Publications by authors named "Ramm D"

We present an investigation of the ultrafast dynamics of the polycyclic aromatic hydrocarbon fluorene initiated by an intense femtosecond near-infrared laser pulse (810 nm) and probed by a weak visible pulse (405 nm). Using a multichannel detection scheme (mass spectra, electron and ion velocity-map imaging), we provide a full disentanglement of the complex dynamics of the vibronically excited parent molecule, its excited ionic states, and fragments. We observed various channels resulting from the strong-field ionization regime.

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Dynamics of optically excited plasmonic nanoparticles are presently understood as a series of scattering events involving the initiation of nanoparticle breathing oscillations. According to established models, these are caused by statistical heat transfer from thermalized electrons to the lattice. An additional contribution by hot-electron pressure accounts for phase mismatches between theory and experimental observations.

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Inner-shell photoelectron spectroscopy provides an element-specific probe of molecular structure, as core-electron binding energies are sensitive to the chemical environment. Short-wavelength femtosecond light sources, such as Free-Electron Lasers (FELs), even enable time-resolved site-specific investigations of molecular photochemistry. Here, we study the ultraviolet photodissociation of the prototypical chiral molecule 1-iodo-2-methylbutane, probed by extreme-ultraviolet (XUV) pulses from the Free-electron LASer in Hamburg (FLASH) through the ultrafast evolution of the iodine 4d binding energy.

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Background: Stereotactic radiosurgery (SRS) is the preferred treatment for vestibular schwannoma (VS) in patients with preserved hearing and tumour diameter < 3 cm. Emerging evidence suggests restricting cochlear dose could preserve hearing. This retrospective replanning study aims to compare dynamic conformal arc therapy (DCAT), intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans for superiority of cochlear dose sparing without compromising tumour coverage.

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We investigated the dissociation of dications and trications of three polycyclic aromatic hydrocarbons (PAHs), fluorene, phenanthrene, and pyrene. PAHs are a family of molecules ubiquitous in space and involved in much of the chemistry of the interstellar medium. In our experiments, ions are formed by interaction with 30.

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Polycyclic aromatic hydrocarbons (PAHs) play an important role in interstellar chemistry and are subject to high energy photons that can induce excitation, ionization, and fragmentation. Previous studies have demonstrated electronic relaxation of parent PAH monocations over 10-100 femtoseconds as a result of beyond-Born-Oppenheimer coupling between the electronic and nuclear dynamics. Here, we investigate three PAH molecules: fluorene, phenanthrene, and pyrene, using ultrafast XUV and IR laser pulses.

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The non-monochromatic beamline BL1 at the FLASH free-electron laser facility at DESY was upgraded with new transport and focusing optics, and a new permanent end-station, CAMP, was installed. This multi-purpose instrument is optimized for electron- and ion-spectroscopy, imaging and pump-probe experiments at free-electron lasers. It can be equipped with various electron- and ion-spectrometers, along with large-area single-photon-counting pnCCD X-ray detectors, thus enabling a wide range of experiments from atomic, molecular, and cluster physics to material and energy science, chemistry and biology.

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Extreme ultraviolet (XUV) and X-ray free-electron lasers enable new scientific opportunities. Their ultra-intense coherent femtosecond pulses give unprecedented access to the structure of undepositable nanoscale objects and to transient states of highly excited matter. In order to probe the ultrafast complex light-induced dynamics on the relevant time scales, the multi-purpose end-station CAMP at the free-electron laser FLASH has been complemented by the novel multilayer-mirror-based split-and-delay unit DESC (DElay Stage for CAMP) for time-resolved experiments.

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New clinical radiotherapy dosimetry systems need comprehensive demonstration of measurement quality. Practicality and reliability are other important aspects for clinical dosimeters. In this work the performance of an optical CT scanner for true 3D dosimetry is assessed using a radiochromic gel dosimeter.

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Three dimensional dosimetry by optical CT readout of radiosensitive gels or solids has previously been indicated as a solution for measurement of radiotherapy 3D dose distributions. The clinical uptake of these dosimetry methods has been limited, partly due to impracticalities of the optical readout such as the expertise and labour required for refractive index fluid matching. In this work a fast laser beam optical CT scanner is described, featuring fluid-less and dual wavelength operation.

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The German federal law of equal treatment of disabled persons (Behindertengleichstellungsgesetz des Bundes, BGG) came into effect in 2002. An evaluation of this law was required by the national plan of action for the implementation of the United Nations Convention on the Rights of Persons with Disabilities (CRPD). Project evaluation objectives were to estimate whether the needs of disabled persons were being met and whether the instruments proved to be adequate for fulfilling the aims of the law.

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Background: The benefits of peer teaching and assessment are well documented within nurse education literature. However, research to date has predominantly focused on the advantages and disadvantages for the inexperienced learner, with a dearth of knowledge relating to the perceptions of senior nursing students involved in teaching their peers.

Aim: This study sought to investigate the student experience of taking part in a peer teaching and assessment initiative to include the perceptions of both first year nursing students and second/third year participants.

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Optical CT scanners for a 3D readout of externally irradiated radiosensitive hydrogels currently require the use of a refractive index (RI) matching liquid bath to obtain suitable optical ray paths through the gel sample to the detector. The requirement for a RI matching liquid bath has been negated by the design of a plastic cylindrical gel container that provides parallel beam geometry through the gel sample for the majority of the projection. The design method can be used for various hydrogels.

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Unlabelled: The article is based on the results of the project “Company integration management in small and medium-sized companies. Legal requirements and prerequisites for a successful implementation” (01 January 2009-31 August 2010).

Background: Since 2004 all employers have been legally bound to offer company integration management (BEM, Betriebliches Eingliederungsmanagement) for all employees who have been incapacitated for work for more than 6 weeks within a year (Section 84 SGB IX, Book 9 of the German Social Code).

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Aim: This paper is a report of a study exploring the lived experiences and emotional responses of female patients learning to perform clean intermittent self-catheterisation (CISC).

Background: There is general consensus that CISC should be considered in preference to in-dwelling catheterisation wherever feasible. Published literature has tended to focus on quality of life issues and technical and physical aspects.

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Over the last few years in vitro cell systems have been established for toxicological investigations. These systems permit the evaluation of effects on the basis of cultured cells in order to replace animal studies. Not only qualitative assessment of cytotoxic effects, but also efforts to quantify these intracellular changes have become more and more important to objectify the results which have been obtained.

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Schreiber and Neubauer (Photosynthesis Research 25: 279-293, 1990) have proposed a model which explains energy quenching by enhanced triplet formation as caused by charge recombination due to pH-dependent donor-side limitation. Quenching under these conditions is assumed to result from two mechanisms. Firstly, there is the withdrawal of excited states by charge recombination and formation of triplet states.

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The effects of alcohol on performance were investigated in 10 ovulating young women. Placebo drink and three doses of alcohol were administered in a random order both during follicular and luteal phases of the menstrual cycle. The women had significantly slower verbal information processing rate and poorer visual detection performance during the follicular than the luteal phase of the menstrual cycle.

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Age and low doses of alcohol had a synergistic deleterious effect on subjects' performance on a continuous tracking task.

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The effects of five major life events, and of three types of resources, on the physical and social-psychological adaptation of 375 participants in a longitudinal study were examined. As expected, medical events had the most impact on physical adaptation, but they had surprisingly little impact on social-psychological adaptation. Retirement had the most negative social-psychological effects, but had little effect on physical adaptation.

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Each geriatric patient has observable problems which can generate treatment goals implemented by a treatment plan. Extensive record keeping would be required to document this tripartite scheme. In practice, either problem-oriented or goal-oriented records are used.

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