bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical Engineering, Fractal and Disordered System Theory
Authors: Giona Massimiliano 
Published: May 2003

This article critically discusses the applications of fractal and disordered system theory to chemical engineering problems in order to highlight some promising research directions and the difficulties that may be encountered. Starting from the analysis of transport and reaction kinetics, the question is addressed, with the aid of some examples, of whether and how engineering research could help in the study of complex phenomenologies on fractals and disordered systems. The effects of thermodynamical nonidealities in transport and adsorption, and the influence of nonlinearities in reaction kinetics are discussed in some detail. Examples of typical engineering problems in which fractal analysis may help towards a better understanding of the physical phenomenologies in the presence of complex porous substrata and fluid mixtures are discussed. The role played by the boundary conditions on transport phenomena involving fractal structures is also analyzed. A critical discussion on the perspectives in the characterization of disordered and fractal porous structures, and in the study of turbulent transport and mixing is also developed.
An Example of How Nonlinear Dynamics Tools Can be Successfully Applied to A Chemical System
Authors: Pellegrini L. , Possio C. Tablino , Biardi G. 
Published: May 2003

The nonlinear dynamic behavior of a Proportional-Integral controlled Continuously Stirred Tank Reactor (CSTR) is analyzed in depth progressing from chaos characterization, through the high codimension bifurcation theory, up to the application of Controlling Chaos techniques. All these tools can be successfully applied to recognize, to avoid and to use chaos in practical applications, so that the nonlinear dynamic theory turns out to be an indispensable science to constrain dynamic systems to work in the most suitable operative conditions.
PROBABILITY MODELS FOR SEQUENTIAL-STAGE SYSTEM RELIABILITY GROWTH VIA FAILURE MODE REMOVAL
Authors: GAVER DONALD P. , JACOBS PATRICIA A. , GLAZEBROOK KEVIN D. , SEGLIE ERNEST A. 
Published: May 2003

This paper provides guidance for the planners of a test of any system that operates in sequential stages: only if the first stage functions properly (e.g., a vehicle's starter motor rotates adequately) can the second stage be activated (ignition system performs) and hence tested, followed by a third stage (engine starts and propels vehicle), with further stages such as wheels, and steering, and finally brakes eventually brought to test. Each sequential stage may fail to operate because its design, manufacture, or usage has faults or defects that may give rise to failure. Testing of all stages in the entire system in appropriate environments allows failures at the various stages to reveal defects, which are targets for removal. Early stages' fault activations thus postpone exposure of later stages to test. It is clear that only by allowing the entire system to be tested end-to-end, through all stages, and to observe several total system successes can one be assured that the integrated system is relatively free of defects and is likely to perform well if fielded. The methodology of the paper permits a test planner to hypothesize the numbers of (design) faults present in each stage, and the stagewise probability of a fault activation, leading to a system failure at that stage, given survival to that stage. If the test item fails at some stage, then rectification ("fix") of the design occurs, and the fault is (likely) removed. Failure at that stage is hence less likely on future tests, allowing later stages to be activated, tested, and fixed. So reliability grows. To allow many Test and Fix (TAF) cycles is obviously impractical. A stopping criterion proposed by E. A. Seglie that suggests test stopping as soon as an uninterrupted run/sequence of r (e.g., 5) consecutive system successes has been achieved is studied quantitatively here. It is shown how to calculate the probability of eventual field success if the design is frozen and the system fielded after such a sequential stopping criterion is achieved. The mean test length is also calculated. Many other calculations are possible, based on formulas presented.
HERBERT SCREW FIXATION OF SCAPHOID FRACTURES
Authors: Low C. K. , Ang B. T. 
Published: May 2003

Forty-four scaphoid fractures treated with open reduction and internal fixation using the Herbert screw were available for evaluation at an average follow-up period of 2.1 years and a range of 1 to 6 years. They were classified according to Herbert into 25 unstable (type B); 8 delayed unions (type C); and 11 nonunions (type D). Bone grafting was required in 22 cases. Sound radiological union was achieved in 42 cases at an average of 3.2 months. The two nonunions healed after revision grafting.Using the Mayo wrist score, excellent results were achieved in 14 cases; good in 22; fair in 4; and poor in 4. Poor results were associated with nonunion in two; untreated scapholunate dissociation in 1; and screw protrusion in 1.
PERCUTANEOUS A1 PULLEY RELEASE A CLINICAL STUDY
Authors: Bain G. I. , Wallwork N. A. 
Published: May 2003

Percutaneous A1 pulley release is being increasingly used as an alternative to open surgical release and injection of local steroids for the treatment of the trigger digit.In 31 cases (26 patients), a percutaneous release was performed with a 14-gauge intravenous catheter needle under local anaesthesia in the outpatient setting.We report a 97% successful release and only one case of incomplete release. There were no digital nerve injuries, flexor tendon injuries, bowstringing or infections. By two months, all the patients had no pain at the operative site, and their preoperative range of motion had returned or improved.The percutaneous release is a safe and effective technique which provides significant cost savings. We recommend the percutaneous technique for typical cases of trigger finger with a palpable nodule and reproducible mechanical triggering. We recommend a steroid injection for patients with tenosynovitis and those who do not have reproducible triggering at the time of presentation. The open technique is reserved for complicated cases such as florid tenosynovitis, locked digit, failed percutaneous release or those involving the thumb.
MESSY BROADCASTING IN MULTIDIMENSIONAL DIRECTED TORI
Authors: COMELLAS FRANCESC , HARUTYUNYAN HOVHANNES A. , LIESTMAN ARTHUR L. 
Published: May 2003

In classical broadcast models, once a vertex receives the broadcast message, it sends the message out in such a way as to achieve the minimum possible broadcasting time. It is assumed either that there is a leader who coordinates the actions of all vertices during the broadcasting process, or that the vertices have a coordinated set of protocols which allow them to achieve minimum time broadcast for any originator. In the messy broadcast model, there is no leader, the vertices of the network do not know the starting time of the broadcast or the originator, the state of the whole scheme is unknown to any vertex, and the protocols are not coordinated. This model also describes a network with vertices that have small memories insufficient to store a set of coordinated protocols. In this paper, we continue the study of messy broadcasting and present the first results for directed graphs. We obtain exact values for and bounds on the messy broadcast times of multidimensional directed tori.
A COMPACT LAYOUT OF THE BUTTERFLY
Authors: DINITZ YEFIM , EVEN SHIMON , ZAPOLOTSKY MARIA 
Published: May 2003

For the Butterfly of N input/output vertices we present a layout on the rectilinear (square) grid of area ½N2 + o(N2). A lower bound of the same order is proved. The encompassing rectangle which defines the area is 45° slanted w.r.t. the grid axes and the input/output vertices are not on the boundary of this rectangle. The layout is component-scalable, i.e., if one allocates for each switch a square of a × a area, the layout remains of area ½N2 + o(N2); that is, the value of a affects only the o(N2) term. The layout is also free of knock-knees.
Estimation of Entropy and Mutual Information
Authors: Paninski Liam 
Published: May 2003

We present some new results on the nonparametric estimation of entropy and mutual information. First, we use an exact local expansion of the entropy function to prove almost sure consistency and central limit theorems for three of the most commonly used discretized information estimators. The setup is related to Grenander's method of sieves and places no assumptions on the underlying probability measure generating the data. Second, we prove a converse to these consistency theorems, demonstrating that a misapplication of the most common estimation techniques leads to an arbitrarily poor estimate of the true information, even given unlimited data. This “inconsistency” theorem leads to an analytical approximation of the bias, valid in surprisingly small sample regimes and more accurate than the usual [Formula: see text] formula of Miller and Madow over a large region of parameter space. The two most practical implications of these results are negative: (1) information estimates in a certain data regime are likely contaminated by bias, even if “bias-corrected” estimators are used, and (2) confidence intervals calculated by standard techniques drastically underestimate the error of the most common estimation methods. Finally, we note a very useful connection between the bias of entropy estimators and a certain polynomial approximation problem. By casting bias calculation problems in this approximation theory framework, we obtain the best possible generalization of known asymptotic bias results. More interesting, this framework leads to an estimator with some nice properties: the estimator comes equipped with rigorous bounds on the maximum error over all possible underlying probability distributions, and this maximum error turns out to be surprisingly small. We demonstrate the application of this new estimator on both real and simulated data.
Partner choice in piranha shoals
Authors: Magurran Anne , Queiroz Helder 
Published: May 2003

AbstractAlthough the red-bellied piranha, Pygocentrus nattereri is widely portrayed as a pack-hunting predator virtually nothing is known about its shoaling behaviour. Using fish collected in the flooded forest of the Brazilian Amazon, we conducted a range of choice tests to determine whether individual piranhas make non-random shoaling decisions. These revealed that partner size had a significant impact on shoaling preferences. Piranha shoals were size structured with large, sexually mature, individuals occupying the central zone (defined as within the polygon connecting fish at the edge of the shoal). Small, non-reproductive individuals showed greater motivation to feed. Fish did not discriminate between size-matched individuals from the same and different locality and we found no evidence of intraspecific aggression, despite the piranha's reputation for cannibalism.
Ejaculate size variation in the migratory locust, Locusta migratoria
Authors: Arlt Debora , Reinhardt Klaus 
Published: May 2003

AbstractSperm competition models suggest that ejaculate size (ES) is adjusted in relation to female fecundity and the risk of sperm competition, depending on the information males have about that risk. We tested these ideas in the migratory locust, Locusta migratoria, a species in which ES may be an important male fitness parameter. Copulation duration was positively correlated with ES. Males did not increase copulation duration but sperm transfer in the presence of competitors during mating. They did so only when they were reared in conditions that allowed female perception prior to mating. Males that prior to mating were kept with other males only did not show ES variation with regard to different sex ratios at mating. Increased female availability did not affect ES. A male size and condition related parameter was not significantly correlated to ES but older males delivered smaller ejaculates. Females of larger size were inseminated larger amounts of sperm. There was a positive correlation between female size and ES only for males of lower condition and lower relative testis weight but not for males of good condition or higher relative testis weight.
African wild dog pup vocalizations with special reference to Morton's model
Authors: Robbins Robert , McCreery E. Kim 
Published: May 2003

AbstractAfrican wild dog (Lycaon pictus) pup vocalizations were studied in Hwange National Park, Zimbabwe for weeks 3 through 7 of the socialization period. Here we present the vocal repertoire, including the use of repetitive and mixed sounds, and investigate the extent to which the emerging sound system of Lycaon conforms to predicted design features of Morton's (MS) motivation-structural rules. Features of the pup sound system are highlighted by comparison with adults and other social canids. Data were collected at three den sites (litter sizes: 8, 8, and 9) of two study packs. A total of 1903 vocalizations were classified, and eight vocal classes and seven subclasses were identified. Although all sounds identified persist into adulthood, observations indicate a delayed onset in some vocal classes, including both the lowest (i.e. rumbles) and highest (i.e. twitters) frequency sounds. As predicted by the (MS) model, pups invested heavily in high frequency, harmonic care/social soliciting sounds (91%, N = 1586 unmixed vocalizations), however, no clear association between acoustic structure and sound repetition was found. Significantly more repetition was heard in all vocal classes with the exception of moans and barks. Intra-pack aggression is generally muted in this obligate social carnivore suggesting that repetition may be a low cost strategy to induce social outcomes and obtain food. The patterning of mixed vocalizations (N = 317) was consistent with the (MS) model. Given the high degree of cooperation necessary for individual survival, the predominant use of cross-mixed sounds may serve to minimize conflict as pups begin to form relationships with littermates and adults. Noisy/noisy sounds were exceptionally rare. Comparative data suggest a relationship between the early patterning of mixed sounds and species-specific social organization in canids.
Dynamic changes in alarm call structure: a strategy for reducing conspicuousness to avian predators?
Authors: Evans Christopher , Bayly Karen 
Published: May 2003

AbstractThe design of many animal signals reflects the need to maximize signal efficacy while minimizing conspicuousness to eavesdroppers. The aerial alarm calls of birds have been a useful model system for exploring such evolutionary tradeoffs at the level of general call structure, but much less is known about changes in fine-scale signal characteristics over the course of an encounter with a potential predator. We analyzed variation in the alarm calls that male fowl, Gallus gallus, produced in response to raptor silhouettes moving overhead. Spectrogram cross-correlation was used to test for changes in structure over the course of a call bout. This analysis revealed that aerial alarm calls are individually distinctive and that they vary significantly from the first call to the second. We then measured single acoustic parameters, including the duration, dominant frequency and frequency bandwidth of each component in successive calls. Males almost invariably began the first call in a bout with a high amplitude broad-band pulse, which was followed by a much longer and highly variable sustained element. They then selectively reduced or eliminated the introductory pulse, while leaving other aspects of alarm structure unchanged. Recent work has shown that the introductory pulse is potentially costly because it has attributes that are readily localized by raptors. We suggest that male fowl have adaptive plasticity in alarm call structure, allowing them to manage short-term predation risk while continuing to signal to companions.
Mixed-species associations of Diana and Campbell's monkeys: the costs and benefits of a forest phenomenon
Authors: Wolters Sonja , Zuberbühler Klaus 
Published: May 2003

AbstractOne of the most striking behavioural patterns of many forest primates concerns their tendency to live in semi-permanent mixed-species groups. Functional investigations have ascertained that individuals obtain some antipredator benefits without paying the costs of intra-species resource competition. Despite these advances, very little is known about the subtle mechanisms that keep mixed species groups together on a daily basis. Our results showed that in the Diana-Campbell's monkey association both species benefited from each other in diverse and idiosyncratic ways. In the presence of Campbell's monkeys the conspicuous Diana monkeys were more likely to descend into the lower forest strata, increased their foraging behaviour, and individuals became less vigilant. The cryptic Campbell's monkeys, in turn, were able to use the higher forest strata and exposed areas more often, spread out over larger areas, were more likely to travel, and engaged in more conspicuous vocal behaviour when associated with Diana monkeys. These data suggested that both species benefited from each other in ways that went beyond passive group-size related antipredator benefits, such as a dilution effect and increased chances of predator detection. Instead, the increased safety of the mixed species group allowed individuals to exploit their ecological niche more broadly, to forage more efficiently, and to engage in more social behaviour, suggesting that the benefits of mixed species groups are much more varied and diverse than currently thought.
COPD: problems in diagnosis and measurement
Authors: Weiss S.T. , DeMeo D.L. , Postma D.S. 
Published: May 2003

Chronic obstructive pulmonary disease (COPD) is the most rapidly rising cause of death in individuals >65 yrs of age, the most rapidly growing segment of the USA population.Advancing the clinical research agenda for COPD entails careful consideration of several issues and problems: defining COPD, reliance on physiological testing, outcome measurements and comorbidities.In addition, issues pertaining to the recent dramatic increase in chronic obstructive pulmonary disease mortality in females, smoking susceptibility and the relationship of respiratory symptoms with hyperresponsiveness, as well as chronic obstructive pulmonary disease heterogeneity, are discussed.
The effect of temporal variation in biochemical markers of trisomy 21 across the first and second trimesters of pregnancy on the estimation of individual patient-specific risks and detection rates for Down's syndrome
Authors: Spencer K , Crossley JA , Aitken DA , Nix ABJ , Dunstan FDJ , Williams K 
Published: May 2003

Background: In a previous study we examined the changes in the median multiple of the median (MoM) with gestation of free beta human chorionic gonadotrophin (Fβ-hCG), total human chorionic gonadotrophin (ThCG), α-fetoprotein (AFP) and pregnancy-associated plasma protein A (PAPP-A) in a large series of Down's syndrome pregnancies. Results showed that there was a significant temporal variation of the MoM for each marker. In this paper, we assess the impact of this temporal shift on the estimation of patient-specific risks and the detection rates (DRs) for Down's syndrome pregnancies. Methods: Individual patient-specific risks, DRs and false positive rates were estimated using statistical modelling techniques and computer simulations. The data for these simulations were the regressed mean log10 analyte MoMs, marker standard deviations (as log10 MoM) and correlation coefficients derived from the analysis of over 1000 cases of Down's syndrome and 150 000 unaffected pregnancies between 6 and 20 weeks of gestation reported in our previous study. Two models were compared: the classical constant median separation model, which assumes no variation in median shift with gestation (model 1), and a variable median separation model (model 2), which takes account of the changes in median shift with gestation as described in our previous study. Results: When individual patient-specific risks calculated for various MoM values using model 1 were compared with those derived from model 2, considerable differences in risk estimates were observed for all marker combinations, particularly in the first trimester. Using a 1 in 250 cut-off risk, DRs at each gestation in the second trimester for the AFP+Fβ-hCG combination were maximized at 14-17 weeks of gestation and were virtually identical at 63-65% for model 1 and model 2. A similar trend was observed for the AFP+ThCG combination, with an optimum gestational range of 15-18 weeks and DRs of 66-68%. In the first trimester, using a 1 in 250 cut-off risk, DRs were more variable with gestation for the prime marker combination of Fβ-hCG+PAPP-A, varying from 73% at 8 weeks to 65% at 13 weeks with model 1 and from 75% to 66% with model 2. Conclusion: Risk algorithms should take into account temporal variation in marker MoMs in order to produce accurate patient-specific risks. This also helps to maximize DRs, particularly when samples are taken outwith the optimal gestational range.
Urinary PC-1 and N-acetyl-β-D-glucosaminidase activity in patients with type 2 diabetes treated with metformin, gliclazide or glibenclamide
Authors: Stefanovicć V , Anticć S , Miticć-Zlatkovicć M , Stojiljkovicć S , Milojkovicć M , Bogicevicć M , Vlahovicć P 
Published: May 2003

Background: Insulin resistance is a key feature of type 2 diabetes mellitus. Plasma cell differentiation antigen (PC-1) is an inhibitor of insulin receptor tyrosine kinase, and has been implicated in the pathogenesis of insulin resistance. Methods: Urinary excretion of PC-1 was determined in 45 newly detected, obese diabetic patients treated with metformin (16 patients), gliclazide (14 patients) or glibenclamide (15 patients). Urinary N-acetyl-β-D-glucosaminidase (NAGA), a lysosomal enzyme, was determined as a marker of tubular damage in diabetes. Results: Basal urinary PC-1 excretion in all three groups of diabetic patients was at the level of healthy controls. Treatment with oral hypoglycaemic drugs did not change significantly the group level or the number of patients in each group with increased PC-1 activity. Urinary excretion of NAGA in patients with type 2 diabetes was not statistically different from the control level. Metformin and gliclazide treatment did not change significantly the group levels of NAGA excretion. However, glibenclamide treatment produced an increased urinary NAGA excretion in the whole group, and in about twice as many patients as in the pre-treatment period.