ß Decay of

The interpretation of observations of cooling neutron star crusts in quasipersistent x-ray transients is affected by predictions of the strength of neutrino cooling via crust Urca processes. The strength of crust Urca neutrino cooling depends sensitively on the electron-capture and ß-decay ground-state-to-ground-state transition strengths of neutron-rich rare isotopes. Nuclei with a mass number of A=61 are predicted to be among the most abundant in accreted crusts, and the last remaining experimentally undetermined ground-state-to-ground-state transition strength was the ß decay of ^{61}V. This Letter reports the first experimental determination of this transition strength, a ground-state branching of 8.1_{-3.1}^{+4.0}%, corresponding to a log ft value of 5.5_{-0.2}^{+0.2}. This result was achieved through the measurement of the ß-delayed γ rays using the total absorption spectrometer SuN and the measurement of the ß-delayed neutron branch using the neutron long counter system NERO at the National Superconducting Cyclotron Laboratory at Michigan State University. This method helps to mitigate the impact of the pandemonium effect in extremely neutron-rich nuclei on experimental results. The result implies that A=61 nuclei do not provide the strongest cooling in accreted neutron star crusts as expected by some predictions, but that their cooling is still larger compared to most other mass numbers. Only nuclei with mass numbers 31, 33, and 55 are predicted to be cooling more strongly. However, the theoretical predictions for the transition strengths of these nuclei are not consistently accurate enough to draw conclusions on crust cooling. With the experimental approach developed in this work, all relevant transitions are within reach to be studied in the future.

Strong neutrino cooling by cycles of electron capture and ß- decay in neutron star crusts.

The temperature in the crust of an accreting neutron star, which comprises its outermost kilometre, is set by heating from nuclear reactions at large densities, neutrino cooling and heat transport from the interior. The heated crust has been thought to affect observable phenomena at shallower depths, such as thermonuclear bursts in the accreted envelope. Here we report that cycles of electron capture and its inverse, ß(-) decay, involving neutron-rich nuclei at a typical depth of about 150 metres, cool the outer neutron star crust by emitting neutrinos while also thermally decoupling the surface layers from the deeper crust. This 'Urca' mechanism has been studied in the context of white dwarfs and type Ia supernovae, but hitherto was not considered in neutron stars, because previous models computed the crust reactions using a zero-temperature approximation and assumed that only a single nuclear species was present at any given depth. The thermal decoupling means that X-ray bursts and other surface phenomena are largely independent of the strength of deep crustal heating. The unexpectedly short recurrence times, of the order of years, observed for very energetic thermonuclear superbursts are therefore not an indicator of a hot crust, but may point instead to an unknown local heating mechanism near the neutron star surface.

Low-temperature triple-alpha rate in a full three-body nuclear model.

A new three-body method is used to compute the rate of the triple-alpha capture reaction, which is the primary source of 12C in stars. In this Letter, we combine the Faddeev hyperspherical harmonics and the R-matrix method to obtain a full solution to the three-body α+α+α continuum. Particular attention is paid to the long-range effects caused by the pairwise Coulomb interactions. The new rate agrees with the Nuclear Astrophysics Compilation of Reaction rates for temperatures greater than 0.07 GK, but a large enhancement at lower temperature is found (≈10(12) at 0.02 GK). Our results are compared to previous calculations where additional approximations were made. We show that the new rate does not significantly change the evolution of stars around one solar mass. In particular, such stars still undergo a red-giant phase consistent with observations, and no significant differences are found in the final white dwarfs.

Time-of-flight mass measurements for nuclear processes in neutron star crusts.

We present results from time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory that are relevant for neutron star crust models. The masses of 16 neutron-rich nuclei in the scandium-nickel range were determined simultaneously, with the masses of (61)V, (63)Cr, (66)Mn, and (74)Ni measured for the first time with mass excesses of -30.510(890) MeV, -35.280(650) MeV, -36.900(790) MeV, and -49.210(990) MeV, respectively. With these results the locations of the dominant electron capture heat sources in the outer crust of accreting neutron stars that exhibit super bursts are now experimentally constrained. We find the experimental Q value for the (66)Fe→(66)Mn electron capture to be 2.1 MeV (2.6σ) smaller than predicted, resulting in the transition occurring significantly closer to the neutron star surface.

Phase separation in the crust of accreting neutron stars.

Nucleosynthesis, on the surface of accreting neutron stars, produces a range of chemical elements. We perform molecular dynamics simulations of crystallization to see how this complex composition forms new neutron star crust. We find chemical separation, with the liquid ocean phase greatly enriched in low atomic number elements compared to the solid crust. This phase separation should change many crust properties such as the thermal conductivity and shear modulus.

CT herniography in the diagnosis of occult groin hernias.

AIM: To evaluate the role of computed tomography (CT) after herniography in the diagnosis and management of primary and recurrent groin hernias not detectable on clinical examination. MATERIAL AND METHODS: Fifty-one patients underwent CT post-herniography over a 6-year period for suspected primary or recurrent inguinal hernia. The herniography and post-herniography CT findings were retrospectively compared with clinical and surgical follow-up. Statistical analysis was performed to assess the role of herniography and CT post-herniography in the primary and recurrent groups. RESULTS: Of the 51 patients investigated for occult inguinal hernia, 19 had previous hernia repair with possible recurrence. The most common symptom at presentation was groin pain or discomfort (84%). Seventy-five percent in the primary group and 84% in the recurrent group had no findings on herniography or CT. Nine percent in the primary group and 16% in the recurrent group had hernias diagnosed by herniography. CT did not enhance the detection of hernia. Sensitivity for herniography and CT herniography in the primary groin hernia group was 75% as against specificity, which was 100 and 90%, respectively. For the recurrent groin hernias, sensitivity was 60% for herniography and 40% for CT herniography and specificity 100% for both. CONCLUSION: CT performed post-herniography did not provide any benefit over performing herniography alone in the diagnosis of occult primary or recurrent inguinal hernias.

Weight outcomes among antidepressant users in nursing facilities.

OBJECTIVES: Depression is a common and treatable condition among nursing facility residents, with low body weight being a frequent concomitant concern. A common prescribing dictum is that older tricyclic antidepressants (TCAs) enhance appetite and may facilitate weight gain, while newer selective serotonin reuptake inhibitors (SSRIs) cause anorexia and resultant weight loss in older adults. Evidence is lacking on whether the small weight changes noted during short-term antidepressant efficacy trials translate into larger weight changes during prolonged treatment periods. Our main objective was to compare weight outcomes at 6 months among users of three different antidepressant groups with a control group of non-antidepressant users. A secondary objective was to determine whether antidepressant selection was associated with weight pattern before drug initiation, to capture possible prescribing bias that would affect study inferences. DESIGN: Retrospective cohort design using the Minimum Data Set--Plus (MDS+). SETTING: Kansas nursing facilities. PARTICIPANTS: 1,157 antidepressant users age 65 and older who started an antidepressant after admission and remained on the same single agent for at least 6 months, and 4,852 persons meeting the same inclusion/exclusion criteria but not receiving an antidepressant. MEASUREMENTS: Antidepressant use was identified by drug code data and divided into four groups for analysis: TCAs, SSRIs, others, and none. (Amitriptyline and trazodone were excluded because of frequent use for nondepression purposes.) Rates of clinically important loss and gain (assigned for a 10% change from baseline weight or presence of the significant loss or gain markers on the 6-month MDS assessment) and mean weight changes were compared across the four groups. Regression models were used to control for age, gender, baseline weight, confounding comorbidity, and functional variables related to eating. Previous weight patterns (loss, gain, neither, or unknown) before antidepressant initiation were compared across drug groups. RESULTS: Clinically important weight loss and gain occurred at 6 months in 14.8% and 14.4% of the sample, respectively. In unadjusted analyses, an increased likelihood of loss was found for users of SSRIs (Odds Ratio 1.57; CI 1.30, 1.90) and others (OR 1.89; CI 1.18, 3.03), compared with none. In logistic models accounting for potential confounding factors, however, SSRI use showed a modest association with gain (OR 1.31, CI 1.01, 1.70) and a trend toward a similarly modest association with loss (OR 1.28; CI 0.995, 1.64). TCA use was not associated with weight gain. When weight was examined as a continuous variable, all groups demonstrated a broad range of both loss and gain with mean-unadjusted weight changes < 3 pounds. Pairwise comparisons of adjusted differences in weight change at 6 months for SSRIs (mean loss of 1.6 pounds) and TCAs (mean gain of 0.4 pounds) were of marginal importance (P = .046) given the large sample size. No evidence was found for prescribing bias based on prior weight pattern. CONCLUSIONS: TCAs do not facilitate weight gain more than other antidepressant groups and SSRIs are not associated disproportionately with weight loss when other important clinical variables are accounted for. Small but statistically significant differences in mean weight changes between groups are largely a reflection of large sample size rather than clinically important differences. Clinicians may wish to reconsider the widely held notions that TCAs facilitate weight gain and that SSRIs place depressed older nursing facility residents at disproportionate risk for weight loss.

Tube feeding in nursing home residents with severe and irreversible cognitive impairment.

OBJECTIVES: This study was undertaken to determine the degree to which selected demographic and clinical variables are associated with the use of feeding tubes in older nursing home residents with very severe and irreversible cognitive impairment. DESIGN: Descriptive, cross-sectional, population-based study. SETTING: Kansas nursing homes from January 1, 1994, through June 30, 1998. PARTICIPANTS: A total of 4,997 nursing home residents with very severe and irreversible cognitive impairment comprised the study population. Subjects were identified using data in Minimum Data Set (MDS) reports. Those who were included in the study population were over the age of 65, had two consecutive Cognitive Performance Scale scores of 6, were without evidence of significant subsequent improvement, and were not comatose. MEASUREMENTS: The MDS data on each resident were examined to determine subjects' age, ethnicity, gender, Medicaid eligibility, disease diagnoses, physical functioning, and oral/nutritional status, including feeding tube status. The MDS was also used to determine urban versus rural location of the nursing home. The association between the use of feeding tubes and selected demographic and clinical characteristics was then examined using bivariate and logistic regression tests. RESULTS: Of the 4,997 residents in the study population, 577 (11.6%) had feeding tubes. In multivariate analysis, feeding tube use was found to be associated with swallowing problems (odds ratio (OR) 5.4, 95% confidence interval (CI) 4.3-6.8); urban location of nursing home (OR 2.9, 95% CI 2.3-3.5); non-white race (OR 2.7, 95% CI 1.9-3.6); stroke (OR 2.5, 95% CI 2.0-3.1); and absence of dementia (OR 2.5, 95% CI 2.0-3.1). Feeding tubes were also more weakly associated with age <86 years, male gender, dependency for all activities of daily living, and absence of a living will. Feeding tube use was not found to be associated with chewing problems, Medicaid status, or resuscitation status. CONCLUSIONS: Clinical variables including swallowing problems, stroke, and absence of dementia were strongly associated with the use of feeding tubes in this cross-sectional, population-based study. In addition, urban location of nursing home and non-white race were significantly associated with feeding tubes. These findings suggest that feeding tube decisions are strongly influenced by nonclinical factors and invite further investigation.

Very long survival in pediatric cancer between 1944 and 1993.

OBJECTIVE: To identify factors associated with very long survival among all cancer cases diagnosed at age 19 years or younger registered by the Cancer Data Service at the University of Kansas Medical Center in Kansas City, Kansas, U.S.A. in the 40-year period between 1944 and 1983, with follow-up to 1993. METHODS: There were 2720 pediatric patients with 2750 cancers who were studied. Forty-four types of cancer were grouped into 11 diagnostic categories. Diagnosis years spanned four eras: 1944-1953, 1954-1963, 1964-1973, and 1974-1983. Cases were compared using specific characteristics and were divided into short-term and long-term survivors with the division generously set at seven years. The proportions of the long-term survivors were compared by specific characteristics. RESULTS: Among the diagnostic categories, leukemias were the most common (29.8%), followed by CNS tumors (15.2%), and Hodgkin's disease (9.0%). Male to female ratio was 4:3; average age at diagnosis was 8.83 +/- 6.08 years. Long-term survivors totaled 1148 (41.7%). Prognosis was better in cases diagnosed in earlier stages and in later eras. Proportion of long-term survivors increased from 18.7% in era I to 52.6% in era IV. Improvement of survival was statistically significant in most diagnostic categories. CONCLUSIONS: This study shows continuing improvement of survival during four consecutive eras for childhood and adolescent cancer. Early diagnosis was associated with better survival. Unstaged cases decreased over time reflecting progress in diagnostic techniques. Many patients died before seven years after diagnosis. Those who survived more than seven years had excellent survival. Pediatricians can expect to participate in the care of these patients long after the original dianosis and treatment.

A new bioelectrical impedance method for measurement of the erythrocyte sedimentation rate.

A new bioelectrical impedance method was developed to determine the erythrocyte sedimentation rate (ESR) by measuring the settling velocity of red blood cells. A sample of blood was collected in a plastic tube with two electrodes, one positioned above the other. Measurements of electrical resistance were made in the upper region of the blood column. As the red blood cells settled towards the bottom of the container, the resistance decreased continuously. The velocity of settling red blood cells was calculated in 45 samples. The values obtained compared favourably with the ESR determined by the standard Westergren method, giving a correlation coefficient of 0.96 and a standard error estimation of 7.0 mmh-1. We conclude that bioelectrical impedance can be used to measure ESR accurately and that this method has important advantages over existing methods.

Colliding forces in radiology: technologic imperative, resource limitations, and accountability demands.

Advances in radiology over the past 20 years are the product of a technologic imperative that has produced new approaches to the acquisition of medical images and modifications to conventional approaches. The imperative has placed radiology at the leading edge of the computer-technology era of modern medicine and has also produced several big-ticket technologies that have been identified as major contributors to rising health care costs. Consequently, the demands for quantitative data on the impact and cost-effectiveness of the use of these technologies in the clinical arena are increasing. Meeting the growing demand for accountability in radiology requires that the discipline adopt innovative approaches for assessing its technologies and acquire new types of data, including documentation of cost savings accrued by selective use of radiologic technologies and demonstration of the efficiency and cost-effectiveness of triage schemes that lead to more effective decision making. The requirement of quantitative accountability represents a new way of doing business for radiology and a new approach to management for those responsible for business.

An electronic method for rapid measurement of haematocrit in blood samples.

The bioelectrical impedance method was used to determine the haematocrit in patient blood samples. The resistance (R) and reactance (X) of a constant volume of blood were measured at a low (50 kHz) and high (1 MHz) frequency. These dual-frequency impedance measurements were then used to determine the intracellular and extracellular (plasma) fluid volume of the blood and thus the haematocrit in 308 blood samples. The values compared favourably with the microhaematocrit determined on the same samples, giving a correlation coefficient of 0.989 and a standard error estimation of 1.41%. Reactance at 1 MHz was a better parameter for predicting haematocrit than resistances. Factors affecting the resistivity of plasma, such as electrolyte and protein concentrations, were the error sources in the impedance technique. Our technique reduced such errors significantly. In conclusion, this electronic method can be used to measure haematocrit accurately and may be more desirable than conventional methods in certain clinical situations.

Are events after endotoxemia related to circulating phospholipase A2?

OBJECTIVE: The authors sought to determine whether the signs and symptoms of endotoxemia were related to the endotoxin-stimulated increase in circulating phospholipase A2 (PLA2) activity. BACKGROUND: Because hypotension and pulmonary injury have been associated with elevated PLA2 activity in septic shock and PLA2 levels are reduced with the administration of glucocorticoids, the PLA2 response to endotoxin was investigated in volunteers pretreated with and without hydrocortisone. METHODS: Carefully screened human subjects were studied under four conditions: (1) saline, (2) hydrocortisone, (3) endotoxin, and (4) hydrocortisone administration before endotoxin exposure. Pulse rate, blood pressure, temperature, and symptoms of endotoxemia were serially measured. Plasma for tumor necrosis factor concentrations and PLA2 activity was obtained. RESULTS: After lipopolysaccharide, pulse rate and tumor necrosis factor concentrations rose at 1 to 2 hours; temperature increased maximally at 4 hours. PLA2 activity reached peak levels at 24 hours. With hydrocortisone pretreatment, a 50% reduction in the concentrations of tumor necrosis factor and PLA2 occurred. Significant correlations between other variables and PLA2 activity were not observed. The enzyme identified by monoclonal antibody was the secreted nonpancreatic PLA2 (SNP-PLA2). CONCLUSIONS: The results of this study suggest that elevations in circulating SNP-PLA2 activity and systemic events associated with intravenous endotoxin administration are unrelated.

Elaboration of interleukin 1-receptor antagonist is not attenuated by glucocorticoids after endotoxemia.

The body's response to infection/inflammation is initiated by the elaboration of cytokines, such as tumor necrosis factor, interleukin 1-beta (IL-1-beta), IL-6, and IL-8. Cytokines, in turn, stimulate the pituitary-adrenal axis, and it has been suggested that the corticosteroids elaborated serve as negative feedback signals to diminish inflammatory events. To test this hypothesis, we administered hydrocortisone shortly before endotoxin administration to normal volunteers. Steroids greatly reduced the clinical response to endotoxin and attenuated the appearance of tumor necrosis factor, IL-6, and IL-8 in the circulation. In contrast, IL-1-receptor antagonist, a competitive antagonist of the IL-1 receptor, was unaffected by steroid administration. These data suggest that IL-1-receptor antagonist may act in synergism with corticosteroids to reduce inflammation. Elevation of concentrations of these two factors, corticosteroids and IL-1-receptor antagonist, in plasma appears to be the mechanism used by the body to overcome the effects of inflammatory cytokines.

Diagnostic and therapeutic technology assessment. Radiofrequency catheter ablation of aberrant conducting pathways of the heart.

Radiofrequency catheter ablation has very quickly generated considerable enthusiasm among electrophysiologists because it offers a less invasive alternative to an open surgical procedure and potentially offers an alternative to lifelong drug therapy. Early literature on RF catheter ablation focused on the technical aspects of the procedure. In contrast, the literature of the past several years is dominated by very favorable reports of large series of patients and the experience of individual institutions. The larger series have focused on the treatment of accessory pathways as opposed to AV nodal reentry pathways. The opinions of the DATTA panelists parallel the literature. The panelists considered the technology to be established in terms of its safety and effectiveness as a curative treatment of accessory pathways, and promising in terms of its safety and between promising and established in terms of its effectiveness as a treatment of AV nodal reentrant tachycardias.

Outcomes of co-morbid alcoholic men: a 1-year follow-up.

In this prospective, 1-year study, 360 males admitted to an inpatient alcoholism treatment program were administered a DSM-III compatible structured interview and subtyped by co-occurring psychiatric disorder. Forty percent satisfied diagnostic criteria for alcohol dependence while 27% met criteria for alcohol dependence and one additional psychiatric syndrome. The dually diagnosed patients were divided into: alcohol dependence plus drug abuse, alcohol dependence plus antisocial personality and alcohol dependence plus depression. These subtypes were compared on multiple dimensions at intake and at 1-year follow-up. At follow-up, all groups showed significant improvement in drinking and psychosocial functioning. The results suggest that subtyping alcoholics by co-morbid psychiatric disorders may be a good postdictor of clinical history, but a poor predictor of drinking outcome.

99Tcm-mercapto acetyl triglycine in paediatric renal tract disease.

The use of 99Tcm-mercapto acetyl triglycine (99Tcm-MAG3), a new hippuran substitute, has been reported widely in adults but not in children. Our experience of its use in 100 infants and children for renography and indirect micturating cystography (IMC) is reported. The average age was 5.6 years. 65 patients completed IMC studies and nine patients had 99Tcm-dimercaptosuccinic acid (99Tcm-DMSA) scans performed on the same day. The majority of patients were referred for the investigation of urinary tract infection. 32 kidneys were found to be scarred on 99Tcm-MAG3 scans, 17 kidneys and ureters refluxed on IMC and 14 kidneys were obstructed. The results of 99Tcm-MAG3 scans were compared with those of other urinary tract investigations including ultrasound, micturating cystography (MCUG), intravenous urography (IVU) and 99Tcm-DMSA scintigraphy. No kidney which was scarred had a normal 99Tcm-MAG3 scan. All significant degrees of dilatation or obstruction on IVU or ultrasound were also detected by 99Tcm-MAG3. 99Tcm-MAG3 gave more information than any other single imaging modality and we believe it represents an ideal initial screening test in the investigation of urinary tract infection in older toilet-trained children.