Rod Components Research Articles

Analysis of the influence of bottom flow holes in control rod guide tubes on flow field and control rod displacement

During the operation of pressurized water reactors, flow-induced vibration issues are commonly encountered, where control rod components vibrate due to the impact of coolant flow, leading to wear, thereby posing a threat to the safe operation of the reactor. This paper conducts a detailed numerical simulation of the flow field and force distribution inside a full-scale lower control rod guide tube based on the CFD method. The fluid–structure interaction analysis is performed to reveal the influence of cross-flow under various operating conditions on the vibration and displacement of control rods. The research subject consists of 24 control rods, one continuous guide section, and six control rod guide cards. The lower part of the guide tube has two flow holes on each surface, with one assumed to be a cross-flow inlet and the others as outlets. The results indicate that when considering the cross-flow effect at the flow holes, 90 % of the coolant flows out from other flow holes at the bottom of the guide tube, resulting in increased transverse velocity at the bottom and the presence of numerous vortices. The magnitude and location of the force exerted on the control rod by coolant impact are correlated. The control rod closest to the inlet of the flow hole experiences the greatest force, approximately 5.35 times the average at other positions. At a cross-flow velocity of 0.4 m/s and a low frequency of 10 Hz, the maximum displacement of the control rod is 0.3355 mm.

A flexible design framework for lattice-based chiral mechanical metamaterials considering dynamic energy absorption

While chiral mechanical metamaterials (CMMs) are reported promising in energy absorption due to the unique chiral effect, the energy-absorbing CMMs lack effective and generalized design methodologies and corresponding structure-property relationship studies. To this end, a design framework for lattice-based CMMs was proposed, and the dynamic compressive behaviors of CMMs were systematically investigated. Firstly, based on a predefined design baseline that considered a support-free metal additive manufacturing process, a screw-theory-based assembly rule was presented, which enabled the scalable twist effects and the characterization of chiral features. Secondly, an aperiodic design process that sequentially defines joints, strut connections, and geometrical features was proposed. This framework via parameterization enables the rapid generation of geometric and finite element models that contain a large number of unit cells. It also enables the integration of joint enhancement design, bio-inspired helical design, and gradient design. Finally, by finite element analysis and experiments of uniaxial medium-strain-rate (50 s−1) compression, the effects of chirality on mechanical properties (compressive strength, yield plateau, energy absorption, etc.) during the nonlinear large-deformation responses were elucidated. Results show that a comprehensive and flexible method is presented by independently defining each rod component or joint of the lattice type metamaterials, which enables the design from chiral to achiral, from rectangular to helical, and from uniform to gradient. The bidirectional gradient CMMs design along the axial and radial directions achieves a 52.0 % specific energy absorption enhancement compared with achiral lattices, demonstrating the energy absorption advantage of CMMs, and laying the foundation for further optimization, inverse design, and engineering applications.

JUSTIFICATION OF THE STEP OF WRAPPING THE THREAD WITH A MICROWIRE TO AVOID ITS BREAKING WHEN THE COMPLEX THREAD IS STRETCHED

JUSTIFICATION OF THE STEP OF WRAPPING THE THREAD WITH A MICROWIRE TO AVOID ITS BREAKING WHEN THE COMPLEX THREAD IS STRETCHED

Probabilistic approach of state transition elements of truss structures at corrosion

The purpose of the presented study is to determine and mathematically model the reliability of a steel truss with different variants of local failures of rod elements due to corrosion processes. In order to achieve a quantitative reliability assessment, the truss structure is considered as a combination of subsystems containing relatively small groups of rod components. Numerical calculations of truss structures taking into account the influence of corrosion have been carried out. It is shown that the components of the truss system can change their state by different schemes. The transition from one state to another depends on the level of stress state, which is caused by corrosion effects. It is easier to visualize this in a binary system. The probability of failure-free performance of rod components over the operating time can be written in vector form. By the matrix analysis method, failure states and functional states can be determined. As an example, a 5-bar structural system of a metal staircase type truss is considered.

ANALISA CACAT PENYUSUTAN MATERIAL FCD450 DAN ALUMINIUM A356 PADA PROSES PENGECORAN STANG PISTON DINDING TIPIS MENGGUNAKAN SIMULASI

Metal castings are generally used to manufacture machine parts with complex shapes, including the manufacture of thin wall components. Thin wall casting (TWC) is a casting method for producing lightweight component objects by thinning the component walls such as plates or parts of the cast object that can be thinned. Thin wall ductile iron (TWDI) is nodular cast iron, casted through TWC. TWDI makes nodular cast iron possible to compete with aluminum when compared to the weight between these two materials. The application of aluminium to TWC aluminum will lead to lighter components production. The main reason aluminum is replacing cast iron in the automotive field is the inability or lack of interest on the part of cast iron manufacturers to produce lightweight iron components, which is TWDI. The use of simulation in the casting process helps to show the whole process in casting. This research was conducted to determine the effect of using the TWC design made for nodular cast iron on aluminum and the defects formed by using this design through software simulation. The casting design used uses Sulamet-Ariobimo et al. casting design [10] which has succeeded in producing connecting rod components using TWDI on an industrial scale. The simulation software used is the Altair Inspire Cast simulation (serial number: 680344) owned by PT. Wisma Teknik Lestari. Simulations were carried out for both FCD450 and A356 materials. Based on the results of the shrinkage simulation, there are shrinkage defects in the TWDI material and there are no shrinkage defects in Aluminum A356. This is due to the solidification characteristics and cooling rate of the two materials, where the cooling rate for TWDI is 3.84E+4 J, and 8.85E+4 J for Aluminum A356. In addition, based on the solid fraction simulation results, there are hotspots on cast components for TWDI materials which result in shrinkage defects in the components

Characterization of scotopic and mesopic rod signaling pathways in dogs using the On–Off electroretinogram

BackgroundThe On–Off, or long flash, full field electroretinogram (ERG) separates retinal responses to flash onset and offset. Depending on degree of dark-adaptation and stimulus strength the On and Off ERG can be shaped by rod and cone photoreceptors and postreceptoral cells, including ON and OFF bipolar cells. Interspecies differences have been shown, with predominantly positive Off-response in humans and other primates and a negative Off-response in rodents and dogs. However, the rod signaling pathways that contribute to these differential responses have not been characterized. In this study, we designed a long flash protocol in the dog that varied in background luminance and stimulus strength allowing for some rod components to be present to better characterize how rod pathways vary from scotopic to mesopic conditions.ResultsWith low background light the rod a-wave remains while the b-wave is significantly reduced resulting in a predominantly negative waveform in mesopic conditions. Through modeling and subtraction of the rod-driven response, we show that rod bipolar cells saturate with dimmer backgrounds than rod photoreceptors, resulting in rod hyperpolarization contributing to a large underlying negativity with mesopic backgrounds.ConclusionsReduction in rod bipolar cell responses in mesopic conditions prior to suppression of rod photoreceptor responses may reflect the changes in signaling pathway of rod-driven responses needed to extend the range of lighting conditions over which the retina functions.

Features of the behavior of the dispersion fuel METMET under irradiation

The paper considers the behavior under irradiation of the METMET fuel composition, which consists of particles of uranium-molybdenum alloy in a matrix of zirconium alloys. Post-reactor investigations confirmed the satisfactory performance of pilot fuel elements irradiated in the MIR reactor to a burnup of 61 MW day/kgU under significant thermal loads. The structural stability of the fuel under irradiation, good compatibility of the fuel rod components with each other could be noted. Fuel rods with METMET fuel composition have good prospects for use in reactors of floating nuclear power units and low-capacity nuclear plants, as well as a tolerant fuel.

Structural Optimization Design and Strength Test Research of Connecting Rod Assembly of High-Power Low-Speed Diesel Engine

The connecting rod assembly of a high-power low-speed diesel engine has high quality and high cost. If the connecting rod component is damaged, the whole machine may be paralyzed, resulting in serious economic losses and safety problems, so it is necessary to carry out strength analysis and structure optimization, reduce the failure rate, and increase its life. This paper takes the connecting rod of a low-speed diesel engine as the research object, builds the crank connecting rod mechanism model, and carries on the strength simulation analysis through professional simulation software. During this period, the accurate S-N curve of connecting rod material is obtained through a fatigue test, and the static strength test of the connecting rod assembly is carried out by an electro-hydraulic servo universal testing machine. The numerical modeling is validated based on the test results. Therefore, the influence of the structural parameters of the cross-section and the large end transition fillet on the stress of the connecting rod is analyzed. The results show that optimizing matching between the large end fillet of the connecting rod and the long diameter of the rod section not only reduces the mass but also improves the safety factor. After optimizing the structure of the connecting rod, the mass of the connecting rod is reduced by 5.85%, the maximum stress is reduced by 13.7%, and the safety factor is increased by 16.0%. In addition, due to the low-speed diesel engine connecting rod assembly weight is big, and the simulation computation efficiency is low, this paper by studying the influence of the cross-section parameters of the rod body and the large end transition fillet on the stress of the connecting rod, fitted the empirical formula calculating the maximum stress of connecting rod, for this model and similar type in the conceptual design, technology design provides a new analysis method, improved the efficiency of structural optimization and strength analysis of connecting rod assembly, filled the research gap of strength analysis and structural optimization of low-speed diesel engine connecting rod.

Analysis on the influence of protection electrodes on the capacitance control rod position sensor

Control rod position sensors are the core measuring components of the control rod drive system. For the capacitance control rod position sensor with protection electrodes, the sensitivity of the sensor is obtained by experiments. The calculated model of the sensor is established, and it is verified by experimental results. Based on the calculated model, the regulation method of protection electrodes on the unevenness of the sensitivity field of the sensor is systematically studied. Performance analysis of the sensitivity field, the structure design, and error analysis of the sensor are carried out. The results show that the sensor sensitivity is 0.007 563 pF/mm and the maximum measuring error can be limited within ±0.5 mm, which can meet the actual use demands. The results provide a new technical scheme for the subsequent research of capacitance control rod position sensors.

Investigation of PTC124-mediated translational readthrough in a retinal organoid model of AIPL1-associated Leber congenital amaurosis.

SummaryLeber congenital amaurosis type 4 (LCA4), caused by AIPL1 mutations, is characterized by severe sight impairment in infancy and rapidly progressing degeneration of photoreceptor cells. We generated retinal organoids using induced pluripotent stem cells (iPSCs) from renal epithelial cells obtained from four children with AIPL1 nonsense mutations. iPSC-derived photoreceptors exhibited the molecular hallmarks of LCA4, including undetectable AIPL1 and rod cyclic guanosine monophosphate (cGMP) phosphodiesterase (PDE6) compared with control or CRISPR-corrected organoids. Increased levels of cGMP were detected. The translational readthrough-inducing drug (TRID) PTC124 was investigated as a potential therapeutic agent. LCA4 retinal organoids exhibited low levels of rescue of full-length AIPL1. However, this was insufficient to fully restore PDE6 in photoreceptors and reduce cGMP. LCA4 retinal organoids are a valuable platform for in vitro investigation of novel therapeutic agents.

Targeting early proximal-rod component substrate FlgB to FlhB for flagellar-type III secretion in Salmonella.

The Salmonella flagellar secretion apparatus is a member of the type III secretion (T3S) family of export systems in bacteria. After completion of the flagellar motor structure, the hook-basal body (HBB), the flagellar T3S system undergoes a switch from early to late substrate secretion, which results in the expression and assembly of the external, filament propeller-like structure. In order to characterize early substrate secretion-signals in the flagellar T3S system, the FlgB, and FlgC components of the flagellar rod, which acts as the drive-shaft within the HBB, were subject to deletion mutagenesis to identify regions of these proteins that were important for secretion. The β-lactamase protein lacking its Sec-dependent secretion signal (Bla) was fused to the C-terminus of FlgB and FlgC and used as a reporter to select for and quantify the secretion of FlgB and FlgC into the periplasm. Secretion of Bla into the periplasm confers resistance to ampicillin. In-frame deletions of amino acids 9 through 18 and amino acids 39 through 58 of FlgB decreased FlgB secretion levels while deleting amino acid 6 through 14 diminished FlgC secretion levels. Further PCR-directed mutagenesis indicated that amino acid F45 of FlgB was critical for secretion. Single amino acid mutagenesis revealed that all amino acid substitutions at F45 of FlgB position impaired rod assembly, which was due to a defect of FlgB secretion. An equivalent F49 position in FlgC was essential for assembly but not for secretion. This study also revealed that a hydrophobic patch in the cleaved C-terminal domain of FlhB is critical for recognition of FlgB at F45.

Study and numerical analysis of Von Mises stress of a new tumor-type distal femoral prosthesis comprising a peek composite reinforced with carbon fibers: finite element analysis

Research on carbon-fiber-reinforced polyetheretherketone (CF-PEEK/CFR-PEEK) as a bone tumor joint prosthesis remains limited. Herein we numerically determine the feasibility of CF-PEEK material containing 30% Wt carbon fiber (CF30-PEEK) as a material for the dual-action tumor-type distal femoral prosthesis. Use CT scan method to build a complete finite element model of the knee joint. Simulate the resection of the distal femoral tumor, and then reconstruct it with the dual-action tumor-type distal femoral prosthesis. The femoral condyle and extension rod components were simulated with cobalt chromium molybdenum (CoCrMo), PEEK and CF30-PEEK materials respectively. When simulating the standing state, a vertical stress of 700 N is applied to the femoral head. When simulating the squatting state, a vertical stress of 2800 N is applied to the femoral head. The displacement and rotation angle of each node of the distal tibia are fully restrained in three directions (X-axis, Y-axis, Z-axis). We examined the stress magnitude, stress distribution, and stability of the prosthesis and each of its components by means of finite element analysis (FE analysis). The FE analysis results show: after replacing the distal femur and the extension rod with CF30-PEEK material, the stress is still evenly distributed, and the average stress is significantly reduced. In addition, the stability is similar to CoCrMo material. Therefore, CF30-PEEK is an appropriate material for this type of prosthesis.

CONCEPTUAL DESIGN OF CONTROL ROD DRIVE MOTOR TYPE MAGNETIC JACK FOR NUCLEAR POWER PLANT

The Control Rod Drive Motor (CRDM) controls the reactor power of a G.A Siwabessy and automatically shuts it down during an emergency using a three-phase motor that drives a ball-nut spindle attached to the magnetic SCRAM through the transmission gear. However, there are several weaknesses associated with this design, such as the inability of the ball nut to rotate when a disturbance occurs at the motor limit switch continuously. This causes the threads on the control rod shaft to wear out due to friction and release from the holder. Therefore, this research aims to develop a CRDM with a magnetic jack for a nuclear plant, which moves the extension shaft and the control rod components vertically and linearly. The control rod's motor must pull, insert, hold, or drop it from any point. This conceptual design is the first step in determining prototyping design criteria with a magnetic jack to understand the working mechanism. The control rod gripping motion simulation was also presented using ANSYS Rigid Dynamics to reduce the failure at the design phase before prototyping. The simulation results showed no collision on each component capable of affecting the overall system performance. Therefore, the control rod motor functions properly in carrying out the pulling and lowering movements on 19.1 mm infrequency.

Modulation of the Enzymatic Activity of the Flagellar Lytic Transglycosylase SltF by Rod Components and the Scaffolding Protein FlgJ in Rhodobacter sphaeroides.

Macromolecular cell-envelope-spanning structures such as the bacterial flagellum must traverse the cell wall. Lytic transglycosylase enzymes are capable of enlarging gaps in the peptidoglycan meshwork to allow the efficient assembly of supramolecular complexes. In the periplasmic space, the assembly of the flagellar rod requires the scaffold protein FlgJ, which includes a muramidase domain in the canonical models Salmonella enterica and Escherichia coli. In contrast, in Rhodobacter sphaeroides, FlgJ and the dedicated flagellar lytic transglycosylase SltF are separate entities that interact in the periplasm. In this study, we show that sltF is expressed, along with the genes encoding the early components of the flagellar hierarchy that include the hook-basal body proteins, making SltF available during the rod assembly. Protein-protein interaction experiments demonstrated that SltF interacts with the rod proteins FliE, FlgB, FlgC, FlgF, and FlgG through its C-terminal region. A deletion analysis that divides the C terminus in two halves revealed that the interacting regions for most of the rod proteins are not redundant. Our results also show that the presence of the rod proteins FliE, FlgB, FlgC, and FlgF displace the previously reported SltF-FlgJ interaction. In addition, we observed modulation of the transglycosylase activity of SltF mediated by FlgB and FlgJ that could be relevant to coordinate rod assembly with cell wall remodeling. In summary, different mechanisms regulate the flagellar lytic transglycosylase, SltF, ensuring a timely transcription, a proper localization and a controlled enzymatic activity. IMPORTANCE Several mechanisms participate in the assembly of cell-envelope-spanning macromolecular structures. The sequential expression of substrates to be exported, selective export, and a specific order of incorporation are some of the mechanisms that stand out to drive an efficient assembly process. Here, we analyze how the structural rod proteins, the scaffold protein FlgJ and the flagellar lytic enzyme SltF, interact in an orderly fashion to assemble the flagellar rod into the periplasmic space. A complex arrangement of transient interactions directs a dedicated flagellar muramidase toward the flagellar rod. All of these interactions bring this protein to the proximity of the peptidoglycan wall while also modulating its enzymatic activity. This study suggests how a dynamic network of interactions participates in controlling SltF, a prominent component for flagellar formation.

Radiation effects related to repaired BWR core shrouds

The material properties of the core shroud and supporting tie rod components are important factors for Boiling Water Reactor (BWR) life extension considerations. Given the variability of nickel and boron content found in 304 stainless steel shroud plates, and XM-19 and Inconel X-750 tie rod materials, this paper combines the latest spectral information in the vicinity of the core shroud to calculate hydrogen and helium gas production limits as well as atomic displacement damage spanning 80 full-power years (FPY) using the SPECTER code. Results indicate that, whereas boron has little effect on the atomic displacement damage, helium production from boron can be important and must be included in weldability assessments. Since the boron concentration is uncertain, helium generation is calculated assuming a composition range based on specifications and reported measurements. The results show that helium production caused by transmutations in the 304 SS shroud material are dominated by the concentration of boron and will have a significant impact on weldability after only a few years of service. For tie rods, the susceptibility to irradiation-assisted stress corrosion cracking (IASCC) has been assessed by determining helium production in Inconel X-750 IASCC specimens irradiated in the Advanced Test Reactor (ATR) reactor and correlating with the helium produced in a BWR. As a tie rod material in a high thermal neutron flux environment, Inconel X-750 is more likely to be IASCC sensitive during service in a BWR due to helium than the XM-19 stainless steel alloy because of a greater nickel content and boron concentration. Weldability of the core shroud plate material, IASCC of the tie rod materials, and the gamma photon contribution to radiation damage are discussed.

Precision Control Technology and Device for Miniature Bearing Assembly

The traditional assembly equipment of tension link components has a degree of automation and few types of equipment, which have a greater impact on the assembly quality, assembly accuracy, and assembly efficiency of the linkage mechanism. This article firstly combines the current assembly status of the tension connecting rod components in my country and proposes a high-precision press-fitting method for connecting rods with continuous clamping, alignment, press-fitting, and pre-tightening actions. Secondly, an assembly platform for high-precision automatic press-fitting of tension connecting rods was developed and designed, and the structure design of the high-precision tension connecting rod press-fitting platform and the working principle of each module were explained, including a non-destructive clamping mechanism, a two-degree-of-freedom macro-motion platform, and vision alignment module, and other designs. Then through the assembly force experiment, the distribution of the bearing press-fitting force is obtained. The platform can increase the assembly coaxially of the 10mm inner bearing to within 5μm.

Fabrication and Microstructure Optimization of TiAl Castings Using a Combined Melting/Pouring/Heat Treatment Device

In this paper, a vacuum melting furnace which combines melting, pouring, mold preheating and heat treatment was designed and built, for the purpose of fabrication and microstructure optimization of TiAl castings. The apparatus provides the accurate control of pouring, mold preheating and subsequent heat treatment with various cooling rates, which makes the complete process from casting to final heat treatment can be carried out in one equipment and avoids the sample transfer process from casting to heat treatment device. The performance of the furnace was evaluated by casting the Ti–48Al–2Cr–2Nb and high-Nb-containing TiAl sheet and rod components. The X-ray detection images and scanning electron microscope results showed that the cavity and segregation were eliminated obviously. Significantly, an optimal nearly lamellar microstructure and fine fully lamellar microstructure were obtained, respectively. In addition, the transmission electron microscopy results show the lamellar spacing size after moving out of the heat treatment chamber is thinner than that cooling in the chamber. The results are of interest to researchers devoted to technical innovations and modifications for TiAl investment casting at the industrial scale.

Self-assembly in rod/coil block copolymers: Degenerate behavior under nonconfinement

The self-assembly of block copolymers containing rigid blocks have received abiding attention due to its rich phase behavior and potential for use in a variety of applications. In this work, under asymmetric interactions between rod/coil components, the self-assembly of coil/coil/rod ABC triblock copolymers is studied using self-consistent field of lattice model. In addition to micelles, centrosymmetric lamellae (CSLM), lamellae, perforated lamellae, strips and gyroids, non-centrosymmetric (NCSLM) lamellae and wavy morphologies are observed as stable phases. The phase diagram of interaction between rod and coil components versus the rod fraction is constructed given a fixed interaction between coil components. For intermediate rod fraction, degenerate behavior is observed. NCSLM and CSLM are degenerate structures. It is found that the entropy of chain conformation plays an important role for this rich behavior. A mechanism of the degenerate behavior is proposed in coil/rod block copolymers under noncofinement. This study provides some new insights into the degenerate behavior of block compolymers, which can offer a theoretical reference for related experiments.

The Light and the Dark of Early and Intermediate AMD: Cone- and Rod-Mediated Changes Are Linked to Fundus Photograph and FAF Abnormalities.

The purpose of this paper is to describe the extent to which scotopic and photopic measures of visual function predict color fundus photograph (CFP) and fundus autofluorescence (FAF) changes in early and intermediate nonexudative AMD. Sixty-nine observers were recruited: 56 AMD patients (mean age, 73 ± 12.98 years) and 13 controls (mean age, 67.77 ± 9.72 years). A nonmydriatic retinal camera was used to obtain stereo fundus photographs and FAF images were recorded with a cSLO Heidelberg Spectralis HRA+OCT. Visual acuity (VA) was measured using an Early Treatment of Diabetic Retinopathy Study chart. Contrast sensitivity (CS) was assessed with a Pelli-Robson chart. Dark adaptation (DA) curves were recorded at 3° eccentricity using a PC-based technique. Analysis of these curves yielded five parameters: cone threshold (CT), cone time constant (CC), cone-rod break (α), slope of the second rod component (S2), and rod-rod break (β). Both cone and rod sensitivity recovery were grossly abnormal in the patients. The rod recovery slope (S2) most accurately predicted the fundus photograph-based grade and the FAF classification (ρ = 0.61 and ρ = 0.60, respectively; both P < 0.0001). CS showed a strong association with FAF (ρ = 0.50, P < 0.0001) and with fundus photograph-based grade (ρ = 0.38, P < 0.002). There was no correlation between VA and either imaging method. Dynamic, rod-based measures most accurately reflect the severity of early AMD. Although less specific to AMD than DA changes, static photopic abnormalities such as CS also correspond with morphologic changes. Assessment of function in early AMD should include dynamic rod- and cone-mediated measurements of sensitivity recovery.

Voltage-clamp recordings of light responses from wild-type and mutant mouse cone photoreceptors.

We describe the first extensive study of voltage-clamp current responses of cone photoreceptors in unlabeled, dark-adapted mouse retina using only the position and appearance of cone somata as a guide. Identification was confirmed from morphology after dye filling. Photocurrents recorded from wild-type mouse cones were biphasic with a fast cone component and a slower rod component. The rod component could be eliminated with dim background light and was not present in mouse lines lacking the rod transducin-α subunit (Gnat1-/- ) or connexin 36 (Cx36-/- ). Cones from Gnat1-/- or Cx36-/- mice had resting membrane potentials between -45 and -55 mV, peak photocurrents of 20-25 picoamps (pA) at a membrane potential Vm = -50 mV, sensitivities 60-70 times smaller than rods, and a total membrane capacitance two to four times greater than rods. The rate of activation (amplification constant) was largely independent of the brightness of the flash and was 1-2 s-2, less than half that of rods. The role of Ca2+-dependent transduction modulation was investigated by recording from cones in mice lacking rod transducin (Gnat1), recoverin, and/or the guanylyl-cyclase-activating proteins (GCAPs). In confirmation of previous results, responses of Gnat1-/- ;Gcaps-/- cones and triple-mutant Gnat1-/- ;Gcaps-/- ;Rv-/- cones recovered more slowly both to light flashes and steps and were more sensitive than cones expressing the GCAPs. Cones from all four mouse lines showed significant recovery and escaped saturation even in bright background light. This recovery occurred too rapidly to be caused by pigment bleaching or metaII decay and appears to reflect some modulation of response inactivation in addition to those produced by recoverin and the GCAPs. Our experiments now make possible a more detailed understanding of the cellular physiology of mammalian cone photoreceptors and the role of conductances in the inner and outer segment in producing cone light responses.