2,934 research outputs found
Why Do Computers Depreciate?
The value of installed computers falls rapidly and therefore computers have a very high user cost. The paper provides a complete account of the non-financial user cost of personal computers -- decomposing it into replacement cost change, obsolescence, instantaneous depreciation, and age-related depreciation. The paper uses data on the resale price of computers and a hedonic price index for new computers to achieve this decomposition. Once obsolescence is taken into account, age-related depreciation -- which is often identified as deterioration -- is estimated to be negligible. While the majority of the loss in value of used computers comes from declines in replacement cost, this paper shows the second most important source of decline in value is obsolescence. Obsolescence is accelerated by the decline in replacement cost of computers. Cheaper computing power drives developments in software and networks that make older computers less productive even though their original functionality remains intact.
Optical properties of current carrying molecular wires
We consider several fundamental optical phenomena involving single molecules
in biased metal-molecule-metal junctions. The molecule is represented by its
highest occupied and lowest unoccupied molecular orbitals, and the analysis
involves the simultaneous consideration of three coupled fluxes: the electronic
current through the molecule, energy flow between the molecule and
electron-hole excitations in the leads and the incident and/or emitted photon
flux. Using a unified theoretical approach based on the non-equilibrium Green
function method we derive expressions for the absorption lineshape (not an
observable but a ueful reference for considering yields of other optical
processes) and for the current induced molecular emission in such junctions. We
also consider conditions under which resonance radiation can induce electronic
current in an unbiased junction. We find that current driven molecular emission
and resonant light induced electronic currents in single molecule junctions can
be of observable magnitude under appropriate realizable conditions. In
particular, light induced current should be observed in junctions involving
molecular bridges that are characterized by strong charge transfer optical
transitions. For observing current induced molecular emission we find that in
addition to the familiar need to control the damping of molecular excitations
into the metal substrate the phenomenon is also sensitive to the way in which
the potential bias si distributed on the junction.Comment: 56 pages, 8 figures; submitted to JC
Cynodont from the Upper Triassic of East Greenland: tooth replacement and double-rootedness
Journal ArticleA new genus and species of cynodont from the Upper Triassic Fleming Fjord Formation of East Greenland possesses double-rooted postcanine teeth and a nonalternate pattern of tooth replacement. The specimen represents an addition to the known diversity of Early Mesozoic taxa with multi-rooted dentitions (tritylodontids, Sinoconodon sp., haramiyids, morganucodontids, Meurthodon gallicus), and casts doubt on traditional interpretations of the interdependency of reduced tooth replacement patterns and teeth with multiple roots
Divergence, convergence, and the ancestry of feral populations in the domestic rock pigeon
ManuscriptDomestic pigeons are spectacularly diverse and exhibit variation in more traits than any other bird species [1]. In The Origin of Species, Charles Darwin repeatedly calls attention to the striking variation among domestic pigeon breeds - generated by thousands of years of artificial selection on a single species by human breeders - as a model for the process of natural divergence among wild populations and species [2]. Darwin proposed a morphology-based classification of domestic pigeon breeds [3], but the relationships among major groups of breeds and their geographic origins remain poorly understood [4, 5]. We used a large, geographically diverse sample of 361 individuals from 70 domestic pigeon breeds and two free-living populations to determine genetic relationships within this species. We found unexpected relationships among phenotypically divergent breeds that imply convergent evolution of derived traits in several breed groups. Our findings also illuminate the geographic origins of breed groups in India and the Middle East, and suggest that racing breeds have made substantial contributions to feral pigeon populations
Turnover of sex chromosomes in the stickleback fishes (Gastrosteidae)
Journal ArticleDiverse sex-chromosome systems are found in vertebrates, particularly in teleost fishes, where different systems can be found in closely related species. Several mechanisms have been proposed for the rapid turnover of sex chromosomes, including the transposition of an existing sex-determination gene, the appearance of a new sex-determination gene on an autosome, and fusions between sex chromosomes and autosomes
Center for Progressive Reform Report: Protecting Workers In A Pandemic--What The Federal Government Should Be Doing
The re-opening of the American economy while the coronavirus that causes COVID-19 is still circulating puts workers at heightened risk of contracting the deadly virus. In some blue-collar industries, the risk is particularly acute because of the inherent nature of the work itself and of the workplaces in which it is conducted. And the risk, for a variety of reasons, falls disproportionately on people of color and low-income workers. With governors stay-at-home orders and other pandemic safety restrictions, Center for Progressive Reform Member Scholars Thomas McGarity, Michael Duff, and Sidney Shapiro examine the federal government\u27s many missed opportunities to stem the spread of the virus in the nation\u27s workplaces, and make recommendations for what needs to happen next to protect employees on the job
A case of severe adolescent obsessive-compulsive disorder treated with inpatient hospitalization, risperidone and sertraline
Background: The initial treatment of obsessive-compulsive disorder (OCD) has generally been limited to serotonergic agents, cognitive-behavioral therapy (CBT), or a combination of the two. These findings were supported by the POTS study for OCD in children and adolescents. However, treatment with serotonergic agents or CBT can take several weeks before benefit is seen; severe cases of OCD may require more immediate treatment. Case report: The authors present a case of severe OCD in an adolescent that required immediate treatment due to her critical medical condition. The patient's symptoms included not eating or taking medications or fluids by mouth due to fears of contamination. A medical hospitalization was previously required due to dehydration. As treatment with an SSRI would not have quick enough onset and the patient was initially resistant to participating in CBT, the patient was psychiatrically hospitalized and first started on liquid risperidone. After several doses of risperidone, the patient was able to participate in CBT and start sertraline. Discussion: The authors discuss the differential diagnosis of such a patient, including the continuum of OCD symptoms and psychotic symptoms. The authors discuss the different treatment options, including the utilization of inpatient psychiatric hospitalization. The authors discuss the potential risks and benefits of using atypical antipsychotics in lieu of benzodiazepines for the initial treatment of severe adolescent OCD. The authors also discuss other current treatment recommendations and rationale for the treatment that was pursued. Conclusions: This patient received benefit of her symptoms relatively quickly with psychiatric hospitalization and an atypical antipsychotic. The diagnosis of a psychotic disorder should be considered. These treatment options must be weighed against the risks of atypical antipsychotics, including extrapyramidal symptoms, weight gain, and metabolic syndrome; benzodiazepines also have their risks and benefits. Additionally, the cost of time and finances of inpatient hospitalization must be considered. More research is needed regarding the short- and long-term efficacy and safety of antipsychotics in the treatment of OCD in the child and adolescent population
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