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Chorion type may significantly influence the prenatal environment of twins. This study explored the associations between chorion type and gestational age, birth weight, birth length, and the timing of emergence of the first primary tooth in two populations of twins, Australian and Dutch. Additionally, we investigated the relationship between chorion type and birth weight discordance (BWD) in order to determine whether a significant relationship existed between discordance in birth weight and discordance in the timing of emergence of the first primary tooth. The two study samples consisted of 409 Australian twin pairs and 301 Dutch twin pairs, all of European ancestry. Data were collected through a combination of questionnaires and recording charts administered to the parents and through linkage with biological databases. In the Australian sample, monozygotic monochorionic (MZMC) twins experienced the shortest mean gestation time (35 weeks), the lowest mean birth length (46 cm) and the lowest mean birth weight (2.3 kg) compared with other twin groups. For the same variables in the Dutch sample, these trends with MZMC twinning were not observed. Chorion type did not significantly affect the mean timing of emergence of the first primary tooth in either sample. Monochorionicity was found to be significantly associated with BWD in both samples, but there was a significant association between BWD in MZMC twin pairs and timing of emergence of the first primary tooth only in the Australian sample. Results from this study support previous findings that the timing of emergence of the first primary tooth is influenced strongly by genetic factors and is well protected from environmental disturbances.
Thin films of ZnO co-doped with lithium and phosphorus were deposited on sapphire substrates by RF magnetron sputtering. The films were sequentially deposited from ultra pure ZnO and Li3PO4 solid targets. Post deposition annealing was carried using a rapid thermal processor in O2 and N2 at temperatures ranging from 500 °C to 1000 °C for 3 min. Analyses performed using low temperature photoluminescence spectroscopy measurements reveal luminescence peaks at 3.359, 3.306, 3.245 eV for the co-doped samples. The x-ray diffraction 2θ-scans for all the films showed a single peak at about 34.4° with full width at half maximum of about 0.17°. Hall Effect measurements revealed conductivities that change from p-type to n-type over time.
Zinc Oxide thin films were deposited on sapphire substrates by radio frequency (RF) magnetron sputtering from an ultra-high purity ZnO solid target. The ZnO films were deposited on sapphire substrates heated in oxygen and/or in vacuum prior to deposition. Additional parameters investigated included the substrate temperature varied from 25 °C to 600 °C, the deposition gas pressure varied from 5 mTorr to 40 mTorr and the gas flow rate varied from 5 to 30 standard cubic centimeter per minute (sccm). The resulting films were annealed using a rapid thermal processor in N2 gas at 900 °C for 5 min. Analyses carried out using photoluminescence spectroscopy (PL) and X-ray diffraction (XRD) measurements indicate that films deposited at 300 °C using Ar:O2 (1:1) had the best optical and microstructure qualities. Pre-heating the sapphire substrate in oxygen prior to deposition was found to create a smoother sapphire surface, and this produced a ZnO film with greatly improved qualities. This film had a luminescence peak at 3.362 eV with a full-width-half maximum (FWHM) value of 15.3 meV when measured at 11 K. The XRD 2θ-scans had peaks at 34.4° with the best FWHM value of only 0.10°. Production of high quality ZnO materials is a necessary step towards realizing highly conductive p-type doped ZnO materials which is currently a major goal in research efforts on ZnO.
We have used a direct imaging technique, in situ atomic force microscopy(AFM) to observe the earliest stages of the dissolution of a biotite surface byoxalic acid at temperatures close to ambient conditions, using a speciallydesigned AFM liquid cell and non-invasive intermittent contact mode of operation. From the nm-resolution data sets in x, yand z dimensions, we have measured dissolution rates and determined activation energies for the process as a function of temperature, via a mass-loss calculation. The value of Ea obtained, 49±2 kJ mol-1, appears to be too high to indicate a diffusion-controlled process and is more in line with expectations based on a process limited by the rate of ligand-induced metal cation detachment from the (001) surface. This is consistent with visual observations of the relative rates of etch-pit formation and growth, and accepted knowledge of the biotite crystal structure. Separate calculations based on planar area etch-pit growth, and measurements of etch-pit perimeters confirm this result, and also indicate substantiallyhigher activation energy, up to 80 kJ mol-1, when the edge pits are in an incipient stage.
The goal of this study was to examine sexual harassment in early adolescence. Available data
indicate that peer to peer sexual harassment is prevalent in high school and is associated with
psychosocial problems for both victims and perpetrators. For the present study, we adopted a
developmental contextual model to examine the possibility that this behavior develops during the
late elementary and middle school years and is linked to the biological and social changes that
occur at this time. Youths from Grades 6–8 (N = 1,213) enrolled in seven
elementary and middle schools in a large south-central Canadian city were asked to report on their
sexual harassment behaviors with same- and cross-gender peers; their pubertal development, and
the gender composition of their peer network. The results revealed that cross-gender harassment
was distinct from same-gender harassment, increased in frequency from Grade 6 to Grade 8, and
was linked to pubertal maturation and participation in mixed-gender peer groups. The implications
of a developmental contextual model for understanding the emergence of this problematic
behavior in adolescence are discussed.
It is known that the only topological invariants P for which anti(P) = anti2 (P), anti( ) denoting Bankston's total negation operator, are those which are determined purely by the cardinality of the underlying point-set. We examine equations of the form antin (P) = antin (not P), reaching similar conclusions for n ≤ 2 but weaker ones for n > 3. A corresponding investigation for total negation within a constraint is initiated.
This paper presents the dynamic injury tolerances for the female humerus and forearm derived from
dynamic 3-point bending tests using 22 female cadaver upper extremities. Twelve female humeri were tested
at an average strain rate of 3.7±1.3%/s. The strain rates were chosen to be representative of those observed
during upper extremity interaction with frontal and side airbags. The average moment to failure when mass
scaled for the 5th centile female was 128±19 Nm. Using data from the in situ strain gauges during the drop
tests and geometric properties obtained from pretest CT scans, an average dynamic elastic modulus for the
female humerus was found to be 24.4±3.9 GPa. The injury tolerance for the forearm was determined from
10 female forearms tested at an average strain rate of 3.94±2.0%/s. Using 3 matched forearm pairs, it was
determined that the forearm is 21% stronger in the supinated position (92±5 Nm) versus the pronated
position (75±7 Nm). Two distinct fracture patterns were seen for the pronated and supinated groups. In
the supinated position the average difference in fracture time between the radius and ulna was a negligible
0.4±0.3 ms. However, the pronated tests yielded an average difference in fracture time of 3.6±1.2 ms, with
the ulna breaking before the radius in every test. This trend implies that in the pronated position, the ulna
and radius are loaded independently, while in the supinated position the ulna and radius are loaded together
as a combined structure. To produce a conservative injury criterion, a total of 7 female forearms were tested
in the pronated position, which resulted in the forearm injury criterion of 58±12 Nm when scaled for the
5th centile female. It is anticipated that these data will provide injury reference values for the female forearm
during driver air bag loading, and the female humerus during side air bag loading.
The major surface glycoprotein of Leishmania, referred to as GP63, is a zinc metalloproteinase of 63000 Mr present on promastigotes and amastigotes from diverse species of Leishmania. GP63 shares several characteristics with the members of the matrix metalloproteinase family including degradation of at least one component of the extracellular matrix, location at the cell surface, requirement for Zn2+ for proteinase activity and inhibition of the proteinase activity by chelating agents and α2–macroglobulin. Site-directed mutagenesis of the cloned L. major GP63 genes was carried out to determine whether the proposed active site of Leishmania GP63 was homologous to those of other zinc metalloproteinases. The codon encoding the catalytic glutamic acid was modified to encode an aspartic acid and when expressed in COS–7 cells the resulting mutant GP63 had no demonstrable proteinase activity compared to wild type GP63. GP63 was predicted to be synthesized as a precursor protein containing a pro region at the NH2–terminus of GP63 implicated to be involved with the regulation of proteinase activity. As with many other proteinases, including matrix metalloproteinases, these enzymes are synthesized as latent proteinases that require activation for full proteinase activity. L. major recombinant GP63 (rGP63) has been produced in the baculovirus expression system where rGP63 was secreted as a latent proteinase. To study the activation of baculovirus rGP63, purified rGP63 was incubated with the mercurial compound, HgCl2, at concentrations previously shown to result in activation of other latent matrix degrading metalloproteinases and resulted in a significant enhancement of GP63 proteinase activity. The similarity of GP63 to the family of matrix-degrading proteinases suggests that the proteinase activity of GP63 maybe involved with the pathology of lesion formation in the mammalian host and may also be involved with the promastigote life stage in the sandfly vector. To study the functional role of GP63 proteinase, mutant strains of L. major, deficient in the expression of GP63, are currently being derived by targeted gene deletion. Using this strategy results have demonstrated the deletion of an entire L. major GP63 locus, containing in total six GP63 genes. Strategies to delete the second GP63 gene locus are developed and will determine whether deletion of both loci results in viable promastigotes. L. major strains deficient in the expression of GP63 may then be used to address the function of GP63 glycoprotein in the life cycle of Leishmania.
Recent progress in the field of liquid crystal materials and oriented polymers studied by nearfield scanned probe microscopies (SPM) is presented here. The investigations were focused on scanning tunneling microscopy (STM) results of antiferroelectric liquid crystalline molecules observed at different elevated temperatures corresponding to different bulk mesophases of the material, and on surface morphological studies of a liquid crystalline polymer by scanning force microscopy (SFM). In the field of oriented thermoplastic polymers, SFM images of the morphology and molecular packing in the outermost surface of poly(butene-1) films are presented.
Schweizer and Sklar, in their book Probabilistic Metric Spaces, raise the question of whether every triangle function is causal. This note provides a negative answer, by observing certain properties of a suitable partial quaternary operation on the unit interval.
For the investigation of certain kinds of reflexivity in topological vector spaces, Sova has shown that the ideas of panneaux and of espaces pannelés are as crucial as are those of barrels and of barrelled spaces. The objectives of this note are: (i) to establish the existence of (concentrated) barrels which are not panneaux, and (ii) to observe the equivalence of the conditions “pannelé” and “barrelled” for metrizable spaces, and the failure of this equivalence for general spaces.
Muon diffusion can be studied in metals without nuclear moments by the addition of paramagnetic impurities. We describe the theory and report measurements of muon depolarization in gold and silver doped with gadolinium and erbium. As well as diffusion rates, strength of the magnetic interaction and spin lattice relaxation rate of the paramagnetic ion are inferred from the data.
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