Maximum Detection Rate Research Articles

Minimal Residual Disease (MRD) Detection By Deep Sequencing In Newly Diagnosed Multiple Myeloma Patients Treated With Carfilzomib, Lenalidomide and Dexamethasone

BackgroundMultiple myeloma (MM) therapies are becoming increasingly effective with deeper responses. Indeed, recent prospective clinical trials based on carfilzomib, lenalidomide and dexamethasone (CRd) show complete response (CR)/near (n)-CR rates of over 75%. Consequently, newer techniques are needed to detect minimal residual disease (MRD). We are conducting a prospective Phase II clinical trial studying response to CRd in newly diagnosed MM patients. We assessed treatment responses obtained by traditional IMWG response criteria, MRD measurement by 8-color multiparameter flow cytometry (MFC) based on a minimum of 3 million events (maximum detection rate: 0.0005%), and MRD measurement by high throughput sequencing in 14 newly diagnosed MM patients who achieved very good partial response (VGPR)/CR/nCR. MethodsBone marrow (BM) and/or plasma samples were obtained from 14 newly diagnosed MM patients receiving CRd therapy. Samples were subjected to deep sequencing using the LymphoSIGHT™ platform, which has a sensitivity to detect one cancer cell per million leukocytes in peripheral blood (Faham et al, Blood 2012). Briefly, using universal primer sets, we amplified immunoglobulin heavy and kappa chain (IGH and IGK) variable, diversity, and joining gene segments from genomic DNA obtained from CD138+ BM cell lysate at baseline, as well as post-treatment plasma samples. Amplified products were sequenced and analyzed using standardized algorithms for clonotype determination. Myeloma-specific clonotypes were identified for each patient based on their high frequency within the B-cell repertoire in the CD138+ cell lysate BM sample. The presence of the myeloma-specific clonotype was then quantified in plasma samples obtained post-treatment. A quantitative and standardized measure of clone level among all leukocytes in the sample was determined using internal reference DNA. For patients who achieved VGPR/CR/nCR, we compared the results from MFC of the BM with those obtained by sequencing the cell free DNA in plasma samples. ResultsWe detected a high frequency myeloma-specific gene rearrangement in 13 of 14 (93%) CD138+ BM cell lysate samples obtained at diagnosis. We assessed for MRD by flow cytometry and deep sequencing for the seven patients who were in VGPR/CR/nCR based on traditional protein response criteria. One patient was MRD positive by flow cytometry of the marrow and negative by deep sequencing in blood. Another patient was MRD positive by deep sequencing but negative by flow cytometry. Additionally, in the diagnostic BM sample of one patient, we observed two distinct high-frequency IGH clones that were related through a process of somatic hypermutation. The specific mutation pattern observed is consistent with a branched model of evolution where the two observed clones did not evolve from each other but rather from a common ancestor. We are currently analyzing samples collected at baseline and post-treatment in an additional 23 MM patients enrolled on the CRd trial, and results will be presented. ConclusionsThe development of sensitive, non-invasive MRD assays is becoming increasingly important to assess the impact of modern anti-myeloma therapies. One novel approach for MRD detection, termed the LymphoSIGHT™ platform, relies on high-throughput sequencing of VDJ rearrangements at the immunoglobulin locus. Based on our CRd clinical trial for newly diagnosed MM patients, we found sequencing of cell free tumor DNA in bone marrow aspirates and peripheral blood (plasma) to be technically feasible. Among 6 patients who obtained VGPR/CR/nCR and were found to be MRD negative by MFC of the BM, we found one patient to be MRD positive by sequencing in the peripheral blood (plasma compartment). One patient was MRD positive by flow cytometry but negative by deep sequencing. These preliminary results suggest that a sequencing-based MRD blood test may be more sensitive than standard protein response criteria and complementary to MFC-based BM tests. Analysis of additional samples will be presented. Disclosures:Faham:Sequenta: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Weng:Sequenta, Inc.: Employment, Equity Ownership. Moorhead:Sequenta, Inc.: Employment, Research Funding.

Disentangling different functional roles of evoked K-complex components: Mapping the sleeping brain while quenching sensory processing

During non-REM sleep the largest EEG response evoked by sensory stimulation is the K-complex (eKC), composed of an initial positive bump (P200) followed by a bistable cortical response: a giant negative deflection (N550) and a large positive one (P900), respectively reflecting down states and up states of <1Hz oscillations.Sensory-modality-independent topology of N550 and P900, with maximal detection rate on fronto-central areas, has been consistently reported, suggesting that sensory inputs arise to the cortex avoiding specific primary sensory areas. However, these studies neglected latencies of all KC components as a function of electrode sites.Our aim is to identify, component by component, which topological/dynamical properties of eKCs depend on stimulus modality and which are mainly related to local cortical properties. We measured temporal and morphological features of acoustic, tactile and visual eKCs to disentangle specific sensory excitatory activities from aspecific responses due to local proneness to bistability, measured by means of the N550 descending steepness (synchronization in falling into down state).While confirming the sensory-modality independence of N550 and P900 topology with maximal detection rate in fronto-central areas, four main original results emerge from this study: (i) the topology of P200 latency depends on the sensory modality with earliest waves in the stimulation-related primary sensory areas; (ii) P200 rapidly travels as a cortical excitation; (iii) P200-like excitations when KCs are not evoked are detected over the scalp with significantly smaller amplitudes in fronto-central areas, compared to eKC P200s; and (iv) N550 latency mirrors its mean local steepness which is a function of topological proneness to bistability.From these results we can describe the emergence N550/P900 complex as the interplay between a waxing P200 cortical travel and higher fronto-central proneness to bistability.In conclusion, eKCs exhibit a physiological dichotomy: P200 acts as a traveling cortical excitation whose function is to induce the bistable cortical response (N550/P900), which in turn is crucial for maintaining sleep and unconsciousness.

Threshold computation for fault detection in linear discrete‐time Markov jump systems

SUMMARYThis paper proposes a threshold computation scheme for an observer‐based fault detection (FD) in linear discrete‐time Markovian jump systems. An observer‐based FD scheme typically consists of two stages known as residual generation and residual evaluation. Even information of faults is contained inside a residual signal, a decision of faults occurrence is consequently made by a residual evaluation stage, which consists of residual evaluation function and threshold setting. For this reason, a successful FD strongly depends on a threshold setting for a given residual evaluation function. In this paper, Kalman filter (KF) is used as a residual generator. Based on an accessibility of Markov chain to KF, two types of residual generations are considered, namely mode‐dependent and mode‐independent residual generation. After that threshold is computed in a residual evaluation stage such that a maximum fault detection rate is achieved, for a given false alarm rate. Without any knowledge of a probability density function of residual signal before and after fault occurrence, a threshold is computed by using an estimation of residual evaluation function variance in a fault‐free case. Finally, a detection performance is demonstrated by a numerical example. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Improved Relative-transformation Principal Component Analysis Based on Mahalanobis Distance and Its Application for Fault Detection

Principal component analysis (PCA) has been widely used in process industries, which could maintain the maximum fault detection rate. Although many issues have been addressed in PCA, some essential problems remain unresolved. This study improves PCA for fault detection performance in the following ways. Firstly, a relative transformation scheme based on Mahalanobis distance (MD) is introduced to eliminate the effect of dimension of data instead of dimensionless standardization, and improve the accuracy and real-time performance of fault detection. The theoretical derivation proves that relative transformation based on MD can directly eliminate the effect of dimension and give reasonable explanation of PCA in the relative space, the analysis and simulation results show its superiority and effectiveness. Secondly, an improved squared prediction error (SPE) statistic is given to improve the fault detection performance of standardized PCA, which can make the standardized PCA-based fault detection method more suitable for the actual industrial process. Finally, two improved methods are combined to detect the fault more effectively. The proposed methods are applied to detect single fault and multi-fault of looper system in hot continuous rolling process, simulation results demonstrate the effectiveness of these improvements for fault detection performance in terms of sensitiveness, accuracy and real-time performance of fault detection.

Effect of Tide Level and Time of Day on Detection Rate and Abundance of Clapper Rails (Rallus longirostris) in a Mid-Atlantic Tidal Marsh System

Obligate marsh bird detection rates during surveys are affected by the time of day and the tide level, but previous research on both factors has produced conflicting results and no research has been conducted in east coast tidal marshes. Relative abundance and detection rate of Clapper Rails (Rallus longirostris) were compared between morning and evening surveys at high, medium, and low tide levels in Worcester County, Maryland, during 2006. The detection rate of Clapper Rails was greatest in the morning at the medium tide level ( = 0.69, SE = 0.14, F5,40 = 5.87, P = 0.001). Morning surveys ( = 1.2, SE = 0.14) resulted in a greater relative abundance of Clapper Rail detections compared to evening surveys ( = 0.8, SE = 0.12, F1,195 = 5.31, P = 0.022), and surveys done at medium tide level ( = 1.3, SE = 0.17) resulted in greater relative abundance than those conducted at low ( = 0.8, SE = 0.15) or high levels ( = 0.7, SE = 0.15, F2,195 = 6.56, P = 0.002). The results suggest that surveys should be conducted in the morning at medium tide to maximize detection rate of Clapper Rails. The detection rate of obligate marsh birds during surveys is affected by time and tide level so additional research is necessary to determine how these variables affect the detection rate of marsh birds other than Clapper Rails.

Online monitoring of nonlinear multivariate industrial processes using filtering KICA–PCA

In this paper, a novel approach for processes monitoring, termed as filtering kernel independent component analysis–principal component analysis (FKICA–PCA), is developed. In FKICA–PCA, first, a method to calculate the variance of independent component is proposed, which is significant to make Gaussian features and non-Gaussian features comparable and to select dominant components legitimately; second, Genetic Algorithm is used to determine the kernel parameter through minimizing false alarm rate and maximizing detection rate; furthermore, exponentially weighted moving average (EWMA) scheme is used to filter the monitoring indices of KICA–PCA to improve monitoring performance. In addition, a novel contribution analysis scheme is developed for FKICA–PCA to diagnosis faults. The feasibility and effectiveness of the proposed method are validated on the Tennessee Eastman (TE) process.

Benzotriazoles and benzothiazoles in human urine from several countries: A perspective on occurrence, biotransformation, and human exposure

Benzotriazole (BTR) and benzothiazole (BTH) derivatives are high-production-volume chemicals that are mainly used as corrosion inhibitors, and are widely distributed in the environment. BTR derivatives are found in plastics, dishwasher detergents, dry cleaning equipment, and de-icing/anti-icing fluids. BTH derivatives are found in rubber materials, herbicides, slimicides, algicides, fungicides, photosensitizers, azo dyes, drugs, de-icing/anti-icing fluids, and food flavors. However, exposure of humans to BTRs and BTHs is still not known. In this study, six BTRs (1H-benzotriazole, 1-hydroxy-benzotriazole, 4- and 5-hydroxy-benzotriazole [mixture of two isomers], tolyltriazole, xylyltriazole [or 5,6-dimethyl-1H-benzotriazole], and 5-chloro-benzotriazole) and six BTHs (benzothiazole, 2-morpholin-4-yl-benzothiazole, 2-hydroxy-benzothiazole, 2-methylthio-benzothiazole, 2-amino-benzothiazole, and 2-thiocyanomethylthio-benzothiazole) were determined in human urine collected from general populations in seven countries (the U.S., Greece, Vietnam, Korea, Japan, China, and India). The median urinary concentration of the sum of five BTRs (Σ5BTRs; 4- and 5-hydroxy-benzotriazole were not included) ranged from 0.2 (Korea) to 2.8 (India)ng/mL among the countries studied, with the highest concentration of 24.5ng/mL found in a sample from China. Xylyltriazole was found more frequently in urine from all five Asian countries than in urine from the U.S. and Greece. The median concentration of the sum of the six BTHs (Σ6BTHs) ranged from 3.6 (U.S.) to 10.9 (Japan)ng/mL among the countries studied, with a maximum detection rate of 100% in urine samples from Vietnam; BTH was the predominant derivative, accounting for, on average, 43% of the Σ6BTH concentration. Based on the concentrations and detection rates of several BTR and BTH derivatives in urine, possible metabolic transformation pathways of these compounds were presented and human exposure doses calculated. The estimated daily intake doses of BTRs and BTHs were on the order of a few to few tens of micrograms per day.

Improving Intrusion Detection Using Genetic Algorithm

Intrusion Detection System (IDS) is one of the key security components in today’s networking environment. A great deal of attention has been recently paid to anomaly detection to accomplish intrusion detection. However, a major problem with this approach is maximizing detection rate and accuracy, as well as minimizing false alarm i.e., inability to correctly discover particular types of attacks. To overcome this problem, a genetic algorithm approach is proposed. Genetic Algorithm (GA) is most frequently employed as a robust technology based on machine learning for designing IDS. GAs are search algorithms which are based on the principles of natural selection and genetics. GA functions on a number of possible solutions using the principle of survival of the fittest with the aim to generate better approximations to solve a particular problem GA is facing. The validity of this approach is verified using Knowledge Discovery and Data Mining Cup 1999 (KDD Cup ’99) dataset. The experimental results demonstrate that the proposed approach outperforms the existing techniques, with the detection rate of attack and false alarm rates of 95.7265 and 4.2735, respectively.

Detection of alcohol intoxication via online handwritten signature verification

The Internet has recently facilitated various methods of personal authentication based on biometrics. Personal authentication techniques based on human physical features include fingerprint matching, vein matching, facial recognition, speech recognition, and signature recognition. In this study, we investigate the detection of alcohol intoxication on the basis of handwritten signatures. As in the case of previous related studies, we found that the signature attestation rate varies at an individual level according to sex, age, acetaldehyde removal efficiency, and individual constitution.In this study, we employed 30 people to evaluate the change in a handwritten signature before and after alcoholic intake. First, we measured the signature verification rate using the online signature verification system. The signature verification rate measured using the WACOM Tablet pen before alcohol consumption was 97.0%. Moreover, the size of the characters and the interval between the characters were measured for signatures collected after alcohol consumption. We detected the level of alcohol intoxication on the basis of the total time taken for writing the signature, the average pressure of the brush, the two-dimensional writing speed, and internal angle of stroke turns. The maximum alcohol detection rate of this method was 95.1%, which was achieved when the examinees were tested 35min after alcohol consumption. The rate of alcohol detection increases with the alcohol density in an examinee’s breath.

A Universal Steganalysis Algorithm for JPEG Image Based on Selective SVMs Ensemble

Universal steganalysis include feature extraction and steganalyzer design. Most universal steganalysis use Support Vector Machine (SVM) as steganalyzer. However, most SVM-based universal steganalysis are not to be very much effective at lower embedding rates. The reason why selective SVMs ensemble improve the generalization ability was analyzed, and an algorithm to select a part of individual SVMs according to their difference to build the ensemble classifier was proposed, which based on the selected ensemble theory-Many could be better than all. In this paper, the selective SVMs ensemble algorithm was used to construct a strong steganalyzer to improve the performance of steganographic detection. The twenty five experiments on the benchmark with 2000 different types of images show that: for popular steganography methods, and under different conditions of embedding rate, the average detection rate of proposed steganalysis method outperforms the maximum average detection rate for the steganalysis method based on single SVM with improving by 3.05%-12.05%; and for the steganalysis method based on BaggingSVM with improving by 0.2%-1.3%.

Dynamic CT Angiography after Abdominal Aortic Endovascular Aneurysm Repair: Differences in Contrast Agent Dynamics in the Aorta and Endoleaks—Preliminary Results

PurposeTo assess differences in aortic and endoleak enhancement in patients after endovascular aneurysm repair (EVAR) with dynamic computed tomography (CT) angiography. Materials and MethodsTwenty-one consecutive patients (mean age, 74.5 y ± 6; range, 61–88 y) with endoleaks after EVAR of the abdominal aorta were examined on a second-generation dual-source CT unit with 10 unidirectional scan phases (temporal resolution, 5 s; 80 kV; 120 reference-mAs; z-axis field of view, 283 mm), followed by a venous scan phase. Enhancement was assessed in aorta and endoleaks for all phases by density measurements. The diagnostic reliability of endoleak detection was assessed on a five-point confidence scale. ResultsIn total, 26 endoleaks (type I, n = 1; type II, n = 25) were detected. The highest detection rate was found in phase 5 (22 s after threshold; P < .01 vs other dynamic phases). Mean peak aortic enhancement (560 HU ± 96) was present in an early arterial phase (phase 3, 12 s after threshold), whereas the mean peak endoleak enhancement (398 HU ± 174) for type II endoleaks was present later, in phase 4 (17 s after threshold). Despite perceived high diagnostic confidence in phases 1 and 2 (ie, typical arterial phase of biphasic CT protocol), only 23% and 62% of endoleaks were detected, respectively, whereas peak diagnostic confidence (phases 4 and 5) corresponded well with the maximum endoleak detection rate but decreased significantly in later phases (ie, 6–10). ConclusionsPreliminary dynamic CT angiography results in post-EVAR follow-up revealed notably different peaks of endoleak and aortic enhancement, which are not covered sufficiently by conventional biphasic CT protocols. Phase 5 demonstrated the highest type II endoleak detection rate, with high diagnostic confidence.

Secure Cooperative Sensing in IEEE 802.22 WRANs Using Shadow Fading Correlation

Cooperative (or distributed) sensing has been recognized as a viable means to enhance the incumbent signal detection by exploiting the diversity of sensors. However, it is challenging to secure such distributed sensing due mainly to the unique features of dynamic spectrum access networks-openness of low-layer protocol stacks in software-defined radio devices and the absence of interactions/coordination between primary and secondary devices. To meet this challenge, we propose an attack-tolerant distributed sensing protocol (ADSP) for DTV signal detection in IEEE 802.22 WRANs, under which sensors in close proximity are grouped as a cluster, and sensors within a cluster cooperate to safeguard the integrity of sensing. The heart of ADSP is a novel filter based on shadow-fading correlation, by which the fusion center cross-validates reports from the sensors to identify and penalize abnormal sensing reports. By realizing this correlation filter, ADSP significantly reduces the impact of an attack on the performance of distributed sensing, while incurring minimal processing and communication overheads. ADSP also guarantees the detectability requirements of 802.22 to be met even with the presence of sensing report manipulation attacks by scheduling sensing within the framework of sequential hypothesis testing. The efficacy of ADSP is validated on a realistic 2D shadow-fading field. Our extensive simulation-based study shows that ADSP reduces the false-alarm rate by 99.2 percent while achieving 97.4 percent of maximum achievable detection rate, and meets the detection requirements of IEEE 802.22 in various attack scenarios.

CCD Imaging Definition Controlling Methods in Continuous Casting Slab Surface Defects Acquisition

In hot slab continuous casting (CC) process, the Machine Vision (MV) inspection method for slab surface defects has been becoming a research focus with the development of charge-coupled device (CCD) camera imaging technologies. To acquire a informative and reliable defects image is a prerequisite that means a maximum defects detection rate and minimum false recognition in the next image processing stage. In this paper, based on the CCD imaging principle and definition evaluation algorithm, the slab surface radiation feature at high temperature and CCD optical imaging properties had been analyzed under the focal plane, meanwhile, the CCD image definition of optical integral time controlling method had also been studied, which the defect image variance (IV) function, image average gradient (IAG) and information entropy (IIE) were calculated and analyzed. In the end, the image definition controlling algorithm for hot slab surface ROI imaging that adopted IIE evaluation algorithm, based on CCD integral time imaging controlling principle, had been proposed. This method also can support practical value for other machine vision engineering.

Deceptive Detection Methods for Effective Security with Inadequate Budgets: The Testing Power Index

Detection of contraband depends on countermeasures, some of which involve examining cargo containers and/or their associated documents. Document screening is the least expensive, physical methods, such as gamma ray detection are more expensive, and definitive manual unpacking is most expensive. We cannot apply the full array of methods to all incoming cargoes, for budgetary reasons. We study the problem using principles of game theory, and find that best detection rates are achieved when the available budget is allocated between screening and definitive unpacking using a mixture of strategies that maximize detection rate and, further, serve to deceive opponents as to the specific tests to which contraband will be subjected. This yields increases of as much as 100% in detection, with essentially no increase in inspection cost.

Ultrashort dead time of photon-counting InGaAs avalanche photodiodes

We report a 1.036 GHz gated Geiger mode InGaAs avalanche photodiode with a detection dead time of just 1.93 ns. This is demonstrated by full recovery of the detection efficiency two gate cycles after a detection event, as well as a measured maximum detection rate of 497 MHz. As an application, we measure the second order correlation function g(2) of the emission from a diode laser with a single detector that works reliably at high speed owing to the extremely short dead time of the detector. The device is ideal for high bit rate fiber wavelength quantum key distribution and photonic quantum computing.

15 GHz single-photon detection at telecommunication wavelengths using sinusoidally gated InGaAs/InP avalanche photodiode

We report a telecom-band single-photon detector for gigahertz clocked quantum key distribution systems. The single-photon detector is based on a sinusoidally gated InGaAs/InP avalanche photodiode. The gate repetition frequency of the single-photon detector reached 1.5 GHz. A quantum efficiency of 10.8 % at 1550 nm was obtained with a dark count probability per gate of 6.3 x 10(-7) and an afterpulsing probability of 2.8 %. Moreover, the maximum detection rate of the detector is 20 MHz.

Cost-sensitive learning of top-down modulation for attentional control

A biologically-inspired model of visual attention known as basic saliency model is biased for object detection. It is possible to make this model faster by inhibiting computation of features or scales, which are less important for detection of an object. To this end, we revise this model by implementing a new scale-wise surround inhibition. Each feature channel and scale is associated with a weight and a processing cost. Then a global optimization algorithm is used to find a weight vector with maximum detection rate and minimum processing cost. This allows achieving maximum object detection rate for real time tasks when maximum processing time is limited. A heuristic is also proposed for learning top-down spatial attention control to further limit the saliency computation. Comparing over five objects, our approach has 85.4 and 92.2% average detection rates with and without cost, respectively, which are above 80% of the basic saliency model. Our approach has 33.3 average processing cost compared with 52 processing cost of the basic model. We achieved lower average hit numbers compared with NVT but slightly higher than VOCUS attentional systems.

Down's syndrome screening: population statistic dependency of screening performance

The choice of parameter sets used to calculate Down's syndrome risks is important. This study details analysis of samples from affected and unaffected pregnancies and evaluates whether published population data is optimal. Screening efficiency realized with measurement procedure-specific population parameters is compared with selected population sets available in the literature. In a retrospective experiment, double and triple testing was performed on maternal serum samples from 286 randomly chosen unaffected singleton pregnancies and 95 Down's syndrome affected pregnancy samples. Using a risk cut-off of 1 in 250, detection rates and false positive rates were estimated for different population settings to select a model giving the best overall efficacy. Receiver operation characteristics curve analysis was performed and detection rates realized with the different population settings was estimated at a 5% fixed false positive rate. Geometric mean weight corrected multiples of the median values were 1.01 for alpha-fetoprotein (AFP), 1.02 for human chorionic gonadotropin (hCG) and 1.01 for unconjugated estriol (uE3) in unaffected pregnancies and 0.77 (95% CI: 0.71-0.83) for AFP, 2.42 (95% CI: 2.17-2.71) for hCG and 0.78 (95% CI: 0.73-0.83) for uE3 in affected pregnancies. Differences in double and triple risks obtained with the different models were significantly different from each other (p < 0.001). At a cut-off of 1 in 250, the maximum triple test detection rate was 75.8% for a false positive rate of 4.9% and was obtained with the measurement procedure-specific setting. At a fixed false positive rate of 5%, the maximum detection rate for the triple test was 77.9% (95% CI: 62.2%-85.8%). The maximum double test detection rate at 5% false positive rate was 69.6% (95% CI: 59.5%-78.5%). Except for two models, the area under the curve for the triple test was higher than that of the double test. The Access triple test meets the typical performance characteristics for this test combination. The assay-specific settings yielded the overall best efficacy for the criteria studied. Therefore, the availability of measurement procedure-specific mid-trimester reference values for unaffected and affected pregnancies in prenatal screening programs is essential. Such reference values are established for the Beckman Coulter Access triple test: maternal serum AFP, uE3 and hCG.

In situ measurements of nitric oxide in coal-combustion exhaust using a sensor based on a widely tunable external-cavity GaN diode laser

A diode-laser-based sensor has been developed to measure nitric oxide mole fractions using absorption spectroscopy. The sensor is based on sum-frequency mixing of a 395 nm external-cavity diode laser (ECDL) and a 532 nm laser in a beta-barium-borate crystal. Using a new tuning scheme, the GaN ECDL wavelength was modulated over 90 GHz without mode hops. The sensor was applied for measurements of the NO mole fraction in the exhaust of a laboratory-scale, 30 kW(t) coal-fired boiler burner. Absorption measurements were successfully performed despite severe attenuation by scattering from ash particles in the exhaust stream and on the exhaust-section windows. A detection limit (1sigma) of 4.5 ppm m/(square root)Hz at 700 K was demonstrated in coal- combustion exhaust at a maximum detection rate of 5 Hz.

Ultrasound and fetal diagnosis

The purpose of this review is to highlight publications from the last year that have advanced the use of ultrasound in obstetrics. Anatomic examination of the fetus in the first trimester has been emphasized because it allows for early diagnosis of many conditions. The prevalence of absent nasal bone, a marker for trisomy 21, in euploid fetuses depends on ethnicity. Nasal bone hypoplasia is another marker for Down syndrome. Studies on genetic screening in the first trimester have involved various serum analytes, adjustments in timing and calculations, use in multiple gestations, and the association of extreme measurements with adverse outcomes. A first-trimester integrated screening approach, which incorporates nuchal translucency, nasal bone, crown-rump length, pregnancy-associated plasma protein-A, and free beta-human chorionic gonadotropin, has the potential to maximize detection rates of Down syndrome and trisomy 18 and minimizes the screen-positive rate. The value of combining first and second-trimester results in sequential, contingent, or integrated screening protocols has been assessed. Isolated mild ventriculomegaly (10-12 mm) may prove to be a normal variant, and the role of 'soft' ultrasound markers in genetic counseling continues to be debated. Anomaly or high-risk status detection in the second trimester has been enhanced by the use of Doppler, 3D/4D ultrasound, and magnetic resonance imaging. Imaging techniques have been critical in the development of screening methods for Down syndrome or trisomy 18 and for euploid fetuses at high risk for adverse outcomes.