Preparation and Properties of Mo Coating on H13 Steel by Electro Spark Deposition Process

H13 steel is often damaged by wear, erosion, and thermal fatigue. It is one of the essential methods to improve the service life of H13 steel by preparing a coating on it. Due to the advantages of high melting point, good wear, and corrosion resistance of Mo, Mo coating was fabricated on H13 steel by electro spark deposition (ESD) process in this study. The influences of the depositing parameters (deposition power, discharge frequency, and specific deposition time) on the roughness of the coating, thickness, and properties were investigated in detail. The optimized depositing parameters were obtained by comparing roughness, thickness, and crack performance of the coating. The results show that the cross-section of the coating mainly consisted of strengthening zone and transition zone. Metallurgical bonding was formed between the coating and substrate. The Mo coating mainly consisted of Fe_9.7Mo_0.3, Fe-Cr, FeMo, and Fe₂Mo cemented carbide phases, and an amorphous phase. The Mo coating had better microhardness, wear, and corrosion resistance than substrate, which could significantly improve the service life of the H13 steel.     

High maneuverability guidewire with functionally graded properties using new superelastic alloys

Nitinol shape memory alloys (SMAs) are attracting considerable attention as core materials for medical guidewires because of their excellent flexibility and shape retention. However, since Nitinol guidewires possess low rigidity, the pushability and torquability of the guidewires are insufficient. On the other hand, although guidewires made of stainless steel have high pushability, plastic deformation occurs easily. We have developed a new class of superelastic guidewires with functionally graded properties from the tip to the end by using new SMA core materials such as Cu‐Al‐Mn‐based or Ni‐free Ti‐Mo‐Sn SMAs. The tip portion of the guidewire shows excellent superelasticity (SE), while the body portion possesses high rigidity. These functionally graded characteristics can be realized by microstructural control. These guidewires with functionally graded properties show excellent pushability and torquability and are considerably easier to handle than conventional guidewires with Nitinol or stainless steel cores. Moreover, a metallic catheter using a Ni‐free Ti‐based SMA with high biocompatibility is introduced.     

Antigenic and chromosomal changes in thymus and spleen of Balb/Mo mice during leukemogenesis

The Balb/Mo mouse strain carries a single copy of the germ line integrated Moloney leukemia virus (M-MuLV) and shows a high leukemia frequency. According to the clinical manifestations lymphomas can be divided into two major categories. In one type the thymus appears to be the primary site for lymphoma development. The second type is dominated by the generalized enlargement of spleen and lymph nodes. Individual lymphomas differ in the cell surface expression of Thy 1.2 MCSA (designated operationally as the M-MuLV-determined cell surface antigen) and viral p30 antigens. In addition, spleen and thymus of the same leukemic animal often differ antigenically. The karyotype of cells from enlarged organs in diploid or shows trisomy of chromosomes 15. Lymphomas developing in Balb/Mo mice are thus heterogeneous with regard to clinical manifestations, cell surface antigens and karyotype and, in this respect, do not differ from lymphomas arising after the inoculation of exogenous M-MuLV. Amplification of the M-MuLV genome in young Balb/Mo mice is not accompanied by the appearance of MCSA on thymus cells. Still, 32% of lymphomas are MCSA positive. The results suggest that MCSA is related to a virus activated in a minority of Balb/Mo mice during the late phase of leukemogenesis.     

Management of breast lesions in children and adolescents.

The records of 207 patients evaluated and treated for breast abnormalities during a 10-yr period were reviewed. Patients ranged in age from 1 wk through 16 yr. Seventy-eight per cent were female. Operative procedures were performed in 134 patients (64%). Most common diagnoses were fibroadenoma, premature thelarche, and precocious puberty in the females, and pubertal gynecomastia in the males. Age and sex separate patients into natural subgroups. In females beyond the neonatal period, premature thelarche and precocious puberty are the most likely cause of breast enlargement. Breast biopsy is only rarely indicated for a distinct mass lesion in the prepubertal breast. Mass lesions in the breast of adolescent females require excisional biopsy. In the male, pubertal gynecomastia is the most common form of breast enlargement and only occasionally requires subcutaneous mastectomy for cosmetic and psychologic reasons. Careful evaluation of all children with breast enlargement is indicated to uncover underlying causes and to avoid unnecessary operative procedures.     

Epidemiology and child psychiatry: Future prospects

Child psychiatric epidemiology is on the threshold of an important future in its capacity to investigate the psychologic health of large aggregates of children. Within the last decade this field of study has made notable contributions to the establishment of a scientific child psychiatry by emphasizing empirical and logical formulations, and by applying methods derived from such reasoning to the study of psychiatric disorder in different social and cultural contexts. This base of knowledge is certain to expand over the next few decades, a time when the relationship of child psychiatry to pediatrics and general psychiatry is very likely to evolve in new directions.Recent developments in child psychiatric epidemiology must be viewed in the context of changing pediatric priorities. Public health practices are well established to reduce the major causes of infant mortality and many types of acute infectious diseases which contribute to childhood mortality. The application of these methods is currently more likely to be limited by cultural and political barriers than by scientific knowledge. As infant and childhood mortality decline, higher rates of psychosocial and intellectual morbidity are undoubtedly developing.The purpose of this article, the last of three exploring the relationship between epidemiology and child psychiatry, is to examine research objectives that will be useful in understanding the social and emotional handicaps of populations of children in different parts of the world.^1.2 As is traditional in any epidemiological pursuit, the interest is in studying the distribution of psychiatric disorders and maladaptive behavior within and across societies in an effort to understand and ultimately control their causes. Topics to be discussed in this article relate to diagnosis and incidence of child psychiatric disorders, the definition of risk and protective factors, the importance of comparative and cohort studies, the integration of biologic and social variables in research designs, and the implications and possible consequences of epidemiological research on the practice of child psychiatry.     

Synaptic transmission between rat superior cervical ganglion neurons in dissociated cell cultures.

The principal neurons of the rat superior cervical ganglion (SCGN) when established as dissociated cells in tissue culture form synapses among themselves. In the present study we have examined this synaptic interaction when these neurons are co-cultured with several other types of tissues. Dissociated SCGN were prepared from perinatal rats and studied, after 3-4 weeks maturation, with intracellular recording techniques. Synaptic interactions between sympathetic neurons were demonstrated when these cells were: (a) grown with explants from newborn rat thoracic spinal cord, (b) when the SCGN had survived for several weeks subsequent to removal of the spinal cord explants, and (c) when the SCGN were grown in the presence of an adrenergic target (interscapular brown fat cells). Unidirectional, reciprocal, recurrent and complex chemical synaptic networks, consisting of convergence and divergence, characterized connections between SCGN. All synaptic responses were cholinergic since they were reversibly blocked by hexamethonium or mecamylamine but were not sensitive to 10(-5) M phenoxybenzamine. Removal of the spinal cord explants did not significantly alter the proportion of chemical synaptic interactions between SCGN (more than 25%) from matched cultures. Anatomical observations established that in cultures with brown fat, innervating neurites appeared on the fat cells; these neurites frequently expanded to form varicosities that resembled the adrenergic terminals normally seen on brown fat in the animal. Synaptic profiles also occurred on the neurons in these cultures and some of these were shown to be cholinergic. The proportion of neuronal interactions in the combined SCGN + fat cultures was low, however, suggesting that co-culture with target tissue might influence the frequency of interconnections developed between SCGN in culture. Other factors, such as the presence of non-neuronal cells, degree of dissociation, cellular density, culture age and the survival of certain types of SCGN in culture are discussed as variables related to the formation of synapses between SCGN. Non-rectified electrical coupling between SCGN was also observed in 17 out of 679 pairs (2.5%) of neurons. Attenuation factor for electrically coupled action potentials ranged between 1 and 43.5.