Effects of temperature and other abiotic and biotic factors on development and survival of the immature stages of the alfalfa leafcutting bee, Megachile pacifica (Panzer) (=rotundata (F.)) (Hymenoptera:Megachilidae)

Larval mortality of leafcutting bee, Megachile pacifica (Panzer) (= rotundata (F.)), is high, usually exceeding 50%. Parasites and predators are not a limiting factor in the survival of the progeny. The disease chalk brood has been an important mortality factor since 1974. Inadequate food supply, pollen and nectar, may affect the survival of the progeny. Genetic differences within and between populations and the saponin content of alfalfa leaves do not affect brood production or survival. Domicile design and protection may also have a great influence on survival. Temperatures exceeding 50°C occur in cells when nesting material receives direct sunlight or when nesting material is housed in domiciles with poor ventilation and insulation. There are temperature differences between cells in a series, between nest positions within a domicile, and between types of nesting materials. There is no direct relationship between ambient and cell temperatures because the latter are influenced by exposure, nesting media, placement, and domicile structure. High internal bee body temperatures may occur during most bee activities, excluding resting. The effects of high temperatures on the adult bee or the eggs she contains are not known. Although larval development can proceed at temperatures below 21°C, survival is reduced. Adult activity, like metabolic larval development, can be conditioned to unusually high or low temperatures; thus, there is no absolute temperature threshold for development or activity in this bee. Eggs and young larvae reared at a constant 30°C had over 85% survival, in most years. An ambient temperature of 45°C applied for one to three hours resulted in a higher mortality of eggs and early instars than the control temperature of 30°C; at 50°C, mortality was complete. Exceptions were obtained for either situation. Half hour exposure at 50°C ambient temperature was also detrimental to immatures. An ambient temperature of 40°C in general does not affect survival of immatures. In-cell temperatures were at least 5°C lower than ambient temperatures in incubators during treatments. Repeating heat treatments on two or more days was not as severe as the duration of treatments. Larvae showed heat tolerance when exposed to two to three hours at 45°C but not to one hour, but some exceptions occurred. The mechanism for heat tolerance is not well understood, and may be related to a conditioning of individuals to high temperatures. A seasonal effect on survival was obtained and appears not to be related to the age of the laying females, nor to the generations, but rather to the thermal history to which the immatures were exposed. Heat susceptibility of eggs and early instars seemed to be similar. Fourth and fifth instars were the most heat tolerant of all larval stages. Exposure of young larvae to low temperatures before they were exposed to high temperatures did not increase mortality. However, sublethal high temperatures were generally less harmful to the immatures that were conditioned but this acclimation of the larvae did not occur in every test. Upper threshold temperature limits cannot be precisely defined, nevertheless, cell temperatures over 40°C result in egg and larval mortality. Brief exposure to 45°C was the upper limit that developing pupae could tolerate; 50°C was lethal. Pupae were most heat sensitive between three and six days before emergence. When exposed to high temperatures, pupae and emerging adults were able to arrest development. Pupae and emerging adults can be conditioned to tolerate short exposures to lethal temperatures up to seven days before emergence. Low temperatures did not affect the survival of pupae. Development of pupae and emerging adults could be arrested for up to a week at 15.6°C without harmful effect. Development and emergence proceed at 21 °C, but pupae need at least 2.5 hours per day of temperatures above 21°C to survive when not in an arrested state. Pupae not exposed to temperature above 29°C during 24 hours, emerged normally. Incubation at 29.5°C for less than 10 hours per day delayed the emergence. Pupae maintained at 15.6 °C for 22 hours per day for 8 days or for 20 hours per day for 16 days emerged after a delay longer than the period of cold. Cooling the emerging bees after high temperature treatment appeared to be more detrimental than cooling before exposures to high temperatures. The detrimental effect of extreme temperatures was shown on the survival of eggs, young larvae, and pupae, but possible chronic effects on later stadia were not studied

Spatial Selectivity in Cochlear Implants: Effects of Asymmetric Waveforms and Development of a Single-Point Measure.

Three experiments studied the extent to which cochlear implant users' spatial selectivity can be manipulated using asymmetric waveforms and tested an efficient method for comparing spatial selectivity produced by different stimuli. Experiment 1 measured forward-masked psychophysical tuning curves (PTCs) for a partial tripolar (pTP) probe. Maskers were presented on bipolar pairs separated by one unused electrode; waveforms were either symmetric biphasic ("SYM") or pseudomonophasic with the short high-amplitude phase being either anodic ("PSA") or cathodic ("PSC") on the more apical electrode. For the SYM masker, several subjects showed PTCs consistent with a bimodal excitation pattern, with discrete excitation peaks on each electrode of the bipolar masker pair. Most subjects showed significant differences between the PSA and PSC maskers consistent with greater masking by the electrode where the high-amplitude phase was anodic, but the pattern differed markedly across subjects. Experiment 2 measured masked excitation patterns for a pTP probe and either a monopolar symmetric biphasic masker ("MP_SYM") or pTP pseudomonophasic maskers where the short high-amplitude phase was either anodic ("TP_PSA") or cathodic ("TP_PSC") on the masker's central electrode. Four of the five subjects showed significant differences between the masker types, but again the pattern varied markedly across subjects. Because the levels of the maskers were chosen to produce the same masking of a probe on the same channel as the masker, it was correctly predicted that maskers that produce broader masking patterns would sound louder. Experiment 3 exploited this finding by using a single-point measure of spread of excitation to reveal significantly better spatial selectivity for TP_PSA compared to TP_PSC maskers

Chalk brood disease in the leafcutting bee

Published January 1978. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalo

Field domiciles and incubators for the leafcutting bee : their form and function in management

Published April 1979. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalo

Socioeconomic factors associated with antimicrobial resistance of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli in Chilean hospitals (2008-2017).

OBJECTIVE: To identify socioeconomic factors associated with antimicrobial resistance of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli in Chilean hospitals (2008-2017). METHODS: We reviewed the scientific literature on socioeconomic factors associated with the emergence and dissemination of antimicrobial resistance. Using multivariate regression, we tested findings from the literature drawing from a longitudinal dataset on antimicrobial resistance from 41 major private and public hospitals and a nationally representative household survey in Chile (2008-2017). We estimated resistance rates for three priority antibiotic-bacterium pairs, as defined by the Organisation for Economic Co-operation and Development; i.e., imipenem and meropenem resistant P. aeruginosa, cloxacillin resistant S. aureus, and cefotaxime and ciprofloxacin resistant E. coli. RESULTS: Evidence from the literature review suggests poverty and material deprivation are important risk factors for the emergence and transmission of antimicrobial resistance. Most studies found that worse socioeconomic indicators were associated with higher rates of antimicrobial resistance. Our analysis showed an overall antimicrobial resistance rate of 32.5%, with the highest rates for S. aureus (40.6%) and the lowest for E. coli (25.7%). We found a small but consistent negative association between socioeconomic factors (income, education, and occupation) and overall antimicrobial resistance in univariate (p < 0.01) and multivariate analyses (p < 0.01), driven by resistant P. aeruginosa and S. aureus. CONCLUSION: Socioeconomic factors beyond health care and hospital settings may affect the emergence and dissemination of antimicrobial resistance. Preventing and controlling antimicrobial resistance requires efforts above and beyond reducing antibiotic consumption

A prospective cohort study to assess seroprevalence, incidence, knowledge, attitudes and practices, willingness to pay for vaccine and related risk factors in dengue in a high incidence setting

Abstract Background Dengue is one of the most important vector-borne diseases in the world, causing significant morbidity and economic impact. In Colombia, dengue is a major public health problem. Departments of La Guajira, Cesar and Magdalena are dengue endemic areas. The objective of this research is to determine the seroprevalence and the incidence of dengue virus infection in the participating municipalities from these Departments, and also establish the association between individual and housing factors and vector indices with seroprevalence and incidence. We will also assess knowledge, attitudes and practices, and willingness-to-pay for dengue vaccine. Methods A cohort study will be assembled with a clustered multistage sampling in 11 endemic municipalities. Approximately 1000 homes will be visited to enroll people older than one year who living in these areas, who will be followed for 1 year. Dengue virus infections will be evaluated using IgG indirect ELISA and IgM and IgG capture ELISA. Additionally, vector indices will be measured, and adult mosquitoes will be captured with aspirators. Ovitraps will be used for continuous estimation of vector density. Discussion This research will generate necessary knowledge to design and implement strategies with a multidimensional approach that reduce dengue morbidity and mortality in La Guajira and other departments from Colombian Caribbean

Basic Neural Mechanisms of the Electrically Stimulated Auditory Nerve

Worldwide, Cochlear Implants (CIs) have already partially restored hearing to over 219000 profoundly hearing-impaired people. CIs attempt to stimulate the survival Auditory Nerve (AN) fibers directly by means of electrical pulses. Electrical stimulation is provided via an array of electrodes implanted inside the cochlea, which directly activates the AN fibers by means of biphasic Symmetric (SYM) pulses, i.e. an initial phase followed by a second phase with the same amplitude but with opposite polarity. Because electrical stimulation is delivered extracellularly, AN fibers could become depolarized and hyperpolarized at several neural sites and the excitation may be substantially different depending on AN status, electrode-neuron interface, and polarity. The necessity of charge balanced stimulation has precluded the use of monophasic stimuli (pulses consisting only in one phase) to study polarity effects in human CI users and most of the research concerning polarity effectiveness has been investigated in animal and computational models. However, recently, asymmetric charge-balanced pulse shapes and CI devices with recording capabilities have allowed researchers to study polarity effectiveness on CI users either by means of Electrically evoked Compound Action Potential (ECAP) or by means of behavioral measurements. Contrary to the majority of the results obtained with animals and computational models, those studies suggest that the positive (anodic) current stimulates the AN more effectively than the cathodic one in human CI users. The studies presented in this document aim to examine how neurons at different sites are affected by different stimulus shapes as well as the potential benefits of combining non-standard pulse shapes by means of objective ECAP and Electrically evoked Auditory Brainstem Response (EABR) as well as behavioral experiments.In chapter 2 we study whether the high sensitivity to the anodic current observed formerly for an electrode in the middle of the array, can be generalized to stimulation at the base and apex of the CI array. Threeexperiments studied the effect of stimulus polarity on the ECAP obtained with the masker-probe paradigm on different sites along the cochlea in CI users. The results of all the experiments extend those of a previous study, showing that the AN in humans is preferentially activated by anodic stimulation, to different sites along the cochlea by means of Monopolar (MP) stimulation.In chapter 3 we present a quantitative analysis of ECAP responses in order to determine an objective detection criterion based on the statistical properties of the noise. The study quantitatively investigates the properties of the Background Noise (BN) and the remaining post average Residual Noise (RN) in ECAP responses recorded from human CI users with the Across-sweeps Noise Estimator (ASNE) method. The analysis of the statistical properties of the noise indicated that a Signal-to-Noise Ratio (SNR) of 1.7 dB as a detection criterion corresponds to a false positive detection rate of 1% with the used measurement setup. In chapter 4 we study whether the high sensitivity to the anodic current is also observed in Bipolar (BP) stimulation mode. Spreads of Excitation (SOEs) produced by different masking pulse shapes presented in MP and BP mode are examined by means of the ECAP, obtained using the forward-masked paradigm in human CI users. The SOEs obtained with the MP masker showed a main excitation peak close to the masker electrode, whereas SYM maskers produced bimodal excitation patterns showing two peaks close to the electrodes of the masker channel. The SOEs obtained using Symmetric with a long Inter-Phase Gap (SYM-IPG) (for which the masker s second phase is responsible for most of the masking) and Pseudomonophasic (PS) maskers were more pronounced close to the masker electrode for which the effective phase was anodic. These results showed that the anodic polarity is the most effective one in BP mode and that the bimodal patterns produced by SYM maskers could be partially reduced by using asymmetric pulses.Chapter 5 investigates polarity effects at the level of the brainstem. Previous behavioral studies showing that the human AN of CI users is mainly excited by the anodic polarity have only been obtained with asymmetric PS, and it was assumed that only the short high-amplitude phase was responsible for the excitation. Similarly, in our previous studies it has been shown that ECAPs could only be obtained in response to the anodic phases of asymmetric pulses. However, it is possible that ECAP responses to cathodic responses were not detected due to the characteristics of the effective place of excitation across and along the AN fibers. In this chapter we measured EABRs to SYM and asymmetric pulse shapes presented for both polarities. It is shown that responses were time-locked to the short high-amplitude phase of asymmetric pulses, and were smaller, but still measurable, when that phase was cathodicthan when it was anodic. A behavioral experiment studied the polarity sensitivity at different intensities by means of a loudness balancing task between asymmetric stimuli of opposite polarity. The results showed that cathodic stimuli required higher amplitudes than anodic stimuli to reach the same loudness at different stimulus levels. This study provides the first evidence that cathodic stimulation can excite the auditory system of human CI listeners, and confirms that this stimulation is nevertheless less effective than for the anodic polarity.nrpages: 245status: publishe

Intrusion of buildings in natural environments : identifying the new environmental change regime

This thesis examines the degenerative processes of planning procedures and buildings intruding in natural environments as the result of a dysfunctional social value of nature. Such intrusions are assumed to embody a notion of detachment of artificial processes from those of nature, leading to unexpected changes in the natural environment. Unlike urban environments, previously undeveloped locations present no artificial thresholds in the ecological relationship between buildings and nature. The likely isolation of these "social" artefacts intervening in previously undeveloped natural environments is examined in order to stress the functional interaction between natural and artificially contrasting systems as developing a new environmental change regime. Such direct connections highlight the need for accurate design considerations regarding the local conditions of ecological functioning, especially if such conditions are to be maintained. Therefore, a central question of this thesis is not whether buildings should or should not be placed in non-urban locations, but how. Revisiting core concepts from scientific fields, and especially, understanding how theories about the natural environment are constructed comprise a driving strategy in specifying the potential role of planning and design within these processes of land modification. A common ground of analysis and understanding for both scientific disciplines and design processes not (traditionally) involved in environmental evaluations is thus encouraged. The core intent of this thesis is to offer an integrated vision of an ongoing and yet dysfunctional relationship between buildings and natural environments. If the final artificial intervention's layout and its consequent environmental performance considers the landscape structure and functioning as an integral part of the building system, then the building becomes unique to that particular place. By embracing a profound understanding of this functional dependency on the larger natural system, a "sustainable synthesis of nature and culture" (Forman 2001) may hopefully be accomplished.Applied Science, Faculty ofArchitecture and Landscape Architecture (SALA), School ofGraduat

Simultaneous subcortical and cortical electrophysiological recordings of spectro-temporal processing in humans.

Objective assessment of auditory discrimination has often been measured using the Auditory Change Complex (ACC), which is a cortically generated potential elicited by a change occurring within an ongoing, long-duration auditory stimulus. In cochlear implant users, the electrically-evoked ACC has been used to measure electrode discrimination by changing the stimulating electrode during stimulus presentation. In addition to this cortical component, subcortical measures provide further information about early auditory processing in both normal hearing listeners and cochlear implant users. In particular, the frequency-following response (FFR) is thought to reflect the auditory encoding at the level of the brainstem. Interestingly, recent research suggests that it is possible to simultaneously measure both subcortical and cortical physiological activity. The aim of this research was twofold: first, to understand the scope for simultaneously recording both the FFR (subcortical) and ACC (cortical) responses in normal hearing adults. Second, to determine the best recording parameters for optimizing the simultaneous capture of both responses with clinical applications in mind. Electrophysiological responses were recorded in 10 normally-hearing adults while they listened to 16-second-long pure tone sequences. The carrier frequency of these sequences was either steady or alternating periodically throughout the sequence, generating an ACC response to each alternation-the alternating ACC paradigm. In the "alternating" sequences, both the alternating rate and the carrier frequency varied parametrically. We investigated three alternating rates (1, 2.5, and 6.5 Hz) and seven frequency pairs covering the low-, mid-, and high-frequency range, including narrow and wide frequency separations. Our results indicate that both the slowest (1 Hz) and medium (2.5 Hz) alternation rates led to significant FFR and ACC responses in most frequency ranges tested. Low carrier frequencies led to larger FFR amplitudes, larger P1 amplitudes, and N1-P2 amplitude difference at slow alternation rates. No significant relationship was found between subcortical and cortical response amplitudes, in line with different generators and processing levels across the auditory pathway. Overall, the alternating ACC paradigm can be used to measure sub-cortical and cortical responses as indicators of auditory early neural encoding (FFR) and sound discrimination (ACC) in the pathway, and these are best obtained at slow alternation rates (1 Hz) in the low-frequency range (300-1200 Hz)