Vertical Opening Research Articles

Modular approach to fabrication of three-dimensional microchannel systems in PDMS-application to sheath flow microchips.

A modular approach to fabrication of three-dimensional microchannel systems in polydimethylsiloxane (PDMS) is presented. It is based on building blocks with microstructuring on up to three faces. The assembled 3D-microchip consists of three building blocks in two layers. For assembly of the bottom layer two building blocks are joined horizontally, whereby the side structuring of the first is sealed against the flat side surface of the other. This results in the formation of a vertical interconnection opening between the building blocks to supplement the microstructuring on the lower faces. The 3D microchannel system is completed by placing a third building block, with microstructuring only on its lower face, on top of the assembled layer. While plasma assisted bonding is used between the two building blocks of the bottom layer, inherent adhesion is sufficient between the layers and for attaching the assembled 3D-microchip to a substrate. This modular approach was applied to the fabrication of a 3D-sheath flow microchip. It comprises a 20 microm deep microchannel system with sample inlet, open sensing area and outlet in the bottom layer and sheath flow inlet in the top layer. 100 microM fluorescein at 6 microL min(-1) was used as sample flow and water at increasing flow rates as sheath flow. With ratios of sheath to sample flow up to 20:1 sample layers down to 1 microm thickness could be generated. Sample layer thickness was determined via volume detection on an epi-fluorescence microscope followed by image analysis.

Long-term evaluation of arthrocentesis for the treatment of internal derangements of the temporomandibular joint

Purpose: Arthrocentesis is being used for treatment of patients with temporomandibular joint disorders, including anterior disc displacement with and without reduction. This study was designed to examine the long-term effects of temporomandibular joint arthrocentesis in such patients and to evaluate their overall satisfaction with this treatment. Patients and Methods: The study was based on the review of patients' records, a written questionnaire (self-evaluation), and clinical examination. Visual analog scales (VAS) were used for evaluation of pain and dysfunction. Twenty-six patients (39 joints) who had been treated at the Medical College of Virginia Hospital, Virginia Commonwealth University, were included in the study. There were 32 joints with anterior disc displacement without reduction (ADsR) and 7 joints with anterior displacement with reduction (ADcR). Patients all had undergone arthrocentesis as outpatients. Follow-up evaluations ranged from 10 to 96 months, with a mean of 48.7 months. Results: Maximum vertical opening (MVO) prearthrocentesis ranged from 20 to 40 mm, with a mean of 25.3 ± 5.5 mm. Immediately after arthrocentesis, the MVO ranged from 30 to 55 mm, with a mean of 43.8 ± 5.6 mm. Maximum vertical opening at long-term follow-up ranged from 15 to 50 mm, with a mean of 37.1 ± 8.8 mm. There was a significant increase in MVO between prearthrocentesis and postarthrocentesis both short- and long-term (P <.001). The short- and long-term postoperative VAS values for pain and dysfunction showed a significant decrease (P <.001) when compared with the VAS values preoperatively. Fourteen of the 26 patients (54%) no longer experienced pain, and the remaining 9 had less pain than before arthrocentesis as assessed by self-evaluation and clinical examination. Three of 26 patients had improvement for a period, later relapsed, and required subsequent surgery. Twenty-three of the 26 patients (88%) were completely satisfied with their treatment. Overall, an 88% success rate was achieved. Conclusion: Arthrocentesis can reduce pain and dysfunction, both short- and long-term, in patients with anterior disc displacement. © 2000 American Association of Oral and Maxillofacial Surgeons

Long-term evaluation following temporomandibular joint arthroscopy with lysis and lavage

Although temporomandibular joint arthrocentesis has been utilized for almost 20 years, most papers which evaluate the success of this procedure present relatively short-term data (less than two years). The purpose of this paper is to present the longer-term condition of 22 patients who were re-examined 2 to 10.8 years after arthroscopic surgery with lysis and lavage. Assessment of symptoms reported by the patient as well as of objective signs noted on clinical examination confirms resolution of pain on movement and increased vertical opening. These findings suggest that arthroscopic surgery of the temporomandibular joint is successful in the long term for patients with painful motion.

Long-term evaluation following temporomandibular joint arthroscopy with lysis and lavage

Although temporomandibular joint arthrocentesis has been utilized for almost 20 years, most papers which evaluate the success of this procedure present relatively short-term data (less than two years). The purpose of this paper is to present the longer-term condition of 22 patients who were re-examined 2 to 10.8 years after arthroscopic surgery with lysis and lavage. Assessment of symptoms reported by the patient as well as of objective signs noted on clinical examination confirms resolution of pain on movement and increased vertical opening. These findings suggest that arthroscopic surgery of the temporomandibular joint is successful in the long term for patients with painful motion.

Het effect van de stand van het hoofd op de verticale mandibulaire opening

Effect of head position on vertical mandibular opening [Journal of Orthopaedic and Sports Physical Therapy 1999;29:127-30]

Relationship between premature loss of primary teeth and the development of temporomandibular disorders in children.

This study evaluated the prevalence of signs of temporomandibular disorders (TMD) in children with and without premature loss of primary teeth. Fifty-eight children, aged 4-6 years, with missing primary molars, were compared with 58 age- and sex-matched control children with complete primary dentitions. All the children underwent an examination that consisted of palpation and assessment of the joints and associated muscles for tenderness and joint sounds. Maximum vertical opening and deviation during jaw opening were also recorded. Children with any single anomalous finding were designated positive for TMD signs. There were no statistically significant differences in the prevalence of single or collective TMD signs between the two groups. The results of this study show that premature loss of primary teeth, uncomplicated by other factors, does not appear to be an aetiological factor for TMD development.

Vector wind field determination by bistatic multiple-doppler radar

At Oberpfaffenhofen a bistatic Doppler radar network to determine wind vector fields was installed consisting of the transmitting C-band radar POLDIRAD and 3 bistatic receivers. The separation of transmitter and receiver results in a dependency of most radar properties (e.g. resolution volume, Nyquist velocity) on the scattering angle between transmitter, scatterer and bistatic receiver. Therefore, location of the receiving antennas play a major role in the distribution of variances of the horizontal wind field and will be discussed herein. The standard deviation of the horizontal wind field considering only geometrical issues within the inner part of the bistatic network is about 1–2 m/s.Other sources that influences the accuracy of the wind field are discussed as well.Furthermore, a procedure transforming the measured wind fields into quality-proved real-time wind vector fields is presented on measured wind fields.An outlook of the technical concept of the bistatic multiple-Doppler network is given, e.g. the use of antennas with different horizontal and vertical opening angles depending on the investigation topic.

Efficiency of the bottom trawl used for the Mediterranean international trawl survey (MEDITS)

The aim of the work presented in this paper was to assess the relative efficiency of the GOC 73 sampling trawl used for the Mediterranean international trawl survey programme (MEDITS) compared with that of a typical Italian commercial trawl. The latter was chosen because it is commonly used by fishermen in the central Adriatic, where the experiment was conducted, and therefore appeared as the best possible sampler of the commercial species present in those areas. Moreover, this trawl is similar to the various trawls used for the Italian national survey programme (GRUND). Four fishing trips were conducted between 1996 and 1997 in different areas and seasons to sample different species. Each trip was conducted in the same fishing area. A codend cover mounted on the commercial trawl ensured that the codends of the two nets had the same mesh opening. The two trawls were alternated daily. Net geometry (horizontal and vertical net opening) was measured during all tows. Catch data were converted into abundance per swept area before comparing the trawls. Efficiency comparisons were performed on ten fish species, one crustacean and four molluscs belonging to the MEDITS list of main reference species. The MEDITS trawl was significantly less efficient in terms of both weight and numbers of individuals fished for hake ( Merluccius merluccius), common sole ( Solea vulgaris) and Norway lobster ( Nephrops norvegicus). A highly significant difference in favour of the commercial trawl was found in the weight, but not the numbers, of common pandora ( Pagellus erythrinus). Efficiency differences were negligible for red mullet ( Mullus barbatus), while the MEDITS trawl was significantly more efficient for the numbers of Atlantic horse mackerel ( Trachurus trachurus). For all the other main reference species differences were not significant. The commercial trawl was more efficient for large individuals of some species. The relative efficiency of the MEDITS trawl was especially low for small-size classes of N. norvegicus. The results confirm the lower efficiency of the MEDITS compared with the commercial Italian trawl for benthic species, and its greater efficiency for some others released from the bottom as well as for the pelagic ones. These data allow the results of the MEDITS surveys to be compared with those of the GRUND programme and with commercial-fleet catches in areas where the commercial trawls used are similar to the one studied here.

Trawl sampling of small pelagic fish off Angola: effects of avoidance, towing speed, tow duration, and time of day

Pelagic fish distributed near the surface oV Angola were sampled with a medium-sized pelagic trawl having a vertical opening of about 20 m. Numerous trawls targeting on dense sardinella schools (Sardinella maderensis and Sardinella aurita) failed to yield large catches. Schools that were at the trawl depth as the vessel passed over them were often observed far below the foot rope of the trawl, indicating vertical avoidance. The net sonde transducer often recorded schools in the net mouth for long periods: it was assumed that these fast-swimming fish were able to swim along with the trawl, and escaped when the towing speed was reduced during hauling. No correlations were found, however, between towing speed (2.7‐5.0 knots) and the total catch of sardinella. Increasing the two duration during the day to more than 2 h also failed to yield consistently higher catches. A negative correlation at night between tow duration (15‐60 min) and catch size arose simply because the trawl was towed for a longer time to obtain adequate samples in areas with scattered recordings. During the day, sardinella was caught both inshore and further oVshore, while horse mackerel (Trachurus trecae and Trachurus capensis) was caught further oVshore only. Both species were well represented in catches made at night. There were substantial day and night diVerences in the length distributions of sardinella, with small sardinella being caught only at night. ? 1999 International Council for the Exploration of the Sea

Effect of head position on vertical mandibular opening.

A within-subjects repeated measures design. To determine differences in the amount of vertical opening of the mandible among 3 different head positions. Results from several studies have suggested that the position of the head and neck may affect temporomandibular joint function. Presently no standardized position of the head and neck has been recommended for measuring vertical opening of the mandible. Twenty males and 20 females (32.9 +/- 8.3 years) participated in the study. We obtained 3 measurements of vertical mandibular opening using a millimeter ruler on each subject in the forward, neutral, and retracted head positions. A 1-way repeated measures analysis of variance followed by pairwise comparisons indicated that the vertical mandibular opening was significantly greater in the forward head position (44 +/- 5.3 mm) than in the neutral head position (41.5 +/- 4.8 mm) and in the retracted head position (36.2 +/- 4.5 mm). In addition, vertical mandibular opening was significantly greater in the neutral head position than in the retracted head position. Interclass correlation coefficients for the 3 head positions ranged from 0.90 to 0.97 for intrarater, interrater, and day-to-day reliability. Head position is an important factor in determining the amount of vertical mandibular opening in healthy adults.

The influence of mandibular movements on joint sounds in patients with temporomandibular disorders

Statement of problem. There are discrepancies among researchers concerning the reliability and use of temporomandibular joint sounds. Purpose. This study examined the reliability of mandibular movements and sounds and determined the correlation between movements and sounds. Material and methods. The mandibular movements of 35 subjects diagnosed with temporomandibular disorders were recorded with 2 CCD cameras, and sounds were recorded bilaterally with Panasonic electret condenser microphones in the ear canal. Subjects performed 3 movements, each repeated 5 times. Results. Reliability of maximum movements across the 5 trials was good to excellent, with Intraclass Correlation Coefficients (ICC) between 0.76 and 0.91 for all movements except protrusion. Temporomandibular sound event counts were reliable for most movements, including vertical opening, protrusion, and right and left laterotrusion (ICCs between 0.41 and 0.81). Most subjects produced sound events either in 100% or in none of the trials. Reliability for sound events was better during protrusion (ICCs between 0.56 and 0.81) than vertical opening (ICCs 0.41 to 0.64). Subjects with sound events during vertical opening (followed by closing) were significantly more likely to have sound events during protrusion (followed immediately by vertical opening and closing) ( P <.01). Conclusion. Temporomandibular sound events are generally reliable and warrant study regarding their use in classifying and diagnosing patients with temporomandibular disorders. Condylar translation, which occurs during both vertical opening and protrusion, appears to have a strong influence on the production of temporomandibular sound events. (J Prosthet Dent 1999;81:186-95.)

Pit crater formation on Kilauea volcano, Hawaii.

Most of the known pit craters in Hawaii occur along the East and Southwest Rift Zones of Kilauea volcano. The pit craters typically are either astride a single rift zone fracture or between a pair of rift zone fractures. These fractures are prominent in the pit crater walls. The pit craters are elliptical in plan view, with their major diameters ranging from 8 to 1140 m. They range in depth from 6 m to 186 m. They typically develop with initially steep, locally overhanging walls, but as the walls collapse, the craters fill with talus and become shaped like inverted elliptical cones. None of the craters apparently formed as eruptive vents, although some have been subsequently filled by lava. Devil's Throat is the best-exposed pit crater along the East Rift Zone. It is sited at a `waist' between two east-striking zones of ground cracks; the spacing between the crack zones decreases towards Devil's Throat. East-striking fractures are also prominent in the pit crater walls. Pit craters along the Southwest Rift Zone typically are elongate in plan view along the direction of the rift, have large caves at their bases along the long axes of the craters, and are smaller than those of the East Rift Zone. Some closely spaced pits there have coalesced to form a trough. Based on our observations and mechanical considerations, we infer that pit craters form by stoping over an underlying large-aperture rift zone fracture, and not by piston-like collapse over broad magma bodies or voids. Flow of magma along the underlying fracture may remove stoped blocks and prevent the fracture from being choked with debris. This mechanism is consistent with pit crater location, ground crack patterns, the preferred orientation of fractures in pit crater walls, and pit crater geometry (both in map view and cross-section). The mechanism also fits with observations of stoping into a gaping rift fracture that conducted lava from Kilauea caldera during the 1920s. Additionally, the ratio of pit crater width to depth of 0.5 to 2 is consistent with pit craters forming over a nearly vertical opening mode fracture.

Auditory, visual and audiovisual perception of segmental speech features by severely hearing-impaired children.

Auditory alone, visual alone and audiovisual recognition of consonant-vowel consonant syllables were measured in 32 severely hearing-impaired children with hearing loss (PTA) in a narrow range around 90 dB HL when using their hearing aids. Multidimensional scaling analysis (INDSCAL) and information transmission analysis (ITA), applied to the confusion matrices obtained from the responses in each presentation mode and for each phoneme category, revealed perceptual dimensions and percentages of transmitted feature information (PTI). These were studied in relation to PTA, the auditory alone score and in relation to the efficiency of the audiovisual interaction (enhancement) over the probalistic summation of the auditory alone and visual alone score. INDSCAL analysis shows that auditory alone recognition of vowels is based on the perceptual dimensions F2 and F1 and that of consonants on the dimensions 'frication' and 'voicing'. In the auditory mode the interpretation of the INDSCAL dimensions in the stimulus spaces is in reasonable agreement with the ITA results. PTI decreases gradually with decreasing auditory alone phoneme score. Audiovisual recognition of vowels is based on a combination of the auditory dimension 'open/closed' (F1), and the visual dimensions 'lip rounding' and 'vertical lip opening'. Audiovisual recognition of initial consonants is based on a combination of the visual dimension 'front/back' and the auditory dimension 'continuance'. Recognition of final consonants is based on a combination of the visual dimension 'front/back' and an uninterpretable dimension. The perceptual dimensions are independent of both the level of the auditory alone phoneme score and audiovisual enhancement. Audiovisual enhancement is mainly a property of an individual and independent of both auditory alone and visual alone scores. ITA analysis, based on a phonological classification of the features, supports the results of the INDSCAL analysis in the auditory alone mode. It is not useful in the description of the audiovisual interaction, probably due to the phonological basis of the feature classification.

Nd:YAG LLLT IN THE TREATMENT OF TEMPOROMANDIBULAR DISORDERS: A TREATMENT PROTOCOL AND PRELIMINARY REPORT

Temporomandibular disorders (TMD) are a series of diseases which affect the masticatory system including temporomandibular joint (TMJ). Low reactive-level laser therapy (LLLT) has beenr eported as having good effects in various joint related pains and conditions. In this study, a suitable LLLT treatment protocol was proposed and the preliminary outcome was demonstrated in a short-term period of follow-up. Thirty (2 men and 28 women) patients with TMD who did not respond to initial conservative therapy were enrolled. The patients were divided into three groups according to their clinical signs, symptoms, and imaging modalities: disk derangement with clicking (DDC), disk derangement with locking (DDL), and osteoarthritis (OA). Low level laser therapy (LLLT) was administrated using a pulsed Nd:YAG laser at an output of 2.8 Watts and 20 pps. The treatment was started by bilaterally irradiating the C1/C2 zone, followed by irradiation of the TMJ area on the affected side. Subsequent treatment was given at intervals of 1 or 2 weeks for a total of two to five sessions. Although LLLT with the pulsed Nd:YAG laser significantly decreased pain in general, some patients, especially those in the DDL group, experienced little decrease in pain. Mean vertical maximal mouth opening increased from 36.8 to 40 mm. However, LLLT did not substantially improve maximal mouth opening in patients with severe impairment of mouth opening (i.e. closed lock). In total, LLLT was effective in 21 of 30 (70 %) of the subjects. The results suggest that LLLT at the wavelength and parameters used in the present study is somewhat effective for reducing pain in the TMJ area, but produces little improvement in mouth opening in patients with closed lock. The degree of efficacy, however, warrants the investigation of other wavelengths and parameters for LLLT for TMD.

Trawling blue whiting for surimi: A study of catch variations in low season

The paper consists of a comparative analysis of blue whiting ( Micromesishius poutassou) catch rates for surimi production in the low summer season in the Faroe Islands and Norwegian Economic Zones. The data come from commercial Russian trawlers for the period 1991–1995 and from fishery research carried out by the Japanese vessel M/Tr. Shinkai Maru during 1994–1995. Vessel size, engine power, net size, stock density, searching capacity and timing are the main factors explaining variations in catch rate. The catch potential was between 50 and 70 tons per day and was highest for vessels over 7001 gross tons (GRT) and with greater than 7000 hp. The largest catches are taken with Norwegian types of blue whiting trawl nets with a vertical opening of around 100 m. The paper explains the variation and limitations of these factors influencing catch rate and the implications for management.

Near-field modifications of stress induced by dyke injection at shallow depth

SUMMARY The deformation and stress fields accompanying dyke injection in rift zones are described in terms of a vertical crack opening in response to internal overpressure, in plane-strain configuration. Previous numerical computations of the displacement field induced by shallow dykes are found to be affected, in some cases, by significant distortion, mainly due to the limited extension of the computational domain, difficulties in handling the singularities in the proximity of the free surface and an incorrect choice of the reference frame; in particular, it is found that no subsidence can be ascribed to the mere opening of a tensile crack in a homogeneous, elastic half-space. If analytical constant-dislocation models are employed, surface displacements compare reasonably well with crack-model solutions if the upper tip is not too shallow; however, constant dislocation solutions present unphysical singularities along the tips, which distort significantly the near-field stress pattern with respect to crack solutions. If the principal stress axes are computed from crack models, a broad region is found on both sides of the dyke where the induced stress has a nearly vertical intermediate axis while the compressive axis is normal to the dyke plane. Strike-slip earthquakes are expected to prevail in this region. Above the upper crack tip, a small region is present where the tensile stress is dominant and the intermediate stress is still vertical. In the proximity of the free surface, typically within a few tens of metres of it, induced tensile stresses are greater than the lithostatic pressure: open fissures might then develop in cohesionless soil or pre-faulted rock. The induced pressure in the host rock is found to be negative (suction) in the proximity of the ground surface and positive at greater depth: fluid flow within the aquifers can be significantly altered by this induced overpressure and by the anisotropic modification of the pre-existing permeability. According to the modified Coulomb failure criterion, in the short term the shallower region, characterized by suction, is strengthened, while the deeper, pressurized region is weakened. These results can explain in a straightforward way the abundance of strike-slip focal mechanisms in volcanic areas, the switch between tensional and compressional axes inferred from focal mechanisms of earthquakes in connection with a dyke injection episode on Mount Etna, en echelon fracture systems observed at Piton de la Fournaise above the feeding dyke and precursory geochemical anomalies.

Comparison of two dental devices for treatment of obstructive sleep apnea syndrome (OSAS)

Previous case reports have indicated dental devices can be an effective nonsurgical treatment for snoring and obstructive sleep apnea. This pilot study evaluated the effectiveness of two intraoral devices in reducing the Respiratory Disturbance Index (RDI) and Epworth Sleepiness Scale (ESS) scores in a group of 24 adult volunteers with a history of loud snoring. Subjects were randomly assigned to two groups. Twelve subjects were fitted with a dental device designed to increase vertical dimension and protrude the mandible (device A). The other 12 subjects received a different device designed to minimally increase vertical opening without protruding the mandible (device B). Unattended home sleep monitoring (Edentrace II Digital Recorder, Edentech Corp.) was used to compute RDI at two time periods: (T0) before using any dental device and (T1) while using a dental device 2 weeks after the initial delivery date. The mean RDI and ESS scores at T0 for subjects in the device A group were 35.6 ± 28.4 and 12.0 ± 3.9, respectively. Means for the same measures at T1 were 21.1 ± 21.4 and 8.2 ± 4.0. For subjects in the device B group, means for RDI and ESS scores at T0 were 36.5 ± 43.7 and 13.0 ± 4.5, the means at T1 were 46.8 ± 47.0 and 12.5 ± 5.7. The effectiveness of the two devices was estimated by comparing the difference in RDI scores from T0 to T1 for the 10 subjects who were using device A and completed the study and the 8 subjects who were using device B and completed the study. Six subjects withdrew for various reasons. From T0 to T1, device A reduced RDI scores in 9 of 10 subjects, with a mean reduction in RDI of 14.5 ( p ≤ 0.05) and in ESS score of 3.8 ( p ≤ 0.005). Device B showed no change or an increased RDI score in 8 of 8 subjects. Seven of the eight subjects who showed no improvement in RDI with device B were then fitted with device A. Four of these seven subjects showed a reduction in RDI and five showed a reduction in ESS after using device A for 2 weeks. The mean reduction in RDI and ESS was 2.4 ± 19.8 and 2.4 ± 3.0, respectively. Hence, we conclude that a dental device that advances the mandible and increases the vertical dimension to open the upper airway is more effective in reducing the number of apneic and snoring events during sleep than one which does not.

Reliability of measuring active mandibular excursion using a new tool: the Mandibular Excursiometer.

Measurement tools improve the reliability and validity of measurement. The purpose of this study was to test the intrarater and interrater reliability of a new instrument, the Mandibular Excursiometer, for measuring mandibular excursion on the X and Y axis in the coronal plane during active opening. Two raters measured 12 volunteers. Four ratio, three nominal, and one ordinal scale measurements were analyzed using percent agreement. The Mandibular Excursiometer had high intrarater reliability for vertical opening (100%) and for the categorization of the presence or absence and direction of lateral deviation at the maximum point during opening (92-100%). Overall, moderate intrarater reliability existed for the quantity of lateral deviation at the maximum point during opening (66-83%), presence and direction of deflection (66-83%), presence of deviation or deflection during opening (66-83%), and in which third of opening the maximum point of lateral deviation occurred (66-83%). Moderate interrater reliability existed for vertical opening (75%) and for the classification of presence and direction of lateral deviation at the maximum point during opening (91%). All other measurements had low reliability. The Mandibular Excursiometer had higher intrarater and interrater reliability for measuring deviation and deflection during active mandibular opening than observation alone, based on a comparison with the literature. This measurement can assist in documenting progress while treating patients with TMJ disorders.

Age of the micronektonic squid Pterygioteuthis gemmata (Cephalopoda: Pyroteuthidae) from the central-east Atlantic based on statolith growth increments

Pterygioteuthis gemmata Chun, 1910 occurs worldwide in tropical oceanic waters except in the western Atlantic, Caribbean and Mediterranean Seas.This species is one of the smallest oceanic squids, with mature males and females attaining 25 and 32 mm mantle length (ML), respectively. Paralarvae, juveniles and adults of P. gemmata are most common in epipelagic and mesopelagic waters of the tropical Atlantic. Their abundance is approximately similar to that of the predominant epiand mesopelagic tropical squids, the micronektonic Abraliopsis atlantica (Enoploteuthidae), Onychoteuthis banksi (Onychoteuthidae) and planktonic cranchiids. The biology of P. gemmata is poorly-known. The hectocotylus of males lacks a chitinous hook which is found in the closely-related species Pterygioteuthis giardi; additionally in females only the right oviduct is functional.'Because of frequent occurrence of both mature females and small paralarvae (1.3-1.5 mm ML), spawning of P. gemmata has been considered to take place in upper epipelagic layers of the Gulf of Guinea. Juveniles (> 100 mm ML) and adults make diel vertical migrations, ascending to the epipelagic water layers at night and descending into mesopelagic layers during the daytime. Age and growth rates in micronektonic oceanic squids have been studied by statolith ageing techniques in the enoploteuthids Abraliopsis atlantica, Abraliopsis pfefferi and Enoploteuthis leptura from the tropical Atlantic-and Abralia tngonura from the North Pacific. The daily nature of growth increments within A. trigonura statoliths has been validated by statolith analysis in newly hatched paralarvae kept in aquaria. It has been found that all these enoploteuthids are rather slow-growing animals with life span of around 6 months.-The aim of this study was to estimate growth rates and maximum age of mature P. gemmata by statolith growth increment studies. Ninety-five Pterygioteuthis gemmata of 10-32 mm ML were caught during the biological surveys of the orange-back squid Sthenoteuthis pteropus (Ommastrephidae) in the central-eastern Atlantic carried out by Russian research vessels 'Prognoz' and 'Ocher' in June-September 1985 and in September 1988. Samples were taken in open waters of the western part of the Gulf of Guinea (latitudes 215'N-3°3O'S and longitudes 4°05'-15°W) off the Exclusive Economic Zones of African countries. Squid were caught at night (20-04 h) at depths of 25-300 m using the Russian zoological pelagic trawl RT/TM 33 type (vertical opening 8-10 m) equipped with a 6 mm mesh liner. Squid were identified using the key elaborated by Nesis. The dorsal mantle length was measured to the nearest 1 mm. Maturity stages were assigned from the scale developed for omnastrephid squids. Statoliths were removed from 12 maturing and mature females and 4 mature males with mantle lengths close to maximum known values for this species. Statoliths were then stored in 96% ethanol for further analysis in the laboratory using statolithageing techniques. Total statolith length (TSL) was measured after Clarke. From each pair, one statolith was ground, first the anterior side, then posterior side on a wet waterproof sandpaper (1500 grit) and embedded in Canada balsam. Growth increments were counted from the nucleus to the edge of the lateral dome by two observers using the eye-piece micrometer of a 'Biolam-R14' light microscope (magnification x400). Statolith growth increments were well-resolved and similar in appearance and microstructure to daily gTowth increments of the enoploteuthid A. trigonura. Assuming them to be daily, the total number of growth increments in the ground statolith of P. gemmata was considered to be the age of the squid in days. Total number of growth increments for each specimen was obtained as an average of count numbers, if deviation between the average and counts was less than 5%.

A Vertical Multiple Opening and Closing Plankton Sampler

A Vertical Multiple Opening and Closing Plankton Sampler