Determination of dehydroacetic acid and its sodium salt in food products and polymeric packing materials

HPLC method of determination of dehydroacetic acid and its sodium salt in food products and polymeric packing materials has been developed. The migration of DGA from food-contacting materials to food matrix has been investigated.     

An effective lacticin biopreservative in fresh pork sausage

Lacticin 3147 is a novel heat-stable bacteriocin, produced by Lactococcus lactis DPC 3147, that exhibits a broad-range inhibition spectrum similar to nisin. In this study, the effect of lacticin 3147 and nisin on the shelf life of fresh pork sausage and their ability to control pathogens (Clostridium perfringens DSM 756, Salmonella Kentucky AT1) and nonpathogenic Listeria innocua DPC 1770 was investigated. The following preservative regimens were evaluated, both in broth and sausage systems: (i) 450 ppm of sodium metabisulphite; (ii) 500 IU g(-1) or ml(-1) of nisin, (iii) 2500 arbitary units (AU) g(-1) or ml(-1) of lacticin 3147; (iv) 2% sodium lactate and 500 IU of nisin; (v) 2% sodium citrate and 500 IU g(-1) or ml(-1) of nisin; (vi) 2% sodium lactate and 2500 AU g(-1) or ml(-1) of lacticin 3147, (vii) 2% sodium citrate and 2500 AU g(-1) or ml(-1) of lacticin 3147, (viii) 2% sodium lactate, and (ix) 2% sodium citrate. There was no significant difference in the activity of nisin and lacticin 3147 against any of the target strains used, both bacteriocins performing significantly better than sodium metabisulfite against gram-positive strains in broth systems. Trends indicate that the combination of organic acids with either bacteriocin enhanced its activity against Salmonella Kentucky and L. innocua and was particularly effective in the inhibition of C. perfringens in fresh pork sausage. In addition, lacticin 3147 combined with either sodium citrate or sodium lactate maintained significantly lower (P < 0.05) total aerobic plate counts for the duration of the trials and may function as an alternative to sodium metabisulfite in the preservation of fresh pork sausage.     

Effects of antibiotic regimens on the fecal shedding patterns of pigs infected with salmonella typhimurium

An experiment was conducted to determine (i) the effects of antibiotic regimens on the shedding patterns of pigs infected with Salmonella Typhimurium and (ii) whether antibiotic resistance increases the incidence of pathogen shedding. The experiment involved 48 50-day-old pigs challenged with Salmonella Typhimurium and receiving one of four antibiotic regimens including (i) intramuscular injection of ceftiofur sodium followed by inclusion of oxytetracycline in the feed; (ii) apramycin in the feed for 14 days followed by oxytetracycline; (iii) carbadox in the feed until pigs reached 35 kg followed by oxytetracycline; (iv) no antibiotics (control). Fecal samples were collected preinoculation, 2 and 4 days postinoculation (DPI) and at weekly and biweekly intervals thereafter to determine shedding patterns. Salmonella Typhimurium isolates from 2, 4, 7, 21, 42, and 70 DPI were analyzed for antibiotic resistance. A time effect (P < 0.05) was observed, indicating that the proportion of isolates resistant to at least one antibiotic varied over time. Overall resistance was determined to be 46% at 2 DPI and increased significantly (P < .05) thereafter. Treatment x time and antibiotic x time interactions were also observed (P < 0.05) as the percentage of isolates resistant to each test antibiotic increased over time. In no case did the development of antibiotic resistance result in an increased incidence of shedding of the original inoculate. The incidence of shedding was reduced in pigs receiving the apramycin-oxytetracycline treatment, when compared to control pigs; however, no differences were observed between antibiotic treatments.     

电化学方法制备掺杂二氧化钛纳米管阵列

通过阳极氧化制备二氧化钛纳米管阵列。然后用制成的纳米管阵列作阴极、Pt作阳极,分别以Zr(NO3)4、NH4Cl及Zr(NO3)4和NH4Cl的混合溶液为电解液,制备锆掺杂、氮掺杂及锆、氮共掺杂二氧化钛纳米管阵列。通过FESEM、UV-vis 漫反射、XRD、XPS等手段对纳米管阵列进行表征。结果表明,制成的纳米管阵列管径约70 nm,管长约400 nm。共掺杂后的吸收带边有了明显的红移。在锆掺杂纳米管中锆含量是0.51%,氮掺杂纳米管中氮含量为1.92%,共掺杂中锆、氮含量分别是0.77%和1.29%（均为原子分数）。N1s峰在单独掺氮纳米管中是一个峰,而在混合掺杂中是双峰,说明氮在单独掺杂和混合掺杂中的存在状态并不一致。通过降解罗丹明B水溶液对其光催化性能进行检测。结果显示,锆掺杂可以增强TiO2 纳米管阵列在紫外光下的催化活性,氮掺杂提高了TiO2 纳米管阵列在可见区的光催化活性,锆、氮共掺杂产生了协同作用,使TiO2纳米管阵列的催化活性在紫外和可见区都得到了明显的提高。     

FPGA与工业以太网迷津

今天，有超过25种基于以太网的工业通讯系统在市场上共存。工业设备的制造商们需要开发一种解决方案，使用单一硬件平台就可以为多个RTE（实时以太网）协议提供支持。同时，这一平台还应该可以现场更新，在不替换任何硬件的情况下，支持现有协议的新版本甚至是完全不同的协议。     

Antarctic springtime depletion of atmospheric mercury

Unlike other heavy metals that are inherently associated with atmospheric aerosols, mercury in ambient air exists predominantly in the gaseous elemental form. Because of its prolonged atmospheric residence time, elemental mercury vapor is distributed on a global scale. Recently, Canadian researchers have discovered that total gaseous mercury levels in the lower tropospheric boundary layer in the Canadian Arctic are often significantly depleted during the months after polar sunrise. A possible explanation may involve oxidation of elemental mercury, followed by adsorption and deposition of the oxidized form, leading to an increased input of atmospheric mercury into the Arctic ecosystem. Here we present the first continuous high-time-resolution measurements of total gaseous mercury in the Antarctic covering a 12-month period between January 2000 and January 2001 at the German Antarctic research station Neumayer (70 degrees 39' S, 8 degrees 15' W). We report that mercury depletion events also occur in the Antarctic after polar sunrise and compare our measurements with a data setfrom Alert, Nunavut, Canada. We also present indications that BrO radicals and ozone play a key role in the boundary-layer chemistry during springtime mercury depletion events in the Antarctic troposphere.     

Evanescent wave coupling in light scattering of an off-axis normally incident Gaussian beam by two parallel nonabsorbing cylinders

A theoretical and numerical investigation is devised for resonant light scattering of an off-axis normally incident Gaussian beam by two parallel nonabsorbing cylinders based on the related beam theory developed in J. Opt. Soc. Am. A 14, 640 (1997). By varying the half-beam width, we show that the multireflection process between the two scatterers can be minimized. Moreover, the study is an attempt to understand the underlying physics present in the process of resonance excitation by evanescent wave coupling.     

Composition of explosives by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Commercial explosives are complex mixtures that contain not only the active explosive agent(s) but also a host of other organic and inorganic compounds. The ultrahigh mass resolving power (m/delta m50% >200,000) and mass accuracy (<1 ppm) of electrospray ionization Fourier transform ion cyclotron resonance (ESI FTICR) mass spectrometry allow for definitive identification of various species in TNT, RDX, and HMX. We are thereby able to correct prior misassignments of the elemental compositions of the most abundant negative ions from electrospray of RDX and HMX. Although the (known) active agents of many explosives may be identified by low-resolution MS or MS/MS, it is the other characteristic components (indigenous or artificial additives) whose presence and elemental composition can potentially identify the source of the product. ESI FTICR mass spectrometry of smokeless powder, TNT, and Powermite resolves and identifies numerous nonactive ingredients, many of which are recovered in a postblast residue. In contrast, the residue recovered from an explosion of military C4 yielded several species derived from RDX but virtually none from other ingredients.     

Baseline resolution of isobaric phosphorylated and sulfated peptides and nucleotides by electrospray ionization FTICR ms: another step toward mass spectrometry-based proteomics

Electrospray ionization broadband FTICR mass spectrometry at a mass resolving power, m/delta m50% > or = 400,000 has achieved the first direct mass spectral resolution of phosphorylated and sulfated peptides (or nucleotides) of the same nominal mass. The elemental composition difference in each case is PH versus S (9.5 mDa), requiring a minimum mass resolving power ((m2 - m1)/ml) of 118,000 (C terminal amidated cholecystekinin fragment 26-33 (CCK-8), DY(PO3H2)MGWMDF-NH2 versus DY(SO3H)MGWMDF-NH2) or 65,400 (adenosine triphosphate vs 3-phosphoadenosine 5'-phosphosulfate). The isobaric mass doublets were detected in broadband mode (400 < m/z <1400) in the presence of dozens of other species. It is therefore now possible to distinguish phosphorylated from sulfated peptides, even when both species are present at the same time in a protein digest.