High-pressure structural stability and elasticity of supercrystals self-assembled from nanocrystals

We report here combined quasi-hydrostatic high-pressure small-angle X-ray scattering (SAXS) and X-ray diffraction (XRD) studies on faceted 3D supercrystals (SCs) self-assembled from colloidal 7.0 nm spherical PbS nanocrystals (NCs). Diamond anvil cell (DAC) SAXS experiments in the pressure range from ambient to 12.5 GPa revealed nearly perfect structural stability of the SCs, with face-centered cubic organization of the NCs. Pressure-induced ordering (annealing effect) of the superstructure was observed. The ambient pressure bulk modulus of the SCs was calculated to be ～5 GPa for compression and ～14.5 GPa for decompression from fitting of Vinet and Birch-Murnaghan equations of state. XRD measurements revealed strong preferential crystallographic orientation of the NCs through all phase transformations to as high as 55 GPa without any indication of NC sintering. The first phase transition pressure of the NCs was found between 8.1 and 9.2 GPa and proceeds through homogeneous nucleation. Bulk modulus of PbS NCs was calculated to be ～51 GPa based on fitting to the equations of state (K(PbS,bulk) ～ 51-57 GPa). Closest surface-to-surface distance between the NCs in the SCs was calculated based on combined XRD and SAXS data, to reversibly tune from ～1.56 nm to ～0.9-0.92 nm and back to ～1.36 nm in the ambient-12.5 GPa-ambient pressure cycle. The bulk modulus of the ligand matrix was extrapolated to be ～2.2-2.95 GPa. These results show a general method of tuning NC interactions in packed nanoparticle solids.     

Micro/nanosized refractive lens arrays formed by means of conformal thin film deposition

We provide a 'growing' method for fabricating a microlens array with lateral size of a few microns or less. Instead of using complicated etching techniques, the method forms a spherical profile of the lens using conformal chemical vapor deposition. We have fabricated two lens arrays. One has a pitch of 1200?nm, a circular aperture 1000?nm in diameter and a sag height of 130?nm. The other array has a pitch of 600?nm, and a square aperture of 600?nm × 600?nm, with a fill factor close to 100%. The maximum profile deviation between the fabricated lens and an ideal sphere is about 11% and 14% respectively. The calculation indicates that the curvature difference of the profile of the square lens in the orthogonal and diagonal direction is 5.5%. The roughness of the lens is measured as approximately 6?nm.     

Managing complex documents over the WWW: a case study for XML

The use of the World Wide Web as a communication medium for knowledge engineers and software designers is limited by the lack of tools for writing, sharing, and verifying documents written with design notations. For instance, the Z language has a rich set of mathematical characters, and requires graphic-rich boxes and schemas for structuring a specification document. It is difficult to integrate Z specifications and text on WWW pages written with HTML, and traditional tools are not suited for the task. On the other hand, a newly proposed standard for markup languages, namely XML, allows one to define any set of markup elements; hence, it is suitable for describing any kind of notation. Unfortunately, the proposed standard for rendering XML documents, namely XSL, provides for text-only (although sophisticated) rendering of XML documents, and thus it cannot be used for more complex notations. We present a Java-based tool for applying any notation to elements of XML documents. These XML documents can thus be shown on current-generation WWW browsers with Java capabilities. A complete package for displaying Z specifications has been implemented and integrated with standard text parts. Being a complete rendering engine, text parts and Z specifications can be freely intermixed, and all the standard features of XML (including HTML links and form elements) are available outside and inside Z specifications. Furthermore, the extensibility of our engine allows any additional notations to be supported and integrated with the ones we describe     

Rheological Analysis of Sucrose Solution at High Temperatures Using a Microwave‐Heated Pressurized Capillary Rheometer

Thermal process design, optimization, and deviation require the knowledge of engineering properties of food, such as rheological behavior, which is highly dependent on temperature. If a process is calculated based on the parameters obtained by extrapolation, it might lead to over‐ or underprocessing. The long time required for the product to reach the desired temperature, which is usual in many rheometers, may induce unexpected changes on the product. Model solutions are often used in engineering projects in order to simulate characteristics of real products. Thus, the objective of this study was to obtain rheological data of sucrose model solution at the actual high UHT (ultra‐high temperature) process temperatures using a pressurized capillary rheometer, heated by a microwave system. The results provide the rheological behavior of the sucrose solutions and show that there is no deviation of the linearity of the Arrhenius plot above 100 °C for this product. This work was useful to illustrate the use of the applied methodology and to validate the newly built microwave‐heated capillary rheometer. The data obtained confirm the stability of nonsaturated sucrose solution when treated above 100 °C and presents an important contribution to the literature database, since sucrose solutions are used as models for many table syrups, such as maple and sorghum syrups.     

Estimate of European 129I releases supported by 129I analysis in an Alpine ice core

129I in the European environment originates predominantly from the industrial nuclear fuel reprocessing plants Sellafield (Great Britain), Marcoule, and La Hague (both France). While reliable data on 129I releases from La Hague exist for the whole period of operation, less is known about the contributions from Sellafield and Marcoule. For those periods where no data are available, i.e., for the first 16 years of the Sellafield operation and for the first 3 decades of the Marcoule operation, we estimated releases into the atmosphere of 118 GBq and 825 GBq, respectively. Hence, Marcoule was the major European source of airborne 129I, contributing about 45% to the total airborne 129I releases from all the European reprocessing facilities, until it was decommissioned in 1997. The estimated total emissions were compared with 129I deposition fluxes for the time period 1970-2002, obtained from the analysis of an ice core from Fiescherhorn glacier, Swiss Alps (46 degrees 33'N, 08 degrees 04'E; 3900 m asl). The temporal evolution of the 129I deposition agrees well with the total 129I releases into the atmosphere from the European reprocessing facilities and from atmospheric nuclear weapons tests, supporting our estimated release rates. However,the 129I concentrations and deposition fluxes at Fiescherhorn glacier were a factor of 6 lower than values obtained from the analysis of rainwater collected near Zurich (408 m asl) in Switzerland in the years 1994-97. This suggests a strong vertical concentration gradient of 129I, typical for water-soluble atmospheric trace species which are removed from the atmosphere in the course of days by precipitation scavenging, and must be taken into account if glaciers are used as an archive for a retrospective quantification of 129I deposition fluxes. In addition, the temporal evolution of the contribution of 129I re-emitted from the ocean's surface for the 129I inventory in the atmosphere was quantified for the first time. Although the annual amount of 129I released this way was very low until the early 1990s, it is similar to the airborne 129I releases from Sellafield and La Hague in the present time.     

Seasonal pattern of mortality and relationships between mortality and temperature-humidity index in dairy cows

The 2 studies described investigated seasonal variations of mortality and temperature-humidity index (THI)-mortality relationships in dairy cows. Mortality data were extracted from the Italian Bovine Spongiform Encephalopathy databases, which contain records on cows older than 24 mo that died on a farm from all causes (98% of total records), were slaughtered in an emergency state, or were sent for normal slaughter but were sick in the preslaughter inspection (2% of total records). Both studies evaluated mortality data during a 6-yr period (2002 to 2007). The seasonal pattern study was conducted throughout Italy and was based on 320,120 deaths. An association between season and deaths was found for all 6 yr. Summer and spring were the seasons with the highest and lowest frequency of deaths (15,773.3 ± 2,861 and 11,619.3 ± 792.3), respectively, and within summer months, the number of deaths in July and August (5,435 ± 284 and 5,756 ± 676.2, respectively) was higher than in June (4,839 ± 344.8). The THI-mortality relationships study was carried out only for deaths (51,240) reported for the Lombardia and Emilia Romagna regions. For this study, the mortality databases were integrated with THI data, which were calculated by using data from 73 weather stations. Each farm where deaths were recorded was assigned the THI values (maximum and minimum) calculated at the closest weather station for each day the events (deaths) were reported. Analysis of data indicated that approximate THI values of 80 and 70 were the maximum and minimum THI, respectively, above which the number of deaths in dairy farms starts to increase. Maximum and minimum THI values of 87 and 77 were the upper critical THI above which the risk of death for dairy cows becomes maximum. This study defined quantitative relationships between mortality risk and THI in dairy cows and may help to provide emergency interventions and mitigation measures, which may ensure survival of dairy cows and reduce replacement costs associated with heat stress-related mortality.     

PCR detection of Bifidobacterium strains and Streptococcus thermophilus in feces of human subjects after oral bacteriotherapy and yogurt consumption

Streptococcus thermophilus, Bifidobacterium infantis Y1 and Bifidobacterium breve Y8 strains were identified and enumerated by PCR assay in human fecal samples after intake of the pharmaceutical preparation VSL-3 or yogurt. ThI/ThII primer set, specific for S. thermophilus, was selected testing its specificity against several strains of enterococci, streptococci and other genera colonizing the human intestine. A culture-independent PCR protocol, developed in this study, allowed to directly detect and enumerate S. thermophilus in human feces, excluding culture-based techniques or time consuming DNA isolation and purification procedures. Intestinal persistence of S. thermophilus was studied in feces of 10 healthy subjects given VSL-3 or yogurt. Streptococcal population was detected after 3 days of administration and persisted for 6 days after the treatment suspension. In the same trial, the colonization kinetics of B. infantis Y1 and B. breve Y8 were studied by amplification of colonies with the strain-specific primer sets InfY-BV.L/R and BreY-BV.R/L, showing a host-dependent transient colonization behaviour. PCR analysis of feces from 10 patients affected by inflammatory bowel diseases (IBD) and treated with VSL-3 for 2 months showed a colonization pattern of S. thermophilus, B. infantis Y1 and B. breve Y8 similar to that observed with the healthy subjects.     

Multi-fidelity design of stiffened composite panel with a crack

Crack propagation is an important concern in the design of aircraft composite fuselage and wing panels. However, numerical simulation of crack propagation is computationally expensive. This work proposes combining high-fidelity analysis model with low-fidelity model to calculate the crack propagation constraint in the design optimization process. Correction response surfaces are employed to relate the high-fidelity models to the low-fidelity models. Four different forms of correction response surface methods are explored and their prediction capabilities are compared. The multi-fidelity approach is found to be more accurate than single-fidelity response surface method at the same computational cost.     

The effect of bicarbonate/fluoride dentifrices on human plaque pH

The acidogenic response in dental plaque after rinsing with sodium bicarbonate/fluoride dentifrice slurries was studied using three intra-oral models. In the first model, resting plaque pH was monitored in mesiobuccal plaque on upper molars and premolars in six healthy subjects after abstinence from normal oral hygiene for three days. These measurements were followed by a three-minute rinse with 10% sucrose and, following a two-minute interval, a three-minute rinse with a test dentifrice slurry. After the test dentifrice rinse, pH was monitored at regular intervals up to 60 minutes. Flow rate, pH and buffer capacity of stimulated saliva were also determined. Changes in resting pH, plaque pH minima, and maximum pH drop were calculated. A clear elevation in the resting pH was observed after bicarbonate/fluoride dentifrice rinses, and a significant increase was obtained in the pH minima. The smallest pH drop also was found after treatment with the bicarbonate/fluoride dentifrice rinse treatment (p < 0.02). A second model using telemetric partial dentures with interproximally placed micro-antimony pH electrodes was used to study the effects of rinsing with increasing concentrations of sodium bicarbonate and calcium carbonate solutions, and with a fluoride dentifrice containing sodium bicarbonate. The response to these treatments was found to be rapid, dose-dependent, and was the greatest from the sodium bicarbonate. A third model used 24 subjects to assess the effects of sodium bicarbonate/fluoride dentifrice on plaque pH before and after a glucose challenge. The use of the bicarbonate/fluoride dentifrice resulted in significantly less measurable plaque acid than the fluoride dentifrice treatment. Collectively, these results indicate bicarbonate in dentifrice to be an effective buffering agent for stabilizing the pH and neutralizing plaque acids in dental plaque.