Effects of hole self-trapping by polarons on transport and negative bias illumination stress in amorphous-IGZO

The effects of hole injection in amorphous-IGZO is analyzed by means of first-principles calculations. The injection of holes in the valence band tail states leads to their capture as a polaron, with high self-trapping energies (from 0.44 to 1.15 eV). Once formed, they mediate the formation of peroxides and remain localized close to the hole injection source due to the presence of a large diffusion energy barrier (of at least 0.6eV). Their diffusion mechanism can be mediated by the presence of hydrogen. The capture of these holes is correlated with the low off-current observed for a-IGZO transistors, as well as, with the difficulty to obtain a p-type conductivity. The results further support the formation of peroxides as being the root cause of Negative bias illumination stress (NBIS). The strong self-trapping substantially reduces the injection of holes from the contact and limits the creation of peroxides from a direct hole injection. In presence of light, the concentration of holes substantially rises and mediates the creation of peroxides, responsible for NBIS.Comment: 8 pages, 8 figures, to be published in Journal of Applied Physic

Treatment need and dental service provided at the Faculty of Odontology

Efst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinnInngangur: Tilgangur rannsóknarinnar var að kanna meðferðarþörf og aldurs- og kynjaskiptingu þeirra sem koma til skoðunar á klínik Tannlæknadeildar Háskóla Íslands og umfang þeirrar þjónustu sem sjúklingum er veitt eftir frumskoðun. Efniviður og aðferðir: Megindleg aðferðarfræði var notuð við framkvæmd rannsóknarinnar og niðurstöður settar fram með lýsandi tölfræði í töflum og skýringarmyndum. Meðferðarþörf þeirra sem komu í frumskoðun á vormisseri 2011 var skráð samkvæmt frumskoðunarblöðum og upplýsingar um meðferð voru skráðar af handskrifuðum og rafrænum sjúkraskrám deildarinnar. Við tölfræðivinnslu voru notuð forritin Microsoft Excel og SPSS 20. Niðurstöður: Heildarfjöldi skoðunarsjúklinga var 261, en 254 (97,3%) frumskoðunarblöð voru tæk til skráningar. Meðferðarþörf frumskoðunarsjúklinga reyndist mjög mismunandi, allt frá því að vera engin í það að vera mjög umfangsmikil. Alls fengu 143 (55,1%) skoðunarsjúklinganna einhverja meðferð á deildinni. Af körlum sem sem leituðu til deildarinnar fengu 61% meðferð, en marktækt lægra hlutfall kvennanna eða 48% (p=0,035). Flestir skoðunarsjúklingar voru fæddir á áratugnum 1980-1989 (30,2%) en fæstir 1920-1929 (1,2%). Ályktun: Tannlæknanemar á klínik deildarinnar sinna rúmum helmingi þeirra sjúklinga sem þangað leita. Frá sjónarhorni deildarinnar er mikið offramboð af sjúklingum í ákveðnum greinum, til dæmis í tannfyllingu, en skortur á viðfangsefnum fyrir nemendur í öðrum greinum, eins og heilgóma- og partagerð og bitlækningumIntroduction: The purpose of the study was to assess treatment need, age and gender of those attending the University of Iceland’s dental clinic and to analyse the service provided by dental students in relation to the patients´ needs. Materals and methods: The sample comprised all patients attending the clinic for a primary consultation in the spring term of 2011. Information was collected from the original registration sheets and patient files and radiographs. Quantitative methods were used and results presented with descriptive statistics in text, tables and charts. Microsoft Excel and SPSS 20 were used for statistical analysis. Results: The total number of primary examination patients was 261, and 254 (97,3%) had complete registration sheets. The need for dental treatment ranged from none to severe. A total of 143 examination patients (55,1%) received some treatment at the clinic. According to a chi-square test (p=0,035) the ratio of men that received treatment (61%) was significantly higher than that of women (48%). Patients born in the years 1980-89 comprised 30,2% of the sample. Conclusion: Students at the dental clinic manage to treat a little over half of the patients that seek their assistance. From the Faculty´s perspective there is a surplus of subjects in operative dentistry and most other fields of the study, while some types of prosthetic tasks are lacking

Prevalence of Streptococcus pyogenes and methisillin-resistant Staphylococcus aureus in the pharynx of healthy children in the town of Gardabaer

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenBACKGROUND: Treating S. pyogenes pharyngitis with antibiotics is recommended after confirming its presence using culture or rapid antigen tests. Limiting unnecessary antibiotics use is important in attempt to avoid rising resistance to drugs such as macrolides. Not all individuals carrying S. pyogenes are infected. OBJECTIVE: To evaluate the carriage rate of S. pyogenes and methicillin resistant S. aureus (MRSA) among healthy children in the Reykjavík capital area. SUBJECTS AND METHODS: Cross-sectional study for the carriage of S. pyogenes and MRSA among healthy children in the town of Gardabaer. The study took place in March and April 2005. Throat cultures were collected from 270 asymptomatic healthy primary school students and cultured selectively for S. pyogenes and MRSA and tested for antimicrobial susceptibilities. RESULTS: Prevalence of S. pyogenes was found to be 22%. The proportion of carriers in 1st to 6th grade was 28%, compared with 11% in 7th to 10th grade students. The highest proportion was in 1st grade, 45%. The proportion S. pyogenes resistant to erythromycin was 17%, to tetracycline 13% and clindamycin 2%. All strains were susceptible to penicillin. No MRSA strains were found. CONCLUSIONS: The study reveals a high S. pyogenes carriage rate in primary school children in Garethabaer. Physicians should consider the prevalence of streptococcal carriage when diagnosing streptococcal pharyngitis in children, and only perform culture and/or antigen tests when clinically indicated.Inngangur: Hálsbólgur skal meðhöndla með sýklalyfjum ef S. pyogenes (hemólýtískir streptókokkar af flokki A) er talin orsök þeirra. Mikilvægt er að staðfesta tilvist S. pyogenes í hálsi til að forðast óþarfa sýklalyfjanotkun en vaxandi ónæmi til dæmis gegn makrólíðum er orðið algengt. Ekki er þó fullvíst að um streptókokkahálsbólgu sé að ræða þó S. pyogenes finnist í hálsi því viðkomandi gæti verið beri og haft veiruhálsbólgu. Tilgangur: Kanna beratíðni og sýklalyfjanæmi S. pyogenes meðal heilbrigðra barna á höfuðborgarsvæðinu og hvort eitthvert barnanna beri methisillín ónæma Staphylococcus aureus (MÓSA) í hálsi. Efniviður og aðferðir: Þversniðsrannsókn á algengi S. pyogenes og MÓSA hjá heilbrigðum börnum. Rannsóknin var gerð í mars og apríl 2005. Hálsstrok voru tekin úr 270 einkennalausum heilbrigðum grunnskólabörnum í Garðabæ og ræktuð fyrir S. pyogenes og MÓSA. Sýklalyfjanæmi bakteríanna var kannað. Niðurstöður: Algengi S. pyogenes reyndist vera 22%. Beratíðnin í 1.-6. bekk var 28% en 11% í 7.-10. bekk. Hæst var tíðnin í 1. bekk eða 45%. Sýklalyfjaónæmi S. pyogenes fyrir erýtrómýcíni reyndist 17% og fyrir tetracýklíni 13%, 0% fyrir penicillíni og 2% fyrir klindamýcíni. Engir MÓSA stofnar ræktuðust úr hálsstrokum barnanna. Ályktun: Niðurstöðurnar sýna háa beratíðni hjá grunnskólabörnum í Garðabæ. Læknar ættu að hafa beratíðnina í huga við greiningu streptókokkahálsbólgu hjá börnum og ekki gera hraðgreiningarpróf og/eða hálsræktun nema einkenni gefi tilefni til

Stress release mechanisms for Cu on Pd(111) in the submonolayer and monolayer regimes

We study the strain relaxation mechanisms of Cu on Pd(111) up to the monolayer regime using two different computational methodologies, basin-hopping global optimization and energy minimization with a repulsive bias potential. Our numerical results are consistent with experimentally observed layer-by-layer growth mode. However, we find that the structure of the Cu layer is not fully pseudomorphic even at low coverages. Instead, the Cu adsorbates forms fcc and hcp stacking domains, separated by partial misfit dislocations. We also estimate the minimum energy path and energy barriers for transitions from the ideal epitaxial state to the fcc-hcp domain pattern.Comment: 4 pages, 4 figure

Varieties of distributive rotational lattices

A rotational lattice is a structure (L;\vee,\wedge, g) where L=(L;\vee,\wedge) is a lattice and g is a lattice automorphism of finite order. We describe the subdirectly irreducible distributive rotational lattices. Using J\'onsson's lemma, this leads to a description of all varieties of distributive rotational lattices.Comment: 7 page

Self-learning Kinetic Monte-Carlo method: application to Cu(111)

We present a novel way of performing kinetic Monte Carlo simulations which does not require an {\it a priori} list of diffusion processes and their associated energetics and reaction rates. Rather, at any time during the simulation, energetics for all possible (single or multi-atom) processes, within a specific interaction range, are either computed accurately using a saddle point search procedure, or retrieved from a database in which previously encountered processes are stored. This self-learning procedure enhances the speed of the simulations along with a substantial gain in reliability because of the inclusion of many-particle processes. Accompanying results from the application of the method to the case of two-dimensional Cu adatom-cluster diffusion and coalescence on Cu(111) with detailed statistics of involved atomistic processes and contributing diffusion coefficients attest to the suitability of the method for the purpose.Comment: 18 pages, 9 figure

A view of canonical extension

This is a short survey illustrating some of the essential aspects of the theory of canonical extensions. In addition some topological results about canonical extensions of lattices with additional operations in finitely generated varieties are given. In particular, they are doubly algebraic lattices and their interval topologies agree with their double Scott topologies and make them Priestley topological algebras.Comment: 24 pages, 2 figures. Presented at the Eighth International Tbilisi Symposium on Language, Logic and Computation Bakuriani, Georgia, September 21-25 200

Immunization coverage in the Monkey Bay Head zone Malawi

Hægt er að lesa greinina í heild sinni með því að smella á hlekkinn View/OpenOBJECTIVE: To assess the immunization coverage of children in the Monkey Bay head zone, Malawi where the Icelandic International Development Agency (ICEIDA) has been working to improve health care services in the recent years. MATERIALS AND METHODS: A 30 by 7 cluster sample survey, as defined by WHO's Expanded Programme on Immunization (EPI) was conducted to estimate immunization coverage of children aged 12-23 months for tuberculosis (BCG), diphtheria, tetanus and pertussis (DTP), polio (OPV) and measles immunizations. The Head Zone consists of 97 villages with a population of around 105,000 inhabitants. Five health centres provide immunization services in the area. In total were 217 children in 30 clusters randomly selected and their immunization status by card or history registered. RESULTS: Immunization coverage by card or history was 97% for BCG, and 99%, 95% and 85% for DTP1, DTP2 and DTP3 respectively. Coverage of OPV1, OPV2 and OPV3 by card or history was 99%, 93% and 85% respectively. Coverage for measles by card or history was 78%. Fully immunized children by card or history were 152 or 70%. Two children had not received any immunizations. Drop-out rate from DTP1 to DTP3 vaccination by immunization card or history was 14.5%, and drop-out from DTP1 to Measles by card or history was 21%. CONCLUSION: These results indicate that access to childhood immunization in the Monkey Bay head zone is good while drop-out rate is high. This indicates that access to health services is adequate. However, the coverage of measles appears to be insufficient to prevent outbreaks, and must be improved. The efficacy in delivering immunization can be improved and enhanced utilization of the services offered should be sought.Tilgangur: Að leggja mat á þekjun bólusetningar barna í Monkey Bay héraði í Malaví þar sem að Þróunarsamvinnustofnun Íslands (ÞSSÍ) hefur unnið að uppbyggingu heilsugæslu undanfarin ár. Efniviður og aðferðir: Notast var við aðferðir alþjóðaheilbrigðismálastofnunarinnar (WHO) til þess að meta þekjun bólusetningar barna á aldrinum 12-23 mánaða í Monkey Bay héraði. Í héraðinu búa um það bil 105.000 íbúar í 97 þorpum. Fimm heilsugæslustöðvar veita þjónustu á svæðinu. Börn á svæðinu voru bólusett fyrir berklum (BCG), barnaveiki, stífkrampa og kíghósta (DTP), mænu­veiki (OPV) og mislingum. Ef börn voru ekki bólusett voru ástæður þess skráðar. Valin voru 217 börn af handahófi í 30 þorpum/klösum (clusters) og þekjun metin með skoðun bólusetningarkorta eða samkvæmt heilsufarssögu. Niðurstöður: Þekjun bólusetningar miðað við kort eða sögu var 97% fyrir BCG, og 99%, 95% og 85% fyrir DTP1, DTP2 og DTP3. Þekjun OPV1, OPV2 og OPV3 miðað við kort eða sögu var 99%, 93% og 85%. Þekjun mislinga miðað við kort eða sögu var 78%. Fullbólusett börn miðað við kort eða sögu voru 152, eða 70%. Tvö börn höfðu ekki fengið neinar bólu­setningar. Brottfall milli DTP1 og DTP3 miðað við kort eða sögu var 14,5 prósentustig, og brottfall milli DTP1 og mislinga var 21 prósentustig. Ályktun: Aðgengi að bólusetningu á svæðinu virðist gott. Brottfall frá fyrstu bólusetningu til síðustu er áhyggjuefni, sérstaklega hvað varðar mislinga en sú bólusetning er einnig oft gefin of seint. Því verður að huga að leiðum til þess að auka skilvirkni þeirrar þjónustu sem er í boði