On the Nature and Elimination of Stimulus Artifact in Nerve Signals Evoked and Recorded Using Surface Electrodes

The electrical stimulus pulse and the surface electrodes commonly used to study compound action potentials of peripheral nerves give rise to an artifact consisting of an initial spike and a longer lasting tail which often interferes with the recorded signal. The artifact has four sources: 1) the voltage gradient between the recording electordes caused by stimulus current flowing through the limb, 2) the common-mode voltage of the limb caused by current escaping through the ground electrode, 3) the capacitive coupling between the stimulating and recording leads, and 4) the high-pass filtering characteristics of the recording amplifier. This paper models these sources and presents several methodological rules for minimizing their effects. Also presented are three computer-based methods for subtracting the residual artifact from contaminated records using estimates of the artifact obtained from: 1) subthreshold stimulation, 2) a second recording site remote from the nerve, or 3) stimulation during the refractory period of the nerve.     

Raman spectroscopy of the human nail: A potential tool for evaluating bone health?

Dual X-ray absorptiometry (DEXA) is the current gold standard for the diagnosis of osteoporosis. However, patients can suffer osteoporotic fractures despite normal bone mineral density, partly because of unmeasured influences of both the protein and mineral phases of bone that are affected in osteoporosis. There is currently no clinically applicable method of evaluating the health of the protein phase. The proteins in human nail (keratin) and bone (collagen) require sulphation and disulphide bond (S–S) formation for structural integrity and disorders of either sulphur metabolism or cystathione beta-synthase can lead to structural abnormalities in these tissues. Raman protein spectra provide a method of non-invasive measurement of the degree of sulphation of structurally related proteins that may be indicative of bone health. Raman spectroscopy was used to evaluate the disulphide (S–S) content of fingernails. The nail samples came from from 169 women (84 pre- and 85 post-menopausal), of which 39 had a history of osteoporotic fracture. BMD was measured by DXA at the spine. Analyses included parametric and non-parametric tests, dependent on the distribution of the test variable. Mean disulphide content of the nail reduced with age and was slightly higher in pre-, compared to post-menopausal women (P = 0.187). Significantly lower disulphide content was observed in nails obtained from subjects with a history of fracture (P = 0.025). When either disulphide content or BMD was used as a predictor, the odds ratio of these two measures were found to be comparable predictors for fracture status. This suggests that measurements of change in the protein phase of structural proteins such as keratin in the human nail may be correlated with clinically relevant changes in bone proteins that are important in fracture risk.     

Selective etching of polylactic acid in poly(styrene)‐block‐poly(d,l)lactide diblock copolymer for nanoscale patterning

Self‐assembled thin films of a lamellar forming polystyrene‐block‐poly(d,l )lactide (PS‐b‐PLA) block copolymer (BCP) contain a “reactive” block that can be readily removed to provide a template for substrate pattern formation. Various methods of PLA removal were studied here with a view to develop the system as an on‐chip etch mask for substrate patterning. Solvo‐microwave annealing was used to induce microphase separation in PS‐b‐PLA BCP with a periodicity of 34 nm (L_o) on silicon and silicon on insulator (SOI) substrates. Wet etches based on alkaline and enzymatic solutions were studied in depth. Fourier transform‐infrared (FT‐IR) analysis showed that basic hydrolysis using sodium hydroxide (NaOH) or ammonium hydroxide (NH₄OH) solutions resulted in greater PLA removal in comparison to an enzymatic approach using Proteinase K in a Tris‐HCl buffer solution. However, in the enzymatic approach, the characteristic self‐assembled fingerprint patterns were retained with less damage. Comparison to a dry etch procedure using a reactive ion etch (RIE) technique was made. A detailed study of the etch rate of PS and PLA homopolymer and PS‐b‐PLA shows depending on DC bias, the etch selectivity of PLA and PS can be almost doubled from 1.7 at DC bias 145 V to 3 at DC bias 270 V. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40798. Together with Krebs et al., J. Appl. Polym. Sci. (2014) 131 , 40795, doi: 10.1002/app.40795 , this article is part of a Special Issue on Polymers for Microelectronics. The remaining articles appear in J. Appl. Polym. Sci. (2014) volume 131 , issue 24. This note was added on 1st July 2014.     

Development of metal supported solid oxide fuel cells for operation at 500–600 °C

A novel metal-supported solid oxide fuel cell has been developed that is capable of operating at temperatures of 500–600 °C. The rationale behind the materials used to construct this fuel cell type is given, and results are presented from cell testing on hydrogen and reformed natural gas, including durability trials of some 2500 h duration. This new fuel cell variant is shown to be tolerant of carbon monoxide, durable, robust to thermal and redox cycling, and capable of delivering technologically relevant power densities. This paper was presented at the Fuel Cells: Materials, Processing, and Manufacturing Technologies Symposium sponsored by the Energy/Utilities Industrial Sector & Ground Transportation Industrial Sector and the Specialty Materials Critical Technologies Sector at the ASM International Materials Solutions Conference, October 13–15, 2003, in Pittsburgh, PA. The symposium was organized by P. Singh, Pacific Northwest National Laboratory, S.C. Deevi, Philip Morris USA, T. Armstrong, Oak Ridge National Laboratory, and T. Dubois, U.S. Army CECOM.     

酸性矿山废水（AMD）地球化学工程防治技术

酸性矿山废水（AMD）的地球化学工程防治技术,意指根据AMD的生成机理,采用地球化学方法（包括AMD预测评价、覆盖和渗透反应栅等技术）对AMD（及重金属）污染进行预防控制和治理的集成技术。该项技术具有长效、低成本、易施工,以及原位治理等特点,适用于处理排放持续时间长、富含毒性重金属的酸性污水,值得在我国的金属硫化物矿山开发应用。     

The effect of adding organic polymers on the handling properties, strengths and bioactivity of a Ca–Sr–Zn–Si glass polyalkenoate cement

This work demonstrates the addition of a number of naturally occurring proteins/polymers to a zinc based glass polyalkenoate cements (GPCs). Chitin (Chi.), collagen (Col.), cysteine (Cys.) and keratin (Ker.) were added with the intention of improving the bioactivity of this cement. Initial testing involved characterization of the glass with X-ray diffraction (XRD) and differential thermal analysis (DTA) before and after sterilization with γ-irradiation. No significant changes occurred as a result of sterilization. Handling properties of the modified cements were not significantly different from those of the control, BT 101 (Working T _w—36 s, and setting time T _s—70 s) except for Chi. (30 s, p ≤ 0.016) and Cys. (105 s, p ≤ 0.0001) respectively. Comparison of the mechanical properties of BT 101 (compression—σ_c and biaxial flexural—σ_f) to the modified cements revealed a significant decrease in σ_c with Chi. and Col., after 1, 7 and 30 days. However, there were little changes occurring in σ_f. Cement structural testing was investigated and found that the addition of these polymers greatly reduced the cements surface area, however, the only significant change to occur in the solubility testing was Ker. (p ≤ 0.009). Simulated body fluid (SBF) testing resulted in increased calcium phosphate (CaP) deposition of Chi. and Col. compared to BT 101. Cell culture studies determined only Col. significantly increased (p ≤ 0.0001) in comparison to the control cement.     

A spectroscopic investigation into the setting and mechanical properties of titanium containing glass polyalkenoate cements

Titanium (Ti) implants are extensively used in a number of biomedical and dental applications. This work introduces Ti into the glass phase of a zinc based glass polyalkenoate cement (GPC) and investigates changes in handling and mechanical properties considering two molecular weight polyacrylic acids (PAA), E9 and E11. Considering the handling properties, the working time (T _w) increased from 50 s_E9, 32 s_E11 (BT 101, Ti-free) to 169 s_E9, 74 s_E11 with TW-Z (highest Ti content), respectively. The setting time (T _s) increased from 76 s_E9, 47 s_E11 (BT 101) to 303 s_E9, 232 s_E11 with TW-Z, respectively. Ti was also found to have a significant increase on both compressive (σ _c) and biaxial flexural strength (σ _f), where σ _c increased from 36 MPa_E9, 56 MPa_E11 (BT 101) to 56 MPa_E9 and 70 MPa_E11 with TW-Z respectfully. σ _f also increased from 11 MPa_E9, 22 MPa_E11 (BT 101) to 22 MPa_E9 and 77 MPa_E11 with TW-Z, respectively. No increase in mechanical properties was evident with respect to maturation. Raman Spectroscopy was employed to investigate changes in glass structure and the setting of the cements with. This revealed increased glass network disruption with increasing TiO₂ content and matured cement setting with TW-Z as compared to the control BT 101. FT-IR was then employed to investigate any additional setting mechanism and changes with time. Spectroscopy determined that Ca²⁺/Sr²⁺PAA complexes are primarily responsible for the setting and mechanical strength with no changes occurring over time.     

Effect of dietary acid detergent fiber on responses to high environmental temperature.

Twenty-seven multiparous Holstein cows averaging 120.7 DIM, 9 per diet, were assigned at random to 20, 17, or 14% ADF diets of corn, corn silage, and soybean meal, following a covariant period when all cows received the 14% ADF diet. An 18-d period (period 1) of cool weather preceded the onset of high environmental temperature from June 1988 to the end of July 1988 (period 2). Mean daily maximum air temperatures were 35.2, 36.8, and 34.7 degrees C for the covariant period and for periods 1 and 2, respectively. Minimum temperatures were 14.5, 16.0, and 21.5 degrees C. Milk production during both periods was higher, and the decrease in milk production associated with the onset of hot weather was lower, in cows fed the 14% ADF diet. Intake was not affected by diet during period 1 but was lower in cows fed the 17 and 14% ADF diets in period 2 relative to period 1. At any given environmental temperature, DMI was higher in cows fed lower ADF diets. Although DMI declined more rapidly with increasing daily minimum temperature with lower ADF diets, milk production was less sensitive to daily minimum temperature in cows fed the 14% ADF diet.