provide a unique opportunity to examine hydrological extremes in the central United States because there are no other examples of two such highly contrasting precipitation extremes occurring in consecutive years at the Southern Great Plains (SGP) in recorded history. The HY06 annual precipitation in the state of Oklahoma, as observed by the Oklahoma Mesonet, is around 61% of the normal (92.84 cm, based on the 1921-2008 climatology), which results in HY06 as the second-driest year in the record. In particular, the total precipitation during the winter of 2005-2006 is only 27% of the normal, and this winter ranks as the driest season. On the other hand, the HY07 annual precipitation amount is 121% of the normal, and HY07 ranks as the seventh-wettest year for the entire state and the wettest year for the central region of the state. Summer 2007 is the second-wettest season for the state. Large-scale dynamics play a key role in these extreme events. During the extreme dry period (11/2005-02/2006), a dipole pattern in the 500 hPa geopotential height anomaly existed where an anomalous high was over the southwestern U.S. region and an anomalous low was over the Great Lakes. This pattern is associated with inhibited moisture transport from the Gulf of Mexico and strong sinking motion over the SGP, both contributing to the extreme dryness. The precipitation deficit over the SGP during the extreme dry period is clearly linked to significantly suppressed cyclonic activity over the southwestern United States, which shows a robust relationship with the western Pacific teleconnection pattern. The precipitation events during the extreme wet period (May-July 2007) were initially generated by active synoptic weather patterns, linked with moisture transport from the Gulf of Mexico by the northward low-level jet, and enhanced the frequency of thunderstorms and their associated latent heat release. Although the drought and pluvial conditions are dominated by large-scale dynamic patterns, we have found two possible positive feedback processes during the extreme dry and wet periods in this study that play key certain roles to maintain and reinforce the length and severity of existing drought and flood events. For example, during the extreme dry period, with less clouds, liquid water path, precipitable water vapor, precipitation, and thinner Cu cloud thickness, more net radiation was absorbed and used to evaporate water from the ground. The evaporated moisture, however, was removed by low-level divergence. Thus, with less precipitation and removed atmospheric moisture, more absorbed incoming solar radiation was used to increase surface temperature and to make the ground drier.

Well-determined physical parameters of 130 W UMa systems have been collected from the literature. Based on these data, the evolutionary status and dynamical evolution of W UMa systems are investigated. It is found that there is no evolutionary difference between W- and A-type systems in $M-J$ diagram which is consistent with the results derived from the analysis of observed spectral type, $M-R$ and $M-L$ diagrams of W UMa systems. $M-R$ and $M-L$ diagrams of W- and A-type systems indicate that a large amount of energy should be transferred from the more massive to the less massive component so that they are not in thermal equilibrium and undergo thermal relaxation oscillation (TRO). Meanwhile, the distribution of angular momentum, together with the distribution of mass ratio, suggests that the mass ratio of the observed W UMa systems is decreased with the decrease of their total mass. This could be the result of the dynamical evolution of W UMa systems which suffer angular momentum loss (AML) and mass loss due to magnetic stellar wind (MSW). Consequently, the tidal instability forces these systems towards the lower q values and finally to fast rotating single stars.Comment: 8 pages, 5 figures, accepted for publication in MNRA

HBx is a hepatitis B virus protein that is required for viral infectivity and replication. Anti-apoptotic Bcl-2 family members are thought to be among the important host targets of HBx. However, the structure and function of HBx are poorly understood and the molecular mechanism of HBx-induced carcinogenesis remains unknown. In this study, we report biochemical and structural characterization of HBx. The recombinant HBx protein contains metal ions, in particular iron and zinc. A BH3-like motif in HBx (residues 110-135) binds Bcl-2 with a dissociation constant of ∼193 μM, which is drastically lower than that for a canonical BH3 motif from Bim or Bad. Structural analysis reveals that, similar to other BH3 motifs, the BH3-like motif of HBx adopts an amphipathic α-helix and binds the conserved BH3-binding groove on Bcl-2. Unlike the helical Bim or Bad BH3 motif, the C-terminal portion of the bound HBx BH3-like motif has an extended conformation and makes considerably fewer interactions with Bcl-2. These observations suggest that HBx may modulate Bcl-2 function in a way that is different from that of the classical BH3-only proteins.Bcl-2 | hepatitis B virus | apoptosis | crystal structure T he human hepatitis B virus (HBV) is a prototypical hepadnavirus that specifically infects hepatocytes (1, 2). Over 240 million people worldwide are chronically infected by HBV according to the World Health Organization. Persistent HBV infection is one of the major risk factors for the development of hepatocellular carcinoma (HCC), accounting for over 50% of all HCC cases (3, 4). The genome of HBV encodes only four proteins, among which the product of the X gene (HBx) is least understood (1).HBx contains 154 residues and is closely associated with HCC development. The X gene is most frequently integrated and preferentially maintained in HBV-associated HCC, and HBx expression is frequently detected in HCC patients (5, 6). Several studies using transgenic mice and cell culture models yielded contrasting conclusions. Some studies suggest that the development of HCC is closely linked to HBx expression (7-10), although HBx alone may be insufficient for HCC development (11,12). Other results suggest that HBx has the ability to suppress cell transformation through induction of apoptosis (13,14). As such, the molecular mechanism of HBx-induced cellular transformation remains enigmatic.Numerous cellular activities are reported to be modulated by HBx through interactions with various host targets. For example, HBx-mediated transcriptional activation is achieved through its interaction with transcription factors (15, 16) or components involved in the basal transcriptional machinery (17-19). HBx can also modulate cellular proliferation and viability through interactions with p53 and Bcl-2 family members. Reflecting its enigmatic functions, HBx has been demonstrated to either induce apoptosis (20) or prevent apoptosis (21).HBx was recently found to contain a BH3-like motif in its C-terminal sequences (22). Experiments carried out in human hepato...