Persistence of Timothy in Mixture with Smooth Meadow Grass

Timothy (Phleum pratense) is the most common grass species in Iceland for the production of high quality herbage for dairy cows. For this purpose timothy is cut early, often around heading. The high quality, however, is at the cost of limited persistence of timothy. If cut late, three to four weeks after heading, timothy cultivars of northern origin can sometimes dominate for a long time, especially if the aftermath is not cut or grazed. Earlier experiments have shown that, relative to a late cutting treatment, the percentage timothy in the first harvest is reduced by one unit for each week that the harvest is moved forward (Helgadóttir & Hermannsson, 1991). This effect is cumulative over the years and the result applies to swards where all of the fertiliser is applied in spring and smooth meadow grass (Poa pratensis) is present in the sward, either sown or invaded. Experiments were run to further study the persistence of timothy under different cutting treatments and N applications and the effect of cultivars of both timothy and smooth meadow grass

Development of a Computationally Efficient Fabric Model for Optimization of Gripper Trajectories in Automated Composite Draping

An automated prepreg fabric draping system is being developed which consists of an array of actuated grippers. It has the ability to pick up a fabric ply and place it onto a double-curved mold surface. A previous research effort based on a nonlinear Finite Element model showed that the movements of the grippers should be chosen carefully to avoid misplacement and induce of wrinkles in the draped configuration. Thus, the present study seeks to develop a computationally efficient model of the mechanical behavior of a fabric based on 2D catenaries which can be used for optimization of the gripper trajectories. The model includes bending stiffness, large deflections, large ply shear and a simple contact formulation. The model is found to be quick to evaluate and gives very reasonable predictions of the displacement field

Afterglow Light Curves and Broken Power Laws: A Statistical Study

In gamma-ray burst research it is quite common to fit the afterglow light curves with a broken power law to interpret the data. We apply this method to a computer simulated population of afterglows and find systematic differences between the known model parameters of the population and the ones derived from the power law fits. In general, the slope of the electron energy distribution is overestimated from the pre-break light curve slope while being underestimated from the post-break slope. We also find that the jet opening angle derived from the fits is overestimated in narrow jets and underestimated in wider ones. Results from fitting afterglow light curves with broken power laws must therefore be interpreted with caution since the uncertainties in the derived parameters might be larger than estimated from the fit. This may have implications for Hubble diagrams constructed using gamma-ray burst data.Comment: 4 pages, 5 figures, accepted for publication in ApJ Letter

Energy Injection Episodes in Gamma Ray Bursts: The Light Curves and Polarization Properties of GRB 021004

Several GRB afterglow light curves deviate strongly from the power law decay observed in most bursts. We show that these variations can be accounted for by including refreshed shocks in the standard fireball model previously used to interpret the overall afterglow behavior. As an example we consider GRB 021004 that exhibited strong light curve variations and has a reasonably well time-resolved polarimetry. We show that the light curves in the R-band, X-rays and in the radio can be accounted for by four energy injection episodes in addition to the initial event. The polarization variations are shown to be a consequence of the injections.Comment: 4 pages, 2 figures. To appear in ApJ

Star formation efficiency and host galaxies of Gamma-Ray Bursts

Gamma-ray bursts are likely to be associated with regions of active star formation and may therefore be useful as cosmological tracers of galaxy formation. Using hydrodynamical/N-body simulations the cosmological properties of host galaxies are investigated. Assuming the hosts to be efficient star-forming objects, i.e. with high specific star formation rates, the majority of the candidate hosts are found to below mass, young galaxies with a moderate star formation rate. This picture, consistent with most observations of GRB host galaxies, corroborates the idea that gamma-ray bursts do not follow the cosmic star formation rate. More importantly the hosts should contribute to unveil the faint end of the galaxy luminosity function

Energy injection episodes in GRBs: The case of GRB 021004

A number of GRB afterglow light curves deviate substantially from the power law decay observed in most bursts. These variations can be accounted for by including refreshed shocks in the standard fireball model previously used to interpret the overall afterglow behavior. We show that the light curves of GRB 021004 can be accounted for by four energy injection episodes in addition to the initial event. The polarization variations are shown to be a consequence of the injections

Study of medications use of elderly admitted to acute care hospital

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenObjective: The prevalence of diseases increases with age and so does use of medications. Thus illness related to medications use does also become more prevalent. This study aims at evaluating medications of elderly people admitted to an acute care hospital, and demonstrate adverse reactions and quality indicators. Material and methods: This is a study of patients 75 years of age and older admitted acutely to internalmedicine at the Reykjavik Hospital over a three month period in the spring of 1995. All medications and diagnoses were registered and the medical records reviewed. The contribution of adverse medication effects to the admission was assessed. Quality of treatment was evaluated according to evidence based medicine for the diagnoses chosen. The study included 208 individuals, 133 women and 75 men with the mean age of 82.4 years. Results: Mean length of stay for women was 19.9 days and men 15.2 days. Number of drugs on admission and discharge ranged from 0 to 18. The mean number of drugs were for women 5.8 and 6.9 and men 6.6 and 7.7 on admission and discharge, respectively. In 16 cases or 7.7% it was judged that there was a high likelihood of the admission being due to an adverse effect. Potential drug interactions according to a computer software package were not judged to be of clinical importance in any case. Conclusions: Treatment for coronary heart disease, heart failure, osteoporosis, insomnia and long term prednisolon treatment is not completely optimal according to evidence based medicine. The results of this study indicate that treatment could be improved for example with use of clinical guidelines.Tilgangur: Með hækkandi aldri vex algengi sjúkdóma og jafnframt lyfjanotkun. Veikindi sem tengjast lyfjanotkun verða því tíðari meðal aldraðra. Rannsóknin lýsir lyfjanotkun aldraðra á bráðasjúkrahúsi, aukaverkunum og gæðavísum. Efniviður og aðferðir: Þessi rannsókn tekur til allra aldraðra, 75 ára og eldri, sem lögðust inn brátt á lyflækningadeildir Borgarspítalans á þriggja mánaða tímabili vorið 1995. Öll lyf og allar sjúkdómsgreiningar voru skráð og sjúkraskrár yfirfarnar. Lagt var mat á það hvort lyfjanotkun ætti þátt í innlögn. Gæði lyfjameðferðar voru metin meðal annars með tilliti til fyrri og núverandi sjúkdómsgreininga. Niðurstöður: Könnunin náði til 208 einstaklinga, 133 kvenna og 75 karla á aldrinum 75 til 98 ára, meðalaldur 82,4 ár. Meðallegudagar kvennanna voru 19,9 dagar og karlanna 15,2 dagar. Skráður fjöldi lyfja við innskrift var á bilinu 0 til 18 lyf og við útskrift mest 18. Meðalfjöldi lyfja hjá konum við innskrift var 5,8 lyf og við útskrift 6,9. Karlar höfðu 6,6 lyf við innskrift að meðaltali og 7,7 við útskrift. Í 16 tilvikum eða 7,7% voru taldar miklar líkur á að sjúklingur hefði lagst inn vegna aukaverkana lyfja. Engin vísbending um milliverkun samkvæmt tölvuútskrift reyndist hafa klíníska þýðingu að mati höfunda. Ályktanir: Aldraðir sem leggjast inn á bráðasjúkrahús eru á fjölda lyfja og eiga aukaverkanir lyfja nokkurn þátt í innlögnum. Hvað varðar meðferð á kransæðasjúkdómi, hjartabilun, beinþynningu, svefntruflunum og langtímameðferð með sykursterum kom fram að all nokkuð vantar upp á að bestu meðferð, samkvæmt niðurstöðum rannsókna, sé beitt. Niðurstöður rannsóknarinnar, ásamt þeim grófu gæðavísum sem beitt var, benda til að gera megi betur til dæmis með klínískum leiðbeiningum

Luminosity Functions of Gamma-Ray Burst Afterglows

Aims: Use the standard fireball model to create virtual populations of gamma-ray burst afterglows and study their luminosity functions. Methods: We randomly vary the parameters of the standard fireball model to create virtual populations of afterglows. We use the luminosity of each burst at an observer's time of 1 day to create a luminosity function and compare our results with available observational data to assess the internal consistency of the standard fireball model. Results: We show that the luminosity functions can be described by a function similar to a log normal distribution with an exponential cutoff. The function parameters are frequency dependent but not very dependent on the model parameter distributions used to create the virtual populations. Comparison with observations shows that while there is good general agreement with the data, it is difficult to explain simultaneously the X-ray and optical data. Possible reasons for this are discussed and the most likely one is that the standard fireball model is incomplete and that decoupling of the X-ray and optical emission mechanism may be needed.Comment: 5 pages, 4 figures; accepted for publication in A&