bluuebunny/crossref_metadata_2025 huggingface dataset:
High and low brushing force in relation to efficacy and gingival abrasion
Authors: Van der Weijden G. A. , Timmerman M. F. , Versteeg P. A. , Piscaer M. , Van der Velden U.
Published: July 2004

Objectives: Does a high brushing force induce more gingival abrasion than a low (regular) brushing force? Furthermore, what is the effect of a low or high force on the efficacy?

Methods: Thirty‐five non‐dental students were selected. All received an appointment prior to which they abstained from oral hygiene for at least 48 h. At baseline the teeth and surrounding tissues were disclosed using Mira‐2‐Tone® disclosing solution. Next, the examiner (PAV) evaluated the number of sites with gingival abrasion and the amount of dental plaque (Quigley & Hein) at 6 surfaces of each tooth. In the absence of this examiner, the subject's teeth were brushed by a hygienist (MP) using the Braun/Oral‐B®‐D17 oscillating rotating toothbrush. Brushing was performed in two randomly selected contra‐lateral quadrants for 60 s with either a low force (±1.5 N) or high force (±3.5 N) and in the opposing quadrants for 60 s with the alternative force. Visual feedback was given to control force. The brush was moved from the distal tooth to the central incisor perpendicular to the tooth surface with an angle of approximately 10–15° towards the gingival margin. Next, the number of sites with abrasion and the remaining plaque were assessed again.

Results: The overall baseline gingival abrasion scores were 3.1 and 3.2 sites for high and low force, respectively, and increased to 5.0 and 5.9 sites respectively after brushing. There was no significant difference with respect to incidence of abrasion. At baseline, 48 h. plaque levels were 2.2. The reduction in plaque scores with the low force was 60% and with the high force 56%. This difference was significant.

Conclusion: With the oscillating rotating power toothbrush (Braun/Oral‐B D17) the use of high force (±3.5 N) is less efficacious as compared to a regular low force (±1.5 N) while the incidence of gingival abrasion sites was comparable. (This study was sponsored by Gillette.)
Periodontal repair in dogs: effect of recombinant human bone morphogenetic protein‐12 (rhBMP‐12) on regeneration of alveolar bone and periodontal attachment
Authors: Wikesjö Ulf M. E. , Sorensen Rachel G. , Kinoshita Atsuhiro , Jian Li X. , Wozney John M.
Published: July 2004

Objectives: Recombinant human bone morphogenetic protein‐2 (rhBMP‐2) has been shown to stimulate alveolar bone and cementum formation in periodontal defects but not a functionally oriented periodontal ligament (PDL). Subcutaneous and intramuscular implants of BMP‐12 have been shown to induce tendon formation and ligament‐like tissue. The objective of this study was to evaluate rhBMP‐12 for periodontal regeneration, in particular PDL formation.

Methods: Six young adult Hound Labrador mongrel dogs were used. Routine supraalveolar periodontal defects were created around the mandibular premolar teeth. Three animals received rhBMP‐12(0.04 mg/ml) in an absorbable collagen sponge (ACS) carrier vs. rhBMP‐12(0.2 mg/mL)/ACS in contralateral defects. Three animals received rhBMP‐12(1.0 mg/ml)/ACS vs. rhBMP‐2(0.2 mg/ml)/ACS (total implant volume/defect ∼1 ml). The animals were euthanized 8 weeks postsurgery and block biopsies were processed for histometric analysis.

Results: Bone regeneration appeared increased in sites receiving rhBMP‐2/ACS compared to sites receiving rhBMP‐12/ACS. Cementum regeneration was similar comparing sites implanted with rhBMP‐2/ACS to sites implanted with rhBMP‐12/ACS. In contrast, sites receiving rhBMP‐12/ACS exhibited a functionally oriented PDL bridging the gap between newly formed bone and cementum whereas this was a rare observation in sites receiving rhBMP‐2/ACS. Ankylosis appeared increased in sites receiving rhBMP‐2/ACS compared to those receiving rhBMP‐12/ACS.

Conclusions: The outcomes of this study suggest that rhBMP‐12 may have significant effects on regeneration of the PDL. Additional preclinical evaluation is needed to confirm these initial observations prior to clinical application.
Matrix metalloproteinases, their physiological inhibitors and osteoclast factors are differentially regulated by the cytokine profile in human periodontal disease
Authors: Garlet Gustavo P. , Martins Walter , Fonseca Benedito A.L. , Ferreira Beatriz R. , Silva João S.
Published: July 2004

Objective: Inflammatory reactions raised in response to periodontopathogens are thought to trigger pathways of periodontal tissue destruction. We therefore investigated the expression of matrix metalloproteinases (MMPs) and the osteoclastogenic factor receptor activator of nuclear factor‐κB ligand (RANKL), their respective tissue inhibitors of metalloproteinases (TIMPs) and osteoprotegerin (OPG) in different forms of human periodontal diseases (PDs), and the possible correlation with the expression of inflammatory and regulatory cytokines.

Material and Methods: Quantitative polymerase chain reaction (real‐time PCR) was performed with gingival biopsies mRNA from aggressive (AP) and chronic periodontitis (CP) patients.

Results: Periodontitis patients exhibit higher expression of all analyzed factors when compared with healthy tissues. The expression of MMPs and RANKL were similar in AP and CP, as well as the expression of TNF‐α. On the other hand, the expression of TIMPs and OPG was higher in CP, and was associated with lower IFN‐γ and higher IL‐10 expression, compared with AP.

Conclusion: It is possible that the pattern of cytokines expressed determines the stable or progressive nature of the lesions and regulates the severity of PD, driving the balance between MMPs and TIMPs, RANKL and OPG expression in the gingival tissues controlling the breakdown of soft and bone tissues and, consequently, the disease severity.
Genetic variations in the matrix metalloproteinase‐1 promoter and risk of susceptibility and/or severity of chronic periodontitis in the Czech population
Authors: Izakovičová Hollá L. , Jurajda M. , Fassmann A. , Dvorakova N. , Znojil V. , Vacha J.
Published: July 2004

Objectives: Matrix metalloproteinase‐1 (MMP‐1) is a potent enzyme degrading extracellular matrix that was implicated in the pathogenesis of chronic periodontitis. Therefore, the aim of our study was to examine the association between three promoter polymorphisms of the MMP‐1 gene and chronic periodontitis susceptibility and/or severity in a Czech population.

Materials and Methods: A total of 329 Caucasian subjects were enrolled in this study. They were 133 patients with mild to severe chronic periodontitis and 196 unrelated control subjects. MMP‐1 promoter polymorphisms (−1607 1G/2G, −519A/G, and −422A/T) were genotyped using standard polymerase chain reaction–restriction fragment length product methods.

Results: Genotype analysis of the three single nucleotide polymorphisms across 27 different combinations showed significant association with chronic periodontitis (p<0.05). Analyses of individual polymorphisms showed no differences in distribution of the −519A/G and −422A/T variants between periodontitis and control groups. However, a trend to increased frequency of the −1607 1G allele was observed in patients with chronic periodontitis compared with the controls (p=0.054). When the groups were further stratified by smoking status, the 1G allele was associated with chronic periodontitis among non‐smokers but not among smokers (p=0.033). On the contrary, the distribution of genotype frequencies of the MMP‐1 −422A/T polymorphism was different between the patient and control smokers with respect to heterozygotes (73.91% versus 50.91%; p=0.017).

Conclusions: Our results demonstrate that the polymorphisms in the MMP‐1 promoter may have only a small effect on the etiopathogenesis of chronic periodontitis.
A longitudinal study of the relationship between periodontal disease and bone mineral density in community‐dwelling older adults
Authors: Yoshihara Akihiro , Seida Yoshikazu , Hanada Nobuhiro , Miyazaki Hideo
Published: July 2004

Objective: Bone loss is a common feature of periodontitis and osteoporosis. Both diseases may share common etiologic agents which may either affect or modulate the process of both diseases. The purpose of this study was to evaluate the relationship between systemic bone mineral density (BMD) and periodontal disease among older people.

Materials and Methods: Among all 4542 inhabitants aged 70 years according to a registry of residents in Niigata city in Japan, 600 people were selected randomly. One hundred and eighty‐four subjects who did not have diabetes mellitus, whose blood sugar was <140 mg/dl, who had more than 20 teeth, who were non‐smokers, and who did not take medication for osteoporosis, were included in the study. Four dentists performed clinical evaluations on probing attachment level (PAL). We also utilized the data on BMD of the heel, which we measured using an ultrasound bone densitometer. Follow‐up clinical surveys were done by measuring PAL after 3 years. Finally, 179 subjects who could participate in both the baseline and the follow‐up examinations were included in the analysis. After dividing the subjects into an osteopenia group (OG) and non‐osteopenia group (NOG), we evaluated the relationship between BMD and the number of progressive sites which had 3 mm additional attachment loss during 3 years after controlling the known confounding factors.

Results: The mean number of progressive sites for the OG and the NOG, respectively, were 4.65±5.51 and 3.26±3.01 in females and 6.88±9.41 and 3.41±2.79 in males. Two‐way analysis of variance was performed to discriminate among effects of gender, BMD, and gender–BMD interaction. A significant effect of BMD (OG or NOG, p=0.043) with a significant interaction (p=0.038) was observed. Furthermore, BMD was associated with the number of progressive sites which had 3 mm additional attachment loss during the 3 years (p=0.001) by multiple linear regression analysis.

Conclusions: This study suggested that there was a significant relationship between periodontal disease and general BMD.
The electric toothbrush: analysis of filaments under stereomicroscope
Authors: Checchi L. , Farina E. , Felice P. , Montevecchi M.
Published: July 2004

Background: The use of manual and electric toothbrushes has a fundamental role in primary prevention in oral hygiene. However, aggressive use of the toothbrush, especially those with non‐rounded filaments, can result in lesions in both soft and hard oral tissue. Without doubt, the electric toothbrush is a useful aid for the patient, and it is therefore interesting to evaluate not only its effectiveness in plaque removal, but also the relationship between morphology of filaments and incidence of muco‐gingival pathologies.

Objective: The aim of this research was to evaluate various forms of bristles of electric toothbrushes under a stereomicroscope vision.

Data sources: Brushes tested included two samples of toothbrushes from six different types. Tufts from the same position on the toothbrush head were removed and examined under stereomicroscope. In this study the percentage of rounded filaments that is considered acceptable and non‐traumatic was evaluated according to the Silverstone and Featherstone classification.

Conclusions: Morphological analysis of electric toothbrush filaments revealed a low percentage of rounded filaments. In only four of 12 electric toothbrushes tested there were more than 50% of the filaments rounded in appearance.
Numerical modelling of slag flows in an electric furnace
Authors: Xia J. L. , Ahokainen T.
Published: July 2004

A three‐dimensional mathematical model has been developed to simulate the flow and heat transfer in a slag‐cleaning furnace. The magnetohydraudynamic model has been implemented into the CFX4 code using user subroutines. The physical model is an industrial furnace with three electrodes immersed into the slag. Predictions reveal that the slag flow is quite complex and three‐dimensional. The electric potential, the electric current density and the heat generation drop sharply near the electrode surface. The slag temperature increases with increasing the electric potential. Predictions are validated by comparing the dependence of the slag temperature on the electric potential with the available plant data. The present model can reasonably predict the reasonable range of operational parameters of the furnaces.
High‐temperature reduction of iron oxides by solid carbon or carbon dissolved in liquid iron–carbon alloy
Authors: Santos Dener Martins dos , Mourão Marcelo Breda
Published: July 2004

The reaction between iron oxides and carbon was experimentally studied at temperatures higher than 1473 K employing solid carbon or carbon dissolved in liquid iron as a reducing agent. Iron oxides–carbon composite pellets were submitted to thermogravimetric analysis under inert gas in the range 1473–1623 K; the carbon was in the form of graphite, coke fines and charcoal. It has been determined that the type of carbonaceous material has little effect in the reaction rate at high temperatures. The activation energies obtained varied from 46 to 120 kJ/mol, well below the ones obtained at lower temperature ranges, and it is proposed that at high temperatures the controlling mechanism of the reaction is heat transfer. Composite pellets and fired or cold bonded iron oxide pellets were also added to iron–carbon baths in the temperature range 1573–1912 K. It has been found that up to 1711 K the composite pellets present reaction times significantly shorter than the pure oxide pellets, whereas at higher temperatures the reaction times of both pellets are similar.
Decarburization of Fe/C melts in a crucible: Effects of bath sulfur level and bath surface area
Authors: Zughbi Habib Daoud
Published: July 2004

Experiments to investigate decarburization of Fe/C/S melts in a crucible were carried out. The effects of the concentration of sulfur and the surface area of bath open to reaction were investigated. Using controlled Fe/C melts, it was found that sulfur significantly retards the decarburization of Fe/C melts. The retardation reached its maximum for sulfur concentrations higher than 0.1%. Similar results were also obtained for melts of commercial type metal. Retardation was observed when either O2 and/or CO2 were used as a decarburizing gas. Sulfur in the melt did not react with the oxidizing gas during decarburization. It was also observed that the formation of droplets was enhanced by the presence of sulfur. Finally the effects of surface tension, known as the Marangoni effect, were clearly observed during experiments.
Investigation of efficient conditions for chromate production from chromite concentrate by alkali fusion
Authors: Yildiz Kenan , Sengil I. Ayhan
Published: July 2004

The alkali‐fusion method was carried out by reacting chromite concentrate with molten sodium hydroxide under oxidizing conditions to form sodium chromate. The fusion product was leached with methanol to remove the unreacted NaOH and then leached with water to obtain chromate solution. The effect of parameters such as fusion temperature (550, 600 and 650°C), fusion time (20, 40, 60 and 90 min) and the weight ratio of NaOH to Cr2O3 in the chromite on alkali fusion was investigated. In both methanol and water leaching steps, the parameters were solid/liquid (s/l) ratio (1/2, 1/3, 1/4 and 1/5), leaching time (10, 20 and 30 min) and temperature (25, 35 and 50°C for methanol leaching, 25 and 50°C for water leaching). The highest extraction efficiency (96.2%) of chromium in the chromite was obtained at 650°C and a fusion time of 60 min. The weight ratio of NaOH to Cr2O3 in chromite was 6/1. In methanol leaching, 82.6% of the unreacted NaOH was recovered at 50°C, a leaching time of 60 min and 1/4 of s/l ratio. The kinetics of alkali fusion was also studied and the results showed that the reaction was chemically controlled and activation energy was 94.6 kJ/mol.
Invasive cervical resorption
Authors: Heithersay Geoffrey S.
Published: July 2004

Invasive cervical resorption (cervical resorption) is a relatively uncommon form of external root resorption which has been a source of interest and academic debate by clinicians and researchers for over a century. Clinical, radiologic and pathologic features of invasive cervical resorption provide the basis for a clinical classification which is of use both in treatment planning and for comparative clinical research. Although the etiology of this condition remains obscure, knowledge of potential predisposing factors is important in assessing patients at risk. Treatment, where indicated, should aim at the inactivation of all resorbing tissue and the reconstitution of the resorptive defect either by the placement of a suitable filing material or by the use of biological systems.
Microbiological and molecular analysis of endodontic infections
Authors: Baumgartner J. Craig
Published: July 2004

This article reviews microbiological and molecular methods used to study the microorganisms associated with endodontic infections. Over 500 species of bacteria have been cultivated from the oral cavity. Endodontic infections are polymicrobial with usually from 3–12 species cultivable from either infected root canals or periradicular abscesses. Molecular methods are able to detect and identify many additional species of bacteria associated with endodontic infections. Molecular methods provide precise identification of the microbes at the DNA level and detection of microbes that are not cultivable. Future research will detect and identify other as yet unknown species of bacteria, viruses, and fungi involved in endodontic infections. Which microorganisms produce virulence factors associated with serious endodontic infections will also be better defined using molecular methods. An increase in knowledge and understanding of the organisms associated with endodontic infections will improve our ability to clinically manage endodontic infections.
Technical equipment for assessment of dental pulp status
Authors: Pitt Ford Thomas R. , Patel Shanon
Published: July 2004

Assessment of dental pulp status is normally undertaken using thermal or electrical tests that indicate the functioning of Aδ nerve fibers. The tests are quick and usually reliable, although nothing is absolute. Newer tests have involved assessment of blood flow, and of these laser Doppler flowmetry has been the most widely used and beneficial to patients particularly after traumatic injury. The high cost of flowmeters and the time‐consuming procedure have limited uptake.
Oxytocin and estrogen receptor α and β knockout mice provide discriminably different odor cues in behavioral assays
Authors: Kavaliers M. , Ågmo A. , Choleris E. , Gustafsson J.‐Å. , Korach K. S. , Muglia L. J. , Pfaff D. W. , Ogawa S.
Published: July 2004

Social behavior involves both the recognition and production of social cues. Mice with selective deletion (knockout) of either the gene for oxytocin (OT) or genes for the estrogen receptor (ER) ‐α or ‐β display impaired social recognition. In this study we demonstrate that these gene knockout mice also provide discriminably different social stimuli in behavioral assays. In an odor choice test, which is a measure of social interest and discrimination, outbred female Swiss‐Webster mice discriminated the urine odors of male knockouts (KO: OTKO, αERKO, βERKO) from the odors of their wildtype littermates (WT: OTWT, αERWT, βERWT). Females showed marked initial choices of the urine odors of OTWT and βERWT males over those of OTKO and βERKO males, and αERKO males over αERWT males. The odors of OTKO and βERKO males also induced aversive, analgesic responses, with the odors of WTs having no significant effects. Odors of both the αERWT and αERKO males induced aversive, analgesic responses, with the odors of the WT inducing significantly greater analgesia. The odors of restraint stressed WT and KO males also elicited analgesia with, again, females displaying significantly greater responses to the odors of stressed OTKO and βERKO males than their WTs, and significantly lower analgesia to the odors of stressed αERKO than αERWT males. These findings show that the KO mice are discriminated from their WTs on the basis of odor and that the various KOs differ in the relative attractiveness/aversiveness of their odors. Therefore, in behavioral assays one causal route by which gene inactivation alters the social behavior of knockout mice may be mediated through the partners' modified responses to their odors.
Human TRPC5 channel activated by a multiplicity of signals in a single cell
Authors: Zeng Fanning , Xu Shang‐Zhong , Jackson Philippa K. , McHugh Damian , Kumar Bhaskar , Fountain Samuel J. , Beech David J.
Published: July 2004

Here we explore the activation mechanisms of human TRPC5, a putative cationic channel that was cloned from a region of the X chromosome associated with mental retardation. No basal activity was evident but activity was induced by carbachol stimulation of muscarinic receptors independently of Ca2+ release. This is ‘receptor activation’, as described for mouse TRPC5. In addition, and in the absence of receptor stimulation, extracellular gadolinium (0.1 mm) activated TRPC5, an effect that was mimicked by 5–20 mm extracellular Ca2+ with intracellular Ca2+ buffered. We refer to this as ‘external ionic activation’. TRPC5 was also activated by modest elevation of [Ca2+]i in the absence of GTP –‘calcium activation’. A putative fourth activation mechanism is a signal from depleted intracellular Ca2+ stores. Consistent with this idea, human TRPC5 was activated by a standard store‐depletion/Ca2+ re‐entry protocol, an effect that was difficult to explain by calcium activation. Multiplicity of TRPC5 activation was demonstrated in single cells and thus not dependent on heterogeneity of expression levels or cellular context. Therefore, human TRPC5 is activated by a range of stimuli, avoiding dependence on a single critical activator as in many other ion channels. One of these stimuli would seem to be a change in Ca2+ handling by the endoplasmic reticulum.
Citrate transport in the human prostate epithelial PNT2‐C2 cell line: electrophysiological analyses
Authors: Mycielska Maria E. , Djamgoz Mustafa B. A.
Published: July 2004

Although prostate synthesizes and releases large amounts of citrate, the mechanism of the release is not well understood. Most known citrate transporters mediate uptake of citrate from extracellular space and, consequently, are driven by the transmembrane Na+ gradient, which would not be appropriate for prostatic function. In the present study, we investigated citrate transport in a normal human prostate cell line, PNT2‐C2, using mainly electrophysiological methods. Intracellular application of citrate through the patch pipette in the whole‐cell recording mode induced an outward current whilst in response to extracellular citrate an inward current was recorded. Membrane currents induced by citrate were bigger than those elicited by other (equimolar) Krebs cycle intermediates. Both inward and outward citrate‐induced currents had the same ionic dependence, inhibitor profile and reversal potential. In particular, the currents were strongly dependent on the transmembrane K+ gradient. Uptake and release of citrate and their K+ dependence were confirmed by spectrophotometric enzyme analyses. Citrate‐induced membrane currents were also sensitive to pH, consistent with the transporter preferring the trivalent form. Application of intracellular Zn2+ generated an outward current which had the same quantitative K+ dependence as the citrate‐induced currents. Extracellular application of a membrane‐permeant Zn2+ chelator generated an inward current. These experiments suggested that m‐aconitase was tonically active in PNT2‐C2 cells. Determination of ‘forward’ and ‘reverse’ K+ stoichiometry both suggested a citrate: K+ ratio of 1: 4. We conclude that normal prostatic epithelial cells possess an electrogenic citrate transporter which mediates the cotransfer of 1 trivalent citrate anion alongside 4 K+ out of cells and thus generates a net outward current.
Requirement of neuronal‐ and cardiac‐type sodium channels for murine sinoatrial node pacemaking
Authors: Lei Ming , Jones Sandra A. , Liu Jie , Lancaster Matthew K. , Fung Simon S.‐M. , Dobrzynski Halina , Camelliti Patrizia , Maier Sebastian K. G. , Noble Denis , Boyett Mark R.
Published: July 2004

The majority of Na+ channels in the heart are composed of the tetrodotoxin (TTX)‐resistant (KD, 2–6 μm) Nav1.5 isoform; however, recently it has been shown that TTX‐sensitive (KD, 1–10 nm) neuronal Na+ channel isoforms (Nav1.1, Nav1.3 and Nav1.6) are also present and functionally important in the myocytes of the ventricles and the sinoatrial (SA) node. In the present study, in mouse SA node pacemaker cells, we investigated Na+ currents under physiological conditions and the expression of cardiac and neuronal Na+ channel isoforms. We identified two distinct Na+ current components, TTX resistant and TTX sensitive. At 37°C, TTX‐resistant iNa and TTX‐sensitive iNa started to activate at ∼−70 and ∼−60 mV, and peaked at −30 and −10 mV, with a current density of 22 ± 3 and 18 ± 1 pA pF−1, respectively. TTX‐sensitive iNa inactivated at more positive potentials as compared to TTX‐resistant iNa. Using action potential clamp, TTX‐sensitive iNa was observed to activate late during the pacemaker potential. Using immunocytochemistry and confocal microscopy, different distributions of the TTX‐resistant cardiac isoform, Nav1.5, and the TTX‐sensitive neuronal isoform, Nav1.1, were observed: Nav1.5 was absent from the centre of the SA node, but present in the periphery of the SA node, whereas Nav1.1 was present throughout the SA node. Nanomolar concentrations (10 or 100 nm) of TTX, which block TTX‐sensitive iNa, slowed pacemaking in both intact SA node preparations and isolated SA node cells without a significant effect on SA node conduction. In contrast, micromolar concentrations (1–30 μm) of TTX, which block TTX‐resistant iNa as well as TTX‐sensitive iNa, slowed both pacemaking and SA node conduction. It is concluded that two Na+ channel isoforms are important for the functioning of the SA node: neuronal (putative Nav1.1) and cardiac Nav1.5 isoforms are involved in pacemaking, although the cardiac Nav1.5 isoform alone is involved in the propagation of the action potential from the SA node to the surrounding atrial muscle.
Steppingstones in Hamiltonian dynamics
Authors: Jordan Thomas F.
Published: July 2004

Easy steps through essential Hamiltonian dynamics are outlined, from necessary definitions of Poisson brackets and canonical transformations, to a quick proof that Hamiltonian evolution is made by canonical transformations, the quickest proof of Liouville’s theorem, and on to the Poincaré-Cartan integral invariants and completely integrable dynamics, making room and providing tools for more recent developments.
Unfamiliar trajectories for a relativistic particle in a Kepler or Coulomb potential
Authors: Boyer Timothy H.
Published: July 2004

Relativistic particles in the Kepler and Coulomb potentials may have trajectories that are qualitatively different from the trajectories found in nonrelativistic mechanics. Spiral scattering trajectories were pointed out by C. G. Darwin in 1913 in connection with the relativistic Rutherford scattering of classical charged particles. Relativistic trajectories are of current interest in connection with Cole and Zou’s computer simulation of the hydrogen ground state in classical physics.
Visual appearance of a Morris–Thorne-wormhole
Authors: Müller Thomas
Published: July 2004

Following the paper of Morris and Thorne on wormholes as a tool for teaching general relativity, we present the visual appearance of this simple spacetime using an embedding diagram and a raytracing program. Even if such a wormhole is not physically reasonable, we take the risk and take a short trip to an unreasonable parallel universe.
Analytical solution for photonic band-gap crystals using Drude conductivity
Authors: Schulkin Brian , Sztancsik Laszlo , Federici John F.
Published: July 2004

An analytical solution for the photonic band-gap of semiconductor structures in the terahertz (THz) frequency range is discussed. In analogy with the Kronig–Penney model for electronic band-gaps in periodic potentials, Maxwell’s equations for the propagation of light in the photonic crystal are transformed into an equivalent form of Schrödinger’s equation. In the THz frequency range, the refractive index of the semiconductor is well represented by a frequency-dependent Drude model. We thus find a Kronig–Penney type solution for the photonic band-gap crystal.
The sled race
Authors: Hite Gerald E.
Published: July 2004

If two sleds with the same initial speed cross a valley, one over a horizontal bridge and the other through the valley, which sled will reach the other side first? If there is no friction and the sled in the valley does not leave the ground, it is easy to see that it will win. To answer the question when friction is present, a valley consisting of circular arcs of equal radii is considered. For this simple, but realistic valley, analytic solutions for the speed of the sleds are used to determine how the outcome of the race depends on friction.
Lenz vector operations on spherical hydrogen atom eigenfunctions
Authors: Burkhardt C. E. , Leventhal J. J.
Published: July 2004

We show that operators capable of converting certain spherical hydrogen atom eigenfunctions into others by raising the angular momentum quantum number ℓ can be constructed from components of the quantum mechanical Lenz vector operator. The derivation is performed using formalism no more sophisticated than that used to derive the properties of the angular momentum ladder operators in undergraduate quantum mechanics courses. The properties of these Lenz vector operators illustrate the accidental degeneracy of the hydrogen atom because they change the quantum number ℓ without affecting n.
A differential formulation of diffraction theory for the undergraduate optics course
Authors: Pritchett Timothy M. , Trubatch A. David
Published: July 2004

The integral formulation of the Huygens–Fresnel principle embodied by the Fresnel–Kirchhoff and Rayleigh–Sommerfeld diffraction formulas constitutes standard treatment of scalar diffraction theory. It is not generally appreciated that the same results can be obtained by using standard methods to solve the relevant partial differential equations: the exact Rayleigh–Sommerfeld integral is equivalent to the scalar Helmholtz equation, and the Rayleigh–Sommerfeld integral in the Fresnel approximation is equivalent to the paraxial wave equation. In view of students’ familiarity with the latter partial differential equation, some pedagogical advantages may be realized if diffraction theory is also formulated in terms of partial differential equations as a supplement to the usual integral formulation.
Reappraising Einstein’s 1909 application of fluctuation theory to Planckian radiation
Authors: Irons F. E.
Published: July 2004

Einstein’s 1909 application of fluctuation theory to Planckian radiation is challenged by the fact that radiation within a completely reflecting cavity is not in thermal equilibrium and therefore should not qualify as a candidate for analysis by Einstein’s theory. We offer an alternative interpretation wherein Planck’s function, to which Einstein applied his theory, represents the source function in the wall material surrounding a real, partially reflecting cavity. The source function experiences thermal fluctuations and radiation within the cavity (which originates in the wall material and has an intensity equal to the source function) fluctuates in concert. That is, blackbody radiation within a real cavity exhibits the thermal fluctuations predicted by Einstein, but the fluctuations have their origin in the wall material and are not intrinsic to radiation.
Structure and Flexibility Adaptation in Nonspecific and Specific Protein-DNA Complexes
Authors: Kalodimos Charalampos G. , Biris Nikolaos , Bonvin Alexandre M. J. J. , Levandoski Marc M. , Guennuegues Marc , Boelens Rolf , Kaptein Robert
Published: July 2004

Interaction of regulatory DNA binding proteins with their target sites is usually preceded by binding to nonspecific DNA. This speeds up the search for the target site by several orders of magnitude. We report the solution structure and dynamics of the complex of a dimeric
lac
repressor DNA binding domain with nonspecific DNA. The same set of residues can switch roles from a purely electrostatic interaction with the DNA backbone in the nonspecific complex to a highly specific binding mode with the base pairs of the cognate operator sequence. The protein-DNA interface of the nonspecific complex is flexible on biologically relevant time scales that may assist in the rapid and efficient finding of the target site.
Steroid-Dependent Auditory Plasticity Leads to Adaptive Coupling of Sender and Receiver
Authors: Sisneros Joseph A. , Forlano Paul M. , Deitcher David L. , Bass Andrew H.
Published: July 2004

For seasonally breeding vertebrates, reproductive cycling is often coupled with changes in vocalizations that function in courtship and territoriality. Less is known about changes in auditory sensitivity to those vocalizations. Here, we show that nonreproductive female midshipman fish treated with either testosterone or 17β-estradiol exhibit an increase in the degree of temporal encoding of the frequency content of male vocalizations by the inner ear that mimics the reproductive female's auditory phenotype. This sensory plasticity provides an adaptable mechanism that enhances coupling between sender and receiver in vocal communication.
Impact of Anthropogenic CO
2
on the CaCO
3
System in the Oceans
Authors: Feely Richard A. , Sabine Christopher L. , Lee Kitack , Berelson Will , Kleypas Joanie , Fabry Victoria J. , Millero Frank J.
Published: July 2004

Rising atmospheric carbon dioxide (CO
2
) concentrations over the past two centuries have led to greater CO
2
uptake by the oceans. This acidification process has changed the saturation state ofthe oceans with respect to calcium carbonate (CaCO
3
) particles. Here we estimate the in situ CaCO
3
dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO
2
on CaCO
3
shell–forming species. CaCO
3
dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO
3
dissolution rate for the global oceans is approximately 0.5 ± 0.2 petagrams of CaCO
3
-C per year, which is approximately 45 to 65% of the export production of CaCO
3
.
The Oceanic Sink for Anthropogenic CO
2
Authors: Sabine Christopher L. , Feely Richard A. , Gruber Nicolas , Key Robert M. , Lee Kitack , Bullister John L. , Wanninkhof Rik , Wong C. S. , Wallace Douglas W. R. , Tilbrook Bronte , Millero Frank J. , Peng Tsung-Hung , Kozyr Alexander , Ono Tsueno , Rios Aida F.
Published: July 2004

Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic anthropogenic carbon dioxide (CO
2
) sink for the period from 1800 to 1994 of 118 ± 19 petagrams of carbon. The oceanic sink accounts for ∼48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO
2
to the atmosphere of about 39 ± 28 petagrams of carbon for this period. The current fraction of total anthropogenic CO
2
emissions stored in the ocean appears to be about one-third of the long-term potential.
Electronic Transitions in Perovskite: Possible Nonconvecting Layers in the Lower Mantle
Authors: Badro James , Rueff Jean-Pascal , Vankó György , Monaco Giulio , Fiquet Guillaume , Guyot François
Published: July 2004

We measured the spin state of iron in magnesium silicate perovskite (Mg
0.9
,Fe
0.1
)SiO
3
at high pressure and found two electronic transitions occurring at 70 gigapascals and at 120 gigapascals, corresponding to partial and full electron pairing in iron, respectively. The proportion of iron in the low spin state thus grows with depth, increasing the transparency of the mantle in the infrared region, with a maximum at pressures consistent with the D″ layer above the core-mantle boundary. The resulting increase in radiative thermal conductivity suggests the existence of nonconvecting layers in the lowermost mantle.
Cognitive Imitation in Rhesus Macaques
Authors: Subiaul Francys , Cantlon Jessica F. , Holloway Ralph L. , Terrace Herbert S.
Published: July 2004

Experiments on imitation typically evaluate a student's ability to copy some feature of an expert's motor behavior. Here, we describe a type of observational learning in which a student copies a cognitive rule rather than a specific motor action. Two rhesus macaques were trained to respond, in a prescribed order, to different sets of photographs that were displayed on a touch-sensitive monitor. Because the position of the photographs varied randomly from trial to trial, sequences could not be learned by motor imitation. Both monkeys learned new sequences more rapidly after observing an expert execute those sequences than when they had to learn new sequences entirely by trial and error.
New Insights from a Classic System
Authors: Hwa Terence
Published: July 2004

A Genetic Switch
Third Edition, Phage Lambda Revisited. by Mark Ptashne. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 2004. 168 pp. Paper, $39, £24.99. ISBN 0-87969-716-4.

This revision includes a new chapter that considers discoveries such as interactions among proteins that bind to widely separated sites on DNA.
An Open Sandwich or an Open Question?
Authors: Clayton Nicola S.
Published: July 2004

Do Animals Think?
. by Clive D. L. Wynne. Princeton University Press, Princeton, NJ, 2004. 276 pp. $26.95, £17.95. ISBN 0-691-11311-4.

Unlike the authors of many other popular accounts of animal cognition, Wynne argues that "animals have neither the 'theory-of-mind' capabilities that humans have...nor the capacity for higher-level reasoning."
Adeno-Associated Virus Site-Specific Integration and AAVS1 Disruption
Authors: Hamilton Henry , Gomos Janette , Berns Kenneth I. , Falck-Pedersen Erik
Published: July 2004

Adeno-associated virus (AAV) is a single-stranded DNA virus with a unique biphasic lifestyle consisting of both a productive and a latent phase. Typically, the productive phase requires coinfection with a helper virus, for instance adenovirus, while the latent phase dominates in healthy cells. In the latent state, AAV is found integrated site specifically into the host genome at chromosome 19q13.4 qtr (AAVS1), the only animal virus known to integrate in a defined location. In this study we investigated the latent phase of serotype 2 AAV, focusing on three areas: AAV infection, rescue, and integration efficiency as a function of viral multiplicity of infection (MOI); efficiency of site-specific integration; and disruption of the AAVS1 locus. As expected, increasing the AAV MOI resulted in an increase in the percentage of cells infected, with 80% of cells infected at an MOI of 10. Additional MOI only marginally effected a further increase in percentage of infected cells. In contrast to infection, we found very low levels of integration at MOIs of less than 10. At an MOI of 10, at which 80% of cells are infected, less than 5% of clonal cell lines contained integrated AAV DNA. At an MOI of 100 or greater, however, 35 to 40% of clonal cell lines contained integrated AAV DNA. Integration and the ability to rescue viral genomes were highly correlated. Analysis of integrated AAV indicated that essentially all integrants were AAVS1 site specific. Although maximal integration efficiency approached 40% of clonal cell lines (essentially 50% of infected cells), over 80% of cell lines contained a genomic disruption at the AAVS1 integration locus on chromosome 19 (≈100% of infected cells). Rep expression by itself and in the presence of a plasmid integration substrate was able to mediate this disruption of the AAVS1 site. We further characterized the disruption event and demonstrated that it resulted in amplification of the AAVS1 locus. The data are consistent with a revised model of AAV integration that includes preliminary expansion of a defined region in AAVS1.
Compartmentalization of Human Immunodeficiency Virus Type 1 between Blood Monocytes and CD4+T Cells during Infection
Authors: Fulcher Jennifer A. , Hwangbo Yon , Zioni Rafael , Nickle David , Lin Xudong , Heath Laura , Mullins James I. , Corey Lawrence , Zhu Tuofu
Published: July 2004

Distinct sequences of human immunodeficiency virus type 1 (HIV-1) have been found between different tissue compartments or subcompartments within a given tissue. Whether such compartmentalization of HIV-1 occurs between different cell populations is still unknown. Here we address this issue by comparing HIV-1 sequences in the second constant region through the fifth hypervariable region (C2 to V5) of the surface envelope glycoprotein (Env) between viruses in purified blood CD14+monocytes and CD4+T cells obtained longitudinally from five infected patients over a time period ranging from 117 to 3,409 days postseroconversion. Viral populations in both cell types at early infection time points appeared relatively homogeneous. However, later in infections, all five patients showed heterogeneous populations in both CD14+monocytes and CD4+T cells. Three of the five patients had CD14+monocyte populations with significantly more genetic diversity than the CD4+T-cell population, while the other two patients had more genetic diversity in CD4+T cells. The cellular compartmentalization of HIV-1 between CD14+monocytes and CD4+T cells was not seen early during infections but was evident at the later time points for all five patients, indicating an association of viral compartmentalization with the time course of HIV-1 infection. The majority of HIV-1 V3 sequences indicated a macrophage-tropic phenotype, while a V3 sequence-predicted T-cell tropic virus was found in the CD4+T cells and CD14+monocytes of two patients. These findings suggest that HIV-1 in CD14+monocytes could disseminate and evolve independently from that in CD4+T cells over the course of HIV-1 infection, which may have implications on the development of new therapeutic strategies.
Canine Distemper Virus and Measles Virus Fusion Glycoprotein Trimers: Partial Membrane-Proximal Ectodomain Cleavage Enhances Function
Authors: von Messling Veronika , Milosevic Dragana , Devaux Patricia , Cattaneo Roberto
Published: July 2004

The trimeric fusion (F) glycoproteins of morbilliviruses are activated by furin cleavage of the precursor F
0
into the F
1
and F
2
subunits. Here we show that an additional membrane-proximal cleavage occurs and modulates F protein function. We initially observed that the ectodomain of approximately one in three measles virus (MV) F proteins is cleaved proximal to the membrane. Processing occurs after cleavage activation of the precursor F
0
into the F
1
and F
2
subunits, producing F
1a
and F
1b
fragments that are incorporated in viral particles. We also detected the F
1b
fragment, including the transmembrane domain and cytoplasmic tail, in cells expressing the canine distemper virus (CDV) or mumps virus F protein. Six membrane-proximal amino acids are necessary for efficient CDV F
1a/b
cleavage. These six amino acids can be exchanged with the corresponding MV F protein residues of different sequence without compromising function. Thus, structural elements of different sequence are functionally exchangeable. Finally, we showed that the alteration of a block of membrane-proximal amino acids results in diminished fusion activity in the context of a recombinant CDV. We envisage that selective loss of the membrane anchor in the external subunits of circularly arranged F protein trimers may disengage them from pulling the membrane centrifugally, thereby facilitating fusion pore formation.
A Mouse-Adapted Enterovirus 71 Strain Causes Neurological Disease in Mice after Oral Infection
Authors: Wang Ya-Fang , Chou Chun-Ting , Lei Huan-Yao , Liu Ching-Chuan , Wang Shih-Min , Yan Jing-Jou , Su Ih-Jen , Wang Jen-Reng , Yeh Trai-Ming , Chen Shun-Hua , Yu Chun-Keung
Published: July 2004

A mouse-adapted enterovirus 71 (EV71) strain with increased virulence in mice, MP4, was generated after four serial passages of the parental EV71 strain 4643 in mice. Strain MP4 exhibited a larger plaque size, grew more rapidly, and was more cytotoxic in vitro than strain 4643. Although strains 4643 and MP4 both induced apoptosis of SK-N-SH human neuroblastoma cells, MP4 was more virulent than 4643 in 1-day-old mice (50% lethal doses, 10
2
and 10
4
PFU/mouse, respectively). Strain MP4 (5 × 10
6
PFU/mouse), but not 4643, could orally infect 7-day-old mice, resulting in rear-limb paralysis followed by death 5 to 9 days after inoculation with the virus. Histopathologically, neuronal loss and apoptosis were evident in the spinal cords as well as the brain stems of the infected mice. The limb muscles displayed massive necrosis. There was early and transient virus replication in the intestines, whereas the spinal cord, brain, and muscle became the sites of viral replication during the late phase of the infection. Virus transmission occurred among infected and noninfected cagemates, as demonstrated by the occurrence of seroconversion and the presence of viable viruses in the stool samples of the latter. Protection against EV71 challenge was demonstrated following administration of hyperimmune serum 1 day after inoculation with the virus. Nucleotide sequence analysis of the genome of EV71 strain MP4 revealed four nucleotide changes on the 5′ untranslated region, three on the VP2 region, and eight on the 2C region, resulting in one and four amino acid substitutions in the VP2 and 2C proteins, respectively.
Inhibition of Infectious Pancreatic Necrosis Virus Replication by Atlantic Salmon Mx1 Protein
Authors: Larsen Rannveig , Røkenes Torunn P. , Robertsen Børre
Published: July 2004

Mx proteins form a family of interferon (IFN)-induced GTPases with potent antiviral activity against various single-stranded RNA viruses in mammals and chickens. In fish, alpha/beta IFN has been reported to inhibit the replication of infectious pancreatic necrosis virus (IPNV), but the mode of action has not been elucidated. A correlation between the inhibition of IPNV and Mx protein expression has, however, been observed. To examine whether Atlantic salmon Mx1 protein (ASMx1) possesses antiviral activity against IPNV, CHSE-214 cells constitutively expressing ASMx1 were established. ASMx1 appeared to be localized in the cytoplasm. The ASMx1-expressing clone selected showed a severely reduced IPNV-induced cytopathic effect, which was confirmed by a 500-fold reduction in virus yield. The antiviral activity against IPNV was further confirmed by the inhibition of virus protein synthesis and the reduced accumulation of virus transcripts. The present work further adds to the body of evidence which suggests that antiviral activity is a major functional role of vertebrate Mx proteins. Moreover, the list of viruses inhibited by Mx proteins is extended to include double-stranded RNA viruses.