Adventures of III-V Semiconductor Surfaces

Tailoring the surface composition and morphology of materials to enable new electronic devices is important for a wide range of applications such as quantum computing or spintronics. A fundamental understanding of the changes induced in the surface during different process steps can help to establish new synthesis routes as well as devices. This thesis focuses on the manipulation of III-V semiconductor compounds, in particularthe surfaces of InAs and GaAs crystals.By implementing lithographically defined metal islands on the InAs surface, we push the boundaries of substrate annealing temperatures inhibiting the formation of In droplets locally. The employed Pd layer acts as a sink for freely diffusing In atoms above the congruent melting temperature. Here, As atoms go into gas phase at a higher rate compared to In due to the difference in vapor pressure. This lateral control over the concentration of In on the surface was investigated via scanning electron, atomic force as well as X-ray photoemission electron microscopy (XPEEM), and opens new pathways for epitaxy and the synthesis of heterostructures. Furthermore, theoretical studies have shown that the implementation of Bi atoms into the lattice of III-V compound semiconductors can facilitate band gap reduction and increased spin-orbit coupling desirable for fabricating of topological insulators. Particularly, the interaction of group III elements with Bi has attracted great interest. However, manufacturing these diluted Bismides is not trivial, since most approaches like molecular beam epitaxy, synthesis from the melt or metal organic vapor deposition suffer from limited and inhomogeneous Bi incorporation into the crystal.By following the approach of depositing Bi atoms onto a III-V sample and subsequent annealing, this thesis aims to synthesize and characterize heterostructures displaying III-V bulk properties and a surface made of III-As-Bi compounds. Different sample preparation routes were explored focusing on GaAs and InAs substrates with zinc blende (ZB) and wurtzite (WZ) crystal structure. The latter is only achievable in low-dimensional materials and will be employed in the form of InAs nanosheets. Part of this study focusses on the investigation of Bi-induced structural and chemical changes in the surface of the III-V compounds by utilizing surface sensitive techniques such as scanning tunneling microscopy, X-ray photoemission spectroscopy, low energy electron diffraction and XPEEM. Our results show that the mechanism of Bi incorporation is highly dependent on the underlying crystal structure, as well as process parameters such as time and substrate temperature. Additionally, first band structure measurements of InAs WZ crystal nanosheets collected via averaging angleresolved photoemission spectroscopy (ARPES) are presented. In contrast to other ZB crystal facets, a 2D electron gas (2DEG) is already detected after removing the native oxide and diminished after Bi deposition. We attribute the origin of the 2DEG to unique step and edge morphologies found on the WZ nanosheets. The thesis concludes with an ARPES study on InAs(111)B substrates presenting new electronic states inside the band gap based on the interaction of Bi and As atoms

Teaching Speaking Skills in English Language using Classroom Activities in Secondary School Level in Eldoret Municipality, Kenya

There is a general public concern in Kenya that majority of Form Four school leavers lack communicative and linguistic competence and thus cannot sustain conversation in English language without occasionally code switching to Sheng or Kiswahili. This study sought to find out the classroom activities used by teachers to promote learners’ active participation in speaking skills lessons in eight secondary schools in Eldoret Municipality, Kenya. The study was based on Krashen’s (1985), Monitor Model specifically the input and the affective filter hypotheses which emphasize that learners acquire target language when they are motivated and involved actively in the learning process. The study adopted mixed methods design and simple random sampling to select schools, students and English language teachers from National, Provincial and District schools. In certain cases, purposive sampling technique was also used.  Data on classroom activities used to teach speaking skills were collected using Questionnaires administered to teachers and students,   direct observation during speaking skills lessons in Form three classrooms. The data collected was analyzed using descriptive statistics. The study found out that:  there was variation in use of classroom activities for example discussion was the most used classroom activity while oral drill was the least used, during classroom discussions, students code switched to Kiswahili or Sheng due to low oral skills and teachers did not integrate various classroom activities in one lesson thus denied learners chances of using authentic language in context. The study recommends that: 1) students should be given chances to practice using authentic English language in context, 2) teachers should integrate various activities in a lesson to meet learners’ needs and 3) Curriculum to acknowledge learners’ cultural backgrounds in order to enhance their learning outcomes. This study is useful to language educators and teachers of English language. Keywords: speaking skills, classroom  activities, English, language, motivation, teacher, learne

A Retrospective Study of Handwriting Skills of Kindergarten Students

OBJECTIVE: The purpose of this study was to guide teachers and occupational therapist in recognizing handwriting needs in order to provide appropriate early intervention support for handwriting. METHOD: 218 kindergarten students in a public school district were screened for handwriting ability using the Handwriting Without Tears and the Public School’s copy screeners. Students were assessed three times during the 2014 to 2015 school year on letter memory, line placement, letter orientation, copy legibility, and copy placement skills. RESULTS: The results indicated that winter scores were a better predictor of spring scores. Significant effects in four out of five variables were found when utilizing repeated measures of retrospective data. CONCLUSION: Winter scores were shown to be significant in determining handwriting outcomes measured in the spring. The Handwriting Without Tears’ screener and the Public School’s screener are appropriate tools for school-based occupational therapists to use to identify intervention needs

English Language Cultural Dynamics in ELT at Secondary School Level in Kenya

The debate on cultural issues of English language has recently taken centre stage in educational research in Kenya. Language educators have voiced their concern due to lack of recognition of the important role of culture in English language curriculum at secondary school level in Kenya. In addition, Kenya being an ethnically diverse country has realized problems of cultural intolerance in the recent past. Yet, culture of a language plays a major role in language development and acquisition of intercultural competence of learners in any society in the world. However, the contribution of English language culture has rarely been studied in the Kenyan context. This study sought to determine English language cultural related issues in English language pedagogy at secondary school level in Kenya. This was one of the objectives in a PhD Thesis research. The study adopted qualitative design, multiple case study method. The raw data was generated through the use of interview schedule, focused group discussions, document analysis and lesson observations. The research was carried out in Uasin Gishu County in six secondary schools based on categories girls, boys and mixed. The sample comprised of 60 participants: twelve teachers of English language and forty-eight form three students who were purposively sampled. The data was analyzed basing on emerging themes. The findings included etiquette, pronunciation of sounds, stress and intonation, grammar rules, English language cultural beliefs and indigenous languages. The study is useful to language educators, teachers of English language and curriculum designers. The study concludes that English language native culture could be enhanced more in the curriculum to help second language learners to learn English language with ease. Keywords: English language culture, teaching, curriculum, indigenous language culture DOI: 10.7176/JEP/14-2-03 Publication date: January 31st 202

О некоторых особенностях структуры участков коры выветривания серпентинитов Кемпирсайского массива

New diode laser devices use the modular character of diode lasers to form beam shapes that are adapted to the processing task. In this paper cutting and welding applications of these tools are presented. A linear laser line is applied for the cutting-to-length of coil material. Diode laser modules that form an annular laser spot are utilized for optical flame cutting of steel material and simultaneous welding of annular seams. Furthermore, cutting of thin materials with a diode laser cutting plotter device is demonstrated. Moreover, new results of welding experiments with commercial diode lasers are presented

Derivation of MTM-UAS® analyses from virtual reality tools using MTMmotion®

Designing human work in a productive way plays a vital role in maintaining competitiveness of industrial companies. In order to fulfil this task, practitioners can use different methods to describe, analyse and design work processes. One widely used method is the process building block system MTM-UAS. Analysing the work processes manually (with or MTM-UAS or other methods) requires manual effort for data collection and interpretation of the method user. Due to this fact, not every industrial company has the capacities to design work productively. One possibility to reduce this effort is the automatic interpretation of digitized human motion data. Motion data describes human movements and includes, for example, distances covered, joint positions or object interactions. The technology virtual reality is capable to generate this movement data. Thanks to the advances in the technology in recent years, it can be used in a large number of workplaces. This article presents an approach how one can use the motion data of virtual reality tools to derive an automated MTM-UAS analysis. The technology thus reduces the analysis effort significantly and offers the possibility of expanding the areas of application. First, the article describes a workplace example, that was modelled in a virtual reality tool. It then explains the data that is needed to automatically generate MTM-UAS analyses and that can be generated by the virtual reality tool. It then shows how the data is translated into a valid MTM-UAS analysis. The article concludes with an outlook on how this approach can be transferred to other technologies like human simulation. With such a transfer it is conceivable to design a higher number of workplaces in a productive way and thus to maintain the competitiveness of industrial companies

Teaching Speaking Skills: Challenges of using Integrated Approach in Secondary Schools in Kenya

The integrated approach to teaching English language in secondary schools in Kenya was introduced in 1986 with the inception of the 8-4-4 system of education. One of the aims of this approach in Kenya was to address the problem of poor oral skills among form four school leavers. However, evaluation of the challenges teachers face in using this approach to teach has not been adequately done. Thus a study was carried out in 2010 to identify and suggest solutions to these challenges to teaching speaking skills in English in secondary schools. This study was important because English as used in real life situation is integrated. Additionally, speaking skill is key to effective communication. When one has control of language he/she feels confident and comfortable when talking to other people. Communication is important in any carrier. A descriptive survey was carried out in secondary schools in Eldoret Municipality. This paper is, therefore, an overview of the results obtained from the study. A total of 7 secondary schools, selected using multiple sampling techniques made up the study population. Fourteen Form Three teachers of English language responded to the questionnaires, while fourteen speaking skill lessons were observed and tape-recorded. The study adopted a mixed methods approach and subsequently analyzed the data using both descriptive and inferential statistics. The study revealed that all schools, irrespective of their category, faced similar challenges in the use of the integrated approach in teaching speaking skills. The major challenge for the integration of language and literature in teaching speaking skills was its demanding nature in terms of preparation and time requirements. Other challenges included shortage of teaching time, large number of students in the classroom hampering the use of more effective approaches in teaching, and mother tongue interference. From these findings, teachers would want to see the need to organize skill-based workshops and seminars to give teachers necessary capacity on how to integrate the approach in the classroom activities among other solutions. The study makes recommendations to the Ministry of Education to ensure that all schools have adequate human and non-human resources for teaching speaking skills. Keywords: Speaking Skills, Integrated Approach, Challenge

Teachers’ and Learners’ Attitudes towards the Impact of Availability and Use of Daily Newspapers on Students’ Speaking Competence in English Language in Secondary Schools in Bungoma County, Kenya

This paper highlights the results of a research conducted in Bungoma County of Kenya between 2008- 2009.The objective of the study was to investigate the attitudes of teachers and students towards the impact of availability and use of daily newspapers on students’ speaking  competence in English language. The study was based on the Communicative Language Teaching Approach and the theory underlying this approach is Krashen’s Second Language Acquisition, the monitor model. The study used the mixed methods research approach adopting a correlation research design. Stratified, purposive and simple random sampling techniques were used to get the sample. The sample involved 16 teachers of English language and 135 form three students. The questionnaire, students’ focused group discussions, and interview guide were used to collect data from the students and teachers respectively. The data collected was analyzed using both descriptive and inferential statistics. The hypotheses were tested using non –parametric inferential statistics-Mann-Whitney U-test. From the analysis and interpretation of data, it was deduced that students who used daily newspapers showed better speaking competence in English language than those  who did not  use them. Consequently, it is recommended that the use of the daily newspapers as an instructional resource in teaching speaking skills in English language should be encouraged and improved in secondary schools in Kenya. Keywords: Attitudes, daily newspapers, English language, teachers, students

Molluscicidal Activity of Selected Plant Extracts against Adult and Juvenile Biomphalaria Pfeifferi

Human Schistosomiasis is a debilitating infection whose transmission depends solely on the presence of snail intermediate hosts. It is a major public health problem second only to malaria in terms of morbidity and mortality and predominant in tropical and subtropical countries. Globally, over 240 million people are infected and close to 600milion are at risk.Strategies for Control of Schistosomiasis include; Chemotherapy with praziquantel, mollusciciding with Niclosamide, health education, community participation, provision of clean water and improved sanitation. Chemotherapy and use of synthetic molluscicides faces serious drawbacks of being costly, poses negative impact on environment and development of resistant strains of intermediate host snails and parasites. Plant extracts that are effective against host snails and non-toxic to non-target organisms could provide an alternative molluscicide to the current Niclosamide.This study evaluated molluscicidal activity of aqueous and methanol extracts against juvenile and adult Biomphalaria pfeifferi in vitro.Assesment of snail susceptibility to extracts was done by immersion method in accordance to WHO protocal.10 adult and juvenile snails were exposed separately to serial dilutions of 10, 20, 50, 100 and 150ppm (mg/l) of both aqueous and methanol extracts for 48 hours. Mean mortality of snails was subjected to probit analysis to determine the lethal dose (LD50) that killed 50% of the snails. The most active extracts on both juvenile and adults were Phytolacca dodecandra (LD50 8.78 and 12.58ppm) and Solannum linaeanum (LD50 16.81 and 23.25ppm) respectively.This was followed by Solanum americanum (LD50 36.17 and 38.00ppm) and Annona squamosa (LD50 51.96 and 59.00ppm) respectively. The least active extracts were Piper nigrum (LD50 74.13 and 89.95ppm) and Rhizophora mucranata LD50 94.56 and 109.82 ppm) respectively. Average mortality of Phytolacca dodecandra and solanum linaeanum was significantly similar (p ˃ 0.05) to that of niclosamide the currently used molluscicde.Since a good molluscicide should kill snails at a concentration of 100ppm or lower, this study demonstrated potency of four plant species from Kenya with molluscicidal activity against the intermediate hosts of Schistosoma mansoni. Keywords: Schistosomiasis, Biomphalaria pfeifferi, Schistosoma mansoni, Molluscicide, Phytolacca dodecandra, Solanum linaeanum, Solanum americanum, Annona squamosa

Effect of Debt Financing Options on Financial Performance of Firms Listed at the Nairobi Securities Exchange, Kenya

In spite of the dominance of the capital structure debate among both academic researchers and practitioners in the field of corporate finance over the last three decades, finding an optimal capital structure remains an ever-elusive gem. In particular, many contemporary firms are yet to find the optimum debt levels that maximises shareholder value. The purpose of this study was to examine the effects of debt configurations namely short-term, long-term and total debt on firm financial performance measured as return on assets and return on equity of listed firms in Kenya. The study utilizes panel econometric techniques named pooled ordinary least squares (OLS), fixed effects (FE) and random effects (RE) to analyze the effects of debt on financial performance of 40 non-financial firms listed on the Nairobi Securities Exchange between 2009 and 2015. Empirical results show that short-term, long-term and total debt have negative and statistically significant effects on returns on assets across OLS and RE. However, the debt measures have no significant effects on returns on equity across all estimation methods. These mixed empirical results partially follow both the trade-off and Modigliani and Miller’s theoretical predictions and partly contradict the very theories. Consequently, financial managers should adjust debt levels to ensure that they operate at the optimum points. On the other hand, credit institutions should only finance businesses up to the point where profitability is maximized to mitigate against default risks associated with overleveraging