共查询到20条相似文献，搜索用时 562 毫秒
1.
Chung Yu Chan Vasiliy N. Goral Michael E. DeRosa Tony Jun Huang Po Ki Yuen 《Biomicrofluidics》2014,8(4)
In this article, we present a simple, rapid prototyped polystyrene-based microfluidic device with three-dimensional (3D) interconnected microporous walls for long term perfusion cell culture. Patterned 3D interconnected microporous structures were created by a chemical treatment together with a protective mask and the native hydrophobic nature of the microporous structures were selectively made hydrophilic using oxygen plasma treatment together with a protective mask. Using this polystyrene-based cell culture microfluidic device, we successfully demonstrated the support of four days perfusion cell culture of hepatocytes (C3A cells). 相似文献
2.
以结构化学指导新型金属 有机纳米器件的合理合成和物理性能研究,探索它们的自组装规律,共设计合成了 1 2个含N、S及COO- 基团的具有不同对称性和立体选择性的新颖大骨架多官能团柔性配体,以及由它们与金属离子自组装合成了 1 8个新型金属 有机纳米笼、纳米管和配位聚合物,开辟了一条合成金属 有机纳米器件的新途经。其中,一个具有Oh对称的金属纳米笼,笼内体积超过 1 0 0 0 A3,可以同时容纳多种离子和小分子,是目前已测定单晶结构的金属纳米笼中容量最大的一个。而用金属离子把纳米管串联成的金属 有机纳米管则是国际上首例报道的结构有序无机 有机纳米管阵列;并创新性的采用低温溶剂热法合成了一个新颖的具有半导体和顺磁性质的Ni 巯基嘧啶二维层状聚合物和两个二维折叠格子状化合物;另外,用巯基嘧啶作为难溶盐CuCN的溶解模板,得到了国际上首例六角形CuCN大环化合物和另外一个新颖的类石墨层状CuCN化合物. 过渡金属与多官能团配体通过配位键来驱动和引导自组装,形成具有均一尺寸和特定形状的金属 有机纳米器件,是当今化学与材料领域研究的前沿之一。而通过设计合成具有特定对称性和立体选择性的有机配体,并把它们与金属离子自组装形成具有纳米尺寸和特殊功能的纳米球和纳米管,更是在纳米科技、 相似文献
3.
Jin Tang Yaodong Wu Lingyao Kong Weiwei Wang Yutao Chen Yihao Wang Y Soh Yimin Xiong Mingliang Tian Haifeng Du 《国家科学评论(英文版)》2021,8(6)
We report differential phase contrast scanning transmission electron microscopy (TEM) of nanoscale magnetic objects in Kagome ferromagnet Fe3Sn2 nanostructures. This technique can directly detect the deflection angle of a focused electron beam, thus allowing clear identification of the real magnetic structures of two magnetic objects including three-ring and complex arch-shaped vortices in Fe3Sn2 by Lorentz-TEM imaging. Numerical calculations based on real material-specific parameters well reproduced the experimental results, showing that the magnetic objects can be attributed to integral magnetizations of two types of complex three-dimensional (3D) magnetic bubbles with depth-modulated spin twisting. Magnetic configurations obtained using the high-resolution TEM are generally considered as two-dimensional (2D) magnetic objects previously. Our results imply the importance of the integral magnetizations of underestimated 3D magnetic structures in 2D TEM magnetic characterizations. 相似文献
4.
Despite numerous advantages, applications of conventional microporous metal–organic frameworks (MOFs) are hampered by their limited pore sizes, such as in heterogeneous catalysis and guest delivery, which usually involve large molecules. Construction of hierarchically porous MOFs (HP-MOFs) is vital to achieve the controllable augmentation of MOF pore size to mesopores or even macropores, which can enhance the diffusion kinetics of guests and improve the storage capacity. This review article focuses on recent advances in the methodology of HP-MOF synthesis, covering preparation of HP-MOFs with intrinsic hierarchical pores, and modulated, templated and template-free synthetic strategies for HP-MOFs. The key factors which affect the formation of HP-MOF architectures are summarized and discussed, followed by a brief review of their applications in heterogeneous catalysis and guest encapsulation. Overall, this review presents a roadmap that will guide the future design and development of HP-MOF materials with molecular precision and mesoscopic complexity. 相似文献
5.
本文采用2006—2013年期间实施股权激励的公司为研究样本,以逆米尔斯比率作为管理层私人信息的计量变量,采用Heckman方法估计管理层私人信息,股权激励实施对研发投入的影响。研究结果发现：管理层私人信息与企业研发投入显著相关,即企业研发投入与股权激励实施具有内生性;在控制内生性基础上股权激励实施决策与之后三年企业的研发投入相关,即实施股权激励企业的管理层倾向于在之后的三年中增加企业研发投入。但结合样本选择模型结果,高管持股比例高以及高管薪酬高的企业越倾向于实施股权激励,说明实施股权激励是内部人控制的结果。因此,研发投入增加并不能被视为代理问题的缓解,实质是代理问题的表现结果,即激励效应与企业研发投入显著正相关是企业代理问题的表现结果,并非缓解企业代理问题。 相似文献
6.
Nilima N. Dongre Adinath N. Suryakar Arun J. Patil Indira A. Hundekari Basavaraj B. Devarnavadagi 《Indian journal of clinical biochemistry : IJCB》2013,28(1):65-70
Lead is one of the most widely scattered toxic metals in the environment and used by mankind for over 9,000 years. Lead in the environment may be derived from natural or anthropogenic sources. In humans, lead can cause a wide range of biological effects depending upon the level and duration of exposure. The purpose of this study was to find out the effect of lead exposure on systolic and diastolic blood pressure, serum calcium, ionized calcium, phosphorus, parathyroid hormone and vitamin D and examine the overall effect of all these parameters on the bone mineral density of battery manufacture workers. For this study ninety battery manufacture workers were selected and divided in three groups depending upon duration of lead exposure. Group I—workers with duration of lead exposure 1–5 years, Group II—workers with duration of lead exposure 6–10 years and Group III—workers with duration of lead exposure more than 10 years. Each group consisted of thirty workers. Thirty age matched healthy control subjects were taken for comparison. Demographic, occupational and clinical data were collected by using questionnaire and interview. The venous blood samples were collected from the study groups and normal healthy control group. At the time of blood collection random urine samples were collected in amber coloured bottles. The biochemical parameters were estimated by using standard assay procedures. Statistical analysis of the data was done using independent student‘t’ test for parametric variables. Values were expressed as mean ± standard deviation (SD). P values of 0.05 or less were considered to be statistically significant. The blood lead levels and urinary lead levels of all workers were significantly increased (P < 0.001) in proportion to the duration of lead exposure as compared to controls. Systolic and diastolic blood pressure were significantly raised (P < 0.001) in all three study groups of battery manufacture workers as compared to controls. Serum Calcium, Ionized calcium, phosphorus were significantly decreased (P < 0.001) in all the three study groups. Serum vitamin D levels were lowered (P < 0.01) and serum PTH was increased (P < 0.01) in workers as compared to controls. The results of this study clearly indicate that the absorption of lead is more in these workers which adversely affects blood pressure, disturbs calcium and phosphorus metabolism which further impairs mineralization of bone resulting in decreased bone mineral density observed in these workers. Lead toxicity is still persistent in battery manufacture workers though they are using sophisticated techniques in these industries. There is a need to protect the workers from the health hazards of occupational lead exposure. 相似文献
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Homogeneous molecular catalysts and heterogeneous catalysts possess complementary strengths, and are of great importance in laboratory/commercial procedures. While various porous hosts, such as polymers, carbons, silica, metal oxides and zeolites, have been used in an attempt to heterogenize homogeneous catalysts, realizing the integration of both functions at the expense of discounting their respective advantages, it remains a significant challenge to truly combine their intrinsic strengths in a single catalyst without compromise. Here, we describe a general template-assisted approach to incorporating soluble molecular catalysts into the hollow porous capsule, which prevents their leaching due to the absence of large intergranular space. In the resultant yolk (soluble)–shell (crystalline) capsules, the soluble yolks can perform their intrinsic activity in a mimetic homogeneous environment, and the crystalline porous shells endow the former with selective permeability, substrate enrichment, size-selective and heterogeneous cascade catalysis, beyond the integration of the respective advantages of homogeneous and heterogeneous catalysts. 相似文献
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A technique for microfluidic, pH modulated DNA capture and purification using chitosan functionalized glycidyl methacrylate monoliths is presented. Highly porous polymer monoliths are formed and subsequently functionalized off-chip in a batch process before insertion into thermoplastic microchannels prior to solvent bonding, simplifying the overall fabrication process by eliminating the need for on-chip surface modifications. The monolith anchoring method allows for the use of large cross-section monoliths enabling high flowrates and high DNA capture capacity with a minimum of added design complexity. Using monolith capture elements requiring less than 1 mm2 of chip surface area, loading levels above 100 ng are demonstrated, with DNA capture and elution efficiency of 54.2% ± 14.2% achieved. 相似文献
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Separation and quantitative estimation of the isoenzymes of lactate dehydrogenase(LD) in serum were accomplished with capillary electrophoresis system. An uncoated fused silica capillary column 50 cm long, 75μm I.D. and substrate containing running buffer including L-lactic acid and NAD+ were used for the separation of serum LD isoenzymes. The resulting product of “NADH” was detected at 340 nm. Injection of 10 nL of five fold diluted serum sample were performed by pressure injection within 2 seconds. The isoenzymes were separated at 10 kV of voltage for 5 min, by turning off the voltage applied for 30 min incubation at 24°C for reaction between substrate and isoenzymes, and applying voltage of 30 min. Under these conditions, the isoenzymes of LD were detected by a NADH generated as isoenzyme of LD-5 emerged at 20 min, LD-1 peak at 23.5 min with close to baseline separation of the other isoenzymes which emerge between LD-5 to LD-1, after the emergence to LD-1 peak, followed another peak, termed “sample shock”: The results obtained by the proposed method correlated well with those by gel electrophoresis systemes (r=0.92∼0.98) for each five LD isoenzymes, respectively. Within-run precision CVs for 5 replicate analysis were 3.01 (LD-3, mean 14.6%)%∼7.82% (LD-4, mean 4.22%.), respectively. 相似文献
10.
开放性有利于企业获取更多的创新机会,但开放式创新过程中也需要考虑独占性损失的风险,因为独占性对企业创新新颖性和效率等绩效存在重要的影响。本研究旨在剖析独占性机制和开放性对创新漏斗不同阶段的创新绩效的影响。整合企业跨界搜索理论与知识保护理论,基于332家广东省制造业企业的问卷调查数据,探讨开放性与独占性机制对创新漏斗不同阶段的创新绩效影响。研究发现：正式独占性机制的使用负向影响创新漏斗创意形成阶段的创新效率,半正式独占性机制的使用有利于提升创新漏斗创意形成阶段的创新效率,而非正式独占性机制则有助于创新漏斗创意形成和新产品开发与商业化阶段的创新新颖性的提升;另外,创新新颖性通过创新漏斗整个阶段的横向合作开放性来解释,尤其是与高校科研院所的合作,与竞争对手合作开放性对新产品开发与商业化阶段的创新新颖性积极正相关,而垂直合作开放性则对新产品开发与商业化阶段的创新效率具有正相关关系。 相似文献
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本文研究了服务贸易开放影响工业绿色全要素生产率的阻滞和疏通机制。结果显示：在工业全行业层面,研发投入的技术促进传导机制存在阻滞,提升研发人员和研发经费投入的匹配度可以疏通这种阻滞的机制。分行业层面,在清洁行业和低技术密集型行业,研发投入的技术促进传导机制存在阻滞,可以通过提升研发投入匹配度来疏通阻滞的机制。但是在高技术密集型行业,通过提升研发投入匹配度带来的疏通作用不大。在高度污染行业,这种传导机制并没有受阻,相对比较通畅。 相似文献
12.
针对1995-2016年间SCI核心数据库中有关“3D打印”主题的2769条文献记录,借助CitespaceIII科学知识图谱软件,选用“聚类”、“标志性文献”、“突发文献”和“突现关键词”四大指标,综合性探索3D打印的研究热点及其演化过程,并展望未来的3D打印研究热点。研究发现：(1)3D打印的研究热点最早出现在1993年,从2005年开始迅猛增长,在2013年出现高峰；(2)热点主要集中在“医疗支架、器官与药品”、“快速成型”、“增材制造”和“化学合成反应”等领域,也出现在“超声波固化”、“激光烧结”和“金属基复合材料”等技术层面；(3)“医疗领域”的相关研究出现最早,并且至今保持异常活跃；(4)“增材制造”、“3D生物打印”、“钛合金”与“化学合成反应”等是近年来最新兴的研究热点；(5)“商业化运营”和“与大数据等新兴技术的融合”等有可能成为未来的研究热点。研究成果可以促进3D打印相关理论的发展,为科研人员确定3D打印领域的研究重点和方向提供参考,为企业掌握市场竞争主动权和政府规划3D打印产业发展提供借鉴。 相似文献
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居民是城市生活垃圾分类回收系统中的关键主体之一,其分类回收参与率的高低直接关系到整个城市垃圾分类工作的成败。为分析居民垃圾分类行为决策机制,本文以苏州市为案例,对其中心城区居民开展实地问卷调查,并运用结构方程统计分析方法,探讨影响居民生活垃圾分类行为的主要因素和作用路径。研究结果表明：居民生活垃圾分类行为主要由4个主观因素和7个外部情境因素共同作用的结果,且外部条件因素的综合影响是个体主观因素的近2倍,其中,“环境设施和服务”潜变量相关因素对居民行为的综合影响最大,公共宣传教育、回收设施便利性、分类设施便利性、参与意愿和环保意识为对居民垃圾生活处理行为影响最显著的前5个因素。为进一步加快推进中国城市生活垃圾分类工作,建议加强城市生活垃圾分类回收配套设施规划建设,广泛开展垃圾分类回收宣传教育,完善相关法律法规并建立有效的激励约束机制。 相似文献
15.
Understanding the influence of polymer grafted bilayers on the physicomechanical properties of lipid membranes is important while developing liposomal based drug delivery systems. The melting characteristics and bending moduli of polymer grafted bilayers are investigated using dissipative particle dynamics simulations as a function of the amount of grafted polymer and lipid tail length. Simulations are carried out using a modified Andersen barostat, whereby the membrane is maintained in a tensionless state. For lipids made up of four to six tail beads, the transition from the low temperature L(β) phase to the L(α) phase is lowered only above a grafting fraction of G(f)=0.12 for polymers made up of 20 beads. Below G(f)=0.12 small changes are observed only for the HT(4) bilayer. The bending modulus of the bilayers is obtained as a function of G(f) from a Fourier analysis of the height fluctuations. Using the theory developed by Marsh et al. [Biochim. Biophys. Acta 1615, 33 (2003)] for polymer grafted membranes, the contributions to the bending modulus due to changes arising from the grafted polymer and bilayer thinning are partitioned. The contributions to the changes in κ from bilayer thinning were found to lie within 11% for the lipids with four to six tail beads, increasing to 15% for the lipids containing nine tail beads. The changes in the area stretch modulus were also assessed and were found to have a small influence on the overall contribution from membrane thinning. The increase in the area per head group of the lipids was found to be consistent with the scalings predicted by self-consistent mean field results. 相似文献
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创新的公共产品特性和金融市场失灵是影响企业研发创新的两个重要因素,前者可通过税收激励来调节,而后者产生的主要原因是融资约束。本文基于2010—2017年沪深两市A股上市公司数据,从融资约束视角采用双固定效应模型、动态回归模型、负二项回归模型等方法研究了税收激励对企业研发创新的影响。结果表明：税收激励对研发投入强度具有正向促进效应,而且税基优惠的促进效应大于税率优惠,但税收激励对研发创新质量的促进效应不足。融资约束对研发投入强度影响显著为负,税收激励可通过缓解融资约束提高研发投入强度,其中税基优惠主要有利于缓解内部融资约束,税率优惠更有助于缓解外部融资约束。文章最后提出应关注每项税收激励政策有效性、提升创新质量等建议。 相似文献
18.
Suitability of Stem Latex of Jatropha Gossypifolia as a Protein Precipitant for Biochemical Analysis
O. G. Adeosun T. Oduola F. A. Fagbomedo S. O. Oyedeji B. O. Akanji A. A. Adesina 《Indian journal of clinical biochemistry : IJCB》2014,29(2):210-212
The extract of Jatropha Gossypifolia stem was obtained by cutting the stem with a sharp knife and the fluid expressed out. The suitability of the stem latex extract as a precipitant for biochemical analysis was determined. The precipitating efficacy of the extract for creatinine and protein estimation was found to be optimum at 1/4 and 1/5 dilutions respectively aqueous solution. Plasma protein was precipitated with stem extract of J. Gossypifolia at the stated dilution. The mean plasma creatinine values obtained from 0.5 % sodium tungstate as a protein precipitant were compared with the values of plasma creatinine obtained when ¼ dilution of stem extract of J. Gossypifolia was used as protein precipitant. Similarly mean cerebrospinal fluid (CSF) and urinary protein values obtained from 3 % Tricholoro-acetic acid as protein precipitant were compared with values obtained from 1/5 dilution of stem extract of J. Gossypifolia as protein precipitant. The values obtained from the stem latex extract at the stated dilutions were comparable with values obtained from the conventional protein precipitants (p < 0.05). The stem latex extract of J. Gossypifolia is suitable as a protein precipitant for creatinine, CSF and urinary protein estimations. However further work need to be done to purify the extract and determine the exact concentration at the stated dilutions as well as the active ingredient in stem latex. 相似文献
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已有研究侧重于探索供应商如何为制造企业提升研发创新,但忽视了非研发创新的内在价值。事实上,非研发创新同样是提升企业创新绩效的重要途径,鲜有研究探明供应链情境下非研发创新的结构与前因。基于社会资本理论,破解如何提升研发创新与非研发创新,并探明供应商为制造商带来更多的研发创新还是非研发创新。选取538份有效问卷,采用结构方程模型验证,实证结果表明：（1）制造商——供应商社会资本各维度均正向影响研发创新与非研发创新;（2）相对于研发创新,结构资本与认知资本更能提升制造企业非研发创新;而相对于非研发创新,关系资本更能提升制造企业研发创新;（3）社会资本各维度对非研发创新的各维度（产品或工艺改进、模仿创新、技术引进与市场创新）均产生正向影响。研究结论厘清了制造企业制造商——供应商社会资本不同维度提升研发创新/非研发创新的差异性影响,为制造企业提升研发创新/非研发创新提供理论解释与实践启示。 相似文献
20.
Most metal–organic frameworks (MOFs) hardly maintain their physical and chemical properties after exposure to alkaline aqueous solutions, thus precluding their use as potential electrode materials for electrochemical energy storage devices. Here, we present the design and synthesis of a highly alkaline-stable metal oxide@MOF composite, Co3O4 nanocube@Co-MOF (Co3O4@Co-MOF), via a controllable and facile one-pot hydrothermal method under highly alkaline conditions. The obtained composite possesses exceptional alkaline stability, retaining its original structure in 3.0 M KOH for at least 15 days. Benefitting from the exceptional alkaline stability, unique structure, and larger surface area, the Co3O4@Co-MOF composite shows a specific capacitance as high as 1020 F g−1 at 0.5 A g−1 and a high cycling stability with only 3.3% decay after 5000 cycles at 5 A g−1. The as-constructed solid-state flexible device exhibits a maximum energy density of 21.6 mWh cm−3. 相似文献