Elevated temperature but not elevated CO2 affects long-term patterns of stem diameter and height of Douglas-fir seedlings

1998 ◽  
Vol 28 (7) ◽  
pp. 1046-1054 ◽  
Author(s):  
D Olszyk ◽  
Claudia Wise ◽  
Erica VanEss ◽  
David Tingey
Keyword(s):  
Elevated Temperature ◽  
Ambient Temperature ◽  
Elevated Temperatures ◽  
Woody Biomass ◽  
Douglas Fir ◽  
Stem Diameter ◽  
Leaf Biomass ◽  
Growing Seasons ◽  
Reduced Height ◽  
Woody Growth

Global climatic change may impact forest productivity, but data are lacking on potential effects of elevated CO2 and temperature on tree growth. We determined changes in shoot growth for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings exposed to ambient or elevated CO2 ( µmol·mol-1), and ambient or elevated temperature . Seedings were grown for 4 years (three complete growing seasons) in outdoor, sunlit chambers. In each season, height growth was initiated earlier and, in two seasons, ceased earlier for elevated compared with ambient temperature trees. Elevated temperature reduced intermediate and final plant heights. Stem diameter growth began earlier each season at the elevated compared with the ambient temperature, but temperature had no affect on final stem diameter. Elevated temperature tended to reduce leaf (p = 0.07) but not woody biomass. Elevated CO2 had no significant effects on stem diameter, height, and leaf or woody biomass, and there were no significant CO2 × temperature interactions. Thus, elevated temperatures (but not elevated CO2) associated with climate change may decrease seedling canopy growth as indicated by reduced height and leaf biomass but have little or no effect on overall woody growth as indicated by stem diameter and woody biomass.

Phenology and growth of shoots, needles, and buds of Douglas-fir seedlings with elevated CO2 and (or) temperature

1998 ◽  
Vol 76 (12) ◽  
pp. 1991-2001 ◽  
Author(s):  
D Olszyk ◽  
Claudia Wise ◽  
Erica VanEss ◽  
Martha Apple ◽  
David Tingey
Keyword(s):  
Elevated Temperature ◽  
Pseudotsuga Menziesii ◽  
Elevated Temperatures ◽  
Leaf Nitrogen ◽  
Douglas Fir ◽  
Growing Seasons ◽  
Combined Stresses ◽  
Terminal Bud ◽  
Early Seedling ◽  
Terminal Shoot

Increased atmospheric CO2 and global warming may affect overall tree growth, but impacts of these combined stresses are largely unknown in terms of multiple growing season impacts on specific flushes. Thus, the effects of ambient or elevated CO2 (approximately 200 µmol·mol-1 above ambient) and ambient or elevated temperature (approximately 4°C above ambient) were evaluated for both main and second (lammas) flushes of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Established seedlings were grown for three full growing seasons in outdoor, sunlit chambers, which maintained diel and seasonal variation in climate. A reconstructed forest soil was used with a seasonal wet and dry cycle and without added fertilizer. Compared with ambient CO2, elevated CO2 had no impact on overall phenology and growth of terminal shoots, needles, or buds. In contrast, compared with ambient temperature, elevated temperature resulted in higher shoot and needle growth rates early in the season; reduced final terminal shoot length; and either reduced, increased, or unchanged final needle length, depending on season. Initiation of the lammas flush was delayed and (or) decreased at elevated temperature. Leading terminal bud break and growth occurred earlier; however, resting bud length was reduced, and bud width tended to increase with elevated temperature. Thus, at least during early seedling growth, elevated temperatures may reduce both main- and lammas-flush growth, thereby altering tree productivity, whereas elevated CO2 may have little effect on main or lammas growth at either the current or elevated temperature.Key words: climate change, leaf nitrogen, Pseudotsuga menziesii, shoot growth, lammas growth.

Swelling Behavior and Drug Release of Polymer Coated Nano Iron Oxide Embedded Hydroxyapatite

2019 ◽  
Vol 829 ◽  
pp. 108-113
Author(s):  
Yoshiyuki Yokogawa ◽  
Rina Ohkura ◽  
Yoko Inoue ◽  
Atsumasa Shishido ◽  
Ereath Beeran Ansar ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Elevated Temperature ◽  
Ambient Temperature ◽  
Polyelectrolyte Complex ◽  
Elevated Temperatures ◽  
Release Behavior ◽  
Swelling Properties ◽  
Gel Beads ◽  
Calcium Alginate Gel ◽  
Ca Alginate

Spherical calcium-alginate gel beads containing HAIO, iron oxide (IO) nanoparticles embedded on hydroxapatite (HA), were prepared along with and poly (N-isopropylacrylamide) (PNIPAAM) or chitosan. These spheres, HAIO, HAIO-PNIPAAM and HAIO-chitosan spheres, were used as carriers of 5-fluorouracil (5-FU), one of the drugs for cancer chemical therapy, and the 5-FU release behavior in PBS solution was investigated at ambient and elevated temperatures using U-V spectrometry. The amount of the released 5-FU from the HAIO spheres was somewhat higher than that from HAIO-PNIPAAM and HAIO-chitosan spheres at ambient temperature. At elevated temperature, HAIO spheres showed an increase in quantity of released 5-FU. The amount of released 5-FU from HAIO-PNIPAAM spheres was almost the same, and that from HAIO-chitosan spheres was reduced compared to those at ambient temperature. These spheres, HAIO, HAIO-PNIPAAM and HAIO-chitosan spheres, show the similar swelling properties at elevated temperature. However, the combinations of Ca-alginate - PNIPAAM or Ca-alginate - chitosan may produce the different structures, which are core-shell network for HAIO-PNIPAAM spheres and or a polyelectrolyte complex for HAIO-chitosan spheres, leading to a different release behavior of 5-FU.

Dynamic Crush Test of Subcomponent Composite Front Frame Rails

2001 ◽  
Author(s):  
Thomas Brimhall ◽  
Hasetetsion G. Mariam
Keyword(s):  
Elevated Temperature ◽  
Bond Strength ◽  
Ambient Temperature ◽  
Energy Absorption ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Absorbed Energy ◽  
Steel Rail ◽  
Composite Matrix ◽  
Lap Shear

Abstract Testing of components is a usual method to evaluate structures, joining methods, and materials prior to full scale testing. Ambient temperature dynamic crush testing was performed on steel and composite sub-component front frame rails to compare the energy absorption and evaluate crush behavior. The sub-component composite frame rails were fabricated from two parts, an upper and lower, and bonded using three adhesives: Ashland polyurethane, Lord epoxy, and 3M epoxy. Prior to the dynamic test of the rails, single lap shear coupon tests were performed at ambient temperature and elevated temperature, 135°C, to evaluate relative bond strength of these adhesives. Testing was performed at elevated temperature because adhesives used for structural bonding in automotive, specifically under-hood, applications can be subjected to elevated temperatures. All three adhesives tested showed reduced bond strength at elevated temperatures. At room temperature, the Ashland urethane and Lord epoxy adhesives were observed to have comparable higher bond strength with the composite-to-composite lap shear coupons compared to the 3M epoxy. However, the crush failure mode for the composite tubes was confined to the substrate and the mean crush load was independent of the adhesive used for fabrication. Progressive crushing of the rail specimens was observed for all specimens tested. The amount of energy absorbed and crush mode for each rail design depended on its structural and material characteristics. The steel specimen absorbed energy by localized buckling in an accordion crush mode. The composite specimens absorbed energy by fracturing the composite matrix, delamination, fracture of the reinforcement fibers, and friction between the fracture and crushing surfaces. The crushing process of the steel rail was initiated by fabricated corrugations in the rail comers at the front, or impact, end of the rail. The composite rail crush event was initiated with an aluminum plug trigger designed to cause the composite rail to split at the comers with fracture of the composite matrix and delamination of the composite plies. Glass fibers were observed to fracture primarily at the tube corners. Fiber fracture elsewhere was infrequent. Close examination of the bonded joint fracture surface showed extensive fiber tear-out indicating that the failure was in the composite, not the adhesive. Mean crush load for the steel rail was 60% higher than the average mean load for the composite rails. The peak load for the steel rail was 71% higher than the average peak load for the composite rails. Specific energy absorption (SEA) of the steel rail was calculated to be 6.34 kJ/kgm compared with an average of 10.5 kJ/kgm for the composite rails.

Strength and Toughness of Interface Between EBC and Ceramic Substrates at Elevated Temperature

2003 ◽  
Author(s):  
Shanti Nair ◽  
Ellen Y. Sun
Keyword(s):  
Elevated Temperature ◽  
Ambient Temperature ◽  
Elevated Temperatures ◽  
Ceramic Substrates ◽  
Substrate Interface ◽  
Test Methodology ◽  
Barrier Coating ◽  
Coating Layers ◽  
Strength And Toughness

In a previous study, the strength of the interface between an environmental barrier coating (EBC) and the substrate was measured at ambient temperature using a unique compression test methodology. In this study, the method was extended for elevated temperature characterization of the strength of this interface. The extension of the method also allowed for the characterization of the elevated temperature toughness ofthe EBC/substrate interface. An essential component of measuring elevated temperature interface strength and toughness was characterization of the elevated temperature elastic modulus of the EBC coating layers. The elastic moduli of EBC layers were characterized at both ambient and at elevated temperature. The results point to a substantial decrease in the moduli of the EBC coating layers at elevated temperature. Preliminary results also indicate a decrease in both the strength and toughness of the EBC/substrate interface at elevated temperatures compared to ambient temperature.

Analysis of the Effect of Elevated Temperature on Reliability of Shear Strengthened Concrete Beams

2016 ◽  
Vol 691 ◽  
pp. 160-171
Author(s):  
Peter Sabol ◽  
Sergej Priganc
Keyword(s):  
Elevated Temperature ◽  
Ambient Temperature ◽  
Elevated Temperatures ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Polymer Materials ◽  
Shear Strengthening ◽  
Near Surface ◽  
Concrete Members ◽  
Original Strength

This article presents the results of experimental research focused on the shear strengthening of reinforced concrete beams with one of the latest and most promising method: NSM - Near surface mounted reinforcement. In recent years, research in this area focuses on combination of epoxy and FRP (fiber reinforced polymer) materials suitable for strengthening concrete elements. A traditional material: stainless steel was also used in this study but in non-traditional T-cross section in terms of strengthening of concrete members. Structural epoxy adhesives offer excellent properties but are very sensitive to elevated temperatures. Effect of increasing temperature gradually degrade their properties and subsequently decreased bond strength, whereas during cooling may acquire significant parts of the original strength. The influences of these factors were investigated in shear resistance of NSM strengthened concrete beams under four point bending at ambient temperature, at elevated temperature and after cooling to ambient temperature.

A New Technique for Testing Abrasion Resistance of Refractories at Elevated Temperatures

2010 ◽  
Vol 105-106 ◽  
pp. 230-233
Author(s):  
Xi Gao Peng ◽  
Jia Lin Sun ◽  
Gan Shi ◽  
Shao Ping Huang
Keyword(s):  
Elevated Temperature ◽  
Ambient Temperature ◽  
Abrasion Resistance ◽  
Elevated Temperatures ◽  
Sample Surface ◽  
Compressed Air ◽  
New Technique ◽  
High Alumina ◽  
Sample Chamber ◽  
A New Technique

Based on an extensive comparison of test methods for abrasion resistance from home and abroad, a new technique for abrasion resistance at elevated temperature has been developed with some improvements. Two connected airtight chambers are designed to prevent compressed air from entering the sample chamber, so that heat loss of the sample chamber can be reduced and the chamber temperature is less disturbed. The sample surface temperature can reach stable within 5 min and the temperature fluctuation on sample surface can be less than 20°C in the course of inleting the compressed air at working temperatures up to1400°C. The repeatability was tested using float-glass plate as reference sample at ambient temperature and using high alumina bricks for elevated temperature. A variation coefficient under 7% at ambient temperature has been achieved. Comparison of abrasion resistance at elevated temperature was tested respectively on a high alumina brick and on a silicon nitride bonded silicon carbide brick and the results could be significantly distinguished. Nitrogen can be blown into sample chamber during heating the furnace to prevent nonoxide bearing samples from being oxidized.

scholarly journals Effect of Elevated Ambient Temperature on Simulator-Derived Oscillometric Blood Pressure Measurement

2020 ◽  
Author(s):  
Jennifer S Ringrose ◽  
Michael D Kennedy ◽  
Jalisa Kassam ◽  
Omar Mouhammed ◽  
Sangita Sridar ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Elevated Temperature ◽  
Ambient Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Blood Pressure Measurement ◽  
Ambient Temperatures ◽  
Oscillometric Blood Pressure Measurement ◽  
Increasing Temperature ◽  
Relative Differences

Abstract BACKGROUND Oscillometric blood pressure (BP) devices are typically labeled for use up to 40 °C. Many geographic regions have ambient temperatures exceeding 40 °C. We assessed the effect of increased ambient temperature (40–55 °C) on simulator-derived oscillometric BP measurement. METHODS Three Omron BP769CAN devices, 3 A&D Medical UA-651BLE devices, and accompanying cuffs were used. A custom heat chamber heated each device to the specified temperature. A noninvasive BP simulator was used to take 3 measurements with each device at differing temperatures (22, 40, 45, 50, and 55 °C) and BP thresholds: 80/50, 100/60, 120/80, 140/90, 160/110, and 180/130 mm Hg. Using each device as its own control (22 °C), we determined the relative differences in mean BP for each device at each temperature and BP setting, assessed graphical trends with increasing temperature, and examined variability. RESULTS Graphical trends of mean simulator-subtracted BP differences from room temperature showed no discernable pattern, with differences clustered around zero. Overall mean difference in BP (combined elevated temperatures minus room temperature) was −0.8 ± 2.1 (systolic ± SD)/1.2 ± 3.5 (diastolic ± SD) mm Hg for the A&D device and 0.2 ± 0.4 (systolic ± SD)/−0.1 ± 0.1 (diastolic ± SD) mm Hg for the Omron. All individual elevated temperature differences (elevated temperature minus room temperature) except A&D diastolic BP at 50 °C were within 5 mm Hg. CONCLUSIONS In this simulator-based study assessing within-device differences, higher ambient temperatures resulted in oscillometric BP measurements that were comparable to those performed at room temperature.

scholarly journals Material Characterization of PMC/TBC Composite Under High Strain Rates and Elevated Temperatures

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 167
Author(s):  
Przemysław Golewski ◽  
Alexis Rusinek ◽  
Tomasz Sadowski
Keyword(s):  
Elevated Temperature ◽  
Ambient Temperature ◽  
Composite Structures ◽  
High Speed ◽  
Elevated Temperatures ◽  
Split Hopkinson Pressure Bar ◽  
Polymer Matrix Composites ◽  
Dynamic Compression ◽  
Thermal Barrier ◽  
Hopkinson Pressure Bar

Polymer matrix composites (PMC), despite their many advantages, have limited use at elevated temperatures. To expand the scope of their uses, it becomes necessary to use thermal barrier coatings (TBC). In addition to elevated temperatures, composite structures, and thus TBC barriers, can be exposed to damage from impacts of foreign objects. Therefore, before using the thermal barrier in practice, knowledge about its behavior under high-speed loads is necessary. The paper presents results for samples with the PMC/TBC system subjected to dynamic compression using a split Hopkinson pressure bar (SHPB). The substrate was made of CFRP (carbon reinforced polymer) with epoxy matrix and twill fabric. TBC was made of ceramic mat saturated by commercial hardener from Vitcas company. The tests were carried out at ambient temperature and elevated temperature—55 °C and 90 °C. Tests at ambient temperature were carried out for three pressure levels: 1, 1.5, and 2 bar. Only the pressure of 1 bar was used for the elevated temperature. Studies have shown that the limit load is 1 bar for ambient temperature. At 1.5 bar, cracks occurred in the TBC structure. Increased temperature also adversely affects the TBC barrier strength and it is damaged at a pressure of 1 bar.

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