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Biomedical subjects

W Fujita

Publications and source records attributed to W Fujita.

7 recordsLinked to original sources
PubMed2006

Quasi-one-dimensional molecular magnets based on derivatives of (fluorobenzyl)pyridinium with the [M(mnt)2] monoanion (M = Ni, Pd or Pt; mnt2- = maleonitriledithiolate): syntheses, crystal structures and magnetic properties.

The syntheses, structural characterizations and magnetic behaviors of three new complexes, 1-(3',4',5'-trifluorobenzyl)pyridinium [M(mnt)2]- [M = Ni (1), Pd (2) or Pt (3)], are reported. These complexes are isomorphous and their prominent structural character is that the [M(mnt)2]- anions form columnar stacks, in which the dimerization was observed. Complexes 2 and 3 are diamagnetic, while 1 possesses an energy gap of 2474 K. For crystal 4, 1-(4'-fluorobenzyl)pyridinium [Ni(mnt)2] (its structure and magnetic susceptibility were briefly reported earlier), the magnetic behavior can be divided into two regimes, namely, weakly ferromagnetic coupling above 93 K and strongly antiferromagnetic coupling below 93 K. A transition occurs at 93 K which switches the magnetic exchange nature from ferromagnetic to antiferromagnetic. A sharp thermal abnormality with lambda-shape, associated with the transition, appears from its heat capacity measurement to indicate that the transition is first order. The temperature dependences of the superlattice diffractions revealed the existence of the pretransitional phenomena up to at least 140 K. The unusual magnetic behavior of 4, such as the origin of the ferromagnetic interaction in the high temperature phase and what causes the spin transition, are discussed further.

Journal Article↗
PubMed2005

Structural phase transition driven by spin-lattice interaction in a quasi-one-dimensional spin system of [1-(4'-iodobenzyl)pyridinium][Ni(mnt)2].

Crystal structures and magnetic properties were determined for two novel compounds, [1-(4'-iodobenzyl)pyridinium][M(mnt)2] (mnt2- = maleonitriledithiolate; M = Ni (1) or Cu (2)). At room temperature, single crystals of 1 and 2 were isostructural, featuring the formation of segregated columnar structures with regular stacks of cations and anions. For crystal 1, a magnetic transition was observed at approximately 120 K; furthermore, its magnetic behavior was consistent with that of a regular Heisenberg antiferromagnetic (AFM) chain of S = 1/2 in the high-temperature phase (HT phase) and that of a spin-gap system in the low-temperature phase (LT phase). Such a phenomenon is similar to the spin-Peierls transition. However, the crystal structure of 1 in the LT phase at 100 K revealed that its structural transition is associated with the magnetic transition. Because crystal 2 (S = 0) did not exhibit a structural transition, the structural transition of 1 is driven by spin-lattice interaction.

Journal Article↗
PubMed2003

Photoinduced phase transition in an organic radical crystal with room-temperature optical and magnetic bistability.

A phase control by photoirradiation is successfully achieved in a spin-Peierls system of the organic radical crystal, 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA), which exhibits optical and magnetic bistability around room temperature with a large hysteresis loop. A nanosecond laser pulse is found to induce a transition from a diamagnetic low-temperature phase to a paramagnetic high-temperature phase both inside (296 K) and outside (11 K) the hysteresis loop. Comparison of the excitation energy dependence between transition efficiency and photoconductivity suggests that the photoinduced transition is driven by suppression of the spin-Peierls instability by the accumulation of photocarriers.

Journal Article↗
PubMed1999

Room-Temperature Magnetic Bistability in Organic Radical Crystals.

A large first-order magnetic phase transition in an organic radical, 1,3,5-trithia-2,4,6-triazapentalenyl, is described. The transition occurs with a wide thermal hysteresis loop over the temperature range 230 to 305 kelvin. The high-temperature phase is paramagnetic, and its structure consists of a uniform one-dimensional stacking of the radical. The low-temperature phase is diamagnetic because of strong dimerization along the stacking direction. The results may have applications in thermal sensors, switching units, and information storage media based on organic radical crystals.

Journal Article↗
PubMed1985

[Acute appendicitis: a study on 118 patients].

One hundred eighteen patients with acute appendicitis operated on at Kawasaki Medical School Hospital during the 8-year period from Aug. 1, 1976 to Feb. 29, 1984 were reviewed. There were 78 children and 40 adults. The clinico-pathological types of acute appendicitis were: simple acute in 35 cases (29.7%); phlegmonous in 30 cases (25.4%); gangrenous in 24 cases (20.3%) and perforated in 29 cases (24.6%). Of the 78 children, 27 (34.6%) had perforated appendixes, whereas of the 40 adults only 2 (5.0%) showed perforated appendicitis. The initial symptoms were abdominal pain in 96.6%; nausea, vomiting or both in 33.1%, and fever in 11.9%. The physical findings on admission were abdominal tenderness in 99.2%, rebound tenderness in 52.5% and palpable mass in 17.8%. The mean body temperature on admission was 37.2 degrees C, and mean WBC count was 12,900/mm3. The roentgenography of the abdomen revealed the "sentinel loop sign" in 66.3%. In the patients under 15 years of age, the frequency of perforation seen in those underwent operation within 24 hours after onset and in those after 24 hours was 12.7% and 56.4%, respectively. From this result, it is advised that all the young patients suspected of having acute appendicitis should be admitted to the hospital promptly, and the diagnosis should be made within 24 hours.

Acute Disease↗