12,326 research outputs found
Unusual light spectra from a two-level atom in squeezed vacuum
We investigate the interaction of an atom with a multi-channel squeezed
vacuum. It turns out that the light coming out in a particular channel can have
anomalous spectral properties, among them asymmetry of the spectrum, absence of
the central peak as well as central hole burning for particular parameters. As
an example plane-wave squeezing is considered. In this case the above phenomena
can occur for the light spectra in certain directions. In the total spectrum
these phenomena are washed out.Comment: 16 pages, LaTeX, 3 figures (included via epsf
Team Cognitive Ability as a Predictor of Team Performance
This manuscript presents two studies of the relationship between team cognitive ability (average Scholastic Aptitude Test score of team members) and team performance (a subjective coach\u27s evaluation and an objective measure using Sagarin\u27s Power Rankings) among NCAA Division 1 Men\u27s Basketball teams. Study 1 was conducted following the 1991-92 season whereas Study 2 was conducted during the 1993-94 season. Both studies indicated that team cognitive ability was significantly related to the coach\u27s evaluation but not to the power ranking measure, and that team strategy moderated the relationship between cognitive ability and the coach\u27s evaluation of performance. Cognitive ability moderated the relationship between team strategy and power ranking, but the nature of the interaction was different across the two studies
Fast Desynchronization For Decentralized Multichannel Medium Access Control
Distributed desynchronization algorithms are key to wireless sensor networks
as they allow for medium access control in a decentralized manner. In this
paper, we view desynchronization primitives as iterative methods that solve
optimization problems. In particular, by formalizing a well established
desynchronization algorithm as a gradient descent method, we establish novel
upper bounds on the number of iterations required to reach convergence.
Moreover, by using Nesterov's accelerated gradient method, we propose a novel
desynchronization primitive that provides for faster convergence to the steady
state. Importantly, we propose a novel algorithm that leads to decentralized
time-synchronous multichannel TDMA coordination by formulating this task as an
optimization problem. Our simulations and experiments on a densely-connected
IEEE 802.15.4-based wireless sensor network demonstrate that our scheme
provides for faster convergence to the steady state, robustness to hidden
nodes, higher network throughput and comparable power dissipation with respect
to the recently standardized IEEE 802.15.4e-2012 time-synchronized channel
hopping (TSCH) scheme.Comment: to appear in IEEE Transactions on Communication
The use of the McIlwain L-parameter to estimate cosmic ray vertical cutoff rigidities for different epochs of the geomagnetic field
Secular changes in the geomagnetic field between 1955 and 1980 have been large enough to produce significant differences in both the verical cutoff rigidities and in the L-value for a specified position. A useful relationship employing the McIlwain L-parameter to estimate vertical cutoff rigidities has been derived for the twenty-five year period
Research study of droplet sizing technology leading to the development of an advanced droplet sizing system
An instrument to measure the size and velocity of droplets was developed. The instrument uses one of two techniques, as appropriate. In the first technique two small laser beams of one color identify the center of a larger laser beam of a different color. This defines a region of almost uniform intensity where the light scattered by the individual droplets can be related to their size. The first technique uses the visibility of a Doppler burst and validates it against the peak intensity of the signal's pedestal. Results are presented for monodisperse, bimodal, trimodal, and polydisperse sprays produced by the Berglund-Liu droplet generator and a pressure nozzle. Size distributions of a given spray obtained using three different size ranges show excellent self-consistency in the overlapping region. Measurements of sprays of known characteristics exhibit errors in the order of 10%. The principles of operation and design criteria of the instrument are discussed in great detail
Deep carbon storage potential of buried floodplain soils.
Soils account for the largest terrestrial pool of carbon and have the potential for even greater quantities of carbon sequestration. Typical soil carbon (C) stocks used in global carbon models only account for the upper 1āmeter of soil. Previously unaccounted for deep carbon pools (>1ām) were generally considered to provide a negligible input to total C contents and represent less dynamic C pools. Here we assess deep soil C pools associated with an alluvial floodplain ecosystem transitioning from agricultural production to restoration of native vegetation. We analyzed the soil organic carbon (SOC) concentrations of 87 surface soil samples (0-15ācm) and 23 subsurface boreholes (0-3ām). We evaluated the quantitative importance of the burial process in the sequestration of subsurface C and found our subsurface soils (0-3ām) contained considerably more C than typical C stocks of 0-1ām. This deep unaccounted soil C could have considerable implications for global C accounting. We compared differences in surface soil C related to vegetation and land use history and determined that flooding restoration could promote greater C accumulation in surface soils. We conclude deep floodplain soils may store substantial quantities of C and floodplain restoration should promote active C sequestration
Response of pteropods and foraminifera to changing pCO2 and pH: Examples from the Mediterranean Sea
Queer beauty: illness, illegitimacy and visibility in Dickens's Bleak House and its 2005 BBC adaptation
The blue suns of 1831: was the eruption of Ferdinandea, near Sicily, one of the largest volcanic climate forcing events of we nineteenth century?
One of the largest climate forcing eruptions of the nineteenth century was, until recently, believed to have taken place at the Babuyan Claro volcano, in the Philippines, in 1831. However, a recent investigation found no reliable evidence of such an eruption, suggesting that the 1831 eruption must have taken place elsewhere. We here present our newly compiled dataset of reported observations of a blue, purple and green sun in August 1831, which we use to reconstruct the transport of a stratospheric aerosol plume from that eruption. The source of the aerosol plume is identified as the eruption of Ferdinandea, which took place about 50ākm off the south-west coast of Sicily (37.1āāN, 12.7āāE), in July and August 1831. The modest magnitude of this eruption, assigned a volcanic explosivity index (VEI) of 3, has commonly caused it to be discounted or overlooked when identifying the likely source of the stratospheric sulfate aerosol in 1831. It is proposed, however, that convective instability in the troposphere contributed to aerosol reaching the stratosphere and that the aerosol load was enhanced by addition of a sedimentary sulfur component to the volcanic plume. Thus, one of the largest climate forcing volcanic eruptions of the nineteenth century would effectively have been hiding in plain sight, arguably ālowering the barā for the types of eruptions capable of having a substantial climate forcing impact. Prior estimates of the mass of stratospheric sulfate aerosol responsible for the 1831 Greenland ice core sulfate deposition peaks which have assumed a source eruption at a low-latitude site will, therefore, have been overstated. The example presented in this paper serves as a useful reminder that VEI values were not intended to be reliably correlated with eruption sulfur yields unless supplemented with compositional analyses. It also underlines that eye-witness accounts of historical geophysical events should not be neglected as a source of valuable scientific data
Expression of CCAAT/Enhancer Binding Proteins (C/EBP) is Associated with Squamous Differentiation in Epidermis and Isolated Primary Keratinocytes and is Altered in Skin Neoplasms
The epidermis is a stratified squamous epithelium composed primarily of keratinocytes that undergo sequential changes in gene expression during differentiation. CCAAT/enhancer binding proteins (C/EBP) are members of the bZIP family of DNA binding proteins/transcription factors. Northern analysis demonstrated that C/EBPĪ±, C/EBPĪ², and C/EBPĪ“ mRNA are expressed in mouse epidermis and their mRNA levels were generally greater than those observed in other tissues known to express high levels of C/EBP. Western analysis of isolated epidermal cell nuclei demonstrated the presence of a 42 and 30 kDa C/EBPĪ± protein and 35 kDa C/EBPĪ² protein. Immunohistochemical localization of C/EBPĪ± and C/EBPĪ² in intact interfollicular epidermis revealed that C/EBPĪ² expression is exclusive to the nuclei of a three-cell cluster of suprabasal keratinocytes that is morphologically consistent with the central column of the epidermal proliferative unit, and that C/EBPĪ± is expressed in the nuclei and cytoplasm of suprabasal keratinocytes and weakly expressed in a perinuclear manner in some basal keratinocytes. In squamous cell carcinomas the expression of C/EBPĪ± and C/EBPĪ² was greatly diminished as both the intensity of nuclear staining and the number of cells expressing C/EBPĪ± and C/EBPĪ² were reduced. In isolated primary mouse keratinocytes, calcium-induced differentiation was accompanied by specific temporal changes in the expression of C/EBPĪ±, C/EBPĪ², and C/EBPĪ“ mRNA and C/EBPĪ± and C/EBPĪ² protein. These results implicate a role for the C/EBP family in the regulation of genes involved in or specifically expressed during the process of squamous differentiation in epidermis
- ā¦