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PubMed2002

Analysis for the convergence problem of the plane-wave expansion method for photonic crystals.

The convergence feature of two types of plane-wave expansion methods commonly used for photonic crystals is analyzed. It is shown that the reason for the slow convergence of these plane-wave expansion methods is not the slow convergence of the Fourier series for the permittivity profile of the photonic crystal but the inappropriate formulation of the eigenproblem. A new formulation of the eigenproblem is presented to improve the convergence in the one-dimensional case.

Journal Article↗

PubMed2005

Optimal nonmonotonic convergence of the iterative Fourier-transform algorithm.

The increase of the monotonic convergence rate is an important issue for iterative Fourier-transform algorithms. However, the steepest monotonic convergence of the iterative Fourier-transform algorithm does not always promise an optimal solution in the design of a diffractive optical element. The optimal nonmonotonic convergence of the iterative Fourier-transform algorithm is investigated by employing a microgenetic algorithm. The proposed hybrid scheme of the iterative Fourier-transform algorithm and the microgenetic algorithm show nonmonotonic convergence, and this results in a superior design.

Journal Article↗

PubMed2006

NMDA and dopamine converge on the NMDA-receptor to induce ERK activation and synaptic depression in mature hippocampus.

The formation of enduring internal representation of sensory information demands, in many cases, convergence in time and space of two different stimuli. The first conveys the sensory input, mediated via fast neurotransmission. The second conveys the meaning of the input, hypothesized to be mediated via slow neurotransmission. We tested the biochemical conditions and feasibility for fast (NMDA) and slow (dopamine) neurotransmission to converge on the Mitogen Activated Protein Kinase signaling pathways, crucial in several forms of synaptic plasticity, and recorded its effects upon synaptic transmission. We detected differing kinetics of ERK2 activation and synaptic strength changes in the CA1 for low and high doses of neurotransmitters in hippocampal slices. Moreover, when weak fast and slow inputs are given together, they converge on ERK2, but not on p38 or JNK, and induce strong short-term synaptic depression. Surprisingly, pharmacological analysis revealed that a probable site of such convergence is the NMDA receptor itself, suggesting it serves as a detector and integrator of fast and slow neurotransmission in the mature mammalian brain, as revealed by ERK2 activation and synaptic function.

Animals↗

PubMed2004

Convergence and segregation of the multiple rod pathways in mammalian retina.

Using a multidisciplinary approach, we demonstrate that three different pathways are responsible for the transmission of rod signals across the mouse retina. Each pathway serves a primarily nonoverlapping range of stimulus intensities, with ganglion cells receiving either segregated or convergent inputs. For both on-center (ON) and off-center (OFF) ganglion cells, the primary rod pathway carries signals with the lowest threshold, whereas the secondary rod pathway is less sensitive by approximately 1 log unit. In addition, OFF signaling uses a tertiary rod pathway that is approximately 1 log unit less sensitive than the secondary. Although some ganglion cells received rod inputs exclusively from one of the pathways, others showed convergent inputs. Using pharmacological and genetic approaches, we defined classes of ON and OFF ganglion cells for which the scotopic inputs derive only from the primary pathway or from both primary and secondary pathways. In addition, we observed a class of OFF ganglion cell receiving mixed input from primary and tertiary pathways. Interestingly, OFF ganglion cells receiving convergent inputs from all three rod pathways or from the secondary and tertiary pathways together were never observed. Overall, our data show a complex arrangement of convergence and segregation of rod inputs to ganglion cells in the mammalian retina.

Action Potentials↗

PubMed1995

Effect of initial setting on convergence to optimal hearing aid setting using a simplex method.

We examined the final preferred frequency gain response (i.e. final setting) selected using different starting points (i.e. initial settings) with a modified simplex procedure. These starting points included a frequency response close to the one recommended by NAL-R (Byrne and Dillon, 1986), a frequency response with the high and low frequency gain set to the maximum (max), a frequency response with the high and low frequency gain set to the minimum (min), and one in-between these values (mid). The time taken to converge to the final setting was also recorded. Subjects judged the clarity of short discourse passages presented at 63 dB(A) in the presence of babble noise (S/N = 0). The results indicated that the majority of subjects selected the same preferred frequency response regardless of initial settings. Variations in initial settings mainly affected the convergence time to the final choice. The frequency response recommended by NAL-R required the least time to converge, while those of the extremes (min and max) required the longest convergence time. Clinical implications are discussed.

Adult↗

PubMedDate not supplied

Test-retest reliability and convergent validity of the Fatigue Impact Scale for persons with multiple sclerosis.

OBJECTIVE: The test-retest reliability and the convergent validity of the Fatigue Impact Scale (FIS) were evaluated using secondary data from 54 persons with multiple sclerosis (MS). METHODS: This reliability and validity study used FIS data from before and after two control periods to evaluate test-retest reliability. Convergent validity of the FIS with the Fatigue Severity Scale and with subscales of the SF-36 Health Survey was evaluated using data collected before the first control period. RESULTS: No significant differences between before and after FIS measurements and intraclass correlation coefficients ranging from .68 to .85 indicate that the FIS has good test-retest reliability except for the physical subscale. The expected moderate correlations between the FIS and several subscales of the SF-36 support its convergent validity. In contrast, the unexpected low correlation between the FIS and Fatigue Severity Scale does not support convergent validity. CONCLUSION: The FIS has adequate reliability and validity and is recommended to evaluate the effectiveness of fatigue management interventions such as energy conservation education for persons with MS.

Adult↗

PubMed2004

Convergence angle, occlusal reduction, and finish line depth of full-crown preparations made by dental students.

OBJECTIVE: To measure the convergence angle, incisal/occlusal clearance, and finish line depth, which indicate the amount of axial reduction of full metal-ceramic crown preparations made by final-year dental students. METHOD AND MATERIALS: A total of 157 preparations were assessed. Convergence angle and finish line depths were measured by Tool Maker Microscope, while crown height was measured using a digital caliber. RESULTS: The mean convergence angle, faciolingually and mesiodistally, was 22.4 and 25.3 degrees, respectively. The mean for molars was statistically significantly greater than that for other teeth. The incisal/occlusal reduction ranged from 1.8 to 2.2 mm and averaged 2 mm. Buccal shoulder finish line depth averaged 0.86 mm, and mean chamfer finish line depth was 0.74 mm lingually, 0.7 mm mesially, and 0.66 mm distally. The buccal shoulder for mandibular anterior teeth was significantly smaller than for other teeth and averaged only 0.45 mm. CONCLUSION: The mean convergence angle was clinically acceptable. However, shoulder depth was less than the recommended depth of 1.0 to 1.5 mm for metal ceramic crowns. Incisal/occlusal reduction was clinically adequate to provide enough structural durability and color matching.

Analysis of Variance↗

PubMed2006

[Influence of different convergence angles on the retention of cast metal post and core].

Fifty-four simulated tooth roots made of polymethacrylate (PMMA) were divided into six groups according to the root canal convergence angles of 0 degrees, 3.93 degrees, 5.71 degrees, 7.48 degrees, 11.31 degrees, 14.71 degrees. Cast post and cores were manufactured and cemented with Zinc phosphate cement (ZP). The retention capacities of the posts were tested. The bonding strength of ZP at different convergence angles were tested with some casted wafers, and linear regression was made. So the effect of interlocking and the proportion could be calculated. With these results, we made some curvilinear regressions. The results showed that the retention of cast post declined and the bonding strength of ZP fell with the increase of convergence angles. There were significant differences in the bonding strength and retention among groups, P<0.05. The experiment indicates that the dentists should reduce the convergence angles of posts as much as possible to obtain greater retention.

Cementation↗

PubMed1991

[Supranuclear vertical gaze palsy and convergence nystagmus caused by unilateral riMLF lesion].

We report a case showing supranuclear vertical gaze palsy and convergence nystagmus caused by a unilateral lesion of the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). The patient was a 54-year-old female with mitral stenosis and regurgitation and atrial fibrillation, who suddenly developed vertigo and double vision. She was admitted to our hospital because of persisting diplopia 4 days after onset, although vertigo had resolved within 1 hour. On admission she was alert, but presented with supranuclear vertical gaze palsy and convergence nystagmus. Other cranial nerves were intact and motor strength, deep tendon reflexes, sensations were also normal. There were no cerebellar signs. Cranial MRI demonstrated a unilateral ischemic lesion at the left thalamo-mesencephalic junction that involved the unilateral riMLF. Cerebral angiography revealed no abnormalities. Vertical gaze palsy has been reported to be caused by a lesion involving bilateral riMLF or unilateral posterior commissure, and convergence nystagmus usually by a lesion near or within the dorsal mesencephalon. However, recent reports have demonstrated a histopathologic evidence that vertical gaze palsy was caused by unilateral riMLF lesion. The present case confirms clinically that both vertical gaze palsy and convergence nystagmus can be developed by a lesion of unilateral riMLF.

Brain Diseases↗

PubMed1990

Relationship between critical convergence angle and surface defects in stone casts.

Surface defects on stone casts threaten the accuracy of cast restorations. The aim of this study was to examine the relationship between critical convergence angle and voids in stone casts. Three addition silicone materials, one condensation silicone material, and one polyether impression material were used. The highest convergence angle at which voids presented at the tip of the specimens was recorded, and the number of voids found at margins and line angles of the tooth preparations were counted. Results showed a positive and significant correlation between the critical convergence angle and the number of voids at margins and line angles of stone casts. Casts poured from polyether impressions registered significantly lower critical convergence angle values and presented with fewer voids than did those fabricated from silicone materials.

Calcium Sulfate↗

PubMed1989

[Theoretical patterns of the panel D-15 test in congenital red-green dichromats as a function of the chromaticity coordinate of the convergence points].

In order to determine whether or not the patterns of the panel D-15 test for congenital red-green dichromats change when the convergence point is changed, a simulation experiment was attempted assuming that dichromats arrange the color caps in the order of the slope of the line between the chromaticity coordinates of the color cap and the convergence point. For this procedure, chromaticity coordinates of the color cap were calculated using both the spectral distribution of standard illuminant C and the daylight fluorescent lamp (Toshiba-EDL). For this prediction, the chromaticity coordinates of the convergence points were changed according to y = 1-x. The results show several different patterns for both protanopia and deuteranopia under both illuminants. The range of the x chromaticity coordinates common to both illuminants was 0.6868 to 0.8552 when the protanopic patterns were obtained, while the range of the x chromaticity coordinates common to both illuminants for deuteranopic patterns was 1.0878 to infinity and minus infinity to -1.8153. As a result, it was suggested that the patterns of the panel D-15 test for red-green dichromats change according to the convergence points. Therefore, it was considered that this test cannot be used as a dependable measurement for color discrimination ability in cases showing dichromatic patterns.

Color Perception↗

PubMedDate not supplied

[Effect of the convergence angle of the ground tooth and the force of cast crown fastening using various types of cement].

The authors measured the effect of the convergence angle of the ground tooth on the fastening of cast crowns. The study was carried out on phantom models of teeth made of stainless steel with abutement convergence angles from 1 to 10 degrees. The force of the connection was measured using the Instron testing device. The avulsing force acted along the long axis of the abutement. Additionally the fixing force of phosphate, polycarboxylate and ionomer-glass was compared. A fall of the force of crown fastening was observed with increasing value of the convergence angle of the abutement, especially for phosphorus and ionomer-glass cement. The crowns fastened with polycarboxylate cement showed a threefold smaller fall of the fastening force with increasing value of the convergence angle of the abutement.

Crowns↗

PubMed1977

Interaction of converging peripheral and cerebellar cortical inputs on interpositus neurons of the cat.

Anesthetized and immobilized cats were used. The interval between the peripheral (conditioning) and the cortical (testing) stimulation equalled the latency of the response to effective peripheral input. Efferent nuclear neurons were identified by antidromic stimulations from contralateral brainstem nuclei. Various sequences of excitation and inhibition of different duration were induced by peripheral inputs. Initial excitation was observed in efferent neurons in cases of selective reactions to one of the peripheral stimulations. In some neurons both initial excitation and inhibition were observed. Besides selective reactions, in neurons with background activity a convergence of different peripheral inputs was seen. Responses to converging peripheral influences had usually a similar pattern of PSTH, with the shortest latent period to the dominant afferent input. Effects of cerebellar cortical stimulation were observed in nuclear neurons, both efferent and intranuclear. Effects of cortical stimulation were evoked from a limited area of the stimulated cortical surface; convergence and divergence of influences were observed. Peripheral and cortical stimulations induced various patterns of impulse activity of nuclear neurons. Interaction of converging peripheral and cortical inputs on a nuclear neuron was determined by the level of excitation or inhibition evoked by the peripheral stimulus and the phase of the cortical action (inhibition or "disinhibition"). Besides its participation in integrative processes at the nuclear level, the cerebellar cortex determines the duration and frequency of successive onsets of excitatory bursts at the "output" of the cerebellum, thus playing a decisive role in the coding of information to other structures of the brain.

Animals↗

PubMed1980

[Convergence effects evoked in neurons of the thalamic ventrolateral (VL) nucleus by the stimulation of paleo- and neocerebellar nuclear efferents].

The functional characteristics of the cerebellar nuclear outputs (fastigial, F.; interpositus, I.; dentate, D. nuclei) convergence on single neurones of th ventrolateral (VL) thalamic nucleus were studied in chloralosed, curarized and artificially ventilated cats (pCO2 continuously monitored), by means of the usual electrophysiological stimulation and intracellular recording techniques. From the experimental results on 90 VL n. neurones, with the analysis of the evoked cerebellar nuclear outputs unitary responses, it is possible to conclude: a) 69% of the reactive VL n. units are convergence neurones (CN); b) 34% of the CN are reactive to stimulation of all three cerebellar nuclei, showing similar patterns, with predominantly excitatory effects when located in the dorso-medial VL n. region and opposite patterns (excitation and inhibition) when located in the ventro-lateral VL n. region; c) 30% of the CN are reactive to the F.n and I.n. stimulation, often with opposite patterns; d) 36% of the CN are reactive to the D.n.-F.n. and D.n.--I.n. stimulation, usually with similar patterns. From this evidence, the effects evoked by the D.n. stimulation on to VL n. neurones seem to potentiate the F.n. and I.n. actions, whereas teh convergent F.n.-I.n. inputs exert often opposite effects on the same neurone. The dorso-medial and the ventro--lateral VL n. regions also seem to receive different actions from the converging cerebellar nuclear outputs. All the results are functionally discussed in terms of a possible integration between posture and voluntary movements at the level of the thalamic relay nucleus of the cerebello-cortical pathway.

Animals↗

PubMed1994

Convergence of topographic projections to the inferior colliculus from the auditory subcollicular nuclei.

Light and electron microscope studies on experimental material were undertaken in order to identify the composition of sets of specific subcollicular afferents converging to distinct groups of neurons in the inferior colliculus and the morphological characteristics of their parent cells. Microinjections of the retrograde tracer HRP placed in gride-like distribution into the CNIC revealed topographical order and quantitative differences in the convergence of axon projections from specific regions of the VCN, DCN, MSO, LSO, VNLL and DNLL. Pilot studies indicated very low number of labelled neurons and without discernible topographic arrangement in the auditory brain-stem nuclei, when the microinjections were in or largely in the cortical or external nuclei of the inferior colliculus. Neurons occupying the ventromedial quadrant of CNIC receive converging contralateral input projections from the dorsal part of the DCN, dorsomedial half of the LSO, and DNLL as well as ipsilateral connections from the ventral part of the VNLL, DNLL and the dorsal half of the MSO. The set of converging afferents to neurons in the ventrolateral quadrant of CNIC arises from the contralateral part of the VCN, the DNLL and from the ipsilateral ventral part of the VNLL, dorsal part of the MSO and the dorsolateral half of the LSO. Projections to cells of the dorsomedial and dorsolateral quadrants are mirror images of those to the ventral ones across the transverse axis of the CNIC.

Animals↗

PubMed1994

Gustatory, olfactory, and visual convergence within the primate orbitofrontal cortex.

Behavioral and perceptual responses to food depend on a convergence between gustatory, olfactory, and visual information. In previous studies a secondary cortical taste area has been found in the caudolateral orbitofrontal cortex of the primate. Furthermore, neurons with olfactory responses have been recorded in a more medial part of the orbitofrontal cortex, and visual inputs have been shown to influence neurons in an intermediate region. These studies suggest that the orbitofrontal cortex may act as a region for convergence of multiple sensory modalities including chemosensation. In the present study neurons throughout the caudal two-thirds of the orbitofrontal cortex of the macaque were tested to gustatory, to olfactory, and to visual stimulation to investigate whether convergence occurs. Neurons in this region of cortex were found that responded to stimulation of the taste, olfactory, or visual system. In addition, some neurons were found with bimodal responses, responding for example to both taste and olfactory, or taste and visual stimuli. Since these multimodal neurons were found in very close proximity to unimodal neurons, and the unimodal sensory neurons were intermingled, it is possible that the orbitofrontal cortex represents the first cortical area of convergence for these three modalities in primates.

Acoustic Stimulation↗

PubMed1996

Dynamic radio-ulnar convergence after the Darrach procedure.

We reviewed 23 patients who had had 25 Darrach procedures for traumatic or post-traumatic disorders of the wrist at a mean follow-up of 75.5 months (36 to 121). The mean age at the time of operation was 61.1 years (34 to 82). All patients were reviewed in person. Assessment included a history, a questionnaire on patient satisfaction and a detailed physical examination. Standardised radiographs of both wrists were taken with the patient's hands in a resting position and during maximal grip. Convergence of the distal ulnar stump towards the distal radius during maximal grip (dynamic radio-ulnar convergence) was seen in 14 wrists including five with actual contact (dynamic radio-ulnar impingement), but this produced symptoms in only two cases. The presence of dynamic radio-ulnar convergence did not correlate with grip strength, pinch strength, range of movement or wrist score, but was associated with increased length of excision of the distal ulna. Nineteen of the 23 patients were satisfied with the procedure. Dynamic radio-ulnar convergence is common after the Darrach procedure, but is rarely symptomatic; resection of the distal ulna remains a reliable procedure in the older patient with pain and loss of movement. Excision of the lower end of the ulna should be restricted to the least required to restore full rotation.

Activities of Daily Living↗

PubMed1996

[Color Doppler echocardiography of the flow convergence region in vitro: effect of the orifice shape on proximal velocity profile].

The flow convergence method serves to determine flow across orifices (like valve leaks) by color Doppler. Both the PISA method (proximal isovelocity surface areas) and the PVP method (proximal velocity profile) were developed in vitro at circular orifice plates. Therefore, we studied the influence of a non-circular orifice shape on the color map of the flow convergence. Steady flow across orifices of the following shapes was imaged by color Doppler: Oval (6 x 2 mm), slit (12 x 1.5 mm), three-star (diameter 100, area 30 mm2), circular twin-orifice (two circular orifices diameter 2 mm at 10 mm distance from each other) and oval twin-orifice (two ovals 6 x 2 mm at 10 mm distance). As reference we imaged circular orifices with a similar opening area. The alias method was used to locate discrete velocities within the color map, and the proximal velocity profile along the flow center line was analyzed (mean of 24 subsequent images). The local velocity was plotted (y-axis) against its distance to the orifice (x-axis) providing proximal velocity profile curves. The more the orifice shape differed from circular, the more the proximal velocity profile was shifted downward: The profile proximal to the oval was not different from the reference profile proximal to the circular orifice. The profile proximal to the slit was considerably slowed, and proximal to the three-star was even slightly slower (local velocity -12 %, -23 % and -29 % at 14, 8 and 5 mm distance to the orifice). If the circular reference orifice corresponded to total flow across the twin-orifice, the proximal velocity profile of the latter was also shifted markedly downward (-20 %, -18 % and -23 % at 14, 8 and 5 mm distance to the circular twin-orifice). However, if the reference profile corresponded to flow across only one opening of the twin-orifice, the proximal velocity profile of the latter was shifted considerably upwards (+60 %, +71 % and +50 % at 14, 8, and 5 mm distance). Deviation of the orifice shape from circular leads to lower local velocities within the flow convergence; thus neglecting this orifice shape would result in underestimation of flow by the flow convergence method. However, presence of parallel neighboring flow increases the local velocities; neglecting this effect would lead to corresponding overestimation of flow.

Blood Flow Velocity↗