bluuebunny/crossref_metadata_2025 huggingface dataset:
The targeting information of the mitochondrial outer membrane isoform of cytochrome b5 is contained within the carboxyl‐terminal region
Authors: De Silvestris Marcella , D'Arrigo Antonello , Borgese Nica
Published: July 2002

Two isoforms of mammalian cytochrome b
5, which have homologous cytosolic amino‐terminal catalytic domains, are located one on endoplasmic reticulum (ER b
5) the other on mitochondrial outer membranes (OM b
5). A cDNA coding for the previously unknown carboxyl‐terminal domain of OM b
5 was cloned and a chimera between the catalytic domain of ER b
5 and the carboxyl‐terminal region of OM b
5 was expressed in cultured mammlian cells. The chimera localized to mitochondria, indicating that the carboxyl‐terminal 43 amino acids of OM b5 contain sufficient information to target the catalytic domain of ER b
5 to the mitochondrial outer membrane.
Does DNA acid fixation produce left‐handed Z structure?
Authors: Tajmir-Riahi H.A. , Neault J.F. , Naoui M.
Published: July 2002

The effects of acetic acid (HCOOCH3) on the solution structure of calf‐thymus DNA are studied at pH 7.3−2.5 with acid/DNA(P) (phosphate) molar ratios (r) of , 1, 2, 10, 20 and 40. Fourier Transform infrared (FTIR) difference spectroscopy is used to establish correlations between spectral changes and base protonation, DNA conformational transition and structural variations of the acid‐DNA complexes in aqueous solution. The FTIR difference spectroscopic results showed that protonation of cytosine and subsequent unpairing of the G‐C base pairs begins at pH 4‐3 and continues up to pH 2.5, where a complete base separation and base unstacking occur. Similarly, protonation of A‐T base pairs starts at pH 4‐3 and is completed at pH 2.5, where base separation and base unstacking are observed. The protonation of the G‐C base pair leads to the formation of Hoogsteen‐type H‐bonding, before a complete G‐C disruption. The biopolymer protonation leads to the formation of several non‐B‐DNA structures, including left‐handed Z conformation.
Radiation inactivation analysis of H+‐pyrophosphatase from submitochondrial particles of etiolated mung bean seedlings
Authors: Jiang Shih Sheng , Yang Su Jing , Kuo Soong Yu , Pan Rong Long
Published: July 2002

Radiation inactivation analysis was employed to determine the functional masses of enzymatic activity and proton translocation of H+‐pyrophosphatase from submitochondrial particles of etiolated mung bean seedlings. The activities of H+‐pyrophosphatase decayed as a simple exponential function with respect to radiation dosage. D
37 values of 6.9±0.3 and 7.5±0.5 Mrad were obtained for pyrophosphate hydrolysis and its associated proton translocation, yielding molecular masses of 170±7 and 156±11 kDa, respectively. In the presence of valinomycin and 50 mM KCl, the functional size of H+‐pyrophosphatase of tonoplast was decreased, while that of submitochondrial particles remained the same, indicating that they are two distinct types of proton pump using PPi as their energy source.
Reduction of the cesarean delivery rate in Ecuador
Authors: Sloan N.L. , Pinto E. , Calle A. , Langer A. , Winikoff B. , Fassihian G.
Published: July 2002

Objective: This quasi‐experimental study tested a method to safely reduce the rate of cesarean delivery in Ecuador. Method: Hospital policy was modified to provide co‐management for cesarean candidates at the major maternity hospital in Quito. Cesarean rates before (n=14 743) and after (n=12 351) the intervention were compared by chi‐square and multiple logistic regression with other major maternity hospitals (before, n=12 514; after, n=9590). Characteristics of cesarean candidates who had vaginal or cesarean deliveries in the intervention hospital were compared by chi‐square (n=1584). Result: Cesarean rates declined by 4.5% (P<0.001) in the intervention hospital. A smaller (2.1%, P<0.01) reduction occurred in the other major public hospital in Quito where students of the co‐principal investigator attempted to reduce cesarean delivery. Cesarean rates were unchanged in the public maternity hospitals of other major cities. Conclusion: Case co‐management, a simple, locally appropriate, and inexpensive intervention, safely reduced surgical delivery, hospital stay and cost of care.
Effect of Glucose and NH4+ Levels on Poly(β‐hydroxybutyrate) Production and Growth in a Continuous Culture of Alcaligenes eutrophus
Authors: Gostomski Peter A. , Bungay Henry R.
Published: July 2002

The effect of glucose and NH4+ concentrations on poly(β‐hydroxybutyrate) (PHB) production was investigated with an NH4+:pH‐auxostat. Reactor concentrations were controlled between 1.5 μM and 10 mM for NH4+ and between 1 and 20 g/L for glucose. Dilution rates between 0.07 and 0.24 h−1 were achieved, but little correlation was observed between nutrient concentrations or dilution rate on PHB concentration, which varied between 10 and 20% of the cell dry weight. However experiments demonstrated that glucose levels above 1 g/L affected the growth rate when the culture was NH4+‐limited, implying a non‐Monod growth model. The residual biomass yield on glucose was estimated to be 0.5 g of cells/g of glucose and was independent of dilution rate. However, the estimated yield on NH4+ decreased linearly with increasing dilution rate between 9 and 6 g of cells/g of NH4+. A qualitative model for PHB formation based on the cellular response to the environmental stress of low NH4+ concentrations is discussed.
Asthma and allergy: the significance of chronic conditions for individual health behaviour
Authors: Bolin K. , Lindgren B.
Published: July 2002

Background: In health economics, health is regarded as part of an individual's human capital. As such it depreciates over time, and investments in health are made in order to keep the stock of health capital at the desired level. Using this framework for analysis of health‐related behaviour and Swedish panel data, we examined whether the presence of asthma or allergy affects perceived health and investments in health.

Methods: A set of panel data for approximately 3800 individuals interviewed repeatedly in 1980/81, 1988/89, and 1996/97 was created from the Swedish biannual survey of living conditions. Self‐assessed health was chosen as the indicator of health capital and the reported number of sick days as the indicator of health investment. The presence of asthma or allergy, age, wage rate, wealth, marital status, number of children, exercise and smoking habits, gender, and geographic location of household were all chosen as explanatory variables. An ordered probit model was estimated for the health equation and a Poisson model for the investment equation.

Results: We found that both asthmatics and those who suffer from allergy invested more in their health than the general population. We also found that asthmatics reported significantly lower self‐assessed health than the general population, while those who suffered from allergy did not differ significantly from the general population regarding their self‐assessed health.

Conclusion: The human capital approach was found suitable for studying the impact of asthma and allergy on individual health behaviour. Health policy measures, which reduce the individual's costs of investing in his or her health, would improve health levels. Because asthmatics were found less healthy than those suffering from allergy, the potential gains would be larger for patients with asthma than for patients with allergy. The issue of whether this would be a cost‐effective policy or not would require a different design and, hence, could not be solved within the present study.
Effect of end‐of‐day irradiations on polyamine accumulation in petal cultures of Araujia sericifera
Authors: Moysset Luisa , Trull Olga , Santos M. Asunción , Simón Esther , Torné Josep M.
Published: July 2002

We have studied photoperiodic control and the effect of phytochrome photoconversion at the end‐of‐day (EOD) on polyamine (PA) accumulation in petal explants of Araujia sericifera. Petals from immature flowers were cultured under long (LD) and short (SD) days. Light was provided by Gro‐lux fluorescent lamps (90–100 µmol m−2 s−1). Red (R), far red (FR), red followed by far‐red (R‐FR) and far‐red followed by red (FR‐R) light treatments were applied daily at the end of the photoperiod. The free and bound putrescine (Put), spermidine (Spd) and spermine (Spm) fractions in petal explants were determined 40 days after the beginning of the culture. We also aimed to clarify the involvement of PA changes by using two inhibitors of PA biosynthesis: D‐l‐α‐difluoromethylarginine (DFMA) and methylglyoxal bis(guanylhydrazone) (MGBG). We found PA accumulation to be under photoperiodic control, and the inhibitory effect of DFMA on this accumulation suggests that arginine decarboxylase (ADC) is the major pathway for Put biosynthesis. Polyamine levels were higher under LD, mainly as a result of the accumulation of free and bound Put. FR‐EOD treatment, which dramatically reduced the R : FR ratio after LD, increased the accumulation of PA, mainly as free Put and free and bound Spd. Sequential R‐FR and FR‐R‐EOD treatments strongly increased bound Spd. The concentration of MGBG used increased total PA accumulation, mainly as Put. However, all EOD light treatments dramatically reduced Put accumulation in the presence of MGBG. This may be due to a dual role of FR light in PA accumulation: (1) FR per se stimulates PA production, probably via ADC, and (2) in the presence of MGBG, FR inhibits Put accumulation, probably via ethylene production.
Preparation, biochemical characterization and biological properties of radiolabelled N-alkylated deoxynojirimycins
Authors: MELLOR Howard R. , NOLAN James , PICKERING Lea , WORMALD Mark R. , PLATT Frances M. , DWEK Raymond A. , FLEET George W.J. , BUTTERS Terry D.
Published: July 2002

We have reductively alkylated deoxynojirimycin imino sugars using sodium cyanoborohydride to provide an efficient means of generating a series of N-alkylated compounds containing 4–18 carbon side chains. The yields were greater than 90% using a variety of aldehydes of different chain lengths, and after purification were >95% pure using 1H-NMR. Radiolabelled compounds were prepared using sodium cyanoborotriti-ide to selectively label the first carbon atom in the alkyl chain and used in protein-binding and cell- and tissue-uptake experiments. Protein binding was chain-length-dependent with compounds of intermediate chain length (C9—C12), demonstrating an equal distribution between the aqueous and protein-bound phase. The extent of cell uptake also increased proportionally with increased chain length in a time-dependent manner. When administered to mice, the longer alkyl-chain compounds showed reduced absorption from the intestine and a marked deposition of compound in the liver and brain, suggesting that the more hydrophobic compounds were poorly cleared by the major tissues. In tissue-culture cells compounds with 8 or fewer carbon atoms were non-toxic and had CC50 (the concentration at which the number of cells or cell proliferation is reduced by 50%) values greater than 1mM. Compounds with chain lengths above C8 showed a chain-length-dependent increase in cytotoxicity. N-alkylated deoxynojirimycins (C4—C18) were evaluated for their inhibitory effects on ceramide-specific glucosyltransferase and glycoprotein-processing α-glucosidase. Increasing the alkyl chain length had little effect on α-glucosidase activity, but inhibition of ceramide-specific glucosyltransferase increased 10-fold when C4 and C9—C18 compounds were compared. Overall these data provide further definition of the molecular features of alkylated imino sugars that influence tissue selectivity and efficacy for cellular enzyme inhibition.
Different mechanisms for cellular internalization of the HIV‐1 Tat‐derived cell penetrating peptide and recombinant proteins fused to Tat
Authors: Silhol Michelle , Tyagi Mudit , Giacca Mauro , Lebleu Bernard , Vivès Eric
Published: July 2002

Translocation through the plasma membrane is a major limiting step for the cellular delivery of macromolecules. A␣promising strategy to overcome this problem consists in the chemical conjugation (or fusion) to cell penetrating peptides (CPP) derived from proteins able to cross the plasma membrane. A large number of different cargo molecules such as oligonucleotides, peptides, peptide nucleic acids, proteins or even nanoparticles have been internalized in cells by this strategy. One of these translocating peptides was derived from the HIV‐1 Tat protein. The mechanisms by which CPP enter cells remain unknown. Recently, convincing biochemical and genetic findings has established that the full‐length Tat protein was internalized in cells via the ubiquitous heparan sulfate (HS) proteoglycans. We demonstrate here that the short Tat CPP is taken up by a route that does not involve the HS proteoglycans.
Trisomy 6 in Merkel cell carcinoma: a recurrent chromosomal aberration
Authors: Gancberg D , Feoli F , Hamels J , De Saint‐Aubain N , André J , Rouas G , Verhest A , Larsimont D
Published: July 2002

We retrospectively investigated 17 cases of primary and metastasizing Merkel cell carcinomas (MCC) from 14 patients using chromosomal in‐situ hybridization (CISH) to study the occurrence of trisomy 6 in these lesions.

Methods and results

Histological diagnosis on all tumour samples was obtained on haematoxylin and eosin stained sections. Immunohistochemistry was performed with antibodies against pancytokeratin (CAM 5.2), cytokeratin 20 (CK20), MIC2 antigen (CD99), neuron‐specific enolase (NSE), and chromogranin A (chrA). Sections (4 µm) of the paraffin‐embedded tumours were analysed with α‐satellite centromeric probes for chromosome 6 or 17 using CISH. The signal was amplified by the Tyramide Signal Amplification (TSA) assay. Immunohistochemically, the tumours showed the same general epithelial neuroendocrine pattern: 11/13 expressed cytokeratin 20, and 47% exhibited trisomy 6, with no significant difference between primary and metastatic lesions. Incomplete follow‐up data did not allow us to establish a prognostic value of trisomy 6, however, this aberration might be an additional diagnostic tool in distinguishing MCC from other small round blue cell tumours.

Conclusions

CISH seems to be a promising adjunctive method to diagnose Merkel cell carcinoma. Trisomy 6 should be investigated more closely in these cases, as has been done for chromosomes 1 and 11. Of particular interest would be identification of modifications in proto‐oncogene(s) located on chromosome 6.
The impact of a practice development project on the quality of in‐patient small group therapy
Authors: Taylor R. , Coombes L. , Bartlett H.
Published: July 2002

In 1993 a mental health service in South‐east England initiated a practice development project that aimed at continuously improving the quality of in‐patient small group therapy provided within its four acute wards. From the outset it was intended that the project and the practice it focused on should be robust and research based. In support of this an evaluative study was carried out in 1998. The evaluation covered a 6‐month period and coincided with concerns being reported elsewhere about the adequacy of therapeutic activity within acute psychiatric settings across the country. Data collected for the evaluation focused on the quality dimensions of effectiveness, relevance to need, social acceptability, accessibility, efficiency and economy, and equity. Quantitative and qualitative methods were deployed and data were collected at three points in time over the evaluation period to provide a picture of change within each ward. The quantitative data gathered were mainly obtained through two self‐report questionnaires that were developed specifically for the study. Both instruments were tested and found to have a high degree of internal consistency. The qualitative data gathered were collected using semistructured interviews. Analysis of the qualitative and quantitative data sets indicated that practice quality diminished rather than improved during the 6‐month study period. Factors that emerged from the data as having influenced this outcome were: increases in ward team’s overall workload, inadequate staffing levels and changes in expectations placed on those providing small group therapy. The findings are consistent with a national trend of deteriorating quality in in‐patient care and point to some of the limitations of action learning as a practice development method. They also point to service factors that work against effective practice development.
Carcinoid tumour of the orbital muscles: A rare occurrence
Authors: Khaw Pearly , Ball David , Duchesne Gillian
Published: July 2002

Malignant carcinoid tumours are rare and usually follow an indolent course. Metastases from these tumours are uncommon, and usually involve bone, liver and lymph nodes. Orbital metastases have rarely been described, and generally involve the choroid rather than orbital structures. Our knowledge of the response of these tumours to radiotherapy is extremely limited. Two cases of orbital metastases treated with radiotherapy are presented here and the literature on the efficacy of palliative radiotherapy for this tumour is reviewed. Recommendations are made regarding an effective radiotherapy regimen for treating orbital metastases from malignant carcinoid tumours.
Gastro‐oesophageal reflux: Clinical profiles and outcome
Authors: Lee WS , Beattie RM , Meadows N , Walker‐Smith JA
Published: July 2002

Objectives: To assess the clinical features, investigations and outcome of 69 children (40 males, 29 females) with gastro‐oesophageal reflux (GOER) referred to a tertiary referral centre in paediatric gastroenterology.

Methods: A study of all patients with significant GOER seen at the Paediatric Gastroenterology Unit, Queen Elizabeth Hospital for Children, Hackney Road, London, between December 1994 and August 1995.

Results: The median age at referral was 16 months. Presenting symptoms were recurrent vomiting (72%), epigastric and abdominal pain (36%), feeding difficulties (29%), failure to thrive (28%) and irritability (19%). Continuous 24‐h lower oesophageal pH studies performed in 57 children showed 20 (35%) had a reflux index of between 10% to 20%, 14 (25%) had a index > 20%, and six (11%) had a postprandial reflux index > 10%. Reflux was shown in 38 (62%) of 62 children who underwent barium studies. None had significant anatomical abnormalities, but in the 22 children who had a negative barium studies, six had severe reflux (reflux index > 20%). Upper gastrointestinal endoscopy performed in 47 children showed reflux oesophagitis in 29 (62%), oesophageal ulceration in three, and Barrett’s oesophagus in one. All of the children were treated with standard medical therapy. Sixty‐six per cent were able to discontinue medication within 12 months and remained well. Four children (6%) required Nissen’s fundoplication for failure to respond to medical therapy.

Conclusions: Most infants with GOER have an uncomplicated course. False negative results were noted in both pH monitoring and barium meal. Up to 80% of children, with therapy, will improve within 12 months.
Patient controlled analgesia in children and adolescents: a randomized controlled trial
Authors: Peters J.W.B , Bandell Hoekstra I.E.N.G , Huijer Abu‐Saad H , Bouwmeester J , Meursing A.E.E , Tibboel D
Published: July 2002

In children, patient controlled analgesia (PCA) and continuous infusion (CI) of morphine are well established methods of relieving postoperative pain. This study was designed to assess the efficacy of PCA plus background infusion (BI) (15 μg·kg−1·h−1 and bolus doses of 15 μg·kg−1 with a lock‐out interval of 10 min) with CI (20 to 40 μg·kg−1·h−1) in terms of analgesia, morphine needs and side‐effects. A stratified randomized controlled trial was carried out. 47 children aged 5–18 years undergoing major elective lower/upper abdominal or spinal surgery were allocated. The magnitude of surgery was assessed by the Severity of Surgical Stress scoring (SSS) system. Pain was assessed by self‐report every three h. Side‐effects compatible with morphine as well as morphine consumption were recorded. Morphine consumption was significantly increased in the PCA group compared with the CI group. Moreover, morphine consumption was associated with SSS, independent of the technique of administration. There were no significant differences between groups in pain scores or in the incidence of side‐effects.
How to select patients suitable for transurethral microwave thermotherapy: a systematic evaluation of potentially predictive variables
Authors: WaldÉN  , Dahlstrand  , SchÄfer  , Pettersson
Published: July 2002

Objective

 To identify clinical variables useful in predicting outcome after transurethral microwave thermotherapy (TUMT) of the prostate with Prostasoft v. 2.0.

Patients and methods

 Thirty‐eight men with symptomatic benign prostatic hyperplasia (BPH) were treated with TUMT using the Prostatron device with the low‐energy (v. 2.0) software. Before and 6 months after treatment symptoms were evaluated using the Madsen‐Iversen (M‐I) symptom score, a clinical examination and suprapubic pressure‐flow measurement, free urinary peak flow rate (Qmax ) and determination of post‐void residual urine volume (PVR). Bladder outlet obstruction was assessed from urodynamic pressure‐flow studies using the classification of Abrams and Griffiths, the obstruction grading of Schäfer, and calculation of other published factors, e.g. the urethral resistance, an obstruction index and the detrusor adjusted mean passive urethral resistance factor (DAMPF). Categories of M‐I score (total, irritative and obstructive), PVR and Qmax were investigated to determine whether any could predict the outcome after low‐energy TUMT. The values after treatment and changes in Qmax , M‐I score and PVR were used as efficacy variables.

Results

 Variables describing infravesical obstruction had predictive characteristics that may be useful in selecting patients for TUMT v. 2.0 and significantly better results were obtained in patients with a low to moderate obstruction as graded using the DAMPF classification of obstruction. The results also indicated that patients with a high irritative M‐I score or a Qmax of 7–14 mL/s were those who fared best after TUMT.

Conclusions

 Variables expressing the obstruction grade seem to be useful in predicting outcome after TUMT (v. 2.0). Patients with a high obstruction index are probably unsuitable for TUMT (v 2.0).
Bladder cancer recurrence by implantation of exfoliated cells: is γ‐linolenic acid an effective tumoricidal agent?
Authors: Solomon  , Jennings  , Foley  , Birch  , Cooper
Published: July 2002

Objective

 To compare the tumoricidal efficacy of meglumine γ‐linolenic acid (MeGLA), mitomycin C, epirubicin and water on two urothelial cell lines, and to establish the effect of serum protein levels derived from bladder cancer resection craters on the action of these agents.

Materials and methods

 The human urothelial cell lines MGHU‐1 and RT112 and their drug‐resistant variants were exposed to short pulses of aqueous MeGLA, mitomycin, epirubicin and water. Both adherent and suspended cells were exposed to these agents. The MTT viable biomass assay and a clonogenic assay were used to establish tumoricidal efficacy. These experiments were then repeated to assess the effect of added serum proteins on the test results. Estimates of protein in the waste irrigation fluid from 10 patients undergoing transurethral resection of bladder tumour (TURBT) were used to select the quantity of protein used in the study, to establish the clinical relevance.

Results

 MeGLA caused >95% reduction in the residual viable biomass of adherent cells, compared with <50% reduction with any other agent. Both epirubicin and mitomycin were as effective as MeGLA in preventing colony formation from suspended drug‐sensitive (parental) cells. However, using multidrug‐resistant (MDR) cell lines, only MeGLA prevented any colony formation, although counts were greatly reduced by mitomycin and epirubicin. Water was least effective as a tumoricidal agent on both adherent and suspended cells. On the latter, water was markedly inactivated by adding 5% serum. TURBT waste irrigation fluid was found frequently to contain such quantities of serous fluid contamination, as shown by albumin estimates in waste fluid from 10 consecutive patients undergoing this procedure.

Conclusion

 MeGLA is an effective tumoricidal agent against both parental and MDR cell lines. Its efficacy is maintained in the presence of clinically relevant serum contamination.
The choice of an H1‐antihistamine for the 21st century
Authors: Howarth P. H.
Published: July 2002

It is clear that as a starting point an H1‐antihistamine for the 21st century should be effective, but non‐sedative and non‐cardiotoxic. In addition it is desirable that an oral H1‐antihistamine should be rapidly absorbed so that it can be distributed to the target organ sites, be readily bioavailable, and have a half‐life sufficient to enable once daily dosing and to have clinical effect throughout a 24‐h dosing interval. The effect of the drug should be maintained with repeated dosing. To give confidence in drug administration it should require no dosage adjustment in renally or hepatically impaired individuals and have no significant drug interactions, especially in view of past experience with drugs such as ketoconazole and macrolide antibiotics that may modify hepatic metabolism. In addition to these considerations there is a desire for a designer molecule that has activity over and beyond H1‐receptor blockade, thus providing an oral therapy with a broader ‘anti‐inflammatory’ activity. Such activity may underlie the improved benefit in quality of life that is evident with some antihistamines over others. As we enter the 21st century there are a number of oral H1‐antihistamines that fulfil the majority of these requirements, with fexofenadine, out of those most widely used, appearing to come closest to the desired profile.
Efficacy of Different Low‐Density Lipoprotein Apheresis Methods
Authors: Parhofer K.G. , Geiss H.C. , Schwandt P.
Published: July 2002

Abstract: Low‐density lipoprotein (LDL) apheresis is a treatment option in patients with coronary heart disease and drug resistant hypercholesterolemia. Various apheresis systems based on different elimination concepts are currently in use. We compared the efficacy of 4 different apheresis systems concerning the elimination of lipoproteins. The study included 7 patients treated by heparin extracorporeal LDL precipitation (HELP), 10 patients treated by immunoadsorption, 8 patients treated by dextran‐sulfate adsorption, and 4 patients treated by cascade filtration. Ten subsequent aphereses were evaluated in patients undergoing regular apheresis for more than 6 months. Total cholesterol decreased by approximately 50% with all 4 systems. LDL cholesterol (LDL‐C) (64–67%) and lipoprotein a [Lp(a)] (61–64%) were decreased more effectively by HELP, immunoadsorption, and dextran‐sulfate apheresis than by the less specific cascade filtration system [LDL‐C reduction 56%, Lp(a) reduction 53%]. Triglyceride concentrations were reduced by 40% (dextran‐sulfate) to 49% (cascade filtration) and high‐density lipoproteins (HDL) by 9% (dextran‐sulfate) to 25% (cascade filtration). On the basis of plasma volume treated, HELP was the most efficient system (LDL‐C reduction 25.0%/L plasma), followed by dextran‐sulfate (21.0%/L plasma), cascade (19.4%/L plasma), and immunoadsorption (17.0%/L plasma). However, a maximal amount of 3 L plasma can be processed with HELP due to concomitant fibrinogen reduction while there is no such limitation with immunoadsorption. Therefore, the decision of which system should be used in a given patient must be individualized taking the pre‐apheresis LDL concentration, concomitant pharmacotherapy, and fibrinogen concentration into account.
DIEL PATTERNS OF GROWTH AND DIVISION IN MARINE PICOPLANKTON IN CULTURE
Authors: Jacquet Stéphan , Partensky Frédéric , Lennon Jean‐François , Vaulot Daniel
Published: July 2002

The effect of a 12:12‐h light:dark (LD) cycle on the phasing of several cell parameters was explored in a variety of marine picophytoplanktonic strains. These included the photosynthetic prokaryotes Prochlorococcus (strains MED 4, PCC 9511, and SS 120) and Synechococcus (strains ALMO 03, ROS 04, WH 7803, and WH 8103) and five picoeukaryotes (Bathycoccus prasinos Eikrem et Throndsen, Bolidomonas pacifica Guillou et Chrétiennot‐Dinet, Micromonas pusilla Manton et Parke, Pelagomonas calceolata Andersen et Saunders, and Pycnococcus provasolii Guillard et al.). Flow cytometric analysis was used to determine the relationship between cell light scatter, pigment fluorescence, DNA (when possible), and the LD cycle in these organisms. As expected, growth and division were tightly coupled to the LD cycle for all of these strains. For both Prochlorococcus and picoeukaryotes, chl and intracellular carbon increased throughout the light period as estimated by chl fluorescence and light scatter, respectively. In response to cell division, these parameters decreased regularly during the early part of the dark period, a decrease that either continued throughout the dark period or stopped for the second half of the dark period. For Synechococcus, the decrease of chl and scatter occurred earlier (in the middle of the light period), and for some strains these cellular parameters remained constant throughout the dark period. The timing of division was very similar for all picoeukaryotes and occurred just before the subjective dusk, whereas it was more variable between the different Prochlorococcus and Synechococcus strains. The burst of division for Prochlorococcus SS 120 and PCC 9511 was recorded at the subjective dusk, whereas the MED 4 strain divided later at night. Synechococcus ALMO 03, ROS 04, and WH 7803, which have a low phycourobilin to phycoerythrobilin (PUB:PEB) ratio, divided earlier, and their division was restricted to the light period. In contrast, the high PUB:PEB Synechococcus strain WH 8103 divided preferentially at night. There was a weak linear relationship between the FALSmax:FALSmin ratio and growth rate calculated from cell counts (r = 0.83, n = 11, P < 0.05). Because of the significance of picoplanktonic populations in marine systems, these results should help to interpret diel variations in oceanic optical properties in regions where picoplankton dominates.
Late‐Onset Multiple Sclerosis
Authors: Polliack Michael Leon , Barak Yoram , Achiron Anat
Published: July 2002

OBJECTIVE: The onset of multiple sclerosis (MS) after age 50 is infrequent and presents a diagnostic challenge. The purpose of the present study was to review the prevalence, presentation, and clinical characteristics of late‐onset MS.

DESIGN: A retrospective chart review.

SETTING: The Multiple Sclerosis Center at Sheba Medical Center, Israel.

PARTICIPANTS: 640 patients with a definite diagnosis of MS.

MEASUREMENTS: Diagnosis of MS was established according to Poser criteria and confirmed by brain magnetic resonance imaging (MRI) using our unit's computerized database. Late‐onset MS was defined as the first presentation of clinical symptoms after the age of 50 years. For each patient, age, gender, clinical presentation, disease course, neurological involvement, disease duration, neurological disability assessed, and Progression Index (PI) were analyzed. All patients were interviewed using the structured clinical interview for DSM‐IV, SCID‐lifetime Hebrew version.

RESULTS: Of 640 MS patients, 30 (4.6%) were diagnosed as suffering from late‐onset MS. Mean age at onset was 53.5 ± 3.1, range 50 to 62 years. Female to male ratio was 1.73:1. Mean disease duration was 7.6 years, range 2 to 11 years. In 50% of patients the disease course was relapsing‐remitting. Motor symptoms were the most common neurological presentation at onset (63.3%). Major depressive episode was diagnosed in 6 out of 30 patients (20%) in the two years prior to the diagnosis of MS. After a mean disease duration of 7.6 years there was a marked increase in sphincteric and cerebellar involvement. In addition 7 out of 30 patients had suffered a major depressive episode within 4 years of diagnosis. Mean PI was 0.81, suggesting rapid neurological deterioration.

CONCLUSIONS: Late‐onset MS is not rare and may present as major depression and, although neurological presentation at onset is similar to that of young adults, progression to disability is more rapid and a primary progressive course is more prevalent.
Free-carrier and temperature effects in amorphous silicon thin films
Authors: Tanguy C. , Hulin D. , Mourchid A. , Fauchet P. M. , Wagner S.
Published: July 2002

The electronic and thermal contributions to photoinduced changes in the optical properties of hydrogenated amorphous silicon (a-Si:H) films can be distinguished in pump-probe experiments by an appropriate choice of the probe wavelength. Intraband absorption decreases strongly with carrier localization.
Microstructural and compositional variations in laser-deposited superconducting thin films
Authors: Singh R. K. , Biunno N. , Narayan J.
Published: July 2002

We have investigated thickness and composition variations in laser-deposited superconducting thin films and their effects on the microstructure development after subsequent annealing to recover the superconducting properties. Superconducting thin films were deposited on magnesium oxide substrates using a pulsed excimer laser (λ=308 nm, τ=45×10−9 s). These films were annealed at about 900 °C in helium and oxygen atmospheres followed by slow cooling to room temperature. The forward directed nature of the laser-induced deposition process in controlling the spatial variation in thickness of the film was examined using gas dynamics of the laser generated plasma. The compositional variation as a function of spatial distance was determined by Rutherford backscattering spectrometry. Correlation of the presence of different phases with the average composition in the film was done using transmission electron microscopy combined with x-ray microanalysis techniques. The slight enrichment of yttrium in the film resulted in yttrium-rich phases in the microstructure.
New high-efficiency quasi-continuous operation of a KrF(B→X) excimer lamp excited by microwave discharge
Authors: Kumagai Hiroshi , Obara Minoru
Published: July 2002

A quasi-continuous KrF(B→X) fluorescence of >8 ms pulse duration with 100 Hz operation frequency was observed in a microwave discharge-pumped KrF lamp. The average KrF fluorescence power was 53 W, obtained with an intrinsic efficiency of 8.3% with a 678 W average microwave power deposition. We also obtained a peak KrF fluorescence power of 120 W with a power efficiency of 12.1%.
Reflection high-energy electron diffraction and x-ray photoelectron spectroscopic study on (NH4)2Sx-treated GaAs (100) surfaces
Authors: Hirayama Hiroyuki , Matsumoto Yoshishige , Oigawa Haruhiro , Nannichi Yasuo
Published: July 2002

(NH4)2Sx-treated GaAs (100) surfaces were heated in an ultrahigh vacuum. Reflection high-energy electron diffraction (RHEED) and Ga, As, S, and O x-ray photoelectron spectroscopic (XPS) changes were observed. The sulfide-treated surface showed a streaky 1×1 RHEED pattern without heating. A 2×1 RHEED pattern appeared during heating to 260 and 420 °C. At these temperatures, the S XPS peak was still observed. The 2×1 pattern is thought to be S induced. On the (NH4)2Sx-treated surface, no oxidized As XPS signal was observed. Moreover, the O XPS peak disappeared rapidly during the heating above 260 °C. These results suggest that the 2×1 S structure caused the GaAs (100) surface passivation.
Observation of fast nonbolometric optical response of nongranular high T
c Y1Ba2Cu3O7−x superconducting thin films
Authors: Frenkel A. , Saifi M. A. , Venkatesan T. , Lin Chinlon , Wu X. D. , Inam A.
Published: July 2002

We report fast optical response measurements in predominantly c-axis oriented crystalline Y1Ba2Cu3O7−x superconducting thin films at the wavelength of 1.06 μm. We identify two distinct components contributing to the optical response: a nonbolometric (as fast as 1 ns) and a bolometric component (several ns). The bolometric component is stronger at temperatures in the vicinity of the transition region to the normal state. The nonbolometric component is dominant at temperatures below the transition region showing weak temperature dependence and a linear dependence on the bias current. This nonbolometric component may be evidence for nonequilibrium effects (e.g., breaking of Cooper pairs and generation of quasiparticles or other mechanisms). These results suggest that with proper optimization of device parameters (its geometry, critical current density, etc.) high-speed detectors with reasonable sensitivity covering a broad electromagnetic spectrum (visible and infrared) may be developed.
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t
u reflectivity measurement in a rapid thermal processor for the study of platinum silicide formation
Authors: Dilhac Jean-Marie , Ganibal Christian , Castan Thierry
Published: July 2002

The reflectivity of thin-film platinum silicide was measured by means of a helium-neon (He-Ne) laser when samples of platinum films deposited on top of silicon wafers were annealed in a rapid thermal processor. This processor consists of two rows of tungsten-halogen quartz lamps placed above and below a quartz processing chamber. The thermal cycles consisted of a fast heating (about 200 °C/s), followed by an isothermal plateau at temperatures ranging between 410 and 600 °C. Film reflectivities dropped in two stages, as a result of the reaction between platinum and silicon. This two-stage drop was identified as due to the transformation of the platinum film, first into Pt2Si, and then into PtSi. The amounts of time required to complete the transformations were found to be in good agreement with the Arrhenius laws derived from the work of J. T. Pan and I. A. Blech [Thin Solid Films 113, 129 (1984)] on isothermal low-temperature (220–330 °C) sintering of platinum films on silicon, who unambiguously established the correlation between reflectivity changes and silicide formation.
Measurement of the carrier dependence of differential gain, refractive index, and linewidth enhancement factor in strained-layer quantum well lasers
Authors: Rideout W. , Yu B. , LaCourse J. , York P. K , Beernink K. J. , Coleman J. J.
Published: July 2002

Measurements of the variation of differential gain, refractive index, and linewidth enhancement factor with carrier density in InGaAs-GaAs strained-layer quantum well lasers are presented for the first time. These results verify predictions of improvement over unstrained bulk or quantum well lasers, but only at certain carrier densities. Differential gain (dg/dN) is found to vary from 7.0×10−16 to 2.5×10−16 cm2 over the range of carrier densities studied, while the carrier dependence of the real part of the refractive index (dn/dN) ranges from a peak of −2.8×10−20 down to −7.0×10−21 cm3. From these measurements the resulting linewidth enhancement factor (α) is found to vary from 5 to a minimum of 1.7. This information is critical to successfully exploiting the potential advantages of strained-layer lasers for such devices as high-frequency or narrow linewidth lasers.
Electrical response of Ba1−xKxBiO3 polycrystalline thin films to infrared radiation
Authors: Tanabe K. , Enomoto Y. , Yamaji A.
Published: July 2002

The electrical response to infrared radiation of polycrystalline Ba1−xKxBiO3 thin films on MgO(100) and sapphire substrates with Tc’s of approximately 20 K is studied using modulated laser light at a wavelength of 1.3 μm. These films clearly show nonbolometric responses which are quite similar to those observed in BaPb1−xBixO3 optical detectors based on nonequilibrium superconductivity. The responsivity values at about 15 K are one or two orders of magnitude larger than those for the copper-oxide-based high Tc superconductors with much larger electronic density of states at the Fermi level. These results indicate that Ba1−xMxBiO3(M=K,Rb) is a promising candidate for a sensitive nonequilibrium infrared detector which can be operated using a closed-cycle refrigerator.
Elemental boron doping behavior in silicon molecular beam epitaxy
Authors: Parry C. P. , Newstead S. M. , Barlow R. D. , Augustus P. , Kubiak R. A. A. , Dowsett M. G. , Whall T. E. , Parker E. H. C.
Published: July 2002

Boron-doped Si epilayers were grown by molecular beam epitaxy (MBE) using an elemental boron source, at levels up to 2×1020 cm−3, to elucidate profile control and electrical activation over the growth temperature range 450–900 °C. Precipitation and surface segregation effects were observed at doping levels of 2×1020 cm−3 for growth temperatures above 600 °C. At growth temperatures below 600 °C, excellent profile control was achieved with complete electrical activation at concentrations of 2×1020 cm−3, corresponding to the optimal MBE growth conditions for a range of Si/SixGe1−x heterostructures.
Epitaxy of GdSi≊1.7 on 〈111〉Si by solid phase reaction
Authors: Molnár G. , Gerõcs I. , Petõ G. , Zsoldos E. , Gyulai J. , Bugiel E.
Published: July 2002

Epitaxial hexagonal GdSi≊1.7 was grown by in situ vacuum annealing of 50 and 250 nm Gd layers on 〈111〉 silicon. The epitaxy was investigated by x-ray and electron diffraction measurements.
Production and direct measurement of circularly polarized vacuum-ultraviolet light with multireflection optics
Authors: Koide T. , Shidara T. , Yuri M. , Kandaka N. , Fukutani H.
Published: July 2002

The conversion of linearly polarized synchrotron radiation to circular polarization has been successfully achieved beyond the LiF transmission cutoff in the vacuum ultraviolet by utilizing a triple-reflection polarizer as a quarter-wave retarder. The Stokes parameters of the emerging beam were directly measured at 30 eV with a reflection-type polarimeter as a function of the rotation angle of the ‘‘circular polarizer’’ around the optical axis. The results show that a degree of circular polarization of up to ∼±82% was attained at ∼±25° rotation angles, respectively, between the incidence plane for the polarizer and the horizontal plane. This result is in good agreement with a calculation which took into account the independently measured Stokes parameters of the incoming beam.
Structure of newly synthesized BC3 films
Authors: Krishnan Kannan M.
Published: July 2002

We have measured the electron energy-loss spectrum (EELS) of BC3 at sub-eV resolution. Important differences between the total density of states of BC3 at the threshold of the K edge, predicted by earlier ab initio calculations, have been observed. We conclude from our measurements that the atomic arrangement in these materials can be described as graphite sheets with B replacing every third C atom. We suggest that further understanding of the electronic structure of BC3 can be derived by comparing such EELS data with calculations of the local density of states of bulk BC3 and including interlayer interaction.
Electrical properties of distributed electron cyclotron resonance plasma-deposited SiO2-InP diodes
Authors: Plais F. , Agius B. , Proust N. , Cassette S. , Ravel G. , Puech M.
Published: July 2002

Low-temperature deposition (room temperature, RT-250 °C) of high-resistivity SiO2 layers has been successfully developed on InP substrates. Complete electrical characteristics of metal-insulator-semiconductor (MIS) diodes show promising characteristics in terms of barrier height at the SiO2-InP interface and in terms of interface state distribution (NSS). Leakage current is essentially bulk limited (ρ=4×1015 Ω cm) until a high electrical field in the range 4–6 MV cm−1 and a minimum value of NSS of 2×1011 cm−2 eV−1 range is achieved, without particular surface treatment. These results show that the technique is well adapted to n-type depletion-mode MIS field-effect transistor processing.
Characterization of Si/SiGe strained-layer superlattices grown by ultrahigh vacuum/chemical vapor deposition technique
Authors: Wang P. J. , Goorsky M. S. , Meyerson B. S. , LeGoues F. K. , Tejwani M. J.
Published: July 2002

We employed high-resolution double-crystal x-ray diffraction and transmission electron microscopy to characterize Si/Si1−xGex strained-layer superlattices grown by ultrahigh vacuum/chemical vapor deposition technique. Rocking curve analyses showed uniform layer thickness and alloy composition across superlattices of 10 periods. Extensive dynamical x-ray simulation indicated that heterointerfaces were abrupt and the Si layer was found to be 206±5 Å thick and SiGe layer was 8.25% Ge and 185±5 Å thick. The thickness values were confirmed by the cross-sectional transmission electron microscopy. A tilt angle of 26 arcsec was observed between the (001) planes in the superlattice and the substrate, resulting from steps on the surface of 〈100〉 2° off oriented Si substrates.
Short-circuit current and energy efficiency enhancement in a low-dimensional structure photovoltaic device
Authors: Barnham K. W. J. , Braun B. , Nelson J. , Paxman M. , Button C. , Roberts J. S. , Foxon C. T.
Published: July 2002

We have studied the forward bias behavior of AlGaAs/GaAs p-i-n multiquantum well (MQW) photodiodes. In samples with low background impurity levels in the intrinsic region the high quantum efficiency observed in reverse bias is maintained into forward bias even for carriers photoexcited in the wells. We compare our MQW devices with structures which are identical apart from having AlGaAs intrinsic regions without quantum wells. The short-circuit currents in the MQW structures are much higher than in the control samples though the open-circuit voltages are somewhat smaller. In one case the energy conversion efficiency of the MQW device in white light is 110% higher than the control. We discuss the implications of our results for the development of low-dimensional structure solar cells.
Photoluminescence characterization of pseudomorphic modulation-doped quantum wells at high carrier sheet densities
Authors: Brierley Steven K. , Hoke William E. , Lyman Peter S. , Hendriks Henry T.
Published: July 2002

A systematic study has been made of the photoluminescence spectra of modulation-doped strained-layer quantum wells at high electron sheet densities. Peaks associated with both the n=1 and n=2 electron subbands are observed, and the relative intensities are shown to be a result of the symmetry properties of the quantum wells. It is demonstrated that only the full width half maximum of the n=2 subband peak is useful for characterizing high carrier densities.
Broadband optical detection of ultrasound by two-wave mixing in a photorefractive crystal
Authors: Ing R. K. , Monchalin J.-P.
Published: July 2002

A method which allows broadband (from typically 1 KHz) optical detection of ultrasound with large light gathering from a scattering surface is presented. The wave scattered by the surface is mixed inside a BaTiO3 photorefractive crystal with a pump wave directly derived from the laser to provide a sideband-free reference wave. A polarization configuration which provides sensitive and linear ultrasonic displacement detection is described. This method is demonstrated by detecting laser generated ultrasound.
Field-effect conductance activation energy in an undoped polycrystalline silicon thin-film transistor
Authors: Dimitriadis C. A. , Economou N. A. , Coxon P. A.
Published: July 2002

We investigate the temperature dependence of the field-effect (FE) conductance of thin-film transistors on undoped polycrystalline silicon layers. The FE conductance is thermally activated at a fixed gate voltage. The conductance prefactor G0 increases exponentially with the FE activation energy Ea, in accordance with the Meyer–Neldel rule. Using these results, a model of exponentially decaying band tails explains the FE activation energy data. By fitting the FE activation energy data with the theory, we determine the trap distribution in polysilicon layers deposited at various pressures. The results indicate that the existence of band tails is not an intrinsic property of grain boundaries.