Structural and optical characterization of RbLaP4O12:Ln3+ (Ln3+ = Ce3+, Nd3+, Tm3+, or Yb3+).

In this work, for the first time, detailed structural and optical characterization of RbLaP4O12 doped with different concentrations of Ce3+, Nd3+, Tm3+, or Yb3+ ions is reported. The samples were obtained via a precipitation technique. Their structural characterization was performed using X-ray diffraction (XRD), and infrared and Raman spectroscopies. Following XRD data, the unit cell parameters of host lattices were calculated using Rietveld refinement. It was found that an increase in the dopant content leads to a decrease in the unit cell volume. The optical characterization of RbLaP4O12:Ln3+ was carried out by collecting absorption and emission spectra, as well as luminescence decay profiles. Following absorption spectra, the energy band gap of the studied matrix was determined. It was found that the broad absorption band located in the ultra-violet range, in most cases ascribed to charge transfer or f-d transitions, is in fact related to the absorption of the host lattice. The analysis of luminescence properties allowed us to investigate possible ways of depopulation emission levels of impurities.

Laser induced white emission generated by infrared excitation from Eu3+:Sr2CeO4 nanocrystals.

The laser induced white emission (LIWE) was observed from Eu3+:Sr2CeO4 nanocrystals. The samples were obtained in form of powders by the modified sol-gel route. The structure and morphology of the phosphors were investigated by powder X-ray diffraction and transmission electron microscope techniques. The intense LIWE occurred under reduced pressure and focused beam of near infrared laser excitation. The power and pressure dependencies exhibit evident threshold character typical for the avalanche effect. The photoconductivity of the Eu3+:Sr2CeO4 nanocrystals measured as a function of different powers of excitation source was analyzed.

Broadband anti-Stokes white emission of Sr2CeO4 nanocrystals induced by laser irradiation.

The laser induced white emission (LIWE) from Sr2CeO4 nanocrystals upon irradiation with a focused IR laser beam was investigated. It was observed to be a threshold phenomenon with its intensity increasing exponentially with the excitation power density. This process was investigated under double laser beam simultaneous excitation in the UV range leading to Stokes emission in the visible range and in the IR range leading to anti-Stokes LIWE. With increasing LIWE intensity, the Stokes emission intensity strongly decreased. The LIWE is accompanied by efficient photocurrent generation depending on laser excitation density followed by multiphoton absorption and ionization processes. Photoimpedance measurements showed a sharp increase of the dielectric constant by several orders of magnitude in the Sr2CeO4 nanocrystals during the LIWE process demonstrating a metallic-like behaviour. The mechanisms of LIWE include multiphoton absorption and ionization that lead to the creation of a coupled pair of Ce3+ and Ce4+ ions that allow for the intervalence charge transfer (IVCT) emission transitions in the white light range. A strong decrease of absorption band intensity of Sr2CeO4 with increasing LIWE intensity confirms the creation of (Ce3+, Ce4+) pairs.

Near infrared absorbing near infrared emitting highly-sensitive luminescent nanothermometer based on Nd(3+) to Yb(3+) energy transfer.

A new type of near infrared absorbing near infrared emitting (NANE) luminescent nanothermometer is presented, with a physical background that relies on efficient Nd(3+) to Yb(3+) energy transfer under 808 nm photo-excitation. The emission spectra of LiLa0.9-xNd0.1YbxP4O12 (x = 0.05, 0.1, 0.2, 0.3, 0.5) nanocrystals were measured in a wide 100-700 °C temperature range. The ratio between the Nd(3+) ((4)F3/2→(4)I9/2) and Yb(3+) ((2)F5/2→(2)F7/2) luminescence bands, and the thermometer sensitivity were found to be strongly dependent on the Yb(3+) concentration. These phenomenological relations were discussed in terms of the competition between three phenomena, namely (a) Nd(3+)→ Yb(3+) phonon assisted energy transfer, (b) Yb(3+)→ Nd(3+) back energy transfer and (c) energy diffusion between Yb(3+) ions. The highest sensitivity of the temperature measurement was found for x = 0.5 (LiLa0.4Nd0.1Yb0.5P4O12), which was equal to 4 × 10(-3) K(-1) at 330 K. In stark contrast to conventional approaches, the proposed phosphate host matrix allows for a high level of doping, and thus, owing to the negligible concentration quenching, the presented luminophores exhibit a high absorption cross section and bright emission. Moreover, such optical remote thermometers, whose excitation and emission wavelengths are weakly scattered or absorbed and fall into the optical transmission window of the skin, may therefore become a practical solution for biomedical applications, such as remote control of thermotherapy.

Synthesis and up-conversion luminescence of Er(3+) and Y b(3+) codoped nanocrystalline tetra- (KLaP4O12) and pentaphosphates (LaP5O14).

The up-converting nanocrystals of KLa0.95Er0.05Y bxP4O12 and La0.95-xEr0.05Y bxP5O14 were prepared using co-precipitation method. The spectroscopic properties of these materials were investigated in a function of Y b(3+) concentration. The up-conversion emission, power dependence of emission intensities, and the luminescence decay times were investigated. It was found that the green to red and (2)H11/2 → (4)I15/2 to (4)S3/2 → (4)I15/2 emission intensity ratio were strongly affected by the Y b(3+) concentration. Moreover, the order of up-conversion emission and threshold power rises up with Y b(3+) concentration for (4)S3/2 → (4)I15/2 transition. The luminescence decay time of the (4)S3/2 → (4)I15/2 emission increases with Y b(3+) concentration while the (4)F9/2 → (4)I15/2 emission is independent of dopant concentration. The influence of the Y b(3+) concentration on the up-conversion emission intensities was discussed in terms of concentration dependent hetero looped photon avalanche process. A comparison of the up-conversion properties of KLa0.95Er0.05Y bxP4O12 and La0.95-xEr0.05Y bxP5O14 nanocrystals was presented.

Influence of grain size on optical properties of Sr2CeO4 nanocrystals.

The absorption, excitation, and emission spectra of the Sr2CeO4 nanocrystals prepared by the modified sol-gel method were investigated. The impact of the average grain size of Sr2CeO4 nanocrystals on their optical properties was investigated. It was observed that with increasing the average grain size of Sr2CeO4 nanocrystals, the emission decay times decreased significantly. A similar behavior was observed for the emission quantum efficiencies and the Huang-Rhys factors. The grain size dependence of optical parameters of Sr2CeO4 nanocrystals was found well fitted by functions of the reciprocal of the grain diameter. It was shown that this dependence may be rationalized assuming that the correction for electric local field associated with effective refractive index affecting the spherical nanoparticle is governed by its shell.

[Influence of bodily constitution and physical activity on postural stability]. / Einfluss von Konstitution und Belastung auf die posturale Stabilität.

CONTEXT AND OBJECTIVE: In order for balance to be maintained, the postural control system must process above all visual, vestibular and proprioceptive information and translate this input into appropriate motor responses. The influence of bodily constitution and physical activity on motor responses and thus on postural stability is still unclear. To use computerized dynamic posturography (CDP) to investigate the influence of body height, body mass index (BMI), regular sporting activity and acute maximal exercise on balance. SUBJECTS AND METHODS: Eighty-four subjects completed a standardized questionnaire on their height, BMI and sporting activity. We then assessed the postural stability of the subjects. Seventeen further subjects performed a maximal exercise test on a bicycle ergometer. We used CDP and a predefined protocol to assess balance at rest, at maximal exercise and then at 5-minute intervals until recovery. RESULTS: Body height and regular physical activity did not influence balance ability. By contrast, BMI and acute physical exercise had a strong effect. Immediately after maximal exercise, postural stability deteriorated by 44 % compared to the baseline level (p < 0.017). Complete recovery occurred within only 15 minutes. CONCLUSIONS: Whereas body height and regular physical activity do not influence balance performance, a high BMI value and acute maximal exercise lead to a considerable decrease in postural stability. Our results can thus explain the increasing risk of injury after strenuous physical activity, especially in association with sports that require excellent balance.

Methodological issues in coding sleep states in immature infants.

Thirty-five healthy, premature infants, ranging from 30-39 weeks postconceptional age, were observed continuously for 6 to 24 hr. Behavioral state and electroencephalographic patterns were coded for each minute. Using these data, three questions regarding coding of states of sleep were addressed: What is the concordance between behavioral codes and specific EEG patterns? Does the concordance between behavioral codes and EEG patterns change with postconceptional age? What range of error can be expected when observation periods shorter than 24-hr are used to estimate the daily distribution of quiet sleep (QS) and active sleep (AS)? With behavioral codes as the standard, concordances of EEG patterns for QS and AS were 72.5 and 92.1% respectively. With EEG patterns as the standard, behavioral codes for QS and AS agreed 83.0 and 88.9%. Agreement between behavioral codes and EEG patterns for QS increased with age. Finally, variation in estimates of the daily distribution of QS and AS decreased dramatically as the length of observation increased from 3 to 24 hr.

Curdlan sulfate and HIV-1: II. In vitro long-term treatment of HIV-1 infection with curdlan sulfate.

Short-term (1 h) treatment with a newly synthesized sulfated polysaccharide, curdlan sulfate (CRDS), showed relatively weak blocking effects on the binding of human immunodeficiency virus type 1 (HIV-1) to the surface of H9 cells. To investigate whether long-term treatment with CRDS could strengthen this effect, CRDS in various doses (0.1, 1, 10, and 100 micrograms/ml) was used in 2-week treatment periods in four separate protocols or "Procedures." SF titers and p24 antigen levels were partially suppressed during long-term CRDS treatment but returned to control levels after the treatment was terminated. In addition, no direct cytotoxicity of CRDS to H9 cells or H9/HIV-1 cells was observed in vitro in the course of continuous exposure to 100 micrograms/ml CRDS for 2 weeks. These results demonstrate the effectiveness of long-term treatment of cells infected with HIV-1 in inhibiting virus expression. The most dramatic inhibition results were obtained when the compound was present both at the time of exposure of cells to virus and during a long-term follow-up treatment. These results show that CRDS inhibits both the cell-free and cell-associated transmission of HIV-1 to host cells and interferes with early events in virus infection. In contrast, CRDS exhibits no significant virucidal activity and has little effect on already infected cells.

Curdlan sulfate and HIV-1. I. In vitro inhibitory effects of curdlan sulfate on HIV-1 infection.

Action mechanisms of a newly synthesized polysaccharide, curdlan sulfate (CRDS), on human immunodeficiency virus type 1 (HIV-1) infection were investigated in vitro using syncytium formation microassay and p24 antigen capture enzyme-linked immunosorbent assay. These assays measured the titer of infectious virions and the amounts of HIV-1 core antigen p24 in soluble, intraviral, and intracellular forms. CRDS treatments were performed for 1 h at 37 degrees C. H9 cells pretreated with 0.1 to 100.0 micrograms/ml of CRDS appreciably inhibited HIV-1 infection. CRDS-treated HIV-1 virions were less able to infect H9 cells than untreated virions. The simultaneous treatment of H9 cells and HIV-1 virions with CRDS induced a significant inhibition of HIV-1 infection, resulting in the temporary disappearance of virions at the highest dose of CRDS. In contrast, CRDS treatment of newly HIV-1-infected H9 cells caused a significant decrease in the titer of infectious HIV-1 and the p24 amounts of all three forms, but no absolute elimination. Taken together, these results indicate that CRDS may block the binding of the HIV-1 envelope to the H9 cell surface, with emphasis on the high affinity of CRDS to the HIV-1 envelope.

Energy expenditure, energy balance, and composition of weight gain in low birth weight infants fed diets of different protein and energy content.

The effect of energy and protein intakes on energy expenditure, energy balance, and amount and relative rate of both protein and fat deposition in new tissue was investigated in 19 low birth weight infants whose mean protein and energy intakes, respectively, were 2.24 g/kg/d and 113 kcal/kg/d (formula A, n = 8), 3.6 g/kg/d and 115 kcal/kg/d (formula B, n = 5), and 3.5 g/kg/d and 149 kcal/kg/d (formula C, n = 6). The higher energy intake (formula C) but not the higher protein intake (formula B) resulted in greater energy expenditure. Both the higher protein (formula B vs formula A) and higher energy intakes (formula C vs formula B) resulted in greater weight gain secondary, in group B, to a greater absolute rate of protein deposition and, in group C, to a greater absolute rate of fat deposition. The relative composition of the new tissue deposited reflected the proportional intakes of protein and energy. The numerical value of the protein/fat ratio (g/g) of the new tissue deposited by infants fed formulas A and C, the protein contents of which were low relative to energy contents, were similar and significantly lower than the numerical value of the protein/fat ratio of the new tissue deposited by infants fed formula B, which had a higher protein content relative to energy content. These findings suggest that the composition of weight gain is related to both the absolute amounts and the proportions of dietary protein and energy; thus, both must be considered in formulation of nutritional regimens for LBW infants.

An analysis of the variability in estimates of bioenergetic variables in preterm infants.

Estimates of average daily energy expenditure and minimal observed oxygen consumption are commonly used to characterize the energy metabolism of neonates. Yet, the errors inherent in these estimates have not been defined. Using measurements of oxygen consumption and carbon dioxide production made in healthy growing low birth weight infants during eight consecutive 3-h interfeeding epochs, we have determined the variability in the mean oxygen consumption, carbon dioxide production, respiratory quotient, total daily energy expenditure, and the minimal observed oxygen consumption among the feeding epochs. The coefficient of variation for oxygen consumption ranged from 3.1 to 9.1%, for minimal observed oxygen consumption from 3.7 to 16.7%, for carbon dioxide production from 3.3 to 7.4%, and for total daily energy expenditure from 2.9 to 7.6%. The SDs for respiratory quotient ranged from 0.008 to 0.066. From these 24-h data we have calculated the error in predicting daily estimates of the mean values for these variables if observations are made for less than 24 h. As expected, this error decreases with increasing duration of observation. These data should prove useful in the design and interpretation of investigations of neonatal energy expenditure.

A scoring system for states of sleep and wakefulness in term and preterm infants.

We designed and validated a system for determining the state of sleep or wakefulness in both term and preterm infants. The system is based on independent assessments of behavioral and electroencephalographic (EEG) patterns. Overall agreement between observers in coding individual behavioral patterns was 77.6%. Agreement between observers in coding EEG patterns was 87.4%. Designation of an infant's state is made by combining concurrent behavioral and EEG scores into a single two-number code. The distribution of sleep state for eight infants greater than 36 wk postconceptional age (PCA) was the following: quiet sleep (QS), 30.4%; active sleep (AS), 50.0%; indeterminate sleep (IS), 11.4%, and wakefulness (W), 7.5%. The distribution of sleep state for 15 infants less than 36 wk PCA was as follows: QS, 18.9%; AS, 52.9%; IS, 16.4%; and W, 10.5%. Our experience with the system suggests that it is useful for relating sleep state to physiologic variables during neonatal experimental studies.

Instrumentation for the continuous measurement of gas exchange and ventilation of infants during assisted ventilation.

A system of instrumentation for continuous measurement of oxygen consumption (VO2), carbon dioxide production (VCO2) and minute ventilation (V1) in human newborns on assisted ventilation is described. VO2 and VCO2 are measured by open-circuit indirect calorimetry utilizing a Servomex OA 184 differential paramagnetic oxygen analyzer and a Beckman LB 2 infrared CO2 analyzer. Minute volume is measured with a body plethysmograph. Bench performance is described, limitations of the system are defined, and sample clinical data are presented. The instrumentation can measure safely, accurately, and continuously physiologic variables in sick infants on assisted ventilation.

Spontaneous variability in minute ventilation oxygen consumption and heart rate of low birth weight infants.

Continuous measurements of minute ventilation (VI), oxygen consumption (VO2), heart rate (HR), activity, and temperature were made in eleven low birth weight infants during the interval between feedings. Significant increases in VI, VO2, and HR were noted between quiet and active sleep. (VI Active - VI Quiet/VI Quiet) X 100 = 18.4% VO2 Active - VO2 Quiet/VO2 Quiet) X 100 = 10.1% and HR Active - HR Quiet/HR Quiet) X 100 = 6.4%. Significant differences were also noted within epochs of the same state of sleep: mean slope VI versus time in epoch (t) = -156 ml/kg . min/hr, VO2 versus t. = 1.49 ml/kg . min/hr and HR versus t = -15.0 beats/min/hr. Differences between successive epochs of the same state of sleep were also observed: VI, +5.9 to 46.6%; VO2, 4.7 to 24.6%; HR, 1.0 to 9.7%. These differences were related to the length of time after feeding. These data indicate that steady state conditions do not occur in growing low birth weight infants and that the design of studies of respiration and metabolism in these infants should include continuous assessment of the state of sleep or activity and time after feeding to ensure that experimental and control periods are truly comparable.

Continuous measurement of minute ventilation and gaseous metabolism of newborn infants.

A system of instrumentation for continuous measurement of gaseous metabolism and minute volume (VI) in the human newborn is described. O2 uptake and CO2 production are measured by open-circuit techniques utilizing a Servomex OA184 differential paramagnetic O2 analyzer and a BEckman LB-2 infrared CO2 analyzer. VI is measured with bias-flow pneumotachometry. Bench performance is described, methodological errors are defined, and clinical data are presented. The instrumentation is capable of safe, accurate, and continuous measurement of respiratory and metabolic variables in low-birth-weight infants.