102 research outputs found
Circuital and Numerical Models for Calculation of Shielding Effectiveness of Enclosure with Apertures and Monitoring Dipole Antenna Inside
In this paper, circuital and numerical models of metal In this paper, circuital and numerical models of metal enclosure with apertures are considered for the purpose of accurate shielding effectiveness calculation. An improved circuital model is presented to account for the presence of receiving dipole antenna which is often used in practice to measure the level of electromagnetic field at selected points inside the enclosure. Receiving antenna of finite dimensions could significantly change the EM field distribution inside the enclosure and thus affect the results for SE. TLM method incorporating wire node is used to create a numerical model. Both models are compared in terms of their ability to account for receiving antenna impact on shielding effectiveness of rectangular enclosure with aperture. In addition, comparison of both models is carried out for the case when an array of apertures with different aperture separation is present on one of the enclosure walls whereby the numerical TLM model is additionally enhanced with compact air-vent model
The Red Flour Beetle as a Model for Bacterial Oral Infections
Experimental infection systems are important for studying antagonistic interactions and coevolution between hosts and their pathogens. The red flour beetle Tribolium castaneum and the spore-forming bacterial insect pathogen Bacillus thuringiensis (Bt) are widely used and tractable model organisms. However, they have not been employed yet as an efficient experimental system to study host-pathogen interactions. We used a high throughput oral infection protocol to infect T. castaneum insects with coleopteran specific B. thuringiensis bv. tenebrionis (Btt) bacteria. We found that larval mortality depends on the dietary spore concentration and on the duration of exposure to the spores. Furthermore, differential susceptibility of larvae from different T. castaneum populations indicates that the host genetic background influences infection success. The recovery of high numbers of infectious spores from the cadavers indicates successful replication of bacteria in the host and suggests that Btt could establish infectious cycles in T. castaneum in nature. We were able to transfer plasmids from Btt to a non-pathogenic but genetically well-characterised Bt strain, which was thereafter able to successfully infect T. castaneum, suggesting that factors residing on the plasmids are important for the virulence of Btt. The availability of a genetically accessible strain will provide an ideal model for more in-depth analyses of pathogenicity factors during oral infections. Combined with the availability of the full genome sequence of T. castaneum, this system will enable analyses of host responses during infection, as well as addressing basic questions concerning host-parasite coevolution
Crystal Structure and Properties of Theoretically Predicted AlB12
Aluminum borides have various industrial applications, used in fuels, explosives, abrasives, and as additives to consolidated materials based on boron carbide. The structure of AlB12 is similar to that of boron carbide, including almost regular icosahedrons of boron atoms. The absence of the structure data of some higher aluminum borides and the presence of a large number of reflexes in their diffraction patterns makes the identification of phase compositions very difficult and limits the possibilities of the computer modeling of the AlB12. The crystal structure of AlB12 is usually considered as tetragonal Ī±-AlB12 (space group P43212) and orthorhombic Ī³-AlB12 (space group P212121) which can be synthesized from high-temperature Al-B melts. In our work, we have performed ab initio optimization of the experimentally observed Yannoniās AlB12 using GGA-PBE functional and obtained relaxed unit cell parameters and atomic positions. Furthermore, we have predicted three different AlB12 structure candidates obtained as a result of the ICSD data mining. The most favorable structure according to total energy ranking was found in the UB12 structure type, which crystallizes in the cubic space group Fm-3m. Therefore, for the new cubic AlB12, we have calculated mechanical properties on different pressures and made the comparison with available experimental data in the AlB12 system
Makroporozni kopolimer na bazi glicidilmetakrilata funkcionalizovan sa dietilentriaminom kao sorbent tekstilne boje Reactive Black 5
In this paper, macroporous glycidyl methacrylate and ethylene glycol dimethacrylate copolymer functionalized with diethylene triamine (PGME-deta), was evaluated as Reactive Black 5 (RB5) sorbent. Batch RB5 removal from aqueous solution by PGME-deta was investigated by varying pH, contact time, sorbent dosage, initial dye concentration and temperature. The sorption is pH sensitive having maximum at pH 2 (dye removal of 85%), decreasing with the increase of pH (dye removal of 24% at pH 11) after 60 min. Sorption kinetics was fitted to chemical-reaction and particle-diffusion models (pseudo-first-, pseudo-second-order, intraparticle diffusion and Mckay models). The pseudo-second-order kinetic model accurately predicted the RB5 amount sorbed under all investigated operating conditions, while the intraparticle diffusion was the dominant rate-limiting mechanism. The diffusion mechanism was more prevalent with the decrease in temperature and the increase in concentration. The isotherm data was best fitted with the Langmuir model, indicating homogeneous distribution of active sites on PGME-deta and monolayer sorption, with the maximum sorption capacity of 353 mg g(-1). The calculated sorption rates improved with increasing temperature and an activation energy close to 40 kj mol(-1) was determined, suggesting that chemisorption was also rate-controlling.U okviru ovog rada ispitana je moguÄnost koriÅ”Äenja makroporoznog kopolimera glicidilmetakrilata i etilenglikoldimetakrilata funkcionalizovanog reakcijom otvaranja epoksidnih grupa sa dietilentriaminom (PGME-deta) kao sorbenta reaktivne tekstilne boje Reactive Black 5 (RB5). U Å”aržnim uslovima je ispitano uklanjanje RB5 iz vodenog rastvora pomoÄu PGME-deta, variranjem pH, vremena kontakta, mase sorbenta, poÄetne koncentracije boje i temperature. PGME-deta je pokazao afinitet za sorpciju RB5 zbog prisustva protonovanih amino grupa koje privlaÄe anjonske sulfonatne grupe u molekulu boje i moguÄnosti stvaranja vodoniÄnih veza izmeÄu sorbenta i sorbata. Kinetika sorpcije je analizirana pomoÄu Äetiri kinetiÄka modela (pseudo-prvog, pseudo-drugog reda, unutarÄestiÄne difuzije i Mekej) da bi se odredilo koji model najbolje opisuje sorpciju RB5. Zapažen je izrazit uticaj pH vrednosti na sorpciju RB5, sa maksimumom na pH 2 (pri Äemu je efikasnost uklanjanja boje 85%), i smanjenjem koliÄine sorbovane boje sa poveÄanjem pH (koliÄina uklonjene boje na pH 11 posle 60 min iznosi samo 24%). IzuÄavanjem kinetike sorpcije pokazalo se da sorpcija RB5 pomoÄu PGME-deta sledi kinetiÄki model pseudo-drugog reda (PSO), sugeriÅ”uÄi da je brzina sorpcije kontrolisana kapacitetom sorbenta i koncentracijom sorbata. Mehanizam procesa dominantno Äini unutarÄestiÄna difuzija, uz manji uticaj difuzije kroz film. Ovi mehanizmi difuzije su izraženiji pri nižim temperaturama i veÄim koncentracijama. Langmirov model najbolje opisuje ravnotežnu izotermu, ukazujuÄi na homogenu raspodelu aktivnih mesta na povrÅ”ini PGME-deta i monoslojnu sorpciju. Maksimalni sorpcioni kapacitet izraÄunat iz Langmirove izoterme iznosi 353 mg g-1. Zapaženo je da se brzina sorpcije poveÄava sa poveÄanjem temperature. IzraÄunata vrednost aktivacione energije od oko 40 kJ mol-1 potvrÄuje da se radi o procesu koji dominantno kontroliÅ”e hemisorpcija
Strategija 3+2 Osne Obrade Na Novoj Brusilici Za Izradu Profilnih Koturastih Glodala
Rezni alati predstavljaju važan segment u finalnoj obradi drveta. Rezni alati svojom složenom geometrijom omoguÄuju da se, u jednom prolazu, naprave složene povrÅ”ine na izratku koje su ranijih godina mogle da se kreiraju u viÅ”e prolaza, koriÅ”Äenjem manje složenih alata, uz obavezno prisustvo vrlo iskusnih operatera na maÅ”inama. Izrada profilnih koturastih glodala pored konvencionalnih maÅ”ina alatki zahteva i petoosnu CNC brusilicu koja profiliÅ”e seÄivo alata koje je složenog oblika. U ovom radu posebna pažnja posveÄena je strategiji 3+2 osne obrade na novoj CNC brusilici uzimajuÄi u obzir Äinjenicu da je na istoj napravljen veliki broj profilnih koturastih glodala Äime je potvrÄena industrijska primena nove CNC brusilice i uspostavljene tehnologije
Effects of Dietary Milled Seed Mixture on Fatty Acid Status and Inflammatory Markers in Patients on Hemodialysis
Background. Plant seeds have gained interest for their health benefits due to their fatty acid content. The objective of this study was to determine the effects of dietary consumption of milled sesame/pumpkin/flax seed mixture on glycemic control, serum lipids, phospholipid fatty acid status, and inflammatory factors in patients on hemodialysis. Methods. Thirty patients with well nutrition status (18 male, 12 female) were enrolled in the study. Participants consumed 30 g of milled sesame/pumpkin/flax (6 g/6 g/18 g, resp.) seeds mixture added to their habitual diet. Results. Total n-6 and n-3 polyunsaturated fatty acids and levels of linoleic, dihomo-gamma-linolenic (DGLA), arachidonic, alpha-linolenic (ALA), eicosapentaenoic, docosapentaenoic, and docosahexaenoic (DHA) acid were increased after 12 weeks of supplementation. A significant decrease of the serum triglyceride level (P lt 0.001), glucose, insulin, calculated IR HOMA (P lt 0.05), and inflammatory markers (TNF-alpha, IL-6, and hs-CRP,P lt 0.001) was observed after seed mixture treatment. The serum levels of CRP and TNF-alpha negative correlate with ALA, DHA, and DGLA. Conclusion. Results of this study indicated that dietary milled sesame/pumpkin/flax seed mixture added to a habitual diet lowered triglyceride and CRP, TNF-alpha, IL-6 levels, affect glycemic control and improved fatty acid profile and pruritus symptoms in hemodialysis patients
The z = 0.0777 C III Absorber Towards PHL 1811 as a Case Study of a Low Redshift Weak Metal Line Absorber
We consider the physical conditions and origin of the z = 0.0777 absorption
system observed in C III, C II, Si III, C IV, O VI, and H I absorption along
the line of sight towards the quasar PHL 1811. We analysed the HST/STIS and
FUSE spectra of this quasar and compared the results to Cloudy photoionization
and collisional ionization models in order to derive densities, temperatures,
and metallicities of the absorbing gas. The absorption can be explained by two
C III clouds, offset by 35 km/s in velocity, with metallicities of ~one-tenth
the solar value. One cloud has a density of order n_H = 1.2 +0.9 -0.5 * 10^-3
cm^-3 (thickness 0.4 +0.3 -0.2 kpc) and produces the observed C II and Si III
absorption, while the other has a density of order n_H = 1.2 +0.9 -0.5 * 10^-5
cm^-3 (thickness 80 +70 -40 kpc) and gives rise to the observed weak C IV
absorption. Cloud temperatures are ~14,000 +3000 -2000 K and ~34,000 -4000
+2000 K for photoionized models. Although collisionally ionized clouds with T ~
70,000 K are possible, they are less likely because of the short cooling
time-scales involved. Previous studies revealed no luminous galaxy at the
absorber's redshift, so it is probably related to tidal debris, ejected
material, a dwarf galaxy, or other halo material in a galaxy group. Our models
also indicate that one of the two clouds would produce detectable weak Mg II
absorption if spectral coverage of that transition existed. We predict what the
system would look like at z ~ 1 when the ionizing background radiation was more
intense. We find that at z ~ 1 the denser component resembles a C IV absorber.
The second C III cloud in this z = 0.0777 absorber may be analogous to a subset
of the more diffuse O VI absorbers at higher redshift.Comment: 15 pages, 6 figures, accepted by MNRA
Infection routes matter in population-specific responses of the red flour beetle to the entomopathogen Bacillus thuringiensis
Background: Pathogens can infect their hosts through different routes. For studying the consequences for host resistance, we here used the entomopathogen Bacillus thuringiensis and the red flour beetle Tribolium castaneum for oral and systemic (i. e. pricking the cuticle) experimental infection. In order to characterize the molecular mechanisms underpinning the two different infection routes, the transcriptomes of beetles of two different T. castaneum populations ā one recently collected population (Cro1) and a commonly used laboratory strain (SB) ā were analyzed using a next generation RNA sequencing approach. Results: The genetically more diverse population Cro1 showed a significantly larger number of differentially expressed genes. While both populations exhibited similar reactions to pricking, their expression patterns in response to oral infection differed remarkably. In particular, the Cro1 population showed a strong response of cuticular proteins and developmental genes, which might indicate an adaptive developmental flexibility that was lost in the SB population presumably as a result of inbreeding. The immune response of SB was primarily based on antimicrobial peptides, while Cro1 relied on responses mediated by phenoloxidase and reactive oxygen species, which may explain the higher resistance of this strain against oral infection. Conclusions: Our data demonstrate that immunological and physiological processes underpinning the two different routes of infection are clearly distinct, and that host populations particularly differ in responses to oral infection. Furthermore, gene expression upon pricking infection entailed a strong signal of wounding, highlighting the importance of pricking controls in future infection studies
Textural properties of macroporous acid modified montmorillonite nanocomposites
Macroporous crosslinked copolymer, poly(glycidyl methacrylate-co-ethylene
glycol dimethacrylate) and its nanocomposites with acid modified montmorillonite
(WA) were synthesized by radical suspension copolymerization. Nanocomposites
were obtained by introducing various amounts of WA into the reaction system.
Textural properties of synthesized samples were analyzed by mercury intrusion
porosimetry. The synthesized nanocomposites have significantly higher specific
surface area in comparison to the copolymer. Total pore volume and the most
dominant pore diameter decrease with incorporation of acid modified
montmorillonite in copolymer matrix.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201
Stres na radu i zdravlje medicinskih sestara u jedinicama intenzivne njege u Srbiji
The aim of this study was to identify and analyse professional stressors, evaluate the level of stress in nurses in Intensive Care Units (ICU), and assess the correlation between the perception of stress and psychological and somatic symptoms or diseases shown by nurses. The research, designed as a crosssectional study, was carried out in the Intensive Care Units (ICU), in health centres in Serbia. The sample population encompassed 1000 nurses. Expanded Nursing Stress Scale (ENSS) was used as the research instrument. ENSS revealed a valid metric characteristic within our sample population. Nurses from ICUs rated situations involving physical and psychological working environments as the most stressful ones, whereas situations related to social working environment were described as less stressful; however, the differences in the perception of stressfulness of these environments were minor. Socio-demographic determinants of the participants (age, marital status and education level) significantly affected the perception of stress at work. Significant differences in the perception of stressfulness of particular stress factors were observed among nurses with respect to psychological and somatic symptoms (such as headache, insomnia, fatigue, despair, lower back pain, mood swings etc.) and certain diseases (such as hypertension, myocardial infarction, stroke, diabetes mellitus etc). In view of permanent escalation of professional stressors, creating a supportive working environment is essential for positive health outcomes, prevention of job-related diseases and better protection of already ill nurses.Cilj je ovoga rada bio identifi cirati i analizirati profesionalne stresore, procijeniti razinu stresa kod medicinskih sestara u jedinicama intenzivne njege te procijeniti korelaciju izmeÄu percepcije stresa i prisutnosti psiholoÅ”kih i somatskih simptoma ili bolesti kod medicinskih sestara. Istraživanje je provedeno u obliku studije presjeka u Jedinicama intenzivne njege u zdravstvenim centrima u Srbiji. Uzorak se sastojao od 1000 medicinskih sestara-tehniÄara. Za procjenu i analizu profesionalnih stresora koriÅ”ten je upitnik Expanded Nursing Stress Scale (ENSS), koji je pokazao validne metrijske karakteristike na naÅ”oj ispitanoj populaciji. Medicinske sestre u Jedinicama intenzivne njege ocijenile su situacije iz fiziÄkoga i psiholoÅ”koga radnog okruženja kao izrazito optereÄujuÄe, a situacije iz socijalnoga radnog okruženja kao manje optereÄujuÄe. Razlika u percepciji stresogenosti navedenih radnih okruženja nije bila statistiÄki znaÄajna. Sociodemografske determinante ispitanika (dob, braÄno stanje i stupanj obrazovanja) znaÄajno utjeÄu na percepciju stresa na radnom mjestu. UtvrÄena je statistiÄki znaÄajna razlika u opažanju stresogenosti pojedinih stresnih situacija na radnom mjestu izmeÄu medicinskih sestara u odnosu na postojanje psihosomatskih simptoma (kao Å”to su glavobolja, nesanica, umor, oÄaj, bol u leÄima, Äeste promjene raspoloženja) ili odreÄenih bolesti (kao Å”to su poviÅ”ena hipertenzija, infarkt miokarda, cerebrovaskularni inzult, Å”eÄerna bolest). Zbog sve izraženije prisutnosti profesionalnih stresora nužno je poduzeti odreÄene strateÅ”ke mjere kod medicinskih sestara u Jedinicama intenzivne njege. StrateÅ”ke mjere podrazumijevaju unaprjeÄenje psihosocijalne radne klime, Å”to bi unaprijedilo njihovo zdravlje i sprijeÄilo nastanak bolesti u svezi s radom, ali i omoguÄilo bolju zaÅ”titu veÄ oboljelim medicinskim sestrama
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