The speed limit of optoelectronics.

Light-field driven charge motion links semiconductor technology to electric fields with attosecond temporal control. Motivated by ultimate-speed electron-based signal processing, strong-field excitation has been identified viable for the ultrafast manipulation of a solid's electronic properties but found to evoke perplexing post-excitation dynamics. Here, we report on single-photon-populating the conduction band of a wide-gap dielectric within approximately one femtosecond. We control the subsequent Bloch wavepacket motion with the electric field of visible light. The resulting current allows sampling optical fields and tracking charge motion driven by optical signals. Our approach utilizes a large fraction of the conduction-band bandwidth to maximize operating speed. We identify population transfer to adjacent bands and the associated group velocity inversion as the mechanism ultimately limiting how fast electric currents can be controlled in solids. Our results imply a fundamental limit for classical signal processing and suggest the feasibility of solid-state optoelectronics up to 1 PHz frequency.

Olfactory activity in the human brain identified by fMRI.

BACKGROUND: Modern imaging methods such as functional magnetic resonance imaging (fMRI) or positron emission tomography (PET) enable us to map brain activities associated with stimulation of various functional systems in the human brain. Data concerning the localization and lateralization of secondary olfactory areas are not in agreement. THE AIM OF THE STUDY: localization of secondary olfactory brain areas activated by a pleasant stimulus--vanillin. METHODS AND MATERIAL: Our fMRI method was based on the blood-oxygen-level dependent effect. All measurements were carried out on a 1.5 T scanner (Siemens-Vision), using gradient-echo EPI technic. The basic block-like scheme included no odour/and odour was repeated 8 times. In the definitive phase of the study, experiments were performed on 12 healthy volunteers aged from 20 to 68 (9 men and 3 women) stimulated birhinally by vanillin odour. RESULTS: Bilateral activations of the inferior frontal gyrus, anterior insular-periinsular area, hippocampus, amygdala, caudate nucleus and cerebellum were seen. A greater extent of activation was evident in the right hemisphere and in the right half of the cerebellum. CONCLUSIONS: The anterior insular-periinsular area and hippocampus can be considered as secondary olfactory areas in human brain. Strong activation of the right inferior frontal gyrus demonstrated in our study may be related to effort to name the presented odour. Activation of the cerebellum may be evaluated as a consequent phenomenon due to extensive activation of the frontal lobe.

[Dyspnea remains a complicated medical (clinical) problem]. / Dusnost zustává slozitým lékarským (klinickým) problémem.

Dyspnoea is a subjective sensation which probably develops as a result of integration of signals from the central nervous system and some peripheral receptors. Known dyspnoegenic stimuli include the sensation of an increased effort of the respiratory muscles, information from chemoreceptors on the inadequacy of ventilation, from pulmonary receptors on the compression of the airways and disharmony between information on the tension of the respiratory muscles and the corresponding shortening of the muscle. Pathological dyspnoea, incl. that of cardiac origin is usually associated with impaired breathing. Dyspnoea can be measured. Possible influencing of dyspnoea depends on knowledge of the mechanism of genesis of this sensation. Treatment of dyspnoea can be focused on increasing the efficiency of respiratory muscles, reduction of afferentation from receptors or suppression of the central integration of the mentioned stimuli.

Brain activation during volitional control of breathing.

Functional magnetic resonance imaging (fMRI) was used to demonstrate the brain activation during volitional control of breathing in nine healthy human subjects. This type of breathing was induced by acoustic stimuli dictating the respiratory frequency. During the period of dictated breathing not only the frontal and temporal lobes of the brain, but also the parietal lobes were bilaterally activated. The frontal lobe was activated bilaterally in all subjects, with frequent activation of Brodmann areas 4 and 6. In the parietal lobe, activation could mostly be demonstrated in gyrus postcentralis and the same was true for area 22 in the temporal lobe.

Control of breathing and brain activation in human subjects seen by functional magnetic resonance imaging.

Functional magnetic resonance imaging (fMRI) was used to demonstrate the brain activation during transition from unconscious to conscious breathing in seven healthy human subjects. In right-handed volunteers, the activated areas were found in both hemispheres. The medial part of the precentral gyrus (area 4) was constantly activated in the left hemisphere. Additional activated areas were demonstrated in the premotor cortex and in the posterior parietal cortex. The activated cortical sites exhibited analogous distribution in the right hemisphere. In two out of the seven subjects. activated sites were also observed in the cerebellar hemispheres, and in the lentiform and caudate nuclei.

Procedural memory trace for increased tidal volume can be demonstrated in healthy volunteers.

The minority of healthy subjects can (without previous learning) breathe at exactly double of their resting tidal volume on demand. The aim of the present study was to find whether this estimate of tidal volume value can be learned and at what speed. Basic spirometric values were measured by Oxycon B in 20 healthy volunteers. They learned in one day to breathe at double of the resting tidal volume twice for 3 min. The existence and duration of the memory trace was ascertained four times (three times on the same day, once three weeks later). This engram can be demonstrated on the day of learning after 1 or 2 trials of 3 min each. Three weeks later the memory trace is weak but still present. This fact means that a new breathing pattern can be learned. During learning and tests the subjects hyperventilate but no correlation was seen between learning ability and intensity of hyperventilation.

[Hormonal treatment of non-malignant diseases of the breast]. / Hormonální lécba nezhoubných onemocnení mlécné zlázy.

The authors summarize possibilities of hormonal treatment of non-malignant diseases of the mammary gland. Attention is paid in particular to progestins (progesterone, derivatives of hydroxyprogesterone, derivatives of 19 nor-testosterone), their combination with estrogens (hormonal contraceptives, minipills) and hormonal substitution therapy, methods of chemoprevention of mammary cancer. In conjunction with the subject the authors mention also the possibility to use some other preparations (Danazol, Gonadotropin releasing hormones, tamoxifen etc.). The authors submit their own pattern of hormonal treatment of non-malignant diseases of the mammary gland.

[The function of respiratory muscles in healthy persons during tube breathing]. / Výkon dýchacích svalu u zdravých lidí behem dýchání pridanou trubicí.

BACKGROUND: Tube breathing (added dead space of 600 ml) stimulates ventilation by hypercapnia and is proposed as a new test of respiratory chemosensitivity. In this study the increase of respiratory work during tube breathing was evaluated by two methods. METHODS AND RESULTS: In the first one respiratory values were measured and the rate of respiratory work was calculated according Otis, Crosfill and Widdicombe. In the second one the increase was indicated by changes in oxygen consumption at various levels of ventilation. The control rate of total respiratory work in healthy subjects was 0.07 +/- 0.04 W, during the test it was 0.18 +/- 0.07 W. The control oxygen consumption was e.g. 0.28 +/- 0.09 l.min-1 and during the test 0.32 +/- 0.06 l.min-1. CONCLUSIONS: The increase of work of breathing during the test is relatively small and is related especially to higher minute ventilation. The new test of respiratory chemosensitivity could be therefore accepted even for patients with respiratory disease.

[The dead space in volitional changes in respiratory volume]. / Mrtvý prostor pri volních zmenách dechového objemu.

The objective of the investigation was to assess changes of the dead space under conditions of volitional changes of the respiratory volume. The authors assessed therefore in repeated experiments in 11 healthy volunteers basic respiratory variables and the effective dead space using a Mijnhardt spirometer at rest and during cortically conditioned changes of the tidal volume. When the breath deepens the effective dead space reaches higher absolute values, but the relative values decline. When the breathing is more shallow, the reverse occurs. Thus e. g. in men of the investigated group a mean value of the respiratory volume at rest was assessed which amounted to 0.74 +/- 0.10 l, the relative dead space declined to 19 +/- 7%, when breathing was shallow it rose to 37 +/- 10%.

[Changing from spontaneous to volitional regulation of respiration decreases dyspnea]. / Prechod ze spontánní na volní regulaci dýchání snizuje dusnost.

The objective of the investigation was to assess whether volitional control of respiration can influence the intensity of dyspnoea. In 17 volunteers the author assessed, using Borg's method, the intensity of dyspnoea during breathing with an added dead space of 600 ml and with a flow resistance. The experiments were made in two sessions. During the first session when the examined subjects breathed spontaneously the author recorded spirographically the respiratory volume during control ventilation and after inclusion of the dead space and resistance. During the second session the experimental subjects were asked to attempt to imitate during inclusion of the dead space and resistance, as closely as possible, the respiratory pattern from the first session. In both instances the author assessed the partial pressure of CO2 in the air at the end of the expiration (P(ET)CO2). During the first session the tested subjects evaluance the dyspnoea: it had an average grade of 5.9 +/- 1.9. Volitional regulation of breathing led not only to a significant decline of the sensation of dyspnoea to 3.4 +/- 1.5 points of Borg's scale but also to a decline of the CO2 partial pressure (on average by 0.4 kPa). The author selected therefore among the tested subjects only those who were able to imitate closely the respiratory pattern from the first session (they had the same P(ET)CO2 in both instances). Also in these 8 subjects the intensity of dyspnoea during volitional control of ventilation declined from 6.5 +/- 1.8 grade to 3.8 +/- 1.5 grade according to Borg. The change from spontaneous to volitional regulation of breathing thus reduced the intensity of dyspnoea.

[Folk healing causing severe diabetic coma]. / Lidový lécitel jako prícina tezkého diabetického kómatu.

The authors demonstrate on the case of a 21-year-old female diabetic (type I), who had been well compensated with insulin for five years, the life threatening procedure of a popular healer. By eliminating insulin he induced severe keto acidotic coma.

Breathlessness in healthy subjects at physical load.

The aim of the study was to ascertain the reasons which lead to discontinuance of exercise on the bicycle ergometer in healthy untrained subjects and to assess the dependence of dyspnea on breathing pattern and on ventilation. The physical load was progressively increased to the maximum in 11 volunteers at the age of 21 +/- 1 years. During exercise some cardiovascular and respiratory parameters were measured simultaneously with the degree of dyspnea. Breathlessness was rated by means of a scaling according Borg, where 0 indicates no, 10 maximal dyspnea. Dyspnea was not a reason for termination of maximal exercise, its value being 6 +/- 1.9 in men and 4.5 +/- 2.3 in women at the end of exercise. The reasons for termination of exercise were the sensations of general fatigue and pain in lower the extremities. The degree of dyspnea correlated with the minute ventilation, with the decrease of end-tidal CO2 concentration, with the duration of exercise and some other values. The grading varied among subjects. The mathematical dependence of dyspnea was summarised by two regression equations, one without suppression, the other with suppression of interindividual differences in responses.