1,133 research outputs found
Can the Renormalization Group Improved Effective Potential be used to estimate the Higgs Mass in the Conformal Limit of the Standard Model?
We consider the effective potential in the standard model with a single
Higgs doublet in the limit that the only mass scale present is
radiatively generated. Using a technique that has been shown to determine
completely in terms of the renormalization group (RG) functions when using the
Coleman-Weinberg (CW) renormalization scheme, we first sum leading-log (LL)
contributions to using the one loop RG functions, associated with five
couplings (the top quark Yukawa coupling , the quartic coupling of the Higgs
field , the SU(3) gauge coupling , and the couplings
and ). We then employ the two loop RG functions with the three couplings
, , to sum the next-to-leading-log (NLL) contributions to and
then the three to five loop RG functions with one coupling to sum all the
contributions to . In order to compute these sums, it is
necessary to convert those RG functions that have been originally computed
explicitly in the minimal subtraction (MS) scheme to their form in the CW
scheme. The Higgs mass can then be determined from the effective potential: the
result is decreases to at
order and at order. No reasonable
estimate of can be made at orders or . This is taken
to be an indication that this mechanism for spontaneous symmetry breaking is in
fact viable, though one in which there is slow convergence towards the actual
value of . The mass is argued to be an upper bound on
.Comment: 24 pages, 5 figures. Updated version contains new discussion,
references, figures, and corrects errors in reference
A Laboratory Investigation of Supersonic Clumpy Flows: Experimental Design and Theoretical Analysis
We present a design for high energy density laboratory experiments studying
the interaction of hypersonic shocks with a large number of inhomogeneities.
These ``clumpy'' flows are relevant to a wide variety of astrophysical
environments including the evolution of molecular clouds, outflows from young
stars, Planetary Nebulae and Active Galactic Nuclei. The experiment consists of
a strong shock (driven by a pulsed power machine or a high intensity laser)
impinging on a region of randomly placed plastic rods. We discuss the goals of
the specific design and how they are met by specific choices of target
components. An adaptive mesh refinement hydrodynamic code is used to analyze
the design and establish a predictive baseline for the experiments. The
simulations confirm the effectiveness of the design in terms of articulating
the differences between shocks propagating through smooth and clumpy
environments. In particular, we find significant differences between the shock
propagation speeds in a clumpy medium compared to a smooth one with the same
average density. The simulation results are of general interest for foams in
both inertial confinement fusion and laboratory astrophysics studies. Our
results highlight the danger of using average properties of inhomogeneous
astrophysical environments when comparing timescales for critical processes
such as shock crossing and gravitational collapse times.Comment: 7 pages, 6 figures. Submitted to the Astrophysical Journal. For
additional information, including simulation animations and the pdf and ps
files of the paper with embedded high-quality images, see
http://pas.rochester.edu/~wm
Perforated Sheets as the Porous Material for a Suction-flap Application
Two-dimensional tests were made of an NACA 0006 airfoil with area suction applied to a porous region on a 0.3-chord trailing-edge flap deflected 50 degrees. The lift with suction approached the value computed from thin-airfoil theory. The lift gains and suction quantity requirements were unaffected by the perforation patterns of the surface over a wide range of hole sizes and spacings
Cutaneous leiomyosarcoma arising in a smallpox scar
BACKGROUND: Cutaneous leiomyosarcoma (CLM) is a very rare smooth muscle tumour that accounts for about 2–3% of all superficial soft tissue sarcomas. Although the development of various malignancies in scar tissue is well known, we report the first case of a CLM developing in a small pox scar. CASE PRESENTATION: A 66-year-old man presented with a painless, slow-growing lump in a small pox scar on his left shoulder. Histological biopsies showed the lesion to be a primary, well-differentiated cutaneous leiomyosarcoma. A CT scan of the thorax was conducted, which showed no signs of metastases. The complete lesion was then surgically excised, and histopathological examination revealed a radically excised cutaneous type leiomyosarcoma After 13 months’ review the patient was doing well with no evidence of tumour recurrence. CONCLUSIONS: This is the first report of a CLM arising in a small pox scar. Although the extended time interval between scarring and malignant changes makes it difficult to advise strict follow-up for patients with small pox scars, one should be aware that atypical changes and/or symptoms occurring in a small pox scar could potentially mean malignant transformation
Synchronizing Sequencing Software to a Live Drummer
Copyright 2013 Massachusetts Institute of Technology. MIT allows authors to archive published versions of their articles after an embargo period. The article is available at
New Directions in Degenerate Dipolar Molecules via Collective Association
We survey results on the creation of heteronuclear Fermi molecules by tuning
a degenerate Bose-Fermi mixture into the neighborhood of an association
resonance, either photoassociation or Feshbach, as well as the subsequent
prospects for Cooper-like pairing between atoms and molecules. In the simplest
case of only one molecular state, corresponding to either a Feshbach resonance
or one-color photoassociation, the system displays Rabi oscillations and rapid
adiabatic passage between a Bose-Fermi mixture of atoms and fermionic
molecules. For two-color photoassociation, the system admits stimulated Raman
adiabatic passage (STIRAP) from a Bose-Fermi mixture of atoms to stable Fermi
molecules, even in the presence of particle-particle interactions. By tailoring
the STIRAP sequence it is possible to deliberately convert only a fraction of
the initial atoms, leaving a finite fraction of bosons behind to induce
atom-molecule Cooper pairing via density fluctuations; unfortunately, this
enhancement is insufficient to achieve a superfluid transition with present
ultracold technology. We therefore propose the use of an association resonance
that converts atoms and diatomic molecules (dimers) into triatomic molecules
(trimers), which leads to a crossover from a Bose-Einstein condensate of
trimers to atom-dimer Cooper pairs. Because heteronuclear dimers may possess a
permanent electric dipole moment, this overall system presents an opportunity
to investigate novel microscopic physics.Comment: 10 pages, 5 figures, 77+ references, submitted to Euro. Phys. J.
topical issue on "Ultracold Polar Molecules: Formation and Collisions
Alternative Chelator for 89Zr Radiopharmaceuticals: Radiolabeling and Evaluation of 3,4,3-(LI-1,2-HOPO)
Zirconium-89 is an effective radionuclide for antibody-based positron emission tomography (PET) imaging because its physical half-life (78.41 h) matches the biological half-life of IgG antibodies. Desferrioxamine (DFO) is currently the preferred chelator for 89Zr4+; however, accumulation of 89Zr in the bones of mice suggests that 89Zr4+ is released from DFO in vivo. An improved chelator for 89Zr4+ could eliminate the release of osteophilic 89Zr4+ and lead to a safer PET tracer with reduced background radiation dose. Herein, we present an octadentate chelator 3,4,3-(LI-1,2-HOPO) (or HOPO) as a potentially superior alternative to DFO. The HOPO ligand formed a 1:1 Zr-HOPO complex that was evaluated experimentally and theoretically. The stability of 89Zr-HOPO matched or surpassed that of 89Zr-DFO in every experiment. In healthy mice, 89Zr-HOPO cleared the body rapidly with no signs of demetalation. Ultimately, HOPO has the potential to replace DFO as the chelator of choice for 89Zr-based PET imaging agents
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