For infinitely many primes p = 4k+1 we give a slightly improved upper bound for the maximal cardinality of a set B ⊂ Zp such that the difference set B−B contains only quadratic residues. Namely, instead of the ”trivial” bound |B| ≤ √p we prove |B| ≤ √ p − 1, under suitable conditions on p. The new bound is valid for approximately three quarters of the primes p = 4k + 1.

introduction integrated nutrient management involving crop residue/green manures and chemical fertilizer is potential alternative to provide a balanced supply of nutrients, enhance soil quality and thereby sustain higher productivity. the present experiment was undertaken to evaluate the effect of different crop residue management practices and npk levels on yield components and yield of wheat....

Introduction: RBT 04262 and LAR 06319 are two Martian meteorites recently discovered in Antarctica. Both contain abundant olivines, and were classified as olivinephyric shergottites [1]. A detailed petrographic study of RBT 04262 by [2] suggested it should be reclassified as a lherzolitic shergottite. However, the moderately LREE-depleted REE distribution pattern [3] indicated that it is closel...

mulches often use for weed control, hold soil moisture, decrease soil temperature, soil fertility, soil conservation, soil against rain and soil quality in organic farming. a field experiment was conducted to evaluate the effect of different wheat residue and sunflower densities on sunflower growth and yield during 2007 growing season at the research field of birjand university. the experimenta...

crop residue is a non-chemical method of weed control in agricultural sustainable systems. this research was conducted at the alarogh site of ardabilto evaluate the effect of integrated use of mulch and herbicide on weed emergence and growth in potato in 2007. treatments were four levels herbicide including: (1) paraquat [n,n'-dimethyl-4,4'-bipyridinium dichloride] herbicide as pre-pl...

A simplified model of earth structure based on the Nd and Sr isotopic characteristics of oceanic and continental tholeiitic flood basalts is presented, taking into account the motion of crustal plates and a chemical balance for trace elements. The resulting structure that is inferred consists of a lower mantle that is still essentially undifferentiated, overlain by an upper mantle that is the r...

abstract in order to study the sensitivity of seven crops to total herbicide soil residue, an experiment was carried out under controlled conditions in 2009 at the college of agriculture, ferdowsi university of mashhad-iran. in this study 7 crops (pea, bean, lentil, corn, rape, beet and tomato), across 7 simulated soil residual concentration of total herbicide (0, 0.0002, 0.0005, 0.001, 0.002, ...

field experiment was conducted to assess the efficacy of wheat residues and different densities of sunflower in weed control during 2007 growing season. the experimental design was a randomized complete block with three replications. the experiment was set up in factorial arrangement, amount of 0, 1250, 2500, 3750, 5000 kg ha-1 of wheat residue and burning of residue (5000 kg ha-1) were the lev...

a four - year field experiment (1999-2002) was conducted on a silty clay loam soil at laklak research field of hamedan to determine the effects of crop residue management and plowing depth on soil fertility and wheat yield in a maize-wheat rotation. in this investigation, four corn residue managements were used consisting of 1) stalk shredding by maize stalk shredder 2) stalk shredding by disk ...