Multi-focal laser surgery: cutting enhancement by hydrodynamic interactions between cavitation bubbles

Transparent biological tissues can be precisely dissected with ultrafast lasers using optical breakdown in the tight focal zone. Typically, tissues are cut by sequential application of pulses, each of which produces a single cavitation bubble. We investigate the hydrodynamic interactions between simultaneous cavitation bubbles originating from multiple laser foci. Simultaneous expansion and collapse of cavitation bubbles can enhance the cutting efficiency by increasing the resulting deformations in tissue, and the associated rupture zone. An analytical model of the flow induced by the bubbles is presented and experimentally verified. The threshold strain of the material rupture is measured in a model tissue. Using the computational model and the experimental value of the threshold strain one can compute the shape of the rupture zone in tissue resulting from application of multiple bubbles. With the threshold strain of 0.7 two simultaneous bubbles produce a continuous cut when applied at the distance 1.35 times greater than that required in sequential approach. Simultaneous focusing of the laser in multiple spots along the line of intended cut can extend this ratio to 1.7. Counter-propagating jets forming during collapse of two bubbles in materials with low viscosity can further extend the cutting zone - up to a factor of 1.54.Comment: 16 pages, 8 figures. Paper is accepted for publication in Physical Review

Inferring fish escape behaviour in trawls based on catch comparison data: Model development and evaluation based on data from Skagerrak, Denmark

During the fishing process, fish react to a trawl with a series of behaviours that often are species and size specific. Thus, a thorough understanding of fish behaviour in relation to fishing gear and a scientific understanding of the ability of different gear designs to utilize or stimulate various behavioural patterns during the catching process are essential for developing more efficient, selective, and environmentally friendly trawls. Although many behavioural studies using optical and acoustic observation systems have been conducted, harsh observation conditions on the fishing grounds often hamper the ability to directly observe fish behaviour in relation to fishing gear. As an alternative to optical and acoustic methods, we developed and applied a new mathematical model to catch data to extract detailed and quantitative information about species- and size-dependent escape behaviour in towed fishing gear such as trawls. We used catch comparison data collected with a twin trawl setup; the only difference between the two trawls was that a 12 m long upper section was replaced with 800 mm diamond meshes in one of them. We investigated the length-based escape behaviour of cod (Gadus morhua), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), witch flounder (Glyptocephalus cynoglossus), and lemon sole (Microstomus kitt) and quantified the extent to which behavioural responses set limits for the large mesh panel's selective efficiency. Around 85% of saithe, 80% of haddock, 44% of witch flounder, 55% of lemon sole, and 55% of cod (below 68 cm) contacted the large mesh panel and escaped. We also demonstrated the need to account for potential selectivity in the trawl body, as it can bias the assessment of length-based escape behaviour. Our indirect assessment of fish behaviour was in agreement with the direct observations made for the same species in a similar section of the trawl body reported in the literature

Поликультурное образование как направление деятельности открытого университета

Авторы дают определение понятий "поликультурное образование" и "открытый университет"; обращаются к правовым актам и учебным программам, целью которых является поликультурное просвещение, и приходят к выводу о значимости этого направления в деятельности открытого образования в условиях многокультурного информационного общества

A case report of hereditary apolipoprotein A-I amyloidosis associated with a novel APOA1 mutation and variable phenotype

Apolipoprotein A-I (apo A-I) amyloidosis is a non-AL, non-AA, and non-transthyretin type of amyloidosis associated with mutations in the APOA1 gene inherited in an autosomal dominant fashion. It is a form of systemic amyloidosis, but at presentation, can also mimic localized amyloidosis. The renal presentation generally involves interstitial and medullary deposition of apo A-I amyloid protein. We describe the identification of apo A-I amyloidosis by mass spectrometry in a 52-year old male, with no family history of amyloidosis, presenting with nephrotic syndrome and associated with heterozygosity for a novel APOA1 mutation (c.220 T > A) which encodes the known amyloidogenic Trp50Arg variant. Renal amyloid deposits in this case were confined to the glomeruli alone, and the patient developed progressive renal impairment. One year after diagnosis, the patient had a successful kidney transplant from an unrelated donor. Pathogenic mutations in the APOA1 gene are generally associated with symptoms of amyloidosis. In this family however, genotyping of family members identified several unaffected carriers suggesting a variable disease penetrance, which has not been described before in this form of amyloidosis and has implications when counselling those with APOA1 mutations

Health policy for sickle cell disease in Africa: experience from Tanzania on interventions to reduce under-five mortality.

Tanzania has made considerable progress towards reducing childhood mortality, achieving a 57% decrease between 1980 and 2011. This epidemiological transition will cause a reduction in the contribution of infectious diseases to childhood mortality and increase in contribution from non-communicable diseases (NCDs). Haemoglobinopathies are amongst the most common childhood NCDs, with sickle cell disease (SCD) being the commonest haemoglobinopathy in Africa. In Tanzania, 10,313 children with SCD under 5 years of age (U5) are estimated to die every year, contributing an estimated 7% of overall deaths in U5 children. Key policies that governments in Africa are able to implement would reduce mortality in SCD, focusing on newborn screening and comprehensive SCD care programmes. Such programmes would ensure that interventions such as prevention of infections using penicillin plus prompt diagnosis and treatment of complications are provided to all individuals with SCD

2018 Beam-park observations of space debris with the EISCAT radars

Source at https://conference.sdo.esoc.esa.int/proceedings/neosst1/paper/480.Monitoring the evolution of the space debris environment requires regular radar observations of the space debris population. This study presents the results from 24 hours of beam-park observations of space objects conducted simultaneously with the EISCAT Svalbard and Tromsø radars on and between January 4th and 5th, 2018. The measurements are processed with a new matched filter bank analysis program, which doubles the coherent integration time, and hence sensitivity, compared with the previous program. We observe 2077 objects with the Tromsø radar and 2400 objects with the Svalbard radar. The detections are correlated with the NORAD catalog. We find that 68% of the Tromsø and 85% of the Svalbard radar detections are from objects in the NORAD catalog, with most of the catalog object detections being in the side lobes of the radar antenna. The beam-park data are compared with a simulated beam-park experiment for catalog objects. The simulation uses a radar detection model that includes the effects of coherent integration and an antenna beam shape with side lobes. We find that the simulation agrees well with the measurements, indicating that the radar sensor response is accurately modeled. Our results highlight the importance of modeling antenna side lobes when analyzing beam-park measurements. Not taking taking into account side lobe detections can lead to an underestimation of radar cross-sections and an overestimation of population density

Drag and Solar Sail Deorbiting: Re-Entry Time Versus Cumulative Collision Probability

Solar and drag sailing have been proposed as passive end-of-life deorbiting methods, and technological demonstrators are under development. For orbit above 800 km altitude solar radiation pressure can be exploited for increasing the orbit eccentricity until the perigee enters the drag region until final re-entry. The performance of the sailing strategy is determined by four parameters: the required effective area-to-mass ratio to deorbit the spacecraft, which determine the sail size given the satellite’s mass, the time to deorbit and the augmented collision probability caused on and by the sail through its passage in the Low Earth Orbit protected region densely populated by space debris. In this paper we assess the sail dimension with respect to the augmented collision risk depending on the sail area and the deorbiting time