Relación entre metodologías de control de la carga en el baloncesto profesional / Relationship Between Methodologies for Load Control in Professional Basketball

El objetivo de este trabajo fue determinar la relación existente entre diferentes metodologías de medición de la carga de entrenamiento en un equipo profesional de baloncesto. 12 jugadores de un mismo equipo fueron sometidos a estructuras de entrenamiento iguales en cuanto a diseño y fueron monitorizados diariamente con frecuencia cardiaca, GPS y percepción subjetiva de esfuerzo. Los resultados indicaron diferencias significativas entre todas las metodologías de control utilizadas. RPE (x2=12.4; P=.015), sRPE (x2=21.5; P<.001), TRIMP (x2=23.5; P<.001), SHRZ (x2=19.3; P<.001) y distancia (x2=21.7; P<.001). Se observó una correlación entre todas ellas exceptuando la variable distancia recorrida; Borg (p=.19; P=79), sRPE (p=.14; P=.299) y sHR-Z (p=.17; P=.197). Estos resultados sugieren que los diferentes métodos de evaluación utilizados para el control de la carga de entrenamiento determinan resultados variables en un equipo de baloncesto profesional. Se consideró que el ratio de esfuerzo percibido por sesión resulta el instrumento más eficaz para el control de la carga de entrenamiento. (AU)

The aim of this study was to determine the relationship between different load assessment methods in a professional basketball team. Twelve professional basketball players of the same team were subjected to the same training plan design and were monitored daily with heart rate monitors, GPS tools and perceived exertion scales. Results suggested that there were significant differences in training load between all monitoring methods: RPE (x2=12.4; P=.015), sRPE (x2=21.5; P<.001), TRIMP (x2=23.5; P<.001), SHRZ (x2=19.3; P<.001) and distance (x2=21.7; P<.001). Correlations were found between RPE and heart rate but not between these methods and the distance travelled during sessions: Borg (p=.19; P=79), sRPE (p=.14; P=.299) and sHR-Z (p=.17; P=.197). These results suggested that different load assessment methods render varying results in a professional basketball team. In this sample, perceived exertion rate was suggested as the best method for assessing training load in professional basketball players. (AU)

Time to exhaustion at estimated functional threshold power in road cyclists of different performance levels.

OBJECTIVES: This study assessed the functional threshold power and the time to exhaustion estimated from the Allen & Coggan test and verify whether performance level has an influence on this parameter. DESIGN: Cross-sectional study. METHODS: Twenty-minute test proposed by Allen & Coggan and cycling test to exhaustion were used to obtain the functional threshold power and a time to exhaustion. Cyclists were divided into performance groups based into 4 categories according to their VO2max. RESULTS: The median (interquartile range) time to exhaustion at the functional threshold power was 35 (31-38) minutes for recreationally trained cyclists, 42 (38-51) for trained ones, 47 (41-56) for well-trained ones and 51 (44-59) for professional level cyclists. Time to exhaustion increased with cyclists' experience and performance level (p < 0.001). CONCLUSIONS: The high time to exhaustion variability observed in this study suggests that functional threshold power and time to exhaustion should be assessed and reported independently for each subject. Also, cyclists' performance level and experience should be factored in when attempting to study the time to exhaustion, as better performing and more experienced cyclists consistently show longer times to exhaustion at the functional threshold power.

Molecular study of hypersensitivity to spores in adults and children from Castile & Leon

Introduction and objectives: Biological aerosols play a vital role in the interactions between the atmosphere, biosphere, climate and public health and fungal spores are a component with allergic importance. We constructed a database in Castile & Leon (Spain) and carry out molecular-level component-resolved diagnosis to complete the air quality study carried out since 2006 by our aerobiological network (RACYL) to aid clinical diagnosis and treatment. Methods: We reviewed a database of 19,774 patients (adults and children) with allergic respiratory disease treated in our unit during the last 12 years. We also made a component-resolved diagnosis of the molecules involved in the pathology in a randomly selected population of 150 patients. Results: The dimeric glycoprotein Alt a1 from Alternaria is the most prevalent and most useful allergen in the diagnosis of patients with allergy to fungi in our area (94.4%), followed by enolase Alt a 6 (Alternaria), ribonuclease Asp f 1 of Aspergillus and mannitol dehydrogenase from Cla h 8 (Cladosporium). Conclusions: Our results have helped determine which spore molecules are most-closely associated with allergies. Molecular analysis will be useful to determine more accurate and useful immunotherapy in these patients

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Molecular study of hypersensitivity to spores in adults and children from Castile & Leon.

INTRODUCTION AND OBJECTIVES: Biological aerosols play a vital role in the interactions between the atmosphere, biosphere, climate and public health and fungal spores are a component with allergic importance. We constructed a database in Castile & Leon (Spain) and carry out molecular-level component-resolved diagnosis to complete the air quality study carried out since 2006 by our aerobiological network (RACYL) to aid clinical diagnosis and treatment. METHODS: We reviewed a database of 19,774 patients (adults and children) with allergic respiratory disease treated in our unit during the last 12 years. We also made a component-resolved diagnosis of the molecules involved in the pathology in a randomly selected population of 150 patients. RESULTS: The dimeric glycoprotein Alt a1 from Alternaria is the most prevalent and most useful allergen in the diagnosis of patients with allergy to fungi in our area (94.4%), followed by enolase Alt a 6 (Alternaria), ribonuclease Asp f 1 of Aspergillus and mannitol dehydrogenase from Cla h 8 (Cladosporium). CONCLUSIONS: Our results have helped determine which spore molecules are most-closely associated with allergies. Molecular analysis will be useful to determine more accurate and useful immunotherapy in these patients.

Maternal care boosted by paternal imprinting in mammals.

In mammals, mothers are the primary caregiver, programmed, in part, by hormones produced during pregnancy. High-quality maternal care is essential for the survival and lifelong health of offspring. We previously showed that the paternally silenced imprinted gene pleckstrin homology-like domain family A member 2 (Phlda2) functions to negatively regulate a single lineage in the mouse placenta called the spongiotrophoblast, a major source of hormones in pregnancy. Consequently, the offspring's Phlda2 gene dosage may influence the quality of care provided by the mother. Here, we show that wild-type (WT) female mice exposed to offspring with three different doses of the maternally expressed Phlda2 gene-two active alleles, one active allele (the extant state), and loss of function-show changes in the maternal hypothalamus and hippocampus during pregnancy, regions important for maternal-care behaviour. After birth, WT dams exposed in utero to offspring with the highest Phlda2 dose exhibit decreased nursing and grooming of pups and increased focus on nest building. Conversely, 'paternalised' dams, exposed to the lowest Phlda2 dose, showed increased nurturing of their pups, increased self-directed behaviour, and a decreased focus on nest building, behaviour that was robustly maintained in the absence of genetically modified pups. This work raises the intriguing possibility that imprinting of Phlda2 contributed to increased maternal care during the evolution of mammals.

Gestación en paciente mayor de cincuenta años. Mola hidatiforme completa / Pregnancy in a patient aged more than fifty years. Complete hydatidiform mole

La enfermedad trofoblástica gestacional es más frecuente en las edades extremas de la vida. No ha de olvidarse como diagnóstico diferencial de las irregularidades menstruales en la perimenopausia. Aunque su confirmación es anatomopatológica, son de utilidad la ecografía transvaginal y la cuantificación de gonadotropina coriónica humana. En el caso que presentamos de mola hidatiforme completa, la enfermedad queda resuelta con un legrado aspirativo (AU)

Gestational trophoblastic disease is more frequent in extreme ages of life and should be included in the differential diagnosis of menstrual disorders in the perimenopause. Although definitive diagnosis is pathological, transvaginal sonography and determination of human chorionic gonadotropin levels are useful. We present a case of complete hydatidiform mole, which was resolved with aspiration curettage (AU)

Laser emission from mirrorless waveguides based on photosensitized polymers incorporating POSS.

Laser emission from leaky waveguides based in dye-doped organic gain media incorporating Polyhedral Oligomeric Silsesquioxanes (POSS) nanoparticles is reported. The samples consist of thin film gain media deposited onto glass substrate defining a planar asymmetric slab waveguide, which does not incorporate any resonant substructure. The presence of POSS results in additional amplified spontaneous emission (ASE) spectral narrowing, and conditions have been found for which directional multimode laser emission is achieved. The spectral narrowing is ascribed to the photon path enlargement caused by a non-resonant feedback mechanism provided by individual scatterers, which enhances incoherently the magnitude of the amplification process. On the contrary, the appearance of multimode lasing is attributed to coherent random lasing from a many scatterers collective effect.

Red-edge-wavelength finely-tunable laser action from new BODIPY dyes.

New BODIPY dyes with two 4-formylphenyl, 4-(2,2-dimethoxycarbonylvinyl)phenyl and 4-(2,2-dicyanovinyl)phenyl groups at the 3- and 5-positions have been successfully designed and synthesized via palladium-catalyzed coupling reaction or Knoevenagel-type condensations. Structural modification of the BODIPY core via conjugation-extending residues significantly affects the spectroscopy and photophysical properties of the BODIPY fluorophore. These substituents cause the largest bathochromic shift in both absorption and emission spectra, which are shifted toward the red compared to its 4-phenylsubstituted analogue. Additionally, the fluorescence quantum yields and the Stokes shifts are also significantly higher than the corresponding phenyl-substituted dye. New BODIPY dyes have a high laser photostability, superior to that of commercial dyes with laser emission in the same spectral region, such as Perylene Red and Rhodamine 640. The substitution introduced in these derivatives allows to obtain tunable laser emission with a bandwidth of 0.15 cm(-1) and a tuning range of up to 50 nm. So with these three dyes it is possible to cover the spectral range 590-680 nm in a continuous way and with stable laser emission and small linewidth.

Enhanced laser action of Perylene-Red doped polymeric materials.

The laser action of Perylene-Red doped in linear, crosslinked, fluorinated and sililated polymeric materials is reported. The purity of dye was found to be a key factor to enhance its solid-state laser behaviour. The samples were transversely pumped at 532 nm, with 5.5 mJ/pulse and 10 Hz repetition rate. Perylene-Red doped copolymers of methyl methacrylate with a 10 vol% proportion of 2,2,2-trifluoroethyl-methacrylate exhibited a lasing efficiency of 26% with a high photostability since the dye laser output remained at the same level after 100,000 pump pulses in the same position of the sample. This lasing behaviour is, to the best of our knowledge, the highest achieved to date for organic, inorganic, and hybrid materials doped with Perylene-Red.

New analogues of the BODIPY dye PM597: photophysical and lasing properties in liquid solutions and in solid polymeric matrices.

New tailormade BODIPY dyes have been synthesized by a simple protocol to reach wavelength finely tunable laser action from 540 to 625 nm while maintaining highly efficient and photostable laser emission. The new dyes are analogues of the commercial dye PM597 with the eight position free (PTH8) or substituted by the groups acetoxymethyl (PTAlk) or p-acetoxymethylphenyl (PTAr). The photophysical properties strongly depend on the geometrical distortion from planarity of the indacene core generated by the presence of the bulky 2,6-di-tert-butyl groups and the eight substituent. In both liquid and polymeric solid solutions, lasing efficiencies of up to 63 and 48%, respectively, were observed under transversal pumping at 532 nm with high photostabilities. In the case of PTAlk incorporated into silicon-containing solid organic matrices, the laser emission remained at 92% of its initial intensity value after 100,000 pumping pulses in the same position of the sample at 30 Hz repetition rate. The laser action of the new dyes enhances that of the parent dye PM597 and outperforms the lasing behavior of dyes considered to be benchmarks over the green-yellow to red spectral region.

Photophysical and laser emission studies of 8-polyphenylene-substituted BODIPY dyes in liquid solution and in solid polymeric matrices.

In our search for efficient and photostable laser dyes, four new dyes with the basic structure of the commercial BODIPY laser dye PM567, with either an 8-diphenylene or an 8-p-triphenylene group, both substituted at the terminal polyphenylene position with an acetoxymethyl (dyes P2Ar1Ac and P3Ar1Ac, respectively) or a methacryloyloxymethyl group (dyes P2Ar1MA and P3Ar1MA, respectively), have been synthesized. The photophysical and lasing properties of the dyes have been studied both dissolved in liquid solvents (acetoxymethyl dyes) and incorporated into solid polymeric matrices, in the latter case as solutions (acetoxymethyl dyes) or as copolymers with methyl methacrylate (methacryloyloxymethyl dyes). In liquid solution, the photophysics of P2Ar1Ac and P3Ar1Ac is scarcely affected by the number (two or three) of p-phenylene units. Quantum mechanical calculations reveal that the p-phenylene units in these dyes are twisted ca. 37 degrees each other, an that the first 8-p-phenylene group stands nearly perpendicular to the aromatic BODIPY plane, resulting in electronic decoupling of the two chromophores. P2Ar1Ac exhibits a somewhat lower photodegradation quantum yield under UV and visible irradiation, if compared with P3Ar1Ac or with PM567, likely because of its also lower rate constant for the reaction with in situ-generated singlet molecular oxygen. Both acetoxymethyl dyes emit laser radiation in solution in all the solvents tried, under transversal pumping at 532 nm. In ethyl acetate, with a dye concentration of 0.80 x 10(-3) M, laser efficiencies as high as 80% have been observed. When the 8-polyphenylene dyes were incorporated into solid poly(methyl methacrylate) (PMMA) matrices, as solutions or as copolymers, the fluorescence emission increased with respect to that of the parent PM567 dye dissolved in the same matrix, and lasing efficiencies in the range 18-31% were obtained, with good photostability. The dye P2Ar1Ac dissolved in PMMA was found to exhibit the best overall laser behavior, with a good balance between efficiency and photostability.

Amplified spontaneous emission and optical gain measurements from pyrromethene 567--doped polymer waveguides and quasi-waveguides.

Amplified spontaneous emission from planar waveguides and quasi-waveguides based on Pyrromethene 567-doped poly(methyl methacrylate) thin films deposited onto quartz and glass substrates is investigated. Films with different thickness were prepared and pumped optically at 532 nm with pulses of up to 8 MW/cm(2). Pump thresholds for the onset of ASE emission, optical gains and losses were assessed. Net gain coefficients were estimated by fitting the data provided by variable stripe length measurements with a theoretical expression which takes into account saturation. In this way, net gain coefficients of up to 56 +/- 9 cm(-1) at a pump intensity of 5.3 MW/cm(2) for quasi-waveguides and up to 20.6 +/- 2.7 cm(-1) at a pump intensity of 3.4 MW/cm2 for waveguides, were obtained. Loss coefficients in the waveguides were estimated to be 3.8 +/- 0.4 cm-1 and 6.1 +/- 1.3 cm(-1) for 15 microm and 5 microm thick films, respectively. The results obtained seem to indicate a stronger self-mode-restriction capability in the quasiwaveguides than in conventional total internal-reflection waveguides.

[Platelet-rich plasma (platelet gel) in secondary alveoloplasty in cleft patients]. / Plasma enriquecido en plaquetas en la alveoloplastia de pacientes fisurados.

INTRODUCTION: The use of Platelet-rich plasma (platelet gel--PRP--) was introduced in the oral and maxilofacial surgery 10 years ago. Its good results are due to the quickly generation of new bone and the acceleration of the period of surgical scar formation. Its employment in the alveolar reconstruction of the cleft patient is not still consistent and the works published in the literature are infrequent. The objective of this preliminary study is presenting our experience with the use of PRP in the reconstruction of the alveolar congenital defects of cleft patients. PATIENTS AND METHODS: Between July 2002 and January 2004 were operated 14 patients with congenital alveolar cleft carrying out an standard secondary alveoloplasty. In 12 cases was employed cancellous bone of iliac crest and in two cases the donor area was tibial. The laboratory of Hematology of our Hospital prepared the plasma gel rich in platelets by means of a double centrifuge of autologous serum of the patient. After adding calcium a rich gel in platelets in approximate quantities of 1-2 ml was obtained. In this preliminary report we have studied the aspect of the surgical injury the 3er postoperative day, and the first and second weeks after intervention. These results were compared carried out previously with the Standard alveoloplasty without use of the PRP. Likewise we evaluated the bony density by means of intraoral Rx at 3 and 6 months postoperative. RESULTS: The injury of the alveoloplasty healed more quickly in the patients in which plasma enriched gel was employed. The patients referred less pain and edema in the first days of the postoperative period. The alveolar bony regeneration was faster to the 3 months, though the result was similar in the intraoral Rx to the 6 months. The necessary quantities of cancellous bone were smaller in all cases in which the plasma enriched gel was used (30% less). CONCLUSIONS: The use of Platelet-rich plasma (PRP) is a valid protocol for the reconstruction in patients with congenital alveolar clefts. Its low price and morbidity do it recommendable for its employment in cleft patients.

Plasma enriquecido en plaquetas en la alveoloplastia de pacientes fisurados / Platelet-rich plasma (platelet gel) in secondary alveoloplasty in cleft patients

Introducción. El uso de plasma autólogo enriquecido en plaquetas (PRP) fue introducido en la cirugía oral y maxilofacial hace unos 10 años. Sus buenos resultados se deben a la rapidez con la que genera nuevo hueso y la aceleración del período de cicatrización quirúrgico. Su empleo en la reconstrucción alveolar del paciente fisurado no es todavía consistente y los trabajos publicados en la literatura son muy escasos. El objetivo de este estudio preliminar es el de presentar nuestra experiencia con la utilización del plasma rico en plaquetas en la reconstrucción de las fisuras alveolares congénitas de pacientes fisurados. Material y métodos. Entre julio de 2002 y enero de 2004 fueron intervenidos 14 pacientes con fisura alveolar congénita realizando una alveoloplastia secundaria estándard. En 12 casos se empleó injerto óseo esponjoso de cresta ilíaca y en dos casos la zona dadora fue tibial. El laboratorio de Hematología de nuestro centro preparó el concentrado plasmático rico en plaquetas mediante un doble centrifugado de suero autólogo del paciente y pipeteado del mismo. Tras añadir gluconato cálcico se obtuvo un gel rico en plaquetas en cantidades aproximadas de 1-2 ml. En este estudio preliminar hemos estudiado el aspecto de la herida quirúrgica el 3er día postoperatorio, y la primera y segunda semanas de la intervención. Se compararon estos resultados con los realizados previamente en la alveoloplastia estándard sin uso del plasma rico en plaquetas. Igualmente se valoró la densidad ósea mediante Rx intraoral a los 3 y 6 meses. Resultados. La herida de la alveoloplastia cicatrizó mucho más rápidamente en los pacientes en los que se empleó plasma (..) (AU)

Introduction. The use of Platelet-rich plasma (platelet gel–PRP-) was introduced in the oral and maxilofacial surgery 10 years ago. Its good results are due to the quickly generation of new bone and the acceleration of the period of surgical scar formation. Its employment in the alveolar reconstruction of the cleft patient is not still consistent and the works published in the literature are infrequent. The objective of this preliminary study is presenting our experience with the use of PRP in the reconstruction of the alveolar congenital defects of cleft patients. Patients and methods. Between July 2002 and January 2004 were operated 14 patients with congenital alveolar cleft carrying out an standard secondary alveoloplasty. In 12 cases was employed cancellous bone of iliac crest and in two cases the donor area was tibial. The laboratory of Hematology of our Hospital prepared the plasma gel rich in platelets by means of a double centrifuge of autologous serum of the patient. After adding calcium a rich gel in platelets in approximate quantities (..) (AU)

Polymer-filled nanoporous silica aerogels as hosts for highly stable solid-state dye lasers.

New hybrid solid-state dye laser materials based on highly porous silica aerogels have been synthesized. The open porous network of the aerogel was saturated with laser dyes dissolved in appropriate organic monomers, and polymerization took place inside the silica structure. The resulting polymer-filled nanoporous aerogel (PFNPA) was cast in a cylindrical shape, forming monoliths that were used as gain media in solid-state dye lasers. When the PFNPA incorporated pyrromethene dyes, highly photostable laser emission with good lasing efficiency was obtained. Under the demanding conditions of tightly focused transversal pumping with 532 nm, 5 mJ pulses at 10 Hz repetition rate, the commercial dye Pyrromethene 567 exhibited laser action with only a 10% drop in the laser output after 10(6) pump pulses in the same position of the sample.

Synthesis, structure, and physical properties of hybrid nanocomposites for solid-state dye lasers.

We report on the synthesis, structural characterization, physical properties, and lasing action of two organic dyes, Rhodamine 6G (Rh6G) and Pyrromethene 597 (PM597), incorporated into new hybrid organic-inorganic materials, where the organic component was either poly(2-hydroxyethyl-methacrylate) (PHEMA) or copolymers of HEMA with methyl methacrylate (MMA), and the inorganic counterpart consisted of silica derived from hydrolysis-condensation of methyltriethoxysilane (TRIEOS) in weight proportion of up to 30%. Lasing efficiencies of up 23% and high photostabilities, with no sign of degradation in the initial laser output after 100 000 pump pulses at 10 Hz, were demonstrated when pumping the samples transversely at 534 nm with 5.5 mJ/pulse. A direct relationship could be established between the structure of the hybrid materials, analyzed by solid-state NMR, and their laser behavior. An inorganic network dominated by di-/tri- substituted silicates in a proportion approximately 35:65, corresponding to samples of HEMA with 15 and 20 wt % proportion of TRIEOS, optimizes the lasing photostability. The thermal properties of these materials, together with the high homogeneity revealed by atomic force microscopy (AFM) images, even in compounds with high silica content, indicate their microstructure to be a continuous phase, corresponding to the polymer matrix, which "traps" the silica components at molecular level via covalent bonding, with few or no silica islands.

5-Fluorouracil-loaded microspheres prepared by spray-drying poly(D,L-lactide) and poly(lactide-co-glycolide) polymers: characterization and drug release.

5-Fluorouracil (5-FU), a hydrosoluble anti-neoplastic drug, was encapsulated in microspheres of poly(D,L-lactide) (PLA) and poly(lactide-co-glycolide) (PLGA) polymers using the spray-drying technique, in order to obtain small size microspheres with a significant drug entrapment efficiency. Drug-loaded microspheres included between 47 +/- 11 and 67 +/- 12 microg 5-FU mg(-1) microspheres and the percentage of entrapment efficiency was between 52 +/- 12 and 74 +/- 13. Microspheres were of small size (average diameter: 0.9 +/- 0.4-1.4 +/- 0.8 microm microspheres without drug; 1.1 +/- 0.5-1.7 +/- 0.9 microm 5-FU-loaded microspheres) and their surface was smooth and slightly porous, some hollows or deformations were observed in microspheres prepared from polymers with larger Tg. A fractionation process of the raw polymer during the formation of microspheres was observed as an increase of the average molecular weight and also of Tg of the polymer of the microspheres. The presence of 5-FU did not modify the Tg values of the microspheres. Significant interactions between the drug and each one of the polymers did not take place and total release of the included drug was observed in all cases. The time needed for the total drug release (28-129 h) was in the order PLA > PLGA 75/25 > PLGA 50/50. A burst effect (17-20%) was observed during the first hour and then a period of constant release rate (3.52 +/- 0.82-1.46 +/- 0.26 microg 5-FU h(-1) per milligram of microspheres) up to 8 or 13 h, depending on the polymer, was obtained.

Sustained release of bupivacaine from devices based on chitosan.

Chitosan beads loaded with bupivacaine (16+/-3 microg of drug per milligram of beads) were prepared by cross-linking with glutaraldehyde. In vitro drug release at pH and temperature conditions similar to those of the biological systems were studied. Maximum release of bupivacaine was obtained between 100 and 120 h, depending on the presence of lysozyme in the release medium, since the enzyme facilitates the release process. A constant release rate of the drug, between 11 and 15 microg/h, was observed for 30 h. In order to prolong bupivacaine release, the drug-loaded chitosan beads were coated with a poly(DL-lactide-co-glycolide) film. The resulting device allows the drug to be released in a sustained form; a constant release rate between 28.5 and 29.5 microg/h was obtained for 3 days, and the maximum release of bupivacaine took place at day 9. The in vitro results indicate a possible application of these bupivacaine loaded chitosan systems as drug release devices with an analgesic action. Thus, they could be used in the treatment of dental pain in the buccal cavity, where drug release would be made easier by lysozyme of the saliva.

Photophysical and lasing properties of new analogs of the boron-dipyrromethene laser dye pyrromethene 567 incorporated into or covalently bounded to solid matrices of poly(methyl methacrylate).

The photophysical, lasing and thermostability properties of newly synthesized analogs of the commercial dye pyrromethene 567 (PM567) have been measured in polymeric matrices of poly(methyl methacrylate) both when used as a dopant and when covalently bounded to the polymeric chain. These analogs have an acetoxy or a polymerizable methacryloyloxy group at the end of a polymethylene chain at Position 8 of the PM567 chromophore core. Clear correlations between photophysical and lasing characteristics are observed. Linking chain lengths with three or more methylene units give the highest fluorescence quantum yields (as high as 0.89) and lasing efficiencies (as high as 41%). The covalent linkage of the chromophore to the polymeric chain via the methacryloyloxy group improves the photostability of the PM567 chromophore.

The efficiency of titanocene as photoinitiator in the polymerization of dental formulations.

A comparative kinetic study of the polymerization of tetraethyleneglycol dimethacrylate (TEEGDM) under visible light irradiation was carried out in order to determine the effectiveness of titanocene as photoinitiator in this process. The pair camphorquinone/dimethylaminoethyl methacrylate, CQ/DMAEMA (0.5/0.5%, by weight), was used as a reference photoinitiatior system. The reactions were carried out both in the presence and absence of oxygen (in N2) and with variable and constant titanocene concentration and incident light intensity. It was observed that in both atmospheres the polymerization reaction commenced rapidly and its initial rate was comparable with that obtained in the presence of the classic initiation system. However, after reacting for a few seconds this process suffered abrupt deactivation, this tendency being more noticeable at low titanocene concentrations. To explain the observed kinetic behavior, the study of the photofragmentation of titanocene upon irradiation with visible light in both atmospheres was carried out. The quantum yield calculated in the presence of O2 (phifr = 8 at 465 nm) suggests the existence of a chain reaction with participation of oxygen, and this explains, in turn, the high value of the initial rate of polymerization and also the rapid disappearance of the photoinitiator. In an inert atmosphere the photofragmentation occurs in a conventional way, this being a very effective process with quantum yield of 0.7 at 465 nm. However, it seems that only a small part of the active species acts as initiating radicals and these are not sufficient to achieve the appropriate monomer conversion.