Study of the microstructure information of GaAs epilayers grown on silicon substrate using synchrotron radiation.

Williamson-Hall (WH) analysis is a well established method for studying the microstructural properties of epilayers grown on foreign substrates. However, the method becomes inapplicable in specific cases where the structure factor considerations and the presence of anti-phase domains forbid the data acquisition for certain reflections in conventional high-resolution X-ray diffraction (HRXRD) measurements. Here, this limitation is overcome by exploiting the large intensity (25 µW mm(-2)) and high photon energy (15.5 keV) of the X-ray beam obtained from a synchrotron radiation source. The lateral coherence length, vertical coherence length, tilt and micro-strain of GaAs epilayers grown on Si substrate have been successfully measured using the conventional WH analysis. The microstructure information obtained from the conventional WH analysis based on the data acquired at the synchrotron radiation source is in reasonable agreement with the results obtained from atomic force microscope and surface profiler measurements. Such information cannot be obtained on a laboratory-based HRXRD system where modification of the WH method by involving a set of parallel asymmetric crystallographic planes is found to be essential. However, the information obtained from the modified WH method is along a different crystallographic orientation.

Generation of more than 40 W of average output power from a passively Q-switched Yb-doped fiber laser.

We report on the generation of 41.6 W of average output power from a passively Q-switched ytterbium-doped fiber laser using Cr4+:YAG crystal as a saturable absorber (SA). This is the highest average power from passively Q-switched fiber lasers reported so far in the literature, to our knowledge, and it has been achieved by using a specially designed T-type double-end pumping configuration. Variation in average output power, pulse energy, pulse duration, pulse frequency, and pulse-to-pulse stability has also been studied using SAs of different linear transmissions. The effect of an intracavity SA on self-pulsing dynamics was also investigated and it was observed that, at lower input pump power near threshold, the presence of an SA enhances the peak power of relaxation oscillations to trigger the generation of stimulated Raman scattering in the gain fiber. With an increase in pump power, when the passive Q-switching threshold is reached, high peak power random self-pulses regenerate into low amplitude regular Q-switched pulses. The effect of the length of the gain medium on dual-wavelength generation at very low input pump power and broadband generation at sufficiently higher pump power has also been explored.

Modular pump geometry for diode side-pumped high-power Nd:YAG rod laser.

In this paper, we present a modular design configuration to side-pump an Nd:YAG rod of a diode-pumped high-power CW laser. Independent modules in the form of discs are loaded with three-diode linear bar arrays at 120° with respect to each other and are assembled along the length of the rod. By keeping successive discs at three different angular separations (the minimum, intermediate, and maximum), helical, 60° rotated, and linear geometries, respectively, were created. Parameters like thermal lensing, fluorescence profile, laser beam profile, and beam quality factor (M2) were studied to compare the performances of different geometries. The results indicate that the 60° rotated configuration provides the best performance when compared with rest of the schemes. To the best of our knowledge, this is the first time that such novel modular-type pump geometries with a provision for the angular separation of pump diodes have been tried.

Surgical checklist application and its impact on patient safety in pediatric surgery.

BACKGROUND: Surgical care is an essential component of health care of children worldwide. Incidences of congenital anomalies, trauma, cancers and acquired diseases continue to rise and along with that the impact of surgical intervention on public health system also increases. It then becomes essential that the surgical teams make the procedures safe and error proof. The World Health Organization (WHO) has instituted the surgical checklist as a global initiative to improve surgical safety. AIMS: To assess the acceptance, application and adherence to the WHO Safe Surgery Checklist in Pediatric Surgery Practice at a university teaching hospital. MATERIALS AND METHODS: In a prospective study, spanning 2 years, the checklist was implemented for all patients who underwent operative procedures under general anesthesia. The checklist identified three phases of an operation, each corresponding to a specific period in the normal flow of work: Before the induction of anesthesia ("sign in"), before the skin incision ("time out") and before the patient leaves the operating room ("sign out"). In each phase, an anesthesiologist,-"checklist coordinator," confirmed that the anesthesia, surgery and nursing teams have completed the listed tasks before proceeding with the operation and exit. The checklist was used for 3000 consecutive patients. RESULTS: No major perioperative errors were noted. In 54 (1.8%) patients, children had the same names and identical surgical procedure posted on the same operation list. The patient identification tag was missing in four (0.1%) patients. Mention of the side of procedures was missing in 108 (3.6%) cases. In 0.1% (3) of patients there was mix up of the mention of side of operation in the case papers and consent forms. In 78 (2.6%) patients, the consent form was not signed by parents/guardians or the side of the procedure was not quoted. Antibiotic orders were missing in five (0.2%) patients. In 12 (0.4%) cases, immobilization of the patients was suboptimal, which led to displacement of diathermy grounding pad. In 54 (1.8%) patients, the checklist was not used at all. In 76 (2.5%) patients the checklist was found to be incompletely filled. CONCLUSIONS: Our study supports the use of the checklist as an essential safety tool and reinforcement of the same. The checklist may act as a valuable prompt to focus the team, to ensure that even the simple things have been cared for.

Demonstration of CW mode locked Cr:forsterite laser using self-shortening and transverse mode degeneracy driven mode locking.

This paper reports a nearly Fourier transform limited CW mode locked Cr:forsterite laser at 1282 nm, with 131 fs pulse duration, based on self-shortening and transverse mode degeneracy (TMD) driven mode locking, operating near the point of fourth-order TMD. The cavity employs a combination of instantaneous intensity driven self-shortening, and operation on the right side of the fourth-order TMD, to generate the self-amplitude modulation necessary for self-mode locking.

Medical simulation: a virtual world at your doorstep.

Medical simulation has come a long way in Western health care; however, in developing world, health education sectors have not adequately addressed its significance and role in preparing and updating heath care personnel. Validification, standardization, paucity of trainers, deficiency of a structured syllabus, and cost of equipments need to be overcome in the next decade. Despite these problems, worldwide acceptance of the concept of medical simulation is growing. It is undoubtedly the wave of future. Multidisciplinary, interprofessional, and multimodal simulation training is possible. Virtual worlds are increasing the vistas of training, making the actual health care dispensing more skilled and safe.

Needle in a haystack: Intraoperative breakage of pediatric minimal access surgery instruments.

The search for tiny bits of broken pediatric minimal access surgery (MAS) instruments in an operative field is akin to the search for a needle in a haystack. With the extension of MAS to the pediatric age group, instruments are becoming smaller and equitably more prone to breakage. When breakages occur, retrieval, especially in the pediatric abdominal cavity, can be challenging. Inability to do so would affect patient safety and also lead to a web of medico legal and ethical issues. We present two cases of intraoperative breakage: An eyeless 3-0 polyamide suture needle and a 2-mm grasper blade both of which were successfully retrieved and fortuitously escaped becoming retained surgical items.

Radiographic joint space width is correlated with 4-year clinical outcomes in patients with knee osteoarthritis: data from the osteoarthritis initiative.

OBJECTIVE: To evaluate if quantitative joint space width (JSW) measurements from radiographs correlate with 4-year Knee injury and Osteoarthritis Outcome Scores (KOOS) and clinical performance measures. METHOD: The study group consisted of 942 patients with symptomatic knee osteoarthritis (OA). 4-year outcomes for six measures (KOOS Pain, Symptom, Quality of Life, and Function scores, 20-m walk pace, and chair stand time) were used to create six multiple linear regression models. Primary predictors were baseline minimum JSW and 4-year change in JSW measured from fixed flexion radiographs. Age, gender, body mass index (BMI), race, knee alignment, and baseline measures of the outcomes of interest were covariates. RESULTS: Lower baseline minimum JSW and a greater decrease in 4-year JSW significantly correlated with worse 4-year KOOS Pain, Symptom, and Quality of Life. With all other factors constant, a 4.1, 4.8, and 5.6 mm lower baseline JSW correlated with a clinically significant eight-point drop in 4-year KOOS Pain, Symptom, and Quality of Life scores respectively. Additionally, a 3.5, 3.1, and 4.0 mm loss of JSW over 4 years correlated with a clinically significant eight-point drop in 4-year KOOS Pain, Symptom, and Quality of Life scores respectively. CONCLUSIONS: Our results indicate quantitative radiographic JSW measurements correlate with 4-year clinical outcomes. Since patients with narrower JSW at the onset of study had lower KOOS scores at 4 years even after controlling for 4-year change in JSW and baseline KOOS scores, clinical outcomes in knee OA may be predetermined once the disease process begins. These findings suggest early treatment with disease modifying therapies may be necessary to influence outcomes.

Study on effective cleaning of gold layer from fused silica mirrors using nanosecond-pulsed Nd:YAG laser.

A study on effective laser cleaning of gold layer deposited on fused silica substrates used in beamlines of synchrotron radiation (SR) sources using nanosecond-pulsed Nd:YAG laser has been carried out. The influence of pulse duration, beam incidence angle, spot overlapping, laser fluence, and number of passes on cleaning efficiency has been investigated. An approximately 48 nm thick gold layer from a mirror surface area of ~48 cm2 has been cleaned in 3 min. Laser clean quality and efficiency has been analyzed using microscope, scanning electron microscope (SEM), and angle-dependent reflectivity measurement techniques using SR beamline. Optimization of cleaning parameters resulted in a cleaning efficiency of ~98%. This study provides an alternate and low-cost solution for reuse of gold-coated, damaged mirrors.

Immunoglobulin subclass profiles of anti-idiotypic antibodies to GAD65Ab differ between type 1 diabetes patients and healthy individuals.

Previously we reported the presence of anti-idiotypic antibodies (anti-Id)-specific to autoantibodies against GAD65 (GAD65Ab) in healthy individuals while the activity of anti-Id directed to GAD65Ab in type 1 diabetes (T1D) patients was significantly lower. These anti-Id recognize the antigen-binding site of GAD65Ab, thus preventing their binding to GAD65. Here, we characterized the IgG subclass profile of these anti-Id (GAD65Ab specific) and of the associated GAD65Ab themselves. The IgG subclass response of anti-Id in healthy individuals (n = 16) was IgG3-dominated, while in T1D patients (n = 8) IgG1 was the major IgG subclass. The GAD65Ab bound by anti-Id in both healthy individuals (n = 38) and GAD65Ab-negative T1D patients (n = 35) showed a predominant rank order of IgG1 > IgG2 > IgG4 > IgG3. However, the frequency of GAD65Ab of the IgG4 subclass was significantly higher in T1D patients (P < 0.05). We conclude that the IgG subclass profile of anti-Id (GAD65Ab specific) in healthy individuals differs from that in T1D patients. These differences may provide insights into the development of these antibodies.

Beam quality degradation of a higher order transverse mode beam due to spherical aberration of a lens.

An analysis of the increase in the beam-propagation factor, M2, of a higher order transverse mode beam caused by quartic phase aberration after transmission through a spherically aberrated lens is reported. The analysis shows that for a given beam size, the increase in the M2 parameter is less for a higher order transverse mode beam as compared to that for a diffraction limited beam. Experimental results using a multimode laser diode beam show good agreement with the theoretical results.

Investigation of optical limiting in iron oxide nanoparticles.

We present the study of optical limiting in iron oxide nanoparticles of diameters 31, 44, and 61 nm dispersed in toluene under exposure to nanosecond laser pulses at 532 nm. In the low fluence region smaller size nanoparticles show better optical limiting compared to larger size nanoparticles while in the high fluence region all the three samples show same limiting performance. Experimental results were compared with the well reported limiter fullerene C(60) dissolved in toluene. Iron oxide nanoparticles show better optical limiting compared to C(60) in the intermediate fluence region and comparable performance in the high fluence region. The pico-second Z-scan studies indicate that the contribution of electronic nonlinear refractive index and the two-photon absorption to the optical limiting is negligible. Our observations further indicate that the dominant mechanism for the optical limiting in iron oxide nanoparticles is nonlinear scattering.

Autoantibody epitopes to the smaller isoform of glutamate decarboxylase do not differ in Swedish and Japanese type 1 diabetes patients and may be associated with high-risk human leucocyte antigen class II alleles.

Type 1 diabetes (T1D) is an autoimmune disease with a strong human leucocyte antigen (HLA) class II association. Depending on geographic locations, the disease-associated HLA class II alleles vary. We evaluated the beta cell-specific autoimmunity reflected in autoantibodies directed to the smaller isoform of glutamate decarboxylase (GAD65) in Japanese and Swedish T1D patients. GAD65Ab epitope specificities were assessed using GAD65-specific recombinant Fab. GAD65Ab epitope specificities did not differ between Swedish and Japanese patients. Only recognition of the MICA-4-defined middle epitope was significantly stronger in the Japanese T1D patient group compared to the Swedish T1D patients (P = 0.001). Binding to the b96.11-defined middle epitope was substantial in both groups and showed significant associations with high-risk HLA class II haplotypes. In the Japanese T1D group the association was with haplotype DRB1*0802-DQB1*0302 (P = 0.0008), while in the Swedish T1D patients binding to the b96.11-defined epitope as associated with the presence of high-risk HLA genotypes DR3-DQB1*0201 and/or DR4-DQB1*0302 (P = 0.02). A significant association between reduction in binding in the presence of recombinant Fab (rFab) DPD and high-risk allele DQB1*0201 was found (P = 0.008) in the Swedish T1D patients only. We hypothesize that epitope-specific autoantibodies effect the peptide presentation on HLA class II molecules by modulating antigen uptake and processing. Molecular modelling of the high-risk HLA class II molecules will be necessary to test whether these different molecules present similar peptide-binding specificities.

Mechanisms of generation of multi-peak and mode-locked resembling pulses in Q-switched Yb-doped fiber lasers.

The output pulse characteristics of Q-switched Yb-doped fiber lasers have been investigated experimentally. It has been observed that for any typical modulation frequency, the pump power and the modulator OFF-time govern the shape of the output Q-switched pulse. At a fixed modulation frequency, with a fine adjustment of acousto-optic modulation window ON-time, pump power and cavity mirror position, it was possible to obtain modulation free single-peak pulse, multi-peak pulse, mode-locked resembling pulse and multi-pulse structured pulse shapes in a Q-switched fiber laser output. These observations have been analyzed and explained. Our investigations show that multi-peak pulse output is due to onset of nonlinear phenomena like SBS and SRS. Similarly, we have found that the mode-locked resembling periodically modulated output pulse shape is due to mode beating between the zeroeth order and the first order diffracted beams of the intra-cavity acousto-optic Q-switch.

Making of a pediatric urologist.

The million-dollar question that we wish to address in this article is who should be the specialist for urological problems in children in India. What are the special attributes of a pediatric urologist? The answer to this question is far from simple and straightforward. Dogmatic rules do not provide a functional solution. While one has to admit that in India pediatric urological problems will be dealt with by urologists, as well as by pediatric and general surgeons, one has to also accept that lacunae do exist in the current curriculum and the methodology of training.A pediatric urologist by the virtue of definition would be a specially trained surgeon who would deal with urological diseases of children from newborn to adolescence (0-14 years). (In some instances e.g. exstrophy, renal transplant and continent procedures the age of treatment may even exceed up to 16 and above). He has the experience and the expertise to treat a child. Children are not miniaturized adults and newborns are not miniaturized children. Their physiology is different, they cannot always express their problems, answer questions and may not be cooperative during clinical examination.

Effect of carrier confinement on effective mass of excitons and estimation of ultralow disorder in Al x Ga1-x As/GaAs quantum wells by magneto-photoluminescence.

Effect of charge carrier confinement and ultra-low disorder acquainted in AlGaAs/GaAs multi-quantum well system is investigated via Magneto-photoluminescence spectroscopy. Significant increase of effective mass is observed for the confined exciton in narrow QWs. The foremost reason behind such an observation is due to the induced non-parabolicity in bands. Moreover, as the thickness of the QW are reduced, confined excitons in QW experience atomic irregularities at the hetero-junctions and their effects are prominent in the photoluminescence linewidth. Amount of photoluminescence line-broadening caused by the atomic irregularities at the hetero-junctions is correlated with average fluctuation (δ 1) in QW thickness. The estimated δ 1 for Al0.3Ga0.7As/GaAs QWs are found to be ±(0.14 - 1.6)× 'one monolayer thickness of GaAs layer'. Further, the strong perturbations due to magnetic field in a system helps in realizing optical properties of exciton in QWs, where magnetic field is used as a probe to detect ultralow defects in the QW. Additionally, the influence of magnetic field on the free and bound exciton luminescence is explained by a simple model. The proposed approach for measuring the interface and volume defects in an ultra-low disordered system by Magneto-PL spectroscopy technique will be highly beneficial in high mobility devices for advanced applications.

Phytophthora tropicalis Isolated from Diseased Leaves of Pieris japonica and Rhododendron catawbiense and Found in Irrigation Water and Soil in Virginia.

An unidentified species of Phytophthora was isolated from irrigation water at a production nursery in Suffolk, VA in 2000 and 2001. Water samples were assayed using a filtration method (3). A similar species was recovered from soil samples collected in two mixed-hardwood forests in Fairfax County in 2002. Soil samples were air dried, remoistened, flooded, and then baited with rhododendron and camellia leaf pieces at room temperature (22 to 24°C) (2). A Phytophthora sp. was recovered from bait pieces cultured on PARPH-V8 selective medium (2). This same species also was isolated from symptomatic leaves of Pieris japonica cv. Temple Bells and Rhododendron catawbiense cv. Maximum Roseum at a garden center in Virginia Beach in 2004. On P. japonica, symptoms appeared as water-soaked, necrotic lesions and marginal necrosis on leaves and necrosis of shoot tips; on R. catawbiense, symptoms were wilting, dieback, and death of shoots. Representative isolates produced semipapillate to papillate sporangia with tapered bases that were caducous and had long pedicels (16 to 120 µm). Sporangia on four isolates were measured: mean lengths were 40.6 to 48.4 µm, mean widths were 26.9 to 31.4 µm, and length/width ratios consistently were 1.5. Sporangia occasionally were distorted and had dual apices, and they often contained a large globule after zoospore release. Chlamydospores ranged from 25 to 32 µm in diameter. All isolates were heterothallic; four isolates paired with known isolates of P. nicotianae were found to be mating type A1. Optimum temperature for mycelium growth on cornmeal agar was 25°C with slight growth at 35°C by some isolates and no growth at 4°C. These morphological characteristics were mostly consistent with those of P. tropicalis (1). P. tropicalis is reported to have sporangia that are papillate, have lengths of 40 to 55 µm, widths of 19 to 27 µm, and length/width ratios of 1.8 to 2.4 (1). The identity of these isolates as P. tropicalis was confirmed using single-strand conformational polymorphism analysis with comparison to a reference isolate (4). These isolates have been retained in permanent collections in the Hong and Jeffers labs. One isolate from each host plant and one isolate from irrigation water were tested for pathogenicity; agar blocks of mycelium (4 × 4 mm) were placed on wounded and nonwounded leaves of P. japonica cv. Mountain Fire and R. catawbiense cv. Olga plants and wrapped with Parafilm to prevent desiccation. Lesions formed on wounded and nonwounded leaves after 4 days at 20 to 30°C, and P. tropicalis was reisolated; no lesions formed on noninoculated control leaves. To our knowledge, this is the first report of P. tropicalis in the continental United States, in irrigation water systems, and as a cause of Phytophthora foliage blight on P. japonica and R. catawbiense (1). This study suggests that the host range of this pathogen is not limited to tropical plants. Although this pathogen did not cause significant economic loss in the garden center surveyed, it was isolated in irrigation water at the production nursery from late spring through fall. An investigation of its impact on nursery crops is warranted. References: (1) M. Aragaki and J. Y. Uchida. Mycologia 93:137, 2001. (2) A. J. Ferguson and S. N. Jeffers. Plant Dis. 83:1129, 1999. (3) C. X. Hong et al. Phytopathology 92:610, 2002. (4) P. Kong et al. Fungal Genet. Biol. 39:238, 2003.

Minimal access surgery in children - 5 years institutional experience.

CONTEXT: Minimal access surgery (MAS) in children are common place and performed worldwide with gratifying results as the learning curve of the surgeon attains plateau. We share our experience of this technically evolving modality of surgery, performed at our setup over a period of 5 years. We also review and individually compare the data for commonly performed procedures with other available series. Author also briefly discuss potential advantages of MAS in certain debatable conditions performed quickly and with cosmesis as open procedure. MATERIALS AND METHODS: We performed 677 MAS in children aged between 7 days and 12 years. Five hundred and sixty-eight of these were Laparoscopic procedures and 109 were Video assisted thoracoscopic surgeries (VATS). In all laparoscopic procedures, the primary port placement was by the Hasson's open technique. We have used 5, 3 and 2 mm instruments. Our study include 259 inguinal hernia, 161 Appendectomies, 95 VATS for empyema, 51 orchiopexies, 49 diagnostic laparoscopy, 29 cholecystectomies, 22 adhesionlysis and other uncommonly performed procedures. RESULTS: The ultimate outcome of all the performed procedures showed gratifying trend, the data of which are discussed in detail in the article. CONCLUSION: As we gained experience the operating time showed a decreasing trend, the complication rates and conversion rate also reduced. The advantages we came across were better postoperative appearances, less pain and early return to unrestricted activities.

Metabolic and morphologic changes in the corneal endothelium. The effects of potassium cyanide, iodoacetamide, and ouabain.

The metabolic pathways of glycolysis and mitochondrial respiration in the corneal endothelial cell are the primary sources of the adenosine triphosphate (ATP) necessary to maintain endothelial structure and pump fluid to maintain the corneal stroma in its normally dehydrated and transparent state. The correlation between endothelial metabolism and morphology in rabbits was studied for 7 days after the application of three different agents: (1) iodoacetamide, used to inhibit ATP synthesis from both glycolysis and respiration; (2) potassium cyanide (KCN), used to inhibit ATP synthesis from respiration only; and (3) ouabain, used to inhibit fluid pumping but not ATP synthesis. After application of each of these three drugs to the corneal endothelium, changes in endothelial morphology were measured. The greatest change resulted from the use of iodoacetamide. Specular microscopic examination of the endothelium after the application of iodoacetamide showed progressive degradation of the integrity of the cellular structure; after 6 hr, there were no discernible cell borders. In those corneas treated with either KCN or ouabain, only minor changes in the endothelium were seen during the full 7 days of the investigation. Computer-assisted morphometric analysis showed an increase in the coefficient of variation of both cell area and perimeter in all cases. This increase was greater in the corneas treated with ouabain than those treated with either iodoacetamide or KCN. Redox fluorometry showed that the metabolic ratio (autofluorescence of reduced pyridine nucleotides divided by that of oxidized flavoproteins) decreased significantly in the iodoacetamide-treated corneas, increased significantly in the KCN group, and showed no significant change in the corneas in the ouabain group, all compared with a control group. The results showed that (1) when ATP produced by both glycolysis and respiration was inhibited by 0.1 mmol/l iodoacetamide, the endothelial cells could not survive, but (2) when ATP synthesis produced by respiration alone was inhibited by 1.0 mmol/l KCN, the cells could survive for at least 1 wk on the ATP produced by anaerobic glycolysis. Furthermore, the polymegathism seen after application of ouabain, a drug that is not believed to affect ATP synthesis but inhibits the endothelial pump function, is greater than that seen as a result of reduced pump function caused by inhibited respiration produced by 1.0 mmol/l KCN. Combining specular microscopy, computer-assisted morphometric analysis, redox fluorometry, and corneal pachymetry allowed correlations between corneal endothelial metabolism, pump function, and morphology to be studied.