A complete scheme for creating predefined networks of individual carbon nanotubes

We describe and demonstrate a method of creating arrays of patterned, individual, single-walled carbon nanotubes, including the spectroscopic mapping of the array. The process consists of creating networks of nanotubes suspended between silicon pillars, which are then transferred onto other substrates by an innovative process of direct stamping. Raman spectroscopy is used to spatially map and assign the specific properties of the suspended network prior to transfer. This method provides a simple and inexpensive means for deriving nanoscale devices utilizing individually assigned carbon nanotubes in a robust and non-surface-specific technique.     

Electrically controlled molecular recognition harnessed to activate a cellular response

Seamless embedment of electronic devices in biological systems is expected to add the outstanding computing power, memory, and speed of electronics to the biochemical toolbox of nature. Such amalgamation requires transduction of electronic signals into biochemical cues that affect cells. Inspired by biology, where pathways are directed by molecular recognition, we propose and demonstrate a generic electrical-to-biological transducer comprising a two-state electronic antigen and a chimeric cell receptor engineered to bind the antigen exclusively in its "on" state. T-cells expressing these receptors remain inactivated with the antigen in its "off" state. Switching the antigen to its "on" state by an electrical signal leads to its recognition by the T-cells and correspondingly to cell activation.     

Effects of electrons on the shape of nanopores prepared by focused electron beam induced etching

The fabrication of nanometric pores with controlled size is important for applications such as single molecule detection. We have recently suggested the use of focused electron beam induced etching (FEBIE) for the preparation of such nanopores in silicon nitride membranes. The use of a scanning probe microscope as the electron beam source makes this technique comparably accessible, opening the way to widespread fabrication of nanopores. Since the shape of the nanopores is critically important for their performance, in this work we focus on its analysis and study the dependence of the nanopore shape on the electron beam acceleration voltage. We show that the nanopore adopts a funnel-like shape, with a central pore penetrating the entire membrane, surrounded by an extended shallow-etched region at the top of the membrane. While the internal nanopore size was found to depend on the electron acceleration voltage, the nanopore edges extended beyond the primary electron beam spot size due to long-range effects, such as radiolysis and diffusion. Moreover, the size of the peripheral-etched region was found to be less dependent on the acceleration voltage. We also found that chemical etching is the rate-limiting step of the process and is only slightly dependent on the acceleration voltage. Furthermore, due to the chemical etch process the chemical composition of the nanopore rims was found to maintain the bulk membrane composition.     

Thirdhand smoke: heterogeneous oxidation of nicotine and secondary aerosol formation in the indoor environment

Tobacco smoking is well-known as a significant source of primary indoor air pollutants. However, only recently has thirdhand smoke (THS) been recognized as a contributor to indoor pollution due to the role of indoor surfaces. Here, the effects of relative humidity (<10% RH and ～ 45% RH) and substrate (cellulose, cotton, and paper) on secondary organic aerosol (SOA) formation from nicotine-ozone-NO(x) reactions are discussed. SOA formation from the sorbed nicotine-ozone reaction ([O(3)] = 55 ppb) varied in size distribution and number, depending on RH and substrate type, indicating the role of substrate and water interactions in SOA formation. This led to SOA yields from cellulose sorbed nicotine-ozone reaction of ～ 1 and 2% for wet and dry conditions, respectively. SOA formation from nicotine-NO(x) reactions was not distinguishable from background levels. Simultaneously, cellulose sorbed nicotine-ozone reaction kinetics ([O(3)] = 55 ppb) were obtained and revealed pseudofirst-order surface rate constants of k(1) = (1 ± 0. 5) × 10(-3) and k(1) < 10(-4) min(-1) under <10% and ～ 45% RH, respectively. Given the toxicity of some of the identified products and that small particles may contribute to adverse health effects, the present study indicates that exposure to THS ozonation products may pose additional health risks.     

How Do Xanthan and Hydroxypropyl Methylcellulose Individually Affect the Physicochemical Properties in a Model Gluten‐Free Dough?

To better understand the physicochemical changes imparted by hydrocolloids on gluten-free dough, 2 hydroxypropyl methylcelluloses (HPMCs) and xanthan gum were added at 2%, 3%, and 5% to rice cassava dough without the addition of alternative proteins. The formulated doughs were analyzed using thermoanalytic and rheological techniques to determine the role of water and subsequent flow behavior upon hydrocolloid addition. The baked loaves were then measured for specific loaf volume and tensile strength to determine bread quality. Thermogravimetric analysis (TGA) results revealed that hydrocolloid-added dough held water more tightly than the rice cassava control with an additional water distribution at 85 to 88 °C. Rheologically, the increase of elastic moduli in the low methoxy HPMC and xanthan-added dough became more pronounced with gum addition; however, both HPMC formulations had increased viscous moduli allowing the gas cells to expand without collapsing. In the bread, the final specific loaf volume increased with high methoxy HPMC (2% to 5%) and low methoxy HPMC (2%) but was depressed with increased addition of low methoxy HPMC (5%) and xanthan (3% and 5%). Crumb hardness was decreased in high methoxy HPMC loaves but was increased significantly in low methoxy HPMC (5%) and xanthan (5%) formulations. From the gums studied, it was concluded that high methoxy HPMC was the optimum hydrocolloid in the rice cassava gluten-free dough. PRACTICAL APPLICATION: Two types of hydrocolloids, xanthan gum and HPMC, were individually added to a gluten-free rice cassava formulation. Based on the thermoanalytic and rheological studies on dough, as well as the bread quality studies, high methoxy HPMC at 5% addition was determined to optimally improve the bread quality when only gum addition was considered. This study indicates the potential use of high methoxy HPMC as an additive in gluten-free bread formulations prior to considering alternative proteins.     

Using a passive multilayer sampler for measuring detailed profiles of gas-phase VOCs in the unsaturated zone

The purpose of this study was to test in the laboratory the performance of a passive multilayer sampler (MLS) for obtaining detailed profiles of gas-phase volatile organic compounds (VOCs) in unsaturated sediments. The MLS is essentially a chain of isolated, cylindrical stainless steel dialysis cells filled with distilled water and closed with membranes at both ends. The sampling principle is based on passive equilibration of the unsaturated zone gas phase with water in the cells. Using trichloroethene (TCE) as a model VOC, and after testing the required equilibration time in the laboratory (about 50 h), results of a large container (210 L) experiment show that TCE concentrations obtained by the MLS deployed inside a well screen corresponded very well to the profile obtained by dialysis cells buried in the sediment. A field profile taken at the saturated-unsaturated interface region of a VOC-contaminated area using the MLS shows steep TCE concentration gradients (1119 microg TCE/L-air/cm) in the gas phase of the unsaturated zone just above the water table.     

A comparison of satiety, glycemic index, and insulinemic index of wheat-derived soft pretzels with or without soy

The consumption of nutrient-poor snack foods in Western diets is thought to be contributing to the increasing prevalence of obesity and diabetes. Soy offers unique potential to provide high quality protein, dietary fiber, and phytochemicals to snack foods to produce a more healthful nutritional profile. In this study, 27.3% of wheat flour was replaced with soy ingredients in a soft pretzel and evaluated for impact on satiety, glycemic index (GI), and insulinemic index (II). We first tested the soy pretzel for consumer acceptability by 51 untrained sensory panelists on a 9-point hedonic scale. Second, in a crossover trial, 20 healthy adults consumed soy and traditional pretzels (1000 kJ or 239 kcal each) after an overnight fast. They reported their levels of satiety on a 10 cm visual analog scale (VAS) for 2 h postprandially. Third, 12 healthy, non-diabetic subjects consumed soy or traditional pretzels (50 ± 2 g available carbohydrates) to determine the GI and II of both products. Blood glucose and insulin responses were monitored for 2 h after consumption and compared to a glucose reference. It was found that a consumer-acceptable soy soft pretzel had a lower mean (±SD) GI than its traditional counterpart: 39.1 (±20.4) for soy and 66.4 (±15.3) for wheat, (p = 0.002). However, soy addition did not statistically affect II (p = 0.15), or satiety (p = 0.91). In conclusion, a nutrient-dense soy pretzel formulation with 27.3% of wheat flour replaced by soy ingredients had attenuated postprandial glycemia without significantly affecting insulinemia or satiety in healthy adults.     

The effects of soy on freezable bread dough: a magnetic resonance study

Hygroscopic soy ingredients were hypothesised to slow the rate of water migration in unleavened bread dough during frozen storage. Thawed soy (18% dry weight) and wheat dough samples were assessed using non-destructive nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) for up to 8 wks frozen storage time. MRI suggested a spatially homogeneous, net increase in proton mobility with frozen storage and, with solution state proton NMR, distinct "free" and "bound" states were discerned. T(2) relaxation times of the majority proton population suggested increased mobility with frozen storage time, and statistical difference from the fresh sample was seen later for the soy samples than the wheat samples. As seen by (13)C-solid state NMR, the crystallinity of the starch was not affected by either soy addition or frozen storage. In conclusion, addition of soy to bakery products led to slightly enhanced preservation of "fresh" characteristics of the dough during frozen storage.     

A Spider's Fang: How to Design an Injection Needle Using Chitin‐Based Composite Material

Spiders mainly feed on insects. This means that their fangs, which are used to inject venom into the prey, have to puncture the insect cuticle that is essentially made of the same material, a chitin‐protein composite, as the fangs themselves. Here a series of structural modifications in the fangs of the wandering spider Cupiennius salei are reported, including texture variation in chitin orientation and arrangement, gradients in protein composition, and selective incorporation of metal ions (Zn and Ca) and halogens (Cl). These modifications influence the mechanical properties of the fang in a graded manner from tip to base, allowing it to perform as a multi‐use injection needle that can break through insect cuticle, which is made of a chitin composite as well.