bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanically stimulated osteocytes maintain tumor dormancy in bone metastasis of non-small cell lung cancer by releasing small extracellular vesicles
Authors: Xie Jing , Xu Yafei , Liu Xuhua , Long Li , Chen Ji , Huang Chunyan , Shao Yan , Cai Zhiqing , Zhang Zhimin , Zhou Ruixin , Leng Jiarong , Bai Xiaochun , Song Qiancheng
Published: March 2024

Although preclinical and clinical studies have shown that exercise can inhibit bone metastasis progression, the mechanism remains poorly understood. Here, we found that non-small cell lung cancer (NSCLC) cells adjacent to bone tissue had a much lower proliferative capacity than the surrounding tumor cells in patients and mice. Subsequently, it was demonstrated that osteocytes, sensing mechanical stimulation generated by exercise, inhibit NSCLC cell proliferation and sustain the dormancy thereof by releasing small extracellular vesicles with tumor suppressor micro-RNAs, such as miR-99b-3p. Furthermore, we evaluated the effects of mechanical loading and treadmill exercise on the bone metastasis progression of NSCLC in mice. As expected, mechanical loading of the tibia inhibited the bone metastasis progression of NSCLC. Notably, bone metastasis progression of NSCLC was inhibited by moderate exercise, and combinations with zoledronic acid had additive effects. Moreover, exercise preconditioning effectively suppressed bone metastasis progression. This study significantly advances the understanding of the mechanism underlying exercise-afforded protection against bone metastasis progression.
The Rapidly Evolving X-linked miR-506 Family Finetunes Spermatogenesis to Enhance Sperm Competition
Authors: Wang Zhuqing , Wang Yue , Zhou Tong , Chen Sheng , Morris Dayton , Magalhães Rubens Daniel Miserani , Li Musheng , Wang Shawn , Wang Hetan , Xie Yeming , McSwiggin Hayden , Oliver Daniel , Yuan Shuiqiao , Zheng Huili , Mohammed Jaaved , Lai Eric C. , McCarrey John R. , Yan Wei
Published: March 2024

Despite rapid evolution across eutherian mammals, the X-linked
miR-506
family miRNAs are located in a region flanked by two highly conserved protein-coding genes (
Slitrk2
and
Fmr1
) on the X chromosome. Intriguingly, these miRNAs are predominantly expressed in the testis, suggesting a potential role in spermatogenesis and male fertility. Here, we report that the X-linked
miR-506
family miRNAs were derived from the MER91C DNA transposons. Selective inactivation of individual miRNAs or clusters caused no discernable defects, but simultaneous ablation of five clusters containing nineteen members of the
miR-506
family led to reduced male fertility in mice. Despite normal sperm counts, motility and morphology, the KO sperm were less competitive than wild-type sperm when subjected to a polyandrous mating scheme. Transcriptomic and bioinformatic analyses revealed that these X-linked
miR-506
family miRNAs, in addition to targeting a set of conserved genes, have more targets that are critical for spermatogenesis and embryonic development during evolution. Our data suggest that the
miR-506
family miRNAs function to enhance sperm competitiveness and reproductive fitness of the male by finetuning gene expression during spermatogenesis.The X-linked
miR-506
family has rapidly evolved in mammals, but their physiological significance remains elusive. Given their abundant and preferential expression in the testis and sperm, these X-linked miRNAs likely play a functional role in spermatogenesis and/or early embryonic development. However, the deletion of either individual miRNA genes or all of the five miRNA clusters encoding 38 mature miRNAs did not cause major fertility defects in mice. When these mutant males were subjected to conditions resembling polyandrous mating, the mutant sperm were much less competitive than the wild-type sperm, rendering the mutant males “functionally sub-fertile”. Our data suggest that the
miR-506
family of miRNAs regulates sperm competition and the reproductive fitness of the male.
Physiological roles of endocytosis and presynaptic scaffold in vesicle replenishment at fast-signaling and slow-plastic synapses
Authors: Mahapatra Satyajit , Takahashi Tomoyuki
Published: March 2024

After exocytosis, release sites are cleared of vesicular residues to be replenished with transmitter-filled vesicles. Endocytic and scaffold proteins are thought to underlie this mechanism. However, physiological significance of the site-clearance mechanism among diverse central synapses remains unknown. Here, we tested this using action-potential evoked EPSCs at fast-signaling calyx and slow-plastic hippocampal CA1 synapses in post-hearing mice brain slices at physiological temperature and Ca
2+
. Pharmacological block of endocytosis enhanced synaptic depression at the calyx synapse, whereas it attenuated synaptic facilitation at the hippocampal synapse. Block of scaffold protein activity likewise enhanced synaptic depression at the calyx but had no effect at the hippocampal synapse. At the calyx, enhancement of synaptic depression by blocking endocytosis or scaffold activity occurred at nearly identical time courses with a time constant of several milliseconds starting immediately after the stimulation onset. Neither endocytic nor scaffold protein inhibitors prolonged the recovery from short-term depression. We conclude that endocytic release-site clearance can be a universal phenomenon supporting vesicle replenishment across fast-signaling and slow-plastic synapses, whereas presynaptic scaffold mechanism likely plays a specialized role in vesicle replenishment predominantly at fast synapses.
Endocrine disruptor-induced epimutagenesis in vitro: Insight into molecular mechanisms
Authors: Lehle Jake D. , Lin Yu-Huey , Gomez Amanda , Chavez Laura , McCarrey John R.
Published: March 2024

Endocrine disrupting chemicals (EDCs) such as bisphenol S (BPS) are xenobiotic compounds that can disrupt endocrine signaling following exposure due to steric similarities to endogenous hormones within the body. EDCs have been shown to induce disruptions in normal epigenetic programming (epimutations) that accompany dysregulation of normal gene expression patterns that appear to predispose disease states. Most interestingly, the prevalence of epimutations following exposure to many different EDCs often persists over multiple subsequent generations, even with no further exposure to the causative EDC. Many previous studies have described both the direct and prolonged effects of EDC exposure in animal models, but many questions remain about molecular mechanisms by which EDCs initially induce epimutations or contribute to the propagation of EDC-induced epimutations either within the exposed generation or to subsequent generations. Additional questions remain regarding the extent to which there may be differences in cell type-specific susceptibilities to various EDCs, and whether this susceptibility is correlative with expression of relevant hormone receptors and/or the location of relevant hormone response elements (HREs) in the genome. To address these questions, we exposed cultured mouse pluripotent (induced pluripotent stem [iPS]), somatic (Sertoli and granulosa), and germ (primordial germ cell like [PGCLCs]) cells to BPS and measured changes in DNA methylation levels at the epigenomic level and gene expression at the transcriptomic level. We found that there was indeed a difference in cell type-specific susceptibility to EDC-induced epimutagenesis and that this susceptibility correlated with differential expression of relevant hormone receptors and, in many cases, tended to generate epimutations near relevant HREs within the genome. Additionally, however, we also found that BPS can induce epimutations in a cell type that does not express relevant receptors and in genomic regions that do not contain relevant HREs, suggesting that both canonical and non-canonical signaling mechanisms can be disrupted by BPS exposure. Most interestingly, we found that when iPS cells were exposed to BPS and then induced to differentiate into PGCLCs, the prevalence of epimutations and differentially expressed genes (DEGs) initially induced in the iPSCs was largely retained in the resulting PGCLCs, however, >90% of the specific epimutations and DEGs were not conserved but were rather replaced by novel epimutations and DEGs following the iPSC to PGCLC transition. These results suggest a unique mechanism by which an EDC-induced epimutated state may be propagated transgenerationally following a single exposure to the causative EDC.
A Memory Model of Rodent Spatial Navigation: Place Cells are Memories Arranged in a Grid and Grid Cells are Non-spatial
Authors: Huber David E
Published: March 2024

A theory and neurocomputational model are presented that explain grid cell responses as the byproduct of equally dissimilar hippocampal memories. On this account, place and grid cells are best understood as the natural consequence of memory encoding and retrieval. In the proposed memory model, place cells represent memories that are conjunctions of both spatial and non-spatial attributes, and grid cells primarily represent the non-spatial attributes (e.g., sounds, surface texture, etc.) found throughout the two-dimensional recording enclosure. Place cells support memories of the locations where non-spatial attributes can be found (e.g., positions with a particular sound), which are arranged in a hexagonal lattice owing to memory encoding and consolidation processes (pattern separation) as applied to situations in which the non-spatial attributes are found at all locations of a two-dimensional surface. Grid cells exhibit their spatial firing pattern owing to feedback from hippocampal place cells (i.e., a hexagonal pattern of remembered locations for the non-spatial attribute represented by a grid cell). The model explains: 1) grid fields that appear to be centered outside the box; 2) the toroidal nature of grid field representations; 3) grid field alignment with the enclosure borders; 4) modules in which grid cells have the same orientation and spacing but different phases; 5) head direction conjunctive grid cells that become simple head direction cells in the absence of hippocampal feedback; 6) the instant existence of grid fields in a novel environment; 7) the slower learning of place cells; 8) the manner in which head direction sensitivity of place cells changes near borders and in narrow passages; 9) the kinds of changes that underlie remapping of place cells; and 10) grid-like responses for two-dimensional coordinate systems other than navigation.
Human induced pluripotent stem cell-derived cardiomyocytes to study inflammation-induced diastolic dysfunction
Authors: Tatekoshi Yuki , Chen Chunlei , Shapiro Jason , Chang Hsiang-Chun , Blancard Malorie , Burridge Paul W. , Burridge Paul , Feinstein Matthew , D’Aquila Richard , Hsue Priscilla , Ardehali Hossein
Published: March 2024

Heart failure with preserved ejection fraction (HFpEF) is commonly found in persons living with HIV (PLWH) even when antiretroviral therapy (ART) suppresses HIV viremia. However, studying this condition has been challenging because an appropriate animal model is not available. In this paper, we study the relaxation function of human induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs) in culture to simulate HFpEF and to assess whether various drugs have an effect. We show that treatment of hiPSC-CMs with inflammatory cytokines (such as interferon-γ or TNF-α) impair their relaxation and that SGLT2 inhibitors, clinically proven as effective for HFpEF, reverse this effect.Additionally, treatment with mitochondrial antioxidants (like mito-Tempo) and certain antiretrovirals resulted in the reversal of the effects of these cytokines on cardiomyocyte relaxation. Finally, incubation of hiPSC-CMs with serum from HIV patients with and without diastolic dysfunction (DD) did not alter their relaxation, indicating that short exposure to the serum of these patients is not sufficient to induce DD
in vitro
. Together, our results indicate that hiPSC-CMs can be used as a model to study molecular mechanisms of inflammation-mediated abnormal cardiomyocyte relaxation and screen for potential new interventions.
The first occurrence of machimosaurid crocodylomorphs from the Oxfordian of south-central Poland provides new insights into the distribution of macrophagous teleosauroids
Authors: Weryński Łukasz , Błażejowski Błazej , Szczygielski Tomasz , Young Mark T.
Published: March 2024

Teleosauroid thalattosuchians were a clade of semi-aquatic crocodylomorphs that achieved a broad geographic distribution during the Mesozoic. While their fossils are well documented in Western European strata, our understanding of teleosauroids (and thalattosuchians in general) is notably poorer in Central-Eastern Europe, and from Poland in particular. Herein, we redescribe a teleosauroid rostrum (MZ VIII Vr-72) from middle Oxfordian strata of Załęcze Wielkie, in south-central Poland. Until now, the specimen has been largely encased in a block of limestone. After preparation, its rostral and dental morphology could be evaluated, showing the specimen to be a non-machimosaurin machimosaurid, similar in morphology to taxa Neosteneosaurus edwardsi and Proexochokefalos heberti. The well-preserved teeth enable us to study the specimen feeding ecology through the means of comparing its teeth to other teleosauroids through PCoA analysis. Comparisons with inferred closely related taxa suggest that the referred specimen was a macrophagous generalist. Notably, MZ VIII Vr-72 displays a prominent pathological distortion of the anterior rostrum, in the form of lateral bending. The pathology affects the nasal passage and tooth size and position, and is fully healed, indicating that, despite its macrophagous diet, it did not prevent the individual from food acquisition.
Cultural Existence in World Art History and Dominant Cultural Identity Traces in Works of Art
Authors: Esen BAYKURT Arif , GÖĞEBAKAN Yüksel
Published: March 2024

A work of art has the capacity to be an independent examination of the culture from which it emerges. From the birth of art to the present day, works of art analyze their own culture and present messages to society through works of
art. With these messages and analyses, they improve society and bring new perspectives, norms, regulations, and even previously forgotten cultures and norms into it. The culture of each nation includes its contexts; it derives
from religious, social, political, economic, traditional, and moral values. These values used by the artist are embodied as different products in different branches of art, such as painting, sculpture, architecture, and performance.
Universal works of artists, are shaped by the dominant characters of their culture and help to protect their society and new generations in the future. The research aims to identify dominant cultural traces in art using examples
from world art history within the disciplines of art and anthropology. In addition, it is to draw attention to the necessity of new aesthetic approaches by excluding Kitsch art, which emerged in the early modern age and corrupted
art and culture. The research is important in terms of guiding artists in the context of cultural contacts in art. The following results emerged from the qualitative research: Art acts as an intercultural bridge by infiltrating
culture and society. Universal and political messages in art should be used in the context of "doing art politically, not political art" for the benefit of society. Moreover, if care is not taken, it is inevitable that "kitsch
art" will corrupt society. Therefore, a work of art must preserve its society by avoiding Kitsch art. On the other hand, an artist must be a good sociologist and an anthropologist. Finally, the artist or the universal work of art
protects, secures, strengthens, and develops the future of culture. Otherwise, the opposite will happen.
Priorities during the COVID-19 Pandemic in the Context of Post-Traumatic Growth among University Students: A Phenomenological Approach
Authors: YAKUT İPEKOĞLU Hilal , KURTOĞLU Mustafa Batuhan
Published: March 2024

Savaş, doğal afet, hastalık ve salgın süreçlerinin travmatik etkisinin bireyler üzerinde yalnızca olumsuz etkilerinin olmadığı, süreç ve sonrası deneyimlerin insanların yaşantılarında önemli değişimlere yol açtığı bilinmektedir. Bu
araştırmanın amacı travma sonrası büyüme bağlamında, koronavirüs pandemisi sonrası üniversite öğrencilerinin değişen önceliklerini incelemektir. Veri analiz süreci fenomenolojik yaklaşım kullanılarak gerçekleştirilmiştir. Isparta’da
yer alan devlet üniversitelerinde ve Gaziantep’te bulunan bir vakıf üniversitesinde öğrenim gören 64 öğrenci araştırmaya katılmıştır. Öğrencilere, pandemi sürecinin yaşam önceliklerinde ne gibi bir değişime yol açtığını sorgulayan
tek bir soru yöneltilmiştir. Soru çevrimiçi ortamda yazılı olarak gönderilmiş, ayrıntılı ve samimi bir biçimde duygu ve düşüncelerini yine yazılı olarak aktarmaları istenmiştir. Kendilerini özgür bir şekilde ifade etmelerini etkileyebileceği
düşüncesi ile hiçbir demografik bilgi istememiştir. Veriler, 2021 yılı Nisan-Mayıs aylarında toplanmıştır. Analiz aşamasında öncelikle öğrencilerin vermiş oldukları metinler incelenmiş, yaşadıkları deneyimle ve önceliklerindeki
değişimlerle ilgili görüşleri listelenmiştir. Ortak ifadeler sıralanmış, öğrencilerin önemle bahsettikleri konular içerisinden anlam birimleri oluşturulmuş ve ardından temalar belirlenmiştir. Çalışmanın temaları; aile ve sosyalleşme,
sağlık, kendilik ve tüketim alışkanlıklarıdır. Araştırma kapsamında elde edilen sonuçlar üniversite öğrencilerinin pandemi sürecinde kendilerini ve yaşamlarını anlama ve anlamlandırmada önemli değişimler yaşadıklarını göstermiştir.
Öncelikleri arasında yer alan unsurların önem sıralamalarının değiştiği ve kendilerine yeni öncelikler edindikleri gözlenmektedir. Bu değişim ve gelişimlerin ilgili yazında yer alan travma sonrası büyüme boyutları ile ilişkili
olduğu görülmektedir. İlgili yazınla da paralel olarak bulgularımıza göre pandeminin, diğerleriyle daha yakın ilişkiler kurma, sosyalleşmede artış, kendilik algısında gelişim ve önceliklerin genel olarak değişimi gibi etkileri
ile travma sonrası büyümeyi beraberinde getirdiğini söylemek mümkündür.
The Process of the Establıshment of the Ziyârîds Rulıng ın the Regıon of Tabaristân end Jıbâl
Authors: GENÇTÜRK Cihan
Published: March 2024

İsmini kurucusu Merdâvîc’in babası Ziyâr b. Verdânşâh’dan almış olan Ziyârîler, X. ve XI. yüzyıllar arasında Cibâl ve Taberistân bölgesinde hüküm sürmüştür. Ziyârîler’in hüküm sürmüş olduğu Cibâl ve Taberistân bölgesi ise Ziyârîler’in
kuruluşundan önce uzun yıllar Taberistân Zeydîleri ile onlara karşı savaşan Bâvendîler, Sâmânîler ve Abbâsîler’in hâkimiyet mücadelelerine sahne olmuştur. Ziyârî Hanedanı’nın kurucusu Merdâvîc b. Ziyâr ise tarih sahnesine çıktığı
ilk dönemlerde bu mücadelede Sâmânî ordusunda görev almaktaydı. Daha sonra ise Sâmânîler’in hizmetinde bulunan Deylemli komutan Esfâr b. Şîreveyh’in hizmetine girerek onun ordu kumandanı olmuştur. Merdâvîc b. Ziyâr, Esfâr b. Şîreveyh’in
hizmetine girdikten sonra özellikle Taberistân bölgesinde Zeydîler’e karşı elde ettiği başarılar sonucunda adından söz ettirmeyi başarmıştır. Ancak Merdâvîc b. Ziyâr elde ettiği başarıların da etkisiyle hizmetinde bulunduğu Esfâr
b. Şîreveyh’e karşı isyan ederek Hicri 316 (928-929) yılında onu öldürmüştür. Merdâvîc b. Ziyâr, Esfâr b. Şîreveyh’i öldürdükten sonra onun hâkimiyetinde bulunan Cibâl bölgesinin önemli şehirleri olan Rey, Hemedân ve İsfahân şehirlerini
ele geçirmiştir. Merdâvîc b. Ziyâr daha sonraları ise Esfâr b. Şîreveyh’e karşı işbirliği yaptığı Mâkân b. Kâkî’ye de saldırmış ve Esfâr b. Şîreveyh’in öldürülmesinden sonra Mâkân b. Kâkî’nin hâkimiyetine girmiş olan Taberistân
bölgesini ve bölgenin önemli şehri olan Cürcân şehrini ele geçirerek Mâkân b. Kâkî’yi bölgeden uzaklaştırmıştır. Böylece Merdâvîc b. Ziyâr bu başarılarının ardından başta Cibâl bölgesindeki şehirler olmak üzere Cürcân ve Taberistân’ı
hâkimiyeti altına alarak kaynaklarda Ziyârîler olarak adlandırın hanedanlığı kurmuştur.
Temporary Shelter Areas After Earthquakes: Building Studio Proposals for Emergency Shelter in Earthquake Zones
Authors: ÖZMEN Fulya , GÜLTEK Mediha , AVİNÇ Güneş Mutlu , SARICIOĞLU Pelin , YILDIZ Aslı
Published: March 2024

Eğitim, afet yönetimi konusunda farkındalığı artıracak en hızlı araç olarak önemli bir işleve sahiptir. Eğitimin bireylere kazandırdığı yenilikçi fikirleri eyleme dönüştürme potansiyeli, deprem sonrası yaşam alanlarının sağlıklı ve
sürdürülebilir gelişimi açısından önemlidir. Dolayısıyla afetlere karşı tepkisel yaklaşımdan önleyici yaklaşıma geçiş için mimar ve mühendislerin eğitimi büyük önem taşımaktadır. Bu bağlamda, Gazi Üniversitesi Mimarlık Bölümünde
2022-2023 bahar dönemi içerisinde “M 3091-Mimarlık ve Yapı Projesi Stüdyosu” dersinde deprem sonrası yaşam alanları için çözüm önerileri araştırılmıştır. Buradan hareketle öğrencilerden üç veya dört kişilik gruplar olarak, belirli
bir bölgeye kültürel ve bağlamsal olarak uygun bir afet sonrası yaşam alanları tasarımı geliştirmeleri istenmiştir. Buna ek olarak, öğrenciler sürdürülebilir, kolayca taşınabilir ve inşa edilebilir çözümler geliştirmeye teşvik
edilmiştir. Bu yönde eğitim alan ve proje üreten öğrenciler/mimarlar, toplum sorunlarına aşinalık kazanmak ile birlikte afet sonrası yaşam alanlarının yapısal, sosyal ve kültürel açıdan uygulanabilirliğini ortaya koymaktadırlar.
Dersin kazanımı olarak öğrenciler, afet sonrası yaşam alanları ihtiyaçları, yerleşimi, prefabrikasyon, yerinde üretim ve yeniden kullanım gibi konularda bilgi sahibi olmuşlardır. Yapı stüdyosu eğitimine yönelik bu yaklaşım, öğrenilenleri
sınıf ötesine aktarabilme, olumlu değişimi etkileme ve mimarlık aracılığıyla sürdürülebilir bir geleceğe katkıda bulunma potansiyelini ortaya koymaktadır. Ayrıca öğrencilerin dönem sonunda ortaya koydukları yaşam merkezi önerileri
olası afet sonrası planlamalar için fikir olabileceği düşünülmektedir. Buradan hareketle bu araştırmanın benzer eğitim araştırmalarına da yol gösterebileceği öngörülmektedir.
Ancient Period, Early Geographies in the Western Geographical Tradition
Authors: ALİAĞAOĞLU Alpaslan
Published: March 2024

Coğrafya insan ve doğal çevrenin yeryüzünde bıraktığı izleri açıklayan bilimdir. Coğrafyanın evriminde farklı aşamalar ayırt edilmektedir. Klasik dönem, modern dönem ve çağdaş dönem modern zamanlarda ortaya çıkan dönemlerdir. Bu aşamalardan
biri de coğrafyanın erken dönem hafızası olarak nitelenecek Antik dönemdir. Bu dönem coğrafyanın adının koyulduğu dönem olmak gibi bir özelliğe de sahiptir. Eldeki çalışmada, antik dönem coğrafyası kaynak tarama yöntemi ile ele
alınmaktadır. Çalışmanın amacı, bu dönemde farklı düşünürlerin coğrafyaya yaptıkları katkıları ve dönemin genel özelliklerini ortaya koymaktır. Sonuç olarak görülmektedir ki Antik dönem coğrafik katkıları etkisini mutlak manada
16. hatta 17.yüzyıla kadar devam ettirmiştir. Arap coğrafyacıları da bu dönemden etkilenmiştir. Bu etki kısmen de olsa bugün devam etmektedir. Herodot, Eratosthenes, Strabo, Batlamyüs’un önemli katkıları olmuştur. Coğrafyacıların
coğrafi kökeni nedeniyle Anadolu coğrafik düşüncenin merkezinde yer alır. İskenderiye ve Milet şehirleri bilimsel merkez olmak gibi bir özelliğe sahiptir. Coğrafya Helen kökenli olup, küçük bir alanda yapılmaktadır. Evren dünya
merkezlidir. Coğrafik olan, harita yapımı gibi, birçok ilk bu dönemde ortaya çıkmıştır. Dönemin kendine has gelenekleri vardır. Bunlar, topoğrafik, matematik ve astronomik ve teolojik gelenektir. Ancak coğrafi düşüncenin gelişiminde
etkili olan başka bazı gelenek ve yaklaşımların kökeni de bu döneme kadar uzanmaktadır. Mekânsal gelenek, alan incelemeleri geleneği (bölgesel yaklaşım), çevreci determinizm, probabilizm bunlar arasındadır.
Genetics and Gene Science (Classical)
Authors: De Baldo A.C.
Published: August 2007

Fundamentals of Genetics

Defining the Gene

Deoxyribonucleic Acid (DNA)

Ribonucleic Acid (RNA)

Mutations of Genes

RecombinantDNATechnology

Genes and Diseases

New Advances in UnderstandingDNAReplication

The Human Genome Project (HGP)
Origins Program
Authors:   NASA/Jet Propulsion Laboratory
Published: August 2007

Science

Gravity's Role in Galaxy Formation

How Galaxies Produce Chemicals for Stars, Planets, and Living Organisms

Young Planetary Systems in Formation

Mature Planetary Systems

Worlds Where Life Can Thrive

Identifying Life‐Bearing Worlds

How Matter is Organized Into Living Systems

Limits to Life in Different Planetary Environments

Missions

Space‐Based Observatories

The Precursor Missions

The First Generation Missions

The Second Generation Mission

The Third Generation Missions

Ground‐Based Observatories
A Novel Mesoporous CaO‐Loaded In2O3 Material for CO2 Sensing
Authors: Prim A. , Pellicer E. , Rossinyol E. , Peiró F. , Cornet A. , Morante J. R.
Published: August 2007

A mesoporous CaO‐loaded In2O3 material (with Ca/In2O3 ratios ranging from 2.5 to 8.5 at %) has been synthesized and used as resistive gas sensor for the detection of CO2. A nanostructured In2O3 matrix has been obtained by hard template route from the SBA‐15 silica template. Additive presence does not distort the lattice of In2O3, which crystallizes in the Ia3 cubic space group. It has been proved by XRD, HRTEM, Raman and XPS measurements that samples contain not only CaO but also CaCO3 in calcite phase as a consequence of CaO carbonation. Pure In2O3 based sensors are low sensitive to CO2, whereas those containing the additive show an important response in the 300–5000 ppm range of gas concentrations. As seen by DRIFTS, the electrical response arises from the interaction between CO32– and CO2, yielding bicarbonates products. The reaction is water‐assisted, so that hydration of the sensing material ensures sensor reliability whilst its dehydration would inhibit sensor response. The use of CaCO3 instead of CaO does not cause significant differences in electrical and DRIFTS data, which corroborates the important role played by carbonate species in the sensing mechanism.
Printable Single‐Crystal Silicon Micro/Nanoscale Ribbons, Platelets and Bars Generated from Bulk Wafers
Authors: Baca A. J. , Meitl M. A. , Ko H. C. , Mack S. , Kim H.‐S. , Dong J. , Ferreira P. M. , Rogers J. A.
Published: August 2007

This article demonstrates a method for fabricating high quality single‐crystal silicon ribbons, platelets and bars with dimensions between ∼ 100 nm and ∼ 5 cm from bulk (111) wafers by using phase shift and amplitude photolithographic methods in conjunction with anisotropic chemical etching procedures. This “top‐down” approach affords excellent control over the thicknesses, lengths, and widths of these structures and yields almost defect‐free, monodisperse elements with well defined doping levels, surface morphologies and crystalline orientations. Dry transfer printing these elements from the source wafers to target substrates by use of soft, elastomeric stamps enables high yield integration onto wafers, glass plates, plastic sheets, rubber slabs or other surfaces. As one application example, bottom gate thin‐film transistors that use aligned arrays of ribbons as the channel material exhibit good electrical properties, with mobilites as high as ∼ 200 cm2 V–1 s–1 and on/off ratios > 104.
Organic Solar Cells by Annealing Stacked Amorphous and Microcrystalline Layers
Authors: Osasa T. , Yamamoto S. , Matsumura M.
Published: August 2007

Organic solar cells were fabricated by stacking aromatic amine and C60 layers. The energy conversion efficiency of these solar cells was low because of poor photoabsorption by these layers and short diffusion length of excitons. However, the photocurrent density was increased by about 3 times by the application of heat treatment to the stacked organic layers at 140 °C, and the maximum energy conversion efficiency reached 1.1 % under AM 1.5, 100 mW cm–2 simulated solar light. The internal quantum efficiency of the photocurrent after the annealing reached about 45 %. When the aromatic amine layer was about 100 nm thick, the organic layers after the annealing showed a wrinkled structure under an optical microscope. The annealing temperature needed for the formation of this structure was in good agreement with the temperature needed for the increase in the photocurrent. The morphological change caused by the annealing was attributed to infiltration of the amorphous aromatic amine compound into grain boundaries of the microcrystalline C60 layer, resulting in expansion of the C60 layer and the wrinkled structure of the organic layers. From observation by electron microscopy, the mixed form of these two compounds near the interface was found to be suited to solar cells because the C60 and aromatic amine phases wedge each other in a direction normal to two electrodes. However, the annealing slightly lowered photovoltage of the solar cell. This effect was attributed to a partial contact of the C60 layer with a counter electrode through the aromatic amine layer.
Solution‐Processible Multi‐component Cyclometalated Iridium Phosphors for High‐Efficiency Orange‐Emitting OLEDs and Their Potential Use as White Light Sources
Authors: Ho C.‐L. , Wong W.‐Y. , Zhou G.‐J. , Yao B. , Xie Z. , Wang L.
Published: August 2007

The synthesis and photophysical studies of several multifunctional phosphorescent iridium(III) cyclometalated complexes consisting of the hole‐transporting carbazole and fluorene‐based 2‐phenylpyridine moieties are reported. All of them are isolated as thermally and morphological stable amorphous solids. Extension of the π‐conjugation through incorporation of electron‐pushing carbazole units to the fluorene fragment leads to bathochromic shifts in the emission profile, increases the highest occupied molecular orbital levels and improves the charge balance in the resulting complexes because of the propensity of the carbazole unit to facilitate hole transport. These iridium‐based triplet emitters give a strong orange phosphorescence light at room temperature with relatively short lifetimes in the solution phase. The photo‐ and electroluminescence properties of these phosphorescent carbazolylfluorene‐functionalized metalated complexes have been studied in terms of the coordinating position of carbazole to the fluorene unit. Organic light‐emitting diodes (OLEDs) using these complexes as the solution‐processed emissive layers have been fabricated which show very high efficiencies even without the need for the typical hole‐transporting layer. These orange‐emitting devices can produce a maximum current efficiency of ∼ 30 cd A–1 corresponding to an external quantum efficiency of ∼ 10 % ph/el (photons per electron) and a power efficiency of ∼ 14 lm W–1. The homoleptic iridium phosphors generally outperform the heteroleptic counterparts in device performance. The potential of exploiting these orange phosphor dyes in the realization of white OLEDs is also discussed.
Highly Stable Nickel Hexacyanoferrate Nanotubes for Electrically Switched Ion Exchange
Authors: Chen W. , Xia X. H.
Published: August 2007

Nickel hexacyanoferrate (NiHCF) nanotubes are fabricated by an electrokinetic method based on the distinct surface properties of porous anodic alumina. By this method, nanotubes can be formed rapidly with the morphologies faithfully replicating the nanopores in the template. The prepared nanotubes were carefully characterized using SEM and TEM. Results from IR, UV, EDX, and electrochemical measurements show that the NiHCF nanotubes exist only in the form of K2Ni[Fe(CN)6]. Because of this single composition and unique nanostructure, NiHCF nanotubes show excellently stable cesium‐selective ion‐exchange ability. The capacity for electrodes modified with NiHCF nanotubes after 500 potential cycles retains 95.3 % of its initial value. Even after 1500 and 3000 cycles, the NiHCF nanotubes still retain 92.2 % and 82.9 %, respectively, of their ion‐exchange capacity.
Polyelectrolyte‐Clay‐Protein Layer Films on Microfluidic PDMS Bioreactor Surfaces for Primary Murine Bone Marrow Culture
Authors: Mehta G. , Kiel M. J. , Lee J. W. , Kotov N. , Linderman J. J. , Takayama S.
Published: August 2007

Poly(dimethylsiloxane) (PDMS) microbioreactors with computerized perfusion controls would be useful for engineering the bone marrow microenvironment. However, previous efforts to grow primary bone marrow cells on PDMS substrates have not been successful due to the weak attachment of cells to the PDMS surface even with adsorption of cell adhesive proteins such as collagen or fibronectin. In this work, modification of the surface of PDMS with biofunctional multilayer coatings is shown to promote marrow cell attachment and spreading. An automated microfluidic perfusion system is used to create multiple types of polyelectrolyte nanoscale coatings simultaneously in multiple channels based on layer‐by‐layer deposition of PDDA (poly(diallyldimethyl ammonium chloride)), clay, type IV collagen and fibronectin. Adherent primary bone marrow cells attached and spread best on a surface with composition of (PDDA/clay)5 (Collagen/Fibronectin)2 with negatively charged fibronectin exposed on the top, remaining well spread and proliferating for at least two weeks. Compared to traditional more macroscopic layer‐by‐layer methods, this microfluidic nanocomposite process has advantages of greater flow control, automatic processing, multiplexed fabrication, and use of lesser amounts of polymers and protein solutions.
Addressable Protein Patterning via Switchable Superhydrophobic Microarrays
Authors: Shiu J.‐Y. , Chen P. L.
Published: August 2007

We report on a simple process to create a switchable superhydrophobic surface where the water contact angle can be switched from a superhydrophobic state (ca. 167°) to a completely wetted state (< 10°). In the superhydrophobic state, the switchable superhydrophobic surface was resistant to the adsorption of proteins. However, once converted to a wetted state, the same surface promoted protein adsorption. We have developed a novel multicomponent protein‐patterning technique based on this unique property of the switchable superhydrophobic surface. It is demonstrated that up to 100 × 100 protein spots can be created within one second. Each element on the switchable superhydrophobic microarray can be addressed individually and different types of biomolecules can be selectively deposited on the microarray without losing their activity. When integrated with microfluidic channels, the switchable superhydrophobic surface allows the parallel patterning of protein molecules to be carried out without cross contamination.
A Novel Fluorene‐Triphenylamine Hybrid That is a Highly Efficient Host Material for Blue‐, Green‐, and Red‐Light‐Emitting Electrophosphorescent Devices
Authors: Shih P.‐I , Chien C.‐H. , Wu F.‐I. , Shu C.‐F.
Published: August 2007

TFTPA (tris[4‐(9‐phenylfluoren‐9‐yl)phenyl]amine), a novel host material that contains a triphenylamine core and three 9‐phenyl‐9‐fluorenyl peripheries, was effectively synthesized through a Friedel‐Crafts‐type substitution reaction. Owing to the presence of its sterically bulky 9‐phenyl‐9‐fluorenyl groups, TFTPA exhibits a high glass transition temperature (186 °C) and is morphologically and electrochemically stable. In addition, as demonstrated from atomic force microscopy measurements, the aggregation of the triplet iridium dopant is significantly diminished in the TFTPA host, resulting in a highly efficient full‐color phosphorescence. The performance of TFTPA‐based devices is far superior to those of the corresponding mCP‐ or CBP‐based devices, particularly in blue‐ and red‐emitting electrophosphorescent device systems. The efficiency of the FIrpic‐based blue‐emitting device reached 12 % (26 cd A–1) and 18 lm W–1 at a practical brightness of 100 cd m–2; the Ir(piq)2acac‐based red‐emitting device exhibited an extremely low turn‐on voltage (2.6 V) and a threefold enhancement in device efficiency (9.0 lm W–1) relative to those of reference devices based on the CBP host material.
Arbitrarily Shaped Fiber Assemblies from Spun Carbon Nanotube Gel Fibers
Authors: Razal J. M. , Coleman J. N. , Muñoz E. , Lund B. , Gogotsi Y. , Ye H. , Collins S. , Dalton A. B. , Baughman R. H.
Published: August 2007

Experimental methods, apparatus, and practically useful theoretical analysis are provided for the coagulation‐based spinning of effectively unlimited lengths of carbon nanotube fibers having exceptional toughness and reasonably high strength. This spinning process fundamentally depends on the mechanical properties of intermediate gel state fibers, which we find are surprising elastic up to about 20 % strain and sufficiently strong for diverse processing methods. More specifically, we show that assemblies of these gel fibers can be used as intermediates for making nanotube sheets, large diameter fibers, and conformal coatings. When suitably processed, these composites (comprising many parallel solution‐spun nanotube fibers) have useful strength and extraordinary toughness.
Label‐Free and Self‐Signal Amplifying Molecular DNA Sensors Based on Bioconjugated Polyelectrolytes
Authors: Lee K. , Povlich L. K. , Kim J.
Published: August 2007

Hybrid bio/‐synthetic sensory conjugated polyelectrolytes were developed to achieve selective label‐free detection of target oligonucleotides with amplified fluorescence signal in solution. A completely water soluble and highly fluorescent conjugated poly(p‐phenyleneethynylene) (PPE) was rationally designed and synthesized as a signal amplifying unit and chemically modified with carboxylic functional groups at the ends of the polymer chains to bioconjugate with amine functionalized single‐stranded oligonucleotides as a receptor using carbodiimide chemistry. This approach allows the functional groups on the polymers to be effectively linked to DNA without any damage to the conjugated π‐system of the polymers. DNA detection results using the PPE‐DNA hybrid system confirmed large signal amplification by means of efficient Förster energy transfer from the energy harvesting PPE to the fluorescent dye attached to the complementary analyte DNA. To realize label‐free detection, we also connected a DNA molecular beacon to the newly developed conjugated polymer as a self‐signaling molecular switch. A DNA detection study by using the resulting PPE‐DNA beacon and single strand analyte DNAs showed not only signal‐amplification properties but also self‐signaling properties.
Characteristics of participants with self‐reported hemochromatosis or iron overload at HEIRS study initial screening
Authors: Barton James C. , Acton Ronald T. , Leiendecker‐Foster Catherine , Lovato Laura , Adams Paul C. , Eckfeldt John H. , McLaren Christine E. , Reiss Jacob A. , McLaren Gordon D. , Reboussin David M. , Gordeuk Victor R. , Speechley Mark R. , Press Richard D. , Dawkins Fitzroy W.
Published: August 2007

There are few descriptions of young adults with self‐reported hemochromatosis or iron overload (H/IO). We analyzed initial screening data in 7,343 HEmochromatosis and IRon Overload Screening (HEIRS) Study participants ages 25–29 years, including race/ethnicity and health information; transferrin saturation (TS) and ferritin (SF) measurements; andHFEC282Y and H63D genotypes. We used denaturing high‐pressure liquid chromatography and sequencing to detect mutations inHJV,TFR2,HAMP,SLC40A1, andFTL. Fifty‐one participants reported previous H/IO; 23 (45%) reported medical conditions associated with H/IO. Prevalences of reports of arthritis, diabetes, liver disease or liver cancer, heart failure, fertility problems or impotence, and blood relatives with H/IO were significantly greater in participants with previous H/IO reports than in those without. Only 7.8% of the 51 participants with previous H/IO reports had elevated TS; 13.7% had elevated SF. Only one participant had C282Y homozygosity. Three participants aged 25–29 years were heterozygous for potentially deleterious mutations inHFE2,TFR2, andHAMPpromoter, respectively. Prevalences of self‐reported conditions, screening iron phenotypes, and C282Y homozygosity were similar in 1,165 participants aged 30 years or greater who reported previous H/IO. We conclude that persons who report previous H/IO diagnoses in screening programs are unlikely to have H/IO phenotypes or genotypes. Previous H/IO reports in some participants could be explained by treatment that induced iron depletion before initial screening, misdiagnosis, or participant misunderstanding of their physician or the initial screening questionnaire. Am. J. Hematol., 2008. © 2007 Wiley‐Liss, Inc.
Keipert syndrome (Nasodigitoacoustic syndrome) is X‐linked and maps to Xq22.2–Xq28
Authors: Amor David J. , Dahl Hans‐Henrik M. , Bahlo Melanie , Bankier Agnes
Published: August 2007

Keipert syndrome is a rare condition comprising sensorineural deafness associated with facial and digital abnormalities. To date, Keipert syndrome has been reported in six male patients including two sib pairs; however the genetic basis of Keipert syndrome is yet to be elucidated. We report on the diagnosis of Keipert syndrome in the nephew of the brothers in the first report of Keipert syndrome, with a pedigree consistent with X‐linked recessive inheritance. Linkage analysis using microsatellite markers along the X‐chromosome suggests that the gene for Keipert syndrome is located in the region Xq22.2–Xq28. We postulate the Keipert syndrome is caused by a novel gene at Xq22.2–Xq28. © 2007 Wiley‐Liss, Inc.
Social, emotional, and behavioral functioning of children with NF1
Authors: Noll Robert B. , Reiter‐Purtill Jennifer , Moore Bartlett D. , Schorry Elizabeth K. , Lovell Anne M. , Vannatta Kathryn , Gerhardt Cynthia A.
Published: August 2007

Children with neurofibromatosis type 1 (NF1) can have varying degrees of cognitive impairment, and are at risk for social, emotional, and behavioral dysfunction. We undertook an evaluation of social, emotional, and behavioral functioning of youth with NF1 and peers from multiple perspectives. We hypothesized that children with NF1 would have more psychosocial difficulties, which would be positively associated with neurological involvement. We compared 58 children with NF1, ages 7–15, with comparison classroom peers, classmates who were same race/gender and closest date of birth. Peer relationships, emotional well‐being, and behavior were evaluated from multiple perspectives in multiple settings. Results showed that teachers perceived children with NF1 as more prosocial (i.e., polite, helpful to others). Teachers and peers viewed children with NF1 as displaying less leadership behavior and as more socially sensitive‐isolated (i.e., often left out, trouble making friends). Children with NF1 had fewer friendships and were less well liked by peers. Mothers and fathers reported more problems with social functioning among children with NF1. Few group differences in emotional well‐being and behavior were identified according to child and father report. However, mothers perceived children with NF1 to have more emotional problems relative to comparison peers, predominantly among older children. Neurological involvement was significantly related to psychosocial problems. We conclude that children with NF1 are frequently socially isolated and rejected by peers; and that greater neurological involvement is associated with more emotional problems. Central nervous system involvement appears to play a key role in identifying children at risk for problems with friendships, social acceptance, and emotional functioning (i.e., depression). © 2007 Wiley‐Liss, Inc.
Risk factors for isolated biliary atresia, National Birth Defects Prevention Study, 1997–2002
Authors: The Natalie S. , Honein Margaret A. , Caton Alissa R. , Moore Cynthia A. , Siega‐Riz Anna Maria , Druschel Charlotte M.
Published: August 2007

Biliary atresia is a rare birth defect that affects 1 in 12,000 to 1 in 19,500 live births. We used data from the National Birth Defects Prevention Study, a multistate case‐control study, to identify potential risk factors for isolated biliary atresia (no additional unrelated major birth defects diagnosed). Infants were identified from eight states from 1997 to 2002, with clinical information abstracted from medical records. Potential risk factors assessed include: demographic factors, seasonality, preterm birth, maternal smoking, maternal alcohol use, maternal illicit drug use, maternal health, maternal medication use, maternal vitamin use, and maternal nutrition. Infants of non‐Hispanic black mothers were more likely to have biliary atresia than infants of non‐Hispanic white mothers (adjusted odds ratio (aOR) = 2.29, 95% confidence interval (CI) 1.07–4.93) and infants conceived during the spring season were more likely to have biliary atresia than infants conceived in winter (aOR = 2.33, 95%CI 1.05–5.16). Low intakes of vitamin E, copper, phosphorus, and beta tocopherol were associated with the occurrence of isolated biliary atresia (borderline significance). Low iron intake had a borderline inverse association with biliary atresia. While this analysis provides support for previous reports of a possible association between seasonal variation and the occurrence of biliary atresia, more data are needed to evaluate whether the seasonal variation is related to infectious agents. The role of nutrients in the development of biliary atresia remains unclear. Further studies of genetic, infectious, and nutrient exposures and the association of biliary atresia are warranted. Published 2007 Wiley‐Liss, Inc.
NAT2variation and idiopathic talipes equinovarus (clubfoot)
Authors: Hecht Jacqueline T. , Ester Audrey , Scott Allison , Wise Carol A. , Iovannisci David M. , Lammer Edward J. , Langlois Peter H. , Blanton Susan H.
Published: August 2007

Idiopathic talipes equinovarus (ITEV), or isolated clubfoot, is a common developmental anomaly that is characterized by a rigid foot, adducted forefoot, cavus midfoot, equinovarus of the hindfoot, and hypoplastic calf musculature. The etiology of this common birth defect is largely unknown, but genetic factors have been implicated in population and family studies and maternal smoking during pregnancy has been identified as an environmental risk factor. The biotransformation of exogenous substances, such as tobacco smoke, is modulated by numerous genes includingN‐acetylation genes,NAT1andNAT2. Functional variants of these genes exist and can be distinguished by genotyping. We hypothesized that variation inNAT1andNAT2genes might be associated with ITEV. To test this hypothesis,NAT1andNAT2were genotyped in a sample of 56 multiplex ITEV families, 57 trios with a positive family history and 160 simplex trios with ITEV. The results detected a slight decrease in the expected number of homozygotes for theNAT2normal allele in the Hispanic simplex trios. In addition, in a pilot case–control study of ITEV, there were significantly more slowNAT2acetylators among the cases. This suggests that slow acetylation may be a risk factor for ITEV. This study is the first to find evidence suggesting a role for a biotransformation candidate gene in the etiology of ITEV and provides a scientific foundation to further explore the contributions of other tobacco metabolism genes in the etiology of clubfoot. © 2007 Wiley‐Liss, Inc.
Die Jagd auf Palau'amin
Authors: Köck Matthias , Grube Achim , Seiple Ian B. , Baran Phil S.
Published: August 2007

Seit der Entdeckung im Jahr 1993 hat Palau'amin die Naturstoffchemiker fasziniert. Seine ungewöhnliche Molekülstruktur und die beschriebene biologische Aktivität machen diesen marinen Naturstoff zu einem lohnenden Ziel für die organische Synthese. Im Laufe der Jahre und im Zusammenhang mit der Isolierung verwandter mariner Alkaloide wurde die postulierte chemische Struktur von Palau'amin angezweifelt, und vor kurzem wurde die relative Konfiguration von Palau'amin schließlich revidiert. Dieser Kurzaufsatz gibt eine sorgfältige Übersicht über die Strukturrevision und deren Bedeutung für die Biosynthese sowie die Totalsynthese.