10 research outputs found
Recombination of H3+ Ions in the Afterglow of a He-Ar-H2 Plasma
Recombination of H3+ with electrons was studied in a low temperature plasma
in helium. The plasma recombination rate is driven by two body, H3+ + e, and
three-body, H3+ + e + He, processes with the rate coefficients 7.5x10^{-8}cm3/s
and 2.8x10^{-25}cm6/s correspondingly at 260K. The two-body rate coefficient is
in excellent agreement with results from storage ring experiments and
theoretical calculations. We suggest that the three-body recombination involves
formation of highly excited Rydberg neutral H3 followed by an l- or m- changing
collision with He. Plasma electron spectroscopy indicates the presence of H3.Comment: 4 figure
Temperature dependence of binary and ternary recombination of H3+ ions with electron
We study binary and the recently discovered process of ternary He-assisted
recombination of H3+ ions with electrons in a low temperature afterglow plasma.
The experiments are carried out over a broad range of pressures and
temperatures of an afterglow plasma in a helium buffer gas. Binary and
He-assisted ternary recombination are observed and the corresponding
recombination rate coefficients are extracted for temperatures from 77 K to 330
K. We describe the observed ternary recombination as a two-step mechanism:
First, a rotationally-excited long-lived neutral molecule H3* is formed in
electron-H3+ collisions. Second, the H3* molecule collides with a helium atom
that leads to the formation of a very long-lived Rydberg state with high
orbital momentum. We present calculations of the lifetimes of H3* and of the
ternary recombination rate coefficients for para and ortho-H3+. The
calculations show a large difference between the ternary recombination rate
coefficients of ortho- and para-H3+ at temperatures below 300 K. The measured
binary and ternary rate coefficients are in reasonable agreement with the
calculated values.Comment: 15 page
Comparative effect of interactive mobiles (clickers) and communicative approach on the learning outcomes of the educationally disadvantaged Nigerian pupils in ESL classrooms
Effective teaching that promotes learnersâ active engagement and the development of
communicative proficiency has been a challenge to teachers of English as a second
language (ESL). Previous research on second language (L2) teaching has shown that
L2 learners improve better in communicative skills when they are actively engaged,
participate in communicative tasks that facilitate interaction and are provided with the
opportunity to use the target language in the classroom. This study focuses on
improving ESL learnersâ learning outcomes in remotely-located primary schools in
Nigeria.
The study aimed to test whether the introduction of Personal Response System (PRS)
and communicative approach can improve pupilsâ English-language communicative
competences and their attitudes towards English learning. Specifically, this study
examined the extent to which significant differences exist in pupilsâ communicative
competence performance scores and learning gains based on teachersâ use of a
communicative approach, PRS and lecture methods in the ESL classroom.
Furthermore, the research also attempted to find out whether pupilsâ attitudes towards
the learning of English would significantly differ based on teaching strategy. Attitudes
of pupils and teachers towards the interventions were also investigated.
A pre-test and post-test non-randomised control group design was adopted in this study.
Some qualitative data were also collected to augment the quantitative main data. Ninety
nine pupils from three intact classes in different schools in Ijebu-North local
government, Ogun-State, Nigeria were assigned to two experimental groups and one
control group. In addition to the traditional use of textbooks, one of the experimental
groups was taught using communicative activities, while the second experimental
group experienced communicative tasks blended with the use of a personal response
system. The control group received the conventional classroom instruction (lecture
method), including the use of the English language textbook. In order to provide
answers to the research questions and the hypothesis of this study, English Language
Listening Tests and English Language Speaking Tests, Pupilsâ Attitude to English
Language Lesson Questionnaire, Pupilsâ Attitude to Clickersâ Questionnaire and
Pupilsâ Attitude to Communicative Approach Questionnaire were administered at the
pre-and post-test stages of the research. These instruments were also complemented
with data from classroom observation, video recording of the instructional process, and
audio-recorded interviews with the teachers and selected pupils in the experimental
groups.
The results indicate that the two experimental groups showed greater
improvement in communicative competence than did the control group; but the PRS
group improved more than the communicative approach group both in listening and
speaking skills development. Moreover, pupilsâ learning gains were statistically
different, with the PRS group having the highest gain scores above the communicative
approach group, while the control group did not experience increased learning gains.
The results also reveal pupilsâ mixed-reactions with respect to their attitudes toward the
English language lesson and the interventions. Teachersâ attitudes toward the
interventions were in the positive direction
Recombination Of H\u3csup\u3e+\u3c/sup\u3e3 Ions In The Afterglow Of A He-Ar-H2 Plasma
Recombination of H+3 with electrons is studied in a low-temperature plasma containing He, H2 and Ar at different He and H2 densities. The effective plasma recombination rate is driven by binary, H+3 + e-, and ternary, H +3 + e-+ He, processes with the rate coefficients 7.5 à 10-8 cm3 s-1 and 2.8 à 10-25 cm6 s-1 respectively at 260 K. We suggest that the ternary recombination involves formation of neutral highly excited Rydberg H3 followed by an l-changing collision with He. The difference between recombination of para- and ortho-H+3 is discussed. © 2008 IOP Publishing Ltd
Survival and growth rates of wels catfish (Siluris glanisLinnaeus, 1758) larvae originating from fertilization with cryopreserved or fresh sperm
Non-Maxwellian electron energy distribution function in He, He/Ar, He/Xe/H
Experimental studies of the electron energy distribution function âEEDFâ under well defined conditions in flowing afterglow plasma, using a Langmuir probe are reported. The EEDF is measured in He2+ and Ar+ dominated plasmas and in XeH+ and XeD+ dominated recombining plasmas. He is used as a buffer gas at medium pressures in all experiments (1600Â Pa, 250Â K). The deviation of the measured EEDF from Maxwellian distribution is shown to depend on plasma composition and on the processes governing the plasma decay. The influence of energetic electrons produced during the plasma decay on the body and tail of the EEDF is observed. The mechanism of energy balance in afterglow plasma is discussed