Beam combinable, kilowatt, all-fiber amplifier based on phase-modulated laser gain competition.

We report power scaling results of a highly efficient narrow-linewidth monolithic Yb-doped fiber amplifier seeded with two signals, operating at 1038 and 1064 nm. With the appropriate seed power ratio applied, this technique was shown to suppress stimulated Brillouin scattering in conjunction with phase modulation, while generating the output power in predominantly the longer wavelength signal. Notably, the integration of laser gain competition with pseudo-random bit sequence phase modulation, set at a clock rate of 2.5 GHz and utilizing an optimized pattern to match the shortened effective nonlinear length, yielded 1 kW of output power. The beam quality was measured to be near the diffraction limit with no sign of transverse mode instability. Furthermore, the coherent beam combination performance of the amplifier provided a 90% combining efficiency with no indication of spectral broadening when compared to the single-tone case. Overall, the power scaling results represent a significant reduction in spectral linewidth compared to that of commercially available narrow-linewidth Yb-doped fiber amplifiers.

High-efficiency, kilowatt 1034 nm all-fiber amplifier operating at 11 pm linewidth.

We present power scaling results of a monolithic Yb-doped 1034 nm fiber amplifier well-suited for beam combining applications. Stimulated Brillouin scattering suppression is achieved through optical linewidth broadening, and results were compared for both white noise source (WNS) and pseudo-random bit sequence (PRBS) phase modulation schemes. Notably, through PRBS modulation at a clock rate of 3.5 GHz, 1 kW of output power with a slope efficiency of 81% was demonstrated. Beam quality measurements indicated near diffraction-limited operation with no sign of modal instability. At a comparable linewidth and fiber length, power scaling via WNS modulation yielded only 470 W. The kilowatt-class output at a linewidth of 11 pm is the highest power reported for a spectrally narrow all-fiber amplifier operating at the short wavelength end of the high gain range in Yb-doped silica.

Strong optical injection and the differential gain in a quantum dash laser.

By optically injecting a quantum dash laser and simultaneously producing a significant lowering of the device threshold, a large enhancement in the differential gain is realized. This effect is observed by way of a dramatic reduction in the linewidth enhancement factor and a large increase in the 3-dB modulation bandwidth, especially as the injection wavelength is blue-shifted. Compared to its free-running value, a 50X improvement in the laser's differential gain is found.

Psychometric study of the Persian short-form eight-item Parkinson's disease questionnaire (PDQ-8) to evaluate health related quality of life (HRQoL).

BACKGROUND: To assess validation and reliability of the Persian version of the short-form 8-item Parkinson's disease questionnaire (PDQ-8) and to compare its psychometric properties with that of the long-form questionnaire (PDQ-39) in order to evaluate the health-related quality of life (HRQoL) in patients with Parkinson's disease (PD). METHODS: This cross-sectional study was conducted on 114 non-demented idiopathic PD (IPD) patients consecutively recruited from an outpatient referral movement disorder clinic. Patients were interviewed to fill in the Persian version of PDQ-39 and PDQ-8 questionnaires and clinical examination was performed to measure disease severity indices. RESULTS: The Cronbach's alpha coefficient of the entire PDQ-8 was 0.740 (95% CI: 0.661-0.806). Replacement of PDQ-8 items with other questions with the highest internal consistency within each dimension of the original PDQ-39 did not improve Cronbach's alpha coefficient [0.723 (95% CI: 0.639-0.794)]. The scores from both PDQ-8 and PDQ-39 had significant correlation with the Hoehn & Yahr (rPDQ-8 = 0.376, rPDQ-39 = 0.442), and Schwab & England (rPDQ-8 = -0.503, rPDQ-39 = -0.598) disease severity scales and disease duration (rPDQ-8 = 0.342, rPDQ-39 = 0.396). CONCLUSIONS: Persian version of the short-form PDQ (PDQ-8) was shown to be a valid and reliable instrument to assess disease-specific HRQoL in a PD population when used independently. Although the PDQ-8 items were not necessarily those with the highest internal consistency in the components of PDQ-39, they entirely showed proper psychometric properties especially in mental and behavioral aspects. PDQ-8 is a practical and informative instrument in daily clinical practice where clinicians are in shortage of time and when a validated self-reported brief questionnaire is of value.

Developing a Paradigm Model for Resilience of Rural Entrepreneurial Businesses in Dealing With the COVID-19 Crisis; Application of Grounded Theory in Western of Iran.

Pandemic the COVID-19 is a global threat to rural entrepreneurial businesses with an uncertain ending. Therefore, it is necessary to provide a paradigm model to reduce the negative effects of this crisis, increase the resilience of rural entrepreneurial businesses or even turn this threat into an opportunity for the development of rural entrepreneurial businesses in the long run. This study, using a qualitative approach, investigated the resilience of rural entrepreneurial businesses in dealing with the COVID-19 crisis in Kermanshah province using a paradigm model. Using purposeful and theoretical sampling, 26 cases were selected. The tools used for data collection were open questionnaires (unstructured), individual depth interviews, and taking notes. The results provide a relatively comprehensive model that consists of six basic parts: causal conditions (included economic management, health factors, human resources management, and adaptation factors), the phenomenon (included low resilience of rural entrepreneurial businesses in the face of the COVID-19 crisis), contextual conditions (including social factors; cultural factors and psychological factors), interventing conditions (included business management and legal supports), action strategies (included Planned resilient actions and Unplanned resilient actions), finally, the consequences (included adapting to crisis conditions and increasing resilience in the long run, and also lack of adaptation to crisis conditions and lack of continuity of business survival in the long run). In general, rural entrepreneurial businesses in the face of crisis must, through planned resilience measures, both increase their business resilience in the short term, as well as develop the business and gain a competitive advantage in the long run. Finally, based on the findings and in order to developing resilience in rural entrepreneurial businesses during the COVID-19 crisis, some recommendations were presented.

Two-color multi-section quantum dot distributed feedback laser.

A dual-wavelength emission source is realized by asymmetrically pumping a two-section quantum-dot distributed feedback laser. It is found that under asymmetric bias conditions, the powers between the ground-state and excited-state modes of the two-section device can be equalized, which is mainly attributed to the unique carrier dynamics of the quantum-dot gain medium. As a result, a two-color emission with an 8-THz frequency difference is realized that has potential as a compact THz source. It is also shown that the combination of significant inhomogeneous broadening and excited-state coupled mode operation allows the manipulation of the quantum-dot states through external optical stabilization.

Prediction of nanofiber diameter and optimization of electrospinning process via response surface methodology.

Response surface methodology (RSM) was used to obtain a more systematic understanding of the electrospinning conditions of polyamide 6 solutions. This method was used to establish a quantitative basis for the relationships between the electrospinning parameters such as applied electric field, the polymer concentrations, the rate of injection and nozzle-collector distance with the diameter of the produced nanofibers, and to predict the optimum conditions for electrospinning to produce nanofibers with controlled size. A response function was empirically determined by central composite design (CCD) using fiber diameter as an observed response and the electrospinning parameters as variables. The relationship between the response and the variables is visualized by a response surface or contour plots. The study of the graphical representations of contour plots, prediction formulas and prediction profiler can predict the operating conditions necessary to generate nanofibers with the desired diameters.

Heterogeneous Determinants of Quality of Life in Different Phenotypes of Parkinson's Disease.

OBJECTIVES: Health-related quality of life (HRQoL) is considered a very important outcome indicator in patients with Parkinson's disease (PD). A broad list of motor and non-motor features have been shown to affect HRQoL in PD, however, there is a dearth of information about the complexity of interrelationships between determinants of HRQoL in different PD phenotypes. We aimed to find independent determinates and the best structural model for HRQoL, also to investigate the heterogeneity in HRQoL between PD patients with different phenotypes regarding onset-age, progression rate and dominant symptom. METHODS: A broad spectrum of demographic, motor and non-motor characteristics were collected in 157 idiopathic PD patients, namely comorbidity profile, nutritional status, UPDRS (total items), psychiatric symptoms (depression, anxiety), fatigue and psychosocial functioning through physical examination, validated questionnaires and scales. Structural equation model (SEM) and multivariate regressions were applied to find determinants of Parkinson's disease summary index (PDSI) and different domains of HRQoL (PDQ-39). RESULTS: Female sex, anxiety, depression and UPDRS-part II scores were the significant independent determinants of PDSI. A structural model consisting of global motor, global non-motor and co-morbidity indicator as three main components was able to predict 89% of the variance in HRQoL. In older-onset and slow-progression phenotypes, the motor domain showed smaller contribution on HRQoL and the majority of its effects were mediated through non-motor features. Comorbidity component was a significant determinant of HRQoL only among older-onset and non-tremor-dominant PD patients. Fatigue was not a significant indicator of non-motor component to affect HRQoL in rapid-progression PD. CONCLUSIONS: Our findings showed outstanding heterogeneities in the pattern and determinants of HRQoL among PD phenotypes. These factors should be considered during the assessments and developing personalized interventions to improve HRQOL in PD patients with different phenotypes or prominent feature.

Real life practice in the management of benign prostatic hyperplasia.

PURPOSE OF REVIEW: To review the current diagnostic and treatment options of lower urinary tract symptom due to benign prostatic hyperplasia and to put data from real life practice into perspective. RECENT FINDINGS: The overall incidence rate of lower urinary tract symptom/benign prostatic hyperplasia was found at 15 per 1000 man-years (95% CI 14.8-16.1). The incidence increases with age from 3/1000 man-years at 45-49 years to 38/1000 man-years at 75-79 years. Recent diagnostic studies include the use of PSA to estimate prostate volume and its predictive value for the long-term risk of prostate enlargement. Variability of the International Prostate Symptom Score when filled at home and in the hospital is discussed. The first-line treatment option remains medical therapy. The most prescribed alpha-blockers are terazosin, alfuzosin, and tamsulosin, which are comparable in efficacy. The efficacy of finasteride is also confirmed, especially for enlarged prostates with the possibility of volume reduction up to 30%. Interventional therapy begins when there is evidence of moderate to severe symptoms. Long term results put transurethral microwave thermotherapy in advantage over other minimally invasive modalities. Surgical treatment remains the procedure with the best results. Open prostatectomy is still indicated for severely enlarged prostates. Transurethral resection for medium-sized prostates and bladder-neck incision for small prostates also remain the best option. SUMMARY: Real life practice studies in the last few years have broadened our insight into the application of different diagnostic and treatment modalities. Since results from randomized controlled trials can not always be extrapolated to daily urological practice, real life practice studies made data available to complement data from randomized controlled trials.