Amplification of advanced modulation formats with a semiconductor optical amplifier cascade.

The convergence of optical metro networks and access networks extends the area of network coverage, and therefore requires the use of optical amplifiers. For this purpose, semiconductor optical amplifiers (SOA) would be attractive, because they are broadband, can be centered between 1250 nm and 1600 nm, and because they are cheap in production and operation. We show that signals encoded with advanced modulation formats such as BPSK, QPSK, 8PSK, and 16QAM can be amplified by a cascade of at least four SOAs. This enables high-capacity paths with a capacity in the order of Tbit/s for converged metro-access networks.

Demonstration of an SOA-assisted open metro-access infrastructure for heterogeneous services.

An open converged metro-access network approach allows for sharing optical layer resources like fibers and optical spectrum among different services and operators. We demonstrated experimentally the feasibility of such a concept by the simultaneous operation of multiple services showing different modulation formats and multiplexing techniques. Flexible access nodes are implemented including semiconductor optical amplifiers to create a transparent and reconfigurable optical ring network. The impact of cascaded optical amplifiers on the signal quality is studied along the ring. In addition, the influence of high power rival signals in the same waveband and in the same fiber is analyzed.

Linear semiconductor optical amplifiers for amplification of advanced modulation formats.

The capability of semiconductor optical amplifiers (SOA) to amplify advanced optical modulation format signals is investigated. The input power dynamic range is studied and especially the impact of the SOA alpha factor is addressed. Our results show that the advantage of a lower alpha-factor SOA decreases for higher-order modulation formats. Experiments at 20 GBd BPSK, QPSK and 16QAM with two SOAs with different alpha factors are performed. Simulations for various modulation formats support the experimental findings.

Quantum dot SOA input power dynamic range improvement for differential-phase encoded signals.

Experimentally we find a 10 dB input power dynamic range advantage for amplification of phase encoded signals with quantum dot SOA as compared to low-confinement bulk SOA. An analysis of amplitude and phase effects shows that this improvement can be attributed to the lower alpha-factor found in QD SOA.

Optical grooming switch with regenerative functionality for transparent interconnection of networks.

We demonstrate a regenerative optical grooming switch for buffer-less interconnection of metro/access and metro/core ring networks with switching functionality in time, space and wavelength domain. Key functionalities of the router are the traffic aggregation with time-slot interchanging (TSI) functionality, the WDM-to-ODTM multiplexing and the OTDM-to-WDM demultiplexing of high-speed channel into lower bit-rate tributaries as well as multi-wavelength all-optical 2R regeneration of several higher-speed signals. BER and Q-factor measurements of different switching scenarios show excellent performance with no error floor and Q-factors above 21 dB.

Slow and fast dynamics of gain and phase in a quantum dot semiconductor optical amplifier.

Gain and phase dynamics in InAs/GaAs quantum dot semiconductor optical amplifiers are investigated. It is shown that gain recovery is dominated by fast processes, whereas phase recovery is dominated by slow processes. Relative strengths and time constants of the underlying processes are measured. We find that operation at high bias currents optimizes the performance for nonlinear cross-gain signal processing if a low chirp is required.

Computed tomography without oral contrast solution for blunt diaphragmatic injuries in abdominal trauma.

OBJECTIVE: The aim of this study was to estimate the sensitivity, specificity, and positive predictive value (PPV) of computed tomography (CT) without oral contrast for diaphragm injuries (DIs) in blunt abdominal trauma. METHODS: We prospectively enrolled 500 consecutive "trauma-one" patients who received CT imaging and interpretation (CT-Read1) of the abdomen within 45 minutes of their arrival from July 2000 to December 2001. All patients were imaged without oral contrast but with intravenous contrast. Computed tomographic images were reviewed within 24 hours of admission by research radiologists (CT-Read2) blinded to CT-Read1. True DIs were determined hierarchically by either laparotomy or autopsy. RESULTS: There were 9 patients with laparotomy or autopsy-proven blunt DIs; 8 of these injuries involved the left hemidiaphragm. The CT-Read1 correctly detected only 6 of 9 blunt DIs, thus missing 3 DIs. One of these involved the right hemidiaphragm, whereas the other 2 were left sided. There were no false-positive findings with CT-Read1 for blunt DI. The sensitivity and specificity of CT imaging with respect to DI were 66.7% (95% CI, 29.9%-92.5%) and 100% (95% CI, 99.2%-100%), respectively. The PPV for the test was 1.00 (95% CI, 0.65-1.00). CONCLUSION: Although the low number of blunt DIs in this study limits its general applicability, CT imaging of the diaphragm without oral contrast appears to perform within the range of reported imaging techniques using oral contrast. Still, CT scanning appears to have an unsatisfactorily low sensitivity to be reliably used in eliminating the diagnosis of blunt DI.

Computed tomographic scanning without oral contrast solution for blunt bowel and mesenteric injuries in abdominal trauma.

BACKGROUND: Computed tomographic (CT) scanning using intravenous and oral contrast material has traditionally been advocated for the evaluation of intra-abdominal injury, including blunt bowel and mesenteric injuries (BBMIs). The necessity of oral contrast in detecting these injuries has recently been called into question. The purpose of this study was to determine the sensitivity and specificity of CT scanning without oral contrast for BBMIs. METHODS: We prospectively enrolled 500 consecutive blunt trauma patients who received CT imaging and interpretation (CT-Read1) of the abdomen from July 2000 to November 2001. All patients were imaged without oral contrast, but with intravenous contrast. CT images were reviewed within 24 hours of admission by a research radiologist (CT-Read2) blinded to CT-Read1. For study purposes, true BBMI was determined to be present if either laparotomy or autopsy identified bowel or mesenteric injury, or both CT-Read2 and the hospital discharge summary described bowel or mesenteric injury. Three-month telephone follow-up was also completed. RESULTS: CT-Read1 detected 19 of 20 bowel and mesenteric injuries. CT-Read1 missed one duodenal perforation. There were two patients with false-positive interpretations of CT-Read1 for bowel injury. The sensitivity and specificity of CT imaging for the detection of BBMIs were 95.0% and 99.6%, respectively. CONCLUSION: CT imaging of the abdomen without oral contrast for detection of BBMIs compares favorably with CT imaging using oral contrast.

A prototype device for standardized calibration of pulse oximeters II.

OBJECTIVE: There is no commonly accepted in vivo calibration method for pulse oximeters available up to now. On the basis of a prototype device for the calibration of pulse oximeters which was introduced recently, a second approach based on the same concept was tackled in order to design a reliable method for standardized calibration of pulse oximeters. METHODS: An extensive clinical database of time-resolved optical transmission spectra of patient fingers is used to simulate the behavior of patients. A device which is capable of playing back these spectroscopic data to pulse oximeters, and a database where the oxygen status measured with the reference method (Co-Oximetry) is stored, are the main parts of the concept. The playback device has an artificial finger as interface to the pulse oximeters and serves to collect light from the pulse oximeter for analysis and to playback simulated light to the pulse oximeter. The light intensity emitted by two LEDs which illuminates the pulse oximeter detector is controlled via a computer in such a way that it is the same as if the pulse oximeter light had passed the finger. The pulse oximeter display during the data playback can thus be compared to the true SaO2 of the patient. The device is tested with 4 pulse oximeters based on 100 patient spectra. RESULTS: For the four pulse oximeters used in this investigation, an Agilent Technologies CMS monitor (formerly Hewlett-Packard), an Ivy 2000 with Masimo Set technology and Nellcor N-3000 and N-395, there is good correlation between SPO2 and SaO2, and mean and standard deviation of in vivo SpO2-SaO2 and playback SpO2-SaO2 are in good agreement. For two instruments, Nellcor N3000 and Agilent CMS Monitor, a quantitative comparison between the in vivo and in vitro SpO, results was derived. A mean of the deviation playback vs. in vivo SpO2 is less than 0.5% SpO2. The error limits are comparable with the calibration error of the conventional calibration routine. The device is also capable of data playback even in situations with rapid desaturation changes, as displayed in Figure 2. For the other tested pulse oximeters the results are comparable. CONCLUSIONS: Compared to the first prototype the current version is simpler and less expensive in production. Many of previously existing problems are solved and the applicability to a large variety of pulse oximeters and sensors is given. The novel concept for the calibration of pulse oximeters is a tool for assessing the performance of pulse oximeters.

Design and validation of a pulse oximeter calibrator.

The performance of a new calibrator for pulse oximeters is tested with five pulse oximeters from different manufacturers. The calibrator is based on time resolved transmission spectra of human fingers. Finger spectra with different arterial oxygen saturation can be selected to simulate real patients. The results obtained with this calibration device are compared with the results of conventional calibration procedures with volunteers. Beside accuracy tests the suitability for artifact simulation with the new device is discussed. The response of the five tested pulse oximeters is in good agreement with the response of the pulse oximeters connected to real patients. A test procedure for pulse oximeters similar to the conventional desaturation practice is possible; some of the typical artifacts pulse oximetry has to cope with can be simulated easily.

Time-of-flight MR angiography with Gd-DTPA hexamethylene diamine co-polymer blood pool contrast agent: comparison of enhanced MRA and conventional angiography for arterial stenosis induced in rabbits.

Vascular stenoses were induced in the external iliac arteries of New Zealand white rabbits by a combination of hypercholesterolemic diet and repeat balloon injury. Two-dimensional (2D) and three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) was performed with a specifically designed phased array coil in a 1.5 T system. Enhancement with gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) hexamethylene diamine co-polymer (Nycomed: NC 22181), a blood pool MR contrast agent, was measured after contrast administration and compared with pre-contrast images at the same levels. Vessel diameter measurements were obtained at multiple levels and compared with comparable levels on conventional angiograms of the same animals. Stable enhancement, averaging 227% above baseline, was observed with the 3D TOF MRA over the 40 minutes of this study. Enhancement was not observed with the 2D TOF technique. Measurement of the smallest vessels in this study with 3D TOF MRA was slightly improved following contrast enhancement, although both pre- and post-contrast diameter measurements tended to underestimate the assumed true vessel diameter. Thus, Gd-DTPA hexamethylene diamine co-polymer (Nycomed: NC 22181), a blood pool MR contrast agent, produces significant, stable enhancement with the 3D TOF technique and may improve MRA measurement of small vessels.

A prototype device for standardized calibration of pulse oximeters.

OBJECTIVE: To develop and test a method for standardized calibration of pulse oximeters. METHODS: A novel pulse oximeter calibration technique capable of simulating the behavior of real patients is discussed. It is based on an artificial finger with a variable spectral-resolved light attenuator in conjunction with an extensive clinical database of time-resolved optical transmission spectra of patients fingers in the wavelength range 600-1000 nm. The arterial oxygen saturation of the patients at the time of recording was derived by analyzing a corresponding blood sample with a CO-oximeter. These spectra are used to compute the modulation of the light attenuator which is attached to the artificial finger. This calibration method was tested by arbitrarily playing back recorded spectra to pulse oximeters and comparing their display to the value they displayed when the spectra were recorded. RESULTS: We were able to demonstrate that the calibrator could generate physiological signals which are accepted by a pulse oximeter. We also present some experience of playing back recorded patient spectra. The mean difference between the original reading of the pulse oximeters and the display when attached to the calibrator is 1.2 saturation points (displayed oxygen saturation SpO2) with a standard deviation of 1.9 saturation points. CONCLUSIONS: The tests have shown the capabilities of a spectral light modulator for use as a possible calibration standard for pulse oximeters. If some improvements of the current prototype can be achieved we conclude from the experience with the device that this novel concept for the calibration of pulse oximeters is feasible and that it could become an important tool for assessing the performance of pulse oximeters.

Case report: adult Class I, constricted arches, crowding and impacted cuspid.

The patient presented with constriction of both arches, moderate crowding and an unerupted and impacted maxillary cuspid. The Crozat appliance therapy efficiently developed the arches, reduced skeletal asymmetry on the sagittal plane, and distalized the upper left posteriors although this was aided by the removal of the second molar. Alignment and the development of a good functional occlusion was accomplished efficiently with the straight wire appliance. Facial balance and good lip support was maintained. No stripping was present and the periodontal health remains excellent. A significant improvement was made in the patient's smile. The teeth have been stabler during the two-year period following the initial placement of retainers. And the patient is very pleased with the treatment results.

Dynamic competition as an exploratory model of healthcare policy for the antihypertensive market.

Dynamic competition based on innovation, rather than classical competition based on price, may better explain the research-intensive pharmaceutical market. In an exploratory comparison of these models, economic indicators of annual change in price and price elasticity of demand were tested in a repeated-measures design by analysis of variance. Between 1990 and 1992, updated US prescribing guidelines for hypertension provided a framework in which the contrast between 2 newer classes and 2 older classes of first-line therapies served as a marker for innovation. The principal hypothesis was that newer classes would be less elastic than older classes, but with such innovation-based differences eroding over time. Although temporarily greater inelasticities for newer classes supported dynamic competition, initially extreme inelasticities for newer classes indicated a market distortion or a shifting demand curve. These exploratory results, although requiring substantiation, point toward using dynamic competition in crafting healthcare policy for the pharmaceutical market.

[Greater mobility in Europe--current European developments for barrier-free transportation]. / Mehr Mobilität in Europa--Aktuelle europäische Entwicklungen zur barrierefreien Verkehrsgestaltung.

Harmonization and coordination at the European level of all measures taken on behalf of disabled persons is an indispensable prerequisite for enabling convergence of conditions to occur at the highest possible level. This is true above all for the initiatives and activities that go beyond the specific domain of social policy, and in particular for the developments in the field of accessible, barrier-free environmental design. The Federal Rehabilitation Council (Bundesarbeitsgemeinschaft für Rehabilitation) cooperates in a number of European activities directed at achieving accessibility of regional, rail and air transport, as well as of passenger ships. This involvement is aimed at bringing long-term national experience in this respect to bear in the context of European developments, and at inclusion of the standards already achieved in the transport sector in Germany also in the efforts undertaken toward accessibility in European transport.

Drug expenditures in a balanced strategy for healthcare policy.

The US, like many countries, has turned its public focus onto its healthcare system, with drug prices drawing particular attention. Expenditure trends indicate that drugs do not represent a large portion of the overall healthcare picture; the typical US consumer, however, feels these costs more personally because large portions of outpatient drugs in the US are purchased with out-of-pocket funds. Using data trends for US expenditures, we contrasted projections in the year 2000 under the current US system relative to a strategic policy with full coverage of prescription drugs. Under this proposed scenario, drugs still captured just a small portion of overall healthcare expenditures, but with major shifting to private insurance and government programmes. Thus, as society increasingly views some level of healthcare as a basic human right, effective policies for the healthcare system--including the drug sector--must balance competing regulatory and market pressures.

Efficacy of limited CT for nonvisualized lower cervical spine in patients with blunt trauma.

Records of 100 patients with blunt injury and nonvisualization of C7 and T1 on cross-table lateral and swimmer's views were reviewed to evaluate the usefulness of limited computed tomographic (CT) scans in "clearing" the lower cervical vertebrae of injury. CT was deemed necessary and performed in all of these cases because the lower cervical spine could not be evaluated clinically or with plain radiographs. Ninety-seven of these 100 patients had normal findings on CT and only three patients showed cervical spine fractures. All three had isolated and stable fractures. Two of these patients had "clay-shoveler" fractures at C6 and C7, respectively, and one had a single laminar fracture at C7. All three patients were conservatively treated. This study emphasizes the value of clinical correlation in the evaluation of cervical spine trauma. When deemed necessary in symptomatic patients, CT is useful to exclude skeletal injury in the lower cervical spine thus avoiding delay in the patient's workup and unnecessary hospitalization, and expediting patient discharge. Lack of pain and neurological findings in nonintoxicated, conscious, and alert patients is generally not associated with significant soft tissue or skeletal injury.