An energy model of interframe interval effects in single-step apparent motion

A computational model was developed to explain the effects of an interframe interval (IFI) in single-step apparent motion experiments. In these experiments a stimulus appears in one position, disappears, and then reappears in a shifted position after a short or long IFI. If the luminance during the IFI matches the mean luminance of the stimulus frames, long IFIs result in perceived motion opposite the short-IFI conditions. Brighter or darker IFIs, however, do not support the reversed motion effect. The model possess the following defining characteristics: (1) a biphasic ("transient") channel whose signalled direction of motion reverses with changes of IFI duration; (2) a combined direction-opponent output which is the sum of directional responses developed in two channels--biphasic ("transient") and monophasic ("sustained"); (3) a signal/noise weighting of the contributions of the two channels to the final directional output of the system. Predictions of the model about the effects of IFI intensity and viewing eccentricity were tested and confirmed in two new psychophysical experiments. The interpretations of past studies which included a role for second-order motion mechanisms in explaining IFI duration effects were reexamined. Further empirical tests of the model were outlined.     

Hamstrings and psoas lengths during normal and crouch gait: implications for muscle-tendon surgery

OBJECTIVE: To study the relative contribution of the lung and the chest wall on the total respiratory system mechanics, gas exchange, and work of breathing in sedated-paralyzed normal subjects and morbidly obese patients, in the postoperative period. SETTING: Policlinico Hospital, University of Milan, Italy. METHODS: In ten normal subjects (normal) and ten morbidly obese patients (obese), we partitioned the total respiratory mechanics (rs) into its lung (L) and chest wall (w) components using the esophageal balloon technique together with airway occlusion technique, during constant flow inflation. We measured, after abdominal surgery, static respiratory system compliance (Cst,rs), lung compliance (Cst,L), chest wall compliance (Cst,w), total lung (Rmax,L) and chest wall (Rmax,w) resistance. Rmax,L includes airway (Rmin,L) and "additional" lung resistance (DR,L). DR,L represents the component due to viscoelastic phenomena of the lung tissue and time constant inequalities (pendelluft). Functional residual capacity (FRC) was measured by helium dilution technique. RESULTS: We found that morbidly obese patients compared with normal subjects are characterized by the following: (1) reduced Cst,rs (p < 0.01), due to lower Cst,L (55.3 +/- 15.3 mL x cm H2O-1 vs 106.6 +/- 31.7 mL x cm H2O-1; p < 0.01) and Cst,w (112.4 +/- 47.4 mL x cm H2O-1 vs 190.7 +/- 45.1 mL x cm H2O-1; p < 0.01); (2) increased Rmin,L (4.7 +/- 3.1 mL x cm H2O x L-1 x s; vs 1.0 +/- 0.8 mL x cm H2O x L-1 x s; p < 0.01) and DR,L (4.9 +/- 2.6 mL x cm H2O x L-1 x s; vs 1.5 +/- 0.8 mL x cm H2O x L-1 x s; p < 0.01); (3) reduced FRC (0.665 +/- 0.191 L vs 1.691 +/- 0.325 L; p < 0.01); (4) increased work performed to inflate both the lung (0.91 +/- 0.25 J/L vs 0.34 +/- 0.08 J/L; p < 0.01) and the chest wall (0.39 +/- 0.13 J/L vs 0.18 +/- 0.04 J/L; p < 0.01); and (5) a reduced pulmonary oxygenation index (PaO2/PAO2 ratio). CONCLUSION: Sedated-paralyzed morbidly obese patients, compared with normal subjects, are characterized by marked derangements in lung and chest wall mechanics and reduced lung volume after abdominal surgery. These alterations may account for impaired arterial oxygenation in the postoperative period.     

The whistle and the rattle: the design of sound producing muscles

Vertebrate sound producing muscles often operate at frequencies exceeding 100 Hz, making them the fastest vertebrate muscles. Like other vertebrate muscle, these sonic muscles are "synchronous," necessitating that calcium be released and resequestered by the sarcoplasmic reticulum during each contraction cycle. Thus to operate at such high frequencies, vertebrate sonic muscles require extreme adaptations. We have found that to generate the "boatwhistle" mating call (approximately 200 Hz), the swimbladder muscle fibers of toadfish have evolved (i) a large and very fast calcium transient, (ii) a fast crossbridge detachment rate, and (iii) probably a fast kinetic off-rate of Ca2+ from troponin. The fibers of the shaker muscle of rattlesnakes have independently evolved similar traits, permitting tail rattling at approximately 90 Hz.     

Yearly stepwise increments of the growth hormone dose results in a better growth response after four years in girls with Turner syndrome. Dutch Working Group on Growth Hormone

To optimize the growth promoting effect of growth hormone (GH), 65 previously untreated girls with Turner syndrome (TS), chronological age (CA) 2-11 yr, were randomized into 3 dosage regimen groups: A, B, and C, with a daily recombinant-human GH dose during 4 study years of 4-4-4-4, 4-6-6-6, and 4-6-8-8 IU/m2 b.s. The first GH dosage increase in groups B and C resulted in a significantly higher mean height velocity (HV) compared with constant dose group A. During the third year, when the dose was raised again only in group C, mean HV was significantly higher in groups B and C than in group A, and in group C compared with group B. In year 4 only group C mean HV remained significantly higher than group A. The pattern of change in HSDSCA (Dutch-Swedish-Danish Turner references) was identical; however, in year 4 mean delta HSDSCA in group B also remained significantly higher than group A. After 4 yr GH treatment, the following was determined. 1) The mean delta HSDSCA was significantly higher for groups B and C compared with group A, but not significantly different between groups B and C. 2) Although significantly higher compared with estimated values for untreated Dutch girls with TS, bone maturation of the GH treated girls was not significantly different between groups. 3) It was positively related with the degree of bone age (BA) retardation at start of study and negatively with baseline CA. 4) Both the modified Index of Potential Height (mIPHRUS) and a recently developed Turner-specific final height (FH) prediction method (PTSRUS), based on regression coefficients for H, CA, and bone age, showed significant increases in mean FH prediction, without significant differences between groups. PTSRUS values were markedly higher than the mIPHRUS values. Dose dependency could be shown for the area under the curve (AUC) for GH, but delta HSDSCA was not linearly related with AUC. Baseline GH binding protein (BP) levels were in 84% of the cases within the normal age range; the decrease in mean levels after 6 months GH was not significant. Mean insulin-like growth factor I (IGF-I) and IGFBP-3 plasma levels increased significantly, without significant differences between groups. delta HSDSCA during GH was dependent on IGF-I plasma levels at baseline and during the study period, beta-0.002 and beta-0.0004. Thus, a stepwise GH-dosing approach reduced the "waning" effect of the growth response after 4 yr treatment without undue bone maturation. FH prediction was not significantly different between treatment groups. Irrespective of the GH dose used, initiation of GH treatment at a younger age was beneficial after 4 yr GH when expressed as actual cm gained or as gain in FH prediction, but was not statistically significant when expressed as delta HSDSCA over the study period.     

Community resources for clients with mobility problems

Clients are leaving the hospital "quicker and sicker," and they frequently have acute care needs that must be met by resources outside the hospital setting. Community resources are diverse, vary widely from place to place, and have no central administration. Thus, using them can be challenging for both the nurse, client, and family. Reimbursement mechanisms underlie a person's ability to use resources and receive health care. By presenting two actual case scenarios where clients have mobility problems commonly seen by orthopaedic nurses, the authors discuss the community resources available, avenues of access to them, and their reimbursement mechanisms.     

Adaptive records for volume irradiance caching

In this paper, we present a new irradiance caching scheme using Monte Carlo ray tracing for efficiently rendering participating media. The irradiance cache algorithm is extended to participating media. Our method allows to adjust the density of cached records depending on illumination changes. Direct and indirect contributions can be stored in the records but also multiple scattering. An adaptive shape of the influence zone of records, depending on geometrical features and irradiance variations, is introduced. To avoid a high density of cached records in low interest areas, a new method controls the density of the cache when adding new records. This record density control depends on the interpolation quality and on the photometric characteristics of the medium. Reducing the number of records accelerates both the computation pass and the rendering pass by decreasing the number of queries to the cache data structure (Kd-tree). Finally, instead of using an expensive ray marching to find records that cover the ray, we gather all the contributive records along the ray. With our method, pre-computing and rendering passes are significantly speeded-up.     

Topology-controlled volume rendering

Topology provides a foundation for the development of mathematically sound tools for processing and exploration of scalar fields. Existing topology-based methods can be used to identify interesting features in volumetric data sets, to find seed sets for accelerated isosurface extraction, or to treat individual connected components as distinct entities for isosurfacing or interval volume rendering. We describe a framework for direct volume rendering based on segmenting a volume into regions of equivalent contour topology and applying separate transfer functions to each region. Each region corresponds to a branch of a hierarchical contour tree decomposition, and a separate transfer function can be defined for it. The novel contributions of our work are: 1) a volume rendering framework and interface where a unique transfer function can be assigned to each subvolume corresponding to a branch of the contour tree, 2) a runtime method for adjusting data values to reflect contour tree simplifications, 3) an efficient way of mapping a spatial location into the contour tree to determine the applicable transfer function, and 4) an algorithm for hardware-accelerated direct volume rendering that visualizes the contour tree-based segmentation at interactive frame rates using graphics processing units (GPUs) that support loops and conditional branches in fragment programs     

Pancreatic xanthomatous neuropathy associated with hyperlipidemia: a cause of abdominal pain mimicking chronic pancreatitis

"Hyperlipidemic crisis" is a term used to describe episodic abdominal pain in patients with hyperlipidemia. The morphologic correlates of this phenomenon have not been investigated and the etiology of the disorder is uncertain. We report a unique histologic finding in the pancreas of a 34-year-old woman with a 17-year history of episodic abdominal pain, sometimes accompanied by hyperamylasemia. At the age of 18 years, grossly elevated cholesterol and triglyceride levels were documented and type V hyperlipidemia was diagnosed. At the age of 34 years, subtotal pancreatectomy was performed for intractable abdominal pain. Histologic examination identified an increased number of enlarged pancreatic nerves that were infiltrated by foamy macrophages and encircled by fibrous tissue; endoneurial infiltration with macrophages occasionally split nerves into individual fascicles. Otherwise, the pancreas had only minimal fibrosis, nesidioblastosis, mucinous metaplasia of some pancreatic ducts, and scattered small collections of chronic inflammatory cells, subtle features suggesting very mild chronic pancreatitis. We propose that this novel xanthomatous neuropathy mimicked pancreatitis and was one of the underlying pathophysiologic mechanisms of abdominal pain in this patient. Further studies are necessary to document the prevalence of this new entity in patients with hyperlipidemia and to correlate its occurrence with "hyperlipidemic crisis" in those individuals.