Absence Of Shadow Research Articles

The art of the float.

For more than 2000 years, artists have exploited cast shadows to influence how objects appear to be positioned in a scene. A contact cast shadow can anchor an object to the ground and a detached cast shadow can make an object appear to float. However, there is a period of approximately 1000 years when there were virtually no cast shadows in art. How were states of contact versus floating depicted by artists without cast shadows? Here, we survey various techniques used by artists to anchor relative position with and without cast shadows. We then conduct experimental tests of the hypothesized surface attraction principles that underlie these techniques. In the absence of cast shadows, an object (a wooden box) was often seen as resting on a surface as long as that surface offered information about ground orientation and support (a tiled floor). When the ground surface was ambiguous and cloud-like (1/fnoise), the box was more likely to be seen to float. The presence of cast shadows made the box appear to contact the ground whether it was well-defined or ambiguous. Both shadows and surface support also increased the accuracy with which participants detected when the box was tilted up from the ground. These results indicate that artists long ago discovered the important power of support relationships to anchor objects to surfaces in the absence of shadows.

Defect 3-D Profile Estimation Using SEM Images

In semiconductor wafer manufacturing process, the height of random defects provides an important physical parameter to understand their impact and root cause. In this work, we demonstrate a novel method of defect height estimation based on SEM images without using ground truth or any external reference data of target defect types. Our method is applicable in conditions such as absence of shadows, self-obstruction by defects, lack of precise knowledge of SEM detector geometry and does not require sample tilting or imaging at different working distances, thereby removing major limitations of previous work. The error in our height estimation is 3% compared with 11% for current manual method on same dataset. In addition to improving accuracy and precision, our method reduces the time and manual effort required and can be easily extended to past and new defects for trend monitoring purpose, thus satisfying some key requirements of manufacturing environment.

Immersion, presence, and episodic memory in virtual reality environments

ABSTRACT Although virtual reality (VR) represents a promising tool for psychological research, much remains unknown about how properties of VR environments affect episodic memory. Two closely related characteristics of VR are immersion (i.e., the objective degree to which VR naturalistically portrays a real-world environment) and presence (i.e., the subjective sense of being “mentally transported” to the virtual world). Although some research has demonstrated benefits of increased immersion on VR-based learning, it is uncertain how broadly and consistently this benefit extends to individual components of immersion. Moreover, it is unclear whether presence may mediate the effect of immersion on memory. Three experiments assessed how presence and memory were affected by three manipulations of immersion: field of view, unimodal (visual only) vs. bimodal (audiovisual) environments, and the realism of lighting effects (e.g., the occurrence or absence of shadows). Results indicated that effects of different manipulations of immersion are heterogeneous, affecting memory in some instances and presence in others, but not necessarily both. Importantly, no evidence for a mediating effect of presence emerged in any of these experiments, nor in a combined cross-experimental analysis. This outcome demonstrates a degree of independence between immersion and presence with regard to their influence on episodic memory performance.

First known case of canine focal metatarsal fistulation in a Shikoku dog

AbstractThis report is the first to describe a case of canine metatarsal fistulation in a Shikoku dog. A male Japanese Shikoku (9 years old; weight, 18 kg) presented with an ulcer and hemorrhagic discharge from a fistula on the metatarsal region of the left hind leg. X‐ray examination showed a normal foot structure and the absence of shadows that might suggest the presence of a foreign body in the metatarsal region of the left hind leg. Histological examination of a biopsy of the lesion revealed granulation tissue; with mild infiltration by lymphocytes, plasma cells, and histiocytes, but no apparent infectious microorganisms. Oral administration of prednisolone with cyclosporin was effective in treating this disease, which might have been immune mediated.

Ultrasound and clinical characteristics of uterine smooth muscle tumors of uncertain malignant potential (STUMPs)

Objective(s)Smooth muscle tumors of uncertain malignant potential are rare uterine neoplasms. Their identification through imaging is still limited due to the few available descriptions in the scientific literature. The objective of this paper is to provide clinical and ultrasound features that could support an early identification of these neoplasms. Study designWe retrospectively evaluated preoperative sonographic data of patients receiving a histopathological diagnosis of smooth muscle tumors of uncertain malignant potential between 2014 and 2019 at the S. Anna Hospital (Turin, Italy), a tertiary gynecological center. Tumors were characterized on the basis of ultrasound images using terms and definitions according to the morphological uterus sonographic assessment group. ResultsA total of fourteen patients with smooth muscle tumors of uncertain malignant potential (20 lesions, including 18 pure and 2 with associated leiomyosarcoma) were identified. The median age was 47 years (range 28–77) and nine (64%) patients were of reproductive age. Six patients (43%) were asymptomatic, two (14%) presented with abdominal pain, two (14 %) with menorrhagia and four (29%) with both symptoms. Two (14%) patients developed local recurrences as uterine smooth muscle tumor of uncertain malignant potential and leiomyosarcoma, respectively.At ultrasound imaging, nine (69%) smooth muscle tumors of uncertain malignant potential were poorly or moderately vascularized and nine (82%) showed both circumferential and intra-lesional flows. Only three (15%) showed shadowing. The outlines were well-defined in seventeen cases (85%) and most (90%) showed isoechoic or mixed echogenicity with microcystic anechoic areas in fourteen (70%) of cases. Conclusion(s)Sonographic features of smooth muscle tumors of uncertain malignant potential may vary and a pathognomonic description has not been recognized. However, the identification of single or multiple lesions with specific ultrasound features should raise the suspicion of tumors of uncertain malignant potential. These features include isoechogenicity or mixed echogenicity, regular borders, presence of internal microcystic and anechoic areas, circumferential and intralesional vascularization ranging from minimal to high and absence of shadowing.

Adherence to Photographic Standards:A Review of ASPS and ASAPS Member Surgeons' Websites

Background: To evaluate the adherence of images on plastic surgeons' websites with the photographic standards established in 2006 by the American Society of Plastic Surgeons (ASPS) and the Plastic Surgery Foundation (PSF). Methods and findings: The membership rosters of the ASPS and the American Society for Aesthetic Plastic Surgery (ASAPS) were combined, and a random selection of 10% of these members was chosen for evaluation. Surgeons from the United States and Canada were included. Surgeons who were international members, who did not have websites or who had websites but did not have the images of interest were excluded. A total of 122 members of the 10% sample met the criteria. Breast augmentation, abdominoplasty and rhinoplasty images were reviewed and evaluated for focus, framing, positioning, presence of uniform background, absence of shadow, absence of clothing, absence of jewelry, use of photo garments, and exposure. Results: None of the websites evaluated universally adhered to the photographic standards, and the average was 66.3%. The average adherence was 76.2-77.0%, 64.6-63.8% and 57.6-58.2% for breast, face and abdominal images pre and postoperative respectively. Breast postoperative compliance was significantly improved for correct positioning, focus, and no cast shadow. Facial compliance was significantly improved for good background postoperatively whereas makeup compliance was higher preoperatively, and abdominal compliance was significantly improved for postoperative correct position although preoperative photo garments compliance was higher. Conclusion: Sixty-six percent of images on ASPS and ASAPS plastic surgeons' websites were adherent to the photographic standards, and pre and post adherence were similar.

Bootstrapping de-shadowing and self-calibration for scanning electron microscope photometric stereo

In this paper, we present a novel approach that addresses the blind reconstruction problem in scanning electron microscope (SEM) photometric stereo. Using only two observed images that suffer from shadowing effects, our method automatically calibrates the parameter and resolves shadowing errors for estimating an accurate three-dimensional (3D) shape and underlying shadowless images. We introduce a novel shadowing compensation model using image intensities for both cases of presence and absence of shadowing. With this model, the proposed de-shadowing algorithm iteratively compensates for image intensities and modifies the corresponding 3D surface. Besides de-shadowing, we introduce a practically useful self-calibration criterion by enforcing a good reconstruction. We show that incorrect parameters will engender significant distortions of 3D reconstructions in shadowed regions during the de-shadowing procedure. This motivated us to design the self-calibration criterion by utilizing shadowing to pursue the proper parameter that produces the best reconstruction with least distortions. As a result, we develop a bootstrapping approach for simultaneous de-shadowing and self-calibration in SEM photometric stereo. Extensive experiments on real image data demonstrate the effectiveness of our method.

Verifying Temporal Data in Geotagged Images Via Sun Azimuth Estimation

Image metadata provides useful information for applications such as image retrieval, content description and geolocation. However, it is relatively easy to tamper with this data using metadata manipulation tools. In this paper, we address the issue of authenticating the time of capture of an image based on its geolocation information. By utilizing a novel two-stage shadow detection process, we are able to estimate the azimuthal direction of the sun in an image and compare it against a calculated theoretical value to establish the authenticity of the time of capture. In case of ambiguous direction estimation from shadows, we improve an existing method using cues from vertical surfaces to resolve the ambiguity. The sky is used as a cue to perform verification in difficult scenarios such as the absence of shadows. Results are provided which show that our technique is able to estimate the sun azimuth with good accuracy. Additional results pertaining to date verification and camera direction estimation are also provided.

Photometric stereo using LCD displays

This paper considers the problem of shape-from-shading using nearby extended light sources. The paper reviews a number of methods that employ nearby illuminants, and describes a new technique that assumes a rectangular planar nearby distributed uniform isotropic illuminant. It is shown that such a light source illuminating a small Lambertian surface patch is equivalent to a single isotropic point light source at infinity, in the absence of shadowing. A closed-form solution is given for the equivalent point light source direction in terms of the illuminant corner locations. Equivalent point light sources can be obtained for distinct illuminant patterns allowing standard photometric stereo algorithms to be used. An extension is given to the case of a rectangular planar illuminant with arbitrary radiance distribution. Experimental results are shown demonstrating the application of the theory to photometric stereo using illumination from a LCD computer monitor. Details on the photometric calibration of the illumination source and image acquisition device are provided.

Impact of power control and lognormal shadowing on the mean transmit power of Bluetooth devices

This letter analyzes Bluetooth's power-control algorithm with a goal to study the mean transmit power required in the presence of lognormal shadowing. The following results are found. 1) A smaller power-control step size yields a lower mean transmit power. 2) When the standard deviations of lognormal shadowing are 3 and 6 dB, respectively, a Bluetooth device needs to consume 11.1 dB and 15.0 dB more in the transmit energy than the minimum one required in the absence of shadowing. 3) The transmit energy consumption varies by around 6 dB among Bluetooth devices as a result of the /spl plusmn/6 dB tolerance in the golden receive power range, which has a nominal size of 20 dB.

Development of the Endo-Periscope

The indirect method of observing and manipulating impairs the depth perception and eye-hand coordination of a laparoscopic surgeon. Important factors that impair depth perception are absence of shadows in endoscopic camera pictures and a restricted ability to observe organs from different sides. One important factor that impairs eye-hand coordination is the unnatural endoscopic line-of-sight, which results in a misorientation between the surgeon's hand movements and the instrument movements on the screen. In order to solve these problems, a new type of steerable endoscope was developed by close cooperation between the Delft University of Technology and the Tokyo Institute of Technology. The endoscope, called Endo-Periscope, is designed for use in combination with a miniature camera on the tip. Shadows are introduced by a light source on the shaft. The steerable tip, which can move in six degrees of freedom (DoF), can be used to observe anatomic structures from the side and to eliminate misorientations. The steerable tip is controlled by the handgrip via a spatial parallelogram mechanism. The handgrip contains an arrow that points always in the direction of the camera's line-of-sight. This provides intuitive control of the tip, showing how the camera is oriented in the abdominal cavity. The tip contains a new kind of spring that enables the tip to bend over 180° within a very small bending radius. We have applied for two international patents to cover the construction of the Endo-Periscope and the spring in the tip.

Theoretical background and conceptual solution for depth perception and eye-hand coordination problems in laparoscopic surgery

SummaryThe indirect method of observation and manipulation in laparoscopic surgery complicates the surgeon's depth perception and impairs his/her eye-hand coordination. Depth perception problems are due to misfits in accommodation and convergence, absence of shadows in endoscopic camera pictures and absence of stereo-vision and movement parallax. Eye-hand coordination problems are caused by the distant location of the monitor and by the fact that the surgeon's hand movements are rotated, mirrored and amplified when they appear on the monitor. These effects are very confusing, especially for trainee laparoscopic surgeons and require a long and intensive training period to overcome. This paper gives a theoretical background of the depth perception and eye-hand coordination problems. A technical concept of an endoscope positioning system is described that compensates misorientations by using a flexible 90° endoscope. Movement parallax is achieved using a motorised endoscope positioner controlled by the surgeon's head movements.

Diffuse Illumination as a Default Assumption for Shape-From-Shading in the Absence of Shadows

Sinusoidal luminance patterns appear dramatically saturated toward the brighter regions. The saturation is not perceptually logarithmic but exhibits a hyperbolic (Naka–Rushton) compression behavior at normal indoor luminance levels. The object interpretation of the spoke patterns is not consistent with the default assumption of any unidirectional light source but implies a diffuse illumination source (as if the object were looming out of a fog). The depth interpretation is, however, consistent with the hypothesis that the compressed brightness profile provided the neural signal for perceived shape, as an approximation to computing the diffuse Lambertian illumination function for this surface. The surface material of the images is perceived as non-Lambertian to varying degrees, ranging from a chalky matte to a lustrous metallic.

Landscape as viewed in the 320-nm ultraviolet

Wood’s 1910 study of the UV landscape by photography [ WoodR. W., Photog. J.50, 329 ( 1910)] is resumed. Through a narrow-band filter at 320 nm we find uniform skies even under broken clouds, a Rayleigh veiling that attenuates distant detail, an absence of shadows, and a low reflectivity for most natural substances (except snow). Rainbows broaden by a factor of more than 2 when the UV is included. The fact that glass is opaque at 320 nm causes cities to be dark at night in this wavelength, with astronomical consequences. The aphakic human eye (i.e., the eye after removal of its crystalline lens for a cataract condition) proves to have a practical sensitivity at 320 nm so that the aphakic observer can verify the unique character of the UV scene.

SUPPLEMENTARY FINDINGS ON THE SIALOGRAPHY OF TUMORS OF THE PAROTID GLANDS

Studies of the sialogram of 49 cases of tumor of the parotid glands performed by the author from 1950 to March, 1957 have revealed the following findings: 1. In cases of benign tumor, the presence of stenosis, dilatation or abnormal distribution of the ductal system was found, and the absence of shadows was observed in sialograms of type VIII 1. 2. In cases of malignant tumor, sialograms showed discontinuation or intermittent brea-king-off of the duct and the seepage of the contrast medium into the adjacent tissue, and the absence of shadows was observed in sialograms of type VIII 2. The seepage of the contrast medium was noted also in the residual gland. 3. In view of the fact that examination or treatment which had been given before the sialography was performed made the picture confused, sialography should be performed prior to the start of a treatment. 4. It is sometimes impossible to determine the nature of the tumor by means of sialog-raphy. Nevertheless, it is important that an accurate diagnosis should be made concerning the extent and the location of the tumor before it is referred for surgery. And acccurate diagnosis of a tumor is not possible without sialograpey. 5. In taking the sialograms of the tumor, no only lateral view but also anteroposterior view should be taken. If it seems necessary, anteroposterior tomography should also be perfo-rmed.

Gall Bladder Visualization in Experimental Achylia

Hines1 has reported 11 cases of Achylia gastrica in which the Graham test was done; these patients received the tetraiodophenolpphthalein intravenously. In most of these cases the gall bladder failed to visualize and in the others the shadow was reported as abnormal. Patients with absence of shadow showed visualization in some instances when HCl was given by mouth. More recently Davis and Talley2 have reported 20 cases of anacidity, in the majority of which they obtained good visualization although 9 of these cases presented clinical evidence of gall bladder disease. They gave the dye by mouth.To determine whether the absence of hydrochloric acid from the gastrointestinal tract was capable of interfering with gall bladder visualization, 5 dogs with pouches of the entire stomach (esophagoduodenal anastomosis) in which all of the gastric secretion drained to the outside were subjected to the Graham test. Tetraiodophenolphthalein, 0.18 gm. per kilo, was given intravenously and 10 to 12 hours later roentgenog...