This study puts forward a powerful new strategy that allows highly efficient generation of the shaping transverse nondiffracting caustics that concentrate around the expected curve. First, under the ...condition of stationary phase approximation, as the typical example of caustic beams, the analytical formula of nondiffracting deltoid and pentagram caustics is theoretically derived. Based on the obtained analytical formula, the desired caustics of deltoid and pentagram are numerically simulated. Hence, their optical shape and the propagation characteristics of nondiffracting caustics can be investigated. Then, based on the given generating mechanism, the corresponding experimental system to experimentally explore the nondiffracting deltoid and pentagram caustics with good self‐healing properties is constructed. Compared with the previous generating methods, the proposed method has a high light energy utilization.
This study puts forward a powerful new strategy that allows highly efficient generation of the shaping transverse nondiffracting caustics that concentrate around the expected curve. First, the analytical formula of nondiffracting deltoid and pentagram caustics is theoretically derived. Then, the corresponding experimental system to experimentally explore the nondiffracting deltoid and pentagram caustics with good self‐healing properties is constructed.
Many animals avoid detection or recognition using camouflage tailored to the visual features of their environment.1,2,3 The appearance of those features, however, can be affected by fluctuations in ...local lighting conditions, making them appear different over time.4,5 Despite dynamic lighting being common in many terrestrial and aquatic environments, it is unknown whether dynamic lighting influences the camouflage patterns that animals adopt. Here, we test whether a common form of underwater dynamic lighting, consisting of moving light bands that can create local fluctuations in the intensity of light (“water caustics”), affects the camouflage of cuttlefish (Sepia officinalis). Owing to specialized pigment cells (chromatophores) in the skin,6 these cephalopod mollusks can dynamically adjust their body patterns in response to features of their visual scene.7,8,9 Although cuttlefish resting on plain or patterned backgrounds usually expressed uniform or disruptive body patterns, respectively,10,11,12 exposure to these backgrounds in dynamic lighting induced stronger disruptive patterns regardless of the background type. Dynamic lighting increased the maximum contrast levels within scenes, and these maximum contrast levels were associated with the degree of cuttlefish disruptive camouflage. This adoption of disruptive camouflage in dynamically lit scenes may be adaptive, reducing the likelihood of detection, or alternatively, it could represent a constraint on visual processing.
•Investigated how natural forms of dynamic lighting affect camouflage•Cuttlefish displayed stronger disruptive patterning under dynamic lighting•Disruptive camouflage may be a widely adopted strategy in dynamically lit scenes
Natural forms of dynamic lighting can rapidly change the appearance of visual scenes. Drerup et al. find that cuttlefish adopt disruptive body patterns under dynamic lighting, highlighting that dynamically lit scenes can affect the camouflage patterns animals adopt.
Nonoperative management of severe caustic injuries has demonstrated its feasibility, avoiding the need for emergency esogastric resection and resulting in low mortality rates. However, leaving ...superficial necrosis in place could increase the risk of esophageal stricture development. Data on the risk factors of esophageal stricture secondary to caustic ingestion are scarce. The aim of our study was to identify the risk factors for esophageal strictures after caustic ingestion at admission. From February 2015 to March 2021, all consecutive patients with esophageal or gastric caustic injury score ≥ II according to the Zargar classification were retrospectively analyzed. For each patient, we collected over 50 criteria at admission to the emergency room and then selected among them 20 criteria with the best clinical relevance and limited missing data for risk factor analyses. Among the 184 patients included in this study, 37 developed esophageal strictures (cumulative rate 29.4%). All esophageal strictures occurred within 3 months. In multivariate analyses, the risk factors for esophageal strictures were voluntary ingestion (cause-specific hazard ratio 5.92; 95% confidence interval 1.76-19.95, P = 0.004), Zargar's esophageal score ≥ III (cause-specific hazard ratio 14.30; 95% confidence interval 6.07-33.67, P < 0.001), and severe ear, nose, and throat lesions (cause-specific hazard ratio 2.15; 95% confidence interval 1.09-4.22, P = 0.027). Intentional ingestion, severe endoscopic grade, and severe ENT lesions were identified as risk factors for esophageal stricture following caustic ingestion. Preventive measures for this population require further evaluation.
Femto-photography Velten, Andreas; Wu, Di; Jarabo, Adrian ...
ACM transactions on graphics,
07/2013, Letnik:
32, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We present
femto-photography
, a novel imaging technique to capture and visualize the propagation of light. With an effective exposure time of 1.85 picoseconds (ps) per frame, we reconstruct movies ...of ultrafast events at an equivalent resolution of about one half trillion frames per second. Because cameras with this shutter speed do not exist, we re-purpose modern imaging hardware to record an ensemble average of repeatable events that are synchronized to a streak sensor, in which the time of arrival of light from the scene is coded in one of the sensor's spatial dimensions. We introduce reconstruction methods that allow us to visualize the propagation of femtosecond light pulses through macroscopic scenes; at such fast resolution, we must consider the notion of
time-unwarping
between the camera's and the world's space-time coordinate systems to take into account effects associated with the finite speed of light. We apply our femto-photography technique to visualizations of very different scenes, which allow us to observe the rich dynamics of time-resolved light transport effects, including scattering, specular reflections, diffuse interreflections, diffraction, caustics, and subsurface scattering. Our work has potential applications in artistic, educational, and scientific visualizations; industrial imaging to analyze material properties; and medical imaging to reconstruct subsurface elements. In addition, our time-resolved technique may motivate new forms of computational photography.
Ballistic miniband conduction in a graphene superlattice Lee, Menyoung; Wallbank, John R.; Gallagher, Patrick ...
Science (American Association for the Advancement of Science),
09/2016, Letnik:
353, Številka:
6307
Journal Article
Recenzirano
Odprti dostop
Rational design of long-period artificial lattices yields effects unavailable in simple solids. The moiré pattern in highly aligned graphene/hexagonal boron nitride (h-BN) heterostructures is a ...lateral superlattice with high electron mobility and an unusual electronic dispersion whose miniband edges and saddle points can be reached by electrostatic gating. We investigated the dynamics of electrons in moiré minibands by measuring ballistic transport between adjacent local contacts in a magnetic field, known as the transverse electron focusing effect. At low temperatures, we observed caustics of skipping orbits extending over hundreds of superlattice periods, reversals of the cyclotron revolution for successive minibands, and breakdown of cyclotron motion near van Hove singularities. At high temperatures, electron-electron collisions suppress focusing. Probing such miniband conduction properties is a necessity for engineering novel transport behaviors in superlattice devices.
Caustics method has been widely used in dynamic stress intensity factors (DSIFs) measurements in PMMA by the size of caustics patterns. However, caustics geometry may be different between low and ...high loading rate conditions. To make data interpretation of caustics method as precise as possible, in this paper, mode I crack propagation under drop weight and blast stress wave loadings were investigated by caustics method with high-speed photography. It was found that approximate circle caustics patterns occurred under drop weight loading, while ellipse caustics patterns appeared under blast stress wave loading. These caustics patterns with different geometry were recreated by mathematical simulation, and then a new relationship between DSIFs and diameters of caustics patterns was built for precise DSIFs measurements. Finally, optical microscopic view of fracture surfaces shown that circle and ellipse caustics patterns corresponded to smooth and rough fracture surfaces, respectively. This paper indicates that caustics geometry and fracture surface roughness are important considerations when measuring DSIFs by caustics method in high loading rate conditions, otherwise large errors may occur.
•Mode I SIFs measurements under drop weight and blast stress wave loadings were compared.•Circle and ellipse caustics patterns correspond to drop weight and blast stress wave loadings, respectively.•Ellipse caustics patterns were recreated mathematically.•Fracture surfaces were observed and linked to caustics geometry.
Ingestion of Caustic Substances Hoffman, Robert S; Burns, Michele M; Gosselin, Sophie
The New England journal of medicine,
04/2020, Letnik:
382, Številka:
18
Journal Article
Spent caustic streams (SCS) are produced during alkaline scrubbing of sulfide containing sour gases. Conventional methods mainly involve considerable chemical dosing or energy expenditures entailing ...high cost but limited benefits. Here we propose an electrochemical treatment approach involving anodic sulfide oxidation preferentially to sulfur coupled to cathodic caustic recovery using a two-compartment electrochemical system. Batch experiments showed sulfide removal efficiencies of 84 ± 4% with concomitant 57 ± 4% efficient caustic production in the catholyte at a final concentration of 6.4 ± 0.1 wt% NaOH (1.6 M) at an applied current density of 100 A m−2. Subsequent long-term continuous experiments showed that stable cell voltages (i.e. 2.7 ± 0.1 V) as well as constant sulfide removal efficiencies of 67 ± 5% at a loading rate of 47 g(S) L−1 h−1 were achieved over a period of 77 days. Caustic was produced at industrially relevant strengths for scrubbing (i.e. 5.1 ± 0.9 wt% NaOH) at current efficiencies of 96 ± 2%. Current density between 0 and 200 A m−2 and sulfide loading rates of 50–200 g(S) L−1 d−1 were tested. The higher the current density the more oxidized the sulfur species produced and the higher the sulfide oxidation. On the contrary, high loading rate resulted in a reduction of sulfide oxidation efficiency. The results obtained in this study together with engineering calculations show that the proposed process could represent a cost-effective approach for sodium and sulfur recovery from SCS.
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•Electrochemical spent caustic treatment allows economical product recovery.•Current density and sulfide loading rate determine sulfide oxidation products.•Sodium is recovered at high coulombic efficiencies and alleviates costs.•Reactor materials remained unaffected during long term electrochemical operation.
Caustic ingestion in adults may result in death or severe digestive sequelae. The scarcity of nationwide epidemiological data leads to difficulties regarding the applicability of their analysis to ...less specialized centers, which are nevertheless largely involved in the emergency management of adverse outcomes following caustic ingestion.
To assess outcomes associated with caustic ingestion in adults across a nationwide prospective database.
Adult patients aged 16 to 96 admitted to the emergency department for caustic ingestion between January 2010 and December 2019 were identified from the French Medical Information System Database, which includes all patients admitted in an emergency setting in hospitals in France during this period.
Esophageal caustic ingestion.
The primary end point was in-hospital patient outcomes following caustic ingestion. Multivariate analysis was performed to assess independent predictors of in-hospital morbidity and mortality.
Among 22 657 226 patients admitted on an emergency outpatient basis, 3544 (0.016%) had ingested caustic agents and were included in this study. The median (IQR) age in this population was 49 (34-63) years, and 1685 patients (48%) were women. Digestive necrosis requiring resection was present during the primary hospital stay in 388 patients with caustic ingestion (11%). Nonsurgical management was undertaken in 3156 (89%). A total of 1198 (34%) experienced complications, and 294 (8%) died. Pulmonary complications were the most frequent adverse event, occurring in 869 patients (24%). On multivariate analysis, predictors of mortality included old age, high comorbidity score, suicidal ingestion, intensive care unit admission during management, emergency surgery for digestive necrosis, and treatment in low-volume centers. On multivariate analysis, predictors of morbidity included old age, higher comorbidity score, intensive care unit admission during management, and emergency surgery for digestive necrosis.
In this study, referral to expert centers was associated with improved early survival after caustic ingestion. If feasible, low-volume hospitals should consider transferring patients to larger centers instead of attempting on-site management.
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