Several studies link adverse childhood experiences (ACEs) to delinquency. Yet, developmental sequalae accounting for this association remain unclear, with previous research limited by cross-sectional research designs and investigations of singular mediating processes. To redress these shortcomings, this study examines the longitudinal association between ACEs and delinquency as mediated by both sleep problems and low self-control, two factors which past research implicates as potentially important for understanding how ACEs contribute to antisocial behavior. Data collected from 480 adolescents (71.3% boys; 86.3% White) and their parents participating in the Michigan Longitudinal Study was used to conduct a serial mediation analysis. The association between ACEs (prior to age 11) and delinquency in late adolescence was found to operate indirectly via sleep problems in early adolescence and low self-control in middle adolescence. Nonetheless, a direct association between ACEs and later delinquency remained. Pathways through which ACEs contribute to later delinquency are complex and multiply determined. Findings indicate that early behavioral interventions, including improving sleep and self-control, could reduce later delinquency. Still, more research is needed to identify additional avenues through which the ACEs–delinquency association unfolds across development.

We study whether it is better to enforce the zero lower bound (ZLB) in models of U.S. Treasury yields using a shadow rate model or a quadratic term structure model. We show that the models achieve a similar in-sample fit and perform comparably in matching conditional expectations of future yields. However, when the recent ZLB period is included in the sample, the models’ ability to match conditional expectations away from the ZLB deteriorates because the time-series dynamics of the pricing factors change. In addition, neither model provides a reasonable description of conditional volatilities when yields are away from the ZLB.

This study reports data from teachers in regular classrooms about their experiences of inclusion for 143 young children with disabilities. Children were recruited from early intervention programs and their experiences were tracked across 3 years, from a Preparatory year to Year 2 of school. Children's teachers rated the appropriateness of the child's placement in their classroom as high to very high. However, most teachers rated the resources and supports available to support inclusion as only adequate. Teachers perceived a range of benefits for the child, peers, and themselves from inclusion but also identified significant challenges, including time pressures and increased responsibilities, as well as various behavioural and developmental concerns that had an impact on all children's learning. Challenges identified deserve continued attention for successful inclusive practice.

Seasonal peaks in both human campylobacter infections and poultry isolates have been observed in several European countries but remain unexplained. We compared weekly data on human campylobacter infections with thermophilic Campylobacter isolation rates from fresh, retail chicken samples (n=514) purchased weekly in Wales between January and December 2002. Human isolates (n=2631) peaked between weeks 22 and 25 (early June) and chicken isolates (n=364) between weeks 24 and 26 (late June). In the absence of a temporal association, we postulate that the seasonal rise in humans is not caused by a rise in isolation rates in poultry but that both are more likely to be associated with a common, but as yet unidentified, environmental source.

In January 1999, an outbreak of viral gastroenteritis affected more than 300 people who attended a metropolitan concert hall over a 5-day period. Norwalk-like virus (NLV) was confirmed in faecal samples by reverse transcription polymerase chain reaction assay. The index case was a concert attendee who vomited in the auditorium and adjacent male toilet. Gastrointestinal illness occurred among members of 8/15 school parties who attended the following day. Children who sat on the same level of the auditorium as the index case were much more likely to be ill than those seated elsewhere (relative risk 7.1, 95% confidence interval 5.4–9.2, P<0.001). The majority of other reported cases had not been present on the evening of the vomiting incident. Disinfection procedure was poor and the disinfectant used contained no sodium hypochlorite. Transmission most likely occurred through direct contact with contaminated fomites. The outbreak has implications for disinfection procedures following vomiting incidents at public venues.

The fundamental studies of metallic nanoparticles embedded in various host materials have been made. The host-guest interaction causes the shapes of embedded nanoparticles, and the surface plasmon resonances of the metallic nanoparticles are affected by the host materials. The control of the surface plasmon resonance condition is a challenging question. We will discuss the interface effect of the systems where gold nanoparticles were fabricated between materials of MgO and SiO2.

The fundamental studies of metallic nanoparticles embedded in various host materials have been made. The host-guest interaction causes the shapes of embedded nanoparticles, and the surface plasmon resonances of the metallic nanoparticles are affected by the host materials. The control of the surface plasmon resonance condition is a challenging question. We will discuss the interface effect of the systems where gold nanoparticles were fabricated between materials of MgO and SiO2.

Ion implantation and thermal processing were used to create a layer of Co nanoclusters embedded in the near-surface region of single-crystal sapphire. The Co nanoparticles ranged in size from 2-20 nm and were crystallographically aligned with the host sapphire. Specimens were irradiated with Xe and Pt ions, and the microstructural evolution of the nanoclusters was investigated by transmission electron microscopy. With increasing Pt or Xe ion dose, the Co nanoparticles lost their initially excellent faceting, although they remained crystalline. The host Al2O3 became amorphous and the resulting microstructure consisted of a buried amorphous layer containing the still-crystalline Co nanoparticles. EDS mapping and electron diffraction were used to determine the distribution of the implanted species, and the magnetic properties of the composite were measured with a SQUID magnetometer. The results show that ion beams can be applied to modify and control the properties of ferromagnetic nanocomposites, and, combined with lithographic techniques, will find applications in exercising fine-scale spatial control over the properties of magnetic materials.

Ion implantation was used to form compound semiconductor nanocrystal precipitates of ZnS, CdS, and PbS in both glass and crystalline matrices. The precipitate microstructures and size distributions were investigated by cross-sectional transmission electron microscopy techniques. Several unusual features were observed, including strongly depth-dependent size variations of the ZnS precipitates and central void features in the CdS nanocrystals. The morphology and crystal structure of the nanocrystal precipitates could be controlled by selection of the host material. The size distribution and microstructural complexity were significantly reduced by implanting a low concentration of ions into a noncrystalline host, and by using multi-energy implants to give a flat concentration profile of the implanted elements.

Silicon ions were implanted into fused silica substrates at doses of 1×1021, 2×1021, 5×1021, and 1×1022 ions/cm3. The implanted substrates were annealed at 1100°C for one hour in a reducing atmosphere (95% Ar+5% H2). Optical absorption spectra recorded after the annealing treatment showed absorption onsets at 3.86, 3.73, 2.86 and 2.52 eV for substrates implanted with 1×1021, 2×1021, 5×1021, and 1×1022 ions/cm3, respectively. Static photoluminescence (PL) measurements indicated red emission between 1.72 and 1.61 nm with a slightly increasing red shift with ion dose. Time resolved PL at room temperature revealed slow (∼50 μs) and fast (×20 μs) lifetimes which increased with decreasing temperature. TEM studies showed that the particle size increased with increasing ion dose. Typical particle sizes ranged between 2 and 5 nm indicating quantum confinement of the exciton, which can account for the blue shift in the absorption edge with decreasing ion dose. However, the maxima in the PL spectra for all ion doses are relatively independent of the ion dose and are strongly shifted from the absorption spectra. This suggests that radiative recombination occurs from a common luminescent center, possibly a surface or interfacial state in thexs SiOx, layer surrounding the nanocrystal.

Several groups have irradiated single crystals of synthetic and natural zircon (ZrSiO4) with a wide range of ions (from He to Bi) over a wide range of temperatures. The results of these studies show that amorphization in zircon is controlled by a variety of parameters and is a more complex process than previously thought. The critical dose for amorphization increases with temperature, similar to other materials. However, the critical displacement dose (in dpa) for amorphization is significantly higher at lower temperatures (below 500 K) for very heavy ions, such as Pb and Bi. This unusual dependence on the damage energy density has not been observed previously in other materials. Possible explanations for this behavior in terms of amorphization mechanisms are discussed. In addition, there is a significant difference in the temperature dependence of the critical dose in synthetic and natural zircons, which suggests that the impurities in natural zircons may affect the kinetics of recovery processes.

Amorphous, polycrystalline, and single crystal nanometer dimension particles can be formed in a variety of substrates by ion implantation and subsequent annealing. Such composite colloidal materials exhibit unique optical properties that could be useful in optical devices, switches, and waveguides. However colloids formed by blanket implantation are not uniform in size due to the nonuniform density of the implant, resulting in diminution of the size dependent optical properties. The object of the present work is to form more uniform size particles arranged in a 2-dimensional lattice by using a finely focused ion beam to implant identical ion doses only into nanometer size regions located at each point of a rectangular lattice. Initial work is being done with a 30 keV Ga beam implanted into Si. Results of particle formation as a function of implant conditions as analyzed by Rutherford backscattering, x-ray analysis, atomic force microscopy, and both scanning and transmission electron microscopy will be presented and discussed.

Synthetic ZrSiO4, HfSiO4, and ThSiO4 single-crystal specimens were irradiated by 800 keV Kr+ ions, and the microstructural evolution was observed in-situ in a transmission electron microscope. All three compounds were found to become amorphous up to temperatures in excess of 600°C. Using a new model, the activation energies for annealing were found to be in the range of 3.1 to 3.6 eV for these compounds. At temperatures above 600°C, the orthosilicates were observed to decompose into the component oxides (e.g., tetragonal ZrO2 + amorphous SiO2 in the case of zircon). A single-crystal zircon specimen was also irradiated with a pulsed picosecond Nd:YAG laser operated at 355 nm, and the resulting microstructure was investigated by optical absorption, SEM, AFM, and TEM techniques.

Ion implantation is a versatile technique by which compound semiconductor nanocrystals may be synthesized in a wide variety of host materials. The component elements that form the compound of interest are implanted sequentially into the host, and nanocrystalline precipitates then form during thermal annealing. Using this technique, we have synthesized compound semiconductor nanocrystal precipitates of ZnS, CdS, PbS, and CdSe in a fused silica matrix. The resulting microstructures and size distributions were investigated by cross-sectional transmission electron microscopy. Several unusual microstructures were observed, including a band of relatively large nanocrystals at the end of the implant profile for ZnS and CdSe, polycrystalline agglomerates of a new phase such as γ-Zn 2SiO4, and the formation of central voids inside CdS nanocrystals. While each of these microstructures is of fundamental interest, such structures are generally not desirable for potential device applications for which a uniform, monodispersed array of nanocrystals is required. Methods were investigated by which these unusual microstructures could be eliminated.