Air-conditioned Laboratory Research Articles

The Effects of Caffeine on Heart Rate and Heart Rate Variability at Rest and During Submaximal Cycling Exercise

ABSTRACT The aim of this study was to investigate the effects of caffeine on heart rate and heart rate variability (HRV) at rest and during submaximal exercise. Using a balanced, double-blind, randomized, crossover design, 16 male cyclists (age: 37 ± 9 years; V ˙ O2max: 4.44 ± 0.67 L·min−1) completed three trials in an air-conditioned laboratory. In Trial 1, cyclists completed two incremental cycling tests to establish the V ˙ O2-power output relationship and V ˙ O2max. In trials 2 and 3, cyclists were evaluated for heart rate and HRV at rest, after which they ingested a capsule containing 5 mg·kg−1 of caffeine or placebo. Thirty-five minutes post-supplementation, additional resting heart rate and HRV readings were taken after which cyclists completed a submaximal incremental cycling test (6 min stages) at 40–80% of V ˙ O2max; with HR and HRV measurements taken in the last 5 min of each increment. HRV was determined from the root mean square of successive differences between R–R intervals. There were significant supplement × exercise intensity interactions on heart rate (p = .019) and HRV (p = .023), with post hoc tests on the latter showing that caffeine increased HRV at 40%, 50%, and 60% of V ˙ O2max by 3.6 ± 4.9, 2.6 ± 2.8, and 0.6 ± 1.7 ms, respectively. There was a supplement × time interaction effect on resting HRV (p < .001), but not on heart rate (p = .351). The results of this study support the suggestion that caffeine increases the parasympathetic modulation of heart rate.Clinical trial registration number: NCT05521386.

Field entomologists in public health?

Mosquito-borne disease research in India has remained stagnant for decades, and will continue to remain. This is so as the hard work in the field by entomologists has given way to comfortable work in air-conditioned laboratories, with computer as the main tool. Critical reviews are being written by men not of science, and also others, but our government totally ignores them.

NITROGEN AND PHOSPHOROUS EFFECTS ON GROWTH OF Stevia rebaudiana Bertoni UNDER LIGHT EMITTING DIODE (LED)

Studies on planting of Stevia rebaudiana, an important industrial crop that provides non-caloric sweeteners for the beverage sector, is lacking in an indoor controlled environment. In the present study, using a nutrient film technique, nitrogen (N) and phosphorous (P) levels needed for S. rebaudiana were determined. The plants were grown under light emitting diodes (LED) at 16h/8h light/darkness photoperiod in an air-conditioned laboratory. The results obtained indicated that in terms of growth performance and leaf production, the half strength Hoagland solution, where N was 100 mg L-1 and P was 15 mg L-1 , enabled the optimum gain in this crop. The results have implications for economic purposes

Effect of Fins spacing on the Performance Evaluation of a Refrigeration System using LPG as Refrigerant

In this paper, experimental analysis was carried out on a vapour compression system by varying the parallel tube condenser fins spacing under the same atmospheric condition in a selected Refrigeration and Air-conditioning laboratory to examine the performance characteristics of the refrigeration system. The fins spacing were 2, 4 and 6 mm using Liquefied petroleum gas (LPG) as working fluid with a mixture proportion of 17.2% isobutene, 56.4% butane, 24.4% propane. The result shows that the coefficient of performance of the system when working with condenser fins spacing of 2 mm was 28.8 and 35.9% higher compared to when the system worked with the fins spacing of 4 and 6 mm respectively. Energy consumed by the single hermetic compressor when the system worked with condenser fins spacing of 2 mm reduced by 16.4 and 18.7% compared to when the refrigerator worked with fins spacing of 4 and 6 mm respectively. The pull down time of the cooling system was attained in 2 hours 45 minute with minimum evaporator temperature of -13 °C while working with 30 g mass charge of LPG.

Impact of condensate cooled air purging on indoor air quality in an air conditioned laboratory

An air conditioned laboratory is assessed for improvement in IAQ with intermittent purging of pre-cooled fresh air. The base case refers to regular operation without admission of any external fresh air. Air quality studies for the base case, revealed that 58% of occupants reported unpleasant odor and 70% of occupants felt suffocation inside the laboratory. The modified case corresponds to the admission of pre-cooled fresh air at 28 ± 0.3 °C, achieved by passing through a Pre-Cooling Unit (PCU) which gainfully utilizes AC condensate discharged at 16–17 °C. PCU helps in reducing the outdoor air temperature by 3–3.5 °C through sensible and latent storage cooling systems. Experimental and simulation studies were carried out to analyze the effect of admission of pre-cooled fresh air into the laboratory. Results show that the CO2 concentration dropped to 42% in the vicinity of the first two rows. Further experimental and simulation studies conducted in a 44 m3 scaled-down room showed that the concentration of CO2 could be maintained below 1000 ppm with the supply of pre-cooled fresh air. The air quality studies carried out through a questionnaire survey to assess the occupant perception were in line with the experimental and simulation studies carried out for the full room and the scaled-down room.

Thermal comfort prediction of air-conditioned and passively cooled engineering testing centres in a higher educational institution using CFD

PurposeThe purpose of this paper is to analyse the thermal environment of two engineering testing centres cooled via different means using computational fluid dynamics (CFD), focussing on the indoor temperature and air movement. This computational technique has been used in the analysis of thermal environment in buildings where the profiles of thermal comfort parameters, such as air temperature and velocity, are studied.Design/methodology/approachA pilot survey was conducted at two engineering testing centres – a passively cooled workshop and an air-conditioned laboratory. Electronic sensors were used in addition to building design documentation to collect the required information for the CFD model–based prediction of air temperature and velocity distribution patterns for the laboratory and workshop. In the models, both laboratory and workshop were presumed to be fully occupied. The predictions were then compared to empirical data that were obtained from field measurements. Operative temperature and predicted mean vote (PMV)–predicted percentage dissatisfied (PPD) indices were calculated in each case in order to predict thermal comfort levels.FindingsThe simulated results indicated that the mean air temperatures of 21.5°C and 32.4°C in the laboratory and workshop, respectively, were in excess of the recommended thermal comfort ranges specified in MS1525, a local energy efficiency guideline for non-residential buildings. However, air velocities above 0.3 m/s were predicted in the two testing facilities, which would be acceptable to most occupants. Based on the calculated PMV derived from the CFD predictions, the thermal sensation of users of the air-conditioned laboratory was predicted as −1.7 where a “slightly cool” thermal experience would prevail, but machinery operators in the workshop would find their thermal environment too warm with an overall sensation score of 2.4. A comparison of the simulated and empirical results showed that the air temperatures were in good agreement with a percentage of difference below 2%. However, the level of correlation was not replicated for the air velocity results, owing to uncertainties in the selected boundary conditions, which was due to limitations in the measuring instrumentation used.Research limitations/implicationsDue to the varying designs, the simulated results of this study are only applicable to laboratory and workshop facilities located in the tropics.Practical implicationsThe results of this study will enable building services and air-conditioning engineers, especially those who are in charge of the air-conditioning and mechanical ventilation (ACMV) system design and maintenance to have a better understanding of the thermal environment and comfort conditions in the testing facilities, leading to a more effective technical and managerial planning for an optimised thermal comfort management. The method of this work can be extended to the development of CFD models for other testing facilities in educational institutions.Social implicationsThe findings of this work are particularly useful for both industry and academia as the indoor environment of real engineering testing facilities were simulated and analysed. Students and staff in the higher educational institutions would benefit from the improved thermal comfort conditions in these facilities.Originality/valueFor the time being, CFD studies have been carried out to evaluate thermal comfort conditions in various building spaces. However, the information of thermal comfort in the engineering testing centres, of particular those in the hot–humid region are scantily available. The outcomes of this simulation work showed the usefulness of CFD in assisting the management of such facilities not only in the design of efficient ACMV systems but also in enhancing indoor thermal comfort.

Optimization of sterlet (Acipenser ruthenus) egg incubation

Sterlet Acipenser ruthenus was used to assess egg and embryo development when incubated at 17 °C in Petri dishes placed in a hatchery tank (300 L recirculating dechlorinated water) with incubation occurring in a static tabletop system in an air-conditioned laboratory, or in a 700 L Q-cell incubator. Eggs in each dish were placed in a plastic box with 300 mL dechlorinated water. Separated eggs from three individual females were fertilized using pooled sperm from four males with there being four replicates. There were no differences (P > 0.05) in mean percentages of neurulation and embryos undergoing cleavage for eggs incubated in the hatchery tank and with use of the static tabletop system. Furthermore, there were no differences (P > 0.05) in percentage of embryos undergoing cleavage, neurulation and hatching for each female when eggs were incubated using the two systems. Results indicate a Petri dish placed in a small plastic box with 300 mL of dechlorinated water was adequate for incubation of sterlet eggs. Results of the study also indicate that with the static system: 1) eggs should be fertilized from each female to retain individual identity; 2) eggs should be dispersed in Petri dishes to avoid clumping; 3) water should be changed at 24 h, but not at 48 h (neurulation) post-fertilization; and 4) embryos that do not optimally develop should be removed the day after neurulation (72 h of post-fertilization period) and water should be exchanged every day subsequent to the 48 h time-point post-fertilization.

AN EXPERIMENTAL CHAMBER FOR TESTING ABATEMENT EFFECTS OF RADON EXPOSURE WITH DIFFERENT MEASURES.

For more effective testing the abatement effects of radon exposure with different counter measures, an air-conditioned laboratory room was reformed as an experimental chamber. Based on the well control and real time monitoring of concentrations of 222Rn, its attached and unattached progeny and their size distributions, the chamber could provide three modules corresponding to ventilation, source reduction and filtration for abating radon exposure. Preliminary results showed that the chamber was useful for testing the abatement effect of indoor radon exposure.

A field study of indoor air quality and occupant perception in experimental laboratories and workshops

Purpose Maintaining good indoor air quality (IAQ) in the built environment is essential to assure health, safety and productivity of occupants. The purpose of this paper is to report on the preliminary IAQ assessment of selected air-conditioned laboratories and naturally ventilated workshops in a tropical education institution. Design/methodology/approach The concentration levels of five major indoor air pollutants (IAPs) – carbon dioxide, carbon monoxide, respirable particulates, formaldehyde (HCHO) and total volatile organic compounds (TVOC) in each sampling area were measured using calibrated air sampling sensors and the tracer-gas analysis was used to determine the ventilation effectiveness. A questionnaire survey was carried out concurrently to study the prevalence of sick building syndrome (SBS) among users of laboratories and workshops and the data collected were statistically analysed using χ2 test. Findings The air pollutant levels were found to be below the threshold limit values set in the local code of practice on IAQ, except for two of the air-conditioned laboratories. This is possibly due to insufficient ventilation, smaller floor area per occupant ratio, long-term exposure to chemical substances, and improper disposal of the used chemical substances. The total particulate levels were higher in naturally ventilated workshops because such spaces were assigned for mechanical works which involved grinding, welding and fabrication. Besides, it was identified that most of the air contaminant levels were not normally distributed (p&lt;0.05) within the sampling areas and SBS like dry eyes, watery eyes, tiredness and dry throat were reported in both laboratories and workshops. The outcomes of this work suggest that an increase of ventilation rate was necessary to reduce the concentration of the IAPs in air-conditioned laboratories and improved housekeeping would help mitigate the prevalence of SBS symptoms. Research limitations/implications This research was carried out in selected laboratories and workshops in a Malaysian educational institution and only five major IAPs stipulated in the Department of Occupational Safety and Health (DOSH) code of practice were measured. Practical implications The results of this study will enable facility engineers and managers to understand the IAPs concentration levels and potential SBS problems in academic laboratories and workshops. The recommended strategies can be considered to improve IAQ conditions in such spaces. Originality/value Most of the previously conducted IAQ studies focused only on commonly occupied building spaces such as offices, classrooms and houses. Information of the quality of air and SBS conditions in experimental facilities in developing nations that is available is currently very limited. This case study provides detailed information on IAQ in laboratories and workshops in Malaysia with focuses on the concentration levels of particular harmful gases, the prevalence of SBS among users of these facilities and the appropriate mitigation strategies. The results presented are of value to both academic and industry communities.

Thermal Environment Analysis of a Scientific Laboratory using Computational Fluid Dynamics

University staff and students typically spend most of their time indoors. This paper evaluates the thermal environment of an air-conditioned scientific laboratory in a tertiary educational institution in Malaysia using Computational Fluid Dynamics (CFD). This computational technique has been used in analysing the indoor environments and has been found to be useful in aiding facilities management. A pilot survey was conducted to collect the required information such as indoor parameters and boundary conditions for the setting up of a CFD model of the laboratory. The model was then simulated based on the data obtained from field observations. Results indicate that the laboratory users sitting at different rows and work desks would experience different thermal sensations. The mean air temperature was below the recommended comfort zone specified in the local energy standard, but the air velocities were generally within the acceptable range. Based on the calculated predicted mean vote (PMV) and predicted percentage dissatisfied (PPD) indices, most of the users would be thermally uncomfortable, and a warmer environment was preferred. Recommendations were made to regulate the inlet air temperature of the laboratory to improve thermal comfort of laboratory users and for energy saving purposes.

Cereal Sources Alter Response to Supplementary Polyphenols on Performance, Serum Biochemistry and Internal Organs in Wistar Rats

An experiment was carried out with 21-d old weaned Wistar rats (n=60) to assess the polyphenols response to dietary manipulations. The rats were divided into six groups with five replicated having two in each. The rats were fed with two different types of cereal sources (corn vs. rice-sorghum combined) as soybean meal served as protein source in both cereal categories. The treatment groups included cornsoybean meal without polyphenol extract (PPE) supplementation (T1), corn-soybean meal with 50 ppm of PPE (T2), corn-soybean meal with 100 ppm of PPE (T3), rice-sorghum-soybean meal diet without PPE (T4), rice-sorghum-soybean meal diet with 50 ppm of PPE (T5) and rice-sorghum-soybean meal diet with 100 ppm of PPE (T6). The rats were maintained under polypropylene cages and reared for 45 d under air-conditioned laboratory animal house. The body weight of rats was significantly higher in corn based diet supplemented with PPE at 50 and 100 ppm than the rice-sorghum based diet. The supplementation of PPE significantly reduced the serum total cholesterol, triglycerides and plasma glucose content in rats irrespective of cereal sources. The organ weights and tibial bone weight did not affect by the combination of cereal sources and PPE levels. The caecal and colon aerobic, E. coli and lactobacillus population remained unaffected by the diet composition and PPE levels. It could be concluded that supplementation of pomegranate peel extract exhibited better performance with corn-soybean meal based diet.

A COMPUTATIONAL AND EXPERIMENTAL INVESTIGATION OF AIR FLOW AND CONTAMINANTS CONCENTRATION IN A LABORATORY WITH MIXING VENTILATION SYSTEM

In this research an experimental and computational analysis under Iraqi climate of temperature distribution, velocity and contaminants concentration in the air-conditioned laboratory have been studied for two case studies. Case-I chosen internal combustion engine laboratory of dimensions (10.3 x 8.7 x 3.75) m with a different number of engines used in the experiments and Case-II chosen laboratory of chemical and petroleum products dimensions (3.7x3.6x3.3)m with different locations of the supply air terminal diffuser compared to the existing design situation. ANSYS FLUENT 14 used to simulate the model's laboratories for compared between the present practical work and numerical work results which are acquired by using RNG K-ε and SST k-ω models and found that the SST k-ω model more accurate. The SST (k-w) turbulence model were employed to solve the governing equations numerically with Reynold number 28,933 and validated by comparing the numerical results with experimental data, and this comparison gives a good agreement. The numerical results for case-I compared with experimental data, while for case-II, the numerical results compared with the standard value due to Iraqi cooling code and ASHRAE standards. The results showed that the mixing ventilation system is able to remove various types of pollutants effectively up to 90% in addition to providing human thermal comfort conditions with the effectively of heat removal up to 85% for the state of the internal combustion laboratory. The second case at laboratory of chemical and petroleum products when the supply air terminal diffuser in the same side, the results showed an increase in comfort conditions by up to 40%.Lastly, from the research, it was found that the pollutant transportation and distribution depend in general upon several factors such as type and location of contaminant source, building geometry, the arrangement of air terminal diffuser opening, and thermal/fluid boundary conditions for example flow rate. Numerical simulation of the velocity and diffusion fields in a conventional flow in laboratories is very useful in comprehending flow and diffusion patterns within different changes of the flow conditions.

Predicting the whirlwind

Across the wide open plains of the central US and inside air-conditioned computer laboratories, scientists of different stripes are probing one of nature's most devastating phenomena: tornadoes. Stephen Ornes offers a snapshot of their work

Whole body precooling attenuates the extracellular HSP72, IL-6 and IL-10 responses after an acute bout of running in the heat

ABSTRACTThe impact of whole-body precooling on the extracellular heat shock protein 72 (eHSP72) and cytokine responses to running in the heat is undefined. The aim of this study was to determine whether precooling would attenuate post-exercise eHSP72 and cytokine responses. Eight male recreational runners completed two 90-minute bouts of running at 65% O2max in 32 ± 0.9°C and 47 ± 6 % relative humidity (RH) preceded by either 60-minutes of precooling in 20.3 ± 0.3°C water (COOL) or 60 min rest in an air-conditioned laboratory (20.2 ± 1.7°C, 60 ± 3% RH; CON). eHSP72, TNF-α, IL-6, IL-10 IL-1ra were determined before and immediately after exercise. The elevation in post-exercise eHSP72 was attenuated after COOL (+0.04 ± 0.10 ng.mL−1) compared to CON (+ 0.29 ± 0.26 ng.mL−1;P < 0.001). No changes in TNF-α were observed at any stage. COOL reduced the absolute post-exercise change in IL-6 (P = 0.011) and IL-10 (P = 0.03) compared to CON. IL-1ra followed this trend (P = 0.063). A precooling-induced attenuation of eHSP72 and proinflammatory cytokines may aid recovery during multi-day sporting events, but could be counterproductive if a training response or adaptation to environmental stress is a desired outcome.

Experimental and theoretical investigation of the effect of radiation heat flux on human thermal comfort

In this study, the effect of radiation heat flux from lighting lamps on human thermal comfort was investigated by both experimental and theoretical approaches. The experiments were carried out in an air-conditioned laboratory room in both the summer and autumn seasons. To determine the thermal response of a human body exposed to radiation heat flux from lighting lamps, a simulation model based on the Gagge model with some modifications was developed, and the effect of radiation heat flux from lighting lamps on human thermal comfort was investigated under transient conditions. The human body was separated into 16 sedentary segments, and the change in temperature was observed both experimentally and theoretically. During transient conditions, heat and mass transfer between the human body and the interior environment of a climate chamber were simulated using a computational model, and predictions were compared to the measured data. It is observed that there is a good agreement between the model predictions and experimental results.

Experimental investigation of radiation effect on human thermal comfort by Taguchi method

In this study, the effect of radiation heat flux of lighting lamps on human thermal comfort was investigated by using Taguchi method. In addition, at indoor conditions, clothing color and posture position under the radiation effect on thermal comfort were also investigated. For this purpose, experiments were performed in an air conditioned laboratory room in summer and autumn seasons. The amount of temperature rise on the back was considered as performance parameter. An L8 orthogonal array was selected as an experimental plan for the third parameters mentioned above for summer and autumn seasons. The results were analyzed for the optimum conditions using signal-to-noise (S/N) ratio and ANOVA method.The optimum results were found to be clear halogen lamp as lighting lamp, white as t-shirt color, standing as posture position, in summer season. The optimum levels of the lighting lamp, t-shirt color and posture position were found to be clear halogen lamp, white, sitting in autumn season, respectively.

Fingermark initial composition and aging using Fourier transform infrared microscopy (μ-FTIR)

This study investigated fingermark residues using Fourier transform infrared microscopy (μ-FTIR) in order to obtain fundamental information about the marks’ initial composition and aging kinetics. This knowledge would be an asset for fundamental research on fingermarks, such as for dating purposes. Attenuated total reflection (ATR) and single-point reflection modes were tested on fresh fingermarks. ATR proved to be better suited and this mode was subsequently selected for further aging studies. Eccrine and sebaceous material was found in fresh and aged fingermarks and the spectral regions 1000–1850cm−1 and 2700–3600cm−1 were identified as the most informative. The impact of substrates (aluminium and glass slides) and storage conditions (storage in the light and in the dark) on fingermark aging was also studied. Chemometric analyses showed that fingermarks could be grouped according to their age regardless of the substrate when they were stored in an open box kept in an air-conditioned laboratory at around 20°C next to a window. On the contrary, when fingermarks were stored in the dark, only specimens deposited on the same substrate could be grouped by age. Thus, the substrate appeared to influence aging of fingermarks in the dark. Furthermore, PLS regression analyses were conducted in order to study the possibility of modelling fingermark aging for potential fingermark dating applications. The resulting models showed an overall precision of ±3 days and clearly demonstrated their capability to differentiate older fingermarks (20 and 34 days old) from newer ones (1, 3, 7 and 9 days old) regardless of the substrate and lighting conditions. These results are promising from a fingermark dating perspective. Further research is required to fully validate such models and assess their robustness and limitations in uncontrolled casework conditions.

Self-normalizing phase measurement in multimode terahertz spectroscopy based on photomixing of three lasers

Photomixing of two near-infrared lasers is well established for continuous-wave terahertz spectroscopy. Photomixing of three lasers allows us to measure at three terahertz frequencies simultaneously. Similar to Fourier spectroscopy, the spectral information is contained in an interferogram, which is equivalent to the waveform in time-domain spectroscopy. We use one fixed terahertz frequency νref to monitor temporal drifts of the setup, i.e., of the optical path-length difference. The other two frequencies are scanned for broadband high-resolution spectroscopy. The frequency dependence of the phase is obtained with high accuracy by normalizing it to the data obtained at νref, which eliminates drifts of the optical path-length difference. We achieve an accuracy of about 1–2 μm or 10−8 of the optical path length. This method is particularly suitable for applications in nonideal environmental conditions outside of an air-conditioned laboratory.

Air-conditioned university laboratories: Comparing CO2 measurement for centralized and split-unit systems

Universities are designed for higher education learning, and improving university indoor air quality (IAQ) is essential to the enhanced performances of students and staff members alike. The majority of IAQ problems are due to inadequate ventilation in university buildings. Carbon Dioxide (CO2) measurements have become a commonly used screening test of IAQ because measurement levels can be used to evaluate the amount of ventilation and general comfort. This paper examines CO2 field measurement for undergraduate practical classes. Ten air conditioned laboratories with ventilation were chosen for CO2 field measurement. CO2 was monitored under indoor and outdoor conditions. Indoor CO2 concentration for Laboratories 1 and 10 is observed to be higher than 1000ppm which indicated inadequate ventilation, while other laboratories showed CO2 concentrations less than 1000ppm. Air capacity and outdoor air were calculated based on the design documentation. A comparison between design and actual outdoor air/person values indicates that the air conditioning systems of the laboratories had adequate ventilation.

Thermal comfort study of air-conditioned university laboratories

In tertiary education institutions, good indoor air quality (IAQ) provides a conducive environment for teaching and learning activities. A field study on the environmental conditions and occupants’ comfort was carried out in six laboratories at Universiti Sains Malaysia. The study evaluates the current thermal comfort conditions using objective measurement and subjective assessment. The measured environment parameters were air dry-bulb temperature, relative humidity and air velocity. The subjective assessment concerned the judgement of the respondents about the thermal environment at the moment of measurement. The results obtained showed that the mean air dry-bulb temperatures recorded in the six laboratories are ranged between 22.7°C and 24.4°C. The range is within the recommended range based on the Code of Practice on Indoor Air Quality (2010). The measured air velocity and relative humidity (RH) were within the limits of thermal comfort standards. Based on the occupants’ perception of thermal sensation, RH and air movement, generally more than 70% of the respondents were satisfied with the existing conditions in the laboratories. The overall comfort vote and predicted mean vote (PMV) index found the occupants to be in the range of ‘0’ (neutral) and ‘+1’ (comfortable).