bluuebunny/crossref_metadata_2025 huggingface dataset:
Thrombotic complications after valve replacement with porcine heterografts
Authors: Hetzer Roland , Gerbode Frank , Kerth William J. , Hill J. Donald , Adappa Gokuldas M.
Published: April 2005

The incidence of thrombotic and thromboembolic (TE) complications after Hancock valve replacement was reviewed in 140 patients with mitral valve prostheses and 150 patients with aortic valve prostheses. In patients with aortic valves, 1 embolus occurred and another patient was found at autopsy to have thrombi on a degenerated valve. Both patients had been on aspirin treatment. There was no TE event in patients receiving no anticoagulant therapy.

In patients with mitral valves, 16 showed pre‐ and/or postoperative low output syndrome (Group A); 8 of these patients died and 6 had autopsies that showed major thrombi in the heterograft. In 126 long‐term survivors, 9 thromboembolic events occurred (TE incidence 5.4% per patient year). All patients with emboli had atrial fibrillation. The majority (7/9) of emboli occurred during the first 3 postoperative months. Five occurred in patients who were not on anticoagulation (Group B), and 2 occurred in patients receiving warfarin therapy (Group C). There was no thromboembolic event in patients receiving aspirin treatment (Group D).

It is concluded that patients with Hancock aortic valves have a very small risk of TE, and do not need anticoagulation. Patients with Hancock mitral valves with stable hemodynamics have a decreased risk of TE and do not require anticoagulation. Patients with atrial fibrillation have an increased risk of TE and should be on warfarin for 3 months after surgery and then on aspirin therapy.
Selection of patients for direct myocardial revascularization
Authors: Anderson Robert W. , Ring W. Steves
Published: April 2005

The high incidence of ischémic heart disease and its associated mortality, morbidity, and socioeconomic implications have stimulated a great deal of interest and controversy regarding the relative roles of surgical and medical therapy. There is general agreement that stable angina pectoris can be substantially improved or relieved by coronary artery bypass grafting in at least 80% of patients, and that stable angina not responding to medical treatment is a firm indication for this procedure if adequate distal vessels for grafting are present. The effect of myocardial revascularization on longevity in stable angina patients is not certain except in the presence of significant obstruction of the left main coronary artery, where improved prognosis has been demonstrated. Evidence appears to be accumulating that surgical treatment improves prognosis in disease involving 3 vessels and 2 vessels, particularly if reversible left ventricular dysfunction is present. The prognosis in single‐vessel coronary artery disease does not appear to be influenced by surgical therapy.

Unstable angina pectoris appears to be best managed initially by intensive medical therapy and coronary angiography, with urgent surgery being done for significant left main coronary artery disease or uncontrolled angina, and elective surgery being done for multiple‐vessel disease. Coronary artery bypass grafting for acute myocardial infarction remains of limited value unless complications such as cardiogenic shock occur, when the prognosis may be somewhat improved by an early aggressive surgical approach in selected cases.

Improved selection of patients for direct myocardial revascularization in the future appears to depend on the development and application of diagnostic methods that will quantify the relationship between coronary artery obstructive disease and myocardial function.
The influence of coronary bypass grafting on longevity
Authors: Spencer Frank C. , Isom O. Wayne
Published: April 2005

Of 1,219 patients who underwent elective coronary bypass grafting for severe angina between 1968 and 1975 at New York University, the 5‐year survival rate calculated by the life table method was 88%, suggesting that longevity was greatly improved. These data are far better than those reported in most nonoperative series. The data can be criticized, of course, as not being obtained from a randomized trial, but the fact that such a high survival rate was obtained in patients with angina not responding to medical therapy seems highly significant. Randomization studies are currently being done in collaboration with other universities under the auspices of the National Institutes of Health in patients with mild, stable angina and in asymptomatic patients following myocardial infarction.

For the future, several goals may be projected, considering both the prevalence and the wide range in clinical severity of the disease. Undoubtedly, certain patients do not need operation because the disease process is mild and collateral circulation is adequate. Equally obvious is the fact that certain patients with disabling angina urgently need operation to survive. A current, somewhat conservative, approach is to employ medical therapy for 6–12 months after onset of symptoms if possible, and then determine if significant ischemia remains. If collateral circulation does not become adequate within this time, operation should be seriously considered. The importance of starting medical therapy beforehand is important not only to determine the necessity for bypass grafting but also to maintain medical therapy in the postoperative years. Of course, operation does nothing for the fundamental atherosclerotic process, so long‐term control of the disease depends on nonoperative methods of control of the atherosclerotic process. A particularly troublesome question at present, about which there are sharp differences of opinion, is whether asymptomatic patients with triple vessel disease demonstrated on angiography should be operated upon regardless of symptoms. This is a particularly important group for randomization. At New York University, we have usually not recommended operation unless significant symptoms were present.

A noninvasive method of determining the severity of coronary disease, perhaps a modification of exercise electrocardiography and echocardiography, would greatly simplify both the diagnosis of the disease and the effectiveness of different forms of therapy. It is to be hoped that this will emerge in the near future, perhaps in combination with certain types of radioisotope scanning.
Operative technique of myocardial revascularization
Authors: Ochsner John L. , Mills Noel L. , Bethea Morrison C.
Published: April 2005

With time and experience, improvements in the operative techniques of myocardial revascularization have evolved. Like operations in other areas, the individual preferences of different surgeons play a major role in the selection of the operative procedure or the technical maneuvers to be used. Employment of a systematic approach that encompasses adequate myocardial protection, principles of micro‐vascular surgery, precise correction, and complete revascularization has produced an operative mortality rate of less than 1%.
Myocardial protection during revascularization for myocardial ischemia
Authors: Wechsler Andrew S.
Published: April 2005

Operations that reestablish flow to proximally obstructed coronary arteries are being applied with greater frequency and greater success. The long‐term effects of such operations will ultimately be measured by increased longevity for patients with coronary artery disease, providing that perioperative injury is held to an absolute minimum and technical expertise is maintained at an absolute maximum. Application of myocardial protective techniques requires a knowledge of coronary and myocardial physiology. The use of nonrandomized applications of new protective techniques is strongly discouraged since such adventures provide little insight for the future. Further elucidation of the safe intervals for brief periods of ischemia in hearts with and without obstructed coronary arteries is needed, as are more refined measurements of physiologic and biochemical effects of revascularization techniques in regions of myocardium supplied by heterogeneously affected coronary arteries.
Preoperative and postoperative management of patients undergoing coronary artery bypass grafts
Authors: Caves Philip K.
Published: April 2005

In the preoperative care of patients for coronary artery bypass grafting, emphasis is given to the need for good coronary arteriograms and left ventricular cineangiograms, and the proper timing of operation after these investigations. The special measures needed for dealing with unstable and variant angina are discussed, and it is recommended that betaadrenergic blocking drugs should not be discontinued before operation.

Good postoperative care is easiest when the operation habeen correctly performed. The management of postoperative hypertension, arrhythmias, low output syndrome, and myocardial infarction is discussed. Following discharge from the hospital, it is important to minimize known risk indicators for coronary artery disease and to encourage the patient to achieve as complete functional rehabilitation as possible. Excellent relief of angina is obtained in about 80% of patients initially, but in those who have recurrence of chest pain postoperatively, the possibility of a second coronary artery bypass grafting operation may be considered. The need for long‐term follow‐up and aftercare of coronary artery surgical patients is stressed, so that the true benefit to the patient in terms of improved quality and quantity of life may be established.
Anastomotic leakage, stenosis, and reflux after esophageal replacement
Authors: Borst Hans G. , Dragojevic D. , Stegmann T. , Hetzer R.
Published: April 2005

Esophageal resection was performed in 119 patients between 1968 and 1977. The esophagus was replaced by stomach in 94 patients with a hospital mortality rate of 17%, and by an interposed segment of colon in 25 patients with a hospital mortality rate of 20%. Anastomotic leakage occurred in 10 patients (8.4%), of whom 6 died. Anastomotic leakage in the neck was not fatal, while two‐thirds of patients with intrathoracic leakage died. Stenosis of the anastomosis developed in 11 patients (9%), 6 of whom required dilatation or resection. The incidence of stricture was highest in patients with esophagocolic anastomoses in the neck. Development of esophageal reflux was investigated in 55 patients with gastroesophageal anastomoses 6–46 months postoperatively by questions about symptoms, x‐ray examination and, in 37 patients, by endoscopy. Mild symptoms of reflux occurred in 6 of 26 patients with high intrathoracic anastomoses, while regular symptoms of reflux were reported by 17 of 29 patients with low intrathoracic anastomoses and only 2 such patients were free of symptoms. Similarly, 25 of 26 patients with high anastomoses had no reflux on x‐ray or had reflux only in the head‐down position, while all 29 patients with low anastomoses had reflux on x‐ray, and 24 had reflux in the upright and/or supine positions. On endoscopy, 12 of 17 patients with high anastomoses had no esophagitis, while only 1 of 20 patients with low anastomoses had no esophagitis and in 9 patients, esophagitis was moderate or severe. There was a low incidence of reflux in patients with colon interposition. These results indicate that replacement of the esophagus with a high intrathoracic gastroesophageal anastomosis or with interposed colon is the preferable procedure.
Long‐term results of thoracoabdominal bypass graft for atypical coarctation of the aorta
Authors: Wada Juro , Kazui Teruhisa
Published: April 2005

Seven patients with atypical coarctation of the aorta were treated with a long thoracoabdominal bypass graft. One of them had a right renal bypass at the same time. One patient who had undergone a patch angioplasty 4 years previously died of bleeding at the time of surgery. Five out of 6 patients who survived the operation have remained normotensive and free of symptoms for up to 12 years, with an average followup period of 4 years. One patient died 3 1/2 years postoperatively from rupture of a pseudoaneurysm. Our experience indicates that atypical coarctation of the elongated type can be treated satisfactorily by the long thoracoabdominal bypass graft. If associated lesions of renal stenosis are present, renal revascularization is also necessary to overcome hypertension.
Gene expression and characterization of two 2‐oxoacid:ferredoxin oxidoreductases from Aeropyrum pernix K1
Authors: Nishizawa Yumie , Yabuki Takashi , Fukuda Eriko , Wakagi Takayoshi
Published: April 2005

A hyperthermophilic and aerobic crenarchaeon, Aeropyrum pernix K1, has two sets of genes possibly encoding 2‐oxoacid:ferredoxin oxidoreductases. One is encoded in open reading frames (ORFs) ape2126 and ape2128, and the other in ORFs ape1473 and ape1472. The two sets of genes were expressed. The product enzymes, Ape2126/2128 and Ape1473/1472, showed optimal temperatures of 105 and over 110 °C, and optimal pHs of 8.5 and 9.0, respectively, using pyruvate as a substrate. Pyruvate, 2‐oxobutyrate, and glyoxylate were the best substrates for both enzymes, and additionally Ape1473/1472 was able to act on 2‐oxoglutarate, suggesting the enzyme operates in the TCA cycle.
Crystal structure of α‐hordothionin at 1.9 Å resolution
Authors: Johnson Kenneth A. , Kim Eunsung , Teeter Martha M. , Suh Se Won , Stec Boguslaw
Published: April 2005

Crystal structure of ubiquitous toxin from barley α‐hordothionin (α‐HT) has been determined at 1.9 Å resolution by X‐ray crystallography. The primary sequence as well as the NMR solution structure of α‐HT firmly established that α‐HT belongs to a family of membrane active plant toxins–thionins. Since α‐HT crystallized in a space group (P41212) that is different from the space group (I422) of previously determined α1‐ and β‐purothionins, and visocotoxin A3, therefore, it provided independent information on protein–protein interactions that may be relevant to the toxin mechanism. The structure of α‐HT not only confirms overall architectural features (crambin fold) but also provides an additional confirmation of the role for crucial solute molecules, that were postulated to be directly involved in the mechanism of toxicity for thionins.
AtCCS is a functional homolog of the yeast copper chaperone Ccs1/Lys7
Authors: Abdel-Ghany Salah E. , Burkhead Jason L. , Gogolin Kathryn A. , Andrés-Colás Nuria , Bodecker Jared R. , Puig Sergi , Peñarrubia Lola , Pilon Marinus
Published: April 2005

In plant chloroplasts two superoxide dismutase (SOD) activities occur, FeSOD and Cu/ZnSOD, with reciprocal regulation in response to copper availability. This system presents a unique model to study the regulation of metal‐cofactor delivery to an organelle. The Arabidopsis thaliana gene AtCCS encodes a functional homolog to yeast Ccs1p/Lys7p, a copper chaperone for SOD. The AtCCS protein was localized to chloroplasts where it may supply copper to the stromal Cu/ZnSOD. AtCCS mRNA expression levels are upregulated in response to Cu‐feeding and senescence. We propose that AtCCS expression is regulated to allow the most optimal use of Cu for photosynthesis.
Human mitochondrial peroxiredoxin 5 protects from mitochondrial DNA damages induced by hydrogen peroxide
Authors: Banmeyer Ingrid , Marchand Cécile , Clippe André , Knoops Bernard
Published: April 2005

Peroxiredoxin 5 is a thioredoxin peroxidase ubiquitously expressed in mammalian tissues. Peroxiredoxin 5 can be addressed intracellularly to mitochondria, peroxisomes, the cytosol and the nucleus. Here, we show that mitochondrial human peroxiredoxin 5 protects mitochondrial DNA (mtDNA) from oxidative attacks. In an acellular assay, recombinant peroxiredoxin 5 was shown to protect plasmid DNA from damages induced by metal‐catalyzed generation of reactive oxygen species. In Chinese hamster ovary cells, overexpression of mitochondrial peroxiredoxin 5 significantly decreased mtDNA damages caused by exogenously added hydrogen peroxide. Altogether our results suggest that mitochondrial peroxiredoxin 5 may play an important role in mitochondrial genome stability.
Analysis of expressed sequence tags from oil palm (Elaeis guineensis)
Authors: Jouannic Stefan , Argout Xavier , Lechauve Frédéric , Fizames Cécile , Borgel Alain , Morcillo Fabienne , Aberlenc-Bertossi Frédérique , Duval Yves , Tregear James
Published: April 2005

This is the first report of a systematic study of genes expressed by means of expressed sequence tag (EST) analysis in oil palm, a species of the Arecales order, a phylogenetically key clade of monocotyledons that is not widely represented in the sequence databases. Five different cDNA libraries were generated from male and female inflorescences, shoot apices and zygotic embryos and unidirectional systematic sequencing was performed. A total of 2411 valid EST sequences were thus obtained. Cluster analysis enabled the identification of 209 groups of related sequences and 1874 singletons. Putative functions were assigned to 1252 of the set of 2083 non‐redundant ESTs obtained. The EST database described here is a first step towards gene discovery and cDNA array‐based expression analysis in oil palm.
Unusual usage of wobble modifications in mitochondrial tRNAs of the nematode Ascaris suum
Authors: Sakurai Masayuki , Ohtsuki Takashi , Suzuki Tsutomu , Watanabe Kimitsuna
Published: April 2005

To understand the decoding property of nematode mitochondrial tRNAs with unusual secondary structures, post‐transcriptional modifications at wobble positions of Ascaris suum mitochondrial tRNAs corresponding to two‐codon families ending with a purine were analyzed. 5‐Carboxymethylaminomethyluridine (cmnm5U) was identified at the wobble positions of tRNALys, tRNAGlu and tRNAGln, while 5‐carboxymethylaminomethyl‐2‐thiouridine (cmnm5s2U) was present in . In most bacterial and mitochondrial tRNAs, the 2‐thiouridine derivative is present in tRNAs for Lys, Glu and Gln. These is no report that cmnm5s2U is used in . The unusual usage of wobble modifications might assist decoding of nematode mitochondrial mRNAs.
Vacuum extraction and herpes simplex virus infection
Authors: Sadan O. , Dishi M. , Somekh E. , Kohelet D. , Lurie S. , Glezerman M.
Published: April 2005

Objective

To search for an association between delivery by vacuum extraction and an increased neonatal risk for herpes simplex virus (HSV) infection.

Methods

In a cross‐sectional, descriptive, controlled study, the study (vacuum extraction) and control (spontaneous delivery) groups each included 50 consecutive women with no history of HSV infection. Cultures for HSV were obtained from the genital tracts of all parturient women and the scalps of their newborns.

Results

Following operative vaginal delivery, two newborns (4%) had scalp vesicles and cultures were positive for HSV for both mothers and newborns; two newborns (4%) had scalp vesicles and cultures were negative for HSV; and two newborns (4%) without scalp vesicles had cultures positive for HSV. Following spontaneous delivery, cultures were positive for HSV for four women and their newborns (8%).

Conclusion

Herpes simplex virus isolated from the scalps of newborns may often result from colonization rather than infection.
Isolationism revisited: seven persistent myths in the contemporary American foreign policy debate
Authors: Dunn David
Published: April 2005

‘Isolationism’ is a much used and abused term in the contemporary American foreign policy debate. This article seeks to illuminate some of the misunderstandings that surround the use of this term by challenging seven persistent myths about isolationism. In so doing it sheds light on the often unarticulated role that this and other ideas play in the US foreign policy debate. It also seeks to demonstrate the nature of the main ideational cleavages within this debate which the isolationist name-calling obscures, and to show the way in which language is used in the political discourse and how its meaning in this debate changes over time.
Cosmopolitan liberalism and the faces of injustice in International Relations
Authors: Lu Catherine
Published: April 2005

The most significant intellectual contribution of Charles Beitz's book, Political Theory and International Relations, was captured by his use of the word ‘and’ in the book's title to connect the previously estranged fields of political theory and international relations (IR). His book constituted a bold challenge to a prevailing realist view in the field of IR, that was sceptical ‘about the status of moral principles’ in a Hobbesian state-eat-state world. Beitz's work also challenged the traditional orientation of contemporary political theory, that took for granted the bounded rather than ‘universal community’ as the locus of inquiry about issues of justice and political morality. The marriage of political theory and IR has produced in the past twenty-five years a rich and diverse body of international political theory that engages, in a direct and rigorous fashion, previously obscured or marginalised normative dimensions of international issues ranging from war and intervention to global poverty and economic inequality.
Antiphase OH and OI airglow emissions induced by a short‐period ducted gravity wave
Authors: Snively Jonathan B. , Pasko Victor P.
Published: April 2005

Numerical simulation of a ducted gravity wave event suggests that OH (8,3) and O(1S) 557.7 nm airglow emissions layers may exhibit opposite‐phase intensities when perturbed by a short‐period wave undergoing vertical reflection. This effect arises due to the time and temperature dependance of the OH excitation reaction, coupled with the linear polarization properties of vertically‐standing waves.
Dike propagation driven by volcano collapse: A general model tested at Stromboli, Italy
Authors: Acocella Valerio , Tibaldi Alessandro
Published: April 2005

Analogue experiments investigate how flank collapse affects dike propagation within volcanoes. Water (magma analogue) is injected within a gelatin cone (volcano analogue) with a lateral collapse. The injections form dikes that, away from the collapse, become radial. The dikes propagating nearby the collapse focus towards the collapse sides, becoming subparallel to them, because of the stress reorientation due to the unbuttressing. Only dikes formed along the collapse axis (passing through the mean points of the collapse, map view) propagate radially within the collapse. This general model is applied at Stromboli. The Stromboli dikes cluster along and parallel to the collapse sides, similar to the experiments. Nevertheless, the current location of the conduit, along the collapse axis, leads to dike propagation within the collapse infill, rather than at its sides. This may have occurred during the 2002–03 eruption, when diking in the collapse triggered a landslide and tsunami within the collapse.
Features of additional stratification in ionospheric F2 layer observed for half a solar cycle over Indian low latitudes
Authors: Rama Rao P. V. S. , Niranjan K. , Prasad D. S. V. V. D. , Brahmanandam P. S. , Gopikrishna S.
Published: April 2005

The features of the additional stratification in the ionospheric F2 layer often referred to as the F3 layer observed over an Indian low‐latitude station Waltair (17.7°N, 83.3°E, magnetic latitude (Mag. Lat.) 8.2°N) during the period 1997–2003 are presented along with the data from two other Indian stations. The observations grossly confirm those reported earlier in the occurrence and seasonal variability of the F3 layer. From an analysis of half a solar cycle ionosonde data (1997–2003), it is observed that the layer appeared more frequently during the summer solstice months of low solar activity period and persisted for longer durations during this season compared with equinox and winter solstice. The best stratification is seen between 10–12 hours IST. The occurrence of the F3 layer does not seem to depend on magnetic activity but the percentage of occurrence decreased with increasing solar activity. The solar activity dependence over Waltair confirms the model predictions of Balan et al. (1998) that the layer becomes less distinct and less frequent as solar activity increases. The ionosonde data for the same period (1997–2003) from an equatorial station, Trivandrum (8.4°N, 76.9°E, Mag. Lat. 0.47°N) and another low‐latitude station, SHAR (14°N, 80°E, Mag. Lat. 6.8°N) are also analyzed with a view to examine the effect of the equatorial plasma dynamics on the occurrence of such events.
A plasmaspheric mass density model and constraints on its heavy ion concentration
Authors: Berube D. , Moldwin M. B. , Fung S. F. , Green J. L.
Published: April 2005

The first empirical model of the equatorial mass density of the plasmasphere is constructed using ground‐based ULF wave diagnostics. Plasmaspheric mass density between L = 1.7 and L = 3.2 has been determined using over 5200 hours of data from pairs of stations in the MEASURE array of ground magnetometers. The least squares fit to the data as a function of L shows that mass density falls logarithmically with L. Average ion mass as a function of L is also estimated by combining the mass density model with plasmaspheric electron density profiles determined from the IMAGE Radio Plasma Imager (RPI). Additionally, we use the RPI electron density database to examine how the average ion mass changes under different levels of geomagnetic activity. We find that average ion mass is greatest under the most disturbed conditions. This result indicates that heavy ion concentrations (percent by number) are enhanced during large geomagnetic disturbances. We also find that the average ion mass increases with increasing L (below L = 3.2), indicating the presence of a heavy ion torus during disturbed times. Heavy ions must play an important role in storm‐time plasmaspheric dynamics. The average ion mass is also used to constrain the concentrations of He+ and O+. Estimates of the He+ concentration determined this way may be useful for interpreting IMAGE Extreme Ultraviolet Imager (EUV) images.
Identification of the magnetization low of the Lucky Strike hydrothermal vent using surface magnetic data
Authors: Miranda J. M. , Luis J. F. , Lourenço N. , Santos F. M.
Published: April 2005

Two surface magnetic surveys, covering the Lucky Strike hydrothermal area, are merged into a single magnetic anomaly description, which, when inverted in the presence of topography, shows a magnetization low at the segment center, close to the central volcano, in the middle of which is located the hydrothermal vent. To test if this magnetization is in any way connected with the hydrothermal vent field, we devised a method to distinguish a “regional” field that can be attributed to the “normal” spreading geometry from the “local” field that can be attributed to the hydrothermal vent area itself. This is achieved by the computation of a three‐dimensional regional magnetic field that takes into consideration bathymetry, location of the “zero‐age” axis, asymmetry in the half spreading rates, magnetization decay with age, polarity reversals, and the transition between consecutive magnetic blocks. This model was fitted to the observed surface magnetic data, and the “magnetic residual” was inverted to allow a better definition of the magnetization anomalies. We show that as far as surface magnetic data are concerned, the magnetization low has only partial correlation with the hydrothermal field and is the signature of a relatively large area in which bulk magnetization is lower than average.
Stress and earthquakes in southern California, 1850–2004
Authors: Kagan Yan Y. , Jackson David D. , Liu Zhen
Published: April 2005

We compute the stress tensor in the upper crust of southern California as a function of time and compare observed seismicity with the estimated stress at the time of each earthquake. Several recent developments make it possible to do this much more realistically than before: (1) a wealth of new geodetic and geologic data for southern California and (2) a catalog of moment tensors for all earthquakes with magnitudes larger than 6 since 1850 and larger than 5 since 1910. We model crustal deformation using both updated geodetic data and geologically determined fault slip rates. We subdivide the crust into elastic blocks, delineated by faults which move freely at a constant rate below a locking depth with a rate determined by the relative block motion. We compute normal and shear stresses on nodal planes for each earthquake in the catalog. We consider stress increments from previous earthquakes (“seismic stress”) and aseismic tectonic stress, both separately and in combination. The locations and mechanisms of earthquakes are best correlated with the aseismic shear stress. Including the cumulative coseismic effects from past earthquakes does not significantly improve the correlation. Correlations between normal stress and earthquakes are always very sensitive to the start date of the catalog, whether we exclude earthquakes very close to others and whether we evaluate stress at the hypocenter or throughout the rupture surface of an earthquake. Although the correlation of tectonic stress with earthquake triggering is robust, other results are unstable apparently because the catalog has so few earthquakes.
A New Functional Form and New Fitting Techniques for Equations of State with Application to Pentafluoroethane (HFC-125)
Authors: Lemmon Eric W. , Jacobsen Richard T
Published: April 2005

A widely used form of an equation of state explicit in Helmholtz energy has been modified with new terms to eliminate certain undesirable characteristics in the two phase region. Modern multiparameter equations of state exhibit behavior in the two phase that is inconsistent with the physical behavior of fluids. The new functional form overcomes this dilemma and results in equations of state for pure fluids that are more fundamentally consistent. With the addition of certain nonlinear fitting constraints, the new equation now achieves proper phase stability, i.e., only one solution exists for phase equilibrium at a given state. New fitting techniques have been implemented to ensure proper extrapolation of the equation at low temperatures, in the vapor phase at low densities, and at very high temperatures and pressures. A formulation is presented for the thermodynamic properties of refrigerant 125 (pentafluoroethane, CHF2–CF3) using the new terms and fitting techniques. The equation of state is valid for temperatures from the triple point temperature (172.52 K) to 500 K and for pressures up to 60 MPa. The formulation can be used for the calculation of all thermodynamic properties, including density, heat capacity, speed of sound, energy, and saturation properties. Comparisons to available experimental data are given that establish the accuracy of calculated properties. The estimated uncertainties of properties calculated using the new equation are 0.1% in density, 0.5% in heat capacities, 0.05% in the vapor phase speed of sound at pressures less than 1 MPa, 0.5% in the speed of sound elsewhere, and 0.1% in vapor pressure. Deviations in the critical region are higher for all properties except vapor pressure.
Isotopic Compositions of the Elements, 2001
Authors: Böhlke J. K. , de Laeter J. R. , De Bièvre P. , Hidaka H. , Peiser H. S. , Rosman K. J. R. , Taylor P. D. P.
Published: April 2005

The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the “best measurement” of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E) and its uncertainty U[Ar(E)] recommended by CAWIA in 2001.
Self-similarity in Hall plasma discharges: Applications to particle models
Authors: Taccogna Francesco , Longo Savino , Capitelli Mario , Schneider Ralf
Published: April 2005

Electron transport is a key process in the physics of Hall thruster discharges. Therefore, a kinetic description of the heavy particles (Xe) as well as electrons is required. The ideal numerical model would be a particle model for all the species. Nowadays, such a model is unpractical because it would need too large an amount of computation time due to the very different time scales of electrons and heavy particles dynamics. For this purpose two scalings to speed-up the execution time of a two-dimensional fully kinetic Particle-in-Cell/Monte Carlo Collision simulation of the Hall thruster SPT-100 are proposed. These two different scaling schemes generate self-similar systems of the acceleration channel including the process of secondary electron emission from the dielectric walls. Instead of using the common approach of a smaller neutral and ion mass or a larger vacuum permittivity the channel dimensions are reduced keeping the main dimensionless physics parameters constant. This leads to scaling laws for the input (magnetic field, mass flow rate, current and voltage discharge, etc.) and output parameters obeying self-similarity. This scaling methodology makes the simulation faster and allows improved modeling of electron interactions and fundamental processes. This model has demonstrated its outstanding capability in improving the physics insight into the processes in SPT-100 under the scaling constraints for the geometrical reduction. The application to particle models of different plasma based devices is suggested for such systems where a linearization of the Boltzmann equation is possible.
Additional evidence for the universality of the probability distribution of turbulent fluctuations and fluxes in the scrape-off layer region of fusion plasmas
Authors: van Milligen B. Ph. , Sánchez R. , Carreras B. A. , Lynch V. E. , LaBombard B. , Pedrosa M. A. , Hidalgo C. , Gonçalves B. , Balbín R. ,   The W7-AS Team
Published: April 2005

Plasma density fluctuations and electrostatic turbulent fluxes measured at the scrape-off layer of the Alcator C-Mod tokamak [B. LaBombard, R. L. Boivin, M. Greenwald, J. Hughes, B. Lipschultz, D. Mossessian, C. S. Pitcher, J. L. Terry, and S. J. Zweben, Phys. Plasmas 8, 2107 (2001)], the Wendelstein 7-Advanced Stellarator [H. Renner, E. Anabitarte, E. Ascasibar et al., Plasma Phys. Controlled Fusion 31, 1579 (1989)], and the TJ-II stellarator [C. Alejaldre, J. Alonso, J. Botija et al., Fusion Technol. 17, 131 (1990)] are shown to obey a non-Gaussian but apparently universal (i.e., not dependent on device and discharge parameters) probability density distribution (pdf). The fact that a specific shape acts as an attractor for the pdf seems to suggest that emergent behavior and self-regulation are relevant concepts for these fluctuations. This shape is closely similar to the so-called Bramwell, Holdsworth, and Pinton distribution, which does not have any free parameters.
Hole mobility of p-type β-FeSi2 thin films grown from Si∕Fe multilayers
Authors: Takakura K. , Ohyama H. , Takarabe K. , Suemasu T. , Hasegawa F.
Published: April 2005

The hole mobility of intentionally undoped p-type β-FeSi2 thin films grown by a multilayer method was investigated. With increasing annealing temperature and time, the hole mobility increased to approximately 450cm2∕Vs at room temperature (RT). The observed hole mobility was analyzed by considering various carrier scatterings such as acoustic-phonon and polar-optical-phonon scatterings, intervalley scattering, ionized impurity scattering, and grain-boundary scattering. The nice fit of the mobility to the experimental results reveals that the polar-optical-phonon scattering determines the hole mobility at RT.
Tunable one-dimensional ordered structure in a magnetic fluid microstrip under parallel magnetic fields
Authors: Yang S. Y. , Chao Y. H. , Horng H. E. , Hong Chin Yin , Yang H. C.
Published: April 2005

This paper investigates the structural evolution in a magnetic fluid microstrip under external magnetic fields parallel to the strip surface. It is shown that as the field strength increases, the structure evolves from an originally monodispersed state to a disordered magnetic chain state, and then to a one-dimensional ordered structure of chains. For the ordered structure state, the chain spacing is reduced with an increase in field strength, because more columns form under higher fields. Thus, a tunable one-dimensional ordered structure can be achieved in magnetic fluid films under parallel magnetic fields. The manipulations of the tunability of the ordered structure under various control parameters, such as the sweep rate of the magnetic field, the fluid concentration, and the strip width, are also discussed.
Viscous fingering in shear thickening silica suspensions
Authors: Kagei Naoki , Kanie Daisuke , Kawaguchi Masami
Published: April 2005

We make an experimental study of the viscous fingering behavior of air displacing shear thickening silica suspensions in linear Hele-Shaw cells with different cell gaps as a function of the injection pressure. The imposed shear rate defined by the ratio of the finger tip velocity and the half of a cell gap, at which the onset of the viscous fingering instability is observed, is close to the critical shear rates of the corresponding shear thickening silica suspensions, irrespective of the cell gap and the injection pressure. The modified Darcy’s law, where the constant viscosity is replaced by the shear dependent viscosity, gives good agreement with the experiments when the imposed shear rate is less than the critical shear rate. When the imposed shear rate is beyond the critical shear rate, the shear thickening silica suspensions give the more negative deviation from the modified Darcy’s law, irrespective of the injection pressure and the cell gap. The relative finger width can be related with non-Newtonian behavior of the silica suspensions.
Electron acceleration caused by small pulses in shock waves
Authors: Sato Masatoshi , Miyahara Seiji , Ohsawa Yukiharu
Published: April 2005

A new particle acceleration mechanism is studied with theory and particle simulations. Around small pulses that are generated in a large-amplitude shock wave in a magnetized plasma, electrons can be accelerated to ultrarelativistic energies. Simulations demonstrate electron acceleration to energies γ>100 in weak magnetic fields such that ∣Ωe∣∕ωpe<1 as well as in strong magnetic fields. The theoretical model accounts for the basic features of the electron motion in the simulations.
Improvement of a “mini” two-stage light-gas gun for hypervelocity impact experiments: Technical devices to accelerate and detect a “minute” projectile efficiently
Authors: Saito Fumikazu , Usui Toshitika , Tamura Hideki , Tanaka Yusuke , Shimizu Michiaki , Kondo Ken-ichi
Published: April 2005

A gas-gun system was improved and optimized in order to obtain higher projectile velocity. The gas gun used in this study was a “mini” two-stage light-gas gun suitable for the acceleration of a “minute” projectile. As a major improvement in the mini gun, the high-pressure coupler was divided into two parts. One part was a generation section of the hot and high-pressure working gas by compression with a piston, and the other was a flow rate control section of the working gas. The mini gun, after installing the improved high-pressure coupler, showed an increase not only in the projectile velocity but also in the energy efficiency converting the combustion energy to the projectile kinetic energy, compared with the conventional mini gun. In the firing test using hydrogen as a working gas, a projectile velocity of 5.91km∕s was achieved by the use of the improved mini gun, as compared with a velocity of 4.70km∕s before the improvements were made. The modifications to the mini-gun system and their effects on the performance of the mini gun are discussed.
Charging a double Kerr solution in five-dimensional Einstein–Maxwell–Kalb–Ramond theory
Authors: Becerril Ricardo , Herrera-Aguilar Alfredo
Published: April 2005

We consider the low-energy effective action of the five-dimensional (5D) Einstein–Maxwell–Kalb–Ramond theory. After compactifying this truncated model on a two-torus and switching off the U(1) vector fields of this theory, we recall a formulation of the resulting three-dimensional action as a double Ernst system coupled to gravity. Further, by applying the so-called normalized Harrison transformation on a generic solution of this double Ernst system we recover the U(1) vector field sector of the theory. Afterward, we compute the field content of the generated charged configuration for the special case when the starting Ernst potentials correspond to a pair of interacting Kerr black holes, obtaining in this way an exact field configuration of the 5D Einstein–Maxwell–Kalb–Ramond theory endowed with effective Coulomb and dipole terms with momenta. Some physical properties of this object are analyzed as well as the effect of the normalized Harrison transformation on the double Kerr seed solution.
Micromachined chemical sensor with dual-transduction mechanisms
Authors: Chen Ing-Shin , Stawasz Michele , DiMascio Susan K. , Welch James J. , Neuner Jeffrey W. , Chen Philip S. H. , DiMeo Frank
Published: April 2005

Chemical sensors based on a microhotplate platform generally function via a conductometric or calorimetric transduction mechanism. In addition to these mechanisms, a mechanical transduction mechanism is proposed based on the detection of the microhotplate bending due to volume change of functional layers. In this letter, we demonstrate sensing of gaseous hydrogen based on volumetric expansion of Pd∕Y functional layers. In this case, the embedded polysilicon heater element also serves as the piezoresistive strain-detecting element, changing its resistance as the microhotplate bends. This transduction mechanism can be used independently of, or in conjunction with, a simultaneous conductometric or calorimetric mechanism.
Growth-temperature-dependent cathodoluminescence properties of GaSb/GaAs quantum-dot multilayer structures
Authors: Drozdowicz-Tomsia Krystyna , Goldys Ewa M. , Motlan Motlan , Zareie Hadi , Phillips Matthew R.
Published: April 2005

Multilayer GaSb/GaAs quantum-dot (QD) structures grown by atmospheric-pressure metalorganic chemical vapor deposition on semi-insulating GaAs (100) substrates with varying growth temperature of the confinement layers are studied by the cathodoluminescence (CL). Two main features assigned to wetting layer and QDs are observed in the CL spectra. Their relative positions strongly depend on the growth conditions of the confinement layers. The highest separation of 270 meV is achieved for GaAs confinement layers grown at 540 °C.
Synthesis kinetics of CdSe quantum dots in trioctylphosphine oxide and in stearic acid
Authors: Dickerson B. D. , Irving D. M. , Herz E. , Claus R. O. , Spillman W. B. , Meissner K. E.
Published: April 2005

A diffusion-barrier model described the early evolution of size-dependent photoluminescence emission from CdSe quantum dots formed by organometallic synthesis. Emission peak widths, emission redshift rates, and nanocrystal growth rates all decreased to a minimum at a reaction completion time. Growth after the completion time by Ostwald ripening was marked by a doubling of the activation energy. The temperature dependence of both reaction completion rates and photoluminescence redshift rates followed Arrhenius behavior governed by activation energies that increased with solvent molecular weight, in this limited case. In stearic acid and in trioctylphosphine oxide, the typical activation energies were 0.6±0.1 and 0.92±0.26eV∕molecule, respectively.
Ligand-induced dimerization of
Drosophila
peptidoglycan recognition proteins
in vitro
Authors: Mellroth Peter , Karlsson Jenny , Håkansson Janet , Schultz Niklas , Goldman William E. , Steiner Håkan
Published: April 2005

Drosophila
knockout mutants have placed peptidoglycan recognition proteins (PGRPs) in the two major pathways controlling immune gene expression. We now examine PGRP affinities for peptidoglycan. PGRP-SA and PGRP-LCx are bona fide pattern recognition receptors, and PGRP-SA, the peptidoglycan receptor of the Toll/Dif pathway, has selective affinity for different peptidoglycans. PGRP-LCx, the default peptidoglycan receptor of the Imd/Relish pathway, has strong affinity for all polymeric peptidoglycans tested and for monomeric peptidoglycan. PGRP-LCa does not have affinity for polymeric or monomeric peptidoglycan. Instead, PGRP-LCa can form heterodimers with LCx when the latter is bound to monomeric peptidoglycan. Hence, PGRP-LCa can be said to function as an adaptor, thus adding a new function to a member of the PGRP family.
A coherent framework for multiresolution analysis of biological networks with “memory”: Ras pathway, cell cycle, and immune system
Authors: Barbano Paolo Emilio , Spivak Marina , Feng Jiawu , Antoniotti Marco , Mishra Bud
Published: April 2005

Various biological processes exhibit characteristics that vary dramatically in response to different input conditions or changes in the history of the process itself. One of the examples studied here, the Ras-PKC-mitogen-activated protein kinase (MAPK) bistable pathway, follows two distinct dynamics (modes) depending on duration and strength of EGF stimulus. Similar examples are found in the behavior of the cell cycle and the immune system. A classification methodology, based on time-frequency analysis, was developed and tested on these systems to understand global behavior of biological processes. Contrary to most traditionally used statistical and spectral methods, our approach captures complex functional relations between parts of the systems in a simple way. The resulting algorithms are capable of analyzing and classifying sets of time-series data obtained from
in vivo
or
in vitro
experiments, or
in silico
simulation of biological processes. The method was found to be considerably stable under stochastic noise perturbation and, therefore, suitable for the analysis of real experimental data.
Massive nitrogen loss from the Benguela upwelling system through anaerobic ammonium oxidation
Authors: Kuypers Marcel M. M. , Lavik Gaute , Woebken Dagmar , Schmid Markus , Fuchs Bernhard M. , Amann Rudolf , Jørgensen Bo Barker , Jetten Mike S. M.
Published: April 2005

In many oceanic regions, growth of phytoplankton is nitrogen-limited because fixation of N
2
cannot make up for the removal of fixed inorganic nitrogen (NH
+
4
, NO
-
2
, and NO
-
3
) by anaerobic microbial processes. Globally, 30-50% of the total nitrogen loss occurs in oxygen-minimum zones (OMZs) and is commonly attributed to denitrification (reduction of nitrate to N
2
by heterotrophic bacteria). Here, we show that instead, the anammox process (the anaerobic oxidation of ammonium by nitrite to yield N
2
) is mainly responsible for nitrogen loss in the OMZ waters of one of the most productive regions of the world ocean, the Benguela upwelling system. Our
in situ
experiments indicate that nitrate is not directly converted to N
2
by heterotrophic denitrification in the suboxic zone. In the Benguela system, nutrient profiles, anammox rates, abundances of anammox cells, and specific biomarker lipids indicate that anammox bacteria are responsible for massive losses of fixed nitrogen. We have identified and directly linked anammox bacteria to the removal of fixed inorganic nitrogen in the OMZ waters of an open-ocean setting. We hypothesize that anammox could also be responsible for substantial nitrogen loss from other OMZ waters of the ocean.