Mass, Spectroscopy, and Two-Neutron Decay of ^{16}Be

The structure and decay of the most neutron-rich beryllium isotope, ^{16}Be, has been investigated following proton knockout from a high-energy ^{17}B beam. Two relatively narrow resonances were observed for the first time, with energies of 0.84(3) and 2.15(5) MeV above the two-neutron decay threshold and widths of 0.32(8) and 0.95(15) MeV, respectively. These were assigned to be the ground (J^{π}=0^{+}) and first excited (2^{+}) state, with E_{x}=1.31(6)  MeV. The mass excess of ^{16}Be was thus deduced to be 56.93(13) MeV, some 0.5 MeV more bound than the only previous measurement. Both states were observed to decay by direct two-neutron emission. Calculations incorporating the evolution of the wave function during the decay as a genuine three-body process reproduced the principal characteristics of the neutron-neutron energy spectra for both levels, indicating that the ground state exhibits a strong spatially compact dineutron component, while the 2^{+} level presents a far more diffuse neutron-neutron distribution.

Quasifree Neutron Knockout Reaction Reveals a Small s-Orbital Component in the Borromean Nucleus ^{17}B

A kinematically complete quasifree (p,pn) experiment in inverse kinematics was performed to study the structure of the Borromean nucleus ^{17}B, which had long been considered to have a neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for 1s_{1/2} and 0d_{5/2} orbitals, and a surprisingly small percentage of 9(2)% was determined for 1s_{1/2}. Our finding of such a small 1s_{1/2} component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in ^{17}B. The present work gives the smallest s- or p-orbital component among known nuclei exhibiting halo features and implies that the dominant occupation of s or p orbitals is not a prerequisite for the occurrence of a neutron halo.

Surface Localization of the Dineutron in ^{11}Li

The formation of a dineutron in the ^{11}Li nucleus is found to be localized to the surface region. The experiment measured the intrinsic momentum of the struck neutron in ^{11}Li via the (p,pn) knockout reaction at 246  MeV/nucleon. The correlation angle between the two neutrons is, for the first time, measured as a function of the intrinsic neutron momentum. A comparison with reaction calculations reveals the localization of the dineutron at r∼3.6  fm. The results also support the density dependence of dineutron formation as deduced from Hartree-Fock-Bogoliubov calculations for nuclear matter.

Intracystic hemorrhage of the middle fossa arachnoid cyst and subdural hematoma caused by ruptured middle cerebral artery aneurysm

We report a case of a cerebral aneurysm arising from the bifurcation of the left middle cerebral artery that ruptured into a left middle cranial fossa arachnoid cyst, associated with acute subdural hematoma. We discuss the relationships of aneurysm, arachnoid cyst, and subdural hematoma.

Ultrastructure of obstructive tissue in malfunctioning ventricular catheters without infection

The obstructive tissue in eight malfunctioning ventricular catheters without infection was studied using scanning and transmission electron microscopy. Shunt obstruction was due to debris from ventricular structures such as the choroid plexus and ependymal tissue. There was a preponderance of collagen fibers, and many fibroblasts were present within these tissues. The cytoplasm of the fibroblasts contained extended endoplasmic reticulum. The tissues filled the lumen of the catheters in radially arranged layers. Peeling the silicone was seen on the surface of the ventricular catheters but was not present in normal silicone catheters. Finger-like microvilli were observed on the free surface of the tissue. Many vessels were seen in the transverse section of the tissue. Activated fibroblasts and vascularization may be important in tissue growth in ventricular catheters.

Ultrastructure of collagen fibers in the outer membrane of recurrent chronic subdural hematoma

The three-dimensional structure of the collagen fibers in the outer membrane of recurrent chronic subdural hematoma was studied by scanning electron microscopy (SEM). Specimens obtained at surgery were treated with NaOH at room temperature to digest away all cellular components and expose the collagen fibers. SEM observation of the dural side of the outer membrane showed the collagen fibers were woven into a compact feltwork with a dense arrangement. The fiber bundles had a honeycomb structure framed by the collagen fibers. Observation of the hematoma side found the collagen bundles had a sparse wavy appearance. The arrangement of the collagen fibers on the dural side is different from that on the hematoma side. The thick outer membrane may be formed by granulation resulting from inflammatory reaction. Collagen fibrillar networks are not fragile, and may reinforce the outer membrane of the recurrent hematoma.

[Drug distribution of pelvic intraarterial infusion chemotherapy by bilateral internal iliac arterial catheter placement with coil occlusion of superior, inferior gluteal and obturator arteries]

The anticancer drug distribution in pelvic arterial infusion chemotherapy with bilateral internal iliac arterial catheter placement with coil occlusion of the superior, inferior and obturator arteries was indirectly evaluated by serially performed DSA, CTA and RI on 18 patients with pelvic malignancies. The distribution was judged to be Excellent (E), defined as uniform distribution in the entire lesion alone, in 9 of 18 patients (50%) evaluated prior to the start of the arterial infusion (AI), and as Good (G), defined as uniform distribution in the entire lesion and partly on an unaffected portion, in 9 (50%). Of the 11 patients evaluated after 7 times AI, E was found in 3 patients (27%), G in 7 (64%) and Fair (F), defined as distribution with a defect in the lesion, in one patient (9%). Of the 11 patients evaluated after 14 AI, E was found in 5 (45%), G in 4 (36%) and F in 2 (18%). Of the 7 patients evaluated after 21 AI, E was found in 2 (29%), G in 4 (57%) and F in one (14%). G was found in 2 of 2 patients (100%) evaluated after 28 AI. These results suggest that this method can maintain a favorable anticancer drug distribution even after multiple sessions of AI.

Postoperative chronic subdural hematoma following craniotomy--four case reports

Postoperative chronic subdural hematoma (CSH) following craniotomy developed in only four of 372 patients undergoing craniotomy for aneurysm surgery (1 patient) and brain tumor surgery (3 patients) between April, 1991 and November, 1993, an incidence of only 1.1%. There were three males and one female, aged from 32 to 66 years (mean 56 yrs). The period between craniotomy and development of CSH ranged from 3 to 5 months (mean 4.3 mos). Postoperative hematomas were located on the operative sides in three patients and the contralateral side in the other. Early postoperative computed tomographic scans found subdural fluid collection in all patients. Magnetic resonance images showed linear meningeal enhancement in all patients. Postoperative CSH may be caused by mixture of blood in subdural cerebrospinal fluid collection which persists due to reduced brain elasticity and wide subarachnoid membrane opening resulting in neomembrane formation and finally development of hematoma.

Antitumor effect of forphenicinol, a low molecular weight immunomodifier, on murine transplantable tumors and microbial infections

The antitumor activities of forphenicinol against murine transplantable tumors were examined. Ehrlich carcinoma was suppressed by treatment with 0.08 approximately 0.31 mg/kg/day of forphenicinol given for 10 days starting 5 days after tumor inoculation. IMC carcinoma was also suppressed by treatment with 0.5 approximately 5 mg/kg/day given for 5 days starting 8 days after the inoculation. The antitumor activity was dependent on the number of tumor cells inoculated, schedule of administration and dose. However, even in case of fast growing tumors such as L1210 and inoculation with a large number of tumor cells, forphenicinol markedly enhanced the antitumor effect of 6-mercaptopurine, aclacinomycin and cyclophosphamide. Forphenicinol showed a protective effect on Pseudomonas infection in mice.