Are the evidences of forensic entomology preserved in ethanol suitable for SEM studies?

In forensic practice, the use of arthropod evidences to estimate the postmortem interval is a very good approach when the elapsed time from death is long, but it requires the correct identification of the specimens. This is a crucial step, not always easy to achieve, in particular when dealing with immature specimens. In this case, scanning electronic microscopy (SEM) can be useful, but the techniques used to preserve specimens in forensic practice are usually different from those used to prepare specimens for SEM studies. To determine whether forensic evidences preserving techniques are also compatible with SEM analysis, we have compared specimens of all the immature stages of Calliphora vicina Robineau-Desvoidy, 1830 (Diptera, Calliphoridae) preserved in 70% ethanol, with others prepared with aldehydic fixative techniques that are more appropriate for SEM studies. At the same time, two drying techniques have also been compared with both fixative techniques, the critical point drying and air-drying following with hexamethyldisilizane treatment (HMDS). Our results indicate that there are not basis against recommending the use of ethanol to preserve forensic entomological evidences and that both drying methods appear to offer good results for second and third instar larvae, although HMDS behaves better with eggs and pupae.     

Electrical,thermal and infrared studies on semicarbazide hydrochloride and semicarbazide hydrobromide

Semicarbazide hydrochloride (SEM.HCl) was reported to be a prototype of another possible family of ferroelectrics [Appl. Phys. Lett. 20, 49 (1972)]. The present dielectric, resistivity, thermal and infrared absorption studies carried out on SEM.HCl and SEM.HBr do not confirm this suggestion. However these studies reveal that some observable changes do occur in the thermal amplitude of the molecular cation with the lowering of temperature.     

Scanning and transmission electron microscopy studies on a model series of spherulitic segmented polyurethanes

Scanning (SEM) and transmission (TEM) electron microscopy studies were made on a model series of four segmented polyurethanes. The morphologies of both the homopolymers and of their mixtures were made by SEM while TEM was utilized to study only ultrathin films of the homopolymers. It was found that well-structured spherulitic morphologies could be induced in these systems and their mixtures, and that control over the textures could be maintained by solution casting conditions. The domains were observable via TEM, and the general orientation of this structure within the spherulites was noted. Deformation studies of the spherulitic textures were followed by both SEM and small-angle light scattering. It was concluded that, in general, the spherulites deform in a nonaffine manner–this is particularly true for the systems possessing a porous texture.     

Microstructure,crystallography and diagenetic alteration in fossil ostrich eggshells from Upper Palaeolithic sites of Indian peninsular region

Biominerals studies are of importance as they provide an understanding of natural evolutionary processes. In this study we have investigated the fossil ostrich eggshells using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Electron Backscatter Diffraction (EBSD). SEM studies demonstrated the ultrastructure of fossil eggshells and formation of calcified cuticular layer. The presence of calcified cuticle layer in eggshell is the basis for ancient DNA studies as it contains preserved biomolecules.EBSD accentuates the crystallographic structure of the ostrich eggshells with sub-micrometer resolution. It is a non-destructive tool for evaluating the extent of diagenesis in a biomineral. EBSD analysis revealed the presence of dolomite in the eggshells. This research resulted in the complete recognition of the structure of ostrich eggshells as well as the nature and extent of diagenesis in these eggshells which is vital for genetic and paleoenvironmental studies.     

Studies on short isora fibre-reinforced polyester composites

This paper reports the use of a natural fibre, isora, as reinforcement in unsaturated polyester resin. Isora is a bast fibre separated from the bark of Helicteres isora plant by retting process. Properties like tensile strength, flexural strength etc. have been studied as a function of fibre length and fibre loading using treated and untreated fibre. The mechanical properties were found to be optimum at a fibre length of 30 mm and a fibre loading of 30% by volume. The effects of alkali treatment on the fibre properties were investigated by SEM, IR and TGA. The mechanical performance of the treated isora fibre-reinforced polyester composites has also been investigated. SEM studies were carried out to investigate the fibre surface morphology, fibre pull-out and fibre–polyester interface bonding. SEM gave evidence for the changes that had occurred on the fibre surface during chemical treatment. The properties were found to be superior for the composite reinforced with treated fibre compared to the untreated fibre.     

Synthesis and morphological change in poly(ethylene oxide)-sodium chlorate based polymer electrolyte complex with polyaniline

The composites of polyethylene oxide:polyaniline:sodium chlorate is prepared by stirring with anhydrous acetonitrile for 5-6 h to form homogeneous solutions/gels at different weight percentages. The composites are characterized by FTIR and SEM. The predominant peaks that appeared in FTIR spectra confirm the formation of PEO:PANI:NaClO₄ composites. It is found from the SEM studies that there is a significant change in the morphology of various weight percentages of NaClO₄ in PEO-PANI matrix, i.e. from ellipsoidal to square. DC conductivity behavior is seen due to hopping of polarons from one localized state to another that can be confirmed by Mott theory. It is observed from the DC conductivity and SEM studies that these composites can be promising candidates for solid state electrolytes.     

扫描电镜-能谱仪在生物质炭特性分析上的应用

利用扫描电镜—能谱仪分析不同温度产生的生物质炭的化学与结构特性。结果表明： 随温度升高,芒草碳的平均碳含量和最大碳含量均呈现增加趋势,平均碳含量和最大碳含量与最高处理温度之间为显著正相关关系(r值为0.76和0.86)。平均碳含量和最大碳含量与高温灼烧法测定的碳含量之间为显著正相关关系(r值为0.83和0.91),最大碳含量的相关性好于平均碳含量。因此,应用该方法获得芒草炭的碳含量与温度相关性好,最大碳含量可以用于生物炭组分分析;电镜扫描结果可以有效分析芒草炭的结构特性。基于该方法快速、简便、稳定以及可对生物质炭的结构和组分同时分析的优点,它是一种极具发展前途的分析方法,有助于生物质炭等其他材料的结构特性与组分研究。     

Spectroscopic studies of hydroxyapatite in PVP/PVA polymeric matrix as biomaterial

This system is focusing on characterization and spectroscopic studies of PVA and PVP blend and the blend filled with various mass fractions (2.5, 5 and 10%) of HAp because it has great potential for applications in the medical purposes. The films have been prepared by solution casting technique. The characteristic properties of the films were examined by FT-IR, X-ray, SEM, TGA and DSC techniques from room temperature to 500 °C. XRD scans reveal the semicrystalline nature of the prepared films and demonstrated that complexation between the blend and the HAp were occur. SEM and thermal studies confirmed these results. Three main weight loss regions were observed in TGA thermograms that reveal reduction in the thermal stability of the prepared samples as HAp content increases. Three main transition peaks were observed in DSC with a single T_g which indicates a good miscibility of the films. The ratio Ca:P is 1.65:1 which confirm the formation of hydroxyapatite. So, the present work can be used in various bio-applications.     

In situ scanning electron microscopy of graphene growth on polycrystalline Ni substrate

Scanning electron microscopy (SEM) is shown to be capable of imaging a monolayer of graphene, and is employed to observe in situ the graphene growth process by segregation of bulk-dissolved carbon on a polycrystalline nickel surface. Because of a wide field of view, SEM could easily track the rapid graphene growth induced by carbon segregation. Monolayer graphene extended on (111)- and (011)-oriented nickel grains, but was excluded from the (001) grains. This is due to the difference in carbon-nickel binding energy among these crystalline faces. This work proves the usefulness of in situ SEM imaging for the investigation of large area graphene growth.     

New possibilities and some artifacts of the cathodoluminescent mode in scanning electron microscopy

Lightning inside the chamber of a scanning electron microscope (SEM), caused by electrons being scattering from a sample (and parts of the chamber), is observed and analyzed. These electrons generate the luminescence in a Thornly–Everhart collector. This parasitic effect (artifact) must be considered and eliminated in all experiments with the cathodoluminescent (CL) mode of SEM. A new technique for measuring surface potential on dielectric samples is proposed. It is based on variations in the CL signal during electron irradiation of a sample in SEM.     

Principle of structural equation modeling for exploring functional interactivity within a putative network of interconnected brain areas

Functional neuroimaging first allowed researchers to describe the functional segregation of regionally activated areas during a variety of experimental tasks. More recently, functional integration studies have described how these functionally specialized areas, interact within a highly distributed neural network. When applied to the field of neurosciences, structural equation modeling (SEM) uses theoretical and/or empirical hypotheses to estimate the effects of an experimental task within a putative network. SEM represents a linear technique for multivariate analysis of neuroimaging data and has been developed to simultaneously examine ratios of multiple causality in an experimental design; the method attempts to explain a covariance structure within an anatomical constrained model. This method, when combined with the concept of effective connectivity, can provide information on the strength and direction of the functional interactions that take place between identified brain regions of a putative network.     

Photoconductive properties of some chemically deposited (Cd–Pb)s films

Films of (Cd–Pb)S have been prepared using chemical deposition in aqueous alkaline bath and their subsequent condensation on substrates. Important achievements in terms of electrical response, optical absorption and photoconductivity (PC) excitation spectra, SEM, XRD and photoluminescence (PL) studies are presented and discussed. From the photocurrent curves, the ratio I_PC (saturated photocurrent)/I_DC (dark current) was observed to be of the order of 10⁶ for the systems prepared with CdCl₂, and to be 10⁷ when doped with samarium nitrate. Values of trap depth E, lifetime and mobility are evaluated from the PC decay. Band-gaps are determined from the two spectra. Diffraction lines in XRD studies are associated to CdS and PbS, and according to SEM studies layered growth of the films takes place. PL of samarium doped (Cd–Pb)S films shows an emission peak in the green-yellow region under 365?nm excitation. The PL brightness decreases with temperature.     

掺杂半导体扫描电镜二次电子像

综述了用扫描电镜的二次电子像获得掺杂半导体衬度剖析的方法．实验发现掺杂半导体扫描电镜像对杂质浓度的灵敏度可以达到1016cm^-3，且空间分辨率高达nm量级，是最有可能发展成为下一代掺杂剖析成像的主流技术．文中还探讨了半导体掺杂衬度的可能的机理，详细介绍了两种主要机理：表面能带弯曲和样品外局域电场的出现．     

Secondary-electron SEM bioimaging of human erythrocytes in bloodstains on high-carbon steel substrate without specimen preparation

The imaging of most biological samples via conventional scanning electron microscope (SEM) in secondary-electron mode involves routinely some kind of specimen preparation. Conventional SEMs are still used when a low-vacuum or variable-pressure SEM (usually known as 'environmental', or ESEM) is not available. But that preparatory approach may be undesirable in certain cases, for instance in museum specimens, forensic evidences or clinical samples. This report details a simple, low-cost, and sample-saving bioimaging protocol without specimen preparation, by using removable plastic conducting carbon cement, and then working under ex-profeso SEM conditions, i.e., by using an SEM in secondary-electron mode just like an ESEM. The successful use to image up to high magnifications human erythrocytes in bloodstains on an extensively bloodsmeared, high-carbon steel surgical blade is reported as an example of the potential of this procedure.     

Adsorption and kinetic studies of L-leucine as an inhibitor on mild steel in acidic media

L-Leucine is evaluated as a potential inhibitor for mild steel in acidic medium by galvanostatic polarization and potentiostatic polarization techniques. The electrochemical results were supplemented by scanning electron microscopy (SEM) and infrared studies (IR).The electrochemical polarization results show that L-leucine is most effective at 10⁻¹ M concentration at room temperature (298 K). The efficiencies were found to decrease with decrease in concentration and increase in temperature. Electrochemical results also show that L-leucine acts as a mixed type of inhibitor (blocks the cathodic and anodic sites to same extent) which is evident from insignificant shift of open circuit potential.Potentiostatic polarization data shows that they are passivating type of inhibitors. The effect of this inhibitor on anodic reaction is mainly attributed to physical adsorption of the additive on the anodic metal surface and the electron pairs on oxygen atoms. This additive exists in the protonated form (a positive charge on nitrogen atom) in the present acid medium. Therefore, on the cathodic sites, the interaction between additive and metal surface is thought to be electrostatic in nature.The results of SEM and IR data supplement the results obtained by electrochemical techniques.     

多孔硅发光稳定性的改进

采用在热ＨＮＯ₃中对多孔度较低的多孔硅样品进行氧化的方法，我们获得了稳定性和均匀性都较好的多孔硅样品。这是一种不同于快速热氧化且更方便易行的方法。另外还用ＳＥＭ和ＦＴＩＲ对其特性进行了研究。 关键词：     

SEM法观察原子吸收石墨炉管表面形貌以及分析性能的研究

本文利用扫描电镜观察了自制以及商品化原子吸收石墨管表面在使用期间的形貌变化,并对不同石墨管材料对分析性能的影响进行了讨论,从扫描电镜图片上观察到了一些有意义的现象。     

Photoluminescence, optical absorption and XRD studies on X-ray irradiated terbium doped KBr crystals

This paper reports the optical absorption, photoluminescence (PL), XRD, SEM studies made on KBr:Tb³⁺ crystals. The integrated light intensity is enhanced by about two orders of magnitude as compared to the undoped samples in spite of some OH^- present in the samples. PL of these crystals exhibits characteristic Tb³⁺ emissions due to transitions from the ⁵D₃ to ⁵D₄ levels to various levels of the ⁷F septet on F-bleaching X-ray irradiated crystals Z₃ centers are observed. The bands observed in the emission spectra of Tb³⁺ doped KBr are found to be shifted to higher wavelength. The stokes-shift of KBr:Tb³⁺ is determined and it is found to have a large value. The XRD studies have been made to determine the crystalline structure of KBr and KBr:Tb³⁺ and also the Miller indices. The SEM studies made reveal the presence of microcrystalline structure.     

Raman-in-SEM,a multimodal and multiscale analytical tool: Performance for materials and expertise

The availability of Raman spectroscopy in a powerful analytical scanning electron microscope (SEM) allows morphological, elemental, chemical, physical and electronic analysis without moving the sample between instruments. This paper documents the metrological performance of the SEMSCA commercial Raman interface operated in a low vacuum SEM. It provides multiscale and multimodal analyses as Raman/EDS, Raman/cathodoluminescence or Raman/STEM (STEM: scanning transmission electron microscopy) as well as Raman spectroscopy on nanomaterials. Since Raman spectroscopy in a SEM can be influenced by several SEM-related phenomena, this paper firstly presents a comparison of this new tool with a conventional micro-Raman spectrometer. Then, some possible artefacts are documented, which are due to the impact of electron beam-induced contamination or cathodoluminescence contribution to the Raman spectra, especially with geological samples. These effects are easily overcome by changing or adapting the Raman spectrometer and the SEM settings and methodology. The deletion of the adverse effect of cathodoluminescence is solved by using a SEM beam shutter during Raman acquisition. In contrast, this interface provides the ability to record the cathodoluminescence (CL) spectrum of a phase. In a second part, this study highlights the interest and efficiency of the coupling in characterizing micrometric phases at the same point. This multimodal approach is illustrated with various issues encountered in geosciences.     

Focused ion beam preparation of samples for X‐ray nanotomography

The preparation of hard material samples with the necessary size and shape is critical to successful material analysis. X‐ray nanotomography requires that samples are sufficiently thin for X‐rays to pass through the sample during rotation for tomography. One method for producing samples that fit the criteria for X‐ray nanotomography is focused ion beam/scanning electron microscopy (FIB/SEM) which uses a focused beam of ions to selectively mill around a region of interest and then utilizes a micromanipulator to remove the milled‐out sample from the bulk material and mount it on a sample holder. In this article the process for preparing X‐ray nanotomography samples in multiple shapes and sizes is discussed. Additionally, solid‐oxide fuel cell anode samples prepared through the FIB/SEM technique underwent volume‐independence studies for multiple properties such as volume fraction, average particle size, tortuosity and contiguity to observe the characteristics of FIB/SEM samples in X‐ray nanotomography.