可持续框架下的城市低碳社区

城市碳排放引发的气候问题日益严峻。作为低碳城市的重要组成单元和载体,低碳社区的规划建设逐渐成为研究重点。基于低碳社区的概念和内涵,提出了可持续框架下低碳社区的规划理念,引导低碳社区在经济、社会、环境协同发展的基础上实现碳减排目标。通过分析中外城市低碳社区的实践经验,将低碳社区规划总结为创新型规划、资源型规划和学习型规划三种模式,提出可持续框架下的低碳社区规划策略:制定可持续的发展目标及规划;政府主导与社区共建相结合;多尺度规划和多举措建设相匹配。建议加强对既有社区的低碳改造研究;完善低碳社区建设的评价标准与考核机制;加强对低碳社区运行的内在机制研究。对可持续框架下低碳社区的发展理念和规划策略研究,探索城市尺度可持续发展途径,实现低碳城市转型具有重要意义。     

Metabolism of lipoproteins in nonhuman primates. Studies on the origin of low density lipoprotein apoprotein in the plasma of the squirrel monkey.

The plasma of squirrel monkeys contains extremely low levels of very low density lipoproteins. The delipidated apoproteins from the different lipoprotein density classes of this species show a heterogeneity similar to that of man and the rat. The biosynthesis of the apoproteins of squirrel monkey lipoproteins was studied in fasted normal and Triton WR1339-treated animals. After intravenous injection of [3-H] leucine, maximal labeling of very low density lipoproteins occurred after 1 h, intermediate density lipoproteins (d 1.006--1.019) in 2 h, and low density lipoproteins after 3 h. At all times, however, low density lipoproteins had the greatest percentage of radioactivity. Polyacrylamide gel electrophoresis revealed that the apoprotein B moiety of very low density and intermediate density lipoproteins contained 62% and 81% of the total radioactivity in these lipoproteins whereas the fast-migrating peptides were minimally labeled. In monkeys injected with Triton WR1339, 70--80% of the radioactivity incorporated into d smaller than 1.063 lipoproteins was in very low density lipoproteins with only 10--15% in intermediate and low density lipoproteins. After injection of 3-H-labeled very low density lipoproteins and [14-C] leucine into Triton-treated monkeys, catabolism of 3-H-labeled very low density lipoprotein to intermediate and low density lipoproteins was small and was significantly less than corresponding values for the incorporation of [14-C] leucine. Thus, breakdown of very low density lipoproteins could not account for all the labeled apoprotein B present in the intermediate and low density lipoprotein fractions. The results indicate that most, but not all, of the newly synthesized apoprotein B enters plasma in very low density lipoproteins and that the low concentrations of this lipoprotein in squirrel monkey plasma are a consequence of its rapid turnover.     

Synthesis and release of low density lipoproteins by the isolated perfused pig liver.

In previous studies, we have shown that a relatively large amount of low density lipoproteins is released into the perfusate during isolated pig liver perfusion. The present studies were done to determine the source of these lipoproteins. Breakdown of the very low density lipoproteins to low density lipoproteins by the perfusion apparatus or by hepatic catabolism was excluded by adding 125I very low density lipoproteins to the perfusate in the presence and absence of a liver and then measuring the radioactivity in the low density lipoprotein fraction after rate-zonal ultracentrifugation. Release of preformed low density, lipoproteins from the liver was investigated by injecting iodine-labeled low density lipoproteins in vivo several hours prior to perfusion of the liver and then measuring the release of labeled low density lipoproteins into the perfusate. It was shown that intact labeled low density lipoproteins were released by the perfused liver. De novo synthesis of the low density lipoproteins was established by measuring the incorporation of [1-14C]leucine into this lipoprotein fraction. The radioactivity in the low density lipoprotein fraction increased with time and accounted for 20 to 25% of the total radioactivity incorporated into all the lipoprotein fractions. The incorporation of [1-14C]leucine into the low density lipoproteins was confirmed by rate-zonal analysis. We conclude that the low density lipoproteins in the perfusate from pig liver perfusions were derived mainly from a preformed liver pool, but also partly from de novo synthesis by the liver.     

温度和盐度对浒苔生长和光合生理特性的影响

为研究海水盐度和温度对大型海藻光合生理影响的复合效应,选取浒苔（Ulva prolifera）为实验材料,探讨不同温度（22℃和15℃）和不同盐度（25和10）对浒苔的相对生长速率、色素含量、叶绿素荧光参数、超氧化物歧化酶（SOD）活性、可溶性蛋白含量等影响。结果表明:在低温条件下,盐度对浒苔生长的影响不显著,而在正常温度条件下,盐度降低显著降低了浒苔的生长;在低盐条件下,尽管差异不显著,温度降低呈现出促进浒苔生长的趋势,但在正常盐度条件下,低温降低了浒苔的生长。相对于温度变化,盐度变化对浒苔潜在的光合效率（F_v/F_m）影响不明显,但低温低盐处理下浒苔具有较高的效光化学效率（F_v’/F_m’）、光能利用效率（α）、非光化学淬灭（NPQ）、SOD酶活性及可溶性蛋白含量。     

Regulatory role of insulin in the degradation of low density lipoprotein by cultured human skin fibroblasts.

The degradation of 125I-labeled low density lipoprotein by cultured human skin fibroblasts was enhanced 25% by preincubation of cells with insulin. This effect of insulin appeared to be mediated via stimulation of low density lipoprotein binding to its cell surface receptor, since binding and subsequent internalization of low density lipoprotein were stimulated to a similar extent as was degradation. In addition, insulin enhanced binding of low density lipoprotein at 4 degrees C, at which temperature internalization of the lipoprotein does not occur. A similar effect of insulin on the interaction of very low density lipoprotein with cultured fibroblasts was observed. Insulin-induced changes in the degradation of low density lipoprotein and very low density lipoprotein appeared to be a function of the change in lipoprotein binding. Thus, insulin may play a role in the regulation of low density lipoprotein and very low density lipoprotein degradation by peripheral cells by influencing the receptor-mediated transport of these lipoproteins.     

The advantages of being evergreen

Recent research shows that the dominance of evergreen species in nutrient-poor environments can be explained by their low nutrient loss rates. From this work It appears that the plant traits that are associated with low nutrient loss rates lead to low maximum-dry-matter production and to low rates of litter decomposition. This suggests a positive feedback between the evergreen habit and low nutrient availability. The growth characteristics of evergreens lead to a low responsiveness to environmental changes. As a result, global warming may lead to changes in the distribution of evergreens.     

Mycobacterium tuberculosis DosR is Required for Activity of the PmbtB and PmbtI Promoters under Hypoxia

Mycobacterium tuberculosis has the ability to survive for extended periods of time under conditions of low oxygen, low pH, low iron and low nutrients. The mycobactins (M. tuberculosis siderophores) play a key role in scavenging iron from the environment and are induced in response to low iron in an IdeR-regulated manner. We demonstrate that the promoters of two mycobactin gene (mbt) operons are also expressed during adaptation to low oxygen, and that this expression is dependent on the DosR regulator. Up-regulation of mbt operons induced by low iron was not DosR-dependent. DosR is a member of a two component regulatory system which responds to oxygen availability. Deletion of the DosR regulator led to increased expression of bacterioferritin and increased capacity to grow under iron depletion. These data provide a link between the mycobacterial response to two conditions likely to be encountered in vivo, low iron and low oxygen.     

Low cost of locomotion in lizards that are active at low temperatures

The nocturnality hypothesis of K. Autumn and coworkers states that nocturnal geckos have evolved a low energetic cost of locomotion (C(min)). A low C(min) increases maximum aerobic speed and partially offsets the decrease in maximum oxygen consumption caused by activity at low nocturnal temperatures. We tested whether a low C(min) is unique to nocturnal geckos or represents a more general pattern of convergent evolution among lizards that enables nocturnality and/or cold-temperature activity. We measured C(min) in four carefully selected lizard species from New Zealand (two nocturnal and two diurnal; n=5-9 individuals per species), including a nocturnal and diurnal gecko (a low C(min) is a gecko trait and is not related to nocturnality), a nocturnal skink (a low C(min) is related to being nocturnal), and a diurnal skink active at low temperatures (a low C(min) is related to being active at low body temperatures). The C(min) values of the four species measured in this study (range=0.21-2.00 mL O(2) g(-1) km(-1)) are lower than those of diurnal lizards from elsewhere, and the values are within or below the 95% confidence limits previously published for nocturnal geckos. A low C(min) increases the range of locomotor speeds possible at low temperatures and provides an advantage for lizards active at these temperatures. We accepted the hypothesis that nocturnal lizards in general have a low C(min) and provide evidence for a low C(min) in lizards from cool-temperate environments. The low C(min) in lizards living at high latitudes may enable extension of their latitudinal range into otherwise thermally suboptimal habitats.     

Stream channel experiments on downstream movement of recently emerged trout, Salmo trutta L., and salmon, S. salar L.—11. Effects of constant and changing velocities and of day and night upon dispersal rate

Four experimental stream channels were used to study instantaneous downstream dispersal rates of young trout and salmon relative to day and night, constant low and high water velocities and changes of velocity from high to low and vice versa.
At high and low velocity for trout and at high velocity for salmon, the dispersal rate was higher by night than by day. Changes of velocity during daytime from high to low or low to high for trout and from high to low for salmon, were associated with much higher dispersal rates than were constant velocities.     

Identification of a population of cells with hematopoietic stem cell properties in mouse aorta-gonad-mesonephros cultures

The aorta-gonad-mesonephros (AGM) region is a primary source of definitive hematopoietic cells in the midgestation mouse embryo. In cultures of dispersed AGM regions, adherent cells containing endothelial cells are observed first, and then non-adherent hematopoietic cells are produced. Here we report on the characterization of hematopoietic cells that emerge in the AGM culture. Based on the expression profiles of CD45 and c-Kit, we defined three cell populations: CD45(low) c-Kit(+) cells that had the ability to form hematopoietic cell colonies in methylcellulose media and in co-cultures with stromal cells; CD45(low) c-Kit(-) cells that showed a granulocyte morphology; CD45(high) c-Kit(low/-) that exhibited a macrophage morphology. In co-cultures of OP9 stromal cells and freshly prepared AGM cultures, CD45(low) c-Kit(+) cells from the AGM culture had the abilities to reproduce CD45(low) c-Kit(+) cells and differentiate into CD45(low) c-Kit(-) and CD45(high) c-Kit(low/-) cells, whereas CD45(low) c-Kit(-) and CD45(high) c-Kit(low/-) did not produce CD45(low) c-Kit(+) cells. Furthermore, CD45(low) c-Kit(+) cells displayed a long-term repopulating activity in adult hematopoietic tissue when transplanted into the liver of irradiated newborn mice. These results indicate that CD45(low) c-Kit(+) cells from the AGM culture have the potential to reconstitute multi-lineage hematopoietic cells.     

Lipoprotein metabolism in the ovariectomized rat

The hyperlipoproteinemia observed after ovariectomy in rats was previously shown to be associated with increased concentrations of cholesterol, triglycerides, and apolipoproteins B, E, and C. In the present study, it was shown that increases in low density lipoproteins and high density lipoproteins were almost entirely responsible for the changes in plasma lipids and apolipoproteins after ovariectomy. The size of the low density lipoproteins and high density lipoproteins isolated from the plasma of ovariectomized rats as determined by agarose chromatography appeared to be somewhat different from that of control rats. Specifically, the apolipoprotein B appeared to be associated with somewhat smaller particles, whereas the apolipoprotein E from those rats appeared to be associated with larger particles than that of control rats. To determine the mechanism for the increased plasma low density lipoproteins, apolipoprotein B pool sizes and turnover rates were calculated and compared. In addition to an increased mass of low density lipoproteins in ovariectomized rats, the turnover rate of low density lipoproteins was increased almost twofold, indicating an increased low density lipoprotein synthesis and catabolism in those animals. We postulate that the increased low density lipoprotein levels of ovariectomized rats are due to an initial increased production of low density lipoproteins, followed by an enhanced catabolism of low density lipoproteins to establish a steady state at higher plasma low density lipoprotein concentrations.     

Uptake of the aromatic retinoids Ro 10-9359 (etretinate) and Ro 10-1670 (acitretin), its main metabolite, delivered to cultured human fibroblasts by serum proteins. Lack of evidence for perturbation of LDL catabolism

Etretinate or acitretin are efficiently delivered to cultured human fibroblasts in the presence of low density lipoproteins, high density lipoproteins or human serum albumin. In contrast to acitretin, delivery of etretinate to fibroblasts is more efficiently achieved with human serum albumin than with lipoproteins. The uptake of etretinate and acitretin via low density lipoproteins delivery, does not take place via the low density lipoprotein-receptor endocytotic pathway but mostly through a passive exchange with the plasma membrane. However, in contrast to acitretin, the exchange of etretinate seems to occur alter binding of etretinate-loaded low density lipoproteins to the apolipoprotein B receptors. No differences are observed in binding, internalization and degradation of native, etretinate-loaded low density lipoproteins and acitretin-loaded low density lipoproteins, suggesting that the presence of these retinoids in low density lipoproteins does not alter their processing by the cells. Furthermore, the presence of these retinoids in the cells does not notably affect, under our experimental conditions, the catabolism of native low density lipoproteins.     

Characterization of the Ehrlich ascites tumor plasma lipoproteins.

1. The lipoproteins of the Ehrlich ascites tumor plasma were separated into 3 distinct fractions, very low density, low density and high density lipoproteins by preparative ultracentrifugation combined with agarose column chromatography. 2. High density lipoproteins contained 74% of the total protein in the lipoproteins. By contrast, most of the lipids were present in the very low density lipoprotein fraction. 3. The fatty acid compositions of the cholesteryl esters were appreciably different in the very low, low and high density lipoproteins, whereas phospholipid and triacylglycerol fatty acid compositions were quite similar in the 3 lipoprotein fractions. 4. Very low and high density apoprotein electrophoretic patterns on sodium dodecyl sulfate-acrylamide gels were similar to those observed in the corresponding lipoprotein fractions obtained from other mammalian species. The low density fraction, however, contained 7 apoprotein bands, and 32% of the low density apoprotein was soluble in tetramethyl urea. 5. The average molecular weights as determined by analytical ultracentrifugation were 2-10(7) (very low density), 6-10(6) (low density) and 4.4-10(5) (high density).     

Work-related low back pain: secondary intervention.

A review of the literature indicates that non-specific low back pain is basically an age-related disorder that is affected by differences in occupation, genetics and personal behavior. The cause of low back pain is unknown in most cases, and most of the treatments in routine use are ineffective. There is no evidence that low back pain has decreased in recent years. Consequently, there are a growing number of investigators who believe that efforts at preventing low back pain are futile; that low back pain is an unavoidable consequence of life that will afflict two thirds of the adult population at some point in their lives. These investigators believe that programs aimed at reducing low back disability are likely to be more effective and less costly. Only a small percentage of people with low back pain become disabled, but this small percentage consumes most of the cost. The literature pertaining to the reduction of low back disability is reviewed and discussed. It is concluded that low back disability can be reduced, and that management (not the health care provider) has the primary responsibility for reducing disability.     

Differential scanning calorimetric studies of native and freeze-damaged very low density lipoproteins in hen’s egg yolk plasma

Lipid thermal transition patterns of the very low density lipoproteins in native and variously treated egg yolk plasma and extracted total very low density lipoproteins lipids have been recorded by differential scanning calorimetry in the temperature range 220–300 K, after lowering the freeze endotherm of free water in the sample with ethylene glycol. Three distinguishable patterns of lipid endotherms, designated types 1, 2 and 3 were obtained, respectively, from (i) native very low density lipoproteins in egg yolk plasma, (ii) freeze damaged very low density lipoproteins in gelled egg yolk plasma and (iii) extracted total lipids of very low density lipoproteins dispersed in water. Protein-depleted ‘lipid core’ particles of very low density lipoproteins obtained by exhaustive proteolysis of egg yolk plasma gave type 2 lipid transition pattern suggesting similarities in its lipid association with that of the freeze damaged very low density lipoproteins. Freezing the ‘lipid cores’ of very low density lipoproteins led to phase separation and gave type 3 lipid transition pattern of water-dispersed, phase-separated total very low density lipoprotein lipids. Relative heat uptake of native very low density lipoproteins in egg yolk plasma was about 15% lower than the freeze damaged sample or of the extracted total lipids. Treatments which prevented aggregation and gelation of very low density lipoproteins in egg yolk plasma during frozen storage, namely with additives such as glycerol or NaCl, gave subsequent lipid transition pattern intermediate between type 1 and 2, indicating that while very low density lipoprotein aggregation is prevented, additives do not altogether prevent changes in lipid association in these particles.     

Accumulation of calcium, potassium and magnesium in apple fruits under various conditions of humidity

In each of two experiments done under controlled conditions, starting at bloom, 4 humidity treatments were applied to potted trees of apple ( Malus pumila Mill. cv. Cox's Orange Pippin), i. e. in experiment 1: (1) high humidity throughout, (2) low humidity throughout, (3) low humidity for 7 weeks followed by high humidity for 6-7 weeks, and (4) the reverse (first high and then low humidity); in experiment 2: (1) day/night humidity high/high, (2) low/low, (3) low/high, and (4) high/low.
In both experiments high humidity favoured shoot growth appreciably. Change from low to high humidity after 7 weeks resulted in some growth stimulation but in the reverse situation growth was markedly reduced. Shoot growth responded little to different night humidities. In the two experiments fruit growth was little affected by treatments. In experiment 2 irrespective of night humidity, water consumption was higher at low than at high day humidity. In the high/low humidity regime water use during the night was high and leaf water potential low, relatively; during the day water potential was little affected by treatments.
At any time leaf Ca and Mg were clearly highest at low day humidity; night humidity had no effect. Leaf K did not respond to treatments. Fruit Ca at high humidity throughout was lower than at low humidity throughout. Increasing humidity later in the season was ineffective but a decrease at that time tended to reduce fruit Ca slightly. The clearly lowest Ca values occurred in the high/low day/night treatment. Fruit K and Mg were not or hardly affected by treatments.
The findings are discussed in terms of humidity effects on transpiration, shoot and fruit growth, and xylem mineral concentration and ion exchange translocation along the xylem walls.     

高频超声联合低频超声检查诊断新生儿颅脑病变的临床价值研究

摘要 目的：探讨高频联合低频超声对新生儿颅脑病变的诊断价值,为新生儿颅脑病变的诊断提供依据。方法：选择2019年1月-2021年4月安徽省儿童医院接诊并疑似出现颅脑病变的新生儿62例作为研究对象,所有研究对象均应用高频超声联合低频超声探头对颅脑进行检查,并住院治疗。比较高频超声、低频超声、高频联合低频超声对新生儿颅脑病变的检出率;根据出院诊断结果比较高频超声、低频超声及联合检查与临床诊断符合情况及对颅脑病变的诊断价值。结果：高频超声检出颅脑病变35例（56.45%）,低频超声检出颅脑病变27例（43.55%）,高频超声联合低频超声检出颅脑病变53例（85.48%）,高频超声联合低频超声对新生儿颅脑病变的检出率显著高于高频超声、低频超声（P<0.05）;高频超声对新生儿颅脑病变的检出率显著高于低频超声（P<0.05）。高频联合低频超声对新生儿颅脑疾病诊断与临床诊断总体符合率高于高频超声、低频超声,高频超声对新生儿颅脑疾病诊断与临床诊断总体符合率高于低频超声（P<0.05）。高频联合低频超声对新生儿不同颅脑疾病诊断灵敏度、准确度显著高于高频超声、低频超声（P<0.05）,高频超声对新生儿不同颅脑疾病诊断灵敏度、准确度显著高于低频超声（P<0.05）,三种检查方法对新生儿不同颅脑疾病诊断特异度比较无统计学意义（P>0.05）。结论：高频联合低频超声检查诊断新生儿不同颅脑病变的灵敏度、准确度均较高,具有一定的临床应用价值。     

Exploring rarity using a general model for distribution and abundance

We describe a simple model for changes in the distribution and abundance of a metapopulation and use it to explore the conditions leading to different types of rarity. The model suggests that localized populations (those with low patch occupancy but high local abundance) arise from low dispersal, low heterogeneity in extant population size, and frequent local extinctions relative to the potential for recolonization. Scarce populations (with low distribution and abundance) arise when relative local extinction rate is low to moderate and heterogeneity is high or successful dispersal is relatively low. Sparse populations (widespread, but with low local abundance) arise when relative local extinction rate is very low and either spatial heterogeneity or mortality through unsuccessful dispersal is high. In sparse or common species, there may be unstable as well as stable equilibria, implying a threshold distribution and abundance for persistence. The model supports a general correlation between distribution and abundance and suggests that persistence may be threatened by dispersal rates being either too high or too low. The model provides a new perspective on rarity and suggests a simple theoretical foundation for understanding the population-dynamic mechanisms that determine distribution and abundance.     

The effect of ethanol on the lipoprotein metabolism of aortic smooth muscle cells

The effect of ethanol exposure on the binding and metabolism of bovine low density lipoprotein by bovine arterial smooth muscle cells was studied. In cells exposed to ethanol (80 mM) for 48 hr or 14 days and incubated with low density lipoprotein for 24 hr there was a reduction in the amount of low density lipoprotein internalised at all concentrations of lipoprotein. There was no effect on the rate of degradation of the low density lipoprotein and no demonstrable changes in the amount of low density lipoprotein bound to the cell surface at high concentrations of low density lipoprotein. Similar results for internalisation and degradation were obtained in a time dependent study. Binding was shown to be reduced in the ethanol treated cells (48 hr) when low concentrations (5 micrograms/ml) of low density lipoprotein were incubated for short periods (less than 3 hr). Scatchard plot analysis indicated that this reduced binding may be due to a reduction of receptor numbers in these cells.     

氮磷水平对龙须菜生长和光合特性的影响

研究不同营养盐条件对龙须菜(Gracilaria lemaneiformis)的生理效应, 对深入了解龙须菜与近海环境的相互作用具有重要意义。在低氮低磷(LNLP)、低氮高磷(LNHP)、高氮低磷(HNLP)和高氮高磷(HNHP) 4种营养盐条件下培养龙须菜15 d, 以探讨不同氮、磷水平对龙须菜生长和光合特性的影响。结果表明: 1) LNHP、HNLP和HNHP处理促进了龙须菜的生长, 其中HNHP处理下龙须菜具有最大的相对生长速率和生物量; 2) LNHP、HNLP和HNHP处理提高了龙须菜的光合无机碳利用能力, 其中HNHP处理下龙须菜具有最大的无机碳饱和光合速率和表观半饱和常数, 比LNLP处理分别提高了118%倍和48.71%; 3) LNHP、HNLP和HNHP处理显著影响龙须菜的光化学效率, 与LNLP处理相比, LNHP处理提高了龙须菜的光化学效率, 而HNLP和HNHP处理降低了龙须菜的光化学效率。研究结果表明, HNHP处理条件下, 龙须菜的生长和光合无机碳利用能力最高, 光化学效率最低。