Soliton dynamics in photonic-crystal fibers for coherent Raman microspectroscopy and microscopy

We describe various generation schemes that employ soliton dynamics in photonic-crystal fibers to generate a red-shifted femtosecond pulse with high efficiency. We then detail how to use this pulse along with the initial femtosecond laser pulse for coherent Raman experiments. We describe various measurement schemes that, though utilizing this pair of femtosecond pulses, mimick the preferred measurement scheme for coherent Raman microspectroscopy where one pulse is transform-limited and of picosecond duration; or for coherent Raman microscopy where both pulses are transform-limited and of picosecond duration. We finally discuss how to increase pulse energy and give some perspective on the realization of a coherent Raman endoscope based on soliton dynamics.     

The effect of viscous substances on the transit time of barley digesta in rats

The influence of a number of hydrocolloids on the transit time of digesta, stool weight and colour of stools was investigated in rats. All hydrocolloids tested gave the stools a lighter colour and increased their size and water content. The hydrocolloids could be divided into two groups according to their action on digesta passage: pectin, gum arabic, oxidised starch and barley β-glucan retarded it, while guar gum, carrageenan, tragacanth gum, carob bean gum, sodium alginate and sodium carboxymethyl cellulose accelerated it. After feeding carrageenan for 1 week it took several weeks before water content and transit time returned to normal. Gum arabic was found to cause caecal distension.     

In vitro availability of starch in heat‐treated potatoes as related to genotype,weight and storage time

The objective of the study was to determine the influence of potato variety, weight and storage time after lifting on the glycaemic index (GI) and resistant starch (RS) content predicted from measurement of the rate and extent of in vitro starch hydrolysis, respectively. The potatoes were either boiled, or boiled and subjected to different heat‐cycling conditions selected to promote retrogradation of amylose or amylopectin, respectively. The hydrolysis indices (HI) and predicted GIs of all 19 potato products were high and fell within narrow ranges of 122–144 and 118–138, respectively. No correlation between average weight of the potato tuber and HI was found. Furthermore, there was no difference in HI between potatoes stored for 1–3 or 8–10 months, nor between varieties of new potato and winter potato. However, the HI was significantly lowered by temperature cycling at conditions known to promote retrogradation of amylopectin (6 °C, 48 h) compared with 6 °C for 24 h followed by 70 °C for 24 h. RS content was already substantial in boiled potatoes, 4.5 g 100 g^?1 (starch basis), and could be increased further by temperature cycling, the highest yield obtained, 9.8 g 100 g^?1 (starch basis), following heat treatment at 6 °C for 24 h followed by 70 °C for 24 h; that is at conditions known to favour amylose retrogradation. Copyright © 2004 Society of Chemical Industry     

Occurrence and fate of corrosion-induced zinc in runoff water from external structures

This paper comprises data from an extensive cross-disciplinary research project aiming to elucidate the environmental fate of corrosion-induced zinc release from external structures. It includes an exposure assessment that provide long-term runoff rates, concentrations and chemical speciation of zinc, from 14 zinc-based materials exposed during 5 years in Stockholm, Sweden, and an effect assessment including bioavailability and ecotoxicity measurements, both at the immediate release situation and after soil interaction. Runoff rates of total zinc ranged from 0.07 to 2.5 g Znm-2 yr-1 with zinc primarily released as the free ion for all materials investigated. The average effect concentration, causing a 50% growth reduction after 72 h to the green algae Raphidocelis subcapitata, was at the immediate release situation 69 microg ZnL-1. Upon interaction of runoff water with soil, which simulated 18 to 34 years of exposure, the total zinc concentration was significantly reduced, from milligram per litre to microgram per litre levels. Simultaneously, the most bioavailable fraction of zinc in runoff, the hydrated zinc(II)-ion, decreased from more than 95% to about 30%. The major fraction, 98-99%, of the introduced total zinc concentration in the runoff water was retained within the soil. As long as the soil retention capacity was not reached, this resulted in zinc concentrations in the percolate water transported through the soil layer, close to background values and below growth inhibition concentrations for the green algae investigated. Zinc retained in soil was to a large extent (85-99.9%) extractable with EDTA, and available for plant uptake after 5 to 7 months of ageing.     

The potential for the SCC of titanium alloys under repository-relevant environments for U.S. nuclear waste

Stress corrosion cracking (SCC) is one of the most common corrosion-related causes of premature failure of metal structural components. This paper presents an assessment of the performance of titanium alloys (titanium grade 7 for the drip shield and grade 29 for the structural support), which may be subjected to SCC under proposed U.S. nuclear waste repository environments. The threshold stresses for SCC initiation, SCC crack propagation rates, and the threshold stress intensity factors for titanium grades 7, 28, and 29 are discussed.     

Performance of a self-administered mailed version of the Quality of Well-Being (QWB-SA) questionnaire among older adults

OBJECTIVES: The Quality of Well-Being questionnaire is a measure of health-related quality of life (HRQoL) that has several desirable properties. Its widespread use has been hindered because it is difficult to administer. To overcome this limitation, a new self-administered form has recently been developed. This study examined the feasibility of using the Quality of Well-Being-Self-Administered (QWB-SA) questionnaire in an older population. METHODS: The Quality of Well-Being-Self-Administered questionnaire was sent to 430 community-dwelling individuals aged 65 years and older who were randomly selected from primary care physicians' offices. Response patterns, scaling distributions, and the acceptability of the survey were examined for all respondents. The results of the QWB-SA questionnaire were compared to the Sickness Impact Profile (SIP) and the Medical Outcomes Study 36-item Short-Form Health Survey (SF-36) for those individuals who also had completed the latter two surveys approximately 10 months earlier and whose health had not changed substantially in the meantime. RESULTS: Three hundred and one older adults (70%) responded. The mean QWB-SA questionnaire score was 0.7035. The scores were not skewed, and there were no floor or ceiling effects. The mean time to complete the QWB-SA questionnaire was 14.2 minutes, which was significantly shorter than for the SIP (19.3 minutes) but significantly longer than for the SF-36 (12.5 minutes). Subjects rated their satisfaction with the QWB-SA questionnaire somewhat lower than for the SIP and similar to SF-36. Correlations between the QWB-SA questionnaire and the SIP and SF-36 were moderate and were generally stronger for measures of physical health than for other domains such as mental health. CONCLUSIONS: The self-administered QWB questionnaire was acceptable to older respondents, and it correlated with other measures of health-related quality of life. It can be considered as a candidate for some research applications among older adults.     

Grain boundary segregation in austenitic stainless steels and its effect on intergranular corrosion and stress corrosion cracking

This paper reports a study of grain boundary segregation, intergranular corrosion, and intergranular stress corrosion cracking in austenitic stainless steels. The results show that phosphorus, nitrogen, and sulfur all segregate to grain boundaries in these materials and that they can affect one another's segregation through site compctition. In particular, the results demonstrate that phosphorus segregation can be lowered by the presence of nitrogen and sulfur in the steel. Also, if manganese is present in the steel, sulfur segregation will be greatly decreased as a result of formation of manganese sulfides. Phosphorus, sulfur, and nitrogen will not initiate intergranular corrosion in the modified Strauss test, although if corrosion is initiated by chromium depletion, these elements might enhance the corrosion process. Phosphorus segregation does enhance corrosion in the Huey test, even in steels that have not undergone grain boundary chromium depletion, although there does not appear to be a precise correlation between the depth of corrosion penetration and phosphorus segregation. Intergranular stress corrosion cracking in 288 °C water at a pH of 2.5 and electrochemical potential of OV_SHE can occur in these steels even in the absence of chromium depletion if sulfur is present on the grain boundaries. Phosphorus segregation appears to have very little effect.     

Chaotic noise in superconducting microbridge 4-photon,X-band parametric amplifier

The anomalous noise rise observed in nearly all types of parametric amplifiers based on Josephson junctions has been an intriguing as well as annoying problem for many years. This phenomenon has been most spectactular in microbridge amplifiers. Here we present measurements on externally pumped single microbridge 4-photon unbiased amplifiers, where the slit with the bridge is used as a slotline resonantly coupled to the waveguide in an exceptionally simple coupling scheme. This scheme may be of interest in itself, particularly if the noise problem can be overcome, and in other connections. Up to 16 dB gain was obtained at the top of the waveguide. However, the noise rise was observed as usual. An analog computer study on a model including an input/output circuit was performed. The results are in very good agreement with the experiments. The amplification is heralded by a seemingly chaotic noise rise. this noise is then amplified linearly when gain occurs. Amplification is found to take place very close to where the supercurrent is completely suppressed by the pump. The cause of the noise rise has previously been interpreted as loss of phaselock. However, the power spectra of the time-derivative of the phase show this still to be locked in the region of positive gain. Furthermore, computations of the Lyapunov exponents show one to be positive in the region where gain occurs, reaching a maximum value at the parameters corresponding to maximum gain. We therefore conclude that chaotic noise is indeed present in Josephson junction parametric amplifiers where low-impedance devices such as microbridges with negligible capacitance are used as the active elements.