Monitoring chemical changes of dry-cured Parma ham during processing by surface autofluorescence spectroscopy     

Møller JK  Parolari G  Gabba L  Christensen J  Skibsted LH 《Journal of agricultural and food chemistry》2003,51(5):1224-1230

Parma hams at various processing stages were investigated by surface autofluorescence spectroscopy. Fluorescence "landscapes" of raw meat and salted (3 months), matured (11 and 12 months), and aged (15 and 18 months) Parma hams were obtained, and a three-dimensional data array (sample x emission x excitation) was used to develop a PARAFAC model including five components, which all exhibited characteristics of pure fluorophores regarding both excitation and emission spectra. The relative amount of each component related strongly to the processing stage, and sample age showed good correlation to fluorescence data (R = 0.98), with a relative error of prediction of approximately 1 month. Fluorescence measurements from samples of either semimembranosus or biceps femoris were used to predict chemical or sensory reference data, yielding good correlation for biceps femoris data, thereby enabling moisture content, sensory and instrumental color, and proteolysis value to be fairly well predicted. Overall, surface autofluorescence of Parma hams proved to hold relevant information, relating to major chemical/physical changes during processing. It is concluded that fluorescence spectroscopy has potential as an innovative method of quality control in dry-cured ham.  相似文献   

Density loss and respiration rates in coarse woody debris of Pinus radiata, Eucalyptus regnans and Eucalyptus maculata     

Jens Mackensen  Jürgen Bauhus 《Soil biology & biochemistry》2003,35(1):177-186

This study compared field and laboratory decomposition rates of coarse woody debris (CWD) (>10 cm diameter) from three tree species: Pinus radiata, Eucalyptus regnans, and Eucalyptus maculata. For this purpose, the density loss of logs on the ground sampled from chronosequences of sites following harvesting was determined using the water replacement technique. P. radiata logs were sampled 1, 2.5, 6, and 9 years following harvesting, and logs of E. regnans and E. maculata were collected from sites that were harvested 1, 3.5, 6.5, and 12 and 1.5, 6.5, and 11.5 years ago, respectively. In addition, the C/N ratio of wood was determined and current respiration rates of logs from these different age classes were measured through laboratory incubation. The times for loss of 95% of material (t_0.95) determined from density loss for these species were 24 years for P. radiata, 43 years for E. regnans, and 62 years for E. maculata. The decomposition rates of CWD derived from laboratory respiration were 6.1, 5.9 and 11.9 times higher than the decay rates from density loss in P. radiata, E. regnans, and E. maculata, respectively. This points to severe constraints of decomposition through adverse conditions in the field. The changes in respiration rates and C/N ratio with age of decaying logs indicated that the single component, negative exponential decay model could be applied satisfactorily only to P. radiata. In the case of the eucalypt species, substrate quality (expressed through respiration rates) declined in the oldest samples. This may be explained by the loss of rapidly decomposing sapwood and the retention of more decay-resistant heartwood. In these cases, a two-component model will be more suitable to describe the density loss of decaying wood.  相似文献   

Photosynthetic water‐use efficiency of irrigated winter and summer crops in a typical mountain oasis of northern Oman     

Sabine D. Golombek  Jens Gebauer  Andreas Buerkert 《植物养料与土壤学杂志》2007,170(1):98-105

The millenia‐old existence of traditional, surface‐irrigated Omani mountain oases implies a remarkable sustainability of such systems in a hyperarid environment. This study was conducted in the mountain oasis of Balad Seet, situated in the Al‐Jabal‐al‐Akhdar mountains of northern Oman, to investigate the water‐use efficiency (WUE) of these oases and how farmers regulate it. In 2005, gas exchange of single leaves of 9–16 plants was measured for the most important perennial field crop alfalfa in both February and August, for the typical winter crop oat in February, and the dominating summer crop sorghum in August. The measurements were conducted five times a day in subplots irrigated the evening before and in the surrounding control plots, where plants had been withheld from irrigation for 14–16 d. Water deficit at the end of the irrigation interval reduced the stomatal conductance (g_s) strongly in summer alfalfa, oat, and sorghum, but only slightly in winter alfalfa. In oat, the reduction of net photosynthetic rate (P_N) at the end of the irrigation cycle was caused mainly by stomatal closure, in sorghum by nonstomatal factors and in summer alfalfa by both, whereas P_N in winter alfalfa remained unaffected. The ratio of net photosynthetic rate to stomatal conductance (P_N/g_s), the “intrinsic water‐use efficiency”, increased in all investigated crops in response to drought because of a stronger reduction of g_s than of P_N. This increase was small in winter alfalfa, but much stronger in oat, sorghum, and summer alfalfa. The data indicate that alfalfa maintains a relatively high CO₂ assimilation rate year‐round, contributing to a relatively high annual dry‐matter production. The decrease of the light intensity in the late afternoon caused by the shading effect of the surrounding mountains diminishes the crop evapotranspiration in the oasis.  相似文献   

Emerging roles of presynaptic proteins in Ca++-triggered exocytosis     

Rettig J  Neher E 《Science (New York, N.Y.)》2002,298(5594):781-785

The twinning of techniques from biophysics and molecular biology has led to remarkable progress in understanding the molecular mechanisms of synaptic transmission. Here we review the current picture of Ca++-triggered exocytosis, which has emerged from studies of a simple cellular model, the adrenal chromaffin cell. We discuss the molecular players that have been assigned a specific role in a particular step of this process and give a brief outlook on what these insights might tell us about mechanisms of short-term plasticity at classical synapses.  相似文献   

Revealing magnetic interactions from single-atom magnetization curves     

Meier F  Zhou L  Wiebe J  Wiesendanger R 《Science (New York, N.Y.)》2008,320(5872):82-86

The miniaturization of magnetic devices toward the limit of single atoms calls for appropriate tools to study their magnetic properties. We demonstrate the ability to measure magnetization curves of individual magnetic atoms adsorbed on a nonmagnetic metallic substrate with use of a scanning tunneling microscope with a spin-polarized tip. We can map out low-energy magnetic interactions on the atomic scale as evidenced by the oscillating indirect exchange between a Co adatom and a nanowire on Pt(111). These results are important for the understanding of variations that are found in the magnetic properties of apparently identical adatoms because of different local environments.  相似文献   

A gain-of-function mutation in a cytokinin receptor triggers spontaneous root nodule organogenesis     

Tirichine L  Sandal N  Madsen LH  Radutoiu S  Albrektsen AS  Sato S  Asamizu E  Tabata S  Stougaard J 《Science (New York, N.Y.)》2007,315(5808):104-107

Legume root nodules originate from differentiated cortical cells that reenter the cell cycle and form organ primordia. We show that perception of the phytohormone cytokinin is a key element in this switch. Mutation of a Lotus japonicus cytokinin receptor gene leads to spontaneous development of root nodules in the absence of rhizobia or rhizobial signal molecules. The mutant histidine kinase receptor has cytokinin-independent activity and activates an Escherichia coli two-component phosphorelay system in vivo. Mutant analysis shows that cytokinin signaling is required for cell divisions that initiate nodule development and defines an autoregulated process where cytokinin induction of nodule stem cells is controlled by shoots.  相似文献   

Cryopreservation: freezing and vitrification     

Karlsson JO 《Science (New York, N.Y.)》2002,296(5568):655-656

  相似文献   

Comment on "Transmembrane segments of syntaxin line the fusion pore of Ca2+-triggered exocytosis"     

Szule JA  Coorssen JR 《Science (New York, N.Y.)》2004,306(5697):813; author reply 813

  相似文献   

Delineating the drivers of waning wildlife habitat: The predominance of cotton farming on the fringe of protected areas in the Mid-Zambezi Valley, Zimbabwe     

Frédéric Baudron  Marc Corbeels  Jens A. Andersson  Mbulisi Sibanda  Ken E. Giller 《Biological conservation》2011,(5):1481-1493

Zimbabwe’s Mid-Zambezi Valley is of global importance for the emblematic mega-fauna of Africa. Over the past 30 years rapid land use change in this area has substantially reduced wildlife habitat. Tsetse control operations are often blamed for this. In this study, we quantify this change for the Dande Communal Area, Mbire District, of the Mid-Zambezi Valley and analyse the contribution of three major potential drivers: (1) increase in human population; (2) increase in cattle population (and the expansion of associated plough-based agriculture), and; (3) expansion of cotton farming. Although direct effects of land use change on wildlife densities could not be proven, our study suggests that the consequences for elephant and buffalo numbers are negative. All three of the above drivers have contributed to the observed land use change. However, we found farmland to have expanded faster than the human population, and to have followed a similar rate of expansion in cattle sparse, tsetse infested areas as in tsetse free areas where cattle-drawn plough agriculture dominates. This implies the existence of a paramount driver, which we demonstrate to be cotton farming. Contrary to common belief, we argue that tsetse control was not the major trigger behind the dramatic land use change observed, but merely alleviated a constraint to cattle accumulation. We argue that without the presence of a cash crop (cotton), land use change would have been neither as extensive nor as rapid as has been observed. Therefore, conservation agencies should be as concerned by the way people farm as they are by population increase. Conserving biodiversity without jeopardising agricultural production will require the development of innovative technological and institutional options in association with policy and market interventions.  相似文献   

A dog model to study ovary, ovarian ligament and visceral pain     

Boscan P  Monnet E  Mama K  Twedt DC  Congdon J  Eickhoff JC  Steffey EP 《Veterinary anaesthesia and analgesia》2011,38(3):260-266

Objective A dog model was developed to study visceral pain by stimulating the ovarian ligament. Study design Prospective experimental trial. Animals Twelve 1‐year old female hound dogs weighing 25.7 ± 3.6 kg. Methods Dogs were anesthetized with sevoflurane. The right ovary was accessed via laparoscopy. A suture was placed around the ovarian ligament and exteriorized through the abdominal wall for stimulation. The noxious stimulus consisted of pulling the ovary and ovarian ligament with a force transducer. The response to noxious stimulation was determined using the anesthetic minimum alveolar concentration requirement (MAC) for sevoflurane. The ovarian MAC was compared to the standardized somatic noxious stimulation tail clamp MAC. The results are depicted as mean ± SD and corrected to sea‐level. Results The stimulus–response curve during ovarian stimulation in three dogs was hyperbolic and best represented by a three‐parameter logistic growth curve model. The curve plateaued at 7.12 ± 4.19 N. From the stimulus‐response curve, we chose 6.61 N to test the consistency and repeatability of the model in nine dogs. The ovarian stimulation MAC for sevoflurane in these dogs was 2.16 ± 0.46%. The ovarian stimulation confidence interval and limits are comparable to the results from tail stimulation MAC. The tail stimulation MACs before and after laparoscopy surgery were not different (1.86 ± 0.28% and 1.77 ± 0.38% respectively; p > 0.05) but lower when compared to the ovarian MAC (p < 0.01). The dogs recovered from anesthesia without complications. Conclusions and clinical relevance The ovarian stimulation model is an adequate and repeatable means of producing visceral stimulation to determine MAC. The model may provide a humane mechanism to study the effectiveness of analgesics for acute ovarian pain.  相似文献