Angular momentum generation in nuclear fission.

When a heavy atomic nucleus splits (fission), the resulting fragments are observed to emerge spinning1; this phenomenon has been a mystery in nuclear physics for over 40 years2,3. The internal generation of typically six or seven units of angular momentum in each fragment is particularly puzzling for systems that start with zero, or almost zero, spin. There are currently no experimental observations that enable decisive discrimination between the many competing theories for the mechanism that generates the angular momentum4-12. Nevertheless, the consensus is that excitation of collective vibrational modes generates the intrinsic spin before the nucleus splits (pre-scission). Here we show that there is no significant correlation between the spins of the fragment partners, which leads us to conclude that angular momentum in fission is actually generated after the nucleus splits (post-scission). We present comprehensive data showing that the average spin is strongly mass-dependent, varying in saw-tooth distributions. We observe no notable dependence of fragment spin on the mass or charge of the partner nucleus, confirming the uncorrelated post-scission nature of the spin mechanism. To explain these observations, we propose that the collective motion of nucleons in the ruptured neck of the fissioning system generates two independent torques, analogous to the snapping of an elastic band. A parameterization based on occupation of angular momentum states according to statistical theory describes the full range of experimental data well. This insight into the role of spin in nuclear fission is not only important for the fundamental understanding and theoretical description of fission, but also has consequences for the γ-ray heating problem in nuclear reactors13,14, for the study of the structure of neutron-rich isotopes15,16, and for the synthesis and stability of super-heavy elements17,18.

Large Impact of the Decay of Niobium Isomers on the Reactor ν[over ¯]_{e} Summation Calculations.

Even mass neutron-rich niobium isotopes are among the principal contributors to the reactor antineutrino energy spectrum. They are also among the most challenging to measure due to the refractory nature of niobium, and because they exhibit isomeric states lying very close in energy. The ß-intensity distributions of ^{100gs,100m}Nb and ^{102gs,102m}Nb ß decays have been determined using the total absorption γ-ray spectroscopy technique. The measurements were performed at the upgraded Ion Guide Isotope Separator On-Line facility at the University of Jyväskylä. Here, the double Penning trap system JYFLTRAP was employed to disentangle the ß decay of the isomeric states. The new data obtained in this challenging measurement have a large impact in antineutrino summation calculations. For the first time the discrepancy between the summation model and the reactor antineutrino measurements in the region of the shape distortion has been reduced.

Anomalies in the Charge Yields of Fission Fragments from the

Fast-neutron-induced fission of ^{238}U at an energy just above the fission threshold is studied with a novel technique which involves the coupling of a high-efficiency γ-ray spectrometer (MINIBALL) to an inverse-kinematics neutron source (LICORNE) to extract charge yields of fission fragments via γ-γ coincidence spectroscopy. Experimental data and fission models are compared and found to be in reasonable agreement for many nuclei; however, significant discrepancies of up to 600% are observed, particularly for isotopes of Sn and Mo. This indicates that these models significantly overestimate the standard 1 fission mode and suggests that spherical shell effects in the nascent fission fragments are less important for low-energy fast-neutron-induced fission than for thermal neutron-induced fission. This has consequences for understanding and modeling the fission process, for experimental nuclear structure studies of the most neutron-rich nuclei, for future energy applications (e.g., Generation IV reactors which use fast-neutron spectra), and for the reactor antineutrino anomaly.

Leukocyte Responsiveness to Exercise in Individuals Positive for Human Cytomegalovirus.

Human cytomegalovirus (HCMV) infects 50% of adults in the United States. HCMV can become a cause for concern in individuals who have a compromised immune system, which may occur after high-intensity exercise. The purpose of this preliminary study was to characterize the lymphocyte, monocyte, and neutrophil responses to exercise in HCMV+individuals. Participants were either positive (HCMV +) or negative (HCMV-) for HCMV. Participants visited the laboratory on 3 separate occasions: HCMV screening, 100% VO2max test, and 80% VO2max run. Mixed-model factorial ANOVA procedures with repeated measures on sampling condition were performed on absolute and relative circulating lymphocytes, monocytes, and neutrophils. Significant main effects for time for both absolute and relative values were seen for all leukocyte subsets regardless of virus status. Significant differences for absolute and relative values were seen between sampling conditions for all leukocyte subsets. We report for the first time that HCMV status does not affect circulating neutrophil responses to high-intensity exercise, though exercise-induced neutrocytosis is seen during the post-exercise and 60 min post-exercise sampling conditions, regardless of HCMV status. There is no HCMV effect on circulating monocyte responses to exercise, though exercise-induced monocytosis was seen during the post-exercise sampling condition regardless of HCMV status.

Observation of large scissors resonance strength in actinides.

The orbital M1 scissors resonance has been measured for the first time in the quasicontinuum of actinides. Particle-γ coincidences are recorded with deuteron and (3)He-induced reactions on (232)Th. The residual nuclei (231,232,233)Th and (232,233) Pa show an unexpectedly strong integrated strength of B(M1)=11-15µ(n)(2) in the E(γ)=1.0-3.5 MeV region. The increased γ-decay probability in actinides due to scissors resonance is important for cross-section calculations for future fuel cycles of fast nuclear reactors and may also have an impact on stellar nucleosynthesis.

Photoreaction of the rutile TiO2(011) single-crystal surface: reaction with acetic acid.

The reaction of acetic acid with stoichiometric and reduced rutile TiO(2)(011) single-crystal surfaces has been studied under dark and UV illumination conditions. The surface coverage after the dissociative adsorption of acetic acid with respect to Ti was found to be 0.55. Monitoring XPS Ti, O, and C lines revealed that the surface population decreased incrementally with temperature up to 650 K. The decrease in the slope of both the -CH(3)- and -COO- XPS peaks was not monotonic and followed two slopes in agreement with TPD results. The first channel involves the removal of surface acetates to acetic acid by recombinative desorption, and the second mainly involves dehydration to ketene. UV-light illumination was conducted at 300 K in the absence and presence of molecular oxygen at different pressures: in the 10(-6)-10(-9) Torr range. Acetate species were found to decrease with illumination time, and their decrease is seen to be dependent on the oxygen pressure. Plausible decomposition pathways are presented. Deliberately reducing the surface by electron bombardment prior to the adsorption of acetic acid did not affect the photoreaction rate within the experimental limits.

Biochemical and molecular studies of mitochondrial function in diabetes insipidus, diabetes mellitus, optic atrophy, and deafness.

OBJECTIVE: To determine if diabetes insipidus, diabetes mellitus, optic atrophy, and deafness (DIDMOAD) combined with a cerebellar syndrome is associated with a systemic disorder of respiratory chain function as found in similar genetic syndromes. CASE: A muscle biopsy was taken from a patient with DIDMOAD, and a mitochondrial fraction was prepared. Respiratory chain function was assessed by analysis of intermediary metabolites, histochemical analysis of muscle biopsy, measurement of the activity of individual respiratory chain complexes, oxidative flux through the respiratory chain, and cytochrome concentration and compared with a population with normal respiratory chain function. Mitochondrial DNA from skeletal muscle, brain, and pancreas was examined for major rearrangements and specific point mutations. Brain tissue was examined neuropathologically for abnormalities, particularly those previously described in association with DIDMOAD. RESULTS: No abnormality was found in mitochondrial oxidation, individual complex activity, or cytochrome concentration. Histochemical analysis and electron microscopy showed no abnormality known to be associated with mitochondrial dysfunction. A single-base substitution at position 12308 of the mitochondrial genome was found, but no major rearrangement of mitochondrial DNA was demonstrated. Neuropathological examination revealed severe demyelination and gliosis in the optic nerves and loss of Purkinje cells associated with gliosis in the white matter in the cerebellum. CONCLUSIONS: We have found no evidence that DIDMOAD is associated with a systemic abnormality of respiratory chain function. The mitochondrial DNA single-base substitution noted is likely to be a polymorphism rather than a pathogenic point mutation. We have confirmed that DIDMOAD may be associated with a neurodegenerative disorder, but the cause of this remains undetermined.

Influence of genetic hyperlipemia in the Zucker rat upon the lipemic response to graded estradiol exposure.

The present investigation was designed to examine the influence of genetic Type IV hyperlipoproteinemia on the metabolism of lipids in response to estrogen exposure. The influence of 17-Beta-estradiol * was examined in a dose-response study over a range of hormone concentration from 10 to 100 pg/ml in genetic hyperlipidemic Zucker rats. In oophorectomized female rats, replacement levels of plasma estradiol of 40 pg/ml resulted in maximal hypertriglyceridemia of approximately 500 mg/dl representing a 5-fold exaggeration of that observed in control genetically norm-lipemic animals. This hypertriglyceridemia was associated with an increased production of triglyceride (TG) in excess of clearance, with a resulting production: clearance ratio of approximately 1.5. Exposure to maximum blood levels of estradiol, approximately 100 pg/ml, resulted in sub-normal levels of plasma TG (-145 mg/dl) in association with a reduced production: clearance ratio of approximately 0.36. In contrast to the marked hypocholesterolemic response to maximum estrogen exposure seen in normolipemic animals, the genetic Type IV hyperlipemic animal failed to demonstrate reduced plasma cholesterol concentration. This phenomenon was related to a rise in plasma LDL concentration in conjunction with parallel reduction in plasma HDL2 levels.Thus, an abnormal ratio of excessive LDL: HDl emerged in response to estrogen exposure in this model of human Type IV lipemia. This observation suggests that the genetic predisposition of the host may be critical to both the quantitative as well as the qualitative response to estrogen.

Kienböck's disease: the role of silicone replacement arthroplasty.

A review of thirty-eight patients with Kienböck's disease indicated that both delay in diagnosis and prolonged treatment by plaster immobilization led to progressive collapse of the lunate and an unsatisfactory result in most instances. Four clinical and roentgenographic stages were identified, and the results of silicone replacement arthroplasty were correlated with the preoperative stage after an average follow-up of twenty-seven months. The results were satisfactory in fourteen of twenty wrists in which the procedure was performed before collapse of the lunate had occurred. The importance of early diagnosis and early surgical treatment of this disorder was emphasized by the findings in this study.

Osteotomy in the treatment of osteoarthritis of the first carpometacarpal joint.

Degenerative changes of the first carpometacarpal joint commonly cause pain, weakness and adduction deformity. Many patients respond to conservative treatment, but in resistant cases an abduction wedge osteotomy of the base of the first metacarpal has been found to relieve symptoms with less complications than other operations. Twenty-one patients with 23 osteotomies have been reviewed, with a follow-up from 2 to 17 years. All have had lasting relief from pain and consider that they have full function, with no stiffness or limited abduction. Osteotomy is indicated mainly for cases where the arthritis is confined to the carpometacarpal joint, but also relieves pain in cases of peritrapezial arthritis.

Acute blue fingers in women.

A previously undescribed syndrome affecting the fingers of women is presented. The patients experience a sharp pain and then the fingers become blue and numb. The discoloration resolves within 72 hours without the changes normally associated with an ecchymosis. Clinical and haematological examination of six patients failed to show any common factors or associated systemic disease. This syndrome is of no clinical significance to the patient, but it is important for clinicians to be aware of it because the acute phase can cause anxiety, suggesting more serious vascular disease.

Entrapment of the superficial peroneal nerve. Three case reports.

Entrapment of the superficial peroneal nerve is an unusual cause of pain in the ankle and foot. In such cases decompression of the nerve at the point of exit from the deep fascia will produce a good result. Three cases are described.

Endoprosthetic replacement of the proximal humerus.

Endoprosthetic replacement of the proximal humerus has been performed in our unit on 25 occasions between 1950 and 1982. The indication for surgery was destruction of the proximal half of the humerus so extensive that the only alternatives were reconstruction or amputation. Of the patients with tumours two died from metastases, and three from unrelated causes; local recurrence necessitated amputation in two patients. Minor complications were frequent, but there were no deep infections and, after 1964, no prosthesis became loose. Active shoulder movement after operation was considerably limited, but passive movement was good and function of the elbow and hand were preserved.

Excision of tumours of humerus and femur, with restoration by internal prostheses.

A personal experience is recounted of operations in cases of tumour involving the humerus or femur with restoration by endoprostheses. Twenty-four patients were treated in this way from 1950 to 1969 inclusive and have been followed up for between four and twenty-four years. The patients selected for treatment have presented chondrosarcoma (ten), so-called benign giant-cell tumour of bone, usually recurrent (nine), angiomatous osteolysis (two), seemingly single thyroid or renal metastasis (two), and ununited pathological fracture after irradiation of a tumour (one). Development of the prostheses from early beginnings is outlined. Some points in surgical management are referred to. The complications and results are recorded.

Distal femoral replacement by custom-made prostheses. Clinical follow-up and survivorship analysis.

We report the long-term clinical follow-up and survivorship analysis of 40 distal femoral replacements performed between 1964 and 1980 for traumatic, locally aggressive and malignant conditions. Custom-made prostheses with fully-constrained knee joints were used to replace a mean of 42% of the length of the femur. Survivorship analysis showed a cumulative success rate of 80% at eight years, with no subsequent deterioration at 18 years. Clinical assessment revealed 78% excellent or good results. Failure was due to infection in three cases, and in two to fracture of a now-outmoded femoral stem.

Endoprosthetic replacement of the proximal femur and acetabulum. A survival analysis.

A series of 81 patients has been reviewed to determine the value of endoprosthetic replacement of the proximal femur and hip in the treatment of bone tumours. Standard statistical methods were used to evaluate the survival of the replacements and the patients. Taking removal of the prosthesis, irrespective of the cause, as the criterion for failure the survival of the replacements was found to be 63 per cent after 10 years. If deaths are regarded as failures, then the survival value falls to 48 per cent. The survival of patients with chondrosarcoma and osteoclastoma treated by endoprosthetic replacement compares favourably with survival after amputation or excision of the tumour.

Reactive oxygen species in acute respiratory distress syndrome.

In the metabolism of almost all human cells, a sequential addition of electrons to oxygen leads to the formation of reactive oxygen species (ROS). ROS have been implicated in more than 100 diseases and may be the common denominator in the pathogenesis of the most important health problems facing the world today. The last decade has been characterized by a progressive increase in the understanding of oxidant chemistry and the role of ROS in pulmonary disease. The majority of deaths among critically ill patients are the result of sepsis and its sequelae, including acute respiratory distress syndrome (ARDS). Nurses must understand the processes involving ROS that are in play when they are caring for patients with ARDS. This article describes what is known about the formation of ROS, the pathophysiology of ARDS, and the role ROS play in the pathogenesis of ARDS.

Bone marrow transplantation: critical care implications.

Bone marrow transplantation is an effective treatment for a growing list of disease processes both malignant and non-malignant. Complications associated with marrow transplantation may be related to ablative therapy, immunosuppression, graft-versus-host disease, and recurrence of the underlying disease. Survival depends upon prompt recognition of problems and timely institution of specific interventions, both medical and nursing. Nurses caring for bone marrow transplant recipients face a never-ending and ever-changing challenge to stay on top of the day-to-day problems and patient care crises that can occur.