bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal structure and solution characterization of the activation domain of human methionine synthase
Authors: Wolthers Kirsten R. , Toogood Helen S. , Jowitt Thomas A. , Marshall Ker R. , Leys David , Scrutton Nigel S.
Published: December 2006

Human methionine synthase (hMS) is a multidomain cobalamin‐dependent enzyme that catalyses the conversion of homocysteine to methionine by methyl group transfer. We report here the 1.6 Å crystal structure of the C‐terminal activation domain of hMS. The structure is C‐shaped with the core comprising mixed α and β regions, dominated by a twisted antiparallel β sheet with a β‐meander region. These features, including the positions of the active‐site residues, are similar to the activation domain of Escherichia coli cobalamin‐dependent MS (MetH). Structural and solution studies suggest a small proportion of hMS activation domain exists in a dimeric form, which contrasts with the monomeric form of the E. coli homologue. Fluorescence studies show that human activation domain interacts with the FMN‐binding domain of human methionine synthase reductase (hMSR). This interaction is enhanced in the presence of S‐adenosyl‐methionine. Binding of the D963E/K1071N mutant activation domain to the FMN domain of MSR is weaker than with wild‐type activation domain. This suggests that one or both of the residues D963 and K1071 are important in partner binding. Key differences in the sequences and structures of hMS and MetH activation domains are recognized and include a major reorientation of an extended 310‐containing loop in the human protein. This structural alteration might reflect differences in their respective reactivation complexes and/or potential for dimer formation. The reported structure is a component of the multidomain hMS : MSR complex, and represents an important step in understanding the impact of clinical mutations and polymorphisms in this key electron transfer complex.
Forest Structure and Primary Productivity in a Bornean Heath Forest
Authors: Miyamoto Kazuki , Rahajoe Joeni S. , Kohyama Takashi , Mirmanto Edi
Published: December 2006

Aboveground forest structure, biomass, and primary productivity in a tropical heath forest in Central Kalimantan (Indonesian Borneo) were examined using data from 1‐ha plots and stand‐level allometric equations developed from harvested tree samples. The study site experienced a severe drought in 1997–1998 associated with the El Niño Southern Oscillation event. The drought effect on heath forest productivity was also assessed by evaluating changes in wood mass increment rates. Allometric relationships suggested that heath forest trees had leaves with smaller specific leaf area (SLA), and large heath forest trees allocate more to leaf mass compared to mixed dipterocarp forest trees. Aboveground biomass (for trees ≥ 4.8 cm DBH) in two 1‐ha plots, P1 and P4, totaled 244.8 and 232.0 Mg/ha. Aboveground wood mass increment rate was –0.1 and 4.7 Mg/ha/yr in P1 and P4 during the drought period (from February to August 1998), while it quickly recovered to 8.1 and 8.5 Mg/ha/yr during the post‐drought period (from August 1998 to August 1999 for P1 and from August 1998 to November 1999 for P4). This suggests a severe impact of the drought on heath forest productivity. Leaf characteristics of heath forest such as small SLA and long‐lived leaves probably play a significant role in effective assimilation and maintenance of heath forest productivity under stressful conditions.
Spatial and Temporal Patterns of Abundance and Diversity of an East African Leaf Litter Amphibian Fauna
Authors: Gardner Toby A. , Fitzherbert Emily B. , Drewes Robert C. , Howell Kim M. , Caro Tim
Published: December 2006

We present data on sample richness, relative abundance, and community structure of a leaf litter amphibian assemblage from globally important miombo‐mopane woodlands characteristic of western Tanzania. We describe patterns of diversity across major habitat types and between different seasons from an annual pitfall‐trapping campaign. We recorded 28 species of amphibians, which is significantly higher than existing richness estimates for other miombo woodland sites elsewhere in sub‐Saharan Africa. We found that cultivation of native habitat reduces frog diversity, a conclusion that has important implications in light of the rapid conversion of miombo woodland for agriculture and fuel‐wood across much of southern and central Africa. Many species showed strongly ansynchronized patterns of seasonality in relative abundance, which has significant implications for the establishment of successful monitoring programs and biodiversity surveys. These conclusions emphasize the importance of stratified long‐term sampling in biodiversity studies and demonstrate that superficial levels of sampling effort can lead to erroneous conclusions regarding patterns of diversity in amphibian communities. The relatively poor focus on herpetofaunal research in African miombo‐mopane woodland is out of proportion to its ecological and conservation significance.
Bat Diversity and Movement in an Agricultural Landscape in Matiguás, Nicaragua
Authors: Medina Arnulfo , Harvey Celia A. , Merlo Dalia Sánchez , Vílchez Sergio , Hernández Blas
Published: December 2006

Although agriculture dominates much of Central America, little is known about the bat assemblages that occur within agricultural landscapes and how bats use different types of tree cover within these landscapes. Using mist‐nets and a mark‐recapture protocol, we compared bat diversity and movement across six types of tree cover within an agricultural landscape in central Nicaragua. The tree cover types surveyed included secondary forests, riparian forests, forest fallows, live fences, pastures with high tree cover and pastures with low tree cover. We captured a total of 3084 bats of 39 species, including two new species records for the country (Lonchorhina aurita and Molossops greenhalli). Of these, 2970 bats and 27 species were in the Phyllostomidae family. There were significant differences in mean species density, abundance and evenness of phyllostomid bats across the different types of tree cover, but not in bat diversity. Riparian forests had the highest mean species density and bat abundance per plot. In contrast, mean bat abundance and species density were lowest in pastures with low tree cover. Of the 1947 phyllostomid bats marked, a total of 64 bats of eight species were recaptured. The average linear distance between extra‐site recaptures was 2227 m (± 228 SE) and the maximum distance was 10.6 km. Bats were recorded moving between almost all types of tree cover, and especially to and from riparian forests. Our study suggests that agricultural landscapes retaining a heterogeneous tree cover may maintain a diverse bat assemblage, and that bats visit and use a variety of tree cover types within the agricultural matrix.
Phosphorus Limits Tropical Rain Forest Litter Fauna
Authors: McGlynn Terrence P. , Salinas Daniel J. , Dunn Robert R. , Wood Tana E. , Lawrence Deborah , Clark Deborah A.
Published: December 2006

The stoichiometry of resources may explain bottom‐up regulation of higher trophic levels. We tested the effects of soil and litter nutrient stoichiometry on the invertebrate litter fauna of a Costa Rican tropical rain forest. Animal densities were estimated from 15 sites across a phosphorus gradient. The density of the invertebrate litter fauna varied considerably, and was strongly tied to soil and litter phosphorus concentrations. An increase in phosphorus concentrations corresponded with an equally proportionate increase in animal densities. Natural variation in nutrient levels can thus serve as a predictor of density in a highly diverse tropical animal community.
Frugivory by Small Vertebrates Within a Deforested, Dry Tropical Region of Central America
Authors: Griscom Heather P. , Kalko Elisabeth K.V. , Ashton Mark S.
Published: December 2006

Small vertebrates were inventoried within three habitat types in a degraded dry forest region of Panama. Animals were classified as frugivorous if they were observed foraging on fruit or if fecal samples contained mostly or exclusively seeds. Overall, we found that eight bat species and 21 bird species consumed fruit. The greatest numbers of birds were observed within live fences and bird species richness was greatest within riparian forests. Bat assemblages were not significantly different between habitats. The implication is that ecosystem services such as seed dispersal may still be functional in this landscape.
Resource Partitioning in Sympatric Cynopterus bats in Lowland Tropical Rain Forest, Thailand
Authors: Bumrungsri Sara , Leelapaibul Watcharee , Racey Paul A.
Published: December 2006

Diet and habitat use of the closely related and size‐overlapping sympatric Cynopterus brachyotis and C. sphinx were established in lowland dry evergreen forest, Thailand, between March 1998 and March 2000. Feces from netted bats were analyzed, and the recapture rate determined. Although both species share a set of food plants, and fruits from early successional forest contribute about half of their diet, C. brachyotis, the smaller of the two species, ate a significantly greater proportion of fruits from early successional forest than C. sphinx. The latter ate a significantly greater proportion of fruit species in larger size classes. More C. brachyotis were captured in early successional forest in almost every month, while C. sphinx is more common in old‐growth forest. However, the capture rate of C. sphinx increased in early successional forest in the mid‐dry season when its preferred fruits become available. The recapture rate of C. brachyotis in early successional forest was significantly higher than that of C. sphinx, and the reverse situation was observed in old‐growth forest. Male C. sphinx had a significantly higher recapture rate in early successional forest than females. Fruit size and habitat use are the major determinants of resource partitioning between these size‐overlapping congeners.
Successful Treatment by Double Filtrate Plasmapheresis in a Pregnant Woman With the Rare P Blood Group and a History of Multiple Early Miscarriages
Authors: Hanafusa Norio , Noiri Eisei , Yamashita Takahiro , Kondo Yasushi , Suzuki Makoto , Watanabe Yasuyuki , Kanai Takao , Miyashita Emiko , Tsuno Nelson H , Fujii Tomoyuki , Kozuma Shiro , Takahashi Koki , Taketani Yuji , Nakao Akihide , Fujita Toshiro
Published: December 2006

Abstract:  Individuals of P type, a rare blood group, have anti‐PP1Pk antibody in their serum, which causes spontaneous abortion in the early stages. We report a patient of p type suffering from multiple spontaneous abortions. We also review previously reported cases from published work. A 36‐year‐old woman (gravida 2, para 0) was referred to our hospital because of habitual abortion. At the third pregnancy, we started double filtration plasmapheresis (DFPP) from 7 weeks 3 days to remove the antibody. We attained rapid decline in the titer and normal fetal growth. Gradual tapering of the DFPP frequency caused neither a rebound of the titer nor growth retardation. During the course, she experienced only one episode of catheter infection as an adverse effect. At 37 weeks 3 days, after 57 DFPP repetitions, a 2496 g girl was delivered by cesarean section. The infant suffered neither from anemia nor from severe jaundice. A review of previous reports indicates that the titer of the pathogenic antibody should be kept as low as possible from the early gestational stage in P‐incompatible habitual abortion cases, otherwise the case typically comes to an unfavorable outcome. Plasma exchanges with fresh plasma potentially induce contamination by either known or unknown pathogens. Such risks are reduced using DFPP because the volume of albumin solution that replaces fresh plasma is less than that by plasma exchange. The present case, along with previous reports, shows that DFPP is an effective therapy for treating P‐incompatible pregnancy.
Ectopic Calcification as Abnormal Biomineralization
Authors: Kazama Junichiro James , Amizuka Norio , Fukagawa Masafumi
Published: December 2006

Abstract:  Vascular calcification is observed frequently in hemodialysis patients. The guidelines for kidney disease outcomes quality initiative recommend a strict control of serum calcium and phosphorus concentrations. Calcium–phosphorus product in extracellular fluids is almost at an oversaturation level in dialysis patients and in healthy individuals as well, but crystallization of hydroxyapatite does not occur in healthy individuals. Presumably, some systemic mechanism that has yet to be defined works to block the formation of hydroxyapatite crystals in healthy individuals, whereas in dialysis patients this defense mechanism is disrupted in hard tissues, leading to progressive biomineralization. Matrix vesicles released from specialized mesenchymal cells such as osteoblasts, play a central role in disrupting the putative defense mechanism against calcification. Matrix vesicles are internally in a highly favorable environment for progressive calcification, and essentially a nidus for hydroxyapatite crystal nucleation and its external growth through disruption of the defense mechanism. Osteoblastic cells release matrix vesicles that form initial crystal hydroxyapatite by condensation of phosphate and calcium, referred to as matrix vesicle calcification. Hydroxyapatite crystals break through vesicular membranes to reach a nearby collagen fiber network and form a continuous layer of calcified bone matrix. Thereafter follows the formation of additive bone matrix by osteoblasts and the advance of the calcification front. Therefore, ectopic calcification arises mechanistically from: (i) disruption of a systemic defense mechanism against calcification; and (ii) appearance of osteoblast‐like cells in hard tissues that normally are localized in soft tissues. Abnormal accumulation of calcium/inorganic phosphate in dialysis patients is accounted for by the former disruption of systemic defense mechanism against calcification, and arterial calcification in dialysis patients by the latter osteoblast‐like cells transformed from tunica media or vascular smooth‐muscle cells.
Improved Coronary Vasodilatatory Capacity by H.E.L.P. Apheresis: Comparing Initial and Chronic Treatment
Authors: Mellwig Klaus P , Van Buuren Frank , Schmidt Henning K , Wielepp Peter , Burchert Wolfgang , Horstkotte Dieter
Published: December 2006

Abstract: Hypercholesterolemia impairs endothelial function and subsequently decreases coronary vasodilatatory capacity. We examined the quantitative effects of one single LDL apheresis on vasodilatatory capacity. Using N‐13 ammonia as a tracer for dynamic quantitative positron emission tomography (PET), mean myocardial perfusion measurements were carried out before and 20 h later after LDL apheresis, both under resting conditions and after pharmacological vasodilatation with dipyridamole. LDL apheresis was carried out using the heparin induced extracorporeal LDL precipitation (H.E.L.P.) procedure. We examined 47 patients (12 women and 35 men), with angiographically‐proven coronary artery disease. All of them suffered from hypercholesterolemia. Of the patients, 35 received a chronic weekly H.E.L.P. procedure (group A), while H.E.L.P. procedure treatment was started for the first time in 12 patients, who were subsequently enrolled in a chronic apheresis program (group B). H.E.L.P. apheresis was combined with cholesterol lowering drugs in all patients. Both groups underwent positron emission tomography twice (prior to LDL apheresis and 20 h later). In group A, LDL cholesterol levels decreased from 175 ± 50 mg/dL to 60 ± 21 mg/dL immediately after H.E.L.P. (77 ± 25 mg/dL before the second PET). Corresponding values for fibrinogen levels were 287 ± 75 mg/dL to 102 ± 29 mg/dL (155 ± 52 mg/dL), minimal coronary resistance dropped from 0.56 ± 0.20 to 0.44 ± 0.17 mm Hg × 100 g × min/mL (P < 0.0001). Plasma viscosity decreased by 7.8%. In group B, LDL cholesterol decreased from 187 ± 45 mg/dL to 75 ± 27 mg/dL (85 ± 29 mg/dL) and fibrinogen from 348 ± 65 mg/dL to 126 ± 38 mg/dL (168 ± 45 mg/dL). Minimal coronary resistance was reduced from 0.61 ± 0.23 to 0.53 ± 0.19 mm Hg × 100 g × min/mL (P < 0.01). Plasma viscosity was observed to decrease by 7.6%. The strong LDL drop in patients under chronic H.E.L.P. treatment has a significant impact on coronary vasodilatatory capacity within 20 h leading to an improved overall cardiac perfusion. Nearly the same effect can be seen in patients after their first H.E.L.P. treatment.
The isocurvature fraction after WMAP 3-yr data
Authors: Trotta Roberto
Published: December 2006

I revisit the question of the adiabaticity of initial conditions for cosmological perturbations in view of the 3-yr Wilkinson Microwave Anisotropy Probe (WMAP) data. I focus on the simplest alternative to purely adiabatic conditions, namely a superposition of the adiabatic mode and one of the three possible isocurvature modes, with the same spectral index as the adiabatic component.

I discuss findings in terms of posterior bounds on the isocurvature fraction and Bayesian model selection. The Bayes factor (models likelihood ratio) and the effective Bayesian complexity are computed for several prior ranges for the isocurvature content. I find that the cold dark matter isocurvature fraction is now constrained to be less than about 10 per cent, while the fraction in either the neutrino entropy or velocity mode is below about 20 per cent. Model comparison strongly disfavours mixed models that allow for isocurvature fractions larger than unity, while current data do not allow one to distinguish between a purely adiabatic model and models with a moderate (i.e. below about 10 per cent) isocurvature contribution.

The conclusion is that purely adiabatic conditions are strongly favoured from a model selection perspective. This is expected to apply in even stronger terms to more complicated superpositions of isocurvature contributions.
Perceptions of veterinarians and clients to expressions of clinical uncertainty
Authors: Mellanby R. J. , Crisp J. , De Palma G. , Spratt D. P. , Urwin D. , Wright M. J. H. , Zago S.
Published: December 2006

Objectives: The aim of this study was to explore the attitudes of veterinarians and clients towards expressions of clinical uncertainty.

Methods: Questionnaires that assessed the respondent’s attitudes towards expressions of clinical uncertainty were completed by clients at six small animal practices. In addition, questionnaires that evaluated what veterinarians thought their client’s attitudes would be towards expressions of clinical uncertainty were completed by veterinarians. The responses from clients and veterinarians were statistically compared.

Results: Veterinarians significantly underestimated the desire of clients to be told about uncertainties in treatment and significantly overestimated how the expression of uncertainty would generally reduce client confidence. Veterinarians significantly overestimated the loss of client confidence resulting from saying “I am not sure about this” and from asking a nurse for advice. Both clients and veterinarians considered that verbal expressions of uncertainty would lead to a greater reduction in client confidence than behavioural expressions of uncertainty.

Clinical Significance: This study suggests that most clients want to be told about their veterinarian’s clinical uncertainties, and how this uncertainty is expressed can markedly influence client confidence.
KILLER WHALES AND MARINE MAMMAL TRENDS IN THE NORTH PACIFIC—A RE‐EXAMINATION OF EVIDENCE FOR SEQUENTIAL MEGAFAUNA COLLAPSE AND THE PREY‐SWITCHING HYPOTHESIS
Authors: Wade Paul R. , Burkanov Vladimir N. , Dahlheim Marilyn E. , Friday Nancy A. , Fritz Lowell W. , Loughlin Thomas R. , Mizroch Sally A. , Muto Marcia M. , Rice Dale W. , Barrett‐Lennard Lance G. , Black Nancy A. , Burdin Alexander M. , Calambokidis John , Cerchio Sal , Ford John K. B. , Jacobsen Jeff K. , Matkin Craig O. , Matkin Dena R. , Mehta Amee V. , Small Robert J. , Straley Janice M. , McCluskey Shannon M. , VanBlaricom Glenn R. , Clapham Phillip J.
Published: December 2006

Abstract

Springeret al. (2003)contend that sequential declines occurred in North Pacific populations of harbor and fur seals, Steller sea lions, and sea otters. They hypothesize that these were due to increased predation by killer whales, when industrial whaling's removal of large whales as a supposed primary food source precipitated a prey switch. Using a regional approach, we reexamined whale catch data, killer whale predation observations, and the current biomass and trends of potential prey, and found little support for the prey‐switching hypothesis. Large whale biomass in the Bering Sea did not decline as much as suggested by Springeret al., and much of the reduction occurred 50–100 yr ago, well before the declines of pinnipeds and sea otters began; thus, the need to switch prey starting in the 1970s is doubtful. With the sole exception that the sea otter decline followed the decline of pinnipeds, the reported declines were not in fact sequential. Given this, it is unlikely that a sequential megafaunal collapse from whales to sea otters occurred. The spatial and temporal patterns of pinniped and sea otter population trends are more complex than Springeret al. suggest, and are often inconsistent with their hypothesis. Populations remained stable or increased in many areas, despite extensive historical whaling and high killer whale abundance. Furthermore, observed killer whale predation has largely involved pinnipeds and small cetaceans; there is little evidence that large whales were ever a major prey item in high latitudes. Small cetaceans (ignored by Springeret al.) were likely abundant throughout the period. Overall, we suggest that the Springeret al. hypothesis represents a misleading and simplistic view of events and trophic relationships within this complex marine ecosystem.
Yogācāra Strategies against Realism: Appearances (ākti) and Metaphors (upacāra)
Authors: Gold Jonathan C.
Published: December 2006

This paper describes and elucidates two philosophical parallels: the first between two early Yogācāra Buddhist positions, and the second between these positions and a contemporary discussion in analytic philosophy. The two Yogācāra positions are (1) that reality is a mere appearance (ākti); and (2) that all language is metaphorical (upacāra). First, the distinctive Yogācāra belief in the reality of mere appearances is clarified by carefully distinguishing the terminological uses in Vasubandhu's Three Natures Exposition (Trisvabhāvanirdeśa) from the terms used to make parallel conceptual moves in a very similar passage from the Ornament to the Mahāyāna Sūtras (Mahāyānasūtrāla kāra). Second, the theory of language advocated by Sthiramati in his commentary to Vasubandhu's Thirty Verses (Triśikākārikā) is explained as a counter to arguments that Yogācāra non‐realism is self‐defeating. This latter view shows how Yogācāra may be fruitfully brought into dialogue with Hilary Putnam's famous antiskeptical Brain‐in‐a‐Vat argument. The paper finds basic accord within Vasubandhu's ontology and theory of reference, and shows how they represent a new, coherent Yogācāra response to Putnam's realist challenge.
Caribbean Children's Geographies: A Case Study of Jamaica
Authors: Ferguson Therese
Published: December 2006

Understanding children's lives within the various spaces, places, and environments they inhabit is critical to making their worlds safer, facilitating their participatory roles in society, and implementing policies relevant to their realities. While the children's geographies scholarship is rapidly growing, much of the research is still centred on children in the ‘West’, with less focus on those in developing countries. Within the Third World, the Caribbean itself is slightly marginalised. This article uses the island‐nation of Jamaica as a case study within the Caribbean region, examining some of the areas of interest in research on children's environments, and reflecting upon progress made in the range of methodological and theoretical approaches brought to the research agenda. It suggests prospective directions for future research to further a critical approach to this expanding field, both within Jamaica and the wider region. It ends by briefly raising some ethical issues for consideration, arising from advancing a research agenda with children at its fore.
ENACTMENTS IN THE COUNTERTRANSFERENCE: WITH SPECIAL REFERENCE TO RESCUE FANTASIES WITH HYSTERICAL PATIENTS
Authors: Gerrard Jackie
Published: December 2006

abstract  This paper describes enactments in the countertransference – spanning fantasies, actions, words and sexual responses to patients. It will explore the origins and reverberations of the analyst’s enactments in an effort to understand whether they have obstructed progress or created special moments in the therapy where shifts in the patients’ inner world, or further understanding on the part of the analyst could be created.

Clinical vignettes will be used from work with several patients, although the analyst will focus mainly on work with patients who present with hysterical personality. The paper is an endeavour to tease out what, if any, differences there may be in working with hysterical patients, as opposed to patients with other personality types, in the nature of countertransference enactments. The author examines the role of rescue fantasies in the c reation of an enactment.
VISUALIZING THE MIND: LOOKING AT TITIAN’S ‘THE FLAYING OF MARSYAS’
Authors: Hart Melanie
Published: December 2006

abstract  This painting prompted me to wonder whether it is possible to find the capacities and structures of the mind, as described by psychoanalysis, represented unconsciously in visual form. I explain why this exceptional painting seems to be one worth exploring for this purpose and, although there are myriad ways of approaching such a rich work of art, lay particular stress on its abstract, structural aspects. Doing this seems to reveal that Titian would have had no difficulty in understanding psychoanalytic formulations about mental structure had anyone been able to describe them to him verbally. Perhaps the human mind records its own activity, and understands itself, at a depth we have not understood.
Survey trends of North American shorebirds: population declines or shifting distributions?
Authors: Bart Jonathan , Brown Stephen , Harrington Brian , I. Guy Morrison R.
Published: December 2006

We analyzed data from two surveys of fall migrating shorebirds in central and eastern North America to estimate annual trends in means per survey and to determine whether trends indicate a change in population size or might have been caused by other factors. The analysis showed a broad decline in means per survey in Atlantic Canada and the northeastern United States (North Atlantic region). For example, 9 of 9 significant trends in this region were <1 (P=0.004), and the mean, annual rate of change among 30 species was 0.9783, a decline of −2.17% per year (P<0.001). Trends in the midwestern United States (Midwest region) showed no clear pattern. The mean among 29 species was 1.0090 (P=0.35). Only 4 of the trends were significant. Several hypotheses were evaluated to identify causes of the declining means per survey in the North Atlantic region. The most likely hypothesis appears to be a decline in the breeding populations that supply migrants to the North Atlantic region, but a change in movements, for example passing through the region more quickly in recent years, cannot be excluded as an explanation. Further surveys of arctic breeding areas coupled with analysis of long‐term survey data from western North America would be helpful in determining whether the declines found in this analysis are also occurring in other areas.
A Study of On-Line and Off-Line Turbine Washing to Optimize the Operation of a Gas Turbine
Authors: Boyce Meherwan P. , Gonzalez Francisco
Published: December 2006

This paper highlights the procedure followed in order to establish an effective on-line and off line water wash program on a fleet of 36 small industrial turbines. To determine the efficacy of water washing, a program of tests under controlled conditions was organized. With proper condition monitoring techniques, a set of tests were developed in order to identify the proper water wash frequency and the dissolving agent used to water wash. The goal of the water wash program is to maximize turbine power, and efficiency, while minimizing maintenance labor, and material. The gas turbine compressor isentropic efficiency, the overall heat rate, and the overall thermal efficiency were used to compare the tests and evaluate the performance of different water wash frequencies and solvents. 8760 points defined each test as the data were taken over a 1yr time period, at a 1h interval.
Pool Boiling Using Thin Enhanced Structures Under Top-Confined Conditions
Authors: Ghiu Camil-Daniel , Joshi Yogendra K.
Published: December 2006

An experimental study of pool boiling using enhanced structures under top-confined conditions was conducted with a dielectric fluorocarbon liquid (PF 5060). The single layer enhanced structures studied were fabricated in copper and quartz, had an overall size of 10×10mm2, and were 1mm thick. The parameters investigated in this study were the heat flux (0.8-34W∕cm2) and the top space S(0-13mm). High-speed visualizations were performed to elucidate the liquid/vapor flow in the space above the structure. The enhancement observed for plain surfaces in the low heat fluxes regime is not present for the present enhanced structure. On the other hand, the maximum heat flux for a prescribed 85°C surface temperature limit increased with the increase of the top spacing, similar to the plain surfaces case. Two characteristic regimes of pool boiling have been identified and described: isolated flattened bubbles regime and coalesced bubbles regime.
Heat Transfer and Wall Heat Flux Partitioning During Subcooled Flow Nucleate Boiling—A Review
Authors: Warrier Gopinath R. , Dhir Vijay K.
Published: December 2006

In this paper we provide a review of heat transfer and wall heat flux partitioning models/correlations applicable to subcooled forced flow nucleate boiling. Details of both empirical and mechanistic models that have been proposed in the literature are provided. A comparison of the experimental data with predictions from selected models is also included.
Pool Boiling Experiments on Multiwalled Carbon Nanotube (MWCNT) Forests
Authors: Ahn Hee Seok , Sinha Nipun , Zhang Mei , Banerjee Debjyoti , Fang Shaoli , Baughman Ray H.
Published: December 2006

In this study, two silicon wafer substrates were coated with vertically aligned multiwalled carbon nanotubes (MWCNT) “forests” and were used for pool boiling studies. The MWCNT forests (9 and 25μm in height) were synthesized on the silicon wafer substrates using chemical vapor deposition (CVD) process. The substrates were clamped on a cylindrical copper block with embedded cartridge heaters. The heat flux was measured using sheathed K-type thermocouples, which were placed inside the cylindrical copper block. Pool boiling experiments using refrigerant PF-5060 as the working liquid were conducted to obtain the pool “boiling curve.” The experiments were conducted in nucleate and film boiling regimes to investigate the effect of MWCNT height on pool boiling performance. Reference (control) experiments were also performed with an atomically smooth bare silicon wafer (without MWCNT coating). The results show that the MWCNT forests enhanced critical heat flux (CHF) by 25-28% compared to control experiments. For the film boiling regime, Type-B MWCNT (25μm in height) yields 57% higher heat flux at Leidenfrost point (film boiling regime) compared to control experiments. However, for the Type-A MWCNT (9μm in height) the film boiling heat flux values are nearly identical to the values obtained for the control experiments performed on bare silicon.
Three-Dimensional Modeling and Simulation of a Falling Electronic Device
Authors: Shan Hua , Su Jianzhong , Zhu Jiansen , Xu Leon
Published: December 2006

This article focuses on a realistic mathematical model for multiple impacts of a rigid body to a viscoelastic ground and its comparison to theoretic results. The methodology is used to study impact on an electronic device. When an electronic device drops to the floor at an uneven level, the rapid successions of impact sequence are important for their shock response to internal structure of the devices. A three-dimensional, continuous contact, computational impact model has been developed to simulate a sequence of multiple impacts of a falling rigid body with the ground. The model simulates the impact procedure explicitly and thus is capable of providing detailed information regarding impact load, impact contact surface, and the status of the body during the impact. For the purposes of model verification, we demonstrate the numerical simulation of a falling rod problem, in which the numerical results are in good agreement with the analytic solutions based on discrete contact dynamics impact models. It is indicated by the numerical experiments that simultaneous impacts occurred to multiple locations of the body and that subsequent impacts might be larger than initial ones due to different angles of impact. The differential equation-based computational model is shown to be realistic and efficient in simulating impact sequence and laid a foundation for detailed finite element analysis of the interior impact response of an electronic device.
Nonlinear Dynamics and Control of an Ideal/Nonideal Load Transportation System With Periodic Coefficients
Authors: Peruzzi N. J. , Balthazar J. M. , Pontes B. R. , Brasil R. M. L. R. F.
Published: December 2006

In this paper, a loads transportation system in platforms or suspended by cables is considered. It is a monorail device and is modeled as an inverted pendulum built on a car driven by a dc motor. The governing equations of motion were derived via Lagrange’s equations. In the mathematical model we consider the interaction between the dc motor and the dynamical system, that is, we have a so called nonideal periodic problem. The problem is analyzed, qualitatively, through the comparison of the stability diagrams, numerically obtained, for several motor torque constants. Furthermore, we also analyze the problem quantitatively using the Floquet multipliers technique. Finally, we devise a control for the studied nonideal problem. The method that was used for analysis and control of this nonideal periodic system is based on the Chebyshev polynomial expansion, the Picard iterative method, and the Lyapunov-Floquet transformation (L-F transformation). We call it Sinha’s theory.
Adomian Decomposition Method for Solving a Cantilever Beam of Varying Orientation with Tip Mass
Authors: Yaman Mustafa
Published: December 2006

A uniform cantilever beam of varying orientation with a tip mass at the free end can be used as a basic model of many practical structures such as flexible robot arm or antenna mast. The aim of the study described here is to investigate the influence of the orientation effect on the natural frequency of the cantilever beam carrying a tip mass. An analytic solution is obtained by using the Adomian decomposition method. The accuracy of the Adomian decomposition method with a varying number of terms in the series is investigated by comparing its results with those generated by the finite element method.
Influence of Torsional Motion on the Axial Vibrations of a Drilling Tool
Authors: Voronov Sergey A. , Gouskov Alexander M. , Kvashnin Alexey S. , Butcher Eric A. , Sinha S. C.
Published: December 2006

The nonlinear dynamics of a tool commonly employed in deep hole drilling is analyzed. The tool is modeled as a two-degree of freedom system that vibrates in the axial and torsional directions as a result of the cutting process. The mechanical model of cutting forces is a nonlinear function of cutting tool displacement including state variables with time delay. The equations of new surface formation are constructed as a specific set. These equations naturally include the regeneration effect of oscillations while cutting, and it is possible to analyze continuous and intermittent cutting as stationary and nonstationary processes, respectively. The influence of the axial and torsional dynamics of the tool on chip formation is considered. The Poincaré maps of state variables for various sets of operating conditions are presented. The obtained results allow the prediction of conditions for stable continuous cutting and unstable regions. The time domain simulation allows determination of the chip shape most suitable for certain workpiece material and tool geometry. It is also shown that disregarding tool torsional vibrations may significantly change the chip formation process.
Mixed Slip-Deceleration Control in Automotive Braking Systems
Authors: Savaresi Sergio M. , Tanelli Mara , Cantoni Carlo
Published: December 2006

In road vehicles, wheel locking can be prevented by means of closed-loop anti-lock braking systems (ABS). Automatic braking is extensively used also for electronic stability control (ESC) systems. In braking control systems, two output variables are usually considered for regulation purposes: wheel deceleration and wheel longitudinal slip. Wheel deceleration is the controlled output traditionally used in ABS, since it can be easily measured with a simple wheel encoder; however, the dynamics of a classical regulation loop on the wheel deceleration critically depend on the road conditions. A regulation loop on the wheel longitudinal slip is simpler and dynamically robust; moreover, slip control is perfectly suited for both ABS and ESC applications. However, the wheel-slip measurement is critical, since it requires the estimation of the longitudinal speed of the vehicle body, which cannot be directly measured. Noise sensitivity of slip control hence is a critical issue, especially at low speed. In this work a new control strategy called mixed slip-deceleration (MSD) control is proposed: the basic idea is that the regulated variable is a convex combination of wheel deceleration and longitudinal slip. This strategy turns out to be very powerful and flexible: it inherits all the attractive dynamical features of slip control, while providing a much lower sensitivity to slip-measurement noise.
Robust Control of Nonlinear Tape Transport Systems With and Without Tension Sensors
Authors: Baumgart Matthew D. , Pao Lucy Y.
Published: December 2006

Web-winding systems, such as tape drives, are often modeled as linear and time-invariant, but at least two nonlinearities are common in these systems. First, the reel radii and moments of inertia change as web media spools from one reel to another. Second, friction can draw a thin layer of air between the layers of web media wrapped on the take-up reel, making the system’s spring and damping characteristics nonlinear by allowing a greater length of media to vibrate freely. In addition to these nonlinearities, there is often uncertainty in the motor parameters. In the first part of this paper, feedback linearization ideas motivate state feedback and changes of variables that transform the system into decoupled and intuitively meaningful tension and velocity loops. For the case where tension measurements are available, Lyapunov redesign techniques are then used to develop control laws that are robust with respect to these nonlinearities and uncertainties. The second part of this paper then develops an observer-based controller for the case where no tension measurements are available. Performance is established analytically for both the measurement-based and observer-based schemes. Simulations illustrate this performance.
Implicit Quasi-Steady-State Approximation and Application to a Power Plant Evaporator
Authors: Eitelberg Eduard , Boje Edward
Published: December 2006

Construction of reduced order models using the conventional quasi-steady-state (QSS) or singular perturbation approach may not yield good low frequency approximations, especially if there is not a distinct time scale separation into slow and fast subsystems. An implicit QSS technique is proposed for general nonlinear models. The resulting reduced order model is accurate to first order in the perturbation parameter and its linearization is accurate to first order in frequency. An example is included showing the application of the proposed method to model reduction on a power plant evaporator.
Robust Regional Eigenvalue-Clustering Analysis for Linear Discrete Singular Time-Delay Systems With Structured Parameter Uncertainties
Authors: Chen Shinn-Horng , Chou Jyh-Horng , Zheng Liang-An
Published: December 2006

In this paper, the regional eigenvalue-clustering robustness problem of linear discrete singular time-delay systems with structured (elemental) parameter uncertainties is investigated. Under the assumptions that the linear nominal discrete singular time-delay system is regular and causal, and has all its finite eigenvalues lying inside certain specified regions, two new sufficient conditions are proposed to preserve the assumed properties when the structured parameter uncertainties are added into the linear nominal discrete singular time-delay system. When all the finite eigenvalues are just required to locate inside the unit circle, the proposed criteria will become the stability robustness criteria. For the case of eigenvalue clustering in a specified circular region, one proposed sufficient condition is mathematically proved to be less conservative than those reported very recently in the literature. Another new sufficient condition is also proposed for guaranteeing that the linear discrete singular time-delay system with both structured (elemental) and unstructured (norm-bounded) parameter uncertainties holds the properties of regularity, causality, and eigenvalue clustering in a specified region. An example is given to demonstrate the applicability of the proposed sufficient conditions.
A Bond Graph Approach to the Analysis of Prosthesis for a Partially Impaired Hand
Authors: Vaz Anand , Hirai Shinichi
Published: December 2006

A system dynamics approach, based on bond graphs, is presented for the analysis of prosthetic devices for a partially impaired hand. The partial impairment implies that the hand has lost one or more fingers but retains the ability of its remaining natural fingers. It is shown that the existing natural joints can be used for the actuation of prosthetic finger joints and enable performance of tasks that would not have been possible otherwise. This is a challenging task as motion has to be transmitted from the remaining natural joints to the prosthetic joints. The joint axes move with respect to each other during performance of tasks and do not have any fixed relative orientation. In this work, basic concepts for the actuation of the prosthesis required for such tasks are developed systematically. Based on these concepts, Bowden cable based joint actuation mechanisms for transmission of motion from natural joints to corresponding prosthetic joints are presented and analyzed. The analysis of dynamics of the resulting under-actuated prosthesis with joint actuation mechanism is based on bond graph models that are systematically developed. Using these models, system equations are derived and numerical simulations performed for the analysis. One- and two-joint actuated prototypes of the prosthesis have been presented and effectively demonstrate the proposed concepts.
Routes to Chaos Exhibited by Closed Flexible Cylindrical Shells
Authors: Awrejcewicz J. , Krysko V. , Saveleva N.
Published: December 2006

Complex vibrations of closed cylindrical shells of circular cross section and finite length subjected to nonuniform sign-changeable external load in the frame of classical nonlinear theory are studied. A transition from partial differential equations to ordinary differential equations (Cauchy problem) is carried out using the higher order Bubnov–Galerkin’s approach and Fourier’s representation. On the other hand, the Cauchy problem is solved using the fourth-order Runge–Kutta method. Results are analyzed owing to the application of nonlinear dynamics and qualitative theory of differential equations. The present work is devoted to the analysis of influence of the system dynamics of the following parameters: length of pressure width φ0, relative linear shell dimension λ=L∕R, and frequency ωp and amplitude q0 of external transversal load. Some new scenarios of vibrations of closed cylindrical shells exhibiting a transition from harmonic to chaotic vibrations are illustrated and studied.
Human Catechol-O-Methyltransferase Haplotypes Modulate Protein Expression by Altering mRNA Secondary Structure
Authors: Nackley A. G. , Shabalina S. A. , Tchivileva I. E. , Satterfield K. , Korchynskyi O. , Makarov S. S. , Maixner W. , Diatchenko L.
Published: December 2006

Catechol-O-methyltransferase (COMT) is a key regulator of pain perception, cognitive function, and affective mood. Three common haplotypes of the humanCOMTgene, divergent in two synonymous and one nonsynonymous position, code for differences in COMT enzymatic activity and are associated with pain sensitivity. Haplotypes divergent in synonymous changes exhibited the largest difference in COMT enzymatic activity, due to a reduced amount of translated protein. The majorCOMThaplotypes varied with respect to messenger RNA local stem-loop structures, such that the most stable structure was associated with the lowest protein levels and enzymatic activity. Site-directed mutagenesis that eliminated the stable structure restored the amount of translated protein. These data highlight the functional significance of synonymous variations and suggest the importance of haplotypes over single-nucleotide polymorphisms for analysis of genetic variations.
Structure of Dual Function Iron Regulatory Protein 1 Complexed with Ferritin IRE-RNA
Authors: Walden William E. , Selezneva Anna I. , Dupuy Jérôme , Volbeda Anne , Fontecilla-Camps Juan C. , Theil Elizabeth C. , Volz Karl
Published: December 2006

Iron regulatory protein 1 (IRP1) binds iron-responsive elements (IREs) in messenger RNAs (mRNAs), to repress translation or degradation, or binds an iron-sulfur cluster, to become a cytosolic aconitase enzyme. The 2.8 angstrom resolution crystal structure of the IRP1:ferritin H IRE complex shows an open protein conformation compared with that of cytosolic aconitase. The extended, L-shaped IRP1 molecule embraces the IRE stem-loop through interactions at two sites separated by ∼30 angstroms, each involving about a dozen protein:RNA bonds. Extensive conformational changes related to binding the IRE or an iron-sulfur cluster explain the alternate functions of IRP1 as an mRNA regulator or enzyme.
The Heartbeat of the Oligocene Climate System
Authors: Pälike Heiko , Norris Richard D. , Herrle Jens O. , Wilson Paul A. , Coxall Helen K. , Lear Caroline H. , Shackleton Nicholas J. , Tripati Aradhna K. , Wade Bridget S.
Published: December 2006

A 13-million-year continuous record of Oligocene climate from the equatorial Pacific reveals a pronounced “heartbeat” in the global carbon cycle and periodicity of glaciations. This heartbeat consists of 405,000-, 127,000-, and 96,000-year eccentricity cycles and 1.2-million-year obliquity cycles in periodically recurring glacial and carbon cycle events. That climate system response to intricate orbital variations suggests a fundamental interaction of the carbon cycle, solar forcing, and glacial events. Box modeling shows that the interaction of the carbon cycle and solar forcing modulates deep ocean acidity as well as the production and burial of global biomass. The pronounced 405,000-year eccentricity cycle is amplified by the long residence time of carbon in the oceans.