13,192 research outputs found
Innovation and Foreign Investment Behavior of the U.S. Pharmaceutical Industry
This paper deals with the links between the development of new drugs, and particularly of innovative new drugs, and the international activities of U.S. drug companies. While U.S. drug companies have developed new production processes - the most notable being the fermentation process for making penicillin - we concentrate in this paper on new products. Since production costs comprise less than 40 percent of the selling price of drugs and since the person choosing the drug rarely pays for it, growth in company sales and profits comes more from introducing new products than from cutting costs and prices of old products. The main novelty of our study is our examination of "innovative" as contrasted with "imitative" new drugs. Previous studies have generally focused on the total number of new drugs produced each year, but since our interest is in the causes and consequences of innovation, we have concentrated on the products we have rated as innovative. Section I explains our criteria for this distinction and presents our enumeration of the innovative new drugs for each of the 22 companies in our sample. In Section II we discuss trends in the rate of drug innovation and the factors influencing those trends. Section III describes our sample of drug companies and characterizes them with respect to their size, research investment, and innovativeness. Section IV examines the relation of innovativeness to the foreign activities of individual firms. In Section V we analyze, for a sample of 7 new drugs introduced by two companies, the rate at which use of the drugs was diffused among various countries arid the impact of the presence of manufacturing plants on the rate of diffusion.
Implications of the Visible and X-Ray Counterparts to GRB970228
The gamma-ray burst source GRB970228 has been observed after a delay of 8--12
hours in X-rays and after one day in visible and near infrared light. This
marks the first detection of emission at lower frequencies following the
gamma-ray observation of a GRB and the first detection of any visible
counterpart to a GRB. We consider possible delayed visible and X-ray emission
mechanisms, and conclude that the intrinsic gamma-ray activity continued at a
much reduced intensity for at least a day. There are hints of such continued
activity in other GRB, and future observations can decide if this is true of
GRB in general. The observed multi-band spectrum of GRB970228 agrees with the
predictions of relativistic shock theory when the flux is integrated over a
time longer than that required for a radiating electron to lose its energy.Comment: 5 pp., tex, 1 figur
What Have We Learned From GRB Afterglows?
The discovery by BeppoSAX and coordinated ground-based observations of
persistent X-ray, visible and radio counterparts to GRB has successfully
concluded a search begin in 1973. The problem of explaining the mechanisms of
GRB and their persistent counterparts remains. There are two classes of models:
1) GRB continue weakly for days at all frequencies; 2) GRB emission shifts to
lower frequencies as relativistic debris sweeps up surrounding gas (in an
``external shock'') and slows. In 1) the visible afterglow is accompanied by
continuing gamma-ray emission, as hinted by the high energy emission of
GRB940217 and the ``Gang of Four'' bursts of October 27--29, 1996; the
persistent emission may fluctuate. Behavior of this sort may be found in
``internal shock'' models. Models of class 2) have been the subject of several
theoretical studies which disagree in assumptions and details but which predict
that at each frequency the flux should rise and then decline, with the maximum
coming later at lower frequencies. Some of this behavior has been observed, but
data from GRB970508 show that its afterglow cannot be simply extrapolated from
its gamma-ray emission. It is likely that both classes of processes occur in
most GRB. Comparisons between GRB show that they are not all scaled versions of
the same event. These results suggest that most gamma-ray emission is the
result of ``internal shocks'' while most afterglow is the result of ``external
shocks'', and hint at the presence of collimated outflows. Self-absorption in
the radio spectrum of GRB970508 permitted the size of the radiating surface to
be estimated, and in future GRB it may be possible to follow the expansion of
the shell in detail and to construct an energy budget.Comment: 10 pp., latex (aipproc), 2 figs., Proc. 4th Huntsville Gamma-Ray
Burst Symp. Now latex2.0
Test and evaluate passive orbital disconnect struts (PODS 3)
The objectives of the Passive Orbital Disconnect Struts (PODS) test are to evaluate modal resonance of the PODS-III supports to obtain engineering data required for use of PODS-III on flight systems; determine possible performance improvements in large LO2/LH2 space applications. (1) Modal Vibration Tests. A modal resonance survey is performed on a set of six PODS-III struts assembled in a dewar simulator. The survey conditions simulate both launch and orbital loadings of the struts. The orbital load range spans a full to an empty tank. The frequencies surveyed cover the range consistent with Shuttle qualification requirements and the principal resonant modes of the strut system. (2) Benefit study. The benefit of using PODS-III supports on OTV and Space Station LO sub 2 and LH sub 2 reference tanks was compared to nondisconnect supports. Four LO sub 2 and LH sub 2 tanks were studied under various conditions: (1) holding the launch resonance at 35 Hz and varying the orbit resonance; (2) analyzing both full and emtpy tanks at launch; (3) varying orbit boundary temperaure; (4) varying the number of struts; (5) varying orbit times; and (6) using or not using vapor cooling
Thermodynamics of a black hole in a cavity
We present a unified thermodynamical description of the configurations
consisting on self-gravitating radiation with or without a black hole. We
compute the thermal fluctuations and evaluate where will they induce a
transition from metastable configurations towards stable ones. We show that the
probability of finding such a transition is exponentially small. This indicates
that, in a sequence of quasi equilibrium configurations, the system will remain
in the metastable states till it approaches very closely the critical point
beyond which no metastable configuration exists. Near that point, we relate the
divergence of the local temperature fluctuations to the approach of the
instability of the whole system, thereby generalizing the usual fluctuations
analysis in the cases where long range forces are present. When angular
momentum is added to the cavity, the above picture is slightly modified.
Nevertheless, at high angular momentum, the black hole loses most of its mass
before it reaches the critical point at which it evaporates completely.Comment: 27 pages, latex file, contains 3 figures available on request at
[email protected]
Optically-Induced Polarons in Bose-Einstein Condensates: Monitoring Composite Quasiparticle Decay
Nonresonant light-scattering off atomic Bose-Einstein condensates (BECs) is
predicted to give rise to hitherto unexplored composite quasiparticles:
unstable polarons, i.e., local ``impurities'' dressed by virtual phonons.
Optical monitoring of their spontaneous decay can display either Zeno or
anti-Zeno deviations from the Golden Rule, and thereby probe the temporal
correlations of elementary excitations in BECs.Comment: 4 pages, 3 figure
- …