On the Pairwise Nonorthogonality Problem in Quantum Chemistry

It is shown that, starting from a set of local hybrid orbitals if>; (i = 1, . .. n) one can construct pairwise nonorthogonal set of functions Xi (i = 1, ... n) with the following feature calculated by employing maximum overlap criterion or by max,imizim. g the average distance between the centroids of charge of the electronic pairs. The use of the pairwise nonorthogonal functions is advantageous in semiempirical methods since it minimizes the error introduced by the neglect of the many-center electron repulsion integrals

Tribological wear mechanisms of molds for high pressure die casting

The goal of this article is to analyze and define mold wear in relation to: mold material, casting alloy and casting parameters. These are the main elements for design of the experimental laboratory for die casting equipment. Additionally, preliminary tests have been undertaken to ensure there is no adhesion between the mold material sample and molten aluminum during the simulation. Factors that were tested were: geometrical shape of the sample, sample preheating temperature, surface roughness and lubrication

Isoflavone content and antioxidant properties of soybean seeds

The isoflavone content and antioxidant properties of five Croatian soybean seed cultivars from two locations were analysed. The content of total and individual isofavones was determined by high performance liquid chromatography. For determination of antioxidant properties scavenging capacity on DPPHֹ radicals has been applied. The total phenolic content, oil and protein content in soybean cultivars were also determined. Significant differences in the content of individual isoflavones were observed within the soybean cultivars. The total phenol content in soybean cultivars ranged from 87.2 to 216.3 mg GAE/100g of soybean. The total isoflavone content in soybean seeds ranged from 80.7 to 213.6 mg/100g of soybean. The most abundant isoflavone in soybean seeds was genistein. There was statistically significant difference (p < 0.05) among two locations in total and individual isoflavone contents. The highest contents of total isoflavones were found in cultivar “os55-95”. Conversely, cultivars poor in isoflavones also showed low levels of DPPH-radical scavenging activity

Analiza napona i deformacija ferocementnih konstrukcijskih elemenata u kombinaciji sa konvencionalno armiranim betonom

This thesis deals with the implementation of Ferrocement for strengthening of reinforced concrete beams exposed mainly to flexure. Ferrocement belongs to the group of cement-based composites, and it is defined as micro-reinforced concrete. An effect of flexural strengthening was studied, through application of ferrocement elements (strips) on the tensed side of RC beams. The goal of this research is finding potential of application, feasibility and cost-effectiveness of usage of ferrocement as a material for strengthening of RC structures exposed to flexure. The strengthening procedure, implemented in the thesis, consists of joining the reinforced concrete beam and previously produced ferrocement strip by adhesion, using adhesive epoxy-mortar. The scientific research method was a combination of analytical, experimental and numerical research. Experimental researches were conducted on RC beams strengthened with four types of ferrocement elements, with the accompanying research of non-reinforced (control) RC beams. Behavior of experimental models under the action of short-term static load causing pure flexure was researched. An analytical formulation of the problem was provided and a numerical non-linear analysis using FEM was performed, and verified by experimentally obtained results. The issues of limit states of strength and serviceability of beams were treated

Mechanical properties of different muscle groups assessed with functional tests

Poznavanjem mehaničkih svojstava mišića može se bolje razumeti funkcionisanje lokomotornog aparata i proceniti uspeh u sportu i ishod rehabilitacije. Svakodnevna ljudska kretanja, odnosno prirodni oblici kretanja zasnivaju se na višezglobnim pokretima. Odnos između sile i brzine (F-V relacija) pri izvođenju višezglobnih pokreta je jedna od često proučavanih mehaničkih osobina mišića. Jedan od glavnih razloga za to je mogućnost da se F-V relacijom istrovremeno procenjuje sila (F), brzina (V) i snaga (P) mišićnih kapaciteta, što nije slučaj kod jednozglobnih pokreta koji se često primenjuju u rutinskim testiranjima. Cilj ove disertacije je bio da istraži (1) oblik i jačinu F-V relacije kod različitih mišićnih grupa koji se zasnivaju na višezglobnim pokretima, pri tom da (2) uporedi vrednosti dobijene iz srednjih (SV) i maksimalnih (MAX) varijabli F i V, a zatim da (3) ispita parametre sile, brzine i snage koji predstavljaju mehanička svojstva testiranih mišića, kao i da (4) proceni nivo slaganja između standardnog regresionog modela baziranog na više različitih opterećenja i modela dva opterećenja, koji se zasniva na direktnoj proceni F-V relacije na osnovu samo dva opterećenja. U ovoj disertaciji uzorak je činilo 12 ispitanika koji su izvodili četiri motorička testa sa različitim veličinama opterećenja: Skok uvis sa počučnjem (SKOK), Kratki Vingejt test u trajanju 6 s (BICIKL), Izbačaj tega sa grudi (IZBAČAJ) i Vučenje tega (VUČENJE). Zatim je primenjena linearna regresija na SV i MAX vrednostima varijabli F i V kako bi se odredila linearna F-V relacija i regresioni parametri. Dobijene individualne F-V relacije su bile veoma visoke (medijane koeficijenata korelacije imale su vrednosti od 0.930 do 0.995) i približno linearne nezavisno od testa i tipa varijabli. Parametri relacije dobijeni iz SV i MAX vrednosti varijabli F i V su bili visoko povezani kod svih testova (0.789-0.991), osim delom kod testa SKOK (0.485-0.930). Ipak, generalizacija parametara dobijenih iz F-V relacije bila je nekonzistenta i u proseku umerena...By knowing the mechanical properties of muscles we can better understand the function of the locomotor system and also be able to evaluate the outcomes of various athletic training and rehabilitation procedures. Everyday human motor activity is inevitably based on the multi-joint movements. The force-velocity (F-V) relationship of the muscles performing multi-joint maximum performance tasks has been often used to evaluate the mechanical properties of the tested muscles. An important reason for that is the possibility to selectively assess the force (F), velocity (V) and power (P) generating capacities of muscles performing functional movements that cannot be assessed from a single mechanical condition typically applied in routine testing procedures. The aims of the present study were to (1) investigate the pattern and strength of the F-V relationships observed in different muscle group based on multi-joint movements, (2) compare the outcomes observed from averaged (AVG) and maximum (MAX) F and V variables, (3) explore the parameters depicting F, V and P producing capacities of the tested muscles, and (4) evaluate the level of agreement between the routinely used “multiple-load model” based on a number of loading conditions and a simple “two-load model” based on direct assessment of the F–V relationship from only 2 external loads applied. Twelve subjects were tested on the maximum performance countermovement vertical jumps without arm swing (JUMP), short Wingate test (CYCLING), bench press throws (BPRESS), and bench pulls (BPULL) performed against different external resistances. Thereafter, a linear regression obtained from both the AVG and MAX F and V variables was used for calculating the F-V relationship and its regression parameters. The observed individual force–velocity relationships were exceptionally strong (median correlation coefficients ranged from r = 0.930 to r = 0.995) and approximately linear independently of the test and variable type. Most of the relationship parameters observed from the averaged and maximum force and velocity variable types were strongly related in all tests (r = 0.789-0.991), except partly for those in JUMP (r = 0.485-0.930)..

Multiple solutions of coupled-cluster equations for PPP model of [10]annulene

Multiple (real) solutions of the CC equations (corresponding to the CCD, ACP and ACPQ methods) are studied for the PPP model of [10]annulene, C_{10}H_{10}. The long-range electrostatic interactions are represented either by the Mataga--Nishimoto potential, or Pople's R^{-1} potential. The multiple solutions are obtained in a quasi-random manner, by generating a pool of starting amplitudes and applying a standard CC iterative procedure combined with Pulay's DIIS method. Several unexpected features of these solutions are uncovered, including the switching between two CCD solutions when moving between the weakly and strongly correlated regime of the PPP model with Pople's potential.Comment: 5 pages, 4 figures, RevTeX

The Derivatives of Single-Center Integrals Involving Gaussian Functions

In an »ab initio« calculation of -harmonic force constants from a singlecenter wave function, derivatives of various one- and two-electron integrals are required. Using Slater orbitals as basic functions, the derivatives of single-center integrals were evaluated in analytical form by Bishop and RandiC1 • Since wider applications of Gaussian orbitals in molecular calculations may be anticipated, we have undertaken to derive formulae for the derivatives of these integrals using Gaussian functions as a basis

Site-selective quantum correlations revealed by magnetic anisotropy in the tetramer system SeCuO3

We present the investigation of a monoclinic compound SeCuO3 using x-ray powder diffraction, magnetization, torque and electron-spin-resonance (ESR). Structurally based analysis suggests that SeCuO3 can be considered as a 3D network of tetramers. The values of intra-tetramer exchange interactions are extracted from the temperature dependence of the susceptibility and amount to ~200 K. The inter-tetramer coupling leads to the development of long-range antiferromagnetic order at TN = 8 K. An unusual temperature dependence of the effective g-tensors is observed, accompanied with a rotation of macroscopic magnetic axes. We explain this unique observation as due to site-selective quantum correlations

Subjektivna sigurnost u ispravnost reakcije pri detektiranju rijetkih signala

While detecting rare visual signals subjects were asked to state their confidence that the signal to respond at was actually present whenever they emitted the reaction. Generally this subjective confidence proved to be higher for responses which were correct detections than for those which turned out to be false alarms. However, a substantial number of detections was made with low confidence and a substantial number of false alarms was made with complete certainty that the critical signal was actually present.Za sat i pol detektiranja rijetkih vidnih signala od opažača se tražilo da nakon svake reakcije deklarira stupanj sigurnosti da su reagirali na signal na koji treba reagirati. Rezultati pokazuju da taj dodatni zahtjev općenito poboljšava radni učinak; u usporedbi s·kontrolnim pokusom, broj ispravnih detekcija značajno je veći, a broj tzv. lažnih uzbuna značajno manji. Nadalje, prosječni stupanj sigurnosti u ispravnost reakcije veći je od one reakcije koje su zaista detekcije, nego uz one koje su lažne uzbune. Ali samo 50% detekcija dano je uz potpunu (100) sigurnost da se reagiralo na signal koji treba reagirati, a čak 30% lažnih uzbuna učinjeno je s punim uvjerenjem da se reagiralo na takav kritični signal