ABSTRACT
The effect of 15 polar solvents on absorption and fluorescence energies of a typical fluorinated azo dye, 4-(2,3,5,6-tetrafluoro-pyridin-4-yl azo)-phenol, was reported for its acidic, MH, and basic, M, structures. For MH, the absorption energy is described on the basis of multi-linear equation with Taft's π* (solvent polarity) and ß (hydrogen bond acceptor) parameters while the fluorescence energy varies rectilinearly with free energy of transferring the proton to the surrounding solvent, ΔG(t)°. For M, the hydrogen bonding donor ability of protic solvent, α, is a predominant factor which affects the absorption energy while in aprotic solvents, the absorption energy correlates linearly with Kirkwood function. As the ability of the solvent for hydrogen bonding increases, the absorption band width will increase in parallel with the transition energy.
Subject(s)
Azo Compounds/chemistry , Coloring Agents/chemistry , Fluorine/chemistry , Solvents/chemistry , Spectrometry, Fluorescence/methods , Absorption , Hydrogen Bonding , Hydrogen-Ion Concentration , Models, Chemical , Protons , Pyridines/chemistry , Spectrophotometry/methods , ThermodynamicsABSTRACT
The spectral behavior and fluorescence quantum yield of perylene-3,4,9,10-tetracarboxylic tetramethylester (PTME) have been measured in different solvents. Both electronic absorption and fluorescence spectra are not sensitive to medium polarity. The dye exhibits high fluorescence quantum yield and high photostable. Crystalline solid of PTME gives excimer-like emission at 530 nm. The laser activity of PTME has been investigated. The dye solution in N,N-dimethylformamide (DMF) gives laser emission around 480 nm upon excitation by 337.1 nm nitrogen laser pulse. The excitation energy transfer from 7-dimethylamino-4-methylcoumarine (DMC) to PTME has also has been studied and the value of energy transfer rate constant, k(ET), and critical transfer distance, R(0) indicate a Förster-type mechanism. The photodecomposition of PTME in chloromethane solvents has been also studied. We applied semiempirical MO calculations using (PM3 and ZINDO-CI) calculations to explain the geometric and electronic behaviors of the PTME molecule in both ground and excited states and make a correlation with the experimental observations.
Subject(s)
Fluorescent Dyes/chemistry , Perylene/analogs & derivatives , Crystallization , Energy Transfer , Lasers , Methyl Chloride , Molecular Structure , Perylene/chemistry , Photochemical Processes , Quantum Theory , Solutions , Solvents , Spectrometry, Fluorescence , SpectrophotometryABSTRACT
BACKGROUND: Systemic lupus erythematosus is a disease of unknown etiology, which at onest may involve only one organ system or be multisystemic. The aim of our study is to determine the clinical presentation of SLE patients presenting to AKUH to establish whether guidelines laid down about this disease are in agreement with our experience. METHODS: A retrospective log review was carried out at AKUH, based on data obtained from 165 files of individuals admitted to the hospital over a period of 12 years with a confirmed diagnosis of SLE. RESULTS: From the sample size of 165, 143 (86.7%) were females and 22 (13.3%) males. The mean age of diagnosis was 30.9 years. Frequency of symptomatology was observed to be in the following order: systemic 78.8%, musculoskeletal 63% and hematological 60.6%. Oninvestigation ANA levels were positive in 112 patients. CONCLUSION: Our result lead us to conclude that the classification set forth by the American Rheumatological Association is applicable to patients presenting with SLE in our setting.
Subject(s)
Lupus Erythematosus, Systemic/diagnosis , Adolescent , Adult , Child , Female , Humans , Male , Pakistan , Retrospective StudiesABSTRACT
Oesophagogastrectomy is the best available treatment for patients with carcinoma of the oesophagus or cardia. A retrospective analysis of our experience with 485 patients who were treated surgically forms the basis of this report. Of the 317 patients who underwent resection (resectability rate of 65%) only 210 were considered to be potentially curative. Overall, the 5-year survival rate for oesophageal cancer was 3%, whilst curative resection had a 5-year survival rate of 22% and varied according to stages. Five-year survival rate was 67.7% for patients with Stage I disease compared with 27.6, 9.4 and 6.4% for Stages IIa, IIb and III disease respectively. There were no 5-year survivors with Stage IV disease or with those patients who underwent an incomplete resection. Curative resection carried a mortality rate of 3.8%, whereas incomplete resection or palliative procedure carried higher mortality rates of 14 and 20.7% respectively. Adequate post-operative analgesia was provided by continuous extrapleural intercostal nerve block. Morbidity, mainly caused by respiratory complications, occurred in 30 patients (6.2%), with three patients requiring ventilatory support. Outcome was influenced mostly by the extent of the disease and the completeness of surgical resection rather than by histological type. We conclude that surgical treatment provides better longevity than any other type of therapy and remains the standard against which combined modality treatment should be compared. Our experience suggests that surgical treatment can be achieved with minimal morbidity and mortality.
