Horizontal Band Research Articles

Thin Phytoplankton Layers: Characteristics, Mechanisms, and Consequences

For over four decades, aggregations of phytoplankton known as thin layers have been observed to harbor large amounts of photosynthetic cells within narrow horizontal bands. Field observations have revealed complex linkages among thin phytoplankton layers, the physical environment, cell behavior, and higher trophic levels. Several mechanisms have been proposed to explain layer formation and persistence, in the face of the homogenizing effect of turbulent dispersion. The challenge ahead is to connect mechanistic hypotheses with field observations to gain better insight on the phenomena that shape layer dynamics. Only through a mechanistic understanding of the relevant biological and physical processes can we begin to predict the effect of thin layers on the ecology of phytoplankton and higher organisms.

A Face Recognition Scheme Using Wavelet Based Dominant Features

In this paper, a multi-resolution feature extraction algorithm for face recognition is proposed based on two-dimensional discrete wavelet transform (2D-DWT), which efficiently exploits the local spatial variations in a face image. For the purpose of feature extraction, instead of considering the entire face image, an entropy-based local band selection criterion is developed, which selects high-informative horizontal segments from the face image. In order to capture the local spatial variations within these highinformative horizontal bands precisely, the horizontal band is segmented into several small spatial modules. Dominant wavelet coefficients corresponding to each local region residing inside those horizontal bands are selected as features. In the selection of the dominant coefficients, a threshold criterion is proposed, which not only drastically reduces the feature dimension but also provides high within-class compactness and high between-class separability. A principal component analysis is performed to further reduce the dimensionality of the feature space. Extensive experimentation is carried out upon standard face databases and a very high degree of recognition accuracy is achieved by the proposed method in comparison to those obtained by some of the existing methods.

A Face Recognition Scheme Using Wavelet Based Dominant Features

In this paper, a multi-resolution feature extraction algorithm for face recognition is proposed based on two-dimensional discrete wavelet transform (2D-DWT), which efficiently exploits the local spatial variations in a face image. For the purpose of feature extraction, instead of considering the entire face image, an entropy-based local band selection criterion is developed, which selects high-informative horizontal segments from the face image. In order to capture the local spatial variations within these highinformative horizontal bands precisely, the horizontal band is segmented into several small spatial modules. Dominant wavelet coefficients corresponding to each local region residing inside those horizontal bands are selected as features. In the selection of the dominant coefficients, a threshold criterion is proposed, which not only drastically reduces the feature dimension but also provides high within-class compactness and high between-class separability. A principal component analysis is performed to further reduce the dimensionality of the feature space. Extensive experimentation is carried out upon standard face databases and a very high degree of recognition accuracy is achieved by the proposed method in comparison to those obtained by some of the existing methods.

Pallial origin of basal forebrain cholinergic neurons in the nucleus basalis of Meynert and horizontal limb of the diagonal band nucleus

The majority of the cortical cholinergic innervation implicated in attention and memory originates in the nucleus basalis of Meynert and in the horizontal limb of the diagonal band nucleus of the basal prosencephalon. Functional alterations in this system give rise to neuropsychiatric disorders as well as to the cognitive alterations described in Parkinson and Alzheimer's diseases. Despite the functional importance of these basal forebrain cholinergic neurons very little is known about their origin and development. Previous studies suggest that they originate in the medial ganglionic eminence of the telencephalic subpallium; however, our results identified Tbr1-expressing, reelin-positive neurons migrating from the ventral pallium to the subpallium that differentiate into cholinergic neurons in the basal forebrain nuclei projecting to the cortex. Experiments with Tbr1 knockout mice, which lack ventropallial structures, confirmed the pallial origin of cholinergic neurons in Meynert and horizontal diagonal band nuclei. Also, we demonstrate that Fgf8 signaling in the telencephalic midline attracts these neurons from the pallium to follow a tangential migratory route towards the basal forebrain.

Band growth and localization of vesicle exocytosis in the red alga Antithamnion nipponicum (Ceramiales)

In uniseriate ceramiacean red algae, intercalary cells grow in a longitudinal direction by the formation of new cell surface in narrow, transverse bands of the cell. This localized growth mode is known as ‘band growth’. In this study, the distribution of vesicle exocytosis in the axial cells of the red alga Antithamnion nipponicum was investigated by transmission electron microscopy in specimens prepared by freeze-substitution. Two zones of band growth, which were detected as dark, horizontal bands after fluorescent cell wall staining followed by 24-h incubation in stain-free medium, were observed in the apical and basal regions of the cell. The width of the band was much greater in the basal region than in the apical region. Comparisons between the total elongation of the cells and the total width of the apical and basal bands during a 24-h incubation indicated that all of the cell elongation could be attributed to band growth. A short incubation in stain-free medium revealed that cell elongation in the basal band occurred in a narrower zone, less than 5 µm wide. Small depressions in the plasma membrane and small vesicles located beneath the plasma membrane were observed in actively growing axial cells. The distribution of these structures was limited to the narrow zones near the bases of the cells (the basal bands) where cell elongation occurred. A significant longitudinal elongation of the axial cells was still detectable after 24-h treatment of the plants with the microtubule inhibitor griseofulvin or the actin filament inhibitor cytochalasin D, but there was scarcely any discernible localization of cell growth to the band. The inhibitory treatments also caused dispersion of the plasma membrane depressions and vesicles along the plasma membrane. These results suggest that these membranous structures are related to the vesicle exocytosis that occurs during longitudinal elongation of the axial cells of Antithamnion and that cytoskeletal elements, such as microtubules and actin filaments, control the localization of vesicle exocytosis and the mode of cell growth.

Seismogenic structure and processes associated with magma inflation and hydrothermal circulation beneath the East Pacific Rise at 9°50′N

A dense ocean bottom seismometer array recorded more than 7,300 microearthquakes between October 2003 and April 2004 on the fast spreading East Pacific Rise at 9°50′ N. A previous initial analysis of these data revealed the general structure of an along-axis oriented hydrothermal circulation cell, with an inferred down-flow zone near a 4th-order axial discontinuity, a horizontal band of seismicity overlying the axial magma chamber (AMC), and an upflow zone that correlates with activity patterns of hydrothermal vents. Here we present cross-correlation-based double-difference hypocenter locations that reveal further insight into the detailed structure and kinematics that control seismic failure. We find that the majority of events within the inferred down flow pipe occur near the surface where the entrenched seawater presumably lowers the frictional strength of faults generated by local tectonic stresses. Beneath the eastern side of the ridge axis, just above the AMC at ∼1.4 km depth, we observe repeated shear failure along well defined steeply east dipping faults. Composite focal mechanisms indicate reverse motion, suggesting that slip on these faults is caused by AMC inflation and possibly injection of magma into a narrow sill. We resolve a small counterclockwise skew in the strike of the reverse faults relative to the direction of the ridge axis, consistent with Nuvel 1A spreading direction suggesting that the regional tectonic stress field may be controlling the seismogenic structures at depth. Earthquakes on the reverse faults occur preferentially during peak extensional tidal stresses, indicating that these faults are critically stressed.

Geotechnical synthesis of 2D_Electrical resistivity tomography of geomaterial_laboratory model study

In this paper, a laboratory scale model study was conducted on interbeded geomaterial using electrical resistivity instrument. The electrical resistivity value of individual material was determined and modeled as mass scale. The tank was filled with composite geomaterial constituted of interbedding of cement mortar as hard layer and residual sedimentary soil. Forty-one copper electrodes of 15 cm long were used and installed at 4 cm spacing in the tank. The composite geomaterials were labeled as Model 1, Model 2 and Model 3, where they were referred respectively to interbedding of hard layer and layers of residual soil at natural dry state and wet state. The electrical resistivity terrameter was used to obtain the georesistivity pseudo-section by adopting Werner protocol. The georesistivity pseudo-sections were derived from 3 models simulated the subsurface of rock mass in humid tropic environment. The objective was to synthesize the composite georesistivity pseudo-section based on geo-engineering principle. It was observed that the pseudo-section of the composite geomaterial was represented by range of colors with range of georesistivity values. The horizontal bands of color differentiated the georesistivity of models vertically but constant in horizontal direction. The georesistivity value at material scale was comparable to the range of georesistivity values derived from the 2D electrical resistivity pseudo-sections. The contrasts in the conductivity of clay fraction, silica and electrolytes have differentiated the electrical resistivity pseudo-section of sandy soil mass and cement mortar hard material.

Clinical study of nail changes in leprosy and comparison with nail changes in diabetic patients

Nail changes in leprotic patients are not specific to leprosy, and may be observed in other peripheral neuropathies. Diabetes is one of the diseases that present with nail dystrophy secondary to peripheral neuropathy, vasculopathy, trauma and infections. Therefore, nail changes in diabetic neuropathy are expected to be very similar to that of leprosy. To evaluate the frequency and pattern of nail changes in Egyptian leprotic patients with the different spectrums of the disease, and to compare nail changes in leprosy with those seen in patients with diabetic neuropathy. The study included 115 leprosy patients and 60 patients with diabetic peripheral neuropathy. Nail examination was thoroughly carried out and various nail changes were recorded including the location of the involved nails (fingers, toes). Our study detected similar incidence of nail changes in both multibacillary (MB) (86%) and paucibacillary (PB) patients (86%). Flag sign (alternating horizontal bands of whitish and pinkish discoloration of the nail) observed in our study was not reported before. It was more commonly seen in MB patients (21%) than in PB patients (14%). Our results also revealed that the nail changes were more commonly seen in leprosy patients (86%) than in diabetic patients (68%). Nail changes in leprosy are multifactorial, and could be related to one or more of the following: neuropathy, endarteritis, trauma, drugs or superimposed infections. Nail changes in leprosy may be used as an additional clue that helps in the diagnosis.

An axial convective flow in a rotating tube with a longitudinal temperature gradient

47 The solution describing the established planar motion of a liquid in a horizontal band under the effect of a longitudinal temperature gradient and transverse gravity force is well known [1]. The asymptotic char� acter of this exact solution is confirmed by the results of [2], where the problem of convection in a long hor� izontal cuvette with a constant temperature gradient being held on its side boundaries was investigated by experimental and numerical methods. The generaliza� tion of a plane flow to the case of motion in a cylindri� cal channel of an arbitrary cross section is given in [3]. Other generalizations of this solution and a detailed bibliography are contained in review [4]. We consider below the convection in a rotating round tube excited by the interaction of the centrifugal force and thermal flow along the tube axis. In the simplest case, when the transverse gravity force is absent and the motion is

Self-matching bands in the paperfolding sequence

We compare term by term the paperfolding sequence with a copy displaced by d terms to obtain the matching fraction M (d). It is shown that M(d) has an interesting structure in that if d=2b(1+2s), then M(d)= |1-3/2b+1| thereby generating horizontal bands for each value of b. That is, M(d) depends only on b.

Ultrafast carrier dynamics in pristine and FeCl3-intercalated bilayer graphene

Ultrafast carrier dynamics of pristine bilayer graphene (BLG) and bilayer graphene intercalated with FeCl3 (FeCl3-G), were studied using time-resolved transient differential reflection (delta R/R). Compared to BLG, the FeCl3-G data showed an opposite sign of delta R/R, a slower rise time, and a single (instead of double) exponential relaxation. We attribute these differences in dynamics to the down-shifting of the Fermi level in FeCl3-G, as well as the formation of numerous horizontal bands arising from the d-orbitals of Fe. Our work shows that intercalation can dramatically change the electronic structure of graphene, and its associated carrier dynamics.

Magnetic Resonance Imaging of Tissues Compatible with Supernumerary Extraocular Muscles

To determine by magnetic resonance imaging (MRI) the prevalence and anatomy of anomalous extraocular muscle (EOM) bands. Prospective, observational case series. High-resolution, multipositional, surface coil orbital MRI was performed using T1 or T2 fast spin echo weighting with target fixation control under a prospective protocol in normal adult subjects and a diverse group of strabismic patients between 1996 and 2009. Images demonstrating anomalous EOM bands were analyzed digitally to evaluate their sizes and paths, correlating findings with complete ophthalmic and motility examinations. Among 118 orthotropic and 453 strabismic subjects, 1 (0.8%) orthotropic and 11 (2.4%) strabismic subjects exhibited unilateral or bilateral orbital bands having MRI signal characteristics identical to EOM. Most bands occurred without other EOM dysplasia and coursed in the retrobulbar space between rectus EOMs such as the medial rectus to lateral rectus, from superior to inferior rectus, or from 1 EOM to the globe. In 2 cases, horizontal bands from the medial rectus to lateral rectus muscles immediately posterior to the globe apparently limited supraduction by collision with the optic nerve. All bands were too deep to be approached via conventional strabismus surgical approaches. Approximately 2% of humans exhibit on MRI deep orbital bands consistent with supernumerary EOMs. Although band anatomy is nonoculorotary, some bands may cause restrictive strabismus.

Contact Stress at the Anterior Aspect of the Tibial Post in Posterior-Stabilized Total Knee Replacement

Retrieval studies have demonstrated polyethylene wear and deformation of the anterior aspect of the tibial post of posterior-stabilized total knee replacements. We are not aware of any study that has analyzed the effects of the design of the femoral notch and the anterior aspect of the tibial post of posterior-stabilized total knee replacements on contact area, stress, and location. The purpose of the present study was to determine the levels of contact stress generated in three posterior-stabilized total knee replacement designs when the femoral intercondylar notch impinges on the anterior aspect of the tibial post. The contact area, mean and peak contact stresses, and contact location at the anterior aspect of the tibial post were determined when a posterior force of 100 N was applied to a NexGen LPS Flex, Genesis II, and Scorpio NRG total knee replacement. Measurements were performed at -15 degrees, -10 degrees, -5 degrees, 0 degrees, and 5 degrees of flexion of the femoral component both in neutral and with 5 degrees of rotation of the tibial component. Each measurement was sequentially performed five times, and the data were compared within and between the designs with use of analysis of variance and a post-hoc Scheffé F test. The NexGen LPS Flex exhibited two contact areas on the medial and lateral corners of the anterior aspect of the post, whereas both the Genesis II and Scorpio NRG exhibited a single horizontal band. The NexGen LPS Flex showed the largest total contact area of the three designs at -15 degrees, -10 degrees, and 5 degrees of flexion. The NexGen LPS showed the lowest mean contact stress at -15 degrees and 5 degrees but showed the highest peak contact stress at -5 degrees and 0 degrees. The Scorpio NRG showed the highest mean contact stress under all conditions and showed the highest peak contact stress at -15 degrees, -10 degrees, and 5 degrees. With 5 degrees of rotation of the tibial component, peak contact stress increased, relative to neutral, 1.2 to twofold (depending on the flexion angle) in the Genesis II design. The mean and peak contact stresses were variable for all three designs and the test conditions, approaching and in some cases exceeding the compressive yield stress for polyethylene. The geometry of the metal femoral notch and polyethylene tibial post in the axial and sagittal planes significantly affected contact area, mean and peak stresses, and contact location at the anterior aspect of the tibial post.

Validation of a method to estimate direct normal irradiance of UVA and PAR bands from global horizontal measurements for cloudless sky conditions in Valencia, Spain, by a measurement campaign

A method is proposed to provide measurement of direct normal solar irradiance of bands with wavelength ranges (315–400 nm, 400–700 nm) from measurements of global horizontal band irradiance for cloudless sky conditions in Valencia. Global and normal direct irradiance data for every air mass were obtained by applying the SMART2 model to the atmosphere of Valencia. The direct normal to global irradiance ratio was parameterized versus the relative optical air mass. A measurement campaign of global horizontal and diffuse irradiance of UVA and PAR bands was carried out in Valencia, after which, the inferred direct normal irradiance was compared with those provided by the method. The result of the comparison shows that the method is acceptably accurate. The proposed model tends to underestimate the direct normal irradiance of the UVA band by 6%, although for values below 25 W/m2 the model overestimates the direct irradiance by 6%, while for values above 25 W/m2 the model underestimates it by 10%. The other two error estimators used ranging from 11% to 15% are similar in the defined interval measurements in relation to the whole UVA band. Regarding the PAR band, the model overestimates the direct normal irradiance of the PAR band by only 2.2%. With this, the results of the PAR band are more conclusive, as it has been found that for direct normal irradiance values higher than 280 W/m2 the MBE error is almost zero and the other two estimator errors are small, about 5%.

The organisation of space and orientation preference in V1 of the marmoset monkey

The common marmoset monkey (Callithrix jacchus) is a small new world primate with excellent spatial vision. Previous electrophysiological studies have mapped the gross retinotopy of V1 and some of its response properties (for example Bourne et al, Cereb Cortex 2002 12:1132–45; Fritsches & Rosa, J Comp Neurol 1996, 372:264–82). In this study we present the first optical maps of the fine retinotopic organisation of V1 along with maps of orientation preference from the same regions of cortex. Specifically, marmosets were anaesthetised and paralysed using standard procedures (McLoughlin & Blasdel, NeuroImage 1998, 7:326–336) and refracted so that they focused onto a computer monitor that contained our moving stimuli. Preference for orientation was mapped by collecting camera frames when the marmoset viewed moving bars of one orientation and subtracting these frames from camera frames collected during presentation of the orthogonal orientation. Images were then processed using a combination of first frame analysis and the extended spatial decorrelation algorithm (Schiessl et al., IEEE Trans. on Biomed. Engin., 2000, 47:573–577.). Retinotopic strips of space were imaged in a similar manner. Our results demonstrate that V1 exhibits a smooth and regular retinotopic organisation with relatively isotropic cortical magnification, similar to that of the squirrel monkey (Blasdel & Campbell, J Neurosci. 2001, 8286–301). Vertical bands of space run parallel to the V1/V2 border (as determined histologically) with horizontal bands of space running at approximately right angles to the border. Strips of space aligned at 45 and 135 degrees run at intermediate angles. Orientation is mapped continuously over the surface of V1 but we find no obvious correlation between the retinotopic organisation of space and the organisation of orientation preference. This is in agreement with previous results of ours from V1 in the macaque monkey (McLoughlin & Blasdel, 1988, Soc. Neurosci. Abstr. 24:9).

Clinical Reasoning: An unusual pattern of optic disc swelling and visual loss

A 9-year-old boy was seen for bilaterally decreased vision. The patient noted gradual decrease in his visual acuity over a few months with difficulty seeing the blackboard. Otherwise, he was asymptomatic with no headaches. His examination showed visual acuities of 20/60 in his right eye and 20/400 in his left eye. For color vision, pseudo-isochromatic plates were 15/16 right eye and 0/16 in the left eye. There was a left relative afferent pupil defect. Ocular motility was normal. Funduscopy showed swelling of both optic discs affecting mainly the upper and lower aspects with sparing of the horizontal part of the disc, suggesting band atrophy. Maculae were normal (figure 1). Figure 1 Fundus photographs and Goldmann visual field (A) Bilateral optic disc swelling affecting the upper and lower aspect of the optic discs (arrows). There is a horizontal band of atrophy that shows no swelling. Note the blurry margins of the upper and lower pole in contrast with the clear margins on the nasal and temporal aspects of the discs. (B) Goldmann visual field showing complete bitemporal hemianopia, with some involvement of the nasal field and macular region in the left eye, in keeping with the reduced acuity. ### Questions for consideration: 1. What is the differential diagnosis? 2. What initial investigations would help you in narrowing the differential? Optic disc swelling with visual loss is always a worrisome presentation. Optic neuritis in children is usually bilateral and associated with …

THE DYNAMICS OF THREE-PLANET SYSTEMS: AN APPROACH FROM A DYNAMICAL SYSTEM

We study in detail the motions of three planets interacting with each other under the influence of a central star. It is known that the system with more than two planets becomes unstable after remaining quasi-stable for long times, leading to highly eccentric orbital motions or ejections of some of the planets. In this paper, we are concerned with the underlying physics for this quasi-stability as well as the subsequent instability and advocate the so-called "stagnant motion" in the phase space, which has been explored in the field of dynamical system. We employ the Lyapunov exponent, the power spectra of orbital elements and the distribution of the durations of quasi-stable motions to analyze the phase space structure of the three-planet system, the simplest and hopefully representative one that shows the instability. We find from the Lyapunov exponent that the system is almost non-chaotic in the initial quasi-stable state whereas it becomes intermittently chaotic thereafter. The non-chaotic motions produce the horizontal dense band in the action-angle plot whereas the voids correspond to the chaotic motions. We obtain power laws for the power spectra of orbital eccentricities. Power-law distributions are also found for the durations of quasi-stable states. All these results combined together, we may reach the following picture: the phase space consists of the so-called KAM tori surrounded by satellite tori and imbedded in the chaotic sea. The satellite tori have a self-similar distribution and are responsible for the scale-free power-law distributions of the duration times. The system is trapped around one of the KAM torus and the satellites for a long time (the stagnant motion) and moves to another KAM torus with its own satellites from time to time, corresponding to the intermittent chaotic behaviors.

Analysing the impact of reflectance distributions and well geometries on vertical surface daylight levels in atria for overcast skies

This study investigated the impacts of different diffuse reflectance distributions and well geometries on vertical daylight factors and vertical internally reflected components in atria. Two forms of reflectance distribution patterns of wall surface were examined: horizontal and vertical reflectance band variation. The square atrium models studied have a broader WI range of 0.25–2.0, which represent shallow, medium and high atria. Radiance, a powerful package based on backward ray tracing technique, was used for the simulations of vertical daylight levels. The results show that different reflectance distributions of square atrium walls do have an impact on the vertical daylight factors and vertical internally reflected components under overcast sky condition. The impact relates to the orientation of the band with different reflectance distributions on the wall. Compared with the vertical band surface, the horizontal band surface has a much more complicated effect. The horizontal distributions of the reflectances significantly affects the vertical daylight levels at the locations more than 30% atrium height on the wall. For an atrium with a height more than 1/2 the width, the effect tends to increase with the increasing well index. The vertical distributions of the reflectance, nevertheless, do not substantially take effect on the vertical daylight levels in atria except for some special reflectance distribution patterns.

Modeling Strain Localization Bands in Metal Foams

Experimental evidence has documented that during compression of metal foams, deformation is governed by the development of horizontal strain localization bands. Higher-order theories, such as the micromorphic continuum and gradient plasticity have been successfully employed to model experimental data. In the present study after comparing the aforementioned theoretical approaches, an analytical model, using gradient plasticity, is developed that can predict the strain distribution within the foam localization bands. Furthermore, in order to obtain a better understanding of the foam mechanics a numerical approach using cellular automata is used to predict the damage evolution and the stress–strain response during compression;the resulting stress-strain graphs are in very good agreement with experimental data.

The morphological features of the mediopatellar and lateral folds of the developing knee joint: a fetus cadaveric study

The aim of the study was to evaluate the morphological features of the mediopatellar and lateral folds in fetal knees in the absence of any exposure to certain stress factors such as exercise or trauma. The study was performed in the knee joints of 15 fetuses (6 males, 9 females) obtained as spontaneous abortion material at 20-34 weeks of gestation. The mediopatellar and lateral folds of the fetuses were classified into eight subgroups according to the following morphological features: A- Absence of folds; B- Short vertical band; C- Long vertical band; D- Narrow horizontal band; E- Broad horizontal band; F- Horizontal band accompanied by a vertical band; G- Horizontal band without a vertical band; H- Fenestrated band. The synovial membrane, covering the infrapatellar fat pad and forming the alar folds, extended upwards and formed the medial and lateral horizontal folds that covered the inferior part of the posterior aspect of the patella. These horizontal folds were thicker in the lower parts (close to their insertions) and became thinner towards the free ends. The horizontal band of the mediopatellar fold was observed in all cases, with an accompanying vertical band in 76.7% of the cases. A horizontally located lateral fold was absent in both knees of one fetus. The frequency of a horizontally located lateral fold was 93.3% and a vertical fold was accompanying in only 28.6% of these cases. It is of note that the horizontal band of the mediopatellar fold observed in all specimens has never been defined in previous classifications. In 10% of the knees, the vertically located part of the mediopatellar fold presented as a large band extending upward and being squeezed between the articular surface of the patella and the medial condyle of the femur. The lateral fold was observed as a large band in 10% of the knees. Another observation was that the higher level the vertical band of the mediopatellar and lateral folds began, the wider the horizontal band was, occupying more place in the patellofemoral space. It was remarkable that the frequencies of the vertically located parts of the lateral and mediopatellar folds in fetuses were higher than those reported for the adults in the literature. Our findings suggest that the resorption process of the mesenchymal tissue, particularly in the lateral part, continues until adulthood and causes age-dependent alterations in the formation of intra-articular folds. The synovial folds occupy more space between the patella and femur in the early stages of life than seen in adults. This may be a more frequent cause of unexplained knee pain in children than expected.