Smaller Bi Research Articles

Solar pyrolysis of biomass - part I: Volatile evolution mechanism

• Solar pyrolysis process of willow pellet is dynamically studied. • The effect of thickness and heat flux density on product yields is analyzed. • The intra-particle secondary reactions of volatile composition are further studied. • Dimensionless number Bi∙Prmass is proposed to predict solar pyrolysis behavior. • Mechanism of volatile evolution during solar pyrolysis is revealed. To study the volatile evolution mechanism during solar pyrolysis of biomass, willow pellets with thicknesses of 3 mm, 1 mm and 0.5 mm were used to investigate the dynamic pyrolysis characteristics at heat flux densities of 0.5 and 1.1 MW/m 2 . The results showed that the larger thickness significantly reduced oil yield (by 23%–35%) and increases gas yield (by 19%–20%), while increasing heat flux density showed a similar trend. These changes in solar pyrolysis behavior and product composition were governed by intra-particle secondary reactions due to the heat and mass transfer conditions. The evolution of heavy compounds (molecular weight ≥ 200 Da) was integrated into the volatile evolution mechanism of solar pyrolysis. Results showed the secondary reactions promoted the cracking, deoxygenation and condensation of sugars and phenolic species, and also led to the growth of condensed aromatic hydrocarbons. A novel dimensionless number (Bi∙Pr mass ) was proposed in this study to estimate the solar pyrolysis behavior of wood pellets. A smaller Bi∙Pr mass indicates that the conversion process is dominated by primary pyrolysis, while a higher value indicates that it is dominated by intra-particle secondary reactions. Depending on the degree of condensation, a critical value of Bi∙Pr mass around 0.1 was adopted in this study. This work can provide guidance about operating conditions optimization for solar gasification of biomass.

Local structure inBaTiO3−BiScO3dipole glasses

Local structures in cubic perovskite-type $(\mathrm{B}{\mathrm{a}}_{0.6}\mathrm{B}{\mathrm{i}}_{0.4})(\mathrm{T}{\mathrm{i}}_{0.6}\mathrm{S}{\mathrm{c}}_{0.4}){\mathrm{O}}_{3}$ solid solutions that exhibit reentrant dipole glass behavior have been studied with variable-temperature x-ray/neutron total scattering, extended x-ray absorption fine structure, and electron diffraction methods. Simultaneous fitting of these data using a reverse Monte Carlo algorithm provided instantaneous atomic configurations, which have been used to extract local displacements of the constituent species. The smaller Bi and Ti atoms exhibit probability density distributions that consist of 14 and 8 split sites, respectively. In contrast, Ba and Sc feature single-site distributions. The multisite distributions arise from large and strongly anisotropic off-center displacements of Bi and Ti. The cation displacements are correlated over a short range, with a correlation length limited by chemical disorder. The magnitudes of these displacements and their anisotropy, which are largely determined by local chemistry, change relatively insignificantly on cooling from room temperature. The structure features a nonrandom distribution of local polarization with low-dimensional polar clusters that are several unit cells in size. In situ measurements of atomic pair-distribution function under applied electric field were used to study field-induced changes in the local structure; however, no significant effects besides lattice expansion in the direction of the field could be observed up to electric-field values of $4\phantom{\rule{0.16em}{0ex}}\mathrm{kV}\phantom{\rule{0.16em}{0ex}}\mathrm{m}{\mathrm{m}}^{\ensuremath{-}1}$.

May clinical neurophysiology help to predict the recovery of neurological early rehabilitation patients?

BackgroundSo far, the role of clinical neurophysiology in the prediction of outcome from neurological and neurosurgical early rehabilitation is unclear.MethodsClinical and neurophysiological data of a large sample of 803 early rehabilitation cases of the BDH-Clinic Hessisch Oldendorf in Northern Germany have been carefully reviewed. Most patients (43.5 %) were transferred to rehabilitation after stroke, mean age was 66.6 (15.5) years. Median somatosensory (SEP), auditory (AEP) and visual evoked potentials (VEP) along with EEG recordings took place within the first two weeks after admission. Length of stay (LOS) in early rehabilitation was 38.3 (37.2) days.ResultsAbsence of SEP on one or both sides was associated with poor outcome, χ2 = 12.98 (p = 0.005); only 12.5 % had a good outcome (defined as Barthel index, BI ≥50) when SEP were missing on both sides. In AEP, significantly longer bilateral latencies III were observed in the poor outcome group (p < 0.05). Flash VEP showed that patients in the poor outcome group had a significantly longer latency III on both sides (p < 0.05). The longer latency III, the smaller BI changes (BI discharge minus admission) were observed (latency III right r = −0.145, p < 0.01; left r = −0.206, p < 0.001). While about half of the patients with alpha EEG activity belonged to the good outcome group (80/159, 50.3 %), only 39/125 (31.2 %) with theta and 5/41 (12.2 %) with delta rhythm had a favourable outcome, χ2 = 24.2, p < 0.001.ConclusionsResults from this study suggest that loss of median SEP, prolongation of wave III in AEP and flash-VEP as well as theta or delta rhythms in EEG are associated with poor outcome from neurological early rehabilitation. Further studies on this topic are strongly encouraged.

Polymetallic mineralization of the Boranja orefield, Podrinje Metallogenic District, Serbia: zonality, mineral associations and genetic features

In the Serbo-Macedonian Metallogenetic Province, which is a part of the Alpine metallogenic unit, the ore deposits lie in number geotectonic units; they embrace part of the Vardar Zone, Serbo-Macedonian massif, and a small part of the Dinarides. This metallogenic province has been delineated mostly by reference to the Neogene metallogeny, related predominantly to granodiorite magma. These deposits include the most significant Pb-Zn and Sb deposits in Serbia, as well as smaller Bi, Mo, Cu, Fe, Sn, Au and minor U, W and Hg deposits. The Podrinje Metallogenic District belongs to the Serbo-Macedonian Metallogenetic Province. Smaller metallogenic provinces are isolated within the scope of the following orefields: Cer (Northwest Serbia), Boranja (West Serbia), and Srebrenica (East Bosnia & Herzegovina). Polymetallic deposits in the Boranja orefield are genetically related to the emplacement of a Tertiary granodiorite complex. It consists primarily of a large number of sulfide deposits with Pb-Zn, and Sb; with subordinate Cu, As, Bi and Ag. Among them, the presence of small magnetite deposits, connected to the pyrometasomatic (skarn) stage is significant. Skarns are of calcic type, and were formed along contacts of Triassic limestones and quartz diorites. Ore minerals are similar among the various types of orebodies in the Boranja orefield and consist of sulfides (pyrrhotite, pyrite, marcasite, chalcopyrrhotite, chalcopyrite, cubanite, mackinawite, valleriite, covelline, chalcocite, bismuthinite, molybdenite, sphalerite, mercurian sphalerite, greenockite, galena, arsenopyrite, stibnite, duranusite, realgar, orpiment, cinnabar, metacinnabar); sulfosalts (bursaite, cannizzarite, cosalite, aikinite, ustarasite, tetradymite, ferrian tetrahedrite, argentian tetrahedrite, pyrargyrite, diaphorite, freieslebenite, schirmerite, fizelyite, stannite, jamesonite, boulangerite, bournonite, As-bournonite, falkmanite, zinkenite, fuloppite, robinsonite, plagionite, twinnite, geocronite, gratonite); telluride (calaverite); native metals and alloys (gold, silver, electrum, bismuth, arsenic); oxides and complex-oxides (magnetite, hematite, rutile, anatase, scheelite, powellite, valentinite, senarmontite, kermesite, adamite, arsenolite); and gangue minerals (silicates, carbonates, fluorite, calcite, siderite, Mn-Zn siderite, fluorite, apatite, barite, dolomite, anglesite, cerussite, smithsonite, otavite, malachite, azurite, scorodite, quartz, limonite, organic matter). Minerals of the titled orefield were formed in several successive stages, which together correspond to a unique cycle of mineralization that is genetically related to the subvulcanic-plutonic intrusion of the Neogene-aged magmatic Boranja complex. Mineral associations, which have spatial-zonal arrangement, are rhythmically developed from the Tertiary granodiorite of Boranja to outside surroundings: A) Fe-Cu(Bi) belt → B) Pb(Ag)-Zn belt → C) Sb(As) belt → D) CaF 2 (Pb-Zn) belt.