Resonant Absorption in GaAs-Based Nanowires by Means of Photo-Acoustic Spectroscopy

Semiconductor nanowires made of high refractive index materials can couple the incoming light to specific waveguide modes that offer resonant absorption enhancement under the bandgap wavelength, essential for light harvesting, lasing and detection applications. Moreover, the non-trivial ellipticity of such modes can offer near field interactions with chiral molecules, governed by near chiral field. These modes are therefore very important to detect. Here, we present the photo-acoustic spectroscopy as a low-cost, reliable, sensitive and scattering-free tool to measure the spectral position and absorption efficiency of these modes. The investigated samples are hexagonal nanowires with GaAs core; the fabrication by means of lithography-free molecular beam epitaxy provides controllable and uniform dimensions that allow for the excitation of the fundamental resonant mode around 800 nm. We show that the modulation frequency increase leads to the discrimination of the resonant mode absorption from the overall absorption of the substrate. As the experimental data are in great agreement with numerical simulations, the design can be optimized and followed by photo-acoustic characterization for a specific application

Structural properties of GaAsN/GaAs quantum wells studied at the atomic scale by cross-sectional scanning tunnelling microscopy

The nitrogen distribution in GaAsNGaAs quantum wells _QWs_ grown by molecular beam epitaxy is studied on the atomic scale by cross-sectional scanning tunneling microscopy. No nitrogen clustering is observed in the range of N contents studied _between 1.0% and 2.5%, as measured by counting the individual N atoms inside the QW_. Nevertheless, the upper interface roughness increases with the amount of N. A residual N concentration in the GaAs barriers is found, which strongly increases with the amount of N in the QW

Puolisoiden ja alaikäisten lasten kokemukset perheenjäsenen afasiasta sekä tiedon, tuen ja kommunikaatio-ohjauksen saatavuus

Tiivistelmä. Afasia vaikuttaa laajasti sekä afaattisen ihmisen itsensä että hänen perheensä ja lähipiirinsä elämään. Perhesuhteissa tavallista on perheen sisäisten roolien muuttuminen ja perheenjäsenten etääntyminen toisistaan kommunikaatiovaikeuksien myötä. Afasian kuntoutuksessa on viime vuosina alettu yhä enemmän huomioida ja ohjata afaattisen ihmisen itsensä lisäksi myös perhettä ja muita lähi-ihmisiä, esimerkiksi tarjoamalla myös lähi-ihmiselle kommunikaatio-ohjausta, joka helpottaa afaattisen henkilön kanssa kommunikointia. Useimmiten kuntoutukseen osallistuva terve läheinen on puoliso. Tämä tutkielma käsittelee afaattisten ihmisten perheisiin liittyen sekä puolisoiden että alaikäisten lasten kokemuksia afasiasta yleisesti sekä mahdollisuuksia saada logopedistä ohjausta, tietoa ja tukea perheenjäsenen kommunikaatiovaikeuksiin sopeutumiseen. Tämä kandidaatintutkielma on kirjallisuuskatsaus, joka perustuu kahdeksaan vuosina 2001–2020 julkaistuun tutkimukseen. Tutkittavien joukossa on afaattisia henkilöitä, heidän puolisoitaan ja lapsiaan, sekä afasiatyötä tekeviä puheterapeutteja. Etenkin lapsia koskeva tutkimustieto aihepiiristä on niukkaa ja sirpaleista, joten näkökulmat vaihtelevat. Yleisiä puolisoiden kokemuksia afasiasta ovat keskusteluroolien muuttuminen, keskusteluiden väheneminen, puolisoiden emotionaalinen sulkeutuminen toisiltaan ja vaikeat tunteet, kuten suru ja turhautuminen. Joissain tapauksissa afasia on kuitenkin johtanut positiivisiinikin muutoksiin, kuten yhteisen ajan lisääntymiseen ja tarkemman kuuntelemisen oppimiseen. Lapset vaikuttavat yleisesti kokeneen vanhemman aivoverenkiertohäiriön jälkeen paljon yksin jäämistä ja pelkoa, ja afasia on ollut erityisesti lasten ja vanhempien välistä henkistä kuilua syventävä tekijä. Kuntoutuksen käytännöt perheisiin liittyen vaihtelevat, eikä viitteitä kansallisella tasolla vakiintuneista käytännöistä tai tarkoista ohjeistuksista edes puolisoiden osallistamiseen löytynyt, vaikka kansainvälisissä suosituksissa perheiden mukaan ottamista suositellaan. Lasten tiedottaminen, ohjaaminen ja tukeminen vaikuttaa olevan vielä satunnaisempaa ja myös vähemmän tutkittua. Suhteessa aiempaan tutkimustietoon tulokset vaikuttavat olevan samansuuntaisia. Etenkin lapsiin kohdistuvaa tutkimusta tarvitaan enemmän, ja sen pitäisi näkyä myös kliinisen työn kehittämisessä esimerkiksi lapsille soveltuvina materiaaleina, ammattilaisten koulutuksena ja lapsille suunniteltuna kommunikaatio-ohjauksena

Catalyst-free growth of In(As)P nanowires on silicon

The catalyst-free metal organic vapor phase epitaxialgrowth of In(As)P nanowires on silicon substrates is investigated using in situ deposited In droplets as seeds for nanowiregrowth. The thin substrate native oxide is found to play a crucial role in the nanowire formation. The structure of the nanowires is characterized by photoluminescence and electron microscopy measurements. The crystal structure of the InPnanowires is wurtzite with its c axis perpendicular to the nanowire axis. Adding arsenic precursor to the gas phase during growth results in a bimodal photoluminescence spectrum exhibiting peak at the InAsP and InP band gap energies.Peer reviewe

Enhanced luminescence from catalyst-free grown InP nanowires

The surface effects in the optical properties of catalyst-free grownInPnanowires are investigated. Both as-grown nanowires and nanowires treated with hydrofluoric acid are studied using low- and room-temperature continuous-wave and time-resolved photoluminescence measurements and transmission electron microscopy. It is shown that the room-temperature photoluminescence intensity is increased by two orders of magnitude after the surface treatment, and that there is also a significant increase in the double-exponential photoluminescence decay time.Peer reviewe

Longitudinal evolution of catheter-related bloodstream infections, kidney function and liver status in a nationwide adult intestinal failure cohort

Objectives The development of intestinal failure-related complications in Finnish adults is unknown. This study aimed to investigate the incidence of catheter-related bloodstream infections (CRBSI), and the longitudinal changes in biochemical liver and kidney tests in a nationwide cohort. Materials and methods The search for Finnish adults with intestinal failure (IF) utilized a survey to Finnish health-care providers (n = 111) with the potential to provide long-term parenteral support (PS) for adult IF. Our nationwide, cross-sectional cohort included all IF patients aged >= 18 years who had received PS for >= 120 d in 2017. Data regarding CRBSI and biochemical liver and kidney tests were collected from patient records at the start of PS up to the latest available measurement in 2017. Results In the nationwide cohort of 52 patients, the CRBSI incidence was 1.35/1000 catheter days. Seventy-three percent of CRBSI in a long-term catheter led to catheter replacement. During a median PS duration of 27.5 (interquartile range [IQR] 11.3-57.3) months, a statistically significant median change occurred in estimated glomerular filtration rate (eGFR; -8.5 ml/min/1.73 m(2), IQR -30-7, p = .005) and alkaline phosphatase (ALP; 26 U/l, IQR -11-95, p = .019). In a multiple regression model for eGFR at data collection, baseline eGFR and age were strong explanatory variables. Conclusions Incidence of CRBSI, but not treatment strategies, in this nationwide adult IF population correspond well to those reported from specialized centers. Decreased kidney function and abnormal liver test results are frequent findings, and even more so over time, emphasizing the importance of regular monitoring.Peer reviewe

In situ determination of nitrogen content in InGaAsN quantum wells

The growth of InGaAsN/GaAs multiple quantum well structures by metal-organic vapor phase epitaxy is monitored by in situ reflectometry. The nitrogen incorporation is found to depend superlinearly on the precursor flow and a threshold value for the flow is observed. By in situmeasurements of the InGaAsN quantum well samples with a fixed indium content, the change in the reflectance during the quantum wellgrowth is found to be linearly dependent on the quantum well nitrogen content. A model to determine the nitrogen content already during the growth is developed. Moreover, the field of application of in situ reflectance monitoring is extended from thick layers to thin layers, including quantum wells.Peer reviewe

Validating Entrepreneurial Intentions Questionnaire to Assess the Impact of Entrepreneurship Education

Entrepreneurship education plays an important role in social and economic development of a society through providing self-employment and job opportunities for others. Entrepreneurship education can catalyse entrepreneurial mindset through developing entrepreneurial intentions of graduates. Current study aims to validate entrepreneurial intentions questionnaire in order to study the impact of entrepreneurship education on student's intentions to become an entrepreneur. The question under study is "does entrepreneurship education impact entrepreneurial intentions of the students?" Study has the following objectives; 1) to study the impact of entrepreneurship education on attitude of the students to become an entrepreneur; 2) to find out perceived behavioural control of the entrepreneurship education students to become an entrepreneur; 3) to understand the impact of subjective norms on entrepreneurship education students to become an entrepreneur; 4) to assess the impact of entrepreneurship education on entrepreneurial intentions of the students. This study will utilize theory of planned behaviour as theoretical framework of the study. According to theory of planned behaviour entrepreneurial intentions of a person are formed through a complex process with some antecedents. The antecedents of entrepreneurial intentions are comprised of attitude of the persons towards entrepreneurship; Subjective norms of a person towards entrepreneurship; and perceived behavioural control of a person towards entrepreneurial intentions. It is a quantitative study based on casual comparative research design. Entrepreneurial Intentions Questionnaire was developed based on theory of planned behaviour. It was pilot tested on students (n=60) for reliability and validation tests. It was validated to make a comparison between technology education students' (n=240) who have participated in entrepreneurship education and technology education students' (n=302) who have not participated in entrepreneurship education. The findings of the study have shown appropriateness of theory of planned behaviour to measure entrepreneurial intentions of the students. Students who have participated in entrepreneurship education have shown higher intentions than non participants. Study was concluded with the fact entrepreneurship education does not impact directly to the intentions of the students but it has influence on entrepreneurial intentions of the students through antecedents of intentions. The questionnaire validated for study can be useful for further measurement of entrepreneurial intentions of the students. Cronbach's Alpha was used to test reliability of questionnaire. Factor analysis was used to test validity of the questionnaire. t-test was applied to find out difference in intentions between entrepreneurship education participants and non participants. Structural equation model (SEM)was used to find out relationship between entrepreneurship education and antecedents of entrepreneurial intentions. This study was knowledge addition about entrepreneurial intentions of the students in Pakistani context and impact of entrepreneurship education. Future study can be conducted to study the new venture creation process of the students with high entrepreneurial intentions.Peer reviewe

Microwave-assisted methacrylation of chitosan for 3D printable hydrogels in tissue engineering

Light processable natural polymers are highly attractive for 3D printing of biomedical hydrogels with defined geometries and sizes. However, functionalization with photo-curable groups, such as methacrylate or acrylate groups, is required. Here, we investigated a microwave-assisted process for methacrylation of chitosan to replace conventional methacrylation processes that can be time consuming and tedious. The microwave-assisted methacrylation reaction was optimized by varying the synthesis parameters such as the molar ratio of chitosan to the methacrylic agent, the launch and reaction times and process temperature. The optimized process was fast and efficient and allowed tuning of the degree of substitution and thereby the final hydrogel properties. The successful methacrylation and degree of substitution were verified by H-1 NMR and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The influence of the degree of methacrylation on photo-rheology, mechanical stiffness, swelling degree and gel content was evaluated. Furthermore, favourable 3D printability, enzymatic degradability, biocompatibility, cell migration and proliferation were demonstrated giving promise for further applications in tissue engineering

On dimension reduction in Gaussian filters

A priori dimension reduction is a widely adopted technique for reducing the computational complexity of stationary inverse problems. In this setting, the solution of an inverse problem is parameterized by a low-dimensional basis that is often obtained from the truncated Karhunen-Loeve expansion of the prior distribution. For high-dimensional inverse problems equipped with smoothing priors, this technique can lead to drastic reductions in parameter dimension and significant computational savings. In this paper, we extend the concept of a priori dimension reduction to non-stationary inverse problems, in which the goal is to sequentially infer the state of a dynamical system. Our approach proceeds in an offline-online fashion. We first identify a low-dimensional subspace in the state space before solving the inverse problem (the offline phase), using either the method of "snapshots" or regularized covariance estimation. Then this subspace is used to reduce the computational complexity of various filtering algorithms - including the Kalman filter, extended Kalman filter, and ensemble Kalman filter - within a novel subspace-constrained Bayesian prediction-and-update procedure (the online phase). We demonstrate the performance of our new dimension reduction approach on various numerical examples. In some test cases, our approach reduces the dimensionality of the original problem by orders of magnitude and yields up to two orders of magnitude in computational savings