The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes

The near-Earth carbonaceous asteroid 162173 Ryugu is thought to have been produced from a parent body that contained water ice and organic molecules. The Hayabusa2 spacecraft has obtained global multicolor images of Ryugu. Geomorphological features present include a circum-equatorial ridge, east-west dichotomy, high boulder abundances across the entire surface, and impact craters. Age estimates from the craters indicate a resurfacing age of [Formula: see text] years for the top 1-meter layer. Ryugu is among the darkest known bodies in the Solar System. The high abundance and spectral properties of boulders are consistent with moderately dehydrated materials, analogous to thermally metamorphosed meteorites found on Earth. The general uniformity in color across Ryugu's surface supports partial dehydration due to internal heating of the asteroid's parent body.

Role of Multichance Fission in the Description of Fission-Fragment Mass Distributions at High Energies

Fission-fragment mass distributions were measured for ^{237-240}U, ^{239-242}Np, and ^{241-244}Pu populated in the excitation-energy range from 10 to 60 MeV by multinucleon transfer channels in the reaction ^{18}O+^{238}U at the Japan Atomic Energy Agency tandem facility. Among them, the data for ^{240}U and ^{240,241,242}Np were observed for the first time. It was found that the mass distributions for all the studied nuclides maintain a double-humped shape up to the highest measured energy in contrast to expectations of predominantly symmetric fission due to the washing out of nuclear shell effects. From a comparison with the dynamical calculation based on the fluctuation-dissipation model, this behavior of the mass distributions was unambiguously attributed to the effect of multichance fission.

Effect of abutment tooth reinforcement techniques on the fracture resistance of removable partial denture master casts

PURPOSE

The purpose of this study was to compare the mean loads required to fracture an isolated stone abutment tooth when various reinforcement techniques were used: (A) no reinforcement, (B) surface hardening, (C) impression trimming, (D) dowel placement, and (E) impression trimming plus dowel placement.

MATERIALS AND METHODS

Die stone premolar specimens for each group (n = 4) were loaded perpendicular to the tooth long axis in 100-g increments 25 hours after pouring the impression. Mean load to failure was determined for each group. Data were evaluated with a one-way analysis of variance (alpha = 0.05) to determine differences among groups. Paired comparisons of factor level means were made with Tukey's q-test.

RESULTS

The mean fracture load for Group E (7.6 kg) was significantly greater than Groups A (2.0 kg), B (2.1 kg), and C (3.4 kg). No significant difference was found between Groups D (6.0 kg) and E.

CONCLUSIONS

Dowel reinforcement with impression trimming at the cervical portion of the abutment tooth resulted in significantly greater fracture resistance than the control, surface model hardener, or impression trimming alone. J Prosthodont 2001;10:22-25.

Significance of hematoma size for evaluating the grade of blunt renal trauma

BACKGROUND

The hematoma size relative to the body size was measured on computed tomography films using a personal computer system in order to define whether that parameter is useful for decision-making in the management of blunt renal trauma.

METHODS

From 1982 to 1997, 33 patients with intermediate or severe grade blunt renal trauma were retrospectively divided into three groups: group 1, managed conservatively without transcatheter embolization; group 2, managed by bedrest after selective transcatheter embolization; and group 3, managed operatively. In these three groups, the hematoma area (H) and the ratio of hematoma area to body area on CT (H/B) were measured and the chronological changes of the H/B in groups 1 and 2 were studied.

RESULTS

The H and H/B of group 3 were significantly larger than those of group 1. The H/B was more clearly distinguished for each group compared with the H alone. Well-preserved kidney integrity, despite the presence of a large hematoma in group 2, allowed the conservative treatment following transcatheter embolization of the bleeding site. The H/B of all group 1 patients gradually decreased and on the 40th or 50th day after injury they reached a level equivalent to the ratio of contra-lateral normal kidney area to body area.

CONCLUSION

The ratio of hematoma area to body area on CT was very useful in evaluating the grade of blunt renal trauma. In conservative treatment for blunt renal trauma changes of the hematoma size is a useful indicator for management.

[Experimental studies on a compartment syndrome caused by a tourniquet]

The muscle proteins of rabbits with the compartment syndrome caused by tourniquet were studied by SDS-polyacrylamide gel electrophoresis and the compartment pressure post-ischemia was measured. The post-ischemic pressure in the anterior compartment increased more than that in the deep-posterior compartment. The phoretic patterns of structural and soluble proteins changed after ischemia, and their degeneration appeared to depend on the degree of pressure increase. In ischemic contracture, the patterns of myosin light chains of type 1 fibers changed to those of type 2 fibers. This indicated the possibility of fiber type transformation from type 1 to type 2 in ischemic contracture.

Unexplained infertility. A reappraisal

During a 30-month period 229 couples were evaluated for infertility at the Naval Regional Medical Center, Oakland. Laparoscopy was used in all cases of otherwise unexplained infertility. The resulting laparoscopic examination of the female partner of 24 such couples demonstrated abnormal findings in 18 (75%). Of these 18 subjects, unsuspected endometriosis was found in 11 (46%) and peritubal adhesions in 7 (29%). Of the 229 couples evaluated, only 8 (3.5%) failed to show some etiologic factor associated with infertility. Thus, the previously reported 10 to 20% incidence of unexplained infertility is too high an estimate in view of the additional information made available through pelvic endoscopy.