Tunnel-like Structure Research Articles

Crystal structure of the alcoholates and the ansolvate of PNU-97018, an angiotensin II receptor antagonist.

The title compound, PNU-97018 [systemic name: 2-butyl-3,6,7,8,9,11-hexahydro-6,9-dimethyl-3-([2'-(2H-tetrazol-5-yl)[1,1'-biphenyl]-4-yl]methyl)-6,9-ethano-4H-imidazo[4,5-d]-pyridazino[1,2-a]pyridazin-4-one] is a newly developed angiotensin II receptor antagonist. The compound and its methanolate and ethanolate were characterized by X-ray crystallography and thermal analysis. The methanolate and ethanolate crystals have an almost identical molecular conformation and crystal packing. In both alcoholates, each alcohol molecule is fixed to the compound with a molar ratio of 1 : 1 by a hydrogen bond between the hydroxyl group of the alcohol molecule and the tetrazole group of the compound. The hydroxyl group of each alcohol molecule further links with the imidazole ring of the neighboring compound by hydrogen bond to form a hydrogen-bond network in both alcoholates. A tunnel-like structure that includes alcohol molecules is formed in each alcoholate. The ansolvate crystal showed completely different thermal and X-ray crystallographic characteristics from the alcoholates, where the compound molecules were directly linked by hydrogen bonds between the tetrazole group of a molecule and the imidazole ring of the neighboring molecule. The position of the hydrogen atom in the tetrazole ring was different between the ansolvate and alcoholates. Unlike alcoholates, a layer structure stacked on the b-c plane was observed in the ansolvate crystal. It was concluded that the molecular conformation and the arrangement of the compound molecules were largely different between ansolvate and alcoholate crystals.

Kenduskeag East CSO Storage Facility in Bangor, Maine

Bangor, Maine, a community of 33,000, is one of several hundred communities nationwide undertaking projects to control Combined Sewer Overflows. The City's Long Term Control Plan recommends several control technologies for Bangor's CSO situation, including the construction of CSO storage facilities in three locations. In 1998, Bangor constructed the 1.2 million-gallon Davis Brook CSO Storage Facility, an inline tunnel-like structure constructed of pre-cast concrete box sections and located under a future waterfront park area. The project was extremely successful from a construction and operational perspective, and very cost-effective with a construction cost at about $1.3 million. In September 2000, construction commenced on the City's second CSO storage project, the 1.2 million-gallon Kenduskeag East CSO Storage Facility. Bangor again utilized pre-cast concrete box sections to construct this off-line structure underneath an existing public parking lot in the downtown area. At a cost to the City of less than $2.2 million, this project is $3.1 million less than a proposed cast-in-place tank. By utilizing precast sections, the entire structure was installed within a threemonth time frame, with only minimal disruption to the public. The precast units were manufactured locally under a separate contract; with over half of the units manufactured by the time installation began. Units were delivered to the project on an as needed basis. The facility fit nicely under a public parking lot, thereby requiring no additional land area. The project includes a flushing system to remove settled solids from the bottom of the tank. The facility is connected to the City's Supervisory Control and Data Acquisition (SCADA) system, which will provide real time monitoring and remote control by Treatment Plant personnel. The local economy benefited with design, precast manufacturing, and construction all accomplished locally. This paper discusses several issues that should be of interest to other CSO (or SSO) communities contemplating storage projects, including design considerations, advantages of precast concrete, low costs, ease and speed of construction, and operational experience.

Synthesis of Titanate Derivatives Using Ion‐Exchange Reaction

Two types of titanate derivatives, layered hydrous titanium dioxide (H2Ti4O9·nH2O) and potassium octatitanate (K2Ti8O17) with a tunnellike structure, were synthesized using an ion‐exchange reaction. Fibrous potassium tetratitanate (K2Ti4O9·nH2O) was prepared by calcination of a mixture of K2CO3 and TiO2 with a molar ratio of 2.8 at 1050°C for 3 h, followed by boiling‐water treatment of the calcined products for 10 h. The material then was transformed to layered H2Ti4O9·nH2O through an exchange of K+ ions with H+ ions using HCl. K2Ti8O17 was formed by a thermal treatment of KHTi4O9·nH2O. Pure KHTi4O9·nH2O phase was effectively produced by a treatment of K2Ti4O9 with 0.005M HCl solution for 30 min. Thermal treatment at 250°–500°C for 3 h resulted in formation of only K2Ti8O17.

Rigid Rod-Shaped Polyols: Functional Nonpeptide Models for Transmembrane Proton Channels

The present study concerns the mode of action of a rigid rod-shaped polyol 1 and the corresponding hexamer 2. Proton flux mediated by 1 is shown to be strongly favored over metal cations and anions. The modest selectivity for monovalent cations (Rb+ > Cs+ > K+ > Na+ ≈ Li+, Eisenman sequence II) is determined by the dehydration energy and is weakly influenced by the local electric (ionophoric) field. The induction of membrane defects was ruled out by the absence of dye leakage. Structural studies by circular dichroism and fluorescence spectroscopy imply that 1 aggregates in polar and nonpolar solvents, but not in lipid bilayers. Furthermore, it is shown that a very small fraction of 1 adopts a monomeric transmembrane tunnel-like structure which accounts for activity, while the remainder forms inactive self-assemblies. The above results suggest that 1 acts as a functional unimolecular proton wire which mimics the hydrogen-bonded chain mechanism found in bioenergetic systems.

Studies on the subcommissural organ of Salmo gairdneri

The light microscopic analysis of serial sections of the subcommissural organ (SCO) of the rainbow trout (Salmo gairdneri) shows that the form of the groove-like (in cross section) organ varies over its total length. Its rostral origin is a tunnel-like structure anterior to the orifice of the hollow pineal stalk. The SCO forms the dorsal wall of the brain. Caudally the SCO is increasingly displaced from the surface of the brain by the fibers of the posterior commissure; the organ ends in a tabular area beyond the latter. The orifice of the pineal stalk is surrounded by the ependyma of the SCO that invaginates like a funnel and joins with the ependyma of the pineal stalk after a considerable narrowing. The rudimentary parapineal organ is located on the left side of the brain and is connected with the left habenular ganglion through the parapineal tract. It contacts the third ventricle with a short channel within the ependyma of the SCO. The histological organization of the ependymal and hypendymal cells of the SCO is typical of teleosts. Secretory material is located basally and apically in relation to the nucleus, but there is no indication of a basal secretory release. Basal ependymal processes terminate with broadened endings at the membrana limitans externa. The apical product is discharged into the third ventricle, where it aggregates into the thread-like structure of Reissner's fibre. The SCO cells have no direct contact with cerebral or meningeal blood vessels.

Transposition of the great arteries with ventricular septal defects: Surgical considerations concerning the Rastelli operation

We studied the anatomy of the ventricular septal defect in 20 heart specimens and eight operated patients with transposition of the great arteries regarding the feasibility of the Rastelli operation. They were divided into three groups. In Group I, comprising eight cases, creation of a left ventricle-aorta connection was not prevented by interposition of the atrioventricular valve tissue, and the ventricular septal defect was large or could be enlarged sufficiently. Thus, the Rastelli operation was feasible in all cases. In Group II, comprising 12 cases, interposition of the atrioventricular valves was not present, but the ventricular septal defect was inadequate in size for a good left ventricle-aorta connection. Small or even medium-sized ventricular septal defects were not enlargeable because of surrounding structures or inadequate septum for resection. In all cases, the ventricular septal defect was a tunnellike structure with two orifices; attempted enlargement would be more difficult at the left ventricular end (not obvious to the surgeon's view) than at the right one. The Rastelli operation was judged inadvisable in these cases. In Group III, comprising eight cases, the Rastelli operation was considered inadvisable because of interposition of atrioventricular valve tissue. The size of the ventricular septal defect and the presence of interposed atrioventricular valves can be diagnosed preoperatively. The presence of enough available space for resection, especially at the left ventricular end, should be determined preoperatively and/or intraoperatively in patients with medium-sized ventricular septal defects requiring enlargement. The anatomy of the ventricular septal defect may significantly alter the surgical approach for patients with transposition of the great arteries and ventricular septal defect.

Double-outlet right ventricle with tunnel from left ventricle to aorta

The successful surgical correction of an unusual form of double-outlet right ventricle (DORV) in a 4-year-old boy is described. A long tunnel-like structure was present between the left ventricle and the aorta and also communicated with the right ventricle. hemodynamic and angiographic evaluation demonstrated restrictive communications between the tunnel, the aorta, and each of the ventricles. A pathological concept explaining the anatomic abnormality seen in this patient is discussed.