TIFAX 2017 Campaign Report: Sea ice thickness measurements with Polar 6 from Station Nord and Alert

Arctic sea ice extent and thickness have undergone dramatic changes in the past decades: Summer sea ice extent has declined at an annual rate of approximately 12.7 % per decade over the satellite record (1978 – present, Meier et al., 2014) and its mean thickness has decreased by 0.58 m +/- 0.07 m per decade over the period 2000 - 2012 (Lindsay et al., 2015). The thinning of sea ice is accompanied by an increase of ice drift velocity (Spreen et al., 2011), deformation (Rampal et al., 2009) and a decrease of net ice growth rates. Climate model simulations indicate that ice extent and thickness will further decline through the 21st century in response to atmospheric greenhouse gas increases (Vravus et al., 2012). However, the mass balance of Arctic sea ice is not only determined by changes in the energy balance of the coupled ice-ocean-atmosphere system but also by the increasing influence of dynamic effects. One aspect of the mass balance of Arctic sea ice are changes of ice volume export rates through Fram Strait and the decline of thick and old multi-year ice North of Ellesmere Island. Thickness surveys carried out North of Greenland and Fram Strait give insight into composition and properties of Arctic sea ice in general and how it changes over time. An extensive data set of ground-based and airborne electromagnetic ice thickness measurements were collected between 2001 and 2016 during several aircraft (PAMARCMIP, TIFAX) and Polarstern campaigns. The first aim of the TIFAX 2017 campaign is to complement earlier measurements made north of Svalbard, Greenland and in Fram Strait. Sea ice thickness information will be used to examine the connection between thickness variability, ice age and source area. Together with satellite based information on sea ice motion, data will be used to number sea ice outflow through Fram Strait in summer. These estimates shall improve the understanding of interannual variability in summer sea ice outflow and complement existing winter volume flux calculations. A second objective is to extent sea ice thickness measurements to the Lincoln Sea where we will study thinning of sea ice due to reduction of old multi-year ice in this area. Like the measurements planned over Fram Strait area, the surveys are a continuation of earlier aircraft campaigns made North of Alert and shall improve understanding of ice mass balance changes in the Arctic. In addition to measurements over sea ice, laser scanner flights over glaciers were made within the framework of MABANG

Spatio-temporal coherent control of thermal excitations in solids

X-ray reflectivity (XRR) measurements of femtosecond laser-induced transient gratings are applied to demonstrate the spatio-temporal coherent control of thermally induced surface deformations on ultrafast timescales. Using gracing incidence X-ray diffraction we unambiguously measure the amplitude of transient surface deformations with sub-\AA{} resolution. Understanding the dynamics of femtosecond TG excitations in terms of superposition of acoustic and thermal gratings makes it possible to develop new ways of coherent control in X-ray diffraction experiments. Being the dominant source of TG signal, the long-living thermal grating with spatial period $\Lambda$ can be canceled by a second, time-delayed TG excitation shifted by $\Lambda/2$. The ultimate speed limits of such an ultrafast X-ray shutter are inferred from the detailed analysis of thermal and acoustic dynamics in TG experiments

a study to discover novel tumor-specific mutations

Background Splenic marginal zone lymphoma (SMZL) is an indolent B-cell non- Hodgkin lymphoma and represents the most common primary malignancy of the spleen. Its precise molecular pathogenesis is still unknown and specific molecular markers for diagnosis or possible targets for causal therapies are lacking. Methods We performed whole exome sequencing (WES) and copy number analysis from laser-microdissected tumor cells of two primary SMZL discovery cases. Selected somatic single nucleotide variants (SNVs) were analyzed using pyrosequencing and Sanger sequencing in an independent validation cohort. Results Overall, 25 nonsynonymous somatic SNVs were identified, including known mutations in the NOTCH2 and MYD88 genes. Twenty-three of the mutations have not been associated with SMZL before. Many of these seem to be subclonal. Screening of 24 additional SMZL for mutations at the same positions found mutated in the WES approach revealed no recurrence of mutations for ZNF608 and PDE10A, whereas the MYD88 L265P missense mutation was identified in 15 % of cases. An analysis of the NOTCH2 PEST domain and the whole coding region of the transcription factor SMYD1 in eight cases identified no additional case with a NOTCH2 mutation, but two additional cases with SMYD1 alterations. Conclusions In this first WES approach from microdissected SMZL tissue we confirmed known mutations and discovered new somatic variants. Recurrence of MYD88 mutations in SMZL was validated, but NOTCH2 PEST domain mutations were relatively rare (10 % of cases). Recurrent mutations in the transcription factor SMYD1 have not been described in SMZL before and warrant further investigation

Whole exome sequencing of microdissected splenic marginal zone lymphoma: a study to discover novel tumor-specific mutations

BACKGROUND: Splenic marginal zone lymphoma (SMZL) is an indolent B-cell non-Hodgkin lymphoma and represents the most common primary malignancy of the spleen. Its precise molecular pathogenesis is still unknown and specific molecular markers for diagnosis or possible targets for causal therapies are lacking. METHODS: We performed whole exome sequencing (WES) and copy number analysis from laser-microdissected tumor cells of two primary SMZL discovery cases. Selected somatic single nucleotide variants (SNVs) were analyzed using pyrosequencing and Sanger sequencing in an independent validation cohort. RESULTS: Overall, 25 nonsynonymous somatic SNVs were identified, including known mutations in the NOTCH2 and MYD88 genes. Twenty-three of the mutations have not been associated with SMZL before. Many of these seem to be subclonal. Screening of 24 additional SMZL for mutations at the same positions found mutated in the WES approach revealed no recurrence of mutations for ZNF608 and PDE10A, whereas the MYD88 L265P missense mutation was identified in 15 % of cases. An analysis of the NOTCH2 PEST domain and the whole coding region of the transcription factor SMYD1 in eight cases identified no additional case with a NOTCH2 mutation, but two additional cases with SMYD1 alterations. CONCLUSIONS: In this first WES approach from microdissected SMZL tissue we confirmed known mutations and discovered new somatic variants. Recurrence of MYD88 mutations in SMZL was validated, but NOTCH2 PEST domain mutations were relatively rare (10 % of cases). Recurrent mutations in the transcription factor SMYD1 have not been described in SMZL before and warrant further investigatio

Epigenetic Silencing of the Circadian Clock Gene CRY1 is Associated with an Indolent Clinical Course in Chronic Lymphocytic Leukemia

Disruption of circadian rhythm is believed to play a critical role in cancer development. Cryptochrome 1 (CRY1) is a core component of the mammalian circadian clock and we have previously shown its deregulated expression in a subgroup of patients with chronic lymphocytic leukemia (CLL). Using real-time RT-PCR in a cohort of 76 CLL patients and 35 normal blood donors we now demonstrate that differential CRY1 mRNA expression in high-risk (HR) CD38+/immunoglobulin variable heavy chain gene (IgVH) unmutated patients as compared to low-risk (LR) CD38−/IgVH mutated patients can be attributed to down-modulation of CRY1 in LR CLL cases. Analysis of the DNA methylation profile of the CRY1 promoter in a subgroup of 57 patients revealed that CRY1 expression in LR CLL cells is silenced by aberrant promoter CpG island hypermethylation. The methylation pattern of the CRY1 promoter proved to have high prognostic impact in CLL where aberrant promoter methylation predicted a favourable outcome. CRY1 mRNA transcript levels did not change over time in the majority of patients where sequential samples were available for analysis. We also compared the CRY1 expression in CLL with other lymphoid malignancies and observed epigenetic silencing of CRY1 in a patient with B cell acute lymphoblastic leukemia (B-ALL)

Einfluss von Gitterverspannung und Zusammensetzung auf die strukturellen und piezo/ferroelektrischen Eigenschaften von epitaktischen NaNbO3 und KxNa1-xNbO3 Dünnschichten und Übergittern gewachsen mittels PLD

The subject of this thesis is the systematic study of the impact of pulsed laser deposition (PLD) conditions on the growth mode, strain state and film composition of ferroelectric NaNbO3 and KxNa1-xNbO3 thin films and superlattices. Lattice mismatched (011)NdGaO3, (001)SrTiO3, (011)DyScO3, (011)TbScO3 and (011)NdScO3 single crystalline substrates have been used in order to induce tensile or compressive biaxial lattice strain of different magnitude in the films. Coherent 2D growth of thin NaNbO3 films was achieved by optimizations of the growth process. The key interests were to adjust the deposition conditions allowing for near stoichiometric film growth and to analyze the dependence of ferroelectric domain formation and local hysteresis loops on the composition of films, incorporating different biaxial lattice strains. The amount of sodium and oxygen vacancies in the films was found to be critically affected by the oxygen background pressure and the Na/Nb ratio in the applied targets. By increasing the oxygen pressure from 0.05 mbar to 2 mbar or the Na/Nb ratio in the targets up to 1.17, a substantial reduction of sodium and oxygen vacancies was achieved. No extended defects were found in fully tensilely strained films deposited under thus optimized deposition conditions. In contrast, in compressively strained films deposited under otherwise identical conditions, the presence of columnar defects was observed, which provide stress relief in compressively strained films. In films incorporating full tensile lattice strain, regular lateral ferroelectric a1/a2 domain patterns were obtained only in the case of near-stoichiometric growth. In ferroelectric films under partially relaxed tensile lattice strain, typically a1/c/a2/c patterns are observed. In partially relaxed PLD-grown NaNbO3 films, additionally a vertical polarization evolves, resulting in an a1c/a2c domain pattern. Distinct local ferroelectric hysteresis loops were observed in near-stoichiometric films under low compressive lattice strain. Thus, it was confirmed that a ferroelectric room temperature phase can be induced by biaxial lattice strain in NaNbO3, which is antiferroelectric in the unstrained state. In the case of KxNa1-xNbO3, the key interest was to investigate the impact of K/Na ratio and biaxial lattice strain on local piezoelectric coefficients. It was found that the thickness up to which KxNa1-xNbO3 films could be deposited in a 2D-growth mode is lower compared to NaNbO3 films, which is correlated to the amount of incorporated K. As a promising alternative to the growth of single films, superlattices with alternating layers under compressive and tensile lattice strain were deposited on DyScO3 substrates. This way, both 2D growth and full in-plane lattice strain of the individual layers were retained for remarkably increased thicknesses compared to single films. In agreement with theoretical predictions made for ferroelectric/ferroelectric superlattices, 2D-grown, fully strained NaNbO3/K0.5Na0.5NbO3 superlattices on DyScO3 substrates were found to exhibit very promising local piezo/ferroelectric properties.Das Ziel dieser Arbeit war die systematische Untersuchung des Einflusses von Wachstumsbedingungen der Laserstrahlverdampfung (PLD) auf den Wachstumsmodus, den Verspannungszustand und die Zusammensetzung von NaNbO3- und KxNa1-xNbO3-Dünnschichten und Übergittern. Einkristalline (011)NdGaO3, (001)SrTiO3, (011)DyScO3, (011)TbScO3 und (011)NdScO3 Substrate mit kontrollierter Gitter-Fehlanpassung wurden verwendet, um biaxial kompressive oder tensile Gitterverspannungen in den Filmen zu erzeugen. Im Fall von NaNbO3 lag der Fokus auf der Erforschung von Abscheidebedingungen, die ein nahezu stöchiometrisches, 2D Film-Wachstum ermöglichen. Es wurde untersucht, wie sich Sauerstoff- und Natriumvakanzen auf (i) die ferroelektrische Domänenbildung in tensil und (ii) lokale Hysteresen in kompressiv verspannten Filmen auswirken. Es wird gezeigt, dass die Dichte von Natrium- und Sauerstoffvakanzen kritisch von dem Sauerstoffhintergrunddruck während des Wachstums und dem Na/Nb-Verhältnis des verwendeten Targets abhängt. Eine signifikante Verringerung dieser Vakanzdichte konnte sowohl durch Anheben des Sauerstoff-Hintergrunddruckes von 0,05 auf 2 mbar, als auch durch die Verwendung eines Targets mit einem Na/Nb-Verhältnis von 1,17 erreicht werden. In nahezu stöchiometrischen, tensil verspannten Filmen wurden keine ausgedehnten Defekte beobachtet. Im Gegensatz dazu sind säulenartige Defekte in kompressiv verspannten Filmen präsent, die unter ansonsten identischen Wachstums-Bedingungen abgeschieden wurden. Es wurde ermittelt, dass dieser Defekt-typ in der Lage ist, kompressive Verspannung in den Filmen abzubauen. In tensil verspannten Filmen konnten gut geordnete laterale ferroelektrische a1/a2 Domänen nur beobachtet werden, wenn die Filme nahezu stöchiometrisch waren. Die Art der Domänenkonfiguration in Filmen unter reduzierter tensiler Verspannung (a1c/a2c) weicht deutlich von üblicherweise beobachteten a1/c/a2/c Domänen ab. Gut ausgeprägte lokale ferroelektrische Hysteresen konnten in nahezu stöchiometrischen Filmen unter geringer kompressiver Verspannung nachgewiesen werden. Damit wurde bestätigt, dass bei Raumtemperatur durch Gitterverspannung eine stabile ferroelektrische Phase in NaNbO3 erzeugt werden kann, welches im relaxierten Zustand antiferroelektrisch ist. Im Fall von KxNa1-xNbO3 lag das Hauptaugenmerk auf der Untersuchung des Zusammenhanges zwischen dem K/Na-Verhältnis und Gitterverspannungen auf der einen und den lokalen piezoelektrischen Koeffizienten auf der anderen Seite. Dabei wurde 2D-Wachstum von voll kompressiv verspannten Filmen gegenüber nahezu stöchiometrischer Film-Abscheidung priorisiert. Die Dicke, bis zu der glatte KxNa1-xNbO3-Schichten abgeschieden werden konnten war deutlich geringer als im Fall von ähnlich verspannten NaNbO3 Filmen. Als alternativer Ansatz wurde die Abscheidung von Übergittern mit alternierenden Schichten unter kompressiver und tensiler Verspannung auf DyScO3 Substraten verfolgt. Auf diese Weise war es möglich sowohl 2D-Wachstum als auch voll kompressiv verspannte Systeme für signifikant dickere Schicht-Stapel im Vergleich zu Einzelschichten zu erreichen. Theoretische Vorhersagen lassen auf exzellente ferro/piezoelektrische Eigenschaften von Übergittern aus zwei ferroelektrischen Materialien schließen. In dieser Arbeit wird gezeigt, dass 2D-gewachsene und voll kompressiv verspannte NaNbO3/K0.5Na0.5NbO3-Übergitter auf DyScO3 Substraten viel versprechende lokale piezoelektrische Eigenschaften haben