Environmental Chamber (environmental + chamber)

Distribution by Scientific Domains

Selected Abstracts

Relationship between ambient temperature and heat flux in the scrotal skin

G.-S. Song
Summary Excessive scrotal heating or cooling may lead to the cessation of spermatogenesis. Data regarding heat exchange rates in scrotal skin can be used to control testicular temperature within the appropriate range. Heat flux (HF) in the scrotal skin surface is generated based on the surrounding environment. This study aims to elucidate the HF of scrotal skin by varying ambient temperature. Twenty college students including seven varicoceles volunteered as the subjects (mean age: 22.95 SD 1.96 years; height: 175.00 5.17 cm; weight: 68.40 8.65 kg; body mass index: 22.28 2.15), and participated in the experiments from September 11 to October 4, 2006. The environmental temperature was controlled at 20 C and 25 C in the first and second experiment respectively. The HF and skin temperature on both sides of the scrotal surface were measured for 60 min in the environmental chamber. The results revealed that the HF was 87.64 12.69 W/m2 and 78.91 12.09 W/m2 in the left and right side of the scrotum respectively. The scrotal skin temperature (SST) was 30.28 0.75 C and 30.24 0.62 C on the left and right side of the scrotum in the 20 C environment respectively. In the 25 C environment the HF was 53.54 8.86 W/m2 and 45.25 8.32 W/m2, and the SST was 32.29 0.61 C and 32.07 0.36 C on the left and right side of the scrotum respectively. The cooling source power to decrease testicular temperature is suggested at 290 W/m2. This suggested value could be adopted a cooling device as clinical therapy for a heat stress patient to decrease testicular temperature affecting spermatogenesis. [source]

Changes in the scrotal temperature of subjects in a sedentary posture over a heated floor

Gook-Sup Song
Summary As Koreans habitually sit on the heated floor in their residential buildings, the male testis is directly exposed, and is therefore affected by the floor surface temperature. The purpose of this study was to investigate the changes in the scrotal temperature of the subjects in a sedentary posture over the heated floor. A rigid screening test was performed to select healthy subjects. Finally, six college students volunteered to participate in the experiments. Two experiments were performed in a controlled environmental chamber. Experiment I was designed for a low metabolism state, with the subjects reading a book in a sedentary posture for 50 min. The floor surface temperature (tf) was controlled by varying the temperature of water (tw) flowing into the floor coil from 15 to 50 C, at 5 C intervals. Experiment I revealed that the final scrotal surface temperature was 32.27, 32.62, 33.51, 33.34, 34.14, 34.28, 34.34 and 35.04 C at the tw 15 C (tf 17.0 C), 20 C (tf 20.8 C), 25 C (tf 24.1 C), 30 C (tf 27.8 C), 35 C (tf 31.7 C), 40 C (tf 35.9 C), 45 C (tf 38.6 C) and 50 C (tf 42.2 C), respectively. At tf 17.0 and 20.8 C, the scrotal temperature exhibited a declining pattern and a low temperature for spermatogenesis. At tf 24.1, 27.8 and 31.7 C, however, the thermal regulatory system of the scrotum and testis was activated appropriately. On the contrary, scrotal temperature ascended at tf 35.9, 38.6 and 42.2 C. Of the six subjects, two subjects demonstrated scrotal temperatures above 35 C at tf 38.6 C and four subjects exhibited scrotal temperatures above 35 C at tf 42.2 C. Experiment II was designed for a high metabolism state, with the subjects playing a card game in a sedentary posture for 180 min. The tf was controlled by varying the tw from 30 to 40 C, at 5 C intervals. Experiment II revealed that the final scrotal temperature was 33.43, 34.78 and 35.61 C, and the difference between the initial and final scrotal temperatures was +0.34, +1.06 and +2.24 C, at tw 30 C (tf 27.8 C), 35 C (tf 31.7 C) and tw 40 C (tf 35.9 C), respectively. The scrotal temperature was affected by the floor surface temperature and by the rate of metabolism of the subject in a sedentary posture. As derived from regression analysis, the recommended surface temperature of a heated floor is within 23,33 C under the assumption that scrotal and consecutively testicular temperature above 35 C impairs spermatogenesis. [source]

An experimental and mathematical study of efforts of a novel photovoltaic-Trombe wall on a test room

Ji Jie
Abstract A novel photovoltaic-Trombe wall (PV-TW) is proposed and investigated experimentally and theoretically in this paper. The PV-TW was installed at the south-facing external wall of an environmental chamber that carried two identical test rooms. Both of the test rooms have a double window of the same size. One test room was installed with the PV-TW (known as the PV-TW room), and the other without PV-TW (known as the reference room). The influence of the PV-TW on the thermal environment of the test room was investigated under different operating conditions. The experimental results show the dual benefits of the PV-TW system: improving the room thermal condition and at the same time generating electricity. Compared with the reference room, the maximum indoor temperature was found to be 5,7C higher in winter, and the daily electrical output reached about 0.3,kWh with a PV cell area of 0.72,m2. Also, a detailed model is given to evaluate the performance of PV-TW theoretically, and the PV-TW room is simulated under one certain operating condition. The simulated and measured air temperatures of PV-TW room are found to be in good agreement. Copyright 2007 John Wiley & Sons, Ltd. [source]

Moisture absorption behavior of epoxies and their S2 glass composites

Amit Chatterjee
Abstract The influence of moisture exposure on the behavior of three toughened epoxy,amine systems (scrimp resins SC11, SC15, and SC79, Applied Poleramic, Inc., Benicia, CA) was investigated. Neat resin samples were conditioned by immersion in distilled water at 71C and in an environmental chamber at 85% relative humidity and 87.8C until saturation. The equilibrium weight gain ranged from 1.8 to 3.8% for the resins. The long-chain, low-crosslink-density epoxy system (SC11) absorbed the highest amount of water and was saturated first, and it was followed by the medium-crosslink-density (SC15) and high-crosslink-density materials (SC79). The moisture diffusivity decreased with the increasing crosslink density of the resins. The percentage reduction of the glass-transition temperature (Tg) at equilibrium moisture absorption was highest for the low-crosslink molecule. The percentage reductions for the medium-crosslink and higher crosslink systems were comparable. A net weight loss after drying was observed for the SC11 and SC79 resin systems. Fourier transform infrared analysis confirmed the segment breakage and leaching of molecules from the epoxy,amine network. The effects of moisture cycling on Tg were dependent on the epoxy,amine morphology. During the drying stage, Tg increased to a value higher than that of the unaged dry systems. The S2 glass composite samples were conditioned under identical conditions for the resin system. Composite systems absorbed less moisture than the neat resins as expected. 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source]

Creep dominates tensile fatigue damage of the cement,bone interface

Do-Gyoon Kim
Abstract Fatigue damage from activities of daily living has been considered to be a major cause of aseptic loosening in cemented total hip arthroplasty. The cement,bone interface is one region where loosening could occur, but to date the fatigue response of the interface has not been examined. Cement,bone specimens were prepared from fresh frozen human cadaver tissue using simulated in vivo conditions. Tensile fatigue tests to failure were performed in an environmental chamber. Loss of specimen stiffness (stiffness damage) and permanent displacement after unloading (creep damage) were found in all specimens. At failure, creep damage accounted for the majority (79.9 10.6%) of the total strain damage accumulation at failure (apparent strain, , = 0.0114 0.00488). A power law relationship between strain-damage rate and time-to-failure showed that the strain-damage rate was an excellent predictor of the fatigue life of the cement,bone interface. The S,N response of the interface was obtained as a function of the applied stress ratio and the initial apparent strain. The total motion between cement and bone (72.2 29.8 ,m) prior to incipient failure due to both stiffness and creep fatigue damage may be sufficient to result in fibrous tissue formation and contribute to eventual clinical loosening. 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source]

Effect of electron beam treatments on degradation kinetics of polylactic acid (PLA) plastic waste under backyard composting conditions

L. Fernando Vargas
Abstract The effects of electron beam irradiation on backyard composting behaviour of polylactic acid (PLA) polymer were evaluated. Samples (10,mm2 0.75,mm) from thermoformed PLA drinking cups were exposed to 10,MeV electron beam irradiation at doses of 0, 72, 144 and 216,kGy. Irradiated PLA samples were placed in heat-sealed, plastic screen and added to organic feedstock in a rotating composter within a computer-controlled environmental chamber for 10 weeks at 35C. Changes in weight, structural integrity and molecular weight were assessed over time. Results show that irradiation enhanced PLA breakdown. PLA weight decreased by increasing amounts as irradiation dose increased. Sample brittleness increased with irradiation dose and composting time. Finally, PLA molecular weight decreased as irradiation dose and compost time increased. Molecular weight D values for irradiated PLA were found to be about 430,kGy. After 1 week in a typical backyard composter, molecular weight D values increased to about 560,kGy and then fell to about 380,kGy after 2 weeks of composting. Samples irradiated at 216,kGy showed a reduction in weight of 9.4% after 10 weeks of composting, and a reduction of weight-average molecular weight of 93.7% after 6 weeks. Copyright 2008 John Wiley & Sons, Ltd. [source]

Critical analysis of potential body temperature confounders on neurochemical endpoints caused by direct dosing and maternal separation in neonatal mice: a study of bioallethrin and deltamethrin interactions with temperature on brain muscarinic receptors

Jrgen Pauluhn
Abstract The present investigation was conducted to understand better possible confounding factors caused by direct dosing of neonatal mice during the pre-weaning developmental period. By direct dosing, pups might encounter thermal challenges when temporarily removed from their ,natural habitat'. Typically, this leads to a cold environment and food deprivation (impaired lactation) and modulation of the toxic potency of the substance administered. Growth retardation as a consequence of such behavioural changes in pups makes it increasingly difficult to differentiate specific from non-specific mechanisms. Neonatal NMRI mice were dosed daily by gavage (0.7 mg kg,1 body wt.) from postnatal day (PND) 10,16 with S -bioallethrin, deltamethrin or the vehicle. Then the pups, including their non-treated foster dams, were subjected temporarily for 6 h day to a hypo-, normo- or hyperthermic environment, which was followed by normal housing. The measured temperatures in the environmental chambers were ca. 21, 25 and 30C, respectively. Thus, temperatures in the hypo- and normothermic groups are comparable to the temperatures commonly present in testing laboratories, whereas the hyperthermic condition is that temperature typically present in the ,natural habitat' of pups. A deviation from the normal behaviour of both pups and dams was observed in the hypo- and normothermic groups. In these groups the rectal temperatures of pups were markedly decreased, especially in the early phase of the study (PND 10,12). Neonates that received either test substance displayed changes in body weights and brain weights at terminal sacrifice (PND 17) when subjected temporarily to a non-physiological environment. An enormous influence of environmental temperature on the density of muscarinic receptors in the crude synaptosomal fraction of the cerebral cortex was ascertained. In summary, these results demonstrate that the direct dosing of thermolabile neonatal mice by gavage is subject to significant artefacts that render the interpretation of findings from such studies difficult. It appears that if direct dosing of neonatal pups is mandated, and inhalation is a relevant route of exposure, the combined inhalation exposure of dams with their litters is an alternative procedure that does not cause disruption of the ,natural habitat' of pups. However, owing to their higher ventilation, under such conditions the pups may receive dosages at least double those of the dams. Copyright 2003 John Wiley & Sons, Ltd. [source]