Noninvasive Versus Invasive Doppler Renal Blood Velocity and Flow Measurements

We compared simultaneous noninvasive and invasive determinations of blood velocity and flow in the renal arteries of 5 mongrel dogs. Noninvasive measurements of blood velocity spectra (?FN) were made using an ultrasonic echo-Doppler duplex scanner. Vessel diameters (DN) and Doppler angles (?N) were measured from sector images of the renal artery. Invasive measurements of blood velocity spectra (?F1) were made using a catheter Doppler velocimeter. Vessel lumen diameter (D1) and Doppler angle (?1) were measured angiographically. Using the Doppler and continuity equations, temporal mean blood velocities (VN, V1) and flows (QN, Q1) of five cardiac cycles were calculated. The ranges of velocity (8-48 cm/s) and flow (40-380 ml/min) were varied by pharmacological intervention. Standard linear regressions (n = 33) were Results suggest that simultaneous noninvasive echo-Doppler and invasive catheter Doppler measurements of canine renal artery blood velocity and flow correlate significantly. Nevertheless, large standard errors of the estimates exist which suggest that important systematic and experimental errors are present in both methods.     

Design of a composite sulfuric acid decomposition reactor,concentrator, and preheater for hydrogen generation processes

The Hybrid Sulfur Process, as well as similar sulfur cycles for the production of nuclear hydrogen, requires the decomposition of sulfuric acid into sulfur dioxide, oxygen, and water at temperatures above 800 °C and at pressures up to 9 MPa. The design of a reactor for this process presents numerous challenges in terms of maintaining small pressure differentials and utilizing currently available materials of construction. This paper focuses on design calculations for a composite reactor that preheats, concentrates, and decomposes sulfuric acid for use in the production of hydrogen. The decomposition reaction takes place within individual tubes of a multitube reactor.     

Fabrication and characterization of poly(methyl methacrylate)/CaCu3Ti4O12 composites

Composites comprising Poly(Methyl Methacrylate) (PMMA) and CaCu₃Ti₄O₁₂ (CCTO) via melt mixing followed by hot pressing were fabricated. These were characterized using X‐ray diffraction, thermo gravimetric, scanning electron microscopy, and Impedance analyzer for their structural, morphology, and dielectric properties. Composites were found to have better thermal stability than that of pure PMMA. The composite, with 38 Vol % of CCTO (in PMMA), exhibited remarkably low dielectric loss at high frequencies and the low frequency relaxation is attributed to the space charge polarization/MWS effect. Theoretical models were employed to rationalize the dielectric behavior of these composites. At higher temperatures, the relaxation peak shifts to higher frequencies, due to the merging of both β and α relaxations into a single dielectric dispersion peak. The AC conductivity in the high frequency region was attributed to the electronic polarization. POLYM. ENG. SCI., 54:551–558, 2014. © 2013 Society of Plastics Engineers     

Potassium ferrioxalate as a new inexpensive photochemical pyranometer for extensive field work

The feasibility of using a potassium ferioxalate actinometer as a photochemical pyranometer was studied. The preparation, exposure, and spectrophotometric analysis of the pyranometer cell are described. By calibrating it against a Yellot Mark IV solameter, linear correlations were obtained with respect to total insolation and time of exposure. The spectral response, the quantum yields at different wavelengths, the mechanism of photochemical reaction, and the conversion factor for converting the absorption reading into cal/cm²/min are discussed. The advantages of the new pyranometer are its low cost, simplicity of operation and calibration, high sensitivity, and high tolerance to field conditions. It is useful for mapping solar intensity distribution over a wide area.     

Enthalpy- versus Entropy-Driven Molecular Recognition in the Era of Biologics

Our laboratory has recently identified two nanobodies (small antibodies produced by camelids)—Nb1 and Nb6—that bind efficiently to epithelial growth factor (EGF) and inhibit its ability to activate its receptor (EGFR). Because of the relevance of the EGF/EGFR axis as a target in oncology, these new nanobodies have promising therapeutic potential. This article, however, is focused on another feature of these nanobodies: their distinct thermodynamic signatures. Nb1 binds to EGF through an entropy-driven mechanism whereas Nb6 binds to this factor under enthalpic control. We discuss the advantages and disadvantages of each mechanism in the contexts of traditional medical chemistry (small-molecule drugs) and also of biological drugs. In this latter case, the implications in terms of selectivity are far from being clearly established and further experimental data are required. Their monomeric natures, high stability, and ease of recombinant production make nanobodies ideally suited for thermodynamic studies. Moreover, nanobodies, thanks to their simpler structures in comparison with conventional antibodies, might provide better understanding of the structural basis of the thermodynamic parameters of antigen recognition.     

Severity of delayed (“secondary”) cerebral energy failure after acute hypoxia-ischemia is related to the time integral of acute ATP depletion

The aim of this study was to reproduce the delayed (secondary) cerebral energy failure previously described in birth-asphyxiated newborn infants and to investigate relationships between primary insult severity and the extent of the delayed energy failure. Phosphorus (³¹P) magnetic resonance spectroscopy (MRS) at 7 T was used to study the brains of 12 newborn piglets during an acute, reversible, cerebral hypoxic-ischemic episode which continued until nucleotide triphosphates (NTP) were depleted. After reperfusion and reoxygenation, spectroscopy was continued for 48 h. High-energy metabolite concentrations returned to near normal levels after the insult, but later they fell as delayed energy failure developed. The time integral of NTP depletion in the primary insult correlated strongly with the minimum [phosphocreatine (PCr)]/[inorganic orthophosphate (P_i)] observed 24–48 h after the insult. (Linear regression analysis gave slope –8.04 h^–1; ordinate intercept=1.23;r=0.92;P<0.0001.) This model is currently being used to investigate the therapeutic potential of various cerebroprotective strategies including hypothermia.     

Synthesis and Biological Evaluation of Novel Epothilone B Side Chain Analogues

The design, synthesis, and biological evaluation of a series of epothilone analogues with novel side chains equipped with an amino group are described. Their design facilitates potential conjugation to selective drug delivery systems such as antibodies. Their synthesis proceeded efficiently via Stille coupling of a readily available vinyl iodide and heterocyclic stannanes. Cytotoxicity studies and tubulin binding assays revealed two of these analogues to be more potent than epothilones A–D and the anticancer agent ixabepilone, currently in clinical use.     

Tensile testing and fracture mechanism analysis of polyvinyl alcohol nanofibrous webs

A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs.     

Shrinkage behavior and optimization of injection molded parts studied by the taguchi method

Shrinkage behavior of a plastic plays a critical role in determining the final dimensions of an injection‐molded part. It is well known that process conditions affect many properties of plastic parts, including shrinkage. This study applies the Taguchi method to systematically investigate the effects of process conditions on the shrinkage (along‐ and across‐the‐flow directions) of three plastics: high‐density polyethylene (HDPE), general‐purpose polystyrene (GPS), and acrylonitrile‐butadiene‐styrene (ABS). The results show that HDPE, a semicrystalline plastic, shrinks more than GPS and ABS, two amorphous materials. The extent of anisotropic shrinkage in the along‐the‐flow and across‐the‐flow directions for HDPE is different from GPS and ABS. More shrinkage occurs in the across‐the‐flow direction of HDPE than in its along‐the‐flow direction. The reverse is true for GPS and ABS. Mold and melt temperatures, along with holding pressure and holding time, are the most significant influences on the shrinkage behaviors of three materials, although the importance of each is different for each plastic. The optimal conditions for reducing shrinkage identified by the Taguchi method are experimentally verified and validated by t‐statistic tests. The prediction matches very well with the experimental value for the along‐the‐flow shrinkage of GPS.