Vannstandsendringer i Vågsbøpollen og Ådlandsstraumen som følge av kanalbygging. Målinger og befaringer, juli-oktober 1998

Høsten 1996 ble det åpnet en ny båtkanal mellom Vestrepollen og Vågsbøpollen i Fana. Kanalen har medført økte tidevannsforskjeller og bedre vannutskifting i Vågsbøpollen. Tidligere var Ådlandsstraumen eneste forbindelse mellom Vågsbøpollen og sjøen. På grunn av kanalen er vanngjennomstrømmingen i Ådlandsstraumen blitt mindre, og lavvann-nivået er senket. For å dokumentere eventuelle effekter som følge av kanalen gjennomførte NIVA i samarbeid med UiB et prosjekt sommeren 1998 for å registrere biologiske endringer i strandsonen. I tillegg ble det gjort målinger av vannstand og utført modellsimuleringer. Den biologiske kartleggingen ga ingen entydige verdier for endringer i høyvann- og lavvannsnivå, men indikerer lavvannssenking på 20-30 cm i Vågsbøpollen. Vannstandsmålingene viser en økning av vannstandsamplituden på inntil 50 cm (i det vesentligste lavvanns-senking) og en middel amplitudeendring på 25 cm. I Ådlandsstraumen oppstrøms den nederste innsnevringen er det tale om senking av vann-nivået ved fjære sjø på inntil 29 cm i forhold til tidligere. Dette forekommer kun kortvarig ved spring lavvann. Lavvanns-senking med 25 cm eller mer i dette området skjer i følge beregningene i 1,2% av tiden, tilsvarende mange korte perioder med lavvann med samlet varighet på 8,6 timer i løpet av en måned

On Aharonov-Casher bound states

In this work bound states for the Aharonov-Casher problem are considered. According to Hagen's work on the exact equivalence between spin-1/2 Aharonov-Bohm and Aharonov-Casher effects, is known that the $\boldsymbol{\nabla}\cdot\mathbf{E}$ term cannot be neglected in the Hamiltonian if the spin of particle is considered. This term leads to the existence of a singular potential at the origin. By modeling the problem by boundary conditions at the origin which arises by the self-adjoint extension of the Hamiltonian, we derive for the first time an expression for the bound state energy of the Aharonov-Casher problem. As an application, we consider the Aharonov-Casher plus a two-dimensional harmonic oscillator. We derive the expression for the harmonic oscillator energies and compare it with the expression obtained in the case without singularity. At the end, an approach for determination of the self-adjoint extension parameter is given. In our approach, the parameter is obtained essentially in terms of physics of the problem.Comment: 11 pages, matches published versio

Integrating Imagery from Hull Mounted Sidescan Sonars with Multibeam Bathymetry

Multibeam echo sounders produce high quality bathymetric data, however, for acoustic imaging their alongtrack beamwidth is much wider than what is used on conventional sidescan sonars, so the imagery produced by sidescan sonars are of a better quality and are often preferred. A hullmounted combination instrument package that integrates both the accurate multibeam bathymetry and the high resolution sidescan imagery is an attractive and relatively low cost solution for detailed surveys of harbors, canals, rivers and other shallow areas. Especially in these shallow water areas the sidescan sonar benefits from being hull mounted rather than towed, since this arrangement is easier and safer to handle and the sensor position is known with high accuracy. The paper addresses how the backscatter from the hull-mounted sidescan sonar system can be radiometrically and geometrically corrected, by using the bathymetry from the multibeam echo sounder, and how the 2 data sets can be presented together in 2D and 3D. A practical experiment is described, whereby EM 3002D multibeam echo sounder and a hull mounted EA 400 sidescan sonar system are mounted together and deployed over the bow of a small survey launch. The co-registered data sets are analyzed using the UNH GEOCODER processing scheme, and the results are presented and interpreted in terms of capability to resolve small objects. A comparison is made between the EA 400 sidescan backscatter and the EM 3002D seabed imagery

Konsekvensutredning Uhellsutslipp av olje til Årdalsfjorden

Natt til 26. desember 2011 skjedde det et oljeutslipp ved Årdalstangen. Utslippet har sannsynligvis ikke medført alvorlig skade på livet i Årdalsfjorden. Værforholdene mens utslippet foregikk, og i dagene etterpå, har ført til at oljen har blitt sterkt fortynnet og innblandet i vannmassene. Oljen har en nedbrytning på 55,5 % i løpet av 24 timer, men man må renge med at det har tatt tid før denne nedbrytningen kom i gang. Det er rapportert at oljetypen er lite toksisk for fisk, plankton og alger. Det er ikke sannsynlig at oljekonsentrasjonen i vannmassene har vært høy nok til å skade økosystemet i fjorden. Hovedbestanddelen i oljen, hydrogenerte terfenyler er imidlertid bioakkumulerende og vil ha potensiale til å oppkonsentreres i næringskjeden. På generelt teoretisk grunnlag er det derfor risiko for langtidseffekter av hydrogenerte terfenyler i Årdalsfjorden, men risikoen ansees som svært liten i dette tilfellet.Hydro Aluminium Årdal v/ Hanne Hoel Pederse

Sink i ferskvann - kjemi, tilførsler og biologiske effekter

Det er laget en kunnskapsstatus for betydningen av sink i ferskvann med særlig vekt på tilførsler fra gruveavrenning. I tillegg ble det utført en undersøkelse av biologiske effekter i et vassdrag. Sveselva, med sink-belastning, men få andre metaller. Alle levende organismer har behov for sink, men det er begrensede kunnskaper om mekanismene bak giftigheten til metallet. Effekt-grenser for akvatiske organismer varier fra 10 til over 1000 µg/l. Blant de mest følsomme organismene er enkelte alger, planktoniske krepsdyr og utviklingsstadier hos fisk. I Sveselva var det tilsynelatende effekter på vegetasjon (begroing) allerede ved 20-30 µg/l, men det er usikkert om dette var det reelle belastningsnivået. Både vegetasjon og bunndyr var klart påvirket på stasjoner med konsentrasjoner i området 250-670 µg/l. Kadmium og sink akkumulerte i gjellene til utplassert dammusling på alle stasjoner nedenfor tilførslene og førte til noe forhøyede konsentrasjoner av metallotionein. Dammusling med høye metall-nivåer i gjellene filtrerte mindre alger og hadde høyere respirasjon enn dammusling med lavere metall-nivåer i gjellene. Resultatene viser at det er viktig å benytte flere mål for biologiske effekter i overvåking av effektene av metall-forurensning og å integrere kjemisk og biologisk overvåking

Interacting damage models mapped onto Ising and percolation models

We introduce a class of damage models on regular lattices with isotropic interactions, as e.g. quasistatic fiber bundles. The system starts intact with a surface-energy threshold required to break any cell sampled from an uncorrelated quenched-disorder distribution. The evolution of this heterogeneous system is ruled by Griffith's principle which states that a cell breaks when the release in elastic energy in the system exceeds the surface-energy barrier necessary to break the cell. By direct integration over all possible realizations of the quenched disorder, we obtain the probability distribution of each damage configuration at any level of the imposed external deformation. We demonstrate an isomorphism between the distributions so obtained and standard generalized Ising models, in which the coupling constants and effective temperature in the Ising model are functions of the nature of the quenched-disorder distribution and the extent of accumulated damage. In particular, we show that damage models with global load sharing are isomorphic to standard percolation theory, that damage models with local load sharing rule are isomorphic to the standard Ising model, and draw consequences thereof for the universality class and behavior of the autocorrelation length of the breakdown transitions corresponding to these models. We also treat damage models having more general power-law interactions, and classify the breakdown process as a function of the power-law interaction exponent. Last, we also show that the probability distribution over configurations is a maximum of Shannon's entropy under some specific constraints related to the energetic balance of the fracture process, which firmly relates this type of quenched-disorder based damage model to standard statistical mechanics.Comment: 16 pages, 3 figure

Can air pollution affect tear film stability? a cross-sectional study in the aftermath of an explosion accident

<p>Abstract</p> <p>Background</p> <p>After an explosion and fire in two tanks containing contaminated oil and sulphur products in a Norwegian industrial harbour in 2007, the surrounding area was polluted. This caused an intense smell, lasting until the waste was removed two years later. The present study reports examinations of tear film break up time among the population. The examinations were carried out because many of the people in the area complained of sore eyes. The purpose of the study was to assess the relationship between living or working close to the polluted area and tear film stability one and a half years after the explosion.</p> <p>Methods</p> <p>All persons working or living in an area less than six kilometres from the explosion site were invited to take part in the study together with a similar number of persons matched for age and gender living more than 20 kilometres away. Three groups were established: workers in the explosion area and inhabitants near the explosion area (but not working there) were considered to have been exposed, and inhabitants far away (who did not work in the explosion area) were considered to be unexposed. A total of 734 people were examined, and the response rate was 76 percent. Tear film stability was studied by assessing non-invasive break-up time (NIBUT) using ocular microscopy. In addition Self-reported Break Up Time (SBUT) was assessed by recording the time the subject could keep his or hers eyes open without blinking when watching a fixed point on a wall. Background information was obtained using a questionnaire. Non-parametric Wilcoxon-Mann-Whitney-tests with exact p-values and multiple logistic regression analyses were performed.</p> <p>Results</p> <p>Both NIBUT and SBUT were shorter among the male exposed workers than among the inhabitants both near and far away from the explosion area. This was also found for SBUT among males in a multiple logistic regression analysis, adjusting for age and smoking.</p> <p>Conclusions</p> <p>Reduced tear film stability was found among workers in an area where an explosion accident had occurred.</p

Demasculinization of male guppies increases resistance to a common and harmful ectoparasite

Parasites are detrimental to host fitness and therefore should strongly select for host defence mechanisms. Yet, hosts vary considerably in their observed parasite loads. One notable source of inter-individual variation in parasitism is host sex. Such variation could be caused by the immunomodulatory effects of gonadal steroids. Here we assess the influence of gonadal steroids on the ability of guppies (Poecilia reticulata) to defend themselves against a common and deleterious parasite (Gyrodactylus turnbulli). Adult male guppies underwent 31 days of artificial demasculinization with the androgen receptor-antagonist flutamide, or feminization with a combination of flutamide and the synthetic oestrogen 17 β-estradiol, and their parasite loads were compared over time to untreated males and females. Both demasculinized and feminized male guppies had lower G. turnbulli loads than the untreated males and females, but this effect appeared to be mainly the result of demasculinization, with feminization having no additional measurable effect. Furthermore, demasculinized males, feminized males and untreated females all suffered lower Gyrodactylus-induced mortality than untreated males. Together, these results suggest that androgens reduce the ability of guppies to control parasite loads, and modulate resistance to and survival from infection. We discuss the relevance of these findings for understanding constraints on the evolution of resistance in guppies and other vertebrates

Development of an International SMA Bulbar Assessment for Inter-professional Administration

BACKGROUND: Progressive weakness can affect bulbar muscles in individuals with moderate to severe forms of spinal muscular atrophy (SMA). The paucity of standardized, valid bulbar assessments capturing clinically significant deficits in SMA impedes the ability to monitor function, facilitate intervention, or detect treatment response. OBJECTIVE: To fill this void, an international multidisciplinary team gathered to develop an agreed upon consensus-derived assessment of bulbar function in SMA for inter-professional administration to enhance our ability to monitor disease progression, support clinical management, and evaluate treatment effects. METHODS: Fifty-six international clinicians experienced in SMA were invited and engaged using the Delphi method over multiple rounds of web-based surveys to establish consensus. RESULTS: Serial virtual meetings occurred with 42 clinicians (21 speech and language therapists, 11 physical therapists, 5 neurologists, 4 occupational therapists, and 1 dentist). Seventy-two validated assessments of bulbar function were identified for potential relevance to individuals with SMA (32 accessible objective, 11 inaccessible objective, 29 patient-reported outcomes). Delphi survey rounds (n = 11, 15, 15) achieved consensus on individual items with relevance and wording discussed. Key aspects of bulbar function identified included: oral intake status, oral facial structure and motor strength, swallowing physiology, voice & speech, and fatigability. CONCLUSIONS: Multidisciplinary clinicians with expertise in bulbar function and SMA used Delphi methodology to reach consensus on assessments/items considered relevant for SMA across all age groups. Future steps include piloting the new scale moving towards validation/reliability. This work supports the advancement of assessing bulbar function in children and adults with SMA by a variety of professionals