Heavy metal concentrations in soils as determined by laser-induced breakdown spectroscopy (LIBS), with special emphasis on chromium

Soil is unanimously considered as one of the most important sink of heavy metals released by human activities. Heavy metal analysis of natural and polluted soils is generally conducted by the use of atomic absorption spectroscopy (AAS) or inductively coupled plasma optical emission spectroscopy (ICP-OES) on adequately obtained soil extracts. Although in recent years the emergent technique of laser-induced breakdown spectroscopy (LIBS) has been applied widely and with increasing success for the qualitative and quantitative analyses of a number of heavy metals in soil matrices with relevant simplification of the conventional methodologies, the technique still requires further confirmation before it can be applied fully successfully in soil analyses. The main objective of this work was to demonstrate that new developments in LIBS technique are able to provide reliable qualitative and quantitative analytical evaluation of several heavy metals in soils, with special focus on the element chromium (Cr), and with reference to the concentrations measured by conventional ICP spectroscopy. The preliminary qualitative LIBS analysis of five soil samples and one sewage sludge sample has allowed the detection of a number of elements including Al, Ca, Cr, Cu, Fe, Mg, Mn, Pb, Si, Ti, V and Zn. Of these, a quantitative analysis was also possible for the elements Cr, Cu, Pb, V and Zn based on the obtained linearity of the calibration curves constructed for each heavy metal, i.e., the proportionality between the intensity of the LIBS emission peaks and the concentration of each heavy metal in the sample measured by ICP. In particular, a triplet of emission lines for Cr could be used for its quantitative measurement. The consistency of experiments made on various samples was supported by the same characteristics of the laser-induced plasma (LIP), i.e., the typical linear distribution confirming the existence of local thermodynamic equilibrium (LTE) condition, and similar excitation temperatures and comparable electron number density measured for all samples. An index of the anthropogenic contribution of Cr in polluted soils was calculated in comparison to a non-polluted reference soil. Thus, the intensity ratios of the emission lines of heavy metal can be used to detect in few minutes the polluted areas for which a more detailed sampling and analysis can be useful.     

Impasses in Psychoanalytic Therapy

Blending the genres of creative nonfiction and personal essay, the author explores the movement of longing as it emerged in the intersubjective space of one psychoanalysis.     

陡脉冲电场对荷瘤BALB/c小鼠癌细胞杀伤效应的实验研究

观测陡脉冲电场对荷瘤BALB/c小鼠癌细胞的杀伤效应。处理后的癌细胞在光镜下表现为细胞核固缩、核碎裂、核溶解;在电镜下表现为异染色质增加,边集,呈团块样改变,细胞质肿胀,脂滴数量增加,质膜破裂;核固缩,碎裂,线粒体肿胀。实验揭示了陡脉冲电场能有效地杀伤癌细胞,明显抑制了荷瘤小鼠恶性肿瘤的生长、增殖,有着良好的应用前景。     

Basic metabolism: proteins

Proteins serve a range of physiological functions in health and in disease. Their overall structure is determined predominantly by the sequence of amino acids when they are synthesized, which in turn is a derivative of the sequence of nucleotides in the corresponding segment of DNA. There is a constant turnover of body protein, the rate of which exceeds dietary protein intake and therefore suggests a degree of recycling. Some amino acids that enter the body protein pool can be synthesized (‘non-essential’ amino acids) while others can only be obtained through dietary means (‘essential’ amino acids). During critical illness and significant trauma there appears to be dysregulation such that synthesis of some non-essential amino acids is limited, while there is an increase in amino acid oxidation. Modification of dietary intake to address the potential imbalance in illness is probably insufficient in isolation to prevent muscle wasting.     

医疗设备紧急修理工艺初探

本文从传统故障检测方法入手，另辟蹊径，发掘速诊、急修工艺内涵，通过故障表象揭露本质，把难捉膜难下手的故障进行系统总结，先简单后复杂，先容易后困难。创造性地发展了医疗设备维修工艺为临床提供及时、高效、经济的服务。对医疗设备管理、维修人员有较高的参考价值。     

Causes and Prevention of Diabetic Foot Skin Breakdown

As the number of persons with diabetes increases, there is an increased incidence of foot skin breakdown and lower extremity amputations. Approximately 44%–85% of those amputations can be prevented. Prevention requires an understanding of the causes of diabetic foot skin breakdown and the measures necessary for prevention. As rehabilitation nurses, we care for patients with strokes, hip fractures, spinal cord injuries, or joint replacements, who are diabetic and are at risk for foot skin breakdown. We also care for patients with amputations who are at risk for skin breakdown of the remaining foot. This article identifies the causes of foot skin breakdown, such as neuropathy, peripheral vascular disease, trauma, and infection. Discussion includes patients who are at risk, the foot areas at risk, preventive measures, and patient and family education for the prevention of foot skin breakdown in the diabetic patient.     

Mechanical and thermal effects in striated muscle irradiated by ns-laserpulses

The therapeutic application of laser light is required to minimize defects in the non-irradiated tissue. The primary mechanism of interaction is determined by the duration of laser action. In the case of continuous wave laser light a tissue layer surrounding the irradiated volume is thermally affected. With the pulses of a Q-switched laser (duration some ns) tissue cutting will be obtained by the laser-induced breakdown. To be able to distinguish between thermal and mechanical effects by histological examination, experiments were performed with laser pulse durations of 8ns and 100μs under the same conditions with a Nd-YAG laser at 1064nm. The beam was focused through air below the tissue surface. The beam geometry in the focal region was identical for both cases. The defective region after irradiation could be divided into four zones surrounding a crater. In the μs-experiments the zones corresponded to the temperature distribution in the tissue, so the changes were all classified as thermal. In the ns-experiments, in general larger craters were found. Increasing the number of pulses to 200 the picture is similar to that produced with μs-pulses. These results show that a few ns-pulses suffice to form a crater. Additional ns-pulses lead to heat accumulation and produce thermal lesions like those of the μs-case.     

Organizational and individual factors associated with breakdown of residential placements for people with intellectual disabilities

Background People with intellectual disabilities (IDs) whose behaviour challenges services are at increased risk of placement breakdown. Most previous research has tended to focus on the role of individual characteristics in predicting breakdown. A small number of studies have suggested that service variables may impact on intervention effectiveness and hence placement breakdown. Method This study used a non‐experimental group comparison design to investigate potential differences between two groups of residential homes, one of which had experienced placement breakdown, and one of which had successfully maintained placements in the community. Results More residents in the breakdown group had inappropriate sexual behaviours but there were no other differences. Services in the breakdown group had more limited procedural guidance for staff, weaker training, supervision and team meetings and less external professional support. Conclusion Placement characteristics may be an important determinant of community placement success for people with IDs and challenging behaviour. Those selecting and funding residential placements for such people should attend to the technical competence of the placement (in terms of its use of procedural guidance, training and professional advice) and to the extent of support for staff (in terms of training, supervision and team meetings).     

Implant‐tissue interfaces following treatment of peri‐implantitis using guided tissue regeneration. A light and electron microscopic study.

This study details the structural and ultrastructural features of the interfaces between titanium implants and their surrounding tissues. The material stemmed from an experiment in dogs in which guided tissue regeneration with Gore‐Text membranes was used to treat peri‐implant, ligature‐induced tissue breakdown around submerged and nonsubmerged com-mercially pure titanium implants. Specimens from the nonsubmerged group were evaluated under light microscopy and scanning and transmission electron microscopy. A healthy gingiva and a gingival sulcus were formed around the implant necks. A regenerated junctional epithelium provided the epithelial union between implant and gingiva. The supracrestal connective tissue was characterized by a 3‐dimensional network of collagen fibers, fibroblasts and blood vessels. Near the implant surface the collagen fibers ran parallel to the titanium surface or were orientated perpendicular to the implant. The connective tissue-implant interface was characterized by a fine fibrillar material interposed between the implant surface and the connective tissue. An unidentified material was also observed between the endings of functionally orientated collagen fibrils and the metallic surface. The apical portions of the implants were anchored in compact bone. At the bone‐implant interface, either mineralized bone matrix was intimately adapted to the titanium surface without any intervening space or a 0.5 μm wide unmineralized layer was interposed. These findings indicate that a perimucosal seal was formed around the implants consisting of a junctional epithelium‐implant union coronally and supported by the connective tissue-implant junction apically. The implants were integrated in connective tissue, but only tightly adapted to bone.