Long-period gratings for monitoring the resin transfer molding of fiber-reinforced polymer composites.

The spectral characteristics of long-period gratings (LPGs) have been researched over the last two decades, and many sensing applications of LPGs have been proposed due to their spectral sensitivity to many surrounding environmental parameters such as the temperature, pressure, and refractive index. However, this sensitivity to many parameters can also be a curse due to cross-sensitivity and the inability to distinguish which environmental parameter is responsible for the LPG's spectral behavior. For the application proposed here-monitoring the progress of a resin flow front, its velocity, and the permeability of the reinforcement mats during the infusion stage of resin transfer molding-the multi-sensitivity of LPGs is a distinct advantage, as it provides the ability to monitor the mold environment at various stages of manufacturing.

Low-dimensional nano-patterned surface fabricated by direct-write UV-chemically induced geometric inscription technique.

We investigate a nano-patterning process which creates reproducible periodic surface topological features that range in size from ∼100 µm to ∼20 µm. Specifically, we have fabricated multi-layered thin films consisting of germanium/silicon strata on a planar substrate, with each layer having nanometers thickness. The material processing exploits focused 244 nm ultra-violet laser light and an opto-mechanical setup typically applied to the inscription of fiber gratings, and is based upon the well-known material compaction interaction of ultra-violet light with germanium oxides. We show this process can be extended to create arrays of metal nano-antennas by adding a metal overlay to the thin film. This results in arrays with dimensions that span nanometer- to centimeter-length scales. Also, each nano-antenna consists of "nano-blocks." Experimental data are presented that show the UV irradiance dosage used to create these metal nanostructures on D-shaped optical fibers has a direct relationship to their transmission spectral characteristics as plasmonic devices.

Real-time chest-wall-motion tracking by a single optical fibre grating: a prospective method for ventilator triggering.

OBJECTIVE: The ventilators involved in non-invasive mechanical ventilation commonly provide ventilator support via a facemask. The interface of the mask with a patient promotes air leaks that cause errors in the feedback information provided by a pneumatic sensor and hence patient-ventilator asynchrony with multiple negative consequences. Our objective is to test the possibility of using chest-wall motion measured by an optical fibre-grating sensor as a more accurate non-invasive ventilator triggering mechanism. APPROACH: The basic premise of our approach is that the measurement accuracy can be improved by using a triggering signal that precedes pneumatic triggering in the neuro-ventilatory coupling sequence. We propose a technique that uses the measurement of chest-wall curvature by a long-period fibre-grating sensor. The sensor was applied externally to the rib-cage and interrogated in the lateral (edge) filtering scheme. The study was performed on 34 healthy volunteers. Statistical data analysis of the time lag between the fibre-grating sensor and the reference pneumotachograph was preceded by the removal of the unwanted heartbeat signal by wavelet transform processing. MAIN RESULTS: The results show a consistent fibre-grating signal advance with respect to the standard pneumatic signal by (230 ± 100) ms in both the inspiratory and expiratory phases. We further show that heart activity removal yields a tremendous improvement in sensor accuracy by reducing it from 60 ml to 0.3 ml. SIGNIFICANCE: The results indicate that the proposed measurement technique may lead to a more reliable triggering decision. Its imperviousness to air leaks, non-invasiveness, low-cost and ease of implementation offer good prospects for applications in both clinical and homecare ventilation.

Real-time kinetic binding studies at attomolar concentrations in solution phase using a single-stage opto-biosensing platform based upon infrared surface plasmons.

Here we present a new generic opto-bio-sensing platform combining immobilised aptamers on an infrared plasmonic sensing device generated by nano-structured thin film that demonstrates amongst the highest index spectral sensitivities of any optical fibre sensor yielding on average 3.4 × 104 nm/RIU in the aqueous index regime (with a figure of merit of 330) This offers a single stage, solution phase, atto-molar detection capability, whilst delivering real-time data for kinetic studies in water-based chemistry. The sensing platform is based upon optical fibre and has the potential to be multiplexed and used in remote sensing applications. As an example of the highly versatile capabilities of aptamer based detection using our platform, purified thrombin is detected down to 50 attomolar concentration using a volume of 1mm3 of solution without the use of any form of enhancement technique. Moreover, the device can detect nanomolar levels of thrombin in a flow cell, in the presence of 4.5% w/v albumin solution. These results are important, covering all concentrations in the human thrombin generation curve, including the problematic initial phase. Finally, selectivity is confirmed using complementary and non-complementary DNA sequences that yield performances similar to those obtained with thrombin.

Rib-cage-movement measurements as a potential new trigger signal in non-invasive mechanical ventilation.

Non-invasive ventilation performed through an oronasal mask is a standard in clinical and homecare mechanical ventilation. Besides all its advantages, inevitable leaks through the mask cause errors in the feedback information provided by the airflow sensor and, hence, patient-ventilator asynchrony with multiple negative consequences. Here we investigate a new way to provide a trigger to the ventilator. The method is based on the measurement of rib cage movement at the onset of inspiration and during breathing by fibre-optic sensors. In a series of simultaneous measurements by a long-period fibre grating sensor and pneumotachograph we provide the statistical evidence of the 200 ms lag of the pneumo with respect the fibre-optic signal. The lag is registered consistently across three independent delay metrics. Further, we discuss exceptions from this trend and identify the needed improvements to the proposed fibre-sensing scheme.

Non-invasive respiratory monitoring using long-period fiber grating sensors.

In non-invasive ventilation, continuous monitoring of respiratory volumes is essential. Here, we present a method for the measurement of respiratory volumes by a single fiber-grating sensor of bending and provide the proof-of-principle by applying a calibration-test measurement procedure on a set of 18 healthy volunteers. Results establish a linear correlation between a change in lung volume and the corresponding change in a local thorax curvature. They also show good sensor accuracy in measurements of tidal and minute respiratory volumes for different types of breathing. The proposed technique does not rely on the air flow through an oronasal mask or the observation of chest movement by a clinician, which distinguishes it from the current clinical practice.

Physical characteristics of localized surface plasmons resulting from nano-scale structured multi-layer thin films deposited on D-shaped optical fiber.

Novel surface plasmonic optical fiber sensors have been fabricated using multiple coatings deposited on a lapped section of a single mode fiber. UV laser irradiation processing with a phase mask produces a nano-scaled surface relief grating structure resembling nano-wires. The resulting individual corrugations produced by material compaction are approximately 20 µm long with an average width at half maximum of 100 nm and generate localized surface plasmons. Experimental data are presented that show changes in the spectral characteristics after UV processing, coupled with an overall increase in the sensitivity of the devices to surrounding refractive index. Evidence is presented that there is an optimum UV dosage (48 joules) over which no significant additional optical change is observed. The devices are characterized with regards to change in refractive index, where significantly high spectral sensitivities in the aqueous index regime are found, ranging up to 4000 nm/RIU for wavelength and 800 dB/RIU for intensity.

Arbitrary real-time three-dimensional corporal object sensing and reconstruction scheme.

A real-time three-dimensional (3D) object sensing and reconstruction scheme is presented that can be applied on any arbitrary corporeal shape. Operation is demonstrated on several calibrated objects. The system uses curvature sensors based upon in-line fiber Bragg gratings encapsulated in a low-temperature curing synthetic silicone. New methods to quantitatively evaluate the performance of a 3D object-sensing scheme are developed and appraised. It is shown that the sensing scheme yields a volumetric error of 1% to 9%, depending on the object.

Characterisation and performance of a Terfenol-D coated femtosecond laser inscribed optical fibre Bragg sensor with a laser ablated microslot for the detection of static magnetic fields.

We present a novel device for the characterisation of static magnetic fields through monitoring wavelength shifts of femtosecond inscribed fibre Bragg grating and micromachined slot, coated with Terfenol-D. The device was sensitive to static magnetic fields and can be used as a vectoral sensor for the detection of magnetic fields as low as 0.046 mT with a resolution of ± 0.3mT in transmission and ± 0.7mT in reflection. The use of a femtosecond laser to both inscribe the FBGs and micromachine the slot in a single stage prior to coating the device significantly simplifies the fabrication.

Optimization of a novel enzyme treatment process for early-stage processing of sheepskins.

An enzyme treatment process for early-stage processing of sheepskins has been previously reported by the Leather and Shoe Research Association of New Zealand (LASRA) as an alternative to current industry operations. The newly developed process had marked benefits over conventional processing in terms of a lowered energy usage (73%), processing time (47%) as well as water use (49%), but had been developed as a "proof of principle''. The objective of this work was to develop the process further to a stage ready for adoption by industry. Mass balancing was used to investigate potential modifications for the process based on the understanding developed from a detailed analysis of preliminary design trials. Results showed that a configuration utilising a 2 stage counter-current system for the washing stages and segregation and recycling of enzyme float prior to dilution in the neutralization stage was a significant improvement. Benefits over conventional processing include a reduction of residual TDS by 50% at the washing stages and 70% savings on water use overall. Benefits over the un-optimized LASRA process are reduction of solids in product after enzyme treatment and neutralization stages by 30%, additional water savings of 21%, as well as 10% savings of enzyme usage.

Exploitation of multilayer coatings for infrared surface plasmon resonance fiber sensors.

We demonstrate surface plasmon resonance (SPR) fiber devices based upon ultraviolet inscription of a grating-type structure into both single-layered and multilayered thin films deposited on the flat side of a lapped D-shaped fiber. The single-layered devices were fabricated from germanium, while the multilayered ones comprised layers of germanium, silica, and silver. Some of the devices operated in air with high coupling efficiency in excess of 40 dB and an estimated index sensitivity of Delta lambda/Delta n=90 nm from 1 to 1.15 index range, while others provided an index sensitivity of Delta lambda/Delta n=6790 nm for refractive indices from 1.33 to 1.37.

Assessment of pelt quality in leather making using a novel non-invasive sensing approach.

Excessive removal of structural material from skin during leather processing results in unattractive crease formation in leather. It is difficult to detect this in pelts at an early processing stage as it only becomes really apparent once the skin is made into leather. There would be great advantages in detecting the problem at the pickled pelt stage (skins treated with sodium sulphide and lime, bated with enzymes, and then preserved in NaCl and sulphuric acid) so that adjustments to the processing could be made to mitigate the effect. A novel bio-sensor for inspection of pickled lamb pelts has been fabricated and developed. The sensor has the planar Interdigital structure. The experimental results show that the sensor has a great potential to predict the quality of leather in a non-invasive and non-destructive way.

Use of a proteomics approach to identify favourable conditions for production of good quality lambskin leather.

It is necessary to understand the changes that occur during the initial processing of lamb skins, because these will affect the final quality of the leather. The types of collagen, their macro and micro structures, the presence of proteins other than collagens, and the quantity and the type of proteoglycans, all have a profound effect on the quality of leather. Proteins isolated from untreated or raw sheep skin and from pickled skin (skins treated with sodium sulfide and lime followed by bating with enzymes, then preserved in sodium chloride and sulfuric acid) were significantly different when analysed by use of 2D gel electrophoresis and mass spectrometry. Agarose gel electrophoresis with a very sensitive sequential staining procedure has been used to identify the glycosaminoglycans present in raw and treated skin and their impact on quality of leather. Results showed that effective removal of proteoglycans acting as inter-fibrillar adhesives of collagen fibrils seemed to improve leather quality. Removal of these molecules not only opens up the fibre structure of the skin but may also be important in wool removal. The presence of elastin, which imparts elastic properties to skin, is of significant importance to tanners. The amino acids desmosine and isodesmosine, found exclusively in elastin, were quantitatively analysed to assess the role of elastin in leather quality.

The role of condensed tannins in the nutritional value of Lotus pedunculatus for sheep. 5. Effects on the endocrine system and on adipose tissue metabolism.

1. Three experiments were conducted using Lotus pedunculatus containing high concentrations of condensed tannins (CT), and utilizing the principle that polyethylene glycol (PEG) application (molecular weight 3350) will irreversibly bind a portion of the CT and thus reduce the dietary reactive (i.e. non-PEG bound) CT concentration. Lotus diets containing 95, 45 and 14 g total reactive CT/kg dry matter (DM), induced by spraying with three PEG rates, were given to sheep at hourly intervals (600 g DM/d) for 21 d (Expt 1). In Expts 2 and 3, lambs grazed areas oversown with either lotus (89 g CT/kg DM) or clovers (Trifolium repens and Trifolium pratense; less than 1 g CT/kg DM) for 42 and 92 d respectively. In Expt 2 half the animals grazing each forage received oral PEG (75 g/d), whilst in Expt 3 half the lambs were sired by rams selected respectively for low or high levels of subcutaneous fat deposition. 2. Hormone concentrations in plasma (Expt 1 only) were determined by radioimmunoassay. Rates of [U-14C]-acetate and D-[U-14C]glucose incorporation and oxidation by subcutaneous and abdominal adipose tissue removed at slaughter, together with rate of glycerol release, were determined during in vitro incubation in all three experiments. 3. Plasma concentration of growth hormone was positively and linearly related to dietary reactive CT concentration, whilst 3,5,3'-triiodothyronine (T3) concentration tended to be negatively and linearly related to dietary reactive CT concentration. Diet CT concentration had no effect on plasma concentrations of the other hormones measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Transfer of magnesium across the perfused choroid plexus of sheep.

Isolated perfused choroid plexus preparations from sheep were used to study the effects of low concentrations of magnesium in the perfusion fluid on the transfer of magnesium into choroid plexus fluid (CPF). A perfusion fluid of similar electrolyte composition to sheep blood resulted in CPF similar to ventricular cerebrospinal fluid at a rate of 2.2 microliter min-1 mg-1 dry choroidal tissue. Decreasing the concentration of magnesium in the perfusion fluid caused a fall in the concentration of magnesium in the CPF, although it remained higher than in the perfusion fluid. The rate of transfer of magnesium from the perfusion fluid to the CPF decreased in the presence of high levels of potassium in the perfusion fluid. But decreasing the concentration of calcium in the perfusion fluid had no effect on magnesium transfer rates. These results suggest that the ability of the choroid plexus to transport magnesium against a concentration gradient is an important control of the concentration of the cerebrospinal fluid. However, this ability is insufficient to maintain cerebrospinal fluid concentrations of magnesium at normal levels when the blood magnesium concentration is below about 0.5 mmol l-1.

Endocrine regulation of metabolism in sheep given kale (Brassica oleracea) and ryegrass (Lolium perenne)-clover (Trifolium repens) fresh-forage diets.

Diets of fresh kale (Brassica oleracea) and ryegrass (Lolium perenne)-clover (Trifolium repens) herbage were fed to growing sheep in three experiments. In Expts 1 and 3 the sheep were confined indoors and fed at hourly intervals, and all were given supplementary iodine to counteract kale goitrogens. Lambs grazed the two forages for 24 weeks in Expt 2, with and without intramuscular injections of iodized oil. The kale and herbage contained respectively 11 and less than 0.1 g S-methyl-L-cysteine sulphoxide (SMCO)/kg dry matter (DM) and values for readily fermentable: structural carbohydrate (CHO) were 3.1 and 0.8, respectively. Blood samples were withdrawn from indwelling catheters (Expts 1 and 3) or venipuncture (Expt 2) and the plasma analysed for a range of hormones using radioimmunoassay procedures. Glucose irreversible loss (GIL) was measured in Expt 1 using primed continuous infusions of D-[U-14C]glucose. Samples of adipose tissue were removed from the shoulder area in Expt 3, and rates of D-[U-14C]glucose and [U-14C]acetate incorporation and oxidation were measured in vitro, together with the rate of glycerol release. In the presence of supplementary I2, kale feeding was associated with an elevation in plasma concentration of free thyroxine (T4). Regardless of I2 supplementation, sheep fed on kale had much higher plasma growth hormone concentrations than sheep fed on ryegrass-clover herbage, and this was accompanied by reduced plasma somatostatin concentrations. Plasma insulin and glucagon concentrations were similar for sheep fed on the two diets; GIL tended to be slightly but not significantly greater (9.4%) for sheep fed on kale than for those fed on ryegrass-clover herbage.(ABSTRACT TRUNCATED AT 250 WORDS)

Failure of copper or vitamin D supplements to affect the dental condition of young sheep on two Wairarapa farms.

Regular injections of copper or vitamin D had no overall effect on growth rate, fleece weight, or the amount of wear of the central incisor teeth of sheep on two Wairarapa farms over 26 months. The greatest amount of tooth wear occurred during the period when soil ingestion (measured by acid-insoluble residue, titanium or aluminium in the faeces) was also greatest. Various indicators of copper, calcium or nutritional status were measured in the blood of control sheep and those receiving vitamin D or copper. At no sampling time was there a significant difference for any of these between groups on either farm. Pasture samples were analysed regularly for calcium, cobalt, copper, magnesium, manganese, molybdenum, phosphorus, sulphur, zinc and percentage ash. At most times values were, on the basis of existing criteria, considered normal. Although the pasture calcium/phosphorus ratio fell below one on several occasions this did not result in a change in plasma calcium or phosphorus levels. On the basis of criteria established for pen-fed sheep, dietary available copper levels on both farms were considered low for much of the time. However, liver and blood copper values were adequate at alI times.

Magnesium concentrations in the ventricular and lumbar cerebrospinal fluid of hypomagnesaemic cows.

Samples of ventricular and lumbar cerebrospinal fluid (CSF) were taken at intervals from six lactating dairy cows, made hypomagnesaemic by feeding a magnesium-deficient diet. Initially the ventricular CSF had a higher magnesium concentration than lumbar CSF but as the cows became hypomagnesaemic the magnesium concentration in ventricular CSF decreased more rapidly than that in lumbar CSF. Tetany occurred when the concentration of magnesium in ventricular CSF fell below about 0.5 mmol litre-1. Intravenous infusion of magnesium into two hypomagnesaemic cows increased the concentration of magnesium in ventricular CSF before there was any change in the lumbar CSF. Newly formed CSF from the ventricles appeared to be more sensitive to changes in the concentration of magnesium in plasma than lumbar CSF which equilibrates with the diffusible magnesium of the central nervous system.

Responses to the lowering of magnesium and calcium concentrations in the cerebrospinal fluid of unanesthetized sheep.

A technique for ventriculolumbar perfusion of the cerebrospinal fluid space has been used to study the neuromuscular effects of low concentrations of magnesium and calcium in the cerebrospinal fluid of conscious sheep. Perfusion with synthetic cerebrospinal fluid solutions containing less than 0-6 mg magnesium/100 ml produced episodes of tetany which were abolished by perfusion with a solution of normal magnesium concentration. This suggests that the low cerebrospinal fluid magnesium concentrations reported in cases of hypomagneseamic tetany may result in changes within the central nervous system that could produce the nervous signs. Perfusates with a calcium concentration below 2-0 mg/100 ml caused hyperpnoea and continuous muscle tremors. Magnesium (0-6 mg/100 ml) and calcium (2-0 mg/100 ml) perfused simultaneously acted synergistically to produce signs characteristic of low levels of each of the ions.