Difference In Mean Depth Research Articles

Guided Bone Regeneration Effects on Bone Quantity and Outcomes of Dental Implants in Patients With Insufficient Bone Support: A Single-Center Observational Study.

Background Guided bone regeneration (GBR)is used to influence on stabilization of dental implants in patients with insufficient bone quantity and anatomical problems.But many studies using GBR resulted in divergent results according to the efficiency of new bone quantity formation and implant survival. This research aimed to study the effects of GBR on the increase of bone quantity and short-term stabilization of dental implants in patients with insufficient bone support. Methodology The study included 26 patientsthat underwent the procedure for 40 dental implants from September 2020 to September 2021. In each case, the vertical bone support was intraoperatively measured, through the MEDIDENT Italia paradontal millimetric probe (Medident Italia, Carpi, Italy). The vertical bone defect was considered when the mean vertical depth between the abutment junction and the marginal bone wasgreater than 1mm up to 8mm. In the group with the presence of the vertical bone defect, GBR technique was used duringthe procedure of dental implantsrealized with synthetic bone graft, resorbable membrane, and platelet-rich fibrin (PRF), and the group was considered the study (GBR) group. The group of patients with no vertical bone defects(less than 1mm) and no need for any GBR technique usewas considered the control (no-GBR) group. The bone support was evaluated again intraoperatively after six months in both groups when the healing abutmentswere positioned. The vertical bone defect for each group in baseline and after six months is presented as mean±SD and compared using a t-test. A t-test for Equality of Means was used to calculate the mean depth difference (MDD) between baseline and six months values in each group (GBR and no-GBR) and also between both groups. P-value ≤ 0.05 is considered statistically significant. Results Overall 40 dental implants were placed, 20 of them were included in the GBR group and 20 in the no-GBR group. In the GBR group, a statistically significant greater mean vertical bone defect in baseline (day 1), compared to the no-GBR group was found (-4.46±2.76 vs -0.27±0.22; MDD = -4.19 [-5.44 to -2.94] p<0.001). At six months of follow-up in the GBR group, a new bone around the implant was formed, presenting a significantly lower bone defect compared to the baseline measure (-0.39±0.43 vs -4.46±2.76; MDD = -4.07 mm [-5.37 to -2.78]p<0.001). In six months, no statistically significant difference between GBR and no-GBR group in bone support was found (-0.39±0.43 vs -0.27±0.22; MDD = -0.19 [-0.40 to -0.03] p=0.10). In each group, only one implant failure was observed. Conclusions The use of GBR showed an important reduction of vertical depth defect between healing abutment and marginal bone predisposing similarshort-term stability and survival of dental implants. The use of GBR techniques could be essential in the stabilization of dental implants in patients with insufficient bone support.

The Posterior Belly of Digastric Muscle as the Landmark in Facial Nerve Anastomosis Surgery: Anatomical Study and Case Illustration

To establish a new method for fast exposure of the facial nerve and hypoglossal nerve during facial nerve anastomosis surgery. Dissection of 12 formalin-fixed cadaveric specimens was performed to explore the positional relationship between the posterior belly of digastric muscle (PBD) and the facial nerve and hypoglossal nerve. We retrospectively reviewed patients who underwent facial nerve reconstruction surgery between 2015 and 2020 at Xuanwu Hospital, Capital Medical University, and the optimized surgical strategy based on the PBD was proposed. The trunk of the hypoglossal nerve runs across the external carotid artery after giving off the descendens hypoglossi located within the 1-cm scope deep to the junction of the tendon and belly of the PBD. The mean depth difference between the hypoglossal nerve and the junction of the tendon and belly of the PBD was 5.48 ± 2.24 mm (range, 1.88-9.27 mm). The stylomastoid foramen segment of the facial nerve was revealed after the parotid gland was dissected within the angle between the anterior margin of the mastoid tip and the inferior margin of the cartilage of the external acoustic meatus. The facial nerve and hypoglossal nerve can be rapidly identified using the PBD as an anatomical landmark. The end-to-end facial-descendens hypoglossi anastomosis is a reliable facial nerve reconstruction method for patients whose facial nerve was damaged during operation.

ANALYSIS OF THE CONCHAL BOWL DEPTH IN PROMINENT EARS PRE AND POST OTOPLASTY

The prominent ear is the most common congenital ear disorder. Some of its discovered features include the overdeveloped concha and the underdeveloped antihelix. The present study focuses on the analysis of the conchal bowl, while assessing its depth before and after otoplasty. Despite its anatomical and surgical importance for the correction of protruding ears, that ear structure has been little discussed in the literature. With the aim of contributing, by providing fresh information, an attempt was made to recognize a surgical parameter of the concha, while assisting in the perception of the depth change after its partial resection, as well as to compare that change to the thickness of the studied cartilage, and to show the statistical data of that structure in the prominent ear. While reviewing the data from the study, it was noted that the mean conchal bowl depth of patients with prominent ears pre-otoplasty surgery was approximately 17 millimeters (mm). In the late postoperative period, a value of approximately 12 mm was reached. That means a mean depth difference of 5 mm in the surgical evolution, with no statistically significant difference between sexes, ear cartilage grading, and operated ear side. Most of the ears (96.9%) showed an increase in the conchal depth postoperatively, which is the main goal of every surgeon when performing conchal resection.

Population diversification in the frog Mantidactylus bellyi on an isolated massif in northern Madagascar based on genetic, morphological, bioacoustic and ecological evidence.

In the processes that give rise to new species, changes first occur at the population level. But with the continuous nature of the divergence process, change in biological properties delimiting the shift from “individuals of divergent populations” towards “individuals of distinct species”, as well as abiotic factors driving the change, remain largely ambivalent. Here we study diversification processes at the population level in a semi-aquatic frog, Mantidactylus (Brygoomantis) bellyi, across the diverse vegetation types of Montagne d’Ambre National Park (MANP), Madagascar. Genetic diversity was assessed with seven newly developed microsatellite markers as well as mitochondrial DNA sequences and concordance with patterns of ecological, morphological, and bioacoustic divergence evaluated. We found M. bellyi lacking mitochondrial differentiation within MANP, while microsatellite datasets partitioned them into three highly differentiated, geographically separated subpopulations (with indications for up to five subpopulations). The molecular grouping–primarily clustering individuals by geographic proximity–was coincident with differences in mean depth and width of waters, suggesting a possible role of fluvial characteristics in genetic exchange in this stream-breeding species. Genetic clustering not consistent with differences in call properties, except for dominant call frequencies under the two-subpopulations model. Morphological divergence was mostly consistent with the genetic clustering; subpopulations strongly differed by their snout-vent length, with individuals from high-elevation subpopulations smaller than those from populations below 1000 m above sea level. These results exemplify how mountains and environmental conditions might primarily shape genetic and morphological divergence in frog populations, without strongly affecting their calls.

Effect of Nano-hydroxyapatite Crystal Incorporated Herbal Dentifrice on Remineralization of Incipient Caries Lesion- A Pilot Study

Fluoridated dentifrices are considered as an effective method for preventing dental caries. Nano-hydroxyapatite crystals which have remineralizing potential can be combined with herbs with antimicrobial activity and used as a dentifrice without any risks like cytotoxicity and adverse effects. Nano-hydroxyapatite crystals are formulated by wet chemical precipitation method and tested using X-ray diffractometer. An herbal dentifrice is formulated from extract of Salvadora persica to which Nano-hydroxyapatite crystals are added. A 3x3mm wide window has been created in 14 extracted first premolars which are then processed through a pH cycling for 7 days. The depth of the lesion is assessed using a confocal microscope. The difference in mean depth of the lesion between test dentifrice (Herbal dentifrice with Hydroxyapatite) (240.33.± 23.47) and fluoride dentifrice (272.75±29.38) was found to be statistically significant. Herbal dentifrice with Hydroxyapatite group mean depth of the lesion was 763.13+66.18 before and 240.33+23.48 after the remineralization cycle. In the Fluoride dentifrice group the mean depth of the lesion is 763.14±66.18 before and 272.55+29.38 after the pH cycle. Herbal dentifrice incorporated with hydroxyapatite had higher remineralizing potential compared to a fluoride dentifrice.

Assessment of Burrowing Behavior of Freshwater Juvenile Mussels in Sediment

Standard laboratory sediment toxicity methods have been adapted for conducting toxicity tests with juvenile freshwater mussels. However, studies looking at juvenile mussel burrowing behavior at the water-sediment interface are limited. Juvenile mussels burrow in sediment for the first 0 to 4 yr of life but also may inhabit the sediment-water interface. The objective of this study was to evaluate burrowing behavior of various species and ages of juvenile freshwater mussels in three control sediments: West Bearskin Lake, Spring River, and coarse commercial sand. Species tested included (1) Fatmucket (Lampsilis siliquoidea), (2) Notched Rainbow (Villosa constricta), (3) Washboard (Megalonaias nervosa), (4) Rainbow (Villosa iris), (5) Arkansas Fatmucket (Lampsilis powellii), and (6) Oregon Floater (Anodonta oregonensis). Greater than 95% of the mussels burrowed into test sediment within 15 min. Across species, life stage, and substrate type, most mussels were recovered from the upper layers of sediment (91% at a sediment depth of 3.4 mm or less), and only 2% of the mussels were recovered at a depth >5.1 mm. No mussels were recovered from a depth >6.8 mm. There was no difference in mussel burrowing depth at 4 h versus 24 h across species, age, and sediment type. Two ages of Fatmucket burrowed to a significantly greater depth in the West Bearskin Lake sediment compared to the Spring River sediment or Coarse Sand. However, there was no significant difference in mean depth across sediment type with the other five species of mussels tested. Based on species and age of mussels tested, juvenile mussels up to an age of at least 20 wk and a length of at least 5 mm readily burrow into sediment and likely would be exposed to contaminants in whole sediment and associated pore water throughout a laboratory sediment toxicity test.

Corneal Cross-linking as an Adjunct for The Management of Refractory Fungal Keratitis.

PURPOSE:To evaluate the effectiveness of ultraviolet (UV)-A/Riboflavin corneal cross-linking (CXL) for the treatment of the refractory cases of fungal keratitis.METHODS:In this prospective interventional study, 9 patients with the diagnosis of fungal keratitis that were referred to our emergency eye center were included. These patients were resistant to conventional treatment and underwent therapeutic UV-A/Riboflavin CXL. Response to the treatment was considered as good if rapid epithelialization and rapid decrease in stromal infiltration was occurred after PACK-CXL, and poor when the emergency transplantation was necessary to eradicate the infection.RESULTS:Nine patients treated with CXL due to recalcitrant fungal keratitis. Culture of the corneal scrapings showed Aspergillus species in 4 patients, Candida albicans in 1 patient and Fusarium species in the remainder of them. CXL was performed from 1 to 20 days after the presentation of corneal ulcers (Mean: 9.12 ± 4.02; range: 5–20 days). Postoperatively, the mean time to epithelialization was 14.25 ± 2.38 days, and mean time to resolution of stromal infiltration was 22.5 ± 7.29 days, in responsive cases. Four out of 9 eyes showed good response, and five patients showed no response, and corneal transplantation was performed to eradicate the infection. There was no statistically significant difference in mean depth of infiltration and mean size of ulcer between responsive and unresponsive patients (P = 0.86 and 0.08, respectively).CONCLUSION:Although UV-A/Riboflavin CXL is not a definite treatment for all of the fungal keratitis, it seems promising in the management of some refractory cases.

Computed tomography-based virtual simulation versus ultrasound-based clinical setup in electron breast boost radiotherapy: Methodology for CT-based electron virtual simulation

PurposeTo compare clinical setup using ultrasound (U/S)-delineated target versus computed tomography (CT) virtual simulation using CT-outlined target in breast electron boost. To describe a methodology for electron virtual simulation and collision testing with the treatment planning system (TPS). MethodsThe two techniques were compared in a prospective study on 12 patients, who were treated using a clinical setup. Target definition was performed by both U/S and CT imaging. The U/S-based target was made visible on CT images by placing a radio-opaque wire on U/S skin markings. The dose distribution of the clinical setup was reproduced in the TPS using the actual electron patient treatment parameters. A CT-based TPS virtual simulation/dose optimization was compared to the clinical setup technique. ResultsMean beam aperture was larger by 16.3 cm2 (p = 0.011) for U/S compared to CT-outlined target. Target mean depth difference (CT minus U/S) was 0.03 cm (p = 0.875). Target coverage at depth was adequate in all cases with CT-based simulation while under/overcovering the target at depth by more than 5 mm in 2 out of 12 cases with clinical setup. Mean target V90% was 98.5% (CT-based simulation) and 84.4% (clinical setup). Ipsilateral lung/breast were better spared with CT-based simulation. To date, the methodology for CT virtual simulation was applied on 152 patients and collision was avoided in all cases. ConclusionsCT-based simulation and target delineation allows for improved definition of the en-face electron field with less amount of normal tissue irradiated while including the entire target with an adequate margin and optimal electron energy.

Evaluation of two alternative ablation treatments for cervical pre-cancer against standard gas-based cryotherapy: a randomized non-inferiority study.

Gas-based cryotherapy is the conventional ablative treatment for cervical pre-cancer in low-income settings, but the use of gas poses significant challenges. We compared the depth of necrosis induced by gas-based cryotherapy with two gas-free alternatives: cryotherapy using CryoPen,and thermoablation. We conducted a five-arm randomized non-inferiority trial: double-freeze carbon dioxide (CO2) cryotherapy (referent), single-freeze CO2 cryotherapy, double-freeze CryoPen, single-freeze CryoPen, and thermoablation. Subjects were 130 women scheduled for hysterectomy for indications other than cervical pathology, and thus with healthy cervical tissue available for histological evaluation of depth of necrosis post-surgery. The null hypothesis was rejected (ie, conclude non-inferiority) if the upper bound of the 90% confidence interval (90% CI) for the difference in mean depth of necrosis (referent minus each experimental method) was <1.14 mm. Patient pain during treatment was reported on a scale of 0 (no pain) to 10 (worst pain). A total of 133 patients were enrolled in the study. The slides from three women were deemed unreadable. One patient was excluded because her hysterectomy was postponed for reasons unrelated to the study, and two patients were excluded because treatment application did not follow the established protocol. For the remaining 127 women, mean depth of necrosis for double-freeze CO2 (referent) was 6.0±1.6 mm. Differences between this and other methods were: single-freeze CO2 = 0.4 mm (90% CI -0.4 to 1.2 mm), double-freeze CryoPen= 0.7 mm (90% CI 0.04 to 1.4 mm), single-freeze CryoPen= 0.5 mm (90% CI -0.2 to 1.2 mm), and thermoablation = 2.6 mm (90% CI 2.0 to 3.1 mm). Mean pain levels were 2.2±1.0 (double-freeze CO2 cryotherapy), 1.8±0.8 (single-freeze CO2 cryotherapy), 2.5±1.4 (double-freeze CryoPen), 2.6±1.4 (single-freeze CryoPen), and 4.1±2.3 (thermoablation). Compared with the referent, non-inferiority could not be concluded for other methods. Mean pain scores were low for all treatments. Depth of necrosis is a surrogate for treatment efficacy, but a randomized clinical trial is necessary to establish true cure rates.

Length and Depth of the Central Sulcus: A Postmortem Study

Context: The central sulcus, which is located between the primary motor and primary somatic sensory cortex is an important structure and landmark of the cerebral hemisphere. Morphology of the central sulcus varies with age, sex, manual skill, handedness and in many diseases. This study is carried out to establish a normal standard in different age groups in length and depth of the central sulcus. Materials and Methods: A cross-sectional, analytical type of study was conducted in the department of Anatomy, Dhaka Medical College, on one hundred and forty (140) on human cerebral hemispheres. The samples were divided into four different age groups i.e. Group A (20-29 years), Group B (30-39 years), Group C (40-49 years) and Group D (50-59 years). All the samples were studied morphologically. Results: The mean length of central sulcus was 102.89±3.55 mm to 96.83±3.92 mm in male and 98.00±5.17 mm to 96.29±2.56 mm in female. Depth of the central sulcus was 20.02±2.41 mm to 21.50±2.21 mm in male and 20.50±2.57 mm to 21.36±1.87 mm in female. The difference in mean length of the right central sulcus between male and female was statistically significant in group A (p&lt;0.05) and B (p&lt;0.05). The difference in mean depth of the central sulcus between male and female was not statistically significant in any age groups. No significant difference was found between right and left hemisphere for both length and depth of the central sulcus. The difference in mean length and depth of the central sulcus between different age groups for both left and right hemisphere was not statistically significant in any age group. Conclusion: The length and depth of the central sulcus showed gradual decreasing values with advancing age. DOI: http://dx.doi.org/10.3329/bja.v11i1.20504 Bangladesh Journal of Anatomy, January 2013, Vol. 11 No. 1 pp 19-24

Tunneling nanotubes and intercellular communication: a novel approach to chemo-resistance in ovarian cancer

RESULTS: Sixty-five hysterectomy specimens were examined for depth of thermal spread. There was no difference in mean depth of thermal spread at the anterior (1.11 mm vs 1.05 mm; p1⁄40.6) or posterior margin (1.04 mm vs 0.91 mm; p1⁄40.2) between standard energy and V mode , respectively. There was no difference in incidence of vaginal cuff dehiscence (p1⁄40.31), with one dehiscence in the standard group. Rate of vaginal cuff granulation tissue, dehiscence or infection was 24% overall, with no difference between groups.

FBxW7 as a predictor of outcomes in ovarian cancer

RESULTS: Sixty-five hysterectomy specimens were examined for depth of thermal spread. There was no difference in mean depth of thermal spread at the anterior (1.11 mm vs 1.05 mm; p1⁄40.6) or posterior margin (1.04 mm vs 0.91 mm; p1⁄40.2) between standard energy and V mode , respectively. There was no difference in incidence of vaginal cuff dehiscence (p1⁄40.31), with one dehiscence in the standard group. Rate of vaginal cuff granulation tissue, dehiscence or infection was 24% overall, with no difference between groups.

Fluttering Characteristics of the Ropes and Nets as an Active Stimulating Device inside the Cod End of a Trawl Net

An active stimulating device (ASD) consisting of a net panel or ropes fluttering in the turbulence inside the cod end was effective in driving fish near the cod end to reduce juvenile by-catch. The fluttering characteristics of the rope and net panel were examined by video observations and analyzed for fluttering amplitude and period in a water channel and in field experiments with a bottom trawl. The amplitude ratio of the fluttering ropes or nets in the tank test increased with the fluttering index as the diameter of the twine, mesh size, flexibility, and flow velocity changed, whereas the period decreased with the above factors. In bottom trawl experiments, the range of mean depth difference in the fluttering net panel was 12-17% of the length of the fluttering net, and the period of depth difference or three-dimensional (3D) tilt was revealed, with shorter ones ranging from 2 to 6 s. The amplitude as depth difference and period from field measurements were similar to those of nets in tank experiments and also to the period of 3D flow velocity inside the cod end. These results could be used to design an ASD that could be used for to the cod end of actual towed fishing gear to reduce juvenile by-catch.

Physical Effects of Sodium Hypochlorite on Bone: An Ex Vivo Study

IntroductionSodium hypochlorite (NaOCl) accidents during endodontic therapy require accurate and prompt action. Understanding the physical properties of bone and evaluating the resultant cell damage from NaOCl exposure could improve management of these accidents. This study assessed the physical and histologic properties of dog femurs exposed to NaOCl for a period of 30 minutes. MethodsFour dog femurs were dissected and frozen. Twelve 40-mm-long sections were obtained and cut into 20-mm paired sections. Adjacent surfaces were randomly selected for shallow injection of either NaOCl or saline. Sections were visually assessed for gross physiologic effects. The structural integrity of the cancellous bone was measured by micro-indentation testing, and statistical analysis of needle penetration was conducted. Histologic evaluation of specimens was also conducted. ResultsGrossly, NaOCl caused remarkable changes in cancellous structure, leaving craters of apparent demineralization. There was a significant difference in mean depth of needle penetration and demineralization between the treatments (P = .0397), with NaOCl showing greater mean depth than saline. The NaOCl group showed degradation of the organic matrix collagen. ConclusionsThese results indicate that NaOCl compromises the integrity of cancellous bone. Calcified elements, especially cortical bone, appeared less affected.

Vertical distribution and ontogenetic "migration" in coral reef fish larvae

Vertical distribution patterns were studied in the community of coral reef fish larvae around Tetiaroa (French Polynesia) using vertically stratified net tows within the first 100 m of the water column. These patterns were examined statistically using an approach based on the center of mass of larval patches. Regression trees first highlighted large differences between taxa, followed by an ontogenetic effect within each taxon. Many families displayed a vertical spread during ontogeny that accounted in part for a downward shift in the distribution of centers of mass. The spread suggests that, throughout ontogeny, individuals move within a wider range of depths rather than migrate downward synchronously. Both the spread and the shift were consistent at the community level despite the taxonomic differences. No difference in mean depth or spread was discernible between day and night, except for Serranidae, which were shallower at night. Environmental factors (such as thermocline depth or current shear) usually explained little variance, except for Lethrinidae and Blennidae, which were consistently deeper when the halocline was deeper. Although the overall effect of the observed ontogenetic spread in such a mildly stratified environment is likely to be small, it might still favor exceptional cases of retention, which can be important given the very low recruitment rate of coral reef fishes.

Depth Distribution Dynamics of the Sculpin Community in Lake Michigan

AbstractUsing data from our annual lakewide bottom trawl survey of Lake Michigan, we calculated the mean depths of capture for deepwater sculpin Myoxocephalus thompsonii and slimy sculpin Cottus cognatus for each combination of transect (Frankfort, Ludington, Saugatuck, and Manistique in Michigan, Waukegan in Illinois, and Port Washington and Sturgeon Bay in Wisconsin) and year (1973‐2005). The mean depth of capture of both sculpin species significantly decreased during the recovery phase of the deepwater sculpin population at four of the transects but did not significantly change for either species at the other three transects during this time. During the postrecovery phase of the deepwater sculpin population, the mean depth of capture of deepwater sculpins significantly increased at six of the seven transects, whereas that for slimy sculpins significantly increased at only four of the seven transects. The mean depth of capture of deepwater sculpins was most strongly correlated with that of slimy sculpins at Frankfort (r = 0.73); the correlation was weakest at Manistique (r = 0.00). Long‐term mean depths of capture (averaged over all years) for deepwater sculpins ranged from 90 to 108 m among the seven transects, whereas the long‐term mean depths of capture for slimy sculpins ranged from 60 to 83 m. The long‐term mean depth difference between the two species was least at Frankfort (21 m) and greatest at Manistique (38 m); at all seven transects, the mean depth difference was significantly greater than zero. We concluded that these two sculpin populations in Lake Michigan maintained some degree of spatial separation during 1973‐2005.

Effects of Catchment Development on the Trophic Status of a Deep and a Shallow Reservoir in Portugal

Although catchment nutrient flux regulation is considered vital for controlling eutrophication, direct measurement of runoff loads is difficult. Shallow eutrophic Divor and smaller deep mesotrophic Apartadura, with different catchment uses but almost identical lake-to-watershed area ratios, were studied. Ratios suggest both reservoirs should be oligo- to meso-trophic. Divor catchment intensive livestock farming opposes to subsistence farming in Apartadura catchment. Runoff coefficients indicated that cattle accounted for 75% of TP mass export in Divor but only about a third in Apartadura, where goats and sheep dominated. In both watersheds agriculture, including pasture, dominated TP export over woodland/brush cover. Because of the large agricultural component, people contributed <1% TP loading to Divor and 2–4% to Apartadura, reflecting population densities. Despite differences in watershed use and lake morphometry, reservoirs showed similar behaviour (summer hypolimnion anoxia, photic zone algal biomass). Transparent Apartadura was dominated by large algal particles and probably P-limited, while turbid Divor contained surplus phosphorus because of large amounts of fine suspended clay particles. The differences in mean depth, not watershed loading, apparently accounted for most of the differences in trophic state. Based on results, management actions to reduce eutrophication in the two reservoirs will differ. Divor drainage will primarily require better manure disposal and fertilizer use reduction but will probably not show trophic state improvement. Apartadura drainage will require diffuse-source P-control (constructed wetlands, riparian buffers) and it should respond by regaining an oxygenated hypolimnion. Stakeholder voluntary cooperation as well as modifying people's perceptions regarding water resources will be needed to comply with the legally binding EU Water Directives.

Automated Subpixel Photobathymetry and Water Quality Mapping

New photobathymetry and water quality software is described here that utilizes subpixel analysis software (Subpixel Classifier) with an autonomous image calibration procedure and analytic retrieval algorithm to simultaneously retrieve and report bottom depth and the concentrations of suspended chlorophyll, suspended sediments, and colored dissolved organic carbon on a per-pixel basis from four-band multispectral image data. From the derived composition, the QSC2 (Quantitative Shoreline Characterization, Version 2.0) software also computes and reports water column visibility parameters (vertical and horizontal subsurface sighting ranges and turbidity, each at four wavelength band passes, plus Secchi depth as a scalar) as well as depth and turbidity confidence. QSC2 compensates for the effects of the atmosphere, sun and sky reflections from the water surface, subpixel contributions from exposed land, and variations in the bottom material properties. All information is derived automatically from the pixel data alone. The performance of the QSC2 software was demonstrated using a four-band Ikonos image of Plymouth, Massachusetts. Accuracies of the image-derived compositions, water clarity, and depths were assessed using field and laboratory measurements for eight representative lakes in the scene. The means of the differences of the field-measured and image-derived suspended chlorophyll and colored dissolved organic carbon concentrations for the eight lakes were 1.82 � g/l and 4.34 mgC/l, respectively. The image-derived concentrations of suspended sediments were all below the threshold of detection for the field samples (5 mg/l), in agreement with the field data. The mean of the differences between field-measured and image-derived Secchi depths was 0.76 m. The mean depth difference was 0.57 m.

Migratory behaviour of north-east Arctic cod, studied by use of data storage tags

To understand the variation in availability of demersal fish to bottom trawls and to evaluate the reliability of the target strength used in acoustic surveys, more knowledge about individual fish behaviour, such as the range, speed and repeatability of the vertical movements, is required. In this paper, data storage tags have been used to study vertical movements of individually tagged cod ( Gadus morhua L.). In general, the short term vertical movements were less than 10 m. Rapid movements of up to 250 m within 2 h interval were recorded sporadically. During restricted periods some of the fish did move vertically with a distinct diel rhythm. Calculations of the time needed to equalise the pressure to remain at a constant buoyant state indicated that the fish probably were negatively buoyant most of the time. However, the direct effect of the vertical movements on the acoustical target strength could not be quantified. Seasonal differences in mean depth and ambient temperature were observed. As a result of horizontal and vertical migrations, north-east Arctic cod experience higher temperatures in winter and spring than in summer and autumn.

Odour‐induced antipredator behaviour of the water flea, Ceriodaphnia reticulata, in varying predator and prey densities

1. A new marking technique was developed and used to track individual water flea behaviour. A single clone of Ceriodaphnia reticulata exhibited no significant differences in mean depth, mean activity (antennae beats used in swimming), and mean travel (total vertical displacement) for fast‐green dyed and control animals (n = 30, each treatment).2. Individual and group antipredator responses were recorded in three vertebrate predator densities (three odour concentrations of green sunfish Lepomis cyanellus; 0.00, 0.03 and 0.10 fish L–1) and four water flea group sizes (1, 5, 15 and 25), with n = 18 for each of the twelve treatment combinations. Water flea groups were probably mixtures of clones. Differences in behaviour after addition of predator odour showed that increasing predator density increased mean depth of marked individuals and mean proportion of water fleas descending. Additionally, increasing prey density decreased both mean depth of marked individuals and mean proportion of water fleas descending.3. Predator density and prey density had opposing affects on activity and travel for marked individuals. Higher predator density decreased mean activity (antennae beats), yet increased mean travel. Higher prey density increased mean activity, but decreased mean travel. Descending animals altered their swimming pattern by using fewer swimming beats to travel greater vertical distances in the presence of predator odour.