Analytical Derivatives for Markov Switching Models

This paper presents analytical gradients for a broad class of regime-switching models with Markovian state-transition probabilities. Such models are usually estimated by maximum likelihood methods, which require the derivatives of the likelihood function with respect to the parameter vector. These gradients are usually calculated by means of numerical techniques. The paper shows that analytical gradients considerably speed up maximum-likelihood estimation.     

表面贴技术选择的问题探讨

表面贴连接器的设计优点更胜以往，但更为重要的是了解其关键功能的细节以配合与满足不同性能的要求。     

Effects of Electrical Stimulation, Temperature of Boning and Storage Time on Bacterial Counts and Shelf-Life Characteristics of Beef Cuts

Strip loins and eye of rounds from 16 beef carcasses were used to study the effects of electrical stimulation (ES), no stimulation (NS), hot-boning (HB), and cold-boning (CB) on bacteriological and shelf-life evaluations. Following 7 days of vacuum-packaged storage, coliform counts were higher in the drip fluid from strip loins and lean surfaces of eye of rounds from ES compared to NS carcasses. A major advantage for HB in this study was the additional time required in retail display before the occurrence of lean surface discoloration. A previously identified benefit of lighter lean color with ES beef in carcass and primal cut form was also found in this study during display of retail cuts.     

Bacteriological Quality of Hot-Boned Primal Cuts from Electrically Stimulated Beef Carcasses

The objective of this study was to determine bacterial numbers on primal cuts from hot and cold-boned beef carcass sides, and to determine the influence of U.S. Grade and electrical stimulation of the cracass on the incidence of bacteria. Ten boneless primal cuts were removed from each of ten beef carcass sides either 1 or 48 hr after animal slaughter. The primal cuts included the brisket, clod, chuck roll, ribeye, striploin, tenderloin, top sirloin, knuckle, inside round, and gooseneck. The primal cuts were sampled for aerobic (APC 5°C, 20°, 35°C) and coliform bacteria at time of removal from the side and after 20 days' vacuum packaged storage at 2°C. The psychrotrophic bacteria enumerated at 5°C were more numerous (P<0.05) on the primals from the hot-boned sides than from the cold-boned sides before storage, but not after 20 days' storage at 2°C. The mesotrophic and psychrotrophic bacteria enumerated at 20°C, and the mesotrophic bacteria enumerated at 35°C, were more numerous on the hot-boned primals than on the cold boned primals both before and after storage (P<0.05). The magnitude of the difference, on some primals, was greater than one logarithm. Coliform bacteria were not influenced (P<0.05) by hot boning before or after storage. Storage of the primal cuts resulted in some profuse growth of the coliforms. Neither U.S. grade nor electrical stimulation had any apparent influence on the incidence or growth of aerobic bacteria.     

Direct measurement of hydraulic properties in developing berries of Vitis vinifera L. cv Shiraz and Chardonnay

Berries of Vitis vinifera L. cv Shiraz can undergo weight loss during later stages of ripening. Existing published views on how weight loss occurs are based on changes in capacity of the vascular system to import water during development (McCarthy and Coombe, Australian Journal of Grape and Wine Research, 5, 17–21, 1999). One important element of these views is the proposed cessation of water flow through the xylem after veraison. We have now measured the water flow into berries of Shiraz and Chardonnay as they develop using the pressure probe and the high pressure flow meter (HPFM). The pressure probe connected to the pedicel of individual berries provided measurements of single berry hydraulic conductance. By systematic excision of tissue segments of the berry and pedicel we determined where in the pathway hydraulic conductance changed during development. The HPFM was used on whole bunches showing that berries (including pedicels) represent parallel high hydraulic resistances and that the hydraulic resistance of the bunch axis was rather small. The hydraulic conductance per berry could be determined from excision experiments. There was close agreement between the pressure probe and HPFM measurements. Both showed a ten‐fold reduction in hydraulic conductance of whole berries from veraison to full ripeness. Shiraz had hydraulic conductances that were 2‐ to 5‐fold higher than those for Chardonnay. Shiraz maintained a higher hydraulic conductance past 90 days after flowering than Chardonnay. The decrease in hydraulic conductance occurred in both the distal and proximal parts of the berry for both varieties. The pressure probe also provided measurements of the xylem pressure that non‐transpiring berries could develop. These pressures were –0.2 to –0.1 MPa until veraison and increased to zero when the juice osmotic potential reached about –3 MPa in Chardonnay and –4 MPa in Shiraz. The results suggest values of the reflection coefficient of the osmotic barrier around the xylem vessels of about 0.1–0.2 at veraison decreasing to 0 at harvest. It is suggested that in addition to changes in xylem anatomy, aquaporins in berry membranes may play a role in regulating hydraulic conductance. Water movement from the berry back to the parent vine via the xylem (backflow) may be an important component of berry weight loss in Shiraz, particularly if the phloem ceases functioning at high osmotic potentials near maximum weight. Backflow could account for a weight loss of 43 mg per day in Shiraz berries for a relatively small gradient of 0.1 MPa.     

Destruction of Trichinella spiralis During Cooking

Center cut chops (longissimus dorsi), 2.5 cm in thickness, from 31 pigs experimentally infected with Trichinella spiralis larvae and containing 37 ± 5 larvae per gram were cooked to a final internal temperature of 66, 71, 77 or 82° C by one of eight methods to determine their efficacy in killing encysted larvae. The results indicate that with the time and temperatures used in this study, some rapid methods of cooking pork chops that involved the use of a microwave oven did not completely destroy T. spiralis larvae at 77 or 82° C. The data also showed that cooking pork chops to an internal temperature of 77° C in the conventional oven, convection oven, flat grill, charbroiler or deep fat gryer did inactivate encysted T. spiralis larvae in pork chops.     

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