46 research outputs found
Some Computational Aspects of Gaussian CARMA Modelling
No full textRepresentation of continuous-time ARMA, CARMA, models is reviewed. Computational aspects of simulating and calculating the likelihood-function of CARMA are summarized. Some numerical properties are illustrated by simulations. Some real data applications are shown.CARMA, maximum-likelihood, spectrum, Kalman filter, computation
Push-ups, fracture patterns, and paleoseismology of the Leirubakki Fault, South Iceland
No full textJournal of Structural Geology, v. 25, n. 4, p. 591-609, 2003. http://dx.doi.org/10.1016/S0191-8141(02)00051-2International audienc
“Adiós sui generis” : A Study of the legal Feasibility of the Sui Generis Right in the Context of Research Biobanks
No full textThe European protection of databases has been criticized for having a negative impact on the scientific development and the process of discovery. In the paper it is checked whether one of the most important research infrastructures, such as biobanks, could be entitled with the sui generis right as shaped within the current European legal system
Computer Simulated Migration of Meandering Rivers in Minnesota
No full textIn the present work, a computer model for simulation of the migration of meandering rivers, developed by Beck [1985a], was applied to four rivers in the State of Minnesota. The computer model is based on a theoretical approach developed by Ikeda, Parker, and Sawai [1981]. The major objective was to evaluate the overall performance of the computer model and to estimate the rates of river migration in Minnesota.
By using the model to analysis the past history of the four rivers, it was found that the model is able to reproduce the past river migration but needs considerable calibration. In all the case studies it was necessary to increase the dimensionless friction factor, Cf considerably.
In all the study areas the rivers flow alternately through forested and non-forested areas. It was found that the rivers typically eroded about two times faster thtough non-forested areas than through forested areas. This result is of some interest, especially in agricultural areas. It indicates the importance of having a grove of trees lining the river instead of farming all the way to the river bank.LEGISLATIVE COMMISSION ON MINNESOTA RESOURCES
State of MinnesotaJohannesson, Helgi; Parker, Gary. (1985). Computer Simulated Migration of Meandering Rivers in Minnesota. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/113348
Theory of River Meanders
No full textA mathematical model is developed for the calculation of flow field and bed
topography in curved channels with an erodible bed. A small perturbation approach is used
to linearize the governing equations.
The downstream convective acceleration of the secondary flow is shown to give
rise to a phase lag between secondary flow and channel centerline curvature, and also to
suppress the magnitude of the secondary flow. The model further accounts for the
convective transport of primary flow momentum by the secondary flow. This oft-neglected
influence of the secondary flow is shown to be an important cause of the redistribution of
the primary flow velocity.
The governing equations retain the full coupling between the flow field, the bedload
transport, and the bed topography. This coupling is shown to increase significantly the
lateral bed slope in the upstream part of a channel bend, even beyond the value for fully
developed bend flow which is approached in the downstream part of a channel bend. This
coupling is also shown to give rise to resonant behavior for certain combinations of input
variables; the common origin of the two phenomena is explained. The predicted flow field
and bed topography compare very well with both laboratory and field data.
Further, assuming the banks to be erodible, the model is used to predict
wavelengths of river meanders. The results compare favorably with both laboratory and
field data.Legislative Commission of Minnesota ResourcesJohannesson, Helgi; Parker, Gary. (1988). Theory of River Meanders. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/114112
Anson VCF Dot Airplane - 02
No full textPhotograph - Three men and supplies beside the Anson VCF Dot plane belonging to Joe Irwin, at Namur Lake, Alberta. Left to right: Jack Neilson, Helgi Eskielson and Joe Irwi
Anson VCF Dot Airplane
No full textPhotograph - Three men and supplies beside the Anson VCF Dot plane belonging to Joe Irwin, at Namur Lake, Alberta. Left to right: Jack Neilson, Helgi Eskielson and Joe Irwi
Góðkynja meinvarpandi sléttvöðvaæxli [sjúkratilfelli]
No full textNeðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenFimmtíu og tveggja ára kona leitaði til læknis í janúar 1998 vegna hita og hósta. Hún var talin vera með lungnabólgu og meðhöndluð með sýklalyfjum. Einkennin hurfu en á röntgenmynd af lungum sem tekin var sem hluti af eftirliti sást stakur hnútur í vinstra lunga (mynd 1). Tekin var tölvusneiðmynd af brjóstholi sem sýndi marga litla hnúta dreifða um bæði lungu og voru þeir stærstu allt að 1,5 sm að stærð (mynd 2). Ómskoðun af lifur, beinaskann, brjóstamyndataka og kvenskoðun leiddu ekki í ljós neinar meinsemdir sem líktust æxlum. Einn hnútanna í hægra lunga þótti liggja vel við ástungu gegnum brjóstvegg og var það reynt tvívegis án þess að nægilegur vefur fengist til greiningar. Í heilsufarssögu sjúklings kemur fram vanstarfsemi á skjaldkirtli og nýrnahettum og tekur sjúklingur að staðaldri hormónalyf til uppbótar vegna þess. Sjúklingur hefur einnig sögu um krampa sem unglingur en ekki hefur borið á þeim í yfir 30 ár. Árið 1982 greindist sjúklingur með æxli í munnvatnskirtli, það var fjarlægt og reyndist vera vel þroskað slímþekjukrabbamein. Ekki hefur borið á endurvexti æxlisins eða meinvörpum fram að þessu. Leg konunnar (en ekki eggjastokkar) var fjarlægt 1986 vegna stækkunar. Við vefjaskoðun komu í ljós fjölmargir sléttvöðvahnútar
Comparison of video-assisted thoracoscopic surgery and limited axillary thoracotomy for spontaneous pneumothorax
No full textNeðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenINTRODUCTION: Historically, surgery for SP has been performed with open thoracotomy. Today video-assisted thoracoscopic surgery (VATS) has replaced open surgery for SP in most centers. Long-term results (i.e. recurrent pneumothorax) following VATS have been debated. In Iceland surgery for SP has been performed with both VATS and limited axillary thoracotomy (LAT). The aim of this study was to compare these two approaches, especially reoperations for prolonged airleakage and late recurrences. MATERIAL AND METHODS: This is a retrospective non-randomized study on all patients operated first time for SP at our institution between 1991-2005. Out of 210 patients that underwent 234 procedures (160 males, mean age 29 yrs.), 200 had primary SP (95%) and 10 secondary SP. The cases were divided into two groups; 134 VATS procedures and 100 thoracotomies (LAT). Three surgeons performed a LAT and four performed VATS. RESULTS: Wedge resection was performed in all cases and mechanical pleurodesis was added in 25% of the VATS and 67% of the LAT cases. Median operation time was 20 minutes longer for VATS (p=0.006). Reoperations for late recurrent pneumothorax were 10 vs. 3 in the VATS and LAT group, and reoperations for persistent airleakage 3 vs. 0, respectively (p=0.03). Operative mortality within 30 days from surgery was 0%. Median hospital stay was one day longer after LAT. CONCLUSION: Reoperations following VATS for SP are more common compared to open thoracotomy, explained by a higher rate of both late recurrent pneumothoraces and prolonged early postoperative airleakage. Both approaches are safe and major complications are infrequent. Hospital stay is shorter after VATS, however, VATS takes longer and the higher reoperation rate is a shortcoming and is of concern.Inngangur: Á síðasta áratug hafa aðgerðir með brjóstholssjá rutt sér til rúms við sjálfkrafa loftbrjósti. Umdeilt er hvort langtímaárangur sé jafn góður og eftir hefðbundna opna aðgerð. Hérlendis hafa báðar aðgerðirnar verið framkvæmdar jöfnum höndum. Markmið þessarar rannsóknar er að kanna árangur þessara aðgerða og bera þær saman, sérstaklega með tilliti til tíðni enduraðgerða vegna viðvarandi loftleka og endurtekins loftbrjósts. Efniviður og aðferðir: Rannsóknin er afturvirk og nær til allra sjúklinga sem fóru í aðgerð vegna sjálfkrafa loftbrjósts á Landspítala 1991-2005. Alls fóru 210 sjúklingar í 234 aðgerðir, þar af tíu með þekktan lungnasjúkdóm. Sjúklingunum var skipt í tvo hópa: sjúklinga sem fóru í aðgerð með speglun (n=134) og 100 sjúklinga sem fóru í brjóstholsskurð (mini-axillary thoracotomy). Þrír skurðlæknar framkvæmdu opna aðgerð og fjórir brjóstholsspeglun. Niðurstöður: Fleygskurður á lungnatoppi var framkvæmdur í öllum aðgerðum og fleiðruertingu bætt við í 25% brjóstholsspeglana og í 67% opnu aðgerðanna. Aðgerðartími var 20 mínútum lengri fyrir speglunarhópinn (p=0,006). Enduraðgerðir vegna síðkomins endurtekins loftbrjósts voru þrjár eftir opna aðgerð og tíu eftir brjóstholsspeglun og vegna viðvarandi loftleka voru þær engar og þrjár hjá sjúklingum í sömu hópum (p=0,03). Enginn sjúklingur lést innan 30 daga frá aðgerð. Legutími (miðgildi) var einum degi lengri eftir opna aðgerð. Ályktanir: Enduraðgerðir eru algengari eftir brjóstholsspeglanir og skýrist aðallega af hærra hlutfalli viðvarandi loftleka og endurtekins loftbrjósts. Báðar aðgerðir eru öruggar og meiriháttar fylgikvillar eru sjaldgæfir. Legutími er styttri eftir brjóstholsspeglun, en á móti kemur að aðgerðartími er lengri. Brýnt er að finna lausnir á því hvernig lækka megi tíðni enduraðgerða eftir brjóstholsspeglun
