Radiofrequency tissue ablation inside of metal stent – A thermographic study

Biliary stents are used to treat obstructions that occur in the bile ducts. The stents can be blocked by new tissue in a few months after their implanting. This complication can be solved by using radiofrequency ablation. The present article deals with monitoring of the process of monopolar thermoablation of a metal stent by using an infrared camera ex vivo. The metallic EGIS Biliary stents 10 mm × 80 mm were used in experiments; radiofrequency ablation due by catheter EndoHPB 8F at 460 kHz was used. The Flir B200 thermocamera was used for monitoring. The results show an increase in temperature of the stent's material during thermoablation process. It is believed that the metal stent becomes an active electrode. The results show an increase in temperature of the stent and the surrounding tissue during the treatment. Temperature distribution measured on stent was affected by power applied and obviously non-homogeneous. The maximum temperature values were observed at the ends of the stent. The temperature value of the stent during termoablation depended also on the position of the second (inactive) surface electrode. Results of this study have shown that there are many factors able to affect the final temperature or process of tissue ablation inside of the stent and around the stent. Infrared camera seems to be an appropriate instrument for observing the distribution and changes in temperature during ex vivo radiofrequency ablation.     

Parametric study of radiofrequency ablation in the clinical practice with the use of two-compartment numerical models

The objective of the current work was to simulate radiofrequency ablation (RFA) with theoretical and realistic computational models, which correspond to single-compartment models and clinical scenarios. A 3D model in a cubic region of 12 cm edge was studied representing either a homogeneous model or real clinical scenarios in three human tissues, i.e., liver, lung and kidney. An active electrode was placed at the center of the model. Various tumor sizes (1–3 cm) and source voltages (10–30 V) were investigated for the second case of a two-compartment model. In the case of a 3-cm tumor in diameter, the electrical and thermal problems (at steady state) were solved to calculate the temperature distribution within the tumor and tissue. Lesion volume was quantified using the Arrhenius equation and the isothermals of 50 and 60 °C. The physical properties of all materials were constant during the simulations, i.e., no changes with temperature were considered. It was found that tumor conductivity was low to achieve significant damage in the tumor; in all clinical scenarios, saline-enhanced RFA was necessary and led to a more efficient tumor destruction. It was also shown that highly perfused tissues, such as liver and kidney, block the energy deposition within them, in contrast to lung, and, thus, require a further saline enhancement. Finally, the effect of perfusion on lesion size was studied, and it was concluded that tumor perfusion was more significant than surrounding tissue perfusion.     

Investigation of temperature-dependent viscoelastic properties of thermal lesions in ex vivo animal liver tissue

The viscoelastic characteristics of thermal lesions in ex vivo animal liver are investigated in this paper. Characterization of the moduli of thermal lesions prepared at several temperatures will provide additional information for the elastographic monitoring of radio frequency ablation of hepatic tumors. In this study, the frequency-dependent complex modulus of thermal lesions prepared at temperatures ranging from 60 to 90 °C over a frequency range from 0.1 to 50 Hz are presented. Lesions were prepared using either radio frequency ablation or double immersion boiling. It was found that both the magnitude and phase of the modulus increase with frequency, a behavior that has been noted in the literature. A new result reported shows that the modulus dependence on temperature reveals a local maximum around 70–75 °C corresponding to the temperature at which tissue has released most of its water content. The modulus values at temperatures higher than 70 °C continued to increase, but the extent of increase depend on animal species and other factors.     

Health-Related Quality of Life After Percutaneous Radiofrequency Ablation of Cold,Solid, Benign Thyroid Nodules: A 2-Year Follow-Up Study in 40 Patients

Objective: We studied the impact of radiofrequency ablation (RFA) on health-related quality of life (HRQL) in patients with benign thyroid nodules (TN) in a 2-year follow-up.Methods: Forty patients (35 women and 5 men; age, 54.9 ± 14.3 years) with cold thyroid solitary nodules or a dominant nodule within a normofunctioning multi-nodular goiter (volume range, 6.5 to 90.0 mL) underwent RFA of thyroid nodular tissue under ultrasound real-time assistance.Results: Data are mean and standard deviation. Energy delivered was 37,154 ± 18,092 joules, with an output power of 37.4 ± 8.8 watts. Two years after RFA, nodule volume decreased from 30.0 ± 18.2 mL to 7.9 ± 9.8 mL (-80.1 ± 16.1% of initial volume; P<.0001). Thyroid-stimulating hormone, free triiodothyronine, and free thyroxine levels remained stable. Symptom score measured on a 0- to 10-cm visual analogue scale (VAS) declined from 5.6 ± 3.1 cm to 1.9 ± 1.3 cm (P<.0001). Cosmetic score (VAS 0–10 cm) declined from 5.7 ± 3.2 cm to 1.9 ± 1.5 cm (P<.0001). Two patients became anti-thyroglobulin antibody–positive. Physical Component Summary (PCS)-12 improved from 50.4 ± 8.9 to 54.5 ± 5.3, and the Mental Component Summary (MCS)-12 improved from 36.0 ± 13.3 to 50.3 ± 6.3 (P<.0001 for both score changes).Conclusion: Our 2-year follow-up study confirms that RFA of benign TNs is effective in reducing nodular volume and compressive and cosmetic symptoms, without causing thyroid dysfunction or life-threatening complications. Our data indicate that the achievement of these secondary endpoints is associated with HRQL improvement, measured both as PCS and MCS.Abbreviations: fT₃ = free triiodothyronine fT₄ = free thyroxine HRQL = health-related quality of life MCS-12 = Mental Component Summary-12 PLA = percutaneous laser ablation PCS-12 = Physical Component Summary-12 RF = radiofrequency RFA = radiofrequency ablation SF-12 = Short-Form 12 Health Survey TgAb = anti-thyroglobulin antibody TN = thyroid nodule TRAb = anti-TSH-receptor antibody TSH = thyroid-stimulating hormone US = ultrasound VAS = visual analogue scale     

Nano-assisted radiofrequency ablation of clinically extracted irregularly-shaped liver tumors

Radiofrequency ablation (RFA) for liver tumors is a minimally invasive procedure that uses electrical energy and heat to destroy cancer cells. One of the critical factors that impedes its successful outcome is the use of inappropriate radiofrequency levels that will not completely destroy the target tumor tissues, resulting in therapy failure. Additionally, the surrounding healthy tissues may suffer from serious damage due to excessive ablation. To address these challenges, this work proposes the employment of injected nanoparticles to thermally promote the ablation efficacy of conventional RFA. A three-dimensional finite difference analysis is employed to simulate the RFA treatment. Based on the data acquired from measured experiments, the simulation results have demonstrated close agreement with experimental data with a maximum discrepancy of within ±8.7%. Several types of nanoparticles were selected to evaluate their influences on liver tissue's thermal and electrical properties. We analysed the effects of nanoparticles on liver RFA via a tumor rending process incorporating several clinically-extracted tumor profiles and vascular systems. Simulations were conducted to explore the temperature difference responses between conventional RFA treatment and one with the inclusion of assisted nanoparticles on several irregularly-shaped tumors. Results have indicated that applying selected nanoparticles with high thermal conductivity and electrical conductivity on the targeted tissue zone promotes heating rate while sustaining a similar ablation zone that experiences lower maximum temperature when compared with the conventional RFA treatment. In sum, incorporating thermally-enhancing nanoparticles promotes heat transfer during the RFA treatment, resulting in improved ablation efficiency.     

Vascularity-Targeted Percutaneous Ethanol Injection of Toxic Thyroid Adenomas: Outcomes of A Feasibility Study Performed in the USA

Objective: The recommended treatment options for toxic adenoma (TA) in the USA are radioactive iodine ablation and surgical resection, with continued observation for pre-toxic adenoma (PTA). Percutaneous ethanol ablation (PEI) has proven efficacy in the treatment of TA and is widely available in Europe but not in the USA.Methods: Retrospective analysis was performed of all patients who underwent PEI for TA/PTA at the University of Utah, from January 2010 to 2018. Ultrasound-guided PEI, with injections targeting power Doppler–mapped blood vessels within the adenomas, was conducted. Functionality was confirmed using thyroid scintigraphy prior to PEI.Results: Eighteen adults (15 female) underwent PEI. Mean age was 41 ± 13.7 years. Baseline thyroid-stimulating hormone (TSH) was suppressed (0.06 ± 0.09 mU/L), with normal free thyroxine (FT4) 1.43 ± 0.39 ng/dL. Median nodule volume was 5.7 cm³ (interquartile range &lsqb;IQR], 4.8 to 7.7 cm³). Seventy-eight percent (n = 14) underwent two or less PEI sessions. Median volume of ethanol used was 0.46 mL/mL nodule volume (IQR, 0.3 to 0.6 mL). There was a significant increase in TSH concentrations within the first 3 months after PEI (0.06 ± 0.09 mU/L vs. 1.22 ± 1.88 mU/L; P = .02), with a concomitant significant decrease in FT4 concentrations (1.43 ± 0.39 ng/day vs. 1.13 ± 0.25 ng/day; P<.01). Significant nodular volume reduction was observed following PEI (median 5.7 cm³ &lsqb;IQR 4.8–7.7 cm³] vs. 2.5 cm³ &lsqb;IQR 2.0–7.8 cm³]; P<.01).Conclusion: Vascularity-targeted PEI is safe and effective for treating PTA and TA. This unique approach required lower injected alcohol volume and fewer injections for therapeutic success.Abbreviations: ATA = American Thyroid Association; FT4 = free thyroxine; IQR = interquartile range; PD = power Doppler; PEI = percutaneous ethanol injection; PTA = pre-toxic adenoma; RAI = radioactive iodine ablation; RFA = radiofrequency ablation; TA = toxic adenoma; TT3 = total triiodothyronine; US = ultrasound     

Numerical study to establish relationship between coagulation volume and target tip temperature during temperature-controlled radiofrequency ablation

The present study aims at proposing a relationship between the coagulation volume and the target tip temperature in different tissues (viz., liver, lung, kidney, and breast) during temperature-controlled radiofrequency ablation (RFA). A 20-min RFA has been modelled using commercially available monopolar multi-tine electrode subjected to different target tip temperatures that varied from 70°C to 100°C with an increment of 10°C. A closed-loop feedback proportional-integral-derivative (PID) controller has been employed within the finite element model to perform temperature-controlled RFA. The coagulation necrosis has been attained by solving the coupled electric field distribution, the Pennes bioheat and the first-order Arrhenius rate equations within the three-dimensional finite element model of different tissues. The computational study considers temperature-dependent electrical and thermal conductivities along with the non-linear piecewise model of blood perfusion. The comparison between coagulation volume obtained from the numerical and in vitro experimental studies has been done to evaluate the aptness of the numerical models. In the present study, a total of 20 numerical simulations have been performed along with 12 experiments on tissue-mimicking phantom gel using RFA device. The study revealed a strong dependence of the coagulation volume on the pre-set target tip temperature and ablation time during RFA application. Further, the effect of target tip temperature on the applied input voltage has been studied in different tissues. Based on the results attained from the numerical study, statistical correlations between the coagulation volume and treatment time have been developed at different target tip temperatures for each tissue.     

The effect of tumour geometry on the quantification accuracy of planar 123I phantom images

IntroductionAccurate activity quantification is applied in radiation dosimetry. Planar images are important for quantification of whole-body images, enabling assessment of biodistribution from radionuclide administrations. We evaluated the effect of tumour geometry on quantification accuracy of ¹²³I planar phantom studies, including various tumour sizes, tumour-liver distances and two tumour-background ratios.Methods and materialsAn in-house manufactured abdominal phantom was equipped with a liver, different size cylindrical tumours, and a rod for tumour-liver distance variation. The geometric mean method with scatter and attenuation corrections was used for image processing. Scatter and attenuation corrections were made using the triple energy window scatter correction technique and a printed transmission sheet source, respectively. Region definitions for tumour activity distribution compensated for the partial volume effect (PVE). Activity measured in the dose calibrator served as reference for determining quantification accuracy.ResultsThe smallest tumour had the largest percentage deviation with an average activity underestimation of 34.6 ± 1.2%. Activity values for the largest tumour were overestimated by 3.1 ± 3.0%. PVE compensation improved quantification accuracy for all tumour sizes yielding accuracies of <12.4%. Scatter contribution to the tumours from the liver had minimal effect on quantification accuracy at tumour-liver distances >3 cm. With PVE compensation, increased tumour-background ratio resulted in a percentage increase of up to 26.3%.ConclusionWhen applying relevant corrections for scatter, attenuation and PVE without background activity, quantification accuracy of <13% was obtained. We demonstrated the successful implementation of a practical technique to obtain quantitative information from ¹²³I planar images.     

Effect of rearing temperature on growth and thermal tolerance of Schizothorax (Racoma) kozlovi larvae and juveniles

Effect of rearing temperature on growth and thermal tolerance of Schizothorax (Racoma) kozlovi Nikolsky larvae and juveniles was investigated. The fish (start at 12 d post hatch) were reared for nearly 6 months at five constant temperatures of 10, 14, 18, 22 and 26 °C. Then juvenile fish being acclimated at three temperatures of 14, 18 and 22 °C were chosen to determine their critical thermal maximum (CTMax) and lethal thermal maximum (LTMax) by using the dynamic method. Growth rate of S. kozlovi larvae and juveniles was significantly influenced by temperature and fish size, exhibiting an increase with increased rearing temperature, but a decline with increased fish size. A significant ontogenetic variation in the optimal temperatures for maximum growth were estimated to be 24.7 °C and 20.6 °C for larvae and juveniles of S. kozlovi, respectively. The results also demonstrated that acclimation temperature had marked effects on their CTMax and LTMax, which ranged from 32.86 °C to 34.54 °C and from 33.79 °C to 34.80 °C, respectively. It is suggested that rearing temperature must never rise above 32 °C for its successful aquaculture. Significant temperature effects on the growth rate and thermal tolerance both exhibit a plasticity pattern. Determination of critical heat tolerance and optima temperature for maximum growth of S. kozlovi is of ecological significance in the conservation and aquaculture of this species.     

Shifts in thermoregulatory strategy during ontogeny in harp seals (Pagophilus groenlandicus)

Heat balance can be difficult for young and/or small animals in polar regions because environmental conditions in combination with small body size or physiological immaturity can increase heat loss. We investigated how thermoregulatory patterns change with ontogeny in 5 age classes of harp seal (Pagophilus groenlandicus) from birth to post-molt to further understand the timing of thermoregulatory development in relation to their potential vulnerability to ongoing fluctuations in the extent and stability of Arctic pack ice. We measured changes in the amount, conductivity, and resistance of the seal pups׳ insulative layers (blubber and fur), the potential for endogenous heat-generation by shivering (muscle enzyme activity), and nonshivering thermogenesis (NST; brown adipose tissue (BAT) uncoupling protein 1 (UCP1) expression and mitochondrial density). There was no significant difference in blubber conductivity among age classes, though the amount of blubber insulation significantly increased from birth to weaning. Pelage conductivity was low (0.12±0.01 W m⁻¹ °C⁻¹) except in 9-day old pups (0.40±0.08 W m⁻¹ °C⁻¹); the significantly higher conductivity may signal the beginning of the molt, and this age group may be the most vulnerable to early water entry. Citrate synthase activity significantly increased (49.68±3.26 to 75.08±3.52 μmol min⁻¹ g wet weight⁻¹) in the muscle; however it is unlikely that increasing a single enzyme greatly impacts heat generation. BAT of younger pups contained UCP1, though expression and mitochondrial density quickly declined, and the ability of pups to produce heat via NST was lost by weaning. While total thermal resistance did not differ, neonatal and early nursing animals gained the majority of their thermal resistance from lanugo (82.5±0.03%); however, lanugo is not insulative when wet, and NST may be important to maintain euthermia and dry the coat if early immersion in water occurs. By late nursing, blubber seems sufficient as insulation (75.87±0.01% of resistance after 4 weeks), but high conductivity of fur may be responsible for retention of UCP1 expression. Weaned animals rely on blubber insulation, and no longer need NST, as wetted fur is no longer a threat to euthermia.     

Characterization of heat transfer of large orbitally shaken cylindrical bioreactors

Disposable shaking bioreactors are a promising alternative to other disposable bioreactors owing to their ease of operation, flexibility, defined hydrodynamics and characterization. Shaken bioreactors of sizes 20 L and 50 L are characterized in terms of heat transfer characteristics in this research work. Water and an 80% glycerol–water system were used as fluid. Results indicated large heat generation due to shake mixing which was observed by temperature difference between the fluid inside the vessel and the surrounding air outside the vessel. Maximum temperature difference of ca. 30 K was encountered for a 50 L vessel, at 300 rpm and 20 L filling volume. Outside heat transfer rate was governing the overall heat transfer process. Lateral air flow did increase heat transfer rates to large extent. An empirical correlation of overall heat transfer coefficient was obtained in terms of filling volume, rotational speed and lateral air flow rate. However, as the vessel thickness increased, the overall heat transfer process was limited by vessel wall resistance.     

Characterizing the range of simulated prostate abnormalities palpable by digital rectal examination

Background: Although the digital rectal exam (DRE) is a common method of screening for prostate cancer and other abnormalities, the limits of ability to perform this hands-on exam are unknown. Perceptible limits are a function of the size, depth, and hardness of abnormalities within a given prostate stiffness. Methods: To better understand the perceptible limits of the DRE, we conducted a psychophysical study with 18 participants using a custom-built apparatus to simulate prostate tissue and abnormalities of varying size, depth, and hardness. Utilizing a modified version of the psychophysical method of constant stimuli, we uncovered thresholds of absolute detection and variance in ability between examiners. Results: Within silicone-elastomers that mimic normal prostate tissue (21 kPa), abnormalities of 4 mm diameter (20 mm³ volume) and greater were consistently detectable (above 75% of the time) but only at a depth of 5 mm. Abnormalities located in simulated tissue of greater stiffness (82 kPa) had to be twice that volume (5 mm diameter, 40 mm³ volume) to be detectable at the same rate. Conclusions: This study finds that the size and depth of abnormalities most influence detectability, while the relative stiffness between abnormalities and substrate also affects detectability for some size/depth combinations. While limits identified here are obtained for idealized substrates, this work is useful for informing the development of training and allowing clinicians to set expectations on performance.     

The influence of maternal thermal environments on reproductive traits and hatchling traits in a Lacertid lizard,Takydromus septentrionalis

The thermal environment can induce substantial variation in important life-history traits. Experimental manipulation of the thermal environment can help researchers determine the contribution of this factor to phenotypic variation in life-history traits. During the reproductive season, we kept female northern grass lizards, Takydromus septentrionalis (Lacertidae), in three temperature-controlled rooms (25, 28 and 32 °C) to measure the effect of the maternal thermal environment on reproductive traits. Maternal thermal environment remarkably affected reproductive frequency and thereby seasonal reproductive output, but had little effect on reproductive traits per clutch or hatchling traits. Females kept at 32 °C produced more clutches and thus had shorter clutch intervals than females from 28 to 25 °C. Clutch size, clutch mass, relative clutch mass, egg size and hatchling traits did not vary among the three treatments. The eggs produced by the females were incubated at 27 °C and the traits of hatchlings were measured. The result that egg (offspring) size was independent of maternal thermal environments is consistent with the prediction of the optimal egg size (offspring) theory. The eggs produced by low temperature females (28 and 25 °C) took longer time to complete their post-oviposition development than did eggs produced by high temperature females (32 °C). This suggests that the eggs from low temperatures might have been laid when the embryos were at relatively early stages. Therefore, maternal thermal environment prior to oviposition could affect post-oviposition development in T. septentrionalis.     

Finite Element Analysis of Hepatic Radiofrequency Ablation Probes using Temperature-Dependent Electrical Conductivity

Background

Few finite element models (FEM) have been developed to describe the electric field, specific absorption rate (SAR), and the temperature distribution surrounding hepatic radiofrequency ablation probes. To date, a coupled finite element model that accounts for the temperature-dependent electrical conductivity changes has not been developed for ablation type devices. While it is widely acknowledged that accounting for temperature dependent phenomena may affect the outcome of these models, the effect has not been assessed.

Methods

The results of four finite element models are compared: constant electrical conductivity without tissue perfusion, temperature-dependent conductivity without tissue perfusion, constant electrical conductivity with tissue perfusion, and temperature-dependent conductivity with tissue perfusion.

Results

The data demonstrate that significant errors are generated when constant electrical conductivity is assumed in coupled electrical-heat transfer problems that operate at high temperatures. These errors appear to be closely related to the temperature at which the ablation device operates and not to the amount of power applied by the device or the state of tissue perfusion.

Conclusion

Accounting for temperature-dependent phenomena may be critically important in the safe operation of radiofrequency ablation device that operate near 100°C.

     

Breaking the temperature-size rule: Thermal effects on growth,development and fecundity of a crustacean from temporary waters

The temperature-size rule (TSR) is a well-established phenomenon to describe the growth response of ectotherms to temperature by which individuals maintained at low temperatures grow more slowly, but attain a larger size upon maturity. Although there are adaptive and non-adaptive theories about the plasticity of body size in response to temperature, these cannot be applied to all ectotherms, and little is known about the changes in growth and development rates through ontogeny. The ostracod species Heterocypris bosniaca, an inhabitant of freshwater temporary ponds, was used to examine the growth and development rates of its nine growth stages and female fecundity at four different temperatures (15 °C, 20 °C, 25 °C and 30 °C). The development rate of this species accelerates with increasing temperature, reaching a maximum value at 25 °C. The growth factor has a reverse-TSR in younger instars, and the typical TSR is followed only in the last two moults, resulting in non-monotonic response of adult size to temperature. Fecundity (total offspring per female) was not directly related to adult size and was generally higher at lower temperatures. Our results agree with recent research showing that the TSR may vary during ontogeny, and may not be a general trend in ostracod species from temporary waters. Indeed, adult carapace size seems to follow the pattern of a thermal reaction norm, probably influenced by the reduction of oxygen bioavailability at low temperature and the drastic increase in metabolic demand at the upper extreme of the thermal gradient.     

Comparison between ambulatory measurement of effective thermal conductivity and laser Doppler flowmetry method to assess skin microcirculatory activity

The main objective of this paper was to assess the performance of the ambulatory device μHematron to measure indirectly skin blood flow relative to the well-established Laser Doppler flowmetry method. The μHematron device is dedicated to the non-invasive measurement of effective thermal conductivity of living tissues, based on the thermal clearance method. Its major advantage is its ambulatory functionality, as available methods for evaluation of microcirculatory activity are non-ambulatory methods. An experiment was conducted on ten healthy women exposed for one hour in three different thermal environments (22 °C, 25 °C and 30 °C). Skin microcirculatory activity was analyzed after an acclimatization period of 30 minutes. The time between each exposure was at least one hour. Performances of the μHematron device were assessed and a comparative study with a laser Doppler perfusion monitor (LDPM) was performed. Good correlation coefficients between the two devices (r = 0.71 at T1 = 22 °C, r = 0.77 at T2 = 25 °C and r = 0.83 at T3 = 30 °C) were obtained while the LDPM signal was filtered by a low pass filter (0.1 Hz). These results showed that continuous monitoring of effective thermal conductivity was possible in neutral and warm ambiences. Then, the μHematron device could be considered as a complementary tool to Doppler techniques for the investigation of skin blood flow, when ambulatory conditions are required.     

Effects of temperature on the nitric oxide-dependent modulation of the Frank–Starling mechanism: the fish heart as a case study

The Frank–Starling law is a fundamental property of the vertebrate myocardium which allows, when the end-diastolic volume increases, that the consequent stretch of the myocardial fibers generates a more forceful contraction. It has been shown that in the eel (Anguilla anguilla) heart, nitric oxide (NO) exerts a direct myocardial relaxant effect, increasing the sensitivity of the Frank–Starling response (Garofalo et al., 2009). With the use of isolated working heart preparations, this study investigated the relationship between NO modulation of Frank–Starling response and temperature challenges in the eel. The results showed that while, in long-term acclimated fish (spring animals perfused at 20 °C and winter animals perfused at 10 °C) the inhibition of NO production by L-N5 (1-iminoethyl)ornithine (L-NIO) significantly reduced the Frank–Starling response, under thermal shock conditions (spring animals perfused at 10 or 15 °C and winter animals perfused at 15 or 20 °C) L-NIO treatment resulted without effect. Western blotting analysis revealed a decrease of peNOS and pAkt expressions in samples subjected to thermal shock. Moreover, an increase in Hsp90 protein levels was observed under heat thermal stress. Together, these data suggest that the NO synthase/NO-dependent modulation of the Frank–Starling mechanism in fish is sensitive to thermal stress.     

Sensitivity of Norway spruce physiology and terpenoid emission dynamics to elevated ozone and elevated temperature under open-field exposure

Volatile organic compounds (VOCs) emitted from vegetation to the atmosphere contribute to global climate change, but climate change factors also affect VOC emission from vegetation. Soil-grown Norway spruce seedlings were exposed to elevated ozone (1.4 × ambient ozone concentration) and elevated temperature (ambient + 1.3 °C) alone and in combination as well as to ambient ozone and temperature treatments under open-field conditions. VOC emissions (mainly terpenoids), genes involved in early steps of plastidial monoterpene and isoprene synthesis, photosynthetic parameters and growth were measured. In July, when daytime elevated ozone concentrations had been over 40 ppb, ozone doubled the total terpenoid emissions by increasing the emissions of many monoterpenes and sesquiterpenes. Elevated temperature changed the terpenoid profile by increasing the emissions of oxygenated monoterpenes, but did not influence total emissions. Terpenoid emission profiles also differed between elevated ozone alone and elevated ozone in combination with elevated temperature. In August, when daytime elevated ozone concentrations had been ca. 30 ppb, significant treatment effects were not found. Ozone and temperature reduced the expression of DXS2B (1-deoxy-d-xylulose 5-phosphate synthase type II), and ozone that of DXR (1-deoxy-d-xylulose 5-phosphate reductoisomerase) in August. Elevated temperature reduced the stem diameter growth, net photosynthesis and stomatal conductance, but elevated ozone did not have effects on these parameters. Results suggest that elevated temperature may not modify the ozone responses, or vice versa, in terms of gas exchange, growth or total terpenoid emission rates of young Norway spruces in a near-future climate. However, observed changes in terpenoid emission profiles may be important in the future climate, as reactivity in the troposphere differs between individual terpenoids.     

Size exclusion chromatography of zein and xanthophylls: Optimization of operating parameters

Ethanol-soluble components of corn (zein and xanthophylls) were separated and purified by size exclusion chromatography. Aqueous ethanol was used as the solvent for the entire process from extraction through chromatography. The effect of operating and design parameters, such as temperature, flow rate, loading mass, loading volume, column height and diameter, on productivity and resolution of the components was studied. Using a one-variable-at-a-time (OVAT) approach with 1 cm × 60 cm columns, optimum conditions were determined to be 40 °C temperature, 0.25 mL/min flow rate, volume loading of 22 mL corn extract, mass loading at 70 g/L of corn extract. All components could be resolved with base line separation with a 240 cm column length. Column diameter did not affect separation, implying linear scalability with constant flow distribution.