红枣干果过热蒸汽杀菌试验研究

[目的]减少红枣在杀菌过程中的营养物质损失,提高免洗红枣品质。[方法]研究不同蒸汽温度(130、140、150、160℃)和处理时间(10、20、30、40 s)对于过热蒸汽灭菌红枣干果中菌落总数、VC、还原糖含量的影响,设计了2因素4水平红枣干果过热蒸汽灭菌正交试验,并寻找过热蒸汽杀菌的最优工艺。[结果]经过热蒸汽处理后,红枣表面菌落总数远低国家标准;红枣中VC含量随着杀菌温度的升高而减少,且随着杀菌时间的延长而减少;而还原糖含量虽较未处理时的红枣降低,但是随温度升高含量有明显的增加。通过正交试验确定红枣干果过热蒸汽杀菌最优工艺:温度150℃,杀菌时间10 s。[结论]过热蒸汽技术可在干果杀菌领域推广应用。     

培养料微波灭菌对平菇子实体营养成分的影响研究

对传统湿热高温灭菌和微波灭菌培养料栽培的平菇子实体的营养成分进行了对比研究.结果表明,氨基酸、蛋白质、粗脂肪及水分的含量,2种子实体间相差不大,而总糖、粗纤维、粗灰分、矿物元素和维生素的含量有明显的区别.主要表现为总糖、铜、铁和钙在湿热高温灭菌培养料栽培的平菇子实体中的含量较高,而粗纤维、磷、锌、硒、VB1及VB2含量在微波灭菌培养料栽培的子实体中较高.试验证明,微波灭菌培养料栽培平菇对其营养价值没有不利影响,硒、VB1等营养成分还有明显提高,微波灭菌技术可以在平菇培养料灭菌中应用.     

Polar Volatiles on Mars--Theory versus Observation: Excess solid carbon dioxide is probably present in the north residual cap

The residual frost caps of Mars are probably water-ice. They may be the source of the water vapor associated with seasonal polar hoods. A permanent reservoir of solid CO(2) is also probably present within the north residual cap and may comprise a mass of CO(2) some two to five times that of the present atmosphere of Mars. The martian atmospheric pressure is probably regulated by the temperature of the reservoir and not by the annual heat balance of exposed solid CO(2) (37). The present reservoir temperature presumably reflects a long-term average of the polar heat balance. The question of a large permanent north polar cap is reexamined in light of the Mariner 9 data. The lower general elevation of the north polar region compared to the south and the resulting occurrence in the north of a permanent CO(2) deposit are probably responsible for the differences in size and shape of the two residual caps. The details of the processes involved are less apparent, however. It might be argued that the stability of water-ice deposits depends on both insolation and altitude. The present north and south residual caps should be symmetrically located with respect to such a hypothetical stability field. However, the offset of the south cap from the geometrical pole, the non-symmetrical outline of the north cap, and the apparently uniform thickness of the thin, widespread water-ice all argue against control by simple solid-vapor equilibrium of water under present environmental conditions. We think that the present location of the water-ice may reflect, in part, the past location of the permanent CO(2) reservoir. The extreme stability of polar water-ice deposits increases the likelihood that past environmental conditions may be recorded there. Detailed information on elevations in the vicinity of the residual caps is needed before we can further elucidate the nature and history of the residual caps. This, along with measurements of polar infrared emission, should be given high priority in future missions to Mars. Two conclusions follow from the limitation of the mass of solid CO(2) on Mars at present to two to five times the mass of CO(2) in the atmosphere. If all of this CO(2) was entirely sublimated into the atmosphere as a result of hypothetical astronomical or geophysical effects, the average surface pressure would increase to 15 to 30 mbar. Although such a change would have considerable significance for eolian erosion and transportation, there seems to be little possibility that a sufficiently earthlike atmosphere could result for liquid water to become an active erosional agent, as postulated by Milton (38). The pressure broadening required for a green-house effect requires at least 10 to 20 times more pressure (39). If liquid water was ever active in modifying the martian surface, it must have been at an earlier epoch, before the present, very stable CO(2)/H(2)O system developed. There can be no intermittent earthlike episodes now. Furthermore, the present abundance of CO(2) on Mars may be an indicator of the cumulative evolution of volatiles to the surface of the planet (40). Thus, even the possibility of an earlier earth-like episode is dimmed. On Mars, the total CO(2) definitely outgassed has evidently been about 60 +/- 20 g/cm(2). On the earth, about 70 +/- 30 kg/cm(2) of CO(2) have been released to the surface (41). Hence, the total CO(2) devolved by Mars per unit area is about 0.1 percent of that evolved by the earth. Thus, the observational limits we place on solid CO(2) presently located under the north residual cap also may constitute considerable constraints on the total differentiation and devolatilization of the planet. If they are valid, it would seem unlikely that Mars has devolatilized at all like the earth, or ever experienced an earthlike environment on its surface.     

火龙果果汁饮料的杀菌工艺

为筛选出最佳的杀菌方法,保证火龙果果汁饮料的品质,将配制好的火龙果果汁饮料分别进行水浴、微波加热、臭氧杀菌处理,通过感官评分、微生物检验及理化指标测定,并进行Duncan多重比较。结果表明:最佳的杀菌工艺参数为微波高火加热1.5min,杀菌后饮料中的氨基态氮为4.85mg/100mL,维生素C含量为0.85mg/L,对总糖、氨基态氮和维生素C等营养成分的破坏较小。     

Planetary Contamination II: Soviet and U.S. Practices and Policies

The accompanying article of Horo witz et al. concluded with the view that the COSPAR recommendations re garding Mars should be adjusted to re flect new environmental information. Specifically, it was concluded that viable terrestrial microorganisms which are transported to Mars inside solid components in sealed spaces have a low probability of being released to the sur face or atmosphere, and that, if any are released, they are not likely to in fect the planet. We suggest, in addition, that both the COSPAR recommenda tions and U.S. planetary quarantine policy should be altered to take into account past and continuing Soviet prac tice regarding the. exploration of Mars and Venus. No amount of analysis by COSPAR, or of costly, self-imposed restrictions by the U.S. on its own planetary exploration program, can reduce the probability of contamination of either Venus or Mars below what the Soviets have already made it, or will make it as they continue their large planetary effort. All that U.S. policy can accomplish is to insure that U.S. efforts do not significantly increase the probability above that level. Any rec ommended policy which would require the U.S. to apply significantly more stringent restrictions is illogical in that, in effect, the U.S. would be asked to increase greatly the cost and complexity of its planetary program without achieving any significant reduction in the probability of actual contamination. There exists some parallelism be tween the problem of planetary quaran tine and that of radioactive fallout from atmospheric nuclear testing, al though the desirable solution to the quarantine problem is not merely to stop all activity. Both are multilateral problems, and individual national policy necessarily must reflect the policy of other nations. Thus, the real questions that must be faced by COSPAR, and by the U.S., are, (i) What is the prob able number of viable terrestrial micro organisms alreadyr transported to Venus and to Mars? and (ii) What is the to tal number to be expected in the next decade or so from foreseeable Soviet efforts alone? Then COSPAR can rec ommend, and the U.S. can decide, that the total U.S. contribution should be equal to some specified fraction of the total present and future Soviet contribu tion. This approach in turn suggests that every effort should be made to induce the Soviets to supply additional de tails on the Zond 2 and Venus 3 mis sion and trajectory and, particularly, on the procedure used for sterilizing the components and assembly of both space craft. With such information, the proba ble number of viable terrestrial microor ganisms deposited on Venus and Mars could be estimated well enough to per mit a. realistic quantitative analysis of what U.S. policy and practice should be. However, if more complete informa tion on Soviet practice cannot be ob tained, then, it seems to us, the U.S. has no logical alternative but to per mit greater engineering freedom in lander delivery technique and to ac cept gaseous and other nonthermal sterilization procedures, where neces sary, in its own program. By relying on the demonstrated U.S. spacecraft reliability to insure that the U.S. con tribution to planetary contamination will remain significantly less than the Soviet contribution, we could reduce significantly the cost and time required to carry out serious scientific investiga tions of the surfaces of Venus and Mars.     

基于新近重力场模型MRO120D的火星探测器轨道仿真与分析

针对火星探测器在轨运行时间的问题,利用动力学方法和最新火星重力场模型MRO120D,对220km和150km初始轨道高度的火星探测器进行轨道仿真分析.结果表明,考虑重力场模型二阶位系数C_(20)时,探测器在220km轨道高度能够在计算时间内长期稳定地运行,不考虑该系数的探测器在轨运行时间不足40d,说明位系数C_(20)是稳定轨道的重要因素.在相同条件下,探测器在150km轨道高度运行时间不足18d,说明大气阻力效应对低轨探测器的影响较大.在满足相关科学任务的条件下,建议初始轨道设计在220km以上,以此获得较长的在轨运行时间.     

Seasat altimeter calibration: initial results

Preliminary analysis of radar altimeter data indicates that the instrument has met its specifications for measuring spacecraft height above the ocean surface (+/- 10 centimeters) and significant wave height (+/- 0.5 meter). There is ample evidence that the radar altimeter, having undergone development through three earth orbit missions [Skylab, Geodynamics Experimental Ocean Satellite 3 (GEOS-3), and Seasat], has reached a level of precision that now makes possible its use for important quantitative oceanographic investigations and practical applications.     

基于极点配置农用轮式机器人横向控制

农业机器人工作对象是复杂的非结构性地面,机器人在工作中经常由于环境的不确定性而偏离轨道。如何设计控制器使机器人偏离轨道后能够快速回归是一个很重要的问题。针对农用轮式移动机器人的运动学线性化模型,研究当农用轮式移动机器人横向偏离运动轨道时,提出使用极点配置方法设计控制器。仿真试验的结果也表明机器人在不同的纵向速度下都可以满足要求。     

Magnetic lineations in the ancient crust of mars

The Mars Global Surveyor spacecraft, in a highly elliptical polar orbit, obtained vector magnetic field measurements above the surface of Mars (altitudes >100 kilometers). Crustal magnetization, mainly confined to the most ancient, heavily cratered martian highlands, is frequently organized in east-west-trending linear features, the longest extending over 2000 kilometers. Crustal remanent magnetization exceeds that of terrestrial crust by more than an order of magnitude. Groups of quasi-parallel linear features of alternating magnetic polarity were found. They are reminiscent of similar magnetic features associated with sea floor spreading and crustal genesis on Earth but with a much larger spatial scale. They may be a relic of an era of plate tectonics on Mars.     

不同消毒方式对华中枸骨组织培养的影响

[目的]考察不同消毒方式对华中枸骨组织培养的影响.[方法]以华中枸骨的带芽新梢茎段为外植体,分顶芽和侧芽,研究乙醇、升汞的作用时间以及吐温的用量对外植体消毒的影响.[结果]华中枸骨新梢顶芽的最佳消毒方式为：浓度75％乙醇作用50 s,浓度0.1％升汞作用6 min,Tween-801滴;侧芽的最佳消毒方式为：浓度75％乙醇作用50 s,浓度0.1％升汞作用7min.[结论]该方法优化了华中枸骨组织培养的消毒方法,为华中枸骨的进一步开发利用提供依据.     

设施土壤灭菌与摩西球囊霉对黄瓜幼苗生长及养分吸收的影响

【目的】研究摩西球囊霉（Glomus mosseae）与设施连作土壤灭菌处理对黄瓜幼苗生长及养分吸收的影响,以明确该真菌在缓解黄瓜连作障碍中的潜力。【方法】以津春3号黄瓜为试验品种,在日光温室进行盆钵培养试验,设置连作土壤处理和摩西球囊霉两因素,完全方案设计,土壤处理设灭菌与未灭菌2个水平,摩西球囊霉设接种与未接种2个...     

橡胶树内生真菌分离方法研究

以同一株橡胶树的枝条和叶片为材料,采用5种不同的组织表面消毒方法,在加入3种不同细菌生长抑制剂的PDA培养基中培养橡胶树内生真菌。结果表明,在加入Rifamicin15mg／L的PDA培养基中,运用M2培养分离效果最佳。     

低聚木糖在食品加工过程中的稳定性研究

研究了低聚木糖在食品杀菌过程中的热稳定性变化。对低聚木糖采用4种杀菌法,即,常温杀菌,巴氏杀菌(缓冲液控制pH值2.0~8.0,温度65℃,加热30 min),高温杀菌(缓冲液控制pH值2.0~8.0,在常压60~100℃下加热15 min)和高压杀菌(121℃,加热10~60 min),通过DNS测定法测定低聚木糖的OD值,研究了低聚木糖在4种杀菌条件下的热稳定性。巴氏杀菌(pH值2.6~7.0),高温杀菌(pH值5.0~7.0)和高压杀菌(pH值3.0~6.8)时,P70低聚木糖具有良好的热稳定性。当P70低聚木糖作为添加剂添加到一般食品中时,在pH值4.2~7.0,在巴氏杀菌、高温杀菌、高压杀菌过程中具有良好的稳定性。     

A wetter, younger Mars emerging

Most researchers have believed that the days were long gone when water splashed on the surface of Mars or even near it. Now continuing analyses of martian meteorites and stunning images from the Mars Global Surveyor (MGS), which has been in orbit since 1997, are breathing new life into the Red Planet. Last month's announcement that the camera aboard MGS had spied signs of geologically recent--possibly even ongoing--water seeps has caught everyone's attention. Other, perhaps more persuasive, signs also suggest that water may even now flow on or beneath the frigid surface.     

Scientific results of the viking missions

The two Viking missions to Mars have been extraordinarily successful. Thirteen scientific investigations yielded information about the atmosphere and surface. Two orbiters and landers operating for several months photographed the surface extensively from 1500 kilometers and directly on the surface. Measurements were made of the atmospheric composition, the surface elemental abundance, the atmospheric water vapor, temperature of the surface, and meteorological conditions; direct tests were made for organic material and living organisms. The question of life on Mars remains unanswered. The Viking spacecraft are designed to continue the investigations for at least one Mars year.     

土壤灭菌对连作大豆生长发育的影响

用连作大豆茬土壤和玉米茬土壤灭菌后栽培大豆表明，灭菌可基本消除大豆连作土壤的不良影响，表现出大豆生长发育良好，产量提高；而且大豆连作土壤还略优于玉米土壤，据此认为前作大豆所形成的土壤生物环境乃为大豆连作障碍主要因素之一．     

空气凤梨组培快繁技术优化

以空气凤梨(Tillandsia ionantha)子株为外植体,研究了不同的消毒处理和培养基配方对生长的影响,优化了其组培快繁技术。结果表明,对空气凤梨子株适宜的消毒处理方法是75%乙醇4 s+0.1%Hg Cl26 min,外植体污染率低,仅为16.7%,且色泽嫩绿;诱导丛生芽适宜的培养基为MS+BA 5.0 mg/L+NAA 0.2 mg/L,增殖率达161.9%,丛生芽生长良好;利用壮苗培养基MS+NAA(1.0~2.0 mg/L)进行培养,幼苗生长健壮。     

即食海带的脱腥与杀菌工艺

探讨了淡干海带加工成即食海带过程中海带脱腥、杀菌温度和杀菌时间的最佳工艺条件,结果表明,醋酸对海带有良好的脱腥效果,海带经体积分数为1.0%醋酸溶液脱腥20 min后,在100℃下杀菌22 min,所得产品无腥臭味、色泽翠绿、口感脆嫩,达到商业无菌要求.     

Planetary science. A dripping wet early Mars emerging from new pictures

The latest images from the Red Planet, a sampling of which is shown on page 1927, are suggesting that water ponded across its equatorial region eons ago, just when life might have been emerging. Although the authors offer more than one interpretation, the one they prefer has the sediments laid down beneath broad lakes and shallow seas at a relatively clement time in the planet's history. The geologic implications of the pictures plus supportive signs from earlier missions mean that these possible lake sediments will be prime candidates for NASA missions seeking signs of past life on Mars.     

Space research: at a crossroads

The current state and future directions of the U.S. space-science program are assessed in the wake of the Challenger accident, the Gramm-Rudman-Hollings budget reduction act, and the report of the National Commission on Space. A renewed emphasis on moderate-scale, quickresponse missions will be of special importance for scientific progress and will compensate in part for the postponement of most major space missions. Satellites and manned space stations in Earth orbit, along with unmanned planetary missions, will continue to be the dominant elements in the space program. Future progress and the continuation of U.S. leadership depend on the vitality of U.S. space research.