A latent class model for obesity

We extend the discrete data latent class literature by explicitly defining a latent variable for class membership as a function of both observables and unobservables, thereby allowing the equations defining the class membership and observed outcomes to be correlated. The procedure is then applied to modelling observed obesity outcomes, based upon an underlying ordered probit equation

Passive Surveillance of \u3cem\u3eIxodes scapularis\u3c/em\u3e (Say), Their Biting Activity, and Associated Pathogens in Massachusetts

A passive surveillance of tick-borne pathogens was conducted over a 7-year period (2006–2012), in which a total of 3551 ticks were submitted to the University of Massachusetts for PCR testing. The vast majority of these ticks were Ixodes scapularis from Massachusetts (N = 2088) and hence were the focus of further analysis. Two TaqMan duplex qPCR assays were developed to test I. scapularis ticks for the presence of three human pathogens: Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti. I. scapularis submissions were concentrated from Cape Cod, the eastern half of the state outside of the Boston metropolitan area, parts of Franklin and Hampshire counties along the Quabbin Reservoir watershed, and southwestern Berkshire county. Differences in seasonal activity pattern were observed for different developmental stages of I. scapularis. The largest proportion of tick bite victims were age 9 years and under. Nymphal ticks were found more often on lower extremities of their hosts, while more adult ticks were found on the head. Overall infection rate of B. burgdorferi, A. phagocytophilum, and B. microti in human-biting ticks was 29.6%, 4.6%, and 1.8%, respectively. B. burgdorferi-infected ticks were widely distributed, but A. phagocytophilum- and B. microti-infected I. scapularis were found mainly in the eastern half of the state. We found that 1.8%, 1.0%, and 0.4% of ticks were coinfected by B. burgdorferi and A. phagocytophilum, B. burgdorferi and B. microti, and A. phagocytophilum and B. microti, respectively, and 0.3% of ticks had triple coinfection

Rotational Evolution During Type I X-Ray Bursts

The rotation rates of six weakly-magnetic neutron stars accreting in low-mass X-ray binaries have most likely been measured by Type I X-ray burst observations with RXTE. The nearly coherent oscillations detected during the few seconds of thermonuclear burning are most simply understood as rotational modulation of brightness asymmetries on the neutron star surface. We show that, as suggested by Strohmayer and colleagues, the frequency changes of 1-2 Hz observed during bursts are consistent with angular momentum conservation as the burning shell hydrostatically expands and contracts. We calculate how vertical heat propagation through the radiative outer layers of the atmosphere and convection affect the coherence of the oscillation. We show that the evolution of the rotational profile depends strongly on whether the burning layers are composed of pure helium or mixed hydrogen/helium. Our results help explain the absence (presence) of oscillations from hydrogen-burning (helium-rich) bursts that was found by Muno and collaborators. We investigate angular momentum transport within the burning layers and the recoupling of the burning layers with the star. We show that the Kelvin-Helmholtz instability is quenched by the strong stratification, and that mixing between the burning fuel and underlying ashes by the baroclinic instability does not occur. However, the baroclinic instability may have time to operate within the differentially rotating burning layer, potentially bringing it into rigid rotation.Comment: To appear in The Astrophysical Journal; minor corrections made to tables and figure

Ureteral Stents for Impassable Ureteroscopy

Background: For the narrow ureter that will not accommodate a ureteroscope, it is common practice to place a ureteral stent, to allow subsequent ureteroscopy in the passively dilated ureter. Surprisingly, there are limited data on the effectiveness or safety of these maneuvers. Methods: We retrospectively analyzed patients managed with ureteral stent placement followed by another attempt at ureteroscopy after an initial attempt of flexible ureteroscopy failed because the ureteroscope would not pass up an otherwise normal ureter. Results: Of 41 patients with follow-up who underwent ureteral stenting for this reason, the ureteroscope passed with ease poststenting in 29 (71%) and there was continued resistance in 12. Of these 12 patients, the ureteroscopy was continued despite resistance in 9, while another stent was placed in the remaining 3. Of these three patients, the third attempt at ureteroscopy was successful in two, and further attempts at ureteroscopy were not made after the third attempt failed in one. With a mean overall follow-up of 32 months, two patients (5%) developed ureteral strictures. Both were among nine patients in whom repeat ureteroscopy was performed despite resistance, with a rate of obstruction of 22% in this subgroup. Overall, ureteral stenting allowed successful ureteroscopy in 98% of patients. Conclusions: Ureteral stenting with subsequent ureteroscopy is a successful and safe method of addressing a narrow ureter that initially does not allow passage of a flexible ureteroscope, as long as persistent subsequent attempts to insert the ureteroscope are made only if it passes easily.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140373/1/end.2012.0414.pd

Phase control during the synthesis of nickel sulfide nanoparticles from dithiocarbamate precursors

Square-planar nickel bis(dithiocarbamate) complexes, [Ni(S2CNR2)2], have been prepared and utilised as single source precursors to nanoparticulate nickel sulfides. While they are stable in the solid-state to around 300 °C, heating in oleylamine at 230 °C, 5 mM solutions afford pure α-NiS, where the outcome is independent of the substituents. DFT calculations show an electronic effect rather than steric hindrance influences the resulting particle size. Decomposition of the iso-butyl derivative, [Ni(S2CN(i)Bu2)2], has been studied in detail. There is a temperature-dependence of the phase of the nickel sulfide formed. At low temperatures (150 °C), pure α-NiS is formed. Upon raising the temperature, increasing amounts of β-NiS are produced and at 280 °C this is formed in pure form. A range of concentrations (from 5-50 mM) was also investigated at 180 °C and while in all cases pure α-NiS was formed, particle sizes varied significantly. Thus at low concentrations average particle sizes were ca. 100 nm, but at higher concentrations they increased to ca. 150 nm. The addition of two equivalents of tetra-iso-butyl thiuram disulfide, ((i)Bu2NCS2)2, to the decomposition mixture was found to influence the material formed. At 230 °C and above, α-NiS was generated, in contrast to the results found without added thiuram disulfide, suggesting that addition of ((i)Bu2NCS2)2 stabilises the metastable α-NiS phase. At low temperatures (150-180 °C) and concentrations (5 mM), mixtures of α-NiS and Ni3S4, result. A growing proportion of Ni3S4 is noted upon increasing precursor concentration to 10 mM. At 20 mM a metastable phase of nickel sulfide, NiS2 is formed and as the concentration is increased, α-NiS appears alongside NiS2. Reasons for these variations are discussed

Synthesis, Molecular Structures and Electrochemical Investigations of [FeFe]-Hydrogenase Biomimics [Fe₂(CO)_{6-n}(EPh₃)_{n}(mu-edt)] (E = P, As, Sb; n = 1, 2)

A series of ethane‐dithiolate (edt = S(CH_{2})_{2}S) complexes [Fe_{2}(CO)_{5}(EPh_{3})(µ‐edt)] and [Fe_{2}(CO)4(EPh_{3})_{2}(µ‐edt)] (E = P, As, Sb), biomimics of the core of [FeFe]‐hydrogenases, have been prepared and structurally characterised. The introduced ligand(s) occupies apical sites lying trans to the iron‐iron bond. NMR studies reveal that while in the mono‐substituted complexes the Fe(CO)_{3} moiety undergoes facile trigonal rotation, the Fe(CO)2(PPh3) centres do not rotate on the NMR timescale. The reductive chemistry has been examined by cyclic voltammetry both in the presence and absence of CO and the observed behavior is found to be dependent upon the nature of the substituents. With L = CO or SbPh_{3} potential inversion is seen leading to a two‐electron reduction, while for others (L = PPh_{3}, AsPh_{3}) a quasi‐reversible one‐electron reduction is observed. Protonation studies reveal that [Fe_{2}(CO)_{5}(PPh_{3})(µ‐edt)] is only partially protonated by excess HBF_{4}·Et_{2}O, thus ruling complexes [Fe_{2}(CO)_{5}(EPh3)(µ‐edt)(µ‐H)]^{+} out as a catalytic intermediates, but [Fe_{2}(CO)_{4}(PPh_{3})_{2}(µ‐edt)] reacts readily with HBF_{4}·Et_{2}O to produce [Fe_{2}(CO)_{4}(PPh3)_{2}(µ‐edt)(µ‐H)]^{+}. While all new complexes are catalysts for the reduction of protons in MeCN, their poor stability and relatively high reduction potentials does not make them attractive in this respect

Electrocatalytic proton reduction by [Fe(CO)2(κ2-dppv)(κ1-SAr)2] (dppv = cis-1,2-bis(diphenylphosphino)ethylene; Ar = C6F5, C6H5, C6H4CH3-p)

Electrocatalytic reduction of protons to hydrogen by mononuclear iron complexes which are developed as models of the distal iron center of [FeFe]-hydrogenase active site are described. A series of iron(II) bis(thiolate) complexes [Fe(CO) 2 (κ 2 -dppv)(κ 1 -SAr) 2 ] (1, Ar = C 6 F 5 ; 2, Ar = C 6 H 4 ; 3, Ar = C 6 H 4 CH 3 -p; dppv = cis-1,2-bis(diphenylphosphino)ethylene) have been prepared from direct reactions between the corresponding hexacarbonyl [Fe 2 (CO) 6 (μ-SAr) 2 ] and dppv at elevated temperatures. Structurally they are similar being coordinated by a chelating dppv, two carbonyls and two thiolate ligands bonded in an all cis-arrangement. Solution spectroscopic data indicate that they exist in two isomeric forms in solution. All reversibly protonate at sulphur atom(s) upon addition of HBF 4 ·Et 2 O and lose a thiolate ligand as thiol. They show a common quasi-reversible reductive feature (attributed to the Fe II /Fe I couple) in their CVs in addition to other redox responses and are able to catalyze reduction of protons to hydrogen at their Fe(I) oxidation state in presence of HBF 4 ·Et 2 O. Complex 1 is the most efficient catalyst and catalyzes proton reduction at ca. −1.5 V showing i cat /i p ≥46 in the presence of ten equivalents of HBF 4 ·Et 2 O

Ficus insipida subsp. insipida (Moraceae) reveals the role of ecology in the phylogeography of widespread Neotropical rain forest tree species

Aim: To examine the phylogeography of Ficus insipida subsp. insipida in order to investigate patterns of spatial genetic structure across the Neotropics and within Amazonia. Location: Neotropics. Methods: Plastid DNA (trnH-psbA; 410 individuals from 54 populations) and nuclear ribosomal internal transcribed spacer (ITS; 85 individuals from 27 populations) sequences were sampled from Mexico to Bolivia, representing the full extent of the taxon's distribution. Divergence of plastid lineages was dated using a Bayesian coalescent approach. Genetic diversity was assessed with indices of haplotype and nucleotide diversities, and genetic structure was examined using spatial analysis of molecular variance (SAMOVA) and haplotype networks. Population expansion within Amazonia was tested using neutrality and mismatch distribution tests. Results: trnH-psbA sequences yielded 19 haplotypes restricted to either Mesoamerica or Amazonia; six haplotypes were found among ITS sequences. Diversification of the plastid DNA haplotypes began c. 14.6 Ma. Haplotype diversity for trnH-psbA was higher in Amazonia. Seven genetically differentiated SAMOVA groups were described for trnH-psbA, of which two were also supported by the presence of unique ITS sequences. Population expansion was suggested for both markers for the SAMOVA group that contains most Amazonian populations. Main conclusions: Our results show marked population genetic structure in F. insipida between Mesoamerica and Amazonia, implying that the Andes and seasonally dry areas of northern South America are eco-climatic barriers to its migration. This pattern is shared with other widespread pioneer species affiliated to wet habitats, indicating that the ecological characteristics of species may impact upon large-scale phylogeography. Ficus insipida also shows genetic structure in north-western Amazonia potentially related to pre-Pleistocene historical events. In contrast, evident population expansion elsewhere in Amazonia, in particular the presence of genetically uniform populations across the south-west, indicate recent colonization. Our findings are consistent with palaeoecological data that suggest recent post-glacial expansion of Amazonian forests in the south