Honeycomb micro-textures for light trapping in multi-crystalline silicon thin-film solar cells.

The liquid phase crystallization (LPC) of silicon is an emerging technology for fabricating 10 - 20 µm thin multi-crystalline silicon layers on glass. LPC silicon solar cells exhibit similar electronic performance to multi-crystalline wafer-based devices. Due to the reduced absorber thickness, however, effective measures for light trapping have to be taken. We present tailor-made micro-structures for light trapping at the LPC silicon back-side, whereby a nano-imprinted resist layer serves as a three-dimensional etching mask in subsequent reactive ion etching. Contrary to state-of-the-art random pyramid textures produced by wet-chemical etching, this method allows to produce tailor-made textures independent of grain orientation. Differently shaped micro-textures were replicated in LPC silicon. Absorptance and external quantum efficiency of periodic honeycomb patterns and random pyramids were found to be equivalent. Thus, the method enables the potential to further optimize light trapping in LPC silicon solar cells.

5 × 5 cm² silicon photonic crystal slabs on glass and plastic foil exhibiting broadband absorption and high-intensity near-fields.

Crystalline silicon photonic crystal slabs are widely used in various photonics applications. So far, the commercial success of such structures is still limited owing to the lack of cost-effective fabrication processes enabling large nanopatterned areas (≫ 1 cm(2)). We present a simple method for producing crystalline silicon nanohole arrays of up to 5 × 5 cm(2) size with lattice pitches between 600 and 1000 nm on glass and flexible plastic substrates. Exclusively up-scalable, fast fabrication processes are applied such as nanoimprint-lithography and silicon evaporation. The broadband light trapping efficiency of the arrays is among the best values reported for large-area experimental crystalline silicon nanostructures. Further, measured photonic crystal resonance modes are in good accordance with light scattering simulations predicting strong near-field intensity enhancements greater than 500. Hence, the large-area silicon nanohole arrays might become a promising platform for ultrathin solar cells on lightweight substrates, high-sensitive optical biosensors, and nonlinear optics.

Hemodynamic effects of argon pneumoperitoneum.

The hemodynamic effects of argon pneumoperitoneum were studied to define its possible role as an alternative gas for intraperitoneal insufflation during minimally invasive surgery. Adult pigs were anesthetized and placed on mechanical ventilation. Parameters measured or determined included mean arterial (MAP), pulmonary arterial (PAP), pulmonary arterial wedge (PAWP), right atrial (CVP), and inferior vena cava venous (IVC) pressures, total excretion of CO2 (VCO2), oxygen consumption (VO2), minute ventilation, and arterial blood gases. Also determined were cardiac output, stroke volume, and systemic vascular resistance all indexed to weight (CI, SVI, SVRI). Data were recorded during a 1-h baseline, 2 h of insufflation with argon gas at a constant pressure of 15 mmHg, and 1 h recovery after desufflation. There was no significant change from baseline in VCO2, VO2, MAP, PAP, PAWP, CVP, PaCO2, or arterial pH. Argon pneumoperitoneum significantly increased systemic vascular resistance index and exerted a depressant effect on stroke volume index and cardiac index by 25% and 30% from baseline values, respectively (P < 0.05). Inferior vena cava pressure increased as a reflection of the intraabdominal pressure. Argon insufflation had no effect on respiratory function. Argon gas may not be physiologically inert, and in patients with cardiovascular disease its effects may be clinically important.

Management of large scalp defects with local pedicle flaps.

Recent reports have emphasized free-flap reconstruction for large defects of the scalp and calvarium following resection of tumors, infection, or trauma. In most cases, however, a carefully planned local transposition or rotation flap may be equally effective, and the technical difficulties and donor-site problems associated with microsurgical tissue transfer are then avoided. We present 10 patients whose full-thickness scalp defects covered an average area of 241 cm2, or 27 percent, of the skull surface. Although this series included defects as large as 450 cm2, or 50 percent, of the skull surface area, each was easily managed with a local pedicle flap transfer. Four patients were reconstructed with parietal scalp transfer, four with an occipital scalp flap, and two with temporal scalp transfer. The technique and results are discussed.

A new nerve pedicle for finger sensibility: the dorsal digital sensory nerve.

Restoration of sensibility to the traumatized finger can be a difficult problem. Two patients with insensibility to the volar distal finger after trauma underwent delayed digital nerve repair. In the first patient, the dorsal branch of the radial proper digital nerve was approximated to the distal stump as a pedicle to span a 12-mm gap resulting from neuroma excision. The second patient had a 14-mm defect after scar-tissue excision 8 months following primary neurorrhaphy after trauma. Reconstruction was performed by approximating the dorsal branch of the radial proper digital nerve to the distal stump. Both patients had fingertip sensibility restored 1 year postoperatively, as documented by two-point discrimination. Anatomic dissections of 12 fresh cadaver fingers revealed a consistent pattern. Of the 24 proper digital nerves dissected, 23 had a distal dorsal sensory branch arising at the midportion of the proximal phalanx. The dorsal branch-vascularized pedicle of the proper digital nerve has not been described previously as a method for restoring finger sensibility in cases not amenable to primary neurorrhaphy. We believe this technique should be added to the repertoire of the practicing hand surgeon.

Upper eyelid ptosis correction by a revised tarsal resection technique.

Many techniques have been developed for the correction of eyelid ptosis. A new tarsal plate resection technique is described for use in cases of minimal ptosis with fair to good levator function. The procedure involves a horizontal lenticular excision of the tarsal plate, placed so that equal amounts of tarsus remain above and below the excision. The height of the excision is equal to the amount of ptosis correction desired, as determined in the preoperative examination. This precision in surgical correction is the chief advantage of the procedure. The technique also spares Müller's muscle, thus retaining the lid-elevating action of that muscle. Good results have been achieved in 6 patients, some showing excellent results after nine years.

Aging and cellular maturation cause changes in ubiquitin-eye lens protein conjugates.

The eye lens is a useful tissue for studying phenomena related to aging since it can be separated into differentially aged or matured zones. This work establishes correlations between ubiquitin-lens protein conjugating capabilities and age, as well as the stage of maturation of bovine lens tissue. When exogenous 125I-ubiquitin was combined with supernatants of epithelial (least mature), cortex, and core (most mature) tissue, ATP-dependent conjugation of 125I-ubiquitin to lens proteins was most effective with the epithelial tissue preparation. Conjugate formation was greatest when lenses were obtained from young animals. Supernatants from cultured bovine lens epithelial (BLE) cells conjugated more 125I-ubiquitin to lens proteins than any tissue preparation. In all cases the predominant conjugates formed in these cell-free assays were of high molecular mass, although conjugates with masses in the 25-70 kDa range were also observed. Lens tissue and cultured BLE cell preparations were also probed with antibodies to ubiquitin to detect in vivo ubiquitin-lens protein conjugates. There was more free ubiquitin and ubiquitin conjugates in tissue from young as compared with older lenses. The greatest levels of conjugates were observed in cultured BLE cells. Specificity in the ubiquitination system is indicated since some of the conjugates formed in vivo appear identical to those formed in the cell-free assays and in reticulocytes using exogenous 125I-ubiquitin. Upon development and maturation of lens tissue (i.e., core as opposed to epithelium), there is accumulation of lower molecular mass conjugates.

Myocardial contusion in the stable patient: what level of care is appropriate?

To evaluate the significance of myocardial contusion, we evaluated 243 stable patients hospitalized for blunt chest trauma between 1982 and 1986. The groups were identified according to results of radionuclide angiography, mean injury severity score (ISS), and outcome. Group I (n = 71; mean ISS = 12.7) patients were those without myocardial contusion by radionuclide angiography. Two patients with cardiac complications were in this group. The patients with myocardial contusion were divided into two groups. Group II (n = 69; ISS = 19.5) patients had myocardial contusion as an isolated injury, and group III (n = 103; ISS = 30.9) patients had myocardial contusion and injury to at least one other organ system. Three patients from group II had cardiac complications. Eleven patients from group III had cardiac complications. There were no significant differences between the cardiac complication rate in the three groups, and each complication was present when the patient arrived in the emergency department. The predicted mortality rate based on ISS was 10% to 20% for patients with myocardial contusion, whereas the observed mortality rate for the groups (II and III) overall was 0.58%. We conclude that in the stable trauma patient myocardial contusion (1) does not by itself increase the risk of complication, (2) does not necessitate intensive care unit monitoring, (3) should be devalued when computing ISS scores, (4) may account for lengthy and often unnecessary hospitalization, and (5) in patients at risk for complications may be identified by ECG abnormalities on arrival to the emergency department.

Intracellular protein degradation in cultured bovine lens epithelial cells.

Although several proteases have been identified in homogenates of cultured epithelial cells of the eye lens and in lens tissues, there is little information regarding intracellular protein degradation in intact lens cells in vitro. Cultured lens cells may be useful in the study of intracellular protein degradation in the lens, a tissue with a wide range of protein half-lives. This is of interest because alterations in protein turnover in the lens have been implicated in cataract formation. This study examines intracellular protein degradation in cultured bovine lens epithelial cells (BLEC). Cell cultures were incubated with radiolabeled leucine to label intracellular proteins. Protein degradation was measured by monitoring the release of trichloroacetic-acid-soluble radioactivity into the culture medium. The average half-life of long-lived proteins (half-life greater than 50 h) was typically about 57 h in serum-supplemented medium. Average rates of degradation of long-lived proteins increased by up to 73% when fetal bovine serum was withdrawn from the culture medium. Serum had no effect on the degradation of short-lived proteins (half-life less than 10 h). Degradation of long-lived proteins in the presence and absence of serum was further studied in cultured BLEC from population doubling level (PDL) 2 to 43. Average half-life of proteins in serum-supplemented medium was 52 to 58 h and did not vary significantly as a function of PDL. Degradation rates in serum-free medium increased approximately twofold up to PDL 7, but returned by PDL 25 to original levels, which were maintained through PDL 43.

Protease activities in cultured beef lens epithelial cells peak and then decline upon progressive passage.

Beef lens cells in culture are readily obtained and provide many opportunities to study phenomena related to cell differentiation and maturation, environmental stress, disease, and perhaps mechanisms of transformation. Although altered rates of proteolysis are known to accompany these phenomena, the proteolytic activities available in cultured beef lens epithelial cells have not been documented. In this work are documented the specific activities, based on protein and DNA content, of neutral exo- and endopeptidase, cathepsins B- and D-like enzymes and acid phosphatase in lens epithelial cortical and core tissue and in cultured epithelial cells at passages 1-43. Maximal activity of each protease occurs almost routinely at passage 5 or 9, reaching values of approx. 1400-, 0.77-, 4520-nmol min-1 per mg protein for neutral exopeptidase (passage 5), neutral endopeptidase (passage 5) and cathepsin B (passage 5) respectively, and 7.1 micrograms trichloroacetic acid soluble peptide min-1 per mg protein for cathepsin D (passage 15). On a microgram-1 DNA basis, the maximal specific activities for the same enzymes were 48 (passage 5), 0.03 (passage 5), 283 (passage 9), and 0.5 (passage 9) respectively. In subsequent passages, the specific activities declined to values which were similar to or lower than the specific activities observed for these proteases in lens epithelial tissue.

Lens proteins are substrates for the reticulocyte ubiquitin conjugation system.

In the aged lens postsynthetically altered molecules comprise the majority of lens proteins. Many proteolytic activities have been observed in lens supernatants. Since damaged or altered proteins are usually selectively and rapidly degraded in other cells and tissues, the accumulation of these species in the lens seemed enigmatic. Initiation of proteolysis has been studied most extensively in reticulocytes and ts 85 cells. In these systems proteolysis is absolutely ATP dependent, occurs effectively on high molecular weight substrates and, at least for a majority of proteolytic reactions, requires conjugation of ubiquitin to putative substrates. It seemed plausible that the accumulation of high molecular weight protein aggregates in older lenses might be due to the attenuated function of these ubiquitin- and ATP-dependent components in the initial committing processes of proteolysis. This research shows that: ubiquitin is present in the lens; lens proteins are conjugated to 125I-ubiquitin using reticulocyte conjugating systems; the reaction is ATP dependent; proteins from lens epithelium/outer cortex and core form different ubiquitin conjugates; lens proteins compete with lysozyme and reticulocyte proteins for the ubiquitin conjugating apparatus; most of the conjugates are of very high molecular weight; there is a temporal nature to the pattern of conjugates observed; and the ubiquitin conjugation system shows extreme selectivity.

The eye lens has an active ubiquitin-protein conjugation system.

Using exogenous 125I-ubiquitin, ubiquitin-lens protein conjugation was observed with supernatants of cultured rabbit lens epithelial cells and lens cortex tissue. Conjugation was ATP-dependent with the greatest variety and amount of conjugates larger than 150 kDa. In vivo production of ubiquitin-protein conjugates in cultured rabbit and beef lens epithelial cells and rabbit lens tissues of different developmental age was established using immunological detection. There were limited similarities between conjugates found in youngest as opposed to oldest tissue. Cultured rabbit cells contained 27 pmol/mg free ubiquitin and 18 pmol/mg conjugated ubiquitin. Levels of free ubiquitin in lens tissue epithelium, cortex, and core were 36, 5, and 5 pmol/mg, respectively. There were only 2 pmol/mg conjugated ubiquitin in each of these tissues. Hydrolysis of 125I-ubiquitin was catalyzed by supernatants of cultured lens cells, beef and human lens tissues, and reticulocytes. Degradation was greatest in epithelial tissues, and least in core. This corroborates studies which show that proteolytic capabilities are attenuated in older tissue. Decreased initiation of proteolysis by ubiquitination as well as diminished proteolysis in older lens tissue may be related to the accumulation of damaged proteins in aging lens tissue.

A novel dipeptidyl peptidase II from the porcine ovary. Purification and characterization of a lysosomal serine protease showing enhanced specificity for prolyl bonds.

A variant form of dipeptidyl peptidase II (DPP II), initially reported under the name of "DPP V" (Eisenhauer, D. A., and McDonald, J. K. (1982) Fed. Proc. 41, 507), was detected in aqueous extracts of porcine ovaries on the basis of a markedly enhanced action on prolyl bonds. This porcine form of DPP II, which was most sensitively assayed on Phe-Pro-2-naphthylamide (Phe-Pro-NNap), was purified 1400-fold to a specific activity of 28 mumol/min/mg of protein (pH 6.0, 37 degrees C) from an aqueous extract of hog ovaries taken during pregnancy, when ovarian levels of DPP II are some 3- to 8-fold higher. Purification involved ammonium sulfate fractionation, molecular exclusion chromatography, chromatofocusing, affinity chromatography on concanavalin A-Sepharose 4B, and high performance ion exchange chromatography. The purified enzyme, which was apparently electrophoretically homogeneous at pH 3, 7, and 8.8 (pI = 5.0), was shown to be an Mr = 110,000 glycoprotein containing about 2% carbohydrate (primarily mannose) and less than 1% sialic acid, and to consist of two noncovalently linked Mr = 54,000 subunits. A serine catalytic mechanism was supported by inhibitor studies and by common mobilities seen during electrophoresis for (histochemically detected) Phe-Pro-arylamidase activity and the [14C]diisopropyl fluorophosphate-labeled enzyme. In the standard fluorometric assay at 37 degrees C, Phe-Pro-NNap (0.2 mM) was hydrolyzed optimally at pH 6.0 (Km = 45 microM; kcat = 54 s-1). In comparison to the rate seen on Lys-Ala-NNap, the usual DI P II assay substrate, rates seen on Phe-Pro-, Lys-Pro-, and Arg-Pro-NNap were about 8-, 4-, and 2-fold higher, respectively. No action occurred on N-blocked derivatives or on Pro-NNap. Action on oligopeptides appeared to be limited to tripeptides, in particular those containing proline or alanine in the P1 position, i.e. Phe-Pro-Ala (100%), Lys-Ala-Ala (35%), Ala-Ala-Ala (33%), and Gly-Pro-Ala (26%). Only a trace of activity was seen on Phe-Pro-Ala-Ala, and none on Z-Phe-Pro-Ala or Ala-Ala-Ala-OMe. Evidence for the lysosomal localization of DPP II included sedimentability and latency and its distribution, coincident with acid phosphatase, in two distinct isopycnic regions following equilibrium density centrifugation. Lysosomal heterogeneity was suggested by this dual isopycnic banding.(ABSTRACT TRUNCATED AT 400 WORDS)

Partial purification and characterization of an ovarian tripeptidyl peptidase: a lysosomal exopeptidase that sequentially releases collagen-related (Gly-Pro-X) triplets.

The pregnant hog ovary is a rich source of a novel exopeptidase that catalyzes the release, at pH 5.0, of collagen-related (P3-P2-P1) "triplets" such as Gly-Pro-Met, Gly-Pro-Arg, and Gly-Pro-Ala from arylamide derivatives, provided the N termini are unsubstituted. Corresponding derivatives of related (P2-P1) dipeptides (Pro-Met, Pro-Ala) or (P1) amino acids (Met, Arg, Ala) are not attacked. The enzyme was purified 58-fold from a detergent extract of a water-extracted tissue residue. Activity was determined on Gly-Pro-Met-2-naphthylamide at pH 4.5 and 37 degrees C (Km 0.45 mM; Vmax 722 nmoles/min/mg protein). The responsible Mr 55,000 exopeptidase, termed "tripeptidyl peptidase", forms high-Mr aggregates, belongs to the serine catalytic class, and has a lysosomal localization. Gly-Pro-Ala triplets were released sequentially at pH 5.0 from a Mr 14,000 polypeptide, poly(Gly-Pro-Ala-). When this reaction was coupled to that of homologous dipeptidyl peptidase II, the liberated tripeptides were reduced to dipeptides and free amino acids: (Gly-Pro-Ala)n----nGly-Pro-Ala----nGly-Pro + nAla.

Identification of a cathepsin b-like protease in the crevicular fluid of gingivitis patients.

Crevicular fluid from gingivitis patients contains significant levels of a cysteine protease which was characterized as the lysosomal protease cathepsin B, as judged by substrate specificity, thiol dependence, pH optimum, kinetic parameters, pH stability, and inhibitor sensitivities. A highly-sensitive fluorometric assay procedure was used to establish the mean level of cathepsin B activity for 25 gingivitis patients.