bluuebunny/crossref_metadata_2025 huggingface dataset:
Infections  Controlling exit site infections: Does it decrease the incidence of catheter‐related bacteremia in children on hemodialysis?
Authors: Onder A.M. , Chandar J. , Coakley S. , Abitbol C. , Montane B. , Zilleruelo G.
Published: January 2005

The most common complication of tunneled‐cuffed hemodialysis catheters is catheter‐related bacteremia (CRB), which contributes to patient morbidity and loss of vascular access. Gram positive microorganisms are the most common etiologic agents; coagulase negative staphylococcus and corynebacterium species are the two most prevalent strains in our center. These are the common inhabitants of skin flora, suggesting that infection of catheters occur through the exit site. The Biopatch is a chlorhexidine impregnated dressing designed to keep the exit site from colonization with skin flora. This may decrease the incidence of CRB due to organisms from the skin. Objective: To investigate whether the application of the biopatch at the exit site has any effect on the incidence and the etiology of CRB. Methods: Chart review of 63 pediatric chronic hemodialysis patients who were dialysed between January 1999 and December 2003 was performed. The mean age at start of hemodialysis was 13.9 ± 4.6 years. The pre‐Biopatch era started in January 1999 till the end of June 2001, and the Biopatch era started in July 2001 to December 2003. Biopatch was applied at the beginning of every dialysis week after Betadine cleansing of the exit site, which was then covered with a transparent dressing. In the pre‐Biopatch era, the exit site was cleansed with Betadine at every dialysis session and then covered with a transparent dressing. Results: The use of the Biopatch at the exit site caused a significant decrease in the exit site infections. However, contrary to what was expected, there was no decrease in the incidence of CRB.

Pre‐Biopatch Era
Biopatch Era
p value

Gram positive infections %
76%
76%
NS

Gram negative infections %
10%
14%
NS

Polymicrobial infections %
14%
10%
NS

Total number of infections
108 (19 patients)
143 (29 patients)
NS

Exit site infections‐number
20 (9 patients)
5 (3 patients)
p < 0.05

Conclusion: 
The use of the Biopatch decreases exit site infections. However, it fails to decrease the incidence of CRB. It has no effect on the etiologic agent of the bacterial infection.
Clinical Experiences  Calcium and phosphate balance in children on home nocturnal hemodialysis (NHD)
Authors: D.K. Hothi , E. Piva , L. Keating , E. Harvey , D.F. Geary
Published: January 2005

Objective:
To evaluate and describe biochemical indices of bone metabolism in 4 children on NHD. Method:The children, aged 12, 13, 14, and 16 yrs, have been treated exclusively on NHD for 6, 9, 9, and 15 mos. Subsequently, Pt 1 converted to a hybrid program of 4 nights on home nocturnal plus 1 session of in center conventional HD per week. Biochemical indices of bone metabolism have been collected prospectively. Results:All baseline pre‐dialysis calcium levels were within normal ranges and each patient was started on a dialysis calcium concentration of 3.0 mEq/L. However, over time the number of asymptomatic biochemical hypocalcaemic episodes increased. The dialysate calcium concentration was increased to 3.5 mEq/L in one and decreased to 2.0 mEq/L in another who was hypercalcemic and receiving concurrent calcitonin for bone pain related to osteoporosis. In Pt 1, the dialysate calcium was increased to 3.5 mEq/L during nocturnal and continued on hybrid therapy. Including an evaluation of dietary intake, all 4 patients had a net positive calcium balance, ranging between 9.8 to 23.5 mmol (393–942 mg). A significant reduction in the predialysis phosphate level was observed in all 4 patients, and none required dietary restrictions or the use of phosphate binders within 2 months or vitamin D within 6 months of HND. In addition, phosphate was added to provide a dialysate concentration of 2.4–6.1 mEq/L to prevent hypophosphatemia. This is reflected by significant reductions in intact PTH levels to the desired range (twice the normal range) in all 4, but the level continued to drop to the normal range and below in 2. In Pt 1, after introduction of hybrid therapy, both levels of phosphate and PTH rose, necessitating recommencement of phosphate binders and vitamin D. Likewise, the (Ca × PO4) dropped and remained <55 in all 4 patients exclusively on NHD, but started to climb in Pt 1 during hybrid therapy. Conclusion:In our cohort of patients, NHD rapidly lowered plasma phosphate and PTH levels. With NHD, additional dialysate phosphate and possibly calcium may be necessary to prevent chronic losses and development of renal osteodystrophy, and caution is required to prevent either oversuppression of PTH and extraskeletal calcification.
Obesity promotes forearm primary arteriovenous fistula creation in chronic haemodialyzed patients
Authors: Weyde W. , Porazko T. , Kusztal M. , Banasik M. , Bartosik H. , Trafidlo E. , Letachowicz W. , Krajewska M. , Klinger M.
Published: January 2005

The increase in number of obese people seen in the general population, is also what is seen in the hemodialyzed population. It is generally believed that the location of deep forearm vessels in the subcutaneous fat tissue makes primary arteriovenous fistula (AVF) a disadvantage because of difficulties in vessel puncturing. For obese patients, it is suggested that a fistula with PTFE is created or a central catheter inserted, but these solutions increase already high morbidity rate and significantly increase mortality rate. Methods: The deep location of veins situated on the anterior part of the forearm involved 57 patients (45 female and 12 male) aged 13–87 years (mean 67 ± 15.2 years). Patients’ body mass index (BMI) ranged from 29.1 to 53.73 (mean 34.6 ± 7.8). The causes of the renal failure were diabetic nephropathy in 30 patients, chronic glomerulonephritis in 4, hypertensive nephrosclerosis in 5, lupus nephritis in 2, interstitial nephritis in 4, primary amyloidosis in 1, polycystic kidney disease in 3, and unknown in 3 patients.Two‐step surgical procedure was performed in all patients. In the first stage, the standard distal radiocephalic AVF in the wrist region was created. In case of its failure, the next attempt was performed above the point of the first intervention. In the second stage, superficialization of the venous part of AVF was performed in the mode described by us (Kidney 2002;.1:1170). Results: The first stage of the procedure was successful in 46 patients. In 6 cases it was necessary to perform a second attempt, and 2 cases required three operations. The second stage was undertaken in all of these patients (n = 54), and complete success was achieved in 51. In 3 cases, in spite of superficialization, AVF was not suitable for puncturing because of poor blood flow. The causes of failure of the first stage procedure in 2 patients were severe arteriosclerosis and venous anomaly. All patients had non‐altered cephalic veins in the wrist region, as opposed to patients with cannulated veins. In 51 pts (90%) an efficient flow of the blood through AVF was successfully obtained and allowed satisfactory dialyses. Conclusions: The primary AVF creation on the forearm is feasible in 90% of obese patients. This result is similar to the general population of chronic renal disease patients of our center (95%)(NDT 1998;13:527) and is possible thanks to the location of the veins deep in the subcutaneous fat tissue, which protects against repeated cannulation and hence mechanical destruction in the pre‐dialysis period.
Sodium citrate as a capping for permacaths
Authors: Scott G.E.
Published: January 2005

Purpose: 
Tunneled catheters as chronic dialysis access is a reality of chronic hemodialysis. Infection of the catheter is an unavoidable complication. We researched the possibility of using Na Citrate as capping because of its anticoagulant effects and bactericidal properties. Methods: Rate of infections per 1000 calendar days with heparin capping was recorded for an eight month period before using Na Citrate. Flows <300 ml/min via catheters were also recorded for an eight month period before Na Citrate use, using treatments per 1000 calendar days. Both these parameters were recorded for an eight month period following the initiation of Na Citrate 4% for all catheters. Results: Our infection rate using heparin was 2.2 infections per 1000 catheter days. Infection rate after use of Na citrate was 1.2 infections per 1000 calendar days. Catheter flows <300 were 5.6 per 1000 calendar days using heparin, and 9.2 per 1000 calendar days after use of Na Citrate. There were no reactions related to Na Citrate, and no symptomatic hypocalcemia. Conclusions: Na Citrate is effective at reducing the number of infections when used as a capping solution for tunneled catheters. Na Citrate–capped catheters had more frequent declines in QB compared with heparin capping. Because of the availability of anti‐thrombolytic agents to preserve catheter patency, Na Citrate makes a safe option as a capping agent for long‐term catheter capping.
The effect of dialysis needle size on hemodialysis adequacy
Authors: Kim Y.O. , Song W.J. , Park J.A. , Yoon S.A. , Kim Y.S. , Chang Y.S. , Bang B.K.
Published: January 2005

Objective: 
Dialysis adequacy indexed by Kt/V in hemodialysis (HD) patients is recommended as a single pool Kt/V at least 1.2 per session thrice weekly. But many patients cannot achieve this adequacy target. Although dialysis time is the most important factor influencing Kt/V, it is difficult to prolong dialysis time in practice because of its economic impact and poor patient compliance. This study was performed to investigate the effect of increasing dialysis needle size on dialysis adequacy in HD patients. Methods: This study enrolled 73 patients receiving HD thrice weekly for more than 3 months with arteriovenous fistula (AVF) or graft in a single center. Dialysis blood flow rate was 200 ml/min in 12 patients, 250 ml/min in 32 patients, and 300 ml/min in 29 patients. Surface area of dialyzer was 1.2 m2 in 56 patients and 1.6 m2 in 17 patients. We first performed HD using a 16‐gauge needle. Then we increased needle size up to 15‐gauge without change of any other dialysis conditions such as blood and dialysate flow rates, dialysis time, or distance between needle insertion sites. We compared compression time after removing the needles, venous dialysis pressure (VDP), Kt/V, and urea reduction ratio (URR) between these two methods. Results: The mean age was 54 ± 13 years and the number of patients with diabetes mellitus was 27 (37%). Fifty‐eight patients (79.5%) have native AVF. Mean Kt/V at HD method using a 15‐gauge needle was higher than at HD method using a 16‐gauge needle (1.30 ± 0.18 vs. 1.23 ± 0.18, p < 0.001). URR at HD method using a 15‐gauge needle was also higher than at HD method using a 16‐gauge needle. In contrast, VDP at HD method using a 15‐gauge needle was lower than at HD method using a 16‐gauge needle (88 ± 22 mmHg vs. 118 ± 28 mmHg, p < 0.001). There was no difference in compression time between the two methods. Conclusion: This study suggests that increasing dialysis needle size is a safe and effective method in improving dialysis adequacy without increasing blood flow rate or dialysis time.
Consideration of free coagulant hemodialysis within our facility
Authors: Ishida Y. , Kasahara M. , Sakaji I. , Yoshikawa M. , Nitta T. , Matsushima Y. , Iwatani Y , Yoshimoto A. , Suzuki T.
Published: January 2005

Purpose: 
Performed free coagulant hemodialysis to patients having hemorrhage with the hope to avoid aggravation of bleeding caused by anticoagulant agent from dialysis. Method:  Examined 19 cases of patients with bleeding tendency, whether it is possible to perform free coagulant hemodialysis by using PAES membrane, EVAL membrane, PS membrane, Cellulose triacetate membrane and Vitamin‐E modified‐dialysis membrane. Result: With PAES membrane, the result showed a non‐ blockade rate of 91% after four hours and 100% after two hours. Therefore, blockade was prevented with a fairly high rate. In cases of blockade, most of them were possibly avoidable with a little contrivance as the reason were lack of establish blood flow rate, faulty position of a needle, etc. Conclusions: By using PAES membrane, it was possible to perform free coagulant hemodialysis. In order to completely have no blockade of blood lines in the future, we must strive further on.
Full fit sanitary membranes
Authors: Brown R.H.
Published: January 2005

The dialysis industry has become increasingly concerned about microbial contamination of reverse osmosis (RO) systems. Conventional membranes cannot be thoroughly sanitized due to the use of a peripheral seal which creates a stagnant area between the pressure vessel inner diameter and the membrane outer area. Cleaning procedures cannot adequately sanitize this annular area and control microbiological contamination. Sanitary full fit membranes ensure that a percentage of the feed water is free to bypass or flow around the outside of the membrane element to assure the annular area is continuously flushed and that there are no stagnant areas not exposed to CIP cleaning and sanitizing procedures. For this reason, the dairy industry has for many years used sanitary membranes, which are required by and approved by the USDA. Of the several full fit sanitary membranes available, the cage wrap, net wrap, and tail wrap, only the hard shell TurboCleanTM eliminates the inconsistent bypass flows inherent in the other designs, controlling the distribution of cleaning and sanitizing agents and providing better cleaning and lower microbial levels.
Dialyzer reuse and clinical outcomes—A 3‐year comparison between high flux polysulfone and polyflux® dialyzers
Authors: Sorrill M.A.
Published: January 2005

Purpose: 
This study evaluated improvements in dialyzer reuse parameters and clinical outcomes associated with a CQI project in a hospital‐based dialysis center in which high flux polysulfone dialyzers were replaced with high flux Polyflux® dialyzers (GAMBRO® Renal Products). Methods: Dialyzers were reprocessed using a Renatron® II Dialyzer Reprocessing System in conjunction with Renalin® sterilant (Minntech Corp.). Renalog® RM software was used to track dialyzer reprocessing rates and failures. Reasons for dialyzer failure included inadequate dialyzer volume; excess pressure; appearance; clotting during use; and maximum number of uses reached. The average number of dialyzer reuses with polysulfone dialyzers between January and June 2002 were compared to that achieved with Polyflux® dialyzers for the same periods in 2003 and 2004. Analysis periods were separated to avoid the impact of dialyzer transition on clinical parameters. Achievement of URR goals during these same periods was likewise compared. Results: Transition from polysulfone to Polyflux® dialyzers was associated with a >40% increase in average number of reuses between 2002 and 2003 and a >63% increase comparing the 2002 and 2004 periods. During the 2002 analysis period with polysulfone dialyzers the target URR of 65% was achieved in approximately 75% of hemodialysis patients; this increased to nearly 95% with Polyflux® dialyzers in both the 2003 and 2004 periods, despite more reprocessing of these dialyzers. Conclusions: These results demonstrate an improvement in both reuse efficiency and clinical outcomes associated with Polyflux dialyzers. Identifying clinical products through CQI studies that provide an economic and clinical advantage plays an important role in the success of hospital‐based hemodialysis.
Inflammation and Epilepsy
Authors: Vezzani Annamaria
Published: January 2005

In recent years, increasing evidence has indicated that immune and inflammatory reactions occur in brain in various central nervous system (CNS) diseases. Furthermore, inflammatory processes, such as the production of proinflammatory cytokines and related molecules, have been described in brain after seizures induced in experimental models and in clinical cases of epilepsy. Although little is known about the role of inflammation in epilepsy, it has been hypothesized that activation of the innate immune system and associated inflammatory reactions in brain may mediate some of the molecular and structural changes occurring during and after seizure activity. Whether the innate immune response that takes place in epileptic tissue is beneficial or noxious to the CNS is still an open and intriguing question that should be addressed by further investigations.
Internal and External Integration for Product Development: The Contingency Effects of Uncertainty, Equivocality, and Platform Strategy
Authors: Koufteros Xenophon , Vonderembse Mark , Jayaram Jayanth
Published: January 2005

Effective product development requires firms to unify internal and external participants. As companies attempt to create this integrated environment, two important questions emerge. Does a high level of internal integration lead to a higher level of external integration? In the context of product development, this study considers whether internal integration in the form of concurrent engineering practices affects the level of external integration as manifested by customer integration, supplier product integration, and supplier process integration. External integration, in turn, may influence competitive capabilities, namely product innovation performance and quality performance. Second, using contingency theory, do certain contextual variables moderate the linkages between integration strategy (external and internal) and performance? Specifically, this study considers whether uncertainty, equivocality, and platform development strategy change the relationships among internal integration, external integration, and competitive capabilities. Data collected from 244 manufacturing firms across several industries were used to test these research questions. The results indicate that both internal and external integration positively influence product innovation and quality and ultimately, profitability. With respect to contingency effects, the results indicate that equivocality moderates the relationships between integration and performance.
Heart Rate Variability in Patients with Essential Hyperhidrosis: Dynamic Influence of Sympathetic and Parasympathetic Maneuvers
Authors: Kaya Dayimi , Karaca Semsettin , Barutcu Irfan , Esen Ali Metin , Kulac Mustafa , Esen Ozlem
Published: January 2005

Background: Essential hyperhidrosis has been associated with an increased activity of the sympathetic system. In this study, we investigated cardiac autonomic function in patients with essential hyperhidrosis and healthy controls by time and frequency domain analysis of heart rate variability (HRV).

Method: In this study, 12 subjects with essential hyperhidrosis and 20 healthy subjects were included. Time and frequency domain parameters of HRV were obtained from all of the participants after a 15‐minute resting period in supine position, during controlled respiration (CR) and handgrip exercise (HGE) in sitting position over 5‐minute periods in each stage.

Results: Baseline values of HRV parameters including RR interval, SDNN and root mean square of successive R‐R interval differences, low frequency (LF), high frequency (HF), normalized unit of high frequency (HFnu), normalized unit of low frequency (LFnu), and LF/HF ratio were identical in two groups. During CR, no difference was detected between the two groups with respect to HRV parameters. However, the expected increase in mean heart rate (mean R‐R interval) did not occur in hyperhidrotic group, whereas it did occur in the control group (Friedman's P = 0.000). Handgrip exercise induced significant decrease in mean R‐R interval in both groups and no difference was detected between the two groups with respect to the other HRV parameters. When repeated measurements were compared with two‐way ANOVA, there was statistically significant difference only regarding mean heart rate in two groups (F = 6.5; P = 0.01).

Conclusion: Our overall findings suggest that essential hyperhidrosis is a complex autonomic dysfunction rather than sympathetic overactivity, and parasympathetic system seems to be involved in pathogenesis of this disorder.
Effect of the September 11, 2001 Terrorist Attack on a State Highway Patrol Trooper's Heart Rate Variability
Authors: Riediker Michael , Herbst Margaret C. , Devlin Robert B. , Griggs Thomas R. , Bromberg Philip A. , Cascio Wayne E.
Published: January 2005

Background: On September 11, 2001, terrorists attacked the United States. By coincidence, a North Carolina highway patrol trooper was wearing an ambulatory ECG Holter monitor at this time as part of an air pollution study.

Methods: Heart rate variability parameters were analyzed: standard deviation of normal to normal beat intervals (SDNN) and percentage of interval differences >50 ms (PNN50).

Results: The trooper's heart rate variability changed immediately after learning about the terrorist attacks. Heart rate increased and PNN50 decreased, while SDNN increased strongly.

Conclusions: These changes suggest strong emotional sympathetic stress associated with parasympathetic withdrawal in response to the news about the terrorist attack.
Stability of the major allergen Brazil nut 2S albumin (Ber e 1) to physiologically relevant in vitro gastrointestinal digestion
Authors: Moreno F. Javier , Mellon Fred A. , Wickham Martin S. J. , Bottrill Andrew R. , Mills E. N. Clare
Published: January 2005

The major 2S albumin allergen from Brazil nuts, Ber e 1, was subjected to gastrointestinal digestion using a physiologically relevant in vitro model system either before or after heating (100 °C for 20 min). Whilst the albumin was cleaved into peptides, these were held together in a much larger structure even when digested by using a simulated phase 1 (gastric) followed by a phase 2 (duodenal) digestion system. Neither prior heating of Ber e 1 nor the presence of the physiological surfactant phosphatidylcholine affected the pattern of proteolysis. After 2 h of gastric digestion, ≈ 25% of the allergen remained intact, ≈ 50% corresponded to a large fragment of Mr 6400, and the remainder comprised smaller peptides. During duodenal digestion, residual intact 2S albumin disappeared quickly, but a modified form of the ‘large fragment’ remained, even after 2 h of digestion, with a mass of ≈ 5000 Da. The ‘large fragment’ comprised several smaller peptides that were identified, by using different MS techniques, as deriving from the large subunit. In particular, sequences corresponding to the hypervariable region (Q37–M47) and to another peptide (P42–P69), spanning the main immunoglobulin E epitope region of 2S albumin allergens, were found to be largely intact following phase 1 (gastric) digestion. They also contained previously identified putative T‐cell epitopes. These findings indicate that the characteristic conserved skeleton of cysteine residues of 2S albumin family and, particularly, the intrachain disulphide bond pattern of the large subunit, play a critical role in holding the core protein structure together even after extensive proteolysis, and the resulting structures still contain potentially active B‐ and T‐cell epitopes.
A single mutation in Escherichia coli ribonuclease II inactivates the enzyme without affecting RNA binding
Authors: Amblar Mónica , Arraiano Cecília M.
Published: January 2005

Exoribonuclease II (RNase II), encoded by the rnb gene, is a ubiquitous enzyme that is responsible for 90% of the hydrolytic activity in Escherichia coli crude extracts. The E. coli strain SK4803, carrying the mutant allele rnb296, has been widely used in the study of the role of RNase II. We determined the DNA sequence of rnb296 and cloned this mutant gene in an expression vector. Only a point mutation in the coding sequence of the gene was detected, which results in the single substitution of aspartate 209 for asparagine. The mutant and the wild‐type RNase II enzymes were purified, and their 3′ to 5′ exoribonucleolytic activity, as well as their RNA binding capability, were characterized. We also studied the metal dependency of the exoribonuclease activity of RNase II. The results obtained demonstrated that aspartate 209 is absolutely essential for RNA hydrolysis, but is not required for substrate binding. This is the first evidence of an acidic residue that is essential for the activity of RNase II‐like enzymes. The possible involvement of this residue in metal binding at the active site of the enzyme is discussed. These results are particularly relevant at this time given that no structural or mutational analysis has been performed for any protein of the RNR family of exoribonucleases.
Probing the mechanism of the bifunctional enzyme ketol‐acid reductoisomerase by site‐directed mutagenesis of the active site
Authors: Tyagi Rajiv , Lee Yu‐Ting , Guddat Luke W. , Duggleby Ronald G.
Published: January 2005

Ketol‐acid reductoisomerase (EC 1.1.1.86) is involved in the biosynthesis of the branched‐chain amino acids. It is a bifunctional enzyme that catalyzes two quite different reactions at a common active site; an isomerization consisting of an alkyl migration, followed by an NADPH‐dependent reduction of a 2‐ketoacid. The 2‐ketoacid formed by the alkyl migration is not released. Using the pure recombinant Escherichia coli enzyme, we show that the isomerization reaction has a highly unfavourable equilibrium constant. The reductase activity is shown to be relatively nonspecific and is capable of utilizing a variety of 2‐ketoacids. The active site of the enzyme contains eight conserved polar amino acids and we have mutated each of these in order to dissect their contributions to the isomerase and reductase activities. Several mutations result in loss of the isomerase activity with retention of reductase activity. However, none of the 17 mutants examined have the isomerase activity only. We suggest a reason for this, involving direct reduction of a transition state formed during the isomerization, which is necessitated by the unfavourable equilibrium position of the isomerization. Our mechanism explains why the two activities must occur in a single active site without release of a 2‐ketoacid and provides a rationale for the requirement for NADPH by the isomerase.
Light‐induced global structural changes in phytochrome A regulating photomorphogenesis in plants
Authors: Nakasako Masayoshi , Iwata Tatsuya , Inoue Katsuaki , Tokutomi Satoru
Published: January 2005

Phytochromes are photoreceptor proteins that monitor the light environment and regulate a variety of photomorphogenic responses to optimize the growth and development of plants. Phytochromes comprise N‐terminal photosensory and C‐terminal regulatory domains. They are mutually photoconvertible between a red‐light‐absorbing (Pr) and a far‐red‐light‐absorbing (Pfr) form. Their interconversion by light stimuli initiates downstream signaling cascades. Here we report the molecular structures of pea phytochrome A lacking the N‐terminal 52 amino‐acid residues in the Pr and Pfr forms studied by small‐angle X‐ray scattering. A new purification protocol yielded monodispersive sample solutions. The molecular mass and the maximum dimension of Pr determined from scattering data indicated its dimeric association. The molecular structure of Pr predicted by applying the ab initio simulation method to the scattering profile was approximated as a stack of two flat bodies, comprising two lobes assignable to the functional regions. Scattering profiles recorded under red‐light irradiation showed small but definite changes from those of Pr. The molecular dimensions and predicted molecular structure of Pfr suggest global structural changes such as movement of the C‐terminal domains in the Pr‐to‐Pfr phototransformation. Red‐light‐induced structural changes in Pfr were reversible, mostly due to thermal relaxation processes.
Growth of heteroepitaxial ZnO thin film and ZnO∕(Mg,Zn)O nanomultilayer by off-axis rf magnetron sputtering
Authors: Park Jae-Wan , Park Yumi , Park Jong-Wan , Jeon Minhyon , Lee Jeon-Kook
Published: January 2005

Heteroepitaxial ZnO thin film was deposited on a sapphire (001) substrate using off-axis radio-frequency magnetron sputtering. The crystallinity of the ZnO thin film was affected by deposition pressure, substrate temperature, and postannealing temperature. The low-temperature photoluminescence of heteroepitaxial ZnO thin film grown under optimum conditions of 650°C, 120W, and 10mTorr showed strong UV emission at 3.36eV with a full width at half maximum (FWHM) of 16.0meV. After annealing in an O2 ambient at 950°C, the high-resolution x-ray diffraction rocking curve FWHM of the ZnO thin film markedly decreased from 0.38° to 0.19° although UV emission decreased. These results indicated that a heteroepitaxial ZnO thin film with strong UV emission can be grown by off-axis rf sputtering and that O2 annealing helps enhance the crystallinity of ZnO thin film which can be used as a buffer layer in ZnO∕(Mg,Zn)O multiple quantum well structures. To demonstrate an application of the ZnO thin film, a ZnO∕(Mg,Zn)O nanomultilayer was grown on a ZnO-buffered sapphire substrate and its optical properties were measured.
Collisional ion dynamics in capacitively coupled rf discharges
Authors: Xiang N. , Waelbroeck F. L.
Published: January 2005

Based on a one-dimensional fluid model, the collision-dominated ion dynamics in capacitively coupled rf discharges are studied theoretically as well as numerically in the low rf frequency regime ω⩽VB∕l (here ω is the rf frequency, VB is the Bohm velocity, and l is the plasma length). It is found that the ion current entering the sheath varies with time as we have shown in the collisionless sheath [N. Xiang and F. L. Waelbroeck, J. Appl. Phys. 93, 5034 (2003)]. The mechanisms for the ion current modulation in the collision-dominated and collisionless sheaths, however, are different. It is also shown that the sheath dynamics and ion energy distribution are affected significantly by this time-varying ion current.
Feature-scale model of Si etching in SF6 plasma and comparison with experiments
Authors: Belen Rodolfo Jun , Gomez Sergi , Kiehlbauch Mark , Cooperberg David , Aydil Eray S.
Published: January 2005

We have developed a semiempirical feature scale model of Si etching in SF6 plasma, which incorporates the addition of small amounts of O in the discharge coming from the etching of the oxide mask and quartz window. The degrees of freedom in the model are reduced by using information from plasma diagnostics and previously published data to estimate the ion flux, the ion energy and angle distributions, and the relative F and O fluxes. Experimentally inaccessible parameters such as the F sticking coefficient, chemical etch rate constant, and the ion-enhanced etch yield are determined by matching simulated feature profiles with those obtained from carefully designed etching experiments. Excellent agreement between experiments and simulations is obtained.
Plasma deposition of fluorocarbon thin films from c-C4F8 using pulsed and continuous rf excitation
Authors: Labelle Catherine B. , Opila Robert , Kornblit Avi
Published: January 2005

Fluorocarbon films of varying composition have been deposited from pulsed and continuous plasmas of octafluorocyclobutane (c-C4F8) and c-C4F8/Ar. Continuous plasma deposition rates are a very weak function of applied rf power (may be within experimental error). Pulsed plasma deposition rates are significantly lower than continuous plasma rates at the same average power. The pulsed plasma deposition rates can be attributed almost entirely to the plasma on time during the pulse, but there is a slight dependence on pulse off time. Ar addition affects the deposition rates through a residence time effect, but also affects the deposition chemistry by reducing the degree of C4F8 dissociation, resulting in more fluorinated films. Refractive indices for all films increase approximately linearly with applied rf power, with the pulsed plasma-deposited films falling on the same curve. Carbon 1s x-ray photoelectron spectroscopy shows that the continuous plasma-deposited films become increasingly fluorinated as the rf power is decreased. Pulsed plasma films are more fluorinated than similar average power continuous plasma films: 44% CF2 for 10/50 (400 W on time, 67 W average power) versus 37% for 50 W continuous. Literature and preliminary gas-phase measurements suggest that the C4F8 is not fully dissociated in either plasma system and that larger species in the gas phase may play a significant role in the deposition mechanisms.
Deep dry-etch of silica in a helicon plasma etcher for optical waveguide fabrication
Authors: Li W. T. , Bulla D. A. P. , Love J. , Luther-Davies B. , Charles C. , Boswell R.
Published: January 2005

Dry-etch of SiO2 layers using a CF4 plasma in a helicon plasma etcher for optical waveguide fabrication has been studied. Al2O3 thin films, instead of the conventional materials, such as Cr or photoresist, were employed as the masking materials. The Al2O3 mask layer was obtained by periodically oxidizing the surface of an Al mask in an oxygen plasma during the breaks of the SiO2 etching process. A relatively high SiO2/Al2O3 etching selectivity of ∼100:1, compared with a SiO2/Al selectivity of ∼15:1, was achieved under certain plasma condition. Such a high etching selectivity greatly reduced the required Al mask thickness from over 500 nm down to ∼100nm for etching over 5-μm-thick silica, which make it very easy to obtain the mask patterns with near vertical and very smooth sidewalls. Accordingly, silica wavegudies with vertical sidewalls whose roughness was as low as 10 nm were achieved. In addition, the mechanism of the profile transformation from a mask to the etched waveguide was analyzed numerically; and it was found that the slope angle of the sidewalls of the mask patterns only needed to be larger than 50° for achieving vertical sidewalls of the waveguides, if the etching selectivity was increased to 100.
Downstream microwave ammonia plasma treatment of polydimethylsiloxane
Authors: Pruden K. G. , Beaudoin S. P.
Published: January 2005

To control the interactions between surfaces and biological systems, it is common to attach polymers, proteins, and other species to the surfaces of interest. In this case, surface modification of polydimethylsiloxane (PDMS) was performed by exposing PDMS films to the effluent from a microwave ammonia plasma, with a goal of creating primary amine groups on the PDMS. These amine sites were to be used as binding sites for polymer attachment. Chemical changes to the surface of the PDMS were investigated as a function of treatment time, microwave power, and PDMS temperature during plasma treatment. Functional groups resulting from this treatment were characterized using attenuated total reflectance infrared spectroscopy. Plasma treatment resulted in the incorporation of oxygen- and nitrogen-containing groups, including primary amine groups. In general, increasing the treatment time, plasma power and substrate temperature increased the level of oxidation of the films, and led to the formation of imines and nitriles. PDMS samples treated at 100 W and 23 °C for 120 s were chosen for proof-of-concept dextran coating. Samples treated at this condition contained primary amine groups and few oxygen-containing groups. To test the viability of the primary amines for attachment of biopolymers, functionalized dextran was successfully attached to primary amine sites on the PDMS films.
A social network analysis of research collaboration in physics education
Authors: Yeung Yau-Yuen , Liu Timon Cheng-Yi , Ng Pun-Hon
Published: January 2005

Based on the author indices over the past ten years in three international journals of physics teaching, we have constructed networks of physics educators. The latter are connected if they have published one or more articles together in any one of the three journals. We obtained some important sociological characteristics of the research collaborations or linkages between physics teachers. These results indicate how experiences, ideas, and methods are shared, the degree of collaboration, the existence of clusters between physics teachers, and the productivity distribution. Many aspects of our results differ significantly from those recently found by other researchers on the co-authorship networks of scientists in various fields. The present work can serve as an example of the application of the concepts and features of social network analysis.
Fabrication of a modular neutron array: A collaborative approach to undergraduate research
Authors: Howes R. H. , Baumann T. , Thoennessen M. , Brown J. , DeYoung P. A. , Finck J. , Hinnefeld J. , Kemper K. W. , Luther B. , Pancella P. V. , Peaslee G. F. , Rogers W. F. , Tabor S.
Published: January 2005

The construction of the modular neutron array, a highly efficient time-of-flight detector, for use with the recently upgraded coupled cyclotron facility at the National Superconducting Cyclotron Laboratory has been accomplished by a collaboration of undergraduate physics departments. The collaboration presents an opportunity for involving faculty and students from undergraduate physics programs in state-of-the-art physics experiments at large user facilities.
Interference with correlated photons: Five quantum mechanics experiments for undergraduates
Authors: Galvez E. J. , Holbrow Charles H. , Pysher M. J. , Martin J. W. , Courtemanche N. , Heilig L. , Spencer J.
Published: January 2005

We describe five quantum mechanics experiments that have been designed for an undergraduate setting. The experiments use correlated photons produced by parametric down conversion to generate interference patterns in interferometers. The photons are counted individually. The experimental results illustrate the consequences of multiple paths, indistinguishability, and entanglement. We analyze the results quantitatively using plane-wave probability amplitudes combined according to Feynman’s rules, the state-vector formalism, and amplitude packets. The apparatus fits on a 2′×4′ optical breadboard.
Pauli, an ergodic theorem and related matters
Authors: Landsberg Peter T.
Published: January 2005

Time averages are important in physics and in statistical mechanics. An ergodic theorem is a way of justifying the replacement of time averages by averages in phase space. A derivation of this theorem from quantum mechanics was given by von Neumann in 1929. Pauli and Fierz found a shorter argument in 1937. They agreed that for ergodicity to hold there should be no energy degeneracy in the Hamiltonian. I trace the circumstances and consequences of a disproof of these arguments.
Teaching computational physics as a laboratory sequence
Authors: Spencer Ross L.
Published: January 2005

In spite of the difficulty of adding new courses to an already full undergraduate physics curriculum, the education of undergraduate physics students would be greatly enhanced by learning computational methods. The standard method of addressing this need is to offer a computational physics course. We have chosen to use the standard three credit hours allotted to computational physics by offering three separate one-credit laboratories, one for sophomores, one for juniors, and one for seniors. Students are introduced to symbolic methods using MAPLE when they are sophomores, and to numerical methods using MATLAB beginning in their junior year. This introduction helps prepare students for their upper division courses, for the research they will do for their senior projects, and spreads computational methods throughout the undergraduate curriculum.
Anticonvulsant Medications Extend Worm Life-Span
Authors: Evason Kimberley , Huang Cheng , Yamben Idella , Covey Douglas F. , Kornfeld Kerry
Published: January 2005

Genetic studies have elucidated mechanisms that regulate aging, but there has been little progress in identifying drugs that delay aging. Here, we report that ethosuximide, trimethadione, and 3,3-diethyl-2-pyrrolidinone increase mean and maximum life-span of
Caenorhabditis elegans
and delay age-related declines of physiological processes, indicating that these compounds retard the aging process. These compounds, two of which are approved for human use, are anticonvulsants that modulate neural activity. These compounds also regulated neuromuscular activity in nematodes. These findings suggest that the life-span–extending activity of these compounds is related to the anticonvulsant activity and implicate neural activity in the regulation of aging.
Time-Domain Measurements of Nanomagnet Dynamics Driven by Spin-Transfer Torques
Authors: Krivorotov I. N. , Emley N. C. , Sankey J. C. , Kiselev S. I. , Ralph D. C. , Buhrman R. A.
Published: January 2005

We present time-resolved measurements of gigahertz-scale magnetic dynamics caused by torque from a spin-polarized current. By working in the time domain, we determined the motion of the magnetic moment throughout the process of spin-transfer–driven switching, and we measured turn-on times of steady-state precessional modes. Time-resolved studies of magnetic relaxation allow for the direct measurement of magnetic damping in a nanomagnet and prove that this damping can be controlled electrically using spin-polarized currents.
Encapsulation of Molecular Hydrogen in Fullerene C
60
by Organic Synthesis
Authors: Komatsu Koichi , Murata Michihisa , Murata Yasujiro
Published: January 2005

In spite of their importance in fundamental and applied studies, the preparation of endohedral fullerenes has relied on difficult-to-control physical methods. We report a four-step organic reaction that completely closes a 13-membered ring orifice of an open-cage fullerene. This process can be used to synthesize a fullerene C
60
encapsulating molecular hydrogen, which can be isolated as a pure product. This molecular surgical method should make possible the preparation of a series of C
60
fullerenes, encapsulating either small atoms or molecules, that are not accessible by conventional physical methods.
Voice of the Turtle
Authors: Janzen Fredric J.
Published: January 2005

Sea Turtles
A Complete Guide to Their Biology, Behavior, and Conservation.
By James R. Spotila
. Johns Hopkins University Press, Baltimore, MD, 2004. 240 pp. $24.95, £17. ISBN 0-8018-8007-6.

The author and the striking photographs provide a superb introduction to sea turtles, their biology, and the human impacts that threaten to bring their long history to an end.
Subtle Mutational Changes in the SU Protein of a Natural Feline Leukemia Virus Subgroup A Isolate Alter Disease Spectrum
Authors: Chandhasin Chandtip , Coan Patricia N. , Levy Laura S.
Published: January 2005

FeLV-945 is a representative isolate of the natural feline leukemia virus (FeLV) variant predominant in non-T-cell malignant, proliferative, and degenerative diseases in a geographic cohort. The FeLV-945 surface glycoprotein (SU) is closely related to natural horizontally transmissible FeLV subgroup A (FeLV-A) but was found to differ from a prototype to a larger extent than the members of FeLV-A differ among themselves. The sequence differences included point mutations restricted largely to the functional domains of SU, i.e., VRA, VRB, and PRR. Despite the sequence differences in these critical domains, measurements of receptor utilization, including host range and superinfection interference, confirmed the assignment of FeLV-945 to subgroup A. Other proviruses isolated from the cohort contained similar sequence hallmarks and were assigned to FeLV subgroup A. A provirus from cat 1046 contained a histidine-to-proline change at SU residue 6 within an SPHQ motif that was previously identified as a critical mediator of fusion events during virus entry. The 1046 pseudotype virus entered cells only in the presence of the soluble cofactor FeLIX provided intrans, but it retained an ecotropic host range even in the presence of FeLIX. The mutational changes in FeLV-945 were shown to confer significant functional differences compared to prototype FeLV-A viruses. The substitution of FeLV-945 envelope gene sequences for FeLV-A/61E sequences conferred a small but statistically significant replicative advantage in some feline cells. Moreover, substitution of the unique FeLV-945 long terminal repeat and envelope gene for those of FeLV-A/61E altered the disease spectrum entirely, from a thymic lymphoma of a T-cell origin to an as yet uncharacterized multicentric lymphoma that did not contain T cells.
Rearrangement of Simian Virus 40 Regulatory Region Is Not Required for Induction of Progressive Multifocal Leukoencephalopathy in Immunosuppressed Rhesus Monkeys
Authors: Dang Xin , Axthelm Michael K. , Letvin Norman L. , Koralnik Igor J.
Published: January 2005

Rearrangements of the JC virus (JCV) regulatory region (RR) are consistently found in the brains of patients with progressive multifocal leukoencephalopathy (PML), whereas the archetype RR is present in their kidneys. In addition, the C terminus of the large T antigen (T-Ag) shows greater variability in PML than does the rest of the coding region. To determine whether similar changes in simian virus 40 (SV40) are necessary for disease induction in monkeys, we sequenced the SV40 RR and the C terminus of the T-Ag from the brain of simian/human immunodeficiency virus (SHIV)-infected monkey 18429, which presented spontaneously with an SV40-associated PML-like disease, as well as from the peripheral blood mononuclear cells (PBMC), kidneys, and brains of SV40-seronegative, SHIV-infected monkeys 21289 and 21306, which were inoculated with the 18429 brain SV40 isolate. These animals developed both SV40-associated PML and meningoencephalitis. Thirteen types of SV40 RR were characterized. Compared to the SV40 archetype, we identified RRs with variable deletions in either the origin of replication, the 21-bp repeat elements, or the late promoter, as well as deletions or duplications of the 72-bp enhancer. The archetype was the most prominent RR in the brain of monkey 18429. Shortly after inoculation, a wide range of RRs could be found in the PBMC of monkeys 21289 and 21306. However, the archetype RR became the predominant type in their blood, kidneys, and brains at the time of sacrifice. On the contrary, the T-Ag C termini remained identical in all compartments of the three animals. These results indicate that unlike JCV in humans, rearrangements of SV40 RR are not required for brain disease induction in immunosuppressed monkeys.
The Ataxia Telangiectasia-Mutated and Rad3-Related Protein Is Dispensable for Retroviral Integration
Authors: DeHart Jason L. , Andersen Joshua L. , Zimmerman Erik S. , Ardon Orly , An Dong Sung , Blackett Jana , Kim Baek , Planelles Vicente
Published: January 2005

Integration into the host cell DNA is an essential part of the retroviral life cycle and is required for the productive replication of a retrovirus. Retroviral integration involves cleavage of the host DNA and insertion of the viral DNA, forming an integration intermediate that contains two gaps, each with a viral 5′ flap. The flaps are then removed, and the gap is filled by as yet unidentified nuclease and polymerase activities. It is thought that repair of these gaps flanking the site of retroviral integration is achieved by host DNA repair machinery. The ATM and Rad3-related protein (ATR) is a member of the phosphatidylinositol 3 kinase-related family of protein kinases that play a major role in sensing and triggering repair of DNA lesions in mammalian cells. In an effort to examine the role of ATR in retroviral integration, we used RNA interference to selectively downregulate ATR and measured integration efficiency. In addition, we examined the possible role that Vpr may play in enhancing integration and, in particular, whether activation of ATR by Vpr (Roshal et al., J. Biol. Chem.
278:
25879-25886, 2003) will favor human immunodeficiency virus type 1 integration. We conclude that cells in which ATR has been depleted are competent for retroviral integration. We also conclude that the presence of Vpr as a virion-bound protein does not enhance integration of a lentivirus vector in dividing cells.