Sex-specific dispersal behaviour of crawlers in the mealybug Planococcus citri

Όταν η διασπορά σχετίζεται με το φύλο είναι δυνατό να έχει σημαντικές εξελικτικές και οικο- λογικές επιπτώσεις, επηρεάζοντας τη δομή των πληθυσμών, την αναλογία φύλου καθώς και την ταχύτητα με την οποία αποικίζονται νέα ενδιαιτήματα. Στα κοκκοειδή έντομα, οι προνύμ- φες πρώτης ηλικίας (έρπουσες) θεωρούνται ως το κύριο στάδιο διασποράς. Αν και στα κοκκο- ειδή έντομα υπάρχει μορφολογικός διμορφισμός φύλου, στα περισσότερα είναι αδύνατος ο διαχωρισμός φύλου στο στάδιο των ερπουσών προνυμφών. Στην παρούσα εργασία μελετήθη- κε η διασπορά του εντόμου Planococcus citri (Risso) (Hemiptera: Coccidae) από και προς διαθέσιμα ενδιαιτήματα. Σκοπός της μελέτης ήταν να εξετάσουμε αν: (1) η συμπεριφορά δια- σποράς στις έρπουσες προνύμφες διαφέρει στα δύο φύλα και πώς επηρεάζεται από συνθήκες όπως η πυκνότητα πληθυσμού ή η αναλογία φύλου, και (2) αν τα δύο φύλα διαφέρουν ως προς την επιτυχία διασποράς σε νέο φυτό ξενιστή. Σύμφωνα με τα αποτελέσματά μας παρατηρήθη- κε ότι τα αρσενικά και θηλυκά άτομα κατά το στάδιο της έρπουσας προνύμφης δε διαφέρουν στη συμπεριφορά διασποράς όταν αυτή συμβαίνει με βαδιστική μετακίνηση. Αυτά τα εργα- στηριακά πειράματα αποτελούν ένα σημαντικό πρώτο βήμα για την κατανόηση της εξέλιξης της συμπεριφοράς διασποράς του P. citri στη φύση ενώ απαιτούνται περαιτέρω πειράματα με διαφορετικούς τρόπους διασποράς, εκτός της μετακίνησης, για να κατανοήσουμε καλύτερα τη δεδομένη συμπεριφορά του εντόμου.Sex-specific dispersal can have important evolutionary and ecological implications, influencing local population structure and sex ratio, as well as the speed at which new habitats can be colonized. In scale insects, first-instar nymphs (crawlers) are assumed to be the main dispersal stage. Although all scale insects are extremely sexually dimorphic, in most species the sexes are indistinguishable as crawlers. Here we consider the mealybug Planococcus citri (Risso), and dispersal by crawlers to or from resource patches. The aim of this study was to test if: (1) crawler dispersal behaviour differs between the sexes and how this is affected by local conditions (population density and sex ratio); and (2) there is a difference between the sexes in crawler dispersal success to a new host plant. Using two experiments, which differed in how resources were spread between dispersal sources and sinks, we show that male and female nymphs do not differ in their dispersal behaviour or in their dispersal success when dispersal is via crawler locomotion. These laboratory experiments are an important starting point for understanding the evolution of dispersal behaviour of P. citri in the field, suggesting that more attention might need to be paid to different methods of dispersal as well as crawler locomotion

Virtual files: a Framework for Experimental Design

The increasing power and decreasing cost of computers has resulted in them being applied in an ever widening area. In the world of Computer Aided Design it is now practicable to involve the machine in the earlier stages where a design is still speculative, as well as in the later stages where the computer's calculating ability becomes paramount. Research on database systems has not followed this trend, concentrating instead on commercial applications, with the result that there are very few systems targeted at the early stages of the design process. In this thesis we consider the design and implementation of the file manager for such a system, first of all from the point of view of a single designer working on an entire design, and then from the point of view of a team of designers, each working on a separate aspect of a design. We consider the functionality required of the type of system we are proposing, defining the terminology of experiments to describe it. Having ascertained our requirements we survey current database technology in order to determine to what extent it meets our requirements. We consider traditional concurrency control methods and conclude that they are incompatible with our requirements. We consider current data models and conclude that, with the exception of the persistent programming model, they are not appropriate in the context required, while the implementation of the persistent programming model provides transactions on data structures but not experiments. The implementation of experiments is considered. We examine a number of potential methods, deciding on differential files as the one most likely both to meet our requirements and to have the lowest overheads. Measurements conducted on both a preliminary and a full-scale implementation confirm that this is the case. There are, nevertheless, further gains in convenience and performance to be obtained by exploiting the capabilities of the hardware to the full; we discuss these in relation to virtual memory systems, with particular reference to the VAX/VMS environment. Turning to the case where several designers are each working on a (nearly) distinct part of a design, we consider how to detect conflicts between experiments. Basing our approach on optimistic concurrency control methods, we show how read and write sets may be used to determine those areas of the database where conflicts might arise. As an aside, we show how the methods we propose can be used in an alternative approach to optimistic concurrency control, giving a reduction in system overheads for certain applications. We consider implementation techniques, concluding that a differential files approach has significant advantages in maintaining write sets, while a two-level bitmap may be used to maintain read sets efficiently

Revisiting the Tradespace Exploration Paradigm: Structuring the Exploration Process

A number of case applications of tradespace exploration have further extended the types of analyses and knowledge insights that can be gained about tradeoffs between design choices and perceived utility and cost of alternatives. These extensions include application beyond its heritage aerospace domain to the transportation domain, comparing distinct concepts on a common tradespace, considering the impact of changing needs and contexts over time, evaluation of alternatives in a “light effort” manner. In parallel with these case applications, a formalization of the tradespace exploration process has emerged, using a question-driven approach to ensure the knowledge generated is practical and useful to decision makers. These questions are introduced and applied to three example space systems in order to illustrate insights gained in answering the questions. The insights include identifying “good” designs, the strengths and weakness of selected alternatives across a tradespace, limiting constraints and requirements that could allow for less expensive solutions. Additionally, advanced insights include understanding the sensitivities of designs to changes in contexts and needs, and consideration of the differential impact of uncertainty across a set of alternatives with potential opportunities for risk mitigation.Massachusetts Institute of Technology. Engineering Systems Division (Systems Engineering Advancement Research Initiative (SEAri)

The fine-tuning cost of the likelihood in SUSY models

In SUSY models, the fine tuning of the electroweak (EW) scale with respect to their parameters gamma_i={m_0, m_{1/2}, mu_0, A_0, B_0,...} and the maximal likelihood L to fit the experimental data are usually regarded as two different problems. We show that, if one regards the EW minimum conditions as constraints that fix the EW scale, this commonly held view is not correct and that the likelihood contains all the information about fine-tuning. In this case we show that the corrected likelihood is equal to the ratio L/Delta of the usual likelihood L and the traditional fine tuning measure Delta of the EW scale. A similar result is obtained for the integrated likelihood over the set {gamma_i}, that can be written as a surface integral of the ratio L/Delta, with the surface in gamma_i space determined by the EW minimum constraints. As a result, a large likelihood actually demands a large ratio L/Delta or equivalently, a small chi^2_{new}=chi^2_{old}+2*ln(Delta). This shows the fine-tuning cost to the likelihood (chi^2_{new}) of the EW scale stability enforced by SUSY, that is ignored in data fits. A good chi^2_{new}/d.o.f.\approx 1 thus demands SUSY models have a fine tuning amount Delta<<exp(d.o.f./2), which provides a model-independent criterion for acceptable fine-tuning. If this criterion is not met, one can thus rule out SUSY models without a further chi^2/d.o.f. analysis. Numerical methods to fit the data can easily be adapted to account for this effect.Comment: 10 pages (v3: small comment added

Persistence of myelofibrosis treated with ruxolitinib: biology and clinical implications

Activation of JAK-STAT signaling is one of the hallmarks of myelofibrosis, a myeloproliferative neoplasm that leads to inflammation, progressive bone marrow failure, and a risk of leukemic transformation. Around 90% of patients with myelofibrosis have a mutation in JAK2, MPL, or CALR: so-called 'driver' mutations that lead to activation of JAK2. Ruxolitinib, and other JAK2 inhibitors in clinical use, provide clinical benefit but do not have a major impact on the abnormal hematopoietic clone. This phenomenon is termed 'persistence', in contrast to usual patterns of resistance. Multiple groups have shown that type 1 inhibitors of JAK2, which bind the active conformation of the enzyme, lead to JAK2 becoming resistant to degradation with consequent accumulation of phospho-JAK2. In turn, this can lead to exacerbation of inflammatory manifestations when the JAK inhibitor is discontinued, and it may also contribute to disease persistence. The ways in which JAK2 V617F and CALR mutations lead to activation of JAK-STAT signaling are incompletely understood. We summarize what is known about pathological JAK-STAT activation in myelofibrosis and how this might lead to future novel therapies for myelofibrosis with greater disease-modifying potential.David M. Ross, Jeffrey J. Babon, Denis Tvorogov2and Daniel Thoma

Ancient pre-glacial erosion surfaces preserved beneath the West Antarctic Ice Sheet

Open access journalpresent ice-penetrating radar evidence for ancient (pre-glacial) and extensive erosion surfaces preserved beneath the upstream Institute and Möller ice streams, West Antarctica. Radar data reveal a smooth, laterally continuous, gently sloping topographic block, comprising two surfaces separated by a distinct break in slope. The erosion surfaces are preserved in this location due to the collective action of the Pirrit and Martin–Nash hills on ice sheet flow, resulting in a region of slow flowing, cold-based ice downstream of these major topographic barriers. Our analysis reveals that smooth, flat subglacial topography does not always correspond to regions of either present or former fast ice flow, as has previously been assumed. We discuss the potential origins of the erosion surfaces. Erosion rates across the surfaces are currently low, precluding formation via present-day glacial erosion. We suggest that fluvial or marine processes are most likely to have resulted in the formation of these surfaces, but we acknowledge that distinguishing between these processes with certainty requires further data.Natural Environment Research Council (NERC

Boundary conditions of an active West Antarctic subglacial lake: Implications for storage of water beneath the ice sheet

Open access journalRepeat-pass ICESat altimetry has revealed 124 discrete surface height changes across the Antarctic Ice Sheet, interpreted to be caused by subglacial lake discharges (surface lowering) and inputs (surface uplift). Few of these active lakes have been confirmed by radio-echo sounding (RES) despite several attempts (notable exceptions are Lake Whillans and three in the Adventure Subglacial Trench). Here we present targeted RES and radar altimeter data from an "active lake" location within the upstream Institute Ice Stream, into which at least 0.12 km3 of water was previously calculated to have flowed between October 2003 and February 2008. We use a series of transects to establish an accurate depiction of the influences of bed topography and ice surface elevation on water storage potential. The location of surface height change is downstream of a subglacial hill on the flank of a distinct topographic hollow, where RES reveals no obvious evidence for deep (> 10 m) water. The regional hydropotential reveals a sink coincident with the surface change, however. Governed by the location of the hydrological sink, basal water will likely "drape" over topography in a manner dissimilar to subglacial lakes where flat strong specular RES reflections are measured. The inability of RES to detect the active lake means that more of the Antarctic ice sheet bed may contain stored water than is currently appreciated. Variation in ice surface elevation data sets leads to significant alteration in calculations of the local flow of basal water indicating the value of, and need for, high-resolution altimetry data in both space and time to establish and characterise subglacial hydrological processesNatural Environment Research Council (NERC

Fine tuning as an indication of physics beyond the MSSM

We investigate the amount of fine tuning of the electroweak scale in the presence of new physics beyond the MSSM, parametrized by higher dimensional operators. We show that these significantly reduce the MSSM fine tuning to Delta<10 for a Higgs mass between the LEPII bound and 130 GeV, and a corresponding scale M_* of new physics as high as 30 to 65 times the Higgsino mass. If the fine-tuning criterion is indeed of physical relevance, the findings indicate the presence of new physics in the form of new states of mass of O(M_*) that generated the effective operators in the first instance. At small $\tan\beta$ these states can be a gauge singlet or a SU(2) triplet. We derive analytical results for the EW scale fine-tuning for the MSSM with higher dimensional operators, including the quantum corrections which are also applicable to the pure MSSM case in the limit the coefficients of the higher dimension operators vanish. A general expression for the fine-tuning is also obtained for an arbitrary two-Higgs doublet potential.Comment: 27 pages, 6 Figures; Eqs.(15)-(18) and (A.2)-(A.5) simplified; figures 1-3 update

Hydrogen-Helium Mixtures at High Pressure

The properties of hydrogen-helium mixtures at high pressure are crucial to address important questions about the interior of Giant planets e.g. whether Jupiter has a rocky core and did it emerge via core accretion? Using path integral Monte Carlo simulations, we study the properties of these mixtures as a function of temperature, density and composition. The equation of state is calculated and compared to chemical models. We probe the accuracy of the ideal mixing approximation commonly used in such models. Finally, we discuss the structure of the liquid in terms of pair correlation functions.Comment: Proceedings article of the 5th Conference on Cryocrystals and Quantum Crystals in Wroclaw, Poland, submitted to J. Low. Temp. Phys. (2004