On stability conditions for the quintic threefold

We study the Clifford type inequality for a particular type of curves $C_{2,2,5}$, which are contained in smooth quintic threefolds. This allows us to prove some stronger Bogomolov-Gieseker type inequalities for Chern characters of stable sheaves and tilt-stable objects on smooth quintic threefolds. Employing the previous framework by Bayer, Bertram, Macr\`i, Stellari and Toda, we construct an open subset of stability conditions on every smooth quintic threefold in $\mathbf{P}^4_{\mathbb C}$.Comment: pre-journal version, 32 pages, 7 figures, comments are very welcome

Smoothness and Poisson structures of Bridgeland moduli spaces on Poisson surfaces

Let X be a projective smooth holomorphic Poisson surface, in other words, whose anti-canonical divisor is effective. We show that moduli spaces of certain Bridgeland stable objects on X are smooth. Moreover, we construct Poisson structures on these moduli spaces.Comment: We would like to thank Sergey Mozgovoy for pointing out a mistake in the first and journal version of this paper. Our result only holds for $H$ that is numerically parallel to $K_X

Study on China's timber resource shortage and import structure:natural forest protection program outlook,1998 to 2008

The state of China's ecological environment has improved to some extent since the Chinese government initiated the Natural Forest Protection Program (NFPP) in 1998. The logging prohibition and limitation policies adopted by the NFPP, however, have reduced domestic timber supply. Together with the thriving economy, decreasing domestic timer supply continues to widen the gap between supply and demand. Importation is considered to be the primary solution to this issue, making China the world's largest timber importer. China's major timber suppliers are Russia, Malaysia, Papua New Guinea, New Zealand, and Gabon, among which Russia accounts for more than 61 percent of China's total timber imports. The relatively cheaper conifers imported from Russia account for more than 60 percent of all imported timber, with volumes continually increasing because of the rapid pace at which China has been implementing its infrastructure projects. In addition, as living standards continue to improve, requirements for home decor and furniture also grow, further increasing the demand for tropical to temperate timber. In the long term, imports will remain the main solution to the insufficient domestic timber supply in China.NFPP; timber resource shortage; timber import structure

Acid Resistance Mechanisms in Staphylococcus aureus

Staphylococcus aureus is a leading cause of opportunistic infections in community and health care settings. To thrive in a great variety of environments, S. aureus has developed the capability of tolerating temporary pH changes, as well as resisting constant acid stress. To evaluate the impact of strong and weak acid stress on S. aureus, growth patterns of JE2 were monitored when cultured in chemically defined media (CDM) at various pH in the presence of hydrochloric acid (HCl), acetic acid, and lactic acid. Our results showed that S. aureus responds to strong and weak acids in different manners. S. aureus is more susceptible to acetic acid than HCl and is able to alleviate lactate acid stress by consuming lactate. In-depth investigations of lactate catabolism revealed that lactate quinone oxidoreductase (Lqo), and lactate dehydrogenases (Ldh1 and Ldh2) are crucial for lactic acid resistance. In addition, we explored the in vitro and in vivo functions of urease in S. aureus with approaches such as genetic manipulations, growth assays, as well as mouse model systems. We discovered that in contrast to Staphylococcus epidermidis, S. aureus primarily employs the urease pathway to rescue survival under acid stress. Examination of urease regulation indicated that the regulation network is mainly comprised of CcpA, agr, and CodY, suggesting that urease transcription responds to metabolic changes and is tied closely to virulence. Our data demonstrated that urease is essential for S. aureus to resist clearance by host immunity and to persist in the mouse kidneys, underscoring the potential role of urease as a critical virulence factor required for renal infection with S. aureus. Collectively, in these studies we have identified and characterized important systems S. aureus employs when adapting to unfavorable acidic niches, and this knowledge lays the foundation for broadening our understanding of acid resistance mechanisms of S. aureus