THz laser based on dipolaritons

We develop the microscopic theory of a terahertz (THz) laser based on the effects of resonant tunneling in a double quantum well heterostructure embedded in both optical and THz cavities. In the strong coupling regime the system hosts dipolaritons, hybrid quasiparticles formed by the direct exciton, indirect exciton and optical photon, which possess large dipole moments in the growth direction. Their radiative coupling to the mode of a THz cavity combined with strong non-linearities provided by exciton-exciton interactions allows for stable emission of THz radiation in the regime of the continuous optical excitation. The optimal parameters for maximizing the THz signal output power are analyzed.Comment: 8 pages, 7 figure

Control of electronic transport in graphene by electromagnetic dressing

We demonstrated theoretically that the renormalization of the electron energy spectrum near the Dirac point of graphene by a strong high-frequency electromagnetic field (dressing field) drastically depends on polarization of the field. Namely, linear polarization results in an anisotropic gapless energy spectrum, whereas circular polarization leads to an isotropic gapped one. As a consequence, the stationary (dc) electronic transport in graphene strongly depends on parameters of the dressing field: A circularly polarized field monotonically decreases the isotropic conductivity of graphene, whereas a linearly polarized one results in both giant anisotropy of conductivity (which can reach thousands of percents) and the oscillating behavior of the conductivity as a function of the field intensity. Since the predicted phenomena can be observed in a graphene layer irradiated by a monochromatic electromagnetic wave, the elaborated theory opens a substantially new way to control electronic properties of graphene with light.Comment: Published versio

Continuous THz emission from dipolaritons

We propose a scheme of continuous tunable THz emission based on dipolaritons --- mixtures of strongly interacting cavity photons and direct excitons, where the latter are coupled to indirect excitons via tunnelling. We investigate the property of multistability under continuous wave (CW) pumping, and the stability of the solutions. We establish the conditions of parametric instability, giving rise to oscillations in density between the direct exciton and indirect modes under CW pumping. In this way we achieve continuous and tunable emission in the THz range in a compact single-crystal device. We show that the emission frequency can be tuned in a certain range by varying an applied electric field and pumping conditions. Finally, we demonstrate the dynamic switching between different phases in our system, allowing rapid control of THz radiation.Comment: Main article 6 pages and 5 figures, two appendices 8 pages and 2 figure

Turning the tide of antimicrobial resistance: Europe shows the way

To access publisher full text version of this article. Please click on the hyperlink in Additional Links fieldTen years ago, European officials, experts and other stakeholders met in Copenhagen, Denmark, at the invitation of the Danish Ministry of Health and the Danish Ministry of Food, Agriculture and Fisheries. This European conference on "The Microbial Threat" due to antimicrobial resistance resulted in the publication of "Copenhagen Recommendations" calling for action to limit the emerging problem of antimicrobial-resistant microorganisms [1]. Following the conference, the European Commission prepared a comprehensive Community strategy against antimicrobial resistance, which was published in 2001 [2] and presented in Eurosurveillance [3]. Later the same year, European Union (EU) Health Ministers adopted a Council Recommendation on the prudent use of antimicrobial agents in human medicine with a series of specific measures aimed at containing the spread of antimicrobial resistance by prudent use of antimicrobial agents [4

Catching the Bound States in the Continuum of a Phantom Atom in Graphene

We explore theoretically the formation of bound states in the continuum (BICs) in graphene hosting two collinear adatoms situated at different sides of the sheet and at the center of the hexagonal cell, where a phantom atom of a fictitious lattice emulates the six carbons of the cell. We verify that in this configuration the local density of states (LDOS) near the Dirac points exhibits two characteristic features: i) the cubic dependence on energy instead of the linear one for graphene as found in New J. Phys. 16, 013045 (2014) and ii) formation of BICs as aftermath of a Fano destructive interference assisted by the Coulomb correlations in the adatoms. For the geometry where adatoms are collinear to carbon atoms, we report absence of BICs

Quantum phase transition triggering magnetic BICs in graphene

Graphene hosting a pair of collinear adatoms in the phantom atom configuration has pseudogap with cubic scaling on energy, $\Delta\propto|\varepsilon|^{3}$ which leads to the appearance of spin-degenerate bound states in the continuum (BICs) [Phys. Rev. B 92, 045409 (2015)]. In the case when adatoms are locally coupled to a single carbon atom the pseudogap scales linearly with energy, which prevents the formation of BICs. In this Letter, we explore the effects of non-local coupling characterized by the Fano factor of interference $q_{0},$ tunable by changing the slope of the Dirac cones in the graphene band-structure. We demonstrate that three distinct regimes can be identified: i) for $q_{0}<q_{c1}$ (critical point) a mixed pseudogap $\Delta\propto|\varepsilon|,|\varepsilon|^{2}$ appears yielding a phase with spin-degenerate BICs; ii) near $q_{0}=q_{c1}$ when $\Delta\propto|\varepsilon|^{2}$ the system undergoes a quantum phase transition in which the new phase is characterized by magnetic BICs and iii) at a second critical value $q_{0}>q_{c2}$ the cubic scaling of the pseudogap with energy $\Delta\propto|\varepsilon|^{3}$ characteristic to the phantom atom configuration is restored and the phase with non-magnetic BICs is recovered. The phase with magnetic BICs can be described in terms of an effective intrinsic exchange field of ferromagnetic nature between the adatoms mediated by graphene monolayer. We thus propose a new type of quantum phase transition resulting from the competition between the states characterized by spin-degenerate and magnetic BICs

Long-term results of NOPHO ALL-92 and ALL-2000 studies of childhood acute lymphoblastic leukemia

To access publisher full text version of this article. Please click on the hyperlink in Additional Links fieldAnalysis of 2668 children with acute lymphoblastic leukemia (ALL) treated in two successive Nordic clinical trials (Nordic Society of Paediatric Haematology and Oncology (NOPHO) ALL-92 and ALL-2000) showed that 75% of all patients are cured by first-line therapy, and 83% are long-term survivors. Improvements in systemic and intrathecal chemotherapy have reduced the use of central nervous system (CNS) irradiation to <10% of the patients and provided a 5-year risk of isolated CNS relapse of 2.6%. Improved risk stratification and chemotherapy have eliminated the previous independent prognostic significance of gender, CNS leukemia and translocation t(1;19)(q23;p13), whereas the post-induction level of minimal residual disease (MRD) has emerged as a new risk grouping feature. Infant leukemia, high leukocyte count, T-lineage immunophenotype, translocation t(4;11)(q21;q23) and hypodiploidy persist to be associated with lower cure rates. To reduce the overall toxicity of the treatment, including the risk of therapy-related second malignant neoplasms, the current NOPHO ALL-2008 protocol does not include CNS irradiation in first remission, the dose of 6-mercaptopurine is reduced for patients with low thiopurine methyltransferase activity, and the protocol restricts the use of hematopoietic stem cell transplantation in first remission to patients without morphological remission after induction therapy or with high levels of MRD after 3 months of therapy

Survival and causes of death in children diagnosed with cancer in Iceland 1981-2006

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn Skoða/Opna(view/open)OBJECTIVE: Of children diagnosed with cancer, approximately one fourth die of the disease or disease related complications. The aim of this study was to investigate survival and causes of death in children with cancer in Iceland. METHODS: This study is retrospective; population based and includes all children, less than 18 years of age, diagnosed with cancer in Iceland from 1981 to 2006. Information was extracted from the Icelandic Cancer Registry, patients hospital records and data from Statistics Iceland. RESULTS: Of 279 children diagnosed with cancer in the research period 215 were alive at the end of 2008. The overall 5-year survival was 81.2% and 10-year survival was 76.7%. There was not a significant survival difference with respect to age at diagnosis, year of diagnosis, gender or geographical residence. The small cohort size could be the explanation. Eleven individuals developed secondary neoplasm, eight of whom died. Sixteen of the 64 nonsurvivors were treated with curative intent until death, 12 of them died of therapy related complications. CONCLUSIONS: Survival rate in childhood cancer in Iceland is comparable to other Western countries. As previously reported, prognosis of patients with secondary neoplasm is unfavorable. Therapy related complications are the most common cause of death in patients treated with curative intent.Inngangur: Um fjórðungur barna sem greinist með krabbamein deyr vegna sjúkdóms síns eða meðferðartengdra fylgikvilla. Tilgangur rannsóknarinnar var að kanna lifun og dánarorsakir barna sem greinst hafa með krabbamein á Íslandi. Aðferðir: Rannsóknin var afturskyggn, lýðgrunduð og náði til allra einstaklinga yngri en 18 ára sem greindust með krabbamein á Íslandi frá upphafi árs 1981 til loka ársins 2006. Upplýsingum var safnað frá Krabbameinsskrá Íslands, sjúkraskrám og Hagstofu Íslands. Niðurstöður: Á rannsóknartímabilinu greindust 279 börn með krabbamein á Íslandi. Af þeim voru 215 á lífi í lok árs 2008. Á tímabilinu var fimm ára lifun 81,2% og 10 ára lifun 76,7%. Ekki var marktækur munur á lifun milli kynja, greiningartímabila, aldurs eða búsetu. Gæti það skýrst af smæð þýðisins. Lifun var mismunandi eftir krabbameinstegundum. Ellefu einstaklingar greindust síðar með meðferðartengd krabbamein, átta þeirra létust. Sextán þeirra 64 sem létust voru í læknandi meðferð fram að andláti. Var dánarorsök meðferðartengdir fylgikvillar hjá 12 úr þeim hópi. Ályktun: Horfur barna og unglinga á Íslandi með krabbamein eru sambærilegar við önnur vestræn ríki. Horfur eru mun verri í meðferðartengdum krabbameinum samanborið við frumkrabbamein. Meðferðartengdir fylgikvillar eru algengasta dánarorsök ef krabbameinsmeðferð er gefin með læknanlegum tilgangi

Utility of oropharyngeal real-time PCR for S. pneumoniae and H. influenzae for diagnosis of pneumonia in adults.

Efst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn To access publisher's full text version of this article click on the hyperlink at the bottom of the pageor click on the hyperlink at the To access publisher's full text version of this article, please click on the hyperlink in Additional Links field top of the page marked FilesA lack of sensitive tests and difficulties obtaining representative samples contribute to the challenge in identifying etiology in pneumonia. Upper respiratory tract swabs can be easily collected and analyzed with real-time PCR (rtPCR). Common pathogens such as S. pneumoniae and H. influenzae can both colonize and infect the respiratory tract, complicating the interpretation of positive results. Oropharyngeal swabs were collected (n = 239) prospectively from adults admitted to hospital with pneumonia. Analysis with rtPCR targeting S. pneumoniae and H. influenzae was performed and results compared with sputum cultures, blood cultures, and urine antigen testing for S. pneumoniae. Different Ct cutoff values were applied to positive tests to discern colonization from infection. Comparing rtPCR with conventional testing for S. pneumoniae in patients with all tests available (n = 57) resulted in: sensitivity 87 %, specificity 79 %, PPV 59 % and NPV 94 %, and for H. influenzae (n = 67): sensitivity 75 %, specificity 80 %, PPV 45 % and NPV 94 %. When patients with prior antimicrobial exposure were excluded sensitivity improved: 92 % for S. pneumoniae and 80 % for H. influenzae. Receiver operating characteristic curve analysis demonstrated for S. pneumoniae: AUC = 0.65 (95 % CI 0.51-0.80) and for H. influenzae: AUC = 0.86 (95 % CI 0.72-1.00). Analysis of oropharyngeal swabs using rtPCR proved both reasonably sensitive and specific for diagnosing pneumonia caused by S. pneumoniae and H. influenzae. This method may be a useful diagnostic adjunct to other methods and of special value in patients unable to provide representative lower airway samples.Icelandic Center for Research Rannis Landspitali University Hospital Science Fund University of Iceland Research Fun

Childhood cancer in Iceland 1981-2006

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn Skoða/Opna(view/open)BACKGROUND: Childhood cancer is the second most common cause of death in children. The aim of this study was to gather epidemiological information on childhood cancer in Iceland. METHODS: The study was population based and included all children younger than 18 years of age, diagnosed with cancer in Iceland from 1981 to 2006. Information was extracted from the Icelandic Cancer Registry and patient hospital records. RESULTS: During the study period 288 cancer cases were diagnosed in 279 children, 10 cases were secondary neoplasms. Age standardized incidence was 16.1 per 100.000 (95% CI 13,6-18,6) for boys and 12.8 per 100.000 (95% CI 10,5-15,0) for girls. There was no significant difference in the incidence rate between the first and second half of the study period. For children aged 0-14 years, the age standardized incidence was 13.6 per 100.000. The incidence was highest in the 0-4 year age group (17.3 per 100.000) and in the 15-17 year age group (19.6 per 100.000). Brain tumors (27.1%) and leukemia (25.0%) were the most common cancer groups diagnosed. Lymphoid leukemia was the most common cancer type (17.9%) and astrocytoma (13.1%) came second. CONCLUSIONS: The incidence of childhood cancer in Iceland is similar to other Western countries. Long-term follow-up is very important in childhood cancer survivors.Inngangur: Krabbamein er næst algengasta dánarorsök barna á eftir slysum. Tilgangur rann-sóknarinnar var að kanna nýgengi krabbameina hjá börnum á Íslandi.
 Aðferðir: Rannsóknin var lýðgrunduð og náði til allra <18 ára sem greindust með krabbamein á Íslandi frá upphafi árs 1981 til ársloka 2006. Upplýsingum var safnað frá Krabbameinsskrá Íslands og úr sjúkraskrám.
 Niðurstöður: Alls greindust 288 krabbameinstilfelli á tímabilinu hjá 279 börnum. Í 10 tilvikum var um meðferðartengd krabbamein að ræða. Árlegt aldursstaðlað nýgengi hjá drengjum var 16,1 af 100.000 (95% CI; 13,6-18,6) en hjá stúlkum 12,8 af 100.000 (95% CI; 10,5-15,0) en ekki var marktækur munur á nýgengi milli fyrri og seinni hluta rannsóknartímabilsins. Fyrir aldursbilið 0-14 ára var árlegt aldursstaðlað nýgengi 13,6 af 100.000. Miðtaugakerfisæxli og hvítblæði voru samanlagt 52,1% allra krabbameinstilvika. Algengasta grein-ingin var bráða eitilfrumuhvítblæði (17,9%) og stjarnfrumnaæxli (13,1%) næstalgengust. Nýgeng-ið var hæst hjá aldursbilunum 0-4 ára (17,3 af 100.00) og 15-17 ára (19,6 af 100.000). Tíu börn voru með þekkta meðfædda áhættuþætti.
 Ályktun: Nýgengi krabbameina hjá börnum á Íslandi er sambærilegt við nágrannalöndin. Mikilvægt er að fylgja vel eftir börnum sem gengið hafa í gegnum krabbameinsmeðferð og þeim sem hafa þekkta meðfædda áhættuþætti.