A non-injective version of Wigner's theorem

Let $H$ be a complex Hilbert space and let ${\mathcal F}_{s}(H)$ be the real vector space formed by all self-adjoint finite rank operators on $H$. We prove the following non-injective version of Wigner's theorem: every linear operator on ${\mathcal F}_{s}(H)$ sending rank one projections to rank one projections (without any additional assumption) is induced by a linear or conjugate-linear isometry or it is constant on the set of rank one projections

Kogeneracija na biomasu snage 1 MWel

Kogeneracija je postupak istovremene proizvodnje električne i korisne toplinske energije u jedinstvenom procesu. Toplina dobivena iz postrojenja je na nižoj energetskoj razini i najčešće se koristi za grijanje ili u nekim drugim proizvodnim procesima koji koriste toplinu. Kogeneracija se odlično uklapa u drvne industrije jer imaju mogućnost koristiti otpad od obrade drveta kao gorivo. U obrađenom primjeru drvne industrije, uz standardnu temperaturu tople vode za opskrbljivanje sušara i za grijanje potrebna je i topla voda na većem temperaturnom nivou za parenje bukovih proizvoda. U obzir su se uzela tri rješenja. Tri su moguće varijante kogeneracije: -Kogeneracija s parnim kotlom i kondenzacijskom turbinom s reguliranim oduzimanjem pare \Najskuplja varijanta koja uz dodatne kotlove za pokrivanje vršnih opterećenja i opterećenja za vrijeme remonta može bez problema opskrbljivati toplinom potrošače na nižem i višem temperaturnom nivou. -Kogeneracija s parnim kotlom i protutlačnom turbinom Varijanta sa najvećim stupnjem iskoristivosti jer se toplina proizvodi po potrebi i ne baca se u okoliš. Sniženjem proizvodnje topline pada i proizvodnja električne energije što doprinosi smanjenju prihoda od prodaje električne energije. -Kogeneracija s vrelouljnim kotlom i ORC (Organic Rankine Cycle) modulom Najniža investicija sa upola manjim brojem zaposlenih od ostalih varijanti zbog zakonskih propisa za posude pod tlakom. \Nemogućnost opskrbljivanja toplinskom energijom potrošače na većem temperaturnom nivou tako da je za njih potreban rezervni kotao. Izvan sezone grijanja sva toplina se baca u okoliš što rezultira najnižim stupnjem iskoristivosti od svih predloženih varijanti. Detaljnom tehno-ekonomskom analizom obrađeni su svi troškovi i prihodi za svaku varijantu kogeneracije

Solution structure of a modified 2′,5′-linked RNA hairpin involved in an equilibrium with duplex

The isomerization of phosphodiester functionality of nucleic acids from 3′,5′- to a less common 2′,5′-linkage influences the complex interplay of stereoelectronic effects that drive pseudorotational equilibrium of sugar rings and thus affect the conformational propensities for compact or more extended structures. The present study highlights the subtle balance of non-covalent forces at play in structural equilibrium of 2′,5′-linked RNA analogue, 3′-O-(2-methoxyethyl) substituted dodecamer *CG*CGAA*U*U*CG*CG, 3′-MOE-2′,5′-RNA, where all cytosines and uracils are methylated at C5. The NMR and UV spectroscopic studies have shown that 3′-MOE-2′,5′-RNA adopts both hairpin and duplex secondary structures, which are involved in a dynamic exchange that is slow on the NMR timescale and exhibits strand and salt concentration as well as pH dependence. Unusual effect of pH over a narrow physiological range is observed for imino proton resonances with exchange broadening observed at lower pH and relatively sharp lines observed at higher pH. The solution structure of 3′-MOE-2′,5′-RNA hairpin displays a unique and well-defined loop, which is stabilized by Watson–Crick A5·*U8 base pair and by n → π* stacking interactions of O4′ lone-pair electrons of A6 and *U8 with aromatic rings of A5 and *U7, respectively. In contrast, the stem region of 3′-MOE-2′,5′-RNA hairpin is more flexible. Our data highlight the important feature of backbone modifications that can have pronounced effects on interstrand association of nucleic acids

Playing-related health risks among students and teachers of music department at the Koper Art School

The study of a musical instrument demands several hours of practicing on a daily basis as well as playing and performing. Consequently, the musician can be subjected to various health risks during his or her study process but also afterwards. Health problems depend on the individual physical and mental fitness, but also on the features and structure of the instrument as well as on the playing technique, which consists of repeated movements and mainly of static body position. Because of the possibility of chronic injuries, especially neuromuscular disorders but also others, it is important for the musician to regularly maintain his or her physical and mental fitness and movement performance by preventive and compensating activities and immediate action in case of pain or when noticing the first signs of medical problems or limitations. The study included 43 students (16.7 ± 1.5 year, 31 females and 12 males) and 15 teachers (36.9 ± 8.8 years, 7 females and 8 males) that attend and teach at the Music Department of The Koper Art School, which is a part of The Koper High School. The aim of the study was to recognize the risk factors in health status that occur as a consequence of playing a music instrument. A questionnaire consisting of 26 questions was used in the research. The results of the study showed that a half of the interviewed students practices every day but teachers practice less (p = 0.04). Therefore, teachers value the importance of physical (p = 0.013) and mental (p = 0.000) fitness more than students. Teachers also estimate their current physical and mental fitness to be higher (p = 0.003). 89.7 % of the respondents feel pain of discomfort during or after playing, out of these 95.3 % are students, and 73.3 % are teachers. These musicians state that they most frequently feel pain in the back and neck area and in the shoulders and wrists. 36.2 % of the musicians, 41.9 % of students and 20 % of teachers, affirmed to have had strains or pain, both of physical and psychological nature. It is indispensable for both students and teachers to be aware of suitable preventive, practicing and therapeutic measures. Preventive activities and control over risk factors can contribute significantly to the motivation for playing, to the quality of producing and reproducing musical works and to the absence of pain, discomfort and injury occurrences among musicians

Preservers of Matrix Pairs with a Fixed Inner Product Value

Let y\u27 be the set of n x n hermitian matrices, the set of n x n symmetric matrices, the set of all effects, or the set of all projections of rank one. Let c be a real number. We characterize bijective maps phi : y\u27 -\u3e y\u27 satisfying tr (AB) = c double left right arrow tr (phi(A)phi(B)) = c with some additional restrictions on c, depending on the underlying set of matrices

Bioenergana u prehrambenoj industriji

Tema ovog diplomskog zadatka je modernizacija sustava za proizvodnju tehnološke pare za potrebe prehrambene industrije. Kotlovi na fosilna goriva, kao sve nestabilniji i nesigurniji izvor energije zamjenjuju se kotlovima na obnovljivi izvor energije – biomasu. Prehrambena industrija predstavlja velikog potrošača toplinske energije s diskontinuiranim procesima. Takvi procesi zahtijevaju velike količine energije u kratkom periodu s naglim promjenama u opterećenju. Biomasa predstavlja najvažniji obnovljivi izvor za dobivanje toplinske energije ali klasični sustavi izgaranja biomase ne mogu pratiti nagle promjene opterećenja. Za rješavanje tih problema napravljena je tehno-ekonomska analiza provjerene tehnologije – kogeneracije na biomasu s izgaranjem na rešetki, parnom turbinom i reguliranim oduzimanjem pare. Kao alternativa takvom sustavu detaljno je objašnjen sustav s vrelouljnim kotlom, akumulatorom vrelog ulja i izmjenjivačem topline – isparivačem za proizvodnju tehnološke pare, te je napravljena tehno-ekonomska analiza za usporedbu s kogeneracijom. U drugom dijelu rada je sustav s termo uljem je matematički modeliran u SIMULINK-u kako bi se pokazali odzivi sustava. Prikazana je dinamika pojedinih dijelova sustava kao i cijelog sustava. Na kraju rada napravljen je proračun akumulatora vrelog ulja s pripadajućim nacrtom