Frequency stability of <400MHz without discontinuous jumps over a period of 30 hours has been demonstrated in a high-power, fiber laser-pumped, single frequency CW OPO operating at 3 microns wavelength without active frequency locking.

Continuous-wave optical parametric oscillators producing multiwatt powers are established in the near- to mid infrared region. New nonlinear materials promise to extend their capalibity into the visible and long-wave mid-IR regions.

Spectrally beam-combined (SBC) laser systems, wherein multiple laser outputs are spectrally multiplexed into a single high-quality beam, are rapidly advancing the power scaling frontier for high-average-power beam-combined fiber lasers with near-perfect beam quality. We describe two- and three-channel SBC fiber lasers featuring 93% power-combining efficiency, near-diffraction-limited beam quality, average output powers in excess of 500 W, and excellent prospects for additional power scaling. To our knowledge, this level of optical performance represents the highest combination of beam quality and average power obtained so far for a beam-combined fiber laser system.

We report a three-channel, spectrally beam-combined (SBC), 1 mum fiber laser that produces 522 W of average power with near-diffraction-limited (M2 ~ 1.2) beam quality. The laser features a SBC power combining efficiency of 93%, versatile master-oscillator, power-amplifier fiber channels with up to 260 W of narrow-band, polarized, and near-diffraction-limited output that is tunable over nearly the entire 1 micro m Yb(3+) gain bandwidth, and excellent prospects for significant power scaling. To our knowledge, these results represent the highest beam quality and average power achieved to date for a beam-combined fiber laser system.

We describe a three-channel, spectrally beam combined (SBC), 1-&mgr;m fiber laser that features a SBC power combining efficiency of 93%, versatile master-oscillator, power-amplifier (MOPA) fiber channels with up to 260 W of narrowband, polarized, and near-diffraction limited output, and currently produces 522 W of average power with a dispersed (non-dispersed) beam quality at 522 W of 1.18x (1.22x) diffraction limited. To our knowledge, these results represent the best combination of output power and beam quality achieved by SBC to date.

We report on progress toward power scaling Yb fiber lasers beyond kW levels by an efficient and versatile architecture that maintains near diffraction limited beam quality. For this work, power scaling is performed at two distinct levels. The first utilizes a diffraction grating to spectrally beam combine (SBC) the output from several master-oscillator, poweramplifier (MOPA) fiber lasers with a goal of producing high quality combined beams with > 1 kW of power. The second involves scaling individual MOPA outputs to > 200 W, thereby reducing the number of lasers required for SBC. As a first step toward reaching these goals, we have developed Yb fiber MOPAs producing up to 208 W of polarized, narrow band, and near diffraction limited output and have demonstrated two-channel fiber laser SBC with a power combining efficiency of 93%, a combined beam power of 258 W, and a dispersed axis M2 of 1.06. These results represent a significant advance in high brightness, spectrally beam combined laser systems.

College freshmen with low literacy skills are underprepared to meet the challenges presented to them in the area of reading comprehension. According to Applebee, Langer, and Mullis (1985), beginning undergraduate students have the basic reading skills needed to understand a newspaper, but many of them have difficulty reading and studying college textbooks. By the time most poor readers enter college, their ability to decode words has become automated. What they have difficulty with is understanding the complex nature of expository prose because of the complexity of the written language and their inability to successfully organize and integrate the material (Norris & Hoffman, 1993). Additionally, these individuals have few strategies and poor flexibility when it comes to reading and comprehending expository text. The ability to selfregulate one's thinking and learning has been found to be highly predictive of students' academic success (Pintrich & DeGroot, 1990; Zimmerman & Paulsen, 1995). The current thinking in the teaching of developmental reading is to link a reading course with a credit-bearing, content-area course so that skills may be directly applied to the content course (Stahl, Simpson, & Hayes, 1992). In this type of instruction, students learn specific reading strategies, such as increasing reading efficiency, developing technical vocabulary, and preparing for exams, within the context of actual course work. Although many researchers have found these paired or adjunct courses to be successful (Adams & Mikulecky, 1989; Balajthy, Bacon, & Hasby, 1985; Blanc, DeBuhr, & Martin, 1983; Bullock, Madden, & Harter, 1987; Elliott & Fairbanks, 1986; Stone, 1991), none have focured on the complexity of the text and the difficulties students have integrating textual information within the targeted courses. The ability to read and comprehend text does not solely depend on letter recognition but also on meaning and context. All aspects of language aid the reader in comprehending text (Adams, 1990). These include the following types of information: orthographic, phonologic, lexical, syntactic, semantic, and contextual. Processing units from each of these types of information are integrated into patterns of recognized words, concepts, and syntactic structures (Norris, 1998; Weaver, 1994). All units of information are connected to every other unit either directly or indirectly. Meaning is derived from the text as all elements are processed simultaneously. That is, the different elements can jointly contribute to the meaning of a word or groups of words (Seidenberg, 1992). The presentation of visual stimuli (i.e., letters, words, and sentences) causes the reader to begin both perceptual and conceptual processing (Norris, 1998). Perceptual processors receive sensory input and include visual images, such as individual letters; groups of letters and general structures of sentences; paragraphs and passages; and phonological units, phonemic units, orthographic units, and word forms. Conceptual processors attach meaning to the perceptual units through the following: lexicon, concepts, prior knowledge, discourse structure, and context. The vast amount of expository text required of college students consumes the majority of their class preparation time. Nowhere is expository text more important, nor more demanding, than at this level (Hiebert, Englert, & Brennan, 1983). College texts contain words that have erudite meanings and are highly specialized to a particular field of study. Studies have shown that when students come across an unknown word in a text, they spend little time searching the text for context cues or looking up the word's meaning in a dictionary (Nist & Olejnik, 1995). Syntax is often of a complex nature, with references that may or may not be signaled by words in the text. Concepts are often abstract and present difficulty to poor readers because meaning must be derived from unfamiliar information. …

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReexamination of the reactions of Ph2P(CH2)nPPh2 (n = 1-4) with RuCl2(PPh3)3Chu W. Jung, Philip E. Garrou, Paul R. Hoffman, and Kenneth G. CaultonCite this: Inorg. Chem. 1984, 23, 6, 726–729Publication Date (Print):March 1, 1984Publication History Published online1 May 2002Published inissue 1 March 1984https://pubs.acs.org/doi/10.1021/ic00174a018https://doi.org/10.1021/ic00174a018research-articleACS PublicationsRequest reuse permissionsArticle Views1207Altmetric-Citations86LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Seven multiple-phoneme misarticulating children (ages 5.6 to 6.6) and seven age-matched normally articulating children labeled a seven-step VOT continuum (/pi/ to /bi/) via a picture pointing task. The normal children identified the first three stimuli as /b/ at greater than chance level (p < 0.01), stimulus 4 was identified at chance level (54% /b/) and stimuli 5–7 were identified as /p/ (p < 0.01). The misarticulating children also identified stimuli 1 through 3 as /b/ at greater than chance level (p < 0.05). However, their phoneme boundary included both stimuli 4 and 5 (55% and 40% /b/). Stimuli 6 and 7 were identified as /p/ (75% and 74% /p/) at greater than chance level. Results suggest that multiply misarticulating children may misperceive the VOT contrast even when voicing is not among their production errors.

Ten children (ages 6.6–8.6) who dentalized /s/, ten children (6.4–8.2) who labialized /r/, and 10 normal children identified a 17-step /is-i∫/ stimulus continuum or a 7-step /rεd-wεd/ continuum via a picture pointing task. Normals and /s/-children identified stimuli 1–7 as /is/ at greater than chance probability and stimuli 10–17 as /i∫/ above chance as well. Stimuli 8–9, at chance levels, were the phoneme boundary for both groups. /r/-misarticulating children both identified and discriminated /r-w/ stimuli at a level significantly below that of normal children, whose identification and discrimination functions were similar to those of adults. Results indicate that older children who misarticulate /s/ do not necessarily have faulty /s/ boundaries for phonemes which are not similar to their production errors, whereas /r/-misarticulating children display depressed identification and discrimination scores as well as a widened phoneme boundary.