First observation of 28O

Subjecting a physical system to extreme conditions is one of the means often used to obtain a better understanding and deeper insight into its organization and structure. In the case of the atomic nucleus, one such approach is to investigate isotopes that have very different neutron-to-proton (N/Z) ratios than in stable nuclei. Light, neutron-rich isotopes exhibit the most asymmetric N/Z ratios and those lying beyond the limits of binding, which undergo spontaneous neutron emission and exist only as very short-lived resonances (about 10-21 s), provide the most stringent tests of modern nuclear-structure theories. Here we report on the first observation of 28O and 27O through their decay into 24O and four and three neutrons, respectively. The 28O nucleus is of particular interest as, with the Z = 8 and N = 20 magic numbers1,2, it is expected in the standard shell-model picture of nuclear structure to be one of a relatively small number of so-called 'doubly magic' nuclei. Both 27O and 28O were found to exist as narrow, low-lying resonances and their decay energies are compared here to the results of sophisticated theoretical modelling, including a large-scale shell-model calculation and a newly developed statistical approach. In both cases, the underlying nuclear interactions were derived from effective field theories of quantum chromodynamics. Finally, it is shown that the cross-section for the production of 28O from a 29F beam is consistent with it not exhibiting a closed N = 20 shell structure.

Pairing Forces Govern Population of Doubly Magic ^{54}Ca from Direct Reactions

Direct proton-knockout reactions of ^{55}Sc at ∼220  MeV/nucleon were studied at the RIKEN Radioactive Isotope Beam Factory. Populated states of ^{54}Ca were investigated through γ-ray and invariant-mass spectroscopy. Level energies were calculated from the nuclear shell model employing a phenomenological internucleon interaction. Theoretical cross sections to states were calculated from distorted-wave impulse approximation estimates multiplied by the shell model spectroscopic factors, which describe the wave function overlap of the ^{55}Sc ground state with states in ^{54}Ca. Despite the calculations showing a significant amplitude of excited neutron configurations in the ground-state of ^{55}Sc, valence proton removals populated predominantly the ground state of ^{54}Ca. This counterintuitive result is attributed to pairing effects leading to a dominance of the ground-state spectroscopic factor. Owing to the ubiquity of the pairing interaction, this argument should be generally applicable to direct knockout reactions from odd-even to even-even nuclei.

Extending the Southern Shore of the Island of Inversion to ^{28}F

Detailed spectroscopy of the neutron-unbound nucleus ^{28}F has been performed for the first time following proton/neutron removal from ^{29}Ne/^{29}F beams at energies around 230  MeV/nucleon. The invariant-mass spectra were reconstructed for both the ^{27}F^{(*)}+n and ^{26}F^{(*)}+2n coincidences and revealed a series of well-defined resonances. A near-threshold state was observed in both reactions and is identified as the ^{28}F ground state, with S_{n}(^{28}F)=-199(6)  keV, while analysis of the 2n decay channel allowed a considerably improved S_{n}(^{27}F)=1620(60)  keV to be deduced. Comparison with shell-model predictions and eikonal-model reaction calculations have allowed spin-parity assignments to be proposed for some of the lower-lying levels of ^{28}F. Importantly, in the case of the ground state, the reconstructed ^{27}F+n momentum distribution following neutron removal from ^{29}F indicates that it arises mainly from the 1p_{3/2} neutron intruder configuration. This demonstrates that the island of inversion around N=20 includes ^{28}F, and most probably ^{29}F, and suggests that ^{28}O is not doubly magic.

Quasifree Neutron Knockout from ^{54}Ca Corroborates Arising N=34 Neutron Magic Number

Exclusive cross sections and momentum distributions have been measured for quasifree one-neutron knockout reactions from a ^{54}Ca beam striking on a liquid hydrogen target at ∼200  MeV/u. A significantly larger cross section to the p_{3/2} state compared to the f_{5/2} state observed in the excitation of ^{53}Ca provides direct evidence for the nature of the N=34 shell closure. This finding corroborates the arising of a new shell closure in neutron-rich calcium isotopes. The distorted-wave impulse approximation reaction formalism with shell model calculations using the effective GXPF1Bs interaction and ab initio calculations concur our experimental findings. Obtained transverse and parallel momentum distributions demonstrate the sensitivity of quasifree one-neutron knockout in inverse kinematics on a thick liquid hydrogen target with the reaction vertex reconstructed to final state spin-parity assignments.

Approaching the Gamow Window with Stored Ions: Direct Measurement of ^{124}Xe(p,γ) in the ESR Storage Ring

We report the first measurement of low-energy proton-capture cross sections of ^{124}Xe in a heavy-ion storage ring. ^{124}Xe^{54+} ions of five different beam energies between 5.5 and 8 AMeV were stored to collide with a windowless hydrogen target. The ^{125}Cs reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window for hot, explosive scenarios such as supernovae and x-ray binaries. The results serve as an important test of predicted astrophysical reaction rates in this mass range. Good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. Larger deviations are found above the neutron emission threshold, where also neutron and γ widths significantly impact the cross sections. The newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies.

How Robust is the N=34 Subshell Closure? First Spectroscopy of ^{52}Ar

The first γ-ray spectroscopy of ^{52}Ar, with the neutron number N=34, was measured using the ^{53}K(p,2p) one-proton removal reaction at ∼210  MeV/u at the RIBF facility. The 2_{1}^{+} excitation energy is found at 1656(18) keV, the highest among the Ar isotopes with N>20. This result is the first experimental signature of the persistence of the N=34 subshell closure beyond ^{54}Ca, i.e., below the magic proton number Z=20. Shell-model calculations with phenomenological and chiral-effective-field-theory interactions both reproduce the measured 2_{1}^{+} systematics of neutron-rich Ar isotopes, and support a N=34 subshell closure in ^{52}Ar.

First Accurate Normalization of the β-delayed α Decay of ^{16}N and Implications for the ^{12}C(α,γ)^{16}O Astrophysical Reaction Rate

The ^{12}C(α,γ)^{16}O reaction plays a central role in astrophysics, but its cross section at energies relevant for astrophysical applications is only poorly constrained by laboratory data. The reduced α width, γ_{11}, of the bound 1^{-} level in ^{16}O is particularly important to determine the cross section. The magnitude of γ_{11} is determined via sub-Coulomb α-transfer reactions or the β-delayed α decay of ^{16}N, but the latter approach is presently hampered by the lack of sufficiently precise data on the β-decay branching ratios. Here we report improved branching ratios for the bound 1^{-} level [b_{β,11}=(5.02±0.10)×10^{-2}] and for β-delayed α emission [b_{βα}=(1.59±0.06)×10^{-5}]. Our value for b_{βα} is 33% larger than previously held, leading to a substantial increase in γ_{11}. Our revised value for γ_{11} is in good agreement with the value obtained in α-transfer studies and the weighted average of the two gives a robust and precise determination of γ_{11}, which provides significantly improved constraints on the ^{12}C(α,γ) cross section in the energy range relevant to hydrostatic He burning.

High-precision measurement of isotopic fission yields of 236U*

We report on the second SOFIA experiment, dedicated to the fission yields of 236U*, analog to 235U(n,f). The measurement is based on the inverse kinematics method, using a relativistic, secondary beam of 236U. Both fission fragments are identified in mass and charge in the SOFIA recoil spectrometer. The obtained isotopic yields are compared with existing spectroscopy measurements and the elemental yields are used to discuss the treatment of the even-odd effect with energy in nuclear data libraries.

(97)(37)Rb(60): The Cornerstone of the Region of Deformation around A ∼ 100 [corrected]

Excited states of the neutron-rich nuclei (97,99)Rb were populated for the first time using the multistep Coulomb excitation of radioactive beams. Comparisons of the results with particle-rotor model calculations provide clear identification for the ground-state rotational band of (97)Rb as being built on the πg(9/2) [431] 3/2(+) Nilsson-model configuration. The ground-state excitation spectra of the Rb isotopes show a marked distinction between single-particle-like structures below N=60 and rotational bands above. The present study defines the limits of the deformed region around A∼100 and indicates that the deformation of (97)Rb is essentially the same as that observed well inside the deformed region. It further highlights the power of the Coulomb-excitation technique for obtaining spectroscopic information far from stability. The (99)Rb case demonstrates the challenges of studies with very short-lived postaccelerated radioactive beams.

Ozone exposure enhances mast-cell inflammation in asthmatic airways despite inhaled corticosteroid therapy

Asthmatics are recognised to be more susceptible than healthy individuals to adverse health effects caused by exposure to the common air pollutant ozone. Ozone has been reported to induce airway neutrophilia in mild asthmatics, but little is known about how it affects the airways of asthmatic subjects on inhaled corticosteroids. We hypothesised that ozone exposure would exacerbate the pre-existent asthmatic airway inflammation despite regular inhaled corticosteroid treatment. Therefore, we exposed subjects with persistent asthma on inhaled corticosteroid therapy to 0.2 ppm ozone or filtered air for 2 h, on 2 separate occasions. Lung function was evaluated before and immediately after exposure, while bronchoscopy was performed 18 h post exposure. Compared to filtered air, ozone exposure increased airway resistance. Ozone significantly enhanced neutrophil numbers and myeloperoxidase levels in airway lavages, and induced a fourfold increase in bronchial mucosal mast cell numbers. The present findings indicate that ozone worsened asthmatic airway inflammation and offer a possible biological explanation for the epidemiological findings of increased need for rescue medication and hospitalisation in asthmatic people following exposure to ambient ozone.

Continent cutaneous urinary diversion in patients with spinal cord injury

STUDY DESIGN

Retrospective study.

OBJECTIVE

To examine the functional results and effect on quality of life of continent cutaneous urinary diversion in spinal cord injured patients.

SETTING

Department of Urology, Sahlgrenska University Hospital, Göteborg, Sweden.

SUBJECTS

A total of 10 patients with spinal cord injury (SCI).

METHOD

The patients were operated on with an ileal reservoir (Kock reservoir or T-pouch), Cr-EDTA clearance was determined preoperatively and at follow-up. The patients answered a questionnaire concerning reservoir function, various activities and quality of life. The patient charts were reviewed.

RESULTS

One patient died of pulmonary embolism 3 years after surgery. Two patients were reoperated on for reservoir perforation. All patients were satisfied/very satisfied with their reservoirs. Half of them reported improved ability to perform various activities. Eight out of nine patients reported improved quality of life.

CONCLUSION

For a selected group of patients with SCI, continent cutaneous urinary diversion provides successful outcome with improved quality of life.

The potential of telemedicine: barriers, incentives and possibilities in the implementation phase

Between 1998 and 1999, the Swedish Institute for Health Services Development (Spri) evaluated three applications in which specialist competence was being accessed via telemedicine. The results indicated that these kinds of application can be cost-effective in an organization well adapted to new technology and that telemedicine can improve continuity of care for patients. However, the new technology was seldom supported by the old organization and better education and technical support are needed. In a study called 'Incentives and Implementation', the Federation of Swedish County Councils interviewed people in Swedish health-care with a lot of experience of telemedicine. The interviewees agreed that telemedicine was likely to affect the whole structure of health-care. Peripheral competence was expected to increase and referral patterns to change, as well as the functions of the personnel and the hospitals. New working conditions and methods of work were expected to be made possible by telemedicine and health-care was expected to become more process oriented, partly because patients are likely to be more demanding and better informed. To be able to utilize this potential, health-care managers will have to show more interest in and commitment to telemedicine. Old organizational patterns must be called into question and be developed along with information technology and telemedicine. It is also important to give priority to training in telemedicine for physicians and nurses.

Long-time experience with the Kock ileal reservoir for continent urinary diversion

OBJECTIVES

N.G. Kock performed the first continent cutaneous ileal reservoir for urinary diversion in 1975 at the Sahlgrenska University Hospital, Göteborg, Sweden. We have investigated the fate of the patients operated during the following 25 years at this hospital and analyzed their health-related quality of life (SF-36) as well as their psychological adjustment to a life with a continent urinary reservoir (OAS).

MATERIAL AND METHODS

Between 1975 and 1999, 176 patients underwent continent urinary diversion using a Kock reservoir. At the end of 1999, 126 patients were known to be alive. Their reservoir function was estimated from their journals as well as from a questionnaire answered by the patients.

RESULTS

Almost 90% of the survivors had a well-functioning reservoir at the time of follow-up. The need for reoperation has been high, mainly due to nipple problems. Kidney function is not influenced by the continent diversion per se. The health status of the patients is more influenced by the underlying disease than by their reservoirs. Patients with benign functional or inflammatory diseases experience comparatively more problems with their reservoirs.

CONCLUSIONS

The functional end results as well as patient acceptance of continent urinary diversion with a Kock reservoir are excellent.

Brain tumours in Sweden 1996: care and costs

OBJECTIVES

Brain tumours cause considerable concern due to a high mortality and there are increasing efforts to provide adequate care, sometimes outside hospitals. Health care utilisation, direct costs of care, and the indirect social cost of morbidity and early mortality caused by brain tumours in Sweden in the year 1996 was analysed.

METHODS

Quantification of ambulatory care, care in hospital, long term and palliative/terminal care, drug consumption, temporary as well as long term morbidity, and mortality from comprehensive national data sources. Direct costs were calculated using 1996 charges. Indirect costs were calculated by sex and age specific salaries. A sensitivity analysis considered the impact of alternative estimates of each item.

RESULTS

Indirect costs were 75% of the total and were caused mainly by early mortality. Direct costs were predominantly for care in hospital, long term care, and home health care. Among direct costs, astrocytomas III-IV and meningiomas accounted for 42% and 30% respectively.

CONCLUSIONS

The cost of illness from brain tumours reflects the characteristics of these malignancies. Despite their low incidence rate, the economic impact caused by high mortality among young persons is a predominant trait. Costs of acute hospital care and also long term care and home care are considerable.

Blockade of the B7-CD28 pathway by CTLA4-Ig counteracts rejection and prolongs survival in small bowel transplantation

Allograft rejection involves T-cell activation, requiring T-cell receptor interactions with major histocompatibility complex (MHC) molecules and costimulatory signals delivered through the B7-CD28 pathway. We evaluated the effect of blocking this pathway on graft rejection and survival, in a rat experimental model of small bowel transplantation. Heterotopic small bowel transplantation was performed between PVG donor rats and DA recipient rats. The recipient animals were treated with CTLA4-Ig or irrelevant immunoglobulin (Ig)G as control and followed for 18, 30 or 90 days. The survival rate and degree of inflammation and accumulation of CD4+ T cells and macrophages were determined in the transplanted bowels. We found that administration of CTLA4-Ig significantly improved the survival rate compared to control rats: after 30 days 73% of the treated rats had survived and at 90 days 5/8 rats were still living, whereas in the control group only 2/8 rats had survived. The grafts showed preserved mucosal structure with only a mild degree of subacute inflammation and the accumulation of CD4+ T cells and macrophages was noticeably reduced in treated animals as compared to control rats. Necrosis was extensive in control rats, whereas CTLA4-Ig treated animals had grafts with at least some preserved villus morphology and no necrotic tissue. Although small bowel transplantation has proven exceptionally difficult, in this study we have shown that CTLA4-Ig treatment may provide a promising strategy to prevent rejection and induce long term tolerance and graft survival.

Telemedicine in Sweden--a diffusion study

A survey of telemedicine use in Sweden was carried out. The response rate by hospital management was high at almost 90%. Sixty per cent of hospitals were involved in some kind of telemedicine activity in Sweden, with a further 15% planning telemedicine implementation. In rural areas of north Sweden good links exist between primary and secondary care. In the more populated southern region good links exist between the county hospitals and specialist university hospitals. Fifty-four per cent of telemedicine applications were used for specialist consultations, 13% for consultation between paramedics and hospitals and 10% for rounds. Teleradiology was the most frequent service.

The anterior stress fracture of the tibia: an atrophic pseudoarthosis?

Histopathological examination of biopsies from the fracture site in two cases of anterior stress fractures of the tibia demonstrated no bone remodelling activity, absence of inflammatory cells, extensive fibrotic infiltration and local avascular bone necrosis. The biopsies were taken peroperatively from two elite soccer players who earlier had to stop training due to severe exertional pain. When non-operative treatment failed to heal the fractures within 1 year and 6 months, respectively, surgery was performed in order to stabilize the fractures. Both subjects were relieved from exertional pain within 6 months of surgery. Consecutive radiographs showed the pattern of direct healing and 8 months postoperatively confirmed complete healing without callus formation. Both elite soccer players returned to pre-injury activity level. We suggest that the excessive fibrotic tissue ingrowth and hypovascularity under repetitive stress causes the delayed healing and histopathological signs similar to an atrophic pseudoarthosis. Treatment should consequently consider the pseudoarthrotic character of the anterior stress fracture of the tibia.

Twelve months, treatment with inhaled salmeterol in asthmatic patients. Effects on beta 2-receptor function and inflammatory cells

Salmeterol is a new beta 2-receptor agonist with a prolonged duration of action after inhalation, exceeding 12 h in most patients. We have performed a 12-month open follow-up study on 11 patients with reversible asthma. All patients were given salmeterol inhalations (50 micrograms twice daily). Additional asthma treatment included inhaled corticosteroids in all patients, and oral slow-release theophylline or beta 2-receptor agonists in a minority of patients (3 and 1, respectively). Before salmeterol treatment was initiated and after 3, 6, 9 and 12 months of salmeterol treatment, a cumulative dose-response curve to inhaled salbutamol (100, 300 and 900 micrograms) was performed, and FEV1 measured. We also evaluated the effect of each salbutamol dose on finger tremor, systemic blood pressure and heart rate. Blood tests, including white blood count and electrolytes, were taken at each visit. After salmeterol treatment was initiated, morning FEV1, measured before the morning asthma medication, was significantly improved (p < 0.05). The responsiveness to inhaled salbutamol was not decreased during salmeterol treatment, except in one patient with asthma worsening over the study year. Baseline finger tremor measured before salbutamol dose-response curves, was significantly lower at the 12-month visit than before treatment was initiated (p < 0.05). Effects of salbutamol on systemic blood pressure, heart rate or finger tremor was not significantly changed during salmeterol treatment. We found a successive and significant decrease in blood eosinophils (p < 0.05) during the 12 months of salmeterol treatment, when the patient with asthma worsening was excluded in the analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Shoulder function in patients with unoperated anterior shoulder instability

A functional analysis, including Rowe score and measurements of isokinetic peak torque and range of motion of the shoulder, and a subjective assessment were performed in 26 consecutive patients (23 males and 3 females) with unoperated anterior shoulder instability. Patients experienced the initial dislocation at an average age of 23 +/- 8 years and 58% occurred during sports activity. No patient had gone through any controlled rehabilitation program. In this study, an average of 7 years (range, 1 to 28) had passed since the initial dislocation. Fifty-nine percent of the patients complained of markedly reduced ability to perform in sports because of instability, impaired strength, decreased range of motion, and pain induced by activity. The majority (65%) of the patients reported instability only during physical activity. The average Rowe score was 68 +/- 14 on a scale of 100. In comparison with the healthy side, the injured shoulder had a significantly lower isokinetic peak torque during abduction and internal rotation, as well as a reduced range of motion in extension, abduction, and external rotation, but not in flexion. The severity of impairment (Rowe score, deficit in range of motion, and peak torque) was not related to the number of dislocations sustained or to the duration of instability.

Tibia nonunions treated by interlocked nailing: increased risk of infection after previous external fixation

Eighteen patients, mean age 36 years (range of 22-76 years), with tibia-shaft nonunions were treated with interlocked nailing. There were 12 nonunions originally treated with either cast, lag screws, plate, or Ender nails (nine closed, two open grade I and one grade II injury). The remaining six nonunions, all open fractures (five grade II and one grade III injury) initially received external fixation. After removal of the fixator, 72 days postinjury (range of 58-111 days), there was a delay of 218 days (range of 112-449 days) before the nailing procedure in those patients primarily treated with external fixation. All 12 nonunions not primarily treated with external fixation healed without complications after nailing within 17 weeks (range of 12-24 weeks). All six nonunions primarily treated with external fixation had temporary pin-tract infections, which healed after pin extraction. Two of the nonunions healed without any complication, whereas four developed intramedullary infection with the same bacteria as from the pin-tract site. Although the number of patients is small in this report, there is an apparently high incidence of intramedullary infection in the group originally treated with external fixation. The sequential procedure of external fixation followed by intramedullary nailing is, therefore, not recommended in the treatment of open tibia fractures.