Structural insights into the membrane-extracted dimeric form of the ATPase TraB from the Escherichia coli pKM101 conjugation system

Background: Type IV secretion (T4S) systems are involved in secretion of virulence factors such as toxins or transforming molecules, or bacterial conjugation. T4S systems are composed of 12 proteins named VirB1-B11 and VirD4. Among them, three ATPases are involved in the assembly of the T4S system and/or provide energy for substrate transfer, VirB4, VirB11 and VirD4. The X-ray crystal structures of VirB11 and VirD4 have already been solved but VirB4 has proven to be reluctant to any structural investigation so far. Results: Here, we have used small-angle X-ray scattering to obtain the first structural models for the membrane-extracted, dimeric form of the TraB protein, the VirB4 homolog encoded by the E. coli pKM101 plasmid, and for the monomeric soluble form of the LvhB4 protein, the VirB4 homolog of the T4S system encoded by the Legionella pneumophila lvh operon. We have obtained the low resolution structures of the full-length TraB and of its N- and C-terminal halves. From these SAXS models, we derive the internal organisation of TraB. We also show that the two TraB N- and C-terminal domains are independently involved in the dimerisation of the full-length protein. Conclusions: These models provide the first structural insights into the architecture of VirB4 proteins. In particular, our results highlight the modular arrangement and functional relevance of the dimeric-membrane-bound form of TraB

A Two-Pressure Humidity Generator

A device for precisely humidifying a process gas is presented, with particular application to document preservation. The machine is designed to minimize the risk of damage from overpressure by incorporating multiple safety mechanisms and a simple user interface. The design theory is presented, discussed, and verified. This device is capable of generating humidified gases with relative humidities between 7 and 96 to high accuracy. At conditions suitable for document preservation, the machine is accurate to within 3.5 %, generating a relative humidity of (40 1.4)

Sudden To Adiabatic Transition in Beta Decay

We discuss effects in beta decays at very low beta energies, of the order of the kinetic energies of atomic electrons. As the beta energy is lowered the atomic response changes from sudden to adiabatic. As a consequence, the beta decay rate increases slightly and the ejection of atomic electrons (shake off) and subsequent production of X rays is turned off. We estimate the transition energy and the change in decay rate. The rate increase is largest in heavy atoms, which have a small Q value in their decay. The X ray switch-off is independent of Q value.Comment: 6 pages LaTe

Analytic evaluation of two-loop renormalization constants of enhanced electroweak strength in the Higgs sector of the Standard Model

We calculate renormalization constants Z_H, Z_w, the Higgs and W-boson mass and tadpole counterterms in the on-mass-shell renormalization scheme to two loops in the heavy-Higgs-boson limit m_H >> M_W. Explicit analytic formulae are presented for the two-loop integrals with masses, which are not known in the literature. As an application, the analytic expression for the two-loop leading correction to the fermionic Higgs boson width is obtained.Comment: 8 pages, 3 Postscript figures, uses epsfig.st

Molecular systematics, phylogeny and biogeography of roaches (Rutilus, Teleostei, Cyprinidae)

The aims of the present study are: (1) to produce a phylogenetic hypothesis for the genus Rutilus by using sequence variation of the entire mitochondrial (mt) cytochrome b (cyt-b) gene. To accomplish this we had sampled a total of 22 populations from the Eastern peri-Mediterranean area and Central Europe. These include 12 species (five of which with multiple populations; Fig. 1 and Table 1) out of the 14 reported in FishBase; (2) to test whether molecular data support the current systematics of the genus; and (3) to produce a biogeographic hypothesis for its diversification based on estimates of divergence times. Results will be discussed in light of the two contrasting biogeographic scenarios available for Southern European primary freshwater fishes

Smart street lamp Unit (SslU) with Embedded System

The Smart street light System (SslU) is an advance lighting system. This system conserves energy by reducing light intensity and detects the damaged lights in a street. It uses sensors such as LDR and Ultrasonic. The LDR is used to sense the presents of light in morning to switch off the street lights automatically and the Ultrasonic sensor is used to sense object on the street to increase the intensity of the light. A relay is used to supply the different voltage to the street lights (half intensity and full intensity). Arduino microcontroller is used to control the sensors and the network of lights to work by the program loaded on the microprocessor. The main control center is notified if any damage or malfunction is detected using a GSM module. The process of error detection in this large hard-wired system is done using main control boxes or by using any wireless communicator for defined number of streets, the output commands to GSM module to the main control center

Casimir interaction between plane and spherical metallic surfaces

We give an exact series expansion of the Casimir force between plane and spherical metallic surfaces in the non trivial situation where the sphere radius $R$, the plane-sphere distance $L$ and the plasma wavelength $\lambda_\P$ have arbitrary relative values. We then present numerical evaluation of this expansion for not too small values of $L/R$. For metallic nanospheres where $R, L$ and $\lambda_\P$ have comparable values, we interpret our results in terms of a correlation between the effects of geometry beyond the proximity force approximation (PFA) and of finite reflectivity due to material properties. We also discuss the interest of our results for the current Casimir experiments performed with spheres of large radius $R\gg L$.Comment: 4 pages, new presentation (highlighting the novelty of the results) and added references. To appear in Physical Review Letter

A Population of Compact Elliptical Galaxies Detected with the Virtual Observatory

Compact elliptical galaxies are characterized by small sizes and high stellar densities. They are thought to form through tidal stripping of massive progenitors. However, only a handful of them were known, preventing us from understanding the role played by this mechanism in galaxy evolution. We present a population of 21 compact elliptical galaxies gathered with the Virtual Observatory. Follow-up spectroscopy and data mining, using high-resolution images and large databases, show that all the galaxies exhibit old metal-rich stellar populations different from those of dwarf elliptical galaxies of similar masses but similar to those of more massive early-type galaxies, supporting the tidal stripping scenario. Their internal properties are reproduced by numerical simulations, which result in compact dynamically hot remnants resembling the galaxies in our sample.Comment: 26 pages, 5 figures, 2 tables. Science in press, published in Science Express on 1/Oct/2009. Full resolution figures in the supplementary online material are available from the Science Magazine web-sit