Trade Liberalization and Trade Performance of Environmental Goods: Evidence from Asia-Pacific Economic Cooperation Members

In this article, we study the impact of trade liberalization, including reductions in both tariff and nontariff trade barriers, on environmental goods (EGs) exports. Using bilateral trade data from 20 Asia-Pacific Economic Cooperation members, we find that tariff reduction in an exporting country has a larger positive impact on its exports of EGs than tariff reduction in an importing country. Our results also show that a lower nontariff barrier in an importing country increases its imports of EGs. A considerable amount of heterogeneity also exists in subsample results based on countries’ income levels

Double Helical Hydrogen-Bonded AAA-DDD Complexes and Supramolecular Polymers

The design and characterization of linear oligomers that self-assemble into double helical structures has been a subject of interest to chemists since the elucidation of the double helix structure of DNA in 1953. Transition metal templates have been widely used in the construction of artificial double helical complexes from linear multidentate ligands. The use of other non-covalent interactions as the driving force in the self-assembly of these types of complexes is less common. Aromatic stacking interactions, anion templates, and salt-bridges have all been applied in this context. The great majority of these investigations have been concerned with the dimerization of identical linear oligomers to form homoduplex products. There are very few examples of artificial double helices that form from complementary strands to give heteroduplexes. Notably, Yashima, Furusho and coworkers have demonstrated that two complementary molecules may interact via amidinium-carboxylate salt bridges in a sequence dependent manner resembling the hybridization of ss-DNA. Our group has reported the formation of a double helical complex based on self-complementary molecular strands containing alternating hydrogen bond donors and acceptors but its association constant was very low. In this thesis, we attempt to design and synthesize complementary hydrogen bonded AAAA-DDD double helices with high association constants and further develop supramolecular polymers based on them. The first non-coplanar DDD molecule including three thiazine dioxide subunits and AAA component including two pyridine and one 3,5-lutidine subunits can form the double helical structure. The DDD component insoluble in chloroform resulted in that high association constant is not figured out. However, DDD analogue based on indole and thiazine dioxide subunits can be dissolved in chloroform and the AAA-DDD binding property in solution was investigated. Electron- withdrawing groups on DDD component increase the stabilities of AAA-DDD complexes and electron-donating groups on AAA component also improve the stabilities of AAA-DDD complexes. Substituent groups on DDD or AAA molecules not only change their electronic distributions but also their original conformations. Therefore, substituent effect is not simply equal to electronic effect. Two DDD and AAA components were linked with an aliphatic chain respectively. The main-chain AA-BB supramolecular polymer is formed from the 1:1 mixture of bisAAA and bisDDD. BisAAA and bisDDD follow the ring-chain supramolecular polymerization mechanism. Relative to the same length linkers in bisAAA and bisDDD, the largely different length of linkers led to the lower critical polymerization concentration

Tumor-associated EGFR over-expression specifically activates Stat3 and Smad7 resulting in desensitization of TGF-β signaling

Transforming Growth Factor-[beta] (TGF-[beta]) and Epidermal Growth Factor (EGF) signaling pathways are both independently implicated as key regulators in tumor formation and progression. Here, we demonstrate that activation of the tumor-associated and over-expressed EGFR desensitizes TGF-[beta] signaling and its cytostatic regulation through specific Stat3 activation and Smad7 induction. In normal and tumor human cell lines, reduction of TGF-[beta]-mediated Smad2 phosphorylation, nuclear translocation and Smad3 target gene activation were observed where EGFR is over-expressed, but not in cells which expressed EGFR at normal levels. The EGFR downstream signaling molecules phosphatidyinositol-3 Kinase (PI3K) or mitogen-activated protein kinase/ERK kinase (MEK) are not responsible for the down-regulation of TGF-[beta] signaling since blockade of them by specific pharmacological inhibitors LY294002 and U0126 had little effects on the sensitivity of TGF-[beta] signaling. We identified Stat3 as a signaling molecule activated specifically and persistently by over-expressed EGFR, but not by normal levels. Importantly, Stat3 is responsible for the reduced TGF-[beta] sensitivity, since its knockdown by siRNA restored TGF-[beta] signaling sensitivity. Furthermore, over-expressed EGFR, through Stat3 activates Smad7 promoter activity, increasing its protein levels, which is a negative regulator of TGF-[beta] signaling. Consequently, cells were re-sensitized to TGF-[beta] when Smad7 expression was reduced using siRNA. Therefore we establish a novel EGFR-Stat3-Smad7-TGF-[beta] signaling molecular axis where tumor-associated over-expression of EGFR in epithelial cells results in hyperactivation of Stat3, which activates Smad7 expression, compromising the TGF-[beta]'s cytostatic regulation of epithelium and consequent tumor formation

A Mutual Attraction Model for Both Assortative and Disassortative Weighted Networks

In most networks, the connection between a pair of nodes is the result of their mutual affinity and attachment. In this letter, we will propose a Mutual Attraction Model to characterize weighted evolving networks. By introducing the initial attractiveness $A$ and the general mechanism of mutual attraction (controlled by parameter $m$), the model can naturally reproduce scale-free distributions of degree, weight and strength, as found in many real systems. Simulation results are in consistent with theoretical predictions. Interestingly, we also obtain nontrivial clustering coefficient C and tunable degree assortativity r, depending on $m$ and A. Our weighted model appears as the first one that unifies the characterization of both assortative and disassortative weighted networks.Comment: 4 pages, 3 figure

Localized Surface Plasmons in Vibrating Graphene Nanodisks

Localized surface plasmons are confined collective oscillations of electrons in metallic nanoparticles. When driven by light, the optical response is dictated by geometrical parameters and the dielectric environment and plasmons are therefore extremely important for sensing applications. Plasmons in graphene disks have the additional benefit to be highly tunable via electrical stimulation. Mechanical vibrations create structural deformations in ways where the excitation of localized surface plasmons can be strongly modulated. We show that the spectral shift in such a scenario is determined by a complex interplay between the symmetry and shape of the modal vibrations and the plasmonic mode pattern. Tuning confined modes of light in graphene via acoustic excitations, paves new avenues in shaping the sensitivity of plasmonic detectors, and in the enhancement of the interaction with optical emitters, such as molecules, for future nanophotonic devices