12,991 research outputs found
Large Firm Dynamics and the Business Cycle
Do large firm dynamics drive the business cycle? We answer this question by developing a quantitative theory of aggregate fluctuations caused by firm-level disturbances alone. We show that a standard heterogeneous firm dynamics setup already contains in it a theory of the business cycle,
without appealing to aggregate shocks. We offer an analytical characterization of the law of motion of the aggregate state in this class of models – the firm size distribution – and show that aggregate output and productivity dynamics display: (i) persistence, (ii) volatility and (iii) time-varying second moments. We explore the key role of moments of the firm size distribution – and, in particular, the role of large firm dynamics – in shaping aggregate fluctuations, theoretically, quantitatively and in the data.ERC, Keynes Fun
Constraints on Non-Newtonian Gravity from Recent Casimir Force Measurements
Corrections to Newton's gravitational law inspired by extra dimensional
physics and by the exchange of light and massless elementary particles between
the atoms of two macrobodies are considered. These corrections can be described
by the potentials of Yukawa-type and by the power-type potentials with
different powers. The strongest up to date constraints on the corrections to
Newton's gravitational law are reviewed following from the E\"{o}tvos- and
Cavendish-type experiments and from the measurements of the Casimir and van der
Waals force. We show that the recent measurements of the Casimir force gave the
possibility to strengthen the previously known constraints on the constants of
hypothetical interactions up to several thousand times in a wide interaction
range. Further strengthening is expected in near future that makes Casimir
force measurements a prospective test for the predictions of fundamental
physical theories.Comment: 20 pages, crckbked.cls is used, to be published in: Proceedings of
the 18th Course of the School on Cosmology and Gravitation: The Gravitational
Constant. Generalized Gravitational Theories and Experiments (30 April- 10
May 2003, Erice). Ed. by G. T. Gillies, V. N. Melnikov and V. de Sabbata,
20pp. (Kluwer, in print, 2003
Light Stop NLSPs at the Tevatron and LHC
How light can the stop be given current experimental constraints? Can it
still be lighter than the top? In this paper, we study this and related
questions in the context of gauge-mediated supersymmetry breaking, where a stop
NLSP decays into a W, b and gravitino. Focusing on the case of prompt decays,
we simulate several existing Tevatron and LHC analyses that would be sensitive
to this scenario, and find that they allow the stop to be as light as 150 GeV,
mostly due to the large top production background. With more data, the existing
LHC analyses will be able to push the limit up to at least 180 GeV. We hope
this work will motivate more dedicated experimental searches for this simple
scenario, in which, for most purposes, the only free parameters are the stop
mass and lifetime.Comment: 31 pages, 11 figures; v2: added minor clarifications and reference
Physicochemical characteristics of geophagic clayey soils from South Africa and Swaziland
Physicochemical properties of geophagic clayey soils from South Africa and Swaziland were determined in order to appreciate their capability to perform the functions for which they are consumed and possible consequences of the practice in humans. Tests conducted included colour, texture, pH, electrical conductivity (EC), water retention capacity (WRC), organic matter (OM) content and cation exchange capacity (CEC). The colour of the clayey soils ranged from grey to red. The soils varied texturally from loam to clay and had pH values of between 5.0 and 7.4. Values obtained for EC and OM content were generally low but those for WRC of the clayey soils were above 50% for all samples. These clayey soils, due to their colour are inferred to contain different forms of iron oxide minerals including haematite and goethite, which may help alleviate symptoms of iron deficiency anaemia. Their relatively high WRC may increase their effectiveness in the absorption of moisture in the gastrointestinal tract and therefore confirms the possibility of using these clays in the treatment of diarrhoea.Keywords: Soil pH, texture, cation exchange capacity, diarrhoea, water retention capacityAfrican Journal of Biotechnology Vol. 9(36), pp. 5929-5937, 6 September, 201
Critical current modulation induced by an electric field in superconducting tungsten-carbon nanowires
The critical current of a superconducting nanostructure can be suppressed by applying an electric field in its vicinity. This phenomenon is investigated throughout the fabrication and electrical characterization of superconducting tungsten-carbon (W-C) nanostructures grown by Ga+ focused ion beam induced deposition (FIBID). In a 45 nm-wide, 2.7 mu m-long W-C nanowire, an increasing side-gate voltage is found to progressively reduce the critical current of the device, down to a full suppression of the superconducting state below its critical temperature. This modulation is accounted for by the squeezing of the superconducting current by the electric field within a theoretical model based on the Ginzburg-Landau theory, in agreement with experimental data. Compared to electron beam lithography or sputtering, the single-step FIBID approach provides with enhanced patterning flexibility and yields nanodevices with figures of merit comparable to those retrieved in other superconducting materials, including Ti, Nb, and Al. Exhibiting a higher critical temperature than most of other superconductors, in which this phenomenon has been observed, as well as a reduced critical value of the gate voltage required to fully suppress superconductivity, W-C deposits are strong candidates for the fabrication of nanodevices based on the electric field-induced superconductivity modulation
What is the contribution of physician associates in hospital care in England? A mixed methods, multiple case study.
OBJECTIVES: To investigate the deployment of physician associates (PAs); the factors supporting and inhibiting their employment and their contribution and impact on patients' experience and outcomes and the organisation of services. DESIGN: Mixed methods within a case study design, using interviews, observations, work diaries and documentary analysis. SETTING: Six acute care hospitals in three regions of England in 2016-2017. PARTICIPANTS: 43 PAs, 77 other health professionals, 28 managers, 28 patients and relatives. RESULTS: A key influencing factor supporting the employment of PAs in all settings was a shortage of doctors. PAs were found to be acceptable, appropriate and safe members of the medical/surgical teams by the majority of doctors, managers and nurses. They were mainly deployed to undertake inpatient ward work in the medical/surgical team during core weekday hours. They were reported to positively contribute to: continuity within their medical/surgical team, patient experience and flow, inducting new junior doctors, supporting the medical/surgical teams' workload, which released doctors for more complex patients and their training. The lack of regulation and attendant lack of authority to prescribe was seen as a problem in many but not all specialties. The contribution of PAs to productivity and patient outcomes was not quantifiable separately from other members of the team and wider service organisation. Patients and relatives described PAs positively but most did not understand who and what a PA was, often mistaking them for doctors. CONCLUSIONS: This study offers new insights concerning the deployment and contribution of PAs in medical and surgical specialties in English hospitals. PAs provided a flexible addition to the secondary care workforce without drawing from existing professions. Their utility in the hospital setting is unlikely to be completely realised without the appropriate level of regulation and authority to prescribe medicines and order ionising radiation within their scope of practice
Vectorlike Confinement at the LHC
We argue for the plausibility of a broad class of vectorlike confining gauge
theories at the TeV scale which interact with the Standard Model predominantly
via gauge interactions. These theories have a rich phenomenology at the LHC if
confinement occurs at the TeV scale, while ensuring negligible impact on
precision electroweak and flavor observables. Spin-1 bound states can be
resonantly produced via their mixing with Standard Model gauge bosons. The
resonances promptly decay to pseudo-Goldstone bosons, some of which promptly
decay to a pair of Standard Model gauge bosons, while others are charged and
stable on collider time scales. The diverse set of final states with little
background include multiple photons and leptons, missing energy, massive stable
charged particles and the possibility of highly displaced vertices in dilepton,
leptoquark or diquark decays. Among others, a novel experimental signature of
resonance reconstruction out of massive stable charged particles is
highlighted. Some of the long-lived states also constitute Dark Matter
candidates.Comment: 33 pages, 6 figures. v4: expanded discussion of Z_2 symmetry for
stability, one reference adde
Prompt Decays of General Neutralino NLSPs at the Tevatron
Recent theoretical developments have shown that gauge mediation has a much
larger parameter space of possible spectra and mixings than previously
considered. Motivated by this, we explore the collider phenomenology of gauge
mediation models where a general neutralino is the lightest MSSM superpartner
(the NLSP), focusing on the potential reach from existing and future Tevatron
searches. Promptly decaying general neutralino NLSPs can give rise to final
states involving missing energy plus photons, Zs, Ws and/or Higgses. We survey
the final states and determine those where the Tevatron should have the most
sensitivity. We then estimate the reach of existing Tevatron searches in these
final states and discuss new searches (or optimizations of existing ones) that
should improve the reach. Finally we comment on the potential for discovery at
the LHC.Comment: 41 pages, minor changes, added refs and discussion of previous
literatur
On direct measurement of the W production charge asymmetry at the LHC
The prospects for making a direct measurement of the W production charge
asymmetry at the LHC are discussed. A modification to the method used at the
Tevatron is proposed for measurements at the LHC. The expected sensitivity for
such a measurement to parton distribution functions is compared to that for a
measurement of the lepton charge asymmetry. The direct measurement approach is
found to be less useful for placing constraints on parton distribution
functions at the LHC than a measurement of the lepton charge asymmetry.Comment: 18 pages, 10 figures, v2: references and keywords updated v3:
Additional paragraph discussing inclusion of W asymmetry in global fits adde
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