Primary photodissociation mechanisms of pyruvic acid on S1: observation of methylhydroxycarbene and its chemical reaction in the gas phase.

Pyruvic acid, a representative alpha-keto carboxylic acid, is one of the few organic molecules destroyed in the troposphere by solar radiation rather than by reactions with free radicals. To date, only its stable final products were identified, often with contribution from secondary chemistry, making it difficult to elucidate photodissociation mechanisms following excitation to the lowest singlet excited-state (S1) and the role of the internal hydrogen bond in the most-stable Tc conformer. Using multiplexed photoionization mass spectrometry we report the first direct experimental evidence, via the observation of singlet methylhydroxycarbene (MHC) following 351 nm excitation, supporting the decarboxylation mechanism previously proposed. Decarboxylation to MHC + CO2 represents 97-100% of product branching at 351 nm. We observe vinyl alcohol and acetaldehyde, which we attribute to isomerization of MHC. We also observe a 3 ± 2% yield of the Norrish Type I photoproducts CH3CO + DOCO, but only from d1-pyruvic acid. At 4 Torr pressure, we measure a photodissociation quantum yield of 1.0+0-0.4, consistent with IUPAC recommendations. However, our measured product branching fractions disagree with IUPAC. In light of previous calculations, these results support a mechanism in which hydrogen transfer on the S1 excited state occurs at least partially by tunneling, in competition with intersystem crossing to the T1 state. We present the first evidence of a bimolecular reaction of MHC in the gas phase, where MHC reacts with pyruvic acid to produce a C4H8O2 product. This observation implies that some MHC produced from pyruvic acid in Earth's troposphere will be stabilized and participate in chemical reactions with O2 and H2O, and should be considered in atmospheric modeling.

Looking at the bigger picture: Identifying the photoproducts of pyruvic acid at 193 nm.

Photodissociation of pyruvic acid (PA) was studied in the gas-phase at 193 nm using two complementary techniques. The time-sliced velocity map imaging arrangement was used to determine kinetic energy release distributions of fragments and estimate dissociation timescales. The multiplexed photoionization mass spectrometer setup was used to identify and quantify photoproducts, including isomers and free radicals, by their mass-to-charge ratios, photoionization spectra, and kinetic time profiles. Using these two techniques, it is possible to observe the major dissociation products of PA photodissociation: CO2, CO, H, OH, HCO, CH2CO, CH3CO, and CH3. Acetaldehyde and vinyl alcohol are minor primary photoproducts at 193 nm, but products that are known to arise from their unimolecular dissociation, such as HCO, H2CO, and CH4, are identified and quantified. A multivariate analysis that takes into account the yields of the observed products and assumes a set of feasible primary dissociation reactions provides a reasonable description of the photoinitiated chemistry of PA despite the necessary simplifications caused by the complexity of the dissociation. These experiments offer the first comprehensive description of the dissociation pathways of PA initiated on the S3 excited state. Most of the observed products and yields are rationalized on the basis of three reaction mechanisms: (i) decarboxylation terminating in CO2 + other primary products (∼50%); (ii) Norrish type I dissociation typical of carbonyls (∼30%); and (iii) O-H and C-H bond fission reactions generating the H atom (∼10%). The analysis shows that most of the dissociation reactions create more than two products. This observation is not surprising considering the high excitation energy (∼51 800 cm-1) and fairly low energy required for dissociation of PA. We find that two-body fragmentation processes yielding CO2 are minor, and the expected, unstable primary co-fragment, methylhydroxycarbene, is not observed because it probably undergoes fast secondary dissociation and/or isomerization. Norrish type I dissociation pathways generate OH and only small yields of CH3CO and HOCO, which have low dissociation energies and further decompose via three-body fragmentation processes. Experiments with d1-PA (CH3COCOOD) support the interpretations. The dissociation on S3 is fast, as indicated by the products' recoil angular anisotropy, but the roles of internal conversion and intersystem crossing to lower states are yet to be determined.

N(delta)-(5-hydroxy-4,6-dimethylpyrimidine-2-yl)-l-ornithine, a novel methylglyoxal-arginine modification in beer.

N(delta)-(5-Hydroxy-4,6-dimethylpyrimidine-2-yl)-L-ornithine, or Argpyrimidine, was identified and quantified in beer by high-performance liquid chromatography (HPLC) and coupled gas chromatography-mass spectrometry (HRGC-MS). This novel fluorescent arginine Maillard modification represents the first amino acid modification reported in beer retaining the full backbone of the original amino acid. Two mechanisms of formation could be verified: the major pathway via methylglyoxal and the minor pathway via 5-deoxypentoses. Argpyrimidine concentrations, determined in 35 lager-type beer varieties, reached up to 27 nmol/L and could be positively correlated to beer color and wort content. Within this context, 5-deoxy-D-ribose was identified as a novel intermediate of the Maillard reaction of maltose by HRGC-MS and independent synthesis.

Psychological and sport-specific characteristics of football players.

It is hypothesized that players of different levels of play might differ not only in their football skills but also in their way of playing football and with respect to psychological factors such as concentration, reaction time, or competitive anxiety. The psychological characteristics of a player might influence his way of playing football (in particular with respect to fair play) and also his risk of injury. A group of 588 football players were studied by questionnaire; additionally, reaction time tests were performed. Psychological characteristics were assessed by three established self-evaluation questionnaires: the Athletic Coping Skills Inventory, the State Competitive Anxiety Test, and the State-Trait-Anger-Expression-Inventory. Football-specific characteristics that were investigated included playing experience and positions played, style of play, number of training hours and games, as well as aspects of fair play. Reaction time was tested twice: without the influence of physical exercise and immediately after a 12-minute run. A significant reduction in reaction time was observed after physical exercise. In high-level players, the reaction time immediately after the 12-minute run was significantly shorter than it was in low-level players. The questionnaire answers given regarding fair play clearly indicated that fair play is not paid sufficient respect. The relationship between psychological characteristics and attitudes toward fair play was analyzed and discussed.

Assessment and evaluation of football performance.

The most important variables for measuring performance in team sports such as football are physical condition and technical and tactical performance. However, because of the complexity of the game of football it is difficult to ascertain the relative importance of each of these variables. The aim of the present study was to develop a standardized test battery to evaluate physical performance in football players. The F-MARC test battery was designed to closely relate to the football player's normal activity and comprised a functional, structured training session of approximately 2.5 hours. It included a "quality rating" of the warm-up procedure, tests of flexibility, football skills, power, speed, and endurance. The players finished with a cool-down. A total of 588 football players underwent the F-MARC test battery. Mean values for performance on each test are presented for groups of differing age and skill levels. The test battery proved to be a feasible instrument to assess both physical performance and football skills. This study supports the proposal by Balsom (1994) that analysis of an individual player's physical profile, in relation to mean values for a similar age group and skill level, might be of assistance to the coach in objectively evaluating the effects of a specific training program. It may also be of use to the physician and physical therapist responsible for monitoring progress during rehabilitation after football injuries.

Risk factor analysis for injuries in football players. Possibilities for a prevention program.

Review of the literature shows that information concerning risk factors for football injuries is incomplete and partly contradictory. The aim of this study was to analyze the influence of medical history, physical findings, football skills, and football performance, as well as psychosocial characteristics on the occurrence and severity of football injuries. The prospective outline of the study was as follows: after a baseline examination was performed to ascertain possible predictors of injury, all players were followed up weekly for 1 year to register subsequent injuries and complaints. Two hundred sixty-four of 398 players (67%) had complete weekly follow-ups over 1 year. A majority of the players (N = 216; 82%) were injured during the observation period. In comparing injured and uninjured players, several differences were observed. To create a multidimensional predictor score for football injuries, 17 risk factors were selected. These risk factors covered a wide spectrum, such as previous injuries, acute complaints, inadequate rehabilitation, poor health awareness, high life-event stress, playing characteristics, poor reaction time, poor endurance, and insufficient preparation for games. By summing up the individual risk factors, a predictive sum was calculated for each player. The more risk factors present at the baseline examination, the higher the probability of that player incurring an injury in the ensuing year. Using two risk factors as the cut-off score, more than 80% of the players were correctly classified as to whether they went on to incur an injury. Based on these findings, knowledge from the literature, and practical experience, possibilities for a prevention program are suggested.

[Acquired toxoplasmosis with cerebral involvement and subsequent hearing loss]. / Erworbene Toxoplasmose mit zerebraler Beteiligung und nachfolgender Hörstörung.

In immunocompetent patients the postnatally acquired toxoplasmosis is usually a mild or asymptomatic disease. CNS manifestations are rare, e.g. in patients with HIV infection or in patients with other types of immunosuppression. We report on a 9-year old healthy boy, who was hospitalized after one week with subfebrile temperatures and headache with clinical signs of encephalitis and unilateral deafness. We diagnosed a toxoplasmosis and treated the patient with pyrimethamine and sulfadiazine. While most of the signs and symptoms disappeared rapidly the deafness persisted.

Drug addicts attending specialised institutions: towards a drug addiction data bank?

In 1986, a national survey was carried out in France among 4846 drug abusers attending specialised agencies and treatment centres. Data are analysed and compared with the results of a previous study in 1972. Most French drug abusers are men (74%) ranged in age from 20 to 29 years (68%). Data suggest increasing problems with heroin (69%), cocaine (13%), solvents (5%), alcohol (26%) and multiple drug dependence. Women are younger, they have attempted suicide more often than men but have been incarcerated half as often. Concerning drug abuse trends, women appear to use increasingly sedatives in combination with other drugs. Partial data concerning HIV seropositivity reveal a rate of 48% among drug abusers having been tested.

[Use of psychotropic drugs and addiction: approaches to epidemiologic research]. / Usage de psychotropes et toxicomanie: voies de recherche epidemiologique.

Although the phenomenon of drug abuse in France is well delimited, it constitutes a public health problem. The way it spreads is sometimes 'epidemic' in sub-groups especially exposed. The somtic or relational consequences are short-term and it concerns more and more adolescents or young adults. Two main research axes have been developed: studies in the general population, adolescents or adults, in order to know the general context of licit and illicit psychotropic use in France, and specific studies in detoxification centers in order to describe the characteristics of drug addicts and to evaluate their requirements. Results of some recent surveys can illustrate these axes. Total abstinence is exceptional. Psychotropic drug abuse is deeply established in traditional French social customs. Most subjects had a narrow relation with psychoactive drugs. The variety as well as quantity of products allow everyone to adopt a style of consumption. Globally, alcohol consumption has decreased. Moderate consumers seem to be those who especially confine their drinking to daily wine consumption. On the other hand, the consumption of aperitifs and other drinks in on the increase. The dissociation of alcohol consumption from meals enhances drunkness. Nicotine-poisoning in men had a parallel evolution and has increased in women. Psychotropic drugs (tranquillizers and hypnotics) are specially used by aged women on medical prescription. For the study of drug abuse, data is collected in specialised centers and prisons regarding socio-demographic variables, intoxication profile and medical and social consequences. For both the general and addict population, epidemiological research, especially typological analysis, allows to identify some sub-groups at risk of drug addiction.