Quantum delocalization in photon-pair generation

The generation of correlated photon pairs is a key to the production of entangled quantum states, which have a variety of applications within the area of quantum information. In spontaneous parametric down-conversion—the primary method of generating correlated photon pairs—the associated photon annihilation and creation events are generally thought of as being colocated: The correlated pair of photons is localized with regards to the pump photon and its positional origin. A detailed quantum electrodynamical analysis highlights a mechanism exhibiting the possibility of a delocalized origin for paired output photons: The spatial extent of the region from which the pair is generated can be much larger than previously thought. The theory of both localized and nonlocalized degenerate down-conversion is presented, followed by a quantitative analysis using discrete-volume computational methods. The results may have significant implications for quantum information and imaging applications, and the design of nonlinear optical metamaterials

Exploring Mating Loads for Modern Beef Bulls

One of the biggest challenges facing cow/calf producers today is cutting their costs of production. One possible strategy for lowering costs is to increase the production efficiency of the cow herd. A key area to focus on is the reproductive function of the beef bull because natural mating accounts for over 95% of the pregnancies achieved each year in the 33.7 million beef cows in the U.S. It is becoming apparent that perhaps because of increased selection pressure on scrotal circumference, the modern beef bull is more fertile than the bull of yesterday, yet the majority of beef bulls are still being mated at traditional bull to female ratios of 1:20 to 1:30. Utilizing bulls to their full breeding potential is one of the quickest and simplest ways a producer can cut costs. Unfortunately, however, determining a bulls breeding potential has been either elusive in the case of yearling bulls or labor intensive in the case of mature bulls. As a predictor of natural service fertility, most beef bulls undergo a breeding soundness examination prior to either sale or breeding; however, sex drive and mating ability are not commonly measured though both are essential for impregnation of females. Tests have been developed to measure a bulls mating ability or serving capacity. However, past studies investigating the relationship between serving capacity and herd fertility have been inconclusive with some researchers finding no relationship and other researchers reporting serving capacity tests to be an accurate predictor of bull fertility. Many of these studies differed in testing procedures and utilized bulls of different ages with varying levels of sexual experience; thus, differences in the findings may rest with these factors. Because most cattle producers in the United States are purchasing bulls at 12 to 15 months of age (virgins), most serving capacity work in the United States has focused on the serving capacity testing of yearling bulls

Bull Power: Productivity and Profitability

One of the biggest challenges facing cow/calf producers today is cutting their costs of production. One possible strategy for lowering costs is to increase the production efficiency of the cow herd. A key area to focus on is the reproductive function of the beef bull because natural mating accounts for over 95% of the pregnancies achieved each year in the 33.7 million beef cows in the U.S. It is becoming apparent that perhaps because of increased selection pressure on scrotal circumference, the modern beef bull is more fertile than the bull of yesterday. Yet, according to the 1992 National Beef Cow/Calf Health and Productivity Audit (USDA), yearling and mature beef bulls are being mated at bull-to-female ratios of 1:19 and 1:29, respectively. Utilizing bulls to their full breeding potential is one of the quickest and simplest ways a producer can cut costs

Mating and Grazing Behavior of Low and High Serving Capacity Beef Bulls During Average and Heavy Mating Loads at Pasture

Although artificial insemination is widely used in dairy cattle, it has found only limited application in beef cattle. Use of bulls in natural mating programs accounts for over 90% of the pregnancies achieved each year in the U.S. beef cattle industry, and a large percentage of the beef bulls used for natural mating are purchased as yearlings. Many of these yearling bulls undergo a breeding soundness examination prior to sale or the breeding season. This involves visual and manual examination of the genital system as well as assessment of semen, which is usually collected by electroejaculation. However, sex drive and mating ability, which are essential for the delivery of viable spermatozoa and impregnation of females, are not commonly measured. Among beef bulls used for single-sire mating, large ranges in pregnancy rates have been reported, and only low correlations were found between pregnancy rates and semen characteristics. These differences may be potentially explained by differences in the levels of serving capacity (SC) between bulls. Several procedures for testing SC have been used; however, studies investigating the relationship between bulls\u27 SC and herd fertility are inconclusive, with some researchers finding no relationship and other researchers reporting SC test results to be a good predictor of bull fertility. These studies differed in testing procedures used for measuring SC. Thus, differences in the findings may lie in the procedures used for tests or may be due to differences in bull-to-female ratios used when measuring fertility. At present, there is a lack of research relating the SC of yearling beef bulls in a standardized test with their behavior and fertility under pasture mating conditions. The first objective of this study was to evaluate the sexual and grazing behavior of low and high SC yearling bulls when placed with naturally cycling and estrus synchronized cows under pasture mating conditions during bot

Serum Concentrations of Luteinizing Hormone, Testosterone, and Thyroid Hormones in Low and High Serving Capacity Beef Bulls

Adequate sex drive in bulls is essential for natural mating to be successful. Expression of male sexual behavior and mating ability during sexual maturation is dependent upon attaining adequate testicular development and blood levels of luteinizing hormone (LH) and testosterone (T). Several researchers have investigated the relationship between levels of sexual behavior in postpubertal bulls and blood concentrations of LH and T. Some of these researchers reported a positive relationship between T and serving capacity (SC), and others found that individual differences in sexual performance could not be predicted based on circulating levels of T or LH. In those studies, comparisons between sexual behavior of bulls and hormone levels were based on a single blood sample or on infrequent blood sampling. Because no previous studies have utilized a frequent enough sampling regime to determine the episodic release of LH and T, there is a lack of research characterizing the hormonal patterns such as peak frequency, height, and area under the peaks of these hormones in bulls of differing serving capacity. Hormones other than LH and T may influence SC, but little research is available relating these to sexual behavior in bulls. However, thyroid hormones may have some relationship to sexual behavior because earlier research found that removal of the thyroid gland in the bull resulted in disappearance of sex drive and that the feeding of thyroid substance promptly restored sex drive in the hypothyroid bull. Whether this is an effect of a lowered metabolism or a specific endocrine effect has not been established. The objective of the present study was to provide more definitive information on the relationship between the serving capacity of yearling beef bulls and their profiles of LH and T during sexual rest and their blood levels of thyroid hormones. In addition, the interrelationships between these hormones and parameters of testicular function, such as scrotal circumference, paired testicular volume, and seminal traits, were studied

Regeneration of the heart in diabetes by selective copper chelation

Heart disease is the major cause of death in diabetes, a disorder characterized by chronic hyperglycemia and cardiovascular complications. Although altered systemic regulation of transition metals in diabetes has been the subject of previous investigation, it is not known whether changed transition metal metabolism results in heart disease in common forms of diabetes and whether metal chelation can reverse the condition. We found that administration of the Cu-selective transition metal chelator trientine to rats with streptozotocin-induced diabetes caused increased urinary Cu excretion compared with matched controls. A Cu(II)-trientine complex was demonstrated in the urine of treated rats. In diabetic animals with established heart failure, we show here for the first time that 7 weeks of oral trientine therapy significantly alleviated heart failure without lowering blood glucose, substantially improved cardiomyocyte structure, and reversed elevations in left ventricular collagen and beta(1) integrin. Oral trientine treatment also caused elevated Cu excretion in humans with type 2 diabetes, in whom 6 months of treatment caused elevated left ventricular mass to decline significantly toward normal. These data implicate accumulation of elevated loosely bound Cu in the mechanism of cardiac damage in diabetes and support the use of selective Cu chelation in the treatment of this condition