THz parametric gain in semiconductor superlattices in the absence of electric domains

We theoretically show that conditions for THz gain and conditions for formation of destructive electric domains in semiconductor superlattices are fairly different in the case of parametric generation and amplification. Action of an unbiased high-frequency electric field on a superlattice causes a periodic variation of energy and effective mass of miniband electrons. This parametric effect can result in a significant gain at some even harmonic of the pump frequency without formation of electric domains and corruption from pump harmonics.Comment: 4 pages, 3 figures. Accepted to Appl. Phys. Let

Terahertz Bloch oscillator with suppressed electric domains: Effect of elastic scattering

We theoretically consider the amplification of THz radiation in a superlattice Bloch oscillator. The main dilemma in the realization of THz Bloch oscillator is finding operational conditions which allow simultaneously to achieve gain at THz frequencies and to avoid destructive space-charge instabilities. A possible solution to this dilemma is the extended Limited Space-Charge Accumulation scheme of Kroemer (H. Kroemer, cond-mat/0009311). Within the semiclassical miniband transport approach we extend its range of applicability by considering a difference in the relaxation times for electron velocity and electron energy. The kinetics of electrons and fields establishing a stationary signal in the oscillator is also discussed.Comment: Submitted to proceedings of the summer school-conference of AQDJJ programme of ESF, Kiten, Bulgaria, 9-24 June 200

Hirsirakenteinen huoneistohotelli Iso-Syötteelle

Tiivistelmä. Tämä diplomityö on suunnitelmapainotteinen työ, jonka aiheena on uusi hirsirakenteinen huoneistohotelli Iso-Syötteen laskettelukeskukseen. Suunnitelma on toteutettu osana Moderni Hirsikaupunki -hanketta, joka tutkii nykyaikaisen hirsirakentamisen käyttömahdollisuuksia kaupunkiympäristössä, sen haasteita ja hyötyjä. Diplomityö on tehty syksyn 2018 ja kevään 2019 aikana, Moderni Hirsikaupunki -hankkeen loppupuolen arviointivaiheessa, mutta työn suunnittelullisen aiheen vuoksi se kuuluu varsinaisesti hankkeen suunnittelututkimusvaiheeseen. Suunnittelutyön aihe on saatu Hotelli Iso-Syötteen johtajalta, jonka aikeena on ollut rakentaa laskettelukeskuksen ala-aseman läheisyyteen uusi huoneistohotelli. Toiveena oli tutkia mahdollisuutta toteuttaa suhteellisen suurikokoinen hotellirakennus hirsirakenteisena, mihin tässä diplomityössä onkin tartuttu. Annetut lähtötiedot itse suunnittelulle olivat suhteellisen niukat, sisältäen lähinnä suunnittelualueen suurpiirteisen rajauksen ja toivotun huoneistojen määrän, joten suunnittelussa on otettu paljon vapauksia esimerkiksi muun tilaohjelman sekä arkkitehtuurin suhteen. Diplomityö jakautuu karkeasti ottaen kolmeen toisiinsa linkittyvään osaan: aiheen taustoitukseen, suunnittelupaikan tutkimiseen, sekä varsinaiseen suunnitelmaosuuteen. Tausta -osuus on kirjallisena tehty osio, joka antaa suunnitelman kannalta olennaisia taustatietoja aiheeseen liittyen. Taustoituksessa on rrottu lyhyesti Suomen hirsirakentamisesta, sekä esitelty Pohjois-Suomen matkailuarkkitehtuurin historiaa ja pohdittu sen nykytilaa ja tulevaisuutta. Matkailuarkkitehtuuri on 1960-luvulle saakka ollut suhteellisen laadukasta, mutta sen jälkeen massaturismin alettua taso on heikentynyt ja erityisesti Suomen laskettelukeskuksiin on noussut mitä ihmeellisempiä tyylittömiä luomuksia. Eriskummallisella kulissiarkkitehtuurilla pyritään houkuttelemaan turiseja, mutta ehkä samaan lopputulokseen voitaisiin päästä myös oikeasti laadukkaalla arkkitehtuurilla. Paikka -osuudessa on esitelty tarkemmin suunnittelualuetta, Iso-Syötettä, ja kerrottu sen historiasta ja tulevaisuudesta sekä esitelty nykyistä tilannetta suunnittelun pohjaksi. Iso-Syöte on Pohjois-Pohjanmaalla sijaitseva tunturi, jonka alueen historia ulottuu kivikaudelle asti. 1980-luvulta lähtien tunturilla on toiminut laskettelukeskus Iso-Syöte, jonka toiminta on pyörinyt pääosin menestyksekkäästi tähän päivään saakka. Iso-Syötteen ympäristö ja toiminnot tarjoavat kiinnostavat lähtökohdat diplomityön suunnitteluosuudelle. Suunnitelma -osuus esittelee diplomityön varsinaisen suunnittelutyön, Hirsirakenteisen huoneistohotellin Iso-Syötteelle. Huoneistohotelli koostuu maantasokerrokseen ja kellariin sijoittuvista julkisista tiloista, kuten ravintolasta, baarista, liiketiloista ja saunatiloista, sekä tilaelementtitekniikalla toteutetuista majoitushuoneistoista kolmessa kerroksessa. Hotellissa on pyritty yhdistelemään klassisen luontomatkailun piirteitä, paikalla vallalla olevaan aktiiviseen laskettelumatkailuun. Suunnitelman lähtökohdat ovat vahvasti kontekstissa ja paikallisuudessa, ja perinteikästä hirsirakentamista on siinä käytetty modernilla tavalla laadukkaan arkkitehtuurin luomiseen.Log-structured apartment hotel for Iso-Syöte. Abstract. This master’s thesis is a design oriented work, whose topic is a design for a new log-structured apartment hotel, for the ski resort of Iso-Syöte. The work is done as a part of the Modern Log City (Moderni Hirsikaupunki) -research project, which studies the potential of log structures in the urban environment; the challenges and the benefits. The master’s thesis has been done during the autumn of 2018 and spring of 2019, during the evaluation period of the Modern Log City -research project, but due to the design oriented character of the work, it is more a part of the design-based research period of the project. The topic of the thesis was given by the manager of the Hotel Iso-Syöte, whose aim has been to build a new apartment hotel close to the bottom of the ski slopes. His request was to study the possibility of constructing a rather extensive hotel building using a log structure, and that is the issue which has been dealt with in this master’s thesis. The given initial data was rather scarce, including essentially the rough boundaries of the design area and the desirable amount of rooms, so a lot of liberties have been taken considering the space programme and architecture for example. This master’s thesis is coarsely divided into three interlinking parts: the background of the subject, the examination of the site and ultimately the actual project of the apartment hotel. The background part is a written part, presenting some essential information in relation to the subject. In the background section, the history of log buildings in Finland is being briefly described, as well as the history, present state and the future of the tourism related architecture in northern Finland. The tourism related architecture has been quite high-class until the 1960’s, but after that, since the era of mass tourism, the quality has been decreasing, and run-down architectural creations have emerged throughout the ski resorts in Finland. Odd, counterfeit architecture is being used as a method for attracting tourists, even though the same results could likewise be achieved with some genuine high-quality architecture. The site part introduces more closely the area of interest, Iso-Syöte, by telling about its history, future and the present state as a grounding for the design work. Iso-Syöte is a fjeld in the North Ostrobothnia, and the area has a history stretching all the way to the Stone Age. Since the 1980’s the Iso-Syöte ski resort has been operating at the fjeld, doing quite successfully to this day. The environment and the activities of the Iso-Syöte provide a truly fascinating starting point for the design phase of the master’s thesis. The design part presents the actual design work of the master’s thesis, the apartment hotel with a log structure for the ski resort of Iso-Syöte. The apartment hotel consists of some public spaces in the ground floor and basement such as a restaurant, a bar, a public sauna and some commercial spaces, as well as accommodations in three floors, conducted with prefabricated box units. With the design of the hotel, some characteristics of the classical tourism have been introduced to the existing environment of active tourism. The design is strongly based on the context and locality, and the traditional log construction has been used in a modern manner in order to achieve admirable architecture

Obstructive sleep apnoea-related respiratory events and desaturation severity are associated with the cardiac response

Obstructive sleep apnoea (OSA) causes, among other things, intermittent blood oxygen desaturations, increasing the sympathetic tone. Yet the effect of desaturations on heart rate variability (HRV), a simple and noninvasive method for assessing sympathovagal balance, has not been comprehensively studied. We aimed to study whether desaturation severity affects the immediate HRV.MethodsWe retrospectively analysed the electrocardiography signals in 5-min segments (n=39 132) recorded during clinical polysomnographies of 642 patients with suspected OSA. HRV parameters were calculated for each segment. The segments were pooled into severity groups based on the desaturation severity (i.e.the integrated area under the blood oxygen saturation curve) and the respiratory event rate within the segment. Covariate-adjusted regression analyses were performed to investigate possible confounding effects.ResultsWith increasing respiratory event rate, the normalised high-frequency band power (HFNU) decreased from 0.517 to 0.364 (p<0.01), the normalised low-frequency band power (LFNU) increased from 0.483 to 0.636 (p<0.01) and the mean RR interval decreased from 915 to 869 ms (p<0.01). Similarly, with increasing desaturation severity, the HFNUdecreased from 0.499 to 0.364 (p<0.01), the LFNUincreased from 0.501 to 0.636 (p<0.01) and the mean RR interval decreased from 952 to 854 ms (p<0.01). Desaturation severity-related findings were confirmed by considering the confounding factors in the regression analyses.ConclusionThe short-term HRV response differs based on the desaturation severity and the respiratory event rate in patients with suspected OSA. Therefore, a more detailed analysis of HRV and desaturation characteristics could enhance OSA severity estimation

Naisjohtajuuden haasteet

Tiivistelmä. Tässä tutkimuksessa käsitellään naisjohtajuuden haasteita ja mahdollisia esteitä, joita miehet eivät vastaavissa tehtävissä kohtaa. Tutkimuksen tarkoituksena on ilmentää, mitkä tekijät muodostavat paljon puhutun lasikaton, ja tuoda esille mistä nämä tekijät ovat peräisin. Tutkimuksen avulla halutaan herättää kiinnostusta naisiin kohdistuvaa syrjintää kohtaan työelämässä ja erityisesti johtoportaassa

The milliarcsecond-scale jet of PKS 0735+178 during quiescence

We present polarimetric 5 GHz to 43 GHz VLBI observations of the BL Lacertae object PKS 0735+178, spanning March 1996 to May 2000. Comparison with previous and later observations suggests that the overall kinematic and structural properties of the jet are greatly influenced by its activity. Time intervals of enhanced activity, as reported before 1993 and after 2000 by other studies, are followed by highly superluminal motion along a rectilinear jet. In contrast the less active state in which we performed our observations, shows subluminal or slow superluminal jet features propagating through a twisted jet with two sharp bends of about 90 deg. within the innermost three-milliarcsecond jet structure. Proper motion estimates from the data presented here allow us to constrain the jet viewing angle to values < 9 deg., and the bulk Lorentz factor to be between 2 and 4.Comment: 11 pages, 12 figures. Accepted for publication in A&

A dynamic adjustment model of saccade lengths in reading for word-spaced orthographies: evidence from simulations and invisible boundary experiments

Contemporary models of eye movement control in reading assume a discrete target word selection process preceding saccade length computation, while the selection itself is assumed to be driven by word identification processes. However, a potentially more parsimonious, dynamic adjustment view allows both next word length and its content (e.g. orthographic) to modulate saccade length in a continuous manner. Based on a recently proposed center-based saccade length account (a new regression model of forward saccade length is introduced and validated in a simulation study. Further, additional simulations and gaze-contingent invisible boundary experiments were used to study the cognitive mechanisms underlying skipping. Overall, the results support the plausibility of dynamic adjustment of saccade length in word-spaced orthographies. In the future, the present regression formula-based computational model will allow a straightforward implementation of influences of current and next word content (visual, orthographic, or contextual) on saccade length computation