Biomedical subjects
Publications and source records attributed to Matthew J Davis.
Single crystals of La(2.47)Na(1.53)RhO6, Pr(2.45)Na(1.55)RhO6, Nd(2.45)Na(1.55)RhO6, La2Na2PtO6, and Nd2Na2PtO6 were grown from carbonate and "wet" hydroxide fluxes. All were found to crystallize in the trigonal space group R3c and adopt the K4CdCl6 structure.
We apply the projected Gross-Pitaevskii equation (PGPE) formalism to the experimental problem of the shift in critical temperature Tc of a harmonically confined Bose gas as reported in Gerbier et al., Phys. Rev. Lett. 92, 030405 (2004). The PGPE method includes critical fluctuations and we find the results differ from various mean-field theories, and are in best agreement with experimental data. To unequivocally observe beyond mean-field effects, however, the experimental precision must either improve by an order of magnitude, or consider more strongly interacting systems. This is the first application of a classical field method to make quantitative comparison with experiment.
The calculation of quantum dynamics is currently a central issue in theoretical physics, with diverse applications ranging from ultracold atomic Bose-Einstein condensates to condensed matter, biology, and even astrophysics. Here we demonstrate a conceptually simple method of determining the regime of validity of stochastic simulations of unitary quantum dynamics by employing a time-reversal test. We apply this test to a simulation of the evolution of a quantum anharmonic oscillator with up to 6.022x10(23) (Avogadro's number) of particles. This system is realizable as a Bose-Einstein condensate in an optical lattice, for which the time-reversal procedure could be implemented experimentally.
OBJECTIVE: To test whether parenting style and smoking-specific parenting practices prospectively predicted adolescent smoking. METHODS: Three hundred eighty-two adolescents (age 10-17 years, initial nonsmokers, 98% non-Hispanic whites) and their parents were interviewed, with smoking also assessed 1-2 years later. RESULTS: Adolescents from disengaged families (low acceptance and low behavioral control) were most likely to initiate smoking. Adolescents' reports of parents' smoking-related discussion was related to lowered smoking risk for adolescents with nonsmoking parents, but unrelated to smoking onset for adolescents with smoking parents. Smoking-specific parenting practices did not account for the effects of general parenting styles. CONCLUSIONS: Both parenting style and smoking-specific parenting practices have unique effects on adolescent smoking, although effects were largely confined to adolescents' reports; and for smoking-specific parenting practices, effects were confined to families with nonsmoking parents. Interventions that focus only on smoking-specific parenting practices may be insufficient to deter adolescent smoking.
Cryptococcus neoformans is an opportunistic human fungal pathogen that elaborates several virulence attributes, including a polysaccharide capsule and melanin pigments. A conserved Galpha protein/cyclic AMP (cAMP) pathway controls melanin and capsule production. To identify targets of this pathway, we used an expression profiling approach to define genes that are transcriptionally regulated by the Galpha protein Gpa1. This approach revealed that Gpa1 transcriptionally regulates multiple genes involved in capsule assembly and identified two additional genes with a marked dependence on Gpa1 for transcription. The first is the LAC1 gene, encoding the laccase enzyme that catalyzes a rate-limiting step in diphenol oxidation and melanin production. The second gene identified (LAC2) is adjacent to the LAC1 gene and encodes a second laccase that shares 75% nucleotide identity with LAC1. Similar to the LAC1 gene, LAC2 is induced in response to glucose deprivation. However, LAC2 basal transcript levels are much lower than those for LAC1. Accordingly, a lac2 mutation results in only a modest delay in melanin formation. LAC2 overexpression suppresses the melanin defects of gpa1 and lac1 mutants and partially restores virulence of these strains. These studies provide mechanistic insights into the regulation of capsule and melanin production by the C. neoformans cAMP pathway and demonstrate that multiple laccases contribute to C. neoformans melanin production and pathogenesis.
A large bis-urea macrocycle was synthesized and assembled into columnar nanotubes containing a sizable cavity. This purely organic nanotube is held together primarily by hydrogen bonding and yet shows remarkable thermal stability up to 180 degrees C in the presence and absence of acetic acid guest. This enables the nanotube to be used as reusable organic zeolite.
Crystals of (NaLa(2))NaPtO(6) were grown in an acidic ("wet") NaOH flux. (NaLa(2))NaPtO(6) forms in a 2H-perovskite related structure type and contains mixed cation (Na/La) occupancy on the A-site. The crystal was a rhombohedral obverse-reverse twin, and it crystallizes in the space group R3c (hexagonal setting) with lattice parameters of a = 9.5031(2) A and c = 11.4625(5) A. (NaLa(2))NaPtO(6) is the first example of an m = 0, n = 1 (A(3)A'BO(6)) member of the A(3n)+3m)A'(n)B(3m+n)O(9m+6n) family of oxides where either a lanthanide or a sodium cation occupies the A-site.
Two twisted 1,2-bis(2-pyridyl)ethyne ligands bridge two Cd(2+) centers in the C(2)-symmetric title complex, [Cd(2)(NO(3))(4)(mu-C(12)H(8)N(2))(2)(H(2)O)(2)]. The bridging ligands arch across one another creating a 'zigzag loop' molecular geometry. Two nitrate ions and a water molecule complete the irregular seven-coordinate Cd-atom environment. The dihedral angles between the equivalent pyridyl ring planes of the two independent ligands are 67.2 (1) degrees. O(water)-H.O(nitrate) hydrogen bonding creates two-dimensional layers parallel to the ab plane.
Single crystals of two new osmium-containing triple perovskites, Ba(3)LiOs(2)O(9) and Ba(3)NaOs(2)O(9), were grown from reactive molten hydroxide fluxes in sealed silver tubes. They crystallize in the space group P6(3)/mmc with lattice parameters of a = 5.8025(1) A, c = 14.1468(4) A for Ba(3)LiOs(2)O(9) and a = 5.8858(1) A, c = 14.3451(5) A for Ba(3)NaOs(2)O(9). The magnetic susceptibility of these osmates indicates significant Os-Os coupling within the octahedra pair.