Antenna dimensions of synthetic aperture radar systems on satellites

Design of a synthetic aperture radar (SAR) for a satellite must take into account the limitation in weight and dimensions of the antenna. The lower limits of the antenna area are derived from the conditions of unambiguity of the SAR system. This result is applied to estimate the antenna requirements for SARs on satellites in circular orbits of various altitudes around Earth and Venus

Conductance of a molecular wire attached to mesoscopic leads: contact effects

We study linear electron transport through a molecular wire sandwiched between nanotube leads. We show that the presence of such electrodes strongly influences the calculated conductance. We find that depending on the quality and geometry of the contacts between the molecule and the tubular reservoirs, linear transport can be tuned between an effective Newns spectral behavior and a more structured one. The latter strongly depends on the topology of the leads. We also provide analytical evidence for an anomalous behavior of the conductance as a function of the contact strength.Comment: 5 pages, 1 figure, to appear in Acta Physica Polonica

Possibilities and limitations of protein supply in organic poultry and pig production

It is one of the general recommendations in animal nutrition that the diet should be formulated according to the specific requirements of animals at the various stages of their development. To which degree the farmer can adapt the nutrient supply to the specific requirements of the animals depends primarily on the production goal and on the availability of nutrient resources. This report gives a general introduction to the present situation for dietary protein supply to poultry and pig production in relation to the principles for organic agriculture and husbandry production. Furthermore it includes partly literature based on research from conventional animal production, as the requirements on the level of the animals are not different in both systems. Moreover, there only few research projects of organic production systems available. This report is primarily focussing on the question whether a nutrient supply of 100% organic feed can and should be realised. In this context, it is not possible to cover all aspects in detail as the report cannot replace a textbook. The main emphasis is laid on a coherent argumentation based on the leading ideas of organic agriculture. Concerning further relevant aspects it is referred to the report ”Supply and demand for concentrated organic feed in the EU in 2002 and 2003” by Susanne Padel as part of the same EU-project: ‘Research to support the EU-regulation on Organic Agriculture’ (www.organic-revision.org) and to the project “Availability of organically reared livestock” (S. Gomez, JRC, Institute for Prospective Technological Studies, this study is expected to be completed in November 2005). In conventional animal production, a nutrient supply that is closely related to the requirements is an important tool in the performance-oriented production (FLACHOWSKY, 1998). The objective of animal nutrition is to adapt the nutrient supply as accurately as possible to the requirements resulting from maintenance and performance need. Soybean meal, due to the high protein content and high protein quality, has developed into the most important protein source in the nutrition of monogastric animals. Additionally, synthetic amino acids (DL-methionine) and industrial amino acids (produced from microbial fermentation, L-amino acids) are used to balance the supply of essential amino acids. While the use of soybean meal and synthetic amino acids is normal practice in conventional animal production, the Council-Regulation No. 2092/91, amended by Council Regulation No. 1804/99 on organic livestock production bans the use of chemically extracted soybean meal and synthetic amino acids on organic farms as livestock must be fed primarily on organically produced feedstuffs (Annex 1, paragraph 4.2). By way of a derogation from paragraph 4.2, for a transitional period expiring on 24 August 2005, the use of a limited proportion of non-organic feedstuffs is authorised where farmers can show to the satisfaction of the inspection body that they are unable to obtain feed exclusively from organic production (paragraph 4.8). The derogation, although with a declining percentage of non-organic feedstuffs over the next years, has been prolonged in July 2005. The preferable use of home-grown feedstuffs and limitations in the choice of boughtin feedstuffs can be the cause of considerable variation in the composition of the diets, and considerably restrict the possibilities for the adaptation of the feed ration to the specific requirements. Due to the limited availability of essential amino acids in particular, there is concern that nutritional imbalances encountered in practice might lead to deteriorating animal health and welfare. On the other hand, there is also the concern that allowing conventional feedstuffs to be fed in organic livestock production will result in intensification of production. The intensification might cause the same problems in organic production as conventional production already shows (animal health problems, risk of residues and GM contamination etc.). Thus, the use of non-organic feedstuffs may have a damaging effect on consumer confidence in organic products of animal origin. In the following the nutritional-physiological effects of a variation in protein supply with respect to growth performance and protein accretion in broilers, turkeys, laying hens, and pigs are examined by means of a literature review. Additionally, the potential effects of the protein content in the diet on product quality, animal health and environmental damage are addressed. It is the aim of the report to provide an overview of the many different aspects of the protein supply in organic poultry and pig production. Many different aspects are taken into account to elaborate possibilities to handle the use of organic and non-organic feedstuffs with respect to the objectives and framework conditions of organic livestock production. However, due to the complex interactions not all aspects can be covered. There is room and need for explanation and for further research

Almost holomorphic Poincare series corresponding to products of harmonic Siegel-Maass forms

We investigate Poincar\'e series, where we average products of terms of Fourier series of real-analytic Siegel modular forms. There are some (trivial) special cases for which the products of terms of Fourier series of elliptic modular forms and harmonic Maass forms are almost holomorphic, in which case the corresponding Poincar\'e series are almost holomorphic as well. In general this is not the case. The main point of this paper is the study of Siegel-Poincar\'e series of degree $2$ attached to products of terms of Fourier series of harmonic Siegel-Maass forms and holomorphic Siegel modular forms. We establish conditions on the convergence and nonvanishing of such Siegel-Poincar\'e series. We surprisingly discover that these Poincar\'e series are almost holomorphic Siegel modular forms, although the product of terms of Fourier series of harmonic Siegel-Maass forms and holomorphic Siegel modular forms (in contrast to the elliptic case) is not almost holomorphic. Our proof employs tools from representation theory. In particular, we determine some constituents of the tensor product of Harish-Chandra modules with walls

Sturm Bounds for Siegel Modular Forms

We establish Sturm bounds for degree g Siegel modular forms modulo a prime p, which are vital for explicit computations. Our inductive proof exploits Fourier-Jacobi expansions of Siegel modular forms and properties of specializations of Jacobi forms to torsion points. In particular, our approach is completely different from the proofs of the previously known cases g=1,2, which do not extend to the case of general g

Application of the parametrical surface-wave prediction model to rapidly varying wind fields during JONSWAP 1973

The capability of a parametrical surface wave model to predict the sea state on a small array for highly variable wind fields is shown for three examples. The model treats the wind sea, for which the nonlinear interaction is most effective, in a parametrical sense. The swell is propagated along characteristics, and the source function for the swell is assumed to be zero. The model output is compared with wave measure- ments from the JONSWAP 73 experimen

Multiplicative combinatorial properties of return time sets in minimal dynamical systems

We investigate the relationship between the dynamical properties of minimal topological dynamical systems and the multiplicative combinatorial properties of return time sets arising from those systems. In particular, we prove that for a residual sets of points in any minimal system, the set of return times to any non-empty, open set contains arbitrarily long geometric progressions. Under the separate assumptions of total minimality and distality, we prove that return time sets have positive multiplicative upper Banach density along $\mathbb{N}$ and along multiplicative subsemigroups of $\mathbb{N}$, respectively. The primary motivation for this work is the long-standing open question of whether or not syndetic subsets of the positive integers contain arbitrarily long geometric progressions; our main result is some evidence for an affirmative answer to this question.Comment: 32 page

Single and multiple recurrence along non-polynomial sequences

We establish new recurrence and multiple recurrence results for a rather large family $\mathcal{F}$ of non-polynomial functions which includes tempered functions defined in [11], as well as functions from a Hardy field with the property that for some $\ell\in \mathbb{N}\cup\{0\}$, $\lim_{x\to\infty }f^{(\ell)}(x)=\pm\infty$ and $\lim_{x\to\infty }f^{(\ell+1)}(x)=0$. Among other things, we show that for any $f\in\mathcal{F}$, any invertible probability measure preserving system $(X,\mathcal{B},\mu,T)$, any $A\in\mathcal{B}$ with $\mu(A)>0$, and any $\epsilon>0$, the sets of returns $$R_{\epsilon, A}= \big\{n\in\mathbb{N}:\mu(A\cap T^{-\lfloor f(n)\rfloor}A)>\mu^2(A)-\epsilon\big\}$$ and $$R^{(k)}_{A}= \big\{ n\in\mathbb{N}: \mu\big(A\cap T^{\lfloor f(n)\rfloor}A\cap T^{\lfloor f(n+1)\rfloor}A\cap\cdots\cap T^{\lfloor f(n+k)\rfloor}A\big)>0\big\}$$ possess somewhat unexpected properties of largeness; in particular, they are thick, i.e., contain arbitrarily long intervals.Comment: 51 page