bluuebunny/crossref_metadata_2025 huggingface dataset:
The Functional Thr130Ile and Val255Met Polymorphisms of the Hepatocyte Nuclear Factor-4α (HNF4A): Gene Associations with Type 2 Diabetes or Altered β-Cell Function among Danes
Authors: Ek Jakob , Rose Christian Schack , Jensen Dorit Packert , Glümer Charlotte , Borch-Johnsen Knut , Jørgensen Torben , Pedersen Oluf , Hansen Torben
Published: May 2005

HNF4A encodes an orphan nuclear receptor that plays crucial roles in regulating hepatic gluconeogenesis and insulin secretion. The aim of the present study was to examine two rare missense polymorphisms of HNF4A, Thr130Ile and Val255Met, for altered function and for association with type 2 diabetes (T2D). We have examined these polymorphisms 1) by in vitro transactivation studies and 2) by genotyping the variants in 1409 T2D patients and in 4726 glucose-tolerant Danish white subjects. When tested in COS7 cells, both the Thr130Ile and the Val255Met variants showed a significant decrease in transactivation activity compared with wild-type (73% of wild-type, P = 0.02, and 76%, P = 0.04, respectively). The Thr130Ile variant had a significantly increased carrier frequency among T2D patients compared with glucose-tolerant subjects [odds ratio, 1.26 (1.01–1.57); P = 0.04]. The rare Val255Met polymorphism had a similar frequency among T2D patients and glucose-tolerant subjects. Heterozygous glucose-tolerant carriers of the variant showed, however, decreased levels of fasting serum C-peptide (76%; P = 0.03) and decreased fasting serum triglyceride (58%; P = 0.02). In conclusion, The Thr130Ile and the Val255Met polymorphisms decrease the transcriptional activity of HNF4A, and the Thr130Ile polymorphism associates with T2D, whereas the Val255Met variant associates with a decrease in fasting serum C-peptide.
Phenotypic Variation in Hyperandrogenic Women Influences the Findings of Abnormal Metabolic and Cardiovascular Risk Parameters
Authors: Carmina E. , Chu M. C. , Longo R. A. , Rini G. B. , Lobo R. A.
Published: May 2005

In hyperandrogenic women, several phenotypes may be observed. This includes women with classic polycystic ovary syndrome (C-PCOS), those with ovulatory (OV) PCOS, and women with idiopathic hyperandrogenism (IHA), which occurs in women with normal ovaries. Where other causes have been excluded, we categorized 290 hyperandrogenic women who were seen consecutively for this complaint between 1993 and 2004 into these three subgroups. The aim was to compare the prevalence of obesity, insulin resistance, and dyslipidemia as well as increases in C-reactive protein and homocysteine in these different phenotypes with age-matched ovulatory controls of normal weight (n = 85) and others matched for body mass index (BMI) with women with C-PCOS (n = 42). Although BMI affected fasting serum insulin and the Quantitative Insulin-Sensitivity Check Index, these markers of insulin resistance were greatest in C-PCOS (n = 204), followed by OV-PCOS (n = 50) and then IHA (n = 33). Androgen levels were similar in OV-PCOS and IHA but were higher in C-PCOS, whereas gonadotropins were similar in all groups. Lipid abnormalities were highest in C-PCOS and OV-PCOS and were normal in IHA. C-reactive protein was elevated in C-PCOS and OV-PCOS but not IHA. Homocysteine was elevated only in C-PCOS. Overall, the prevalence of obesity (BMI > 30) was 29% in C-PCOS, 8% in OV-PCOS, and 15% in IHA and insulin resistance (Quantitative Insulin-Sensitivity Check Index < 0.33) was 68% in C-PCOS, 36% in OV-PCOS, and 26% in IHA. The prevalence of having at least one elevated cardiovascular risk marker was 45% in C-PCOS 38% in OV-PCOS and was not increased on IHA (6%). These results suggest that among hyperandrogenic women the prevalence of abnormal metabolic and cardiovascular risk parameters is greatest in C-PCOS, followed by OV-PCOS and then women with IHA. Moreover, in that in OV-PCOS and IHA, ages and weights were similar yet the prevalence of metabolic and cardiovascular risk was greater in OV-PCOS, the finding of polycystic ovaries may be a significant modifying factor.
Graded Inhibition of Pulsatile Luteinizing Hormone Secretion by a Selective Gonadotropin-Releasing Hormone (GnRH)-Receptor Antagonist in Healthy Men: Evidence That Age Attenuates Hypothalamic GnRH Outflow
Authors: Takahashi Paul Y. , Liu Peter Y. , Roebuck Pamela D. , Iranmanesh Ali , Veldhuis Johannes D.
Published: May 2005

Healthy older men manifest concomitant hypoandrogenemia and attenuation of LH pulse size. Because exogenous GnRH remains effective, a plausible intuition is that aging reduces hypothalamic GnRH secretion, thus mediating relative hypogonadotropic hypogonadism. To assess the impact of age on central GnRH outflow indirectly, we quantitated graded suppression of pulsatile LH secretion by saline and escalating doses of a potent and selective GnRH-receptor antagonist, ganirelix, in 18 healthy men ages 23–72 yr. The rationale is that ganirelix should reduce the amplitude of LH pulses in proportion to both drug concentration and endogenous GnRH feedforward. To this end, blood was sampled every 10 min for 2 h before and 16 h after sc administration of saline or ganirelix and for 3 additional hours after iv injection of a fixed dose of GnRH (100 ng/kg); concentrations of LH and ganirelix were measured by immunochemiluminometry and RIA, respectively; and pulsatile LH secretion was quantitated by a deconvolution procedure. Log-linear regression analysis was used to estimate the sensitivity of pulsatile LH secretion to inhibition by a unit increase in serum ganirelix concentrations in each subject. Statistical analyses revealed that increasing age markedly attenuated the capability of ganirelix to decrease LH pulse size (viz., r = −0.648; P = 0.004). In contrast, age did not modify the competitive interaction between injected GnRH and ganirelix. These joint outcomes support the clinical hypothesis that age diminishes hypothalamic GnRH outflow without impairing GnRH action in healthy men.
Matching catalytic activity to developmental function: Tolloid-related processes Sog in order to help specify the posterior crossvein in theDrosophilawing
Authors: Serpe Mihaela , Ralston Amy , Blair Seth S. , O'Connor Michael B.
Published: May 2005

The Drosophila tolloid (tld) and tolloid related(tlr) gene products belong to a family of developmentally important proteases that includes Bone Morphogenetic Protein 1 (Bmp1). Tld is required early in Drosophila development for proper patterning of dorsal embryonic structures, whereas Tlr is required later during larval and pupal stages of development. The major function of Tld is to augment the activity of Decapentaplegic (Dpp) and Screw (Scw), two members of the Bmp subgroup of the Tgfβ superfamily, by cleaving the Bmp inhibitor Short gastrulation (Sog). In this study, we provide evidence that Tlr also contributes to Sog processing. Tlr cleaves Sog in vitro in a Bmp-dependent manner at the same three major sites as does Tld. However, Tlr shows different site selection preferences and cleaves Sog with slower kinetics. To test whether these differences are important in vivo, we investigated the role of Tlr and Tld during development of the posterior crossvein (PCV) in the pupal wing. We show that tlr mutants lack the PCV as a result of too little Bmp signaling. This is probably caused by excess Sog activity, as the phenotype can be suppressed by lowering Sog levels. However, Tld cannot substitute for Tlr in the PCV; in fact, misexpressed Tld can cause loss of the PCV. Reducing levels of Sog can also cause loss of the PCV, indicating that Sog has not only an inhibitory but also a positive effect on signaling in the PCV. We propose that the specific catalytic properties of Tlr and Tld have evolved to achieve the proper balance between the inhibitory and positive activities of Sog in the PCV and early embryo, respectively. We further suggest that, as in the embryo, the positive effect of Sog upon Bmp signaling probably stems from its role in a ligand transport process.
Shifting boundaries of retinoic acid activity control hindbrain segmental gene expression
Authors: Sirbu Ioan Ovidiu , Gresh Lionel , Barra Jacqueline , Duester Gregg
Published: May 2005

Retinoic acid (RA) generated by Raldh2 in paraxial mesoderm is required for specification of the posterior hindbrain, including restriction of Hoxb1 expression to presumptive rhombomere 4 (r4). Hoxb1expression requires 3′ and 5′ RA response elements for widespread induction up to r4 and for r3/r5 repression, but RA has previously been detected only from r5-r8, and vHnf1 is required for repression of Hoxb1 posterior to r4 in zebrafish. We demonstrate in mouse embryos that an RA signal initially travels from the paraxial mesoderm to r3, forming a boundary next to the r2 expression domain of Cyp26a1 (which encodes an RA-degrading enzyme). After Hoxb1 induction, the RA boundary quickly shifts to r4/r5, coincident with induction of Cyp26c1 in r4. A functional role for Cyp26c1 in RA degradation was established through examination of RA-treated embryos. Analysis of Raldh2–/– and vHnf1–/– embryos supports a direct role for RA in Hoxb1 induction up to r4 and repression in r3/r5, as well as an indirect role for RA in Hoxb1 repression posterior to r4 via RA induction of vHnf1 up to the r4/r5 boundary. Our findings suggest that Raldh2 and Cyp26 generate shifting boundaries of RA activity, such that r3-r4 receives a short pulse of RA and r5-r8 receives a long pulse of RA. These two pulses of RA activity function to establish expression of Hoxb1 and vHnf1 on opposite sides of the r4/r5 boundary.
Cytoplasmic carbonic anhydrase isozymes in rainbow troutOncorhynchus mykiss: comparative physiology and molecular evolution
Authors: Esbaugh A. J. , Perry S. F. , Bayaa M. , Georgalis T. , Nickerson J. , Tufts B. L. , Gilmour K. M.
Published: May 2005

It is well established that the gills of teleost fish contain substantial levels of cytoplasmic carbonic anhydrase (CA), but it is unclear which CA isozyme(s) might be responsible for this activity. The objective of the current study was to determine if branchial CA activity in rainbow trout was the result of a general cytoplasmic CA isozyme, with kinetic properties,tissue distribution and physiological functions distinct from those of the red blood cell (rbc)-specific CA isozyme. Isolation and sequencing of a second trout cytoplasmic CA yielded a 780 bp coding region that was 76% identical with the trout rbc CA (TCAb), although the active sites differed by only 1 amino acid. Interestingly, phylogenetic analyses did not group these two isozymes closely together, suggesting that more fish species may have multiple cytoplasmic CA isozymes. In contrast to TCAb, the second cytoplasmic CA isozyme had a wide tissue distribution with high expression in the gills and brain, and lower expression in many tissues, including the red blood cells. Thus, unlike TCAb, the second isozyme lacks tissue specificity and may be expressed in the cytoplasm of all cells. For this reason, it is referred to hereafter as TCAc (trout cytoplasmic CA). The inhibitor properties of both cytoplasmic isozymes were similar (Ki acetazolamide 1.21±0.18 nmol l-1 and 1.34±0.10 nmol l-1for TCAc and TCAb, respectively). However, the turnover of TCAb was over three times greater than that of TCAc (30.3±5.83 vs 8.90±1.95 e4 s-1, respectively), indicating that the rbc-specific CA isoform was significantly faster than the general cytoplasmic isoform. Induction of anaemia revealed differential expression of the two isozymes in the red blood cell; whereas TCAc mRNA expression was unaffected, TCAb mRNA expression was significantly increased by 30- to 60-fold in anaemic trout.
The effect of desiccation on water management and compartmentalisation in scorpions: the hepatopancreas as a water reservoir
Authors: Gefen Eran , Ar Amos
Published: May 2005

Scorpions of the Family Buthidae have lower water loss rates (WLR) and enhanced osmoregulatory capacities in comparison with sympatric species of F. Scorpionidae. In this study we followed changes in water content of different body compartments in four scorpion species under prolonged desiccation conditions. The high initial WLR previously reported for Scorpionidae result in rapid depletion of body water stores. A significant decrease in total body water content of Scorpionidae was recorded following loss of only 5% of initial mass, whereas no such decrease was recorded for Buthidae following severe desiccation. When desiccated, scorpions lose water primarily from the hepatopancreas, while haemolymph volume is more tightly regulated. However,the haemolymph volume of Scorpionidae decreases as a result of depletion of hepatopancreas water stores following severe desiccation. The increasing lipid fraction in the hepatopancreas of Scorpionidae during desiccation suggests that depletion of body water stores may induce enhanced catabolism of carbohydrates, which may contribute to volume regulation by making initially glycogen-bound water available to the desiccating scorpion.
Hypoxic responses of Na+/K+ ATPase in trout hepatocytes
Authors: Bogdanova A. , Grenacher B. , Nikinmaa M. , Gassmann M.
Published: May 2005

Reduction in oxygenation induces inhibition of Na+/K+ATPase in a number of cells and tissues, including hepatocytes. When not reversed, decrease in Na+/K+ pump activity leads to a gradual Na+ accumulation, cell swelling and death. However, when accompanied by suppression of dissipative cation pathways, it has also been shown to be a beneficial adaptive strategy used by some hypoxia-tolerant species to reduce ATP consumption during prolonged periods of anoxia. This study aims to investigate acute hypoxic responses of the Na+/K+ ATPase in primary cultures of trout hepatocytes. Gradual decrease in oxygenation was followed by an instantaneous transient dose-dependent downregulation of the Na+/K+ ATPase transport activity, but was without an effect on hydrolytic function of the enzyme. Hypoxia-induced inhibition of active K+ influx was reversed spontaneously when hypoxic incubation time exceeded 20 min. The stimulating effect of prolonged hypoxic exposure on the Na+/K+ pump is most probably secondary to hypoxia-induced activation of the Na+/H+ exchanger with the following Na+accumulation leading to Na+/K+ ATPase activation. Hypoxia-induced inhibition of the Na+/K+ pump was not caused by ATP depletion or global oxidative stress. However, local controlled production of reactive oxygen species seems to play an important role in hypoxia-induced regulation of the Na+/K+ ATPase. Treatment of cells with mercaptopropionyl glycine (MPG), a scavenger of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{O}\mathrm{H}^{.-}\) \end{document}, abolished hypoxia-induced inhibition of the Na+/K+ ATPase. Earlier on we have shown that activation of Na+/H+ exchanger under hypoxic conditions can be opposed by MPG treatment as well. Taken together our results suggest that regulation of both oxygen-sensitive transporters may be accomplished by local changes in free radical production.
Contractile properties of mouse single muscle fibers, a comparison with amphibian muscle fibers
Authors: Edman K. A. P.
Published: May 2005

Single fibers, 25-40 μm wide and 0.5-0.7 mm long, were isolated from the flexor digitorum brevis muscle of the mouse. Force and movement were recorded(21-27°C) from the fiber as a whole and, in certain experiments, from a short marked segment that was held at constant length by feedback control. The maximum tetanic force, 368±57 kN/m2 (N=10), was not significantly different from that recorded in frog muscle fibers at equal temperature. However, the rising phase of the tetanus was considerably slower in the mammalian fibers, 202±20 ms (N=17) being required to reach 90% of maximum tetanic force as compared with 59±4 ms(N=20) in the frog muscle fibers. Similar to the situation in frog muscle fibers, the force-velocity relation exhibited two distinct curvatures located on either side of a breakpoint near 80% of the isometric force. Maximum speed of shortening was 4.0±0.3 fiber lengths s-1(N=6). The relationship between tetanic force and sarcomere length was studied between 1.5 and 4.0 μm sarcomere spacings, based on length-clamp recordings that were free of `tension creep'. There was a flat maximum (plateau) of the length-tension relation between approximately 2.0 and 2.4 μm sarcomere lengths. The descending limb of the length-tension relation (linear regression) intersected the length axis (zero force) at 3.88μm and reached maximum force at 2.40 μm sarcomere length. The slope of the descending limb is compatible with a thick filament length of 1.63 μm and an average thin filament length of 1.10 μm. These values accord well with recent electron microscope measurements of myofilament length in mammalian muscle.
Insect egg deposition induces defence responses inPinus sylvestris: characterisation of the elicitor
Authors: Hilker Monika , Stein Claudia , Schröder Roland , Varama Martti , Mumm Roland
Published: May 2005

Egg deposition by the phytophagous sawfly Diprion pini L.(Hymenoptera, Diprionidae) is known to induce locally and systemically the emission of volatiles in Scots pine (Pinus sylvestris L.) that attract the egg parasitoid Chrysonotomyia ruforum Krausse(Hymenoptera, Eulophidae). The egg parasitoids kill the eggs and thus prevent damage to the plant from feeding sawfly larvae. The elicitor inducing the pine's response is known to be located in the oviduct secretion which the female sawfly applies to the eggs when inserting them into a slit in the pine needle using the sclerotized ovipositor valves. In this study we have characterized the elicitor. The elicitor was still active when isolated from the oviduct and applied directly to slits made in the pine needles. However,as soon as the oviduct secretion was dissolved in Aqua dest. and stored for 3 h at room temperature or kept frozen at -80°C, its activity was lost. In contrast, oviduct secretion kept its eliciting activity, when dissolved in Ringer solution (pH 7.2) both after storage at room temperature and after freezing. The activity of the elicitor vanished after treatment of the oviduct secretion with proteinase K, which destroyed all proteins. This suggests that the elicitor in the oviduct secretion is a peptide or protein, or a component bound to these. SDS-PAGE revealed a similar, but not identical protein pattern from hemolymph and oviduct secretion. Hemolymph itself has no eliciting effect. The elicitor in the oviduct secretion is only active when transferred to slit pine needles, since its application on undamaged needles did not induce the emission of attractive volatiles.
A 3-D kinematic analysis of gliding in a flying snake,Chrysopelea paradisi
Authors: Socha John J. , O'Dempsey Tony , LaBarbera Michael
Published: May 2005

Flying snake species (Chrysopelea) locomote through the air despite a lack of appendages or any obvious external morphological specialization for flight. Here photogrammetric techniques were used to investigate C. paradisi's aerial trajectory in three dimensions. Two videocameras arranged in stereo were used to record head, midpoint and vent landmarks on snakes that jumped from a horizontal branch at a height of 9.62 m and landed in an open field. The coordinates of these landmarks were reconstructed in three dimensions and used to analyze patterns of position,glide angle and speed concurrently with changes in body posture in 14 glide sequences from different individuals. C. paradisi's trajectory was composed of a ballistic dive followed by a shallowing phase in which the path became more horizontal; for most glide trials, no equilibrium phase was observed. In the ballistic dive, the snake changed posture from generally straight to a wide `S' shape in planview and began aerial undulation. Shortly after the ballistic dive, the snake's speed transitioned from an initial acceleration to stable or to a different rate of increase or decrease. Aerial undulation, in which high-amplitude traveling waves pass posteriorly down the body, was a prominent locomotor behavior. In mid-glide, this undulation occurred with the anterior body oriented approximately parallel with the ground and the posterior body cycling up and down in the vertical plane. The body angle of attack for the anterior body for one trial was 20-40°. Snakes traveled a horizontal distance of 10.14±2.69 m (mean ± s.d.) while reaching an airspeed of 10.0±0.9 m s-1, sinking speed of 6.4±0.8 m s-1 and horizontal speed of 8.1±0.9 m s-1. The glide path shallowed at a rate of 20±6° s-1 and reached a minimum glide angle of 28±10°, with a minimum recorded glide angle of 13°. C. paradisi are surprisingly good gliders given their unconventional locomotor style, with performance characteristics that rival or surpass more familiar gliding taxa such as flying squirrels. As in other gliders, C. paradisi is potentially capable of using aerial locomotion to move effectively between trees, chase aerial prey, or avoid predators.
Changes in gut and Malpighian tubule transport during seasonal acclimatization and freezing in the gall flyEurosta solidaginis
Authors: Yi Shu-Xia , Lee Richard E.
Published: May 2005

Since few studies have examined cold tolerance at the organ level in insects, our primary objective was to characterize the functional responses of the gut and Malpighian tubules (MT) to seasonal acclimatization, chilling and freezing in larvae of the goldenrod gall fly Eurosta solidaginisFitch (Diptera, Tephritidae). From September to December, hemolymph osmolality(455-926 mOsmol kg l-1) and freezing tolerance increased markedly in field-collected larvae. Chlorophenol Red was readily transported into the lumen of the foregut, the posterior portion of the midgut, the ureter, the proximal region of the anterior pair of MT, and entire posterior pair of MT. Ouabain and KCN inhibited transport of Chlorophenol Red in the gut and MT. Transport was readily detected at 0°C and the rate of transport was directly related to temperature. The rate of fluid transport by the MT decreased steadily from a monthly high in September (10.7±0.8 nl min-1 for the anterior pair; 12.7±1.0 nl min-1for the posterior pair) until secretion was no longer detectable in December;this decrease parallels entry into diapause for this species. Even in larvae that died following freezing for 40 days at -20°C, individual organ function was retained to a limited extent. Through the autumn, cholesterol concentrations in the hemolymph increased nearly fourfold. In contrast, the ratio of cholesterol to protein content (nmol mg l-1) in the MT membrane remained relatively constant (22∼24 nmol mg l-1protein) during this period. Freezing of larvae for 20 days at -20°C caused a significant decrease in cholesterol levels in the hemolymph and the MT membranes compared to unfrozen controls. These results suggest that cholesterol plays a role in seasonal cold hardening and freeze tolerance in insects.
Cardiac preload and venous return in swimming sea bass (Dicentrarchus labraxL.)
Authors: Sandblom Erik , Farrell Anthony P. , Altimiras Jordi , Axelsson Michael , Claireaux Guy
Published: May 2005

Cardiac preload (central venous pressure, Pcv), mean circulatory filling pressure (MCFP), dorsal aortic blood pressure(Pda) and relative cardiac output(Q̇) were measured in sea bass(Dicentrarchus labrax) at rest and while swimming at 1 and 2 BL s-1. MCFP, an index of venous capacitance and the upstream venous pressure driving the return of venous blood to the heart, was measured as the plateau in Pcv during ventral aortic occlusion. Compared with resting values, swimming at 1 and 2 BLs-1 increased Q̇ (by 15±1.5 and 38±6.5%, respectively), Pcv (from 0.11±0.01 kPa to 0.12±0.01 and 0.16±0.02 kPa,respectively), MCFP (from 0.27±0.02 kPa to 0.31±0.02 and 0.40±0.04 kPa, respectively) and the calculated pressure gradient for venous return (ΔPv, from 0.16±0.01 kPa to 0.18±0.02 and 0.24±0.02 kPa, respectively), but not Pda. In spite of an increased preload, the increase in Q̇ was exclusively mediated by an increased heart rate (fh, from 80±4 beats min-1 to 88±4 and 103±3 beats min-1,respectively), and stroke volume (Vs) remained unchanged. Prazosin treatment (1 mg kg-1Mb) abolished pressure and flow changes during swimming at 1 BL s-1, but not 2 BL s-1, indicating that other control systems besides an α-adrenoceptor control are involved. This study is the first to address the control of venous capacitance in swimming fish. It questions the generality that increased Q̇ during swimming is regulated primarily through Vs and shows that an increased cardiac filling pressure does not necessarily lead to an increased Vs in fish, but may instead compensate for a reduced cardiac filling time.
Design of a novel cutter for manufacturing helical cutting tools
Authors: Chang S-L , Tseng H-C
Published: May 2005

Owing to the complex geometry of helical cutting tools, several manufacturing processes are required to produce the profile of the cutter and the cutting angles. If the traditional method of manufacture were used, the cost would be frustratingly expensive. In this paper, a novel straight-sided hob cutter design consisting of two curved cutting edges and three straight cutting edges with different pressure angles is proposed. By applying designed rake profile equations of a hob cutter, the principle of coordinate transformation, the theory of differential geometry, and the theory of gearing, a mathematical model of the helical cutting tool is derived. In addition, the cutting angles, the condition of full undercutting, and the width of the top land of the cutter are also studied. The novelty of the design is such that the multiangles of the helical cutting tool can be manufactured in one hobbing process, thereby simplifying the manufacturing process. The results and concepts proposed in the paper will be beneficial as design guidance for tool designers, will enhance the manufacturing processes of helical cutting tools, and will assist tool-related industries in upgrading their technology and competitiveness.
Numerical study on the propulsive performance of a submerged wiggling micromachine in straight conduit
Authors: Uchiyama T , Kikuyama K
Published: May 2005

The propulsive performance of a submerged micromachine wiggling in a straight conduit is numerically analysed. The micromachine, whose geometry is similar to a hydrofoil, is mounted in a straight conduit of width W, and the wiggling motion is expressed by a progressive wave. The flow around the micromachine is simulated by a two-dimensional finite element method. The Reynolds number Re, based on the flow velocity upstream of the micromachine and the micromachine length L, is varied from 1 to 100, while the blockage ratio L/W is independently changed in the range of 0.36 ≤ L/W ≤ 1.25. The flow around the micromachine varies according to the wiggling motion, and it presents complicated behaviour owing to the large-scale eddies. The increment of L/W reduces the minimum pressure on the micromachine surface, while it increases the velocity near the micromachine. The propulsive performance is more affected by L/W at Re = 10 than at Re = 100. When L/W is increased in the case of Re = 10, the thrust force decreases at 0.36 ≤ L/W ≤ 0.81 and increases at L/W ≥ 0.81. The decrement is due to the increase of the skin friction, and the increment is attributable to the change in the pressure distribution. The lift force and the power become larger with L/W. The efficiency takes its minimum value at L/W = 0.81.
The torsional response of rotor systems
Authors: Whalley R , Ebrahimi M , Jamil Z
Published: May 2005

The torsional response of rotor systems comprising bearings, inertia discs, and relatively long, slim shafts is considered. Lumped, finite element and hybrid, distributed-lumped parameter procedures are employed to represent the rotor systems of concern in efforts aimed at increasing accuracy, integrity, and computational efficiency. Rotor, shaft, and bearing elements of arbitrary dimensions, constructed from materials with differing mechanical properties, can be accommodated within the system models formulated. General results for multiple rotor assemblies are derived. Simple computational techniques are employed to obtain the frequency response and time domain characteristics for the models proposed. Analytical validation of the resonance conditions identified is provided. Application studies are presented for purposes of comparison.
Understanding the infiuence of valve timings on controlled autoignition combustion in a four-stroke port fuel injection engine
Authors: Cao Li , Zhao Hua , Jiang Xi , Kalian Navin
Published: May 2005

Controlled autoignition (CAI) combustion, also known as homogeneous charge compression ignition (HCCI), was achieved through the negative valve overlap approach by using small- lift camshafts. Three-dimensional multicycle engine simulations were carried out in order better to understand the effects of variable intake valve timings on the gas exchange process, mixing quality, CAI combustion, and pollutant formation in a four-stroke port fuel injection (PFI) gasoline engine. Full engine cycle simulation, including complete gas exchange and combustion processes, was carried out over several cycles in order to obtain the stable cycle for analysis. The combustion models used in the present study are a modified shell ignition model and a laminar and turbulent characteristic time model, which can take high residual gas fraction into account. After the validation of the model against experimental data, investigations of the effects of variable intake valve timing strategies on the CAI combustion process were carried out. These analyses show that the intake valve opening (IVO) and intake valve closing (IVC) timings have a strong infiuence on the gas exchange and mixing processes in the cylinder, which in turn affect the engine performance and emissions. Symmetric IVO timing relative to exhaust valve closing (EVC) timing tends to produce a more stratified mixture, earlier ignition timing, and localized combustion, and hence higher NO x and lower unburned HC and CO emissions, whereas retarded IVO leads to faster mixing, a more homogeneous mixture, and uniform temperature distribution.
A quasi steady state approach to race car lap simulation in order to understand the effects of racing line and centre of gravity location
Authors: Brayshaw D L , Harrison M F
Published: May 2005

Using an established seven-degree-of-freedom (7DOF) model of an open wheel race car, a new quasi steady state lap simulation method is described. The method is based on optimal control techniques. It produces a GG speed diagram as an interim result, and is shown to have a low computational expenditure when compared with the current transient optimal control method. This paper shows a validation step, reports a case study using the new method, and compares the result with a transient optimal control method. The sensitivity of the optimal line for simulation studies is discussed in terms of a centre of gravity location change. Both simulation methods show improvements in lap time owing to a 6 per cent centre of gravity set-up change. The difference in optimal lines caused by a 6 per cent CG change rearward is shown to be so small that a driver is unlikely to find the information useful. In light of this observation, the computational effort required to generate a new optimal line for each set-up change may be misspent
Uncertainty modelling of a suspension unit
Authors: Goh Y M , Booker J D , McMahon C A
Published: May 2005

Many organizations are increasingly relying on design simulation rather than expensive and time-consuming prototype testing for product evaluation. However, uncertainties in analytical and computational methods need to be understood in order to improve confidence in their use, and models need to be validated. This paper presents a case study of a MacPherson strut automotive suspension analysis, and evaluates the uncertainties in the modelling of this complex dynamic problem using a simplified analytical model and a complex computational model. In both cases, variability in design variables is characterized using probabilistic design methods. As a first step, the model variables are described by assumed datasets, which are collated from several sources such as tolerances specified in drawings, expert opinion, published data, etc. Measurement of the properties of the suspension system components is then performed (spring stiffness, damping coeffcient, etc.), and the statistical parameters so obtained are used in probabilistic calculations for specified time sequences from measured test track road load data. The results are used to accumulate evidence of uncertainties in analytical and computational methods, to correlate predicted results to experimental data for vehicle chassis top mount force, and to derive sensitivity measures. A response surface function is approximated which is useful for parametric studies for new variants of the system studied. Sources of uncertainty in this case study and methods for improving the correlations are then suggested.
Mitigation of biodynamic response to vibratory and blast-induced shock loads using magnetorheological seat suspensions
Authors: Choi Y-T , Wereley N M
Published: May 2005

The mitigation of biodynamic response to vibratory and blast-induced shock loads using a magnetorheological (MR) seat suspension is addressed in this study. To this end, an MR seat suspension model for military vehicles including seated personnel is constructed in terms of a detailed lumped parameter model. The lumped parameter model of the human body consists of four parts: pelvis, upper torso, viscera, and head. From the model, the governing equation of motion of the MR seat suspension considering the human body is derived. Based on this equation, a semi-active nonlinear optimal control algorithm appropriate for the MR seat suspension is developed. The simulated control performance of the MR seat suspension is evaluated under three different excitations of sinusoidal and random vibration and tremendous shock load due to a mine explosion. In addition, the mitigation of injuries to humans due to such a shock load is evaluated and compared with a passive hydraulic seat suspension and a passive MR seat suspension with a constant yield force.
Longitudinal road unevenness with periodic components: Characterization and effects on people in a traversing vehicle and the loading of the pavement
Authors: Kropáč O , Múčka P
Published: May 2005

Firstly, the effect of periodic components (undulation) appearing in the otherwise random longitudinal profile of road on standard indicators of random unevenness is studied. The power spectral density characterized by its parameters, i.e. the unevenness index and waviness, three band variances, and international roughness index are considered. Secondly, a series of simulation examples is given of the response of two planar vehicle models (a passenger car and a truck) traversing along the road with periodic components of longitudinal unevenness. The effects on people sitting in the vehicle and on the loading of the vehicle undercarriage and pavement structure are studied. The wavelengths of undulation and the running speeds that appear as most inconvenient are emphasized
Oxidative Addition Reactions Involving Molybdenum Polyhydrides
Authors: Ito Takashi
Published: May 2005

Versatile reactions of tetrahydridomolybdenum, [MoH4(dppe)2] (1, dppe = Ph2PCH2CH2PPh2), one of the typical polyhydrido complexes, are shown. It releases one or two moles of dihydrogen on irradiation or heating in solution to give a coordinatively unsaturated intermediate {MoH2(dppe)2} (A) and/or {Mo(dppe)2} (B) which reacts with (1) methacrylic esters to cause olefinic C–H bond activation, (2) allyl carboxylates to give an carboxylato-κ2O complex and propene as a result of C–O bond activation, (3) β-diketones and catechols to give chelated diketonato and catecholato derivatives, respectively, (4) cyclic imines and amides to cleave their N–H bonds to give N-acylamido complexes, or finally (5) aryl silanes to give a novel hydrido-silyl complex which has a quinquedentate ligand comprising a P∼P∼Si∼P∼P framework. The last complex was further investigated in view of the reactivity resulting from its unique structure. Most of these reaction products are characterized spectroscopically as well as by X-ray crystallography.
Positronium Annihilation in Fluorinated Benzene Derivatives
Authors: Hirata Kouichi , Kobayashi Yoshinori , Wang Cai-Lin
Published: May 2005

Positron lifetime measurements have been carried out to study formation and annihilation of ortho-positronium (o-Ps) in a series of fluorinated benzene derivatives. The o-Ps lifetimes (τ3) are longer than those expected from Tao’s empirical relationship for hydrocarbons, τ3−1 (ns−1) = 0.061σ0.5, where σ is the surface tension of the liquids in units of mN m−1. It was found that there is a rather good correlation between the o-Ps intensity I3 and the dipole moment for the fluorinated compounds.
Picosecond Energy Transfer at Gold/Electrolyte Interfaces Using Transient Reflecting Grating Method under Surface Plasmon Resonance Condition
Authors: Katayama Kenji , Sawada Tsuguo , Tsuyumoto Isao , Harata Akira
Published: May 2005

The energy transfer dynamics at gold/NaCl aq (0—0.5 M) interfaces was investigated using our recently developed surface plasmon resonance transient reflecting grating (SPR-TRG) method. We focused on two exponential decays in the SPR-TRG signals. The two decays correspond to the relaxation of hot electrons and interfacial heat transfer, respectively. The intensity of each decay changes systematically with increases in the concentration of NaCl, i.e., the former becomes smaller and the latter becomes larger. Considering the relation between the intensity and the dynamics, we concluded that there is some interaction between the hot electrons and the adsorbate on the interface and that the following temperature rise in gold after relaxation of the hot electrons becomes large. This conclusion shows that an ultrafast energy transfer processes by hot electrons exists, and that the process is hindered by the adsorbate. Finally, we discuss the ultrafast energy transfer in relation to the hot electrons and adsorbate on a molecular scale.
Electronic Spectra of Tetrafluorobenzene Cations Produced by Pulsed Glow Discharge in a Supersonic Free Jet
Authors: Nibu Yoshinori , Fujii Noriaki , Shimada Hiroko
Published: May 2005

Cold ions of tetrafluorobenzene isomers were produced by pulsed glow discharge in a supersonic free jet and the electronic spectra due to D2–D0 transitions were observed. The vibrational frequencies of the ions were determined for the ground and electronically excited states through observations of the fluorescence excitation and dispersed fluorescence spectra under collision-free conditions. The vibronic bands observed in the spectra were assigned to totally symmetric vibrations. The difference in the vibrational frequencies between the ion and neutral molecules is very small in spite of the ejection of an electron from the π orbital. A very small frequency change is observed in the electronic excited state of the ions. The frequencies observed for the ions show that the bonding π orbitals are less effective for chemical bonds of the molecules. The electronic spectra of the 1,2,4,5-tetrafluorobenzene cation, whose neutral parent molecule is distorted in the S1 state along the fluorine-wagging normal mode, gave no sign of such a structural change in the electronic excited D2 state.
A Simple Method for Enumeration of Non-Rigid Isomers. An Application of Characteristic Monomials
Authors: Fujita Shinsaku
Published: May 2005

A new and simple procedure for counting isomers derived from non-rigid parent molecules has been developed by the combination of the promolecule concept with the characteristic-monomial method. This procedure has been applied to the enumeration of diphenylmethanes, 2,2-diphenylpropanes, and 2,2-dimethylpropanes, after the characteristic monomial tables for the point groups C2v and C3v have been prepared.
Complex Formation between Cationic Surfactants and Insoluble Drugs
Authors: Iimura Nahoko , Sawada Keiju , Ohashi Yuji , Hirata Hirotaka
Published: May 2005

Water-insoluble drugs, 1-(2,4,6-trihydroxyphenyl)-1-propanone (flopropione) and 4-chloro-m-cresol, formed crystalline complexes with cationic surfactants, such as hexadecyl-, tetradecyl-, dodecyl-, and decyltrimethylammonium bromides, in a solubilized solution system when the solutions were kept at temperatures lower than 288 K and the solubilities of the crystalline complexes were significantly greater than those of only the drugs. Moreover, the complex crystals were more thermostable than only the drugs. The crystal structures of three complexes (4-chloro-m-cresol and hexadecyltrimethylammonium bromide (I), flopropione and tetradecyltrimethylammonium bromide (II), and flopropione and hexadecyltrimethylammonium bromide (III)) were analyzed by the X-ray diffraction method. These complexes were composed of the surfactant and drug molecules in a ratio of 1 : 1 (III) or 2 : 1 (I or II). In each crystal, the drug molecule was sandwiched by the alkyl chains of the surfactant molecules; the hydroxy group of the drug made a hydrogen bond with the bromide anion. Those structural characteristics were similar to those of the complexes between the surfactants and aromatic compounds. Such intermolecular interactions were responsible for the increased solubility and thermal stability of the complex.
Hydrogen Insertion on Alkali Metal Decamolybdates by Spillover
Authors: Eda Kazuo , Ito Takayoshi , Sotani Noriyuki
Published: May 2005

A hydrogen-insertion process by spillover on alkali metal decamolybdates was investigated in situ. Hydrogens were inserted, leading to the formation of OH groups. The insertion induced dehydration (release of the crystallization water of the molybdates), which resulted in distortions in the Mo–O framework. The dehydration behaviour varied depending on the kinds of decamolybdates or the manners in which the decamolybdates have crystallization-water species. Furthermore, structural changes of the resultant compounds with heat-treatments in N2 were also investigated. It was then confirmed that these compounds could become starting materials, leading to the formation of alkali metal molybdenum bronzes at lower temperatures, ca. 200 K below those used in ordinary syntheses.
The Response Behavior of PAA–B12C4 Electrode to Li+, Mg2+, and Ca2+ in Some Aprotic Solvents and Its Thermodynamic Application
Authors: Nakamura Toshio , Makino Kaori , Yanagisawa Masashi , Miyasaka Takahiro
Published: May 2005

The potentiometric response behavior of an electrode, which consists of a non-plasticized carboxyl-modified polyacrylamide polymer (PAA) coupled to benzo-12-crown-4 (PAA–B12C4) to Li+, Mg2+, and Ca2+ in such aprotic solvents as acetonitrile (AN), propylene carbonate (PC), and γ-butyrolactone (GBL), were examined. The electrode showed a Nernstian response to Li+ and Ca2+ in AN, and Li+, Mg2+, and Ca2+ in PC and a near-Nernstian response to Mg2+ in GBL. From the response to Ca2+ it could be confirmed that the membrane potential was mainly established at the polymer membrane–solution interface. The electrode was applied to a study of their complexing with such other basic aprotic solvent molecules (D) as N,N-dimethylformamide, dimethyl sulfoxide, and hexamethylphosphoric triamide. The successive complex formation constants (βi) and Gibbs energies of transfer (ΔGtr(j)) of Li+ in AN and Mg2+ in PC in relation to such D were obtained.
Efficient Oxygen Consumption by Hydroxo(protoporphyrinato)iron(III) Adsorbed on Magnesium Oxide Powder in the Presence of Cysteine
Authors: Noda Hiroyuki , Ohya Hiroaki , Kamada Hitoshi
Published: May 2005

The oxygen reduction ability of hydroxo(protoporphyrinato)iron(III) (HEM) adsorbed on powdery supports in the presence of cysteine was investigated using a Clark-type oxygen electrode. All of the oxygen consumption rates for HEM adsorbed on powdery supports having different surface basicity values (CaO > MgO > TiO2) were larger than the cases of HEM in aqueous solution and of MgO suspension without HEM in the presence of cysteine. Maximum oxygen consumption rate was obtained in the case of the HEM/MgO system. This result suggests that the optimum surface basicity of powdery support is necessary to achieve efficient oxygen consumption. From the measurements for ESR and Raman spectra of the HEM/MgO system, we confirmed the change for the iron valence of HEM from III to II in the presence of cysteine. The production of cystine through the dimerization of cysteinyl radicals in the reaction mixture was also confirmed by the measurements of ESR spectra and capillary electrophoresis (CE). A possible mechanism for accelerating the oxygen consumption rate of the HEM/MgO system in the presence of cysteine is discussed, concerning the effect of the catalytic ability of MgO on the turnovers of iron valence.
Room-Temperature Metallation of 2-Substituted 1,3-Dithiane Derivatives and Subsequent Coupling with 2,3-Disubstituted Oxiranes
Authors: Ide Mitsuaki , Nakata Masaya
Published: May 2005

2-Substituted 1,3-dithiane derivatives, (S)-1-(t-butyldiphenylsiloxy)-2-(1,3-dithian-2-yl)propane (9), (S)-1-(t-butyldimethylsiloxy)-2-(1,3-dithian-2-yl)propane, 1-(t-butyldiphenylsiloxy)-2-(1,3-dithian-2-yl)-2-methylpropane, and 1,2-bis(t-butyldiphenylsiloxy)-3-(1,3-dithian-2-yl)propane, were subjected to lithiation in THF with n-BuLi at room temperature (r.t.); the resulting anions reacted with 2,3-disubstituted oxirane, trans-2-methyl-3-(triphenylmethoxymethyl)oxirane (22), at r.t., giving the coupling products in satisfactory yield. On the other hand, the lithium salt formed in ether from (S)-2-(1,3-dithian-2-yl)-1-(4-methoxybenzyloxy)propane with n-BuLi at r.t. reacted with 22 at r.t. in the presence of hexamethylphosphoric triamide to afford the coupling product in moderate yield. In addition, a mixed organometallic reagent, n-BuLi / Bu2Mg, was found to be an effective metallation reagent for 9 and the resulting anion reacted with 22 to afford the coupling product in good yield.
Practical Synthesis of Four Stereoisomers of 6-(t-Butyldiphenylsiloxy)-3,5-dimethyl-1-(triphenylmethoxy)hexane-2,4-diol via Dithiane Coupling with Oxirane
Authors: Ide Mitsuaki , Tsunashima Keiji , Nakata Masaya
Published: May 2005

The anion derived from 2-substituted 1,3-dithiane derivative, (S)-2-[2-(t-butyldiphenylsiloxy)-1-methylethyl]-1,3-dithiane, with n-BuLi at room temperature (r.t.) in THF was subjected to coupling with 2,3-disubstituted oxirane, (2S,3S)- or (2S,3R)-2,3-epoxy-1-(triphenylmethoxy)butane, at r.t., giving the coupling products in satisfactory yield. These coupling products were subjected to de-dithioacetalization, and the resulting carbonyl compounds were stereoselectively reduced to afford four stereoisomers of 6-(t-butyldiphenylsiloxy)-3,5-dimethyl-1-(triphenylmethoxy)hexane-2,4-diol.
Oxidation of 2-Substituted Cycloalkanones with Cerium(IV) Sulfate Tetrahydrate in Alcohols and Acetic Acid
Authors: He Liangyou , Horiuchi C Akira
Published: May 2005

The reaction of 2-substituted cycloalkanones with cerium(IV) sulfate tetrahydrate (CS) in alcohols and acetic acid gave the corresponding alkyl esters of oxo acids (80—96%) and oxo acids (78—96%), respectively, by oxidative cleavage of the C(R)–C=O bond. In the case of 2-iodocycloalkanones in methanol, the dimethyl ester was obtained in good yield. A treatment of 5α-cholestan-3-one with CS in methanol produced 2-acetal 3-ester of 2,3-seco derivative in good yield. The effects of cerium(IV) and copper(II) salts are also discussed.
Syntheses and Properties of Novel Liquid Crystals Containing a Trifluoromethylamino Group
Authors: Kanie Kiyoshi , Mizuno Katsuya , Kuroboshi Manabu , Takehara Sadao , Hiyama Tamejiro
Published: May 2005

Liquid crystals (LCs) containing a trifluoromethylamino group are prepared by the cross-coupling reaction of p-bromo-substituted-(hetero)aryl(trifluoromethyl)amines that are derived from the corresponding dithiocarbamates through oxidative desulfurization–fluorination. The novel LCs are shown to exhibit mainly a smectic phase over a wide range of temperatures. Their electro-optical properties as a component of nematic LCs are compared with those of the corresponding methylamines.