Cage Depth Research Articles

The Effect of Interbody Cage Parameters on the Rate of Subsidence in Single-Level Anterior Cervical Discectomy and Fusion (ACDF): A Retrospective Analysis of 98 Patients.

Subsidence is arelatively common consequence after anterior cervical discectomy and fusion (ACDF) surgery. This study aimed to identify the effect of radiological and non-radiological risk factors on subsidence after a single-level ACDF surgery with cage and plate. This is a retrospective cohort study of patients who underwent ACDF for radiculopathy or myelopathy at an academic center, University of Kentucky Albert Chandler Hospital, Lexington, Kentucky, United States, between January 2010 and January 2020.Subsidence was defined as the sinking of the interbody cage into the vertebral body at either the superior end plate (SEP) or inferior end plate (IEP) at the ACDF level and was measured manually on lateral standing x-ray. The numerical amount of subsidence was measured in millimeters as the sum of subsidence in the SEP and IEP and was further categorized into subsidence2 and subsidence3 (i.e., presence of subsidence > 2 mm and subsidence > 3 mm, respectively). Multivariateregression analysis was used to assess the effect of variables such as age, gender, body mass index (BMI), tobacco use, follow-up length, cage type, anterior cage height, posterior cage height, anterior cage height ratio, posterior cage height ratio, cage position, cage-end plate interface and cervical alignment on outcomes such as subsidence, subsidence2, and subsidence3. A total of 98 patients were included, of which 46 (47.1%) were male. The mean age of the population was 47.6±8.4 years. Fifty-one patients (52%) experienced subsidence more than 3 mm. Anterior disc height ratio (ADHR) was calculated by dividing the anterior cage height by the anterior disc height (pmADH). The posterior disc height ratio (PDHR) was calculated by dividing the posterior cage height by the posterior disc height (pmPDH). There was no significant correlation between ADHR and PDHR with subsidence, (p=0.93 and 0.56, respectively). Gender, age, BMI, and smoking status did not affect subsidence either. Cage type significantly affected subsidence with a higher subsidence rate in VG2 cages compared to Bengal cages (p=0.05). This study showed that in patients undergoing single-level ACDF with cage and plate, cage size and in particular cage height (if adjusted for individual patients) did not affect subsidence. Other factors such as cage-endplate interface, cage depth in interbody space, and cervical alignment did not significantly affect subsidence either. This might be attributable to the use of an anterior plating system that conducts the force and reduces the stress on the graft-bone interface.

The Effect of Different Submerged Cage (Vietnamese Style) Depth on The Growth of Green Lobster (Panulirus homarus) in The East Coast of Pangandaran District

The purpose of this study was to determine the effect of submerged cage depth on the growth of green lobsters (Panulirus homarus) in Vietnamese-style cultivation on the East Coast of Pangandaran. The submerged cage was intended so that the lobsters are not disturbed by the situation/water quality in the upper layer of the water. The research method used a completely randomized design using 3 submerge cage depth treatments and 4 repetitions with different ones, A (2 meters); B (3.5 meters); and C (5 meters). Lobster maintenance was carried out for 40 days using a submerged cage with a diameter of 80 cm and a height of 90 cm. Each cage contains 10 lobster seeds measuring 40 g. Frequency of feeding 2 times a day. The amount of test feed given was 20% of the lobster weight each day. Measurement of water quality as supporting data was carried out at the beginning and end of the research. Sampling was done every 10 days and the observed parameters were growth rate, feed conversion ratio (FCR), and feed efficiency (FE). Lobster growth performance showed that treatment C (placement of cages at a depth of 5 meters) was the best among the others, as well as the daily growth rate (LPH) of 1.35%, feed conversion ratio (FCR) of 12.8, and feed efficiency ( EP) of 8.6%. The water quality in the submerged cage with a depth of 5 meters was DO 5.22 mg/L, the water temperature was 28 Celsius, pH was 7 and salinity was 34 ppt.

Morphological patterns of the rib cage and lung in the healthy and adolescent idiopathic scoliosis.

The morphology of the rib cage affects both the biomechanics of the upper body's musculoskeletal structure and the respiratory mechanics. This becomes particularly important when evaluating skeletal deformities, as in adolescent idiopathic scoliosis (AIS). The aim of this study was to identify morphological characteristics of the rib cage in relation to the lung in patients with non‐deformed and scoliotic spines. Computed tomography data of 40 patients without any visible spinal abnormalities (healthy group) and 21 patients with AIS were obtained retrospectively. All bony structures as well as the right and left lung were reconstructed using image segmentation. Morphological parameters were calculated based on the distances between characteristic morphological landmarks. These parameters included the rib position, length, and area, the rib cage depth and width, and the rib inclination angle on either side, as well as the spinal height and length. Furthermore, we determined the left and right lung volumes, and the area of contact between the rib cage and lung. Differences between healthy and scoliotic spines were statistically analysed using the t‐test for unpaired data. The rib cage of the AIS group was significantly deformed in the dorso‐ventral and medio‐lateral directions. The anatomical proximity of the lung to the ribs was nearly symmetrical in the healthy group. By contrast, within the AIS group, the lung covered a significantly greater area on the left side of the rib cage at large thoracic deformities. Within the levels T1–T6, no significant difference in the rib length, depth to width relationship, or area was observed between the healthy and AIS groups. Inferior to the lung (T7–T12), these parameters exhibited greater variability. The ratio between the width of the rib cage at T6 and the thoracic spinal height (T1–T12) was significantly increased within the thoracic AIS group (1.1 ± 0.08) compared with the healthy group (1.0 ± 0.05). No statistical differences were found between the lung volumes among all the groups. While the rib cage was frequently strongly deformed in the AIS group, the lung and its surrounding ribs appeared to be normally developed. The observed rib hump in AIS appeared to be formed particularly by a more ventral position of the ribs on the concave side. Furthermore, the rib cage width to spinal height ratio suggested that the spinal height of the thoracic AIS‐spine is reduced. This indicates that the spine would gain its growth‐related height after correcting the spinal deformity. These are the important aspects to consider in the aetiology research and orthopaedic treatment of AIS.

Stress analysis of anchor chain on the floating breakwater structure with cage culture function

The physical model test of floating breakwater and cage structure is carried out. Under the action of irregular waves, the structure is obtained. Different depth of immersion, Cage depth and wave period work on its Stress analysis of anchor chain. The results show that, when the period is short, the stress on the anchor chain increases exponentially with the increase of wave height. However, under the condition of long period, the variation of anchor chain force with net depth is not obvious, so it is not recommended to hang net cage for breeding.

Deformation and drag force of model square fish cages in a uniform flow

Model experiments were carried out to investigate the performance of different types of 1:8.3-scale model square fish cages in a uniform flow. The model cages were designed using different netting materials, mesh types, and cage depths. Shape deformation, volume reduction, and drag force were used as key parameters to characterize the cage performance. The results indicate that cages using polyethylene netting for the four sides and wire-netting for the bottom generally show better performance than those composed entirely of polyethylene netting; specifically, the former undergoes less shape deformation and volume reduction than the latter. The mesh type (square or diamond mesh) had a noticeable effect on shape deformation and drag force but a limited effect on cage volume reduction. Moreover, for the cages with wire-netting bottom and polyethylene sides, the bottom net tended to drift parallel to its undisturbed orientation when the sides were composed of square mesh netting. In contrast, the bottom net drifted obliquely upward on the downstream side when diamond mesh netting was used for the side nets. It was also confirmed that drag force per unit volume of the cages with wire-netting bottom was larger than that for the cages composed entirely of polyethylene netting.

Economic analysis of vermicompost production in Guntur District of Andhra Pradesh

The study was conducted to understand the economic feasibility of the vermicompost production using Edururilles euginia. The study was adopted both open and cage method of vermicompost production. About 550 kg of agricultural wastes and fresh cow dung was spread on the cage with dimensions of 5 m length and 2 m width with a cage depth of 30 cm. The water was sprinkled twice a day for keeping the moisture levels optimum. The study was carried about for 4 months and produced 600 kg of vermicompost manure and 4 kg of earthworms. The study revealed that total production cost was about Rs.3150/-with variable costs of Rs.2350/-and fixed costs of Rs.800/-. The gross return obtained was Rs.4400/-and thus, net profit came out to be Rs.1250/-.

Age-related changes in thoracic skeletal geometry of elderly females

ABSTRACTObjective: Both females and the elderly have been identified as vulnerable populations with increased injury and mortality risk in multiple crash scenarios. Particularly in frontal impacts, older females show higher risk to the chest and thorax than their younger or male counterparts. Thoracic geometry plays a role in this increase, and this study aims to quantify key parts of that geometry in a way that can directly inform human body models that incorporate the concept of person age.Methods: Computed tomography scans from 2 female subject groups aged 20–35 and 65–99 were selected from the International Center for Automotive Medicine scan database representing young and old female populations. A model of thoracic skeletal anatomy was built for each subject from independent parametric models of the spine, ribs, and sternum, along with further parametric models of those components’ spatial relationships. Parameter values between the 2 groups are directly compared, and average parameter values within each group are used to generate statistically average skeletal geometry for young and old females. In addition to the anatomic measures explicitly used in the parameterization scheme, key measures of rib cage depth and spine curvature are taken from both the underlying subject pool and from the resultant representative geometries.Results: Statistically significant differences were seen between the young and old groups’ spine and rib anatomic components, with no significant differences in local sternal geometry found. Vertebral segments in older females had higher angles relative to their inferior neighbors, providing a quantification of the kyphotic curvature known to be associated with age. Ribs in older females had greater end-to-end span, greater aspect ratio, and reduced out-of-plane deviation, producing an elongated and overall flatter curvature that leads to distal rib ends extending further anteriorly in older individuals. Combined differences in spine curvature and rib geometry led to an 18-mm difference in anterior placement of the sternum between young and old subjects.Conclusions: This study provides new geometric data regarding the variability in anthropometry of adult females with age and has utility in advancing the veracity of current human body models. A simplified scaffold representation of underlying 3-dimensional bones within the thorax is presented, and the reported young and old female parameter sets can be used to characterize the anatomic differences expected with age and to both validate and drive morphing algorithms for aged human body models. The modular approach taken allows model parameters to hold inherent and intuitive meaning, offering advantages over more generalized methods such as principal component analysis. Geometry can be assessed on a component level or a whole thorax level, and the parametric representation of thorax shape allows direct comparisons between the current study and other individuals or human body models.

Stereotactic guidance for navigated percutaneous sacroiliac joint fusion.

Arthrodesis of the sacroiliac joint (SIJ) for surgical treatment of SIJ dysfunction has regained interest among spine specialists. Current techniques described in the literature most often utilize intraoperative fluoroscopy to aid in implant placement; however, image guidance for SIJ fusion may allow for minimally invasive percutaneous instrumentation with more precise implant placement. In the following cases, we performed percutaneous stereotactic navigated sacroiliac instrumentation using O-arm® multidimensional surgical imaging with StealthStation® navigation (Medtronic, Inc. Minneapolis, MN). Patients were positioned prone and an image-guidance reference frame was placed contralateral to the surgical site. O-arm® integrated with StealthStation® allowed immediate auto-registration. The skin incision was planned with an image-guidance probe. An image-guided awl, drill and tap were utilized to choose a starting point and trajectory. Threaded titanium cage(s) packed with autograft and/or allograft were then placed. O-arm® image-guidance allowed for implant placement in the SIJ with a small skin incision. However, we could not track the cage depth position with our current system, and in one patient, the SIJ cage had to be revised secondary to the anterior breach of sacrum.

Depth distribution of the amoebic gill disease agent, Neoparamoeba perurans, in salmon sea-cages

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 7:67-74 (2015) - DOI: https://doi.org/10.3354/aei00137 Depth distribution of the amoebic gill disease agent, Neoparamoeba perurans, in salmon sea-cages Daniel W. Wright1,*, Barbara Nowak2, Frode Oppedal3, Andrew Bridle2, Tim Dempster1 1Sustainable Aquaculture Laboratory - Temperate and Tropical (SALTT), School of Biosciences, University of Melbourne, Parkville, VIC 3010, Australia 2Institute of Marine and Antarctic Studies, University of Tasmania, Launceston, TAS 7250, Australia 3Institute of Marine Research, 5984 Matredal, Norway *Corresponding author: danielw1@student.unimelb.edu.au ABSTRACT: Identifying where and when parasites occur in farming environments is vital to understand transmission dynamics and develop preventative measures that reduce host-parasite encounters. A major parasite concern for Atlantic salmon farming is Neoparamoeba perurans, a marine amoeba that causes the potentially fatal amoebic gill disease (AGD), for which few control options exist. We explored whether free-living N. perurans abundance differs among depths in commercial Atlantic salmon Salmo salar sea-cages. Water samples collected from the surface to 10 m depth at multiple cage sites and times, and subsequently subjected to qPCR analysis, revealed that N. perurans abundance was influenced by depth at the time of year when amoeba numbers were highest, with more amoebae in surface waters. No distinct depth patterns were observed when amoebae were in low abundance. Across all times, temperature and salinity were largely homogeneous throughout cage depths. Possible factors explaining the presence of amoebae at the surface are discussed. Our results suggest that excluding caged salmon from upper cage depths where N. perurans is more abundant could be an effective management strategy to reduce the speed at which initial infections occur and delay the development of AGD outbreaks. KEY WORDS: Parasite control · Atlantic salmon · Salmo salar · Neoparamoeba perurans · Depth distribution · Sea-cages Full text in pdf format Supplementary material PreviousNextCite this article as: Wright DW, Nowak B, Oppedal F, Bridle A, Dempster T (2015) Depth distribution of the amoebic gill disease agent, Neoparamoeba perurans, in salmon sea-cages. Aquacult Environ Interact 7:67-74. https://doi.org/10.3354/aei00137 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 7, No. 1. Online publication date: July 16, 2015 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2015 Inter-Research.

Accumulation and distribution of skin fluke Neobenedenia girellae eggs on a culture cage

Skin fluke causes chronic problems in marine finfish aquaculture. Their eggs possess a long filamentous appendage that allows them to easily attach to culture cages. Fish farmers periodically change and clean cage nets to remove eggs from the culture sites. However, there is very little information about the accumulation rate and distribution of skin fluke eggs on culture cages. We conducted an experiment at a culture site to assess the accumulation of eggs of the Neobenedenia girellae skin fluke at different culture cage depths. In all three trials, we observed the highest egg accumulation in shallow areas, and the egg number decreased with the depth; however, the second highest accumulation was observed at the deepest depth. These distribution patterns likely reflect the behavior of fish within the cage. The highest accumulation rate was 161.2 eggs/cm2/day, with an estimated daily accumulation of more than 10 million eggs on the entire cage (excluding the cage floor). Such information is useful for optimizing and managing cage net changing and also for the development of a new method of removing/killing parasite eggs.

Low intensity light of different colours modifies Atlantic salmon depth use

Underwater anti-maturation-lights have recently been exploited to position sea-caged Atlantic salmon (Salmo salar L.) deeper at night in an effort to reduce infections by salmon lice (Lepeophtheirus salmonis) in surface layers. However, anti-maturation-light use is impermanent because lighting during decreasing day-lengths stimulates sexual maturation which is detrimental for fish welfare, growth and meat quality. The effects from lights on maturation are related to both light intensity and light spectrum. Here, we explored caged salmon depth use in response to lights of four low intensities (0.01, 0.10, 1.0 and 10.0μE as measured 1m from the lamps) and seven different colours (broadband white LED lamp and narrow spectrum violet, blue, green, yellow, red and deep red LED lamps). Triplicate sea cages (12×12m and 11m deep) holding approximately 5000 fish of 1.5kg were exposed to each light positioned at 10m depth for one night. Echo sounders registered fish vertical positioning on nights of light treatments and no light (control nights) before and after each light exposure. Results showed that submerged lights generally caused fish to maintain their day-time swimming depth near 10m (light depth) during the night, as opposed to the typical migration of salmon to upper cage depths at dusk observed on control nights. Quantities of fish staying deep decreased with lowered light intensity, but even 0.1μE had effects. All light colours, except deep red, significantly affected swimming depth, with a trend of increased effect at lower wavelength colours. Temperature stratification strengthened light effects when warmer water was near the lamps and weakened effects in the case of warmer water near the surface. This study opens up the potential of using low intensity lights at decreasing day-lengths that may not affect sexual maturation and remain suitable for guiding salmon away from surface waters rich in lice infective stages.

Tibial tuberosity transposition-advancement for lateralization of the tibial tuberosity: an ex vivo canine study.

To evaluate the degree of lateralization achievable and strength of tibial tuberosity transposition and advancement (TTTA) relative to pin and tension band wiring (PTBW) for lateral tibial tuberosity transposition. Six pairs of cadaveric tibiae were used. Tibial tuberosity position was determined with computed tomography (CT); bones were then randomly assigned into TTTA and PTBW groups. The PTBW group had a tibial tuberosity osteotomy and fixation with pin and tension band wiring. The TTTA group had a tibial tuberosity advancement performed with lateralization of the tibial tuberosity by 50% of cage depth, using spacers on the cranial cage screw. Postoperative CT images showed lateralization and craniocaudal deviation. Single axial distractive loading was applied to the patella at 90˚ to the tibial plateau, and peak load, energy, and stiffness were calculated. There were significant differences in lateralization (PTBW: 67.92 ± 5.1 %; TTTA: 88.51 ± 5.5 %) (p = 0.0173) and craniocaudal deviation (PTBW: -8.30 ± 1.4 %; TTTA: 6.83 ± 0.6) (p = 0.0001). There were no significant differences in peak load to failure (N) (PTBW: 1448 ± 121; TTTA: 1597 ± 43) (p = 0.4541), energy to failure (N/mm) (PTBW: 15013 ± 2719; TTTA: 17314 ± 887) (p = 0.646), or stiffness (N/mm)(PTBW: 102.8 ± 4.7; TTTA: 92.9 ± 4.8) (p = 0.2716). The TTTA was more effective at lateralization of the tibial tuberosity, and of comparable strength to PTBW. Greater support of the osteotomized fragment with TTTA may resist cyclic loading, and requires evaluation.

Automatic submerging and surfacing performances of model submersible fish cage system operated by air control

An automatic, submersible fish cage system using air control was developed and a set of model experiments were conducted to examine the automatic submerging characteristics of the cage. The components of the fish cage consist of a rigid frame assembly with 6 variable ballast tanks and 6 fixed ballast tanks. The variable ballast tanks were used to change the buoyancy characteristics of the system by air control so that the fish cage can either be placed at the surface or submerged. The cage is free to move vertically within a water column by adjusting the weight and the buoyancy with an air control system. The model of this system, with dimensions of 2.20 m in diameter and length and 1.04 m in net cage depth, was constructed to be 1/10 the size of the full-scale system. In the model experiments, the submerging and surfacing characteristics of the cage were regulated with measurements from a water-pressure gauge and a gyroscope incorporated into the automatic control system. Model tests were performed in a still water tank and a large wave tank to develop the algorithm required to control the cage system and to verify the ability of the automatic submersion mechanism to function. The control system was designed so that when the variable ballast tanks were flooded with water, the model descended. To raise the system, compressed air is injected into the tanks by opening the main evacuation valve on the manifold. After the required amount of compressed air is supplied, the main evacuation valves can be shut and as a result, the fish cage becomes buoyant. Measured performance results in a still water tank are then compared with calculations from a previously developed numerical technique. The submerging and surfacing characteristics of the fish cage were relatively similar to the measurements obtained with the physical model experiments using air control. The cage was submerged to a target depth when incidence wave heights were higher than the critical wave height and raised when little wave actions were detected in a wave tank. On the other hand, the cage was placed at the surface when incidence wave heights were the same as the critical wave height or lower.

Physiological welfare of commercially reared cod and effects of crowding for harvesting

A greater understanding of the effects of pre-slaughter practices on farmed fish is needed, particularly for more recently farmed marine fish species such as the Atlantic cod, Gadus morhua. In the present studies, in order to understand the impacts of crowding prior to harvesting on the physiological well-being of farmed Atlantic cod, we measured blood haematocrit, plasma osmolality, and plasma concentrations of cortisol, glucose, lactate, chloride and sodium of cod held in two commercial sea cages. To investigate any effects of our presence alongside the cages, cod were captured from two non-manipulated cages by rod and line, with a minimal time on the line. Measurements of blood parameters were comparable with those from published laboratory studies, and showed minimal change over the 3 h maximum sampling period. By comparison, a small number of cod that were caught easily in a hand net showed severe osmoregulatory, metabolic and endocrine disturbances. These cod were predominantly mature females, from one cage in which female cod had a low muscle mass (i.e. K based on body mass after removal of viscera), which suggests that maturation and spawning of farmed cod, particularly females, may have welfare implications. Plasma cortisol (ng ml − 1 ) for net-caught cod ( n = 9) was 88.5 ± 20.6 (mean ± SE) compared to 8.13 ± 3.43 for rod–line-caught cod ( n = 54), and plasma osmolality (mOsm kg − 1 ) was 383.27 ± 13.03 compared to 338.55 ± 0.73. Two commercial cages, suspended at 15 m depth, were used to investigate the physiological effects of crowding of cod in a sweep net, comparing initial values in line-caught cod to values observed during crowding. The effects of crowding time, gender and cage were examined. In both cages, crowding caused a rapid and sustained elevation of blood haematocrit and plasma lactate concentrations, probably due to increased physical exertion. Plasma lactate peaked at mean concentrations of 4.17 mM and 3.02 mM in the two cages, compared to initial concentrations of 0.29 mM and 0.17 mM respectively. Disturbed osmoregulation during crowding was not accompanied by parallel changes in plasma concentrations of sodium or chloride. Plasma cortisol during crowding reached peak concentrations of approximately 60 ng ml − 1 in both male and female cod but female cod showed a more rapid and prolonged response. Interpretation of our results suggests that cod crowded for harvesting will benefit from (i) reduced cage depth to minimise swim bladder inflation during the sweep and unnecessary exertion, (ii) limiting crowd density as far as practical to reduce bursts of activity, and (iii) minimising the crowding period.

Effects of pellet contrast and light intensity on salmonid feeding behaviours

Two of the outstanding questions related to fish feeding in enclosures are why all fish do not feed at once and why daily feeding rates vary. Our results will indicate that few fish feeding at once may be caused by a desire to feed under low light if pellets are detectable there, while variable daily feed discharge rates (kg min −1) under similar ration level are correlated with underwater light levels. We hypothesized that non-uniform feeding and variable feeding rates were linked and related to poor food detectability at large cage depths. We tested this hypothesis by feeding fish in cages on salmon farms different food pellet types (silver and regular brown) while simultaneously measuring feed discharge rate, lighting conditions and feeding activities near the surface and cage bottom. Images of pellet and fish obtained from underwater cameras that were positioned near the cage bottom were used as a basis for judging satiation and setting the feed discharge rate. In morning feedings, the discharge rate of fish given silver pellets was lower than the rate for conventional brown pellets ( P-value=0.002). In both treatments, feed discharge rates decreased with increasing levels of background light intensity (0.44< r 2<0.84). Contrary to our expectations, there was no significant difference in time spent feeding in different spatial locations between treatments ( P-value>0.6). Generally fish in both treatments did not feed throughout the cage at the same time, and fish never appeared to be eating all at the same time. A general feeding pattern emerged; at some time during the feeding event, feeding fish would start to follow food from the surface down into the cage (instead of letting it pass by them). To feed these fish and prevent pellet wastage, discharge rate would be lowered by researchers when the fish reached the cage bottom. Fish given silver pellets and fed under bright conditions would reach the cage bottom sooner then fish given regular pellets and fed under darker conditions (hence the discharge rates under the former conditions were lower than the rates under the latter conditions). The results imply a preference by salmonids for eating at a low light level if pellets are easily available and detectable there. This tendency for fish to eat under restricted conditions (that may not be available for all fish in a cage at any given time) could cause non-uniform feeding patterns.

The motion of a deep-sea remotely operated vehicle system: Part 1: Motion observations

Rapid and high-resolution motion and tension measurements were made of a caged deep-sea remotely operated vehicle (ROV) system. Simultaneous measurements were made of all six components of motion at the cage and ship A-frame and of the tension in the tether at the ship. Data were collected for cage depths of 0–1765 m. The most significant forcing was in the wave-frequency band (0.1–0.25 Hz) and accounted for over 90% of the variance of vertical acceleration. The vertical acceleration of the cage lagged the acceleration of the A-frame by up to 1.9 s and its variance was larger by up to a factor 2.2. For moderate displacements of the A-frame (≤2 m), the system is only weakly non-linear because the harmonics (3rd and 5th) of the vertical acceleration of the cage account for less than 2% of the total variance. The system is essentially one-dimensional because only the vertical motion of the cage and the vertical motion of the A-frame were coherent, while horizontal motions of the cage were weak and incoherent with any component of motion of the A-frame. The natural frequency of the system is 0.22 Hz at 1730 m, and we estimate that it is within the waveband for depths between 1450 m and the full operating depth of 5000 m. Large vertical excursions of the A-frame produce momentary slack in the tether near the cage. Retensioning results in snap loads with vertical accelerations of 0.5 gravity. Large rates of change of tension and vertical acceleration first occur at the cage during its downward motion and propagate to the surface with the characteristic speed (3870 m s −1) of tensile waves for the tether. Six echoes are clearly detectable at both ends of the tether, and their pattern is extremely repeatable in different snap loads. Due to misalignment of the tether termination with the centres of mass and buoyancy, the cage pitches by up 14° during a snap. The resulting small radius of curvature poses the greatest stress on the tether.

尾索をもつ巻索の動張力について

An abnormal dynamic tension on winding rope with a tail rope installed in rope guided winding shaft may be resulted from an emergency braking or a rough loading into the cage. This paper discusses the effectiveness of tail rope on such the dynamic tension of winding ropes. Some results obtained are as follows:(1) Following on an emergency braking or a rough loading into the cage, the excursion of the acceleration value at the cage reaches almost twice of that value at the driving sheave.(2) During emergency braking, ascending tail rope tends to float, by which the necessary grip on the driving sheave may be lost.(3) When a load is dropped into the cage with zero head, the winding rope with no tail rope performs the 1st mode vibration. On winding rope with tail rope, the 2nd and 3rd mode vibrations are significant when the cage is nearby the pit mouth.(4) At the cage depths where the tail rope is twice as long as the winding rope, the dynamic tension on the winding rope caused by a sudden loading is effectively reduced.(5) A dynamic tension of 4-5 times greater than the loaded weight may appear at the driving end. when the load is dropped into the cage with a head of 0.1-0.2m.(6) As the loading weight increases, the ratio of the peak value of dynamic tension to the loaded weight decreases.

EFFECTS OF CAGE FLOOR SHAPE ON LAYER PERFORMANCE

In a factorial split plot experiment, 1536 pullets were tested for 60 wk in four replications with two rearing systems (cage vs. floor), two genetic stocks, two population size-density combinations, and two cage shapes. Three and four Shaver 288 layers per cage were each tested at 464 cm2 and 542 cm2 per bird and three and four Hubbard Comets per cage each at 542 cm2 and 610 cm2 per bird. Layers were housed in both deep and shallow cages. Cage depth had no effect upon nervousness, feather wear (except for the wings), mortality, egg specific gravity, broken eggs or net egg returns over feed and bird costs. Birds in shallow cages had significantly less wing feather wear, laid more eggs, consumed more feed, had inferior feed conversion, larger body size and lower percentage of Grade A eggs. With the exception of the feathering on the neck, back and underside, there were no consistent two-and three-way interactions between the main effects. It was concluded that layers in shallow cages consumed more feed than required, gained an unnecessary amount of body weight and did not lay compensatory extra eggs. Feeding twice a day to provide continuity of supply may have stimulated layers in deep cages to consume enough food to equal the net egg returns of those in shallow cages. Possible reasons for the differences between the results at this station and elsewhere were also discussed.

Effects of cage shape, colony size, floor area and cannibalism preventatives on laying performance

1. Wire cages of variable width and depth, with a floor slope of 1 : 12, were used in two experiments to study the effects of cage depth, feeding space (= cage width), floor area, colony size and two methods of controlling cannibalism in White Leghorn x Australorp laying hens. 2. The least floor area (0.035 m2/bird) depressed production in two‐bird cages. Floor area had little effect on the performance of larger colonies. 3. Birds in colonies of three, four or six laid and survived equally well when feeding space/bird and floor area/bird were constant. 4. Production per hen d and food intake were higher, but return on estimated capital outlay was lower, with 102 mm than with 76 mm feeding space/bird when colony size and floor area/bird were constant. 5. Production and food intake of birds which were not treated to prevent cannibalism declined, and mortality increased, as cage depth increased from 385 to 915 mm concomitantly with increasing colony size from 2 to 7 birds and decreasing feeding space from 152 to 43 mm/bird. 6. Increasing cage depth did not increase the proportion of cracked eggs. 7. Mortality was higher among birds fitted with plastic spectacles than among debeaked birds.

Hydrodynamic design of ballbearing cage pockets

This paper reports results of a theoretical study of hydrodynamic load capacity and power consumed in a ball bearing straight sided annular cage pocket. Design curves show how these quantities vary with eccentricity ratio, radial clearance and cage depth and enable suitable pocket proportions to be chosen