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Background Noise (background + noise)
Selected AbstractsMapQuant: Open-source software for large-scale protein quantificationPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 6 2006Kyriacos C. Leptos Abstract Whole-cell protein quantification using MS has proven to be a challenging task. Detection efficiency varies significantly from peptide to peptide, molecular identities are not evident a,priori, and peptides are dispersed unevenly throughout the multidimensional data space. To overcome these challenges we developed an open-source software package, MapQuant, to quantify comprehensively organic species detected in large MS datasets. MapQuant treats an LC/MS experiment as an image and utilizes standard image processing techniques to perform noise filtering, watershed segmentation, peak finding, peak fitting, peak clustering, charge-state determination and carbon-content estimation. MapQuant reports abundance values that respond linearly with the amount of sample analyzed on both low- and high-resolution instruments (over a 1000-fold dynamic range). Background noise added to a sample, either as a medium-complexity peptide mixture or as a high-complexity trypsinized proteome, exerts negligible effects on the abundance values reported by MapQuant and with coefficients of variance comparable to other methods. Finally, MapQuant's ability to define accurate mass and retention time features of isotopic clusters on a high-resolution mass spectrometer can increase protein sequence coverage by assigning sequence identities to observed isotopic clusters without corresponding MS/MS data. [source] Logistic mixture of multivariate regressions for analysis of water quality impacted by agrochemicalsENVIRONMETRICS, Issue 5 2007Yongsung Joo Abstract In this paper, we study the impacts of two representative agricultural activities, fertilizers and lime application, on water quality. Because of heavy usage of nitrogen fertilizers, nitrate (NO) concentration in water is considered as one of the best indicators for agricultural pollution. The mixture of normal distributions has been widely applied with (NO) concentrations to cluster water samples into two environmentally interested groups (water impacted by agrochemicals and natural background water groups). However, this method fails to yield satisfying results because it cannot distinguish low-level fertilizer impact and natural background noise. To improve performance of cluster analysis, we introduce the logistic mixture of multivariate regressions model (LMMR). In this approach, water samples are clustered based on the relationships between major element concentrations and physicochemical variables, which are different in impacted water and natural background water. Copyright © 2006 John Wiley & Sons, Ltd. [source] Cortical auditory dysfunction in benign rolandic epilepsyEPILEPSIA, Issue 6 2008Dana F. Boatman Summary Purpose: To evaluate cortical auditory function, including speech recognition, in children with benign rolandic epilepsy (BRE). Methods: Fourteen children, seven patients with BRE and seven matched controls, underwent audiometric and behavioral testing, simultaneous EEG recordings, and auditory-evoked potential recordings with speech and tones. Speech recognition was tested under multiple listening conditions. Results: All participants demonstrated normal speech recognition abilities in quiet, as well as normal peripheral and subcortical auditory function. BRE patients performed significantly worse than controls when speech recognition was tested under adverse listening conditions, including background noise. Five BRE patients who were impaired on two or more tests had centrotemporal spiking on awake EEG. There were no significant group differences in the latency or amplitude of early N100 cortical responses to speech or tones. Conversely, the mismatch negativity, a preattentive index of cortical processing that is elicited passively, was absent or prolonged for speech, but not tones, in BRE patients as compared to controls. Discussion: Children with BRE demonstrated specific speech recognition impairments. Our evoked potential findings indicate that these behavioral impairments reflect dysfunction of nonprimary auditory cortex and cannot be attributed solely to attention difficulties. A possible association between auditory impairments and centrotemporal spiking (>1/min) on awake EEG was identified. The pattern of speech recognition impairments observed is a known risk factor for academic difficulties in school-age children. Our results underscore the importance of comprehensive auditory testing, using behavioral and electrophysiological measures, in children with BRE. [source] Diversity of the Vocal Signals of Concave-Eared Torrent Frogs (Odorrana tormota): Evidence for Individual SignaturesETHOLOGY, Issue 11 2009Albert S. Feng Male concave-eared torrent frogs (Odorrana tormota) have an unusually large call repertoire and have been shown to communicate ultrasonically. We investigated the individual specificity of male advertisement calls in order to explore the acoustic bases of individual recognition, which was demonstrated in an accompanying study. Vocalizations of 15 marked males were recorded in the field. A quantitative analysis of the signals revealed eight basic call-types. Two of them (the single- and multi-note long-calls) were investigated in more detail. Long-calls were characterized by pronounced and varying frequency modulation patterns, and abundant occurrence of nonlinear phenomena (NLP), i.e., frequency jumps, subharmonics, biphonations and deterministic chaos. The occurrence of NLP was predictable from the contour of the fundamental frequency in the harmonic segment preceding the onset of the NLP, and this prediction showed individual-specific patterns. Fifteen acoustic variables of the long calls were measured, all of which were significantly different among individuals, except biphonic segment duration. Discriminant function analysis (DFA) showed that 54.6% of the calls could be correctly assigned to individual frogs. The correct classification was above chance level, suggesting that individual specificity of calls underlie the ability of males to behaviorally discriminate the vocal signals of their neighbors from those of strangers, a remarkable feat for a frog species with a diverse vocal repertoire. The DFA classification results were lower than those for other anurans, however. We hypothesize that there is a tradeoff between an increase in the fundamental frequency of vocalizations to avoid masking by low-frequency ambient background noise, and a decrease in individual-specific vocal tract information extractable from the signal. [source] MASKING INTERFERENCE AND THE EVOLUTION OF THE ACOUSTIC COMMUNICATION SYSTEM IN THE AMAZONIAN DENDROBATID FROG ALLOBATES FEMORALISEVOLUTION, Issue 9 2006Adolfo Amézquita Abstract The efficacy of communication relies on detection of species-specific signals against the background noise. Features affecting signal detection are thus expected to evolve under selective pressures represented by masking noise. Spectral partitioning between the auditory signals of co-occurring species has been interpreted as the outcome of the selective effects of masking interference. However, masking interference depends not only on signal's frequency but on receiver's range of frequency sensitivity; moreover, selection on signal frequency can be confounded by selection on body size, because these traits are often correlated. To know whether geographic variation in communication traits agrees with predictions about masking interference effects, we tested the hypothesis that variation in the male-male communication system of the Amazonian frog, Allobates femoralis, is correlated with the occurrence of a single species calling within an overlapping frequency range, Epipedobates trivittatus. We studied frogs at eight sites, four where both species co-occur and four where A. femoralis occurs but E. trivittatus does not. To study the sender component of the communication system of A. femoralis and to describe the use of the spectral range, we analyzed the signal's spectral features of all coactive species at each site. To study the receiver component, we derived frequency-response curves from playback experiments conducted on territorial males of A. femoralis under natural conditions. Most geographic variation in studied traits was correlated with either call frequency or with response frequency range. The occurrence of E. trivittatus significantly predicted narrower and asymmetric frequency-response curves in A. femoralis, without concomitant differences in the call or in body size. The number of acoustically coactive species did not significantly predict variation in any of the studied traits. Our results strongly support that the receiver but not the sender component of the communication system changed due to masking interference by a single species. [source] Regional monitoring of infrasound events using multiple arrays: application to Utah and Washington StateGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2008Stephen J. Arrowsmith SUMMARY In this paper, we present an integrated set of algorithms for the automatic detection, association, and location of low-frequency acoustic events using regional networks of infrasound arrays. Here, low-frequency acoustic events are characterized by transient signals, which may arise from a range of natural and anthropogenic sources, examples of which include (but are not limited to) earthquakes, volcanic eruptions, explosions, rockets and bolides. First, we outline a new technique for detecting infrasound signals that works successfully in the presence of correlated noise. We use an F -statistic, sequentially adapted to ambient noise conditions, in order to obtain detections at a given statistical significance while accounting for real background noise. At each array, individual arrivals are then grouped together based on measured delay-times and backazimuths. Each signal is identified as either a first or later arrival. First arrivals at spatially separated arrays are then associated using a grid-search method to form events. Preliminary event locations are calculated from the geographic means and spreads of grid nodes associated with each event. We apply the technique to regional infrasound networks in Utah and Washington State. In Utah, over a period of approximately 1 month, we obtain a total of 276 events recorded at three arrays in a geographic region of 6 × 4°. For four ground-truth explosions in Utah, the automatic algorithm detects, associates, and locates the events within an average offset of 5.4 km to the actual explosion locations. In Washington State, the algorithm locates numerous events that are associated with a large coalmine in Centralia, Washington. An example mining-explosion from Centralia is located within 8.2 km of the mine. The methodology and results presented here provide an initial framework for assessing the capability of infrasound networks for regional infrasound monitoring, in particular by quantifying detection thresholds and localization errors. [source] Assessing the influence of scanner background noise on auditory processing.HUMAN BRAIN MAPPING, Issue 8 2007Abstract We compared two experimental designs aimed at minimizing the influence of scanner background noise (SBN) on functional MRI (fMRI) of auditory processes with one conventional fMRI design. Ten subjects listened to a series of four one-syllable words and had to decide whether two of the words were identical. This was contrasted with a no-stimulus control condition. All three experimental designs had a duration of ,17 min: 1) a behavior interleaved gradients (BIG; Eden et al. [1999] J Magn Reson Imaging 41:13,20) design (repetition time, TR, = 6 s), where stimuli were presented during the SBN-free periods between clustered volume acquisitions (CVA); 2) a sparse temporal sampling technique (STsamp; e.g., Gaab et al., [2003] Neuroimage 19:1417,1426) acquiring only one set of slices following each of the stimulations with a 16-s TR and jittered delay times between stimulus offset and image acquisition; and 3) an event-related design with continuous scanning (ERcont) using the stimulation design of STsamp but with a 2-s TR. The results demonstrated increased signal within Heschl's gyrus for the STsamp and BIG-CVA design in comparison to ERcont as well as differences in the overall functional anatomy among the designs. The possibility to obtain a time course of activation as well as the full recovery of the stimulus- and SBN-induced hemodynamic response function signal and lack of signal suppression from SBN during the STsamp design makes this technique a powerful approach for conducting auditory experiments using fMRI. Practical strengths and limitations of the three auditory acquisition paradigms are discussed. Hum Brain Mapp, 2006. © 2006 Wiley-Liss, Inc. [source] Assessing the influence of scanner background noise on auditory processing.HUMAN BRAIN MAPPING, Issue 8 2007Abstract Several studies reported decreased signal intensities within auditory areas for experimental designs employing continuous scanner background noise (SBN) in comparison to designs with less or no SBN. This study examined the source for this SBN-induced masking effect of the blood oxygenation level-dependent (BOLD) response by directly comparing two experimental sessions with the same auditory stimulation, which was presented either with or without recorded scanner background noise (RecSBN). Ten subjects listened to a series of four one-syllable words and had to decide whether two of the words were identical. The words were either presented with a silent background or with added RecSBN. This was then contrasted with either silence or RecSBN. A sparse temporal sampling method was used in both sessions, which enabled us to directly assess the influence of RecSBN without varying scanning parameters, acquisition quantities, or auditory stimulations. Our results suggest that previously reported SBN-induced masking of the BOLD response in experimental designs with SBN might be caused by an interaction between increased baseline levels and nonlinearity effects within auditory cortices. Adding SBN to an experimental condition does not enhance signal intensities to the same degree that SBN does when presented with a silent background, and therefore contrasting an experimental and baseline condition that both have SBN may lead to signal decreases. In addition, our study shows this effect is greatest in Heschl's gyrus, but can also be observed in higher-order auditory areas. Hum Brain Mapp, 2006. © 2006 Wiley-Liss, Inc. [source] Extraction of Stimulus-Selective Intrinsic Optical Signals From the Cat Visual CortexIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 6 2009Midori Nagai Non-member Abstract Optical imaging based on intrinsic optical signals has been widely utilized in studies on the functional organization of various areas of the brain. Because of the small size of the optical signals and the large amount of background noise that is present, it is critical to be able to separate the stimulus-driven optical change from the background. In this study, we propose a novel method and apply it to the analysis of the orientation preference structure in cat area 17. The three criteria used to determine the activation included the amplitude of the optical change in the optical intensity, the statistical significance level of the change, and the temporal relationship between the optical change and the visual stimulation. In the activated region extracted by the new method, 82.4 ± 8.2% of the cells were electrophysiologically responsive to the stimuli that evoked the optical change. This was significantly higher than the 46.4 ± 7.1% value obtained when the activation region was extracted by the most widely used method, i.e. a differential map between two complementary stimuli, such as orthogonal orientations. Our newly proposed method provides a robust and an effective way to reduce manual operations used in the signal extraction process. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] In Pursuit of Zero: Polymer Brushes that Resist the Adsorption of ProteinsADVANCED MATERIALS, Issue 23 2009Angus Hucknall Abstract Protein resistant or "non-fouling" surfaces are of great interest for a variety of biomedical and biotechnology applications. This article briefly reviews the development of protein resistant surfaces, followed by recent research on a new methodology to fabricate non-fouling surfaces by surface-initiated polymerization. We show that polymer brushes synthesized by surface-initiated polymerization that present short oligo(ethylene glycol) side chains are exceptionally resistant to protein adsorption and cell adhesion. The importance of the protein and cell resistance conferred by these polymer brushes is illustrated by their use as substrates for the fabrication of antibody microarrays that exhibit femtomolar limits of detection in complex fluids such as serum and blood with relaxed requirements for intermediate wash steps. This example highlights the important point that the reduction in background noise afforded by protein-resistant surfaces can greatly simplify the development of ultrasensitive heterogeneous, surface-based clinical and proteomic assays with increased sensitivity and utility. [source] Cross-correlation-based trans-impedance amplifier for current noise measurementsINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 6 2009Gino Giusi Abstract This work proposes a cross-correlation-based trans-impedance amplifier for current noise measurements in the low-frequency range. The proposed solution is compared with the classical cross-correlation trans-impedance amplifier showing a lower background noise. Furthermore, a three-step measurement method, based on the new trans-impedance amplifier, is proposed to cancel the residual background noise. SPICE simulations and noise measurements performed on prototype circuits demonstrate the validity of the proposed approach. Copyright © 2008 John Wiley & Sons, Ltd. [source] Effects of construction noise on behaviour of and exhibit use by Snow leopards Uncia uncia at Basel zooINTERNATIONAL ZOO YEARBOOK, Issue 1 2008C. E. SULSER Noise caused by human activities can cause stress in animals. We examined whether noise from construction sites affects the behaviour of and exhibit use by three Snow leopards Uncia uncia at Basel zoo. The behaviour and location of the animals were recorded at 1 minute intervals, using the instantaneous scan sampling method over a period of 216 hours (104 hours on noisy days and 112 hours on quiet days). The animals differed individually in their responses to the construction noise. On noisy days, the Snow leopards generally spent less time in locomotion and more time resting, but even on quiet days, resting was the predominant behaviour performed. Under noisy conditions, they increased social resting and decreased resting alone. Walking and social walking were also reduced on noisy days. Furthermore, the Snow leopards spent considerably more time in the remote off-exhibit enclosure under noisy conditions. Independent of background noise, they stayed more than half of the time in the caves and the forecourts of the outdoor enclosure. On quiet days, the Snow leopards used more sectors of their exhibit than on noisy days. The results indicate that the Snow leopards responded to construction noise by increasing the amount of time spent resting and by withdrawing to the remote parts of their exhibit. [source] A comparison of three noise reduction procedures applied to bird vocal signalsJOURNAL OF FIELD ORNITHOLOGY, Issue 3 2007Myron C. Baker ABSTRACT Recordings of avian vocal signals in natural habitats include ambient noise. Often this background noise corrupts across all frequencies and is of substantial amplitude. Reducing this ambient noise to prepare vocal signals for playback stimuli or to remove habitat-specific noise signatures prior to analyzing a signal's acoustic characteristics can be useful. We conducted experimental evaluations of three noise reduction procedures to determine their effectiveness. We embedded two bird vocalizations ("clean" signals) in four kinds of natural noise, resulting in eight noise-signal combinations. We then applied three noise reduction procedures (Noise Profile, Band Pass, and Noise Estimate) to each of the embedded signals and compared the recovered signals to the original (clean) signals. Noise Profile filtering was effective in reducing noise and returning fairly high-quality signals from even severe levels of masking noise. The other two noise reduction procedures did not perform as well. For the two most corrupting maskers, however, Noise Profile filtering also altered the signal properties by reducing signal amplitude at those frequencies containing high levels of noise. Apart from this loss of amplitude, the quantitative features of the filtered signals were similar to those of the original model sounds. We conclude that Noise Profile filtering produces good results for cases where noise is approximately constant over the signal duration and the signal intensity exceeds noise intensity over the frequencies of interest. SINOPSIS La grabación de sonidos de aves en hábitats naturales incluye ruidos ambientales. A menudo este ruido es de amplitud sustancial y afecta todas las frecuencias. Antes de analizar una señal vocal, podría ser útil reducir este ruido ambiental, bien para preparar vocalizaciones grabadas para provocar respuestas de aves como para remover ruidos asociados a hábitats. Llevamos a cabo una serie de experimentos con tres procedimientos de reducción de ruido para determinar su efectividad. Insertamos dos vocalizaciones de aves (señales "limpias") en cuatro tipos de ruidos naturales, obteniendo como resultado ocho combinaciones de señales con ruido. Posteriormente, aplicamos tres procedimientos de reducción de ruido ("Perfil de Ruido,""Paso de Banda" y "Estimaciones de Ruido") a cada una de las señales insertadas y comparamos las señales recuperadas con los sonidos originales (limpios). La filtración tipo "Perfil de Ruido" resultó efectiva para reducir el ruido y producir señales de razonablemente buena calidad, aún en situaciones de ruido severo. Los otros dos tratamientos no funcionaron tan bien. Para los dos tipos de ruido con mayores efectos, el "Perfil de Ruido" alteró las propiedades de la señal y redujo la amplitud de la misma, en aquellas frecuencias que contenían altos niveles de ruido. Además de la pérdida de amplitud, los elementos cuantitativos de las señales filtradas fueron similares a las de los modelos sonoros originales. Concluimos que el procedimiento de filtrado "Perfil de Ruido" produce buenos resultados para casos en donde el ruido es de duración aproximadamente constante a lo largo de la señal y cuando la intensidad de la señal excede la intensidad del ruido sobre las frecuencias de interés. [source] PAMAM dendrimer-based contrast agents for MR imaging of Her-2/neu receptors by a three-step pretargeting approachMAGNETIC RESONANCE IN MEDICINE, Issue 4 2008Wenlian Zhu Abstract Pretargeting of receptors is a useful approach in molecular imaging and therapy to reduce background noise or toxicity and enhance selectivity. In this study a three-step pretargeting approach that includes a biotinylated antibody, avidin/streptavidin, and a biotinylated imaging agent is described. A PAMAM dendrimer generation 4 (G4D)-based MRI T1 agent biotin-G4D-DTPA-Gd (bG4D-Gd) and its sister compound with remaining free surface amine groups blocked by succinic anhydride to reduce positive charges (bG4D-Gd-SA) were synthesized. Limited selective enhancement in MRI was observed in a Her-2/neu mouse tumor xenograft by this three-step pretargeting approach that includes biotinylated trastuzumab, avidin and bG4D-Gd, or bG4D-Gd-SA. However, these dendrimer-based MRI agents with molecular weight around 29 kD reached and remained in the tumor through the enhanced permeability and retention effect. Prolonged and extensive accumulation of both bG4D-Gd and b-G4-Gd-SA in the kidneys was also observed. Magn Reson Med, 2008. © 2008 Wiley-Liss, Inc. [source] SEASONAL OCCURRENCE OF SPERM WHALE (PHYSETER MACROCEPHALUS) SOUNDS IN THE GULF OF ALASKA, 1999,2001MARINE MAMMAL SCIENCE, Issue 1 2004David K. Mellinger Abstract An acoustic survey for sperm whales was conducted in the Gulf of Alaska. Six autonomous hydrophones continuously recorded sound signals below 500 Hz from October 1999 to May 2001. After recovery, recordings were processed using an automatic process to detect usual clicks of sperm whales. The detection algorithm equalized background noise, summed the data in a frequency band, and then used autocorrelation to detect the whales' highly regular clicks. Detections were checked manually, revealing that 98% of detections did contain clicks. Results indicate that sperm whales are present in the Gulf of Alaska year-round; this result extends what is known from whaling data, which were gathered principally in summer. Sperm whales were more common in summer than winter by a factor of roughly two, and occurred less often at the westernmost site surveyed (52°N, 157°W) than elsewhere in the Gulf. This is the first study of sperm whales based exclusively on remote acoustic sensing. This methodology is feasible because sperm whale clicks extend to frequencies (,100 Hz) low enough to be recorded by low-sample-rate instruments that operate continuously, and because the detection algorithm has a low false-detection rate. The methodology may be replicated to facilitate comparisons between different time periods and geographic regions. [source] Logic of experiments in ecology: is pseudoreplication a pseudoissue?OIKOS, Issue 1 2001Lauri Oksanen Hurlbert divides experimental ecologist into ,those who do not see any need for dispersion (of replicated treatments and controls), and those who do recognize its importance and take whatever measures are necessary to achieve a good dose of it'. Experimental ecologists could also be divided into those who do not see any problems with sacrificing spatial and temporal scales in order to obtain replication, and those who understand that appropriate scale must always have priority over replication. If an experiment is conducted in a spatial or temporal scale, where the predictions of contesting hypotheses are convergent or ambiguous, no amount of technical impeccability can make the work instructive. Conversely, replication can always be obtained afterwards, by conducting more experiments with basically similar design in different areas and by using meta-analysis. This approach even reduces the sampling bias obtained if resources are allocated to a small number of well-replicated experiments. For a strict advocate of the hypothetico-deductive method, replication is unnecessary even as a matter of principle, unless the predicted response is so weak that random background noise is a plausible excuse for a discrepancy between predictions and results. By definition, a prediction is an ,all-statement', referring to all systems within a well-defined category. What applies to all must apply to any. Hence, choosing two systems and assigning them randomly to a treatment and a control is normally an adequate design for a deductive experiment. The strength of such experiments depends on the firmness of the predictions and their a priori probability of corroboration. Replication is but one of many ways of reducing this probability. Whether the experiment is replicated or not, inferential statistics should always be used, to enable the reader to judge how well the apparent patterns in samples reflect real patterns in statistical populations. The concept ,pseudoreplication' amounts to entirely unwarranted stigmatization of a reasonable way to test predictions referring to large-scale systems. [source] Repeated fluorescence in situ hybridization by a microwave-enhanced protocolPATHOLOGY INTERNATIONAL, Issue 9 2006Yasuhiko Kitayama A novel re-hybridization protocol for pathology archive sections that uses microwave-assisted fluorescence in situ hybridization (FISH) is described. Stripping the probe from the pathology archive sections with HCl and re-hybridizing with the next probe by intermittent microwave irradiation generated clear signals without background noise. Repeated stripping and hybridization with numerous bacterial artificial chromosome (BAC)-derived probes would identify the profile of genome-wide changes in small lesions on sections. [source] Influence of focused auditory attention on cochlear activity in humansPSYCHOPHYSIOLOGY, Issue 1 2001Stéphane Maison The mammalian auditory system contains descending pathways that originate in the cortex and relay at various intermediate levels before reaching the peripheral sensory organ of Corti. The last link in this chain consists of the olivocochlear bundle. The activity of this bundle can be measured through otoacoustic emissions, which are acoustic signatures of the cochlear biomechanical activity. In the present study, it was hypothesized that frequency-specific activation of the olivocochlear bundle in the contralateral ear would show up as frequency-specific variations in otoacoustic emission amplitude in the ipsilateral ear. Two groups of young adult subjects participated in this experiment. Evoked otoacoustic emissions were recorded in the ipsilateral ear at two test frequencies (1 and 2 kHz). Subjects had to detect probe tones at a given frequency in background noise in the contralateral ear. Larger efferent activation was measured at test frequencies on which attention is focused. This result provides evidence for an influence of attention on the auditory periphery via descending projections. [source] Comparison of flow injection analysis electrospray mass spectrometry and tandem mass spectrometry and electrospray high-field asymmetric waveform ion mobility mass spectrometry and tandem mass spectrometry for the determination of underivatized amino acidsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2006Margaret McCooeye Twenty proteinogenic amino acids (AAs) were determined without derivatization using flow injection analysis followed by electrospray ionization mass spectrometry and tandem mass spectrometry (ESI-MS and ESI-MS/MS) and electrospray ionization high-field asymmetric waveform ion mobility mass spectrometry and tandem mass spectrometry (ESI-FAIMS-MS and ESI-FAIMS-MS/MS), in positive and negative ionization modes. Three separate sets of ESI-FAIMS conditions were used for the separation and detection of the 20 AAs. Typically ESI-FAIMS-MS showed somewhat improved sensitivity and significantly better signal-to-noise ratios than ESI-MS mainly due to the elimination of background noise. However, the difference between ESI-FAIMS-MS and ESI-MS/MS was significantly less. ESI-FAIMS was able to partially or completely resolve all the isobaric amino acid overlaps such as leucine, isoleucine and hydroxyproline or lysine and glutamine. Detection limits for the amino acids in ESI-FAIMS-MS mode ranged from 2,ng/mL for proline to 200,ng/mL for aspartic acid. Overall, ESI-FAIMS-MS is the preferred method for the quantitative analysis of AAs in a hydrolyzed yeast matrix. Copyright © 2006 Crown in the right of Canada. Published by John Wiley & Sons, Ltd. [source] Data processing issues in large-area GPR surveys: correcting trace misalignments, edge discontinuities and stripingARCHAEOLOGICAL PROSPECTION, Issue 2 2008Eileen G. Ernenwein Abstract Ground-penetrating radar (GPR) lags behind other archaeogeophysical methods in terms of speed, efficiency and ability to produce clean site-wide composites owing to complex and time-consuming data processing requirements. Two North American case studies illustrate problems that occur when survey is conducted over long and short periods of time. Some GPR defects have been blamed on differential solar heating of antennae and battery power levels but we show these effects to be negligible. Major problems include gradual changes over time in ground moisture and low-level background noise, which can create discontinuities between adjacent survey blocks when data are collected at different times. These problems are often remedied by globally aligning traces using a stable trace position. Variations in ground moisture through time also cause differences in reflection amplitudes, necessitating different range gain curves to match amplitudes between survey blocks. In some cases changes in ground moisture cause noticeable differences in velocity between survey blocks requiring time-scales to be converted to depths to correctly match the data. These problems must be remedied before horizontal slicing can be considered. Subsequent image processing may also be necessary to generate a seamless mosaic and eliminate striping artefacts commonly seen in slice maps. The latter are probably caused by antenna lift and tilt and can be removed by a de-striping algorithm that uses a one-dimensional low-pass filter to characterize stripes followed by their subtraction from the data. Copyright © 2008 John Wiley & Sons, Ltd. [source] Imaging geophysical data,taking the viewer into accountARCHAEOLOGICAL PROSPECTION, Issue 1 2004T. J. Dennis Abstract A common way of presenting geophysical data from two-dimensional sources is as a grey-scale image. Some theoretical background to discrete image representation is described, and the deleterious effects of inappropriate (too sparse) sampling and display of such images discussed in an archaeological context. In high-quality images, such as magazine illustrations or digital television, the sampling densities can be sufficiently high to avoid the appearance of artefacts. Geophysical images in contrast are often sampled at very low densities; if the effective area of each sample is significantly less than the sample spacing, then the classic effect called ,aliasing' in communication engineering, caused by the violation of Nyquist's criterion, will be seen. Knowledge of the sensor's footprint can be used to select an appropriate sample density, and so minimize this source of distortion. To maximize the visibility of what may be low-contrast structures immersed in a high level of background noise, it is helpful also to consider the bandpass nature of the spatial frequency response of the human visual system. The non-linear phenomenon of visual masking is shown to influence the choice on presentation methods. Copyright © 2004 John Wiley & Sons, Ltd. [source] A framework for describing correlated excitation of solar p-modesASTRONOMISCHE NACHRICHTEN, Issue 5 2008W. J. Chaplin Abstract In a previous paper we suggested that, for a given p mode, the excitation function is the same as the component of the solar background noise that has an identical surface spherical harmonic projection (over the corresponding range of temporal frequency). An important consequence of this surmise is that the excitation of overtones of a given angular degree and azimuthal order will be correlated in time. In this note, we introduce the basic principles and a mathematical description of correlated mode excitation. We use simple, illustrative examples, involving two modes. Our treatment suggests that in the real observations, any signatures of the correlation would not appear as a correlation of the output amplitudes of overtones, but rather as subtle modifications to the power spectral density at frequencies between the central frequencies of the overtones. These modifications give a contribution to the observed peak asymmetries. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Analytische Herleitung von Anforderungen an den Luftschallschutz zwischen RäumenBAUPHYSIK, Issue 4 2009Beratender Ingenieur VBI Wolfgang Moll Prof. Ing. Schall; Technische Regelwerke; sound protection and acoustics; technical recommendations Abstract Vor dem Hintergrund der Auseinandersetzungen um die Höhe des Schallschutzes der zurzeit überarbeiteten DIN 4109 "Schallschutz im Hochbau" befasst sich der Autor kritisch mit der bisherigen Art der Festlegung bauakustischer Anforderungen. In Anbetracht der fehlenden physikalischen Legitimation dieser Anforderungen , früher an die Schalldämmwerte, jetzt an die Schallschutzwerte , schlägt der Verfasser die gezielte Berechnung der nachhallzeitbezogenen Schallschutzanforderungen vor, und zwar auf der Basis allgemein bekannter Ausgangsdaten, wie z. B. der Schallleistung der einzelnen Quellen, der Verdeckung durch den Grundpegel etc. Das Verfahren wird ausführlich erläutert und beispielhaft erklärt. Für die Abstufungen Mindestschallschutz, erhöhter Schallschutz, hoher Schallschutz werden Basiswerte vorgeschlagen, die dann in die gezielte Bestimmung der Anforderungsgrößen einfließen. Analytical derivation of requirements for airborne sound insulation between rooms. Against the background of the debate about sound protection levels in the current revision of DIN 4109 "Sound insulation in buildings" the author critically examines the existing methodology for determining acoustic requirements. In view of the lack of physical legitimation of these requirements , previously sound insulation values, now sound protection values , the author proposes targeted calculation of reverberation-related sound protection requirements based on generally known basic data, including the sound power levels of individual sources, masking through background noise, etc. The technique is explained in detail and illustrated by means of examples. Basic values are proposed for minimum sound protection, increased sound protection and high sound protection, which are then used for determining the requirements for individual parameters. [source] Oscillations in growth of multicellular tumour spheroids: a revisited quantitative analysisCELL PROLIFERATION, Issue 4 2010A. S. Gliozzi Objectives:, Multicellular tumour spheroids (MTS) provide an important tool for study of the microscopic properties of solid tumours and their responses to therapy. Thus, observation of large-scale volume oscillations in MTS, reported several years ago by two independent groups (1,2), in our opinion represent a remarkable discovery, particularly if this could promote careful investigation of the possible occurrence of volume oscillations of tumours ,in vivo'. Materials and methods:, Because of high background noise, quantitative analysis of properties of observed oscillations has not been possible in previous studies. Such an analysis can be now performed, thanks to a recently proposed approach, based on formalism of phenomenological universalities (PUN). Results:, Results have provided unambiguous confirmation of the existence of MTS volume oscillations, and quantitative evaluation of their properties, for two tumour cell lines. Proof is based not only on quality of fitting of the experimental datasets, but also on determination of well-defined values of frequency and amplitude of the oscillations for each line investigated, which would not be consistent with random fluctuation. Conclusions:, Biological mechanisms, which can be directly responsible for observed oscillations, are proposed, which relates also to recent work on related topics. Further investigations, both at experimental and at modelling levels, are also suggested. Finally, from a methodological point of view, results obtained represent further confirmation of applicability and usefulness of the PUN approach. [source] 3134: Identification of potential human corneal endothelial stem-like cell nichesACTA OPHTHALMOLOGICA, Issue 2010G THURET Purpose to study the localization of potential stem-(like) cells in human adult corneal endothelium Methods Fresh (6-12h post mortem) and organ cultured (OC) corneas were studied after flat mount. The whole endothelium and posterior limbus (PL) was observed after triple staining with Trypan blue, Alizarin red and Hoechst 33342, in order to determine cells shape, localization and viability. The level of endothelial cell (EC) differenciation was determined after immunostaining (fluorescence) for ZO-1, Na+/K+ ATPase and COX IV; the cell proliferation status was assessed using Ki67; four markers for stem cells were used: Oct-4, BCRP, Nestin and Telomerase; ability for cell migration was evaluated from Myosin IIA expression Results In several corneas, the nuclei of peripheral EC were centripetally aligned suggesting continuous slow central migration. Numerous small cells with a reduced expression of differenciation markers were accumulated near peripheral Hassall Henle bodies. In these potential niches, cells were distributed in 3-5 layers. A high expression of Myosin II was found in peripheral cells. Ki67+ cells were found in PL and peripheral EC only after OC. None of the 4 stem cell markers was found in EC, and their expression in PL was poorly reliable because of high background noise. Numerous trypan blue positive cells were located at the PL and in the extreme periphery of endothelium Conclusion several strong arguments suggest the location of corneal endothelial stem-like cell niches in endothelial periphery or in the PL, and the capacity of EC to migrate from these niches toward the centre. Trypan blue staining pattern suggests that they could rapidly die in ex vivo corneas, and be therefore hard to indentify [source] | |||||||||||||||||||||||||