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1.
The experimental investigation of the laws governing the excitation of x-rays by electron impact appears to be near completion. However, the existence of the proton, with its mass of 1,846 times that of the electron, provides the possibility of introducing anew variable—the mass—into collision experiments. Previous investigations have led to inconclusive results except that it is known that when fast α-particles fall on an element, its characteristic x-ray spectrum is excited.In the writer's experiments, a mass spectrograph is used to bring either protons or electrons, of same energy in the range from 15 kv. to 25 kv., onto a copper target. The arrangement eliminates several known sources of error. X-radiation produced passed into an argon filled Geiger counter.The procedure was to compare two currents: (1) the current composing an electron beam just intense enough to produce detectable x-rays; and (2) that composing the strongest proton beam which certainly produced less radiation.The ratio of these currents is a minimum value for p, the ratio of the efficiencies for excitation of electrons and protons respectively.The results were that (1) no radiation from proton impacts was observed, (2) the minimum value of p from three sets of experiments was 740; 237,000; and 6,400.In view of the directness of the experiment, the order of magnitude of the highest figure is presented as the result, i.e. ? = 105. This may be compared with (M/m = 1,846, W/m)32 = 79,310, (M/m)2 = 3,408,000.Wave mechanical considerations of impact processes indicate that radiation should be produced by proton impacts of energy greater than the critical energy (for copper, 8.86 kv.) but intensity formulas have not been derived.If they can be derived the present results offer the possibility of checking the wave mechanics of impact processes.  相似文献   

2.
A short review is included of previous work on the blackening of photographic plates by positive rays and rays of an analogous nature.The blackening of Eastman x-ray plates, by positive ions, has been measured as a function of the energy of the ions of Li, Na, K, Rb, and Cs. The energy of the ions required to produce a photographic density of D = 0.3 with a one minute exposure at a current density of 1.32 × 10?8 amperes per cm.2 ranged from 1420 electron-volts in the case of cæsium to 860 electron-volts in the case of Li7. Approximately 105 ions are required at these energies to render developable one silver-halide grain. For a threshold density, D = 0.04, under the same conditions the energy ranged from approximately 920 to 460 electron-volts for Cs and Li7 respectively.Sensitivity comparisons were made between x-ray plates and process and schumannized process plates. Potassium ions with an energy as low as 137 electron-volts were recorded on Schumann plates, and it is possible that positive ions of one-third this energy can be recorded.  相似文献   

3.
The structural organization of metazoan cells and their shape are established through the coordinated interaction of a composite network consisting of three individual filament systems, collectively termed the cytoskeleton. Specifically, microtubules and actin filaments, which assemble from monomeric globular proteins, provide polar structures that serve motor proteins as tracks. In contrast, intermediate filaments (IFs) assemble from highly charged, extended coiled coils in a hierarchical assembly mechanism of lateral and longitudinal interaction steps into non-polar structures. IF proteins are expressed in a distinctly tissue-specific way and thereby serve to generate the precise plasticity of the respective cells and tissues. Accordingly, in the cell, numerous parameters such as pH and salt concentration are adjusted such that the generation of functional networks is ensured. Here, we transfer the problem for the mesenchymal IF protein vimentin to an in vitro setting and combine small angle x-ray scattering with microfluidics and finite element method simulations. Our approach is adapted to resolve the early assembly steps, which take place in the sub-second to second range. In particular, we reveal the influence of ion species and concentrations on the assembly. By tuning the flow rates and thus concentration profiles, we find a minimal critical salt concentration for the initiation of the assembly. Furthermore, our analysis of the surface sensitive Porod regime in the x-ray data reveals that the formation of first assembly intermediates, so-called unit length filaments, is not a one-step reaction but consists of distinct consecutive lateral association steps followed by radial compaction as well as smoothening of the surface of the full-width filament.  相似文献   

4.
Building on recent breakthroughs in the field of microfluidic-based capture of rare cancer cells circulating in the blood, the present article reports on the use of Herceptin functionalized PDMS devices designed to efficiently capture from blood cancer cells, overexpressing the tyrosine kinase human epidermal growth factor receptor (HER2). The identification of patients overexpressing HER2 is critical as it typically associates with an aggressive disease course in breast cancer and poor prognosis. Importantly, HER2 positive patients have been found to significantly benefit from Herceptin (Trastuzumab), a humanized monoclonal antibody (MAb) against HER2. Disposable PDMS devices prepared using standard soft lithography were functionalized by the plasma polymerization of an epoxy-containing monomer. The epoxy-rich thin film (AGEpp) thus created could be conjugated with Herceptin either directly or through a polyethylene glycol interlayer. The properties and reactivity toward the monoclonal antibody conjugation of these coatings were determined using x-ray photoelectron spectroscopy; direct conjugation provided a good compromise in reactivity and resistance to biologically nonspecific fouling and was selected. Using the breast cancer cell line SK-BR-3 as a model for cells overexpressing HER2, the immunocapture efficacy of the Herceptin functionalized PDMS was demonstrated in model studies. Validation studies confirmed the ability of the device to efficiently capture (～80% capture yield) HER2 positive cells from full blood.  相似文献   

5.
Jena RK  Yue CY 《Biomicrofluidics》2012,6(1):12822-1282212
This report studies the surface modification of cyclic olefin copolymer (COC) by 2-methacryloyloxyethyl phosphorylcholine (MPC) monomer using photografting technique for the purpose of biointerface applications, which demonstrate resistance to both protein adsorption and cell adhesion in COC-based microfluidic devices. This is essential because the hydrophobic nature of COC can lead to adsorption of specific compounds from biological fluids in the microchannel, which can affect the results during fluidic analysis and cause clogging inside the microchannel. A correlation was found between the irradiation time and hydrophobicity of the modified substrate. Static water contact angle results show that the hydrophilicity property of the MPC-grafted substrate improves with increasing irradiation time. The contact angle of the modified surface decreased to 20 ± 5° from 88 ± 3° for the untreated substrate. The surface characterization of the modified surface was evaluated using x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR spectroscopy). Attenuated total reflection-FTIR and XPS results show the presence of the phosphate group (P-O) on modified COC substrates, indicating that the hydrophilic MPC monomer has successfully grafted on COC. Finally, it was demonstrated that cell adhesion and protein adsorption on the MPC modified COC specimen has reduced significantly.  相似文献   

6.
The authors report a feasible and simple microfluidic approach for synthesizing anisotropic gel particles based on template method. By filling arrays of microwells with alginate hydrogel and synthesizing gold nanoparticles (AuNPs) on the gel surface, anisotropic alginate gel particles with single side gold nanoparticles layers were produced in microwells on the polydimethylsiloxan template. AuNPs and the anisotropic feature were characterized using scanning electron microscopy and x-ray photoelectron spectrum analyses. The anisotropic particles made of biocompatible gels could be released from the template and collected with uniform sizes, which might have a powerful potential in biological detection and sensing.  相似文献   

7.
One of the most conspicuous nonmedical uses of the x-ray was the shoe-fitting fluoroscope. It allowed visualization of the bones and soft tissues of the foot inside a shoe, purportedly increasing the accuracy of shoe fitting and thereby enhancing sales. From the mid 1920s to the 1950s, shoe-fitting fluoroscopes were a prominent feature of shoe stores in North America and Europe. Despite the widespread distribution and popularity of these machines, few have studied their history. In this essay we trace the origin, technology, applications, and significance of the shoe-fitting fluoroscope in Britain, Canada, and the United States. Our sources include medical and industrial literature, oral and written testimony of shoe retailers, newspapers, magazines, and government reports on the uses and dangers of these machines. The public response to shoe-fitting fluoroscopes changed from initial enthusiasm and trust to suspicion and fear, in conjunction with shifting cultural attitudes to radiation technologies.  相似文献   

8.
Found in all eukaryotic cells, linker histones H1 are known to bind to and rearrange nucleosomal linker DNA. In vitro, the fundamental nature of H1∕DNA interactions has attracted wide interest among research communities-from biologists to physicists. Hence, H1∕DNA binding processes and structural and dynamical information about these self-assemblies are of broad importance. Targeting a quantitative understanding of H1 induced DNA compaction mechanisms, our strategy is based on using small-angle x-ray microdiffraction in combination with microfluidics. The usage of microfluidic hydrodynamic focusing devices facilitates a microscale control of these self-assembly processes, which cannot be achieved using conventional bulk setups. In addition, the method enables time-resolved access to structure formation in situ, in particular, to transient intermediate states. The observed time dependent structure evolution shows that the H1∕DNA interaction can be described as a two-step process: an initial unspecific binding of H1 to DNA is followed by a rearrangement of molecules within the formed assemblies. The second step is most likely induced by interactions between the DNA and the H1's charged side chains. This leads to an increase in lattice spacing within the DNA∕protein assembly and induces a decrease in the correlation length of the mesophases, probably due to a local bending of the DNA.  相似文献   

9.
A 50 year old male was admitted in our hospital with anemia and impaired renal function. He was subsequently found to have extremely elevated serum phosphate level (24 mg/dL, reference interval: 2.5–4.5 mg/dL) with normal serum calcium when assayed on a Beckman Coulter AU 480® analyser. Clinico-biochemical discrepancy led to the suspicion of spurious hyperphosphatemia. Serum total protein was grossly elevated with gross reversal of albumin to globulin ratio. Serum electrophoresis revealed a large M band and was confirmed as Ig G-Kappa type on immunofixation. Subsequently a bone marrow aspiration biopsy confirmed the diagnosis of multiple myeloma. The patient serum was then reassayed for phosphate on a Vitros® 250 Dry Chemistry platform and the result was within normal reference interval. Paraproteinemias are a common cause of analytical interference in clinical biochemistry laboratories and as multilayered film technology platforms like Vitros® assay most routine analytes on a protein free filtrate they are unaffected by paraprotein interference. Clinically discordant patient results should always be interpreted keeping such interferences in mind.  相似文献   

10.
Cryptosporidiosis has been reported to be associated with HIV/acquired immune deficiency syndrome, which greatly reduces the quality of life and shortens the life expectancy of HIV-infected patients. In order to properly treat the infected patients, accurate and automatic diagnostic tools need to be developed. In this study, a novel microfluidic immunochip system was presented for the surveillance and the rapid detection of Cryptosporidium infection in 190 HIV-infected patients from Guangxi, China, using the P23 antigen of Cryptosporidium. The procedure of detection can be completed within 10 min with 2 μl sample consumption. The system also was evaluated using the standard ELISA method. Among 190 HIV-infected individuals, the rate of P23 positivity was 13.7%. Seropositivity in HIV-infected individuals was higher in female patients. The seropositivity to P23 was higher in HIV-infected individuals with high viral load, although the difference was statistically insignificant. Significantly higher Cryptosporidium seropositivity was observed in HIV-infected individuals with a CD4+ T-cell count of <200 cells/μl than in those with ≥200 cells/μl. Our results also demonstrate that a lower CD4+ T-cell count may reflect an increased accumulated risk for cryptosporidiosis. The detection system was further validated using the standard ELISA method and good correlation between the two methods was found (r = 0.80). Under the same sensitivity, this new microfluidic chip device had a specificity of 98.2%. This developed system may provide a powerful platform for the fast screening of Cryptospordium infection in HIV-infected patients.  相似文献   

11.
Infants with respiratory distress syndrome (RDS) may suffer from severe hypoxia, asphyxia. In this study, we aimed to evaluate serum ischemia-modified albumin (IMA) level as a diagnostic marker for hypoxia in preterm infants with RDS. Thirty-seven premature newborns with RDS were allocated as the study group and 42 healthy preterm neonates were selected as the control group. IMA was measured as absorbance unit (ABSU) in human serum with colorimetric assay method which is based on reduction in albumin cobalt binding. IMA levels were significantly higher in neonates with RDS as compared to the control group (P < 0.001). Cut-off value of IMA (ABSU) was 0.72, the sensitivity level was 91.9 %, the specificity was 78.6 %, positive predictive value was 79.1 % and negative predictive value was 91.7 % at RDS. Area under curve values was 0.93 (P < 0.001; 95 % CI, 0.88–0.98) in the receiver operating characteristic curve. We concluded that elevated blood IMA levels might be accepted as a useful marker for hypoxia in newborn with RDS.  相似文献   

12.
Simple and sensitive Liquid Chromatography-Tandem Mass Spectrometry (LCMS/MS) method was developed and validated, then was implicated on hypertensive human subjects to study drug interaction of atorvastatin (ATVS) and Olmesartan (OLM) on status of Angiotensin-II (ANG-II). The ANG-II in plasma was extracted with 5 mL methanol containing 5 % formic acid through C18 (cartridges) liquid–liquid extraction, dried and reconstituted with 1 mL of 16 % acetonitrile in 0.1 % formic acid in water. The chromatographic separation of ANG-II with a Agilent technology 6410 Triple quadrupole was carried multiple reaction monitoring scan mode with a Agilent 1290 Infinity LC system for UHPLC. The sample were separated on a (Thermo Scientific) Hy-Purity advance (50 × 4.6 mm, 5 μm) using Mobile Phase A: 16 % acetonitrile in 0.1 % formic acid in water and Mobile Phase B: 0.1 % formic acid in methanol at a flow rate of 0.3 mL/min, performed at ambient temperature. The mobile phase gradient of 16 % acetonitrile in water was linearly increased to 38 % acetonitrile over 10 min and subsequently the mobile-phase was increased to 100 % acetonitrile over 15 min. The developed method was validated for specificity, accuracy, precision, stability, linearity, sensitivity and recovery. The method was linear between peak area ratio of standard and internal standard over the range of 50–800 ng/mL. The method was successfully applied for the drug interaction study revealed levels of ANG-II were significantly higher in ATVS + OLM treatment condition as compared to individual treatment of OLM. This reflects the reason of low effectiveness of ATVS + OLM in combination instead of synergistic activity.

Electronic supplementary material

The online version of this article (doi:10.1007/s12291-014-0457-x) contains supplementary material, which is available to authorized users.  相似文献   

13.
Method validation is pursued as the first step in establishing Lean-Total Quality Management in a new clinical laboratory, in order to eliminate error in test results. Validation of all the new tests were done (with particular reference to alkaline phosphatase) by verifying reference intervals, analytical accuracy and precision, inter-assay and intra-assay variations, analytical sensitivity, limit of detection, linearity and reportable range, i.e. (i) Analytical measurement range (AMR) and (ii) Clinically reportable range (CRR). Our obtained reference range was within that of the manufacturer’s and showed high degree of analytical accuracy between two laboratories (r 2 = 0.99). Precision was comparable with the manufacturer’s claim with inter-assay variation CV 1.04% and intra-assay variation CV 1.54%. Lowest limit of detection was 1.0324 ± 0.007 with CV 0.34%. AMR was also verified with CV 1.26 and 0.69%, for level 1 and level 2 control sera, respectively. The assay was linear with different dilutions. Lean concept was also verified with high recovery percentage. Validation ensures that accurate and precise results are reported in a clinically relevant turn around time.  相似文献   

14.
中国西北地区太阳总辐射的气候特征   总被引：4，自引：0，他引：4  
利用中国西北地区28个测站1961年-2003年1月-12月太阳总辐射资料,采用趋势分析、Mann-Kendall分析、相关分析、对比分析等方法,分析了43年来西北地区太阳总辐射的时空分布特征及其变化规律。结果表明:①西北地区太阳总辐射在(4300～7000)MJ(/m2·a)之间,从东南和西北向中部增加,高值区在青海高原。冬季总辐射最少,夏季最多,春季多于秋季;区域内总辐射表现出"愈多愈稳"的分布特征;②西北地区年总辐射以92.07MJ(/m2·10a)的速率递减,1973年是突变点,北疆和西北地区东部的减少率最大,减少中心在吐鲁番和西宁;总辐射年、季变化相似,20世纪60年代-70年代偏多,80年代达到最小值,90年代以后有所增加但仍以偏少为主,这与全球的变化趋势一致;③青海高原的太阳总辐射呈双峰型分布,其余大多数地方为单峰型;④通过分析发现云量、相对湿度、降水等影响总辐射的地理分布,间接证明大气气溶胶含量的增加可能是总辐射下降的原因。  相似文献   

15.
Mucopolysaccharidoses, a group of inherited disorders are associated with defects in glycosaminoglycan metabolism. Thus, assessment of urinary glycosaminoglycan is used as a screening test for mucopolysaccharidoses. The detection methods range from qualitative spot tests to quantification using metachromatic dyes. In our laboratory we optimized a spectrophotometric quantitative method using a metachromatic dye, dimethylmethylene blue. Heparan sulfate was used for quantification. The glycosaminoglycan–dye complex showed a marked shift in color with increase in concentration. The color complex was quantified at 520 nm. The method was linear from 10–89 mg/L. An age matched normal range was obtained in 177 healthy individuals, grouped in 8 different age groups from neonates to adults. Urinary glycosaminoglycan concentration varied distinctly amongst the study population wherein the lowest range in healthy neonates was more than 3 times the upper limit of healthy adults. Urine samples from 10 patients with mucopolysaccharidoses were also included in the study for clinical validation. The method qualified both analytical and clinical validation and was found to be simple, robust and ideal to be offered as a screening test for mucopplysaccharidoses in a routine clinical chemistry laboratory.  相似文献   

16.
IntroductionThe COVID-19 pandemic has posed several challenges to clinical laboratories across the globe. Amidst the outbreak, errors occurring in the preanalytical phase of sample collection, transport and processing, can further lead to undesirable clinical consequences. Thus, this study was designed with the following objectives: (i) to determine and compare the blood specimen rejection rate of a clinical laboratory and (ii) to characterise and compare the types of preanalytical errors between the pre-pandemic and the pandemic phases.Materials and methodsThis retrospective study was carried out in a trauma-care hospital, presently converted to COVID-19 care centre. Data was collected from (i) pre-pandemic phase: 1st October 2019 to 23rd March 2020 and (ii) pandemic phase: 24th March to 31st October 2020. Blood specimen rejection rate was calculated as the proportion of blood collection tubes with preanalytical errors out of the total number received, expressed as percentage.ResultsTotal of 107,716 blood specimens were screened of which 43,396 (40.3%) were received during the pandemic. The blood specimen rejection rate during the pandemic was significantly higher than the pre-pandemic phase (3.0% versus 1.1%; P < 0.001). Clotted samples were the commonest source of preanalytical errors in both phases. There was a significant increase in the improperly labelled samples (P < 0.001) and samples with insufficient volume (P < 0.001), whereas, a significant decline in samples with inadequate sample-anticoagulant ratio and haemolysed samples (P < 0.001).ConclusionIn the ongoing pandemic, preanalytical errors and resultant blood specimen rejection rate in the clinical laboratory have significantly increased due to changed logistics. The study highlights the need for corrective steps at various levels to reduce preanalytical errors in order to optimise patient care and resource utilisation.  相似文献   

17.
A novel microfluidic device which consists of two stages for particle focusing and separation using a viscoelastic fluid has been developed. A circular capillary tube was used for three-dimensional particle pre-alignment before the separation process, which was inserted in a polydimethylsiloxane microchannel. Particles with diameters of 5 and 10 μm were focused at the centerline in the capillary tube, and the location of particles was initialized at the first bifurcation. Then, 5 and 10 μm particles were successfully separated in the expansion region based on size-dependent lateral migration, with ∼99% separation efficiency. The proposed device was further applied to separation of MCF-7 cells from leukocytes. Based on the cell size distribution, an approximate size cutoff for separation was determined to be 16 μm. At 200 μl/min, 94% of MCF-7 cells were separated with the purity of ∼97%. According to the trypan blue exclusion assay, high viability (∼90%) could be achieved for the separated MCF-7 cells. The use of a commercially available capillary tube enables the device to be highly versatile in dealing with particles in a wide size range by using capillary tubes with different inner diameters.  相似文献   

18.
Elevated plasma Homocysteine level is an independent risk factor for age related (senile) cataract. Certain nutritional deficiencies, in particular Folate, Vitamin B12, Vitamin B6 relate inversely with Homocysteine level. This study was undertaken to evaluate the plasma level of Vitamin B12, Folate, and Homocysteine of cataract patients and to study the interplay between them. Serum Homocysteine level is significantly increased in cataract patients when compared with control (p< 0.001). There was a significant decrease in the level of Folate as compared with control (p<0.001). There was a negative correlation between Homocysteine vs. Vitamin B12 (p<0.01) and Folate (p<0.01) in the Cataract patients. Our findings suggest that increased plasma Homocysteine level is associated with decreased plasma levels of Folate and VitaminB12 in Cataract patients, which might have a possible role in the root cause of cataract pathogenesis.  相似文献   

19.
Synthetic lethality was proposed nearly a century ago by geneticists and recently applied to develop precision anti-cancer therapies. To exploit the synthetic lethality concept in the design of chemical anti-cancer agents, we developed a bio-orthogonally catalyzed lethality (BCL) strategy to generate targeting anti-tumor metallodrugs both in vitro and in vivo. Metallodrug Ru-rhein was generated from two non-toxic species Ru-N3 and rhein-alkyne via exclusive endogenous copper-catalyzed azide alkyne cycloaddition (CuAAC) reaction without the need of an external copper catalyst. The non-toxic species Ru-arene complex Ru-N3 and rhein-alkyne were designed to perform this strategy, and the mitochondrial targeting product Ru-rhein was generated in high yield (>83%) and showed high anti-tumor efficacy in vitro. This BCL strategy achieved a remarkable tumor suppression effect on the tumor-bearing mice models. It is interesting that the combination of metal-arene complexes with rhein via CuAAC reaction could transform two non-toxic species into a targeting anti-cancer metallodrug both in vitro and in vivo, while the product Ru-rhein was non-toxic towards normal cells. This is the first example that exclusive endogenous copper was used to generate metal-based anti-cancer drugs for cancer treatment. The anti-cancer mechanism of Ru-rhein was studied and autophagy was induced by increased reactive oxygen species and mitochondrial damage. The generality of this BCL strategy was also studied and it could be extended to other metal complexes such as Os-arene and Ir-arene complexes. Compared with the traditional methods for cancer treatment, this work presented a new approach to generating targeting metallodrugs in vivo via the BCL strategy from non-toxic species in metal-based chemotherapy.  相似文献   

20.
Prickles act against herbivores, pathogens or mechanical injury, while also preventing water loss. However, whether prickles have new function and the molecular genetics of prickle patterning remain poorly explored. Here, we generated a high-quality reference genome assembly for ‘Basye''s Thornless’ (BT), a prickle-free cultivar of Rosa wichuraiana, to identify genetic elements related to stem prickle development. The BT genome harbors a high level of sequence diversity in itself and with cultivar ‘Old Blush’ (R. chinensis), a founder genotype in rose domestication. Inheritance of stem prickle density was determined and two QTL were identified. Differentially expressed genes in QTL were involved in water-related functions, suggesting that prickle density may hitchhike with adaptations to moist environments. While the prickle-related gene-regulatory-network (GRN) was highly conserved, the expression variation of key candidate genes was associated with prickle density. Our study provides fundamental resources and insights for genome evolution in the Rosaceae. Ongoing efforts on identification of the molecular bases for key rose traits may lead to improvements for horticultural markets.  相似文献   

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