Narrow-linewidth broadly tunable Yb-doped Q-switched fiber laser using multimode interference filter.

A narrow-linewidth broadly tunable Yb-doped Q-switched fiber laser using an acousto-optic modulator and multimode interference filter (MMIF) in the linear bulk cavity resonator and an all-fiber ring cavity resonator has been demonstrated. Insertion of an MMIF in the linear cavity resonator using bulk components decreased the spectral bandwidth of the Q-switched signal by two orders of magnitude from 11 to less than 0.1 nm. Spectral tunability of more than 16 nm in the range from 1057 to 1073 nm has also been achieved by the combination of MMIF and a standard polarization controller (SPC). A decrease in the pulse duration with a decrease in the spectral bandwidth of the output signal has also been recorded. The pulse duration of the Q-switched signal was reduced from ∼305 to ∼240 ns by the introduction of the MMIF in the resonator at the same value of the input pump power. In the case of the all-fiber Q-switched ring cavity resonator, the spectral bandwidth of the Q-switched signal was reduced by two orders of magnitude from ∼17 to less than 0.1 nm due to the introduction of the MMIF in the resonator. The spectral tunability of more than 12 nm in the range from 1038 to 1050 nm was achieved by an MMIF and an SPC.

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 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.

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.

Prediction of disease-gene-drug relationships following a differential network analysis.

Great efforts are being devoted to get a deeper understanding of disease-related dysregulations, which is central for introducing novel and more effective therapeutics in the clinics. However, most human diseases are highly multifactorial at the molecular level, involving dysregulation of multiple genes and interactions in gene regulatory networks. This issue hinders the elucidation of disease mechanism, including the identification of disease-causing genes and regulatory interactions. Most of current network-based approaches for the study of disease mechanisms do not take into account significant differences in gene regulatory network topology between healthy and disease phenotypes. Moreover, these approaches are not able to efficiently guide database search for connections between drugs, genes and diseases. We propose a differential network-based methodology for identifying candidate target genes and chemical compounds for reverting disease phenotypes. Our method relies on transcriptomics data to reconstruct gene regulatory networks corresponding to healthy and disease states separately. Further, it identifies candidate genes essential for triggering the reversion of the disease phenotype based on network stability determinants underlying differential gene expression. In addition, our method selects and ranks chemical compounds targeting these genes, which could be used as therapeutic interventions for complex diseases.

Scrub Typhus: An Emerging Neglected Tropical Disease in Nepal.

BACKGROUND: Scrub typhus is a neglected tropical disease and is under reported from Nepal. The objective of this study was to investigate the sero-epidemiology of scrub typhus in patients suffering from acute febrile illness. METHODS: A total of 434 specimens collected from July to November 2015 at National Public Health Laboratory (NPHL) were investigated for detection of immunoglobulin M (IgM) antibody to Orientiatsutsugamushi.The Scrub Typhus Detect TM kit (InBios, USA) was used to detect the antibodies to O.tsutsugamushi in human serum. Randomly selected 10% positive specimens were used for confirmation by dot- enzyme-linked immunosorbent assay and indirect immunofluorescence assay. RESULTS: Of the total, 175 (40.3%) were positive for IgM antibodies to O. tsutsugamushi. Positive results of scrub typhus were highest among female in 11-20 year followed by males in 41-50 years age group. The IgM antibodies to O. tsutusugamushi were positive in specimens of various geographical regions including 30 districts of Nepal. Positive cases were found in various ecological regions of Nepal. CONCLUSIONS: Scrub typhus is one of the neglected tropical diseases in Nepal. Patients with acute febrile illness should be investigated for scrub typhus with high priority. There is an urgent need of reliable and affordable diagnostic tests at all level of health facilities of Nepal. Surveillance and public health awareness about the disease transmission and preventive measures needs to be initiated.

Outbreak Investigation of Influenza in Pajaru VDC of Jajarkot District of Nepal.

BACKGROUND: An outbreak investigation study was conducted in Pajaru, one of the initially affected Village Development Committees (VDCs) of the Jajarkot district in Nepal following an outbreak of respiratory illness in early 2015. The objectives of this study were to identify the cases and magnitude of the outbreak. METHODS: A cross-sectional study was carried out in mid-April 2015 covering five most affected wards of Pajaru VDC to assess the patients using standard case definition for Influenza like Illness (ILI). Throat and nasal swabs were collected and sent to the National Influenza Center (NIC) in Kathmandu for laboratory confirmation. RESULTS: The throat swab samples tested at NIC found Influenza A H1N1 pdm09. The attack rate was calculated to be 3% in ward number 9 and 41% in ward number 8. Wavelength of the infection was nearly two weeks in both the wards. Nearly 54% of the specimens were positive for Influenza A H1N1 pdm09. There was no ILI case fatality in the study area. Children aged 0-15 years were most affected. Majority of the patients presented with symptoms of fever, cough and sore throat. CONCLUSIONS: There was gradual decline in the number of cases in all five wards suggestive of development of natural immunity in the community. True severity of the outbreak was not accurately reflected as compared to media reports.

Double-blind randomised trial of the antiemetic efficacy and safety of ondansetron and metoclopramide in advanced breast cancer patients treated with epirubicin and cyclophosphamide.

Ondansetron was compared with metoclopramide for antiemetic efficacy in a randomised double-blind trial in 122 patients with advanced breast cancer. All patients were treated with epirubicin (greater than 50 mg/m2) and cyclophosphamide (greater than 500 mg/m2). 50 patients receiving ondansetron and 60 with metoclopramide were considered evaluable. Ondansetron was at least as effective as metoclopramide in the control of vomiting and nausea. The percentage of patients with complete plus major control was 72% (59-85%) vs. 61% (48-74%) on day 1 (P = 0.230) and 79% (67-91%) vs. 66% (53-78%) on days 2-3 after chemotherapy (P = 0.122). Over the 3-day study period, nausea was absent or mild in 60% of the patients treated with ondansetron, compared to 45% given metoclopramide (P = 0.064). No major drug-related side-effects were reported. 1 patient receiving ondansetron experienced gastrointestinal disturbance and headache. Episodes of diarrhoea, fever, hyperkinetic syndrome, fatigue, restlessness and migraine with vomiting were reported by 5 patients treated with metoclopramide. None of the changes in the biochemical or haematological parameters was attributed to the antiemetic treatments.

A prospective randomized double-blind trial comparing ondansetron versus prochlorperazine for the prevention of nausea and vomiting in patients undergoing fractionated radiotherapy.

In a multicentre, international double-blind trial, patients undergoing courses of five or more daily radiotherapy treatments to the upper abdomen were randomized to receive either oral ondansetron 8 mg t.d.s. or oral prochlorperazine 10 mg t.d.s. throughout their radiation course in order to try to prevent nausea and vomiting. A total of 192 patients were recruited, 135 of whom were included in the efficacy analysis; of these, 70 received ondansetron and 65 prochlorperazine. Forty-three (61%) of the patients prescribed ondansetron and 23 (35%) of those given prochlorperazine had a complete response, with no emetic episodes throughout their treatment course (P = 0.002). There was, however, no significant difference between the two groups with respect to the incidence and severity of nausea. Seventeen (24%) of the patients on ondansetron and 19 (29%) of those given prochlorperazine were treatment failures, experiencing more than five emetic episodes on their worst day during the study. Both drugs were well tolerated, although constipation was seen more commonly with ondansetron.

Results of a randomized, double-blind comparative study of ondansetron and metoclopramide in the prevention of nausea and vomiting following high-dose upper abdominal irradiation.

Ondansetron is a 5-hydroxytryptamine 3-receptor antagonist which has shown activity in the prevention of cytotoxic-induced emesis. Preliminary non-randomized studies also indicated efficacy in preventing sickness following radiotherapy. The present study was therefore undertaken to compare the efficacy and safety of ondansetron (8 mg tds orally) and metoclopramide (10 mg tds orally) in preventing sickness after single-exposure radiotherapy treatments of 8-10 Gy to the upper abdomen. Of 82 evaluable patients 38 received ondansetron and 44 metoclopramide. On the first day after irradiation vomiting or retching was prevented in all but one of the patients on ondansetron whereas metoclopramide achieved complete control of these symptoms in only 46% of subjects (P less than 0.001). Similarly nausea was significantly better controlled by ondansetron in the first 24 hours after treatment (P = 0.001). Complete or major control of vomiting or retching was maintained for 92%-100% of patients on ondansetron during the five days of the study period. In the metoclopramide group the proportion of patients with equivalent control improved from 70% on day 1 to 95 on day 5. Both drugs were well-tolerated.

Efficacy of twice daily versus three times daily oral ondansetron in the prevention of chemotherapy induced emesis: a randomized, single-blind, multicentre study. The Ondansetron International Emesis Study Group.

Following a single intravenous dose given pre-chemotherapy, the efficacy and tolerability of oral ondansetron treatment given twice daily was compared with the established three times daily oral supplementary regimen in the prophylaxis of nausea and vomiting induced by cyclophosphamide (greater than or equal to 500 mg/m2) in combination with doxorubicin (greater than or equal to 40 mg/m2) or epirubicin (greater than or equal to 40 mg/m2). Oral ondansetron given twice daily or three times daily was equally effective in controlling nausea and emesis. The twice daily oral treatment prevented emesis in 73% of patients in the first 24 hours and in 65% of patients over 3 days. Both dose schedules were safe and were tolerated well. Twice daily oral ondansetron showed good efficacy for controlling emesis and nausea in oncology outpatients.

Does dexamethasone enhance control of acute cisplatin induced emesis by ondansetron?

OBJECTIVE: To determine the contribution of dexamethasone to the efficacy of the 5-hydroxytryptamine antagonist ondansetron in control of cisplatin induced nausea and vomiting. DESIGN: Randomised double blind crossover study. SETTING: Two cancer centres in teaching hospitals, one in the United Kingdom and the other in Germany. SUBJECTS: 100 patients (53 men and 47 women) new to cisplatin chemotherapy, 84 of whom completed two consecutive courses of chemotherapy. INTERVENTIONS: Patients were given intravenous dexamethasone (20 mg) or physiological saline with intravenous ondansetron 8 mg before cisplatin, then ondansetron 1 mg/h for 24 hours. Oral ondansetron 8 mg was taken three times daily on days 2-6. MAIN OUTCOME MEASURES: Incidence of complete or major control of emesis (0-2 episodes in the 24 hours after chemotherapy). RESULTS: Complete or major control was obtained in 49 out of 71 (69%) of patients after receiving ondansetron plus dexamethasone compared with 40 out of 71 (56%) when they were given ondansetron alone (p = 0.012). This effect was most pronounced in the first 12 hours after chemotherapy. Patients receiving the combination also had significantly less nausea. Of the 53 patients who expressed a preference, 38 (72%) preferred the combination treatment (p = 0.002) to ondansetron alone. The effect of ondansetron on delayed emesis was less pronounced. CONCLUSIONS: Dexamethasone makes a significant contribution to the efficacy of ondansetron in the control of acute platinum induced emesis.

Post-operative nausea and vomiting in patients undergoing day-case surgery: an international, observational study.

Post-operative nausea and vomiting (PONV) are complications of surgical procedures, and are of particular relevance in the day-case setting. The aim of this study was to examine the incidence and impact of PONV before and after discharge from day surgery units. Patients recorded the incidence, severity and impact of PONV for 5 days following surgery. The incidence of PONV in the 561 eligible patients was 17% upon waking, 14% travelling home and 3% by the 5th day post-surgery. PONV was most common in gastrointestinal, obstetric and gynaecological surgery. Although freedom from pain and PONV are requirements for discharge after ambulatory surgery, PONV is still a problem post-discharge.

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%.

Extended spectrum â-lactamase producing multidrug resistant clinical bacterial isolates at National Public Health Laboratory, Nepal.

Extended Spectrum â-lactamase (ESBL) producing multidrug resistant bacteria complicate therapeutic management and limit treatment options. Therefore, detection of ESBL-producing multidrug resistant (MDR) pathogens has a paramount importance. Between April 2009 and January 2010, a prospective study was carried out in National Public Health Laboratory with an objective to determine the status of ESBL producing MDR bacterial isolates from different clinical samples. Identification of the isolates was done by standard microbiological techniques and antibiotic susceptibility testing was done by Kirby Bauer disc diffusion method following Clinical and Laboratory Standard Institute (CLSI) guidelines. ESBL screening among MDR isolates was done using Ceftriaxone, Aztreonam, Cefotaxime, Ceftazidime and Cefpodoxime followed by confirmation using MASTDISCS ID ES2L Detection Discs (CPD10). Data analysis was done by SPSS 16 software. Of the 314 bacterial isolates from 1601 different clinical specimens, 199 (63.4%) were MDR. Cefotaxime was found the reliable screening agent for ESBL detection with sensitivity and positive predictive value of 98.6% and 76.4% respectively. Sixtey nine (62.7%) isolates of the 110 tested MDR isolates were ESBL positive with at least one of the Combined Disk (CD) Assays. Escherichia coli (80%) was the major ESBL producer followed by Klebsiella pneumoniae (5.8%). A statistically significant relationship was found between increasing spectrum of drug resistance and ESBL production (p<0.05). Thus it is concluded that a higher rate of ESBL production prevail among MDR clinical bacterial isolates underscoring the need for routine ESBL detection in clinical laboratories.

A Clinical Study on the use of Puskara Mooladi Choorna in Tamaka Shvasa (Bronchial Asthma) with Pulmonary Function Tests.

Tamaka Shvasa which has been mentioned in Ayurvedic classics shares multiple similarities with Bronchial Asthma. Symptom of breathlessness is the main complaint in Bronchial Asthma which can be assessed objectively by Pulmonary Function Test (PFT).The assessment of respiratory function is now a routine part of clinical practice. The expiratory flow rates- Forced Expiratory Volume in first second (FEV), Forced Vital Capacity (FVC) and Peak Expiratory Flow Rate (PEFR) are assessed by an Electronic Spirometer (Kent, England). Six weeks treatment with a compound preparation of herbs including - Sati (Hedichum spicatum, Rose), Puskaramoola (Innula racemosa, Linn), and Amalaki (Emblica officinalis, Gaertn) powder showed a significant effect of increase in Pulmonary Function values. The mean grade score plus standard deviation before trial of FEV, FVC, and PEFR were 62.6±15.06, 2.03±o.53 and 189±44.05 respectively. After six weeks of treatment with Puskaramooladi choorna FEV, FVC and PEFR showed highly significant results with values 63.45±15.9, 2.81±0.33 and 199.6±41.58 respectively. Puskaramooladi choorna can be used as one of the potent medicine in the treatment of the Bronchial Asthma.

Study of patients presenting with symptoms of peripheral neuropathy and thickened greater auricular nerve.

OBJECTIVE: To analyze symptoms and make a clinical diagnosis of leprosy in patients presenting with symptoms of peripheral neuropathy and found to have thickened greater auricular nerve. DESIGN: Cross-sectional study. SETTING: Kathmandu Medical College Teaching Hospital, Sinamangal, Kathmandu. Patients attending the medical out-patient department of this hospital were taken in the study. MATERIALS AND METHODS: 40 patients presenting with symptoms of peripheral neuropathy and are found to have thickened greater auricular nerve were included. RESULTS: Thickened greater auricular nerve and sensory symptoms showed male predominance (97.5%). Mean age of involvement was 28.65 years. The symptom most frequently complained of was chest pain (75%), followed by pins and needle sensation 67.5%, burning of the upper extremities, nape of the neck and chest 57.5%, palpitation 45%, disturbed sleep mostly said to be due to burning 35%, sweating 20%, dizziness 17.5%, shortness of breath 7.5%, and numbness of the limbs in 2.5%. None of the patients had somatic neuropathy. Autonomic neuropathy was present in 42.5 %. CONCLUSIONS: 1. In endemic areas patients with thickened peripheral nerve and sensory symptoms should be diagnosed clinically as primary neuritic leprosy. 2. In absence of objective loss of somatic sensation autonomic neuropathy may be the only early indicator of neuritis. 3. Close follow up of these patients is necessary.

Postoperative pain management and recovery after remifentanil-based anaesthesia with isoflurane or propofol for major abdominal surgery. Remifentanil Study Group.

We have assessed if recovery times after morphine or fentanyl, given before terminating remifentanil anaesthesia with isoflurane or propofol, are compromised. We studied patients undergoing elective, major abdominal surgery, allocated randomly to receive remifentanil and isoflurane (n = 277) or remifentanil and propofol (n = 274) anaesthesia. Twenty-five minutes before the end of surgery, patients received fentanyl 0.15 mg or morphine 15 mg in a randomized, double-blind manner followed by a second dose (fentanyl 0.05 mg, morphine 7 mg) for moderate or severe pain in recovery. Recovery was rapid and at an Aldrete score > or = 9 (median 12-15 min), 42-51% of patients reported none or mild pain. However, 26-35% of patients reported severe pain and > 90% required a second dose of opioid within 21-27 min after anaesthesia.

A comparison of anaesthesia using remifentanil combined with either isoflurane, enflurane or propofol in patients undergoing gynaecological laparoscopy, varicose vein or arthroscopic surgery.

BACKGROUND: Anaesthesia comprising remifentanil plus isoflurane, enflurane or propofol was randomly evaluated in 285, 285 and 284 patients, respectively, undergoing short-procedure surgery. METHODS: Anaesthesia was induced with propofol (0.5 mg x kg(-1) and 10 mg x 10 s(-1)), and a remifentanil bolus (1 microg x kg(-1)) and infusion at 0.5 microg x g(-1) x min(-1). Five minutes after intubation, remifentanil infusion was halved and 0.5 MAC of isoflurane or enflurane, or propofol at 100 microg x kg(-1) x min(-1) were started and titrated for maintenance. RESULTS: Patient demography and anaesthesia duration were similar between the groups. Surgery was performed as daycases (52%) or inpatients (48%). The median times (5-7 min) to extubation and postoperative recovery were similar between the groups. Responses to tracheal intubation (15% vs 8%) and skin incision (13% vs 7%) were significantly greater in the total intravenous anaesthesia (TIVA) group (P<0.05). Fewer patients given remifentanil and isoflurane (21%) or enflurane (19%) experienced > or =1 intraoperative stress response compared to the TIVA group (28%) (P<0.05). Median times to qualification for and actual recovery room discharge were 0.5-0.6 h and 1.1-1.2 h, respectively. The most common remifentanil-related symptoms were muscle rigidity (6-7%) at induction, hypotension (3-5%) and bradycardia (1-4%) intraoperatively and, shivering (6-7%), nausea and vomiting postoperatively. Nausea (7%) and vomiting (3%) were significantly lower with TIVA compared with inhaled anaesthetic groups (14-15% and 6-8%, respectively; P<0.05). CONCLUSION: Anaesthesia combining remifentanil with volatile hypnotics or TIVA with propofol was effective and well tolerated. Times of extubation, postanaesthesia recovery and recovery room discharge were rapid, consistent and similar for all three regimens.