2,628 research outputs found
Software and example data for error grid analysis
No full textSupplement of the article
Grothe O, Kaplan A, Kouz K, Saugel B. "Computer program for error grid analysis in arterial blood pressure method comparison studies"
to provide the error grid analysis suggested in
Saugel B, Grothe O, Nicklas JY. "Error Grid Analysis for Arterial Pressure Method Comparison Studies. Anesthesia and analgesia 2018;126:1177-85.Detailed information for usage is provided in the article
Spectroscopic Studies on Nitric Acid Hydrates
No full textMixtures of nitric acid hydrates and water ice are important constituents of solid Cirrus cloud particles. Due to the phase diagram only hexagonal ice and nitric acid trihydrate
should have a reasonable thermodynamic stability and are commonly observed. However, a number of metastable modifications might also exist: NAD, -NAT, and cubic ice. The persistence of these metastable compounds remains uncertain and has not
been proofed yet. In the laboratory we have developed a model procedure in order to prepare and investigate
all hydrates and ice mixtures. The investigation methods are X-ray diffraction [1, 2], FTIR spectroscopy [3], Raman spectroscopy [4, 5] and Environmental SEM [6, 7]. Only recently, we have also applied Inelastic Neutron Scattering. The aim was to verify the phase composition by diffraction and to collect the spectroscopic data,
which are needed for interpretation of field measurements and aerosol chamber experiments. Here, the morphology of the particles has to be considered, since it can have an important impact on the respective extinction spectra.
[1] H. Tizek, E. Knözinger, H. Grothe, PCCP 4 (2002), 5128.
[2] H. Tizek, E. Knözinger, H. Grothe, PCCP 6 (2004), 972.
[3] H. Grothe, C.E. Lund Myhre, H. Tizek, Vibr. Spectr. 34 (2004), 55.
[4] H. Grothe, C.E. Lund Myhre, C.J. Nielsen, JPC A 110 (2006), 110, 171.
[5] R. Escribano, D. Fernández-Torre, V. Herrero, B. Martín-Llorente, B. Maté, I.
Ortega, H. Grothe, Vibr. Spectr. 43 (2007), 254.
[6] H. Grothe, H. Tizek, D Waller, D Stokes, PCCP 8 (2006), 2232.
[7] H. Grothe, H. Tizek and I. K. Ortega, Faraday Discussion 137 (2008) 223
Software and example data for error grid analysis
No full textSupplement of the article
Grothe O, Kaplan A, Kouz K, Saugel B. "Computer program for error grid analysis in arterial blood pressure method comparison studies"
to provide the error grid analysis suggested in
Saugel B, Grothe O, Nicklas JY. "Error Grid Analysis for Arterial Pressure Method Comparison Studies. Anesthesia and analgesia 2018;126:1177-85
Interaction of excitation and inhibition in processing of pure tone and amplitude-modulated stimuli in the medial superior olive of the mustached bat
Get PDF 1. In mammals with good low-frequency hearing, the medial superior olive (MSO) processes interaural time or phase differences that are important cues for sound localization. Its cells receive excitatory projections from both cochlear nuclei and are thought to function as coincidence detectors. The response patterns of MSO neurons in most mammals are predominantly sustained. In contrast, the MSO in the mustached bat is a monaural nucleus containing neurons with phasic discharge patterns. These neurons receive projections from the contralateral anteroventral cochlear nucleus (AVCN) and the ipsilateral medial nucleus of the trapezoid body (MNTB). 2. To further investigate the role of the MSO in the bat, the responses of 252 single units in the MSO to pure tones and sinusoidal amplitude-modulated (SAM) stimuli were recorded. The results confirmed that the MSO in the mustached bat is tonotopically organized, with low frequencies in the dorsal part and high frequencies in the ventral part. The 61-kHz region is overrepresented. Most neurons tested (88%) were monaural and discharged only in response to contralateral stimuli. Their response could not be influenced by stimulation of the ipsilateral ear. 3. Only 11% of all MSO neurons were spontaneously active. In these neurons the spontaneous discharge rate was suppressed during the stimulus presentation. 4. The majority of cells (85%) responded with a phasic discharge pattern. About one-half (51%) responded with a level-independent phasic ON response. Other phasic response patterns included phasic OFF or phasic ON-OFF, depending on the stimulus frequency. Neurons with ON-OFF discharge patterns were most common in the 61-kHz region and absent in the high-frequency region. 5. Double tone experiments showed that at short intertone intervals the ON response to the second stimulus or the OFF response to the first stimulus was inhibited. 6. In neuropharmacological experiments, glycine applied to MSO neurons (n = 71) inhibited any tone-evoked response. In the presence of the glycine antagonist strychnine the response patterns changed from phasic to sustained (n = 35) and the neurons responded to both tones presented in double tone experiments independent of the intertone interval (n = 5). The effects of strychnine were reversible. 7. Twenty of 21 neurons tested with sinusoidally amplitude-modulated (SAM) signals exhibited low-pass or band-pass filter characteristics. Tests with SAM signals also revealed a weak temporal summation of inhibition in 13 of the 21 cells tested.(ABSTRACT TRUNCATED AT 400 WORDS) </jats:p
The Mammalian Interaural Time Difference Detection Circuit Is Differentially Controlled by GABAB Receptors during Development
Get PDFThroughout development GABAB receptors (GABABRs) are widely expressed in the mammalian brain. In mature auditory brainstem neurons, GABABRs are involved in the short-term regulation of the strength and dynamics of excitatory and inhibitory inputs, thus modulating sound analysis. During development, GABABRs also contribute to long-term changes in input strength. Using a combination of whole-cell patch-clamp recordings in acute brain slices and immunostainings in gerbils, we characterized developmental changes in GABABR-mediated regulation of synaptic inputs to neurons in the medial superior olive (MSO), an auditory brainstem nucleus that analyzes interaural time differences (ITDs). Here, we show that, before hearing onset, GABABR-mediated depression of transmitter release is much stronger for excitation than inhibition, whereas in mature animals GABABRs mainly control the inhibition. During the same developmental period, GABABR immunoreactivity shifts from the dendritic to the somatic region of the MSO. Furthermore, only before hearing onset (postnatal day 12), stimulation of the fibers originating in the medial and the lateral nucleus of the trapezoid body (MNTB and LNTB) activates GABABRs on both the inhibitory and the excitatory inputs. After hearing onset, GAD65-positive endings devoid of glycine transporter reactivity suggest GABA release from sources other than the MNTB and LNTB. At this age, pharmacological increase of spontaneous synaptic release activates GABABRs only on the inhibitory inputs. This indicates not only a profound inhibitory effect of GABABRs on the major inputs to MSO neurons in neonatal animals but also a direct modulatory role of GABABRs for ITD analysis in the MSO of adult animals
Metastable nitric acid hydrates - PSC constituents
No full textNitric acid hydrates are important constituents of solid PSC and Cirrus cloud particles.
Due to the phase diagram only hexagonal ice and nitric acid trihydrate have a reasonable
thermodynamic stability and are commonly observed in the stratosphere. Besides,
also a number of metastable modifications might exist: -NAD, -NAD, -NAT, NAP
and cubic ice. The existence of these metastable compounds remains uncertain and has
not been proofed yet.
In the laboratory we have developed a model procedure in order to prepare and investigate
all hydrates as pure phases. The investigation methods are X-ray diffraction
[1], [2], FTIR spectroscopy [3], Raman spectroscopy [4] and Environmental SEM [5].
The aim is to verify the phase composition by diffraction and collect the spectroscopic
data of the respective phases, which are needed for interpretation of field measurements
and aerosol chamber experiments. Here, the morphology of the particles has to
be considered since it has an important impact on the respective extinction spectra.
Particular interest has been directed towards the modifications of NAD, which have
been discriminated for the first time by spectroscopic methods. The morphologies of
NAD particles have been recorded by ESEM and the respective extinction spectra
have been determined by T-matrix calculations. Beside the mid-IR region, where normal
vibrations have been assigned, we have also focused on the low-frequency region
below 200 cm−1 where phonon bands are observed by Raman spectroscopy. These
intermolecular vibrations are closely connected to the symmetry and structure of the
unit cell of a hydrate crystal [6]. Thus, a distinction between the phases becomes easily
accessible.
[1] H. Tizek, E. Knözinger, H. Grothe, PCCP 4 (2002), 5128.
[2] H. Tizek, E. Knözinger, H. Grothe, PCCP 6 (2004), 972.
[3] H. Grothe, C.E. Lund Myhre, H. Tizek, Vibr. Spectr. 34 (2004), 55.
[4] H. Grothe, C.E. Lund Myhre, C.J. Nielsen, JPC A 110 (2006), 110, 171.
[5] H. Grothe, H. Tizek, D Waller, D Stokes, PCCP 8 (2006), 2232.
[6] R. Escribano, D. Fernández-Torre, V. Herrero, B. Martín-Llorente, B. Maté, I.
Ortega, H. Grothe, Vibr. Spectr. 43 (2007), 254
Bilateral inhibition by glycinergic afferents in the medial superior olive
Get PDF 1. Coincidence-detection of excitatory synaptic potentials has long been considered to be the mechanism by which medial superior olivary (MSO) neurons compute interaural time differences. Here we demonstrate the contribution of synaptic inhibition in this circuit using a gerbil brain slice preparation. 2. Nearly all cells exhibited excitatory postsynaptic potentials (EPSPs) and action potentials (APs) after stimulation of either the ipsilateral or contralateral afferent pathway. In 44% of cells, the latency of APs depended on stimulus amplitude, exhibiting shifts of 0.25-2 ms. 3. Nearly all neurons (89%) exhibited stimulus-evoked synaptic inhibition. The inhibitory effects were enhanced at greater stimulus amplitudes and were usually able to block synaptically evoked APs. In addition, APs and EPSPs were reversibly blocked by delivering the inhibitory transmitter glycine in almost all tested cells (91%). 4. In the presence of the glycine antagonist strychnine, the effects of synaptic inhibition were suppressed. 5. The stimulus level-dependent inhibitory potentials influenced the probability that an MSO neuron would fire an AP, as well as the precise timing. Therefore, the present results have implications for the processing of interaural time differences by the MSO and at higher auditory centers. </jats:p
Sensitivity to interaural time differences in the medial superior olive of a small mammal, the Mexican free-tailed bat
Get PDFNeurons in the medial superior olive (MSO) are thought to encode interaural time differences (ITDs), the main binaural cues used for localizing low-frequency sounds in the horizontal plane. The underlying mechanism is supposed to rely on a coincidence of excitatory inputs from the two ears that are phase-locked to either the stimulus frequency or the stimulus envelope. Extracellular recordings from MSO neurons in several mammals conform with this theory. However, there are two aspects that remain puzzling. The first concerns the role of the MSO in small mammals that have relatively poor low-frequency hearing and whose heads generate only very small ITDs. The second puzzling aspect of the scenario concerns the role of the prominent binaural inhibitory inputs to MSO neurons. We examined these two unresolved issues by recording from MSO cells in the Mexican free-tailed bat. Using sinusoidally amplitude-modulated tones, we found that the ITD sensitivities of many MSO cells in the bat were remarkably similar to those reported for larger mammals. Our data also indicate an important role for inhibition in sharpening ITD sensitivity and increasing the dynamic range of ITD functions. A simple model of ITD coding based on the timing of multiple inputs is proposed. Additionally, our data suggest that ITD coding is a by-product of a neuronal circuit that processes the temporal structure of sounds. Because of the free-tailed bat's small head size, ITD coding is most likely not the major function of the MSO in this small mammal and probably other small mammals
Efficient Temporal Processing of Naturalistic Sounds
Get PDFIn this study, we investigate the ability of the mammalian auditory pathway to adapt its strategy for temporal processing under natural stimulus conditions. We derive temporal receptive fields from the responses of neurons in the inferior colliculus to vocalization stimuli with and without additional ambient noise. We find that the onset of ambient noise evokes a change in receptive field dynamics that corresponds to a change from bandpass to lowpass temporal filtering. We show that these changes occur within a few hundred milliseconds of the onset of the noise and are evident across a range of overall stimulus intensities. Using a simple model, we illustrate how these changes in temporal processing exploit differences in the statistical properties of vocalizations and ambient noises to increase the information in the neural response in a manner consistent with the principles of efficient coding
Spectroscopy, microscopy and diffraction experiments devoted to ice clouds
No full textWater ice and nitric acid hydrates exhibit very different particle morphologies, which have an enormous impact on its ability to scatter and reflect light. This has an effect not only on the detection of ice particles by satellite instruments or ground-based optical remote sensing but also interferes with earth´s radiation balance. Since most morphological investigations in the atmosphere are hampered due to an interference of the microscopic technique to the ice particles, one is dependent on laboratory model experiments. In the past, a scanning electron microscope required a sufficient vacuum in the sample chamber in order to prevent a diversion of the electron beam. Modern environmental electron microscopy uses an imaging gas (water or nitrogen), which connects different advantages and prevents several handicaps. Firstly, the imaging gas works as secondary-emission multiplier. Secondly, the gas discharges the sample surface regularly and makes insulators accessible to SEM. Thirdly, a mixture of water and nitrogen prevents dehydration of the sample. Here, we present ESEM pictures of nitric acid hydrates and water ices. These particles exhibit morphological changes during an annealing program which can be related to respective phase changes, which have been corroborated by X-ray diffraction and vibrational spectroscopy in former experiments. [1,2] Different techniques of sample preparation have been applied, which range from gas phase deposition, to quenching techniques and oil-matrix isolation of frozen droplets. Beside the assignment of ice and hydrate particles and the evaluation of their impact on the spectroscopic data, we could also identify phase separations into hydrates and ice or impurities. This is an interesting result since it gives an idea of the topology of frozen atmospheric particles, which comprise a mixture of different organic and inorganic substances.[3]
[1] H. Grothe, H. Tizek and I. K. Ortega "Metastable Nitric Acid Hydrates - Possible Constituents of Polar Stratospheric Clouds?" Faraday Discussion 2008, 137, 223-234.
[2] H. Grothe, H. Tizek, D. Waller and D. J. Stokes "The crystallization kinetics and morphology of nitric acid trihydrate" Phys. Chem. Chem. Phys. 2006, 8, 2232-2239.
[3] H. Grothe "Interactive comment on "Inhibition of ice crystallisation in highly viscous aqueous organic acid droplets" by B. J. Murray"; Atmospheric Chemistry and Physics Discussion, 2008, 8, 3992-3995
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