyric acid, an inhibitory neurotransmitter. The aim of this study is to investigate our hypothesis that VB6 deficiency in the brain may play a role in AESD. Methods We obtained cerebrospinal fluid (CSF) samples from pediatric patients with AESD after early seizures and those with FS. We measured pyridoxal 5′-phosphate (PLP) and pyridoxal (PL) concentrations in the CSF samples using high-performance liquid chromatography with fluorescence detection. Results The subjects were 5 patients with AESD and 17 patients with FS. Age did not differ significantly between AESD and FS. In AESD, CSF PLP concentration was marginally lower (p = 0.0999) and the PLP-to-PL ratio was significantly (p = 0.0417) reduced compared to those in FS. Conclusions Although it is impossible to conclude that low PLP concentration and PLP-to-PL ratio are causative of AESD, this may be a risk factor for developing AESD. When combined with other markers, this finding may be useful in distinguishing AESD from FS upon initial presentation

Formation flying along libration point orbits using chattering attenuation sliding mode control

This paper studies a control law to achieve formation flying in cislunar space. Utilizing the eigenstructure of the linearized flow around a libration point of the Earth-Moon circular restricted three-body problem, the fuel efficient formation flying controller based on the chattering attenuation sliding mode controller is designed and analyzed. Numerical studies are conducted for the Earth-Moon L 2 point and a halo orbit around it. The total velocity change required to achieve formation as well as to maintain the orbit is calculated. Simulation results show that the chattering attenuation sliding mode controller has good performance and robustness in the presence of unmodeled nonlinearity along the halo orbit with moderate fuel consumption

Hydrated Seal Lip for Live Center in Machine Tools

When performing a cutting operation, a water-soluble cutting fluid may be used for cooling. Labyrinth and oil seals are commonly used in the rotating centers of machine tools to prevent the cutting fluid and dust from entering the inner parts. However, these seals do not demonstrate adequate functionality in a water-based environment. Therefore, a new rotary shaft seal was devised to separate the water-soluble cutting fluid from interacting with air. The rotary shaft seal was made from polyvinyl formal (PVF). Because PVF is a hydrophilic material, it is expected to provide suitable functionality as a seal in a water-based environment. Performance evaluations of PVF and oil seals were experimentally obtained and compared from the point of view of frictional torque, water-soluble cutting fluid leakage volume, and service life as a seal

Left Atrial Spontaneous Echo Contrast in Hypertrophic Cardiomyopathy with Atrial Fibrillation

Transesophageal echocardiography was performed to assess the incidence of left atrial spontaneous echo contrast in patients with hypertrophic cardiomyopathy, who were divided into two groups according to the presence (group 1-A; 10 patients) or absence (group 1-B; 5 patients) of persistent atrial fibrillation. Twelve patients with atrial fibrillation (group 2) served as control. Among these, 5 patients had mitral regurgitation and 8 patients lone atrial fibrillation. Left atrial spontaneous echo contrast was detected in 8 patients (80%) in group 1-A, none in group 1-B, and 3 patients (25%) in group 2. The incidence of echo contrast in group 1-A was significantly higher than that in the other 2 groups. The size of the left atrium was not statistically different among the 3 groups. Accordingly, hypertrophic cardiomyopathy with atrial fibrillation seemed to be a specific diseased state to favor the development of the left atrial spontaneous echo contrast. Previous reports suggested that the presence of left atrial spontaneous contrast was considered as a warning sign of left atrial thrombus and would be an indicator of increased risk of embolism. 1)2)3) Three of the 8 patients who had spontaneous echo contrast in group 1-A had a history of systemic embolization. We proposed that patients with hypertrophic cardiomyopathy with atrial fibrillation were in a high risk state of thromboembolism