External Margin Research Articles

Amblyomma triste (Koch, 1844) (Acari: Ixodidae): Ovaries: An ultrastructural analysis

This study presents an ultrastructural analysis of the ovary of the tick, Amblyomma triste. The ovary of this species is of the panoistic type that is, without nursing and follicular cells. It is composed of a layer of epithelial cells forming a wall and of germinative cells that generate the oocytes which remain attached to the external margin of this wall by a multicellular pedicel. The different developmental stages in the oocytes had been described by Oliveira et al. [Oliveira, P.R., Bechara, G.H., Camargo-Mathias, M.I., 2006. Amblyomma triste (Koch, 1844) (Acari: Ixodidae): Morphological description of the ovary and of vitellogenesis. Experimental Parasitology 113, 179–185]. The results of the investigation suggest that besides exogenous production of vitellogenic elements, endogenous production can take place simultaneously, contributing to the development and growth of the oocytes.

A New Species of Burrowing Crayfish Virilastacus Retamali (Decapoda: Parastacidae) from the Southern Chile Peatland

Abstract Virilastacus retamali, a new species of burrowing parastacid, is described from the peatland in Rucapihuel located along the Coastal Cordillera from the province of Osorno, southern Chile. This is the third species of the genus Virilastacus described to date. It differs from V. araucanius and V. rucapihuelensis in the following morphological characters: 1) large eyes; 2) short rostral carina; 3) long antennal scale with prominent spine at the distal end of its external margin; 4) basal podomere of the antennula with a prominent ventral spine; 5) posterior plate of the epistome bears a cluster of prominent anterolateral tubercles; 6) ventral surface of the ischiopodite of the third maxilliped with a band of prominent tubercles and abundant pilosity; 7) U-shaped cervical groove; and 8) subtriangular telson. Finally, the habitat also differs from that of congeneric species, with V. retamali inhabiting a geogenous peatland whereas the other two species inhabit semi-marshland. We also present a comple...

Laccolithic, as opposed to cauldron subsidence, emplacement of the Eastern Mourne pluton, N. Ireland: evidence from anisotropy of magnetic susceptibility

The structural evolution and emplacement of the Eastern Mourne pluton was investigated using anisotropy of magnetic susceptibility (AMS) measurements (carried out on 112 oriented block samples) and structural data from the host rocks. From these new data cauldron subsidence, as the emplacement mechanism, is disputed and evidence for an alternative, laccolithic style model involving inflation is presented. This includes deflection and uplift of host-rock bedding close to contacts and the magnetic fabric pattern, which has a gentle dome geometry, even close to contacts. The magnetic lineations usually plunge down-dip near the external margins but otherwise have a general SSW–NNE trend that diverges northward. This suggests a northward-directed inflow direction. The model for the emplacement of the Eastern Mourne pluton is a laterally fed laccolith, emplaced south to north. The eastern margin is interpreted as a faulted contact facilitating the inflation of an asymmetrical ‘breached’ laccolith.

A Pennsylvanian microbial boundstone-dominated carbonate shelf in a distal foreland margin (Picos de Europa Province, NW Spain)

A Pennsylvanian (Bashkirian–Moscovian) high-rising, microbial boundstone-dominated carbonate platform (> 12,000 km 2) developed in the external margin of a Variscan foreland basin. Intensely studied in the northern domain (Cuera area), the stratigraphy and sedimentology of the southern domain (the Picos de Europa Province) is here revisited. Distribution of the Bashkirian facies (Valdeteja Formation) defines a ramp/low-angle platform with an internal zone (central and eastern sectors of the Picos de Europa Province) consisting of huge amounts of massive, cement-rich microbial boundstones, surrounded by an external zone comprising lower-slope boundstone-derived breccias and basinal lime mudstones. From the Bashkirian–Moscovian transition to the early Kasimovian (Picos de Europa Formation), the carbonate platform moderately aggraded acquiring a high-rising and flat-topped geometry and then prograded rapidly into the external zone, where platform-derived carbonate sediment and clay, sourced from the orogen, were deposited. Seismic-scale exposures of the western margin of the shelf show angular-bedding relationship between basin/toe-of-slope, slope and platform-top stratal domains; with slope inclination up to 32° and a topographic relief of 550 m. The platform evolution above described for the Picos de Europa Province significantly differs with respect to the Cuera area, where platform mostly prograded during the Bashkirian and subsequently aggraded during early Moscovian. The evolutionary differences between these two carbonate domains, which are geographically close, are interpreted as changes in tectonic subsidence distribution, acting as the major factor controlling the large-scale platform geometries in the active foreland basin context. Finally, the tectonic overload due to the emplacement of the Cuera thrust sheets during the Moscovian–Kasimovian transition changed the platform growth style from progradational to aggradational and consequently the stacking pattern of the platform-top cycles in the Picos de Europa Province.

Laparoscopic Repair of Incarcerated Low Spigelian Hernia With Transperitoneal PTFE DualMesh

There are different types of hernias that can develop at certain sites in the abdominal wall. Spigelian hernia (SH) is a protrusion of abdominal contents through a defect in the spigelian aponeurosis, in proximity to the external margin of the rectus muscle. Usually, abdominal wall hernia sac contains the omentum but may also contain small intestine that might become trapped in the hernia. When ischemia of herniated contents is suspected, urgent surgical treatment is advocated. Elective laparoscopic repair of SH is still under discussion. However, a recent randomized study comparing open and laparoscopic repair as elective treatment suggested that extraperitoneal laparoscopic repair is the technique that offers best results for the patients. Recent development of new biologic materials and technologies in laparoscopy has led to improved results. We report the successful repair of incarcerated low SH that was successfully managed by urgent laparoscopic intraperitoneal onlay polytetrafluoroethylene mesh hernioplasty.

Kinematic evolution of the Araçuaí-West Congo orogen in Brazil and Africa: Nutcracker tectonics during the Neoproterozoic assembly of Gondwana

The Neoproterozoic Araçuaí-West Congo (A-WC) orogen is one of many Brasiliano/Pan-African orogens that developed during the assembly of West Gondwana. This orogen was split apart in Mesozoic time, due to opening of the South Atlantic—the Araçuaí orogen now underlies eastern Brazil, whereas the West Congo belt fringes central Africa's Atlantic coast. Significantly, at the time it formed, the A-WC orogen was bounded on the west, north, and east by the São Francisco-Congo craton, a crustal block that had the shape of a lopsided, upside-down ‘U’. Thus, the orogen was “partially confined” during tectonism, in that it occupied an enclave surrounded on three sides by cratonic crust. Formation of the A-WC orogen resulted in kinematically complex deformation, substantial crustal shortening, and production of a large volume of magma. How such features could develop in this particular setting has long been a mystery. Our field studies in the Araçuaí orogen, together with published data on the West Congo belt, characterize the kinematic picture of the A-WC orogen, and lead to a tectonic model that addresses its evolution. In our model, the A-WC orogen formed in response to closure of the Macaúbas basin. This basin was underlain by oceanic crust in the south, but tapered northward into a continental rift which terminated against the cratonic bridge linking the eastern and western arms of the São Francisco-Congo craton. Closure occurred when the western arm (now the São Francisco craton) rotated counterclockwise towards the eastern arm (now the Congo craton). This closure may have been driven by collision of the Paranapanema, Amazonian, and Kalahari cratons against the external margins of the São Francisco-Congo craton, rather than by slab-pull associated with subduction of the Macaúbas basin's floor. Thus, the process of forming the A-WC orogen resembled the process of crushing of a nut between two arms of a nutcracker. Such “nutcracker tectonics” led to a series of kinematically distinct deformation stages. Initially, internal portions of the orogen flowed northwards. Then, substantial crustal thickening occurred in the orogen's interior, and the deformation front migrated outwards, producing thrust belts that overlapped the internal margins of the craton. With continued closure, space in the enclave became restricted and the orogen's interior underwent lateral escape to the south. Late-stage extensional collapse triggered both production of late- to post-collisional granites and exhumation of high-grade rocks from mid-crustal levels.

Geologie der Iberger Klippen und ihrer Flysch-Unterlage

Geologie der Iberger Klippen und ihrer Flysch-Unterlage

Amblyomma triste (Koch, 1844) (Acari: Ixodidae): Morphological description of the ovary and of vitellogenesis

The present study presents the morphology, histology, and the dynamics of vitellogenesis in females of the tick Amblyomma triste. The ovary in this species is of the panoistic type, therefore it lacks nurse cells. It is composed of a layer of epithelial cells that outwardly form the wall of the ovary, but also originate the pedicel, the structure that attaches the oocytes to its external margin, as well the oocytes themselves. In Amblyomma triste, the oocytes develop in four synchronic stages, which differs from the process in other tick species. The classification of the stages of the oocytes was carried out based on the presence of four morphologic characteristics: cytoplasm appearance; site of the germ vesicle; presence, quantity, and constitution of the yolk granules and presence of chorium.

Gorgoderina festoni n. sp. (Digenea: Gorgoderidae) in Anurans (Amphibia) from Mexico

Gorgoderina festoni n. sp. is described from the urinary bladder of Gastrophryne usta, Leptodactylus labialis, L. melanonotus and Bufo marinus from localities at low altitude in the states of Veracruz, Oaxaca, Guerrero and Colima, Mexico. This species differs from most other species of the genus by a combination of the following characters: lobed vitelline masses, body size 3.45-4.26 (mean 3.75) mm and sucker-ratio 1:1.3-1.52 (mean 1:1.44). The new species shares these three features with G. bilobata Rankin, 1937, G. schistorchis Steelman, 1938, G. tenua Rankin, 1937, G. vitelliloba (Olsson, 1876) and G. cryptorchis Travassos, 1924, but it differs from the first four in having gonads with entire margins. G. festoni most closely resembles G. cryptorchis, but differs from this species in body width at the level of the ventral sucker and in the absence of oesophageal glands. The autapomorphy that distinguishes G. festoni from all other members of the genus is the presence of a tegumental extension (festoon) on the external margin of the ventral sucker.

Early diagenesis of carbonate biocrystals : isomineralogical changes in aragonite coral skeletons

Abstract Early diagenetic changes occurring in aragonite coral skeletons were characterized at the micro- and ultra-structural scales in living and fossil scleractinian colonies, the latter of Pleistocene age. The skeleton of scleractinian corals, like all biomineralized structures, is a composite material formed by the intimate association of inorganic aragonite crystallites and organic matrices. In addition to its organo-mineral duality, the scleractinian skeleton is formed by the three-dimensional arrangement of two clearly distinct basic structural features, the centers of calcification and the fibers. The latter are typically characterized by a transverse micron-scale zonation revealing their incremental growth process. The size, geometry and three-dimensional arrangement of calcification centers and fibers are taxon-specific. The earliest diagenetic modifications of these skeletons have been clearly recognized in the older parts of living colonies. The first steps of diagenesis therefore take place only a few years after the skeleton had been secreted by the living polyps, and in the same environmental conditions. Comparisons with the uppermost living parts of the coral colonies clearly show that these first diagenetic changes are driven by the biological ultrastructural characteristics of these skeletons and are conditioned by the presence of organic envelopes interbedded with and surrounding aragonite crystallites. These first diagenetic processes induce the development of thin fringes of fibrous aragonite cements growing syntaxially on the aragonitic coral fibers, an alteration of the incremental zonation of coral fibers and also preferential diagenetic changes in the calcification centers, including dissolution of their minute internal crystals. Diagenetic patterns observed in Pleistocene coral colonies typically involve the same processes already recognized in the older skeletal parts of living colonies, suggesting that diagenesis occurs through continuous processes instead of clearly differentiated stages. Selective dissolution affects calcification centers and some growth increments of coral fibers. Alteration of the initial transverse zonation of coral fibers also occur through the development of micro-inclusions clearly seen in ultra-thin sections. Although usually thicker than those observed in the ancient skeletal parts of living colonies, syntaxial aragonite cements commonly occur in these fossil skeletons. These cements are often associated with gradual textural modifications of the underlying coral fibers, in particular the loss of the transverse micron-scale zonation. This suggests that the coral skeleton forming the substratum of diagenetic cements is progressively recrystallized in secondary aragonite. This recrystallization of coral aragonite begins at the external margin of the skeleton, just below the diagenetic cements and gradually moves towards the internal skeletal parts. Recrystallization takes place through concomitant fine-scale dissolution-precipitation processes and occurs with textural changes but no mineralogical change. The process of recrystallization is likely initiated by a biological degradation of organic skeletal matrices and can be also driven by thermodynamical constraints involving the lowering of surface free energies resulting from changes in crystal size. Alteration of skeletal organic matrix, textural changes in coral biocrystals through recrystallization and precipitation of secondary diagenetic aragonite may bias the original geochemical characteristics of coral skeletons. Although more work is needed to establish the influence of these early diagenetic processes on the geochemical signatures, it is already well known that the breakdown of organic skeletal envelopes and early recrystallization of shallow-water carbonates alter the stable isotopic composition. The widespread use of coral skeletons as environmental and climatic proxies makes strongly necessary a better understanding of these early diagenetic mechanisms and a precise characterization of the fine-scale diagenetic patterns of specimens for the optimization of geochemical interpretations. In particular, it cannot be assumed that an entire aragonitic composition can guarantee that there is no or slight diagenetic alteration.

Variations du rythme du développement chez les trilobites Phacopidae néodévoniens

Developmental variations in neodevonian phacopide trilobites. Heterochrony refers to changes in the timing and the rate of development of ancestral morphological features. This phenomenon has been observed in some neodevonian phacopide trilobites. Their evolution is marked by progressive displacement of the visual complex towards the external margins, accompanied by displacement of the facial suture. This evolutionary pathway is a result of paedomorphosis. These features seem to be adaptative, and may occur in all lineages, leading to convergences between several taxa. A paedomorphic phenomenon also concerns the change of moulting behaviour. This particular feature may not be related to environment but represents a feature inherited from the ancestral forms. To cite this article: C. Crônier, P. Courville, C. R. Palevol 2 (2003).

Detrital blue amphiboles from the western Othrys Mountain and their relationship to the blueschist terrains of the Hellenides (Greece)

In contrast to blue amphiboles of the Ossa and Olympos tectonic windows in Thessaly, detrital blue amphiboles in Paleocene flysch deposits in the western Othrys Mountain (Pelagonian Zone s.l.) are chemically comparable with blue amphiboles from the Cyclades. For the detrital material, therefore, a source with "Cycladic" chemical affinities is assumed. The occurrence of these detrital minerals is in line with a Cretaceous onset of blueschist facies metamorphism in parts of the Hellenides, especially in the Cycladic belt. This was in response to Cretaceous subduction of the Pindos oceanic plate along the external margin of the Pelagonian micro-continent. Blueschist complexes were exhumed latest in the Paleocene when the terrigenous flysch sedimentation started in the Pelagonian and Pindos zones.

Bladder substitution in women.

Bladder substitution in women with transitional cell carcinoma (TCC) is not a universally accepted procedure. There are many concerns, one of which is the potential risk of metachronous and synchronous urethral transitional cell carcinoma involvement. Another concern is that voiding dysfunction may be more frequent than in male patients. The numbers of female patients who have had this procedure are still small, and follow-up data are relatively brief. Thus, the true role for orthotopic bladder substitution in the female is still being evaluated. This paper reviews the data on this type of surgery in women, with emphasis on urethral TCC risk and on voiding dysfunction. Early results from a number of institutions are encouraging, particularly in correctly selected patients. Based on more than 15 years experience in an albeit small number of patients, we believe that if there is a functional external sphincter and tumor margins can be safely cleared, this form of surgery offers patients the best opportunity to preserve quality of life following cystectomy.

Melorheostosis in a 12-year-old child

Melorheostosis (of Leriand Joanny) is a rare, non-genetic sclerotic dysplatic bone disorder presenting at any age, usually from late childhood to adulthood. Its aetiology is unknown. It affects mainly the long bones of the upper and lower limbs, but also the short bones of the hand and foot and, rarely, the axial skeleton. Onset is usually insidious, with pain, deformity of the extremity, limb stiffness and limitation of joint motion, as well as thickening and fibrosis of the overlying skin and muscle atrophy being the common clinical features found on presentation. In adults the characteristic radiographic appearance consists of irregular hyperostotic changes of the cortex, generally on one side of the bone, resembling melted wax dripping down one side of a candle, from which melorheostosis derives its name. This, however, is not a feature of the radiographic appearance in children, where the external cortical margin retains its regular outline. Children more often present with a discrepancy in limb size rather than with pain (as is seen in adults). We present our case of melorheostosis in a 12-year-old child to highlight the main clinical and radiological differences found between children and adults.

Morronia brevirostris, a new genus and species of Entimini (Coleoptera: Curculionidae: Entiminae) from Islas Malvinas

AbstractA new genus of entimine weevils, Morronia gen. n., is described as endemic to the Islas Malvinas (Falkland Islands). It is distinguished from the other genera of Entimini by the following combination of characters: frons without fovea; rostrum lacking carinae, as long as wide; and foretibia with external margin straight and a spatula-like projection. Diagnoses, descriptions and illustrations of the new genus and its only species, M. brevirostris sp. n., are given. We also present a check-list of the Curculionidae recorded from the Islas Malvinas. It contains 22 species in 13 genera and 3 subfamilies. Also included is a key to the species of the Entiminae that inhabit the archipelago.

Argulus chicomendesi sp. n. (Crustacea: Argulidae) parasita de peixes da Amazônia brasileira

Uma nova espécie de Branchiura é descrita para o Brasil. Os espécimens foram coletados parasitando peixes da Amazônia brasileira. A nova espécie é caracterizada pela: coloração e desenhos da superfície dorsal da carapaça, tórax e abdômen; presença de espinhos em toda a margem externa da superfície ventral do abdômen (pléon); ornamentações das antenas, antênulas, maxilas, pernas, superfície ventral do corpo; forma e pigmentação das estruturas copulatórias acessórias do macho.

Bladder substitution in women.

Although numbers are still small and follow-up is often limited, female orthotopic bladder reconstruction has been shown to provide excellent, near-normal voiding and storage function in selected patients, and its popularity has been growing over the last decade. The true role of this form of surgery, however, is not yet fully established. This paper discusses the indications for patient selection, operative technique and outcome of female bladder substitution. Outcome is equivalent to that seen in male patients, although in some series there is a higher rate of voiding dysfunction requiring intermittent self-catheterization. Although further data regarding urethral recurrence rates are awaited, it would seem that with careful patient selection and operative technique, cancer surgery may not be compromised. Functional results have been excellent and patient satisfaction is very high. Provided there is a functional external sphincter and tumor margins can be safely cleared, this form of surgery offers patients the best opportunity to preserve quality of life following cystectomy.

Active stress along the ne external margin of the Apennines: the Ferrara arc, northern Italy

We have analysed borehole breakout data from 12 deep wells in order to constrain the direction of the minimum and maximum horizontal stress in a part of the Po Plain, northern Italy, characterised by a ∼N–S prevailing compressional stress regime, and in order to shed light on the regional state of stress and on the correlation between the active stress field and the orientation of tectonic structures. The results have been compared with seismological data relating to 1988–1995 crustal seismicity (2.5< M d<4.8) and to the 1983 Parma ( M s=5.0) and the 1996 Reggio Emilia ( M s=5.1) events. Plio-Pleistocene mesostructural data are also described in order to better define the present-day stress field and to understand the active tectonic processes in particular stress provinces. The borehole breakout analysis, in accordance with the seismicity and mesostructural data, shows the presence of a predominant compression area, characterised by approximately N–S maximum horizontal stress, along the outer thrust of the Ferrara arc. Particularly, the breakout analysis indicates a minimum horizontal stress, N81W±22° relative to a total of eleven analysed wells, with 3746 m cumulative total length of breakout zones. Among these, nine wells are located in the same tectonic structure, consisting of an arc of asymmetric folds overthrust towards the NE. The breakout results for these wells are quite similar in terms of minimum horizontal stress direction (∼E–W oriented). The other two wells are located in the outside sector of the arc and one of them shows a different minimum horizontal stress direction, probably distinctive of another tectonic unit. On the basis of these new reliable stress indicators, the active compressive front in this area is located along the termination of the external northern Apenninic arc.

COMPRESSIVE NEOGENE‐QUATERNARY TECTONICS IN THE HINTERLAND AREA OF THE NORTHERN APENNINES

The NW‐SE trending Northern Apennine Mountains consist of a series of allochthonous units which were thrust generally to the NE during Neogene crustal shortening, in the direction of a foreland basin to the east andNE. On the hinterland (internal) side of this fold‐and‐thrust belt, a series of small‐scale sedimentary basins developed from the late Miocene and were deformed at the same time. The late Tortonian‐Pleistocene evolution of the Northern Apennines has previously been considered by most authors in terms of a classical model of a NE‐migrating compressional front, which was followed in time and space by a hinterland extensional regime related to the development of the Tyrrhenian Basin.This paper presents new structural data from both the external parts of the Northern Apennines and the late Tortonian‐Pleistocene basins located in the internal sector. In the Northern Apennine thrust belt, reactivation and out‐of‐sequence geometries for the thrust faults have been recorded. In the hinterland basins, compressional deformation has been documented and is usually associated with thrust ramps and regional unconformities. The timing of both thrust reactivation and of the major compressional phases affecting the hinterland basins is closely correlated with periods of magmatic quiescence, and with compressional phases detected in the external margin of the Northern Apennines (the Padan‐Adriatic foredeep).Data presented in this paper indicate that compressional deformation has played a major role in the recent evolution of the Northern Apennines. The mechanism envisaged to explain this tectonic framework takes account of the piggy‐back emplacement of basement thrusts from internal to external sectors, which occurred in post‐Serravallian time. Activity on basement thrusts may have caused reactivation of thrusts in the internal cover sequence, giving rise to out‐of‐sequence geometries and controlling the development and/or deformation of the hinterland basins. This type of structural evolution has resulted in a complex geometry for the thrust sheets, and this must be taken into consideration during re‐interpretation of the structure of the Northern Apennines. It may also have important implications for petroleum exploration.

Environmental enrichment alters organizational features of the forepaw representation in the primary somatosensory cortex of adult rats.

The cortical forepaw area of young adult rats was mapped by recording the response properties of small clusters of neurons in layer IV of the primary somatosensory (SI) cortex. First we quantitatively analyzed the somatotopic organizational features of the cortical forepaw representation in terms of areal extent and topography, receptive field (RF) sensory modality, size, and location. We also assessed the influence of environmental enrichment, known to induce structural alterations in cortical connectivity, on the representational characteristics of the forepaw maps. Long-Evans rats were housed in environments (standard, SE; enriched, EE) promoting differential tactile experience for 71-113 days from weaning. Within the SI, we found a single and complete topographic map of the cutaneous surfaces of the forepaw consisting of a rostrolateral-caudomedial sequence of digit and pad representational zones. Small islets of noncutaneous responses (NCR; high-threshold, deep-receptor input) within the boundaries of the cutaneous maps were a conspicuous feature of the forepaw map for SE rats. These islets created discontinuities in the representation of contiguous skin territories. In the SE rats, about 79% of the cortical sites activated by light tactile stimulation had a single cutaneous RF, whereas about 21% exhibited multiple RFs. Most single-digit RFs we delineated in the SE rats extended across two or three phalanges. As a result, the representations of the phalangeal skin surfaces were not segregated but formed an overlapping continuum. Moreover, within these regions, as the electrode was displaced in regular steps across the mediolateral axis, RFs did not shift across the digit skin surface in an orderly manner, suggesting a lack of internal topography in the finger representation zones. Tactile experience promoted by environmental enrichment induced alterations in the representational features of the SI cutaneous map of the forepaw. In EE rats, the areal extent of the forepaw cutaneous representation was 1.5 times larger than in SE rats. Indeed, the cutaneous map extended into NCR cortical sectors along its external margins and also into NCR islets found in the forepaw area. Consequently, in EE rats there were fewer representational discontinuities. The areal enlargement was due to a selective increase in the areal extent of the glabrous but not the hairy skin surface representations. Furthermore, protuberant glabrous skin (digit tips, palmar pads) was represented over larger cortical regions than were other glabrous skin territories less likely to be stimulated during object palpation and manipulation. Maps from EE rats were also characterized by a larger proportion of sites with single RFs (88% compared with 79%). In addition, glabrous RFs from EE rats were smaller and more clustered on the digit tips and palmar pads than were RFs in SE rat maps. RF size on hairy skin surfaces remained unchanged. Because the RFs were smaller, the cutaneous maps of EE rats contained distinct representations of digit phalangeal glabrous skin. RFs tended to exhibit more orderliness in their progression across the digit glabrous skin of EE rats than they did in SE rats. The phalanges of EE rats were represented in distinct patches. Neurons in EE rats were more sensitive to light tactile stimulation than were neurons in SE rats. These alterations were presumably mediated by the selective potentiation of cutaneous over deep-receptor activation. More generally, the present study corroborates the view that cortical cutaneous maps are maintained in a permanent state of use-dependent fluctuation.