Electromagnetic Form Factors and the Localization of Quark Orbital Angular Momentum in the Proton

A new picture is given of generalized parton distributions probed in experiments in which the probe scale $Q^{2}$ and the momentum transfer \DD^{2} are well separated. Application of this picture to the $Q^{2}$ dependence of the form factors $F_{1}, F_{2}$ shows that gauge invariant quark orbital angular momentum can be measured and indeed {\it localized} in the transverse profile of the proton. A previous prediction that $\sqrt{Q^{2}}F_{2}(Q^{2})/F_{1}(Q^{2}) \sim const.$ is generalized to GPD language. This prediction appears to have been confirmed by recent CEBAF data.Comment: 6 pages, 1 figure. To appear in DIS 2001, 9th International Workshop on Deep Inelastic Scattering, Bologna, 27 April - 1 May, 200

The Transverse Quark Distribution and Proton Electromagnetic Form Factors in Skew Distribution Formalism

Skew density matrices can be diagonalized to yield probability interpretation. The power-counting prediction of perturbative QCD is found consistent with recent CEBAF data on $F_2(Q^2)/F_1(Q^2)$Comment: 4 pages, Presented May 23, 2000 by John Ralston. Published in the Proceedings of the 7th International Conference on Intersections of Particle and Nuclear Physics, (May 22-28, 2000 Quebec City), Edited by Z. Parseh and W. Marciano, (AIP Conference Proceedings Number 549.

Vacuum Photon Splitting in Lorentz-Violating Quantum Electrodynamics

Radiative corrections arising from Lorentz violation in the fermion sector induce a nonzero amplitude for vacuum photon splitting. At one loop, the on-shell amplitude acquires both CPT-even and CPT-odd contributions forbidden in conventional electrodynamics.Comment: 4 pages, minor wording changes, references added, accepted in Physical Review Letter

Switching the sign of Josephson current through Aharonov-Bohm interferometry

We investigate the DC Josephson effect in a superconductor-normal metal-superconductor junction where the normal region consists of a ballistic ring. We show that a fully controllable $\pi$-junction can be realized through the electro-magnetostatic Aharonov-Bohm effect in the ring. The sign and the magnitude of the supercurrent can be tuned by varying the magnetic flux and the gate voltage applied to one arm, around suitable values. The implementation in a realistic set-up is discussed.Comment: 4 pages, 3 figure

Possible roles, positions, factors and components of dairying in organic farming – a rewiev, mapping, survey and comparison in the Czech Republic

The full-value experiment is questionable in evaluation organic dairying. It is problem to do a trial under comparable conditions for comparison of organic and conventional farming because of legislative reasons and necessity of long period of such event. Most of comparisons are carried out as practice descriptive observations and any of them has been carried out about milk production. That is main reason, why the aim of this work is to carry out a opening of monitoring of some production conditions and results of bio-dairying in the Czech Republic (CR). The quality aspects of sources, procedures and products are main topics of solution of projects about organic farming philosophy, in particular in solution of organic dairy foodstuff chain. There were choosen twelve organic dairy farms (survey II, 2006) for more detail research of production conditions according to results of exploratory questionnaire (2006, survey I, n = 85 pieces of questionnaire and 58 organic farms, which practicise dairying) in the CR. The climatology characteristics of selected organic dairy farms were as follows: (I) 562±149 m above sea level on the average (from 270 to 970 m a. s. l.); (II) 571.0±69.9 m above sea level, mean year temperature 6.0±1.1 ºC and average year rainfall sum 843.0±184.3 mm. It is clear according to previously mentioned figures that the organic (ecology) dairy farming is realized mostly in the mountain or sub-mountain areas (less favourable areas, LFAs) as compared to climatic conditions of CR mean profile. The results of investigation of organic farm (E) and breeder conditions and dairy cow health state, reproduction performance and milk quality in organic farms (I data file) as compared to conventional dairy cow herds (K) were: milk yield (E) was 14.2±3.4 kg of milk/cow/day on average and 5165±1112 kg/cow/year; E farms have 50 % free stables, some of them as different untraditional modifications (mostly in herds with low number of dairy cows); it is necessary to increase this amount for welfare improvement in the future; there are 52 % of binding stables in K herds; there (E) is high occurrence frequency of can milking equipments (46.4 %); there are 5.4 % cases of hand milking, 21.4 % of pipeline milking equipments and 26.8 % of milking parlours; there (K) are 3 % of can milking equipments, 50 % of pipeline milking equipments and 47 % of milking parlours; the average organic herd has 60±91 heads it means about 1/3 of K herd in the CR; geometrical average (xg) of organic herd size is 17 heads; daily milk deliveries were 1318±1475 kg in summer and 976±1368 kg in winter season (there is too high variability in the mentioned indicators); breed structure of E herds is 59.8 % of Bohemian Spotted cattle, 18.8 % of Holstein (H), 12.5 % of Jersey breed; H breed is dominating 47.5 % in K herds; average ratio of excluded milk (for secretion disorders or treatment) is 2.99 % in E herds and 4.6 % in K herds (P<0.01); also there (E) is lower occurrence of clinical mastitis 0.53±1.97 %; service period is 124.3 days in K and 98.7±46,1 days in E herds on average (P<0.01); there (E) is better insemination index 1.66±0.45 in comparison to K herds 2.07 (P<0.01); there is longer longevity as duration of production life of dairy cows in E herds (6.02 lactations, „about 141 % better”) in comparison to K herds (2.50 lactations, P<0.01); milk quality showed the average total mesophilic bacteria count (CPM) 36.0±26.8 ths. CFU/ml in organic farms (E), which is comparable to the conventional farms (K); somatic cell count (PSB) was 192±87 ths./ml in E herds and 256 ths./ml in K herds, which is in connection with the lower ratio of milk exclusion from delivery in E herds; an occurrence of residues of inhibitory substances (RIL) was not reported in E herds, which is more advantageous in comparison to the K herds (0.16 %) and it could be an impact of lowered antibiotica drug use; the average fat and lactose contents (T; 4.05±0.19 %) and (L; 4.83±0.15 %) are well comparable with K farms and the results show on higher energy deficiency in E herd nutrition. The water quality (II) is necessary in dairying as well. Drinking water is necessary for health of animals (their watering) and for milk quality (milking equipment sanitation) as well. Drinking water is asked in dairy farms by legislation. The E farm water quality: the nitrate level varied in the range from 1.63 to 28 mg/l with average 10.5 mg/l in ecological farms and standard limit 50 mg/l was not exceeded; the levels of nitrite and ammonia ions were mostly under detection limit of method; legislative limit <0.5 mg/l was not exceeded by nitrite and once by ammonia ions 0.81 mg/l. The microbiological indicators are more sensitive of course. In total the limits were exceeded 7× u in coliform bacteria, 3× in streptococci and Escherichia coli was confirmed 3× (in comparison to demand 0). Therefore it is necessary to take care of incidental water source sanitation. The effect of origin of water source (communal water pipes or own well in the organic farm area) which was used in the organic farming (II) was: the more marked result differences were not observed between own wells (S) and communal water supply (V) in E farms; an exception was stated in insignificantly better results of hygienic indicators of communal supply; therefore it is necessary to put the higher importance on sanitation of own water sources. There were identified eight own wells and four communal supply. E. g. nitrate levels were a little higher for wells 11.7 > 8.2 mg/l. The nitrites were not different. Chemical oxygen consumption was 0.45 and 0.52 mg/l. The more expressive differences were identified in chlorides, sulphates and Mg: 8.33 and 3.02 mg/l; 27.9 and 16.8 mg/l; 18.9 and 3.5 mg/l

Phase-slip avalanches in the superflow of 4^4He through arrays of nanopores

Recent experiments by Sato et al. [1] have explored the dynamics of $^4$He superflow through an array of nanopores. These experiments have found that, as the temperature is lowered, phase-slippage in the pores changes its character, from synchronous to asynchronous. Inspired by these experiments, we construct a model to address the characteristics of phase-slippage in superflow through nanopore arrays. We focus on the low-temperature regime, in which the current-phase relation for a single pore is linear, and thermal fluctuations may be neglected. Our model incorporates two basic ingredients: (1) each pore has its own random value of critical velocity (due, e.g., to atomic-scale imperfections), and (2) an effective inter-pore coupling, mediated through the bulk superfluid. The inter-pore coupling tends to cause neighbours of a pore that has already phase-slipped also to phase-slip; this process may cascade, creating an avalanche of synchronously slipping phases. As the temperature is lowered, the distribution of critical velocities is expected to effectively broaden, owing to the reduction in the superfluid healing length, leading to a loss of synchronicity in phase-slippage. Furthermore, we find that competition between the strength of the disorder in the critical velocities and the strength of the inter-pore interaction leads to a phase transition between non-avalanching and avalanching regimes of phase-slippage. [1] Sato, Y., Hoskinson, E. Packard, R. E. cond-mat/0605660.Comment: 8 pages, 5 figure

A COMPARISON OF SELECTED MILK INDICATORS IN ORGANIC HERDS WITH CONVENTIONAL HERD AS REFERENCE

In a historical sense, current organic farming is an old-new alternative under changed world conditions. Organic dairying (O) is an alternative of friendly use of the environment in time of presupposed global climate changes. Potential impact of organic farming on raw cow-milk quality, composition and properties, as conpared to conventional milk production (C), were evaluatedin this paper on the basis of selectedm ilk indicators (MIs). Total solids, whey volume, pH of milk fermentation ability (FAM-pH), FAM streptococci, FAM noble lactic acid bacteria, I and Cu were higher in C milk (P0.05) were observed in pH, rennet coagulation time, curd quality, FAM lactobacilli and streptococci/lactobacilli, Na, Mn and Zn. In general, the differences were a little more advantageous for O milk from both technological and nutritional point of view, particularly because of AS (0.461 .81m m), FAM-T (27.3 4.6 ) , Ca (1172 < l257 mg.kg-1)P, ( 950 < l004 mg. kg-1) and Mg 107.4<ll2.0mg.kg{) results. Organic milk can also produce better environment for yoghurt fermentation. Nevertheless, the results obtained should not be overestimated as both sources produced milk of good quality. Additional results are needed to prove organic milk benefits