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Direct measurements of aerosol absorption coefficient using photo-thermal interferometry - methodology, traceable calibration and laboratory and ambient measurements
No full textMeasuring the aerosol absorption coefficient is central for the determination of the aerosol influence on the climate and for the determination of sources of carbonaceous aerosol, especially black carbon (BC). Different methods can be used to determine or measure the aerosol absorption coefficient. Filter absorption photometers (FPs) are most easy to deploy but feature artefacts and require sophisticated calibration with a reference method. Few direct methods for in-situ aerosol absorption measurement exist, with photothermal interferometry (PTI) showing several advantages. We present how the PTI can be traceably calibrated, used as a reference method in the laboratory and in the field. A photothermal interferometer measures the change of the refractive index caused by light absorption in (and the subsequent heating of) the sample – the change of phase in the interferometer is proportional to the aerosol absorption coefficient. The detection is linear and can be traced to first principles. Since the laser-sample interaction region is monitored continuously, the method does not suffer from artefacts. The interferometric measurement can be calibrated to first principles. In-situ absorption instruments use different calibration schemes. NO2 is used for calibration in the visible range and can be traceable to SI units. Particles, on the other hand, allow calibration without wavelength limitations. We compare different calibration schemes in light of their measurement uncertainty and ease of implementation. The experimental results and a comparison with the Mie model monodisperse nigrosin aerosols show that mass-based parameters are more suitable for the modelling rather than mobility-based ones. The resulting aerosol absorption coefficient uncertainty is smaller than 5%.Laboratory and ambient campaigns have shown similar FP calibration parameter values for ambient aerosols and laboratory experiments. We have also determined the absorption enhancement by coating BC with non-absorbing secondary organic matter in laboratory and ambient campaigns in contrasted environments (Slovenia, France). Mass absorption cross-section increase due to coatings were determined using different mass metrics – elemental carbon or refractory black carbon.We present measurements with calibrated FPs at the Virtual Alpine Observatory station Otlica, where we determined the BC emission rates, and airplane measurements, where the atmospheric heating rate was measured separately for BC and Saharan desert dust. This work was supported by EURAMET (22NRM02 stanBC), ARIS (P1-0385, I-0033, L2-4485) and ESA (4000131931/20/NL/FF/an)
Pan-slavism among Slovenian Americans and their relationship with Yugoslavia during the period 1938–1945
No full textRad se bavi razvojem panslavizma među američkim Slovencima u periodu između 1938. i 1945. godine, analizirajući različite interpretacije ove ideje i njihov značaj za učvršćivanje slovenačkog identiteta u Sjedinje- nim Američkim Državama. Na osnovu analize arhivske građe, novinskih članaka i relevantne literature, rad osvetljava ulogu panslavizma kao ideo- loškog i praktičnog sredstva u kontekstu antifašističke borbe i transnacio- nalnih veza. Posebna pažnja posvećena je ključnim ličnostima poput Luja Adamiča, Ivana Moleka i Jurija Trunka, čiji različiti pristupi panslavizmu – od političkog pragmatizma i rezervisanosti prema Sovjetskom Savezu do kulturnog i verskog ujedinjenja – ilustruju širinu ove ideje među slovenač- kim iseljenicima. Istraživanje pokazuje kako su američki Slovenci koristili panslavizam kao okvir za jačanje zajednice, borbu protiv fašizma i očuva- nje kulturnog nasleđa u sredini koja je podsticala asimilaciju. Nakon rata, značaj panslavizma postepeno je opadao usled političkih promena u Evropi i ideoloških raskola
A review of chaotification techniques for discrete-time systems
No full textThis work provides a thorough review on the research topic of chaotification for discrete-time systems. Chaotification refers to the process of designing new chaotic maps, using existing maps from the literature as seed functions, with the goal of achieving a more complex behavior. This problem is of great theoretical interest, but also of practical importance, as highly complex chaotic systems are sought after in many applications. This review aims at providing a roadmap on the topic of chaotification, by presenting the recent developments in the topic, organized by the methodologies that are considered. Future challenges are also identified
Validating a chaos based PRBG under different chaotic maps
No full textChaos-based random bit generators are abundantly used in chaos-based encryption and security applications, as a fast, deterministic source of randomness, to perform actions like permutation and substitution. The chaotic map used as a source of randomness though may heavily affect the bit generator’s statistical randomness, key space, and speed. Thus, any given bit generator may not be equally efficient for all the chaotic maps used as a seed. Motivated by this, the present work considers a bit generator that utilizes a common modulo-based hashing technique, and studies its performance under a plethora of different chaotic maps. For each map, the generator is evaluated with respect to randomness, key space, and operations per bit ratio. This analysis can serve as a guideline for random bit generator usage in future chaos-based encryption designs
Ideological struggles within ethnic communities
No full textThis article examines the efforts of the Slovenian section of the Communist Party USA (CPUSA) to influence public opinion within the Slovenian American community during the 1930s. It explores the interplay between ideology, ethnic identity, and political activism, focusing on how events like the Spanish Civil War, the annexation of Austria, and the Nazi-Soviet Pact shaped public attitudes. Central to this activity was the magazine Naprej, which served as an informal CPUSA organ for disseminating anti-fascist and communist ideas. Slovenian American communists aimed to guide the community\u27s political engagement by adopting grassroots tactics reminiscent of the Communist Party of Yugoslavia\u27s (CPY) strategies under the Popular Front policy. However, they encountered resistance from major Slovenian American organizations and publications, which rejected their ideological stance. Despite these challenges, their discourse influenced certain segments of the community, contributing to ideological divides that became evident during World War II, particularly regarding Yugoslavia\u27s postwar future. Methodologically, this study draws on archival, newspaper, and memoir sources to contextualize these activities within broader trends in ethnic and leftist politics, offering a new perspective on the intersection of communism and ethnic identity in pre-war America
