bluuebunny/crossref_metadata_2025_split huggingface dataset:
The burden of illness of gastro‐oesophageal reflux disease: impact on work productivity
Authors: Dean B. B. , Crawley J. A. , Schmitt C. M. , Wong J. , Ofman J. J. 
Published: May 2003

SummaryBackground:  The impact of gastro‐oesophageal reflux disease on work productivity has become increasingly important, as the symptoms of gastro‐oesophageal reflux disease affect individuals in their productive years of life.Aims:  To assess the impact of gastro‐oesophageal reflux disease on reduced work productivity and to identify the predictors of reduced productivity.Methods:  A sample of employed individuals reporting chronic heartburn was selected from US household mail survey respondents. Heartburn severity and frequency were recorded using a diary, and work productivity was assessed using the Work Productivity and Activity Impairment Questionnaire for Patients with Symptoms of Gastro‐oesophageal Reflux Disease. Predictors of reduced productivity were evaluated.Results:  Over 30% of heartburn sufferers reported reduced productivity. Individuals with symptoms of gastro‐oesophageal reflux disease (n = 1003) reported 6.0% reduced productivity attributable to symptoms. Over 48% of respondents with severe symptoms reported reduced productivity, compared with 40% and 12% of respondents with moderate and mild symptoms, respectively. Using logistic regression, severity, a younger age and nocturnal symptoms were associated with increased odds of reduced productivity. In those reporting nocturnal heartburn, medication use and sleep interference increased the odds of reduced productivity.Conclusions:  Reduced work productivity is seen in a large proportion of subjects on prescription medication for gastro‐oesophageal reflux disease. Symptom severity and nocturnal heartburn are significantly associated with reduced work productivity, particularly when nocturnal heartburn interferes with sleep.
Testing the resource concentration hypothesis with tarnished plant bug on strawberry: density of hosts and patch size influence the interaction between abundance of nymphs and incidence of damage
Authors: Rhainds Marc , English‐Loeb Greg 
Published: May 2003

Abstract. 1. Attributes of patches with strawberry plants were manipulated experimentally to assess the impact of patch size and host density on the abundance of tarnished plant bug (Hemiptera: Miridae) and incidence of fruit damage.2. The density of nymphs per inflorescence increased with patch size and host density for some but not all generations of plant bug, providing partial support for the resource concentration hypothesis, while emphasising the importance of replicating experiments across several generations of herbivore.3. Increasing density of nymphs with increasing patch size and host density did not translate into a high incidence of damage, which may be due to the relatively low feeding impact of nymphs in patches with numerous fruits and to the relatively high perimeter‐to‐area ratio in small patches resulting in a relatively high proportion of damaged fruits.4. The decreasing proportion of damaged fruits with increasing density of fruits per patch suggests that nymphs exhibit a saturating functional response to density of strawberry fruits. Functional responses of herbivores may be a critical yet overlooked component that influences interactions between insects and their host plant. In particular, concentrated plant resources may result in increased numbers of herbivores yet sill have a negligible influence on plant damage and/or fitness.
Canopy herbivore community structure: large‐scale geographical variation and relation to forest composition
Authors: Franklin Anne J. , Liebhold Andrew M. , Murray Kathleen , Donahue Charlene 
Published: May 2003

Abstract.  1. Geographical distributions of individual foliage‐feeding forest herbivore species have been found to be aligned closely with the distribution of their host trees, however little is known about the extent to which broad herbivore communities are geographically associated with distinct host communities.2. Large‐scale geographic variation in canopy herbivore communities in a 80 000 km2 area (the state of Maine, U.S.A.) was characterised using historical insect survey data. Variation in insect communities was compared with corresponding variation in forest over‐storey composition, which was quantified using data from a regional forest inventory survey.3. Principal components analysis was used to characterise associations among herbivore and tree species. Analysis of the herbivore data identified three main insect groups: group A corresponded to a single species (Choristoneura fumiferana), group B corresponded to pine‐feeding species including Semiothisa sp., and group C corresponded to the spruce‐feeding species Gilpinia hercyniae and Pikonema alaskensis. Analysis of the forest inventory data characterised three important forest types: northern hardwoods, eastern white pine, and northern spruce‐fir forest types.4. Spatial analyses were carried out on the first two components of each of the principal components analyses. Factor 1 of the insect data showed a trend of decreasing values from south to north, while factor 2 of the forest inventory data showed an opposite trend. These inverse trends reflected the distribution of the main contributing species to the principal components analysis, C. fumiferana and Pinus strobus respectively. These distributions were highlighted further by the significant negative cross‐correlations that were found between the two factors up to distances of 120 km.5. Analyses indicated a parallel between the geographic variation in the insect guilds associated with conifers and the geographic pattern of their conifer hosts. Hardwood‐feeding caterpillars, on the other hand, did not form well‐defined guilds and showed varying geographical distributions. The survey data showed varying quality in defining large‐scale associations in the structures of herbivore and host communities.6. Implications for biodiversity management are discussed.
Clutch size in frugivorous insects as a function of host firmness: the case of the tephritid fly Anastrepha ludens
Authors: Díaz‐Fleischer Francisco , Aluja Martín 
Published: May 2003

Abstract. 1. Optimal clutch size theory predicts that individuals will oviposit the number of eggs that increases their fitness. In Anastrepha ludens Loew (Diptera: Tephritidae), females oviposit larger clutches in unripe (firm) fruits than in ripe (soft) fruits. The following hypotheses were tested: (1) Using fruit firmness as an indicator of fruit quality, A. ludens females vary the number of eggs per clutch every time they reach an oviposition decision. (2) Maximising offspring survival with respect to either unripe or ripe fruit requires placing large clutches in firm fruit and smaller clutches in soft fruit.2. Agar spheres were used as artificial hosts. Three agar concentrations resulted in three degrees of firmness. Mango fruits Mangifera indica L. served as natural hosts. Ripe and unripe fruits were used to test soft and firm host conditions respectively. Females laid significantly larger clutches in the firmer artificial hosts than in the softer hosts. They also laid significantly more eggs in artificial hosts without sugar than in hosts with sugar. Firm (unripe) mangoes also received significantly larger clutches than soft (ripe) mangoes.3. When an individual female was first presented with a firm artificial host, it laid a large clutch. If subsequently offered a soft host, the female laid a significantly smaller clutch. Finally, if again offered a firm host, clutch size was increased significantly.4. Possible trade‐offs in offspring fitness were explored in ripe and unripe mangoes by measuring offspring egg‐to‐adult survival, pupal weight, mean adult longevity, and fecundity. Despite the fact that larval survival was greater in soft fruit than in firm fruit, parameters such as pupal weight, mean longevity, and fecundity of adults stemming from both fruit types did not differ significantly.5. A probable trade‐off between high offspring mortality caused by host unsuitability and low offspring and adult mortality caused by parasitism and predation is discussed as the reason for the exploitation of sub‐optimal hosts.
The effect of prey species and environmental complexity on the functional response of Franklinothrips orizabensis: a test of the fractal foraging model
Authors: Hoddle Mark S. 
Published: May 2003

Abstract. 1. The hypothesis proposed by the fractal foraging model, that prey procurement by predators declines as habitat complexity increases, was tested. To evaluate this hypothesis, the effect of two prey species, second‐instar larvae of Scirtothrips perseae Nakahara and Heliothrips haemorrhoidalis (Bouché) (both Thysanoptera: Thripidae), and environmental complexity on the functional response of the predatory thrips Franklinothrips orizabensis Johansen (Thysanoptera: Aeolothripidae) was examined.2. The Koch curve, a well‐studied fractal, was used to generate the shapes of experimental arenas to test the effect of environmental complexity on the functional response of F. orizabensis. Complexity was defined in terms of the number of acute vertices in which prey thrips could seek refuge and the length of the perimeter that had to be searched by the predator. Four shapes were tested: a circle (zero acute vertices, circumference = 186.61 mm), equilateral triangle (three acute vertices, perimeter = 240 mm), star (six acute vertices, perimeter = 277.13 mm), and snowflake (18 acute vertices, perimeter = 333.65 mm). All shapes were scaled so that the area of each arena was 2771 mm2.3. Franklinothrips orizabensis exhibited a Type II functional response for both prey species and all four experimental arenas tested. Significantly fewer S. perseae larvae were killed in the most complex arena (i.e. the snowflake) when prey densities exceeded 16. For H. haemorrhoidalis, significant differences in mortality were observed only when prey densities equalled four. These results demonstrated that the fractal foraging model was supported when certain prey densities coincided with particular levels of environmental complexity.4. Subtle changes in environmental complexity and different prey species of varying density can affect prey–predator interactions significantly.
Use of low frequencies for sub‐basalt imaging
Authors: Ziolkowski Anton , Hanssen Peter , Gatliff Robert , Jakubowicz Helmut , Dobson Andrew , Hampson Gary , Li Xiang‐Yang , Liu Enru 
Published: May 2003

ABSTRACTMany prospective passive ocean margins are covered by large areas of basalts. These basalts are often extremely heterogeneous and scatter the seismic energy of the conventional seismic reflection system so that it becomes difficult to obtain information on deeper reflectors. Since high frequencies are scattered more than low frequencies, we argue that the acquisition system for sub‐basalt targets should be modified to emphasize the low frequencies, using much larger airguns, and towing the source and receivers at about 20 m depth. In the summer of 2001 we obtained seismic reflection data over basalt in the northeast Atlantic using a system modified to enhance the low‐frequency energy. These new data show deep reflections that are not visible on lines shot in the same places with a conventional system.
Imaging and regional distribution of basalt flows in the Faeroe‐Shetland Basin
Authors: White Robert S. , Smallwood John R. , Fliedner Moritz M. , Boslaugh Brian , Maresh Jenny , Fruehn Juergen 
Published: May 2003

ABSTRACTWe demonstrate that the use of long‐offset seismic data allows wide‐angle reflections and diving waves to be recorded, and that these can be used in conjunction with prestack depth migrations to constrain and to image the base of the basalt flows and the underlying structure in the Faeroe‐Shetland Basin. Crustal velocity models are built first by inverting the traveltimes of the recorded reflections and diving waves using ray‐tracing methods. Finer details of the velocity structure can then be refined by analysis of the amplitudes and waveforms of the arrivals. We show that prestack depth migration of selected wide‐angle arrivals of known origin, such as the base‐basalt reflection, using the crustal velocity model, allows us to build a composite image of the structure down to the pre‐rift basement. This has the advantage that the wide‐angle first‐arriving energy must be primary, and not from one of the many multiples or mode‐converted phases that plague near‐offset seismic data. This allows us to ‘tag’ these primary arrivals with confidence and then to identify the same arrivals on higher‐resolution prestack migrations that include data from all offsets. Examples are drawn from the Faeroe‐Shetland Basin, with a series of regional maps of the entire area showing the basalt depths and the thickness of the basalt flows and underlying sediment down to the top of the pre‐rift basement. The maps show how the basalts thin to the southeast away from their presumed source west of the present Faeroe Islands, and also show the extent to which the structure of the pre‐rift basement controls the considerable variations in sediment thickness between the basement and the cap formed by the overlying basalt flows.
Velocity imaging by tau–p transformation of refracted seismic traveltimes
Authors: Barton P. , Barker N. 
Published: May 2003

ABSTRACTWe present a new method for producing a ‘brute’ velocity image rapidly and automatically from traveltimes picked from densely sampled refraction data. The procedure involves imaging by data transformation from the time–offset domain into the tau–p (intercept–slope) domain, and does not include conventional modelling steps. Differences in apparent velocity and tau along reciprocal paths in the up‐ and downdip directions allow the estimation of the true velocity and geometrical position of the ray turning points. The tau–velocity–turningpoint (τ–ν–x) map distributes phases automatically on the basis of geometry and velocity to give a two‐dimensional representation of subsurface structure. This map may be converted simply to depth and two‐way‐time images. Such images have potential for direct geological interpretation, for use as a starting model for seismic inversion, for superimposition on to conventional reflection images, or for input into prestack depth migration and other processing routines.
Combined structure and velocity stacks via the tau–p transform
Authors: Jones G.D. , Barton P.J. , Singh S.C. 
Published: May 2003

ABSTRACTReflection and refraction data are normally processed with tools designed to deal specifically with either near‐ or far‐offset data. Furthermore, the refraction data normally require the picking of traveltimes prior to analysis. Here, an automatic processing algorithm has been developed to analyse wide‐angle multichannel streamer data without resorting to manual picking or traveltime tomography. Time–offset gathers are transformed to the tau–p domain and the resulting wavefield is downward continued to the depth–p domain from which a velocity model and stacked section are obtained. The algorithm inputs common‐depth‐point (CDP) gathers and produces a depth‐converted stacked section that includes velocity information. The inclusion of long‐offset multichannel streamer data within the tau–p transformation enhances the signal from high‐velocity refracted basalt arrivals. Downward continuation of the tau–p transformed wavefield to the depth–p domain allows the reflection and refraction components of the wavefield to be treated simultaneously. The high‐slowness depth–p wavefield provides the velocity model and the low‐slowness depth–p wavefield may be stacked to give structural information. The method is applied to data from the Faeroe Basin from which sub‐basalt velocity images are obtained that correlate with an independently derived P‐wave model from the line.
A quantitative study on the use of converted waves for sub‐basalt imaging
Authors: Hanssen Peter , Ziolkowski Anton , Li Xiang‐Yang 
Published: May 2003

ABSTRACTThe idea of imaging beneath a high‐velocity layer using converted waves has been popular since 1990. Because these wave types have their maximum amplitudes at mid‐ to far‐offsets, the search for pure P‐waves at the highly multiple‐contaminated near‐offsets can be avoided. For the Atlantic Margin, with buried thin‐layered basalts, our quantitative study shows that the initial single‐layered approach is not viable. Even in an unrealistic ideal geological setting, the amplitude of the symmetrical PSP‐mode is far too weak to be recognized on towed streamer data. Furthermore, in the far‐offset window, where locally converted waves have their strongest amplitudes, there is a multitude of other reflections, refractions and interbedded multiples, which have similar moveouts and, often, higher amplitudes. Without the removal of these events, a reliable image of the subsurface cannot be produced. We show that even if this problem were solved, it would be far easier to use the P‐wave reflection from beneath the basalt at near‐offsets. Our study shows that this wave type is by far the strongest response. A borehole‐derived model using a thin‐layered basalt sequence reveals that the strongest locally converted wave has an asymmetrical path and is 10 times weaker. All our results indicate that the pure P‐modes provide the best chance of imaging sub‐basalt sedimentary interfaces.
A case study of sub‐basalt imaging in land region covered with basalt flows
Authors: Reshef Moshe , Shulman Haim , Ben‐Avraham Zvi 
Published: May 2003

ABSTRACTIn this study, a set of 20 2D seismic lines, acquired over the Golan Heights basaltic plateau, was processed and analysed. Although the data were acquired and processed by standard techniques, in some cases good‐quality seismic images were obtained under several hundred metres of basalts. We describe how the seismic characteristics of the top basalt layer were defined and show the effect of the numerous widespread volcanic sources on the quality of the final images. The new data reveal the first images of the sedimentary sequence under the basalt flows, and indicate that strands of the Dead Sea Transform extend into this area. The entire region was found to be very deformed. Several attractive traps for hydrocarbon exploration were also identified on the output sections.
Separation of P‐ and S‐wavefields from wide‐angle multicomponent OBC data for a basalt model
Authors: Wang Yanbin , Singh Satish C. 
Published: May 2003

ABSTRACTWide‐angle multicomponent ocean‐bottom cable (OBC) data should further enhance sub‐basalt imaging by using both compressional and converted shear wavefields. The first step in analysing multicomponent OBC data is to decompose the recorded wavefields into pure P‐ and pure S‐wavefields, and extract the upgoing P‐ and S‐waves. This paper presents a new scheme to separate P‐ and S‐wavefields from wide‐angle multicomponent OBC data in the τ–p domain. By considering plane‐wave components with a known horizontal slowness, the P‐ and S‐wavefields are separated into the directions of observed P‐ and S‐wave oscillations using the horizontal and vertical components of the data. The upgoing P‐ and S‐waves are then extracted from the separated P‐ and S‐wavefields. The parameters used in the separation are the seismic wave velocities and the density at the receiver location, which can be estimated from the first reflection phase observed on the horizontal and vertical components. Numerical tests on synthetic data for a plane‐layered model show good performance and demonstrate the accuracy of the scheme. Separation of wavefields from a basalt model is performed using synthetic wide‐angle multicomponent OBC data. The results show that both near‐offset and wide‐angle reflections and conversions from within and below basalt layers are enhanced and clearly identified on the separated wavefields.
Expression of mCLOCK and Other Circadian Clock‐Relevant Proteins in the Mouse Suprachiasmatic Nuclei
Authors: Maywood E. S. , O'Brien J. A. , Hastings M. H. 
Published: May 2003

AbstractCircadian timing in mammals is based upon the cell‐autonomous clockwork located in the suprachiasmatic nuclei (SCN) of the hypothalamus. It is thought to involve interlocked feedback loops in which periodic transcriptional drive to core clock genes is mediated by CLOCK/BMAL1 heterodimers. Negative‐feedback actions of the encoded proteins PER and CRY terminate this phase of the cycle. In lower species, rhythmic abundance of the mCLOCK homologue initiates the subsequent cycle. By contrast, it is proposed that the new circadian cycle in mammals is triggered by indirect, positive transcriptional actions leading to a subsequent surge in BMAL1. The aim of this study was to test predictions made by this model concerning the behaviour of the native clock factor mCLOCK in the mouse SCN. Using in situ hybridization, immunocytochemistry, Western blotting and immunoprecipitation, we demonstrate constitutive expression of mCLOCK as a nuclear antigen in the SCN. mCLOCK forms alternating, periodic associations with either mBMAL1 or the negative regulators mPER and mCRY. The results confirm predictions made by the ‘two‐loop’ model of the mouse clock, and further highlight the role of interlocked cycles of positive and negative transcriptional regulatory complexes at the heart of the circadian clockwork.
Melatonin Action in the Pituitary: Neuroendocrine Synchronizer and Developmental Modulator?
Authors: . Johnston J. D , Messager S. , Barrett P. , Hazlerigg D. G. 
Published: May 2003

AbstractMelatonin inhibits the gonadotropin‐releasing hormone (GnRH)‐stimulated secretion of luteinizing hormone and follicle‐stimulating hormone from the pars distalis region of the neonatal rat pituitary gland. Over the initial weeks of postnatal life, this response to melatonin declines in parallel with a loss of iodo‐melatonin binding sites. Although neonatal gonadotrophs have since been extensively used to study melatonin receptor signalling pathways, the mechanisms driving this phenomenon, together with its physiological significance, remain unknown. Melatonin receptors are expressed in the foetal pars distalis before activation of the GnRH system. Furthermore, the MT1 melatonin receptor promoter contains response elements for transcription factors involved in both pituitary differentiation and gonadotroph regulation. These data, coupled with the known ability of melatonin to regulate rhythmical gene expression in adult pars tuberalis cells, leads us to propose that melatonin acts in the developing animal as a regulator of internal synchrony between tissues.
Photic and Circadian Regulation of Retinal Melatonin in Mammals
Authors: Tosini G. , Fukuhara C. 
Published: May 2003

AbstractSeveral studies have established that melatonin synthesis occurs in the retina of vertebrates, including mammals. In mammals, a subpopulation of photoreceptors (probably the cones) synthesize melatonin. Melatonin synthesis in the retina is elevated at night and reduced during the day in a fashion similar to events in the pineal gland. Both the MT1 and MT2 melatonin receptors are present in the retina and retinal melatonin does not contribute to circulating levels, suggesting that retinal melatonin acts locally as a neurohormone and/or neuromodulator. Melatonin synthesis in the retina of mammals is under the control of a circadian oscillator, and circadian rhythms in melatonin synthesis and/or release have been described for several species of mammals. These rhythms are present in vivo, persist in vitro, are entrained by light and are temperature compensated. The cloning of the gene responsible for the synthesis of the enzyme arylalkylamine N‐acetyltransferase (the key enzyme in the melatonin biosynthetic pathway) has allowed studies of the molecular mechanisms responsible for the generation of retinal melatonin rhythmicity. The present review focuses on the cellular and molecular mechanisms that regulate melatonin synthesis. In particular, we discuss how the photic environment and the circadian clock interact in determining melatonin levels, in addition to the role that melatonin plays in retinal physiology.