22 research outputs found
Recommended from our members
Anomalous vomume expansion of plutonium alloys
A simple heuristic model for the valence of Pu in its various phases is used to explain the large positive deviations from Vegard's Law in ..cap alpha..-Pu(Al), ..cap alpha..-Pu(Ti), and delta-Pu(Sc)
Recommended from our members
Alpha decay self-damage in cubic and monoclinic zirconolite
Samples of primarily-monoclinic /sup 238/Pu-doped zirconolite were stored at ambient temperature to allow accumulation of alpha decay self-damage to a dose of 1 x 10/sup 24/ ..cap alpha../m/sup 3/ (equivalent to a SYNROC age of approx. 10/sup 3/y). Bulk swelling reached 2.3 vol% with no tendency toward saturation, a damage response similar to that observed for cubic Pu-doped zirconolite. X-ray volumetric swelling at 4 x 10/sup 24/ ..cap alpha../m/sup 3/ was 1 vol%, considerably less than that for the cubic material. Changes in cell dimensions differed significantly from those reported by others for a monoclinic natural mineral. Extensive microcracking was observed, and is attributed at least partially to swelling differences between the matrix and minor phases
Effective killing of the human pathogen Candida albicans by a specific inhibitor of non-essential mitotic kinesin Kip1p
Kinesins from the bipolar (Kinesin-5) family are conserved in eukaryotic organisms and play critical roles during the earliest stages of mitosis to mediate spindle pole body separation and formation of a bipolar mitotic spindle. To date, genes encoding bipolar kinesins have been reported to be essential in all organisms studied. We report the characterization of CaKip1p, the sole member of this family in the human pathogenic yeast Candida albicans. C. albicans Kip1p appears to localize to the mitotic spindle and loss of CaKip1p function interferes with normal progression through mitosis. Inducible excision of CaKIP1 revealed phenotypes unique to C. albicans, including viable homozygous Cakip1 mutants and an aberrant spindle morphology in which multiple spindle poles accumulate in close proximity to each other. Expression of the C. albicans Kip1 motor domain in Escherichia coli produced a protein with microtubule-stimulated ATPase activity that was inhibited by an aminobenzothiazole (ABT) compound in an ATP-competitive fashion. This inhibition results in ‘rigor-like’, tight association with microtubules in vitro. Upon treatment of C. albicans cells with the ABT compound, cells were killed, and terminal phenotype analysis revealed an aberrant spindle morphology similar to that induced by loss of the CaKIP1 gene. The ABT compound discovered is the first example of a fungal spindle inhibitor targeted to a mitotic kinesin. Our results also show that the non-essential nature and implementation of the bipolar motor in C. albicans differs from that seen in other organisms, and suggest that inhibitors of a non-essential mitotic kinesin may offer promise as cidal agents for antifungal drug discovery
Recommended from our members
Calculated x-ray powder diffraction patterns of plutonium
The X-ray powder diffraction patterns of the six phases of plutonium were calculated for Cu K..cap alpha../sub 1/ (lambda = 1.540598 A.) The results listed are 2 theta, sin/sup 2/ theta, d values, integrated intensities, and diffraction indices hkl
Recommended from our members
Evidence for stacking faults in multiaxial strained alpha-brass
Two different techniques of x-ray diffraction have been applied to the examination of multiaxial strained alpha-brass. From an examination of the unfolded Fourier coefficients describing the shape of the diffraction profile it has been determined that the true crystallite size probably exceeds 2000 A, a practical upper limit for determining crystallite size by x-ray methods. The localized strain is approximately 0.225% and a combined stacking fault probability (1.5 ..cap alpha..' + ..beta..) = 0.0185 +- 1. From lattice constant variations the single stacking fault probability, ..cap alpha..', has been determined to be 0.0054 +- 22. The twinning stacking fault, ..beta.., is thus 0.0104 +- 22. The reciprocal of the probability is the number of planes of atoms between the indicated stacking fault. The magnitude of the numbers indicates that twinning is twice as common as single stacking faults
Recommended from our members
X-ray diffraction on radioactive materials
X-ray diffraction studies on radioactive materials are discussed with the aim of providing a guide to new researchers in the field. Considerable emphasis is placed on the safe handling and loading of not-too-exotic samples. Special considerations such as the problems of film blackening by the gamma rays and changes induced by the self-irradiation of the sample are covered. Some modifications of common diffraction techniques are presented. Finally, diffraction studies on radioactive samples under extreme conditions are discussed, with primary emphasis on high-pressure studies involving diamond-anvil cells
Recommended from our members
Structural examination of iridium-based single-crystal preparations. [AlIr; IrSi]
A high-temperature crystal growth experiment produced discrete single-crystal products of AlIr and IrSi. The preparation and examination of these phases is described within. This project is part of a materials compatibility study relating to radioisotopic heat sources. These heat sources are comprised of a PuO/sub 2/ fuel pellet encapsulated in an Ir alloy containment shell. Th is introduced as an additive within the Ir to maintain ductility. Si and P are picked up inadvertently in the fuel processing. The compatibility of the heat sources with Al is of interest because of potential interactions with Al alloy hardware associated with the heat source environment
Recommended from our members
Structural damage in a self-irradiated zirconolite-based ceramic
The zirconolite phase of SYNROC nuclear waste was fabricated with 5 mol % /sup 238/PuO/sub 2/ substituted for a like amount of ZrO/sub 2/, in order to induce self-irradiation damage. The resulting product exhibited a matrix of monoclinic zirconolite containing approx. 3.8 mol % PuO/sub 2/ along with roughly 20 vol % of the cubic polymorph with approximately twice the PuO/sub 2/ content of the matrix. After a dose of 2.1 x 10/sup 25/ ..cap alpha.. decays/m/sup 3/ at room temperature (800 days' storage), swelling reached 5.5 vol % and neared saturation. The monoclinic phase became x-ray metamict at approx. 1.0 x 10/sup 25/ ..cap alpha../m/sup 3/ after slight atomic rearrangement within the crystalline material. Periodic TEM examination revealed a gradual evolution from the crystalline state to an amorphous condition with residual crystallites, consistent with a model involving conversion by alpha recoil tracks. Optical metallography showed extensive microcracking, attributed to differences in swelling rates of the two zirconolite polymorphs. 7 figures