Space charge limited currents in organic semiconductors are frequently observed to obey the power law J−Vm and are attributed to an exponential distribution of traps having two parameters, namely the characteristic distribution energy Et and the trap concentration Ht. We determine these parameters from the J(V) characteristics at two or more temperatures reported in literature.

It is well known in classical mechanics that, the frequencies of a periodic system can be obtained rather easily through the action variable, without completely solving the equation of motion. The equivalent quantum action variable appearing in the quantum Hamilton-Jacobi formalism, can, analogously provide the energy eigenvalues of a bound state problem, without having to solve the corresponding Schrödinger equation explicitly. This elegant and useful method is elucidated here in the context of some known and not so well known solvable potentials. It is also shown, how this method provides an understanding, as to why approximate quantization schemes such as ordinary and supersymmetric WKB, can give exact answers for certain potentials.

The bound state wave functions for a wide class of exactly solvable potentials are found utilizing the quantum Hamilton-Jacobi formalism of Leacock and Padgett. It is shown that, exploiting the singularity structure of the quantum momentum function, until now used only for obtaining the bound state energies, one can straightforwardly find both the eigenvalues and the corresponding eigenfunctions. After demonstrating the working of this approach through a few solvable examples, we consider Hamiltonians, which exhibit broken and unbroken phases of supersymmetry. The natural emergence of the eigenspectra and the wave functions, in both unbroken and the algebraically non-trivial broken phase, demonstrates the utility of this formalism. * akksprs@uohyd.ernet.in † akksprs@uohyd.ernet.in ‡ akksp@uohyd.ernet.in § prasanta@prl.ernet.in

Septicaemia is a major threat to survival during the early stages of life. There are several reports that suggest that reactive oxygen species (ROs) play a role in a wide variety of diseases. We estimated the activity of xanthine oxidase (XO), malondialdehyde (MDA) content, creatine phosphokinase (CPK) activity, activities of key enzymatic antioxidants, such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and peroxidase (PO), and non-enzymatic antioxidants, viz. uric acid (UA) and albumin (ALB), in 30 neonates with sepsis and 20 age-matched controls. The babies were categorized as preterm/term, early onset/late onset, and shock/without shock, as per clinical and laboratory investigations. The study was carried out to evaluate the status of antioxidant enzymes and non-enzymatic antioxidants with a view to suggesting the introduction of antioxidant therapy in neonatal sepsis. The activities of serum XO, CPK, SOD and GPx, and the content of MDA were found to be significantly elevated in the neonates with sepsis when compared with controls. Conversely, the activity of PO and the levels of UA and ALB were decreased. The septic, full-term neonates registered significantly higher CPK activity (70%) than the preterm septic neonates. However, infants with late-onset and shock sepsis had a significant decrease in CPK activity (p < 0.05) compared with their corresponding sub-groups. Likewise, UA levels were found to be 28% depressed (p < 0.05) in the babies with late-onset sepsis and 51% increased (p < 0.001) in babies with shock compared with their respective sub-groups. Neonates with septic shock also registered a significant elevation in GPx activity (28%) compared with those without shock. This study suggests increased production of ROs in neonates with sepsis, as evidenced by the positive regulation of XO, SOD and GPx activity. The elevation of antioxidant enzymes, however, was not so effective as to protect from cellular damage and thereby result in higher MDA production. It is evident that antioxidant therapy might be useful in the management of neonates with sepsis but further detailed clinico-biochemical investigations are required to define effective antioxidant therapy.

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