368 research outputs found
Abraham Lincoln letter to Godfrey Weitzel
No full textDated April 6, 1865, this is a letter from President Abraham Lincoln to Major General Weitzel in Richmond, Virginia. This letter was written to Weitzel three days after he successfully gained control of Richmond, the Confederacy's capital. Here Lincoln acknowledges that some men who served on the Virginia legislature would like to reside in Richmond in support of the rebellion, and he gives his permission as long as they do not become hostile
The effect of Q on performance: Evidence from US M&A deals
No full textThis thesis investigates the influence of firm valuation, measured by Tobin's Q, on U.S. M&A performance. Contrary to traditional Q-theory, our findings reveal that high-Q acquirers consistently underperform in both short-term market reactions and long-term operating profitability. This could suggests high valuations may be linked to managerial overconfidence and capital misallocation, leading to value-destroying acquisitions.
Furthermore, mergers involving jointly high-Q firms or those within the same industry did not consistently yield superior outcomes. Notably, Q-value mismatches in same-industry mergers negatively impacted long-term performance. This thesis also find that large deal values in high-Q to low-Q transactions did not signal successful capital reallocation and were associated with poorer long-term results.
These findings underscore that managerial discipline and effective post-merger integration are crucial for M&A success rather than only firm valuation or industry overlap. This thesis cautions against uncritically interpreting high valuations or large deal sizes. Future research should explore nuanced measures and qualitative factors impacting M&A outcomes
Time-Performance Design and Study of Ultra-Wideband Amplifiers for SiPM
No full textThe recent advances in SiPM technology and the high demanding performance required by the current applications, especially in the field of time-of-flight estimation, call for a new approach in the design of the front-end amplifier to preserve the correct timing of the signals. Currently, SiPM manufacturers are offering devices with dedicated pins for fast-time outputs and recommending front-end amplifiers based on commercial devices for microwave and radio-frequency. We present in this paper our experience in designing customized wide-band amplifier front-ends for SiPM signals in high-resolution timing applications. The design consists of two stages, the first based on a low noise device (typically a JFET/MOSFET, but we have tried heterojunction transistors as well) to achieve the minimum noise figure and the second based on a MMIC used as a gain stage to boost the signal and maximize the power transfer to the output. The design procedure relies on a combination of the traditional approach of circuit simulation integrated with techniques involving the use of S-parameters, typical of RF applications. Two versions of the amplifier have been laid out and assembled and are currently under test. We present the preliminary characterization results, which demonstrates the effectiveness of the proposed design approach
(IPO. Studien B zur Verkehrswissen-(R)M.27Munchen, IFO-Institut fur Wirtschaftsforschungen e.v.s 1933. 85 295 pPost- und Fernmeldp'gebuhren in ausgewahlten Wirtschaftsbereichen. /Von/ Q. Weitzel H. Arnold, R. Ratzenbergers r. hfl ft:. IRKv. Weitzel (G), Arnold (H) & Ratzenberger.ERRORMISSINGTITL
Validation of targeting the ventrointermediate thalamic nucleus using Q-ball calculation in deep brain stimulation for tremor
No full textObjective: Identification of the ventrointermediate thalamic nucleus (Vim) in modern 3T high-field MRI for image-based targeting in deep brain stimulation (DBS) is still challenging. To evaluate the usefulness and reliability of analyzing the connectivity with the cerebellum using Q-ball-calculation we performed a retrospective analysis.
Method: 5 patients who underwent bilateral implantation of electrodes in the Vim for treatment of Essential Tremor between 2011 and 2012 received additional preoperative Q-ball imaging. Targeting was performed according to atlas coordinates and standard MRI. Additionally we performed a retrospective identification of the Vim by analyzing the connectivity of the thalamus with the dentate nucleus. The exact position of the active stimulation contact in the postoperative CT was correlated with the Vim as it was identified by Q-ball calculation.
Results: Localization of the Vim by analysis of the connectivity between thalamus and cerebellum was successful in all 5 patients on both sides. The average position of the active contacts was 14.6 mm (SD 1.24) lateral, 5.37 mm (SD 0.094 posterior and 2.21 mm (SD 0.69) cranial of MC. The cranial portion of the dentato-rubro-thalamic tract was localized an average of 3.38 mm (SD 1.57) lateral and 1.5 mm (SD 1.22) posterior of the active contact.
Conclusions: Connectivity analysis by Q-ball calculation provided direct visualization of the Vim in all cases. Our preliminary results suggest, that the target determined by connectivity analysis is valid and could possibly be used in addition to or even instead of atlas based targeting. Larger prospective calculations are needed to determine the robustness of this method in providing refined information useful for neurosurgical treatment of tremor
Precision Meson Spectroscopy: Diffractive Production at COMPASS and Development of a GEM-based TPC for PANDA
No full textMeson spectroscopy is a unique way to access Quantum Chromo Dynamics (QCD) and learn about its properties. Due to the non-Abelian structure, QCD predicts new states of matter with gluonic degrees of freedom. In particular q ¯ qg hybrids, which can have spin-exotic quantum numbers forbidden for conventional q ¯ q mesons, are expected to exist. Such states were searched for in the past, mostly in the light-quark sector. However, the experimental situation is still ambiguous and needs to be clarified. Further insights will certainly also come from the heavy-quark spectroscopy. Several new charmonium-like resonances were for example discovered during the last years, which have to be studied in more detail by future experiments to reveal their nature. Diffractive dissociation reactions at COMPASS provide clean access to meson resonances with masses below 2.5 GeV/c2. During a pilot run in 2004 using pion beams on lead targets, a competitive number of −−+ final state events were recorded within a few days of data taking. A full partial wave analysis (PWA) of these data has been performed for this dissertation, concentrating on the kinematic domain of large momentum transfer (t0 2 [0.1, 1.0] GeV2/c2). While well-known mesons are resolved with high quality, also a strong signal consistent with the much disputed hybrid candidate 1(1600) is observed in the spin-exotic JPC = 1−+ partial wave. A Breit-Wigner parameterization yields a mass and width of 1.660+0.010 −0.074 and 0.269+0.063 −0.085 GeV/c2, respectively. In addition, a first PWA of events with small momentum transfer (t0 2 10−3, 10−2 GeV2/c2) has been carried out, yielding several high-mass radial-excitation states. In the future, the PANDA experiment at the FAIR facility will perform highprecision spectroscopy in the charm-sector employing ¯ pp annihilations. Due to its excellent tracking capabilities for charged particles, a time projection chamber (TPC) has been proposed for the central tracker of PANDA. A continuous operation without ion gate is foreseen, which constitutes a novel development in high-rate particle physics experiments. Gas Electron Multiplier (GEM) foils offer an intrinsic ion back-flow suppression combined with high gains, and will therefore be used for gas amplification. A small-size GEM-TPC test chamber has been constructed during this thesis and commissioned using both X-rays and muons from cosmic-ray air-showers. From the latter data, a spatial resolution down to 140 μm has been achieved. The detector has been operated stably for many months with Ar/CO2 (70/30) and at typical gas amplification factors of (5-10)·10
Theory and Evidence on Mergers and Acquisitions by Small and Medium Enterprises
No full textThe theory of mergers and acquisitions (M&As) has been developed almost exclusively from the study of large deals by large firms. In this paper we argue that the behaviour and success of M&As by small and medium sized enterprises (SMEs) may be significantly different. Accordingly, we revisit established M&A theories, and develop a theoretical framework, and several testable hypotheses, regarding the distinctive features of SME M&As. Our empirical results support our expectations and show that, compared to large firms, acquiring SMEs: rely more intensively on external growth via M&As; are more likely to be withdrawn, suggesting that SMEs are more flexible, and more able to avoid deals that turn sour; and, finally, SME M&As are more likely to be financed with equity rather than debt, indicating that the influential financial pecking order theory is of less relevance to SMEs.mergers, acquisitions, small and medium sized enterprises
Investigation of the structure correlated ion transport through ultra thin polymer films by BIIT and ToF-SIMS
No full textGegenstand dieser Arbeit sind die Untersuchungen von sehr dünnen deponierten Polymerfilmen im Bereich von 4 nm bis etwa 400 nm und deren Einfluss auf den Ionentransport bei der Variation der Dicke des Polymerfilms, beim Wechsel des Materials der verwendeten Rückseitenelektrode und der Art des Emitterions. Explizit stehen das thermoplastische, oberfächenkonforme, semikristalline Polymer Polyparaxylol (PPX) und die Polymerelektrolyt-membranen (PAH/PSS)n bestehend aus Schichten von Poly(allylaminhydrochlorid) und Poly(styrol-4-natriumsulfonat) im Fokus der Arbeit. Die verwendeten Messtechniken beinhalten den in der AG Weitzel entwickelten Bombardement induzierten Ionentransport (BIIT) zum Beschuss der deponierten Polymerfilme mit einem homogenen niederenergetischen Alkaliionenstrahl. Anschließend erfolgt die Vermessung der bombardierten Proben mittels Flugzeit-Sekundärionen-Massenspektrometrie (ToF-SIMS) zur Ermittlung der räumlichen Konzentrationsverteilung. Über die BIIT-Technik lassen sich Strom-Zeit- und Strom-Spannungs-Kurven aufnehmen durch welche Rückschlüsse auf die strukturelle Beschaffenheit des Polymers gezogen werden können. Aus den Strom-Zeit-Kurven können die Zeitkonstanten τ und die eingetragenen Ladungsmengen Q in Abhängigkeit von der strukturellen Beschaffenheit des Polymers und durch die Verwendung unterschiedlicher metallischer Substrate ermittelt werden. Insbesondere kann in dieser Arbeit erstmalig der Unterschied von Proben mit durchgehenden Korngrenzen, den NIPs (engl. non-intermittent pathways), und Proben ohne NIPs in Form von linearen und quadratischen Strom-Spannungs-Kurven dargestellt und über ToF-SIMS Tiefenprofilierung visualisiert werden. Aus den Strom-Spannungs-Kurven werden die Diffusionskonstanten und die Aktivierungsenergie aus temperaturabhängigen Messungen in Bezug auf das verwendete Alkaliion und das verwendete Substrat ermittelt. Ex-situ erfolgt eine Tiefenprofilierung der durch BIIT bestrahlten Proben. Durch die geringe Dicke der Polymerfilme kann erstmalig die Ausbildung einer Alkaliion beinhaltenden Interphase, analog zur SEI (engl. solid electrolyte interphase), als Resultat der Neutralisation der Alkaliionen an der Rückseitenelektrode via ToF-SIMS betrachtet werden. Daneben werden in dieser Arbeit die Einflüsse auf die Strom-Spannungs-Kurven durch den Wechsel des Substratmaterials und den Wechsel des Emitterions hinsichtlich der elektrochemischen Beschreibung des BIIT Experiments und gemäß ihrer unterschiedlichen Diffusionskonstanten diskutiert. Durch die Kopplung von BIIT und anschließender ToF-SIMS Tiefenprofilierung können gezielt die Mischbarkeiten bzw. Unmischbarkeiten von Metall-Metallsystemen untersucht werden. Für die (PAH/PSS)n-Schichten werden in dieser Arbeit dickenabhängige und temperaturabhängige Leitfähigkeitsstudien mittels BIIT aufgezeigt und in Hinblick auf die Präparationsmethode diskutiert.The central aspect of this thesis is the investigation of ultra-thin deposited polymer films in the range between 4 nm to 400 nm and its influence on the ion transport by varying the thickness of the polymer film, the material of the backside electrode and the species of the emitted ions. Explicitly, the thermoplastic, surface conform and semi crystalline polymer poly-para-xylylene (PPX) and the polyelectrolyte multilayer (PAH/PSS)n consisting of layers of poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) are investigated extensively. The measurement techniques applied in this work are on the one hand the bombardment induced ion transport (BIIT) which has been established in the working group of Prof. Dr. Weitzel and results in a homogeneous, low-energetic alkaline ion beam hitting the polymer surface. On the other hand, ex-situ measurements of the bombarded polymer samples are performed via time-of-flight secondary ion mass spectrometry (ToF-SIMS) in order to obtain space-dependent concentration profiles. BIIT technique enables the generation of current-time- and current-voltage-curves structural characteristics of the samples can be derived from. Time constants τ and the amount of inserted charge Q into the PPX-Films can be obtained from current-time-curves as a function of the PPX structure and of the underlying metallic substrate. In this work the differences of samples with non-intermittent pathways (NIPs) and samples with no NIPs can be distinguished by different behavior of the current-voltage-curves and are visualized by ToF-SIMS depth profiling. A linear current-voltage-characteristic is obtained if NIPs are dominating the sample. If the bulk material of the polymer is dominating, a quadratic current-voltage curve can be fitted. Furthermore the diffusion constant and the activation energy of temperature dependent measurements can be derived from the current-voltage-characteristics as a function of the used alkaline ion and the used substrate. Ex-situ depth profiling with ToF-SIMS on BIIT long-time bombarded samples allows to get insight in the concentration distribution within the samples. Due to the low extend of the polymer layers the formation of an alkali ion interphase, analogous to the solid electrolyte interphase (SEI) in batteries, can be observed via ToF-SIMS depth profiling for the first time. The interphase is formed between the polymer film and the metal substrate as a consequence of the alkaline ion neutralization at the backside electrode. Further investigations consider the behavior of current-voltage-curves as a function of the underlying substrate material and the type of emitted ion in comparison to the electrochemical description of BIIT experiment and the different diffusion coefficients. The interconnection of BIIT and ToF-SIMS measurements allows to obtain information about miscibility and immiscibility of metal-metal-systems. For (PAH/PSS)n systems thickness- and temperature-dependent conductivity studies are performed by BIIT and discussed as a function of their preparation method
Targeting the thalamic ventrointermediate nucleus for neurosurgical treatment of tremor using Q-ball calculation
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