Fractionally δ-Doped Oxide Superlattices for Higher Carrier Mobilities

A two-dimensional (2D) electron gas system in an oxide heterostructure serves as an important playground for novel phenomena. Here, we show that, by using fractional δ-doping to control the interface's composition in La(x)Sr(1-x)TiO(3)/SrTiO(3) artificial oxide superlattices, the filling-controlled 2D insulator-metal transition can be realized. The atomic-scale control of d-electron band filling, which in turn contributes to the tuning of effective mass and density of the charge carriers, is found to be a fascinating route to substantially enhanced carrier mobilities.     

Effect of contaminant hydrophobicity on hydrogen peroxide dosage requirements in the Fenton-like treatment of soils

A homologous series of n-alcohols was used as model contaminants to investigate the effect of hydrophobicity on the hydrogen peroxide concentration necessary in Fenton-like treatment for near-complete (>99%) destruction of compounds sorbed to soil. These probe compounds were selected because they exhibit equal reactivities with hydroxyl radicals, but have varied hydrophobicities. The standard Fenton reaction was first used to confirm equal hydroxyl radical reactivity for the n-alcohols. Central composite rotatable design experiments were then used to determine the conditions in an iron(III)-hydrogen peroxide system that resulted in 99% degradation of each of the probe compounds when sorbed to soil. The hydrogen peroxide concentrations required for 99% destruction of the sorbed compounds increased with probe compound hydrophobicity. Furthermore, hydrogen peroxide concentration requirements were directly proportional to the log octanol-water partition coefficients (logK(OW)) of each probe compound. This quantitative relationship may not be directly applicable to other organic contaminants, but a strong correlation between logK(OW) and hydrogen peroxide requirements for other contaminants will likely be found. These results confirm that hydrogen peroxide requirements for soil treatment increase as a function of contaminant hydrophobicity and provide a basis for the development of an algorithm for hydrogen peroxide requirements when modified Fenton's reagent is used for in situ chemical oxidation (ISCO).     

A method of HIV-1 inactivation compatible with antibody-based depletion of abundant proteins from plasma

We have examined several methods, including heat treatment and treatment with detergents, to inactivate HIV-1 present in plasma to be depleted of abundant proteins utilizing an antibody-based technology. Treatment with Triton X-100 was not compatible with abundant protein depletion with an antibody column and heat treatment alters the composition of the plasma proteome. However, treatment with 1.2% N-octylglucoside for 5?min completely inhibited HIV-1 infectivity. The detergent was easily removed through buffer exchange, and this treatment had no discernable effect on protein depletion.     

The effects of sensory impairments on product experience and personal well-being

To determine the roles that the sensory modalities play in user product interactions, one modality was blocked during the execution of eight simple tasks. Participants reported how they experienced the products and how they felt during the experiment. Blocking vision resulted in the largest loss of functional information, increased task difficulty and task duration, and fostered dependency. On the other hand, the other senses were used more and product experiences increased in perceived intenseness. When touch was blocked, the perceived loss of information was smaller and participants reported that familiar products felt less like their own. Blocking audition resulted in communication problems and a feeling of being cut off. Blocking olfaction mainly decreased the intenseness of the experience. These outcomes suggest that vision mainly plays a functional role in everyday user-product interactions, whereas the main role for olfaction lies in the affective domain. Sensory impairments change the way people experience products. Blocking a single modality during everyday tasks gives insight into the impact of impairments. These insights can be used to develop products for multiple user groups (inclusive design) or products used under extreme environmental conditions.     

Reader preference for report typefaces

A postal survey of typeface preference is described. The survey was designed to help in the choice of typeface to be used for the internal technical Reports produced by the Post Office Research Department. Type setting for these Reports is carried out using an IBM Selectric Composer for which seven typefaces suitable for reports are available. One hundred and twenty-five people who regularly receive copies of these Reports and 57 Trainee Technicians (Apprentices) were asked to arrange these seven typefaces in order of preference and record this ranking on a response sheet. About 85% of both groups returned response sheets for statistical analysis. The results showed a significant preference for three of the typefaces: Press Roman, Theme and Univers. Of these, Press Roman is used for the text of Research Department Reports and Univers is used on diagrams and tables.     

Measurement of attogram quantities of 231Pa in dissolved and particulate fractions of seawater by isotope dilution thermal ionization mass spectroscopy

A technique has been developed to quantify ultratrace 231Pa (50-2000 ag; 1 ag = 10(-18) g) concentrations in seawater using isotope-dilution thermal ionization mass spectrometry (TIMS). The method is a modification of a process developed by Pickett et al. (Pickett, D. A.; Murrell, M. T.; Williams, R. W. Anal. Chem. 1994, 66, 1044-1049) and extends the technique to very low levels of protactinium. The procedural blank is 16 +/- 15 ag (2sigma), and the ionization efficiency (ions generated/atom loaded) approaches 0.5%. Measurement time is <1 h. The amount of 231Pa needed to produce 231Pa data with an uncertainty of +/-4-12% is 100-1000 ag (approximately 3 x 10(5) to 3 x 10(6) atoms). Replicate measurements made on known standards and seawater samples demonstrate that the analytical precision approximates that expected from counting statistics and that, based on detection limits of 38 and 49 ag, protactinium can be detected in a minimum sample size of surface seawater of approximately 2 L for suspended particulate matter and <0.1 L for filtered (<0.4 microm) seawater, respectively. The concentration of 231Pa (tens of attograms per liter) can be determined with an uncertainty of +/-5-10% (2sigma) for suspended particulate matter filtered from 5 to 10 L of seawater. For the dissolved fraction, 0.5-1 L of seawater yields 231Pa measurements with a precision of 1-10%. Sample size requirements are orders of magnitude less than traditional decay-counting techniques and significantly less than previously reported ICP-MS techniques. Our technique can also be applied to other environmental samples, including cave waters, rivers, and igneous rocks.     

Design and performance of capping layers for extreme-ultraviolet multilayer mirrors

Multilayer lifetime has emerged as one of the major issues for the commercialization of extreme-ultraviolet lithography (EUVL). We describe the performance of an oxidation-resistant capping layer of Ru atop multilayers that results in a reflectivity above 69% at 13.2 nm, which is suitable for EUVL projection optics and has been tested with accelerated electron-beam and extreme-ultraviolet (EUV) light in a water-vapor environment. Based on accelerated exposure results, we calculated multilayer lifetimes for all reflective mirrors in a typical commercial EUVL tool and concluded that Ru-capped multilayers have approximately 40x longer lifetimes than Si-capped multilayers, which translates to 3 months to many years, depending on the mirror dose.     

Simple synthesis of hierarchically ordered mesocellular mesoporous silica materials hosting crosslinked enzyme aggregates

Hierarchically ordered mesocellular mesoporous silica materials (HMMS) were synthesized using a single structure-directing agent. The mesocellular pores are synthesized without adding any pore expander; the pore walls are composed of SBA-15 type mesopores. Small-angle X-ray scattering revealed the presence of uniform pore structures with two different sizes. Using HMMS as a nanoscopic template, hierarchically ordered mesocellular mesoporous carbon (HMMC) and polymer (HMMP) materials were synthesized. HMMS was used as a host for enzyme immobilization. To improve the retention of enzymes in HMMS, we adsorbed enzymes, and then employed crosslinking using glutaraldehyde (GA). The resulting crosslinked enzyme aggregates (CLEAs) show an impressive stability with extremely high enzyme loadings. For example, 0.5 g alpha-chymotrypsin (CT) could be loaded in 1 g of silica with no activity decrease observed with rigorous shaking over one month. In contrast, adsorbed CT without GA treatment resulted in a lower loading, which further decreased due to continuous leaching of adsorbed CT under shaking. The activity of crosslinked CT aggregates in HMMS was approximately 10 times higher than that of the adsorbed CT, which represents a 74-fold increase in activity per unit weight of HMMS due to higher CT loading.