Space neutron spectrometer design with SSPM-based instrumentation

The compact, robust nature of the CMOS solid-state photomultiplier (SSPM) allows the creation of small, low-power scintillation-based radiation measurement devices. Monitoring space radiation including solar protons and secondary neutrons generated from high-energy protons impinging on spacecraft is required to determine the dose to astronauts. Small size and highly integrated design are desired to minimize consumption of payload resources.RMD is developing prototype radiation measurement and personal dosimeter devices using emerging scintillation materials coupled to CMOS SSPM’s for multiple applications. Spectroscopic measurements of high-energy protons and gamma-rays using tissue-equivalent, inorganic scintillators coupled to SSPM devices demonstrate the ability of an SSPM device to monitor the dose from proton and heavy ion particles, providing real time feedback to astronauts. Measurement of the dose from secondary neutrons introduces additional challenges due to the need to discriminate neutrons from other particle types and to accurately determine their energy deposition. We present strategies for measuring neutron signatures and assessing neutron dose including simulations of relevant environments and detector materials.     

Humidity‐dependent bending recovery and relaxation of human hair

The time‐dependent bending recovery of human hair fibers was investigated for a variety of relative humidities and aging times. The data were analyzed on the basis of a viscoelastic filament/matrix model and the Denby‐equation, containing the parameter K as the ratio of the elastic bending rigidities of the matrix and the filaments and the Kohlrausch‐Williams‐Watts (KWW) function as relaxation function. The first stage of the analysis ascertained that the recovery curves shift with aging time on the time scale with the expected aging rate of μ ≈ 1. The second stage showed that the shape factor of the KWW function exhibits a mean value across the aging and humidity range of m = 0.28, which is close to the “universal” value of 1/3. On this basis, it was found that virtually no change occurs for the modulus ratio for low water contents up to about 10%, being constant at K₀= 6 .1, while linearly decreasing beyond this threshold. The reduced, characteristic relaxation time drops on the log‐time scale from logτ_r(0) = 0.47 for the dry fiber linearly with water content, covering about two thirds of a decade for 0–20% water content. With the pronounced humidity dependence of the parameters, hair shows what is termed hydro‐rheologically complex (HRC) in analogy to thermo‐rheologically complex behavior. Using the HRC approach, the dynamical mechanical performance of hair (1 Hz) was calculated for a range of water contents and aging times and found to be in good general agreement with experimental data. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Complementary use of MALDI and ESI for the HPLC-MS/MS analysis of DNA-binding proteins

Proteins from Escherichia coli were isolated based on their ability to bind DNA and digested in-solution with trypsin; the resulting peptides were separated using HPLC and subsequently analyzed using MALDI TOF/TOF and ESI Q-TOF instruments. Various properties of the peptides observed with the two ionization techniques were compared taking into account the differences between the mass analyzers. This empirical analysis of a data set containing hundreds of peptides and thousands of individual amino acids supports some of the currently held notions regarding the complementary nature of the two ionization processes. Specifically, ESI tends to favor the identification of hydrophobic peptides whereas MALDI tends to lead to the identification of basic and aromatic species. Findings from the present study suggest that ESI and MALDI may be complementary due to the biases of the two ionization techniques for certain classes of amino acids. From a practical standpoint, these biases indicate that, for the present at least, analyses must be performed on both types of instruments in order to gain the most information possible out of a given set of samples in a proteomics study.