Publications

Differential scanning calorimetry (DSC) and isothermal calorimetric batch technique were used to monitor the heat-induced structural changes and adsorption properties of human IgG, in native and hydrophobized states. The transition temp. (Tmax) and enthalpy of heat-induced conformational changes (ΔcalH) of IgG in soln. as well as the enthalpy change accompanying the adsorption of IgG onto hydrophilic silica (ΔadsH), were shown to depend on the degree of the protein hydrophobicity (no. of covalently attached alkyl chains). The adsorption enthalpy for all forms of IgG at all surface concns. was found to be endothermic, that is the process is entropy driven. Factors affecting the IgG adsorption onto silica are discussed. [on SciFinder(R)]

In an earlier study, we found that human voices evoked a positive event-related potential (ERP) peaking at approximately 320 ms after stimulus onset, distinctive from those elicited by instrumental tones. Here we show that though similar in latency to the Novelty P3, this Voice-Sensitive Response (VSR) differs in antecedent conditions and scalp distribution. Furthermore, when participants were not attending to stimuli, the response to voices was undistinguished from other harmonic stimuli (strings, winds, and brass). During a task requiring attending to a feature other than timbre, voices were not distinguished from voicelike stimuli (strings), but were distinguished from other harmonic stimuli. We suggest that the component elicited by voices and similar sounds reflects the allocation of attention on the basis of stimulus significance (as opposed to novelty), and propose an explanation of the task and attentional factors that contribute to the effect.

With varying aptitudes in different occupations, individuals typically maximize income by specializing in one occupation which promises the highest income. Due to numerous labor market imperfections and uncertainties, the choice of best occupation is accomplished with only partial success. We demonstrate that an income tax that reduces after-tax income differentials across occupations tends to exacerbate the errors of choice made by individuals. Following a model proposed by Tinbergen (1951) and developed by Houthakker (1974), we use Luce’s (1959) multinominal logit approach to evaluate the magnitude of the distortions due to errors in occupational choice caused by income taxation. In an example, we show that the deadweight loss can be as high as a third of total income.

With varying aptitudes in different occupations, individuals typically maximize income by specializing in one occupation which promises the highest income. Due to numerous labor market imperfections and uncertainties, the choice of best occupation is accomplished with only partial success. We demonstrate that an income tax that reduces after-tax income differentials across occupations tends to exacerbate the errors of choice made by individuals. Following a model proposed by Tinbergen (1951) and developed by Houthakker (1974), we use Luce’s (1959) multinominal logit approach to evaluate the magnitude of the distortions due to errors in occupational choice caused by income taxation. In an [...]

In a perfectly competitive market for annuities with full information, the price of annuities is equal to individuals’ (discounted) survival probabilities. That is, prices are actuarially fair. In contrast, the pricing implicit in social security systems invariably allows for cross subsidization between different risk groups (males/females). We examine the utilitarian approach to the optimum pricing of annuities and show how the solution depends on the joint distribution of survival probailities and incomes in the population.

In a perfectly competitive market for annuities with full information, the price of annuities is equal to individuals’ (discounted) survival probabilities. That is, prices are actuarially fair. In contrast, the pricing implicit in social security systems invariably allows for cross subsidization between different risk groups (males/females). We examine the utilitarian approach to the optimum pricing of annuities and show how the solution depends on the joint distribution of survival probailities and incomes in the population. [...]

The nuclear lamina is a structure near the inner nuclear membrane and the peripheral chromatin. It is composed of lamins, which are also present in the nuclear interior, and lamin-associated proteins. The increasing number of proteins that interact with lamins and the compound interactions between these proteins and chromatin-associated proteins make the nuclear lamina a highly complex but also a very exciting structure. The nuclear lamina is an essential component of metazoan cells. It is involved in most nuclear activities including DNA replication, RNA transcription, nuclear and chromatin organization, cell cycle regulation, cell development and differentiation, nuclear migration, and apoptosis. Specific mutations in nuclear lamina genes cause a wide range of heritable human diseases. These diseases include Emery-Dreifuss muscular dystrophy, limb girdle muscular dystrophy, dilated cardiomyopathy (DCM) with conduction system disease, familial partial lipodystrophy (FPLD), autosomal recessive axonal neuropathy (Charcot-Marie-Tooth disorder type 2, CMT2), mandibuloacral dysplasia (MAD), Hutchison Gilford Progeria syndrome (HGS), Greenberg Skeletal Dysplasia, and Pelger-Huet anomaly (PHA). Genetic analyses in Caenorhabditis elegans, Drosophila, and mice show new insights into the functions of the nuclear lamina, and recent structural analyses have begun to unravel the molecular structure and assembly of lamins and their associated proteins.

Gp210 is an evolutionarily conserved membrane protein of the nuclear pore complex (NPC). We studied the phenotypes produced by RNAi-induced downregulation of gp210 in both human (HeLa) cells and Caenorhabditis elegans embryos. HeLa cell viability requires Gp210 activity. The dying cells accumulated clustered NPCs and aberrant membrane structures at the nuclear envelope, suggesting that gp210 is required directly or indirectly for nuclear pore formation and dilation as well as the anchoring or structural integrity of mature NPCs. Essential roles for gp210 were confirmed in C. elegans, where RNAi-induced reduction of gp210 caused embryonic lethality. The nuclear envelopes of embryos with reduced gp210 also had aberrant nuclear membrane structures and clustered NPCs, confirming that gp210 plays critical roles at the nuclear membrane through mechanisms that are conserved from nematodes to humans.

This paper presents a model in which government may affect outcomes by manipulating individual choice probabilities through the design of the domain of choice or the use of fiscal instruments. Such manipulations are ineffective when individuals are perfectly rational, provided all alternatives are permitted. However, even a small deviation from perfect rationality is shown to call for policy that substantially manipulates choice probabilities. This policy aims to lend weight to alternatives preferred by individuals who are prone, more than others, to make mistakes. At very low levels of rationality, when choices are largely random, it is always socially optimal to entirely eliminate individual choice in order to prevent the errors generated by such choice. It is better to impose one alternative that is not the preferred one for some individuals instead of inducing a completely random draw by everybody.

This paper presents a model in which government may affect outcomes by manipulating individual choice probabilities through the design of the domain of choice or the use of fiscal instruments. Such manipulations are ineffective when individuals are perfectly rational, provided all alternatives are permitted. However, even a small deviation from perfect rationality is shown to call for policy that substantially manipulates choice probabilities. This policy aims to lend weight to alternatives preferred by individuals who are prone, more than others, to make mistakes. At very low levels of rationality, when choices are largely random, it is always socially optimal to [...]

When information on longevity (survival functions) is unknown early in life, individuals have an interest to insure themselves against future ’risk-class’ classification. Accordingly, the First-Best typically involves transfers across states of nature. Competitive equilibrium cannot provide such transfers if insurance firms are unable to precommit their customers. On the other hand, public insurance plans that do not distinguish between ’risk-class’ realizations are also inefficient. It is impossible, a-priori, to rank these alternatives from a welfare point of view. [...]

When information on longevity (survival functions) is unknown early in life, individuals have an interest to insure themselves against future ’risk-class’ classification. Accordingly, the First-Best typically involves transfers across states of nature. Competitive equilibrium cannot provide such transfers if insurance firms are unable to precommit their customers. On the other hand, public insurance plans that do not distinguish between ’risk-class’ realizations are also inefficient. It is impossible, a-priori, to rank these alternatives from a welfare point of view.

A central question for pension design is how benefits should vary with the age of retirement beyond early eligibility age. It is often argued that in order to be neutral with respect to individual retirement decisions benefits should be actuarially fair, that is, the present value of additional contributions and benefits (’Delayed Retirement Credit’ - DRC) due to postponed retirement should be equal. We show that in a self-selection, asymmetric information model, because individual decisions are suboptimal, the socially optimal benefit structure should be less than actuarially fair.

A central question for pension design is how benefits should vary with the age of retirement beyond early eligibility age. It is often argued that in order to be neutral with respect to individual retirement decisions benefits should be actuarially fair, that is, the present value of additional contributions and benefits (’Delayed Retirement Credit’ - DRC) due to postponed retirement should be equal. We show that in a self-selection, asymmetric information model, because individual decisions are suboptimal, the socially optimal benefit structure should be less than actuarially fair. [...]