Universal Heat Conduction in YBa_2Cu_3O_6.9

The thermal conductivity of YBa_2Cu_3O_6.9 was measured at low temperatures in untwinned single crystals with concentrations of Zn impurities from 0 to 3% of Cu. A linear term kappa_0/T = 0.19 mW/K^2.cm is clearly resolved as T -> 0, and found to be virtually independent of Zn concentration. The existence of this residual normal fluid strongly validates the basic theory of transport in unconventional superconductors. Moreover, the observed universal behavior is in quantitative agreement with calculations for a gap function of d-wave symmetry.Comment: Latex file, 4 pages, 3 EPS figures, to appear in Physical Review Letter

Letter from Sherman D. Thacher to John Muir, 1910 Dec 14.

THE THACHER SCHOOLAT CASA DE PIEDEA RANCHIN THE OJAI VALLEYVENTURA COUNTY, CALIFORNIA[illegible]SHERMAN DAY THACHERWILLIAM LARNED THACHERASSOCIATE HEADMASTERSNORDHOFF, CALIFORNIA, December 14, 1910.My dear Mr. Muir:A small group of our boys are thinking of going to the Yosemite in the Christmas vacation. It occurs to me, naturally how delightful it would be to have you with us for a few days at least before the boys start, to teach them a little of the way to love your beloved Yosemite. You need not think we shall make you make a speech, but we should simply set about, and walk about, with you, and hear you talk in the way that I know the pleasure of so well.Please do not think me importunate. I only write because I know that some day it may happen to be entirely convenient and agreeable for you to run up here. If you take the eight o\u27clock a.m. train or the 2:30 p.m. train, you connect with the Ojai train very conveniently, or I will meet you in Ventura by automobile. You can talk with me directly by Sunset telephone any morning between 8:15 and 10:,-- and often at other times. Do not bother to reply to this unless you happen to feel like falling in with my suggestion.Yours most sincerely,[illegible]To:Mr. John Muir,Care Mr. J. D. Hooker,West Adams Street, Los Angeles.0491

Letter from Sherman D. Thacher to John Muir, 1910 Mar 7.

THE THACHER SCHOOLAT CASA DE PIEDRA RANCHIN THE OJAI VALLEYVENTURA COUNTY, CALIFORNIASHERMAN DAY THACHERWILLIAM LARNED THACHER }ASSOCIATES HEADMASTERSNORDHOFF,CALIFORNIA,...March 7, 1910.My dear Mr. Muir:Won1! you come down and make us a little visit? I am not going to ask you to deliver an address because I know you do not like to, but it would be the best thing in the world for my boys to have a chance to get acquainted with you. And I should like to show you some of the charms of this beautiful little valley. A party of about Four or five is thinking of going to the Yosemite the last week in March. Would they enjoy it at that time, or would they be unable to ride the trails, and find it slushy everywhere under foot. I wish you could come to us sometime within the next two weeks, but before March 21st, as the boys begin to scatter for the Easter vacation on that date. If you cannot come now, I wish you could come sometime in May. Or, if you could be here for our closing exercises, June 10th to 15th, it would be delightful.You know this is an out of door school, in the mountains, and I think as the Archbishop of the California uplands, it is your duty to pay us a parochial visit! Your Grand Canyon friend, Miss Breck, is in the valley just now, and I know would add her petition to mine. It would do us all good to see you.04724 Muir-2I congratulate you on the conversion of Ballinger.Yours very sincerely,[Illegible]To:Mr. John Muir,Martinez, Cal.0472

Low-temperature electronic heat transport in La_{2-x}Sr_{x}CuO_{4} single crystals: Unusual low-energy physics in the normal and superconducting states

The thermal conductivity \kappa is measured in a series of La_{2-x}Sr_{x}CuO_{4} (x = 0 - 0.22) single crystals down to 90 mK to elucidate the evolution of the residual electronic thermal conductivity \kappa_{res}, which probes the extended quasiparticle states in the d-wave gap. We found that \kappa_{res}/T grows smoothly, except for a 1/8 anomaly, above x = 0.05 and shows no discontinuity at optimum doping, indicating that the behavior of \kappa_{res}/T is not governed by the metal-insulator crossover in the normal state; as a result, \kappa_{res}/T is much larger than what the normal-state resistivity would suggest in the underdoped region, which highlights the peculiarities in the low-energy physics in the cuprates.Comment: 5 pages, 3 figures, final version published in PRL. Discussions have been modified and an analysis of the phonon term has been adde

Thermal conductivity of Mg-doped CuGeO_3 at very low temperatures: Heat conduction by antiferromagnetic magnons

Thermal conductivity \kappa is measured at very low temperatures down to 0.28 K for pure and Mg-doped CuGeO_3 single crystals. The doped samples carry larger amount of heat than the pure sample at the lowest temperature. This is because antiferromagnetic magnons appear in the doped samples and are responsible for the additional heat conductivity, while \kappa of the pure sample represents phonon conductivity at such low temperatures. The maximum energy of the magnon is estimated to be much lower than the spin-Peierls-gap energy. The result presents the first example that \kappa at very low temperatures probes the magnon transport in disorder-induced antiferromagnetic phase of spin-gap systems

Indoor environment and tobacco smoke exposure in relation to allergic disease and lung function

Asthma and other allergy related diseases are the most common chronic diseases in childhood, and have become a major public health concern. The rapid increase in the occurrence of these diseases, especially in high-income countries, has led to the study of the role ofvarious environmental and lifestyle factors. The overall aim of this thesis was to evaluate the association between indoor environmental factors and the development of allergic diseases in childhood and adolescence, and more specifically, to study the association between tobacco smoke exposure during pre- or postnatal life as well as exposure to indoor mold or dampness and allergic diseases from birth to age 16 years. We used data from the Swedish prospective birth cohort BAMSE (N = 4089) and in study III data from BAMSE combined with four other European birth cohorts (N = 10860). We found that exposure to maternal smoking during pregnancy was associated with asthma up to adolescence, especially early-transient asthma. Additionally, exposure to high doses of maternal smoking during pregnancy (≥10 cigarettes/day) was associated with persistent asthma as well as persistent rhinoconjunctivitis up to age 16 years. Based on spirometry, exposure to maternal smoking during pregnancy was also associated with lower FEV1/FVC ratios at age 16 years. Additionally, indices from impulse oscillometry indicated increased peripheral airway resistance at age 16 years among subjects exposed to maternal smoking during pregnancy. Exposure to secondhand smoke (SHS) during infancy was associated with overall increased risks of asthma, rhinitis, and eczema up to adolescence. However, we found suggestive evidence that the association between SHS during infancy and asthma was likely driven by exposure in utero. Our findings indicate that exposure to SHS during infancy, without prior exposure to maternal smoking during pregnancy, was associated with food allergen sensitization up to age 16 years. Furthermore, exposure to SHS during infancy was associated with increased risks ofrhinitis without concomitant sensitization and eczema with concomitant sensitization. SHS exposure during other periods of childhood was not associated with the onset of asthma or rhinoconjunctivitis in adolescence. Compared with non-smokers, participants who smoked daily or occasionally tended to have reduced FEV1/FVC ratios at age 16 years, even after controlling for maternal smoking during pregnancy. Using indices from impulse oscillometry (IOS) we found increased peripheral airway resistance among adolescent smokers. These findings were corroborated when we used saliva cotinine concentrations to discriminate smokers from non-smokers. Exposure to indicators of mold or dampness during infancy were associated with increased risk of asthma up to age 16 years, as well as an increased risk of persistent asthma. We also found suggestive evidence of an association between reported mold odor or visible mold during infancy and rhinitis up to age 16 years. No association between exposure to indicators of mold or dampness and IgE sensitization was observed. In conclusion, findings from the studies included in this thesis suggest that exposure to maternal smoking during pregnancy is associated with asthma and measures of airway obstruction, such as reduced FEV1/FVC ratios, up to adolescence. Exposure to SHS during infancy seems to be associated with food allergen sensitization and rhinitis up to age 16 years. Adolescent smoking is associated with reduced FEV1/FVC ratios and increased peripheral airway resistance at age 16 years. Exposure to indicators of mold or dampness during infancy may be associated with an increased risk of asthma, and more specifically with persistent asthma up to age 16 years. The results from this thesis can be used to help inform public health policy as well as clinicians to motivate their patients to abstain from smoking. Indoor mold and dampness is a modifiable risk factor related to the onset and persistence of asthma in children and adolescence, and further research should focus on identifying the causal agents

Absence of residual quasiparticle conductivity in the underdoped cuprate YBa2Cu4O8

We report here measurements of the in-plane thermal conductivity K(T) of the underdoped cuprate YBa2Cu4O8 (Y124) below 1K. K(T) is shown to follow a simple, phononic T^3 dependence at the lowest temperatures for both current directions, with a negligible linear, quasiparticle contribution. This observation is in marked contrast with behavior reported in optimally doped cuprates, and implies that extended zero-energy (or low energy) low-energy quasiparticles are absent in YBa2Cu4O8 at low temperatures.Comment: RevTex, 4 pages, 2 figures, Revised versio

Fin development in a cartilaginous fish and the origin of vertebrate limbs

Recent fossil finds and experimental analysis of chick and mouse embryos highlighted the lateral fin fold theory, which suggests that two pairs of limbs in tetrapods evolved by subdivision of an elongated single fin1. Here we examine fin development in embryos of the primitive cartilaginous fish, Scyliorhinus canicula (dogfish) using scanning electron microscopy and investigate expression of genes known to be involved in limb positioning, identity and patterning in higher vertebrates. Although we did not detect lateral fin folds in dogfish embryos, Engrailed-1 expression suggests that the body is compartmentalized dorso-ventrally. Furthermore, specification of limb identity occurs through the Tbx4 and Tbx5 genes, as in higher vertebrates. In contrast, unlike higher vertebrates, we did not detect Shh transcripts in dogfish fin-buds, although dHand (a gene involved in establishing Shh) is expressed. In S. canicula, the main fin axis seems to lie parallel to the body axis. 'Freeing' fins from the body axis and establishing a separate 'limb' axis has been proposed to be a crucial step in evolution of tetrapod limbs2, 3. We suggest that Shh plays a critical role in this process