Little finitistic dimensions and generalized derived categories

In this paper, we introduced a generalization of a derived category, which is called $n$-derived category and denoted by $D_{n}(R)$, of a given ring $R$ for each $n\in\mathbb{N}\cup\{\infty\}$. The $n$-derived category of a ring is proved to be very closely connected with its left little finitistic dimension. We also introduce and investigate the notions of $n$-exact sequences, $n$-projective (resp., $n$-injective) modules and $n$-exact complexes. In particular, we characterize the left little finitistic dimensions in terms of all above notions. Besides, the $n$-global dimension $n$-gldim$(R)$ of $R$ is introduced and investigated. Finally, we build a connection of the classical derived categories and $n$-derived categories

Online Muscle Activation Onset Detection Using Likelihood of Conditional Heteroskedasticity of Electromyography Signals

Surface electromyography (sEMG) signals are crucial in developing human-machine interfaces, as they contain rich information about human neuromuscular activities. &lt;italic&gt;Objective:&lt;/italic&gt; The real-time, accurate detection of muscle activation onset (MAO) is significant for EMG-triggered control strategies in embedded applications like prostheses and exoskeletons. &lt;italic&gt;Methods:&lt;/italic&gt; This paper investigates sEMG signals using the generalized autoregressive conditional heteroskedasticity (GARCH) model, focusing on variance. A novel feature, the likelihood of conditional heteroskedasticity (LCH) extracted from the maximum likelihood estimation of GARCH parameters, is proposed. This feature effectively distinguishes signal from noise based on heteroskedasticity, allowing for the detection of MAO through the LCH feature and a basic threshold classifier. For online calculation, the model parameter estimation is simplified, enabling direct calculation of the LCH value using fixed parameters. &lt;italic&gt;Results:&lt;/italic&gt; The proposed method was validated on two open-source datasets and demonstrated superior performance over existing methods. The mean absolute error of onset detection, compared with visual detection results, is approximately 65 ms under online conditions, showcasing high accuracy, universality, and noise insensitivity. &lt;italic&gt;Conclusion:&lt;/italic&gt; The results indicate that the proposed method using the LCH feature from the GARCH model is highly effective for real-time detection of muscle activation onset in sEMG signals. &lt;italic&gt;Significance:&lt;/italic&gt; This novel approach shows great potential and possibility for real-world applications, reflecting its superior performance in accuracy, universality, and insensitivity to noise.</p

Augmentation of neovascularization in murine hindlimb ischemia by combined therapy with simvastatin and bone marrow-derived mesenchymal stem cells transplantation

<p>Abstract</p> <p>Objectives</p> <p>We postulated that combining high-dose simvastatin with bone marrow derived-mesenchymal stem cells (MSCs) delivery may give better prognosis in a mouse hindlimb ischemia model.</p> <p>Methods</p> <p>Mouse hindlimb ischemia model was established by ligating the right femoral artery. Animals were grouped (n = 10) to receive local injection of saline without cells (control and simvastatin groups) or with 5 × 10⁶MSCs (MSCs group).Animals received either simvastatin (20 mg/kg/d, simvastatin and combination groups) or saline(control and MSCs group) gavages for continual 21 days. The blood flow was assessed by laser Doppler imaging at day 0,10 and 21 after surgery, respectively. Ischemic muscle was harvested for immunohistological assessments and for VEGF protein detection using western blot assay at 21 days post-surgery. In vitro, MSCs viability was measured by MTT and flow cytometry following culture in serum-free medium for 24 h with or without simvastatin. Release of VEGF by MSCs incubated with different doses of simvastatin was assayed using ELISA.</p> <p>Results</p> <p>Combined treatment with simvastatin and MSCs induced a significant improvement in blood reperfusion, a notable increase in capillary density, a highest level of VEGF protein and a significant decrease in muscle cell apoptosis compared with other groups. In vitro, simvastatin inhibited MSCs apoptosis and increased VEGF release by MSCs.</p> <p>Conclusions</p> <p>Combination therapy with high-dose simvastatin and bone marrow-derived MSCs would augment functional neovascularization in a mouse model of hindlimb ischemia.</p

Use of Nanoindentation and Silviscan to Determine the Mechanical Properties of 10 Hardwood Species

The objectives of this study were to investigate the properties of bulk wood and cell walls of 10 hardwoods, Alder Birch (Betula spp.), Asian White Birch (Betula platyphylla spp.), Manchurian Ash (Fraxinus mandshurica spp.), Mongolian Oak (Quercus spp.), Poplar (Populus spp.), Red Oak (Quercus spp), White Oak (Quercus spp.), Iroko (Chlorophora excelsa spp.), Keranji (Dialium spp.), and Kwila (Intsia spp.). The relationship between wood species and mechanical properties as well as the relativity of wood species and microfibril angle to the hardness and elastic modulus were investigated. It showed that lower density hardwoods had higher microfibril angle than higher density hardwoods. The elastic moduli of bulk wood and cell walls of wood were both significantly different, whereas the hardness of the cell wall was not significantly different among the 10 species. The SilviScan elastic modulus increased with wood density and decreased with microfibril angle. At the cell wall level, the elastic modulus and hardness obtained by nanoindentation were more related to the properties of natural libriform fibers. However, there was no significant trend found for the hardness of the cell wall as affected by either wood bulk density or microfibril angle