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Robug IIs, an intelligent legged climbing service robot designed to work in relatively unstructured and rough terrain, and has the capability of walking, climbing vertical surfaces and performing autonomous floor to wall transfer is being tested. A test result on a real-scale model of a Magnox nuclear reactor pressure vessel has proved the usefulness of the robot.

The signal-to-noise ratio and bandwidth of photonic time-stretch (PTS) systems have previously been limited due to the nonlinear distortion caused by modulator response and dispersive propagation. In this paper, we present a novel method for the reconstruction of the input signal from two phase-diverse intensity measurements. The method consists of optical phase retrieval at the measurement point followed by simulated optical backpropagation to the modulation point. By numerical simulation of a PTS system with realistic parameters, we analyze the proposed method and compare it with the previously suggested maximum ratio combining (MRC) method. We show that the proposed optical backpropagation method, unlike the MRC method that treats the system as being linear from electrical input to output, can reconstruct the signal even at a large modulation depth and that the method is insensitive to biasing error or drift and not overly sensitive to misestimation of system parameters. Furthermore, to reduce the computational effort associated with the simulation of PTS systems, we present a numerical propagation method whereby the required number of sampling points is reduced by several orders of magnitude. [ABSTRACT FROM PUBLISHER]

Background: The Venous Window Needle Guide (VWING; Vital Access Corp, Salt Lake City, Utah) is a surgically implanted titanium device designed to facilitate cannulation of uncannulatable dialysis access arteriovenous fistulas (AVFs) because of excessive depth, aneurysm formation, or tortuosity but that exhibit sufficient flow volume to support hemodialysis. We report the 18-month fistula patency, functionality, and complications of the use of the VWING device., Methods: This retrospective study examined AVF patency, VWING functionality, interventions, and device infections at 18 months after VWING implantation. The study population comprised the eligible patients enrolled in the VWING Salvage of AV Fistula (SAVE) trial., Results: Fifty-four patients were originally enrolled in the SAVE trial, and 35 were enrolled in the follow-up study. At 18 months, when considering surgical or percutaneous interventions at the VWING site(s) only, the primary AVF patency rate was 78%. Interventions elsewhere on the AVF, outside the boundaries of the VWING, resulted in a primary patency rate of 38%. The VWING accounted for 13% loss of AVF primary patency compared with 53% loss from the remaining AVFs. The overall AVF assisted primary patency rate was 91%, and the primary patency rate was 21%. VWING secondary functionality, the continued ability to access the fistula through the VWING using a constant site cannulation technique, was 65%. During the 12 months after the SAVE Study 80% of patients did not require the use of a central venous catheter. Eleven VWING devices were removed from eight patients, all but one for cannulation difficulties. One device was removed during the SAVE trial because of infection. No device or systemic infection was identified in the ensuing 12 months, for an overall systemic infection rate of 0.014 per device-year. An intervention rate of 0.32 per device-year was required to maintain device functionality during the 18-month follow-up period., Conclusions: Implantation of the VWING device is a safe and effective means of establishing hemodialysis access in an otherwise functional but uncannulatable AVF. The device infection rate is acceptably low., (Published by Elsevier Inc.)

Surface-stabilized orthoconic antiferroelectric liquid crystals (OAFLCs) have a director tilt of theta = 45 degrees and are, with no field applied, negatively uniaxial with the optic axis perpendicular to the cell substrates. We demonstrate that OAFLCs can be utilized to achieve lossless phase modulation with three almost equidistant phase levels. This turns out to be true also for polymer-stabilized OAFLCs, where the polymer network increases the switching speed of the device without affecting the phase modulation appreciably.

We describe a characterization method based on diffraction for obtaining the phase response of spatial light modulators (SLMs), which in general exhibit both amplitude and phase modulation. Compared with the conventional interferometer-based approach, the method is characterized by a simple setup that enables in situ measurements, allows for substantial mechanical vibration, and permits the use of a light source with a fairly low temporal coherence. The phase determination is possible even for a SLM with a full amplitude modulation depth, i.e., even if there are nulls in the amplitude transmission characteristic of the SLM. The method successfully determines phase modulation values in the full 2pi rad range with high accuracy. The experimental work includes comparisons with interferometer measurements as well as a SLM characterization with a light-emitting diode (LED).

We have studied the analog (V-shaped switching) mode in ferroelectric liquid crystals in reflective mode for analog phase modulation applications. We have found that several combinations of cell thicknesses and input polarization states exist for which near-lossless analog phase modulation with a range of approximately 2pi rad is obtained, and we demonstrate one such combination experimentally. Despite a slight deviation from the ideal conditions, e.g., the tilt angle was 38 degrees instead of the desired 45 degrees , virtually pure 1.6pi rad phase modulation was obtained; the measured values agree very well with our numerical simulations of the real device.

The analog switching mode in ferroelectric liquid crystals, sometimes referred to as 'V-shaped switching,' has, thanks to its submillisecond switching capability, attracted much interest for future fast electro-optic displays where it is to be used for amplitude modulation. We have studied this mode for analog phase-only modulation. As V-shaped switching is based on a conical motion of the index ellipsoid this presents a challenging problem since both the orientation of the slow and fast axes, as well as the amount of birefringence varies in the switching process. We show theoretically, partly by means of Poincaré sphere analysis, that it is in fact possible to obtain near-lossless analog phase modulation between zero and pi radians in an ideal V-shaped switching cell through careful tuning of the polarization state of the input light. Furthermore, we were able to demonstrate this experimentally in a fabricated cell. Although this cell deviated slightly from the ideal conditions, e.g., the tilt cone half-angle was 38 degrees instead of the desired 45 degrees , we still obtained a continuous phase modulation between zero and 0.78pi rad with less than 2% modulation of the amplitude; the measured values agree very well with our numerical simulations of the real device.

The performance of wavelength-based photonic analog-to-digital converters (ADCs) is theoretically analyzed in terms of resolution and bandwidth as well as of noise tolerance. The analysis applies to any photonic ADC in which the analog input signal is converted into the wavelength of an optical carrier, but special emphasis is put on the spectrometerlike setup in which the wavelength is mapped to a spatial spot position. The binary output signals are then retrieved by an array of fan-out diffractive optical elements that redirect the beam onto the correct detectors. In particular, the case when the input signal controls the wavelength directly such that it will chirp in frequency during each sampling pulse or interval is studied. This chirping obviously broadens the spot on the diffractive optical element array; the effect of this broadening on noise tolerance and comparator accuracy is analytically analyzed, and accurate numerical calculations of the probability of error are presented.

A gas cell filed with argon gas under pressure is placed in a tightly focused laser beam to provide a limiter for laser pulses above a certain peak power, corresponding to the optical breakdown threshold for the creation of a laser-induced plasma. Measurements of the threshold intensity as a function of argon gas pressure are given for a laser wavelength of 1.064 microm (Nd:YAG) and a pulse length of 6.4 ns. Threshold intensities for optical breakdown in fused silica were measured with the same optical system, enabling a relative comparison of breakdown thresholds, of interest for protecting fused-silica optical components in fiber-optic delivery systems for laser material processing applications. The threshold intensity was measured to 220 GW/cm2 in Ar at 1.0 x 10(5) N/m2 (1 atm), 80 GW/cm2 in Ar at 8.0 x 10(5) N/m2 (7.9 atm), and 55 GW/cm2 in fused silica. Even though the threshold in argon is higher than that in fused silica, the limiter will protect the optical components if the laser beam is focused to a tighter spot in the gas cell than at the input end of the fiber.

Dynamic behavior of an analog-to-digital converter (ADC) based on diffractive optical element(s) (DOE)(s) was studied and found to be in agreement with predictions. The analog signal was translated to an angular deflection of a laser beam by means of an acousto-optic (AO) cell. The number of bits in this experimental demonstration was three, using an eight-element DOE array. The maximum sample rate was found to be 2.5 MS/s, the limiting factor being the transit time for the acoustic wave across the width of the laser beam in the AO cell. The study is intended as a first dynamic demonstration of a proposed ADC scheme previously demonstrated in a quasi-static version. The full potential of the ADC scheme will require the use of a fast tunable diode laser to replace the AO deflection scheme used here.

Circulating monocytes adhere to platelets and matrix proteins at sites of vascular injury, where engagement of specific surface tethering molecules mediates outside-in signaling and synthesis of gene products by the leukocytes. Here we demonstrate that interaction of isolated human monocytes with collagen induces matrix metalloproteinase-9 (MMP-9; gelatinase B) synthesis by monocytes, a process that is greatly enhanced in the presence of platelets. MMP-9 is a potent matrix degrading enzyme implicated in atherosclerotic plaque rupture, aneurysm formation, and other vascular syndromes. Synthesis of MMP-9 by monocytes is tightly regulated and synergistically increased following adhesion to collagen and platelets. Adhesion to control matrix proteins alone did not result in MMP-9 protein production and, similarly, adhesion of monocytes to platelets activated with thrombin in suspension was not sufficient to induce MMP-9 synthesis in the absence of monocyte adhesion to collagen. Interruption of intercellular contact between platelets and monocytes dramatically inhibited MMP-9 synthesis. These observations demonstrate that discrete adhesion-dependent signaling pathways govern MMP-9 synthesis by monocytes. The synthesis of MMP-9 by monocytes may be critical in vascular syndromes and other pathological processes that are dependent on dysregulated cell-cell and cell-matrix interactions.

Some epidemiological studies indicate an association between extremely low frequency electromagnetic field (ELF-EMF) exposure and cancer risks. These studies have mainly taken residential and occupational exposure into consideration. Outdoor environments are often considered as low level areas, but in this paper we show that this is not true in a city environment. We have mapped the ELF magnetic flux densities along certain stretches of sidewalk in central Göteborg City, Sweden. About 50% of the investigated street length shows flux densities of the same order of magnitude (0.2 microT and above) as those associated with increased risks of cancer in epidemiological studies. We conclude that the outdoor exposures in a city environment also should be considered in exposure assessments and risk evaluations. These elevated flux densities are probably due to stray currents. We also found strong magnetic flux densities (> 1.0 microT) close to ordinary distribution pillars, power substations, shoplifting alarms, and other electrical devices., (Copyright 2001 Wiley-Liss, Inc.)

Objective: To determine the percentage of elective abdominal aortic aneurysms (AAAs)/aortoiliac aneurysms that currently can be repaired with endovascular grafts (EVGs), the reasons for rejection of EVGs, and the future role of EVG in the treatment of AAA., Methods: From January 1997 to May 1998, patients at three hospitals (a university hospital, a university-affiliated teaching hospital, and a Veterans Administration hospital with university faculty and residents) were evaluated for EVGs as part of a national clinical trial with grafts manufactured by Endovascular Technologies (EVT, Menlo Park, Calif). All patients at two hospitals and patients treated by the participating surgeons at the third hospital were screened for EVG. Patients with AAAs that were ruptured, symptomatic, or involved renal or mesenteric arteries and patients who declined treatment were excluded from the study. Evaluation included clinical examination, computed tomography scan, and selective arteriography. The decision to proceed with EVG was made by the vascular surgeon, with input and concurrence of medical personnel from a company with extensive experience in endograft repair. The main outcome measures were the determination of the percentage of elective AAAs currently being treated with an EVG and the reasons for exclusion of patients from EVG placement., Results: A total of 162 patients underwent elective treatment of an AAA, 22 (14%) with an EVG (14 bifurcated, eight tube) and 140 (86%) with traditional resection. Indications for not proceeding with an EVG included insufficient proximal cuff in 29 patients (21%), distal common iliac aneurysm or insufficient distal iliac neck in 29 patients (21%), proximal neck too large for an EVG in 24 patients (17%), symptomatic iliac stenosis in 23 patients (16%), iliac stenosis precluding introducer passage in 17 patients (12%), patient preference in 11 patients (8%), and calcification, kink, or extensive thrombus involving the proximal neck precluding safe graft attachment in seven patients (5%). Of the 22 patients treated with an EVG, three were converted to open resection, because of iliac stenosis in two patients and premature stent deployment in one patient (initial technical success rate, 86%)., Conclusion: Based on currently available technology, 80% of patients were not candidates for an EVG because of proximal calcification, short aortic or distal cuff, coexisting distal iliac aneurysm, and stenotic iliac disease. Even with the use of adjunctive procedures, most patients still require open repair. Significant changes in design will be necessary to apply these devices to most patients with an AAA.

The effect of 50 Hz magnetic fields on the cytosolic calcium oscillator in Jurkat E6.1 cells was investigated for field strengths within the range from 0 to 0.40 mT root mean square. The intracellular Ca2+ concentration data were collected for single Jurkat cells that exhibited a sustained spiking for at least 1 h while repeatedly exposing them to an alternating magnetic field in 10-min intervals interposed with nonexposure intervals of the same length. The obtained data were analysed by computing spectral densities of the Ca2+ oscillating patterns for each of these 10-min intervals. For every single-cell experiment the spectra of all exposure as well as nonexposure periods were then averaged separately. A comparison between the resulting averages showed that the total spectral power of the cytosolic Ca2+ oscillator was reduced by exposure of the cells to an alternating magnetic field and that the effect increased in an explicit dose-response manner. The same relationship was observed within the 0-10 mHz (10 x 10(-3) Hz) subinterval of the Ca2+ oscillation spectrum. For subintervals at higher frequencies, the change caused by the exposure to the magnetic field was not significant.

Purpose: Studies have shown that 11% to 18% of patients with an abdominal aortic aneurysm (AAA) have a first-degree relative with an AAA. A familial pattern among patients with peripheral arterial aneurysms and arteriomegaly has not been reported. The objective of this study was to examine familial patterns among patients with peripheral arterial aneurysm and arteriomegaly and compare them with patterns among patients with AAA., Methods: Pedigrees were constructed for first-degree relatives of patients who received the diagnosis of peripheral arterial aneurysm, arteriomegaly, or AAA from 1988 through 1996. The presence of aneurysms and risk factors was confirmed for patients and relatives by means of telephone interviews and review of hospital and physician records., Results: Seven hundred three first-degree relatives older than 50 years were contacted for 140 probands with peripheral arterial aneurysm, AAA, or arteriomegaly. There were differences in risk factors for hernia and diabetes mellitus among the probands with peripheral arterial aneurysm, AAA, or arteriomegaly but none for relatives. Patients with peripheral arterial aneurysm (n = 40) had a 10% (4/40) familial incidence rate of an aneurysm, patients with AAA (n = 86) had a 22% (19/86) familial incidence rate, and patients with arteriomegaly (n = 14) had a 36% (5/14) familial incidence rate. AAA (24/28, or 86%) was the aneurysm diagnosed most commonly among first-degree relatives. Most aneurysms (85%) occurred among men., Conclusion: There appears to be a gradation of familial patterns from peripheral arterial aneurysm to AAA to arteriomegaly among patients with degenerative aneurysmal disease, and there appears to be a predominance among men. Relatives of patients with any of the 3 lesions-peripheral arterial aneurysm, AAA, arteriomegaly--most frequently have AAA. Relatives of patients with AAA, peripheral arterial aneurysm, or arteriomegaly may be screened by means of a physical examination for peripheral aneurysmal disease. Screening by means of ultrasound examination of the aorta should be limited to first-degree relatives of patients with aortic aneurysms or arteriomegaly.

Purpose: To determine whether graft revision on the basis of a duplex scan alone without an arteriogram is effective in identifying graft stenosis and allowing for repair to preserve bypass graft patency., Methods: From 1994 to 1997, all patients in whom infrainguinal grafts were placed at a University-affiliated teaching hospital were entered into a prospective protocol using duplex scanning to detect stenotic lesions. Studies were performed after the operation, at 1 month, at 3 months, and every 3 months thereafter. All grafts were composed of reversed autogenous vein and were placed subcutaneously to allow for easier monitoring and correction. Patients who had failing grafts underwent operative correction without preoperative arteriography., Results: During this interval, 48 lesions in 31 grafts were repaired. The indication for repair was a velocity ratio greater than 2.5 in all patients and greater than 3.0 for 43 lesions. Forty-four lesions had a peak systolic velocity greater than 250 cm/sec. Twenty-nine lesions reduced the distal graft velocity to less than 45 cm/sec. Sixteen lesions involved the proximal anastomosis, 26 the body of the graft, three the distal anastomosis, two involved inflow arteries, and one affected the outflow vessel. Repair included patch angioplasty for 39 lesions, resection with interposition graft for five, a proximal jump graft for three, and a distal extension graft for one. The severity and location of the stenosis was confirmed at operation in all cases. Twenty-eight of the 31 patients (90%) are currently alive, and follow-up on these patients has ranged from 5 to 36 months (mean, 19 months). Twenty-nine of the 31 grafts (94%) remained patent, with a 92% patency rate by life table analysis at 3 years. Follow-up duplex scans found improvement in the ankle-brachial index (mean increase, 0.33) and distal graft velocity (mean increase, 43 cm/sec) in all patients. After repair, 27 patients had a distal graft velocity greater than 45 cm/sec and no patient had a velocity ratio greater than 1.5. Complications included wound infection in two patients and bleeding that required reoperation in one. All symptomatic patients had clinical improvement, and none required early reexploration for residual stenosis., Conclusions: Graft repair may be safely performed on the basis of duplex scanning alone with preservation of bypass patency and correction of hemodynamic deterioration. Duplex scanning can detect inflow or outflow disease in addition to intrinsic graft stenoses and can identify sequential lesions, eliminating the need for, expense of, and risk of arteriography.

We have studied the effects of 50-Hz 100-microT rms magnetic fields on intracellular Ca2+ concentration in the Jurkat T lymphocyte variant E6.1 using fluorescent probes Indo-1 and Fura-2. We found, however, that the pattern of intracellular Ca2+ fluctuations also depended on the agent used for cell attachment, in our case the polypeptide poly-L-lysine. In order to isolate possible effects of magnetic field exposure from those of poly-L-lysine, the action of polypeptide on cytosolic Ca2+ was studied as well. It was found that a 10(-7)% concentration of polypeptide triggered prolonged Ca2+ spiking. Higher (10(-4)%) concentrations induced rapid increases in intracellular Ca2+ followed by high, unstable Ca2+ levels. The response of these cells to the monoclonal antibody anti-CD3 was also inhomogeneous, similar to one caused by poly-L-lysine. The effect of magnetic field exposure was studied on cells initially exhibiting (1) non-oscillating, low Ca2+ concentration and (2) prolonged Ca2+ concentration oscillations. In case (1) the result was negative. In case (2), statistically significant changes were found: the oscillation amplitude was reduced on average by 30%, and the frequency composition was shifted towards higher frequencies.

Background: Abdominal aortic aneurysm and renal neoplasm are occasionally discovered concurrently. Simultaneous operative therapy may be an effective alternate management strategy to a staged procedure., Patients and Methods: The medical records of 10 consecutive patients undergoing abdominal aortic aneurysm repair and nephrectomy for renal neoplasm were reviewed. Data collected included mode of presentation, preoperative evaluation, renal pathology, and in-hospital morbidity and mortality. Long-term follow-up was obtained through office records and telephone contact., Results: In 7 patients, the renal mass was identified during evaluation of abdominal aortic aneurysm. The aneurysm was identified during evaluation of hematuria in 2 patients. One patient was discovered to have both conditions simultaneously. All patients underwent successful aneurysm repair and nephrectomy. Pathology revealed 6 renal cell carcinomas, 2 complex cysts, 1 hemangiopericytoma, and 1 oncocytoma. Four patients have died in the follow-up period: 1 of metastatic cancer and 3 of unrelated causes. There have been no cases of graft infection., Conclusion: Simultaneous abdominal aortic aneurysm repair and nephrectomy for neoplasm is an appropriate management strategy for selected patients.

The total current of Ca2+ ions through patch-clamped cell membranes was measured while exposing clonal insulin-producing beta-cells (RINm5F) to a combination of DC and AC magnetic fields at so-called cyclotron resonance conditions. Previous experimental evidence supports the theory that a resonant interaction between magnetic fields and organisms can exist. This experiment was designed to test one possible site of interaction: channels in the cell membrane. The transport of Ca2+ ions through the protein channels of the plasma membrane did not show any resonant behavior in the frequency range studied.

Purpose: This study was undertaken to evaluate the effect of blood flow on the dimensions and cellular composition of normal arteries and freshly placed vein grafts (VG)., Methods: Bilateral jugular vein interposition grafts were placed in the common carotid arteries of 12 New Zealand white rabbits, and blood flow was reduced on one side by external carotid artery ligation. Shear stress, tangential stress, vessel dimensions, and smooth muscle cell (SMC) proliferation of reduced-flow arteries and VG were compared with these measures in contralateral controls (CON)., Results: A sustained reduction in blood flow was documented at 4 weeks (13 +/- 4 ml/min reduced-flow vs 21 +/- 4 ml/min CON; p < 0.05). Reduced-flow carotid arteries had a smaller lumen radius and greater medial thickness compared with normal-flow arteries, but there was no difference in medial cross-sectional area or medial SMC volume and no differences in any intimal measurements. These changes resulted in normalization of shear stress (15.2 +/- 4.6 dynes/cm2 reduced-flow vs 13.6 +/- 2.5 dynes/cm2 CON; p = NS). All VG underwent a marked postimplantation hyperplasia in intima and media, but the major effect of flow reduction on VG dimensions occurred in the intima. Intimal thickness in reduced-flow VG was 60% greater than that in control VG (57 +/- 12 microns vs 35 +/- 5 microns; p = 0.05), and intimal area was 70% greater than that in controls (0.83 +/- 0.24 microns 2 vs 0.48 +/- 0.08 microns 2; p > 0.05). Smaller differences were found in medial thickness (74 +/- 4 microns reduced-flow vs 63 +/- 4 microns CON; p = 0.02) and medial area (1.03 +/- 0.36 microns 2 reduced-flow vs 0.84 +/- 0.22 microns 2 CON; p = 0.05). Intimal SMC volume in reduced-flow VG was 37% greater than that in control VG (p = 0.07). Tangential stress in VG equaled that in ipsilateral arteries, whereas shear stress in VG remained much lower than that in arteries., Conclusions: In this model, arteries and VG responded to flow reduction by wall thickening, but the mechanism differed. Arteries underwent medial remodeling, lumen caliber reduction, and shear stress normalization, whereas VG responded by an upward modulation of the proliferative response that follows graft placement. These data support a primary role for tangential stress and a secondary role for shear stress in determination of VG dimensions.

The hypothesis that specific combinations of DC and low frequency AC magnetic fields at so-called cyclotron-resonance conditions could affect the transport of ions through ion channels, or alter the kinetics of ion channels (opening and closing rates), has been tested. As a model system, the ion channels formed by gramicidin A incorporated in lipid bilayer membranes were studied. No significant changes in channel conductance, average lifetime, or formation rate as a function of applied fields could be detected over a wide range of frequencies and field strengths. Experiments were carried out to measure the time-resolved single-channel events and the average conductances of many-channel events in the presence of K+ and H+ ions. The channel blocking effect of Ca++ was also studied.

Numerical solutions are presented to the equation of motion for an ion confined to a region of space by a restoring force and subject to DC and AC magnetic fields. We have expanded on the theoretical work of Durney et al. [1988] by including a potential well as a confining factor. This additional term in the equation of motion, being nondissipative, could allow for the buildup of stored energy within the system to a level necessary for a macroscopic resonant phenomenon. Resonant behaviour has been studied, including calculation of the trajectory and energy (kinetic and potential) of a confined ion, with emphases on the appearance of both amplitude and frequency windows. The results are discussed in relation to ion transport through transmembrane channels exposed to magnetic fields. When realistic values of the frictional and restoring-force coefficients are considered, all predicted resonant behaviour disappears, except at very high field strengths.