Optical properties of ZnFe2O4 nanoparticles and Fe-decorated inversion domain boundaries in ZnO

The maximum efficiency of solar cells utilizing a single layer for photovoltaic conversion is given by the single junction Shockley-Queisser limit. In tandem solar cells, a stack of materials with different band gaps contribute to the conversion, enabling tandem cells to exceed the single junction Shockley-Queisser limit. An intriguing variant of this approach is to embed semiconducting nanoparticles in a transparent conducting oxide (TCO) solar cell front contact. This alternative route would enhance the functionality of the TCO layer, allowing it to participate directly in photovoltaic conversion via photon absorption and charge carrier generation in the nanoparticles. Here, we demonstrate the functionalization of ZnO through incorporation of either ZnFe2O4 spinel nanoparticles (NPs) or inversion domain boundaries (IDBs) decorated by Fe. Diffuse reflectance spectroscopy and electron energy loss spectroscopy show that samples containing spinel particles and samples containing IDBs decorated by Fe both display enhanced absorption in the visible range at around 2.0 and 2.6 eV. This striking functional similarity was attributed to the local structural similarity around Fe-ions in spinel ZnFe2O4 and at Fe-decorated basal IDBs. Hence, functional properties of the ZnFe2O4 arise already for the two-dimensional basal IDBs, from which these planar defects behave like two-dimensional spinel-like inclusions in ZnO. Cathodoluminescence spectra reveal an increased luminescence around the band edge of spinel ZnFe2O4 when measuring on the spinel ZnFe2O4 NPs embedded in ZnO, whereas spectra from Fe-decorated IDBs could be deconvoluted into luminescence contributions from bulk ZnO and bulk ZnFe2O4.

Formation and functionalization of Ge-nanoparticles in ZnO

Semiconductor nanocrystals are often proposed as a viable route to improve solar energy conversion in photovoltaics and photoelectrochemical systems. Embedding the nanocrystals in, e.g. a transparent and conducting electrode of a solar cell will promote the photon absorption and subsequent transfer of the generated charge carriers from the nanocrystal, and thereby enhance the function of the electrode. This can be accomplished by embedding a semiconducting nanocrystal with a small bandgap in a transparent conducting oxide (TCO), which is commonly utilized as electrode in new generation solar cells. Here, we demonstrate the incorporation, formation, and functionalization of germanium (Ge) nanocrystals in zinc oxide utilizing ion implantation, where post implantation annealing at 800 °C results in diamond cubic Ge nanocrystals with sizes between 2 and 20 nm. Photoluminecence spectra show a distinct emission around 0.7 eV arising from the Ge nanocrystals, and with additional emission features up to 1.15 eV due to quantum confinement, demonstrating a novel functionalization and tunability of the TCO electrode.

Role of temperature in de-mixing absorbance spectra composed of compound electrolyte solutions

This work is focused on the role of temperature in the de-mixing of absorbance spectra measured in mixed aqueous Na₂SO₄ and NaNO₃ solutions. First, the influence of temperature on the absorbance spectrum of demineralized water was determined. Second, the absorbance spectra of five separate electrolytes (NaNO₂, NaNO₃, CaCl₂, K₂CO₃, and NaOH) at three temperatures (4°C, 25°C, and 50°C) for concentrations ranging from 0.0625 M to 0.5 M were examined. These five electrolytes show similar temperature dependencies. Finally, absorbance spectra of mixed solutions were investigated at temperatures of 5°C, 15°C, 25°C, 35°C, and 45°C for concentrations ranging from 0.0625 M to 0.5 M per electrolyte in the mixture. The spectral window from 650 to 1100 nm was utilized to observe the ionic and temperature influences on the vibrational modes of the OH bond in the solvent molecules. The effects of dissolving Na₂SO₄ and NaNO₃ are nonlinearly cumulative at lower temperatures indicating extended alteration of the water structure beyond the first hydration shell. A similar trend was observed for a mixture of Na₂CO₃ and NaCl. Furthermore, it was found that higher temperatures are better for recovering the separate component absorption signatures of an electrolyte mixture. The near-infrared spectral regime is well suited for integrated sensing, and therefore these results can help in designing an integrated sensor to identify inorganic species in water.

Can algae-based technologies be an affordable green process for biofuel production and wastewater remediation?

Algae is a well-known organism that its characteristic is prominent for biofuel production and wastewater remediation. This critical review aims to present the applicability of algae with in-depth discussion regarding three key aspects: (i) characterization of algae for its applications; (ii) the technical approaches and their strengths and drawbacks; and (iii) future perspectives of algae-based technologies. The process optimization and combinations with other chemical and biological processes have generated efficiency, in which bio-oil yield is up to 41.1%. Through life cycle assessment, algae bio-energy achieves high energy return than fossil fuel. Thus, the algae-based technologies can reasonably be considered as green approaches. Although selling price of algae bio-oil is still high (about $2 L^-1) compared to fossil fuel's price of $1 L^-1, it is expected that the algae bio-oil's price will become acceptable in the next coming decades and potentially dominate 75% of the market.

Investigating enhanced thermoelectric performance of graphene-based nano-structures

Recently, it has been demonstrated that graphene nano-ribbons (GNRs) exhibit superior thermoelectric performance compared to graphene sheets. However, the underlying mechanism behind this enhancement has not been systematically investigated and significant opportunity remains for further enhancement of the thermoelectric performance of GNRs by optimizing their charge carrier concentration. In this work, we modulate the carrier concentration of graphene-based nano-structures using a gate voltage and investigate the resulting carrier-concentration-dependent thermoelectric parameters using the Boltzmann transport equations. We investigate the effect of energy dependent scattering time and the role of substrate-induced charge carrier fluctuation in optimizing the Seebeck coefficient and power factor. Our approach predicts the scattering mechanism and the extent of the charge carrier fluctuation in different samples and explains the enhancement of thermoelectric performance of GNR samples. Subsequently, we propose a route towards the enhancement of thermoelectric performance of graphene-based devices which can also be applied to other two-dimensional materials.

Interface phenomena in magnetron sputtered Cu2O/ZnO heterostructures

The interface between ZnO and Cu₂O has been predicted to be a good candidate for use in thin film solar cells. However, the high predicted conversion efficiency has yet to be fully realized experimentally. To explore the underlying causes of this we investigate the interface between ZnO and Cu₂O in magnetron sputtered samples. Two different sample geometries were made: In the first set thin layers of ZnO were deposited on Cu₂O (type A), while in the second set the order was reversed (type B). Using x-ray photoelectron spectroscopy (XPS), an intermediate CuO layer was identified regardless of the order in which the Cu₂O and ZnO layers were deposited. The presence of a CuO layer was supported by transmission electron microscopy (TEM) results. Changes in the electron hole screening conditions were observed in CuO near the interface with ZnO, manifested as changes in the relative peak-to-satellite ratio and the degree of asymmetric broadness in the Cu 2p peak. The suppression of the Cu 2p satellite characteristic of CuO may cause the CuO presence to be overlooked and cause errors in determinations of valence band offsets (VBOs). For the type A samples, we compare four different approaches to XPS-based determination of VBO and find that the most reliable results are obtained when the thin CuO layer and the altered screening conditions at the interface were taken into account. The VBOs were found to range between 2.5 eV and 2.8 eV. For the B type samples a reduction of the Cu 2p-LMM Auger parameter was found as compared to bulk Cu₂O, indicative of quantum confinement in the Cu₂O overlayer.

Environmentally friendly power generator based on moving liquid dielectric and double layer effect

An electrostatic power generator converts mechanical energy to electrical energy by utilising the principle of variable capacitance. This change in capacitance is usually achieved by varying the gap or overlap between two parallel metallic plates. This paper proposes a novel electrostatic micro power generator where the change in capacitance is achieved by the movement of an aqueous solution of NaCl. A significant change in capacitance is achieved due to the higher than air dielectric constant of water and the Helmholtz double layer capacitor formed by ion separation at the electrode interfaces. The proposed device has significant advantages over traditional electrostatic devices which include low bias voltage and low mechanical frequency of operation. This is critical if the proposed device is to have utility in harvesting power from the environment. A figure of merit exceeding 10000(10⁸μW)/(mm²HzV²) which is two orders of magnitude greater than previous devices, is demonstrated for a prototype operating at a bias voltage of 1.2 V and a droplet frequency of 6 Hz. Concepts are presented for large scale power harvesting.

Negative differential resistance effect in planar graphene nanoribbon break junctions

Graphene is an interesting material with a number of desirable electrical properties. Graphene-based negative differential resistance (NDR) devices hold great potential for enabling the implementation of several elements required in electronic circuits and systems. In this article we propose a novel device structure that exhibits NDR using single layer graphene that is able to be fabricated using standard lithography techniques. Using theoretical simulation, we show that graphene nanoribbon (GNR) junctions exhibit NDR effect if a gap is introduced in the structure in the transport direction of the ribbon. Using standard lithography techniques, we produce a GNR and use electro-migration to create a nanogap by breaking the GNR device. Scanning electron microscopy images show the formation of a tunnel gap. The predicted NDR phenomenon is experimentally verified in the current-voltage characteristic of the device. The linear and non-linear characteristics of the I-V responses before and after breakdown confirm that the NDR effect arises from the tunnel gap.

Modification of agricultural waste/by-products for enhanced phosphate removal and recovery: potential and obstacles

There is a growing trend to employ agricultural waste/by-products (AWBs) as the substrates for the development of phosphate biosorbents. Nevertheless, due to the lack of anion binding sites, natural AWBs are usually inefficient in phosphate decontamination. Consequently, modification plays a vital role in improving phosphate sorption's property of raw AWBs. This review paper evaluates all existing methods of modification. The literatures indicate that modification can significantly improve phosphate removal ability of AWBs by retaining phosphate ion onto modified AWBs principally via ion exchange (electrostatic interaction) and ligand exchange mechanisms. So far, little work has been done on the beneficial use of modified AWBs for the phosphorus recovery from aqueous solutions. The poor recyclability of modified AWBs could be responsible for their limited application. Hence, further study is essential to search for novel, cost-effective, and green methods of modification.

Localized production of human E-cadherin-derived first repeat in Escherichia coli

E-cadherin is a cell surface adhesion molecule that is expressed in both epithelial and endothelial tissues. In this study, an improved method for the simple production of the human E-cadherin-derived first repeat E-CAD1 was developed by exporting it into the periplasmic space of Escherichia coli. Localization of the recombinant protein into the periplasm allowed the isolation of E-CAD1 without cell lysis. The N-terminus of E-CAD1 is fused to a streptavidin-derived peptide to allow single-step purification using a Streptag affinity column. Optimal expression in LB medium produced 3.2 mg/L while expression in minimal medium containing 15NH(4)Cl as the sole source of nitrogen produced 4.2 mg/L purified (15)N-labeled E-CAD1. Heteronuclear NMR spectroscopy confirmed that the purified E-CAD1 produced in this manner was correctly folded. The expression and purification protocol for unlabeled and isotopically labeled E-CAD1 permits rapid preparative production of this protein for mechanistic and structural studies.

Acquisition of oral phencyclidine self-administration in rhesus monkeys: effect of sex

RATIONALE

There are increasing reports of sex differences in the etiology of drug abuse in humans. A nonhuman primate model is useful for examining sex as a variable in drug abuse.

OBJECTIVES

To determine whether there are sex differences in the acquisition of oral phencyclidine (PCP) self-administration and to compare the effect of altered feeding conditions on drug self-administration in male and female monkeys.

METHODS

Acquisition of orally delivered PCP was studied using 7 female and 11 male adult rhesus monkeys. Initially, the monkeys were not food restricted, and they were given access to water under concurrent fixed-ratio (FR) 1 schedules during daily 3-h sessions. Each lip-contact response on a drinking spout resulted in a 0.3 ml liquid delivery. After baseline levels of water intake were obtained for 5 days, water was replaced with PCP (0.125 mg/ml) at both drinking spouts. Body weights were then reduced to 85% of free-feeding weights, and the monkeys were fed 30 min before the session began. The FR value was increased from 1 to 2, 4, and 8, at both drinking spouts. As a final step in the procedure, water and PCP were concurrently available at the two spouts under FR 8 schedules. Acquisition of PCP-reinforced behavior was considered to have occurred if PCP intake was consistently greater than water intake.

RESULTS

Lip-contact responses and liquid deliveries were not significantly different between the females and males throughout the acquisition period, but there was a significant increase in responding and decrease in liquid intake as FR increased, and a significant increase in PCP consumption due to food restriction that did not differ in males and females. On a milligram per kilogram basis, female monkeys consumed nearly twice as much PCP as the males; however, this effect was not significant. The females showed significantly higher PCP than water intake while the males consumed approximately equal amounts of PCP and water. Of the seven females, 100% met the acquisition criterion of significantly greater PCP than water intake, while only 36.4% of the males met the criterion.

CONCLUSION

These results concur with previous rat studies and indicate that female monkeys are more likely than males to acquire drug-reinforced behavior.

Evaluation of a computerized antimicrobial susceptibility system with bacteria isolated from animals

The BIOMIC is a computerized system used to calculate the minimal inhibitory concentration (MIC) of an antimicrobial agent from a zone of inhibition generated by a disk diffusion test. This system was developed using bacterial pathogens of human origin. This study investigated the use of the BIOMIC system for determining MICs for bacterial pathogens from animals. The MICs generated by the BIOMIC system were compared with the MICs generated using a broth microdilution testing method. A total of 663 drug-organism combinations was tested. These combinations included 3 species of gram-positive bacteria, 5 species of gram-negative bacteria, and the antimicrobial agents ampicillin, gentamicin, cephalothin, ciprofloxacin, enrofloxacin, trimethoprim/sulfamethoxazole, tetracycline, and erythromycin. Overall, the MICs generated by the BIOMIC system correlated with the broth microdilution MICs for 72% of the total drug-organism combinations tested. The Pseudomonas aeruginosa strains tested showed the highest agreement between the 2 systems, with 100% for all antibacterial agents tested, whereas Pasteurella haemolytica, Pasteurella multocida, and enterococci showed the least agreement (76%, 57%, and 47%, respectively). Among these organisms, trimethoprim-sulfa showed the least agreement (31%) and ciprofloxacin showed the greatest (91%). These results indicate that the BIOMIC system could be a useful tool in veterinary medicine for producing quantitative antimicrobial susceptibility results. However, it is currently unreliable for some drug-bacteria combinations. This discrepancy possibly could be corrected by modification of the software using data points generated by a large-scale study.

Plasmodium falciparum: mutation pattern in the dihydrofolate reductase-thymidylate synthase genes of Vietnamese isolates, a novel mutation, and coexistence of two clones in a Thai patient

Pyrimethamine and cycloguanil resistance of Plasmodium falciparum has been linked to mutations in the dihydrofolate reductase (dhfr) portion of the dhfr-ts gene. In this paper, the DNA sequence of the dhfr-ts gene of 50 isolates from Vietnam and 2 clones (T9/94 and T9/96) isolated from a malaria patient from Thailand have been analyzed. A comparison between these isolates and clones showed differential mutation patterns. Forty-eight isolates were found to consist of mutations associated with Pyr. A novel leucine mutation at position 140 was found in the isolate VP8 and in clone T9/94. The isolate VP8 and the clone T9/94 were found to also have the characteristic changes at positions 16 (Val) and 108 (Thr) that have been found in cycloguanil-resistant isolates. The isolate VP35 was shown to be resistant to both antifolates, while the clone T9/96 was found to be sensitive to both antifolates and to have a sequence identical to that of wild-type dhfr-ts. The two clones from a single patient showed the coexistence of resistant and sensitive clones in the absence of treatment by antifolates. Since cycloguanil resistance seems to be rare in Vietnam, cycloguanil alone or in combination with other antimalarial agents might be an alternative for treatment and prophylaxis, even in areas with high resistance to pyrimethamine.

Correction of blood pH attenuates changes in hemodynamics and organ blood flow during permissive hypercapnia

OBJECTIVES

To determine whether changes in cardiac output, regional blood flow, and intracranial pressure during permissive hypercapnia are blood pH-dependent and can be attenuated by correction of intravascular acidemia.

DESIGN

Prospective, controlled study.

SETTING

Research laboratory.

SUBJECTS

Female Marino ewes.

INTERVENTIONS

Animals were instrumented with a pulmonary artery catheter, femoral arterial and venous catheters, a catheter in the third cerebral ventricle, and ultrasonic flow probes on the left carotid, superior mesenteric, and left renal arteries 1 wk before experimentation. At initiation of the protocol, ewes underwent endotracheal intubation and mechanical ventilation under general anesthesia. Minute ventilation was reduced to induce hypercapnia with a target PaCO2 of 80 torr (10.7 kPa). In the pH-uncorrected group (n = 6), arterial blood pH was allowed to decreased without treatment. In the pH-corrected group (n = 5), 14.4 mEq/kg of sodium bicarbonate was given intravenously as a bolus to correct arterial blood pH toward a target arterial pH of 7.40 (dose calculated by the Henderson-Hasselbalch equation).

MEASUREMENTS AND MAIN RESULTS

Arterial blood pH, PCO2, cardiac output, intracranial pressure, and carotid, superior mesenteric, and renal artery blood flow rates were measured at normocapnic baseline and at every hour during hypercapnia for 6 hrs. In the pH-uncorrected group, arterial blood pH decreased from 7.41 +/- 0.03 at normocapnia to 7.14 +/- 0.01 (p < .01 vs. normocapnia) as blood PCO2 increased to 81.2 +/- 1.8 torr (10.8 +/- 0.2 kPa). In the pH-corrected group, arterial blood pH was 7.42 +/- 0.02 at normocapnia and was maintained at 7.37 +/- 0.01 while PaCO2 was increased to 80.3 +/- 0.9 torr (10.7 +/- 0.1 kPa). Significant increases in cardiac output occurred with the initiation of hypercapnia for both groups (pH-uncorrected group: 4.3 +/- 0.6 L/min at normocapnia vs. 6.8 +/- 1.0 L/min at 1 hr [p < .05]; pH-corrected group: 4.1 +/- 0.4 at normocapnia vs. 5.7 +/- 0.4 L/min at 1 hr [p < .05]). However, this increase was sustained only in the uncorrected group. Changes in carotid and mesenteric artery blood flow rates, as a percent of baseline values, showed sustained significant increases in the pH-uncorrected groups (p < .05) and only transient (carotid at 1 hr) or no (superior mesenteric) significant change in the pH-corrected groups. Conversely, significant increases in renal artery blood flow were seen only in the pH-uncorrected group during the last 2 hrs of the experiment (p < .05). Organ blood flow, as a percent of cardiac output, did not change significantly in either group. Intracranial pressure increased significantly in the pH-uncorrected group (9.0 +/- 1.5 mm Hg at normocapnia vs. 26.8 +/- 5.1 at 1 hr, p < .05), and remained increased, while showing no significant change in the pH-corrected group (8.5 +/- 1.6 mm Hg at normocapnia to 7.7 +/- 4.2 at 1 hr).

CONCLUSIONS

Acute hypercapnia, induced within 1 hr, is associated with significant increases in cardiac output, organ blood flow, and intracranial pressure. These changes can be significantly attenuated by correction of blood pH with the administration of sodium bicarbonate, without adverse effects on hemodynamics.

Improved gas exchange performance of the intravascular oxygenator by active blood mixing

The intravascular oxygenator and carbon dioxide removal device (IVOX; CardioPulmonics, Salt Lake City, UT) has been shown to perform 30% of the gas exchange in animals and patients with acute respiratory failure. Among the factors that limit gas exchange is the mass transfer resistance in the blood phase. To determine if a reduction in mass transfer resistance by mixing venous blood can enhance the O2 transfer and CO2 removal by IVOX, a right atrium-pulmonary artery venovenous bypass circuit was used in sheep to model the adult vena cava. A size 9 IVOX (894 fibers with 0.41 m2 surface area, n = 5) was incorporated in the bypass circuit and the blood flow controlled by a roller pump ranging from 1 to 4 l/min. An intra-aortic balloon was placed near the shaft of the IVOX and pulsated at the rate adjusted to best improve CO2 removal (100-120 bpm). O2 transfer and CO2 removal were measured with balloon pulsation on and off at different flow rates. Results showed that blood mixing by pulsation of the balloon caused a 25-49% increase in O2 transfer by IVOX, and this increase remained relatively constant throughout the full flow range. CO2 removal was also increased by up to 35%, but at flows between 3.5 and 4 l/min, the effect of mixing was diminished. It is concluded that reduction in the mass transfer resistance by blood mixing improves gas exchange. Because O2 is more diffusion limited, it is more dependent upon mixing of blood for gas exchange than CO2. More design improvements to incorporate active mixing may further enhance the gas exchange performance of IVOX.

Treatment of malaria in Vietnam with oral artemisinin

In this study, 638 patients with either Plasmodium falciparum or P. vivax malaria were treated with artemisinin (qinghaosu) that was isolated and formulated into tablets and capsules in Vietnam. In all cases, artemisinin treatment resulted in a rapid clearance of parasitemia and fever. Recrudescence rates were highest in those groups receiving treatment for five or less days (50%), but were between 10% and 23% for those groups receiving the drug for 5-10 days. A low recrudescent rate (9.5%) was also found when patients were treated with a combination of artemisinin for three days and tetracycline for five days. Thus, artemisinin represents a useful and economically feasible component of the malaria control program in Vietnam.

Mitomycin-C/5-FU and radiation therapy for locally advanced uterine cervical cancer

To assess the feasibility and effectiveness of combined therapy on locally advanced cervical cancer, we entered 38 patients into a study. The patients were treated with mitomycin-C (10 mg/m2) on Days 1 and 30 and 5-FU (1000 mg/m2) on Days 1 to 4 and Days 30 to 33. In 5 weeks 4500-5000 cGy was given concurrently, followed by radioactive implants. Twenty-six patients had an early-stage disease (IB-IIB) and twelve had a late-stage disease (IIIB-IVA). Eighty-seven percent (33/38) of the patients had a tumor measuring 5 cm or more. The other 5 patients with a tumor size under 5 cm had biopsy-proven positive pelvic nodes; 2 of these 5 patients had a pretherapy hysterectomy. Tumor response, complete (CR) vs partial (PR), was assessed in 36 patients 3 months after completion of therapy. A CR was noted in 80% (29/36) of the patients. The PR status conferred a detrimental effect on the pelvic disease control (PDC), disease-free survival (DFS), and survival (S) while late stage correlated with the development of distant metastases (DM) and a poor DFS. PDC was obtained in 93% (27/29) of the patients who had a CR, as compared to only 43% (3/7) of those with a PR (P = 0.0228). The DFS and S rates were 59 and 77% for patients with a CR and 21 and 19% for those with a PR; respective P values were 0.0340 and 0.0002. Eleven percent (3/26) of the patients with an early stage developed DM, as compared to 50% (6/12) of those with late stage, (P = 0.0016). The DFS rates were 80 and 37% for patients with an early and late stage, respectively (P = 0.0141). Four patients developed transient neutropenia and one had transient thrombocytopenia. The second dose of mitomycin-C was omitted in 4 patients due to persistent neutropenia in 3 and to transfusion-related hepatitis in 1. Two percent (5/21) of the patients who had a staging laparotomy developed wound dehiscence. Three patients developed non-cancer-related small bowel obstruction requiring surgery. We concluded that this combined regimen was well tolerated. Although it was effective in controlling the cancer in the pelvis, this regimen failed to control DM in late-stage patients.

Temporal aggregate size distributions from simulation of platelet aggregation and disaggregation

A modification of the Smoluchowski collision theory for platelet aggregation is proposed with additional kinetic terms to accommodate observed disaggregation behavior. This model, consisting of a set of coupled, nonlinear, first-order differential equations, approximates size distributions with time for normal human platelets in plasma after the addition of a stimulus. Parameters controlling the kinetics of the formation and breakup of aggregates are numerically investigated. The aggregation coefficient, predominant during the aggregation phase, is strongly dependent on both time and aggregating agent doses. For the disaggregation phase, the disaggregation rate constants are a function of aggregate size, with a time-dependent disaggregation coefficient. Numerical results generated by the model are compared with experimental volume-size distribution curves from the literature.

Adenosquamous carcinoma of the cervix: prognosis in stage IB

The outcome of women with adenosquamous carcinoma of the cervix has been a controversial issue. To assess the prognostic significance of this cell type, the medical records of 29 patients with stage IB primary adenosquamous carcinoma of the cervix were reviewed. Twenty-six had cervical tumors measuring 3 cm or less. With a median follow-up of 60 months, the overall disease-free 5-year survival was 85%. Pelvic lymph node metastases were found in three of 19 patients (16%) with stage IB, and periaortic lymph nodes were negative in eight. A log-likelihood chi 2 test comparing lymphatic spread, recurrence rate, and 5-year disease-free survival in patients with stage IB disease and tumors less than 3 cm versus a similar group of 58 patients with pure squamous cell carcinoma of equivalent stage and comparable size treated during the same time disclosed no significant differences in any of the indicators analyzed. We conclude that stage IB adenosquamous carcinoma of the cervix does not differ in its metastatic potential or outcome from the more common pure squamous cell carcinoma.

Dose distribution around a 3.0-mm type 6702 I-125 seed

The 3M Company recently produced a special version of the type 6702 seed for use in animal studies of ocular melanoma. The seed consists of a single I-125 impregnated ion exchange resin sphere encapsulated in a 3.0-mm-long titanium cylinder, as opposed to the normal 4.5-mm cylinder containing from three to five resin spheres. Monte Carlo simulations and measurements show that the dose distribution around the 3-mm capsule differs in places by up to 10% from that of the 4.5-mm seed. In addition, the two seed types differ by 12% in the ratio of dose in tissue along the transverse seed axis to apparent activity. These differences must be taken into account when using these seeds.

Accelerated thrombolysis and reperfusion in a canine model of myocardial infarction by liposomal encapsulation of streptokinase

The aim of thrombolytic therapy for acute myocardial infarction with plasminogen activators such as streptokinase is to lyse the coronary thrombus and reestablish blood flow as quickly as possible so that heart tissue loss is minimized and mortality rates are improved. Streptokinase has been encapsulated in large unilamellar phospholipid vesicles and tested in an animal model of acute myocardial infarction. The time required to restore vessel patency has been reduced more than 50% when compared with findings for free streptokinase. The total dosage of streptokinase required was lower, and smaller remnant thrombi were observed with the encapsulated agent. Results from this initial unoptimized study may have significant implications for further reduction in mortality from heart attacks by therapy with plasminogen activators.

Thrombolysis using liposomal-encapsulated streptokinase: an in vitro study

The clot-lysing ability of streptokinase (SK) was examined using membrane-bound thrombi. Encapsulation of SK in large unilamellar phospholipid vesicles (liposomes) resulted in entrapping approximately 30% of its original activity. Measurements of streptokinase activity for liposomal-encapsulated streptokinase (LESK) indicated little loss of activity or leakage in Tris-buffered saline over a 24-hr period at temperatures of 4 and 23 degrees C. However, incubation of free SK and LESK in platelet-poor plasma (PPP) at 37 degrees C resulted in a decrease of SK activity. The retention of SK activity in LESK was considerably higher than that of unentrapped SK. Clot-dissolving time (CDT) was measured by monitoring the pressure drop during slow filtration in plasma through membrane-bound thrombi. The results indicated that both LESK and free SK were able to activate the fibrinolytic system. Without prior incubation in PPP at 37 degrees C, the CDT of a SK and PPP mixture (SK/PPP) was 10.7 +/- 1.9 min (n = 12), while that of a LESK and PPP mixture (LESK/PPP) was 12.4 +/- 1.7 min (n = 12). The CDT-detected clot-lysing abilities of both SK and LESK were diminished by incubation in PPP, but to different extents. After 15- and 30-min incubations, the CDT of SK/PPP increased significantly to 15.5 +/- 1.5 and 24.1 +/- 2.4 min (n = 5, P less than 0.05), respectively. In contrast, the CDT of LESK/PPP increased to 13.3 +/- 0.8 min (n = 5) after 15 min of incubation and to 16.0 +/- 1.1 min (n = 5, P less than 0.05) after a 30-min incubation. These results suggest that entrapment of SK in liposomes preserves the thrombolytic potential of the plasminogen activator by limiting its exposure to the components of the plasma.

Dynamic evaluation of clotting phenomena in vitro and perfluorochemical oxygen transport across a membrane-bound thrombus model

Citrated platelet-rich plasma was used to occlude 3-microns and 10-microns poresize Nuclepore membranes after recalcification as a thrombus model. Morphologic studies, using both light microscopy and scanning electron microscopy, indicated that over 90 percent of the number of pores available for filtration in hydrophilic and hydrophobic membranes were occluded either partially or completely. Results of transient and steady state pressure drop measurements supported the morphologic studies. It was found that the percentage of oxygen transported across the occluded membranes was greater for filtration of red blood cell suspensions diluted with a perfluorochemical emulsion than that of those diluted with Ringers. The findings in this study suggested that perfluorochemical emulsions might transport oxygen across a thrombus to maintain tissue viability during acute ischemic events.

A diverging gynecological template for radioactive interstitial/intracavitary implants of the cervix

The Syed-Neblett perineal template has been in use at our institution since 1984. We have occasionally encountered problems in inserting the needles through the peripheral rows of the template and have seen significant convergence of the needles cephalad to the template. To solve these problems we have modified the Syed-Neblett template. In the new design, the entrance holes are closer together than in the original template, but they are angled so as to achieve a more compact design while maintaining a dose distribution close to that of the Syed-Neblett design. We have seen significantly fewer clinical problems with this design. In addition, a smaller number of needles achieve the same dose distribution; this simplifies their visualization on radiographs.