Optisch detektierte Magnetresonanz an NV-Zentren in Diamant

Die rasante Entwicklung der Computerindustrie durch die stetige Verkleinerung der Transistoren führt immer schneller zum Erreichen der Grenze der Si-Technologie, ab der die Tunnelprozesse in den Transistoren ihre weitere Verkleinerung und Erhöhung ihrer Dichte in den Prozessoren nicht mehr zulassen. Die Zukunft der Computertechnologie liegt in der Verarbeitung der Quanteninformation. Für die Entwicklung von Quantencomputern ist die Detektion und gezielte Manipulation einzelner Spins in Festkörpern von größter Bedeutung. Die Standardmethoden der Spindetektion, wie ESR, erlauben jedoch nur die Detektion von Spinensembles. Die Idee, die das Auslesen von einzelnen Spins ermöglich sollte, besteht darin, die Manipulation getrennt von der Detektion auszuführen.rn Bei dem NV−-Zentrum handelt es sich um eine spezielle Gitterfehlstelle im Diamant, die sich als einen atomaren, optisch auslesbaren Magnetfeldsensor benutzen lässt. Durch die Messung seiner Fluoreszenz sollte es möglich sein die Manipulation anderer, optisch nicht detektierbaren, “Dunkelspins“ in unmittelbarer Nähe des NV-Zentrums mittels der Spin-Spin-Kopplung zu detektieren. Das vorgeschlagene Modell des Quantencomputers basiert auf dem in SWCNT eingeschlossenen N@C60.Die Peapods, wie die Einheiten aus den in Kohlenstoffnanoröhre gepackten Fullerenen mit eingefangenem Stickstoff genannt werden, sollen die Grundlage für die Recheneinheiten eines wahren skalierbaren Quantencomputers bilden. Die in ihnen mit dem Stickstoff-Elektronenspin durchgeführten Rechnungen sollen mit den oberflächennahen NV-Zentren (von Diamantplatten), über denen sie positioniert sein sollen, optisch ausgelesen werden.rnrnDie vorliegende Arbeit hatte das primäre Ziel, die Kopplung der oberflächennahen NV-Einzelzentren an die optisch nicht detektierbaren Spins der Radikal-Moleküle auf der Diamantoberfläche mittels der ODMR-Kopplungsexperimente optisch zu detektieren und damit entscheidende Schritte auf dem Wege der Realisierung eines Quantenregisters zu tun.rn Es wurde ein sich im Entwicklungsstadium befindende ODMR-Setup wieder aufgebaut und seine bisherige Funktionsweise wurde an kommerziellen NV-Zentrum-reichen Nanodiamanten verifiziert. Im nächsten Schritt wurde die Effektivität und Weise der Messung an die Detektion und Manipulation der oberflächennah (< 7 nm Tiefe) implantieren NV-Einzelzenten in Diamantplatten angepasst.Ein sehr großer Teil der Arbeit, der hier nur bedingt beschrieben werden kann, bestand aus derrnAnpassung der existierenden Steuersoftware an die Problematik der praktischen Messung. Anschließend wurde die korrekte Funktion aller implementierten Pulssequenzen und anderer Software-Verbesserungen durch die Messung an oberflächennah implantierten NV-Einzelzentren verifiziert. Auch wurde der Messplatz um die zur Messung der Doppelresonanz notwendigen Komponenten wie einen steuerbaren Elektromagneten und RF-Signalquelle erweitert. Unter der Berücksichtigung der thermischen Stabilität von N@C60 wurde für zukünftige Experimente auch ein optischer Kryostat geplant, gebaut, in das Setup integriert und charakterisiert.rn Die Spin-Spin-Kopplungsexperimente wurden mit dem sauerstoffstabilen Galvinoxyl-Radikalals einem Modell-System für Kopplung durchgeführt. Dabei wurde über die Kopplung mit einem NVZentrum das RF-Spektrum des gekoppelten Radikal-Spins beobachtet. Auch konnte von dem gekoppelten Spin eine Rabi-Nutation aufgenommen werden.rn Es wurden auch weitere Aspekte der Peapod Messung und Oberflächenimplantation betrachtet.Es wurde untersucht, ob sich die NV-Detektion durch die SWCNTs, Peapods oder Fullerene stören lässt. Es zeigte sich, dass die Komponenten des geplanten Quantencomputers, bis auf die C60-Cluster, für eine ODMR-Messanordnung nicht detektierbar sind und die NV-Messung nicht stören werden. Es wurde auch betrachtet, welche Arten von kommerziellen Diamantplatten für die Oberflächenimplantation geeignet sind, für die Kopplungsmessungen geeignete Dichte der implantierten NV-Zentren abgeschätzt und eine Implantation mit abgeschätzter Dichte betrachtet.

Thermal model for optimization of vascular laser tissue soldering

Laser tissue soldering (LTS) is a promising technique for tissue fusion based on a heat-denaturation process of proteins. Thermal damage of the fused tissue during the laser procedure has always been an important and challenging problem. Particularly in LTS of arterial blood vessels strong heating of the endothelium should be avoided to minimize the risk of thrombosis. A precise knowledge of the temperature distribution within the vessel wall during laser irradiation is inevitable. The authors developed a finite element model (FEM) to simulate the temperature distribution within blood vessels during LTS. Temperature measurements were used to verify and calibrate the model. Different parameters such as laser power, solder absorption coefficient, thickness of the solder layer, cooling of the vessel and continuous vs. pulsed energy deposition were tested to elucidate their impact on the temperature distribution within the soldering joint in order to reduce the amount of further animal experiments. A pulsed irradiation with high laser power and high absorbing solder yields the best results.

Femtosecond Rotational Raman Coherence Spectroscopy of Cyclohexane in a Pulsed Supersonic Jet

We combine the technique of femtosecond degenerate four-wave mixing (fs-DFWM) with a high repetition-rate pulsed supersonic jet source to obtain the rotational coherence spectrum (RCS) of cold cyclohexane (C(6)H(12)) with high signal/noise ratio. In the jet expansion, the near-parallel flow pattern combined with rapid translational cooling effectively eliminate dephasing collisions, giving near-constant RCS signal intensities over time delays up to 5 ns. The vibrational cooling in the jet eliminates the thermally populated vibrations that complicate the RCS coherences of cyclohexane at room temperature [Bragger, G.; et al. J. Phys. Chem. A 2011, 115, 9567]. The rotational cooling reduces the high-J rotational-state population, yielding the most accurate ground-state rotational constant to date, B(0) = 4305.859(9) MHz. Based on this B(0), a reanalysis of previous room-temperature gas-cell RCS measurements of cydohexane gives improved vibration rotation interaction constants for the v(32), v(6), v(16), and v(24) vibrational states. Combining the experimental B(0)(C(6)H(12)) with CCSD(T) calculations yields a very accurate semiexperimental equilibrium structure of the chair isomer of cyclohexane

Does a pulsed mode offer advantages over a continuous wave mode for excisional biopsies performed using a carbon dioxide laser?

Animal studies of excisional biopsies have shown less thermal damage when a carbon dioxide (CO(2)) laser (10.6 μm) is used in a char-free (CF) mode than in a continuous-wave (CW) mode. The authors' aim was to evaluate and compare clinical and histopathologic findings of excisional biopsies performed with CW and CF CO(2) laser (10.6 μm) modes.

Use of the Agilent 2100 bioanalyzer for rapid and reproducible molecular typing of Streptococcus pneumoniae

Restriction fragment length polymorphism (RFLP) analysis is an economic and fast technique for molecular typing but has the drawback of difficulties in accurately sizing DNA fragments and comparing banding patterns on agarose gels. We aimed to improve RFLP for typing of the important human pathogen Streptococcus pneumoniae and to compare the results with the commonly used typing techniques of pulsed-field gel electrophoresis and multilocus sequence typing. We designed primers to amplify a noncoding region adjacent to the pneumolysin gene. The PCR product was digested separately with six restriction endonucleases, and the DNA fragments were analyzed using an Agilent 2100 bioanalyzer for accurate sizing. The combined RFLP results for all enzymes allowed us to assign each of the 47 clinical isolates of S. pneumoniae tested to one of 33 RFLP types. RFLP analyzed using the bioanalyzer allowed discrimination between strains similar to that obtained by the more commonly used techniques of pulsed-field gel electrophoresis, which discriminated between 34 types, and multilocus sequence typing, which discriminated between 35 types, but more quickly and with less expense. RFLP of a noncoding region using the Agilent 2100 bioanalyzer could be a useful addition to the molecular typing techniques in current use for S. pneumoniae, especially as a first screen of a local population.

Localized annealing of polysilicon microstructures by inductively heated ferromagnetic films

The monolithic integration of dissimilar microsystems is often limited by conflicts in thermal budget. One of the most prevalent examples is the fabrication of active micro-electromechanical systems (MEMS), as structural films utilized for surface micromachining such as polysilicon typically require processing at temperatures unsuitable for microelectronic circuitry. A localized annealing process could provide for the post-deposition heat treatment of integrated structures without compromising active devices. This dissertation presents a new microfabrication technology based on the inductive heating of ferromagnetic films patterned to define regions for heat treatment. Support is provided through theory, finite-element modeling, and experimentation, concluding with the demonstration of inductive annealing on polysilicon inertial sensing structures. Though still in its infancy, the results confirm the technology to be a viable option for integrated MEMS as well as any microsystem fabrication process requiring a thermal gradient.

Thermal release rate studies of nuclear reaction products from polycrystalline metal matrices

The thermal release rate of nuclear reaction products was investigated in offline annealing experiments. This work was motivated by the search for a high melting catcher material for recoiling products from heavy ion induced nuclear fusion reactions. Polycrystalline refractory metal foils of Ni, Y, Zr, Nb, Mo, Hf, W, and Re were investigated as catcher metals. Diffusion data for various tracer/host combinations were deduced from the measured release rates. This work focuses on the diffusion and the release rate of volatile p-elements from row 5 and 6 of the periodic table as lighter homologues of the superheavy elements with Z ≥ 113 to be studied in future experiments. A massive radiation damage enhancement of the diffusion velocity was observed. Diffusion trends have been established along the groups and rows of the periodic table based on the dependence of diffusion velocity on atomic sizes.

Pulsed versus continuous wave CO2 laser excisions of 100 oral fibrous hyperplasias: a randomized controlled clinical and histopathological study

BACKGROUND In experimental animal studies, pulsing the CO2 laser beam has been shown to reduce the thermal damage zone of excised oral mucosal tissue. However, there is still controversy over whether this is borne out under clinical conditions. OBJECTIVE To compare the outcome following excisional biopsies of fibrous hyperplasias using a pulsed (cf) versus a continuous wave (cw) CO2 laser mode regarding the thermal damage zone, duration of surgeries, intra- and postoperative complications, postoperative pain sensation, scarring and/or relapse during the initial 6 months. MATERIALS AND METHODS One hundred Swiss-resident patients with a fibrous hyperplasia in their buccal mucosa were randomly assigned to the cw mode (5 W) or the cf mode (140 Hz, 400 microseconds, 33 mJ, 4.62 W) group. All excisions were performed by one single oral surgeon. Postoperative pain (2 weeks) was recorded by visual analogue scale (VAS; ranging from 0 to 100). Intake of analgesics and postoperative complications were recorded in a standardized study form. The maximum width of the collateral thermal damage zone was measured (µm) in excision specimens by one pathologist. Intraoral photographs at 6-month follow-up examinations were evaluated regarding scarring (yes/no). RESULTS Median duration of the excision was 65 seconds in the cw and 81 seconds in the cf group (P = 0.13). Intraoperative bleeding occurred in 16.3% of the patients in the cw and 17.7% of the cf group. The median value of the thermal damage zone was 161(±228) μm in the cw and 152(± 105) μm in the cf group (P = 0.68). The reported postoperative complications included swelling in 19% and minor bleeding in 6% without significant differences between the two laser modes. When comparing each day separately or the combined mean VAS scores of both groups between Days 1-3, 1-7, and 1-15, there were no significant differences. However, more patients of the cw group (25%) took analgesics than patients of the cf group (9.8%) resulting in a borderline significance (P = 0.04). Scarring at the excision site was found in 50.6% of 77 patients after 6 months, and more scars were identified in cases treated with the cf mode (P = 0.03). CONCLUSIONS Excision of fibrous hyperplasias performed with a CO2 laser demonstrated a good clinical outcome and long-term predictability with a low risk of recurrence regardless of the laser mode (cf or cw) used. Scarring after 6 months was only seen in 50.6% of the cases and was slightly more frequent in the cf mode group. Based on the findings of the present study, a safety border of 1 mm appears sufficient for both laser modes especially when performing a biopsy of a suspicious soft tissue lesion to ensure a proper histopathological examination.

Daily and seasonal thermal stresses in tilings: a field survey combined with numeric modeling

This study investigates thermally induced tensile stresses in ceramic tilings. Daily and seasonal thermal cycles, as well as, rare but extreme events, such as a hail-storm striking a heated terrace tiling, were studied in the field and by numerical modeling investigations. The field surveys delivered temperature– time diagrams and temperature profiles across tiling systems. These data were taken as input parameters for modeling the stress distribution in the tiling system in order to detect potential sites for material failure. Dependent on the thermal scenario (e.g., slow heating of the entire structure during morning and afternoon, or a rapid cooling of the tiles by a rain storm) the modeling indicates specific locations with high tensile stresses. Typically regions along the rim of the tiling field showed stresses, which can become critical with respect to the adhesion strength. Over the years, ongoing cycles of thermal expansion–contraction result in material fatigue promoting the propagation of cracks. However, the installation of flexible waterproofing membranes (applied between substrate and tile adhesive) represents an efficient technical innovation to reduce such crack propagation as confirmed by both numerical modeling results and microstructural studies on real systems.

Thermal dependence of luminescence lifetimes and radioluminescence in quartz

During time-resolved optical stimulation experiments (TR-OSL), one uses short light pulses to separate the stimulation and emission of luminescence in time. Experimental TR-OSL results show that the luminescence lifetime in quartz of sedimentary origin is independent of annealing temperature below 500 °C, but decreases monotonically thereafter. These results have been interpreted previously empirically on the basis of the existence of two separate luminescence centers LH and LL in quartz, each with its own distinct luminescence lifetime. Additional experimental evidence also supports the presence of a non-luminescent hole reservoir R, which plays a critical role in the predose effect in this material. This paper extends a recently published analytical model for thermal quenching in quartz, to include the two luminescence centers LH and LL, as well as the hole reservoir R. The new extended model involves localized electronic transitions between energy states within the two luminescence centers, and is described by a system of differential equations based on the Mott–Seitz mechanism of thermal quenching. It is shown that by using simplifying physical assumptions, one can obtain analytical solutions for the intensity of the light during a TR-OSL experiment carried out with previously annealed samples. These analytical expressions are found to be in good agreement with the numerical solutions of the equations. The results from the model are shown to be in quantitative agreement with published experimental data for commercially available quartz samples. Specifically the model describes the variation of the luminescence lifetimes with (a) annealing temperatures between room temperature and 900 °C, and (b) with stimulation temperatures between 20 and 200 °C. This paper also reports new radioluminescence (RL) measurements carried out using the same commercially available quartz samples. Gaussian deconvolution of the RL emission spectra was carried out using a total of seven emission bands between 1.5 and 4.5 eV, and the behavior of these bands was examined as a function of the annealing temperature. An emission band at ∼3.44 eV (360 nm) was found to be strongly enhanced when the annealing temperature was increased to 500 °C, and this band underwent a significant reduction in intensity with further increase in temperature. Furthermore, a new emission band at ∼3.73 eV (330 nm) became apparent for annealing temperatures in the range 600–700 °C. These new experimental results are discussed within the context of the model presented in this paper.

Analysis of Synthetic Diamond Wafer Interferograms Using a Parallelized Simulated Annealing Algorithm

Diamonds are known for both their beauty and their durability. Jefferson National Lab in Newport News, VA has found a way to utilize the diamond's strength to view the beauty of the inside of the atomic nucleus with the hopes of finding exotic forms of matter. By firing very fast electrons at a diamond sheet no thicker than a human hair, high energy particles of light known as photons are produced with a high degree of polarization that can illuminate the constituents of the nucleus known as quarks. The University of Connecticut Nuclear Physics group has responsibility for crafting these extremely thin, high quality diamond wafers. These wafers must be cut from larger stones that are about the size of a human finger, and then carefully machined down to the final thickness. The thinning of these diamonds is extremely challenging, as the diamond's greatest strength also becomes its greatest weakness. The Connecticut Nuclear Physics group has developed a novel technique to assist industrial partners in assessing the quality of the final machining steps, using a technique based on laser interferometry. The images of the diamond surface produced by the interferometer encode the thickness and shape of the diamond surface in a complex way that requires detailed analysis to extract. We have developed a novel software application to analyze these images based on the method of simulated annealing. Being able to image the surface of these diamonds without requiring costly X-ray diffraction measurements allows rapid feedback to the industrial partners as they refine their thinning techniques. Thus, by utilizing a material found to be beautiful by many, the beauty of nature can be brought more clearly into view.

Sr/Ca ratios of coccoliths from the Paleocene-Eocene Thermal Maximum

During the Paleocene-Eocene Thermal Maximum (PETM), rapid release of isotopically light C to the ocean-atmosphere system elevated the greenhouse effect and warmed temperatures by 5-7 °C for 105 yr. The response of the planktic ecosystems and productivity to the dramatic climate changes of the PETM may represent a significant feedback to the carbon cycle changes, but has been difficult to document. We examine Sr/Ca ratios in calcareous nannofossils in sediments spanning the PETM in three open ocean sites as a new approach to examine productivity and ecological shifts in calcifying plankton. The large heterogeneity in Sr/Ca among different nannofossil genera indicates that nannofossil Sr/Ca reflects primary productivity-driven geochemical signals and not diagenetic overprinting. Elevated Sr/Ca ratios in several genera and constant ratios in other genera suggest increased overall productivity in the Atlantic sector of the Southern Ocean during the PETM. Dominant nannofossil genera in tropical Atlantic and Pacific sites show Sr/Ca variations during the PETM which are comparable to background variability prior to the PETM. Despite acidification of the ocean there was not a productivity crisis among calcifying phytoplankton. We use the Pandora ocean box model to explore possible mechanisms for PETM productivity change. If independent proxy evidence for more stratified conditions in the Southern Ocean during the PETM is robust, then maintenance of stable or increased productivity there likely reflects increased nutrient inventories of the ocean. Increased nutrient inventories could have resulted from climatically enhanced weathering and would have important implications for burial rates of organic carbon and stabilization of climate and the carbon cycle.

Planktonic foraminifera, nannofossils and stable isotope record across tghe Paleocene-Eocene thermal maximum of ODP Hole 113-690B

The carbonate saturation profile of the oceans shoaled markedly during a transient global warming event known as the Paleocene-Eocene thermal maximum (PETM) (circa 55 Ma). The rapid release of large quantities of carbon into the ocean-atmosphere system is believed to have triggered this intense episode of dissolution along with a negative carbon isotope excursion (CIE). The brevity (120-220 kyr) of the PETM reflects the rapid enhancement of negative feedback mechanisms within Earth's exogenic carbon cycle that served the dual function of buffering ocean pH and reducing atmospheric greenhouse gas levels. Detailed study of the PETM stratigraphy from Ocean Drilling Program Site 690 (Weddell Sea) reveals that the CIE recovery period, which postdates the CIE onset by ~80 kyr, is represented by an expanded (~2.5 m thick) interval containing a unique planktic foraminiferal assemblage strongly diluted by coccolithophore carbonate. Collectively, the micropaleontological and sedimentological changes preserved within the CIE recovery interval reflect a transient state when ocean-atmosphere chemistry fostered prolific coccolithophore blooms that suppressed the local lysocline to relatively deeper depths. A prominent peak in the abundance of the clay mineral kaolinite is associated with the CIE recovery interval, indicating that continental weathering/runoff intensified at this time as well (Robert and Kennett, 1994). Such parallel stratigraphic changes are generally consonant with the hypothesis that enhanced continental weathering/runoff and carbonate precipitation helped sequester carbon during the PETM recovery period (e.g., Dickens et al., 1997, doi:10.1130/0091-7613(1997)025<0259:ABOGIT>2.3.CO;2 ; Zachos et al., 2005, doi:10.1126/science.1109004).

Calcareous nannofossil species richness across the Paleocene-Eocene Thermal Maximum

The Paleocene-Eocene Thermal Maximum (PETM, ~5 million years ago) was an interval of global warming and ocean acidification attributed to rapid release and oxidation of buried carbon. We show that the onset of the PETM coincided with a prominent increase in the origination and extinction of calcareous phytoplankton. Yet major perturbation of the surface-water saturation state across the PETM was not detrimental to the survival of most calcareous nannoplankton taxa and did not impart a calcification or ecological bias to the pattern of evolutionary turnover. Instead, the rate of environmental change appears to have driven turnover, preferentially affecting rare taxa living close to their viable limits.

Calcareous nannofossil during the Paleocene Eocene Thermal Maximum in sediments of Walvish Ridge

Compositions and abundances of calcareous nannofossil taxa have been determined in a ca 170 kyrs long time interval across the Paleocene/Eocene boundary at 1-cm to 10-cm resolution from two ODP Sites (1262, 1263) drilled along the flank of the Walvis Ridge in the South Atlantic. The results are compared to published data from ODP Site 690 in the Weddell Sea. The assemblages underwent rapid evolution over a 74 kyrs period, indicating stressed, unstable and/or extreme photic zone environments during the PETM hyperthermal. This rapid evolution, which created 5 distinct stratigraphic horizons, is consistent with the restricted brief occurrences of malformed and/or weakly calcified morphotypes. The production of these aberrant morphotypes is possibly caused by major global scale changes in carbon cycling in the ocean-atmosphere system, affecting also photic zone environments. No marked paleoecologically induced changes are observed in abundances of the genera Discoaster, Fasciculithus and Sphenolithus at the Walvis Ridge sites. Surprisingly, there is no significant correlation in abundance between these three genera, presumed to have had a similar paleoecological preference for warm and oligotrophic conditions.