Blast wave pressure measurement and analysis in air and granular media inside a shock tube using a fiber Bragg grating sensor

In this work, we have demonstrated the use of a fiber Bragg grating (FBG) sensor to measure the pressure profile of blast waves generated inside a vertical shock tube (VST). An FBG pressure sensor probe has been designed and developed that can be incorporated into the wall of the VST. The VST facility is used to generate blast waves with decay times of the order of a few milliseconds to simulate explosive events. Pressure measurement experiments have been carried out at different incident blast wave peak pressures inside the VST. The FBG pressure sensor measurements are validated against a standard piezoelectric pressure transducer at an acquisition rate of 1 MHz. The pressure signals of both sensors are found to match well with similar rise times and decay profiles. The validated FBG pressure sensor is then incorporated into a sand column mounted in the test section of the VST to measure the pressure profile of blast wave-induced stress waves in granular media. The FBG and piezoelectric pressure sensor data are compared using fast Fourier transform analysis and continuous wavelet transform. The feasibility of FBG sensors for blast pressure measurement under harsh conditions imposed inside shock tube environments is established.

Estimation of dislocated phases and tunable orbital angular momentum using two cylindrical lenses

A first-order optical system consisting of two cylindrical lenses separated by a distance is considered. It is found to be non-conserving of orbital angular momentum of the incoming paraxial light field. The first-order optical system is effectively demonstrated to estimate phases with dislocations using a Gerchberg-Saxton-type phase retrieval algorithm by making use of measured intensities. Tunable orbital angular momentum in the outgoing light field is experimentally demonstrated using the considered first-order optical system by varying the distance of separation between the two cylindrical lenses.

Detection of polarization-spatial classical optical entanglement in partially coherent light fields using intensity measurements

Detection of polarization-spatial classical optical entanglement through implementation of partial transpose on measured intensities is explored. A sufficient criterion for polarization-spatial entanglement in partially coherent light fields based on intensities measured at various orientations of the polarizer, as implied through partial transpose, is outlined. Detection of polarization-spatial entanglement using the outlined method is demonstrated experimentally through a Mach-Zehnder interferometer setup.

Polarization-spatial Gaussian entanglement in partially coherent light fields

The problem of bipartite entanglement in partially coherent paraxial vector light fields is addressed. A generalized uncertainty principle suited for the polarization-spatial degrees of freedom is introduced. Partial transpose is implemented through the obtained generalized uncertainty principle. Partial transpose is shown to be necessary and sufficient in detecting entanglement for a class of partially coherent vector light fields which have a spatial part to be Gaussian. An experimental realization of the studied entangled states using classical optical interferometry is outlined.

Estimation of dislocated phases in wavefronts through intensity measurements using a Gerchberg-Saxton type algorithm

Estimation of the phase of a singular paraxial light field from experimentally measured intensities using a Gerchberg-Saxton type algorithm is demonstrated. A combination of cylindrical lenses which does not conserve the orbital angular momentum of the light field is used in obtaining the measured intensities. Consistent extraction of the phases in regard of the orbital angular momentum is demonstrated both at the input and output transverse planes, using the measured intensities.

Gaussian spatial-polarization entanglement in a folded Mach-Zehnder interferometer

Gaussian spatial-polarization entanglement in a coherent vectorial paraxial light field is studied. Detection of spatial-polarization entanglement through fringe movement on rotation of a linear polarizer, with the light field passing through the polarizer, is outlined. The fringe movement is shown to be a sufficient condition for the detection of spatial-polarization entanglement in coherent paraxial vector light fields. Two Gaussian light fields with a small relative tilt but with significant spatial overlap and with orthogonal polarizations are shown to possess close to 1 ebit of spatial-polarization entanglement. Tunable Gaussian spatial-polarization entanglement is experimentally demonstrated in a folded Mach-Zehnder interferometer.

Impact of different modes of school dental health education on oral health-related knowledge, attitude and practice behaviour: an interventional study

PURPOSE

The study was planned to evaluate the effectiveness of three modes of school dental health education (SDHE) on the oral health-related knowledge, attitude and practice (KAP) behaviour of school children.

METHODS

An interventional study was carried out among 8-9 year old school children from January 2016 to January 2018. Three hundred and sixty children from three schools in Tiruchengode, Tamil Nadu, India participated in this study. Each school was randomly allotted with a mode (drama, modified snake and ladder game, flashcard) of SDHE, which was delivered for 20 min, every 6 months for 2 years. A validated questionnaire with 18 questions was used to record oral health-related KAP behaviour at baseline and after 2 years.

RESULTS

At the end of 2 years, there was an increase in the percentage of correct response for all the nine knowledge questions, in all the three modes. The mean difference in the cumulative knowledge score between baseline and 2 years was 1.39 ± 2.05 for drama mode, 1.8 ± 1.51 for game mode and 1.7 ± 1.5 for flashcard mode of SDHE. There was a significant difference in three knowledge questions and one attitude practice behaviour question between the three groups at the end of 2 years.

CONCLUSIONS

All the three modes were effective in improving the oral health-related KAP behaviour of school children. Game mode made a better impact on the knowledge scores of these children, and it was observed to be more child-friendly and entertaining.

Temperature sensor based on multi-layer MoS2 coated etched fiber Bragg grating

The development of an etched fiber Bragg grating (eFBG)-based temperature sensor with a uniform multi-layer molybdenum-di-sulphide (MoS₂) coating is presented in this paper. Multi-layer MoS₂ has been coated on clad etched FBG sensors by DC magnetron sputtering of molybdenum (Mo) and subsequent sulfurization. The dependence of temperature sensitivity on the coating thickness of MoS₂ on eFBGs has been tested from room temperature to 100°C. It has been found that MoS₂ coated clad etched FBG sensors with a coating thickness of around 10 nm exhibit a maximum temperature sensitivity of ∼95  pm/°C (almost one order higher than that of bare fiber Bragg gratings), with a resolution of ∼0.01°C obtained using an FBG interrogator with 1 pm resolution.

Highly sensitive fiber Bragg grating-based pressure sensor using side-hole packaging

In this work, an analysis of pressure response of a fiber Bragg grating (FBG) sensor in a side-hole package is presented using the finite element method. Various parameters of the side-hole packaging such as hole radius, the distance of separation between them, the radius and length of the package, and the choice of the package material are considered and optimized in order to promote maximum pressure sensitivity of the FBG sensor. This investigation on optimization of the side-hole package parameters gives rise to pressure sensitivity of nearly 10⁵ times as compared with the bare FBG sensor, with the numerical values of 3 pm/MPa for a bare FBG sensor to ∼280,000  pm/MPa for an optimized side-hole package FBG sensor. Such high-pressure sensitivity of an FBG sensor is being reported for the very first time in this work, to the best of our knowledge, and can be considered as the initial step toward the realization of a highly sensitive hydrophone based on FBG for sensing underwater acoustic signals.

Radial-angular entanglement in Laguerre-Gaussian mode superpositions

Classical optic entanglement between the radial and angular degrees of freedom in Laguerre-Gaussian mode superpositions is explored within the framework of symmetric first-order optical systems. The Gouy phase picked by a Laguerre-Gaussian mode on free propagation is seen to be of consequence to the radial-angular entanglement in the mode superpositions. We illustrate examples of mode superpositions for which radial-angular entanglement is preserved on passage through symmetric first-order optical systems. An indicator of radial-angular entanglement in two-mode Laguerre-Gaussian superpositions is demonstrated to be a robust free space signaler in the presence of atmospheric turbulence, through examples.

Ag nanowire-assisted low threshold WGM lasing from polymer optical fiber

Whispering Gallery Mode (WGM) emission has been observed from Ag nanowire doped polymer optical fiber laser. Low threshold lasing and high photostability of the active medium has been noticed with a given concentration of Ag nanowires in the microcavity of the fiber. Quantum yield and lifetime measurements of the dye (active medium) with and without nanowires confirm that presence of nanowires enhance the rate of radiative decay of the fluorophore, thereby providing low pump pulse energy for the excitation of lasing modes in the cavity, as compared with a bare dye-doped polymer fiber laser.

Fiber bragg grating sensor based device for simultaneous measurement of respiratory and cardiac activities

This paper reports a novel optical ballistocardiography technique, which is non-invasive, for the simultaneous measurement of cardiac and respiratory activities using a Fiber Bragg Grating Heart Beat Device (FBGHBD). The unique design of FBGHBD offers additional capabilities such as monitoring nascent morphology of cardiac and breathing activity, heart rate variability, heart beat rhythm, etc., which can assist in early clinical diagnosis of many conditions associated with heart and lung malfunctioning. The results obtained from the FBGHBD positioned around the pulmonic area on the chest have been evaluated against an electronic stethoscope which detects and records sound pulses originated from the cardiac activity. In order to evaluate the performance of the FBGHBD, quantitative and qualitative studies have been carried out and the results are found to be reliable and accurate, validating its potential as a standalone medical diagnostic device. The developed FBGHBD is simple in design, robust, portable, EMI proof, shock proof and non-electric in its operation which are desired features for any clinical diagnostic tool used in hospital environment.

Optical detection of glucose and glycated hemoglobin using etched fiber Bragg gratings coated with functionalized reduced graphene oxide

An enhanced optical detection of D-glucose and glycated hemoglobin (HbA1c ) has been established in this study using etched fiber Bragg gratings (eFBG) coated with aminophenylboronic acid (APBA)-functionalized reduced graphene oxide (RGO). The read out, namely the shift in Bragg wavelength (ΔλB ) is highly sensitive to changes that occur due to the adsorption of glucose (or HbA1c ) molecules on the eFBG sensor coated with APBA-RGO complex through a five-membered cyclic ester bond formation between glucose and APBA molecules. A limit of detection of 1 nM is achieved with a linear range of detection from 1 nM to 10 mM in the case of D-glucose detection experiments. For HbA1c , a linear range of detection varying from 86 nM to 0.23 mM is achieved. The observation of only 4 pm (picometer) change in ΔλB even for the 10 mM lactose solution confirms the specificity of the APBA-RGO complex coated eFBG sensors to glucose molecules.

Enhanced strain and temperature sensing by reduced graphene oxide coated etched fiber Bragg gratings

This Letter reports on an etched fiber Bragg grating (eFBG) sensor coated with reduced graphene oxide (RGO) having enhanced sensitivity for physical parameters such as strain and temperature. The synergetic effect of the changes in grating pitch and refractive index of RGO with change in temperature or strain enhances the shift in Bragg wavelength (λ_B). The RGO-coated eFBG sensors exhibit a strain sensitivity of 5.5 pm/μϵ (∼5 times that of bare fiber Bragg gratings) and temperature sensitivity of 33 pm/°C (∼3 times that of bare fiber Bragg gratings). The resolutions of ∼1  μϵ and ∼0.3°C have been obtained for strain and temperature respectively, using RGO-coated eFBG sensors.

Sensitive detection of C-reactive protein using optical fiber Bragg gratings

An accurate and highly sensitive sensor platform has been demonstrated for the detection of C-reactive protein (CRP) using optical fiber Bragg gratings (FBGs). The CRP detection has been carried out by monitoring the shift in Bragg wavelength (ΔλB) of an etched FBG (eFBG) coated with an anti-CRP antibody (aCRP)-graphene oxide (GO) complex. The complex is characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. A limit of detection of 0.01mg/L has been achieved with a linear range of detection from 0.01mg/L to 100mg/L which includes clinical range of CRP. The eFBG sensor coated with only aCRP (without GO) show much less sensitivity than that of aCRP-GO complex coated eFBG. The eFBG sensors show high specificity to CRP even in the presence of other interfering factors such as urea, creatinine and glucose. The affinity constant of ∼1.1×10(10)M(-1) has been extracted from the data of normalized shift (ΔλB/λB) as a function of CRP concentration.

Radial arterial compliance measurement by fiber Bragg grating pulse recorder

In the present work, we report a novel, in vivo, noninvasive technique to determine radial arterial compliance using the radial arterial pressure pulse waveform (RAPPW) acquired by fiber Bragg grating pulse recorder (FBGPR). The radial arterial compliance of the subject can be measured during sphygmomanometric examination by the unique signatures of arterial diametrical variations and the beat-to-beat pulse pressure acquired simultaneously from the RAPPW recorded using FBGPR. This proposed technique has been validated against the radial arterial diametrical measurements obtained from the color Doppler ultrasound. Two distinct trials have been illustrated in this work and the results from both techniques have been found to be in good agreement with each other.

CO2 sensing at room temperature using carbon nanotubes coated core fiber Bragg grating

The sensing of carbon dioxide (CO2) at room temperature, which has potential applications in environmental monitoring, healthcare, mining, biotechnology, food industry, etc., is a challenge for the scientific community due to the relative inertness of CO2. Here, we propose a novel gas sensor based on clad-etched Fiber Bragg Grating (FBG) with polyallylamine-amino-carbon nanotube coated on the surface of the core for detecting the concentrations of CO2 gas at room temperature, in ppm levels over a wide range (1000 ppm-4000 ppm). The limit of detection observed in polyallylamine-amino-carbon nanotube coated core-FBG has been found to be about 75 ppm. In this approach, when CO2 gas molecules interact with the polyallylamine-amino-carbon nanotube coated FBG, the effective refractive index of the fiber core changes, resulting in a shift in Bragg wavelength. The experimental data show a linear response of Bragg wavelength shift for increase in concentration of CO2 gas. Besides being reproducible and repeatable, the technique is fast, compact, and highly sensitive.

Evaluation of different health education interventions among preschoolers: a randomized controlled pilot trial

OBJECTIVE

The aim of this study is to assess the impact of three different health education methods among preschoolers.

STUDY DESIGN

The study group included 100 preschoolers of the same socio-economic status randomly selected and divided into four groups. Debris index (DI-S) was recorded for all children followed by the dental health education. Group A received dental health education from the Dentist; Group B from the class teacher trained by the Dentist and Group C from the dental residents dressed mimicking cartoon characters. Group D acted as the control group. Post-intervention evaluation program was carried out after 3 months. Data were analyzed by Chi-square test, paired t-test and analysis of variance (ANOVA) appropriately using the SPSS Version 17.1.

RESULTS

Comparison of pre- and post-intervention data showed that there was a statistically significant improvement in the (DI-S) scores in all groups except the control group. Group C showed a significant improvement compared to the other Groups A, B, and D (P<0.04).

CONCLUSION

Drama as a method of health education can have a bigger impact on the oral health attitude and practices of the preschoolers. These modes can serve to reinforce as well as improve the oral health practices among pre-school children.

A high precision instrument to measure angular and binocular deviation introduced by aircraft windscreens by using a shadow casting technique

Objects viewed through transparent sheets with residual non-parallelism and irregularity appear shifted and distorted. This distortion is measured in terms of angular and binocular deviation of an object viewed through the transparent sheet. The angular and binocular deviations introduced are particularly important in the context of aircraft windscreens and canopies as they can interfere with decision making of pilots especially while landing, leading to accidents. In this work, we have developed an instrument to measure both the angular and binocular deviations introduced by transparent sheets. This instrument is especially useful in the qualification of aircraft windscreens and canopies. It measures the deviation in the geometrical shadow cast by a periodic dot pattern trans-illuminated by the distorted light beam from the transparent test specimen compared to the reference pattern. Accurate quantification of the shift in the pattern is obtained by cross-correlating the reference shadow pattern with the specimen shadow pattern and measuring the location of the correlation peak. The developed instrument is handy to use and computes both angular and binocular deviation with an accuracy of less than ±0.1 mrad (≈0.036 mrad) and has an excellent repeatability with an error of less than 2%.

Experimental investigation of link between growth and decay of fiber Bragg gratings

We report here an experimental investigation for establishing and quantifying a link between the growth and decay characteristics of fiber Bragg gratings. One of the key aspects of our work is the determination of the defect energy distribution from the grating characteristics measured during their fabrication. We observe a strong correlation between the growth-based defect energy distribution and that obtained through accelerated aging experiments, paving the way for predicting the decay characteristics of fiber Bragg gratings from their growth data. Such a prediction is significant in simplifying the postfabrication steps required to enhance the thermal stability of fiber Bragg gratings.

Improved lithium cyclability and storage in a multi-sized pore ("differential spacers") mesoporous SnO2

A wide pore distribution mesoporous morphology stabilizes SnO(2) structure during lithium insertion and removal and in the process remarkably enhances the lithium storage and cyclability.

Bariatric to metabolic surgery: management options and experience at a tertiary centre

Obesity proves to be a growing pandemic with severe health and economic implications. Bariatric surgeries are now recognised as metabolic surgeries given the excellent resolution of metabolic derangements accompanying obesity. This concept of metabolic surgery is now applied to non-obese population with metabolic disorders. The type II diabetes mellitus remission rates as high as 95% have been reported, least with restrictive procedures and maximum with malabsorptive procedures and such effect occurs even before substantial weight loss. This has led to increased understanding of diabetes pathophysiology and formulation of foregut and hindgut hypothesis. The aim of this study was to briefly review the management options for morbid obesity and present the results at a high volume centre. Data from 518 patients who underwent laparoscopic bariatric surgeries at this institute since 2002 were taken up for analysis retrospectively. Study population included 518 patients with 310 males and 208 females. Excess body weight loss and comorbidity resolution rates were analysed. Laparoscopic bariatric surgery is safe and effective for excess body weight loss and confers excellent resolution of associated comorbidities.

Nanoindentation study on germania-doped silica glass preforms: evidence for the compaction-densification model of photosensitivity

Nanoindentation technique was employed to measure the changes in mechanical properties of a glass preform subjected to different levels of UV exposure. The results reveal that short-term exposure leads to an appreciable increase in the Young's modulus (E), suggesting the densification of the glass, confirming the compaction-densification model. However, on prolonged exposure, E decreases, which provides what we believe to be the first direct evidence of dilation in the glass leading into the Type IIA regime. The present results rule out the hypothesis that continued exposure leads to an irreversible compaction and prove that index modulation regimes are intrinsic to the glass matrix.

Studies on nest construction and nest microclimate of the Baya weaver, Ploceus philippinus (Linn.)

The nest construction pattern at different stages of nest and variations in the nest microclimate, i.e., temperature and light intensity were assessed in different nests of Baya weaver (Ploceus philippinus) between November 2002 and March 2003 in Nagapattinam and Tiruvarur District of Tamil Nadu, India. The Baya weaver constructed nests in palm (Borassus flabellifer), coconut (Cocos nucifera) and date palm trees (Phoneix psuilla) and majority of the nests were found in the solitary palm. The male bird only involved in the construction and took 18 days to construct a single nest. The birds spent different amount of working hours (in terms of days) for completing various stages of nests viz., wad, ring and helmet stage and in which the 'helmet stage took a maximum of eight days. Furthermore, totally eight active nests were selected and once in a week the variations in the nest microclimate was investigated with reference to atmospheric temperature and light intensity (two active nests) across day throughout the study period. The mean temperature of the nests ranged from 25 degrees C to 29 degrees C and light intensity varied between 25 Lux and 625 Lux. The analysis of variance (ANOVA and ANCOVA) indicated that the nest microclimate varied among the nests in different hr of a day

Effect of oil pulling on Streptococcus mutans count in plaque and saliva using Dentocult SM Strip mutans test: a randomized, controlled, triple-blind study

BACKGROUND

Oil pulling has been used extensively for many years, without scientific evidence or proof, as a traditional Indian folk remedy to prevent teeth decay, oral malodor, bleeding gums, dryness of throat and cracked lips, and for strengthening the teeth, gums, and jaws.

AIMS

The aim of this study was to evaluate the effect of oil pulling with sesame oil on the count of Streptococcus mutans in plaque and saliva of children, using the Dentocult SM Strip mutans test, and to compare its efficacy with that of chlorhexidine mouthwash.

MATERIALS AND METHODS

Twenty age-matched adolescent boys were selected based on information obtained through a questionnaire. They were divided randomly into two groups: the control or chlorhexidine group (group I) and the study or oil pulling group (group II); there were ten subjects in each group. Plaque and saliva samples were collected from all the 20 subjects on the strips from the Dentocult SM kit and, after incubation, the presence of S. mutans was evaluated using the manufacturers' chart. The study group practiced oil pulling with sesame oil and the control group used chlorhexidine mouthwash for 10 min every day in the morning before brushing. Samples were collected from both groups after 24 h, 48 h, 1 week, and 2 weeks and the efficacy of oil pulling was compared with that of chlorhexidine mouthwash.

RESULTS

There was a reduction in the S. mutans count in the plaque and saliva samples of both the study and the control groups. The reduction in the S. mutans count in the plaque of the study group was statistically significant after 1 and 2 weeks (P=0.01 and P=0.008, respectively); the control group showed significant reduction at all the four time points (P=0.01, P=0.04, P=0.005, and P=0.005, respectively, at 24 h, 48 h, 1 week, and 2 weeks). In the saliva samples, significant reduction in S. mutans count was seen in the control group at 48 h, 1 week, and 2 weeks (P=0.02, P=0.02, P=0.008, respectively).

CONCLUSION

Oil pulling can be used as an effective preventive adjunct in maintaining and improving oral health.

Noonan syndrome: a case report

Noonan syndrome is a developmental disorder characterized by facial dysmorphia, short stature, cardiac defects and skeletal malformations. It may be sporadic or inherited as an autosomal dominant or recessive trait and occurs, one in 1,000-2,500 children. This is a case report of a 13 year-old girl who was referred by a general dental practitioner to a pediatric dentist for management. Full mouth dental rehabilitation was done and the child was brought to a dental institution for correction of orofacial and occlusal defects. Multidisciplinary treatment is the key to success in managing children with Noonan syndrome and the pediatric dentists play an important position to lead the health team.

Nonlinear I-V characteristics of nanocrystalline SnO2

Current versus voltage characteristics (I-V) of nanocrystalline SnO2 materials have been investigated in air at room temperature. The samples were prepared by the inert gas condensation technique (IGCT) as well as by chemical methods. X-ray diffraction studies showed a tetragonal rutile structure for all the samples. Microstructural studies were performed with transmission electron microscopy. All the samples exhibited nonlinear I-V characteristics of the current-controlled negative resistance (CCNR) type. The results show that the threshold field (break down) voltage is higher for the samples prepared by the IGCT method than for those prepared by the chemical method due to the formation of a tin oxide layer over the crystalline tin. It is also found that the threshold field increases with the decrease in grain size.

Crown dilaceration of maxillary right permanent central Incisor - A case report

Dilaceration of teeth can occur as a result of trauma to its primary predecessors. Root dilaceration is more common than dilaceration of the crown. A rare case of crown dilaceration of maxillary permanent central incisor has been reported in this article.

Studies on Merops orientalis Latham 1801 with special reference to its population in Mayiladuthurai, Tamil Nadu

Role of habitat-structure and climatic factors in the population dynamics of the small green bee-eater Merops orientalis was evaluated in three habitats viz., agricultural lands, river banks and human habitations during 1991-1993. The river banks supported relatively high population of bee-eaters (157/Km2) followed by the agricultural lands (101/Km2) and human habitations (58/Km2). Bee-eater populations showed year-wise variations in river banks and human habitations having high values during 1992 (123/Km2) and 1993 (43/Km2) respectively. Agricultural lands showed a significantly low mean density in 1991 than other years. Seasonal variations in the bee-eater densities among the habitats were also recorded. Vegetation structure, food (insects) availability, climatic conditions and human disturbance were the casual factors for variations in bee-eater populations.

Post partum splenic artery aneurysm rupture

Ruptured splenic artery aneurysm during pregnancy is a rare event with high maternal and fetal mortality rate. A case of ruptured splenic artery aneurysm in the post partum period is presented. The literature is reviewed on pathophysiology, clinical presentation and management of this rare and potentially fatal entity.

Refinement of the spinal muscular atrophy locus to the interval between D5S435 and MAP1B

The childhood-onset SMA locus has been mapped to chromosome 5q13, in a region bounded by the proximal locus, D5S6, and the closely linked distal loci, D5S112 and MAP1B. We now describe a highly polymorphic, tightly linked microsatellite marker (D5S435) that is very likely the closest proximal marker to the SMA locus. Multipoint linkage analysis firmly establishes the following order of markers at 5q13: centromere-D5S76-D5S6-D5S435-MAP1B/D5S112- D5S39-telomere. The data indicate that SMA resides in an approximately 0.7-cM (range 0.1-2.1) region between D5S435 and MAP1B. This finding reduces by approximately fourfold the genetic region that most likely harbors the SMA locus and will facilitate the physical mapping and cloning of the disease gene region.

Diminished support for linkage between manic depressive illness and X-chromosome markers in three Israeli pedigrees

The hypothesis that chromosomal region Xq27-28 harbours a gene for manic-depression has been a focus of interest in human genetics. X-linked inheritance of manic depressive illness has been re-examined in 3 multigeneration Israeli kindreds. Extension and re-evaluation of pedigree data, including new individuals, diagnostic follow-up, and analysis with DNA markers, shows greatly diminished support for linkage to Xq28. The peak lod scores in two of the pedigrees have dropped several lod units to clearly negative values at the RCP-F8-G6PD gene cluster. On the other hand, positive lod scores (Zmax = 2.09) are sustained in another pedigree at the same map location. None of the pedigrees show linkage to more proximal markers, including the Xq27 locus DXS98. Our analysis underscores the uncertainties in studying complex disorders.