bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal drought plays a stronger role than wildfire in shaping macroinvertebrate communities of Mediterranean streams
Authors: Verkaik Iraima , Vila‐Escalé Mireia , Rieradevall Maria , Prat Narcís
Published: August 2013

Mediterranean climate ecosystems are characterised by frequent fires, but few studies have focused on the effects of fire disturbance on biological communities in streams in these ecosystems. To compare the responses of macroinvertebrate communities to wildfire, eight sites were established and annually sampled for 5 years. Two months after fire, the number and abundance of macroinvertebrate taxa were not significantly different from those in control streams, but their composition and functional attributes had changed. As expected, an increase in r‐strategy taxa was observed during the year following fire. Above all, macroinvertebrate assemblages responded more strongly to hydrology (previous spring precipitation) than to fire. Drought was found to be an overriding disturbance factor, but macroinvertebrate assemblages showed high resilience. In a climate change scenario coupled with human demand for water, it will be important to study the effects of drought interacting with other disturbances like wildfire (which is in turn driven by drought).
Inflammatory responses and morphological changes of radiofrequency‐induced rat sciatic nerve fibres
Authors: Choi S. , Choi H.J. , Cheong Y. , Chung S.H. , Park H.K. , Lim Y.J.
Published: August 2013

Background

Recently, the pulsed radiofrequency (PRF, pulsed fashion) procedure was introduced for neuropathic pain management. Since PRF‐induced lesions do not need high temperature compared with conventional continuous RF (CRF)‐induced lesions, there is no significant loss of sensory fibres after application.

Methods

The progressive changes in the expression of eight representative inflammatory cytokines – glial fibrillary acidic protein, tumour necrosis factor alpha, interleukin‐6, cyclooxygenase‐II, inducible nitric oxide synthase, nuclear factor‐κB, monocyte chemoattractant protein‐1 and macrophage inflammatory protein‐1α – as well as the morphological changes in extracellular matrices by Masson's trichrome and Verhoeff–van Gieson staining and atomic force microscopy were assessed for normal (control), sham (no RF current), PRF and CRF (positive control) rats. The RF procedure used in this study was similar to the methods used in human clinical trials.

Results

All proposed inflammatory proteins showed up‐regulation after RF thermal treatments. Specifically, PRF‐treated rats showed recovery of up‐regulated inflammatory cytokines on day 30 after application, while CRF rats showed significant up‐regulation that persisted until day 30. The control and sham groups showed normal unmyelinated axon and collagen structures. PRF‐induced lesions showed less fibre destruction than CRF‐induced lesions. PRF‐induced lesions also showed mild axonal damage and little swelling of the mitochondria. CRF‐induced lesions showed ultrastructural changes of sciatic nerve fibres that were irreversible.

Conclusions

PRF‐induced pain relief may be due to temporary blockage of nerve signals through the nerve pathway responsible for reversible neuronal depression. However, CRF‐induced pain relief may be due to permanent blockage of nerve signals through other nerve pathways. Therefore, CRF could be applied to chronic inflammatory models used to study the mechanism of neuropathic pain.
Ligand- and Stage-Dependent Divergent Functions of BMP Signaling in the Differentiation of Embryonic Skeletogenic Progenitors In Vitro
Authors: Lorda-Diez Carlos I , Montero Juan A , Choe Senyon , Garcia-Porrero Juan A , Hurle Juan M
Published: August 2013

Bone morphogenetic proteins (BMPs) are key molecules in the differentiation of skeletal tissues. We have investigated whether differentiation of limb embryonic mesodermal progenitors into different connective tissue lineages depends on specific stimulation of distinct BMP ligands or on the differential response of target cells to a common BMP stimulus. We show that Bmp2,4,5,7 and Gdf5 exhibit differential expression domains during the formation of tendons, cartilages, and joint tissues in digit development, but their respective effects on digit progenitors cell cultures cannot sustain the divergent differentiation of these cells into tendons, joints, and cartilage. However, the influence of BMPs differs based on the culture length. Early cultures respond to any of the BMPs by inducing chondrogenic factors and inhibiting fibrogenic and osteogenic markers. Later, a second phase of the culture occurs when BMPs attenuate their prochondrogenic influence and promote the fibrogenic marker Scleraxis. At advanced culture stages, BMPs inhibit prochondrogenic and profibrogenic markers and promote osteogenic markers. The switch from the prochondrogenic to the profibrogenic response appears critically dependent on the basal expression of Noggin. Thus, the differential regulation of Scleraxis at these stages was abrogated by treatments with a BMP-analogous compound (AB204) that escapes NOGGIN antagonism. Gene regulation experiments in absence of protein synthesis during the first period of culture indicate that BMPs activate at the same time master chondrogenic and fibrogenic genes together with cofactors responsible for driving the signaling cascade toward chondrogenesis or fibrogenesis. Gene-silencing experiments indicate that Id2 is one of the factors limiting the profibrogenic influence of BMPs. We propose that connective tissues are dynamic structures composed of cartilage, fibrous tissue, and bone that form in successive steps from the differentiation of common progenitors. This sequential differentiation is regulated by BMPs through a process that is dependent on the basal expression of BMP cofactors or signaling modulators. © 2014 American Society for Bone and Mineral Research.
Atypical Femoral Fractures: Transverse Morphology at Lateral Cortex Is a Critical Feature
Authors: Ng Alvin C , Png Meng Ai , Mohan P Chandra , Koh Joyce SB , Howe Tet Sen
Published: August 2013

In 2010, the American Society for Bone and Mineral Research (ASBMR) task force defined major and minor features to assist in the case finding and reporting of atypical femoral fractures (AFFs). One major feature that was proposed was a “transverse or short oblique configuration.” Our primary aim was to compare the conventional overall fracture morphology (OFM) with its associated angle (OFMA) and our proposed lateral cortical fracture angle (LCFA) in the assessment of fracture configuration in suspected AFFs and non-AFFs. The radiographs of 79 patients with AFFs and 39 patients with non-AFFs were each analyzed by two blinded reviewers to obtain the OFM, OFMA, and LCFA. Using the overall fracture morphology to assess the suspected AFFs resulted in discordance between reviewers in 18 cases (22.8%), of which 5 (6.3%) were discordant between short oblique (>30° to 60°) and long oblique (>60° to 90°) configurations, therefore affecting their classifications as AFFs. By assessing only the critical component within the lateral cortex, all the suspected AFFs fell well within the classification as transverse fractures with a mean LCFA of 4.8° (range 0.3 to 18.0, SD = 4.23). The inter-reader variability was also lower for LCFA versus OFMA (4.1° versus 6.9°, p = 0.001) when used to assess AFFs. Fracture angles were significantly different in AFFs versus non-AFFs regardless of whether the OFMA or LCFA methodology was employed, but the greater difference associated with LCFA suggests its greater discriminating power. When LCFA was used in conjunction with 0° to 30° as the criteria for transverse morphology, all the AFFs and non-AFFs were correctly classified. By using a standardized and precise method in measuring the fracture angle, specifically using only the component of the lateral cortex and limiting to truly transverse fractures, ie, between 0° and 30°, the LCFA is a robust and accurate method to assess the fracture morphology in suspected AFFs. © 2014 American Society for Bone and Mineral Research.
Effects of changeover delay on response allocation during probe tests
Authors: McDevitt Margaret A. , Bell Matthew C.
Published: August 2013

The present study assessed whether a pattern of responding that develops when choosing between two alternatives generalizes to novel choice tests when alternatives are presented in new combinations. Pigeons were trained on a two‐component multiple schedule. In both components, a concurrent variable‐interval (VI) 40‐s VI 80‐s schedule was used. The COD was 1 s in one component and 10 s in the other. The long COD produced consistently longer dwell times than the short COD did. Following training, subjects were presented with four types of probe‐test components in which one alternative was drawn from the component with the short COD and one alternative was drawn from the component with the long COD. When the schedule values of the two alternatives were identical (VI 40 vs. VI 40 and VI 80 vs. VI 80), subjects preferred the alternative trained with the long COD (Ms = .78 and .61, respectively). Additionally, subjects preferred the VI 40‐s alternative trained with the long COD to the VI 80‐s alternative that was trained with the short COD (M = .85). Systematic preference was not observed when subjects were given a choice between the VI 40‐s alternative that was trained with the short COD and the VI 80‐s alternative that was trained with the long COD. These results demonstrate that a stimulus associated with a longer COD, and thus longer dwell times in baseline training, may be more preferred during probe tests than expected on the basis of the rate of primary reinforcement associated with that stimulus.
Search for the Slichter modes based on a new method: Optimal sequence estimation
Authors: Ding Hao , Shen Wen‐Bin
Published: August 2013

The inner core translational mode (1S1), known as the Slichter triplet, can provide important information particularly on the Earth's inner core and its dynamics. A time domain spectral analysis method, the optimal sequence estimation (OSE), is devised and applied to search for the Slichter modes. Applications of the OSE and the multistation experiment (MSE) technique for detection of the singlets of 3S1 and 2S1 show that both OSE and MSE can isolate their singlets, but OSE provides a higher signal‐to‐noise ratio. OSE also can completely isolate the modes 0S2 and 1S2. Using two superconducting gravimeter data sets from nine Global Geodynamic Project stations before and after the 2004 Sumatra earthquake, we search for the possible Slichter triplet via OSE and provide a simple validation using the product spectrum. We set two preliminary criteria in order to identify possible signals; results show three signals as candidates for the Slichter triplet, more likely in the data after the 2004 Sumatra earthquake. While choosing the most reasonable criteria needs further studies, we emphasize here the effectiveness of the OSE in searching for the Slichter modes rather than claiming actual detections.
Semiautomated tremor detection using a combined cross‐correlation and neural network approach
Authors: Horstmann T. , Harrington R. M. , Cochran E. S.
Published: August 2013

Despite observations of tectonic tremor in many locations around the globe, the emergent phase arrivals, low‐amplitude waveforms, and variable event durations make automatic detection a nontrivial task. In this study, we employ a new method to identify tremor in large data sets using a semiautomated technique. The method first reduces the data volume with an envelope cross‐correlation technique, followed by a Self‐Organizing Map (SOM) algorithm to identify and classify event types. The method detects tremor in an automated fashion after calibrating for a specific data set, hence we refer to it as being “semiautomated”. We apply the semiautomated detection algorithm to a newly acquired data set of waveforms from a temporary deployment of 13 seismometers near Cholame, California, from May 2010 to July 2011. We manually identify tremor events in a 3 week long test data set and compare to the SOM output and find a detection accuracy of 79.5%. Detection accuracy improves with increasing signal‐to‐noise ratios and number of available stations. We find detection completeness of 96% for tremor events with signal‐to‐noise ratios above 3 and optimal results when data from at least 10 stations are available. We compare the SOM algorithm to the envelope correlation method of Wech and Creager and find the SOM performs significantly better, at least for the data set examined here. Using the SOM algorithm, we detect 2606 tremor events with a cumulative signal duration of nearly 55 h during the 13 month deployment. Overall, the SOM algorithm is shown to be a flexible new method that utilizes characteristics of the waveforms to identify tremor from noise or other seismic signals.
Frictional properties of shale reservoir rocks
Authors: Kohli Arjun H. , Zoback Mark D.
Published: August 2013

We performed laboratory friction experiments on shale samples from three hydrocarbon reservoirs to assess compositional controls on fault slip behavior accompanying hydraulic stimulation. The samples span a range of clay and total organic content from ~10 to 60% by weight and demonstrate fine‐scale heterogeneity within each reservoir. Friction measurements demonstrate strong dependence of strength and rate‐state constitutive properties on shale composition. Shale samples with clay and organic content above ~30% by weight show coefficient of friction ~0.4 and consistently velocity‐strengthening behavior, while those below this threshold show increased strength and velocity‐weakening behavior. This transition in frictional strength and stability suggests a change in the shale grain packing framework from rigid clast supported to clay mineral and organic matter supported. Measurements of gouge dilatancy further support these relationships, showing a negative correlation with clay and organic content. Critical slip evolution distance exhibits similar dependence on composition, implying common micromechanical mechanisms for the observed transition in frictional behavior. We performed microstructural characterization of the experimental samples and observe changes in the gouge load‐bearing framework and shear localization features consistent with these mechanical data. While these results can be applied generally to infer slip stability on faults in clay‐bearing sedimentary rock, we employ the experimental data to place constraints on microearthquake magnitudes and the occurrence of slow shear slip on preexisting faults during hydraulic stimulation in shale reservoirs.
Broadscale interseismic deformation and fault slip rates in the central Tibetan Plateau observed using InSAR
Authors: Garthwaite Matthew C. , Wang Hua , Wright Tim J.
Published: August 2013

Knowledge of the number, location, and interseismic slip rate of crustal faults is key to our understanding of the bulk mechanics of continental deformation. However, at present, the sparsity of geodetic velocity observations is a major limiting factor to improving our knowledge of the fault network. In this study, we combine long‐swath interferometric synthetic aperture radar (InSAR) data to form an interseismic displacement rate map of over 1000 km length spanning the central Tibetan Plateau. Our dense geodetic observations indicate that strain varies smoothly in space without major concentration at previously mapped faults. Discrepancy between line‐of‐sight InSAR and GPS observations between 33°N–35°N could indicate ~4 mm/yr of surface uplift in this region. Derived strain rates are less than 5 × 10−8 yr−1 across the plateau. At the E‐W left‐lateral Kunlun fault, postseismic deformation following the 2001 Kokoxili earthquake results in an observed strain rate of 18 ± 4 × 10−8 yr−1 across a 100 km wide zone. Following removal of a viscoelastic model, we estimate an interseismic slip rate of 12 ± 2 mm/yr for the Kunlun fault. In the central Tibetan conjugate fault zone, the NE‐SW striking Amdo‐Sewa and NW‐SE striking Beng Co faults have right‐lateral slip rates of 6 ± 1 mm/yr and 1–4 ± 1 mm/yr, respectively. Meanwhile, the NE‐SW striking Dongqiao fault has a left‐lateral slip rate of 1–2 ± 1 mm/yr. The low slip rates we estimate for these faults indicate that tectonic strain is more broadly distributed across the plateau interior, perhaps due to the lithosphere being weak and without the abrupt strength contrasts that exist at the plateau margins.
Complex anisotropy beneath the Peruvian flat slab from frequency‐dependent, multiple‐phase shear wave splitting analysis
Authors: Eakin Caroline M. , Long Maureen D.
Published: August 2013

Flat or shallow subduction is a relatively widespread global occurrence, but the dynamics remain poorly understood. In particular, the interaction between flat slabs and the surrounding mantle flow has yet to be studied in detail. Here we present measurements of seismic anisotropy to investigate mantle flow beneath the Peruvian flat‐slab segment, the largest present‐day region of flat subduction. We conduct a detailed shear wave splitting analysis at a long‐running seismic station (NNA) located near Lima, Peru. We present measurements of apparent splitting parameters (fast direction φ and delay time δt) for SKS, ScS, and local S phases from 80 events. We observe well‐defined frequency dependence and backazimuthal variability, indicating the likely presence of complex anisotropy. Forward modeling the observations with two or three layers of anisotropy reveals a likely layer with a trench‐normal fast direction underlying a layer with a more trench‐oblique (to trench‐subparallel) fast direction. In order to further constrain the anisotropic geometry, we analyzed the source‐side splitting from events originating within the slab measured at distant stations. Beneath the flat‐slab segment, we found trench‐normal fast splitting directions in the subslab mantle, while within the dipping portion of the slab further to the east, likely trench‐subparallel anisotropy within the slab itself. This subslab pattern contradicts observations from elsewhere in South America for “normal” (i.e., more steeply dipping) slab conditions. It is similar, however, to inferences from other shallowly dipping subduction zones around the world. While there is an apparent link between slab dip and the surrounding mantle flow, at least beneath Peru, the precise nature of the relationship remains to be clarified.
A Novel Facile Synthesis Method of N‐Vinylpyrroles
Authors: Lan Tian , Chen Xiaofen , Liu Zenglu , Mao Zhenmin
Published: August 2013

A facile and effective synthesis of N‐vinylpyrroles had been explored. The synthetic approach was practicable for preparation of N‐vinylpyrroles for the mild reaction conditions and readily available materials, compared with previously inaccessible N‐vinylpyrroles with electron‐withdrawing groups, especially these pyrroles bearing alkaline sensitive substitution groups.
Synthesis, Characterization, and Antimicrobial Studies of Novel Benzodipyran Analog of Chloramphenicol
Authors: Kalkhambkar Rajesh G. , Kulkarni Geeta M. , Kadakol Jagannath C. , Aridoss G. , Jeong Yeon Tae , Kulkarni Manohar V.
Published: August 2013

A synthesis, characterization, and antimicrobial study of a novel benzodipyran analog of chloramphenicol was carried out. Structure–antimicrobial activity relationship study indicates that benzodipyran analog of chloramphenicol was most active against Gram‐positive bacteria, Staphylococcus aureus, and the fungal strains Rhizoctonia bataticola and Penicillium even at minimum inhibitory concentration 10 µg/mL and showed moderate activity in other bacterial and fungal organisms. All the compounds synthesized during the present investigation were characterized by IR, 1H NMR, 13C NMR, ESI‐MS, and elemental analysis.
Efficient Synthesis of 2,3‐Disubstituted‐1,3‐benzoxazines by Chlorotrimethylsilane‐Mediated Aza‐Acetalizations of Aromatic Aldehydes
Authors: Tang Zilong , Zhu Zhonghua , Yan Lin , Chang Shuhong , Liu Hanwen
Published: August 2013

A series of novel substituted 3,4‐dihydro‐2H‐1,3‐benzoxazines were prepared in moderate to good yields by aza‐acetalizations of aromatic aldehydes with 2‐(N‐substituted aminomethyl)phenols in the presence of chlorotrimethylsilane or SnCl4. It was found that chlorotrimethylsilane was more effective for the reaction, especially for the reaction of fluorobenzaldehyde, and thereby, an efficient method for the preparation of 3,4‐dihydro‐2H‐1,3‐benzoxazines was developed. The structures of the compounds were determined by FT‐IR, 1H NMR, 13C NMR, MS, and elemental analysis.
Use of a handheld Raman spectrometer for fast screening of microbial pigments in cultures of halophilic microorganisms and in microbial communities in hypersaline environments in nature
Authors: Jehlička J. , Oren A.
Published: August 2013

A compact handheld Raman spectrometer equipped with a 532 nm excitation laser was used to detect pigments as possible biomarkers in autotrophic (cyanobacteria and purple sulfur bacteria) and heterotrophic halophilic microorganisms (Archaea of the family Halobacteriaceae, Salinibacter). Common as well as less common carotenoids, including α‐bacterioruberin, salinixanthin, and spirilloxanthin derivatives were detected in cell pellets of model organisms belonging to the genera Haloferax, Haloarcula, Halobacterium (Archaea), Salinibacter (Bacteroidetes), and Ectothiorhodospira (Gammaproteobacteria). Direct measurements on such cultures provide fast and reliable identification of pigments. Bacterioruberin was detected as the dominant carotenoid in pellets of cells collected from the saltern crystallizer ponds in Eilat, Israel. Raman analysis of the colored layered microbial communities in a benthic gypsum crust in the saltern evaporation ponds showed signals consistent with the presence of myxoxanthophyll and echinenone carotenoids in the upper orange and dark‐green cyanobacterial layers. Chlorophyll a and phycocyanin expected in the green layer were not detected using the green excitation. Spirilloxanthin dominates the red layer below, inhabited mainly by purple sulfur bacteria. To our best knowledge, this is the first attempt to detect and identify pigments in natural microbial communities consisting of different types of halophilic microorganisms by direct Raman spectrometric measurements using light compact handheld devices. Copyright © 2013 John Wiley & Sons, Ltd.
Influence of preheating on antioxidant activity of the water extract from black soybean and color and sensory properties of black soybean decoction
Authors: Hsu Cheng‐Kuang , Lin Wei‐Hsuan , Yang Huai‐Wen
Published: August 2013

BACKGROUND

Our previous study indicated that black soybean (BS) tea (BST) made from preheated BS showed a significant protective effect against CCl4‐induced liver damage in Sprague Dawley rats due to BS's antioxidant activity. In this study, we investigated three different preheating methods on the antioxidant activity of water extract from BS (WBS) (Glycine max (L.) Merrill), as well as on the color and sensory properties of BST.

RESULTS

WBS baked at 130 °C for 5 min showed high total phenol, flavonoid and anthocyanin contents among three preheating methods, as well as high DPPH radical‐scavenging activity, ferrous ion chelating ability and reducing power. BST baked at 130 °C for 5 min had higher polyphenol oxidase activity and L*, a* and b* values but lower peroxidase activity then BST made from unheated BS. Sensory evaluation indicated that BST made from baked BS produced better aroma and flavor than the tea made from unheated BS or a commercial preheated BS.

CONCLUSION

An appropriate preheating process improved the amount of extractable antioxidant and the antioxidant activity in WBS. BST baked at 130 °C for 5 min had good flavor properties, as well as high amount of antioxidant. © 2013 Society of Chemical Industry
A study of optimal viewing distance in a parallax barrier 3D display
Authors: Huang Kuo‐Chung , Chou Yi‐Heng , Lin Lang‐chin , Lin Hoang Yan , Chen Fu‐Hao , Liao Ching‐Chiu , Chen Yi‐Han , Lee Kuen , Hsu Wan‐Hsuan
Published: August 2013

The optimal viewing distance was proposed as a parameter for designing a parallax barrier 3D display. It can be designed based on simple geometric method and by considering the pitches of image display pixels and parallax barrier, or even including the aperture ratios of the image display pixels and parallax barrier. It can be analyzed by using ray tracing method. By considering the optical refraction index of the cover glass, the angular behavior of the system becomes more realistic; however, the geometric method is difficult to be used. We propose a revised method for estimating the view distance and angular behavior. In this paper, we have demonstrated a designated eye position (DEP) for each view and shown that multiple DEPs make a circular curve around the center of the display. We prove the new concept by comparing the optical ray tracing calculations and optical measurement.
A Quantitative Structure–Reactivity Assessment of Phenols by Investigation of Rapid Iodination Kinetics Using Hydrodynamic Voltammetry: Applicability of the Hammett Equation in Aqueous Medium
Authors: Borkar Vitthal T. , Bonde Shantaram L. , Dangat Vijay T.
Published: August 2013

Halogenations of aromatic substrates in aqueous medium are essentially electrophilic substitutions proceeding at rates concomitant with the nature of the substrates and substituent motifs. Kinetics as an investigatory tool for the quantitative assessment of the structure–reactivity correlation in these reactions for a diverse range of substrates has rarely been reported, presumably due to the rapidity of these reactions in aqueous medium. We have used hydrodynamic voltammetry to investigate the rapid kinetics of uncatalyzed iodination of phenol and eight substituted phenols by iodine monochloride at constant pH in aqueous medium. The Arrhenius plots for these reactions yield comprehensive kinetic and thermodynamic data. The quantitative structure–reactivity correlation stemming from the regio‐ and stereospecificity of the substituent motifs on the substrates has been examined through the Hammett plot, which shows a negative slope of 1.87. The magnitudes of the rate constants, energies of activation, frequency factors, and entropy change obtained for the nine fast reactions reported, reflect the relative ease of the reaction dynamics in quantitative terms thereby ascertaining the relative reactivities of the phenols studied herein.
Recovery of intrinsic fluorescence from single‐point interstitial measurements for quantification of doxorubicin concentration
Authors: Baran Timothy M. , Foster Thomas H.
Published: August 2013

Background and Objective

We developed a method for the recovery of intrinsic fluorescence from single‐point measurements in highly scattering and absorbing samples without a priori knowledge of the sample optical properties. The goal of the study was to demonstrate accurate recovery of fluorophore concentration in samples with widely varying background optical properties, while simultaneously recovering the optical properties.

Materials and Methods

Tissue‐simulating phantoms containing doxorubicin, MnTPPS, and Intralipid‐20% were created, and fluorescence measurements were performed using a single isotropic probe. The resulting spectra were analyzed using a forward‐adjoint fluorescence model in order to recover the fluorophore concentration and background optical properties.

Results

We demonstrated recovery of doxorubicin concentration with a mean error of 11.8%. The concentration of the background absorber was recovered with an average error of 23.2% and the scattering spectrum was recovered with a mean error of 19.8%.

Conclusion

This method will allow for the determination of local concentrations of fluorescent drugs, such as doxorubicin, from minimally invasive fluorescence measurements. This is particularly interesting in the context of transarterial chemoembolization (TACE) treatment of liver cancer. Lasers Surg. Med. 45:542–550, 2013. © 2013 Wiley Periodicals, Inc.
Low‐level laser (light) therapy (LLLT) for treatment of hair loss
Authors: Avci Pinar , Gupta Gaurav K. , Clark Jason , Wikonkal Norbert , Hamblin Michael R.
Published: August 2013

Objective

Alopecia is a common disorder affecting more than half of the population worldwide. Androgenetic alopecia, the most common type, affects 50% of males over the age of 40 and 75% of females over 65. Only two drugs have been approved so far (minoxidil and finasteride) and hair transplant is the other treatment alternative. This review surveys the evidence for low‐level laser therapy (LLLT) applied to the scalp as a treatment for hair loss and discusses possible mechanisms of actions.

Methods and Materials

Searches of PubMed and Google Scholar were carried out using keywords alopecia, hair loss, LLLT, photobiomodulation.

Results

Studies have shown that LLLT stimulated hair growth in mice subjected to chemotherapy‐induced alopecia and also in alopecia areata. Controlled clinical trials demonstrated that LLLT stimulated hair growth in both men and women. Among various mechanisms, the main mechanism is hypothesized to be stimulation of epidermal stem cells in the hair follicle bulge and shifting the follicles into anagen phase.

Conclusion

LLLT for hair growth in both men and women appears to be both safe and effective. The optimum wavelength, coherence and dosimetric parameters remain to be determined. Lasers Surg. Med. 46:144–151, 2014. © 2013 Wiley Periodicals, Inc.
Porous Hydrogels From Shark Skin Collagen Crosslinked Under Dense Carbon Dioxide Atmosphere
Authors: Fernandes‐Silva Susana , Moreira‐Silva Joana , Silva Tiago H. , Perez‐Martin Ricardo I. , Sotelo Carmen G. , Mano João F. , Duarte Ana Rita C. , Reis Rui L.
Published: August 2013

The possibility to fabricate marine collagen porous structures crosslinked with genipin under high pressure carbon dioxide is investigated. Collagen from shark skin is used to prepare pre‐scaffolds by freeze‐drying. The poor stability of the structures and low mechanical properties require crosslinking of the structures. Under dense CO2 atmosphere, crosslinking of collagen pre‐scaffolds is allowed for 16 h. Additionally, the hydrogels are foamed and the scaffolds obtained present a highly porous structure. In vitro cell culture tests performed with a chondrocyte‐like cell line show good cell adherence and proliferation, which is a strong indication of the potential of these scaffolds to be used in tissue cartilage tissue engineering.
Fabrication of Self‐Healable Hydrogels through Sol–Gel Transition in Metallo‐supramolecular Aqueous Solution by Aeration
Authors: Asoh Taka‐Aki , Yoshitake Haruka , Takano Yota , Kikuchi Akihiko
Published: August 2013

A sol–gel transition and the self‐healing of the resultant hydrogels are achieved utilizing a metallo‐supramolecule composed of terpyridine‐terminated low‐molecular‐weight three‐armed poly(ethylene glycol) (trisPEGtpy450) in water at ambient temperature. The gelation of trisPEGtpy450 with cobalt ions occurs by aerobic oxidation (mild conditions), and therefore the solution can be moulded into any shape hydrogel. The solation of the cured hydrogels occurs spontaneously upon the addition of the reductant, and the solution is then re‐gelled by exposure to air due to the consumption of the reductant. Both a sol–gel transition by aeration and self‐healing of the resultant hydrogels without any stimuli are observed when replacing some of the cobalt ions with nickel ions.

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Soft Nanostructured Films with an Ultra‐Low Volume Fraction of Percolating Hard Phase
Authors: Chenal Marion , Rieger Jutta , Véchambre Cyril , Chenal Jean‐Marc , Chazeau Laurent , Creton Costantino , Bouteiller Laurent
Published: August 2013

In this study, aqueous emulsion polymerization of n‐butyl acrylate is performed in batch conditions without surfactants using a poly(acrylic acid)‐trithiocarbonate macro‐RAFT agent to control the polymerization and to stabilize the emulsion. According to the polymerization‐induced self‐assembly (PISA) approach, well‐defined amphiphilic PAA‐b‐PBA diblock copolymers form and self‐assemble during synthesis to yield highly stable core–shell particles with an extremely thin hard PAA shell. For the first time, we report here the specific properties of films obtained from these particular latexes. After drying the aqueous dispersion, tough and transparent films are obtained. Although the films are not chemically cross‐linked, they do not dissolve in good solvents for PBA. Moreover, they remain transparent even after immersion in water. Rheology shows that the films are both stiff and ductile, thanks to the nanostructured but very low volume fraction (less than 3 wt%) of PAA forming a percolating network in the soft PBA. Compared with conventional core–shell‐based films, this approach affords for the first time a route to a thin percolating honeycomb nanostructure with a sharp and strong interface between the two phases. The versatility of the synthetic procedure opens perspectives for a large range of functional materials.

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Cobalt Replacement in Unsaturated Polyester Resins; Going for Sustainable Composites
Authors: Jansen Johan F.G.A. , Hilker Iris , Kleuskens Engelien , Hensen Guido , Kraeger Ivo , Posthumus Willem
Published: August 2013

As alternative to cobalt based catalysts, various other catalysts based on manganese, iron and/or copper were developed for curing unsaturated polyesters in styrene with a hydroperoxide. This development is based on the simultaneous tuning of the redox chemistry taking place on the transition metal as well as on the ligand. From a mechanical point of view, based on DMA, these systems behave as drop‐ins. Employing these systems, unsaturated polyesters diluted in vinyl esters can also be cured. This makes cobalt‐free and styrene‐ free unsaturated polyesters possible.
Influence of Photopolymerization Characteristics on Thermo‐Mechanical Properties of Nanocomposites Utilizing Polymerizable Organoclays in Thiol‐Acrylate Systems
Authors: Kim Soon Ki , Baguenard Céline , Guymon C. Allan
Published: August 2013

To produce clay nanocomposites, photopolymerizable organoclays can react with monomers and incorporate into polymer matrices during the UV curing process. This research investigates the effects of polymerizable organoclays on the reaction behavior as well as the ultimate composite properties based on in‐situ thiol‐ene photopolymerization. To this end, different types of polymerizable organoclays, prepared by changing the functional group structure, were examined in various thiol‐acrylate systems. Small angle X‐ray diffraction was used to examine the degree of clay exfoliation. Photopolymerization behavior was characterized using real time infrared spectroscopy. Dynamic mechanical analysis was used for analyzing both mechanical and thermal properties. With sufficient clay exfoliation, the incorporation of thiol groups on the clay surfaces significantly increases the photopolymerization rate and final thiol conversion, whereas acrylate group conversion does not change significantly. While increasing monomer functionality does decrease final thiol conversion, the increase of thiol functionality of organoclays enhances thiol‐ene step growth reaction. Dark curing results suggest that the structure of propagating radicals on the clay surface varies by the type of polymerizable organoclays, changing the reaction behavior of the system. In accordance with the reaction behavior, the incorporation of acrylated organoclays significantly increases the storage modulus by inducing dominant acrylate homopolymerization. Addition of thiolated organoclays, on the other hand, makes more flexible polymer chains due to increased thio‐ether linkages.
Synthesis of Model Network Hydrogels via Tetrazine‐Olefin Inverse Electron Demand Diels‐Alder Cycloaddition
Authors: Cok Alexandra M. , Zhou Huaxing , Johnson Jeremiah A.
Published: August 2013

The formation of poly(etheylene glycol) (PEG) model network hydrogels via an A2 + B3 inverse‐electron‐demand tetrazine‐olefin Diels‐Alder cycloaddition is reported. This method provides an efficient, additive‐free, colorimetric gelation reaction that will complement other “click chemistry” approaches to model network synthesis.
Tuning Mechanical Properties of Chondroitin Sulfate‐Based Double‐Network Hydrogels
Authors: Suekama Tiffany C. , Hu Jian , Kurokawa Takayuki , Gong Jian Ping , Gehrke Stevin H.
Published: August 2013

High strength double‐network (DN) biopolymer‐based hydrogels were created using copolymers of methacrylated chondroitin sulfate (MCS) and poly(ethylene glycol) diacrylate (PEGDA) as the first network and polyacrylamide (PAAm) as the second network. The concentration and cross‐linking of the networks were adjusted to control the mechanical properties including the failure stress, failure strain, Young's modulus, and yielding behavior. First, we increased the cross‐linking of the first network both by increasing the MCS concentration from 13 to 20 wt% and by copolymerizing MCS with 2 to 6 wt% PEGDA. The additional cross‐linking increased the Young's modulus as much as five times, reaching 3.3 MPa, and the failure stress up as much as four times, reaching 2.9 MPa. However, this also reduced failure strain from a high of 2.9 mm/mm to a low of 0.12 mm/mm and diminished the yielding region. Changes in the concentrations of acrylamide or its cross‐linking with N,N′‐methylenebisacrylamide (BIS) in the second network had a lesser effect on the DN properties. We hypothesized that to obtain a yielding region which results in high toughness, we need to alter the cross‐linking of the first network such that the yield stress of the MCS‐PEGDA/PAAm DN does not exceed the failure stress of PAAm network. Because of the wide range of mechanical properties achieved in these DNs with limited changes in the swelling degrees, unlike conventional single‐network gels, the DN approach allows attainment of a much greater range of mechanical behavior than is possible with single networks.
Homogeneous Copolymers of Ethylene with α‐olefins Synthesized with Metallocene Catalysts and Their Use as Standards for TREF Calibration
Authors: Cossoul Emilie , Baverel Laetitia , Martigny Elsa , Macko Tibor , Boisson Christophe , Boyron Olivier
Published: August 2013

A range of crystalline copolymers of ethylene with α‐olefins (propene, hexene, octene and octadecene) were prepared using the complexes Et(Ind)2ZrCl2 and (nBuCp)2ZrCl2 activated with MAO. The average composition of the copolymers was measured using 1H‐ and 13C‐NMR. Then the samples were characterized by High Temperature SEC and DSC. These investigations showed that polymers are homogeneous in composition and consequently were suitable to be used as standards for TREF. This work provided calibrations curves for TREF that can be used on a wide range of α‐olefin contents. Finally, these calibrations curves were used to characterize heterogeneous copolymers of ethylene/hexene synthesized using a conventional Ziegler‐Natta catalyst.
Poly(propylene) Heterophasic Copolymers: Molecular Structure Analysis through Fractionation Techniques
Authors: Liberman Susana , de Azeredo Ana Paula , Dos Santos Francisco P. , da Silva Marco A. , Monrabal Benjamin , Mayo Nuria
Published: August 2013

Heterophasic poly(propylene) copolymers obtained by sequential polymerization are multi‐component products formed by a crystalline matrix of poly(propylene) and an ethylene‐propylene rubber phase. Some crystalline polyethylene and poly(ethylene‐co‐propylene) are formed in the rubber synthesis step by copolymerization of ethylene and propylene. These multi‐component systems present a complicated microstructure and heterophasic morphology. In this study, two heterophasic copolymers with the same total amount of rubber but different composition and molecular weight, were thoroughly analyzed. The morphology was evaluated by SEM and AFM techniques. The complexity of the system required some attention in the fractionation methodology to perform an accurate interpretation of results and different methodologies of fractionation, especially for obtaining PE fractions as free of PP as possible, were performed in order to better characterize the crystalline polyethylene fractions in the copolymers. Preparative TREF was used to obtain fractions for further analysis by 13C‐NMR, DSC and GPC. Also samples were submitted to Cross Fractionation Chromatography (CFC). Results obtained by the different methodologies were compared.
The Influence of the Cooling Rate on the Nucleation Efficiency of Isotactic Poly(propylene) with Bis(3,4‐dimethylbenzylidene)sorbitol
Authors: Meijer‐Vissers Tamara , Goossens Han
Published: August 2013

The phase behavior of isotactic poly(propylene) (i‐PP) and 1,3:2,4‐bis(3,4‐dimethylbenzylidene)sorbitol (DMDBS) was studied by using differential scanning calorimetry (DSC), rheology and optical microscopy and can be characterized by a simple binary monotectic phase diagram. DMDBS is a well‐known nucleating and clarifying agent for i‐PP that forms a fibrillar network upon cooling from a homogeneous melt within a specific concentration range. The influence of the cooling rate and the residence time in regime II of the phase diagram on the formation of the fibrillar network and the ratio between the α‐ and mesophase is investigated. This shows that DMDBS is actually a better nucleation agent for i‐PP when it is given less time for gelation, since the formation of a ‘secondary’ structure, in which the thin elementary nano‐fibrils form bundles of thicker fibrils, results in a decrease of the surface area that is available for nucleation.
Mathematical Model of Dynamic Crystallization of Ethylene/1‐Octene Copolymers
Authors: Chokputtanawuttilerd Nuttawat , Anantawaraskul Siripon , Soares João B. P.
Published: August 2013

Dynamic crystallization (DC) is a fractionation technique to enhance physical separation of polymers with different chain crystallizabilities by crystallizing polymer chains from solution in a column under a constant flow rate. In this work, a mathematical model for describing fractionation mechanism of dynamic crystallization based on the concept of population balance, crystallization kinetic, and dispersion models is proposed by the first time. The model was validated with experimental DC analysis of three ethylene/1‐octene copolymers. The simulated DC profiles were found to describe experimental results well.
Cellulose and Soy Proteins Based Membrane Networks
Authors: Zhu Yidan , Douglass Eugene , Theyson Tom , Hogan Robina , Kotek Richard
Published: August 2013

Using the novel ethylenediamine/potassium thiocyanate (ED/KSCN) solvent system developed in our labs, a simpler, environmentally friendlier method was developed to produce membranes using cellulose, proteins, and other polymers. In contrast to current industrial methods that use processes that are relatively expensive with toxic or dangerous solvents, the new system eliminated majority of those concerns. In this study, soy protein concentrate and cellulose was used to develop a nonporous composite membrane with good physical properties. Glutaraldehyde was applied as the crosslinking agent to stabilize the molecular network structure of the blended membranes. Results showed that nonporous membranes were produced that were strong, flexible, and the exposure to the crosslinking agent shown structural and thermal improvement of the network membranes. This resulting blend of biopolymer membranes with improved physical abilities can be useful for food packaging, filtration systems, or even medical applications.
Effect of Multiple Extrusion on Impact Fracture of Three Poly(propylene) Impact Copolymers
Authors: Jancar J. , Tochacek J.
Published: August 2013

The effect of structural changes induced by multiple extrusion on the impact fracture behavior of three reactor poly(propylene) impact‐copolymers (ICPPs) was investigated. The morphogenesis of the complex ICPP structure was controlled by the competition between the intraspherulitic phase separation and crystallization. The rubbery inclusion size was controlled by the rate of spinodal decomposition at the onset of crystallization. The following fast spherulite growth fixed the size and spatial distribution of these inclusions. The Charpy notched impact strength (ak) and critical strain energy release rate (Gc) measured under impact loading decreased significantly with the number of extruder passes. A measurable reduction of the size of the crack tip plastic zone (Rp) with the number of extruder passes was observed using high speed digital camera. While the melt flow index (MFI) dependence of ak exhibited ICPP specific shape, the MFI dependences of Gc fell on a single master curve at both 23 and −20 °C.
Modeling of Free Radical Styrene/Divinylbenzene Copolymerization with the Numerical Fractionation Technique
Authors: Nikitin Anatoly N. , Wulkow Michael , Schütte Christof
Published: August 2013

The modeling approach called “numerical fractionation” has been incorporated into a PREDICI model to simulate crosslinking copolymerization. In order to take inhomogeneities of the considered copolymerization into account, the kinetic parameters of the model are proposed to be different for each generation of the numerical fractionation. Using this approach the chain‐length dependence of the termination has been incorporated into the model so that even the method of moments could be applied to study crosslinking copolymerization. The styrene/m‐divinylbenzene crosslinking copolymerization at low crosslinker content has been simulated. The chain‐length dependence of the termination has been found to accelerate the gel point in monovinyl/divinyl copolymerization and must be taken into account for a correct description of the gel points.
Sequential free tissue transfers for simultaneous upper and lower limb salvage
Authors: Valerio Ian L. , Sabino Jennifer , Bevevino Adam , Tintle Scott M. , Fleming Mark , Kumar Anand
Published: August 2013

Background: The Iraq and Afghanistan Wars have presented military reconstructive surgeons with a high volume of challenging extremity injuries. In recent years, a number of upper and lower extremity injuries requiring multiple tissue transfers for multiple limb salvages in the same casualty have been encountered. Our group will discuss the microsurgical challenges, algorithms, and success and complication rates for this cohort of war injured patients. Methods: All consecutive limb salvage cases requiring free flaps from 2003 to 2012 were reviewed. Cases involving simultaneous free tissue transfers were identified. Data collected included success rates and complications with comparisons made between the single and multiple free‐flap limb salvage cohorts. Results: Seventy‐four free flap limb salvage cases were performed over the 10‐year period. Of these cases, four patients received two free flaps to separate upper and lower extremity injuries for limb salvage within a single operative setting. The complication rate was 63%, which was significantly higher than those cases in which a single microvascular anastomosis was performed (26%, p = 0.046). However, the higher complication rate did not increase the flap or limb salvage failure rates (p = 0.892 and 0.626). Conclusions: The last decade of war trauma has provided a high volume of extremity injuries requiring limb salvage procedures including casualties who underwent single and multiple free flap coverage procedures. Although multiple flap limb salvage procedures have a higher complication rate, they can be performed within the same patient without concern for increased failure rate in carefully selected and appropriately managed patients. © 2013 Wiley Periodicals, Inc. Microsurgery 33:447–453, 2013.