Scaling and Universality in Models of Step Bunching: The "C+-C-" Model

We study further the recently introduced [Ranguelov et al., Comptes Rendus de l'Acad. Bulg. des Sci. 60, 4 (2007) 389] "C+-C-" model of step flow crystal growth over wide range of model parameters. The basic assumption of the model is that the reference ("equilibrium") densities used to compute the supersaturation might be different on either side of a step. We obtain the condition for linear stability of the whole step train in the form CL/CR>1 (L/R stands for left/right in a descending from left to right step train). Further we integrate numerically the equations of step motion to monitor the bunching process in the long times limit. Thus we obtain the exact size- and time- scaling of the step bunches including the numerical prefactors. We show that in a broad range of parameters the morphology is characterized with appearance of the minimal interstep distance in the bunch in the beginning of the bunches (at the trailing edge of the bunch) and may be described by a single universality class, different from those already generated by continuum theories [Krug et al., PRB 71, 045412].Comment: 18 pages, 9 figure

Light emission from thulium silicates and oxides for optical amplifiers on silicon in the extended optical communications band

Films composed of Tm2Si2O7 and Tm2O3 grains formed on SiO2/Si substrates by radio magnetic sputtering and subsequent thermal annealing up to 1250 °C were characterized by synchrotron grazing incidence X-ray diffraction, cross-sectional transmission microscopy, and micro photoluminescence (PL) measurements. The films composed of triclinic (type-B) and monoclinic (type-C) Tm2Si2O7 grains on SiO2/Si and Tm2O3 grains on Si exhibit photoluminescence at the wavelength of about 1620 nm for the silicates and 1630 nm for the oxide, which indicates that they have good potential as light amplifiers on Si in the L and U bands at telecommunications wavelengths

Use of authentic texts to improve students’ discourse competence in Form 10 English lessons

Diplomdarbs “Autentisku tekstu izmantošana skolēnu diskursa kompetences pilnveidē angļu valodas stundās 10.klasē” ir tapis kā vidējās izglītības angļu valodas skolotājas zināšanu un prasmju apliecinājums. Darba autore Liene Lāce strādā Talsu 2.vidusskolā, kur arī tika veikts pētījums zinātniskās vadītājas Sandras Kalniņas, Mg.paed. vadībā. Autore ir izmantojusi kvalitatīvo un kvantitatīvo pētījumu metodes. Gadījuma analīzē autore ir izzinājusi 10.klases skolēnu diskursa kompetenci, kā arī stundās izmanotojusi autentiskas publiskās runas, sagatavojot diskursa un teksta analīzes uzdevumus, pēcāk izvērtējot to devumu skolēnu diskursa kompetences pilnveidē. Pašu skolēnu rakstītās publiskās runas ir analizētas gan kvalitatīvi, gan kvantitatīvi. Pētījumā ir izmantotās datu ievākšanas metodes galvenokārt ir skolēnu publisko runu teksti un to izvērtējums. Autore ir izmantojusi pašas izveidotus kritērijus, lai izvērtētu publisko runu tekstus, kas tapuši pirms un pēc diskursa analīzes uzdevumu izmēģināšanas četrās angļu valodas mācību stundās 10.klasē. Šo stundu laikā tika iegūta atgriezeniskā saite, kas arī ir apkopota un analizēta. Visbeidzot, autore ir intervējusi savu kolēģi - angļu valodas skolotāju Talsu 2.vidusskolā un izveidojusi anketu, lai gūtu priekšstatu par citu angļu valodas skolotāju pieredzi skolēnu diskursa kompetencs pilnveidošanā. Autore secina, ka skolēnu diskursa kompetenci ir iespējams pilnveidot izmantojot rūpīgi izvēlētus autentiskas publiskās runas diskursa izpētei un kā modeli, rezultātā vairums skolēni spēj paši uzrakstīt savas publiskās runas. Publiskās runas pārstāv specifisku žanru, kas sevī apvieno abus diskursa veidus - runā un rakstos. Diemžēl, daļa angļu valodas skolotāju neizmanto publiskās runas savās stundā, jo runu sagatavošana ir laikietilpīgs un sarežģīts uzdevums. Darba atlēgvārdi: diskurss, kompetence, lejupejoša pieeja, autentisks teksts, publiskās runa, publiskās runas teksts.The Diploma Paper „Use of Authentic Texts to Improve Students’ Discourse Competence in Form 10 English Lessons” was written to show the required knowledge and skills to perform as a secondary school English teacher. The author Liene Lāce has been working at Talsi Secondary School No 2 which was also the place of the practical research monitored by the adviser Mg. paed. Sandra Kalniņa. The methods of the research are both qualitative and quantitative. The author has used a case study to find out Form 10 students’ discourse competence and evaluate the impact of using the discourse and text analysis of the authentic speeches in English lessons. The public speeches written by Form 10 students are analysed qualitatively and quantitatively. The methods of the data collection are mainly evaluation and data from the students’ public speech scripts. The author has used a self-designed assessment scale to evaluate the speech scripts prepared before and after the discourse and text analysis tasks of the authentic public speeches were piloted in four English lessons in Form 10. During this process the students’ feedback has been collected and analysed in the research. Finally, the author has interviewed a colleague - another English teacher at Talsi Secondary School No 2 and designed a questionnaire to learn about other English teachers’ experience in improving the learners’ discourse competence. The conclusion is drawn that the students’ discourse competence can be improved by using carefully selected authentic public speeches both to learn about the discourse and looking at them as the models so that the students are able to prepare their own speeches. Public speeches represent a specific genre combining both spoken and written discourse; however, the public speaking is not frequently used in class by a half of English teachers because it is a time consuming and complex task. The key words of the Diploma Paper: discourse, competence, top-down approach, authentic text, public speaking, speech scripts

On the Role of Substrate in Light Harvesting Experiments

An analysis of the emitted light distribution for a single emitter located at the planar interface of two optical media was performed. The interface of a varying refractive index substrate with air was considered, which is a common case in luminescence microscopy (spectroscopy) experiments. A modification of the radiative recombination rate induced by the variation of the substrate together with the emitted radiation spatial redistribution were taken into account. Simulation results show that the collection efficiency of the emitted light can vary several times depending on the substrate choice and the emitter intrinsic quantum efficiency.This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/abstract.cfm?URI=ol-33-16-1807. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.QC 2011112

Optical and Electrical Characterization at the Nanoscale by a Transparent Tip of a Scanning Tunneling Microscope

A new type of scanning probe microscope, combining features of the scanning tunnelling microscope, the scanning tunnelling luminescence microscope with a transparent probe and the aperture scanning near-field optical microscope, is described. Proof-of-concept experiments were performed under ultrahigh vacuum conditions at varying temperature on GaAs/AlAs heterostructures.QC 2011112

Professional burnout in social work and its prevention

Sociālie darbinieki ir pakļauti profesionālās izdegšanas riskam, jo darbs saistīts ar pakalpojumu sniegšanu. Preventīvie pasākumi ir labākais ceļš kā novērst profesionālo izdegšanu sociālo darbinieku dzīvē. Diplomdarba temats ir „Profesionālā izdegšana sociālajā darbā un tās prevence”. Diplomdarba mērķis ir pētīt un analizēt profesionālo izdegšanu un tās preventīvos pasākumus sociālo darbinieku ikdienā. Darbs sastāv no 3 nodaļām. Darba teorētiskajā daļā, balstoties uz zinātniskās literatūras avotiem, aprakstīta profesionālās izdegšanas būtība: sniegti jēdziena definējumi, minēti cēloņi un simptomi, kā arī preventīvie pasākumi individuālajā, starppersonu un organizatoriskajā līmenī pret profesionālo izdegšanu. Darba empīriskajā daļā tika veikta sociālo darbinieku anketēšana, lai pētītu, kādus preventīvos pasākumus sociālie darbinieki izmanto individuālajā, starppersonu līmenī, kā arī kādus saņem un kādi tiek nodrošināti no organizācijas puses. Pētījuma rezultātā tika konstatēts, ka būtiskas atšķirības starp Rīgas un Latvijas reģionu sociālo darbinieku aptaujas rezultātiem nav sniegtas.Social workers are exposed to the risk of professional burnout as their activities are connected with service. Preventive measures are the best way to avoid professional burnout in their life. The topic of the present diploma paper is „Professional burnout in social work and its prevention”. The target of the diploma paper is to study and analyse professional burnout and the preventive measures in the every day life of social workers. The diploma paper consists of 3 parts. The theoretical part includes description of the esence of professional burnout of scientific literature. Its deals with definitions, causes and symptoms as well as preventive measures on the individual, interpersonal and organizational level. The empicical part includes surveys of social workers, their opinions, their preferences of the measures used and chosen by their employing institutions. The result of the present study shows: basic diferences between the situations of Riga and other regions of Latvija social workers survey are displayed