Outflow Structures Research Articles

Spectral domain optical coherence tomography imaging of the aqueous outflow structures in normal participants of the EPIC-Norfolk Eye Study

PurposeTo measure the dimensions of aqueous outflow structures and to investigate associations with intraocular pressure (IOP) and ocular biometry parameters in an older British population.MethodFifty-two participants from the European Prospective...

Experimental study hydraulic roughness for Kan Tin Main Drainage Channei in Hong Kong

The Kam Tin Main Drainage Channel (KTMDC) is an important river for the city drainage in Hong Kong. The roughness and its variations have an obvious effect on the flood control capacity and the flow capacity. So physical model tests are designed to study the KTMDC. Due to its complex channel structure, the tests are completed in two steps. In Step 1, the energy loss is measured along the main channel without inflows, with all inflows and outflows being sealed. In Step 2, all the inflow and outflow structures are measured, with the sealed inflows and outflows being opened on the basis of Step 1. In each step, two schemes are employed. One of the key issues is the choice of suitable materials to make the model's roughness similar to that of the prototype. According to the gravity similarity criterion, the 1:25 scale model is built, with the main channel made of Perspex. The facing slopes of the grasscrete and the stone masonry need to be roughened. A kind of the nylon net is selected to simulate the roughness of the stone masonry and the plastic lawn for the grasscrete facing slope. For the different structure reaches, the roughness coefficients are estimated based on the hydraulic theory. The rationality of the test results is verified in this study. The results of testing can provide a reliable basis for the renovation, the expansion, the optimization of this channel.

Visualization of the Conventional Outflow Pathway in the Living Human Eye

We sought to visualize the aqueous outflow system in 3 dimensions (3D) in living human eyes, and to investigate the use of commercially available spectral-domain optical coherence tomographic (SD-OCT) systems for this purpose. Prospective, observational study. One randomly determined eye in each of 6 normal healthy subjects was included. We performed 3D SD-OCT imaging of the aqueous humor outflow structures with 2 devices: The Cirrus HD-OCT and the Bioptigen SDOIS. We created 3D virtual castings of Schlemm's canal (SC) and more distal outflow structures from scan data from each device. Virtual casting of the SC provided visualization of more aqueous vessels branching from SC than could be located by interrogating the 2-dimensional (2D) image stack. Similarly, virtual casting of distal structures allowed visualization of large and small aqueous outflow channel networks that could not be appreciated with conventional 2D visualization. The outflow pathways from SC to the superficial vasculature can be identified and tracked in living human eyes using commercially available SD-OCT.

Intrusion of the Oyashio water into the eastern mouth of Tsugaru Strait in early summer, 2003

Hydrographic observations based on XBT, XCTD, CTD, and ADCP were performed around the eastern mouth of the Tsugaru Strait in June 2003. This study aims to describe the hydrographic structure of the eastern mouth focusing on the subarctic Oyashio water occupying the northern part, and to discuss the intrusion pathway of this water and its modification after the intrusion. Residual and absolute geostrophic velocities show a nearly barotropic inflow (0–25cm/s) and outflow (0–80cm/s) structures in the northern and southern parts of the strait mouth, respectively. In the north, the Oyashio water, classified as the near-bottom and modified Oyashio waters in this study, inflows into the strait. It is inferred that the near-bottom water is changed to the modified Oyashio water after the intrusion by diapycnal mixing and outflow as the modified Oyashio water from underneath of the Tsugaru Warm Current (TWC) water in the deepest part of the strait mouth, together with the TWC water. Horizontal salinity distribution suggests that the near-bottom water is supplied along the isopycnal surface from the subsurface of Hidaka Bay deeper than the strait.

3D visualization of aqueous humor outflow structures in-situ in humans

Aqueous humor (AH) exiting the eye via the trabecular meshwork and Schlemm’s canal (SC) passes through the deep and intrascleral venous plexus (ISVP) or directly through aqueous veins. The purpose of this study was to visualize the human AH outflow system 360° in three dimensions (3D) during active AH outflow in a virtual casting. The conventional AH outflow pathways of 7 donor eyes were imaged with a modified Bioptigen spectral-domain optical coherence tomography system (Bioptigen Inc, USA; SuperLum LTD, Ireland) at a perfusion pressure of 20 mmHg ( N = 3), and 10 mmHg ( N = 4). In all eyes, 36 scans (3 equally distributed in each clock hour), each covering a 2 × 3 × 2 mm volume (512 frames, each 512 × 1024 pixels), were obtained. All image data were black/white inverted, and the background subtracted (ImageJ 1.40 g, http://rsb.info.nih.gov/ij/). Contrast was adjusted to isolate the ISVP. SC, collector channels, the deep and ISVP, and episcleral veins were observed throughout the limbus. Aqueous veins could be observed extending into the episcleral veins. Individual scan ISVP castings were rendered and assembled in 3D space in Amira 4.1 (Visage Imaging Inc. USA). A 360-degree casting of the ISVP was obtained in all perfused eyes. The ISVP tended to be dense and overlapping in the superior and inferior quadrants, and thinner in the lateral quadrants. The human AH outflow pathway can be imaged using SD-OCT. The more superficial structures of the AH outflow pathway present with sufficient contrast as to be optically isolated and cast in-situ 360° in cadaver eye perfusion models. This approach may be useful as a model in future studies of human AH outflow.

Discovery of universal outflow structures above and below the accretion disc plane in radio-quiet quasars

59 quasars in the background of the Magellanic Clouds had brightness records monitored by the MACHO project during the years 1992–99. Because the circumpolar fields of these quasars had no seasonal sampling defects, their observation produced data sets well suited to further careful analysis. Following a preliminary report wherein we showed the existence of reverberation in the data for one of the radio-quiet quasars in this group, we now show that similar reverberations have been seen in all of the 55 radio-quiet quasars with adequate data, making possible the determination of the quasar inclination to the observer’s line of sight. The reverberation signatures indicate the presence of large-scale elliptical outflow structures similar to that predicted by the Elvis and ‘dusty torus’ models of quasars, whose characteristic sizes vary within a surprisingly narrow range of scales. More importantly, the observed opening angle relative to the polar axis of the universal elliptical outflow structure present was consistently found to be on the order of 78°.

A high-velocity narrow absorption line outflow in the quasar J212329.46 − 005052.9

We report on a variable high-velocity narrow absorption line outflow in the redshift 2.3 quasar J2123-0050. Five distinct outflow systems are detected with velocity shifts from -9710 to -14,050 km/s and CIV 1548,1551 line widths of FWHM = 62-164 km/s. These data require five distinct outflow structures with similar kinematics, physical conditions and characteristic sizes of order 0.01-0.02 pc. The most likely location is ~5 pc from the quasar. The coordinated line variations in <0.63 yr (rest) are best explained by global changes in the outflow ionization caused by changes in the quasar's ionizing flux. The absence of strong X-ray absorption shows that radiative shielding is not needed to maintain the moderate ionizations and therefore, apparently, it is not needed to facilitate the radiative acceleration to high speeds. The kinetic energy yield of this flow is at least two orders of magnitude too low to be important for feedback to the host galaxy's evolution.

Identification and Assessment of Schlemm's Canal by Spectral-Domain Optical Coherence Tomography

Measurements of human Schlemm's canal (SC) have been limited to histologic sections. The purpose of this study was to demonstrate noninvasive measurements of aqueous outflow (AO) structures in the human eye, examining regional variation in cross-sectional SC areas (on/off collector channel [CC] ostia [SC/CC] and nasal/temporal) in the eyes of living humans. SC was imaged by spectral-domain optical coherence tomography with a 200-nm bandwidth light source. Both eyes of 21 healthy subjects and one glaucomatous eye of three subjects were imaged nasally and temporally. Contrast and magnification were adjusted to maximize visualization. Cross-sectional SC on and off SC/CC was traced three times by two independent masked observers using ImageJ (ImageJ 1.40g, http://rsb.info.nih.gov/ij/ Wayne Rasband, developer, National Institutes of Health, Bethesda, MD). The mean SC area was recorded. A linear mixed-effects model was used to analyze eye, nasal/temporal laterality, and SC area on or off SC/CC. SC area was significantly larger on SC/CCs than off (12,890 vs. 7,391 micorm(2), P < 0.0001) and was significantly larger on the nasal side than on the temporal (10,983 vs. 8,308 micorm(2), P = 0.009). SC areas were significantly smaller in glaucoma patients than in normal subjects, whether pooled (P = 0.0073) or grouped by on (P = 0.0215) or off (P = 0.0114) SC/CC. Aqueous outflow structures, including SC and CCs, can be noninvasively assessed in the human eye. These measurements will be useful in physiological studies of AO and will be clinically useful in the determination of the impact of glaucoma therapies on IOP as well as presurgical planning.

PROTOSTELLAR OUTFLOW EVOLUTION IN TURBULENT ENVIRONMENTS

The link between turbulence in star-forming environments and protostellar jets remains controversial. To explore issues of turbulence and fossil cavities driven by young stellar outflows, we present a series of numerical simulations tracking the evolution of transient protostellar jets driven into a turbulent medium. Our simulations show both the effect of turbulence on outflow structures and, conversely, the effect of outflows on the ambient turbulence. We demonstrate how turbulence will lead to strong modifications in jet morphology. More importantly, we demonstrate that individual transient outflows have the capacity to re-energize decaying turbulence. Our simulations support a scenario in which the directed energy/momentum associated with cavities is randomized as the cavities are disrupted by dynamical instabilities seeded by the ambient turbulence. Consideration of the energy power spectra of the simulations reveals that the disruption of the cavities powers an energy cascade consistent with Burgers'-type turbulence and produces a driving scale length associated with the cavity propagation length. We conclude that fossil cavities interacting either with a turbulent medium or with other cavities have the capacity to sustain or create turbulent flows in star-forming environments. In the last section, we contrast our work and its conclusions with previous studies which claim that jets cannot be the source of turbulence.

MHD numerical simulations of Perseus A: formation of filaments and magnetic loops

AbstractThe Perseus Cluster (A426) is the brightest cluster of galaxies observed in X-rays in the sky and its giant central galaxy (NGC1275) hosts the extended double radio source 3C84. There is a spectacular H-alpha nebulosity surrounding NGC1275 with loops and filaments that are probably magnetized and extend over 100 kpc. The continuous blowing of bubbles leading to the propagation of shock fronts is also evident and more recently, outflow and infall velocities of several 1000 km/s have been detected associated to the surrounding filaments. We here present preliminary results of 2.5D MHD simulations of the Perseus cluster central region assuming that the production of the outflow structures and loops that arise from the surface of NGC1275 are due to turbulent injection triggered by recent star formation and SNe activity in the galaxy. This is in turn, probably induced by a continuous gas infall from the satellite galaxies around NGC1275. Our simulations which include both, the turbulent gas outflow and gas infall from the surroundings, have revealed a continuous formation of the observed features, like the filaments, the gigantic magnetic loops and weak shock fronts that propagate into the ICM medium with the observed velocities of 1000–5000 km/s. After 10 Myr, a nearly steady state is established between the outflow material emerging from the central galaxy and the inflow gas from the surrounds. The outflow activity seems to retard the cannibalism action of the central galaxy over the surrounding galaxies. This result may have important implications over the evolution of the whole cluster as it seems to indicate that the SF and SNe production that are induced by the cannibalism may help to decelerate the later due to turbulence and outflow production. These results also offer important clues to the hot halo formation in the center of the cluster and in the suppression of cooling flows.

Congenital Glaucoma-A Brief Review

Congenital glaucomas are present at birth while infantile glaucomas refer to elevated ocular pressures and other sequelae with onset from birth up to three years of life. Developmental glaucomas are associated with developmental anomalies of the eye present at birth. Defective primary development of the outflow structures of the eye causes primary developmental glaucomas whereas other developmental ocular abnormalities secondarily affecting the aqueous outflow structures cause secondary developmental glaucomas (e.g. glaucoma secondary to persistent primary hyperplastic vitreous, spherophakia, retinopathy of prematurity, Sturge Weber syndrome, congenital ectropion uveae, etc). This review will focus on the most common form of developmental glaucomas seen in ophthalmic practice, Primary Congenital Glaucoma. The reader is referred to standard textbooks on glaucoma for a detailed description of the terminology and classification of developmental glaucomas. Buphthalmos is derived form the Greek term for ox-eye and refers to the significant enlargement of the eye that can occur as a consequence of any type of glaucoma present in infancy. Similarly, Hydrophthalmos in Greek refers to the high fluid content present with marked enlargement of the eye. These are merely descriptive terms with no implications on the etiology, pathogenesis or management of the eyes so affected, and are not used diagnostically in clinical practice. Primary congenital glaucoma (commonly, alternately and widely referred to as primary infantile glaucoma as well) is described by Shaffer and Weiss1 as follows: Primary congenital glaucoma is the most common hereditary glaucoma of childhood, inherited as an autosomal recessive pattern, with specific angle anomaly consisting of absence of angle recess with iris insertion directly into trabecular surface. There are no other development anomalies of the eye. Elevated IOP results in corneal enlargement, clouding and breaks in Descemet’s membrane.

DIRECT MICROLENSING-REVERBERATION OBSERVATIONS OF THE INTRINSIC MAGNETIC STRUCTURE OF ACTIVE GALACTIC NUCLEI IN DIFFERENT SPECTRAL STATES: A TALE OF TWO QUASARS

We show how direct microlensing-reverberation analysis performed on two well-known quasars (Q2237, the Einstein Cross, and Q0957, the Twin) can be used to observe the inner structure of two quasars which are in significantly different spectral states. These observations allow us to measure the detailed internal structure of Q2237 in a radio-quiet high-soft state, and compare it to Q0957 in a radio-loud low-hard state. When taken together we find that the observed differences in the spectral states of these two quasars can be understood as being due to the location of the inner radii of their accretion disks relative to the co-rotation radii of the magnetospheric eternally collapsing objects (MECO) in the centers of these quasars. The radiating structures observed in these quasars are associated with standard accretion disks and outer outflow structures, where the latter are the major source of UV-optical continuum radiation. While the observed inner accretion disk structure of the radio-quiet quasar Q2237 is consistent with either a MECO or a black hole, the observed inner structure of the radio-loud quasar Q0957 can only be explained by the action of the intrinsic magnetic propeller of a MECO with its accretion disk. Hence a simple and unified answer to the long-standing question: Why are some quasars radio loud? is found if the central objects of quasars are MECO, with radio-loud and radio-quiet spectral states similar to the case of galactic black hole candidates.

A suitable animal model for laparoscopic hepatic resection training

There is a growing interest in using laparoscopy for hepatic resection. However, structured training is lacking in part because of the lack of an ideal animal training model. We sought to identify an animal model whose liver anatomy significantly resembled that of the human liver and to assess the feasibility of learning laparoscopic hepatic inflow and outflow dissection and parenchyma transection on this model. The inflow and outflow structures of the sheep liver were demonstrated via surgical dissection and contrast studies. Laparoscopic left major hepatic resections were performed. The portal hepatis of all 12 sheep (8 for anatomic study and 4 for laparoscopic hepatic resection) resembled that of human livers. The portal vein (PV) was located posteriorly; the common hepatic artery (CHA) and the common bile duct (CBD) were located anterior medially and anterior laterally with respect to the portal hepatis. The main PV bifurcated into a short right and a long left PV. The extrahepatic right PV then bifurcated into right posterior and anterior sectoral PV. The CBD and CHA bifurcated into left and right systems. The cystic duct originated from the right hepatic duct. The cystic artery originated from the right HA in 11/12 animals. The left hepatic vein drained directly into the inferior vena cava (IVC). The middle and the right hepatic veins formed a short common channel before entering the IVC. Multiple venous tributaries drained directly into IVC. Familiarity with sheep liver anatomy allowed laparoscopic left hepatic lobe (left medial and lateral segments) resection to be performed with accuracy and preservation of the middle hepatic vein. The surgical anatomy of sheep liver resembled that of human liver. Laparoscopic major hepatic resection can be performed with accuracy using this information. Sheep is therefore an ideal animal model for advanced surgical training in laparoscopic hepatic resection.

Nonpenetrating Glaucoma Surgery

Nonpenetrating glaucoma surgery continues to evolve and improve. New technical refinements and increased experience among its practitioners have led to improved efficacy and longer duration of filter survival. These refinements include the use of intraoperative and postoperative antimetabolites, adjunctive space-maintaining devices, and postoperative yttrium-aluminum-garnet laser goniopuncture. Deep sclerectomy and viscocanalostomy vary significantly in their surgical approaches and mechanisms of aqueous outflow. An understanding of the microanatomy of the aqueous outflow structures is necessary to gain surgical access to Schlemm's canal and to augment aqueous outflow surgically through the trabecular meshwork. Indications and contraindications for nonpenetrating glaucoma surgery are discussed.

An estimation of the probable maximum precipitation for river basins in the Czech Republic

The hydro-meteorological evaluation of a flood event in July 1997 (the Odra flood in Central Europe) demonstrated that new procedures to estimate design floods for the reservoir outflow structures in the Czech Republic (CR) were needed. Therefore, the techniques of the estimation of Probable Maximum Precipitation (PMP) were developed in a national research project (1998–2000), and the activity focused on the improvement of the area related PMP estimates was going on within a present national project. In the frame of the evaluation of the next extreme precipitation event in August 2002 (the Labe flood in the CR and Germany), we compared the catchments related precipitation with the PMP estimates. In this paper, an outline of the PMP estimation techniques is given and the use of data from the Czech gauges is described, the aim being the statistical derivation of the point and area PMP estimates for precipitation duration of 1 to 5 days. The use of radar data in assessing the maximized area reduction factor is discussed and the relationship resulting from the radar measurements over the CR territory is presented. An evaluation of the radar-based area rainfall enabled us to transform the point PMP to the area PMP estimate designed for the river basins in CR. In the last part of the paper, the results obtained by comparing the rainfalls in 1997 and 2002 flood events with the PMP estimates are presented. The comparison showed that the maximum area rainfalls over small Czech catchments (the 3rd order river basins) did not exceed 63% of the corresponding PMP values.

Hydrodynamic simulations of molecular outflows driven by slow-precessing protostellar jets

We present hydrodynamic simulations of molecular outflows driven by jets with a long period of precession, motivated by observations of arc-like features and S-symmetry in outflows associated with young stars. We simulate images of not only H2 vibrational and CO rotational emission lines, but also of atomic emission. The density cross-section displays a jaw-like cavity, independent of precession rate. In molecular hydrogen, however, we find ordered chains of bow shocks and meandering streamers which contrast with the chaotic structure produced by jets in rapid precession. A feature particularly dominant in atomic emission is a stagnant point in the flow that remains near the inlet and alters shape and brightness as the jet skims by. Under the present conditions, slow jet precession yields a relatively high fraction of mass accelerated to high speeds, as also attested to in simulated CO line profiles. Many outflow structures, characterized by HH 222 (continuous ribbon), HH 240 (asymmetric chains of bow shocks) and RNO 43N (protruding cavities), are probably related to the slow-precession model.

Numerical simulations of highly collimated protostellar outflows

We present three-dimensional hydrodynamic simulations of jets as a model for protostellar outflows. We investigate molecular jets which are initially heavier, equal or lighter than a uniform ambient molecular medium, as well as a ballistic atomic jet, with the aim of distinguishing the resulting structures and relating them to various proposed protostellar evolutionary stages. We modify the ZEUS numerical code, to include time-dependent molecular hydrogen chemistry, a limited equilibrium C and O chemistry, and a detailed cooling function. We find highly focussed and accelerated flow patterns for outflows driven by molecular jets, caused by the combined strong cooling, small imposed jet shear and precession. We also find shoulders in the interface with associated shocks visible in our simulated near-infrared H2 images. The shoulder location relative to the front of the bow shock distinguishes the relative density. Apart from this, the outflow structures are quite similar provided the jet is molecular. The ratio of jet power to H2 1-0 S(1) line luminosity (increasingly required to interpret observations), is generally in the range 80-600. Sub-millimetre CO properties, including a velocity-position and velocity-channel diagram; are presented. We compare mass-velocity relationships derived directly and via the simulated CO data: significant systematic differences are uncovered. For the future, we identify fine-scale structure in the rotational CO 2-1 and CO 14-13 rotational lines which can be resolved with the millimetre array ALMA and the Herschel (FIRST) Observatory. We identify highly collimated outflows in the near-infrared that can be interpreted by this model.

Laparoscopic procurement model for living donor liver transplantation.

Noting the contribution to renal transplantation by the introduction of the laparoscopic approach to donor nephrectomy, we investigated the possibility of performing a laparoscopic hepatic lobe procurement with the goal of performing a live donor liver transplantation. We describe our technique and determine its feasibility for such a goal. The surgical technique was developed over a series of 12 adult female pigs and adapted in two human cadavers. The technique included pneumoperitoneum with CO2, mobilization of the liver, and transection of the parenchyma into right and left lobes with a laparoscopic cavitron ultrasonic aspirator. The vascular inflow and outflow structures (hepatic artery, portal vein, hepatic veins) of the anatomical specimen being procured were preserved undisturbed during the hepatic transection. No temporary vascular occlusion techniques were utilized. The vascular structures were stapled and sectioned just prior to removal of the specimen. Hepatic lobectomies were successfully performed laparoscopically. Vascular and biliary structures were preserved to allow for subsequent transplantation. Operative time from establishment of pneumoperitoneum to lobe procurement was under 4 h. This study demonstrates the feasibility of laparoscopic living donor procurement for liver transplantation, from both a technical and a physiological perspective.

Expression of endothelins in human cardiogenesis.

Genetic disruption of endothelin (ET) 1, endothelin-converting enzyme (ECE) 1, and endothelin receptor A (ET(A)) in "knockout" or mutant mouse models result in defects in branchial arch derived craniofacial tissues and in cardiac outflow and great vessel structures. Interestingly, certain types of human congenital cardiovascular malformations such as Catch 22 syndrome and type B interruption of the aortic arch strongly resemble defects seen in knockout animal models. To better address the exact involvement of the ET system in heart formation we explored the spatiotemporal pattern of expression of the components of the ET system during critical phases of cardiogenesis in the human embryo (3-6 weeks of development; Carnegie stages 10-17) by in situ hybridization. We detected high ET-1 mRNA expression in endocardial cells lining the heart outflow tract in the region where the future aortic valves will form. No hybridization signal corresponding to pre-pro-ET-3 was observed in the heart. At the same location, the underlying myocytes express ET(A) mRNA. Whereas a functional role of ET in the valve formation can be proposed because of the simultaneous presence of all the components of the endothelin system (ET-1/ECE-1/ET(A)), this seems not to be the case for the formation of the ventricular septum where endocardial cells do not express ET-1, and only a weak ET(A) hybridization signal was detected in the surrounding myocardium. An abnormal hemodynamism indirectly due to valve malformation may be the indirect cause of this septal defect. The results of this study suggest an important role for the ET system in the formation of certain anatomical structures of the developing human heart.

Motion of auroral ion outflow structures observed with CLUSTER and IMAGE FUV

During February 2001 the CLUSTER satellites recorded a number of perigee passes through the midnight auroral zone. We concentrate on one pass, on 23 February 2001, when structured outflow was observed. Simultaneous observations of the aurora were available from the FUV instrument on IMAGE. The features in the ion outflow observed by the Cluster Ion Spectrometry (CIS) experiment are compared with the auroral activity. Observations from the multiple CLUSTER spacecraft are used to determine the velocity of the outflow structures. We find a good correspondence between the observed ion outflow and the auroral arcs, with the highest energy outflow corresponding to the brightest arcs. The features at the equatorward edge, which are trapped precipitating ions, are stationary. In addition, the increased velocity structure at the poleward edge is also stationary. However, the bulk of the ion outflow structures, which are observed between these boundaries, are moving equatorward with a velocity of roughly 7 km/s, which corresponds to a velocity of 0.7 km/s at 100 km. One feature is observed moving poleward, at the same time that the auroral arc is expanding poleward. Comparisons with the motion of the auroral arcs and with the convection velocity measured by the EDI instrument on CLUSTER show that the motion of the structures in general agrees with the convective motion of the field lines.