15,188 research outputs found
Stability of Inhomogeneous Superstructures from Renormalized Mean-field Theory of the t--J Model
Using the t--J model (which can also include Coulomb repulsion) and the
``plain vanilla'' renormalized mean-field theory of Zhang et al. (1988),
stability of inhomogeneous 4a x 4a superstructures as those observed in
cuprates superconductors around hole doping 1/8 is investigated. We find a
non-uniform 4a x 4a bond order wave involving simultaneously small (~ 10^-2 t)
inhomogeneous staggered plaquette currents as well as a small charge density
modulation similar to pair density wave order. On the other hand, no supersolid
phase involving a decoupling in the superconducting particle-particle channel
is found.Comment: 4 page
Low Saturation Intensities in Two-Photon Ultracold Collisions
We have observed violet photon emission resulting from energy-pooling collisions between ultracold Rb atoms illuminated by two colors of near-resonant infrared laser light. We have used this emission as a probe of doubly excited state ultracold collision dynamics. We have observed the lowest saturation intensity for light-induced ultracold collisions seen to date which we identify as due to depletion of incoming ground state flux. We have also varied the detuning of the lasers which allows us to clearly identify the effect of spontaneous emission and optical shielding
Search for long lived heaviest nuclei beyond the valley of stability
The existence of long lived superheavy nuclei (SHN) is controlled mainly by
spontaneous fission and -decay processes. According to microscopic
nuclear theory, spherical shell effects at Z=114, 120, 126 and N=184 provide
the extra stability to such SHN to have long enough lifetime to be observed. To
investigate whether the so-called "stability island" could really exist around
the above Z, N values, the -decay half lives along with the spontaneous
fission and -decay half lives of such nuclei are studied. The
-decay half lives of SHN with Z=102-120 are calculated in a quantum
tunneling model with DDM3Y effective nuclear interaction using
values from three different mass formulae prescribed by Koura, Uno, Tachibana,
Yamada (KUTY), Myers, Swiatecki (MS) and Muntian, Hofmann, Patyk, Sobiczewski
(MMM). Calculation of spontaneous fission (SF) half lives for the same SHN are
carried out using a phenomenological formula and compared with SF half lives
predicted by Smolanczuk {\it et al}. Possible source of discrepancy between the
calculated -decay half lives of some nuclei and the experimental data
of GSI, JINR-FLNR, RIKEN are discussed. In the region of Z=106-108 with N
160-164, the -stable SHN is predicted to have
highest -decay half life () using
value from MMM. Interestingly, it is much greater than the recently measured
() of deformed doubly magic
nucleus. A few fission-survived long-lived SHN which are either -stable
or having large -decay half lives are predicted to exist near
, , and .
These nuclei might decay predominantly through -particle emission.Comment: 14 pages, 6 figures, 1 tabl
OH (1720 MHz) Masers: A Multiwavelength Study of the Interaction between the W51C Supernova Remnant and the W51B Star Forming Region
We present a comprehensive view of the W51B HII region complex and the W51C
supernova remnant (SNR) using new radio observations from the VLA, VLBA,
MERLIN, JCMT, and CSO along with archival data from Spitzer, ROSAT, ASCA, and
Chandra. Our VLA data include the first 400 cm (74 MHz) continuum image of W51
at high resolution (88 arcsec). The 400 cm image shows non-thermal emission
surrounding the G49.2-0.3 HII region, and a compact source of non-thermal
emission (W51B_NT) coincident with the previously-identified OH (1720 MHz)
maser spots, non-thermal 21 and 90 cm emission, and a hard X-ray source.
W51B_NT falls within the region of high likelihood for the position of TeV
gamma-ray emission. Using the VLBA three OH (1720 MHz) maser spots are detected
in the vicinity of W51B_NT with sizes of 60 to 300 AU and Zeeman effect
magnetic field strengths of 1.5 to 2.2 mG. The multiwavelength data demonstrate
that the northern end of the W51B HII region complex has been partly enveloped
by the advancing W51C SNR and this interaction explains the presence of W51B_NT
and the OH masers. This interaction also appears in the thermal molecular gas
which partially encircles W51B_NT and exhibits narrow pre-shock (DeltaV 5 km/s)
and broad post-shock (DeltaV 20 km/s) velocity components. RADEX radiative
transfer modeling of these two components yield physical conditions consistent
with the passage of a non-dissociative C-type shock. Confirmation of the
W51B/W51C interaction provides additional evidence in favor of this region
being one of the best candidates for hadronic particle acceleration known thus
far.Comment: Accepted to Ap
Tuberculosis Drug Resistance and Outcomes among Tuberculosis Inpatients in Lilongwe, Malawi
Setting/Objective: We evaluated clinical characteristics, yield of solid vs. liquid culture, polymerase chain reaction (PCR)-based drug-resistance profiles, and clinical outcomes of tuberculosis (TB) inpatients in Lilongwe, Malawi.Design: We enrolled adult patients admitted to the Bwaila TB Ward from Jan-Aug/2010. Evaluations included questionnaires, clinical exam, chest radiograph, HIV status, CD4 lymphocyte count, plasma HIVRNA and sputum analysis including Auramine-O stain, Lowenstein-Jensen (LJ) and Mycobacterial Growth Indicator Tube (MGIT) culture, and susceptibility testing using the HAIN GenoType® MTBDRplus.Results: Eighty-eight patients were enrolled (88% re-treatment, 42% smear positive, 93% pulmonary TB, 74% HIV co-infected). At baseline, 44/88 (50%) MGIT and 28 (32%) LJ cultures were positive with a mean time to positivity of 12.1 (Range 1-42) and 21.5 (Range 7-58) days, respectively. Four percent (3/77) of retreatment patients or 8% of the 38 MGIT+ PCR-confirmed retreatment cases had multi-drug resistant tuberculosis (MDR TB). One MDR TB patient was smear negative and only one MDR patient was identified with LJ. Lower mean hemoglobin at admission was associated with mortality (10.5 vs. 7.5; p<0.01; CI 101 9.8-11.0).Conclusions: The MDR TB burden among the retreatment population in Lilongwe, Malawi is similar to regional estimates by the WHO (7.7% 95% CI 0-18.1). MDR TB patients are not routinely identified with sputum smear or LJ, suggesting more efficient technology should be adopted
Basic Representations of A_{2l}^(2) and D_{l+1}^(2) and the Polynomial Solutions to the Reduced BKP Hierarchies
Basic representations of A_{2l}^(2) and D_{l+1}^(2) are studied. The weight
vectors are represented in terms of Schur's -functions. The method to get
the polynomial solutions to the reduced BKP hierarchies is shown to be
equivalent to a certain rule in Maya game.Comment: January 1994, 11 page
Theory of temperature dependence of the Fermi surface-induced splitting of the alloy diffuse-scattering intensity peak
The explanation is presented for the temperature dependence of the fourfold
intensity peak splitting found recently in diffuse scattering from the
disordered Cu3Au alloy. The wavevector and temperature dependence of the
self-energy is identified as the origin of the observed behaviour. Two
approaches for the calculation of the self-energy, the high-temperature
expansion and the alpha-expansion, are proposed. Applied to the Cu3Au alloy,
both methods predict the increase of the splitting with temperature, in
agreement with the experimental results.Comment: 4 pages, 3 EPS figures, RevTeX, submitted to J. Phys. Condens. Matter
(Letter to the Editor
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