Optical Spring Stabilization

The Advanced LIGO detectors will soon be online with enough sensitivity to begin detecting gravitational waves, based on conservative estimates of the rate of neutron star inspirals. These first detections are sure to be significant, however, we will always strive to do better. More questions will be asked about the nature of neutron star material, rates of black hole inspirals, electromagnetic counterparts, etc. To begin to answer all of the questions aLIGO will bring us we will need even better sensitivity in future gravitational wave detectors. This thesis addresses one aspect that will limit us in the future: angular stability of the test masses. Angular stability in advanced LIGO uses an active feedback system. We are proposing to replace the active feedback system with a passive one, eliminating sensing noise contributions. This technique uses the radiation pressure of light inside a cavity as a stable optical spring, fundamentally the same as technique developed by Corbitt, et al. [1] with an additional degree of freedom. I will review the theory of the one dimensional technique and discuss the multidimensional control theory and angular trap setup. I will then present results from the one-dimensional trap which we have built and tested. And propose improvements for the angular trap experiment. Along the way we have discovered an interesting coupling with thermal expansion due to round trip absorption in the high reflective coatings. The front surface HR coating limits our spring stability in this experiment due to the high circulating power and small beam spot size

A Report on Utility Participation in Solar Energy Development

The promise of solar energy use in remedying the critical need for energy sources which provide alternatives to oil is the concern of this article. The author examines the role that utility companies could perform in the development and marketing of solar energy systems and considers the potential for anticompetitive abuse that might result. He concludes, however, that congressional plans for solar development have placed unfair, unwarranted, and counterproductive restrictions on utilities and may have precluded otherwise promising development

The development of integrated audit for the training of general practice registrars

In 1991 the Joint Committee on Postgraduate Training for General Practice (JCPTGP) issued a new criterion for training practices stating that they "must provide opportunities for trainees to become familiar with the principles of medical audit and to participate in medical audit; and they must be able to demonstrate their trainees have actually done so." It is possible that no training practice in the west of Scotland could have implemented this criterion. This thesis considers the development of a model appropriate for a training environment which overcame the difficulty in interpreting whether the criterion was being implemented. This required clear learning objectives to be set integrated into a system where competence in achieving these objectives could be assessed. In order to provide support for the trainers and to maximise the opportunities for trainees to participate in audit a programme for the region was constructed covering organisation of appointment systems, chronic disease management and significant event analysis with educational objectives set out for each area. Progress in implementing the programme was assessed at each reaccreditation visit and evaluations were completed in 1998 and 2001. All areas of the programme showed modest improvements between the evaluation dates although few reached statistical significance. The time involved in and the cost of collecting data for audit purposes were evaluated by offering ten training practices audit support staff to collect their data for parts of the audit programme. The costs were compared with the hypothetical use of a practice receptionist or the practice nurse. The conclusion was that data collection carries significant costs both in time and expense for a practice and the need to agree on appropriate use of practice staff is vital. Between 1996 and 1997 an increasing number of registrars was evaluating the change they had proposed in their audit project. There was also a significant increase in the proportion of trainers who felt that a completed audit cycle should now define the audit project. An increase to eight criteria followed with two assessors being used to screen the projects without compromising sensitivity or specificity. Registrars were therefore now expected to demonstrate their competence as defined by evaluating rather than proposing change. Significant event auditing added a qualitative format for an audit project. The analysis of such an event involved addressing four specific questions with two assessors reviewing each analysis. The integration of quantitative and qualitative methods encouraged training practices to think more broadly about different approaches to teaching the assessment of quality of care. Between 1998 and 2001 all senior house officers on vocational training schemes were asked to submit a criterion audit cycle or a significant event analysis in each post. Teaching and support were provided. The output ranged from 28% (accident and emergency) to 45% (geriatrics) of the total number of projects expected. The JCPTGP revised its criterion for audit in training practices in 2000 proposing a model based on the work in this thesis. The lessons learned have implications for the non-training environment of general practice. (Abstract shortened by ProQuest.)

Mitochondrial DNA insertion into nuclear chromosomes of maize

Abstract only availableEvery mitochondrion contains its own DNA separate from the nucleus. Over evolutionary time, most of the mitochondrial genes have moved to the nucleus so that now mitochondria require nuclear DNA to function. This type of transfer is an apparently ongoing process based on our observations that large pieces of the mitochondrial genome have been transferred to the nucleus. The focus of this study was to find the locations of mitochondrial DNA (mtDNA) on nuclear chromosomes in the B73 line of maize and compare these locations to other lines, using fluorescence in situ hybridization (FISH). First, cosmids previously made from a normal mtDNA genotype (NB) were maxi-prepped and then direct labeled with fluorescent tags. Next we prepared slides of B73 root tips and hybridized the labeled cosmids as well as marker probes to the cells. After hybridization, the slides were viewed and chromosome spread pictures were taken showing the location of the cosmids on the chromosomes. This process was then performed on root tip chromosomes from the Mo17, Black Mexican Sweet (BMS), and B37 lines. Twelve cosmids, representing about 71% of the mitochondrial genome, were examined and 8 different nuclear insertion sites were identified. These dispersed locations were predominantly near centromeres or telomeres on chromosomes 2 and 9. These new findings will make understanding the B73 nuclear genome sequence easier because now researchers will know what to expect at these locations and provide new information about the mechanism of mitochondrial genome transfer to the nucleus.NSF-REU Biology & Biochemistr

Analysis of the mtDNA insertion site on chromosome 9L in maize inbreds using fluorescence in situ hybridization

Abstract only availableAlmost all eukaryotic nuclear genomes show evidence of organellar DNA insertions originating from mitochondrial DNA (mtDNA) and chloroplast DNA (cpDNA). While the precise mechanisms of incorporation remain unknown, the phenomenon is frequent and ongoing in many species. In Zea mays, mtDNA insertions differ among inbred lines. A very large mtDNA insertion is found near the centromere of the long arm of chromosome 9 in the B73 inbred. This insertion contains the majority of the mitochondrial genome, while a similarly positioned insertion in the Mo17 inbred line is much smaller. We used recombinant inbred lines from the intermated B73 x Mo17 (IBM) population to determine if the insertions are indeed at the same position. We selected lines with recombination in this region of chromosome 9L. Using two mtDNA probes present in the insertions in both B73 and Mo17, we applied a chromosome painting technique called fluorescence in situ hybridization (FISH) to root-tip metaphase chromosomes and looked for the presence of the mtDNA site on chromosome 9L in the selected IBM lines. If the mtDNA insertion sites in B73 and Mo17 are at different locations, then at least one of the recombinant IBM lines should not display a mtDNA insertion at the chromosome 9 location. However, all of the recombinant IBM lines examined displayed the mtDNA insertion site on chromosome 9L. This indicates that the Mo17 and B73 insertions likely occupy the same region on the chromosome. Furthermore, this suggests that the large mtDNA insertion occurred recently in B73 at a pre-existing site present in both B73 and Mo17.NSF-REU Program in Biological Sciences & Biochemistr

Activin-A and Bmp4 Levels Modulate Cell Type Specification during CHIR-Induced Cardiomyogenesis

The use of human pluripotent cell progeny for cardiac disease modeling, drug testing and therapeutics requires the ability to efficiently induce pluripotent cells into the cardiomyogenic lineage. Although direct activation of the Activin-A and/or Bmp pathways with growth factors yields context-dependent success, recent studies have shown that induction of Wnt signaling using low molecular weight molecules such as CHIR, which in turn induces the Activin-A and Bmp pathways, is widely effective. To further enhance the reproducibility of CHIR-induced cardiomyogenesis, and to ultimately promote myocyte maturation, we are using exogenous growth factors to optimize cardiomyogenic signaling downstream of CHIR induction. As indicated by RNA-seq, induction with CHIR during Day 1 (Days 0–1) was followed by immediate expression of Nodal ligands and receptors, followed later by Bmp ligands and receptors. Co-induction with CHIR and high levels of the Nodal mimetic Activin-A (50–100 ng/ml) during Day 0–1 efficiently induced definitive endoderm, whereas CHIR supplemented with Activin-A at low levels (10 ng/ml) consistently improved cardiomyogenic efficiency, even when CHIR alone was ineffective. Moreover, co-induction using CHIR and low levels of Activin-A apparently increased the rate of cardiomyogenesis, as indicated by the initial appearance of rhythmically beating cells by Day 6 instead of Day 8. By contrast, co-induction with CHIR plus low levels (3–10 ng/ml) of Bmp4 during Day 0–1 consistently and strongly inhibited cardiomyogenesis. These findings, which demonstrate that cardiomyogenic efficacy is improved by optimizing levels of CHIR-induced growth factors when applied in accord with their sequence of endogenous expression, are consistent with the idea that Nodal (Activin-A) levels toggle the entry of cells into the endodermal or mesodermal lineages, while Bmp levels regulate subsequent allocation into mesodermal cell types

Bilinear noise subtraction at the GEO 600 observatory

We develop a scheme to subtract off bilinear noise from the gravitational wave strain data and demonstrate it at the GEO 600 observatory. Modulations caused by test mass misalignments on longitudinal control signals are observed to have a broadband effect on the mid-frequency detector sensitivity ranging from 50 Hz to 500 Hz. We estimate this bilinear coupling by making use of narrow-band signal injections that are already in place for noise projection purposes. A coherent bilinear signal is constructed by a two-stage system identification process where the involved couplings are approximated in terms of stable rational functions. The time-domain filtering efficiency is observed to depend upon the system identification process especially when the involved transfer functions cover a large dynamic range and have multiple resonant features. We improve upon the existing filter design techniques by employing a Bayesian adaptive directed search strategy that optimizes across the several key parameters that affect the accuracy of the estimated model. The resulting post-offline subtraction leads to a suppression of modulation side-bands around the calibration lines along with a broadband reduction of the mid-frequency noise floor. The filter coefficients are updated periodically to account for any non-stationarities that can arise within the coupling. The observed increase in the astrophysical range and a reduction in the occurrence of non-astrophysical transients suggest that the above method is a viable data cleaning technique for current and future gravitational wave observatories

High power and ultra-low-noise photodetector for squeezed-light enhanced gravitational wave detectors

Current laser-interferometric gravitational wave detectors employ a self-homodyne readout scheme where a comparatively large light power (5–50 mW) is detected per photosensitive element. For best sensitivity to gravitational waves, signal levels as low as the quantum shot noise have to be measured as accurately as possible. The electronic noise of the detection circuit can produce a relevant limit to this accuracy, in particular when squeezed states of light are used to reduce the quantum noise. We present a new electronic circuit design reducing the electronic noise of the photodetection circuit in the audio band. In the application of this circuit at the gravitational-wave detector GEO 600 the shot-noise to electronic noise ratio was permanently improved by a factor of more than 4 above 1 kHz, while the dynamic range was improved by a factor of 7. The noise equivalent photocurrent of the implemented photodetector and circuit is about 5 µA/ √\ud Hz above 1 kHz with a maximum detectable photocurrent of 20 mA. With the new circuit, the observed squeezing level in GEO 600 increased by 0.2 dB. The new circuit also creates headroom for higher laser power and more squeezing to be observed in the future in GEO 600 and is applicable to other optics experiments

Low Florida Coral Calcification Rates in the Plio-Pleistocene

In geological outcrops and drill cores from reef frameworks, the skeletons of scleractinian corals are usually leached and more or less completely transformed into sparry calcite because the highly porous skeletons formed of metastable aragonite (CaCO3) undergo rapid diagenetic alteration. Upon alteration, ghost structures of the distinct annual growth bands often allow for reconstructions of annual extension ( =  growth) rates, but information on skeletal density needed for reconstructions of calcification rates is invariably lost. This report presents the bulk density, extension rates and calcification rates of fossil reef corals which underwent minor diagenetic alteration only. The corals derive from unlithified shallow water carbonates of the Florida platform (south-eastern USA), which formed during four interglacial sea level highstands dated approximately 3.2, 2.9, 1.8, and 1.2 Ma in the mid-Pliocene to early Pleistocene. With regard to the preservation, the coral skeletons display smooth growth surfaces with minor volumes of marine aragonite cement within intra-skeletal porosity. Within the skeletal structures, voids are commonly present along centres of calcification which lack secondary cements. Mean extension rates were 0.44 ± 0.19 cm yr−1(range 0.16 to 0.86 cm yr−1), mean bulk density was 0.96 ± 0.36 g cm−3 (range 0.55 to 1.83 g cm−3) and calcification rates ranged from 0.18 to 0.82 g cm−2 yr−1(mean 0.38 ± 0.16 g cm−2 yr−1), values which are 50 % of modern shallow-water reef corals. To understand the possible mechanisms behind these low calcification rates, we compared the fossil calcification rates with those of modern zooxanthellate corals (z corals) from the Western Atlantic (WA) and Indo-Pacific calibrated against sea surface temperature (SST). In the fossil data, we found a widely analogous relationship with SST in z corals from the WA, i.e. density increases and extension rate decreases with increasing SST, but over a significantly larger temperature window during the Plio-Pleistocene. With regard to the environment of coral growth, stable isotope proxy data from the fossil corals and the overall structure of the ancient shallow marine communities are consistent with a well-mixed, open marine environment similar to the present-day Florida Reef Tract, but variably affected by intermittent upwelling. Upwelling along the platform may explain low rates of reef coral calcification and inorganic cementation, but is too localised to account also for low extension rates of Pliocene z corals throughout the tropical WA region. Low aragonite saturation on a more global scale in response to rapid glacial–interglacial CO2 cyclicity is also a potential factor, but Plio-Pleistocene atmospheric pCO2 is generally believed to have been broadly similar to the present day. Heat stress related to globally high interglacial SST only episodically moderated by intermittent upwelling affecting the Florida platform seems to be another likely reason for low calcification rates. From these observations we suggest some present coral reef systems to be endangered from future ocean warming