Melaleuca alternifolia nanoparticles against Candida species biofilms.

Candida infection is an important cause of morbidity and mortality on immunosuppressed patients. This growing trend has been associated with resistance to the antimicrobial therapy and the ability of microorganism to form biofilms. TTO oil is used as antimicrobial which shows antibiofilm activity against Candida species. However, it presents problems due to its poor solubility and high volatility. The present study aimed to evaluate in vitro antibiofilm activity of TTO nanoparticles against many Candida species. It was performed the characterization of the oil and nanoparticles. The levels of exopolysaccharides, proteins, and the biomass of biofilms were measured. The chromatographic profile demonstrated that the TTO oil is in accordance with ISO 4730 with major constituents of 41.9% Terpinen-4-ol, 20.1% of γ-Terpinene, 9,8% of α-Terpinene, and 6,0% of 1,8-Cineole. The TTO nanoparticles showed pH of 6.3, mean diameter of 158.2 ± 2 nm, polydispersion index of 0.213 ± 0.017, and zeta potential of -8.69 ± 0.80 mV. The addition of TTO and its nanoparticles represented a significant reduction of biofilm formed by all Candida species, as well as a reduction of proteins and exopolysaccharides levels. It was possible to visualize the reduction of biofilm in presence of TTO nanoparticles by Calcofluor White method.

Surface micro-morphology, phase transformation, and mechanical reliability of ground and aged monolithic zirconia ceramic.

This study aimed to determine the effects of grinding and low temperature aging on the biaxial flexural strength, structural reliability (Weibull analysis), surface topography, roughness analysis, and phase transformation (t→m) of an yttrium-stabilized tetragonal zirconia polycrystalline ceramic. Ceramic discs (15.0×1.2±0.2mm, VITA In-Ceram YZ) were prepared and randomly assigned into six groups according to 2 factors (n=30): 'grinding' (Ctrl - without treatment, as-sintered; Xfine - grinding with extra fine diamond bur - 30µm; Coarse - grinding by coarse diamond bur - 151µm), and 'aging' (without or with aging: CtrlLTD; XfineLTD; CoarseLTD). Grinding was performed in an oscillatory motion with a contra-angle handpiece under constant water-cooling. Low temperature degradation (LTD) was simulated in an autoclave at 134°C, under 2bar pressure, for 20h. The roughness (Ra and Rz parameters) significantly increased after grinding in accordance with bur grit-size (Coarse>Xfine>Ctrl), and aging promoted distinct effects (Ctrl=CtrlLTD; Xfine>XfineLTD; Coarse=CoarseLTD). Grinding increased the m-phase, and aging led to an increase in the m-phase in all groups. However, different susceptibilities to LTD were observed. Weibull analysis showed a significant increase in the characteristic strength after grinding (Coarse=Xfine>Ctrl), while aging did not lead to any deleterious impact. Neither grinding nor aging resulted in any deleterious impact on material reliability (no statistical decrease in the Weibull moduli). Thus, neither grinding nor aging led to a deleterious effect on the mechanical properties of the evaluated Y-TZP ceramic although a high m-phase content and roughness were observed.

Single-step electrochemical nanolithography of metal thin films by localized etching with an AFM tip.

This work introduces electrochemical nanolithography (ENL), a single-step method in which a metal thin film is locally etched without application of a mask on a 100 nm length scale with an electrochemical atomic force microscope (AFM). The method requires the application of ultra-short voltage pulses on the tip (nanosecond range duration, 2-4 V amplitude), while both the sample and the metalized tip are under independent potentiostatic control for full control of interface reactions in an AFM electrochemical cell. It is demonstrated that Cu films as well as Co and Cu/Co sandwich magnetic films can be patterned if negative voltage pulses are applied to the tip. This method also applies to films deposited on an insulating substrate. Moreover the lateral dimension of lithographed structures is tunable, from a few micrometers down to 150 nm, by appropriate choice of ENL conditions. Simulation of the dissolution process is discussed.

Task-dependent differences in subjective fatigue scores.

The aim of the present study was to evaluate time-on-task effects on subjective fatigue in two different tasks of varying monotony during night-time testing (20:00 to 4:00 hours) in a sleep deprivation intervention. The experiment included eight test runs separated by breaks of approximately 20 min. Twenty healthy volunteers performed a driving simulator and the Mackworth clock vigilance task in four of the test runs each. Sequence of tasks was varied across subjects. Before and after each task, subjective sleepiness was assessed by means of the Karolinska sleepiness scale and subjective fatigue was rated on the Samn-Perelli checklist. Fatigue and sleepiness significantly increased over the course of the night. Both tasks led to an increase in fatigue and sleepiness across test runs. However, this time-on-task effect was larger in the vigilance than in the driving simulator task. It is important to note that fatigue and sleepiness in one test run were not influenced by the task performed in the preceding test run, that is there were no cross-over effects. The results suggest that time-on-task effects superimpose circadian and sleep-related factors affecting fatigue. They depend on the monotony of the task and can be quantified by means of a design including separate test runs divided by breaks.

Human thermohomeostasis onboard "Mir" and in simulated microgravity studies.

Significant changes of thermogomeostatic parameters was obtained by thermotopometric method using the techniques simulate of microgravity effects: bed rest, pressurized isolation, suit immersion (SI). However, each of ground models made rectal temperature (T) trend downward. The autothermometric study (24 and 12 sessions, 2-13th and 6-174th flight days) was carried out onboard "Mir" by two flight engineers who had preliminary tested at SI (1-2 days). Studies of German investigators onboard "Mir" confirmed: rectal T must be higher in space flight as compared to the normal environment (n=4). Comparative studies suggest that microgravity is a key factor for the human body surface T raise and abolishment of the external/internal T-gradient. T-homeostasis was not really changing during missions and could be regarded as acute effect of microgravity. After delineation of changes in body surface T--by Carnot's thermodynamic law--rectal T raise should have been anticipated. Facts pointing to the excess entropy of human body must not be passed over.

Heart period and heart period variability during sleep on the MIR space station.

The long-term acclimation of cardiac rhythms to microgravity was studied in four astronauts aboard the Russian space station MIR during wakefulness and sleep. Sleep polygraphies were obtained between the third and the 30th day in space and, in addition, prior to mission on the ground. From each of the sleep polygraphies, beat-to-beat intervals of cardiac rhythms were determined. The response of heart period and heart period variability to the stimulus microgravity was tested during sleep across sleep stages and during waking. A lengthening of heart period by about 100 ms was found in space compared to measurements on the ground. The slowing of heart rate was more pronounced for non-REM sleep than for REM sleep. A systematic change in heart period in relation to the duration of the stay in space could not be detected. An analysis of heart period variability in the high frequency (respiratory sinus arrhythmia) band supports the hypothesis that the decrease of heart rate under microgravity is produced by an increase in parasympathetic activity. Testing the response of cardiac rhythms to microgravity across distinct behavioural states seems to be a powerful tool to investigate the cardiovascular system.

A circadian oscillator model based on empirical data.

A model based on the van der Pol equation has been developed to predict the pattern of adaptation of aircrew and other travellers to rapid time-zone transitions, when the exposure to light cannot be quantified. The parameters of the model include the stiffness (mu) and the intrinsic period (T0), which together define the free-running period, and the external force (F). The parameter values were estimated by using a simplex minimization technique to fit the output from the model to body temperature data from 12 individuals before, and over a 12-day period immediately after, a 10-h eastward transition between London and Sydney. Data were collected at three equally spaced points during each sleep period and at the end of four 45-min rest periods during the day. The fitting procedure enabled the parameters of the temperature rhythm to be estimated after correcting for the masking effect of sleep. The average estimates of mu (0.38 h) and T0 (24.24 h) were close to earlier estimates based on forced desynchronization experiments, and the mean free-running period, calculated from these, was 24.50 h. The mean value of the external force F (0.54) was surprisingly high, and this may reflect the strong outdoor light levels during the days in Sydney. Estimates of phase, based on the model solutions, suggested that 11 subjects adapted by a phase delay and 1 by a phase advance. However, the amplitude of the rhythms was much reduced at times when the phase was changing rapidly. Simulations using the range of the model parameters for the 12 individuals predicted that adaptation to within 1 h after a 10-h eastward transition would be achieved within between 3 and 11 days. However, since these predictions are dependent on the choice of external force, estimates may need to be more conservative in real-life situations when light exposure cannot be measured.

Joint NASA-ESA-DARA Study. Part three: characterization of sleep under ambient CO2-levels of 0.7% and 1.2%.

An experiment was conducted to study sleep quality and sleep architecture in volunteers living in a closed system under elevated ambient CO2 levels of 0.7% and 1.2%. In a closed system, human life is possible only if the CO2 level is permanently adjusted. For the Russian space station MIR, for example, the CO2 levels of the present study are actual upper limits for the adjustment. Sleep architecture was found to be altered in astronauts on the orbiting MIR station. Sleep quantity and quality were reduced. The latency to the first REM sleep was shorter in space and slow wave sleep was redistributed from the first to the second sleep cycle. The elevated CO2 concentration in the atmosphere on MIR may be one of the reasons for those observations regarding sleep in space. Thus, this experiment was also conducted in order to clarify the interpretation of data obtained from astronauts on MIR. In this study sleep polygraphies could be recorded in 4 subjects who lived for 23 d under 0.7% and then for the same period of time under 1.2% CO2. Findings suggest that these levels of ambient CO2 do not reduce sleep quality. Sleep architecture, however, was slightly changed and showed that the amount of slow wave sleep increased with the duration of the exposure to CO2. But it can be excluded that findings on MIR were caused by elevated CO2-levels.

Joint NASA-ESA-DARA Study. Part three: cardiorespiratory response to elevated CO2 levels during sleep.

Long-term exposure to elevated ambient CO2-levels is a common condition for living in a closed environment such as a spacecraft. In this study, the cardio-respiratory system response to CO2-levels of 0.7% and 1.2% was assessed. The response was investigated during non-REM sleep when the sensitivity of the respiratory system to ambient CO2 is low and only subject to the metabolic respiratory drive. Four subjects were exposed to 0.7% and 1.2% CO2 for 23 d each. Respiration rate and heart rate were determined for the first two phases of slow wave sleep. In addition, the occurrence of central apneas was assessed. Data were analyzed by a repeated measure ANOVA. As a response to CO2 exposure two dynamic effects were observed. Heart rate increased initially with a peak between the second and the sixth night. Over the period of the exposure, respiration rate and heart rate decreased steadily. At least two mechanisms with different time constants must be considered for this dynamic behavior: an uncompensated respiratory acidosis, followed by a phase of relative compensation. At the end of the 23-d exposure, equilibrium in the physiological state had not been reached. Though the experiment did not show severe effects from CO2, it is too early to state that a long-term exposure does not have any consequences for health and well-being.

Two-crew operations: stress and fatigue during long-haul night flights.

BACKGROUND: As part of a research program concerning legal aspects of two-pilot operations on long-haul routes, the purpose of the study was to investigate two-crew extended range operations during a flight roster with two consecutive night flights and a short layover. HYPOTHESIS: Present flight time regulations may not be adequate for two-crew minimum operations. METHODS: The study was conducted in cooperation with a German airline company on the route Frankfurt (FRA)-Mahe (SEZ). There were 11 rotations (22 flights) that were investigated by pre-, in- and post-flight data collection each time from the two pilots. Recordings included sleep, taskload, fatigue and stress by measurement of EEG, ECG, motor activity, and subjective ratings. The average actual flight times were 9:15 h (FRA-SEZ) and 9:53 h (SEZ-FRA). All flights took place at night. The layover duration in Mahe was 13:30 h during day-time. RESULTS: During layover, sleep was shortened by 2 h on average compared with 8-h baseline sleep. The two consecutive night duties resulted in a sleep loss of 9.3 h upon return to home base. Inflight ratings of taskload showed moderate grades, but for fatigue ratings an increasing level was observed. Fatigue was more pronounced during the return flight and several pilots scored their fatigue at a critical level. Motor activity, brainwave activity (occurrences of micro-events) and heart rate indicated drowsiness and a low state of vigilance and alertness during both night flights, but these effects were more pronounced during the second flight. CONCLUSIONS: From the findings it is concluded that a duty roster, as conducted in this study, may impose excessive demands on mental and physiological capacity.

The alteration of human sleep and circadian rhythms during spaceflight.

Numerous anecdotes in the past suggest the concept that sleep disturbances in astronauts occur more frequently during spaceflight than on ground. Such disturbances may be caused in part by exogenous factors, but also an altered physiological state under microgravity may add to reducing sleep quality in a spacecraft. The present investigation aims at a better understanding of possible sleep disturbances under microgravity. For the first time, experiments were conducted in which sleep and circadian regulation could be simultaneously assessed in space. Four astronauts took part in this study aboard the Russian MIR station. Sleep was recorded polygraphically on tape together with body temperature. For a comparison, the same parameters were measured during baseline periods preceding the flights. The circadian phase of body temperature was found to be delayed by about 2 h in space compared with baseline data. A free-run was not observed during the first 30 d in space. Sleep was shorter and more disturbed than on earth. In addition, the structure of sleep was significantly altered. In space, the latency to the first REM episode was shorter, and slow-wave sleep was redistributed from the first to the second sleep cycle. Several mechanisms may be responsible for these alterations in sleep regulation and circadian phase. Most likely, altered circadian zeitgebers on MIR and a deficiency in the process S of Borbély's sleep model cause the observed findings. The change in process S may be related to changes in physical activity as a result of weightlessness.

Sleepiness of civil airline pilots during two consecutive night flights of extended duration.

Sleepiness of civil airline pilots was studied in a two-crew cockpit during two consecutive night flights of about 10 h duration each. Sleepiness was assessed by EEG recordings and subjective ratings during hourly recurrent short experimental phases. On the second night flight, the alertness component that is related to the preceding sleep showed a modification due to reduced quality and quantity of sleep between flights. The daytime sleep during layover was not sufficient to maintain the same alertness level as observed during the initial flight. This result is in coincidence with investigations in shift workers starting a period of night shifts. It is concluded that improvements such as the introduction of a nap schedule should be considered to alleviate spontaneous sleepiness in the cockpit.

Sleep and circadian rhythm during a short space mission.

An experiment was conducted to assess sleep and circadian regulation in an orbiting spacecraft. In orbit the weakened influence of 24-h zeitgebers could result in delayed circadian phases with the possibility of a transition to free-running circadian rhythms. This and the specific stressors of a space mission may lead to changes in ultradian sleep regulation and in reduced sleep quantity and quality. During the mission sleep was recorded polygraphically on tape, as was body temperature. Daytime alertness was rated subjectively by a mood questionnaire. For comparison the same parameters were measured during a baseline period preceding the space mission. The circadian rhythms of body temperature and alertness were found to be delayed in space compared to baseline. This may mark a phase shift or the transition to a circadian state of free-run. Sleep was shorter and more disturbed. The structure of sleep was significantly altered. In space REM latency was shorter, there was less REM sleep in the second non-REM/REM cycle, and slow-wave sleep was redistributed from the first to the second cycle. The self-assessed mood resembled sleep disturbances and adaptation to the space environment. Reduced sleep quality and quantity are likely to result in fatigue and lower daytime performance. Countermeasures should be adopted to improve sleep of astronauts.

[Computer-assisted analysis of the electroencephalogram with a theta ground rhythm variant]. / Rechnergestützte Analysen bei Elektroenzephalogrammen mit einer Theta-Grundrhythmusvariante.

UNLABELLED: From 8 men and 12 women with a slow posterior rhythm on the one hand and from 7 male and 5 female healthy volunteers with a regular alpha-EEG on the other closed-eye-EEGs were registered at 8:00 a.m., 12:00 noon, 4:00 p.m., and 8:00 p.m. and recorded on tape for computer processing. Simultaneously each time the body temperature was measured. RESULTS: In 11 of the 20 patients the slow posterior rhythm shows a right-sided accentuation, in 6 a left-sided. Besides the activity of all frequency-bands favours occipital and occipital-central the right hemisphere. The control group shows only an insignificant right-sided accentuation of alpha-power and alpha-peak-power. The alpha-peak-frequency of the 20 patients is slower than in the controls, the body temperature on the contrary is higher. The physiological circadian shift of the alpha-peak-frequency and of the body temperature does not come up to a similar extent as in the controls. Striking slight is the circadian shift of the frequency of the slow posterior rhythm. Furthermore the day-time related shifts of the alpha-power and of the beta-power take other courses than in the controls. And the maxima of the alpha-power and of the alpha-peak-power are mostly located parietal instead of occipital. All in all the slow posterior rhythm seems to be connected with far-reaching peculiarities of the cerebral function.

A mathematical model of the human circadian system and its application to jet lag.

A mathematical model of the circadian system is described that is appropriate for application to jet lag. The core of the model is a van der Pol equation with an external force. Approximate solutions of this equation in which the external force is composed of a constant and an oscillating term are investigated. They lead to analytical expressions for the amplitude and period of free-running rhythms and for the frequency limits of the entrainment region. The free-running period increases quadratically with stiffness. Both period and amplitude depend on the value of the constant external force. The width of the range of entrainment is mostly determined by the external force, whereas the relative position of this range follows the intrinsic period of the oscillator. Experiments with forced and spontaneous internal desynchronization were evaluated using these analytical expressions, and estimates were obtained for the intrinsic period of the oscillator, its stiffness, and the external force. A knowledge of these model parameters is essential for predictions about circadian dynamics, and there are practical implications for the assessment of the adaptation after rapid trans-meridian travel.

Topographical changes in the ongoing EEG related to the difficulty of mental tasks.

An experiment was carried out to investigate the hypothesis that task difficulty is reflected in changes in the topographical distribution of the ongoing EEG. Subjects had to perform three different tasks at two difficulty levels each; the Sternberg memory scanning task in an auditory and in a visual mode and a task whose performance required mainly visual scanning. Task difficulty was verified by the measurement of response times. Using a commercial Brain Electrical Activity Mapping device, EEG was recorded from 19 scalp electrodes while the subjects performed the tasks. Spectral matrices of the EEG were calculated to investigate spatial relationships in the EEG. Compared to the lower level, higher task difficulty resulted in EEG changes that led to the identification of two factors. One was the reduction of parietal and occipital alpha activity due to the amount of visual scanning and the other an increase of theta activity in the left frontal electrodes which may be associated with the amount of general mental processing.

[EEG studies in Alzheimer dementia and multi-infarct dementia at various times of the day]. / EEG-Untersuchungen bei Demenz vom Alzheimer-Typ und Multiinfarktdemenz zu verschiedenen Tageszeiten.

From three men and seven women (mean age 70 years) with dementia of the Alzheimer-type (DAT), and from four men and six women (mean age 77 years) with multi-infarct dementia (MID) closed-eye EEGs were registered at 0800, 1200, 1600, and 2000 hours and recorded on tape for computer processing. The data of both groups were compared statistically and also compared with data of former investigations conducted with 10 healthy elderly volunteers and 10 patients who suffered from cerebral arteriosclerosis with serious disorder of sleep-walking rhythm (HA). Most pathological EEG deviations are found in the MID-patients, but there is no significant distinction compared to the DAT-patients, although three of the latter showed normal EEGs. Compared to the HA the EEGs of the MID-patients differed more from those of the healthy volunteers; however, the physiological circadian variations were not leveled as in the HA. Even in consideration of daytime dependent fluctuations of frequency-parameters, a clear-cut discrimination between DAT and MID by means of the EEG seems impossible.

Influence of melatonin treatment on human circadian rhythmicity before and after a simulated 9-hr time shift.

The hormone melatonin is currently proposed by some investigators to be an efficient means for decreasing the impairing effects of jet lag. Eight healthy male subjects, aged 20 to 32, underwent a 9-hr advance shift in the isolation facility of our institute during two periods each of 15 days' duration. In a double-blind, crossover design, subjects took either melatonin or placebo at 1800 hr local time for 3 days before the time shift and at 1400 hr for 4 days afterwards. The time shift was simulated on days 7 and 8 by shortening the sleep period by 6 hr and the following wake period by 3 hr. Body temperature was recorded every 90 min, and urine was collected at 3-hr intervals all day and night. Melatonin treatment enhanced the resynchronization speed of some, but not all, hormone and electrolyte excretion rates for several days after the time shift. The adaptation speed of the temperature rhythm significantly increased during one postshift day. In addition, the circadian temperature rhythm had a significantly higher amplitude under melatonin treatment than under placebo after the time displacement. For the placebo group, the rhythm of 6-hydroxymelatoninsulfate excretion exhibited an advance shift in five subjects, whereas the other three showed a delay shift, and adjustment did not achieve more than one-half of the expected value within 8 days. A significantly different adjustment could be observed in the melatonin-treated group: Seven subjects underwent an advance shift of the expected 9 hr within an average of 8 days. The results suggest that melatonin treatment can accelerate resynchronization of the melatonin excretion rhythm after eastward time zone transitions. The improvement is not, however, sufficiently great that we can recommend melatonin for the alleviation of jet lag.

[EEG studies before and following hemofiltration]. / EEG-Untersuchungen vor und nach Hämofiltration.

For a sample of 8 men and 3 women, 47-80 years old, closed-eye-EEGs were registered for the first time in the morning before hemofiltration treatment, again thereafter at 1 p.m., and a third time at 7 p.m. The day after treatment EEG-registrations were conducted at the same times. Apart from traditional visual evaluation every EEG was recorded on tape for computer processing. Simultaneously with every EEG-registration the body temperature was measured. For comparison served corresponding data of 17 hemodialysis patients, and of 10 healthy old and 12 healthy young volunteers. The peak-frequency of the hemofiltration patients turned out significantly slower than that of the healthy persons and of the hemodialysis patients. While in the healthy volunteers the peak-frequency increased corresponding with the body temperature from the morning to the evening, the hemofiltration patients lacked such a correlation, although their temperature ascended in the normal way. As to the circadian variations of the activity in the diverse frequency-bands, the hemofiltration patients, and to a less degree the hemodialysis patients, showed especially in the day after treatment distinct deviations from the healthy volunteers.

Transition between advance and delay responses to eastbound transmeridian flights.

In response to eastbound transmeridian flights, which result in zeitgeber phase advance shifts, adaptation of the circadian system to the new time zone by phase delays and advances are observed. The delay response to an advance zeitgeber shift has been called an antidromic response. For the shift at which the transition from an advance to an antidromic response occurs, the term critical shift is introduced. For the study of critical shifts, a flight experiment across nine time zones and numerical simulations of a van der Pol equation have been evaluated. The interest is focussed on the determination of a range for critical abrupt shifts. An abrupt shift means that the ensemble of zeitgebers including geophysical zeitgebers and the rest-activity cycle is shifted immediately in the new time zone. The range of critical advance shifts has been estimated to reach from +7 to +10 hr. In the literature, results were reported which would imply a much wider range. The discussion of these observations shows that the actual shifts were presumably not abrupt in the quoted experiments. The consequences of critical shifts for jet lag symptoms are investigated. If reduced circadian amplitudes and long times taken for the resynchronization contribute to the feeling of jet lag, the symptoms will be worst for shifts close to the critical one, as numerical simulations revealed. Manipulations of such shifts with the aim to alleviate jet lag are discussed.