Variation in lipid composition of Chinese mitten-handed crab, Eriocheir sinensis during ovarian maturation

This experiment was conducted to investigate the variation in lipid composition during the ovarian maturation of the crab Eriocheir sinensis. The Chinese mitten-handed crab broodstock was divided into six different maturation periods according to the size and color of ovary. Ovary, hepatopancreas, muscle, and hemolymph of broodstock in different maturation periods were analyzed for total lipid and fatty acids using gas chromatography, and lipid classes by thin-layer chromatography. The ovarian lipid concentration (expressed as percent wet ovarian weight) increased steadily from stage II (5.4%) to stage IV (19.1%), and decreased to the lowest levels after spawning (stage V, 6.6%). The hepatopancreatic lipid concentration (expressed as percent wet hepatopancreatic weight) increased with maturity of the ovaries, reached a maximum at stage III(2) (29.9%), and decreased during the subsequent period to spawning (16.7%). The muscular and hemolymph lipid concentration did not change markedly during the ovarian development. These results suggest the possible movement of hepatopancreatic lipids to the ovaries during the ovarian maturation. Both triacylglycerol and phosphatidylcholine were responsible for the increase in ovarian lipid concentration during sexual maturation. The fatty acids of total lipid, triacylglycerol, and phosphatidylcholine of the ovaries did not vary systematically during the ovarian maturation, but the ratio between n-3PUFA (polyunsaturated fatty acid) and n-6PUFA did change regularly with the ovarian lipid. These suggest that enough PUFA, especially n-3PUFA, should be supplied to the crab during ovarian maturation.

Standard errors for the retransformation problem with heteroscedasticity

Economists often estimate models with a log-transformed dependent variable. The results from the log-transformed model are often retransformed back to the unlogged scale. Other studies have shown how to obtain consistent estimates on the original scale but have not provided variance equations for those estimates. In this paper, we derive the variance for three estimates--the conditional mean of y, the slope of y, and the average slope of y--on the retransformed scale. We then illustrate our proposed procedures with skewed health expenditure data from a sample of Medicaid eligible patients with severe mental illness.

Heterozygous loss of Six5 in mice is sufficient to cause ocular cataracts

Myotonic dystrophy (DM) is an autosomal dominant disorder characterized by skeletal muscle wasting, myotonia, cardiac arrhythmia, hyperinsulinaemia, mental retardation and ocular cataracts. The genetic defect in DM is a CTG repeat expansion located in the 3' untranslated region of DMPK and 5' of a homeodomain-encoding gene, SIX5 (formerly DMAHP; refs 2-5). There are three mechanisms by which CTG expansion can result in DM. First, repeat expansion may alter the processing or transport of the mutant DMPK mRNA and consequently reduce DMPK levels. Second, CTG expansion may establish a region of heterochromatin 3' of the repeat sequence and decrease SIX5 transcription. Third, toxic effects of the repeat expansion may be intrinsic to the repeated elements at the level of DNA or RNA (refs 10,11). Previous studies have demonstrated that a dose-dependent loss of Dm15 (the mouse DMPK homologue) in mice produces a partial DM phenotype characterized by decreased development of skeletal muscle force and cardiac conduction disorders. To test the role of Six5 loss in DM, we have analysed a strain of mice in which Six5 was deleted. Our results demonstrate that the rate and severity of cataract formation is inversely related to Six5 dosage and is temporally progressive. Six5+/- and Six5-/- mice show increased steady-state levels of the Na+/K+-ATPase alpha-1 subunit and decreased Dm15 mRNA levels. Thus, altered ion homeostasis within the lens may contribute to cataract formation. As ocular cataracts are a characteristic feature of DM, these results demonstrate that decreased SIX5 transcription is important in the aetiology of DM. Our data support the hypothesis that DM is a contiguous gene syndrome associated with the partial loss of both DMPK and SIX5.

Multimode laser Fizeau interferometer for measuring the surface of a thin transparent plate

A Fizeau interferometer utilizes a multimode laser as a light source for testing thin transparent plate samples. As a result of multimode linear laser operation, interference fringes are obtained only when the optical path difference between two surfaces is equal to twice a multiple of the laser's effective cavity length. For three parallel surfaces, we can either adjust their separations or select a laser such that only two of the three surfaces meet the requirement of twice a multiple of the laser's effective cavity length.

Testing an optical window of a small wedge angle: effect of multiple reflections

Multiple reflections between two surfaces of a window introduce a fixed pattern error in optical measurements. One way to remove these spurious reflections is to use a reasonably large wedge so that the interference fringes formed by the two surfaces are too dense for the detector to resolve. However, this method does not work if the wedge angle is small, e.g., several arcseconds. By tilting both the window and the return mirror properly, it is possible to remove the effect of multiple reflections of a window. Theory and experimental results are presented.

Absolute testing of flats by using even and odd functions

We describe a modified three-flat method. In a Cartesian coordinate system, a flat can be expressed as the sum of even-odd, odd-even, even-even, and odd-odd functions. The even-odd and the odd-even functions of each flat are obtained first, and then the even-even function is calculated. All three functions are exact. The odd-odd function is difficult to obtain. In theory, this function can be solved by rotating the flat 90°, 45°, 22.5°, etc. The components of the Fourier series of this odd-odd function are derived and extracted from each rotation of the flat. A flat is approximated by the sum of the first three functions and the known components of the odd-odd function. In the experiments, the flats are oriented in six configurations by rotating the flats 180°, 90°, and 45° with respect to one another, and six measurements are performed. The exact profiles along every 45° diameter are obtained, and the profile in the area between two adjacent diameters of these diameters is also obtained with some approximation. The theoretical derivation, experiment results, and error analysis are presented.

Effect of retroreflection on a Fizeau phase-shifting interferometer

Phase errors in a Fizeau phase-shifting interferometer caused by multiple-reflected beams from a retroreflective optics, such as a corner cube and a right-angle prism, are studied. Single- and double-pass configurations are presented, and their measurement results are compared. An attenuator is not needed in a double-pass configuration because light is reflected by the retroreflective optics twice and the reference surface once and hence the intensities match. It is more accurate to test a corner cube or a right-angle prism in a double-pass configuration than in a single-pass configuration. Simulations and experimental results are presented.

Interferometric stress birefringence measurement

We describe a sensitive method for measuring the stress birefringence of an optical window that utilizes a phase-measuring Fizeau interferometer incorporating a variable retarder and a nonpolarizing beam splitter. When we test a material in an interferometer cavity, the wave front transmitted through the material is deviated by the surfaces, inhomogeneity, and birefringence of the material. Birefringence causes the transmitted wave front to have different optical path difference (OPD) profiles for the vertical and horizontal orientations of linear polarization. Subtracting these OPD profiles reveals the amount of phase difference between the fast and slow axes of the material. Hence, birefringence may be calculated. Phase-measurement techniques and a computer-controlled interferometer employing a variable liquid-crystal retarder provide a fully automated instrument for measuring stress birefringence. The theoretical derivation, discussion of the instrument, and experimental results are presented.

Accurate measurement of the dihedral angle of a corner cube

The alignment of a corner cube affects the measurement of its dihedral angle. For 5 deg of tilt, the error is up to 7%, depending on the orientation of the tilt. A vector model is devised to derive formulas that take misalignment into account for both solid and hollow corner cubes. When the wave-front tilt caused by the dihedral angle error is not much greater than that caused by the surface figure, because of vignetting for a tilting illumination, the surface figure of the cube facet makes varying contributions to the wave-front tilt for different incident angles. Simulations and experimental results are presented.

Effect of spurious reflection on phase shift interferometry

The phase errors caused by spurious reflection in Twyman-Green and Fizeau interferometers are studied. A practical algorithm effectively eliminating the error is presented. Two other algorithms are reviewed, and the results obtained using the three algorithms are compared.

Effect of piezoelectric transducer nonlinearity on phase shift interferometry

If the nonlinearity of the motion of a piezoelectric transducer (PZT) can be described as a quadratic function, the integrated intensity of one frame in phase shift interferometry can be calculated using the Fresnel integral. For a PZT with smaller nonlinearity, the rms phase error is almost linearly proportional to the quadratic coefficient The effects of PZT nonlinearity on the three- and the four-bucket algorithms are compared.