340 research outputs found
Quantum Computing: Resolving Myths, From Physics to Metaphysics
As the field of quantum computing becomes popularized, myths or misconceptions will inevitably come along with it. From the sci-fi genre to the casual usage of the term quantum, idealism begins to take over our projections of the technological future. But what are quantum computers? And what does quantum mean? How are they any different than the computers we use on an everyday basis? Will there be quantum computing smartphones? Are quantum computers just a faster version of conventional computing or a wholly new way of computing altogether? The objective of this paper is to resolve common myths or misconceptions about the concept of quantum computers, as well as the outlook and potential of this technology. In the attempt to construct a sound narrative involving a wide range of disciplines, we will draw concepts from classical computing, quantum physics, computational complexity, as well as philosophy to decipher the mystery within this unique field
Predicting and controlling the reactivity of immune cell populations against cancer
Heterogeneous cell populations form an interconnected network that determine their collective output. One example of such a heterogeneous immune population is tumor-infiltrating lymphocytes (TILs), whose output can be measured in terms of its reactivity against tumors. While the degree of reactivity varies considerably between different TILs, ranging from null to a potent response, the underlying network that governs the reactivity is poorly understood. Here, we asked whether one can predict and even control this reactivity. To address this we measured the subpopulation compositions of 91 TILs surgically removed from 27 metastatic melanoma patients. Despite the large number of subpopulations compositions, we were able to computationally extract a simple set of subpopulation-based rules that accurately predict the degree of reactivity. This raised the conjecture of whether one could control reactivity of TILs by manipulating their subpopulation composition. Remarkably, by rationally enriching and depleting selected subsets of subpopulations, we were able to restore anti-tumor reactivity to nonreactive TILs. Altogether, this work describes a general framework for predicting and controlling the output of a cell mixture
The Optical and Near-Infrared Transmission Spectrum of the Super-Earth GJ1214b: Further Evidence for a Metal-Rich Atmosphere
We present an investigation of the transmission spectrum of the 6.5 M_earth
planet GJ1214b based on new ground-based observations of transits of the planet
in the optical and near-infrared, and on previously published data.
Observations with the VLT+FORS and Magellan+MMIRS using the technique of
multi-object spectroscopy with wide slits yielded new measurements of the
planet's transmission spectrum from 0.61 to 0.85 micron, and in the J, H, and K
atmospheric windows. We also present a new measurement based on narrow-band
photometry centered at 2.09 micron with the VLT+HAWKI. We combined these data
with results from a re-analysis of previously published FORS data from 0.78 to
1.00 micron using an improved data reduction algorithm, and previously reported
values based on Spitzer data at 3.6 and 4.5 micron. All of the data are
consistent with a featureless transmission spectrum for the planet. Our K-band
data are inconsistent with the detection of spectral features at these
wavelengths reported by Croll and collaborators at the level of 4.1 sigma. The
planet's atmosphere must either have at least 70% water by mass or optically
thick high-altitude clouds or haze to be consistent with the data.Comment: (v2) ApJ in press, no major changes from v
Transcriptional Regulation by Competing Transcription Factor Modules
Gene regulatory networks lie at the heart of cellular computation. In these networks, intracellular and extracellular signals are integrated by transcription factors, which control the expression of transcription units by binding to cis-regulatory regions on the DNA. The designs of both eukaryotic and prokaryotic cis-regulatory regions are usually highly complex. They frequently consist of both repetitive and overlapping transcription factor binding sites. To unravel the design principles of these promoter architectures, we have designed in silico prokaryotic transcriptional logic gates with predefined inputâoutput relations using an evolutionary algorithm. The resulting cis-regulatory designs are often composed of modules that consist of tandem arrays of binding sites to which the transcription factors bind cooperatively. Moreover, these modules often overlap with each other, leading to competition between them. Our analysis thus identifies a new signal integration motif that is based upon the interplay between intramodular cooperativity and intermodular competition. We show that this signal integration mechanism drastically enhances the capacity of cis-regulatory domains to integrate signals. Our results provide a possible explanation for the complexity of promoter architectures and could be used for the rational design of synthetic gene circuits
Genetics and Plant Development
There are only three grand theories in biology: the theory of the cell, the theory of the gene, and the theory of evolution. Two of these, the cell and gene theories, originated in the study of plants, with the third resulting in part from botanical considerations as well. Mendel's elucidation of the rules of inheritance was a result of his experiments on peas. The rediscovery of Mendel's work in 1900 was by the botanists de Vries, Correns, and Tschermak. It was only in subsequent years that animals were also shown to have segregation of genetic elements in the exact same manner as had been shown in plants. The story of developmental biology is different â while the development of plants has long been studied, the experimental and genetic approaches to developmental mechanism were developed via experiments on animals, and the importance of genes in development (e.g., Waddington, 1940) and their use for understanding developmental mechanisms came to botanical science much later â as late as the 1980s
The GJ1214 Super-Earth System: Stellar Variability, New Transits, and a Search for Additional Planets
The super-Earth GJ1214b transits a nearby M dwarf that exhibits 1% intrinsic
variability in the near-infrared. Here, we analyze new observations to refine
the physical properties of both the star and planet. We present three years of
out-of-transit photometric monitoring of the stellar host GJ1214 from the
MEarth Observatory and find the rotation period to be long, mostly likely an
integer multiple of 53 days, suggesting low levels of magnetic activity and an
old age for the system. We show such variability will not pose significant
problems to ongoing studies of the planet's atmosphere with transmission
spectroscopy. We analyze 2 high-precision transit light curves from ESO's Very
Large Telescope along with 7 others from the MEarth and FLWO 1.2 meter
telescopes, finding physical parameters for the planet that are consistent with
previous work. The VLT light curves show tentative evidence for spot
occultations during transit. Using two years of MEarth light curves, we place
limits on additional transiting planets around GJ1214 with periods out to the
habitable zone of the system. We also improve upon the previous photographic V
-band estimate for the star, finding V = 14.71 \pm 0.03.Comment: 16 pages, 10 figures, 6 tables, in emulateapj format. Published in
ApJ. Replaced a missing reference in section 6.
Effects of rasagiline, its metabolite aminoindan and selegiline on glutamate receptor mediated signalling in the rat hippocampus slice in vitro
In Situ Studies of the Primary Immune Response to (4-Hydroxy-3-Nitrophenyl)Acetyl. V. Affinity Maturation Develops in Two Stages of Clonal Selection
Single-Spin Addressing in an Atomic Mott Insulator
Ultracold atoms in optical lattices are a versatile tool to investigate
fundamental properties of quantum many body systems. In particular, the high
degree of control of experimental parameters has allowed the study of many
interesting phenomena such as quantum phase transitions and quantum spin
dynamics. Here we demonstrate how such control can be extended down to the most
fundamental level of a single spin at a specific site of an optical lattice.
Using a tightly focussed laser beam together with a microwave field, we were
able to flip the spin of individual atoms in a Mott insulator with
sub-diffraction-limited resolution, well below the lattice spacing. The Mott
insulator provided us with a large two-dimensional array of perfectly arranged
atoms, in which we created arbitrary spin patterns by sequentially addressing
selected lattice sites after freezing out the atom distribution. We directly
monitored the tunnelling quantum dynamics of single atoms in the lattice
prepared along a single line and observed that our addressing scheme leaves the
atoms in the motional ground state. Our results open the path to a wide range
of novel applications from quantum dynamics of spin impurities, entropy
transport, implementation of novel cooling schemes, and engineering of quantum
many-body phases to quantum information processing.Comment: 8 pages, 5 figure
- âŠ