bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and biochemical observations on specialized membranes of the “filter chamber”, a water‐shunting complex in sap‐sucking homopteran insects
Authors: Hubert Jean‐François , Thomas Daniel , Cavalier Annie , Gouranton Jean
Published: February 2012

Many homopteran insects feed on plant sap which contains solutes in very low concentration. Their digestive tract presents a complex called the “filter chamber” where the excess dietary water is believed to flow directly from the initial part of the midgut to the terminal part of the midgut and the proximal reions of the Malpighian tubules.

Freeze‐fracture experiments carried out on the filter chamber of Cicadella viridis revealed the presence of intramembrane particles on the whole surface of the microvilli and of basal membrane infoldings of the cells.

Examination of negatively stained isolated membranes and of freeze‐dried shadowed membranes revealed that the inner surface of the membrane is covered with particles protruding into the cytoplasm; they correspond to the numerous intramembrane particles observed on the P fracture face of the membrane. The outer surface of the membrane exhibits a regular network which corresponds to that observed on the E fracture face.

SDS‐PAGE analyses were performed on purified membranes of the filter chambers of C. viridis and Philaenus spumarius. In both cases 2 major components, 25 kDa and 75 kDa, were detected. These 2 components appear to be specific for the filter chambers since they were not found in membranes isolated from the other parts of the midgut.

Thus, the membranes of these filter chambers, though to be water‐shunting complexes, possess structural and biochemical peculiarities which are probably related to water permeability.
Saturable urea transport pathway across the urinary bladder of Bufo viridis and salt acclimation
Authors: Shpun S. , Katz U.
Published: February 2012

Urea fluxes across the urinary bladder of Bufo viridis were studied in vitro after modification of the mounting technique. The fluxes increased as a function of the bath urea concentration, saturating near 200 mmol/l. The apparent Km was 88 mmol/l in the bladders from tapwater‐acclimated toads, and 107 mmol/l in toads acclimated to 500 mOsm NaCl. The Vmax which was 300 μmol·h−1·cm−2 at room temperature in bladders from tapwater acclimation, changed to more than 1500 μmol·h−1·cm−2 upon salt acclimation. It is suggested that urea movement across the urinary bladder of this species occurs by facilitated diffusion and that salt acclimation induces an increase in the density of this pathway, but not of its characteristics (Km).
Differential distribution of α‐tubulin isotypes in Euplotes eurystomus determined by confocal immunofluorescence microscopy**
Authors: Olins Donald E. , Olins Ada L. , Robert‐Nicoud Michel , Jovin Thomas M. , Wehland Juergen , Weber Klaus
Published: February 2012

Detergent permeabilized Euplotes eurystomus (a fresh water hypotrichous ciliate) was reacted with monoclonal and polyclonal antibodies specific for either detyrosinated or tyrosinated α‐tubulin (Glu‐ or Tyr‐tubulin). The isolated cytoskeleton‐nuclear complex was examined by Western immunoblotting and by immunofluorescent and electron microscopic methods. Both Glu‐ and Tyr‐tubulins were detected by immunoblot analysis. Immunofluorescent microscopy indicated that the α‐tubulin isotypes are concentrated in different regions of permeabilized cells: Glu‐tubulin is located primarily in cirri, membranelles, and surrounding the macro‐ and micronuclei. Tyr‐tubulin is principally at the bases of cirri and membranelles. This differential distribution of α‐tubulin isotypes is discussed in terms of current concepts concerning the correlation of tubulin post‐translational modifications to microtubule stability. Confocal immunofluorescent imaging was of critical importance in clearly differentiating the Glu‐tubulin isotype surrounding the macro‐ and micronuclei from a brilliantly fluorescent environment originating from cytoskeletal structures. In conjunction with conventional and stereo‐electron microscopy, confocal optical microscopy provided convincing evidence for a “basket” of microtubules surrounding both nuclei.
Are laminin binding sites on tumor cell surface involved in the indomethacin‐induced sensitivity to natural cytotoxic cells?
Authors: Aliño Salvador‐Francisco , Unda Fernando‐José , Perez‐Yarza Gorka , Cañavate Maria‐Luz
Published: February 2012

Prostaglandins are secreted by a variety of tumor cell lines. The prostaglandin synthesis inhibitor indomethacin (IND) inhibits 3LL tumor growth after both intramuscular or intrasplenic transplantation (45 and 72%, respectively). Moreover, when tumor cells were cultured with IND, the sensitivity of 3LL cells to natural cytotoxic (NC) effector cells was increased (30%) and a higher cytotoxicity was reached when both target and effector cells were treated. This effect was reversed partially or totally when the assay was performed in the presence of laminin or an octapeptide from the laminin B1 chain. In addition, we correlate the increased cytotoxicity mediated by IND with an enhanced ability of 3LL tumor cells to bind labeled laminin (55%). In summary, our results show that the blockage or modulation of cell surface laminin binding components could be directly correlated with the sensitivity of tumor target cells to be eliminated by way of natural cytotoxicity.
Coexistence of thyrotropin‐releasing hormone and insulin in cultured fetal rat islets: a light and electron microscopic immunocytochemical study during islet neoformation
Authors: Leduque Patric , Aratan‐Spike Sonia , Scharfmann Raphaël , Basmaciogullari Annié , Czernichow Paul , Dubois Paul‐Marie
Published: February 2012

Pancreatic thyrotropin‐releasing hormone (TRH) is without doubt localized in the insulin‐containing β‐cells. A previous study reported cellular continuity between β‐cells and ducts in cultured fetal rat islets, but it is not known whether these insulin‐containing β‐cells form a cell type that is different from the TRH cells producing insulin. On the other hand, the subcellular coexistence of both peptides as yet remains unresolved.

To overcome these problems the present study was conducted, using light microscopic immunocytochemistry, to verify the cellular distribution of TRH in cultured fetal rat islets with particular regard to the interrelationship between β‐cells and ducts, and using electron microscopic double labeling cytochemistry, to study the subcellular distribution of TRH and insulin. Our data show that both TRH and insulin are expressed in the same cells during islet cell neogenesis, and are localized in the same secretory granules. No topographic segregation of their respective immunoreactive moieties are seen within the secretory granule.
Benzoxazinone derivatives: new fluorescent probes for two‐color flow cytometry analysis using one excitation wavelength
Authors: Monsigny Michael , Midoux Patrick , Le Bris Marie‐Thérèse , Roche Annie‐Claude , Valeur Bernard
Published: February 2012

A new class of fluorescent dye which upon excitation at 488 nm turns red is shown to be probe‐suitable for using in flow cytometry alone or in conjunction with fluorescein derivatives. 7‐dimethylamino 3‐(p‐formylstyryl) 1,4 benzoxazin 2‐one is suitable for rendering microorganisms, such as Plasmodium merozoites and cells detectable by flow cytometry, allowing a dual fluorescence analysis when the cells are labelled with suitable fluoresceinylated ligands such as fluorescein labeled neoglycoproteins or antibodies. The synthesis of the new benzoxazinone derivatives is described: p‐[β‐ (7‐dimethylamino 1,4 benzoxazin 2‐one 3‐yl)‐vinyl]‐phenylpropenoic acid can be easily activated as a hydroxysuccinimide derivative and linked to amino groups of polypeptides. Hydrophilic polypeptides such as poly‐l‐lysine or glycosylated polymers combined with this new fluorescent dye are shown to be helpful in analyzing cell surface receptors, in dual fluorescence flow cytometry analysis, using a single excitation wavelength and two sets of compounds labeled with the new benzoxazinone derivative and with fluorescein isothiocyanate, respectively. The new benzoxazinone derivative has a high molar absorbance, a good quantum yield fluorescence when it is bound to hydrophilic polypeptides and its fluorescence intensity is not dependent on pH in the physiological pH range.
Intracellular pH and the increase in protein synthesis accompanying activation of Xenopus eggs
Authors: Grandin Nathalie , Charbonneau Michel
Published: February 2012

Metabolic activation following egg fertilization corresponds to an increase in protein synthesis and the initiation of DNA synthesis, which lead to cell division and development of the embryo. Since in several biological systems protein synthesis is regulated by intracellular pH (pHi), we have decided to investigate the situation during Xenopus egg activation. We confirmed that egg activation is accompanied by a pHi rise of 0.3 pH unit. Measurements of the rates of protein synthesis in unactivated and activated eggs, after microinjection of 3H‐leucine, demonstrated that activation was followed by a 2.5‐fold increase. Treatment of unactivated eggs with weak bases also increased pHi, but did not result in an increase in the rate of protein synthesis. Moreover, in vitro translation in cytoplasmic extracts was found to be pH‐independent, at least between 6.8 and 8.2.
The effect of adenosine analogue (DRB) on a major nucleolar phosphoprotein nucleolin
Authors: Noaillac‐Depeyre Jacqueline , Dupont Marie‐Ange , Tichadou Jean‐Louis , Gas Nicole
Published: February 2012

Summary— Nucleolin, a phosphorylated nucleolar protein, of 100 kDa selectively stained with bismuth tartrate and silver nitrate, is implicated in the transcription and maturation of pre‐ribosomal RNA. Nucleolin also fulfills a structural function in nucleolar organization. Using immunocytochemistry the action of 5–6‐dichloro‐1‐β‐D‐ribofuranosylbenzimidazole (DRB), an inhibitor of hn/RNA synthesis known to modify the organization of the nucleolus, was studied for its effects on the distribution and the amount of nucleolin present. After DRB treatment, the morphology of the nucleolus was rapidly disturbed, but the distribution of the nucleolin remained unchanged: the dense fibrillar and the granular components were always positively immunostained. Thirty min after incubation with the drug, a strong increase of the amount of nucleolin occurred. Prolonged treatment led to a marked loss of label. Silver and bismuth staining showed that DRB does not seem to significantly affect the phosphorylation of nucleolin.
Nucleolar changes in human embryo during the pre‐implantation stage. Activation of ribosomal genes during the nucleologenesis
Authors: Grillo Jean‐Marie , Vasserot Mireille , Gamerre Marc , Vitry Gaston , Stahl André
Published: February 2012

Summary— We studied the structural and functional organization of human embryo nucleoli during the pre‐implantation stage from spare embryos obtained by in vitro fertilization. In human embryo nucleoli, structural modifications occur during the first cleavages. They lead to the constitution of a reticulated nucleolus from an initial structure called primary nucleolus. They appear during the third cleavage and correspond to the nucleogenesis. Autoradiography shows no transcription in the primary nucleolus. Transcription of rDNA starts on the periphery of the initial structure after the 4‐cell stage. It corresponds to the beginning of the embryonic gene expression. The entire nucleolus will be progressively concerned by this transcription during the reticulation. Silver staining at the ultrastructural level shows that Ag‐NOR proteins are missing in the primary nucleolus. In the beginning of nucleologenesis, Ag‐NOR proteins are first located on the nucleolar periphery. Their following distribution corresponds to the structures containing rDNA in the nucleolus. Nucleologenesis in the human embryo during the pre‐implantation stage first requires an association of rDNA with a primary structure, then an activation of ribosomal genes.
Effects of testosterone on nuclear ribonucleoprotein components of prostate epithelial cells
Authors: Echeverría Olga , Santini Rafael Pagán , Nin Gerardo Vázquez
Published: February 2012

Summary— The changes of the nuclear components caused by castration and testosterone injection were studied in epithelial cells of the ventral prostate of the rat. Castration drastically diminishes the nuclear and nucleolar volume, as well as the fraction of the nuclear volume occupied by non‐nucleolar ribonucleoprotein (RNP) fibrils. However, in castrated animals the frequency of perichromatin granules (PCG) is 79% higher than in controls. Testosterone injection causes a reduction of the number of PCG to 33% of the castrated level in 15 min, and increases the non‐nucleolar RNP fibrils. Other parameters such as nuclear and nucleolar volume and the relative volume of the compact chromatin present only small changes in a period of 2 h following the hormone administration. High resolution quantitative autoradiography demonstrates that the transportation of previously synthesized RNA increases steeper than the RNA synthesis. All these effects are similar to those caused by ovariectomy and estradiol injection on the nuclear structures of endometrial epithelial cells. These similarities and other observations suggest that PCGs contain mRNA, of a few genes, stored in the nucleus by a restriction of its transportation to the cytoplasm.
Oncogenes and expression of endogenous lectins and glycoconjugates
Authors: Hébert Eric , Monsigny Michel
Published: February 2012

Summary— It is now well established that malignant transformation of eucaryotic cells is concomitant with typical alterations of glycosylation and the expression pattern of endogenous lectins. In parallel, oncogene transfection studies revealed a correlation between the expression of some of these genes, the transformed state and perhaps metastasis. These observations lead to the idea that oncogenes may control the expression of enzymes involved in the biosynthetic pathway of cell membrane glycoconjugates and the expression of endogenous lectins. Indeed, several contributions have shown that cells upon transfection with activated oncogenes of the ras family become invasive and/or metastatic and have their membrane glycoproteins modified. Information on the molecular mechanism of this postulated oncogene regulation is still lacking. Because of the diversity of the functions of oncogene‐encoded proteins, further experiments dealing with other activated oncogenes may help in deciphering the regulation of expression of glycoconjugates and endogenous lectins together with their functions.
Distribution of microtubules during the growth of tobacco pollen tubes
Authors: Del Casino Cecilia , Li Yi‐Qin , Moscatelli Alessandra , Scali Monica , Tiezzi Antonio , Cresti Mauro
Published: February 2012

Summary— The distribution of microtubules was investigated in Nicotiana tabacum pollen tubes at different stages of tube growth by immunofluorescence microscopy. Using specific antibodies, the presence of microtubules consisting of different tubulin isoforms was tested. α‐, β‐ and tyrosinated α‐tubulin were present within the tube, whereas the acetylated form was lacking. The presence of tubulin subunits in pollen tube extracts was also investigated by immunoblotting analyses. The use of a confocal laser scanning microscope integrated with computer‐assisted imaging, allowed a detailed visualization of the microtubule distribution and organization. Cytoplasmic microtubules organized as short bundles with various orientations were detected at the apex of long tubes.
Adrenal nuclear matrix isolation. A morphologic and biochemical study
Authors: Neves Delminda , Magalhães Manuel M , Magalhães Maria C
Published: February 2012

Summary— The nuclear matrix of adrenal cells was isolated by using the methods proposed by Commerford et al and Kaufmann et al for the liver nuclear matrix isolation. Both methods permitted, to the best of our knowledge for the first time, to prepare the nuclear matrix of a steroidogenic cell and therefore to study some regulatory mechanisms governing steroidogenesis. Commerford et al's method retains nuclear envelope and so produces a higher contamination; Kaufmann et al's method presents a higher purity since the nuclear envelope was removed by Triton X‐100. No RNase digestion has been employed for the isolation of the residual nuclear matrices. Both methods however, permit the isolation of fractions with a good morphology, retaining a reticular nucleolus, interchromatinic granules, and a fibrogranular scaffold extending from the nucleolus to the nuclear lamina. The major peptides detected by 1‐D SDS‐PAGE were 123, 56, 46 and 41 kDa; with both methods protein profiles were similar. Identification of proteins by immunodetection reveals lamins A and C, 80 and 65 kDa respectively; no labeling was found for actin (45 kDa) and vimentin (57 kDa). In short, adrenal nuclear matrix was isolated, Kaufmann et al's method being the method of choice.
Clinical heterogeneity of adult Japanese diabetes depending on titers of glutamic acid decarboxylase autoantibodies
Authors: Aoyama Tomohisa , Ikeda Hiroki , Hamamoto Yoshiyuki , Honjo Sachiko , Nomura Kazuhiro , Wada Yoshiharu , Fujikawa Jun , Hayashino Yasuaki , Fukuhara Shunichi , Koshiyama Hiroyuki
Published: February 2012

Aims/Introduction:  We examined whether levels of glutamic acid decarboxylase autoantibodies (GADAb) might show the clinical heterogeneity of adult Japanese diabetes.

Materials and Methods:  In this cross‐sectional study, the serum levels of GADAb were measured in a total of 1857 consecutive adult diabetic patients aged 20 years or older. The patients with positive GADAb, arbitrarily defined as ≥1.5 U/mL, were divided into quartiles according to the number of patients. The age‐ and sex‐matched diabetic patients without GADAb were selected as a control group.

Results:  A total of 103 (5.5%) of the diabetic patients had GADAb, and showed higher HbA1c and serum high‐density lipoprotein (HDL) cholesterol levels, lower body mass index (BMI), urinary C‐peptide immunoreactivity (CPR), serum triglycerides (TG) and uric acid (UA) levels, and lower prevalence of metabolic syndrome than the control group (P < 0.05). Quartiles 3 and 4 (i.e. GADAb ≥4.6 U/mL) showed a higher HbA1c level, lower BMI, urinary CPR, serum TG and UA levels, quartile 2 (2.5 ≤ GADAb < 4.6 U/mL) showed a lower BMI level than the control group (P < 0.05). Among the clinical parameters, we observed significant upward trends for both HbA1c and serum HDL cholesterol levels, and significant downward trends for BMI, serum TG and UA, urinary CPR levels, and prevalence of metabolic syndrome across GADAb quartiles (P < 0.05 for trend).

Conclusions:  These results show that the clinical phenotype of adult Japanese diabetes correlates with GADAb levels, and that patients with GADAb (≥2.5 U/mL) show different characteristics from those without GADAb, although further longitudinal studies are required. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00190.x, 2011)
Novel Combined Scratch and Nanoindentation Experiments on Soda‐Lime‐Silica Glass
Authors: Bandyopadhyay Payel , Dey Arjun , Mukhopadhyay Anoop K.
Published: February 2012

Many advanced applications of glass demand fabrication of engineering parts of utmost dimensional precision which require very accurate grinding and polishing that involves controlled removal of glass. Despite the wealth of literature, however; the mechanism of material removal in glass grinding and polishing is still far from well understood. For instance, it is not known at all to what extent the mechanical properties are compromised inside a scratch groove so as to optimize the machining parameters. Therefore, to develop better understanding about the mechanism of material removal, a series of combined nanoindentation and single pass scratch experiments were conducted on a commercially available soda‐lime‐silica glass as a function of various normal loads (2–20 N) and scratch speeds (0.1–1 mm/s). It was found that the nanohardness and Young's modulus at the local microstructural length scale inside the scratch groove could decrease quite dramatically (~30% to 70%) depending on the combination of load and scratching speed. Further, the tribological properties, the severity and the spatial density of damage evolution were sensitive to the normal loads, scratching speeds, and tensile stresses. Extensive scanning electron microscopy leads to interesting observations on material removal mechanisms. These observations were explained by the theoretical predictions of a model for a brittle, microcracked solid.
Catastrophic worries in mothers of adolescents with internalizing disorders
Authors: Triantafyllou Kalliopi , Cartwright‐Hatton Sam , Korpa Terpsichori , Kolaitis Gerasimos , Barrowclough Christine
Published: February 2012

Objectives. This study investigates worrying in mothers of adolescents with internalizing disorders, and tests the hypothesis that these mothers will produce a greater number of worries with higher catastrophic content compared to control groups.

Design. Differences in worry steps and in catastrophic content of worries were investigated in a cross‐sectional, between groups design, employing a clinical internalizing group, a clinical control, and a non‐referred control group.

Methods. Twenty‐five mothers of adolescents with internalizing disorders, 24 mothers of adolescents with externalizing disorders, and 28 mothers with non‐referred adolescents participated in two interviews about their ‘real’ pre‐existing worries and their worries in response to a hypothetical situation.

Results. The internalizing group produced both a greater number of worry steps and a higher catastrophic content when they talked about their ‘real’ worries, compared to both control groups. They also produced a greater number of worry steps in response to a hypothetical situation compared to the other two groups. The number of worry steps and the level of catastrophic content of ‘real’ worries were associated with adolescent depression and anxiety. Additionally, the number of worry steps and the level of catastrophic content of worries in response to a hypothetical situation were related to adolescent depression. The number of worry steps in ‘real’ worries and the level of catastrophic content in hypothetical worries were also associated with maternal depressive symptoms.

Conclusions. Mothers of adolescents with internalizing disorders may worry more catastrophically about their children than other mothers.
Mechanics of myosin function in white muscle fibres of the dogfish, Scyliorhinus canicula
Authors: Park‐Holohan S. , Linari M. , Reconditi M. , Fusi L. , Brunello E. , Irving M. , Dolfi M. , Lombardi V. , West T. G. , Curtin N. A. , Woledge R. C. , Piazzesi G.
Published: February 2012

Key points 

Muscle force and shortening are generated by a structural change called the working stroke in myosin motor proteins that cross‐link the myosin and actin filaments in muscle.

Precise values for two key parameters of the myosin motor – its mechanical stiffness and the size of the working stroke at low load – were previously only available from one type of muscle in one species, fast twitch muscles of the frog, so it was not clear how generally applicable these values were.

We show that in dogfish fast muscle the low‐load working stroke is the same as in frog muscle, but the myosin motor stiffness is smaller.

The results provide new insights into how the molecular properties of myosin motors in different muscle types and species may be adapted for different muscle functions.
Postsynaptic mechanisms of CO2 responses in parafacial respiratory neurons of newborn rats
Authors: Onimaru Hiroshi , Ikeda Keiko , Kawakami Kiyoshi
Published: February 2012

Key points 

The central chemoreceptors for respiratory control in the medulla sense changes in CO2 concentration and regulate respiratory activity.

Neurons that express a transcription factor, Phox2b, in the parafacial region of the rostral and ventrolateral medulla are excited by hypercapnic stimulation and are proposed to play an important role in central chemoreception.

In this study, we show evidence that Phox2b‐expressing parafacial neurons in neonatal rats were sensitive to hypercapnia via direct action on the postsynaptic membrane without contribution of putative presynaptic or other calcium‐dependent components.

Since these parafacial neurons are also a part of the respiratory rhythm generator in neonates, they are essential for postnatal survival, which is probably due to their contribution to central chemoreception as well as respiratory rhythm generation.
Two Algorithms for the Reliable Estimation of Organic Rankine Cycle Performance
Authors: Becquin Guillaume , Lehar Matthew
Published: February 2012

As the demand grows for low-temperature waste heat recovery systems, organic Rankine cycles (ORCs), and other alternatives to traditional steam, Rankine cycles are becoming more common in industry. Although analytical tools exist that can predict the performance of a steam cycle in a given waste-heat application, the development of a similar tool for ORCs has been hampered by the large choice of possible working fluids. In this paper, two methods are presented with the aim of providing an estimate of the best performance possible for any ORC in a given industrial application. The first is a purely analytical approach assuming an idealized fluid, and the second compares real fluids through cycle simulations to select the most appropriate parameters for the application. The analytical approach provides a rough baseline for performance, while the simulation method refines the estimate to give predictions that are more consistent with the documented performance of ORC plants currently in operation. Together, the two approaches represent a robust means of quickly estimating the capability of an ORC plant and to allow quick comparisons with other technologies.
Model-Based Probabilistic Robust Design With Data-Based Uncertainty Compensation for Partially Unknown System
Authors: Lu XinJiang , Li Han-Xiong , Chen C. L. Philip
Published: February 2012

Model uncertainty often results from incomplete system knowledge or simplification made at the design stage. In this paper, a hybrid model/data-based probabilistic design approach is proposed to design a nonlinear system to be robust under the circumstances of parameter variation and model uncertainty. First, the system is formulated under a linear structure which will serve as a nominal model of the system. All model uncertainties and nonlinearities will be placed under a sensitivity matrix with its bound estimated from process data. On this basis, a model-based robust design method is developed to minimize the influence of parameter variation in relation to performance covariance. Since this proposed design approach possesses both merits from the model-based robust design as well as from the data-based uncertainty compensation, it can effectively achieve robustness for partially unknown nonlinear systems. Finally, two practical examples demonstrate and confirm the effectiveness of the proposed method.
Applied Tests of Design Skills—Part 1: Divergent Thinking
Authors: Shah Jami J. , Millsap Roger E. , Woodward Jay , Smith S. M.
Published: February 2012

A number of cognitive skills relevant to conceptual design were identified previously. They include divergent thinking (DT), visual thinking (VT), spatial reasoning (SR), qualitative reasoning (QR), and problem formulation (PF). A battery of standardized tests is being developed for these design skills. This paper focuses only on the divergent thinking test. This particular test has been given to over 500 engineering students and a smaller number of practicing engineers. It is designed to evaluate four direct measures (fluency, flexibility, originality, and quality) and four indirect measures (abstractability, afixability, detailability, and decomplexability). The eight questions on the test overlap in some measures and the responses can be used to evaluate several measures independently (e.g., fluency and originality can be evaluated separately from the same idea set). The data on the twenty-three measured variables were factor analyzed using both exploratory and confirmatory procedures. A four-factor solution with correlated (oblique) factors was deemed the best available solution after examining solutions with more factors. The indirect measures did not appear to correlate strongly either among themselves or with the other direct measures. The four-factor structure was then taken into a confirmatory factor analytic procedure that adjusted for the missing data. It was found to provide a reasonable fit. Estimated correlations among the four factors (F) ranged from a high of 0.32 for F1 and F2 to a low of 0.06 for F3 and F4. All factor loadings were statistically significant.
Kinematic Analysis of Spatial Geared Mechanisms
Authors: Penaud Julie , Alazard Daniel , Amiez Alexandre
Published: February 2012

In this paper, a general method for kinematic analysis of complex gear mechanisms, including bevel gear trains and noncollinear input and output axes, is presented. This new approach is based on the nullspace of the kinematic constraint matrix computed from the mechanism graph or its adjacency matrix. The novelty is that the elements of the adjacency matrix are weighted with complex coefficients allowing bevel gears to be taken into account and the angular velocity of each link to be directly expressed using polar coordinates. This approach is illustrated on a two-degree-of-freedom car differential and applied to a helicopter main gear box. A MATLAB open source software was developed to implement this method.
Low Cetane Fuels in Compression Ignition Engine to Achieve LTC
Authors: Subramanian Swami Nathan , Ciatti Stephen
Published: February 2012

The conventional combustion processes of Spark Ignition (SI) and Compression Ignition (CI) have their respective merits and demerits. Internal combustion engines use certain fuels to utilize those conventional combustion technologies. High octane fuels are required to operate the engine in SI mode, while high cetane fuels are preferable for CI mode of operation. Those conventional combustion techniques struggle to meet the current emissions norms while retaining high efficiency. In particular, oxides of nitrogen (NOx) and particulate matter (PM) emissions have limited the utilization of diesel fuel in compression ignition engines, and conventional gasoline operated SI engines are not fuel efficient. Advanced combustion concepts have shown the potential to combine fuel efficiency and improved emissions performance. Low Temperature Combustion (LTC) offers reduced NOx and PM emissions with comparable modern diesel engine efficiencies. The ability of premixed, low-temperature compression ignition to deliver low PM and NOx emissions is dependent on achieving optimal combustion phasing. Variations in injection pressures, injection schemes and Exhaust Gas Recirculation (EGR) are studied with low octane gasoline LTC. Reductions in emissions are a function of combustion phasing and local equivalence ratio. Engine speed, load, EGR quantity, compression ratio and fuel octane number are all factors that influence combustion phasing. Low cetane fuels have shown comparable diesel efficiencies with low NOx emissions at reasonably high power densities.
A Versatile Acceleration-Based Cam Profile for Single-Dwell Applications Requiring Cam-Follower Clearance During Dwell
Authors: Flocker Forrest W.
Published: February 2012

Presented in this paper is a cam motion program suitable for single-dwell cam-follower systems with built-in clearance between the cam and follower during the dwell portion of the cycle. This makes the motion program particularly well-suited to applications such as valve trains in internal combustion engines in which cam-follower clearance is necessary to ensure proper seating of a poppet valve, preventing gas leakage across the seal. The motion program for the cam follower is derived from the follower acceleration function so that designers can control the ratio of the magnitudes of positive and negative accelerations. This provides cam designers more control over the cam-follower interface force and therefore more control over factors such as cam wear and the potentially destructive phenomenon known as “follower jump.” Included in the motion program is asymmetric rise and fall that allows different times for these events. The follower acceleration is designed to be smooth enough to provide continuous jerk throughout the actuation phase, thereby tending to reduce undesirable residual vibrations. The motion program used to close and open the clearance gap is derived from a velocity function, allowing more control of follower inertia during the important clearance closing event. The motion program is presented in a form appropriate for implementation in standard engineering equation-solving software, giving the cam designer easy control over important parameters in high-speed cam-follower systems.
Evaluation of a Lean-Burn Natural Gas Engine Operating on Variable Methane Number Fuel
Authors: Kreutzer Cory J. , Olsen Daniel B. , Bremmer Robin J.
Published: February 2012

Wellhead gas from which pipeline natural gas originates has significant variability in composition due to natural variations in deposits. Gas quality is influenced by relative concentrations of both inert and hydrocarbon species. Gas compression engines utilizing wellhead gas as a fuel source often require significant installation time and adjustment of stock configuration due to fuel compositions that vary with time and location. Lean burn natural gas engines are chosen as wellhead compression engines for high efficiency and low emissions while minimizing the effect of variable gas composition. Ideal engine conditions are maintained by operating within the knock and misfire limits of the engine. Additional data is needed to find engine operational limitations. In this work, experimental data was collected on a Cummins GTA8.3SLB engine operating on variable methane number fuel under closed-loop equivalence ratio control. A fuel blending system was used to vary methane number to simulate wellhead compositions. NOx and CO emissions were found to increase with decreasing methane number while combustion stability remained constant. In addition, the effects of carbon dioxide and nitrogen diluents in the fuel were investigated. When diluents were present in the fuel, engine performance could be maintained by spark timing advance.
Investigation of Ash Formation, Accumulation, and Distribution in Diesel Particulate Filters Using Lubricant Additive Tracers
Authors: Sappok Alexander , Wong Victor W. , Morrow Ryan , Zisholtz Ethan , Doustar Isaac , Govani Ifran
Published: February 2012

The accumulation of lubricant-derived ash in diesel particulate filters (DPF) adversely affects engine efficiency, and is the single most important factor limiting the filter’s useful service life. The location of the ash deposits in the DPF, whether accumulated in a layer along the channel walls or packed in a pug at the end of the channels, plays a crucial role in determining the extent to which the ash impacts filter performance. This work presents results of targeted experiments designed to carefully track the evolution of the ash deposit formation and accumulation processes. Specially-formulated lubricants containing only calcium, zinc, or magnesium additives were used as chemical tracers and applied to load the same DPF in carefully designed time-sequence variations. Subsequent filter post-mortem analysis utilized scanning electron microscopy in conjunction with energy dispersive x-ray analysis to identify the chemical tracers in the ash layer and channel end-plugs. The results provide a quantitative measure of ash build-up along the channel walls, and the subsequent transport and formation of ash plugs at the end of the DPF channels. Studies with these additive tracers also showed large differences in DPF pressure drop as a function of ash chemistry. In general, calcium- and magnesium-based ash resulted in the largest increase in filter pressure drop, while ash containing primarily zinc compounds exhibited little increase in pressure drop for the same ash level in the DPF. Furthermore, despite being formulated to the same 1% total sulfated ash level, differences in ash accumulation rates between each of the lubricants provide additional insight into the magnitude of individual additives’ impact on DPF performance. Although the ash problem presents a significant challenge to lubricant and additive formulators and engine and aftertreatment system manufacturers alike, these results enhance the fundamental understanding of how ash is accumulated and distributed in the DPF. Further, the results are useful to understand the manner in which the accumulated ash affects exhaust flow restriction and filter pressure drop, as well as catalyst performance. Eventually, means of controlling both the location and packing characteristics of the ash deposits may be developed to extend DPF service life and minimize the impact of the accumulated ash on filter performance.
Simultaneous Imaging of OH* Chemiluminescence and Flame Luminosity of Diesel and Biodiesel Spray Combustion
Authors: Zhang Ji , Fang Tiegang
Published: February 2012

The research on the spray combustion of diesel and biodiesel is vital to the understanding of emission formation and optimal utilization of fuel. This paper studies the biodiesel and diesel spray combustion in a constant volume chamber under different simulated diesel engine conditions. The ambient temperature at fuel injection varied from 800K to 1200K, while the ambient oxygen concentration was maintained at 21%. Simultaneous high speed imaging of OH* chemiluminescence and flame luminosity was employed to visualize the whole combustion process. Heat release rate was analyzed based on the measured combustion pressure. The apparent heat release rate analysis shows that biodiesel has a shorter ignition delay time than diesel, and biodiesel has a smaller cumulative heat release value due to its lower heating value. The overlaying image of OH* chemiluminescence and flame luminosity clearly identifies the high temperature reaction regions and soot formation regions. The line-of-sight images agree with the published observation that the hydroxyl radical is formed on the lean side of the flame edge. Decreasing ambient temperature greatly reduces the OH* chemiluminescence intensity of the diesel combustion, while the impact is smoother and milder for biodiesel combustion. Biodiesel shows a significantly lower level of flame luminosity than diesel under all conditions. These combined observations lead to a speculation that the soot oxidation process may serve as an important contributor to OH* chemiluminescence intensity for late stage combustion, and biodiesel shows a tendency to produce less soot than diesel under the investigated conditions.
An Analytical Model to Predict Nitric Oxide Concentration and Soot Emissivity in a Diesel Engine
Authors: Song Hoseok , Tompkins Brandon T. , Jacobs Timothy J.
Published: February 2012

Zero-dimensional simulation models are often used to interpret experimental pressure data to better understand combustion processes of internal combustion (IC) engines. This study attempts to improve upon the single-zone model, a type of zero-dimensional model, by using a two-stage model rigorously described in the literature, because computed single-zone temperatures are generally too low for accurate modeling of pollutant gases that are very sensitive to temperature, such as nitric oxide. For example, the thermal kinetic of nitric oxide (NO) formation requires temperatures above 1800 K. Upon implementation of the so-called two-stage model, this study shows calculation improvements compared to a single-zone model. Specifically, NO emission is calculated and compared to experimental results taken from a four-cylinder medium duty diesel engine. By using the two-stage model, soot emissivity is also calculated and its relation with NO formation is discussed.
Lean Limit Extension for High BMEP Gas Engines via Novel Electronic Ignition and Prechamber Plug: Higher Efficiency and Lower NOx in Open Chamber Engines
Authors: Chiera Domenico , Ahrens David , Polley Nolan , Petruska David , Riley Mike , Hampson Gregory J.
Published: February 2012

Large bore natural gas engines have the perennial challenge to achieve ever higher efficiency with ever lower NOx emissions, while maintaining stable combustion, avoiding misfire and engine knock. A primary strategτy to achieve these goals is to run leaner and leaner. However, leaner mixtures lead to reduced combustion stability and the operating space between misfire and engine knock shrinks. Leaner operation requires a high performance ignition system. This report will highlight the fundamental challenges related to lean operation and the progress Woodward has made to create a novel high performance prechamber spark plug to achieve good combustion stability in a passive prechamber spark plug under lean conditions. The spark plug in combination with the appropriate ignition system enables faster and more stable combustion under increasingly lean conditions, improving fuel efficiency and emissions. Engine simulation modeling is used to demonstrate the benefits of lean gas mixtures and reduced combustion duration to enhance the NOx versus fuel consumption trade-off for a range of air fuel ratios. With this database available, a design requirements flow-down is performed such that combustion performance requirements can be specified a priori, which if met would ensure the high level engine emissions and performance targets would be met. With combustion requirements in hand, CFD simulations are used to identify the mechanisms by which flame propagation is improved with prechamber spark plugs in general, and by the Lean Quality Plug (WW-LQP) prechamber spark plug under development at Woodward. Experimental validation was carried out to confirm the benefits of lean operation and improvement of combustion stability (COV) on the NOx-efficiency trade-off. Operation with Woodward’s WW-LQP spark plug and IC1100 AC ignition system showed improved fuel efficiency at constant NOx on a high BMEP engine. Additionally, the enhanced stability and low COV of the WW-LQP enables extension of the natural gas lean limit closer to λ = 2.00 for an open chamber engine.
Numerical Study of SI Engine Part Load Operating Conditions Using Different VVA Strategies
Authors: Battistoni Michele , Grimaldi Carlo N. , Mariani Francesco
Published: February 2012

In SI engines, VVA (Variable Valve Actuation) technology is mainly used for the reduction of pumping losses at part load. This paper presents the results of fluid dynamic analyses on a 4V engine about the effects of different VVA strategies, by comparing and discussing the results in terms of organized charge motions, turbulence levels, flame developments, NO and CO emissions. CFD simulations cover five load control cases: comparison is among conventional throttling, EIVC (Early Intake Valve Closure) with symmetric and asymmetric intake lifts, LIVC (Late Intake Valve Closure) and symmetrical Multi-Lift strategies. 3D U-RANS simulations are performed, adopting the Extended Coherent Flamelet Model (ECFM) for the description of premixed SI combustion. The 3D model is also coupled to a 1D engine model which provides inlet/outlet boundary conditions. Simulation results highlight the potential of asymmetric Early Intake Valve Closure (EIVC) strategy which allows reducing pumping losses and, at the same time, achieving good turbulence intensity and combustion speed, if compared to other load control strategies. Multi-Lift strategy resulted excellent in terms of burn duration, but pumping losses are practically the same as in the throttled engine.
Surprising importance of photo-assisted etching of silicon in chlorine-containing plasmas
Authors: Shin Hyungjoo , Zhu Weiye , Donnelly Vincent M. , Economou Demetre J.
Published: February 2012

The authors report a new, important phenomenon: photo-assisted etching of p-type Si in chlorine-containing plasmas. This mechanism was discovered in mostly Ar plasmas with a few percent added Cl2, but was found to be even more important in pure Cl2 plasmas. Nearly monoenergetic ion energy distributions (IEDs) were obtained by applying a synchronous dc bias on a “boundary electrode” during the afterglow of a pulsed, inductively coupled, Faraday-shielded plasma. Such precisely controlled IEDs allowed the study of silicon etching as a function of ion energy, at near-threshold energies. Etching rates increased with the square root of the ion energy above the observed threshold of 16 eV, in agreement with published data. Surprisingly, a substantial etching rate was observed, independent of ion energy, when the ion energy was below the ion-assisted etching threshold. Experiments ruled out chemical etching by Cl atoms, etching assisted by Ar metastables, and etching mediated by holes and/or low energy electrons generated by Auger neutralization of low-energy ions, leaving photo-assisted etching as the only likely explanation. Experiments were carried out with light and ions from the plasma either reaching the surface or being blocked, showing conclusively that the “sub-threshold” etching was due to photons, predominately at wavelengths < 1700 Å. The photo-assisted etching rate was equal to the ion-assisted etching rate at 36 eV, causing substantial complications for processes that require low ion energies to achieve high selectivity and low damage, such as atomic layer etching. Under these conditions, photo-assisted etching likely plays an important role in profile evolution of features etched in Si with chlorine-containing plasmas, contributing to the commonly observed sloped sidewalls and microtrenches.
Separated in Time and Space
Authors: VanHook Annalisa M.
Published: February 2012

Sequential interactions of Notch and Wnt signaling are required for segregation of mesoderm and endoderm in the sea urchin embryo.
Pairing Up for Patterning
Authors: VanHook Annalisa M.
Published: February 2012

Biochemistry and genetics reveal the identity of specific ligand-receptor pairs that affect stomatal development.
Starting a Beneficial Path
Authors: Adler Elizabeth M.
Published: February 2012

Resveratrol acts as a competitive phosphodiesterase inhibitor to initiate pathways that mediate its beneficial effects on metabolic disorders.