bluuebunny/crossref_metadata_2025 huggingface dataset:
Onconase cytotoxicity relies on the distribution of its positive charge
Authors: Turcotte Rebecca F. , Lavis Luke D. , Raines Ronald T.
Published: June 2009

Onconase®(ONC) is a member of the ribonuclease A superfamily that is toxic to cancer cellsin vitroandin vivo. ONC is now in Phase IIIb clinical trials for the treatment of malignant mesothelioma. Internalization of ONC to the cytosol of cancer cells is essential for its cytotoxic activity, despite the apparent absence of a cell‐surface receptor protein. Endocytosis and cytotoxicity do, however, appear to correlate with the net positive charge of ribonucleases. To dissect the contribution made by the endogenous arginine and lysine residues of ONC to its cytotoxicity, 22 variants were created in which cationic residues were replaced with alanine. Variants with the same net charge (+2 to +5) as well as equivalent catalytic activity and conformational stability were found to exhibit large (> 10‐fold) differences in toxicity for the cells of a human leukemia line. In addition, a more cationic ONC variant could be either much more or much less cytotoxic than a less cationic variant, again depending on the distribution of its cationic residues. The endocytosis of variants with widely divergent cytotoxic activity was quantified by flow cytometry using a small‐molecule fluorogenic label, and was found to vary by twofold or less. This small difference in endocytosis did not account for the large difference in cytotoxicity, implicating the distribution of cationic residues as being critical for lipid‐bilayer translocation subsequent to endocytosis. This finding has fundamental implications for understanding the interaction of ribonucleases and other proteins with mammalian cells.
The ferredoxin‐NADP+ reductase/ferredoxin electron transfer system of Plasmodium falciparum
Authors: Balconi Emanuela , Pennati Andrea , Crobu Danila , Pandini Vittorio , Cerutti Raffaele , Zanetti Giuliana , Aliverti Alessandro
Published: June 2009

In the apicoplast of apicomplexan parasites, plastidic‐type ferredoxin and ferredoxin‐NADP+ reductase (FNR) form a short electron transport chain that provides reducing power for the synthesis of isoprenoid precursors. These proteins are attractive targets for the development of novel drugs against diseases such as malaria, toxoplasmosis, and coccidiosis. We have obtained ferredoxin and FNR of both Toxoplasma gondii and Plasmodium falciparum in recombinant form, and recently we solved the crystal structure of the P. falciparum reductase. Here we report on the functional properties of the latter enzyme, which differ markedly from those of homologous FNRs. In the physiological reaction, P. falciparum FNR displays a kcat five‐fold lower than those usually determined for plastidic‐type FNRs. By rapid kinetics, we found that hydride transfer between NADPH and protein‐bound FAD is slower in the P. falciparum enzyme. The redox properties of the enzyme were determined, and showed that the FAD semiquinone species is highly destabilized. We propose that these two features, i.e. slow hydride transfer and unstable FAD semiquinone, are responsible for the poor catalytic efficiency of the P. falciparum enzyme. Another unprecedented feature of the malarial parasite FNR is its ability to yield, under oxidizing conditions, an inactive dimeric form stabilized by an intermolecular disulfide bond. Here we show that the monomer–dimer interconversion can be controlled by oxidizing and reducing agents that are possibly present within the apicoplast, such as H2O2, glutathione, and lipoate. This finding suggests that modulation of the quaternary structure of P. falciparum FNR might represent a regulatory mechanism, although this needs to be verified in vivo.

Structured digital abstract

MINT‐7042675: PfFNR (genbank_protein_gi:46361180) and PfFNR (genbank_protein_gi:46361180) bind (MI:0408) by comigration in sds page (MI:0808)

MINT‐7043503: PfFNR (genbank_protein_gi:46361180) and PfFNR (genbank_protein_gi:46361180) bind (MI:0408) by molecular sieving (MI:0071)

MINT‐7043886, MINT‐7051941: PfFd (uniprotkb:Q8IED5) and PfFNR (genbank_protein_gi:46361180) enzymaticly react (MI:0414) by enzymatic studies (MI:0415)

MINT‐7051926: PfFNR (genbank_protein_gi:46361180) and PfFd (uniprotkb:Q8IED5) enzymaticly react (MI:0414) by biophysical (MI:0013)
Arabidopsis ATPase family gene 1‐like protein 1 is a calmodulin‐binding AAA+‐ATPase with a dual localization in chloroplasts and mitochondria
Authors: Bussemer Johanna , Chigri Fatima , Vothknecht Ute C.
Published: June 2009

Members of the AAA+‐ATPase superfamily (ATPases associated with various cellular activities) are found in all kingdoms of life and they are involved in very diverse cellular processes, including protein degradation, membrane fusion or cell division. The Arabidopsis genome encodes approximately 140 different proteins that are putative members of this superfamily, although the exact function of most of these proteins remains unknown. Using affinity chromatography on calmodulin‐agarose with chloroplast proteins, we purified a 50 kDa protein encoded by AT4G30490 with similarity to the ATPase family gene 1 protein from yeast. Structural analysis showed that the protein possesses a single AAA‐domain characteristic for members of the AAA+‐ATPase superfamily and that this contains all features specific to proteins of the ATPase family gene 1‐like subfamily. In vitro pull‐down as well as cross‐linking assays corroborate calcium‐dependent binding of the protein to calmodulin. The calmodulin binding domain could be located to a region of 20 amino acids within the AAA‐domain in close proximity to the Walker A motif. Our analysis further showed that the protein is localized in both mitochondria and chloroplasts, further supporting the incorporation of both endosymbiotic organelles into the calcium‐signaling network of the cell. Localization of the same calmodulin‐binding protein into mitochondria and chloroplasts could be a means to provide a coordinated regulation of processes in both organelles by calcium signals.

Structured digital abstract

MINT‐7046712:VDAC (uniprotkb:Q9SRH5) and AFG1L1 (uniprotkb:Q8L517) colocalize (MI:0403) by cosedimentation through density gradients (MI:0029)

MINT‐7046498:Calmodulin (uniprotkb:P62157) physically interacts (MI:0915) with AFG1L1 (uniprotkb:Q8L517) by pull down (MI:0096)

MINT‐7046508, MINT‐7046696:Calmodulin (uniprotkb:P62157) binds (MI:0407) to AFG1L1 (uniprotkb:Q8L517) by pull down (MI:0096)

MINT‐7046532:Calmodulin (uniprotkb:P62157) and AFG1L1 (uniprotkb:Q8L517) bind (MI:0407) by cross‐linking studies (MI:0030)
The Endothelial–Erectile Dysfunction Connection: An Essential Update
Authors: Costa Carla , Virag Ronald
Published: June 2009

Introduction

The endothelial monolayer plays a crucial role in the vasodilation and hemodynamic events involved in erection physiology. Due to its relevant functions, a close link has been established between endothelial integrity and erectile dysfunction (ED). Endothelial dysfunction is induced by the detrimental actions of vascular risk factors (VRFs), identified as common correlates for the development of cardiovascular disease and ED. It is currently recognized that ED is the early harbinger of a more generalized vascular systemic disorder, and, therefore, an evaluation of endothelial health in ED patients should be of prime relevance. Several noninvasive methods for endothelial function assessment have been proposed, including the Penile Nitric Oxide Release Test (PNORT).

Aim

To highlight the most recent gathered knowledge on basic and clinical mechanisms underlying loss of cavernosal endothelial function promoted by VRFs and to discuss local and systemic methods for endothelial function assessment in ED individuals, focusing on the PNORT.

Main Outcome Measures

A complete revision on the novel basic and clinical links between endothelial and ED.

Methods

A systematic review of the literature regarding the aforementioned issues.

Results

Risk factor-associated cavernosal endothelial dysfunction is mostly induced by unifying mechanisms, including oxidative stress and impaired endothelial nitric oxide functional activities, which present clinically as ED. Several techniques to evaluate endothelial dysfunction were revised, with advantages and limitations debated, focusing on our detailed expertise using the PNORT method.

Conclusions

The established endothelial–erectile dysfunction connection was thoroughly revised, from basic mechanisms to the clinical importance of endothelial dysfunction assessment as diagnosis for generalized vascular disease. Further studies are required to disclose efficient approaches to repair disabled endothelium and both restore and prevent endothelial dysfunction.
Male Dyspareunia Due to Short Frenulum: The Suture-Free, “Pull and Burn” Method
Authors: Gyftopoulos Kostis
Published: June 2009

Introduction

The presence of a short frenulum is a common cause for dyspareunia in males, often resulting in painful intercourse and trauma to the frenulum. Most of the described techniques use sutures that may sever the frenular artery and lead to meatal stenosis or leave skin tags that create a poor cosmetic result.

Aim

The aim of this study is to describe the “pull and burn” method for the correction of a short frenulum with respect to the anatomy of the glans penis.

Methods

The procedure was performed on 127 young adults presenting with dyspareunia due to short frenulum. Local anesthesia was achieved by application of eutectic mixture of local anesthetic (EMLA) for 15–20 minutes. The point of maximum tension was cut by diathermy and a controlled vertical tear was made on the frenulum by applying gentle but firm retraction on the glans. Minor bleeding was sealed with diathermy. Personal hygiene was advised and no local antiseptics or antibiotics were further used.

Main Outcome Measures

Achievement of adequate anesthesia with EMLA cream, use of sutures, complications of the procedure, and final cosmetic and functional result.

Results

The application of EMLA for 15–20 minutes was sufficient for local anesthesia. Only one patient with very thick frenulum required further lignocaine infiltration. No sutures were applied except in two cases (1.6%), in which a wide and thick frenulum required approximation of the tear edges for a better cosmesis. At 3 months follow up, no inflammation or meatal stenosis were noted. One patient required further release of a scarry frenulum. Functional and cosmetic results were excellent in all cases.

Conclusions

The “pull and burn” method is an easy, bloodless, and sutureless procedure for the correction of a short frenulum. Local anesthesia with EMLA is satisfactory, the procedure respects the glans anatomy, and preserves the frenular artery, achieving an excellent functional and cosmetic result.
The influence of class II transactivator and interleukin‐6 polymorphisms on the production of antibodies to donor human leucocyte antigen mismatches in renal allograft recipients
Authors: Martin J. , Worthington J. , Harris S. , Martin S.
Published: June 2009

The influence of polymorphisms in the CIITA and IL‐6 genes on donor‐specific human leucocyte antigen antibody production was investigated in a cohort of renal transplant recipients and their donors. CIITA and IL‐6 single nucleotide polymorphisms were found to be associated with donor‐specific human leucocyte antigen antibody production post‐transplantation.
Quantitative Structure–Property Relationship (Correlation Analysis) of Phosphonic Acid‐Based Chelates in Design of MRI Contrast Agent
Authors: Tiwari Anjani K. , Ojha Himanshu , Kaul Ankur , Dutta Anupama , Srivastava Pooja , Shukla Gauri , Srivastava Rakesh , Mishra Anil K.
Published: June 2009

Nuclear magnetic resonance imaging is a very useful tool in modern medical diagnostics, especially when gadolinium (III)‐based contrast agents are administered to the patient with the aim of increasing the image contrast between normal and diseased tissues. With the use of soft modelling techniques such as quantitative structure–activity relationship/quantitative structure–property relationship after a suitable description of their molecular structure, we have studied a series of phosphonic acid for designing new MRI contrast agent. Quantitative structure–property relationship studies with multiple linear regression analysis were applied to find correlation between different calculated molecular descriptors of the phosphonic acid‐based chelating agent and their stability constants. The final quantitative structure–property relationship mathematical models were found as – quantitative structure–property relationship Model for phosphonic acid series (Model 1) − log KML = {5.00243(±0.7102)}− MR {0.0263(±0.540)}n = 12 l r l = 0.942 s = 0.183 F = 99.165 quantitative structure–property relationship Model for phosphonic acid series (Model 2) − log KML = {5.06280(±0.3418)}− MR {0.0252(± .198)}n = 12 l r l = 0.956 s = 0.186 F = 99.256.
Blocking UV‐Induced eIF2α Phosphorylation with Small Molecule Inhibitors of GCN2
Authors: Robert Francis , Williams Chris , Yan Yifei , Donohue Elizabeth , Cencic Regina , Burley Stephen K. , Pelletier Jerry
Published: June 2009

The eIF2α kinase general control non‐depressible 2 integrates translation initiation rates to amino acid availability. General control non‐depressible 2 also regulates translation initiation during synaptic plasticity and GCN2−/− mice show improved memory compared with wild‐type mice with a reduced threshold for triggering late long‐term potentiation. This property suggests that inhibiting general control non‐depressible 2 function might represent a therapeutic avenue for improving memory. We screened for general control non‐depressible 2 inhibitors using a small library of known kinase inhibitors and ATP‐analogs and identified three compounds – indirubin‐3′‐monoxime, SP600125 and a SyK inhibitor with activity against general control non‐depressible 2. All three compounds inhibit the ability of general control non‐depressible 2 to phosphorylate eIF2αin vitro as well as in vivo following UV‐treatment of mouse embryonic fibroblasts. Using computer‐assisted modeling, we modeled the binding of the inhibitors in the ATP‐binding site of general control non‐depressible 2. This work provides the molecular basis for undertaking structure–activity relationships of these compounds in order to develop specific inhibitors of general control non‐depressible 2.
Antifungal Activity, Mechanism and QSAR Studies on Chalcones
Authors: Sivakumar Ponnurengam Malliappan , Muthu Kumar Thangavelu , Doble Mukesh
Published: June 2009

In this paper, the synthesis of 48 chalcones and their in vitro antifungal activity against Aspergillus flavus NCIM 594, Fusarium proliferatum NCIM1105, Aspergillus niger NCIM 596 and Candida tropicalis NCIM 3556 are reported. Predominantly, the active compounds (6, 9, 14, 27, and 47) against all four fungi have found to have electron withdrawing substitutions in their para substitution in B‐ring. Quantitative structure–activity relationship indicated that the antifungal activities are correlated with absorption distribution metabolism and excretion, electrophilicity, spatial and topological descriptors. The statistical measures such as r2 (0.68–0.71), r2‐adj (0.62–0.66), q2 (0.60–0.61) and F‐ratio (12–17) are reasonable. The data is divided into training and a test set, the former is used to develop the models, and the later is used to test their predictive capability. The predictions are found to be within the 99% confidence level except for two of the cases. SEM (scanning electron microscopy) and BacLight Live/Dead assay indicate that the chalcones act by disrupting the fungal cell wall.
Utilizing Target–Ligand Interaction Information in Fingerprint Searching for Ligands of Related Targets
Authors: Tan Lu , Bajorath Jürgen
Published: June 2009

Protein–ligand interaction information is captured by determination of interacting fragments (IF) of ligands available in complex X‐ray structures. From IF, fingerprints (IF‐FP) are calculated for similarity searching. Previously, we have shown that IF‐FP often produce higher search performance than general structural fragment‐ or key‐type fingerprints. In this study, we introduce the transfer of target–ligand interaction information from one target to a related one for which no structural information is available. Thus, IFs from a crystallographic target B‐ligand complex are incorporated into structural key fingerprints of known ligands for target A. Similarity searching using these IF transfer fingerprints (IF‐TFP) is shown to further increase the search performance of conventional ligand fingerprints. Thus, interaction information can be transferred between related targets in order to support ligand‐based fingerprint search calculations for targets for which no structural information is currently available.
Synthesis and Analysis of Potential DNA Intercalators Containing Quinoline–Glucose Hybrids
Authors: Li Wei , Zhang Zhong‐Wei , Wang Shi‐Xi , Ren Su‐Mei , Jiang Tao
Published: June 2009

A new series of potential DNA bisintercalators have been designed by linking 8‐hydroxy‐quinoline to the 6‐CH2OH group of glucose and connecting the 1‐OH group of glucose with various linkers, such as quinol, glycol, and triethylene glycol. These new compounds were well‐synthesized and fully characterized. Preliminary binding assays of these compounds to calf thymus DNA (CT‐DNA) were conducted using UV‐absorption and fluorescence spectroscopy analysis. The primary antitumor activity of these compounds was also performed.
Natural Occurring Polyphenols as Template for Drug Design. Focus on Serine Proteases
Authors: Cuccioloni Massimiliano , Mozzicafreddo Matteo , Bonfili Laura , Cecarini Valentina , Eleuteri Anna Maria , Angeletti Mauro
Published: June 2009

Several major physio‐pathological processes, including cancer, inflammatory states and thrombosis, are all strongly dependent upon the fine regulation of proteolytic enzyme activities, and dramatic are the consequences of unbalanced equilibria between enzymes and their cognate inhibitors. In this perspective, the discovery of small‐molecule ligands able to modulate catalytic activities has a massive therapeutic potential and is a stimulating goal. Numerous recent experimental evidences revealed that proteolytic enzymes can be opportunely targeted, reporting on small ligands capable of binding to these biological macromolecules with drug‐like potencies, and primarily with comparable (or even higher) efficiency with respect to their endogenous binding partner. In particular, natural occurring polyphenols and their derivatives recently disclosed these intriguing abilities, making them promising templates for drug design and development. In this review, we compared the inhibitory capacities of a set of monomeric polyphenols toward serine proteases activity, and finally summarized the data with an emphasis on the derivation of a pharmacophore model.
Salvia geminata sp. nov. with remarkable stamen arrangement from southern Yemen, with notes on S. areysiana (Lamiaceae)
Authors: Thulin Mats
Published: June 2009

The new species Salvia geminata, a dwarf shrublet from rocky coastal slopes of the Mahrah Region in Yemen, is described and illustrated. A remarkable feature of the species is that the upper thecae of the stamens are inflexed and connate, a condition that seems to be previously unknown in the genus. The apparently closely related S. areysiana, previously known only from the area of Jebel Areys in the Abyan Region, is reported also from the Hadramaut Region.
The Role of Imagistic Simulation in Scientific Thought Experiments
Authors: Clement John J.
Published: June 2009

Interest in thought experiments (TEs) derives from the paradox: “How can findings that carry conviction result from a new experiment conducted entirely within the head?” Historical studies have established the importance of TEs in science but have proposed disparate hypotheses concerning the source of knowledge in TEs, ranging from empiricist to rationalist accounts. This article analyzes TEs in think‐aloud protocols of scientifically trained experts to examine more fine‐grained information about their use. Some TEs appear powerful enough to discredit an existing theory—a disconfirmatory purpose. In addition, confirmatory and generative purposes were identified for other TEs. One can also use details in transcript data, including imagery reports and gestures, to provide evidence for a central role played by imagistic simulations in many TEs, and to suggest that these simulations can generate new knowledge using several sources, including the “extended application” of perceptual motor schemas, implicit prior knowledge, and spatial reasoning operations, in contrast to formal arguments. These sources suggest what it means for TEs to be grounded in embodied processes that can begin to explain the paradox above. This leads to a rationalistic view of TEs as using productive internal reasoning, but the view also acknowledges the historical role that experience with the world can play in forming certain schemas used in TEs. Understanding such processes could help provide a foundation for developing a larger model of scientific investigation processes grounded on imagistic simulation (Clement, 2008).
Modeling the Emergence of Language as an Embodied Collective Cognitive Activity
Authors: Hutchins Edwin , Johnson Christine M.
Published: June 2009

Two decades of attempts to model the emergence of language as a collective cognitive activity have demonstrated a number of principles that might have been part of the historical process that led to language. Several models have demonstrated the emergence of structure in a symbolic medium, but none has demonstrated the emergence of the capacity for symbolic representation. The current shift in cognitive science toward theoretical frameworks based on embodiment is already furnishing computational models with additional mechanisms relevant to the emergence of symbolic language. An analysis of embodied interaction among captive, but not human‐enculturated, bonobo chimpanzees reveals a number of additional features of embodiment that are relevant to the emergence of symbolic language, but that have not yet been explored in computational simulation models; for example, complementarity of action in addition to imitation, iconic in addition to indexical gesture, coordination among multiple sensory and perceptual modalities, and the orchestration of intra‐ and inter‐individual motor coordination. The bonobos provide an evolutionarily plausible intermediate stage in the development of symbolic expression that can inform efforts to model the emergence of symbolic language.
Optimization of Controllers for Gas Turbine Based on Probabilistic Robustness
Authors: Wang Chuanfeng , Li Donghai , Li Zheng , Jiang Xuezhi
Published: June 2009

An optimization method for controller parameters of a gas turbine based on probabilistic robustness was described in this paper. As is well known, gas turbines, like many other plants, are stochastic. The parameters of a plant model are often of some uncertainties because of errors in measurements, manufacturing tolerances and so on. According to model uncertainties, the probability of satisfaction for dynamic performance requirements was computed as the objective function of a genetic algorithm, which was used to optimize the parameters of controllers. A Monte Carlo experiment was applied to test the control system robustness. The advantage of the method is that the entire uncertainty parameter space can be considered for the controller design; the systems could satisfy the design requirements in maximal probability. Simulation results showed the effectiveness of the presented method in improving the robustness of the control systems for gas turbines.
Controlling n-Heptane HCCI Combustion With Partial Reforming: Experimental Results and Modeling Analysis
Authors: Hosseini Vahid , Neill W. Stuart , Checkel M. David
Published: June 2009

One potential method for controlling the combustion phasing of a homogeneous charge compression ignition (HCCI) engine is to vary the fuel chemistry using two fuels with different auto-ignition characteristics. Although a dual-fuel engine concept is technically feasible with current engine management and fuel delivery system technologies, this is not generally seen as a practical solution due to the necessity of supplying and storing two fuels. Onboard partial reforming of a hydrocarbon fuel is seen to be a more attractive way of realizing a dual-fuel concept, while relying on only one fuel supply infrastructure. Reformer gas (RG) is a mixture of light gases dominated by hydrogen and carbon monoxide that can be produced from any hydrocarbon fuel using an onboard fuel processor. RG has a high resistance to auto-ignition and wide flammability limits. The ratio of H2 to CO produced depends on the reforming method and conditions, as well as the hydrocarbon fuel. In this study, a cooperative fuel research engine was operated in HCCI mode at elevated intake air temperatures and pressures. n-heptane was used as the hydrocarbon blending component because of its high cetane number and well-known fuel chemistry. RG was used as the low cetane blending component to retard the combustion phasing. Other influential parameters, such as air/fuel ratio, EGR, and intake temperature, were maintained constant. The experimental results show that increasing the RG fraction retards the combustion phasing to a more optimized value causing indicated power and fuel conversion efficiency to increase. RG reduced the first stage of heat release, extended the negative temperature coefficient delay period, and retarded the main stage of combustion. Two extreme cases of RG composition with H2/CO ratios of 3/1 and 1/1 were investigated. The results show that both RG compositions retard the combustion phasing, but that the higher hydrogen fraction RG is more effective. A single-zone model with detailed chemical kinetics was used to interpret the experimental results. The effect of RG on combustion phasing retardation was confirmed. It was found that the low temperature heat release was inhibited by a reduction in intermediate radical mole fractions during low temperature reactions and during the early stages of the negative temperature coefficient delay period.
Thermodynamic Analysis and Comparison on Oxy-Fuel Power Generation Process
Authors: Deng Shimin , Hynes Rory
Published: June 2009

In this paper, pressurized oxy-fuel combustion power generation processes are modeled and analyzed based on a 350 MW subcritical reheat boiler associated with a condensing steam turbine. The performance results are obtained. Furthermore, the influences of slurry concentration and coal properties on power plant performance are investigated. An oxy-fuel configuration operating at ambient pressure is studied to compare the performance with pressurized oxy-fuel configuration. Thermodynamic analysis reveals the true potentials of the pressurized oxy-fuel process. Based on the system integration, an improved configuration is proposed in which plant efficiency of pressurized oxy-fuel process is increased by 1.36%.
Passive Control of the Inlet Acoustic Boundary of a Swirled Burner at High Amplitude Combustion Instabilities
Authors: Tran Nicolas , Ducruix Sebastien , Schuller Thierry
Published: June 2009

Perforated panels placed upstream of the premixing tube of a turbulent swirled burner are investigated as a passive control solution for combustion instabilities. Perforated panels backed by a cavity are widely used as acoustic liners, mostly in the hot gas region of combustion chambers to reduce pure tone noises. This paper focuses on the use of this technology in the fresh reactants zone to control the inlet acoustic reflection coefficient of the burner and to stabilize the combustion. This method is shown to be particularly efficient because high acoustic fluxes issued from the combustion region are concentrated on a small surface area inside the premixer. Theoretical results are used to design two types of perforated plates featuring similar acoustic damping properties when submitted to low amplitude pressure fluctuations (linear regime). Their behaviors nonetheless largely differ when facing large pressure fluctuation levels (nonlinear regime) typical of those encountered during self-sustained combustion oscillations. Conjectures are given to explain these differences. These two plates are then used to clamp thermoacoustic oscillations. Significant damping is only observed for the plate featuring a robust response to increasing sound levels. While developed on a laboratory scale swirled combustor, this method is more general and may be adapted to more practical configurations.
Improving Performance of Refrigerant Cooled Steam Power Plant by Using Cooling Thermal Storage
Authors: Hegazy A. S.
Published: June 2009

It is proposed in the current paper to combine the steam plant with two refrigeration cycles and a cooling storage container. Throughout the time of a day, the steam plant is made to work at full power, where the excess power generated over the electric power demand is used to drive the compressors of the refrigeration cycles. The stored cooling is used for dissipating the heat absorbed by the cooling refrigerant in the steam condenser during the period of peak-loads, while the two refrigeration machines are stopped. In this way, the energy used for driving the refrigeration machine is saved so that the whole power generated by the steam plant is exported to the grid. Energy analyses of the proposed combined system has led to inferring that the net power of the steam plant during the period of exclusive direct cooling of the steam condenser (only the first refrigeration machine is running) is about 70–86% of the whole power generated by the steam plant when the coefficient of performance of the first refrigeration cycle lies in the range of 4–10. Also, it has been found that relatively small coefficients of performance of the first and second cycles, less than 6 and 1.5, respectively, result in low net power of the steam plant over the period of charging the cooling storage container (both refrigeration machines run in unison). In this case, the net plant power amounts to less than 26% of the total generated plant power when the time of storing the cooling is lower than double the time of the peak-loads. This necessitates increasing the storing time to assure reasonable available power to be exported to the grid. Economical analyses of the proposed system have showed that both the capital cost and energy charges are less for the proposed system than that of the steam plant without cooling storage for practically possible operating conditions.
Combustion Oscillations in Bluff Body Stabilized Diffusion Flames With Variable Length Inlet
Authors: Madanmohan M. , Pandey S. , Kushari A. , Ramamurthi K.
Published: June 2009

This paper describes the results of an experimental study to understand the influence of inlet flow disturbances on the dynamics of combustion process in bluff body stabilized diffusion flames of liquid petroleum gas and air. The results show the influence of weak disturbances created by the change in incoming pipe length on the amplitude of pressure oscillations and the phase angle between pressure and heat release. It is seen that the phase delay increases as the entry length increases. The rms value of pressure, however, generally falls with the increase in length. The phase angle is seen to be in the second quadrant, showing that the heat release oscillations damp the pressure oscillations. Therefore, the decrease in the phase angle results in the reduction in damping and hence an increase in pressure fluctuations. The dominant frequencies of combustion oscillations are found to be the low frequency oscillations, and the frequency of oscillations increases with a decrease in the inlet pipe length and an increase in the flow Reynolds number. It is suggested that such low frequency oscillations are driven by vortex shedding at the wake of the bluff body, which energizes the diffusion and mixing process.
Design and Experiment of Oil Lubricated Five-Leaf Foil Bearing Test-Bed
Authors: Xu H.-J. , Liu Z.-S. , Zhang G.-H. , Wang Y.-L.
Published: June 2009

Multileaf foil bearing has various advantages including long-life, high-speed, low power loss, etc. Oil lubricated multileaf foil bearing compared with gas lubricated foil bearing is more favorable to greatly decrease foil performance requirements, foil surface coating technology, and foil processing. The special oil lubricated five-leaf foil bearing test-bed is designed and established, and a speed of 30,000 rpm is achieved primarily. The experiments including the influence of different radial clearances on rotor dynamical characteristics, speed run-up and coastdown, etc., are implemented on the test-bed. The experimental results indicate that oil lubricated multileaf foil bearing can offer high-speed, long-life, and lower friction loss. Radial clearance plays an important role to rotor dynamical characteristics. Moreover, oil lubricated multileaf foil bearing represents strong adaptive capacity of speed run-up and coastdown, and the capacity of withstanding impact and vibration.
Modeling of Compressed Air Hybrid Operation for a Heavy Duty Diesel Engine
Authors: Wang Xiaoyong , Tsao Tsu-Chin , Tai Chun , Kang Hyungsuk , Blumberg Paul N.
Published: June 2009

This paper presents the analysis and modeling of a 10.8 l heavy-duty diesel engine modified for operating compressed air hybrid engine cycles. A lumped parameter model is developed to first investigate the engine cylinder-air tank mass and energy interaction. The efficiency of compressed air energy transfer is defined based on the second law of thermodynamics. A high fidelity model is developed using commercially available software (GT-POWER) to capture the effects of engine friction, heat transfer, gas dynamics, etc. Engine valve timing for optimal efficiency in air regeneration and the corresponding engine speed-torque maps are established using the detailed engine model. The compressed air hybrid engine maps are then incorporated into vehicle simulation (ADVISOR) to evaluate the potential fuel economy improvement for a refuse truck under a variety of driving cycles. Depending on the particular driving cycle, the simulation has shown a potential 4–18% fuel economy improvement over the truck equipped with the conventional baseline diesel engine.
Air-Standard Aerothermodynamic Analysis of Gas Turbine Engines With Wave Rotor Combustion
Authors: Nalim M. R. , Li H. , Akbari P.
Published: June 2009

The wave rotor combustor can significantly improve gas turbine engine performance by implementing constant-volume combustion. The periodically open and closed combustor complicates thermodynamic analysis. Key cycle parameters depend on complex gas dynamics. In this study, a consistent air-standard aerothermodynamic model with variable specific heat is established. An algebraic model of the dominant gas dynamics estimates fill fraction and internal wave compression for typical port designs, using a relevant flow Mach number to represent wave amplitudes. Nonlinear equations for thermodynamic state variables are solved numerically by Newton–Raphson iteration. Performance measures and key operating conditions are predicted, and a quasi-one-dimensional computational model is used to evaluate the usefulness of the algebraic model.
Proposal of a Novel Multifunctional Energy System for Cogeneration of Coke, Hydrogen, and Power
Authors: Jin Hongguang , Sun Shien , Han Wei , Gao Lin
Published: June 2009

This paper proposes a novel multifunctional energy system (MES), which cogenerates coke, hydrogen, and power, through the use of coal and coke oven gas (COG). In this system, a new type of coke oven, firing coal instead of COG as heating resource for coking, is adopted. The COG rich in H2 is sent to a pressure swing adsorption (PSA) unit to separate about 80% of hydrogen first, and then the PSA purge gas is fed to a combined cycle as fuel. The new system combines the chemical processes and power generation system, along with the integration of chemical conversion and thermal energy utilization. In this manner, both the chemical energy of fuel and thermal energy can be used more effectively. With the same inputs of fuel and the same output of coking heat, the new system can product about 65% more hydrogen than that of individual systems. As a result, the thermal efficiency of the new system is about 70%, and the exergy efficiency is about 66%. Compared with individual systems, the primary energy saving ratio can reach as high as 12.5%. Based on the graphical exergy analyses, we disclose that the integration of synthetic utilization of COG and coal plays a significant role in decreasing the exergy destruction of the MES system. The promising results obtained may lead to a clean coal technology that will utilize COG and coal more efficiently and economically.
Improved Discharge Measurement Using the Pressure-Time Method in a Hydropower Plant Curved Penstock
Authors: Adamkowski Adam , Krzemianowski Zbigniew , Janicki Waldemar
Published: June 2009

One of the basic flow rate measurement methods applied in hydropower plants and recommended by the International Standard IEC 60041–1999 and American National Standard ASME PTC 18–2002 is the pressure-time method, generally known as Gibson method. The method consists in determining the flow rate (discharge) by integration of the recorded time course of pressure difference variations between two cross sections of the hydropower plant penstock. The accuracy of measurement depends on numerous factors and, according to the International Standard, generally is confined within the range 1.5–2.3%. Following the classical approach, the pressure-time method applicability is limited to straight cylindrical pipelines with constant diameters. However, the International Standard does not exclude application of this method to more complex geometries, i.e., curved pipeline (with elbows). It is obvious that a curved pipeline causes deformation of the uniform velocity field in pipeline cross sections, which subsequently causes aggravation of the accuracy of the pressure-time method flow rate measurement results. The influence of a curved penstock application on flow rate measurements by means of the considered method is discussed in this paper. The special calculation procedure for the problem solution has been developed. The procedure is based on the FLUENT computational fluid dynamic solver. Computations have been carried out in order to find the so-called equivalent value of the geometric pipe factor F required when using the pressure-time method. An example of application of this method to a complex geometry (two elbows in a penstock) is presented. The systematic uncertainty caused by neglecting the effect of the elbows on velocity field deformation has been estimated.
Real-Time Transient Three Spool Turbofan Engine Simulation: A Hybrid Approach
Authors: Rahman Naveed U. , Whidborne James F.
Published: June 2009

This paper presents a transient three-spool turbofan engine simulation model that uses a combination of intercomponent volume and iterative techniques. The engine model runs in real time and has been implemented in MATLAB/SIMULINK environment. The main advantage of this hybrid approach is that it preserves the accuracy of the iterative method while maintaining the simplicity of the intercomponent volume method. The iterative approach is applied at each engine subsystem to solve algebraic thermodynamic equations for exit enthalpy, entropy, and temperature, whereas the intercomponent volume method is used to calculate pressures derivatives and hence pressures at corresponding engine stations. This allows the engine state vector to be updated at each pass through the engine calculations. This technique was applied as a test case on the Rolls Royce Trent 500 three-spool turbofan engine, and the results were compared with an iterative method. As the engine state vector is updated during each cycle, the model lends itself for easy integration into nonlinear aircraft simulations, real-time engine diagnostics/prognostics, and jet engine control applications.
Density Change of an Oxidized Nuclear Graphite by Acoustic Microscopy and Image Processing
Authors: Chi Se-Hwan , Contescu Cristian I. , Burchell Timothy D.
Published: June 2009

The strong correlation between the density and the physical and mechanical properties of graphite suggests that the method of nondestructive density evaluation could be developed into a characterization technique of great value for the overall improvement of the safety of graphite moderator reactors. In this study, the oxidation-induced density changes in nuclear graphite for very high temperature reactor were determined by a conventional destructive bulk density measurement method (BM) and by a new nondestructive method based on acoustic microscopy and image processing (AM). The results were compared in order to validate the applicability of the latter method. For a direct comparison of the results from both measurements, two specimens were prepared from a cylindrical graphite sample (1 in. diameter and 1 in. height, oxidized to 10% weight loss at 973 K in air for 5 h). The specimens were used for characterization by BM and AM methods, respectively. The results show that, even with a large standard deviation of the AM, the density changing trend from both methods appeared the same. The present observation may be attributed to the fact that AM images reflect characteristic density changes of the graphite sample through the acoustic impedance changes. This study demonstrates the possibility of using AM as a nondestructive technique for the evaluation of density changes in graphite when a database is prepared through a systematic series of experiments.
Autonomous Control Strategies for Very High Temperature Reactor Based Systems for Hydrogen Production
Authors: Tsvetkov Pavel V. , Alajo Ayodeji B. , Ames David E.
Published: June 2009

This paper is focused on feasible autonomous control strategies for Generation IV very high temperature reactors (VHTRs)-based systems for hydrogen production. Various burnable poison distributions and fuel compositions are considered. In particular, utilization of transuranium nuclides (TRUs) in VHTRs is explored as the core self-stabilization approach. Both direct cycle and indirect cycle energy conversion approaches are discussed. It is assumed that small-scale VHTRs may be considered for international deployment as grid-appropriate variable-scale self-contained systems addressing emerging demands for hydrogen. A Monte Carlo-deterministic analysis methodology has been implemented for coupled design studies of VHTRs with TRUs using the ORNL SCALE 5.1 code system. The developed modeling approach provides an exact-geometry 3D representation of the VHTR core details properly capturing VHTR physics. The discussed studies are being performed within the scope of the U.S. DOE Nuclear Energy Research Initiative project on utilization of higher actinides (TRUs and partitioned minor actinides) as a fuel component for extended-life VHTR configurations.
Low-cost coincidence-counting electronics for undergraduate quantum optics
Authors: Branning D. , Bhandari S. , Beck M.
Published: June 2009

Coincidence counting is a necessary ingredient for quantum optics experiments at the undergraduate level, but cost has created an entry barrier for many schools. We present a design of a coincidence-counting module that replaces the traditional method based on time-to-amplitude conversion and pulse-height analysis. Our module accepts inputs from up to four detectors, has a coincidence-time window of less than 10ns, and has a throughput of more than triple that of the traditional method. The cost of our coincidence-counting module is less than 5% of the cost of the traditional method.
Reinventing college physics for biologists: Explicating an epistemological curriculum
Authors: Redish Edward F. , Hammer David
Published: June 2009

The University of Maryland Physics Education Research Group has done a five-year project to rethink, observe, and reform introductory algebra-based (college) physics, which primarily serves life-science majors. We refocused the class on helping the students learn to think scientifically—to build coherence, think in terms of mechanisms, and to follow the implications of assumptions. We designed the course to tap into students’ productive conceptual and epistemological resources, based on a theoretical framework from research on learning. The reformed class retains its traditional structure in terms of time and instructional personnel, but we modified existing best-practices curricular materials. We provided class-controlled spaces for student collaboration, which allowed us to observe and record students learning directly. We also scanned all written homework and examinations and administered pre-post conceptual and epistemological surveys. The reformed class enhanced the strong gains on pre-post conceptual tests produced by the best-practices materials while obtaining unprecedented pre-post gains on epistemological surveys instead of the traditional losses.
Harnessing celestial batteries
Authors: Pulkkinen Antti , Viljanen Ari , Pirjola Risto
Published: June 2009

The harnessing of the electric power associated with space weather storms is discussed. A simple system based on a large-scale coil located at high latitudes is devised and the power output of the system for a sample storm is calculated. It is shown that independently of the resistances of the conductors used in the coil and the number of turns in the system the maximum output of the system is restricted to the 1–10MW range, which is comparable to the maximum output of a single large wind turbine.
What does it mean to modify or test Newton’s second law?
Authors: Hacyan Shahen
Published: June 2009

Physicists in the 19th century concluded that Newton’s second law is not a real law of nature but a mere definition, because force cannot be measured directly but only through the acceleration it produces on a given mass. Although the debate seemed settled, it has been proposed in recent years that Newton’s second law could be modified, as if it were a real description of nature, to explain some intriguing aspects of galactic dynamics. Experiments have been performed claiming to test the validity of the second law. The aim of this article is to elucidate, without using the concept of force, what it means to modify or experimentally test Newtonian dynamics.
Analogy between one-dimensional chain models and graphene
Authors: Matulis A. , Peeters F. M.
Published: June 2009

The electron and hole spectrum in single and bilayer graphene is derived from known one-dimensional models, and the relation between the spectrum and symmetry of the lattice is shown.
Resource Letter PBM-1: Physics of biomolecular machines
Authors: Chowdhury Debashish
Published: June 2009

All living creatures are made of cells. The cell is the structural and functional unit of life. This Resource Letter serves as a guide to the literature on nano-machines, which drive not only intracellular movements but also motility of the cell. These machines are usually proteins or macromolecular assemblies that require appropriate fuel for their operations. Although, traditionally, these machines were subjects of investigation in biology and biochemistry, increasing use of the concepts and techniques of physics in recent years have contributed to the quantitative understanding of the fundamental principles underlying their operational mechanisms. The possibility of exploiting these principles for the design and control of artificial nanomachines has opened up a new frontier in the bottom-up approach to nanotechnology.