Comparison of the Liquid-Nitrogen Strength and the High-Stressing-Rate Strength of Soda-Lime Glass

Indentation strength testing is used to compare two methods of avoiding slow crack growth: a high-stressing-rate test under ambient conditions vs testing under liquid nitrogen. The liquid-nitrogen strength of soda-lime glass is found to be 9% greater than the high-stressing-rate strength. This is consistent with previous measurements of an increase in K_c of 9.3% at liquid-nitrogen temperature. The implication of this finding regarding time-to-failure calculations is discussed.     

Nighttime insulin kinetics and glycemic control in type 1 diabetes patients following administration of an intermediate-acting lispro preparation

OBJECTIVE: To determine insulin kinetics and overnight glycemic control after bedtime administration of a new intermediate-acting insulin preparation called neutral protamine lispro (NPL). RESEARCH DESIGN AND METHODS: We studied 12 patients with well-controlled type 1 diabetes. The study had a double-blind, randomized, crossover design. After a lead-in period of 10-14 days two experiments were carried out with an interval of 2-7 days. During these experiments overnight insulin kinetics and fasting blood glucose levels were studied after evening administration of NPH insulin and NPL. Blood glucose levels < 3.8 mmol/l were treated by means of a variable infusion of a 20% glucose solution. RESULTS: A trend toward a shorter time to peak insulin concentration was observed after administration of NPL (P = 0.07). No differences between NPH and NPL were detected in the total area under the curve (AUC) for insulin, in insulin levels before breakfast, or in glucose levels before breakfast (P = 0.5, 0.6, and 0.4, respectively). CONCLUSIONS: We detected no major differences between NPH and NPL in the total AUC for insulin, prebreakfast glucose levels, or prebreakfast insulin levels. Therefore, we conclude that NPH and NPL are equally effective in controlling overnight glycemia.     

Gas chromatography—High resolution selected-ion mass spectrometric identification of trace 21∶0 and 20∶2 fatty acids eluting with conjugated linoleic acid isomers

High-resolution selected-ion recording (SIR) of the exact molecular ion mass was used to confirm unambiguously the presence of conjugated linoleic acid (CLA) derivatives in biological matrices and standard mixtures and to differentiate non-CLA derivatives from CLA derivatives in the CLA region of the gas chromatogram. The success of this method was based on the selectivity of the SIR technique and its sensitivity, which was comparable to that of flame-ionization detection. A minor fatty acid methyl ester (FAME) was identified as methyl heneicosanoate (21∶0), and six isomers of 20∶2 FAME were found to elute in the CLA region. Isomerization of a standard CLA mixture resulted in a non-CLA flame-ionization response eluting in the CLA region of the gas chromatogram. It is therefore recommended that the identification of minor CLA isomers in natural products of biological matrices should include their direct confirmation by mass spectrometry     

Some experiments on powdered PrNi5 in contact with liquid 3He

We Report on two sets of measurements on powdered PrNi₅ in contact with liquid ³He: low-temperature magnetic susceptibility using SQUID magnetometer techniques, and also thermal relaxation and heat capacity measurements. In addition, a demagnetization experiment using the hyperfine enhanced nuclear cooling capability of PrNi₅ to cool liquid ³He to 1.1 mK is described.Work supported by the United States Department of Energy and the National Science Foundation under grant DMR-76-21370.Now at IBM Thomas J. Watson Research Center, Yorktown Heights, New York.     

Optimized Aqueous Extraction of Saponins from Bitter Melon for Production of a Saponin‐Enriched Bitter Melon Powder

Bitter melon, Momordica charantia L. (Cucurbitaceae), aqueous extracts are proposed to have health‐promoting properties due to their content of saponins and their antioxidant activity. However, the optimal conditions for the aqueous extraction of saponins from bitter melon and the effects of spray drying have not been established. Therefore, this study aimed to optimize the aqueous extraction of the saponins from bitter melon, using response surface methodology, prepare a powder using spray drying, and compare the powder's physical properties, components, and antioxidant capacity with aqueous and ethanol freeze‐dried bitter melon powders and a commercial powder. The optimal aqueous extraction conditions were determined to be 40 °C for 15 min and the water‐to‐sample ratio was chosen to be 20:1 mL/g. For many of its physical properties, components, and antioxidant capacity, the aqueous spray‐dried powder was comparable to the aqueous and ethanol freeze‐dried bitter melon powders and the commercial powder. The optimal conditions for the aqueous extraction of saponins from bitter melon followed by spray drying gave a high quality powder in terms of saponins and antioxidant activity.     

Effects of Gac aril microwave processing conditions on oil extraction efficiency,and β-carotene and lycopene contents

The effects of Gac oil extraction conditions including microwave power, microwave time, steaming time and hydraulic pressure on extraction efficiency (EE), and β-carotene and lycopene contents were studied. It was found that the EE, and β-carotene and lycopene contents could be enhanced by suitable extraction conditions. Microwave drying was found to be better than air drying for pretreatment. Moisture content after drying and steaming between 8% and 11% (wt/wt) were best for pressing. Results showed that the most suitable conditions for Gac oil extraction from 900 g samples were microwave power of 630 W, microwave time of 65 min, steaming time of 20 min and hydraulic pressure of 170 kg/cm². Under these conditions, the highest EE of 93% was achieved while Gac oil contained the highest content of β-carotene and lycopene at 140 and 414 mg/100 mL, respectively.     

Nonlinear dynamic modeling of neuron action potential threshold during synaptically driven broadband intracellular activity

Activity-dependent variation of neuronal thresholds for action potential (AP) generation is one of the key determinants of spike-train temporal-pattern transformations from presynaptic to postsynaptic spike trains. In this study, we model the nonlinear dynamics of the threshold variation during synaptically driven broadband intracellular activity. First, membrane potentials of single CA1 pyramidal cells were recorded under physiologically plausible broadband stimulation conditions. Second, a method was developed to measure AP thresholds from the continuous recordings of membrane potentials. It involves measuring the turning points of APs by analyzing the third-order derivatives of the membrane potentials. Four stimulation paradigms with different temporal patterns were applied to validate this method by comparing the measured AP turning points and the actual AP thresholds estimated with varying stimulation intensities. Results show that the AP turning points provide consistent measurement of the AP thresholds, except for a constant offset. It indicates that 1) the variation of AP turning points represents the nonlinearities of threshold dynamics; and 2) an optimization of the constant offset is required to achieve accurate spike prediction. Third, a nonlinear dynamical third-order Volterra model was built to describe the relations between the threshold dynamics and the AP activities. Results show that the model can predict threshold accurately based on the preceding APs. Finally, the dynamic threshold model was integrated into a previously developed single neuron model and resulted in a 33% improvement in spike prediction.     

Thin film polycrystalline silicon nanowire biosensors

Polysilicon nanowire biosensors have been fabricated using a top-down process and were used to determine the binding constant of two inflammatory biomarkers. A very low cost nanofabrication process was developed, based on simple and mature photolithography, thin film technology, and plasma etching, enabling an easy route to mass manufacture. Antibody-functionalized nanowire sensors were used to detect the proteins interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α) over a wide range of concentrations, demonstrating excellent sensitivity and selectivity, exemplified by a detection sensitivity of 10 fM in the presence of a 100,000-fold excess of a nontarget protein. Nanowire titration curves gave antibody-antigen dissociation constants in good agreement with low-salt enzyme-linked immunosorbent assays (ELISAs). This fabrication process produces high-quality nanowires that are suitable for low-cost mass production, providing a realistic route to the realization of disposable nanoelectronic point-of-care (PoC) devices.     

Supersonic Particle Probes: Measurement of Internal Wall Losses

In the present study, the operating characteristics of supersonic particle probes are investigated. In particular, characteristics such as internal wall deposition and pressure recovery are examined. Three basic probe designs were tested in a cold flow experiment designed to simulate the hot, hostile environment of rocket and jet engine plumes. The probe designs consisted of two internal shock probes (Dehne and Colket probes) and one external shock probe (McGregor probe). In the internal shock probes the compression from supersonic to subsonic flow occurred either in a constant area throat (Dehne) or at a sudden expansion (Colket). In the external shock or McGregor probe, the shock was positioned slightly outside the entrance of the probe.

From deposition studies performed on the probes, three factors were found to enhance deposition. These factors were: 1) shock-boundary layer interaction, 2) particle-boundary layer interaction, and 3) stagnation zones at sudden expansions. The probe with the lowest deposition was a McGregor probe with a 2.0° divergence angle. Using test particles with diameters of 1.0, 1.5, 2.0, and 2.5 μm, the average losses in the McGregor probe were 14% while in the Colket and Dehne probes the losses were 18% and 22%, respectively. Pressure recovery was also found to be the greatest in the McGregor probe with 48% of the initial stagnation pressure regained. The Colket probe had only a 7% pressure recovery.     

Use of Micellar Solutions as Draw Agents in Forward Osmosis

Recent advances in membrane technologies have enhanced the viability of water treatment strategies that employ semipermeable barriers. Forward osmosis (FO), which exploits the natural osmotic pressure gradient between a “draw” solution and a “feed” solution to produce potable water, offers a low‐energy, low‐cost alternative to more conventional treatment methods. Surfactants, because of their tendencies to aggregate into micelles and to adsorb at interfaces, provide intriguing osmotic pressures and offer exploitable properties by which draw solutions can be regenerated. The effectiveness of surfactant‐based FO using cellulose triacetate membranes has been assessed in terms of water flux and reverse surfactant diffusion using cetylpyridinium chloride, sodium dodecylsulfate, and Triton X‐100. The ratios of water flux to surfactant flux exceeded 600 L mol^?1 for all surfactants studied. Surfactant recoveries of over 99 % were achieved by ultrafiltration using regenerated cellulose membranes.