Noise Measurement Setup for Quartz Crystal Microbalance

Quartz crystal microbalance (QCM) is a high sensitive chemical sensor which has found widespread spectrum of applications. There are several mechanisms that are related to fluctuation phenomena. Since the aim of our research is oriented to study the sensitivity and influence of different kind of noises on sensor resolution, we modified an existing method to measure the small frequency fluctuation of QCM. The paper describes our measurement setup, in which a quartz crystal oscillator with coated active layers and a reference quartz oscillator are driven by two oscillator circuits. Each one regulates a frequency of a crystal at the minimum impedance which corresponds to the series resonance. A data-acquisition card triggers on the rise-edges of the output signal and stores these corresponding times on which the instantaneous frequency is estimated by own-written software. In comparison to other measurement setups, our approach can acquire immediate change of QCM frequency, thus, chemical processes can be even described on the basis of high-order statistics. The experiments were provided on quartz crystals with the sorption layer of polypyrrole, which is suitable for the construction of QCM humidity sensors

COBE attitude as seen from the FDF

The goal of the Flight Dynamics Facility (FDF) attitude support is twofold: to determine spacecraft attitude and to explain deviations from nominal attitude behavior. Attitude determination often requires resolving contradictions in the sensor observations. This may be accomplished by applying calibration corrections or by revising the observation models. After accounting for all known sources of error, solution accuracy should be limited only by observation and propagation noise. The second half of the goal is to explain why the attitude may not be as originally intended. Reasons for such deviations include sensor or actuator misalignments and control system performance. In these cases, the ability to explain the behavior should, in principle, be limited only by knowledge of the sensor and actuator data and external torques. Documented here are some results obtained to date in support of the Cosmic Background Explorer (COBE). Advantages and shortcomings of the integrated attitude determination/sensor calibration software are discussed. Some preliminary attitude solutions using data from the Diffuse Infrared Background Experiment (DIRBE) instrument are presented and compared to solutions using Sun and Earth sensors. A dynamical model is constructed to illustrate the relative importance of the various sensor imprefections. This model also shows the connection between the high- and low-frequency attitude oscillations

Estimation of attitude sensor timetag biases

This paper presents an extended Kalman filter for estimating attitude sensor timing errors. Spacecraft attitude is determined by finding the mean rotation from a set of reference vectors in inertial space to the corresponding observed vectors in the body frame. Any timing errors in the observations can lead to attitude errors if either the spacecraft is rotating or the reference vectors themselves vary with time. The state vector here consists of the attitude quaternion, timetag biases, and, optionally, gyro drift rate biases. The filter models the timetags as random walk processes: their expectation values propagate as constants and white noise contributes to their covariance. Thus, this filter is applicable to cases where the true timing errors are constant or slowly varying. The observability of the state vector is studied first through an examination of the algebraic observability condition and then through several examples with simulated star tracker timing errors. The examples use both simulated and actual flight data from the Extreme Ultraviolet Explorer (EUVE). The flight data come from times when EUVE had a constant rotation rate, while the simulated data feature large angle attitude maneuvers. The tests include cases with timetag errors on one or two sensors, both constant and time-varying, and with and without gyro bias errors. Due to EUVE's sensor geometry, the observability of the state vector is severely limited when the spacecraft rotation rate is constant. In the absence of attitude maneuvers, the state elements are highly correlated, and the state estimate is unreliable. The estimates are particularly sensitive to filter mistuning in this case. The EUVE geometry, though, is a degenerate case having coplanar sensors and rotation vector. Observability is much improved and the filter performs well when the rate is either varying or noncoplanar with the sensors, as during a slew. Even with bad geometry and constant rates, if gyro biases are independently known, the timetag error for a single sensor can be accurately estimated as long as its boresight is not too close to the spacecraft rotation axis

Comparison of Kalman filter and optimal smoother estimates of spacecraft attitude

Given a valid system model and adequate observability, a Kalman filter will converge toward the true system state with error statistics given by the estimated error covariance matrix. The errors generally do not continue to decrease. Rather, a balance is reached between the gain of information from new measurements and the loss of information during propagation. The errors can be further reduced, however, by a second pass through the data with an optimal smoother. This algorithm obtains the optimally weighted average of forward and backward propagating Kalman filters. It roughly halves the error covariance by including future as well as past measurements in each estimate. This paper investigates whether such benefits actually accrue in the application of an optimal smoother to spacecraft attitude determination. Tests are performed both with actual spacecraft data from the Extreme Ultraviolet Explorer (EUVE) and with simulated data for which the true state vector and noise statistics are exactly known

Exploring the Relationship Between Misophonia Severity and Anterior Insular Cortex Activity

Misophonia is an under-recognized neuropsychological condition involving a severe sensitivity towards specific sounds called triggers. The aim of this study was to investigate how activity in the anterior insular cortex (AIC) differed with varying levels of sound sensitivity (SS); misophonia being the most severe. Data was collected from university undergraduates/young adults (N = 31). Participants completed an online survey to assess their misophonia severity and symptoms. A case study was conducted on some of the students (N = 4) to assess misophonia at a neurological level. In addition to experiencing a heightened sensitivity to sounds, the misophonia group reported having more primary triggers. Disgust, anger and anxiety were experienced more frequently in the misophonia group in response to a trigger. The participant with misophonia demonstrated heightened activity in the AIC in response to a trigger, but unexpectedly this activity did not exceed the activity elicited in the no SS participants. Differences in the misophonic reaction were found amongst varying levels of SS, but more participants are needed before conclusions can be made about whether or not these differences have a neurological basis

The 10 Tesla muSR instrument: detector solutions

Solutions to the detector system of the High-Field muSR instrument at the Paul Scherrer Institut (PSI) in Switzerland are presented. The strict technical requirements are fulfilled through the application of Geiger-mode Avalanche Photodiodes.Comment: 6 pages, 4 figure

Noise in piezoelectric ceramics at the low temperatures

The piezoelectric ceramic belongs to materials with widespread spectrum of applications. It can be found in sensors as well as in ceramic capacitors. The main sources of voltage or current fluctuation in piezoelectric ceramics are thermal noise, polarization noise and low frequency 1/f noise. The observed spectra of fluctuating voltage or current can be very well described by the generalized Nyquist relation for linear dissipative system. In this work, we focused on validity of the Nyquist relation for piezoelectric ceramics in temperatures 150 K-270 K. The electrical impedance and noise spectral density are measured and compared in frequency range 100 kHz - 1 MHz. The measurements were made in thermal stable condition and under equilibrium conditions in the case of noise measurement

QCD Analysis of Dijet Production at Low {\boldmath Q2Q^2} at HERA

Recent H1 data on triple differential dijet cross sections in $e^\pm p$ interactions in the region of low photon virtualities are shown to be in reasonable agreement with the predictions of the NLO QCD calculations obtained using the program NLOJET++. The implications of this observation for the phenomenological relevance of the concept of resolved virtual photon are discussed.Comment: 5 pages, 3 figure

Experiment K-6-09. Morphological and biochemical investigation of microgravity-induced nerve and muscle breakdown. Part 1: Investigation of nerve and muscle breakdown during spaceflight; Part 2: Biochemical analysis of EDL and PLT muscles

The present findings on rat hindlimb muscles suggest that skeletal muscle weakness induced by prolonged spaceflight can result from a combination of muscle fiber atrophy, muscle fiber segmental necrosis, degeneration of motor nerve terminals and destruction of microcirculatory vessels. Damage was confined to the red adductor longus (AL) and soleus muscles. The midbelly region of the AL muscle had more segmental necrosis and edema than the ends. Macrophages and neutrophils were the major mononucleated cells infiltrating and phagocytosing the cellular debris. Toluidine blue-positive mast cells were significantly decreased in Flight AL muscles compared to controls; this indicated that degranulation of mast cells contributed to tissue edema. Increased ubiquitination of disrupted myofibrils may have promoted myofilament degradation. Overall, mitochondria content and SDH activity were normal, except for a decrease in the subsarcolemmal region. The myofibrillar ATPase activity shifted toward the fast type in the Flight AL muscles. Some of the pathological changes may have occurred or been exacerbated during the 2 day postflight period of readaptation to terrestrial gravity. While simple atrophy should be reversible by exercise, restoration of pathological changes depends upon complex processes of regeneration by stem cells. Initial signs of muscle and nerve fiber regeneration were detected. Even though regeneration proceeds on Earth, the space environment may inhibit repair and cause progressive irreversible deterioration during long term missions. Muscles obtained from Flight rats sacrificed immediately (within a few hours) after landing are needed to distinguish inflight changes from postflight readaptation