Harvard University

About: Harvard University is a education organization based out in Cambridge, Massachusetts, United States. It is known for research contribution in the topics: Population & Cancer. The organization has 208150 authors who have published 530388 publications receiving 38152182 citations. The organization is also known as: Harvard & University of Harvard.

NEURAL MECHANISMS OF ADDICTION: The Role of Reward-Related Learning and Memory

Abstract: Addiction is a state of compulsive drug use; despite treatment and other attempts to control drug taking, addiction tends to persist. Clinical and laboratory observations have converged on the hypothesis that addiction represents the pathological usurpation of neural processes that normally serve reward-related learning. The major substrates of persistent compulsive drug use are hypothesized to be molecular and cellular mechanisms that underlie long-term associative memories in several forebrain circuits (involving the ventral and dorsal striatum and prefrontal cortex) that receive input from midbrain dopamine neurons. Here we review progress in identifying candidate mechanisms of addiction.

Role of cell shape in growth control

Abstract: Tissue culture plastic adhesivity was precisely varied by applying different concentrations of poly(2-hydroxyethyl methacrylate). The extent of cell spreading was thus accurately controlled so that cells cultured on these substrata could be held at any one of a graded series of quantitated cell shapes. Cell shape was found to be tightly coupled to DNA synthesis and growth in nontransformed cells. These findings suggest a mechanism that is important in growth control of mammalian cells, and provide a more fundamental interpretation of such phenomena as density dependent inhibition of cell growth and anchorage dependence.

Metalenses at visible wavelengths: Diffraction-limited focusing and subwavelength resolution imaging.

Abstract: Subwavelength resolution imaging requires high numerical aperture (NA) lenses, which are bulky and expensive. Metasurfaces allow the miniaturization of conventional refractive optics into planar structures. We show that high-aspect-ratio titanium dioxide metasurfaces can be fabricated and designed as metalenses with NA = 0.8. Diffraction-limited focusing is demonstrated at wavelengths of 405, 532, and 660 nm with corresponding efficiencies of 86, 73, and 66%. The metalenses can resolve nanoscale features separated by subwavelength distances and provide magnification as high as 170×, with image qualities comparable to a state-of-the-art commercial objective. Our results firmly establish that metalenses can have widespread applications in laser-based microscopy, imaging, and spectroscopy.

Explorations in Personality

Abstract: Foreword by Dan P. McAdams 1. Introduction 2. Proposals for a Theory of Personality 3. Variables of Personality 4. Judgements of Personality 5. The Genetical Investigation of Personality: Childhood Events 6. Procedures 7. Case History: Case of Earnst 8. Conclusions

Prevalence of and risk factors for lifetime suicide attempts in the National Comorbidity Survey.

Abstract: Background General population survey data are presented on the lifetime prevalence of suicide attempts as well as transition probabilities to onset of ideation, plans among ideators, and attempts among ideators either with or without a plan. Risk factors for these transitions are also studied. Methods Data are from part II of the National Comorbidity Survey, a nationally representative survey carried out from 1990 to 1992 in a sample of 5877 respondents aged 15 to 54 years to study prevalences and correlates of DSM-III-R disorders. Transitions are estimated using life-table analysis. Risk factors are examined using survival analysis. Results Of the respondents, 13.5% reported lifetime ideation, 3.9% a plan, and 4.6% an attempt. Cumulative probabilities were 34% for the transition from ideation to a plan, 72% from a plan to an attempt, and 26% from ideation to an unplanned attempt. About 90% of unplanned and 60% of planned first attempts occurred within 1 year of the onset of ideation. All significant risk factors (female, previously married, age less than 25 years, in a recent cohort, poorly educated, and having 1 or more of the DSM-III-R disorders assessed in the survey) were more strongly related to ideation than to progression from ideation to a plan or an attempt. Conclusions Prevention efforts should focus on planned attempts because of the rapid onset and unpredictability of unplanned attempts. More research is needed on the determinants of unplanned attempts.