Modeling biological rhythms in failure time data

Background  

The human body exhibits a variety of biological rhythms. There are patterns that correspond, among others, to the daily wake/sleep cycle, a yearly seasonal cycle and, in women, the menstrual cycle. Sine/cosine functions are often used to model biological patterns for continuous data, but this model is not appropriate for analysis of biological rhythms in failure time data.     

Yield losses due to missing plants in potato crops

Missing plants in potato crops can be caused by diseases and other factors, and can result from non-emergence or from plants incapacitated at any time during the growing season. Field experiments were conducted to simulate missing plants and to estimate the resulting yield losses by removing different percentages of plants at random from plots at emergence and/or later stages. The recorded yield losses were not proportional to the percentage of missing plants. Two surveys of fields of table stock and seed stock of the cultivar Netted Gem in New Brunswick in 1972 showed that approximately 25% of the plants were missing at emergence, probably causing around8% loss in total tuber yield. Assuming all cultivars have similar levels of misses, the yield loss clue to missing plants at emergence in New Brunswick in 1972 was equivalent to a financial loss of approximately $1 1/2 million.     

Nitrogen and potassium fertilization of potatoes: Yield and specific gravity

Potassium and N fertilization is often required for maximum potato (Solanum tuberosum L.) production. Nitrogen, K, and K-sources (KCl, K₂SO₄ are known to affect yield and quality of potatoes but N and K interactions as affected by K-source have not been defined. This study evaluated the N*K and K-source interactions on Russet Burbank tuber yields and specific gravity (SG) in two irrigated field experiments. Nitrogen rates of 0, 112, 224 or 336 kg ha^-1 were combined with selected K rates of 0,112, 224 or 448 kg ha^-1 as either KC1 or K₂SO₄ in an incomplete factorial. A multiple linear regression model was fit to the data and used to predict yield and SG for a complete factorial for each K-source. Both N and K applications increased yields independent of K-source. Nitrogen decreased yields at the 336 kg ha^-1 rate. Potassium increased yields up to 448 kg K ha^-1. Both K-sources decreased SG a similar amount with N application; without N, KC1 decreased SG but K₂SO₄ did not. Nitrogen also decreased SG. Petiole NO₃-N and K concentrations were positively related to yields and negatively to specific gravities. The petiole K concentration 100 days after planting should be above 4.5 for highest tuber yields. The N*K*K-source interaction was important for yields at low available N and for SG at adequate N availabilities. This study showed that N or K fertilizers can be applied according to their respective soil test concentration and the crop’s requirement, generally without consideration of K-source.     

Alturas: A multi-purpose, Russet potato cultivar with high yield and tuber specific gravity

‘Alturas’, a late-maturing, high-yielding, russet potato cultivar with high tuber specific gravity, was released in 2002 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington. Originally selected for dehydration processing, its cold-sweetening resistance also makes it suitable for processing out of storage into french fries and other frozen potato products. Culinary quality is high, with larger tubers suitable for fresh market if heavily russeted skin is not essential. Alturas consistently produced greater total and U.S. No. 1 yields than ‘Russet Burbank’ and ‘Ranger Russet’ in southern Idaho trials. Across other western trial sites, total yields of Alturas have on average been 29% and 14% greater than Russet Burbank and Ranger Russet, respectively. Alturas is resistant to Verticillium wilt (Verticillium dahliae) and early blight (Alternaria solani). Compared with Russet Burbank and Ranger Russet, Alturas is less susceptible to corky ringspot and foliar and tuber infection by late blight (Phytophthora infestans). It also is less susceptible to tuber net necrosis and Fusarium dry rot than Russet Burbank, and is more resistant to common scab (Streptomyces scabies) than Ranger Russet. However, Alturas is more susceptible to infection by PVY and PVX than Ranger Russet. Total nitrogen application recommendations for Alturas are approximately 40% less than those for Russet Burbank. Alturas requires 15% to 20% more water during the growing season than does Russet Bur-bank.     

Bannock russet: A dual-purpose, russet potato cultivar with high U. S. No. 1 yield and multiple disease resistances

Bannock Russet, a late-maturing, long russet potato cultivar, was released in 1999 by the USDA-ARS and the experiment stations of Idaho, Oregon, and Washington. It is suitable for processing into french fries and other frozen products. Its attractive russeted skin and excellent culinary qualities also make it suitable for fresh market. Bannock Russet, in comparisons with Russet Burbank, has consistently produced greater U.S. No. 1 yields in trials conducted throughout southern Idaho. In other western trial sites, total yields of Bannock Russet have been comparable to or smaller than that of Russet Burbank, but its percentage of undersize and cull potatoes is consistently less. Bannock Russet is resistant to potato virus Y (PVY), Verticillium wilt, common scab, and leafroll net necrosis. It also has moderate resistance to early blight (foliar and tuber) andErwinia soft rot. With respect to other potato diseases/disorders, Bannock Russet’s level of susceptibility is similar to that of Russet Burbank; the exception being shatter bruise, with Bannock Russet displaying a greater susceptibility. Cultural management guidelines have been developed to minimize shatter bruise in Bannock Russet. Bannock Russet’s multiple disease resistances coupled with its low nitrogen requirement, make it a low-input cultivar that could significantly reduce growers’ production costs.     

Nitrogen and potassium fertilization of potatoes: Evaluating nutrient element interactions in petioles with response surfaces

We studied the effects of fertilizer N and K rates on the nutrient concentrations in petioles of Russet Burbank potato grown on a low-K, low-Cl, highly calcareous Millville silt loam soil. Phosphate and CaSO₄ were applied uniformly so that P and S did not limit plant growth. An incomplete factorial experimental design, utilizing 14 combinations of fertilizer N and K, including two forms of K, was used to develop a multi-dimensional regression model. This model was then used to produce response surfaces as an aid to analysis of the results and to illustrate the fertilizer treatment effects and their interactions on petiole chemistries. Nitrogen, K and Cl fertilizers had complex effects on petiole concentrations of NO₃-N, SO₄-S, Cl, K, Ca and Mg. Nitrate-N and Cl were mutually antagonistic. Soil N had a large positive effect on petiole K and Mg levels and, to a lesser extent, petiole Ca levels. There was competition between K and Mg in petiole concentration. The sum of K, Ca and Mg was essentially constant across fertilizer treatments and sampling times. The sum of NO₃-N, SO₄-S and Cl was highly variable. The ratio of cations to anions ranged between three and five across fertilizer treatments and sampling times. The data indicate that calibration of the major nutrient element concentrations in potato petioles, as a guide to fertilization, requires knowledge of background soil fertility conditions with respect to N, K, Cl, Ca and Mg, and an understanding of the antagonisms and synergisms among these elements.     

A Fresh Look at the Process of Arriving at a Clinical Prognosis Part 1: Laminitis

Laminitis is a disease that represents a loss of the normal homeostatic mechanisms that control the day-to-day function of the distal phalanx. The degree or severity to which homeostasis is affected is directly related to the severity and the final outcome for the equine patient. A systematic approach including the physical examination, digital radiography, venography, and newer techniques such as computer tomography and magnetic resonance imaging can assist the clinician in developing a prognosis for the acute and chronic laminitis case. How quickly we are able to return the foot back to a normal state of homeostasis or the response to treatment is important as a predictive value for outcome.     

Abdominal aortic aneurysm associated with systemic fungal infection in a German shepherd dog

A 2 yr old spayed female German shepherd presented with a chief complaint of acute onset paraparesis and weight loss. At presentation, the dog was pyrexic, nonambulatory, and had generalized muscle wasting. Neurolocalization was consistent with a thoracolumbar spinal cord lesion. An abdominal ultrasound was performed and revealed a focal dilation (4 cm) of the terminal aorta with evidence of blood stasis consistent with an aortic aneurysm. The dog was euthanized shortly after admission to the hospital and a post mortem examination was performed. Fungal organisms were identified in the aortic aneurysm as well as from the thoracic vertebrae, mesenteric lymph nodes, axillary lymph nodes, spleen, kidneys, liver, lungs, and heart. Although the morphology was consistent with Candida spp., immunohistochemistry and PCR could not definitively identify the causative organism. Mycotic aortic aneurysms are a rare finding in humans and have not been previously reported in the dog. To the authors' knowledge, this is the first known report of an aortic aneurysm associated with systemic fungal infection in a dog.