Update on methodology topics

The following column on methodology topic was prepared by AOCS Technical Director Dave Berner. Questions on these or other topics concerning analytical methodology of fats and oils or related products may be directed to Dave Berner, AOCS, PO Box 3489, Champaign, IL 61821-0489, USA     

Students' predictions of prose forgetting and the effects of study strategies.

377 high school students read and were immediately tested on a prose passage, scored their own tests, then estimated how well they would have scored if tested after a delay of 1, 8, or 15 days. Data for these 3 hypothetical delay periods provided a "predicted forgetting function." An actual forgetting function was also obtained by administering a retention test with comparable questions after 1, 8, or 15 days. Within each of the 9 groups defined by the hypothetical and actual delay factors, there were 2 strategy groups—Ss who could only read the passage and those who took notes. After the immediate test, Ss in each strategy group estimated how well they would have scored if they had employed the alternate strategy. Results indicate a difference between predicted and actual forgetting, with Ss expecting a larger amount of forgetting than actually occurred. Note taking had a small facilitative effect on learning. However, Ss failed to predict positive effects of note taking. Ss' expectations about effects of other strategies were also examined, and implications regarding metamemory and study skills are discussed. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of pictorial integration on children's incidental learning.

Conducted 2 experiments to examine 192 8-, 11-, and 14-yr-old children's incidental learning with the central and incidental pictorial elements in each stimulus (a) presented as separate entities (standard condition), (b) depicted together in an action relation (2 types-weak action and strong action), or (c) depicted together in a static relation. Following a learning task in which attention to a single element in each stimulus was required, incidental learning was measured by having the S indicate the incidental feature associated with each central component. Results show that incidental learning was higher with the action than the standard materials, but the developmental trend in these scores was little affected by pictorial integration. While extending the generality of previous incidental learning results, these data contrast with evidence showing an increase with age in the effects of action portrayal on intentional learning of pictorial associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Efficient testing of segmented aspherical mirrors by use of a reference plate and computer-generated holograms. II. Case study, error analysis, and experimental validation

Segmented mirrors present unique challenges to fabrication and testing that are absent for monolithic optics. Since traditional asphere tests do not address segmented optics adequately, we validate a previously developed method to test large quantities of segments accurately, quickly, and economically. In this test, the aspheric shape of each segment is controlled to high accuracy by use of computer-generated holograms, and the radius of curvature is tightly controlled by use of the reference plate. In an adjoining paper [Appl Opt 43, 5303 (2004)] we developed the theory for this test, and now we present a complete system design and optimization for measuring the 1.4-m segments from a 30-m F/1 primary. A complete tolerance analysis predicts a test accuracy of 4.8-nm rms surface and excellent accuracy for controlling the geometry of the segment. In addition, a laboratory demonstration using 30-cm optics is presented that demonstrated 3.9-nm rms surface accuracy.     

A non-lensed fiber-optic resonance-enhanced multiphoton ionization probe

We have developed a miniature fiber-optic probe with no focusing optics for in situ analysis of volatile organic compounds (VOCs). The probe uses an optical fiber to transmit a laser pulse to a vapor sample causing it to ionize adjacent to the fiber tip through a resonance-enhanced multiphoton ionization (REMPI) process. The distal end of the optical fiber is contained co-axially within 2-mm-inner-diameter stainless steel tubing that serves as an electrode. The electrode is biased at a high positive potential to collect electrons. The current generated is shown to be proportional over about two orders of magnitude to the concentration of the species ionized. Visible wavelength REMPI spectroscopy is used to determine probe sensitivities of 20 ppb (benzene) and 43 ppb (toluene). Designing the probe without focusing optics specifies an achromatic ionization region constant in size and position as the laser wavelength is scanned, which simplifies data collection and reduction. Focusing achromatic systems are discussed and the potential signal improvement is estimated.     

Derivation of the equations of motion for complex structures by symbolic manipulation

This paper outlines a computer program especially tailored to the task of deriving explicit equations of motion for structures with point-connected substructures. The special purpose program is written in FORTRAN and is designed for performing the specific algebraic operations encountered in the derivation of explicit equations of motion. The derivation is by the Lagrangian approach. Using an orderly kinematical procedure and a discretization and/or truncation scheme, it is possible to write the kinetic and potential energy of each substructure in a compact vector-matrix form. Then, if each element of the matrices and vectors encountered in the kinetic and potential energy is a known algebraic expression, the computer program performs the necessary operations to evaluate the kinetic and potential energy of the system explicitly. Lagrange's equations for small motions about equilibrium can be deduced directly from the explicit form of the system kinetic and potential energy.     

A central cholinergic inhibitory system as a basis for tonic immobility (animal hypnosis) in chickens.

4 experiments provided support for the hypothesis that tonic immobility (TI) in chickens, which may be analogous to response suppression in the rat, is a result of fear and is mediated by central cholinergic systems. A total of 124 experimental and 54 control, White Leghorn cockerel chicks were the Ss. Exp I established that scopolamine, a central and peripheral acting anticholinergic, will reduce the duration of TI, whereas methylscopolamine, which acts only peripherally, will not. Exp II established a dose-response curve for scopolamine and TI. Exp III demonstrated that scopolamine increased activity and that this increase may be a factor in reducing the duration of TI. Exp IV showed that physostigmine, which blocks acetylcholinesterase and allows longer action of acetylcholine at the synapse, increased the duration of TI. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Accuracy of continuous ice-core trace-element analysis by inductively coupled plasma sector field mass spectrometry

Trace elements trapped in glaciers are important indicators for the characterization of past biogeochemical cycles, the identification of numerous sources and their varying strength, and thus indirectly provide insight into past climate variations. However, this necessitates highly resolved and continuous records of trace elements in ice. To obtain records corresponding to these requirements, a continuous ice-core melting (CIM) device was coupled to an inductively coupled plasma sector field mass spectrometer (ICP-SFMS). Accuracy of this newly developed method was tested by replicate analysis of longitudinally cut ice-core sections (reproducibility) and by comparing results of the continuous method with the conventional decontamination and analysis procedure. The new, fast method is suited to accurately determine concentrations of a number of elements, such as Li, Na, Mg, Ca, Mn, Co, Br, Sr, Mo, and Tl. However, for 18 elements (including Al and lanthanides) observed concentrations were underestimated when analyzed using the continuous method. Possible explanations of these low concentrations are (i) incomplete dissolution of mineral dust particles contained in the ice resulting from a delayed acidification step and/or (ii) adsorption of dissolved trace elements or mineral dust particles on the surface of the ice melting device.