Host selection in phytophagous insects: a new explanation for learning in adults

Insect learning can change the preferences an egg laying female displays towards different host plant species. Current hypotheses propose that learning may be advantageous in adult host selection behaviour through improved recognition, accuracy or selectivity in foraging. In this paper, we present a hypothesis for when learning can be advantageous without such improvements in adult host foraging. Specifically, that learning can be an advantageous strategy for egg laying females when larvae must feed on more than one plant in order to complete development, if the fitness of larvae is reduced when they switch to a different host species. Here, larvae benefit from developing on the most abundant host species, which is the most likely choice of host for an adult insect which increases its preference for a host species through learning. The hypothesis is formalised with a mathematical model and we provide evidence from studies on the behavioural ecology, of a number of insect species which demonstrate that the assumptions of this hypothesis may frequently be fulfilled in nature. We discuss how multiple mechanisms may convey advantages in insect learning and that benefits to larval development, which have so far been overlooked, should be considered in explanations for the widespread occurrence of learning.

Assessing the Use of Flexible Assessment

A course which has a large student enrolment consequently puts a heavy load on instructors both in the presentation and the assessment areas. In the School of Economics at the University of Queensland, this is the case for the quantitative analysis subjects. Assessment for many years has been through mid-semester and end of semester exams, as well as Computer Managed Learning (CML) assignments. In 2000 it was decided to incorporate a system of flexible assessment where neither the CML nor the mid-semester exam was compulsory. The outcomes are assessed and the advantages and disadvantages discussed.

Post-fledging care, philopatry and recruitment in brown thornbills

1. We describe patterns of post-fledging care, dispersal and recruitment in four cohorts of brown thornbills Acanthiza pusilla. We examine what factors influence post-fledging survival and determine how post-hedging care and the timing of dispersal influence the probability of recruitment in this small, pair breeding, Australian passerine. 2. Fledgling thornbills were dependent on their parents for approximately 6 weeks. Male fledglings were more likely than female fledglings to survive until independence. For both sexes, the probability of reaching independence increased as nestling weight increased and was higher for nestlings that fledged later in the season. 3. The timing of dispersal by juvenile thornbills was bimodal. Juveniles either dispersed by the end of the breeding season or remained on their natal territory into the autumn and winter. Juveniles that delayed dispersal were four times more likely to recruit into the local breeding population than juveniles that dispersed early. 4. Delayed dispersal was advantageous because individuals that remained on their natal territory suffered little mortality and tended to disperse only when a local vacancy was available. Consequently, the risk of mortality associated with obtaining a breeding vacancy using this dispersal strategy was low. 5. Males, the more philopatric sex, were far more likely than females to delay dispersal. Despite the apparent advantages of prolonged natal philopatry, however, only 54% of pairs that raised male fledglings to independence had sons that postponed dispersal, and most of these philopatric sons gained vacancies before their parents bred again. Consequently, few sons have the opportunity to help their parents. Constraints on delayed dispersal therefore appear to play a major role in the evolution of pair-breeding in the brown thornbill.

Habitat complexity, spatial interference, and "minimum risk distribution": a framework for population stability

In the past century, the debate over whether or not density-dependent factors regulate populations has generally focused on changes in mean population density, ignoring the spatial variance around the mean as unimportant noise. In an attempt to provide a different framework for understanding population dynamics based on individual fitness, this paper discusses the crucial role of spatial variability itself on the stability of insect populations. The advantages of this method are the following: (1) it is founded on evolutionary principles rather than post hoc assumptions; (2) it erects hypotheses that can be tested; and (3) it links disparate ecological schools, including spatial dynamics, behavioral ecology, preference-performance, and plant apparency into an overall framework. At the core of this framework, habitat complexity governs insect spatial variance. which in turn determines population stability. First, the minimum risk distribution (MRD) is defined as the spatial distribution of individuals that results in the minimum number of premature deaths in a population given the distribution of mortality risk in the habitat (and, therefore, leading to maximized population growth). The greater the divergence of actual spatial patterns of individuals from the MRD, the greater the reduction of population growth and size from high, unstable levels. Then, based on extensive data from 29 populations of the processionary caterpillar, Ochrogaster lunifer, four steps are used to test the effect of habitat interference on population growth rates. (1) The costs (increasing the risk of scramble competition) and benefits (decreasing the risk of inverse density-dependent predation) of egg and larval aggregation are quantified. (2) These costs and benefits, along with the distribution of resources, are used to construct the MRD for each habitat. (3) The MRD is used as a benchmark against which the actual spatial pattern of individuals is compared. The degree of divergence of the actual spatial pattern from the MRD is quantified for each of the 29 habitats. (4) Finally, indices of habitat complexity are used to provide highly accurate predictions of spatial divergence from the MRD, showing that habitat interference reduces population growth rates from high, unstable levels. The reason for the divergence appears to be that high levels of background vegetation (vegetation other than host plants) interfere with female host-searching behavior. This leads to a spatial distribution of egg batches with high mortality risk, and therefore lower population growth. Knowledge of the MRD in other species should be a highly effective means of predicting trends in population dynamics. Species with high divergence between their actual spatial distribution and their MRD may display relatively stable dynamics at low population levels. In contrast, species with low divergence should experience high levels of intragenerational population growth leading to frequent habitat-wide outbreaks and unstable dynamics in the long term. Six hypotheses, erected under the framework of spatial interference, are discussed, and future tests are suggested.

Read-only-memory-based quantum computation: Experimental explorations using nuclear magnetic resonance and future prospects

Read-only-memory-based (ROM-based) quantum computation (QC) is an alternative to oracle-based QC. It has the advantages of being less magical, and being more suited to implementing space-efficient computation (i.e., computation using the minimum number of writable qubits). Here we consider a number of small (one- and two-qubit) quantum algorithms illustrating different aspects of ROM-based QC. They are: (a) a one-qubit algorithm to solve the Deutsch problem; (b) a one-qubit binary multiplication algorithm; (c) a two-qubit controlled binary multiplication algorithm; and (d) a two-qubit ROM-based version of the Deutsch-Jozsa algorithm. For each algorithm we present experimental verification using nuclear magnetic resonance ensemble QC. The average fidelities for the implementation were in the ranges 0.9-0.97 for the one-qubit algorithms, and 0.84-0.94 for the two-qubit algorithms. We conclude with a discussion of future prospects for ROM-based quantum computation. We propose a four-qubit algorithm, using Grover's iterate, for solving a miniature real-world problem relating to the lengths of paths in a network.

Benchmarking nitrogen removal suspended-carrier biofilm systems using dynamic simulation

We are witnessing an enormous growth in biological nitrogen removal from wastewater. It presents specific challenges beyond traditional COD (carbon) removal. A possibility for optimised process design is the use of biomass-supporting media. In this paper, attached growth processes (AGP) are evaluated using dynamic simulations. The advantages of these systems that were qualitatively described elsewhere, are validated quantitatively based on a simulation benchmark for activated sludge treatment systems. This simulation benchmark is extended with a biofilm model that allows for fast and accurate simulation of the conversion of different substrates in a biofilm. The economic feasibility of this system is evaluated using the data generated with the benchmark simulations. Capital savings due to volume reduction and reduced sludge production are weighed out against increased aeration costs. In this evaluation, effluent quality is integrated as well.

Peanut resistance to Sclerotinia minor and S-sclerotiorum

The fungi Sclerotinia minor and S. sclerotiorum are the causal agents of two similar diseases of peanut (Arachis hypogaea L.). Both diseases cause significant losses in the Australian peanut industry. Development of cultivars with resistance to Sclerotinia will be an important component of integrated control. The aims of this project are to generate information that will assist in breeding for Sclerotinia resistance in peanut: to identify Sclerotinia-resistant peanut germplasm, to understand the inheritance and estimate heritability of resistance, and to test the effectiveness of identified sources of resistance against both S. minor and S. sclerotiorum. This study has clearly established that material that shows resistance to S. minor in the USA is resistant to S. minor and likely to be resistant to S. sclerotiorum in Australia. The high level of resistance to both S. minor and S. sclerotiorum in germplasm from Texas, particularly TxAG-4, was confirmed. VA 93B showed good resistance in the field, which is primarily due to the open bush type rather than physiological resistance. Physiological resistance to S. minor was also identified in a cultivar and a landrace from Indonesia and a rust-resistant line from Queensland. All germplasm found to have high physiological resistance to S. minor belonged to the Spanish type. Inheritance of physiological resistance to S. minor was studied using a Generation Means Analysis (GMA) of the cross TxAG-4/VA 93B and its reciprocal. The broad-sense heritability of physiological resistance on a single plant basis was estimated at 47%, much higher than earlier estimates obtained in field studies. The average gene action of Sclerotinia resistance genes from TxAG-4 was found to be additive. No dominance effects were detected in the GMA. A small but significant reciprocal effect between TxAG-4 and VA 93B indicated that VA 93B passed on some physiological resistance maternally. An experiment was conducted to confirm the value of resistance against both S. minor and S. sclerotiorum. TxAG-4 was found to have physiological resistance to both S. minor and S. sclerotiorum. This resistance was expressed against both Sclerotinia species by progeny that were selected for resistance to S. minor. On the basis of the information obtained, the comparative advantages of 3 strategies for Sclerotinia-resistant cultivar development are discussed: (1) introduction of germplasm; (2) recurrent backcrossing with screening and crossing in the BCnF1 generation; and (3) pedigree selection. At present, introduction and backcrossing are recommended as the preferred strategies.

ROM-based computation: Quantum versus classical

We introduce a model of computation based on read only memory (ROM), which allows us to compare the space-efficiency of reversible, error-free classical computation with reversible, error-free quantum computation. We show that a ROM-based quantum computer with one writable qubit is universal, whilst two writable bits are required for a universal classical ROM-based computer. We also comment on the time-efficiency advantages of quantum computation within this model.

Kinematic analysis of lingual fatigue in myasthenia gravis

This study describes a preliminary examination of the viability and suitability of the physiologic technique electromagnetic articulography (EMA) in investigating lingual fatigue in myasthenia gravis (MG). A 52.9-year-old female diagnosed with MG at the age of 18 years, but who was in remission, participated in the study with a matched control subject. Changes in the duration, speed, and range of tongue-tip and tongue-back movements during repetition of /taka/ over two minutes were investigated. Results revealed that the MG subject did not exhibit significant changes in duration, maximum velocity, maximum acceleration, or the distance travelled by her tongue as measured by EMA over the task. The kinematic results were, in part, expected since the MG subject was in remission. The results, therefore, may not be representative of the majority of individuals with active MG. The examination of the current case did highlight, however, the potential advantages of EMA in providing detailed, objective information regarding lingual kinematics for future investigations of individuals with MG. It also showed that EMA may be sensitive in detecting subclinical kinematic features of fatigue in individuals who are in remission from MG. Finally, EMA led to the identification of possible physiologic factors underlying the CV transform effect, which was evident for the MG subject's syllable productions. In the past, the effect had been assumed to be a purely perceptual-based phenomenon.

Development of axon pathways in the zebrafish central nervous system

The zebrafish has a number of distinct advantages as an experimental model in developmental biology. For example, large numbers of embryos can be generated in each lay, development proceeds rapidly through a very precise temporal staging which exhibits minimal batch-to-batch variability, embryos are transparent and imaging of wholemounts negates the need for tedious histological preparation while preserving three-dimensional spatial relationships. The zebrafish nervous system is proving a convenient model for studies of axon guidance because of its small size and highly stereotypical trajectory of axons. Moreover, a simple scaffold of axon tracts and nerves is established early and provides a template for subsequent development. The ease with which this template can be visualized as well as the ability to spatially resolve individual pioneer axons enables the role of specific cell-cell and molecular interactions to be clearly deciphered. We describe here the morphology and development of the earliest axon pathways in the embryonic zebrafish central nervous system and highlight the major questions that remain to be addressed with regard to axon guidance.

Laparoscopic appendectomy in modern gynecology

Gynecologists frequently manage women with acute or chronic pain in the right iliac fossa. Appendicitis is one of the common conditions encountered in this setting. From the gynecologic perspective, issues regarding the role of laparoscopic appendectomy include radioimaging and laparoscopic diagnosis, operative technique, advantages and disadvantages, and laparoscopic appendectomy in pregnancy and in complicated appendicitis. Most studies are in favor of the procedure, and it seems reasonable to include it in training programs in gynecology.

Design of microchannel free-space optical interconnects based on vertical-cavity surface-emitting laser arrays

We investigate the design of free-space optical interconnects (FSOIs) based on arrays of vertical-cavity surface-emitting lasers (VCSELs), microlenses, and photodetectors. We explain the effect of the modal structure of a multimodeVCSEL beam on the performance of a FSOI with microchannel architecture. A Gaussian-beam diffraction model is used in combination with the experimentally obtained spectrally resolved VCSEL beam profiles to determine the optical channel crosstalk and the signal-to-noise ratio (SNR) in the system. The dependence of the SNR on the feature parameters of a FSOI is investigated. We found that the presence of higher-order modes reduces the SNR and the maximum feasible interconnect distance. We also found that the positioning of a VCSEL array relative to the transmitter microlens has a significant impact on the SNR and the maximum feasible interconnect distance. Our analysis shows that the departure from the traditional confocal system yields several advantages including the extended interconnect distance and/or improved SNR. The results show that FSOIs based on multimode VCSELs can be efficiently utilized in both chip-level and board-level interconnects. (C) 2002 Optical Society of America.

Levels of consensus and majority and minority influence

Three experiments are reported which examine the effects of consensus information on majority and minority influence. In all experiments two levels of consensus difference were examined; large (82% versus 18%) and small (52% versus 48%). Experiment 1 showed that a majority source had more influence than a minority source, irrespective of consensus level. Experiment 2 examined the cause of this effect by presenting only the source label ('majority' versus 'minority'), only the consensus information (percentages) or both. The superior influence of the majority was again found when either (a) both source label and consensus information were given (replicating Experiment 1) and (b) only consensus information was given, but not when (c) only the source label was given. The results showed majority influence was due to the consensus information indicating more than 50% of the population supported that position. Experiment 3 also manipulated message quality (strong versus weak arguments) to identify whether systematic processing had occurred. Message quality only had an impact with the minority of 18%. These studies show that consensus information has different effects' for majority and minority influence. For majority influence, having over 50% support is sufficient to cause compliance while for a minority there are advantages to being numerically small, in terms of leading to detailed processing of its message. Copyright (C) 2002 John Wiley Sons, Ltd.

In vivo DNA electrotransfer

The use of electrotransfer for DNA delivery to prokaryotic cells, and eukaryotic cells in vitro, has been well known and widely used for many years. However, it is only recently that electric fields have been used to enhance DNA transfer to animal cells in vivo, and this is known as DNA electrotransfer or in vivo DNA electroporation. Some of the advantages of this method of somatic cell gene transfer are that it is a simple method that can be used to transfer almost any DNA construct to animal cells and tissues in vivo; multiple constructs can be co-transfected; it is equally applicable to dividing and nondividing cells; the DNA of interest does not need to be subeloned into a specific viral transfer vector and there is no need for the production of high titre viral stocks; and, as no viral genes are expressed there is less chance of an adverse immunologic reaction to vector sequences. The ease with which efficient in vivo gene transfer can be achieved with in vivo DNA electrotransfer is now allowing genetic analysis to be applied to a number of classic animal model systems where transgenic and embryonic stem cell techniques are not well developed, but for which a wealth of detailed descriptive embryological information is available, or surgical manipulation is much more feasible. As well as exciting applications in developmental biology, in vivo DNA electrotransfer is also being used to transfer genes to skeletal muscle and drive expression of therapeutically active proteins, and to examine exogenous gene and protein function in normal adult cells situated within the complex environment of a tissue and organ system in vivo. Thus, in effect providing the in vivo equivalent of the in vitro transient transfection assay. As the widespread use of in vivo electroporation has really only just begun, it is likely that the future will hold many more applications for this technology in basic research, biotechnology and clinical research areas.

Extensive multiple test centre evaluation of the VecTest malaria antigen panel assay

To determine which species and populations of Anopheles transmit malaria in any given situation, immunological assays for malaria sporozoite antigen can replace traditional microscopical examination of freshly dissected Anopheles. We developed a wicking assay for use with mosquitoes that identifies the presence or absence of specific peptide epitopes of circumsporozoite (CS) protein of Plasmodium falciparum and two strains of Plasmodium vivax (variants 210 and 247). The resulting assay (VecTest(TM) Malaria) is a rapid, one-step procedure using a 'dipstick' test strip capable of detecting and distinguishing between P. falciparum and P. vivax infections in mosquitoes. The objective of the present study was to test the efficacy, sensitivity, stability and field-user acceptability of this wicking dipstick assay. In collaboration with 16 test centres world-wide, we evaluated more than 40 000 units of this assay, comparing it to the standard CS ELISA. The 'VecTest(TM) Malaria' was found to show 92% sensitivity and 98.1% specificity, with 97.8% accuracy overall. In accelerated storage tests, the dipsticks remained stable for >15 weeks in dry conditions up to 45degreesC and in humid conditions up to 37degreesC. Evidently, this quick and easy dipstick test performs at an acceptable level of reliability and offers practical advantages for field workers needing to make rapid surveys of malaria vectors.