Combination Of Nd Research Articles

Foam coating on aluminum alloy with laser cladding

This article concentrates on the creation of a foam layer on an Al–Si substrate with laser technology. The cladding of Al–Si powder in the front of a laser track has been separated from the side injection of mixture of Al–Si/TiH2 powder (foaming agent), which allows for fine tuning of the main processing parameters, i.e., melting temperature and laser processing time. A wide operational parameter window has been found and the formation of a porous layer has been observed for all combinations of Nd:YAG laser power in the range of 1.0–1.5 kW and for scanning speeds between 2.5 and 5.8 mm/s. Microstructural examinations were focused on the study of the relationship between process parameters and foam characteristics (porosity and bubbles size distribution). A tensile test confirmed that due to the relatively low porosity the tensile behavior of the foam layer is closer to the behavior of bulk aluminum than conventional closed cell aluminum foams.

Combination of interstitial laser coagulation and transurethral resection of the prostate: ex vivo evaluations

ObjectivesTo evaluate the combination of interstitial laser coagulation (ILC) and transurethral resection of the prostate (TURP) in an ex vivo model. Perioperative bleeding is still regarded as the main complication of conventional TURP. The minimally invasive procedure ILC and the highly effective TURP seem to be a promising concept to improve hemostasis. MethodsIsolated blood-perfused porcine kidneys were used to determine hemostatic efficacy of different interstitial laser procedures (neodymium:yttrium-aluminum-garnet [Nd:YAG], 1064 nm; and holmium:YAG [Ho:YAG], 2100 nm) in combination with conventional TURP. Bleeding could thus be quantified in relation to tissue ablation for the different techniques. Additionally, the specimens were evaluated histologically. ResultsA combination of Nd:YAG ILC, followed by TURP, resulted in significantly (P <0.001) reduced bleeding compared with TURP alone for a standardized ablation volume of 16 cm3 of perfused kidney tissue (5.1 mL/min versus 24.1 mL/min). Similarly, significantly (P <0.001) better hemostasis was demonstrated with the combination of Ho:YAG ILC compared with TURP alone (4.8 mL/min versus 24.1 mL/min). The differences between the two laser procedures were not significant. The histologic examinations revealed significantly larger coagulation zones for the groups pretreated with Nd:YAG ILC or Ho:YAG ILC compared with TURP alone. ConclusionsILC before conventional TURP leads, ex vivo, to a significantly superior hemostasis compared with TURP alone. The hemostatic effects of Nd:YAG and Ho:YAG laser treatments seem comparable.

Highly Active Single-Site Catalysts for the 1,4-cis Polymerization of Butadiene from Allylneodymium(III) Chlorides and Trialkylaluminiums – A Contribution to the Activation of Tris(allyl)neodymium(III) and the Further Elucidation of the Structure-Activity Relationship

To further elucidate the structure-reactivity relationship in the allylneodymium complex-catalyzed 1,4-cis polymerization of butadiene, the following catalyst systems are investigated in toluene more thoroughly: Nd(C3H5)2Cl·1,4-dioxane, Nd(C3H5)Cl2·2.5 tetrahydrofuran (THF)/5–30 AlMe3 and preformed Nd(C3H4R)3 in combination with 2 Ph3CCl, 2 Ph3CCl/5 AlEt3; 2 AlMe2Cl, 2 AlMe2Cl/30 AlMe3; 2 AlEt2Cl and 2 AlEt2Cl/10 AlEt3. From the catalytic activity, cis selectivity, polydispersity, degree of polymerization as a function of conversion, as well as the comparison of theoretical and experimental chain length and kinetic analysis, essential conclusions can be drawn concerning the formation reaction and structure of the real catalyst complex and the course of the polymerization reaction. For the combinations of Nd(C3H4R)3 with 2 AlMe2Cl/30 AlMe3, 2AlEt2Cl and 2 AlEt2Cl/10AlEt3, the rate law rP = kP[Nd][BD]2 is derived with the values for kP of 3.4 (at 35°C), 2.0 and 1.5 L2/(mol2·s1) (at 50°C), respectively. In each case the formation of a η3-butenyl bis(η4-butadiene)neodymium(III) complex [Nd(η3-C3H4R)(η4-C4H6)2(ClAlR′2C3H4R)2] (R′ = Me, Et) is assumed. The insertion reaction proceeds according to the π-allyl insertion mechanism, and the high cis-selectivity in accordance with the anti-cis and syn-trans correlation is a consequence of the preferential η4-cis coordination of butadiene.

Evidence for Paleoproterozoic, Grenvillian, and Pan-African age Gondwanan crust beneath northeastern Mexico

A number of previous studies including two recent reconstructions of Rodinia have considered the Grenvillian basement of Mexico to be continuous with the Laurentian basement of Texas. Isotopic studies and U–Pb dating of zircons from Precambrian granitoids that occur as cobbles and boulders in a Paleozoic conglomerate exposed in the state of Coahuila, northeastern Mexico, indicate the region is underlain by Gondwanan rather than Laurentian basement. Essentially nothing was known of the basement before this study because the region is blanketed with Phanerozoic sedimentary and volcanic deposits. Nine out of ten analyzed samples have Grenvillian crystallization ages (1232±7 to 1214±2 Ma). This phase of magmatic activity in northeastern Mexico was coeval with the construction of volcanic arcs in east-central and southern Mexico (∼1220–1150 Ma), but was later than the arc magmatism of Laurentia (e.g., Elzevirian arcs, >1230 Ma, in Texas and the Grenville Province). A subset of the Grenvillian samples contains xenocrystic ∼1.85 Ga zircons, which are the first evidence of Paleoproterozoic crust south of the Paleozoic Ouachita suture in Mexico. The remaining sample has a Pan-African crystallization age (580±4 Ma), and this is the first sample of Pan-African age basement found in Mexico. The Pan-African orogeny marked the assembly of Gondwana, and Laurentia was unaffected by that event. Two lines of evidence argue that some of the Grenvillian rocks of northeastern Mexico were affected by a Pan-African age event. First, two of the Grenvillian clasts have U–Pb lower intercept ages within error of 580 Ma. Second common Pb and Nd isotopic compositions of the Pan-African granite strongly suggest that it was derived either by melting of Grenvillian basement or by assimilating massive amounts of that basement. Thus far, no other Grenvillian terrane is known to have the exact combination of Nd–Pb isotopic compositions and absolute ages as the Coahuila samples although there are some similarities with the Santa Marta massif of Colombia and the Cordillera de Merida of Venezuela.

The Influence of Photodynamic Therapy on the Wound Healing Process in Rats

In photodynamic therapy (PDT), photosensitisers (PS) are used along with lasers for the treatment of tumors. The combined effect of photosensitisers and lasers on the wound healing process is studied using delta-aminolevulinic acid (ALA) (5 mg/kg) and hematoporphyrin derivative (HPD) (5 mg/kg) as photosensitisers in the open excision wounds of rats. The lasers used were He-Ne laser (3 J/cm2) and Nd:YAG laser (30 J/cm2). This study is important for understanding the healing process involved after PDT. Open excision wounds treated with He-Ne lasers in animals that received ALA as photosensitiser showed complete wound closure at the earliest by 13 +/- 1 days, and with results obtained for HPD and the combination of lasers with complete closing by 14 +/- 1 days. However, the control group of animals that received ALS or HPD with no laser treatment showed wound healing on the twentieth and eighteenth days with a deviation of one day and two days, respectively. ALA with the combination of Nd:YAG and He-Ne lasers and HPD with He-Ne laser alone does not show quicker wound healing effects. Histopathological results also gave similar results. Tensile strength measurements do not vary significantly from control group to the test group. ALA along with He-Ne laser of HPD along with the combination of He-Ne and low power Nd-YAG lasers are found to be ideal methods for quickening the wound healing process in rat.

Laser and multipolar electrocoagulation ablation of early Barrett's adenocarcinoma: long-term follow-up

Background: Endoscopic ablation of Barrett's esophagus, including associated dysplasia and adenocarcinoma, can be achieved by various techniques, but few long-term results are available. The aim of our study was ablation of intramucosal adenocarcinoma with a combination of Nd:YAG laser plus multipolar electrocoagulation. Methods: Patients with documented Barrett's esophagus and adenocarcinoma who either had refused surgery or were poor candidates for surgery because of high risk were offered endoscopic therapy. Patients underwent therapy with Nd:YAG laser and multipolar electrocoagulation. They were treated with omeprazole (20 mg twice daily) as maintenance therapy. Results: Six patients were enrolled in the study over a 7-year period. All were men with a mean age of 78.2 years. The mean length of Barrett's esophagus was 6.0 cm (range, 3 to 10 cm). Seventeen Nd:YAG laser (mean, 2.8/patient) and 20 multipolar electrocoagulation (mean, 3.3/patient) sessions were used during the study period. All patients had a complete initial response to therapy. One patient on chronic immunosuppressive medications had recurrence of the tumor after an initial complete response (36-month follow-up). Two patients have no evidence of Barrett's esophagus, and 3 patients have residual intestinal metaplasia on biopsy of an irregular appearing “neo” Z-line. Mean follow-up in this group is 3.4 years (range, 9 to 86 months). Conclusions: Laser photocoagulation and multipolar electrocoagulation can be successfully and safely used to ablate intramucosal adenocarcinoma in the setting of Barrett's esophagus. Patients remain functional with normal swallowing. (Gastrointest Endosc 1999;49:442-6.)

Crustal Age Domains and the Evolution of the Continental Crust in the Mozambique Belt of Tanzania: Combined Sm-Nd, Rb-Sr, and Pb-Pb Isotopic Evidence

Combination of Nd and Sr model ages and Pb isotopes on leached feldspars reveals distinct model age provinces not recognized previously within the Mozambique Belt of Tanzania. Most boundaries of these age domains are overprinted by Neoproterozoic (Pan-African) tectonism and metamorphism. Granitoids from the Archean craton show Nd model ages of 2.7–3.1 Ga and very primitive Pb isotope systematics in feldspars. Amphibolite-facies migmatites and granulites from the Mozambique Belt have similar characteristics, yet their high 208Pb/204Pb values point to U loss in the Archean, possibly during high-grade metamorphism, and subsequent Pan-African reworking. Eclogite-facies metapelites of the Early Proterozoic Usagaran Belt likewise exhibit Archean Nd model ages, but higher Pb isotopic ratios are consistent with last recrystallization of feldspar at 2 Ga. Granulites with Nd model ages from 1 to 1.5 Ga only occur in NE Tanzania; because of their restricted range in Pb isotopic composition they are interpreted as juvenile additions during late Proterozoic time. Granulites of the W Uluguru Mts have Nd model ages between 2.1 and 2.6 Ga, and highly variable feldspar Pb isotope composition indicating possible derivation from cratonic and/or Usagaran material, reworked and mixed with a small proportion of younger Proterozoic material during the Pan-African orogeny. This could indicate the suture zone between a western Archean–proterozoic continental mass and juvenile arcterranes docking on from the east during subduction of the Mozambique Ocean. The combined isotope data provide strong evidence that parts of the East African crust grew by lateral accretion of Early and Mid Proterozoic segments onto an Archean nucleus. However, the Neoproterozoic (Pan-African) orogeny not only led to addition of new crust in the NE of Tanzania, but also reworked crustal material in most other parts of the Mozambique Belt. This juxtaposition of ancient with juvenile crustal segments is consistent with an active continental margin setting before or during orogenesis. Correlation with adjacent terranes indicates similar processes of mixing and limited juvenile addition prevailing throughout central Gondwana during the Pan-African orogeny.

悪性病変による中枢気道狭窄に対するNd:YAGレーザー照射およびステント留置療法

Endpscopic Nd: YAG laser irradiation were performed in a total of 122 cases including 7 tracheal cancers, 67 lung cancers and 38 metastatic or infiltrated lung cancers. Patients were treated 1 to 12 times irradiating 120 to 68,536 Joules totally and airway obstruction was dissolved successfully in 87.5% of the patients. The survival rates of cases irradiated in carinas and in main bronchi were low as 0% at 32 months and 4.3% at 45 months after first irradiation whereas those of cases irradiated in tracheas and in lobar bronchi were 26.1% at 5 years and 34.0% at 51 months respectively. Airway stents were performed in a total of 7 cases including 2 tracheal cancers, 2 lung cancers and 3 metastatic or infiltrated lung cancers. 5 cases were treated with Nd: YAG laser irradiation of 3,689 to 52,104 Joules before airway stents. A patient with squamous cell carcinoma in her left main bronchus were treated with Dumon stent followed by linac irradiating 60 Gy and surviving more than 4 years without any recurrence. The combination of Nd: YAG irradiation and/or airway stents followed by other adjuvant therapies is considered to be a modality of effective treatment for airway obstruction due to malignant tumors.

Alternation of the q-Switched Nd: YAG Laser and the cw Argon Laser for Tunneling through Organic Material

The rapidly alternating combination of Nd:YAG laser power of the optical break-down mode with cw energy of the argon laser ablates tissue. Blood agar provides a standard test medium as tissue substitute and permits to quantify the effect of various laser energy combinations to achieve optimal ablation. High wattage of the Nd:YAG laser provides destructive pressure that creates fissures which act as the light traps of a black body simulator for efficient cw argon laser energy conversion to pressure and kinetic energy. Within the fissure the deposited cw argon laser energy is directed by gradients toward the tissue surface so that deepening troughs or tunnels are formed by expelling tissue debris.

Use of ND:YAG laser in treatment of bladder cancer

A total of 53 patients were treated with neodymium:yttrium-aluminum garnet (Nd: YAG) laser and followed up for two years. Three patients had carcinoma in situ (CIS); 4 had Ta lesions; and 28 had TINξMo, 8 had T2NξMo, and 10 had T3NξMo lesions. The patients with CIS received a combination of Nd:YAG laser and intravesical bacillus Calmette Guérin (BCG) instillation. The remainder of the patients received no supplementary chemotherapy. No tumor recurrence was noted in those with Ta lesions. Tumor recurred in 18 per cent of patients with TI lesions, and 33 per cent of those with T2 lesions; 80 per cent of patients with T3 lesions had resistant or residual tumors. In patients with CIS, there was no tumor recurrence. Nd:YAG laser is effective in Ta, Tl, and T2 bladder cancers, with low recurrence rate and minimal complications. In very select, high-risk patients with small lesions, and in those who refuse cystectomy, there may be a place for laser therapy for either palliation or definitive treatment of T3 invasive tumors of the bladder.

Nd 3+ and Yb 3+ germanate and tellurite glasses for fluorescent solar energy collectors

The features of fluorescent glass solar collectors are discussed. Combination of Nd 3+ and Yb 3+ in high refractive index glasses is suggested as concentration material. Energy absorbed by Nd 3+ is transferred with high efficiency to Yb 3+ emitting at 970 nm. The self-absorption of Nd 3+ is eliminated and long-wavelength emission at 1.06 μm decreased as a result of energy transfer.