Thermal diffusivity of sintered 12CaO-7Al2O3

The thermal diffusivity and some electrical transport properties of sintered 12CaO-7Al2O3 were determined using a photoacoustic method with a transmission detection configuration. The thermal diffusivity, coefficient of carrier diffusion and the surface recombination velocities were determined by fitting experimental spectra and theoretical photoacoustic amplitude and phase signals

Photoacoustic properties of single crystal PbTe(Ni)

Single crystals of PbTe(Ni) were investigated by the photoacoustic method. They were produced using the Bridgeman method. These crystals have a sodium chloride cubic lattice and could be cleaved paralel to the plane orientation (200). They were of the n-type. Phase and amplitude photoacoustic spectra were measured using a transmision detection configuration set-up. Photoacoustic (PA) spectra (single and normalized) were numerically analyzed using the Rosencwaig-Gersho model. Thermal diffusivity and some electron-transport parameters were determined. These results were compared with existing results for pure single crystal PbTe. Thermal difusivity of PbTe(Ni) is a bit higher than the thermal difusivity of pure PbTe. This is the consequence of a decreasing concentration of the majority free carriers in the doped alloy

Photoacoustic properties of single crystal PbTe(Ni)

Single crystals of PbTe(Ni) were investigated by the photoacoustic method. They were produced using the Bridgeman method. These crystals have a sodium chloride cubic lattice and could be cleaved paralel to the plane orientation (200). They were of the n-type. Phase and amplitude photoacoustic spectra were measured using a transmision detection configuration set-up. Photoacoustic (PA) spectra (single and normalized) were numerically analyzed using the Rosencwaig-Gersho model. Thermal diffusivity and some electron-transport parameters were determined. These results were compared with existing results for pure single crystal PbTe. Thermal difusivity of PbTe(Ni) is a bit higher than the thermal difusivity of pure PbTe. This is the consequence of a decreasing concentration of the majority free carriers in the doped alloy

Multi-frequency study of a new Fe-rich supernova remnant in the Large Magellanic Cloud, MCSNR J0508-6902

We present a detailed radio, X-ray and optical study of a newly discovered Large Magellanic Cloud (LMC) supernova remnant (SNR) which we denote MCSNR J0508-6902. Observations from the Australian Telescope Compact Array (ATCA) and the $\textit{XMM-Newton}$ X-ray observatory are complemented by deep H$\alpha$ images and Anglo Australian Telescope AAOmega spectroscopic data to study the SNR shell and its shock-ionisation. Archival data at other wavelengths are also examined. The remnant follows a filled-in shell type morphology in the radio-continuum and has a size of $\sim$74 pc $\times$ 57 pc at the LMC distance. The X-ray emission exhibits a faint soft shell morphology with Fe-rich gas in its interior $-$ indicative of a Type Ia origin. The remnant appears to be mostly dissipated at higher radio-continuum frequencies leaving only the south-eastern limb fully detectable while in the optical it is the western side of the SNR shell that is clearly detected. The best-fit temperature to the shell X-ray emission ($kT = 0.41^{+0.05}_{-0.06}$ keV) is consistent with other large LMC SNRs. We determined an O/Fe ratio of $<21$ and an Fe mass of 0.5-1.8$~M_{\odot}$ in the interior of the remnant, both of which are consistent with the Type Ia scenario. We find an equipartition magnetic field for the remnant of $\sim$28 $\mu$G, a value typical of older SNRs and consistent with other analyses which also infer an older remnant

Comparison of ICP-MS, ICP-OES, INAA, and WDXRF Techniques in Measuring Elements in Coniferous Needles Samples

The elemental composition of plant matrices has been conventionally determined by spectrometric techniques such as Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) [1]. Wet mineralization (digestion) of samples requires time, equipment, and usage of aggressive and toxic chemicals which are the main drawbacks of those routinely used techniques [2]. The need for suitable analytical methods for direct and multi-elemental analysis of plant samples has been increased in recent years [3]. Instrumental Neutron Activation Analysis (INAA) is one of the techniques for direct analysis which has been previously applied in environmental studies, nevertheless it is not a commonly used technique for plant samples. X-ray fluorescence (XRF) is another technique with the possibility of performing multi-element analysis directly on solid samples with numerous advantages. Although non-destructive techniques (INAA and XRF) are widely accepted in various fields of screening tests regarding the analytical approach, their performance needs to be evaluated in plant sample analysis. The main aim of this research was to assess how reliable non-destructive techniques are in detecting elements in conifer needles regarding routinely used spectrometric techniques. A total of 49 plant samples of four conifer species (Pinus nigra, Abies alba, Taxus baccata, and Larix decidua) were measured using two routinely used (ICPMS and ICP-OES) and two non-destructive instrumental techniques (WD-XRF and INAA). A quality control program included NIST pine needles certified reference material (1575a) analysis using all examined techniques. The techniques were compared by examination of relative ratio (element concentration measured using investigated analytical techniques divided by concentration determined by ICP-MS (figure 1)) and by correlation. Precision of all examined techniques was additionally investigated. This study confirmed that non-destructive spectroscopic techniques can be successfully applied on plant samples since sample preparation for these techniques is fast and in good accordance with the principles of green chemistry. Investigated standardless XRF method can also produce well-correlated results, compared to other techniques based on calibration standards. Obtained results suggest that the high accuracy of the analysis can be ensured by additional analytical and quality control steps (the use of internal standards, standard addition, etc.)

Uticaj sive protivgradne mreže na kvalitet ploda borovnice (Vaccinium corymbosum L.) sorte "Bluecrop"

The main focus of our study was to investigate effects of the modified microclimate under a grey hail protection net (HPN) on biometrical fruit characteristics (fruit weight, index of fruit shape, and seed number per fruit) and nutritional value (soluble solid content - SSC, titratable acidity - TA, total anthocyanins - TACY, total phenolics - TPH and total antioxidant capacity - TAC) of the 'Bluecrop' highbush blueberry (Vaccinium corymbosum L.). The study was conducted in the 'Bluecrop' highbush blueberry plantation located in Mladenovac (Serbia) during two consecutive years (2013, 2014). The orchard was established using two-year-old nursery trees in spring 2011, at a planting density of 3,300 bushes per ha. The grey polyethylene net (SILVERLUX®, Helios Group, Lurano, Italy) with a Leno wave structure and a mesh size of 2.8 x 8 mm was used. During the research period, light intensity was measured weekly at 12.00 hr using a digital lux-meter 'Peak teck' PT-5025 (Germany). Air temperature and relative humidity within the canopy were recorded using climate dataloggers (type DT-171, Shenzhen Flus Technology Co., Ltd, China) both under HPN and in the open field (OF). Twelve readings per treatment were taken at 2-hour intervals every day in each season. In both years of observation, light was reduced by 5-20% under HPN, whereby daily maximum temperature was 2.4°C lower causing 4% higher daily minimum relative air humidity than in OF. 'Bluecrop' had significantly higher average fruit weights under HPN ranging from 1.93 g (2013) to 1.86 g (2014) in comparison to those observed in OF. The SSC did not differ between the treatments in 2014, whereas a significantly higher mean value was registered in the fruits harvested under HPN (12.8%) compared to those from OF in 2013. The mean TA was higher under HPN in 2014 (0.57%), whereas in 2013 a significantly higher TA content was found in OF (0.87%). HPN showed a positive effect on the TPH content (7.12 mg GA/g FW), but an almost 2-fold higher value was registered in 2013. Similar to this, TAC was 2.5-fold higher in 2013, without a significant effect of HPN in both experimental years.U ovom radu su ispitivani efekti izmenjene mikroklime pod sivom protivgradnom mrežom (PGM) na fizičke osobine ploda (masa ploda, indeks oblika ploda i broj semenki u plodu) i nutritivnu vrednost (sadržaj rastvorljive suve materije - RSM, ukupnih kiselina i ukupnih fenola, kao i ukupni antioksidativni kapacitet ploda) sorte borovnice "Bluecrop" (Vaccinium corymbosum L.). Ispitivanja su izvedena u periodu 2013-2014. godina, u zasadu borovnice koji se nalazi u blizini Mladenovca. Zasad je podignut u proleće 2011. godine sa trogodišnjim sadnicama i gustinom sadnje od 3.300 žbunova po ha. Primenjena je siva PGM (SILVERLUX®, Helios Group, Lurano, Italy), težine 48 g/m2, sa veličinom otvora 2,8 x 8 mm. Tokom perioda ispitivanja, intenzitet svetlosti je meren jedanput nedeljno u 12 h korišćenjem luks metra "Peak teck" PT-5025 (Germany). Temperatura i relativna vlažnost vazduha su merene uređajem za evidentiranje podataka (engl. data logger, DT-171, Shenzhen Flus Technology Co., Ltd, China) na svaka 2 h pod PGM i na otvorenom polju (kontrolni tretman) od početka cvetanja do kraja zrenja borovnice u obe ispitivane godine. Intenzitet svetlosti pod PGM je bio u proseku smanjen za 5-20% u obe eksperimentalne godine. Dnevne maksimalne temperature bile su za 2,4 oC niže pod PGM uslovljavajući za 4% višu minimalnu dnevnu relativnu vlažnost vazduha u poređenju sa otvorenim poljem. Značajno veća prosečna vrednost mase ploda kod ispitivane sorte borovnice registrovana je pod PGM u poređenju sa otvorenim poljem, i kretala se od 1,93 g (2013) do 1,86 g (2014). Sadržaj RSM se nije značajno razlikovao između tretmana u 2014. godini, dok je u 2013. godini značajno povećanje registrovano u plodovima koji su ubrani pod PGM (12,8%) u poređenju sa otvorenim poljem (11,6%). Prosečna vrednost sadržaja ukupnih kiselina je bila veća pod PGM u 2014. godini (0,57%), dok je u 2013. godini značajno veći sadržaj pronađen u plodovima ubranim na otvorenom polju (0,87%). PGM je ispoljila pozitivan efekat na sadržaj ukupnih fenola (7,12 mg galne kis. g-1sv.m.pl.), međutim skoro dva puta viša vrednost je bila registrovana u 2013. godini. Slično sadržaju ukupnih fenola, ukupni antioksidativni kapacitet ploda je bio za 2,5 puta veći u 2013. godini, bez značajnog uticaja PGM u obe ispitivane godine

Perturbation Theory in Two Dimensional Open String Field Theory

In this paper we develop the covariant string field theory approach to open 2d strings. Upon constructing the vertices, we apply the formalism to calculate the lowest order contributions to the 4- and 5- point tachyon--tachyon tree amplitudes. Our results are shown to match the `bulk' amplitude calculations of Bershadsky and Kutasov. In the present approach the pole structure of the amplitudes becomes manifest and their origin as coming from the higher string modes transparent.Comment: 26 page

Murchison Widefield Array and XMM-Newton observations of the Galactic supernova remnant G5.9+3.1

In this paper we discuss the radio continuum and X-ray properties of the so-far poorly studied Galactic supernova remnant (SNR) G5.9+3.1. We present the radio spectral energy distribution (SED) of the Galactic SNR G5.9+3.1 obtained with the Murchison Widefield Array (MWA). Combining these new observations with the surveys at other radio continuum frequencies, we discuss the integrated radio continuum spectrum of this particular remnant. We have also analyzed an archival XMM-Newton observation, which represents the first detection of X-ray emission from this remnant. The SNR SED is very well explained by a simple power-law relation. The synchrotron radio spectral index of G5.9+3.1, is estimated to be 0.42$\pm$0.03 and the integrated flux density at 1GHz to be around 2.7Jy. Furthermore, we propose that the identified point radio source, located centrally inside the SNR shell, is most probably a compact remnant of the supernova explosion. The shell-like X-ray morphology of G5.9+3.1 as revealed by XMM-Newton broadly matches the spatial distribution of the radio emission, where the radio-bright eastern and western rims are also readily detected in the X-ray while the radio-weak northern and southern rims are weak or absent in the X-ray. Extracted MOS1+MOS2+PN spectra from the whole SNR as well as the north, east, and west rims of the SNR are fit successfully with an optically thin thermal plasma model in collisional ionization equilibrium with a column density N_H~0.80x$10^{22}$ cm$^{-2}$ and fitted temperatures spanning the range kT~0.14-0.23keV for all of the regions. The derived electron number densities n_e for the whole SNR and the rims are also roughly comparable (ranging from ~$0.20f^{-1/2}$ cm$^{-3}$ to ~$0.40f^{-1/2}$ cm$^{-3}$, where f is the volume filling factor). We also estimate the swept-up mass of the X-ray emitting plasma associated with G5.9+3.1 to be ~$46f^{-1/2}M_{\odot}$.Comment: Accepted for publication in A&

Optical Spectra of SNR Candidates in NGC 300

We present moderate-resolution (<5A) long-slit optical spectra of 51 nebular objects in the nearby Sculptor Group galaxy NGC 300 obtained with the 2.3 meter Advanced Technology Telescope at Siding Spring Observatory, Australia. Adopting the criterion of [SII]/Ha>=0.4 to confirm supernova remnants (SNRs) from optical spectra, we find that of 28 objects previously proposed as SNRs from optical observations, 22 meet this criterion with six showing [SII]/Ha of less than 0.4. Of 27 objects suggested as SNRs from radio data, four are associated with the 28 previously proposed SNRs. Of these four, three (included in the 22 above) meet the criterion. In all, 22 of the 51 nebular objects meet the [SII]/Ha criterion as SNRs while the nature of the remaining 29 objects remains undetermined by these observations.Comment: Accepted for publication in Astrophysics & Space Scienc

Far infrared and transport properties of single crystal PBTE samples doped with Ce

Single crystal samples of lead telluride doped with cerium were made using the Bridgman technique. Single crystals could be easily cleaved parallel to the (002) plane. Room temperature far infrared reflectivity was measured on single crystal samples and a plasma minimum at about 180 cm(-1) and local modes of Ce were observed. A fitting procedure based on a modified four parameter model of plasmon - phonon interaction, was used to determine the values of optical parameters. Carrier concentration and their mobility were measured at room and liquid nitrogen temperatures.Romanian Conference on Advanced Materials (ROCAM 2000), Bucharest, ROMANIA, october 23-25th, 2000