bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative salinity tolerance of macroinvertebrates from the Barwon River, Victoria, Australia
Authors: Kefford Ben J. , Papas Phil J. , Nugegoda Dayanthi
Published: November 2003

Salinity levels are rising in many freshwater environments, yet there are few direct measurements of salinity tolerance of organisms likely to be salt sensitive. The relative salinity tolerance to artificial seawater of macroinvertebrates from the Barwon River in Victoria, Australia, was assessed by measuring the 72-h lethal concentrations required to kill 50% of individuals (LC50). LC50 values ranged from an electrical conductivity of 5.5 to 76 mS cm–1 (mean 31 mS cm–1, n = 57) and followed a log-normal distribution. The most salt-sensitive groups tested were Baetidae (LC50 value range: 5.5–6.2 mS cm–1), Chironomidae (10 mS cm–1) and several soft-bodied non-arthropods (Oligochaeta, Gastropoda, Nematomorpha, Tricladida and Hirudinea; 9–14 mS cm–1). Other groups, from least to most tolerant, were non-baetid Ephmeroptera (>12.6–15 mS cm–1), Plecoptera (>12.6–>20 mS cm–1), Trichoptera (9–>26 mS cm–1), Corixidae (18–26 mS cm–1), non-corixid Hemiptera (33–44 mS cm–1), Coleoptera (19–54 mS cm–1), Hydracarina (39 mS cm–1) and Odonata (30–55 mS cm–1), and macrocrustaceans (Decapoda, Isopoda and Amphipoda; 38–76 mS cm–1).
Phytoplankton responses to wastewater discharges at two sites in Western Australia
Authors: Thompson Peter , Waite Anya
Published: November 2003

The two main wastewater discharges on the west coast of Australia, near the city of Perth, were monitored for their potential impact on phytoplankton communities between 1996 and 2000. The wastewater outlets varied in their location, length and depth (at point of discharge), volume of discharge and nutrient load. Phytoplankton responses were markedly different in the vicinity of the two outlets. In the vicinity of the southern outlet with the greatest effluent volume and nutrient load, phytoplankton responses were at or near the level of detection, except during summer. In the vicinity of the northern outlet significant environmental impacts were noted: light attenuation was 32% greater, phosphate and nitrate concentrations were 301% and 548% greater, respectively, and phytoplankton biomass was 221% greater than the relevant control site. The magnitude of the environmental responses at these two outlets is hypothesized to be associated with differences in current speed and stratification. At the northern outlet, where a greater phytoplankton response was detected, biomass was negatively correlated with wind speed, which suggests that measurable biological impacts were associated with the retention of the buoyant effluent in the vicinity of the outlet during periods of slower along-shore transport.
Comparative effects of the large bioturbators, Trypaea australiensis and Heloecius cordiformis, on intertidal sediments of Western Port, Victoria, Australia
Authors: Katrak Gitanjali , Bird Fiona L.
Published: November 2003

The effect of bioturbation by the ghost shrimp Trypaea australiensis and semaphore crab Heloecious cordiformis was compared in sediment-filled tanks in the laboratory. Effect of bioturbator density was also investigated with high- and low-density treatments. It was hypothesised that the two species would influence the sediment profile in different ways owing to their contrasting burrowing and feeding habits. Both species increased porosity of surface sediments relative to control tanks. Crab activity did not alter redox potential, but low densities of shrimp created more oxidising conditions and high densities of shrimp created more reducing conditions than controls. Burial of tracer particles by crabs was restricted to the top 5 cm, whereas shrimp mixed particles to depths of 25 cm. Bioturbator density had little effect on the extent of particle mixing. The presence of both shrimp and crabs increased benthic microalgae in the sediments relative to the controls. Again, crabs had the greatest effect at the sediment surface, whereas shrimp also enhanced concentrations at 25 cm depth. High densities of shrimp had the greatest effect. Overall, shrimp bioturbation influenced deeper sediments than crab bioturbation, but there was no clear density-dependent effect.
Capacitation status and fertility of fresh and frozen - thawed ram spermatozoa
Authors: Gillan L. , Evans G. , Maxwell W. M. C.
Published: November 2003

The effect of cryopreservation on the capacitation status and fertility of ram
spermatozoa was observed. After the chlortetracycline staining technique was
validated for ram spermatozoa, it was applied to fresh or long-term
frozen-stored spermatozoa. Fresh spermatozoa displayed mainly the F pattern
(non-capacitated; 61·3%), becoming B pattern (capacitated;
54%) and AR pattern (acrosome reacted; 41%) with incubation (6 h
at 37°C). In contrast, frozen spermatozoa displayed the B pattern
(65· 9%), becoming the AR pattern (64·2%) with
incubation. This demonstrates that cryopreservation may cause membrane changes
in ram spermatozoa functionally equivalent to capacitation. The differences in
capacitation status did not affectin vitro fertilization
rates between fresh and frozen spermatozoa, but pregnancy rates at Day 18
after intrauterine artificial insemination were higher for fresh than for
frozen spermatozoa. This difference was not evident at Day 50, possibly as a
result of the high embryonic loss between Days 18 and 50 when fresh
unincubated and frozen incubated spermatozoa were inseminated. Further
research is necessary to determine what part of the cryopreservation process
is responsible for the membrane changes in ram spermatozoa.
Likely targets for immunocontraception in marsupials
Authors: Rodger John C.
Published: November 2003

There is a growing need to manage marsupial populations as a means to mitigate
economic and environmental damage and resolve animal welfare problems. In
Australia, the problems of population management are highly specific and
localized. In contrast, in New Zealand the problem is the control of the many
millions of widely-distributed brushtail possums which are the country’s
major vertebrate pest. The needs of the two countries are thus very different
but immunocontraception may provide an effective and humane alternative to
current lethal control strategies. This paper discusses the features of
marsupial reproduction and development that offer potential as targets for
immunocontraceptive interference, including: (1) sperm
production and maturation in the male; (2) sperm
transport and maturation in the female; and (3) sperm
and egg antigens and the early embryo. Some of these antigen targets are
shared with eutherian mammals but others are likely to be unique to
marsupials.
Comparison of LHRH-peptidase and plasminogen activator activity in rat testis extracts
Authors: Hedger Mark P. , Culler Michael D.
Published: November 2003

Testicular LHRH-peptidase and testicular urokinase-type plasminogen activator
are Sertoli cell-secreted proteases which display similar molecular
properties. However, there is relatively little information regarding the
substrate specificity and potential cross-reactivity of these enzymes.
Testicular extracts were prepared from homogenates of whole rat testes and
assessed by LHRH-peptidase assay, and by radial caseinolysis assays for
plasminogen activator and plasmin-like activity. Following partial
purification of the protease activities in testicular extracts by gel
filtration and ion-exchange chromatography, it was conrmed that testicular
LHRH-peptidase and plasminogen activator are clearly separable. There was no
detectable plasmin-like activity in the testicular extracts; however, the
extracts were found to contain an inhibitor, or inhibitors, of both
plasminogen activator and plasmin activity. In addition to LHRH and Gly
6 -substituted LHRH analogues, the partially purified
LHRH-peptidase degraded both angiotensins I and II, but not the
gonadotrophin-releasing-hormone-associated peptide derived from the LHRH
precursor molecule. These properties of the LHRH-peptidase provide further
evidence that it is a testis-specific prolyl endopeptidase, involved in
regulating and/or limiting peptide activity in the testis.
Control of endometrial phosphoinositide hydrolysis and prostaglandin F2α a secretion in pigs
Authors: Ludwig Tenneille E. , Whiteaker Shawn S. , Carnahan Kevin G. , Tysseling Kelly A. , Mirando Mark A.
Published: November 2003

This study examined the control of endometrial phosphoinositide (PI)
hydrolysis and prostaglandin (PG) F2α release by
oxytocin (OT) and vasopressin in cyclic pigs on Day 15 post oestrus. In Expt
1, OT and arginine-vasopressin (AVP) increased endometrial PI hydrolysis
(P<0.01), but only OT stimulated
(P<0.01) PGF2α secretion.
In Expt 2, OT and lysine-vasopressin (LVP) increased PI hydrolysis
(P<0.01). No difference was detected between the 100
n and 200 n concentrations of OT or between the 100 n and 200 n concentrations
of LVP. The increase in PI hydrolysis was greater
(P<0.05) for 100 n OT plus 100 n LVP than for the 100
or 200 n concentrations of OT or LVP alone. In Expt 3, OT
(P<0.01) and LVP increased
(P<0.01) PI hydrolysis. An OT antagonist abolished
(P<0.01) the OT-induced increase in PI hydrolysis,
but did not significantly alter the LVP-induced increase. A type 2 VP
antagonist completely inhibited (P<0.01) the
LVP-induced increase in PI hydrolysis, but only partially antagonized the
stimulatory effect of OT (P<0.01). These results are
consistent with the proposal that OT acts through specific receptors to
promote endometrial PGF2α secretion in pigs.
Uterine luminal content of insulin-like growth factor (IGF)-I and endometrial expression of mRNA encoding IGF-binding proteins 1 and 2 during the oestrous cycle and early pregnancy in the ewe
Authors: Cann C. H. , Fairclough R. J. , Browne C. A. , Gow C. B.
Published: November 2003

Cyclic (n= 30) and pregnant
(n = 29) Merino ewes were examined (n = 3
to 5 at most time points) over Days 0–16 and 0–22 after oestrus,
respectively. As IGFBP activity was detected in some plasma and ULF samples,
all samples were subjected to acid-gel chromatography before assay for IGF-I.
After oestrus, the overall means of both groups of ewes showed lower ULF IGF-I
content (Days 3 and 12), lower plasma IGF-I concentrations (Days 3–16),
higher endometrial expression of mRNA encoding IGFBP-1 (Days 12–16) and
lower endometrial expression of mRNA encoding IGFBP-2 (Day 8). Between Days 0
and 16 after oestrus, the pregnant ewes had lower plasma IGF-I concentrations
and higher endometrial expression of IGFBP-1 mRNA than did the cyclic ewes.
The presence of IGF-I in the ULF throughout the oestrous cycle and early
pregnancy suggests a role of IGF-I in early pregnancy, influencing both
uterine growth and embryonic survival. The concomitant endometrial expression
of mRNA encoding IGFBP-1 and IGFBP-2 suggests a role of these binding proteins
in the regulation of IGF-I bioavailability in the uterine environment of the
ewe.
Effect of compatible solutes and diluent composition on the post-thaw motility of ram sperm
Authors: Sánchez-Partida L. G. , Setchell B. P. , Maxwell W. M. C.
Published: November 2003

The effect of the compatible solutes proline, glycine betaine and trehalose in
Tris-based diluents at varying pH, concentrations of egg yolk or glycerol on
the post-thaw motility characteristics and fertility of ram sperm was
examined. In addition, the amino acid glycine was compared with proline,
glycine betaine and a standard Tris-based diluent. Post-thaw motility was
assessed using a Hamilton–Thorn motility analyser. In the presence of
glycerol and egg yolk, proline and glycine betaine improved the post-thaw
motility characteristics of ram sperm. Regardless of the pH of the diluent at
which semen was frozen, the percentage of motile sperm was higher when frozen
in the presence of proline or glycine betaine than in their absence, whereas
proline and glycine betaine only improved the progressive and rapid
percentages of sperm for semen frozen in diluents at pH lower than 7.0. When
semen was frozen in the absence of egg yolk or glycerol all the motility
characteristics were reduced. Increasing the concentration of egg yolk in the
diluent from 5% to 10, 15 or 20% had no effect on the post-thaw
motility of sperm. The addition of 27 mM of proline or glycine betaine to the
diluent also improved post-thaw motility. However, at a concentration of 81
mM, proline and glycine betaine had a detrimental effect on the percentage of
motile sperm. Trehalose had no effect on the motility of sperm frozen in
glycerol-containing diluents, but motility was lower after cryopreservation in
glycine than in Tris-, proline- or glycine betaine-based diluents. There were
no differences in the fertility of sperm frozen in Tris-, proline or glycine
betaine diluents after cervical or laparo-scopic insemination of ewes.
Managing the design‐manufacturing interface
Authors: Vandevelde Anneke , Van Dierdonck Roland
Published: November 2003

This paper describes the major barriers across the design‐manufacturing interface and examines ways to overcome them to achieve a smooth production start‐up. An integration model reveals that formalization facilitates a smooth production start‐up. Independent of the degree of formalization during the early development stages, a formal approach is preferred when the new product is introduced into production. Another facilitating factor is the empathy from design towards manufacturing, which can be stimulated by managerial actions. Although the complexity and newness of product and technology hinder a smooth production start‐up, their effect seems to vanish by introducing formalization and by striving for a design team that has empathy towards manufacturing.
Lean manufacturing: a perspective of lean suppliers
Authors: Chun Wu Yen
Published: November 2003

The main thrust of this paper empirically examines the connection between lean production and various aspects of the logistics system. This paper performs a comparison analysis to find whether significant performance/practice differences exist between lean suppliers and non‐lean suppliers. The research findings indicate that, even given the same organizational constraints and resources, lean suppliers gain significant competitive advantages over non‐lean suppliers in production systems, distribution systems, information communications, containerization, transportation systems, customer‐supplier relationships, and on‐time staging/delivery performance.
A multi‐attribute approach to understanding shopper segments
Authors: Yavas Ugur
Published: November 2003

The purpose of this paper is to assess the relative strengths and weaknesses of a mall as viewed by two shopper segments: those shoppers who prefer to shop there, versus those who favor a competitor mall. The importance‐performance technique is used in analyzing the data. Study results and their implications are discussed.
Exploratory evidence of channel performance in single vs multiple channel strategies
Authors: Coelho Filipe , Easingwood Chris , Coelho Arnaldo
Published: November 2003

Channel performance is a key marketing and organisational issue, given the potential and actual impact in the accomplishment of organisational goals. A recent trend in distribution strategy has been the increasing utilisation of multiple channels across sectors. Because of the newness of these channel systems, it is important to understand how they influence key channel performance indicators. With this purpose, a study was conducted in a sample of 62 UK financial services organisations. The research considered several indicators of channel performance, which were statistically reduced to two broad dimensions: sales and profitability. The results show that multiple channels are associated with higher sales performance and lower channel profitability. However, the statistical significance of the results was observed to depend on the extent to which multiple channels were being used. In addition, this article analyses the relationship between the number of channels and company size and product type. Implications for future research are derived.
Market orientation, trust and satisfaction in dyadic relationships:a manufacturer‐retailer analysis
Authors: Bigne Enrique , Blesa Andreu
Published: November 2003

This paper studies the relationships between the manufacturer's market orientation behaviours and the distributor's trust in the relationship and satisfaction with it. It also analyses the effect of the distributor's trust on his/her satisfaction. Following a review of the literature, three alternative models of relationships between trust and satisfaction are compared. For this purpose the article presents the results of a study of the Spanish ceramic industry. These establish that the effect of the manufacturer's market orientation on the distributor's trust and on its satisfaction with the relationship is different depending on which dimension is considered. The model that best fits the data shows that trust improves the distributor's satisfaction with the relationship.
In‐store customer behaviour in the fashion sector: some emerging methodological and theoretical directions
Authors: Newman Andrew J. , Foxall Gordon R.
Published: November 2003

Store layouts are important determinants of behaviour. A review of the academic and commercial literature suggests that the methodological and theoretical approaches have provided methods and approaches that are difficult for practitioners to adopt. This paper offers a robust theoretical approach (the behavioural perspective model) and new innovative methodology that significantly advances the way retailers can plan and measure store layouts, with a view to optimising store performance. Using computer‐aided observation, customers may be tracked and their behaviour analysed in the context of consumer situations and contingencies. Implications for retail management, theory and practice are discussed within the context of fashion shopper situations.
Decision support through knowledge management: the role of the artificial intelligence
Authors: Metaxiotis Kostas , Ergazakis Kostas , Samouilidis Emannuel , Psarras John
Published: November 2003

Knowledge management (KM) has recently received considerable attention in the computer information systems community and is continuously gaining interest by industry, enterprises and government. Decision support and KM processes are interdependent activities in many organizations. In all cases, decision makers always combine different types of data and knowledge available in various forms in the organization. One of the key – but also criticized – building blocks for advancing this field of knowledge management and consequently supporting the decision making is artificial intelligence (AI). In this framework, this paper aims to improve understanding of AI towards knowledge management. It examines and discusses both the potential and the limitations of basic AI technologies in terms of their capability to support the KM process and shares thoughts and estimations on further research on the development of the next generation decision support environments.
Toward strategic use of IT in SMEs: a developing country perspective
Authors: Temtime Z.T. , Chinyoka S.V. , Shunda J.P.W.
Published: November 2003

This article analyzes the strategic use of microcomputers and software packages in corporate planning and decision making in SMEs. Data were collected from 44 SMEs from three cities in the Republic of Botswana to study their perceptions about the use of computer‐based technology to solve managerial problems, and analysed using simple descriptive statistics. The findings indicate that SMEs conduct both strategic and operational planning activities. However, microcomputers and software packages were used primarily for operational and administrative tasks rather than for strategic planning. SMEs perceive that strategic planning is costly and time‐consuming, and hence appropriate only for large firms. The study also showed that firm size and strategic orientation are related to the use of computer technology for strategic decision making. The major implication of the findings for future research has been identified and presented.
An XML‐based administration method on role‐based access control in the enterprise environment
Authors: Yang Cungang , Zhang Chang N.
Published: November 2003

Proposes an object‐oriented role‐based access control (ORBAC) model to efficiently represent the real world. Though ORBAC is a good model, administration of ORBAC, including creating and maintaining an access control security policy, still remains a challenging problem. Presents a practical method that can be employed in an enterprise environment to manage security policies using eXtensible Markup Language (XML). Based on ORBAC security policy expressed in XML, a role assignment algorithm is presented. The computation complexity of the algorithms is O(N) wherenis the number of position roles in a user’s assigned position role scope.
A framework and methodology for evaluating e‐commerce Web sites
Authors: van der Merwe Rian , Bekker James
Published: November 2003

The corporate Web site is an indispensable part of any e‐commerce venture. If users find it difficult to do electronic transactions, they will visit another online source, or go to a physical source instead. Evaluating the performance of e‐commerce Web sites has received some attention in the past few years, but there is still a pressing need for a more comprehensive approach. This paper attempts to address this need by providing an e‐commerce Web site evaluation framework and method built on solid business principles, and using multidimensional scaling to analyse evaluation data and present the results in a graphic manner for easy interpretation.
Web advertising vs other media: young consumers’ view
Authors: Calisir Fethi
Published: November 2003

This paper examines how young consumers perceive the Web as an advertising medium in relation to eight traditional media on 15 constructs elicited from subjects. Results indicate that the Web is perceived to be very far from most of the other media, except point of purchase and direct mail. Conducting correspondence analysis and cluster analysis revealed the reasons for why the Web advertising is located close to point of purchase and direct mail. A noticeable finding was that farthest away from the Web is outdoor. Implications based on the findings are discussed.
The structural factors that affect classroom team performance
Authors: Kent Thomas W. , Hasbrouck Robert B.
Published: November 2003

This study was an attempt to identify, through structural equation modeling, the factors that may be involved in the performance of classroom teams. Confirmatory factor analysis was used to study Katzenbach and Smith’s model of “high performing teams”. While it is often difficult for classroom leaders – professors, instructors, etc. – to intervene on an ongoing basis in the process and interpersonal dimensions of classroom or project teams, it may be possible for them to make structural or programmatic interventions that positively affect all teams in their classes. This study attempted to identify those structural factors using Katzenbach and Smith’s model as a basis. Four such factors were identified. The implications of these factors on classroom leaders’ methods are discussed. The study, however, leaves several questions unanswered. These are described and the implications for further research are enumerated.
Examining the effects of internal and external team learning on team performance
Authors: Chan Christopher C.A. , Pearson Cecil , Entrekin Lanny
Published: November 2003

The effectiveness of using team learning to improve team performance has been well documented in the literature, and this notion makes intuitive sense. However, little empirical research has been dedicated to the relationship between team learning and team performance, probably owing to the lack of a widely acceptable instrument for assessing team learning. In this study, a psychometric (validity and reliability) examination of Edmondson’s Team Learning Survey (TLS) is undertaken. This instrument was then used to examine the effects of internal and external team learning on team performance. Implications and limitations of the study findings are discussed.
Consulting for virtual excellence: virtual teamwork as a task for consultants
Authors: Jünemann Erwin , Lloyd Bruce
Published: November 2003

This paper explores how consulting can contribute to the success of virtual teamwork. Based on an introduction to the concept of virtual teams, the potential of virtual teamwork for consultants and clients is outlined. Central questions are: “For which reasons do virtual teams deserve additional attention by business leaders?” and “What kind of services can be offered by consultants that cannot be performed by the client organisation itself?”. The paper finishes with a discussion of the qualifications and resources consultants should possess if they wish to consult on virtual teamwork, highlighting the broad range of requirements and the need to accumulate extensive experience.
Team leaders, manufacturing strategies and competitive performances
Authors: Leung Samuel H.N. , Chan Joseph W.K. , Lee W.B.
Published: November 2003

Competitive performances of manufacturing firms are affected by the strategies they selected. The implementations of strategies, as usually assumed, rely on the effectiveness of work teams. The performances of teams, to a large degree, are directed by team leaders. Therefore, the compatibility between competitive performances, manufacturing strategies, and the functions of team leaders should be explored. Based on the statistical findings obtained from other literature as well as an analysis of an international survey of manufacturing strategies. It is proposed that the compatibility is basically the relationship between the knowledge seeking behavior of team leaders and the knowledge required for improving competitive performances. We also discovered that it is worth further investigating two particular types of team leaders, i.e. shaper and company builder. Their characteristics may provide a basis to expand our understandings of team leaders’ performances and the competence‐based organizations of today.
The tangibles and intangibles of organisational performance
Authors: Yeo Roland
Published: November 2003

Explores the theoretical linkage between organisational learning and organisational performance by analysing the different systems of performance management. Aside from focusing on the traditional financial aspects of performance, deals with the much‐hyped qualitative nature of non‐financial performance measures. Discusses in conjunction with organisational learning outcomes which can be seen to be operating at two levels: formal and informal. Arguably, the former involves the bottom‐line tangible indicators while the latter, the intangible indicators. Further suggests alternative views of performance measures by examining the cognitive and behavioural development of individuals. This, to a large extent, deals with intellectual capital and knowledge acquisition, and how they can be translated into competence which will in turn benefit the organisation financially.
Indelible impressions of an authentic coach
Authors: Biggs Beverly
Published: November 2003

The article is about a coaching/mentoring style that was developed by an entrepreneur LaFay Davenport. Ms Davenport’s coaching strategy derived from the name of her business – Simply Raw Hair Designs. The name itself implies authenticity, wholesomeness. Ms Davenport has coached, mentored and led staff for over a quarter of a century using a coaching model called “sRAW” by the author. The appeal of this model is its simplicity and universal application. Many apprentices trained under her leadership have become successful entrepreneurs themselves. Repeat business of long‐time clients benchmarks her sustained success.
The role for satellites in the WSIS action plan
Authors: Bernard Keith
Published: November 2003

The particular dimensions of the World Summit on the Information Society (WSIS) action plan that are intended to close the infrastructure shortcomings of the digital divide can best – and possibly only – be addressed through the wide deployment of a new generation of broadband satellites. Yet current business developments do not provide any level of comfort that the present commercial and regulatory regimes are properly structured for such deployment. This paper proposes some particular aspects of a model conceived by the International Telecommunications Satellite Organization (ITSO) that can provide the proper regulatory incentives and conditions that will allow market forces to meet the requirements of the action plan.
The challenges of regulating the Web
Authors: Hart Thomas
Published: November 2003

Although the debate about Internet governance has cooled off as the Internet Corporation for Assigned Names and Numbers (ICANN)’s ambitions have narrowed, there remains a broad variety of regulatory issues that will require an international approach. Apart from ICANN, a diverse set of institutions is already involved in setting standards, allocating resources, and resolving conflicts. This paper looks at how the operations of these institutions, together with the experiences of ICANN, could serve as a starting point for a more integrated and comprehensive approach to tackling the challenges the Internet will face in the years to come.
The digital divide and the competitive behaviour of Internet backbone providers: Part 1 – issues and arguments
Authors: Roseman Daniel
Published: November 2003

Against the background of international telecommunications liberalization and declining settlement payments for many developing countries, charging arrangements for Internet interconnection services have become a controversial issue. This article presents the essence of the complaints and counter‐arguments regarding whether current charging arrangements for Internet interconnection are inequitable and subject to anti‐competitive behaviour on the part of Internet backbone providers. A second paper, to be published in the next issue of info, reviews proposals for action to date and makes a number of recommendations as to how to move the debate usefully forward, including a number of positive measures that developing countries can take.
Age‐Dependent Effects of Captopril on the Arterial Baroreflex Control of Heart Rate in Conscious Lambs
Authors: Monument Michael J. , Smith Francine G.
Published: November 2003

To test the hypothesis that angiotensin (ANG) II modulates the arterial baroreflex control of heart rate (HR) in an age‐dependent manner, various parameters governing the arterial baroreflex control of HR were assessed before and after removal of endogenously produced ANG II by administration of the angiotensin‐converting enzyme (ACE) inhibitor, captopril, to conscious, chronically instrumented lambs aged ∼1 week (8 ± 1 days; n = 8) or ∼6 weeks (46 ± 5 days; n = 8). After administration of captopril, systolic, diastolic and mean arterial pressures decreased significantly from control levels and HR increased; however, the effects were greater in 1‐ than in 6‐week‐old lambs. In 1‐week‐old lambs, after administration of captopril, there was also a significant increase in the slope coefficient, a decrease in minimum HR and a decrease in the point of maximum gain. In 6‐week‐old lambs, there were no effects of captopril on any of the parameters governing the arterial baroreflex. Therefore, we accept our hypothesis and conclude that the role of ANG II in modulating cardiovascular homeostasis appears to be more predominant in the newborn than later in life.
Exercise Heat Stress does not Reduce Central Activation to non‐exercised Human Skeletal Muscle
Authors: Saboisky Julian , Marino Frank E. , Kay Derek , Cannon Jack
Published: November 2003

In this study we measured the central activation ratio (CAR) of the leg extensors and the elbow flexor muscles before and after exhaustive exercise in the heat to determine whether exercise‐induced hyperthermia affects the CNS drive to exercised (leg extensors) and/or non‐exercised (forearm flexors) muscle groups. Thirteen subjects exercised at fixed intensities representative of a percentage of peak power output (PPO) for 10 min periods (50%, 40%, 60%, 50%) and then at 75% PPO until exhaustion in ambient conditions of 39.3 ± 0.8 °C and 60.0 ± 0.8% relative humidity. Before and immediately following exercise subjects performed a series of maximal voluntary contractions (MVCs) with the leg extensors (exercised muscles) and forearm flexors (non‐exercised muscles). The degree of voluntary activation during the sustained MVCs was assessed by superimposing electrical stimulation to the femoral nerve and the biceps brachii. Exercise to exhaustion increased the rectal temperature from 37.2 ± 0.2 to 38.8 ± 0.2 °C (P < 0.0001). The mean heart rate at the end of exercise to exhaustion was 192 ± 3 beats min−1. Leg extensor voluntary force was significantly reduced from 595 ± 143 to 509 ± 105 N following exercise‐induced hyperthermia but forearm flexor force was similar before and after exercise. The CAR of the leg extensors decreased from 94.2 ± 1.3% before exercise to 91.7 ± 1.5% (P < 0.02) following exercise‐induced hyperthermia. However, the CAR for the forearm flexors remained at similar levels before and after exercise. The data suggest that the central nervous system selectively reduces central activation to specific skeletal muscles as a consequence of exercise‐induced hyperthermia.
Anaemia Stimulates Aquaporin 1 Expression in the Fetal Sheep Heart
Authors: Jonker S. S. , Davis L. E. , van der Bilt J. D. W. , Hadder B. , Hohimer A. R. , Giraud G. D. , Thornburg K. L.
Published: November 2003

Interstitial fluid fluxes are much greater in the fetus than in the adult, and filtration rates are increased over control in most tissues of the anaemic fetus. Increased capillary filtration may lead to cardiac oedema which, in turn, severely impacts cardiac function. Mechanisms that underlie these differences in flux are incompletely understood. One possible mechanism is an increase in capillary water permeability. Therefore, the goal of our study was to determine the level of expression of the water channel aquaporin 1 (AQP1) during cardiac development and in the anaemic fetal sheep heart. Hearts from chronically instrumented anaemic sheep fetuses and hearts from normal early fetal, late fetal, neonatal and adult sheep were used for Northern and Western analyses and immunohistochemistry. We found that AQP1 mRNA levels were lower in the young fetal left ventricle than in the adult left ventricle (P < 0.05). We also found that cardiac AQP1 expression was increased in anaemic fetuses compared to age‐matched controls (P < 0.05). Expression of AQP1 in all groups was greatest in the microvascular endothelium. These data suggest that AQP1 plays an important role in the physiological accommodation to fetal anaemia.
Cold Exposure Differentially Stimulates Angiogenesis in Glycolytic and Oxidative Muscles of Rats and Hamsters
Authors: Deveci D. , Egginton S.
Published: November 2003

Control (normothermic) and cold‐acclimated (environmental temperature gradually reduced from 20 to 5 °C for 4 weeks) groups of male rats and hamsters were compared to elucidate the nature of angiogenesis in oxidative and glycolytic muscles of these species during progressive cold exposure. Skeletal muscle capillarity and fibre cross‐sectional area were measured in the tonic soleus (SOL) and phasic tibialis anterior (TA). Cryostat sections were stained for alkaline phosphatase (ALP) activity to identify all capillaries, and proliferating cell nuclear antigen (PCNA) to localise the site of cellular proliferation. Cold‐induced angiogenesis, indicated by an increase in capillary to fibre ratio (C:F), occurred in SOL of rats (∼20% increase, P < 0.05) but not hamsters (∼9.5% increase, n.s.), and in TA of hamsters (∼22% increase, P < 0.01) but not rats (∼1% increase, n.s.). The change in C:F was highest in the glycolytic cortex region of TA where fibre size is larger than in the oxidative core. Capillary‐specific cell proliferation (co‐localised ALP and PCNA labelling) increased in parallel with C:F. The total PCNA label density within the interstitium was some 5‐fold higher than that co‐localised with capillaries, but where angiogenesis occurred the relative increase in capillary labelling was 2‐fold greater than for other cells of the interstitium. These data suggest a significant role for endothelial cell proliferation in the angiogenic response, indicative of the sprouting form of angiogenesis. There was a tendency for fibre hypertrophy in both SOL and TA of rats, especially in the core region of TA (P < 0.01), such that capillary density (CD) and intramuscular diffusion distances (DD) were largely unchanged following cold exposure. In contrast, fibre size was maintained in hamsters, DD reduced and CD increased compared to control TA (P < 0.01). In conclusion, cold acclimation stimulated angiogenesis in muscle of hamsters more than in rats, possibly due to a higher metabolic rate in the smaller species. Angiogenesis was also seen in SOL of rat, where oxidative capacity and muscle activity is higher than the TA. Thus, a combination of oxidative capacity, muscle activity, and fibre size may determine the degree of angiogenesis in response to low environmental temperature.
Whole Cell Recordings From Respiratory Neurones in an Arterially Perfused in situ Neonatal Rat Preparation
Authors: Dutschmann M. , Paton J. F. R.
Published: November 2003

For synaptic and cellular analyses of the mammalian respiratory network, intracellular recording and good pharmacological access to respiratory neurones is required. Using an existing arterially perfused in situ preparation of neonatal rat, we report on a method allowing stable intracellular recordings of ventrolateral medullary respiratory neurones. The in situ preparation generates a recognizable eupnoeic respiratory motor pattern similar to that reported in vivo. Using this preparation, we have developed a methodology for the use of patch pipettes to record from neurones within the ventral respiratory group. This technique in the arterially perfused neonatal rat is novel and has the advantage that neurones can be recorded from an intact and well‐oxygenated brainstem in which the pontine regions are known to be viable. We describe the methods, present the first whole cell recordings of numerous types of respiratory neurones from neonatal rats in such a preparation, and demonstrate the applicability of the model for neuropharmacological experiments.
Recent Insights into Carotid Baroreflex Function in Humans Using the Variable Pressure Neck Chamber
Authors: Fadel Paul J. , Ogoh Shigehiko , Keller David M. , Raven Peter B.
Published: November 2003

The variable pressure neck chamber has provided an invaluable research tool for the non‐invasive assessment of carotid baroreflex (CBR) function in human investigations. The ability to construct complete stimulus‐response curves and define specific parameters of the reflex function curve permits statistical comparisons of baroreflex function between different experimental conditions, such as rest and exercise. Results have convincingly indicated that the CBR stimulus‐response curve is reset during exercise in an intensity‐dependent manner to functionally operate around the prevailing pressure elicited by the exercise workload. Furthermore, both at rest and during exercise, alterations in stroke volume do not contribute importantly to the maintenance of arterial blood pressure by the carotid baroreceptors, and therefore, any reflex‐induced changes in cardiac output (Q) are the result of CBR‐mediated changes in heart rate. However, more importantly, the CBR‐induced changes in mean arterial pressure (MAP) are primarily mediated by alterations in vascular conductance with only minimal contributions from Q to the initial reflex MAP response. Thus, the capacity of the CBR to regulate blood pressure depends critically on its ability to alter vascular tone both at rest and during exercise. This review will emphasize the utility of the variable pressure neck chamber to assess CBR function in human experimental investigations and the mechanisms by which the CBR responds to alterations in arterial blood pressure both at rest and during exercise.
IDENTIFICATION AND MATCHING OF PLANES IN A PAIR OF UNCALIBRATED IMAGES
Authors: BOUFAMA B. S. , O'CONNELL D. J.
Published: November 2003

In this paper, we propose a new method to simultaneously achieve segmentation and dense matching in a pair of stereo images. In contrast to conventional methods that are based on similarity or correlation techniques, this method is based on geometry, and uses correlations only on a limited number of key points. Stemming from the observation that our environment is abundant in planes, this method focuses on segmentation and matching of planes in an observed scene. Neither prior knowledge about the scene nor camera calibration are needed. Using two uncalibrated images as inputs, the method starts with a rough identification of a potential plane, defined by three points only. Based on these three points, a plane homography is then calculated and, used for validation. Starting from a seed region defined by the original three points, the method grows the current region by successive move/confirmation steps until occlusions and/or surface discontinuity occur. In this case, the homography-based mapping of points between the two images will not be valid anymore. This condition is detected by the correlation, used in the confirmation process. In particular, this method grows a region even across different colors as long as the region is planar. Experiments on real images validated our method and showed its capability and performance.
RIGID MEDICAL IMAGE REGISTRATION AND ITS ASSOCIATION WITH MUTUAL INFORMATION
Authors: FOOKES C. , BENNAMOUN M.
Published: November 2003

Image registration plays a crucial role in the computer vision and medical imaging field where it is used to develop a spatial mapping between different sets of data. These transformations can range from simple rigid registrations to complex nonrigid deformations. Mutual information (MI) is a popular entropy-based similarity measure which has recently experienced a prolific expansion in a number of image registration applications. Stemming from information theory, this measure generally outperforms most other intensity-based measures in multimodal applications as it only assumes a statistical dependence between images. This paper provides a thorough introduction to the MI measure and its use in rigid medical image registration. A look at the extensions proposed to the original measure will also be provided. These were developed to improve the robustness of the measure and to avoid certain cases when maximizing MI does not lead to the correct spatial alignment.
ROBUSTLY ESTIMATING DISPARITY FROM ADAPTIVE DENSE CURVES
Authors: LEI B. J. , XU LI-QUN , HENDRIKS E. A. , BIEMOND J.
Published: November 2003

In this paper, we propose a novel area-based algorithm for stereo correspondence estimation. The new dense correspondence estimation algorithm, which we call HACM (Hierarchical Adaptive Curve Matching), is suitable for stereo analysis of both static and dynamic scenes. The core of this method is the derivation of a pixel-based dense adaptive curve representation. For each pixel in the concerned 2-D images, the changes are characterized roughly in the local surface shape, the texture direction, and the luminance properties, all at a slight overhead cost. The matching is carried out in a hierarchical manner that incorporates several novel ideas that improve its efficiency and robustness. Experiments conducted on both synthetic and natural stereo pairs, and natural video streams, reveal the favorable performance of this new algorithm.
EXTRACTION AND MATCHING OF SYMBOLIC CONTOUR GRAPHS
Authors: LOURENS TINO , WÜRTZ ROLF P.
Published: November 2003

We describe an object recognition system based on symbolic contour graphs. The image to be analyzed is transformed into a graph with object corners as vertices and connecting contours as edges. Image corners are determined using a robust multiscale corner detector. Edges are constructed by line-following between corners based on evidence from the multiscale Gabor wavelet transform. Model matching is done by finding subgraph isomorphisms in the image graph. The complexity of the algorithm is reduced by labeling vertices and edges, whereby the choice of labels also makes the recognition system invariant under translation, rotation and scaling. We provide experimental evidence and theoretical arguments that the matching complexity is below O(#V3), and show that the system is competitive with other graph-based matching systems.
ROBUST CORRESPONDENCE METHODS FOR STEREO VISION
Authors: EKLUND MATTHEW P. , FARAG ALY A. , EL-MELEGY MOUMEN T.
Published: November 2003

Correspondence is one of the major problems that must be solved in stereo vision. Correlation has been commonly used in the past for this problem. However, most classical linear correlation methods fail near depth discontinuities and in the presence of occlusions. Many robust methods have been proposed that claim to effectively deal with some or all of these issues. Many of these robust methods are transformation-based, however, other robust methods are non-transformation based. This paper gives five requirements that should be met by a transformation-based robust correlation method. We compare some of the robust correspondence methods and demonstrate their utility on different data sets. Based on these results, we propose a solution to the correspondence problem which represents a compromise between the speed of classical correlation and the improved results obtained from a more robust correspondence method. Also, we propose a median filtering technique that removes noise from the disparity maps while preserving certain image features usually removed by ordinary median filtering.
NON-RIGID REGISTRATION AND CORRESPONDENCE FINDING IN MEDICAL IMAGE ANALYSIS USING MULTIPLE-LAYER FLEXIBLE MESH TEMPLATE MATCHING
Authors: YAO JIANHUA , TAYLOR RUSSELL
Published: November 2003

In this paper we present a novel technique for non-rigid medical image registration and correspondence finding based on a multiple-layer flexible mesh template matching technique. A statistical anatomical model is built in the form of a tetrahedral mesh, which incorporates both shape and density properties of the anatomical structure. After the affine transformation and global deformation of the model are computed by optimizing an energy function, a multiple-layer flexible mesh template matching is applied to find the vertex correspondence and achieve local deformation. The multiple-layer structure of the template can be used to describe different scale of anatomical features; furthermore, the template matching is flexible which makes the correspondence finding robust. A leave-one-out validation has been conducted to demonstrate the effectiveness and accuracy of our method.
ON RIGID AND INFINITESIMAL RIGID DISPLACEMENTS IN THREE-DIMENSIONAL ELASTICITY
Authors: CIARLET PHILIPPE G. , MARDARE CRISTINEL
Published: November 2003

Let Ω be an open connected subset of ℝ3 and let Θ be an immersion from Ω into ℝ3. It is first established that the set formed by all rigid displacements, i.e. that preserve the metric, of the open set Θ(Ω) is a submanifold of dimension 6 and of class [Formula: see text] of the space H1(Ω). It is then shown that the vector space formed by all the infinitesimal rigid displacements of the same set Θ(Ω) is nothing but the tangent space at the origin to this submanifold. In this fashion, the familiar "infinitesimal rigid displacement lemma" of three-dimensional linearized elasticity is put in its proper perspective.