A one-dimensional ultracold medium of extreme optical depth

We report on the preparation of a one-dimensional ultracold medium in a hollow-core photonic crystal fiber, reaching an effective optical depth of 1000(150). We achieved this extreme optical depth by transferring atoms from a magneto-optical trap into a far-detuned optical dipole trap inside the hollow-core fiber, yielding up to 2.5(3)$\times$10$^5$ atoms inside the core with a loading efficiency of $2.5(6)~\%$. The preparation of an ultracold medium of such huge optical depth paves the way towards new applications in quantum optics and nonlinear optics

Improved cell cycle synchronization and chromosome doubling methods in cotton

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 32-34).Cotton is an economically important crop in the U.S., but is relatively poorly characterized genetically. Unlike other, more researched crops, it is lacking highly effective methods for consistent cell cycle manipulation and chromosome doubling. Control over these biological features will enhance the ability to produce high quality cytological preparations of chromosomes and to double the number of chromosomes, i.e., induce polyploidy. The ability to routinely produce large numbers of high quality chromosome preparations from plants facilitates genomic characterization, while chromosome doubling allows integration of desirable genetic diversity from closely related plant species. This research establishes a procedure for cell cycle synchronization of root tips using hydroxyurea, and analyzes the efficacy of known chemicals for metaphase accumulation. Possibilities for adapting the procedure for improved chromosome doubling in shoot apical meristems are also introduced. Experimental evaluations were made by hydroponically treating seedlings with four antitubulin compounds of diverse chemistry - colchicine, amiprophos-methyl (APM), a benzamide designated RH-4032, and a novel phenylcyclohexene colchicine mimic (2d), followed by visual analysis of root tip morphology and cytological determination of the mitotic index, or fraction of cells at metaphase. An 18-hour treatment of 3-5 mM hydroxyurea gave optimum synchronization. Three of the antitubulin compounds, amiprophos-methyl, 2d, and RH-4032, outperformed colchicine, the standard agent for metaphase accumulation, and yielded average mitotic indices of 0.3. Peak mitotic indices exceeding 0.7 were observed for 2d and APM. Shoot bud topical application of APM, 2d, and RH-4032 produced short term changes ranging from sectored and misshapen leaves to meristem necrosis, followed by development of thicker and darker leaves. Cytological data and visual observations suggest these compounds cause somatic doubling of the chromosome number in cotton, and that one or more of them will provide a favorable alternative to the traditional methods based on colchicine, which is highly toxic and mutagenic to humans

How political institutions shape abortion law in the United States, Britain and Canada

The topic of abortion is a complex and controversial one for most contemporary societies, with the arguments around it consisting of multiple dimensions including population control, sanctity of life, freedom of choice and parental consent, to name but a few. In a recent lecture, the director of the London School of Economics and Political Science, Professor Craig Calhoun, promised a provocative discussion as Drew Halfmann, University of Calfornia, argued that political institutions have been, and are, key in the development and implementation of abortion policies. In his book Doctors and Demonstrators, Drew Halfmann looks at how three countries, Britain, Canada and the United States have differed significantly in their policies on abortion despite sharing similar heritage and culture. Here we look at how gatekeeping evolved in all three countries, which actors influenced policy and the how abortion became so politicised in the US

Seafarers, Silk, and Science: Oceanographic Data in the Making

This thesis comprises an empirical case study of scientific data production in oceanography and a philosophical analysis of the relations between newly created scientific data and the natural world. Based on qualitative interviews with researchers, I reconstruct research practices that lead to the ongoing production of digital data related to long-term developments of plankton biodiversity in the oceans. My analysis is centred on four themes: materiality, scientific representing with data, methodological continuity, and the contribution of non-scientists to epistemic processes. These are critically assessed against the background of today’s data-intensive sciences and increased automation and remoteness in oceanographic practices. Sciences of the world’s oceans have by and large been disregarded in philosophical scholarship thus far. My thesis opens this field for philosophical analysis and reveals various conditions and constraints of data practices that are largely uncontrollable by ocean scientists. I argue that the creation of useful scientific data depends on the implementation and preservation of material, methodological, and social continuities. These allow scientists to repeatedly transform visually perceived characteristics of research samples into meaningful scientific data stored in a digital database. In my case study, data are not collected but result from active intervention and subsequent manipulation and processing of newly created material objects. My discussion of scientific representing with data suggests that scientists do not extract or read any intrinsic representational relation between data and a target, but make data gradually more computable and compatible with already existing representations of natural systems. My arguments shed light on the epistemological significance of materiality, on limiting factors of scientific agency, and on an inevitable balance between changing conditions of concrete research settings and long-term consistency of data practices.European Research Counci

Photoionization Suppression by Continuum Coherence: Experiment and Theory

We present experimental and theoretical results of a detailed study of laser-induced continuum structures (LICS) in the photoionization continuum of helium out of the metastable state 2s $^1S_0$. The continuum dressing with a 1064 nm laser, couples the same region of the continuum to the {4s $^1S_0$} state. The experimental data, presented for a range of intensities, show pronounced ionization suppression (by as much as 70% with respect to the far-from-resonance value) as well as enhancement, in a Beutler-Fano resonance profile. This ionization suppression is a clear indication of population trapping mediated by coupling to a contiuum. We present experimental results demonstrating the effect of pulse delay upon the LICS, and for the behavior of LICS for both weak and strong probe pulses. Simulations based upon numerical solution of the Schr\"{o}dinger equation model the experimental results. The atomic parameters (Rabi frequencies and Stark shifts) are calculated using a simple model-potential method for the computation of the needed wavefunctions. The simulations of the LICS profiles are in excellent agreement with experiment. We also present an analytic formulation of pulsed LICS. We show that in the case of a probe pulse shorter than the dressing one the LICS profile is the convolution of the power spectra of the probe pulse with the usual Fano profile of stationary LICS. We discuss some consequences of deviation from steady-state theory.Comment: 29 pages, 17 figures, accepted to PR

Preparation of nondegenerate coherent superpositions in a three-state ladder system assisted by Stark Shifts

We propose a technique to prepare coherent superpositions of two nondegenerate quantum states in a three-state ladder system, driven by two simultaneous fields near resonance with an intermediate state. The technique, of potential application to enhancement of nonlinear processes, uses adiabatic passage assisted by dynamic Stark shifts induced by a third laser field. The method offers significant advantages over alternative techniques: (\i) it does not require laser pulses of specific shape and duration and (\ii) it requires less intense fields than schemes based on two-photon excitation with non-resonant intermediate states. We discuss possible experimental implementation for enhancement of frequency conversion in mercury atoms.Comment: 22 pages, 8 figures, 1 table, submitted to PHys. Rev.

Correction of Arbitrary Errors in Population Inversion of Quantum Systems by Universal Composite Pulses

We introduce universal broadband composite pulse sequences for robust high-fidelity population inversion in two-state quantum systems, which compensate deviations in any experimental parameter (e.g. pulse amplitude, pulse duration, detuning from resonance, Stark shifts, unwanted frequency chirp, etc.) and are applicable with any pulse shape. We demonstrate the efficiency and universality of these composite pulses by experimental data on rephasing of atomic coherences in a $\text{Pr}^{3+}\text{:}\text{Y}_2\text{SiO}_5$ crystal

The Synthetic Biology of N2-Fixing Cyanobacteria for Photosynthetic Terpenoid Production

In the last few decades, concerns over global climate change, energy security, and environmental pollution have been rising. To overcome these challenges, the concept of “-nth generation” biofuels has emerged as a strategy to convert solar radiation into fuels and bulk industrial chemicals for societal use, while decreasing our consumption of nonrenewable energy sources. Nitrogen-fixing cyanobacteria hold a distinct advantage in biofuel production over plants, given their ability to convert sunlight, air (CO2 and N2), and mineralized water to energy-dense carbon molecules, as well as fix atmospheric nitrogen gas into ammonia for metabolism. Engineered cyanobacteria with re-wired metabolic pathways have recently been designed through synthetic biology, and they possess the ability to synthesize new chemicals and biofuels, which are secreted from their cells. Terpenoids constitute one of the largest classes of organic molecules on Earth, and are attractive candidates as a fourth generation biofuel and industrial chemical. In cyanobacteria, the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway is responsible for building essential metabolites involved in photosynthesis, as well as precursors for terpenoid biosynthesis. This dissertation encompasses research focused on redirecting MEP flux in the nitrogen-fixing cyanobacterium Anabaena sp. PCC 7120 to engineered terpenoid sinks, namely, linalool (C10H18O) and farnesene (C15H24). Chapter 1 is a review of literature in the field of biofuels and cyanobacteria, and chapter 2 is an introduction/list of objectives for the research in this dissertation. In chapter 3, we present the genetic engineering of Anabaena to synthesize farnesene by expressing a plant farnesene synthase. In chapter 4, we present the genetic engineering of Anabaena to synthesize linalool during N2-fixation, and increased linalool production is accomplished by the over-expression of three ratelimiting enzymes in the MEP pathway. In chapter 5, we examine the feasibility of a blocking a native carbon reservoir in the cyanobacterium to increase metabolite and energy availability for terpenoid synthesis, as well as physiological aspects of glycogendeficiency in the cyanobacterium during diazotrophic growth. In chapter 6, we focus on introducing a synthetic photorespiratory bypass to reduce photorespiration and increase carbon partitioning towards linalool synthesis

Experimental demonstration of composite stimulated Raman adiabatic passage

We experimentally demonstrate composite stimulated Raman adiabatic passage (CSTIRAP), which combines the concepts of composite pulse sequences and adiabatic passage. The technique is applied for population transfer in a rare-earth doped solid. We compare the performance of CSTIRAP with conventional single and repeated STIRAP, either in the resonant or the highly detuned regime. In the latter case, CSTIRAP improves the peak transfer efficiency and robustness, boosting the transfer efficiency substantially compared to repeated STIRAP. We also propose and demonstrate a universal version of CSTIRAP, which shows improved performance compared to the originally proposed composite version. Our findings pave the way towards new STIRAP applications, which require repeated excitation cycles, e.g., for momentum transfer in atom optics, or dynamical decoupling to invert arbitrary superposition states in quantum memories.Comment: 11 pages, 5 figure

Сучасні INTERNET-технології просування брендів: теоретичний аспект

Стрімке впровадження інформаційного забезпечення соціального маркетингу (SMM) докорінно змінило концепцію просування брендів на ринках України. Таргетована реклама - це реклама, спрямована на цільову аудиторію, яка відповідає певному набору вимог, заданому рекламодавцем. Розглянуто основні види та особливості таргетованої реклами