Effect of electron magnetic trapping in a plasma immersion ion implantation system

In this work we describe a two-dimensional computer simulation of magnetic field enhanced plasma immersion implantation system. Negative bias voltage of 10.0 kV is applied to a cylindrical target located on the axis of a grounded vacuum chamber filled with uniform nitrogen plasma. A pair of external coils creates a static magnetic field with main vector component along the axial direction. Thus, a system of crossed ExB field is generated inside the vessel forcing plasma electrons to rotate in azimuthal direction. In addition, the axial variation of the magnetic field intensity produces magnetic mirror effect that enables axial particle confinement. It is found that high-density plasma regions are formed around the target due to intense background gas ionization by the trapped electrons. Effect of the magnetic field on the sheath dynamics and the implantation current density of the PIII system is investigated. By changing the magnetic field axial profile (varying coils separation) an enhancement of about 30% of the retained dose can be achieved. The results of the simulation show that the magnetic mirror configuration brings additional benefits to the PIII process, permitting more precise control of the implanted dose.

Effects of the high temperature plasma immersion ion implantation (PIII) of nitrogen in AISI H13 steel

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Investigation of Plasma Immersion Ion Implantation Process in Magnetic Mirror Geometry

Plasma immersion ion implantation (PIII) with low external magnetic field has been investigated both numerically and experimentally. The static magnetic field considered is essentially nonuniform and is generated by two magnetic coils installed outside the vacuum chamber. Experiments have been conducted to investigate the effect of two of the most important PIII parameters: target voltage and gas pressure. In that context, it was found that the current density increased when the external parameters were varied. Later, the PIII process was analyzed numerically using the 2.5-D computer code KARAT. The numerical results show that the system of crossed E x B fields enhances the PIII process. The simulation showed an increase of the plasma density around the target under the operating and design conditions considered. Consequently, an increase of the ion current density on the target was observed. All these results are explained through the mechanism of gas ionization by collisions with electrons drifting in crossed E x B fields.

Corrosion resistance enhancement of SAE 1020 steel after Chromium implantation by nitrogen ion recoil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A Study of the Effect of Nitrogen and Air Plasma Immersion Ion Implantation Treatments on the Properties of Carbon Fiber

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Administration of beta(2)-adrenergic agonists during the peri-implantation period does not improve implantation or pregnancy rates in intracytoplasmic sperm injection (ICSI) cycles

Purpose: the objective of the present investigation was to determine implantation and pregnancy rates in patients undergoing ICSI and treated with beta(2)-adrenergic agonists, considering the uterine-relaxing action of these agents.Methods: A total of 225 women undergoing ICSI at the Center for Human Reproduction, Sinha Junqueira Maternity Foundation, entered the study. Patient participation in each group was random, by drawing lots, using a randomization table previously elaborated for the study (2:2:1). The group I (90 women) received 10 mg of terbutaline daily for 15 days starting on the day of oocyte retrieval; group II (90 women) received 20 mg of ritodrine daily during the same period of time as group I; group III (45 patients) received no treatment and was used as control. The evaluation was interrupted in 3 patients of group I and in 30 patients of group II because of a high incidence of side effects.Results: Pregnancy, implantation, and miscarriage rates were not significantly different (p>0.05) between the three groups: 29.88%, 13.25%, and 26.9% for group I; 33.33%, 17.5%, and 10.0% for group II; 28.88%, 15.07%, and 15.38% for group III, respectively.Conclusions: the results of this study do not support the routine use of beta(2)-adrenergic agonists during the peri-implantation period in assisted reproductive technology cycles.

Pregnancy outcomes in women with repeated implantation failures after intracytoplasmic morphologically selected sperm injection (IMSI)

Background: The purpose of this study was to compare laboratory and clinical outcomes of intracytoplasmic morphologically selected sperm injection (IMSI) and conventional intracytoplasmic sperm injection (ICSI) in couples with repeated implantation failures.Methods: A total of 200 couples with at least two prior unsuccessful ICSI cycles were enrolled: 100 couples were submitted to IMSI and 100 were submitted to routine ICSI. For IMSI, spermatozoa were selected at 8400x magnification using an inverted microscope equipped with Nomarski (differential interference contrast) optics. For conventional ICSI, spermatozoa were selected at 400x magnification. Clinical outcomes were evaluated between the two groups.Results: Study patients were comparable in age, number of treatment failures, aetiology of infertility, percentage of normal form assessed by MSOME (motile sperm organelle morphology examination), semen parameters, total number of oocytes collected, number of mature oocytes collected, total number of embryos transferred and number of high-quality embryos transferred. No statistically significant differences between the two groups were observed with regard to rates of fertilisation, implantation and pregnancy/cycle. Although not statistically significant, rates of miscarriage (IMSI:15.3% vs ICSI:31.7%), ongoing pregnancy (IMSI:22% vs ICSI:13%) and live births (IMSI:21% vs ICSI:12%) showed a trend towards better outcomes in the IMSI group. In addition, analysis of subpopulations with or without male factor showed similar results.Conclusions: Our results suggest that IMSI does not provide a significant improvement in clinical outcome compared to ICSI, at least in couples with repeated implantation failures after conventional ICSI. However, it should be noted that there were clear trends for lower miscarriage rates (approximate to 50% reduced) and higher rates of ongoing pregnancy and live births (both nearly doubled) within the IMSI group. Further confirmation as well as randomized large-scale trials are needed to confirm the beneficial effects of IMSI in couples with poor reproductive prognoses.

Clinical and histological evaluation of subepithelial connective tissue after collagen sponge implantation in the human palate

Rocha AL, Shirasu BK, Hayacibara RM, Magro-Filho O, Zanoni JN, Araujo MG. Clinical and histological evaluation of subepithelial connective tissue after collagen sponge implantation in the human palate. J Periodont Res 2012; 47: 758765. (c) 2012 John Wiley & Sons A/S Background and Objective: Successful root-coverage treatment depends on the thickness of the donor tissue. This study aimed to evaluate the thickness of donor tissue after augmentation of the connective tissue in the palatal area by implantation of lyophilized collagen sponge (Hemospon (R)). Material and Methods: Ten patients with an indication for root coverage, whose palate was deficient in adequate connective tissue, were recruited. The procedure was carried out in two stages. In the first stage, the palatal thickness in the donor site was measured at three standardized points (points 1, 2 and 3), from the distal of the canine to the distal of the first molar, and the lyophilized collagen sponge was inserted. In the second stage, the palatal thickness over the implant was measured (at points 1, 2 and 3), two biopsies of the palatal mucosa were collected one over the implant (experimental sample) and the other on the contralateral side (control sample) and then root-coverage treatment was performed. Analyses consisted of clinical assessment of the palatal measurements before and after sponge implantation, and histological assessment of the experimental and control biopsy samples. Data were analyzed using the Wilcoxon test. Results: Both analyses showed a significant increase in mean thickness, of 1.08 mm of neoformed tissue in the clinical analysis (the tissue at point 2 was the thickest of the three points) and of 0.53 mm in the histological analysis. Conclusion: The insertion of lyophilized collagen sponge induced a significant increase in the thickness of palatal connective tissue.

Evaluation of subcutaneous and alveolar implantation surgical sites in the study of the biological properties of root-end filling endodontic materials

Objective: The aim of this study was to compare two methodologies used in the evaluation of tissue response to root-end filling materials in rats. Material and Methods: Forty rats were divided into 4 groups: in Groups I and II (control groups), empty polyethylene tubes were implanted in the extraction site and in the subcutaneous tissue, respectively; in Groups III and IV, polyethylene tubes filled with ProRoot MTA were implanted in the extraction site and in the subcutaneous tissue, respectively. The animals were killed 7 and 30 days after tube implantation, and the hemi-maxillas and the capsular subcutaneous tissue, both with the tubes, were removed. Specimens were processed and evaluated histomorphologicaly under light microscopy. The scores obtained were analyzed statistically by the Kruskal-Wallis test (p<0.05). Results: There were no statistically significant differences between the implantation methods (p=0.78033, p=0.72039). It was observed that the 30-day groups presented a more mature healing process due to smaller number of inflammatory cells. Conclusions: The present study showed no differences in tissue responses as far as the implantation site and the studied period were concerned. Alveolar socket implantation methodology represents an interesting method in the study of the biological properties of root-end filling endodontic materials due to the opportunity to evaluate bone tissue response.

Bone regeneration after demineralized bone matrix and castor oil (Ricinus communis) polyurethane implantation

Innocuous biocompatible materials have been searched to repair or reconstruct bone defects. Their goal is to restore the function of live or dead tissues. This study compared connective tissue and bone reaction when exposed to demineralized bovine bone matrix and a polyurethane resin derived from castor bean (Ricinus communis). Forty-five rats were assigned to 3 groups of 15 animals (control, bovine bone and polyurethane). A cylindrical defect was created on mandible base and filled with bovine bone matrix and the polyurethane. Control group received no treatment. Analyses were performed after 15, 45 and 60 days (5 animals each). Histological analysis revealed connective tissue tolerance to bovine bone with local inflammatory response similar to that of the control group. After 15 days, all groups demonstrated similar outcomes, with mild inflammatory reaction, probably due to the surgical procedure rather than to the material. In the polymer group, after 60 days, scarce multinucleated cells could still be observed. In general, all groups showed good stability and osteogenic connective tissue with blood vessels into the surgical area. The results suggest biocompatibility of both materials, seen by their integration into rat mandible. Moreover, the polyurethane seems to be an alternative in bone reconstruction and it is an inexhaustible source of biomaterial.

Success rate of immediate nonfunctional loaded single-tooth implants: Immediate versus delayed implantation

Purpose: The aim of this study was to evaluate the success rate of maxillary immediate nonfunctional single-tooth loaded implants used into fresh extraction sites (immediate placement condition) or healed ridge (delayed placement condition).Materials and Methods: Eighty-two dental implants were placed in the maxilla of 64 consecutive patients from Private practice office and from a specialization course in Implantology. Forty-six implants were inserted under immediate placement condition, and 36 were inserted under delayed placement condition. The criteria used to evaluate success rate were those previously described by Albrektsson and Zarb (Int J Prosthodont 1993;6: 95-105), and follow-up period ranged from 18.0 to 39.7 months.Results: Seventy-nine implants fulfilled the success rate criteria (96.3%). Moreover, differences concerning implantation condition were not significant (P = 0.33, Qui-square test): three of the failed implants were from immediate placement group (success rate of 93.5%), and none was from delayed placement group (success rate of 100.0%).Conclusion: In the present sample, no statistically significant differences were detected for immediate nonfunctional single-tooth loaded implants under immediate placement condition in comparison with those inserted under delayed placement condition; both protocols had high success rate in maxillary incisors, canines, and premolars areas.

Neurochemistry of the afferents to the rat cochlear root nucleus: Possible synaptic modulation of the acoustic startle

Afferents to the primary startle circuit are essential for the elicitation and modulation of the acoustic startle reflex (ASR). In the rat, cochlear root neurons (CRNs) comprise the first component of the acoustic startle circuit and play a crucial role in mediating the ASR. Nevertheless, the neurochemical pattern of their afferents remains unclear. To determine the distribution of excitatory and inhibitory inputs, we used confocal microscopy to analyze the immunostaining for vesicular glutamate and GABA transporter proteins (VGLUT1 and VGAT) on retrogradely labeled CRNs. We also used reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry to detect and localize specific neurotransmitter receptor subunits in the cochlear root. Our results show differential distributions of VGLUT1- and VGAT-immunoreactive endings around cell bodies and dendrites. The RT-PCR data showed a positive band for several ionotropic glutamate receptor subunits, M1-M5 muscarinic receptor subtypes, the glycine receptor alpha 1 subunit (GlyR alpha 1), GABA(A), GABA(B), and subunits of alpha 2 and beta-noradrenergic receptors. By immunohistochemistry, we confirmed that CRN cell bodies exhibit positive immunoreaction for the glutamate receptor (GluR) 3 and NR1 GluR subunits. Cell bodies and dendrites were also positive for M2 and M4, and GlyR alpha 1. Other subunits, such as GluR1 and GluR4 of the AMPA GluRs, were observed in glial cells neighboring unlabeled CRN cell bodies. We further confirmed the existence of nor-adrenergic afferents onto CRNs from the locus coeruleus by combining tyrosine hydroxylase immunohistochemistry and tract-tracing experiments. Our results provide valuable information toward understanding how CRNs might integrate excitatory and inhibitory inputs, and hence how they could elicit and modulate the ASR. (C) 2008 IBRO. Published by Elsevier Ltd. All rights reserved.

Age impact on the eferent system actitivies in cochlear mechanical properties in normal hearing individuals

O trato olivococlear medial realiza o controle eferente das células ciliadas externas, regulando as contrações lentas e atenuando as rápidas. Com a pesquisa da amplitude das emissões otoacústicas sem e com estimulação acústica contra, ipsi ou bilateralmente, é possível estimar as condições desse trato, uma vez que o efeito resultante de redução/supressão das emissões indica seu funcionamento. O envelhecimento implica em diminuição da atividade do sistema auditivo central, em função da degeneração das estruturas envolvidas nas habilidades auditivas. OBJETIVO: O objetivo foi investigar o efeito da idade na atividade do trato sobre a cóclea, com a análise da amplitude das emissões com estimulação acústica contralateral. MATERIAL E MÉTODO: A casuística foi composta por 75 indivíduos agrupados conforme a idade. A metodologia foi o modo convencional, com clique linear e o ruído branco. ESTUDO DE CASO: A análise considerou a resposta das orelhas e a comparação entre os grupos. RESULTADOS: Os resultados revelam diferenças estatisticamente significantes entre o response das emissões sem e com estimulação acústica contralateral, nos indivíduos (20 a 39 anos). O efeito redução/supressão das emissões diminui com a idade (quarta década). CONCLUSÃO: O envelhecimento prejudica a efetividade da atividade do trato.

Plasma immersion ion implantation of nitrogen into H13 steel under moderate temperatures

Ion implantation of nitrogen into samples of tempered and quenched H13 steel was carried out by plasma immersion technique. A glow discharge plasma of nitrogen species was the ion source and the negative high voltage pulser provided 10-12 kV, 60 mu s duration and 1.0-2.0 kHz frequency, flat voltage pulses. The temperatures of the samples remained between 300 and 450 degrees C, sustained solely by the ion bombardment. In some of the discharges, we used a N-2 + H-2 gas mixture with 1:1 ratio. PIII treatments as long as 3, 6, 9 and up to 12 h were carried out to achieve as thickest treated layer as possible, and we were able to reach over 20 mu m treated layers, as a result of ion implantation and thermal (and possibly radiation enhanced) diffusion. The nitrogen depth profiles were obtained by GDOS (Glow Discharge Optical Spectroscopy) and the exact composition profiles by AES (Auger Electron Spectroscopy). The hardness of the treated surface was increased by more than 250%, reaching 18.8 GPa. No white layer was seen in this case. A hardness profile was obtained which corroborated a deep hardened layer, confirming the high efficacy of the moderate temperature PIII treatment of steels. (c) 2005 Elsevier B.V. All rights reserved.

Numerical simulation of magnetic-field-enhanced plasma immersion ion implantation in cylindrical geometry

Recent studies have demonstrated that the sheath dynamics in plasma immersion ion implantation (PIII) is significantly affected by an external magnetic field. In this paper, a two-dimensional computer simulation of a magnetic-field-enhanced PHI system is described. Negative bias voltage is applied to a cylindrical target located on the axis of a grounded vacuum chamber filled with uniform molecular nitrogen plasma. A static magnetic field is created by a small coil installed inside the target holder. The vacuum chamber is filled with background nitrogen gas to form a plasma in which collisions of electrons and neutrals are simulated by the Monte Carlo algorithm. It is found that a high-density plasma is formed around the target due to the intense background gas ionization by the magnetized electrons drifting in the crossed E x B fields. The effect of the magnetic field intensity, the target bias, and the gas pressure on the sheath dynamics and implantation current of the PHI system is investigated.