Detecting fractions of electrons in the high-TcT_c cuprates

We propose several tests of the idea that the electron is fractionalized in the underdoped and undoped cuprates. These include the ac Josephson effect, and tunneling into small superconducting grains in the Coulomb blockade regime. In both cases, we argue that the results are qualitatively modified from the conventional ones if the insulating tunnel barrier is fractionalized. These experiments directly detect the possible existence of the chargon - a charge $e$ spinless boson - in the insulator. The effects described in this paper provide a means to probing whether the undoped cuprate (despite it's magnetism) is fractionalized. Thus, the experiments discussed here are complementary to the flux-trapping experiment we proposed in our earlier work(cond-mat/0006481).Comment: 7 pages, 5 figure

Incoherent dynamics of vibrating single-molecule transistors

We study the tunneling conductance of nano-scale quantum ``shuttles'' in connection with a recent experiment (H. Park et al., Nature, 407, 57 (2000)) in which a vibrating C^60 molecule was apparently functioning as the island of a single electron transistor (SET). While our calculation starts from the same model of previous work (D. Boese and H. Schoeller, Europhys. Lett. 54, 66(2001)) we obtain quantitatively different dynamics. Calculated I-V curves exhibit most features present in experimental data with a physically reasonable parameter set, and point to a strong dependence of the oscillator's potential on the electrostatics of the island region. We propose that in a regime where the electric field due to the bias voltage itself affects island position, a "catastrophic" negative differential conductance (NDC) may be realized. This effect is directly attributable to the magnitude of overlap of final and initial quantum oscillator states, and as such represents experimental control over quantum transitions of the oscillator via the macroscopically controllable bias voltage.Comment: 6 pages, LaTex, 6 figure

Natural fourth generation of leptons

We consider implications of a fourth generation of leptons, allowing for the most general mass patterns for the fourth generation neutrino. We determine the constraints due to the precision electroweak measurements and outline the signatures to search for at the LHC experiments. As a concrete framework to apply these results we consider the minimal walking technicolor (MWTC) model where the matter content, regarding the electroweak quantum numbers, corresponds to a fourth generation.Comment: 21 pages, 11 figures, 1 table; version to appear in JHE

Mie elän tätä Lappia : kirjailija Annikki Kariniemen luontosuhde

Tänä vuonna tulee kuluneeksi sata vuotta kirjailija Annikki Kariniemen syntymästä (24.7.1913). Kariniemi oli Lapin ensimmäisiä naiskirjailijoita ja Suomen ensimmäinen naispuolinen eräkirjailija. Hänen tuotantonsa käsittää yli kolmekymmentä teosta, näytelmiä, runoja ja lehtiartikkeleita. Sen lisäksi hän oli suosittu juhlapuhuja ja luennoitsija. Tämän tutkimuksen tarkoituksena on kuvata kirjailija Annikki Kariniemen elämänkulku sekä hänen luontosuhteensa ja sen kehitys. Tutkimus on monitieteinen ja -menetelmäinen. Siinä käytettiin hyväksi mikrohistoriallista lähestymistapaa sekä narratiivista omaelämäkertatutkimusta. Kariniemen elämänkulkua tarkasteltiin merkittävien elämäkerrallisten käännekohtien (Denzinin epifanien) kautta. Annikki Kariniemen luontosuhde-narratiivin muutosta tarkasteltiin hänen omaelämäkerrallisten kertomustensa valossa kolmena aikakautena: lapsuudessa, eräkirjailijavaiheessa ja radikalismin aikana. Tässä tarkastelussa käytettiin hyväksi ympäristökasvatuksen Palmerin mallin mukaista jakoa kognitiiviseen, affektiiviseen ja konatiiviseen ulottuvuuteen. Sen mukaan ympäristökasvatuksen onnistuminen edellyttää kaikkien kolmen ulottuvuuden huomioon ottamista samanaikaisesti. Tutkimuksen perusteella Kariniemen luontosuhteen taustalta löytyi monia onnistuneen ympäristökasvatuksen elementtejä: lapsuuden varhaiset, myönteiset luontokokemukset, merkityksellisten henkilöitten luontoharrastus, koulussa opettajien herättämä kiinnostus luontoa kohtaan ja luonnon henkilökohtainen merkitys ihmiselle. Kariniemen ympäristöherääminen tapahtui vähitellen jo 1950-luvulta alkaen. Kirjailija ilmaisi huolensa Kemijoen patoamisen aiheuttamasta lohen sukupuutosta. Myöhemmin hän kiinnitti huomiota metsien avohakkuisiin, luonnon saastumiseen ja jokien patoamiseen. Luonnonsuojeluajattelun ohessa näkyi myös yhteiskunnallisten asenteitten muuttuminen, johon vaikuttavat 1960–1970 -lukujen radikaalit liikkeet. Kirjailija alkoi osallistua aikakauden yhteiskunnalliseen keskusteluun, missä hän puolusti Lapin luontoa ja kulttuuria. Elämänsä viimeisinä vuosina hän oli aktiivisesti mukana lappilaisessa ympäristöliikkeessä. Tämä tutkimus nostaa esille kirjailija Annikki Kariniemen luonnonsuojelijana. Tutkimuksessa tarkastellaan luontosuhdetta monitieteisenä käsitteenä. Luontosuhde nähdään elämänikäisenä prosessina, johon vaikuttavat monet tekijät. Keskustelussa siitä, kenellä on oikeus määritellä luonto, tullaan luontosuhteen yhteiskunnalliselle sektorille, johon liittyy myös toisilleen vastakkaisia intressejä.This year is the one-hundred-year anniversary of author Annikki Kariniemi’s birthday (b. July 24, 1913). Kariniemi was one of the fi rst women authors of Lapland and the fi rst woman in the fi eld of hunting literature in Finland. Her body of work includes over thirty books, plays, poems, and journal articles. In addition, she was a popular speech giver and lecturer. The purpose of this study is to describe author Annikki Kariniemi’s course of life and her relationship with nature, and the development of this relationship. The research is interdisciplinary and uses multiple methods. The research approach is micro-historical and narrative-autobiographical. Kariniemi’s course of life was analyzed through the signifi cant autobiographical turning points (Denzin’s epiphanies). The development of Annikki Kariniemi’s relationship with the nature is discussed in the context of three autobiographical books covering three periods in her life: childhood, time as an author of hunting literature, and radicalism. This analysis leaned on Palmer’s division of cognitive, affective, and conative dimensions was employed. According to this model, successful environmental education requires the simultaneity of all these dimensions. The study showed that Kariniemi’s relationship with nature was based on many factors of successful environmental education: positive early childhood experiences with nature, nature-oriented hobbies of signifi cant others, personal interest toward the nature ignited by school teachers, and personal connection with nature. Kariniemi’s environmental awakening started gradually beginning in the 1950s. The author expressed her concern over the extinction of lax as the result of damming of the Kemijoki River. Later on, she paid attention to clearfelling, nature pollution, and damming. Societal attitudes changed in tandem with environmental awakening, infl uenced by the radical movements of the 1960s and 1970s. The author participated in the contemporary societal discussion defending the nature and culture of Lapland. During her fi nal years, Kariniemi was an activist in a northern-Finnish environmental movement. This study introduces Annikki Kariniemi as a conservationist. The study contributes a multidisciplinary analysis of the relationship with nature. The relationship is seen as a life-long process infl uenced by several factors. When discussing who has the right to defi ne nature, the relationship with nature has a societal level that includes confl icting interests

Seed Storage Reserves and Glucosinolates in Brassica rapa L. Grown on the International Space Station

Although plants are envisioned to play a central role in life support systems for future long-duration space travel, plant growth in space has been problematic due to horticultural problems of nutrient delivery and gas resupply posed by the weightless environment. Iterative improvement in hardware designed for growth of plants on orbital platforms now provides confidence that plants can perform well in microgravity, enabling investigation of their nutritional characteristics. Plants of B. rapa (cv. Astroplants) were grown in the Biomass Production System on the International Space Station. Flowers were hand-pollinated and seeds were produced prior to harvest at 39 days after planting. The material was frozen or fixed while on orbit and subsequently analyzed in our laboratories. Gross measures of growth, leaf chlorophyll, starch and soluble carbohydrates confirmed comparable performance by the plants in spaceflight and ground control treatments. Analysis of glucosinolate production in the plant stems indicated that 3-butenylglucosinolate concentration was on average 75% greater in flight samples than in ground control samples. Similarly, the biochemical make-up of immature seeds produced during spaceflight and fixed or frozen while in orbit was significantly different from the ground controls. The immature seeds from the spaceflight treatment had higher concentrations of chlorophyll, starch, and soluble carbohydrates than the ground controls. Seed protein was significantly lower in the spaceflight material. Microscopy of immature seeds fixed in flight showed embryos to be at a range of developmental stages, while the ground control embryos had all reached the premature stage of development. Storage reserve deposition was more advanced in the ground control seeds. The spaceflight environment thus influences B. rapa metabolite production in ways that may affect flavor and nutritional quality of potential space produce

Effect of Level Statistics on Superconductivity in Ultrasmall Metallic Grains

We examine the destruction of superconducting pairing in metallic grains as their size is decreased for both even and odd numbers of electrons. This occurs when the average level spacing d is of the same order as the BCS order parameter. The energy levels of these grains are randomly distributed according to random matrix theory, and we must work statistically. We find that the average value of the critical level spacing is larger than for the model of equally spaced levels for both parities, and derive numerically the probabilities $P_{o,e}(d)$ that a grain of mean level spacing d shows pairing.Comment: 12 pages, 2 PostScript files, RevTex format, submitted to PR

Electromechanics of charge shuttling in dissipative nanostructures

We investigate the current-voltage (IV) characteristics of a model single-electron transistor where mechanical motion, subject to strong dissipation, of a small metallic grain is possible. The system is studied both by using Monte Carlo simulations and by using an analytical approach. We show that electromechanical coupling results in a highly nonlinear IV-curve. For voltages above the Coulomb blockade threshold, two distinct regimes of charge transfer occur: At low voltages the system behave as a static asymmetric double junction and tunneling is the dominating charge transfer mechanism. At higher voltages an abrupt transition to a new shuttle regime appears, where the grain performs an oscillatory motion back and forth between the leads. In this regime the current is mainly mediated by charges that are carried on the grain as it moves from one lead to the other.Comment: 8 pages, 10 figures, final version to be published in PR