Native cellular architecture of Treponema denticola revealed by cryo-electron tomography

Using cryo-electron tomography, we are developing a refined description of native cellular structures in the pathogenic spirochete Treponema denticola. Tightly organized bundles of periplasmic flagella were readily observed in intact plunge-frozen cells. The periplasmic space was measured in both wild-type and aflagellate strains, and found to widen by less than the diameter of flagella when the latter are present. This suggests that a structural change occurs in the peptidoglycan layer to accommodate the presence of the flagella. In dividing cells, the flagellar filaments were found to bridge the cytoplasmic cylinder constriction site. Cytoplasmic filaments, adjacent to the inner membrane, run parallel to the tightly organized flagellar filaments. The cytoplasmic filaments may be anchored by a narrow plate-like structure. The tapering of the cell ends was conserved between cells, with a patella-shaped structure observed in the periplasm at the tip of each cytoplasmic cylinder. Several incompletely characterized structures have been observed in the periplasm between dividing cells, including a cable-like structure linking two cytoplasmic cylinders and complex foil-shaped structures

Native cellular architecture of Treponema denticola revealed by cryo-electron tomography

Using cryo-electron tomography, we are developing a refined description of native cellular structures in the pathogenic spirochete Treponema denticola. Tightly organized bundles of periplasmic flagella were readily observed in intact plunge-frozen cells. The periplasmic space was measured in both wild-type and aflagellate strains, and found to widen by less than the diameter of flagella when the latter are present. This suggests that a structural change occurs in the peptidoglycan layer to accommodate the presence of the flagella. In dividing cells, the flagellar filaments were found to bridge the cytoplasmic cylinder constriction site. Cytoplasmic filaments, adjacent to the inner membrane, run parallel to the tightly organized flagellar filaments. The cytoplasmic filaments may be anchored by a narrow plate-like structure. The tapering of the cell ends was conserved between cells, with a patella-shaped structure observed in the periplasm at the tip of each cytoplasmic cylinder. Several incompletely characterized structures have been observed in the periplasm between dividing cells, including a cable-like structure linking two cytoplasmic cylinders and complex foil-shaped structures

Comparing Transport Policies in a Full-scale 300mm Wafer Manufacturing Facility

Research in semiconductor manufacturing ideally wants to determine the “best” transport policy to ensure continuous production. Determining such a policy is difficult because it depends on many factors such as the layout, the product types, the equipment, etc. Most of the transport policies found in the literature combine dispatching policies (scheduling of transport requests) and routing policies (selection of the path to move from one point to another). This paper investigates a policy called minimum service which consists in keeping a minimum number of available vehicles in bays, so that they can quickly answer transport requests and empty travel times can be minimized. This paper aims at comparing, through experimental tests on actual instances of a real semiconductor manufacturing facility, two types of transport policies in terms of cycle time, throughput and Carrier Exchange Time. Moreover, the behavior of the “minimum service” policy is studied when the number of vehicles and the number of starting lots are varied. The results show that the “minimum service” policy is in general more effective than a classical policy, but that its key parameters must carefully be determined

Cryo-Electron Tomography Elucidates the Molecular Architecture of Treponema pallidum, the Syphilis Spirochete

Cryo-electron tomography (CET) was used to examine the native cellular organization of Treponema pallidum, the syphilis spirochete. T. pallidum cells appeared to form flat waves, did not contain an outer coat and, except for bulges over the basal bodies and widening in the vicinity of flagellar filaments, displayed a uniform periplasmic space. Although the outer membrane (OM) generally was smooth in contour, OM extrusions and blebs frequently were observed, highlighting the structure’s fluidity and lack of attachment to underlying periplasmic constituents. Cytoplasmic filaments converged from their attachment points opposite the basal bodies to form arrays that ran roughly parallel to the flagellar filaments along the inner surface of the cytoplasmic membrane (CM). Motile treponemes stably attached to rabbit epithelial cells predominantly via their tips. CET revealed that T. pallidum cell ends have a complex morphology and assume at least four distinct morphotypes. Images of dividing treponemes and organisms shedding cell envelope-derived blebs provided evidence for the spirochete’s complex membrane biology. In the regions without flagellar filaments, peptidoglycan (PG) was visualized as a thin layer that divided the periplasmic space into zones of higher and lower electron densities adjacent to the CM and OM, respectively. Flagellar filaments were observed overlying the PG layer, while image modeling placed the PG-basal body contact site in the vicinity of the stator–P-collar junction. Bioinformatics and homology modeling indicated that the MotB proteins of T. pallidum, Treponema denticola, and Borrelia burgdorferi have membrane topologies and PG binding sites highly similar to those of their well-characterized Escherichia coli and Helicobacter pylori orthologs. Collectively, our results help to clarify fundamental differences in cell envelope ultrastructure between spirochetes and gram-negative bacteria. They also confirm that PG stabilizes the flagellar motor and enable us to propose that in most spirochetes motility results from rotation of the flagellar filaments against the PG

Generation of the Baryon Asymmetry of the Universe within the Left--Right Symmetric Model

Fermions scattering off first-order phase transition bubbles, in the framework of $SU(2)_L\otimes SU(2)_R\otimes U(1)$ models, may generate the Baryon Asymmetry of the Universe (BAU), either at the $LR$-symmetry-breaking scale, or at the weak scale. In the latter case, the baryon asymmetry of the Universe is related to CP violation in the $K_0$--$\bar K_0$ system.Comment: 17 pages, CERN--TH 6747/92, ULB--TH--07/92, UAB-FT-298/9

Nonlinearity in NS transport: scattering matrix approach

A general formula for the current through a disordered normal--superconducting junction is derived, which is valid at finite temperature and includes the full voltage dependence. The result depends on a multichannel scattering matrix, which describes elastic scattering in the normal region, and accounts for the Andreev scattering at the NS interface. The symmetry of the current with respect to sign reversal in the subgap regime is discussed. The Andreev approximation is used to derive a spectral conductance formula, which applies to voltages both below and above the gap. In a case study the spectral conductance formula is applied to the problem of an NINIS double barrier junction.Comment: 26 pages, 4 Postscript figures, Latex, to be published in Phys. Rev.

The Cosmic Ultraviolet Baryon Survey (CUBS) I. Overview and the diverse environments of Lyman limit systems at z<1

We present initial results from the Cosmic Ultraviolet Baryon Survey (CUBS). CUBS is designed to map diffuse baryonic structures at redshift z<~1 using absorption-line spectroscopy of 15 UV-bright QSOs with matching deep galaxy survey data. CUBS QSOs are selected based on their NUV brightness to avoid biases against the presence of intervening Lyman Limit Systems (LLSs) at zabs~ 17.2 over a total redshift survey pathlength of dz=9.3, and a number density of n(z)=0.43 (-0.18, +0.26). Considering all absorbers with log N(HI)/cm^-2 > 16.5 leads to n(z)=1.08 (-0.25, +0.31) at z<1. All LLSs exhibit a multi-component structure and associated metal transitions from multiple ionization states such as CII, CIII, MgII, SiII, SiIII, and OVI absorption. Differential chemical enrichment levels as well as ionization states are directly observed across individual components in three LLSs. We present deep galaxy survey data obtained using the VLT-MUSE integral field spectrograph and the Magellan Telescopes, reaching sensitivities necessary for detecting galaxies fainter than 0.1L* at d<~300 physical kpc (pkpc) in all five fields. A diverse range of galaxy properties is seen around these LLSs, from a low-mass dwarf galaxy pair, a co-rotating gaseous halo/disk, a star-forming galaxy, a massive quiescent galaxy, to a galaxy group. The closest galaxies have projected distances ranging from d=15 to 72 pkpc and intrinsic luminosities from ~0.01L* to ~3L*. Our study shows that LLSs originate in a variety of galaxy environments and trace gaseous structures with a broad range of metallicities.Comment: 26 pages, 14 figures, MNRAS in pres

Antiplasmodial Activity shown by Secondary Metabolites Extracted from the Seeds ofPentaclethramacrophyllaBenth

Oil extracts from the African oil bean seed (PentaclethramacrophyllaBenth.) was analyzed for its phytochemical and mineral content and proximate, physicochemical and antimicrobial analyses were also performed. Phytochemical analysis showed the presence of tannins, saponins, quinones, terpenoids, phenols and coumarins in the oil sample. Mineral determination of the cotyledon showed the presence of iron (Fe) (with the highest concentration), Cu, Zn, Mn, Cr, Pb and Cd; while proximate analysis gave the following result: moisture (14.2%), ash content (1.5%), crude fibre (4.9%), crude proteins (12.8%), oil contents (4.9%), and carbohydrate (61.8%). GC-MS analysis of the partitioned petroleum ether and chloroform fractions of the oil revealed the presence of 9-Octadecenoic acid, 9,12- Octadecadienoic acid and their methyl esters,cis-9-Hexadecenal among the many components of the oil extract. Physicochemical analysis of the oil indicateda saponification value (148.67 mg KOH/g), peroxide value(8.0 meq/g), iodine value (10.41 mg iodine/g) and free fatty acid (8.98 mg KOH/g). The need for the development of new drugs for malaria led to our study of the antiplasmodial activity of the oil from the seeds of Pentaclethramacrophylla. Toxicological studies were carried out to determine the LD50with chloroquinediphosphate as positive control and normal saline as negative control. Using the Peter’s 4 day suppressive test a parasite inhibition rate of 47.72% (25 mg/kg), 63.63% (50 mg/kg) and 61.36% (100 mg/kg) on day 4 after treatment was recorded. A 95.45% chemo-suppression was observed for animals treated with 10 mg/kg chloroquine. This resultis an indication that the extract had appreciable signs of chemosuppression

Magnetic Penetration Depth in Unconventional Superconductors

This topical review summarizes various features of magnetic penetration depth in unconventional superconductors. Precise measurements of the penetration depth as a function of temperature, magnetic field and crystal orientation can provide detailed information about the pairing state. Examples are given of unconventional pairing in hole- and electron-doped cuprates, organic and heavy fermion superconductors. The ability to apply an external magnetic field adds a new dimension to penetration depth measurements. We discuss how field dependent measurements can be used to study surface Andreev bound states, nonlinear Meissner effects, magnetic impurities, magnetic ordering, proximity effects and vortex motion. We also discuss how penetration depth measurements as a function of orientation can be used to explore superconductors with more than one gap and with anisotropic gaps. Details relevant to the analysis of penetration depth data in anisotropic samples are also discussed.Comment: topical review, 57 pages, 219 reference