7,935 research outputs found
Extensive infrared spectroscopic study of CuO: signatures of strong spin-phonon interaction and structural distortion
Optical properties of single-crystal monoclinic CuO in the range 70 - 6000
\cm were studied at temperatures from 7 to 300 K. Normal reflection spectra
were obtained from the (001) and (010) crystal faces thus giving for the first
time separate data for the and phonon modes excited in the
purely transverse way (TO modes). Mode parameters, including polarizations of
the modes not determined by the crystal symmetry, were extracted by the
dispersion analysis of reflectivity curves as a function of temperature.
Spectra of all the components of the optical conductivity tensor were obtained
using the Kramers-Kronig method recently extended to the case of the
low-symmetry crystals. The number of strong phonon modes is in agreement with
the factor-group analysis for the crystal structure, currently accepted for the
CuO. However, several "extra" modes of minor intensity are detected. Comparison
of frequencies of "extra" modes with the available phonon dispersion curves
points to possible "diagonal" doubling of the unit cell \{{\bf a}, {\bf b},
{\bf c}\} \{{\bf a}+{\bf c}, {\bf b}, {\bf a}-{\bf c}\} and formation of
the superlattice. The previously reported softening of the mode
( 400 \cm) with cooling at is found to be 10 % for the TO
mode. The mode is very broad at high temperatures and strongly narrows in the
AFM phase. We attribute this effect to strong resonance coupling of this mode
to optical or acoustic bi-magnons and reconstruction of the magnetic
excitations spectrum at the N\'eel point. A significant anisotropy of
is observed: it was found to be 5.9 along the {\bf b}-axis,
6.2 along the {[}101{]} chains and 7.8 the {[}10{]} chains. The
"transverse" effective charge is value is about 2 electrons.Comment: 23 pages, 14 figures, REVTeX, submitted to PR
Computed tomography measures of nutrition in patients with end-stage liver disease provide a novel approach to characterize deficits
Aim
Patients with cirrhosis and end-stage liver disease (ESLD) develop severe nutrition deficits that impact on morbidity and mortality. Laboratory measures of nutrition fail to fully assess clinical deficits in muscle mass and fat stores. This study employs computed tomography imaging to assess muscle mass and subcutaneous and visceral fat stores in patients with ESLD.
Methods
This 1:1 case-control study design compares ESLD patients with healthy controls. Study patients were selected from a database of ESLD patients using a stratified method to assure a representative sample based on age, body mass index (BMI), gender, and model for end-stage liver disease score (MELD). Control patients were trauma patients with a low injury severity score (<10) who had a CT scan during evaluation. Cases and controls were matched for age +/- 5 years, gender, and BMI +/- 2.
Results
There were 90 subjects and 90 controls. ESLD patients had lower albumin levels (p<0.001), but similar total protein levels (p=0.72). ESLD patients had a deficit in muscle mass (-19%, p<0.001) and visceral fat (-13%, p<0.001), but similar subcutaneous fat (-1%, p=0.35). ESLD patients at highest risk for sarcopenia included those over age 60, BMI< 25.0, and female gender. We found degree of sarcopenia to be independent of MELD score.
Conclusions
These results support previous research demonstrating substantial nutrition deficits in ESLD patients that are not adequately measured by laboratory testing. Patients with ESLD have significant deficits of muscle and visceral fat stores, but a similar amount of subcutaneous fat
Dedication of the Palomar Observatory and the Hale Telescope
The dedication of the Palomar Observatory, if it were being held in England, would be accompanied by brilliant pageantry both of the state, with its knights, heralds, pursuivants, kings at arms, admirals and captains, and of the church with its bishops, priests and deacons, crucifiers and choirs; and I am sure that we feel the quality of religion in this ceremony. We would hear the choirs chanting in antiphony that great canticle which so delights the choir boys: Benedicite, omnia opera Domini
B-T phase diagram of CoCr2O4 in magnetic fields up to 14 T
We have measured the magnetization and specific heat of multiferroic CoCr2O4
in magnetic fields up to 14 T. The high-field magnetization measurements
indicate a new phase transition at T* = 5 - 6 K. The phase between T* and the
lock-in transition at 15 K is characterized by magnetic irreversibility. At
higher magnetic fields, the irreversibility increases. Specific-heat
measurements confirm the transition at T*, and also show irreversible behavior.
We construct a field-temperature phase diagram of CoCr2O4.Comment: 4 page
Adaptive feedback analysis and control of programmable stimuli for assessment of cerebrovascular function
The assessment of cerebrovascular regulatory mechanisms often requires flexibly controlled and precisely timed changes in arterial blood pressure (ABP) and/or inspired CO2. In this study, a new system for inducing variations in mean ABP was designed, implemented and tested using programmable sequences and programmable controls to induce pressure changes through bilateral thigh cuffs. The system is also integrated with a computer-controlled switch to select air or a CO2/air mixture to be provided via a face mask. Adaptive feedback control of a pressure generator was required to meet stringent specifications for fast changes, and accuracy in timing and pressure levels applied by the thigh cuffs. The implemented system consists of a PC-based signal analysis/control unit, a pressure control unit and a CO2/air control unit. Initial evaluations were carried out to compare the cuff pressure control performances between adaptive and non-adaptive control configurations. Results show that the adaptive control method can reduce the mean error in sustaining target pressure by 99.57 % and reduce the transient time in pressure increases by 45.21 %. The system has proven a highly effective tool in ongoing research on brain blood flow control
Detection of impaired cerebral autoregulation improves by increasing arterial blood pressure variability
Although the assessment of dynamic cerebral autoregulation (CA) based on measurements of spontaneous fluctuations in arterial blood pressure (ABP) and cerebral blood flow (CBF) is a convenient and much used method, there remains uncertainty about its reliability. We tested the effects of increasing ABP variability, provoked by a modification of the thigh cuff method, on the ability of the autoregulation index to discriminate between normal and impaired CA, using hypercapnia as a surrogate for dynamic CA impairment. In 30 healthy volunteers, ABP (Finapres) and CBF velocity (CBFV, transcranial Doppler) were recorded at rest and during 5% CO(2) breathing, with and without pseudo-random sequence inflation and deflation of bilateral thigh cuffs. The application of thigh cuffs increased ABP and CBFV variabilities and was not associated with a distortion of the CBFV step response estimates for both normocapnic and hypercapnic conditions (P=0.59 and P=0.96, respectively). Sensitivity and specificity of CA impairment detection were improved with the thigh cuff method, with the area under the receiver-operator curve increasing from 0.746 to 0.859 (P=0.031). We conclude that the new method is a safe, efficient, and appealing alternative to currently existing assessment methods for the investigation of the status of CA
Impact of Brown Midrib Trait on the Decomposition Rate of Sorghum-Sudangrass Residue in Pastures
Sorghum-sudangrass (Sorghum bicolor var. bicolor x bicolor var. sudanense) can provide high quality summer grazing. Some varieties possess the brown midrib (BMR) trait which results in reduced lignin resulting in higher digestibility and animal performance. If microbes in the rumen can digest BMR sorghum-sudangrass more completely, then soil macro/micro flora and fauna may do so as well. This could result in nutrients being returned to the soil faster from plants containing the BMR trait. The objective of this study was to determine the decomposition rate of BMR and non-BMR sorghumsudangrass. The experimental design was a random complete with four replications. Sorghum-sudangrass with and without the BMR trait was placed in litter decomposition bags as whole plants or divided into leaves and stems. A composite sample was taken when bags were loaded to determine initial dry matter. Loaded bags were then placed on the soil surface in a pasture and collected at 1, 2, 3, 4, 6, 8, 10, 12, 14, or 16 weeks after placement. Upon collection plant material was dried for 3-days at 55°C in a forced air oven. Dry weights at each collection date were subtracted from the initial dry weight to determine total DM loss. The BMR trait did not impact dry matter loss in the leaves. Stems possessing the BMR trait lost dry matter at a greater rate resulting in dry matter losses at 14 weeks of 78 and 68% and 59 and 47% for the BMR and non-BMR varieties in trials 1 and 2, respectively. Whole plants showed limited differences in dry matter loss at 14 weeks after placement
Establishing Observational Baselines for Two δ Scuti Variables: V966 Herculis and V1438 Aquilae
We have examined the previously understudied δ Scuti stars V966 Herculis and V1438 Aquilae. We find that V966 Her is a stable pulsator with a refined period of 0.1330302 days with a full V amplitude of 0.096 mag. We also find that V966 Her has an average radial velocity of +7.8 km s-1, a full radial velocity amplitude of 7.6 km s-1, and a v sin i = 63.8 km s-1. For V1438 Aql we report a revised Hipparcos period of 0.1612751 days with a full amplitude of 0.056. The average radial velocity is found to be -43 km s-1, with full amplitude of 9.7 km s-1, and a v sin i = 76.7 km s-1. Due to some anomalies seen in V1438 Aql we feel that a much larger photometric and spectroscopic campaign is required to determine the true nature of this star
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