2,720 research outputs found
Mineral fabrication and golgi apparatus activity in the mouse calvarium
There is diverse opinion about the mechanism of bone mineralization with only intermittent reports of any direct organellar role played by the golgi apparatus (juxtanuclear body). Light and laser confocal microscopy was combined with electron microscopy and elemental EDX (energy dispersive X-ray microanalysis) in comparing “young” osteocytes in situ in fresh and “slam” frozen developing mouse calvarium, with similar cells (MC3T3-E1) maintained in vitro. The distribution of “nascent” electron dense mineral was examined histochemically (von Kossa, GBHA), including tetracycline (TC) staining as a fluorescent complex with bone salt, while golgi body activity was demonstrated by transfection with a specific green fluorescent construct (GFP/mannosidase II). In tissue culture golgi body activity and mineralization were both blocked by brefeldin A (an established golgi inhibitor) and restored by forskolin, enabling an association with mineral fabrication to be quantified as changing fluorescence intensity (AU) of GFP or TC markers. Results from osteocytes in situ supported previous descriptions of intracellular electron dense objects (microspheres and nanospheres) in a juxtanuclear pattern, containing Ca, P and transitory Si, in a spectrum recapitulated in the calcifying culture after 10 days, when GFP fluorophore surged from 71.7 ± 1.4SD to 133.7 ± 2.7SD AU by 14 days (p < 0.0001). At this stage TC fluorophore mean intensity was 23.8 ± 3.7SD AU (14 days) rising to 45.0 ± 5.1SD AU by 17 days, compared to its stationary 21.7 ± 3.6SD when treated 3 days previously with BFA golgi inhibitor (p < 0.0001), until forskolin reversal. It was concluded from the changing juxtanuclear morphology, Si mineralization mediation and the variably controlled activity versus stasis that the inorganic phase of bone is a complex golgi-directed fabrication with implications for bone matrix biology and evolution
Circles Minimize most Knot Energies
We define a new class of knot energies (known as renormalization energies)
and prove that a broad class of these energies are uniquely minimized by the
round circle. Most of O'Hara's knot energies belong to this class. This proves
two conjectures of O'Hara and of Freedman, He, and Wang. We also find energies
not minimized by a round circle. The proof is based on a theorem of G. Luko on
average chord lengths of closed curves.Comment: 15 pages with 3 figures. See also http://www.math.sc.edu/~howard
Brane Couplings from Bulk Loops
We compute loop corrections to the effective action of a field theory on a
five-dimensional orbifold. We find that the quantum loop effects of
interactions in the bulk produce infinite contributions that require
renormalization by four-dimensional couplings on the orbifold fixed planes.
Thus bulk couplings give rise to renormalization group running of brane
couplings.Comment: 10 pages, Latex with pictex figure
Rapid readout of a register of qubits using open loop quantum control
Measurements are a primitive for characterizing quantum systems. Reducing the
time taken to perform a measurement may be beneficial in many areas of quantum
information processing. We show that permuting the eigenvalues of the state
matrix in the logical basis, using open loop control, provides a
reduction in the measurement time, where is the number of qubits in the
register. This reduction is of the same order as the (previously introduced)
locally optimal feedback protocol. The advantage of the open loop protocol is
that it is far less difficult experimentally. Because the control commutes with
the measured observable at all times, our rapid measurement protocol could be
used for characterizing a quantum system, by state or process tomography, or to
implement measurement-based quantum error correction
Physics Case for the ILC Project: Perspective from Beyond the Standard Model
The International Linear Collider (ILC) has recently proven its technical
maturity with the publication of a Technical Design Report, and there is a
strong interest in Japan to host such a machine. We summarize key aspects of
the Beyond the Standard Model physics case for the ILC in this contribution to
the US High Energy Physics strategy process. On top of the strong guaranteed
physics case in the detailed exploration of the recently discovered Higgs
boson, the top quark and electroweak precision measurements, the ILC will offer
unique opportunities which are complementary to the LHC program of the next
decade. Many of these opportunities have connections to the Cosmic and
Intensity Frontiers, which we comment on in detail. We illustrate the general
picture with examples of how our world could turn out to be and what the ILC
would contribute in these cases, with an emphasis on value-added beyond the
LHC. These comprise examples from Supersymmetry including light Higgsinos, a
comprehensive bottom-up coverage of NLSP-LSP combinations for slepton, squark,
chargino and neutralino NLSP, a stau-coannihilation dark matter scenario and
bilinear R-parity violation as explanation for neutrino masses and mixing, as
well as generic WIMP searches and Little Higgs models as non-SUSY examples.Comment: 20 pages, 10 figures. Contributed to Snowmass Community Summer Study
201
Measurements of the ClO radical vibrational band intensity and the ClO + ClO + M reaction product
There is considerable interest in the kinetics and concentrations of free radicals in the stratosphere. Chlorine monoxide is a critically important radical because of its role in catalytic cycles for ozone depletion. Depletion occurs under a wide variety of conditions including the Antarctic spring when unusual mechanisms such as the BrO sub x/ClO sub x, ClO dimer (Cl sub 2 O sub 2), and ClO sub x/HO sub x cycles are suggested to operate. Infrared spectroscopy is one of the methods used to measure ClO in the stratosphere (Menzies 1979 and 1983; Mumma et al., 1983). To aid the quantification of such infrared measurements, researchers measured the ClO ground state fundamental band intensity
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