Numerical Uncertainty in Density Estimation for Background Oriented Schlieren

Background Oriented Schlieren (BOS) is an image-based density measurement technique. BOS estimates the density gradient from the apparent distortion of a target pattern viewed through a medium with varying density using cross-correlation, tracking, or optical flow algorithms. The density gradient can then be numerically integrated to yield a spatially resolved estimate of the density [1]. A method was recently proposed to estimate the a-posteriori instantaneous and spatially resolved density uncertainty for BOS [2] and showed good agreement between the propagated uncertainties and the random error. However, the density uncertainty quantification method could not account for the systematic uncertainty in the density field due to the discretization errors introduced during the numerical integration, which could be much larger than the displacement random errors [2]. In this work, we propose a method to estimate the numerical uncertainty introduced by the density integration in BOS measurements, using a Richardson extrapolation framework. A procedure is also introduced to combine this systematic uncertainty with the random uncertainty from the previous work to provide an instantaneous, spatially-resolved total uncertainty on the density estimates. The method will be tested with synthetic fields and synthetic BOS images.

Programmable pattern formation in cellular systems with local signaling

Complex systems, ranging from developing embryos to systems of locally communicating agents, display an apparent capability of “programmable” pattern formation: They reproducibly form target patterns, but those targets can be readily changed. A distinguishing feature of such systems is that their subunits are capable of information processing. Here, we explore schemes for programmable pattern formation within a theoretical framework, in which subunits process local signals to update their discrete state following logical rules. We study systems with different update rules, topologies, and control schemes, assessing their capability of programmable pattern formation and their susceptibility to errors. Only a fraction permits local organizers to dictate any target pattern, by transcribing temporal patterns into spatial patterns, reminiscent of the principle underlying vertebrate somitogenesis. An alternative scheme employing variable rules cannot reach all patterns but is insensitive to the timing of organizer inputs. Our results establish a basis for designing synthetic systems and models of programmable pattern formation closer to real systems.

Role of Computed Tomography (CT) Enterography in the Evaluation of Small Bowel Diseases

BACKGROUND Small bowel imaging often questions clinicians due to its long, tortuous and undulating morphology. The current study was undertaken to establish the efficacy of multidetector computed tomography (MDCT) enterography in the evaluation of small bowel diseases using iso-osmotic mannitol as oral contrast agent. METHODS A prospective observational study was conducted among thirty patients (mean age 40 years; range 14 - 66 years), 16 males and 14 females presenting with clinical suspicion of small bowel diseases based on clinical, laboratory or other imaging investigations underwent CT enterography on a 128 slice CT scanner using isoosmotic mannitol as neutral enteral contrast. RESULTS Intestinal tuberculosis was the most common diagnosis. Non neoplastic cases predominantly showed segmental symmetrical involvement with target pattern of enhancement. Small bowel tumours (adenocarcinoma) were seen in 2 cases. Neoplasms were associated with focal asymmetrical involvement with heterogeneous enhancement pattern. Computerized tomography enterography (CTE) clearly depicted the site, level and cause of the obstruction in all the patients with a sensitivity and specificity of 96 % and 100 % respectively. Diagnostic accuracy of CTE in detection of small bowel diseases came out to be 98 %. CONCLUSIONS CT enterography is an effectual, non-invasive, well-tolerated, sensitive and specific imaging modality for the evaluation of small bowel diseases which provides superior assessment of the intraluminal, mural and extraintestinal pathologies. KEY WORDS CT enterography, mannitol, Tuberculosis, Small Bowel

Programmable pattern formation in cellular systems with local signaling

Diverse complex systems, ranging from developing embryos to systems of locally communicating agents, display an apparent capability of "programmable" pattern formation: They reproducibly form a target pattern, but this target can be readily changed. A distinguishing feature of such systems, as compared to simpler physical pattern forming systems, is that their subunits are capable of information processing. Here, we explore schemes for programmable pattern formation within a theoretical framework, in which subunits process discrete local signals to update their internal state according to logical rules. We study systems with different update rules, different topologies, and different control schemes, to assess their ability to perform programmable pattern formation and their susceptibility to errors. Only a small subset of systems permits local organizer cells to dictate any target pattern. These systems follow a common principle, whereby a temporal pattern is transcribed into a spatial pattern, reminiscent of the clock-and-wavefront mechanism underlying vertebrate somitogenesis. An alternative scheme employing several different rules can only form a fraction of patterns but is robust with respect to the timing of organizer cell inputs. Our results establish a basis for the design of synthetic systems, and for more detailed models of programmable pattern formation closer to real systems.

Alternative Design of Binary Phase Diffractive Optical Element with Non-π Phase Difference

It was found that binary phase diffractive optical element (DOE) with non-π phase difference had higher diffraction efficiency and adjustable zero-order intensity than a 0-π one. However, existing design methods are all based on the simulated annealing algorithm and thus computationally expensive. In this paper, a simple and efficient method using the iterative Fourier transform algorithm (IFTA) is proposed. In this method, the target pattern is first modified via reducing the zero-order intensity. Then, the IFTA is adopted to design the conventional 0-π DOE. Subsequently, the phase distribution remains unchanged and the phase difference is carefully adjusted to increase the zero-order intensity so that the reconstructed pattern is consistent with the target. To verify this method, several typical DOEs for beam splitting were designed and fabricated, and the result showed that the proposed method is effective.

Ultrasonographic Diagnosis of Ileal Intussusception in Calf

Background: Intussusception, characterized by invagination of an intestinal segment into the lumen of the adjacent segment, is one of the main causes of intestinal obstruction in cattle, and occurs more frequently in calves. The diagnosis of the disease is based on the history, clinical examination, and complementary exams, which are a challenge in this species, especially in calves, in which transrectal palpation is limited. As it is a non-invasive, effective, and low-cost test, ultrasonography could be an important tool in the diagnosis of intestinal obstructions, in which time is essential for the prognosis. Therefore, the objective was to report a case of intussusception in a calf diagnosed by ultrasound.Case: A 4-month-old calf, weaned at 3 months and raised intensively, was treated at the Clínica de Bovinos de Garanhuns, campus of the Universidade Federal Rural de Pernambuco (CBG/UFRPE), with a history of apathy, anorexia, and dyschezia for 3 days. On physical examination, fever, moderate dehydration, tachycardia, tachypnea with polypnea, bilaterally bulging abdomen, sound of fluid on ballottement, ruminal and intestinal hypomotility, and melena were observed. The hematological findings revealed leukocytosis due to neutrophilia (degenerate neutrophils), hypoproteinemia, and hyperfibrinogenemia. The analysis of the ruminal fluid showed compromised microbiota and increased chloride content. The transabdominal ultrasonography demonstrated, in the right ventral region, hypermotile and full small bowel loops and an increase in the volume of the peritoneal fluid. In addition, there was a segment of the small intestine which, in cross-section, showed multiple concentric rings (“onion rings”, “target pattern”, or “bull’s eye”) and adherence to adjacent loops, compatible with intestinal obstruction due to intussusception. Due to the seriousness of the clinical condition and the ultrasound findings, the animal was euthanized and the necropsy revealed focal fibrinous peritonitis and intestinal obstruction due to intussusception in ileum intestinal segments.Discussion: Intussusception has previously been reported in calves, however this is the first report of ultrasound diagnosis of the disease in Brazil. Although the etiology is rarely confirmed, the age group and recent changes in diet (weaning) were predisposing factors. The history, clinical signs, and laboratory tests were similar to those described in cattle with intussusception, however they may be present in other gastrointestinal illnesses. Other authors have also reported that the nonspecificity of the signs and the impossibility of performing transrectal palpation made it difficult to diagnose intestinal obstruction in calves without the use of other diagnostic tools. As it is a non-invasive and accurate technique, ultrasound has been used in ruminants for diagnostic purposes, including intestinal obstructions. In the present case, the main findings are described as the presence of a lesion with the appearance of multiple concentric rings, hypermotile, dilated, and full intestinal loops. The pathological findings were compatible with the ultrasound images and similar to those described by other authors, confirming the diagnosis. The use of ultrasonography as a diagnostic tool in cattle should be expanded, aiming at the early determination of diagnosis and prognosis, to reduce producer costs and animal discomfort. In cases of intussusception, late diagnosis makes treatment unfeasible.

One-dimensional uncertainty analysis in two-dimensional space pattern detection task: computational and human vision

Background: It is important to have a critical view of the support provided by Artificial Intelligence (AI) in medical context, in order to trust this support. Design and setting: Cross-sectional study (CAAE: 39292420.2.0000.5169) to measure/compare unidimensional uncertainty of an AI and a human performing the same task. Methods: to a simple algorithm written in Python (blob detection, OpenCV) and to an ophthalmologist were given the task of detecting a two-dimensional pattern (center of the optical disc) in 1,000 digital images of normal/ abnormal fundoscopies. Algorithm performed the task 1x, human performed the task 2x, both using digital register of spatial coordinates. Machine’s unidimensional level of uncertainty was measured by the respective comparison of the x and y coordinates recorded by machine and human. Human’s unidimensional level of uncertainty was measured by comparing the coordinates recorded by human itself. Data analysis was performed using R. Results: AI failed to detect the target pattern onlyin two images. On average, man and machine showed a higher level of uncertainty in the y- coordinates, which was greater (~100 units) in machine’s performance. The level of uncertainty was higher in altered fundoscopy images. Conclusion: the measure of uncertainty of AI and humans in the same task can help understand AI limitations and therefore define its usefulness as a medical support tool.

The bee Tetragonula builds its comb like a crystal

Stingless bees of the genus Tetragonula construct a brood comb with a spiral or a target pattern architecture in three dimensions. Crystals possess these same patterns on the molecular scale. Here, we show that the same excitable-medium dynamics governs both crystal nucleation and growth and comb construction in Tetragonula , so that a minimal coupled-map lattice model based on crystal growth explains how these bees produce the structures seen in their bee combs.

High-quality micropattern printing by interlacing-pattern holographic femtosecond pulses

To improve the efficiency of femtosecond laser direct writing, holographic femtosecond laser patterning using spatial light modulators has been widely used for the processing of micro/nanopatterns. However, the speckle noise of modulated optical fields severely limits the quality of fabricated patterns. We present a simple and effective method which involves interlacing a target pattern into a series of target subpatterns that consist of spaced spots to solve this problem. The separation of spots weakens the random interference between adjacent spots of optical fields, so the speckle noise reduces effectively, which improves the uniformity of the modulated optical fields and makes the fabricated patterns with high quality. With optimal interlacing numbers, complex micropattern arrays containing curved edges and sophisticated structures can be fabricated with superior quality and high efficiency. Binary holograms with improved optical characterization are realized by using the interlacing-pattern method, revealing the extensive potential of this method in micropattern processing and functional device fabrication with high quality and efficiency.