Rate Of Temperature Decline Research Articles

Effects of Three Hotcap Designs on Temperature and Tomato Transplant Development

Hotcaps are covers used to protect individual plants from suboptimal temperatures. Temperature, solar energy, photosynthetic photon flux (PPF), and tomato (Lycopersicon esculentum Mill.) transplant development were compared for three hotcap designs: 3.8-liter, opaque plastic jugs (PJs); 24-cm-tall wax paper (WP); and Wall-O-Water water-filled plastic teepees (PTs). The average solar energy inside the hotcaps was 57.3%, 67.6%, and 28.9% of full sun at midday and PPF was 44.7%, 49.7%, and 43.8% of full sun at midday for WP, PJs, and PTs, respectively. The rate of temperature decline in a growth chamber was fastest for PJs and slowest for PTs. In the field, air and soil temperatures inside hotcaps were higher than ambient during sunny periods and essentially the same during cloudy weather. The overall mean and mean maximum daily soil and air temperatures for all hotcaps were higher than ambient. PTs had the highest minimum daily soil and air temperatures—2.0 and 1.9C above ambient, respectively. The meantime to first ripe fruit was reduced by 10.7 days for PTs, 6.7 days for WP, and increased by 5 days for PJs compared to noncovered plants. Plants grown under hotcaps weighed less and produced fewer fruit on the first cluster. PJs could not maintain night air temperatures above ambient and were not effective hotcaps.

Relation between Winter Temperature and Survival of Larval Atlantic Herring along the Maine Coast

Abstract Larval Atlantic herring Clupea harengus, hatched mainly in late summer and autumn in Maine coastal waters, experienced relatively small temperature declines (1.8–3.1°C) during their autumn transport along the coast to two inshore overwintering locations in the early 1960s and in 1982. Larvae that reached the Sheepscot River estuary on the central Maine coast experienced rates of temperature decline from 0.04 to 0.23°C/d in the early winter of 13 years during the period 1965–1985. Winter larval survival rates were more variable at lower gradients of minimum temperature and declined to lower values at higher gradients. Age-frequency data indicated that the 1984 year-class approached metamorphosis earlier than the 1983 year-class, possibly due to accelerated growth in early spring. Minimum temperatures of 0°C or less were recorded in Boothbay Harbor during the overwintering period for nine year-classes; two of these year-classes were exposed to low temperatures (–1.1°C) that approached the lethal li...

Skin temperature biofeedback for multiple sessions with monetary incentives.

This study evaluated the relative effectiveness of two incentive contingencies in learning biofeedback-assisted control of peripheral skin temperature: positive versus positive/negative monetary incentives. Both incentive groups of 10 participated in six sessions, including pre- and posttraining voluntary control sessions, and four intervening sessions with visual feedback and monetary contingencies. Each session consisted of adaptation, resting baseline, feedback or voluntary control, and a final resting baseline. The results indicated no significant difference in response control between groups and an over-all decline in temperature within sessions. Self-control was evidenced by the slower rate of decline in temperature for the first as compared to the last session, and feedback control by the attenuation in the rate of decline in the last three training sessions. Based on data from other physiological responses, these findings are not likely due to habituation effects. It was concluded that response control should not necessarily be defined in terms of increasing temperature but rather by reference to an appropriate comparison condition. Motivational effects should be further investigated with alternative incentive contingencies.

EFFECTS OF PRERIGOR CONDITIONING TREATMENTS ON LAMB MUSCLE SHORTENING, pH AND ATP

ABSTRACTEffects of prerigor conditioning treatments on processing time, quality characteristics and muscle properties were determined using three muscles from each of 84 lamb carcasses. Carcasses (n = 72) were subjected, beginning 1 hr post‐exsanguination, to one of six conditioning treatments and compared to normally chilled lambs (n = 12). Treatments differed in conditioning period, conditioning chamber environment (temperature, relative humidity, air velocity) and in use of electrical stimulation. All carcasses were maintained at 0°C after the 2‐8 hr conditioning period until fabrication at 72 hr postmortem. Panel ratings (SPR), shear force (SF), water‐holding capacity (WHC) and sarcomere length (SL) were determined for longissimus dorsi (LD), biceps femoris (BF) and semimembranosus (SM) muscles. Lambs in treatments +49 and +32 had the slowest rate of temperature decline, high rates of pH and ATP decline, low WHC, the most pronounced sarcomere shortening and the toughest LD and BF. Carcasses in the +16 treatment reached temperatures critical to cold shortening (9‐11°C) 8‐9 hr later than carcasses in the ‐16 treatment, had longer sarcomeres, had more tender BF (SF) and SM (SPR and SF) muscles but had much lower WHC. Among carcasses conditioned at ‐32°C, those which were electrically stimulated (ES) had lower carcass temperatures at 3 and 4 hr postmortem, had faster rates of pH (LD and BF) and ATP (LD) decline and lower WHC but did not differ in tenderness from those which were not ES. Production of tender lamb, with minimal energy expenditure and no increase in cooler shrinkage, was best accomplished by chilling lambs for 8 hr at +16°C (65% relative humidity and 9m/min air velocity).

FATNESS, RATE OF CHILLING AND TENDERNESS OF LAMB

ABSTRACT40 lambs were selected to vary in amount of finish for use in determining the mechanism by which fatness affects tenderness. Lambs with thick (n = 10), intermediate (n = 20) or thin (n = 10) finish were slaughtered, chilled at 1 ± 1°C and samples obtained from three muscles for chemical, histological, physical and organoleptic analyses. Subcutaneous fat was removed from one side of each carcass in the intermediate finish group to facilitate comparisons on a within‐carcass basis. The data suggest that lamb carcasses which have increased quantities of fat (subjectively determined via live evaluations of finish or objectively determined via subcutaneous fat thickness measurements and marbling scores): (a) chill more slowly; (b) maintain muscle temperatures conducive to autolytic enzyme degradation for greater periods of time postmortem; (c) sustain less shortening of sarcomeres; (d) have muscles with lower ultimate pH values; (e) have less perceptible or softer connective tissue; and (f) are more tender than lamb carcasses which have limited quantities of fat. The data support the hypothesis that deposition of increased quantities of subcutaneous or intramuscular fat (particularly in carcasses with limited quantities of subcutaneous finish) increases tenderness via changes in postmortem chilling rate. An increased quantity of fat decreases the rate of temperature decline (either by insulation or via an increase in carcass mass), enhances the activity (or increases the duration of active proteolysis) of autolytic enzymes in muscle, lessens the extent of myofibrillar shortening and thereby increases the ultimate tenderness of cooked meat from a fatter carcass.

The Influence of Fast and Slow Drops in Ambient Temperature on Egg Production Traits

ACCORDING to Bennion and Warren (1933), Gutteridge et al. (1944), and Warren et al. (1950), egg production is depressed by low winter temperatures. The drop is more pronounced when the onset of cold weather is sudden or when its duration is prolonged (Bruckner, 1936; Hinds, 1949). The available evidence indicates that low temperature has little effect on egg weight (Romanoff and Romanoff, 1949; Wilson et al., 1957), and that shell thickness is greater during the winter (Romanoff and Romanoff, 1949).However, controlled experiments have not been conducted on the effect of the rate of decline in temperature on the performance of birds exposed to extreme cold. We conducted the present experiment to test this.MATERIALS AND METHODSThe stock. Three breeds were used in this study. A Maryland strain of White Leghorns and one of New Hampshires were used in the early part of the study (November, 1956 to March, …