167 research outputs found
A cryogenic liquid-mirror telescope on the moon to study the early universe
We have studied the feasibility and scientific potential of zenith observing
liquid mirror telescopes having 20 to 100 m diameters located on the moon. They
would carry out deep infrared surveys to study the distant universe and follow
up discoveries made with the 6 m James Webb Space Telescope (JWST), with more
detailed images and spectroscopic studies. They could detect objects 100 times
fainter than JWST, observing the first, high-red shift stars in the early
universe and their assembly into galaxies. We explored the scientific
opportunities, key technologies and optimum location of such telescopes. We
have demonstrated critical technologies. For example, the primary mirror would
necessitate a high-reflectivity liquid that does not evaporate in the lunar
vacuum and remains liquid at less than 100K: We have made a crucial
demonstration by successfully coating an ionic liquid that has negligible vapor
pressure. We also successfully experimented with a liquid mirror spinning on a
superconducting bearing, as will be needed for the cryogenic, vacuum
environment of the telescope. We have investigated issues related to lunar
locations, concluding that locations within a few km of a pole are ideal for
deep sky cover and long integration times. We have located ridges and crater
rims within 0.5 degrees of the North Pole that are illuminated for at least
some sun angles during lunar winter, providing power and temperature control.
We also have identified potential problems, like lunar dust. Issues raised by
our preliminary study demand additional in-depth analyses. These issues must be
fully examined as part of a scientific debate we hope to start with the present
article.Comment: 35 pages, 11 figures. To appear in Astrophysical Journal June 20 200
A Computational Approach to Sequential Decision Optimization in Energy Storage and Trading
Due to recent technical progress, battery energy storages are becoming a viable option in the power sector. Their optimal operational management focuses on load shift and shaving of price spikes. However, this requires optimally responding to electricity demand, intermittent generation, and volatile electricity prices. More importantly, such optimization must take into account the so-called deep discharge costs, which have a significant impact on battery lifespan. We present a solution to a class of stochastic optimal control problems associated with these applications. Our numerical techniques are based on efficient algorithms which deliver a guaranteed accurac
Children with Cerebral Palsy can imagine actions like their normally developed peers
The present study aimed at assessing whether children with Cerebral Palsy (CP) can imagine object directed actions similarly to their normally developed peers. We asked children with CP (n = 12) and paired healthy controls (n = 12) to imagine in first person perspective eight daily actions, after observing them through videoclips presented on a computer screen. During motor imagery (MI) children were interrupted at a specific timepoint (e.g., at 2.5 s) from the start. Two frames extracted from the videoclips were then presented on the screen. One of the two depicted the correct timepoint at which the imagined action was interrupted, while the other represented an earlier or later timepoint. Children had to respond by pressing the key associated to the correct frame. Children also underwent VMIQ-2 questionnaire. Both groups performed similarly in the questionnaire and in the requested task, where they showed the same error rate. Errors mainly concerned the later frame, suggesting a similar strategy to solve the task in the two groups. The results support the view that children with CP can imagine actions similarly to their normally developed peers. This encourages the use of MI as a rehabilitative tool in children with motor impairment
Quantum memory for photons: I. Dark state polaritons
An ideal and reversible transfer technique for the quantum state between
light and metastable collective states of matter is presented and analyzed in
detail. The method is based on the control of photon propagation in coherently
driven 3-level atomic media, in which the group velocity is adiabatically
reduced to zero. Form-stable coupled excitations of light and matter
(``dark-state polaritons'') associated with the propagation of quantum fields
in Electromagnetically Induced Transparency are identified, their basic
properties discussed and their application for quantum memories for light
analyzed.Comment: 13 pages, 6 figures, paragraph on photon echo adde
A mechanical time-of-flight neutron diffractometer
A mechanical time-of-flight (TOF) neutron diffractometer has been constructed and a system of data analysis developed for the study of noncrystalline substances through radial density functions. Measurements to wave vector transfer Qmax > 25 A-1 are readily made; a resolution [Delta]Q/Qr[approximate]2[pi]/Qmax[approximate]0.25 A. These can be partially corrected for termination errors to provide a spatial resolution [Delta]r<0.15 A.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22421/1/0000871.pd
Quantum computing with mixed states
We discuss a model for quantum computing with initially mixed states.
Although such a computer is known to be less powerful than a quantum computer
operating with pure (entangled) states, it may efficiently solve some problems
for which no efficient classical algorithms are known. We suggest a new
implementation of quantum computation with initially mixed states in which an
algorithm realization is achieved by means of optimal basis independent
transformations of qubits.Comment: 2 figures, 52 reference
Drug holidays and overall survival of patients with metastatic colorectal cancer
Different de-escalation strategies have been proposed to limit the risk of cumulative toxicity and guarantee quality of life during the treatment trajectory of patients with metastatic colorectal cancer (mCRC). Programmed treatment interruptions, defined as drug holidays (DHs), have been implemented in clinical practice. We evaluated the association between DHs and overall survival (OS). This was a retrospective study, conducted at the University Hospital of Udine and the IRCCS CRO of Aviano. We retrieved records of 608 consecutive patients treated for mCRC from 1 January 2005 to 15 March 2017 and evaluated the impact of different de-escalation strategies (maintenance, DHs, or both) on OS through uni-and multivariate Cox regression analyses. We also looked at attrition rates across treatment lines according to the chosen strategy. In our study, 19.24% of patients received maintenance therapy, 16.12% DHs, and 9.87% both, while 32.07% continued full-intensity first-line treatment up to progression or death. In uni-and multivariate analyses first-line continuous treatment and early discontinuation (treatment for less than 3 months) were associated to worse OS compared to non-continuous strategies (HR, 1.68; 95% CI, 1.22\u20132.32; p = 0.002 and HR,4.89; 95% CI, 3.33\u20137.19; p < 0.001, respectively). Attrition rates were 22.8%, 20.61%, and 19.64% for maintenance, DHs, or both, respectively. For continuous therapy and for treatment of less than 3 months it was 21.57% and 49%. De-escalation strategies are safe and effective options. DHs after initial induction chemotherapy may be considered in clinically selected patients with metastatic colorectal cancer
Critical Dimensions in Architectural Photography: Contributions to Architectural Knowledge
This paper illustrates and explores three critical dimensions of photography in architecture, each of which informs the production of images, texts, and other artifacts which establish what might be called a buildingâs media footprint. The paperâs broad goal is to question the extent to which these critical dimensions are relevant to architectural decision-making processes. Acknowledging that such dimensions as the ones examined here rarely predict an architectâs specific design decisions in a transparent manner, the paper discusses not only the decisions made by architects during the process of designing buildings, but the decisions made by critics, visitors, and members of the general public as they engage in activities such as visiting buildings, writing about them and, particularly, photographing them.
First, the text discusses the potential of buildings to operate as mechanisms for producing images, in the sense originated by Beatriz Colomina. The question is developed through the analysis of the space of photography â mapping of points of view, directions of view, and fields of view of defined photographic collections. Secondly, it considers photographyâs complicity in the canonization of buildings, and specifically, the extent to which photography is responsible for distinguishing between major and minor architectural works. Finally, the essay examines the erosion over time of photographyâs historical power to frame when confronted with contemporary technologies of virtual reality and photo realistically rendered digital models. Each of these critical dimensions, or concepts, develops a specific aspect of how photographic information about buildings is organized, structured, and disseminated, and is thus only part of the larger project of architectural epistemology, which inquires into this wider field. This will be done through an examination of the Mies van der Rohe-designed Commons Building at ITT in Chicago and the evolution of its relationship with architectural photography and photographic representation â both on its own terms and through the prism of the Rem Koolhaas-designed McCormick Tribune Student Center, which adds to and incorporates the Commons Building. Until the end of the twentieth century, the Commons Building on the campus of the Illinois Institute of Technology was generally considered one of Mies van der Roheâs lesser works. Reportedly neglected by its own architect during the design process, and frequently marginalized in academic discussions of the campus, when mentioned at all the building was often cited as an unrefined prototype of Crown Hall. This discourse took a new direction when in 1998, Rem Koolhaas/OMA won a design competition for a student center on the IIT campus: uniquely among the competition
entries, Koolhaasâs design incorporated the Commons Building within a new context â what ultimately became the McCormick Tribune Campus Center (MTCC). When critics concluded that the incorporation of the Commons Building into the larger whole could compromise its integrity as
an exemplar of Miesâs work, the building became the object of renewed interest and controversy. The two projects considered here show a clear evolution in architectureâs relationship with the photographic image. Specifically, the history of the Commons Building can be traced through photographs: during and shortly following its construction, the building was photographed as part
of Miesâs own attention to publicity; it was documented as part of historical analyses; and over time it was visited and photographed by casual and amateur photographers. Following the competition results, photographs of the Commons Building were strategically deployed by both proponents and critics of Koolhaasâs design. Contemporary photographs of the building appear in architectural and campus guidebooks and on websites such as Flickr.com. Examining the ways in which
photographs of the Commons Building appear in these various contexts allows discussion of the critical dimensions identified above and permits us to trace the evolution of the mutually reinforcing relationship between architecture and photography
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