Probe Duration Research Articles

Double-excitation dynamics in m-LPPP probed with sub-20 fs time resolution

We present a modification of transient differential transmission spectroscopy, where the first excited state S 1 is re-excited via a second laser pulse towards a higher lying state S n . The dynamics of the relaxation of this state S n as well as the kinetics of the states created from S n is revealed by a broad-band probe pulse. We find an enhanced charge carrier generation from a higher lying excited state S n . The push and probe durations below 20 fs allow the time resolution of the ultrafast relaxation of the S n state and enables us to identify the two main contributions to enhanced charge generation from S n , energy migration towards quenching sites and exciton dissociation during vibrational relaxation.

Double-Excitation Dynamics in m-LPPP probed with sub-20 fs Time Resolution

AbstractIn a novel modification of transient differential transmission spectroscopy, the first excited state S1 is reexcited via a second laser pulse towards a higher lying state Sn. The dynamics of the relaxation of this state Sn as well as the states created from Sn are revealed by a broad-band probe pulse.We find that the charge carrier generation efficiency from Sn is higher compared to S1. The push and probe durations below 20 fs enable the temporal resolution of the ultrafast relaxation of the Sn state and enables us to identify the two main contributions to enhanced charge generation from Sn, energy migration towards sites of high dissociation probability, and exciton dissociation during vibrational relaxation.

Correlation of lesion volume and brain swelling from a focal brain trauma.

Brain edema and secondary growth of a traumatic brain tissue necrosis are important manifestations of secondary brain damage and of prognostic significance in severe head injury. Aim of the current study was to analyze the interdependency of the resulting brain swelling from the size of the focal traumatic lesion. Male Sprague-Dawley rats were intubated and mechanically ventilated. A trephination was made over the left parietal cortex for induction of a cold lesion. Different injury severities were achieved by varying the contact time of the cooled copper-cylinder and the exposed cortex. Animals were randomized into 12 experimental groups. Hemispheric brain swelling was measured in groups A1-A6 (n = 4-8) by gravimetry 24 hrs after lesions of six increasing severity levels. Correspondingly, in animals of groups B1-B6 (n = 5-7) the volume of necrosis was planimetrically assessed in histological serial sections of the brain obtained 24 hrs after trauma of different severity. In groups A1-A6. hemispheric brain swelling (increase in weight) was growing with increasing contact duration of the cold probe with the exposed cerebral cortex, i.e. from 7.7 +/- 0.4% (5 s) to a maximum of 9.9 +/- 0.5% (25 s). Longer contact periodes (30 s) were not further effective to increase hemispheric brain swelling. The contact times and extent of swelling were linearly correlated between 5 s and 25 s (r = 0.47; p < 0.01). The volume of necrosis in groups B1-B6 increased from 35.7 +/- 3.7 mm3 (5 s) to 106.3 +/- 10.3 mm3 (30 s). There was again a linear correlation between the duration of contact of the cold probe (i.e. injury severity) with the brain cortex and the volume of necrosis (r = 0.77; p < 0.01). Accordingly. the lesion volume could be increased in a reproducible manner from 35.7 up to 106.3 mm3 by extending the contact times of the cooling device and cerebral cortex. Hemispheric swelling, predominantly due to vasogenic brain edema, was expanding in relationship with the volume of necrosis.

Some constraints on the use of ABR in hearing studies: Investigation in dolphins

The main difficulty in using ABR in frequency-tuning measurements arises from the fact that these responses are evoked only by transient acoustic stimuli. This limits their use as probes for measuring frequency selectivity. Even with a slowly rising and falling stimulus, only a shorter part of the stimulus may be effective to evoke the response, and the spectrum of this short part is broader than the spectrum of the whole burst. It was shown in tone–tone masking study in dolphins, that tuning curves at lower frequencies reflect not the real frequency tuning but broad spectral bandwidth of the probe’s effective part. In the bottlenose dolphin, this effective part is not longer than 0.5 ms, irrespective of the actual probe duration. Another problem in the use of the ABR technique is that it is not clear which spectral part of the wideband stimulus participates in ABR generation, and what is the contribution of various parts of the cochlear partition to ABR. ABR to clicks and noise bursts of various frequency bands were recorded in dolphins in order to find these contributions. ABR amplitude increased with increasing the stimulus frequency, thus indicating a higher contribution of basal cochlear parts.

The Effect of Nontemporal Information Processing on Time Estimation in Pigeons

Pigeons' ability to time a stimulus while simultaneously engaged in another information-processing task was examined in three experiments using a matching-to-sample procedure. Pigeons were trained to match temporal samples of 2 and 10 s and were tested with durations of 2, 3, 4.5, 6.7, or 10 s while simultaneously processing information from another dimension. Experiment 1 revealed that the psychophysical curve for long judgments taken when pigeons also had to evaluate line orientation was shifted to the right of a control curve taken from trials on which only time had to be judged. In Experiment 2, results from probe duration tests showed that processing the spatial location of a stimulus while attending to duration caused a more general loss of timing ability across the probe durations (shorter durations were judged as longer and longer durations were judged as shorter). In Experiment 3, a distracter light was illuminated on some probe trials to determine how such a perceptual distraction would affect time judgments on the probe trials. Results showed a general loss of timing ability similar to that found in Experiment 2. It is proposed that the data might best be explained by a divided-attention effect rather than by a systematic effect on the timing mechanism.

The Location and Interpretation of the Bisection Point

In a temporal bisection task with humans, the observer is required to decide whether a probe duration (t) is more similar to the short referent (S), an R(S) response, or to the long referent (L), an RL response. Temporal bisection yields a psychometric function relating the proportion of long responses, P(R(L)), to probe duration t. The value of t at which R(S) and R(L) occur with equal frequency, P(R(L)) = .5, is referred to as the bisection point, T1/2. Bisection models usually interpret T1/2 as identifying the value of t that is equally confusable with S and L, but they differ in their predictions for the location of T1/2. The present paper presents new data relevant to the location and interpretation of T1/2. The data indicate that the empirical values usually are biased, the biases being influenced by duration range, L:S ratio, and probe spacing. Moreover, the biases often are not consistent across observers. It is concluded that empirical values of T1/2 should not be interpreted as indicating the value of t that is equally confusable with S and L.

A Frequency-to-Time Sound-Velocity Transducer

The transducer described is intended to control the sound velocity in sea water and is based on the principle of the tracking balancing of the probing duration by an acoustic pulse of the studied medium at a given basic distance by the pulse period divisible by the pulse period of the frequency-controlled oscillator. The transducer has a high measurement accuracy, which is achieved by the practical exclusion of a random error component caused by amplitude fluctuations of the received signal as a result of abnormalities of the acoustic transparency of the studied medium caused by various disturbing factors. The acoustic base-line distance of the converter is 0.1 m, the measurement range is 1400–1600 m/s, the output signal is a frequency of 140–160 kHz, the absolute basic error is ±0.035 m/s, and the output signal rise time does not exceed ≤0.6 s.

Temporal bisection with trial referents.

In temporal bisection, the subject is required to compare the similarity of a probe duration with two referent durations. Two bisection experiments with human subjects are reported in which performance under three referent conditions was compared. In two of the conditions, no-referent and fixed-referent, the referent pair was constant throughout the session and was varied between sessions. In the no-referent condition, samples of the referents were presented at the beginning of a block of trials, but not on the probe trials. In contrast, in the fixed-referent condition, the referent pair was presented on each probe trial. In the third referent condition, roving-referent, the referent pair was also presented on each probe trial, but the values of the pair varied during a session rather than between sessions. The pseudologistic Model (PLM; Killeen, Fetterman, & Bizo, 1997) provided an excellent account of the data from all referent conditions and indicated that (1) the scalar variability was located in the perception of the probe and was independent of the structure of the bisection task, (2) the role of the referents was to set the criterion, (3) the probe was compared with the criterion rather than with the referents, and (4) the comparison of the probe with the criterion occurred even when trial referents were available.

Effects of plant tissue factors on the acceptance of four greenhouse vegetable host plants by the greenhouse whitefly: an Electrical Penetration Graph (EPG) study

A combination of biological control and host-plant resistance is needed to control greenhouse whitefly, Trialeurodes vaporariorum (Westwood). The high level of susceptibility of several host plants to whitefly, based on their performance on these plants, is well documented. These studies only provide information on the overall host-plant acceptance by whiteflies. Here, we use a method that allows an examination of the different tissue layers in the overall acceptance. The effects of plant tissue factors on whitefly probing profiles were monitored using the electrical penetration graph (EPG) method. The EPGs of whitefly originating from a culture on glasshouse cucumber, were recorded for 8 hours on sweet pepper, tomato, gerbera and cucumber plants produced in a glasshouse. On sweet pepper the graphs showed that whitefly made many short probes, had long xylem phases, short phloem phases, and the shortest duration of first probes. An opposite probing profile was found on cucumber: longer probes, shorter xylem phases, fewer phloem phases but of longer duration, and longer first probes. The values of these parameters for gerbera and tomato were intermediate. Whiteflies encountered the greatest stimulation or the least resistance in the tissues of cucumber, and the least stimulation or the greatest resistance in the tissues of sweet pepper. Rejection of host plants probably occurred before the phloem tissue was reached, as the probes prior to a whitefly leaving a host plant were so short that the stylets cannot have reached the phloem. But phloem factors also determine host-plant rejection, as phloem probing on sweet pepper - a poor host plant - was much shorter than on the other host plants. Resistance factors seem, therefore, to be located both in the epidermis/mesophyll and in the phloem. We hypothesize that the factors encountered by whitefly in the different tissue layers during probing contribute to the acceptance or rejection of a host plant. Based on the performance of whitefly on these plants, which is also reflected in the values of the EPG parameters, the order of acceptance ranked from high to low is cucumber > tomato = gerbera > sweet pepper.

Probing behavior of the brown planthopper, Nilaparvata lugens Stal(Homoptera: Delphacidae) on a non-host barnyard grass, and resistant and susceptible varieties of rice.

The feeding activity of Nilaparvata lugens (Stål) (Homoptera: Delphacidae) was compared on the barnyard grass, Echinochloa Crus-galli var. oryzicola, which contains an antifeedant, (E)-aconitic acid, and on resistant (bph4) and susceptible rice varieties using an AC electronic monitoring system (EMS). N. lugens made more frequent probes on the barnyard grass and the resistant rice than on the susceptible rice. Mean duration of probes tended to be the shortest and the percentage of probes that consisted of the primarily salivation phase only was the highest on the barnyard grass, followed by the resistant rice. The most distinct difference in N. lugens feeding activities between the barnyard grass and the resistant rice was the frequency of the primarily ingestion phase. On the barnyard grass, the insect was rarely successful in achieving the primarily ingestion phase, indicating that probing was interrupted before the arrival of the stylets at the sieve elements. On the other hand, on the resistant rice the primarily ingestion phase was observed as frequently as it was on the susceptible rice. However, it stopped within 5 min on the resistant rice in most cases. Probing activities were strongly inhibited by 1% (E)-aconitic acid diluted with distilled water. The inhibitory effect was considerably mitigated when diluted with 15% sucrose. These results suggest that on the barnyard grass, interruption of probing activity by (E)-aconitic acid can occur in stylet pathway tissues rather than in ingestion tissues (e.g. the phloem where sucrose is located).

Oviposition behavior of Coccidoxenoides peregrinus, a parasitoid of Planococcus ficus

AbstractThe encyrtid parasitoid, Coccidoxenoides peregrinus has been used as a biological control agent against the mealybugs Planococcus citri and Planococcus ficus. This study examined the behavior and host selection of C. peregrinus attacking P. ficus. Adult parasitoids were fed a 0.1% solution of acridine orange, a DNA binding dye used to label C. peregrinus eggs. In a choice test, adult parasitoids were offered equal numbers of first through fourth instars of P. ficus and behavior of C. peregrinus was filmed and analyzed. Acridine orange labeled ova of the parasitoids found within mealybug hosts fluoresced green under fluorescence microscopy and presence of fluorescing eggs in hosts was used to determine oviposition events. A time budget prepared for C. peregrinus indicated that this parasitoid spent the majority of its time searching (71.64%) and grooming (15.06%). The average probing duration over all instars which led to oviposition from single visits was 4.93±0.62 s. A total of 35.51% of probes from all attacks led to ovipositions, whereas 33.72% of single visits to hosts resulted in ovipositions. Detection of fluorescing acridine orange labeled eggs showed all instars of P. ficus were acceptable for oviposition by C. peregrinus. There was a significant preference to probe second, third, and fourth instars rather than first instars of P. ficus. Host feeding was not observed for this parasitoid.

Oviposition behavior of Anagrus nigriventris,an egg parasitoid of beet leafhopper, Circulifer tenellus

Oviposition behavior of Anagrus nigriventris,a parasitoid of the eggs of the beetleafhopper,Circulifer tenellus, wasdescribed on sugar beet. Ovipositor probes ofrelatively long duration were accompanied by a periodof abdominal vibrations toward the end of the probe. These periods began as high frequency, low amplitudevibrations in the abdomen, and climaxed as a tremblingof the whole body in an up and down direction.Oviposition by the parasitoid was associated with theoccurrence of abdominal vibrations during a probe andwith probe durations ≥50 s; however thepresence/absence of abdominal vibrations during aprobe was considered a more reliable indicator ofoviposition than was a threshold probe duration of 50s. The majority of probes (63% of all probes) were inempty plant tissue, lasted 15 s, and were notassociated with abdominal vibrations. While probeswithout abdominal vibrations at host egg sites (14%of all probes) lasted an average of 48 s, probes withabdominal vibrations at host egg sites (23% of allprobes) lasted an average of 102 s, and all were ≥50s. It is hypothesized that the relative frequency ofthe 3 types of probes could be affected by the degreeof wasp experience, by the level of host cues on thesubstrate, and by the relative importance of ovipositor probing (vs. antennation) in the hostdetection process. Data from the study suggest thatA. nigriventris is able to discriminate againstpreviously attacked host eggs.

Host plant evaluation behaviour of Bemisia tabaci and its modification by external or internal uptake of imidacloprid

SummaryThe behaviour of adult Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) was observed on leaves of cotton, Gossypium hirsutum L., to study the process of host plant evaluation. Seven distinct behavioural elements were identified and recorded for a period of 20 min after initial contact with leaves. The behaviour of the whiteflies was observed on untreated leaves or on leaves treated with either foliar or systemically applied imidacloprid. Thus, contact with imidacloprid by whiteflies was either via the external cuticle or by ingestion, allowing determination of the effect of uptake route on host evaluation behaviour. Analysis of behavioural sequences and comparison of latencies, frequencies and durations of elements of behaviour between treatments revealed that host evaluation behaviour was similar on untreated and foliar treated leaves, but markedly different on those treated systemically. After their first probe, whiteflies on systemically treated leaves were much more active, spending significantly greater time walking and dabbing the labium tip onto the leaf surface. There was also a 50% reduction in the total time spent probing into systemically treated leaves, compared to the other treatments. This effect was the result of a shorter mean probe duration, and no effect of treatment was found on the frequency of probing. Pre‐oviposition behaviour was significantly more common on the systemically treated leaves, although the number of eggs laid was similar on all treatments. These results also show that the host evaluation phase of adult female B. tabaci was dominated by probing. The behavioural sequence that leads to probing was affected significantly by imidacloprid when ingested, but not by direct contact with this compound on the leaf surface. The wider implications for the mechanisms of whitefly–host plant interactions are discussed.

Temporal control during maintenance and extinction of conditioned keypecking in ring doves

Timing of conditioned keypecking was investigated using a delay autoshaping procedure. In two experiments, the CS-US interval (ISI) was varied and the temporal pattern of responding during unreinforced probe trials extending beyond the reinforced ISI was recorded. Both experiments showed temporal control of keypecking at ISIs of 4, 8, and 16 sec, regardless of whether the probe duration was held constant (Experiment 1) or covaried with the ISI (Experiment 2). Analyses showed that the timing of keypecking was scalar. Increased responding near the end of the probe was due possibly to independent timing of the probe duration. In a third experiment, a group of subjects trained at an ISI of 8 sec were extinguished by presentation of only probe trials. Although the maximal response rate declined progressively, timing of keypecking did not change.

Ultrasound diagnostic of the blood vessels’ random neoplasm distributed in focus sphere limited environs

The scattering of ultrasonic waves in the cylindrical volume, formed with a height of ct/2 (c—sound velocity, t—probe duration) and a focused beam of R radius in the vicinity of the focal zone is examined. There are N vessels of different diameter and random orientation of stream velocity relative to the beam axis. In the case of random blood vessels orientation, the average Doppler echo-signal frequency also will be random f. The estimation of coherent and noncoherent pressure in echo signal is reduced to statistical averaging for discrete scatters—blood vessels. The probability characteristics of the average effective surface of the vessels scattering with the different rules of wave’s incidence angle in the opposite direction (uniform laws, Gaussian laws, etc.) are determined. It was shown that with uniform law of the vessels’ orientation angle’s distribution, the Doppler frequency is approximately equal to: 〈f〉=f0(1−2〈M〉), but taking into account the random vessel orientation it will be: f=f0(1+2〈M〉cos〈Qinc〉), where 〈M〉 is the average Marh’s number, and a 〈Qinc〉 is the average wave’s angle of incidence. The proposed method serves for classification of the vessel’s neoplasm formation in cancer diagnostics.

Influence of cereal leaf epicuticular wax on Diuraphis noxia probing behavior and nymphoposition

AbstractThe effect of cereal leaf surface wax on Diuraphis noxia (Mordvilko), the Russian wheat aphid, probing behavior and nymphoposition was evaluated. Ultrastructure of leaf epicuticular wax from wheat (Triticum aestivum L.) c.v. ‘Arapahoe’ and ‘Halt’ was different from barley (Hordeum vulgare L.) c.v. ‘Morex’, and oat (Avena sativa L.) c.v. ‘Border’. Both wheat cultivars had similar rod‐shaped epicuticular wax, while barley and oat plants had flakes. The chemical composition comparison of gas chromatograms also indicated that the extract of the two wheat cultivars had similar pattern of peaks, while the barley and oat leaves had similar peaks. Cereal variety significantly affected aphid probing behavior (P &lt; 0.05), but wax removal using ethyl ether swab did not (P &gt; 0.05). Aphids initiated significantly more probes on Border oat leaves than on Morex barley irrespective of wax removal, although total probing duration per aphid was not significantly different among the four cereals examined. Accumulative salivation duration per aphid on oat leaves with wax was significantly longer than other cereal leaves with wax, while accumulative ingestion duration per aphid on Arapahoe wheat and Morex barley was significantly longer than on oat. Nymphoposition of D. noxia on cereal leaves maintained on the benzimidazole‐agar medium showed that aphids produced a greater number of nymphs on Morex barley and less on Border oat leaves, although wax removal did not affect aphid nymphoposition. Removal of leaf epicuticular waxes from the 4 cereal genotypes using ethyl ether swab indicated that the influence of wax on plant resistance to D. noxia probing and reproduction was limited. Morex barley was the most favorable, while Border oat was the least favorable cereal host of D. noxia.

Mating and Oviposition Experience Influence Odor Learning inLeptopilina boulardi(Hymenoptera: Eucoilidae), a Parasitoid ofDrosophila

Abstract In many parasitoid species, behaviors leading to host selection are triggered by the perception of mostly chemical cues, which often depends on learning processes. Among the latter, associative learning, where a neutral stimulus (e.g., an odor) is perceived as associated with a reward (e.g., oviposition or contact with host products), ensures a higher probability of locating a host. In this work we investigated the effect of two physiological factors, mating and oviposition experience, on odor learning involved in the ovipositor search in the parasitoid Leptopilina boulardi (Barbotin et al. ). We developed a bioassay to quantify individual learning performances based on the observation of an odor-conditioned probing response, characterized by several parameters such as the latency (i.e., the time elapsed between the onset of the conditioned odor and the start of the conditioned probing behavior), the duration of the first probing, and the total probing duration. The percentage of females that learned a fruit odor (banana) associated to an oviposition reward did not depend on mating or prior oviposition experience. However, both factors influenced the parameters of the learned response: oviposition experience could induce a higher latency and a shorter probing duration, whereas the opposite changes could result from mating. These results were discussed with regard to physiological changes known to influence host-searching activity. We concluded on the possible consequences of these variabilities at the individual level. The evaluation of how such physiological events affect traits correlated to parasitization efficiency is important for improving biocontrol strategies.

Genetic variability of conditioned probing responses to a fruit odor in Leptopilina boulardi (Hymenoptera: Eucoilidae), a Drosophila parasitoid.

The genetic variability of odor-conditioned probing behavior was investigated in a population of Leptopilina boulardi, a parasitoid of Drosophila larvae. Ovipositor probing is the final step of host location, leading to the discovery of host larvae. It can be triggered by an odor previously experienced during an oviposition as a result of associative learning. This study was based on the analysis of female probing performance over two generations of isofemale lines (using both mother-daughter regressions and one-way analysis of variance). Individual performances of the conditioned response to the odor were characterized by (1) the latency (i.e., the time elapsed between the onset of the odor delivery and the start of the probing response), (2) the duration of the first probing phase, and (3) the total probing duration. Results suggested that the variability of two characters, the latency and the duration of the first probing phase, were under a genetic control in the studied population. This work is the first contribution to quantify the genetic component of this variability.

Effect of Wheat Leaf Epicuticular Structure on Host Selection and Probing Rhythm of Russian Wheat Aphid (Homoptera: Aphididae)

Five genotypes of wheat, Triticum aestivum L. (‘Arapahoe’, ‘Halt’, PI 137739, PI 225245, and PI 262660), were compared for their antixenotic effects on the Russian wheat aphid, Diuraphis noxia (Mordvilko). Comparisons were made by host plant choice tests, diurnal and nocturnal probing behavior of D. noxia , and examination of leaf trichome and epicuticular wax structure. The choice test showed that PI 137739 and PI 225245 were the least preferred hosts among the 5 genotypes evaluated. Electronic monitoring of D. noxia probing behavior showed that the aphids fed differently among the 5 wheat genotypes, and aphid probing behavior was different between diurnal and nocturnal periods. Although the number of probes per aphid was not different among the 5 genotypes either diurnally or nocturnally, the accumulative probing duration per aphid during the 8-h recording period was different. The least probing duration per aphid was on PI 137739 diurnally, but no differences were found among the 5 genotypes nocturnally. Furthermore, aphid piercing duration per probe was significantly longer on PI 137739 than on Arapahoe. D. noxia probing (i.e., salivation and ingestion) duration per probe was significantly different among the 5 wheat genotypes and between diurnal and nocturnal periods. The aphids had the shortest probing duration on PI 137739 among the 5 genotypes diurnally and nocturnally. Irrespective of genotype differences, total probing duration per aphid was significantly longer nocturnally than diurnally. Aphids made numerous short probes diurnally and fewer long probes nocturnally. Adaxial leaf surface examination showed that PI 137739 had the longest trichomes and medium density, whereas Arapahoe and Halt had the shortest trichomes and the highest density. Examination of adaxial leaf epicuticular wax showed that its ultrastructure was similar among the 5 wheat genotypes, although the density of wax Rakes varied among the genotypes. We concluded that Halt and PI 262660 were not antixenotic to D. noxia , but the PI 137739 and PI 225245 were antixenotic to D. noxia based on the host choice test, aphid probing behavior, and examination of leaf surface structure.

Resistance to the pink potato aphid, Macrosiphum euphorbiae, in two accessions of Lycopersicon hirsutum f. glabratum

AbstractAccessions PI 126449 and PI 134417 of wild tomato, Lycopersicon hirsutum f. glabratum C.H. Mull, were assessed for resistance to the pink potato aphid, Macrosiphum euphorbiae (Thomas). Aphid populations under field and greenhouse conditions were significantly lower on the L. hirsutum f. glabratum plants compared to L. esculentum. Removal of trichome glands and exudates by wiping the leaf surface resulted in a dramatic decrease in aphid mortality. Compared to L. esculentum, aphid behavior on the L. hirsutum f. glabratum plants was characterized by 40 to 52% abandonment, delay in time for first probe, reduction of number and duration of probes and decrease in the total proportion of time probing. Removal of the trichomes reduced the percentage of abandonment and increased the total proportion of time probing. Density and type of glandular trichomes varied among plant lines and on adaxial and abaxial leaf surfaces within a line, particularly for the L. hirsutum f. glabratum plants. PI 134417 was, in general, more resistant to the aphids than PI 126449.