Dual-wavelength, mode-locked erbium-doped fiber laser employing a graphene/polymethyl-methacrylate saturable absorber.

Mode-locked fiber laser incorporating a saturable absorber is an attractive configuration due to its stability and simple structure. In this work, we demonstrate a dual-wavelength passively mode-locked erbium-doped fiber laser employing a graphene/polymethyl-methacrylate saturable absorber. A laser resonator is developed based on dual cavity architecture with unidirectional signal oscillation, which is connected by a fiber branch sharing a common gain medium and saturable absorber. Dual wavelength mode-locked fiber lasers are observed at approximately 1530 and 1560 nm with 22.6 mW pump power threshold. Soliton pulse circulates in the laser cavity with pulse duration of 900 and 940 fs at shorter and longer wavelengths, respectively. This work presents a viable option in developing a low threshold mode-locked laser source with closely spaced dual wavelength femtosecond pulses in the C-band wavelength region.

Generation and characterisation of human umbilical cord derived mesenchymal stem cells by explant method.

Mesenchymal stem cells (MSCs) derived from human umbilical cord (UC) have been considered as an important tool for treating various malignancies, tissue repair and organ regeneration. Umbilical cord-derived mesenchymal stem cells (UC-MSCs) are better alternative to MSCs that derived from bone marrow (BM-MSCs) as they are regarded as medical waste with little ethical concern for research and easily culture-expanded. In this present study, the foetal distal end of human UC was utilised to generate MSC by explant method. Upon in vitro culture, adherent cells with fibroblastic morphology were generated with rapid growth kinetics. Under the respective inductive conditions, these cells were capable of differentiating into adipocytes and osteocytes; express an array of standard MSC's surface markers CD29, CD73, CD90, CD106 and MHC-class I. Further assessment of immunosuppression activity revealed that MSCs generated from UC had profoundly inhibited the proliferation of mitogen-activated T lymphocytes in a dosedependent manner. The current laboratory findings have reinforced the application of explant method to generate UCMSCs thus, exploring an ideal platform to fulfil the increasing demand of MSCs for research and potential clinical use.

Adherence to tyrosine kinase inhibitors among adult chronic myeloid leukemia patients in a Malaysia hospital.

Background Tyrosine kinase inhibitors have been demonstrated to improve the survival of patients with chronic myeloid leukaemia. However, medication adherence is vital for patients on chronic treatment. Objective The objective of the current study was to evaluate response to treatment, adherence by patients to tyrosine kinase inhibitors and factors associated with adherence and response. Setting A haematology clinic in a regional referral hospital in Malaysia. Method Patients aged ≥ 13 years who had been on imatinib or nilotinib for ≥ 12 months were included in this cross-sectional study. An optimal response was defined as the achievement of major molecular response at 12 months of treatment. Patient medication adherence was determined using the average medication possession ratio based on the dispensing records. The patients were considered adherent if the medication possession ratio was > 90%. Multiple logistic regression was performed to evaluate the factors associated with adherence. The association of adherence with molecular response was analysed by univariate logistic regression. Main outcome measure The primary outcome measures were the proportion of patients who achieved optimal response and the medication possession ratio. Results A total of 151 patients were screened, and 71 patients were included. Twenty-eight patients (39%) achieved major molecular response at 12 months of treatment. The median time to achieve this was 15.5 months (an interquartile range of 15). The mean medication possession ratio for imatinib and nilotinib was 0.94 (± 0.14) and 0.96 (± 0.10), respectively, but this difference was without statistical significance (t  =  - 0.517, p  =  0.610). Nausea and vomiting (odds ratio [OR] of 0.25, 95% confidence interval [CI]: 0.07-0.83, p  =  0.023) and disease phase at diagnosis (OR of 0.20, 95% CI 0.04-1.06, p  =  0.059) were associated with patient adherence. An association was not found between patient adherence and molecular response (OR of 1.03, 95% CI 0.35-3.09, p  =  0.956). Conclusion The patients in this study demonstrated a relatively deep molecular response and optimal adherence. Nevertheless, one fourth of them were noncompliant with imatinib. Therefore, active interventions are warranted to prevent treatment-associated adverse events and improve adherence.

Photonic crystal fibre as a potential medium for radiotherapy dosimetry.

Present study concerns the key thermoluminescence (TL) properties of photonic crystal fibres (PCFs), seeking development of alternatively structured TL materials that are able to offer a advantages over existing passive dosimeters. In terms of their internal structure and light guiding properties the PCFs, collapsed and structured, differ significantly from that of conventional optical fibres. To investigate the dosimetric parameters of the PCFs use was made of a linear accelerator producing a 6 MV photon beam, delivering doses ranging from 0.5 Gy to 8 Gy. The parameters studied included TL response, linearity index, glow curves, relative sensitivity and TL signal fading, the results being compared against those obtained using TLD-100 chips. At 4 Gy photon dose the Ge-doped collapsed PCFs were found to provide a response 27 × that of structured PCF, also giving a TL yield similar to that of standard TLD-100 chips. Over post-irradiation periods of 15 and 30 days collapsed PCF TL signal fading were 8% and 17% respectively, with corresponding values of 37% and 64% for the structured PCF. Trapping parameters including the order of kinetics (b), activation energy (E) and frequency factor (s-1) were assessed with Chen's peak shape method. Lifetime of trapping centre was found to be (2.36 E+03) s and (9.03 E +01) s regarding the collapsed and structured PCF respectively with 6 Gy of photon beam. For the Ge-doped collapsed PCF, the high TL yield, sensitivity and low fading provide the basis of a highly promising system of TLD for radiotherapy applications.

Thermoluminescence characteristics of Ge-doped optical fibers with different dimensions for radiation dosimetry.

Important thermoluminescence (TL) properties of five (5) different core sizes Ge-doped optical fibers have been studied to develop new TL material with better response. These are drawn from same preform applying different speed and tension during drawing phase to produce Ge-doped optical fibers with five (5) different core sizes. The results of the investigations are also compared with most commonly used standard TLD-100 chips (LiF:Mg,Ti) and commercial multimode Ge-doped optical fiber (Yangtze Optical Fiber, China). Scanning Electron Microscope (SEM) and EDX analysis of the fibers are also performed to map Ge distribution across the deposited region. Standard Gamma radiation source in Secondary Standard Dosimetry Lab (SSDL) was used for irradiation covering dose range from 1Gy to 10Gy. The essential dosimetric parameters that have been studied are TL linearity, reproducibility and fading. Prior to irradiation all samples ∼0.5cm length are annealed at temperature of 400°C for 1h period to standardize their sensitivities and background. Standard TLD-100 chips are also annealed for 1h at 400°C and subsequently 2h at 100°C to yield the highest sensitivity. TL responses of these fibers show linearity over a wide gamma radiation dose that is an important property for radiation dosimetry. Among all fibers used in this study, 100µm core diameter fiber provides highest response that is 2.6 times than that of smallest core (20µm core) optical fiber. These fiber-samples demonstrate better response than commercial multi-mode optical fiber and also provide low degree of fading about 20% over a period of fifteen days for gamma radiation. Effective atomic number (Zeff) is found in the range (13.25-13.69) which is higher than soft tissue (7.5) however within the range of human-bone (11.6-13.8). All the fibers can also be re-used several times as a detector after annealing. TL properties of the Ge-doped optical fibers indicate promising applications in ionizing radiation dosimetry.

The thermoluminescence glow curve and the deconvoluted glow peak characteristics of erbium doped silica fiber exposed to 70-130 kVp x-rays.

In regard to thermoluminescence (TL) applied to dosimetry, in recent times a number of researchers have explored the role of optical fibers for radiation detection and measurement. Many of the studies have focused on the specific dopant concentration, the type of dopant and the fiber core diameter, all key dependencies in producing significant increase in the sensitivity of such fibers. At doses of less than 1 Gy none of these investigations have addressed the relationship between dose response and TL glow peak behavior of erbium (Er)-doped silica cylindrical fibers (CF). For x-rays obtained at accelerating potentials from 70 to 130 kVp, delivering doses of between 0.1 and 0.7 Gy, present study explores the issue of dose response, special attention being paid to determination of the kinetic parameters and dosimetric peak properties of Er-doped CF. The effect of dose response on the kinetic parameters of the glow peak has been compared against other fiber types, revealing previously misunderstood connections between kinetic parameters and radiation dose. Within the investigated dose range there was an absence of supralinearity of response of the Er-doped silica CF, instead sub-linear response being observed. Detailed examination of glow peak response and kinetic parameters has thus been shown to shed new light of the rarely acknowledged issue of the limitation of TL kinetic model and sub-linear dose response of Er-doped silica CF.

Telemedicine in the Malaysian Multimedia Super Corridor: towards personalized lifetime health plans.

The Malaysian Telemedicine initiative advocates a paradigm shift in healthcare delivery patterns by way of implementing a person-centred and wellness-focused healthcare system. This paper introduces the Malaysian Telemedicine vision, its functionality and associated operational conditions. In particular, we focus on the conceptualisation of one key Telemedicine component i.e. the Lifetime Health Plan (LHP) system--a distributed multimodule application for the periodic monitoring and generation of health-care advisories for all Malaysians. In line with the LHP project, we present an innovative healthcare delivery info-structure--LifePlan--that aims to provide life-long, pro-active, personalised, wellness-oriented healthcare services to assist individuals to manage and interpret their health needs. Functionally, LifePlan based healthcare services are delivered over the WWW, packaged as Personalised Lifetime Health Plans that allow individuals to both monitor their health status and to guide them in healthcare planning.

Telemedicine and medical informatics in the multimedia super corridor: the Malaysian vision.

The practice of medicine, with its wide range of environmental conditions and complex dependencies, has long been used as a test bed for various advanced technologies. Telemedicine, as conceptualised within the Multimedia Super Corridor (MSC) context, is seen as the application of several relatively mature technologiesartificial intelligence (AI), multimedia communication and information systems (IS) amongst othersso as to benefit a large cross-section of the Malaysian population. We will discuss in general terms the Malaysian vision on the comprehensive MSC telemedicine solution, its functionality and associated operational conditions. In particular, this paper focuses on the conceptualisation of one key telemedical component i.e. the Lifetime Health Plan (LHP) system, which is eventually intended to be a distributed multi-module application for the periodic monitoring and generation of health-care advisories for upwards of 20 million Malaysians.

Brillouin characterization of holey optical fibers.

We report the results of detailed measurements on the Brillouin frequency shift (BFS), gain bandwidth, and gain coefficients of several small-core holey optical fibers (HFs) of both uniform and axially varying structural characteristics and compare these with measurements on more conventional fibers. Our measurements show that the BFS of HFs is first-order proportional to the modal index for light propagating along the fiber and is thus extremely sensitive to its precise structural parameters. Our results highlight the possibility of using distributed Brillouin scattering measurements to perform nondestructive structural characterization of HFs, and the possibility of producing Brillouin-suppressed HFs using controlled structural variation along the fiber length.

Percutaneous closure of atrial septal defect type ostium secundum using the new Intrasept occluder: initial experience.

We report the first experience obtained with the new Intrasept device. We attempted to treat 35 patients with a mean age of 43 +/- 21 years. The mean size of the defect was 17/15 mm. It was successfully closed in 31 patients. In the remaining four the device could not be stabilized because of excessive defect size. A small residual shunt was present immediately following implantation in three patients. No complications occurred during the procedure and at 6 months, 31 patients had an uneventful outcome. Only one patient had a small residual shunt. No thrombus, embolization, or device fracture was documented during a mean follow-up of 17 +/- 11 months. Percutaneous closure of ASD ostium secundum is feasible with the Intrasept device with a high success rate and very good medium-term outcome. Our initial experience and results were excellent with small to medium size defects, however, large defects (>20 mm) remain challenging.

Raman effects in a highly nonlinear holey fiber: amplification and modulation.

We experimentally demonstrate that a short length of highly nonlinear holey fiber (HF) can be used for strong L(+) -band (1610-1640-nm) Raman amplification and ultrafast signal modulation. We use a pure silica HF with an effective area of just 2.85mum(2) at 1550 nm, which yields an effective nonlinearity ~15 times higher than in conventional silica dispersion-shifted fiber. Using a 75-m length of this fiber, we obtained internal Raman gains of more than 42 dB and a noise figure of ~6 dB under a forward single-pump scheme, and the Raman gain coefficient was experimentally estimated to be 7.6 chi 10(-14)m/W . Also, an 11-dB signal extinction ratio in a Raman-induced all-optical modulation experiment was achieved with the same fiber.