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.

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.

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.

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.

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.

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.

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.

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.

Pump-probe surface photovoltage spectroscopy measurements on semiconductor epitaxial layers.

Pump-probe Surface Photovoltage Spectroscopy (SPS) measurements are performed on semiconductor epitaxial layers. Here, an additional sub-bandgap cw pump laser beam is used in a conventional chopped light geometry SPS setup under the pump-probe configuration. The main role of pump laser beam is to saturate the sub-bandgap localized states whose contribution otherwise swamp the information related to the bandgap of material. It also affects the magnitude of Dember voltage in case of semi-insulating (SI) semiconductor substrates. Pump-probe SPS technique enables an accurate determination of the bandgap of semiconductor epitaxial layers even under the strong influence of localized sub-bandgap states. The pump beam is found to be very effective in suppressing the effect of surface/interface and bulk trap states. The overall magnitude of SPV signal is decided by the dependence of charge separation mechanisms on the intensity of the pump beam. On the contrary, an above bandgap cw pump laser can be used to distinguish the signatures of sub-bandgap states by suppressing the band edge related feature. Usefulness of the pump-probe SPS technique is established by unambiguously determining the bandgap of p-GaAs epitaxial layers grown on SI-GaAs substrates, SI-InP wafers, and p-GaN epilayers grown on Sapphire substrates.

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.

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.

A highly efficient and compact long pulse Nd:YAG rod laser with 540 J of pulse energy for welding application.

We have developed an efficient and high average power flash lamp pumped long pulse Nd:YAG laser capable of generating 1 kW of average output power with maximum 540 J of single pulse energy and 20 kW of peak power. The laser pulse duration can be varied from 1 to 40 ms and repetition rate from 1 to 100 Hz. A compact and robust laser pump chamber and resonator was designed to achieve this high average and peak power. It was found that this laser system provides highest single pulse energy as compared to other long pulsed Nd:YAG laser systems of similar rating. A slope efficiency of 5.4% has been achieved, which is on higher side for typical lamp pumped solid-state lasers. This system will be highly useful in laser welding of materials such as aluminium and titanium. We have achieved 4 mm deep penetration welding of these metals under optimized conditions of output power, pulse energy, and pulse duration. The laser resonator was optimized to provide stable operation from single shot to 100 Hz of repetition rate. The beam quality factor was measured to be M(2) ~ 91 and pulse-to-pulse stability of ±3% for the multimode operation. The laser beam was efficiently coupled through an optical fiber of 600 µm core diameter and 0.22 numerical aperture with power transmission of 90%.

Carotid sheath lipoma: first case report in the English literature.

Lipomas are the most commonly encountered benign mesenchymal tumour, arising in any location where fat is normally present. Lipomas in the head and neck are rare in all age groups. Cases of vascular sheath lipomas in the femoral region have only been reported in adults. In children, vascular sheath lipomas have not been described to date. We report the first case of a carotid sheath lipoma in a seven-year-old boy. He had a non-tender soft mass with ill defined borders occupying the left upper part of the neck. Magnetic resonance imaging showed a mass at the bifurcation of the left common carotid artery without involving the same. The mass was hyperintense on T1 and T2 weighted sequences, suggestive of a lipoma. The lipoma was enucleated after incising the carotid sheath, safeguarding its contents. Histopathology confirmed it as a lipoma.

Ipsilateral stroke with uncrossed pyramidal tracts and underlying right internal carotid artery stenosis treated with percutaneous transluminal angioplasty and stenting. A rare case report and review of the literature.

We present a unique case of ipsilateral stroke in a 55-year-old right-handed hypertensive man with proven uncrossed pyramidal tract demonstrated by tractography. Diffusion-weighted imaging disclosed small acute ischemic infarcts in the right corona radiata with MR angiography showing narrowing of the right internal carotid artery. Significant carotid stenosis of right internal carotid artery (ICA) was detected on digital subtraction angiography as the underlying cause and subsequently treated with percutananeous transluminal angioplasty and stenting with good outcome. The presence of uncrossed pyramidal tract was confirmed by diffusion tensor imaging tractography. To our knowledge there are few reports of ipsilateral stroke with proven uncrossed pyramidal tracts described in the literature. This is the first documented report of ipsilateral stroke with uncrossed fibre tracts due to underlying critical stenosis of the ICA treated successfully with a good recovery.

Endovascular treatment of A1 aneurysms. A series of five cases with a brief literature review.

Aneurysms of the A1 segment of the anterior cerebral artery are rare and represent less than 1% of intracranial aneurysms. There are few reports available in the literature describing the role of endovascular management of these rare aneurysms. In the present series we describe five patients with A1 aneurysms presenting at our institution with various clinical presentations, treated successfully by endovascular method with a good clinical outcome. From January 2008 to July 2011, five patients (two males and three females) with A1 aneurysms were treated by endovascular means. Four of the patients presented with subarachnoid hemorrhage due to rupture of the A1 aneurysm and one patient presented with symptoms of mass effect in the form of headache and ophthalmoplegia. The age group ranges from eight to 52 years with a mean age of 34.2 years. Four of the patients were treated by coiling without any assisted technique whereas one patient who had a dissecting fusiform aneurysm was treated with stent-assisted coiling. Technical success was achieved in all the patients.We did not encounter any procedure-related complications in any of our cases. All the patients had an uneventful course with good clinical outcome. Angiographic follow-up was available in four patients (80%). Endovascular treatment of this rare group of aneurysms is an effective and safe treatment modality, however large series are required to support our findings.

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.

Changes in GAD65Ab-specific antiidiotypic antibody levels correlate with changes in C-peptide levels and progression to islet cell autoimmunity.

CONTEXT: The previously reported absence of 65-kDa glutamate decarboxylase antibody (GAD65Ab)-specific antiidiotypic antibodies (anti-Id) in type 1 diabetes (T1D) patients at clinical onset could be due to an inability to mount an antibody response to GAD65Ab or a longitudinal decline in anti-Id levels. OBJECTIVE AND DESIGN: We investigated anti-Id levels in longitudinal samples obtained from T1D patients (n = 41) (clinical diagnosis - 12 months), and latent autoimmune diabetes in adults (LADA) patients (n = 32) who received alum-formulated human recombinant GAD65 (baseline - 12 months). We also determined anti-Id levels in a small cohort of Type 2 diabetes patients during their development of autoimmune T cell responses. RESULTS: At clinical onset T1D patients presented no or low anti-Id levels. However, 22/41 T1D patients showed ≥50% increase in GAD65Ab-specific anti-Id levels during follow-up; peaking at 3 (n = 1), 6 (n = 10), 9 (n = 10), or 12 (n = 1) months. Increasing anti-Id levels marked patients who experienced a temporary increase in C-peptide levels. Anti-Id levels correlated significantly with glycated hemoglobin and C-peptide levels at 6 and 9 months (P values ranged from <0.001 to <0.05). In LADA patients receiving placebo, anti-Id levels declined in seven of nine patients, whereas four of five patients receiving 20 µg alum-formulated human recombinant GAD65 showed increasing anti-Id levels. Changes in anti-Id and C-peptide levels closely correlated (P < 0.0001). The significant decline in anti-Id levels (P = 0.03) in T2D patients developing T cell autoimmune responses supports our hypothesis that declining anti-Id levels are associated with developing islet autoimmunity. CONCLUSIONS: The close association between GAD65Ab-specific anti-Id levels and ß-cell function may provide a novel marker for the progression of autoimmune diabetes.