ABSTRACT
Monoclinic Yb-sensitized (Tm, Ho)-doped KLu(WO4)2 nanocrystals of ~100 nm size have been synthesized by the modified Pechini sol-gel method. Their diode laser near-infrared (~980 nm) excited upconversion emission properties have been characterized at power densities in the range 30-355 W cm(-2). Bright white light composed of blue ~475 nm, green ~540 nm, and red ~650 nm emissions, corresponding to Tm(3+ 1)G4 â (3)H6, Ho(3+ 5)S2, (5)F4 â (5)I8, and Ho(3+ 5)F5 â (5)I8 electronic transitions, respectively, was generated by adjusting the Yb, Tm, and Ho contents in KLu(WO4)2 nanocrystalline samples. Chromaticity coordinates of the emitted white light can be tuned by modifying the excitation power density. The effect of Tm and Ho on the luminescence dynamics has been described by analyzing the upconverted emission intensity dependence on the excitation power, as well as from Stokes and decay time measurements. The effect on upconversion properties of further codoping with Eu in these (Tm, Ho, Yb)-doped KLu(WO4)2 nanocrystals has also been studied.
Subject(s)
Europium/chemistry , Holmium/chemistry , Light , Lutetium/chemistry , Nanoparticles/chemistry , Thulium/chemistry , Tungsten/chemistry , Ytterbium/chemistry , Particle SizeABSTRACT
We report what is believed to be the first resonantly pumped laser operation based on Er(3+)-doped disordered double tungstate single crystal. Efficient laser operation of an Er(3+):NaY(WO(4))(2) laser at â¼1609.6 nm was demonstrated with the naturally wideband, â¼20 nm, InGaAsP/InP laser diode pumping at â¼1501 nm. Laser wavelength tunability of â¼34 nm was also demonstrated based on disorder-broadened emission features of Er(3+):NaY(WO(4))(2) single crystal.
Subject(s)
Lasers, Solid-State , Spectrum Analysis , Absorption , TemperatureABSTRACT
We report, for the first time to our knowledge, femtosecond-pulse operation of a Tm,Ho:NaY(WO(4))(2) laser at around 2060 nm. Transform-limited 191 fs pulses are produced with an average output power of 82 mW at a 144 MHz pulse repetition frequency. Maximum output power of up to 155 mW is generated with a corresponding pulse duration of 258 fs. An ion-implanted InGaAsSb quantum-well-based semiconductor saturable absorber mirror is used for passive mode-locking maintenance.
Subject(s)
Lasers, Solid-State , Optical Phenomena , Spectrum Analysis , Time FactorsABSTRACT
Time-resolved line-narrowed fluorescence spectroscopy of Eu(3+) ions in a new oxyborate Na(3)La(9)O(3)(BO(3))(8) crystal shows the existence of four independent symmetry crystal field sites for the rare-earth ion. A crystal field analysis and simulation of the experimental results have been performed in order to parametrize the crystal field at the Eu(3+) sites. A plausible argument about the crystallographic nature of these sites is given.
ABSTRACT
A new strategy has been developed to enhance the optical bandwidths of rare earth dopants by partial substitution of the divalent cation (D) in the original DWO(4) or DMoO(4) crystal structures. For demonstration, the monoclinic (space group C2/c) Yb-doped Li(0.75)Gd(0.75)Ba(0.5)(MoO(4))(2) crystal was grown in a Li(2)Mo(2)O(7) flux, and 300 K Yb(3+) laser operation is reported. The laser emission is characterized by rather short wavelengths related to the specific features of the absorption and emission spectra, which leads to very small quantum defect, i.e., as low as 0.7% for E//b-axis. Using a Ti:sapphire laser at 976.6 nm, up to 295 mW of cw power are obtained without special cooling while the tunability range extends over 33 nm around 1020 nm.
Subject(s)
Crystallization/methods , Lasers , Lithium/chemistry , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Lithium/radiation effects , Quantum Theory , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
We studied the temperature-dependent luminescence of GdVO4 nanoparticles co-doped with Er(3+) (1 mol %) and Yb(3+) (20 mol %) and determined their thermal sensing properties through the fluorescence intensity ratio (FIR) technique. We also analyzed how a silica coating, in a core-shell structure, affects the temperature sensing properties of this material. Spectra were recorded in the range of biological temperatures (298-343 K). The absolute sensitivity for temperature determination calculated for the core-shell nanoparticles is double the one calculated for bare nanoparticles, achieving a thermal resolution of 0.4 K. Moreover, silica-coated nanoparticles show good dispersibility in different solvents, such as water, DMSO, and methanol. Also, they show good luminescence stability without interactions with solvent molecules. Furthermore, we also observed that the silica coating shell prevents progressive heating of the nanoparticles during prolonged excitation periods with the 980 nm laser, preventing effects on their thermometric applications.
ABSTRACT
The effects of oleate, spermine and chlorpromazine were assayed in the presence or absence of 0.15 M KCl on the translocation of phosphatidate phosphohydrolase activity from cytosol to endoplasmic reticulum membranes in liver homogenates obtained from rats aged 1, 30, 60, 180 and 360 days. Marked age-associated decreases in phosphatidate phosphohydrolase distribution onto the membranes were demonstrated under nearly all conditions. In liver homogenates taken from 1-day-old rats and incubated with 0.15 M KCl, most of the enzyme was active (associated with the membranes). Physiological salt concentration (0.15 M KCl) produced a 2-fold increase of oleate-induced translocation of phosphatidate phosphohydrolase activity in liver homogenates from 1-day-old rats; it had no effect on those from 60-day-old rats, and produced a notable decline in liver homogenates obtained from 180- and 360-day-old rats. The promoting effect of spermine on oleate-induced translocation of this enzyme activity was higher in younger rats when incubated in the absence of 0.15 M KCl. Chlorpromazine did not show its usual antagonizing effect on oleate-induced translocation of phosphatidate phosphohydrolase when added to homogenates taken from 1-day-old rats. The antagonizing effect was slightly apparent in liver homogenates from 30-day-old rats and was more pronounced in those from 60-day-old rats in which the values diminished to one-half and to one-third either in the presence or absence of 0.15 M KCl.
Subject(s)
Intracellular Membranes/enzymology , Liver/growth & development , Microsomes, Liver/enzymology , Phosphatidate Phosphatase/metabolism , Phosphoric Monoester Hydrolases/metabolism , Aging , Animals , Chlorpromazine/pharmacology , Cytosol/enzymology , Kinetics , Liver/drug effects , Male , Oleic Acid , Oleic Acids/pharmacology , Potassium Chloride/pharmacology , Rats , Rats, Inbred Strains , Reference Values , Spermine/pharmacologyABSTRACT
Rats were injected daily for 8 weeks with 50 mg of thioacetamide per kg to produce liver tumours. Some of these rats were given three doses of 50 mg of an antitumoural Rh(III) complex/kg at 14, 9 and 5 days before the end of the thioacetamide treatment. Thioacetamide decreased the rate of weight gain of the rats and the Rh(III) complex partly restored it. The activities of ATP citrate lyase, acetyl-CoA carboxylase and fatty acid synthetase in the livers were decreased by thioacetamide treatment and the Rh(III) complex partly reversed this effect. By contrast the activity of malic enzyme was increased by both thioacetamide and the Rh(III) complex and this effect probably relates to NADPH production for detoxification rather than for lipogenesis. Treatment with thioacetamide increased the rate of synthesis of di- and triacylglycerols from glycerol phosphate by liver homogenates, the activity of phosphatidate phosphohydrolase and the incorporation of [3H]glycerol into liver triacylglycerol in vivo. The Rh(III) complex did not produce a significant reversal of these effects of thioacetamide on glycerolipid synthesis. The total uptake of intraportally injected [3H]glycerol by the livers of thioacetamide treated rats was decreased and this was associated with a lowered activity of glycerol kinase. Thioacetamide increased the activity of hepatic ornithine decarboxylase by about 40-fold, but the Rh(III) complex did not reverse this effect. However, the decrease in tyrosine aminotransferase activity that was produced by thioacetamide was partly reversed by the Rh(III) complex. These results are discussed in relation to the tumour-promoting effects of thioacetamide and the antitumoural action of the Rh(III) complex.
Subject(s)
Acetamides , Antineoplastic Agents/pharmacology , Diglycerides/biosynthesis , Fatty Acids/biosynthesis , Glycerides/biosynthesis , Liver Neoplasms/chemically induced , Ornithine Decarboxylase/metabolism , Rhodium/pharmacology , Thioacetamide , Triglycerides/biosynthesis , Tyrosine Transaminase/metabolism , ATP Citrate (pro-S)-Lyase/metabolism , Acetyl-CoA Carboxylase/metabolism , Animals , Body Weight/drug effects , Fatty Acid Synthases/metabolism , Glycerol Kinase/metabolism , Glycerol-3-Phosphate O-Acyltransferase/metabolism , Isoenzymes , L-Lactate Dehydrogenase/metabolism , Liver/drug effects , Liver/enzymology , Liver Neoplasms/enzymology , Malate Dehydrogenase/metabolism , Male , Organ Size/drug effects , Phosphatidate Phosphatase/metabolism , Rats , Rats, Inbred StrainsABSTRACT
Lasing of Yb3+ in a disordered single crystal host, NaGd(WO4)2, is reported. Pump efficiencies as high as 20% and slope efficiencies as high as 30% are achieved for both sigma- and pi-polarizations with Ti:sapphire laser pumping. The emission of Yb:NaGd(WO4)2 is centered near 1030 nm. Tunability between 1016 and 1049 nm is obtained with a Lyot filter.
ABSTRACT
The translocation of phosphatidate phosphohydrolase induced by oleate was higher (two-fold) in liver homogenates obtained from long-term thioacetamide-treated rats than from control rats. These differences between thioacetamide-treated and control livers were noticeably higher (four-fold) in the presence of physiological concentrations of salt (0.15 M KCl). In homogenates from control rats, there was a lack of response when physiological concentrations of the salt were present. The enhanced response to translocate phosphatidate phosphohydrolase activity in liver homogenates from thioacetamide-treated rats was due to an increased binding ability of microsomal membranes.
Subject(s)
Acetamides/toxicity , Cytosol/enzymology , Intracellular Membranes/enzymology , Liver Neoplasms/chemically induced , Microsomes, Liver/enzymology , Phosphatidate Phosphatase/metabolism , Phosphoric Monoester Hydrolases/metabolism , Thioacetamide/toxicity , Animals , Liver Neoplasms/enzymology , Male , Oleic Acid , Oleic Acids/pharmacology , Rats , Rats, Inbred Strains , Subcellular Fractions/enzymologyABSTRACT
Mutant ras oncogenes are associated with various human tumors such as pancreas, colon, lung, thyroid, bladder and several types of leukemia. Prenylation of Ras proteins plays a major role in cell proliferation of both normal and cancerous cells. Normal and oncogenic Ras proteins are posttranslationally modified by a farnesyl group that promotes membrane binding. Inhibitors of farnesyl protein transferase (FPTase), the enzyme that catalyzes the prenylation of Ras proteins, inhibit growth of tumor cells. In an effort to identify structurally diverse and unique inhibitors of FPTase, a program devoted to screening of natural products was initiated. This effort led to the identification of 10 different families of compounds, all of which selectively inhibit FPTase with a variety of mechanisms that are reviewed in this manuscript. These compounds originated from the fermentations of a number of microorganisms, either actinomycetes or fungi, isolated from different substrates collected in tropical and temperate areas. A chemotaxonomic discussion on the distribution of each compound among single or different types of microorganisms, either phylogenetically related or unrelated species, is included.
ABSTRACT
Enzyme activities and protein content were determined in the cytosolic and mitochondrial fractions of liver homogenates obtained from Rh(III) complex-, thioacetamide- and thioacetamide + Rh(III) complex-treated rats.The Rh(III) complex administered to nonthioacetamide-treated rats produced no significant changes either in the enzymatic activities assayed or in the protein concentration.The Rh(III) complex administered to thioacetamide-treated rats produced significant restoration of the following altered values: cytosolic and mitochondrial aspartate aminotransferase, glutamate dehydrogenase, NADP-isocitrate dehydrogenase, and protein concentration. However, a further increase was produced in the activities of glucose-6-phosphate dehydrogenase and malic enzyme. These increases can be interpreted in terms of an enhancement of the NADPH-dependent detoxifying processes and of nucleic acid synthesis and repair.
ABSTRACT
The infrared, Raman and 57Fe-Mössbauer spectra of FeTbGe2O7 were recorded and analyzed on the basis of its crystallographic data. For comparative purposes, similar measurements were also performed with FeYGe2O7 and with other isostructural compounds containing different lanthanide cations.
Subject(s)
Ferrous Compounds/chemistry , Spectrum Analysis, RamanABSTRACT
A new zeolite-type structure is adopted by (NH(4))(+)[M(NH(3))(2)](+)(Ge(9)O(19))(2-) (M=Cu, Ag; shown in the picture). These compounds are the first microporous germanates containing a transition metal complex inside their tunnels. The large separation between the metal centers and the unhindered access of reactants to these active sites through uniformly sized channels make these materials a good point of departure for designing new catalysts.
ABSTRACT
Enzyme activities related to fatty acid synthesis were determined in liver extracts of rats treated with thioacetamide (TAM) for 8 weeks. Lipogenesis and cholesterogenesis in vivo were evaluated both in liver and in epididymal adipose tissue. The enzymatic activities of ATP-citrate lyase, acetyl CoA carboxylase, fatty acid synthetase, glycerol kinase and NAD-kinase decrease progressively when TAM was chronically administered. However, in the same experimental conditions malic enzyme and other NADP-enzymes were noticeably increased. This increase can be related to an excess of NADPH production necessary for detoxification rather than for lipogenesis. The rate of in vivo incorporation of 3H2O into non-saponifiable fraction in liver showed an increase in the acute phase (1-3 days) of TAM-treatment. In the chronic phase of TAM intoxication this rate returned to values close to normality. The rate of in vivo incorporation of 3H2O to fatty acid fraction increased in the liver during the acute phase of TAM-treatment and showed a sharp decrease during the subacute and chronic phases of the intoxication. At the end of the 60-day period of TAM-treatment, the radioactivity incorporated into fatty acids was significantly lowered. These data showed that the alterations in hepatic lipogenesis observed during TAM administration are related to changes in the activities of lipogenic enzymes and probably are a consequence of alterations in plasma insulin concentration. Disturbances in lipid metabolism should play an important role in the pathogenesis of liver damage and its physiological significance could involve metabolic changes in proliferative and neoplastic liver diseases.
Subject(s)
Acetamides/toxicity , Adipose Tissue/metabolism , Cholesterol/biosynthesis , Lipid Metabolism , Liver/metabolism , Thioacetamide/toxicity , Animals , Fatty Acids/biosynthesis , Insulin/blood , Male , NADP/metabolism , Rats , Rats, Inbred StrainsABSTRACT
Ethanol or acetaldehyde orally administered (15% and 2% respectively in drinking water) to male Wistar rats for three months induced alterations in the main liver enzymes responsible for ethanol metabolism, aspartate and alanine aminotransferases and NAD glutamate dehydrogenase. Ethanol produced a significant decrease in the activity of soluble alcohol dehydrogenase, while acetaldehyde induced alterations both in soluble and mitochondrial aldehyde dehydrogenases: soluble activity was significantly higher than in the control and ethanol-treated groups, and mitochondrial activity was significantly diminished. Both soluble aspartate and alanine aminotransferases showed pronounced increases by the chronic effect of acetaldehyde, while mitochondrial activities were practically unchanged by the effect of ethanol or acetaldehyde. Mitochondrial NAD glutamate dehydrogenase showed a rise in its activity both by the effect of chronic ethanol and acetaldehyde consumption. The level of metabolites assayed in liver extracts showed marked differences between ethanol and acetaldehyde treatment which indicates that ethanol produced a remarkable increase in glutamate, aspartate and free ammonia together with marked decrease in pyruvate and 2-oxoglutarate concentrations. Acetaldehyde consumption induced a significant decrease in 2-oxoglutarate and pyruvate concentrations. These observations suggest that ethanol has an important effect on the urea cycle enzymes, while the effect of acetaldehyde contributes to the impairment of the citric acid cycle.
Subject(s)
Acetaldehyde/pharmacology , Ethanol/pharmacology , Liver/drug effects , Acetaldehyde/administration & dosage , Alanine Transaminase/metabolism , Alcohol Oxidoreductases/metabolism , Aldehyde Dehydrogenase/metabolism , Ammonia/metabolism , Animals , Aspartate Aminotransferases/metabolism , Citric Acid Cycle/drug effects , Drug Synergism , Ethanol/administration & dosage , Glutamate Dehydrogenase/metabolism , Glutamates/metabolism , Glutamic Acid , Liver/enzymology , Male , Mitochondria, Liver/drug effects , Mitochondria, Liver/enzymology , Rats , Rats, Inbred StrainsABSTRACT
The incubation of hepatocytes with 1-4mM-oleate increased the total activity of phosphatidate phosphohydrolase that was measured in the presence of Mg2+ to about 2-fold. This was accompanied by an increase in the proportion of the enzyme that was isolated with the particulate fractions. Conversely, the addition of up to 4mM-oleate decreased the recovery of phosphatidate phosphohydrolase in the cytosolic fraction from about 70% to 3% when hepatocytes were lysed with digitonin. Most of the increase in the membrane-associated phosphohydrolase activity was isolated after cell fractionation in the microsomal fraction that was enriched with the endoplasmic-reticulum marker arylesterase. It is proposed that the translocation of phosphatidate phosphohydrolase facilitates the increased synthesis of triacylglycerols in the liver when it is presented with an increased supply of fatty acids.