5,204 research outputs found
Photoacoustic detection of stimulated emission pumping in p-difluorobenzene
Photoacoustic detection has been used to monitor a stimulated emission pumping process in pâdifluorobenzene. Using the Ă^(1)B_(2u)5^1 state as an intermediate, several vibrational levels of the ground electronic state were populated. The photoacoustic method is an attractive alternative to other detection techniques because of its sensitivity, simplicity, and its ability to differentiate between stimulated emission pumping and excited state absorption. An example of excited state absorption in aniline is given
Atomic structure of Mn wires on Si(001) resolved by scanning tunneling microscopy
At submonolayer coverage, Mn forms atomic wires on the Si(001) surface
oriented perpendicular to the underlying Si dimer rows. While many other
elements form symmetric dimer wires at room temperature, we show that Mn wires
have an asymmetric appearance and pin the Si dimers nearby. We find that an
atomic configuration with a Mn trimer unit cell can explain these observations
due to the interplay between the Si dimer buckling phase near the wire and the
orientation of the Mn trimer. We study the resulting four wire configurations
in detail using high-resolution scanning tunneling microscopy (STM) imaging and
compare our findings with STM images simulated by density functional theory.Comment: 4 pages, 4 figure
Field induced density wave in the heavy fermion compound CeRhIn5
Metals containing Ce often show strong electron correlations due to the
proximity of the 4f state to the Fermi energy, leading to strong coupling with
the conduction electrons. This coupling typically induces a variety of
competing ground states, including heavy-fermion metals, magnetism and
unconventional superconductivity. The d-wave superconductivity in CeTMIn5
(TM=Co, Rh, Ir) has attracted significant interest due to its qualitative
similarity to the cuprate high-Tc superconductors. Here, we show evidence for a
field induced phase-transition to a state akin to a density-wave (DW) in the
heavy fermion CeRhIn5, existing in proximity to its unconventional
superconductivity. The DW state is signaled by a hysteretic anomaly in the
in-plane resistivity accompanied by the appearance of non-linear electrical
transport at high magnetic fields (>27T), which are the distinctive
characteristics of density-wave states. The unusually large hysteresis enables
us to directly investigate the Fermi surface of a supercooled electronic system
and to clearly associate a Fermi surface reconstruction with the transition.
Key to our observation is the fabrication of single crystal microstructures,
which are found to be highly sensitive to "subtle" phase transitions involving
only small portions of the Fermi surface. Such subtle order might be a common
feature among correlated electron systems, and its clear observation adds a new
perspective on the similarly subtle CDW state in the cuprates.Comment: Accepted in Nature Communication
Estimation of genetic model parameters: Variables correlated with a quantitative phenotype exhibiting major locus inheritance
A major locus that is detected through its effect on one phenotype (a primary trait) may also affect other quantitative phenotypes or qualitative disease endpoints (secondary traits). The pattern of effects for the mutant allele. The effects are directly estimable when âmeasured genotypesâ or a tightly linked marker allow unambiguous assignment of major locus genotypes. When genotype assignments are ambiguous for a major locus detected through its effect on a quantitative primary trait, we propose estimators using genotypic probabilities. Making certain reasonable assumptions, we demonstrate asymptotic unbiasedness of these genotypic probability estimators of the genotypic means and variances for either the quantitative primary or secondary traits, of the covariances between quantitative primary and secondary traits, and of prevalences for the secondary qualitative traits. An important application of genotypic probability estimators is to define an effect of a major locus that cannot be detected upon analysis of the variable; for example, major locus effects may be defined for hypertension or blood pressure as secondary traits, but not detected as primary traits.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/101835/1/1370060203_ftp.pd
Time-resolved two-color photoacoustic and multiphoton ionization spectroscopy of aniline
The multiphoton ionization and photoacoustic signals from aniline have been detected as a function of time delay between two laser pulses of different wavelength. The first pulse excited the S0 â S1 0â0 transition. The second pulse either excited S1 to a higher singlet state, or a triplet state produced by intersystem crossing to a higher triplet state, depending on the time delay between pulses. Both ionization and dissociation processes are observed. By varying the conditions of excitation it appears that a given amount of energy can be selectively channeled almost exclusively into either ionization or dissociation pathways. The results are explained using a simple FranckâCondon factor model
High-energy overtone spectroscopy of some deuterated methanes
High-energy overtone photoacoustic spectroscopy of gas phase CHD3 (ÎÎœCH=5,6, and 7), CH2D2, CH3D, and CH4 (ÎÎœCH=6) is reported. The overtone and combination bands of CHD3 display partially resolved rotational structure with laser limited linewidths (~0.5 cm^â1). A combination sum analysis is used to generate excited state rotational constants B'. We present an analysis of the Fermi resonances of CHD3 which indicates strong interactions of the CH stretch with degenerate bending modes. The relative intensities of the Fermi interacting states are in agreement with those calculated from an analysis based on frequency shifts and a two or three level model. However, the rotational B' constants are not explained by such simple models indicating further interactions with states as yet unobserved. An upper limit of 10 cm^â1 is estimated for the splitting of the |6,0>± local mode states for CH2D2, giving support to a description based on the local mode picture. For CH3D and CH4 the spectra are apparently congested by overlapping overtone and combination bands and perhaps other mechanisms not identified in this work. Generally, our results emphasize the importance of the interactions of CH stretching with CH bending motions
Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5
Electronic nematics are exotic states of matter where electronic interactions
break a rotational symmetry of the underlying lattice, in analogy to the
directional alignment without translational order in nematic liquid crystals.
Intriguingly such phases appear in the copper- and iron-based superconductors,
and their role in establishing high-temperature superconductivity remains an
open question. Nematicity may take an active part, cooperating or competing
with superconductivity, or may appear accidentally in such systems. Here we
present experimental evidence for a phase of nematic character in the heavy
fermion superconductor CeRhIn5. We observe a field-induced breaking of the
electronic tetragonal symmetry of in the vicinity of an antiferromagnetic (AFM)
quantum phase transition at Hc~50T. This phase appears in out-of-plane fields
of H*~28T and is characterized by substantial in-plane resistivity anisotropy.
The anisotropy can be aligned by a small in-plane field component, with no
apparent connection to the underlying crystal structure. Furthermore no
anomalies are observed in the magnetic torque, suggesting the absence of
metamagnetic transitions in this field range. These observations are indicative
of an electronic nematic character of the high field state in CeRhIn5. The
appearance of nematic behavior in a phenotypical heavy fermion superconductor
highlights the interrelation of nematicity and unconventional
superconductivity, suggesting nematicity to be a commonality in such materials
The time-dependent expression of keratins 5 and 13 during the reepithelialization of human skin wounds
The time-dependent reepithelialization of 55 human surgical skin wounds with a wound age between 8h and more than 2 months was investigated by the immunohistochemical localization of cytokeratins 5 and 13. A complete, rebuilt epidermal layer over the wound area was first detectable in a 5-day-old wound, while all wounds of more than 18 days duration contained a completely reepithelialized wound area. Between 5 and 18 days the basal layer of keratinocytes showed â in contrast to normal skin â only some cells positive for cytokeratin 5. In some, but not all lesions with a wound age of 13 days or more, a basal cell layer completely staining for cytokeratin 5 was demonstrable. This staining pattern was found in all skin wounds with a wound age of more than 23 days. The immunohistochemical detection of cytokeratin 13 which can be observed regularly in non-cornifying squamous epithelia provides no information for the time-estimation of human skin wounds, since no significant temporary expression of this polypeptide seems to occur during the healing of human skin wounds
Inverse Low Gain Avalanche Detectors (iLGADs) for precise tracking and timing applications
Low Gain Avalanche Detector (LGAD) is the baseline sensing technology of the
recently proposed Minimum Ionizing Particle (MIP) end-cap timing detectors
(MTD) at the Atlas and CMS experiments. The current MTD sensor is designed as a
multi-pad matrix detector delivering a poor position resolution, due to the
relatively large pad area, around 1 ; and a good timing resolution,
around 20-30 ps. Besides, in his current technological incarnation, the timing
resolution of the MTD LGAD sensors is severely degraded once the MIP particle
hits the inter-pad region since the signal amplification is missing for this
region. This limitation is named as the LGAD fill-factor problem. To overcome
the fill factor problem and the poor position resolution of the MTD LGAD
sensors, a p-in-p LGAD (iLGAD) was introduced. Contrary to the conventional
LGAD, the iLGAD has a non-segmented deep p-well (the multiplication layer).
Therefore, iLGADs should ideally present a constant gain value over all the
sensitive region of the device without gain drops between the signal collecting
electrodes; in other words, iLGADs should have a 100 fill-factor by
design. In this paper, tracking and timing performance of the first iLGAD
prototypes is presented.Comment: Conference Proceedings of VCI2019, 15th Vienna Conference of
Instrumentation, February 18-22, 2019, Vienna, Austri
- âŠ