Evidence Of Coalescence Research Articles

Photoluminescence of Si nanostructured films by Pulsed Laser Deposition

Nanostructured-Si films with inert (Ar) and reactive (O2) atmosphere have been synthesized using laser ablation technique. The size distribution of Si nanoparticles found to depend on background gas pressure, observed by shift in photoluminescence components of energy. As deposited samples are mainly constituted by amorphous or highly defective nanoparticles. The annealing was performed at 400 °C and 1000 °C which induced growth of less defective Si-nanocrystals. The increment in PL intensity is evidence of coalescence. The results are interpreted in terms of size distribution (in the range of 2–5 nm), crystallinity and surface oxidation of the Si nanostructures.

Direct Observation of Distinct Nucleation and Growth Processes in Electrochemically Deposited ZnO Nanostructures Using in Situ XANES

In situ synchrotron X-ray absorption was used to study the nucleation and growth of ZnO nanostructures electrochemically deposited from aqueous solutions. A fixed-energy approach was used, which facilitates faster time resolution for systems that are not amenable to transmission measurements and where species-specific information has so far been elusive. Films formed at low potentials (−0.97 V vs Ag/AgCl) show instantaneous nucleation, continued growth, and coalescence of the nanorods. The resultant film is dense with narrow dispersion of rod diameters. At less negative deposition potentials (−0.77 V vs Ag/AgCl), the nucleation is more protracted, resulting in a polydispersed film. In this higher potential region, the growth rates are slower, and there is less evidence of coalescence in the deposited structures, with continued growth along the c-axis only.

Arthrodesis as an Early Alternative to Nonoperative Management of Charcot Arthropathy of the Diabetic Foot*

This study was performed to evaluate the use of arthrodesis of the tarsal-metatarsal area for the treatment of Eichenholtz stage-I Charcot arthropathy in patients with diabetes. Currently, the standard treatment of stage-I Charcot arthropathy is the application of a non-weight-bearing total-contact cast. Although this treatment can be effective for allowing a patient to walk without undergoing an operation, a nonunion or malunion may still result. The subsequent deformities may lead to complications, including ulceration of the foot and the need for operative intervention. Recently, a group of patients who had had early operative intervention for a variety of reasons provided us with the opportunity to objectively evaluate the effects of such treatment. This analysis provided valuable information about whether this treatment is a reasonable alternative to current nonoperative approaches. Between January 1991 and December 1996, fourteen patients had an operation because of Eichenholtz stage-I diabetic neuropathy. The classification of the disease as Eichenholtz stage I (the developmental stage) was based on radiographic evidence of varying degrees of articular-surface and subchondral-bone resorption and fragmentation as well as joint subluxation or dislocation without evidence of coalescence or callus formation. The operative procedure consisted of extensive debridement, open reduction, and internal fixation of the tarsal-metatarsal region with autologous bone graft. Postoperative treatment consisted of immobilization of the limb in a non-weight-bearing cast for a minimum of six weeks. All of the patients returned for a final follow-up visit at a mean of forty-one months (range, 25.3 to 77.3 months) postoperatively, at which time clinical and radiographic evaluations as well as gait analysis (with measurement of plantar pressures) were performed. The gait-analysis data was compared with similar data from a group of fourteen patients with diabetic neuropathy who had had a below-the-knee amputation and with that from a group of fourteen patients with diabetic neuropathy who had no history of plantar ulceration. All of the arthrodesis procedures were successful. Clinically, none of the patients had immediate or long-term complications postoperatively. No patient reported ulceration after the operation. The mean time to assisted weight-bearing was 10 +/- 3.3 weeks (range, six to fifteen weeks), the mean time to unassisted weight-bearing was 15 +/- 8.8 weeks (range, eight to thirty-four weeks), and the mean time to return to the use of regular shoes was 27 +/- 14.4 weeks (range, twelve to sixty weeks). All of the patients regained the level of walking ability that they had had prior to the arthropathy. The calculated confidence intervals revealed no differences between the arthrodesis group and either of the two comparison groups with regard to the time-distance gait parameters of velocity, cadence, and stride length or with regard to the minimum, maximum, and total range of motion of each of the joints. In contrast to able-bodied subjects, all three groups showed a reduction in sagittal-plane ankle motion that was primarily related to loss of plantar flexion. The first metatarsal, great toe, and heel showed the highest peak plantar pressures, with little difference among the groups. To our knowledge, the present study is the first to demonstrate the potential for early operative treatment to restore anatomical alignment and improve function of diabetic patients with stage-I Charcot arthropathy.

Generation of rhyolitic melt in an artificial magma: Implications for fractional crystallization processes in natural magmas

Abstract A large (1.3 × 107 g) artificial mafic melt with a bulk composition similar to an unusually calcic basalt (17 wt.% CaO) was produced by in-situ heating of soil, and subsequently cooled and crystallized. The final crystalline assemblage consisted dominantly of acicular diopsidic to hedenbergitic pyroxene and anorthitic feldspar, with a subordinate amount of potassic feldspar. Electron microprobe analyses reveal the presence of a small amount (∼10 vol.%) of rhyolitic glass (71% SiO2) within the crystalline network. This glass is the residual material left after crystallization of pyroxene and feldspar, analogous to rhyolitic melt which may be generated from fractional crystallization of a basaltic magma. Ion microprobe imaging indicates that the rhyolitic glass is generally present in isolated triangular- to rectangular-shaped interstices left by crystallization of acicular and tabular phases, and that the glass is enriched in trace elements (such as Zr and Cs) which are incompatible within the crystalline phases. No evidence of coalescence or migration of the rhyolitic melt is suggested by glass morphology. Although these observations were made in an artificial magmatic system, analogies to a natural system may be drawn. The isolated nature and low abundance of the rhyolitic glass highlights the difficulty of extracting and segregating evolved melts produced by high degrees of crystallization of a primitive parent, particularly one characterized by elongated, rather than equant, crystals. The distribution of the rhyolitic glass supports the suggestion that extraction of significant amounts of evolved melts from rocks may require repeated partial melting of crystallized material in order to allow the evolved liquid to physically separate from the parent, and also suggests that the geometry of crystals may be an important factor in melt segregation.

A Pathological Basis for the Cutaneous Papules of Mucopolysaccharidosis II (The Hunter Syndrome)

Cutaneous papules of two patients with the Hunter snydrome (mucopolysaccharidosis II) were compared with their normal appearing skin by light and electron microscopic techniques. While most fibrocytes of normal and papular skin contained metachromatic cytoplasmic material and characteristic vacuoles, only the papules had extracellular accumulation of metachromatic material and evidence of coalescence and rupture of vacuoles. Alcohol fixation provides better preservation of the mucosubstances.

Electron microscopic study of intestinal fat absorption in vitro from mixed micelles containing linolenic acid, monoolein, and bile salt

Sacs and segments of everted hamster gut were incubated in vitro in solutions of mixed micelles (containing taurodeoxycholate, monoolein, and linolenic acid) for various periods and at different temperatures. The appearance of electron micrographs of the tissues was consistent with the hypothesis that the lipids were taken up in small particles (of micellar or molecular dimensions) by means of diffusion. There was no stimulation of pinocytosis or alteration in pinocytotic vesicles in the terminal web during uptake. In the deep cytoplasm the lipids accumulated to form large osmiophilic droplets of two kinds: (a) large, solitary droplets contained only by the matrix of the cytoplasm, without confining membranes; (b) small droplets occurring in clusters, without evidence of coalescence, within the granular and agranular endoplasmic reticulum. There was a progressive accumulation of the small droplets with time. Similar droplets appeared in extracellular spaces, including the lacteals, after prolonged incubations at 37 degrees C. The droplets in the endoplasmic reticulum appear to be the end product of lipid absorption and to be closely related to chylomicrons. These processes resemble those occurring during absorption of triglycerides in vivo and support the idea that this occurs predominantly through the formation of mixed micelles of the type employed in this study.