Properties of length-apodized phase-shifted lpgs operating at the phase matching turning point

The characteristics of length-apodized phase-shifted fiber optic long period gratings with full and partial nanostructured coatings have been explored theoretically and experimentally. The twin rejection bands that are characteristic of length-apodized phase-shifted long period gratings are studied for a long period grating (LPG) operating at the phase matching turning point. When one half of the length of the LPG is coated, complex bandgap like structure appears within the transmission spectrum, which may be of benefit to spectral filter design and for sensing applications

Overwrite fabrication and tuning of long period gratings

The central wavelengths of the resonance bands are critical aspect of the performance of long period gratings (LPGs) as sensors, particularly for devices designed to operate near the phase matching turning point (PMTP), where the sensitivity to measurements can vary rapidly. Generally, LPGs are characterized by their period, but the amplitude of the amplitude of the index modulation is also an important factor in determining the wavelengths of the resonance bands. Variations in fabrication between LPG sensors can increase or decrease the sensitivity of the LPG to strain, temperature or surrounding refractive index. Here, the technique of overwritten UV laser fabrication is demonstrated. It is shown that, on repeated overwriting, the resonance bands of an LPG exhibit significant wavelength shift, which can be monitored and which can be used to tune the resonance bands to the desired wavelengths. This technique is applied to periods in the range 100 to 200 µm, showing the cycle-to-cycle evolution of the resonance bands near the PMTPs of a number of cladding modes. The use of online monitoring is shown to reduce the resonance band sensor-to-sensor central wavelength variation from 10 nm to 3 nm

A simple method for fabricating phase-shifted fibre Bragg gratings with flexible choice of centre wavelength

A simple technique for fabricating phase-shifted fibre Bragg gratings (PSFBGs) without the use of a phase-shifted phase mask is presented. Two, 3-mm long, standard fibre Bragg gratings (FBGs) were inscribed sequentially in singlemode fibre at the same Bragg wavelength such that the FBGs physically overlapped by one grating period. This induces a spectral-hole in the middle of the reflection spectrum of a standard FBG, equivalent to a π-phase shifted FBG. The flexibility of the technique in writing PSFBGs at any choice of wavelength is demonstrated. The results show that PSFBG devices produced by this method are highly reproducible and the process is fas

Dissolved oxygen sensing using an optical fibre long period grating coated with hemoglobin

A long period grating fiber optic sensor coated with hemoglobin is used to detect dissolved oxygen. The sensitivity of this sensor to the ratio of dissolved carbon dioxide to dissolved oxygen is demonstrated via the conversion of carboxyhemoglobin to oxyhemoglobin on the sensor surface. The sensor shows good repeatability with a %CV of less than 1% for carboxyhemoglobin and oxyhemoglobin states with no measurable drift or hysteresis

The cell cycle program of polypeptide labeling in Chlamydomonas reinhardtii

The cell cycle program of polypeptide labeling in syndhronous cultures of wild-type Chlamydomonas reinhardtii was analyzed by pulse-labeling cells with 35SO4 = or [3H]arginine at different cell cycle stages. Nearly 100 labeled membrane and soluble polypeptides were resolved and studied using one-dimensional sodium dodecyl sulfate (SDS)- polyacrylamide gel electrophoresis. The labeling experiments produced the following results. (a) Total 35SO4 = and [3H]arginine incorporation rates varied independently throughout the cell cycle. 35SO4 = incorporation was highest in the mid-light phase, while [3H]arginine incorporation peaked in the dark phase just before cell division. (b) The relative labeling rate for 20 of 100 polypeptides showed significant fluctuations (3-12 fold) during the cell cycle. The remaining polypeptides were labeled at a rate commensurate with total 35SO4 = or [3H]arginine incorporation. The polypeptides that showed significant fluctuations in relative labeling rates served as markers to identify cell cycle stages. (c) The effects of illumination conditions on the apparent cell cycle stage-specific labeling of polypeptides were tested. Shifting light-grown asynchronous cells to the dark had an immediate and pronounced effect on the pattern of polypeptide labeling, but shifting dark-phase syndhronous cells to the light had little effect. The apparent cell cycle variations in the labeling of ribulose 1,5-biphosphate (RUBP)-carboxylase were strongly influenced by illumination effects. (d) Pulse-chase experiments with light-grown asynchronous cells revealed little turnover or inter- conversion of labeled polypeptides within one cell generation, meaning that major polypeptides, whether labeled in a stage-specific manner or not, do not appear transiently in the cell cycle of actively dividing, light-grown cells. The cell cycle program of labeling was used to analyze effects of a temperature-sensitive cycle blocked (cb) mutant. A synchronous culture of ts10001 was shifted to restrictive temperature before its block point to prevent it from dividing. The mutant continued its cell cycle program of polypeptide labeling for over a cell generation, despite its inability to divide

Diagnosing the time-dependence of active region core heating from the emission measure: II. Nanoflare trains

The time-dependence of heating in solar active regions can be studied by analyzing the slope of the emission measure distribution cool-ward of the peak. In a previous study we showed that low-frequency heating can account for 0% to 77% of active region core emission measures. We now turn our attention to heating by a finite succession of impulsive events for which the timescale between events on a single magnetic strand is shorter than the cooling timescale. We refer to this scenario as a "nanoflare train" and explore a parameter space of heating and coronal loop properties with a hydrodynamic model. Our conclusions are: (1) nanoflare trains are consistent with 86% to 100% of observed active region cores when uncertainties in the atomic data are properly accounted for; (2) steeper slopes are found for larger values of the ratio of the train duration $\Delta_H$ to the post-train cooling and draining timescale $\Delta_C$, where $\Delta_H$ depends on the number of heating events, the event duration and the time interval between successive events ($\tau_C$); (3) $\tau_C$ may be diagnosed from the width of the hot component of the emission measure provided that the temperature bins are much smaller than 0.1 dex; (4) the slope of the emission measure alone is not sufficient to provide information about any timescale associated with heating - the length and density of the heated structure must be measured for $\Delta_H$ to be uniquely extracted from the ratio $\Delta_H/\Delta_C$

An evaluation of the IDEEA™ activity monitor for estimating energy expenditure

Peer reviewedPublisher PD

VALUING LOSSES FROM DEPOPULATING MICHIGAN DAIRY HERDS

Depopulating dairy herds in the effort to eradicate disease would have significant economic effects. This paper evaluates farm-level effects that might occur and puts forth a method for quantifying losses. The reader is directed elsewhere for industry or state-level effects of disease eradication or depopulation.Livestock Production/Industries,

Fabrication and optimisation of a fused filament 3D-printed microfluidic platform

A 3D-printed microfluidic device was designed and manufactured using a low cost ($2000) consumer grade fusion deposition modelling (FDM) 3D printer. FDM printers are not typically used, or are capable, of producing the fine detailed structures required for microfluidic fabrication. However, in this work, the optical transparency of the device was improved through manufacture optimisation to such a point that optical colorimetric assays can be performed in a 50 µl device. A colorimetric enzymatic cascade assay was optimised using glucose oxidase and horseradish peroxidase for the oxidative coupling of aminoantipyrine and chromotropic acid to produce a blue quinoneimine dye with a broad absorbance peaking at 590 nm for the quantification of glucose in solution. For comparison the assay was run in standard 96 well plates with a commercial plate reader. The results show the accurate and reproducible quantification of 0–10 mM glucose solution using a 3D-printed microfluidic optical device with performance comparable to that of a plate reader assay

A solution to the slow stabilisation of surface pressure sensors based on the Wilhelmy method

Dynamic measurement of surface pressure is of particular interest in the field of Langmuir monolayers, where the change in surface pressure throughout an experiment can provide information on the properties of the monolayer forming material, or on the reaction kinetics of the monolayer’s interaction with other materials. One of the most common methods for the measurement of dynamic surface pressure is the Wilhelmy plate method. This method measures changes in the forces acting upon a thin plate of material at the air-water interface; this measurement is then converted to surface pressure. One version of this method, which uses filter paper plates at the air-water interface, is particularly popular due to their relatively low cost. However, it has been seen that the use of filter paper plates attached to a Wilhelmy balance requires an initial stabilisation period lasting several hours, during which the readings drift from the original baseline. Here the cause of this drift is explored, considering how changes in the weight of the plate over time influence the assumptions on which the surface pressure is derived from the measurements made by the Wilhelmy balance. A simple method for preventing this drift through pre-soaking of the filter paper plates is presented