Generation of unipolar half-cycle pulse via unusual reflection of a single-cycle pulse from an optically thin metallic or dielectric layer

We present a significantly different reflection process from an optically thin flat metallic or dielectric layer and propose a strikingly simple method to form approximately unipolar half-cycle optical pulses via reflection of a single-cycle optical pulse. Unipolar pulses in reflection arise due to specifics of effectively one-dimensional pulse propagation. Namely, we show that in considered system the field emitted by a flat medium layer is proportional to the velocity of oscillating medium charges instead of their acceleration as it is usually the case. When the single-cycle pulse interacts with linear optical medium, the oscillation velocity of medium charges can be then forced to keep constant sign throughout the pulse duration. Our results essentially differ from the direct mirror reflection and suggest a possibility of unusual transformations of the few-cycle light pulses in linear optical systems

Passive and hybrid mode locking in multi-section terahertz quantum cascade lasers

It is believed that passive mode locking is virtually impossible in quantum cascade lasers (QCLs) because of too fast carrier relaxation time. Here, we revisit this possibility and theoretically show that stable mode locking and pulse durations in the few cycle regime at terahertz (THz) frequencies are possible in suitably engineered bound-to-continuum QCLs. We achieve this by utilizing a multi-section cavity geometry with alternating gain and absorber sections. The critical ingredients are the very strong coupling of the absorber to both field and environment as well as a fast absorber carrier recovery dynamics. Under these conditions, even if the gain relaxation time is several times faster than the cavity round trip time, generation of few-cycle pulses is feasible. We investigate three different approaches for ultrashort pulse generation via THz quantum cascade lasers, namely passive, hybrid and colliding pulse mode locking

Mit Bio blüht die Vielfalt – wildtierfreundlicher Biolandbau

Die geplanten Projektaktivitäten in den Modulen 1 bis 3 konnten 2007 gestartet werden: In Teilprojekten 1 und 2 des Moduls 1 „Forschung“ wurden Grundlagen und Methoden erarbeitet: Einerseits wurden die statistischen Kennzahlen zum ökologischen Ausgleich auf Biobetrieben und ÖLN-Betrieben dargestellt und eine vergleichende Analyse auf drei Ebenen (Zonen, Kanton,Bezirk) vorgenommen. Es wurde festgestellt, dass auf Biobetrieben deutlich mehr Ökoausgleichsmassnahmen umgesetzt werden sowie die Zone (Berg-/Talgebiet) und die Region die Akzeptanz für einzelne Massnahmen wesentlich beeinflusst. Andererseits wurden gesamtbetriebliche Beurteilungssysteme (Naturpunktesystem; Naturbilanz Berggebiet)entwickelt. Das in Zusammenarbeit mit der Vogelwarte Sempach entwickelte Punktesystem beurteilt die ökologische Qualität von Landwirtschaftsbetrieben und beschränkt sich auf die Beurteilung von Zuständen und Massnahmen in Nutzflächen und naturnahen Flächen. Zurzeit wird diese favorisierte Methode noch evaluiert und später auf Betrieben getestet. In einem weiteren Teilprojekt (Modellbetriebe Schmetterlinge) wurden wesentliche Grundlagen und Massnahmen zur Förderung von Tagfaltern erarbeitet. Auf zwei Biogrünland-Betrieben im Jura nahe Saignelégier wurde im Sommer 2007 die Tagfalterfauna erfasst und anschliessend betriebsbezogene Massnahmen zum Schutz und Erhalt der Schmetterlinge abgeleitet und mit den Landwirten diskutiert. Der Ansatz wurde sehr gut von den Landwirten aufgenommen und erwies sich auf Grünlandbetrieben als sehr geeignet. Mit insgesamt 33 Arten auf den beiden Betrieben wurde eine relativ hohe Artenzahl an Schmetterlingen festgestellt, darunter vier Arten der Roten Liste. Insgesamt wurden 19 verschiedene Massnahmen im Bereich Wald und Waldrand,Hecken, Grünland entwickelt und vorgeschlagen. Im Modul 2 „Beratung“ wurden in drei weiteren Regionen Modellbetriebe zur Umsetzung wildtierfreundlicher Bewirtschaftung bearbeitet. Sie wurden gesamtbetrieblich beraten: Auf der Basis einer Ist-Analyse wurden mit den Landwirten mögliche Massnahmen diskutiert und festgelegt. Zur Auswahl und Feinsteuerung der Massnahmen wurden Ziel- und Leitarten eingesetzt. In der Region Entlebuch waren es fünf und in der Region Münsingen zwei Betriebe. Im Unterengadin wurden auf vier Betrieben zusätzlich zur gesamtbetrieblichen Beratung drei betriebswirtschaftliche Szenarien (Extensiv - Optimiert – Intensiv) kalkuliert und den Landwirten für die Entscheidungsfindung zur Verfügung gestellt. Die Untersuchung hat gezeigt, dass auf den vier untersuchten Betrieben eine Verbesserung der Ökologie unter Berücksichtigung gesamtbetrieblicher Aspekte möglich war. In vielen Fällen konnten durch ökologische Aufwertungen betriebswirtschaftliche Vorteile erzielt werden (geringerer Arbeitsaufwand, höhere Direktzahlungen verbunden mit geringerem Verkaufserlös). Im Modul 3 „Öffentlichkeitsarbeit“ war in der ersten Phase das Ziel, ein Basissortiment an Informationen für die am Projekt beteiligten Landwirte und die Beratung bereitzustellen. Dazu gehörten die allgemeine Vorstellung des Projektes, die Gestaltung des Logos, die Erstellung des Flyers und die Informationen im Internet. Speziell für die am Projekt beteiligten Landwirte und die Beratung wurden ein Infoblatt mit den Besonderheiten des Projektes sowie ein Infoordner mit Broschüren zu Einzelthemen zusammengestellt. Drei Feldrandtafeln zum Thema Artenvielfalt im Tal- und Berggebiet und Säume wurden erstellt. Sie dienen den Landwirten auf ihren Betrieben zur Information von Laien. Für den Tag der Offenen Tür am FiBL wurde ein Infostand konzipiert,der interessierte Laien angesprochen hatte

Functional Dissection of the Proton Pumping Modules of Mitochondrial Complex I

A catalytically active subcomplex of respiratory chain complex I lacks 14 of its 42 subunits yet retains half of its proton-pumping capacity, indicating that its membrane arm has two pump modules

Zettawatt-Exawatt Lasers and Their Applications in Ultrastrong-Field Physics: High Energy Front

Since its birth, the laser has been extraordinarily effective in the study and applications of laser-matter interaction at the atomic and molecular level and in the nonlinear optics of the bound electron. In its early life, the laser was associated with the physics of electron volts and of the chemical bond. Over the past fifteen years, however, we have seen a surge in our ability to produce high intensities, five to six orders of magnitude higher than was possible before. At these intensities, particles, electrons and protons, acquire kinetic energy in the mega-electron-volt range through interaction with intense laser fields. This opens a new age for the laser, the age of nonlinear relativistic optics coupling even with nuclear physics. We suggest a path to reach an extremely high-intensity level $10^{26-28}$W/cm$^2$ in the coming decade, much beyond the current and near future intensity regime $10^{23}$W/cm$^2$, taking advantage of the megajoule laser facilities. Such a laser at extreme high intensity could accelerate particles to frontiers of high energy, tera-electron-volt and peta-electron-volt, and would become a tool of fundamental physics encompassing particle physics, gravitational physics, nonlinear field theory, ultrahigh-pressure physics, astrophysics, and cosmology. We focus our attention on high-energy applications in particular and the possibility of merged reinforcement of high-energy physics and ultraintense laser.Comment: 25 pages. 1 figur

Gastric adenocarcinoma in a patient re-infected with H. pylori after regression of MALT lymphoma with successful anti-H. pylori therapy and gastric resection: a case report

BACKGROUND: Helicobacter pylori (H. pylori) has been etiologically linked with primary gastric lymphoma (PGL) and gastric carcinoma (GC). There are a few reports of occurrence of both diseases in the same patient with H. pylori infection. CASE PRESENTATION: We report a patient with PGL in whom the tumor regressed after surgical resection combined with eradication of H. pylori infection. However, he developed GC on follow up; this was temporally associated with recrudescence / re-infection of H. pylori. This is perhaps first report of such occurrence. CONCLUSIONS: Possible cause and effect relationship between H. pylori infection and both PGL and GC is discussed. This case also documents a unique problem in management of PGL in tropical countries where re-infection with H. pylori is supposed to be high

Electrospray deposition in vacuum as method to create functionally active protein immobilization on polymeric substrates

We demonstrate in this work the deposition of a large biological molecule (fibronectin) on polymeric substrates in a high vacuum environment using an electrospray deposition system. Fibronectin was deposited and its distribution and structure investigated and retention of function (ability to promote cell adhesion) on return to liquid environment is shown. AFM was used to monitor changes in the morphology of the surface before and after fibronectin deposition, whilst the biological activity of the deposited protein is assessed through a quantitative analysis of the biomolecular adhesion and migration of fibroblast cells to the modified surfaces. For the first time we have demonstrated that using high vacuum electrospray deposition it is possible to deposit large protein molecules on polymeric surfaces whilst maintaining the protein activity. The deposition of biological molecules such as proteins with the retention of their activity onto clean well-controlled surfaces under vacuum condition, offers the possibility for future studies utilizing high resolution vacuum based techniques at the atomic and molecular scale providing a greater understanding of protein–surface interface behaviour of relevance to a wide range of applications such as in sensors, diagnostics and tissue engineering

Sphingosine 1-phosphate modulates antigen capture by murine langerhans cells via the S1P2 receptor subtype

Dendritic cells (DCs) play a pivotal role in the development of cutaneous contact hypersensitivity (CHS) and atopic dermatitis as they capture and process antigen and present it to T lymphocytes in the lymphoid organs. Recently, it has been indicated that a topical application of the sphingolipid sphingosine 1-phosphate (S1P) prevents the inflammatory response in CHS, but the molecular mechanism is not fully elucidated. Here we indicate that treatment of mice with S1P is connected with an impaired antigen uptake by Langerhans cells (LCs), the initial step of CHS. Most of the known actions of S1P are mediated by a family of five specific G protein-coupled receptors. Our results indicate that S1P inhibits macropinocytosis of the murine LC line XS52 via S1P2 receptor stimulation followed by a reduced phosphatidylinositol 3-kinase (PI3K) activity. As down-regulation of S1P2 not only diminished S1P-mediated action but also enhanced the basal activity of LCs on antigen capture, an autocrine action of S1P has been assumed. Actually, S1P is continuously produced by LCs and secreted via the ATP binding cassette transporter ABCC1 to the extracellular environment. Consequently, inhibition of ABCC1, which decreased extracellular S1P levels, markedly increased the antigen uptake by LCs. Moreover, stimulation of sphingosine kinase activity, the crucial enzyme for S1P formation, is connected not only with enhanced S1P levels but also with diminished antigen capture. These results indicate that S1P is essential in LC homeostasis and influences skin immunity. This is of importance as previous reports suggested an alteration of S1P levels in atopic skin lesions

Isoforms of U1-70k control subunit dynamics in the human spliceosomal U1 snRNP

Most human protein-encoding genes contain multiple exons that are spliced together, frequently in alternative arrangements, by the spliceosome. It is established that U1 snRNP is an essential component of the spliceosome, in human consisting of RNA and ten proteins, several of which are post- translationally modified and exist as multiple isoforms. Unresolved and challenging to investigate are the effects of these post translational modifications on the dynamics, interactions and stability of the particle. Using mass spectrometry we investigate the composition and dynamics of the native human U1 snRNP and compare native and recombinant complexes to isolate the effects of various subunits and isoforms on the overall stability. Our data reveal differential incorporation of four protein isoforms and dynamic interactions of subunits U1-A, U1-C and Sm-B/B’. Results also show that unstructured post- ranslationally modified C-terminal tails are responsible for the dynamics of Sm-B/B’ and U1-C and that their interactions with the Sm core are controlled by binding to different U1-70k isoforms and their phosphorylation status in vivo. These results therefore provide the important functional link between proteomics and structure as well as insight into the dynamic quaternary structure of the native U1 snRNP important for its function.This work was funded by: BBSRC (OVM), BBSRC and EPSRC (HH and NM), EU Prospects (HH), European Science Foundation (NM), the Royal Society (CVR), and fellowship from JSPS and HFSP (YM and DAPK respectively)