Lattice instabilities of cubic NiTi from first principles

The phonon dispersion relation of NiTi in the simple cubic B2 structure is computed using first-principles density-functional perturbation theory with pseudopotentials and a plane-wave basis set. Lattice instabilities are observed to occur across nearly the entire Brillouin zone, excluding three interpenetrating tubes of stability along the (001) directions and small spheres of stability centered at R. The strongest instability is that of the doubly degenerate M5' mode. The atomic displacements of one of the eigenvectors of this mode generate a good approximation to the observed B19' ground-state structure.Comment: 11 pages, 3 figure

Adenovirus Encoding Human Platelet-Derived Growth Factor-B Delivered to Alveolar Bone Defects Exhibits Safety and Biodistribution Profiles Favorable for Clinical Use

Abstract Platelet-derived growth factor (PDGF) gene therapy offers promise for tissue engineering of tooth-supporting alveolar bone defects. To date, limited information exists regarding the safety profile and systemic biodistribution of PDGF gene therapy vectors when delivered locally to periodontal osseous defects. The aim of this preclinical study was to determine the safety profile of adenovirus encoding the PDGF-B gene (AdPDGF-B) delivered in a collagen matrix to periodontal lesions. Standardized alveolar bone defects were created in rats, followed by delivery of matrix alone or containing AdPDGF-B at 5.5-108 or 5.5-109 plaque-forming units/ml. The regenerative response was confirmed histologically. Gross clinical observations, hematology, and blood chemistries were monitored to evaluate systemic involvement. Bioluminescence and quantitative polymerase chain reaction were used to assess vector biodistribution. No significant histopathological changes were noted during the investigation. Minor alterations in specific hematological and blood chemistries were seen; however, most parameters were within the normal range for all groups. Bioluminescence analysis revealed vector distribution at the axillary lymph nodes during the first 2 weeks with subsequent return to baseline levels. AdPDGF-B was well contained within the localized osseous defect area without viremia or distant organ involvement. These results indicate that AdPDGF-B delivered in a collagen matrix exhibits acceptable safety profiles for possible use in human clinical studies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78106/1/hum.2008.114.pd

An n-back task using vibrotactile stimulation with comparison to an auditory analogue.

We report a vibrotactile version of the common n-back task used to study working memory. Subjects wore vibrotactile stimulators on three fingers of one hand, and they responded by pressing a button with the other hand whenever the current finger matched the one stimulated n items back. Experiment 1 showed a steep decline in performance as n increased from 1 to 3; each additional level ofn decreased performance by 1.5 d' units on average. Experiment 2 supported a central capacity locus for the vibrotactile task by showing that it correlated strongly with an auditory analogue; both tasks were also related to standard digit span. The vibrotactile version of n-back may be particularly useful in dual-task contexts. It allows the assessment of cognitive capacity in sensory-impaired populations in which touch remains intact, and it may find use in brain-imaging studies in which vibrotactile stimuli impose a memory load.</p

Structure and ion transport of lithium-rich Li1+Al Ti2−(PO4)3 with 0.3<x<0.5: A combined computational and experimental study

New solid state electrolytes are becoming increasingly sought after in the drive to replace flammable liquid electrolytes. To this end, several Li conducting solids have been identified as promising candidates including Li stuffed garnets and more recently Li-rich materials such as Li1+xAlxTi2−x(PO4)3 with 0.3Ti4+ compared to Li+–>Al3+. Furthermore, our calculated ionic conductivities are in excellent agreement with experimental values, highlighting the robustness of our computational models

Nucleophilic 1,4-Additions for Natural Product Discovery

Natural products remain an important source of drug candidates, but the difficulties inherent to traditional isolation, coupled with unacceptably high rates of compound rediscovery, limit the pace of natural product detection. Here we describe a reactivity-based screening method to rapidly identify exported bacterial metabolites that contain dehydrated amino acids (<i>i.e.</i>, carbonyl- or imine-activated alkenes), a common motif in several classes of natural products. Our strategy entails the use of a commercially available thiol, dithiothreitol, for the covalent labeling of activated alkenes by nucleophilic 1,4-addition. Modification is easily discerned by comparing mass spectra of reacted and unreacted cell surface extracts. When combined with bioinformatic analysis of putative natural product gene clusters, targeted screening and isolation can be performed on a prioritized list of strains. Moreover, known compounds are easily dereplicated, effectively eliminating superfluous isolation and characterization. As a proof of principle, this labeling method was used to identify known natural products belonging to the thiopeptide, lanthipeptide, and linaridin classes. Further, upon screening a panel of only 23 actinomycetes, we discovered and characterized a novel thiopeptide antibiotic, cyclothiazomycin C