Glutamate Transporter Excitatory Amino Acid Experiment

Glutamate Transporter Excitatory Amino Acid Experiment Abstract N-(2-18F-Fluoropropionyl)-L-glutamate(18F-FPGLU) is a potential amino acid tracer for tumor imaging with positron emission tomography (PET). In this study, the  relationship between glutamate transporter excitatory amino acid carrier 1 (EAAC1) expression and 18F-FPGLU uptake in rat C6 glioma cells line and human SPC-A-1 lung adenocarcinoma cells line was investigated. The uptake of 18F-FPGLU in C6 cells increased significantly after induced by ATRA for 24, 48, and 72 h, which was closely related to expression of EAAC1 in C6 cells (R=0.939). Compared with the SPC-A-1(NT) control cells, the uptake of 18F-FPGLU on EAAC1 knock-down SPC-A-1(shRNA) cells significantly decreased to 64.0%. In the PET imaging of 18F-FPGLU of SPC-A-1 and EAAC1 knock-down SPC-A-1(shRNA)-bearing mice models, the uptake of 18F-FPGLU in SPC-A-1(shRNA) xenografts was significantly lower than that in SPC-A-1 xenografts, with Tumor/Muscle ratio of 1.67  ± 0.1 vs. 3.01  ± 0.3 at 60 min post-injection. The result s suggest that transport mechanism of 18F-FPGLU in glioma C6 and lung adenocarcinoma SPC-A-1 cells lines mainly involves in glutamate transporter EAAC1, which is an important transporter of 18F-FPGLU in tumor cells and may be a novel hallmark of tumor glutamate metabolism PET imaging. Keywords: N-(2-18F-fluoropropionyl)-L-glutamate; tumor imaging; glutamate transporter; excitatory amino acid carrier 1 Introduction As the most commonly used positron emission tomography (PET) tracer for tumor diagnosis, 18F-fluoro-2-deoxy-D-glucose (18F-FDG) also has certain false negative and false positive results(Shreve et al. 1999; Fletcher et al. 2008). It has been reported that 18F-FDG negative tumors may use a different metabolic pathway called glutaminolysis(DeBerardinis et al. 2007; Ward et al. 2012). Glutamine and glutamate play key roles in the adapted intermediary metabolism of tumors(Gao et al. 2009; Rajagopalan et al. 2011; Shanware et al. 2011). Several 18F-labeled glutamic acid and 18F-labeled glutamine have been used for metabolic PET imaging of tumor in humans (Baek et al. 2013; Venneti et al. 2015). High uptake of these amino acid tracers in tumor cells is likely related to the increased expression of amino acid transporters. For example, the upregulated system ASC, especially ASCT2 might contributed to the uptake of 18F-labeled (2S,4R)-4-fluoro-L-glutamine(Ploessl et al. 2012), and 18F-fluoro glutamic acid (BAY 85-8050) transport involved in Na+-dependent XAG- and Na+-independent XC- systems with XC- possibly playing a more dominant role, but both of them showed defluorination in vivo(Krasikova et al. 2011). 18F-labeled (4S)-4-(3-[18F]fluoropropyl)-L-glutamate (BAY 94-9392), another derivative of glutamic acid, whose transport was due mostly to upregulation of system XC-, a potential biomarker for tumor oxidative stressà ¯Ã‚ ¼Ã…’can be useful for detecting system XC- activity in vivo and is considered to be a potential tracer for tumor imaging(Koglin et al. 2011). Our recently developed novel N-18F-labeled glutamic acid, N-(2-[18F] fluoropropionyl)-L-glutamate (18F-FPGLU), seemed to be a potential amino acid PET tracer for tumor metabolic imaging, with high tumor-to-background contrast in several tumor-bearing mice models. Preliminary studies showed that 18F-FPGLU was primarily transported through Na+-dependent high-affinity glutamate transporter system XAG-(Hu et al. 2014), but the accurate transport mechanism is unknown. Glutamate transport system includes Na+-dependent excitatory glutamate transporter XAG- system and Na+-independent glutamate transporter XC- system(Avila-Chà ¡vez et al. 1997). System XC- (xCT) is overexpressed on tumor c ells and is a potential biomarker for tumor oxidative stress. As an important member of XAG- system, excitatory amino acid carrier 1 (EAAC1), also called excitatory amino acid transporter 3 (EAAT3), localizes to the post-synaptic structure of neurons and surrounding glial cells as regulator of excitatory neurotransmission, and also exists in peripheral tissues, perhaps as metabolic regulators(Bailey et al. 2011). The expression of EAAC1 was known to be regulated by several mechanisms that modify carrier abundance on the plasma membranes and was markedly induced by all tans-retinoic acid (ATRA) in rat C6 glioma cells, which led to strikingly stimulate amino acid influx(Bianchi et al. 2008). However, EAAC1 transporter may be a potential biomarker for tumor molecular imaging. It has not been reported so far. This study investigated the relationship between EAAC1 expression and 18F-FPGLU uptake in C6 rat glioma cells line and SPC-A-1 human lung adenocarcinoma. The uptake of 18F-FPGLU was assessed in ATRA-treated and untreated C6 cells lines, and also in shRNA-mediated EAAC1 knock-down SPC-A-1 cells and the non-targeted (NT) control cells in vitro. Further prospective researches of PET imaging of tumor-bearing mice models with C6, SPC-A-1 and EAAC1 knock-down SPC-A-1(shRNA) xenografts were performed to reveal the correlation between the uptake of 18F-FPGLU and the expression of EAAC1. Materials and methods Materials All reagents, unless otherwise specified, were of analytical grade and commercially available. All chemicals obtained commercially were used without further purification. Inveon small-animal PET/computed tomography (CT) scanner was purchased from Siemens (Germany). Synthesis of 18F-FPGLU The synthesis of 18F-FPGLU from 4-nitrophenyl-2-18F-fluoropropionate (18F-NFP) via a two-step reaction sequence has been described in detail by the earlier paper(Hu et al. 2014). Cell Culture and Animal Models The C6 rat glioma cells, SPC-A-1 human lung adenocarcinoma cells were obtained from Shanghai Institute of Cellular Biology of Chinese Academy of Sciences (Shanghai, China). The cells were cultured in culture flasks containing DMEM medium(for C6 cells) or RPMI 1640 medium (for SPC-A-1) supplemented with 10% FBS and 1% penicillin/streptomycin at 37oC in a humidified atmosphere of 5% CO2 and 95% air. 24 hours before the experiments in vitro, C6 cells lines or SPC-A-1 cell lines were trypsinized and 2105 cells per well were seeded into 24-well plates. All animal experimental studies were approved by the Institutional Animal Care and Utilization Committee (IACUU) of the First Affiliated Hospital, Sun Yat-Sen University (approval No.[2013]A-173). All efforts were made to minimize animal suffering, to reduce the number of animals used, and to use alternatives to in vivo techniques, if available. The nude mice were obtained from Laboratory Animal Center of the First Affiliated Hospital of Sun Yat-Sen University (Guangzhou, China). The C6, SPC-A-1 and EAAC1 knock-down SPC-A-1(shRNA) tumor models were made using previously described methods(Deng et al. 2011). Tumor cells (2-5-106) were injected subcutaneously and allowed to grow for 1 to 3 weeks. When the tumor reached 6-10 mm (diameter) micro P ET/CT scans were done. C6 induced by ATRA The rat glioma C6 cells were treated by all trans-retinoic acid (ATRA) 12 h after the passage. Culture medium was substituted with fresh medium (containing DMEM medium supplemented with 10% FBS) in the absence or in the present of ATRA at a concentration of 10 ÃŽ ¼M from a 10 mM stock solution in DMSO according to the literature16. After the treatment of ATRA for 24, 48 and 72 h, quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to monitored the mRNA and protein expression levels of EAAC1 in ATRA treated C6 and non-treated C6 cells. Generation of shRNA-mediated EAAC1 knock-down cells. The method of generation of shRNA-mediated EAAC1 knock-down cells was similar to the literature(Youland et al. 2013). SPC-A-1 human lung adenocarcinoma cells was used for shRNA-mediated EAAC1 knock-down experiment. SPC-A-1 cells were transduced with lentivirus ecoding EAAC1-targeted short hairpin RNAs (shRNA). shRNA sequences were selected from human EAAC1 mRNA NM_004170 and the shRNA fragments were cloned in a lentivirus vector pGLV3 plasmid with the sequence 5-GCATTACCACAGGAGTCTTGG-3. A non-specific targeting (NT) shRNA for control was cloned in the same lenvirus plasmid backbone. Lentiviral packaging was performed with trans-lentiviral packaging mix in 293T cells according to the manufacturers instructions. SPC-A-1 cells were plated on 6-well plates at 2-105 cells per well. After 24 hours, medium was aspirated and replaced with 100 ÃŽ ¼L of virus-containing solution was added to each well and incubated at 37oC for 24 h. Cells were selected with puromycin and monitored for green fl uorescence protein (GFP) expression. The EAAC1 mRNA expression level was monitored by quantitative real-time polymerase chain reaction (qRT-PCR). The EAAC1 protein expression level was quantized by western blotting. qRT-PCR for the expression of EAAC1 Relative expression levels of EAAC1 mRNA in C6 and SPC-A-1 cells were calculated using the fluorescence quantitative real-time polymerase chain reaction (qRT-PCR) (Stratagene Mx3000P Real time PCR, Agilent). Total cellular RNA was isolated with the Rneasy mini Kit (TAKARA). 1 ÃŽ ¼g of RNA was synthesized to cDNA in a 20 ÃŽ ¼L reaction system with reverse transcriptase buffer, RT Enzyme Mix and primer MIX (Bestar qPCR RT kit, DBI). Conditions for reverse transcription were 5 min at 65oC, 5 min on ice, then 60 min at 37oC and 10 min at 98oC. Oligodeoxynucleotide primers of EAAC1 gene for PCR amplification was 5-AGTTCAGCAACACTGCCTGT-3 (forward) and (5-GTTGCACCAACGGGTA ACAC-3(reverse). PCR was programmed as follows: 2 min at 94oC, 20 s at 94oC, 20 s at 58oC à ¯Ã‚ ¼Ã…’ then 20 s at 72oC à ¯Ã‚ ¼Ã…’ for 40 cycles. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as a initial control and each sample was amplified in triplicate. The relative expression of EAAC1 mRNA compared with GAPDH was calculated by comparative threshold method (2 -ΔΔCt ). Western blotting for EAAC1 Cells were lysed in a detergent-containing buffer with protease inhibitors for 20 min at 4oC. Glyceraldehyde-3-phosphate dehydrogenase ( GAPDH) was used as a reference protein. After solubilization, cell lysates were collected and centrifuged at 14000 rpm for 10 min. The supernatants were transferred into new tubes, quantification of proteins was performed with Pierce BCA Protein Assay Kit (Thermo) and aliquots of 25 ÃŽ ¼g were loaded on an 10% gel for SDS-PAGE. After electrophoresis, proteins were transferred to polyvinylidene difluorideà ¯Ã‚ ¼Ã‹â€ PVDFà ¯Ã‚ ¼Ã¢â‚¬ °membranes (Millipore) . The membranes with EAAC1 or GAPDH were departed at the middle position, and were blocked and incubated with deferent antibody, respectively. Non-specific binding sites were blocked with an incubation in Tris-buffer saline containing 5% of bovine serum albumin (BSA) for 1h at room temperature. Then the blots were exposed to EAAT3 antibody (rabbit monoclonal antiserum, 1:1000, Abcam) or anti-GAPDH rabbit monoclonal antibody(1:3000, Abcam) diluted in blocking solution for at 4oC overnight. After washing, the blots were exposed for1h at room temperature to goat anti-rabbit IgG HRP diluted 1:5000 in blocking solution. Cellular uptake of 18F-FPGLU Cells were plated in 24-well plates (2x105cells/well) and uptake studies were performed at 24 h after the passage. The cellular uptake of 18F-FPGLU studies was similar to the methods described previously(Krasikova et al. 2013). The medium was aspirated and the cells were washed 3 times with 1 mL warm PBS. 18F-FPGLU was dissolved in PBS solution and was added to each well (74-111 KBq/0.2 mL/well). After incubated with 18F-FPGLU at 37oC for 30 min, the radioactive medium was removed and the cells were washed 3 times with ice-cold PBS. Then, the cells were dissolved in 0.5 mL of 1 N NaOH and the activity was measured by ÃŽ ³ counter (GC-1200, USTC Chuangxin Co. Ltd. Zonkia Branch, China). The cell lysate (25ÃŽ ¼L) was used for determination of protein concentration by BCA protein assay. The uptake data are based on the amount of activity added to each well and the total amount of protein in each well. Each experiment was done in triplicate, averaged and was repeated 5 times on different days. The uptake of 18F-FPGLU was assessed on the ATRA-treated or untreated C6 cells, and on EAAC1 knock-down SPC-A-1(shRNA) cells or SPC-A-1(NT) control cells. The relative uptake ratios were calculated compared to the control cells. Small-animal PET-CT imaging Small-animal PET-CT imaging studies with tumor-bearing mice were carried out using the Inveon small-animal PET/CT scanner (Siemens). 3.7-7.4 MBq of 18F-FPGLU were injected intravenously in conscious animals via the tail vein. The mice were anesthetized with 5% chloral hydrate solution (6 mL/kg) and were kept warm throughout the procedure. Imaging started with a low-dose CT scan, immediately followed by a PET scan. PET images were acquired at 30, 60, 90, 120 min post-injection. For a comparative study, mice were kept fasting for 4 h and were anesthetized with 5% chloral hydrate solution (6 mL/kg) and imaged with 18F-FDG (3.7 MBq) at 60 min after intravenous injection. The images were reconstructed by two-dimensional ordered-subsets expectation maximum (OSEM). For each small-animal PET scan, ROIs were drawn over the tumor and muscle of the thigh on decay-corrected whole-body coronal images using Inevon Research Workplace 4.1 software. The quantification was performed according the meth ods described previously(Hu et al. 2014). Radioactivity concentration within a tumor or other tissue was converted to MBq/g and then divided by the administered activity to obtain an imaging ROI-derived percentage of injected dose per gram of tissue (% ID/g). Then, the ttumor/muscle (T/M) and tumor/brain (T/B) uptake ratios were calculated, respectively. Immunohistochemistry Expression of EAAC1 was assessed by immunohistochemistry on formalin-fixed paraffin embedded rat brain tissues and C6 xenograft samples. Immunohistochemistry experiments were carried out according to the literature(Wang et al. 2013). Normal rat brain tissues and C6 glioma tissues were fixed in 10% neutral buffered formalin overnight at room temperature. Tissues were then dehydrated, embedded in paraffin, and cut into 3-ÃŽ ¼m sections. After antigen retrieval, tissue sections were subject to immunohistochemical incubated with antibodies against EAAC1(Abcam), DAB was stained before mounted onto microscope slides. Tissues were analyzed with a Nikon E800M microscope. Statistical analyses Data were expressed as mean+/-SD. Statistical analysis was performed with SPSS software, version 16.0 (SPSS Inc.), for Windows (Microsoft). Student t test was used to assess differences in the magnitudes of samples from two measurements. A P values of less than 0.05 was considered to indicate statistical significant. A scatter plot was drawn with the relative mRNA expression and the relative uptake of 18F-FPGLU in C6 cells treated with ATRA for 24h, 48h, 72h. Spearman correlation analysis and a linear regression analysis was performed between them. Results EAAC1 expression and 18F-FPGLU uptake in C6 cells induced by ATRA The EAAC1 mRNA relative expression levels in ATRA-treated C6 cells assessed by quantitative real-time polymerase chain reaction (qRT-PCR) are shown by Figure 1A. Compared with the untreated C6 cells, the EAAC1 mRNA relative expression level in ATRA-treated C6 cells treated with ATRA at 10 ÃŽ ¼M for 24, 48 and 72 h was increased to 1.72  ± 0.11à ¯Ã‚ ¼Ã…’3.22  ± 0.22à ¯Ã‚ ¼Ã…’4.0  ± 0.21 times, respectively( Fig. 1A). Meanwhile, the western blotting results also showed that EAAC1 protein expression in ATRA-treated C6 cells was increased gradually(Fig. 1B). Corresponding with the high EAAC1 expression in ATRA-treated C6 cells, 18F-FPGLU uptake was significantly increased to 1.47  ± 0.11à ¯Ã‚ ¼Ã…’2.14  ± 0.29à ¯Ã‚ ¼Ã…’2.12  ± 0.16 times in C6 cells treated by ATRA for 24, 48 and 72 h, respectively(Fig. 1C). There was a high correlation between the relative EAAC1 mRNA expresion and the relative 18F-FPGLU uptake in ATRA treated C6 cells (R = 0.939, Fig. 1D). To summ arize, EAAC1 expression was markedly induced by ATRA in C6 cell lines. As a result, there was more 18F-FPGLU uptake in ATRA-treated C6 cells line which has more EAAC1 expression at both mRNA and protein levels. Figure 1 PET imaging on C6 glioma-bearing mice Small-animal PET-CT scan was performed on C6 glioma-bearing nude mice models 1h post-injection of 18F-FPGLU. PET-CT fusion imaging of the mice models demonstrated that 18F-FPGLU could intensely accumulate in C6 glioma (Fig. 2A). The tumor/brain uptake ratio of 18F-FPGLU on C6 glioma-bearing mice was higher than that of 18F-FDG at 1h post-injection of radiotracers(n = 3, P < 0.05, Fig. 2B). However, the tumor/muscle uptake ratio of 18F-FPGLU in C6 glioma-bearing mice was lower than that of 18F-FDG (n = 3, P < 0.05). Immunohistochemistry showed that widely diffuse EAAC1 transporter staining was shown in C6 glioma, however there was minimal EAAC1 staining in normal rat brain write matter tissue (Fig. 2C). Figure 2 EAAC1 expression and 18F-FPGLU uptake in EAAC1 knock-down SPC-A-1 human lung adenocarcinoma cells The influence of EAAC1 expression on 18F-FPGLU uptake was specifically investigated using RNA interference-mediated EAAC1 knock-down SPC-A-1 human lung adenocarcinoma cells. Lentivirally delivered shRNA significantly reduced EAAC1 mRNA expression in SPC-A-1(shRNA) cells, as compared to the non-targeted (NT) shRNA control cells (SPC-A-1(NT) cells), EAAC1 shRNA reduced EAAC1 mRNA expression by 72% in SPC-A-1(shRNA) cells (P < 0.01) (Fig. 3A). At the protein expression level, EAAC1 shRNA significantly decreased EAAC1 expression in SPC-A-1(shRNA) cells by 59.6% (P < 0.01) (Fig. 3B). Knock-down of EAAC1 expression was associated with a significantly lower 18F-FPGLU uptake by 36% in SPC-A-1(shRNA) cells (P

Energy Ch 11 Presentation

11 Using Energy  © 2010 Pearson Education, Inc. Slide 1  © 2010 Pearson Education, Inc. Slide 2  © 2010 Pearson Education, Inc. Slide 3  © 2010 Pearson Education, Inc. Slide 4 Reading Quiz 1. A machine uses 1000 J of electric energy to raise a heavy mass, increasing its potential energy by 300 J. What is the efficiency of this process? A. B. C. D. E. 100% 85% 70% 35% 30%  © 2010 Pearson Education, Inc. Slide 5 Reading Quiz 2. When the temperature of an ideal gas is increased, which of the following also increases? 1) The thermal energy of the gas; (2) the average kinetic energy of the gas; (3) the average potential energy of the gas; (4) the mass of the gas atoms; (5) the number of gas atoms. A. B. C. D. E. 1, 2, and 3 1 and 2 4 and 5 2 and 3 All of 1–5  © 2010 Pearson Education, Inc. Slide 6 Reading Quiz 3. A refrigerator is an example of a A. B. C. D. E. reversible process. heat pump. cold reservoir. heat engine. hot reservoir.  © 2010 Pearson Education, Inc. S lide 7 Example Problem Light bulbs are rated by the power that they consume, not the light that they emit.A 100 W incandescent bulb emits approximately 4 W of visible light. What is the efficiency of the bulb?  © 2010 Pearson Education, Inc. Slide 8 Efficiency  © 2010 Pearson Education, Inc. Slide 9 Example Problems A person lifts a 20 kg box from the ground to a height of 1. 0 m. A metabolic measurement shows that in doing this work her body uses 780 J of energy. What is her efficiency? A 75 kg person climbs the 248 steps to the top of the Cape Hatteras lighthouse, a total climb of 59 m. How many Calories does he burn?  © 2010 Pearson Education, Inc. Slide 10 Checking UnderstandingWhen you walk at a constant speed on level ground, what energy transformation is taking place? A. B. C. D. E. Echem ? Ug Ug ? Eth Echem ? K Echem ? Eth K ? Eth  © 2010 Pearson Education, Inc. Slide 11 Example Problem How far could a 68 kg person cycle at 15 km/hr on the energy in one slice of pizz a? How far could she walk, at 5 km/hr? How far could she run, at 15 km/hr? Do you notice any trends in the distance values that you’ve calculated? Chemical energy from food is used for each of these activities. What happens to this energy—that is, in what form does it end up? 2010 Pearson Education, Inc. Slide 12 The Ideal Gas Model 2 Kavg T? 3 kB  © 2010 Pearson Education, Inc. Slide 13 Checking Understanding:Temperature Scales Rank the following temperatures, from highest to lowest. A. 300  °C > 300 K > 300  °F B. 300 K > 300  °C > 300  °F C. 300  °F > 300  °C > 300 K D. 300  °C > 300  °F > 300 K  © 2010 Pearson Education, Inc. Slide 14 Checking Understanding Two containers of the same gas (ideal) have these masses and temperatures: †¢ Which gas has atoms with the largest average thermal energy? †¢ Which container of gas has the largest thermal energy?A. P, Q B. P, P C. Q, P D. Q, Q  © 2010 Pearson Education, Inc. Slide 15  © 2010 Pe arson Education, Inc. Slide 16 Example Problem Using a fan to move air in a room will make you feel cooler, but it will actually warm up the room air. A small desk fan uses 50 W of electricity; all of this energy ends up as thermal energy in the air of the room in which it operates. The air in a typical bedroom consists of about 8. 0 x 1026 atoms. Suppose a small fan is running, using 50 W. And suppose that there is no other transfer of energy, as work or heat, into or out of, the air in the oom. By how much does the temperature of the room increase during 10 minutes of running the fan?  © 2010 Pearson Education, Inc. Slide 17 Example Problem: Work and Heat in an Ideal Gas A container holds 4. 0 x 1022 molecules of an ideal gas at 0  °C. A piston compresses the gas, doing 30 J of work. At the end of the compression, the gas temperature has increased to 10  °C. During this process, how much heat is transferred to or from the environment?  © 2010 Pearson Education, Inc. Slide 18 Operation of a Heat Engine  © 2010 Pearson Education, Inc. Slide 19The Theoretical Maximum Efficiency of a Heat Engine  © 2010 Pearson Education, Inc. Slide 20 Example Problem: Geothermal Efficiency At The Geysers geothermal power plant in northern California, electricity is generated by using the temperature difference between the 15  °C surface and 240  °C rock deep underground. What is the maximum possible efficiency? What happens to the energy that is extracted from the steam that is not converted to electricity?  © 2010 Pearson Education, Inc. Slide 21 Operation of a Heat Pump  © 2010 Pearson Education, Inc. Slide 22 Coefficient of Performance of a Heat Pump 2010 Pearson Education, Inc. Slide 23 Checking Understanding: Increasing Efficiency of a Heat Pump Which of the following changes would allow your refrigerator to use less energy to run? (1) Increasing the temperature inside the refrigerator; (2) increasing the temperature of the kitchen; (3) decreasing the t emperature inside the refrigerator; (4) decreasing the temperature of the kitchen. A. All of the above B. 1 and 4 C. 2 and 3  © 2010 Pearson Education, Inc. Slide 24 Entropy Higher entropy states are more likely. Systems naturally evolve to states of higher entropy. 2010 Pearson Education, Inc. Slide 25 Second Law of Thermodynamics  © 2010 Pearson Education, Inc. Slide 26 Example Problem: Coming to a Stop A typical gasoline-powered car stops by braking. Friction in the brakes brings the car to rest by transforming kinetic energy to thermal energy. Electric vehicles often stop by using regenerative braking, with the engine used as a generator, transforming the kinetic energy of the vehicle into electric energy that recharges the battery. The energy is thus ultimately transformed to chemical energy in the battery.Which type of stopping involves a larger change in entropy? Which vehicle is apt to be more efficient? Explain, using energy and entropy concepts.  © 2010 Pearson Educa tion, Inc. Slide 27 Example Problem: A Second-Law Workaround? When you run a heat engine, some (or most) of the energy is â€Å"wasted† as heat transferred to the cold reservoir. Suppose someone suggests making a 100% efficient heat engine by using some of the output of the heat engine to run a heat pump to transfer this heat back to the hot reservoir. Let’s do a calculation to see if this is a workable solution. A.If you have a heat engine that runs between a hot reservoir at 100 °C and a cold reservoir at a temperature of 0 °C, what is the maximum efficiency? B. If the engine draws 100 J from the hot reservoir, what is the maximum possible energy output? How much heat is deposited in the cold reservoir? C. How much energy would it take to run a heat pump between the cold and the hot reservoirs to pump this heat back to the hot reservoir? D. Compare the energy output of the heat engine and the energy input to the heat pump. Comment on the feasibility of the propos ed scheme.  © 2010 Pearson Education, Inc. Slide 28 Summary 2010 Pearson Education, Inc. Slide 29 Summary  © 2010 Pearson Education, Inc. Slide 30 Additional Questions Consider your body as a system. Your body is â€Å"burning† energy in food, but staying at a constant temperature. This means that, for your body, A. Q > 0. B. Q = 0. C. Q < 0.  © 2010 Pearson Education, Inc. Slide 31 Additional Questions The following pairs of temperatures represent the temperatures of hot and cold reservoirs for heat engines. Which heat engine has the highest possible efficiency? A. B. 300 °C 250 °C 30 °C 30 °C C. 200 °C D. 100 °C 20 °C 10 °C E. 90 °C 0 °C  © 2010 Pearson Education, Inc. Slide 32

Reactivity Definition in Chemistry

In chemistry, reactivity is a measure of how readily a substance undergoes a chemical reaction. The reaction can involve the substance on its own or with other atoms or compounds, generally accompanied by a release of energy. The most reactive elements and compounds may ignite spontaneously or explosively. They generally burn in water as well as the oxygen in the air. Reactivity is dependent upon temperature. Increasing temperature increases the energy available for a chemical reaction, usually making it more likely. Another definition of reactivity is that it is the scientific study of chemical reactions and their kinetics. Reactivity Trend in the Periodic Table The organization of elements on the periodic table allows for predictions concerning reactivity. Both highly electropositive and highly electronegative elements have a strong tendency to react. These elements are located in the upper right and lower left corners of the periodic table and in certain element groups. The halogens, alkali metals, and alkaline earth metals are highly reactive. The most reactive element is fluorine, the first element in the  halogen group.The most reactive metal is francium, the last alkali metal (and most expensive element). However, francium is an unstable radioactive element, only found in trace amounts. The most reactive metal that has a stable isotope is cesium, which is located directly above francium on the periodic table.The least reactive elements are the noble gases. Within this group, helium is the least reactive element, forming no stable compounds.Metal can have multiple oxidation states and tend to have intermediate reactivity. Metals with low reactivity are called noble metals.  The least reactive metal is platinum, followed by gold. Because of their low reactivity, these metals dont readily dissolve in strong acids. Aqua regia, a mixture of nitric acid and hydrochloric acid, is used to dissolve platinum and gold. How Reactivity Works A substance reacts when the products formed from a chemical reaction have lower energy (higher stability) than the reactants. The energy difference can be predicted using valence bond theory, atomic orbital theory, and molecular orbital theory. Basically, it boils down to the stability of electrons in their orbitals. Unpaired electrons with no electrons in comparable orbitals are the most likely to interact with orbitals from other atoms, forming chemical bonds. Unpaired electrons with degenerate orbitals that are half-filled are more stable but still reactive. The least reactive atoms are those with a filled set of orbitals (octet). The stability of the electrons in atoms determines not only the reactivity of an atom but its valence and the type of chemical bonds it can form. For example, carbon usually has a valence of 4 and forms 4 bonds because its ground state valence electron configuration is half-filled at  2s2  2p2. A simple explanation of reactivity is that it increases with the ease of accepting or donating an electron. In the case of carbon, an atom can either accept 4 electrons to fill its orbital or (less often) donate the four outer electrons. While the model is based on atomic behavior, the same principle applies to ions and compounds. Reactivity is affected by the physical properties of a sample, its chemical purity, and the presence of other substances. In other words, reactivity depends on the context in which a substance is viewed. For example, baking soda and water are not particularly reactive, while baking soda and vinegar readily react to form carbon dioxide gas and sodium acetate. Particle size affects reactivity. For example, a pile of corn starch is relatively inert. If one applies a direct flame to the starch, its difficult to initiate a combustion reaction. However, if the corn starch is vaporized to make a cloud of particles, it readily ignites. Sometimes the term reactivity  is also used to describe how quickly a material will react or the rate of the chemical reaction. Under this definition the chance of reacting and the speed of the reaction are related to each other by the rate law: Rate = k[A] Where rate is the change in molar concentration per second in the rate-determining step of the reaction, k is the reaction constant (independent of concentration), and [A] is the product of the molar concentration of the reactants raised to the reaction order (which is one, in the basic equation). According to the equation, the higher the reactivity of the compound, the higher its value for k and rate. Stability Versus Reactivity Sometimes a species with low reactivity is called stable, but care should be taken to make the context clear. Stability can also refer to slow radioactive decay or to the transition of electrons from the excited state  to less energetic levels (as in luminescence). A nonreactive species may be called inert. However, most inert species actually do react under the right conditions to form complexes and compounds (e.g., higher atomic number noble gases).

The United States and Cuba An Embargo for the Ages Essay

The United States and Cuba: An Embargo for the Ages Cuba’s colorful history can be documented to before the days of the American Revolution in 1776, but today, American policy directly affects many Cubans’ lifestyles because of a nearly 45-year-old trade embargo that has been placed on the island nation. It is crucial to analyze the development of Cuba and its neighboring island nations in order to discern the reasons for Cuba’s current political situation with the United States. The following paper will discuss the events that shaped Cuba and larger Caribbean nations like Haiti, the Dominican Republic and Jamaica; next, a detailed description of Cuba’s turbulent history will help in explaining the Cuban transformation into a†¦show more content†¦Another similarity is the struggles each country faced after gaining its independence. This will be a quick, but thorough overview of the manner in which each of these countries came into existence today. Christopher Columbus discovered Haiti in 1492 during his inaugural foray into the New World. The island that Haiti now shares with the Dominican Republic was dubbed ‘La Isla Espanola,’ shortened to Hispaniola. Despite this Spanish moniker, the western side of the island soon became an enclave for French Huguenots that had migrated to Hispaniola from the northwest side, via the island of Tortuga. The French took advantage of the Spanish capital, Santo Domingo, being all the way on the other side of the island, and they managed to established a vital trading post in their new territory they called Saint-Domingue, after the Spanish capital. By 1697, a treaty had been signed and the western portion of Hispaniola officially belonged to the French, who made the territory flourish. The French made Hispaniola thrive, producing sixty percent of the world’s coffee supply by the mid-18th century, utilizing land that the Spanish had neglected until the French took over (http ://www.haiti.org). As was the norm in colonial Caribbean island territories, slavery was the main source of labor in Haiti, and slavery practices were especially brutal here, as the majority of black slaves did not survive past the age of reproduction, asShow MoreRelatedShould the U.S. Government Drop Its Sanctions against Cuba?1676 Words   |  7 Pagesuse of force as a primary method of international coercion. Cuba is one of the countries considered as a rogue state by the United States and its allies. The emergence of Cuba as a communist country in the western hemisphere in 1960, and the nationalization of a huge amount of US assets in Cuba by the then new regime led to the sanctions against Cuba. However, starting from the end of the 1980’s the Communist block begin falling apart. Cuba lost its international allies and became helpless both economicallyRead MoreRelationship between Cuba and the United States1430 Words   |  6 PagesCuban Missile Crisis, Cuba is still a ruthless nation. 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