Phase-sensitive frequency conversion of quadrature modulated signals.

Two mechanisms that can make frequency conversion based on nonlinear mixing dependent on the phase of the input signal are identified. A novel phase-to-polarization converter that converts the orthogonal phase components of an input signal to two orthogonally polarized outputs is proposed. The operation of this scheme and a previously reported scheme at an increased symbol rate are simulated with semiconductor optical amplifiers (SOAs) as the nonlinear devices. Experimental results demonstrate the effectiveness of SOAs for nonlinear mixing over a wide range of wavelengths and difference frequencies and confirm the accuracy of the numerical model.

Phase discrimination and simultaneous frequency conversion of the orthogonal components of an optical signal by four-wave mixing in an SOA.

Simultaneous conversion of the two orthogonal phase components of an optical input to different output frequencies has been demonstrated by simulation and experiment. A single stage of four-wave mixing between the input signal and four pumps derived from a frequency comb was employed. The nonlinear device was a semiconductor optical amplifier, which provided overall signal gain and sufficient contrast for phase sensitive signal processing. The decomposition of a quadrature phase-shift keyed signal into a pair of binary phase-shift keyed outputs at different frequencies was also demonstrated by simulation.

Generation of 21.3 Gbaud 8PSK signal using an SOA-based all-optical phase modulator.

We describe a novel SOA-based all-optical pure-phase modulator, and show how deleterious cross-gain modulation from the SOAs can be suppressed by utilizing an integrated interferometer structure. We experimentally demonstrate the use of the optical gate as a π/4 phase modulator producing 21.3 Gbaud 8PSK from 21.3 Gbit/s OOK and 21.3 Gbaud QPSK inputs. The modulator produces 3 dB of gain and coherent detection-based bit error rate measurements indicate a 2.4 dB excess penalty.

All-optical technique for modulation format conversion from on-off-keying to alternate-mark-inversion.

We propose and numerically investigate for the first time a novel all-optical on-off-keying to alternate-mark-inversion modulation format converter operating at 40 Gbps employing a semiconductor optical amplifier (SOA)-based Mach-Zehnder interferometer (MZI). We demonstrate that this SOA-MZI operates as a pulse subtractor, and in the absence of patterning will produce perfectly phase inverted pulses regardless of the individual SOA phase excursions. We use a comprehensive computer model to illustrate the impact of patterning on the output phase modulation, which is quantified through the definition of the phase compression factor.

Pattern compensation in SOA-based gates.

We propose a novel scheme employing complementary data inputs to overcome the patterning normally associated with semiconductor optical amplifier based gates and demonstrate the scheme experimentally at 42.6Gb/s. The scheme not only avoids introducing patterning during switching, but also compensates for much of the patterning present on the input data. A novel gate was developed for the experiment to provide the complementary signals required for the scheme.

Going digital: image preparation for biomedical publishing.

Authors are more often being held responsible for readying their own data figures for digital publication by scanning them at the proper resolution and preparing them for presentation in both print and on-line journals. In this manner, the visuals can be printed at the highest quality the publisher can provide and be ready for rapid electronic distribution on the Internet. Therefore, authors must become knowledgeable in the visual preparation process in order to generate electronic images that will be as true a representation of the original image as possible. Perfecting this procedure can be a learning experience and often requires some experimentation. When accomplished, the author will have more control of exactly how the images will look before they are published. In addition to the scan resolution, the type of digital scanner and software applications used are very important, and instruction manuals should be followed closely so as to understand the full potential of the digitizing equipment. Anat Rec (New Anat): 257:128-136, 1999.

Estrogen/progesterone treatment of diffuse antral vascular ectasia.

A case of acute and chronic gastrointestinal bleeding secondary to antral vascular ectasia is presented. The pattern of antral vascular ectasia was the diffuse form. After attempted treatment with endoscopic laser photocoagulation proved ineffective, the bleeding was treated with an estrogen/progesterone combination. The bleeding ceased with this medical therapy. The lesion of antral vascular ectasia persisted, however, despite the cessation of bleeding. Attempted maintenance therapy, consisting of reduction in frequency of estrogen/progesterone therapy to every third day, resulted in resumption of bleeding, requiring reinstitution of daily therapy for control.

Three-wavelength device for all-optical signal processing.

We describe the operation of a semiconductor laser amplifier as a nonlinear element, using a novel three-wavelength configuration, which enhances the recovery rate of the nonlinear refractive index and permits choice of its sign and magnitude. Simple rate-equation analysis suggests that 100-GHz operation should be possible with powers of ~1 W.

Constant vs variable resistance knee extension training.

To compare the effect of constant resistance (CR) and variable resistance (VR) training on full range-of-motion (ROM) strength development, 22 men and 27 women (age = 26 +/- 5 yr) were randomly assigned to either a CR training group (N = 17), a VR training group (N = 17), or a control group (N = 15) that did not train. The CR and VR groups trained 2 to 3 d.wk-1 for 10 wk. Subjects completed one set of full ROM (120 to 0 degrees of flexion) bilateral knee extensions with an amount of weight that allowed 8 to 12 repetitions during each training session. For the VR group, resistance was varied with a cam supplied by the manufacturer (Nautilus). For the CR group, the cam was removed and replaced with a round sprocket. Prior to and after training, maximal voluntary isometric torque was measured at 9, 20, 35, 50, 65, 80, 95, and 110 degrees of knee flexion. Analysis of covariance indicated that the VR and CR groups gained strength at all angles (P less than or equal to 0.05) when compared to the control. [table: see text] There was no difference (P greater than 0.05) between the CR and VR groups at any angle, and the magnitude of strength gained was similar (P greater than 0.05) among angles for both groups. These data indicate that both CR and VR knee extension training elicit full ROM strength development.

Orientational dependence of degenerate four-wave mixing in multiple-quantum-well structures.

The transient grating technique is used to demonstrate how the temporal response of four-wave mixing in multiple-quantum-well structures depends on sample orientation. Variation of the decay times associated with the short-period grating in a phase-conjugate geometry between 40 and 500 psec is demonstrated in a GaAs/AlGaAs multiple-quantum-well structure and interpreted in terms of the large anisotropy in the carrier diffusion.

Hodgkin's disease presenting as diffuse nonspecific inflammation of small bowel.

I report an unusual case of primary retroperitoneal Hodgkin's disease. The initial presentation radiographically involved diffuse thickening of small bowel folds from the duodenum through the terminal ileum. The histologic picture consisted of diffuse, nonspecific inflammation with an infiltrate resembling that seen in tropical sprue. The clinical picture consisted of progressive diffuse abdominal pain, fever, diarrhea, and weight loss. The histologic and radiographic abnormalities returned to normal with chemotherapy. Computerized search of the English language literature uncovered no similar case presentation.

Studies on the origins of biliary immunoglobulins in rats.

This study was designed to investigate the origins of biliary immunoglobulins in rats. Natural antibodies to species of Lactobacillus and Staphylococcus were detected in blood, bile, and lymph, with predominant activity being associated with immunoglobulin A in lymph and bile and with immunoglobulins M and G in blood. Six hours after thoracic duct cannulation, serum immunoglobulins G, M, and A had fallen to 60%, 65%, and 40%, respectively, of the preoperative levels, whereas the level of total and specific immunoglobulin A in bile was reduced to 25% with no significant decline of immunoglobulin G. Thoracic duct occlusion caused a similar selective reduction in biliary immunoglobulin A. It is calculated that 50% of thoracic duct lymph immunoglobulin A entering the blood is secreted in bile. Synthesis of immunoglobulins M, G, and A in the liver was established by the detection of antibody-secreting cells. It is proposed that the major part of biliary immunoglobulin A is derived from intestinal lymphoid tissues and that a portion of the remainder, as well as part of biliary immunoglobulins M and G, results from local synthesis.

Watery diarrhea syndrome with elevated levels of vasoactive intestinal polypeptide associated with pancreatitis and pancreatic pseudocyst.

A 32-year old patient presented with recurrent pancreatitis, severe watery diarrhea and elevated serum levels of vasoactive intestinal polypeptide. His diarrhea appeared to respond to intramuscular propantheline. Initially he improved but had another attack of pancreatitis while hospitalized. Evaluation by ultrasound revealed the presence of a pseudocyst and endoscopic retrograde pancreatography demonstrated complete occlusion of the main pancreatic duct. Exploratory laparotomy was performed with drainage of a pseudocyst. Analysis of the pseudocyst fluid revealed an elevated amylase, lipase and vasoactive intestinal polypeptide level. It is believed that this patient's severe diarrhea was related to his pancreatitis and pancreatic pseudocyst with elevated levels of vasoactive intestinal polypeptide.

Chronic delta-9-tetrahydrocannabinol. Transient and lasting effects on avoidance behavior.

Delta-9-Tetrahydrocannabinol (THC) was administered to albino rats with extensive experience in free-operant (Sidman) lever-press shock avoidance. Dosing (30 mg/kg intragastrically) continued once daily, 3 hr before testing, for 1 to 6 weeks. Significant changes were noted in the response rates of several animals, but both the magnitude and direction of these were highly variable. However, shock rates were reliably elevated by THC, but complete tolerance was observed within 6 sessions. In several rats this was followed by sessions with significantly lower shock rates than the predrug baseline. These rats continued to perform at this level of proficiency until THC was discontinued, at which point the baseline was reacquired. These data emphasize that an important determinant of tolerance to a drug effect is the consequence of the effect for the organism.