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Rate equations describing the dynamic processes in erbium (Er3+)-doped pentaphosphate crystals were developed to obtain the population processes of all levels of Er3+ ions in pentaphosphate ErP5O14 crystals under 650 nm laser excitation. The effects of pump power on the population (rho) dynamic process were analyzed. The spontaneous radiative processes, multiphonon nonradiative processes, absorption of the pump photons, corresponding stimulated radiation processes, and all other possible energy transfer processes between Er3+ ions were included in the rate equations. The pump power was assumed to be constant with time (t). Considering that the equation rho(t(0)+Deltat)=rho(t(0))+(drho/dt)Deltat would be held if Deltat was small enough and using the initial condition rho(1)=1.0, rho(i)=0(inot equal1), the time-dependent populations of all states could be obtained from the rate equations, from which the steady-state solution of the rate equation was deduced. The comprehensive study of the population dynamic process of all energy-level Er3+ ions in ErP5O14 crystal when excited by 100 mW-10(7) W has resulted in the conclusion that the strong upconversion luminescence would behave excellently when 650 nm pump laser power reaches the level of 1000-10(5) W. The representative population dynamic process when excited by 10(5) W laser power indicates I-4(15/2) and F-4(9/2) levels have a kind of great takeover co-contribution in up-converting population to higher states. The steady-state population probability of I-4(15/2) is as small as 0.0617. The population of the F-4(9/2) state increases rapidly to about a 0.362 high level and sequentially decreases smoothly to a stable value of about a 0.0374 low level, which implies a population already having been upconverted to higher level. Excellent results clearly exhibit that the main up-conversion luminescent level S-4(3/2) has a great population probability of about 0.212, which results in a strong up-conversion luminescence of 543 nm, and it is so exciting that a very strong 379 nm blue up-conversion luminescence could be achieved when 650 nm pump laser power is enhanced to the level of 1000-10(5) W. The results of this article are significant both to science and applications. (C) 2002 American Institute of Physics.

Depolarized light scattering susceptibility spectra of orthoterphenyl (OTP) were analyzed using the idealized and extended versions of mode coupling theory (MCT). The extended MCT fits were combined with KWW fits to the α peaks to provide combined α–β fits from which the KWW stretching coefficient βK was determined. βK was found to be nearly independent of temperature, in agreement with the asymptotic prediction of MCT. The spectra were also analyzed with a five-function phenomenological model developed by Patkowski et al. [J. Non-Cryst. Solids 172–174 (1994) 52]. While this model gives excellent fits to the spectra, we found that it is not able to determine βK uniquely unless other parameters are artificially constrained. Here, and in comparing light scattering and dielectric data for salol, we find the claim that βK approaches 1 at high temperatures not to be justified by the experimental data.

Five years ago, preliminary light scattering studies in our laboratory of the mixed-salt glassforming material CKN (calcium potassium nitrate) revealed spectral structure and scaling properties strikingly similar to the predictions of the mode coupling theory of the liquid glass transition developed by Wolfgang Gotze and his coworkers. Initial correspondence and discussions in 1991 began a collaboration which has grown steadily and has been immensely satisfying and productive. Wolfgang Gotze and his coworkers have constructed the first coherent dynamical theory of supercooled liquids and the glass transition, and he has been exceptionally helpful in working with experimentalists to make critical tests of the theory through detailed data analysis. I have learned much physics from our discussions and have come to deeply prize the friendship and warmth that has characterized our collaboration. Wolfgang and his students have given generously of their time and effort, and this generosity is deeply appreciated. Much work remains to be done. Wolfgang and his group have worked steadily to complete the theory and extend its range of validity; new experiments are needed to test their predictions in detail. I hope to continue to participate in this effort and look forward enthusiastically to our continued collaboration Anyone entering the field of glass transition research will be immediately confronted by a large and frequently contradictory literature spanning over 100 years. Many theoretical papers have appeared, each claiming to “explain” the liquid-glass transition. These theories often contain unstated approximations or imprecisely defined quantities (e.g., the free volume), and their assumptions are usually incompatible with those of other competing theories. Experimental papers (with some exceptions) usually present a limited set of data which is compared with a single favored theory, bypassing the effort required to carry out detailed comparisons with different theories. There is clearly a serious need to begin intercomparing the many competing current theories. We have recently begun to carry out a critical review of existing theories of the liquid-glass transition and the structure and dynamics of the glassy state. Our plan is to use a variety of experimental data, primarily dynamical data obtained from spectroscopic studies of various glasses and supercooled liquids, to carry out comparative fits to various theories. The goal of this program is to determine if one (or more) of the currently available theories, or some combination of these theories, can provide satisfactory descriptions of a range of different experimental data; concurrently, we will try to see if some theories can be definitely shown to be inapplicable on this basis. This is a large program which is still in its early stages. What follows, therefore, is a preliminary report that should be viewed as “work in progress” to be extended as the analysis proceeds.

Depolarized light scattering spectra of orthoterphenyl were analyzed with both the ide­ alized and extended versions of mode coupling theory. The idealized MCT analysis gave ..\ = 0.72 (a= 0.318) and Tc "'290 K, in agreement with previous neutron and light scat­ tering results. The extended MCT analysis gave ,\ = 0.76 (a = 0.30) and Tc "' 276 K, 14 K lower than the idealized result. For the ten spectra at T 2': 320 K where a-peaks were observed, direct KWW fits gave f3K ""0.78 with a slight trend of decreasing f3K with increasing temperature. Fits to Ta(T) gave Tc "'274 K, close to the extended MCT result. Finally, in an effort to resolve the ambiguity in a-peak fits due to overlap of the a and (3 spectral regions, we performed a combined a- (3 fit to six spectra for T 2 320 K. The results suggest a temperature-independent f3K = 0.79.

The red panda (Ailurus fulgens) is a quadrupedal arboreal animal primarily distributed in the Himalayas and southern China. It is a species commonly kept in zoological collections. This study was carried out to describe the morphology of the pelvis and hind limb of the red panda evidenced by gross osteology, radiography and computed tomography as a reference for clinical use and identification of skeletons. Radiography of the pelvis and right hind limb was performed in nine and seven animals, respectively. Radiographic findings were correlated with bone specimens from three adult animals. Computed tomography of the torso and hind limb was performed in one animal. The pelvic bone had a wide ventromedial surface of the ilium. The trochlea of the femur was wide and shallow. The patella was similar to that seen in feline species. The medial fabella was not seen radiographically in any animal. The cochlea grooves of the tibia were shallow with a poorly defined intermediate ridge. The trochlea of the talus was shallow and presented with an almost flattened medial ridge. The tarsal sesamoid bone was always present. The lateral process of the base of the fifth metatarsal (MT) bone was directed laterally. The MT bones were widely spaced. The morphology of the pelvis and hind limb of the red panda indicated flexibility of the pelvis and hind limb joints as an adaptation to an arboreal quadrupedal lifestyle.

There is limited information available on the morphology of the thoracic limb of the ring-tailed lemur (Lemur catta). This study describes the morphology of the thoracic limb of captive ring-tailed lemurs evidenced by gross osteology and radiography as a guide for clinical use. Radiographic findings of 12 captive ring-tailed lemurs are correlated with bone specimens of three adult animals. The clavicle is well developed. The scapula has a large area for the origin of the m. teres major. The coracoid and hamate processes are well developed. The lateral supracondylar crest and medial epicondyle are prominent. The metacarpal bones are widely spread, and the radial tuberosity is prominent. These features indicate the presence of strong flexor muscles and flexibility of thoracic limb joints, which are important in arboreal quadrupedal locomotion. Furthermore, an ovoid ossicle is always seen at the inter-phalangeal joint of the first digit. Areas of increased soft tissue opacity are superimposed over the proximal half of the humerus and distal half of the antebrachium in male animals as a result of the scent gland. Knowledge of the morphology of the thoracic limb of individual species is important for accurate interpretation and diagnosis of musculoskeletal diseases.

Light scattering investigations of supercooled liquids approaching the liquid-glass transition have revealed susceptibility spectra strikingly similar to those predicted by the mode coupling theory. The experimental procedure is described, and fits of the data to both the idealized and extended versions of the theory are reviewed.

In family Lemuridae, anatomical variations exist. Considering its conservation status (near threatened) and presence of similarities between strepsirrhines and primitive animals, it was thought to be beneficial to describe the gross osteology and radiographic anatomy of the pelvis and hind limb of ring-tailed lemurs (Lemur catta) as a reference for clinical use and species identification. Radiography was performed in 14 captive adult ring-tailed lemurs. The radiographic findings were correlated with bone specimens from two adult animals. Additionally, computed tomography of the hind limbs was performed in one animal. The pelvic bone has a well-developed caudal ventral iliac spine. The patella has a prominent tuberosity on the cranial surface. The first metatarsal bone and digit 1 are markedly stouter than the other metatarsal bones and digits with medial divergence from the rest of the metatarsal bones and digits. Ossicles were seen in the lateral meniscus, inter-phalangeal joint of digit 1 and in the infrapatellar fat pad. Areas of mineral opacity were seen within the external genitalia, which are believed to be the os penis and os clitoris. Variations exist in the normal osteology and radiographic appearance of the pelvis and hind limb of different animal species. The use of only atlases from domestic cats and dogs for interpretative purposes may be misleading.

Background Normal ultrasonography of non-reproductive abdominal and male reproductive anatomy in the vervet monkey were prospectively assessed. This has not been previously reported. Methods Ten non-sexually active male and 10 non-gravid female clinically healthy vervet monkeys between 5 and 12 years of age and weighing between 3.13 and 6.85 kg were evaluated with ultrasound. Individuals were randomly divided by gender groups into one of two immobilization protocols and scanned at 18.0 MHz. Results High-quality images of the liver, gallbladder, kidneys, urinary bladder, spleen, adrenal glands, gastrointestinal tract, and testes were acquired. The prostate was never visualized. Abdominal lymph nodes other than an ileocolic, the pancreas, and the female reproductive tract were not evaluated. Gastric and duodenal motility were significantly different between immobilization protocols (P

Depolarized light-scattering measurements have revealed the dynamics of CaKNO 3 and salol near their liquid-glass transition temperatures in the frequency range of ∼ 0.2 GHz to ∼ 4 THz. The two-step relaxation process predicted by the mode coupling theory was observed in the supercooled liquid near T c . Idealized mode coupling theory analysis for the β-relaxation region provided reasonable agreement with the scaling predictions. The crossover temperature was identified from both above and below T c . However, systematic differences between the experimental data and the idealized theoretical β-spectra were observed at low frequencies for temperatures near and below T c . An extended mode coupling theory analysis, which includes the phonon-assisted hopping transport, provided a good description of the complete experimental β-spectra. The hopping rate was quantitatively estimated from the analysis. Transition regions and trajectories were found in the temperature-hopping rate plane.

Supercooled liquids approaching the liquid-glass transition exhibit unusual properties associated with structural relaxation. The mode-coupling theory (MCT) of supercooled liquid dynamics shows that non-linear interactions among density fluctuation modes can produce effects resembling these observations. MCT produces detailed predictions for the dynamics of density fluctuations in supercooled liquids, including a crossover from liquid to glassy dynamics at a critical temperature Tc. Recent light scattering studies of supercooled CaKNO3 are described that have provided detailed tests of MCT both above and below Tc, including a cusp in the scaling time at Tc=105+or-5 degrees C. These experiments are reviewed, and comparisons with both the idealized and extended versions of MCT are described.

Recently reported light-scattering studies of Ca K NO 3 and Salol are reanalyzed, using the extended version of the mode-coupling theory of the liquid-glass transition including activated transport or hopping effects. Problems found in the original fits due to the neglect of hopping terms are largely corrected, and quantitative predictions for the susceptibility minimum below the crossover temperature T c are found. The results are also shown to accurately explain the CaKNO 3 neutron spin-echo data reported by Mezei [J. Non-Cryst. Solids 131-133, 317 (1991)]

The complex dielectric constant of thiourea has been measured in the temperature range from 80 K to 300 K with different measuring-field levels and frequencies, with and without d.c. biasing fields. The temperature interval between the two peaks in the e*a(T) curve near 178 K was found to extrapolate to 0.7 K at zero measuring and biasing fields, which indicates that the ⅛ ferroelectric lock-in phase is intrinsic in a non-zero temperature range. The E-T phase diagram near the ⅛ lock-in region was explored by investigating the effects of biasing fields. D-E hysteresis loops were investigated in the vicinity of the ⅛ ferroelectric phase with measuring frequencies from 0.5 Hz to 5 mHz. The different D-E loops observed clearly demonstrate the difference between the intrinsic and “field-induced” lock-in mechanisms. The Landau free energy was analyzed and shown to produce self-consistent explanations of the experimental results and of the successive phase transitions.

A recently reported analysis (Cummins et al., 1993, Phys. Rev. E, 47, 4223) of depolarized light and neutron scattering experiments in CaKNO3 using the mode-coupling theory is extended. The temperature dependence of the critical amplitudes found in this analysis is explained.

Depolarized light-scattering spectra of propylene carbonate were obtained in the frequency range 0.2 GHz--4 THz at temperatures from 350 to 135 K. Analysis of the resulting susceptibility spectra revealed reasonable agreement with the predictions of the idealized mode coupling theory, yielding critical exponents a=0.29, b=0.50, and an exponent parameter \ensuremath{\lambda}=0.78\ifmmode\pm\else\textpm\fi{}0.05. A scaling analysis demonstrated critical slowing down of the scaling frequencies from both above and below ${\mathit{T}}_{\mathit{C}}$, with the scaling frequency extrapolating to zero at ${\mathit{T}}_{\mathit{C}}$=187\ifmmode\pm\else\textpm\fi{}5 K. The \ensuremath{\alpha}-relaxation peak was fit to a Kohlrausch function, which gave \ensuremath{\beta}=0.77\ifmmode\pm\else\textpm\fi{}0.05 for 210\ensuremath{\le}T\ensuremath{\le}350 K with no sign of systematic temperature dependence. An extended mode coupling theory analysis was also carried out which corroborated the results obtained with the idealized version. Polarized Brillouin spectra were also obtained, and were analyzed with a generalized hydrodynamics approach using low-frequency sound velocity values determined separately in an ultrasonics experiment. The results indicate that the Cole-Davidson function is not an adequate model for the structural relaxation due to the neglect of \ensuremath{\beta}-relaxation processes, so that this analysis cannot provide a meaningful estimate of ${\mathit{T}}_{\mathit{C}}$. Furthermore, the \ensuremath{\alpha}-relaxation time associated with Brillouin scattering was found to be about five times shorter than that probed by depolarized light scattering.

The liquid‐glass transition in calcium potassium nitrage (CKN), salol, and aqueous LiCl solution was investigated by laser light scattering spectroscopy. Combining data obtained with a Sandercock tandem Fabry Perot interferometer and a Spex tandem Raman spectrometer provided spectra spanning more than four decades in frequency. The data was analyzed to test both qualitative and quantitative predictions of the mode coupling theory of the glass transition, and produced generally excellent agreement. For CKN, we found that the MCT crossover temperature Tc is ∼378K, 45° above Tg.

Raman spectra of 15 and 30 mol % aqueous LiCl solutions were studied in the frequency range 3--350 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, from room temperature to 78 K. At high temperatures, the spectra are very similar to the Raman spectrum of pure water. As the temperature is lowered through the glass transition, the broad central peak that is typical of liquids evolves continuously into a narrow central peak plus a broad band centered near 60 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, both with a depolarization ratio of \ensuremath{\sim}0.8. This evolution suggests a common origin for these two features, which are typical of glasses. Comparison of our results with the disorder-induced-scattering model of Martin and Brenig [Phys. Status Solidi B 64, 163 (1974)], which is often used for glasses, produced poor agreement for both the intensity and depolarization ratio. In an alternative approach, we combined Stephen's [Phys. Rev. 187, 279 (1969)] second-order Raman-scattering theory for fluids with generalized hydrodynamics and mode-coupling concepts. This approach gave predictions for the depolarization ratio in excellent agreement with our experimental results. It also produced a qualitatively correct description of the low-frequency Raman spectral shape in both the glass and liquid phases.

Doppler-free saturation spectroscopy in the regime of strong pumping intensities and optically thick atomic samples is investigated experimentally and theoretically. It is shown that a very high signal-to-background ratio can be obtained and, at the same time, subnatural linewidths can be reached. Further contrast and linewidth improvements can be attained by supplementing the primary depleted pumping beam with a second pumping beam. By using the signal beam from a first setup as the pumping beam for a second identical arrangement, extreme values for contrast and linewidth should be attainable.

Fluorescence spectroscopy is used as an aid in the identification of two-photon transitions in Na2. Several methods are introduced and used to identify the transitions and analyze the spectra. By using these methods, the upper-level rotational quantum number, energy, and electronic character may be determined without any assumptions about the state to which the upper level belongs. Twenty-nine two-photon transitions were observed and analyzed. A Dunham expansion for the energy levels allowed 18 of the 29 to be associated with the Σ1g+ (3s+5s) state. They were used to calculate new values of the Dunham coefficients for that state. These were in close agreement with values obtained in polarization-labeling experiments.