Momentum space tomographic imaging of photoelectrons

We apply tomography, a general method for reconstructing 3-D distributions from multiple projections, to reconstruct the momentum distribution of electrons produced via strong field photoionization. The projections are obtained by rotating the electron distribution via the polarization of the ionizing laser beam and recording a momentum spectrum at each angle with a 2-D velocity map imaging spectrometer. For linearly polarized light the tomographic reconstruction agrees with the distribution obtained using an Abel inversion. Electron tomography, which can be applied to any polarization, will simplify the technology of electron imaging. The method can be directly generalized to other charged particles.Comment: Accepted by J. Phys.

Alignment dependent enhancement of the photo-electron cutoff for multi-photon ionization of molecules

The multiphoton ionization rate of molecules depends on the alignment of the molecular axis with respect to the ionizing laser polarization. By studying molecular frame photo-electron angular distributions from N$_2$, O$_2$ and benzene, we illustrate how the angle-dependent ionization rate affects the photo-electron cutoff energy. We find alignment can enhance the high energy cutoff of the photo-electron spectrum when probing along a nodal plane or when ionization is otherwise suppressed. This is supported by calculations using a tunneling model with a single ion state.Comment: 4 pages, 4 figure

Postmortem investigations on winter stranded sperm whales from the coasts of Belgium and the Netherlands

During winter 1994-95, four and three sperm whales (Physeter macrocephalus) were stranded along the Belgian and the Dutch coasts, respectively. Necropsies and tissue samplings were collected 24 hrs post mortem. Lesions on several whales included round and linear skin scars, ventral skin abrasions, acute skin ulcers, acute ulcerative stomatitides, acute to chronic external otitides, and passive visceral congestion. In addition, these sperm whales appeared to be debilitated with severe weight deficit, had blubber thickness reduction, the absence of abdominal fat, and the intestinal tracts were almost empty. Three categories of lesions and their possible relation with the stranding were evaluated. Cutaneous scars observed on the seven whales appeared to have no relation with the stranding. The poor body condition and acute integument ulcerative lesions were present before the stranding. Ventral skin abrasions and visceral passive congestion were caused by the strandings. Absence of food in the alimentary tracts, evidence of weight loss and blubber thickness reduction were compatible with an extended presence of the sperm whales in the North Sea, where adequate food is not available. This might lead to progressive weakness, predisposing the animals to secondary pathogens such as viral diseases. Finally, the coastal configuration of the southern North Sea makes it a trap for sperm whales which have entered the area during their wanderings

Partitioning of the linear photon momentum in multiphoton ionization

The balance of the linear photon momentum in multiphoton ionization is studied experimentally. In the experiment argon and neon atoms are singly ionized by circularly polarized laser pulses with a wavelength of 800 nm and 1400 nm in the intensity range of 10^{14} - 10^{15} W/cm^2. The photoelectrons are measured using velocity map imaging. We find that the photoelectrons carry linear momentum corresponding to the photons absorbed above the field free ionization threshold. Our finding has implications for concurrent models of the generation of terahertz radiation in filaments.Comment: 4 pages, 3 figure

Laparoscopic subtotal hysterectomy versus laparoscopic total hysterectomy: a decade of experience

At present, there are only few data on the surgical outcomes of laparoscopic hysterectomy (LH). Up till now, it has been unclear whether there is a difference in number of complications among the subcategories of laparoscopic total hysterectomy and laparoscopic subtotal hysterectomy (LSH). Therefore, we have performed a retrospective analysis to evaluate the peri- and postoperative outcomes in women undergoing LSH versus LH. This multi-centre retrospective cohort study (Canadian Task Force classification II-2) was conducted in multi-centres (two teaching hospitals and one university medical centre) in the Netherlands, all experienced in minimally invasive gynaecology. In a multi-centre retrospective cohort study we compared the long-term outcomes of laparoscopic subtotal hysterectomy and laparoscopic total hysterectomy (including laparoscopic assisted vaginal hysterectomy, laparoscopic hysterectomy and total laparoscopic hysterectomy). All laparoscopic hysterectomies from the last 10 years (January 1998 till December 2007) were included. Patient characteristics, intra- and postoperative complications, operating time and duration of hospital stay were recorded. The minimum follow-up was 6 months. A total of 390 cases of laparoscopic hysterectomies were included in the analysis: 192 laparoscopic subtotal hysterectomies and 198 laparoscopic total hysterectomies. Patient characteristics such as age and parity were equal in the groups. The overall number of short-term and long-term complications was comparable in both groups: 17% and 15%. Short-term complications (bleeding, fever) were 3% in the LSH group and 12% in the LH group. Long-term complications were (tubal prolapse and cervical stump reoperations) 15% in the LSH group and 3% in the LH group. Laparoscopic subtotal hysterectomy as compared with the different types of laparoscopic total hysterectomy is associated with more long-term postoperative complications, whereas laparoscopic total hysterectomy is associated with more short-term complications

Enamel-based mark performance for marking Chinese mystery snail \u3ci\u3eBellamya chinensis\u3c/i\u3e

The exoskeleton of gastropods provides a convenient surface for carrying marks, and in the interest of improving future marking methods our laboratory assessed the performance of an enamel paint. The endurance of the paint was also compared to other marking methods assessed in the past. We marked the shells of 30 adult Chinese mystery snails Bellamya chinensis and held them in an aquarium for 181 days. We observed no complete degradation of any enamel-paint mark during the 181 days. The enamel-paint mark was superior to a nail-polish mark, which lasted a median of 100 days. Enamel-paint marks also have a lower rate of loss (0.00 month-1 181 days) than plastic bee tags (0.01 month-1, 57 days), gouache paint (0.07 month-1, 18.5 days), or car body paint from studies found in scientific literature. Legibility of enamelpaint marks had a median lifetime of 102 days. The use of enamel paint on the shells of gastropods is a viable option for studies lasting up to 6 months. Furthermore, visits to a capture-mark-recapture site 1 year after application of enamel-paint marks on B. chinensis shells produced several individuals on which the enamel paint was still visible, although further testing is required to clarify durability over longer periods

The structure of causal sets

More often than not, recently popular structuralist interpretations of physical theories leave the central concept of a structure insufficiently precisified. The incipient causal sets approach to quantum gravity offers a paradigmatic case of a physical theory predestined to be interpreted in structuralist terms. It is shown how employing structuralism lends itself to a natural interpretation of the physical meaning of causal sets theory. Conversely, the conceptually exceptionally clear case of causal sets is used as a foil to illustrate how a mathematically informed rigorous conceptualization of structure serves to identify structures in physical theories. Furthermore, a number of technical issues infesting structuralist interpretations of physical theories such as difficulties with grounding the identity of the places of highly symmetrical physical structures in their relational profile and what may resolve these difficulties can be vividly illustrated with causal sets.Comment: 19 pages, 4 figure

Early assisted discharge with generic community nursing for chronic obstructive pulmonary disease exacerbations: Results of a randomised controlled tri

Objectives: To determine the effectiveness of early assisted discharge for chronic obstructive pulmonary disease (COPD) exacerbations, with home care provided by generic community nurses, compared with usual hospital care. Design: Prospective, randomised controlled and multicentre trial with 3-month follow-up. Setting: Five hospitals and three home care organisations in the Netherlands. Participants: Patients admitted to the hospital with an exacerbation of COPD. Patients with no or limited improvement of respiratory symptoms and patients with severe unstable comorbidities, social problems or those unable to visit the toilet independently were excluded. Intervention: Early discharge from hospital after 3 days inpatient treatment. Home visits by generic community nurses. Primary outcome measure was change in health status measured by the Clinical COPD Questionnaire (CCQ). Treatment failures, readmissions, mortality and change in generic health-related quality of life (HRQL) were secondary outcome measures. Results: 139 patients were randomised. No difference between groups was found in change in CCQ score at day 7 (difference in mean change 0.29 (95% CI -0.03 to 0.61)) or at 3 months (difference in mean change 0.04 (95% CI -0.40 to 0.49)). No difference was found in secondary outcomes. At day 7 there was a significant difference in change in generic HRQL, favouring usual hospital care. Conclusions: While patients' disease-specific health status after 7-day treatment tended to be somewhat better in the usual hospital care group, the difference was small and not clinically relevant or statistically significant. After 3 months, the difference had disappeared. A significant difference in generic HRQL at the end of the treatment had disappeared after 3 months and there was no difference in treatment failures, readmissions or mortality. Early assisted discharge with community nursing is feasible and an alternative to usual hospital care for selected patients with an acute COPD exacerbation