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At least 793 records · Page 44Linked to original sources
PubMed2000

Design and fabrication of cast orthopedic implants with freeform surface textures from 3-D printed ceramic shell.

Three-dimensional printing is a solid freeform fabrication process, which creates parts directly from a computer model. The parts are built by repetitively spreading a layer of powder and selectively joining the powder in the layer by ink-jet printing of a binder material. 3D printing was applied to the fabrication of sub-millimeter surface textures with overhang and undercut geometries for use in orthopedic prostheses as bony ingrowth structures. 3D printing is used to fabricate ceramic molds of alumina powder and silica binder, and these molds are used to cast the bony ingrowth surfaces of Co-Cr (ASTM F75) alloy. Minimum positive feature sizes of the ceramic mold and, therefore, minimum negative feature sizes of castings were determined to be approximately 200 x 200 x 175 microm and were limited by the strength of ceramic needed to withstand handling. Minimum negative feature sizes in the ceramic mold and, therefore, minimum positive features in the casting were found to be approximately 350 x 350 x 175 microm and were determined by limitations on removal of powder from the ceramic and the pressure required to fill these small features with molten metal during casting. Textures were designed with 5 layers of distinct geometric definition, allowing for the design of overhung geometry with overall porosity ranging from 30-70%. Features as small as 350 x 350 x 200 microm were included in these designs and successfully cast.

Ceramics↗
PubMedDate not supplied

Genetic heterogeneity in northeastern India: reflection of Tribe-Caste continuum in the genetic structure.

We critically examined the gene frequency data for 11 genetic markers commonly available in the literature for 22 populations of northeastern India in the light of their geographic, linguistic, and ethnic affiliations. The markers investigated were three blood groups (A1A2BO, MNS, and Rh), four serum proteins (KM, Gc, Hp, and Tf), and four enzyme systems (AP, AK, EsD, and Hb). The neighbor-joining tree and multidimensional scaling of the distance matrix suggest relatively high genetic differentiation among the Mongoloid groups, with probably diverse origins when compared to the Caucasoid Indo-European populations, which had probably come from relatively more homogeneous backgrounds. Broadly speaking, the pattern of population affinities conforms to the ethno-historic, linguistic, and geographic backgrounds. An interesting and important feature that emerges from this analysis is the reflection of the effect of the sociological process of a Tribe-Caste continuum on genetic structure. While on one end we have the cluster of Caucasoid caste populations, the other end consists of Mongoloid tribal groups. In between are the populations which were originally tribes but now have become semi-Hinduized caste groups, viz., Rajbanshi, Chutiya, and Ahom. These groups have currently assumed caste status and speak Indo-European languages. Therefore, one may infer that what appears to be a purely sociological phenomenon of a Tribe-Caste continuum may well reflect in their genetic structure.

Blood Group Antigens↗
PubMed2001

William Hunter's casts of the gravid uterus at the University of Glasgow.

The Hunterian Collection at the University of Glasgow possesses 11 plaster casts showing the pregnant uterus. Three correspond to Plates I, IV, and VI of Hunter's The Anatomy of the Gravid Uterus Exhibited in Figures (1774), progressive stages of dissection of the same specimen. A further three casts show consecutive stages of dissection of a uterus containing a fetus presenting by the breech. The other specimens show a normal pregnancy at about 6 months, a normal full-term uterus with the fetal head becoming engaged, a breech presentation with placenta previa and the umbilical cord around the fetal neck, and an obstructed labor with distended bladder and colon. The 10 on display show realistic coloring and are mounted on black wooden stands. An 11th specimen, amateurishly painted, is not on display. The casts differ in their style; some show only the abdomen, pelvis, perineum, and thighs, others show the full torso. They also differ in the amount of detail shown. The first three casts show the cut femur and muscles at the transected ends of the thighs, also shown in some of the plates in the Gravid Uterus. Although these features enhance the artistic impact of both the engravings and the casts, the authors are unconvinced that Hunter deliberately used them to achieve this, as has been claimed.

Adult↗
PubMed2006

Bioactivation of a cobalt alloy by coating with wollastonite during investment casting.

Cobalt alloy samples were bioactivated during investment casting. The cavities of the investment mold were previously coated with wollastonite. Additionally, before coating with wollastonite, some mold cavities were filled out with graphite rods to avoid a chemical reaction between the wollastonite powder and the investment material. Half of the cast samples were heat treated at 1220 degrees C for 1 h. To perform the in vitro bioactivity assessment, the cast and heat-treated samples were immersed in a simulated body fluid solution (SBF) for a period of 21 days. The surface of the samples before and after immersion in SBF was characterized by SEM, EDX, and XRD analyses. During the casting, particles of pseudowollastonite were embedded on the metallic surface. After immersion of the samples in SBF, a ceramic layer was formed on both the alloy obtained by using the investment mold and the alloy obtained by using the graphite-filled cavity. The ceramic layer was thicker on the alloy cast in the investment mold. The layer was identified as hydroxyapatite by XRD analysis, in all the cases. The heat-treated samples after immersion in SBF showed the formation of a thin homogeneous layer consisting of fine grains of apatite.

Alloys↗
PubMed2003

Caste morphology and development in Termitogeton nr. planus (Insecta, Isoptera, Rhinotermitidae).

The termite family Rhinotermitidae displays a wide diversity in its patterns of social organization in castes. The genus Termitogeton probably branched off early in the evolution of this family. We studied the developmental pathways of a putative undescribed species from New Guinea, Termitogeton nr planus. The development begins with two white inactive instars (larvae), the second of which possesses small wing buds. These are followed by a relatively homogenous group of active immature stages (pseudergates) among which a biometric study revealed the presence of four instars. The first of these instars possesses wing buds that regress at subsequent molts. The external morphology of older instars resembles that of higher termite workers. Older pseudergates can differentiate into presoldiers and then into soldiers, but they are also able to molt into a unique stage with long wing pads (nymph), preceding the imago. Colony maturity can be reached with about 10(3) individuals. The sex ratio is near 1:1 in all castes except soldiers, among which females are more numerous than males. The caste pattern of T. nr. planus is reminiscent of those of the Kalotermitidae and Termopsidae, and of Prorhinotermes among the Rhinotermitidae. None of these taxa possess a true worker caste, permanently diverted from imaginal development: social tasks are done by unspecialized immatures that retain a full array of developmental options, including that of proceeding to the imago. The most remarkable trait of T. nr. planus is the presence in all second-instar individuals of wing buds that later regress to reappear in the single nymphal stage. We suggest that the traditional definitions of the terms larvae, nymphs, and pseudergates should be revised because they cannot be satisfactorily applied to the castes of Termitogeton.

Animals↗
PubMed1979

Plastic casts of embryonic respiratory and cardiovascular system: a technique.

This report describes a technique for producing plastic casts of the cardiovascular and respiratory systems of the chick embryo at Stage 36 or older. For casts of the cardiovascular system, polymerization compound is injected in the right ventricle filling the heart, venous, and arterial system. A two stage injection produced more detailed casts of the pulmonary vasculature. For respiratory system casts, the compound is injected in the trachea filling the bronchi and air sacs. Casts are prepared by tissue corrosion in 10% potassium hydroxide. This technique is an alternative to serial section reconstruction in the study of developing cardiovascular and respiratory system.

Animals↗
PubMed1979

The occurrence of DChi and new D and B transferrin variants among caste groups of Andhra Pradesh (S. India).

Serum samples from a total of 862 unrelated individuals belonging to seven Hindu endogamous caste groups residing in Hyderabad and Warangal cities of Andhra Pradesh were examined for electrophoretic variation of transferrin (Tf). In four caste groups, namely, Brahmin, Vysya, Padmashali, and Kapu, the Mongoloid genetic marker DChi was found, with polymorphic frequencies in Brahmin and Vysya groups. The two new D variants found in individuals of Madiga and Mudiraj castes were designated as DMadiga and DMudiraj. Similarly, two new B variants found in individuals of Goldsmith and Madiga castes were designated as BGoldsmith and BMadiga, respectively. These findings suggest a widespread transferrin variation in caste groups of Andhra Pradesh and in the tribal populations of this region.

Alleles↗
PubMed1992

Methods for assessing quality of life in the cardiac arrhythmia suppression trial (CAST).

The CAST was a randomized, double-blind placebo-controlled multicentre trial of antiarrhythmic medications designed to suppress ventricular arrhythmias in patients after an acute myocardial infarction (MI). A collection of 21 items derived from established scales was used to assess aspects of quality of life in CAST. The questions focused on symptoms, mental health, physical functioning, social functioning, life satisfaction, and life expectancy. Additional aspects included exposure to major stressful life events, and perceived social support and social integration. Work status was also recorded. Using the baseline values of 1465 (98%) out of 1498 patients enrolled in the CAST main study between 15 June 1987 and 19 April 1989, the reliability and validity of the scales used in CAST were computed. High internal consistency reliability (> or = 0.70) was found for Symptoms, Mental Health, and Physical Functioning. The discriminative validity, in particular for Symptoms, Mental Health, Physical and Social Functioning, showed that patients with heart failure and previous MI, as well as those suffering from angina and dyspnea, had a worse quality of life than those patients who were not experiencing these symptoms. It was concluded that the scales selected to form the CAST quality of life questionnaire were both reliable and clinically valid for this patient population and therefore could be used to detect disease progression and treatment effects.

Aged↗
PubMed1996

A case of bronchial cast.

We report a case of bronchial cast in a boy 1 year and 5 months old. Bronchial casts often obstruct the main bronchi, causing dyspnea and hypoxia. The bronchial cast was studied pathologically, with findings of eosinophilia and neutrophilic infiltration; the cast seemed to involve an allergic reaction. Such casts can be removed during bronchoscopy, but we used aspiration.

Airway Obstruction↗
PubMed2000

The critical period for caste determination in Bombus terrestris and its juvenile hormone correlates.

The critical period for caste determination and its juvenile hormone (JH III) correlates were studied in Bombus terrestris. Larvae of known age and instar were taken from young colonies, in which they would have been reared as workers, and placed into groups of queenless workers. Under these conditions the critical age for caste determination was 5 days, during the second instar. Endocrine correlates of caste determination were obtained by determining profiles of juvenile hormone titer and juvenile hormone biosynthesis, measured by chiral-specific radioimmunoassay and the in vitro radiochemical assay, respectively. By the middle of the second instar prospective queen larvae had significantly higher rates of juvenile hormone biosynthesis and juvenile hormone titer than prospective worker larvae. Based on the coincidence of timing of both the critical period and the appearance of caste-specific juvenile hormone titer, we suggest that juvenile hormone plays a role in the mechanisms that control caste determination in B. terrestris.

Animals↗
PubMed2003

Left atrial appendage morphology: comparison of transesophageal images and postmortem casts.

BACKGROUND: Aim of the study was to compare 1) transesophageal echocardiographic (TEE) measurements of the left atrial appendage (LAA) with postmortem casts and 2) the TEE with the postmortem diagnosis of LAA thrombi. METHODS: From the TEE images and LAA casts length, orifice, diameter and number of branches were assessed. LAA area was measured by TEE and LAA volume from the cast. RESULTS: In 12 patients who underwent TEE and autopsy, measurements of LAA length and area correlated well with the cast volume ( r=0.6 to r=0.93). The agreement between TEE and LAA casts, concerning the number of branches, was only moderate. In one patient, a false positive diagnosis of a LAA thrombus occurred. CONCLUSIONS: LAA size and orifice diameter can be assessed reliably by TEE. The complex LAA morphology hampers measurements of LAA length, branches, course and diagnosis of thrombi.

Acrylic Resins↗
PubMed1983

Hematuria and red cell casts in typical diabetic nephropathy.

Hematuria and red cell casts are unusual urinary findings in patients with diabetic nephropathy. This glomerular disease is more typically characterized by the presence of moderate to severe proteinuria. Hematuria with red blood cell casts in patients with suspected diabetic nephropathy suggests the presence of a second, unrelated form of glomerulonephritis. The full clinical and renal pathologic findings in eight patients with otherwise typical diabetic nephropathy who also had significant hematuria and red cell casts in the urinary sediment are reported. Three of the patients had an immune-mediated form of glomerulonephritis identified. Careful histologic, electron microscopic, and immunofluorescent examination of the renal tissue from the remaining five patients demonstrated only diabetic nephropathy, without evidence of immune-mediated glomerulonephritis in any. Screening urinalysis in a population of 30 patients with diabetic nephropathy revealed hematuria in 30 percent and red cell casts in 13 percent. It is concluded that significant hematuria with red cell casts may be a clinical feature of diabetic nephropathy.

Adolescent↗
PubMed1987

Vascular casts demonstrate microcirculatory insufficiency in acute frostbite.

The use of vascular microcorrosion casts (vascular replicas) has made it possible to demonstrate the degree of damage to the microcirculation in experimentally induced frostbite. This approach provides a direct method for demonstrating vascular patency. Four groups of animals were used in this investigation. The left hind limbs of anesthetized rats were cooled to -10 degrees C in groups one and three and to -20 degrees C in groups two and four, as measured by needle thermocouples placed under the gastrocnemius muscles. Thermocouples were also placed in the left hind footpads of groups three and four. The sheathed limbs were cooled in an alcohol bath at approximately 1.1 degree C per minute. All limbs exposed to the cold bath were rewarmed to 37 degrees C in a 40 degree C water bath. The right hind limbs served as uninjured controls. The footpad temperatures recorded in groups three and four were used in conjunction with the temperatures recorded under the gastrocnemius muscles to characterize the footpad temperatures in groups one and two. Vascular microcorrosion casts were made from the left and right hind paws of groups one and two using Batson's modified methyl methacrylate. Scanning electron microscopic examination of the casts demonstrated dramatic differences between the vascular integrity of control paws and that of frozen paws. Exposure to the cold temperatures destroyed most of the microcirculation. In addition, the weights of the casts from the control paws were significantly different from the weights of the casts from the frozen paws. It was concluded that this model for evaluating frostbite injury accurately demonstrates the extent of microvascular damage and has significant potential as a method for evaluating therapeutic drug regimens.

Animals↗
PubMed1990

Caste and metamorphosis: hemolymph titers of juvenile hormone and ecdysteroids in last instar honeybee larvae.

Juvenile hormone (JH) and ecdysteroid titers are critical factors for caste development and metamorphosis in the last larval instar of the honeybee, Apis mellifera. Two highly sensitive radioimmunoassays were used for the determination of these hormones in the hemolymph. For juvenile hormone, which is of prime importance for the control of caste development in honeybees, our data show a caste-specific peak in queen larvae of the early fifth instar. A second peak appears in prepupae of both castes which probably is responsible for the regulation of the pupal moult. A single peak of ecdysteroids was observed in prepupae of both castes. In queens, however, the titer increases distinctly earlier than in worker larvae. The ecdysteroid composition of this prepupal peak was determined by high-performance liquid chromatography separation followed by radioimmunoassay. Makisterone A proved to be the main ecdysteroid compound, but 20-hydroxyecdysone was also found in significant amounts.

Animals↗
PubMed1989

Bactericidal effect of a disinfectant dental stone on irreversible hydrocolloid impressions and stone casts.

Infection control in dentistry focuses on the prevention of cross-contamination among patients, dentists, and dental auxilary personnel. This study evaluated the bactericidal effect of a dental gypsum material containing 0.25% chloramine-T on oral irreversible hydrocolloid impressions and dental casts. Eighty irreversible hydrocolloid impressions from 40 human volunteers were prepared. Forty impressions were poured with the disinfectant dental stone and a similar number were poured with a comparable, nondisinfectant stone. After setting for 60 minutes, the impressions and separated casts were sampled for bacterial contamination. The disinfectant stone inhibited bacterial growth in 39 of 40 impressions and casts, whereas all casts and impressions poured with the nondisinfectant stone were contaminated. The disinfectant dental stone containing chloramine-T was effective in eliminating bacterial contamination of both the irreversible hydrocolloid impression and stone cast.

Alginates↗
PubMed1989

Veterans Administration Cooperative Studies Project No. 147. Part IX: A comparison of the mechanical properties of several alternative metal ceramic alloys cast in clinical and research laboratories.

Comparison of mechanical properties of five metal ceramic alloys cast in clinical and research laboratories resulted in significant differences. Tested alloys included one Au-Pd (control), one Pd-Ag, and three Ni-Cr. Mechanical properties included strength, elongation, and microhardness. Tensile bars were torch cast simultaneously with restorations in the clinical laboratory and induction cast by using a preformed design in the research laboratory. Mechanical properties of most alloys showed larger variations when cast in the clinical laboratory. In the clinical laboratory the Au-Pd alloy showed significantly higher values for all properties. One Ni-Cr alloy was not significantly affected by environment for all properties. The remaining alloys were significantly affected for some properties by environment. The different laboratories had no greater or lesser effect on the base metals as a group than on the noble metals. Variation in handling, spruing, casting, and specimen size may account for some of the differences between laboratories.

Ceramics↗
PubMed1989

Microscopic examination of embrittled pin-retained base metal casting.

Differential thermal analysis, optical microscopy, scanning electron microscopy, and energy dispersive radiographic analysis were used to examine and analyze two failed platinum-palladium-gold pin-retained nickel-chromium castings. The microstructure and chemical composition of the pin-casting interface were different from those of the pin and the cast alloy. Porosity was also observed at the interface. The observations with these samples suggest that the pin melted during casting. The embrittlement and failure of plantium-palladium-gold pins cast with nickel-chromium alloy have been attributed to this melting phenomenon. Further study is necessary to determine whether these observations are valid for a large number of samples.

Chemical Phenomena↗
PubMed1990

Effect of internal microblasting on retention of cemented cast crowns.

Microblasting of cast mental crowns is considered a standard procedure in most laboratories and an effective alternative to acid pickling. During the process of devesting and finishing, the surfaces of cast restorations are microblasted with an abrasive agent. This investigation measured the retention of type III cast gold crowns after cleansing with pickling solution (group I) or microblasting with 50-micron aluminum oxide (group II) or 50-micron glass beads (group III). Microblasting the internal surface of cast crowns with 50-micron aluminum oxide significantly improved the retention of castings luted with zinc phosphate cement.

Adhesiveness↗