bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth Hormone Deficiency and Excess Alter the Gut Microbiome in Adult Male Mice
Authors: Jensen Elizabeth A , Young Jonathan A , Jackson Zachary , Busken Joshua , List Edward O , Carroll Ronan K , Kopchick John J , Murphy Erin R , Berryman Darlene E
Published: February 2020

The gut microbiome has been implicated in host metabolism, endocrinology, and pathophysiology. Furthermore, several studies have shown that gut bacteria impact host growth, partially mediated through the growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis. Yet, no study to date has examined the specific role of GH on the gut microbiome. Our study thus characterized the adult gut microbial profile and intestinal phenotype in GH gene-disrupted (GH-/-) mice (a model of GH deficiency) and bovine GH transgenic (bGH) mice (a model of chronic, excess GH action) at 6 months of age. Both the GH-/- and bGH mice had altered microbial signatures, in opposing directions at the phylum and genus levels. For example, GH-/- mice had significantly reduced abundance in the Proteobacteria, Campylobacterota, and Actinobacteria phyla, whereas bGH mice exhibited a trending increase in those phyla compared with respective controls. Analysis of maturity of the microbial community demonstrated that lack of GH results in a significantly more immature microbiome while excess GH increases microbial maturity. Several common bacterial genera were shared, although in opposing directions, between the 2 mouse lines (e.g., decreased in GH-/- mice and increased in bGH mice), suggesting an association with GH. Similarly, metabolic pathways like acetate, butyrate, heme B, and folate biosynthesis were predicted to be impacted by GH. This study is the first to characterize the gut microbiome in mouse lines with altered GH action and indicates that GH may play a role in the growth of certain microbiota thus impacting microbial maturation and metabolic function.
Bis-Indole–Derived Nuclear Receptor 4A1 (NR4A1, Nur77) Ligands as Inhibitors of Endometriosis
Authors: Mohankumar Kumaravel , Li Xi , Sung Nuri , Cho Yeon Jean , Han Sang Jun , Safe Stephen
Published: February 2020

Endometriosis is an inflammatory disease that primarily affects women during their reproductive years, and since current hormonal therapies are of concern, new hormone-independent treatment regimens are needed. The orphan nuclear receptor 4A1 (NR4A1, Nur77) is expressed in patient-derived (stromal) endometriotic cells and also epithelial cell lines, and we observed that knockdown of NR4A1 in patient-derived ectopic endometrium-isolated ovarian endometrioma (ESECT)-7 and ESECT-40 cells decreased cell proliferation and induced apoptosis. Moreover, the treatment of these cells with bis-indole derived NR4A1 ligands 1,1-bis(3’-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH) and its buttressed 3-chloro-5-methoxy analog (DIM-C-pPhOH-3-Cl-5-OCH3) inhibited cell growth and induced apoptosis and related genes. The compounds exhibit NR4A1 antagonist activities in both functional and transactivation assays whereas these effects were not observed in normal endometrial cells. We also observed that NR4A1 knockdown and treatment with NR4A1 antagonists decreased fibrosis, α-smooth muscle actin, and related pro-fibrotic genes in ESECT-7 and ESECT-40 cells, and similar results were observed in epithelial-derived endometriotic cell lines. Moreover, in an endometriosis mouse model with auto-transplantation and also in severe combined immune deficiency mice transplanted with human endometriotic cells treatment with 25 mg/kg/day DIM-C-pPhOH-3-Cl-5-OCH3 significantly inhibited growth and expansion of endometriotic lesions. Thus, bis-indole–derived NR4A1 ligands represent a novel class of drugs as nonhormonal therapy for endometriosis.
Physiological Responses of Female Load Carriage Improves after 10 Weeks of Training
Authors: WILLS JODIE A. , DRAIN JACE , FULLER JOEL T. , DOYLE TIM L. A.
Published: February 2020

Purpose

This study aimed to characterize and evaluate female-specific physiological and perceptual responses during a load carriage walking task before and after a 10-wk physical training program.

Methods

Eleven recreationally active women (age, 21.5 ± 2.2 yr; stature, 1.66 ± 0.8 m; body mass, 64.4 ± 6.8 kg) completed a load carriage task (5 km at 5.5 km·h−1, wearing a 23-kg torso-borne vest) before and after a 10-wk physical training program. Physiological (i.e., maximal oxygen uptake, carbon dioxide production, respiratory exchange ratio (RER), breathing frequency, and pulmonary ventilation) and perceptual (i.e., rating of perceived exertion [RPE]) responses were collected during the load carriage task. Additional physical performance measures (i.e., push-ups, sit-ups, beep test, and isometric midthigh pull) were collected in a separate session before and after the 10-wk of training.

Results

Compared with before training, maximal oxygen uptake requirements reduced during the load carriage task (P < 0.05), whereas heart rate and RPE remained similar. RER reductions over the 5-km march indicated a shift toward fat utilization, with other physiological responses demonstrating an increased ability to sustain the metabolic demands of the load carriage task. Increases in push-up and isometric midthigh pull performance demonstrated improvements in upper-body muscular endurance and lower-body strength after the 10-wk training program (P < 0.05).

Conclusions

During a standardized load carriage task, physiological and perceptual responses indicated physical adaptations to specific training in women. Although positive physiological responses were elicited, additional strategies (i.e., cognitive resilience training, female-specific vest design to reduce pain burden) to build load carriage task-specific resilience (perceptual responses) may be required.
The Prevalence of Expiratory Flow Limitation in Youth Elite Male Cyclists
Authors: COX KATHERINE R. , SMITH JOSHUA R. , LUDEN NICHOLAS D. , SAUNDERS MICHAEL J. , KURTI STEPHANIE P.
Published: February 2020

The present investigation tested the hypotheses that there would be greater prevalence of expiratory flow limitation (EFL) in endurance-trained (ET) youth cyclists compared with a recreationally active control (CON) group.

METHODS

Twelve ET youth male cyclists (16.3 ± 1.0 yr (13–18 yr), 176.5 ± 6.2 cm, 64.2 ± 5.9 kg) and 12 CON subjects (17.6 ± 2.2 yr (13–18 yr), 177.9 ± 7.1 cm, 74.8 ± 11.2 kg) completed an incremental exercise test to determine peak oxygen consumption (V˙O2peak) on a cycle ergometer. Maximal flow volume loops (MFVL), forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC, forced expiratory flow between 25% and 75% of FVC, and peak expiratory flow were assessed before and after exercise, with inspiratory capacity maneuvers and dyspnea ratings measured in the last 20 s of each stage. EFL was quantified as the percentage of the expiratory tidal volume that overlapped with the maximal flow volume loop.

RESULTS

V˙O2peak, dyspnea ratings at peak, and ventilation were higher in the ET compared with CON group (P < 0.05). The ET group experienced greater EFL prevalence at V˙O2peak, with 11 of 12 subjects exhibiting EFL compared with 5 of 12 subjects in the CON group (P = 0.014). When matched for absolute ventilation of 20, 40, 60, 80, and 100 L·min−1, there were no differences in EFL severity between the ET and CON groups (P = 0.473).

CONCLUSIONS

Elite youth male cyclists have a greater prevalence of EFL at maximal exercise than do CON subjects who are similar in age, height, and lung size. Future research should determine whether EFL in youth ET male cyclists may limit their exercise performance.
Voluntary Activation and Reflex Responses after Hamstring Strain Injury
Authors: BUHMANN ROBERT , TRAJANO GABRIEL S. , KERR GRAHAM , SHIELD ANTHONY
Published: February 2020

Introduction

There is a lack of definitive evidence supporting deficits in voluntary activation in participants with prior hamstring injury; moreover, it remains unknown if spinal mechanisms contribute to suspected deficits.

Purpose

This study aimed to determine the effect of prior hamstring strain injury on knee flexor concentric and eccentric strength, voluntary activation, surface electromyographic (sEMG) activity, and stretch and tendon reflex amplitudes.

Methods

Twenty-five participants were recruited, 12 with a history of unilateral hamstring strain injury of at least moderate severity. Voluntary activation, strength, and sEMG activity were recorded during maximal eccentric and concentric knee flexor contractions at 60°·s−1. Stretch and tendon reflexes were also recorded at rest.

Results

Previously injured limbs exhibited lower levels of voluntary activation (mean difference = −24.1%, 95% confidence interval [CI] = −34.1% to −14.0%, P < 0.001), strength (mean difference vs control group = −0.37 Nm·kg−1, 95% CI = −0.71% to −0.03 N·m·kg−1, P = 0.03), and normalized sEMG (mean difference = −17%, 95% CI = −32% to −2%, P = 0.02) during maximal eccentric knee flexor contractions compared with control group. No such differences were seen in concentric contractions. Stretch reflexes (mean difference = −3.8%, 95% CI = −6.8 to −0.8, P = 0.02) and tendon reflexes (mean difference = −13%, 95% CI = −26% to 0%, P = 0.04) were also lower in previously injured compared with control biceps femoris muscles.

Conclusion

Moderate to severe hamstring strain injury is associated with long-term deficits in voluntary activation during maximal eccentric contraction. Hamstring injury history is also associated with deficits in stretch reflex and tendon reflex amplitude.
SNR-Based Early Warning Message Scheme for VANETs
Authors: Obaidat Muath , Shahwan Ihsasn , Hassebo Ahmed , Obeidat Suhaib , Ali Mohamed , Khodjaeva Matluba
Published: February 2020

A Vehicular Ad hoc Network (VANET) is a special type of Mobile Ad hoc Network (MANET). One of the main applications of VANETs is safety. This is accomplished by disseminating an Early Warning Message (EWM) to all vehicles in an emergency zone. However, broadcasting an EWM in a multihop environment, such as a VANET, introduces many challenges. The main challenge is the broadcast storm problem. In this paper, we propose a novel broadcasting communication scheme for VANETs. During an emergency situation a congested scenario is possible when vehicle density on the road is high. This causes contention at the MAC layer, which leads to collisions and increases the number of rebroadcasts, hence reducing packet dissemination, increasing delay and network resource use. Our proposed communication scheme is an SNR-based dynamic suppression scheme that aims to significantly reduce the effects of the broadcast storm problem by minimizing the number of rebroadcasting vehicles. The proposed scheme achieves this by considering the physical layer characteristics and the number of times a vehicle receives an EWM. Moreover, we correlate vehicle density and suppression range through a formula to determine the effective suppression range. The proposed scheme maintains network connectivity and achieves almost 100% reachability to all vehicles throughout the zone. Furthermore, the proposed scheme minimizes delay by 0.4 sec in high density scenarios.
Integrated vortex beam emitter device for optical manipulation
Authors: Cicek Kenan , Kocyigit Adem , Topkaya Ramazan , Cai Xinlun
Published: February 2020

In this study, we provide a theoretical overview for the potential of the integrated vortex beam emitter (IVBE) in optical tweezer applications. To the best of our knowledge, this is the first attempt in the literature to investigate the optical tweezing property of IVBE. The finite-difference time-domain numerical analysis technique has been utilized for the transverse optical trapping calculations. The results show that the basic IVBE device generates an optical force of an order of

10

−
16

N

, which can be increased up to

10

−
15

N

with the duty cycle adjustment. Therefore, this work emphasizes that the IVBE device can provide a compact, efficient, low-cost, and practical optical tweezing ability.
Modular CO2 TEA laser
Authors: Willenbring G. R. , Benser E. T. , Mocker H. W.
Published: February 2020

Two sealed-off CO2 TEA lasers have been developed for military applications. A basic double-discharge device has a pulsed energy output of 300-400 mj/pulse which is aimed at range finder and designator applications. A folded resonator configuration uses two pairs of transverse electrodes and achieves a double-pulse capability with variable pulse separation for crosswind sensing applications.
Moving target imaging radar utilizing both intensity and velocity information
Authors: Biron David G. , Edwards Brian E.
Published: February 2020

Continuous-wave CO2 laser radars have generally been considered for the task of detecting moving targets (MTI).1 After acquiring a target the object could then be imaged by a pulsed-ranging laser radar. However, it is also possible to image the target in Doppler space with a cw laser. A high-resolution velocity image contains a great deal of information useful for target classification. The advantage over conventional imaging systems is the ability to reject stationary background clutter.
Compositional study of a coal surface using a laser microprobe mass detector
Authors: Dutta P. K. , Talmi Y.
Published: February 2020

Laser-induced mass spectrometry offers unique opportunities for studying mass spectra of a nonvolatile sample.1 Molecular and structural information can be obtained from the mass spectra of molecules in the range of 1000 amu.2 Since the coherent beam of the laser can be focused down to very small areas (a few micrometers), opportunities for microprobe analysis also exist.3
Laser double-resonance determination of rapid vibrational and rotational energy transfer rates in carbon dioxide
Authors: Thomason M. D. , Feldman B. J.
Published: February 2020

Rates for resonant vibrational and rotational energy transfer from the 001 state by CO2 + CO2 collisions have been measured. All data were obtained by double-resonance spectroscopy with CO2 lasers in a 2.5-m absorption cell at 700 K. Results for rotation transfer include pumped-level relaxation and the response of other 001 levels with ΔJ up to 18. These data are compared with four relevant collision models via a 35-level rate equation analysis.
Brillouin backscatter from gas Jet targets illuminated by a multiline laser source
Authors: Busch George E. , Maynard Robert L.
Published: February 2020

As laser fusion experiments progress toward longer laser pulses and larger targets, it is expected that Brillouin backscatter of the laser radiation could become a major loss mechanism that could reduce coupling of radiation to targets. The increased backscatter results from the longer plasma density scale lengths that have time to develop with long pulses. Longer scale lengths mean longer gain paths for Brillouin reflection.
Laser separations: do they make sense?
Authors: Hartford Al
Published: February 2020

No summary was available when this Digest went to press.
Laser processes for separation of rare earths and related elements
Authors: Donohue Terence
Published: February 2020

Selective photochemistry is indeed possible in the liquid phase and has been used in the separation of a growing number of elements, particularly the transition metals, the rare earths, and the actinides.1 Selectivity in a photochemical separation process can be obtained in either of two basic methods. One process employs the differences in the absorption spectra of a mixture of elements, where the spectral selectivity must be preserved chemically following the initial photochemical event.
Accurate energy determination of bound J = 0 and two 5sns and 5snd Rydberg states of Sr
Authors: Beigang R. , Lucke K. , Timmermann A. , Frolich D.
Published: February 2020

Extensive investigations of high Rydberg states of alkaline earth elements have been carried out in recent years using tunabe pulsed dye lasers. The primary aim of these investigations was the accurate determination of the level energies. The data were then analyzed and interpreted using multichannel quantum defect theory. However, due to the laser linewidth and Doppler-limited spectroscopic conditions, the experimental accuracy of these measurements was limited to typically ±0.1 cm−1. In addition, the accuracy was dependent on the availability of known reference transitions necessary to calibrate the spectra.
One-side lattice-matched PbSnTe lasers with high output power
Authors: Shinohara Koji , Nishijima Yoshito , Akamatsu Takeshi
Published: February 2020

Lead-tin-telluride tunable diode lasers have found various applications. The lack of reliability, which was a serious problem, has been overcome.1,2 The remaining problem is to increase the power output for applications in isotope separation or heterodyne detection systems.
Quality of phase-conjugation in nondegenerate four-wave mixing
Authors: Garrett M. H. , Hoffman H. J. , Karr T. J.
Published: February 2020

One more promising application of the four-wave mixing process is the correction of arbitrary phase aberrations in an optical beam. In such applications, the fidelity as well as the efficiency of the phase-conjugation process needs to be considered in practice. The process which has received the most extensive attention to date is degenerate four-wave mixing (DFWM). The nonlinear interaction in this case is known to result in a perfect phase-conjugate provided high-quality pump beams are available and competing effects such as local self-focusing (or defocusing) can be neglected.
Scaling law of a laser time-of-flight velocimeter
Authors: She C. Y. , Kelley R. F. , Hsu L. S. , Shimizu H.
Published: February 2020

During the past decade, a variety of laser techniques has been proposed and experimentally demonstrated for atmospheric wind speed measurements1 with a varied degree of success and practical usefulness. In most cases an investigator proposed a technique of laser velocimetry and/or reported a successful atmospheric wind-speed measurement at a convenient range without discussing the time required for such a measurement or the dependence of the measurement rate on laser power and aerosol condition.
Analysis of eye diagram phase jitter caused by coma in the optical disk
Authors: Kubota Shigeo
Published: February 2020

In the compact disk digital audio (CDDA) system proposed by Sony and Philips, a 2-Mbit/sec data stream consisting of audio and parity words is converted into a special channel bit stream of 4.3218 Mbit/sec.1 In this modulation scheme, the minimum and maximum run lengths are 3- and 11-bit cells, respectively, and the window length is a 1-bit cell. Given a typical scanning velocity of 1.25 m/sec, the minimum run length corresponds to 0.87 μm along the scanning direction on a disk.
Experimental investigation of aperture limitations of a heterodyne CO2 laser radar by atmospheric turbulence and rain
Authors: Barthel K.
Published: February 2020

Atmospheric optical effects limit the design of coherent CO2 laser radar systems, in particular the size of the receiver aperture. To study the effects of turbulence and of precipitation on such systems, a setup was implemented with which amplitude and relative phase fluctuations measured at two points of variable distance could be determined. Using the setup the crosswind velocity also could be deduced. Figure 1 shows the experimental setup with the two small subapertures.
Picosecond measurements of spontaneous and stimulated emission from injection lasers
Authors: Damen T. C. , Duguay M. A.
Published: February 2020

We report picosecond measurements of spontaneous and stimulated emission from injection lasers gain-switched by 90-psec electrical pulses. When the laser is operated below threshold, the time profile of the spontaneous emission (or luminescence) gives directly the carrier concentration as a function of time. Precise knowledge of the latter is essential to understanding the dynamics of laser pulse formation and the limits to high-frequency modulation.
Surface plasmon-enhanced electric current generation in metals by picosecond laser pulses
Authors: Mok Walter Y.
Published: February 2020

By using a train of picosecond pulses from a mode-locked Nd glass laser, we have measured electrical current generated on the surface of the thin films of noble metals. Normally the noble metals have very high reflectivity. To enhance the absorption, the surface plasma waves at 1.06 µm were excited at the metal-air interface by the method of attenuated total reflection. The sample signals are calibrated against the optical rectification in KDP. By varying the laser Intensity, we discovered that the sample current varies linearly with the optical rectification in KDP. This indicates that the signal is E2 dependent.
Fiber Intensity discriminator tor optical pulses
Authors: Stolen R. H. , Mollenauer L. F. , Ashkin A. , Botineau J.
Published: February 2020

A birefringent optical fiber can be used to make an intensity discriminator for optical pulses. Such a discriminator would be particularly useful for separating the intense subpicosecond pulses formed by solitonlike compression from the weaker uncompressed background. Compression of 6.5-psec pulses at a wavelength of 1.55 µm by a factor of 5 has been reported,1 and compressions to ~300 fsec have recently been observed.2 Typically, about half of the initial power appears in the compressed pulse and half in the background. The discriminator works because the state of polarization out of the fiber can be intensity dependent permitting separation of the pulse and background with wave plates and a polarizer.
Measurement of oxygen temperature fluctuations by laser-induced fluorescence
Authors: Massey Gail A.
Published: February 2020

This paper describes a noninvasive optical method for measuring temperature and density fluctuations in turbulent airflow in a wind tunnel. In this approach we use an ArF excimer laser tuned to one of the Schumann-Runge absorption lines of O2 near 193 nm. The absorbed photons produce transitions between the lowest vibrational level of the ground state

(

X
3

∑

g
−

)

and the fourth vibrational level (v′ = 4) of the excited state. The rotational sublevels of the excited state rapidly assume a thermal population distribution. Some of the excited molecules decay radiatively back to various levels of the X state, producing the fluorescence band spectrum shown in Fig. 1. The intensities and wavelengths in the figure were computed from published spectroscopic constants. Generally the fluorescence extends from ~220 nm to the visible, with most of the energy in the 220-250-nm range.
Applications of Raman scattering probes to turbulent diffusion flames
Authors: Drake Michael C. , Pitz Robert W. , Lapp Marshall , Penney C. Murray
Published: February 2020

Structural aspects of H2-air turbulent jet diffusion flames (consisting of a central jet of fuel surrounded by a co-flowing stream of air) have been measured by pulsed Raman spectroscopy. This experimental technique is particularly useful for laboratory-scale turbulent combustion studies of hydrogen flames because it provides simultaneous time-resolved (~2 µsec) and space-resolved (~0.1-mm3) measurements of temperature and all major flame species (H2O2,N2,H2O) simultaneously, without appreciably perturbing the flame.
Helical-flow CO2 laser
Authors: Yessik M. , Macken J. A.
Published: February 2020

A CO2 laser based on a helical gas-flow design has been developed. This design results in higher beam quality and greater discharge stability and operates at much lower gas-flow rates than other convection-cooled CO2 lasers.
Transfer efficiencies in guided-wave electrooptic filters mode converters
Authors: Lotspeich James F.
Published: February 2020

This paper examines the effects of a spatially nonuniform electric field in guided-wave electrooptic filters, illustrating specific and distinct ways in which this nonuniformity influences the transfer efficiencies of these important components. Experimental data are presented to support the analysis.
Grating arrays tar integrated optics applications
Authors: Kenan R. P. , Verber Carl M. , Busch J. R.
Published: February 2020

Electrooptic gratings have been used in integrated optics to form deflectors, modulators, and switches by a number of researchers. Recently we demonstrated a correlator based on an array of such individually addressable elements in conjunction with a modulated surface acoustic wave (SAW).1 The device performed as predicted by theory, generating the correlation of two 32-bit binary words at a data rate of 17.5 Mbit/sec.
Second harmonic emission and ponderomotive force in laser-created plasma
Authors: Schwarzenbach A. P. , Balmer J. E. , Ladrach P. , Weber H. P.
Published: February 2020

The absorption of laser radiation by inhomogeneous plasma is of considerable interest in laser fusion research. One process strongly affecting the absorption efficiency is density profile modification due to ponderomotive or radiation pressure at critical density, where most of the absorption occurs.
Infrared picosecond pulse generation with synchronously pumped color-center lasers
Authors: Mollenauer L. F.
Published: February 2020

The generation and application of IR picosecond pulses with synchronously pumped color-center lasers are discussed. Long-term stable operation of a mode-locked
T
l
∘(1) color-center laser in KCI with a pulse width of 9/sec and 1.5-µm wavelength has recently been achieved.
K-line x-ray measurements to determine deposition of hot electrons in inertial confinement fusion targets
Authors: Mitchell Kenneth B. , Grosso John S.
Published: February 2020

The deposition of hot electrons is critical to the performance and preheat of inertial confinement fusion pellets. Electron deposition can be characterized from Kα x-ray measurements in composite or layered targets. In this technique, the front or outer layer is an electron attenuator of known thickness. It is followed by a substrate of different material used as a Kα emitting electron detector. An electron attenuation curve is obtained by observing the detector layer signal as a function of the attenuator layer thickness. The energy distribution of hot electrons in the target is obtained from fitting a simulated electron distribution to the electron attenuation curve.
System and technology trade offs for all-weather atmospheric optical communications
Authors: Titterton Paul J. , Stalla L. S.
Published: February 2020

We have developed system analysis tools which describe the performance of optical communication links which must operate through the atmosphere {and, in some cases, the ocean) in all weather conditions.
Multiphoton processes in molecules: ionization vs fragmentation
Authors: El-Sayed M. A.
Published: February 2020

No abstract available
Lasers in synthetic organic chemistry
Authors: Malatesta V.
Published: February 2020

The use of excimer UV lasers in the photolysis of 7-dehydrocholesterol (provitamin D) allows considerable improvement of the final yield of vitamin D.
San Francisco Laser Center; an NSF regional laser lending facility
Authors: Kung A. H. , Bittenson S. N.
Published: February 2020

The San Francisco Laser Center operates on a lending-library concept in which the Center stocks and maintains state-of-the-art commercial lasers.
Optooptical modulator with liquid crystals
Authors: Martin-Pereda J. A. , Lopez F. J.
Published: February 2020

Liquid crystals have been employed in nonlinear optical devices during the last few years. Effects such as optically induced molecular reorientation, third-order nonlinear optical processes, and degenerate four-wave mixing have been recently reported.
Experimental investigations of injection locking
Authors: Dunn Robert W. , Hendow Sami T. , Small James G.
Published: February 2020

In this paper experimental results are presented that specify the parameters needed to injection lock lasers. This paper is the experimental companion to the theoretical paper, "Theory of an injection locked laser," (WC7).
Multiple-discharge excitation of CO2 lasers
Authors: Harry J. E. , Saleh S. N.
Published: February 2020

Stable electric discharges do not normally exist simultaneously in close proximity to each other.
High-power high-prf TEA CO2 lasers using H2 buffered gas mixtures
Authors: Dyer Peter E. , Tait B. L.
Published: February 2020

Compact TEA CO2 lasers with high peak power and average power are required for a number of applications, e.g., ranging, tracking, and remote monitoring of pollutants.
Laser-enhanced plating and etching from aqueous solutions
Authors: Von Gutfeld Robert J.
Published: February 2020

We have developed an experimental plating and etching technique using a focused laser to write patterns by means of enhanced local plating (etching) at the point of laser absorption on a cathode (anode).1,2 Experiments used premetallized glass slides as substrates, the metallization serving as an equipotential surface. The following different kinds of laser-enhanced plating and etching have been demonstrated with rates as high as 10 μm/sec for incident power densities in the 104-106-W/cm2 range:
Ultraviolet laser deposition at low temperature of silicon oxide and silicon nitride
Authors: Roche G. A. , Boyer P. K. , Collins G. J.
Published: February 2020

We have demonstrated rapid (50-Å/sec) photochemical deposition of oxides and nitrides of silicon from gas-phase donor molecules. Both a pulsed ArF laser (193 nm) and a cw Ar II laser (360 nm) were used. The films were grown on silicon wafers contained in a low-pressure flowing cell with a heated substrate. The incident laser beam angle was varied from parallel to normal with respect to the substrate surface.
Novette: a high-power short-wavelength laser fusion facility
Authors: Speck D. R. , Hunt J. T. , Manes K. R. , Suski G. J.
Published: February 2020

The Novette Laser Fusion Facility, presently under construction at Lawrence Livermore National Laboratory, is a two-beam irradiation facility whose on-target laser energy at 0.53 μm will exceed 10 kJ in pulse lengths of 1.0-5.0 nsec. Its construction was motivated by recent experiments at much lower energy, which confirm more efficient coupling of laser energy to fusion targets at short wavelength. These results indicate the immediate need for a high-energy facility to perform experiments at short wavelength to compare with data previously obtained at 1.06 μm.
Error rate testing of optical data disks
Authors: Shepherd Paul , Capote Miguel , Scheinert Philip
Published: February 2020

In recent years a great number of claims have been made on the bit error rate (BER) requirements and performance specifications of optical data disks. Two major factors are often overlooked. First, the already well-established computer data storage industry cannot accept data reliability which does not meet its minimal standards. Generally accepted are uncorrectable error rates of 10−12. Second, this data reliability performance must be determined at the end of the data's useful life, not when the disk is new. This implies that either test disks are observed over a long period of time or that an acceptable method for accelerating data degradation is used.
Scalar diffraction theory calculations for digital optical recording
Authors: Lou David Y.
Published: February 2020

The theoretical aspects of the playback of an optical videodisk have been extensively investigated by Hopkins1 and others on the basis of scalar diffraction theory. In this paper we describe the results of similar theoretical calculations from the perspective of digital optical recording. It is shown that because of the interference between different diffraction orders in the laser beam readout process, the mapping between the length of the recorded hole on the disk and the pulse length of the recovered electrical signal is highly nonlinear.
Generation and amplification of 70 fsec using a frequency-doubled Nd:YAG pumping source
Authors: Ii Theodore Sizer , Kafka James D. , Mourou Gerard
Published: February 2020

Recently we reported on the generation and amplification of short dye laser pulses pumped by the frequency-doubled output of a cw mode-locked Nd:YAG laser. The advantages of this pumping source over others include a shorter pump pulse, increased component lifetime, and the relative lase of short pulse amplification. Pulses as short as 70 fsec are presently generated by use of a rhodamine 6G-DQOCI dye mixture and are readily amplified.
Amplification of femtosecond optical pulses
Authors: Fork R. L. , Shank C. V. , Yen R.
Published: February 2020

We have previously described the generation of optical pulses as short as 90 fsec by passive mode-locking in the colliding pulse ring configuration.1 In this paper we describe a method of amplifying these pulses to gigawatt power levels while retaining or reducing the short temporal duration of the original pulse. Such intense short optical pulses provide access to a wide variety of nonlinear optical phenomena with a degree of time resolution not previously available.
Spontaneous surface ripples on semiconductors under picosecond laser illumination
Authors: Fauchet P. M. , Siegman A. E.
Published: February 2020

We find that single-picosecond pulses from an actively mode-locked Nd:YAG laser (TEM00 pulses, 100-psec duration at 1.06 μm, 80 psec at 532 nm, amplitude Jitter ~5%) can produce spontaneous periodic surface ripples1’2 as well as laser annealing in both crystalline and ion-implanted silicon and gallium arsenide. Single- and multiple-pulse annealing thresholds for both amorphous-to-polycrystal and amorphous-to-single-crystal transitions have been accurately measured. The distinct surface ripples appearing in an intermediate range of intensities have also been studied (Fig. 1).
Antireflective surfaces for high-energy laser optics formed by neutral-solution processing
Authors: Cook L. M. , Lowdermilk W. H. , Milam D. , Swain J. E.
Published: February 2020

We have produced antireflection (AR) surfaces on borosilicate optical glass by controlled corrosion in nearly neutral solutions and studied their resistance to laser-induced damage. The neutral-solution process reduced surface reflectivity from 4 to below 0.1 % at a wavelength determined by duration of the treatment. This process has been successfully applied to BK-7 and similar borosilicate glasses which are used for optical elements, such as lenses and windows, in high-energy visible and near-IR lasers. In current practice, the reflectivity of those surfaces is reduced by applying multilayer dielectric thin-film AR coatings.
Nova plasma shutter test on Shiva
Authors: Bradley L. P. , Stowers I. F. , Oicles J. , Mitchell A. C.
Published: February 2020

Optical feedback from the target can destroy laser components unless it is prevented from reentering the laser. Conventional Faraday rotator-polarizer isolators are lossy, and their cost increases nonlinearly with the beam diameter to the 2.5 power, precluding their use at large aperture. A 46-cm isolator, for example, costs $500,000 for each of the 20 Nova beams. Each plasma shutter will cost $80,000/beam line.
Strong-field photoionization in the few-optical-cycle regime: the role of the absolute phase
Authors: Nisoli M. , Stagira S. , Priori E. , Sansone G. , De Silvestri S. , Villoresi P. , Paulus G.G. , Grasbon F. , Walther H.
Published: February 2020

Progress in femtosecond laser technology led to the production of laser pulses whose envelope varies on a time scale comparable to that of the electromagnetic field itself [1]. Such pulses consist of less than two optical cycles in FWHM. Under these conditions, the phase of the carrier frequency with respect to the envelope (absolute phase) determines the variation of the laser electric field in time. Since all effects in strong-field laser interaction are driven by the electromagnetic field of the laser, the absolute phase is important for many different topics in laser physics ranging from coherent control of chemical reactions and generation of attosecond pulses to photoionization, production of coherent soft X-rays and particle acceleration. Photoionization using intense laser pulses is characterized by the fact that an atom may absorb more photons than necessary for its ionization. The effect is known as above-threshold ionization (ATI). ATI has found applications for the characterization of few-cycle and attosecond pulses [2-3].
Distortion-free guiding of 0.2×1018 W/cm2 femtosecond pulses through a fully-ionized 1.5 cm He plasma channel
Authors: Gaul E. W. , Grigsby F. , Matlis N. H. , Shim B. , Zgadzaj R. , Downer M. C.
Published: February 2020

Plasma waveguides capable of guiding relativistically intense fs laser pulses without optical distortion are essential to developing GeV-scale Laser Wakefield (LWF) Accelerators [1] and coherent short-wavelength sources. We report, to our knowledge, the highest intensity-length product (0.2×10
18
W/cm
2
× 1.5 cm) to date for distortion-free guiding. We generated our channels in a backfill of He gas (300-700 Torr) using a modification of a method developed by Milchberg et al. [2], who line-focused ~100 ps, ~0.3 J Nd:YAG laser pulses to intensities of ~10
13
W/cm
2
into a gas using an axicon (see Fig. 1a). This intensity readily field-ionizes high-Z gases (e.g. Ar, N2), thus initiating the channel-forming process, but forms an incompletely-ionized channel, in which relativistically intense pulses suffer ionization-induced phase distortion during guiding and ionization-induced defocusing when entering the channel. Indeed we observe distorted exit mode and spectrum (see Fig. 1c) and only 5% throughput when we attempt to guide a pulse at ≥10
17
W/cm
2
through a nitrogen channel.
Control of photoinduced processes by optimally shaped laser pulses: from diatomics to organometallic molecules. Information content coded in the pulse forms
Authors: Vajda Š. , Lupulescu C. , Bartelt A. , Merli A. , Wöste L.
Published: February 2020

Control of multiphotonic bound-bound and bound-free processes with modulated laser pulses is demonstrated and the correlation of the obtained pulse forms to the mechanism and dynamics of the addressed photoinduced processes is discussed in details.
Femtosecond X-ray Diffraction Measurement of a Solid-Solid Phase Transition in VO2
Authors: Cavalleri A. , Tóth Cs. , Siders C.W. , Squier J.A. , Ráksi F. , Forget P. , Kieffer J.C.
Published: February 2020

Femtosecond x-rays were for the first time used to probe a photo-induced solid-solid phase transition in VO2. The fast timescale observed suggests that, in this regime, the structural distortion may not be thermally initiated.
Investigation of low-frequency, condensed phase solvation dynamics using a novel two-dimensional, resonant-pump, third-order Raman-probe technique
Authors: Underwood David F. , Blank David A.
Published: February 2020

We present data from a novel resonant-pump, nonresonant-probe technique which allows direct probing of the inter- and intramolecular motions of a solution in an unlimited variety of guest-host systems.
Dynamics of water in ionic solvation shells
Authors: Kropman Michel F. , Nienhuys Han-Kwang , Bakker Huib J.
Published: February 2020

Using femtosecond mid-infrared pump-probe spectroscopy, we find that the vibrational energy relaxation, the orientational and hydrogen-bond dynamics of water molecules in the solvation shell of an ion are much slower than in neat liquid water.
One step mid-infrared generation from a dual-wavelength Ti:sapphire system and its multi-pass amplifier
Authors: Song Jie , Xia Jiangfan , Strickland Donna T.
Published: February 2020

An area of research receiving considerable attention at present is coherent control of molecules. One of the pursuits in this field is excitation of molecules into high lying vibration states by using chirped excitation. To date, the only experimental work on chirped mid-infrared excitation has been carried out with a free electron laser, which could generate pulse energies of 2 µJ at a wavelength of 5 µm with pulse duration of 350 fs [1]. In this paper, we describe a high intensity, dual-wavelength laser system that can be applied to carry out these types of experiments.
Time-resolved photoelectron-photoion coincidence imaging of the photodissociation and ionization dynamics in CF3I
Authors: Rijs Anouk M. , Hayden Carl C. , Janssen Maurice H.M.
Published: February 2020

The real-time dynamics of the dissociative ionization of CF3I has been studied by femtosecond photoelectron-photoion coincidence imaging. With coincidence imaging, correlated three dimensional scattering data of the recoiling electrons and the parent ion, CF3+ and I+ photofragment are obtained. With the photoelectron spectra of CF3I+ and the correlated images of the fragments, the different multi-photon dissociation pathways producing I+ are unravelled. Furthermore, molecular frame angular correlations are extracted for the CF3+ and I+ photofragments. These molecular frame angular correlations provide details on the photodissociation and ionization dynamics.
Two dimensional analysis of integrated three pulse photon echo
Authors: Nagasawa Yutaka , Seike Kazushige , Muromoto Tadayuki , Okada Tadashi
Published: February 2020

We have carried out two-dimensional measurement of integrated three-pulse photon echo signal of Nile blue doped in poly(methyl methacrylate) (PMMA) at various temperatures (30-230 K). Rephasing and echo formation were still clear even when the population period was extended to >100 ps, indicating that spectral diffusion is a minor process in the picosecond time scale for this sample. The intramolecular vibrational relaxation did not cause a sufficient spectral diffusion.
Breaking bonds with mid IR pulses: Femtosecond photolysis of gas-phase metal carbonyls
Authors: Windhorn L. , Witte T. , Yeston J. , Proch D. , Motzkus M. , Kompa K. L. , Fuss W.
Published: February 2020

Efficient and selective preparation of highly excited vibrational states in molecules is a challenging objective in physical chemistry. One means of achieving high ground-state vibrational excitation, possibly even leading to bond scission, was infrared multiphoton excitation (IRMPE) by ns lasers [1]. In this approach the resulting distribution over vibrational states always remained uncertain, since the role of intramolecular vibrational relaxation (IVR) as a process competing with or assisting excitation was unclear [2,3]. Femtosecond laser pulses resolve the uncertainty by restricting excitation to timescales faster than IVR. We have therefore applied fs mid IR laser technology toward the dissociation of transition metal carbonyls, which were previously dissociated by nanosecond IR pulses [4]. The fs pulse duration allows detailed modeling of the excitation mechanism. Specifically, analysis of the experimental data affords the number of vibrational modes involved in excitation, which in turn could lead to more efficient schemes for laser-driven dissociation.
THz-radiation performance from Multi-energy arsenic-ion-implanted GaAs and semi-insulating GaAs fabricated dipole antennas
Authors: Liu Tze-An , Pan Ci-Ling , Tani Masahiko , Lin Gong-Ru
Published: February 2020

THz radiation from several kinds of semiconductors had been reported from many groups.1~2) The emitters like photoconductive or Bow-tie antennas had been fabricated on S. I. GaAs and LT GaAs3). The receiver had been reported from many methods such as dipole detection, E-O sampling, Bolometer etc. Dipole detection has the advantage of large responsively. Comparison of photoconductive antennas between LT GaAs and S. I. GaAs had been characterized from M. Tani et al3). Arsenic-ion-implant GaAs (GaAs: As+) had been reported with ultrafst carrier lifetime that is similar as LT GaAs4). In this paper, we will introduce the temporal difference between THz radiation from GaAs: As+ and S.I. GaAs fabricated dipole antennas with variant bias field and optical excitation power.
Generation of ultrashort-pulse nondiffracting beams and X-waves with thin-film axicons
Authors: Grunwald R. , Griebner U. , Neumann U. , Kummrow A. , Rini M. , Nibbering E. T. J. , Piché M. , Rousseau G. , Fortin M. , McCarthy N. , Kebbel V.
Published: February 2020

Ultrashort-pulse Bessel beams were generated from Ti:sapphire lasers with transparent and reflecting thin-film axicons. By spatio-temporal autocorrelation, significance of optical X-wave formation was demonstrated at pulse durations below 12 fs in accordance with simulations.
Two-photon standing wave patterned photobleaching to probe DNA dynamics in live cells
Authors: Bardeen C. J. , Davis S. K.
Published: February 2020

Two-photon excitation, which avoids the harmful biological effects of ultraviolet exposure and provides intrinsic axial resolution, has been widely used in confocal microscopes to image static structures in biological samples. We have combined two-photon excitation with patterned photobleaching and a standing wave geometry in order to study macromolecular dynamics in such samples. The aim of this work is to measure the short-range diffusive motion of the DNA-containing chromatin in live cells, which is believed to be important in biological gene expression. Conformational fluctuations of the densely packed chromatin fibers are thought to allow transcription proteins access to buried sequences of DNA in the nucleoplasm.
Solvent control of electron transfer dynamics
Authors: Barthel Erik R. , Martini Ignacio B. , Keszei Erno , Schwartz Benjamin J.
Published: February 2020

Solvents are used to control electron transfer (ET). Sodide (Na− ), which has only electronic degrees of freedom, is prepared in several solvents. Its CTTS dynamics probe the relevant solvent motions in the ET reaction.
Nonergodic dye-to-semiconductor electron transfer
Authors: Benkő Gábor , Yartsev Arkady P. , Sundström Villy
Published: February 2020

The dominating part of electron injection from the transition metal complex Ru(dcbpy)2(NCS)2 into a titanium dioxide nanocrystalline film proceeds extremely rapidly from the initially populated, vibronically nonthermalized, singlet excited state of the molecule.
A mid-infrared photon echo study of liquid water
Authors: Stenger J. , Madsen D. , Hamm P. , Nibbering E. T. J. , Elsaesser T.
Published: February 2020

We present the first mid-infrared photon echo study of HOD/D2O, demonstrating that spectral diffusion occurs on many time scales. Fluctuations of local structure of the hydrogen bond network are relatively long lived (5–15 ps).