998 research outputs found
Thermally assisted ordering in Mott insulators
Ginzburg-Landau theory describes phase transitions as the competition between
energy and entropy: The ordered phase has lower energy, while the disordered
phase has larger entropy. When heating the system, ordering is reduced
entropically until it vanishes at the critical temperature. This established
picture implicitly assumes that the energy difference between ordered and
disordered phase does not change with temperature. We show that for the Mott
insulator KCuF3 this assumption is strongly violated: thermal expansion
energetically stabilizes the orbitally-ordered phase to such and extent that no
phase transition is observed. This new mechanism explains not only the absence
of a phase transition in KCuF3 but even suggests the possibility of an inverted
transition in closed-shell systems, where the ordered phase emerges only at
high temperatures.Comment: 5 pages, 5 figure
Stabilization of colloidal suspensions by means of highly-charged nanoparticles
We employ a novel Monte Carlo simulation scheme to elucidate the
stabilization of neutral colloidal microspheres by means of highly-charged
nanoparticles [V. Tohver et al., Proc. Natl. Acad. Sci. U.S.A. 98, 8950
(2001)]. In accordance with the experimental observations, we find that small
nanoparticle concentrations induce an effective repulsion that prevents
gelation caused by the intrinsic van der Waals attraction between colloids.
Higher nanoparticle concentrations induce an attractive potential which is,
however, qualitatively different from the regular depletion attraction. We also
show how colloid-nanoparticle size asymmetry and nanoparticle charge can be
used to manipulate the effective interactions.Comment: Accepted for publication in Physical Review Letters. See also S.
Karanikas and A.A. Louis, cond-mat/0411279. Updated to synchronize with
published versio
When fear of failure leads to intentions to act entrepreneurially: Insights from threat appraisals and coping efficacy
Calls in the entrepreneurship literature have advocated theory development and empirical studies exploring fear of failure. Often viewed as an inhibitory factor towards entrepreneurial activity, contemporary research has suggested that fear of failure can also motivate entrepreneurial activity. To explore this issue, we draw on Protection Motivation Theory to conceptualise and operationalise fear of failure. We find support for the notion that fear of failure prompts the adoption of entrepreneurial strategies, provided the entrepreneur believes they have the ability to act entrepreneurially, and that by so doing, their financial situation will improve. Our approach extends the literature on fear of failure in an entrepreneurship context by disentangling cognitive and behavioural aspects focusing not only on threat appraisals, but also on how entrepreneurs cope with them
Monte Carlo cluster algorithm for fluid phase transitions in highly size-asymmetrical binary mixtures
Highly size-asymmetrical fluid mixtures arise in a variety of physical
contexts, notably in suspensions of colloidal particles to which much smaller
particles have been added in the form of polymers or nanoparticles.
Conventional schemes for simulating models of such systems are hamstrung by the
difficulty of relaxing the large species in the presence of the small one. Here
we describe how the rejection-free geometrical cluster algorithm (GCA) of Liu
and Luijten [Phys. Rev. Lett 92, 035504 (2004)] can be embedded within a
restricted Gibbs ensemble to facilitate efficient and accurate studies of fluid
phase behavior of highly size-asymmetrical mixtures. After providing a detailed
description of the algorithm, we summarize the bespoke analysis techniques of
Ashton et al. [J. Chem. Phys. 132, 074111 (2010)] that permit accurate
estimates of coexisting densities and critical-point parameters. We apply our
methods to study the liquid--vapor phase diagram of a particular mixture of
Lennard-Jones particles having a 10:1 size ratio. As the reservoir volume
fraction of small particles is increased in the range 0--5%, the critical
temperature decreases by approximately 50%, while the critical density drops by
some 30%. These trends imply that in our system, adding small particles
decreases the net attraction between large particles, a situation that
contrasts with hard-sphere mixtures where an attractive depletion force occurs.Comment: 11 pages, 10 figure
Farmers that engage in entrepreneurship for the âwrongâ reason and the moderating role of cultural intolerance
In the agricultural sector, the Law of Janteâa Scandinavian form of cultural intolerance towards standing out, being different and overachieving (akin to the Tall Poppy Syndrome and The nail that sticks out gets hammered down culture found in other countries)âmay play an important role by influencing when entrepreneurship is an acceptable strategic choice to adversity. Based on a three group, between-subjects experiment of 122 Swedish university students studying agricultural and rural management, we tested whether the advice our participants gave to a fictitious farmer to pursue entrepreneurial activity depended on information regarding the farmer's motivation to pursue entrepreneurship (experimental treatments included motivation scenarios based on necessity vs. opportunity driven vs. control). Moreover, we test whether entrepreneurial advice is moderated by the participants own âJante-nessâ. Unexpectedly, we found that our participants did not adapt the entrepreneurship advice they give to the situational context, nor does Jante play a moderating role; instead we found that Jante had a significant and negative main effect on the entrepreneurial advice given. This finding suggests that Jante is still very much alive and may play an important role in explaining relatively low rates of innovation and entrepreneurship in (Swedish) agriculture
The Stellar and Gas Kinematics of the LITTLE THINGS Dwarf Irregular Galaxy NGC 1569
In order to understand the formation and evolution of dIm galaxies, one needs
to understand their three-dimensional structure. We present measurements of the
stellar velocity dispersion in NGC 1569, a nearby post-starburst dIm galaxy.
The stellar vertical velocity dispersion, , coupled with the
maximum rotational velocity derived from \ion{H}{1} observations, , gives a measure of how kinematically hot the galaxy is, and, therefore,
indicates its structure. We conclude that the stars in NGC 1569 are in a thick
disk with a = 2.4 0.7. In addition to the
structure, we analyze the ionized gas kinematics from \ion{O}{3} observations
along the morphological major axis. These data show evidence for outflow from
the inner starburst region and a potential expanding shell near supermassive
star cluster (SSC) A. When compared to the stellar kinematics, the velocity
dispersion of the stars increase in the region of SSC A supporting the
hypothesis of an expanding shell. The stellar kinematics closely follow the
motion of the gas. Analysis of high resolution \ion{H}{1} data clearly reveals
the presence of an \ion{H}{1} cloud that appears to be impacting the eastern
edge of NGC 1569. Also, an ultra-dense \ion{H}{1} cloud can be seen extending
to the west of the impacting \ion{H}{1} cloud. This dense cloud is likely the
remains of a dense \ion{H}{1} bridge that extended through what is now the
central starburst area. The impacting \ion{H}{1} cloud was the catalyst for the
starburst, thus turning the dense gas into stars over a short timescale,
1 Gyr. We performed a careful study of the spectral energy distribution using
infrared, optical, and ultraviolet photometry producing a state-of-the-art mass
model for the stellar disk. This mass modeling shows that stars dominate the
gravitational potential in the inner 1 kpc.Comment: 49 pages, 25 figures, accepted in A
Colloidal stabilization via nanoparticle haloing
We present a detailed numerical study of effective interactions between
micron-sized silica spheres, induced by highly charged zirconia nanoparticles.
It is demonstrated that the effective interactions are consistent with a
recently discovered mechanism for colloidal stabilization. In accordance with
the experimental observations, small nanoparticle concentrations induce an
effective repulsion that counteracts the intrinsic van der Waals attraction
between the colloids and thus stabilizes the suspension. At higher nanoparticle
concentrations an attractive potential is recovered, resulting in reentrant
gelation. Monte Carlo simulations of this highly size-asymmetric mixture are
made possible by means of a geometric cluster Monte Carlo algorithm. A
comparison is made to results obtained from the Ornstein-Zernike equations with
the hypernetted-chain closure
Logistikutmaningar, lönsamhet och tillfredsstÀllelse i svenska alternativa korta matkanaler
Projektet handlar om logistiska utmaningar för smÄ matproducenter som prövar nya mer direkta
distributionskanaler, s.k. alternativa korta matkanaler (AKM). Denna vÀxande rörelse syftar till att
kortsluta konventionella lÄnga försörjningskedjor med stora livsmedelsproducenter, grossister och
butikskedjor. AKM Àr t.ex. traditionella gÄrdsbutiker, torghandel (t.ex. i form av Bondens marknad)
och andelsjordbruk (CSA) men Àven nya fenomen som Reko-ringar och Lokala matnoder har
spridits snabbt senaste Ären. Vissa smÄ matproducenter försöker genom AKM fÄ mer av
âmatkronanâ och öka sin lönsamhet. För andra aktörer kommer inte ekonomi i första hand, utan
drivkrafterna kan vara mer ideologiskt vÀrderingsgrundade. Oavsett drivkraft, borde AKM bidra till
en mer levande landsbygd.
Logistik och försörjningskedjor (SCM) Ă€r viktigt att förstĂ„ för att fĂ„ mat frĂ„n âjord till bordâ eller
âhage till mageâ, och handlar om att skapa effektiva flöden av varor, information och betalningar.
Vissa AKM innebÀr direktkontakt mellan producent och konsument, dÀr bonden sjÀlv försöker
utföra den logistik och försÀljning som tidigare de större specialiserade aktörerna gjort. I andra AKM
uppstÄr nya mellanhÀnder för att överbrygga gap i logistikflöden.
Projektet undersöker erfarenheter frÄn logistiska utmaningar som olika alternativa korta
matkanaler skapar, och hur olika sÀtt att arbeta med logistik och SCM pÄverkar de mindre aktörernas
upplevda lönsamhet och tillfredsstÀllelse.
Studien inleddes med en förstudie dÀr över 1100 hemsidor (producenters och mellanhÀnders)
hemsidor studerades avseende information kring sortiment, leveransalternativ, leveranstider,
transporter, prissÀttning, betalningsalternativ m.m. Huvudstudien baseras sedan dels pÄ en
enkÀtstudie med svar frÄn 286 olika producenter frÄn olika AKM, samt parallella intervjustudier av
bÄde producenter och nya typer av mellanhÀnder. Resultatet ger en djupare kunskap om uppfattade
logistiska styrkor och utmaningar för olika AKM, samt vilka logistikaktiviteter man lÀgger tid och
energi pÄ, och hur man uppfattar att detta leder till ökad konkurrenskraft, lönsamhet eller
tillfredsstÀllelse.
Producentens bakomliggande motiv verkar pÄverka val av AKM, för olika AKM hur tid och
energi lÀggs pÄ olika logistikaktiviteter, vars bidrag till uppfattad konkurrenskraft sedan skiljer sig
Ät. Generellt lÀggs mer tid pÄ att hantera kundrelationer och ge leveransinformation, men mindre pÄ
transport och lagring trots att man uppfattar sig som mindre konkurrenskraftiga pÄ dessa aktiviteter.
Medan t.ex. CSA i sin logik innebÀr att vissa logistikutmaningar förenklas, sÄ hanteras utmaningar
i andra (t.ex. Reko-ring och Lokala matnoder) genom att virtuella plattformar samordnar
leveransplatser och tidpunkter. Dock upplevs ibland att mycket tid och energi dÄ istÀllet lÀggs pÄ
administration. I motsats till praxis inom andra branscher, eller rekommenderat i annan forskning,
ser vi generellt lite utnyttjande av externa logistikaktörer eller logistiksamarbete mellan producenter,
utan man sköter logistiken sjÀlva. MÄnga producenter rÀknar dock inte med kostnad för egen
arbetstid, och andra anser att man inte fÄr en rÀttvis lön för det arbete man lÀgger ner. Man utnyttjar
istĂ€llet obetalda arbetsinsatser, nĂ„got som ofta kallas âsweat equityâ.
Producenter Àr generellt tillfredsstÀllda oavsett AKM. Men skillnader finns, och olika aspekter
förklarar tillfredsstÀllelse för olika AKM. För mÄnga Àr framtidstro en viktig förklaringsvariabel,
men för andra Àr det rÀttvis lön, eller om kanalen reducerar logistikarbete eller förenklar
kundservice, som verkar viktigast. Dagens lönsamhet verkade generellt pÄverka mindre, och ibland
(t.ex. för Reko-ringar) indikeras t.o.m. ett omvÀnt samband mellan dagens lönsamhet och
producentens tillfredsstÀllelse. IstÀllet verkar producentens syn pÄ framtidsmöjligheter pÄverka
deras tillfredsstÀllelse.
Intervjustudier med andra aktörer, som försökt skapa nya roller som mellanhÀnder, visar att de
inte sÀllan fÄr omarbeta eller utveckla sin affÀrsmodell p.g.a. lÄg lönsamhet, begrÀnsade möjligheter
att skala upp, svÄrigheter att komma in pÄ marknaden och fÄ konsumenter att vÀlja dem istÀllet för
konventionella butiker. Vissa har lÀmnat försöken att sjÀlva driva mellanhandsplattform till att
istÀllet utveckla IT-verktyg för producenterna. De mellanhÀnder som har utvecklat affÀrsmodellen
siktar pÄ ökad lönsamhet, men har ocksÄ viljan att skapa alternativa matkanaler i samarbete med
lokala producenter för att svara pÄ den ökade efterfrÄgan av lokala produkter pÄ marknaden.
Projektet bidrar med fördjupad kunskap kring vikten av att förstÄ logistikutmaningar och nya
kostnader det innebÀr att kortsluta konventionella matkanaler, men ocksÄ en mer nyanserad syn dÀr
olika typer av alternativa korta matkanaler och deras olika utmaningar illustreras. Det bidrar till ökad
förstÄelse kring vad som, ur producentens perspektiv, bidrar till tillfredsstÀllelse och glÀdje vilket Àr
nytt perspektiv. Avslutningsvis trycker vi pÄ vikten av att försöka kombinera plattformar som kan
skapa skalfördelar och samarbete i de logistiska flödena, utan att viktiga vÀrderingsorienterade och
lokala dimensioner försvinner. För att fÄ sÄdana plattformar att fungera, och vara skalbara, kan dock
ofta nÄgon form av mellanhand behövas
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