Uniform Polarization Scattering With Fiber-Coil-Based Polarization Controllers

A detailed study of fiber-coil-based polarization controllers (PCs) is performed. First, a method to deterministically calculate the PC configuration in order to transform between any two states of polarization is presented. In a second stage, the case in which the configuration angles are randomly changed is studied. The cases of a single PC and of the system obtained with the concatenation of several PCs are analyzed. For both cases, a general expression for the variance of the Stokes parameters is obtained. Using this expression, it is demonstrated that it is possible to achieve uniform polarization scattering using a concatenation of fiber-coil-based PCs. Finally, it is shown that fiber-coil-based PCs can be used to emulate both first- and second-order polarization-mode dispersions     

Morphologic and morphometric analysis of testis of Pseudis limellum (Cope, 1862) (Anura, Hylidae) during the reproductive cycle in the Pantanal, Brazil

The spermatogenesis of Pseudis limellum, from the Southern Pantanal, Brazil, was studied from July 1995 to May 1996, through histological sections of the testis. The cells could be differentiated as: primary spermatogonia, large cells, generally with bilobed nucleus; secondary spermatogonia, smaller cells, with darker cytoplasm, chromatin of radial form; primary and secondary spermatocytes, differentiated according to the different stages of the nucleus during the successive cells divisions. Furthermore, we observed cells in process of morphologic differentiation: rounded spermatids much smaller, with nucleus containing chromatin in compacting process and cytoplasm reduction; elongated spermatids, generally parallel organized in well defined bundles, with the anterior region directed toward the periphery of the seminiferous tubule and the tail directed toward the lumen. Spermatozoa are free in the lumen of the seminiferous tubule. All the cells are organized as cysts, which are supported by a large amount of Sertoli cells. The spermatogenesis in P. limellum is very similar to that of other anurans, but peculiarities were observed regarding the organization of the germ cells, the great amount of free Sertoli cells in the lumen of testis collected in May, and the long cytoplasmatic extensions of the cells bearing pigments and involving the seminiferous tubule. The diameter of the seminiferous tubule (SD) exhibited an annual mean of 251.79 +/- 37.57 microm. Spermatozoa number by seminiferous tubule (SN) exhibited an annual mean of 306.66 +/- 39.83, also with higher and lower values at each month. Variations in SD and SN were not significantly correlated with climatic variables. In this species, reproduction occurs throughout the year in ponds and flooded areas, despite the seasonal climate of the Pantanal. Although males varied in their annual reproductive activity, they were considered potentially reproductive in all months throughout the year.     

Multi-step transformation in numerical renormalization group

We compute the temperature dependent magnetic susceptibility of the single-impurity, two-channel Anderson model with an alternative multi-step numerical renormalization-group transformation, previously applied only to the two-impurity single-channel Kondo model. Compared with the traditional transformation, the new procedure requires substantially less memory and computational time, and opens therefore perspectives for the application of the numerical renormalization-group procedure to more complex Hamiltonians.     

A SVET investigation on the modification of zinc dust reactivity

Weldable primers are thin zinc-rich organic coatings that are weldable due to the electrical conductivity provided by the zinc dust. They are used in the automotive industry to provide corrosion protection in regions of difficult access. The zinc particles are highly susceptible to corrosion attack and, due to the small thickness, the protection conferred by these systems is limited.     

A planar integrated RCD snubber/voltage clamp

In order to reduce the cost, size, and weight of power electronic systems, it has become necessary to integrate electromagnetic structures, which until now have been constructed with discrete components. This approach not only reduces the component count, but also gives much greater control over parasitic elements. In this article, the authors describe an electromagnetically integrated resistor-capacitor-diode (RCD) snubber/voltage clamp that uses a planar construction technique. The design and construction are described and the performance is verified experimentally. Some advantages of the integrated component over its discrete counterpart are also given     

Hemodynamic and norepinephrine responses to pacing-induced heart failure in conscious sinoaortic-denervated dogs

The present study was undertaken to determine the effects of chronic sinoaortic (baroreceptor) denervation (SAD) on the hemodynamic and sympathetic alterations that occur in the pacing-induced model of congestive heart failure. Two groups of dogs were examined: intact (n = 9) and SAD (n = 9). Both groups of dogs were studied in the control (prepace) state and each week after the initiation of ventricular pacing at 250 beats/min. After the pacemaker was turned off, hemodynamic and plasma norepinephrine levels returned toward control levels in the prepaced state and after 1 and 2 wk of pacing. However, by 3 wk all hemodynamic and norepinephrine levels remained relatively constant over the 10-min observation period with the pacemaker off. With the pacemaker off, left ventricular end-diastolic pressure went from 2.7 +/- 1.4 (SE) mmHg during the prepace state to 23.2 +/- 2.9 mmHg in the heart failure state in intact dogs (P < 0.01). Left ventricular end-diastolic pressure increased to 27.1 +/- 2.2 mmHg from a control level of 4.2 +/- 1.9 mmHg i SAD dogs (P < 0.0003). Mean arterial pressure significantly decreased in intact and SAD dogs. Resting heart rate was significantly higher in SAD dogs and increased to 135.8 +/- 8.9 beats/min in intact dogs and 136.1 +/- 6.5 beats/min in SAD dogs. There were no significant differences in the hemodynamic parameters between intact and SAD dogs after pacing. Plasma norepinephrine was significantly lower in intact than in SAD dogs before pacing (197.7 +/- 21.6 vs. 320.6 +/- 26.6 pg/ml; P < 0.005). In the heart failure state, plasma norepinephrine increased significantly in both intact (598.3 +/- 44.2 pg/ml) and SAD (644.0 +/- 64.6 pg/ml) groups. There were no differences in the severity or the magnitude of the developed heart failure state in SAD vs. intact dogs. We conclude from these date that the arterial baroreflex is not the sole mechanism for the increase in sympathetic drive in heart failure.     

Parameter estimation and model verification of first order quasistatic error model for three-axis machining centers

Quasistatic error sources, which include thermal, mechanical loading and geometric error sources, are responsible for a very large proportion (typically, 70%) of the volumetric errors of a numerically controlled machine-tool. This paper, the first in a set of three, discusses the development of a very general model for the effects of geometric errors of the components of the kinematic chain (structural members and axes) of a machine on the volumetric errors in the work space. The effects of the other two sources are modeled as changes in the geometric error. The generality of the model arises from the fact that the errors along an axis of the machine can be characterized by any polynomial functions and the model is recursive in the order of these polynomials. This model can be used as the basis of a compensation scheme as well as in budgeting of errors on a machine-tool.     

Distinguishable patterns of connectivity in serum immunoglobulins from SLE patients and healthy individuals

Given that normal individuals maintain significant levels of serum autoantibodies that share many characteristics with those found in association with autoimmune diseases (AID), it has been proposed that disease could result from defects in supraclonal regulation, namely deviations of normal patterns of immunoglobulin (Ig) connectivity. Using conventional methods, together with a recently developed technique to quantitatively score a variety of V-region-dependent serum IgG interactions, the authors have now compared serum Ig connectivity in a group of patients with systemic lupus erythematosus (SLE) to healthy controls. The results demonstrate the existence of V-region interactions of serum IgG and IgM in SLE patients and healthy donors, with comparable connectivity titres, diversity and average affinities (microM range), but a wider individual variation and a tendency for higher F(ab')2 directed reactivities in the group of SLE patients. Multivariate statistics analysis of the data derived from reactivity patterns on F(ab')2 subsets, however, distinguished the two groups of donors, and demonstrated a larger dispersion and wider time-dependent variations in the patient population, as compared to healthy controls. The authors conclude that SLE is associated with circulating antibody repertoires that deviate from the patterns and levels of V-region connectivity characteristic of healthy individuals. These findings may shed light on the mechanisms of disease maintenance, and on the basis for the therapeutic effects of normal polyclonal Igs at high doses.