48 research outputs found
Characterization of the seismic environment at the Sanford Underground Laboratory, South Dakota
An array of seismometers is being developed at the Sanford Underground
Laboratory, the former Homestake mine, in South Dakota to study the properties
of underground seismic fields and Newtonian noise, and to investigate the
possible advantages of constructing a third-generation gravitational-wave
detector underground. Seismic data were analyzed to characterize seismic noise
and disturbances. External databases were used to identify sources of seismic
waves: ocean-wave data to identify sources of oceanic microseisms, and surface
wind-speed data to investigate correlations with seismic motion as a function
of depth. In addition, sources of events contributing to the spectrum at higher
frequencies are characterized by studying the variation of event rates over the
course of a day. Long-term observations of spectral variations provide further
insight into the nature of seismic sources. Seismic spectra at three different
depths are compared, establishing the 4100-ft level as a world-class low
seismic-noise environment.Comment: 29 pages, 16 figure
Transmesocolic Hernia of the Ascending Colon with Intestinal Obstruction
An internal hernia may be either congenital or acquired. The reported incidence of such hernias is 1–2%. In rare cases, internal hernias are the cause of small bowel obstruction, with a reported incidence of 0.2–0.9%. Transmesocolic hernia of the ascending colon is especially rare. We report a case of transmesocolic hernia of the ascending colon with intestinal obstruction diagnosed preoperatively. A 91-year-old Japanese female was admitted to our hospital with abdominal distention and vomiting of 3 days duration. She had no past history of any abdominal surgery. Abdominal examination revealed distention and tenderness in the right iliac fossa. Abdominal computed tomography revealed ileus in the sac at the left side of the ascending colon and dilatation of the oral side of the intestine. We diagnosed a transmesocolic hernia of the ascending colon with intestinal obstruction and performed emergency surgery. At the time of operation, there was internal herniation of ileal loops through a defect in the ascending mesocolon, without any strangulation of the small bowel. The contents were reduced and the tear in the ascending mesocolon was closed. The postoperative course was uneventful and the patient was discharged 14 days after surgery. In conclusion, preoperative diagnosis of bowel obstruction caused by a congenital mesocolic hernia remains difficult despite the techniques currently available, so it is important to consider the possibility of a transmesocolic hernia when diagnosing a patient with ileus with no past history of abdominal surgery
Half-Life Systematics across the N=126 Shell Closure:Role of First-Forbidden Transitions in the beta Decay of Heavy Neutron-Rich Nuclei
This Letter reports on a systematic study of β-decay half-lives of neutron-rich nuclei around doubly magic ^{208}Pb. The lifetimes of the 126-neutron shell isotone ^{204}Pt and the neighboring ^{200-202}Ir, ^{203}Pt, ^{204}Au are presented together with other 19 half-lives measured during the "stopped beam" campaign of the rare isotope investigations at GSI collaboration. The results constrain the main nuclear theories used in calculations of r-process nucleosynthesis. Predictions based on a statistical macroscopic description of the first-forbidden β strength reveal significant deviations for most of the nuclei with N<126. In contrast, theories including a fully microscopic treatment of allowed and first-forbidden transitions reproduce more satisfactorily the trend in the measured half-lives for the nuclei in this region, where the r-process pathway passes through during β decay back to stability