Carrier dynamics of electrons and holes in moderately doped silicon

A time-domain spectroscopic technique, based on the generation and detection of a collimated beam of subpicosecond broadband terahertz pulses, is used to measure the absorption and dispersion of n- and p-type silicon, with resistivities of 0.1, 1, and 10 Ohm-cm in the submillimeter range of 0.1-2 THz. From the transmission measurements performed at room temperature and at 80 K, the absorption and dispersion, and concomitantly the full complex conductivity, of the doped silicon could be obtained. The results provide an accurate view on the dynamics of the electrons and the holes. Although the simple Drude model, with an energy-independent relaxation time, gives a surprisingly accurate description of the observed carrier dynamics, the measurements do show that some refinements are needed. An extended model, with an energy-dependent carrier-relaxation rate, can explain most of the observed deviations from the simple Drude model.Peer reviewedElectrical and Computer Engineerin

Primjena i kompozicija individualiziranih zaštitnih elemenata linijske grafike u projektiranju novčanica

Proces stvaranja novčanica je dugotrajan i složen, što rezultira kompleksnim rješenjima koja predstavljaju pravo remek djelo grafike. Novčanice su prožete brojnim detaljima i prenose različite informacije koje se analiziraju u teorijskom dijelu rada. Prvotno se postavljaju kriteriji po kojima se izrađuje detaljna analiza velikog broja zaštitnih i konceptualnih elemenata na primjerima novčanica. Time je prikazan okvirni povijesni pregled razvoja novčanica i utjecaji kojima je bio izložen. Analizira se međuovisnost dizajna o sigurnosnim značajkama, te se ispituje razina informiranosti javnosti o zaštitama na novčanicama. Zaključuje se koje metode zaštite su najučinkovitije, te kako šira javnost najčešće provjerava autentičnost novčanica. U eksperimentalnom dijelu rada se na temelju donesenih zaključaka iz teorijskog dijela izrađuje prototip novčanice koja je u najvećoj mjeri prožeta individualiziranim PostScript programskim rješenjima elemenata linijske grafike (rozete, mikrotekst, zaštitne linije, brojevi apoena), a od ostalih zaštita modeliran je individualizirani raster transformacijom matematičkog izraza u PostScript programski kod. Sve ostale zaštite tipične za novčanice simulirane su alatima za rastersku i vektorsku grafiku. U radu se ispituje utjecaj kompozicije zaštitnih elemenata na prepoznavanje autentičnosti novčanica, te efikasnost samih individualiziranih programskih rješenja

Clinical Study Bronchial Responsiveness in Patients with Restrictive Spirometry

Background. Improvement in PFT after bronchodilators is characteristic of obstructive airway diseases such as COPD. However, improvement in patients with restrictive pattern is occasionally seen. We aim to determine the clinical significance of a bronchodilator responsive restrictive defect. Methods. Patients with restrictive spirometry and a bronchodilator study were identified at the University of Oklahoma and Oklahoma City VAMC between September 2003 and December 2009. Restriction was defined as a decreased FVC and FEV1, with normal FEV1/FVC. Responsiveness to bronchodilators was defined as an improvement in FEV1 and/or FVC of at least 12% and 200 mL. Patients with lung volume measurements had their clinical and radiographic records reviewed. Results. Twenty-one patients were included in the study. Most were current or ex-smokers, with most being on bronchodilators. The average FVC and FEV1 were 65 ± 11% and 62 ± 10% of the predicted, respectively. Most patients (66%) had a normal TLC, averaging 90 ± 16% of the predicted. RV, RV/TLC, and the TLC-VA values strongly suggested an obstructive defect. Conclusions. Reversible restrictive pattern on spirometry appears to be a variant of obstructive lung disease in which early airway closure results in air trapping and low FVC. In symptomatic patients, a therapeutic trial of bronchodilators may be beneficial

Bronchial Responsiveness in Patients with Restrictive Spirometry

Background. Improvement in PFT after bronchodilators is characteristic of obstructive airway diseases such as COPD. However, improvement in patients with restrictive pattern is occasionally seen. We aim to determine the clinical significance of a bronchodilator responsive restrictive defect. Methods. Patients with restrictive spirometry and a bronchodilator study were identified at the University of Oklahoma and Oklahoma City VAMC between September 2003 and December 2009. Restriction was defined as a decreased FVC and FEV1, with normal FEV1/FVC. Responsiveness to bronchodilators was defined as an improvement in FEV1 and/or FVC of at least 12% and 200 mL. Patients with lung volume measurements had their clinical and radiographic records reviewed. Results. Twenty-one patients were included in the study. Most were current or ex-smokers, with most being on bronchodilators. The average FVC and FEV1 were 65±11% and 62±10% of the predicted, respectively. Most patients (66%) had a normal TLC, averaging 90±16% of the predicted. RV, RV/TLC, and the TLC-VA values strongly suggested an obstructive defect. Conclusions. Reversible restrictive pattern on spirometry appears to be a variant of obstructive lung disease in which early airway closure results in air trapping and low FVC. In symptomatic patients, a therapeutic trial of bronchodilators may be beneficial