Cell dynamics approach to the formation of metastable phases during phase transformation.

In this paper, we use the cell dynamics method to study the dynamics of phase transformation when three phases exist. The system we study is a two-dimensional system. The system is able to achieve three phases coexistence, which for simplicity we call crystal, liquid and vapor phases. We focus our study on the case when the vapor and crystal phases are stable and can coexist while the other intermediate liquid phase is metastable. In this study we examine the most fundamental process of the growth of a composite nucleus which consists of a circular core of one phase surrounded by a circular layer of second phase embedded in a third phase. We found that there is one special configuration that consists of a core stable phase surrounded by another stable phase in a metastable liquid environment which becomes stationary and stable. Then, the nucleus does not grow and the metastable liquid survives. The macroscopic liquid phase does not disappear even though it is thermodynamically metastable. This result seems compatible to the argument of kinetics of phase transition developed by Cahn [J. Am. Ceram. Soc. 52, 118 (1969)] based on the construction of a common tangent of the free energy curve.

1:1 complexes of dimethylthio- and ethylenedithio-tetrathiafulvalenothioquinone-1,3-dithiolemethides with CuBr2 as a new type of pi/d molecular system.

The reaction of dimethylthio- (1) and ethylenedithio-tetrathiafulvalenothioquinone-1,3-dithiolemethides (2) with CuBr2 gave 1:1 complexes between the donors and CuBr2, 1.CuBr2 and 2.CuBr2, in which the Cu atom of CuBr2 binds to the thiocarbonyl S atom in 1 and 2. The electrical conductivity (sigma) of 1.CuBr2 at room temperature was ca. 10(-5) S cm-1, while a comparatively high value of 4.0 S cm-1 was obtained for 2.CuBr2, whose temperature dependence of sigma exhibited, however, semiconducting behavior with a very small activation energy of 0.18 eV. The observed paramagnetic susceptibilities (chi p's) of the Cu complexes were composed of both a component due to the localized Cu spins obeying the Curie-Weiss law and a temperature-independent chi p due to the conducting pi electrons on the 1- or 2-stacked columns. From the Curie constants obtained, the degrees of intramolecular electron transfer from 1 and 2 to CuBr2 moieties were estimated at ca. 90% and 60%, respectively. The small, negative Weiss temperature suggest very weak antiferromagnetic interactions among the Cu spins on the CuBr2 moieties.

2,2'-Spirobi(1,3-benzodithiole).

The X-ray structure analysis of 2,2'-spirobi(1,3-benzodithiole), C(13)H(8)S(4), has been performed. The molecule has crystallographic twofold rotation symmetry, the axis passing through the spiro-C atom. The four S atoms are arranged around the spiro-C atom in two almost orthogonal CS(2) planes. However, because of large bending of the two five-membered rings, close contact is present between two connected C atoms on the benzo group of each 1,3-benzodithiole ring and one S atom on the other 1,3-benzodithiole ring.

A Molecular Theory of Solvation Force Oscillations in Nonpolar Liquids.

A molecular theory based on the nonlocal density functional theory is used to calculate the solvation-force oscillations in nonpolar liquids observed with an atomic-force microscope (AFM) and a surface-force apparatus (SFA) operated within liquid. The fluid-fluid as well as wall-fluid interactions are represented by a Lennard-Jones type potential, whose parameters are related to the Hamaker constant. The density functional calculation shows that a stronger wall-fluid than fluid-fluid interaction is necessary to observe this solvation-force oscillation. The magnitude of the Hamaker constants of various nonpolar organic liquids and various substrates shows that this criterion for the observation of oscillation is normally satisfied. Copyright 1998 Academic Press.

Mediastinal tumor and application of thoracoscopic surgery.

Thoracoscopic resection of a mediastinal tumor or cyst was done in three patients: two with neurogenic tumors and one with a bronchogenic cyst. The tumors and cyst showed evidence of a discrete plane on computed tomography of the chest. The mean operation time and estimated blood loss were 156 min and 45 g, respectively. For all three patients, the chest drain was removed within 48 h after operation, and there were no complications related to thoracoscopic surgery. The advantages of this approach are less pain, early return to normal activity, and an acceptable cosmetic appearance. Based on our experience, thoracoscopic surgery is considered the treatment of choice for certain mediastinal tumors or cyst.

Esophageal stricture in Crohn's disease--a case report.

We treated a 46-year-old Japanese man with Crohn's disease of the esophagus and for whom medical therapy was adequate. Crohn's disease of the esophagus is a rare disease without specific clinical features and establishment of the diagnosis with guided biopsy is extremely difficult. Therefore, Crohn's disease of the esophagus should be considered in the differential diagnosis of biopsy-negative carcinoma of the esophagus in order to avoid major surgery. Treatment of Crohn's disease of the esophagus should primarily be medical and esophagectomy should only be considered in cases of complications, intractability or a suspicion of malignancy in the biopsied specimen.

DNA cytophotometry on atypical glands in stomach carcinogenesis of dogs induced by N-methyl-N'-nitro-N-nitrosoguanidine.

Microspectrophotometric measurement of the DNA content of cell nuclei was performed on the lesions (including atypical glands) in gastric carcinogenesis of 15 male beagle dogs, which had been induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The distribution patterns of DNA content were classified into three types: normal, subnormal, and abnormal. The histograms of the distribution in normal and regenerative glands were a normal type and subnormal type, respectively, while adenocarcinoma showed an abnormal distribution type. In atypical glands, the distribution patterns in autopsy cases were subnormal and abnormal types. When sequential endoscopic observation of the angulus of the stomach in dog No. 3 was carried out, atypical glands were found in an ulcer in the early stage of MNNG administration and a precancerous lesion in the late stage after termination of MNNG. The atypical glands in the early stage were of the subnormal type, while the atypical glands in the late stage were of the abnormal type. According to the results, these two types-subnormal and abnormal - of distribution of DNA content on the atypical glands may be related to regeneration and subsequent development of cancer, respectively.

Endoscopic study of chronological changes leading to cancer in the esophagus of dogs induced by N-ethyl-N'-nitro-N-nitrosoguanidine.

An endoscopical study of chronological change during the carcinogenetic process of cancer of the esophagus induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) in 16 male beagle dogs was performed to clarity whether or not precancerous lesions exist in the esophagus. Redness was first observed in the mucosa in the lower and/or middle portions of the esophagus. A small nodule developed in the redness, followed by a nodule. The nodule then developed into a flat polyp which finally developed into lesions such as an elevated lesions, protrusions or elevations with depressions. Histologically, esophagitis or acanthosis in the redness and acanthosis were found in most of the small nodules. With regard to the nodules, papillomatosis was observed in half of the lesions, while either acanthosis or atypical epithelial proliferation were found in most of the flat polyps. Almost all the elevated or protruding lesions were found to be carcinoma.

Regression of polyploid carcinoma induced by N-methyl-N'-nitro-N-nitrosoguanidine in the stomach of a dog.

Polyploid carcinoma in the gastric antrum of a Beagle dog induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was sequentially studied by endoscopy and biopsy. Ulcer appeared on the angulus of the stomach at the 28th week and resulted in ulcer scar at the 42nd week. A new depression with atypical glands arose on the ulcer scar at the 69th week, developed elevated border at the 77th week, and progressed to a polyploid lesion at the 90th week. Well-differentiated adenocarcinoma in situ was found in the polyploid lesion at the 97th week. It gradually grew with nodular change of its surface. However, the carcinoma was ulcerated at the 126th week, became an elevated lesion with central depression at the 138th week, and finally regressed at the 154th week. At necropsy on the 202nd week, no carcinoma was found in the stomach.

Experimental gastric carcinoma induced by N-methyl-N'-nitro-N-nitrosoguanidine.

Serial studies by endoscopy and biopsy were made in a Beagle dog during and after oral administration of N-methyl-N'-nitro-N-nitroguanidine (MNNG). Between the 23rd and the 45th week of observation erosions and ulcers appeared at the angulus of the stomach and turned into ulcer scar. A depression with atypical glands was seen in the ulcer scar of the posterior wall of the angulus at the 94th week. It developed elevated margins at the 102nd week, when a well differentiated adenocarcinoma was found histopathologically. Ulceration and reepithelialization were observed in the early carcinoma. The carcinoma progressed into a larger one of Borrmann's type 2 at the 115th week and further into its type 3 at the 181st week. A second carcinoma with signet ring cell carcinoma developed in the anterior wall of the angulus. The two carcinomas fused and formed a single lesion. At autopsy in the 216th week the carcinoma invaded the serosa, and metastasis to regional lymph nodes was observed.