Adequacy of the Dicke model in cavity QED: a counter-"no-go" statement

The long-standing debate whether the phase transition in the Dicke model can be realized with dipoles in electromagnetic fields is yet an unsettled one. The well-known statement often referred to as the "no-go theorem", asserts that the so-called A-square term, just in the vicinity of the critical point, becomes relevant enough to prevent the system from undergoing a phase transition. At variance with this common belief, in this paper we prove that the Dicke model does give a consistent description of the interaction of light field with the internal excitation of atoms, but in the dipole gauge of quantum electrodynamics. The phase transition cannot be excluded by principle and a spontaneous transverse-electric mean field may appear. We point out that the single-mode approximation is crucial: the proper treatment has to be based on cavity QED, wherefore we present a systematic derivation of the dipole gauge inside a perfect Fabry-P\'erot cavity from first principles. Besides the impact on the debate around the Dicke phase transition, such a cleanup of the theoretical ground of cavity QED is important because currently there are many emerging experimental approaches to reach strong or even ultrastrong coupling between dipoles and photons, which demand a correct treatment of the Dicke model parameters

Chukchis

This chapter is about the 'Chukchis' the indigenous people of the far northeast of Russia. Historically engaged in reindeer herding and sea mammal hunting. Published in the "Supplement to the Modern Encyclopedia of Russian, Soviet and Eurasian History" published by Academic International Pres

The Chukchis and Siberian Yupiks of the Russian Far East.

The Chukotka Autonomous Region of the Russian Federation is inhabited by several Native and non-Native peoples. The Chukchis and Siberian Yupiks constitute the two most numerous Native groups in the region, while ethnic Russians and Ukrainians dominate among the non-Native population. According to the last census of 1989, there were approx. 15,000 Chukchis and 1,700 Yupiks living within Russia. More than 90% of the Yupiks and most of the Chukchis live within the borders of the Chukotka Autonomous Okrug. Some Chukchis also live in the Sakha Republic to the west and in the Magadan Province to the south. Historically, significant cultural differences developed between the coastal Chukchis and Yupiks in eastern Chukotka (on the Chukchi Peninsula, roughly coinciding with Providenskii and Chukotskii districts) and the tundra or reindeer Chukchi of western Chukotka. Thus, the similarities among coastal Chukchis and Yupiks were often more pronounced than among coastal and reindeer Chukchis. Commensurate with the ethnographic expertise of the authors, our account will focus on the Yupiks and Chukchis of the Chukchi Peninsula and the Chukchis of the Anadyr River Basin (Anadyrskii District)

The Chukchis and Siberian Yupiks of the Russian Far East.

The Chukotka Autonomous Region of the Russian Federation is inhabited by several Native and non-Native peoples. The Chukchis and Siberian Yupiks constitute the two most numerous Native groups in the region, while ethnic Russians and Ukrainians dominate among the non-Native population. According to the last census of 1989, there were approx. 15,000 Chukchis and 1,700 Yupiks living within Russia. More than 90% of the Yupiks and most of the Chukchis live within the borders of the Chukotka Autonomous Okrug. Some Chukchis also live in the Sakha Republic to the west and in the Magadan Province to the south. Historically, significant cultural differences developed between the coastal Chukchis and Yupiks in eastern Chukotka (on the Chukchi Peninsula, roughly coinciding with Providenskii and Chukotskii districts) and the tundra or reindeer Chukchi of western Chukotka. Thus, the similarities among coastal Chukchis and Yupiks were often more pronounced than among coastal and reindeer Chukchis. Commensurate with the ethnographic expertise of the authors, our account will focus on the Yupiks and Chukchis of the Chukchi Peninsula and the Chukchis of the Anadyr River Basin (Anadyrskii District)

The B_s and D_s decay constants in 3 flavor lattice QCD

Capitalizing on recent advances in lattice QCD, we present a calculation of the leptonic decay constants f_{B_s} and f_{D_s} that includes effects of one strange sea quark and two light sea quarks. The discretization errors of improved staggered fermion actions are small enough to simulate with 3 dynamical flavors on lattices with spacings around 0.1 fm using present computer resources. By shedding the quenched approximation and the associated lattice scale ambiguity, lattice QCD greatly increases its predictive power. NRQCD is used to simulate heavy quarks with masses between 1.5 m_c and m_b. We arrive at the following results: f_{B_s} = 260 \pm 7 \pm 26 \pm 8 \pm 5 MeV and f_{D_s} = 290 \pm 20 \pm 29 \pm 29 \pm 6 MeV. The first quoted error is the statistical uncertainty, and the rest estimate the sizes of higher order terms neglected in this calculation. All of these uncertainties are systematically improvable by including another order in the weak coupling expansion, the nonrelativistic expansion, or the Symanzik improvement program.Comment: 4 page

GREEN FLUORESCENT PROTEIN (GFP), SUATU SIGNAL PENANDA QUANTITATIF UNTUK MEMONITOR PROLIFERASI SEL

Banyak penelitian sel kultur yang melibatkan sejumlah besar sampel untuk dianalisis, baik yang berhubungan dengan pertumbuhan sel atau toksisitas senyawa terhadap sel. Green Fluorescent Protein (GFP) adalah suatu protein yang secara alami dapat berfluorescence dan banyak digunakan pada berbagai aplikasi seperti penanda untuk ekspresi gena, produksi heterologous protein atau monitoring efisiensi transfeksi. Penelitian ini bertujuan untuk membandingkan tingkat akurasi, taraf kepercayaan dan reprodusibilitas GFP untuk memonitor pertumbuhan sel.Kurva baku dibuat dengan serial dilusi sel CHO-K1-EGFP dalam media 10% FCS di 96 well plate. Jumlah sel dalam tiap sumuran dihubungkan dengan signal fluorescence. Untuk memonitor pertumbuhan sel, signal fluoresensi dibandingkan dengan metode Trypan Blue Exclusion yang jumlah sel dalam tiap sumuran dihitung selama periode waktu tertentu (n=3). Untuk monitoring pertumbuhan sel, signal dari GFP memperlihatkan korelasi yang baik dengan jumlah sel dengan tingkat linieritas 0,9866 dalam kisaran jumlah sel 1250 – 1 x 105 sell/sumuran (standar error maksimum 11%). Metode ini terbukti memungkinkan pengukuran langsung signal fluoresensi sehingga mampu menurunkan kemungkinan kesalahan yang terjadi pada saat preparasi sel yang dapat mempengaruhi akurasi data yang diperoleh. Sekali klones permanen (stable clones) diperoleh klons ini dapat digunakan untuk banyak aplikasi.Kata Kunci: Green Fluorescent Protein (GFP), Fluorescence, proliferasi sel, Trypan Blue Exclusio

Use of the Nanobridge system for the Rapid Production of Pluipotent Stem Cells and Neural Progenitor Cells

The novel Nanobridge system allows the formation of cellular aggregates of pluripotent stem cells, which can then be grown in suspensions cultures allowing accurate control of the environment in which the cells are growing. The Nanobridge system utilizes a thermo-responsive poly N-isopropyl acrylamide (PNIPAM) polymer decorated with extracellular matrix (ECM) protein fragments (fibronectin or vitronectin) to bind to and bridge between adjacent cells and form cell aggregates at 370 C. A temperature shift from 370 C to 320 C causes the PNIPAM to become water soluble weakening the bonding between adjacent PNIPAM chains and allowing the aggregates to be broken down to smaller aggregates by increased shear forces. By returning the temperature to 370 C and increasing the culture volume with additional medium, the increased number of smaller aggregates are able to grow to a larger diameter. Repeating this cycle allows for the rapid expansion in cell numbers. In addition, the ability to vary the concentrations and ratios of the two components in the Nanobridge system, when coupled with the temperature shift procedure during passaging, allows for tight control over the aggregate diameters at all stages of the expansion process. In this paper, two examples of using the Nanobridge system to culture stem cells will be described: firstly using the system for the rapid expansion of human embryonic stem cells whilst maintaining high viability and pluripotency, and secondly; using the system to develop a process to form neural cell aggregates and maintain and expand cells at a stem/progenitor (NPC) stage, obviating the need for the current cumbersome manual methods to produce larger numbers of NPCs. In the first example, embryonic stem cells (hESC) WA09 were cultured in spinner flasks with the Nanobridge system. At the end of the growth phase, aggregates of 348 micron average diameter were reduced to an average diameter of 139microns after sub-passaging. When this cycle was repeated five times, there was a 500 fold increase in the number of cells produced, with a viability at the end of the process of 90% while maintaining key pluripotent markers NANOG, OCT3/4, SOX2, and DNMT3B. Characterization of the hESC aggregates was performed using the IN Cell Analyser 2200, which demonstrated that there was uniform cell viability and pluripotency marker distribution throughout the aggregates, ie there was no evidence of any diffusional limitations or necrotic regions within the aggregates. At the end of the expansion process it was shown that the cells were able to differentiate into all three germ layers, and that the cells could be converted, to cells types such as cardiomyocytes. The results demonstrate that the Nanobridge system is a simple and scalable method of producing large numbers of PSCs without the need for enzymes during passaging. For the production of the neural progenitors (NPCs), hESC (WA09) cells were formed and cultured as Nanobridge aggregates with diameters of 200-300 mm. Differentiation was initiated by culturing the aggregates in mTESR medium with 5uM SB431542 and 100 nM LDN for 5 days. At day 5, the medium was changed to neural basal medium (NBM) supplemented with EGF and FGF2 for the next 5 days of culture. Cultures were maintained in NBM from day 10 onwards. Passaging was performed at day 5 and day 10 and thereafter on a weekly basis for 4 weeks. Temperature shift and mechanical shear were utilized to breakup aggregates and Nanobridge components and medium were replaced during passaging. Cells demonstrated upregulation and subsequent maintenance of neural-associated markers (PAX6, SOX1, and NCAM) in aggregate culture. Passaging resulted in an overall seven fold increase in the number of cells expressing the neural-associated markers. Furthermore, neural progenitor cell aggregates exhibited the capacity to differentiate towards a more mature phenotype as demonstrated by the outgrowth of neurites. This demonstrated that the Nanobridge system has the potential to facilitate the scale-up of NPC production in bioreactors for applications in regenerative medicine and pharmacological testing

Fetal MRI in management of complicated meconium ileus: Prenatal and surgical imaging

Objective To review fetal MRI cases surgically proven to have meconium ileus (MI) and obstruction, describe the common fetal MRI findings that distinguish cases of complicated MI, and to compare these findings with surgical images and perinatal outcomes. Method We performed a retrospective review of all fetal MRI examinations and the corresponding medical record from our tertiary care children's hospital over an 18‐month period. Postnatal management and outcomes were reviewed for these patients, and those patients with surgical or postmortem diagnosis of complicated MI were included in the study. Results Our analysis revealed 7 cases. In this cohort, 3 imaging features of the fetal bowel were repeatedly seen: gradient appearance of intraluminal bowel contents, abnormally localized meconium signal, and collapsed appearance of the colon on MRI. Surgical diagnoses confirmed MI. All live‐born infants underwent surgical repair. Conclusion Fetal MRI should be included in the diagnostic algorithm of any pregnancy where fetal bowel obstruction is suspected to better risk stratify patients

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Thermoresponsive worms for expansion and release of human embryonic stem cells

The development of robust suspension cultures of human embryonic stem cells (hESCs) without the use of cell membrane disrupting enzymes or inhibitors is critical for future clinical applications in regenerative medicine. We have achieved this by using long, flexible, and thermoresponsive polymer worms decorated with a recombinant vitronectin subdomain that bridge hESCs, aiding in hESC's natural ability to form embryoid bodies (EBs) and satisfying their inherent requirement for cell-cell and cell-extracellular matrix contact. When the EBs reached an optimal upper size where cytokine and nutrient penetration becomes limiting, these long and flexible polymer worms facilitated EB breakdown via a temperature shift from 37 to 25 C. The thermoresponsive nature of the worms enabled a cyclical dissociation and propagation of the cells. Repeating the process for three cycles (over eighteen days) provided a >30-fold expansion in cell number while maintaining pluripotency, thereby providing a simple, nondestructive process for the 3D expansion of hESC