bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties and morphology of recycled poly(ethylene terephthalate)/bisphenol a polycarbonate/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) blends by low‐temperature solid‐state extrusion
Authors: Guo Weihong , Zhang Hongsheng , Yin Guorong , Tang Xianwen , Li Binyao , Wu Chifei
Published: April 2007

Among the various methods available for recycling plastics waste, blending technology is a straightforward and relatively simple method for recycling. In this paper, a new blending technology, low‐temperature solid‐state extrusion, was discussed. Several recycled poly(terephthalate ethylene)/bisphenol a polycarbonate/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) blends (R‐PET/PC/SEBS blends) have been prepared by this technology. The results show that thermal and hydrolytic degradation of R‐PET is improved when extruding temperature was between the glass transition temperature (Tg) and cold crystallization temperature (Tcc). Elongation at break and notched impact strength were increased evidently, from 15.9% to 103.6, and from 8.6 kJ/m2 to 20.4 kJ/m2, respectively. The appropriate rotating speed of screws was between 100 and 150 rpm. At the same time, the appropriate rotating speed of the screws brings a suitable shear viscosity ratio of R‐PET and PC, which is of advantage to blending of R‐PET and PC together with SEBS. Dispersion of minor phase, PC and SEBS, became finer and smaller, to about 1 µm. Chain extender, Methylenediphenyl diisocyanate (MDI) can react with the end‐carboxyl group and end‐hydroxyl group of R‐PET. FT‐IR spectra testified that the reactions have been happened in the extruding process. A chain extending reaction not only increased the molecular weight of PET and PC, but also can synthesize PET‐g‐PC copolymer to act as a reactive compatilizer. An SEM micrograph shows that a micro‐fiber structure of PET was formed in the blend sample. Copyright © 2007 John Wiley & Sons, Ltd.
Microwave‐assisted extraction of the main phenolic compounds in flaxseed
Authors: Beejmohun Vickram , Fliniaux Ophélie , Grand Éric , Lamblin Frédéric , Bensaddek Lamine , Christen Philippe , Kovensky José , Fliniaux Marc‐André , Mesnard François
Published: April 2007

A microwave‐assisted extraction (MAE) method has been applied for the first time to the extraction of the main lignan, secoisolariciresinol diglucoside (SDG), and the two most concentrated hydroxycinnamic acid glucosides in flaxseed. The effects of microwave power, extraction time and alkaline treatment were investigated. It was shown that a 3 min MAE resulted in an SDG content of 16.1 ± 0.4 mg/g, a p‐coumaric acid glucoside content of 3.7 ± 0.2 mg/g and a ferulic acid glucoside content of 4.1 ± 0.2 mg/g. These values were compared with those obtained using conventional extraction methods and the results demonstrated that MAE was more effective in terms of both yield and time consumption. Copyright © 2007 John Wiley & Sons, Ltd.
Chemical investigation of Phyllanthus reticulatus by HPLC‐SPE‐NMR and conventional methods
Authors: Lam Sio‐Hong , Wang Chen‐Yu , Chen Chien‐Kuang , Lee Shoei‐Sheng
Published: April 2007

Eight compounds, including two flavonoid glycosides, were isolated from the butanol‐soluble fraction of the methanolic extract of the leaves of Phyllanthus reticulatus by conventional methods. A polyphenol‐rich fraction, obtained by Sephadex LH‐20 fractionation, was also studied using an HPLC‐SPE‐NMR technique leading to the characterization of six compounds including three additional flavonoid glycosides. The latter approach used only 1 mg of samples, theoretically equivalent to 0.3 g of dry leaves. This study demonstrates that HPLC‐SPE‐NMR is very useful for thorough chemical investigation and also offers the advantages of saving time, plant materials and consumables over more conventional methods. Copyright © 2007 John Wiley & Sons, Ltd.
Twin‐screw compounding of poly(methyl methacrylate)/clay nanocomposites: effects of compounding temperature and matrix molecular weight
Authors: Liaw Jr Hao , Hsueh Tony Yi , Tan Tai‐Sheng , Wang Yeh , Chiao Shu‐Min
Published: April 2007

Poly(methyl methacrylate) (PMMA)/organoclay nanocomposites prepared by melt‐compounding using a co‐rotating twin‐screw extruder were intercalated nanocomposites. Commercially available PMMA resins of various molecular weights were used for comparison. The results showed an optimum compounding temperature for maximum intercalation with balanced shear and diffusion. Higher operating temperature reduced the shear mixing effect, and might have induced early degradation of the organoclay. Lower operating temperature, in contrast, reduced the mobility of the polymer molecules, which not only hampered the intercalation attempts, but also generated high torque in the extrusion. The mechanical behavior of the nanocomposites was studied. The tensile modulus, storage modulus and glass transition temperature of the nanocomposites increased with increasing clay content; however, an associated decrease in strength and strain at break was also observed. The notched impact strength also showed a slight decrease with clay content. Nanocomposites based on the lower molecular weight PMMA yielded more significant improvement in mechanical and thermal properties at the same clay content. Copyright © 2007 Society of Chemical Industry
Preparation, characterization, and thermal properties of hydrophilic copolymers: p‐chlorophenylmaleimides with hydroxylethyl methacrylate and β‐methyl itaconate
Authors: Pizarro Guadalupe del C , Marambio Oscar G , Jeria‐Orell Manuel , Huerta Margarita R , Sánchez Julio , Rivas Bernabé L , Habicher Wolf D
Published: April 2007

This work describes the synthesis, characterization, and thermal behavior of copolymers of p‐chlorophenylmaleimide (Cl‐PhMI) with β‐methyl itaconate (β‐MHI) and 2‐hydroxyethyl methacrylate (HEMA). Copolymerization was carried out with a radical initiator by varying the feed mole fraction of Cl‐PhMI from 0.25 to 0.75. The copolymer composition was determined from the N/C ratio based on elemental analysis data and with 1H NMR spectroscopy for poly(Cl‐PhMI‐co‐HEMA) using a proton signal attributed to the CH3 of HEMA (δ = 0.7–1.4 ppm) and the area of aromatic ring protons (δ = 7.2–7.8 ppm), where the proton/area relationship confirmed the copolymer compositions calculated by elemental analysis. The monomer reactivity ratios r1 and r2 were determined using the Kelen–Tüdös method. These values demonstrated that copolymerization produced random copolymers with an alternation tendency. The molecular weight and polydispersity were also determined. The thermal behavior can be correlated with the copolymer composition. An increase of the thermal decomposition temperature occurred when the content of Cl‐PhMI increased. The glass transition temperature and thermal stability of poly(β‐MHI) or poly(HEMA) increased with an increasing amount of Cl‐PhMI in the polymer backbone. Copyright © 2007 Society of Chemical Industry
The targeting of drugs using polymeric microspheres
Authors: Davis Stanley S. , Illum Lisbeth
Published: April 2007

The use of polymeric microspheres for the targeting of drugs to specific sites in the body is discussed in terms of the physico‐chemical properties that influence the fate and deposition of colloidal particles following intravenous administration. These include particle size, surface charge and surface hydrophobicity. Adsorbed surface coatings and adsorbed blood components also play a significant role in determining the site and extent of deposition. Drug targeting via the intravenous route can be achieved in certain instances. However, following administration the major site of particle deposition for small particles is the liver. The use of monoclonal antibodies as a coating agent to increase site specificity is also considered.
Lessons learned from statistical reform efforts in other disciplines
Authors: Fidler Fiona , Cumming Geoff
Published: April 2007

Compelling arguments for reform of statistical practices have been made in many disciplines, in some cases over several decades, but achieving reform has proved difficult. We discuss how reform has progressed—or not progressed—in psychology, medicine, and ecology and describe case studies of attempts by pioneering journal editors to change statistical practices. Lessons for those seeking reform in education include the need to recognize the importance of journal editors and of provision of articles, books, and software that give practical guidance to researchers wishing to use the recommended statistical techniques. Research is required on recommended techniques so that statistical practice can become evidence based. Also, improvement in statistical practice should be encouraged along with improvement in the way a discipline theorizes. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 441–449, 2007.
Better statistics for better decisions: Rejecting null hypotheses statistical tests in favor of replication statistics
Authors: Sanabria Federico , Killeen Peter R.
Published: April 2007

Despite being under challenge for the past 50 years, null hypothesis significance testing (NHST) remains dominant in the scientific field for want of viable alternatives. NHST, along with its significance level p, is inadequate for most of the uses to which it is put, a flaw that is of particular interest to educational practitioners who too often must use it to sanctify their research. In this article, we review the failure of NHST and propose prep, the probability of replicating an effect, as a more useful statistic for evaluating research and aiding practical decision making. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 471–481, 2007.
Using multilevel modeling to examine the effects of multitiered interventions
Authors: Clements Melissa A. , Bolt Daniel , Hoyt William , Kratochwill Thomas R.
Published: April 2007

Data collected in school settings are inherently hierarchical. At the same time, it is becoming increasingly common for interventions to be implemented within the context of a similar multitiered intervention framework where different interventions are provided at different levels of the hierarchy, often simultaneously. This prevalence of hierarchical structures in educational intervention research makes the use of multilevel models (MMs) an appealing methodology for the study of multitiered interventions. We provide an overview of (1) the hierarchical nature of educational intervention research, (2) relevant practical issues in the design of multitiered intervention studies, and (3) the use of MMs for providing a descriptive characterization of multitiered intervention effects. Findings from a hypothetical data example demonstrate that MMs provide noticeably more accurate estimates of effects than traditional single‐level analyses and clarify the advantages of MMs for examining data analysis issues relevant to multitiered intervention studies. Finally, the article provides recommendations for the use of MMs in future intervention studies, especially within the context of multitiered intervention models and response to intervention frameworks. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 503–513, 2007.
Dynamic modelling in a study of surgical error management
Authors: Solis‐Trapala I. L. , Carthey J. , Farewell V. T. , de Leval M. R.
Published: April 2007

We demonstrate the use of dynamic longitudinal models to investigate error management in cardiac surgery. Case study data were collected from a multicentre study of the neonatal arterial switch operation (ASO). Information on two types of negative events, or ‘errors’, observed during surgery, major and minor events, was extracted from case studies. Each event was judged to be recovered from (compensated) or not (uncompensated). The aim of the study was to model compensation given the occurrence of past events within a case. Two models were developed, one for the probability of compensating for a major event and a second model for the probability of compensating for a minor event. Analyses based on dynamic logistic regression models suggest that the total number of preceding minor events, irrespective of compensation status, is negatively related with the ability to compensate for major events. The alternative use of random effects models is investigated for comparison purposes. Copyright © 2007 John Wiley & Sons, Ltd.
How dynamic can organizational capabilities be? Towards a dual‐process model of capability dynamization
Authors: Schreyögg Georg , Kliesch‐Eberl Martina
Published: April 2007

The recent discussion in the field of strategic management broadly favors the idea of dynamic capabilities in order to overcome potential rigidities of organizational capability building. The major question addressed in this paper is whether capabilities can actually be conceived as being in flux—and if so, to what extent and in which way? After briefly recapitulating the distinguishing features of organizational capabilities, path dependency, structural inertia, and commitment are identified as the main capability‐rigidity drivers causing a managerial dilemma. In the search for a resolution of this dilemma different approaches of dynamic capabilities are identified and discussed. The analysis shows that the approaches suffer from inherent conceptual contradictions: the dynamization runs the risk of dissolving the original idea and strength of organizational capability building. Ultimately, capabilities would lose the strategic power attributed to them in the resource‐based view. The last section of this paper therefore aims to develop an alternative approach, which aims at preserving the original merits of organizational capability and solving the rigidity issue not by integrating a dynamic dimension into the capability construct but rather by establishing a separate function (‘capability monitoring’). The suggestions mount up to a tier solution. Its logic builds on the dynamics of countervailing processes and second‐level observation. Copyright © 2007 John Wiley & Sons, Ltd.
International 800 opens new doors for business overseas
Authors: Sachs Randi T.
Published: April 2007

Companies can economically establish an international presence by installing an international toll‐free line linking them to potential foreign customers.
At Aldus, globalization wasn't an afterthought
Authors: Kalbacker Warren
Published: April 2007

At Aldus, entering foreign markets was not a strategy pursued after its products had been successfully marketed in the U.S. Aldus President Paul Brainerd set out from the beginning to build products that could be quickly adapted to local markets. With a strong competitive position in the European Community, the Seattle‐based computer software producer now looks to the Pacific Rim.
Understanding gift giving in Japan
Authors: Kumayama Akihisa
Published: April 2007

It's frowned on in the U.S., but in Japan gift giving has a long tradition. The practice of gift exchange has many complicated rules that an American should understand if he or she doesn't want to appear illmannered to a prospective business associate.
Doing business in the new Eastern Europe: A risk profile
Authors: Kennedy Peter J.
Published: April 2007

The sweeping changes in Eastern Europe make the area seem very tempting. But it's important not to look through rosey colored glasses before making a major commitment. Recognize that there is a downside to doing business there.
“What is my currency risk?”
Authors: Millman Gregory J.
Published: April 2007

Before a company can manage the currency risks associated with doing business abroad, it must clearly identify and define the risks to be managed. This isn't as easy as it seems. There are transactional risks, but there are also hidden risks that don't show up on financial statements.
Hiring local managers and employees overseas
Authors: Fetterolf Cynthia
Published: April 2007

Hiring and retaining local employees for an overseas plant or office calls for abandoning ordinary American hiring techniques and assumptions and rethinking the entire process. When hiring a national, whether a manager or lower‐level employee, you must be acutely aware of that country's cultural mores. Only then can you best fulfill your organization's goals while simultaneously meeting the needs of the employee.
The “Brain Drain” from Hong Kong
Authors: Shelton Scott K. , Quok David
Published: April 2007

At one time, the top jobs in subsidiaries of Western companies located in Hong Kong were held by Westerners. Only recently have companies moved to fill professional positions with local talent. But as the localization process has speeded up, the once plentiful supply of talent is shrinking dramatically. Hong Kong Chinese professionals are leaving from fear of what repatriation with the PRC will bring.
Running a marketing campaign in Japan
Authors: Huddleston Jackson N.
Published: April 2007

If you are considering selling a product in Japan, you need some idea of what marketing is like in Japan for foreign companies. Here are some insights from an American executive who launched a product in the Japanese marketplace.
The state of North American free trade
Authors: Tancer Shoshana B.
Published: April 2007

In 1989, a Free Trade Agreement was signed between the United States and Canada. This past June, at a meeting between the presidents of the United States and Mexico, agreement was reached to begin negotiations toward a similar agreement between their countries. Could this be the impetus for a trilateral agreement among the three countries and, perhaps, even creation of a North American Common Market?
Design and switch of catalytic activity with the DNAzyme–RNAzyme combination
Authors: Sheng Yongjie , Zeng Zhen , Peng Wei , Jiang Dazhi , Li Shuang , Sun Yanhong , Zhang Jin
Published: April 2007

Design and switch of catalytic activity in enzymology remains a subject of intense investigation. Here, we employ a DNAzyme–RNAzyme combination strategy for construction of a 10–23 deoxyribozyme‐hammerhead ribozyme combination that targets different sites of the β‐lactamase mRNA. The 10–23 deoxyribozyme‐hammerhead ribozyme combination gene was cloned into phagemid vector pBlue‐scriptIIKS (+). In vitro the single‐strand recombinant phagemid vector containing the combination sequence exhibited 10–23 deoxyribozyme activity, and the linear transcript displayed hammerhead ribozyme activity. In bacteria, the 10–23 deoxyribozyme‐hammerhead ribozyme combination inhibited the β‐lactamase expression and repressed the growth of drug‐resistant bacteria. Thus, we created a DNAzyme–RNAzyme combination strategy that provides a useful approach to design and switch of catalytic activities for nucleic acid enzymes.
Ethical issues in geriatric feline medicine
Authors: Rollin Bernard E
Published: April 2007

Most veterinarians hold a ‘pediatric’ rather than ‘garage mechanic’ view of their function. In recent years, sophisticated medical modalities have allowed veterinarians to keep animals alive, and increased value of companion animals in society has increased demand for such treatment. But whereas humans can choose to trade current suffering for extended life, animals seem to lack the cognitive apparatus required to do so. Thus, veterinarians must guard against keeping a suffering animal alive for too long. Clients may be emotionally tied to the animal and blind to its suffering. Part of the veterinarian's role, therefore, is to lead the client to ‘recollect’ quality of life issues. A second major role for the veterinarian in treating geriatric or chronically ill animals is control of pain and distress. Unfortunately, pain and distress have historically been neglected in both human and veterinary medicine for ideological reasons. It is ethically necessary to transcend this ideology which leads to both bad medicine and bad ethics.
Serum carnitine, triglyceride and cholesterol profiles in Korean neonates
Authors: Ahn Eun-Mi , Cho Soo-Chul , Lee Myoungsook , Cha Youn-Soo
Published: April 2007

This study evaluated carnitine and lipid status of fifty Korean newborns. Each subject was assigned to two groups: one according to body weight at birth and the other according to gestational age. Serum total, HDL- and LDL-cholesterol were significantly lower and triacylglycerols were significantly higher, by 14 %, in the low birth weight infant (LBWI, 1310–2490 g) group compared with the normal birth weight infant (NBWI, 2570–4420 g) group. Neither birth weight nor gestational age affected serum total carnitine concentrations. However, serum ASAC (acid-soluble acylcarnitine) concentrations were 43 % higher (P < 0·001) in the LBWI group compared with the NBWI group, and approximately twice as high (P < 0·05) in the 28–32 gestational age group compared with the other gestational age groups. NEC (non-esterified acyl carnitine) fractions were significantly higher in the NBWI and 28–32 week groups (P < 0·001 andP < 0·05); consequently serum acyl/NEC carnitine ratios were four times higher in the LBWI group compared with the NBWI group and 2–3 times higher in the 25–32 week age group compared with the more advanced gestational age groups. Urinary carnitine excretion, including the NEC fraction and total carnitine, was significantly higher (P < 0·001) for LBWI than for NBWI. By gestational age, NEC excretion of the 28–32 week group was significantly (P < 0·05) higher than that of the other two groups, but total carnitine excretion was not different among the groups. This study demonstrated that Korean immature and preterm newborns have higher serum triacylglycerol concentrations but lower carnitine status than NBWI. Therefore, the lower carnitine status and moderately higher triacylglycerols may suggest that LBWI in Korea might be at risk for poor carnitine status and decreased capacity to utilise fatty acids for energy.
Influence of cabbage processing methods and prebiotic manipulationof colonic microflora on glucosinolate breakdown in man
Authors: Fuller Zoë , Louis Petra , Mihajlovski Agnès , Rungapamestry Vanessa , Ratcliffe Brian , Duncan Alan J.
Published: April 2007

Glucosinolate consumption from brassica vegetables has been implicated in reduction of cancer risk. The isothiocyanate breakdown products of glucosinolates appear to be particularly important as chemoprotective agents. Before consumption, brassica vegetables are generally cooked, causing the plant enzyme, myrosinase, to be denatured, influencing the profile of glucosinolate breakdown products produced. Some human intestinal microflora species show myrosinase-like activity (e.g. bifidobacteria). We aimed to increase bifidobacteria by offering a prebiotic (inulin) in a randomised crossover study. Six volunteers consumed inulin (10 g/d) for 21 d followed by a 21 d control period (no inulin). Treatment periods were reversed for the remaining six volunteers. During the last 5 d of each period two cabbage-containing meals were consumed. Total urine output was collected for 24 h following each meal. Cabbage was microwaved for 2 min (lightly cooked) or 5·5 min (fully cooked). Faecal samples were collected at the start and after the inulin and control treatments. Bifidobacteria were enumerated by real-time PCR. Allyl isothiocyanate production was quantified by measuring urinary excretion of allyl mercapturic acid (AMA). Bifidobacteria increased following prebiotic supplementation (P < 0·001) but there was no impact of this increase on AMA excretion. AMA excretion was greater following consumption of lightly cooked cabbage irrespective of prebiotic treatment (P < 0·001). In conclusion, the most effective way to increase isothiocyanate production may be to limit the length of time that brassica vegetables are cooked prior to consumption.
Obstructive sleep apnoea adenotonsillectomy in children: when to refer to a centre with a paediatric intensive care unit?
Authors: Blenke E J S M , Anderson A R , Raja Hemal , Bew S , Knight L C
Published: April 2007

Objective:

To identify regional surgical referral patterns for adenotonsillectomy in children with obstructive sleep apnoea to our tertiary centre with paediatric intensive care unit facilities and to establish guidelines for elective paediatric intensive care unit referral and admission.

Methods:

Two methods were used. A questionnaire was sent to ENT consultants in five surrounding hospitals with no in-house paediatric intensive care facilities. The second was a prospective observational study undertaken in our tertiary centre for a sub-set of patients undergoing obstructive sleep apnoea adenotonsillectomy between January 2002 and February 2005. These children were considered high risk as judged clinically by an ENT surgeon. Most had obstructive sleep apnoea and a co-morbidity. Otherwise healthy children with simple obstructive sleep apnoea were excluded.

Results:

15 out of 20 consultants responded to the questionnaire. Four referred on the grounds of clinical history, five referred based on pulse oximetry, nine referred syndromal children and four did not refer electively. Of the 49 high risk patients operated on, only 12 required paediatric intensive care admission with no emergency paediatric intensive care admissions. No otherwise healthy children with uncomplicated obstructive sleep apnoea symptoms required paediatric intensive care admission during the study period.

Conclusion:

There was no regional consensus regarding paediatric intensive care unit referral for obstructive sleep apnoea adenotonsillectomy. Clinical judgement without complex sleep studies by those experienced in this area was sufficient to detect complicated cases of obstructive sleep apnoea with co-morbidity requiring paediatric intensive care.
Predicting dissolution patterns in variable aperture fractures: Evaluation of an enhanced depth‐averaged computational model
Authors: Detwiler Russell L. , Rajaram Harihar
Published: April 2007

Water‐rock interactions within variable aperture fractures can lead to dissolution of fracture surfaces and local alteration of fracture apertures, potentially transforming the transport properties of fractures over time. Because fractures often provide dominant pathways for subsurface flow and transport, developing models that effectively quantify the role of dissolution on changing transport properties over a range of scales is critical to understanding potential impacts of natural and anthropogenic processes. Dissolution of fracture surfaces is controlled by surface reaction kinetics and transport of reactants and products to and from the fracture surfaces. We present a depth‐averaged model of fracture flow and reactive transport that explicitly calculates local dissolution‐induced alterations in fracture apertures. The model incorporates an effective mass transfer relationship that represents a smooth transition from reaction‐limited dissolution to transport‐limited dissolution. We evaluate the model through direct comparison to previously reported physical experiments in transparent analog fractures fabricated by mating an inert, transparent rough surface with a smooth single crystal of potassium dihydrogen phosphate (KDP). These experiments allowed direct measurement of fracture aperture during dissolution experiments using well‐established light transmission techniques. Comparison of experiments and simulations at different flow rates demonstrates the relative impact of the dimensionless Peclet and Damkohler numbers on fracture dissolution and the ability of the computational model to simulate dissolution. Despite some discrepancies in the small‐scale details of dissolution patterns the simulations predict the evolution of large‐scale features quite well for the different experimental conditions. This suggests that the depth‐averaged approach is useful for modeling fracture dissolution in the context of geological processes and applied problems such as CO2 sequestration and fracture acidization.
Groundwater noble gas, age, and temperature signatures in an Alpine watershed: Valuable tools in conceptual model development
Authors: Manning Andrew H. , Caine Jonathan Saul
Published: April 2007

Bedrock groundwater in alpine watersheds is poorly understood, mainly because of a scarcity of wells in alpine settings. Groundwater noble gas, age, and temperature data were collected from springs and wells with depths of 3–342 m in Handcart Gulch, an alpine watershed in Colorado. Temperature profiles indicate active groundwater circulation to a maximum depth (aquifer thickness) of about 200 m, or about 150 m below the water table. Dissolved noble gas data show unusually high excess air concentrations (>0.02 cm3 STP/g, ΔNe > 170%) in the bedrock, consistent with unusually large seasonal water table fluctuations (up to 50 m) observed in the upper part of the watershed. Apparent 3H/3He ages are positively correlated with sample depth and excess air concentrations. Integrated samples were collected from artesian bedrock wells near the trunk stream and are assumed to approximate flow‐weighted samples reflecting bedrock aquifer mean residence times. Exponential mean ages for these integrated samples are remarkably consistent along the stream, four of five being from 8 to 11 years. The tracer data in combination with other hydrologic and geologic data support a relatively simple conceptual model of groundwater flow in the watershed in which (1) permeability is primarily a function of depth; (2) water table fluctuations increase with distance from the stream; and (3) recharge, aquifer thickness, and porosity are relatively uniform throughout the watershed in spite of the geological complexity of the Proterozoic crystalline rocks that underlie it.
Models for antigen receptor gene rearrangement: CDR3 length
Authors: Saada Ravit , Weinberger Moran , Shahaf Gitit , Mehr Ramit
Published: April 2007

Despite the various processing steps involved in V(D)J recombination, which could potentially introduce many biases in the length distribution of complementarity determining region 3 (CDR3) segments, the observed CDR3 length distributions for complete repertoires are very close to a normal‐like distribution. This raises the question of whether this distribution is simply a result of the random steps included in the process of gene rearrangement, or has been optimized during evolution. We have addressed this issue by constructing a simulation of gene rearrangement, which takes into account the DNA modification steps included in the process, namely hairpin opening, nucleotide additions, and nucleotide deletions. We found that the near‐Gaussian‐ shape of CDR3 length distribution can only be obtained under a relatively narrow set of parameter values, and thus our model suggests that specific biases govern the rearrangement process. In both B‐cell receptor (BCR) heavy chain and T‐cell receptor β chain, we obtained a Gaussian distribution using identical parameters, despite the difference in the number and the lengths of the D segments. Hence our results suggest that these parameters most likely reflect the optimal conditions under which the rearrangement process occurs. We have subsequently used the insights gained in this study to estimate the probability of occurrence of two exactly identical BCRs over the course of a human lifetime. Whereas identical rearrangements of the heavy chain are highly unlikely to occur within one human lifetime, for the light chain we found that this probability is not negligible, and hence the light chain CDR3 alone cannot serve as an indicator of B‐cell clonality.
Numerical simulation of a magnetostatically coupled composite magnet
Authors: Gabay A. M. , Hadjipanayis G. C.
Published: April 2007

The demagnetization behavior of the hard-soft composite magnet has been simulated with a simple model in order to understand better the magnetization reversal of die-upset composite magnets fabricated from blends of Nd–Fe–B ribbons and coarse Fe powders. The calculations show that soft magnetic inclusions of any size can be fully magnetically coupled with the hard matrix by long-range magnetostatic interactions provided that the inclusions form layers perpendicular to the magnetization direction. Though the magnetostatic coupling along does not lead to enhanced hard magnetic properties of the composite magnets, it makes the full exchange coupling between the hard and soft phases unnecessary and, therefore, relaxes the strict requirements for the size of the soft inclusions. The combination of magnetostatic coupling and partial exchange coupling in a die-upset magnet with layered morphology may facilitate the development of anisotropic hard-soft composite magnets with properties superior to the single-phase permanent magnets.
Infrared photodissociation of a water molecule from a flexible molecule-H2O complex: Rates and conformational product yields following XH stretch excitation
Authors: Clarkson Jasper R. , Herbert John M. , Zwier Timothy S.
Published: April 2007

Infrared-ultraviolet hole-burning and hole-filling spectroscopies have been used to study IR-induced dissociation of the tryptamine∙H2O and tryptamine∙D2O complexes. Upon complexation of a single water molecule, the seven conformational isomers of tryptamine collapse to a single structure that retains the same ethylamine side chain conformation present in the most highly populated conformer of tryptamine monomer. Infrared excitation of the tryptamine∙H2O complex was carried out using a series of infrared absorptions spanning the range of 2470–3715cm−1. The authors have determined the conformational product yield over this range and the dissociation rate near threshold, where it is slow enough to be measured by our methods. The observed threshold for dissociation occurred at 2872cm−1 in tryptamine∙H2O and at 2869cm−1 in tryptamine∙D2O, with no dissociation occurring on the time scale of the experiment (∼2μs) at 2745cm−1. The dissociation time constants varied from ∼200ns for the 2869cm−1 band of tryptamine∙D2O to ∼25ns for the 2872cm−1 band of tryptamine∙H2O. This large isotope dependence is associated with a zero-point energy effect that increases the binding energy of the deuterated complex by ∼190cm−1, thereby reducing the excess energy available at the same excitation energy. At all higher energies, the dissociation lifetime was shorter than the pulse duration of our lasers (8ns). At all wavelengths, the observed products in the presence of collisions are dominated by conformers A and B of tryptamine monomer, with small contributions from the other minor conformers. In addition, right at threshold (2869cm−1), tryptamine∙D2O dissociates exclusively to conformer A in the absence of collisions with helium, while both A and B conformational products are observed in the presence of collisions with helium. Using resolution-of-identity approximation to second-order Møller-Plesset binding energies extrapolated to the complete basis set limit and harmonic vibrational frequencies and transition states calculated at the density functional limit B3LYP∕6-31+G* level of theory, Rice-Ramsperger-Kassel-Marcus (RRKM) predictions for the dissociation, isomerization, and water shuttling rates as a function of energy are made. At threshold, the experimental dissociation rate is almost 103 faster than RRKM predictions. Reasons for this apparent non-RRKM behavior will be discussed.
Sectioning of multilayers to make a multilayer Laue lens
Authors: Kang Hyon Chol , Stephenson G. Brian , Liu Chian , Conley Ray , Khachatryan Ruben , Wieczorek Michael , Macrander Albert T. , Yan Hanfei , Maser Jörg , Hiller Jon , Koritala Rachel
Published: April 2007

We report a process to fabricate multilayer Laue lenses (MLL’s) by sectioning and thinning multilayer films. This method can produce a linear zone plate structure with a very large ratio of zone depth to width (e.g., >1000), orders of magnitude larger than can be attained with photolithography. Consequently, MLL’s are advantageous for efficient nanofocusing of hard x rays. MLL structures prepared by the technique reported here have been tested at an x-ray energy of 19.5keV, and a diffraction-limited performance was observed. The present article reports the fabrication techniques that were used to make the MLL’s.
Surface Green’s function calculations: A nonrecursive scheme with an infinite number of principal layers
Authors: Kletsov Aleksey , Dahnovsky Yuri , Ortiz J. V.
Published: April 2007

A novel computational method for a surface Green’s function matrix is introduced for the calculation of electrical current in molecular wires. The proposed nonrecursive approach includes an infinite number of principal layers and yields the second-order matrix equation for the transformed Green’s function matrix. The solution is found by the direct diagonalization of the auxiliary matrix without any iteration process. As soon as complex roots of the auxiliary matrix (≃ĜS) are calculated, the gaps and the bands in the surface electronic structure are found. It is shown that the solution of a second-order matrix equation determines the spectral density matrix, that is, the density of states for noninteracting electrons. Single and double principal layer models are studied both analytically and numerically. The energy interval for nonvanishing spectral matrices is determined. This method is applicable to matrices of any rank.
Semiconducting graphene nanostrips with edge disorder
Authors: Gunlycke D. , Areshkin D. A. , White C. T.
Published: April 2007

Results of calculations are presented which show that edge disorder can easily transform semiconducting graphene nanostrips into Anderson insulators. However, it is also shown that this problem could be overcome by adjusting the nanostrip aspect ratio to decrease the effects of the edge disorder without making the nanostrip so wide as to close the semiconducting band gap or so short as to allow tunneling through the band gap.
Nanometer-scale material contrast imaging with a near-field microwave microscope
Authors: Imtiaz Atif , Anlage Steven M. , Barry John D. , Melngailis John
Published: April 2007

The authors report topography-free material contrast imaging on a nanofabricated boron-doped silicon sample measured with a near-field scanning microwave microscope over a broad frequency range. The boron doping was performed using the focus ion beam technique on a silicon wafer with nominal resistivity of 61Ωcm. A topography-free doped region varies in sheet resistance from 1000Ω∕◻ to about 400kΩ∕◻ within a lateral distance of 4μm. The qualitative spatial resolution in sheet resistance imaging contrast is no worse than 100nm as estimated from the frequency shift signal.
Identification of a regulator of transcription elongation as an accessory factor for the human Mediator coactivator
Authors: Malik Sohail , Barrero María J. , Jones Tara
Published: April 2007

The multiprotein Mediator coactivator complex is universally required for transcription of metazoan genes. It has been proposed to function by interfacing between transcriptional activators and the RNA polymerase II machinery. However,
in vitro
transcription systems reconstituted from homogeneous preparations of RNA polymerase II, the general transcription initiation factors, and the cofactor PC4 display relatively robust activator (HNF-4)-dependent activity, which, nonetheless, can be further stimulated by Mediator. By contrast, an unfractionated nuclear extract-based system in which Mediator has been immunodepleted displays a near-absolute dependence on ectopic Mediator. Here, we identified and purified an activity, MSA-2, that confers extract-like Mediator responsiveness to our reconstituted system. Mass spectrometric analyses identified its two constituent polypeptides as hSpt5 and hSpt4, which also comprise the elongation factor DSIF. Mechanistically, MSA-2/DSIF acts by restricting overall transcription in the pure system, thereby imposing a strong Mediator dependence. Our data thus point to potential mechanisms for Mediator function beyond its presently believed role in promoting the initial formation of the RNA polymerase II-containing preinitiation complex.
Evidence that cochlear-implanted deaf patients are better multisensory integrators
Authors: Rouger J. , Lagleyre S. , Fraysse B. , Deneve S. , Deguine O. , Barone P.
Published: April 2007

The cochlear implant (CI) is a neuroprosthesis that allows profoundly deaf patients to recover speech intelligibility. This recovery goes through long-term adaptative processes to build coherent percepts from the coarse information delivered by the implant. Here we analyzed the longitudinal postimplantation evolution of word recognition in a large sample of CI users in unisensory (visual or auditory) and bisensory (visuoauditory) conditions. We found that, despite considerable recovery of auditory performance during the first year postimplantation, CI patients maintain a much higher level of word recognition in speechreading conditions compared with normally hearing subjects, even several years after implantation. Consequently, we show that CI users present higher visuoauditory performance when compared with normally hearing subjects with similar auditory stimuli. This better performance is not only due to greater speechreading performance, but, most importantly, also due to a greater capacity to integrate visual input with the distorted speech signal. Our results suggest that these behavioral changes in CI users might be mediated by a reorganization of the cortical network involved in speech recognition that favors a more specific involvement of visual areas. Furthermore, they provide crucial indications to guide the rehabilitation of CI patients by using visually oriented therapeutic strategies.
Ubiquitin-conjugating enzyme Ubc13 is a critical component of TNF receptor-associated factor (TRAF)-mediated inflammatory responses
Authors: Fukushima Toru , Matsuzawa Shu-ichi , Kress Christina L. , Bruey Jean Marie , Krajewska Maryla , Lefebvre Sophie , Zapata Juan M. , Ronai Ze'ev , Reed John C.
Published: April 2007

Ubc13 is a ubiquitin-conjugating enzyme responsible for noncanonical ubiquitination of TNF receptor-associated factor (TRAF)-family adapter proteins involved in Toll-like receptor and TNF-family cytokine receptor signaling, which are regulators of innate immunity. Gene ablation was used to study the function of Ubc13 in mice. Whereas homozygous
ubc13
gene disruption resulted in embryonic lethality, heterozygous
ubc13
+/−
mice appeared normal, without alterations in immune cell populations. Haploinsufficient
ubc13
+/−
mice were resistant to lipopolysaccharide-induced lethality, and demonstrated reduced
in vivo
ubiquitination of TRAF6. Macrophages and splenocytes isolated from
ubc13
+/−
mice exhibited reduced lipopolysaccharide-inducible cytokine secretion and impaired activation of TRAF-dependent signal transduction pathways (NF-κB, JNK, and p38 MAPK). These findings document a critical role for Ubc13 in inflammatory responses and suggest that agents reducing Ubc13 activity could have therapeutic utility.
Lipocalin-type prostaglandin D synthase/β-trace is a major amyloid β-chaperone in human cerebrospinal fluid
Authors: Kanekiyo Takahisa , Ban Tadato , Aritake Kosuke , Huang Zhi-Li , Qu Wei-Min , Okazaki Issay , Mohri Ikuko , Murayama Shigeo , Ozono Keiichi , Taniike Masako , Goto Yuji , Urade Yoshihiro
Published: April 2007

The conformational change in amyloid β (Aβ) peptide from its monomeric form to aggregates is crucial in the pathogenesis of Alzheimer's disease (AD). In the healthy brain, some unidentified chaperones appear to prevent the aggregation of Aβ. Here we reported that lipocalin-type prostaglandin D synthase (L-PGDS)/β-trace, the most abundant cerebrospinal fluid (CSF) protein produced in the brain, was localized in amyloid plaques in both AD patients and AD-model Tg2576 mice. Surface plasmon resonance analysis revealed that L-PGDS/β-trace tightly bound to Aβ monomers and fibrils with high affinity (
K
D
= 18–50 nM) and that L-PGDS/β-trace recognized residues 25–28 in Aβ, which is the key region for its conformational change to a β-sheet structure. The results of a thioflavin T fluorescence assay to monitor Aβ aggregation disclosed that L-PGDS/β-trace inhibited the spontaneous aggregation of Aβ (1–40) and Aβ (1–42) within its physiological range (1–5 μM) in CSF. L-PGDS/β-trace also prevented the seed-dependent aggregation of 50 μM Aβ with
K
i
of 0.75 μM. Moreover, the inhibitory activity toward Aβ (1–40) aggregation in human CSF was decreased by 60% when L-PGDS/β-trace was removed from the CSF by immunoaffinity chromatography. The deposition of Aβ after intraventricular infusion of Aβ (1–42) was 3.5-fold higher in L-PGDS-deficient mice and reduced to 23% in L-PGDS-overexpressing mice as compared with their wild-type levels. These data indicate that L-PGDS/β-trace is a major endogenous Aβ-chaperone in the brain and suggest that the disturbance of this function may be involved in the onset and progression of AD. Our findings may provide a diagnostic and therapeutic approach for AD.
A role for a novel centrosome cycle in asymmetric cell division
Authors: Rusan Nasser M. , Peifer Mark
Published: April 2007

Tissue stem cells play a key role in tissue maintenance. Drosophila melanogaster central brain neuroblasts are excellent models for stem cell asymmetric division. Earlier work showed that their mitotic spindle orientation is established before spindle formation. We investigated the mechanism by which this occurs, revealing a novel centrosome cycle. In interphase, the two centrioles separate, but only one is active, retaining pericentriolar material and forming a “dominant centrosome.” This centrosome acts as a microtubule organizing center (MTOC) and remains stationary, forming one pole of the future spindle. The second centriole is inactive and moves to the opposite side of the cell before being activated as a centrosome/MTOC. This is accompanied by asymmetric localization of Polo kinase, a key centrosome regulator. Disruption of centrosomes disrupts the high fidelity of asymmetric division. We propose a two-step mechanism to ensure faithful spindle positioning: the novel centrosome cycle produces a single interphase MTOC, coarsely aligning the spindle, and spindle–cortex interactions refine this alignment.
c-Met is essential for wound healing in the skin
Authors: Chmielowiec Jolanta , Borowiak Malgorzata , Morkel Markus , Stradal Theresia , Munz Barbara , Werner Sabine , Wehland Jürgen , Birchmeier Carmen , Birchmeier Walter
Published: April 2007

Wound healing of the skin is a crucial regenerative process in adult mammals. We examined wound healing in conditional mutant mice, in which the c-Met gene that encodes the receptor of hepatocyte growth factor/scatter factor was mutated in the epidermis by cre recombinase. c-Met–deficient keratinocytes were unable to contribute to the reepithelialization of skin wounds. In conditional c-Met mutant mice, wound closure was slightly attenuated, but occurred exclusively by a few (5%) keratinocytes that had escaped recombination. This demonstrates that the wound process selected and amplified residual cells that express a functional c-Met receptor. We also cultured primary keratinocytes from the skin of conditional c-Met mutant mice and examined them in scratch wound assays. Again, closure of scratch wounds occurred by the few remaining c-Met–positive cells. Our data show that c-Met signaling not only controls cell growth and migration during embryogenesis but is also essential for the generation of the hyperproliferative epithelium in skin wounds, and thus for a fundamental regenerative process in the adult.