SEARCH · PubMed Health

Results for “Meanders”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

492 records · Page 28Linked to original sources

PubMed1993

Stabilization ponds in the tropics: promotion of the sanitary reuse of water.

This article reports the results of efforts by PAHO's Environmental Health Program to lay the groundwork for designing wastewater stabilization ponds suited to tropical areas. The resulting design concepts are flexible (permitting pond construction to be adapted to a broad range of terrains, community sizes, and working temperatures) and directed at meeting WHO standards established for the microbial quality of effluents used in agriculture and aquaculture. The WHO standards (1) call for treated wastewater being used in agriculture or aquaculture to contain less than 1,000 fecal coliforms per 100 ml. The plans outlined here, which are calculated to meet those standards, seek to minimize the pond area and volume needed by using two high-load primary anaerobic ponds discharging into an elongated secondary pond with a length-to-width ratio of at least 15:1. In rough terrain the elongated pond can be allowed to meander, following the land's natural contours. However, where the terrain is level it is recommended that a system of partitions be used to maintain the 15:1 ratio for operating purposes while changing the actual ratio of the secondary pond's outer dimensions to something like 5:3. Basic equations presented in the text will be helpful in estimating the pond sizes needed to cope with different climatic conditions, community sizes, per capita rates of wastewater generation, and per capita biochemical oxygen demands. While these equations should prove of great assistance during initial planning and development of preliminary criteria, nothing in this article supplants the topographic and geotechnologic studies that will be needed in order to clearly determine what is feasible in any given case.

Agriculture↗

PubMed1993

On the pulsatile nature of intracranial and spinal CSF-circulation demonstrated by MR imaging.

Cerebrospinal fluid (CSF) flow was studied in 24 healthy volunteers using gated MR phase imaging. The subarachnoid space (SAS) was divided into 5 compartments depending on the magnitude of the pulsatile CSF flows: a high velocity compartment in the area of the brain stem and spinal cord, 2 slow ones at the upper and lower extremes of the SAS, and finally 2 intermediate velocity compartments in between. The main pulsatile spinal flow channel had a meandering pattern. The extraventricular CSF-circulation can be explained by pulsatile CSF flow without the necessity of assuming existence of a net flow. A successive time offset during the cardiac cycle has been found in the fronto-occipital direction of the interplay between the arterial expansion, brain expansion, volume changes of the CSF spaces and of the veins. It is proposed to name this time offset the intracranial "volume wave" (VoW).

Adult↗

PubMed1996

[Clinical evaluation of power Doppler sonography for the diagnosis of hepatocellular carcinoma].

We compared power Doppler sonography (PDS) with conventional color Doppler sonography (CDS) in the visualization of intratumoral blood flow of hepatocellular carcinoma (HCC) and evaluated the usefulness of PDS for assessing of the effects of TAE with Lipiodol and anticancer agents (Lp-TAE) and for the diagnosis of recurrence of HCC after Lp-TAE. The ability of PDS and CDS to visualize intratumoral blood flow was compared in 36 patients with HCC, and the usefulness of PDS for the diagnosis of HCC was evaluated. Also, in 17 patients with HCC who underwent Lp-TAE, the usefulness of PDS for evaluating the therapeutic effects of Lp-TAE and the diagnosis of recurrence after Lp-TAE was examined. The ability of PDS to visualize intratumoral blood flow and delineate tortuous and meandering intratumoral vasculature was superior to that of CDS. The effects of Lp-TAE could be evaluated and recurrence detected accurately and easily by PDS on the basis of residual intratumoral blood flow and the appearance of new blood flow. PDS is expected to achieve widespread acceptance as a useful imaging modality for the diagnosis of HCC, assessment of therapeutic effects of TAE, and detection of recurrence of HCC after TAE.

Carcinoma, Hepatocellular↗

PubMed1997

[Virtual bronchoscopy: the correlation between endoscopic simulation and bronchoscopic findings].

PURPOSE: We carried out a preliminary clinical validation of 3D spiral CT virtual endoscopic reconstructions of the tracheobronchial tree, by comparing virtual bronchoscopic images with actual endoscopic findings. MATERIALS AND METHODS: Twenty-two patients with tracheobronchial disease suspected at preliminary clinical, cytopathological and plain chest film findings were submitted to spiral CT of the chest and bronchoscopy. CT was repeated after endobronchial therapy in 2 cases. Virtual endoscopic shaded-surface-display views of the tracheobronchial tree were reconstructed from reformatted CT data with an Advantage Navigator software. Virtual bronchoscopic images were preliminarily evaluated with a semi-quantitative quality score (excellent/good/fair/poor). The depiction of consecutive airway branches was then considered. Virtual bronchoscopies were finally submitted to double-blind comparison with actual endoscopies. RESULTS: Virtual image quality was considered excellent in 8 cases, good in 14 and fair in 2. Virtual exploration was stopped at the lobar bronchi in one case only; the origin of segmental bronchi was depicted in 23 cases and that of some subsegmental branches in 2 cases. Agreement between actual and virtual bronchoscopic findings was good in all cases but 3 where it was nevertheless considered satisfactory. The yield of clinically useful information differed in 8/24 cases: virtual reconstructions provided more information than bronchoscopy in 5 cases and vice versa in 3. Virtual reconstructions are limited in that the procedure is long and difficult and needing a strictly standardized threshold value not to alter virtual findings. Moreover, the reconstructed surface lacks transparency, there is the partial volume effect and the branches < or = 4 pixels phi and/or meandering ones are difficult to explore. CONCLUSIONS: Our preliminary data are encouraging. Segmental bronchi were depicted in nearly all cases, except for the branches involved by disease. Obstructing lesions could be bypassed in some cases, making an indication for endoscopic laser therapy. Future didactic perspectives and applications to minimally invasive or virtual reality-assisted therapy seem promising, even though actual clinical applications require further studies.

Adult↗

PubMed1997

The structure of the interstitial tissue of the active and resting avian testis.

The interstitial tissue of the testis was studied in gonadally active and gonadally inactive domestic fowl (Gallus gallus domesticus), guinea-fowl (Numida meleagris), duck (Anas platyrhynchos) and Japanese quail (Coturnix coturnix japonica). Gonadal inactivity in the fowl was induced by a single subcutaneous injection of 50 mg oestradiol benzoate. The structure of this tissue was similar in all the birds studied. Lymphatic vessels were mostly thin and meandered between the peritubular tissue peripherally and the centrally located blood vessels, Leydig cells and macrophages. The basal lamina rested on a closely associated homogeneous microfibrillar layer free of collagen fibres. The myofibroblast layer was several cells thick, and quite compact. The basal lamina of gonadally resting birds was highly irregular, relatively electron-dense, contained electron-lucent globules, and sent numerous finger-like processes or plicae into the seminiferous epithelium, particularly into the Sertoli cells. The Leydig cells were few but typical in structure. In gonadally inactive birds they accumulated lipid droplets, dense heterogeneous bodies, probably lysosomes, and appeared to degenerate. The avian testicular interstitium is similar to that of the human and cat in possessing a multi-layered myofibroblast component, and to that of the rodent in possessing a small number of Leydig cells, as well as in the location of the lymphatic vessels. Thus the bird combines characteristics of the interstitium found variably in mammals.

Animals↗

PubMed1976

Ischemic colitis incidence following abdominal aortic reconstruction: a prospective study.

With few exceptions, the incidence of left colon ischemia following abdominal aortic reconstruction has been reported to be one to 2 percent. All reports of such ischemic events are retrospective analyses of clinically manifest or autopsy. Fifty patients were studied prospectively to determine more accurately the incidence of this complication. Aortic reconstruction was performed in 23 patients for occlusive disease (OD) and in 27 for aneurysm disease (AD). No emergency operations were performed. All patients underwent colonoscopy within 4 days of operation. Three instances of colon ischemia were noted, an incidence of 6 percent (OD 4.3 percent, AD 7.4 percent). Each patient recovered uneventfully. Two patients had diarrhea, but only after colon ischemia was recognized. Arteriographic opacification of the inferior mesenteric artery by the superior mesenteric artery collateral (meandering mesenteric artery) was documented in 35 percent of patients with OD and in 27 percent of patients with AD. Colon ischemia did not develop when this collateral was identified. The inferior mesenteric artery was patent at the aorta in all who developed colon ischema. Although clinically significant colitis following aortic reconstruction is rare, colonoscopy after operation may prove to be valuable for early recognition of ischemic changes before clinical manifestations preclude effective management.

Adult↗