Automorphism groups of cubic fivefolds and fourfolds

In this paper, we introduce notions of partitionability and characteristic sets of homogeneous polynomials and give a complete classification of groups faithfully acting on smooth cubic fivefolds. Specifically, we prove that there exist 20 maximal ones among all such groups. As an application, we classify all possible subgroups of the automorphism groups of smooth cubic fourfolds.Comment: 26 page

Sparse general non-negative matrix factorization based on left semi-tensor product

The dimension reduction of large scale high-dimensional data is a challenging task, especially the dimension reduction of face data and the accuracy increment of face recognition in the large scale face recognition system, which may cause large storage space and long recognition time. In order to further reduce the recognition time and the storage space in the large scale face recognition systems, on the basis of the general non-negative matrix factorization based on left semi-tensor (GNMFL) without dimension matching constraints proposed in our previous work, we propose a sparse GNMFL/L (SGNMFL/L) to decompose a large number of face data sets in the large scale face recognition systems, which makes the decomposed base matrix sparser and suppresses the decomposed coefficient matrix. Therefore, the dimension of the basis matrix and the coefficient matrix can be further reduced. Two sets of experiments are conducted to show the effectiveness of the proposed SGNMFL/L on two databases. The experiments are mainly designed to verify the effects of two hyper-parameters on the sparseness of basis matrix factorized by SGNMFL/L, compare the performance of the conventional NMF, sparse NMF (SNMF), GNMFL, and the proposed SGNMFL/L in terms of storage space and time efficiency, and compare their face recognition accuracies with different noises. Both the theoretical derivation and the experimental results show that the proposed SGNMF/L can effectively save the storage space and reduce the computation time while achieving high recognition accuracy and has strong robustness

De acá a la China: análisis de la imagen estereotipada que tienen de Argentina los estudiantes universitarios chinos

A raíz de la profundización de las relaciones entre Argentina y China, y el impulso del aprendizaje del idioma español en la educación superior del país oriental, los estudiantes universitarios chinos se han convertido en participantes activos, comunicadores y promotores de esas relaciones. Este artículo presta atención a la imagen estereotipada que estos universitarios se han hecho de Argentina. Para ello se utilizan los resultados de un cuestionario aplicado a 412 estudiantes universitarios chinos. El análisis evidencia que en dicho grupo se han formado estereotipos en cinco dimensiones y se determina el impacto entre los encuestados de las relativas a la simpatía y el interés por la nación sudamericana y su población

Role of gut microbiota and inflammatory factors in acute respiratory distress syndrome: a Mendelian randomization analysis

BackgroundAcute respiratory distress syndrome (ARDS) is a serious lung ailment marked by significant inflammation and damage in the alveoli and capillaries of the lungs. Recent research suggests a strong correlation between the onset and advancement of ARDS and an imbalance in the gut microbiota (GM).MethodsIn this investigation, Mendelian randomization (MR) analysis was utilized, drawing on data from publicly accessible genome-wide association studies. The primary focus was on examining the interplay between GM, inflammatory factors (IFs) and ARDS. Instrumental variables were established through genetic modifications of GM and IFs. Various statistical analysis methods including the inverse-variance weighted model, MR-Egger method and Wald ratio test were applied for comprehensive data analysis.ResultsEight bacterial taxa within the GM demonstrated a potential causal link with development of ARDS. Notably, the phylum Actinobacteria and the genus Intestinibacter exhibited a negative association with the risk of ARDS. However, Erysipelotrichales (id. 2,148), Victivallis (id. 2,256), Ruminococcaceae UCG014 (id. 11,371), Eubacterium ruminantium group (id. 11,340), Erysipelotrichaceae (id. 2,149) and Erysipelotrichia (id. 2,147) demonstrated a positive association with ARDS risk. Additionally, the study identified a potential causal relationship between the inflammatory factors interleukin-16 and C-C motif chemokine 3 with the occurrence of ARDS.ConclusionThis study strongly suggests that the interaction between gut microbiota (GM) and inflammatory factors (IFs) significantly contributes to the pathogenesis of acute respiratory distress syndrome (ARDS). This underscores their crucial involvement in both the initiation and advancement of this severe lung disorder

Fabrication of a corrosion resistant superhydrophobic surface on magnesium alloy substrate

Superhydrophobic surface was obtained on pretreated magnesium alloy substrates via Nano silver deposition and electroless Ni-P plating followed by stearic acid modification. The surface with hierarchical structure had a water contact angle of 157.8° and exhibited excellent superhydrophobicity. The surface morphology of the sample, the chemical compositions and wettability were characterized by scanning electron microscopy (SEM), XRD (X-ray diffraction), Fourier transformed infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. The potential polarization curves revealed the corrosion resistance of superhydrophobic sample was enhanced as the corrosion current density decreased by 2 orders of magnitude

A fractional-order model on the dynamic mechanical behavior of magnetorheological elastomers

In order to describe the dynamic behavior of magnetorheological elastomers (MREs) for the realization of vibration control, this study proposes a constitutive model containing a fractional element and nonlinear springs attributed to the viscoelastic and the rheological properties, respectively. The viscoelastic behavior in various magnetic fields was studied experimentally to develop this fractional-order nonlinear model, and the model parameters were identified through experimental data fitting of dynamic modulus in frequency domain. The model predictions were subsequently obtained with the predictor-corrector approach to validate the proposed model by comparing with the experimental results on the stress-strain hysteresis. In addition, the efficiency of the proposed model of MRE was also evaluated by comparing the numerical solution with the results of the revised Bouc-Wen model

Effect of Different Phenolic Compounds on Performance of Organically Cross-Linked Terpolymer Gel Systems at Extremely High Temperatures

The effect of four different phenolic compounds (i.e., phenol, catechol, resorcinol, and hydroquinone) on the performance of organically cross-linked terpolymer gel systems at the temperature of 150°C was investigated. The phenol-based gelant systems were not able to form visible bulk gels at this extremely high temperature because the cross-linked clusters between phenol and hexamethylenetetramine (HMTA) only contained a small number of hydroxyl groups for cross-linking reactions. The catechol- and hydroquinone-based gelants were able to form relatively strong bulk gels because the amount of the cross-linked clusters between these two phenolic compounds and HMTA increased significantly. This increment also contributed to the decrease of the grid sizes of the gel network structures and the emergence of dendritic structures on them, thereby significantly increasing the viscosity, storage modulus, and thermal stability of the obtained gels. However, these two gel systems could not be maintained for long; syneresis began after only 3-12 days of the systems being held at 150°C. When phenol was replaced by resorcinol, bulk gels with excellent strength and long-term thermal stability were able to form at 150°C. The use of the gelation mechanism of the cross-linking reactions between the terpolymer and different cross-linker systems can help researchers and petroleum engineers better understand the differences between the different cross-linker systems and thus develop more suitable polymer gel systems for water management in extremely high temperature reservoirs