| 1. |
|
|
| 2. |
- Lorek, Eleonora, et al.
(författare)
-
High-Order Harmonic Generation and Plasmonics
- 2015
-
Ingår i: Nano-Structures for Optics and Photonics : Optical Strategies for Enhancing Sensing, Imaging, Communication and Energy Conversion - Optical Strategies for Enhancing Sensing, Imaging, Communication and Energy Conversion. - Dordrecht : Springer Netherlands. - 9789401791328 - 9789401791335 ; , s. 531-531
-
Bokkapitel (refereegranskat)abstract
- Attosecond pulses allow for imaging of very fast processes, like electron dynamics. Stockman et al. suggested to use these pulses in connection with a Photoemission electron microscope (PEEM) to study the ultrafast dynamics of plasmons (Stockman et al. Nat Photonics 1:539–544, 2007). For efficient plasmon studies, the repetition rate of the attosecond pulses used needs to be higher than a few kHz (Mikkelsen et al. Rev Sci Instrum 80:123703, 2009). Attosecond pulses are produced in a process called high-order harmonic generation (HHG) (Paul et al. Science 292(5522):1689–1692, 2001; Ferray et al. J Phys B At Mol Opt Phys 21:L31–L35, 1988). In HHG, a strong laser field allows an electron to tunnel out, get accelerated and recombine with a high kinetic energy resulting in extreme ultraviolet attosecond pulses. The large intensity needed to drive the process normally limits the repetition rate of the laser to a few kHz. Using a tight focusing scheme (Heyl et al. Phys Rev Lett 107:033903, 2011; Vernaleken et al. Opt Lett 36:3428–3430, 2011), we, however, generate harmonics at a repetition rate of 200 kHz, both with a commercial turn-key laser and with an advanced laser system. Suitable nanostructures for a strong field enhancement are produced in-house and the field enhancement is studied with PEEM in a non-time resolved manner. With high-order harmonics produced at a high repetition rate, we hope to be able to follow also the ultrafast dynamics of plasmons in these structures (Mårsell et al. Ann der Phys 525:162–170, 2013).
|
|
| 3. |
- Nandi, Saikat, et al.
(författare)
-
Observation of Rabi dynamics with a short-wavelength free-electron laser
- 2022
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 608:7923
-
Tidskriftsartikel (refereegranskat)abstract
- Rabi oscillations are periodic modulations of populations in two-level systems interacting with a time-varying field(1). They are ubiquitous in physics with applications in different areas such as photonics(2), nano-electronics(3), electron microscopy(4) and quantum information(5). While the theory developed by Rabi was intended for fermions in gyrating magnetic fields, Autler and Townes realized that it could also be used to describe coherent light-matter interactions within the rotating-wave approximation(6). Although intense nanometre-wavelength light sources have been available for more than a decade(7-9), Rabi dynamics at such short wavelengths has not been directly observed. Here we show that femtosecond extreme-ultraviolet pulses from a seeded free-electron laser(10) can drive Rabi dynamics between the ground state and an excited state in helium atoms. The measured photoelectron signal reveals an Autler-Townes doublet and an avoided crossing, phenomena that are both fundamental to coherent atom-field interactions(11). Using an analytical model derived from perturbation theory on top of the Rabi model, we find that the ultrafast build-up of the doublet structure carries the signature of a quantum interference effect between resonant and non-resonant photoionization pathways. Given the recent availability of intense attosecond(12) and few-femtosecond(13) extreme-ultraviolet pulses, our results unfold opportunities to carry out ultrafast manipulation of coherent processes at short wavelengths using free-electron lasers.
|
|
| 4. |
- Rantakyrö, F.T., et al.
(författare)
-
50 μas resolution VLBI images of AGN’s at λ3 mm
- 1998
-
Ingår i: Astronomy and Astrophysics. - Berlin : Springer-Verlag. - 0004-6361 .- 1432-0746. ; 131, s. 451-467
-
Tidskriftsartikel (refereegranskat)abstract
- We present 15 images from the global mm-VLBI sessions in 1990 April at 100 GHz and 1993 April at 86 GHz. These observations probe the central engines of the 16 observed AGN's with up to 50 mu as resolution. Among other sources previously observed with lambda 3 mm VLBI we present the first lambda 3 mm maps of 0735+178, 0748+126, 1055+018, 2145+067, and CTA102, in total we have been able to image 13 out of the 16 observed sources. 6 out of the 13 imaged sources observed exhibit curvature and rapid structural changes, although the low dynamic range in two thirds of the maps limits the detection of weak features. Most of the sources have unresolved cores even at this high resolution. There is substantial evidence that the observed sources can be grouped into two general groups: A misaligned population with parsec scale jets in the form of low pitch helices and an aligned population with straight jets with small changes in PA due to intrinsic bends.
|
|
| 5. |
- Weissenbilder, R., et al.
(författare)
-
How to optimize high-order harmonic generation in gases
- 2022
-
Ingår i: Nature Reviews Physics. - : Springer Science and Business Media LLC. - 2522-5820. ; 4:11, s. 713-722
-
Tidskriftsartikel (refereegranskat)abstract
- High-order harmonic generation (HHG) in gases leads to short-pulse extreme ultraviolet (XUV) radiation that is useful in a number of applications, such as attosecond science and nanoscale imaging. However, this process depends on many parameters, and there is still no consensus on how to choose the target geometry to optimize the source efficiency. We review the physics of HHG with emphasis on the macroscopic aspects of the nonlinear interaction, discussing the influence of length of medium, pressure, and intensity of the driving laser on the HHG conversion efficiency. Efficient HHG can be realized over a large range of pressures and medium lengths, if these follow a certain hyperbolic equation. This explains the large versatility in gas target designs for efficient HHG and provides design guidance for future high-flux XUV sources.
|
|
| 6. |
- Berntorp, Erik, et al.
(författare)
-
A prospective registry of European haemophilia B patients receiving nonacog alfa, recombinant human factor IX, for usual use.
- 2012
-
Ingår i: Haemophilia. - : Wiley. - 1351-8216. ; 18:4, s. 503-509
-
Tidskriftsartikel (refereegranskat)abstract
- Summary. Nonacog alfa, a recombinant factor IX (FIX) used for the treatment of haemophilia B, was approved in Europe in 1998. In accordance with European Medicines Agency requirements, a registry study was conducted from 2002 to 2009. A reformulated iso-osmotic version was approved for European use in 2007. This study was conducted to evaluate the safety of nonacog alfa in a usual care setting, and provide clinical trial and postmarketing surveillance data support. This open-label, non-interventional, prospective observational cohort study (registry) comprised 52 sites in nine European countries. Patients with haemophilia B receiving nonacog alfa in either formulation for prevention or treatment were followed on a usual care schedule. A total of 218 patients were enrolled, of whom 66 (30.3%) were <18 years of age. Haemophilia severity was evenly distributed, with baseline FIX activity of <1%, 1-5% and >5% in 33.3%, 36.6% and 30.1% of patients, respectively. One hundred thirty-eight patients received the original formulation alone; 80 switched to or received only the new formulation. There was a low incidence of events of special interest (ESIs), with less-than-expected therapeutic effect in five patients (2.2%), inhibitor development in two (0.9%), thrombosis in one (0.5%) and allergic events in eight (3.7%). These accounted for the majority of the 15 serious AEs reported in six patients. Six patients discontinued because of AEs, primarily related to hypersensitivity. Nonacog alfa was shown to be safe for the treatment of haemophilia B, with a low incidence of serious AEs and ESIs.
|
|
| 7. |
- Hoff, D., et al.
(författare)
-
Quantum Beat Spectroscopy of Helium Photoelectrons
- 2023
-
Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. - 9798350345995
-
Konferensbidrag (refereegranskat)abstract
- The availability of broadband extreme ultraviolet light sources allows for investigation of electron wave-packets from high lying bound states in atoms [1,2]. The dynamics of these states can be mapped out in the ionization continuum with an overlapping infrared field, which may also uncover new, light induced, dressed states [3]. Here, we carry out a complete characterization of these electron wave-packets using a small number of attosecond pulses.
|
|
| 8. |
- Wuu, J., et al.
(författare)
-
Correlates of pregnancy oestrogen, progesterone and sex hormone-binding globulin in the USA and China
- 2002
-
Ingår i: European Journal of Cancer Prevention. - : Ovid Technologies (Wolters Kluwer Health). - 0959-8278 .- 1473-5709. ; 11:3, s. 283-293
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of this study is to examine perinatal correlates of oestradiol (E2), oestriol (E3), progesterone and sex hormone-binding globulin (SHBG) among pregnant women in the USA and China. Three hundred and four Caucasian women in Boston and 335 Chinese women in Shanghai were studied. Levels of E2, E3, progesterone and SHBG were measured in maternal blood at weeks 16 and 27 of gestation, and correlated with maternal, gestational and perinatal characteristics. Height, weight and body mass index (BMI) before pregnancy is inversely associated with E2 and SHBG, whereas E3 is inversely associated with height and progesterone is inversely associated with weight and BMI. A previous live birth is associated with lower E2 and SHBG in the index pregnancy. Total gestation duration is inversely associated with E2, E3 and progesterone, whereas weight gain during pregnancy is inversely associated with progesterone and SHBG. In the US, pregnancies with female fetuses are characterized by significantly reduced progesterone. Pregnancy hormones are associated with several maternal, gestational and neonatal characteristics.
|
|
| 9. |
- Xu, B., et al.
(författare)
-
Maternal and gestational correlates of pregnancy prolactin and growth hormone in USA and China
- 2003
-
Ingår i: European Journal of Cancer Prevention. - : Ovid Technologies (Wolters Kluwer Health). - 0959-8278 .- 1473-5709. ; 12:1, s. 35-42
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of this study is to determine correlates of prolactin and growth hormone levels among pregnant women in the USA and China. We studied 304 pregnant Caucasian and 335 pregnant Chinese women. Levels of prolactin and growth hormone were measured at weeks 16 and 27 of gestation, and correlated with maternal, gestational and perinatal characteristics. Both growth hormone and, to a lesser extent, prolactin were inversely associated with pregnancy weight and body mass index, history of a previous live birth and newborn size, whereas educated women had higher levels of both hormones. Growth hormone levels were lower in women who gained more weight, smoked and had nausea and vomiting during pregnancy, whereas prolactin increased with longer total gestation. We found robust associations between maternal and newborn characteristics on the one hand and prolactin and growth hormone during pregnancy on the other.
|
|
| 10. |
- Carlén, Ida, et al.
(författare)
-
Basin-scale distribution of harbour porpoises in the Baltic Sea provides basis for effective conservation actions
- 2018
-
Ingår i: Biological Conservation. - : Elsevier BV. - 0006-3207 .- 1873-2917. ; 226, s. 42-53
-
Tidskriftsartikel (refereegranskat)abstract
- Knowledge on spatial and seasonal distribution of species is crucial when designing protected areas and implementing management actions. The Baltic Proper harbour porpoise (Phocoena phocoena) population is critically endangered, and its distribution is virtually unknown. Here, we used passive acoustic monitoring and species distribution models to describe the spatial and seasonal distribution of harbour porpoises in the Baltic Proper. Porpoise click detectors were deployed over a systematic grid of 297 stations in eight countries from April 2011 through July 2013. Generalized additive models were used to describe the monthly probability of detecting porpoise clicks as a function of spatially-referenced covariates and time. During the reproductive season, two main areas of high probability of porpoise detection were identified. One of those areas, situated on and around the offshore banks in the Baltic Proper, is clearly separated from the known distribution range of the Belt Sea population during breeding season, suggesting this is an important breeding ground for the Baltic Proper population. We commend the designation of this area as a marine protected area and recommend Baltic Sea countries to also protect areas in the southern Baltic Sea and the Hand Bight where additional important harbour porpoise habitats were identified. Further conservation measures should be carried out based on analyses of overlap between harbour porpoise distribution and potentially harmful anthropogenic activities. Our study shows that large-scale systematic monitoring using novel techniques can give important insights on the distribution of low-density populations, and that international cooperation is pivotal when studying transnationally migratory species.
|
|
