Intense desert dust event in the northern Adriatic (March 2020); insights from the numerical model application and chemical characterization results.

The untypically extreme and sudden particulate matter outbreak set stage over Balkan region from 27 to 30 March 2020. The available observations at air quality stations in Croatia recorded the hourly PM10 concentrations up to 412 μgm-3. Meteorological analysis shows the PM10 concentrations increase was primarily affected by advection of mineral dust from the desert area east to the Caspian Sea. The anticyclone north of Croatia and cyclone over Anatolia formed a strong pressure gradient driving a transport from the east. The backward trajectories as well as satellite products indicated the dry Aral Sea as a major source of dust. A dust plume affected the PM10 increase observed in Croatia, starting at Osijek and easternmost air quality stations . Modeling study shows the vertical extension of a plume was up to ~2 km. However, the PM10 chemical (Pb, Cd, Cu, Zn, Fe, Mn, PAHs) and morphological (SEM analyses) composition at the site in the northeastern Adriatic revealed mainly the presence of the Saharan dust. Preceding the Asian dust advection, the Saharan dust transport towards Balkan driven by Sharav cyclone was observed in PM10 at several stations in the Adriatic and continental Croatia on 26 March 2020. Modeling results showed the Saharan dust transport was at levels below ~ 8 km. The mixing of the Asian and Saharan dust plumes over Balkan was favored by subsidence due to anticyclonic high pressure conditions, and it is the most likely explanation for the observed PMs chemical and morphological results

Grain-Size-Induced Collapse of Variable Range Hopping and Promotion of Ferromagnetism in Manganite La0.5Ca0.5MnO3

mong transition metal oxides, manganites have attracted significant attention because of colossal magnetoresistance (CMR)- a magnetic field-induced metal–insulator transition close to the Curie temperature. CMR is closely related to the ferromagnetic (FM) metallic phase which strongly competes with the antiferromagnetic (AFM) charge ordered (CO) phase, where conducting electrons localize and create a long range order giving rise to insulator-like behavior. One of the major open questions in manganites is the exact origin of this insulating behavior. Here we report a dc resistivity and magnetization study on manganite La1−xCaxMnO3 ceramic samples with different grain size, at the very boundary between CO/AFM insulating and FM metallic phases x = 0.5. Clear signatures of variable range hopping (VRH) are discerned in resistivity, implying the disorder-induced (Anderson) localization of conducting electrons. A significant increase of disorder associated with the reduction in grain size, however, pushes the system in the opposite direction from the Anderson localization scenario, resulting in a drastic decrease of resistivity, collapse of the VRH, suppression of the CO/AFM phase and growth of an FM contribution. These contradictory results are interpreted within the standard core-shell model and recent theories of Anderson localization of interacting particles

Repetitorij i zbirka riješenih zadataka iz valova i optike

Repetitorij i zbirka riješenih zadataka iz valova i optike na sustavan i jednostavan način prati gradivo kolegija Fizika 3: Valovi i optika koji se izvodi na preddiplomskom studiju Fizika Odjela za fiziku, Sveučilišta u Rijeci. Svako poglavlje počinje kratkim i nužnim teorijskim uvodom, nakon čega slijede potpuno riješeni primjeri, a na kraju su zadaci s rješenjima. Veliki broj zadataka uključuje slike s objašnjenjima. Zbirka je podijeljena u četiri cijeline odnosno trinaest poglavlja: Geometrijska optika (Zakoni geometrijske optike; Zrcala; Sferni diopotar i debela leća; Tanka leća; Optički instrumenti), Valna optika (Valna jednadžba i načelo superpozicije; Interferencija; Ogib; Polarizacija i Fresnelove jednakosti; Disperzija, apsorpcija i Dopplerov efekt), Mehanički valovi i akustika (Brzina i energija mehaničkog vala; Stojni val, Dopplerov efekt u akustici), te Fotometrija (Osnovne fotometrijske veličine). Svako poglavlje ima uvodni dio s pregledom definicija i formula koje se u njemu upotrebljavaju, zatim slijede potpuno riješeni primjeri razvrstani prema težini te na kraju zadaci za vježbu uz koje je uvijek navedeno konačno rješenje, a ponegdje i uputa. Zbirka ima 145 ilustracija te preko 140 riješenih zadataka i preko 100 dodatnih zadataka za vježbu

Repetitorij i zbirka riješenih zadataka iz valova i optike

Repetitorij i zbirka riješenih zadataka iz valova i optike na sustavan i jednostavan način prati gradivo kolegija Fizika 3: Valovi i optika koji se izvodi na preddiplomskom studiju Fizika Odjela za fiziku, Sveučilišta u Rijeci. Svako poglavlje počinje kratkim i nužnim teorijskim uvodom, nakon čega slijede potpuno riješeni primjeri, a na kraju su zadaci s rješenjima. Veliki broj zadataka uključuje slike s objašnjenjima. Zbirka je podijeljena u četiri cijeline odnosno trinaest poglavlja: Geometrijska optika (Zakoni geometrijske optike; Zrcala; Sferni diopotar i debela leća; Tanka leća; Optički instrumenti), Valna optika (Valna jednadžba i načelo superpozicije; Interferencija; Ogib; Polarizacija i Fresnelove jednakosti; Disperzija, apsorpcija i Dopplerov efekt), Mehanički valovi i akustika (Brzina i energija mehaničkog vala; Stojni val, Dopplerov efekt u akustici), te Fotometrija (Osnovne fotometrijske veličine). Svako poglavlje ima uvodni dio s pregledom definicija i formula koje se u njemu upotrebljavaju, zatim slijede potpuno riješeni primjeri razvrstani prema težini te na kraju zadaci za vježbu uz koje je uvijek navedeno konačno rješenje, a ponegdje i uputa. Zbirka ima 145 ilustracija te preko 140 riješenih zadataka i preko 100 dodatnih zadataka za vježbu

In Situ X‑ray Photoelectron Spectroscopy Study of Initial Stages of Tungsten Trioxide Reduction by Low-Energy Hydrogen Bombardment

The evolution of different W oxidation states and the oxide reduction mechanism of polycrystalline WO3 thin films, induced by low-energy H2+ bombardment at room temperature, was investigated in situ by X-ray photoelectron spectroscopy around W 4f and O 1s core levels and the valence band. A hydrogen tungsten bronze is formed at the beginning of the reduction process, as is evident from the development of the W5+ oxidation state and the creation of the O–H bonds. With the higher H implantation dose, reduction proceeds with the creation of H2O gas molecules, whose evolution with the bombardment time correlates with the cumulative concentration fractions of W4+, W2+, and W0 oxidation states. The generation of H2O molecules removes O atoms from the WO3 matrix, inducing the reduction of WO3 to lower oxides and, subsequently, metallic W, which is the dominant phase on the surface after 180 min of bombardment

Prevention of spontaneous combustion of cellulose with a thin protective Al2O3 coating formed by atomic layer deposition

We have studied properties of thin protective coating layers of Al2O3, grown by atomic layer deposition (ALD) technique on surfaces of cellulose fibrous materials, using scanning electron microscopy (SEM), scanning transmission microscopy (STEM), energy dispersive x-ray spectroscopy (EDS), high- resolution transmission microscopy (HR-TEM), x- ray diffraction (XRD) and thermal gravimetry (TGA). A minimum thickness of about 50 nm was required to completely inhibit oxygen diffusion into the material and prevent self-ignition at elevated temperatures. No substantial differences were found in morphology or protection performance of Al2O3 coatings produced by thermal or plasma-enhanced ALD (PEALD) methods. However, PEALD technique has shown almost a double growth rate, while, at the same time, it was successfully applied at temperatures as low as 40 °C without degrading quality of the coating