Comparison between required clothing insulation and that actually worn by workers exposed to artificial cold

Required Clothing Insulation (IREQ) is a new thermal index submitted to the International Organisation for Standardisation (ISO) for discussion. It is designed to prevent general body cooling and is based on an analysis of heat exchanges. The thermal clothing insulation actually worn (lcl) is estimated using a new method, also submitted to ISO.

IREQ of 54 workers exposed to artificial cold (air temperature between −30° C and +10° C) was compared with lcl actually worn by these workers. The results of the present study show that, on average, the workers choose accurately lcl they need if their IREQ is below and up to 1·5 clo. Moreover, these workers prefer to wear garments which provide them with thermal comfort. If IREQ of workers is higher than 1·5–2 clo (i e, workers exposed to −20° C), it is difficult for them to increase their thermal insulation with additional garments. Although their lcl is not sufficient, there is no risk of gradual body cooling because of their continuous time exposure (CTE) which is shorter than the calculated Duration Limited Exposure (DLE). On the other hand, Wind Chill Index (WCI), which is proposed to prevent local cooling, is better adapted to prevent cold injuries than physiological thermal strain; for example, impairment of manual dexterity cannot be prevented with this index.     

Determination of reduced glutathione using an amperometric carbon paste electrode chemically modified with TTF–TCNQ

The development of an amperometric sensor for the determination of reduced glutathione (GSH) is described. The sensor is based on tetrathiafulvalene–tetracyanoquinodimethane (TTF–TCNQ) incorporated into the graphite powder/Nujol oil matrix. The electrooxidation of GSH was monitored amperometrically at 200 mV versus SCE (saturated calomel electrode). The amperometric response of the sensor was linearly proportional to the GSH concentration between 20 and 300 μmol l⁻¹, in 0.1 mol l⁻¹ phosphate buffer (pH 8.0), containing 0.1 mol l⁻¹ KCl and 0.5 mmol l⁻¹ Na₂H₂EDTA, as supporting electrolyte.

The detection limit, considering signal/noise ratio equal three, was 4.2 μmol l⁻¹ for GSH and the repeatability obtained as relative standard deviation was of 5.1% for a series of 10 successive measurements.     

Driving performance in cold, warm, and thermoneutral environments

Driving performance deteriorates at high ambient temperatures. Less is known about the effect of low ambient temperatures and the role of subjective aspects like thermal comfort and having control over the ambient temperature. Therefore, an experiment was constructed in which 50 subjects performed a road-tracking task in a cold (5°C), a thermoneutral (20°C) or a warm (35°C) climate. All subjects had a heater/blower (H/B) which generated a fixed amount of heat/wind that could either be controlled or not controlled.

In the cold climate, averaged leg skin temperature dropped to 18.5°C and head skin temperature to 24.9°C; the thermal comfort was rated between ‘cold’ and ‘very cold’. In the warm climate, averaged leg skin temperature rose to 36.6°C and head skin temperature to 30.8°C; the thermal comfort was rated as ‘hot’. Driving performance in the ambient temperature extremes decreased 16% in the cold environment and 13% in the warm situation.

Having control over the local head temperature by adjusting a H/B affected neither thermal comfort nor driving performance. In agreement with the literature on priming effects, subjects who started with the no-control condition performed much better in all driving tasks because they were primed to focus on the driving task as such, rather than the complex combination of temperature controls and driving task.

It can be concluded that a thermoneutral temperature in a car enhances driving performance and may thus positively affect safety. Using manual climatic controls in hot or cold cars may interfere with the driving task.     

Characterization of transition metal oxide ceramic material for continuous thermocouple and its use as NTC fire wire sensor

The ceramic powder prepared from the mixture of Mn₃O₄ and La₂O₃ have been characterized for NTC behavior and the same have been used as CT²C (continuous thermocouple) sensor in the form of a thin metal cable to detect over-heating. These materials have mega ohm resistance at room temperature and showed exponential drop in resistance with the rise in temperature over a temperature range of 100–400 °C. It has been observed that as the concentration of La₂O₃ increases from 0 to 10% the NTC behavior drops from (400–260 °C) ±10%. The material was pressed into pellets and sintered at 700 °C for 3 h resulting in good bonding strength. Electrical characterization of the material was done by measuring the resistance over a temperature range of 100–400 °C. The material showed reproducible NTC characteristics over the temperature range 400, 370, 340, 280, and 260 °C with decreasing thermistor constant values (B = 9588, 9210, 8500, 5170, 3330 K⁻¹) and activation energy (ΔE = 826, 794, 733, 445, 287 meV), respectively. The decrease in activation energy of the ceramic powder with increase in La₂O₃ concentration makes it possible to fabricate thermal sensors which can be used in different temperature ranges. The microstructure was studied using SEM and evidence of a sintered body with grain size around 1 μm was observed in the material. XRD analysis indicated the single-phase tetragonal structure of the ceramic material. The process of using this ceramic material for fabrication of 10 ft continuous fire wire sensor has been explained.     

Composites: A novel alternative to construct solid state Ag/AgCl reference electrodes

An Ag/AgCl solid-state reference electrode is developed by means of a graphite–AgCl–Silver dag-epoxy resin composite. The response of the composite reference electrode (CRE) to chloride ions is evaluated; a linear non-nernstian response is observed associated to the following equation E = −15.15 (±1.10) − 44.05 (±0.38) log[Cl⁻]. Comparing the CRE's response potential versus a saturated commercial Ag/AgCl reference in KCl 0.1 M, a mean of 40.7 ± 0.4 mV of the distribution of potential versus time data is observed over a period of 1 h. The performance of the CRE as reference for a glass membrane electrode by means of direct pH measurements and quantitative determination of acids by acid–base titrations is evaluated obtaining statistically stable, precise and exact results compared with those obtained using a combined glass electrode. The typical cylindrical configuration of the CRE is changed to adapt it to a FIA system for the determination of ammonium ion, obtaining a sensitivity 50.30 ± 0.26 mV/log[NH₄⁺] and a linear range 8.5 × 10⁻⁵ to 0.1 M, which are analytical parameters statistically equivalent to those presented by the classical determination system.     

Hydrolyzed colloid reaction (HCR) technique for phosphor powder preparation

Undoped and Eu³⁺, Ce³⁺ and Tb³⁺-doped YVO₄ YPO₄, LaPO₄ and YV_xP_1−xO₄ were prepared in H₂O by the recently introduced hydrolyzed colloid reaction (HCR) technique working at low temperature (<100°C) and atmospheric pressure. Two intermediate — partially hydrophobic — complex colloidal mixtures with metastable characteristics can transform into the stable orthovanadate–orthophosphate phase due to intensive hydrolysis. In contrast with the other low temperature reacting processes — like the sol-gel technique, which makes an amorphous structure — the HCR method can produce crystalline structures in nanometer size ranges. The reaction, morphology, incorporation of activators and different luminescent characteristics are surveyed in this letter-type paper selected from our previous results.     

Optimizing Reaction Conditions of the NanoOrange® Protein Quantitation Method for Use With Microplate-based Automation

Because of the rapidly expanding need for higher sample throughput in drug discovery, automation of corresponding biochemical analyses is desirable. In particular, automation of protein quantitation is crucial since its results are used extensively. Recently, a single-reagent fluorescent protein quantitation method (NanoOrange®) with attractive performance attributes has become available. While it can potentially be automated with liquid handling workstations, several of this method's reaction parameters need to be optimized.

We studied the time and a temperature dependence of the NanoOrange protein quantitation reaction in ninety-six well black microplates using either a temperature-regulated hot block or a microwave oven as heat sources. Fluorescence of the NanoOrange reaction was quantified with a multimode microplate spectral scanner.

Time-dependent heating profiles of filled microplates placed on hot blocks at fixed temperatures (45, 55, 65, 75, and 95°C) revealed temperature differences of 4–7°C cooler for the outside wells compared to the inner wells, however the maximum well temperature did not exceed 65°C. Similar time-temperature studies of microwave-heated microplates revealed an equilibrium temperature of 45–49°C that was 10–16°C lower than microplates that were block heated.

The bovine serum albumin (BSA): NanoOrange standard curves created using a hot block increased in slope from 45°C to 55°C, but then remained constant from 65 to 85°C.

Fluorescence of the BSA: NanoOrange standard curve created using a microwave oven was about half the magnitude of the hot block-derived curves, possible reflecting a lower energy transfer rate of the microwave oven. We conclude that the NanoOrange protein quantitation method can be automated if a microplatecompatible hot block with a 65-85°C surface can heat the microplate for minimum of 15 min prior to quantifying the reaction's fluorescence.     

Optimization of NASICON composition for Na recognition

Na_1+xZr₂Si_xP_3−xO₁₂ are ceramic materials which are fast ionic conductors by Na⁺. The present work concerns the characterizations of such materials in the range x = 1.4–3.0 for their use as ion sensitive membranes. Samples were prepared by sol-gel route to obtain pellets with a high density. Characteristics, such as lattice parameters and bulk conductivity are given. Results on detection limit and selectivity of such membranes used in ISE devices are presented. The effect of the stoichiometry on electrochemical characteristics is discussed. The best performances are obtained for x = 2.0–2.2, with samples sintered at 1200°C. No influence of sintering temperature is noticeable for the selectivity, excepted for proton which is less interfering after sintering at 1200°C.     

Amperometric biosensor for formic acid in air

The possibility of developing a simple, inexpensive and specific personal passive “real-time” air sampler incorporating a biosensor for formic acid was investigated. The sensor is based on the enzymatic reaction between formic acid and formate dehydrogenase (FDH) with nicotinamide adenine dinucleotide (NAD⁺) as a co-factor and Meldola's blue as mediator. An effective way to immobilise the enzyme, co-factor and Meldola's blue on screen-printed, disposable, electrodes was found to be in a mixture of glycerol and phosphate buffer covered with a gas-permeable membrane. Steady-state current was reached after 4–15 min and the limit of detection was calculated to be below 1 mg/m³. However, the response decreased by 50% after storage at −15°C for 1 day.     

Thermal expansion of Chromium (Cr) to melting temperature

In situ x-ray data on molar volumes of chromium have been collected over the temperature range from 300 K to melting. The sample was heated to melting by passing an electrical current through the sample (the technique of electrical resistance wire heating). The sample consists of a tungsten wire as a heater and a mixture of Cr and W powder, which is placed in a hole of 250 μm diameter. Tungsten was used as an internal standard for temperature determination. In order to prevent the specimen from oxidation, the experiments were carried out in an argon flow. Unit cell parameters of Cr at different temperatures were calculated using (110), (200), (211), and (220) reflections. Precision of determination of lattice parameter is 10⁻⁴ A at 300 K and 5 10⁻⁴ A at 2000 K. Thermal expansion of Cr increases rapidly at temperatures higher than 1200 K. The linear thermal expansion () of chromium between 300 and 2130 K is given by: = 1.220(5) 10⁻⁵ − 1.150(6) 10⁻⁸ T + 1.132(8) 10⁻⁶ T² − 0.507(7)/T² (T, K). In our experiments, Cr melted between 2120 and 2150 K.     

Searching for optimal sensitivity of single-mode D-type optical fiber sensor in the phase measurement

To improve the sensitivity of a single-mode D-type optical fiber sensor, we selected a D-type optical fiber sensor with 4 mm long and 4 μm core thickness made of a single-mode fiber, a Au-coating on the sensor with a thickness range of 15–32 nm, a light wavelength of 632.8 nm, and an incident angle of 86.5–89.5° for different refractive index (1.33–1.40) sensing. These simulations are based on the surface plasmon resonance (SPR) theory using the phase method which shows that the sensitivity is proportional to the refractive index, Au film thickness and lower incident angle on the sensing interface. The sensitivity is higher than 4000 (degree/RIU), and the resolution is better than 2.5 × 10⁻⁶(RIU) as the minimum phase variation is 0.01°. This device is used to detect the refractive index or gas or liquid concentration in real-time. The proposed sensor is small, simple, inexpensive, and provides an in vivo test.     

Manufacture and characterization of sol–gel V1−x−yWxSiyO2 films for uncooled thermal detectors

V_1−x−yW_xSi_yO₂ films for uncooled thermal detectors were coated on sodium-free glass slides with sol–gel process, followed by the calcination under a reducing atmosphere (Ar/H₂ 5%). The V_1−x−yW_xSi_yO₂ films as prepared inherit various phase transition temperatures ranging from 20 to 70 °C depending on the dopant concentrations and the fabrication conditions. Compared to the hysteresis loop of plain VO₂ films, a rather steep loop was obtained with the addition of tungsten components, while a relaxed hysteresis loop with the tight bandwidth was contributed by Si dopants. Furthermore, the films with switching temperature close to room temperature were fabricated to one-element bolometers to characterize their figures of merit. Results showed that the V_0.905W_0.02Si_0.075O₂ film presented a satisfactory responsivity of 2600 V/W and detectivity of 9 × 10⁶ cm  Hz^1/2/W with chopper frequencies ranging from 30 to 60 Hz at room temperature. It was proposed that with appropriate amount of silicon and tungsten dopants mixed in the VO₂, the film would characterize both a relaxed hysteresis loop and a fair TCR value, which effectively reduced the magnitude of noise equivalent power without compromising its performance in detectivity and responsivity.     

Evaluation of three gas collection devices

Traditionally, the mouthpiece, nose-clip, and headgear arrangement (MN) used in indirect calorimetry is uncomfortable for some subjects, interferes with communications, and often interrupts tests if the nose-clip is lost. Gas collection masks (MASK) offer the possibility of alleviating the problems of MN but leakage and increased air dead space have been problematic. The present study compares the use of MN with two MASK designs (with nose-dam which prevents nasal breathing (MASKnd), and without nose-dam (MASKwo), from light to peak work rates in 20 well-trained subjects (M=12, F=8). Ventilation rate (Ve), oxygen uptake (VO₂), respiratory exchange ratio (RER) and heart rate (HR) were measured and comfort was assessed with a questionnaire. At the highest work rate, subjects achieved higher (as determined by repeated measures ANOVA) Ve for MASKnd(114.0±27 L min⁻¹) and MASKwo=(115.0±29 L min⁻¹) than for MN (108±28 L min⁻¹). Likewise, VO₂ in both MASKnd (55.0±10 ml kg min⁻¹) and MASKwo (56.2±11 ml kg min⁻¹) were higher than in the MN (53.7±12 ml kg min⁻¹)(p<0.05). Both MASKnd and MASKwo MASKs resulted in greater subject comfort than that for MASKmn. These data suggest that true maximal VO₂ can be more often attained with a MASK than an MN, since Ve and VO₂ were higher in MASK compared to that in MN.

Relevance to industry

This study will provide an evaluation of gas masks as an alternative to the traditional but uncomfortable mouth-piece and nose-clip used in indirect calorimetry.     

Change in contact temperature of finger touching on cold surfaces

This study deals with human fingers touching cold surfaces of four materials (aluminium, steel, nylon and wood) at different surface temperatures (−20°C, −15°C, −10°C, −4°C, 0°C and 2°C). Contact finger skin-surface interface temperature and subjective responses on thermal and pain sensations were determined during touching. Type of material and their surface temperature clearly affected the contact cooling of the finger. Individual variation in finger contact cooling was significant. Contact temperature limits for human fingers touching cold surfaces are suggested according to the experimental results. In addition, time to reach a critical temperature (7°C, 5°C or 0°C) when contacting a cold metallic surface is discussed.

Relevance to industry

The outcome of this experimental study supplies as a basis for the development of an ergonomics database to determine temperature limit values for cold touchable surfaces. The critical temperatures are relevant to all industries where cold surfaces cause a risk of finger contact cooling for the manual protection in the cold operations.     

Sol–gel derived polycrystalline Cr1.8Ti0.2O3 thick films for alcohols sensing application

The powder sample of Cr_1.8Ti_0.2O₃ (CTO) was obtained by a sol–gel method. The thick films were developed on identical ceramic tubes of 4 mm length comprising of two Au-electrodes and printing an eight-layer film prepared by mixing CTO with glass powder and -terpinol as an organic vehicle. X-ray powder diffraction (XRD) patterns showed the formation of a single phase. The scanning electron microscope (SEM) images of the ceramic sensor treated at 850 °C revealed that the grain size was larger than 400 nm for the individual isolated grains on the surface, and the agglomerated dense spheroidal platelets had the size of 1–4 μm in diameter. The AC impedance measurement in ambient air showed that the resistance decreased nearly by two orders of magnitude with an increase in temperature in the range of 400–600 °C for both the powder sample and the thick film, and the activation energy E_a derived from the measurement was found to be 0.35 and 0.36 eV for the powder and the film, respectively. The films were exposed to various concentrations of alcohols (0.4–1.2 ppm of methanol and 1.0–5.0 ppm of ethanol), followed by determination of sensor response, sensitivity and reversibility and reproducibility. The origin of the gas response was attributed to the surface reaction of R-OH (R = methyl and ethyl group) with O⁻_(ads) to form adsorbed R-CHO, which was desorbed as a gas at 400 °C after the sensor departing from the gas.     

Precise isotope abundance ratio measurement of nitrous oxide using diode lasers

High-precision measurement of the isotope abundance ratio ¹⁴N¹⁵N¹⁶O/¹⁵N¹⁴N¹⁶O/¹⁴N¹⁴N¹⁸O/¹⁴N¹⁴N¹⁶O (0.37/0.37/0.2/100) in nitrous oxide by a laser-spectroscopic method is demonstrated. The abundance ratio is determined from the absorbance ratio of selected absorption lines near 2 μm of the respective isotopic molecular species. Four wavelength-modulated diode lasers whose center wavelengths are stabilized on the selected lines are made to travel different distances in a multipass cell to compensate the large abundance differences. In the test experiment using pure nitrous oxide samples the abundance ratio can be measured with relative uncertainties of ±(2–6)×10⁻⁴ (±0.2–0.6‰). The laser-spectroscopic method is expected to complement mass spectrometry in isotope analyses to trace the geochemical cycles of environmental substances.     

Calorimetric hydrocarbon sensor for automotive exhaust applications

We have developed a calorimetric sensor utilizing a thermoelectric device supported on a planar alumina substrate. By using a highly selective carbon monoxide (CO) oxidation catalyst and a non-selective platinum (Pt) catalyst, the device can be built to detect either CO or hydrocarbons with high selectivity. The CO oxidation catalyst comprises lead-modified platinum and exhibits excellent selectivity over the 200–400 °C temperature range. The thermoelectric device consists of two thick film junctions made of niobium pentoxide (Nb₂O₅)-doped titanium dioxide (TiO₂) and a lithiated nickel (Ni), which are supported on a planar alumina substrate. The thermocouple detects the difference in temperature due to different catalytic reactions over the two junctions and shows a high output signal because of the high Seebeck coefficient of Nb₂O₅-doped TiO₂ (−400 μV/°C). In gas bench tests, the sensor has a linear output of 0–2.75 mV over 0–1000 ppm of propylene and a response time of 2.5 s (at 90% of amplitude) at a gas temperature of 350 °C. An engine dynamometer evaluation shows that the response of the sensor parallels the change in CO and hydrocarbon constituent concentrations when the engine air-to-fuel ratio is varied.     

Evaporative resistance and sustainable work under heat stress conditions for two cloth anticontamination ensembles

When a work scenario in protective clothing is a nominal two hours of work followed by a short break, the level of heat stress must be limited to conditions of thermal equilibrium. By comparing changes in maximum sustainable work rate in a fixed environment, differences due to different protective clothing ensembles can be determined. To illustrate this principle, two protective clothing ensembles were examined. The Basic Ensemble was a cotton blend coverall over gym shorts with hard hat, gloves and full face mask respirator. The Enhanced Ensemble added a light weight, surgical scrub suit under the coveralls, plus a hood worn under the hard hat. Five young, acclimated males were the test subjects. Environmental conditions were fixed at T_db=32°C and T_pwb=26°C. After a physiological steady state was established at a low rate of work, treadmill speed was increased by 0.04 m/s every 5 min. The trial continued until thermal equilibrium was clearly lost. A critical treadmill speed was noted at the point thermal equilibrium was lost for each ensemble and subject. The drop in treadmill speed from the basic to enhanced ensemble was 11%. Based on measured values of average skin temperature and metabolic rate at the critical work rate and estimated values of clothing insulation, the average evaporative resistances for the basic and enhanced ensembles were 0.018 and 0.026 kPa m²/W, respectively.

Relevance to industry

Protective clothing decisions are based on the need to reduce the risk of skin contact with chemical or physical hazards. Sometimes over-protection of the skin results in a hazard secondary to the skin, such as heat stress. With or without over-protection, protective clothing decisions may affect the level of heat stress and result in lower rates of sustainable work. This paper illustrates the affects of a relatively small change in protective clothing requirements on the ability to work in the heat.     

Temperature compensation of fluorescence intensity-based fiber-optic oxygen sensors using modified Stern–Volmer model

In practical sensing applications, temperature effects are of particular concern, and hence it is necessary to develop the means to correct the fluorescence intensity measurement in accordance with the working temperature. Accordingly, this study develops a modified Stern–Volmer model to compensate for the temperature drift of oxygen concentration measurements obtained using fiber-optic sensors. The oxygen sensors considered in this study are based on teraethylorthosilane (TEOS)/n-octyltriethoxysilane (Octyl-triEOS) or n-propyltrimethoxysilane (n-propyl-TriMOS)/3,3,3-trifluoropropyltrimethoxysilane (TFP-TriMOS) composite xerogels doped with platinum meso-tetrakis(pentafluorophenyl)porphine (PtTFPP).

The experimental results are fitted to the modified Stern–Volmer model in order to compute suitable values for a temperature compensation coefficient at different working temperatures. It is found that the proposed temperature compensation method reduces the difference in the oxygen concentration measurement for working temperatures in the range of 25–70 °C as compared to data without compensation. The linearity and sensitivity of PtTFPP-doped n-propyl-TriMOS/TFP-TriMOS sensor are better than PtTFPP-doped TEOS/Octyl-triEOS sensor for working temperatures in the range of 25–70 °C.

The proposed approach could provide a straightforward and effective means of improving the accuracy of fiber-optic oxygen sensors if a variable attenuator is designed according to the temperature compensation coefficient. Thus, the fiber-optic oxygen sensor with a variable attenuator could work in a broad temperature range without using a temperature sensor.