Ubiquitous atmospheric production of organic acids mediated by cloud droplets.

Atmospheric acidity is increasingly determined by carbon dioxide and organic acids1-3. Among the latter, formic acid facilitates the nucleation of cloud droplets4 and contributes to the acidity of clouds and rainwater1,5. At present, chemistry-climate models greatly underestimate the atmospheric burden of formic acid, because key processes related to its sources and sinks remain poorly understood2,6-9. Here we present atmospheric chamber experiments that show that formaldehyde is efficiently converted to gaseous formic acid via a multiphase pathway that involves its hydrated form, methanediol. In warm cloud droplets, methanediol undergoes fast outgassing but slow dehydration. Using a chemistry-climate model, we estimate that the gas-phase oxidation of methanediol produces up to four times more formic acid than all other known chemical sources combined. Our findings reconcile model predictions and measurements of formic acid abundance. The additional formic acid burden increases atmospheric acidity by reducing the pH of clouds and rainwater by up to 0.3. The diol mechanism presented here probably applies to other aldehydes and may help to explain the high atmospheric levels of other organic acids that affect aerosol growth and cloud evolution.

NDM-1 carbapenemase in Acinetobacter baumannii sequence type 32 in Ecuador.

OBJECTIVES: To describe a clinical case of Acinetobacter baumannii sequence type (ST) 32 harbouring a New Delhi metallo-ß-lactamase (NDM) in Ecuador. METHODS: We used multilocus sequence typing (MLST) to confirm the bacterial species and the sequence type of an A. baumannii isolate. We used synergy with the imipenem-EDTA disc method and the carbapenem inactivation method (CIM) to determine carbapenemase production; the presence of a carbapenemase gene was confirmed by PCR amplification and amplicon sequencing. RESULTS: Molecular characterization revealed the presence of A. baumannii ST32 harbouring the bla NDM-1 gene in Ecuador. The bla NDM-1 gene was isolated through PCR and amplified from a purified plasmid. CONCLUSIONS: To the best of our knowledge, this is the first report of A. baumannii ST32 harbouring the bla NDM-1 gene.

Slow oscillatory transcranial direct current stimulation (so-tDCS) during slow wave sleep has no effects on declarative memory in healthy young subjects.

BACKGROUND: The manipulation of specific brain oscillations by applying transcranial electrical stimulation techniques in order to enhance memory processes during sleep has become an intriguing field of research. A seminal study found a positive effect of slow-oscillatory transcranial direct current stimulation (so-tDCS) on sleep-dependent consolidation of declarative memories. Since then several studies have tried to replicate this result with inconsistent findings. OBJECTIVE/HYPOTHESIS: This study aimed to reexamine effects of so-tDCS on declarative memory observed in young participants based on a previously described stimulation protocol used in elderly subjects. METHODS: 23 healthy participants (mean ±â€¯SD: 23.2 ±â€¯1.9 years; 13 women) completed a word-pair test and a sequential finger tapping test before and after sleep. Participants received anodal so-tDCS bifrontaly at a frequency of 0.75 Hz or sham stimulation during NREM sleep N2, following a double-blind, placebo controlled, counterbalanced, randomized crossover design. Data were analyzed with respect to possible effects of stimulation on memory performances, sleep staging, spindle densities and EEG power in eight frequency bands. RESULTS: Stimulation had no significant effect on sleep dependent memory consolidation or on sleep macro- and microstructure. Independent of stimulation, procedural memory performances increased and declarative memory performances decreased overnight. This decline was less pronounced when participants had more than one learning opportunity. Fast parietal but not slow frontal spindle densities diminished from baseline to stimulation-free intervals under both stimulation conditions. CONCLUSION: The present study could not reproduce the results of the seminal study in young subjects, but it is consistent with results observed in elderly subjects using the same protocol. Irrespective of stimulation, re-encoding opportunities in the word-pair test had an impact on memory strength and retrieval performance.

Giant exchange coupling and field-induced slow relaxation of magnetization in Gd2@C79N with a single-electron Gd-Gd bond.

Magnetic properties of the azafullerene Gd2@C79N are studied by SQUID magnetometry. The effective exchange coupling constant jGd,e between the Gd spins and the spin of unpaired electron residing on the single-electron Gd-Gd bond is determined to be 170 ± 10 cm-1. Low temperature AC measurements revealed field-induced millisecond-long relaxation of magnetization.

Optimization and prediction of the electron-nuclear dipolar and scalar interaction in 1H and 13C liquid state dynamic nuclear polarization.

During the last 10-15 years, dynamic nuclear polarization (DNP) has evolved as a powerful tool for hyperpolarization of NMR and MRI nuclides. However, it is not as well appreciated that solution-state dynamic nuclear polarization is a powerful approach to study intermolecular interactions in solution. For solutions and fluids, the 1H nuclide is usually dominated by an Overhauser dipolar enhancement and can be significantly increased by decreasing the correlation time (τc) of the substrate/nitroxide interaction by utilizing supercritical fluids (SF CO2). For molecules containing the ubiquitous 13C nuclide, the Overhauser enhancement is usually a profile of both scalar and dipolar interactions. For carbon atoms without an attached hydrogen, a dipolar enhancement usually dominates as we illustrate for sp2 hybridized carbons in the fullerenes, C60 and C70. However, the scalar interaction is dependent on a Fermi contact interaction which does not have the magnetic field dependence inherent in the dipolar interaction. For a comprehensive range of molecular systems we show that molecules that exhibit weakly acidic complexation interaction(s) with nitroxides provide corresponding large scalar enhancements. For the first time, we report that sp hybridized (H-C) alkyne systems, for example, the phenylacetylene-nitroxide system exhibit very large scalar dominated enhancements. Finally, we demonstrate for a wide range of molecular systems that the Fermi contact interaction can be computationally predicted via electron-nuclear hyperfine coupling and correlated with experimental 13C DNP enhancements.

[Mortality risk factors in ventilator associated pneumonia]. / Factores de riesgo para mortalidad en neumonía asociada a ventilación mecánica.

OBJECTIVE: to identify lethality and mortality rates and, mortality risk factors in ventilator associated pneumonia (VAP) on 114 patients treated between 2000 and 2007. METHOD: Twenty five risk factors were analyzed, emphasizing age, gender, APACHE score, associated diseases, hypotension at intake, coma, hospitalization time, length of time of ventilation, emergency intubation, reintubation, previous antibiotics, and resistant microrganisms. RESULTS: Lethality was 25.4 %, and mortality was 2.4 %. Association between lethality, and APACHE score was found (p: 0.04). Critical APACHE value was 22. Also, in early pneumonia, association between lethality and nasogastric tube (p: 0.01, I.C. 95 % 1.39 - 6.35) was found. No association with late pneumonia was found among mortality and clinical practices. Death's RR (relative risk) increase in following values with: previous neurological disease 2.7 (p: 0.15, IC 95 % 1.15 - 6.5), neurological comaRR 2 (p: 0.2, IC 95 % 0.54 - 7.53). Nevertheless, at multivariate analysis no mortality risk factors were identified. Fair association with time in ICU (p: 0.051 IC 95 % 0.99 - 1.17) and, male sex (p: 0.051, IC 95 % 0.99 - 6.72) was found. CONCLUSIONS: We observed multiple factors associated to mortality in VAP: use of nasogastric catheter, longer stay in ICU and male sex.

Factores de riesgo para mortalidad en neumonía asociada a ventilación mecánica / Mortality risk factors in ventilator associated pneumonia

Objective: to identify lethality and mortality rates and, mortality risk factors in ventilator associated pneumonia (VAP) on 114 patients treated between 2000 and 2007. Method: Twenty five risk factors were analyzed, emphasizing age, gender, APACHE score, associated diseases, hypotension at intake, coma, hospitalization time, length of time of ventilation, emergeney intubation, reintubation, previous antibiotics, and resistant microrganisms. Results: Lethality was 25.4 percent, and mortality was 2.4 percent. Association between lethality, and APACHE score was found (p: 0.04). Critical APACHE valué was 22. Also, in early pneumonia, association between lethality and nasogastric tube (p: 0.01, I.C. 95 percent 1.39 - 6.35) was found. No association with late pneumonia was found among mortality and clinical practices. Death's RR (relative risk) increase in following valúes with: previous neurological disease 2.7 (p: 0.15, IC 95 percent 1.15 - 6.5), neurological comaRR2 (p: 0.2, IC 95 percent 0.54 - 7.53). Nevertheless, at multivariate analysis no mortality risk factors were identified. Fair association with time in ICU (p: 0.051 IC 95 percent 0.99 - 1.17) and, male sex (p: 0.051, IC 95 percent 0.99 - 6.72) was found. Conclusions: We observed múltiple factors associated to mortality in VAP: use of nasogastric catheter, longer stay in ICU and male sex.

Objetivo: Identificar la tasa de letalidad, mortalidad y factores de riesgo de mortalidad en neumonía asociada a ventilación mecánica (NAVM) en 114 pacientes de la cohorte 2000-2007. Se estudiaron 25 factores de riesgo del paciente y de las prácticas clínicas. Resultados: La tasa de letalidad fue 25,4 por ciento) y la tasa de mortalidad de 2,4 por ciento>. Se encontró asociación entre el puntaje APACHE al momento del diagnóstico de neumonía y mortalidad (p: 0,04). El valor crítico de APACHE de alto riesgo fue igual o mayor a 22. En neumonía precoz se identificó como factor de letalidad la presencia de sonda naso-gástrica (p: 0,01, IC 95 por ciento> 1,39-6,35). Para las variables categóricas no se encontró asociación significativa entre la exposición y mortalidad. El RR en presencia de enfermedad neurológica previa (accidente vascular encefálico) fue 2,7 (p: 0,15, IC 95 por ciento 1,15-6,5), coma al ingreso 2 (p: 0,2, IC 95 por ciento 0,54-7,53). En neumonía tardía, no se identificaron factores de riesgo asociados a la atención. El análisis multivariado de todas esas exposiciones no identificó factores significativos asociados a mortalidad. Identificamos una asociación débil con días de estada en UCI (p: 0,051 IC 95 por ciento 0,99-1,17) y sexo masculino (p: 0,051, IC 95 por ciento 0,99-6,72). Conclusiones: Los resultados muestran una relación multifactorial de prácticas clínicas y del paciente para fallecer por NAVM. Como factor de prácticas clínicas encontramos asociado a mortalidad el uso de sonda nasogástrica y mayor permanencia en UCI. Dependiente del paciente encontramos una débil asociación entre mortalidad y sexo masculino.

The effects of donepezil on postlearning sleep EEG of healthy older adults.

INTRODUCTION: Aging is associated with cholinergic hypofunction and memory decline. Cholinergic activity also plays a crucial role in sleep-dependent memory consolidation. The acetylcholinesterase inhibitor (AChE-I) donepezil has been found to increase sleep-related procedural memory consolidation in healthy older adults in a previous study. METHODS: Data of the former study were reanalyzed with regard to the effects of donepezil on the sleep EEG of healthy older adults. This analysis was conducted with a special focus on spectral parameters of sleep, which have previously been linked to plasticity-related processes during sleep, i.e., sigma and delta activity. Forty-two participants (aged: 60-77 years) received 5 mg of the AChE-I donepezil orally 30 min before bedtime in a placebo-controlled, double-blind design. Power values for EEG delta, theta, alpha1, alpha 2, sigma, beta and gamma frequency bands were calculated for stage 2 NREM sleep, SWS and REM sleep. RESULTS: In line with our hypotheses, the AChE-I donepezil led to an increase in sigma activity during stage 2 NREM sleep and delta activity during slow wave sleep. CONCLUSION: These results suggest that an AChE-I facilitates processes of sleep-dependent memory consolidation in older adults.

Exposure setups for laboratory animals and volunteer studies using body-mounted antennas.

For two different in vivo exposure setups body-mounted antenna systems have been designed. The first setup is designed for investigation of volunteers during simulated mobile phone usage. The setup consists of a dual-band antenna for GSM/WCDMA with enhanced carrying properties, which enables exposure for at least 8 h a day. The 10 g averaged localised SAR--normalised to an antenna input power of 1 W--measured in the flat phantom area of the SAM phantom amounts to 7.82 mW g(-1) (900 MHz) and 10.98 mW g(-1) (1966 MHz). The second exposure setup is used for a laboratory behavioural study on rats. The design goal was a localised, well-defined SAR distribution inside the animals' heads at 900 MHz. To fulfil the biological requirements, a loop antenna was developed. For tissues around the ears, a localised SAR value of 50.12 W kg(-1) averaged over a mass of 2.2 g for an antenna input power of 1 W is obtained.

[Cost and outcome of hip's arthroplasty nosocomial infection. Case and control study]. / Costo y desenlace de la infección de artroplastía de cadera. Estudio de caso y control.

Case-control study for evaluation of cost and outcome of nosocomial surgical site infection in primary hip arthroplasty during a period of 5 years. Mean hospitalization time in the orthopedic service was 54 days for cases, and 13 days for control (p<0.05). Mean hospitalization time in Intensive Care Unit (ICU) was 1.1 days for cases. There were 0.83 post primary surgery interventions in cases, and a mean of 2.08 bacteriological cultures in each case. Controls didn't have hospitalizations in the ICU surgical reinterventions nor cultures necessary. The mean cost of infected patients was US $: 6,174.8. Mean cost in controls was US $: 2,354.7. The excess of cost due to infections was US $: 2,354.7 on the average. Outcomes in cases were: normal function 30.8%; moderate or serious sequelae 46.2%; death rate 15, 4%. The measured parameters contributed to raise case costs, and they caused an unsatisfactory outcome for two third of the patients.

Costo y desenlace de la infección de artroplastía de cadera: Estudio de caso y control / Cost and outcome of hip's arthroplasty nosocomial infection: Case and control study

Case-control study for evaluation of cost and outcome of nosocomial surgical site infection in primary hip arthroplasty during a period of 5 years. Mean hospitalization time in the orthopedic service was 54 days for cases, and 13 days for control (p < 0.05). Mean hospitalization time in Intensive Care Unit (ICU) was 1.1 days for cases. There were 0.83 post primary surgery interventions in cases, and a mean of 2.08 bacteriological cultures in each case. Controls didn't have hospitalizations in the ICU surgical reinterventions nor cultures necesary. The mean cost of infected patients was US $: 6,174.8. Mean cost in controls was US $: 2,354.7. The excess of cost due to infections was US $: 2,354.7 on the average. Outcomes in cases were: normal function 30.8 percent; moderate or serious sequelea 46.2 percent; death rate 15, 4 percent. The measured parameters contributed to raise case costs, and they caused an unsatisfactory outcome for two third of the patients.

Estudio de casos y controles efectuado para evaluar el costo y desenlace de la infección del sitio quirúrgico en artroplastía primaria de cadera en cinco años. La media de hospitalización en el Servicio de Traumatología fue de 54 días para los casos y 13 días para los controles (p < 0,05). La media de hospitalización en UCI de los casos fue 1,1 días; hubo 0,83 reintervenciones en los casos y una media de 2,08 cultivos por cada caso. Los controles no tenían hospitalización en UCI, reintervenciones, ni cultivos. El costo promedio de los pacientes infectados fue $ 3.241.800 (US $ 6.174,8). El costo promedio de los controles, alcanzó a $1.236.244 (US $ 2.354,7). El exceso promedio de costo por la infección fue de $ 2.005.556 (US $ 3.820,1). El desenlace fue el siguiente: función normal 30,8 por ciento; secuelas medianas y graves 46,2 por ciento; letalidad 15,4 por ciento. Los factores medidos contribuyeron a encarecer los costos de los casos y produjeron un desenlace insatisfactorio para dos tercios de los pacientes.

Interrater reliability between scorers from eight European sleep laboratories in subjects with different sleep disorders.

Interrater variability of sleep stage scorings is a well-known phenomenon. The SIESTA project offered the opportunity to analyse interrater reliability (IRR) between experienced scorers from eight European sleep laboratories within a large sample of patients with different (sleep) disorders: depression, general anxiety disorder with and without non-organic insomnia, Parkinson's disease, period limb movements in sleep and sleep apnoea. The results were based on 196 recordings from 98 patients (73 males: 52.3 +/- 12.1 years and 25 females: 49.5 +/- 11.9 years) for which two independent expert scorings from two different laboratories were available. Cohen's kappa was used to evaluate the IRR on the basis of epochs and intraclass correlation was used to analyse the agreement on quantitative sleep parameters. The overall level of agreement when five different stages were distinguished was kappa = 0.6816 (76.8%), which in terms of kappa reflects a 'substantial' agreement (Landis and Koch, 1977). For different groups of patients kappa values varied from 0.6138 (Parkinson's disease) to 0.8176 (generalized anxiety disorder). With regard to (sleep) stages, the IRR was highest for rapid eye movement (REM), followed by Wake, slow-wave sleep (SWS), non-rapid eye movement 2 (NREM2) and NREM1. The results of regression analysis showed that age and sex only had a statistically significant effect on kappa when the (sleep) stages are considered separately. For NREM2 and SWS a statistically significant decrease of IRR with age has been observed and the IRR for SWS was lower for males than for females. These variations of IRR most probably reflect changes of the sleep electroencephalography (EEG) with age and gender.

Comparison of the amplitude/intensity function of the auditory evoked N1m and N1 components.

This study compared the intensity dependence of the auditory evoked N1 and N1m components in 10 healthy subjects. The evoked responses were recorded simultaneously at 33 channels for the auditory evoked potentials (AEP) and with a 37-channel magnetometer for the auditory evoked fields (AEF). They were satisfactorily modeled by a tangential and a radial dipole per hemisphere for the N1 component and a tangential dipole in the left hemisphere for the N1m component. The tangential dipoles showed different dipole characteristics. The amplitude of the AEP rose significantly with increasing stimulus intensity whereas the amplitudes of the AEF tended to plateau between the highest intensities. The magnetic dipole shifted to the surface of the skull with higher stimulus intensity whereas the electric tangential dipole moved to the center of the skull. The latencies decreased with increasing stimulus intensity.

Time-of-day variations in different measures of sleepiness (MSLT, pupillography, and SSS) and their interrelations.

The aim of the present study is to analyze how well physiological measures of sleepiness derived from pupillography and the Multiple Sleep Latency Test correlate with a subjective measure, the Stanford Sleepiness Scale (SSS) score. The results are based on data from 12 healthy participants, who underwent these tests every 2 hr from 7:00 a.m. until 11:00 p.m. Sleep latencies were correlated with four different variables derived from pupillography and the SSS score. The results indicate that the physiologically based variables correspond very well. This is reflected by similar patterns of time-of-day variations, a good agreement at the group level, and correlations at the individual level, whereas the SSS shows a quite different pattern of variation. The two physiological measures of sleepiness seem to reflect the same aspect of the level of tonic central nervous activation, which is not correlated with the subjective feeling of sleepiness.

P300 and LORETA: comparison of normal subjects and schizophrenic patients.

It was the aim of the present study 1) to investigate how many cortical activity maxima of scalp-recorded P300 are detected by Low Resolution Electromagentic Tomography (LORETA) when analyses are performed with high time-resolution, 2) to see if the resulting LORETA-solution is in accordance with intracortical recordings as reported by others and 3) to compare the given pattern of cortical activation maxima in the P300-timeframe between schizophrenic patients and normal controls. Current density analysis was performed in 3-D Talairach space with high time resolution i.e. in 6 ms steps. This was done during an auditory choice reaction paradigm separately for normal subjects and schizophrenic patients with subsequent group comparisons. In normal subjects, a sequence of at least seven cortical activation maxima was found between 240-420ms poststimulus: the prefrontal cortex, anterior or medial cingulum, posterior cingulum, parietal cortex, temporal lobe, prefrontal cortex, medial or anterior cingulum. Within the given limits of spatial resolution, this sequential maxima distribution largely met the expectations from reports on intracranial recordings and functional neuroimaging studies. However, localization accuracy was higher near the central midline than at lateral aspects of the brain. Schizophrenic patients less activated their cortex in a widespread area mainly in the left hemisphere including the prefrontal cortex, posterior cingulum and the temporal lobe. From these analyses and comparsions with intracranial recordings as reported by others, it is concluded that LORETA correctly localizes P300-related cortical activity maxima on the basis of 19 electrodes except for lateral cortical aspects which is most likely an edge-phenomenon. The data further suggest that the P300-deficit in schizophrenics involves an extended cortical network of the left hemisphere at several steps in time during the information processing stream.

Rhodium-catalyzed dehydrocoupling of the sterically encumbered phosphine-borane adduct tBu(2)PH.BH(3): synthesis of the linear dimers tBu(2)PH-BH(2)-tBu(2)P-BH(3) and tBu(2)PH-BH(2)-tBu(2)P-BH(2)Cl.

The dehydrocoupling of the sterically hindered phosphine-borane adduct tBu(2)PH.BH(3) above 140 degrees C is catalyzed by the rhodium complexes [Rh(1,5-cod)(2)][OTf] or Rh(6)(CO)(16) to give the four-membered chain tBu(2)PH-BH(2)-tBu(2)P-BH(3) (1), which was isolated in 60% yield and characterized by multinuclear NMR spectroscopy, mass spectrometry, and elemental analysis. Thermolysis of 1 in the temperature range 175-180 degrees C led to partial decomposition and the formation of tBu(2)PH.BH(3). When the dehydrocoupling of tBu(2)PH.BH(3) was performed in the presence of [[Rh(mu-Cl)(1,5-cod)](2)] or RhCl(3) hydrate, the chlorinated compound tBu(2)PH-BH(2)-tBu(2)P-BH(2)Cl (2) was formed which could not be obtained free of 1. The molecular structures of tBu(2)PH.BH(3), tBu(2)PH-BH(2)-tBu(2)P-BH(3) (1), and tBu(2)PH-BH(2)-tBu(2)P-BH(2)Cl (2) together with 1 were determined by single-crystal X-ray diffraction studies.

Reduced event-related current density in the anterior cingulate cortex in schizophrenia.

There is good evidence from neuroanatomic postmortem and functional imaging studies that dysfunction of the anterior cingulate cortex plays a prominent role in the pathophysiology of schizophrenia. So far, no electrophysiological localization study has been performed to investigate this deficit. We investigated 18 drug-free schizophrenic patients and 25 normal subjects with an auditory choice reaction task and measured event-related activity with 19 electrodes. Estimation of the current source density distribution in Talairach space was performed with low-resolution electromagnetic tomography (LORETA). In normals, we could differentiate between an early event-related potential peak of the N1 (90-100 ms) and a later N1 peak (120-130 ms). Subsequent current-density LORETA analysis in Talairach space showed increased activity in the auditory cortex area during the first N1 peak and increased activity in the anterior cingulate gyrus during the second N1 peak. No activation difference was observed in the auditory cortex between normals and patients with schizophrenia. However, schizophrenics showed significantly less anterior cingulate gyrus activation and slowed reaction times. Our results confirm previous findings of an electrical source in the anterior cingulate and an anterior cingulate dysfunction in schizophrenics. Our data also suggest that anterior cingulate function in schizophrenics is disturbed at a relatively early time point in the information-processing stream (100-140 ms poststimulus).

Treating problem-solving deficits on an acute care psychiatric inpatient unit.

Neuropsychological deficits in problem-solving are commonly found in patients with schizophrenia and severe affective disorders. However, in an acute care setting, treatment efforts do not typically target these deficits, even though they can impede recovery. This study aimed to evaluate the effectiveness of short-term problem-solving remediation in acutely ill psychiatric inpatients. Twenty-eight psychiatric inpatients identified as having a verbal problem-solving deficit received 6 h of either verbal problem-solving remediation or placebo instruction. Before and after treatment a nurse rated the patient's psychiatric status and the patient completed verbal and nonverbal problem-solving tests, and a self-report rating of symptoms and ability to cope with symptoms. Both groups of patients improved on the measure of verbal problem solving, but those receiving problem-solving remediation improved significantly more. Both groups made symptomatic improvement, but the patients receiving problem-solving remediation made significantly more improvement on the measure of coping ability and the nurses rated them as more improved, both psychiatrically and with regard to coping skills. Verbal problem-solving deficits are responsive to short-term remediation in an acute care setting, and treatment effects may generalize to improve ability to cope with psychiatric symptoms.

Time-of-day variations of indicators of attention: performance, physiologic parameters, and self-assessment of sleepiness.

BACKGROUND: A study was performed to analyze time-of-day variations of different indicators of attention and their interrelations. METHODS: After a sufficiently long all-night sleep 12 healthy non-sleep-deprived subjects ran through a test battery (Stanford Sleepiness Scale, Visual Analogue Scale, Critical Flicker Fusion Test [CFF], Visualization Test, Number Facility Test, Reaction Time, Pupillometry, and modified Multiple Sleep Latency Test) every 2 hours from 7:00 AM until 11:00 PM. Time-of-day variations were tested nonparametrically with Friedman's test for repeated measurements. Principal component factor analysis (of individually standardized values) was used to identify variable complexes with the same pattern of time-of-day variation. RESULTS: Statistically significant time-of-day variations were found for all variables, except for Fusion Frequency in CFF and Reaction Time. In factor analysis the physiologic parameters (pupillometric variables and sleep latencies) load on one factor, whereas the self-assessment scales, the Visualization Test, Number Faculty Test, and CFF load on the second factor. The variables that load primarily on factor 1 show peak levels of alertness immediately after getting up (at 7:00 AM) and again at 9:00 PM. Those variables that load primarily on factor 2 indicate a peak level of alertness around noon (11:00 AM-3:00 PM). CONCLUSIONS: Different aspects of attention follow different time-of-day variations. It is discussed, that these findings can be attributed to underlying circadian and homeostatic factors.