2,449 research outputs found
Women's business ownership : a review of the academic, popular and internet literature
The objective of this review is to present a detailed analysis of the research and popular literature on women entrepreneurs. The review includes an appraisal of the academic research, the popular literature and Internet based information sources
Social structures and entrepreneurial networks: the strength of strong ties.
The entrepreneurial context provides a fertile arena for the study of networks. This qualitative study critically examines the nature, content and process of strong ties, which are found to fall into three categories: family, business contacts, and suppliers, competitors and customers. These nodal categories each provide a specific range of support to the entrepreneur. Their appropriate and effective utilization greatly facilitates enterprise performance
LISA, binary stars, and the mass of the graviton
We extend and improve earlier estimates of the ability of the proposed LISA
(Laser Interferometer Space Antenna) gravitational wave detector to place upper
bounds on the graviton mass, m_g, by comparing the arrival times of
gravitational and electromagnetic signals from binary star systems. We show
that the best possible limit on m_g obtainable this way is ~ 50 times better
than the current limit set by Solar System measurements. Among currently known,
well-understood binaries, 4U1820-30 is the best for this purpose; LISA
observations of 4U1820-30 should yield a limit ~ 3-4 times better than the
present Solar System bound. AM CVn-type binaries offer the prospect of
improving the limit by a factor of 10, if such systems can be better understood
by the time of the LISA mission. We briefly discuss the likelihood that radio
and optical searches during the next decade will yield binaries that more
closely approach the best possible case.Comment: ReVTeX 4, 6 pages, 1 figure, submitted to Phys Rev
Titanium additions to MgB2 conductors
A series of doping experiments are reported for MgB2 conductors that have
been synthesized using doped boron fibers prepared by chemical vapor
deposition(CVD) methods. Undoped MgB2 samples prepared from CVD prepared fibers
consistently give critical current densities, Jc, in the range of 500,000
A/cm^2 in low field at 5K. These values fall by a factor of about 100 as the
magnetic field increases to 3T. For heavily Ti-doped boron fibers where the
B/Ti ratio is comparable to 1, there is a substantial suppression of both Tc,
superconducting volume fraction, and Jc values. If, however, a sample with a
few percent Ti in B is deposited on a carbon coated SiC substrate and reacted
at 1100 degrees C for 15 min, then Tc is suppressed only a couple of degrees
Kelvin and critical current densities are found to be approximately 2-5 x 10^6
A/cm^2 for superconducting layers ranging from 4-10 micrometers thick. These
materials show Jc values over 10,000 A/cm^2 at 25K and 1.3 T.Comment: 10 pages, 6 figure
Anisotropic optical properties of single-crystal GdBa2Cu3O7-delta
The optical spectrum of reduced-T(c) GdBa2Cu3O7-delta has been measured for polarizations parallel and perpendicular to the ab plane. The sample was an oxygen-deficient single crystal with a large face containing the c axis. The polarized reflectance from this face was measured from 20-300 K in the spectral region from 30-3000 cm-1, with 300 K data to 30 000 cm-1. Kramers-Kronig analysis was used to determine the spectral dependence of the ab and the c components of the dielectric tensor. The optical properties are strongly anisotropic. The ab-plane response resembles that of other reduced-T(c) materials whereas the c axis, in contrast, shows only the presence of several phonons. There is a complete absence of charge carrier response along c above and below T(c). This observation allows us to set an upper limit to the free-carrier spectral weight for transport perpendicular to the CuO2 planes
Remote identification of sheep with flystrike using behavioural observations
Flystrike is a major problem affecting sheep in Australia. Identification of &lsquo;flystruck&rsquo; individuals is crucial for treatment; but requires labour-intensive physical examination. As the industry moves toward more low-input systems; there is a need for remote methods to identify flystruck individuals. The aim of this study was to investigate the behaviour of sheep with breech flystrike within a paddock setting. Video footage of sixteen Merino sheep; eight later confirmed with flystrike and eight without; was collected as they moved freely within the paddock with conspecifics. Quantitative behavioural measurements and a qualitative behavioural assessment (QBA) were conducted and compared to their breech conditions (i.e., faecal/urine staining; flystrike severity). Both qualitative and quantitative assessments indicated behavioural differences between flystruck and non-flystruck animals. Flystruck sheep had a behavioural profile characterised by restless behaviour; abnormal postures and reduced grazing time (<i>p</i> &lt; 0.05). Furthermore; flystruck sheep were scored to have a more &lsquo;exhausted/irritated&rsquo; demeanour using QBA (<i>p</i> &lt; 0.05). The behavioural responses also corresponded to the flystrike severity scores and condition of the breech area. We conclude that remotely assessed behaviour of flystruck sheep diverges markedly from non-flystruck sheep; and thus could be a low-input method for identifying and treating affected animals
Early-Holocene warming in Beringia and its mediation by sea-level and vegetation changes
Arctic land-cover changes induced by recent global climate change (e.g., expansion of woody vegetation into tundra and effects of permafrost degradation) are expected to generate further feedbacks to the climate system. Past changes can be used to assess our understanding of feedback mechanisms through a combination of process modelling and paleo-observations. The sub-continental region of Beringia (Northeast Siberia, Alaska, and northwestern Canada) was largely ice-free at the peak of deglacial warming and experienced both major vegetation change and loss of permafrost when many arctic regions were still ice covered. The evolution of Beringian climate at this time was largely driven by global features, such as the amplified seasonal cycle of Northern Hemisphere insolation and changes in global ice volume and atmospheric composition, but changes in regional land-surface controls, such as the widespread development of thaw lakes, the replacement of tundra by deciduous forest or woodland, and the flooding of the Bering–Chukchi land bridge, were probably also important. We examined the sensitivity of Beringia’s early Holocene climate to these regional-scale controls using a regional climate model (RegCM). Lateral and oceanic boundary conditions were provided by global climate simulations conducted using the GENESIS V2.01 atmospheric general circulation model (AGCM) with a mixed-layer ocean. We carried out two present day simulations of regional climate, one with modern and one with 11 ka geography, plus another simulation for 6 ka. In addition, we performed five ? 11 ka climate simulations, each driven by the same global AGCM boundary conditions: (i) 11 ka “Control”, which represents conditions just prior to the major transitions (exposed land bridge, no thaw lakes or wetlands, widespread tundra vegetation), (ii) sea-level rise, which employed present day continental outlines, (iii) vegetation change, with deciduous needleleaf and deciduous broadleaf boreal vegetation types distributed as suggested by the paleoecological record, (iv) thaw lakes, which used the present day distribution of lakes and wetlands; and (v) post-11 ka “All”, incorporating all boundary conditions changed in experiments (ii)–(iv). We find that regional-scale controls strongly mediate the climate responses to changes in the large-scale controls, amplifying them in some cases, damping them in others, and, overall, generating considerable spatial heterogeneity in the simulated climate changes. The change from tundra to deciduous woodland produces additional widespread warming in spring and early summer over that induced by the 11 ka insolation regime alone, and lakes and wetlands produce modest and localized cooling in summer and warming in winter. The greatest effect is the flooding of the land bridge and shelves, which produces generally cooler conditions in summer but warmer conditions in winter and is most clearly manifest on the flooded shelves and in eastern Beringia. By 6 ka continued amplification of the seasonal cycle of insolation and loss of the Laurentide ice sheet produce temperatures similar to or higher than those at 11 ka, plus a longer growing season
Antiferromagnetic resonance in ferroborate NdFe(BO)$_4
The AFMR spectra of the NdFe(BO) crystal are measured in a wide
range of frequencies and temperatures. It is found that by the type of magnetic
anisotropy the compound is an "easy-plane" antiferromagnet with a weak
anisotropy in the basal plane. The effective magnetic parameters are
determined: anisotropy fields =1.14 kOe and =60 kOe and
magnetic excitation gaps =101.9 GHz and =23.8 GHz.
It is shown that commensurate-incommensurate phase transition causes a shift in
resonance field and a considerable change in absorption line width.
At temperatures below 4.2 K nonlinear regimes of AFMR excitation at low
microwave power levels are observed
Superconductivity in MgB_2 doped with Ti and C
Measurements of the superconducting upper critical field, H_{c2}, and
critical current density, J_c, have been carried out for MgB_2 doped with Ti
and/or C in order to explore the problems encountered if these dopants are used
to enhance the superconducting performance. Carbon replaces boron in the MgB_2
lattice and apparently shortens the electronic mean free path thereby raising
H_c2. Titanium forms precipitates of either TiB or TiB_2 that enhance the flux
pinning and raise J_c. Most of these precipitates are intra-granular in the
MgB_2 phase. If approximately 0.5% Ti and approximately 2% C are co-deposited
with B to form doped boron fibers and these fibers are in turn reacted in Mg
vapor to form MgB_2, the resulting superconductor has H_{c2}(T=0) ~ 25 T and
J_c ~ 10,000 A/cm**2 at 5 K and 2.2 T.Comment: 11 pages, 10 figure
Anomalous c-axis charge dynamics in copper oxide materials
Within the t-J model, the c-axis charge dynamics of the copper oxide
materials in the underdoped and optimally doped regimes is studied by
considering the incoherent interlayer hopping. It is shown that the c-axis
charge dynamics is mainly governed by the scattering from the in-plane
fluctuation. In the optimally doped regime, the c-axis resistivity is a linear
in temperatures, and shows the metallic-like behavior for all temperatures,
while the c-axis resistivity in the underdoped regime is characterized by a
crossover from the high temperature metallic-like behavior to the low
temperature semiconducting-like behavior, which are consistent with experiments
and numerical simulations.Comment: 6 pages, Latex, Three figures are adde
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