A Mathematical Model of Heat Transfer in Partially Insulated Airways in Deep, Frozen Ground Placer Mines

Large seasonal variations in the temperature of the ventilating air in mines in the arctic cause changes in the original thermal field through heat and mass exchanges between the air and the surrounding medium. These thermal interactions have major influence on climatic quality as well as on the stability of the mine openings. Thawing of walls and roof in mine airways can be reduced by various types of thermal-insulation. Application of thermal-insulation prevents deep thawing of the rockmass surrounding an airway. In this case, the mechanism of heat transfer around a frozen, underground airway would be much different. A model of heat transfer in a deep, partially insulated airway has been developed and analyzed using finite element methods. Results of the analysis show that without any thermal control, there will be stable change in temperature around the mine airway. With different insulations on the walls of the airway, roof thawing can be reduced and in certain cases, completely eliminated

High-Performance Direct Methanol Fuel Cells with Precious-Metal-Free Cathode

Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt-based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol-tolerant cathodes must be developed before DMFC technologies become viable. The newly developed reduced graphene oxide (rGO)-based Fe-N-C cathode exhibits high methanol tolerance and exceeds the performance of current Pt cathodes, as evidenced by both rotating disk electrode and DMFC tests. While the morphology of 2D rGO is largely preserved, the resulting Fe-N-rGO catalyst provides a more unique porous structure. DMFC tests with various methanol concentrations are systematically studied using the best performing Fe-N-rGO catalyst. At feed concentrations greater than 2.0 m, the obtained DMFC performance from the Fe-N-rGO cathode is found to start exceeding that of a Pt/C cathode. This work will open a new avenue to use nonprecious metal cathode for advanced DMFC technologies with increased performance and at significantly reduced cost.open0

High-Performance Direct Methanol Fuel Cells with Precious-Metal-Free Cathode

Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt-based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol-tolerant cathodes must be developed before DMFC technologies become viable. The newly developed reduced graphene oxide (rGO)-based Fe-N-C cathode exhibits high methanol tolerance and exceeds the performance of current Pt cathodes, as evidenced by both rotating disk electrode and DMFC tests. While the morphology of 2D rGO is largely preserved, the resulting Fe-N-rGO catalyst provides a more unique porous structure. DMFC tests with various methanol concentrations are systematically studied using the best performing Fe-N-rGO catalyst. At feed concentrations greater than 2.0 m, the obtained DMFC performance from the Fe-N-rGO cathode is found to start exceeding that of a Pt/C cathode. This work will open a new avenue to use nonprecious metal cathode for advanced DMFC technologies with increased performance and at significantly reduced cost.open0

Autocrine Epiregulin Activates EGFR Pathway for Lung Metastasis Via EMT in Salivary Adenoid Cystic Carcinoma

Salivary adenoid cystic carcinoma (SACC) is characterized by invasive local growth and a high incidence of lung metastasis. Patients with lung metastasis have a poor prognosis. Treatment of metastatic SACC has been unsuccessful, largely due to a lack of specific targets for the metastatic cells. In this study, we showed that epidermal growth factor receptors (EGFR) were constitutively activated in metastatic lung subtypes of SACC cells, and that this activation was induced by autocrine expression of epiregulin (EREG), a ligand of EGFR. Autocrine EREG expression was increased in metastatic SACC-LM cells compared to that in non-metastatic parental SACC cells. Importantly, EREG-neutralizing antibody, but not normal IgG, blocked the autocrine EREG-induced EGFR phosphorylation and the migration of SACC cells, suggesting that EREG-induced EGFR activation is essential for induction of cell migration and invasion by SACC cells. Moreover, EREG-activated EGFR stabilized Snail and Slug, which promoted EMT and metastatic features in SACC cells. Of note, targeting EGFR with inhibitors significantly suppressed both the motility of SACC cells in vitro and lung metastasis in vivo. Finally, elevated EREG expression showed a strong correlation with poor prognosis in head and neck cancer. Thus, targeting the EREG-EGFR-Snail/Slug axis represents a novel strategy for the treatment of metastatic SACC even no genetic EGFR mutation

Epidemiological and genomic analyses of human isolates of Streptococcus suis between 2005 and 2021 in Shenzhen, China

Streptococcus suis (S. suis) is an important food-borne zoonotic pathogen that causes swine streptococcosis, which threatens human health and brings economic loss to the swine industry. Three-quarters of human S. suis infections are caused by serotype 2. A retrospective analysis of human S. suis cases in Shenzhen, a megacity in China, with high pork consumption, between 2005 and 2021 was conducted to understand its genomic epidemiology, pathogen virulence, and drug resistance characteristics. The epidemiological investigation showed that human cases of S. suis in Shenzhen were mainly associated with people who had been in close contact with raw pork or other swine products. Whole-genome sequence analysis showed that 33 human isolates in Shenzhen were dominated by serotype 2 (75.76%), followed by serotype 14 (24.24%), and the most prevalent sequence types (STs) were ST7 (48.48%) and ST1 (39.40%). ST242 (9.09%) and ST25 (3.03%), which were rarely reported, were also found. Phylogenetic analysis showed that the Shenzhen human isolates had close genetic relatedness to isolates from Guangxi (China), Sichuan (China), and Vietnam. We found a new 82 KB pathogenicity island (PAI) in the serotype 2 isolate that may play a role in sepsis. Similarly, a serotype 14 isolate, containing 78 KB PAI, was isolated from a patient presenting with streptococcal toxic shock syndrome (STSLS) who subsequently died. Multi-drug resistance (MDR) was high in human isolates of S. suis from Shenzhen. Most human isolates were resistant to tetracycline, streptomycin, erythromycin, and clindamycin, and 13 isolates had intermediate resistance to penicillin. In conclusion, swine importation from Guangxi, Sichuan, and Vietnam should be more closely monitored, and the use of antibiotics limited to reduce the potential for antimicrobial resistance (AMR)

On the Information Rate of Single-Carrier FDMA Using Linear Frequency Domain Equalization and Its Application for 3GPP-LTE Uplink

This paper compares the information rate achieved by SC-FDMA (single-carrier frequency-division multiple access) and OFDMA (orthogonal frequency-division multiple access), where a linear frequency-domain equalizer is assumed to combat frequency selective channels in both systems. Both the single user case and the multiple user case are considered. We prove analytically that there exists a rate loss in SC-FDMA compared to OFDMA if decoding is performed independently among the received data blocks for frequency selective channels. We also provide a geometrical interpretation of the achievable information rate in SC-FDMA systems and point out explicitly the relation to the well-known waterfilling procedure in OFDMA systems. The geometrical interpretation gives an insight into the cause of the rate loss and its impact on the achievable rate performance. Furthermore, motivated by this interpretation we point out and show that such a loss can be mitigated by exploiting multiuser diversity and spatial diversity in multi-user systems with multiple receive antennas. In particular, the performance is evaluated in 3GPP-LTE uplink scenarios.</p

doi:10.1155/2007/39871 Research Article Spatial-Temporal Correlation Properties of the 3GPP Spatial Channel Model and the Kronecker MIMO Channel Model

The performance of multiple-input multiple-output (MIMO) systems is greatly influenced by the spatial-temporal correlation properties of the underlying MIMO channels. This paper investigates the spatial-temporal correlation characteristics of the spatial channel model (SCM) in the Third Generation Partnership Project (3GPP) and the Kronecker-based stochastic model (KBSM) at three levels, namely, the cluster level, link level, and system level. The KBSM has both the spatial separability and spatial-temporal separability at all the three levels. The spatial-temporal separability is observed for the SCM only at the system level, but not at the cluster and link levels. The SCM shows the spatial separability at the link and system levels, but not at the cluster level since its spatial correlation is related to the joint distribution of the angle of arrival (AoA) and angle of departure (AoD). The KBSM with the Gaussian-shaped power azimuth spectrum (PAS) is found to fit best the 3GPP SCM in terms of the spatial correlations. Despite its simplicity and analytical tractability, the KBSM is restricted to model only the average spatial-temporal behavior of MIMO channels. The SCM provides more insights of the variations of different MIMO channel realizations, but the implementation complexity is relatively high. Copyright © 2007 Cheng-Xiang Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1

Functionalization of PET with Phosphazene Grafted Graphene Oxide for Synthesis, Flammability, and Mechanism

Significant improvement in the fire resistance of polyethylene terephthalate (PET) while ensuring its mechanical properties is a tremendous challenge. A novel flame retardant (GO-HCCP, graphene oxide-hexachlorocyclotriphosphazene) was synthesized by nucleophilic substitution of the graphene oxide (GO) and hexachlorocyclotriphosphazene (HCCP) and then applied in PET by an in situ polymerization technique. The scanning electron microscope (SEM) showed a better dispersion of GO-HCCP than GO in the PET matrix. The char yield at 700 °C increased by 32.5% with the addition of GO-HCCP. Moreover, the peak heat release rate (pHRR), peak smoke produce rate (pSPR)and carbon monoxide production (COP)values significantly decreased by 26.0%, 16.7% and 37.5%, respectively, which indicates the outstanding fire and smoke suppression of GO-HCCP. In addition, the composites exhibited higher elastic modulus and tensile strength without compromising the toughness of PET matrix. These significantly reduced fire hazards properties are mainly attributed to the catalytic carbonation of HCCP and the barrier effect of GO. Thus, PET composites with good flame-retardant and mechanical properties were prepared, which provides a new strategy for further flame retardant PET preparation