A multiscale model for analyzing the synergy of CS and WSS on the endothelium in straight arteries

A multiscale model was proposed to calculate the circumferential stress （CS） and wall shear stress （WSS） and analyze the effects of global and local factors on the CS, WSS and their synergy on the arterial endothelium in large straight arteries. A parameter pair [Zs, SPA] （defined as the ratio of CS amplitude to WSS amplitude and the phase angle between CS and WSS for different harmonic components, respectively） was proposed to characterize the synergy of CS and WSS. The results demonstrated that the CS or WSS in the large straight arteries is determined by the global factors, i.e. the preloads and the afterloads, and the local factors, i.e. the local mechanical properties and the zero-stress states of arterial walls, whereas the Zs and SPA are primarily determined by the local factors and the afterloads. Because the arterial input impedance has been shown to reflect the physiological and pathological states of whole downstream arterial beds, the stress amplitude ratio Zs and the stress phase difference SPA might be appropriate indices to reflect the influences of the states of whole downstream arterial beds on the local blood flow-dependent phenomena such as angiogenesis, vascular remodeling and atherosgenesis.

Sensitive electrochemical DNA sensor for the detection of HIV based on a polyaniline/graphene nanocomposite

A nanocomposite of polyaniline/graphene(PAN/GN)was prepared using reverse-phase polymerization.The nanocomposite material was dropcast onto a glassy carbon electrode(GCE).Then,a single-stranded DNA(ssDNA)probe for HIV-1 gene detection was immobilized on the modified electrode,and the negative charged phosphate backbone of the HIV-1 was bound to the modified electrode surface via p-p*stacking interactions.The hybridization between the ssDNA probe and the target HIV-1 formed doublestranded DNA(dsDNA),and the electron transfer resistance of the electrode was measured using impedimetric studies with a[Fe(CN)6]^(3-/4-)redox couple.Under the optimized experimental conditions,the change of the impedance value was linearly related to the logarithm of the concentration of HIV genes in the range from 5.0×10^(-16)M to 1.0×10^(-10)M(R=0.9930),and the HIV sensor exhibited a lower detection limit of 1.0×10^(-16)M(S/N=3).The results show that this biosensor presented wonderful selectivity,sensitivity and specificity for HIV-1 gene detection.Thus,this biosensor provides a new method for the detection of HIV gene fragments.

Characteristics of carbonyls and volatile organic compounds （VOCs） in residences in Beijing, China

Volatile organic compounds （VOCs） and carbonyl compounds were measured both indoors and outdoors in 50 residences of Beijing in heating （December, 2011） and non-heating seasons （April/May, 2012）. SUMMA canisters for VOCs and diffusive samplers for carbonyl compounds were deployed for 24 h at each site, and 94 compounds were quantified. Formaldehyde, acetone and acetaldehyde were the most abundant carbonyl compounds both indoors and outdoors with indoor median concentrations being 32.1, 21.7 and 15.3 μg·m-3, respec- tively. Ethane （17.6 μg·m-3）, toluene （14.4 μg·m-3）, pro- pane （11.2 μg·m-3）, ethene （8.40 μg·m-3）, n-butane （6.87 μg·m-3）, and benzene （5.95 μg·m-3） showed the high median concentrations in indoor air. Dichloromethane, p- dichlorobenzene （p-DCB） and toluene exhibited extremely high levels in some residences, which were related with a number of indoor emission sources. Moreover, isoprene, p- dichlorobenzene and carbonyls showed median indoor/ outdoor （I/O） ratios larger than 3, indicating their indoor sources were prevailing. Chlorinated compounds like CFCs were mainly from outdoor sources for their I/O ratios being less than 1. In addition, indoor concentrations between two sampling seasons varied with different compounds. Carbonyl compounds and some chlorinated compounds had higher concentrations in the non-heating season, while alkanes, alkenes, aromatic compounds showed an increase in the heating season. Indoor concentration of VOCs and carbonyls were influenced by locations, interior decorations and indoor activities, however the specific sources for indoor VOCs and carbonyls could not be easily identified. The findings obtained in this study would significantly enhance our understandings on the prevalent and abundant species of VOCs as well as their concentrations and sources in Beijing residences.

Novel composite Nafion membranes modified with copper phthalocyanine tetrasulfonic acid tetrasodium salt for fuel cell application

In this paper,Nafion membrane was firstly modified by copper phthalocyanine tetrasulfonic acid tetrasodium salt(CuTSPc)to prepare the Nafion/CuTSPc-x composite membranes.FTIR,XRD and SEM results revealed the successful incorporation of CuTSPc into Nafion and good compatibility between the two composites.The proton conductivities of the Nafion/CuTSPc-x composite membranes were evidently higher than pure cast Nafion membrane,and increased with CuTSPc contents.Among them,the Nafion/CuTSPc-6%membrane with the highest ion exchange capacity(1.14 mequiv
g^(-1))exhibited the highest proton conductivity of 0.084 S cm^(-1)at 30℃and 0.131 S cm^(-1)at 80C,respectively.When fabricated of a membrane electrode assembly(MEA),the Nafion/CuTSPc-4.5%membrane displayed an initial fuel cell performance with a power density of 43.3mWcm^(-2)at room temperature,close to that for pure cast Nafion membrane.Benefiting from the compact structure,high proton conductivity and outstanding stability,the Nafion/CuTSPc-x composite membranes show promising potentials for fuel cell applications.