bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of fading, diversity and interference on the performance of multitone CDMA systems
Authors: Matin Sharif A. , Ugweje Okechukwu C. 
Published: February 2003

AbstractThe performance of a multitone Code Division Multiple Access (CDMA) system is investigated in this paper by considering the effect of multipath fading, diversity and narrowband interference. The performance is evaluated in terms of the average bit error rate when both multiple access and partial band interference are present. Results are obtained by deriving the statistics of the receiver output parameters and then tested by numerical evaluation. The bit error rate performance is analyzed as a function of bit rate, bandwidth, delay range and different diversity techniques, while considering issues relevant to system implementation. Comparisons were made between conventional single‐tone CDMA systems and multitone CDMA systems. The effectiveness of multitone CDMA in suppressing interference compared to conventional CDMA system is analyzed. Results reveal considerable performance improvement of multitone CDMA system over conventional CDMA system. Copyright © 2002 John Wiley & Sons, Ltd.
Providing deterministic packet delays and packet losses in multimedia wireless networks
Authors: Hamdi Mounir , Lee Felix K. L. 
Published: February 2003

Abstract‘Anytime, anywhere’ communication, information access and processing are much cherished in modern societies because of their ability to bring flexibility, freedom and increased efficiency to individuals and organizations. Wireless communications, by providing ubiquitous and tetherless network connectivity to mobile users, are therefore bound to play a major role in the advancement of our society. Although initial proposals and implementations of wireless communications are generally focused on near‐term voice and electronic messaging applications, it is recognized that future wireless communications will have to evolve towards supporting a wider range of applications, including voice, video, data, images and connections to wired networks. This implies that future wireless networks must provide quality‐of‐service (QoS) guarantees to various multimedia applications in a wireless environment.Typical traffic in multimedia applications can be classified as either Constant‐Bit‐Rate (CBR) traffic or Variable‐Bit‐Rate (VBR) traffic. In particular, scheduling the transmission of VBR multimedia traffic streams in a wireless environment is very challenging and is still an open problem. In general, there are two ways to guarantee the QoS of VBR multimedia streams, either deterministically or statistically. In particular, most connection admission control (CAC) algorithms and medium access control (MAC) protocols that have been proposed for multimedia wireless networks only provide statistical, or soft, QoS guarantees.In this paper, we consider deterministic QoS guarantees in multimedia wireless networks. We propose a method for constructing a packet‐dropping mechanism that is based on a mathematical framework that determines how many packets can be dropped while the required QoS can still be preserved. This is achieved by employing: (1) An accurate traffic characterization of the VBR multimedia traffic streams; (2) A traffic regulator that can provide bounded packet loss and (3) A traffic scheduler that can provide bounded packet delay. The combination of traffic characterization, regulation and scheduling can provide bounded loss and delay deterministically. This is a distinction from traditional deterministic QoS schemes in which a 0% packet loss are always assumed with deterministically bounding the delay.We performed a set of performance evaluation experiments. The results will demonstrate that our proposed QoS guarantee schemes can significantly support more connections than a system, which does not allow any loss, at the same required QoS. Moreover, from our evaluation experiments, we found that the proposed algorithms are able to out‐perform scheduling algorithms adopted in state‐of‐the‐art wireless MAC protocols, for example Mobile Access Scheme Based on Contention and Reservation for ATM (MASCARA) when the worst‐case traffic is being considered. Copyright © 2002 John Wiley & Sons, Ltd.
Adaptive delivery of video data over wireless and mobile environments
Authors: Helal Sumi , Sampath Latha , Birkett Kevin , Hammer Joachim 
Published: February 2003

AbstractWe present an architecture for the adaptable delivery of video data under variable connection characteristics and into devices of variable capabilities. The main application of the proposed architecture is video delivery in wireless and mobile environments. The architecture is based on the Universal Multimedia Access concept and the MPEG‐7 standard. Based on the network and the mobile device, as well as constraints imposed by user preferences and the multimedia content, video is delivered through a careful application of a combination of off‐line and on‐line reductions to the video stream. We present our architecture and describe an implementation of a system based on the architecture. We present basic performance evaluation results to quantify the merit of our approach. Copyright © 2002 John Wiley & Sons, Ltd.
Effects of Artificial Ultraviolet Light Exposure on Reproductive Success of the Female Panther Chameleon (Furcifer pardalis) in Captivity
Authors: Ferguson Gary W. , Gehrmann W.H. , Chen T.C. , Dierenfeld E.S. , Holick M.F. 
Published: February 2003

AbstractHaving previously documented experimentally the need for ultraviolet B (UVB) irradiation (290–315 nm) in the light environment of captive female panther chameleons (Furcifer pardalis) to ensure hatching success of their eggs, we investigated optimal UVB irradiation levels. From 1996–1998 28 hatchling female panther chameleons were raised to maturity and bred (using vitamin and mineral‐fortified insect diets low in vitamin D) in nine different artificial UVB light environments. Seven of the environments included long (12 hr/day) low irradia‐tion exposures ranging from 1.7 to 22 μW/cm2 UVB, with a corresponding conversion of provitamin D3 to photoproducts in in vitro models of 0.18 to 1.52% in 2 hr. Two environments included short (0.5 and 1.0 hr/day), high irradiation exposures of 55 and 49 μW/cm2 UVB, respectively, with a corres‐ponding conversion of provitamin D3 to photoproducts in in vitro models of 8.3% to 14.6% in the respective 0.5‐ and 1.0‐hr time periods. Females raised with the mid‐level long/low exposures (5–15 μW/cm2 UVB; 0.52–1.32% conversion to photoproducts in in vitro models) produced viable eggs with a significantly higher percentage of hatching compared to those with the extreme (highest or lowest) long/low exposures. Those raised with the short‐/high‐exposure environments produced viable eggs with a generally high percentage of hatching, but success was variable. The results and techniques for light quality assessment are interpreted, with recommendations for practical application by the herpetoculturist desiring to successfully breed panther chameleons in captivity. Zoo Biol 21:525–537, 2002. © 2002 Wiley‐Liss, Inc.
Genetic kinship and social structure in a herd of square‐lipped rhinoceroses (Ceratotherium simum simum) at the zoological center, Tel Aviv/Ramat‐Gan, Israel
Authors: Seror Benjamin , Zorovsky Yehuda , Terkel Amelia , Katcoff Don J. 
Published: February 2003

AbstractZoos and zoological parks serve as genetic and demographic reserves for strengthening endangered populations and reestablishing extinct populations in the wild. Knowing the genetic ties within captive populations is a very helpful tool for successful reproductive management. In the present study we addressed kinship relationships and behavior among rhinoceroses (Ceratotherium simum simum) raised at the Zoological Center, Tel Aviv/Ramat Gan, Israel, with the hope of identifying reasons for the declining rate of reproduction within the herd. We used the random amplified polymorphic DNA (RAPD) technique to reveal the paternity of the rhinos born at the park. In this way, we identified the paternity of five out of seven young born in the herd, which are currently in Ramat Gan. One male accounted for three (37.5%) births, and two other males accounted for one each. The paternity of the two other animals is unknown and may be of animals that are no longer in the Zoological Center. The genetic determinations were accompanied by behavioral observations, which enabled us to determine the social dynamics in the herd. This study suggests that there are at least three contributing factors to the reproductive decline in the herd: 1) a surplus of males, 2) exclusion of potentially reproductive males from the breeding stock, and 3) specific behavioral and physiological problems in some members of the herd. Zoo Biol 21:561–571, 2002. © 2002 Wiley‐Liss, Inc.
Responses to novel foods in captive chimpanzees
Authors: Visalberghi E. , Myowa Yamakoshi M. , Hirata S. , Matsuzawa T. 
Published: February 2003

AbstractHesitancy to eat novel foods hampers the immediate enlargement of the diet but serves to limit the risk of ingesting toxic foods. Neophobia has been systematically investigated in only a few primate species, in which it appears to be affected by social influences. Surprisingly, little is known about neophobia in chimpanzees. We studied the response of eight adult captive chimpanzees to 16 foods (foods commonly eaten by humans and never tasted before by chimpanzees). Each novel food was presented twice to the chimpanzee by a familiar or an unfamiliar human. Between the two trials the human ate the food face to face with the chimpanzee (demonstration). Results showed that some foods were almost unanimously accepted, whereas others were not. Moreover, there were marked interindividual differences in food acceptance and consumption; chimpanzees ranged from being almost completely neophobic to accepting almost all foods. Familiarity with the human and the human's demonstration did not affect responses to the foods. The humans' predictions concerning the chimpanzees' acceptance of the different foods were rather good; furthermore, in seven cases out of eight the humans' preferences did not correlate with their predictions on the chimpanzees' preferences. The finding that most captive chimpanzees are initially cautious toward novel foods supports the little information there is regarding this subject in wild chimpanzees. However, the lack of influence of the humans' familiarity and demonstration on the response to food by the chimpanzees calls for more naturalistic studies, in which social influences are provided by group members. Since novel stimuli provide sensory stimulation and elicit exploration and social interest, occasional presentation of novel foods could be a promising and cheap device for feeding enrichment. Zoo Biol 21:539–548, 2002. © 2002 Wiley‐Liss, Inc.
Change of enclosure in langur monkeys: implications for the evaluation of environmental enrichment
Authors: Little Katherine A. , Sommer Volker 
Published: February 2003

AbstractA group of Hanuman langurs (Presbytis entellus) was studied before and after it was moved from an old cage‐style enclosure to a novel naturalistic environment at the London Zoo. Eating and locomotion occupied more of the langurs' time in their new enclosure, whereas dozing, allogrooming, and aggression decreased, along with an increase in inter‐individual distances. These changes are attributed to the larger area, the stimulating new environment, and the langurs' increased distance from visitors. Nevertheless, the study raises questions about how to define standards of desirable environmental enrichment, as the activity patterns recorded in both the old and new enclosures are within the variation observed in the wild. Zoo Biol 21:549–559, 2002. © 2002 Wiley‐Liss, Inc.
Effect of feeding boxes on the behavior of stereotyping amur tigers (Panthera tigris altaica) in the Zurich Zoo, Zurich, Switzerland
Authors: Jenny Saskia , Schmid Hans 
Published: February 2003

AbstractThe stereotyped pacing shown by the two Amur tigers in the Zurich Zoo was hypothesized as being caused by permanently frustrated appetitive foraging behavior. Several electrically controlled feeding boxes were installed and access to each box was possible only twice a day for 15 min at semi‐random times. The boxes had to be opened actively by the tigers. Two trials were carried out: one with solitary confinement, and one with paired confinement. During box feeding, the female's stereotyped pacing was significantly reduced from 16% (solitary confinement, conventional feeding) and 7% (paired confinement, conventional feeding) to 1% (solitary confinement) and less than 0.01% (paired confinement) of the daily observed time. The female's sleeping increased significantly in both solitary and paired confinement. The male only showed a significant reduction in stereotyped pacing behavior when kept with the female (conventional feeding: 10%; box feeding: <0.01% of the daily observed time). On days with a box‐feeding regime in paired confinement, the male spent 25% (83 min) of the observed time with active behavior at the feeding boxes. The results support the hypothesis that permanently frustrated appetitive foraging behavior causes stereotyped pacing in adult tigers. Zoo Biol 21:573–584, 2002. © 2002 Wiley‐Liss, Inc.
Food access in captive Ammotragus: the role played by hierarchy and mother–infant interactions
Authors: Cassinello Jorge 
Published: February 2003

AbstractAn analysis of individuals' behavior when accessing a restricted food source (troughs) was carried out in a captive population of aoudad (Ammotragus lervia). Access to the troughs followed a strict hierarchical order, as higher‐ranking individuals fed before lower‐ranking ones. Unweaned male and female calves made use of the troughs from the ages of 2 and 3 months, respectively. Both fed from the troughs more frequently and for longer periods when their mother was present, which allowed them to make use of the troughs while skipping the hierarchical order. Calves received fewer threats when in proximity to their mothers, particularly in high‐ranking families. Mothers defended their calves from other herdmates more frequently when at the feeding area than in other areas of the herd. However, only sated mothers let their calves feed freely from the troughs; unsated mothers showed an aggressive behavior even toward their calves. I conclude that a maternal presence is necessary for aoudad calves to successfully feed from troughs, and that families of higher social rank benefit by getting access to this food source earlier in the day and are disturbed less than low‐ranking families. Zoo Biol 21:597–605, 2002. © 2002 Wiley‐Liss, Inc.
Environmental influences on stereotypy and the activity budget of Indian leopards (Panthera pardus) in four zoos in Southern India
Authors: Mallapur Avanti , Chellam Ravi 
Published: February 2003

AbstractTo eliminate abnormal behaviors in leopards (Panthera pardus), such as stereotypic pacing, by utilizing environmental enrichment techniques, a proper understanding of their behavior in captive environments is required. Hence there is a need for animal welfare studies in Indian zoos. The activity budgets of 16 leopards were recorded across four southern Indian zoos: Thiruvananthapuram Zoo, Arignar Anna Zoological Park, Shri Chamarajendra Zoological Gardens, and the Guindy Children's Park. Of the 16 study animals, 14 were studied on‐exhibit on zoo holidays as well as on days with visitors present, and all 16 individuals were studied off‐exhibit on other days with visitors present. The 11 behaviors recorded were categorized into active, resting, and stereotypic behaviors. Leopards exhibited higher levels of activity in the on‐exhibit enclosures on days with no visitors. Feeding time influenced the behavioral repertoire of all 14 leopards studied on‐exhibit. Lower proportions of resting were exhibited during the hours before feeding. The proportion of active behaviors differed significantly across zoos. Stereotypic pacing levels were not influenced by the presence of visitors or by feeding time, but was significantly influenced by enclosure features. Higher levels of stereotypic pacing were exhibited in off‐exhibit than on‐exhibit enclosures. Our study shows that the behavior of captive leopards is influenced by enclosure type, feeding regime, and the presence of visitors. Zoo Biol 21:585–595, 2002. © 2002 Wiley‐Liss, Inc.
Ladder Use and Clubbing by a Bonobo (Pan paniscus) in Apenheul Primate Park
Authors: Gold Kenneth C. 
Published: February 2003

AbstractTwo types of tool use were shown by a captive bonobo (Pan paniscus) in a large outdoor enclosure at Apenheul Primate Park in The Netherlands. A wild‐born young adult female (estimated to be 9 years old) used fallen branches as ladders to bypass protective sheaths to gain access to trees. Later she used a branch as a weapon to beat to death a peahen (Pavo cristatus). None of the other bonobos in the group were seen to use branches as either ladders or weapons. Zoo Biol 21:607–611, 2002. © 2002 Wiley‐Liss, Inc.
First report of albinism in the white‐spotted bamboo shark, Chiloscyllium plagiosum (Orectolobiformes: Hemiscyllidae), with a review of reported color aberrations in elasmobranchs
Authors: Clark Steven 
Published: February 2003

AbstractThree albinistic, white‐spotted bamboo sharks (Chiloscyllium plagiosum) (two males and one female) were hatched at SeaWorld parks. Due to their lack of integumentary and retinal pigments, all three animals were considered true albinos. The term “leucism,” more prominently used within the herpetological discipline, is suggested as a more apt description for previously reported color aberrations in elasmobranchs. Reports of color aberrations in other species of elasmobranchs, and a clarification of the terms used to describe these irregularities in pigmentation, are also presented. Zoo Biol 21:519–524, 2002. © 2002 Wiley‐Liss, Inc.
The physical mechanism for vortex merging
Authors: CERRETELLI C. , WILLIAMSON C. H. K. 
Published: February 2003

In this paper, we study the interaction of two co-rotating trailing vortices. It is
well-known that vortices of like-sign ultimately merge to form a single vortex, and
there has been much work on measuring and predicting the initial conditions for the
onset of merger, especially concerning the critical vortex core radius. However, the
physical mechanism causing this merger has received little attention. In this work,
we directly measure the structure of the antisymmetric vorticity field that causes the
co-rotating vortices to be pushed towards each other during merger. We discover
that the form of the antisymmetric vorticity comprises two counter-rotating vortex
pairs, whose induced velocity field readily pushes the two centroids together. The
merging velocity computed from the antisymmetric vorticity field agrees closely with
the merging velocity measured directly from the total (original) flow field.The co-rotating vortex pair evolves through four distinct phases. The initial stage
comprises a diffusive growth, which can be either viscous or turbulent. In either case,
the number of turns that they rotate around one another until the vortices start
to merge increases with Reynolds number (Re). If one observes the streamlines in
a rotating reference frame (moving with the vortices), then one finds an inner and
outer recirculating region of the flow bounded by a separatrix streamline. When the
vortices grow large enough in the first stage, diffusion across the separatrix places
vorticity into the outer recirculating region of the flow, and this leads to the generation
of the antisymmetric vorticity, causing convective merger. This second (convective)
stage corresponds to the motion of the vortex centroids towards each other, and is a
process which is almost independent of viscosity. During the late part of this stage,
the antisymmetric vorticity is diminished by a symmetrization process, and the final
merging into one vorticity structure is achieved by a second diffusive stage. The fourth
and ultimate phase is one where the merged vortex core grows by diffusion.
Modelling the motion of particles around
choanoflagellates
Authors: ORME B. A. A. , BLAKE J. R. , OTTO S. R. 
Published: February 2003

The three-dimensional particle paths due to a helical beat pattern of the flagellum of
a sessile choanoflagellate, Salpingoeca Amphoridium (SA), are modelled and compared
to the experimental observations of Pettitt (2001). The organism’s main components
are a flagellum and a cell body which are situated above a substrate such that the
interaction between these entities is crucial in determining the fluid flow around the
choanoflagellate. This flow of fluid can be characterized as Stokes flow and a flow
field analogous to one created by the flagellum is generated by a distribution of
stokeslets and dipoles along a helical curve.The model describing the flow considers interactions between a slender flagellum,
an infinite flat plane (modelling the substrate) and a sphere (modelling the cell
body). The use of image systems appropriate to Green’s functions for a sphere
and plane boundary are described following the method of Higdon (1979a). The
computations predict particle paths representing passive tracers from experiments
and their motion illustrates overall flow patterns. Figures are presented comparing
recorded experimental data with numerically generated results for a number of
particle paths. The principal results show good qualitative agreement with the main
characteristics of flows observed in the experimental study of Pettitt (2001).
What vibrations tell about proteins
Authors: Barth Andreas , Zscherp Christian 
Published: February 2003

1. Introduction 3702. Infrared (IR) spectroscopy – general principles 3722.1 Vibrations 3722.2 Information that can be derived from the vibrational spectrum 3722.3 Absorption of IR light 3753. Protein IR absorption 3763.1 Amino-acid side-chain absorption 3763.2 Normal modes of the amide group 3814. Interactions that shape the amide I band 3824.1 Overview 3824.2 Through-bond coupling 3834.3 Hydrogen bonding 3834.4 Transition dipole coupling (TDC) 3835. The polarization and IR activity of amide I modes 3875.1 The coupled oscillator system 3875.2 Optically allowed transitions 3885.3 The infinite parallel β-sheet 3885.4 The infinite antiparallel β-sheet 3895.5 The infinite α-helix 3906. Calculation of the amide I band 3916.1 Overview 3916.2 Perturbation treatment by Miyazawa 3936.3 The parallel β-sheet 3946.4 The antiparallel β-sheet 3956.5 The α-helix 3966.6 Other secondary structures 3987. Experimental analysis of protein secondary structure 3987.1 Band fitting 3987.2 Methods using calibration sets 4017.3 Prediction quality 4038. Protein stability 4048.1 Thermal stability 4048.2 1H/2H exchange 4069. Molecular reaction mechanisms of proteins 4089.1 Reaction-induced IR difference spectroscopy 4089.2 The origin of difference bands 4099.3 The difference spectrum seen as a fingerprint of conformational change 4109.4 Molecular interpretation: strategies of band assignment 41610. Outlook 41911. Acknowledgements 42012. References 420This review deals with current concepts of vibrational spectroscopy for the investigation of protein structure and function. While the focus is on infrared (IR) spectroscopy, some of the general aspects also apply to Raman spectroscopy. Special emphasis is on the amide I vibration of the polypeptide backbone that is used for secondary-structure analysis. Theoretical as well as experimental aspects are covered including transition dipole coupling. Further topics are discussed, namely the absorption of amino-acid side-chains, 1H/2H exchange to study the conformational flexibility and reaction-induced difference spectroscopy for the investigation of reaction mechanisms with a focus on interpretation tools.