Constant Wattage Research Articles

Heterogeneous microstructures tuned in a high throughput architecture

A new method applied to the sensor proposed by Zhang et al. in 2018 is demonstrated in this paper that combines the benefits of this design with the fast heating possible with nanocalorimetry. By applying a PID regulated pulse instead of a constant wattage, we unlock an accessible method to sense morphological changes occurring over short time periods that would be invisible to methods based only on heat capacity. In this study, multilayer Ni/Al thin films were linearly heated at 25, 50, 100, and 200 K/s to over 700°C, showing two distinct peaks in resistance change with activation energies of 55±4 and 74±7 kJ/mol, respectively. Through Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive X-ray Analysis (EDX) analysis on cross sections taken ex situ from samples quenched before and after the peaks of interest, we find strong evidence that peak 1 corresponds to Ni diffusing through Al grain boundaries forming intermetallic phases that essentially block the highly conductive Al pathway. This presents the potential to design and calibrate novel heterogeneous structures in a high throughput manner.

How do climate change experiments alter plot-scale climate?

To understand and forecast biological responses to climate change, scientists frequently use field experiments that alter temperature and precipitation. Climate manipulations can manifest in complex ways, however, challenging interpretations of biological responses. We reviewed publications to compile a database of daily plot-scale climate data from 15 active-warming experiments. We find that the common practices of analysing treatments as mean or categorical changes (e.g. warmed vs. unwarmed) masks important variation in treatment effects over space and time. Our synthesis showed that measured mean warming, in plots with the same target warming within a study, differed by up to 1.6 C (63% of target), on average, across six studies with blocked designs. Variation was high across sites and designs: for example, plots differed by 1.1 C (47% of target) on average, for infrared studies with feedback control (n=3) vs. by 2.2 C (80% of target) on average for infrared with constant wattage designs (n=2). Warming treatments produce non-temperature effects as well, such as soil drying. The combination of these direct and indirect effects is complex and can have important biological consequences. With a case study of plant phenology across five experiments in our database, we show how accounting for drier soils with warming tripled the estimated sensitivity of budburst to temperature. We provide recommendations for future analyses, experimental design, and data sharing to improve our mechanistic understanding from climate change experiments, and thus their utility to accurately forecast species' responses.

Effects of Solvent and Temperature on Free Radical Formation in Electronic Cigarette Aerosols.

The ever-evolving market of electronic cigarettes (e-cigarettes) presents a challenge for analyzing and characterizing the harmful products they can produce. Earlier we reported that e-cigarette aerosols can deliver high levels of reactive free radicals; however, there are few data characterizing the production of these potentially harmful oxidants. Thus, we have performed a detailed analysis of the different parameters affecting the production of free radical by e-cigarettes. Using a temperature-controlled e-cigarette device and a novel mechanism for reliably simulating e-cigarette usage conditions, including coil activation and puff flow, we analyzed the effects of temperature, wattage, and e-liquid solvent composition of propylene glycol (PG) and glycerol (GLY) on radical production. Free radicals in e-cigarette aerosols were spin-trapped and analyzed using electron paramagnetic resonance. Free radical production increased in a temperature-dependent manner, showing a nearly 2-fold increase between 100 and 300 °C under constant-temperature conditions. Free radical production under constant wattage showed an even greater increase when going from 10 to 50 W due, in part, to higher coil temperatures compared to constant-temperature conditions. The e-liquid PG content also heavily influenced free radical production, showing a nearly 3-fold increase upon comparison of ratios of 0:100 (PG:GLY) and 100:0 (PG:GLY). Increases in PG content were also associated with increases in aerosol-induced oxidation of biologically relevant lipids. These results demonstrate that the production of reactive free radicals in e-cigarette aerosols is highly solvent dependent and increases with an increase in temperature. Radical production was somewhat dependent on aerosol production at higher temperatures; however, disproportionately high levels of free radicals were observed at ≥100 °C despite limited aerosol production. Overall, these findings suggest that e-cigarettes can be designed to minimize exposure to these potentially harmful products.

Multiple effect concentration of ethanol by ohmic-assisted hydrodistillation

Our previous work on ethanol distillation by ohmic-assisted hydrodistillation (OAHD) successfully concentrated ethanol from 10 to 50% (v/v). In this work, two additional concentration steps were conducted using the 50% (v/v) product obtained from the first concentration stage at a constant wattage of 168W using the same OAHD device. The second distillation step resulted in a product with ethanol concentration of 76% (v/v) and the third step yielded ethanol concentration of 84% (v/v). Results were compared to conventional hydrodistillation (HD), and were indicative that OAHD reduces one third of energy cost in ethanol distillation process. Not only was OAHD superior to HD in terms of time and energy consumption, but also resulted in higher ethanol concentrations than HD after the third step of distillation: 84.3±0.3% vs. 82.5±0.5%, respectively. OAHD also showed better process control and was able to stop the distillation process faster than HD. In both second and third distillation steps, the time required to stop the process with OAHD (1min) was shorter than for HD process (10min). The findings of this study further confirm our previous work, and reveal that this emerging distillation technique has the potential of yielding high concentrations of ethanol from dilute alcoholic solutions in a more economical and environmental friendly way.

Ethanol concentration of fermented broth by ohmic-assisted hydrodistillation

Abstract Ohmic-assisted hydrodistillation (OAHD) as an innovative extraction method was employed to concentrate ethanol from corn beer. OAHD reduces the time and energy required for distillation of bioethanol production compared to traditional method. OAHD process was compared to traditional hydrodistillation (HD) for 3 l of 13% (v/v) beer at a constant wattage of 168 W. Test results indicate that the required energy for separation of ethanol in OAHD is 77% less than HD. Moreover, OAHD completed the distillation process in 70.6 ± 1.8 min while HD required 116.1 ± 7.8 min. The concentrations of ethanol in the final distilled product from both methods were similar (56.5% ± 1.3 for OAHD vs. 52.3% ± 4.0 for HD). Interestingly, the process control in OAHD is faster and distillation can be stopped quickly, and consequently, it will contain less unwanted distillate in comparison with HD. The findings of this study introduce OAHD as a potentially economical and environmentally friendly method for bioethanol distillation process. Industrial relevance In this research, ohmic-assisted hydrodistillation (OAHD) was used as an advanced hydrodistillation (HD) technique and compared with traditional HD in concentration of ethanol from industrial fermented corn beer. OAHD method was quicker, more economical, more sustainable and with a better ability of process control than HD method. Such advantages can make OAHD as an alternative technique for the production of larger quantities and higher concentrations of ethanol by scaling up the equipments and process in biofuel factories, instead of the conventional HD process.

The Effects of a Polymorphism in the Cytochrome P450CYP1A2Gene on Performance Enhancement with Caffeine in Recreational Cyclists

Background: The purpose of the present study was to determine if a polymorphism in the cytochrome P450 CYP1A2 gene impacts performance enhancement with caffeine treatment in recreational cyclists. Furthermore, we explored the impact of this polymorphism on circulating caffeine concentrations during acute exercise. Methods: Twenty subjects (13 males, 7 females) who reported non-to-moderate caffeine usage visited the Exercise Science Laboratory on three occasions. During the first visit, subjects underwent a graded exercise test to determine maximal oxygen consumption (VO2max). A venous blood sample was then obtained for genotyping analysis through polymerase chain reaction and gel electrophoresis. For the next two visits, three pieces of chewing gum (caffeine vs. placebo) were administered in a counterbalanced double blind manner. Subjects remained resting for 10 min and then completed a standard warm-up on a Lode cycle ergometer. Following the warm-up, subjects cycled at 75% VO2max (constant Wattage) for 15 min, rested for 10 min, and then completed a 15-min performance ride. Venous blood samples were collected at baseline (Base), during the warm-up (+25), and immediately before (+50) and after (+65) the performance ride. Serum samples were analyzed for caffeine concentrations through high-performance liquid chromatography. Subjects were grouped based on genotype and performance, and serum caffeine data were analyzed through a repeated-measures analysis of variance (ANOVA). Results: Eleven subjects possessed the AA genotype, while nine subjects were C allele carriers. Independent samples t-tests confirmed that groups were of similar age, body mass, and fitness. The data demonstrated that performance enhancement with caffeine treatment was not evident in this subject population (p ≥ 0.258). Furthermore, the ANOVA demonstrated that ergogenic responses to caffeine did not differ across genotype groups (p ≥ 0.861). Finally, circulating caffeine concentrations were similar across groups with caffeine treatment (p = 0.613). Conclusions: We conclude that a polymorphism in the cytochrome P450 CYP1A2 gene did not impact the ergogenic benefit of caffeine in recreational cyclists. Furthermore, circulating caffeine concentrations did not differ across genotype groups during acute exercise with caffeine treatment.

Ohmic-assisted hydrodistillation: A novel method for ethanol distillation

Distillation is one of the most time and energy consuming steps in bioethanol production and some food operations. Ohmic-assisted hydrodistillation (OAHD) is a new proposed extraction method which uses the advantages of ohmic heating and has been used for essential oil separation. In this study, an OAHD device was designed and developed for ethanol distillation using titanium electrodes. Results of the OAHD process were compared to those of traditional hydrodistillation (HD) at constant wattage of 168W for 3L of 10% (v/v) ethanol solution containing 0.5% (w/v) sodium chloride as the electrolyte. Results indicated that the required energy for separation of ethanol in OAHD was 33% less than HD. In addition, OAHD completed the distillation process in 75.2±2.2min while HD required 108.4±5.3min. The concentrations of ethanol in the final distilled product from both methods were similar (47.3%±3.2 for OAHD vs. 50.0%±2.6 for HD). Interestingly, in OAHD, process control is faster and distillation can be stopped in seconds and consequently, less unwanted distillate in comparison to HD (0.05%±0.01 and 2.28%±0.03 of total distilled product, respectively). The findings of this study introduce OAHD as a potentially economical and environmentally friendly method for the ethanol distillation process.

Low intensity exercise does not impact cognitive function during exposure to normobaric hypoxia

Exposure to hypoxia is associated with cognitive impairment, mediated by cerebral deoxygenation. This can be problematic for individuals who perform mental tasks at high altitude. Eight healthy men completed two experimental trials consisting of 5h of exposure to normobaric hypoxia (12.5% O2). In one of the experimental trials (Hypoxia) subjects remained resting in a seated position the entire 5h; in the other experimental trial (Hypoxia and Exercise) subjects rested 2h, cycled for 1h at constant wattage (workload equivalent to 50% of altitude adjusted VO2max), then rested the last 2h. Cerebral oxygenation was measured continuously via near-infrared spectroscopy and cognitive performance was assessed by Trail Making Test A and B. Cerebral oxygenation and cognitive performance both were impaired during exposure to hypoxia. In the Hypoxia and Exercise trial, subjects experienced further declinations in cerebral oxygenation without concomitant decreases in cognitive function. These data demonstrate that cognitive function declines during exposure to normobaric hypoxia and this decline is not exacerbated by low intensity exercise.

In vivo determination of a modified heat capacity of small hepatocellular carcinomas prior to radiofrequency ablation: Correlation with adjacent vasculature and tumour recurrence

Purpose: To calculate a modified heat capacity (mHC) of small hepatocellular carcinomas (HCCs) in vivo during radio frequency ablation (RFA) and to determine if mHC correlates with tumour vascularity, adjacent vessels or local recurrence.Patients and methods: This study was IRB approved and informed consent was obtained from all patients. Before formal RFA, ambient HCC temperature and temperature 1 min after heating at constant wattage were measured in 29 patients. From temperature change and wattage, individual mHCs (joules required to increase tumour temperature by 1° Celsius) were calculated. Pre‐RFA, three‐phase computerised tomography (CT) scans were reviewed blindly for hepatic arteries, hepatic veins and portal veins abutting or within 3 mm of tumour edge from which twelve vascular parameters were quantified. Tumour enhancement (homogeneous or heterogeneous on arterial phase) was also assessed. Multiple regression was used to correlate mHC with vascular parameters and tumour enhancement. Cox proportional hazard model was used to examine the relationship of mHC to local recurrence.Results: There was significant correlation of mHC with lesion enhancement (P = 0.0018), length of hepatic arteries (P < 0.0001) and total hepatic vein volume in contact with tumour (P = 0.016). No correlation was found with any non‐abutting vessel or portal vein parameter. The chance of local recurrence increased with increasing mHC.Conclusion: Because the modified heat capacity of small HCCs in our study population correlated with HCC enhancement, abutting hepatic arteries, the volume of abutting hepatic veins and local recurrence, it may be an indicator of the heat sink effect (HSE) and supports the HSE as a risk factor for local recurrence.

Why does the lumen maintenance of sodium–scandium metal halide lamps improve by VHF operation?

Lifetime experiments show that sodium–scandium metal halide lamps perform better on very high frequency (VHF) drivers than on low frequency (LF) constant wattage autotransformer (CWA) ballasts. The question why, will be addressed with focus on arc tube aspects. It is argued that at high frequency operation sodium loss is less, and that the absence of thermal fluctuations in the electrode tip causes less damage and cracking to this part of the electrode. Sudden lm W−1 drops, observed with CWA-operated lamps, most probably occur when the arc attaches on such a corroded and cracked surface.Thorium is effective as an emitter both in the CWA and the VHF operation mode, despite the absence of cataphoretic transport to the cathode in the VHF case.

Perceptual Responses to Cycling Following Caffeine Administration in Chewing Gum

Research has demonstrated that caffeine ingestion may lower effort and pain perception during exercise. Stay Alert™ chewing gum (100mg caffeine/piece) offers a quick and effective delivery of caffeine via the buccal mucosa. PURPOSE: The purpose of the current investigation was twofold: 1) to determine if caffeine administered in chewing gum (Stay Alert™) lowers effort and pain perception during cycling, 2) to determine the most efficacious time to administer Stay Alert™ to lower effort and pain perception during cycling. METHODS: Eight male cyclists participated in five separate laboratory sessions, with a one week washout period between sessions. During the first visit, subjects underwent a graded exercise test on an Excalibur 1300Wcycle ergometer to determine maximal oxygen consumption (VO2max) For each of the next four visits, 3 pieces of chewing gum [caffeine (CAFF) or placebo (PLA)] were administered at 3 time points, 120 min pre-exercise (-120), 60 min pre-exercise (-60), and 5 min pre-exercise (-5). In 3 of the 4 experimental trials, CAFF was administered at one of the three time points and PLA at the other two time points. During the control trial (CON), PLA gum was administered at all three time points. Following baseline measurements, time allotted for gum administration, and a standard warm-up, participants cycled at 75% VO2max (constant Wattage) for 15 min. Ratings of perceived exertion (RPE) and perceived leg pain (LP) measures were obtained at baseline and every 3 min during cycling. RESULTS: Data were analyzed using a 4 (Trial) by 5 (Time) repeated measures analysis of variance. Both RPE and LP increased during cycling (p < 0.01); however, no between trial differences were observed (p≥0.318). Further, no trial by time interaction was observed (p ≥ 0.387) for RPE or LP. CONCLUSION: A single dose of 300mg of caffeine administered in chewing gum did not impact perceptual responses to cycling.

The Effects of Caffeine Administered in Chewing Gum on Mood at Rest and Following Exercise

Research has demonstrated that caffeine ingestion and exercise is associated with mood alterations. PURPOSE: The purpose of the current investigation was to determine the effects of caffeine (administered in gum) on mood at rest and following exhaustive exercise. METHODS: Eight male cyclists participated in five separate laboratory sessions, with a one week washout period between sessions. During the first visit, subjects underwent a graded exercise test on an Excalibur 1300Wcycle ergometer to determine maximal oxygen consumption (VO2max) and were familiarized with the Profile of Mood States (POMS). The POMS is a standardized questionnaire that quantifies transient mood state. For each of the next four visits, 3 pieces of chewing gum [caffeine (CAFF) or placebo (PLA)] were administered at 3 time points, 120 min pre-exercise, 60 min pre-exercise, and 5 min pre-exercise. In 3 of the 4 experimental trials, CAFF was administered at one of the three time points (CAFF-120, CAFF-60, CAFF-5) and PLA at the other two time points. During the control trial PLA gum was administered at all three time points. Following baseline measurements, time allotted for gum administration, and a standard warm-up, participants cycled at 75% VO2max (constant Wattage) for 15 min then completed a 7 kj·kg-1 cycling time trial. The POMS was administered at baseline (BASE), 100 min prior to cycling (-100), 40 min prior to cycling (-40), and immediately after cycling (POST). RESULTS: Data were analyzed using a 4 (trial) by 4 (time) repeated measures analysis of variance (ANOVA). The ANOVA revealed no main effect of treatment (p > 0.05); however, a main effect of time (p = 0.008) was observed for changes in POMS scores. Post hoc t-tests revealed that POMS scores decreased from BASE to -100 (p ≤ 0.004), remained stable to -40, then increased following exercise (p = 0.029). The ANOVA also revealed a treatment x time interaction (p = 0.012). Peak change scores were computed and compared with paired samples t-test; peak change scores were higher in the CAFF-120 trial versus PLA (p = 0.017). CONCLUSION: Mood improved overtime at rest and worsened following exhaustive cycling across all treatments. Larger fluctuations in POMS scores were observed when caffeine was administered 120 min prior to exercise.

Evaluation of System Energy Savings of Ceramic Metal Halide Lamps Suitable for Probe-Start and Pulse-Start Systems

Energy saving ceramic discharge metal halide lamps (CDM) have been developed to start and operate on magnetic probe and pulse start ballasts originally designed for quartz metal halide (QMH) lamps. The energy saving performance of these retrofit CDM lamps has been evaluated on several types of commercial magnetic ballast systems including constant wattage auto-transformers (CWA), reactors, and magnetic regulated lag (mag-reg) types. System evaluations result in linear models that depend on ballast type and lamp power. These models, which show excellent agreement with measurements, are used in Monte Carlo simulations to estimate the relative power savings that can be expected when replacing an installation of QMH lamps having a range of electrical characteristics, with the energy saving CDM retrofit lamps. The system evaluations show that the CDM lamps save 18 percent lamp power and an average system power savings of up to 17 percent.

Pathobiological Influence of a Radiofrequency Ablation System

Purpose: The objective of this study was to optimize the least invasive technique of radiofrequency ablation (RFA) for the degenerated renal parenchyma and to develop a novel RFA system. Materials and Methods: Tissue temperature and pathological degeneration were investigated at regular time intervals and distances from the RFA needle electrode in the renal parenchyma of the pig kidney. We also examined whether interruption of the renal artery or irrigation in the renal pelvis had an influence on the therapeutic effects. Results: Pathological investigations showed a core necrotic area surrounded by an ischemic layer around the needle electrode. Interestingly, interruption of the renal artery and irrigation in the renal pelvis markedly enhanced the degeneration of the parenchyma. Especially the electric conductivity of irrigation solutions in the renal pelvis influenced the therapeutic effect. In this novel system which retains the flow of electricity between the 2 electrodes and maintains the electric power at a constant wattage, a marked therapeutic effect was observed between the 2 electrodes rather than on their outsides, and this was not influenced by renal artery interruption and/or renal parenchyma cooling. Conclusions: This novel RFA system may contribute to more effective and highly reproducible therapeutic results.

Erbe constant voltage electrocautery versus conventional variable voltage electrocautery for tonsillectomy in children

This prospective, randomized study was performed to compare postoperative pain, blood loss, and procedure time using the Erbe electrocautery device and conventional electrocautery. The Erbe device differs from conventional cautery devices in that it produces constant voltage and variable wattage whereas conventional devices produce variable voltage and constant wattage. This means that the conventional devices allow voltage surges and constant wattage no matter what type of tissue is encountered. The Erbe device has the inherent capability to maintain constant voltage, i.e. no surging as well as varying wattage according to tissue resistance. This, in theory, allows the Erbe device to impose less tissue damage and, theoretically, less postoperative pain. Fifty-seven patients 5–21 years of age who were scheduled for adenotonsillectomy were enrolled in the study. Results indicated less postoperative pain, although blood loss appeared to be increased compared to conventional electrocautery. The Erbe electrocautery device appears to be a viable device to perform tonsillectomy in children.

Predicting and understanding thermal performance in today's instrument loops

Solution oriented products and state of the art design and analysis techniques are available today to aid the instrument engineer is designing thermally efficient and functional instrument loops. This paper demonstrates how these new analysis techniques are being applied today in predicting and understanding how today's heat traced instrument loop solutions perform from a thermal perspective. Some of the designs/applications covered are (1) preinsulated heat traced lines, (2) self-limiting, constant wattage, and temperature varying power electric tracing, and (3) field and factory built instrument insulation and tracing systems.

A microprocessor-regulated constant voltage, current, wattage, and temperature electrophoresis power supply

The analog control circuitry typically found in commercial electrophoresis power supplies was replaced by a digital microcomputer. Analog to digital converters were used to monitor the voltage applied to and current passed through an electrophoresis cell. Microcomputer programming was employed to compare converter input values with preselected operating parameters and then calculate a required output voltage. Timing sequences were generated through programming utilizing clocks located on the interface boards. A digital to analog converter was employed to apply a control voltage to a constant voltage power supply. This process was completed at least 20 times each second. BASIC programming subroutines were written to maintain constant voltage, current, power (wattage), and temperature. To these operating procedures, other techniques such as automated endpoint detection of isoelectric focusing and pulsed waveform outputs were easily added. This power supply containing a microcomputer system as the feedback element was shown to have a greater stability and versatility than conventional supplies.

Analysis of heat tracing pipe temperatures as a function of physical and operational parameters

Variations in voltage, thermal conductivity, manufacturing tolerance, and other parameters that contribute to the actual system performance deviation from the calculated system performance are studied, as well as the effect of these variations on the performance of the system. A sample system consisting of 1 in. pipe with 2 in. of fiberglass insulation is studied for freeze protection. The concept of the load line is used to further understand the sensitivity of the heat tracing system to variations in parameters. Constant wattage and self-regulating systems, along with insulation and installation techniques, are also discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Selecting a heating system for FRP and plastic tanks and vessels

Tank heating system design considerations such as temperature differentials and limits, thermal resistance components, and power requirements are reviewed, and the merits of two heater styles are analyzed in terms of efficiency, safety, and economy of operation. The two heater styles considered are self-limiting and low-watt-density constant wattage. Both styles are available as panel or strip heaters. The benefits and drawbacks of each design are noted with respect to a particular design example, while neither style is preferred overall, it is noted that for safe operation the self-limiting heater should be used with a thermostatic control.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Evaporative Cutting of a Semi-infinite Body With a Moving CW Laser

The formation of a deep groove by evaporation on a moving semi-infinite solid is considered. Evaporative removal of material is achieved by focusing a high-power, highly concentrated Gaussian laser beam of constant wattage (CW laser) onto the surface of the solid. Assuming thermal losses due to conduction and convection to be relatively minor, these losses are treated in an approximate fashion using a simple integral method. The relevant nonlinear partial differential equations are solved numerically, and results for groove depth and shape are presented for a variety of laser and solid parameters.