bluuebunny/crossref_metadata_2025 huggingface dataset:
A Three-Dimensional Linearized Euler Analysis of Classical Wake/Stator Interactions: Validation and Unsteady Response Predictions
Authors: Prasad D. , Verdon J.M.
Published: October 2002

A comprehensive validation of the linearized Euler analysis, LINFLUX, for wake/blade row interaction is carried out. The flow configuration is that of the benchmark problem for rotor-stator interaction proposed at the Third Computational Aeroacoustics Workshop. It consists of an unstaggered, annular, flat-plate blade row excited by the vortical gusts associated with the wakes shed from an upstream rotor. The numerical results for the unsteady pressure responses of the stator are compared with semi-analytic lifting surface and lifting line solutions. The validation is first conducted for narrow-annulus flows, where the numerical results are shown to agree well with classical two-dimensional solutions over a range of frequencies. We then carry out a detailed comparison of the three-dimensional LINFLUX results with the lifting surface results of Namba and Schulten for a blade row with a hub-to-tip ratio of 0.5. This study encompasses gust excitation frequencies for which the stator responses vary from cut off to propagating, as well as gusts with varying degrees of spanwise variation. The numerical and semi-analytical analyses yield results for the stator pressure response, including the complex amplitudes of the propagating and least attenuated, evanescent, pressure modes that are in very good agreement. The effect of increasing the spanwise phase variation of the gust is generally, but not necessarily, to reduce the power associated with the acoustic response of the blade row. A comparison of the present numerical results with those obtained from a stripwise application of classical linear theory reveals that the latter approach can be erroneous and, therefore, of questionable applicability to realistic turbomachinery unsteady flows.
Propagation of Acoustic Waves through Regions of Non-Uniform Temperature
Authors: Tarau C. , Ötügen M.V.
Published: October 2002

The reflection and transmission of acoustic waves through regions of non-uniform temperature in a gas medium was numerically studied. The propagation of planar sound waves through the various finite-length non-uniform gas regions was investigated by solving the unsteady one-dimensional Euler's equations using a finite-difference scheme. The main thrust of the investigation was to determine the effectiveness of using glow discharge plasma as sound barriers in aerospace applications. The effect, on sound transmission, of the length and shape of the high-temperature zone characterizing the plasma was determined.
THE UNITARY EVOKED POTENTIAL AT THE FROG NERVE‐MUSCLE JUNCTION RESULTS FROM SYNCHRONOUS GATING OF FUSI0N PORES AT DOCKED VESICLES
Authors: Kriebel Mahlon E. , Keller Bruce
Published: October 2002

Exocytosis of a single vesicle has been proposed as the mechanism which determines quantal size by releasing a prepackaged and standard amount of acetylcholine. As first described by del Castillo and Katz (1954) the endplate potential is composed of 100 unitary events and the small variance suggests a binomial release from 100 “discrete patches of membrane”. However, exocytosis of 100 vesicles selected randomly from 5000 docked vesicles would yield a variance that is 7 times greater than observed values. We propose that the presynaptic ridge with its compliment of docked vesicles functions as the “discrete patch of membrane” such that arrays of calcium activated fusion pores meter transmitter to form the unit of release. A model based on the synchronous flicker of a large number of fusion pores produces the small variance of both miniature end plate potentials and unitary end plate potentials. Release from a single locus (fusion pore) would generate the sub‐MEPP. This model permits vesicle trafficking and vesicular content depletion during tetanic stimulation and explains the frequency dependency of MEPP amplitudes and changes in sub‐MEPP to bell‐MEPP class ratios.
A new isidiate species of Catillaria from the Netherlands
Authors: van den Boom P. P. G.
Published: October 2002

A new lichen species, Catillaria nigroisidiata, is described from the Netherlands: it is the first isidiate species known in the genus and has been collected growing on granite on dykes in the north-eastern part of the country. This new species is easily overlooked because of the completely black appearance. A key to Catillaria s.str. in western Europe is provided.
Absence of Glaciation in Illinois during Marine Isotope Stages 3 through 5
Authors: Curry B. Brandon , Pavich Milan J.
Published: October 2002

A10Be inventory and14C ages of material from a core from northernmost Illinois support previous interpretations that this area was ice free from ca. 155,000 to 25,000 yr ago. During much of this period, from about 155,000 to 55,000 yr ago, 10Be accumulated in the argillic horizon of the Sangamon Geosol. Wisconsinan loess, containing inherited 10Be, was deposited above the Sangamon Geosol from ca. 55,000 to 25,000 yr ago and was subsequently buried by late Wisconsinan till deposited by the Lake Michigan Lobe of the Laurentide Ice Sheet. The Sangamonian interglacial stage has been correlated narrowly to marine oxygen isotope substage 5e; our data indicate instead that the Sangamon Geosol developed during late stage 6, all of stages 5 and 4, and early stage 3.
A Large California Flood and Correlative Global Climatic Events 400 Years Ago
Authors: Schimmelmann Arndt , Zhao Meixun , Harvey Colin C. , Lange Carina B.
Published: October 2002

A gray silt layer 1–2 cm thick in the central Santa Barbara Basin, dated by varve counts to A.D. 1605 ± 5 yr, implies an intensity of precipitation, flooding of regional rivers, and transport of terrigenous detritus unmatched in the last 1000 yr. The inferred flood may correlate with the reported rare occurrence of a perennial lake (14C dated to 390 ± 90 B.P.) in California's Mojave Desert, 300 km east of the area draining into the Santa Barbara Basin. The dating of the A.D. 1605 ± 5 yr flood event is consistent with tree-ring evidence for a wet and cold paleoclimate elsewhere in the region. Regional and global climate evidence indicates that much of the world also experienced rapid, intense cooling around A.D. 1605. This cooling was probably accompanied by an equatorward shift of prevailing wind patterns and associated storm tracks.
Moisture History and Small Mammal Community Richness during the Latest Pleistocene and Holocene, Northern Bonneville Basin, Utah
Authors: Grayson Donald K.
Published: October 2002

Precipitation and net primary productivity are positively correlated in arid environments. Both variables are, in turn, correlated with mammal species richness, but this relationship is not necessarily positive. With increasing precipitation in arid areas of low to moderate productivity, mammal richness increases linearly; as rainfall and productivity increase beyond this point, mammal richness is known to decline in some areas, producing a relationship that has been termed “unimodal” or “humped.” In the Great Basin of the arid western United States, studies of the relationship between rodent species richness and precipitation have revealed only a positive relationship between these two variables. It has, however, been argued that if areas of higher precipitation were to be sampled within this region, the decline phase would become evident. When latest Pleistocene and Holocene small mammal assemblages from the northern Bonneville Basin (central Utah) are examined across a temporal moisture gradient, species richness declines as moisture declines. Since the Great Basin was significantly moister during the latest Pleistocene and Early Holocene than it has been since that time, the unimodal response model does not appear to apply to this region.
Do Stable Isotope Data from Calcrete Record Late Pleistocene Monsoonal Climate Variation in the Thar Desert of India?
Authors: Andrews Julian E. , Singhvi Ashok K. , Kailath Ansu J. , Kuhn Ralph , Dennis Paul F. , Tandon Sampat K. , Dhir Ram P.
Published: October 2002

Late Pleistocene terrestrial climate records in India may be preserved in oxygen and carbon stable isotopes in pedogenic calcrete. Petrography shows that calcrete nodules in Quaternary sediments of the Thar Desert in Rajasthan are pedogenic, with little evidence for postpedogenic alteration. The calcrete occurs in four laterally persistent and one nonpersistent eolian units, separated by colluvial gravel. Thermoluminescence and infrared- and green-light-stimulated luminescence of host quartz and feldspar grains gave age brackets for persistent eolian units I–IV of ca. 70,000–60,000, ca. 60,000–55,000, ca. 55,000–43,000, and ca. 43,000–∼25,000 yr, respectively. The youngest eolian unit (V) is <10,000 yr old and contains no calcrete. Stable oxygen isotope compositions of calcretes in most of eolian unit I, in the upper part of eolian unit IV, and in the nonpersistent eolian unit, range between −4.6 and −2.1‰ PDB. These values, up to 4.4‰ greater than values from eolian units II and III, are interpreted as representing nonmonsoonal18O-enriched “normal continental” waters during climatic phases when the monsoon weakened or failed. Conversely, 25,000–60,000-yr-old calcretes (eolian units II and III) probably formed under monsoonal conditions. The two periods of weakened monsoon are consistent with other paleoclimatic data from India and may represent widespread aridity on the Indian subcontinent during isotope stages 2 and 4. The total variation in δ13C is 1.7‰ (0.0–1.7‰), and δ13C covaries positively and linearly with δ18O. δ13C values are highest when δ18O values indicate the most arid climatic conditions. This is best explained by expansion of C4grasses at the expense of C3plants at low latitudes during glacial periods when atmospheric pCO2was lowered. C4dominance was overridingly influenced by global change in atmospheric pCO2despite the lowered summer rainfall.
Late Quaternary Vegetation and Climate Change in the Amazon Basin Based on a 50,000 Year Pollen Record from the Amazon Fan, ODP Site 932
Authors: Haberle Simon G. , Maslin Mark A.
Published: October 2002

Hemipelagic sediments from the Amazon deep-sea fan, ODP Site 932 (5° 12.7′N, 47° 1.8′W), and continental shelf provide a 50,000-yr-long pollen record of Amazon Basin vegetation. The age model for Hole 932A is constrained by eight magnetic remanence intensity features, one paleomagnetic excursion, and three AMS14C dates.Alchornea,Melastomataceae, Myrtaceae, and Moraceae/Urticaceae are dominant taxa in the pollen record between 40,200 and 19,800 cal yr B.P. Andean taxa, such asPodocarpusandHedyosmum,increase in abundance between 19,800 and 11,000 cal yr B.P. and prior to 40,200 cal yr B.P. The Holocene pollen assemblage, derived from Amazon River and continental shelf sediments, is dominated by secondary growth taxa, such asCecropia.Climatic factors influencing the development of glacial and interglacial tropical vegetation are considered by comparing marine with terrestrial records of vegetation change. This comparison shows that the Amazon Basin forests were not extensively replaced by savanna vegetation during the glacial period, contradicting the refugia hypothesis.
A 560-Year Record of Santa Ana Fires Reconstructed from Charcoal Deposited in the Santa Barbara Basin, California
Authors: Mensing Scott A. , Michaelsen Joel , Byrne Roger
Published: October 2002

Microscopic charcoal from varved Santa Barbara Basin sediments was used to reconstruct a 560-yr record (A.D. 1425 to 1985) of Santa Ana fires. Comparison of large (>3750 μm2) charcoal with documented fire records in the Santa Barbara Ranger District shows that high accumulations correspond to large fires (>20,000 ha) that occurred during Santa Ana conditions. The charcoal record reconstructed a minimum of 20 large fires in the Santa Barbara region during the study period. The average time between fires shows no distinct change across three different land use periods: the Chumash period, apparently characterized by frequent burning, the Spanish/Early American period with nominal fire control, and the 20th century with active fire suppression. Pollen data support the conclusion that the fire regime has not dramatically changed during the last 500 yr. Comparison of large charcoal particle accumulation rates and precipitation reconstructed from tree rings show a strong relationship between climate and fire history, with large fires consistently occurring at the end of wet periods and the beginning of droughts.
Environmental and Archaeological Implications of a Late Quaternary Palynological Sequence, Poyang Lake, Southern China
Authors: Jiang Qinhua , Piperno Dolores R.
Published: October 2002

Paleoecological data from Poyang Lake, southern China, indicate that significant natural and human-induced vegetational changes have occurred during the Late Quaternary in the Middle Yangtze River valley, the likely location of rice (Oryza sativa L.) domestication. During the late Pleistocene (from ca. 12,830 to ca. 10,500 yr B.P.), the climate was cooler and drier than today's. The subtropical, mixed deciduous–evergreen broad-leaved forest which constitutes the modern, potential vegetation was reduced and herbaceous vegetative cover expanded. A hiatus in sedimentation occurred in Poyang Lake, beginning sometime after ca. 10,500 yr B.P. and lasting until the middle Holocene (ca. 4000 yr B.P.). At ca. 4000 yr B.P., the regional vegetation was a diverse, broad-leaved forest dominated by many of the same arboreal elements (e.g., Quercus, Castanopsis, Liquidambar) that grow in the area today. A significant reduction of arboreal pollen and an increase of herbaceous pollen at ca. 2000 yr B.P. probably reflect human influence on the vegetation and the expansion of intensive rice agriculture into the dryland forests near the river valleys.
Stratigraphy, Chronology, and Paleoenvironmental Reconstruction of the Quaternary Sedimentary Infilling of a Volcanic Tube in Fuerteventura, Canary Islands
Authors: Coello Juan J. , Castillo Carolina , Martı́n González Esther
Published: October 2002

La Cueva del Llano is a volcanic tube of Pleistocene age on Fuerteventura Island, in the Canary Islands. Part of it is infilled with sediments of external origin. These deposits are exceptional in stratigraphic complexity and thickness compared with other known tube infillings, and they comprise nine stratigraphic units deposited in five phases. In Phase I, which has not been dated, sedimentation of cinder from a nearby cone occurred. Phase II began ca. 16,830 ± 90014C yr B.P., whereas phase IV dates to 9280 ± 37014C yr B.P. The interpretation of sedimentary features shows that phases III and V correspond to a dry climate, similar to the present one, whereas the climate was much wetter during phases II and IV. This paleoclimatic sequence agrees with those suggested by the study of deposits formed in other sedimentary environments, not only in Fuerteventura but on other islands of the Canary group and the Sud-Maroc region.
The impact of gold price on the value of gold mining stock
Authors: Blose Laurence E. , Shieh Joseph C.P.
Published: October 2002

The value of a gold mine is shown to be a function of the return on gold, production costs, the level of gold reserves, and the proportion of assets unrelated to gold price risk. Assuming that forward gold prices are the market's unbiased expectations of future spot prices, a model is derived that estimates the theoretical gold price elasticity of gold mining stock. The model shows that if a company's primary business is gold mining, the gold price elasticity of the company's stock is greater than one. Using monthly data over the ten year period 1981 through 1990, the model is tested for a sample of 23 publicly traded gold mining companies.
Dap‐SL: a new site‐directed nitroxide spin labeling approach for determining structure and motions in synthesized peptides and proteins
Authors: McNulty Joe C , Thompson Darren A , Carrasco Michael R , Millhauser Glenn L
Published: October 2002

A new approach for site‐directed placement of nitroxide spin labels in chemically synthesized peptides and proteins is described. The scheme takes advantage of a novel diaminopropionic acid scaffold to independently control backbone and side chain elongation. The result is a spin‐labeled side chain, referred to as Dap‐SL, in which an amide bond forms a linker between the nitroxide and the peptide backbone. The method was demonstrated in a series of helical peptides. Circular dichroism and nuclear magnetic resonance showed that Dap‐SL introduces only a minor perturbation in the helical structure. The electron paramagnetic resonance spectrum of the singly labeled species allowed for determination of the spin label rotational correlation time and suggests that the Dap‐SL side chain is more flexible than the modified Cys side chain frequently used in site‐directed spin label studies. Spectra of the doubly labeled peptides indicate a mixture of 310‐helix and α‐helix, which parallels findings from previous studies. The scheme demonstrated here offers a fundamentally new approach for introducing spin labels into proteins and promises to significantly extend biophysical investigations of large proteins and receptors. In addition, the technique is readily modified for incorporation of any biophysical probe.
The Politics of Pension Reform in Latin America
Authors: MESA-LAGO CARMELO , MÜLLER KATHARINA
Published: October 2002

Latin America has been a world pioneer of neoliberal, structural reform of social security pensions (‘privatisation’). This article focuses on the diverse political economy circumstances that enabled such reform, analysing why policy makers have chosen such a costly strategy and how they have managed to implement it. First, in nine countries with diverse regimes (authoritarian and democratic) it examines the internal political process that led to the adoption of reform. There tends to be an inverse relationship between the degree of democratisation and that of privatisation, but the political regime alone cannot fully explain the reform outcomes in all cases. To expand the search for explanatory variables, other key factors that might have influenced the reform design are studied, among them relevant political actors (driving and opposing forces), existing institutional arrangements, legal constraints, internal and external economics and policy legacy.
Does Multiculturalism Menace? Governance, Cultural Rights and the Politics of Identity in Guatemala
Authors: HALE CHARLES R.
Published: October 2002

This article challenges the assumption that the underlying principles of state-endorsed ‘multiculturalism’ stand in tension with neoliberal political-economic policies. Based on ethnographic research in Guatemala, it is argued that neoliberalism's cultural project entails pro-active recognition of a minimal package of cultural rights, and an equally vigorous rejection of the rest. The result is a dichotomy between recognised and recalcitrant indigenous subjects, which confronts the indigenous rights movement as a ‘menace’ even greater than the assimilationist policies of the previous era. It is suggested that the most effective response to this menace is probably not to engage in frontal opposition to neoliberal regimes, but rather to refuse the dichotomy altogether.
Immigration of southern fish species to south-west England linked to warming of the North Atlantic (1960–2001)
Authors: Stebbing A.R.D. , Turk S.M.T. , Wheeler A. , Clarke K.R.
Published: October 2002

Evidence is provided that warming of the North Atlantic is responsible for the northward extensions of the ranges of warm water fish species, causing increasing numbers of southern immigrant species to appear off the Cornish coast of the UK. The increasing number of immigrant species is significantly correlated with temperature increases in the North Atlantic over the last 40 years.
Predation on cephalopods by the giant red shrimp Aristaeomorpha foliacea
Authors: Bello Giambattista , Pipitone Carlo
Published: October 2002

The stomachs of 427 giant red shrimps, Aristaeomorpha foliacea, caught in the Strait of Sicily (Mediterranean Sea) during four seasonal surveys contained 73 cephalopods, or 8·6% of prey. Cephalopods ranked third as prey following crustaceans (49·2% of prey) and bony fish (20·5% of prey). The following cephalopod taxa were identified: Heteroteuthis dispar, Sepietta oweniana, Brachioteuthis sp., Abraliopsis morisii, Onychoteuthis banksii, Ancistroteuthis lichtensteinii, Histioteuthis bonnellii, H. reversa, Taoniinae sp., Octopodidae sp.; the dominant species was Heteroteuthis dispar (13 specimens). All remains pertained to small and very small specimens, including early juveniles; rostral length of 13 beaks (=17·8% of cephalopods) measured <1 mm. Early juveniles were found in stomach contents only in summer and winter. Cephalopod size was found to be positively correlated to shrimp size. No seasonal nor predator sex-related differences were found in the quantities and frequencies of ingested cephalopods.
Microplankton community structure and the impact of microzooplankton grazing during an Emiliania huxleyi bloom, off the Devon coast
Authors: Fileman E.S. , Cummings D.G. , Llewellyn C.A.
Published: October 2002

Phytoplankton and microzooplankton community structure and the impact of microzooplankton grazing were investigated during a one-day study of an Emiliania huxleyi bloom off the coast of Devon during July 1999. Vertical profiles were undertaken at four stations, along a transect which crossed from a low reflectance to a high reflectance area as seen by satellite imagery. Microzooplankton dilution grazing experiments, coupled with pigment analysis to determine class specific grazing rates, were performed at two of these stations.

Highest concentrations of chlorophyll-a (5·3 mg m−3) and accessory pigments were measured inside the area of high reflectance. Phytoplankton standing stocks ranged between 1588 and 5460 mg C m−2 and were also highest in the area of high reflectance. The phytoplankton community was dominated by coccolithophores and diatoms in low reflectance waters and by photosynthetic dinoflagellates in high reflectance areas. Microzooplankton standing stocks ranged between 905 and 2498 mg C m−2. Protozoa dominated the microzooplankton community. The protozoan community comprised a relatively even mixture of heterotrophic dinoflagellates, non-choreotrich and choreotrich ciliates in low reflectance waters. However, non-choreotrich ciliates dominated the communities inside the high reflectance area. Of the heterotrophic ciliates, a predatory ciliate Askenasia sp. dominated both non-choreotrich abundance and biomass.

Results from grazing experiments showed that 60–64% of the chlorophyll-a biomass was consumed daily by the microzooplankton. Highest grazing mortality was associated with peridinin (dinoflagellates) and alloxanthin (cryptophytes). Lower grazing rates were found on fucoxanthin (diatoms and prymnesiophytes). Our results indicate that grazing on E. huxleyi in the area of remotely sensed high reflectance was low and highest grazing was on photosynthetic dinoflagellates and cryptophytes.
Trends in strandings and by-catch of marine mammals in north-west Spain during the 1990s
Authors: López A. , Santos M.B. , Pierce G.J. , González A.F. , Valeiras X. , Guerra A.
Published: October 2002

Strandings of marine mammals on the north-western Spanish coast (Galicia) have been systematically recorded since 1990. A total of 1433 marine mammals belonging to 15 species was recorded from 1990 to 1999. The most frequently recorded species stranded were common dolphin (47%), bottlenose dolphin (11%) and harbour porpoise (7%). The number of strandings recorded increased annually over the study period, probably reflecting an increased observer effort. During 1996–1999, an average of 1·65 animals were stranded annually for each 10 km of coastline, the highest density of strandings recorded on the Atlantic coast of the Iberian Peninsula. More than 80% of the strandings were located on the western coast of Galicia, mainly in autumn and winter. During the study period, 42 proven incidental catches were recorded, although signs of by-catch were seen in a further 198 animals. The average size of stranded common dolphins and the proportion of males both increased towards the end of the calendar year.
Special values of the hypergeometric series III
Authors: JOYCE G. S. , ZUCKER I. J.
Published: October 2002

In two previous papers [7, 10] the algebraic and transcendental
values of the Gauss hypergeometric series

F(a, b; c; z) = 1+abcz1!+a(a+1)b(b+1)c(c+1)z22!+…
(1·1)

were investigated, for various real rational parameters a; b; c and
algebraic and rational values of z ∈ (0, 1), by applying the singular values of the
complete elliptic integral of the first kind K(k) to certain classical
F transformation formulae, where k denotes the modulus. Our main aim in the
present paper is to use similar methods to determine the special values of (1·1) for
the case a = 112, b = 712
and c = 23.
The aged foot
Authors: Evans Gareth
Published: October 2002

Foot problems are common in elderly people and healthy feet are recognized as a key factor in maintaining activity and independence. People aged over 75 years exhibit a greater degree of foot pathology than a younger population and foot pain is prevalent in a high percentage of elderly patients. Foot problems impair mobility in many older people and may also contribute to falls. The immobility that results from a local foot problem can have a significant impact on the patient’s ability to maintain life as a useful member of society and has been identified as a common cause of unreported disability, often accepted as an accompaniment of the aging process. With increasing age, many foot problems which may have been well compensated for earlier in life will begin to reduce an elderly person’s mobility and health-related quality of life.
The Beginnings of Astrobiology
Authors: Wickramasinghe Chandra
Published: October 2002

With the present surge of interest in astrobiology and its emergence as a new scientific
discipline in its own right, the role of a celebrated pioneer is all too often forgotten.
There can be little doubt that the late Sir Fred Hoyle played a key part in relating
astronomical phenomena to questions of life. One of his first contributions in this area
was his introduction of the so-called anthropic principle to astronomy. By the late
1940's astronomers had worked out how the simplest chemical element Hydrogen could
be converted into Helium in stars, thus providing the main energy source by which stars
shine. The building of nuclei beyond Helium by stellar nuclear processes appeared
difficult at the time because of instabilities in nuclei with atomic masses 5 and 8. Hoyle
had the grand vision of making most if not all of the elements in the Periodic Table in
stars. In the early 1950's Hoyle argued that by the very fact of our existence, the
existence of life, the element Carbon had to be synthesised in quantity in stars. This
could not happen, Hoyle concluded, unless the nucleus of Carbon possessed an energy
level corresponding to a hitherto unknown excited state which he was able to calculate.
This was necessary so that three Helium nuclei could combine first to form a Carbon
nucleus in the excited state that subsequently decayed into the ground state. One of the
major triumphs of Hoyle's Anthropic Principle was that his predicted excited state was
subsequently discovered in the laboratory by Ward Whaling and Willy Fowler at
Caltech. This discovery opened the door to a brand new discipline of Nuclear
Astrophysics. In a seminal paper published in 1957, Hoyle together with Willy Fowler,
Geoffrey and Margaret Burbidge showed that all the chemical elements needed for life
C, N, O, P, Mg, Fe, S … were made in stars. In a sense Hoyle's work in 1957 already
provided the foundation stone for astrobiology. He showed that in essence we were
made of stardust.
A new model for the interpretation of the unidentified infrared bands (UIBS) of the diffuse interstellar medium and of the protoplanetary nebulae
Authors: Cataldo Franco , Keheyan Yeghis , Heymann Dieter
Published: October 2002

In this work we started from the basic idea that the pure polycyclic aromatic hydrocarbons (PAHs) cannot be the real carriers of the unidentified infrared bands (UIBs), the emission spectra coming from a large variety of astronomical objects. Instead we propose a new model taken from petroleum chemistry which, we can show, is able to match both the UIBs and even the protoplanetary nebulae (PPNe) spectra. PAHs such as phenanthrene, benzoperylene, coronene and pentacene, are too pure and too specific to really exist in the interstellar medium. Instead our model proposes that the carrier of UIBs and PPNe are complex molecular mixtures like those obtained as fractions during the petroleum refining processes. These molecular mixtures are so complex that practically the investigators did not try to identify each individual component but characterized the mixture with an average molecular structure that takes into account both the average molecular weight and the average content of aromatic, naphtenic (cycloaliphatic) and aliphatic (paraffinic) fraction. We show by infrared spectroscopy that petroleum fractions obtained at certain steps of the refining process are able to match the UIBs and the PPNe infrared bands with the advantage of not being so specific as PAHs are. Namely we have used as samples a distillate aromatic extract (DAE) a treated residual aromatic extract (T-RAE) and finally a naphtenic oil. Among the three samples examined, the DAE sample was the best in matching the UIBs and PPNe spectra.
Innervation Pattern of the Abductor Digiti Minimi Muscle of the Hand
Authors: GUDEMEZ E. , TEKDEMIR I. , USLU M. , EKSIOGLU F. , ELHAN A.
Published: October 2002

This cadaver study investigated the innervation patterns of the abductor digiti minimi in Guyon’s canal. There was only one branch to the abductor digiti minimi in 22 of the 30 specimens. Two branches were found in three hands, and three branches in two. Three other variations were documented.
“Pepper-Pot” Arthrodesis of the Small Joints of the Hand: Our Experience in 68 Cases
Authors: SHANKER H. K. , JOHNSTONE A. J. , RIZZO L. , CHESNEY R. B.
Published: October 2002

Sixty-eight small joint arthrodeses were performed in the hand using a new technique. Following removal of the articular cartilage, multiple drill holes are made through the subchondral bone, connecting the medullary canal with the joint space. The final joint position is maintained with an intraosseous wire loop and a Kirschner wire. Union was achieved at a mean of 7 weeks and our results are comparable with those of other series. This technique is easy to perform but is contraindicated if there is extreme joint destruction. Its main advantages are that the position of the fusion can be adjusted as bone-to-bone congruency is maintained through an arc of flexion and the overall length and shape of the digit is preserved.
Scaphoid Nonunion: Treatment with a Pedicled Vascularized Bone Graft Based on the 1,2 Intercompartmental Supraretinacular Branch of the Radial Artery
Authors: STRAW R. G. , DAVIS T. R. C. , DIAS J. J.
Published: October 2002

Pedicled vascularized bone grafts (Zaidemberg’s technique) were used to treat 22 established scaphoid fracture nonunions, 16 of which were found to have avascular proximal poles at surgery. After a follow-up of 1–3 years, only six (27%) of the 22 fracture nonunions had united. Only two of the 16 nonunions with avascular proximal poles united, compared with four of the six nonunions with vascular proximal poles. We conclude that this technique of pedicled vascularized bone grafting may not improve the union rate for scaphoid fracture nonunions with avascular proximal pole fragments.
Spreading-resistance profiling of silicon and germanium at variable temperature
Authors: Voss S. , Stolwijk N. A. , Bracht H.
Published: October 2002

We have developed the concept of variable-temperature spreading-resistance profiling (VT-SRP) for the characterization of electrical active impurities or defects in semiconductor crystals. Unlike conventional SRP systems, which are exclusively operated at room temperature, our home-built VT-SRP device allows for measurements at different temperatures typically ranging from 150 to 400 K. VT-SRP is able to combine the accurate resolution of an impurity depth profile with a determination of the predominant impurity-related electronic level in the semiconductor band gap. This feature was exploited on germanium crystals with diffusion-induced gold distributions. Another application concerns the depth profile analysis of foreign elements that occur in various defect configurations. This was demonstrated on Si samples diffused with sulfur or selenium since these impurities may be present as isolated atoms as well as pairs. Given the well-known energy levels of the two S or Se configurations in Si we were able to resolve not only the shape and depth of the diffusion profile but also the ratio of isolated atoms to pairs in the diffusion zone.
Time domain reflectrometry: Calibration techniques for accurate measurement of the dielectric properties of various materials
Authors: Pettinelli Elena , Cereti Annamaria , Galli Alessandro , Bella Francesco
Published: October 2002

In this work, an extensive theoretical and experimental analysis has been carried out on the main factors that affect the accurate evaluation of dielectric properties using time domain reflectometry (TDR). Dielectric constant measurements have been performed under different experimental conditions for various types of materials having a wide range of permittivity values. Interpretation of the results on the basis of the transmission-line theory emphasizes the importance of a suitable calibration procedure that takes into account several critical aspects, some of which seem to have been disregarded or underestimated in the literature. Qualitative and quantitative information is given on the kind of corrections needed in order to significantly improve the reliability of the TDR technique for permittivity measurements.
A low-temperature ultrahigh vacuum scanning force microscope with a split-coil magnet
Authors: Liebmann M. , Schwarz A. , Langkat S. M. , Wiesendanger R.
Published: October 2002

We present the design of a scanning force microscope, which is optimized for magnetic force microscopy experiments. It can be operated at temperatures down to 5.2 K, in ultrahigh vacuum, and in magnetic fields of up to 5 T. Cooling is provided by a liquid helium bath cryostat, and the magnetic field is generated by a superconducting split-coil magnet. The design allows easy access from the side through a shutter system for fast in situ tip and sample exchange, while the microscope stays at temperatures below 25 K. The microscope itself features an all-fiber interferometric detection system, a 7.5×7.5 μm2 scan area at 5.2 K, and an xy table. The topographic resolution is demonstrated by imaging monoatomic steps on a nickel oxide surface, while magnetic contrast is shown on cobalt platinum multilayers and on a manganite perovskite film.
Raman scattering and photoluminescence from Si nanoparticles in annealed SiOx thin films
Authors: Nesheva D. , Raptis C. , Perakis A. , Bineva I. , Aneva Z. , Levi Z. , Alexandrova S. , Hofmeister H.
Published: October 2002

Silicon-rich silicon oxide thin films have been prepared by thermal evaporation of silicon monoxide in vacuum. The SiOx film composition (1.1⩽ x ⩽1.7) has been controlled by varying the deposition rate and residual pressure in the chamber. Long time stability of all films has been ensured by a postdeposition annealing at 523 K for 30 min in Ar atmosphere. Some films were further annealed at 973 K and some others at 1303 K. Raman scattering measurements have implied the formation of amorphous silicon nanoparticles in films annealed at 973 K and Si nanocrystals in films annealed at 1303 K. The latter conclusion is strongly supported by high resolution electron microscopy studies which show a high density of Si nanocrystals in these films. Photoluminescence has been observed from both amorphous and crystalline nanoparticles and interpreted in terms of band-to-band recombination in the nanoparticles having average size greater than 2.5 nm and carrier recombination through defect states in smaller nanoparticles.
Electron excitation energies using a consistent third-order propagator approach: Comparison with full configuration interaction and coupled cluster results
Authors: Trofimov A. B. , Stelter G. , Schirmer J.
Published: October 2002

A recently developed consistent third-order propagator method for the treatment of electronic excitation in molecules is tested in first applications. The method referred to as third-order algebraic-diagrammatic construction [ADC(3)] extends the existing second-order approximation and aims at a more accurate computation of excitation energies and transition moments than afforded at the second-order level. For a stringent test of the method we compare the ADC(3) energies for over 40 singlet and triplet vertical transitions in H2O, HF, N2, and Ne with the results of recent full configuration interaction (FCI) and coupled cluster (CC) computations. The ADC(3) results reflect a substantial and uniform improvement with respect to the second-order description. The mean absolute deviation of the single excitation energies from the FCI results is below 0.2 eV. Although this does not equal the accuracy of the third-order CC3 model, the ADC(3) method, scaling as N6 with the number of orbitals, may be viewed as a good compromise between accuracy and computational cost.
Equilibrium polymerization of cyclic carbonate oligomers. III. Chain branching and the gel transition
Authors: Ballone P. , Jones R. O.
Published: October 2002

Ring-opening polymerization of cyclic polycarbonate oligomers, where monofunctional active sites act on difunctional monomers to produce an equilibrium distribution of rings and chains, leads to a “living polymer.” Monte Carlo simulations [two-dimensional (2D) and three-dimensional (3D)] of the effects of single [J. Chem. Phys. 115, 3895 (2001)] and multiple active sites [J. Chem. Phys. 116, 7724 (2002)] are extended here to trifunctional active sites that lead to branching. Low concentrations of trifunctional particles c3 reduce the degree of polymerization significantly in 2D, and higher concentrations (up to 32%) lead to further large changes in the phase diagram. Gel formation is observed at high total density and sizable c3 as a continuous transition similar to percolation. Polymer and gel are much more stable in 3D than in 2D, and both the total density and the value of c3 required to produce high molecular weight aggregates are reduced significantly. The degree of polymerization in high-density 3D systems is increased by the addition of trifunctional monomers and reduced slightly at low densities and low c3. The presence of branching makes equilibrium states more sensitive (in 2D and 3D) to changes in temperature T. The stabilities of polymer and gel are enhanced by increasing T, and—for sufficiently high values of c3—there is a reversible polymer–gel transformation at a density-dependent floor temperature.
Dynamics and rheology of inhomogeneous polymeric fluids: A complex Langevin approach
Authors: Fredrickson Glenn H.
Published: October 2002

A complex Langevin framework is described for carrying out numerical simulations of coupled field equations for flow and structure of inhomogeneous polymeric fluids. The formalism permits an exact embedding of the relevant thermodynamic forces into the dynamical equations, regardless of the characteristic length scale of the inhomogeneities in the fluid. As such, it is capable of treating a wide variety of systems, such as dilute and semidilute polymer solutions, microemulsions, block copolymers, and micellar solutions, including those whose equilibrium properties and self-assembly characteristics are not well described by mean-field theory. The formalism also integrates with existing molecular and continuum descriptions of coupled stress and species concentration dynamics. In this report, we present the method for the simplest case of a homopolymer solution.
Multichannel collimator for structural investigation of liquids and amorphous materials at high pressures and temperatures
Authors: Mezouar M. , Faure P. , Crichton W. , Rambert N. , Sitaud B. , Bauchau S. , Blattmann G.
Published: October 2002

A new multichannel collimator optimized for Paris–Edinburgh press geometry and a two-dimensional imaging plate detector have been developed at beamline ID30 at the European Synchrotron Radiation Facility. This system allows in situ collection of high quality x-ray diffraction data of liquids and amorphous materials simultaneously at high pressure and high temperature conditions. Excellent improvements in terms of signal to background ratio have been obtained. In order to illustrate the potential of this new device, preliminary results on liquid tin and lead under high pressure are presented.
Athermal annealing at room temperature and enhanced activation of low- energy boron implants with high-energy Si coimplantation
Authors: Shao Lin , Wang Xuemei , Liu Jiarui , Bennett Joe , Larsen Larry , Chu Wei-Kan
Published: October 2002

Interactions between shallow implanted boron and high-energy silicon implants have been investigated. Athermal annealing of implantation damage induced by low energy boron implants at room temperature was observed after coimplantation and such annealing effects were more obvious when the dosage of preimplanted Si was increased. Electrical measurements after rapid thermal annealing showed that the activation of B was greatly increased with the dosages of high-energy Si coimplantation. An enhancement of substitutional ratio of B was observed by aligned nuclear reaction analysis.
Comment on “Conduction and low frequency channel noise of GaAs based pseudomorphic high electron mobility transistors” [J. Appl. Phys. 91, 3318 (2002)]
Authors: Py M. A. , Buehlmann H.-J.
Published: October 2002

In order to analyze the low-frequency noise of GaAs based pseudomorphic high electron mobility transistors, Valenza et al. [J. Appl. Phys. 91, 3318 (2002)] proposes a model of the conduction at low drain bias with a procedure to extract the few relevant parameters. However, the original derivation of this analytical model and the parameter extraction procedure were published in 1991, 1994, and in connection with a detailed 1/f noise analysis in 1996. This fact is not clearly recognized in the aforementioned article, due in particular to a misquotation of the first equation. Apart from clarifying this point, we give a comment on the noise results.
Approximate simulation of coupled fast and slow reactions for stochastic chemical kinetics
Authors: Haseltine Eric L. , Rawlings James B.
Published: October 2002

Exact methods are available for the simulation of isothermal, well-mixed stochastic chemical kinetics. As increasingly complex physical systems are modeled, however, these methods become difficult to solve because the computational burden scales with the number of reaction events. This paper addresses one aspect of this problem: the case in which reacting species fluctuate by different orders of magnitude. By partitioning the system into subsets of “fast” and “slow” reactions, it is possible to bound the computational load by approximating “fast” reactions either deterministically or as Langevin equations. This paper provides a theoretical background for such approximations and outlines strategies for computing these approximations. Two motivating examples drawn from the fields of particle technology and biotechnology illustrate the accuracy and computational efficiency of these approximations.
Coupled ion–interface dynamics and ion transfer across the interface of two immiscible liquids
Authors: Kornyshev A. A. , Kuznetsov A. M. , Urbakh M.
Published: October 2002

When an ion moves across the interface of two immiscible electrolytes it moves together with the ion-induced protrusion of one solvent into the other. For an infinitely slow motion of an ion the height of the protrusion, heq, is a function of the position of the ion z. Due to a finite relaxation time the protrusion may not be able to spontaneously follow the motion of the ion, and this will cause slowing down of the ion transfer. The relaxation of the protrusion involves the movements of many solvent molecules and must be considered on the same footing as the motion along the coordinate of the ion. In this paper we develop a theory of such coupled motion which determines the kinetic laws of the ion transfer across the interface. When the equilibrium electrochemical potential for the ion has no barrier, the process of ion transport is purely diffusional and the effective diffusion coefficient may be evaluated as Deff=kBT/{6η[ri+(4/3)(hmax/Λ)2L]}, where η is the average viscosity of the liquids, ri is the Stokes radius of an ion, L and hmax is the lateral size and the maximal height of the protrusion, and Λ is the half width of the function heq(z), which characterizes equilibrium ion–interface coupling. When there is a barrier, the theory recovers, depending on the height of the barrier, the mechanisms of ion transfer considered by Marcus or Gurevich–Kharkats–Schmickler. The effect of the nature of the ion and the solvents in contact is discussed.
Self-consistent nonperturbative theory: Application to a two-dimensional square-well system
Authors: Serrano-Illán J. , Mederos L. , Navascués G. , Velasco E.
Published: October 2002

A self-consistent, nonperturbative theory, developed to describe the structure and thermodynamics of a classical system of particles and presented in a previous paper [Phys. Rev. E 65, 016131 (2002)], is generalized to a two-dimensional system and applied to the square-well potential. The theory predicts a phase diagram which turns out to be in very good agreement with that obtained by computer simulations performed by us. This is a consequence of the very accurate results of the theory as concerns the angle-averaged two-body distribution function and the Helmholtz free energy, which we also present and compare with computer simulations. By contrast, a first-order perturbation theory only provides qualitative agreement, showing that higher-order terms play an important role and that these terms are well accounted for by the nonperturbative theory.
Homogeneous nucleation of droplets from a supersaturated vapor phase
Authors: Moody Michael P. , Attard Phil
Published: October 2002

An approximate semianalytic theory is developed to describe the homogeneous nucleation of droplets from a supersaturated vapor, beginning with a partition function and including rigorously the translation and surface tension contributions. The liquid and vapor phases are treated as uniform (step density profile) and may be described by any accurate equation of state. It is shown that the classical approximation for the free energy of droplet formation may be derived from the present theory by making additional approximations (ideal gas, incompressible liquid), and the two are compared for the case where the vapor phase forms a reservoir (constant supersaturation). In the case of a finite-sized vapor phase, where the supersaturation decreases as the droplet grows, a free energy minimum exists beyond the critical radius, and this stable droplet equilibrium is examined in detail. Comparison with computer simulations proves the quantitative accuracy of the present theory for a Lennard-Jones system. Also derived is a new, formally exact expression for the surface tension that is useful for computer simulations.