The relation between shift work and chronic fatigue among educational hospital nurses in Yazd

Introduction: Shift work is one of the threatening factors on Health. The important effects of shift work can be noted chronic fatigue. This study aimed to determine the association between Shift Work and chronic Fatigue among Educational Hospital Nurses. Materials and Methods: This cross-sectional study was carried out in Educational Hospital in Yazd. Using Stratified sampling technique, 200 Nurses were selected. The data was collected by using questionnaires of Demographic and chronic Fatigue. The data was analyzed using SPSS20 software and applying chi-square and Pearson correlation coefficients. Result: 57 nurse’s man and 143 nurse’s women Participated in this study. There wasn’t a significant relation between the Gender, marital status, work experience and education level with chronic Fatigue. Because Between the age group with chronic fatigue there was a significant difference. Analysis of the results of this study showed that significant relation between Shift Work and chronic Fatigue. Conclusion: Shift work can be affected on chronic fatigue that causes the difference in constant and non-constant shifts. So, chronic fatigue in people with constant shifts less than non-constant shifts.

Optimization of Energy Consumption and Mass Transfer Parameters in a Surface Aeration Vessel

This paper reports tests on a lab-scale surface aeration vessel was equipped with a Rushton turbine to examine its performance in terms of standard aeration efficiency (SAE), mixing time, and void fraction characteristics. These characteristics were investigated by tests using variations of rotor speed, impeller immersion depth, and water level. Results showed that variation of impeller immersion depth had a greater effect on the SAE compared to variation of water level. Moreover, the SAE increased with rotor speeds up to about 150 to 200 rpm and then decreased. In addition, void fraction improved by impeller immersion depth and rotor speed enhancement; however, mixing time and power number were reduced as rotor speed increased. According to the response surface methodology statistical optimizations, optimum values for rotor speed, impeller immersion depth, and water level were 168.90 rpm, 25 mm, and 30 cm, respectively, to achieve the maximum value of SAE.

Transient and permanent hypoparathyroidism following thyroidectomy

AIM

This study was designed to identify the risk factors of transient and permanent hypoparathyroidism in patients undergoing thyroidectomy. We also studied the duration of transient hypoparathyroidism following thyroid surgery.

METHODS

A prospective study was conducted on 163 consecutive patients undergoing thyroidectomy. Serum Levels of calcium and parathyroid hormone (PTH) were determined the day before surgery and then on the 1st and 10th postoperative day to determine the postoperative course of serum PTH and calcium. Patients were followed for six months after surgery.

RESULTS

The incidence of transient and permanent hypoparathyroidism was 8.6% and 0%, respectively. Among all of variables, only the extent of surgery had a significant relationship with postoperative hypoparathyroidism (P=0.010). PTH measurement at 10th day postoperatively became normal, except in one patient in whom it continued to be low until two months.

CONCLUSION

The extent of surgery is the leading cause of postoperative hypoparathyroidism, though, in most of the patients this is a transient complication and PTH level revert to normal within 10 days after surgery.

Parametric light generation

Since its invention more than 40 years ago, the laser has become an indispensable optical tool, capable of transforming light from its naturally incoherent state to a highly coherent state in space and time. Yet, due to fundamental limitations, operation of the laser remains confined to restricted spectral and temporal regions. Nonlinear optics can overcome this limitation by allowing access to new spectral and temporal regimes through the exploitation of suitable dielectric materials in combination with the laser. In particular, optical parametric oscillators are versatile coherent light sources with unique flexibility that can provide optical radiation across an entire spectral range from the ultraviolet to the far-infrared and over all temporal scales from continuous wave to the ultrafast femtosecond domain.

Quasi-phase-matched second-harmonic generation in a GaAs/AlAs superlattice waveguide by ion-implantation-induced intermixing

We report type I second-harmonic generation by use of first-order quasi-phase matching in a GaAs/AlAs symmetric superlattice structure with femtosecond fundamental pulses at 1.55 microm. Periodic spatial modulation of the bulklike second-order susceptibility chi(zxy)(2) was achieved with quantum-well intermixing for which the group III vacancies were created by As+-ion implantation. A narrow second-harmonic bandwidth of approximately 0.9 nm (FWHM) with an average power of approximately 1.5 microW was detected, corresponding to an internal conversion efficiency of approximately 0.06%, which was considerably limited by the spectral bandwidth of the fundamental.

Compact, continuous-wave, singly resonant optical parametric oscillator based on periodically poled RbTiOAsO4 in a Nd:YVO4 laser

We describe a compact all-solid-state continuous-wave, singly resonant optical parametric oscillator (SRO) based on periodically poled RbTiOAsO4. The SRO is pumped at 1.064 microm by a Nd:YVO4 laser, which is itself pumped by a 3-W diode laser. Using the intracavity technique produced an oscillation threshold for the SRO of only 1.6 W (diode-laser power). For 3 W of diode pump power some 65 mW was obtained in the (nonresonant) idler (wavelength 3.52 microm). Temperature tuning over the range 10-100 degrees C resulted in tuning ranges of 1.52-1.54 and 3.41-3.54 microm for the signal and the idler waves, respectively. Importantly, relaxation oscillations were absent.

High-power picosecond optical parametric oscillator based on periodically poled lithium niobate

A high-power picosecond optical parametric oscillator (OPO) based on a 47-mm periodically poled lithium niobate crystal is described. More than 12 W of total average power-almost 8 W of signal power at 1.85 microm and more than 4 W of idler radiation at 2.5 microm -is simultaneously extracted from less than 18 W of average pump power. The OPO is synchronously pumped by 80-ps (FWHM) cw mode-locked pulses at 1.064 microm , and its output is tunable from 1.7 to 2.84microm . Nearly transform-limited signal pulses are obtained following the introduction of two intracavity etalons.

Efficient second-harmonic generation in birefringently phase-matched GaAs/Al(2)O(3) waveguides

We report efficient second-harmonic generation of femtosecond pulses in birefringently phase-matched GaAs/Al(2)O(3) waveguides pumped at 2.01mum. By use of pump pulses of ~200-fs duration and type I interaction, practical second-harmonic average powers of up to ~650muW were obtained, with an average input power of ~50muW. Waveguides of four different widths and two different lengths were investigated, and a normalized conversion efficiency of greater than 1000%W(-1)cm(-2) was obtained for a 1-mm waveguide. Measurements of pump and second-harmonic spectra provided clear evidence of phase matching and depletion of the pump spectrum. The measured bandwidth of the second harmonic was ~1.3nm. From the measurements of transmitted pump power at the phase-matching wavelength, pump depletions of more than 80% were recorded.

Quasi phase matching in GaAs--AlAs superlattice waveguides through bandgap tuning by use of quantum-well intermixing

We report the observation of second-harmonic generation by type I quasi phase matching in a GaAs-AlAs superlattice waveguide. Quasi phase matching was achieved through modulation of the nonlinear coefficient chi((2))(zxy), which we realized by periodically tuning the superlattice bandgap. Second-harmonic generation was demonstrated for fundamental wavelengths from 1480 to 1520 nm, from the third-order gratings with periods from 10.5 to 12.4microm . The second-harmonic signal spectra demonstrated narrowing owing to the finite bandwidth of the quasi-phase-matching grating. An average power of ~110 nW was obtained for the second harmonic by use of an average launched pump power of ?2.3mW .

Five-optical-cycle pulse generation in the mid infrared from an optical parametric oscillator based on aperiodically poled lithium niobate

We describe an optical parametric oscillator based on aperiodically poled lithium niobate that generates nearly transform-limited 53-fs duration pulses at a center wavelength of 3mum, corresponding to only 5 optical cycles. Results are presented illustrating the effect of pump- and grating-period chirp on the idler pulses, and a configuration capable of producing idler bandwidths in excess of 700 nm is discussed.

Extended mode-hop-free tuning by use of a dual-cavity, pump-enhanced optical parametric oscillator

We report extended mode-hop-free tuning in a continuous-wave, pump-enhanced optical parametric oscillator (PE-OPO). We employ a dual-cavity configuration to allow independent control of the resonant pump and signal fields, and so we can suppress frequent mode hops in the signal as the pump is tuned in frequency. With the signal field clamped in frequency by an uncoated etalon, the idler field can be scanned smoothly through a range of 10.8 GHz. The PE-OPO outputs can also be tuned coarsely from 1.01 to 1.18 mum in the signal and from 2.71 to 3.26 mum and 4.07 to 5.26 mum in the idler. We find that increased idler absorption only slightly increases the oscillation threshold.

Continuous-wave, singly-resonant, optical parametric oscillator based on periodically poled KTiOPO4

A continuous-wave singly-resonant optical parametric oscillator (SRO) has been implemented using a 20 mm long crystal of periodically poled KTiOPO 4 (PPKTP) intracavity-pumped at room temperature within a Ti:sapphire laser. The device delivers a maximum output power of 455 mW at a non-resonant idler wavelength of 2.47 microm. The 28.5-microm grating PPKTP crystal provides SRO tuning over 1.14-1.27 microm (signal) and 2.23-2.73 microm (idler) limited by optical coating bandwidths and corresponding to a pump tuning range of 805.5-811.2 nm. Temperature tuning of the device generated signal and idler ranges of 1.18-1.26 microm and 2.29-2.57 microm, respectively, corresponding to an average tuning rate of 1.2 nm/degree (signal) and 4.5 nm/degree (idler). Ring-cavity configuration of the device resulted in generation of 115 mW of single-frequency idler output at 2.35 microm.

Parametric Generation of Tunable Light from Continuous-Wave to Femtosecond Pulses

By exploiting nonlinear optical effects, a technology of unprecedented flexibility for the production of tunable coherent light has been developed. Referred to as optical parametric generation, it provides sources with spectral coverage extending all the way from the ultraviolet to the mid-infrared, and with temporal coverage extending over all time domains from the femtosecond pulse to the continuous wave. Such sources generate coherent light of outstanding optical quality and are now finding wide-ranging applications.

Simultaneous femtosecond-pulse compression and second-harmonic generation in aperiodically poled KTiOPO(4)

We report both extracavity and intracavity simultaneous second-harmonic generation and compression of pulses at 1.25 mum from a synchronously pumped RbTiOAsO(4) -based optical parametric oscillator, using an aperiodically poled crystal of KTiOPO(4) . The 290-fs input pulses were temporally compressed to 120 fs, with average output powers as great as 120 mW. The experimental results are compared with a numerical model that uses data obtained by characterization of the input pulses by use of the frequency-resolved optical gating technique.

Continuous-wave optical parametric oscillator based on periodically poled KTiOPO(4) and its application to spectroscopy

We report a continuous-wave, doubly resonant optical parametric oscillator (OPO) based on the nonlinear material periodically poled KTiOPO(4) and its application to spectroscopy. The OPO, which is pumped by a diode-pumped frequency-doubled Nd:YLF laser at 523 nm, has a low pump-power threshold of 25 mW and can deliver 10 mW of single-frequency output at 1.65 mum for a pump power of 200 mW. The idler wavelength can be temperature tuned at a rate of 0.73 nm/( degrees )C , and smooth tuning of the output frequency over ~3 GHz is achieved by smooth tuning of the pump laser. We demonstrate the practicality of the OPO by recording the absorption spectrum of methane near 1649 nm.

Low-pump-threshold continuous-wave singly resonant optical parametric oscillator

We describe a compact all-solid-state continuous-wave singly resonant optical parametric oscillator (SRO) with a minimal pump-power requirement. The SRO is based on periodically poled LiNbO(3) as the nonlinear material and is pumped by a 1-W diode-pumped Nd:YVO(4) minilaser at 1.064 microm . By exploiting the intracavity pumping technique in a 50-mm crystal, we have achieved SRO operation threshold at a diode pump power of only 310 mW.At 1 W of input diode power, the SRO delivers 70 mW of output power in the nonresonant idler at 3.66 microm , at a photon conversion efficiency of 55%. Multiparameter tuning of the SRO yields a signal wavelength range from 1.45 to 1.60 microm and an idler wavelength range from 3.16 to 4.02 microm in the mid infrared. The device is characterized by robust turnkey operation and long-term amplitude-stable performance.

Doubly resonant continuous-wave optical parametric oscillator pumped by a single-mode diode laser

The performance characteristics of a doubly (signal and idler) resonant continuous-wave optical parametric oscillator based on periodically poled lithium niobate and pumped by a 100-mW single-mode laser diode at 810 nm are reported. Pump power thresholds as low as 16 mW and wavelength tuning over the range 1.15-1.25 microm at the signal and 2.31-2.66 microm at the idler were achieved through variation of crystal temperature, pump wavelength, and grating period. Up to 5 mW of signal output was obtained with the single-mode diode pump, and signal powers of up to 39 mW were obtained when pumping with a 400-mW injection-locked broad-area diode laser.

Efficient Continuous-Wave and Q-Switched Operation of a 946-nm Nd:YAG Laser Pumped by an Injection-Locked Broad-Area Diode Laser

The efficient, low-threshold operation of a 946-nm Nd:YAG laser pumped by an injection-locked broad-area diode laser is reported. The implications of pump-beam quality for efficient, low-threshold operation, particularly with intrinsically inefficient transitions, are discussed in the context of previously published models. Results are presented showing that the M(2) = 1.3 pump beam of the injection-locked diode laser enabled a cw slope efficiency of 48% and a threshold of 52 mW to be attained. When Q-switched, 335 mW of pump power gave 27-ns, 5.2-muJ pulses. These were frequency doubled to obtain 19-ns, 1-muJ pulses at 473 nm. These results represent significant improvements over similar systems pumped by free-running broad-area diode lasers or arrays.

Continuous-wave singly resonant optical parametric oscillator based on periodically poled RbTiOAsO(4)

We report a continuous-wave optical parametric oscillator (OPO) based on periodically poled RbTiOAsO(4) (PPRTA). The singly resonant OPO, which is located within a Ti:sapphire laser, has a high-finesse signal cavity and delivers a maximum output power of 270 mW to the nonresonant idler wave at 2.92mum , through a 4.5-mm PPRTA crystal. For room-temperature operation and a crystal with a 30-mu;m grating period, pump tuning over 838-848 nm results in OPO tuning over 1.13-1.27mum (signal) and 2.53-3.26mum (idler), limited by the bandwidth of optical coatings. PPRTA exhibits thermal properties superior to those of periodically poled LiNbO(3) .

Near- to mid-infrared picosecond optical parametric oscillator based on periodically poled RbTiOAsO(4)

We describe a Ti:sapphire-pumped picosecond optical parametric oscillator based on periodically poled RbTiOAsO(4) that is broadly tunable in the near to mid infrared. A 4.5-mm single-grating crystal at room temperature in combination with pump wavelength tuning provided access to a continuous-tuning range from 3.35 to 5microm , and a pump power threshold of 90 mW was measured. Average mid-infrared output powers in excess of 100 mW and total output powers of 400 mW in ~1-ps pulses were obtained at 33% extraction efficiency.

Broadly tunable infrared femtosecond optical parametric oscillator based on periodically poled RbTiOAsO(4)

We present results from what we believe is the first reported example of an optical parametric oscillator based on periodically poled RbTiOAsO(4). The oscillator is pumped by a femtosecond self-mode-locked Ti:sapphire laser and, with a single-grating 2-mm-long crystal and one mirror set, a combination of pump and cavity-length tuning provided wavelength coverage from 1060 to 1225nm (signal) and 2.67 to 4.5 microm (idler). Average output powers were as much as 120mW in the signal and 105mW in the idler and interferometric autocorrelations recorded at signal and idler wavelengths of 1.1 and 3.26 microm, respectively, imply pulse durations of 125 and 115fs, respectively.

Compact, efficient 344-MHz repetition-rate femtosecond optical parametric oscillator

We describe configurations of a novel synchronously pumped femtosecond optical parametric oscillator based on the crystal RbTiOAsO(4) and operating with a signal-pulse-repetition frequency as high as 344 MHz. Average signal powers as high as 600 mW and pulse durations of 78 fs are demonstrated at a wavelength of 1.25 microm, and a characterization of the signal output using frequency-resolved optical gating implies asymmetric near-sech(2)(t) intensity-profile pulses with significant amounts of spectral cubic phase.

Continuous-wave, singly resonant, intracavity parametric oscillator

Performance characteristics of a continuous-wave intracavity optical parametric oscillator are described by use of an experimental arrangement comprising a KTP singly resonant oscillator located within a Ti:sapphire laser cavity and analyzed by use of a steady-state model. Internal and external powers, circulating fields, tuning ranges, spectral bandwidths, and amplitude-stability levels are measured and discussed. The nonresonant idler tunes from 2.53 to 2.87 microm, delivers a maximum output power of approximately 0.4W and displays long-term amplitude-stable operation. The total downconverted power approaches the optimum power coupled out of the Ti:sapphire laser in the absence of frequency conversion.

High-power, high-repetition-rate picosecond optical parametric oscillator tunable in the visible

We describe an intracavity frequency-doubled high repetition-rate picosecond optical parametric oscillator for the visible based solely on the nonlinear crystal LiB(3)O(5) and synchronously pumped by a self-mode-locked Ti:sapphire laser. Under temperature-tuned noncritical type I and type II phase matching, average visible output powers of 320 mW have been generated at an 81-MHz repetition rate. With the available mirror set, continuous tuning from 584 to 771 nm is demonstrated for a range of phase-matching temperatures. Transform-limited pulses with durations of 840-880 fs have been obtained across the visible range for pump pulse durations of 1-1.2 ps.

High-power, high-repetition-rate picosecond optical parametric oscillator for the near- to mid-infrared

A high-repetition-rate, singly resonant optical parametric oscillator based on KTiOAsO(4) and synchronously pumped by a self-mode-locked Ti:sapphire laser is reported. Under the conditions of pump-tuned noncritical type II phase matching, average near-infrared output powers of 403 mW have been generated at a repetition rate of 81 MHz. With the available mirror set, signal tuning over 1.116-1.281 microm and idler tuning over 2.260-3.160 microm are demonstrated for a range of pump wavelengths. Without dispersion compensation, signal (idler) pulses with durations of 1.01-1.03 (1.61-2.91) ps have been obtained for 1.2-ps input pump pulses.

Picosecond Ti:sapphire-pumped optical parametric oscillator based on LiB(3)O(5)

We report a high-repetition-rate, singly resonant optical parametric oscillator based on the nonlinear crystal LiB(3)O(5), which is synchronously pumped by a continuous train of picosecond pulses from a self-mode-locked Ti:sapphire laser. Under temperature-tuned noncritical type I phase matching, total average near-infrared output powers of 90 mW at a repetition rate of 81 MHz have been generated over a signal (idler) tuning range of 1.374-1.530 microm (1.676-1.828 microm). Without dispersion compensation, transform-limited signal pulses with durations of 520-780 fs have been obtained at 1.2 times threshold for 1.8-ps input pump pulses.

Noncritically phase-matched Ti:sapphire-pumped femtosecond optical parametric oscillator based on RbTiOAsO(4)

The operation of a Ti:sapphire-laser-pumped femtosecond optical parametric oscillator based on the new nonlinear material RbTiOAsO(4) is described. Oscillation has been observed for pump powers as low as 50 mW, and output powers as high as 185 mW have been measured. With intracavity prisms for dispersion compensation, transformlimited pulses of less than 70-fs duration have been produced. Under noncritical phase matching, a signal (idler) tuning range over 110 nm (330 nm) is demonstrated with pump tuning.

Soliton formation in a femtosecond optical parametric oscillator

We report evidence for soliton formation in a Ti:sapphire-laser-pumped femtosecond optical parametric oscillator. Appropriate conditions of dispersion are discussed, and temporal and spectral measurements of the output pulses are presented. Quantitative agreement with existing theory is implied.

Singly resonant, all-solid-state, mode-locked LiB(3)O(5) optical parametric oscillator tunable from 652 nm to 2.65 microm

We describe a singly resonant mode-locked optical parametric oscillator that is based on temperature-tuned LiB(3)O(5) and synchronously pumped by a frequency-doubled, mode-locked, Q-switched, diode-laser-pumped Nd:YLF laser at 523.5 nm. The oscillator is broadly tunable throughout the range of 652 nm to 2.65 microm and can simultaneously generate two pairs of signal and idler beams, leading to four-color operation of the device over an extensive wavelength range from ~664 nm to 2.47 microm. Oscillation thresholds of ~2.5 GW/cm(2) and internal pump depletions of ~20% have been measured.

Picosecond infrared optical parametric generation in KTP using a diode-laser-pumped solid-state laser

We report the generation of tunable picosecond pulses in the near infrared by synchronous pumping of an optical parametric oscillator based on the crystal KTP with a frequency-doubled, actively mode-locked, Q-switched, diode-laser-pumped Nd:YLF laser at 523.5 nm. The oscillator provides tunable radiation over the ranges of 0.946-1.020 microm and 1.075-1.172 microm in pulses of ~8-ps duration, with average output powers approaching 2 mW, at a 500-Hz repetition rate. The threshold Q-switched pulse energy was 4 microJ, and pump depletions as high as 56% were observed when pumping 5.5 times above threshold. At this pumping intensity the amplitude stability of the optical parametric oscillator output pulses was +/-2%.

Efficient ultraviolet LiB(3)O(5) optical parametric oscillator

We report what is to our knowledge the first optical parametric oscillator (OPO) generating coherent laser radiation with high optical-to-optical conversion efficiency in the near ultraviolet. The OPO, pumped at 307.8 nm by a pulsed injection-seeded XeCl excimer laser, employs a crystal of LiB(3)O(5) in a noncritical phase-matching geometry to generate tunable output over the range 381-387 nm in the near ultraviolet and 1.5-1.6 microm in the near infrared. We report internal energy conversion efficiencies as high as 28% for the signal wave at 385.5 nm and 7% for the idler wave at 1.53 microm, leading to a total internal conversion efficiency of 35%. Studies of oscillation threshold, external and internal conversion efficiency, spectral linewidth, and temporal variation of output pulses are also reported. Temperature tuning of the LiB(3)O(5) OPO under the noncritical phase-matching condition is demonstrated for the first time to our knowledge.

Highly efficient visible urea optical parametric oscillator pumped by a XeCl excimer laser

We report the successful operation of a visible optical parametric oscillator (OPO) that uses urea as the nonlinear medium and is pumped in the near field of an injection-seeded pulsed XeCl excimer laser operating at 308 nm. The OPO can generate continuously tunable radiation from 537 to 720 nm with a single set of dichroic mirrors, and conversion efficiencies as high as 37% have been achieved in a 15-mm-long crystal at 90 degrees phase matching. The influence of crystal double refraction (and hence beam walk-off) on the conversion efficiency across the OPO tuning range is discussed, and some oscillator parameters, including spectral linewidth and temporal behavior, are characterized.