7,374 research outputs found
Competition, restructuring and firm performance: evidence of an inverted-U relationship from a cross-country survey of firms in transition economies
This paper examines the importance of competition in the growth anddevelopment of firms. We draw on a survey of 3,300 firms in 25transition countries to shed light on the factors that influencerestructuring by firms and their subsequent performance. These datahave three main advantages over those used in previous work. First,they measure directly the degree of competition perceived by each firmin its principal market rather than attempting to infer this from marketdata as measured by statistical agencies. Second, the fact that transitioncountries have market structures inherited from the past avoids some ofthe endogeneity problems associated with measures of competition inmarket economies. Third, the breadth of cross-country variationprovides a method of dealing with the fact that firm-level measures ofthe external environment will not be independent of the firm?s ownperformance. We find evidence of a robust inverted-U effect ofcompetition on performance that is both statistically and economicallysignificant. This paper examines the importance of competition in the growth anddevelopment of firms. We draw on a survey of 3,300 firms in 25transition countries to shed light on the factors that influencerestructuring by firms and their subsequent performance. These datahave three main advantages over those used in previous work. First,they measure directly the degree of competition perceived by each firmin its principal market rather than attempting to infer this from marketdata as measured by statistical agencies. Second, the fact that transitioncountries have market structures inherited from the past avoids some ofthe endogeneity problems associated with measures of competition inmarket economies. Third, the breadth of cross-country variationprovides a method of dealing with the fact that firm-level measures ofthe external environment will not be independent of the firm?s ownperformance. We find evidence of a robust inverted-U effect ofcompetition on performance that is both statistically and economicallysignificant
Variable-speed Generators with Flux Weakening
A cost-competitive, permanent-magnet 20 kW generator is designed such that the following criteria are satisfied: an (over) load capability of at least 30 kW over the entire speed range of 60-120 rpm, generator weight of about 550 lbs with a maximum radial stator flux density of 0.82 T at low speed, unity power factor operation, acceptably small synchronous reactances and operation without a gear box. To justify this final design four different generator designs are investigated: the first two designs are studied to obtain a speed range from 20 to 200 rpm employing rotor field weakening, and the latter two are investigated to obtain a maximum speed range of 40 to 160 rpm based on field weakening via the stator excitation. The generator reactances and induced voltages are computed using finite element/difference solutions. Generator losses and efficiencies are presented for all four designs at rated temperature of Tr=120C
Deletion of Tsc2 in nociceptors reduces target innervation, ion channel expression, and sensitivity to heat
AbstractThe mechanistic target of rapamycin complex 1 (mTORC1) is known to regulate cellular growth pathways, and its genetic activation is sufficient to enhance regenerative axon growth following injury to the central or peripheral nervous systems. However, excess mTORC1 activation may promote innervation defects, and mTORC1 activity mediates injury-induced hypersensitivity, reducing enthusiasm for the pathway as a therapeutic target. While mTORC1 activity is required for full expression of some pain modalities, the effects of pathway activation on nociceptor phenotypes and sensory behaviors are currently unknown. To address this, we genetically activated mTORC1 in mouse peripheral sensory neurons by conditional deletion of its negative regulator Tuberous Sclerosis Complex 2 (Tsc2). Consistent with the well-known role of mTORC1 in regulating cell size, soma size and axon diameter of C-nociceptors were increased in Tsc2-deleted mice. Glabrous skin and spinal cord innervation by C-fiber neurons were also disrupted. Transcriptional profiling of nociceptors enriched by fluorescence-associated cell sorting (FACS) revealed downregulation of multiple classes of ion channels as well as reduced expression of markers for peptidergic nociceptors in Tsc2-deleted mice. In addition to these changes in innervation and gene expression, Tsc2-deleted mice exhibited reduced noxious heat sensitivity and decreased injury-induced cold hypersensitivity, but normal baseline sensitivity to cold and mechanical stimuli. Together, these data show that excess mTORC1 activity in sensory neurons produces changes in gene expression, neuron morphology and sensory behavior.</jats:p
Optimal, reliable estimation of quantum states
Accurately inferring the state of a quantum device from the results of
measurements is a crucial task in building quantum information processing
hardware. The predominant state estimation procedure, maximum likelihood
estimation (MLE), generally reports an estimate with zero eigenvalues. These
cannot be justified. Furthermore, the MLE estimate is incompatible with error
bars, so conclusions drawn from it are suspect. I propose an alternative
procedure, Bayesian mean estimation (BME). BME never yields zero eigenvalues,
its eigenvalues provide a bound on their own uncertainties, and it is the most
accurate procedure possible. I show how to implement BME numerically, and how
to obtain natural error bars that are compatible with the estimate. Finally, I
briefly discuss the differences between Bayesian and frequentist estimation
techniques.Comment: RevTeX; 14 pages, 2 embedded figures. Comments enthusiastically
welcomed
Native American families in the city: American Indian socialization to urban life-final report.
This report, sponsored by the Minority Studies Center of the National Institute of Mental Health, was conceived, researched and written by Native Americans. To answer questions about the problems young Native American families were facing raising children, the authors conducted a three-year study of 120 families who resided primarily in Oakland, California, and the surrounding area. Some areas of interest in the study include Indian identity, experiences of Native American parents and children in the city, the urbanization process, and social policy recommendations
Electrodynamics of Media
Contains reports on six research projects.Joint Services Electronics Program (Contract DAABO7-71-C-0300)U. S. Army Research Office - Durham (Contract DAHC04-72-C-0044)National Science Foundation (Grant GK-31012X), Cornell Universit
Determining the 7Li(n,gamma) cross section via Coulomb dissociation of 8Li
The applicability of Coulomb dissociation reactions to determine the cross
section for the inverse neutron capture reaction was explored using the
reaction 8Li(gamma,n)7Li. A 69.5 MeV/nucleon 8Li beam was incident on a Pb
target, and the outgoing neutron and 7Li nucleus were measured in coincidence.
The deduced (n,gamma) excitation function is consistent with data for the
direct capture reaction 7Li(n,gamma)8Li and with low-energy effective field
theory calculations.Comment: Accepted for publication in Phys. Rev.
Superconductivity in Cu_xTiSe_2
Charge density waves (CDWs) are periodic modulations of the conduction
electron density in solids. They are collective states that arise from
intrinsic instabilities often present in low dimensional electronic systems.
The layered dichalcogenides are the most well-studied examples, with TiSe_2 one
of the first CDW-bearing materials known. The competition between CDW and
superconducting collective electronic states at low temperatures has long been
held and explored, and yet no chemical system has been previously reported
where finely controlled chemical tuning allows this competition to be studied
in detail. Here we report how, upon controlled intercalation of TiSe_2 with Cu
to yield Cu_xTiSe_2, the CDW transition is continuously suppressed, and a new
superconducting state emerges near x = 0.04, with a maximum T_c of 4.15 K found
at x = 0.08. Cu_xTiSe_2 thus provides the first opportunity to study the CDW to
Superconductivity transition in detail through an easily-controllable chemical
parameter, and will provide new insights into the behavior of correlated
electron systems.Comment: Accepted to Nature Physic
Thermal and magnetic properties of integrable spin-1 and spin-3/2 chains with applications to real compounds
The ground state and thermodynamic properties of spin-1 and spin-3/2 chains
are investigated via exactly solved su(3) and su(4) models with physically
motivated chemical potential terms. The analysis involves the Thermodynamic
Bethe Ansatz and the High Temperature Expansion (HTE) methods. For the spin-1
chain with large single-ion anisotropy, a gapped phase occurs which is
significantly different from the valence-bond-solid Haldane phase. The
theoretical curves for the magnetization, susceptibility and specific heat are
favourably compared with experimental data for a number of spin-1 chain
compounds. For the spin-3/2 chain a degenerate gapped phase exists starting at
zero external magnetic field. A middle magnetization plateau can be triggered
by the single-ion anisotropy term. Overall, our results lend further weight to
the applicability of integrable models to the physics of low-dimensional
quantum spin systems. They also highlight the utility of the exact HTE method.Comment: 38 pages, 15 figure
Solving spin quantum-master equations with matrix continued-fraction methods: application to superparamagnets
We implement continued-fraction techniques to solve exactly quantum master
equations for a spin with arbitrary S coupled to a (bosonic) thermal bath. The
full spin density matrix is obtained, so that along with relaxation and
thermoactivation, coherent dynamics is included (precession, tunnel, etc.). The
method is applied to study isotropic spins and spins in a bistable anisotropy
potential (superparamagnets). We present examples of static response, the
dynamical susceptibility including the contribution of the different relaxation
modes, and of spin resonance in transverse fields.Comment: Resubmitted to J. Phys. A: Math. Gen. Some rewriting here and there.
Discussion on positivity in App.D3 at request of one refere
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