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PubMed1990

Susceptibility of hepatic microcirculation to reperfusion injury: a comparison of adult and suckling rats.

Primary graft failure and vascular thromboses are frequent complications of liver transplantation, yet the mechanisms responsible remain unclear. Previous work from our laboratory has shown that hepatic reperfusion injury results in damage at the microvessel level. The present study was performed to determine whether an increased susceptibility of immature animals to microvascular injury during reperfusion might be a contributing factor in these complications. Suckling (35 to 50 g) or adult (250 to 400 g) rats were subjected to 30 or 60 minutes of hepatic ischemia to the left and median lobes followed by 90 minutes of reperfusion. Control animals were sham-operated, time-matched rats. At the end of reperfusion, fluorescein-labeled albumin was injected systemically to mark perfused sinusoids. Frozen sections of liver biopsies were viewed under fluorescence microscopy. The perfused sinusoid density was determined by point count analysis and expressed as the number of intersections of perfused sinusoids with 25 randomly oriented points superimposed on the sinusoid field. In sham-operated rats, at both 30 and 60 minutes, there were no differences between sucklings and adults. After 30 minutes of ischemia and 90 minutes of reperfusion, adults showed a significantly decreased density of perfused sinusoids (4.5 +/- 0.1 intersections per field) when compared with suckling rats (6.0 +/- 0.3 intersections per field, P less than .001). However, in rats subjected to 60 minutes of ischemia followed by 90 minutes of reperfusion, the microvascular injury was more severe in suckling rats (2.7 +/- 0.2 intersections per field) than in adults (4.7 +/- 0.2 intersections per field, P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed2005

Determination of atmospheric nitrate particulate size distribution and dry deposition velocity for three distinct areas.

In this study, both atmospheric particulates and dry deposited particulates were collected at a highway intersection, coastal location and suburban area in Taichung, Taiwan for the characterization of nitrate containing particulates (NCPs) in size distribution and dynamic properties. Collected particulates were placed in contact with nitron (C20H16N4) to form distinctive products of NCPs, which were examined by a SEM. For total atmospheric particulates, the sum of NCP and non-nitrate containing particulate (NNCP), the average shape factor values are 1.69, 1.49, and 1.36 for the highway intersection, coastal area and suburban area, respectively. The calculated shape factors show no significant differences with sizes. Dry deposition fluxes and atmospheric concentrations at various size ranges were estimated. The mass distributed in fine particle range (<or=2.5 microm) were 45%, 40%, and 43% for NCP at the highway intersection, coastal, and suburban areas, respectively. The average dry deposition velocities (Vds) of total particulate are 2.5, 1.5, and 1.2 cm s(-1) for highway intersection, coastal area, and suburban area, respectively. The highest Vd was observed from samples taken at highway intersection, suggesting that dust resuspension and particulates from vehicles in the ambient air is of great significance. The Vds of total particulates range over three orders of magnitude for size ranges from 0.32 to 18 microm. The value of Vd increases with the diameter of particles significantly.

Air Movements↗

PubMed1999

Influence of patient positioning on dose-volume histogram and normal tissue complication probability for small bowel and bladder in patients receiving pelvic irradiation: a prospective study using a 3D planning system and a radiobiological model.

PURPOSE: A prospective study was undertaken to evaluate the influence of patient positioning (prone position using a belly board vs. supine position) on the dose-volume histograms (DVHs) of organs of risk, and to analyze its possible clinical relevance using radiobiological models. METHODS AND MATERIALS: From November 1996 to August 1997 a computed tomography (CT) scan was done in the prone position using a belly board and in supine position in 20 consecutive patients receiving postoperative pelvic irradiation because of rectal cancer. Using a three-dimensional (3D) planning system (Helax, TMS) the DVH for small bowel, bladder, a standard planning target volume (PTV) of postoperative irradiation of rectal cancer, the intersection of volume of PTV and small bowel (PTV intersection V(SB), respectively, of PTV and bladder (PTV intersection V(B)) were defined in each axial CT slice. The normal tissue complication probability (NTCP) was determined by the radiobiological model of Lyman and Kutcher using the tolerance data of Emami. For evaluation of late toxicity alpha/beta ratio was 2.5; for evaluation of acute toxicity, it was 10. Total dose was 50.4 Gy (1.8 Gy/fraction) (ICRU 50). RESULTS: Using the prone position compared to the supine position, the median volume of PTV intersection V(B) was reduced by 18.5 cm3 (62%). Median dose (related to the reference dose) to the bladder was 44.5% (22.4 Gy) in prone and 66.05% (33.3 Gy) in supine position (p<0.001). Median V(B) within the 90% (45.4 Gy), 80% (40.3 Gy), 60% (30.2 Gy), and 40% (20.2 Gy) isodose was significantly lower in the prone position when compared to the supine position. Using the radiobiological models, however, there was no difference of NTCP between prone position or supine position. In the prone position, median volume of PTV intersection V(SB) was reduced by 32.5 cm3 (54%). The median dose to small bowel was 30.85% (15.4 Gy) in the prone position and 47.35% (23.9Gy) in the supine position (p<0.001). Significant differences between prone and supine position were found for median V(SB) within the 90% (45.4 Gy), 80% (40.3 Gy), 60% (30.2 Gy), and 40% (20.2 Gy) isodose. According to the method of Lyman, median NTCP of small bowel was significant lower in prone than in supine position. CONCLUSION: The prone position with a standard belly board should be the standard positioning technique for patients receiving adjuvant postoperative radiation therapy following surgery of rectal cancer. Both irradiated volume and total dose to the organs of risk can be reduced significantly. As a consequence of this, radiation induced toxicity will be minimized.

Adult↗

PubMed2005

A multireference configuration interaction investigation of the excited-state energy surfaces of fluoroethylene (C2H3F).

Multireference configuration interaction with singles and doubles (MR-CISD) calculations has been performed for the optimization of conical intersections and stationary points on the fluoroethylene excited-state energy surfaces. For the planar ground state geometry, the vertical spectrum including 3s and 3p Rydberg states was calculated. From this geometry, a rigid torsion around the CC bond strongly reduces the energy gap between S0 and S1 states. Furthermore, a search for the minimum of the crossing seam shows that there exists a conical intersection close to the twisted structure and two additional ones for cis and trans pyramidalized structures. These three intersections are connected by the same seam. We have shown that the Hula-Twist process is an alternative way to the direct CC twisting in order to reach this part of the seam. Other conical intersections were also located in the CH3CF and CH2FCH, H-migration, and C(3v) structures. The photodynamics of the system is discussed based on topological features of these intersections.

Journal Article↗

PubMed1999

The relationship between the intercondylar roof and the tibial plateau with the knee in extension: relevance for tibial tunnel placement in anterior cruciate ligament reconstruction.

The relationship between the intercondylar roof and the tibial plateau with the knee in full extension was studied in 100 patients with a unilateral anterior cruciate ligament (ACL) lesion. A lateral view of both knees in full extension with superimposition of the femoral condyles was obtained with the fluoroscope. We found that, in the normal knee, the roof line intersects the tibial plateau (roof-plateau intersection ratio) at 31.5% (SD +/- 5%) of its width and at 33.9% (+/- 5.4%) in the ACL deficient knee (P < .001). The difference was attributable to a subtle anterior tibial displacement in the ACL-deficient knee. Multiple regression analysis showed a direct relationship between roof-plateau intersection ratio and the angle between roof line and tibial plateau (P = .0006). A direct relationship of borderline significance (P = .06) was present with the knee recurvatum measured clinically. In conclusion, the roof-plateau intersection ratio has a wide range of variability (22% to 41%). The larger the roof-plateau angle the more posterior the roof-plateau intersection ratio.

Adolescent↗

PubMed2006

Geometric phase effects in the coherent control of the branching ratio of photodissociation products of phenol.

Optimal control simulation is used to examine the control mechanisms in the photodissociation of phenol within a two-dimensional, three-electronic-state model with two conical intersections. This model has two channels for H-atom elimination, which correspond to the (2)pi and (2)sigma states of the phenoxyl radical. The optimal pulse that enhances (2)sigma dissociation initially generates a wave packet on the S(1) potential-energy surface of phenol. This wave packet is bifurcated at the S(2)-S(1) conical intersection into two components with opposite phases because of the geometric phase effect. The destructive interference caused by the geometric phase effect reduces the population around the S(1)-S(0) conical intersection, which in turn suppresses nonadiabatic transitions and thus enhances dissociation to the (2)sigma limit. The optimal pulse that enhances S(0) dissociation, on the other hand, creates a wave packet on the S(2) potential-energy surface of phenol via an intensity borrowing mechanism, thus avoiding geometric phase effects at the S(2)-S(1) conical intersection. This wave packet hits the S(1)-S(0) conical intersection directly, resulting in preferred dissociation to the (2)pi limit. The optimal pulse that initially prepares the wave packet on the S(1) potential-energy surface (PES) has a higher carrier frequency than the pulse that prepares the wave packet on the S(2) PES. This counterintuitive effect is explained by the energy-level structure and the S(2)-S(1) vibronic coupling mechanism.

Journal Article↗

PubMed1984

Global factors in the Hermann grid illusion.

Most explanations of the Hermann grid illusion are local in nature. For example, in Baumgartner's model the effect is generated by the response of cells having concentric on-off or off-on receptive fields. Such models predict that the magnitude of the illusion at a given intersection should be the same whether that intersection is viewed in isolation or in conjunction with other intersections in a grid. Two experiments are reported. The first demonstrates that illusion magnitude grows with the number of intersections. The second shows that this growth is seen when the intersections are arranged in an orderly grid but not when they are placed irregularly. These results suggest that a purely local model for the Hermann grid illusion is not a complete explanation. Global factors must be involved.

Discrimination, Psychological↗

PubMed1986

A completely automatic method of processing 131I-labelled Rose Bengal dynamic liver studies.

A completely automatic method of measuring Rose Bengal uptake by the liver, expressed in terms of the half-time T1/2, is described. There is no requirement to construct time-activity curves with blood background activity correction as in the conventional regions-of-interest method. All the dixels in the image of a study are used in the actual data analysis. The method is therefore independent of operator influence. The intersection method is offered as an alternative to the manual method. The intersection method uses principal components analysis as a first step in the computation of the intersection of a theory space and a study space. A simple exponential function is used to generate the liver theory space. Sixty 131I Rose Bengal liver function studies were processed by the intersection method. The first forty minutes of patient data were used in the analysis. To validate the new method, computed T1/2 values were compared with those obtained by the manual method. A standard statistical test showed no significant difference between the two methods. Regression analysis gave a value for the coefficient of correlation of 0.89. The intersection method is currently in routine use for the automatic analysis of Rose Bengal liver studies and is faster than the manual method.

Autoanalysis↗

PubMed2000

A quality assurance device for the accuracy of the isocentres of teletherapy and simulation machines.

A new quality assurance device has been designed to measure the location and wobble of the radiation isocentre of linacs and simulation machines as a function of gantry rotation. The radiation isocentre is the intersection in space of the central x rays of a linac or simulation machine at different gantry angles. Six radio-opaque markers 1 mm in size are embedded in a radio-transparent calibration object (specifically, a hollowed cube) in such a way that the markers are non-coplanar and uniquely identifiable in radiographic projections. The projective radiographs are obtained on the films held by the film holder attached to the gantry during the QA procedure. The marker positions of the calibration object define a known 3D reference frame, and their image positions on each radiograph determine the projective (3D to 2D matrix) transformation for that radiograph. Once the transformation is found, a 3D ray from the radiation source to any radiograph pixel becomes known. The radiographic pixels are coordinated (positioned and scaled) with respect to the projected image of radio-opaque fiducial cross-hairs fixed to a block tray and thus to the gantry. We select the central ray to correspond to the radiographic pixel whose rays at different gantry angles intersect in the smallest spatial domain. That pixel is found by a spiral search in the radiograph outward from the image of the radio-opaque cross-hair intersection. The wobble of the isocentre is defined by the set of points (on the central rays) at closest approach to the isocentre. The device was tested and compared with commercially available QA devices. It is able to locate the isocentre to within 0.5 mm. The offset of this derived radiation isocentre from the intersection of the positioning lasers can be found. To do this, the calibration object is initially placed so that the laser intersection point falls on a seventh radio-opaque marker near the centre of the hollow cube calibration object. The seventh marker is embedded in a thin radio-transparent rod that diagonally spans the hollowed space.

Algorithms↗

PubMed2006

Developing pulsatile flow in a deployed coronary stent.

A major consequence of stent implantation is restenosis that occurs due to neointimal formation. This patho-physiologic process of tissue growth may not be completely eliminated. Recent evidence suggests that there are several factors such as geometry and size of vessel, and stent design that alter hemodynamic parameters, including local wall shear stress distributions, all of which influence the restenosis process. The present three-dimensional analysis of developing pulsatile flow in a deployed coronary stent quantifies hemodynamic parameters and illustrates the changes in local wall shear stress distributions and their impact on restenosis. The present model evaluates the effect of entrance flow, where the stent is placed at the entrance region of a branched coronary artery. Stent geometry showed a complex three-dimensional variation of wall shear stress distributions within the stented region. Higher order of magnitude of wall shear stress of 530 dyn/cm2 is observed on the surface of cross-link intersections at the entrance of the stent. A low positive wall shear stress of 10 dyn/cm2 and a negative wall shear stress of -10 dyn/cm2 are seen at the immediate upstream and downstream regions of strut intersections, respectively. Modified oscillatory shear index is calculated which showed persistent recirculation at the downstream region of each strut intersection. The portions of the vessel where there is low and negative wall shear stress may represent locations of thrombus formation and platelet accumulation. The present results indicate that the immediate downstream regions of strut intersections are areas highly susceptible to restenosis, whereas a high shear stress at the strut intersection may cause platelet activation and free emboli formation.

Animals↗

PubMed2006

Sex and age specific effects of chromosomal regions linked to body mass index in the Framingham Study.

BACKGROUND: Previously, we reported significant linkage of body mass index (BMI) to chromosomes 6 and 11 across six examinations, covering 28 years, of the Framingham Heart Study. These results were on all individuals available at each exam, thus the sample size varied from exam to exam. To remove any effect of sample size variation we have now constructed six subsets; for each exam individuals were only included if they were measured at every exam, i.e. for each exam, included individuals comprise the intersection of the original six exams. This strategy preferentially removed older individuals who died before reaching the sixth exam, thus the intersection datasets are smaller (n = 1114) and significantly younger than the full datasets. We performed variance components linkage analysis on these intersection datasets and on their sex-specific subsets. RESULTS: Results from the sex-specific genome scans revealed 11 regions in which a sex-specific maximum lodscore was at least 2.0 for at least one dataset. Randomization tests indicated that all 11 regions had significant (p < 0.05) differences in sex-specific maximum lodscores for at least three datasets. The strongest sex-specific linkage was for men on chromosome 16 with maximum lodscores 2.70, 3.00, 3.42, 3.61, 2.56 and 1.93 for datasets 1-6 respectively. Results from the full genome scans revealed that linked regions on chromosomes 6 and 11 remained significantly and consistently linked in the intersection datasets. Surprisingly, the maximum lodscore on chromosome 10 for dataset 1 increased from 0.97 in the older original dataset to 4.23 in the younger smaller intersection dataset. This difference in maximum lodscores was highly significant (p < 0.0001), implying that the effect of this chromosome may vary with age. Age effects may also exist for the linked regions on chromosomes 6 and 11. CONCLUSION: Sex specific effects of chromosomal regions on BMI are common in the Framingham study. Some evidence also exists for age-specific effects of chromosomal regions.

Adult↗

PubMed2003

Color separation of signature and stamp inks to facilitate handwriting examination.

The questioned documents laboratory often encounters cases where handwriting that is to be examined intersects with some interfering factor such as a rubber stamp, typewriting or background printing. In these cases, line direction, beginning and ending features of letters and other fine details of the handwriting may be lost in the "noise" of the intersecting ink. The purpose of this paper is to show several new digital photography methods that may be used to "subtract" the effect of the intersecting ink, thereby enhancing that of the handwriting ink in order to enable the document examiner to conduct a complete examination. These methods have the advantage of being fast and do not involve the use of expensive material or equipment. Several new methods are described that may be used to separate the colors of the handwriting ink from that of the intersecting ink: the analog method and several digital methods such as RGB-HSB-CMYK, L*a*b color, and color separation using the Channel Mixer function of Adobe Photoshop. Successful application of these color separation methods to specific handwriting ink/rubber stamp ink color combinations shows that the effect of the intersecting ink may indeed be minimalized if not canceled altogether. Application of the suggested methods may well make the difference between a nonconclusive handwriting examination and a full analysis of the questioned handwriting.

Journal Article↗

PubMed2005

Head movements while crossing streets: effect of vision impairment.

BACKGROUND: Crossing the street is an activity that requires gathering information over a large area. The challenge in safely crossing a street is to acquire the necessary information for a decision of when to cross within a limited window of time. The purpose of this study was to compare the head movement behavior of visually impaired pedestrians with fully sighted pedestrians at two types of complex intersections: a plus intersection and a roundabout. METHOD: We measured the head movement behavior of 12 subjects with normal vision, 11 subjects with age-related macular degeneration (AMD), and 10 subjects with glaucoma as they approached and crossed at the two intersections. The primary measures were the percentage of time the head was directed to the left, center, or right and the frequency of head turns. We compared measures across groups and relative to three criteria of head movement behavior for maximizing street-crossing safety. RESULTS: Crossing the street can be divided into three phases: walking to the curb, standing at the curb, and crossing the street. We found that while moving, the majority of subjects directed their head to the center. This was true at the plus intersection and roundabout. Group differences were found in the frequency of head turns at the plus intersection, with the AMD pedestrians having a lower frequency of head turns compared with the fully sighted pedestrians. However, the frequency of head turns increased for all the groups during the last 4 seconds before crossing, with the frequency being the greatest during the last second. Numerous subjects had head movements consistent with pedestrian safety, although there were subjects in each group who failed to demonstrate maximum safety. More of the visually impaired pedestrians exhibited less safe head movement behavior than the fully sighted pedestrians. CONCLUSIONS: The effects of visual impairment on head movement behavior were associated with pedestrian safety at critical moments in the street-crossing process. Mobility training programs aimed at teaching safe head movement behavior for street crossing could help to increase the safety of visually impaired pedestrians.

Accident Prevention↗

PubMed1988

[Correlation between the anterior antral branches of the vagus nerve and the antral-fundic boundary in duodenal ulcer].

The distances from the pylorus to the most proximal branch (proximal branch) and the most distal branch (distal branch) of the anterior antral branches were measured in 37 duodenal ulcer patients. The resected specimens were examined histologically to determine the antral-fundic boundary (F-line) and the distance from the pylorus to F-line was calculated. The distances from the pylorus to proximal branch, distal branch and F-line were 7.8 +/- 1.6 cm, 5.1 +/- 1.2 cm, 6.7 +/- 1.4 cm (M +/- SD), respectively. The mucosal area of proximal branch was fundic in 77% and pyloric in 23%. The mucosal area of distal branch was fundic in 14% and pyloric in 86%. There were three types of distribution of anterior antral branches in relation to F-line. In fundic type both proximal and distal branches intersect fundic mucosa. In ordinary type proximal branch intersects fundic mucosa whereas distal branch intersects pyloric mucosa. In pyloric type both proximal and distal branches intersect pyloric mucosa. The numbers of each type were 5(14%), 22(63%) and 8(23%), respectively. In conclusion, selective proximal vagotomy is not indicated for cases of fundic type in which the entire anterior antral branches intersect fundic mucosa.

Adolescent↗

PubMed1977

Visual extrapolation of two converging nonintersecting line segments.

Fifty subjects were tested to determine the point of intersection between two converging line segments. The angle between the two nonintersecting line segments was 30 degrees. The orientation of the display as well as the distance between the line segments and the point of their intersection was varied. Two-dimensional normal distributions can be accepted to describe the results - the 50 estimates of the point of intersection for each of the five displays presented. The parameters of these distributions are influenced mainly by two factors characterizing the test line segments: (1) proximity to one of the main axes - vertical and horizontal, and (2) distance to the actual point of intersection. The possible mechanisms that might be involved in the estimation of the point of intersection between two converging line segments are discussed.

Adult↗

PubMed1982

Anatomy of the myenteric plexus of the opossum esophagus.

Silver-impregnated stretch preparations of the opossum esophageal body and lower esophageal sphincter were compared as to the general aspect of the plexus, density of perikarya and ganglia, type and size of ganglia, nerve bundle diameter, density of nerve bundle intersections, and relations between ganglia and nerve bundle intersections. Density of perikarya and ganglia, but not density of nerve bundle intersections, declined along the esophagus, with a nadir at the sphincter. The proximal body contained 960-1358 perikarya/cm2 and the sphincter, 70-333 perikarya/cm2. Ganglia contained 3-100 cells, 54% having less than 10. Many small ganglia lay outside nerve bundles (parafascicular ganglia), the proportion being greatest in the sphincter (25%-54%). Many ganglia (15%-22%) were remote from nerve bundle intersections and many intersections were remote from ganglia, 28%-35% in the body and 66%-69% in the sphincter. Nerve bundle diameter was a single population with a skewed distribution; the mode was about 0.1 mm.

Animals↗

PubMed1994

Differences in child pedestrian injury events by location.

OBJECTIVE: To compare child pedestrian injury events occurring in driveways and parking lots and at midblock and intersections with respect to characteristics and activity of the child, injury outcome measures, and characteristics of the vehicle and roadway. DESIGN: Descriptive case series. SETTING: Data were obtained from a multihospital/coroner monitoring system, during 2 years in an urban county, by record review and interviews. PATIENTS: The sample consisted of 345 pedestrians 0 through 14 years of age treated for injuries at one of the participating facilities. RESULTS: Eleven percent were injured in driveways, 8% in parking lots, 53% at midblock, and 28% at intersections. Median age was 2 years for driveways, 4 years for parking lots, 6 years for midblock, and 10 years for intersection. Events in driveways and parking lots had significantly more vehicles backing up, fewer automobiles, and more pedestrians with adults. Events at intersections occurred more often on streets with more than two lanes, with speed limits > 25 mph, and with moderate or heavy traffic than events at midblock. Sixteen percent of those injured in driveways and parking lots sustained head injury of moderate or greater severity versus 35% injured in the street. CONCLUSIONS: Interventions to prevent child pedestrian injuries must consider normal child behavior and driver awareness as it relates to location of the events. Driveway events involve small children, larger vehicles, and backing up. Midblock events involve children too young to cross even quiet residential streets safely. Traffic controls and safe street crossing skills are measures to consider for intersection events involving older children.

Accident Prevention↗

PubMed2000

Detailed motion analysis of the left ventricular myocardium using an MR tagging method with a dense grid.

Detailed analysis of myocardial deformation through a whole cardiac cycle was accomplished using a tagging method with a high-density grid. Four sets of tagged images with a 4-mm-spacing grid were measured by generating four tagging pulses arranged at regular intervals in the cardiac cycle. Through each set of images, tag intersections were tracked semi-automatically. The estimated motions of tag intersections were concatenated so that sequential positions of myocardium were connected through a whole cardiac cycle. In vitro evaluation of the precision of this technique showed that the mean error of tracked 4-mm tag intersections was less than 0.47 +/- 0.17 mm, even on the quite low-contrast images, and the concatenation error caused by double concatenation was comparable to the interpolation error in the subendocardial area obtained with 8-mm tag intersection motion. The small difference between the two mean distance curves of the in vivo evaluation indicated that the method is useful for analyzing heart wall abnormalities. Magn Reson Med 44:73-82, 2000.

Algorithms↗