Apparent Occlusion Research Articles

On the Use of Circadian Cycles to Monitor Individual Young Plants

Occlusion is a very common problem in computer vision. The presence of objects seen as overlapped under a camera negatively impacts object recognition, object counting or shape estimation. This problem is especially important in plant imaging because plants are very self-similar objects which produce a lot of self-occlusions. A possible way to disentangle apparent occlusions is to acquire the same scene from different points of view when the object is motionless. Such a realization is not necessary if the objects move themselves under the camera and thus offer different points of view for free. This is the case in plant imagery, since plants have their own natural movements, including the so-called circadian rhythms. We propose to use these movements to solve some self-occlusion problems with a set of simple yet innovative sampling algorithms to monitor the growth of individualized young plants. The proposed sampling methods make it possible to monitor the growth of the individual plants until their overlap is definitive. The gain is significant with an average maximum duration of observation increase from 3 days to more than 10 days by comparison with a sampling method that would stop when the first overlap occurs.

Catheter-directed venography for evaluating internal jugular vein pseudo-occlusion

The incidence and effects of stenosis of the cerebral venous system are poorly understood. When noninvasive computed tomography venography (CTV) of the head and neck suggests complete internal jugular vein (IJV) occlusion, invasive catheter-directed venography can discordantly show venous patency. We compared CTV vs digital subtraction venography (DSV) in the evaluation of patency/occlusion in the suspected IJV and contralateral IJV. We queried the venous intervention database of our U.S. academic tertiary-care hospital to identify patients with complete or near-complete IJV occlusion per CTV from March 1, 2019 to March 1, 2020. We included patients with both noninvasive and invasive imaging of the target segment and the contralateral IJV. Four patients had suspected occlusion of the IJV at the skull base. Invasive catheter-directed venography consisted of DSV to assess direction of flow and vessel caliber, as well as manometry proximal and distal to areas of suspected stenosis. DSV showed patency in all 4 IJVs for which CTV had shown suspected occlusions. CTV findings of the contralateral IJVs were patency (n = 2), moderate stenosis (n = 1), and severe/critical stenosis (n = 1). Contralateral IJV caliber, measured by DSV, was concordant with CTV findings. Median mean-pressure gradients across the apparent occlusion and contralateral segments were 1 (range, 1–4) mmHg and 0 (range, 0–5) mmHg, respectively. Although noninvasive CTV may suggest absence of or attenuated flow within the IJV, this technique may be insufficient to establish complete occlusion. Catheter-directed venography can be used to evaluate patency, vessel caliber, and mean-pressure gradient.

Massively augmented hippocampal dentate granule cell activation accompanies epilepsy development

In a mouse model of temporal lobe epilepsy, multicellular calcium imaging revealed that disease emergence was accompanied by massive amplification in the normally sparse, afferent stimulation-induced activation of hippocampal dentate granule cells. Patch recordings demonstrated reductions in local inhibitory function within the dentate gyrus at time points where sparse activation was compromised. Mimicking changes in inhibitory synaptic function and transmembrane chloride regulation was sufficient to elicit the dentate gyrus circuit collapse evident during epilepsy development. Pharmacological blockade of outward chloride transport had no effect during epilepsy development, and significantly increased granule cell activation in both control and chronically epileptic animals. This apparent occlusion effect implicates reduction in chloride extrusion as a mechanism contributing to granule cell hyperactivation specifically during early epilepsy development. Glutamine plays a significant role in local synthesis of GABA in synapses. In epileptic mice, sparse granule cell activation could be restored by glutamine application, implicating compromised GABA synthesis. Glutamine had no effect on granule cell activation earlier, during epilepsy development. We conclude that compromised feedforward inhibition within the local circuit generates the massive dentate gyrus circuit hyperactivation evident in animals during and following epilepsy development. However, the mechanisms underlying this disinhibition diverge significantly as epilepsy progresses.

New Freshwater Gomphonemoid Diatoms from Streams in the Sierra Nevada Mountains, California, USA

Light and scanning electron microscopic observations of three new species of freshwater gomphonemoid diatoms are presented from mountain streams in California: Gomphonema californicum sp. nov., Gomphonema sierrianum sp. nov., and Gomphoneis oreophila sp. nov. Two of the species have morphological novelties related to the structure of the areolae, which are discussed in comparison with similar taxa. Gomphonema californicum shows a variety of areolar morphologies (i.e. lineola-like, c-shaped, and circular) within a single uniseriate stria. Unique to Gomphoneis oreophila, a member of the Herculeana subgroup, are the uniform areolae with circular openings without apparent occlusions. All of these species are distributed in remote streams of the Sierra Nevada Mountains of California, suggesting there are still new species to be found in this biodiversity-rich region.

Endovascular treatment in patients with acute ischemic stroke and apparent occlusion of the extracranial internal carotid artery on CTA

BackgroundIntra-arterial treatment is gaining importance in acute ischemic stroke, but its role in patients with apparent occlusion of the extracranial internal carotid artery (ICA) on computed tomographic angiography (CTA) is...

Temporal Bone Findings in a Case of Susac's Syndrome

To describe the histopathologic findings in the temporal bones of a patient with Susac's syndrome (SS). The key clinical features of SS consist of symptoms of encephalopathy, visual defects due to occlusion of branches of the retinal artery, and sensorineural hearing loss. The otopathology in SS has not been described. A 51-year-old woman was hospitalized with severe headache, rapidly progressive encephalopathy, and bilateral low-frequency sensorineural hearing loss. Magnetic resonance imaging showed lesions of the corpus callosum. Fluorescein angiography of the eyes showed focal areas of irregular retinal artery caliber and leakage from small vessels. SS was diagnosed. She died of a pulmonary embolus 1 month after onset of symptoms. Both temporal bones were prepared in celloidin and examined using light microscopy. Findings were nearly identical in both temporal bones. The apical halves of both cochleae showed widespread atrophy of structures of the cochlear duct (inner and outer hair cells, tectorial membranes, striae vasculares, spiral ligaments, and spiral limbi). The apical parts of both cochleae also showed apparent occlusion of capillaries within the stria vascularis and related areas of the cochlear duct. Cochlear neurons were present in normal numbers. There was no endolymphatic hydrops. The vestibular sense organs were normal for age. This first reported otopathologic case of SS with hearing loss showed atrophy and degeneration involving the apical halves of the cochlear duct without inflammation or infection. The findings were consistent with capillary occlusion as being responsible for the atrophy.

Probabilistic people tracking with appearance models and occlusion classification: The AD-HOC system

AD-HOC ( Appearance Driven Human tracking with Occlusion Classification) is a complete framework for multiple people tracking in video surveillance applications in presence of large occlusions. The appearance-based approach allows the estimation of the pixel-wise shape of each tracked person even during the occlusion. This peculiarity can be very useful for higher level processes, such as action recognition or event detection. A first step predicts the position of all the objects in the new frame while a MAP framework provides a solution for best placement. A second step associates each candidate foreground pixel to an object according to mutual object position and color similarity. A novel definition of non-visible regions accounts for the parts of the objects that are not detected in the current frame, classifying them as dynamic, scene or apparent occlusions. Results on surveillance videos are reported, using in-house produced videos and the PETS2006 test set.

Grouping puts figure-ground assignment in context by constraining propagation of edge assignment

Figure-ground organization involves the assignment of edges to a figural shape on one or the other side of each dividing edge. Established visual cues for edge assignment primarily concern relatively local rather than contextual factors. In the present article, we show that an assignment for a locally unbiased edge can be affected by an assignment of a remote contextual edge that has its own locally biased assignment. We find that such propagation of edge assignment from the biased remote context occurs only when the biased and unbiased edges are grouped. This new principle, whereby grouping constrains the propagation of figural edge assignment, emerges from both subjective reports and an objective short-term edge-matching task. It generalizes from moving displays involving grouping by common fate and collinearity, to static displays with grouping by similarity of edge-contrast polarity, or apparent occlusion. Our results identify a new contextual influence on edge assignment. They also identify a new mechanistic relation between grouping and figure-ground processes, whereby grouping between remote elements can constrain the propagation of edge assignment between those elements. Supplemental materials for this article may be downloaded from http://app.psychonomic-journals.org/content/supplemental.

Branch-Specific Sialylation of IgG-Fc Glycans by ST6Gal-I

Sialylated forms of the Fc fragment of immunoglobulin G, produced by the human alpha2-6 sialyltransferase ST6Gal-I, were identified as potent anti-inflammatory mediators in a mouse model of rheumatoid arthritis and are potentially the active components in intravenous IgG anti-inflammatory therapies. The activities and specificities of hST6Gal-I are, however, poorly characterized. Here MS and NMR methodology demonstrates glycan modification occurs in a branch-specific manner with the alpha1-3Man branch of the complex, biantennary Fc glycan preferentially sialylated. Interestingly, this substrate preference is preserved when using a released glycan, suggesting that the apparent occlusion of glycan termini in Fc crystal structures does not dominate specificity.

Illusory contours and surfaces without amodal completion and depth stratification

Cognitive and figural cues were studied in modified Ehrenstein figures made from letters of the alphabet instead of radial lines. Capital letters with and without terminators (L, J vs O, D) were used, oriented towards or away from the central gap. Three groups, of 14 subjects each, estimated the magnitude of either (i) the illusory contour, (ii) brightness enhancement, or (iii) apparent depth. Strong illusory contour formation and brightness enhancement, but no depth stratification, were perceived in figures devoid of apparent occlusion and amodal completion. These results demonstrate that the Ehrenstein illusion can arise from line ends––with no need for perceptual completion, showing that illusory boundaries and surfaces can be dissociated from apparent depth. Results support a bottom-up explanation in terms of end-stopped neurons in the visual cortex. Conversely, top-down processes appear to be responsible for depth stratification.

Preparation and Characterization of Composite Films of Polypyrrole with Metal Oxide /Hydroxides Using Galvanic Corrosion Reaction

The interactions of electropolymerized polypyrrole (PPy) films with evaporated aluminum and indium layers were investigated. The apparent occlusion of the metals into the PPy films was induced simply by their storage in air, giving rise to PPy-metal oxide/hydroxides composite films. More important, the composites showed stability against the electrochemical redox cyclings and metal-dependent electric conductivity. The formation of the composite materials was explained by assuming the corrosion reaction that proceeds in the galvanic cells formed between the PPy films and the metals. This assumption was experimentally supported by various control and simulation experiments.

Restoration of patency after apparent occlusion of the λ-graft's right branch

The "string sign" is a physiological and reversible response of the internal mammary artery (IMA) anastomosed to a moderately stenotic coronary artery. We describe a patient who presented postoperatively with a string sign phenomenon of the right branch of the lambda-composite graft. The graft regained full patency 32 months after the surgical procedure with progression of the native coronary artery stenotic lesion. This case demonstrates that under specific conditions, such as the progression of native coronary artery disease, a no-flow composite graft employing IMAs can only regain patency and functional status in the same way as in situ IMAs. These findings confirm that the IMA remains the conduit of choice not only for its long-term patency, but also for its physiological adaptation characteristics.

Distal vessel pullback angiography and pressure gradient measurement: an innovative diagnostic approach to evaluate the no-reflow phenomenon.

The angiographic appearance of "no-reflow" in saphenous vein grafts or native coronary arteries has been described following administration of thrombolytic therapy or performance of percutaneous transluminal coronary angioplasty or atherectomy. Apparent occlusion may represent spasm, dissection, thrombosis, or competitive collateral circulation, all of which must be excluded to make the diagnosis of "no-reflow." We describe an innovative approach to the diagnostic dilemma created by the appearance of "no-reflow" at coronary angiography. Pressure gradient measurement with distal vessel pull-back (retrograde) angiography provides maximal information regarding the severity of disease and the etiology of "no-reflow," while exposing both the patient and angiographer to less risk compared to standard strategies.

Harmonic decomposition of diastolic heart sounds associated with coronary artery disease

Previous studies done by our group have indicated heart sounds contain information useful in the detection of occluded coronary arteries. In order to further explore the application of advanced signal processing techniques to noninvasive detection of coronary artery disease, an eigenvector (minimum-norm) method is proposed because of its higher resolution, particularly in the presence of noise. In order to enhance the diastolic heart sounds and eliminate background noise, an adaptive filter was used as a preprocessor. The poles obtained with the minimum-norm method were used to determine the number of the coronary occlusions associated with coronary artery disease. Results showed that normal and abnormal records were incorrectly distinguished in only 18 of 100 cases. After separating normal from abnormal records, the data base including 100 normal and abnormal cases was divided into three groups (A, B and C). Group A, used to classify the patients with three or more occlusions, correctly identified 20 of 27 cases; Group B, used to classify the patients with one or two occlusions correctly identified 24 of 37 cases; and 32 of 36 of Group C, used to classify the patients with no apparent occlusions, were identified correctly. All measurements used a blind protocol without prior knowledge of the actual disease states of the patients to guard against human bias.

A diagnostic study of an apparent instant occlusion” cyclogenesis event during ERICA

Abstract The phenomenon commonly known to operational mereorologists as an “instant occlusion” is a signature in satellite imagery that indicates cyclogenesis. The process consists of the merging of a cloud mass associated with an Arctic vortex with a pre‐existing baroclinic zone resulting in a system that resembles a fully occluded system. Although the process may be familiar to operational meteorologists, the details of the structure and life cycle are not well understood. Although some work has been conducted on instant occlusions, most of the studies have involved cases in the eastern Atlantic and eastern Pacific. No such feature has ever been studied in Canada. A well documented instant occlusion case (which also happened to be a rapid deepener) occurred during the ERICA field experiment. Observations indicate that the merging process resulted in increased baroclinicity in the system as well as an interesting frontal structure. The influence of local topographic features of the eastern seaboard was i...

Venous Thrombi—A Cause of Intestinal Infarction After Aortic Valve Replacement—A Case Report

This report deals with a case of massive intestinal infarction without appar ent occlusion of the mesenteric artery after aortic valve replacement. Fibrin thrombi in the small veins of the gangrenous intestinal wall, which might be induced by vasospasm of the splanchnic vascular bed, seem to be a causative factor of this uncommon complication. The authors call attention to this compli cation in open-heart surgery because of the difficulty in diagnosis and its cata strophic consequence. Arteriography is essential for both diagnosis and therapy.

Clinical correlates of Doppler/ultrasound errors in the detection of internal carotid artery occlusion.

One recognized limitation of carotid Doppler/ultrasound is its accuracy in differentiating occlusion from near-total occlusion of the internal carotid artery, which is a crucial issue in management decisions. Clinical histories were reviewed in 58 patients with apparent occlusion of an internal carotid artery diagnosed by Doppler/ultrasound who also underwent angiography. False-positive results were detected in eight patients, for an overall accuracy of 86%. Among a group of 25 patients with acute cerebral or ocular events ipsilateral to an apparently occluded artery, false-positive results occurred in seven (accuracy of 72%). Among a group of 33 patients with asymptomatic or remotely symptomatic apparent occlusions, only one false-positive occurred, for an accuracy of 97%. This difference in accuracy between groups was significant. Thus, a Doppler/ultrasound diagnosis of occlusion was most inexact in those patients for whom the detection of continued patency was most likely to influence management.

Effects of artificial and natural diets on success in tip recording and on galeal chemosensillum morphology of European Corn Borer larvae

Abstract. Larvae of Ostrinia nubilalis(Hübner) (Lepidoptera: Pyralidae) were reared on artificial diet, fresh cut corn, or switched from diet to corn for 5 days prior to tip recording. Electrophysiological responses to a standard mixed chemical stimulus were obtained from the galeal uniporous chemosensilla of the early fifth‐stadium larvae. Mouthparts of some larvae were briefly treated with protease, then recorded again. Larvae were then processed for scanning electron microscopy (SEM) of chemosensilla terminal pores. Spike:noise ratios were significantly higher for corn‐reared, switched‐to‐corn, and protease‐ treated larvae, relative to diet‐reared larvae. Morphology of the chemo‐ sensilla terminal pores, as assessed by SEM, reveals that apparent occlusion of the pore tip is significantly greater for diet‐reared larvae relative to the other groups. The data suggest an association between quality of the electrophysiological recordings and physical blockage of the terminal sensillum pore. These data should serve as a caveat for those engaged in chemosensory studies of insect herbivores.

The Internal Carotid Artery With Chronic Complete Occlusion: Angiographic Evaluation

DOI: http://dx.doi.org/10.5915/15-3-12408 Chronic complete occlusion of the internal carotid artery is usually considered a contraindication to carotid endarterectomy in view of the very low rate of successful reconstruction. Our observation has shown, however, that a certain type of apparent complete occlusion in a small number of patients can be reconstructed with a relatively high rate of success. This particular type of occlusion is associated with a characteristic angiographic appearance. The involved internal carotid artery in these patients appears to be completely occluded about 7-10 mm distal to its origin, as opposed to occlusion exactly at the origin, which is typical for the inoperable complete occlusion. Five cases are reported with this type of potentially correctable occlusion. Successful reconstruction was achieved in three (60%) of these cases. The radiologist and particularly the vascular surgeon should be aware of and be able to recognize this condition so that proper management can be provided whenever indicated. Patho-physiologic explanation for this angiographic phenomenon is discussed.

The “occluded” internal mammary artery graft: Restoration of patency after apparent occlusion associated with progression of coronary disease

We report an instance of coronary reconstruction with internal mammary artery (IMA) in which catheterization demonstrated patency at 1 week, loss of patency at 1 year, and return of patency associated with progression of proximal coronary disease at 5 years. Although narrowing or distal occlusion of IMA grafts has long been recognized, and it has been suggested that this is a physiological or reversible phenomenon, this is the first instance in which reversibility has been documented.